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Sample records for surface emitting lasers

  1. Surface emitting ring quantum cascade lasers for chemical sensing

    Science.gov (United States)

    Szedlak, Rolf; Hayden, Jakob; Martín-Mateos, Pedro; Holzbauer, Martin; Harrer, Andreas; Schwarz, Benedikt; Hinkov, Borislav; MacFarland, Donald; Zederbauer, Tobias; Detz, Hermann; Andrews, Aaron Maxwell; Schrenk, Werner; Acedo, Pablo; Lendl, Bernhard; Strasser, Gottfried

    2018-01-01

    We review recent advances in chemical sensing applications based on surface emitting ring quantum cascade lasers (QCLs). Such lasers can be implemented in monolithically integrated on-chip laser/detector devices forming compact gas sensors, which are based on direct absorption spectroscopy according to the Beer-Lambert law. Furthermore, we present experimental results on radio frequency modulation up to 150 MHz of surface emitting ring QCLs. This technique provides detailed insight into the modulation characteristics of such lasers. The gained knowledge facilitates the utilization of ring QCLs in combination with spectroscopic techniques, such as heterodyne phase-sensitive dispersion spectroscopy for gas detection and analysis.

  2. Commercial mode-locked vertical external cavity surface emitting lasers

    Science.gov (United States)

    Lubeigt, Walter; Bialkowski, Bartlomiej; Lin, Jipeng; Head, C. Robin; Hempler, Nils; Maker, Gareth T.; Malcolm, Graeme P. A.

    2017-02-01

    In recent years, M Squared Lasers have successfully commercialized a range of mode-locked vertical external cavity surface emitting lasers (VECSELs) operating between 920-1050nm and producing picosecond-range pulses with average powers above 1W at pulse repetition frequencies (PRF) of 200MHz. These laser products offer a low-cost, easy-to-use and maintenance-free tool for the growing market of nonlinear microscopy. However, in order to present a credible alternative to ultrafast Ti-sapphire lasers, pulse durations below 200fs are required. In the last year, efforts have been directed to reduce the pulse duration of the Dragonfly laser system to below 200fs with a target average power above 1W at a PRF of 200MHz. This paper will describe and discuss the latest efforts undertaken to approach these targets in a laser system operating at 990nm. The relatively low PRF operation of Dragonfly lasers represents a challenging requirement for mode-locked VECSELs due to the very short upper state carrier lifetime, on the order of a few nanoseconds, which can lead to double pulsing behavior in longer cavities as the time between consecutive pulses is increased. Most notably, the design of the Dragonfly VECSEL cavity was considerably modified and the laser system extended with a nonlinear pulse stretcher and an additional compression stage. The improved Dragonfly laser system achieved pulse duration as short as 130fs with an average power of 0.85W.

  3. Submonolayer Quantum Dots for High Speed Surface Emitting Lasers

    Directory of Open Access Journals (Sweden)

    Zakharov ND

    2007-01-01

    Full Text Available AbstractWe report on progress in growth and applications of submonolayer (SML quantum dots (QDs in high-speed vertical-cavity surface-emitting lasers (VCSELs. SML deposition enables controlled formation of high density QD arrays with good size and shape uniformity. Further increase in excitonic absorption and gain is possible with vertical stacking of SML QDs using ultrathin spacer layers. Vertically correlated, tilted or anticorrelated arrangements of the SML islands are realized and allow QD strain and wavefunction engineering. Respectively, both TE and TM polarizations of the luminescence can be achieved in the edge-emission using the same constituting materials. SML QDs provide ultrahigh modal gain, reduced temperature depletion and gain saturation effects when used in active media in laser diodes. Temperature robustness up to 100 °C for 0.98 μm range vertical-cavity surface-emitting lasers (VCSELs is realized in the continuous wave regime. An open eye 20 Gb/s operation with bit error rates better than 10−12has been achieved in a temperature range 25–85 °Cwithout current adjustment. Relaxation oscillations up to ∼30 GHz have been realized indicating feasibility of 40 Gb/s signal transmission.

  4. Modeling of circular-grating surface-emitting lasers

    Science.gov (United States)

    Shams-Zadeh-Amiri, Ali M.

    Grating-coupled surface-emitting lasers became an area of growing interest due to their salient features. Emission from a broad area normal to the wafer surface, makes them very well suited in high power applications and two- dimensional laser arrays. These new possibilities have caused an interest in different geometries to fully develop their potential. Among them, circular-grating lasers have the additional advantage of producing a narrow beam with a circular cross section. This special feature makes them ideal for coupling to optical fibers. All existing theoretical models dealing with circular- grating lasers only consider first-order gratings, or second-order gratings, neglecting surface emission. In this thesis, the emphasis is to develop accurate models describing the laser performance by considering the radiation field. Toward this aim, and due to the importance of the radiation modes in surface-emitting structures, a theoretical study of these modes in multilayer planar structures has been done in a rigorous and systematic fashion. Problems like orthogonality of the radiation modes have been treated very accurately. We have considered the inner product of radiation modes using the distribution theory. Orthogonality of degenerate radiation modes is an important issue. We have examined its validity using the transfer matrix method. It has been shown that orthogonality of degenerate radiation modes in a very special case leads to the Brewster theorem. In addition, simple analytical formulas for the normalization of radiation modes have been derived. We have shown that radiation modes can be handled in a much easier way than has been thought before. A closed-form spectral dyadic Green's function formulation of multilayer planar structures has been developed. In this formulation, both rectangular and cylindrical structures can be treated within the same mathematical framework. The Hankel transform of some auxiliary functions defined on a circular aperture has

  5. Linearly Polarized Dual-Wavelength Vertical-External-Cavity Surface-Emitting Laser (Postprint)

    National Research Council Canada - National Science Library

    Fan, Li; Fallahi, Mahmoud; Hader, Joerg; Zakharian, Aramais R; Moloney, Jerome V; Stolz, Wolfgang; Koch, Stephan W; Bedford, Robert; Murray, James T

    2007-01-01

    The authors demonstrate the multiwatt linearly polarized dual-wavelength operation in an optically pumped vertical-external-cavity surface-emitting laser by means of an intracavity tilted Fabry-Perot...

  6. III-Nitride Vertical-Cavity Surface-Emitting Lasers

    Science.gov (United States)

    Leonard, John T.

    Vertical-cavity surface-emitting lasers (VCSELs) have a long history of development in GaAs-based and InP-based systems, however III-nitride VCSELs research is still in its infancy. Yet, over the past several years we have made dramatic improvements in the lasing characteristics of these highly complex devices. Specifically, we have reduced the threshold current density from ˜100 kA/cm2 to ˜3 kA/cm2, while simultaneously increasing the output power from ˜10 muW to ˜550 muW. These developments have primarily come about by focusing on the aperture design and intracavity contact design for flip-chip dual dielectric DBR III-nitride VCSELs. We have carried out a number of studies developing an Al ion implanted aperture (IIA) and photoelectrochemically etched aperture (PECA), while simultaneously improving the quality of tin-doped indium oxide (ITO) intracavity contacts, and demonstrating the first III-nitride VCSEL with an n-GaN tunnel junction intracavity contact. Beyond these most notable research fronts, we have analyzed numerous other parameters, including epitaxial growth, flip-chip bonding, substrate removal, and more, bringing further improvement to III-nitride VCSEL performance and yield. This thesis aims to give a comprehensive discussion of the relevant underlying concepts for nonpolar VCSELs, while detailing our specific experimental advances. In Section 1, we give an overview of the applications of VCSELs generally, before describing some of the potential applications for III-nitride VCSELs. This is followed by a summary of the different material systems used to fabricate VCSELs, before going into detail on the basic design principles for developing III-nitride VCSELs. In Section 2, we outline the basic process and geometry for fabricating flip-chip nonpolar VCSELs with different aperture and intracavity contact designs. Finally, in Section 3 and 4, we delve into the experimental results achieved in the last several years, beginning with a discussion on

  7. 2 W high efficiency PbS mid-infrared surface emitting laser

    Science.gov (United States)

    Ishida, A.; Sugiyama, Y.; Isaji, Y.; Kodama, K.; Takano, Y.; Sakata, H.; Rahim, M.; Khiar, A.; Fill, M.; Felder, F.; Zogg, H.

    2011-09-01

    High efficiency laser operation with output power exceeding 2 W was obtained for vertical external-cavity PbS based IV-VI compound surface emitting quantum-well structures. The laser showed external quantum efficiency as high as 16%. Generally, mid-infrared III-V or II-VI semiconductor laser operation utilizing interband electron transitions are restricted by Auger recombination and free carrier absorption. Auger recombination is much lower in the IV-VI semiconductors, and the free-carrier absorption is significantly reduced by an optically pumped laser structure including multi-step optical excitation layers.

  8. Transverse-mode-selectable microlens vertical-cavity surface-emitting laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Debernardi, Pierluigi; Lee, Yong Tak

    2010-01-01

    of the mode selection properties of the new structure is rigorously analyzed and compared to other structures reported in the literature. The possibility of engineering the emission shape while retaining strong single mode operation is highly desirable for low-cost mid-range optical interconnects applications......A new vertical-cavity surface-emitting laser structure employing a thin microlens is suggested and numerically investigated. The laser can be made to emit in either a high-power Gaussian-shaped single-fundamental mode or a high-power doughnut-shaped higher-order mode. The physical origin...

  9. Polymer-coated vertical-cavity surface-emitting laser diode vapor sensor

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgaard; Larsen, Niels Bent

    2010-01-01

    We report a new method for monitoring vapor concentration of volatile organic compounds using a vertical-cavity surface-emitting laser (VCSEL). The VCSEL is coated with a polymer thin film on the top distributed Bragg reflector (DBR). The analyte absorption is transduced to the electrical domain ...

  10. Spectral-Modulation Characteristics of Vertical-Cavity Surface-Emitting Lasers

    Science.gov (United States)

    Vas'kovskaya, M. I.; Vasil'ev, V. V.; Zibrov, S. A.; Yakovlev, V. P.; Velichanskii, V. L.

    2018-01-01

    The requirements imposed on vertical-cavity surface-emitting lasers in a number of metrological problems in which optical pumping of alkali atoms is used are considered. For lasers produced by different manufacturers, these requirements are compared with the experimentally observed spectral characteristics at a constant pump current and in the microwave modulation mode. It is shown that a comparatively small number of lasers in the microwave modulation mode make it possible to obtain the spectrum required for atomic clocks based on the coherent population-trapping effect.

  11. VCSELs Fundamentals, Technology and Applications of Vertical-Cavity Surface-Emitting Lasers

    CERN Document Server

    2013-01-01

    The huge progress which has been achieved in the field is covered here, in the first comprehensive monograph on vertical-cavity surface-emitting lasers (VCSELs) since eight years. Apart from chapters reviewing the research field and the laser fundamentals, there are comprehensive updates on red and blue emitting VCSELs, telecommunication VCSELs, optical transceivers, and parallel-optical links for computer interconnects. Entirely new contributions are made to the fields of vectorial three-dimensional optical modeling, single-mode VCSELs, polarization control, polarization dynamics, very-high-speed design, high-power emission, use of high-contrast gratings, GaInNAsSb long-wavelength VCSELs, optical video links, VCSELs for optical mice and sensing, as well as VCSEL-based laser printing. The book appeals to researchers, optical engineers and graduate students.

  12. Acetone vapor sensing using a vertical cavity surface emitting laser diode coated with polystyrene

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgaard; Larsen, Niels Bent

    2009-01-01

    We report theoretical and experimental on a new vapor sensor, using a single-mode vertical-cavity surface-emitting laser (VCSEL) coated with a polymer sensor coating, which can detect acetone vapor at a volume fraction of 2.5%. The sensor provides the advantage of standard packaging, small form......-factor, mechanical stability and low cost when combined with a monolithically integrated photodiode detector....

  13. Photodegradation and polarization properties of vertical external surface-emitting organic laser

    International Nuclear Information System (INIS)

    Leang, Tatiana

    2014-01-01

    Although organic solid-state dye lasers can provide wavelength tunability in the whole visible spectrum and offers perspectives of low-cost compact lasers, they are still limited by several drawbacks, especially photodegradation. The geometry of a Vertical External Cavity Surface-emitting Organic Laser (VECSOL) enables organic lasers to reach high energies, excellent conversion efficiencies and good beam quality, it also enables an external control on many parameters, a feature that we have used here to study the photodegradation phenomenon as well as some polarization properties of organic solid-state lasers. In the first part of this thesis, we studied the lifetime of the laser upon varying several parameters (pump pulse-width, repetition rate, output coupling,...) and we found that the intracavity laser intensity, independently of the pump intensity, had a major on photodegradation rate. Moreover, we observed that the profile of the laser beam was also degrading with time: while it is Gaussian in the beginning it gradually shifts to an annular shape. In the second part, we investigated the polarization properties of VECSOLs, with a special emphasis on fluorescence properties of some typical dyes used in lasers. The crucial role played by resonant non-radiative energy transfers between dye molecules (HOMO-FRET) is evidenced and enables explaining the observed fluorescence depolarization, compared to the expected limiting fluorescence anisotropy. Energy transfers happen to play a negligible role above laser threshold, as the organic laser beam is shown to be linearly polarized in a wide range of experimental conditions when excitation occurs in the first singlet state. (author) [fr

  14. Controllable spiking patterns in long-wavelength vertical cavity surface emitting lasers for neuromorphic photonics systems

    Energy Technology Data Exchange (ETDEWEB)

    Hurtado, Antonio, E-mail: antonio.hurtado@strath.ac.uk [Institute of Photonics, SUPA Department of Physics, University of Strathclyde, TIC Centre, 99 George Street, Glasgow G1 1RD (United Kingdom); Javaloyes, Julien [Departament de Fisica, Universitat de les Illes Balears, c/Valldemossa km 7.5, 07122 Mallorca (Spain)

    2015-12-14

    Multiple controllable spiking patterns are achieved in a 1310 nm Vertical-Cavity Surface Emitting Laser (VCSEL) in response to induced perturbations and for two different cases of polarized optical injection, namely, parallel and orthogonal. Furthermore, reproducible spiking responses are demonstrated experimentally at sub-nanosecond speed resolution and with a controlled number of spikes fired. This work opens therefore exciting research avenues for the use of VCSELs in ultrafast neuromorphic photonic systems for non-traditional computing applications, such as all-optical binary-to-spiking format conversion and spiking information encoding.

  15. Vertical-cavity surface-emitting laser vapor sensor using swelling polymer reflection modulation

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgård; Dohn, Søren

    2012-01-01

    Vapor detection using a low-refractive index polymer for reflection modulation of the top mirror in a vertical-cavity surface-emitting laser (VCSEL) is demonstrated. The VCSEL sensor concept presents a simple method to detect the response of a sensor polymer in the presence of volatile organic co...... compounds. We model the physics as a change in the top mirror loss caused by swelling of the polymer upon absorbing the target volatile organic compound. Further we show how acetone vapors at 82 000 ppm concentration can change the polymer coated VCSEL output power by 20 mu W....

  16. A Study of the interaction of radiation and semiconductor lasers: an analysis of transient and permanent effects induced on edge emitting and vertical cavity surface emitting laser diodes

    International Nuclear Information System (INIS)

    Pailharey, Eric

    2000-01-01

    The behavior of laser diodes under transient environment is presented in this work. The first section describes the basic phenomena of radiation interaction with matter. The radiative environments, the main characteristics of laser diodes and the research undertaken on the subject are presented and discussed. The tests on 1300 nm edge emitting laser diode are presented in the second section. The response to a transient ionizing excitation is explored using a 532 nm laser beam. The time of return to steady state after the perturbation is decomposed into several steps: decrease of the optical power during excitation, turn-on delay, relaxation oscillations and optical power offset. Their origins are analyzed using the device structure. To include all the phenomena in a numerical simulation of the device, an individual study of low conductivity materials used for the lateral confinement of the current density is undertaken. The effects of a single particle traversing the optical cavity and an analysis of permanent damages induced by neutrons are also determined. In the last section, 850 nm vertical cavity surface emitting laser diodes (VCSEL) are studied. The behavior of these devices which performances are in constant evolution, is investigated as a function of both temperature and polarization. Then VCSEL are submitted to transient ionizing irradiation and their responses are compared to those of edge emitting diodes. When proton implantation is used in the process, we observe the same behavior for both technologies. VCSEL were submitted to neutron fluence and we have studied the influence of the damages on threshold current, emission patterns and maximum of optical power. (author) [fr

  17. Continuously tunable monomode mid-infrared vertical external cavity surface emitting laser on Si

    Science.gov (United States)

    Khiar, A.; Rahim, M.; Fill, M.; Felder, F.; Hobrecker, F.; Zogg, H.

    2010-10-01

    A tunable PbTe based mid-infrared vertical external cavity surface emitting laser is described. The active part is a ˜1 μm thick PbTe layer grown epitaxially on a Bragg mirror on the Si-substrate. The cavity is terminated with a curved Si/SiO Bragg top mirror and pumped optically with a 1.55 μm laser. Cavity length is <100 μm in order that only one longitudinal mode is supported. By changing the cavity length, up to 5% wavelength continuous and mode-hop free tuning is achieved at fixed temperature. The total tuning extends from 5.6 to 4.7 μm at 100-170 K operation temperature.

  18. 5-μm vertical external-cavity surface-emitting laser (VECSEL) for spectroscopic applications

    Science.gov (United States)

    Rahim, M.; Khiar, A.; Felder, F.; Fill, M.; Zogg, H.; Sigrist, M. W.

    2010-08-01

    Mid-IR tunable VECSELs (Vertical External-Cavity Surface-Emitting Lasers) emitting at 4-7 μm wavelengths and suitable for spectroscopic sensing applications are described. They are realized with lead-chalcogenide (IV-VI) narrow band gap materials. The active part, a single 0.6-2-μm thick PbTe or PbSe gain layer, is grown onto an epitaxial Bragg mirror consisting of two or three Pb1- y Eu y Te/BaF2 quarter-wavelength layer pairs. All layers are deposited by MBE in a single run employing a BaF2 or Si substrate, no further processing is needed. The cavity is completed with an external curved top mirror, which is again realized with an epitaxial Bragg structure. Pumping is performed optically with a 1.5-μm laser. Maximum output power for pulsed operation is currently up to >1 Wp at -173°C and >10 mW at 10°C. In continuous wave (CW) operation, 18 mW at 100 K are reached. Still higher operating temperatures and/or powers are expected with better heat-removal structures and better designs employing QW (Quantum-Wells). Advantages of mid-IR VECSELs compared to edge-emitting lasers are their very good beam quality (circular beam with 15 μm are accessible with Pb1- y X y Z (X=Sr, Eu, Sn, Z=Se, Te) and/or including QW.

  19. Design of photonic crystal surface emitting lasers with indium-tin-oxide top claddings

    Science.gov (United States)

    Huang, Shen-Che; Hong, Kuo-Bin; Chiu, Han-Lun; Lan, Shao-Wun; Chang, Tsu-Chi; Li, Heng; Lu, Tien-Chang

    2018-02-01

    Electrically pumped GaAs-based photonic crystal surface emitting lasers were fabricated using a simple fabrication process by directly capping the indium-tin-oxide transparent conducting thin film as the top cladding layer upon a photonic crystal layer. Optimization of the separate-confinement heterostructures of a laser structure is crucial to improving characteristics by providing advantageous optical confinements. The turn-on voltage, series resistance, threshold current, and slope efficiency of the laser with a 100 × 100 μm2 photonic crystal area operated at room temperature were 1.3 V, 1.5 Ω, 121 mA, and 0.2 W/A, respectively. Furthermore, we demonstrated a single-lobed lasing wavelength of 928.6 nm at 200 mA and a wavelength redshift rate of 0.05 nm/K in temperature-dependent measurements. The device exhibited the maximum output power of approximately 400 mW at an injection current of 2 A; moreover, divergence angles of less than 1° for the unpolarized circular-shaped laser beam were measured at various injection currents. Overall, the low threshold current, excellent beam quality, small divergence, high output power, and high-operating-temperature (up to 343 K) of our devices indicate that they can potentially fill the requirements for next-generation light sources and optoelectronic devices.

  20. Nonlinear dynamic behaviors of an optically injected vertical-cavity surface-emitting laser

    International Nuclear Information System (INIS)

    Li Xiaofeng; Pan Wei; Luo Bin; Ma Dong; Wang Yong; Li Nuohan

    2006-01-01

    Nonlinear dynamics of a vertical-cavity surface-emitting laser (VCSEL) with external optical injection are studied numerically. We consider a master-slave configuration where the dynamic characteristics of the slave are affected by the optical injection from the master, and we also establish the corresponding Simulink model. The period-doubling route as well as the period-halving route is observed, where the regular, double-periodic, and chaotic pulsings are found. By adjusting the injection strength properly, the laser can be controlled to work at a given state. The effects of frequency detuning on the nonlinear behaviors are also investigated in terms of the bifurcation diagrams of photon density with the frequency detuning. For weak injection case, the nonlinear dynamics shown by the laser are quite different when the value of frequency detuning varies contrarily (positive and negative direction). If the optical injection is strong enough, the slave can be locked by the master even though the frequency detuning is relatively large

  1. The simulation of thermal characteristics of 980 nm vertical cavity surface emitting lasers

    Science.gov (United States)

    Fang, Tianxiao; Cui, Bifeng; Hao, Shuai; Wang, Yang

    2018-02-01

    In order to design a single mode 980 nm vertical cavity surface emitting laser (VCSEL), a 2 μm output aperture is designed to guarantee the single mode output. The effects of different mesa sizes on the lattice temperature, the output power and the voltage are simulated under the condition of continuous working at room temperature, to obtain the optimum process parameters of mesa. It is obtained by results of the crosslight simulation software that the sizes of mesa radius are between 9.5 to 12.5 μm, which cannot only obtain the maximum output power, but also improve the heat dissipation of the device. Project supported by the Beijing Municipal Eduaction Commission (No. PXM2016_014204_500018) and the Construction of Scientific and Technological Innovation Service Ability in 2017 (No. PXM2017_014204_500034).

  2. Optically pumped GaN vertical cavity surface emitting laser with high index-contrast nanoporous distributed Bragg reflector.

    Science.gov (United States)

    Lee, Seung-Min; Gong, Su-Hyun; Kang, Jin-Ho; Ebaid, Mohamed; Ryu, Sang-Wan; Cho, Yong-Hoon

    2015-05-04

    Laser operation of a GaN vertical cavity surface emitting laser (VCSEL) is demonstrated under optical pumping with a nanoporous distributed Bragg reflector (DBR). High reflectivity, approaching 100%, is obtained due to the high index-contrast of the nanoporous DBR. The VCSEL system exhibits low threshold power density due to the formation of high Q-factor cavity, which shows the potential of nanoporous medium for optical devices.

  3. Operation of a novel hot-electron vertical-cavity surface-emitting laser

    Science.gov (United States)

    Balkan, Naci; O'Brien-Davies, Angela; Thoms, A. B.; Potter, Richard J.; Poolton, Nigel; Adams, Michael J.; Masum, J.; Bek, Alpan; Serpenguzel, Ali; Aydinli, Atilla; Roberts, John S.

    1998-07-01

    The hot Electron Light Emission and Lasing in Semiconductor Heterostructures devices (HELLISH-1) is novel surface emitter consisting of a GaAs quantum well, within the depletion region, on the n side of Ga1-xAlxAs p- n junction. It utilizes hot electron transport parallel to the layers and injection of hot electron hole pairs into the quantum well through a combination of mechanisms including tunnelling, thermionic emission and diffusion of `lucky' carriers. Super Radiant HELLISH-1 is an advanced structure incorporating a lower distributed Bragg reflector (DBR). Combined with the finite reflectivity of the upper semiconductor-air interface reflectivity it defines a quasi- resonant cavity enabling emission output from the top surface with a higher spectral purity. The output power has increased by two orders of magnitude and reduced the full width at half maximum (FWHM) to 20 nm. An upper DBR added to the structure defines HELLISH-VCSEL which is currently the first operational hot electron surface emitting laser and lases at room temperature with a 1.5 nm FWHM. In this work we demonstrate and compare the operation of UB-HELLISH-1 and HELLISH-VCSEL using experimental and theoretical reflectivity spectra over an extensive temperature range.

  4. High-beam-quality, efficient operation of passively Q-switched Yb:YAG/Cr:YAG laser pumped by photonic-crystal surface-emitting laser

    Science.gov (United States)

    Guo, Xiaoyang; Tokita, Shigeki; Fujioka, Kana; Nishida, Hiro; Hirose, Kazuyoshi; Sugiyama, Takahiro; Watanabe, Akiyoshi; Ishizaki, Kenji; Noda, Susumu; Miyanaga, Noriaki; Kawanaka, Junji

    2017-07-01

    A passively Q-switched Yb:YAG/Cr:YAG laser pumped by a photonic-crystal surface-emitting laser (PCSEL) was developed. Yb:YAG crystal was cryogenically cooled by liquid nitrogen at 77 K. Excellent Gaussian beam profile ( M 2 = 1.02) and high slope efficiency of 58% were demonstrated without using a coupling optics between a laser material and PCSEL.

  5. Final report on LDRD project: Semiconductor surface-emitting microcavity laser spectroscopy for analysis of biological cells and microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Gourley, P.L.; McDonald, A.E. [Sandia National Labs., Albuquerque, NM (United States). Nanostructure and Semiconductor Physics Dept.; Gourley, M.F. [Washington Hospital Center, DC (United States); Bellum, J. [Coherent Technologies, Boulder, CO (United States)

    1997-08-01

    This article discusses a new intracavity laser technique that uses living or fixed cells as an integral part of the laser. The cells are placed on a GaAs based semiconductor wafer comprising one half of a vertical cavity surface-emitting laser. After placement, the cells are covered with a dielectric mirror to close the laser cavity. When photo-pumped with an external laser, this hybrid laser emits coherent light images and spectra that depend sensitively on the cell size, shape, and dielectric properties. The light spectra can be used to identify different cell types and distinguish normal and abnormal cells. The laser can be used to study single cells in real time as a cell-biology lab-on-a-chip, or to study large populations of cells by scanning the pump laser at high speed. The laser is well-suited to be integrated with other micro-optical or micro-fluidic components to lead to micro-optical-mechanical systems for analysis of fluids, particulates, and biological cells.

  6. Electron spin injection from a regrown Fe layer in a spin-polarized vertical-cavity surface-emitting laser

    Science.gov (United States)

    Holub, M.; Bhattacharya, P.; Shin, J.; Saha, D.

    2007-04-01

    An electroluminescence circular polarization of 23% and threshold current reduction of 11% are obtained in an electrically pumped spin-polarized vertical-cavity surface-emitting laser. Electron spin injection is accomplished utilizing a regrown Fe/ n-AlGaAs Schottky tunnel barrier deposited around the base of the laser mesas. Negligible circular polarizations and threshold current reductions are measured for nonmagnetic and Fe-based control VCSELs, which provides convincing evidence of spin injection, transport, and detection in our spin-polarized laser.

  7. Eigenmodes of spin vertical-cavity surface-emitting lasers with local linear birefringence and gain dichroism

    Science.gov (United States)

    Fördös, T.; Jaffrès, H.; Postava, K.; Seghilani, M. S.; Garnache, A.; Pištora, J.; Drouhin, H. J.

    2017-10-01

    We present a general method for the modeling of semiconductor lasers such as a vertical-cavity surface-emitting laser and a vertical-external-cavity surface-emitting laser containing multiple quantum wells and involving anisotropies that may reveal (i) a local linear birefringence due to the strain field at the surface or (ii) a birefringence in quantum wells due to phase amplitude coupling originating from the reduction of the biaxial D2 d symmetry group to the C2 v symmetry group at the III-V ternary semiconductor interfaces. From a numerical point of view, a scattering S-matrix recursive method is implemented using a gain or amplification tensor derived analytically from the Maxwell-Bloch equations. It enables one to model the properties of the emission (threshold, polarization, and mode splitting) from the laser with multiple quantum well active zones by searching for the resonant eigenmodes of the cavity. The method is demonstrated on real laser structures and is presently used for the extraction of optical permittivity tensors of surface strain and quantum wells in agreement with experiments. The method can be generalized to find the laser eigenmodes in the most general case of circular polarized pumps (unbalance between the spin-up and spin-down channels) and/or dichroism allowing an elliptically polarized light emission as recently demonstrated experimentally when the linear birefringence is almost compensated [Joly et al., Opt. Lett. 42, 651 (2017), 10.1364/OL.42.000651].

  8. Nonpolar III-nitride vertical-cavity surface-emitting lasers incorporating an ion implanted aperture

    KAUST Repository

    Leonard, J. T.

    2015-07-06

    © 2015 AIP Publishing LLC. We report on our recent progress in improving the performance of nonpolar III-nitride vertical-cavity surface-emitting lasers (VCSELs) by using an Al ion implanted aperture and employing a multi-layer electron-beam evaporated ITO intracavity contact. The use of an ion implanted aperture improves the lateral confinement over SiNx apertures by enabling a planar ITO design, while the multi-layer ITO contact minimizes scattering losses due to its epitaxially smooth morphology. The reported VCSEL has 10 QWs, with a 3nm quantum well width, 1nm barriers, a 5nm electron-blocking layer, and a 6.95- λ total cavity thickness. These advances yield a single longitudinal mode 406nm nonpolar VCSEL with a low threshold current density (∼16kA/cm2), a peak output power of ∼12μW, and a 100% polarization ratio. The lasing in the current aperture is observed to be spatially non-uniform, which is likely a result of filamentation caused by non-uniform current spreading, lateral optical confinement, contact resistance, and absorption loss.

  9. Transverse mode dynamics in vertical-cavity surface-emitting lasers: Spatiotemporal versus modal expansion descriptions

    International Nuclear Information System (INIS)

    Mulet, Josep; Balle, Salvador

    2002-01-01

    We discuss the range of validity of a modal description for the spatiotemporal dynamics of the optical field in vertical-cavity surface-emitting lasers. We focus on the secondary pulsations that appear during the turn-off transients when the injection current is modulated by a square-wave signal. We compare the results obtained with both a full spatiotemporal model [J. Mulet and S. Balle, IEEE J. Quantum. Electron. 38, 291 (2002)] and a modal expansion derived from this model. We find that the results obtained from the two descriptions agree for strong lateral guiding. However, for weak lateral guiding we find differences because the optical-field profile changes significantly due to spatial changes in the refractive index induced by the carrier density. The reason is that in the full spatiotemporal model a shrinkage of the mode profile occurs, which leads to an enhancement of the secondary pulsations. This effect is not included in the modal expansion, and it determines the limits of validity of such an approach for gain-guided devices

  10. Optical Injection Locking of Vertical Cavity Surface-Emitting Lasers: Digital and Analog Applications

    Science.gov (United States)

    Parekh, Devang

    With the rise of mobile (cellphones, tablets, notebooks, etc.) and broadband wireline communications (Fiber to the Home), there are increasing demands being placed on transmitters for moving data from device to device and around the world. Digital and analog fiber-optic communications have been the key technology to meet this challenge, ushering in ubiquitous Internet and cable TV over the past 20 years. At the physical layer, high-volume low-cost manufacturing of semiconductor optoelectronic devices has played an integral role in allowing for deployment of high-speed communication links. In particular, vertical cavity surface emitting lasers (VCSEL) have revolutionized short reach communications and are poised to enter more markets due to their low cost, small size, and performance. However, VCSELs have disadvantages such as limited modulation performance and large frequency chirp which limits fiber transmission speed and distance, key parameters for many fiber-optic communication systems. Optical injection locking is one method to overcome these limitations without re-engineering the VCSEL at the device level. By locking the frequency and phase of the VCSEL by the direct injection of light from another laser oscillator, improved device performance is achieved in a post-fabrication method. In this dissertation, optical injection locking of VCSELs is investigated from an applications perspective. Optical injection locking of VCSELs can be used as a pathway to reduce complexity, cost, and size of both digital and analog fiber-optic communications. On the digital front, reduction of frequency chirp via bit pattern inversion for large-signal modulation is experimentally demonstrated showing up to 10 times reduction in frequency chirp and over 90 times increase in fiber transmission distance. Based on these results, a new reflection-based interferometric model for optical injection locking was established to explain this phenomenon. On the analog side, the resonance

  11. Highly Selective Volatile Organic Compounds Breath Analysis Using a Broadly-Tunable Vertical-External-Cavity Surface-Emitting Laser.

    Science.gov (United States)

    Tuzson, Béla; Jágerská, Jana; Looser, Herbert; Graf, Manuel; Felder, Ferdinand; Fill, Matthias; Tappy, Luc; Emmenegger, Lukas

    2017-06-20

    A broadly tunable mid-infrared vertical-external-cavity surface-emitting laser (VECSEL) is employed in a direct absorption laser spectroscopic setup to measure breath acetone. The large wavelength coverage of more than 30 cm -1 at 3.38 μm allows, in addition to acetone, the simultaneous measurement of isoprene, ethanol, methanol, methane, and water. Despite the severe spectral interferences from water and alcohols, an unambiguous determination of acetone is demonstrated with a precision of 13 ppbv that is achieved after 5 min averaging at typical breath mean acetone levels in synthetic gas samples mimicking human breath.

  12. 4.5 μm wavelength vertical external cavity surface emitting laser operating above room temperature

    Science.gov (United States)

    Rahim, M.; Khiar, A.; Felder, F.; Fill, M.; Zogg, H.

    2009-05-01

    A midinfrared vertical external cavity surface emitting laser with 4.5 μm emission wavelength and operating above room temperature has been realized. The active part consists of a single 850 nm thick epitaxial PbSe gain layer. It is followed by a 2 1/2 pair Pb1-yEuyTe/BaF2 Bragg mirror. No microstructural processing is needed. Excitation is done optically with a 1.5 μm wavelength laser. The device operates up to 45 °C with 100 ns pulses and delivers 6 mW output power at 27 °C heat-sink temperature.

  13. High-Speed Semiconductor Vertical-Cavity Surface-Emitting Lasers for Optical Data-Transmission Systems (Review)

    Science.gov (United States)

    Blokhin, S. A.; Maleev, N. A.; Bobrov, M. A.; Kuzmenkov, A. G.; Sakharov, A. V.; Ustinov, V. M.

    2018-01-01

    The main problems of providing a high-speed operation semiconductor lasers with a vertical microcavity (so-called "vertical-cavity surface-emitting lasers") under amplitude modulation and ways to solve them have been considered. The influence of the internal properties of the radiating active region and the electrical parasitic elements of the equivalent circuit of lasers are discussed. An overview of approaches that lead to an increase of the cutoff parasitic frequency, an increase of the differential gain of the active region, the possibility of the management of mode emission composition and the lifetime of photons in the optical microcavities, and reduction of the influence of thermal effects have been presented. The achieved level of modulation bandwidth of ˜30 GHz is close to the maximum achievable for the classical scheme of the direct-current modulation, which makes it necessary to use a multilevel modulation format to further increase the information capacity of optical channels constructed on the basis of vertical-cavity surface-emitting lasers.

  14. Evolution of the Novalux extended cavity surface-emitting semiconductor laser (NECSEL)

    Science.gov (United States)

    McInerney, John G.

    2016-03-01

    Novalux Inc was an enterprise founded by Aram Mooradian in 1998 to commercialise a novel electrically pumped vertical extended cavity semiconductor laser platform, initially aiming to produce pump lasers for optical fiber telecommunication networks. Following successful major investment in 2000, the company developed a range of single- and multi-mode 980 nm pump lasers emitting from 100-500 mW with excellent beam quality and efficiency. This rapid development required solution of several significant problems in chip and external cavity design, substrate and DBR mirror optimization, thermal engineering and mode selection. Output coupling to single mode fiber was exceptional. Following the collapse of the long haul telecom market in late 2001, a major reorientation of effort was undertaken, initially to develop compact 60-100 mW hybrid monolithically integrated pumplets for metro/local amplified networks, then to frequency-doubled blue light emitters for biotech, reprographics and general scientific applications. During 2001-3 I worked at Novalux on a career break from University College Cork, first as R&D Director managing a small group tasked with producing new capabilities and product options based on the NECSEL platform, including high power, pulsed and frequency doubled versions, then in 2002 as Director of New Product Realization managing the full engineering team, leading the transition to frequency doubled products.

  15. Vertical-cavity surface-emitting lasers enable high-density ultra-high bandwidth optical interconnects

    Science.gov (United States)

    Chitica, N.; Carlsson, J.; Svenson, L.-G.; Chacinski, M.

    2015-03-01

    Vertical-Cavity Surface-Emitting Lasers (VCSELs) are key components enabling power- and cost-efficient, high-density, ultra-high bandwidth parallel optical interconnects for data center and high-performance computing applications. This paper presents recent developments at TE Connectivity (TE) in the area of 25 Gb/s per channel-class VCSEL and optical transmitter technology for applications such as 100G and 400G Ethernet and Enhanced Data Rate InfiniBand pluggable and mid-board connectivity solutions.

  16. Lead-chalcogenide mid-infrared vertical external cavity surface emitting lasers with improved threshold: Theory and experiment

    Science.gov (United States)

    Fill, Matthias; Debernardi, Pierluigi; Felder, Ferdinand; Zogg, Hans

    2013-11-01

    Mid-infrared Vertical External Cavity Surface Emitting Lasers (VECSEL) based on narrow gap lead-chalcogenide (IV-VI) semiconductors exhibit strongly reduced threshold powers if the active layers are structured laterally for improved optical confinement. This is predicted by 3-d optical calculations; they show that lateral optical confinement is needed to counteract the anti-guiding features of IV-VIs due to their negative temperature dependence of the refractive index. An experimental proof is performed with PbSe quantum well based VECSEL grown on a Si-substrate by molecular beam epitaxy and emitting around 3.3 μm. With proper mesa-etching, the threshold intensity is about 8-times reduced.

  17. Lead-chalcogenide mid-infrared vertical external cavity surface emitting lasers with improved threshold: Theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Fill, Matthias [ETH Zurich, Laser Spectroscopy and Sensing Lab, 8093 Zurich (Switzerland); Phocone AG, 8005 Zurich (Switzerland); Debernardi, Pierluigi [IEIIT-CNR, Torino 10129 (Italy); Felder, Ferdinand [Phocone AG, 8005 Zurich (Switzerland); Zogg, Hans [ETH Zurich (Switzerland)

    2013-11-11

    Mid-infrared Vertical External Cavity Surface Emitting Lasers (VECSEL) based on narrow gap lead-chalcogenide (IV-VI) semiconductors exhibit strongly reduced threshold powers if the active layers are structured laterally for improved optical confinement. This is predicted by 3-d optical calculations; they show that lateral optical confinement is needed to counteract the anti-guiding features of IV-VIs due to their negative temperature dependence of the refractive index. An experimental proof is performed with PbSe quantum well based VECSEL grown on a Si-substrate by molecular beam epitaxy and emitting around 3.3 μm. With proper mesa-etching, the threshold intensity is about 8-times reduced.

  18. Modular PbSrS/PbS mid-infrared vertical external cavity surface emitting laser on Si

    Science.gov (United States)

    Khiar, A.; Rahim, M.; Fill, M.; Felder, F.; Zogg, H.; Cao, D.; Kobayashi, S.; Yokoyama, T.; Ishida, A.

    2011-07-01

    A mid-infrared vertical external cavity surface emitting laser (VECSEL) based on undoped PbS is described herein. A 200 nm-thick PbS active layer embedded between PbSrS cladding layers forms a double heterostructure. The layers are grown on a lattice and thermal expansion mismatched Si-substrate. The substrate is placed onto a flat bottom Bragg mirror again grown on a Si substrate, and the VECSEL is completed with a curved top mirror. Pumping is done optically with a 1.55 μm laser diode. This leads to an extremely simple modular fabrication process. Lasing wavelengths range from 3-3.8 μm at 100-260 K heat sink temperature. The lowest threshold power is ˜210 mWp and highest output power is ˜250 mWp. The influence of the different recombination mechanism as well as free carrier absorption on the threshold power is modeled.

  19. A GaInAsP/InP Vertical Cavity Surface Emitting Laser for 1.5 m m operation

    Science.gov (United States)

    Sceats, R.; Balkan, N.; Adams, M. J.; Masum, J.; Dann, A. J.; Perrin, S. D.; Reid, I.; Reed, J.; Cannard, P.; Fisher, M. A.; Elton, D. J.; Harlow, M. J.

    1999-04-01

    We present the results of our studies concerning the pulsed operation of a bulk GaInAsP/InP vertical cavity surface emitting laser (VCSEL). The device is tailored to emit at around 1.5 m m at room temperature. The structure has a 45 period n-doped GaInAsP/InP bottom distributed Bragg reflector (DBR), and a 4 period Si/Al2O3 dielectric top reflector defining a 3-l cavity. Electroluminescence from a 16 m m diameter top window was measured in the pulsed injection mode. Spectral measurements were recorded in the temperature range between 125K and 240K. Polarisation, lasing threshold current and linewidth measurements were also carried out at the same temperatures. The threshold current density has a broad minimum at temperatures between 170K and 190K, (Jth=13.2 kA/cm2), indicating a good match between the gain and the cavity resonance in this temperature range. Maximum emitted power from the VCSEL is 0.18 mW at 180K.

  20. Amplification of an Autodyne Signal in a Bistable Vertical-Cavity Surface-Emitting Laser with the Use of a Vibrational Resonance

    Science.gov (United States)

    Chizhevsky, V. N.

    2018-01-01

    For the first time, it is demonstrated experimentally that a vibrational resonance in a polarization-bistable vertical-cavity surface-emitting laser can be used to increase the laser response in autodyne detection of microvibrations from reflecting surfaces. In this case, more than 25-fold signal amplification is achieved. The influence of the asymmetry of the bistable potential on the microvibration-detection efficiency is studied.

  1. Single-exposure two-dimensional superresolution in digital holography using a vertical cavity surface-emitting laser source array.

    Science.gov (United States)

    Granero, Luis; Zalevsky, Zeev; Micó, Vicente

    2011-04-01

    We present a new implementation capable of producing two-dimensional (2D) superresolution (SR) imaging in a single exposure by aperture synthesis in digital lensless Fourier holography when using angular multiplexing provided by a vertical cavity surface-emitting laser source array. The system performs the recording in a single CCD snapshot of a multiplexed hologram coming from the incoherent addition of multiple subholograms, where each contains information about a different 2D spatial frequency band of the object's spectrum. Thus, a set of nonoverlapping bandpass images of the input object can be recovered by Fourier transformation (FT) of the multiplexed hologram. The SR is obtained by coherent addition of the information contained in each bandpass image while generating an enlarged synthetic aperture. Experimental results demonstrate improvement in resolution and image quality.

  2. GaN-based vertical-cavity surface emitting lasers with sub-milliamp threshold and small divergence angle

    Science.gov (United States)

    Yeh, P. S.; Chang, C.-C.; Chen, Y.-T.; Lin, D.-W.; Liou, J.-S.; Wu, C. C.; He, J. H.; Kuo, H.-C.

    2016-12-01

    A GaN-based vertical-cavity surface emitting laser (VCSEL) structure featuring a silicon-diffusion-defined current blocking layer for lateral confinement is described. Sub-milliamp threshold currents were achieved for both 3- and 5-μm-aperture VCSELs under continuous-wave operation at room temperature. The vertical cavity was defined by a top dielectric distributed Bragg reflector (DBR) and a bottom epitaxial DBR. The emission spectrum exhibited a single peak at 411.2 nm with a linewidth of 0.4 nm and a side mode suppression ratio of more than 10 dB before device packaging. The full-width-at-half-maximum divergence angle of the 3-μm-aperture VCSEL was as small as approximately 5° which is the lowest number reported. These results implied the 3-μm-aperture VCSEL was in near single-mode operation.

  3. Circular polarization switching and bistability in an optically injected 1300 nm spin-vertical cavity surface emitting laser

    Energy Technology Data Exchange (ETDEWEB)

    Alharthi, S. S., E-mail: ssmalh@essex.ac.uk; Henning, I. D.; Adams, M. J. [School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Hurtado, A. [School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Institute of Photonics, Physics Department, University of Strathclyde, Wolfson Centre, 106 Rottenrow East, Glasgow G4 0NW, Scotland (United Kingdom); Korpijarvi, V.-M.; Guina, M. [Optoelectronics Research Centre (ORC), Tampere University of Technology, P.O. Box 692, FIN-33101 Tampere (Finland)

    2015-01-12

    We report the experimental observation of circular polarization switching (PS) and polarization bistability (PB) in a 1300 nm dilute nitride spin-vertical cavity surface emitting laser (VCSEL). We demonstrate that the circularly polarized optical signal at 1300 nm can gradually or abruptly switch the polarization ellipticity of the spin-VCSEL from right-to-left circular polarization and vice versa. Moreover, different forms of PS and PB between right- and left-circular polarizations are observed by controlling the injection strength and the initial wavelength detuning. These results obtained at the telecom wavelength of 1300 nm open the door for novel uses of spin-VCSELs in polarization sensitive applications in future optical systems.

  4. Steady-state characteristics of lateral p-n junction vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Ryzhii, V.; Tsutsui, N.; Khmyrova, I.; Ikegami, T.; Vaccaro, P. O.; Taniyama, H.; Aida, T.

    2001-09-01

    We developed an analytical device model for lateral p-n junction vertical-cavity surface-emitting lasers (LJVCSELs) with a quantum well active region. The model takes into account the features of the carrier injection, transport, and recombination in LJVCSELs as well as the features of the photon propagation in the cavity. This model is used for the calculation and analysis of the LJVCSEL steady-state characteristics. It is shown that the localization of the injected electrons primarily near the p-n junction and the reabsorption of lateral propagating photons significantly effects the LJVCSELs performance, in particular, the LJVCSEL threshold current and power-current characteristics. The reincarnation of electrons and holes due to the reabsorption of lateral propagating photons can substantially decrease the threshold current.

  5. PbSe quantum well mid-infrared vertical external cavity surface emitting laser on Si-substrates

    Science.gov (United States)

    Fill, M.; Khiar, A.; Rahim, M.; Felder, F.; Zogg, H.

    2011-05-01

    Mid-infrared vertical external cavity surface emitting lasers based on PbSe/PbSrSe multi-quantum-well structures on Si-substrates are realized. A modular design allows growing the active region and the bottom Bragg mirror on two different Si-substrates, thus facilitating comparison between different structures. Lasing is observed from 3.3 to 5.1 μm wavelength and up to 52 °C heat sink temperature with 1.55 μm optical pumping. Simulations show that threshold powers are limited by Shockley-Read recombination with lifetimes as short as 0.1 ns. At higher temperatures, an additional threshold power increase occurs probably due to limited carrier diffusion length and carrier leakage, caused by an unfavorable band alignment.

  6. Passive cavity surface-emitting lasers: option of temperature-insensitive lasing wavelength for uncooled dense wavelength division multiplexing systems

    Science.gov (United States)

    Shchukin, V. A.; Ledentsov, N. N.; Slight, T.; Meredith, W.; Gordeev, N. Y.; Nadtochy, A. M.; Payusov, A. S.; Maximov, M. V.; Blokhin, S. A.; Blokhin, A. A.; Zadiranov, Yu. M.; Maleev, N. A.; Ustinov, V. M.; Choquette, K. D.

    2016-03-01

    A concept of passive cavity surface-emitting laser is proposed aimed to control the temperature shift of the lasing wavelength. The device contains an all-semiconductor bottom distributed Bragg reflector (DBR), in which the active medium is placed, a dielectric resonant cavity and a dielectric top DBR, wherein at least one of the dielectric materials has a negative temperature coefficient of the refractive index, dn/dT < 0. This is shown to be the case for commonly used dielectric systems SiO2/TiO2 and SiO2/Ta2O5. Two SiO2/TiO2 resonant structures having a cavity either of SiO2 or TiO2 were deposited on a substrate, their optical power reflectance spectra were measured at various temperatures, and refractive index temperature coefficients were extracted, dn/dT = 0.0021 K-1 for SiO2 and dn/dT = -0.0092 K-1 for TiO2. Using such dielectric materials allows designing passive cavity surface-emitting lasers having on purpose either positive, or zero, or negative temperature shift of the lasing wavelength dλ/dT. A design for temperature-insensitive lasing wavelength (dλ/dT = 0) is proposed. Employing devices with temperature-insensitive lasing wavelength in wavelength division multiplexing systems may allow significant reducing of the spectral separation between transmission channels and an increase in number of channels for a defined spectral interval enabling low cost energy efficient uncooled devices.

  7. Attractor hopping between polarization dynamical states in a vertical-cavity surface-emitting laser subject to parallel optical injection

    Science.gov (United States)

    Denis-le Coarer, Florian; Quirce, Ana; Valle, Angel; Pesquera, Luis; Rodríguez, Miguel A.; Panajotov, Krassimir; Sciamanna, Marc

    2018-03-01

    We present experimental and theoretical results of noise-induced attractor hopping between dynamical states found in a single transverse mode vertical-cavity surface-emitting laser (VCSEL) subject to parallel optical injection. These transitions involve dynamical states with different polarizations of the light emitted by the VCSEL. We report an experimental map identifying, in the injected power-frequency detuning plane, regions where attractor hopping between two, or even three, different states occur. The transition between these behaviors is characterized by using residence time distributions. We find multistability regions that are characterized by heavy-tailed residence time distributions. These distributions are characterized by a -1.83 ±0.17 power law. Between these regions we find coherence enhancement of noise-induced attractor hopping in which transitions between states occur regularly. Simulation results show that frequency detuning variations and spontaneous emission noise play a role in causing switching between attractors. We also find attractor hopping between chaotic states with different polarization properties. In this case, simulation results show that spontaneous emission noise inherent to the VCSEL is enough to induce this hopping.

  8. Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts

    KAUST Repository

    Leonard, J. T.

    2016-03-01

    We report on the lasing of III-nitride nonpolar, violet, vertical-cavity surface-emitting lasers (VCSELs) with III-nitride tunnel-junction (TJ) intracavity contacts and ion implanted apertures (IIAs). The TJ VCSELs are compared to similar VCSELs with tin-doped indium oxide (ITO) intracavity contacts. Prior to analyzing device results, we consider the relative advantages of III-nitride TJs for blue and green emitting VCSELs. The TJs are shown to be most advantageous for violet and UV VCSELs, operating near or above the absorption edge for ITO, as they significantly reduce the total internal loss in the cavity. However, for longer wavelength III-nitride VCSELs, TJs primarily offer the advantage of improved cavity design flexibility, allowing one to make the p-side thicker using a thick n-type III-nitride TJ intracavity contact. This offers improved lateral current spreading and lower loss, compare to using ITO and p-GaN, respectively. These aspects are particularly important for achieving high-power CW VCSELs, making TJs the ideal intracavity contact for any III-nitride VCSEL. A brief overview of III-nitride TJ growth methods is also given, highlighting the molecular-beam epitaxy (MBE) technique used here. Following this overview, we compare 12 mu m aperture diameter, violet emitting, TJ and ITO VCSEL experimental results, which demonstrate the significant improvement in differential efficiency and peak power resulting from the reduced loss in the TJ design. Specifically, the TJ VCSEL shows a peak power of similar to 550 mu W with a threshold current density of similar to 3.5 kA/cm(2), while the ITO VCSELs show peak powers of similar to 80 mu W and threshold current densities of similar to 7 kA/cm

  9. Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts

    Science.gov (United States)

    Leonard, J. T.; Young, E. C.; Yonkee, B. P.; Cohen, D. A.; Shen, C.; Margalith, T.; Ng, T. K.; DenBaars, S. P.; Ooi, B. S.; Speck, J. S.; Nakamura, S.

    2016-02-01

    We report on the lasing of III-nitride nonpolar, violet, vertical-cavity surface-emitting lasers (VCSELs) with IIInitride tunnel-junction (TJ) intracavity contacts and ion implanted apertures (IIAs). The TJ VCSELs are compared to similar VCSELs with tin-doped indium oxide (ITO) intracavity contacts. Prior to analyzing device results, we consider the relative advantages of III-nitride TJs for blue and green emitting VCSELs. The TJs are shown to be most advantageous for violet and UV VCSELs, operating near or above the absorption edge for ITO, as they significantly reduce the total internal loss in the cavity. However, for longer wavelength III-nitride VCSELs, TJs primarily offer the advantage of improved cavity design flexibility, allowing one to make the p-side thicker using a thick n-type III-nitride TJ intracavity contact. This offers improved lateral current spreading and lower loss, compare to using ITO and p-GaN, respectively. These aspects are particularly important for achieving high-power CW VCSELs, making TJs the ideal intracavity contact for any III-nitride VCSEL. A brief overview of III-nitride TJ growth methods is also given, highlighting the molecular-beam epitaxy (MBE) technique used here. Following this overview, we compare 12 μm aperture diameter, violet emitting, TJ and ITO VCSEL experimental results, which demonstrate the significant improvement in differential efficiency and peak power resulting from the reduced loss in the TJ design. Specifically, the TJ VCSEL shows a peak power of ~550 μW with a threshold current density of ~3.5 kA/cm2, while the ITO VCSELs show peak powers of ~80 μW and threshold current densities of ~7 kA/cm2.

  10. Blue-emitting laser diodes

    Science.gov (United States)

    Nakano, K.; Ishibashi, A.

    This paper reviews the recent results of blue-emitting laser diodes. These devices are based on ZnMgSSe alloy II-VI semiconductors. Recently we have achieved room temperature continuous-wave operation of ZnMgSSe blue lasers for the first time. ZnMgSSe alloys offer a wide range of band-gap energy from 2.8 to 4.5 eV, while maintaining lattice matching to GaAs substrates. These characteristics make ZnMgSSe suitable for cladding layers of blue lasers. In this article, the feasibilities of ZnMgSSe will be reviewed. The laser structures and characteristics will be also mentioned.

  11. Theory and Modeling of Lasing Modes in Vertical Cavity Surface Emitting Lasers

    Directory of Open Access Journals (Sweden)

    Benjamin Klein

    1998-01-01

    modes that the VCSEL can support are then determined by matching the gain necessary for the optical system in both magnitude and phase to the gain available from the laser's electronic system. Examples are provided.

  12. Near-infrared wafer-fused vertical-cavity surface-emitting lasers for HF detection

    Czech Academy of Sciences Publication Activity Database

    Civiš, Svatopluk; Zelinger, Zdeněk; Nevrlý, V.; Dorogan, A.; Ferus, Martin; Iakovlev, V.; Sirbu, A.; Mereuta, A.; Caliman, A.; Suruceanu, G.; Kapon, E.

    2014-01-01

    Roč. 147, NOV 2014 (2014), s. 53-59 ISSN 0022-4073 R&D Projects: GA MŠk(CZ) LD14022 Grant - others:Ministerstvo financí, Centrum zahraniční pomoci(CZ) PF049 Institutional support: RVO:61388955 ; RVO:68081707 Keywords : High resolution absorption spectroscopy * Monitoring of hydrogen fluoride, methane , and ammonia * Tunable diode laser spectroscopy (TDLS) Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.645, year: 2014

  13. Research of the use of silver nanowires as a current spreading layer on vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Guo, Xia; Shi, Lei; Li, Chong; Dong, Jian; Liu, Bai; Hu, Shuai; He, Yan

    2016-11-01

    Silver nanowire (AgNW) film was proposed to apply on the surface of the vertical-cavity surface-emitting lasers (VCSELs) with large aperture in order to obtain a uniform current distribution in the active region and a better optical beam quality. Optimization of the AgNW film was carried out with the sheet resistance of 28.4 Ω/sq and the optical transmission of 94.8% at 850 nm. The performance of VCSELs with and without AgNW film was studied. When the AgNW film was applied to the surface of VCSELs, due to its better current spreading effect, the maximum output optical power increased from 23.4 mW to 24.4 mW, the lasing wavelength redshift decreased from 0.085 nm/mA to 0.077 nm/mA, the differential resistance decreased from 23.95 Ω to 21.13 Ω, and the far field pattern at 50 mA decreased from 21.6° to 19.2°. At the same time, the near field test results showed that the light in the aperture was more uniform, and the far field exhibited a better single peak characteristic. Various results showed that VCSELs with AgNW on the surface showed better beam quality. Project supported by the National Natural Science Foundation of China (Grant Nos. 61335004 and 61505003), the National High Technology Research and Development Program of China (Grant No. 2015AA017101), and the National Key Research and Development of China (Grant No. 2016YFB0400603).

  14. Tradeoffs of vertical-cavity surface emitting lasers modeling for the development of driver circuits in short distance optical links

    Science.gov (United States)

    Sialm, Gion; Erni, Daniel; Vez, Dominique; Kromer, Christian; Ellinger, Frank; Bona, Gian-Luca; Morf, Thomas; Jäckel, Heinz

    2005-10-01

    In short-distance optical links, the development of driving circuits for vertical-cavity surface-emitting lasers (VCSELs) requires precise and computationally efficient VCSEL models. A small-signal model of a VCSEL is computationally efficient and simple to implement; however, it does not take into account the nonlinear output behavior of the VCSEL. In contrast, VCSEL models that are highly based on first principles cannot be implemented in standard circuit device simulators, because the simulation of eye diagrams becomes too time consuming. We present another approach using VCSEL models, which are based on the 1-D rate equations. Our analysis shows that they combine efficient extraction and short simulation time with an accurate calculation of eye diagrams over a wide range of ambient temperatures. As different implementations of the rate equations exist, tradeoffs between three different versions are presented and compared with measured GaAs oxide-confined VCSELs. The first model has a linear and the second a logarithmic function of the gain versus the carrier density. The third model considers the additional transport time for carriers to reach the active region with quantum wells. For parameter extraction, a minimum set of parameters is identified, which can be determined from fundamental measurements.

  15. Coupled-wave analysis for photonic-crystal surface-emitting lasers on air holes with arbitrary sidewalls.

    Science.gov (United States)

    Peng, Chao; Liang, Yong; Sakai, Kyosuke; Iwahashi, Seita; Noda, Susumu

    2011-11-21

    The coupled-wave theory (CWT) is extended to a photonic crystal structure with arbitrary sidewalls, and a simple, fast, and effective model for the quantitatively analysis of the radiative characteristics of two-dimensional (2D) photonic-crystal surface-emitting lasers (PC-SELs) has been developed. For illustrating complicated coupling effects accurately, sufficient numbers of waves are included in the formulation, by considering their vertical field profiles. The radiation of band-edge modes is analyzed for two in-plane air-hole geometries, in the case of two types of sidewalls: i.e. "tapered case" and "tilted case." The results of CWT analysis agree well with the results of finite-difference time-domain (FDTD) numerical simulation. From the analytical solutions of the CWT, the symmetry properties of the band-edge modes are investigated. In-plane asymmetry of the air holes is crucial for achieving high output power because it causes partial constructive interference. Asymmetric air holes and tilted sidewalls help in inducing in-plane asymmetries. By breaking the symmetries with respect to the two orthogonal symmetric axes of the band-edge modes, the two factors can be tuned independently, so that the radiation power is enhanced while preserving the mode selectivity performance. Finally, top-down reactive ion etching (RIE) approach is suggested for the fabrication of such a structure. © 2011 Optical Society of America

  16. Optically pumped vertical-cavity surface-emitting laser at 374.9 nm with an electrically conducting n-type distributed Bragg reflector

    Science.gov (United States)

    Liu, Yuh-Shiuan; Saniul Haq, Abul Fazal Muhammad; Mehta, Karan; Kao, Tsung-Ting; Wang, Shuo; Xie, Hongen; Shen, Shyh-Chiang; Yoder, P. Douglas; Ponce, Fernando A.; Detchprohm, Theeradetch; Dupuis, Russell D.

    2016-11-01

    An optically pumped vertical-cavity surface-emitting laser with an electrically conducting n-type distributed Bragg reflector was achieved at 374.9 nm. An epitaxially grown 40-pair n-type AlGaN/GaN distributed Bragg reflector was used as the bottom mirror, while the top mirror was formed by a dielectric distributed Bragg reflector composed of seven pairs of HfO2/SiO2. A numerical simulation for the optical mode clearly demonstrated that a high confinement factor was achieved and the threshold pumping power density at room temperature was measured as 1.64 MW/cm2. The achieved optically pumped laser demonstrates the potential of utilizing an n-type distributed Bragg reflector for surface-emitting optical devices.

  17. Printed Large-Area Single-Mode Photonic Crystal Bandedge Surface-Emitting Lasers on Silicon (Open Access Publisher’s Version)

    Science.gov (United States)

    2016-01-04

    beam shape, catastrophic optical damage free, and two-dimensional integration capabilities with CMOS electronics , vertical-cavity surface-emitting...longitudinal and transverse mode over a large lasing area , narrow linewidth, high power output, small beam divergence angle, polarization control...crystal lasers—ultimate nanolasers and broad - area coherent lasers [Invited]. J. Opt. Soc. Am. B 27, B1–B8 (2010). 13. Painter, O. et al. Two-dimensional

  18. Mode-locking of an InAs Quantum Dot Based Vertical External Cavity Surface Emitting Laser Using Atomic Layer Graphene

    Science.gov (United States)

    2015-07-16

    Vertical External Cavity Surface Emitting Lasers). 2)! Installation of a FTIR based temperature dependent reflectivity setup for characterizing VECSELs...and SESAMs (Semiconductor Saturable Absorber Mirrors). 3)! Demonstration of up to 6 Watts CW with InAs QD (Quantum Dot) VECSELs (1250 nm) and 15...AFRL and at other university collaborators such as the University of Arizona. 2.#Installation#of#a# FTIR #based#temperature#dependent#reflectivity

  19. Nonpolar III-nitride vertical-cavity surface-emitting laser with a photoelectrochemically etched air-gap aperture

    Energy Technology Data Exchange (ETDEWEB)

    Leonard, J. T., E-mail: jtleona01@gmail.com; Yonkee, B. P.; Cohen, D. A.; Megalini, L.; Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Lee, S. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); DenBaars, S. P.; Nakamura, S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

    2016-01-18

    We demonstrate a III-nitride nonpolar vertical-cavity surface-emitting laser (VCSEL) with a photoelectrochemically (PEC) etched aperture. The PEC lateral undercut etch is used to selectively remove the multi-quantum well (MQW) region outside the aperture area, defined by an opaque metal mask. This PEC aperture (PECA) creates an air-gap in the passive area of the device, allowing one to achieve efficient electrical confinement within the aperture, while simultaneously achieving a large index contrast between core of the device (the MQW within the aperture) and the lateral cladding of the device (the air-gap formed by the PEC etch), leading to strong lateral confinement. Scanning electron microscopy and focused ion-beam analysis is used to investigate the precision of the PEC etch technique in defining the aperture. The fabricated single mode PECA VCSEL shows a threshold current density of ∼22 kA/cm{sup 2} (25 mA), with a peak output power of ∼180 μW, at an emission wavelength of 417 nm. The near-field emission profile shows a clearly defined single linearly polarized (LP) mode profile (LP{sub 12,1}), which is in contrast to the filamentary lasing that is often observed in III-nitride VCSELs. 2D mode profile simulations, carried out using COMSOL, give insight into the different mode profiles that one would expect to be displayed in such a device. The experimentally observed single mode operation is proposed to be predominantly a result of poor current spreading in the device. This non-uniform current spreading results in a higher injected current at the periphery of the aperture, which favors LP modes with high intensities near the edge of the aperture.

  20. On the importance of cavity-length and heat dissipation in GaN-based vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Liu, W. J.; Hu, X. L.; Ying, L. Y.; Chen, S. Q.; Zhang, J. Y.; Akiyama, H.; Cai, Z. P.; Zhang, B. P.

    2015-04-01

    Cavity-length dependence of the property of optically pumped GaN-based vertical-cavity surface-emitting lasers (VCSELs) with two dielectric distributed Bragg reflectors was investigated. The cavity lengths were well controlled by employing etching with inductively coupled plasma and chemical mechanical polishing. It was found that the lasing characteristics including threshold, slope efficiency and spontaneous emission coupling factor were substantially improved with reducing the cavity length. In comparison with the device pumped by a 400 nm pulsed laser, the lasing spectrum was featured by a red shift and simultaneous broadening with increasing the pumping energy of a 355 nm pulsed laser. Moreover, the lasing threshold was much higher when pumped by a 355 nm pulsed laser. These were explained by taking into account of the significant heating effect under 355 nm pumping. Our results demonstrate that a short cavity length and good heat-dissipation are essential to GaN-based VCSELs.

  1. Mid-infrared PbTe vertical external cavity surface emitting laser on Si-substrate with above 1 W output power

    Science.gov (United States)

    Rahim, M.; Fill, M.; Felder, F.; Chappuis, D.; Corda, M.; Zogg, H.

    2009-12-01

    Mid-infrared vertical external cavity surface emitting lasers (VECSELs) emitting above 1 W output power in pulsed mode and up to 17 mW in continuous mode at -172 °C were realized. Emission wavelength changes from 5 μm at -172 °C to 3.6 μm at 20 °C heat sink temperature. The active medium is a one wavelength thick PbTe layer grown by molecular beam epitaxy on a Si-substrate. It is followed by a 2.5 pair Pb1-yEuyTe/EuTe epitaxial Bragg mirror. The cavity is completed with an external curved Pb1-yEuyTe/BaF2 mirror. The VECSEL is optically pumped with 1.55 μm wavelength laser and In-soldered to Cu heat sink. No microstructural processing is needed.

  2. Surface photovoltage spectroscopy as a valuable nondestructive characterization technique for GaAs/GaAlAs vertical-cavity surface-emitting laser structures

    CERN Document Server

    Liang, J S; Huang, Y S; Tien, C W; Chang, Y M; Chen, C W; Li, N Y; Tiong, K K; Pollak, F H

    2003-01-01

    We have investigated an 850 nm GaAs/GaAlAs (001) vertical-cavity surface-emitting laser (VCSEL) structure using angle- and temperature-dependent surface photovoltage spectroscopy (SPS). The SPS measurements were performed as functions of angle of incidence (0 deg. <= theta <= 60 deg.) and temperature (25 deg. C <= T <= 215 deg. C) for both the metal-insulator-semiconductor (MIS) and wavelength-modulated MIS configurations. Angle-dependent reflectance (R) measurements have also been performed to illustrate the superior features of the SPS technique. The SPS spectra exhibit both the fundamental conduction to heavy-hole excitonic transition of quantum well and cavity mode (CM) plus a rich interference pattern related to the mirror stacks, whereas in the R spectra only the CM and interference features are clearly visible. The variations of SPS spectra as functions of incident angle and temperature enable exploration of light emission from the quantum well confined in a microcavity with relation to the...

  3. Non-paraxial contributions to the far-field pattern of surface-emitting lasers: a manifestation of the momentum-space wavefunctions of quantum billiards

    International Nuclear Information System (INIS)

    Yu, Y T; Huang, Y J; Chiang, P Y; Lin, Y C; Huang, K F; Chen, Y F

    2011-01-01

    We investigated experimentally non-paraxial contributions to the high-order far-field pattern of large-area vertical-cavity surface-emitting lasers in order to explore by analogy the momentum-space wave distributions of quantum billiards. Our results reveal that non-paraxial contributions significantly influence the morphology of the high-order far-field pattern. A fast reliable method is developed for transforming the experimental far-field patterns to the correct Fourier transform of the corresponding near-field lasing modes. In this way we visualize the momentum-space (p–q) wavefunctions of quantum billiards

  4. A UWOC system based on a 6 m/5.2 Gbps 680 nm vertical-cavity surface-emitting laser

    Science.gov (United States)

    Li, Chung-Yi; Tsai, Wen-Shing

    2018-02-01

    This study proves that an underwater wireless optical communication (UWOC) based on a 6 m/5.2 Gbps 68 nm vertical-cavity surface-emitting laser (VCSEL)-based system is superior to a 405 nm UWOC system. This UWOC application is the first to use a VCSEL at approximately 680 nm. The experiment also proved that a 680 nm VCSEL has the same transmission distance as that of an approximately 405 nm laser diode. The 680 nm VCSEL has a 5.2 Gbps high transmission rate and can transmit up to 6 m. Thus, the setup is the best alternative solution for high-speed UWOC applications.

  5. Low threshold continuous-wave lasing of yellow-green InGaN-QD vertical-cavity surface-emitting lasers.

    Science.gov (United States)

    Weng, Guoen; Mei, Yang; Liu, Jianping; Hofmann, Werner; Ying, Leiying; Zhang, Jiangyong; Bu, Yikun; Li, Zengcheng; Yang, Hui; Zhang, Baoping

    2016-07-11

    Low threshold continuous-wave (CW) lasing of current injected InGaN quantum dot (QD) vertical-cavity surface-emitting lasers (VCSELs) was achieved at room temperature. The VCSEL was fabricated by metal bonding technique on a copper substrate to improve the heat dissipation ability of the device. For the first time, lasing was obtained at yellow-green wavelength of 560.4 nm with a low threshold of 0.61 mA, corresponding to a current density of 0.78 kA/cm2. A high degree of polarization of 94% were measured. Despite the operation in the range of "green gap" of GaN-based devices, single longitudinal mode laser emission was clearly achieved due to the high quality of active region based on InGaN QDs and the excellent thermal design of the VCSELs.

  6. Dynamics of 1.55 μm Wavelength Single-Mode Vertical-Cavity Surface-Emitting Laser Output under External Optical Injection

    Directory of Open Access Journals (Sweden)

    Kyong Hon Kim

    2012-01-01

    Full Text Available We review the temporal dynamics of the laser output spectrum and polarization state of 1.55 μm wavelength single-mode (SM vertical-cavity surface-emitting lasers (VCSELs induced by external optical beam injection. Injection of an external continuous-wave laser beam to a gain-switched SM VCSEL near the resonance wavelength corresponding to its main polarization-mode output was critical for improvement of its laser pulse generation characteristics, such as pulse timing-jitter reduction, linewidth narrowing, pulse amplitude enhancement, and pulse width shortening. Pulse injection of pulse width shorter than the cavity photon lifetime into the SM VCSEL in the orthogonal polarization direction with respect to its main polarization mode caused temporal delay of the polarization recovery after polarization switching (PS, and its delay was found to be the minimum at an optimized bias current. Polarization-mode bistability was observed even in the laser output of an SM VCSEL of a standard circularly cylindrical shape and used for all-optical flip-flop operations with set and reset injection pulses of very low pulse energy of order of the 3.5~4.5 fJ.

  7. Time-resolved spectral characterization of ring cavity surface emitting and ridge-type distributed feedback quantum cascade lasers by step-scan FT-IR spectroscopy.

    Science.gov (United States)

    Brandstetter, Markus; Genner, Andreas; Schwarzer, Clemens; Mujagic, Elvis; Strasser, Gottfried; Lendl, Bernhard

    2014-02-10

    We present the time-resolved comparison of pulsed 2nd order ring cavity surface emitting (RCSE) quantum cascade lasers (QCLs) and pulsed 1st order ridge-type distributed feedback (DFB) QCLs using a step-scan Fourier transform infrared (FT-IR) spectrometer. Laser devices were part of QCL arrays and fabricated from the same laser material. Required grating periods were adjusted to account for the grating order. The step-scan technique provided a spectral resolution of 0.1 cm(-1) and a time resolution of 2 ns. As a result, it was possible to gain information about the tuning behavior and potential mode-hops of the investigated lasers. Different cavity-lengths were compared, including 0.9 mm and 3.2 mm long ridge-type and 0.97 mm (circumference) ring-type cavities. RCSE QCLs were found to have improved emission properties in terms of line-stability, tuning rate and maximum emission time compared to ridge-type lasers.

  8. Investigation of single-mode vertical-cavity surface-emitting lasers with graphene-bubble dielectric DBR

    Science.gov (United States)

    Guan, Baolu; Li, Pengtao; Arafin, Shamsul; Alaskar, Yazeed; Wang, Kang L.

    2018-02-01

    An inter-cavty contact single mode 850 nm VCSEL was fabricated with a graphene assisted self-assembly curved dielectric bubble Bragg mirror for the first time. Taking the advantage of graphene's uniform low surface energy, the low cost dielectric bubble DBR (Si3N4/SiO2) was deposited on top of the graphene/half-VCSEL structure via van der Waals Force (vdWF) without using any additional spacing elements and sacrificial layer release-etch process. The continuous-wave operating VCSELs with an aperture diameter of 7 μm exhibit single-mode output power of more than 1 mW with a slope efficiency of 0.2 W/A. The sidemode suppression ratios are >40 dB. This novel modification into the lasers can also be applied to a variety of other optoelectronic devices, such as resonance photodetecter and super narrow linewidth VCSEL.

  9. Characterization of 2.3 μm GaInAsSb-based vertical-cavity surface-emitting laser structures using photo-modulated reflectance

    Energy Technology Data Exchange (ETDEWEB)

    Chai, G. M. T. [Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Johor Bahru 81310 (Malaysia); Hosea, T. J. C., E-mail: j.hosea@surrey.ac.uk [Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Johor Bahru 81310 (Malaysia); Advanced Technology Institute and Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Fox, N. E.; Hild, K.; Ikyo, A. B.; Marko, I. P.; Sweeney, S. J. [Advanced Technology Institute and Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Bachmann, A.; Arafin, S.; Amann, M.-C. [Walter Schottky Institut, Technische Universität Munchen, Am Coulombwall 4, D-85748 Garching (Germany)

    2014-01-07

    We report angle dependent and temperature dependent (9 K–300 K) photo-modulated reflectance (PR) studies on vertical-cavity surface-emitting laser (VCSEL) structures, designed for 2.3 μm mid-infrared gas sensing applications. Changing the temperature allows us to tune the energies of the quantum well (QW) transitions relative to the VCSEL cavity mode (CM) energy. These studies show that this VCSEL structure has a QW-CM offset of 21 meV at room temperature. Consequently the QW ground-state transition comes into resonance with the CM at 220 ± 2 K. The results from these PR studies are closely compared with those obtained in a separate study of actual operating devices and show how the PR technique may be useful for device optimisation without the necessity of having first to process the wafers into working devices.

  10. Compact electro-absorption modulator integrated with vertical-cavity surface-emitting laser for highly efficient millimeter-wave modulation

    International Nuclear Information System (INIS)

    Dalir, Hamed; Ahmed, Moustafa; Bakry, Ahmed; Koyama, Fumio

    2014-01-01

    We demonstrate a compact electro-absorption slow-light modulator laterally-integrated with an 850 nm vertical-cavity surface-emitting laser (VCSEL), which enables highly efficient millimeter-wave modulation. We found a strong leaky travelling wave in the lateral direction between the two cavities via widening the waveguide width with a taper shape. The small signal response of the fabricated device shows a large enhancement of over 55 dB in the modulation amplitude at frequencies beyond 35 GHz; thanks to the photon-photon resonance. A large group index of over 150 in a Bragg reflector waveguide enables the resonance at millimeter wave frequencies for 25 μm long compact modulator. Based on the modeling, we expect a resonant modulation at a higher frequency of 70 GHz. The resonant modulation in a compact slow-light modulator plays a significant key role for high efficient narrow-band modulation in the millimeter wave range far beyond the intrinsic modulation bandwidth of VCSELs.

  11. Blue laser diode (LD) and light emitting diode (LED) applications

    International Nuclear Information System (INIS)

    Bergh, Arpad A.

    2004-01-01

    The family of blue LEDs, edge emitting and surface emitting lasers, enable a number of applications. Blue lasers are used in digital applications such as optical storage in high density DVDs. The resolution of the spot size and hence the storage density is diffraction limited and is inversely proportional to the square of the wavelength of the laser. Other applications include printing, optical scanners, and high-resolution photo-lithography. As light emitters, blue LEDs are used for signaling and in direct view large area emissive displays. They are also making inroads into signage and LCD back-lighting, mobile platforms, and decorative accent lighting in curtains, furniture, etc. Blue LEDs produce white light either with phosphor wavelength converters or in combination with red and green LEDs. The full potential of LED light sources will require three devices to enable complete control over color and intensity. Sensing and medical/bio applications have a major impact on home security, on monitoring the environment, and on health care. New emerging diagnostic and therapeutic applications will improve the quality and reduce the cost of health care. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Laser-surface interactions

    CERN Document Server

    Ganeev, Rashid A

    2014-01-01

    This book is about the interaction of laser radiation with various surfaces at variable parameters of radiation. As a basic principle of classification we chose the energetic or intensity level of interaction of laser radiation with the surfaces. These two characteristics of laser radiation are the most important parameters defining entire spectrum of the processes occurring on the surfaces during interaction with electromagnetic waves. This is a first book containing a whole spectrum of the laser-surface interactions distinguished by the ranges of used laser intensity. It combines the surface response starting from extremely weak laser intensities (~1 W cm-2) up to the relativistic intensities (~1020 W cm-2 and higher). The book provides the basic information about lasers and acquaints the reader with both common applications of laser-surface interactions (laser-related printers, scanners, barcode readers, discs, material processing, military, holography, medicine, etc) and unusual uses of the processes on t...

  13. INTERACTION OF LASER RADIATION WITH MATTER: Influence of a target on operation of a pulsed CO2 laser emitting microsecond pulses

    Science.gov (United States)

    Baranov, V. Yu; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.

    1987-12-01

    The profile of pulses emitted by a TEA CO2 laser with an unstable resonator changed as a result of interaction of laser radiation with the surface of a metal in the presence of a breakdown plasma. This influence of a target on laser operation and its possible applications in laser processing of materials are analyzed.

  14. Fabrication Processes for Surface-Emitting via External 45-DEGREE Reflectors, High-Power via Arrayed Ridge - Single-Mode Phase-Locked Aluminum Gallium Arsenide/gallium Arsenide Semiconductor Laser Sources.

    Science.gov (United States)

    Porkolab, Gyorgy Arpad

    The fabrication of monolithically integrated configurations of semiconductor lasers incorporating multiple functions is still an open issue today in engineering. A useful set of functions to integrate are: surface-emitting, high -power, phase-locked, single-mode, and collimated laser beam output. In this work new materials and advanced fabrication processes are developed for integrating the first four of the five functions listed. The interest in semiconductor lasers is due to their greater than 90% internal quantum efficiency in converting current-flux to photon-flux, their small size and weight, and their wavelength range from 400 to 1,550 nm. Multitudes of applications are possible for semiconductor laser sources ranging from the low-volume market of satellite-based communications systems to the high-volume market of image display screens. Semimetallic amorphous carbon (SMAC) thin film is introduced as an etch mask for chemically assisted ion beam etching (CAIBE) resulting in smooth etched facets in AlGaAs/GaAs at normal- and 45-degrees- incidence angles. A self-aligned etch technique is introduced using 4 separate photoresist selector-masks on top of a fixed SMAC master -mask on top of the AlGaAs/GaAs substrate to perform 4 separate CAIBE etches at 3 different angles and to 3 different depths to create self-aligned 3-dimensional microstructures of 1.3-μm deep ridge waveguides (RWG), 6-μm deep laser facets, and 11- μm long back-to-back 45-degree reflectors arranged in 3 by 100 arrays. Trenches on topside and underside of laser facets are introduced to deflect current away from laser facets. Silicon-rich nitro-oxide thin film is introduced as triple-use encapsulation to provide chemical passivation of AlGaAs/GaAs, optical anti-reflection coating by being refractive-index matched to AlGaAs/GaAs, and electrical insulation. A pincer-action sample-holder for CAIBE is introduced allowing samples to heat up by ion beam heating. Various surface preparations

  15. Inkjet-printed vertically emitting solid-state organic lasers

    Energy Technology Data Exchange (ETDEWEB)

    Mhibik, Oussama; Chénais, Sébastien; Forget, Sébastien [Laboratoire de Physique des Lasers - Equipe Photonique Organique, Université PARIS 13 et CNRS (UMR 7538), 99, Avenue Jean-Baptiste Clément, 93430 Villetaneuse (France); Defranoux, Christophe [SEMILAB Semiconductor Physics Laboratory Co., Ltd., Prielle Kornelia u.2., H-1117 Budapest (Hungary); Sanaur, Sébastien, E-mail: sanaur@emse.fr [Département of Bioelectronics, Centre Microélectronique de Provence, Ecole Nationale Supérieure des Mines de Saint Etienne, 880, route de Mimet, 13541 Gardanne (France)

    2016-05-07

    In this paper, we show that Inkjet Printing can be successfully applied to external-cavity vertically emitting thin-film organic lasers and can be used to generate a diffraction-limited output beam with an output energy as high as 33.6 μJ with a slope efficiency S of 34%. Laser emission shows to be continuously tunable from 570 to 670 nm using an intracavity polymer-based Fabry-Perot etalon. High-optical quality films with several μm thicknesses are realized, thanks to ink-jet printing. We introduce a new optical material where EMD6415 commercial ink constitutes the optical host matrix and exhibits a refractive index of 1.5 and an absorption coefficient of 0.66 cm{sup −1} at 550–680 nm. Standard laser dyes like Pyrromethene 597 and Rhodamine 640 are incorporated in solution to the EMD6415 ink. Such large size “printed pixels” of 50 mm{sup 2} present uniform and flat surfaces, with roughness measured as low as 1.5 nm in different locations of a 50 μm × 50 μm AFM scan. Finally, as the gain capsules fabricated by Inkjet printing are simple and do not incorporate any tuning or cavity element, they are simple to make, have a negligible fabrication cost, and can be used as fully disposable items. This work opens the way towards the fabrication of really low-cost tunable visible lasers with an affordable technology that has the potential to be widely disseminated.

  16. Considerations on the determining factors of the angular distribution of emitted particles in laser ablation

    International Nuclear Information System (INIS)

    Konomi, I.; Motohiro, T.; Kobayashi, T.; Asaoka, T.

    2010-01-01

    Simulations of particles which are emitted in laser ablation have been performed by the method of Direct Simulation Monte Carlo to investigate the deposition profiles of the emitted particles. The influences of the temperature, pressure and stream velocity of the initial evaporated layer formed during laser ablation process on the profile of the deposited film have been examined. It is found that the temperature gives a minor influence on the deposition profile, whereas the stream velocity and the pressure of the initial evaporated layer have a greater impact on the deposition profile. The energy in the direction of surface normal (E perpendicular ) and that in the parallel direction of the surface (E || ) are shown to increase and decrease, respectively after the laser irradiation due to collisions between the emitted particles, and this trend is magnified as the pressure increases. As a consequence, the stream velocity in the direction of surface normal increases with the increase in the pressure. A mechanism of the phenomenon that a metal with a lower sublimation energy shows a broader angular distribution of emitted particles is presented. It is suggested that low density of evaporated layer of a metal with a low sublimation energy at its melting point decreases the number of collisions in the layer, leading to the low stream velocity in the direction of surface normal, which results in the broader deposition profile of the emitted particles.

  17. Systematic characterization of a 1550 nm microelectromechanical (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) with 7.92 THz tuning range for terahertz photomixing systems

    Science.gov (United States)

    Haidar, M. T.; Preu, S.; Cesar, J.; Paul, S.; Hajo, A. S.; Neumeyr, C.; Maune, H.; Küppers, F.

    2018-01-01

    Continuous-wave (CW) terahertz (THz) photomixing requires compact, widely tunable, mode-hop-free driving lasers. We present a single-mode microelectromechanical system (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) featuring an electrothermal tuning range of 64 nm (7.92 THz) that exceeds the tuning range of commercially available distributed-feedback laser (DFB) diodes (˜4.8 nm) by a factor of about 13. We first review the underlying theory and perform a systematic characterization of the MEMS-VCSEL, with particular focus on the parameters relevant for THz photomixing. These parameters include mode-hop-free CW tuning with a side-mode-suppression-ratio >50 dB, a linewidth as narrow as 46.1 MHz, and wavelength and polarization stability. We conclude with a demonstration of a CW THz photomixing setup by subjecting the MEMS-VCSEL to optical beating with a DFB diode driving commercial photomixers. The achievable THz bandwidth is limited only by the employed photomixers. Once improved photomixers become available, electrothermally actuated MEMS-VCSELs should allow for a tuning range covering almost the whole THz domain with a single system.

  18. Investigation of cavity mode and excitonic transition in an InGaAs/GaAs/AlGaAs vertical-cavity surface emitting laser structure by variable-temperature micro-photoluminescence, reflectance and photomodulated reflectance

    International Nuclear Information System (INIS)

    Yu, J L; Chen, Y H; Jiang, C Y; Zhang, H Y

    2012-01-01

    Variable-temperature micro-photoluminescence (μ-PL), reflectance (R) and photomodulated reflectance (PR) have been used to study an InGaAs/GaAs/AlGaAs vertical-cavity surface emitting laser (VCSEL) structure. μ-PL and R spectra have been recorded at different temperatures between 80 K and 300 K By comparing μ-PL with R spectra, both the excitonic transition and cavity mode are clearly identified. The Variable-temperature μ-PL and PR results of the etched sample with the top distributed Bragg reflectors (DBR) being removed further confirmed our identification. Our results demonstrate that variable-temperature μ-PL is a powerful noninvasive tool to measure accurate the quantum well transition and the cavity mode alignment.

  19. Swept-source optical coherence tomography powered by a 1.3-μm vertical cavity surface emitting laser enables 2.3-mm-deep brain imaging in mice in vivo

    Science.gov (United States)

    Choi, Woo June; Wang, Ruikang K.

    2015-10-01

    We report noninvasive, in vivo optical imaging deep within a mouse brain by swept-source optical coherence tomography (SS-OCT), enabled by a 1.3-μm vertical cavity surface emitting laser (VCSEL). VCSEL SS-OCT offers a constant signal sensitivity of 105 dB throughout an entire depth of 4.25 mm in air, ensuring an extended usable imaging depth range of more than 2 mm in turbid biological tissue. Using this approach, we show deep brain imaging in mice with an open-skull cranial window preparation, revealing intact mouse brain anatomy from the superficial cerebral cortex to the deep hippocampus. VCSEL SS-OCT would be applicable to small animal studies for the investigation of deep tissue compartments in living brains where diseases such as dementia and tumor can take their toll.

  20. Organic light emitting diode with surface modification layer

    Science.gov (United States)

    Basil, John D.; Bhandari, Abhinav; Buhay, Harry; Arbab, Mehran; Marietti, Gary J.

    2017-09-12

    An organic light emitting diode (10) includes a substrate (12) having a first surface (14) and a second surface (16), a first electrode (32), and a second electrode (38). An emissive layer (36) is located between the first electrode (32) and the second electrode (38). The organic light emitting diode (10) further includes a surface modification layer (18). The surface modification layer (18) includes a non-planar surface (30, 52).

  1. Broad tunable photonic microwave generation based on period-one dynamics of optical injection vertical-cavity surface-emitting lasers.

    Science.gov (United States)

    Ji, Songkun; Hong, Yanhua; Spencer, Paul S; Benedikt, Johannes; Davies, Iwan

    2017-08-21

    Photonic microwave generation based on period-one dynamics of an optically injected VCSEL has been study experimentally. The results have shown that the frequency of the generated microwave signal can be broadly tunable through the adjustment of the injection power and the frequency detuning. Strong optical injection power and higher frequency detuning are favorable for obtaining a high frequency microwave signal. These results are similar to those found in systems based on distributed feedback lasers and quantum dot lasers. The variation of the microwave power at the fundamental frequency and the second-harmonic distortion have also been characterized.

  2. Laterally injected light-emitting diode and laser diode

    Science.gov (United States)

    Miller, Mary A.; Crawford, Mary H.; Allerman, Andrew A.

    2015-06-16

    A p-type superlattice is used to laterally inject holes into an III-nitride multiple quantum well active layer, enabling efficient light extraction from the active area. Laterally-injected light-emitting diodes and laser diodes can enable brighter, more efficient devices that impact a wide range of wavelengths and applications. For UV wavelengths, applications include fluorescence-based biological sensing, epoxy curing, and water purification. For visible devices, applications include solid state lighting and projection systems.

  3. Continuous wave operation of high power GaN-based blue vertical-cavity surface-emitting lasers using epitaxial lateral overgrowth

    Science.gov (United States)

    Hamaguchi, Tatsushi; Fuutagawa, Noriyuki; Izumi, Shouichiro; Murayama, Masahiro; Narui, Hironobu

    2016-02-01

    We have succeeded in achieving continuous-wave operation of gallium nitride (GaN) based vertical-cavity surfaceemitting lasers (VCSELs), which was fabricated by epitaxial lateral overgrowth (ELO) using dielectric distributed Bragg reflectors(DBRs) as masks for selective growth. The device exhibited CW operation at a wavelength of 453.9nm. The maximum output power was 1.1 mW, which is the highest value reported in previously published articles. The ELO process used for this study represents a breakthrough for challenges which were indicated by other former reports for GaN-based VCSELs and is suitable for mass production.

  4. (In,Ga,Al)P-GaP laser diodes grown on high-index GaAs surfaces emitting in the green, yellow and bright red spectral range

    Science.gov (United States)

    Ledentsov, N. N.; Shchukin, V. A.; Shernyakov, Yu M.; Kulagina, M. M.; Payusov, A. S.; Gordeev, N. Yu; Maximov, M. V.; Cherkashin, N. A.

    2017-02-01

    We report on low threshold current density (<400 A cm-2) injection lasing in (Al x Ga1-x )0.5In0.5P-GaAs-based diodes down to the green spectral range (<570 nm). The epitaxial structures are grown on high-index (611)A and (211)A GaAs substrates by metal-organic vapor phase epitaxy and contain tensile-strained GaP-enriched insertions aimed at reflection of the injected nonequilibrium electrons preventing their escape from the active region. Extended waveguide concept results in a vertical beam divergence with a full width at half maximum of 15° for (611)A substrates. The lasing at the wavelength of 569 nm is realized at 85 K. In an orange-red laser diode structure low threshold current density (190 A cm-2) in the orange spectral range (598 nm) is realized at 85 K. The latter devices demonstrated room temperature lasing at 628 nm at ˜2 kA cm-2 and a total power above 3 W. The red laser diodes grown on (211)A substrates demonstrated a far field characteristic for vertically multimode lasing indicating a lower optical confinement factor for the fundamental mode as compared to the devices grown on (611)A. However, as expected from previous research, the temperature stability of the threshold current and the wavelength stability were significantly higher for (211)A-grown structures.

  5. Single-mode 850-nm vertical-cavity surface-emitting lasers with Zn-diffusion and oxide-relief apertures for > 50 Gbit/sec OOK and 4-PAM transmission

    Science.gov (United States)

    Shi, Jin-Wei; Wei, Chia-Chien; Chen, Jyehong; Ledentsov, N. N.; Yang, Ying-Jay

    2017-02-01

    Vertical-cavity surface-emitting lasers (VCSELs) has become the most important light source in the booming market of short-reach (targeted at 56 Gbit/sec data rate per channel (CEI-56G) with the total data rate up to 400 Gbit/sec. However, the serious modal dispersion of multi-mode fiber (MMF), limited speed of VCSEL, and its high resistance (> 150 Ω) seriously limits the >50 Gbit/sec linking distance (50 Gbit/sec transmission due to that it can save one-half of the required bandwidth. Nevertheless, a 4.7 dB optical power penalty and the linearity of transmitter would become issues in the 4-PAM linking performance. Besides, in the modern OI system, the optics transreceiver module must be packaged as close as possible with the integrated circuits (ICs). The heat generated from ICs will become an issue in speed of VSCEL. Here, we review our recent work about 850 nm VCSEL, which has unique Zn-diffusion/oxide-relief apertures and special p- doping active layer with strong wavelength detuning to further enhance its modulation speed and high-temperature (85°C) performances. Single-mode (SM) devices with high-speed ( 26 GHz), reasonable resistance ( 70 Ω) and moderate output power ( 1.5 mW) can be achieved. Error-free 54 Gbit/sec OOK transmission through 1km MMF has been realized by using such SM device with signal processing techniques. Besides, the volterra nonlinear equalizer has been applied in our 4-PAM 64 Gbit/sec transmission through 2-km OM4 MMF, which significantly enhance the linearity of device and outperforms fed forward equalization (FFE) technique. Record high bit-rate distance product of 128.km is confirmed for optical-interconnect applications.

  6. Surface processing by high power excimer laser

    International Nuclear Information System (INIS)

    Stehle, M.

    1995-01-01

    Surface processing with lasers is a promising field of research and applications because lasers bring substantial advantages : laser beams work at distance, laser treatments are clean in respect of environment consideration and they offer innovative capabilities for surface treatment which cannot be reached by other way. Excimer lasers are pulsed, gaseous lasers which emit in UV spectral range - the most common are XeCl (308 nm), KrF (248 nm), ArF (193 nm). From 1980 up to 1994, many of them have been used for research, medical and industrial applications such as spectroscopy, PRK (photo-refractive keratotomy) and micro-machining. In the last six years, from 1987 up to 1993, efforts have been done in order to jump from 100 W average power up to 1 kW for XeCl laser at λ = 308 nm. It was the aim of AMMTRA project in Japan as EU205 and EU213 Eureka projects in Europe. In this framework, SOPRA developed VEL (Very large Excimer Laser). In 1992, 1 kW (10 J x 100 Hz) millstone has been reached for the first time, this technology is based on X-Ray preionization and large laser medium (5 liters). Surface treatments based on this laser source are the main purpose of VEL Lasers. Some of them are given for instance : a) Turbine blades made with metallic substrate and ceramic coatings on the top, are glazed in order to increase corrosion resistance of ceramic and metal sandwich. b) Selective ablation of organic coatings deposited on fragile composite material is investigated in Aerospace industry. c) Chock hardening of bulk metallic materials or alloys are investigated for automotive industry in order to increase wear resistance. d) Ablation of thin surface oxides of polluted steels are under investigation in nuclear industry for decontamination. (J.P.N.)

  7. Laser surface cleaning

    International Nuclear Information System (INIS)

    Freiwald, J.G.; Freiwald, D.A.

    1994-01-01

    The objective of this work is a laboratory demonstration that red-lead primer and two-part epoxy paints can be stripped from concrete and metal surfaces using surface cleaning systems based on pulsed-repetition CO 2 lasers. The three goals are to: (1) demonstrate coatings removal, including surface pore cleaning; (2) demonstrate that there is negligible release of ablated contaminants to the environment; and (3) demonstrate that the process will generate negligible amounts of additional waste compared to competing technologies. Phase 1 involved site visits to RMI and Fernald to assess the cleaning issues for buildings and parts. In addition, Phase 1 included detailed designs of a more powerful system for industrial cleaning rates, including laser, articulating optics, ablated-material capture suction nozzle attached to a horizontal raster scanner for floor cleaning, and filtration system. Some concept development is also being done for using robots, and for parts cleaning. In Phase 2 a transportable 6 kW system will be built and tested, with a horizontal surface scanner for cleaning paint from floors. The laboratory tests will again be instrumented. Some concept development will continue for using robots, and for parts cleaning. This report describes Phase 1 results

  8. Electrically driven surface plasmon light-emitting diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke

    We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  9. Erbium–ytterbium fibre laser emitting more than 13 W of power in ...

    Indian Academy of Sciences (India)

    2014-01-05

    ytterbium fibre laser emitting more than 13W of ... Proceedings of the International Workshop/Conference on Computational Condensed Matter Physics and Materials Science (IWCCMP-2015). Posted on November 27, 2015.

  10. High power, low divergent, substrate emitting quantum cascade ring laser in continuous wave operation

    Directory of Open Access Journals (Sweden)

    D. H. Wu

    2017-03-01

    Full Text Available We demonstrate a surface grating coupled substrate emitting quantum cascade ring laser with high power room temperature continuous wave operation at 4.64 μm. A second order surface metal/semiconductor distributed-feedback grating is used for in-plane feedback and vertical out-coupling. A device with 400 μm radius ring cavity exhibits an output power of 202 mW in room temperature continuous wave operation. Single mode operation with a side mode suppression ratio of 25 dB is obtained along with a good linear tuning with temperature. The far field measurement exhibits a low divergent concentric ring beam pattern with a lobe separation of ∼0.34°, which indicates that the device operates in fundamental mode (n = 1.

  11. Laser beam shaping optical system design methods and their application in edge-emitting semiconductor laser-based LIDAR systems

    Science.gov (United States)

    Serkan, Mert

    LIDAR (Light Detection And Ranging) systems are employed for numerous applications such as remote sensing, military applications, optical data storage, display technology, and material processing. Furthermore, they are superior to other active remote sensing tools such as RADAR systems, considering their higher accuracy and more precise resolution due to their much shorter wavelengths and narrower beamwidth. Several types of lasers can be utilized as the radiation source of several LIDAR systems. Semiconductor laser-based LIDAR systems have several advantages such as low cost, compactness, broad range of wavelengths, and high PRFs (Pulse Repetition Frequency). However, semiconductor lasers have different origins and angles of divergence in the two transverse directions, resulting in the inherent astigmatism and elliptical beam shape. Specifically, elliptical beam shape is not desirable for several laser-based applications including LIDAR systems specifically designed to operate in the far-field region. In this dissertation, two mirror-based and two lens-based beam shapers are designed to circularize, collimate, and expand an edge-emitting semiconductor laser beam to a desired beam diameter for possible application in LIDAR systems. Additionally, most laser beams including semiconductor laser beams have Gaussian irradiance distribution. For applications that require uniform illumination of an extended target area, Gaussian irradiance distribution is undesirable. Therefore, a specific beam shaper is designed to transform the irradiance distribution from Gaussian to uniform in addition to circularizing, collimating, and expanding the semiconductor laser beam. For the design of beam shapers, aperture sizes of the surfaces are preset for desired power transmission and allowed diffraction level, surface parameters of the optical components and the distances between these surfaces are determined. Design equations specific to these beam shaping optical systems are

  12. Non-radially polarized THz pulse emitted from femtosecond laser filament in air.

    Science.gov (United States)

    Zhang, Y; Chen, Y; Marceau, C; Liu, W; Sun, Z-D; Xu, S; Théberge, F; Châteauneuf, M; Dubois, J; Chin, S L

    2008-09-29

    Femtosecond laser filament could produce THz wave in forward direction. In our experiment, THz pulse emitted from a femtosecond laser filament has been investigated. It was found that the polarization of the studied THz pulse mainly appears as elliptical. This observation supplements the previous conclusion obtained by C. D'Amico et al. that THz wave emitted by a filament is radially polarized. The mechanism of generating elliptically polarized THz wave has been interpreted by either four-wave optical rectification or second order optical rectification inside the filament zone where centro-symmetry of the air is broken by the femtosecond laser pulse.

  13. A method enabling height-control of chips for edge-emitting laser stacking

    Science.gov (United States)

    Thanh Tung, Bui; Ma, Laina; Amano, Takeru; Kikuchi, Katsuya; Mori, Masahiko; Aoyagi, Masahiro

    2015-04-01

    In this paper we present a stacking method that enables the mounting of edge-emitting laser (EEL) devices at compulsory positions for feeding a coupling waveguide at a low temperature, i.e., 110 °C. Bonding laser chips are integrated to an interposer with embedded waveguides using an electrically conductive adhesive (ECA), i.e., silver-filled epoxy resin that relied on the surface tension phenomenon. A simple dispensing technique based on the capillary effect was used to generate adhesive droplets for bonding purposes. The ability to control the bonding height from 3 to 25 µm was demonstrated. While the post-bond in-plane offsets of the bonding EEL chip are determined by the accuracy of the bonder (i.e., within 2 µm range), the bonding height can be engineered, with a deviation within 1 µm, by balancing the external bonding forces with the surface tension of a certain adhesive volume. The reliability of the bond, i.e., bond strength of 106 gf, and heat dissipation function of the ECA, were also validated. The results obtained in this work imply that the use of this low-temperature, height-controllable approach for the stacking of EEL continues to look highly promising.

  14. Laser and Optical Properties of Green-Emitting ZnCdSe Quantum Dot Based Heterostructures

    Science.gov (United States)

    Vainilovich, Aliaksei G.; Lutsenko, E. V.; Yablonskii, G. P.; Sedova, I. V.; Sorokin, S. V.; Gronin, S. V.; Ivanov, S. V.; Kop'ev, P. S.

    Green-emitting laser diodes are in great demand for mobile projection media (pico-projector), navigation, underwater communication but they are still absent on the market. InGaN/GaN-based quantum well structures are approaching green spectral region by use of polar, semipolar as well as free-standing GaN substrates. However such heterostructures suffer from high laser thresholds with increase of indium content. A promising alternative way is the use of highly efficient green-emitting undoped ZnCdSe based quantum dot (QD) laser heterostructures optically pumped by blue InGaN laser diodes. Operation of blue-green laser converter based on MBE grown heterostructure with two ZnCdSe QD layers was shown for the first time in [1].

  15. Light-emitting diode versus laser irradiation phototherapy with lutetium texaphyrin (PCI-0123)

    Science.gov (United States)

    Woodburn, Kathryn W.; Young, Stuart W.; Qing, Fan; Miles, Dale R.; Thiemann, Patricia A.

    1997-05-01

    Lutetium texaphyrin (PCI-0123) is presently in clinical trials for the treatment of neoplasms. An argon-pumped dye laser has mostly been used to generate light for PCI-0123 photoactivation. However, lasers are expensive and produce a limited area of illumination, so the efficacy of light emitting diodes (LEDs) was investigated. An LED array was developed so that the spectral emission matched the far red absorption spectrum of PCI-0123. A preclinical PDT efficacy study comparing the laser and the LED was undertaken using EMT6-bearing animals. The LED and laser light sources were statistically comparable in eradicating the murine mammary sarcomas using PCI-0123 as the photosensitizer.

  16. Light-emitting diode and laser fluorescence-based devices in detecting occlusal caries

    Science.gov (United States)

    Rodrigues, Jonas A.; Hug, Isabel; Neuhaus, Klaus W.; Lussi, Adrian

    2011-10-01

    The aim of this study was to assess the performance of two light-emitting diode (LED)- and two laser fluorescence-based devices in detecting occlusal caries in vitro. Ninety-seven permanent molars were assessed twice by two examiners using two LED- (Midwest Caries - MID and VistaProof - VP) and two laser fluorescence-based (DIAGNOdent 2095 - LF and DIAGNOdent pen 2190 - LFpen) devices. After measuring, the teeth were histologically prepared and classified according to lesion extension. At D1 the specificities were 0.76 (LF and LFpen), 0.94 (MID), and 0.70 (VP); the sensitivities were 0.70 (LF), 0.62 (LFpen), 0.31 (MID), and 0.75 (VP). At D3 threshold the specificities were 0.88 (LF), 0.87 (LFpen), 0.90 (MID), and 0.70 (VP); the sensitivities were 0.63 (LF and LFpen), 0.70 (MID), and 0.96 (VP). Spearman's rank correlations with histology were 0.56 (LF), 0.51 (LFpen), 0.55 (MID), and 0.58 (VP). Inter- and intraexaminer ICC values were high and varied from 0.83 to 0.90. Both LF devices seemed to be useful auxiliary tools to the conventional methods, presenting good reproducibility and better accuracy at D3 threshold. MID was not able to differentiate sound surfaces from enamel caries and VP still needs improvement on the cut-off limits for its use.

  17. Quantum-cascade laser photoacoustic detection of methane emitted from natural gas powered engines

    Science.gov (United States)

    Rocha, M. V.; Sthel, M. S.; Silva, M. G.; Paiva, L. B.; Pinheiro, F. W.; Miklòs, A.; Vargas, H.

    2012-03-01

    In this work we present a laser photoacoustic arrangement for the detection of the important greenhouse gas methane. A quantum-cascade laser and a differential photoacoustic cell were employed. A detection limit of 45 ppbv in nitrogen was achieved as well as a great selectivity. The same methodology was also tested in the detection of methane issued from natural gas powered vehicles (VNG) in Brazil, which demonstrates the excellent potential of this arrangement for greenhouse gas detection emitted from real sources.

  18. Direct periodic patterning of GaN-based light-emitting diodes by three-beam interference laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeomoh; Ji, Mi-Hee; Detchprohm, Theeradetch [Center for Compound Semiconductors and School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Dr. NW, Atlanta, Georgia 30332-0250 (United States); Yuan, Dajun; Guo, Rui [Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States); Liu, Jianping [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215125 (China); Asadirad, Mojtaba [Materials Engineering Program, University of Houston, Houston, Texas 77204-4005 (United States); Kwon, Min-Ki [Department of Photonic Engineering, Chosun University, Seosuk-dong, Gwangju 501-759 (Korea, Republic of); Dupuis, Russell D. [Center for Compound Semiconductors and School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Dr. NW, Atlanta, Georgia 30332-0250 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 (United States); Das, Suman [Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 (United States); Ryou, Jae-Hyun, E-mail: jryou@uh.edu [Materials Engineering Program, University of Houston, Houston, Texas 77204-4005 (United States); Department of Mechanical Engineering and Texas Center for Superconductivity at the University of Houston (TcSUH), University of Houston, Houston, Texas 77204-4006 (United States)

    2014-04-07

    We report on the direct patterning of two-dimensional periodic structures in GaN-based light-emitting diodes (LEDs) through laser interference ablation for the fast and reliable fabrication of periodic micro- and nano-structures aimed at enhancing light output. Holes arranged in a two-dimensional hexagonal lattice array having an opening size of 500 nm, depth of 50 nm, and a periodicity of 1 μm were directly formed by three-beam laser interference without photolithography or electron-beam lithography processes. The laser-patterned LEDs exhibit an enhancement in light output power of 20% compared to conventional LEDs having a flat top surface without degradation of electrical and optical properties of the top p-GaN layer and the active region, respectively.

  19. A simulation of laser energy absorption by nanowired surface

    International Nuclear Information System (INIS)

    Vasconcelos, Miguel F.S.; Ramos, Alexandre F.

    2017-01-01

    Despite recent advances on research about laser inertial fusion energy, to increase the portion of energy absorbed by the target's surface from lasers remains as an important challenge. The plasma formed during the initial instants of laser arrival shields the target and prevents the absorption of laser energy by the deeper layers of the material. One strategy to circumvent that effect is the construction of targets whose surfaces are populated with nanowires. The nanowired surfaces have increased absorption of laser energy and constitutes a promising pathway for enhancing laser-matter coupling. In our work we present the results of simulations aiming to investigate how target's geometrical properties might contribute for maximizing laser energy absorption by material. Simulations have been carried out using the software FLASH, a multi-physics platform developed by researchers from the University of Chicago, written in FORTRAN 90 and Python. Different tools for generating target's geometry and analysis of results were developed using Python. Our results show that a nanowired surfaces has an increased energy absorption when compared with non wired surface. The software for visualization developed in this work also allowed an analysis of the spatial dynamics of the target's temperature, electron density, ionization levels and temperature of the radiation emitted by it. (author)

  20. Laser method of acoustical emission control from vibrating surfaces

    Science.gov (United States)

    Motyka, Zbigniew

    2013-01-01

    For limitation of the noise in environment, the necessity occurs of determining and location of sources of sounds emitted from surfaces of many machines and devices, assuring in effect the possibility of suitable constructional changes implementation, targeted at decreasing of their nuisance. In the paper, the results of tests and calculations are presented for plane surface sources emitting acoustic waves. The tests were realized with the use of scanning laser vibrometer which enabled remote registration and the spectral analysis of the surfaces vibrations. The known hybrid digital method developed for determination of sound wave emission from such surfaces divided into small finite elements was slightly modified by distinguishing the phase correlations between such vibrating elements. The final method being developed may find use in wide range of applications for different forms of vibrations of plane surfaces.

  1. Ion Production by Laser Impact on a Silver Surface

    DEFF Research Database (Denmark)

    Christensen, Bo Toftmann; Schou, Jørgen

    Even at moderate fluence (0.6 -2.4 J/cm2) laser impact on metals in the UV regime results in a significant number of ions emitted from the surface. Even at this low fluence the particles ejected from a surface interact with each other in a so-called laser ablation plume. The ablated particles...... are largely neutrals at low fluence, but the fraction of ions increases strongly with fluence. We have irradiated silver in a vacuum chamber (~ 10-7 mbar) with a Nd:YAG laser at a wavelength of 355 nm. The ion flow in different directions has been measured with a hemispherical array of Langmuir probes...... range considered is also a typical range for pulsed laser deposition (PLD), by which the material is collected on a suitable substrate for thin film growth. PLD has the advantage compared with other film deposition methods, that even a complicated stoichiometry, e.g. metal oxides or alloys, can...

  2. Transverse single-mode edge-emitting lasers based on coupled waveguides.

    Science.gov (United States)

    Gordeev, Nikita Yu; Payusov, Alexey S; Shernyakov, Yuri M; Mintairov, Sergey A; Kalyuzhnyy, Nikolay A; Kulagina, Marina M; Maximov, Mikhail V

    2015-05-01

    We report on the transverse single-mode emission from InGaAs/GaAs quantum well edge-emitting lasers with broadened waveguide. The lasers are based on coupled large optical cavity (CLOC) structures where high-order vertical modes of the broad active waveguide are suppressed due to their resonant tunneling into a coupled single-mode passive waveguide. The CLOC lasers have shown stable Gaussian-shaped vertical far-field profiles with a reduced divergence of ∼22° FWHM (full width at half-maximum) in CW (continuous-wave) operation.

  3. Near Field and Far Field Effects in the Taguchi-Optimized Design of AN InP/GaAs-BASED Double Wafer-Fused Mqw Long-Wavelength Vertical-Cavity Surface-Emitting Laser

    Science.gov (United States)

    Menon, P. S.; Kandiah, K.; Mandeep, J. S.; Shaari, S.; Apte, P. R.

    Long-wavelength VCSELs (LW-VCSEL) operating in the 1.55 μm wavelength regime offer the advantages of low dispersion and optical loss in fiber optic transmission systems which are crucial in increasing data transmission speed and reducing implementation cost of fiber-to-the-home (FTTH) access networks. LW-VCSELs are attractive light sources because they offer unique features such as low power consumption, narrow beam divergence and ease of fabrication for two-dimensional arrays. This paper compares the near field and far field effects of the numerically investigated LW-VCSEL for various design parameters of the device. The optical intensity profile far from the device surface, in the Fraunhofer region, is important for the optical coupling of the laser with other optical components. The near field pattern is obtained from the structure output whereas the far-field pattern is essentially a two-dimensional fast Fourier Transform (FFT) of the near-field pattern. Design parameters such as the number of wells in the multi-quantum-well (MQW) region, the thickness of the MQW and the effect of using Taguchi's orthogonal array method to optimize the device design parameters on the near/far field patterns are evaluated in this paper. We have successfully increased the peak lasing power from an initial 4.84 mW to 12.38 mW at a bias voltage of 2 V and optical wavelength of 1.55 μm using Taguchi's orthogonal array. As a result of the Taguchi optimization and fine tuning, the device threshold current is found to increase along with a slight decrease in the modulation speed due to increased device widths.

  4. Monolithic electrically injected nanowire array edge-emitting laser on (001) silicon

    KAUST Repository

    Frost, Thomas

    2014-08-13

    A silicon-based laser, preferably electrically pumped, has long been a scientific and engineering goal. We demonstrate here, for the first time, an edge-emitting InGaN/GaN disk-in-nanowire array electrically pumped laser emitting in the green (λ = 533 nm) on (001) silicon substrate. The devices display excellent dc and dynamic characteristics with values of threshold current density, differential gain, T0 and small signal modulation bandwidth equal to 1.76 kA/cm2, 3 × 10-17 cm2, 232 K, and 5.8 GHz respectively under continuous wave operation. Preliminary reliability measurements indicate a lifetime of 7000 h. The emission wavelength can be tuned by varying the alloy composition in the quantum disks. The monolithic nanowire laser on (001)Si can therefore address wide-ranging applications such as solid state lighting, displays, plastic fiber communication, medical diagnostics, and silicon photonics. © 2014 American Chemical Society.

  5. Decalin-assisted light emitting porous Si formation and its optical, surface and morphological properties

    Science.gov (United States)

    Karatutlu, Ali; Istengir, Sumeyra; Cosgun, Sedat; Seker, Isa; Unal, Bayram

    2017-11-01

    In this research paper, light emitting porous silicon (Lep-Si) samples were fabricated by a surfactant-mediated chemical stain etching solution in order to form homogenous luminescent nanostructures at room temperature. As an industrially important solvent, decalin (decahydronaphtalene) was used as a surfactant in the HF/HNO3 solutions in order to control the etching process. Morphological, surface and optical properties of the Lep-Si samples were examined using atomic force microscopy, X-ray photoelectron spectroscopy, photoluminescence (PL) spectroscopy, and laser scanning confocal microscopy (LSCM) techniques. These characterization techniques were correlated with the various etching times including depth dependent luminescence profiles for the first time. We report the optimum conditions for production of the most efficient Lep-Si using decalin (decahydronaphtalene) and possible structural origins of light emission using the depth dependent luminescence measurements.

  6. Characterization of laser-tissue interaction processes by low-boiling emitted substances

    Science.gov (United States)

    Weigmann, Hans-Juergen; Lademann, Juergen; Serfling, Ulrike; Lehnert, W.; Sterry, Wolfram; Meffert, H.

    1996-01-01

    Main point in this study was the investigation of the gaseous and low-boiling substances produced in the laser plume during cw CO2 laser and XeCl laser irradiation of tissue by gas chromatography (GC)/mass spectrometry. The characteristic emitted amounts of chemicals were determined quantitatively using porcine muscular tissue. The produced components were used to determine the character of the chemical reaction conditions inside the interaction zone. It was found that the temperature, and the water content of the tissue are the main parameter determining kind and amount of the emitted substances. The relative intensity of the GC peak of benzene corresponds to a high temperature inside the interaction area while a relative strong methylbutanal peak is connected with a lower temperature which favors Maillard type reaction products. The water content of the tissue determines the extent of oxidation processes during laser tissue interaction. For that reason the moisture in the tissue is the most important parameter to reduce the emission of harmful chemicals in the laser plume. The same methods of investigation are applicable to characterize the interaction of a controlled and an uncontrolled rf electrosurgery device with tissue. The results obtained with model tissue are in agreement with the situation characteristic in laser surgery.

  7. 700 W blue fiber-coupled diode-laser emitting at 450 nm

    Science.gov (United States)

    Balck, A.; Baumann, M.; Malchus, J.; Chacko, R. V.; Marfels, S.; Witte, U.; Dinakaran, D.; Ocylok, S.; Weinbach, M.; Bachert, C.; Kösters, A.; Krause, V.; König, H.; Lell, A.; Stojetz, B.; Löffler, A.; Strauss, U.

    2018-02-01

    A high-power blue laser source was long-awaited for processing materials with low absorption in the near infrared (NIR) spectral range like copper or gold. Due to the huge progress of GaN-based semiconductors, the performance of blue diode-lasers has made a major step forward recently. With the availability of unprecedented power levels at cw-operating blue diode-lasers emitting at 450 nm, it was possible to set up a high-power diode-laser in the blue spectral range to address these conventional laser applications and probably beyond that to establish completely new utilizations for lasers. Within the scope of the research project "BlauLas", funded within the German photonic initiative "EFFILAS" [8] by the German Federal Ministry of Education and Research (BMBF), Laserline in cooperation with OSRAM aims to realize a cw fiber-coupled diode-laser exceeding 1 kW blue laser power. In this paper the conceptual design and experimental results of a 700 W blue fiber-coupled diode-laser are presented. Initially a close look had to be taken on the mounting techniques of the semiconductors to serve the requirements of the GaN laser diodes. Early samples were used for extensive long term tests to investigate degradation processes. With first functional laser-modules we set up fiber-coupled laser-systems for further testing. Besides adaption of well-known optical concepts a main task within the development of the laser system was the selection and examination of suitable materials and assembling in order to minimize degradation and reach adequate lifetimes. We realized R&D blue lasersystems with lifetimes above 5,000 h, which enable first application experiments on processing of various materials as well as experiments on conversion to white-light.

  8. Surface Plasmon Enhanced Phosphorescent Organic Light Emitting Diodes

    International Nuclear Information System (INIS)

    Bazan, Guillermo; Mikhailovsky, Alexander

    2008-01-01

    The objective of the proposed work was to develop the fundamental understanding and practical techniques for enhancement of Phosphorescent Organic Light Emitting Diodes (PhOLEDs) performance by utilizing radiative decay control technology. Briefly, the main technical goal is the acceleration of radiative recombination rate in organometallic triplet emitters by using the interaction with surface plasmon resonances in noble metal nanostructures. Increased photonic output will enable one to eliminate constraints imposed on PhOLED efficiency by triplet-triplet annihilation, triplet-polaron annihilation, and saturation of chromophores with long radiative decay times. Surface plasmon enhanced (SPE) PhOLEDs will operate more efficiently at high injection current densities and will be less prone to degradation mechanisms. Additionally, introduction of metal nanostructures into PhOLEDs may improve their performance due to the improvement of the charge transport through organic layers via multiple possible mechanisms ('electrical bridging' effects, doping-like phenomena, etc.). SPE PhOLED technology is particularly beneficial for solution-fabricated electrophosphorescent devices. Small transition moment of triplet emitters allows achieving a significant enhancement of the emission rate while keeping undesirable quenching processes introduced by the metal nanostructures at a reasonably low level. Plasmonic structures can be introduced easily into solution-fabricated PhOLEDs by blending and spin coating techniques and can be used for enhancement of performance in existing device architectures. This constitutes a significant benefit for a large scale fabrication of PhOLEDs, e.g. by roll-to-roll fabrication techniques. Besides multieexciton annihilation, the power efficacy of PhOLEDs is often limited by high operational bias voltages required for overcoming built-in potential barriers to injection and transport of electrical charges through a device. This problem is especially

  9. Surface Plasmon Enhanced Phosphorescent Organic Light Emitting Diodes

    Energy Technology Data Exchange (ETDEWEB)

    Guillermo Bazan; Alexander Mikhailovsky

    2008-08-01

    The objective of the proposed work was to develop the fundamental understanding and practical techniques for enhancement of Phosphorescent Organic Light Emitting Diodes (PhOLEDs) performance by utilizing radiative decay control technology. Briefly, the main technical goal is the acceleration of radiative recombination rate in organometallic triplet emitters by using the interaction with surface plasmon resonances in noble metal nanostructures. Increased photonic output will enable one to eliminate constraints imposed on PhOLED efficiency by triplet-triplet annihilation, triplet-polaron annihilation, and saturation of chromophores with long radiative decay times. Surface plasmon enhanced (SPE) PhOLEDs will operate more efficiently at high injection current densities and will be less prone to degradation mechanisms. Additionally, introduction of metal nanostructures into PhOLEDs may improve their performance due to the improvement of the charge transport through organic layers via multiple possible mechanisms ('electrical bridging' effects, doping-like phenomena, etc.). SPE PhOLED technology is particularly beneficial for solution-fabricated electrophosphorescent devices. Small transition moment of triplet emitters allows achieving a significant enhancement of the emission rate while keeping undesirable quenching processes introduced by the metal nanostructures at a reasonably low level. Plasmonic structures can be introduced easily into solution-fabricated PhOLEDs by blending and spin coating techniques and can be used for enhancement of performance in existing device architectures. This constitutes a significant benefit for a large scale fabrication of PhOLEDs, e.g. by roll-to-roll fabrication techniques. Besides multieexciton annihilation, the power efficacy of PhOLEDs is often limited by high operational bias voltages required for overcoming built-in potential barriers to injection and transport of electrical charges through a device. This problem is

  10. Lateral mode control in edge-emitting lasers with modified mirrors

    Science.gov (United States)

    Payusov, A.; Serin, A.; Mukhin, I.; Shernyakov, Y.; Zadiranov, Y.; Maximov, M.; Gordeev, N.

    2017-11-01

    We present a study on lateral mode control in edge-emitting lasers with profiled mirror reflectivity. The object was to eliminate high-order lateral modes in conventional ridge-waveguide InAs/InGaAs QD (quantum dot) lasers with the stripe width of 10 μm. We have used a FIB (focused ion beam) technique to selectively etch windows in the AR (anti-reflection) facet coatings in order to introduce extra mirror losses for the high order modes. This approach allowed us to eliminate the first-order mode lasing without deterioration of the laser parameters. We suppose that further optimisation of the laser heterostructure and window designs may lead to a pure lateral single-mode lasing in the broadened ridge waveguides.

  11. Low-cost photoacoustic imaging systems based on laser diode and light-emitting diode excitation

    Directory of Open Access Journals (Sweden)

    Qingkai Yao

    2017-07-01

    Full Text Available Photoacoustic imaging, an emerging biomedical imaging modality, holds great promise for preclinical and clinical researches. It combines the high optical contrast and high ultrasound resolution by converting laser excitation into ultrasonic emission. In order to generate photoacoustic signal efficiently, bulky Q-switched solid-state laser systems are most commonly used as excitation sources and hence limit its commercialization. As an alternative, the miniaturized semiconductor laser system has the advantages of being inexpensive, compact, and robust, which makes a significant effect on production-forming design. It is also desirable to obtain a wavelength in a wide range from visible to near-infrared spectrum for multispectral applications. Focussing on practical aspect, this paper reviews the state-of-the-art developments of low-cost photoacoustic system with laser diode and light-emitting diode excitation source and highlights a few representative installations in the past decade.

  12. Comparative effectiveness of light emitting diodes (LEDs) and Lasers in near infrared photoimmunotherapy

    Science.gov (United States)

    Sato, Kazuhide; Watanabe, Rira; Hanaoka, Hirofumi; Nakajima, Takahito; Choyke, Peter L.; Kobayashi, Hisataka

    2016-01-01

    Near infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that combines the specificity of antibodies for targeting tumors with the toxicity induced by photosensitizers after exposure to near infrared (NIR) light. Herein we compare two NIR-light sources; light emitting diodes (LEDs) and Lasers, for their effectiveness in NIR-PIT. A photosensitizer, IRDye-700DX, conjugated to panitumumab (pan-IR700), was incubated with EGFR-expressing A431 and MDA-MB-468-luc cells. NIR-light was provided by LEDs or Lasers at the same light dose. Laser-light produced more cytotoxicity and greater reductions in IR700-fluorescence intensity than LED-light. Laser-light also produced more cytotoxicity in vivo in both cell lines. Assessment of super-enhanced permeability and retention (SUPR) effects were stronger with Laser than LED. These results suggest that Laser-light produced significantly more cytotoxic effects compared to LEDs. Although LED is less expensive, Laser-light produces superior results in NIR-PIT. PMID:26885688

  13. Comparative effectiveness of light emitting diodes (LEDs) and Lasers in near infrared photoimmunotherapy.

    Science.gov (United States)

    Sato, Kazuhide; Watanabe, Rira; Hanaoka, Hirofumi; Nakajima, Takahito; Choyke, Peter L; Kobayashi, Hisataka

    2016-03-22

    Near infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that combines the specificity of antibodies for targeting tumors with the toxicity induced by photosensitizers after exposure to near infrared (NIR) light. Herein we compare two NIR-light sources; light emitting diodes (LEDs) and Lasers, for their effectiveness in NIR-PIT. A photosensitizer, IRDye-700DX, conjugated to panitumumab (pan-IR700), was incubated with EGFR-expressing A431 and MDA-MB-468-luc cells. NIR-light was provided by LEDs or Lasers at the same light dose. Laser-light produced more cytotoxicity and greater reductions in IR700-fluorescence intensity than LED-light. Laser-light also produced more cytotoxicity in vivo in both cell lines. Assessment of super-enhanced permeability and retention (SUPR) effects were stronger with Laser than LED. These results suggest that Laser-light produced significantly more cytotoxic effects compared to LEDs. Although LED is less expensive, Laser-light produces superior results in NIR-PIT.

  14. Electrochemical testing of laser treated bronze surface

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsyilbas@kfupm.edu.sa [Dept. of Mechanical Engineering, King Fahd University of Petroleum and Minerals (KFUPM), Dhahran 31261 (Saudi Arabia); Toor, Ihsan-ul-Haq; Malik, Jahanzaib; Patel, F. [Dept. of Mechanical Engineering, King Fahd University of Petroleum and Minerals (KFUPM), Dhahran 31261 (Saudi Arabia); Karatas, C. [Engineering Faculty, Hacettepe University, Ankara (Turkey)

    2013-06-25

    Highlights: ► Laser treated surface is free from asperities. ► Laser treated layer extends uniformly below the surface with a thickness in the order of 40 μm. ► Presence of Cu{sub 3}N nitrides is evident from X-ray diffractogram. ► Dendritic structure is formed below the surface due to relatively slower cooling rates as compared to that at the surface. ► The corrosion current density for the laser treated surface is much less than that of the as-received surface. -- Abstract: Electrochemical testing of laser treated bronze surface is carried out and corrosion resistance of the surface is assessed. Morphological and metallurgical changes in the laser treated layer are examined using scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. The pit sites formed at the surface are analyzed using scanning electron microscope. It is found that laser treatment improves the corrosion resistance of the treated surface. Fine grains are formed in the surface region of the laser treated layer, which are attributed to the large cooling rates from the surface.

  15. Laser welding, cutting and surface treatment

    International Nuclear Information System (INIS)

    Crafer, R.C.

    1984-01-01

    Fourteen articles cover a wide range of laser applications in welding, cutting and surface treatment. Future trends are covered as well as specific applications in shipbuilding, the manufacture of heart pacemakers, in the electronics industry, in automobile production and in the aeroengine industry. Safety with industrial lasers and the measurement of laser beam parameters are also included. One article on 'Lasers in the Nuclear Industry' is indexed separately. (U.K.)

  16. Electromagnetic radiation emitted by a plasma produced in air by laser pulses with lambda = 10.6 μm

    International Nuclear Information System (INIS)

    Danilychev, V.A.; Zvorykin, V.D.; Kholin, I.V.; Chugunov, A.Y.

    1981-01-01

    The spectrum, brightness, and energy have been measured for the electromagnetic radiation emitted by a plasma produced in air near a solid surface by pulses from a high-power CO 2 laser. The air pressure was varied over the range p 0 = 0.1--760 torr, and the laser power density was varied over the range q = 5 x 10 6 --10 8 W/cm 2 . At p 0 > or approx. =2--5 torr the radiation properties of the plasma are determined by a laser-beam absorption wave which arises in the gas. The maximum brightness temperature, T/sub b/approx. =50 000 K (lambda = 400 +- 20 nm), is reached at p 0 = 25 torr. The emission spectrum is quite different from an equilibrium spectrum, consisting primarily of NII, OII, and NIII lines. The total energy radiation by the plasma in the wavelength interval 360--2600 nm into a solid angle of 4π sr reaches 2.3% of the laser pulse energy

  17. Laser surface texturing of tool steel: textured surfaces quality evaluation

    Science.gov (United States)

    Šugár, Peter; Šugárová, Jana; Frnčík, Martin

    2016-05-01

    In this experimental investigation the laser surface texturing of tool steel of type 90MnCrV8 has been conducted. The 5-axis highly dynamic laser precision machining centre Lasertec 80 Shape equipped with the nano-second pulsed ytterbium fibre laser and CNC system Siemens 840 D was used. The planar and spherical surfaces first prepared by turning have been textured. The regular array of spherical and ellipsoidal dimples with a different dimensions and different surface density has been created. Laser surface texturing has been realized under different combinations of process parameters: pulse frequency, pulse energy and laser beam scanning speed. The morphological characterization of ablated surfaces has been performed using scanning electron microscopy (SEM) technique. The results show limited possibility of ns pulse fibre laser application to generate different surface structures for tribological modification of metallic materials. These structures were obtained by varying the processing conditions between surface ablation, to surface remelting. In all cases the areas of molten material and re-cast layers were observed on the bottom and walls of the dimples. Beside the influence of laser beam parameters on the machined surface quality during laser machining of regular hemispherical and elipsoidal dimple texture on parabolic and hemispherical surfaces has been studied.

  18. Tradeoff between laser diodes and light-emitting diodes (LEDs) for the common weapon control system

    Science.gov (United States)

    Greenwell, R. A.

    1982-07-01

    The use of laser diodes or light emitting diodes (LEDs) for the ground-launched cruise missile (GLCM) is comparatively evaluated. Source characteristics of interest, including radiated power output, spectral width and peak emission, modulation bandwidth, size coupling efficiency, lifetime, rise time, and price, are presented for noncoherent LED and the coherent laser diode. The advantages and disadvantages of laser diodes and LEDs are briefly discussed, and nuclear explosion effects on these instruments, including catastrophic damage, transient ionization effects, and permanent degradation, are summarized. A link analysis of the cable parameters required for the GLCM fiber optic data link is given, arriving at power levels consistent with a LED-PIN link. Two LEDs which meet these requirements are briefly discussed.

  19. Viability of fibroblasts cultured under nutritional stress irradiated with red laser, infrared laser, and red light-emitting diode

    Science.gov (United States)

    Volpato, Luiz Evaristo Ricci; de Oliveira, Rodrigo Cardoso; Espinosa, Mariano Martinez; Bagnato, Vanderley Salvador; Machado, Maria A. A. M.

    2011-07-01

    Phototherapy is noninvasive, painless and has no known side effect. However, for its incorporation into clinical practice, more well-designed studies are necessary to define optimal parameters for its application. The viability of fibroblasts cultured under nutritional stress irradiated with either a red laser, an infrared laser, or a red light-emitting diode (LED) was analyzed. Irradiation parameters were: red laser (660 nm, 40 mW, 1 W/cm2), infrared laser (780 nm, 40 mW, 1 W/cm2), and red LED (637 +/- 15 nm, 40 mW, 1 W/cm2). All applications were punctual and performed with a spot with 0.4 mm2 of diameter for 4 or 8 s. The Kruskal-Wallis test and analysis of variance of the general linear model (p phototherapy with low-intensity laser and LED showed no toxicity at the cellular level. It even stimulated methylthiazol tetrazolium assay (MTT) conversion and neutral red uptake of fibroblasts cultured under nutritional stress, especially in the group irradiated with infrared laser (p = 0.004 for MTT conversion and p phototherapy used, it can be concluded that phototherapy stimulated the viability of fibroblasts cultured under nutritional deficit resembling those found in traumatized tissue in which cell viability is reduced.

  20. Impact toughness of laser surface alloyed Aluminium

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2012-03-01

    Full Text Available Laser surface alloying of aluminium AA1200 was performed with a 4kW Nd:YAG laser and the impact resistance of the alloys was investigated. The alloying powders were a mixture of Ni, Ti and SiC in different proportions. Surfaces reinforced...

  1. Angular distributions of emitted particles by laser ablation of silver at 355 nm

    DEFF Research Database (Denmark)

    Svendsen, Winnie Edith; Schou, Jørgen; Hansen, T.

    1998-01-01

    The angular distribution of laser ablated silver in vacuum has been measured in situ with an array of quartz-crystal microbalances. The silver surface was irradiated by ns pulses from a Nd:YAG laser operating at 355 nm for fluences ranging from 0.7 J/cm2 to 8 J/cm2. The distribution is strongly...

  2. MOVPE growth and characterization of (In,Ga)N quantum structures for laser diodes emitting at 440 nm

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Veit

    2011-04-18

    The presented work describes the metal organic vapor phase epitaxy and characterization of nitride-based quantum structures which are used in laser heterostructures emitting in the wavelength range between 400 nm and 440 nm. Aiming at current injection and optically pumped laser structures with low threshold current or respectively threshold power densities, the device properties were correlated with the material properties of the indium gallium nitride (InGaN) active region. Furthermore, the influence of the active region and waveguide heterostructure layout on the material gain as well as the modal gain was investigated. In order to understand the InGaN growth process and the formation of structural imperfections, 15 nm-100 nm thick InGaN single layers were deposited on gallium nitride (GaN) on sapphire substrates and analyzed subsequently. It turned out that the spiral pattern of the growth edges around screw dislocations, threading from the substrate to the growth surface, and the formation of additional V-shaped surface defects are the main cause for the deterioration of the crystal perfection of the InGaN. As a result of the transition from a layer-by-layer to a 3D growth regime stable facets with preferred indium incorporation are formed that increase the lateral variation of the indium mole fraction in the layer. The higher indium incorporation at the facets is explained by dynamical elasticity theory and proven by the growth and characterization of InGaN layers on differently oriented GaN. The material properties of the InGaN quantum wells were correlated with laser device properties using 400 nm laser structures: In the case of thin quantum wells the 3D growth results in a lateral variation of the band gap due to variations of the indium mole fraction and the well width. Systematical investigations of laser structures with different band gap fluctuations show an increase of the threshold power density as the lateral variation of the band gap increases. It

  3. Surface changes of implants after laser irradiation

    Science.gov (United States)

    Rechmann, Peter; Sadegh, Hamid M. M.; Goldin, Dan S.; Hennig, Thomas

    1999-05-01

    Periimplantitis is one of the major factors for the loss of dental implants. Due to the minor defense ability of the tissue surrounding the implant compared to natural teeth treatment of periimplantitis in the early stage is very important. Reducing bacteria with a laser might be the most successful step in therapy of periimplantitis. Aim of the study was to observe changes in surface morphology of seven different implants after irradiation with three different lasers. Two kinds of flat round samles were prepared by the manufacturers either identical to the body surface or to the cervical area of the corresponding implants. The samples were irradiated using different power settings. The lasers used were a CO2 laser (Uni Laser 450P, ASAH Medico Denmark; fiber guided, wavelength 10.6 μm, max. average power 8.3 W, "soft-pulse" and cw) an Er:YAG laser (KaVo Key Laser II, wavelength 2.94 μm, pulse duration 250-500μs, pulse energy 60-500 mJ, pulse repetition rate 1-15 Hz, focus diameter 620 μm, air-water cooling; Biberach, Germany; a frequency doubled Alexandrite laser (laboratory prototype, q-switched, fiber guided, wavelength 377 nm, pulse duration 1 μs, pulse repetition rate 30 Hz, water cooling). After irradiation the implant surfaces were investigated with a Scanning Electron Microscope. Ablation thresholds were determined. After CO2 laser irradiation no changes in surface morphology were observed whereas using the pulsed Er:YAG laser or frequency doubled Alexandrite laser even at low energies loss of integrity or melting of the surface was observed. The changes in surface morphology seem to depend very strongly on the type of surface coating.

  4. XRF-analysis of fine and ultrafine particles emitted from laser printing devices.

    Science.gov (United States)

    Barthel, Mathias; Pedan, Vasilisa; Hahn, Oliver; Rothhardt, Monika; Bresch, Harald; Jann, Oliver; Seeger, Stefan

    2011-09-15

    In this work, the elemental composition of fine and ultrafine particles emitted by ten different laser printing devices (LPD) is examined. The particle number concentration time series was measured as well as the particle size distributions. In parallel, emitted particles were size-selectively sampled with a cascade impactor and subsequently analyzed by the means of XRF. In order to identify potential sources for the aerosol's elemental composition, materials involved in the printing process such as toner, paper, and structural components of the printer were also analyzed. While the majority of particle emissions from laser printers are known to consist of recondensated semi volatile organic compounds, elemental analysis identifies Si, S, Cl, Ca, Ti, Cr, and Fe as well as traces of Ni and Zn in different size fractions of the aerosols. These elements can mainly be assigned to contributions from toner and paper. The detection of elements that are likely to be present in inorganic compounds is in good agreement with the measurement of nonvolatile particles. Quantitative measurements of solid particles at 400 °C resulted in residues of 1.6 × 10(9) and 1.5 × 10(10) particles per print job, representing fractions of 0.2% and 1.9% of the total number of emitted particles at room temperature. In combination with the XRF results it is concluded that solid inorganic particles contribute to LPD emissions in measurable quantities. Furthermore, for the first time Br was detected in significant concentrations in the aerosol emitted from two LPD. The analysis of several possible sources identified the plastic housings of the fuser units as main sources due to substantial Br concentrations related to brominated flame retardants.

  5. First demonstration of InGaP/InAlGaP based orange laser emitting at 608 nm

    KAUST Repository

    Majid, Mohammed Abdul

    2015-06-26

    The fabrication of orange-emitting semiconductor laser on interdiffused InGaP/InAlGaP structure is reported. The lasers lased at 22°C at a wavelength as short as 608 nm with threshold current density of 3.4 KAcm −2 and a maximum output power of ∼46 mW. This is the shortest wavelength electrically pumped semiconductor laser emission from the InGaP/InAlGaP structure.

  6. High power cascade diode lasers emitting near 2 μm

    Energy Technology Data Exchange (ETDEWEB)

    Hosoda, Takashi; Feng, Tao; Shterengas, Leon, E-mail: leon.shterengas@stonybrook.edu; Kipshidze, Gela; Belenky, Gregory [State University of New York at Stony Brook, Stony Brook, New York 11794 (United States)

    2016-03-28

    High-power two-stage cascade GaSb-based type-I quantum well diode lasers emitting near 2 μm were designed and fabricated. Coated devices with cavity length of 3 mm generated about 2 W of continuous wave power from 100-μm-wide aperture at the current of 6 A. The power conversion efficiency peaked at 20%. Carrier recycling between quantum well gain stages was realized using band-to-band tunneling in GaSb/AlSb/InAs heterostructure complemented with optimized electron and hole injector regions. Design optimization eliminated parasitic optical absorption and thermionic emission, and included modification of the InAs quantum wells of electron and composition and doping profile of hole injectors. Utilization of the cascade pumping scheme yielded 2 μm lasers with improved output power and efficiency compared to existing state-of-the-art diodes.

  7. Effect of Different Contact Materials on Approximal Caries Detection by Laser Fluorescence and Light-Emitting Diode Devices.

    Science.gov (United States)

    Ozsevik, A Semih; Kararslan, Emine Sirin; Aktan, Ali Murat; Bozdemir, Esin; Cebe, Fatma; Sarı, Fatih

    2015-10-01

    The aim of this in vitro study was to investigate the influence of the adjacent tooth surface on pen type laser fluorescence (LFpen) and light-emitting diode (LED) device readings in detecting approximal caries lesions in permanent teeth. Early detection of noncavitated dental caries is important, because disease progression can be easily halted at this stage with certain applications, such as fluoride therapy, antibacterial therapy, dietary changes, or low-intensity laser irradiation. A total of 87 permanent molars with 156 approximal surfaces were assessed with LED- and LF-based devices in contact with sound tooth surfaces (the control group) as well as approximal amalgam, composite, zirconia, and full ceramic restorations. All teeth were assessed once by one trained examiner. After the LF and LED assessments, the teeth were histologically evaluated using stereomicroscopy as the gold standard. The sensitivity, specificity, accuracy, and area under the receiver operating characteristics (ROC) curve were calculated according to the appropriate thresholds (T1, sound surface or enamel caries; T2, dentin caries). For the LFpen device, higher sensitivity and accuracy was found when the adjacent surface was sound at the T1 threshold and no significant differences were found among accuracy at the T2 threshold. For the LED-based device, no significant differences were found among sensitivities at the T1 threshold. At the T2 threshold, specificity was higher when the adjacent tooth had a zirconia restoration. It was found that both devices could be used effectively for evaluating approximal surfaces with adjacent restored teeth, regardless of the different kinds of restorative materials.

  8. Metal surface nitriding by laser induced plasma

    Science.gov (United States)

    Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

    1996-10-01

    We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

  9. Fine and ultrafine particles emitted from laser printers as indoor air contaminants in German offices.

    Science.gov (United States)

    Tang, Tao; Hurraß, Julia; Gminski, Richard; Mersch-Sundermann, Volker

    2012-11-01

    Various publications indicate that the operation of laser printers and photocopiers may be associated with health effects due to the release of gaseous components and fine and ultrafine particles (UFP). However, only sparse studies are available that evaluate the possible exposure of office workers to printer emissions under real conditions. Therefore, the aim of our study was to assess the exposure of office workers to particulate matter released from laser printers and photocopiers. Concentrations of fine particles and UFP were measured before, during, and after the operation of laser printing devices in 63 office rooms throughout Germany. Additionally, the particles were characterized by electron microscopy and energy-dispersive X-ray spectroscopy. A significant increase of fine particles and UFP was identified in ambient workplace air during and after the printing processes. Particle fractions between 0.23 and 20 μm emitted by the office machines significantly affect particle mass concentrations while printing 500 pages, i.e., during the printing process, PM(0.23-20), PM(2.5), and PM(10) concentrations increased in 43 out of the evaluated 62 office rooms investigated. Additionally, a significant increase was observed in submicrometer particles, with median particle number concentrations of 6,503 particles/cm(3) before and 18,060 particles/cm(3) during the printing process. Our data indicate that laser printers and photocopiers could be a relevant source of fine particles and particularly UFP in office rooms.

  10. Study on the GaAs(110) surface using emitted atom spectrometry

    International Nuclear Information System (INIS)

    Gayone, J.E.; Sanchez, E.A.; Grizzi, O.; Universidad Nacional de Cuyo, Mendoza

    1998-01-01

    The facilities implemented at Bariloche for the ion scattering spectrometry is described, and recent examples of the technique application to determine the atomic structure and the composition of metallic and semiconductor surfaces, pure and with different adsorbates. The surface analysis technique using emitted atom spectrometry is discussed. The sensitivity to the GaAs(110) surface atomic relaxation is presented, and the kinetic of hydrogen adsorption by the mentioned surface is studied

  11. Vertical-cavity surface-emitting lasers for medical diagnosis

    DEFF Research Database (Denmark)

    Ansbæk, Thor

    and high tuning rate. The VCSEL is highly single-mode and inherently polarization stable due to the use of a High-index Contrast subwavelength Grating (HCG). HCG VCSELs are presented with 1.5% relative tuning range at a tuning rate of 850 kHz. The thesis reports on the analysis of narrow linewidth Fabry...

  12. Excimer laser irradiation of metal surfaces

    Science.gov (United States)

    Kinsman, Grant

    In this work a new method of enhancing CO2 laser processing by modifying the radiative properties of a metal surface is studied. In this procedure, an excimer laser (XeCl) or KrF) exposes the metal surface to overlapping pulses of high intensity, 10(exp 8) - 10(exp 9) W cm(exp -2), and short pulse duration, 30 nsec FWHM (Full Width Half Maximum), to promote structural and chemical change. The major processing effect at these intensities is the production of a surface plasma which can lead to the formation of a laser supported detonation wave (LSD wave). This shock wave can interact with the thin molten layer on the metal surface influencing to a varying degree surface oxidation and roughness features. The possibility of the expulsion, oxidation and redeposition of molten droplets, leading to the formation of micron thick oxide layers, is related to bulk metal properties and the incident laser intensity. A correlation is found between the expulsion of molten droplets and a Reynolds number, showing the interaction is turbulent. The permanent effects of these interactions on metal surfaces are observed through scanning electron microscopy (SEM), transient calorimetric measurements and Fourier transform infrared (FTIR) spectroscopy. Observed surface textures are related to the scanning procedures used to irradiate the metal surface. Fundamental radiative properties of a metal surface, the total hemispherical emissivity, the near-normal spectral absorptivity, and others are examined in this study as they are affected by excimer laser radiation. It is determined that for heavily exposed Al surface, alpha' (10.6 microns) can be increased to values close to unity. Data relating to material removal rates and chemical surface modification for excimer laser radiation is also discussed. The resultant reduction in the near-normal reflectivity solves the fundamental problem of coupling laser radiation into highly reflective and conductive metals such as copper and aluminum. The

  13. Investigations of thin p-GaN light-emitting diodes with surface plasmon compatible metallization

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke

    2016-01-01

    We investigate device performance of InGaN light-emitting diodes with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of InGaN light-emitting diodes with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  14. Application of Surface Plasmonics for Semiconductor Light-Emitting Diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed

    . By placing metallic thin films or nanoparticles (NPs) in the near-field of QW light-emitters, it is possible to improve their internal quantum efficiency (IQE) through the Purcell enhancement effect. It has been a general understanding that in order to achieve surface plasmon (SP) coupling with QWs......-QW coupling does not necessarily lead to emission enhancement. The findings of this work show that the scattering and absorption properties of NPs play a crucial role in determining whether the implementation will improve or degrade the optical performance. By applying these principles, a novel design...... methods are presented to improve the efficiency of the QWs. Furthermore, a design for electrically driven LED device with SP compatibility is proposed, and requirements on p-type GaN layer thickness and current spreading properties are investigated experimentally....

  15. Process control of laser surface alloying

    NARCIS (Netherlands)

    Römer, Gerardus Richardus, Bernardus, Engelina; Meijer, J.; Olde Benneker, Jeroen

    1998-01-01

    In spite of the many advantages of laser surface treatment, such as high production rates and low induced thermal distortion, and its great potential for modifying the surface properties of a wide range of new and existing materials, industrial applications are still limited. This is not only

  16. Morphological and atomic analytical changes after CO2 laser irradiation emitted at 9.3 microns on human dental hard tissues.

    Science.gov (United States)

    Takahashi, K; Kimura, Y; Matsumoto, K

    1998-06-01

    The purposes of this study were to examine the effects of CO2 laser emitted at 9.3 microns on human sound and carious dental hard tissue ablation with a stereoscope, scanning electron microscope (SEM), and energy dispersive X-ray spectrometer (SEM-EDX) and to identify possible applications of this laser in clinical treatment. There has been no report of morphological changes or atomic analytical studies on carious hard tissues after laser irradiation with 9.3 microns CO2 laser. Sixty extracted human teeth with no caries and sixty teeth with enamel or dentin caries were used for this study. All teeth were horizontally sectioned into slices (approximately 3 mm in thickness) and the samples were irradiated with CO2 laser using the following two parameters: a fluence of 78 J/cm2 and 5 pps for 2 sec. After laser irradiation, half of the samples were observed by stereoscopy and SEM and the other half were analyzed by SEM-EDX. The lased sound enamel and dentin surfaces showed crater-like structures which had been produced by the high laser energy. On the other hand, some portions of carious hard tissues were evaported by the laser. A slight amount of carbonization was observed by stereoscopy. Calcium (Ca) and phosphorus (P) content of sound or carious hard tissues was increased significantly (p laser irradiation, but the ratio of Ca to P after laser irradiation was significantly increased (p CO2 laser may be useful for the prevention or removal of caries in clinical situations.

  17. Excimer laser surface modification: Process and properties

    Energy Technology Data Exchange (ETDEWEB)

    Jervis, T.R.; Nastasi, M. [Los Alamos National Lab., NM (United States); Hirvonen, J.P. [Technical Research Institute, Espoo (Finland). Metallurgy Lab.

    1992-12-01

    Surface modification can improve materials for structural, tribological, and corrosion applications. Excimer laser light has been shown to provide a rapid means of modifying surfaces through heat treating, surface zone refining, and mixing. Laser pulses at modest power levels can easily melt the surfaces of many materials. Mixing within the molten layer or with the gas ambient may occur, if thermodynamically allowed, followed by rapid solidification. The high temperatures allow the system to overcome kinetic barriers found in some ion mixing experiments. Alternatively, surface zone refinement may result from repeated melting-solidification cycles. Ultraviolet laser light couples energy efficiently to the surface of metallic and ceramic materials. The nature of the modification that follows depends on the properties of the surface and substrate materials. Alloying from both gas and predeposited layer sources has been observed in metals, semiconductors, and ceramics as has surface enrichment of Cr by zone refinement of stainless steel. Rapid solidification after melting often results in the formation of nonequilibrium phases, including amorphous materials. Improved surface properties, including tribology and corrosion resistance, are observed in these materials.

  18. Laser surface treatment of grey cast iron for automotive applications

    NARCIS (Netherlands)

    Ocelik, V.; Tang, P.N.; de Boer, M.C.; de Oliveira, U.; de Hosson, J.T.M.; DeHosson, JTM; Brebbia, CA; Nishida, SI

    2005-01-01

    The surface of pearlitic grey cast iron was treated using a 2 kW Nd:YAG laser beam with the final aim to improve its surface properties, mainly for automotive applications. Two kinds of laser surface treatments were experimentally applied. In the laser surface hardening approach the surface of cast

  19. Ultraviolet Laser SQUID Microscope for GaN Blue Light Emitting Diode Testing

    International Nuclear Information System (INIS)

    Daibo, M; Kamiwano, D; Kurosawa, T; Yoshizawa, M; Tayama, N

    2006-01-01

    We carried out non-contacting measurements of photocurrent distributions in GaN blue light emitting diode (LED) chips using our newly developed ultraviolet (UV) laser SQUID microscope. The UV light generates the photocurrent, and then the photocurrent induces small magnetic fields around the chip. An off-axis arranged HTS-SQUID magnetometer is employed to detect a vector magnetic field whose typical amplitude is several hundred femto-tesla. Generally, it is difficult to obtain Ohmic contacts for p-type GaN because of the low hole concentration in the p-type epitaxial layer and the lack of any available metal with a higher work function compared with the p-type GaN. Therefore, a traditional probecontacted electrical test is difficult to conduct for wide band gap semiconductors without an adequately annealed electrode. Using the UV-laser SQUID microscope, the photocurrent can be measured without any electrical contact. We show the photocurrent vector map which was reconstructed from measured magnetic fields data. We also demonstrate how we found the position of a defect of the electrical short circuits in the LED chip

  20. Laser microstructuring for fabricating superhydrophobic polymeric surfaces

    Science.gov (United States)

    Cardoso, M. R.; Tribuzi, V.; Balogh, D. T.; Misoguti, L.; Mendonça, C. R.

    2011-02-01

    In this paper we show the fabrication of hydrophobic polymeric surfaces through laser microstructuring. By using 70-ps pulses from a Q-switched and mode-locked Nd:YAG laser at 532 nm, we were able to produce grooves with different width and separation, resulting in square-shaped pillar patterns. We investigate the dependence of the morphology on the surface static contact angle for water, showing that it is in agreement with the Cassie-Baxter model. We demonstrate the fabrication of a superhydrophobic polymeric surface, presenting a water contact angle of 157°. The surface structuring method presented here seems to be an interesting option to control the wetting properties of polymeric surfaces.

  1. The influence of surface contamination on the ion emission from nanosecond-pulsed laser ablation of Al and Cu

    Science.gov (United States)

    Ullah, S.; Dogar, A. H.; Qayyum, H.; Rehman, Z. U.; Qayyum, A.

    2018-04-01

    Ions emitted from planar Al and Cu targets irradiated with a 1064 nm pulsed laser were investigated with the help of a time-resolving Langmuir probe. It was found that the intensity of the ions emitted from a target area rapidly decreases with the increasing number of laser shots, and seems to reach saturation after about 10 laser shots. The saturated intensity of Al and Cu ions was approximately 0.1 and 0.3 times the intensity of the respective ions measured at the first laser shot, respectively. The higher target ion intensity for the first few shots is thought to be due to the enhanced ionization of target atoms by vacuum-ultraviolet radiations emitted from the thermally excited/ionized surface contaminants. The reduction of target ion intensity with an increasing number of laser shots thus indicates the removal of contaminants from the irradiated surface area. Laser-cleaned Al and Cu surfaces were then allowed to be recontaminated with residual vacuum gases and the ion intensity was measured at various time delays. The prolonged exposure of the cleaned target to vacuum residual gases completely restores the ion intensity. Regarding surface contaminants removal, laser shots of higher intensities were found to be more effective than a higher number of laser shots having lower intensities.

  2. Astigmatism-free high-brightness 1060 nm edge-emitting lasers with narrow circular beam profile.

    Science.gov (United States)

    Miah, Md Jarez; Kalosha, Vladimir P; Bimberg, Dieter; Pohl, Johannes; Weyers, Markus

    2016-12-26

    1060 nm high-brightness vertical broad-area edge-emitting lasers providing anastigmatic high optical power into a narrow circular beam profile are demonstrated. Ridge-waveguide (RW) lasers yield record 2.2 W single-transverse mode power in the 1060-nm wavelength range under continuous-wave (cw) operation at room temperature with excellent beam quality factor M2 ≤ 2. Independent of operating current the astigmatism is only 2.5 µm. 3 mm long broad-area (BA) lasers produce a θvert as narrow as 9° full width at half maximum, which agrees well with our simulation results, being insensitive to drive current. 5 mm long BA lasers deliver highest ever reported cw 12 W multimode output power among lasers showing θvert <10° in the 1060-nm wavelength range. The emitted laser beams from both RW and BA lasers show a perfect circular shape with ≤10° divergence angle at record 2.1 W and 4.2 W cw-mode output power, respectively.

  3. Edge-emitting InGaAs/GaAs laser with high temperature stability of wavelength and threshold current

    International Nuclear Information System (INIS)

    Gordeev, N Yu; Novikov, I I; Chunareva, A V; Il'inskaya, N D; Shernyakov, Yu M; Maximov, M V; Kalyuzhnyy, N A; Mintairov, S A; Lantratov, V M; Payusov, A S; Shchukin, V A; Ledentsov, N N

    2010-01-01

    We have investigated an edge-emitting tilted wave laser (TWL) with the active region based on GaInAs/GaAs quantum wells. In the TWL the wavelength stabilization is based on the coupling of the laser active waveguide cavity to a specially introduced thick epitaxial layer and the emission wavelength is defined by the combined cavity mode preferably by a single dominating mode. The TWL wafer has been grown by metal-organic chemical vapour deposition. Laser parameters have been investigated both in pulsed and CW mode in the temperature range of 15–60 °C. In the temperature window of 20–50 °C under CW excitation the lasers have shown high wavelength temperature stability with the temperature shift of 0.05 nm K −1 and threshold current stability with the characteristic temperature of 500 K. The data obtained prove the concept of thermal stability in tilted wave lasers

  4. Surface plasmon enhanced organic light emitting diodes by gold nanoparticles with different sizes

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Chia-Yuan; Chen, Ying-Chung [Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Chen, Kan-Lin [Department of Electronic Engineering, Fortune Institute of Technology, Kaohsiung, Taiwan (China); Huang, Chien-Jung, E-mail: chien@nuk.edu.tw [Department of Applied Physics, National University of Kaohsiung, Kaohsiung, Taiwan (China)

    2015-11-30

    Highlights: • Different varieties, sizes, and shapes for nanoparticles will generate different surface plasmon resonance effects in the devices. • The red-shift phenomenon for absorption peaks is because of an increasing contribution of higher-order plasmon modes for the larger gold nanoparticles. • The mobility of electrons in the electron-transport layer of organic light-emitting diodes is a few orders of magnitude lower than that of holes in the hole-transport layer of organic light-emitting diodes. - Abstract: The influence of gold nanoparticles (GNPs) with different sizes doped into (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)) (PEDOT:PSS) on the performance of organic light-emitting diodes is investigated in this study. The current efficiency of the device, at a current density of 145 mA/cm, with PEDOT:PSS doped with GNPs of 8 nm is about 1.57 times higher than that of the device with prime PEDOT:PSS because the absorption peak of GNPs is closest to the photoluminescence peak of the emission layer, resulting in maximum surface plasmon resonance effect in the device. In addition, the surface-enhanced Raman scattering spectroscopy also reveals the maximum surface plasmon resonance effect in the device when the mean particle size of GNPs is 8 nm.

  5. Needle-like focus generation by radially polarized halo beams emitted by photonic-crystal ring-cavity laser

    Science.gov (United States)

    Kitamura, Kyoko; Nishimoto, Masaya; Sakai, Kyosuke; Noda, Susumu

    2012-11-01

    Focused fields that possess a small spot size and long depth of focus (DOF) are expected to lead to the further development of optical applications. Here, we develop a photonic-crystal ring-cavity laser that emits a beam with a radially polarized halo shape (rinner/router > 0.9). This beam has a needle-like focus with a spot size of less than 0.4λ and a depth of focus longer than 10 λ for a 0.9 numerical aperture objective lens. We evaluate the focusing properties of the emitted beam and demonstrate that it has a longer depth of focus than conventional beams.

  6. THz wave parametric oscillator with a surface-emitted ring-cavity configuration

    Science.gov (United States)

    Yang, Zhen; Wang, Yuye; Xu, Degang; Tang, Longhuang; Xu, Wentao; Duan, Pan; Yan, Chao; Yao, Jianquan

    2016-11-01

    A surface-emitted ring-cavity terahertz (THz) wave parametric oscillator has been demonstrated for high-energy THz output and fast frequency tuning. Through the special optical design with a Galvano optical scanner and four-mirror ring-cavity structure, a maximum THz output of 12.9 μJ/pulse is achieved at 1.359 THz under the pump pulse energy of 172.8 mJ with the repetition rate of 10 Hz. A further research on the performance of the SE ring-cavity TPO has done to explore more characteristics of THz output. The THz pulse instability and the influence of cavity loss has analyzed. Moreover, the pump depletion rate of the ring-cavity configuration is much lower than the conventional surface-emitted terahertz wave parametric oscillator at the same experimental conditions.

  7. High-energy terahertz wave parametric oscillator with a surface-emitted ring-cavity configuration.

    Science.gov (United States)

    Yang, Zhen; Wang, Yuye; Xu, Degang; Xu, Wentao; Duan, Pan; Yan, Chao; Tang, Longhuang; Yao, Jianquan

    2016-05-15

    A surface-emitted ring-cavity terahertz (THz) wave parametric oscillator has been demonstrated for high-energy THz output and fast frequency tuning in a wide frequency range. Through the special optical design with a galvano-optical scanner and four-mirror ring-cavity structure, the maximum THz wave output energy of 12.9 μJ/pulse is achieved at 1.359 THz under the pump energy of 172.8 mJ. The fast THz frequency tuning in the range of 0.7-2.8 THz can be accessed with the step response of 600 μs. Moreover, the maximum THz wave output energy from this configuration is 3.29 times as large as that obtained from the conventional surface-emitted THz wave parametric oscillator with the same experimental conditions.

  8. Laser Surface Hardening of Groove Edges

    Science.gov (United States)

    Hussain, A.; Hamdani, A. H.; Akhter, R.; Aslam, M.

    2013-06-01

    Surface hardening of groove-edges made of 3Cr13 Stainless Steel has been carried out using 500 W CO2 laser with a rectangular beam of 2.5×3 mm2. The processing speed was varied from 150-500 mm/min. It was seen that the hardened depth increases with increase in laser interaction time. A maximum hardened depth of around 1mm was achieved. The microhardness of the transformed zone was 2.5 times the hardness of base metal. The XRD's and microstructural analysis were also reported.

  9. Thomson Parabola Spectrometer for Energetic Ions Emitted from Sub-ns Laser Generated Plasmas

    Directory of Open Access Journals (Sweden)

    Mariapompea Cutroneo

    2013-01-01

    Full Text Available Laser-generated plasmas were obtained in high vacuum by irradiating micrometric thin films (Au, Au/Mylar, Mylar with the Asterix laser at the PALS Research Infrastructure in Prague. Irradiations at the fundamental wavelength, 300 ps pulse duration, at intensities up to about 1016W/cm2, enabled ions to be accelerated in forward direction with kinetic energies of the order of 2 MeV/charge state. Protons above 2 MeV were obtained in the direction orthogonal to the target surface in selffocusing conditions. Gold ions up to about 120 MeV and 60+ charge state were detected. Ion collectors and semiconductor SiC detectors were employed in time-of-flight arrangement in order to measure the ion velocities as a function of the angle around the normal direction to the target surface. A Thomson parabola spectrometer (TPS with a multi-channel-plate detector was used to separate the different ion contributions to the charge emission in single laser shots, and to get information on the ion charge states, energy and proton acceleration. TPS experimental spectra were compared with accurate TOSCA simulations of TPS parabolas.

  10. Double surface plasmon enhanced organic light-emitting diodes by gold nanoparticles and silver nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Chia-Yuan; Chen, Ying-Chung [Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Chen, Kan-Lin [Department of Electronic Engineering, Fortune Institute of Technology, Kaohsiung, Taiwan (China); Huang, Chien-Jung, E-mail: chien@nuk.edu.tw [Department of Applied Physics, National University of Kaohsiung, Kaohsiung, Taiwan (China)

    2015-12-30

    Graphical abstract: - Highlights: • The buffer layer is inserted between PEDOT: PSS and the emitting layer in order to avoid that the nonradiative decay process of exciton is generated. • The silver nanoclusters will generate surface plasmon resonance effect, resulting that the localized electric field around the silver nanoclusters is enhanced. • When the recombination region of the excitons is too close to the nanoparticles of the hole-transport layer, the nonradiative quenching of excitons is generated. - Abstract: The influence of gold nanoparticles (GNPs) and silver nanoclusters (SNCs) on the performance of organic light-emitting diodes is investigated in this study. The GNPs are doped into (poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate)) (PEDOT: PSS) and the SNCs are introduced between the electron-injection layer and cathode alumina. The power efficiency of the device, at the maximum luminance, with double surface plasmon resonance and buffer layer is about 2.15 times higher than that of the device without GNPs and SNCs because the absorption peaks of GNPs and SNCs are as good as the photoluminescence peak of the emission layer, resulting in strong surface plasmon resonance effect in the device. In addition, the buffer layer is inserted between PEDOT: PSS and the emitting layer in order to avoid that the nonradiative decay process of exciton is generated.

  11. [Measuring microhardness of laser exposed tooth surface].

    Science.gov (United States)

    Florin, R; Herrmann, C; Bernhardt, W

    1990-02-01

    In principle it is possible to homogenize the enamel surface by melting structural elements with the continuous wave CO2 laser. Using the precision instrument NEOPHOT 2 (Carl Zeiss JENA) the microhardness of extracted laserexposed premolares were tested so as to clarify the functional strain capasity and the mechanical characteristics of laserexposed regions of enamel surfaces. The proven higher hardness in the centre of the laserinduced fusing zones (in comparison with adjacent enamel) objectify an attainable refining of the enamel surface that probably causes an increase in the caries-preventive resistance.

  12. CO 2 laser photoacoustic detection of ethylene emitted by diesel engines used in urban public transports

    Science.gov (United States)

    Teodoro, C. G.; Schramm, D. U.; Sthel, M. S.; Lima, G. R.; Rocha, M. V.; Tavares, J. R.; Vargas, H.

    2010-03-01

    In this work, CO 2 laser photoacoustic spectroscopy was used to detect and monitor ethylene concentrations from about 0.6 ppmV up to 47 ppmV emitted by urban public transports in Campos dos Goytacazes city in Rio de Janeiro state, Brazil. The photoacoustic method proved to be a very sensitive and selective gas detection technique. As ethylene is a rather reactive compound due to its double bond between the two carbon atoms, it acts as one of the precursors for the tropospheric ozone generation, a gas species that is present in the photochemical smog, is an important greenhouse gas and whose formation is strongly associated with the presence of sun light and nitrogen oxide compounds. For this reason, ethylene renders itself an important pollutant in the atmosphere. In addition, the valid Brazilian legislation is only concerned with the total emission of hydrocarbons from the vehicle exhausts. It means that it does not discriminate the emission of some pollutant gas compounds, such as ethylene. This situation is greatly aggravated by the fact that most of the mass and cargo transport in Brazil is made by roads and powered by diesel oil.

  13. High-energy coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator

    Science.gov (United States)

    Yang, Xue; Brunetti, Enrico; Jaroszynski, Dino A.

    2018-04-01

    High-charge electron beams produced by laser-wakefield accelerators are potentially novel, scalable sources of high-power terahertz radiation suitable for applications requiring high-intensity fields. When an intense laser pulse propagates in underdense plasma, it can generate femtosecond duration, self-injected picocoulomb electron bunches that accelerate on-axis to energies from 10s of MeV to several GeV, depending on laser intensity and plasma density. The process leading to the formation of the accelerating structure also generates non-injected, sub-picosecond duration, 1–2 MeV nanocoulomb electron beams emitted obliquely into a hollow cone around the laser propagation axis. These wide-angle beams are stable and depend weakly on laser and plasma parameters. Here we perform simulations to characterise the coherent transition radiation emitted by these beams if passed through a thin metal foil, or directly at the plasma–vacuum interface, showing that coherent terahertz radiation with 10s μJ to mJ-level energy can be produced with an optical to terahertz conversion efficiency up to 10‑4–10‑3.

  14. Nanoscale surface characterization using laser interference microscopy

    Science.gov (United States)

    Ignatyev, Pavel S.; Skrynnik, Andrey A.; Melnik, Yury A.

    2018-03-01

    Nanoscale surface characterization is one of the most significant parts of modern materials development and application. The modern microscopes are expensive and complicated tools, and its use for industrial tasks is limited due to laborious sample preparation, measurement procedures, and low operation speed. The laser modulation interference microscopy method (MIM) for real-time quantitative and qualitative analysis of glass, metals, ceramics, and various coatings has a spatial resolution of 0.1 nm for vertical and up to 100 nm for lateral. It is proposed as an alternative to traditional scanning electron microscopy (SEM) and atomic force microscopy (AFM) methods. It is demonstrated that in the cases of roughness metrology for super smooth (Ra >1 nm) surfaces the application of a laser interference microscopy techniques is more optimal than conventional SEM and AFM. The comparison of semiconductor test structure for lateral dimensions measurements obtained with SEM and AFM and white light interferometer also demonstrates the advantages of MIM technique.

  15. Light emitting polymer blends and diffractive optical elements in high-speed direct laser writing of microstructures

    International Nuclear Information System (INIS)

    Suyal, H; Waddie, A J; Taghizadeh, M R; McCarthy, A; Walker, A C; Mackintosh, A R; Kuehne, A J C; Pethrick, R A; Gu, E; Dawson, M D; Bradley, D D C

    2008-01-01

    In this paper, we describe a series of improvements that have been made to our direct laser writing waveguide/microfluidic fabrication technology. We demonstrate significant increases in the writing speed (measured in micrometres of written structure per second) by both the use of customized photopolymers containing light emitting polymer and the inclusion of a diffractive optical element to enable the writing of multiple channels in a single pass

  16. LASER SURFACE CLADDING FOR STRUCTURAL REPAIR

    OpenAIRE

    SANTANU PAUL

    2018-01-01

    Laser cladding is a powder deposition technique, which is used to deposit layers of clad material on a substrate to improve its surface properties. It has widespread application in the repair of dies and molds used in the automobile industry. These molds and dies are subjected to cyclic thermo-mechanical loading and therefore undergo localized damage and wear. The final clad quality and integrity is influenced by various physical phenomena, namely, melt pool morphology, microst...

  17. Micropatterning on cylindrical surfaces via electrochemical etching using laser masking

    International Nuclear Information System (INIS)

    Cho, Chull Hee; Shin, Hong Shik; Chu, Chong Nam

    2014-01-01

    Highlights: • Various micropatterns were fabricated on the cylindrical surface of a stainless steel shaft. • Selective electrochemical dissolution was achieved via a series process of laser masking and electrochemical etching. • Laser masking characteristics on the non-planar surface were investigated. • A uniform mask layer was formed on the cylindrical surface via synchronized laser line scanning with a rotary system. • The characteristics of electrochemical etching on the non-planar surface were investigated. - Abstract: This paper proposes a method of selective electrochemical dissolution on the cylindrical surfaces of stainless steel shafts. Selective electrochemical dissolution was achieved via electrochemical etching using laser masking. A micropatterned recast layer was formed on the surface via ytterbium-doped pulsed fiber laser irradiation. The micropatterned recast layer could be used as a mask layer during the electrochemical etching process. Laser masking condition to form adequate mask layer on the planar surface for etching cannot be used directly on the non-planar surface. Laser masking condition changes depending on the morphological surface. The laser masking characteristics were investigated in order to form a uniform mask layer on the cylindrical surface. To minimize factors causing non-uniformity in the mask layer on the cylindrical surface, synchronized laser line scanning with a rotary system was applied during the laser masking process. Electrochemical etching characteristics were also investigated to achieve deeper etched depth, without collapsing the recast layer. Consequently, through a series process of laser masking and electrochemical etching, various micropatternings were successfully performed on the cylindrical surfaces

  18. Laser controlled melting of pre-treated zirconia surface

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsyilbas@kfupm.edu.sa [ME Department, KFUPM, Dhahran 31261, (Saudi Arabia); Akhtar, S.S. [ME Department, KFUPM, Dhahran 31261, (Saudi Arabia); Karatas, C. [Engineering College, Hacettepe University, (Turkey)

    2011-05-15

    Laser treatment of pre-prepared zirconia surface is carried out. The pre-prepared surface, prior to laser treatment, consists of 50 {mu}m carbon film and 7% titanium carbide particles, which are imbedded in the carbon film. The microstructural and morphological changes in the laser treated surface layer are examined using optical and scanning electron microscopes, energy dispersive spectroscopy, and X-ray diffraction. The fracture toughness of the laser treated surface is measured and the residual stress formed at the surface vicinity is determined from the X-ray diffraction technique. It is found that the microhardness of the laser treated surface increased slightly due to the dense layer formed at the surface vicinity. However, the laser treatment process reduces the fracture toughness of the surface due to improved surface hardness and the residual stress formed in the surface vicinity.

  19. Surface-Passivated AlGaN Nanowires for Enhanced Luminescence of Ultraviolet Light Emitting Diodes

    KAUST Repository

    Sun, Haiding

    2017-12-19

    Spontaneously-grown, self-aligned AlGaN nanowire ultraviolet light emitting diodes still suffer from low efficiency partially because of the strong surface recombination caused by surface states, i.e., oxidized surface and high density surface states. Several surface passivation methods have been introduced to reduce surface non-radiative recombination by using complex and toxic chemicals. Here, we present an effective method to suppress such undesirable surface recombination of the AlGaN nanowires via diluted potassium hydroxide (KOH) solution; a commonly used chemical process in semiconductor fabrication which is barely used as surface passivation solution in self-assembled nitride-based nanowires. The transmission electron microscopy investigation on the samples reveals almost intact nanowire structures after the passivation process. We demonstrated an approximately 49.7% enhancement in the ultraviolet light output power after 30-s KOH treatment on AlGaN nanowires grown on titanium-coated silicon substrates. We attribute such a remarkable enhancement to the removal of the surface dangling bonds and oxidized nitrides (Ga-O or Al-O bonds) at the surface as we observe the change of the carrier lifetime before and after the passivation. Thus, our results highlight the possibility of employing this process for the realization of high performance nanowire UV emitters.

  20. [INVITED] Laser treatment of Inconel 718 alloy and surface characteristics

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.; Al-Aqeeli, N.; Karatas, C.

    2016-04-01

    Laser surface texturing of Inconel 718 alloy is carried out under the high pressure nitrogen assisting gas. The combination of evaporation and melting at the irradiated surface is achieved by controlling the laser scanning speed and the laser output power. Morphological and metallurgical changes in the treated surface are analyzed using the analytical tools including optical, electron scanning, and atomic force microscopes, energy dispersive spectroscopy, and X-ray diffraction. Microhardnes and friction coefficient of the laser treated surface are measured. Residual stress formed in the surface region is determined from the X-ray diffraction data. Surface hydrophobicity of the laser treated layer is assessed incorporating the sessile drop method. It is found that laser treated surface is free from large size asperities including cracks and the voids. Surface microhardness increases significantly after the laser treatment process, which is attributed to the dense layer formation at the surface under the high cooling rates, dissolution of Laves phase in the surface region, and formation of nitride species at the surface. Residual stress formed is compressive in the laser treated surface and friction coefficient reduces at the surface after the laser treatment process. The combination of evaporation and melting at the irradiated surface results in surface texture composes of micro/nano-poles and pillars, which enhance the surface hydrophobicity.

  1. Focusing of Intense Laser via Parabolic Plasma Concave Surface

    Science.gov (United States)

    Zhou, Weimin; Gu, Yuqiu; Wu, Fengjuan; Zhang, Zhimeng; Shan, Lianqiang; Cao, Leifeng; Zhang, Baohan

    2015-12-01

    Since laser intensity plays an important role in laser plasma interactions, a method of increasing laser intensity - focusing of an intense laser via a parabolic plasma concave surface - is proposed and investigated by three-dimensional particle-in-cell simulations. The geometric focusing via a parabolic concave surface and the temporal compression of high harmonics increased the peak intensity of the laser pulse by about two orders of magnitude. Compared with the improvement via laser optics approaches, this scheme is much more economic and appropriate for most femtosecond laser facilities. supported by National Natural Science Foundation of China (Nos. 11174259, 11175165), and the Dual Hundred Foundation of China Academy of Engineering Physics

  2. Light extraction efficiency improvement by multiple laser stealth dicing in InGaN-based blue light-emitting diodes.

    Science.gov (United States)

    Zhang, Yiyun; Xie, Haizhong; Zheng, Haiyang; Wei, Tongbo; Yang, Hua; Li, Jing; Yi, Xiaoyan; Song, Xiangyang; Wang, Guohong; Li, Jinmin

    2012-03-12

    We report a multiple laser stealth dicing (multi-LSD) method to improve the light extraction efficiency (LEE) of InGaN-based light-emitting diodes (LEDs) using a picosecond (Ps) laser. Compared with conventional LEDs scribed by a nanosecond (Ns) laser and single stealth-diced LEDs, the light output power (LOP) of the LEDs using multi-LSD method can be improved by 26.5% and 11.2%, respectively. The enhanced LOP is due to the increased side emission from the large-area roughened sidewalls of the sapphire substrates fabricated in the multi-LSD process. Numerical simulation results show that the multi-LSD process has little thermal damages to the multiple quantum wells (MQWs) of the LEDs.

  3. The constitution and microstructure of laser surface-modified metals

    Science.gov (United States)

    Singh, Jogender

    1992-09-01

    The applications oflasers in the processing of metals, ceramics, and semiconductors range from surface glazing of thin films on semiconductors to thick surface cladding on metals. Lasers have the unique capability of rapid heating, melting, and quenching of the substrate, which results in the formation of new engineering materials with metastable microstructures. This article describes the microstructural evolution of laser-glazed and laser-clad alloys treated with a pulse or continuous-wave CO2 laser.

  4. Using a terrestrial laser scanner to measure spatiotemporal surface moisture dynamics

    Science.gov (United States)

    Smit, Y.; Donker, J.; Ruessink, G.

    2017-12-01

    A terrestrial laser scanner (TLS) is an active remote sensing technique that utilizes the round trip time of an emitted laser beam to provide the range between the laser scanner and the backscattering object. It is routinely used for topographic mapping, forest measurements or 3D city models since it derives useful object representations by means of a dense three-dimensional (3D) point cloud. Here, we present a novel application using the returned intensity of the emitted beam to detect surface moisture with the RIEGL VZ-400. Because this TLS operates at a wavelength near a water absorption band (1550 nm), reflectance is an accurate parameter to measure surface moisture over its full range. Five days of intensive laser scanning were performed on a Dutch beach to illustrate the applicability of the TLS. Concurrent gravimetric surface moisture samples were collected to calibrate the relation between reflectance and surface moisture. Results reveal the reflectance output is a robust parameter to measure surface moisture from the thin upper layer over its full range from 0% to 25%. The obtained calibration curve of the presented TLS, describing the relationship between reflectance and surface moisture, has a root-mean-square error of 2.7% and a correlation coefficient squared of 0.85. This relation holds to about 60 m from the TLS. Within this distance the TLS typically produces O(10^6-10^7) data points, which we averaged into surface moisture maps with a 1 x 1 m resolution. This grid size largely removes small moisture disturbances induced by, for example, footprints or tire tracks, while retaining larger scale trends. Concluding, TLS (RIEGL-VZ 400) is a highly suited technique to accurately and robustly measure spatiotemporal surface moisture variations on a coastal beach with high spatial ( 1 x 1 m) and temporal ( 15-30min.) resolution.

  5. Laser Surface Engineering of Magnesium Alloys: A Review

    Science.gov (United States)

    Singh, Ashish; Harimkar, Sandip P.

    2012-06-01

    Magnesium (Mg) and its alloys are well known for their high specific strength and low density. However, widespread applications of Mg alloys in structural components are impeded by their insufficient wear and corrosion resistance. Various surface engineering approaches, including electrochemical processes (plating, conversion coatings, hydriding, and anodizing), gas-phase deposition (thermal spray, chemical vapor deposition, physical vapor deposition, diamond-like coatings, diffusion coatings, and ion implantation), and organic polymer coatings (painting and powder coating), have been used to improve the surface properties of Mg and its alloys. Recently, laser surface engineering approaches are attracting significant attention because of the wide range of possibilities in achieving the desired microstructural and compositional modifications through a range of laser-material interactions (surface melting, shock peening, and ablation). This article presents a review of various laser surface engineering approaches such as laser surface melting, laser surface alloying, laser surface cladding, laser composite surfacing, and laser shock peening used for surface modification of Mg alloys. The laser-material interactions, microstructural/compositional changes, and properties development (mostly corrosion and wear resistance) accompanied with each of these approaches are reviewed.

  6. Modeling laser-induced periodic surface structures: an electromagnetic approach

    NARCIS (Netherlands)

    Skolski, J.Z.P.

    2014-01-01

    This thesis presents and discusses laser-induced periodic surface structures (LIPSSs), as well as a model explaining their formation. LIPSSs are regular wavy surface structures with dimensions usually in the submicrometer range, which can develop on the surface of many materials exposed to laser

  7. Vertical‐cavity surface‐emitting laser based digital coherent detection for multigigabit long reach passive optical links

    DEFF Research Database (Denmark)

    Rodes Lopez, Roberto; Jensen, Jesper Bevensee; Zibar, Darko

    2011-01-01

    We report on experimental demonstration of digital coherent detection based on a directly modulated vertical‐cavity surface‐emitting laser with bit rate up to 10 Gbps. This system allows a cooler‐less, free running, and unamplified transmission without optical dispersion compensation up to 105 km...... at 5 Gbps long reach passive optical links. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2462–2464, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26331...

  8. High modulation bandwidth of a light-emitting diode with surface plasmon coupling (Conference Presentation)

    Science.gov (United States)

    Lin, Chun-Han; Tu, Charng-Gan; Yao, Yu-Feng; Chen, Sheng-Hung; Su, Chia-Ying; Chen, Hao-Tsung; Kiang, Yean-Woei; Yang, Chih-Chung

    2017-02-01

    Besides lighting, LEDs can be used for indoor data transmission. Therefore, a large modulation bandwidth becomes an important target in the development of visible LED. In this regard, enhancing the radiative recombination rate of carriers in the quantum wells of an LED is a useful method since the modulation bandwidth of an LED is related to the carrier decay rate besides the device RC time constant To increase the carrier decay rate in an LED without sacrificing its output power, the technique of surface plasmon (SP) coupling in an LED is useful. In this paper, the increases of modulation bandwidth by reducing mesa size, decreasing active layer thickness, and inducing SP coupling in blue- and green-emitting LEDs are illustrated. The results are demonstrated by comparing three different LED surface structures, including bare p-type surface, GaZnO current spreading layer, and Ag nanoparticles (NPs) for inducing SP coupling. In a single-quantum-well, blue-emitting LED with a circular mesa of 10 microns in radius, SP coupling results in a modulation bandwidth of 528.8 MHz, which is believed to be the record-high level. A smaller RC time constant can lead to a higher modulation bandwidth. However, when the RC time constant is smaller than 0.2 ns, its effect on modulation bandwidth saturates. The dependencies of modulation bandwidth on injected current density and carrier decay time confirm that the modulation bandwidth is essentially inversely proportional to a time constant, which is inversely proportional to the square-root of carrier decay rate and injected current density.

  9. Guiding of Long-Distance Electric Discharges by Combined Femtosecond and Nanosecond Pulses Emitted by Hybrid KrF Laser System

    Science.gov (United States)

    2014-01-30

    laser pulse initiated HV discharge with a time delay of tens nanoseconds – evidently it is developing due to an avalanche -like growth of electron...AFRL-AFOSR-UK-TR-2014-0040 Guiding of long-distance electric discharges by combined femtosecond and nanosecond pulses emitted by...and guiding electric discharge , KrF laser, femtosecond pulse , nanosecond pulse , filamentation, plasma channel, lightning control, laser control of

  10. Material, Mechanical, and Tribological Characterization of Laser-Treated Surfaces

    Science.gov (United States)

    Yilbas, Bekir Sami; Kumar, Aditya; Bhushan, Bharat; Aleem, B. J. Abdul

    2014-10-01

    Laser treatment under nitrogen assisting gas environment of cobalt-nickel-chromium-tungsten-based superalloy and high-velocity oxygen-fuel thermal spray coating of nickel-chromium-based superalloy on carbon steel was carried out to improve mechanical and tribological properties. Superalloy surface was preprepared to include B4C particles at the surface prior to the laser treatment process. Material and morphological changes in the laser-treated samples were examined using scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction (XRD) analysis. Residual stresses present at the surface region of the laser-treated layer were determined from the XRD data. The microhardness of the laser-treated surface was measured by indentation tests. Fracture toughness of the coating surfaces before and after laser treatment were also measured using overload indentation tests. Macrowear and macrofriction characterization were carried out using pin-on-disk tests.

  11. Surface treatment of CFRP composites using femtosecond laser radiation

    Science.gov (United States)

    Oliveira, V.; Sharma, S. P.; de Moura, M. F. S. F.; Moreira, R. D. F.; Vilar, R.

    2017-07-01

    In the present work, we investigate the surface treatment of carbon fiber-reinforced polymer (CFRP) composites by laser ablation with femtosecond laser radiation. For this purpose, unidirectional carbon fiber-reinforced epoxy matrix composites were treated with femtosecond laser pulses of 1024 nm wavelength and 550 fs duration. Laser tracks were inscribed on the material surface using pulse energies and scanning speeds in the range 0.1-0.5 mJ and 0.1-5 mm/s, respectively. The morphology of the laser treated surfaces was investigated by field emission scanning electron microscopy. We show that, by using the appropriate processing parameters, a selective removal of the epoxy resin can be achieved, leaving the carbon fibers exposed. In addition, sub-micron laser induced periodic surface structures (LIPSS) are created on the carbon fibers surface, which may be potentially beneficial for the improvement of the fiber to matrix adhesion in adhesive bonds between CFRP parts.

  12. Surface wettability of silicon substrates enhanced by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Shih-Feng [National Applied Research Laboratories, Instrument Technology Research Center, Hsinchu (China); National Chiao Tung University, Department of Mechanical Engineering, Hsinchu (China); Hsiao, Wen-Tse; Huang, Kuo-Cheng; Hsiao, Sheng-Yi [National Applied Research Laboratories, Instrument Technology Research Center, Hsinchu (China); Chen, Ming-Fei [National Changhua University of Education, Department of Mechatronics Engineering, Changhua (China); Lin, Yung-Sheng [Hungkuang University, Department of Applied Cosmetology and Graduate Institute of Cosmetic Science, Taichung (China); Chou, Chang-Pin [National Chiao Tung University, Department of Mechanical Engineering, Hsinchu (China)

    2010-11-15

    Laser-ablation techniques have been widely applied for removing material from a solid surface using a laser-beam irradiating apparatus. This paper presents a surface-texturing technique to create rough patterns on a silicon substrate using a pulsed Nd:YAG laser system. The different degrees of microstructure and surface roughness were adjusted by the laser fluence and laser pulse duration. A scanning electron microscope (SEM) and a 3D confocal laser-scanning microscope are used to measure the surface micrograph and roughness of the patterns, respectively. The contact angle variations between droplets on the textured surface were measured using an FTA 188 video contact angle analyzer. The results indicate that increasing the values of laser fluence and laser pulse duration pushes more molten slag piled around these patterns to create micro-sized craters and leads to an increase in the crater height and surface roughness. A typical example of a droplet on a laser-textured surface shows that the droplet spreads very quickly and almost disappears within 0.5167 s, compared to a contact angle of 47.9 on an untextured surface. This processing technique can also be applied to fabricating Si solar panels to increase the absorption efficiency of light. (orig.)

  13. Metallic surfaces decontamination by using laser light

    International Nuclear Information System (INIS)

    Moggia, Fabrice; Lecardonnel, Xavier

    2013-01-01

    Metal surface cleaning appears to be one of the major priorities for industries especially for nuclear industries. The research and the development of a new technology that is able to meet the actual requirements (i.e. waste volume minimization, liquid effluents and chemicals free process...) seems to be the main commitment. Currently, a wide panel of technologies already exists (e.g. blasting, disk sander, electro-decontamination...) but for some of them, the efficiency is limited (e.g, Dry Ice blasting) and for others, the wastes production (liquid and/or solid) remains an important issue. One answer could be the use of a LASER light process. Since a couple of years, the Clean- Up Business Unit of the AREVA group investigates this decontamination technology. Many tests have been already performed in inactive (i.e. on simulants such as paints, inks, resins, metallic oxides) or active conditions (i.e. pieces covered with a thick metallic oxide layer and metallic pieces covered with grease). The paper will describe the results obtained in term of decontamination efficiency during all our validation process. Metallographic characterizations (i.e. SEM, X-ray scattering) and radiological analysis will be provided. We will also focus our paper on the future deployment of the LASER technology and its commercial use at La Hague reprocessing facility in 2013. (authors)

  14. Laser composite surfacing of stainless steel with SiC

    Science.gov (United States)

    Dutta Majumdar, J.; Chandra, B. Ramesh; Nath, A. K.; Manna, I.

    2006-07-01

    In the present study, an attempt has been made to improve wear resistance of AISI 304 stainless steel by laser composite surfacing with SiC. Laser processing has been carried out by pre-deposition of Fe + SiC powders (in the ratio of 85:15 and thickness of 100 m) on AISI 304 stainless steel substrate and subsequently, melting it using a 2 kW continuous wave CO2 laser. Following laser processing, a detailed characterization and evaluation of mechanical/electrochemical properties of the composite layer were undertaken to study the influence of laser processing on the characteristics and properties of the composite layer. Microstructure of the composite layer consisted of uniformly dispersed SiC particles in grain refined -Fe dendrites. Laser composite surfacing led to a significant improvement in microhardness and wear resistance as compared to as-received substrate. However, pitting corrosion property was marginally deteriorated due to laser composite surfacing.

  15. Thin planar package for cooling an array of edge-emitting laser diodes

    Science.gov (United States)

    Mundinger, David C.; Benett, William J.

    1992-01-01

    A laser diode array is disclosed that includes a plurality of planar assemblies and active cooling of each assembly. The laser diode array may be operated in a long duty cycle, or in continuous operation. A laser diode bar and a microchannel heat sink are thermally coupled in a compact, thin planar assembly having the laser diode bar located proximate to one edge. In an array, a number of such thin planar assemblies are secured together in a stacked configuration, in close proximity so that the laser diodes are spaced closely. The cooling means includes a microchannel heat sink proximate to the laser diode bar to absorb heat generated by laser operation. To provide the coolant to the microchannels, each thin planar assembly comprises passageways that connect the microchannels to inlet and outlet corridors. Each inlet passageway may comprise a narrow slot that directs coolant into the microchannels and increases the velocity of flow therethrough. The corridors comprises holes extending through each of the assemblies in the array. The inlet and outlet corridors are connected to a conventional coolant circulation system. The laser diode array with active cooling has applications as an optical pump for high power solid state lasers, or by mating the diodes with fiber optic lenses. Further, the arrays can be useful in applications having space constraints and energy limitations, and in military and space applications. The arrays can be incorporated in equipment such as communications devices and active sensors.

  16. Laser grooving of surface cracks on hot work tool steel

    Directory of Open Access Journals (Sweden)

    D. Klobčar

    2011-10-01

    Full Text Available The paper presents the analysis of laser grooving of 1.2343 tool steel hardened to 46 HRC. The effect of laser power and grooving speed on groove shape (i.e. depth and width, the material removal rate and the purity of produced groove as a measure of groove quality was investigated and analyzed using response surface methodology. Optimal parameters of laser grooving were found, which enables pure grooves suitable for laser welding.

  17. Emitting far-field multicolor patterns and characters through plastic diffractive micro-optics elements illuminated by common Gaussian lasers in the visible range.

    Science.gov (United States)

    Zhang, Xinyu; Li, Hui; Liu, Kan; Luo, Jun; Xie, Changsheng; Ji, An; Zhang, Tianxu

    2011-04-01

    Far-field multicolor patterns and characters are emitted effectively in a relatively wide and deep spatial region by plastic diffractive micro-optics elements (DMOEs), which are illuminated directly by common Gaussian lasers in the visible range. Phase-only DMOEs are composed of a large number of fine step-shaped phase microstructures distributed sequentially over the plastic wafer selected. The initial DMOEs in silicon wafer are fabricated by an innovative technique with a combination of a single-mask ultraviolet photolithography and low-cost and rapid wet KOH etching. The fabricated silicon DMOEs are further converted into a nickel mask by the conventional electrochemical method, and they are finally transferred onto the surface of the plastic wafer through mature hot embossing. Morphological measurements show that the surface roughness of the plastic DMOEs is in the nanometer range, and the feature height of the phase steps in diffractive elements is in the submicrometer scale, which can be designed and adjusted flexibly according to requirements. The dimensions of the DMOEs can be changed from the order of millimeters to centimeters. A large number of pixel phase microstructures with a square microappearance employed to construct the phase-only DMOEs are created by the Gerchberg-Saxton algorithm, according to the target patterns and characters and common Gaussian lasers manipulated by the DMOEs fabricated. © 2011 Optical Society of America

  18. Diode Laser Surface Alloying of Armor Steel with Tungsten Carbide

    OpenAIRE

    Janicki D.; Górka J.; Kwaśny W.; Gołombek K.; Kondracki M.; Żuk M.

    2017-01-01

    Metal matrix composite (MMC) surface layers reinforced by WC were fabricated on armor steel ARMOX 500T plates via a laser surface alloying process. The microstructure of the layers was assessed by scanning electron microscopy and X-ray diffraction.

  19. Three body abrasion of laser surface alloyed aluminium AA1200

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2012-06-01

    Full Text Available Laser surface alloying of aluminium AA1200 was performed with a 4 kW Nd:YAG laser to improve the abrasion wear resistance. Aluminium surfaces reinforced with metal matrix composites and intermetallic phases were achieved. The phases present depended...

  20. Dependence of absolute photon flux on infrared absorbance alteration and surface roughness on photoresist polymers irradiated with vacuum ultraviolet photons emitted from HBr plasma

    Science.gov (United States)

    Zhang, Yan; Takeuchi, Takuya; Ishikawa, Kenji; Hayashi, Toshio; Takeda, Keigo; Sekine, Makoto; Hori, Masaru

    2017-12-01

    The absolute fluxes of vacuum ultraviolet (VUV) photons emitted from HBr plasma were analyzed and the effects of VUV photons on a photoresist polymer in ArF-excimer-laser (193 nm) lithography were quantitatively investigated on the basis of the infrared spectra attributed to the C=O region. The spectral peak intensity assigned to the methacrylic acid (MAA) in the photoresist drastically decreased owing to the loss of this monomer caused by the irradiation of VUV photons at dosages below 16 × 1016 photons/cm2. X-ray photoelectron spectroscopy observation showed that the removed monomer moved to the surface and generated volatile products that induced a decrease in film thickness. As a consequence, the surface became rough during the early-stage irradiation at dosages lower than 16 × 1016 photons/cm2 owing to the monomer loss of MAA with volatile product formation and subsequent cross-linking reactions.

  1. Development of blue lasers, from second harmonic generation using a Nd:YAG laser emitting at 946 nm

    International Nuclear Information System (INIS)

    Nogueira, Gustavo Bernardes

    2010-01-01

    Blue lasers have attracted much attention for applications such as blue-ray, displays and as pumped source for the Ti:sapphire laser. A Nd:YAG crystal with diffusion bonded end-caps was used together with a pump wavelength of 802,3 nm, detuned from the absorption peak at 808 nm in order to minimize the thermal lens effect by providing for a better temperature distribution inside the crystal. Using different input mirror radii, the best relation between pump waist and laser was achieved in a linear cavity and resulted in 6.75W cw (continuous wave) laser power at 946 nm and slope efficiency of 48%. In a second step, a second harmonic generation crystal for blue emission at 473 nm was inserted into different types of resonators, and the blue output power at 473 nm was measured as a function of absorbed pump power. (author)

  2. Laser activation of diamond surface for electroless metal plating

    Science.gov (United States)

    Pimenov, S. M.; Shafeev, G. A.; Laptev, V. A.; Loubnin, E. N.

    1994-04-01

    Selective area electroless nickel and copper deposition onto the surface of diamond single crystals and polycrystalline diamond films has been realized. Three methods of laser-assisted activation of diamond surface were applied: (i) prenucleation of diamond surface with a thin layer of palladium catalyst via laser-induced decomposition of a palladium acetyl-acetonate [Pd(acac)2] solid film; (ii) deposition of palladium by means of the decomposition of Pd(acac)2 dissolved in dimethylformamide; (iii) laser-induced damage of diamond surface.

  3. Clinical comparison between the bleaching efficacy of light-emitting diode and diode laser with sodium perborate.

    Science.gov (United States)

    Koçak, Sibel; Koçak, Mustafa Murat; Sağlam, Baran Can

    2014-04-01

    The aim of this clinical study was to test the efficacy of a light-emitting diode (LED) light and a diode laser, when bleaching with sodium perborate. Thirty volunteers were selected to participate in the study. The patients were randomly divided into two groups. The initial colour of each tooth to be bleached was quantified with a spectrophotometer. In group A, sodium perborate and distilled water were mixed and placed into the pulp chamber, and the LED light was source applied. In group B, the same mixture was used, and the 810 nm diode laser was applied. The final colour of each tooth was quantified with the same spectrophotometer. Initial and final spectrophotometer values were recorded. Mann-Whitney U-test and Wicoxon tests were used to test differences between both groups. Both devices successfully whitened the teeth. No statistical difference was found between the efficacy of the LED light and the diode laser. © 2013 The Authors. Australian Endodontic Journal © 2013 Australian Society of Endodontology.

  4. Characterization of extreme ultraviolet light-emitting plasmas from a laser-excited fluorine containing liquid polymer jet target

    International Nuclear Information System (INIS)

    Abel, B.; Assmann, J.; Faubel, M.; Gaebel, K.; Kranzusch, S.; Lugovoj, E.; Mann, K.; Missalla, T.; Peth, Ch.

    2004-01-01

    The operation of a liquid polymer jet laser-plasma target and the characterization of the absolute x-ray emission in the extreme ultraviolet wavelength window from 9-19 nm is reported. The target is a liquid polymer (perfluoro-polyether) that is exposed to pulsed and focused laser light at 532 nm in the form of a thin, liquid microjet (d=40 to 160 μm) in vacuum. The spectral brightness of the source in the 13 nm range is relatively high because a large fraction of radiative energy is emitted in one single line only, which is assigned to be the 2p-3d F VII doublet at 12.8 nm, with a laser energy conversion efficiency of 0.45% (2π sr, 2% bandwidth) in our initial experiment. A further increase of the relative emission has been found in the wavelength range between 7 and 17 nm when the jet diameter was increased from 40 to 160 μm. The two-dimensional spatial profile of the source plasma (d=40 to 50 μm) has been analyzed with a pinhole camera

  5. Power Spectral Density Evaluation of Laser Milled Surfaces

    Directory of Open Access Journals (Sweden)

    Raoul-Amadeus Lorbeer

    2017-12-01

    Full Text Available Ablating surfaces with a pulsed laser system in milling processes often leads to surface changes depending on the milling depth. Especially if a constant surface roughness and evenness is essential to the process, structural degradation may advance until the process fails. The process investigated is the generation of precise thrust by laser ablation. Here, it is essential to predict or rather control the evolution of the surfaces roughness. Laser ablative milling with a short pulse laser system in vacuum (≈1 Pa were performed over depths of several 10 µm documenting the evolution of surface roughness and unevenness with a white light interference microscope. Power spectral density analysis of the generated surface data reveals a strong influence of the crystalline structure of the solid. Furthermore, it was possible to demonstrate that this effect could be suppressed for gold.

  6. SURFACE CAST IRON STRENGTHENING USING COMBINED LASER AND ULTRASONIC PROCESSING

    Directory of Open Access Journals (Sweden)

    O. G. Devojno

    2013-01-01

    Full Text Available The paper provides an analysis of ultrasonic surface plastic deformation and subsequent laser thermal strengthening of gray cast iron parts in the regime of hardening from a solid state with the purpose to obtain strengthened surface layers of bigger depth and less roughness of the processed surface. Program complex ANSYS 11.0 has been used for calculation of temperature fields induced by laser exposure.  The appropriate regime of laser processing without surface fusion has been selected on the basis of the applied complex. The possibility of displacement in the bottom boundary of α–γ-transformation temperature  for СЧ20 with 900 °С up to 800 °С is confirmed due to preliminary ultrasonic surface plastic deformation of the surface that allows to expand technological opportunities of laser quenching  of gray  cast iron from a solid state. 

  7. High-resolution spectroscopy of X-rays emitted from electron bombarded surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Jabłoński, Ł. [Institute of Physics, Jan Kochanowski University, 25-406 Kielce (Poland); Banaś, D., E-mail: d.banas@ujk.edu.pl [Institute of Physics, Jan Kochanowski University, 25-406 Kielce (Poland); Jagodziński, P. [Department of Physics, Kielce University of Technology, 25-314 Kielce (Poland); Kubala-Kukuś, A.; Sobota, D.; Pajek, M. [Institute of Physics, Jan Kochanowski University, 25-406 Kielce (Poland)

    2015-07-01

    The investigations of a compact 6-crystal Johann/Johansson diffraction X-ray spectrometer, covering a wide range (70 eV–15 keV) of photon energies, applied to observe the X-rays emitted from electron bombarded surfaces are discussed in terms of its focusing properties and achievable energy resolution. In the present study the X-ray spectra of Si-Kα{sub 1,2} and Al-Kα{sub 1,2} X-ray lines excited by 5 keV electron beam were measured using PET and TAP crystal, respectively, in the “out-of-focus” geometry which will be used to study the electron/ion surface interactions at the electron beam ion source (EBIS) facility. The measured X-ray spectra were interpreted in terms of the performed ray-tracing simulations which demonstrate the key features of the “out-of-focus” geometry. It was demonstrated that in this case the energy resolution in the range 1–3 eV for photon energy 1–2 keV can be achieved with an increased acceptance for the extension of X-ray source, of about 1 mm, which is important feature for practical applications. Additionally, a dependence of the X-ray intensity and energy resolution on slit opening was studied in details. The results are important for investigations of surfaces with electron and ion impact, in particular, for the future high-resolution X-ray spectroscopy experiments at the EBIS facility.

  8. Diagnostics of Particles emitted from a Laser generated Plasma: Experimental Data and Simulations

    Science.gov (United States)

    Costa, Giuseppe; Torrisi, Lorenzo

    2018-01-01

    The charge particle emission form laser-generated plasma was studied experimentally and theoretically using the COMSOL simulation code. The particle acceleration was investigated using two lasers at two different regimes. A Nd:YAG laser, with 3 ns pulse duration and 1010 W/cm2 intensity, when focused on solid target produces a non-equilibrium plasma with average temperature of about 30-50 eV. An Iodine laser with 300 ps pulse duration and 1016 W/cm2 intensity produces plasmas with average temperatures of the order of tens keV. In both cases charge separation occurs and ions and electrons are accelerated at energies of the order of 200 eV and 1 MeV per charge state in the two cases, respectively. The simulation program permits to plot the charge particle trajectories from plasma source in vacuum indicating how they can be deflected by magnetic and electrical fields. The simulation code can be employed to realize suitable permanent magnets and solenoids to deflect ions toward a secondary target or detectors, to focalize ions and electrons, to realize electron traps able to provide significant ion acceleration and to realize efficient spectrometers. In particular it was applied to the study two Thomson parabola spectrometers able to detect ions at low and at high laser intensities. The comparisons between measurements and simulation is presented and discussed.

  9. Edge-emitting lasers based on coupled large optical cavity with high beam stability

    Science.gov (United States)

    Serin, A.; Gordeev, N.; Payusov, A.; Shernyakov, Y.; Kalyuzhnyy, y.; Mintairov, S.; Maximov, M.

    2017-11-01

    In this paper we present a study on temperature and current stability of far-field patterns of lasers based on the coupled large optical cavity (CLOC) concept. Previously it has been shown that the CLOC structures allows effective suppressing of high-order mode lasing in broadened waveguides. For the first time we report on transverse single-mode emission from the CLOC lasers with 4.8 μm thick waveguide. Using broadened waveguide allowed us to reduce the divergence of the far-field patterns down to 14° in continuous-wave (CW) regime. Far-field patterns proved to be insensitive to current and temperature changes.

  10. Inexpensive laser-induced surface modification in bismuth thin films

    Energy Technology Data Exchange (ETDEWEB)

    Contreras, A. Reyes [Facultad de Ciencias, Universidad Autónoma del Estado de México, Carretera Toluca, Ixtlahuaca Kilómetro 15.5, C.P. 50200 Edo. de México (Mexico); Hautefeuille, M., E-mail: mathieu_h@ciencias.unam.mx [Facultad de Ciencias, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Circuito Exterior S/N, Coyoacán, Ciudad Universitaria, C.P. 04510 D.F. Mexico (Mexico); García, A. Esparza [Fotofísica y Películas Delgadas, Departamento de Tecnociencias, CCADET-UNAM, Circuito exterior s/n C.P. 04510 Cd. Universitaria, D.F. Mexico (Mexico); Mejia, O. Olea [Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Carretera Toluca-Atlacomulco, Km 14.5, Unidad El Rosedal, 50200 San Cayetano, Estado de México (Mexico); López, M.A. Camacho [Facultad de Química, Universidad Autónoma del Estado de México, Tollocan s/n, esq. Paseo Colón, Toluca, Estado de México 50110 (Mexico)

    2015-05-01

    Highlights: • Laser-induced microbumps were formed on bismuth films using a simple, low-cost, laser setup. • The patterns, similar to those typically obtained with high-power lasers, were characterized. • Control of laser ablation conditions is critical in the fabrication of surface microbumps. - Abstract: In this work, we present results on texturing a 500 nm thick bismuth film, deposited by sputtering onto a glass slide using a low-cost homemade, near-infrared pulsed laser platform. A 785 nm laser diode of a CD–DVD pickup head was precisely focused on the sample mounted on a motorized two-axis translation stage to generate localized surface microbumps on the bismuth films. This simple method successfully transferred desired micropatterns on the films in a computer-numerical control fashion. Irradiated zones were characterized by atomic force microscopy and scanning electron microscopy. It was observed that final results are strongly dependent on irradiation parameters.

  11. An enhanced surface passivation effect in InGaN/GaN disk-in-nanowire light emitting diodes for mitigating Shockley–Read–Hall recombination

    KAUST Repository

    Zhao, Chao

    2015-07-24

    We present a detailed study on the effects of dangling bond passivation and the comparison of different sulfides passivation process on the properties of InGaN/GaN quantum-disk (Qdisk)-in-nanowire based light emitting diodes (NW-LEDs). Our results demonstrated the first organic sulfide passivation process for nitride nanowires (NWs). The results from Raman spectroscopy, photoluminescence (PL) measurements, and X-ray photoelectron spectroscopy (XPS) showed octadecylthiol (ODT) effectively passivated the surface states, and altered the surface dynamic charge, thereby recovered the band-edge emission. The effectiveness of the process with passivation duration was also studied. Moreover, we also compared the electro-optical performance of NW-LEDs emitting at green wavelength before and after ODT passivation. We have shown that the Shockley-Read-Hall (SRH) non-radiative recombination of NW-LEDs can be greatly reduced after passivation by ODT, which led to a much faster increasing trend of quantum efficiency, and higher peak efficiency. Our results highlighted the research opportunity in employing this technique for further design and realization of high performance NW-LEDs and NW-lasers.

  12. Improved performance of organic light-emitting diode with vanadium pentoxide layer on the FTO surface

    Science.gov (United States)

    Saikia, D.; Sarma, R.

    2017-06-01

    Vanadium pentoxide layer deposited on the fluorine-doped tin oxide (FTO) anode by vacuum deposition has been investigated in organic light-emitting diode (OLED). With 12 nm optimal thickness of V2O5, the luminance efficiency is increased by 1.66 times compared to the single FTO-based OLED. The improvement of current efficiency implies that there is a better charge injection and better controlling of hole current. To investigate the performance of OLED by the buffer layer, V2O5 films of different thicknesses were deposited on the FTO anode and their J- V and L- V characteristics were studied. Further analysis was carried out by measuring sheet resistance, optical transmittance and surface morphology with the FE-SEM images. This result indicates that the V2O5 (12 nm) buffer layer is a good choice for increasing the efficiency of FTO-based OLED devices within the tunnelling region. Here the maximum value of current efficiency is found to be 2.83 cd / A.

  13. In vitro performance of DIAGNOdent laser fluorescence device for dental calculus detection on human tooth root surfaces.

    Science.gov (United States)

    Rams, Thomas E; Alwaqyan, Abdulaziz Y

    2017-10-01

    This study assessed the reproducibility of a red diode laser device, and its capability to detect dental calculus in vitro on human tooth root surfaces. On each of 50 extracted teeth, a calculus-positive and calculus-free root surface was evaluated by two independent examiners with a low-power indium gallium arsenide phosphide diode laser (DIAGNOdent) fitted with a periodontal probe-like sapphire tip and emitting visible red light at 655 nm wavelength. Laser autofluorescence intensity readings of examined root surfaces were scored on a 0-99 scale, with duplicate assessments performed using the laser probe tip directed both perpendicular and parallel to evaluated tooth root surfaces. Pearson correlation coefficients of untransformed measurements, and kappa analysis of data dichotomized with a >40 autofluorescence intensity threshold, were calculated to assess intra- and inter-examiner reproducibility of the laser device. Mean autofluorescence intensity scores of calculus-positive and calculus-free root surfaces were evaluated with the Student's t -test. Excellent intra- and inter-examiner reproducibility was found for DIAGNOdent laser autofluorescence intensity measurements, with Pearson correlation coefficients above 94%, and kappa values ranging between 0.96 and 1.0, for duplicate readings taken with both laser probe tip orientations. Significantly higher autofluorescence intensity values were measured when the laser probe tip was directed perpendicular, rather than parallel, to tooth root surfaces. However, calculus-positive roots, particularly with calculus in markedly-raised ledges, yielded significantly greater mean DIAGNOdent laser autofluorescence intensity scores than calculus-free surfaces, regardless of probe tip orientation. DIAGNOdent autofluorescence intensity values >40 exhibited a stronger association with calculus (36.6 odds ratio) then measurements of ≥5 (20.1 odds ratio) when the laser probe tip was advanced parallel to root surfaces. Excellent

  14. InGaAs/GaAs frequency tunable twin-guide quantum-well laser designed for steerable surface emission

    Science.gov (United States)

    Rosenberger, Matthias; Koeck, Anton; Gmachl, Claire F.; Gornik, Erich; Riechert, Henning; Bernklau, D.

    1993-11-01

    Based on a frequency tunable twin-guide (TTG) InGaAs/GaAs multiple quantum well (MQW) laser structure, we developed a novel design concept for a surface emitting laser device enabling spatial beam steering. Utilizing a change in the refractive index of the parallel monolithically integrated modulator diode due to carrier injection, we observe a continuous emission frequency (wavelength) shift up to (Delta) f equals 85 GHz ((Delta) (lambda) equals -0.35 nm). For this preliminary structure the experimental results are consistent with our model calculations. Based on the theoretical model, for an optimized device a tuning range of (Delta) f equals 1600 GHz ((Delta) (lambda) >= 5 nm) is expected. For the novel surface emitting device design, we make use of an additional structure on top of the TTG laser including a second waveguide and a grating. This will enable a wavelength dependent surface emission angle, i.e., continuous beam steering, by coupling the laser and the surface mode. A calculational model was developed to estimate the steering characteristics in dependence on the dielectric device structure including mode guiding and the surface grating shape.

  15. Nickel-like spectrum of platinum emitted from a laser-produced plasma

    International Nuclear Information System (INIS)

    Zigler, A.; Zmora, H.; Spector, N.; Klapisch, M.; Schwob, J.L.; Bar-Shalom, A.

    1980-01-01

    The X-ray spectrum of a laser-produced platinum plasma in the range 4.8-6.4 Angstroem has been obtained. The lines belonging to the 3d-4p and 3d-4f transitions in the Nil isoelectronic sequence have been identified. (orig.)

  16. Laser photoacoustic analysis of trace gases emitted during electro-knife surgery on human tissue

    Science.gov (United States)

    Sigrist, Markus W.; Naegele, Markus; Lauchenauer, Daniel; Hollmann, Ralph; Kammer, Erich

    2002-06-01

    We present a fully automated mobile laser spectrometer with photoacoustic (PA) detection for trace gas analysis. A novel PA cell design permits extracavity measurements with detection limits in the sub-ppb concentration range. The setup also allows measurements with low-power sources such as quantum cascade lasers (QCL). The multicomponent capability as an important feature of the spectrometer is realized by the implementation of two sealed-off CO2 lasers with 12CO2 and 13CO2 fillings covering the spectral range between 868 cm-1 and 1088 cm-1 with 132 laser lines. The performance is demonstrated with measurements on air samples with a priori unknown composition. In particular we report on the analysis of samples taken during surgery on human breast tissue with a high-frequency (HF) electro-knife in a hospital. Besides advantages of less bleeding and lower risk of infection, the drawback of this technique is the generated fume, which in general contains dozens of species at low concentrations, some of them presumably harmful to the patient and the medical team. Our analysis of an unfiltered fume sample revealed a total of 15 species. Most of their concentrations were below the allowed workplace concentrations (if at all available). 2-Furan-carboxaldehyde (C5H4O2), however, exceeded this value of 2 ppm considerably.

  17. Biocompatibility of Er:YSGG laser radiated root surfaces

    Science.gov (United States)

    Benthin, Hartmut; Ertl, Thomas P.; Schmidt, Dirk; Purucker, Peter; Bernimoulin, J.-P.; Mueller, Gerhard J.

    1996-01-01

    Pulsed Er:YAG and Er:YSGG lasers are well known to be effective instruments for the ablation of dental hard tissues. Developments in the last years made it possible to transmit the laser radiation at these wavelengths with flexible fibers. Therefore the application in the periodontal pocket may be possible. The aim of this study was to evaluate the in-vitro conditions to generate a bioacceptable root surface. Twenty extracted human teeth, stored in an antibiotic solution, were conventionally scaled, root planed and axially separated into two halves. Two main groups were determined. With the first group laser radiation was carried out without and in the second group with spray cooling. The laser beam was scanned about root surface areas. Laser parameters were varied in a selected range. The biocompatibility was measured with the attachment of human gingival fibroblasts and directly compared to conventionally treated areas of the root surfaces. The fibroblasts were qualified and counted in SEM investigations. On conventionally treated areas gingival fibroblasts show the typical uniform cover. In dependance on the root roughness after laser treatment the fibroblasts loose the typical parallel alignment to the root surface. With spray cooling a better in-vitro attachment could be obtained. Without spray cooling the higher increase in temperature conducted to less bioacceptance by the human gingival fibroblasts to the root surface. These results show the possibility of producing bioacceptable root surfaces with pulsed laser radiation in the range of very high water absorption near 3 micrometer.

  18. Measuring and modeling near-surface reflected and emitted radiation fluxes at the FIFE site

    Science.gov (United States)

    Blad, Blaine L.; Walter-Shea, Elizabeth A.; Starks, Patrick J.; Vining, Roel C.; Hays, Cynthia J.; Mesarch, Mark A.

    1990-01-01

    Information is presented pertaining to the measurement and estimation of reflected and emitted components of the radiation balance. Information is included about reflectance and transmittance of solar radiation from and through the leaves of some grass and forb prairie species, bidirectional reflectance from a prairie canopy is discussed and measured and estimated fluxes are described of incoming and outgoing longwave and shortwave radiation. Results of the study showed only very small differences in reflectances and transmittances for the adaxial and abaxial surfaces of grass species in the visible and infrared wavebands, but some differences in the infrared wavebands were noted for the forbs. Reflectance from the prairie canopy changed as a function of solar and view zenith angles in the solar principal plane with definite asymmetry about nadir. The surface temperature of prairie canopies was found to vary by as much as 5 C depending on view zenith and azimuth position and on the solar azimuth. Aerodynamic temperature calculated from measured sensible heat fluxes ranged from 0 to 3 C higher than nadir-viewed temperatures. Models were developed to estimate incoming and reflected shortwave radiation from data collected with a Barnes Modular Multiband Radiometer. Several algorithms for estimating incoming longwave radiation were evaluated and compared to actual measures of that parameter. Net radiation was calculated using the estimated components of the shortwave radiation streams, determined from the algorithms developed, and from the longwave radiation streams provided by the Brunt, modified Deacon, and the Stefan-Boltzmann models. Estimates of net radiation were compared to measured values and found to be within the measurement error of the net radiometers used in the study.

  19. Influence of Light Emitting Diode-Derived Blue Light Overexposure on Mouse Ocular Surface.

    Science.gov (United States)

    Lee, Hyo Seok; Cui, Lian; Li, Ying; Choi, Ji Suk; Choi, Joo-Hee; Li, Zhengri; Kim, Ga Eon; Choi, Won; Yoon, Kyung Chul

    2016-01-01

    To investigate the influence of overexposure to light emitting diode (LED)-derived light with various wavelengths on mouse ocular surface. LEDs with various wavelengths were used to irradiate C57BL/6 mice at an energy dose of 50 J/cm2, twice a day, for 10 consecutive days. The red, green, and blue groups represented wavelengths of 630 nm, 525 nm, and 410 nm, respectively. The untouched group (UT) was not exposed to LED light and served as the untreated control. Tear volume, tear film break-up time (TBUT), and corneal fluorescein staining scores were measured on days 1, 3, 5, 7, and 10. Levels of interferon (IFN)-γ, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α were measured in the cornea and conjunctiva using a multiplex immunobead assay at day 10. Levels of malondialdehyde (MDA) were measured with an enzyme-linked immunosorbent assay. Flow cytometry, 2'7'-dichlorofluorescein diacetate (DCF-DA) assay, histologic analysis, immunohistochemistry with 4-hydroxynonenal, and terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) staining were also performed. TBUT of the blue group showed significant decreases at days 7 and 10, compared with the UT and red groups. Corneal fluorescein staining scores significantly increased in the blue group when compared with UT, red, and green groups at days 5, 7, and 10. A significant increase in the corneal levels of IL-1β and IL-6 was observed in the blue group, compared with the other groups. The blue group showed significantly increased reactive oxygen species production in the DCF-DA assay and increased inflammatory T cells in the flow cytometry. A significantly increased TUNEL positive cells was identified in the blue group. Overexposure to blue light with short wavelengths can induce oxidative damage and apoptosis to the cornea, which may manifest as increased ocular surface inflammation and resultant dry eye.

  20. CO2 laser photoacoustic detection of ammonia emitted by ceramic industries.

    Science.gov (United States)

    Sthel, M S; Schramm, D U; Lima, G R; Carneiro, L; Faria, R T; Castro, M P P; Alexandre, J; Toledo, R; Silva, M G; Vargas, H

    2011-01-01

    A homemade photoacoustic spectrometer has been constructed for monitoring gas emission from several sources. Numerous air pollutant gases are emitted exhaust of industries, vehicles and power plants. The photoacoustic technique is extremely sensitive and selective in detecting various gases. This work focuses on the gas emitted by the ceramic industry in northern Rio de Janeiro State in Brazil, the ceramic industry plays a remarkable role in the economy activity of this region, in recent years, this region developed into a significant red ceramic complex. The potential impact on the atmospheric environment of the region due to gaseous pollutant emissions from these anthropogenic sources needs to be evaluated. In this work we identified NH3 present in the samples collected in the kiln of a ceramic plant, in the concentration range of 33-52 ppmV. The ammonia gas present in our collected samples might come from the excess nitrogen in the manure soil from where the ceramic material was extracted. This soil was used for the sugarcane culture which is another important economic activity of this region. Copyright © 2010 Elsevier B.V. All rights reserved.

  1. CO 2 laser photoacoustic detection of ammonia emitted by ceramic industries

    Science.gov (United States)

    Sthel, M. S.; Schramm, D. U.; Lima, G. R.; Carneiro, L.; Faria, R. T., Jr.; Castro, M. P. P.; Alexandre, J.; Toledo, R.; Silva, M. G.; Vargas, H.

    2011-01-01

    A homemade photoacoustic spectrometer has been constructed for monitoring gas emission from several sources. Numerous air pollutant gases are emitted exhaust of industries, vehicles and power plants. The photoacoustic technique is extremely sensitive and selective in detecting various gases. This work focuses on the gas emitted by the ceramic industry in northern Rio de Janeiro State in Brazil, the ceramic industry plays a remarkable role in the economy activity of this region, in recent years, this region developed into a significant red ceramic complex. The potential impact on the atmospheric environment of the region due to gaseous pollutant emissions from these anthropogenic sources needs to be evaluated. In this work we identified NH 3 present in the samples collected in the kiln of a ceramic plant, in the concentration range of 33-52 ppmV. The ammonia gas present in our collected samples might come from the excess nitrogen in the manure soil from where the ceramic material was extracted. This soil was used for the sugarcane culture which is another important economic activity of this region.

  2. Compact environmental spectroscopy using advanced semiconductor light-emitting diodes and lasers

    Energy Technology Data Exchange (ETDEWEB)

    Fritz, I.J.; Klem, J.F.; Hafich, M.J. [and others

    1997-04-01

    This report summarizes research completed under a Laboratory Directed Research and Development program funded for part of FY94, FY95 and FY96. The main goals were (1) to develop novel, compound-semiconductor based optical sources to enable field-based detection of environmentally important chemical species using miniaturized, low-power, rugged, moderate cost spectroscopic equipment, and (2) to demonstrate the utility of near-infrared spectroscopy to quantitatively measure contaminants. Potential applications would include monitoring process and effluent streams for volatile organic compound detection and sensing head-space gasses in storage vessels for waste management. Sensing is based on absorption in the 1.3-1.9 {mu}m band from overtones of the C-H, N-H and O-H stretch resonances. We describe work in developing novel broadband light-emitting diodes emitting over the entire 1.4-1.9 {mu}m wavelength range, first using InGaAs quantum wells, and second using a novel technique for growing digital-alloy materials in the InAlGaAs material system. Next we demonstrate the utility of near-infrared spectroscopy for quantitatively determining contamination of soil by motor oil. Finally we discuss the separability of different classes of organic compounds using near-infrared spectroscopic techniques.

  3. Laser surface modification of polyethersulfone films: effect of laser wavelength on biocompatibility

    International Nuclear Information System (INIS)

    Pazokian, H; Jelvani, S; Mollabashi, M; Barzin, J

    2013-01-01

    In this paper laser ablation of polyethersulfone (PES) films regarding to the change in biocompatibility of the surface is investigated at 3 different wavelengths of 193nm (ArF), 248 nm (KrF) and 308 nm (XeCl). The optimum laser fluence and number of pulses for the improvement of the surface biocompatibility is found by examination of the surface behavior in contact with platelets and fibroblasts cells at 3 wavelengths. These biological modifications are explained by alteration of the surface morphology and chemistry following irradiation. The results show that the KrF laser is the best choice for treatment of PES in biological applications.

  4. Inverse calculation of power density for laser surface treatment

    NARCIS (Netherlands)

    Römer, Gerardus Richardus, Bernardus, Engelina; Meijer, J.

    2000-01-01

    Laser beam surface treatment requires a well-defined temperature profile. In this paper an analytic method is presented to solve the inverse problem of heat conduction in solids, based on the 2-dimensional Fourier transform. As a result, the required power density profile of the laser beam can be

  5. Laser-assisted surface cleaning of metallic components

    Indian Academy of Sciences (India)

    2014-02-09

    Feb 9, 2014 ... Keywords. YAG laser, oxide layer, contamination, cleaning. Abstract. Removal of a thin oxide layer from a tungsten ribbon and ThO2 particulates from zircaloy surface was achieved using a pulsed Nd:YAG laser. The removal mechanism of the oxide layer from the tungsten ribbon was identified as spallation ...

  6. Laser induced damage threshold on metallic surfaces during laser cleaning

    CSIR Research Space (South Africa)

    Labuschagne, K

    2005-07-01

    Full Text Available In view of the importance of material degradation during laser irradiation, which can have deleterious effects on mechanical and chemical properties of a component, a study was initiated to determine a threshold at which damage takes place during...

  7. Characterization of electrically-active defects in ultraviolet light-emitting diodes with laser-based failure analysis techniques

    International Nuclear Information System (INIS)

    Miller, Mary A.; Tangyunyong, Paiboon; Cole, Edward I.

    2016-01-01

    Laser-based failure analysis techniques demonstrate the ability to quickly and non-intrusively screen deep ultraviolet light-emitting diodes (LEDs) for electrically-active defects. In particular, two laser-based techniques, light-induced voltage alteration and thermally-induced voltage alteration, generate applied voltage maps (AVMs) that provide information on electrically-active defect behavior including turn-on bias, density, and spatial location. Here, multiple commercial LEDs were examined and found to have dark defect signals in the AVM indicating a site of reduced resistance or leakage through the diode. The existence of the dark defect signals in the AVM correlates strongly with an increased forward-bias leakage current. This increased leakage is not present in devices without AVM signals. Transmission electron microscopy analysis of a dark defect signal site revealed a dislocation cluster through the pn junction. The cluster included an open core dislocation. Even though LEDs with few dark AVM defect signals did not correlate strongly with power loss, direct association between increased open core dislocation densities and reduced LED device performance has been presented elsewhere [M. W. Moseley et al., J. Appl. Phys. 117, 095301 (2015)

  8. Formation of multiscale surface structures on nickel via above surface growth and below surface growth mechanisms using femtosecond laser pulses.

    Science.gov (United States)

    Zuhlke, Craig A; Anderson, Troy P; Alexander, Dennis R

    2013-04-08

    The formation of self-organized micro- and nano-structured surfaces on nickel via both above surface growth (ASG) and below surface growth (BSG) mechanisms using femtosecond laser pulse illumination is reported. Detailed stepped growth experiments demonstrate that conical mound-shaped surface structure development is characterized by a balance of growth mechanisms including scattering from surface structures and geometric effects causing preferential ablation of the valleys, flow of the surface melt, and redeposition of ablated material; all of which are influenced by the laser fluence and the number of laser shots on the sample. BSG-mound formation is dominated by scattering, while ASG-mound formation is dominated by material flow and redeposition. This is the first demonstration to our knowledge of the use of femtosecond laser pulses to fabricate metallic surface structures that rise above the original surface. These results are useful in understanding the details of multi-pulse femtosecond laser interaction with metals.

  9. Pulsed laser stereophotography of plasmas and dynamically moving surfaces

    International Nuclear Information System (INIS)

    Paisley, D.L.

    1987-01-01

    A pulsed laser is used as a light source for illuminating the surface of a dynamic event of 3 mm//μs. At a predetermined time during the dynamic action, a stereo camera is used to record a pair of images of the dynamically moving surface. The stereoimage pair can be quantified for surface contour

  10. Laser surface alloying on aluminum and its alloys: A review

    Science.gov (United States)

    Chi, Yiming; Gu, Guochao; Yu, Huijun; Chen, Chuanzhong

    2018-01-01

    Aluminum and its alloys have been widely used in aerospace, automotive and transportation industries owing to their excellent properties such as high specific strength, good ductility and light weight. Surface modification is of crucial importance to the surface properties of aluminum and its alloys since high coefficient of friction, wear characteristics and low hardness have limited their long term performance. Laser surface alloying is one of the most effective methods of producing proper microstructure by means of non-equilibrium solidification which results from rapid heating and cooling. In this paper, the influence of different processing parameters, such as laser power and scanning velocity is discussed. The developments of various material systems including ceramics, metals or alloys, and metal matrix composites (MMCs) are reviewed. The microstructure, hardness, wear properties and other behaviors of laser treated layer are analyzed. Besides, the existing problems during laser surface treatment and the corresponding solutions are elucidated and the future developments are predicted.

  11. Thomson parabola spectrometer for energetic ions emitted from sub-ns laser generated plasmas

    Czech Academy of Sciences Publication Activity Database

    Cutroneo, M.; Torrisi, L.; Andó, L.; Cavallaro, S.; Ullschmied, Jiří; Krása, Josef; Margarone, Daniele; Velyhan, Andriy; Krouský, Eduard; Pfeifer, Miroslav

    2013-01-01

    Roč. 53, č. 2 (2013), s. 138-141 ISSN 1210-2709 R&D Projects: GA MŠk LM2010014 Institutional research plan: CEZ:AV0Z20430508; CEZ:AV0Z10100523 Keywords : Thomson parabola spectrometer * high intensity laser * focal position * Opera 3D Tosca code * simulation Subject RIV: BL - Plasma and Gas Discharge Physics; BL - Plasma and Gas Discharge Physics (FZU-D) http://ctn.cvut.cz/ap/index.php?idissue=85

  12. Laser ablation of liquid surface in air induced by laser irradiation through liquid medium

    Science.gov (United States)

    Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro; Nakahara, Motonao

    2010-10-01

    The pulse laser ablation of a liquid surface in air when induced by laser irradiation through a liquid medium has been experimentally investigated. A supersonic liquid jet is observed at the liquid-air interface. The liquid surface layer is driven by a plasma plume that is produced by laser ablation at the layer, resulting in a liquid jet. This phenomenon occurs only when an Nd:YAG laser pulse (wavelength: 1064 nm) is focused from the liquid onto air at a low fluence of 20 J/cm2. In this case, as Fresnel’s law shows, the incident and reflected electric fields near the liquid surface layer are superposed constructively. In contrast, when the incident laser is focused from air onto the liquid, a liquid jet is produced only at an extremely high fluence, several times larger than that in the former case. The similarities and differences in the liquid jets and atomization processes are studied for several liquid samples, including water, ethanol, and vacuum oil. The laser ablation of the liquid surface is found to depend on the incident laser energy and laser fluence. A pulse laser light source and high-resolution film are required to observe the detailed structure of a liquid jet.

  13. Small signal modulation characteristics of red-emitting (λ = 610 nm) III-nitride nanowire array lasers on (001) silicon

    KAUST Repository

    Jahangir, Shafat

    2015-02-16

    The small signal modulation characteristics of an InGaN/GaN nanowire array edge- emitting laser on (001) silicon are reported. The emission wavelength is 610 nm. Lattice matched InAlN cladding layers were incorporated in the laser heterostructure for better mode confinement. The suitability of the nanowire lasers for use in plastic fiber communication systems with direct modulation is demonstrated through their modulation bandwidth of f-3dB,max = 3.1 GHz, very low values of chirp (0.8 Å) and α-parameter, and large differential gain (3.1 × 10-17 cm2).

  14. Picosecond laser induced periodic surface structure on copper thin films

    International Nuclear Information System (INIS)

    Huynh, Thi Trang Dai; Petit, Agnès; Semmar, Nadjib

    2014-01-01

    LIPSS (Laser Induced Periodic Surface Structure) formation on copper thin films induced by a picosecond laser beam (Nd:YAG laser at 266 nm, 42 ps and 10 Hz) was studied experimentally. Copper thin films were deposited on glass and silicon substrates by magnetron sputtering. The surface modifications of irradiated zones were analyzed by scanning electron microscopy. Two distinct types of LIPSS were identified with respect to the laser fluence (F), number of laser shots (N) and substrate material. Namely, with a number of laser shots (1000 2 2 ), Low Spatial Frequency LIPSS (LSFL with a spatial period of Λ ∼ 260 nm and an orientation perpendicular to polarization) and High Spatial Frequency LIPSS (HSFL with a spatial period of Λ ∼ 130 nm and an orientation parallel to the polarization) were observed. The regime of regular spikes formation was determined for N ≥ 1000. Moreover, the 2D-map of the relationship among LIPSS formation, laser fluence and number of laser shots on copper thin film with two different substrates was established. A physics interpretation of regular spikes and LIPSS formation on copper thin film induced by ps laser with overlapping multi-shots is proposed based on experimental data and the theory of Plateau-Rayleigh instability.

  15. Laser surface and subsurface modification of sapphire using femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Eberle, G., E-mail: eberle@iwf.mavt.ethz.ch [Institute of Machine Tools and Manufacturing, ETH Zurich, Leonhardstrasse 21, 8092 Zurich (Switzerland); Schmidt, M. [Chair of Photonic Technologies, University of Erlangen-Nuremberg, Konrad-Zuse-Strasse 3-5, 91052 Erlangen (Germany); Pude, F. [Inspire AG, Technoparkstrasse 1, 8005 Zurich (Switzerland); Wegener, K. [Institute of Machine Tools and Manufacturing, ETH Zurich, Leonhardstrasse 21, 8092 Zurich (Switzerland); Inspire AG, Technoparkstrasse 1, 8005 Zurich (Switzerland)

    2016-08-15

    Highlights: • Single and multipulse ablation threshold of aluminium oxide is determined. • Laser ablation, and in-volume modification followed by wet etching are demonstrated. • Quality following laser processing and laser-material interactions are studied. - Abstract: Two methods to process sapphire using femtosecond laser pulses are demonstrated, namely ablation (surface), and in-volume laser modification followed by wet etching (subsurface). Firstly, the single and multipulse ablation threshold is determined and compared with previous literature results. A unique application of ablation is demonstrated by modifying the entrance aperture of water jet orifices. Laser ablation exhibits advantages in terms of geometric flexibility and resolution, however, defects in the form of edge outbreaks and poor surface quality are evident. Secondly, the role of material transformation, polarisation state and formation of multi-focus structures after in-volume laser modification is investigated in order to explain their influence during the wet etching process. Laser scanning and electron microscopy as well as electron backscatter diffraction measurements supported by ion beam polishing are used to better understand quality and laser-material interactions of the two demonstrated methods of processing.

  16. Robust non-wetting PTFE surfaces by femtosecond laser machining.

    Science.gov (United States)

    Liang, Fang; Lehr, Jorge; Danielczak, Lisa; Leask, Richard; Kietzig, Anne-Marie

    2014-08-08

    Nature shows many examples of surfaces with extraordinary wettability,which can often be associated with particular air-trapping surface patterns. Here,robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE). The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters,both of which make it a strong candidate for industrial applications.

  17. Robust Non-Wetting PTFE Surfaces by Femtosecond Laser Machining

    Directory of Open Access Journals (Sweden)

    Fang Liang

    2014-08-01

    Full Text Available Nature shows many examples of surfaces with extraordinary wettability, which can often be associated with particular air-trapping surface patterns. Here, robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE. The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters, both of which make it a strong candidate for industrial applications.

  18. Surface hardening using cw CO2 laser: laser heat treatment, modelation, and experimental work

    Science.gov (United States)

    Muniz, German; Alum, Jorge

    1996-02-01

    In the present work are given the results of the application of laser metal surface hardening techniques using a cw carbon dioxide laser as an energy source on steel 65 G. The laser heat treatment results are presented theoretically and experimentally. Continuous wave carbon dioxide laser of 0.6, 0.3, and 0.4 kW were used. A physical model for the descriptions of the thermophysical laser metal interactions process is given and a numerical algorithm is used to solve this problem by means of the LHT code. The results are compared with the corresponding experimental ones and a very good agreement is observed. The LHT code is able to do predictions of transformation hardening by laser heating. These results will be completed with other ones concerning laser alloying and cladding presented in a second paper.

  19. Surface characterization and wear behaviour of laser surface melted AISI 316L stainless steel

    CSIR Research Space (South Africa)

    Kumar, A

    2010-01-01

    Full Text Available The present study concerns an in depth investigation of the influence of laser surface melting of AISI 316L stainless steel using Ar and N2 as shrouding atmosphere. Laser surface melting has been carried out using a 5 kW continuous wave (CW) fibre...

  20. Laser spectroscopy and photochemistry on metal surfaces, pt.2

    CERN Document Server

    Dai, HL

    1995-01-01

    Using lasers to induce and probe surface processes has the advantages of quantum state specificity, species selectivity, surface sensitivity, fast time-resolution, high frequency resolution, and accessibility to full pressure ranges. These advantages make it highly desirable to use light to induce, control, or monitor surface chemical and physical processes. Recent applications of laser based techniques in studying surface processes have stimulated new developments and enabled the understanding of fundamental problems in energy transfer and reactions. This volume will include discussions on sp

  1. Laser spectroscopy and photochemistry on metal surfaces, pt.1

    CERN Document Server

    Dai, HL

    1995-01-01

    Using lasers to induce and probe surface processes has the advantages of quantum state specificity, species selectivity, surface sensitivity, fast time-resolution, high frequency resolution, and accessibility to full pressure ranges. These advantages make it highly desirable to use light to induce, control, or monitor surface chemical and physical processes. Recent applications of laser based techniques in studying surface processes have stimulated new developments and enabled the understanding of fundamental problems in energy transfer and reactions. This volume will include discussions on sp

  2. Laser surface alloying of aluminium-transition metal alloys

    International Nuclear Information System (INIS)

    Almeida, A.; Vilar, R.

    1998-01-01

    Laser surface alloying has been used as a tool to produce hard and corrosion resistant Al-transition metal (TM) alloys. Cr and Mo are particularly interesting alloying elements to produce stable high-strength alloys because they present low diffusion coefficients and solid solubility in Al. To produce Al-TM surface alloys a two-step laser process was developed: firstly, the material is alloyed using low scanning speed and secondly, the microstructure is modified by a refinement step. This process was used in the production of Al-Cr, Al-Mo and Al-Mo and Al-Nb surface alloys by alloying Cr, Mo or Nb powder into an Al and 7175 Al alloy substrate using a CO 2 laser . This paper presents a review of the work that has been developed at Instituto Superior Tecnico on laser alloying of Al-TM alloy, over the last years. (Author) 16 refs

  3. Improved ion acceleration via laser surface plasma waves excitation

    Energy Technology Data Exchange (ETDEWEB)

    Bigongiari, A. [CEA/DSM/LSI, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); TIPS/LULI, Université Paris 6, CNRS, CEA, Ecole Polytechnique, 3, rue Galilée, 94200 Ivry-sur-Seine (France); Raynaud, M. [CEA/DSM/LSI, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); Riconda, C. [TIPS/LULI, Université Paris 6, CNRS, CEA, Ecole Polytechnique, 3, rue Galilée, 94200 Ivry-sur-Seine (France); Héron, A. [CPHT, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France)

    2013-05-15

    The possibility of enhancing the emission of the ions accelerated in the interaction of a high intensity ultra-short (<100 fs) laser pulse with a thin target (<10λ{sub 0}), via surface plasma wave excitation is investigated. Two-dimensional particle-in-cell simulations are performed for laser intensities ranging from 10{sup 19} to 10{sup 20} Wcm{sup −2}μm{sup 2}. The surface wave is resonantly excited by the laser via the coupling with a modulation at the target surface. In the cases where the surface wave is excited, we find an enhancement of the maximum ion energy of a factor ∼2 compared to the cases where the target surface is flat.

  4. True Yellow Light-Emitting Diodes as Phosphor for Tunable Color-Rendering Index Laser-Based White Light

    KAUST Repository

    Janjua, Bilal

    2016-10-11

    An urgent challenge for the lighting research community is the lack of efficient optical devices emitting in between 500 and 600 nm, resulting in the “green-yellow gap”. In particular, true green (∼555 nm) and true yellow (∼590 nm), along with blue and red, constitute four technologically important colors. The III-nitride material system, being the most promising choice of platform to bridge this gap, still suffers from high dislocation density and poor crystal quality in realizing high-power, efficient devices. Particularly, the high polarization fields in the active region of such 2D quantum confined structures prevent efficient recombination of carriers. Here we demonstrate a true yellow nanowire (NW) light emitting diode (LED) with peak emission of 588 nm at 29.5 A/cm2 (75 mA in a 0.5 × 0.5 mm2 device) and a low turn-on voltage of ∼2.5 V, while having an internal quantum efficiency of 39%, and without “efficiency droop” up to an injection current density of 29.5 A/cm2. By mixing yellow light from a NW LED in reflective configuration with that of a red, green, and blue laser diode (LD), white light with a correlated color temperature of ∼6000 K and color-rendering index of 87.7 was achieved. The nitride-NW-based device offers a robust, long-term stability for realizing yellow light emitters for tunable color-rendering index solid-state lighting, on a scalable, low-cost, foundry-compatible titanium/silicon substrate, suitable for industry uptake.

  5. Ultrabroad linewidth orange-emitting nanowires LED for high CRI laser-based white lighting and gigahertz communications

    KAUST Repository

    Janjua, Bilal

    2016-08-10

    Group-III-nitride laser diode (LD)-based solid-state lighting device has been demonstrated to be droop-free compared to light-emitting diodes (LEDs), and highly energy-efficient compared to that of the traditional incandescent and fluorescent white light systems. The YAG:Ce3+ phosphor used in LD-based solid-state lighting, however, is associated with rapid degradation issue. An alternate phosphor/LD architecture, which is capable of sustaining high temperature, high power density, while still intensity- and bandwidth-tunable for high color-quality remained unexplored. In this paper, we present for the first time, the proof-of-concept of the generation of high-quality white light using an InGaN-based orange nanowires (NWs) LED grown on silicon, in conjunction with a blue LD, and in place of the compound-phosphor. By changing the relative intensities of the ultrabroad linewidth orange and narrow-linewidth blue components, our LED/LD device architecture achieved correlated color temperature (CCT) ranging from 3000 K to above 6000K with color rendering index (CRI) values reaching 83.1, a value unsurpassed by the YAG-phosphor/blue-LD counterpart. The white-light wireless communications was implemented using the blue LD through on-off keying (OOK) modulation to obtain a data rate of 1.06 Gbps. We therefore achieved the best of both worlds when orange-emitting NWs LED are utilized as “active-phosphor”, while blue LD is used for both color mixing and optical wireless communications.

  6. Laser surface processing with controlled nitrogen-argon concentration levels for regulated surface life time

    Science.gov (United States)

    Obeidi, M. Ahmed; McCarthy, E.; Brabazon, D.

    2018-03-01

    Laser surface modification can be used to enhance the mechanical properties of a material, such as hardness, toughness, fatigue strength, and corrosion resistance. Surface nitriding is a widely used thermochemical method of surface modification, in which nitrogen is introduced into a metal or other material at an elevated temperature within a furnace. It is used on parts where there is a need for increased wear resistance, corrosion resistance, fatigue life, and hardness. Laser nitriding is a novel method of nitriding where the surface is heated locally by a laser, either in an atmosphere of nitrogen or with a jet of nitrogen delivered to the laser heated site. It combines the benefits of laser modification with those of nitriding. Recent work on high toughness tool steel samples has shown promising results due to the increased nitrogen gas impingement onto the laser heated region. Increased surface activity and nitrogen adsorption was achieved which resulted in a deeper and harder surface compared to conventional hardening methods. In this work, the effects of the laser power, pulse repetition frequency, and overlap percentage on laser surface treatment of 316 L SST steel samples with an argon-nitrogen jet will be presented. Resulting microstructure, phase type, microhardness, and wear resistance are presented.

  7. Laser treatment of boron carbide surfaces: Metallurgical and morphological examinations

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsilbas@kfupm.edu.sa; Karatas, C.

    2014-08-01

    Highlights: • Dense layer with fine grains is formed at surface. • Irregular shaped grains and dendrites are formed below dense layer. • Assisting gas forms nitride species (BN and BC{sub 2}N) at surface. • Fracture toughness of treated surface reduces because of high hardness. • Residual stress is compressive and the maximum residual stress is about 0.9 GPa. - Abstract: Laser treatment of B{sub 4}C tile surfaces is carried out under high pressure nitrogen assisting gas environment. Morphological and metallurgical changes in the laser treated layer are examined by incorporating scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. Microhardness and fracture toughness of the laser treated surface are determined from the indentation data. Residual stress formed at the treated surface is obtained by using X-ray diffraction technique. It is found that laser treated surface is free from large scale asperities including cracks and voids; however, some locally scattered shallow cavities with 1.5–2 μm widths are formed at the surface because of high temperature processing. Dense layer, consisting of fine grains, and formation of nitride species (BN and BC{sub 2}N) enhance microhardness and lower fracture toughness at the surface. Residual stress formed in the treated layer is compressive and the maximum residual stress is in the order of −0.9 GPa.

  8. Laser surface modification of stainless steels for cavitation erosion resistance

    Science.gov (United States)

    Kwok, Chi Tat

    1999-12-01

    Austenitic stainless steel UNS S31603 (Fe -17.6Cr -11.2Ni -2.5Mo -1.4Mn -0.4Si -0.03C) has higher pitting corrosion resistance but lower cavitation erosion resistance than that of UNS S30400. This is because of its lower tendency for strain induced martensitic transformation and higher stacking fault energy as compared with those of UNS S30400. In order to improve its cavitation erosion resistance, surface modification of S31603 was performed by laser surface melting and laser surface alloying using a 2-kW CW Nd-YAG laser and a 3-kW CW CO2 laser. For laser surface melting, austenitic stainless steel UNS S30400, super duplex stainless steel UNS S32760 and martensitic stainless steel UNS S42000 were also investigated for comparison purpose. For laser surface alloying, alloying materials including various elements (Co, Cr, Ni, Mo, Mn, Si & C), alloys (AlSiFe & NiCrSiB), ceramics (Si3N 4, SiC, Cr3C2, TiC, CrB & Cr2O 3) and alloys-ceramics (Co-WC, Ni-WC, Ni-Al2O3, Ni-Cr2C3) were used to modify the surface of S31603. The alloyed surface was achieved first by flame spraying or pre-placing of the alloy powder on the S31603 surface and then followed by laser surface remelting. The cavitation erosion characteristics of laser surface modified specimens in 3.5% NaCl solution at 23°C were studied by means of a 20-kHz ultrasonic vibrator at a peak-to-peak amplitude of 30 mum. In addition, their pitting corrosion behaviour was evaluated by electrochemical techniques. The microstructures, compositions, phase changes and damage mechanisms under cavitation erosion were investigated by optical microscopy, SEM, EDAX and X-ray diffractometry. Mechanical properties such as microhardness profile were also examined. The cavitation erosion resistance Re (reciprocal of the mean depth of penetration rate) of laser surface melted S31603 was found to be improved by 22% and was attributed to the existence of tensile residual stress. Improvement on the Re of S42000 was found to be 8.5 times

  9. Laser machining micro-structures on diamond surface with a sub-nanosecond pulsed laser

    Science.gov (United States)

    Wu, Mingtao; Guo, Bing; Zhao, Qingliang

    2018-02-01

    Micro-structure surface on diamond material is widely used in a series of industrial and scientific applications, such as micro-electromechanical systems (MEMS), nanoelectromechanical systems (NEMS), microelectronics, textured or micro-structured diamond machining tools. The efficient machining of micro-structure on diamond surface is urgently demanded in engineering. In this paper, laser machining square micro-structure on diamond surface was studied with a sub-nanosecond pulsed laser. The influences of laser machining parameters, including the laser power, scanning speed, defocusing quantity and scanning pitch, were researched in view of the ablation depth, material removal rate and machined surface topography. Both the ablation depth and material removal rate increased with average laser power. A reduction of the growth rate of the two parameters was induced by the absorption of the laser plasma plume at high laser power. The ablation depth non-linearly decreased with the increasing of the scanning speed while the material removal rate showed an opposite tendency. The increasing of the defocusing quantity induced complex variation of the ablation depth and the material removal rate. The maximum ablation depth and material removal rate were achieved at a defocusing position. The ablation depth and material removal rate oppositely varied about the scanning pitch. A high overlap ratio was meaningful for achieving a smooth micro-structure surface topography. Laser machining with a large defocusing quantity, high laser power and small scanning pitch was helpful for acquiring the desired micro-structure which had a large depth and smooth micro-structure surface topography.

  10. Laser-induced nanoscale superhydrophobic structures on metal surfaces

    NARCIS (Netherlands)

    Radhakrishnan, J.; Pathiraj, B.; Karatay, Elif; Römer, Gerardus Richardus, Bernardus, Engelina; Huis in 't Veld, Bert

    2011-01-01

    The combination of a dual-scale (nano and micro) roughness with an inherent low-surface energy coating material is an essential factor for the development of superhydrophobic surfaces. Ultrashort pulse laser (USPL) machining/structuring is a promising technique for obtaining the dual-scale

  11. Osteogenic potential of laser modified and conditioned titanium zirconium surfaces

    Directory of Open Access Journals (Sweden)

    P David Charles

    2016-01-01

    Full Text Available Statement of Problem: The osseointegration of dental implant is related to their composition and surface treatment. Titanium zirconium (TiZr has been introduced as an alternative to the commercially pure titanium and its alloys as dental implant material, which is attributed to its superior mechanical and biological properties. Surface treatments of TiZr have been introduced to enhance their osseointegration ability; however, reliable, easy to use surface modification technique has not been established. Purpose: The purpose of this study was to evaluate and compare the effect of neodymium-doped yttrium aluminum garnet (Nd-YAG laser surface treatment of TiZr implant alloy on their osteogenic potential. Materials and Methods: Twenty disc-shaped samples of 5 mm diameter and 2 mm height were milled from the TiZr alloy ingot. The polished discs were ultrasonically cleaned in distilled water. Ten samples each were randomly selected as Group A control samples and Group B consisted of Nd-YAG laser surface etched and conditioned test samples. These were evaluated for cellular response. Cellular adhesion and proliferation were quantified, and the results were statistically analyzed using nonparametric analysis. Cellular morphology was observed using electron and epiflurosence microscopy. Results: Nd-YAG laser surface modified and conditioned TiZr samples increased the osteogenic potential. Conclusion: Nd-YAG laser surface modification of TiZr, improves the cellular activity, surface roughness, and wettability, thereby increasing the osteogenic potential.

  12. Diode Laser Surface Alloying of Armor Steel with Tungsten Carbide

    Directory of Open Access Journals (Sweden)

    Janicki D.

    2017-06-01

    Full Text Available Metal matrix composite (MMC surface layers reinforced by WC were fabricated on armor steel ARMOX 500T plates via a laser surface alloying process. The microstructure of the layers was assessed by scanning electron microscopy and X-ray diffraction.

  13. Short range laser obstacle detector. [for surface vehicles using laser diode array

    Science.gov (United States)

    Kuriger, W. L. (Inventor)

    1973-01-01

    A short range obstacle detector for surface vehicles is described which utilizes an array of laser diodes. The diodes operate one at a time, with one diode for each adjacent azimuth sector. A vibrating mirror a short distance above the surface provides continuous scanning in elevation for all azimuth sectors. A diode laser is synchronized with the vibrating mirror to enable one diode laser to be fired, by pulses from a clock pulse source, a number of times during each elevation scan cycle. The time for a given pulse of light to be reflected from an obstacle and received is detected as a measure of range to the obstacle.

  14. Pulsed Nd:YAG laser deposition of indium tin oxide thin films in different gases and organic light emitting device applications

    Energy Technology Data Exchange (ETDEWEB)

    Yong, T.Y. [Faculty of Engineering, Multimedia University, Cyberjaya, 63100 Selangor (Malaysia); Tou, T.Y. [Faculty of Engineering, Multimedia University, Cyberjaya, 63100 Selangor (Malaysia)], E-mail: tytou@mmu.edu.my; Yow, H.K. [Faculty of Engineering, Multimedia University, Cyberjaya, 63100 Selangor (Malaysia); Safran, G. [Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, 1121 Konkoly-Thege ut 29-33, Budapest XII (Hungary)

    2008-04-30

    The microstructures, electrical and optical properties of indium-doped tin oxide (ITO) films, deposited on glass substrates in different background gases by a pulsed Nd:YAG laser, were characterized. The optimal pressure for obtaining the lowest resistivity in ITO thin film is inversely proportional to the molecular weight of the background gases, namely the argon (Ar), oxygen (O{sub 2}), nitrogen (N{sub 2}) and helium (He). While substrate heating to 250 deg. C decreased the ITO resistivity to < 4 x 10{sup -4} {omega} cm, obtaining the optical transmittance of higher than 90% depended mainly on the background gas pressure for O{sub 2} and Ar. Obtaining the lowest ITO resistivity, however, did not beget a high optical transmittance for ITO deposition in N{sub 2} and He. Scanning electron microscope pictures show distinct differences in microstructures due to the background gas: nanostructures when using Ar and N{sub 2} but polycrystalline for using O{sub 2} and He. The ITO surface roughness varied with the deposition distance. The effects on the molecularly doped, single-layer organic light emitting device (OLED) operation and performance were also investigated. Only ITO thin films prepared in O{sub 2} and Ar are suitable for the fabrication OLED with performance comparable to that fabricated on the commercially available, magnetron-sputtered ITO.

  15. GaN nanostructure-based light emitting diodes and semiconductor lasers.

    Science.gov (United States)

    Viswanath, Annamraju Kasi

    2014-02-01

    GaN and related materials have received a lot of attention because of their applications in a number of semiconductor devices such as LEDs, laser diodes, field effect transistors, photodetectors etc. An introduction to optical phenomena in semiconductors, light emission in p-n junctions, evolution of LED technology, bandgaps of various semiconductors that are suitable for the development of LEDs are discussed first. The detailed discussion on photoluminescence of GaN nanostructures is made, since this is crucial to develop optical devices. Fabrication technology of many nanostructures of GaN such as nanowires, nanorods, nanodots, nanoparticles, nanofilms and their luminescence properties are given. Then the optical processes including ultrafast phenomena, radiative, non-radiative recombination, quantum efficiency, lifetimes of excitons in InGaN quantum well are described. The LED structures based on InGaN that give various important colors of red, blue, green, and their design considerations to optimize the output were highlighted. The recent efforts in GaN technology are updated. Finally the present challenges and future directions in this field are also pointed out.

  16. Surface modification of titanium with lasers

    NARCIS (Netherlands)

    Kloosterman, Annejan Bernard

    1998-01-01

    In engineering applications the material demands often differ between bulk and surface. As a matter of fact, it is beneficial to select two different materials with the appropriate properties, for the bulk and the surface, respectively. Therefore, substantial effort has been devoted to the surface

  17. Laser Surface Alloying of Aluminum for Improving Acid Corrosion Resistance

    Science.gov (United States)

    Jiru, Woldetinsay Gutu; Sankar, Mamilla Ravi; Dixit, Uday Shanker

    2018-04-01

    In the present study, laser surface alloying of aluminum with magnesium, manganese, titanium and zinc, respectively, was carried out to improve acid corrosion resistance. Laser surface alloying was conducted using 1600 and 1800 W power source using CO2 laser. Acid corrosion resistance was tested by dipping the samples in a solution of 2.5% H2SO4 for 200 h. The weight loss due to acid corrosion was reduced by 55% for AlTi, 41% for AlMg alloy, 36% for AlZn and 22% for AlMn alloy. Laser surface alloyed samples offered greater corrosion resistance than the aluminum substrate. It was observed that localized pitting corrosion was the major factor to damage the surface when exposed for a long time. The hardness after laser surface alloying was increased by a factor of 8.7, 3.4, 2.7 and 2 by alloying with Mn, Mg, Ti and Zn, respectively. After corrosion test, hardness was reduced by 51% for AlTi sample, 40% for AlMg sample, 41.4% for AlMn sample and 33% for AlZn sample.

  18. Refining femtosecond laser induced periodical surface structures with liquid assist

    International Nuclear Information System (INIS)

    Jiao, L.S.; Ng, E.Y.K.; Zheng, H.Y.

    2013-01-01

    Highlights: ► LIPSS on silicon wafer was made in air and in ethanol environment. ► Ethanol environment produce cleaner surface ripples. ► Ethanol environment decrease spatial wavelength of the LIPSS by 30%. ► More number of pulses produce smaller spatial wavelength in air. ► Number of pulses do not influence spatial wavelength in ethanol environment. - Abstract: Laser induced periodic surface structures were generated on silicon wafer using femtosecond laser. The medium used in this study is both air and ethanol. The laser process parameters such as wavelength, number of pulse, laser fluence were kept constant for both the mediums. The focus of the study is to analyze spatial wavelength. When generating surface structures with air as a medium and same process parameter of the laser, spatial wavelength results showed a 30% increase compared to ethanol. The cleanliness of the surface generated using ethanol showed considerably less debris than in air. The results observed from the above investigation showed that the medium plays a predominant role in the generation of surface structures.

  19. A parametric study of laser interference surface patterning of dental zirconia: Effects of laser parameters on topography and surface quality.

    Science.gov (United States)

    Roitero, Erica; Lasserre, Federico; Anglada, Marc; Mücklich, Frank; Jiménez-Piqué, Emilio

    2017-01-01

    The aim of this work is to generate micrometric linear patterns with different topography on dental grade zirconia by means of UV laser interference and to assess the quality of the produced surface, both in term of the geometry produced and of the surface damage induced in the material. The third harmonic of a Q-switched Nd:YAG laser (355nm, pulse duration of 10ns and repetition rate of 1Hz) was employed to pattern the surface of 3Y-TZP with micrometric-spaced lines. The resulting topography was characterized with White Light Interferometry and Scanning electron microscopy: pattern depth (H), amplitude roughness parameters (S a , filtered-S a ), Fourier spatial analysis and collateral damages were related to laser fluence and number of pulses employed. With our experimental setup, line-patterning of zirconia surfaces can be achieved with periodicities comprised within 5 and 15μm. Tuning laser parameters allows varying independently pattern depth, overall roughness and surface finish. Increasing both fluence and number of pulses allows producing deeper patterns (maximum achievable depth of 1μm). However, increasing the number of pulses has a detrimental effect on the quality of the produced lines. Surface damage (intergranular cracking, open porosity and nano-droplets formation) can be generated, depending on laser parameters. This work provides a parametric analysis of surface patterning by laser interference on 3Y-TZP. Best conditions in terms of quality of the produced pattern and minimum material damage are obtained for low number of pulses with high laser fluence. With the employed method we can produce zirconia materials with controlled topography that are expected to enhance biological response and mechanical performance of dental components. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  20. Air-void embedded GaN-based light-emitting diodes grown on laser drilling patterned sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hao; Li, Yufeng; Wang, Shuai; Feng, Lungang; Xiong, Han; Yun, Feng, E-mail: fyun2010@mail.xjtu.edu.cn [Key Laboratory of Physical Electronics and Devices of Ministry of Education and Shaanxi Provincial Key Laboratory of Photonics and Information Technology, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Solid-State Lighting Engineering Research Center, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Su, Xilin [Shaanxi Supernova Lighting Technology Co., Ltd., Xi’an, Shaanxi 710075 (China)

    2016-07-15

    Air-void structure was introduced in GaN-based blue light-emitting diodes (LED) with one-step growth on periodic laser drilling patterned sapphire substrate, which free of any photolithography or wet/dry etching process. The influence of filling factors (FF) of air-void on crystal quality and optical performance were investigate. Transmission electron microscopy images and micro-Raman spectroscopy indicated that the dislocation was bended and the partially compressed strain was released. When FF was 55.43%, compared with the LED structure grown on flat sapphire substrate, the incorporation of air-void was observed to reduce the compressed stress of ∼20% and the luminance intensity has improved by 128%. Together with the simulated reflection intensity enhancement by finite difference time-domain (FDTD) method, we attribute the enhanced optical performance to the combined contribution of strong back-side light reflection of air-void and better GaN epitaxial quality. This approach provides a simple replacement to the conventional air-void embedded LED process.

  1. Laser techniques for radioactive decontamination gives metallic surfaces

    International Nuclear Information System (INIS)

    Escobar Alracon, L.; Molina, G.; Vizuet Gonzalez, J.

    1998-01-01

    In this work it presented the prototype for system decontamination at diverse component with removable superficial contamination, using the technique gives laser ablation, for the evaporation at the pollutant. It discusses the principle in the fact that system, as well as the different elements that compose it. The are presented the obtained results when irradiating with a laser a surface without radioactive contamination to verify the system operation

  2. Laser assisted fabrication of random rough surfaces for optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Brissonneau, V., E-mail: vincent.brissonneau@im2np.fr [Thales Optronique SA, Avenue Gay-Lussac, 78995 Elancourt (France); Institut Materiaux Microelectronique Nanosciences de Provence, Aix Marseille Universite, Avenue Escadrille Normandie Niemen, 13397 Marseille (France); Escoubas, L. [Institut Materiaux Microelectronique Nanosciences de Provence, Aix Marseille Universite, Avenue Escadrille Normandie Niemen, 13397 Marseille (France); Flory, F. [Institut Materiaux Microelectronique Nanosciences de Provence, Ecole Centrale Marseille, Marseille (France); Berginc, G. [Thales Optronique SA, Avenue Gay-Lussac, 78995 Elancourt (France); Maire, G.; Giovannini, H. [Institut Fresnel, Aix Marseille Universite, Avenue Escadrille Normandie Niemen, 13397 Marseille (France)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Random rough surfaces are photofabricated using an argon ion laser. Black-Right-Pointing-Pointer Speckle and surface correlation function are linked. Black-Right-Pointing-Pointer Exposure beam is modified allowing tuning the correlation. Black-Right-Pointing-Pointer Theoretical examples are presented. Black-Right-Pointing-Pointer Experimental results are compared with theoretical expectation. - Abstract: Optical surface structuring shows great interest for antireflective or scattering properties. Generally, fabricated surface structures are periodical but random surfaces that offer new degrees of freedom and possibilities by the control of their statistical properties. We propose an experimental method to create random rough surfaces on silicon by laser processing followed by etching. A photoresist is spin coated onto a silicon substrate and then exposed to the scattering of a modified laser beam. The beam modification is performed by using a micromirror matrix allowing laser beam shaping. An example of tuning is presented. An image composed of two white circles with a black background is displayed and the theoretical shape of the correlation is calculated. Experimental surfaces are elaborated and the correlation function calculated from height mapping. We finally compared the experimental and theoretical correlation functions.

  3. Surface quality of human corneal lenticules after femtosecond laser surgery for myopia comparing different laser parameters.

    Science.gov (United States)

    Kunert, Kathleen S; Blum, Marcus; Duncker, Gernot I W; Sietmann, Rabea; Heichel, Jens

    2011-09-01

    To determine the surface characteristics of human corneal lenticules after femtosecond laser surgery for myopia. The Carl Zeiss Meditec AG VisuMax® femtosecond laser system was used for refractive correction called Femtosecond Lenticule Extraction on 24 myopic eyes. The surface regularity on the refractive corneal lenticules recovered was evaluated by assessing scanning electron microscopy images using an established scoring system. Three different energy levels 150, 180, and 195 nJ were compared (n = 8 in each group). Surface irregularities were caused by tissue bridges, cavitation bubbles, or scratches. The surface regularity index (R(2) = 0.74) decreased as pulse energy increased. The average surface regularity score obtained was 7.5 for 150 nJ, 7.25 for 180 nJ, and 6.25 for 195 nJ. The human corneal lenticules created with the VisuMax® femtosecond laser system are of predictable, good-quality surface. This study shows the influence of pulse energy on surface regularity in human eyes. Further studies should focus on optimization of laser parameters as well as surgical technique to improve the regularity of the corneal stromal bed and so make the advantages of the femtosecond laser technology over conventional techniques clearer in the future.

  4. Laser microscope-spectrum analyzer for studying intracellular accumulation of near infrared emitting photosensitizers in vitro

    Directory of Open Access Journals (Sweden)

    Yu. S. Maklygina

    2015-01-01

    Full Text Available Measuring system based on the binocular microscope for analysis of intracellular accumulation of infrared IR photosenstizers allowing to obtain graphic data about state of analyzed objects, location of fluorescence foci and to obtain details of spectral profile of fluorescence emission centers in IR spectral region was developed. According to image of fluorescence signal distribution the location of photosensitizer accumulation in the cell may be detected accurately and the spectrum of fluorescence signal of near IR-range in the targeted point may be obtained. The developed system is quite comprehensive because there is an opportunity to choose technical parameters, operating modes, measuring methods and analysis. The advantage of the developed microscope-spectrum analyzer is an opportunity to focus emission and create high power intensity on the irradiated area by means of laser source with small-angle beam spreading, all this allow to perform ultra-precise operations with cells. Particularly, tunable size of the diaphragm opening in the far field allows to register fluorescence signal on certain cell organoids. By means of developed system the studies of accumulation of the new bacteriochlorine photosensitizers on HeLa cell line were performed. The system allowed to register accumulation of cancer cells with definite sites of selectively accumulated photosensitizer. The sites of fluorescence were the centers of accumulation of bacteriochlorine photosensitizer, this suggests that studied photosensitizer has a tendency for local accumulation in cellular organoids. The authors suggested that the developed system allowed to perform the effective and rapid screening of new photosensitizers, particularly IR bacteriochlorine photosensitizers. 

  5. Optodynamics: dynamic aspects of laser beam-surface interaction

    International Nuclear Information System (INIS)

    Možina, J; Diaci, J

    2012-01-01

    This paper presents a synthesis of the results of our original research in the area of laser-material interaction and pulsed laser material processing with a special emphasis on the dynamic aspects of laser beam-surface interaction, which include the links between the laser material removal and the resulting material motion. In view of laser material processing, a laser beam is not only considered as a tool but also as a generator of information about the material transformation. The information is retained and conveyed by different kinds of optically induced mechanical waves. Several generation/detection schemes have been developed to extract this information, especially in the field of non-destructive material evaluation. Blast and acoustic waves, which propagate in the air surrounding the work-piece, have been studied using microphone detection as well as various setups of the laser beam deflection probe. Stress waves propagating through the work-piece have been studied using piezoelectric transducers and laser interferometers.

  6. LASER CLEANING OF CONTAMINATED PAINTED SURFACES

    Energy Technology Data Exchange (ETDEWEB)

    Ames A. Grisanti; Charlene R. Crocker; Robert R. Jensen

    1999-11-19

    Several techniques are available or under development for surface decontamination in nuclear facilities. Each technique has its merits; however, none of them is universally the best choice for all surface decontamination applications. Because of the multitude of factors which influence the environmental and economic aspects of selecting a surface decontamination technique, it is difficult to select the best method in a given situation; an objective basis for comparing techniques is needed. The objective of this project was to develop a software tool for use by personnel selecting a surface decontamination technique. The software incorporates performance data for available surface decontamination techniques. The beta release version of the Surface Decontamination Assistant Software has been completed and has undergone testing at the Energy and Environmental Research Center. Minor modifications to the software were completed, and a final release version of the software is ready to be issued.

  7. Passively mode-locked diode-pumped Tm3+:YLF laser emitting at 1.91 µm using a GaAs-based SESAM

    Science.gov (United States)

    Tyazhev, A.; Soulard, R.; Godin, T.; Paris, M.; Brasse, G.; Doualan, J.-L.; Braud, A.; Moncorgé, R.; Laroche, M.; Camy, P.; Hideur, A.

    2018-04-01

    We report on a diode-pumped Tm:YLF laser passively mode-locked with an InGaAs saturable absorber. The laser emits a train of 31 ps pulses at a wavelength of 1.91 µm with a repetition rate of 94 MHz and a maximum average power of 95 mW. A sustained and robust mode-locking with a signal-to-noise ratio of ~70 dB is obtained even at high relative air humidity, making this system attractive for applications requiring ultra-short pulses in the spectral window just below 2 µm.

  8. 1.9 W continuous-wave single transverse mode emission from 1060 nm edge-emitting lasers with vertically extended lasing area

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. J., E-mail: jarez.miah@tu-berlin.de; Posilovic, K.; Kalosha, V. P.; Rosales, R.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Kettler, T. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); PBC Lasers GmbH, Hardenbergstr. 36, 10623 Berlin (Germany); Skoczowsky, D. [PBC Lasers GmbH, Hardenbergstr. 36, 10623 Berlin (Germany); Pohl, J.; Weyers, M. [Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

    2014-10-13

    High-brightness edge-emitting semiconductor lasers having a vertically extended waveguide structure emitting in the 1060 nm range are investigated. Ridge waveguide (RW) lasers with 9 μm stripe width and 2.64 mm cavity length yield highest to date single transverse mode output power for RW lasers in the 1060 nm range. The lasers provide 1.9 W single transverse mode optical power under continuous-wave (cw) operation with narrow beam divergences of 9° in lateral and 14° (full width at half maximum) in vertical direction. The beam quality factor M{sup 2} is less than 1.9 up to 1.9 W optical power. A maximum brightness of 72 MWcm{sup −2}sr{sup −1} is obtained. 100 μm wide and 3 mm long unpassivated broad area lasers provide more than 9 W optical power in cw operation.

  9. Highly Efficient Perovskite-Quantum-Dot Light-Emitting Diodes by Surface Engineering

    KAUST Repository

    Pan, Jun

    2016-08-16

    A two-step ligand-exchange strategy is developed, in which the long-carbon-chain ligands on all-inorganic perovskite (CsPbX3, X = Br, Cl) quantum dots (QDs) are replaced with halide-ion-pair ligands. Green and blue light-emitting diodes made from the halide-ion-paircapped quantum dots exhibit high external quantum efficiencies compared with the untreated QDs.

  10. Fabrication of Super Hydrophobic Surfaces by fs Laser Pulses : How to Produce Self-Cleaning Surfaces

    NARCIS (Netherlands)

    Groenendijk, M.N.W.

    2008-01-01

    The chair of Applied Laser Technology of the University of Twente, The Netherlands, is performing research into applications of ultrashort pulsed lasers for micromachining. In a recent project, PhD student Max Groenendijk developed a method for the production of super water repellant surfaces by

  11. Surface Emitting, High Efficiency Near-Vacuum Ultraviolet Light Source with Aluminum Nitride Nanowires Monolithically Grown on Silicon.

    Science.gov (United States)

    Zhao, S; Djavid, M; Mi, Z

    2015-10-14

    To date, it has remained challenging to realize electrically injected light sources in the vacuum ultraviolet wavelength range (∼200 nm or shorter), which are important for a broad range of applications, including sensing, surface treatment, and photochemical analysis. In this Letter, we have demonstrated such a light source with molecular beam epitaxially grown aluminum nitride (AlN) nanowires on low cost, large area Si substrate. Detailed angle dependent electroluminescence studies suggest that, albeit the light is TM polarized, the dominant light emission direction is from the nanowire top surface, that is, along the c axis, due to the strong light scattering effect. Such an efficient surface emitting device was not previously possible using conventional c-plane AlN planar structures. The AlN nanowire LEDs exhibit an extremely large electrical efficiency (>85%), which is nearly ten times higher than the previously reported AlN planar devices. Our detailed studies further suggest that the performance of AlN nanowire LEDs is predominantly limited by electron overflow. This study provides important insight on the fundamental emission characteristics of AlN nanowire LEDs and also offers a viable path to realize an efficient surface emitting near-vacuum ultraviolet light source through direct electrical injection.

  12. Laser surface modification of Ti implants to improve osseointegration

    International Nuclear Information System (INIS)

    Marticorena, M; Corti, G; Olmedo, D; Guglielmotti, M B; Duhalde, S

    2007-01-01

    Commercially Pure Titanium foils, were irradiated using a pulsed Nd:YAG laser under ambient air, in order to produce and characterize a well controlled surface texture (roughness and waviness) that enhances osseointegration. To study the 'peri-implant' reparative process response, the laser treated Ti foils were implanted in the tibia of 10 male Wistar rats. At 14 days post-implantation, the histological analysis showed a tendency to more bone formation compared to the untreated control implants. The formation of a layer of TiN on the surface and the obtained roughness, have been demonstrated to improve bone response

  13. Modeling of laser damage initiated by surface contamination

    International Nuclear Information System (INIS)

    Feit, M.D.; Rubenchik, A.M.; Faux, D.R.; Riddle, R.A.; Shapiro, A.; Eder, D.C.; Penetrante, B.M.; Milam, D.; Genin, F.Y.; Kozlowski, M.R.

    1996-11-01

    The authors are engaged in a comprehensive effort to understand and model the initiation and growth of laser damage initiated by surface contaminants. This includes, for example, the initial absorption by the contaminant, heating and plasma generation, pressure and thermal loading of the transparent substrate, and subsequent shockwave propagation, 'splashing' of molten material and possible spallation, optical propagation and scattering, and treatment of material fracture. The integration use of large radiation hydrodynamics codes, optical propagation codes and material strength codes enables a comprehensive view of the damage process The following picture of surface contaminant initiated laser damage is emerging from our simulations

  14. Surface alloying of nickel based superalloys by laser

    International Nuclear Information System (INIS)

    Rodriguez, G.P.; Garcia, I.; Damborenea, J.J. de

    1998-01-01

    Ni based superalloys present a high oxidation resistance at high temperature as well as good mechanical properties. But new technology developments force to research in this materials to improve their properties at high temperature. In this work, two Ni based superalloys (Nimonic 80A and Inconel 600) were surface alloyed with aluminium using a high power laser. SEM and EDX were used to study the microstructure of the obtained coatings. Alloyed specimens were tested at 1.273 K between 24 and 250 h. Results showed the generation of a protective and continuous coating of alumina on the laser treated specimens surface that can improve oxidation resistance. (Author) 8 refs

  15. Study of the laser cleaning on plaster sculptures. The effect of laser irradiation on the surfaces

    Science.gov (United States)

    Pelosi, C.; Fodaro, D.; Sforzini, L.; Rubino, A. R.; Falqui, A.

    2013-06-01

    The focus of this paper is to study the effects caused by the laser irradiation on nineteenth and twentieth century plaster sculptures. Before applying the laser cleaning on the sculptures, it was tested on samples prepared in laboratory according to the results of the scientific investigation carried out on the selected works of art. The characterization of the surface finishing materials of the sculptures was performed by Fourier Transform Infrared spectrometry (FTIR), X-ray Fluorescence spectroscopy (XRF), UV fluorescence photography, and internal micro stratigraphic analysis. Regarding the finishing materials, shellac, zinc white, siccative oil and proteins were found on the surfaces. The results of the scientific investigation, together with the examination of the ancient technical manuals, were used to create the laboratory samples to carry out the irradiation tests with laser. The laser irradiation and cleaning tests were carried out with a Q-switched Nd:YAG system. The irradiated surfaces were analyzed before and after the laser tests with the aid of a video microscope and a reflectance spectrophotometer, in order to evaluate the color changes of the surfaces. The possible morphological modifications caused by laser irradiation were also investigated by Scanning Electron Microscopy (SEM) together with ancillary Energy Dispersive Spectroscopy (EDS) elemental analysis. Concerning the laser cleaning test on the samples, in general little color changes were observed both with the 532 and 1064 nm wavelength. Total color changes, expressed as Δ E*, are always small apart from the samples made of shellac and zinc white in linseed oil, as finishing layer. As regards these samples the surface irradiated with the laser greyed lightly, corresponding to a decrease of L* parameter (lightness). SEM imaging of the treated and not-treated samples, both at low and high magnification, does not show evidence of significant morphological differences due to the laser beam

  16. Laser decontamination of epoxy painted concrete surfaces in nuclear plants

    Science.gov (United States)

    Anthofer, A.; Lippmann, W.; Hurtado, A.

    2014-04-01

    Laser technology offers an efficient decontamination of surfaces contaminated by polychlorinated biphenyls (PCB) by precise application of highly focused laser beam power. In the context of nuclear decommissioning all walls and floors of a reactor building have to be cleaned from chemical-toxic substances. State of the art is a manual and mechanic ablation and a subsequent treatment in a hazardous waste incinerator. In this study, alternatively, a laser-based system exhibiting, decontamination rates of up to 6.4 m2/h has been operated using a 10 kW diode laser in continuous wave (CW) mode with a spot size of 45×10 mm2 and a wavelength of 980-1030 nm. The system allows a rapid heating of the surfaces up to temperatures of more than 1000 °C leading to ablation and thermal decomposition of PCB in one process step. Thermal quenching prevents formation of polychlorinated dioxines (PCDD) and polychlorinate furans (PCDF) in the flue gas. Additionally, an in situ measurement system based on laser induced fluorescence (LIF) is developed to monitor the thermal decomposition of PCB. For initial experiments samples covered with epoxy paint were used to evaluate the process and to carry out finite element based simulations. In this paper, experimental results of ablation tests by laser irradiation of epoxy painted concrete are presented and discussed.

  17. Femtosecond laser surface structuring of molybdenum thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Mthunzi, P. [Council for Scientific and Industrial Research (CSIR), Biophotonics Lab: National Laser Centre Pretoria, 0001 (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Itala (Italy); Sechoghela, P.; Mongwaketsi, N. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Ramponi, R. [Institute for Photonics and Nanotechnologies (IFN)–CNR, Piazza Leanardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa)

    2015-10-30

    Highlights: • Color change of the molybdenum thin film from shinny to violet–yellowish color after laser irradiation at various laser powers. • Formation of the molybdenum dioxide coating after laser exposure, as confirmed by the X-ray diffraction spectrometry. • Selective solar absorbing nature of the laser exposed films. • Study of the binding energies is presented in this contribution using the XPS spectrometry. - Abstract: This contribution reports on the femtosecond surface structuring of molybdenum thin coatings deposited by electron beam evaporation onto Corning glass substrates. The 1-D type periodic grating lines created by such an ablation showed that the widths of the shallow grooves followed a logarithmic dependence with the laser energy incident on the molybdenum film. The electronic valence “x” of the created oxide surface layer MoO{sub x} was found to be incident laser power dependent via Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction investigations. Such a photo-induced MoO{sub x}–Mo nanocomposite exhibited effective selective solar absorption in the UV–vis–IR spectral range.

  18. Slim planar apparatus for converting LED light into collimated polarized light uniformly emitted from its top surface.

    Science.gov (United States)

    Teng, Tun-Chien; Tseng, Li-Wei

    2014-10-20

    This study proposes a slim planar apparatus for converting nonpolarized light from a light-emitting diode (LED) into an ultra-collimated linearly polarized beam uniformly emitted from its top surface. The apparatus was designed based on a folded-bilayer configuration comprising a light-mixing collimation element, polarization conversion element, and polarization-preserving light guide plate (PPLGP) with an overall thickness of 5 mm. Moreover, the apparatus can be extended transversally by connecting multiple light-mixing collimation elements and polarization conversion elements in a side-by-side configuration to share a considerably wider PPLGP, so the apparatus can have theoretically unlimited width. The simulation results indicate that the proposed apparatus is feasible for the maximal backlight modules in 39-inch liquid crystal panels. In the case of an apparatus with a 480 × 80 mm emission area and two 8-lumen LED light sources, the average head-on polarized luminance and spatial uniformity over the emission area was 5000 nit and 83%, respectively; the vertical and transverse angular distributions of the emitting light were only 5° and 10°, respectively. Moreover, the average degree of polarization and energy efficiency of the apparatus were 82% and 72%, respectively. As compared with the high-performance ultra-collimated nonpolarized backlight module proposed in our prior work, not only did the apparatus exhibit outstanding optical performance, but also the highly polarized light emissions actually increased the energy efficiency by 100%.

  19. Laser induced surface modification of low temperature cofired ceramics (LTCC)

    Energy Technology Data Exchange (ETDEWEB)

    Duitsch, U.; Rohde, M.; Heidinger, R. [Forschungszentrum Karlsruhe GmbH, Karlsruhe (Germany). Inst. for Materials Research

    2004-07-01

    In the present study a laser induced surface modification process is used to increase the electrical conductivity of ceramic substrates locally. The laser experiments were carried out with a CO{sub 2}-Laser ({lambda}=10,6 {mu}m, cw) on LTCC-Substrates DuPont 951 by using tungsten powder as additive. The resulting microstructures within the modified lines were characterised and changes in the electrical properties have been determined. By means of the laser process and using preheating substrates to avoid thermoshock a composite of LTCC and tungsten particles was produced. The tungsten volume fraction within the modified lines was determined between 15.. 50 vol.%. The electrical conductivity in the paths reached a level of {sigma}=10{sup 5}-10{sup 6} S/m, which is only one or two orders of magnitude below the value of bulk tungsten. (orig.)

  20. Semiconductor lasers stability, instability and chaos

    CERN Document Server

    Ohtsubo, Junji

    2017-01-01

    This book describes the fascinating recent advances made concerning the chaos, stability and instability of semiconductor lasers, and discusses their applications and future prospects in detail. It emphasizes the dynamics in semiconductor lasers by optical and electronic feedback, optical injection, and injection current modulation. Applications of semiconductor laser chaos, control and noise, and semiconductor lasers are also demonstrated. Semiconductor lasers with new structures, such as vertical-cavity surface-emitting lasers and broad-area semiconductor lasers, are intriguing and promising devices. Current topics include fast physical number generation using chaotic semiconductor lasers for secure communication, development of chaos, quantum-dot semiconductor lasers and quantum-cascade semiconductor lasers, and vertical-cavity surface-emitting lasers. This fourth edition has been significantly expanded to reflect the latest developments. The fundamental theory of laser chaos and the chaotic dynamics in se...

  1. Effect of laser modified surface microtopochemistry on endothelial cell growth.

    Science.gov (United States)

    Duncan, A C; Rouais, F; Lazare, S; Bordenave, L; Baquey, Ch

    2007-02-15

    The introduction of microelectronics technology in the area of biological sciences has brought forth previously unforeseeable applications such as DNA or protein biochips, miniaturized, multiparametric biosensors for high performance multianalyte assays, DNA sequencing, biocomputers, and substrates for controlled cell growth (i.e. tissue engineering). We developed and investigated a new method using "cold" excimer laser beam technology combined with microlithographical techniques to create surfaces with well defined 3D microdomains in order to delineate critical microscopic surface features governing cell-material interactions. Microfabricated surfaces with microgrooves 30-3 microm deep, 10 - 1 microm wide spaced 30 microm apart were obtained with micron resolution, by "microsculpturing" polymer model surfaces using a computer controlled laser KrF excimer beam coupled with a microlithographic projection technique. The laser beam after exiting a mask was focused onto the polymer target surface via an optical setup allowing for a 10-fold reduction of the mask pattern. Various 3D micropatterned features were obtained at the micron level. Reproducible submicron features could also be obtained using this method. Subsequently, model human umbilical endothelial cells (HUVEC) were cultured on the laser microfabricated surfaces in order to study the effects of specific microscopic surface features on cell deposition and orientation. Cell deposition patterns were found to be microstructure dependant, and showed cell orientation dependency for features in the cell range dimension, a behaviour significantly different from that of a previously studied cell model (osteoprogenitor cell). This model may be a promising in so far as it is very rapid (a time frame less than a second per square centimeter of micropatterned surface) and provides further insights into the effects of surface microtopography on cell response with possible applications in the field of biosensors

  2. Field-emitting Townsend regime of surface dielectric barrier discharges generated in CO2 emerging at high pressure

    Science.gov (United States)

    Pai, David; Stauss, Sven; Terashima, Kazuo

    2015-09-01

    Surface dielectric barrier discharges (DBDs) in CO2 from atmospheric pressure up to supercritical conditions (Tc = 304.13 K, pc = 7.4 MPa) generated using 10-kHz ac excitation are studied experimentally. Two discharge regimes are obtained: the standard and field-emitting Townsend regimes. The former resembles typical surface DBDs that have streamer-like characteristics, but the latter has not been reported previously. Here we present an analysis of the electrical and optical diagnostics of the field-emitting Townsend discharge regime using current-voltage and charge-voltage measurements, imaging, optical emission spectroscopy, and spontaneous Raman spectroscopy. Using an electrical model, it is possible to calculate the discharge-induced capacitances of the plasma and the dielectric, as well as the space-averaged values of the surface potential and the potential drop across the discharge. The model also accounts for the space-averaged Laplacian field by including the capacitance due to the fringe electric field from the electrode edge. The electrical characteristics are similar to those of atmospheric-pressure Townsend DBDs, i.e. self-sustained DBDs with minimal space-charge effects. The purely continuum emission spectrum is due to electron-neutral bremsstrahlung, with a corresponding average electron temperature of 2600 K. Raman spectra of CO2 near the critical point demonstrate that the discharge increases the average gas temperature by less than 1 K. This work was supported financially in part by MEXT and JSPS.

  3. Self-assembly surface modified indium-tin oxide anodes for single-layer light-emitting diodes

    CERN Document Server

    Morgado, J; Charas, A; Matos, M; Alcacer, L; Cacialli, F

    2003-01-01

    We study the effect of indium-tin oxide surface modification by self assembling of highly polar molecules on the performance of single-layer light-emitting diodes (LEDs) fabricated with polyfluorene blends and aluminium cathodes. We find that the efficiency and light-output of such LEDs is comparable to, and sometimes better than, the values obtained for LEDs incorporating a hole injection layer of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid. This effect is attributed to the dipole-induced work function modification of indium-tin oxide.

  4. Self-assembly surface modified indium-tin oxide anodes for single-layer light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Morgado, Jorge [Instituto de Telecomunicacoes and Departamento de Engenharia Quimica, Instituto Superior Tecnico, Avenida Rovisco Pais, P-1049-001 Lisbon (Portugal); Barbagallo, Nunzio [Instituto de Telecomunicacoes and Departamento de Engenharia Quimica, Instituto Superior Tecnico, Avenida Rovisco Pais, P-1049-001 Lisbon (Portugal); Charas, Ana [Instituto de Telecomunicacoes and Departamento de Engenharia Quimica, Instituto Superior Tecnico, Avenida Rovisco Pais, P-1049-001 Lisbon (Portugal); Matos, Manuel [Departamento de Engenharia Quimica, Instituto Superior de Engenharia de Lisboa, Rua Conselheiro Emidio Navarro-1, P-1949-001 Lisbon (Portugal); Alcacer, Luis [Instituto de Telecomunicacoes and Departamento de Engenharia Quimica, Instituto Superior Tecnico, Avenida Rovisco Pais, P-1049-001 Lisbon (Portugal); Cacialli, Franco [Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT (United Kingdom)

    2003-03-07

    We study the effect of indium-tin oxide surface modification by self assembling of highly polar molecules on the performance of single-layer light-emitting diodes (LEDs) fabricated with polyfluorene blends and aluminium cathodes. We find that the efficiency and light-output of such LEDs is comparable to, and sometimes better than, the values obtained for LEDs incorporating a hole injection layer of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid. This effect is attributed to the dipole-induced work function modification of indium-tin oxide.

  5. A comparative study of the influence of nickel oxide layer on the FTO surface of organic light emitting diode

    Science.gov (United States)

    Saikia, Dhrubajyoti; Sarma, Ranjit

    2018-03-01

    The influence of thin layer of nickel oxide (NiO) over the fluorine-doped tin oxide (FTO) surface on the performance of Organic light-emitting diode (OLED) is reported. With an optimal thickness of NiO (10 nm), the luminance efficiency is found to be increased as compared to the single FTO OLED. The performance of OLED is studied by depositing NiO films at different thicknesses on the FTO surface and analyzed their J-V and L-V characteristics. Further analysis is carried out by measuring sheet resistance and optical transmittance. The surface morphology is studied with the help of FE-SEM images. Our results indicate that NiO (10 nm) buffer layer is an excellent choice to increase the efficiency of FTO based OLED devices within the charge tunneling region. The maximum value of current efficiency is found to be 7.32 Cd/A.

  6. Guyana dolphins (Sotalia guianensis) from Costa Rica emit whistles that vary with surface behaviors.

    Science.gov (United States)

    May-Collado, Laura J

    2013-10-01

    Guyana dolphins show remarkable intraspecific whistle variation. This variation has been largely explained in terms of distance among populations; however, other factors such as behavior may also be important. A broadband recording system recorded the whistles of Guyana dolphins under three behavioral states. A discriminant analysis found that during social and travel events, dolphins emit whistles with high delta and minimum frequency, respectively. Whistle duration was also important in discriminating behaviors. This study indicates that behavior is an important factor contributing to whistle variation of Guyana dolphins. Understanding how dolphin whistles vary with behavioral context will advance our understanding of dolphin communication and enable appropriate comparative studies.

  7. Laser polishing for topography management of accelerator cavity surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Liang [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Klopf, J. Mike [College of William and Mary, Williamsburg, VA (United States); Reece, Charles E. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Kelley, Michael J. [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2015-07-20

    Improved energy efficiency and reduced cost are greatly desired for advanced particle accelerators. Progress toward both can be made by atomically-smoothing the interior surface of the niobium superconducting radiofrequency accelerator cavities at the machine's heart. Laser polishing offers a green alternative to the present aggressive chemical processes. We found parameters suitable for polishing niobium in all surface states expected for cavity production. As a result, careful measurement of the resulting surface chemistry revealed a modest thinning of the surface oxide layer, but no contamination.

  8. Pollution Encrustation Removal by Means of Combined Ultraviolet and Infrared Laser Radiation: The Application of this Innovative Methodology on the Surface of the Parthenon West Frieze

    Science.gov (United States)

    Pouli, P.; Frantzikinaki, K.; Papakonstantinou, E.; Zafiropulos, V.; Fotakis, C.

    This study refers to the innovative laser cleaning methodology developed at FORTH IESL on the combination of ultraviolet and infrared laser radiation emitted from a Q-switched Nd:YAG laser for the successful removal of pollution encrustation from marble substrates. The above-mentioned methodology is presented as regards its successful application on the fragile and demanding surface of the Parthenon West Frieze in collaboration with the Committee for the Preservation of the Acropolis Monuments. The aim of this intervention was to remove encrustation, accumulated on the stone due to the atmospheric pollution, without any discoloration or structural alteration to the original surface. The preliminary experiments on all the possible substrates and encrustations present on the surface of the Acropolis monuments and the laser cleaning parameters are presented in detail.

  9. Developing a more useful surface quality metric for laser optics

    Science.gov (United States)

    Turchette, Quentin; Turner, Trey

    2011-02-01

    Light scatter due to surface defects on laser resonator optics produces losses which lower system efficiency and output power. The traditional methodology for surface quality inspection involves visual comparison of a component to scratch and dig (SAD) standards under controlled lighting and viewing conditions. Unfortunately, this process is subjective and operator dependent. Also, there is no clear correlation between inspection results and the actual performance impact of the optic in a laser resonator. As a result, laser manufacturers often overspecify surface quality in order to ensure that optics will not degrade laser performance due to scatter. This can drive up component costs and lengthen lead times. Alternatively, an objective test system for measuring optical scatter from defects can be constructed with a microscope, calibrated lighting, a CCD detector and image processing software. This approach is quantitative, highly repeatable and totally operator independent. Furthermore, it is flexible, allowing the user to set threshold levels as to what will or will not constitute a defect. This paper details how this automated, quantitative type of surface quality measurement can be constructed, and shows how its results correlate against conventional loss measurement techniques such as cavity ringdown times.

  10. Method and apparatus for aligning laser reflective surfaces

    International Nuclear Information System (INIS)

    Caruolo, A.B.; Davis, J.W.; Walch, A.P.

    1975-01-01

    Methods and apparatus used in the alignment of high power laser systems to obtain optimum performance are disclosed. An external source of visible radiation provides an alignment beam which is reflected along the axis of a resonator. Reflecting surfaces of the resonator are aligned with respect to the axis located by the visible beam

  11. Holmium:YAG laser in dentistry: photoconditioning of dentinal surfaces

    Science.gov (United States)

    Holt, Raleigh A.; Nordquist, Robert E.

    1994-09-01

    This in vitro study was undertaken to determine energy levels necessary to produce tubule closure and surface smoothing on dentinal surfaces of human teeth and their resultant temperature increases within the pulpal canals with the Holmium:YAG laser. An optimal working spot size and even absorption pattern were produced by defocusing the laser beam and evaluated by images produced on light exposed and developed photographic paper. The surface effects on dentin were examined by scanning electron microscopy. A thermocouple was positioned in the canals of fresh dissected dog jaws and attached to a recorder which produced a graph of the temperature changes. The in vitro research model for intrapulpal temperatures changes was verified by comparing premortem and postmortem temperature readings. The same protocol was used to evaluate temperature changes in fresh human extracted teeth. In vivo histological studies were conducted to evaluate the effects of HO:YAG laser energy on pulpal tissues. The results of these studies indicate the HO:YAG laser at a wavelength of 2.12 microns can be safely and effectively used for photoconditioning of the dentinal surfaces of teeth in clinical conditions.

  12. Laser alloying of aluminium to improve surface properties - MSSA 2010

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2010-07-01

    Full Text Available Aluminium is vastly used in industry due to its low cost, light weight and excellent workability, but lacks in wear resistance and hardness. Laser alloying is used to improve the surface properties such as hardness by modifying the composition...

  13. Laser-induced periodic surface structures: fingerprints of light localization

    NARCIS (Netherlands)

    Skolski, J.Z.P.; Römer, G.R.B.E.; Obona, J.V.; Ocelik, V.; Huis in 't Veld, A.J.; Hosson, J.Th.M. de

    2012-01-01

    The finite-difference time-domain (FDTD) method is used to study the inhomogeneous absorption of linearly polarized laser radiation below a rough surface. The results are first analyzed in the frequency domain and compared to the efficacy factor theory of Sipe and coworkers. Both approaches show

  14. Laser-assisted surface cleaning of metallic components

    Indian Academy of Sciences (India)

    2014-02-09

    Feb 9, 2014 ... for effective utilization of uranium and thorium reserves to fulfill the ever growing need of energy [3]. ... nism of laser-assisted removal of ThO2 particulates off the metal surface and present here results of some ... samples (tungsten ribbon, thoria-contaminated zircaloy metal) were irradiated inside a chamber ...

  15. Surface texturing of sialon ceramic by femtosecond pulsed laser

    CSIR Research Space (South Africa)

    Tshabalala, Lerato C

    2017-01-01

    Full Text Available AlONSi(sub3)N(sub4) ceramic using the Ti: Sapphire Femtosecond laser system was investigated. Parametric analysis was conducted using surface drilling, unidirectional and cross-hatching machining procedures performed on the substrate at a varied power...

  16. Laser bioengineering of glass-titanium implants surface

    Science.gov (United States)

    Lusquiños, F.; Arias-González, F.; Penide, J.; del Val, J.; Comesaña, R.; Quintero, F.; Riveiro, A.; Boutinguiza, M.; Pascual, M. J.; Durán, A.; Pou, J.

    2013-11-01

    Osseointegration is the mean challenge when surgical treatments fight against load-bearing bone diseases. Absolute bone replacement by a synthetic implant has to be completed not only from the mechanics point of view, but also from a biological approach. Suitable strength, resilience and stress distribution of titanium alloy implants are spoiled by the lack of optimal biological characteristics. The inert quality of extra low interstitial titanium alloy, which make it the most attractive metallic alloy for biomedical applications, oppose to an ideal surface with bone cell affinity, and capable to stimulate bone attachment bone growth. Diverse laser treatments have been proven as effective tools to modify surface properties, such as wettability in contact to physiological fluids, or osteoblast guided and slightly enhanced attachment. The laser surface cladding can go beyond by providing titanium alloy surfaces with osteoconduction and osteoinduction properties. In this research work, the laser radiation is used to produce bioactive glass coatings on Ti6Al4V alloy substrates. Specific silicate bioactive glass compositions has been investigated to achieve suitable surface tension and viscosity temperature behavior during processing, and to provide with the required release of bone growth gene up regulation agents in the course of resorption mediated by physiological fluids. The produced coatings and interfaces, the surface osteoconduction properties, and the chemical species release in simulated physiological fluid were characterized by scanning electron microscopy (SEM), hot stage microscopy (HSM), X-ray diffraction (XRD), X ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR).

  17. Frictional Performance Assessment of Cemented Carbide Surfaces Textured by Laser

    Science.gov (United States)

    Fang, S.; Llanes, L.; Klein, S.; Gachot, C.; Rosenkranz, A.; Bähre, D.; Mücklich, F.

    2017-10-01

    Cemented carbides are advanced engineering materials often used in industry for manufacturing cutting tools or supporting parts in tribological system. In order to improve service life, special attention has been paid to change surface conditions by means of different methods, since surface modification can be beneficial to reduce the friction between the contact surfaces as well as to avoid unintended damage. Laser surface texturing is one of the newly developed surface modification methods. It has been successfully introduced to fabricate some basic patterns on cemented carbide surfaces. In this work, Direct Laser Interference Patterning Technique (DLIP) is implemented to produce special line-like patterns on a cobalt (Co) and nickel (Ni) based cemented tungsten carbide grade. It is proven that the laser-produced patterns have high geometrical precision and quality stability. Furthermore, tribology testing using a nano-tribometer unit shows that friction is reduced by the line-like patterns, as compared to the polished one, under both lubricated and dry testing regimes, and the reduction is more pronounced in the latter case.

  18. Enhancement of endothelialisation of coronary stents by laser surface engineering.

    Science.gov (United States)

    Li, Lin; Mirhosseini, Nazanin; Michael, Alun; Liu, Zhu; Wang, Tao

    2013-11-01

    Coronary stents have been widely used in the treatment of coronary heart disease. However, complications have hampered the long-term success of the device. Bare-metal stents (BMS) have a high rate of restenosis and poor endothelialisation. The drug-eluting stents (DES), although dramatically reduce restenosis, significantly prevent endothelialisation leading to late thrombosis and behave the same way as BMS after drug releasing. Rapid adhesion and growth of endothelial cells on the stent surface is a key process for early vascular healing after coronary stenting which contributes to the reduction of major complications. Surface properties manipulate cell growth and directly determine the success and life-span of the implants. However, the ideal surface properties of coronary stents are not yet fully understood. The objective of this research is to understand how surface micro/nano textures and associated material chemistry changes generated by a laser beam affect the behavior of endothelial cells on bare metal 316L stents. A high power laser beam was applied to modifying the surface properties of 316L coronary stent material and the commercial coronary stents, followed by examination of the adhesion and proliferation of human coronary endothelial cells that were growing on the surfaces. Surface properties were examined by scanning electron microscopy, contact angle measurement, and X-ray photoelectron spectroscopy. A novel surface with combined micro/nano features was created on stent material 316L and coronary stent with a specific surface chemistry. This surface gives rise to a threefold increase in the adhesion and eightfold increase in the proliferation of endothelial cells. Interestingly, such effects were only observed when the surface texture was produced in the nitrogen atmosphere suggesting the importance of the surface chemistry, including the dramatic increase of chromium nitride, for the interaction of endothelial cells with the material surface. This

  19. ArF laser surface modification of polyethersulfone film: Effect of laser fluence in improving surface biocompatibility

    International Nuclear Information System (INIS)

    Pazokian, H.; Jelvani, S.; Mollabashi, M.; Barzin, J.; Azizabadi Farahani, G.

    2011-01-01

    ArF laser treatment of polyethersulfone (PES) films was performed to improve biocompatibility of surfaces. For this purpose, the threshold fluence for laser ablation of PES was obtained from experimental measurements and then samples were irradiated at 2 separate ranges of fluences, i.e. below and above the ablation threshold. In order to investigate the physico-chemical changes, the modified surfaces were characterized by attenuated total reflectance (ATR) infrared spectroscopy and contact-angle measurements. The biocompatibility of the treated samples in comparison to those untreated was examined in vitro using a platelet adhesion test. The number of adhered platelets was obtained using the lactate dehydrogenase (LDH) method. For surfaces irradiated below the ablation threshold, a high reduction in the number of the adhered platelets was observed; while this number increased in samples treated at the fluence above the ablation threshold. The change in platelet adhesion was attributed to the change in chemistry and roughness of the irradiated surfaces.

  20. Precision metrology of NSTX surfaces using coherent laser radar ranging

    International Nuclear Information System (INIS)

    Kugel, H.W.; Loesser, D.; Roquemore, A. L.; Menon, M. M.; Barry, R. E.

    2000-01-01

    A frequency modulated Coherent Laser Radar ranging diagnostic is being used on the National Spherical Torus Experiment (NSTX) for precision metrology. The distance (range) between the 1.5 microm laser source and the target is measured by the shift in frequency of the linearly modulated beam reflected off the target. The range can be measured to a precision of < 100microm at distances of up to 22 meters. A description is given of the geometry and procedure for measuring NSTX interior and exterior surfaces during open vessel conditions, and the results of measurements are elaborated

  1. Remote Laser Cutting of CFRP: Improvements in the Cut Surface

    Science.gov (United States)

    Stock, Johannes; Zaeh, Michael F.; Conrad, Markus

    In the automotive industry carbon fibre reinforced plastics (CFRP) are considered as a future key material to reduce the weight of the vehicle. Therefore, capable production techniques are required to process this material in mass industry. E.g., state of the art methods for cutting are limited by the high tool wear or the feasible feed rate. Laser cutting processes are still under investigation. This paper presents detailed new studies on remote laser cutting of CFRP focusing on the influence of the material properties and the quality of the cut surface. By adding light absorbing soot particles to the resin of the matrix, the cutting process is improved and fewer defects emerge.

  2. Laser surface sealing and strenghtening of zirconia coatings

    International Nuclear Information System (INIS)

    Petitbon, A.; Boquet, L.; Delsart, D.

    1991-01-01

    Plasma-sprayed zirconia coatings are of general interest as thermal barriers in diesel and gas turbine engines. However, their residual porosity and poor mechanical properties require surface sealing and strengthening. Moreover, dense zirconia is not impervious to oxygen at high temperatures (ionic conductivity). Surface densification was achieved by melting a thin layer, using a continuous wave CO 2 laser. The cracks induced by shrinkage and differential stresses were controlled by spraying alumina powder in the laser beam during surface melting. The formation of alumina-zirconia composites, or possibly eutectics, generates improved chemical resistance and mechanical properties. Both laser-sealed and as-sprayed coatings were tested for bond strength, wear, corrosion and thermal cycling up to 900degC. The bond strength and thermal barrier efficiency of as-sprayed coatings were retained after laser treatment, whilst wear, corrosion and thermal shock resistances were clearly improved. Future works include thermal cycling up to 1200degC and erosion tests. The main objective is to lower the operating and maintenance costs of gas turbine engines for electric power generation. (orig.)

  3. Friction Evaluation of Laser Textured Tool Steel Surfaces

    Directory of Open Access Journals (Sweden)

    Šugárová Jana

    2017-06-01

    Full Text Available Surface textures can be defined as a regularly arranged micro-depressions or grooves with defined shape and dimensions. These textures, if they are manufactured by laser ablation process, contribute to a significant improvement of the tribological, optical or various biological properties. The aim of this paper is to analyze the influence of the surface textures prepared by laser surface texturing (LST at the friction coefficient value measured on the tool (90MnCrV8 steel – workpiece (S235JRG1 steel interface. Planar frontal surfaces of compression platens have been covered by parabolic dimple-like depressions with different dimensions. The morphological analysis of such manufactured depressions has been performed by laser scanning microscopy. Influence of such created textures on the tribological properties of the contact pair has been analyzed by the ring compression test method in the terms of hydrodynamic lubrication regime. The experimental research shown that by applying of surface textures with defined shape and dimensions and using an appropriate liquid lubricant at the same time, the coefficient of contact friction can be reduced nearly to the half of its original value.

  4. Assessment of radiation emitted by the colour video monitors using a silicon surface-barrier detection system

    International Nuclear Information System (INIS)

    Tykva, R.; Sabol, J.

    1998-01-01

    About 5% of the commonly used colour monitors tested showed radiation levels on the screen surface approaching the dose rate of 5 μGy/h. There is practically no difference between 'low radiation' monitors and other monitors. The level of radiation emitted to the sides is generally higher than that of X-ray photons emerging from the surface of the screen. Although the contribution to the effective dose of a person exposed to radiation from the monitors may be below the limit set for the general public, the skin and eye lens dose may reach significant levels, taking into account some factors such as a high density of monitors in small rooms, short distance, long exposure time, etc. (M.D.)

  5. Visible laser and superluminescent diode based free space and underwater communications

    KAUST Repository

    Ooi, Boon S.

    2017-01-30

    We report on our recent progress in high-modulation-efficiency, InGaN-based integrated waveguide modulator-laser diodes (IWM-LDs), high-speed violet and blue emitting superluminescent diodes (SLDs), InGaN-based vertical-cavity surface-emitting lasers (VCSELs), and their applications for gigahertz laser based free-space and underwater wireless optical communications.

  6. Wettability transition of laser textured brass surfaces inside different mediums

    Science.gov (United States)

    Yan, Huangping; Abdul Rashid, Mohamed Raiz B.; Khew, Si Ying; Li, Fengping; Hong, Minghui

    2018-01-01

    Hydrophobic surface on brass has attracted intensive attention owing to its importance in scientific research and practical applications. Laser texturing provides a simple and promising method to achieve it. Reducing wettability transition time from hydrophilicity to hydrophobicity or superhydrophobicity remains a challenge. Herein, wettability transition of brass surfaces with hybrid micro/nano-structures fabricated by laser texturing was investigated by immersing the samples inside different mediums. Scanning electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy and surface contact angle measurement were employed to characterize surface morphology, chemical composition and wettability of the fabricated surfaces of brass samples. Wettability transition time from hydrophilicity to hydrophobicity was shortened by immersion into isopropyl alcohol for a period of 3 h as a result of the absorption and accumulation of organic substances on the textured brass surface. When the textured brass sample was immersed into sodium bicarbonate solution, flower-like structures on the sample surface played a key role in slowing down wettability transition. Moreover, it had the smallest steady state contact angle as compared to the others. This study provides a facile method to construct textured surfaces with tunable wetting behaviors and effectively extend the industrial applications of brass.

  7. Laser Surface Preparation for Adhesive Bonding of Aerospace Structural Composites

    Science.gov (United States)

    Belcher, M. A.; Wohl, C. J.; Hopkins, J. W.; Connell, J. W.

    2010-01-01

    Adhesive bonds are critical to the integrity of built-up structures. Disbonds can often be detected but the strength of adhesion between surfaces in contact is not obtainable without destructive testing. Typically the number one problem in a bonded structure is surface contamination, and by extension, surface preparation. Standard surface preparation techniques, including grit blasting, manual abrasion, and peel ply, are not ideal because of variations in their application. Etching of carbon fiber reinforced plastic (CFRP) panels using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser appears to be a highly precise and promising way to both clean a composite surface prior to bonding and provide a bond-promoting patterned surface akin to peel ply without the inherent drawbacks from the same (i.e., debris and curvature). CFRP surfaces prepared using laser patterns conducive to adhesive bonding were compared to typical pre-bonding surface treatments through optical microscopy, contact angle goniometry, and post-bonding mechanical testing.

  8. Improved adhesion at titanium surfaces via laser-induced surface oxidation and roughening

    Energy Technology Data Exchange (ETDEWEB)

    Zimmermann, S. [Fraunhofer-Institut fuer Fertigungstechnik und Angewandte Materialforschung, Wiener Str. 12, 28359 Bremen (Germany); Institut fuer Mikro- und Nanotechnologien, Technische Universitaet Ilmenau, PF 100565, 98684 Ilmenau (Germany); Specht, U., E-mail: uwe.specht@ifam.fraunhofer.de [Fraunhofer-Institut fuer Fertigungstechnik und Angewandte Materialforschung, Wiener Str. 12, 28359 Bremen (Germany); Spiess, L.; Romanus, H.; Krischok, S.; Himmerlich, M. [Institut fuer Mikro- und Nanotechnologien, Technische Universitaet Ilmenau, PF 100565, 98684 Ilmenau (Germany); Ihde, J. [Fraunhofer-Institut fuer Fertigungstechnik und Angewandte Materialforschung, Wiener Str. 12, 28359 Bremen (Germany)

    2012-12-15

    Commercial titanium was treated in ambient atmosphere using pulsed Nd:YAG ({lambda}=1064nm) laser irradiation. Repeated laser treatments induce a removal of surface contaminants as well as the formation of a nanostructured top layer exhibiting a large effective surface and nanometer roughness. The laser induced oxidation leads to the presence of a surface layer with strongly improved, hydrothermally stable adhesion when joined to a one-component, hot-curing epoxy-based adhesive. Changes in the material properties have been characterized with respect to the topography, the chemical composition and the crystal structure using SEM, cross-beam FIB, XPS and XRD analyses in order to correlate the adhesion behavior with the structural and chemical characteristics of the surface.

  9. Physical and chemical modifications of PET surface using a laser-plasma EUV source

    Science.gov (United States)

    Bartnik, A.; Fiedorowicz, H.; Jarocki, R.; Kostecki, J.; Szczurek, M.; Biliński, A.; Chernyayeva, O.; Sobczak, J. W.

    2010-06-01

    Extreme ultraviolet (EUV) radiation is the electromagnetic radiation ranging from vacuum ultraviolet to soft X-rays. A single EUV photon carries enough energy to ionize any atom or molecule. The penetration depth of the radiation in any material is very short, ranging from tens to hundreds nanometers. Intense EUV pulses can remove material from the surface or modify its morphology or/and chemical structure. In this work, the radiation from a laser-plasma EUV source based on a double-stream gas-puff target was used for surface modification of polyethylene terephthalate (PET). The PET samples were irradiated with the EUV pulses emitted from krypton plasma and focused with a gold-plated ellipsoidal collector. The spectrum of the focused radiation covered the wavelength range from 9 to 70 nm. The PET samples were irradiated for 1 s-2 min at a 10-Hz repetition rate. Surface morphology of polymer samples after irradiation was investigated using a scanning electron microscope. Changes in chemical surface structure of the irradiated samples were investigated using an X-ray photoelectron spectroscopy. Different kinds of surface microstructures were obtained depending on the EUV fluence in a single pulse and the total EUV fluence. XPS measurements also revealed a modification of the chemical structure.

  10. A Numerical Simulation for Prediction of Infrared Radiation Emitted from Plain Surfaces with Different Geometries

    Directory of Open Access Journals (Sweden)

    Vakilabadi K.A.

    2017-08-01

    Full Text Available In this paper, infrared radiation exiting plain surfaces with different geometries is numerically simulated. Surfaces under consideration are assumed to have steady uniform heat generation inside. Moreover, the boundaries of the surfaces are considered to be at the surroundings temperature. Infrared radiation is calculated based on the temperature profile determined for the surface. The temperature profile of the surface is determined assuming the two dimensional heat conduction equations to govern the problem. The physical domain is transformed into the appropriate computational domain and the governing equation is mapped into the suitable forms in the new coordinate system of variables. After that the temperature profile of the surface is computed, the infrared radiation distribution of the surface is evaluated based on the equations given in the manuscript. The temperature profile as well as the IR images are given in the results section. It is concluded that the maximum value of infrared radiation of the surface occurs at the center. Moreover, it is concluded that among surfaces with equal areas, the one having the largest perimeter has the least value of IR at its center.

  11. Quantum dynamics of STM and laser induced desorption of atoms and molecules from surfaces

    CERN Document Server

    Boendgen, G

    2001-01-01

    The manipulation of atoms and molecules at solid surfaces by electronic excitations with electrons (or holes) emitted from the tip of a scanning tunneling microscope (STM) or with laser radiation is both of applied and fundamental interest, e.g. for micro- and nanostructuring of materials, the clarification of elementary (catalytic) reaction mechanisms and for the question of how to treat the quantum dynamics of a laser or STM driven 'system' (the adsorbate) in contact with a dissipative (energy-withdrawing) 'bath' (the substrate). Desorption induced by electronic transitions (DIET) and its variant DIMET (M = multiple) are among the simplest possible 'reactions' of adsorbate-surface systems; usually involving extremely short-lived electronically excited intermediates. In this thesis, the ultra-short dynamics of directly (localised to the adsorbate-substrate complex) and indirectly (i.e., through the substrate) stimulated DIET and DIMET processes was studied for Si(100)-(2x1):H(D) and Pt(111):NO. Isotope effec...

  12. Laser surface modification of boronickelized medium carbon steel

    Science.gov (United States)

    Bartkowska, Aneta; Pertek, Aleksandra; Kulka, Michał; Klimek, Leszek

    2015-11-01

    A two-step process was applied to produce the multicomponent boride layers. Boronickelizing consisted of nickel plating and diffusion boriding. Two different methods of heat treatment of boronickelized C45 steel were used: a typical through-hardening, and a laser surface modification with remelting. Microstructure and some mechanical properties of these layers were examined. Microstructural characterization was studied using optical microscope, Scanning Electron Microscope, energy-dispersive X-ray microanalysis, Electron Back-Scatter Diffraction and X-ray diffraction. The laser modification improved wear resistance, cohesion as well as low-cycle fatigue of the boronickelized layer. Compressive stresses, occurring after laser remelting, could be the reason for the advantageous mechanical behavior of the layer.

  13. TOPICAL REVIEW: Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers

    Science.gov (United States)

    Willander, M.; Nur, O.; Zhao, Q. X.; Yang, L. L.; Lorenz, M.; Cao, B. Q.; Zúñiga Pérez, J.; Czekalla, C.; Zimmermann, G.; Grundmann, M.; Bakin, A.; Behrends, A.; Al-Suleiman, M.; El-Shaer, A.; Che Mofor, A.; Postels, B.; Waag, A.; Boukos, N.; Travlos, A.; Kwack, H. S.; Guinard, J.; LeSi Dang, D.

    2009-08-01

    Zinc oxide (ZnO), with its excellent luminescent properties and the ease of growth of its nanostructures, holds promise for the development of photonic devices. The recent advances in growth of ZnO nanorods are discussed. Results from both low temperature and high temperature growth approaches are presented. The techniques which are presented include metal-organic chemical vapour deposition (MOCVD), vapour phase epitaxy (VPE), pulse laser deposition (PLD), vapour-liquid-solid (VLS), aqueous chemical growth (ACG) and finally the electrodeposition technique as an example of a selective growth approach. Results from structural as well as optical properties of a variety of ZnO nanorods are shown and analysed using different techniques, including high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), photoluminescence (PL) and cathodoluminescence (CL), for both room temperature and for low temperature performance. These results indicate that the grown ZnO nanorods possess reproducible and interesting optical properties. Results on obtaining p-type doping in ZnO micro- and nanorods are also demonstrated using PLD. Three independent indications were found for p-type conducting, phosphorus-doped ZnO nanorods: first, acceptor-related CL peaks, second, opposite transfer characteristics of back-gate field effect transistors using undoped and phosphorus doped wire channels, and finally, rectifying I-V characteristics of ZnO:P nanowire/ZnO:Ga p-n junctions. Then light emitting diodes (LEDs) based on n-ZnO nanorods combined with different technologies (hybrid technologies) are suggested and the recent electrical, as well as electro-optical, characteristics of these LEDs are shown and discussed. The hybrid LEDs reviewed and discussed here are mainly presented for two groups: those based on n-ZnO nanorods and p-type crystalline substrates, and those based on n-ZnO nanorods and p-type amorphous substrates. Promising electroluminescence

  14. Gigabit-per-second white light-based visible light communication using near-ultraviolet laser diode and red-, green-, and blue-emitting phosphors

    KAUST Repository

    Lee, Changmin

    2017-07-12

    Data communication based on white light generated using a near-ultraviolet (NUV) laser diode (LD) pumping red-, green-, and blue-emitting (RGB) phosphors was demonstrated for the first time. A III-nitride laser diode (LD) on a semipolar (2021) substrate emitting at 410 nm was used for the transmitter. The measured modulation bandwidth of the LD was 1 GHz, which was limited by the avalanche photodetector. The emission from the NUV LD and the RGB phosphor combination measured a color rendering index (CRI) of 79 and correlated color temperature (CCT) of 4050 K, indicating promise of this approach for creating high quality white lighting. Using this configuration, data was successfully transmitted at a rate of more than 1 Gbps. This NUV laser-based system is expected to have lower background noise from sunlight at the LD emission wavelength than a system that uses a blue LD due to the rapid fall off in intensity of the solar spectrum in the NUV spectral region.

  15. Evaluation of the morphological alteration of the root surface radiated with a diode laser

    International Nuclear Information System (INIS)

    Gulin, Mauricio

    2003-01-01

    The diode laser has been studied for periodontal therapy, as much for removal of calculus as for microbial reduction of periodontal pockets, as well as the visible analgesic effects and biomodulation capacity. For this reason the purpose of this study was to evaluate the morphological alteration of the root surface after radiation with the diode laser, 808 nm through analysis by scanning electron microscopy (SEM). Besides this, to verify the temperature variations caused during the radiation, a thermometer put into the dentinal wall of the root canal was used. In all, 18 teeth were used, 15 of which for the SEM study, and the other 3 were used to temperature variation analysis. The 25 samples were scraped on the root surface and planed with manual instruments. The other 5 were not subjected to any type of treatment. This, 6 groups of 5 samples each were formed. Control Group C whose samples had not received any treatment; Control Group C 1 was only scraped and polished conventionally with Hu-Friedy Gracey curettes 5 and 6; the other samples groups L1, L2, L3, L4 were radiated by diode laser using parameters of power 1,0 W; 1,2 W; 1,4 W; and 1,6 W respectively, 2 times for 10 seconds with 20 seconds intervals between each radiation in continuous mode. The results with relation to the increase of temperature in the interior of the root canal demonstrated that there was an increase of more than 5 degree Celsius. The results of the scanning electron microscope analysis of Control Group C demonstrated great irregularity and ridges on the root surface, with the presence of a dentine layer. Control Group C1 presented a similar aspect to Group L 1's, smoother and more homogeneous surface. Groups L2, L3, and L4 presented scratches alternating with smoother areas showing that fiber contacted the surface of the sample. The results reconfirmed the necessity of further studies using diode laser, with a beam of light emitted in an interrupted mode to improve the control of the

  16. Two dimensional simulation of high power laser-surface interaction

    International Nuclear Information System (INIS)

    Goldman, S.R.; Wilke, M.D.; Green, R.E.L.; Johnson, R.P.; Busch, G.E.

    1998-01-01

    For laser intensities in the range of 10 8 --10 9 W/cm 2 , and pulse lengths of order 10 microsec or longer, the authors have modified the inertial confinement fusion code Lasnex to simulate gaseous and some dense material aspects of the laser-matter interaction. The unique aspect of their treatment consists of an ablation model which defines a dense material-vapor interface and then calculates the mass flow across this interface. The model treats the dense material as a rigid two-dimensional mass and heat reservoir suppressing all hydrodynamic motion in the dense material. The computer simulations and additional post-processors provide predictions for measurements including impulse given to the target, pressures at the target interface, electron temperatures and densities in the vapor-plasma plume region, and emission of radiation from the target. The authors will present an analysis of some relatively well diagnosed experiments which have been useful in developing their modeling. The simulations match experimentally obtained target impulses, pressures at the target surface inside the laser spot, and radiation emission from the target to within about 20%. Hence their simulational technique appears to form a useful basis for further investigation of laser-surface interaction in this intensity, pulse-width range. This work is useful in many technical areas such as materials processing

  17. Multiple-beam output of a surface-emitted terahertz-wave parametric oscillator by using a slab MgO:LiNbO₃ crystal.

    Science.gov (United States)

    Wang, Weitao; Zhang, Xingyu; Wang, Qingpu; Cong, Zhenhua; Chen, Xiaohan; Liu, Zhaojun; Qin, Zengguang; Li, Ping; Tang, Guanqi; Li, Ning; Wang, Cong; Li, Yongfu; Cheng, Wenyong

    2014-02-15

    A MgO:LiNbO₃ slab configuration for the surface-emitted terahertz-wave parametric oscillator (TPO) is presented. The pump and the oscillating Stokes beams were totally reflected at the slab surface and propagated zigzaggedly in the slab MgO:LiNbO₃ crystal. Up to five terahertz beams were emitted perpendicularly to the surface of the crystal. The total output energy of the five THz-wave beams was 3.56 times as large as that obtained from the conventional surface-emitted TPO at the same experimental conditions. The intensity distributions of the THz wave beams were measured, and they were unsymmetrical in the horizontal direction while symmetrical in the vertical direction.

  18. Research on Laser Micro Polishing of SLS Technology Sintered Iron-Based Powder Surface

    OpenAIRE

    Gerda Vaitkūnaitė; Vladislav Markovič; Olegas Černašėjus

    2015-01-01

    The article analyzes laser micro polishing of 1.2083 steel samples produced applying selective laser sintering (SLS) method. The study has evaluated the distribution of the shape, size and temperature of the laser beam treated area in the surface layer of sintered and laser polished samples. Experimental tests have shown the impact of the technical parameters of laser micro polishing on the width and hardness of the impact zone of the treated sample. The microstructure analysis of laser treat...

  19. Method and system for laser-based formation of micro-shapes in surfaces of optical elements

    Science.gov (United States)

    Bass, Isaac Louis; Guss, Gabriel Mark

    2013-03-05

    A method of forming a surface feature extending into a sample includes providing a laser operable to emit an output beam and modulating the output beam to form a pulse train having a plurality of pulses. The method also includes a) directing the pulse train along an optical path intersecting an exposed portion of the sample at a position i and b) focusing a first portion of the plurality of pulses to impinge on the sample at the position i. Each of the plurality of pulses is characterized by a spot size at the sample. The method further includes c) ablating at least a portion of the sample at the position i to form a portion of the surface feature and d) incrementing counter i. The method includes e) repeating steps a) through d) to form the surface feature. The sample is free of a rim surrounding the surface feature.

  20. New horizons in selective laser sintering surface roughness characterization

    Science.gov (United States)

    Vetterli, M.; Schmid, M.; Knapp, W.; Wegener, K.

    2017-12-01

    Powder-based additive manufacturing of polymers and metals has evolved from a prototyping technology to an industrial process for the fabrication of small to medium series of complex geometry parts. Unfortunately due to the processing of powder as a basis material and the successive addition of layers to produce components, a significant surface roughness inherent to the process has been observed since the first use of such technologies. A novel characterization method based on an elastomeric pad coated with a reflective layer, the Gelsight, was found to be reliable and fast to characterize surfaces processed by selective laser sintering (SLS) of polymers. With help of this method, a qualitative and quantitative investigation of SLS surfaces is feasible. Repeatability and reproducibility investigations are performed for both 2D and 3D areal roughness parameters. Based on the good results, the Gelsight is used for the optimization of vertical SLS surfaces. A model built on laser scanning parameters is proposed and after confirmation could achieve a roughness reduction of 10% based on the S q parameter. The Gelsight could be successfully identified as a fast, reliable and versatile surface topography characterization method as it applies to all kind of surfaces.

  1. Object 3D surface reconstruction approach using portable laser scanner

    Science.gov (United States)

    Xu, Ning; Zhang, Wei; Zhu, Liye; Li, Changqing; Wang, Shifeng

    2017-06-01

    The environment perception plays the key role for a robot system. The 3D surface of the objects can provide essential information for the robot to recognize objects. This paper present an approach to reconstruct objects' 3D surfaces using a portable laser scanner we designed which consists of a single-layer laser scanner, an encoder, a motor, power supply and mechanical components. The captured point cloud data is processed to remove the discrete points, denoise filtering, stitching and registration. Then the triangular mesh generation of point cloud is accomplished by using Gaussian bilateral filtering, ICP real-time registration and greedy triangle projection algorithm. The experiment result shows the feasibility of the device designed and the algorithm proposed.

  2. Laser gas assisted treatment of steel 309: Corrosion and scratch resistance of treated surface

    Science.gov (United States)

    Toor, Ihsan-ul-Haq; Yilbas, B. S.; Ahmed, Junaid; Karatas, C.

    2017-10-01

    Laser gas assisted surface treatment of steel 309 is carried out and the characteristics of the resulting surface are analyzed using the analytical tools. Scanning electron and 3-D optical microscopes are used to assess the morphological and metallurgical changes in the laser treated layer. Energy spectroscopy and X-ray diffraction are carried out to determine the elemental composition and compounds formed on the laser treated surface. The friction coefficient of the laser treated surface is measured using the micro-tribometer and compared to that of the as received surface. The corrosion resistance of the laser treated and as received surfaces is measured incorporating the electrochemical tests. It is found that laser treatment results in a dense layer and formation of nitride compounds at the surface. This enhances the microhardness at the laser treated surface. The friction coefficient attains lower values at the laser treated surface than that corresponding to the as received surface. The corrosion rate of the surface reduces significantly after the laser treatment process, which can be attributed to the passive layer at the surface via formation of a dense layer and nitride compounds in the surface vicinity. In addition, the number of pit sites decreased for the laser treated surface than that of as received surface.

  3. Laser AMS 14C dating of rock surface accretions

    International Nuclear Information System (INIS)

    Watchman, A.; Campbell, F.

    1997-01-01

    Full text: Equipment has been purchased using a large Earth Sciences and Engineering ARC grant and installed in the Department of Anthropology and Archaeology, James Cook University. A krypton-ion laser used initially at Laval University, Quebec to demonstrate the potential of focusing light energy to induce oxidation of carbon-bearing substances has been replaced by a carbon dioxide laser. This decision was based on reducing the startup cost at James Cook University, increasing options for a wide range of output power, considerations for future applications and the cost of gas refills. A disadvantage of using the carbon dioxide laser is that non-visible light optics are needed because of the infrared output wavelength from the carbon dioxide. This has required the replacement of the glass window of the vacuum-tight micro-combustion chamber with a sodium chloride window and placing the equipment in a dehumidifier room. Laser light power experiments have so far been conducted on optimising the output from the laser and minimising the focal waist of the beam by adjusting the focusing mirrors and lenses. The aim of developing a focused laser system is to enable the dating of carbon in finely laminated rock surface accretions, but before this can be achieved a series of tests is planned to ensure that the focused laser system totally converts all the carbon-bearing substances under the beam into carbon dioxide. This is essential in order that the isotopic values representative of the carbon in the accretions is converted into carbon dioxide. Known quantities of graphite, charcoal, wood cellulose and calcium oxalate salts are being subjected to focused laser combustion or decomposition and the volumes of gas produced at different light powers are being measured. Isotopic measurements are also being conducted on the resulting gases to ensure that fractionation of carbon isotopes is not a problem. The paper will describe the arrangement of equipment and explain the

  4. Laser-induced plasma spectrometry: truly a surface analytical tool

    International Nuclear Information System (INIS)

    Vadillo, Jose M.; Laserna, J.

    2004-01-01

    For a long period, analytical applications of laser induced plasma spectrometry (LIPS) have been mainly restricted to overall and quantitative determination of elemental composition in bulk, solid samples. However, introduction of new compact and reliable solid state lasers and technological development in multidimensional intensified detectors have made possible the seeking of new analytical niches for LIPS where its analytical advantages (direct sampling from any material irrespective of its conductive status without sample preparation and with sensitivity adequate for many elements in different matrices) could be fully exploited. In this sense, the field of surface analysis could take advantage from the cited advantages taking into account in addition, the capability of LIPS for spot analysis, line scan, depth-profiling, area analysis and compositional mapping with a single instrument in air at atmospheric pressure. This review paper outlines the fundamental principles of laser-induced plasma emission relevant to sample surface studies, discusses the experimental parameters governing the spatial (lateral and in-depth) resolution in LIPS analysis and presents the applications concerning surface examination

  5. Thin film surface processing by ultrashort laser pulses (USLP)

    Science.gov (United States)

    Scorticati, D.; Skolski, J. Z. P.; Römer, G. R. B. E.; Huis in't Veld, A. J.; Workum, M.; Theelen, M.; Zeman, M.

    2012-06-01

    In this work, we studied the feasibility of surface texturing of thin molybdenum layers on a borosilicate glass substrate with Ultra-Short Laser Pulses (USLP). Large areas of regular diffraction gratings were produced consisting of Laserinduced periodic surface structures (LIPSS). A short pulsed laser source (230 fs-10 ps) was applied using a focused Gaussian beam profile (15-30 μm). Laser parameters such as fluence, overlap (OL) and Overscans (OS), repetition frequency (100-200 kHz), wavelength (1030 nm, 515 nm and 343 nm) and polarization were varied to study the effect on periodicity, height and especially regularity of LIPSS obtained in layers of different thicknesses (150-400 nm). The aim was to produce these structures without cracking the metal layer and with as little ablation as possible. It was found that USLP are suitable to reach high power densities at the surface of the thin layers, avoiding mechanical stresses, cracking and delamination. A possible photovoltaic (PV) application could be found in texturing of thin film cells to enhance light trapping mechanisms.

  6. Tracking the complete revolution of surface westerlies over Northern Hemisphere using radionuclides emitted from Fukushima

    International Nuclear Information System (INIS)

    Hernández-Ceballos, M.A.; Hong, G.H.; Lozano, R.L.; Kim, Y.I.; Lee, H.M.; Kim, S.H.; Yeh, S.-W.; Bolívar, J.P.; Baskaran, M.

    2012-01-01

    Massive amounts of anthropogenic radionuclides were released from the nuclear reactors located in Fukushima (northeastern Japan) between 12 and 16 March 2011 following the earthquake and tsunami. Ground level air radioactivity was monitored around the globe immediately after the Fukushima accident. This global effort provided a unique opportunity to trace the surface air mass movement at different sites in the Northern Hemisphere. Based on surface air radioactivity measurements around the globe and the air mass backward trajectory analysis of the Fukushima radioactive plume at various places in the Northern Hemisphere by employing the Hybrid Single-Particle Lagrangian Integrated Trajectory model, we show for the first time, that the uninterrupted complete revolution of the mid-latitude Surface Westerlies took place in less than 21 days, with an average zonal velocity of > 60 km/h. The position and circulation time scale of Surface Westerlies are of wide interest to a large number of global researchers including meteorologists, atmospheric researchers and global climate modellers. -- Highlights: ► Evidence of the South Korea contamination with released radiocesium from Fukushima. ► Field samples and air mass analysis were utilized to elucidate the transport of those radionuclides. ► Characterization of the air mass movements at different sites at the Earth's surface. ► Verification of the uninterrupted complete revolution of the artificial radionuclides released in Fukushima. ► Quantification of the velocity of the artificial radionuclides released in Fukushima.

  7. The effect of laser pulse width on laser-induced damage at K9 and UBK7 components surface

    Science.gov (United States)

    Zhou, Xinda; Ba, Rongsheng; Zheng, Yinbo; Yuan, Jing; Li, Wenhong; Chen, Bo

    2015-07-01

    In this paper, we investigated the effects of laser pulse width on laser-induced damage. We measured the damage threshold of K9 glass and UBK7 glass optical components at different pulse width, then analysis pulse-width dependence of damage threshold. It is shown that damage threshold at different pulse width conforms to thermal restriction mechanism, Because of cm size laser beam, defect on the optical component surface leads to laser-induced threshold decreased.

  8. Surface plasmon-enhanced localized electric field in organic light-emitting diodes by incorporating silver nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ying-Chung; Gao, Chia-Yuan [Department of Electrical Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Chen, Kan-Lin [Department of Electronic Engineering, Fortune Institute of Technology, Kaohsiung, Taiwan (China); Huang, Chien-Jung, E-mail: chien@nuk.edu.tw [Department of Applied Physics, National University of Kaohsiung, Kaohsiung, Taiwan (China)

    2014-03-01

    Highlights: • A higher luminance and electron-injection ability are obtained when the mean cluster size of SNCs is 34 nm. • SPRE is the crucial factor to contribute the electron injection. • SPRE induced the enhanced localized electric field around the Ag NPs. - Abstract: The influence of silver nanoclusters (SNCs) on the performance of organic light-emitting diodes is investigated in this study. The SNCs are introduced between the electron-injection layer and cathode alumina by means of thermal evaporation, resulting that different absorption peaks of SNCs were formed. A higher luminance and electron-injection ability are obtained when the mean cluster size is 34 nm. The surface-enhanced Raman scattering spectroscopy reveals that the localized electric field around the SNCs is enhanced, resulting in an increase in electron injection from cathode electrode.

  9. Microstructure and properties of cast iron after laser surface hardening

    Directory of Open Access Journals (Sweden)

    Stanislav

    2013-12-01

    Full Text Available Laser surface hardening of cast iron is not trivial due to the material’s heterogeneity and coarse-grained microstructure, particularly in massive castings. Despite that, hardening of heavy moulds for automotive industry is in high demand. The present paper summarises the findings collected over several years of study of materials structure and surface properties. Phase transformations in the vicinity of graphite are described using examples from production of body parts in automotive industry. The description relates to formation of martensite and carbide-based phases, which leads to hardness values above 65 HRC and to excellent abrasion resistance.

  10. Non-conventional laser surface hardening for axisymmetric components

    Science.gov (United States)

    Liverani, Erica; Battiato, Nadine; Ascari, Alessandro; Fortunato, Alessandro

    2014-02-01

    A new process, based on ring spot geometry, is presented for laser surface hardening of large cylindrical com-ponents. The proposed technique leads to a very hard, deep and uniform treated area along the entire work piece surface without introducing a tempered zone, making the process very attractive compared to conventional induction hardening that exhibits both low energy efficiency and poor flexibility. A complete physical model is presented for the process, together with a study of the influence of process parameters on the final outcome. The results of an extensive validation campaign, carried out following the AISI1040 standard, are also reported.

  11. Ultrafast dark-field surface inspection with hybrid-dispersion laser scanning

    Science.gov (United States)

    Yazaki, Akio; Kim, Chanju; Chan, Jacky; Mahjoubfar, Ata; Goda, Keisuke; Watanabe, Masahiro; Jalali, Bahram

    2014-06-01

    High-speed surface inspection plays an important role in industrial manufacturing, safety monitoring, and quality control. It is desirable to go beyond the speed limitation of current technologies for reducing manufacturing costs and opening a new window onto a class of applications that require high-throughput sensing. Here, we report a high-speed dark-field surface inspector for detection of micrometer-sized surface defects that can travel at a record high speed as high as a few kilometers per second. This method is based on a modified time-stretch microscope that illuminates temporally and spatially dispersed laser pulses on the surface of a fast-moving object and detects scattered light from defects on the surface with a sensitive photodetector in a dark-field configuration. The inspector's ability to perform ultrafast dark-field surface inspection enables real-time identification of difficult-to-detect features on weakly reflecting surfaces and hence renders the method much more practical than in the previously demonstrated bright-field configuration. Consequently, our inspector provides nearly 1000 times higher scanning speed than conventional inspectors. To show our method's broad utility, we demonstrate real-time inspection of the surface of various objects (a non-reflective black film, transparent flexible film, and reflective hard disk) for detection of 10 μm or smaller defects on a moving target at 20 m/s within a scan width of 25 mm at a scan rate of 90.9 MHz. Our method holds promise for improving the cost and performance of organic light-emitting diode displays for next-generation smart phones, lithium-ion batteries for green electronics, and high-efficiency solar cells.

  12. Subwavelength topological structures resulting from surface two-plasmon resonance by femtosecond laser exposure solid surface.

    Science.gov (United States)

    Song, Hai-Ying; Liu, Shi-Bing; Liu, H Y; Wang, Yang; Chen, Tao; Dong, Xiang-Ming

    2016-05-30

    We present that surface two-plasmon resonance (STPR) in electron plasma sheet produced by a femtosecond laser irradiating a solid surface is the self-formation mechanism of periodic subwavelength ripple structures. Peaks of overdense electrons, formed by resonant two-plasmon wave mode, pull bound ions out of the metal surface. Thus, the wave pattern of STPR is "carved" on the surface by Coulomb ablation (removal) due to periodic distributed strong electrostatic field produced by charge separation. To confirm the STPR model, we have performed analogical carving experiments by two femtosecond laser beams with perpendicular polarizations and time delay. The results explicitly show that two wave patterns of STPR generated by each beam are independently created in the pulse exposure area of a target surface, which is like the traditional "layer-carving" technique by comparison with the structured topological features. The time-scale of ablation dynamics and the electron temperature in ultrafast interaction are also verified by a time-resolved spectroscopy experiment and numerical simulation, respectively. The present model can self-consistently explain the formation of subwavelength ripple structures even with spatial periods shorter than half of the laser wavelength, shedding light on the understanding of ultrafast laser-solid interaction.

  13. Correlations for predicting the surface wettability for organic light-emitting-diode patterns by x-ray photoelectron spectroscopy analysis

    Science.gov (United States)

    Yang, L.; Svarnas, P.; Shard, A. G.; Bradley, J. W.; Seah, M. P.

    2010-12-01

    X-ray photoelectron spectroscopy (XPS) and contact angle measurements have been made to characterize patterned organic light-emitting-diode (OLED) substrates comprising indium-tin-oxide and a photoresist, both of which are modified by treatment with oxygen and tetrafluoromethane in a radiofrequency (13.56 MHz) low-power (˜1 W) capacitively coupled plasma as a function of time. Correlations between the surface chemical compositions from XPS and the contact angle, θ, are evaluated in order that the wettability of very small areas may be predicted. Very clear correlations for both the indium-tin-oxide and the photoresist surfaces are obtained enabling the prediction of the contact angles for these plasma-treated OLED materials from XPS data to a standard uncertainty of 9% in cos θ. These correlations need to be extended to a wider range of compositions in order to establish the physicochemical properties of particular surface functional groups that control water contact angles by this method.

  14. Antimicrobial efficacy of semiconductor laser irradiation on implant surfaces.

    Science.gov (United States)

    Kreisler, Matthias; Kohnen, Wolfgang; Marinello, Claudio; Schoof, Jürgen; Langnau, Ernst; Jansen, Bernd; d'Hoedt, Bernd

    2003-01-01

    This study was conducted to investigate the antimicrobial effect of an 809-nm semiconductor laser on common dental implant surfaces. Sandblasted and acid-etched (SA), plasma-sprayed (TPS), and hydroxyapatite-coated (HA) titanium disks were incubated with a suspension of S. sanguinis (ATCC 10556) and subsequently irradiated with a gallium-aluminum-arsenide (GaAlAs) laser using a 600-microm optical fiber with a power output of 0.5 to 2.5 W, corresponding to power densities of 176.9 to 884.6 W/cm2. Bacterial reduction was calculated by counting colony-forming units on blood agar plates. Cell numbers were compared to untreated control samples and to samples treated with chlorhexidine digluconate (CHX). Heat development during irradiation of the implants placed in bone blocks was visualized by means of shortwave thermography. In TPS and SA specimens, laser irradiation led to a significant bacterial reduction at all power settings. In an energy-dependent manner, the number of viable bacteria was reduced by 45.0% to 99.4% in TPS specimens and 57.6% to 99.9% in SA specimens. On HA-coated disks, a significant bacterial kill was achieved at 2.0 W (98.2%) and 2.5 W (99.3%) only (t test, P < .05). For specimens treated with CHX, the bacterial counts were reduced by 99.99% in TPS and HA-coated samples and by 99.89% in SA samples. The results of the study indicate that the 809-nm semiconductor laser is capable of decontaminating implant surfaces. Surface characteristics determine the necessary power density to achieve a sufficient bactericidal effect. The bactericidal effect, however, was lower than that achieved by a 1-minute treatment with 0.2% CHX. The rapid heat generation during laser irradiation requires special consideration of thermal damage to adjacent tissues. No obvious advantage of semiconductor laser treatment over conventional methods of disinfection could be detected in vitro.

  15. Thermal effect of laser ablation on the surface of carbon fiber reinforced plastic during laser processing

    Science.gov (United States)

    Ohkubo, Tomomasa; Sato, Yuji; Matsunaga, Ei-ichi; Tsukamoto, Masahiro

    2018-02-01

    Although laser processing is widely used for many applications, the cutting quality of carbon fiber reinforced plastic (CFRP) decreases around the heat-affected zone (HAZ) during laser processing. Carbon fibers are exposed around the HAZ, and tensile strength decreases with increasing length of the HAZ. Some theoretical studies of thermal conductions that do not consider fluid dynamics have been performed; however, theoretical considerations that include the dynamics of laser ablation are scarce. Using removed mass and depth observed from experiments, the dynamics of laser ablation of CFRP with high-temperature and high-pressure of compressive gas is simulated herein. In this calculation, the mushroom-like shape of laser ablation is qualitatively simulated compared with experiments using a high-speed camera. Considering the removal temperature of the resin and the temperature distribution at each point on the surface, the simulation results suggest that a wide area of the resin is removed when the processing depth is shallow, and a rounded kerf is generated as the processing depth increases.

  16. Broadband subwavelength grating mirror and its application to vertical-cavity surface-emitting laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper; Gilet, Philippe

    2008-01-01

    Various high-index-contrast sub-wavelength grating (HCG) mirror designs have been investigated. It reveals that transverse magnetic (TM-) and transverse electric (TE-) HCG reflect the incident fields in quite different ways and that the TM-HCG enables very thin gap below the grating. Based...... on these results, a new HCG VCSEL design with a thin oxide gap has been suggested. The thin oxide gap structure has a number of advantages including easier fabrication, better mechanical stability, and very strong single-mode properties....

  17. Beam Steering Analysis in Optically Phased Vertical Cavity Surface Emitting Laser Array

    Science.gov (United States)

    Xun, Meng; Sun, Yun; Xu, Chen; Xie, Yi-Yang; Jin, Zhi; Zhou, Jing-Tao; Liu, Xin-Yu; Wu, De-Xin

    2018-03-01

    Not Available Supported by the ‘Supporting First Action’ Joint Foundation for Outstanding Postdoctoral Program under Grant Nos Y7YBSH0001 and Y7BSH14001, the National Natural Science Foundation of China under Grant No 61434006, and the National Key Basic Research Program of China under Grant No 2017YFB0102302.

  18. Vertical-Cavity Surface-Emitting Lasers: Advanced Modulation Formats and Coherent Detection

    DEFF Research Database (Denmark)

    Rodes Lopez, Roberto

    transmission link with real-time demodulation. Furthermore, advanced modulation formats are considered in this thesis to expand the state-of-the-art in high-speed short-range data transmission system based on VCSELs. First, directly modulation of a VCSEL with a 4-level pulse amplitude modulation (PAM-4) signal...... at 50 Gb/s is achieved. This is the highest data rate ever transmitted with a single VCSEL at the time of this thesis work. The capacity of this system is increased to 100 Gb/s by using polarization multiplexing emulation and forward error correction techniques. Compared to a non return-to-zero on-off...

  19. Broadband subwavelength grating mirror and its application to vertical-cavity surface-emitting laser

    OpenAIRE

    Chung, Il-Sug; Mørk, Jesper; Gilet, Philippe; Chelnokov, Alexei

    2008-01-01

    Various high-index-contrast sub-wavelength grating (HCG) mirror designs have been investigated. It reveals that transverse magnetic (TM-) and transverse electric (TE-) HCG reflect the incident fields in quite different ways and that the TM-HCG enables very thin gap below the grating. Based on these results, a new HCG VCSEL design with a thin oxide gap has been suggested. The thin oxide gap structure has a number of advantages including easier fabrication, better mechanical stability, and very...

  20. Design of a surface-emitting, subwavelength metal-clad disk laser in the visible spectrum

    OpenAIRE

    Huang, Jingqing; Kim, Se-Heon; Scherer, Axel

    2010-01-01

    We analyze metal-clad disk cavities designed for nanolasers in the visible red spectrum with subwavelength device size and mode volume. Metal cladding suppresses radiation loss and supports low order modes with room temperature Q of 200 to 300. Non-degenerate single-mode operation with enhanced spontaneous emission coupling factor β is expected with the TE_(011) mode that has a 0.46(λ_0/n)^3 mode volume and Q = 210 in a device of size 0.12λ_0^3. Threshold gain calculations show that room temp...

  1. Laser surface remelting and hardening of an automotive shaft sing a high-power fiber laser

    Directory of Open Access Journals (Sweden)

    Milton Sergio Fernandes de Lima

    2007-12-01

    Full Text Available An automotive shaft was surface-remelted and hardened using a 2 kW fiber laser and an adapted linear axis whose rotating axis produced helical tracks at 120 RPM. The process variable was the laser power, ranging from 300 to 1100 W, which produced two regions in the material: a martensitic region (MR and a partially transformed region (PTR. The MR is formed after rapid solidification or austenitization followed by rapid cooling (10(7 K.s-1. The PTR is composed of martensite, unchanged pearlite and proeutectoid ferrite. The maximum case depth was about 0.3 mm. The microhardness inside the martensitic regions are at least double that of the base material, i.e. between 800 than 600 HV compared to 300 HV. Thermal simulations using a modified Rosenthal formalism help elucidate the phase transformation inside the material and show good agreement with experimental results. The experimental laser-steel absorptivities were measured; they ranged between 38 and 59% depending on the laser power and the amount of liquid at the surface.

  2. Biomimetic surface structuring using cylindrical vector femtosecond laser beams

    Science.gov (United States)

    Skoulas, Evangelos; Manousaki, Alexandra; Fotakis, Costas; Stratakis, Emmanuel

    2017-03-01

    We report on a new, single-step and scalable method to fabricate highly ordered, multi-directional and complex surface structures that mimic the unique morphological features of certain species found in nature. Biomimetic surface structuring was realized by exploiting the unique and versatile angular profile and the electric field symmetry of cylindrical vector (CV) femtosecond (fs) laser beams. It is shown that, highly controllable, periodic structures exhibiting sizes at nano-, micro- and dual- micro/nano scales can be directly written on Ni upon line and large area scanning with radial and azimuthal polarization beams. Depending on the irradiation conditions, new complex multi-directional nanostructures, inspired by the Shark’s skin morphology, as well as superhydrophobic dual-scale structures mimicking the Lotus’ leaf water repellent properties can be attained. It is concluded that the versatility and features variations of structures formed is by far superior to those obtained via laser processing with linearly polarized beams. More important, by exploiting the capabilities offered by fs CV fields, the present technique can be further extended to fabricate even more complex and unconventional structures. We believe that our approach provides a new concept in laser materials processing, which can be further exploited for expanding the breadth and novelty of applications.

  3. Laser surface textured titanium alloy (Ti–6Al–4V): Part 1 – Surface characterization

    Energy Technology Data Exchange (ETDEWEB)

    Pfleging, Wilhelm [Karlsruhe Institute of Technology, IAM-AWP, P.O. Box 3640, 76021 Karlsruhe (Germany); Karlsruhe Nano Micro Facility, H.-von-Helmholtz-Pl. 1, 76344 Egg.-Leopoldshafen (Germany); Kumari, Renu [Department of Metal. and Maters. Eng., I. I. T. Kharagpur, WB 721302 (India); Besser, Heino [Karlsruhe Institute of Technology, IAM-AWP, P.O. Box 3640, 76021 Karlsruhe (Germany); Scharnweber, Tim [Karlsruhe Institute of Technology, IBG-1, P.O. Box 3640, 76021 Karlsruhe (Germany); Majumdar, Jyotsna Dutta, E-mail: jyotsna@metal.iitkgp.ernet.in [Department of Metal. and Maters. Eng., I. I. T. Kharagpur, WB 721302 (India)

    2015-11-15

    Highlights: • Texturing of Ti–6Al–4V with linear and dimple patterns are developed with ArF laser. • Linear textures have width of 25 μm and are at an interval of 20 μm. • Dimple textures are equi-spaced and have a diameter of 60 μm. • Significant refinement of microstructure in textured zone as compared to substrate. • Increased wettability of the textured surface against simulated body fluid. - Abstract: In the present study, a detailed study of the characterization of laser-surface textured titanium alloy (Ti–6Al–4V) with line and dimple geometry developed by using an ArF excimer laser operating at a wavelength of 193 nm with a pulse length of 5 ns is undertaken. The characterization of the textured surface (both the top surface and cross section) is carried out by scanning electron microscopy, electron back scattered diffraction (EBSD) technique and X-ray diffraction techniques. There is refinement of microstructure along with presence of titanium oxides (rutile, anatase and few Ti{sub 2}O{sub 3} phase) in the textured surface as compared to as-received one. The area fractions of linear texture and dimple texture measured by image analysis software are 45% and 20%, respectively. The wettability is increased after laser texturing. The total surface energy is decreased due to linear (29.6 mN/m) texturing and increased due to dimple (67.6 mN/m) texturing as compared to as-received Ti–6Al–4V (37 mN/m). The effect of polar component is more in influencing the surface energy of textured surface.

  4. Treatment of dentin hypersensitivity with a low-level laser-emitting toothbrush: double-blind randomised clinical trial of efficacy and safety.

    Science.gov (United States)

    Ko, Y; Park, J; Kim, C; Park, J; Baek, S H; Kook, Y A

    2014-07-01

    Dentin hypersensitivity (DH) is defined as pain derived from exposed dentin in response to chemical, thermal, tactile, or osmotic stimuli that cannot be explained as having arisen from any other dental defect or disease. The aim of this trial was to test the efficacy and the safety of a low-level laser-emitting toothbrush on management of DH. A prospective, double blind, randomised clinical trial was designed; 96 individuals with hypersensitive teeth without caries or fracture were selected as subjects. The subjects were randomly allocated to either the test group with the 635 nm per 6 mW laser-emitting toothbrush, or the control group with the 635 nm per 12.9 μW light-emitting diode (LED) toothbrush. An air blast was applied with a dental air syringe held 3 mm away from the selected tooth and a visual analogue scale (VAS: 0-10) was used to quantify subjective pain. Assessments were completed at a screening visit and after 2-week and 4-week of using a test/control toothbrush. Results demonstrated that the use of both control and test toothbrushes resulted in decreased discomfort after 4 weeks. In the test group, pain intensity scores decreased from 5.8 ± 1.2 to 2.3 ± 1.6, and in the control group, the scores decreased from 6.4 ± 1.3 to 5.5 ± 2.0 (P toothbrush is a safe and effective treatment option for the management of DH. © 2014 John Wiley & Sons Ltd.

  5. Application of laser tracker technology for measuring optical surfaces

    Science.gov (United States)

    Zobrist, Tom L.

    The pages of this dissertation detail the development of an advanced metrology instrument for measuring large optical surfaces. The system is designed to accurately guide the fabrication of the Giant Magellan Telescope and future telescopes through loose-abrasive grinding. The instrument couples a commercial laser tracker with an advanced calibration technique and a set of external references to mitigate a number of error sources. The system is also required to work as a verification test for the GMT principal optical interferometric test of the polished mirror segment to corroborate the measurements in several low-order aberrations. A set of system performance goals were developed to ensure that the system will achieve these purposes. The design, analysis, calibration results, and measurement performance of the Laser Tracker Plus system are presented in this dissertation.

  6. Multispectral surface plasmon resonance approach for ultra-thin silver layer characterization: Application to top-emitting OLED cathode

    Science.gov (United States)

    Taverne, S.; Caron, B.; Gétin, S.; Lartigue, O.; Lopez, C.; Meunier-Della-Gatta, S.; Gorge, V.; Reymermier, M.; Racine, B.; Maindron, T.; Quesnel, E.

    2018-01-01

    While dielectric/metal/dielectric (DMD) multilayer thin films have raised considerable interest as transparent and conductive electrodes in various optoelectronic devices, the knowledge of optical characteristics of thin metallic layers integrated in such structures is still rather approximate. The multispectral surface plasmon resonance characterization approach described in this work precisely aims at providing a rigorous methodology able to accurately determine the optical constants of ultra-thin metallic films. As a practical example, the refractive index and extinction dispersion curves of 8 to 25 nm-thick silver layers have been investigated. As a result, their extreme dependence on the layer thickness is highlighted, in particular in a thickness range close to the critical threshold value (˜10 nm) where the silver film becomes continuous and its electrical conductance/optical transmittance ratio particularly interesting. To check the validity of the revisited Ag layers constant dispersion curves deduced from this study, they were introduced into a commercial optical model software to simulate the behavior of various optoelectronic building blocks from the simplest ones (DMD electrodes) to much more complex structures [full organic light emitting device (OLED) stacks]. As a result, a much better prediction of the emission spectrum profile as well as the angular emission pattern of top-emitting OLEDs is obtained. On this basis, it is also shown how a redesign of the top encapsulation thin film of OLEDs is necessary to better take benefit from the advanced DMD electrode. These results should particularly interest the micro-OLED display field where bright and directive single color pixel emission is required.

  7. Mechanism of equivalent electric dipole oscillation for high-order harmonic generation from grating-structured solid-surface by femtosecond laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yang; Song, Hai-Ying; Liu, H.Y.; Liu, Shi-Bing, E-mail: sbliu@bjut.edu.cn

    2017-07-12

    Highlights: • Proposed a valid mechanism of high harmonic generation by laser grating target interaction: oscillation of equivalent electric dipole (OEED). • Found that there also exist harmonic emission at large emission angle but not just near-surface direction as the former researches had pointed out. • Show the process of the formation and motion of electron bunches at the grating-target surface irradiating with femtosecond laser pulse. - Abstract: We theoretically study high-order harmonic generation (HHG) from relativistically driven overdense plasma targets with rectangularly grating-structured surfaces by femtosecond laser pulses. Our particle-in-cell (PIC) simulations show that, under the conditions of low laser intensity and plasma density, the harmonics emit principally along small angles deviating from the target surface. Further investigation of the surface electron dynamics reveals that the electron bunches are formed by the interaction between the laser field and the target surface, giving rise to the oscillation of equivalent electric-dipole (OEED), which enhances specific harmonic orders. Our work helps understand the mechanism of harmonic emissions from grating targets and the distinction from the planar harmonic scheme.

  8. Fabrication of Nanostructured Omniphobic and Superomniphobic Surfaces with Inexpensive CO2Laser Engraver.

    Science.gov (United States)

    Pendurthi, Anudeep; Movafaghi, Sanli; Wang, Wei; Shadman, Soran; Yalin, Azer P; Kota, Arun K

    2017-08-09

    Superomniphobic surfaces (i.e., surfaces that are extremely repellent to both high surface tension liquids like water and low surface tension liquid like oils) can be fabricated through a combination of surface chemistry that imparts low solid surface energy with a re-entrant surface texture. Recently, surface texturing with lasers has received significant attention because laser texturing is scalable, solvent-free, and can produce a monolithic texture on virtually any material. In this work, we fabricated nanostructured omniphobic and superomniphobic surfaces with a variety of materials using a simple, inexpensive and commercially available CO 2 laser engraver. Further, we demonstrated that the nanostructured omniphobic and superomniphobic surfaces fabricated using our laser texturing technique can be used to design patterned surfaces, surfaces with discrete domains of the desired wettability, and on-surface microfluidic devices.

  9. Evolution of Oxygen Deficiency Center on Fused Silica Surface Irradiated by Ultraviolet Laser and Posttreatment

    Directory of Open Access Journals (Sweden)

    Hai-Bing Lü

    2014-01-01

    Full Text Available Evolution of oxygen deficiency centers (ODCs on a fused silica surface irradiated using a 355 nm ultraviolet (UV laser beam in both vacuum and atmospheric conditions was quantitatively studied using photoluminescence and X-ray photoelectron spectroscopy. When the fusedsilica surface was exposed to the UV laser in vacuum, the laser damage threshold was decreased whereas the concentration of the ODCs was increased. For the fuse silica operated under the high power lasers, creation of ODCs on their surface resulted from the UV laser irradiation, and this is more severe in a high vacuum. The laser fluence and/or laser intensity have significant effects on the increase of the ODCs concentration. The ODCs can be effectively repaired using postoxygen plasma treatment and UV laser irradiation in an excessive oxygen environment. Results also demonstrated that the “gain” and “loss” of oxygen at the silica surface is a reversible and dynamic process.

  10. Ultrashort Laser Pulses and Electromagnetic Pulse Generation in Air and on Dielectric Surfaces

    National Research Council Canada - National Science Library

    Sprangle, Phillip

    2003-01-01

    ...). The purpose of this paper is to analyze EMP generation from the interaction of ultrashort laser pulses with air and with dielectric surfaces and to determine the efficiency of conversion of laser energy to EMP energy...

  11. Surface Texturing of CVD Diamond Assisted by Ultrashort Laser Pulses

    Directory of Open Access Journals (Sweden)

    Daniele M. Trucchi

    2017-11-01

    Full Text Available Diamond is a wide bandgap semiconductor with excellent physical properties which allow it to operate under extreme conditions. However, the technological use of diamond was mostly conceived for the fabrication of ultraviolet, ionizing radiation and nuclear detectors, of electron emitters, and of power electronic devices. The use of nanosecond pulse excimer lasers enabled the microstructuring of diamond surfaces, and refined techniques such as controlled ablation through graphitization and etching by two-photon surface excitation are being exploited for the nanostructuring of diamond. On the other hand, ultrashort pulse lasers paved the way for a more accurate diamond microstructuring, due to reduced thermal effects, as well as an effective surface nanostructuring, based on the formation of periodic structures at the nanoscale. It resulted in drastic modifications of the optical and electronic properties of diamond, of which “black diamond” films are an example for future high-temperature solar cells as well as for advanced optoelectronic platforms. Although experiments on diamond nanostructuring started almost 20 years ago, real applications are only today under implementation.

  12. Engineering plasmonic nanostructured surfaces by pulsed laser deposition

    Science.gov (United States)

    Ghidelli, Matteo; Mascaretti, Luca; Bricchi, Beatrice Roberta; Zapelli, Andrea; Russo, Valeria; Casari, Carlo Spartaco; Li Bassi, Andrea

    2018-03-01

    The synthesis and the optical response of gold nanoparticles (NPs) and thin nanostructured films grown by pulsed laser deposition (PLD) are here studied. Different PLD process parameters - including background gas pressure and the number of laser shots as well as post-deposition annealing treatments - have been varied to control the growth of Au NPs and films, thus tuning the surface plasmon characteristics. The mechanisms of NPs and film growth have been explored performing a morphological characterization by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), and the correlation with the optical behavior is investigated. We show that the size distribution and the morphology of the as deposited Au NPs depend on growth mechanisms which are controlled by tuning the deposition process, while the optical behavior is strongly affected by the average size and surface density of NPs or by the length of percolated Au domains. Furthermore, nucleation in gas phase has been reported at high (1000 Pa Ar) background pressures, enabling independent control of NP size and coverage, contrary to surface driven NP growth by diffusion and aggregation on substrate.

  13. MeV surface fast electron emission from femtosecond laser pulses interacting with planar and nanowire targets

    Science.gov (United States)

    Tian, Ye; Liu, Jiansheng; Wang, Wentao; Wang, Cheng; Lu, Xiaoming; Leng, Yuxin; Liang, Xiaoyan; Li, Ruxin; Xu, Zhizhan

    2014-07-01

    The mechanics of generating MeV target surface fast electrons (SFEs) is investigated using a 5 J, 50 fs laser pulse focused on a Cu planar and nanowire target. The energy spectrum and spatial angular distribution of fast electrons emitted from the planar target are determined and compared with those from the nanowire target. When the laser intensity reaches 1 × 1019 W cm-2, the coupling from the laser to 1-3 MeV electrons reaches 1.1% on the planar target at a 45° incidence angle, while the number of SFEs generated from the nanowire target is about 10% of those from the planar target. The two-dimensional particle-in-cell simulation results reproduce the electron emission characteristics and reveal a strong continuous surface magnetic field on the surface of the planar target as compared with the discrete magnetic field on the nanowire target which decreases SFEs. A high, hot electron temperature in the forward direction at 556keV is achieved for the nanowire structure capable of guiding and confining fast electrons along the wire direction, compared with 178keV for the planar target.

  14. Femtosecond laser fabrication of microspike-arrays on tungsten surface

    International Nuclear Information System (INIS)

    Sano, Tomokazu; Yanai, Masato; Ohmura, Etsuji; Nomura, Yasumitsu; Miyamoto, Isamu; Hirose, Akio; Kobayashi, Kojiro F.

    2005-01-01

    Microspike-arrays were fabricated by irradiating a femtosecond laser on a tungsten surface through a mask opening in air. The natural logarithms of the calculated intensity distributions diffracted at the edge of the mask opening were qualitatively consistent with the experimental results of the shape and arrays of microspikes fabricated. The shape and the array of microspikes depend on the intensity distribution diffracted at the edge of the mask opening. This microspike-array has the potential to be used as a source of micro emitter tips

  15. Surface modification by EUV laser beam based on capillary discharge

    Czech Academy of Sciences Publication Activity Database

    Frolov, Oleksandr; Koláček, Karel; Schmidt, Jiří; Štraus, Jaroslav; Prukner, Václav; Shukurov, A.

    -, č. 58 (2011), s. 484-487 ISSN 2010-376X. [International Conference on Fusion and Plasma Physics. Bali, Indonésie, 26.10.2011-28.10.2011] R&D Projects: GA AV ČR KAN300100702; GA MŠk LA08024; GA MŠk(CZ) LC528 Institutional research plan: CEZ:AV0Z20430508 Keywords : soft x-ray * EUV * laser * radiation * source * capillary * discharge * plasma * ablation * surface modification Subject RIV: BL - Plasma and Gas Discharge Physics http://www.waset.org/journals/waset/v58/v58-99.pdf

  16. Comparison of laser-based mitigation of fused silica surface damage using mid- versus far-infrared lasers

    Energy Technology Data Exchange (ETDEWEB)

    Yang, S T; Matthews, M J; Elhadj, S; Cooke, D; Guss, G M; Draggoo, V G; Wegner, P J

    2009-12-16

    Laser induced growth of optical damage can limit component lifetime and therefore operating costs of large-aperture fusion-class laser systems. While far-infrared (IR) lasers have been used previously to treat laser damage on fused silica optics and render it benign, little is known about the effectiveness of less-absorbing mid-IR lasers for this purpose. In this study, they quantitatively compare the effectiveness and efficiency of mid-IR (4.6 {micro}m) versus far-IR (10.6 {micro}m) lasers in mitigating damage growth on fused silica surfaces. The non-linear volumetric heating due to mid-IR laser absorption is analyzed by solving the heat equation numerically, taking into account the temperature-dependent absorption coefficient {alpha}(T) at {lambda} = 4.6 {micro}m, while far-IR laser heating is well-described by a linear analytic approximation to the laser-driven temperature rise. In both cases, the predicted results agree well with surface temperature measurements based on infrared radiometry, as well as sub-surface fictive temperature measurements based on confocal Raman microscopy. Damage mitigation efficiency is assessed using a figure of merit (FOM) relating the crack healing depth to laser power required, under minimally-ablative conditions. Based on their FOM, they show that for cracks up to at least 500 {micro}m in depth, mitigation with a 4.6 {micro}m mid-IR laser is more efficient than mitigation with a 10.6 {micro}m far-IR laser. This conclusion is corroborated by direct application of each laser system to the mitigation of pulsed laser-induced damage possessing fractures up to 225 {micro}m in depth.

  17. Radiation emitting devices regulations

    International Nuclear Information System (INIS)

    1970-01-01

    The Radiation Emitting Devices Regulations are the regulations referred to in the Radiation Emitting Devices Act and relate to the operation of devices. They include standards of design and construction, standards of functioning, warning symbol specifications in addition to information relating to the seizure and detention of machines failing to comply with the regulations. The radiation emitting devices consist of the following: television receivers, extra-oral dental x-ray equipment, microwave ovens, baggage inspection x-ray devices, demonstration--type gas discharge devices, photofluorographic x-ray equipment, laser scanners, demonstration lasers, low energy electron microscopes, high intensity mercury vapour discharge lamps, sunlamps, diagnostic x-ray equipment, ultrasound therapy devices, x-ray diffraction equipment, cabinet x-ray equipment and therapeutic x-ray equipment

  18. Laser Induced Reaction for Prebond Surface Preparation of Aluminum Alloys.;Stage 2

    National Research Council Canada - National Science Library

    Rotel, M

    1993-01-01

    ...) using a room temperature cured modified epoxy adhesive(2). Surface treatment of the Al adherend by excimer laser causes the removal of weak surface boundary layers, oxidation and morphological changes of the surface...

  19. Effect of the laser and light-emitting diode (LED) phototherapy on midpalatal suture bone formation after rapid maxilla expansion: a Raman spectroscopy analysis.

    Science.gov (United States)

    Rosa, Cristiane Becher; Habib, Fernando Antonio Lima; de Araújo, Telma Martins; Aragão, Juliana Silveira; Gomes, Rafael Soares; Barbosa, Artur Felipe Santos; Silveira, Landulfo; Pinheiro, Antonio L B

    2014-05-01

    The aim of this study was to analyze the effect of laser or light-emitting diode (LED) phototherapy on the bone formation at the midpalatal suture after rapid maxilla expansion. Twenty young adult male rats were divided into four groups with 8 days of experimental time: group 1, no treatment; group 2, expansion; group 3, expansion and laser irradiation; and group 4, expansion and LED irradiation. In groups 3 and 4, light irradiation was in the first, third, and fifth experimental days. In all groups, the expansion was accomplished with a helicoid 0.020" stainless steel orthodontic spring. A diode laser (λ780 nm, 70 mW, spot of 0.04 cm(2), t = 257 s, spatial average energy fluence (SAEF) of 18 J/cm(2)) or a LED (λ850 nm, 150 mW ± 10 mW, spot of 0.5 cm(2), t = 120 s, SAEF of 18 J/cm(2)) were used. The samples were analyzed by Raman spectroscopy carried out at midpalatal suture and at the cortical area close to the suture. Two Raman shifts were analyzed: ∼ 960 (phosphate hydroxyapatite) and ∼ 1,450 cm(-1) (lipids and protein). Data was submitted to statistical analysis. Significant statistical difference (p ≤ 0.05) was found in the hydroxyapatite (CHA) peaks among the expansion group and the expansion and laser or LED groups. The LED group presented higher mean peak values of CHA. No statistical differences were found between the treated groups as for collagen deposition, although LED also presented higher mean peak values. The results of this study using Raman spectral analysis indicate that laser and LED light irradiation improves deposition of CHA in the midpalatal suture after orthopedic expansion.

  20. The distribution of gamma-emitting radionuclides in surface subtidal sediments near the Sellafield plant

    Science.gov (United States)

    Jones, D. G.; Roberts, P. D.; Miller, J. M.

    1988-08-01

    Detailed distributions of total gamma activity, 137Cs, 106Ru and 95Zr + 95Nb in surface seabed sediments near the Sellafield plant are presented. The results are derived from a towed seabed gamma-ray spectrometer survey in September, 1982. All the distributions are similar, with contours of equal activity parallel to the coast defining a 'ridge' of higher activity which is displaced northwards relative to the outfall. This pattern appears to be largely a response to the transport of particle-associated radioeffluent modified in places by the type of seabed sediment present. At greater distance from Sellafield, the uptake of nuclides from solution seems to be more important. Nuclide concentrations decrease with increasing distance from Sellafield; rates of decrease being in the order Zr + Nb > Ru > Cs. This can be related to the levels of the nuclides discharged, their sorption characteristics and their half lives. The pattern of seabed activity seems to have been fairly stable over the period 1978 - 1985, but there is evidence of a small northward shift. Concentrations of 137Cs and 106Ru in 1985 were considerably lower than in 1978 or 1982. This is explicable in terms of the fall in discharge levels allied, in the case of Ru, to its short half life and, for Cs, the desorption observed in laboratory experiments. Nuclide ratios in sediment samples yield apparent transit times for the transport of nuclides in the survey area of 1·7 - 3·7 years. These times are generally greater than those obtained from sediments in the more distant Solway Firth and Ravenglass Estuary. It is suggested that they reflect fairly intense bioturbation causing mixing of relatively recent effluent with that from earlier discharges. This is supported by structures observed in X-radiographs of box cores, an abundant burrowing benthos and by interpretations of nuclide profiles and radiocarbon dating of sediment cores by other workers. A lag effect, of up to two years across the survey area

  1. A study of laser surface modification of polymers: A comparison in air and water

    DEFF Research Database (Denmark)

    Marla, Deepak; Andersen, Sebastian A.; Zhang, Yang

    2018-01-01

    Laser surface modification is a technique to modify polymer surfaces for various applications. In our earlier work [Physics Procedia, 83:211–217, 2016], we showed that when the laser surface modification process was carried out in water instead of air, the obtained surface characteristics were...... research. The observed images of laser modified surfaces suggest that a hemispherical hump is formed in the case of water at lower laser fluences that breakup with an increase in fluence. Such a behavior was not observed when the process was carried out in air. We explain this phenomenon by simulating...

  2. Applying Terrestrial Laser Scanning for Soil Surface Roughness Assessment

    Directory of Open Access Journals (Sweden)

    Milutin Milenković

    2015-02-01

    Full Text Available Terrestrial laser scanning can provide high-resolution, two-dimensional sampling of soil surface roughness. While previous studies demonstrated the usefulness of these roughness measurements in geophysical applications, questions about the number of required scans and their resolution were not investigated thoroughly. Here, we suggest a method to generate digital elevation models, while preserving the surface’s stochastic properties at high frequencies and additionally providing an estimate of their spatial resolution. We also study the impact of the number and positions of scans on roughness indices’ estimates. An experiment over a smooth and isotropic soil plot accompanies the analysis, where scanning results are compared to results from active triangulation. The roughness measurement conditions for ideal sampling are revisited and updated for diffraction-limited sampling valid for close-range laser scanning over smooth and isotropic soil roughness. Our results show that terrestrial laser scanning can be readily used for roughness assessment on scales larger than 5 cm, while for smaller scales, special processing is required to mitigate the effect of the laser beam footprint. Interestingly, classical roughness parametrization (correlation length, root mean square height (RMSh was not sensitive to these effects. Furthermore, comparing the classical roughness parametrization between one- and four-scan setups shows that the one-scan data can replace the four-scan setup with a relative loss of accuracy below 1% for ranges up to 3 m and incidence angles no larger than 50°, while two opposite scans can replace it over the whole plot. The incidence angle limit for the spectral slope is even stronger and is 40°. These findings are valid for scanning over smooth and isotropic soil roughness.

  3. Influence of different approaches for dynamical performance optimization of monolithic passive colliding-pulse mode-locked laser diodes emitting around 850 nm

    Science.gov (United States)

    Prziwarka, T.; Klehr, A.; Wenzel, H.; Fricke, J.; Bugge, F.; Weyers, M.; Knigge, A.; Tränkle, G.

    2018-02-01

    Monolithic laser diodes which generate short infrared pulses in the picosecond and sub-picosecond ranges with high peak power are ideal sources for many applications like e.g. THz-time-domain spectroscopy (TDS) scanning systems. The achievable THz bandwidth is limited by the length of the optical pulses. Due to the fact that colliding-pulse mode locking (CPM) leads to the shortest pulses which could reached by passive mode locking, we experimentally investigated in detail the dynamical and electro optical performance of InGaAsP based quantum well CPM laser diodes with well-established vertical layer structures. Simple design modifications whose implementation is technically easy were realized. Improvements of the device performance in terms of pulse duration, output power, and noise properties are presented in dependence on the different adaptions. From the results we extract an optimized configuration with which we have reached pulses with durations of ≍1.5 ps, a peak power of > 1 W and a pulse-to-pulse timing jitter < 200 fs. The laser diodes emit pulses at a wavelength around 850 nm with a repetition frequency of ≍ 12.4 GHz and could be used as pump source for GaAs antennas to generate THz-radiation. Approaches for reducing pulse width, increasing output power, and improving noise performance are described.

  4. Study on Surface Modification of Indium Tin Oxide and Resist Surfaces Using CF4/O2 Plasma for Manufacturing Organic Light-Emitting Diodes by Inkjet Printing

    Science.gov (United States)

    Ikagawa, Masakuni; Tohno, Ichiro; Shinmura, Tadashi; Takagi, Shigeyuki; Kataoka, Yoshinori; Fujihira, Masamichi

    2008-12-01

    We studied a surface modification technique for indium tin oxide (ITO) anodes without precleaning and resist banks for manufacturing organic light-emitting diodes (OLEDs) by inkjet printing. The ITO surface modified by inductively coupled plasma (ICP) with an optimized CF4/O2 (7:3) gas mixture improved both its hydrophilicity and its work function, while the resist surface treated by the plasma became hydrophobic. The resist and ITO surfaces treated by plasmas of various gas mixtures (i.e., CF4, CF4/Ar (1:2), CF4/O2 (x:1; x=1, 7/3, 4, and 9) were analyzed by X-ray photoelectron spectroscopy (XPS) of the C 1s, F 1s, O 1s, and In 3d5/2 core levels. On the uncleaned ITO surfaces modified by CF4/O2 plasmas, organic contaminants were removed more efficiently and the deposition of CFx on the remaining contaminants decreased with increasing oxygen. The amount of F in the form of InFx increased using the CF4/O2 (7:3) plasma in comparison with that using the CF4/Ar and CF4 plasmas. We investigated the effect of adding oxygen to CF4 on the change in gaseous species produced in the plasma chamber by mass spectrometry. In the CF4/O2 (7:3) plasma, the peak intensities of F+, HF+, F2+, O+, and O2+ were higher than those in the CF4 plasma. The results suggest that In2O3 was generated by the oxidation of indium with O, and InFx was generated by the fluoridation of indium with HF. By introducing InFx onto ITO surfaces using the CF4/O2 plasma, the hole-injection energy barrier could be reduced.

  5. Simultaneous microstructuring and functionalisation of surfaces with picosecond laser

    Science.gov (United States)

    Hildenhagen, Jens; Dickmann, Klaus; Neyer, Johannes; Wieschendorf, Christoph

    2013-06-01

    The generation of microstructures by ultrashort pulse laser irradiation is - depending on process parameters and the applied material - often accompanied with the creation of substructures like ripples or micro canals on the ablation ground. This side effect can be used to create local topographic modifications on a microscopic scale which can change functional properties of the surface. The combination of micro structuring and functionalisation within one production step can only be successful if the interaction mechanisms are well known. In this study the options to modify the wetting behavior on stainless steel, Al2O3 ceramic and PMMA plastic were analyzed. Therefore the contact angles of water drops on picoseconds-laser-produced samples were measured by a self-made measuring system. Test measurements offered post-process effects on surfaces of steel and ceramic. On those substrates the final contact angle adjusts after several hours up to days. In total with this technique contact angles between 5° and 160° could be realized, depending on the material. This allows generation of hydrophilic up to super-hydrophobic effects on precise defined areas. The combination technique offers novel options particularly for micro fluidic. Some produced samples for "Lab-on-a-Chip- Systems" should demonstrate that.

  6. Tissue surface information for intraoperative incision planning and focus adjustment in laser surgery.

    Science.gov (United States)

    Schoob, Andreas; Kundrat, Dennis; Kleingrothe, Lukas; Kahrs, Lüder A; Andreff, Nicolas; Ortmaier, Tobias

    2015-02-01

    Introducing computational methods to laser surgery are an emerging field. Focusing on endoscopic laser interventions, a novel approach is presented to enhance intraoperative incision planning and laser focusing by means of tissue surface information obtained by stereoscopic vision. Tissue surface is estimated with stereo-based methods using nonparametric image transforms. Subsequently, laser-to-camera registration is obtained by ablating a pattern on tissue substitutes and performing a principle component analysis for precise laser axis estimation. Furthermore, a virtual laser view is computed utilizing trifocal transfer. Depth-based laser focus adaptation is integrated into a custom experimental laser setup in order to achieve optimal ablation morphology. Experimental validation is conducted on tissue substitutes and ex vivo animal tissue. Laser-to-camera registration gives an error between planning and ablation of less than 0.2 mm. As a result, the laser workspace can accurately be highlighted within the live views and incision planning can directly be performed. Experiments related to laser focus adaptation demonstrate that ablation geometry can be kept almost uniform within a depth range of 7.9 mm, whereas cutting quality significantly decreases when the laser is defocused. An automatic laser focus adjustment on tissue surfaces based on stereoscopic scene information is feasible and has the potential to become an effective methodology for optimal ablation. Laser-to-camera registration facilitates advanced surgical planning for prospective user interfaces and augmented reality extensions.

  7. Corrosion behaviour of laser surface melted magnesium alloy AZ91D

    International Nuclear Information System (INIS)

    Taltavull, C.; Torres, B.; Lopez, A.J.; Rodrigo, P.; Otero, E.; Atrens, A.; Rams, J.

    2014-01-01

    A high power diode laser (HPDL) was used to produce laser surface melting (LSM) treatments on the surface of the Mg alloy AZ91D. Different treatments with different microstructures were produced by varying the laser-beam power and laser-scanning speed. Corrosion evaluation, using hydrogen evolution and electrochemical measurements, led to a relationship between microstructure and corrosion. Most corrosion rates for LSM treated specimens were within the scatter of the as-received AZ91D, whereas some treatments gave higher corrosion rates and some of the samples had corrosion rates lower than the average of the corrosion rate for AZ91D. There were differences in corroded surface morphology. Nevertheless laser treatments introduced surface discontinuities, which masked the effect of the microstructure. Removing these surface defects decreased the corrosion rate for the laser-treated samples. - Highlights: • Corrosion behavior of AZ91D Mg alloys is intimately related with its microstructure. • Laser surface melting treatments allows surface modification of the microstructure. • Different laser parameters can achieve different microstructures. • Controlling laser parameters can produce different corrosion rates and morphologies. • Increase of surface roughness due to laser treatment is relevant to the corrosion rate

  8. Utilization of the UV laser with picosecond pulses for the formation of surface microstructures on elastomeric plastics

    Science.gov (United States)

    Antoszewski, B.; Tofil, S.; Scendo, M.; Tarelnik, W.

    2017-08-01

    Elastomeric plastics belong to a wide range of polymeric materials with special properties. They are used as construction material for seals and other components in many branches of industry and, in particular, in the biomedical industry, mechatronics, electronics and chemical equipment. The micromachining of surfaces of these materials can be used to build micro-flow, insulating, dispensing systems and chemical and biological reactors. The paper presents results of research on the effects of micro-machining of selected elastomeric plastics using a UV laser emitting picosecond pulses. The authors see the prospective application of the developed technology in the sealing technique in particular to shaping the sealing pieces co-operating with the surface of the element. The result of the study is meant to show parameters of the UV laser’s performance when producing typical components such as grooves, recesses for optimum ablation in terms of quality and productivity.

  9. [Effects of Nd: YAG laser irradiation on the root surfaces and adhesion of Streptococcus mutans].

    Science.gov (United States)

    Yuanhong, Li; Zhongcheng, Li; Mengqi, Luo; Daonan, Shen; Shu, Zhang; Shu, Meng

    2016-12-01

    This study aimed to evaluate the effects of treatment with different powers of Nd: YAG laser irradiation on root surfaces and Streptococcus mutans (S. mutans) adhesion. Extracted teeth because of severe periodontal disease were divided into the following four groups: control group, laser group 1, laser group 2, and laser group 3. After scaling and root planning, laser group 1, laser group 2, and laser group 3 were separately treated with Nd: YAG laser irradiation (4/6/8 W, 60 s); however, the control group did not receive the treatment. Scanning electron microscopy (SEM) was used to determine the morphology. S. mutans were cultured with root slices from each group. Colony forming unit per mL (CFU·mL⁻¹) was used to count and compare the amounts of bacteria adhesion among groups. SEM was used to observe the difference of bacteria adhesion to root surfaces between control group (scaling) and laser group 2 (6 W, 60 s), thereby indicating the different bacteria adhesions because of different treatments. Morphology alterations indicated that root surfaces in control group contain obvious smear layer, debris, and biofilm; whereas the root surfaces in laser group contain more cracks with less smear layer and debris. The bacteria counting indicated that S. mutans adhesion to laser group was weaker than that of control group (P0.05) was observed. Morphology alterations also verified that S. mutans adhesion to laser group 2 (6 W, 60 s) was weaker than that of control group (scaling). This study demonstrated that Nd: YAG laser irradiation treatment after scaling can reduce smear layer, debris, and biofilm on the root surfaces as compared with conventional scaling. The laser treatment reduces the adhesion of S. mutans as well. However, Nd: YAG laser irradiation can cause cracks on the root surfaces. In this experiment, the optimum laser power of 6 W can thoroughly remove the smear layer and debris, as well as relatively improve the control of thermal damagee.

  10. Improvement of the surface finish obtained by laser ablation with a Nd: YAG laser on pre-ablated tool steel

    CSIR Research Space (South Africa)

    Steyn, J

    2007-01-01

    Full Text Available Surface finish is an important requirement for tool and die makers and remains a challenge with conventional machining technologies. Nd: YAG lasers have been utilised for many years in the area of laser marking, engraving and micro machining...

  11. Development of gallium-nitride-based light-emitting diodes (LEDs) and laser diodes for energy-efficient lighting and displays

    International Nuclear Information System (INIS)

    DenBaars, Steven P.; Feezell, Daniel; Kelchner, Katheryn; Pimputkar, Siddha; Pan, Chi-Chen; Yen, Chia-Chen; Tanaka, Shinichi; Zhao, Yuji; Pfaff, Nathan; Farrell, Robert; Iza, Mike; Keller, Stacia; Mishra, Umesh; Speck, James S.; Nakamura, Shuji

    2013-01-01

    Light-emitting diodes (LEDs) fabricated from gallium nitride (GaN) have led to the realization of high-efficiency white solid-state lighting. Currently, GaN white LEDs exhibit luminous efficacy greater than 150 lm W −1 , and external quantum efficiencies higher than 60%. This has enabled LEDs to compete with traditional lighting technologies, such as incandescent and compact fluorescent (CFL) lighting. Further improvements in materials quality and cost reduction are necessary for widespread adoption of LEDs for lighting. A review of the unique polarization anisotropy in GaN is included for the different crystal orientations. The emphasis on nonpolar and semipolar LEDs highlights high-power violet and blue emitters, and we consider the effects of indium incorporation and well width. Semipolar GaN materials have enabled the development of high-efficiency LEDs in the blue region and recent achievements of green laser diodes at 520 nm

  12. Influence of laser lift-off on optical and structural properties of InGaN/GaN vertical blue light emitting diodes

    Directory of Open Access Journals (Sweden)

    M. H. Doan

    2012-06-01

    Full Text Available The influences of the laser lift-off (LLO process on the InGaN/GaN blue light emitting diode (LED structures, grown on sapphire substrates by low-pressure metalorganic chemical vapor deposition, have been comprehensively investigated. The vertical LED structures on Cu carriers are fabricated using electroplating, LLO, and inductively coupled plasma etching processes sequentially. A detailed study is performed on the variation of defect concentration and optical properties, before and after the LLO process, employing high-resolution transmission electron microscopy (HRTEM, scanning electron microscopy (SEM observations, cathodoluminescence (CL, photoluminescence (PL, and high-resolution X-ray diffraction (HRXRD measurements. The SEM observations on the distribution of dislocations after the LLO show well that even the GaN layer near to the multiple quantum wells (MQWs is damaged. The CL measurements reveal that the peak energy of the InGaN/GaN MQW emission exhibits a blue-shift after the LLO process in addition to a reduced intensity. These behaviors are attributed to a diffusion of indium through the defects created by the LLO and creation of non-radiative recombination centers. The observed phenomena thus suggest that the MQWs, the active region of the InGaN/GaN light emitting diodes, may be damaged by the LLO process when thickness of the GaN layer below the MQW is made to be 5 μm, a conventional thickness. The CL images on the boundary between the KrF irradiated and non-irradiated regions suggest that the propagation of the KrF laser beam and an accompanied recombination enhanced defect reaction, rather than the propagation of a thermal shock wave, are the main origin of the damage effects of the LLO process on the InGaN/GaN MQWs and the n-GaN layer as well.

  13. Laser surface modification of silicone rubber to reduce platelet adhesion in vitro.

    Science.gov (United States)

    Khorasani, M T; Mirzadeh, H

    2004-01-01

    To improve the blood compatibility, the surface of polydimethylsiloxane (PDMS) films were irradiated using a CO2-pulsed laser. Acrylamide (AAm) was grafted onto a pre-irradiated surface. The AAm-grafted and laser-treated films were characterized using different techniques. Platelet adhesion and activation onto the AAm-grafted PDMS, laser-treated (ungrafted) and unmodified PDMS film surfaces were compared. Data from in vitro assays indicated that the platelet adhesion was reduced on the AAm-grafted PDMS and laser treated PDMS films in comparison with the unmodified PDMS. The laser-irradiated sample showed the minimum platelet adhesion. It seems that laser irradiation onto a silicone rubber surface is a versatile technique to produce anti-thrombogenic surface for biomaterial applications.

  14. Laser gas assisted texturing and formation of nitride and oxynitride compounds on alumina surface: Surface response to environmental dust

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.; Al-Sharafi, A.; Al-Aqeeli, N.

    2018-03-01

    Laser gas assisted texturing of alumina surface is carried out, and formation of nitride and oxynitride compounds in the surface vicinity is examined. The laser parameters are selected to create the surface topology consisting of micro/nano pillars with minimum defect sites including micro-cracks, voids and large size cavities. Morphological and hydrophobic characteristics of the textured surface are examined using the analytical tools. The characteristics of the environmental dust and its influence on the laser textured surface are studied while mimicking the local humid air ambient. Adhesion of the dry mud on the laser textured surface is assessed through the measurement of the tangential force, which is required to remove the dry mud from the surface. It is found that laser texturing gives rise to micro/nano pillars topology and the formation of AlN and AlON compounds in the surface vicinity. This, in turn, lowers the free energy of the textured surface and enhances the hydrophobicity of the surface. The liquid solution resulted from the dissolution of alkaline and alkaline earth metals of the dust particles in water condensate forms locally scattered liquid islands at the interface of mud and textured surface. The dried liquid solution at the interface increases the dry mud adhesion on the textured surface. Some dry mud residues remain on the textured surface after the dry mud is removed by a pressurized desalinated water jet.

  15. Ultra short pulse laser generated surface textures for anti-ice applications in aviation

    NARCIS (Netherlands)

    Römer, G.W.; Del Cerro, D.A.; Sipkema, R.C.J.; Groenendijk, M.N.W.; Huis in 't Veld, A.J.

    2009-01-01

    By laser ablation with ultra short laser pulses in the pico- and femto-second range, well controlled dual scaled micro- and nano-scaled surface textures can be obtained. The micro-scale of the texture is mainly determined by the dimensions of the laser spot, whereas the superimposed nano-structure

  16. Effect of surface-breakdown plasma on metal drilling by pulsed CO2-laser radiation

    Science.gov (United States)

    Arutiunian, P. V.; Baranov, V. Iu.; Bobkov, I. V.; Bol'Shakov, L. A.; Dolgov, V. A.

    1988-03-01

    The effect of low-threshold surface breakdown produced by short (5-microsec) CO2-laser pulses on the metal drilling process is investigated. Data on the interaction of metals with laser pulses having the same duration but different shape are shown to be different. The effect of the ambient atmospheric pressure on the laser drilling process is investigated.

  17. Liquid Atomization Induced by Pulse Laser Reflection underneath Liquid Surface

    Science.gov (United States)

    Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro; Nakahara, Motonao

    2009-05-01

    We observed a novel effect of pulse laser reflection at the interface between transparent materials with different refractive indices. The electric field intensity doubles when a laser beam is completely reflected from a material with a higher refractive index to a material with a lower index. This effect appreciably reduces pulse laser ablation threshold of transparent materials. We performed experiments to observe the entire ablation process for laser incidence on the water-air interface using pulse laser shadowgraphy with high-resolution film; the minimum laser fluence for laser ablation at the water-air interface was approximately 12-16 J/cm2. We confirmed that this laser ablation occurs only when the laser beam is incident on the water-air interface from water. Many slender liquid ligaments extend like a milk crown and seem to be atomized at the tip. Their detailed structures can be resolved only by pulse laser photography using high-resolution film.

  18. Biocompatibility enhancement of rare earth magnesium alloy by laser surface processing

    Science.gov (United States)

    Nie, Shilin; Wang, Yuqing; Liu, Haifeng; Guan, Yingchun

    2018-01-01

    Although magnesium and magnesium alloys are considered biocompatible and biodegradable, insufficient biocompatibility in body fluid environment is still the major drawback of magnesium alloys for their successful applications as biodegradable orthopaedic implants. In this work, magnesium alloy surface with both enhanced corrosion resistance and better cell adhesion property was directly fabricated by laser surface processing. Laser surface melting was used to improve corrosion resistance of Mg-6Gd-0.6Ca alloy. After laser surface melting, laser surface texturing was utilized on melted surface for better cell adhesion property. The corrosion resistance of laser-treated and as-received samples were evaluated using electrochemical technique. The effect of laser surface treatment on phase and microstructure evolution was evaluated using scanning electron microscopy, optical microscopy and X-ray diffraction. This work investigated the effect of laser treatment on cell distribution across the surface of magnesium alloy substrates. Osteoblast was cultured on the laser-treated surface and as-received surface. Cell morphology was observed with a scanning electron microscopy, and cell viability was evaluated by optical density measurement.

  19. Reduction of secondary electron yield for E-cloud mitigation by laser ablation surface engineering

    Energy Technology Data Exchange (ETDEWEB)

    Valizadeh, R., E-mail: reza.valizadeh@stfc.ac.uk [ASTeC, STFC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Malyshev, O.B. [ASTeC, STFC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Wang, S. [ASTeC, STFC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Department of Physics, Loughborough University, Loughborough LE11 3TU (United Kingdom); Sian, T. [ASTeC, STFC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); The Photon Science Institute, The University of Manchester, Manchester M13 9PL (United Kingdom); Cropper, M.D. [Department of Physics, Loughborough University, Loughborough LE11 3TU (United Kingdom); Sykes, N. [Micronanics Ltd., Didcot, Oxon OX11 0QX (United Kingdom)

    2017-05-15

    Highlights: • SEY below 1 can be achieved with Laser ablation surface engineering. • SEY <1 surface can be produced with different types of nanosecond lasers. • Both microstructure (groves) and nano-structures are playing a role in reducing SEY. - Abstract: Developing a surface with low Secondary Electron Yield (SEY) is one of the main ways of mitigating electron cloud and beam-induced electron multipacting in high-energy charged particle accelerators. In our previous publications, a low SEY < 0.9 for as-received metal surfaces modified by a nanosecond pulsed laser was reported. In this paper, the SEY of laser-treated blackened copper has been investigated as a function of different laser irradiation parameters. We explore and study the influence of micro- and nano-structures induced by laser surface treatment in air of copper samples as a function of various laser irradiation parameters such as peak power, laser wavelength (λ = 355 nm and 1064 nm), number of pulses per point (scan speed and repetition rate) and fluence, on the SEY. The surface chemical composition was determined by x-ray photoelectron spectroscopy (XPS) which revealed that heating resulted in diffusion of oxygen into the bulk and induced the transformation of CuO to sub-stoichiometric oxide. The surface topography was examined with high resolution scanning electron microscopy (HRSEM) which showed that the laser-treated surfaces are dominated by microstructure grooves and nanostructure features.

  20. LASER INDUCED SELECTIVE ACTIVATION UTILIZING AUTO-CATALYTIC ELECTROLESS PLATING ON POLYMER SURFACE

    DEFF Research Database (Denmark)

    Zhang, Yang; Nielsen, Jakob Skov; Tang, Peter Torben

    2009-01-01

    . Characterization of the deposited copper layer was used to select and improve laser parameters. Several types of polymers with different melting points were used as substrate. Using the above mentioned laser treatment, standard grades of thermoplastic materials such as ABS, SAN, PE, PC and others have been......This paper presents a new method for selective micro metallization of polymers induced by laser. An Nd: YAG laser was employed to draw patterns on polymer surfaces using a special set-up. After subsequent activation and auto-catalytic electroless plating, copper only deposited on the laser tracks....... Induced by the laser, porous and rough structures are formed on the surface, which favours the palladium attachment during the activation step prior to the metallization. Laser focus detection, scanning electron microscopy (SEM) and other instruments were used to analyze the topography of the laser track...

  1. Research on Laser Micro Polishing of SLS Technology Sintered Iron-Based Powder Surface

    Directory of Open Access Journals (Sweden)

    Gerda Vaitkūnaitė

    2015-03-01

    Full Text Available The article analyzes laser micro polishing of 1.2083 steel samples produced applying selective laser sintering (SLS method. The study has evaluated the distribution of the shape, size and temperature of the laser beam treated area in the surface layer of sintered and laser polished samples. Experimental tests have shown the impact of the technical parameters of laser micro polishing on the width and hardness of the impact zone of the treated sample. The microstructure analysis of laser treated and untreated areas of the material has been made.

  2. Evaluation of the morphological alteration of the root surface radiated with a diode laser; Avaliacao da alteracao morfologica da superficie cimentaria irradiada com laser de diodo

    Energy Technology Data Exchange (ETDEWEB)

    Gulin, Mauricio

    2003-07-01

    The diode laser has been studied for periodontal therapy, as much for removal of calculus as for microbial reduction of periodontal pockets, as well as the visible analgesic effects and biomodulation capacity. For this reason the purpose of this study was to evaluate the morphological alteration of the root surface after radiation with the diode laser, 808 nm through analysis by scanning electron microscopy (SEM). Besides this, to verify the temperature variations caused during the radiation, a thermometer put into the dentinal wall of the root canal was used. In all, 18 teeth were used, 15 of which for the SEM study, and the other 3 were used to temperature variation analysis. The 25 samples were scraped on the root surface and planed with manual instruments. The other 5 were not subjected to any type of treatment. This, 6 groups of 5 samples each were formed. Control Group C whose samples had not received any treatment; Control Group C 1 was only scraped and polished conventionally with Hu-Friedy Gracey curettes 5 and 6; the other samples groups L1, L2, L3, L4 were radiated by diode laser using parameters of power 1,0 W; 1,2 W; 1,4 W; and 1,6 W respectively, 2 times for 10 seconds with 20 seconds intervals between each radiation in continuous mode. The results with relation to the increase of temperature in the interior of the root canal demonstrated that there was an increase of more than 5 degree Celsius. The results of the scanning electron microscope analysis of Control Group C demonstrated great irregularity and ridges on the root surface, with the presence of a dentine layer. Control Group C1 presented a similar aspect to Group L 1's, smoother and more homogeneous surface. Groups L2, L3, and L4 presented scratches alternating with smoother areas showing that fiber contacted the surface of the sample. The results reconfirmed the necessity of further studies using diode laser, with a beam of light emitted in an interrupted mode to improve the control of

  3. Measurement of the body surface temperature by the method of laser photothermal radiometry

    International Nuclear Information System (INIS)

    Skvortsov, L A; Kirillov, V M

    2003-01-01

    The specific features of contactless measurements of the body surface temperature by the method of repetitively pulsed laser photothermal radiometry are considered and the requirements to the parameters of the laser and measurement scheme are formulated. The sensitivity of the method is estimated. The advantages of laser photothermal radiometry over the conventional passive radiometric method are discussed. (laser applications and other topics in quantum electronics)

  4. Excimer laser patterning of PEDOT-PSS thin-films on flexible barrier foils: a surface analysis study

    NARCIS (Netherlands)

    Naithani, S.; Schaubroeck, D.; Vercammen, Y.; Mandamparambil, R.; Yakimets, I.; Vaeck, L. van; Steenberge, G. van

    2013-01-01

    Selective laser patterning of thin organic films is an important aspect in the roll-to-roll production of organic electronic devices such as organic light emitting diodes (OLEDs). An excimer laser is well suited for the patterning and structuring of polymer thin films as their UV absorption is

  5. Influence of irradiation conditions on polytetrafluoroethylen ablation induced by soft x-rays emitted from laser-produced plasma

    Czech Academy of Sciences Publication Activity Database

    Viskup, Richard; Juha, Libor; Krása, Josef

    2004-01-01

    Roč. 54, č. 3 (2004), s. 277-284 ISSN 0323-0465 R&D Projects: GA MŠk LA 055; GA MŠk 1P04LA235; GA MŠk LN00A100 Institutional research plan: CEZ:AV0Z1010921 Keywords : ablation * X-rays Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.513, year: 2004

  6. Single crystal silicon carbide detector of emitted ions and soft x rays from power laser-generated plasmas

    Czech Academy of Sciences Publication Activity Database

    Torrisi, L.; Foti, G.; Giuffrida, L.; Puglisi, D.; Wolowski, J.; Badziak, J.; Parys, P.; Rosinski, M.; Margarone, D.; Krása, Josef; Velyhan, Andriy; Ullschmied, Jiří

    2009-01-01

    Roč. 105, č. 12 (2009), 123304/1-123304/7 ISSN 0021-8979 R&D Projects: GA AV ČR IAA100100715 Institutional research plan: CEZ:AV0Z10100523; CEZ:AV0Z20430508 Keywords : laser-produced plasma * SiC detector * ion collector Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.072, year: 2009

  7. [INVITED] Laser gas assisted treatment of Ti-alloy: Analysis of surface characteristics

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.; Karatas, C.

    2016-04-01

    Laser gas assisted treatment of Ti6Al4V alloy surface is carried out and nitrogen/oxygen mixture with partial pressure of PO2/PN2=1/3 is introduced during the surface treatment process. Analytical tools are used to characterize the laser treated surfaces. The fracture toughness at the surface and the residual stress in the surface region of the laser treated layer are measured. Scratch tests are carried out to determine the friction coefficient of the treated surface. It is found that closely spaced regular laser scanning tracks generates a self-annealing effect in the laser treated layer while lowering the stress levels in the treated region. Introducing high pressure gas mixture impingement at the surface results in formation of oxide and nitride species including, TiO, TiO2, TiN and TiOxNy in the surface region. A dense layer consisting of fine size grains are formed in the surface region of the laser treated layer, which enhances the microhardness at the surface. The fracture toughness reduces after the laser treatment process because of the microhardness enhancement at the surface. The residual stress formed is comprehensive, which is in the order of -350 MPa.

  8. Cascade type-I quantum well diode lasers emitting 960 mW near 3 μm

    International Nuclear Information System (INIS)

    Shterengas, Leon; Liang, Rui; Kipshidze, Gela; Hosoda, Takashi; Belenky, Gregory; Bowman, Sherrie S.; Tober, Richard L.

    2014-01-01

    The cascade pumping scheme reduced the threshold current density of high power type-I quantum well GaSb-based λ ∼ 3 μm diode lasers down to ∼100 A/cm 2 at room temperature. Laser heterostructures had single GaInAsSb quantum well gain stages connected in series by means of GaSb/AlSb/InAs tunnel junctions followed by InAs/AlSb electron injectors. Devices with densely stacked two and three gain stages and 100-μm-wide aperture demonstrated peak power conversion efficiency of 16% and continuous wave output power of 960 mW. Corresponding narrow ridge lasers demonstrated above 100 mW of output power. The experiment showed that the bandwidth of the gain and its rate of increase with current depended strongly on the thickness of AlSb layer separating electron injectors from quantum wells. The possible impact of electron injector interfaces and ionized impurities on the carrier scattering and recombination in the active quantum well is discussed.

  9. Cascade type-I quantum well diode lasers emitting 960 mW near 3 μm

    Energy Technology Data Exchange (ETDEWEB)

    Shterengas, Leon, E-mail: leon.shterengas@stonybrook.edu; Liang, Rui; Kipshidze, Gela; Hosoda, Takashi; Belenky, Gregory [State University of New York at Stony Brook, Stony Brook, New York 11794 (United States); Bowman, Sherrie S.; Tober, Richard L. [Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States)

    2014-10-20

    The cascade pumping scheme reduced the threshold current density of high power type-I quantum well GaSb-based λ ∼ 3 μm diode lasers down to ∼100 A/cm{sup 2} at room temperature. Laser heterostructures had single GaInAsSb quantum well gain stages connected in series by means of GaSb/AlSb/InAs tunnel junctions followed by InAs/AlSb electron injectors. Devices with densely stacked two and three gain stages and 100-μm-wide aperture demonstrated peak power conversion efficiency of 16% and continuous wave output power of 960 mW. Corresponding narrow ridge lasers demonstrated above 100 mW of output power. The experiment showed that the bandwidth of the gain and its rate of increase with current depended strongly on the thickness of AlSb layer separating electron injectors from quantum wells. The possible impact of electron injector interfaces and ionized impurities on the carrier scattering and recombination in the active quantum well is discussed.

  10. Electrical characteristics of a vertical light emitting diode with n-type contacts on a selectively wet-etching roughened surface

    International Nuclear Information System (INIS)

    Wang Liancheng; Guo Enqing; Liu Zhiqiang; Yi Xiaoyan; Wang Guohong

    2011-01-01

    Low resistance and thermally stable n-type contacts to N-polar GaN are essentially important for vertical light emitting diodes (VLEDs). The electrical characteristics of VLEDs with n-type contacts on a roughened and flat N-polar surface have been compared. VLEDs with contacts deposited on a roughened surface exhibit lower leakage currents yet a higher operating voltage. Based on this, a new scheme by depositing metallization contacts on a selectively wet-etching roughened surface has been developed. Excellent electrical and optical characteristics have been achieved with this method. An aging test further confirmed its stability. (semiconductor devices)

  11. IceBridge Riegl Laser Altimeter L2 Geolocated Surface Elevation Triplets V001

    Data.gov (United States)

    National Aeronautics and Space Administration — The IceBridge Riegl Laser Altimeter L2 Geolocated Surface Elevation Triplets (ILUTP2) data set contains surface range values for Antarctica and Greenland derived...

  12. IceBridge Riegl Laser Altimeter L2 Geolocated Surface Elevation Triplets

    Data.gov (United States)

    National Aeronautics and Space Administration — The IceBridge Riegl Laser Altimeter L2 Geolocated Surface Elevation Triplets (ILUTP2) data set contains surface range values for Antarctica and Greenland derived...

  13. Response-surface models for deterministic effects of localized irradiation of the skin by discrete {beta}/{gamma} -emitting sources

    Energy Technology Data Exchange (ETDEWEB)

    Scott, B.R.

    1995-12-01

    Individuals who work at nuclear reactor facilities can be at risk for deterministic effects in the skin from exposure to discrete {Beta}- and {gamma}-emitting ({Beta}{gamma}E) sources (e.g., {Beta}{gamma}E hot particles) on the skin or clothing. Deterministic effects are non-cancer effects that have a threshold and increase in severity as dose increases (e.g., ulcer in skin). Hot {Beta}{gamma}E particles are {sup 60}Co- or nuclear fuel-derived particles with diameters > 10 {mu}m and < 3 mm and contain at least 3.7 kBq (0.1 {mu}Ci) of radioactivity. For such {Beta}{gamma}E sources on the skin, it is the beta component of the dose that is most important. To develop exposure limitation systems that adequately control exposure of workers to discrete {Beta}{gamma}E sources, models are needed for systems that adequately control exposure of workers to discrete {Beta}{gamma}E sources, models are needed for evaluating the risk of deterministic effects of localized {Beta} irradiation of the skin. The purpose of this study was to develop dose-rate and irradiated-area dependent, response-surface models for evaluating risks of significant deterministic effects of localized irradiation of the skin by discrete {Beta}{gamma}E sources and to use modeling results to recommend approaches to limiting occupational exposure to such sources. The significance of the research results as follows: (1) response-surface models are now available for evaluating the risk of specific deterministic effects of localized irradiation of the skin; (2) modeling results have been used to recommend approaches to limiting occupational exposure of workers to {Beta} radiation from {Beta}{gamma}E sources on the skin or on clothing; and (3) the generic irradiated-volume, weighting-factor approach to limiting exposure can be applied to other organs including the eye, the ear, and organs of the respiratory or gastrointestinal tract and can be used for both deterministic and stochastic effects.

  14. Surface plasma preionization produced on a specially patterned PCB and its application in a pulsed CO2 laser

    Science.gov (United States)

    Ghorbanzadeh, Atamalek; Pakmanesh, Nahid; Rastegari, Ali; Abdolghader, Pedram; Feizollah, Peyman; Siadati, Neda

    2016-04-01

    The performance of an atmospheric pressure pulsed carbon dioxide laser employing surface plasma preionization, produced on a specially patterned printed circuit board (PCB), is reported. The surface plasma is formed due to many tiny plasma channels produced in millimeter sized open circular gaps, made by lithography on one side of PCB. The preionizing plasma is mostly consisted of corona or glow stage and transition to spark one hardly occurs. This type of preionization allows a maximum of 220 J/l energy deposition into the main plasma, while up scaling is yet possible by more optimization of PCB and the pattern. The laser output energy of 1.2 J per pulse with overall efficiency of 7% has been obtained with gas mixture of He:CO2:N2=3:1:1. This type of surface plasma preionization is specifically appropriate for very large volumes and high pressures, where the conventional UV emitting preionizations like spark arrays or corona are not effective.

  15. Collective migration of adsorbed atoms on a solid surface in the laser radiation field

    International Nuclear Information System (INIS)

    Andreev, V V; Ignat'ev, D V; Telegin, Gennadii G

    2004-01-01

    The lateral (in the substrate plane) interaction between dipoles induced in particles adsorbed on a solid surface is studied in a comparatively weak laser radiation field with a Gaussian transverse distribution. It is shown that the particles migrate over the surface in the radial direction either outside an illuminated spot with the formation of a 'crater' or inside the spot with the formation of a 'mound'. (interaction of laser radiation with matter. laser plasma)

  16. Laser surface treatment for enhanced titanium to carbon fiber-reinforced polymer adhesion

    NARCIS (Netherlands)

    Palavra, Armin; Coelho, Bruno N.; de Hosson, Jeff Th. M.; Lima, Milton S. F.; Carvalho, Sheila M.; Costa, Adilson R.

    The adhesion between carbon fiber-reinforced polymer (CFRP) and titanium parts can be improved by laser surface texturing before gluing them together. Here, a pulsed Nd:YAG laser was employed before bonding of the textured surfaces using an epoxy paste adhesive. To investigate the influence of the

  17. Finite-difference Time-domain Modeling of Laser-induced Periodic Surface Structures

    NARCIS (Netherlands)

    Römer, Gerardus Richardus, Bernardus, Engelina; Skolski, J.Z.P.; Vincenc Obona, J.; Huis in 't Veld, Bert

    2014-01-01

    Laser-induced periodic surface structures (LIPSSs) consist of regular wavy surface structures with amplitudes the (sub)micrometer range and periodicities in the (sub)wavelength range. It is thought that periodically modulated absorbed laser energy is initiating the growth of LIPSSs. The “Sipe

  18. Experimental and numerical investigation of laser forming of cylindrical surfaces with arbitrary radius of curvature

    Directory of Open Access Journals (Sweden)

    Mehdi Safari

    2016-09-01

    Full Text Available In this work, laser forming of cylindrical surfaces with arbitrary radius of curvature is investigated experimentally and numerically. For laser forming of cylindrical surfaces with arbitrary radius of curvature, a new and comprehensive method is proposed in this paper. This method contains simple linear irradiating lines and using an analytical method, required process parameters for laser forming of a cylindrical surface with a specific radius of curvature is proposed. In this method, laser output power, laser scanning speed and laser beam diameter are selected based on laser machine and process limitations. As in the laser forming of a cylindrical surface, parallel irradiating lines are needed; therefore key parameter for production of a cylindrical surface with a specific radius of curvature is the number of irradiating lines. Hence, in the proposed analytical method, the required number of irradiating lines for production of a cylindrical surface with a specific radius of curvature is suggested. Performance of the proposed method for production of cylindrical surface with a specific radius of curvature is verified with experimental tests. The results show that using proposed analytical method, cylindrical surfaces with any radius of curvature can be produced successfully.

  19. Erosion resistant anti-ice surfaces generated by ultra short laser pulses

    NARCIS (Netherlands)

    Del Cerro, D.A.; Römer, G.R.B.E.; Huis in't Veld, A.J.

    2010-01-01

    Wetting properties of a wide range of materials can be modified by accurate laser micromachining with ultra short laser pulses. Controlling the surface topography in a micro and sub-micrometer scale allows the generation of water-repellent surfaces, which remain dry and prevent ice accumulation

  20. Beam waist position study for surface modification of polymethyl-methacrylate with femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Caballero-Lucas, F.; Florian, C.; Fernández-Pradas, J.M., E-mail: jmfernandez@ub.edu; Morenza, J.L.; Serra, P.

    2016-06-30

    Highlights: • Surface modification of PMMA with femtosecond laser pulses. • Z-scan reflectance and transmittance study for controlling the sample surface position in the laser beam waist. • Surface modifications with dimensions in the nanometric scale with a 1027 nm wavelength laser. • Extended range of some microns for placing the sample and precise determination of the beam waist position. - Abstract: Femtosecond lasers are versatile tools to process transparent materials. This optical property poses an issue for surface modification. In this case, laser radiation would not be absorbed at the surface unless the beam is just focused there. Otherwise, absorption would take place in the bulk leaving the surface unperturbed. Therefore, strategies to position the material surface at the laser beam waist with high accuracy are essential. We investigated and compared two options to achieve this aim: the use of reflectance data and transmittance measurements across the sample, both obtained during z-scans with pulses from a 1027 nm wavelength laser and 450 fs pulse duration. As the material enters the beam waist region, a reflectance peak is detected while a transmittance drop is observed. With these observations, it is possible to control the position of the sample surface with respect to the beam waist with high resolution and attain pure surface modification. In the case of polymethyl-methacrylate (PMMA), this resolution is 0.6 μm. The results prove that these methods are feasible for submicrometric processing of the surface.

  1. Deep surface rolling for fatigue life enhancement of laser clad aircraft aluminium alloy

    Science.gov (United States)

    Zhuang, W.; Liu, Q.; Djugum, R.; Sharp, P. K.; Paradowska, A.

    2014-11-01

    Deep surface rolling can introduce deep compressive residual stresses into the surface of aircraft metallic structure to extend its fatigue life. To develop cost-effective aircraft structural repair technologies such as laser cladding, deep surface rolling was considered as an advanced post-repair surface enhancement technology. In this study, aluminium alloy 7075-T651 specimens with a blend-out region were first repaired using laser cladding technology. The surface of the laser cladding region was then treated by deep surface rolling. Fatigue testing was subsequently conducted for the laser clad, deep surface rolled and post-heat treated laser clad specimens. It was found that deep surface rolling can significantly improve the fatigue life in comparison with the laser clad baseline repair. In addition, three dimensional residual stresses were measured using neutron diffraction techniques. The results demonstrate that beneficial compressive residual stresses induced by deep surface rolling can reach considerable depths (more than 1.0 mm) below the laser clad surface.

  2. Core-and-surface-functionalized polyphenylene dendrimers for solution-processed, pure-blue light-emitting diodes through surface-to-core energy transfer.

    Science.gov (United States)

    Zhang, Guang; Baumgarten, Martin; Auer, Manuel; Trattnig, Roman; List-Kratochvil, Emil J W; Müllen, Klaus

    2014-11-01

    Several pyrene-based polyphenylene dendrimers (PYPPDs) with different peripheral chromophores (PCs) are synthesized and characterized. Deep blue emissions solely from the core are observed for all of them in photoluminescence spectra due to good steric shielding of the core and highly efficient surface-to-core Förster resonant energy transfers (FRETs). Device performances are found in good correlation with the energy gaps between the work function of the electrodes and the frontier molecular orbital (FMO) levels of the PCs. Pure blue emission, luminance as high as 3700 cd m(-2) with Commission Internationale de l'Éclairage 1931 (CIE(xy)) = (0.16, 0.21), and a peak current efficiency of 0.52 cd A(-1) at CIE(xy) = (0.17, 0.20) are achieved. These dendrimers are among the best dendritic systems so far for fluorescent blue light-emitting materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Laser Surface Alloying of Copper, Manganese, and Magnesium with Pure Aluminum Substrate

    Science.gov (United States)

    Jiru, Woldetinsay G.; Sankar, M. Ravi; Dixit, Uday S.

    2016-03-01

    Laser surface alloying is one of the recent technologies used in the manufacturing sector for improving the surface properties of the metals. Light weight materials like aluminum alloys, titanium alloys, and magnesium alloys are used in the locomotive, aerospace, and structural applications. In the present work, an experimental study was conducted to improve the surface hardness of commercially pure aluminum plate. CO2 laser is used to melt pre-placed powders of pure copper, manganese, and magnesium. Microstructure of alloyed surface was analyzed using optical microscope. The best surface alloying was obtained at the optimum values of laser parameters, viz., laser power, scan speed, and laser beam diameter. In the alloyed region, microhardness increased from 30 HV0.5 to 430 HV0.5, while it was 60 HV0.5 in the heat-affected region. Tensile tests revealed some reduction in the strength and total elongation due to alloying. On the other hand, corrosion resistance improved.

  4. Surface ion implantation induced by laser-generated plasmas

    Czech Academy of Sciences Publication Activity Database

    Giuffrida, L.; Torrisi, L.; Gammino, S.; Wolowski, J.; Ullschmied, Jiří

    2010-01-01

    Roč. 165, 6-10 (2010), s. 534-542 ISSN 1042-0150. [International Workshop on Pulsed Plasma Laser Ablation (PPLA)/4./. Monte Pieta, Messina, 18.06.2009-20.06.2009] Institutional support: RVO:61389021 Keywords : laser ablation * laser plasma * ion implantation * RBS analysis Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.660, year: 2010

  5. Formation of surface nanolayers in chalcogenide crystals using coherent laser beams

    Science.gov (United States)

    Ozga, K.; Fedorchuk, A. O.; El-Naggar, A. M.; Albassam, A. A.; Kityk, V.

    2018-03-01

    We have shown a possibility to form laser modified surface nanolayers with thickness up to 60 nm in some ternary chalcogenide crystals (Ag3AsS3, Ag3SbS3, Tl3SbS3) The laser treatment was performed by two coherent laser beams split in a space. As the inducing lasers we have applied continuous wave (cw) Hesbnd Cd laser at wavelength 441 nm and doubled frequency cw Nd: YAG laser at 532 nm. The spectral energies of these lasers were higher with respect to the energy gaps of the studied crystals. The optical anisotropy was appeared and defected by monitoring of birefringence at probing wavelength of cw Hesbnd Ne laser at λ = 3390 nm. The changes of the laser stimulated near the surface layer morphology was monitored by TEM and AFM methods as well as by the reflected optical second harmonic generation at fundamental wavelength of microsecond CO2 laser generating at wavelength 10600 nm. This technique may open a new approach for the formation of the near the surface nanolayers in chalcogenides using external cw laser illumination.

  6. Selective metallization of polymers using laser induced surface activation (LISA)—characterization and optimization of porous surface topography

    DEFF Research Database (Denmark)

    Zhang, Yang; Hansen, Hans Nørgaard; De Grave, Arnaud

    2011-01-01

    was performed on the laser-machined polymer using an Alicona InfiniteFocus® microscope. Based on previous experiments, bearing area curve and its parameters are chosen to characterize the surface. In this paper, by comparison of plateable and non-plateable surfaces, and two types of plateable surface made...

  7. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Thresholds of surface plasma formation by the interaction of laser pulses with a metal

    Science.gov (United States)

    Borets-Pervak, I. Yu; Vorob'ev, V. S.

    1995-04-01

    An analysis is made of a model of the formation of a surface laser plasma which takes account of the heating and vaporisation of thermally insulated surface microdefects. This model is used in an interpretation of experiments in which such a plasma has been formed by irradiation of a titanium target with microsecond CO2 laser pulses. A comparison with the experimental breakdown intensities is used to calculate the average sizes of microdefects and their concentration: the results are in agreement with the published data. The dependence of the delay time of plasma formation on the total energy in a laser pulse is calculated.

  8. Hydrodynamic effects on the molten surface of a laser-irradiated aluminum sample

    Energy Technology Data Exchange (ETDEWEB)

    Mosaner, Paolo; Bonelli, Marco; Miotello, Antonio

    2003-03-15

    The role of excimer laser pulse energy density was investigated in connection to the turbulence of the molten bath induced by laser irradiation. Gentle hydrodynamic effects are observed on the surface of a laser-irradiated aluminum surface, when the laser energy density substantially exceeds the melting threshold. Chaotic fluid motion inside the molten bath is observed above a laser energy threshold value which, in the present case of KrF excimer laser irradiating aluminum, is between 7.5 and 8.5 J/cm{sup 2}. Liquid wave motion, which results in typical wavelike frozen structure, can be induced in a reproducible way thus permitting a controlled tailoring of the surface morphology.

  9. Laser Surface Preparation for Adhesive Bonding of Ti-6Al-4V

    Science.gov (United States)

    Belcher, Marcus A.; List, Martina S.; Wohl, Christopher J.; Ghose, Sayata; Watson, Kent A.; Hopkins, John W.; Connell, John W.

    2010-01-01

    Adhesively bonded structures are potentially lighter in weight than mechanically fastened ones, but existing surface treatments are often considered unreliable. Two main problems in achieving reproducible and durable adhesive bonds are surface contamination and variability in standard surface preparation techniques. In this work three surface pretreatments were compared: laser etching with and without grit blasting and conventional Pasa-Jell treatment. Ti-6Al-4V surfaces were characterized by contact angle goniometry, optical microscopy, and X-ray photoelectron spectroscopy (XPS). Laser -etching was found to produce clean surfaces with precisely controlled surface topographies and PETI-5 lap shear strengths and durabilities were equivalent to those produced with Pasa-Jell.

  10. Low-temperature micro-photoluminescence spectroscopy on laser-doped silicon with different surface conditions

    Science.gov (United States)

    Han, Young-Joon; Franklin, Evan; Fell, Andreas; Ernst, Marco; Nguyen, Hieu T.; Macdonald, Daniel

    2016-04-01

    Low-temperature micro-photoluminescence spectroscopy (μ-PLS) is applied to investigate shallow layers of laser-processed silicon for solar cell applications. Micron-scale measurement (with spatial resolution down to 1 μm) enables investigation of the fundamental impact of laser processing on the electronic properties of silicon as a function of position within the laser-processed region, and in particular at specific positions such as at the boundary/edge of processed and unprocessed regions. Low-temperature μ-PLS enables qualitative analysis of laser-processed regions by identifying PLS signals corresponding to both laser-induced doping and laser-induced damage. We show that the position of particular luminescence peaks can be attributed to band-gap narrowing corresponding to different levels of subsurface laser doping, which is achieved via multiple 248 nm nanosecond excimer laser pulses with fluences in the range 1.5-4 J/cm2 and using commercially available boron-rich spin-on-dopant precursor films. We demonstrate that characteristic defect PL spectra can be observed subsequent to laser doping, providing evidence of laser-induced crystal damage. The impact of laser parameters such as fluence and number of repeat pulses on laser-induced damage is also analyzed by observing the relative level of defect PL spectra and absolute luminescence intensity. Luminescence owing to laser-induced damage is observed to be considerably larger at the boundaries of laser-doped regions than at the centers, highlighting the significant role of the edges of laser-doped region on laser doping quality. Furthermore, by comparing the damage signal observed after laser processing of two different substrate surface conditions (chemically-mechanically polished and tetramethylammonium hydroxide etched), we show that wafer preparation can be an important factor impacting the quality of laser-processed silicon and solar cells.

  11. Surface microstructure and chemistry of polyimide by single pulse ablation of picosecond laser

    Science.gov (United States)

    Du, Qifeng; Chen, Ting; Liu, Jianguo; Zeng, Xiaoyan

    2018-03-01

    Polyimide (PI) surface was ablated by the single pulse of picosecond laser, and the effects of laser wavelength (λ= 355 nm and 1064 nm) and fluence on surface microstructure and chemistry were explored. Scanning electron microscopy (SEM) analysis found that different surface microstructures, i.e., the concave of concentric ring and the convex of porous circular disk, were generated by 355 nm and 1064 nm picosecond laser ablation, respectively. X-ray photoelectron spectroscopy (XPS) characterization indicated that due to the high peak energy density of picosecond laser, oxygen and nitrogen from the ambient were incorporated into the PI surface mainly in the form of Cdbnd O and Csbnd Nsbnd C groups. Thus, both of the O/C and N/C atomic content ratios increased, but the increase caused by 1064 nm wavelength laser was larger. It inferred that the differences of PI surface microstructures and chemistry resulted from different laser parameters were related to different laser-matter interaction effects. For 355 nm picosecond laser, no obvious thermal features were observed and the probable ablation process of PI was mainly governed by photochemical effect; while for 1064 nm picosecond laser, obvious thermal feature appeared and photothermal effect was thought to be dominant.

  12. Influence of multi-wavelength laser irradiation of enamel and dentin surfaces on surface morphology and permeability

    Science.gov (United States)

    Chang, Nai-Yuan N.; Jew, Jamison; Simon, Jacob C.; Chan, Kenneth H.; Lee, Robert C.; Fried, William A.; Cho, Jinny; Darling, Cynthia L.; Fried, Daniel

    2017-02-01

    UV and IR lasers can be used to specifically target protein, water, and the mineral phase of dental hard tissues to produce varying changes in surface morphology. In this study, we irradiated enamel and dentin surfaces with various combinations of lasers operating at 0.355, 2.94, and 9.4 μm, exposed those surfaces to topical fluoride, and subsequently evaluated the influence of these changes on surface morphology and permeability. Digital microscopy and surface dehydration rate measurements were used to monitor changes in the samples overtime. The surface morphology and permeability (dehydration rate) varied markedly with the different laser treatments on enamel. On dentin, fluoride was most effective in reducing the permeability.

  13. Surface plasma wave assisted second harmonic generation of laser over a metal film

    International Nuclear Information System (INIS)

    Chauhan, Santosh; Parashar, J.

    2015-01-01

    Second harmonic generation of laser mode converted surface plasma wave (SPW) over a corrugated metal film is studied. The laser, impinged on the metal film, under attenuated total reflection configuration, excites SPW over the metal–vacuum interface. The excited SPW extends over a much wider surface area than the laser spot cross-section. It exerts a second harmonic ponderomotive force on metal electrons, imparting them velocity that beats with the surface ripple to produce a nonlinear current, driving resonant second harmonic surface plasma wave

  14. Multi-Criteria Analysis of Laser Cut Surface Characteristics in CO2 Laser Cutting of Stainless Steel

    Directory of Open Access Journals (Sweden)

    M. Radovanović

    2015-06-01

    Full Text Available In this paper an approach for multi-criteria analysis of laser cut surface characteristics using multi-criteria decision making (MCDM approach was presented. Laser cutting experiment was conducted based on Taguchi’s L27 experimental design by varying laser power, cutting speed, assist gas pressure and focus position at three levels. Multi-criteria analysis was performed by using the weighted aggregated sum product assessment (WASPAS method while considering burr height, drag line separation, depth of separation line, surface roughness and perpendicularity of the cut as assessment criteria. Based on conducted experimental investigation the MCDM model with 27 alternatives (laser cuts and five criteria was developed. The relative importance of criteria was determined by using pair-wise comparison matrix and geometric mean method of the analytic hierarchy process (AHP method.

  15. Effects of different lasers and particle abrasion on surface characteristics of zirconia ceramics.

    Directory of Open Access Journals (Sweden)

    Sakineh Arami

    2014-04-01

    Full Text Available The aim of this study was to assess the surface of yttrium-stabilized tetragonal zirconia (Y-TZP after surface treatment with lasers and airborne-particle abrasion.First, 77 samples of presintered zirconia blocks measuring 10 × 10 × 2 mm were made, sintered and polished. Then, they were randomly divided into 11 groups (n=7 and received surface treatments namely, Er:YAG laser irradiation with output power of 1.5, 2 and 2.5 W, Nd:YAG laser with output power of 1.5, 2 and 2.5 W, CO2 laser with output power of 3, 4 and 5 W, AL2O3 airborne-particle abrasion (50μ and no treatment (controls. Following treatment, the parameters of surface roughness such as Ra, Rku and Rsk were evaluated using a digital profilometer and surface examination was done by SEM.According to ANOVA and Tukey's test, the mean surface roughness (Ra after Nd:YAG laser irradiation at 2 and 2.5 W was significantly higher than other groups. Roughness increased with increasing output power of Nd:YAG and CO2 lasers. Treated surfaces by Er:YAG laser and air abrasion showed similar surface roughness. SEM micrographs showed small microcracks in specimens irradiated with Nd:YAG and CO2 lasers.Nd:YAG laser created a rough surface on the zirconia ceramic with many microcracks; therefore, its use is not recommended. Air abrasion method can be used with Er:YAG laser irradiation for the treatment of zirconia ceramic.

  16. Efficiency enhancement of fluorescence blue organic light-emitting diodes by incorporating Ag nanoparticles layers due to a localized surface plasmon

    Science.gov (United States)

    Nam, Minwoo; Chung, Nak-Kwan; Shim, Seob; Yun, Ju-Young; Kim, Jin-Tae; Pyo, Sung Gyu

    2017-09-01

    Enhanced electroluminescence in blue organic light-emitting diodes (OLEDs) is obtained by incorporating Ag nanoparticles (NPs) into hole injection layer of poly(3,4- ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). The absorption peak of the localized surface plasmons (LSPs) introduced by the 60 nm Ag NPs matches the emission wavelength of the blue OLEDs were matched at wavelength of 442 nm. In addition, to maximize their coupling and to prevent the quenching of the emission, the distance between surface plasmons (SPs) around NPs and organic fluorophores is optimized. Finally, the emission intensity and the current efficiency of diode with Ag NPs were increased by 19% and 18%, respectively.

  17. Multipulse nanosecond laser irradiation of silicon for the investigation of surface morphology and photoelectric properties

    Science.gov (United States)

    Sardar, Maryam; Chen, Jun; Ullah, Zaka; Jelani, Mohsan; Tabassum, Aasma; Cheng, Ju; Sun, Yuxiang; Lu, Jian

    2017-12-01

    We irradiate the single crystal boron-doped silicon (Si) with different number of laser pulses at constant fluence (7.5 J cm-2) in ambient air using Nd:YAG laser and examine its surface morphology and photoelectric properties in details. The results obtained from optical micrographs reveal the increase in heat affected zone (HAZ) and melted area of laser irradiated Si with increasing number of laser pulses. The SEM micrographs evidence the formation of various surface morphologies like laser induced periodic surface structures, crater, microcracks, clusters, cavities, pores, trapped bubbles, nucleation sites, micro-bumps, redeposited material and micro- and nano-particles on the surface of irradiated Si. The surface profilometry analysis informs that the depth of crater is increased with increase in number of incident laser pulses. The spectroscopic ellipsometry reveals that the multipulse irradiation of Si changes its optical properties (refractive index and extinction coefficient). The current-voltage (I-V) characteristic curves of laser irradiated Si show that although the multipulse laser irradiation produces considerable number of surface defects and damages, the electrical properties of Si are well sustained after the multipulse irradiation. The current findings suggest that the multipulse irradiation can be an effective way to tune the optical properties of Si for the fabrication of wide range of optoelectronic devices.

  18. A study of laser surface treatment in bonded repair of composite aircraft structures.

    Science.gov (United States)

    Li, Shaolong; Sun, Ting; Liu, Chang; Yang, Wenfeng; Tang, Qingru

    2018-03-01

    Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen.

  19. Microstructural characterization of laser surface melted AISI M2 tool steel.

    Science.gov (United States)

    Arias, J; Cabeza, M; Castro, G; Feijoo, I; Merino, P; Pena, G

    2010-09-01

    We describe the microstructure of Nd:YAG continuous wave laser surface melted high-speed steel, namely AISI M2, treated with different laser scanning speeds and beam diameters on its surface. Microstructural characterization of the remelted surface layer was performed using light optical and scanning electron microscopy and X-ray diffraction. The combination of the three techniques provided new insights into the substantial changes induced by laser surface melting of the steel surface layer. The advantage of the method is that it avoids the difficult and tedious work of preparing samples of this hard material for transmission electron microscopy, which is the technique normally used to study these fine microstructures. A melted zone with a dendritic structure and a partially melted zone with a heterogeneous cellular structure were observed. M(2)C carbides with different morphologies were identified in the resolidified surface layer after laser melting.

  20. Improvement in Surface Characterisitcs of Polymers for Subsequent Electroless Plating Using Liquid Assisted Laser Processing

    DEFF Research Database (Denmark)

    Marla, Deepak; Zhang, Yang; Jabbaribehnam, Mirmasoud

    2016-01-01

    Metallization of polymers is a widely used process in the electronic industry that involves their surface modification as a pre-treatment step. Laser-based surface modification is one of the commonly used techniques for polymers due to its speed and precision. The process involves laser heating...... of the polymer surface to generate a rough or porous surface. Laser processing in liquid generates superior surface characteristics that result in better metal deposition. In this study, a comparison of the surface characteristics obtained by laser processing in water vis-à-vis air along with the deposition...... characteristics are presented. In addition, a numerical model based on the finite volume method is developed to predict the temperature profile during the process. Based on the model results, it is hypothesized that physical phenomena such as vapor bubble generation and plasma formation may occur in the presence...

  1. CO/sub 2/-laser polishing of fused silica surfaces for increased laser damage resistance at 1. 06. mu. m

    Energy Technology Data Exchange (ETDEWEB)

    Temple, P.A.; Milam, D.; Lowdermilk, W.H.

    1980-04-03

    Bare fused silica surfaces were prepared by subjecting the mechanically polished surface to a rastered cw CO/sub 2/ laser beam. Analysis shows that this processing causes: (a) removal of a uniform layer of fused silica; and (b) a probable re-fusing or healing of existing subsurface fractures. The fused silica removal rate is found to be a function of the laser intensity and scan rate. These surfaces are seen to have very low scatter and to be very smooth. In addition, they have exhibited entrance surface damage thresholds at 1.06 ..mu..m, and 1 nsec, which are substantially above those seen on the mechanically polished surface. When damage does occur, it tends to be at a few isolated points rather than the general uniform damage seen on the mechanicaly polished part. In addition to the damage results, we will discuss an observational technique used for viewing these surfaces which employs dark-field illumination.

  2. Laser surface graphitization to control friction of diamond-like carbon coatings

    Science.gov (United States)

    Komlenok, Maxim S.; Kononenko, Vitaly V.; Zavedeev, Evgeny V.; Frolov, Vadim D.; Arutyunyan, Natalia R.; Chouprik, Anastasia A.; Baturin, Andrey S.; Scheibe, Hans-Joachim; Shupegin, Mikhail L.; Pimenov, Sergei M.

    2015-11-01

    To study the role of laser surface graphitization in the friction behavior of laser-patterned diamond-like carbon (DLC) films, we apply the scanning probe microscopy (SPM) in the lateral force mode (LFM) which allows to obtain simultaneously the lateral force and topography images and to determine local friction levels in laser-irradiated and original surface areas. Based on this approach in the paper, we report on (1) laser surface microstructuring of hydrogenated a-C:H and hydrogen-free ta-C films in the regime of surface graphitization using UV laser pulses of 20-ns duration and (2) correlation between the structure and friction properties of the laser-patterned DLC surface on micro/nanoscale using SPM/LFM technique. The SPM/LFM data obtained for the surface relief gratings of graphitized microstructures have evidenced lower friction forces in the laser-graphitized regions. For the hydrogenated DLC films, the reversible frictional behavior of the laser-graphitized micropatterns is found to take place during LFM imaging at different temperatures (20 and 120 °C) in ambient air. It is revealed that the lateral force distribution in the laser-graphitized areas is shifted to higher friction levels (relative to that of the unirradiated surface) at temperature 120 °C and returned back to the lower friction during the sample cooling to 20 °C, thus confirming an influence of adsorbed water layers on the nanofriction properties of laser-graphitized micropatterns on the film surface.

  3. Surface Contaminant Control Technologies to Improve Laser Damage Resistance of Optics

    Directory of Open Access Journals (Sweden)

    Xiaofeng Cheng

    2014-01-01

    Full Text Available The large high-power solid lasers, such as the National Ignition Facility (NIF of America and the Shenguang-III (SG-III laser facility of China, can output over 2.1 MJ laser pulse for the inertial confinement fusion (ICF experiments. Because of the enhancement of operating flux and the expansion of laser driver scale, the problem of contamination seriously influences their construction period and operation life. During irradiation by intense laser beams, the contaminants on the metallic surface of beam tubes can be transmitted to the optical surfaces and lead to damage of optical components. For the high-power solid-state laser facilities, contamination control focuses on the slab amplifiers, spatial filters, and final-optical assemblies. In this paper, an effective solution to control contaminations including the whole process of the laser driver is put forward to provide the safe operation of laser facilities, and the detailed technical methods of contamination control such as washing, cleanliness metrology, and cleanliness protecting are also introduced to reduce the probability of laser-induced damage of optics. The experimental results show that the cleanliness level of SG-III laser facility is much better to ensure that the laser facility can safely operate at high energy flux.

  4. Controlling the porosity of a polyethersulfone membrane surface with an XeCl laser

    International Nuclear Information System (INIS)

    Pazokian, Hedieh; Mehrabadi, Adeleh H P; Mollabashi, Mahmoud; Barzin, Jalal

    2016-01-01

    Pure and polyvinyl pyrrolidone blend polyethersulfone (PES) membranes were irradiated by an XeCl laser with various numbers of pulses at different fluences to investigate the changes in the surface morphology and the porosity. The results show that the membrane pore size and distribution on the surface can be modified following irradiation dependent on the laser fluence, the number of pulses and the membrane composition. These changes are very attractive for improving the membrane surface in filtration processes and biological applications. (paper)

  5. Reduction of Friction of Metals Using Laser-Induced Periodic Surface Nanostructures

    OpenAIRE

    Zhuo Wang; Quanzhong Zhao; Chengwei Wang

    2015-01-01

    We report on the effect of femtosecond-laser-induced periodic surface structures (LIPSS) on the tribological properties of stainless steel. Uniform periodic nanostructures were produced on AISI 304L (American Iron and Steel Institute steel grade) steel surfaces using an 800-nm femtosecond laser. The spatial periods of LIPSS measured by field emission scanning electron microscopy ranged from 530 to 570 nm. The tribological properties of smooth and textured surfaces with periodic nanostructures...

  6. Development of optical surface contouring technique using laser

    Energy Technology Data Exchange (ETDEWEB)

    Baik, Sung Hoon; Kim, Min Suk; Park, Seung Kyu

    1998-12-01

    Laser contouring system capable of measuring relief profiles using a line-shaped laser beam with anisotropic magnification optics composed with two cylindrical lenses was developed. The anisotropic magnification optical system allows it to obtain higher resolution in the relief profile measurements. The image processing and 3-D display software are developed to reconstruct 3-D shape. The power supply of laser diode with adaptive current control circuit is designed. (author). 4 refs., 5 tabs., 33 figs.

  7. Polycarbonate surface cell's adhesion examination after Nd:YAG laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ramazani, S.A. Ahmad, E-mail: Ramazani@sharif.ir [Polymer Group, Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Mousavi, Seyyed Abbas, E-mail: Musavi@che.sharif.ir [Department of Chemistry, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Seyedjafari, Ehsan [Department of Biotechnology, University College of Science, University of Tehran (Iran, Islamic Republic of); Poursalehi, Reza [Department of Physics, University of Shahed, Tehran (Iran, Islamic Republic of); Sareh, Shohreh [Research Center of Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Silakhori, Kaveh [Laser Research Center, Atomic Energy Organization, Tehran (Iran, Islamic Republic of); Poorfatollah, Ali Akbar [Research Center of Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Shamkhali, Amir Nasser [Department of Chemistry, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2009-05-05

    Nd:YAG laser treatment was used in order to increase surface cell adhesion aspects of polycarbonate (PC) films prepared via melt process. The treatment was carried out under different wavelengths and beam diameters. ATR-FTIR and UV spectra obtained from different samples before and after laser treatment in air showed that laser irradiation has induced some chemical and physical changes in surface properties. The irradiated films were also characterized using scanning electron microscopy (SEM) and contact angle measurements. Effect of pulse numbers on the surface properties was also investigated. Cell culture test was used to evaluate cell adhesion property on the PC films before and after treatment. The results obtained from this test showed that after laser treatment, the cells were attached and proliferated extensively on the Nd:YAG laser treated films in comparison with the unmodified PC. Moreover, it was revealed that a decrease in the laser beam diameter and an increase in the irradiated pulse numbers increased surface wettability and caused a better cell attachment on the polymer surface. The obtained results also showed that a decrease in the laser beam diameter and an increase in the irradiated pulse numbers increased surface wettability and caused a better cell attachment on the polymer surface.

  8. Comparison of KrF and ArF excimer laser treatment of biopolymer surface

    Energy Technology Data Exchange (ETDEWEB)

    Michaljaničová, I. [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Slepička, P., E-mail: petr.slepicka@vscht.cz [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Heitz, J.; Barb, R.A. [Institute of Applied Physics, Johannes Kepler University Linz, A-4040 Linz (Austria); Sajdl, P. [Department of Power Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Švorčík, V. [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic)

    2015-06-01

    Highlights: • The influence of ArF and KrF laser on biopolymer surface was determined. • ArF laser acts predominantly on biopolymer surface. • PHB roughness is increased similarly for both applied wavelengths. • Roughness of nanostructures can be precisely controlled. • ArF laser introduces nitrogen on PHB surface. - Abstract: The goal of this work was the investigation of the impact of two different excimer lasers on two biocompatible and biodegradable polymers (poly-L-lactide and poly hydroxybutyrate). Both polymers find usage in medical and pharmaceutical fields. The polymers were modified by KrF and ArF excimer lasers. Subsequently the impact on surface morphology, surface chemistry changes, and thermal properties was studied by means of confocal and AFM microscopy, FTIR and XPS spectroscopy and DSC calorimetry. Under the same conditions of laser treatment it was observed that ArF laser causes more significant changes on surface chemistry, surface morphology and pattern formation on the polymers under investigation. The data obtained in this work can be used for a wide range of possible applications, in tissue engineering or in combination with metallization in electronics, e.g. for biosensors.

  9. Bio-inspired water repellent surfaces produced by ultrafast laser structuring of silicon

    International Nuclear Information System (INIS)

    Barberoglou, M.; Zorba, V.; Stratakis, E.; Spanakis, E.; Tzanetakis, P.; Anastasiadis, S.H.; Fotakis, C.

    2009-01-01

    We report here an efficient method for preparing stable superhydrophobic and highly water repellent surfaces by irradiating silicon wafers with femtosecond laser pulses and subsequently coating them with chloroalkylsilane monolayers. By varying the laser pulse fluence on the surface one can successfully control its wetting properties via a systematic and reproducible variation of roughness at micro- and nano-scale, which mimics the topology of natural superhydrophobic surfaces. The self-cleaning and water repellent properties of these artificial surfaces are investigated. It is found that the processed surfaces are among the most water repellent surfaces ever reported. These results may pave the way for the implementation of laser surface microstructuring techniques for the fabrication of superhydrophobic and self-cleaning surfaces in different kinds of materials as well

  10. Surface morphological modification of crosslinked hydrophilic co-polymers by nanosecond pulsed laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Primo, Gastón A.; Alvarez Igarzabal, Cecilia I. [IMBIV (CONICET), Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Edificio de Ciencias II, Ciudad Universitaria, Córdoba X5000HUA (Argentina); Pino, Gustavo A.; Ferrero, Juan C. [INFIQC (CONICET), Departamento de Fisicoquímica, Facultad de Ciencias Químicas, and Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba, Córdoba X5000IUS (Argentina); Rossa, Maximiliano, E-mail: mrossa@fcq.unc.edu.ar [INFIQC (CONICET), Departamento de Fisicoquímica, Facultad de Ciencias Químicas, and Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba, Córdoba X5000IUS (Argentina)

    2016-04-30

    Graphical abstract: - Highlights: • Laser-induced surface modification of crosslinked hydrophilic co-polymers by ns pulses. • Formation of ablation craters observed under most of the single-pulse experimental conditions. • UV laser foaming of dried hydrogel samples resulting from single- and multiple-pulse experiments. • Threshold values of the incident laser fluence reported for the observed surface modifications. • Lower threshold fluences for acrylate-based, compared to acrylamide-based hydrogels. - Abstract: This work reports an investigation of the surface modifications induced by irradiation with nanosecond laser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materials, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is made between hydrogels differing in the base co-monomer (N,N-dimethylaminoethyl methacrylate and N-[3-(dimethylamino)propyl] methacrylamide) and in hydration state (both swollen and dried states). Formation of craters is the dominant morphological change observed by ablation in the visible at 532 nm, whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are developed in the ultraviolet at 266 nm. At both irradiation wavelengths, threshold values of the incident laser fluence for the observation of the various surface modifications are determined under single-pulse laser irradiation conditions. It is shown that multiple-pulse irradiation at 266 nm with a limited number of laser shots can be used alternatively for generating a regular microfoam layer at the surface of dried hydrogels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis of currently accepted mechanisms for laser-induced polymer surface modification, with a significant contribution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matrices in biomolecule immobilization are suggested.

  11. GaN-Based Thin Film Vertical Structure Light Emitting Diodes Fabricated by a Modified Laser Lift-off Process and Transferred to Cu

    International Nuclear Information System (INIS)

    Sun Yong-Jian; Yu Tong-Jun; Jia Chuan-Yu; Chen Zhi-Zhong; Tian Peng-Fei; Kang Xiang-Ning; Lian Gui-Jun; Huang Sen; Zhang Guo-Yi

    2010-01-01

    GaN-based thin film vertical structure light-emitting diodes (VS-LEDs) were fabricated by a modified YAG laser lift-off (LLO) process and transferred to Cu substrates. With a comparison of the electrical and optical properties of conventional LEDs on sapphire substrates and of lateral structure thin film LEDs by a KrF LLO process, the vertical structure of LLO LEDs shows obvious superiority. LLO VSLEDs made by modified YAG LLO process show less increase of leakage current than the devices made by conventional KrF LLO process. Furthermore, owing to the well current spreading and less current path, the ideality factors and series resistance of vertical structure LEDs reduce greatly and the efficiency increases more obviously than the lateral structure LEDs, which is also reflected on the relative L-I curves. The output power of vertical structure LEDs is over 3 times greater than that of the lateral structure LLO LEDs within 300mA. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  12. Design considerations for λ ˜ 3.0- to 3.5-μm-emitting quantum cascade lasers on metamorphic buffer layers

    Science.gov (United States)

    Rajeev, Ayushi; Sigler, Chris; Earles, Tom; Flores, Yuri V.; Mawst, Luke J.; Botez, Dan

    2018-01-01

    Quantum cascade lasers (QCLs) that employ metamorphic buffer layers as substrates of variable lattice constant have been designed for emission in the 3.0- to 3.5-μm wavelength range. Theoretical analysis of the active-region (AR) energy band structure, while using an 8-band k•p model, reveals that one can achieve both effective carrier-leakage suppression as well as fast carrier extraction in QCL structures of relatively low strain. Significantly lower indium-content quantum wells (QWs) can be employed for the AR compared to QWs employed for conventional short-wavelength QCL structures grown on InP, which, in turn, is expected to eliminate carrier leakage to indirect-gap valleys (X, L). An analysis of thermo-optical characteristics for the complete device design indicates that high-Al-content AlInAs cladding layers are more effective for both optical confinement and thermal dissipation than InGaP cladding layers. An electroluminescence-spectrum full-width half-maximum linewidth of 54.6 meV is estimated from interface roughness scattering and, by considering both inelastic and elastic scattering, the threshold-current density for 3.39-μm-emitting, 3-mm-long back-facet-coated QCLs is projected to be 1.40 kA/cm2.

  13. Investigation on a TEA-CO II laser with surface corona pre-ionization

    Science.gov (United States)

    Behjat, A.; Aram, M.; Soltanmoradi, F.; Shabanzadeh, M.

    2006-05-01

    The construction of a surface corona UV pre-ionized TEA CO II laser is described and dependence of its average output energy of the laser to gas mixture, discharge voltage and repetition rate is investigated. The electric circuit diagram and geometry of the pre-ionization system are presented. Configuration of circuit has been designed to produce only impulsive voltage difference between the laser electrodes. Also, the triggering configuration of trigatron is prepared for fast operation to minimize the arc occurrence as much as possible. Some data of current, voltage, laser pulses and average output energy versus gas mixture and applied voltages are given. IR spectrometer is used for measurements of central output wavelength of the laser. Operation of the laser on two adjacent vibrational-rotational transitions of CO II molecule has been observed that shows the ability of this laser for working on multi-line in a same time for special applications.

  14. Mechanism of Nanostructure Formation on a Surface of CdZnTe Crystal by Laser Irradiation

    OpenAIRE

    Medvids, A; Mičko, A

    2009-01-01

    Since crystalline Cd1-xZnxTe is widely used in radiation techniques to produce X-ray, gamma-ray, and other hard radiation detectors, present work is a further study of processes, occurring near the surface of Cd1-xZnxTe under laser radiation. Surface morphology and optical property change of Cd0.9Zn0.1Te crystal near-surface layer after irradiation with laser, aimed to create graded band-gap, was investigated. As a radiation source Nd:YAG laser working in Q-modulation mode with parameters...

  15. Laser-assisted cleaning: Dominant role of surface

    Indian Academy of Sciences (India)

    Whereas the generation of thermal stress by choosing appropriate laser parameters is the ... Secondly, as the laser beam can be transported to the job either with the help of beam steering optics or ... fluence can undergo larger thermal stress enabling their ejection at higher fluence. We have attributed the fall in the DF with ...

  16. Experimental study of femtosecond laser-stimulated electrical discharges in small gaps and surface modifications

    International Nuclear Information System (INIS)

    Chen, J.; Farson, D. F.; Rokhlin, S. I.

    2009-01-01

    Femtosecond laser-stimulated discharges in nanoscale and microscale gaps between etched nanoprobe tip cathodes and gold film anodes with applied dc potential were experimentally studied to define parameter ranges for their controlled formation and resulting surface modifications. For appropriate values of gap length, applied potential, and laser irradiance, breakdown discharges could be reliably stimulated by femtosecond laser pulses and the mean breakdown field was approximately an order of magnitude smaller than for breakdown without laser stimulation. For 500 nm gaps, discharges were observed for applied potentials as small as 20 V and controllable gold film surface melting was detected for applied potential of 27.5 V. Minor cathode tip ablation could be observed for femtosecond laser pulses that reliably stimulated discharges, suggesting that cathode material played an important role in stimulation of breakdown discharges in nanoscale gaps. Surface melting produced features as small as 60 nm on gold film when discharge current was limited by 1 MΩ series resistor

  17. Laser decontamination and cleaning of metal surfaces: modelling and experimental studies

    International Nuclear Information System (INIS)

    Leontyev, A.

    2011-01-01

    Metal surface cleaning is highly required in different fields of modern industry. Nuclear industry seeks for new methods for oxidized surface decontamination, and thermonuclear installations require the cleaning of plasma facing components from tritium-containing deposited layer. The laser ablation is proposed as an effective and safe method for metal surface cleaning and decontamination. The important factor influencing the laser heating and ablation is the in-depth distribution of laser radiation. The model of light propagation in a scattering layer on a metal substrate is developed and applied to analyse the features of light distribution. To simulate the contaminated surfaces, the stainless steel AISI 304L was oxidized by laser and in a furnace. Radioactive contamination of the oxide layer was simulated by introducing europium and/or sodium. The decontamination factor of more than 300 was demonstrated with found optimal cleaning regime. The decreasing of the corrosion resistance was found after laser cleaning. The ablation thresholds of ITER-like surfaces were measured. The cleaning productivity of 0.07 m 2 /hour.W was found. For mirror surfaces, the damage thresholds were determined to avoid damage during laser cleaning. The possibility to restore reflectivity after thin carbon layer deposition was demonstrated. The perspectives of further development of laser cleaning are discussed. (author) [fr

  18. A smart car for the surface shape measurement of large antenna based on laser tracker

    Science.gov (United States)

    Gu, Yonggang; Hu, Jing; Jin, Yi; Zhai, Chao

    2012-09-01

    The geometric accuracy of the surface shape of large antenna is an important indicator of antenna’s quality. Currently, high-precision measurement of large antenna surface shape can be performed in two ways: photogrammetry and laser tracker. Photogrammetry is a rapid method, but its accuracy is not enough good. Laser tracker can achieve high precision, but it is very inconvenient to move the reflector (target mirror) on the surface of the antenna by hand during the measurement. So, a smart car is designed to carry the reflector in this paper. The car, controlled by wireless, has a small weight and a strong ability for climbing, and there is a holding bracket gripping the reflector and controlling reflector rise up and drop down on the car. During the measurement of laser tracker, the laser beam between laser tracker and the reflector must not be interrupted, so two high-precision three-dimensional miniature electronic compasses, which can real-time monitor the relative angle between the holding bracket and the laser tracker’s head, are both equipped on the car and the head of laser tracker to achieve automatic alignment between reflector and laser beam. With the aid of the smart car, the measurement of laser tracker has the advantages of high precision and rapidity.

  19. Laser treatment of dental ceramic/cement layers: transmitted energy, temperature effects and surface characterisation.

    Science.gov (United States)

    Pich, Olena; Franzen, René; Gutknecht, Norbert; Wolfart, Stefan

    2015-02-01

    In the present paper, we investigate the behaviour of different dental materials under laser irradiation. We have used e.max Ceram, e.max ZirCAD, and e.max Press dental ceramics and glass ionomer cement Ketac Cem in the present study. The dental ceramics were prepared in the form of samples with thickness of 0.5-2 mm. We used two lasers [solid-state laser (Er:YAG, Fidelis III+, Fotona) and an 810- nm diode laser (FOX, A.R.C)] for the transillumination of ceramic samples. It has been shown that the laser energy transmitted through the ceramic material decreases to 30-40% of the original values along with an increase in the thickness of the irradiated sample. Pigmented ceramic samples show more laser energy loss compared to the samples containing no pigment. We investigated the temperature evolution in composite sandwiched ceramic/cement samples under laser treatment. The increase in the irradiation time and laser power led to a temperature increase of up to 80 °C. The surfaces of irradiated ceramic samples were examined with X-ray photoelectron spectroscopy to evaluate changes in chemical composition, such as a decrease in the C signal, accompanied by a strong increase in the Zr peak for the Er:YAG laser, while the 810-nm diode laser showed no change in the ratio of elements on the surface.

  20. Fabrication of Hierarchically Micro- and Nano-structured Mold Surfaces Using Laser Ablation for Mass Production of Superhydrophobic Surfaces

    Science.gov (United States)

    Noh, Jiwhan; Lee, Jae-Hoon; Na, Suckjoo; Lim, Hyuneui; Jung, Dae-Hwan

    2010-10-01

    Many studies have examined the formation of surfaces with mixed patterns of micro- and nano-sized lotus leaves that have hydrophobic properties. In this study, micro- and nano-shapes such as lotus leaves were fabricated on a metal mold surface using laser ablation and ripple formation. A microstructure on the mold surface was replicated onto poly(dimethylsiloxane) (PDMS) using the polymer casting method to manufacture low-cost hydrophobic surfaces. A PDMS surface with micro- and nano-structures that were the inverse image of a lotus leaf showed hydrophobic characteristics (water contact angle: 157°). From these results, we deduced that portions of the microstructures were wet and that air gaps existed between the microstructures and the water drops. In this paper we suggest the possibility of the mass production of hydrophobic plastic surfaces and the development of a methodology for the hydrophobic texturing of various polymer surfaces, using the polymer casting method with laser-processed molds.

  1. On the formation of nanostructures on a CdTe surface, stimulated by surface acoustic waves under nanosecond laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Vlasenko, A. I.; Baidullaeva, A.; Veleschuk, V. P., E-mail: vvvit@ukr.net; Mozol, P. E.; Boiko, N. I.; Litvin, O. S. [National Academy of Sciences of Ukraine, Lashkaryov Institute of Semiconductors Physics (Ukraine)

    2015-02-15

    The formation of nanoscale structures in the unirradiated part of a p-CdTe crystal surface irradiated by a nanosecond ruby laser is revealed and investigated. It is shown that their formation is caused by the effect of the long-range action of a laser pulse with an intensity of I = 20 MW/cm{sup 2}. Nanoscale-structure formation is explained by the influence of the pressure gradient of the surface acoustic wave, in particular, within the “vacancy-pump” mechanism on the surface.

  2. The Influence of Laser Surface Remelting on the Microstructure of EN AC-48000 Cast Alloy

    Directory of Open Access Journals (Sweden)

    Piątkowski J.

    2016-12-01

    Full Text Available Paper present a thermal analysis of laser heating and remelting of EN AC-48000 (EN AC-AlSi12CuNiMg cast alloy used mainly for casting pistons of internal combustion engines. Laser optics were arranged such that the impingement spot size on the material was a circular with beam radius rb changes from 7 to 1500 μm. The laser surface remelting was performed under argon flow. The resulting temperature distribution, cooling rate distribution, temperature gradients and the depth of remelting are related to the laser power density and scanning velocity. The formation of microstructure during solidification after laser surface remelting of tested alloy was explained. Laser treatment of alloy tests were perform by changing the three parameters: the power of the laser beam, radius and crystallization rate. The laser surface remelting needs the selection such selection of the parameters, which leads to a significant disintegration of the structure. This method is able to increase surface hardness, for example in layered castings used for pistons in automotive engines.

  3. Melt expulsion during ultrasonic vibration-assisted laser surface processing of austenitic stainless steel.

    Science.gov (United States)

    Alavi, S Habib; Harimkar, Sandip P

    2015-05-01

    Simultaneous application of ultrasonic vibrations during conventional materials processing (casting, welding) and material removal processes (machining) has recently been gaining widespread attention due to improvement in metallurgical quality and efficient material removal, respectively. In this paper, ultrasonic vibration-assisted laser surface melting of austenitic stainless steel (AISI 316) is reported. While the application of ultrasonic vibrations during laser processing delays the laser interaction with material due to enhancement of surface convection, it resulted in expulsion of melt from the irradiated region (forming craters) and transition from columnar to equiaxed dendritic grain structure in the resolidified melt films. Systematic investigations on the effect of ultrasonic vibrations (with vibrations frequency of 20 kHz and power output in the range of 20-40%) on the development of microstructure during laser surface melting (with laser power of 900 W and irradiation time in the range of 0.30-0.45 s) are reported. The results indicate that the proposed ultrasonic vibration-assisted laser processing can be designed for efficient material removal (laser machining) and improved equiaxed microstructure (laser surface modifications) during materials processing. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Microprocessing of human hard tooth tissues surface by mid-infrared erbium lasers radiation

    Science.gov (United States)

    Belikov, Andrey V.; Shatilova, Ksenia V.; Skrypnik, Alexei V.

    2015-03-01

    A new method of hard tooth tissues laser treatment is described. The method consists in formation of regular microdefects on tissue surface by mid-infrared erbium laser radiation with propagation ratio M2caries prevention as a result of increasing microhardness and acid resistance of tooth enamel.

  5. Submicrometre periodic surface structures in InP induced by nanosecond UV laser pulses

    International Nuclear Information System (INIS)

    Kumar, Brijesh; Soni, R K

    2008-01-01

    We report fabrication of submicrometre size laser-induced periodic surface structures (ripples) on single crystalline InP by nanosecond (ns) pulsed Nd : YAG laser beam irradiation of fourth harmonic wavelength (266 nm) in HF electrolyte. The ripples are orientated parallel to the laser polarization direction and power spectral density analysis reveals reduction in the spatial period of the ripples with increasing number of laser shots. The formation of periodic structures in the presence of electrolyte is empirically explained on the basis of photoelectrochemical etching and variation of periodicity with refractive index change on laser energy and number of laser pulses. From the analysis of energy dispersive x-ray, photoluminescence (PL) and micro-Raman spectroscopy measurements on the rippled surface we conclude that the ripple structures are capped with a thin layer of In 2 O 3 . Further, a blue shift of 0.328 eV compared with the band-edge luminescence of InP is estimated from the PL spectrum of the structure fabricated with 200 laser shots. The blue shift of the PL peak is attributed to the quantum confinement effect in the nanometre size structures in the rippled surface. Micro-Raman spectra show good crystalline quality of the surface at lower number of laser shots and its degradation caused by oxidation at the higher number of shots

  6. Surface morphology of thin lysozyme films produced by matrix-assisted pulsed laser evaporation (MAPLE)

    DEFF Research Database (Denmark)

    Purice, Andreea; Schou, Jørgen; Pryds, Nini

    2007-01-01

    Thin films of the protein, lysozyme, have been deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. Frozen targets of 0.3-1.0 wt.% lysozyme dissolved in ultrapure water were irradiated by laser light at 355 mn with a fluence of 2 J/cm(2). The surface quality of the thin...

  7. Laser surface alloying of 316L stainless steel with Ru and Ni mixtures

    CSIR Research Space (South Africa)

    Lekala, MB

    2012-05-01

    Full Text Available The surfaces of AISI 316L stainless steel were laser alloyed with ruthenium powder and a mixture of ruthenium and nickel powders using a cw Nd:YAG laser set at fixed operating parameters. The microstructure, elemental composition, and corrosion...

  8. Laser surface alloying of aluminium with WC+Co+NiCr for improved wear resistance

    CSIR Research Space (South Africa)

    Nath, S

    2012-03-01

    Full Text Available In the present study, laser surfac ealloying of aluminium with WC + Co + NiCr (in the ratio of 70:15:15) has been conducted using a 5 kW continuous wave (CW) Nd:YAG laser (at a beam diameter of 0.003 m), with the output power ranging from 3 to 3.5 k...

  9. Laser surface alloying of aluminium with WC+Co+NiCr for improved wear resistance

    CSIR Research Space (South Africa)

    Nath, S

    2012-03-01

    Full Text Available In the present study, laser surface alloying of aluminium with WC + Co + NiCr (in the ratio of 70:15:15) has been conducted using a 5 kW continuous wave (CW) Nd:YAG laser (at a beam diameter of 0.003 m), with the output power ranging from 3 to 3.5 k...

  10. Diamond detectors with laser induced surface graphite electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Komlenok, M. [A.M. Prokorhov General Physics Institute, Russian Academy of Sciences, 38 Vavilova Str., 119991 Moscow (Russian Federation); Bolshakov, A. [A.M. Prokorhov General Physics Institute, Russian Academy of Sciences, 38 Vavilova Str., 119991 Moscow (Russian Federation); Harbin Institute of Technology, 92 Xidazhi Str., 150001 Harbin (China); Ralchenko, V. [A.M. Prokorhov General Physics Institute, Russian Academy of Sciences, 38 Vavilova Str., 119991 Moscow (Russian Federation); Harbin Institute of Technology, 92 Xidazhi Str., 150001 Harbin (China); National Research Nuclear University “MEPhI”, Kashirskoye shosse, 31, 115409 Moscow (Russian Federation); Konov, V. [A.M. Prokorhov General Physics Institute, Russian Academy of Sciences, 38 Vavilova Str., 119991 Moscow (Russian Federation); National Research Nuclear University “MEPhI”, Kashirskoye shosse, 31, 115409 Moscow (Russian Federation); Conte, G. [Department of Sciences, University Roma Tre and INFN, Via Vasca Navale, 84-00148 Rome (Italy); CNR-ISM, Institute for Structure of Matter, National Research Council, Via Salaria km 29, 300, Montelibretti (Italy); Girolami, M. [CNR-ISM, Institute for Structure of Matter, National Research Council, Via Salaria km 29, 300, Montelibretti (Italy); Oliva, P. [University Niccolò Cusano, Via don Carlo Gnocchi, 3-00166 Rome (Italy); Mediterranean Institute of Fundamental Physics ‘MIFP’, Via Appia Nuova, 31-00040 Marino (Rome) (Italy); Salvatori, S. [University Niccolò Cusano, Via don Carlo Gnocchi, 3-00166 Rome (Italy)

    2016-11-21

    We report on the response of metal-less CVD polycrystalline-diamond pixel sensors under β-particles irradiation. A 21×21 array of 0.18×0.18 mm{sup 2} pixels was realized on one side of a 10.0×10.0×0.5 mm{sup 3} polycrystalline diamond substrate by means of laser induced surface graphitization. With the same technique, a large graphite contact, used for detector biasing, was fabricated on the opposite side. A coincidence detecting method was used with two other reference polycrystalline diamond detectors for triggering, instead of commonly used scintillators, positioned in the front and on the back of the sensor-array with respect to the impinging particles trajectory. The collected charge distribution at each pixel was analyzed as a function of the applied bias. No change in the pulse height distribution was recorded by inverting the bias voltage polarity, denoting contacts ohmicity and symmetry. A fairly good pixel response uniformity was obtained: the collected charge most probable value saturates for all the pixels at an electric field strength of about ±0.6 V/μm. Under saturation condition, the average collected charge was equal to =1.64±0.02 fC, implying a charge collection distance of about 285 µm. A similar result, within 2%, was also obtained for 400 MeV electrons at beam test facility at INFN Frascati National Laboratory. Experimental results highlighted that more than 84% of impinging particles involved only one pixel, with no significant observed cross-talk effects.

  11. Effects of laser shock peening with contacting foil on micro laser texturing surface of Ti6Al4V

    Science.gov (United States)

    Dai, Fengze; Zhang, Zidong; Ren, Xudong; Lu, Jinzhong; Huang, Shu

    2018-02-01

    Ti6Al4V samples with micro-dimple arrays were subjected to laser shock peening in contact with foil (HCLSP). The surface roughness, micro-hardness, the residual stress distribution and the surface morphology of the micro-dimple arrays were studied to evaluate the effects of HCLSP. Moreover, the surface topography of the foils in contact was also analyzed. The gap existence between the foil and the to-be treated surface led the mechanism of HCLSP to be different compared to regular laser shock peening. The surface roughness reduction, the work-hardening effects, the compressive residual stress and the micro crack enclosure were achieved. A simplified ball-hitting-surface model was utilized to analyze the HCLSP impact. The model could well explain the experimental results. When treated by the HCLSP with H62 foil at the laser power density of 4.24 GW/cm2, the Ti6Al4V samples with micro-dimple arrays exhibit well surface topography and mechanical performance.

  12. Bond strength enhancement of zirconia-porcelain interfaces via Nd:YAG laser surface structuring.

    Science.gov (United States)

    Henriques, Bruno; Fabris, Douglas; Souza, Júlio C M; Silva, Filipe S; Carvalho, Óscar; Fredel, Márcio C; Mesquita-Guimarães, Joana

    2018-05-01

    The aim of this study was to evaluate the effect of laser surface structuring on the bond strength of feldspar-based porcelain to zirconia, as compared to conventional sandblasting treatment. Thirty cylindrical zirconia substrates, previously sintered, were divided in three groups according to the type of surface conditioning: 1) sandblasting with 50 µm Al 2 O 3 ; 2) laser structuring (Ø25 µm holes); and 3) laser structuring (Ø50 µm holes). Porcelain was injected onto the zirconia substrates. X-ray diffractometry (XRD) was used to evaluate the influence of the laser treatment on zirconia crystallographic phases. Shear bond strength test was performed. Micrographs using SEM were used to evaluate the zirconia surface after each surface treatment and to evaluate the fracture surface after the shear test. The laser-structured groups presented the highest shear bond strength (65 ± 16 MPa and 65 ± 11 MPa, for the 25 µm and 50 µm holes, respectively). The sandblasting samples presented shear bond strength of 37 ± 16 MPa. XRD analysis showed that there was no phase transformation on the thermally affected surface due to laser action. Microcracks were created at some holes due to the high temperature gradient generated by laser. Laser structuring significantly increased (up to 75%) the shear bond strength of zirconia to veneering porcelain as compared to conventional sandblasting treatment. Therefore, laser structuring arises as a surface conditioning method for producing stronger and long lasting zirconia-porcelain interfaces. Copyright © 2018 Elsevier Ltd. All rights reserved.

  13. UV laser ablation of silicon carbide ring surfaces for mechanical seal applications

    Science.gov (United States)

    Daurelio, Giuseppe; Bellosi, Alida; Sciti, Diletta; Chita, Giuseppe; Allegretti, Didio; Guerrini, Fausto

    2000-02-01

    Silicon carbide ceramic seal rings are treated by KrF excimer laser irradiation. Surface characteristics, induced by laser treatment, depend upon laser fluence, the number of laser pulses, their energy and frequency, the rotation rate of the ring and the processing atmosphere. It was ascertained that silicon carbide has to be processed under an inert atmosphere to avoid surface oxidation. Microstructural analyses of surface and cross section of the laser processed samples showed that the SiC surface is covered by a scale due to the melting/resolidification processes. At high fluence there are no continuous scales on the surfaces; materials is removed by decomposition/vaporization and the ablation depth is linearly dependent on the number of pulses. Different surface morphologies are observed. The evolution of surface morphology and roughness is discussed with reference to compositions, microstructure and physical and optical properties of the ceramic material and to laser processing parameters. Preliminary results on tribological behavior of the treated seals are reported.

  14. Enhancing structural integrity of adhesive bonds through pulsed laser surface micro-machining

    KAUST Repository

    Diaz, Edwin Hernandez

    2015-06-01

    Enhancing the effective peel resistance of plastically deforming adhesive joints through laser-based surface micro-machining Edwin Hernandez Diaz Inspired by adhesion examples commonly found in nature, we reached out to examine the effect of different kinds of heterogeneous surface properties that may replicate this behavior and the mechanisms at work. In order to do this, we used pulsed laser ablation on copper substrates (CuZn40) aiming to increase adhesion for bonding. A Yb-fiber laser was used for surface preparation of the substrates, which were probed with a Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS). Heterogeneous surface properties were devised through the use of simplified laser micromachined patterns which may induce sequential events of crack arrest propagation, thereby having a leveraging effect on dissipation. The me- chanical performance of copper/epoxy joints with homogeneous and heterogeneous laser micromachined interfaces was then analyzed using the T-peel test. Fractured surfaces were analyzed using SEM to resolve the mechanism of failure and adhesive penetration within induced surface asperities from the treatment. Results confirm positive modifications of the surface morphology and chemistry from laser ablation that enable mechanical interlocking and cohesive failure within the adhesive layer. Remarkable improvements of apparent peel energy, bond toughness, and effective peel force were appreciated with respect to sanded substrates as control samples.

  15. In vitro performance of DIAGNOdent laser fluorescence device for dental calculus detection on human tooth root surfaces

    Directory of Open Access Journals (Sweden)

    Thomas E. Rams

    2017-10-01

    Conclusions: Excellent intra- and inter-examiner reproducibility of autofluorescence intensity measurements was obtained with the DIAGNOdent laser fluorescence device on human tooth roots. Calculus-positive root surfaces exhibited significantly greater DIAGNOdent laser autofluorescence than calculus-free tooth roots, even with the laser probe tip directed parallel to root surfaces. These findings provide further in vitro validation of the potential utility of a DIAGNOdent laser fluorescence device for identifying dental calculus on human tooth root surfaces.

  16. Surface characterizations of laser modified biomedical grade NiTi shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Pequegnat, A. [Centre for Advanced Materials Joining (CAMJ), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Centre for Bioengineering and Biotechnology (CBB), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Michael, A., E-mail: a2michae@uwaterloo.ca [Centre for Advanced Materials Joining (CAMJ), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Centre for Bioengineering and Biotechnology (CBB), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Wang, J. [Centre for Advanced Materials Joining (CAMJ), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Centre for Bioengineering and Biotechnology (CBB), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Lian, K. [Department of Materials Science and Engineering, University of Toronto, 184 College Street, Suite 140, Toronto, ON M5S 3E4 (Canada); Zhou, Y. [Centre for Advanced Materials Joining (CAMJ), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Centre for Bioengineering and Biotechnology (CBB), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Khan, M.I. [Department of Materials Science and Engineering, University of Toronto, 184 College Street, Suite 140, Toronto, ON M5S 3E4 (Canada); Smarter Alloys, Inc., MaRS Centre, South Tower, 101 College Street, Suite 200, Toronto, ON M5G 1L7 (Canada)

    2015-05-01

    Laser processing of shape memory alloys (SMAs) promises to enable the multifunctional capabilities needed for medical device applications. Prior to clinical implementation, the surface characterisation of laser processed SMA is essential in order to understand any adverse biological interaction that may occur. The current study systematically investigated two Ni-49.8 at.% Ti SMA laser processed surface finishes, including as-processed and polished, while comparing them to a chemically etched parent material. Spectrographic characterisation of the surface included; X-ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES), and Raman spectroscopy. Corrosion performance and Ni ion release were also assessed using potentiodynamic cyclic polarization testing and inductively coupled plasma optical emission spectroscopy (ICP-OES), respectively. Results showed that surface defects, including increased roughness, crystallinity and presence of volatile oxide species, overshadowed any possible performance improvements from an increased Ti/Ni ratio or inclusion dissolution imparted by laser processing. However, post-laser process mechanical polishing was shown to remove these defects and restore the performance, making it comparable to chemically etched NiTi material. - Highlights: • Laser processed NiTi shape memory alloy surfaces were systematically characterized. • Chemistry, oxide thickness, composition, microstructure, and roughness were identified. • Localized superficial defects dictated corrosion and Ni ion release performance. • Mechanical polishing restored corrosion performance. • Bulk material corrosion performance was unaffected by pulsed laser process.

  17. Enhancing the antibacterial performance of orthopaedic implant materials by fibre laser surface engineering

    DEFF Research Database (Denmark)

    Chan, Chi-Wai; Carson, Louise; Smith, Graham C.

    2017-01-01

    /dead staining. Surface chemistry was analysed by XPS and surface wettability was measured using the sessile drop method. The findings of this study indicated that the laser-treated CP Ti and Ti6Al4V surfaces exhibited a noticeable reduction in bacterial adhesion and possessed a bactericidal effect...

  18. X-ray free electron laser as a real-time probe of chemistry on surfaces

    International Nuclear Information System (INIS)

    Katayama, Tetsuo; Ogasawara, Hirohito

    2015-01-01

    X-ray free electron laser has opened up new possibilities for the study of surface chemical reactions on ultrafast time scale. This article reviews the recent work on the desorption of a molecule from a surface, which is one of the most fundamental surface chemical process. (author)

  19. Laser control melting of alumina surfaces with presence of B{sub 4}C particles

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsyilbas@kfupm.edu.sa [Mechanical Engineering Dept., King Fahd University of Petroleum and Minerals (KFUPM), Dhahran (Saudi Arabia); Al-Aqeeli, N. [Mechanical Engineering Dept., King Fahd University of Petroleum and Minerals (KFUPM), Dhahran (Saudi Arabia); Karatas, C. [Engineering faculty, Hacettepe University, Ankara (Turkey)

    2012-10-25

    Highlights: Black-Right-Pointing-Pointer Dense and fine grains are formed in the surface region and columnar structures are formed underneath. Black-Right-Pointing-Pointer The presence of carbon film enables to form AlN, AlON, and Al(C, N) compounds at surface. Black-Right-Pointing-Pointer Presence of B{sub 4}C particles and nitride species increases surface microhardness notably. Black-Right-Pointing-Pointer The residual stress formed at the surface is compressive. - Abstract: Laser gas assisted controlled melting of alumina tile surface is carried out in this work. A carbon coating containing 5% of B{sub 4}C particles is formed at the tile surface prior to laser treatment process. The morphological and microstructural changes in the treated layer are examined using X-ray diffraction, energy dispersive spectroscopy, and scanning electron microscope. The surface microhardness is measured and the residual stress formed at the surface vicinity is obtained from the X-ray diffractograms. It was found that microhardness of the surface increases significantly after the laser treatment process, which is attributed to high cooling rates and the formation of nitride species at the surface. The residual stress formed at the surface is compressive and no micro- or major-cracks are observed at the laser treated surface.

  20. Injection and laser acceleration of ions based on the resonant surface photoionization

    International Nuclear Information System (INIS)

    Antsiferov, V.V.; Smirnov, G.I.; Telegin, G.G.

    1993-01-01

    The collective effects have been investigated of the injection and acceleration of the ion beams due to the resonant surface photoionization. The considered scheme of the laser accelerator allows to obtain positive ions with relativistic velocities. 11 refs., 2 figs

  1. Er:YAG laser scaling of diseased root surfaces: a histologic study.

    Science.gov (United States)

    Crespi, Roberto; Barone, Antonio; Covani, Ugo

    2006-02-01

    The aim of the present study was to observe the effects of an erbium-doped:yttrium, aluminum, and garnet (Er:YAG) laser when used to treat periodontally involved root surfaces. Forty teeth affected by severe periodontal disease and scheduled for extraction were divided into two groups: in group A (control), 20 teeth were treated by hand instrumentation, and in group B (test), 20 teeth were treated by Er:YAG laser. In group A (teeth treated by curets), the root cementum layer was completely removed, but many deep scratches on the dentin layer were also observed. In group B, the laser-treated root surfaces, there was no cracking or carbonization, and the bacterial flora was completely eliminated, leaving a rough and uniform surface. Results of the present study showed that clinical use of an Er:YAG laser in vivo achieves plaque and calculus removal, providing a rough surface morphology.

  2. Ultraviolet Raman Spectral Signatures in Support of Lisa (Laser Interrogation of Surface Agents)

    National Research Council Canada - National Science Library

    Sedlacek, III, Arthur J; Finfrock, Charles C; Christesen, Steve; Chyba, Tom; Higdon, Scott

    2003-01-01

    ... (Laser Interrogation of Surface Agents). This engineering, testing and evaluation effort uses a novel mini-Raman lidar technique for on-the-move, short-range, non-contact detection and identification of chemical agents on the battlefield...

  3. Theoretical and experimental approach to the texturization process of bioreactive surfaces by high-power laser

    Science.gov (United States)

    Conde, J. C.; Riveiro, A.; Comesana, R.; Pou, J.

    2011-11-01

    The properties of orthopaedic/dental implants can be tuned through the laser surface modifications that take place during a laser ablation process. Processing assisted by a laser is adequate to produce macro- and micro-structures on metallic alloys and polymer surfaces in order to improve their biological response. The evaluation of the minimum energy density that causes an optimum ablation process on different kinds of surfaces was theoretically established by numerical simulation of the thermal process and some experiments have been systematically carried out to produce a periodic pattern in the surface. The selection of the laser power has been predicted from numerical analysis solving of the heat conduction differential equation using commercial software, ANSYS (11.0). This analysis has allowed us to predict the extent and the depth of the holes. The theoretical results agree with the experimental measurements that were carried out by profilometry.

  4. Enhancing the antibacterial performance of orthopaedic implant materials by fibre laser surface engineering

    Science.gov (United States)

    Chan, Chi-Wai; Carson, Louise; Smith, Graham C.; Morelli, Alessio; Lee, Seunghwan

    2017-05-01

    Implant failure caused by bacterial infection is extremely difficult to treat and usually requires the removal of the infected components. Despite the severe consequence of bacterial infection, research into bacterial infection of orthopaedic implants is still at an early stage compared to the effort on enhancing osseointegration, wear and corrosion resistance of implant materials. In this study, the effects of laser surface treatment on enhancing the antibacterial properties of commercially pure (CP) Ti (Grade 2), Ti6Al4V (Grade 5) and CoCrMo alloy implant materials were studied and compared for the first time. Laser surface treatment was performed by a continuous wave (CW) fibre laser with a near-infrared wavelength of 1064 nm in a nitrogen-containing environment. Staphylococcus aureus, commonly implicated in infection associated with orthopaedic implants, was used to investigate the antibacterial properties of the laser-treated surfaces. The surface roughness and topography of the laser-treated materials were analysed by a 2D roughness testing and by AFM. The surface morphologies before and after 24 h of bacterial cell culture were captured by SEM, and bacterial viability was determined using live/dead staining. Surface chemistry was analysed by XPS and surface wettability was measured using the sessile drop method. The findings of this study indicated that the laser-treated CP Ti and Ti6Al4V surfaces exhibited a noticeable reduction in bacterial adhesion and possessed a bactericidal effect. Such properties were attributable to the combined effects of reduced hydrophobicity, thicker and stable oxide films and presence of laser-induced nano-features. No similar antibacterial effect was observed in the laser-treated CoCrMo.

  5. Laser surface pretreatment of 100Cr6 bearing steel – Hardening effects and white etching zones

    Energy Technology Data Exchange (ETDEWEB)

    Buling, Anna, E-mail: a.buling@hs-osnabrueck.de [Faculty of Engineering and Computer Science, University of Applied Sciences, 49009 Osnabrück (Germany); Sändker, Hendrik; Stollenwerk, Jochen [Fraunhofer Institute for Laser Technology ILT, Steinbachstrasse 15, 52074 Aachen (Germany); Krupp, Ulrich; Hamann-Steinmeier, Angela [Faculty of Engineering and Computer Science, University of Applied Sciences, 49009 Osnabrück (Germany)

    2016-08-15

    Highlights: • Laser surface pretreatment of the bearing steel 100Cr6 is performed. • Microstructural changes of the surface are examined by light microscopy and SEM. • Topographical changes are observed using white light interferometry. • Micro-hardness testing show the existence of very hard white etching zones (WEZ). • WEZ are attributed to near-surface reaustenitization and rapid quenching. • Dark etching zones (DEZ) are found at the laser path edges after laser pretreatment. - Abstract: In order to achieve a surface pretreatment of the bearing steel 100Cr6 (1–1.5 wt.% Cr) a laser-based process was used. The obtained modification may result in an optimization of the adhesive properties of the surface with respect to an anticorrosion polymer coating on the basis of PEEK (poly-ether-ether-ketone), which is applied on the steel surface by a laser melting technique. This work deals with the influence of the laser-based pretreatment regarding the surface microstructure and the micro-hardness of the steel, which has been examined by scanning electron microscopy (SEM), light microscopy and automated micro-hardness testing. The most suitable parameter set for the laser-based pretreatment leads to the formation of very hard white etching zones (WEZ) with a thickness of 23 μm, whereas this pretreatment also induces topographical changes. The occurrence of the white etching zones is attributed to near-surface re-austenitization and rapid quenching. Moreover, dark etching zones (DEZ) with a thickness of 32 μm are found at the laser path edges as well as underneath the white etching zones (WEZ). In these areas, the hardness is decreased due to the formation of oxides as a consequence of re-tempering.

  6. Finite element analysis of laser-generated ultrasound for characterizing surface-breaking cracks

    International Nuclear Information System (INIS)

    Jeong, Hyun Jo

    2005-01-01

    A finite element method was used to simulate the wave propagation of laser-generated ultrasound and its interaction with surface breaking cracks in an elastic material. Thermoelastic laser line source on the material surface was approximated as a shear dipole and loaded as nodal forces in the plane-strain Finite Element (FE) model. The shear dipole-FE model was tested for the generation of ultrasound on the surface with no defect. The model was found to generate the Rayleigh surface wave. The model was then extended to examine the interaction of laser generated ultrasound with surface-breaking cracks of various depths. The crack-scattered waves were monitored to size the crack depth. The proposed model clearly reproduced the experimentally observed features that can be used to characterize the presence of surface-breaking cracks

  7. Laser micropolishing of AISI 304 stainless steel surfaces for cleanability and bacteria removal capability

    Science.gov (United States)

    De Giorgi, Chiara; Furlan, Valentina; Demir, Ali Gökhan; Tallarita, Elena; Candiani, Gabriele; Previtali, Barbara

    2017-06-01

    In this work, laser micropolishing (LμP) was employed to reduce the surface roughness and waviness of cold-rolled AISI 304 stainless steel sheets. A pulsed fibre laser operating in the ns regime was used and the influence of laser parameters in a N2-controlled atmospheres was evaluated. In the optimal conditions, the surface remelting induced by the process allowed to reduce the surface roughness by closing cracks and defects formed during the rolling process. Other conditions that did not improve the surface quality were analysed for defect typology. Moreover, laser treatments allowed the production of more hydrophobic surfaces, and no surface chemistry modification was identified. Surface cleanability was investigated with Escherichia coli (E. coli), evaluating the number of residual bacteria adhering to the substrate after a washing procedure. These results showed that LμP is a suitable way to lower the average surface roughness by about 58% and average surface waviness by approximately 38%. The LμP process proved to be effective on the bacteria cleanability as approximately five times fewer bacteria remained on the surfaces treated with the optimized LμP parameters compared to the untreated surfaces.

  8. Surface-selective laser sintering of thermolabile polymer particles using water as heating sensitizer

    Energy Technology Data Exchange (ETDEWEB)

    Antonov, E N; Krotova, L I; Minaev, N V; Minaeva, S A; Mironov, A V; Popov, V K [Institute on Laser and Information Technologies of the Russian Academy of Sciencies, Troitsk, Moscow (Russian Federation); Bagratashvili, V N [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

    2015-11-30

    We report the implementation of a novel scheme for surface-selective laser sintering (SSLS) of polymer particles, based on using water as a sensitizer of laser heating and sintering of particles as well as laser radiation at a wavelength of 1.94 μm, corresponding to the strong absorption band of water. A method of sintering powders of poly(lactide-co-glycolide), a hydrophobic bioresorbable polymer, after modifying its surface with an aqueous solution of hyaluronic acid is developed. The sintering thresholds for wetted polymer are by 3 – 4 times lower than those for sintering in air. The presence of water restricts the temperature of the heated polymer, preventing its thermal destruction. Polymer matrices with a developed porous structure are obtained. The proposed SSLS method can be applied to produce bioresorbable polymer matrices for tissue engineering. (interaction of laser radiation with matter. laser plasma)

  9. How to optimize ultrashort pulse laser interaction with glass surfaces in cutting regimes?

    Energy Technology Data Exchange (ETDEWEB)

    Bulgakova, Nadezhda M., E-mail: bulgakova@fzu.cz [HiLASE Centre, Institute of Physics ASCR, Za Radnicí 828, 25241 Dolní Břežany (Czech Republic); Institute of Thermophysics SB RAS, 1 Lavrentyev Ave., Novosibirsk 630090 (Russian Federation); Zhukov, Vladimir P. [Institute of Computational Technologies SB RAS, 6 Lavrentyev Ave., 630090 Novosibirsk (Russian Federation); Novosibirsk State Technical University, 20 Karl Marx Ave., 630073 Novosibirsk (Russian Federation); Collins, Adam R. [NCLA, NUI Galway, Galway (Ireland); Rostohar, Danijela; Derrien, Thibault J.-Y.; Mocek, Tomáš [HiLASE Centre, Institute of Physics ASCR, Za Radnicí 828, 25241 Dolní Břežany (Czech Republic)

    2015-05-01

    Highlights: • The factors influencing laser micromachining of transparent materials are analyzed. • Important role of ambient gas in laser processing is shown by numerical simulations. • The large potential of bi-wavelength laser processing is demonstrated. - Abstract: The interaction of short and ultrashort pulse laser radiation with glass materials is addressed. Particular attention is paid to regimes which are important in industrial applications such as laser cutting, drilling, functionalization of material surfaces, etc. Different factors influencing the ablation efficiency and quality are summarized and their importance is illustrated experimentally. The effects of ambient gas ionization in front of the irradiated target are also analyzed. A possibility to enhance laser coupling with transparent solids by bi-wavelength irradiation is discussed.

  10. Alignment of Ion Accelerator for Surface Analysis using Theodolite and Laser Tracker

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Tae Sung; Seo, Dong Hyuk; Kim, Dae Il; Kim, Han Sung; Kwon, Hyeok Jung; Cho, Yong Sub [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    The method of ion accelerator alignment is used two ways which are a theodolite and laser tracker. For the alignment and maintenance of the proton linear accelerator, the laser tracker is typically used at KOMAC. While the device for alignment by using laser tracker is not installed in all ion accelerator components, it was used in parallel in two methods. In this paper, alignment methods are introduced and the result and comparison of each alignment method are presented. The ion accelerator for surface analysis has aligned using theodolite and laser tracker. The two ways for alignment have advantage as well as weakness. But alignment using laser tracker is stronger than using theodolite. Because it is based on alignment and position data and it is more detailed. Also since the beam distribution is smaller than accelerator component that is direction of beam progress, main component (ex. Magnet, Chamber, Pelletron tank, etc.) alignment using laser tracker is enough to align the ion accelerator.

  11. Non-textured laser modification of silica glass surface: Wettability control and flow channel formation

    Science.gov (United States)

    Aono, Yuko; Hirata, Atsushi; Tokura, Hitoshi

    2016-05-01

    Local wettability of silica glass surface is modified by infrared laser irradiation. The silica glass surface exhibits hydrophobic property in the presence of sbnd CF3 or sbnd (CH3)2 terminal functional groups, which are decomposed by thermal treatment, and degree of the decomposition depends on the applied heat. Laser irradiation can control the number of remaining functional groups according to the irradiation conditions; the contact angle of deionized water on the laser modified surfaces range from 100° to 40°. XPS analysis confirms that the variation in wettability corresponds to the number of remaining sbnd CF3 groups. The laser irradiation achieves surface modification without causing any cracks or damages to the surface, as observed by SEM and AFM; moreover, surface transparency to visible light and surface roughness remains unaffected. The proposed method is applied to plane flow channel systems. Dropped water spreads only on the hydrophilic and invisible line modified by the laser irradiation without formation of any grooves. This indicates that the modified line can act as a surface channel. Furthermore, self-transportation of liquid is also demonstrated on a channel with gradually-varied wettability along its length. A water droplet on a hydrophobic side is self-transported to a hydrophilic side due to contact-angle hysteresis force without any actuators or external forces.

  12. The controlled pulsed laser deposition of Ag nanoparticle arrays for surface enhanced Raman scattering.

    Science.gov (United States)

    D'Andrea, C; Neri, F; Ossi, P M; Santo, N; Trusso, S

    2009-06-17

    An effective method for the production of surface enhanced Raman scattering (SERS) active substrates is presented. Nanostructured silver thin films are pulsed laser deposited in an argon atmosphere. The films consist of arrays of nanoparticles whose size is controlled by the Ar pressure. The surface morphology of the films can be tuned by the laser pulse number. Nanoparticle size is calculated by a phenomenological model taking into account the dynamics of the laser generated silver plasma. The SERS activity of the films is investigated by Raman scattering of adsorbed rhodamine 6G at different concentrations.

  13. Formation of laser-induced periodic surface structures (LIPSS) on tool steel by multiple picosecond laser pulses of different polarizations

    Energy Technology Data Exchange (ETDEWEB)

    Gregorčič, Peter, E-mail: peter.gregorcic@fs.uni-lj.si [Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva 6, 1000 Ljubljana (Slovenia); Sedlaček, Marko; Podgornik, Bojan [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Reif, Jürgen [Brandenburgische Technische Universitaet – BTU Cottbus-Senftenberg, Platz der Deutschen Einheit 1, 03046 Cottbus (Germany)

    2016-11-30

    Highlights: • Low number of differently polarized ps laser pulses is superimposed on tool steel. • Last pulses determine the ripples orientation for single spot and coherent traces. • Previously formed structures are overridden by later incident pulses. • Ripples contrast depends on total exposure, independent on pulses’ polarization. • Weak role of pre-formed structures makes interference scenarios questionable. - Abstract: Laser-induced periodic surface structures (LIPSS) are produced on cold work tool steel by irradiation with a low number of picosecond laser pulses. As expected, the ripples, with a period of about 90% of the laser wavelength, are oriented perpendicular to the laser polarization. Subsequent irradiation with the polarization rotated by 45° or 90° results in a corresponding rotation of the ripples. This is visible already with the first pulse and becomes almost complete – erasing the previous orientation – after as few as three pulses. The phenomenon is not only observed for single-spot irradiation but also for writing long coherent traces. The experimental results strongly defy the role of surface plasmon-polaritons as the predominant key to LIPSS formation.

  14. Interference effects in laser-induced plasma emission from surface-bound metal micro-particles.

    Science.gov (United States)

    Feigenbaum, Eyal; Malik, Omer; Rubenchik, Alexander M; Matthews, Manyalibo J

    2017-05-01

    The light-matter interaction of an optical beam and metal micro-particulates at the vicinity of an optical substrate surface is critical to the many fields of applied optics. Examples of impacted fields are laser-induced damage in high power laser systems, sub-wavelength laser machining of transmissive materials, and laser-target interaction in directed energy applications. We present a full-wave-based model that predicts the laser-induced plasma pressure exerted on a substrate surface as a result of light absorption in surface-bound micron-scale metal particles. The model predictions agree with experimental observation of laser-induced shallow pits, formed by plasma emission and etching from surface-bound metal micro-particulates. It provides an explanation for the prototypical side lobes observed along the pit profile, as well as for the dependence of the pit shape on the incident laser and particle parameters. Furthermore, the model highlights the significance of the interference of the incident light in the open cavity geometry formed between the micro-particle and the substrate in the resulting pit shape.

  15. Implant Surface Temperature Changes during Er:YAG Laser Irradiation with Different Cooling Systems.

    Directory of Open Access Journals (Sweden)

    Abbas Monzavi

    2014-04-01

    Full Text Available Peri-implantitis is one of the most common reasons for implant failure. Decontamination of infected implant surfaces can be achieved effectively by laser irradiation; although the associated thermal rise may cause irreversible bone damage and lead to implant loss. Temperature increments of over 10ºC during laser application may suffice for irreversible bone damage.The purpose of this study was to evaluate the temperature increment of implant surface during Er:YAG laser irradiation with different cooling systems.Three implants were placed in a resected block of sheep mandible and irradiated with Er:YAG laser with 3 different cooling systems namely water and air spray, air spray alone and no water or air spray. Temperature changes of the implant surface were monitored during laser irradiation with a K-type thermocouple at the apical area of the fixture.In all 3 groups, the maximum temperature rise was lower than 10°C. Temperature changes were significantly different with different cooling systems used (P<0.001.Based on the results, no thermal damage was observed during implant surface decontamination by Er:YAG laser with and without refrigeration. Thus, Er:YAG laser irradiation can be a safe method for treatment of periimplantitis.

  16. Temperature evaluation of dental implant surface irradiated with high-power diode laser.

    Science.gov (United States)

    Rios, F G; Viana, E R; Ribeiro, G M; González, J C; Abelenda, A; Peruzzo, D C

    2016-09-01

    The prevalence of peri-implantitis and the absence of a standard approach for decontamination of the dental implant surface have led to searches for effective therapies. Since the source of diode lasers is portable, has reduced cost, and does not cause damage to the titanium surface of the implant, high-power diode lasers have been used for this purpose. The effect of laser irradiation on the implants is the elevation of the temperature surface. If this elevation exceeds 47 °C, the bone tissue is irreversibly damaged, so for a safety therapy, the laser parameters should be controlled. In this study, a diode laser of GaAsAl was used to irradiate titanium dental implants, for powers 1.32 to 2.64 W (real) or 2.00 to 4.00 W (nominal), in continuous/pulsed mode DC/AC, with exposure time of 5/10 s, with/without air flow for cooling. The elevation of the temperature was monitored in real time in two positions: cervical and apical. The best results for decontamination using a 968-nm diode laser were obtained for a power of 1.65 and 1.98 W (real) for 10 s, in DC or AC mode, with an air flow of 2.5 l/min. In our perspective in this article, we determine a suggested approach for decontamination of the dental implant surface using a 968-nm diode laser.

  17. Study on the high-frequency laser measurement of slot surface difference

    Science.gov (United States)

    Bing, Jia; Lv, Qiongying; Cao, Guohua

    2017-10-01

    In view of the measurement of the slot surface difference in the large-scale mechanical assembly process, Based on high frequency laser scanning technology and laser detection imaging principle, This paragraph designs a double galvanometer pulse laser scanning system. Laser probe scanning system architecture consists of three parts: laser ranging part, mechanical scanning part, data acquisition and processing part. The part of laser range uses high-frequency laser range finder to measure the distance information of the target shape and get a lot of point cloud data. Mechanical scanning part includes high-speed rotary table, high-speed transit and related structure design, in order to realize the whole system should be carried out in accordance with the design of scanning path on the target three-dimensional laser scanning. Data processing part mainly by FPGA hardware with LAbVIEW software to design a core, to process the point cloud data collected by the laser range finder at the high-speed and fitting calculation of point cloud data, to establish a three-dimensional model of the target, so laser scanning imaging is realized.

  18. Electrochemical investigation of the effect of different laser surface treatments on Hastelloy G alloy

    Energy Technology Data Exchange (ETDEWEB)

    Toor, Ihsan H.; Yilbas, Bekir S.; Hussein, Mohammed A.; Zafar, Mohammed N. [King Fahd Univ. of Petroleum and Minerals (KFUPM), Dhahran (Saudi Arabia). Dept. of Mechanical Engineering; Karatas, Cihan [Hacettepe Univ., Ankara (Turkey). Engineering Faculty

    2013-10-15

    In the present study, the corrosion resistance behavior of untreated and laser treated Hastelloy was examined. The electrochemical tests including potentiodynamic polarization, Tafel analysis, and linear polarization resistance were carried out in deaerated 0.5% NaCl aqueous solution at room temperature. Surface roughness was measured to correlate it with corrosion resistance properties of the materials. Surface morphology of the samples after corrosion tests was examined using scanning electron microscopy and energy dispersive X-ray spectroscopy. Results showed that laser treated surface exhibited better corrosion resistance properties as compared to untreated surface. (orig.)

  19. Laser-induced generation of surface periodic structures in media with nonlinear diffusion

    Science.gov (United States)

    Zhuravlev, V. M.; Zolotovskii, I. O.; Korobko, D. A.; Morozov, V. M.; Svetukhin, V. V.; Yavtushenko, I. O.; Yavtushenko, M. S.

    2017-12-01

    A model of fast formation of high-contrast periodic structure appearing on a semiconductor surface under action of laser radiation is proposed. The process of growing a surface structure due to the interaction surface plasmon- polaritons excited on nonequilibrium electrons with incident laser radiation are considered in the framework of a medium with nonlinear diffusion of nonequilibrium carriers (defects). A resonance effect of superfast pico- and subpicosecond amplification of the plasmon-polariton structure generated on the surface, the realization of which can result in a high-contrast defect lattice.

  20. Effective removal of calcified deposits on microstructured titanium fixture surfaces of dental implants with erbium lasers.

    Science.gov (United States)

    Takagi, Toru; Aoki, Akira; Ichinose, Shizuko; Taniguchi, Yoichi; Tachikawa, Noriko; Shinoki, Takeshi; Meinzer, Walter; Sculean, Anton; Izumi, Yuichi

    2018-03-13

    Recently, the occurrence of peri-implantitis has been increasing. However, a suitable method to debride the contaminated surface of titanium implants has not been established. The aim of this study was to investigate the morphological changes of the microstructured fixture surface after erbium laser irradiation, and to clarify the effects of the erbium lasers when used to remove calcified deposits from implant fixture surfaces. In experiment 1, sandblasted, large grit, acid etched surface implants were treated with Er:YAG laser or Er,Cr:YSGG laser at 30-60 mJ/pulse and 20 Hz with water spray. In experiments 2 and 3, the effects of erbium lasers used to remove calcified deposits (artificially prepared deposits on virgin implants and natural calculus on failed implants) were investigated and compared with mechanical debridement using either a titanium curette or cotton pellets. After the various debridement methods, all specimens were analyzed by stereomicroscopy (SM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Stereomicroscopy and SEM showed that erbium lasers with optimal irradiation parameters did not have an effect on titanium microstructures. Compared to mechanical debridement, erbium lasers were more capable of removing calcified deposits on the microstructured surface without surface alteration using a non-contact sweeping irradiation at 40 mJ/pulse (ED 14.2 J/cm 2 /pulse) and 20 Hz with water spray. These results indicate that Er:YAG and Er,Cr:YSGG lasers are more advantageous in removing calcified deposits on the microstructured surface of titanium implants without inducing damage, compared to mechanical therapy by cotton pellet or titanium curette. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  1. Effect of LASER Irradiation on the Shear Bond Strength of Zirconia Ceramic Surface to Dentin

    Directory of Open Access Journals (Sweden)

    Sima Shahabi

    2012-09-01

    Full Text Available Background and Aims: Reliable bonding between tooth substrate and zirconia-based ceramic restorations is always of great importance. The laser might be useful for treatment of ceramic surfaces. The aim of the present study was to investigate the effect of laser irradiation on the shear bond strength of zirconia ceramic surface to dentin. Materials and Methods: In this experimental in vitro study, 40 Cercon zirconia ceramic blocks were fabricated. The surface treatment was performed using sandblasting with 50-micrometer Al2O3, CO2 laser, or Nd:YAG laser in each test groups. After that, the specimens were cemented to human dentin with resin cement. The shear bond strength of ceramics to dentin was determined and failure mode of each specimen was analyzed by stereo-microscope and SEM investigations. The data were statistically analyzed by one-way analysis of variance and Tukey multiple comparisons. The surface morphology of one specimen from each group was investigated under SEM. Results: The mean shear bond strength of zirconia ceramic to dentin was 7.79±3.03, 9.85±4.69, 14.92±4.48 MPa for CO2 irradiated, Nd:YAG irradiated, and sandblasted specimens, respectively. Significant differences were noted between CO2 (P=0.001 and Nd:YAG laser (P=0.017 irradiated specimens with sandblasted specimens. No significant differences were observed between two laser methods (P=0.47. The mode of bond failure was predominantly adhesive in test groups (CO2 irradiated specimens: 75%, Nd:YAG irradiated: 66.7%, and sandblasting: 41.7%. Conclusion: Under the limitations of the present study, surface treatment of zirconia ceramics using CO2 and Nd:YAG lasers was not able to produce adequate bond strength with dentin surfaces in comparison to sandblasting technique. Therefore, the use of lasers with the mentioned parameters may not be recommended for the surface treatment of Cercon ceramics.

  2. Effects of intratracheally instilled laser printer-emitted engineered nanoparticles in a mouse model: A case study of toxicological implications from nanomaterials released during consumer use

    Science.gov (United States)

    Pirela, Sandra V.; Lu, Xiaoyan; Miousse, Isabelle; Sisler, Jennifer D.; Qian, Yong; Guo, Nancy; Koturbash, Igor; Castranova, Vincent; Thomas, Treye; Godleski, John; Demokritou, Philip

    2016-01-01

    Incorporation of engineered nanomaterials (ENMs) into toners used in laser printers has led to countless quality and performance improvements. However, the release of ENMs during printing (consumer use) has raised concerns about their potential adverse health effects. The aim of this study was to use “real world” printer-emitted particles (PEPs), rather than raw toner powder, and assess the pulmonary responses following exposure by intratracheal instillation. Nine-week old male Balb/c mice were exposed to various doses of PEPs (0.5, 2.5 and 5 mg/kg body weight) by intratracheal instillation. These exposure doses are comparable to real world human inhalation exposures ranging from 13.7 to 141.9 h of printing. Toxicological parameters reflecting distinct mechanisms of action were evaluated, including lung membrane integrity, inflammation and regulation of DNA methylation patterns. Results from this in vivo toxicological analysis showed that while intratracheal instillation of PEPs caused no changes in the lung membrane integrity, there was a pulmonary immune response, indicated by an elevation in neutrophil and macrophage percentage over the vehicle control and low dose PEPs groups. Additionally, exposure to PEPs upregulated expression of the Ccl5 (Rantes), Nos1 and Ucp2 genes in the murine lung tissue and modified components of the DNA methylation machinery (Dnmt3a) and expression of transposable element (TE) LINE-1 compared to the control group. These genes are involved in both the repair process from oxidative damage and the initiation of immune responses to foreign pathogens. The results are in agreement with findings from previous in vitro cellular studies and suggest that PEPs may cause immune responses in addition to modifications in gene expression in the murine lung at doses that can be comparable to real world exposure scenarios, thereby raising concerns of deleterious health effects. PMID:26989787

  3. Effects of intratracheally instilled laser printer-emitted engineered nanoparticles in a mouse model: A case study of toxicological implications from nanomaterials released during consumer use.

    Science.gov (United States)

    Pirela, Sandra V; Lu, Xiaoyan; Miousse, Isabelle; Sisler, Jennifer D; Qian, Yong; Guo, Nancy; Koturbash, Igor; Castranova, Vincent; Thomas, Treye; Godleski, John; Demokritou, Philip

    2016-01-01

    Incorporation of engineered nanomaterials (ENMs) into toners used in laser printers has led to countless quality and performance improvements. However, the release of ENMs during printing (consumer use) has raised concerns about their potential adverse health effects. The aim of this study was to use "real world" printer-emitted particles (PEPs), rather than raw toner powder, and assess the pulmonary responses following exposure by intratracheal instillation. Nine-week old male Balb/c mice were exposed to various doses of PEPs (0.5, 2.5 and 5 mg/kg body weight) by intratracheal instillation. These exposure doses are comparable to real world human inhalation exposures ranging from 13.7 to 141.9 h of printing. Toxicological parameters reflecting distinct mechanisms of action were evaluated, including lung membrane integrity, inflammation and regulation of DNA methylation patterns. Results from this in vivo toxicological analysis showed that while intratracheal instillation of PEPs caused no changes in the lung membrane integrity, there was a pulmonary immune response, indicated by an elevation in neutrophil and macrophage percentage over the vehicle control and low dose PEPs groups. Additionally, exposure to PEPs upregulated expression of the Ccl5 ( Rantes ), Nos1 and Ucp2 genes in the murine lung tissue and modified components of the DNA methylation machinery ( Dnmt3a ) and expression of transposable element (TE) LINE-1 compared to the control group. These genes are involved in both the repair process from oxidative damage and the initiation of immune responses to foreign pathogens. The results are in agreement with findings from previous in vitro cellular studies and suggest that PEPs may cause immune responses in addition to modifications in gene expression in the murine lung at doses that can be comparable to real world exposure scenarios, thereby raising concerns of deleterious health effects.

  4. In vivo epigenetic effects induced by engineered nanomaterials: A case study of copper oxide and laser printer-emitted engineered nanoparticles.

    Science.gov (United States)

    Lu, Xiaoyan; Miousse, Isabelle R; Pirela, Sandra V; Moore, Jodene K; Melnyk, Stepan; Koturbash, Igor; Demokritou, Philip

    2016-01-01

    Evidence continues to grow on potential environmental health hazards associated with engineered nanomaterials (ENMs). While the geno- and cytotoxic effects of ENMs have been investigated, their potential to target the epigenome remains largely unknown. The aim of this study is two-fold: 1) determining whether or not industry relevant ENMs can affect the epigenome in vivo and 2) validating a recently developed in vitro epigenetic screening platform for inhaled ENMs. Laser printer-emitted engineered nanoparticles (PEPs) released from nano-enabled toners during consumer use and copper oxide (CuO) were chosen since these particles induced significant epigenetic changes in a recent in vitro companion study. In this study, the epigenetic alterations in lung tissue, alveolar macrophages and peripheral blood from intratracheally instilled mice were evaluated. The methylation of global DNA and transposable elements (TEs), the expression of the DNA methylation machinery and TEs, in addition to general toxicological effects in the lung were assessed. CuO exhibited higher cell-damaging potential to the lung, while PEPs showed a greater ability to target the epigenome. Alterations in the methylation status of global DNA and TEs, and expression of TEs and DNA machinery in mouse lung were observed after exposure to CuO and PEPs. Additionally, epigenetic changes were detected in the peripheral blood after PEPs exposure. Altogether, CuO and PEPs can induce epigenetic alterations in a mouse experimental model, which in turn confirms that the recently developed in vitro epigenetic platform using macrophage and epithelial cell lines can be successfully utilized in the epigenetic screening of ENMs.

  5. Laser surface modification of Yttria Stabilized Zirconia (YSZ) thermal barrier coating on AISI H13 tool steel substrate

    Science.gov (United States)

    Reza, M. S.; Aqida, S. N.; Ismail, I.

    2018-03-01

    This paper presents laser surface modification of plasma sprayed yttria stabilized zirconia (YSZ) coating to seal porosity defect. Laser surface modification on plasma sprayed YSZ was conducted using 300W JK300HPS Nd: YAG laser at different operating parameters. Parameters varied were laser power and pulse frequency with constant residence time. The coating thickness was measured using IM7000 inverted optical microscope and surface roughness was analysed using two-dimensional Mitutoyo Surface Roughness Tester. Surface roughness of laser surface modification of YSZ H-13 tool steel decreased significantly with increasing laser power and decreasing pulse frequency. The re-melted YSZ coating showed higher hardness properties compared to as-sprayed coating surface. These findings were significant to enhance thermal barrier coating surface integrity for dies in semi-solid processing.

  6. Induction of subterahertz surface waves on a metal wire by intense laser interaction with a foil

    Science.gov (United States)

    Teramoto, Kensuke; Inoue, Shunsuke; Tokita, Shigeki; Yasuhara, Ryo; Nakamiya, Yoshihide; Nagashima, Takeshi; Mori, Kazuaki; Hashida, Masaki; Sakabe, Shuji

    2018-02-01

    We have demonstrated that a pulsed electromagnetic wave (Sommerfeld wave) of subterahertz frequency and 11-MV/m field strength can be induced on a metal wire by the interaction of an intense femtosecond laser pule with an adjacent metal foil at a laser intensity of 8.5 × 1018W /c m2 . The polarity of the electric field of this surface wave is opposite to that obtained by the direct interaction of the laser with the wire. Numerical simulations suggest that an electromagnetic wave associated with electron emission from the foil induces the surface wave. A tungsten wire is placed normal to an aluminum foil with a gap so that the wire is not irradiated and damaged by the laser pulse, thus making it possible to generate surface waves on the wire repeatedly.

  7. Metal surface coloration by oxide periodic structures formed with nanosecond laser pulses

    Science.gov (United States)

    Veiko, Vadim; Karlagina, Yulia; Moskvin, Mikhail; Mikhailovskii, Vladimir; Odintsova, Galina; Olshin, Pavel; Pankin, Dmitry; Romanov, Valery; Yatsuk, Roman

    2017-09-01

    In this work, we studied a method of laser-induced coloration of metals, where small-scale spatially periodic structures play a key role in the process of color formation. The formation of such structures on a surface of AISI 304 stainless steel was demonstrated for the 1.06 μm fiber laser with nanosecond duration of pulses and random (elliptical) polarization. The color of the surface depends on the period, height and orientation of periodic surface structures. Adjustment of the polarization of the laser radiation or change of laser incidence angle can be used to control the orientation of the structures. The formation of markings that change their color under the different viewing angles becomes possible. The potential application of the method is metal product protection against falsification.

  8. Corrosion resistance of the AISI 304, 316 and 321 stainless steel surfaces modified by laser

    Science.gov (United States)

    Szubzda, B.; Antończak, A.; Kozioł, P.; Łazarek, Ł.; Stępak, B.; Łęcka, K.; Szmaja, A.; Ozimek, M.

    2016-02-01

    The article presents the analysis results of the influence of laser fluence on physical and chemical structure and corrosion resistance of stainless steel surfaces modified by irradiating with nanosecond-pulsed laser. The study was carried out for AISI 304, AISI 316 and AISI 321 substrates using Yb:glass fiber laser. All measurements were made for samples irradiated in a broad range of accumulated fluence (10÷400 J/cm2). The electrochemical composition (by EDX) and surface morphology (by SEM) of the prepared surfaces were carried out. Finally, corrosion resistance was analyzed by a potentiodynamic electrochemical test. The obtained results showed very high corrosion resistance for samples made by fluency of values lower than 100 J/cm2. In this case, higher values of corrosion potentials and breakdown potentials were observed. A correlation between corrosion phenomena, the range of laser power (fluence) and the results of chemical and structural tests were also found.

  9. Tailoring the wetting response of silicon surfaces via fs laser structuring

    Science.gov (United States)

    Zorba, V.; Stratakis, E.; Barberoglou, M.; Spanakis, E.; Tzanetakis, P.; Fotakis, C.

    2008-12-01

    Control over the wettability of solids and manufacturing of functional surfaces with special hydrophobic and self-cleaning properties has aroused great interest because of its significance for a vast range of applications in daily life, industry and agriculture. We report here a simple method for preparing stable superhydrophobic surfaces by irradiating silicon (Si) wafers with femtosecond (fs) laser pulses and subsequently coating them with chloroalkylsilane monolayers. It is possible, by varying the laser pulse fluence on the surface, to achieve control of the wetting properties through a systematic and reproducible variation of roughness at micro- and nano-scale which mimics both the topology of the “model” superhydrophobic surface—the natural lotus leaf—, as well as its wetting response. Water droplets can move along these irradiated superhydrophobic surfaces, under the action of small gravitational forces, and experience subsequent immobilization, induced by surface tension gradients. These results demonstrate the potential of manipulating liquid motion through selective laser patterning.

  10. UV and IR laser radiation's interaction with metal film and teflon surfaces

    Science.gov (United States)

    Fedenev, A. V.; Alekseev, S. B.; Goncharenko, I. M.; Koval', N. N.; Lipatov, E. I.; Orlovskii, V. M.; Shulepov, M. A.; Tarasenko, V. F.

    2003-04-01

    The interaction of Xe ([lambda] [similar] 1.73 [mu]m) and XeCl (0.308 [mu]m) laser radiation with surfaces of metal and TiN-ceramic coatings on glass and steel substrates has been studied. Correlation between parameters of surface erosion versus laser-specific energy was investigated. Monitoring of laser-induced erosion on smooth polished surfaces was performed using optical microscopy. The correlation has been revealed between characteristic zones of thin coatings damaged by irradiation and energy distribution over the laser beam cross section allowing evaluation of defects and adhesion of coatings. The interaction of pulsed periodical CO2 ([lambda] [similar] 10.6 [mu]m), and Xe ([lambda] [similar] 1.73 [mu]m) laser radiation with surfaces of teflon (polytetrafluoroethylene—PTFE) has been studied. Monitoring of erosion track on surfaces was performed through optical microscopy. It has been shown that at pulsed periodical CO2-radiation interaction with teflon the sputtering of polymer with formation of submicron-size particles occurs. Dependencies of particle sizes, form, and sputtering velocity on laser pulse duration and target temperature have been obtained.

  11. High-efficient Nd:YAG microchip laser for optical surface scanning

    Science.gov (United States)

    Šulc, Jan; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav

    2017-12-01

    A CW operating, compact, high-power, high-efficient diode pumped 1064nm laser, based on Nd:YAG active medium, was developed for optical surface scanning and mapping applications. To enhance the output beam quality, laser stability, and compactness, a microchip configuration was used. In this arrangement the resonator mirrors were deposited directly on to the laser crystal faces. The Nd-doping concentration was 1 at.% Nd/Y. The Nd:YAG crystal was 5mm long. The laser resonator without pumping radiation recuperation was investigated {the output coupler was transparent for pumping radiation. For the generated laser radiation the output coupler reflectivity was 95%@1064 nm. The diameter of the samples was 5 mm. For the laser pumping two arrangements were investigated. Firstly, a fibre coupled laser diode operating at wavelength 808nm was used in CW mode. The 400 ¹m fiber was delivering up to 14W of pump power amplitude to the microchip laser. The maximum CW output power of 7.2W @ 1064nm in close to TEM00 beam was obtained for incident pumping power 13.7W @ 808 nm. The differential efficiency in respect to the incident pump power reached 56 %. Secondly, a single-emitter, 1W laser diode operating at 808nm was used for Nd:YAG microchip pumping. The laser pumping was directly coupled into the microchip laser using free-space lens optics. Slope efficiency up to 70% was obtained in stable, high-quality, 1064nm laser beam with CW power up to 350mW. The system was successfully used for scanning of super-Gaussian laser mirrors reflectivity profile.

  12. Femtosecond laser surface texturing of titanium as a method to reduce the adhesion of Staphylococcus aureus and biofilm formation

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, Alexandre [Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Bordeaux University, Institute of Chemistry & Biology of Membranes & Nanoobjects (CBMN UMR 5248, CNRS), European Institute of Chemistry and Biology, 2 Rue Robert Escarpit, 33607 Pessac (France); Elie, Anne-Marie [Bordeaux University, CBMN UMR 5248, CNRS, Bordeaux Science Agro, 1 Rue du G. de Gaulle, 33170 Gradignan (France); Plawinski, Laurent [Bordeaux University, Institute of Chemistry & Biology of Membranes & Nanoobjects (CBMN UMR 5248, CNRS), European Institute of Chemistry and Biology, 2 Rue Robert Escarpit, 33607 Pessac (France); Serro, Ana Paula [Instituto Superior Técnico, Universidade de Lisboa, CQE-Centro de Química Estrutural, Av. Rovisco Pais 1, 1049-001 Lisbon (Portugal); Botelho do Rego, Ana Maria [Instituto Superior Técnico, Universidade de Lisboa, CQFM-Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology - IN, Av. Rovisco Pais 1, 1049-001 Lisbon (Portugal); Almeida, Amélia [Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Urdaci, Maria C. [Bordeaux University, CBMN UMR 5248, CNRS, Bordeaux Science Agro, 1 Rue du G. de Gaulle, 33170 Gradignan (France); Durrieu, Marie-Christine [Bordeaux University, Institute of Chemistry & Biology of Membranes & Nanoobjects (CBMN UMR 5248, CNRS), European Institute of Chemistry and Biology, 2 Rue Robert Escarpit, 33607 Pessac (France); Vilar, Rui, E-mail: rui.vilar@tecnico.ulisboa.pt [Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

    2016-01-01

    Graphical abstract: - Highlights: • The short-term adhesion of Staphylococcus aureus onto femtosecond laser textured surfaces of titanium was investigated. • The laser textured surfaces consist of laser-induced periodic surface structures (LIPSS) and nanopillars. • The laser treatment enhances the hydrophilicity and the surface free energy of the material. • The laser treatment reduces significantly the adhesion of S. aureus and biofilm formation. • Femtosecond laser surface texturing of titanium is a simple and promising method for endowing dental and orthopedic implants with antibacterial properties. - Abstract: The aim of the present work was to investigate the possibility of using femtosecond laser surface texturing as a method to reduce the colonization of Grade 2 Titanium alloy surfaces by Staphylococcus aureus and the subsequent formation of biofilm. The laser treatments were carried out with a Yb:KYW chirped-pulse-regenerative amplification laser system with a central wavelength of 1030 nm and a pulse duration of 500 fs. Two types of surface textures, consisting of laser-induced periodic surface structures (LIPSS) and nanopillars, were produced. The topography, chemical composition and phase constitution of these surfaces were investigated by atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. Surface wettability was assessed by the sessile drop method using water and diiodomethane as testing liquids. The response of S. aureus put into contact with the laser treated surfaces in controlled conditions was investigated by epifluorescence microscopy and scanning electron microscopy 48 h after cell seeding. The results achieved show that the laser treatment reduces significantly the bacterial adhesion to the surface as well as biofilm formation as compared to a reference polished surfaces and suggest that femtosecond laser texturing is a simple and promising method

  13. Improve the surface of silver nanowire transparent electrode using a double-layer structure for the quantum-dot light-emitting diodes

    Science.gov (United States)

    Cho, Seok Hyeon; Been Heo, Su; Kang, Seong Jun

    2018-03-01

    We developed a double-layer structured transparent electrode for use in flexible quantum-dot light-emitting diodes (QLEDs). Silver nanowires (AgNWs) and highly conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were coated on a transparent substrate to obtain a highly conductive and flexible transparent electrode. The highly conductive PEDOT:PSS improved the surface roughness of the AgNWs transparent electrode film as well as the surface coverage area of the film. The double-layer structured transparent electrode showed superior mechanical properties than conventional indium-tin oxide (ITO) and AgNWs transparent electrodes. QLEDs with the double-layer structured transparent electrode also showed good reliability under cyclic bending conditions. These results indicate that the double-layer structured AgNWs/PEDOT:PSS transparent electrode described here is a feasible alternative to ITO transparent electrodes for flexible QLEDs.

  14. Laser surface alloying of commercially pure titanium with boron and carbon

    Science.gov (United States)

    Makuch, N.; Kulka, M.; Dziarski, P.; Przestacki, D.

    2014-06-01

    Laser surface alloying with boron and carbon was applied to produce the composite layers, reinforced by the hard ceramic phases (titanium borides and titanium carbides), on commercially pure titanium. The external cylindrical surface of substrate material was coated by paste containing boron, boron and graphite, or graphite. Then, the laser re-melting was carried out with using the continuous-wave CO2 laser. This enabled the formation of laser-borided, laser-borocarburized, and laser-carburized layers. The microstructure or the re-melted zone consisted of the hard ceramic phases (TiB+TiB2, TiB+TiB2+TiC, or TiC) located in the eutectic mixture of Tiα'-phase with borides, borides and carbides, or carbides, respectively. All the composite layers were characterized by the sufficient cohesion. The significant increase in microhardness and in wear resistance of all the laser-alloyed layers was observed in comparison with commercially pure titanium. The percentage of hard ceramic phases in more plastic eutectic mixture influenced the measured microhardness values. The dominant wear mechanism (abrasive or adhesive) depended on the method of laser alloying, and the type of test used. The wear tests for longer duration, without the change in the counter specimen, created the favourable conditions for adhesive wear, while during the shorter tests the abrasive wear dominated, as a rule.

  15. Microstructural changes due to laser surface melting of an AISI 304 stainless steel

    Directory of Open Access Journals (Sweden)

    d?Oliveira A.S.C.M.

    2001-01-01

    Full Text Available Several techniques can be used to improve surface properties. These can involve changes on the surface chemical composition (such as alloying and surface welding processes or on the surface microstructure, such as hardening and melting. In the present work surface melting with a 3kW CO2 cw laser was done to alter surface features of an AISI 304 stainless steel. Microstructure characterisation was done by optical and scanning electron microscopy. Vickers and Knoop microhardness tests evaluated mechanical features after surface melting. Phase transformation during rapid solidification is analysed and discussed.

  16. Picosecond laser micro/nano surface texturing of nickel for superhydrophobicity

    Science.gov (United States)

    Wang, X. C.; Wang, B.; Xie, H.; Zheng, H. Y.; Lam, Y. C.

    2018-03-01

    A single step direct picosecond laser texturing process was demonstrated to be able to obtain a superhydrophobic surface on a nickel substrate, a key material for mold fabrication in the manufacture of various devices, including polymeric microfluidic devices. A two-scale hierarchical surface structure of regular 2D array micro-bumps with nano-ripples was produced on a nickel surface. The laser textured surface initially showed superhydrophilicity with almost complete wetting of the structured surface just after laser treatment, then quickly changed to nearly superhydrophobic with a water contact angle (WCA) of 140° in less than 1 d, and finally became superhydrophobic with a WCA of more than 150° and a contact angle hysteresis (CAH) of less than 5°. The mechanism involved in the process is discussed in terms of surface morphology and surface chemistry. The ultra-fast laser induced NiO catalytic effect was thought to play a key role in modifying the surface chemistry so as to lower the surface energy. The developed process has the potential to improve the performance of nickel mold in the fabrication of microfluidic devices.

  17. Characterization of sputtered iridium oxide thin films on planar and laser micro-structured platinum thin film surfaces for neural stimulation applications

    Science.gov (United States)

    Thanawala, Sachin

    Electrical stimulation of neurons provides promising results for treatment of a number of diseases and for restoration of lost function. Clinical examples include retinal stimulation for treatment of blindness and cochlear implants for deafness and deep brain stimulation for treatment of Parkinsons disease. A wide variety of materials have been tested for fabrication of electrodes for neural stimulation applications, some of which are platinum and its alloys, titanium nitride, and iridium oxide. In this study iridium oxide thin films were sputtered onto laser micro-structured platinum thin films by pulsed-DC reactive sputtering of iridium metal in oxygen-containing atmosphere, to obtain high charge capacity coatings for neural stimulation applications. The micro-structuring of platinum films was achieved by a pulsed-laser-based technique (KrF excimer laser emitting at lambda=248nm). The surface morphology of the micro-structured films was studied using different surface characterization techniques. In-vitro biocompatibility of these laser micro-structured films coated with iridium oxide thin films was evaluated using cortical neurons isolated from rat embryo brain. Characterization of these laser micro-structured films coated with iridium oxide, by cyclic voltammetry and impedance spectroscopy has revealed a considerable decrease in impedance and increase in charge capacity. A comparison between amorphous and crystalline iridium oxide thin films as electrode materials indicated that amorphous iridium oxide has significantly higher charge capacity and lower impedance making it preferable material for neural stimulation application. Our biocompatibility studies show that neural cells can grow and differentiate successfully on our laser micro-structured films coated with iridium oxide. This indicates that reactively sputtered iridium oxide (SIROF) is biocompatible.

  18. Surface melting of copper by ultrashort laser pulses

    NARCIS (Netherlands)

    Vincenc Obona, J.; Ocelik, V.; De Hosson, J.T.M; Skolski, J.Z.P.; Mitko, S.; Mitko, V.S.; Römer, Gerardus Richardus, Bernardus, Engelina; Huis in 't Veld, Bert; De Hosson, J.T.M; Brebbia, C.A

    2011-01-01

    The main advantage of ultrashort laser pulses in manufacturing technology is their very high removal rate of material and high quality of microstructures with the smallest dimensions at 1 μm level. The accuracy is mainly due to almost absence of thermal diffusion into bulk material. In this paper we

  19. Melting of copper surface by ultrashort laser pulses

    NARCIS (Netherlands)

    Oboňa, J.V.; Ocelík, V.; Hosson, J.T.M. de; Skolski, J.Z.P.; Mitko, V.S.; Römer, G.R.B.E.; Huis in 't Veld, A.J.

    2011-01-01

    The main advantage of ultrashort laser pulses in manufacturing technology is their very high removal rate of material and high quality of microstructures with the smallest dimensions at 1 μm level. The accuracy is mainly due to an almost absence of thermal diffusion into bulk material. In this paper

  20. Surface melting of copper by ultrashort laser pulses

    NARCIS (Netherlands)

    Oboňa, J.V.; Ocelík, V.; De Hosson, J.T.M.; Skolski, J.Z.P.; Mitko, V.S.; Römer, G.R.B.E.; Huis in 't Veld, A.J.

    2011-01-01

    The main advantage of ultrashort laser pulses in manufacturing technology is their very high removal rate of material and high quality of microstructures with the smallest dimensions at 1 μm level. The accuracy is mainly due to an almost absence of thermal diffusion into bulk material. In this paper

  1. Surface modification of Ti dental implants by Nd:YVO4 laser irradiation

    International Nuclear Information System (INIS)

    Braga, Francisco J.C.; Marques, Rodrigo F.C.; Filho, Edson de A.; Guastaldi, Antonio C.

    2007-01-01

    Surface modifications have been applied in endosteal bone devices in order to improve the osseointegration through direct contact between neoformed bone and the implant without an intervening soft tissue layer. Surface characteristics of titanium implants have been modified by addictive methods, such as metallic titanium, titanium oxide and hydroxyapatite powder plasma spray, as well as by subtractive methods, such as acid etching, acid etching associated with sandblasting by either AlO 2 or TiO 2 , and recently by laser ablation. Surface modification for dental and medical implants can be obtained by using laser irradiation technique where its parameters like repetition rate, pulse energy, scanning speed and fluency must be taken into accounting to the appropriate surface topography. Surfaces of commercially pure Ti (cpTi) were modified by laser Nd:YVO 4 in nine different parameters configurations, all under normal atmosphere. The samples were characterized by SEM and XRD refined by Rietveld method. The crystalline phases αTi, βTi, Ti 6 O, Ti 3 O and TiO were formed by the melting and fast cooling processes during irradiation. The resulting phases on the irradiated surface were correlated with the laser beam parameters. The aim of the present work was to control titanium oxides formations in order to improve implants osseointegration by using a laser irradiation technique which is of great importance to biomaterial devices due to being a clean and reproducible process

  2. Surface modification of Ti dental implants by Nd:YVO 4 laser irradiation

    Science.gov (United States)

    Braga, Francisco J. C.; Marques, Rodrigo F. C.; Filho, Edson de A.; Guastaldi, Antonio C.

    2007-09-01

    Surface modifications have been applied in endosteal bone devices in order to improve the osseointegration through direct contact between neoformed bone and the implant without an intervening soft tissue layer. Surface characteristics of titanium implants have been modified by addictive methods, such as metallic titanium, titanium oxide and hydroxyapatite powder plasma spray, as well as by subtractive methods, such as acid etching, acid etching associated with sandblasting by either AlO 2 or TiO 2, and recently by laser ablation. Surface modification for dental and medical implants can be obtained by using laser irradiation technique where its parameters like repetition rate, pulse energy, scanning speed and fluency must be taken into accounting to the appropriate surface topography. Surfaces of commercially pure Ti (cpTi) were modified by laser Nd:YVO 4 in nine different parameters configurations, all under normal atmosphere. The samples were characterized by SEM and XRD refined by Rietveld method. The crystalline phases αTi, βTi, Ti 6O, Ti 3O and TiO were formed by the melting and fast cooling processes during irradiation. The resulting phases on the irradiated surface were correlated with the laser beam parameters. The aim of the present work was to control titanium oxides formations in order to improve implants osseointegration by using a laser irradiation technique which is of great importance to biomaterial devices due to being a clean and reproducible process.

  3. Surface modification of Ti dental implants by Nd:YVO{sub 4} laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Braga, Francisco J.C. [Materials Science and Technology Center, Institute of Energetic and Nuclear Research, Box 11049 (05422-970), Sao Paulo (Brazil); Marques, Rodrigo F.C. [Magnetic Materials and Colloid Group, Institute of Chemistry, Sao Paulo State University, Box 355, Araraquara (Brazil); Filho, Edson de A. [Biomaterials Group, Institute of Chemistry, Sao Paulo State University, Box 355, Araraquara (Brazil); Guastaldi, Antonio C. [Biomaterials Group, Institute of Chemistry, Sao Paulo State University, Box 355, Araraquara (Brazil)], E-mail: guastald@iq.unesp.br

    2007-09-30

    Surface modifications have been applied in endosteal bone devices in order to improve the osseointegration through direct contact between neoformed bone and the implant without an intervening soft tissue layer. Surface characteristics of titanium implants have been modified by addictive methods, such as metallic titanium, titanium oxide and hydroxyapatite powder plasma spray, as well as by subtractive methods, such as acid etching, acid etching associated with sandblasting by either AlO{sub 2} or TiO{sub 2}, and recently by laser ablation. Surface modification for dental and medical implants can be obtained by using laser irradiation technique where its parameters like repetition rate, pulse energy, scanning speed and fluency must be taken into accounting to the appropriate surface topography. Surfaces of commercially pure Ti (cpTi) were modified by laser Nd:YVO{sub 4} in nine different parameters configurations, all under normal atmosphere. The samples were characterized by SEM and XRD refined by Rietveld method. The crystalline phases {alpha}Ti, {beta}Ti, Ti{sub 6}O, Ti{sub 3}O and TiO were formed by the melting and fast cooling processes during irradiation. The resulting phases on the irradiated surface were correlated with the laser beam parameters. The aim of the present work was to control titanium oxides formations in order to improve implants osseointegration by using a laser irradiation technique which is of great importance to biomaterial devices due to being a clean and reproducible process.

  4. CO2 laser surface treatment of failed dental implants for re-implantation: an animal study.

    Science.gov (United States)

    Kasraei, Shahin; Torkzaban, Parviz; Shams, Bahar; Hosseinipanah, Seyed Mohammad; Farhadian, Maryam

    2016-07-01

    The aim of the present study was to evaluate the success rate of failed implants re-implanted after surface treatment with CO2 laser. Despite the widespread use of dental implants, there are many incidents of failures. It is believed that lasers can be applied to decontaminate the implant surface without damaging the implant. Ten dental implants that had failed for various reasons other than fracture or surface abrasion were subjected to CO2 laser surface treatment and randomly placed in the maxillae of dogs. Three failed implants were also placed as the negative controls after irrigation with saline solution without laser surface treatment. The stability of the implants was evaluated by the use of the Periotest values (PTVs) on the first day after surgery and at 1, 3, and 6 months post-operatively. The mean PTVs of treated implants increased at the first month interval, indicating a decrease in implant stability due to inflammation followed by healing of the tissue. At 3 and 6 months, the mean PTVs decreased compared to the 1-month interval (P laser surface debridement is associated with a high success rate in terms of implant stability.

  5. Laser Ablation Surface Preparation of Ti-6A1-4V for Adhesive Bonding

    Science.gov (United States)

    Palmieri, Frank L.; Watson, Kent A.; Morales, Guillermo; Williams, Thomas; Hicks, Robert; Wohl, Christopher J.; Hopkins, John W.; Connell, John W.

    2012-01-01

    Adhesive bonding offers many advantages over mechanical fastening, but requires certification before it can be incorporated in primary structures for commercial aviation without disbond-arrestment features or redundant load paths. Surface preparation is widely recognized as the key step to producing robust and predictable bonds. Laser ablation imparts both topographical and chemical changes to a surface which can lead to increased bond durability. A laser based process provides an alternative to chemical-dip, manual abrasion and grit blast treatments which are expensive, hazardous, polluting, and less precise. This report documents preliminary testing of a surface preparation technique using laser ablation as a replacement for the chemical etch and abrasive processes currently applied to Ti-6Al-4V alloy adherends. Failure mode, surface roughness, and chemical makeup were analyzed using fluorescence enhanced visualization, microscopy, and X-ray photoelectron spectroscopy, respectively. Single lap shear tests were conducted on bonded and aged specimens to observe bond strength retention and failure mode. Some promising results showed increasing strength and durability of lap shear specimens as laser ablation coverage area and beam intensity increased. Chemical analyses showed trends for surface chemical species which correlated with improved bond strength and durability. Combined, these results suggest that laser ablation is a viable process for inclusion with or/and replacement of one or more currently used titanium surface treatments. On-going work will focus on additional mechanical tests to further demonstrate improved bond durability.

  6. Surface modification and laser pulse length effects on internal energy transfer in DIOS.

    Science.gov (United States)

    Luo, Guanghong; Chen, Yong; Siuzdak, Gary; Vertes, Akos

    2005-12-29

    Benzyl-substituted benzylpyridinium (BP) chloride salts were used as a source of thermometer ions to probe the internal energy (IE) transfer in desorption/ionization on porous silicon (DIOS). To modify their wetting properties and the interaction energies with the thermometer ions, the DIOS surfaces were silylated to produce trimethylsilyl- (TMS), amine- (NH2), perfluoroalkyl- (PFA), and perfluorophenyl-derivatized (PFP) surfaces. Two laser sources--a nitrogen laser with pulse length of 4 ns and a mode locked 3 x omega Nd:YAG laser with a pulse length of 22 ps--were utilized to induce desorption/ionization and fragmentation at various laser fluence levels. The corresponding survival yields were determined as indicators of the IE transfer and the IE distributions were extracted. In most cases, with increasing the laser fluence in a broad range (approximately 20 mJ/cm2), no change in IE transfer was observed. For ns excitation, this was in remarkable contrast with MALDI, where increasing the laser fluence resulted in sharply (within approximately 5 mJ/cm2) declining survival yields. Derivatization of the porous silicon surface did not affect the survival yields significantly but had a discernible effect on the threshold fluence for ion production. The IE distributions determined for DIOS and MALDI from alpha-cyano-4-hydroxycinnamic acid reveal that the mean IE value is always lower for the latter. Using the ps laser, the IE distribution is always narrower for DIOS, whereas for ns laser excitation the width depends on surface modification. Most of the differences between MALDI and DIOS described here are compatible with the different dimensionality of the plume expansion and the differences in the activation energy of desorption due to surface modifications.

  7. Thermomechanical modelling of laser surface glazing for H13 tool steel

    Science.gov (United States)

    Kabir, I. R.; Yin, D.; Tamanna, N.; Naher, S.

    2018-03-01

    A two-dimensional thermomechanical finite element (FE) model of laser surface glazing (LSG) has been developed for H13 tool steel. The direct coupling technique of ANSYS 17.2 (APDL) has been utilised to solve the transient thermomechanical process. A H13 tool steel cylindrical cross-section has been modelled for laser power 200 W and 300 W at constant 0.2 mm beam width and 0.15 ms residence time. The model can predict temperature distribution, stress-strain increments in elastic and plastic region with time and space. The crack formation tendency also can be assumed by analysing the von Mises stress in the heat-concentrated zone. Isotropic and kinematic hardening models have been applied separately to predict the after-yield phenomena. At 200 W laser power, the peak surface temperature achieved is 1520 K which is below the melting point (1727 K) of H13 tool steel. For laser power 300 W, the peak surface temperature is 2523 K. Tensile residual stresses on surface have been found after cooling, which are in agreement with literature. Isotropic model shows higher residual stress that increases with laser power. Conversely, kinematic model gives lower residual stress which decreases with laser power. Therefore, both plasticity models could work in LSG for H13 tool steel.

  8. An attemp to use a pulsed CO2 laser for decontamination of radioactive metal surfaces

    Directory of Open Access Journals (Sweden)

    MILAN S. TRTICA

    2000-06-01

    Full Text Available There is a growing interest in laser radioactive decontamination of metal surfaces. It offers advantages over conventional methods: improved safety, reduction of secondary waste, reduced waste volume, acceptable cost. The main mechanism of cleaning by lasers is ablation. A pulsed TEA CO2 laser was used in this work for surface cleaning in order to show that ablation of metal surfaces is possible even at relatively low pulse energies, and to suggest that it could be competitive with other lasers because of much higher energy efficiencies. A brief theoretical analysis was made before the experiments. The laser beam was focused using a KBr-lens onto a surface contaminated with 137Cs (b-, t1/2 = 30.17 y. Three different metals were used: stainless steel, copper and aluminium. The ablated material was pumped out in an air atmosphere and transferred to a filter. The presence of activity on the filter was shown by a germanium detector-multichannel analyzer. The activity levels were measured by a GM counter. The calculated decontamination factors and collection factors showed that ablation occurs with a relatively high efficiency of decontamination. This investigation suggests that decontamination using a CO2 laser should be seriously considered.

  9. Hardness, microstructure and surface characterization of laser gas nitrided commercially pure titanium using high power CO{sub 2} laser

    Energy Technology Data Exchange (ETDEWEB)

    Selvan, J.S.; Subramanian, K. [Anna Univ., Chennai (India). Dept. of Physics; Nath, A.K. [Center for Advanced Technology, Madya Pradesh (India); Gogia, A.K. [DMRL, Hyderabad (India); Balamurugan, A.K.; Rajagopal, S. [Indira Gandhi Centre for Atomic Research, Tamil Nadu (India). Materials Science Div.

    1998-10-01

    Surface nitriding of commercially pure (CP) titanium was carried out using high power CO{sub 2} laser at pure nitrogen and dilute nitrogen (N{sub 2} + Ar) environment. The hardness, microstructure, and melt pool configuration of the laser melted titanium in helium and argon atmosphere was compared with laser melting at pure and dilute nitrogen environment. The hardness of the nitrided layer was of the order of 1000 to 1600 HV. The hardness of the laser melted titanium in the argon and helium atmosphere was 500 to 1000 HV. Using x-ray analysis of the formation of TiN and Ti{sub 2}N phase was identified in the laser nitrided titanium. The presence of nitrogen in the nitrided zone was confirmed using secondary ion mass spectroscopy (SIMS) analysis. The microstructures revealed densely populated dendrites in the sample nitrided at 100% N{sub 2} environment and thinly populated dendrites in dilute environment. The crack intensity was large in the nitrided sample at pure nitrogen, and few cracks were observed in the 50% N{sub 2} + 50% Ar environment.

  10. Strengthening of the nuclear valve sealing surface by laser cladding technology

    International Nuclear Information System (INIS)

    Shi Shihong; Huang Guodong

    1998-07-01

    A 5 kW laser with CO 2 flow transverse for cladding Co-base alloy or Ni-base alloy coat on the austenite matrix of the nuclear valve sealing surface is introduced. The results show that, after the sealing surface of valve is processed by the laser cladding, the coat of 3.0 mm thick can be made with smooth surface. The test and comparison analysis indicate that the structure and all performance have obvious advantages over that of the plasma spurt welding, bead welding and flame welding processing

  11. Nondestructive detection pesticide residue on navel orange surface using laser image

    Science.gov (United States)

    Yao, Mingyin; Liu, Muhua; Yao, Lintao

    2009-07-01

    To detect pesticide residue on navel orange surface by nondestructive means, five group oranges sprayed water, fenvalerate, isocarbophos, fenpropathrin, carbendazim pesticides respectively were chosen as experimental samples. Laser imaging system was built for acquiring images of fruits. Unitary nonlinear regression function was fitted by analyzing gray histogram curves of images within 12-40 range. The coefficient or eigenvalue of functions was different about every navel orange. The threshold coefficient was confirmed by data processing, which can establish fruits surface sprayed pesticide or not. The result showed that laser imaging technique is feasible for detecting pesticide residue on navel orange surface.

  12. Pulsed CO2 laser interaction with a metal surface at oblique incidence

    Science.gov (United States)

    McKay, J. A.; Schriempf, J. T.; Cronburg, T. L.; Eninger, J. E.; Woodroffe, J. A.

    1980-01-01

    Thermal fluence deposition and surface pressure generation produced by a CO2 laser pulse have been measured as a function of angle of incidence theta on sheet aluminum in air. The paper finds that air plasma ignition depends on the laser beam intensity I sub 0 only, not on the surface-normal flux (I sub 0)(cos theta). Conversely, the fluence deposition and surface pressure depend only on the product (I sub 0)(cos theta), and obey the square-root and two-thirds-power dependences observed with simple I sub 0 variation at normal incidence.

  13. Precise surface modification of polymethyl-methacrylate with near-infrared femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Caballero-Lucas, F.; Florian, C.; Fernández-Pradas, J.M., E-mail: jmfernandez@ub.edu; Morenza, J.L.; Serra, P.

    2015-05-01

    Highlights: • Ablation of lines in PMMA with femtosecond laser pulses. • z-Scan transmittance study for controlling the sample surface position in the laser beam waist. • Bulk material modifications appear below lines if beam waist is inside the sample. • Extended range of few microns for placing the sample and getting similar ablation features. - Abstract: The fabrication of lines at the surface of polymethyl-methacrylate (PMMA) was studied. A femtosecond laser with pulse duration of 450 fs and wavelength of 1027 nm was used. The z-scan method was employed as a focusing procedure to control the sample position with respect to the beam waist through transmittance measurements. This allowed the production of continuous lines with a length of 2 mm on the surface of the PMMA sample. The variation of the lines profiles and dimensions was studied for different values of the sample position with reference to the beam waist. Also effects on the lines fabricated at different values of incident energy and separation on the sample surface between consecutive impinging laser pulses were investigated. A range of positions where lines with similar features and sizes were produced was obtained. Submicrometric surface modifications were achieved as surface swelling in form of successive bumps. After inspecting the sample cross section, it was observed that depending on the relative position of the beam waist regarding the sample surface, inner modifications appear under the modified material surface.

  14. Study of plasma formation in CW CO2 laser beam-metal surface interaction

    Science.gov (United States)

    Azharonok, V. V.; Vasilchenko, Zh V.; Golubev, Vladimir S.; Gresev, A. N.; Zabelin, Alexandre M.; Chubrik, N. I.; Shimanovich, V. D.

    1994-04-01

    An interaction of the cw CO2 laser beam and a moving metal surface has been studied. The pulsed and thermodynamical parameters of the surface plasma were investigated by optical and spectroscopical methods. The subsonic radiation wave propagation in the erosion plasma torch has been studied.

  15. Evaluation of light-emitting diode (LED-660 nm) application over primary osteoblast-like cells on titanium surfaces: an in vitro study.

    Science.gov (United States)

    Cankaya, Abdulkadir Burak; Erdem, Mehmet Ali; Erdem, Arzu Pınar; Erguven, Mine; Aybar, Buket; Kasapoglu, Cetin; Bilir, Ayhan

    2011-01-01

    The goal of this study was to evaluate the behavior of neonatal rat calvarial osteoblast-like cells cultured on different implant surfaces and exposed once or three times to a 660-nm light-emitting diode (LED). An LED with a 660-nm wavelength was applied once or three times to cultured cells on standard and modified sandblasted acid-etched surfaces (SLA and SLActive; Straumann, Basel, Switzerland). To analyze the effect of the LED on cell proliferation, numbers, and viability, cells were cultured on titanium discs, and measurements were taken after 72 h. Cell proliferation rates were assessed using a bromodeoxyuridine immunohistochemical technique. Cell morphologies were evaluated by scanning electron microscopy (SEM). Osteoblast-like cells proliferated on all tested surfaces, with differences among groups in cell counts and DNA synthesis values. The application of one LED treatment caused a significant increase in cell count in the SLActive group in comparison with the SLA group (p = 0.001), whereas the application of three LED treatments caused a significant decrease in cell count in the SLA group compared with the SLActive group (p LED. One LED application in the SLActive group resulted in significantly increased cell numbers. However, these findings were not exactly compatible with the SEM findings, which demonstrated fewer cells and weak attachments between cells and to the surface. Thus, further studies using different LED application times are needed to clarify the reason for the increased number of cells that are apparently incapable of attaching to the titanium surfaces after 72 h.

  16. Surface characterisation and functionalisation of indium tin oxide anodes for improvement of charge injection in organic light emitting diodes

    International Nuclear Information System (INIS)

    Davenas, J.; Besbes, S.; Abderrahmen, A.; Jaffrezic, N.; Ben Ouada, H.

    2008-01-01

    Wettability studies have been performed to probe the surface properties of ITO substrates, aimed to be used as hole injecting electrode in OLEDs. The elimination of organic contaminants upon the cleaning treatment (ultrasonic bath in organic solvents) leads to an increase of the free energy of the ITO surface becoming hydrophilic. The surface energy components calculated from the Van Oss model show the appearance of a basic component upon the cleaning treatment. A thermal treatment at 100 deg. C for 3 h leads to a decrease of the surface free energy due to surface dehydration. These properties are attributed to the hydroxides formed at the ITO surface inducing improved adhesion at the ITO/polymer interface. The ITO surfaces have been functionalised with a chloroethylphosphonic acid mono-layer to increase their stability. The appearance of an acid-base component leads to a dipolar character of the ITO surface. The formation of a compact layer of a spin coated poly(phenylenevinylene) derivative induces the shielding of the ITO basic character. The weakening of the near infrared absorption associated to ITO free carriers confirms the formation of a dipole layer at the interface with the molecular layer in contact with ITO. Improved injection properties, shown by the current/voltage characteristics, result from the interface modifications

  17. Method using laser irradiation for the production of atomically clean crystalline silicon and germanium surfaces

    Science.gov (United States)

    Ownby, Gary W.; White, Clark W.; Zehner, David M.

    1981-01-01

    This invention relates to a new method for removing surface impurities from crystalline silicon or germanium articles, such as off-the-shelf p- or n-type wafers to be doped for use as junction devices. The principal contaminants on such wafers are oxygen and carbon. The new method comprises laser-irradiating the contaminated surface in a non-reactive atmosphere, using one or more of Q-switched laser pulses whose parameters are selected to effect melting of the surface without substantial vaporization thereof. In a typical application, a plurality of pulses is used to convert a surface region of an off-the-shelf silicon wafer to an automatically clean region. This can be accomplished in a system at a pressure below 10.sup.-8 Torr, using Q-switched ruby-laser pulses having an energy density in the range of from about 60 to 190 MW/cm.sup.2.

  18. Femtosecond laser-induced periodic nanostructure creation on PET surface for controlling of cell spreading

    Science.gov (United States)

    Sato, Yuji; Tsukamoto, Masahiro; Shinonaga, Togo; Kawa, Takuya

    2016-03-01

    A new method of periodic nanostructure formation on a polyethylene terephthalate (PET) surface has been developed, employing a femtosecond laser with a wavelength of 1045 nm. To generate structured films, the PET was placed in contact with a silicon (Si) wafer, followed by irradiation with the laser focused on the Si wafer, passing through the PET film. In order to evaluate the surface morphology, atomic force microscopy analysis was conducted on both treated and untreated PET surfaces. From the results, nanostructures with a period of 600 nm and height of 100 nm were formed on the PET film surface by laser treatment. A cell cultivation test was carried out on PET films with and without periodic nanostructures, showing that for nanostructured films, the cells (MG-63) were spread along the periodic grooves; in contrast, random cell spreading was observed for cultures grown on the untreated PET film.

  19. Surface profiling of lithium with a laser-desorption mass-spectrometer microprobe

    International Nuclear Information System (INIS)

    Bickel, G.A.; Adams, H.M.

    1999-01-01

    A laser-desorption mass-spectrometer microprobe has been developed to profile Li distributions on the crevice surfaces of Cr-plated rolled-joint hubs. A single laser pulse is used to desorb and ionize the surface species followed by detection of Li + in a time-of-flight mass spectrometer. Images of the surface Li distribution are obtained with are solution of <10 μm. These images are directly compared with Li images from the more conventional secondary ion mass spectrometry technique and evaluated with respect to surface topographical features measured by secondary electron microscopy and atomic force microscopy. The laser-desorption images are shown to provide the same qualitative information as that available from secondary ion mass spectrometry. (author)

  20. Enhancement of the Laser Transmission Weldability between Polyethylene and Polyoxymethylene by Plasma Surface Treatment

    Directory of Open Access Journals (Sweden)

    Huixia Liu

    2017-12-01

    Full Text Available Due to their large compatibility difference, polyethylene (PE and polyoxymethylene (POM cannot be welded together by laser transmission welding. In this study, PE and POM are pretreated using plasma that significantly enhances their laser transmission welding strength. To understand the mechanism underlying the laser welding strength enhancement, surface modification is analyzed using contact angle measurements, atomic force microscopy (AFM, optical microscopy, and X-ray photoelectron spectroscopy (XPS. Characterization results show that the plasma surface treatment improves the surface free energy, significantly enhancing the wettability of the materials. The increase in surface roughness and the generation of homogeneous bubbles contribute to the formation of mechanical micro-interlocking. The oxygen-containing groups introduced by the oxygen plasma treatment improve the compatibility of PE and POM, and facilitate the diffusion and entanglement of molecular chains and the formation of van der Waals force.