WorldWideScience

Sample records for class laser pulses

  1. Laser triggering of water switches in terrawatt-class pulse power accelerators

    International Nuclear Information System (INIS)

    Focused Beams from high-power lasers have been used to command trigger gas switches in pulse power accelerators for more than two decades. This Laboratory-Directed Research and Development project was aimed at determining whether high power lasers could also command trigger water switches on high-power accelerators. In initial work, we determined that focused light from three harmonics of a small pulsed Nd:YAG laser at 1064 nm, 532 nm, and 355 nm could be used to form breakdown arcs in water, with the lowest breakdown thresholds of 110 J/cm2 or 14 GW/cm2 at 532 nm in the green. In laboratory-scale laser triggering experiments with a 170-kV pulse-charged water switch with a 3-mm anode-cathode gap, we demonstrated that ∼90 mJ of green laser energy could trigger the gap with a 1-σ jitter of less than 2ns, a factor of 10 improvement over the jitter of the switch in its self breaking mode. In the laboratory-scale experiments we developed optical techniques utilizing polarization rotation of a probe laser beam to measure current in switch channels and electric field enhancements near streamer heads. In the final year of the project, we constructed a pulse-power facility to allow us to test laser triggering of water switches from 0.6- MV to 2.0 MV. Triggering experiments on this facility using an axicon lens for focusing the laser and a switch with a 740 kV self-break voltage produced consistent laser triggering with a ± 16-ns 1-σ jitter, a significant improvement over the ± 24-ns jitter in the self-breaking mode

  2. High-Field, μJ-Class THz Pulses from a Laser Wakefield Accelerator

    International Nuclear Information System (INIS)

    We present observation and characterization of microjoule-MV/cm-level THz pulses from a laser wakefield accelerator. THz emitted as coherent transition radiation from the plasma-vacuum boundary is collected and refocused by off-axis parabolas to a test stand where a suite of diagnostics is performed, including energy measurement by a Golay cell and electro-optic sampling of the spatio-temporal electric field using a probe pulse split from the main laser. Frequency Domain Holography is also implemented for the first time to capture spatio-temporal field distributions in a single shot. The four techniques strongly corroborate detection of THz pulses of ∼0.4 ps duration, with peak fields of several hundred kV/cm and energies of 5-10 μJ. The advantages and disadvantages of each technique are discussed.

  3. Joule-class 940-nm diode laser bars for millisecond pulse applications

    Czech Academy of Sciences Publication Activity Database

    Crump, P.; Frevert, C.; Ginolas, A.; Knigge, S.; Maassdorf, A.; Lotz, J.; Fassbender, W.; Neukum, J.; Körner, J.; Töpfer, T.; Pranovich, Alina; Divoký, Martin; Lucianetti, Antonio; Mocek, Tomáš; Ertel, K.; De Vido, M.; Erbert, G.; Traenkle, G.

    2015-01-01

    Roč. 27, č. 15 (2015), s. 1663-1666. ISSN 1041-1135 R&D Projects: GA MŠk EE2.3.20.0143; GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.30.0057 Grant ostatní: OP VK 6(XE) CZ.1.07/2.3.00/20.0143; HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 4 POSTDOK(XE) CZ.1.07/2.3.00/30.0057 Institutional support: RVO:68378271 Keywords : semiconductor laser arrays * power conversion * pulse power systems * pumps * YAG lasers * cryogenics Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.110, year: 2014

  4. Development of high damage threshold optics for petawatt-class short-pulse lasers

    Science.gov (United States)

    Stuart, Brent C.; Perry, Michael D.; Boyd, Robert D.; Britten, Jerald A.; Shore, Bruce W.; Feit, Michael D.; Rubenchik, Alexander M.

    1995-04-01

    We report laser-induced damage threshold measurements on pure and multilayer dielectrics and gold-coated optics at 1053 and 526 nm for pulse durations, (tau) , ranging from 140 fs to 1 ns. Damage thresholds of gold coatings are limited to 500 mJ/cm2 in the subpicosecond range from 1053-nm pulses. In dielectrics, qualitative differences in the morphology of damage and a departure from the diffusion-dominated (tau) 1/2 scaling indicate that damage results from plasma formation and ablation for (tau) EQ 10 ps and from conventional melting and boiling for (tau) > 50 ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in quantitative agreement with both the pulsewidth and wavelength scaling of experimental results.

  5. Pulsed laser machining apparatus

    International Nuclear Information System (INIS)

    Apparatus and method for directing a controlled number of laser pulses onto a work piece to be machined. More specifically, the laser machining apparatus includes an excitable laser and an excitation lamp for continuously exciting the laser to emit a sequence of laser pulses. The application of the laser pulses to the work piece is controlled by an inner-cavity shutter that is opened to permit a precise number of pulses to be directed onto the work piece. The frequency (REP RATE) and pulse width of the laser pulses are controlled by the excitation lamp and, in turn, are set to create a progressive weld of significant depth and structural integrity. In particular there is provided control means for counting the number of laser pulses applied to a machining site of the work piece, whereby a known controllable quantity of energy is imparted to each site. To this end, the counting of the laser pulses begins after the completion of a laser pulse, whereby the actuation of the inner-cavity shutter is not synchronized to the computer but rather to the laser emission so that only whole laser pulses will be applied to the site

  6. 12  mJ kW-class ultrafast fiber laser system using multidimensional coherent pulse addition.

    Science.gov (United States)

    Kienel, Marco; Müller, Michael; Klenke, Arno; Limpert, Jens; Tünnermann, Andreas

    2016-07-15

    An ultrafast fiber-chirped-pulse amplification system using a combination of spatial and temporal coherent pulse combination is presented. By distributing the amplification among eight amplifier channels and four pulse replicas, up to 12 mJ pulse energy with 700 W average power and 262 fs pulse duration have been obtained with a system efficiency of 78% and excellent beam quality. To the best of our knowledge, this is the highest energy achieved by an ultrafast fiber-based laser system to date. PMID:27420531

  7. Divided-Pulse Lasers

    OpenAIRE

    Lamb, Erin S.; Wright, Logan G.; Wise, Frank W.

    2014-01-01

    We demonstrate the use of coherent division and recombination of the pulse within an ultrafast laser cavity to manage the nonlinear phase accumulation and scale the output pulse energy. We implement the divided-pulse technique in an ytterbium-doped fiber laser and achieve 16-times scaling of the pulse energy, to generate 6 nJ and 1.4 ps solitons in single mode fiber. Potential extensions of this concept are discussed.

  8. New laser classes

    International Nuclear Information System (INIS)

    By an up-dated international standard (IEC 60825-1 + Amendment 2) on laser safety some new laser classes are introduced. The new set of laser classes consists of 1, 1M, 2, 2M, 3R, 3B, and 4. This is a result of intense discussions in the committee and was laid down in 2000, slightly adjusted 2001. The previous classes 1, 2, 3A, 3B, and 4, established since more than 25 years, are partly abandoned. This paper compares the new classes to the old ones. (orig.)

  9. Excimer Laser Pulse Compress With Pulse Feedback

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>To attain a shorter laser pulse, a compressing technique called pulse feedback was developed from the saturation gain switch applied to the amplification in a discharge pumping excimer laser cavity. It can

  10. Classical Dynamics of Free Electromagnetic Laser Pulses

    OpenAIRE

    Goto, S; Tucker, R. W.; Walton, T. J.

    2015-01-01

    We discuss a class of exact finite energy solutions to the vacuum source-free Maxwell field equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged test particles. These solutions are classified in terms of their chiral content based on their influence on particular charge configurations in space. Such solutions offer a computationally efficient parameterization of compact laser pulses used in laser-matter simulations and provide a poten...

  11. Pulsed inductive HF laser

    Science.gov (United States)

    Razhev, A. M.; Churkin, D. S.; Kargapol'tsev, E. S.; Demchuk, S. V.

    2016-03-01

    We report the results of experimentally investigated dependences of temporal, spectral and spatial characteristics of an inductive HF-laser generation on the pump conditions. Gas mixtures H2 – F2(NF3 or SF66) and He(Ne) – H2 – F2(NF3 or SF6) were used as active media. The FWHM pulse duration reached 0.42 μs. This value corresponded to a pulsed power of 45 kW. For the first time, the emission spectrum of an inductive HF laser was investigated, which consisted of seven groups of bands with centres around the wavelengths of 2732, 2736, 2739, 2835, 2837, 2893 and 2913 nm. The cross section profile of the laser beam was a ring with a diameter of about 20 mm and width of about 5 mm. Parameters of laser operation in the repetitively pulsed regime were sufficiently stable. The amplitude instability of light pulses was no greater than 5% – 6%.

  12. The Dynamics of Compact Laser Pulses

    OpenAIRE

    Goto, S; Tucker, Robin William; Walton, T. J.

    2015-01-01

    We discuss the use of a class of exact finite energy solutions to the vacuum source-free Maxwell equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged point particles. These compact solutions are classified in terms of their chiral content and their influence on particular charge configurations in space. The results of such classical interactions motivate a phenomenological quantum description of a propagating laser pulse in a medium i...

  13. The dynamics of compact laser pulses

    Science.gov (United States)

    Goto, S.; Tucker, R. W.; Walton, T. J.

    2016-07-01

    We discuss the use of a class of exact finite energy solutions to the vacuum source-free Maxwell equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged point particles. These compact solutions are classified in terms of their chiral content and their influence on particular charge configurations in space. The results of such classical interactions motivate a phenomenological quantum description of a propagating laser pulse in a medium in terms of an effective quantum Hamiltonian.

  14. Pulsed laser microtomograph

    Science.gov (United States)

    Antonov, V. B.; Bonch-Bruevich, A. M.; Vasil'Ev, V. I.; Ionov, L. N.; Nikolaev, S. D.; Starobogatov, I. O.

    1994-12-01

    This paper describes a pulsed laser tomographic apparatus that has been implemented in practice and has a spatial resolution of 2-5 microns in the transverse direction and approximately 70 microns in the probe-radiation propagation direction. Experiments have been performed with model objects. Results have been obtained that confirm the possibility of early diagnosis of skin mycoses that cannot be diagnosed by existing methods.

  15. Classical Dynamics of Free Electromagnetic Laser Pulses

    CERN Document Server

    Goto, S; Walton, T J

    2015-01-01

    We discuss a class of exact finite energy solutions to the vacuum source-free Maxwell field equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged test particles. These solutions are classified in terms of their chiral content based on their influence on particular charge configurations in space. Such solutions offer a computationally efficient parameterization of compact laser pulses used in laser-matter simulations and provide a potential means for experimentally bounding the fundamental length scale in the generalized electrodynamics of Bopp, Lande and Podolsky.

  16. Ultrashort pulsed laser technology development program

    Science.gov (United States)

    Manke, Gerald C.

    2014-10-01

    The Department of Navy has been pursuing a technology development program for advanced, all-fiber, Ultra Short Pulsed Laser (USPL) systems via Small Business Innovative Research (SBIR) programs. Multiple topics have been published to promote and fund research that encompasses every critical component of a standard USPL system and enable the demonstration of mJ/pulse class systems with an all fiber architecture. This presentation will summarize published topics and funded programs.

  17. High-power pulsed lasers

    International Nuclear Information System (INIS)

    The ideas that led to the successful construction and operation of large multibeam fusion lasers at the Lawrence Livermore Laboratory are reviewed. These lasers are based on the use of Nd:glass laser materials. However, most of the concepts are applicable to any laser being designed for fusion experimentation. This report is a summary of lectures given by the author at the 20th Scottish University Summer School in Physics, on Laser Plasma Interaction. This report includes basic concepts of the laser plasma system, a discussion of lasers that are useful for short-pulse, high-power operation, laser design constraints, optical diagnostics, and system organization

  18. Laser system using ultra-short laser pulses

    Science.gov (United States)

    Dantus, Marcos; Lozovoy, Vadim V.; Comstock, Matthew

    2009-10-27

    A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and binary pulse shaping (BPS). Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal.

  19. Optical pulses, lasers, measuring techniques

    CERN Document Server

    Früngel, Frank B A

    1965-01-01

    High Speed Pulse Technology: Volume II: Optical Pulses - Lasers - Measuring Techniques focuses on the theoretical and engineering problems that result from the capacitor discharge technique.This book is organized into three main topics: light flash production from a capacitive energy storage; signal transmission and ranging systems by capacitor discharges and lasers; and impulse measuring technique. This text specifically discusses the air spark under atmospheric conditions, industrial equipment for laser flashing, and claims for light transmitting system. The application of light impulse sign

  20. Pulse-Width Jitter Measurement for Laser Diode Pulses

    Institute of Scientific and Technical Information of China (English)

    TANG Jun-Hua; WANG Yun-Cai

    2006-01-01

    @@ Theoretical analysis and experimental measurement of pulse-width jitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is deduced.

  1. Extended propagation of powerful laser pulses in focusing Kerr media

    CERN Document Server

    Malkin, V M

    2016-01-01

    Powerful incoherent laser pulses can propagate in focusing Kerr media much longer distances than can coherent pulses, due to the fast phase mixing that prevents transverse filamentation. This distance is limited by 4-wave scattering, which accumulates waves at small transverse wavenumbers, where phase mixing is too slow to retain the incoherence and thus prevent the filamentation. However, we identify how this theoretical limit can be overcome by countering this accumulation through transverse heating of the pulse by random fluctuations of the refractive index. In these new regimes, the laser pulse propagation distances are significantly extended, making feasible a new class of random lasers, in particular, ultra-powerful random lasers in plasmas.

  2. A method of laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Ragul' skii, V.V.; Nosach, O.U.

    1981-07-08

    A method is proposed for shaping a laser pulse by using its nonlinear interaction with the medium. In order to increase the contrast of the emission pulse over a wide spectrum range without brightness loss, the emission pulse is subjected to induced scattering in the transparent medium, while preserving the solid angle of the emission; the scattered emission is then separated from the initial emission.

  3. Pulsed laser irradiation of silicon

    International Nuclear Information System (INIS)

    Pulsed laser irradiation of silicon was investigated with a ruby laser, having a pulse width of 30 ns and a variable energy up to 1.5 Joules. Peak powers as high as 50 MW are obtained, which is sufficient to cause melting to depths of a few thousand angstroem. In this study, development of heat flow theory made it possible to calculate temperature profiles in silicon during pulsed laser irradiation. Silicon self-diffusion measurements, laser annealing of damage in As implanted silicon, and laser induced doping of single crystal silicon was also investigated. A computer programme was used to calculate the temperature profiles in silicon during pulsed laser irradiation. Radioactive 31Si (half-life = 2.62 hours) was used to determine for the first time the self-diffusion of silicon in silicon during pulsed laser irradiation. Radioactivity profiles in the silicon sample were measured by anodic oxidation, sequential removal of the formed SiO2 by etching in dilute HF and measurement of the radioactivity left in the sample. The removal of damage caused during ion implantation of Si substrates with As was investigated by using laser annealing. Rutherford backscattering of charged nuclear paricles coupled with the channeling technique, showed that an amorphous layer 1140 A thick formed during implantation. Complete removal of this damage only started to take place at energies high enough to cause melting to depths greater than the amorphous/single crystal interface. During resolidification, the molten silicon regrows epitaxially leading to complete removal of all the damage. Disorder removal started at 0.6 Jcm-2, while complete damage removal was achieved at energies above 1.5 Jcm-2. The doping of silicon with Sb, Bi and In by laser assisted diffusion was investigated from evaporated layers as well as solutions of these dopants

  4. High power pulsed ytterbium doped fibre lasers and their applications

    OpenAIRE

    Chen, Kang Kang

    2011-01-01

    The aim of my project is to develop pulsed Ytterbium (Yb) doped fibre master oscillator power amplifier (MOPA) systems seeded by semiconductor lasers. I was principally focused on two specific projects aligned to sponsored programs of research within the ORC pulsed fibre laser group: the first project, TSB funded project LAMPS, aimed to develop an important class of next generation laser system capable of average output powers of more than 100 W when operating in both the nanosecond and pico...

  5. Ultrashort-pulse laser machining

    Energy Technology Data Exchange (ETDEWEB)

    Banks, P S; Feit, M D; Nguyen, H T; Perry, M D; Rubenchik, A M; Sefcik, J A; Stuart, B C

    1998-09-01

    A new type of material processing is enabled with ultrashort (t < 10 ps) laser pulses. Cutting, drilling, sculpting of all materials (biologic materials, ceramics, sapphire, silicon carbide, diamond, metals) occurs by new mechanisms that eliminate thermal shock or collateral damage. High-precision machining to submicron tolerances is enabled resulting in high surface quality and negligible heat affected zone.

  6. Ultrashort-pulse lasers machining

    Energy Technology Data Exchange (ETDEWEB)

    Banks, P S; Feit, M D; Nguyen, H T; Perry, M D, Stuart, B C

    1999-01-22

    A new type of material processing is enabled with ultrashort (t < 10 psec) laser pulses. Cutting, drilling, sculpting of all materials (biologic materials, ceramics, sapphire, silicon carbide, diamond, metals) occurs by new mechanisms which eliminate thermal shock or collateral damage. High precision machining to submicron tolerances is enabled resulting in high surface quality and negligible heat affected zone.

  7. Pulse transformer for GaAs laser

    Science.gov (United States)

    Rutz, E. M.

    1976-01-01

    High-radiance gallium arsenide (GaAs) laser operating at room temperature is utilized in optical navigation system. For efficient transformer-to-laser impedance match, laser should be connected directly to pulse transformer secondary winding.

  8. High-energy, short-pulse, carbon-dioxide lasers

    International Nuclear Information System (INIS)

    Lasers for fusion application represent a special class of short-pulse generators; not only must they generate extremely short temporal pulses of high quality, but they must do this at ultra-high powers and satisfy other stringent requirements by this application. This paper presents the status of the research and development of carbon-dioxide laser systems at the Los Alamos Scientific Laboratory, vis-a-vis the fusion requirements

  9. Investigation of Laser Parameters in Silicon Pulsed Laser Conduction Welding

    Science.gov (United States)

    Shayganmanesh, Mahdi; Khoshnoud, Afsaneh

    2016-03-01

    In this paper, laser welding of silicon in conduction mode is investigated numerically. In this study, the effects of laser beam characteristics on the welding have been studied. In order to model the welding process, heat conduction equation is solved numerically and laser beam energy is considered as a boundary condition. Time depended heat conduction equation is used in our calculations to model pulsed laser welding. Thermo-physical and optical properties of the material are considered to be temperature dependent in our calculations. Effects of spatial and temporal laser beam parameters such as laser beam spot size, laser beam quality, laser beam polarization, laser incident angle, laser pulse energy, laser pulse width, pulse repetition frequency and welding speed on the welding characteristics are assessed. The results show that how the temperature dependent thermo-physical and optical parameters of the material are important in laser welding modeling. Also the results show how the parameters of the laser beam influence the welding characteristics.

  10. Pulsed laser irradiation of silicon

    International Nuclear Information System (INIS)

    Pulsed laser irradiation of silicon was investigated with a ruby laser. Development of heat flow theory made it possible to calculate temperature profiles in silicon during pulsed laser irradiation. Silicon self-diffusion measurements, laser annealing of damage in As implanted silicon, and laser induced doping of single crystal silicon was investigated. A computer programme was writen based on the numerical solution, and was used to calculate the temperature profiles in silicon during irradiation. Radioactive 31Si was used to determine the self-diffusion of silicon in silicon during irradiation. Radioactivity profiles in the silicon sample were measured by anodic oxidation, sequential removal of the formed SiO2 by etching in dilute HF and measurement of the radioactivity left in the sample. Spreading of the radioactive silicon marker started to take place at energy densities above 0.8 Jcm-2, giving an average duffusion coefficient of (5.0 ± 2.7) x 10-8 m2s-1, which is of the order of magnitude expected when melting takes place. The doping of silicon with Sb, Bi and In by laser assisted diffusion was investegated from evaporated layers as well as solutions of these dopants. The threshold energies for doping was 0.6, 0.9 and 0.7 Jcm-2, while maximum dopant concentrations of 2 x 1021, 7 x 1020 and 4 x 1020 respectively was found for Sb, Bi and In. These values exceed the equilibrium solid solubility by orders of magnitude, and can be ascribed to trapping of the dopant atoms, due to the high recrystallization velocities involved. Doping was carried out by placing silicon substrates directly into solutions of SbCl3 and triphenyl antimony. The threshold of solution doping was found to be much greater than doping from evaporated layer. This difference could be ascribed to the much larger absorption coefficient of the laser light in the evaporated layers, as compared to single crystal silicon

  11. Pulse propagation in the laser wakefield accelerator

    International Nuclear Information System (INIS)

    A high-density regime of the laser wakefield accelerator is reviewed in which enhanced acceleration is achieved via resonant self-modulation of the laser pulse. This requires laser power in excess of the critical power for optical guiding and a plasma wavelength short compared to the laser pulse-length. The evolution of the laser pulse is described, including a discussion of self-modulation and laser-hose instabilities. Examples of self-modulated laser wakefield accelerators are presented. copyright 1996 American Institute of Physics

  12. Ultrashort Laser Pulses in Biology and Medicine

    CERN Document Server

    Braun, Markus; Zinth, Wolfgang

    2008-01-01

    Sources of ultrashort laser pulses are nowadays commercially available and have entered many areas of research and development. This book gives an overview of biological and medical applications of these laser pulses. The briefness of these laser pulses permits the tracing of the fastest processes in photo-active bio-systems, which is one focus of the book. The other focus is applications that rely on the high peak intensity of ultrashort laser pulses. Examples covered span non-linear imaging techniques, optical tomography, and laser surgery.

  13. A model for the dissociation pulse, afterglow, and laser pulse in the Cu/CuCl double pulse laser

    OpenAIRE

    Kushner, M J; Culick, F. E. C.

    1980-01-01

    A model which completely describes the Cu/CuCl double pulse laser is presented. The dissociation discharge pulse and afterglow are simulated and the results are used as initial conditions for an analysis of the pumping discharge pulse and laser pulse. Experimental behavior including the minimum, optimum, and maximum delays between pulses, and the dependence of laser pulse energy on dissociation energy are satisfactorily reproduced. An optimum tube temperature is calculated, and the dependence...

  14. A model for the dissociation pulse, afterglow, and laser pulse in the Cu/CuCI double pulse laser

    OpenAIRE

    Kushner, M J; Culick, F. E. C.

    1980-01-01

    A model which completely describes the Cu/CuCI double pulse laser is presented. The dissociation discharge pulse and afterglow are simulated and the results are used as initial conditions for an analysis of the pumping discharge pulse and laser pulse. Experimental behavior including the minimum, optimum, and maximum delays between pulses, and the dependence of laser pulse energy on dissociation energy are satisfactorily reproduced. An optimum tube temperature is calculated, and the depende...

  15. Simple measurement of picosecond laser pulses in a wavelength range above 1μm

    Czech Academy of Sciences Publication Activity Database

    Smrž, Martin; Miura, Taisuke; Straka, Petr; Endo, Akira; Mocek, Tomáš

    Bellingham: SPIE, 2013 - (Hein, J.; Korn, G.; Silva, L.), s. 878013. (Proceedings of SPIE. 8780). ISBN 978-0-8194-9582-2. ISSN 0277-786X. [High-Power, High-Energy, and High-Intensity Laser Technology; and Research Using Extreme Light - Entering New Frontiers with Petawatt-Class Lasers. Praha (CZ), 15.04.2013-17.04.2013] Institutional support: RVO:68378271 Keywords : pulse measurement * pulse retrieval * picosecond pulses * retrieval algorithm * pulse stretcher Subject RIV: BH - Optics, Masers, Lasers

  16. Pulse shaping on the Nova laser system

    International Nuclear Information System (INIS)

    Inertial confinement fusion requires temporally shaped pulses to achieve high gain efficiency. Recently, we demonstrated the ability to produce complex temporal pulse shapes at high power at 0.35 microns on the Nova laser system. 2 refs., 2 figs

  17. Ion Acceleration by Short Chirped Laser Pulses

    CERN Document Server

    Li, Jian-Xing; Keitel, Christoph H; Harman, Zoltán

    2015-01-01

    Direct laser acceleration of ions by short frequency-chirped laser pulses is investigated theoretically. We demonstrate that intense beams of ions with a kinetic energy broadening of about 1 % can be generated. The chirping of the laser pulse allows the particles to gain kinetic energies of hundreds of MeVs, which is required for hadron cancer therapy, from pulses of energies of the order of 100 J. It is shown that few-cycle chirped pulses can accelerate ions more efficiently than long ones, i.e. higher ion kinetic energies are reached with the same amount of total electromagnetic pulse energy.

  18. Dynamic pulsing of a MOPA fiber laser

    Science.gov (United States)

    Romero, Rosa; Guerreiro, Paulo T.; Hendow, Sami T.; Salcedo, José R.

    2011-05-01

    Dynamic Pulsing is demonstrated using a pulsed MOPA fiber laser at 1064nm. The output of the MOPA laser is a pulsed profile consisting of a burst of closely spaced pulses. Tests were performed under several materials with pulse bursts ranging from 10ns to 1μs and operating from 500kHz down to single shot. In particular, percussion drilling in stainless steel is demonstrated showing improvements in quality and speed of the process. These profiles allow high flexibility and optimization of the process addressing the specificity of the end application. Dynamic Pulsing allows the same MOPA fiber laser to be used in diverse materials as well as different processes such us marking, drilling, scribing and engraving. The pulsed fiber laser used in this study is a MOPA-DY by Multiwave Photonics. It is based on a modulated seed laser followed by a series of fiber amplifiers and ending with an optically isolated collimator. This pulsed laser model has an output in such a way that each trigger produces a fast burst of pulses, with a repetition frequency within the burst of the order of tens of MHz. Within the burst it is possible to change the number of pulses, the individual pulse profile, burst pulse period and even to generate non-periodic burst pulse separations. The laser allows full freedom for all these combinations. The study here reported compares the impact of pulse peak power, number of pulses within a burst and the pulse burst period, on process quality (heat affected zone, debris, hole uniformity) and drilling yield.

  19. Analysis of Picosecond Pulsed Laser Melted Graphite

    Science.gov (United States)

    Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M. S.; Huang, C. Y.; Malvezzi, A. M.; Bloembergen, N.

    1986-12-01

    A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm{sup -1} and the disorder-induced mode at 1360 cm{sup -1}, the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nanosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence.

  20. Ultrashort pulse laser technology laser sources and applications

    CERN Document Server

    Schrempel, Frank; Dausinger, Friedrich

    2016-01-01

    Ultrashort laser pulses with durations in the femtosecond range up to a few picoseconds provide a unique method for precise materials processing or medical applications. Paired with the recent developments in ultrashort pulse lasers, this technology is finding its way into various application fields. The book gives a comprehensive overview of the principles and applications of ultrashort pulse lasers, especially applied to medicine and production technology. Recent advances in laser technology are discussed in detail. This covers the development of reliable and cheap low power laser sources as well as high average power ultrashort pulse lasers for large scale manufacturing. The fundamentals of laser-matter-interaction as well as processing strategies and the required system technology are discussed for these laser sources with respect to precise materials processing. Finally, different applications within medicine, measurement technology or materials processing are highlighted.

  1. Theory of laser catalysis with pulses

    CERN Document Server

    Vardi, A

    2001-01-01

    The possibility of accelerating molecular reactions by lasers has attracted considerable theoretical and experimental interest. A particular example of laser-modified reaction dynamics is laser catalysis, a process in which the tunneling through a potential barrier is enhanced by transient excitation to a bound electronic state. We have performed detailed calculations of pulsed laser catalysis on one- and two-dimensional potentials, as a function of the reactants' collision energy and the laser's central frequency. In agreement with previous CW results, the reactive lineshapes are Fano-type curves, resulting from interference between nonradiative tunneling and the optically assisted pathway. In contrast to the CW process, the power requirements of pulsed laser catalysis are well within the reach of commonly used pulsed laser sources, making an experimental realization possible. The laser catalysis scenario is shown to be equivalent in the ``dressed'' state picture, to resonant tunneling through a double-barri...

  2. One laser pulse generates two photoacoustic signals

    CERN Document Server

    Gao, Fei; Zheng, Yuanjin

    2016-01-01

    Photoacoustic sensing and imaging techniques have been studied widely to explore optical absorption contrast based on nanosecond laser illumination. In this paper, we report a long laser pulse induced dual photoacoustic (LDPA) nonlinear effect, which originates from unsatisfied stress and thermal confinements. Being different from conventional short laser pulse illumination, the proposed method utilizes a long square-profile laser pulse to induce dual photoacoustic signals. Without satisfying the stress confinement, the dual photoacoustic signals are generated following the positive and negative edges of the long laser pulse. More interestingly, the first expansion-induced photoacoustic signal exhibits positive waveform due to the initial sharp rising of temperature. On the contrary, the second contraction-induced photoacoustic signal exhibits exactly negative waveform due to the falling of temperature, as well as pulse-width-dependent, signal amplitude which is caused by the concurrent heat accumulation and ...

  3. Relativistic laser pulse compression in magnetized plasmas

    International Nuclear Information System (INIS)

    The self-compression of a weak relativistic Gaussian laser pulse propagating in a magnetized plasma is investigated. The nonlinear Schrödinger equation, which describes the laser pulse amplitude evolution, is deduced and solved numerically. The pulse compression is observed in the cases of both left- and right-hand circular polarized lasers. It is found that the compressed velocity is increased for the left-hand circular polarized laser fields, while decreased for the right-hand ones, which is reinforced as the enhancement of the external magnetic field. We find a 100 fs left-hand circular polarized laser pulse is compressed in a magnetized (1757 T) plasma medium by more than ten times. The results in this paper indicate the possibility of generating particularly intense and short pulses

  4. High Power Picosecond Laser Pulse Recirculation

    Energy Technology Data Exchange (ETDEWEB)

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P

    2010-04-12

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering based light sources. We demonstrate up to 36x average power enhancement of frequency doubled sub-millijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

  5. Ultrashort-pulse lasers and their applications

    International Nuclear Information System (INIS)

    A revolution has occurred over the past ten years in our ability to generate, manipulate, and amplify ultrashort pulses. Laser pulses can be as short as a few femtoseconds (few optical cycles) and possess extreme power up to several terawatts. The applications of these pulses are numerous in physics, chemistry, and biology, where they can be used to time resolve ultrafast events. We review in this article the state of the art in short pulse generation and amplification. (author)

  6. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    Science.gov (United States)

    Ma, Guangjin; Dallari, William; Borot, Antonin; Krausz, Ferenc; Yu, Wei; Tsakiris, George D.; Veisz, Laszlo

    2015-03-01

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ˜100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

  7. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Guangjin, E-mail: guangjin.ma@mpq.mpg.de [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Max-Planck-Institut für Quantenoptik, D-85748 Garching (Germany); Dallari, William; Borot, Antonin; Tsakiris, George D.; Veisz, Laszlo [Max-Planck-Institut für Quantenoptik, D-85748 Garching (Germany); Krausz, Ferenc [Max-Planck-Institut für Quantenoptik, D-85748 Garching (Germany); Department für Physik, Ludwig-Maximilians-Universität, D-85748 Garching (Germany); Yu, Wei [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2015-03-15

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

  8. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    International Nuclear Information System (INIS)

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach

  9. Generation of laser pulse trains for tests of multi-pulse laser wakefield acceleration

    Science.gov (United States)

    Shalloo, R. J.; Corner, L.; Arran, C.; Cowley, J.; Cheung, G.; Thornton, C.; Walczak, R.; Hooker, S. M.

    2016-09-01

    In multi-pulse laser wakefield acceleration (MP-LWFA) a plasma wave is driven by a train of low-energy laser pulses separated by the plasma period, an approach which offers a route to driving plasma accelerators with high efficiency and at high pulse repetition rates using emerging technologies such as fibre and thin-disk lasers. Whilst these laser technologies are in development, proof-of-principle tests of MP-LWFA require a pulse train to be generated from a single, high-energy ultrafast pulse. Here we demonstrate the generation of trains of up to 7 pulses with pulse separations in the range 150-170 fs from single 40 fs pulses produced by a Ti:sapphire laser.

  10. MOPA pulsed fiber laser for silicon scribing

    Science.gov (United States)

    Yang, Limei; Huang, Wei; Deng, Mengmeng; Li, Feng

    2016-06-01

    A 1064 nm master oscillator power amplifier (MOPA) pulsed fiber laser is developed with flexible control over the pulse width, repetition frequency and peak power, and it is used to investigate the dependence of mono-crystalline silicon scribe depth on the laser pulse width, scanning speed and repeat times. Experimental results indicate that long pulses with low peak powers lead to deep ablation depths. We also demonstrate that the ablation depth grows fast with the scanning repeat times at first and progressively tends to be saturated when the repeat times reach a certain level. A thermal model considering the laser pulse overlapping effect that predicts the silicon temperature variation and scribe depth is employed to verify the experimental conclusions with reasonably close agreement. These conclusions are of great benefits to the optimization of the laser material processing with high efficiency.

  11. Propagating Characteristics of Pulsed Laser in Rain

    Directory of Open Access Journals (Sweden)

    Jing Guo

    2015-01-01

    Full Text Available To understand the performance of laser ranging system under the rain weather condition, we need to know the propagating characteristics of laser pulse in rain. In this paper, the absorption and attenuation coefficients were calculated based on the scattering theories in discrete stochastic media, and the propagating characteristics of laser pulse in rain were simulated and analyzed using Monte-Carlo method. Some simulation results were verified by experiments, and the simulation results are well matched with the experimental data, with the maximal deviation not less than 7.5%. The results indicated that the propagating laser beam would be attenuated and distorted due to the scattering and absorption of raindrops, and the energy attenuation and pulse shape distortion strongly depended on the laser pulse widths.

  12. Optical quality of pulsed aerodynamic laser windows

    International Nuclear Information System (INIS)

    The feasibility of using a shock tube-generated pulsed flow field as a single-shot window for short, high-energy laser pulses is investigated, with a view to single pulse gas laser-driven, inertial confinement fusion facility application. A scribed diaphragm shock tube with glass endwalls was used to simulate the window, and a ruby laser pulse was transmitted along the tube axis after the diaphragm burst. Pressure wave field optical quality and turbulent contact interface were recorded holographically at different delay times for a variety of pressures and gas compositions in the driver and driven sections of the shock tube. Interferograms were interpreted by means of digital techniques to determine beam-quality degradations, and showed that a beam quality of 1.33, adequate for laser fusion use, was routinely obtainable at the ruby laser wavelength

  13. Pulse front tilt measurement of femtosecond laser pulses

    Science.gov (United States)

    Dimitrov, Nikolay; Stoyanov, Lyubomir; Stefanov, Ivan; Dreischuh, Alexander; Hansinger, Peter; Paulus, Gerhard G.

    2016-07-01

    In this work we report experimental investigations of an intentionally introduced pulse front tilt on femtosecond laser pulses by using an inverted field correlator/interferometer. A reliable criterion for the precision in aligning (in principle) dispersionless systems for manipulating ultrashort pulses is developed, specifically including cases when the pulse front tilt is a result of a desired spatio-temporal coupling. The results obtained using two low-dispersion diffraction gratings are in good qualitative agreement with the data from a previously developed analytical model and from an independent interferometric measurement.

  14. Characteristics of the pumping pulse and the output laser pulse for a Cu/CuCl double pulse laser

    OpenAIRE

    Kushner, M J; Culick, F. E. C.

    1980-01-01

    Characteristics of the pumping discharge pulse and laser pulse in a Cu/CuCl double pulse laser have been measured as a function of time delay, buffer gas pressure, and tube temperature. We have found that for otherwise fixed discharge conditions, pumping rates decrease as these quantities are increased. The shape of the laser pulse as a function of time delay is shown to be dependent on the rate of current rise of the pumping pulse. The length of time required by the pumping pulse to achieve ...

  15. Molecular wakes for ultrashort laser pulses

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The molecular wake-assisted interaction between two collinear femotosecond laser pulses is investigated in air,which leads to the generation of a controllable 1.8 mJ super-continuum pulse with an elongated self-guided channel due to the cross-phase modulation of the impulsively aligned diatomic molecules in air. For two parallel launched femtosecond laser pulses with a certain spatial separation,controllable attraction and repulsion of the pulses are observed due to the counter-balance among molecular wakes,Kerr and plasma effects,where the molecular wakes show a longer interaction distance than the others to control the propagation of the intense ultrashort laser pulses.

  16. Micro-ablation with high power pulsed copper vapor lasers.

    Science.gov (United States)

    Knowles, M

    2000-07-17

    Visible and UV lasers with nanosecond pulse durations, diffraction-limited beam quality and high pulse repetition rates have demonstrated micro-ablation in a wide variety of materials with sub-micron precision and sub-micron-sized heat-affected zones. The copper vapour laser (CVL) is one of the important industrial lasers for micro-ablation applications. Manufacturing applications for the CVL include orifice drilling in fuel injection components and inkjet printers, micro-milling of micromoulds, via hole drilling in printed circuit boards and silicon machining. Recent advances in higher power (100W visible, 5W UV), diffraction-limited, compact CVLs are opening new possibilities for manufacturing with this class of nanosecond laser. PMID:19404369

  17. Pulsed lasers in dentistry: sense or nonsense?

    Science.gov (United States)

    Koort, Hans J.; Frentzen, Matthias

    1991-05-01

    The great interest in the field of laser applications in dentistry provokes the question, if all these new techniques may really fulfill advantages, which are expected after initial in-vitro studies. Whereas laser surgery of soft oral tissues has been developed to a standard method, laser treatment of dental hard tissues and the bone are attended with many unsolved problems. Different laser types, especially pulsed lasers in a wide spectrum of wavelengths have been proofed for dental use. Today neither the excimer lasers, emitting in the far uv-range from 193 to 351 nm, nor the mid-infrared lasers like Nd:YAG (1,064 μm), Ho:YAG (2,1 μm) and Er:YAG (2,96 μm) or the C02-laser (10,6 μm) show mechanism of interaction more carefully and faster than a preparation of teeth with diamond drillers. The laser type with the most precise and considerate treatment effects in the moment is the short pulsed (15 ns) ArF-excimer laser with a wavelength of 193 nm. However this laser type has not yet the effectivity of mechanical instruments and it needs a mirror system to deliver the radiation. Histological results point out, that this laser shows no significant pathological alterations in the adjacent tissues. Another interesting excimer laser, filled with XeCI and emitting at a wavelength of 308 nm has the advantage to be good to deliver through quartz fibers. A little more thermal influence is to be seen according to the longer wavelength. Yet the energy density, necessary to cut dental hard tissues will not be reached with the laser systems available now. Both the pulsed Er:YAG- (2,94 μm, pulse duration 250 s) and the Ho:YAG -laser (2,1 μm, pulse duration 250 μs) have an effective coupling of the laser energy to hydrogeneous tissues, but they do not work sufficient on healthy enamel and dentine. The influence to adjacent healthy tissue is not tolerable, especially in regard of the thermal damage dentine and pulp tissues. Moreover, like the 193 nm ArF-excimer laser

  18. Short pulse laser train for laser plasma interaction experiments

    International Nuclear Information System (INIS)

    A multiframe, high-time resolution pump-probe diagnostic consisting of a consecutive train of ultrashort laser pulses (∼ps) has been developed for use with a chirped pulse amplification (CPA) system. A system of high quality windows is used to create a series of 1054 nm picosecond-laser pulses which are injected into the CPA system before the pulse stretcher and amplifiers. By adding or removing windows in the pulse train forming optics, the number of pulses can be varied. By varying the distance and thickness of the respective optical elements, the time in between the pulses, i.e., the time in between frames, can be set. In our example application, the CPA pulse train is converted to 527 nm using a KDP crystal and focused into a preformed plasma and the reflected laser light due to stimulated Raman scattering is measured. Each pulse samples different plasma conditions as the plasma evolves in time, producing more data on each laser shot than with a single short pulse probe. This novel technique could potentially be implemented to obtain multiple high-time resolution measurements of the dynamics of physical processes over hundreds of picoseconds or even nanoseconds with picosecond resolution on a single shot

  19. Survey on modern pulsed high power lasers

    International Nuclear Information System (INIS)

    The requirements to be met by lasers for particle acceleration are partially similar to those already known for fusion lasers. The power level wanted in both caes is up to 100 TW or even more. The pulse durations favourable for laser accelerators are in the range from 1 ps to 1000 ps whereas fusion lasers require several ns. The energy range for laser accelerators is thus correspondingly smaller than that for fusion lasers: 1-100 kJ versus several 100 kJ. The design criteria of lasers meeting the requirements are discussed in the following. The CO2, iodine, Nd:glass and excimer lasers are treated in detail. The high repetition rate aspect will not be particularly addressed since for the present generation of lasers the wanted rates of far above 1 Hz are completely out of scope. Moreover, for the demonstration of principle these rates are not needed. (orig./HSI)

  20. Bringing Pulsed Laser Welding into Production

    DEFF Research Database (Denmark)

    Olsen, Flemmming Ove

    1996-01-01

    In this paper, some research and develop-ment activities within pulsed laser welding technology at the Tech-nical University of Denmark will be described. The laser group at the Insti-tute for Manufacturing Technology has nearly 20 years of experience in laser materials process-ing. Inter......-nationally the group is mostly known for its contri-butions to the development of the laser cutting process, but further it has been active within laser welding, both in assisting industry in bringing laser welding into production in several cases and in performing fundamental R & D. In this paper some research...... activities concerning the weldability of high alloyed austenitic stainless steels for mass production industry applying industrial lasers for fine welding will be described. Studies on hot cracking sensitivity of high alloyed austenitic stainless steel applying both ND-YAG-lasers and CO2-lasers has been...

  1. Stretched pulse Yb3+:silica fibre laser

    OpenAIRE

    Cautaerts, V.; Richardson, D.J.; Paschotta, R.; Hanna, D.C.

    1997-01-01

    We report what we believe to be the first results on short-pulse generation in Yb3+:silica fiber. By applying the stretched pulse technique in a unidirectional, polarization-switch Yb3+ fiber laser incorporating a prism-based dispersive delay line, we obtain self-start mode locking and 100pJ pulses that can be compressed to give clean chirp-free

  2. PULSED LASER ABLATION OF CEMENT AND CONCRETE

    Science.gov (United States)

    Laser ablation was investigated as a means of removing radioactive contaminants from the surface and near-surface regions of concrete from nuclear facilities. We present the results of ablation tests on cement and concrete samples using a pulsed Nd:YAG laser with fiber optic beam...

  3. Modeling of pulsed lasers for remote sensing

    Science.gov (United States)

    Walsh, Brian M.; Barnes, Norman P.; Petros, Mulugeta; Yu, Jirong; Singh, Upendra N.

    2005-01-01

    Pulsed lasers are useful for remote sensing of wind and greenhouse gases to better understand the atmosphere and its impact on weather patterns and the environment. It is not always practical to develop and optimize new laser systems empirically due to the time and expense associated with such endeavors. A practical option is to use a laser model to predict various performance parameters and compare these with the needs required for a particular remote sensing application. This approach can be very useful in determining the efficacy of potential laser systems, saving both time and money before proceeding with the actual construction of a laser device. As a pedagogical example, the modeling of diode pumped Tm:Ho:YLF and Tm:Ho:LuLF lasers are examined. Tm:Ho lasers operating around 2.0 μm have been used for wind measurements such as clear air turbulence and wake vortices. The model predictions for the laser systems examined here are compared to the actual laser performance, validating the usefulness of the modeling approach. While Tm:Ho fluoride lasers are used as a pedagogical example, the model is applicable to any lanthanide series pulsed laser system. This provides a useful tool for investigating potential laser systems that meet the requirements desired for a variety of remote sensing applications.

  4. Computer control of pulsed tunable dye lasers

    International Nuclear Information System (INIS)

    Pulsed tunable dye lasers are being used extensively for spectroscopic and photo-chemical experiments, and a system for acquisition and spectral analysis of a volume of data generated will be quite useful. The development of a system for wavelength tuning and control of tunable dye lasers and an acquisition system for spectral data generated in experiments with these lasers are described. With this system, it is possible to control the tuning of three lasers, and acquire data in four channels, simultaneously. It is possible to arrive at the desired dye laser wavelength with a reproducibility of ± 0.012 cm-1, which is within the absorption width (atomic interaction) caused by pulsed dye lasers of linewidth 0.08 cm-1. The spectroscopic data generated can be analyzed for spectral identification within absolute accuracy ± 0.012 cm-1. (author). 6 refs., 11 figs

  5. Laser pulse shaping for high gradient accelerators

    Science.gov (United States)

    Villa, F.; Anania, M. P.; Bellaveglia, M.; Bisesto, F.; Chiadroni, E.; Cianchi, A.; Curcio, A.; Galletti, M.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Gatti, G.; Moreno, M.; Petrarca, M.; Pompili, R.; Vaccarezza, C.

    2016-09-01

    In many high gradient accelerator schemes, i.e. with plasma or dielectric wakefield induced by particles, many electron pulses are required to drive the acceleration of one of them. Those electron bunches, that generally should have very short duration and low emittance, can be generated in photoinjectors driven by a train of laser pulses coming inside the same RF bucket. We present the system used to shape and characterize the laser pulses used in multibunch operations at Sparc_lab. Our system gives us control over the main parameter useful to produce a train of up to five high brightness bunches with tailored intensity and time distribution.

  6. Z-Beamlet: a multikilojoule, terawatt-class laser system

    International Nuclear Information System (INIS)

    A large-aperture (30-cm) kilojoule-class Nd:glass laser system known as Z-Beamlet has been constructed to perform x-ray radiography of high-energy-density science experiments conducted on the Z facility at Sandia National Laboratories, Albuquerque, New Mexico. The laser, operating with typical pulse durations from 0.3 to 1.5 ns, employs a sequence of successively larger multipass amplifiers to achieve up to 3-kJ energy at 1054 nm. Large-aperture frequency conversion and long-distance beam transport can provide on-target energies of up to 1.5 kJ at 527 nm

  7. Pulsed solid state lasers for medicine

    Science.gov (United States)

    Kertesz, Ivan; Danileiko, A. Y.; Denker, Boris I.; Kroo, Norbert; Osiko, Vyacheslav V.; Prokhorov, Alexander M.

    1994-02-01

    The effect on living tissues of different pulsed solid state lasers: Nd:YAG ((lambda) equals 1.06 micrometers ) Er:glass (1.54 micrometers ), Ho:YAG (2.1 micrometers ) and Er:YAG (2.94 micrometers ) is compared with the continuous wave Nd:YAG- and CO2-lasers used in operating theaters. Portable Er:glass- and Er:YAG-lasers are developed for surgery/cosmetics and HIV-safe blood testing.

  8. Heat accumulation during pulsed laser materials processing.

    Science.gov (United States)

    Weber, Rudolf; Graf, Thomas; Berger, Peter; Onuseit, Volkher; Wiedenmann, Margit; Freitag, Christian; Feuer, Anne

    2014-05-01

    Laser materials processing with ultra-short pulses allows very precise and high quality results with a minimum extent of the thermally affected zone. However, with increasing average laser power and repetition rates the so-called heat accumulation effect becomes a considerable issue. The following discussion presents a comprehensive analytical treatment of multi-pulse processing and reveals the basic mechanisms of heat accumulation and its consequence for the resulting processing quality. The theoretical findings can explain the experimental results achieved when drilling microholes in CrNi-steel and for cutting of CFRP. As a consequence of the presented considerations, an estimate for the maximum applicable average power for ultra-shorts pulsed laser materials processing for a given pulse repetition rate is derived. PMID:24921828

  9. RF synchronized short pulse laser ion source

    Energy Technology Data Exchange (ETDEWEB)

    Fuwa, Yasuhiro, E-mail: fuwa@kyticr.kuicr.kyoto-u.ac.jp; Iwashita, Yoshihisa; Tongu, Hiromu; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Okamura, Masahiro [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Yamazaki, Atsushi [Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603 (Japan)

    2016-02-15

    A laser ion source that produces shortly bunched ion beam is proposed. In this ion source, ions are extracted immediately after the generation of laser plasma by an ultra-short pulse laser before its diffusion. The ions can be injected into radio frequency (RF) accelerating bucket of a subsequent accelerator. As a proof-of-principle experiment of the ion source, a RF resonator is prepared and H{sub 2} gas was ionized by a short pulse laser in the RF electric field in the resonator. As a result, bunched ions with 1.2 mA peak current and 5 ns pulse length were observed at the exit of RF resonator by a probe.

  10. High Power Pulsed Gas Lasers

    Science.gov (United States)

    Witteman, W. J.

    1987-09-01

    Gas lasers have shown to be capable of delivering tens of terrawatt aspeak power or tens of kilowatt as average power. The efficiencies of most high power gas lasers are relatively high compared with other types of lasers. For instance molecular lasers, oscillating on low lying vibrational levels, and excimer lasers may have intrinsic efficiencies above 10%.The wavelengths of these gas lasers cover the range from the far infrared to the ultra-violet region, say from 12000 to 193 nm. The most important properties are the scalability, optical homogeneity of the excited medium, and the relatively low price per watt of output power. The disadvantages may be the large size of the systems and the relatively narrow line width with limited tunability compared with solid state systems producing the same peak power. High power gas lasers group into three main categories depending on the waste-heat handling capacity.

  11. Ophthalmic applications of ultrashort pulsed lasers

    Science.gov (United States)

    Juhasz, Tibor; Spooner, Greg; Sacks, Zachary S.; Suarez, Carlos G.; Raksi, Ferenc; Zadoyan, Ruben; Sarayba, Melvin; Kurtz, Ronald M.

    2004-06-01

    Ultrashort laser pulses can be used to create high precision incision in transparent and translucent tissue with minimal damage to adjacent tissue. These performance characteristics meet important surgical requirements in ophthalmology, where femtosecond laser flap creation is becoming a widely used refractive surgery procedure. We summarize clinical findings with femtosecond laser flaps as well as early experiments with other corneal surgical procedures such as corneal transplants. We also review laser-tissue interaction studies in the human sclera and their consequences for the treatment of glaucoma.

  12. An Overview of High Energy Short Pulse Technology for Advanced Radiography of Laser Fusion Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Barty, C J; Key, M; Britten, J; Beach, R; Beer, G; Brown, C; Bryan, S; Caird, J; Carlson, T; Crane, J; Dawson, J; Erlandson, A C; Fittinghoff, D; Hermann, M; Hoaglan, C; Iyer, A; Jones, L; Jovanovic, I; Komashko, A; Landen, O; Liao, Z; Molander, W; Mitchell, A; Moses, E; Nielsen, N; Nguyen, H; Nissen, J; Payne, S; Pennington, D; Risinger, L; Rushford, M; Skulina, K; Spaeth, M; Stuart, B; Tietbohl, G; Wattellier, B

    2004-06-18

    The technical challenges and motivations for high-energy, short-pulse generation with NIF-class, Nd:glass laser systems are reviewed. High energy short pulse generation (multi-kilojoule, picosecond pulses) will be possible via the adaptation of chirped pulse amplification laser techniques on the NIF. Development of meter-scale, high efficiency, high-damage-threshold final optics is a key technical challenge. In addition, deployment of HEPW pulses on NIF is constrained by existing laser infrastructure and requires new, compact compressor designs and short-pulse, fiber-based, seed-laser systems. The key motivations for high energy petawatt pulses on NIF is briefly outlined and includes high-energy, x-ray radiography, proton beam radiography, proton isochoric heating and tests of the fast ignitor concept for inertial confinement fusion.

  13. Development of real-time pulse shaping technology in solid-state lasers

    International Nuclear Information System (INIS)

    We developed real-time pulse shaping technology in solid-state lasers for special cutting and welding applications. Our real-time pulse shaping unit has the capabilities of 20 steps variation in laser intensity, 200 steps in laser pulse width, and 16 pulse shape patterns with MOSFET Pulse Width Modulation method. Also, we improved our previous 250 W class Nd:YAG laser system by using this new technology. Many optical parts were localized and lowered much in cost. Only few parts were imported and almost 90% in cost were localized. Also, to accellerate the commercialization by the joint company, the training and transfer of technology were pursued in the joint participation in design and assembly by company researchers from the early stage. Two Nd:YAG lasers have been assembled and will be tested in industrial manufacturing processes to prove the capability of developed Nd:YAG laser with potential users. (Author)

  14. Pulsed laser treatments of polyethylene films

    Energy Technology Data Exchange (ETDEWEB)

    Torrisi, L. [Physic Department, Messina University, Ctr. Papardo 31, 98186 S. Agata, Messina (Italy); Visco, A.M., E-mail: avisco@unime.i [Industrial Chemistry and Material Engineering Department, Messina University, Ctr. Di Dio, 98186 S. Agata, Messina (Italy); Campo, N. [Industrial Chemistry and Material Engineering Department, Messina University, Ctr. Di Dio, 98186 S. Agata, Messina (Italy); Caridi, F. [Physic Department, Messina University, Ctr. Papardo 31, 98186 S. Agata, Messina (Italy)

    2010-10-01

    A Nd:Yag pulsed laser, 3 ns pulse width, 150 mJ pulse energy, operating at the second harmonics (532 nm) has been used to irradiate in air polyethylene thin films. The thermal and chemical effects induced by the laser irradiation in the polymer are responsible of the hydrogen and C{sub x}H{sub y} groups emission at long irradiation times. A special study, concerning the welding effect between two different types of polyethylene films, one transparent and the other strong absorbent the laser light, was performed. The welding, at the interface of the two pressed polymers, depends on the optical and micro-structural material properties besides the irradiation time. In particular, polymers with different viscosity, melting temperature and crystalline degree exhibit different mechanical behaviour. Different techniques were employed to investigate on the polymeric welding effects, such as the mass quadrupole spectrometry, the scanning electron microscope, the surface profiler and the mechanical strength measurement.

  15. Energy distribution of fast electrons accelerated by high intensity laser pulse depending on laser pulse duration

    Science.gov (United States)

    Kojima, Sadaoki; Arikawa, Yasunobu; Morace, Alessio; Hata, Masayasu; Nagatomo, Hideo; Ozaki, Tetsuo; Sakata, Shohei; Lee, Seung Ho; Matsuo, Kazuki; Farley Law, King Fai; Tosaki, Shota; Yogo, Akifumi; Johzaki, Tomoyuki; Sunahara, Atsushi; Sakagami, Hitoshi; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Fujioka, Shinsuke; Azechi, Hiroshi

    2016-05-01

    The dependence of high-energy electron generation on the pulse duration of a high intensity LFEX laser was experimentally investigated. The LFEX laser (λ = 1.054 and intensity = 2.5 – 3 x 1018 W/cm2) pulses were focused on a 1 mm3 gold cubic block after reducing the intensities of the foot pulse and pedestal by using a plasma mirror. The full width at half maximum (FWHM) duration of the intense laser pulse could be set to either 1.2 ps or 4 ps by temporally stacking four beams of the LFEX laser, for which the slope temperature of the high-energy electron distribution was 0.7 MeV and 1.4 MeV, respectively. The slope temperature increment cannot be explained without considering pulse duration effects on fast electron generation.

  16. Efficient pulsed CO2 laser calculations

    Science.gov (United States)

    Stone, David H.; Honey, David A.

    1991-02-01

    A computationally efficient scheme for generating pumping rates was developed for use with a pulsed CO2 laser model. A steady-state solution of the Boltzmann electron transport equation generates the rates. Vibrational temperatures for the CO2 and N2 populations are determined by iterating the Boltzmann solver with the rate equation model. Rapid convergence and coarse grids allow quick calculations of pulse shape, peak power, and total energy. Results compare well with a fully time-dependent Boltzmann solver.

  17. Pulsed uv nitrogen laser: dynamical behavior

    International Nuclear Information System (INIS)

    Using the time dependent rate equations, the dynamical behavior of a high power pulsed N2 laser radiating at 337.1 nm is derived. The threshold conditions are given. The output peak power and pulse width as a function of length and initial inversion density are shown. The theoretical results derived are compared with experimental data and are found to be in good agreement

  18. Laser pulse shaping with liquid crystals

    OpenAIRE

    Martín Pereda, José Antonio; Muriel Fernández, Miguel Ángel

    1983-01-01

    A method of unpolarized laser pulses shaping is reported. The basis of the method is the use of an hybrid optical bistable device with nematic liquid-crystals, similar to the one previously reported by us. A sample of the input light constrols, by an asymmetrical electronic comparator, a 1 x 2 electro-optical total switch. The output pulses are reshaped and maintain the same polarization properties as the input light. From triangular input light signals, symmetriacl and asymmetrical output pu...

  19. Short pulse high power fiber laser systems

    OpenAIRE

    Malinowski, A.; Piper, A; Price, J.H.V.; He, F.; Ibsen, M; Nilsson, J.; Richardson, D J

    2005-01-01

    We review the rapid recent progress in the development of short pulse high-power fiber laser and amplifier devices. Use of cladding pump technology now provides a route to compact and efficient laser and amplifier systems with high beam quality and high output powers. A new Yb-fiber CPA system incorporating a CFBG stretcher with both 2nd and 3rd order dispersion is presented for high pulse energy applications. In addition, a simplified Yb-fiber parabolic amplifier system is also shown to be s...

  20. Polyethylene welding by pulsed visible laser irradiation

    Science.gov (United States)

    Torrisi, L.; Caridi, F.; Visco, A. M.; Campo, N.

    2011-01-01

    Laser welding of plastics is a relatively new process that induces locally a fast polymer heating. For most applications, the process involves directing a pulsed beam of visible light at the weld joint by going through one of the two parts. This is commonly referred to as “through transmission visible laser welding”. In this technique, the monochromatic visible light source uses a power ns pulsed laser in order to irradiate the joint through one part and the light is absorbed in the vicinity of the other part. In order to evaluate the mechanical resistance of the welded joint, mass quadrupole spectrometry, surface profilometry, microscopy techniques and mechanical shear tests were employed. The welding effect was investigated as a function of the laser irradiation time, nature of the polyethylene materials and temperature.

  1. Polyethylene welding by pulsed visible laser irradiation

    International Nuclear Information System (INIS)

    Laser welding of plastics is a relatively new process that induces locally a fast polymer heating. For most applications, the process involves directing a pulsed beam of visible light at the weld joint by going through one of the two parts. This is commonly referred to as 'through transmission visible laser welding'. In this technique, the monochromatic visible light source uses a power ns pulsed laser in order to irradiate the joint through one part and the light is absorbed in the vicinity of the other part. In order to evaluate the mechanical resistance of the welded joint, mass quadrupole spectrometry, surface profilometry, microscopy techniques and mechanical shear tests were employed. The welding effect was investigated as a function of the laser irradiation time, nature of the polyethylene materials and temperature.

  2. Ceramic dentures manufactured with ultrashort laser pulses

    Science.gov (United States)

    Werelius, Kristian; Weigl, Paul

    2004-06-01

    Conventional manufacturing of individual ceramic dental prosthesis implies a handmade metallic framework, which is then veneered with ceramic layers. In order to manufacture all-ceramic dental prosthesis a CAD/CAM system is necessary due to the three dimensional shaping of high strength ceramics. Most CAD/CAM systems presently grind blocks of ceramic after the construction process in order to create the prosthesis. Using high-strength ceramics, such as Hot Isostatic Pressed (HIP)-zirconia, this is limited to copings. Anatomically shaped fixed dentures have a sculptured surface with small details, which can't be created by existing grinding tools. This procedure is also time consuming and subject to significant loss in mechanical strength and thus reduced survival rate once inserted. Ultra-short laser pulses offer a possibility in machining highly complex sculptured surfaces out of high-strength ceramic with negligible damage to the surface and bulk of the ceramic. In order to determine efficiency, quality and damage, several laser ablation parameters such as pulse duration, pulse energy and ablation strategies were studied. The maximum ablation rate was found using 400 fs at high pulse energies. High pulse energies such as 200μJ were used with low damage in mechanical strength compared to grinding. Due to the limitation of available laser systems in pulse repetition rates and power, the use of special ablation strategies provide a possibility to manufacture fully ceramic dental prosthesis efficiently.

  3. Pulsed YAG laser spot welding under microgravity

    Science.gov (United States)

    Katayama, Seiji; Tanaka, Koji; Mizutani, Masami; Matsunawa, Akira

    2000-02-01

    With the objectives of obtaining a fundamental knowledge of laser welding technology inside and outside the spacecraft in space, pulsed YAG laser spot welding was performed on the metal plates in Ar gas atmosphere or a vacuum in the falling microgravity apparatus equipped with the fiber-delivered laser focusing optics. The influence of gravity or microgravity on penetration and welding defect formation was further clarified by comparing the welds made in the normal flat and overhead positions. Almost all results of weld penetration and defect formation under microgravity were similar to those under normal gravity except the welding result of aluminum alloy A5083 subjected to the high power density laser, and were between normal gravity and overhead position welding results. Welding in a vacuum was characterized by the formation of a narrower and cone-shaped bottom in any alloy weld. Porosity was easily formed in any deeply penetrated weld metal under high power density welding with a rectangular pulse-shaped laser, and could be reduced by utilizing pulse-controlled laser even under microgravity.

  4. Graphene in Ultrafast and Ultrastrong Laser Pulses

    Science.gov (United States)

    Koochakikelardeh, Hamed; Apalkov, Vadym; Stockman, Mark

    2015-03-01

    We have shown that graphene subjected to an ultrafast (near-single-oscillation pulse) and strong (F ~ 1-3 V/Å) pulse exhibits fundamental behavior dramatically different from both insulators and metals. In such an ultrafast and ultrastrong field, the electron dynamics is coherent, in contrast to relatively long pulses (τ>100 fs) where the electron's dephasing becomes important leading to incoherent dynamics. Electron transfer from the valence band (VB) to the conduction band (CB) is deeply irreversible i.e., non-adiabatic, in which the residual CB population (after pulse ends) is close to the maximum one. The residual CB population as a function of wave vector is nonuniform with a few strongly localized spots near the Dirac points, at which the CB population is almost 100%. Furthermore, it is shown the direction of charge transfer depends on the pulse amplitude. Namely, at small pulse amplitude, =1 V/Å, it is in opposite direction of the pulse maximum (negative transferred charge). Consequently, in terms of charge transport, graphene at small pulse intensities behaves as a dielectric while at large intensities acts as a metal. These femtosecond currents and charge transfer in graphene may provide fundamental basis for detection and calibration of ultrashort intense laser pulses and are promising for petahertz information processing. This work was supported by U.S. Office of Naval Research No. N00014-13-1-0649 and NSF Grant No. ECCS-1308473.

  5. Short-pulse laser materials processing

    International Nuclear Information System (INIS)

    The goal of this project was to develop, through experiments and modeling, a better understanding of the physics issues and machining techniques related to short-pulse laser materials processing. Although we have successfully demonstrated many types of cuts in a wide range of materials, our general short-pulse machining scientific knowledge and our ability to model the complex physical processes involved are limited. During this past year we made good progress in addressing some of these issues, but there remain many unanswered questions. Section 2 begins with a theoretical look at short-pulse laser ablation of material using a 1-D radiation-hydrodynamic code which includes a self-consistent description of laser absorption and reflection from an expanding plasma. In Section 3 we present measurements of scaling relationships, hole drilling progression, electric field and polarization effects, and a detailed look at the interesting structures formed during hole drilling of metals under various conditions. Section 4 describes the consequences of the presence of a prepulse before the main drilling pulse. In Section 5 we take a brief look at the plasma plume: how it can be useful, and how we can avoid it. Finally, Section 6 contains a couple of examples of machining non-metals. The laser system used for practically all the experimental results presented here was a short-pulse laser based on Ti:sapphire, which produced 150-fs pulses (minimum) centered at 825 nm, of energy up to 5 mJ at 1 kHz, or 5 W average power

  6. Electromagnetic Pulses at Short-Pulse Laser Facilities

    Energy Technology Data Exchange (ETDEWEB)

    Brown, C G; Throop, A; Eder, D; Kimbrough, J

    2008-02-04

    Electromagnetic Pulse (EMP) is a known issue for short-pulse laser facilities, and will also be an issue for experiments using the advanced radiographic capability (ARC) at the National Ignition Facility (NIF). The ARC diagnostic uses four NIF beams that are compressed to picosecond durations for backlighting ignition capsules and other applications. Consequently, we are working to understand the EMP due to high-energy (MeV) electrons escaping from targets heated by short-pulse lasers. Our approach is to measure EMP in the Titan short-pulse laser at Lawrence Livermore National Laboratory (LLNL) and to employ that data to establish analysis and simulation capabilities. We have installed a wide variety of probes inside and outside the Titan laser chamber. We have high-frequency B-dot and D-dot probes, a photodiode, and fast current-viewing and integrating current transformers. The probe outputs are digitized by 10 and 20 Gsample/s oscilloscopes. The cables and oscilloscopes are well shielded to reduce noise. Our initial measurement campaign has yielded data useful mainly from several hundreds of MHz to several GHz. We currently are supplementing our high-frequency probes with lower-frequency ones to obtain better low-frequency data. In order to establish analysis and simulation capabilities we are modeling the Titan facility using various commercial and LLNL numerical electromagnetics codes. We have simulated EMP generation by having a specified number of electrons leave the target and strike the chamber wall and other components in the chamber. This short impulse of electrons has a correspondingly broad spectrum, exciting high-frequency structure in the resulting EMP. In this paper, we present results of our initial measurement campaign and comparisons between the measurements and simulations.

  7. Ultra-short pulse reconstruction software in high power laser system

    International Nuclear Information System (INIS)

    An ultra-short pulse reconstruction software, validated through a set of experimental measurements on the front-end of the Vulcan laser at the RAL Central Laser Facility is presented. The measurements were acquired in Target Area Petawatt of the Vulcan laser, both using a conventional autocorrelation technique and the GRENOUILLE technique in order to compare the results. The FWHM of the laser pulses considered came out to be comparable for the two techniques. In this experimental campaign for the first time a technique different from the autocorrelation one has been used for a PW class laser as Vulcan

  8. Ultra-short pulse reconstruction software in high power laser system

    Energy Technology Data Exchange (ETDEWEB)

    Galletti, M. [Physics Department of the University and INFN, Pisa (Italy); Galimberti, M. [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Giulietti, D. [Physics Department of the University and INFN, Pisa (Italy)

    2015-07-15

    An ultra-short pulse reconstruction software, validated through a set of experimental measurements on the front-end of the Vulcan laser at the RAL Central Laser Facility is presented. The measurements were acquired in Target Area Petawatt of the Vulcan laser, both using a conventional autocorrelation technique and the GRENOUILLE technique in order to compare the results. The FWHM of the laser pulses considered came out to be comparable for the two techniques. In this experimental campaign for the first time a technique different from the autocorrelation one has been used for a PW class laser as Vulcan.

  9. Pulsed laser deposition of liquid crystals

    OpenAIRE

    Gonzalo de los Reyes, José; Dyer, P. E.; Hird, M.

    1997-01-01

    Thin films of 4-cyano-4’-pentylbiphenyl ~5CB! liquid crystal have been fabricated by pulsed laser deposition. The suitability of different lasers ~ArF, KrF and CO2) has been investigated over a range of fluence using visible-UV and infrared absorption and optical microscopy to characterise the films. High performance liquid chromatography ~HPLC! and matrix assisted laser desorption ionization mass spectroscopy ~MALDI-MS! were used to assess the extent of decomposition of the films. The result...

  10. Femtosecond laser pulse written Volume Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Richter Daniel

    2013-11-01

    Full Text Available Femtosecond laser pulses can be applied for structuring a wide range of ransparent materials. Here we want to show how to use this ability to realize Volume-Bragg-Gratings in various- mainly non-photosensitive - glasses. We will further present the characteristics of the realized gratings and a few elected applications that have been realized.

  11. Pulse solid state lasers in aesthetic surgery

    Science.gov (United States)

    Dobryakov, Boris S.; Greben'kova, Ol'ga B.; Gulev, Valerii S.

    1996-04-01

    The emission of a pulse-periodic laser on alumo-ittrium garnet applied for preventive and medical treatment of a capsule contracture round implanted prostheses in xenoplastics is described in the present paper. The results obtained testify to a high efficiency of suggested method.

  12. Electron photodetachment by short laser pulse

    NARCIS (Netherlands)

    Golovinski, P. A.; Drobyshev, A. A.

    2012-01-01

    Expressions are derived for calculations of the total probabilities and electron spectra for the photodetachment of electrons from negative ions with filled valence s shells by ultrashort laser pulses. Particular calculations have been performed for two negative ions (H- and Li-) and titanium-sapphi

  13. RECENT ADVANCES IN PULSED LASER ABLATED PLASMA PLUMES: A REVIEW

    OpenAIRE

    ASHUTOSH DWIVEDI

    2007-01-01

    Pulsed laser ablation is a process in which an intense laser pulse interacts with the matter producing plasma. The present work describes the theoretical work being conducted in the past for the pulsed laser ablation phenomenon. It incorporates the theoretical models being proposed by various researchers around the globe for pulsed laser ablation. The main processes involved in the laser–matter interaction leading to plasma plume formation are the absorption and the reflection of the incident...

  14. Laser zona dissection using short-pulse ultraviolet lasers

    Science.gov (United States)

    Neev, Joseph; Tadir, Yona; Ho, Peter D.; Whalen, William E.; Asch, Richardo H.; Ord, Teri; Berns, Michael W.

    1992-06-01

    The interaction of pulsed ultraviolet radiation with the zona pellucida of human oocytes which had failed to fertilize in standard IVF cycles, was investigated. Two lasers were studied: a 100 ps pulsed Nd:YAG with a nonlinear crystal emitting light at 266 nm, and a 15 ns XeCl excimer laser with 308 nm radiation. Incisions in the zona were made by aiming the beam tangentially to the oocyte. The results indicate superior, high precision performance by the excimer laser creating trenches as narrow as 1 micrometers and as shallow as 1 micrometers . The incision size was found to be sensitive to the laser's energy and to the position of the microscope's objective focal plane, but relatively insensitive to the laser pulse repetition rate. Once the minimum spot size was defined by the system parameters, the laser beam was used to curve out any desired zona shape. This laser microsurgery technique as applied to partial zone dissection or zona drilling could prove very useful as a high-precision, non-contact method for treatments of low fertilization rate and for enhancing embryo implantation rates in patients undergoing IVF treatments.

  15. Enhanced subthreshold electron-positron production in short laser pulses

    OpenAIRE

    Titov, A. I.; Takabe, H.; Kampfer, B.; Hosaka, A.

    2012-01-01

    The emission of electron-positron pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g.\\ laser) wave field is analyzed. A significant increase of the total cross section of pair production in the subthreshold region is found for decreasing laser pulse duration even in case of moderate laser pulse intensities.

  16. Enhanced subthreshold e+ e- production in short laser pulses.

    Science.gov (United States)

    Titov, A I; Takabe, H; Kämpfer, B; Hosaka, A

    2012-06-15

    The emission of e+ e- pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g., laser) wave field is analyzed. A significant increase of the total cross section of pair production in the subthreshold region is found for decreasing laser pulse duration even in the case of moderate laser pulse intensities. PMID:23004244

  17. Fundamentals of laser pulse irradiation of silicon

    International Nuclear Information System (INIS)

    A computer model has been developed to describe the space and time evolution of carrier concentration, carrier energy and lattice temperature during nanosecond and picosecond laser pulse irradiation of Si single crystals. In particular the dynamic response has been evaluated for energy density of the ps laser pulse below and above the density threshold for surface melting. The obtained data allow a comparison with time-resolved reflectivity measurements reported in the literature. The available data are fitted by the computer model assuming a relaxation time for the energy transfer from the carriers to the lattice of 1 ps. The validity of the thermal model used to describe laser annealing in the nanosecond regime is assessed. (author)

  18. Phase Noise Comparision of Short Pulse Laser Systems

    Energy Technology Data Exchange (ETDEWEB)

    S. Zhang; S. V. Benson; J. Hansknecht; D. Hardy; G. Neil; Michelle D. Shinn

    2006-12-01

    This paper describes the phase noise measurement on several different mode-locked laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on the state of the art short pulse lasers, especially the drive lasers for photocathode injectors. A comparison between the phase noise of the drive laser pulses, electron bunches and FEL pulses will also be presented.

  19. Nanosecond square pulse generation in fiber lasers with normal dispersion

    Science.gov (United States)

    Zhao, L. M.; Tang, D. Y.; Cheng, T. H.; Lu, C.

    2007-04-01

    We report on the generation of nanosecond square pulses in a passively mode-locked fiber ring laser made of purely normal dispersive fibers. Different to the noise-like pulse operation of the laser, the generated square pulses are stable and have no internal structures. We show that the formation of the square pulse is due to the combined action of the pulse peak clamping effect caused by the cavity and the almost linear pulse propagation in the normal dispersive fibers.

  20. Double nanosecond pulses generation in ytterbium fiber laser

    Science.gov (United States)

    Veiko, V. P.; Lednev, V. N.; Pershin, S. M.; Samokhvalov, A. A.; Yakovlev, E. B.; Zhitenev, I. Yu.; Kliushin, A. N.

    2016-06-01

    Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential "opening" radio pulses with a delay of 0.2-1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode.

  1. Production of Picosecond, Kilojoule, and Petawatt Laser Pulses via Raman Amplification of Nanosecond Pulses

    OpenAIRE

    Trines, R. M. G. M.; Fiúza, F.; Bingham, R.; Fonseca, R. A.; Silva, L. O.; Cairns, R. A.; Norreys, P. A.

    2011-01-01

    Raman amplification in plasma has been promoted as a means of compressing picosecond optical laser pulses to femtosecond duration to explore the intensity frontier. Here we show for the first time that it can be used, with equal success, to compress laser pulses from nanosecond to picosecond duration. Simulations show up to 60% energy transfer from pump pulse to probe pulse, implying that multikilojoule ultraviolet petawatt laser pulses can be produced using this scheme. This has important co...

  2. Laser-supported detonation waves and pulsed laser propulsion

    International Nuclear Information System (INIS)

    A laser thermal rocket uses the energy of a large remote laser, possibly ground-based, to heat an inert propellant and generate thrust. Use of a pulsed laser allows the design of extremely simple thrusters with very high performance compared to chemical rockets. The temperatures, pressures, and fluxes involved in such thrusters (104 K, 102 atmospheres, 107 w/cm2) typically result in the creation of laser-supported detonation (LSD) waves. The thrust cycle thus involves a complex set of transient shock phenomena, including laser-surface interactions in the ignition of the LSD wave, laser-plasma interactions in the LSD wave itself, and high-temperature nonequilibrium chemistry behind the LSD wave. The SDIO Laser Propulsion Program is investigating these phenomena as part of an overall effort to develop the technology for a low-cost Earth-to-orbit laser launch system. We will summarize the Program's approach to developing a high performance thruster, the double-pulse planar thruster, and present an overview of some results obtained to date, along with a discussion of the many research question still outstanding in this area

  3. Evaporation of solids by pulsed laser irradiation

    Science.gov (United States)

    Stafast, H.; Von Przychowski, M.

    The focused beam of a KrF laser (248 nm) has been applied to irradiate targets of Al 2O 3, SiC, graphite, Pb, Ni, Cr, quartz, and NaCl at variable laser energy flux is the range 0-13 J/cm 2. The amount of target material ejected into the vacuum (background pressure about 8 × 10 -4 Torr) was determined from the target weight before and after laser irradiation. The average number of particles (formula weight) evaporated per laser pulse and per unit of irradiated target area is non-linearly dependent on the laser energy flux. The evaporation of Al 2O 3, SiC, and graphite is showing a well-defined flux threshold while the vaporization of Pb, Ni and Cr is rising smoothly with increasing flux. With both groups of materials laser evaporation is monotonically increasing with the laser energy flux. NaCl and quartz, on the other hand, are showing an intermediate maximum in the laser vaporization efficiency.

  4. Laser-Material Interaction of Powerful Ultrashort Laser Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Komashko, A

    2003-01-06

    Laser-material interaction of powerful (up to a terawatt) ultrashort (several picoseconds or shorter) laser pulses and laser-induced effects were investigated theoretically in this dissertation. Since the ultrashort laser pulse (USLP) duration time is much smaller than the characteristic time of the hydrodynamic expansion and thermal diffusion, the interaction occurs at a solid-like material density with most of the light energy absorbed in a thin surface layer. Powerful USLP creates hot, high-pressure plasma, which is quickly ejected without significant energy diffusion into the bulk of the material, Thus collateral damage is reduced. These and other features make USLPs attractive for a variety of applications. The purpose of this dissertation was development of the physical models and numerical tools for improvement of our understanding of the process and as an aid in optimization of the USLP applications. The study is concentrated on two types of materials - simple metals (materials like aluminum or copper) and wide-bandgap dielectrics (fused silica, water). First, key physical phenomena of the ultrashort light interaction with metals and the models needed to describe it are presented. Then, employing one-dimensional plasma hydrodynamics code enhanced with models for laser energy deposition and material properties at low and moderate temperatures, light absorption was self-consistently simulated as a function of laser wavelength, pulse energy and length, angle of incidence and polarization. Next, material response on time scales much longer than the pulse duration was studied using the hydrocode and analytical models. These studies include examination of evolution of the pressure pulses, effects of the shock waves, material ablation and removal and three-dimensional dynamics of the ablation plume. Investigation of the interaction with wide-bandgap dielectrics was stimulated by the experimental studies of the USLP surface ablation of water (water is a model of

  5. Long pulse electron gun for laser applications

    International Nuclear Information System (INIS)

    This paper reports on large-area electron guns that are critical components in many high-energy gas laser systems. The secondary emission electron (SEE) gun offers an attractive option for pulsed laser applications. With this type of cold cathode gun, a dc voltage is applied to the cathode and the electron beam is generated by secondary emission due to ion bombardment processes. The gun is controlled by modulating the source of ions which resides at ground potential. This design greatly simplifies the electron gun power system. SEE-gun systems have been developed which provide 150-220 keV beams at current densities exceeding 25 mA/cm2 with current density uniformities of approximately ±10% over areas of up to 5 x 150 cm2. Pulse lengths have ranged from 30 μs to 20 ms at repetition rates from single-pulse to 30 Hz. It is expected that the SEE-gun can be scaled to beam voltages of greater than 300 kV, beam areas greater than 1 m2, peak current densities exceeding 1 A/cm2, time-averaged current densities approx-gt 0.5 mA/cm2, pulse lengths of 0.1 μs to dc, and pulse repetition rates >1 kHz with good uniformity, high reliability and long life. Furthermore, the inherent simplicity of the SEE-gun results in low cost and a compact, light-weight system

  6. Crack imaging by pulsed laser spot thermography

    International Nuclear Information System (INIS)

    A surface crack close to a spot heated by a laser beam impedes lateral heat flow and produces alterations to the shape of the thermal image of the spot that can be monitored by thermography. A full 3D simulation has been developed to simulate heat flow from a laser heated spot in the proximity of a crack. The modelling provided an understanding of the ways that different parameters affect the thermal images of laser heated spots. It also assisted in the development of an efficient image processing strategy for extracting the scanned cracks. Experimental results show that scanning pulsed laser spot thermography has considerable potential as a remote, non-contact crack imaging technique.

  7. Surface characteristic of stainless steel sheet after pulsed laser forming

    International Nuclear Information System (INIS)

    Laser forming is a non-contact and die-less forming technique of producing bending, spatial forming, modifying and adjusting the curvature of the metallic sheet by using the controlled laser beam energy. One of the problems in laser forming is controlling the characteristic of laser scanned surface. The aim of the investigation is to explore the relation between the surface behaviors of heat affected zone (HAZ) scanned by pulse laser and the pulse parameters of the laser. This paper illustrated the fundamental theory of pulsed laser affected material, and pays attention to the microstructure, micro-hardness and the anticorrosion in the HAZ generated by the laser scanning. Metallographic microscope, scanning electron microscope (SEM), micro-hardness testing system are used to examine the surface characteristics. The work presented in this paper is beneficial to understand the mechanism of pulse laser affect to materials and improve controlling the surface behaviors scanned by pulsed laser.

  8. Laser absorption via QED cascades in counter propagating laser pulses

    CERN Document Server

    Grismayer, Thomas; Martins, Joana L; Fonseca, Ricardo A; Silva, Luis O

    2015-01-01

    A model for laser light absorption in electron-positron plasmas self-consistently created via QED cascades is described. The laser energy is mainly absorbed due to hard photon emission via nonlinear Compton scattering. The degree of absorption depends on the laser intensity and the pulse duration. The QED cascades are studied with multi-dimensional particle-in-cell simulations complemented by a QED module and a macro-particle merging algorithm that allows to handle the exponential growth of the number of particles. Results range from moderate-intensity regimes ($\\sim$ 10 PW) where the laser absorption is negligible, to extreme intensities (> 100 PW) where the degree of absorption reaches 80%. Our study demonstrates good agreement between the analytical model and simulations. The expected properties of the hard photon emission and the generated pair-plasma are investigated, and the experimental signatures for near-future laser facilities are discussed.

  9. Pulse-burst laser systems for fast Thomson scattering (invited)

    International Nuclear Information System (INIS)

    Two standard commercial flashlamp-pumped Nd:YAG (YAG denotes yttrium aluminum garnet) lasers have been upgraded to ''pulse-burst'' capability. Each laser produces a burst of up to 15 2 J Q-switched pulses (1064 nm) at repetition rates of 1-12.5 kHz. Variable pulse-width drive (0.15-0.39 ms) of the flashlamps is accomplished by insulated gate bipolar transistor (IGBT) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinch to record the dynamic evolution of the electron temperature profile and temperature fluctuations. To further these investigations, a custom pulse-burst laser system with a maximum pulse repetition rate of 250 kHz is now being commissioned.

  10. Pulse-burst laser systems for fast Thomson scattering (invited).

    Science.gov (United States)

    Den Hartog, D J; Ambuel, J R; Borchardt, M T; Falkowski, A F; Harris, W S; Holly, D J; Parke, E; Reusch, J A; Robl, P E; Stephens, H D; Yang, Y M

    2010-10-01

    Two standard commercial flashlamp-pumped Nd:YAG (YAG denotes yttrium aluminum garnet) lasers have been upgraded to "pulse-burst" capability. Each laser produces a burst of up to 15 2 J Q-switched pulses (1064 nm) at repetition rates of 1-12.5 kHz. Variable pulse-width drive (0.15-0.39 ms) of the flashlamps is accomplished by insulated gate bipolar transistor (IGBT) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinch to record the dynamic evolution of the electron temperature profile and temperature fluctuations. To further these investigations, a custom pulse-burst laser system with a maximum pulse repetition rate of 250 kHz is now being commissioned. PMID:21033868

  11. Molecular alignment using circularly polarized laser pulses

    CERN Document Server

    Smeenk, C T L

    2013-01-01

    We show that circularly polarized femtosecond laser pulses produce field-free alignment in linear and planar molecules. We study the rotational wavepacket evolution of O$_2$ and benzene created by circularly polarized light. For benzene, we align the molecular plane to the plane of polarization. For O$_2$, we demonstrate that circular polarization yields a net alignment along the laser propagation axis at certain phases of the evolution. Circular polarization gives us the ability to control alignment of linear molecules outside the plane of polarization, providing new capabilities for molecular imaging.

  12. Nanosecond pulsed laser blackening of copper

    Science.gov (United States)

    Tang, Guang; Hourd, Andrew C.; Abdolvand, Amin

    2012-12-01

    Nanosecond (12 ns) pulsed laser processing of copper at 532 nm resulted in the formation of homogenously distributed, highly organized microstructures. This led to the fabrication of large area black copper substrates with absorbance of over 97% in the spectral range from 250 nm to 750 nm, and a broadband absorbance of over 80% between 750 nm and 2500 nm. Optical and chemical analyses of the fabricated black metal are presented and discussed. The employed laser is an industrially adaptable source and the presented technique for fabrication of black copper could find applications in broadband thermal radiation sources, solar energy absorbers, irradiative heat transfer devices, and thermophotovoltaics.

  13. Alignment of a petawatt-class pulse compressor with the third-order dispersion completely compensated

    Science.gov (United States)

    Zuo, Yanlei; Zhou, Kainan; Wu, Zhaohui; Wang, Xiao; Xie, Na; Su, Jingqin; Zeng, Xiaoming

    2016-05-01

    It is necessary to eliminate third-order dispersion to acquire an ultrashort pulse of less than 30 fs. We demonstrate for the first time, to the best of our knowledge, the alignment of a petawatt-class laser compressor using the equiphase lines in the spatial and spectral interference patterns. Third-order dispersion has been completely eliminated and a Fourier-transform-limited pulsewidth of 19.6 fs has been approached.

  14. Micromachining of copper by femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S.Y. [ITRI South, Industrial Technology Research Institute, Liujia District, Tainan City 734, Taiwan (China); Ren, Y. [Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, MO 65211 (United States); Cheng, C.W., E-mail: CWCheng@itri.org.tw [ITRI South, Industrial Technology Research Institute, Liujia District, Tainan City 734, Taiwan (China); Chen, J.K.; Tzou, D.Y. [Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, MO 65211 (United States)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer We have reported new experimental and theoretical results on the femtosecond laser ablation for copper at fluences up to 408 J/cm{sup 2}. Black-Right-Pointing-Pointer The present model simulations correlate well with the experimental data over a broad range of laser fluences from 0.8 to 400 J/cm{sup 2}. Black-Right-Pointing-Pointer The good correlation suggests that the proposed model is an efficient and accurate tool for predicting ultrafast laser material ablation. - Abstract: Simulation results of femtosecond laser ablation of copper were compared to experimental data. The numerical analysis was performed using a predictive model, including a two temperature model, an optical critical point model with three Lorentzian terms, two phase change models for melting and evaporation under superheating, and a phase explosion criterion for ejection of metastable liquid decomposing into droplets and vapor phase. The experiments were conducted with a 120-fs, 800-nm Ti:sapphire lasers for fluences up to 408 J/cm{sup 2}. The ablation depths were measured, and the ablation rate was estimated. It was shown that the present numerical simulations correlate well with the experimental data over the entire range of the laser fluences investigated except for those below 0.8 J/cm{sup 2}, indicating that the proposed model is an accurate and efficient tool for predicting ultrashort-pulsed laser material ablation.

  15. Pulse switching for high energy lasers

    Science.gov (United States)

    Laudenslager, J. B.; Pacala, T. J. (Inventor)

    1981-01-01

    A saturable inductor switch for compressing the width and sharpening the rise time of high voltage pulses from a relatively slow rise time, high voltage generator to an electric discharge gas laser (EDGL) also provides a capability for efficient energy transfer from a high impedance primary source to an intermediate low impedance laser discharge network. The switch is positioned with respect to a capacitive storage device, such as a coaxial cable, so that when a charge build-up in the storage device reaches a predetermined level, saturation of the switch inductor releases or switches energy stored in the capactive storage device to the EDGL. Cascaded saturable inductor switches for providing output pulses having rise times of less than ten nanoseconds and a technique for magnetically biasing the saturable inductor switch are disclosed.

  16. Optical reprogramming with ultrashort femtosecond laser pulses

    Science.gov (United States)

    Uchugonova, Aisada; Breunig, Hans G.; Batista, Ana; König, Karsten

    2015-03-01

    The use of sub-15 femtosecond laser pulses in stem cell research is explored with particular emphasis on the optical reprogramming of somatic cells. The reprogramming of somatic cells into induced pluripotent stem (iPS) cells can be evoked through the ectopic expression of defined transcription factors. Conventional approaches utilize retro/lenti-viruses to deliver genes/transcription factors as well as to facilitate the integration of transcription factors into that of the host genome. However, the use of viruses may result in insertional mutations caused by the random integration of genes and as a result, this may limit the use within clinical applications due to the risk of the formation of cancer. In this study, a new approach is demonstrated in realizing non-viral reprogramming through the use of ultrashort laser pulses, to introduce transcription factors into the cell so as to generate iPS cells.

  17. Laser Pulse Heating of Spherical Metal Particles

    CERN Document Server

    Tribelsky, Michael I; Kivshar, Yuri S; Luk'yanchuk, Boris S; Khokhlov, Alexei R

    2011-01-01

    We consider a general problem of laser pulse heating of spherical metal particles with the sizes ranging from nanometers to millimeters. We employ the exact Mie solutions of the diffraction problem and solve heat-transfer equations to determine the maximum temperature at the particle surface as a function of optical and thermometric parameters of the problem. The main attention is paid to the case when the thermometric conductivity of the particle is much larger than that of the environment, as it is in the case of metal particles in fluids. We show that in this case at any given finite duration of the laser pulse the maximum temperature rise as a function of the particle size reaches an absolute maximum at a certain finite size of the particle, and we suggest simple approximate analytical expressions for this dependence which covers the entire range of variations of the problem parameters and agree well with direct numerical simulations.

  18. Rectangular Pulsed Laser-Electromagnetic Hybrid Accelerator

    International Nuclear Information System (INIS)

    Experimental investigation of impulse-bit and propellant consumption rate, or mass shot, per single pulse discharge was conducted to characterize the thrust performance of the rectangular laser-electromagnetic hybrid acceleration thruster with various propellant materials. From the result, alumina propellant showed significantly superior performance. The largest values of the measured impulse-bit, specific impulse and thrust efficiency were 49 μNsec, 6,200 sec and 22%, respectively.

  19. Study on pulsed excimer laser deposited films

    CERN Document Server

    Liu Jing Ru; Li Tie Jun; Yao Dong Sheng; Wang Li Ge; Yuan Xiao; Wang Sheng; Ye Xi Sheng

    2002-01-01

    Pulsed lasers of two different durations (30 ns, 500 fs) are used to deposit Hydrogen-free Diamond Like Carbon (DLC) films over large areas. Analysis of DLC films shows remarkable mechanical, optical, electrical, and chemical properties that are close to those of diamond. By optical emission spectroscopy and ion probe, the effects of plasma characteristic on DLC film are on experimentally studied. Amorphous silicon films deposited by PLD are also experimentally studied

  20. Theoretical Studies of the Output Pulse with Variation of the Pumping Pulse for RF Excited CO2 Pulsed Waveguide Laser

    Institute of Scientific and Technical Information of China (English)

    A Rauf; ZHOU Wei; XIN Jian-guo

    2006-01-01

    The behavior of a RF-excited waveguide CO2 laser in the pulse regime is studied theoretically. The output pulse evolution is studied by applying three types of pulses namely the square, sine and the triangular ones as the excitation pulses. The frequency dependence behavior of the output pulse is also presented.

  1. Heavy ion acceleration using femtosecond laser pulses

    CERN Document Server

    Petrov, G M; Thomas, A G R; Krushelnick, K; Beg, F N

    2015-01-01

    Theoretical study of heavy ion acceleration from ultrathin (<200 nm) gold foils irradiated by a short pulse laser is presented. Using two dimensional particle-in-cell simulations the time history of the laser bullet is examined in order to get insight into the laser energy deposition and ion acceleration process. For laser pulses with intensity , duration 32 fs, focal spot size 5 mkm and energy 27 Joules the calculated reflection, transmission and coupling coefficients from a 20 nm foil are 80 %, 5 % and 15 %, respectively. The conversion efficiency into gold ions is 8 %. Two highly collimated counter-propagating ion beams have been identified. The forward accelerated gold ions have average and maximum charge-to-mass ratio of 0.25 and 0.3, respectively, maximum normalized energy 25 MeV/nucleon and flux . Analytical model was used to determine a range of foil thicknesses suitable for acceleration of gold ions in the Radiation Pressure Acceleration regime and the onset of the Target Normal Sheath Acceleratio...

  2. Pulsed laser deposition of rare earth compounds

    CERN Document Server

    Stone, L A

    2001-01-01

    Magnetostrictive thin films have been deposited using various techniques such as sputtering and evaporation but the use of laser deposition has been limited. This research presents the results from pulsed laser deposition (PLD) of TbFe sub 2 , DyFe sub 2 and Terfenol-D thin films using an infra red Transversely Excited Atmospheric (TEA) CO sub 2 laser at lambda approx 10.6 mu m and an ultra violet Argon-Fluoride (ArF) excimer laser at lambda approx 193 nm. Results have showed that the TEA CO sub 2 laser under the range of conditions studied is not suitable for the production of magnetostrictive films. The problems experienced are a mixture of mostly fracture debris at low fluences (F approx 20 Jcm sup - sup 2) and melt droplets at high fluences (F approx 60 Jcm sup - sup 2). In all cases the destruction of the target is a major problem, with the Terfenol-D targets being the worst affected. Thin films produced were all iron rich. The use of an excimer laser has proved more successful in providing stoichiometri...

  3. Short Pulse Experimental Capability at the Nike Laser Facility

    Science.gov (United States)

    Weaver, J. L.; Chan, Y.; Gardner, J.; Giuliani, J.; Karasik, M.; Kehne, D.; Mostovych, A.; Obenschain, S.; Velikovich, A.; Schmitt, A.; Serlin, V.; Aglitskiy, Y.; Metzler, N.; Smyth, Z.; Terrell, S.

    2004-11-01

    Recent simulations demonstrated high gain for direct drive pellets compressed by a laser pulse incorporating a short pulse prior to the main pulse. Theoretical work has also shown that a short prepulse can create a tailored density profile that reduces the initial instability growth due to laser imprinting. A new short pulse (0.35-0.75 ns FWHM)is being added to the Nike KrF laser system to facilitate hydrodynamic experiments with short prepulses. This capability has been incorporated into the initial stages of the laser system and the propagation of these pulses through the angularly multiplexed amplifiers is being studied. Measurements of pulse shape and energy will be compared to simulations using the KrF physics code Orestes for the next to last amplifier of the laser system, the 20 cm x 20 cm e-beam pumped laser cell. The effects of amplified spontaneous emission (ASE) upon individual output pulses will be also discussed.

  4. Pulsed Nd-YAG laser in endodontics

    Science.gov (United States)

    Ragot-Roy, Brigitte; Severin, Claude; Maquin, Michel

    1994-12-01

    The purpose of this study was to establish an operative method in endodontics. The effect of a pulsed Nd:YAG laser on root canal dentin has been examined with a scanning electron microscope. Our first experimentation was to observe the impacts carried out perpendicularly to root canal surface with a 200 micrometers fiber optic in the presence of dye. Secondarily, the optical fiber was used as an endodontic instrument with black dye. The irradiation was performed after root canal preparation (15/100 file or 40/100 file) or directly into the canal. Adverse effects are observed. The results show that laser irradiation on root canal dentin surfaces induces a nonhomogeneous modified dentin layer, melted and resolidified dentin closed partially dentinal tubules. The removal of debris is not efficient enough. The laser treatment seems to be indicated only for endodontic and periapical spaces sterilization after conventional root canal preparation.

  5. Picoseconds pulse generation and pulse width determination processes of a distributed feedback dye laser

    International Nuclear Information System (INIS)

    A mathematical model has been developed to describe the dynamic emission of Nd-glass, distributed feedback dye laser (DFDL), and periodical grating temperature. The suggested model allows the investigation of the time behavior of Nd-glass laser and DFDL pulsed. Moreover, it allows studying the effect of the laser input parameters of Nd-glass laser on the spectral characteristics of the output DFDL pulses such as pulse width, delay time, and time separation

  6. Eye-safe,single-frequency pulsed all-fiber laser for Doppler wind lidar

    Institute of Scientific and Technical Information of China (English)

    Yuan Liu; Jiqiao Liu; Weibiao Chen

    2011-01-01

    @@ A single-frequency pulsed erbium-doped fiber(EDF)laser with master-oscillator Dower-amplifier comiguration at t bass nm is developed.A short-cavity,erbium-doped phosphate class fiber laser is utilized as a seeaer laser wntn a unewidtn of b khz and power of 40 mW.The seeder laser is modulated to be a pulse laser with a repetition rate of 10 kHz and pulse duration of 500 ns.The amplifier consists of two pre-amplifiers and one main amplifier.The detailed characteristics of the spectrum and linewidth of the amplifiers are presented.A pulse energy of 116 pJ and a linewidth of 1.1 MHz are obtained.This laser can be a candidate transmitter for an all-fiber Doppler wind lidar in the boundarv laver.%A single-frequency pulsed erbium-doped fiber (EDF) laser with master-oscillator power-amplifier configuration at 1533 nm is developed. A short-cavity, erbium-doped phosphate glass fiber laser is utilized as a seeder laser with a linewidth of 5 kHz and power of 40 mW. The seeder laser is modulated to be a pulse laser with a repetition rate of 10 kHz and pulse duration of 500 ns. The amplifier consists of two pre-amplifiers and one main amplifier. The detailed characteristics of the spectrum and linewidth of the amplifiers are presented. A pulse energy of 116 μJ and a linewidth of 1.1 MHz are obtained. This laser can be a candidate transmitter for an all-fiber Doppler wind lidar in the boundary layer.

  7. Twin-Pulse Soliton Operation of a Fiber Laser

    Institute of Scientific and Technical Information of China (English)

    W.; S.; Man; H.; Y.; Tam

    2003-01-01

    We report on the experimental observation of a novel type of twin-pulse soliton in a passively mode-locked fiber ring laser. Twin-pulse soliton interaction in the laser cavity are also experimentally investigated and compared with those of the single pulse soliton.

  8. [Effect of pulsed CO2-laser irradiation on bone tissue].

    Science.gov (United States)

    Kholodnov, S E

    1985-01-01

    Different dynamic effects on biological tissue caused by pulsed laser radiation are described. It is shown that the parameters of these effects which take place on the bone tissue affected by pulsed CO2-laser radiation are directly dependent on the parameters of these pulses and may be predicted for any concrete application. PMID:3931698

  9. Resonant infrared pulsed laser deposition of cyclic olefin copolymer films

    Energy Technology Data Exchange (ETDEWEB)

    Singaravelu, Senthil R. [ODU, JLAB; Klopf, John M. [JLAB; Schriver, Kenneth E. [Vanderbilt; Park, HyeKyoung [JLAB; Kelley, Michael J. [JLAB; Haglund, Jr., Richard F. [Vanderbilt

    2013-08-01

    Barrier materials on thin-film organic optoelectronic devices inhibit the uptake of water, oxygen, or environmental contaminants, and fabricating them is a major challenge. By definition, these barrier layers must be insoluble, so the usual routes to polymer- or organic-film deposition by spin coating are not problematic. In this paper, we report comparative studies of pulsed laser deposition of cyclic olefin copolymer (COC), an excellent moisture barrier and a model system for a larger class of protective materials that are potentially useful in organic electronic devices, such as organic light-emitting diodes (OLEDs). Thin films of COC were deposited by resonant and nonresonant infrared pulsed laser ablation of solid COC targets, using a free-electron laser tuned to the 3.43 μm C–H stretch of the COC, and a high-intensity nanosecond Q-switched laser operated at 1064 nm. The ablation craters and deposited films were characterized by scanning-electron microscopy, Fourier-transform infrared spectrometry, atomic-force microscopy, high-resolution optical microscopy, and surface profilometry. Thermal-diffusion calculations were performed to determine the temperature rise induced in the film at the C–H resonant wavelength. The results show that resonant infrared pulsed laser deposition (RIR-PLD) is an effective, low-temperature thin-film deposition technique that leads to evaporation and deposition of intact molecules in homogeneous, smooth films. Nonresonant PLD, on the other hand, leads to photothermal damage, degradation of the COC polymers, and to the deposition only of particulates.

  10. Drop deformation by laser-pulse impact

    CERN Document Server

    Gelderblom, Hanneke; Klein, Alexander L; Bouwhuis, Wilco; Lohse, Detlef; Villermaux, Emmanuel; Snoeijer, Jacco H

    2015-01-01

    A free-falling absorbing liquid drop hit by a nanosecond laser-pulse experiences a strong recoil-pressure kick. As a consequence, the drop propels forward and deforms into a thin sheet which eventually fragments. We study how the drop deformation depends on the pulse shape and drop properties. We first derive the velocity field inside the drop on the timescale of the pressure pulse, when the drop is still spherical. This yields the kinetic-energy partition inside the drop, which precisely measures the deformation rate with respect to the propulsion rate, before surface tension comes into play. On the timescale where surface tension is important the drop has evolved into a thin sheet. Its expansion dynamics is described with a slender-slope model, which uses the impulsive energy-partition as an initial condition. Completed with boundary integral simulations, this two-stage model explains the entire drop dynamics and its dependance on the pulse shape: for a given propulsion, a tightly focused pulse results in a...

  11. Wavelength stabilisation during current pulsing of tapered laser

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin

    2009-01-01

    The use of external feedback to stabilise the frequency of a tapered laser during current pulsing is reported. Using this technique more than 20 W of peak power in 60 ns pulses from the tapered laser is obtained and owing to the external feedback, the laser is tunable in the 778-808 nm range. The...

  12. The Electron Trajectory in a Relativistic Femtosecond Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    He Feng; Yu Wei; Lu Peixiang; Xu Han; Shen Baifei; Li Ruxin; Xu Zhizhan

    2005-01-01

    In this report, we start from Lagrange equation and analyze theoretically the electron dynamics in electromagnetic field. By solving the relativistic government equations of electron,the trajectories of an electron in plane laser pulse, focused laser pulse have been given for different initial conditions. The electron trajectory is determined by its initial momentum, the amplitude,spot size and polarization of the laser pulse. The optimum initial momentum of the electron for LSS (laser synchrotron source) is obtained. Linear polarized laser is more advantaged than circular polarized laser for generating harmonic radiation.

  13. Amplification of Short Pulse High Power UV Laser

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    At recent year, with the development of CPA and other amplification technology, laser intensity achieves great increase and laser power can be high to PW(105) now, this ultrashort pulse lasers offer scientists a route to investigate laser-matter interaction in an absolute new regime.So far the researches on ultrashort pulse laser-matter interaction concentrated on infrared regime, yet ultraviolet laser has the advantage in intense field physics and ICF researches for its short wavelength and less nonlinear effects. KrF excimer is the best medium in UV ultrashort pulse amplification for its small saturation energy and high contrast ratio accessible.

  14. Pulsed laser deposition: the road to hybrid nanocomposites coatings and novel pulsed laser adaptive technique.

    Science.gov (United States)

    Serbezov, Valery

    2013-01-01

    The applications of Pulsed Laser Deposition (PLD) for producing nanoparticles, nanostructures and nanocomposites coatings based on recently developed laser ablating techniques and their convergence are being reviewed. The problems of in situ synthesis of hybrid inorganic-organic nanocomposites coatings by these techniques are being discussed. The novel modification of PLD called Pulsed Laser Adaptive Deposition (PLAD) technique is presented. The in situ synthesized inorganic/organic nanocomposites coatings from Magnesium (Mg) alloy/Rhodamine B and Mg alloy/ Desoximetasone by PLAD are described. The trends, applications and future development of discussed patented methods based on the laser ablating technologies for producing hybrid nanocomposite coatings have also been discussed in this review. PMID:22747717

  15. Measurement Issues In Pulsed Laser Propulsion

    International Nuclear Information System (INIS)

    Various measurement techniques have been used throughout the over 40-year history of laser propulsion. Often, these approaches suffered from inconsistencies in definitions of the key parameters that define the physics of laser ablation impulse generation. Such parameters include, but are not limited to the pulse energy, spot area, imparted impulse, and ablated mass. The limits and characteristics of common measurement techniques in each of these areas will be explored as they relate to laser propulsion. The idea of establishing some standardization system for laser propulsion data is introduced in this paper, so that reported results may be considered and studied by the general community with more certain understanding of particular merits and limitations. In particular, it is the intention to propose a minimum set of requirements a literature study should meet. Some international standards for measurements are already published, but modifications or revisions of such standards may be necessary for application to laser ablation propulsion. Issues relating to development of standards will be discussed, as well as some examples of specific experimental circumstances in which standardization would have prevented misinterpretation or misuse of past data.

  16. Pulsed laser fluorometry for environmental monitoring

    Science.gov (United States)

    Saunders, G. C.; Martin, J. C.; Jett, J. H.; Wilder, M. E.; Martinez, A.; Bentley, B. F.; Lopez, J.; Hutson, L.

    A compact pulsed laser fluorometer has been incorporated into a continuous flow system developed to detect acetylcholinesterase (AChE) inhibitors and/or primary amine compounds in air and water. A pulsed nitrogen laser pumped dye laser excites fluorescent reactants which flow continuously through a quartz flow cell. Data are collected, analyzed, and displayed using a Macintosh II personal computer. For detection of cholinesterase inhibitors the fluorogenic substrate N methylindoxyl acetate is used to monitor the activity of immobilized enzyme. Presence of inhibitors results in a decrease of steady state fluorescence. Detection of compounds containing primary amines is based on their reaction with fluorescamine to rapidly produce intensely fluorescent products. Compounds of interest to our research were amino acids, peptides, and proteins. An increase in steady state fluorescence could be cause to evaluate the reasons for the change. The detection limit of the protein, bovine serum albumin (BSA) in water, is 10 ppT. Nebulized BSA concentrated by the LANL air sampler can be detected at sub ppT original air concentration.

  17. Nonparaxial propagation of ultrashort laser pulses in plasma channels

    International Nuclear Information System (INIS)

    The propagation characteristics of an ultrashort laser pulse in a preformed plasma channel are analyzed. The plasma channel is assumed to be parabolic and unperturbed by the laser pulse. Solutions to the wave equation beyond the paraxial approximation are derived that include finite pulse length effects and group velocity dispersion. When the laser pulse is mismatched within the channel, betatron oscillations arise in the laser pulse envelope. A finite pulse length leads to a spread in the laser wave number and consequently a spread in betatron wave number. This results in phase mixing and damping of the betatron oscillation. The damping distance characterizing the phase mixing of the betatron oscillation is derived, as is the dispersion distance characterizing the longitudinal spreading of the pulse. copyright 1999 The American Physical Society

  18. Pulsed laser deposition of rare earth compounds

    International Nuclear Information System (INIS)

    Magnetostrictive thin films have been deposited using various techniques such as sputtering and evaporation but the use of laser deposition has been limited. This research presents the results from pulsed laser deposition (PLD) of TbFe2, DyFe2 and Terfenol-D thin films using an infra red Transversely Excited Atmospheric (TEA) CO2 laser at λ ∼10.6 μm and an ultra violet Argon-Fluoride (ArF) excimer laser at λ ∼ 193 nm. Results have showed that the TEA CO2 laser under the range of conditions studied is not suitable for the production of magnetostrictive films. The problems experienced are a mixture of mostly fracture debris at low fluences (F ∼ 20 Jcm-2) and melt droplets at high fluences (F∼ 60 Jcm-2). In all cases the destruction of the target is a major problem, with the Terfenol-D targets being the worst affected. Thin films produced were all iron rich. The use of an excimer laser has proved more successful in providing stoichiometric transfer of the target material, although this is only true under certain conditions. When a rotating target was used the growth of stoichiometric films was difficult due to a process related to the high photon energy of the excimer laser. The use of single spot irradiation did provide films of near stoichiometric composition over a wide range of fluences. Magnetostrictions for both TbFe2 and DyFe2 were found to be quite similar λ// ∼ 280 ppm at an applied field of 980 kAm-1. The results for Terfenol-D films were quite low with λ// ∼ 190 ppm at 980 kAm-1 but these showed signs of being adversely affected by stresses created during deposition. (author)

  19. Landau damping of a driven plasma wave from laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Bu Zhigang [Department of Physics, Shanghai University, Shanghai 200444 (China); Ji Peiyong [Department of Physics, Shanghai University, Shanghai 200444 (China); The Shanghai Key Lab of Astrophysics, Shanghai 200234 (China)

    2012-01-15

    The interaction between a laser pulse and a driven plasma wave with a phase velocity approaching the speed of light is studied, and our investigation is focused on the Gaussian laser pulse. It is demonstrated that when the resonance condition between the plasma wave and the laser pulse is satisfied, the Landau damping phenomenon of the plasma wave originated from the laser pulse will emerge. The dispersion relations for the plasma waves in resonance and non-resonance regions are obtained. It is proved that the Landau damping rate for a driven plasma wave is {gamma}>0 in the resonance region, so the laser pulse can produce an inverse damping effect, namely Landau growth effect, which leads an instability for the plasma wave. The Landau growth means that the energy is transmitted from the laser pulse to the plasma wave, which could be an effective process for enhancing the plasma wave.

  20. Guiding of high intensity ultrashort laser pulses in plasma channels produced with the dual laser pulse ignitor-heater technique

    International Nuclear Information System (INIS)

    The authors present results of experimental investigations of laser guiding in plasma channels. A new technique for plasma channel creation, the Ignitor-Heater scheme is proposed and experimentally tested in hydrogen and nitrogen. It makes use of two laser pulses. The Ignitor, an ultrashort ( 5 x 1017 W/cm2, 75 fs laser pulse

  1. Optodynamic analysis of pulsed-laser processing with a Nd:YAG laser

    OpenAIRE

    Strgar, Simon; Možina, Janez

    2015-01-01

    Laser drilling and laser marking of metals with a pulsed Nd:YAG laser are discussed. Some characteristics of pulsed-laser processing and the possibilities of process optodynamic analysis are presented for the laser-drilling of aluminium. The optodynamic analysis is based on observation of generated shock waves, which propagate in the material as well as in the surrounding air during laser processing. For the detection of laser-induced shock waves in the air and for measurements of their chara...

  2. Controlling electron injection in laser plasma accelerators using multiple pulses

    International Nuclear Information System (INIS)

    Use of counter-propagating pulses to control electron injection in laser-plasma accelerators promises to be an important ingredient in the development of stable devices. We discuss the colliding pulse scheme and associated diagnostics.

  3. An ultra short pulse reconstruction software applied to the GEMINI high power laser system

    Science.gov (United States)

    Galletti, Mario; Galimberti, Marco; Hooker, Chris; Chekhlov, Oleg; Tang, Yunxin; Bisesto, Fabrizio Giuseppe; Curcio, Alessandro; Anania, Maria Pia; Giulietti, Danilo

    2016-09-01

    The GRENOUILLE traces of Gemini pulses (15 J, 30 fs, PW, shot per 20 s) were acquired in the Gemini Target Area PetaWatt at the Central Laser Facility (CLF), Rutherford Appleton Laboratory (RAL). A comparison between the characterizations of the laser pulse parameters made using two different types of algorithms: Video Frog and GRenouille/FrOG (GROG), was made. The temporal and spectral parameters came out to be in great agreement for the two kinds of algorithms. In this experimental campaign it has been showed how GROG, the developed algorithm, works as well as VideoFrog algorithm with the PetaWatt pulse class.

  4. Numerical simulation of copper ablation by ultrashort laser pulses

    OpenAIRE

    Ding, PengJi; Hu, BiTao; Li, Yuhong

    2011-01-01

    Using a modified self-consistent one-dimensional hydrodynamic lagrangian fluid code, laser ablation of solid copper by ultrashort laser pulses in vacuum was simulated to study fundamental mechanisms and to provide a guide for drilling periodic microholes or microgratings on the metal surface. The simulated laser ablation threshold is a approximate constancy in femtosecond regime and increases as the square root of pulse duration in picosecond regime. The ablation depth as a function of pulse ...

  5. Optimizing chirped laser pulse parameters for electron acceleration in vacuum

    Energy Technology Data Exchange (ETDEWEB)

    Akhyani, Mina; Jahangiri, Fazel; Niknam, Ali Reza; Massudi, Reza, E-mail: r-massudi@sbu.ac.ir [Laser and Plasma Research Institute, Shahid Beheshti University, Tehran 1983969411 (Iran, Islamic Republic of)

    2015-11-14

    Electron dynamics in the field of a chirped linearly polarized laser pulse is investigated. Variations of electron energy gain versus chirp parameter, time duration, and initial phase of laser pulse are studied. Based on maximizing laser pulse asymmetry, a numerical optimization procedure is presented, which leads to the elimination of rapid fluctuations of gain versus the chirp parameter. Instead, a smooth variation is observed that considerably reduces the accuracy required for experimentally adjusting the chirp parameter.

  6. Thor: Modeling of a Megabar Class Pulsed Power Accelerator

    Science.gov (United States)

    Haill, T. A.; Reisman, D. B.; Stoltzfus, B. S.; Austin, K. N.; Stygar, W. A.; Brown, J. L.; Davis, J.-P.; Waisman, E. M.

    2015-06-01

    Thor is a compact, economical machine to drive megabar-class shockless compression material physics experiments and multi-mega-ampere HEDP experiments for the physics community. It is capable of driving peak currents up to 7 MA with rise times of 200-500 ns, resulting in material pressures between 1 to 5 Mbar depending upon the load design, and incorporates a pulse tailoring capability required to maintain shockless loading of many materials. Thor is modular in nature with 200 capacitive bricks triggered in groups by independent, de-coupled switches. The current pulse at the load is a simple linear combination of the 200 time-shifted basis pulses. This enables a variety of experiments including shockless compression experiments using smooth ramped pulses, shock-ramp compression experiments using tailored pulses, and strength measurement experiments using flat top pulses. This paper overviews the Thor design and describes an equivalent circuit model of the machine that drives MHD simulations of the load region. 3D ALEGRA MHD simulations explore topics such as the uniformity of the magnetic field along the stripline load and the design modifications to improve uniformity. Optimized current drives and simulations of the aforementioned applications are also presented. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE's NNSA under Contract DE-AC04-94AL85000.

  7. Development of short pulse soft x-ray lasers

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva, L.B.; MacGowan, B.J.; Koch, J.A.; Mrowka, S.; Matthews, D.L.; Eder, D.; London, R.

    1993-02-01

    X-ray lasers with pulse duration shorter than 20 ps allow the possibility of imaging laser produced plasmas with {mu}m resolution. In addition, the high peak brightness of these new sources will allow us to study nonlinear optics in the xuv region. In this paper we will describe our efforts to produce collisionally pumped short pulse x-ray lasers. Initial results, which have produced {approximately} 45 ps (FWHM) x-ray lasers, using a double pulse irradiation technique are presented along with a discussion of the prospects for reducing the pulse width.

  8. Femtosecond laser ablation of Au film around single pulse threshold

    Institute of Scientific and Technical Information of China (English)

    Xiaochang Ni; Ching-Yue Wang; Yinzhong Wu; Li Yang; Wei Jia; Lu Chai

    2006-01-01

    @@ Ablation process of 1-kHz femtosecond lasers (pulse duration of 148 fs, wavelength of 775 nm) of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D2 of the ablated craters and the laser fluence φo. From the plot of the accumulated laser fluence Nφth(N) and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold are in good agreement with the theoretical calculation.

  9. Noncontact microsurgery of living cell membrane using femtosecond laser pulses

    Science.gov (United States)

    Ilina, I. V.; Ovchinnikov, A. V.; Sitnikov, D. S.; Chefonov, O. V.; Agranat, M. B.; Mikaelyan, A. S.

    2013-06-01

    Near-infrared femtosecond laser pulses were applied to initiate reversible permeabilization of cell membrane and inject extrinsic substances into the target cells. Successful laser-based injection of a membrane impermeable dye, as well as plasmid DNA was demonstrated.

  10. 25 years of pulsed laser deposition

    Science.gov (United States)

    Lorenz, Michael; Ramachandra Rao, M. S.

    2014-01-01

    It is our pleasure to introduce this special issue appearing on the occasion of the 25th anniversary of pulsed laser deposition (PLD), which is today one of the most versatile growth techniques for oxide thin films and nanostructures. Ever since its invention, PLD has revolutionized the research on advanced functional oxides due to its ability to yield high-quality thin films, multilayers and heterostructures of a variety of multi-element material systems with rather simple technical means. We appreciate that the use of lasers to deposit films via ablation (now termed PLD) has been known since the 1960s after the invention of the first ruby laser. However, in the first two decades, PLD was something of a 'sleeping beauty' with only a few publications per year, as shown below. This state of hibernation ended abruptly with the advent of high T c superconductor research when scientists needed to grow high-quality thin films of multi-component high T c oxide systems. When most of the conventional growth techniques failed, the invention of PLD by T (Venky) Venkatesan clearly demonstrated that the newly discovered high-T c superconductor, YBa2Cu3O7-δ , could be stoichiometrically deposited as a high-quality nm-thin film with PLD [1]. As a remarkable highlight of this special issue, Venkatesan gives us his very personal reminiscence on these particularly innovative years of PLD beginning in 1986 [2]. After Venky's first paper [1], the importance of this invention was realized worldwide and the number of publications on PLD increased exponentially, as shown in figure 1. Figure 1. Figure 1. Published items per year with title or topic PLD. Data from Thomson Reuters Web of Knowledge in September 2013. After publication of Venky's famous paper in 1987 [1], the story of PLD's success began with a sudden jump in the number of publications, about 25 years ago. A first PLD textbook covering its basic understanding was soon published, in 1994, by Chrisey and Hubler [3]. Within a

  11. Ultrashort Pulse Laser Ablation for Depth Profiling of Bacterial Biofilms

    OpenAIRE

    Milasinovic, Slobodan; Liu, Yaoming; Gasper, Gerald L.; Zhao, Youbo; Johnston, Joanna L.; Gordon, Robert J.; Hanley, Luke

    2010-01-01

    Sample ablation by pulsed lasers is one option for removing material from a sample surface for in situ depth profiling during imaging mass spectrometry, but ablation is often limited by laser-induced damage of the remaining material. A preliminary evaluation was performed of sub-100 fs, 800 nm pulsed laser ablation for depth profiling of bacterial biofilms grown on glass by the drip flow method. Electron and optical microscopy were combined with laser desorption vacuum ultraviolet postionizat...

  12. PHASE NOISE COMPARISON OF SHORT PULSE LASER SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Shukui Zhang; Stephen Benson; John Hansknecht; David Hardy; George Neil; Michelle D. Shinn

    2006-08-27

    This paper describes phase noise measurements of several different laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on state-of-the-art short pulse lasers, especially drive lasers for photocathode injectors. Phase noise comparison of the FEL drive laser, electron beam and FEL laser output also will be presented.

  13. Generation of Intense THz Pulsed Lasers Pumped Strongly by CO2 Pulsed Lasers

    Institute of Scientific and Technical Information of China (English)

    QI Chun-Chao; CHENG Zu-Hai

    2009-01-01

    A theoretical method dealing with two intense laser fields interacting with a three-level molecular system is proposed.A discussion is presented on the properties of the solutions for time-independent and time-dependent absorption coefficients and gain coemcient on resonance for strong laser fields,based on analytic evaluation of the rate equations for a homogeneously broadened,three-level molecular system.The pump intensity range can be estimated according to the analytic expression of pump saturation intensity.The effects of pulse width,gas pressure and path length on the energy absorbed from pump light are studied theoretically.The results can be applied to the analysis of pulsed,optically pumped terahertz lasers.

  14. Vulnerability of CMOS image sensors in megajoule class laser harsh environment

    OpenAIRE

    Goiffon, Vincent; Girard, Sylvain; Magnan, Pierre; Chabane, Aziouz; Paillet, Philippe; Cervantes, Paola; Martin-Gonthier, Philippe; Baggio, Jacques; Estribeau, Magali; Bourgade, Jean-Luc; Darbon, Stéphane; Rousseau, Adrien; Glebov, Vladimir Yu; Pien, Gregory; Sangster, Thomas C.

    2012-01-01

    CMOS image sensors (CIS) are promising candidates as part of optical imagers for the plasma diagnostics devoted to the study of fusion by inertial confinement. However, the harsh radiative environment of Megajoule Class Lasers threatens the performances of these optical sensors. In this paper, the vulnerability of CIS to the transient and mixed pulsed radiation environment associated with such facilities is investigated during an experiment at the OMEGA facility at the Laboratory for Laser En...

  15. Pulsed laser deposition of pepsin thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kecskemeti, G. [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dom ter 9 (Hungary)]. E-mail: kega@physx.u-szeged.hu; Kresz, N. [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dom ter 9 (Hungary); Smausz, T. [Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6720 Szeged, Dom ter 9 (Hungary); Hopp, B. [Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6720 Szeged, Dom ter 9 (Hungary); Nogradi, A. [Department of Ophthalmology, University of Szeged, H-6720, Szeged, Koranyi fasor 10-11 (Hungary)

    2005-07-15

    Pulsed laser deposition (PLD) of organic and biological thin films has been extensively studied due to its importance in medical applications among others. Our investigations and results on PLD of a digestion catalyzing enzyme, pepsin, are presented. Targets pressed from pepsin powder were ablated with pulses of an ArF excimer laser ({lambda} = 193 nm, FWHM = 30 ns), the applied fluence was varied between 0.24 and 5.1 J/cm{sup 2}. The pressure in the PLD chamber was 2.7 x 10{sup -3} Pa. The thin layers were deposited onto glass and KBr substrates. Our IR spectroscopic measurements proved that the chemical composition of deposited thin films is similar to that of the target material deposited at 0.5 and 1.3 J/cm{sup 2}. The protein digesting capacity of the transferred pepsin was tested by adapting a modified 'protein cube' method. Dissolution of the ovalbumin sections proved that the deposited layers consisted of catalytically active pepsin.

  16. Production of picosecond, kilojoule, and petawatt laser pulses via Raman amplification of nanosecond pulses.

    Science.gov (United States)

    Trines, R M G M; Fiúza, F; Bingham, R; Fonseca, R A; Silva, L O; Cairns, R A; Norreys, P A

    2011-09-01

    Raman amplification in plasma has been promoted as a means of compressing picosecond optical laser pulses to femtosecond duration to explore the intensity frontier. Here we show for the first time that it can be used, with equal success, to compress laser pulses from nanosecond to picosecond duration. Simulations show up to 60% energy transfer from pump pulse to probe pulse, implying that multikilojoule ultraviolet petawatt laser pulses can be produced using this scheme. This has important consequences for the demonstration of fast-ignition inertial confinement fusion. PMID:21981507

  17. Intense laser pulse propagation in capillary discharge plasma channels

    International Nuclear Information System (INIS)

    Optical guiding of intense laser pulses is required for plasma-based accelerator concepts such as the laser wakefield accelerator. Reported experiments have successfully transported intense laser pulses in the hollow plasma column produced by a capillary discharge. The hollow plasma has an index of refraction which peaks on-axis, thus providing optical guiding which overcomes beam expansion due to diffraction. In more recent experiments at Hebrew University, 800 nm wavelength, 0.1 mJ, 100 fs pulses have been guided in ∼300 micron radius capillaries over distances as long as 6.6 cm. Simulations of these experiments using a 2-D nonlinear laser propagation model produce the expected optical guiding, with the laser pulse radius rL exhibiting oscillations about the equilibrium value predicted by an analytical envelope equation model. The oscillations are damped at the front of the pulse and grow in amplitude in the back of the pulse. This growth and damping is attributed to finite pulse length effects. Simulations also show that further ionization of the discharge plasma by the laser pulse may hollow the laser pulse and introduce modulations in the spot size. This ionization-defocusing effect is expected to be significant at the high intensities required for accelerator application. Capillary discharge experiments at much higher intensities are in progress on the Naval Research Laboratory T3 laser, and preliminary results are reported. copyright 1999 American Institute of Physics

  18. Solid propellant extinction by laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Novozhilov, B.V. [Russian Academy of Science, Moscow (Russian Federation). Inst. of Chemical Physics; Zanotti, C.; Giuliani, P. [Istituto per la Tecnologia dei Materiali e dei Processi Energetici TeMPE - C.N.R., Milano (Italy)

    2000-12-01

    The possibility to generate a combustion transient of a composite AP.HTPB/86.14 propellant, burning under steady state conditions, was experimentally demonstrated by using a CO{sub 2} laser energy pulse. The experimental results point out that the burning propellant behavior can be defined by the curves separating, for every operating pressure, the continuous burning from the extinction solutions. In this paper, a simplified theoretical approach gives a phenomenological explanation of the energy pulse effect on the combustion process and the consequent burning propellant response after the deradiation transient. In the framework of this study the extinction condition is formulated in terms of the minimum temperature that causes the burning propellant to quench at the Pressure Deflagration Limit. The proposed theoretical work is aimed, first of all, to determine the critical radiant flux values, for different operating pressures, below which the burning propellant extinction is never achieved even if the laser pulse duration tends to infinity. Then, the extinction boundaries are defined choosing two different approximate approaches that take into account the ratio between the condensed phase relaxation time and the radiant energy pulse duration. Two limit cases, defined as slow/fast interaction of the radiant energy with the combustion process, can be used to describe the burning propellant extinction phenomena, and the results of this work indicate that the general trend of the computed boundary limits reproduces the experimental data. (orig.) [German] Mit einem CO{sub 2}-Laser wurde die Moeglichkeit demonstriert, einen Uebergangszustand der Verbrennung eines Komposit-Treibstoffes AP.HTPB/86.14 zu erzeugen, der unter stationaeren Bedingungen brannte. Die experimentellen Ergebnisse zeigen auf, dass das Verbrennungsverhalten durch die Kurven bestimmt werden kann, die fuer jeden Arbeitsdruck die kontinuierlichen Verbrennungsloesungen von den Ausloeschloesung trennen

  19. A new pulsed laser deposition technique: scanning multi-component pulsed laser deposition method.

    Science.gov (United States)

    Fischer, D; de la Fuente, G F; Jansen, M

    2012-04-01

    The scanning multi-component pulsed laser deposition (PLD) method realizes uniform depositions of desired coatings by a modified pulsed laser deposition process, preferably with a femto-second laser-system. Multi-component coatings (single or multilayered) are thus deposited onto substrates via laser induced ablation of segmented targets. This is achieved via horizontal line-scanning of a focused laser beam over a uniformly moving target's surface. This process allows to deposit the desired composition of the coating simultaneously, starting from the different segments of the target and adjusting the scan line as a function of target geometry. The sequence and thickness of multilayers can easily be adjusted by target architecture and motion, enabling inter/intra layer concentration gradients and thus functional gradient coatings. This new, simple PLD method enables the achievement of uniform, large-area coatings. Case studies were performed with segmented targets containing aluminum, titanium, and niobium. Under the laser irradiation conditions applied, all three metals were uniformly ablated. The elemental composition within the rough coatings obtained was fixed by the scanned area to Ti-Al-Nb = 1:1:1. Crystalline aluminum, titanium, and niobium were found to coexist side by side at room temperature within the substrate, without alloy formation up to 600 °C. PMID:22559543

  20. Amplifier similariton laser with extra-broad bandwidth output pulse

    Science.gov (United States)

    Korobko, D. A.; Okhotnikov, O. G.; Zolotovskii, I. O.

    2016-03-01

    We propose an advanced scheme of amplifier similariton laser providing an output pulse spectrum much wider than the gain bandwidth. The upgrade is an additional dispersive element introduced into the cavity to locally increase the peak pulse power. The proposed scheme demonstrates a drastic increase in the output pulse spectrum width, reduction of the pulse duration, and an increase in the output peak pulse power after compression.

  1. High power high repetition rate VCSEL array side-pumped pulsed blue laser

    Science.gov (United States)

    van Leeuwen, Robert; Zhao, Pu; Chen, Tong; Xu, Bing; Watkins, Laurence; Seurin, Jean-Francois; Xu, Guoyang; Miglo, Alexander; Wang, Qing; Ghosh, Chuni

    2013-03-01

    High power, kW-class, 808 nm pump modules based on the vertical-cavity surface-emitting laser (VCSEL) technology were developed for side-pumping of solid-state lasers. Two 1.2 kW VCSEL pump modules were implemented in a dual side-pumped Q-switched Nd:YAG laser operating at 946 nm. The laser output was frequency doubled in a BBO crystal to produce pulsed blue light. With 125 μs pump pulses at a 300 Hz repetition rate 6.1 W QCW 946 nm laser power was produced. The laser power was limited by thermal lensing in the Nd:YAG rod.

  2. Pulsed laser ablation of solids basics, theory and applications

    CERN Document Server

    Stafe, Mihai; Puscas, Niculae N

    2014-01-01

    The book introduces ‘the state of the art' of pulsed laser ablation and its applications. It is based on recent theoretical and experimental studies. The book reaches from the basics to advanced topics of pulsed laser ablation. Theoretical and experimental fundamental phenomena involved in pulsed laser ablation are discussed with respect to material properties, laser wavelength, fluence and intensity regime of the light absorbed linearly or non-linearly in the target material. The energy absorbed by the electrons leads to atom/molecule excitation, ionization and/or direct chemical bond breaking and is also transferred to the lattice leading to material heating and phase transitions. Experimental  non-invasive optical methods for analyzing these phenomena in real time are described. Theoretical models for pulsed laser ablation and phase transitions induced by laser beams and laser-vapour/plasma interaction during the plume expansion above the target are also presented. Calculations of the ablation speed and...

  3. Generation of ultrashort electron bunches by colliding laser pulses

    International Nuclear Information System (INIS)

    A proposed laser-plasma based relativistic electron source [E. Esarey et al., Phys. Rev. Lett. 79, 2682 (1997)] using laser triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counter-propagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses

  4. Development of frequency tunable Ti:sapphire laser and dye laser pumped by a pulsed Nd:YAG laser

    International Nuclear Information System (INIS)

    We investigated lasing characteristics of two kinds of tunable laser, liquid dye laser and solid Ti:sapphire crystal laser, pumped by high pulse repetition rate Nd:YAG laser. Dye laser showed drastically reduced pulsewidth compared with that of pump laser and it also contained large amount of amplified spontaneous emission. Ti:sapphire laser showed also reduced pulsewidth. But, the laser conversion pump laser and Ti:sapphire laser pulse, we used a Brewster-cut Pockel's cell for Q-switching. The laser was frequency doubled by a type I BBO crystal outside of the cavity.

  5. Solitary Nanostructures Produced by Ultrashort Laser Pulse.

    Science.gov (United States)

    Inogamov, Nail A; Zhakhovsky, Vasily V; Khokhlov, Viktor A; Petrov, Yury V; Migdal, Kirill P

    2016-12-01

    Laser-produced surface nanostructures show considerable promise for many applications while fundamental questions concerning the corresponding mechanisms of structuring are still debated. Here, we present a simple physical model describing those mechanisms happened in a thin metal film on dielectric substrate irradiated by a tightly focused ultrashort laser pulse. The main ingredients included into the model are (i) the film-substrate hydrodynamic interaction, melting and separation of the film from substrate with velocity increasing with increase of absorbed fluence; (ii) the capillary forces decelerating expansion of the expanding flying film; and (iii) rapid freezing into a solid state if the rate of solidification is comparable or larger than hydrodynamic velocities. The developed model and performed simulations explain appearance of microbump inside the focal spot on the film surface. The model follows experimental findings about gradual transformation of the bump from small parabolic to a conical shape and to the bump with a jet on its tip with increasing fluence. Disruption of the bump as a result of thinning down the liquid film to a few interatomic distances or due to mechanical break-off of solid film is described together with the jetting and formation of one or many droplets. Developed theory opens door for optimizing laser parameters for intended nanostructuring in applications. PMID:27044306

  6. Solitary Nanostructures Produced by Ultrashort Laser Pulse

    Science.gov (United States)

    Inogamov, Nail A.; Zhakhovsky, Vasily V.; Khokhlov, Viktor A.; Petrov, Yury V.; Migdal, Kirill P.

    2016-04-01

    Laser-produced surface nanostructures show considerable promise for many applications while fundamental questions concerning the corresponding mechanisms of structuring are still debated. Here, we present a simple physical model describing those mechanisms happened in a thin metal film on dielectric substrate irradiated by a tightly focused ultrashort laser pulse. The main ingredients included into the model are (i) the film-substrate hydrodynamic interaction, melting and separation of the film from substrate with velocity increasing with increase of absorbed fluence; (ii) the capillary forces decelerating expansion of the expanding flying film; and (iii) rapid freezing into a solid state if the rate of solidification is comparable or larger than hydrodynamic velocities. The developed model and performed simulations explain appearance of microbump inside the focal spot on the film surface. The model follows experimental findings about gradual transformation of the bump from small parabolic to a conical shape and to the bump with a jet on its tip with increasing fluence. Disruption of the bump as a result of thinning down the liquid film to a few interatomic distances or due to mechanical break-off of solid film is described together with the jetting and formation of one or many droplets. Developed theory opens door for optimizing laser parameters for intended nanostructuring in applications.

  7. Optical gene transfer by femtosecond laser pulses

    Science.gov (United States)

    Konig, Karsten; Riemann, Iris; Tirlapur, Uday K.

    2003-07-01

    Targeted transfection of cells is an important technique for gene therapy and related biomedical applications. We delineate how high-intensity (1012 W/cm2) near-infrared (NIR) 80 MHz nanojoule femtosecond laser pulses can create highly localised membrane perforations within a minute focal volume, enabling non-invasive direct transfection of mammalian cells with DNA. We suspended Chinese hamster ovarian (CHO), rat kangaroo kidney epithelial (PtK2) and rat fibroblast cells in 0.5 ml culture medium in a sterile miniaturized cell chamber (JenLab GmbH, Jena, Germany) containing 0.2 μg plasmid DNA vector pEGFP-N1 (4.7 kb), which codes for green fluorescent protein (GFP). The NIR laser beam was introduced into a femtosecond laser scanning microscope (JenLab GmbH, Jena, Germany; focussed on the edge of the cell membrane of a target cell for 16 ms. The integration and expression efficiency of EGFP were assessed in situ by two-photon fluorescence-lifetime imaging using time-correlated single photon counting. The unique capability to transfer foreign DNA safely and efficiently into specific cell types (including stem cells), circumventing mechanical, electrical or chemical means, will have many applications, such as targeted gene therapy and DNA vaccination.

  8. Glass drilling by longitudinally excited CO2 laser with short laser pulse

    Science.gov (United States)

    Uno, Kazuyuki; Yamamoto, Takuya; Akitsu, Tetsuya; Jitsuno, Takahisa

    2015-03-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance, and a spark-gap switch. The laser pulse had a spike pulse and a pulse tail. The energy of the pulse tail was controlled by adjusting medium gas. Using three types of CO2 laser pulse with the same spike-pulse energy and the different pulse-tail energy, the characteristics of the hole drilling of synthetic silica glass was investigated. Higher pulse-tail energy gave deeper ablation depth. In the short laser pulse with the spike-pulse energy of 1.2 mJ, the spike pulse width of 162 ns, the pulse-tail energy of 24.6 mJ, and the pulse-tail length of 29.6 μs, 1000 shots irradiation produced the ablation depth of 988 μm. In the hole drilling of synthetic silica glass by the CO2 laser, a crack-free process was realized.

  9. Laser-induced condensation by ultrashort laser pulses at 248 nm

    OpenAIRE

    Joly, P; Petrarca, M.; Vogel, A.(Physikalisches Institut, University of Bonn, Bonn, Germany); Pohl, T; Nagy, T.; Jusforgues, Q.; Simon, P.; Kasparian, J.; Weber, K.; Wolf, J.-P.

    2013-01-01

    We compare laser-induced condensation by UV laser pulses of femtosecond, sub-picosecond, and nanosecond duration between each other, as well as with respect to near-infrared (NIR) (800 nm) ultrashort laser pulses. Particle nucleation by UV pulses is so efficient that their growth beyond several hundreds of nm is limited by the local concentration of water vapour molecules. Furthermore, we evidence a dual mechanism: While condensation induced by ultrashort UV pulses rely on nitrogen photo-oxid...

  10. Pulsed power supplies for laser flashlamps. Final report

    International Nuclear Information System (INIS)

    A preliminary engineering design of a compensated pulse alternator for driving laser flashlamps is presented. The work performed by the Center for Electromechanics at The University of Texas at Austin also includes the optimization and revision of the prototype design for a compensated pulse alternator power supply for the NOVA laser system at Lawrence Livermore Laboratory

  11. Advanced pulsed and CW high-power fiber lasers

    OpenAIRE

    Nilsson, J.; Grudinin, A.B.; Turner, P.W.

    2000-01-01

    We examine design issues for high-energy pulsed as well as for high-power cw fiber lasers. Power handling and pump scalability are primary issues for kilowatt fiber lasers. Special core designs are needed for high-energy pulse generation.

  12. Analytical results for nonlinear Compton scattering in short intense laser pulses

    Science.gov (United States)

    Seipt, Daniel; Kharin, Vasily; Rykovanov, Sergey; Surzhykov, Andrey; Fritzsche, Stephan

    2016-04-01

    > We study in detail the strong-field QED process of nonlinear Compton scattering in short intense plane wave laser pulses of circular polarization. Our main focus is placed on how the spectrum of the backscattered laser light depends on the shape and duration of the initial short intense pulse. Although this pulse shape dependence is very complicated and highly nonlinear, and has never been addressed explicitly, our analysis reveals that all the dependence on the laser pulse shape is contained in a class of three-parameter master integrals. Here we present completely analytical expressions for the nonlinear Compton spectrum in terms of these master integrals. Moreover, we analyse the universal behaviour of the shape of the spectrum for very high harmonic lines.

  13. Laser-energy scaling law for neutrons generated from nano particles Coulomb-exploded by intense femtosecond laser pulses

    International Nuclear Information System (INIS)

    To discuss the feasibility of compact neutron sources the yield of laser produced neutrons is scaled by the laser energy. High-energy ions are generated by Coulomb explosion of clusters through intense femtosecond laser-cluster interactions. The laser energy scaling law of the neutron yield is estimated using the laser intensity scaling law for the energy of ions emitted from clusters Coulomb-exploded by an intense laser pulse. The neutron yield for D (D, n) He shows the potential of compact neutron sources with modern laser technology, and the yield for p (Li, n) Be shows much higher than that for Li (p, n) Be with the assumption of 500 nm-class cluster Coulomb explosion. (author)

  14. Clutter discrimination algorithm simulation in pulse laser radar imaging

    Science.gov (United States)

    Zhang, Yan-mei; Li, Huan; Guo, Hai-chao; Su, Xuan; Zhu, Fule

    2015-10-01

    Pulse laser radar imaging performance is greatly influenced by different kinds of clutter. Various algorithms are developed to mitigate clutter. However, estimating performance of a new algorithm is difficult. Here, a simulation model for estimating clutter discrimination algorithms is presented. This model consists of laser pulse emission, clutter jamming, laser pulse reception and target image producing. Additionally, a hardware platform is set up gathering clutter data reflected by ground and trees. The data logging is as clutter jamming input in the simulation model. The hardware platform includes a laser diode, a laser detector and a high sample rate data logging circuit. The laser diode transmits short laser pulses (40ns FWHM) at 12.5 kilohertz pulse rate and at 905nm wavelength. An analog-to-digital converter chip integrated in the sample circuit works at 250 mega samples per second. The simulation model and the hardware platform contribute to a clutter discrimination algorithm simulation system. Using this system, after analyzing clutter data logging, a new compound pulse detection algorithm is developed. This new algorithm combines matched filter algorithm and constant fraction discrimination (CFD) algorithm. Firstly, laser echo pulse signal is processed by matched filter algorithm. After the first step, CFD algorithm comes next. Finally, clutter jamming from ground and trees is discriminated and target image is produced. Laser radar images are simulated using CFD algorithm, matched filter algorithm and the new algorithm respectively. Simulation result demonstrates that the new algorithm achieves the best target imaging effect of mitigating clutter reflected by ground and trees.

  15. Laser-generated ultrasonic pulse shapes at solid wedges.

    Science.gov (United States)

    Pupyrev, Pavel D; Lomonosov, Alexey M; Mayer, Andreas P

    2016-08-01

    Laser pulses focused near the tip of an elastic wedge generate acoustic waves guided at its apex. The shapes of the acoustic wedge wave pulses depend on the energy and the profile of the exciting laser pulse and on the anisotropy of the elastic medium the wedge is made of. Expressions for the acoustic pulse shapes have been derived in terms of the modal displacement fields of wedge waves for laser excitation in the thermo-elastic regime and for excitation via a pressure pulse exerted on the surface. The physical quantity considered is the local inclination of a surface of the wedge, which is measured optically by laser-probe-beam deflection. Experimental results on pulse shapes in the thermo-elastic regime are presented and confirmed by numerical calculations. They pertain to an isotropic sharp-angle wedge with two wedge-wave branches and to a non-reciprocity phenomenon at rectangular silicon edges. PMID:27135188

  16. Ultrafast pulse lasers jump to macro applications

    Science.gov (United States)

    Griebel, Martin; Lutze, Walter; Scheller, Torsten

    2016-03-01

    Ultrafast Lasers have been proven for several micro applications, e.g. stent cutting, for many years. Within its development of applications Jenoptik has started to use ultrafast lasers in macro applications in the automotive industry. The JenLas D2.fs-lasers with power output control via AOM is an ideal tool for closed loop controlled material processing. Jenoptik enhanced his well established sensor controlled laser weakening process for airbag covers to a new level. The patented process enables new materials using this kind of technology. One of the most sensitive cover materials is genuine leather. As a natural product it is extremely inhomogeneous and sensitive for any type of thermal load. The combination of femtosecond pulse ablation and closed loop control by multiple sensor array opens the door to a new quality level of defined weakening. Due to the fact, that the beam is directed by scanning equipment the process can be split in multiple cycles additionally reducing the local energy input. The development used the 5W model as well as the latest 10W release of JenLas D2.fs and achieved amazing processing speeds which directly fulfilled the requirements of the automotive industry. Having in mind that the average cycle time of automotive processes is about 60s, trials had been done of processing weakening lines in genuine leather of 1.2mm thickness. Parameters had been about 15 cycles with 300mm/s respectively resulting in an average speed of 20mm/s and a cycle time even below 60s. First samples had already given into functional and aging tests and passed successfully.

  17. Heat transfer during pulsed laser cutting of thin sheets

    OpenAIRE

    Lindau, Jules Washington

    1989-01-01

    A numerical model of the temperature field during pulsed laser cutting of thin sheets (approximately 2.5 x l0-5 m) was developed. Cutting was simulated through removal of nodes from a finite difference scheme based on sensible heating to the phase change temperature and a single value of latent heat (melting or vaporization). The pulsed laser model predicts a heat-affected zone of less than 0.02 mm for pulsed laser cutting. For comparable cutting with a continuous power laser, ...

  18. Towards manipulating relativistic laser pulses with 3D printed materials

    OpenAIRE

    Ji, L. L.; Snyder, J.; Pukhov, A.; Freeman, R. R.; Akli, K. U.

    2015-01-01

    Efficient coupling of intense laser pulses to solid-density matter is critical to many applications including ion acceleration for cancer therapy. At relativistic intensities, the focus has been mainly on investigating various laser beams irradiating initially flat interfaces with little or no control over the interaction. Here, we propose a novel approach that leverages recent advancements in 3D direct laser writing (DLW) of materials and high contrast lasers to manipulate the laser-matter i...

  19. Additive-pulse modelocking of non-cw neodymium lasers

    Science.gov (United States)

    Heinz, P.; Reuther, A.; Laubereau, A.

    1993-03-01

    Passive modelocking of several flash-lamp pumped neodymium lasers with electro-optic amplitude stabilization is demonstrated using a nonlinear Michelson interferometer. Improved performance is reported for the GSGG- YLF- and glass-laser as compared to the nonlinear absorber, with shorter pulse durations and smaller amplitude fluctuations, e.g. 5 μJ pulses for 460 ± 20 fs for Nd:glass. Evidence is obtained for multi-selfstability of the pulse energy.

  20. Propagation of finite length laser pulses in plasma channels

    International Nuclear Information System (INIS)

    Finite pulse length effects are shown to play a major role in the propagation, stability, and guiding of intense laser beams in plasmas. We present the quasiparaxial approximation (QPA) to the wave equation that takes finite pulse length effects into account. The QPA is an extension of the usual paraxial approximation. The laser field is shown to be significantly modified for pulses less than a few tens of wavelengths long. A pair of coupled envelope-power equations having finite pulse length effects, as well as relativistic and atomic electron nonlinearities, is derived and analyzed. Short laser pulses propagating in plasma channels are found to undergo an envelope oscillation in which the front of the pulse is always damped while the back initially grows. The modulation eventually damps due to frequency spread phase mixing. In addition, finite pulse length effects are shown to modify nonlinear focusing processes significantly. thinsp copyright 1999 The American Physical Society

  1. Parametric study on femtosecond laser pulse ablation of Au films

    International Nuclear Information System (INIS)

    Ablation process of 1 kHz rate femtosecond lasers (pulse duration 148 fs, wavelength 775 nm) with Au films on silica substrates has been systemically studied. The single-pulse threshold can be obtained directly. For the multiple pulses the ablation threshold varies with the number of pulses applied to the surface due to the incubation effect. From the plot of accumulated laser fluence N x φ th(N) and the number of laser pulses N, incubation coefficient of Au film can be obtained (s = 0.765). As the pulse energy is increased, the single pulse ablation rate is increasing following two ablation logarithmic regimes, which can be explained by previous research

  2. Ultra-short pulsed laser engineered metal-glass nanocomposites

    CERN Document Server

    Stalmashonak, Andrei; Abdolvand, Amin

    2013-01-01

    Glasses containing metallic nanoparticles exhibit very promising linear and nonlinear optical properties, mainly due to the surface plasmon resonances (SPRs) of the nanoparticles. The spectral position in the visible and near-infrared range and polarization dependence of the SPR are characteristically determined by the nanoparticles’ shapes. The focus of Ultra-Short Pulsed Laser Engineered Metal-Glass Nanocomposites is the interaction of intense ultra-short laser pulses with glass containing silver nanoparticles embedded in soda-lime glass, and nanostructural modifications in metal-glass nanocomposites induced by such laser pulses. In order to provide a comprehensive physical picture of the processes leading to laser-induced persistent shape transformation of the nanoparticles, series of experimental results investigating the dependences of laser assisted shape modifications of nanoparticles with laser pulse intensity, excitation wavelength, temperature are considered. In addition, the resulting local opti...

  3. Nonlinear laser pulse response in a crystalline lens.

    Science.gov (United States)

    Sharma, R P; Gupta, Pradeep Kumar; Singh, Ram Kishor; Strickland, D

    2016-04-01

    The propagation characteristics of a spatial Gaussian laser pulse have been studied inside a gradient-index structured crystalline lens with constant-density plasma generated by the laser-tissue interaction. The propagation of the laser pulse is affected by the nonlinearities introduced by the generated plasma inside the crystalline lens. Owing to the movement of plasma species from a higher- to a lower-temperature region, an increase in the refractive index occurs that causes the focusing of the laser pulse. In this study, extended paraxial approximation has been applied to take into account the evolution of the radial profile of the Gaussian laser pulse. To examine the propagation characteristics, variation of the beam width parameter has been observed as a function of the laser power and initial beam radius. The cavitation bubble formation, which plays an important role in the restoration of the elasticity of the crystalline lens, has been investigated. PMID:27192252

  4. Optodynamic aspect of a pulsed laser ablation process

    Science.gov (United States)

    Hrovatin, Rok; Možina, Janez

    1995-02-01

    A study of a pulsed laser ablation process is presented from a novel, optodynamic aspect. By quantitative analysis of laser-induced bulk ultrasonic and blast waves in the air the ablation dynamics is characterized. In this way the influence of the laser pulse parameters and of the interacting material on the ablation process was assessed. By the analysis of the laser drilling process of thin layered samples the material influence was demonstrated. Besides the ultrasonic evaluation of the laser pulse power density the plasma shielding for 10 ns laser pulses was analyzed by the same method. All measurements were noncontact. Bulk waves in the solid and blast waves in the air were measured simultaneously, an interferometric and a probe beam deflection method were used, respectively.

  5. Investigation of laser-driven proton acceleration using ultra-short, ultra-intense laser pulses

    International Nuclear Information System (INIS)

    We report optimization of laser-driven proton acceleration, for a range of experimental parameters available from a single ultrafast Ti:sapphire laser system. We have characterized laser-generated protons produced at the rear and front target surfaces of thin solid targets (15 nm to 90 μm thicknesses) irradiated with an ultra-intense laser pulse (up to 1020 W⋅cm−2, pulse duration 30 to 500 fs, and pulse energy 0.1 to 1.8 J). We find an almost symmetric behaviour for protons accelerated from rear and front sides, and a linear scaling of proton energy cut-off with increasing pulse energy. At constant laser intensity, we observe that the proton cut-off energy increases with increasing laser pulse duration, then roughly constant for pulses longer than 300 fs. Finally, we demonstrate that there is an optimum target thickness and pulse duration.

  6. Investigation of laser-driven proton acceleration using ultra-short, ultra-intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Fourmaux, S.; Gnedyuk, S.; Lassonde, P.; Payeur, S.; Pepin, H.; Kieffer, J. C. [INRS-EMT, Universite du Quebec, 1650 Lionel Boulet, Varennes, Quebec J3X 1S2 (Canada); Buffechoux, S.; Albertazzi, B. [INRS-EMT, Universite du Quebec, 1650 Lionel Boulet, Varennes, Quebec J3X 1S2 (Canada); LULI, UMR 7605, CNRS - CEA - Universite Paris 6 - Ecole Polytechnique, 91128 Palaiseau (France); Capelli, D.; Antici, P. [LULI, UMR 7605, CNRS - CEA - Universite Paris 6 - Ecole Polytechnique, 91128 Palaiseau (France); Dipartimento SBAI, Sapienza, Universita di Roma, Via Scarpa 16, 00161 Roma (Italy); Levy, A.; Fuchs, J. [LULI, UMR 7605, CNRS - CEA - Universite Paris 6 - Ecole Polytechnique, 91128 Palaiseau (France); Lecherbourg, L.; Marjoribanks, R. S. [Department of Physics and Institute for Optical Sciences, University of Toronto, Toronto, Ontario M5S 1A7 (Canada)

    2013-01-15

    We report optimization of laser-driven proton acceleration, for a range of experimental parameters available from a single ultrafast Ti:sapphire laser system. We have characterized laser-generated protons produced at the rear and front target surfaces of thin solid targets (15 nm to 90 {mu}m thicknesses) irradiated with an ultra-intense laser pulse (up to 10{sup 20} W Dot-Operator cm{sup -2}, pulse duration 30 to 500 fs, and pulse energy 0.1 to 1.8 J). We find an almost symmetric behaviour for protons accelerated from rear and front sides, and a linear scaling of proton energy cut-off with increasing pulse energy. At constant laser intensity, we observe that the proton cut-off energy increases with increasing laser pulse duration, then roughly constant for pulses longer than 300 fs. Finally, we demonstrate that there is an optimum target thickness and pulse duration.

  7. Interaction of superintense laser pulses with relativistic ions.

    OpenAIRE

    Chirilă, C. C.; Joachain, C. J.; Kylstra, N. J.; Potvliege, R. M.

    2004-01-01

    At high intensities, three-step recollision processes driven by low frequency laser pulses, such as high-order harmonic generation and high-order above-threshold ionization, are normally severely suppressed by the magnetic-field component of the laser field. It is shown that this suppression is not severe, even for ponderomotive energies well above 10keV, for multicharged ions moving at a sufficiently high relativistic velocity against a counterpropagating infrared laser pulse. Numerical resu...

  8. Production of picosecond, kilojoule, petawatt laser pulses via Raman amplification of nanosecond pulses

    CERN Document Server

    Trines, R; Bingham, R; Fonseca, R A; Silva, L O; Cairns, R A; Norreys, P A

    2011-01-01

    Raman amplification in plasma has been promoted as a means of compressing picosecond optical laser pulses to femtosecond duration to explore the intensity frontier. Here we show for the first time that it can be used, with equal success, to compress laser pulses from nanosecond to picosecond duration. Simulations show up to 60% energy transfer from pump to probe pulses, implying that multi-kiloJoule ultra-violet petawatt laser pulses can be produced using this scheme. This has important consequences for the demonstration of fast-ignition inertial confinement fusion.

  9. Development of a compact soft X-ray laser using a pulse-train laser. 4

    International Nuclear Information System (INIS)

    Time behaviour of gain coefficients was studied for the two different pulse train-lasers; one is a normal pulse-train, and the other modified one. The duration time of gain is larger for the modified pulse-train laser compared with the normal one. (author)

  10. Mitigation of Electromagnetic Pulse (EMP) Effects from Short-Pulse Lasers and Fusion Neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Eder, D C; Throop, A; Brown, Jr., C G; Kimbrough, J; Stowell, M L; White, D A; Song, P; Back, N; MacPhee, A; Chen, H; DeHope, W; Ping, Y; Maddox, B; Lister, J; Pratt, G; Ma, T; Tsui, Y; Perkins, M; O' Brien, D; Patel, P

    2009-03-06

    Our research focused on obtaining a fundamental understanding of the source and properties of EMP at the Titan PW(petawatt)-class laser facility. The project was motivated by data loss and damage to components due to EMP, which can limit diagnostic techniques that can be used reliably at short-pulse PW-class laser facilities. Our measurements of the electromagnetic fields, using a variety of probes, provide information on the strength, time duration, and frequency dependence of the EMP. We measure electric field strengths in the 100's of kV/m range, durations up to 100 ns, and very broad frequency response extending out to 5 GHz and possibly beyond. This information is being used to design shielding to mitigate the effects of EMP on components at various laser facilities. We showed the need for well-shielded cables and oscilloscopes to obtain high quality data. Significant work was invested in data analysis techniques to process this data. This work is now being transferred to data analysis procedures for the EMP diagnostics being fielded on the National Ignition Facility (NIF). In addition to electromagnetic field measurements, we measured the spatial and energy distribution of electrons escaping from targets. This information is used as input into the 3D electromagnetic code, EMSolve, which calculates time dependent electromagnetic fields. The simulation results compare reasonably well with data for both the strength and broad frequency bandwidth of the EMP. This modeling work required significant improvements in EMSolve to model the fields in the Titan chamber generated by electrons escaping the target. During dedicated Titan shots, we studied the effects of varying laser energy, target size, and pulse duration on EMP properties. We also studied the effect of surrounding the target with a thick conducting sphere and cube as a potential mitigation approach. System generated EMP (SGEMP) in coaxial cables does not appear to be a significant at Titan. Our

  11. The mechanism for SEU simulation by pulsed laser

    Institute of Scientific and Technical Information of China (English)

    HUANG; Jianguo; HAN; Jianwei

    2004-01-01

    To simulate single event effect (SEE) by pulsed laser is a new approach in ground-based simulation of SEE in recent years. In this paper the way in which picosecond pulsed laser interacts with semiconductor and the mechanism of SEE inducement are analyzed. Additionally, associated calculations are made in the case of Nd:YAG and Ti:Sapphire lasers generally used in experiments and silicon device, with comparisons made between the two lasers. In the meantime, the fundamental principle for determining laser parameters and their typical ranges of values are provided according to the results.

  12. Creation and control of single attosecond XUV pulse by few-cycle intense laser pulse

    Science.gov (United States)

    Carrera, Juan J.; Tong, X. M.; Chu, Shih-I.

    2006-05-01

    We present a theoretical investigation of the mechanisms responsible for the production of single atto-second pulse by using few-cycle intense laser pulses. The atto-second XUV spectral is calculated by accurately integrating the time- dependent Schr"odinger equation. The detailed mechanism for the production of the XUV pulse are also corroborated by analyzing the classical trajectories of the electron. Our study shows that the first return of the rescattering electron is responsible for the high energy atto-second pulse. Furthermore, we can optimize the production of atto-second XUV pulses by modifying the trajectory of the rescattering electron by tuning the laser field envelope.

  13. Trends in ultrashort and ultrahigh power laser pulses based on optical parametric chirped pulse amplification

    International Nuclear Information System (INIS)

    Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992, optical parametric chirped pulse amplification (OPCPA) became the most promising method for the amplification of broadband optical pulses. In the meantime, we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers. The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level. Meanwhile, the output pulse duration based on optical parametric amplification has entered the range of few-optical-cycle field. In this paper, we overview the basic principles, trends in development, and current state of the ultrashort and laser systems based on OPCPA, respectively. (paper)

  14. Tantalum ions produced by 1064 nm pulsed laser irradiation

    Czech Academy of Sciences Publication Activity Database

    Torrisi, L.; Gammino, S.; Andó, L.; Láska, Leoš

    2002-01-01

    Roč. 91, - (2002), s. 4685-4692. ISSN 0021-8979 Institutional research plan: CEZ:AV0Z1010921 Keywords : pulsed laser irradiation * high-temperature plasma production * Nd:YAG laser Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.281, year: 2002

  15. Energy losses estimation during pulsed-laser seam welding

    Czech Academy of Sciences Publication Activity Database

    Šebestová, Hana; Havelková, M.; Chmelíčková, H.

    2014-01-01

    Roč. 45, č. 3 (2014), s. 1116-1121. ISSN 1073-5615 R&D Projects: GA MŠk(CZ) LG13007 Institutional support: RVO:68378271 Keywords : laser welding * pulsed-laser * Nd:YAG laser Subject RIV: JP - Industrial Processing Impact factor: 1.461, year: 2014

  16. [INVITED] Control of femtosecond pulsed laser ablation and deposition by temporal pulse shaping

    Science.gov (United States)

    Garrelie, Florence; Bourquard, Florent; Loir, Anne--Sophie; Donnet, Christophe; Colombier, Jean-Philippe

    2016-04-01

    This study explores the effects of temporal laser pulse shaping on femtosecond pulsed laser deposition (PLD). The potential of laser pulses temporally tailored on ultrafast time scales is used to control the expansion and the excitation degree of ablation products including atomic species and nanoparticles. The ablation plume generated by temporally shaped femtosecond pulsed laser ablation of aluminum and graphite targets is studied by in situ optical diagnostic methods. Taking advantage of automated pulse shaping techniques, an adaptive procedure based on spectroscopic feedback regulates the irradiance for the enhancement of typical plasma features. Thin films elaborated by unshaped femtosecond laser pulses and by optimized sequence indicate that the nanoparticles generation efficiency is strongly influenced by the temporal shaping of the laser irradiation. The ablation processes leading either to the generation of the nanoparticles either to the formation of plasma can be favored by using a temporal shaping of the laser pulse. Insights are given on the possibility to control the quantity of the nanoparticles. The temporal laser pulse shaping is shown also to strongly modify the laser-induced plasma contents and kinetics for graphite ablation. Temporal pulse shaping proves its capability to reduce the number of slow radicals while increasing the proportion of monomers, with the addition of ionized species in front of the plume. This modification of the composition and kinetics of plumes in graphite ablation using temporal laser pulse shaping is discussed in terms of modification of the structural properties of deposited Diamond-Like Carbon films (DLC). This gives rise to a better understanding of the growth processes involved in femtosecond-PLD and picosecond-PLD of DLC suggesting the importance of neutral C atoms, which are responsible for the subplantation process.

  17. Application of Yb:YAG short pulse laser system

    Energy Technology Data Exchange (ETDEWEB)

    Erbert, Gaylen V.; Biswal, Subrat; Bartolick, Joseph M.; Stuart, Brent C.; Crane, John K.; Telford, Steve; Perry, Michael D.

    2004-07-06

    A diode pumped, high power (at least 20W), short pulse (up to 2 ps), chirped pulse amplified laser using Yb:YAG as the gain material is employed for material processing. Yb:YAG is used as the gain medium for both a regenerative amplifier and a high power 4-pass amplifier. A single common reflective grating optical device is used to both stretch pulses for amplification purposes and to recompress amplified pulses before being directed to a workpiece.

  18. Generation of 1.5 cycle 0.3 TW laser pulses using a hollow-fiber pulse compressor.

    Science.gov (United States)

    Park, Juyun; Lee, Jae-Hwan; Nam, Chang Hee

    2009-08-01

    Pulse compression in a differentially pumped neon-filled hollow fiber was used to generate high-power few-cycle laser pulses. The pulse compression process was optimized by adjusting gas pressure and laser chirp to produce the shortest laser pulses. Precise dispersion control enabled the generation of laser pulses with duration of 3.7 fs and energy of 1.2 mJ. This corresponds to an output of 1.5 cycle, 0.3 TW pulses at a 1 kHz repetition rate using positively chirped 33 fs laser pulses. PMID:19649091

  19. Gating attosecond pulse train generation using multicolor laser fields

    International Nuclear Information System (INIS)

    The process of high-order harmonic generation leads to the production of a train of attosecond-duration extreme ultraviolet (XUV) pulses, with one pulse emitted per optical half-cycle. For attosecond pump-probe experiments, a single, isolated attosecond pulse is preferable, requiring an almost continuous spectrum. We show experimentally and numerically that the addition of a second laser field, and later a third, at a noncommensurate frequency relative to the driving field can modify the subcycle shape of the electric field, leading to the appearance of additional spectral components between the usual odd harmonics and in some cases a quasicontinuum. We perform a parametric study of the frequency ratio between the two first laser fields, the result of which is in good agreement with theoretical selection rules. We also show numerically that using three laser frequencies from an optical parametric amplifier can achieve a single attosecond pulse from a 24-fs laser pulse.

  20. Short-pulse laser interactions with disordered materials and liquids

    Energy Technology Data Exchange (ETDEWEB)

    Phinney, L.M.; Goldman, C.H.; Longtin, J.P.; Tien, C.L. [Univ. of California, Berkeley, CA (United States)

    1995-12-31

    High-power, short-pulse lasers in the picosecond and subpicosecond range are utilized in an increasing number of technologies, including materials processing and diagnostics, micro-electronics and devices, and medicine. In these applications, the short-pulse radiation interacts with a wide range of media encompassing disordered materials and liquids. Examples of disordered materials include porous media, polymers, organic tissues, and amorphous forms of silicon, silicon nitride, and silicon dioxide. In order to accurately model, efficiently control, and optimize short-pulse, laser-material interactions, a thorough understanding of the energy transport mechanisms is necessary. Thus, fractals and percolation theory are used to analyze the anomalous diffusion regime in random media. In liquids, the thermal aspects of saturable and multiphoton absorption are examined. Finally, a novel application of short-pulse laser radiation to reduce surface adhesion forces in microstructures through short-pulse laser-induced water desorption is presented.

  1. Laser pulse spectral shaping based on electro-optic modulation

    Institute of Scientific and Technical Information of China (English)

    Yanhai Wang; Jiangfeng Wang; You'en Jiang; Yan Bao; Xuechun Li; Zunqi Lin

    2008-01-01

    A new spectrum shaping method, based on electro-optic modulation, to alleviate gain narrowing in chirped pulse amplification (CPA) system, is described and numerically simulated. Near-Fourier transform-limited seed laser pulse is chirped linearly through optical stretcher. Then the chirped laser pulse is coupled into integrated waveguide electro-optic modulator driven by an aperture-coupled-stripline (ACSL) electricalwaveform generator, and the pulse shape and amplitude are shaped in time domain. Because of the directrelationship between frequency interval and time interval of the linearly chirped pulse, the laser pulse spectrum is shaped correspondingly. Spectrum-shaping examples are modeled numerically to determine the spectral resolution of this technique. The phase error introduced in this method is also discussed.

  2. Double-pulse LIBS of gadolinium oxide ablated by femto- and nano-second laser pulses

    International Nuclear Information System (INIS)

    Emission characteristics of gadolinium (Gd) oxide are studied, using ns and fs laser pulses for ablation in double-pulse laser induced breakdown spectroscopy (LIBS). In the current conditions of pulse energy and signal detection timing, emission intensity enhancement in the reheating mode is 25-fold, but little effect can be observed in a pre-pulse mode. It is shown that the optimum focus position of the ablation pulse is about 5 mm apart from the sample surface in the reheating mode. Although little emission can be observed in the single-pulse configuration with fs ablation pulses, the intense emission can be observed in the reheating mode in the double-pulse configuration. (orig.)

  3. Laser air-jet engine: the action of shock waves at low laser pulse repetition rates

    International Nuclear Information System (INIS)

    The impact and thermal action of laser sparks on the reflector of a laser engine in which the propulsion is produced by repetitively pulsed radiation is estimated. It is shown that for a low pulse repetition rate, the thermal contact of a plasma with the reflector and strong dynamic resonance loads are inevitable. These difficulties can be surmounted by using the method based on the merging of shock waves at a high pulse repetition rate. (laser applications)

  4. Single molecule imaging with longer x-ray laser pulses

    OpenAIRE

    Martin, Andrew V.; Corso, Justine K.; Caleman, Carl; Timneanu, Nicusor; Quiney, Harry M.

    2015-01-01

    During the last five years, serial femtosecond crystallography using x-ray laser pulses has developed into a powerful technique for determining the atomic structures of protein molecules from micrometer and sub-micrometer sized crystals. One of the key reasons for this success is the "self-gating" pulse effect, whereby the x-ray laser pulses do not need to outrun all radiation damage processes. Instead, x-ray induced damage terminates the Bragg diffraction prior to the pulse completing its pa...

  5. Molecular attosecond photoionization with few cycle XUV laser pulses

    International Nuclear Information System (INIS)

    We present molecular attosecond ionization with few cycle XUV laser pulses from numerical solutions of time dependent Schrodinger equations. Simulations performed on aligned H+2 exhibit signature of red-shifts in photoelectron energy spectra. This is shown to be critically sensitive to the the pulse duration and wavelength and is attributed to the broad spectral width of the ionizing pulses and diminishing electronic Franck-Condon factors with short pulses. We analyze the laser parameter dependence of the energy spectra by a perturbative model.

  6. Pulse Splitting in Short Wavelength Seeded Free Electron Lasers

    International Nuclear Information System (INIS)

    We investigate a fundamental limitation occurring in vacuum ultraviolet and extreme ultraviolet seeded free electron lasers (FELs). For a given electron beam and undulator configuration, an increase of the FEL output energy at saturation can be obtained via an increase of the seed pulse duration. We put in evidence a complex spatiotemporal deformation of the amplified pulse, leading ultimately to a pulse splitting effect. Numerical studies of the Colson-Bonifacio FEL equations reveal that slippage length and seed laser pulse wings are core ingredients of the dynamics.

  7. Micromachining soda-lime glass by femtosecond laser pulses

    Science.gov (United States)

    Jia, Wei; Yu, Jian; Chai, Lu; Wang, Ching-Yue

    2015-08-01

    The physical process of forming a modified region in soda-lime glass was investigated using 1 kHz intense femtosecond laser pulses from a Ti: sapphire laser at 775 nm. Through the modifications induced by the femtosecond laser radiation using selective chemical etching techniques, we fabricated reproducible and defined microstructures and further studied their morphologies and etching properties. Moreover, a possible physical mechanism for the femtosecond laser modification in soda-lime glass was proposed.

  8. Generation of elliptically polarized nitrogen ion laser fields using two-color femtosecond laser pulses

    OpenAIRE

    Ziting Li; Bin Zeng; Wei Chu; Hongqiang Xie; Jinping Yao; Guihua Li; Lingling Qiao; Zhanshan Wang; Ya Cheng

    2016-01-01

    We experimentally investigate generation of molecular nitrogen-ion lasers with two femtosecond laser pulses at different wavelengths. The first pulse serves as the pump which ionizes the nitrogen molecules and excites the molecular ions to excited electronic states. The second pulse serves as the probe which leads to stimulated emission from the excited molecular ions. We observe that changing the angle between the polarization directions of the two pulses gives rise to elliptically polarized...

  9. Optically pumped terahertz lasers with high pulse repetition frequency: theory and design

    Institute of Scientific and Technical Information of China (English)

    Yude Sun; Shiyou Fu; Jing Wang; Zhenghe Sun; Yanchao Zhang; Zhaoshuo Tian; Qi Wang

    2009-01-01

    Optically pumped terahertz (THz) lasers with high pulse repetition frequency are designed. Such a laser includes two parts: the optically pumping laser and the THz laser. The structures of the laser are described and analyzed. The rate equations for the pulsed THz laser are given. The kinetic process and laser pulse waveform for this kind of laser are numerically calculated based on the theory of rate equations. The theoretical results give a helpful guide to the research of such lasers.

  10. Generation of elliptically polarized nitrogen-ion laser fields using two-color femtosecond laser pulses

    CERN Document Server

    Li, Ziting; Chu, Wei; Xie, Hongqiang; Yao, Jinping; Li, Guihua; Qiao, Lingling; Wang, Zhanshan; Cheng, Ya

    2015-01-01

    We experimentally investigate generation of molecular nitrogen-ion lasers with two femtosecond laser pulses at different wavelengths. The first pulse serves as the pump which ionizes the nitrogen molecules and excites the molecular ions to excited electronic states. The second pulse serves as the probe which leads to stimulated emission from the excited molecular ions. We observe that changing the angle between the polarization directions of the two pulses gives rise to elliptically polarized molecular nitrogen-ion laser fields, which is interpreted as a result of strong birefringence of the gain medium near the wavelengths of the molecular nitrogen-ion laser.

  11. Stabilizing laser energy density on a target during pulsed laser deposition of thin films

    Energy Technology Data Exchange (ETDEWEB)

    Dowden, Paul C.; Jia, Quanxi

    2016-05-31

    A process for stabilizing laser energy density on a target surface during pulsed laser deposition of thin films controls the focused laser spot on the target. The process involves imaging an image-aperture positioned in the beamline. This eliminates changes in the beam dimensions of the laser. A continuously variable attenuator located in between the output of the laser and the imaged image-aperture adjusts the energy to a desired level by running the laser in a "constant voltage" mode. The process provides reproducibility and controllability for deposition of electronic thin films by pulsed laser deposition.

  12. Ablation characteristics of quantum square pulse mode dental erbium laser

    Science.gov (United States)

    Lukač, Nejc; Suhovršnik, Tomaž; Lukač, Matjaž; Jezeršek, Matija

    2016-01-01

    Erbium lasers are by now an accepted tool for performing ablative medical procedures, especially when minimal invasiveness is desired. Ideally, a minimally invasive laser cutting procedure should be fast and precise, and with minimal pain and thermal side effects. All these characteristics are significantly influenced by laser pulse duration, albeit not in the same manner. For example, high cutting efficacy and low heat deposition are characteristics of short pulses, while vibrations and ejected debris screening are less pronounced at longer pulse durations. We report on a study of ablation characteristics on dental enamel and cementum, of a chopped-pulse Er:YAG [quantum square pulse (QSP)] mode, which was designed to reduce debris screening during an ablation process. It is shown that in comparison to other studied standard Er:YAG and Er,Cr:YSGG laser pulse duration modes, the QSP mode exhibits the highest ablation drilling efficacy with lowest heat deposition and reduced vibrations, demonstrating that debris screening has a considerable influence on the ablation process. By measuring single-pulse ablation depths, we also show that tissue desiccation during the consecutive delivery of laser pulses leads to a significant reduction of the intrinsic ablation efficacy that cannot be fully restored under clinical settings by rehydrating the tooth using an external water spray.

  13. Over 0.5 MW green laser from sub-nanosecond giant pulsed microchip laser

    Science.gov (United States)

    Zheng, Lihe; Taira, Takunori

    2016-03-01

    A sub-nanosecond green laser with laser head sized 35 × 35 × 35 mm3 was developed from a giant pulsed microchip laser for laser processing on organic superconducting transistor with a flexible substrate. A composite monolithic Y3Al5O12 (YAG) /Nd:YAG/Cr4+:YAG/YAG crystal was designed for generating giant pulsed 1064 nm laser. A fibercoupled 30 W laser diode centered at 808 nm was used with pump pulse duration of 245 μs. The 532 nm green laser was obtained from a LiB3O5 (LBO) crystal with output energy of 150 μJ and pulse duration of 268 ps. The sub-nanosecond green laser is interesting for 2-D ablation patterns.

  14. Acceleration Mechanism Of Pulsed Laser-Electromagnetic Hybrid Thruster

    International Nuclear Information System (INIS)

    A fundamental study of a newly developed rectangular pulsed laser-electromagnetic hybrid thruster was conducted. Laser-ablation plasma in the thruster was induced through laser beam irradiation onto a solid target and accelerated by electrical means instead of direct acceleration only by using a laser beam. The performance of the thrusters was evaluated by measuring the ablated mass per pulse and impulse bit. As results, significantly high specific impulses up to 7,200 s were obtained at charge energies of 8.6 J. Moreover, from the Faraday cup measurement, it was confirmed that the speed of ions was accelerated with addition of electric energy.

  15. LONGITUDINAL DISCH. CO2 LASER WITH PULSED PRE-IONIZATION

    Institute of Scientific and Technical Information of China (English)

    Yu Yanning; Wan Chongyi

    2002-01-01

    A novel pre-ionization scheme of helical transverse-pulsed pre-ionization in a longitudinal discharge CO2 laser is presented. The laser tube is made of glass with inner diameter of 7.5mm and discharge length of 50cm. The laser performance characteristics as functions of parameters, such as pressure, charging capacitance and applied voltage, are investigated. Compared with the same laser structure without pre-ionization, the maximum pulse energy improves by 23%, the optimum electro-optical efficiency increases by 31%, and the specific output energy reaches 26 J/(L·atm).

  16. Evaluating the potential for internal injuries from a pulsed 3.8-micron laser

    Science.gov (United States)

    Johnson, Thomas E.; Fitzhugh, Dawn C.; McPherson, Nicole; Winston, Golda C. H.; Winston, Tridaugh D.; Randolph, Donald Q.

    2005-04-01

    The goal of this study is to determine if a high energy laser pulse can cause internal injury that cannot be grossly visualized. High power lasers are currently in development such as the Medical Free Electron Laser (MFEL), the Anti-Ballistic Laser (ABL) and the Tactical High Energy Laser (THEL) and the potential exists for human exposure. Little is known about the effects of these high output lasers on internal organs when a thoracic exposure occurs. This study utilized a 3.8 micron single 8 microsecond pulse laser for all exposures. Yucatan miniature pigs were exposed to a single pulse over the sternum. In addition, some animals were also exposed in the axillary region. Creatine phosphokinase (CPK) and troponin levels were measured prior to and post exposure to assess cardiac muscle damage. Gross and histologic changes were determined for the porcine skin, lung tissue, and cardiac muscle. This study explores if a greater than class 4 laser classification is warranted based on the potential for thoracic injury.

  17. Development of long life pulse power supply for copper vapor laser. Do joki laser yo chojumyo reiki dengen no kaihatsu. ; Saidai shutsuryoku unten oyobi laser hasshin

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, T.; Goto, N.; Nemoto, K. (Central Research Inst. of Electric Power Industry, Tokyo (Japan))

    1990-04-01

    Long life pulse power supply for Cu vapor laser was developed. This is composed of the pulse generation circuit and the pulse compression circuit. Current pulse of 10 mu second pulse width is generated in the pulse generating circuit by switching electric charge on the condensor charged through GTO (gate turn off) thyristors. The pulse compression circuit makes the current pulse fast to 300ms utilizing the difference of inductance at the saturation and the unsaturation on the circuit which uses a reactor having saturable property using a ferromagnetic substance for the core as the magnetic switch. The operation was carried out at the GTO generasting full power. Co base amorphous alloy of low loss was used for the core of saturable inductor and the circuit efficiency of 77% could be obtained by suppressing the heat generation in core even at 4,000Hz operation. The full output power of 8.2kW was possible which corresponds to 100W class laser oscillation. Repeated Cu vapor laser oscillation of 30W succeeded at the condition of 4,000Hz and power supply output of 5.9kW. 7 refs., 21 figs., 8 tabs.

  18. Modulation of ionization on laser frequency in ultra-short pulse intense laser-gas-target

    Institute of Scientific and Technical Information of China (English)

    Hu Qiang-Lin; Liu Shi-Bing

    2006-01-01

    Based on the dispersion relation of intense laser pulse propagating in gradually ionized plasma, this paper discusses the frequency modulation induced by ionization of an ultra-short intense laser pulse interacting with a gas target.The relationship between the frequency modulation and the ionization rate, the plasmas frequency variation, and the polarization of atoms (ions) is analysed. The numerical results indicate that, at high frequency, the polarization of atoms (ions) plays a more important role than plasma frequency variation in modulating the laser frequency, and the laser frequency variation is different at different positions of the laser pulse.

  19. Fundamental studies of pulsed laser ablation

    CERN Document Server

    Claeyssens, F

    2001-01-01

    dopant) have resulted in a coherent view of the resulting plume, which exhibits a multi-component structure correlated with different regimes of ablation, which are attributed to ejection from ZnO and ablation from a Zn melt. OES measurements show that the emitting Zn component within the plume accelerates during expansion in vacuum - an observation attributable to the presence of hot, fast electrons in the plume. The same acceleration behaviour is observed in the case of Al atomic emissions resulting from ablation of an Al target in vacuum. Deposition conditions, substrate temperature and background gas pressure were all varied in a quest for optimally aligned, high quality ZnO thin films. Initial ab initio calculations were performed also, to aid in understanding the stability of these c-axis aligned films. The pulsed ultraviolet (lambda = 193, 248 nm) laser ablation of graphite, polycrystalline diamond and ZnO targets has been investigated. Characteristics of the resulting plumes of ablated material have b...

  20. Laser triggered injection of electrons in a laser wakefield accelerator with the colliding pulse method

    OpenAIRE

    Nakamura, K; Fubiani, G; Geddes, C. G. R.; Michel, P.; van Tilborg, J.; Toth, C; Esarey, E.; Schroeder, C. B.; Leemans, W. P.

    2004-01-01

    An injection scheme for a laser wakefield accelerator that employs a counterpropagating laser (colliding with the drive laser pulse, used to generate a plasma wake) is discussed. The threshold laser intensity for electron injection into the wakefield was analyzed using a heuristic model based on phase-space island overlap. Analysis shows that the injection can be performed using modest counterpropagating laser intensity a_1 < 0.5 for a drive laser intensity of a_0 = 1.0. Preliminary expe...

  1. Monitor and control of neuronal activities with femtosecond pulse laser

    Institute of Scientific and Technical Information of China (English)

    ZHOU Wei; LIU XiuLi; L(U) XiaoHua; LI JiaSong; LUO QingMing; ZENG ShaoQun

    2008-01-01

    Combined with the fluorescence labeling technique, two-photon microscopy excited with femtosecond pulse laser has become an important tool for neuroscience research. In this research, the calcium signals from neurons in rat cortex slice were monitored by a custom-built two-photon microscopy, and the spontaneous calcium signals and the pharmacological responses as well as the responses to femtosecond pulse laser stimulation were recorded. The results showed that the amplitude of the cal-cium signals increased in direct proportion to the corresponding electrical activities. Glutamate induced a calcium transient, but continuous application resulted in smaller response. Simultaneous monitoring of neuronal populations distinguished the neurons of different microcircuits. The femtosecond pulse laser induced local or global calcium signals in the pyramidal neurons. The approach of interrogation and control of neural activities using femtosecond pulse laser is non-contact, nondestructive, repeatable, and without any additional substrates, which will contribute to the development of neuroscience.

  2. Double Ionization by Strong Elliptically Polarized Laser Pulses

    OpenAIRE

    Wang, Xu; Eberly, J. H.

    2009-01-01

    We join the tribute to Professor N.B. Delone in this memorial issue by presenting the results of new calculations on the effects of ellipticity on double ionization by short and strong near-optical laser pulses.

  3. Optimizing ultrashort laser pulse compression by two photon absorption

    International Nuclear Information System (INIS)

    Demonstrated is an approach for relative optimization of ultrashort pulses using two-photon generated photocurrent in a GaAsP photodiode. Two-photon absorption is a nonlinear process, allowing for highly sensitive tuning of ultrashort laser systems

  4. Alignment of symmetric top molecules by short laser pulses

    DEFF Research Database (Denmark)

    Hamilton, Edward; Seideman, Tamar; Ejdrup, Tine;

    2005-01-01

    Nonadiabatic alignment of symmetric top molecules induced by a linearly polarized, moderately intense picosecond laser pulse is studied theoretically and experimentally. Our studies are based on the combination of a nonperturbative solution of the Schrodinger equation with femtosecond time...

  5. Schwinger Vacuum Pair Production in Chirped Laser Pulses

    CERN Document Server

    Dumlu, Cesim K

    2010-01-01

    The recent developments of high intensity ultra-short laser pulses have raised the hopes of observing Schwinger vacuum pair production which is one of the important non-perturbative phenomena in Quantum electrodynamics (QED). The quantitative analysis of realistic high intensity laser pulses is vital for understanding the effect of the field parameters on the momentum spectrum of the produced particles. In this study, we analyze chirped laser pulses with a sub-cycle structure, and investigate the effects of the chirp parameter on the momentum spectrum of the produced particles. The combined effect of the chirp and carrier phase of the laser pulse is also analyzed. These effects are qualitatively explained by investigating the turning point structure of the potential within the framework of the complex WKB scattering approach to pair production.

  6. Miniature, Rugged, Pulsed Laser Source for LIDAR Application Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Princeton Optronics proposes to develop a high energy pulsed laser source based on a novel approach. The approach consists of a technique to combine a large number...

  7. 20 W High Efficiency 1550 nm Pulsed Fiber Laser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — High peak power short pulsed lasers have been considered to be an enabling technology to build high power transmitters for future deep space high rate space...

  8. Femtosecond laser pulse train interaction with dielectric materials

    Science.gov (United States)

    Dematteo Caulier, O.; Mishchik, K.; Chimier, B.; Skupin, S.; Bourgeade, A.; Javaux Léger, C.; Kling, R.; Hönninger, C.; Lopez, J.; Tikhonchuk, V.; Duchateau, G.

    2015-11-01

    The interaction of trains of femtosecond microjoule laser pulses with dielectric materials by means of a multi-scale model is investigated. Theoretical predictions are directly confronted with experimental observations in soda-lime glass. It is shown that due to the low heat conductivity, a significant fraction of the laser energy can be accumulated in the absorption region. Depending on the pulse repetition rate, the material can be heated to high temperatures even though the single pulse energy is too low to induce a significant material modification. Regions heated above the glass transition temperature in the simulations correspond very well to zones of permanent material modifications observed in the experiments. It turns out that pulse-to-pulse variations of the laser absorption are negligible and of minor influence to permanent material modifications.

  9. Laser shaping of a relativistic circularly polarized pulse by laser foil interaction

    International Nuclear Information System (INIS)

    Laser shaping of a relativistic circularly polarized laser pulse in ultra-intense laser thin-foil interaction is investigated by theoretical analysis and particle-in-cell simulations. It is found that the plasma foil as a nonlinear optical shutter has an obvious cut-out effect on the laser temporal and spatial profiles. Two-dimensional particle-in-cell simulations show that the high intensity part of a Gaussian laser pulse can be well extracted from the whole pulse. The transmitted pulse with longitudinal steep rise front and transverse super-Gaussian profile is thus obtained which would be beneficial for the radiation pressure acceleration regime. The Rayleigh-Taylor-like instability is observed in the simulations, which destroys the foil and results in the cut-out effect of the pulse in the rise front of a circularly polarized laser

  10. Longitudinally excited CO2 laser with short laser pulse for hard tissue drilling

    Science.gov (United States)

    Uno, Kazuyuki; Hayashi, Hiroyuki; Akitsu, Tetsuya; Jitsuno, Takahisa

    2014-02-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse with a circular beam and a low divergence angle. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance, and a spark-gap switch. The laser pulse had a spike pulse width of 103 ns and a pulse tail length of 32.6 μs. The beam cross-section was circular and the full-angle beam divergence was 1.7 mrad. The laser was used to drill ivory samples without carbonization at fluences of 2.3-7.1 J/cm2. The drilling depth of the dry ivory increased with the fluence. The drilling mechanism of the dry ivory was attributed to absorption of the laser light by the ivory.

  11. Reduction of the pulse duration of the ultrafast laser pulses of the Two-Photon Laser Scanning Microscopy (2PLSM

    Directory of Open Access Journals (Sweden)

    Reshak Ali

    2008-07-01

    Full Text Available Abstract Background We provide an update of our two-photon laser scanning microscope by compressing or reducing the broadening of the pulse width of ultrafast laser pulses for dispersion precompensation, to enable the pulses to penetrate deeply inside the sample. Findings The broadening comes as the pulses pass through the optical elements. We enhanced and modified the quality and the sharpness of images by enhancing the resolution using special polarizer namely Glan Laser polarizer GL10. This polarizer consists of two prisms separated by air space. This air separation between the two prisms uses to delay the red wavelength when the light leaves the first prism to the air then to second prism. We note a considerable enhancing with using the GL polarizer, and we can see the details of the leaf structure in early stages when we trying to get focus through z-stacks of images in comparison to exactly the same measurements without using GL polarizer. Hence, with this modification we able to reduce the time of exposure the sample to the laser radiation thereby we will reduce the probability of photobleaching and phototoxicity. When the pulse width reduced, the average power of the laser pulses maintained at a constant level. Significant enhancement is found between the two kinds of images of the Two-Photon Excitation Fluorescence (TPEF. Conclusion In summary reduction the laser pulse width allowed to collect more diffraction orders which will used to form the images. The more diffraction orders the higher resolution images.

  12. Layer-by-layer pattern propagtion and pulsed laser deposition

    OpenAIRE

    Westerhoff, F.; Brendel, L.; Wolf, D. E.

    2001-01-01

    In this article kinetic Monte Carlo simulations for molecular beam epitaxy (MBE) and pulsed laser depositon (PLD) are compared. It will be shown that an optimal pattern conservation during MBE is achieved for a specific ratio of diffusion to deposition rate. Further on pulsed laser deposition is presented as an alternative way to control layer by layer growth. First results concerning the island density in the submonolayer regime are shown.

  13. Pulsed Laser Centre (CLPU). The Salamanca peta watt laser; Centro de Laseres Pulsados (CLPU). El laser de Petavatio de Salamanca

    Energy Technology Data Exchange (ETDEWEB)

    Franco, L. R.

    2016-08-01

    With pulses lasting 30 photo seconds, the CLPU VEGA laser is capable of generating a peak power level of one peta watt, this making it one of the worlds most powerful lasers. When focussed it can reach extreme intensities. The way in which a pulse of this nature interacts with an atom or what its applications might be are among the questions answered by this article. (Author)

  14. Ultrashort Laser Pulse Heating of Nanoparticles: Comparison of Theoretical Approaches

    Directory of Open Access Journals (Sweden)

    Renat R. Letfullin

    2008-01-01

    Full Text Available The interaction between nanoparticles and ultrashort laser pulses holds great interest in laser nanomedicine, introducing such possibilities as selective cell targeting to create highly localized cell damage. Two models are studied to describe the laser pulse interaction with nanoparticles in the femtosecond, picosecond, and nanosecond regimes. The first is a two-temperature model using two coupled diffusion equations: one describing the heat conduction of electrons, and the other that of the lattice. The second model is a one-temperature model utilizing a heat diffusion equation for the phonon subsystem and applying a uniform heating approximation throughout the particle volume. A comparison of the two modeling strategies shows that the two-temperature model gives a good approximation for the femtosecond mode, but fails to accurately describe the laser heating for longer pulses. On the contrary, the simpler one-temperature model provides an adequate description of the laser heating of nanoparticles in the femtosecond, picosecond, and nanosecond modes.

  15. Tunable repetitively pulsed Cr2+ : ZnSe laser

    International Nuclear Information System (INIS)

    Methods of wavelength tuning of a polycrystalline Cr2+ : ZnSe laser pumped by a repetitively pulsed Tm : YLF laser (pulse duration ∼100 ns, pulse repetition rate 3 KHz) are studied. With the use of a prism selector, the laser wavelength was tuned within the range of 2070 – 2400 nm at a linewidth of 11 nm for a SiO2 prism and 30 nm for a CaF2 prism. The use of a Lyot filter made it possible to tune the Cr2+ : ZnSe laser wavelength (with replacement of the cavity mirrors) within the spectral ranges of 2130 – 2400 and 2530 – 2750 nm at a linewidth of 4 nm. (lasers)

  16. Long-pulsed dye laser vs. intense pulsed light for the treatment of facial telangiectasias: a randomized controlled trial

    DEFF Research Database (Denmark)

    Nymann, Peter; Hedelund, Lene; Haedersdal, M

    2010-01-01

    This study aims to compare the efficacy and adverse effects of long-pulsed dye laser (LPDL) and intense pulsed light (IPL) in the treatment of facial telangiectasias.......This study aims to compare the efficacy and adverse effects of long-pulsed dye laser (LPDL) and intense pulsed light (IPL) in the treatment of facial telangiectasias....

  17. Pulse properties of external cavity mode locked semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Kroh, Marcel; Mørk, Jesper

    2006-01-01

    The performance of an external-cavity mode-locked semiconductor laser is investigated both theoretically and experimentally. The optimization analysis focuses on the regimes of stable mode locking and the generation of sub-picosecond optical pulses. We demonstrate stable output pulses down to one...

  18. Nonsequential Double Ionization of Atoms in Strong Laser Pulses

    Science.gov (United States)

    Prauzner-Bechcicki, J. S.; Sacha, K.; Eckhardt, B.; Zakrzewski, J.

    2007-10-01

    It is now possible to produce laser pulses with reproducible pulse shape and controlled carrier envelope phase. It is discussed how that can be explored in double ionisation studies. To this end we solve numerically the Schrödinger equation for a limited dimensionality model which nevertheless treats electron repulsion qualitatively correctly and allows to study correlation effects due to the Coulomb repulsion.

  19. Response of dosemeters in the radiation field generated by a TW-class laser system

    International Nuclear Information System (INIS)

    State-of-the-art laser systems are able to generate ionising radiation of significantly high energies by focusing ultra-short and intense pulses onto targets. Thus, measures ensuring the radiation protection of both working personnel and the general public are required. However, commercially available dosemeters are primarily designed for measurement in continuous fields. Therefore, it is important to explore their response to very short pulses. In this study, the responses of dosemeters in a radiation field generated by iodine high-power and Ti:Sapphire laser systems are examined in proton and electron acceleration experiments. Within these experiments, electron bunches of femtosecond pulse duration and 100-MeV energy and proton bunches with sub-nanosecond pulse duration and energy of several megaelectronvolts were generated in single-shot regimes. Responses of typical detectors (TLD, films and electronic personal dosemeter) were analysed and compared. Further, a first attempt was carried out to characterise the radiation field generated by TW-class laser systems. Passive and active dosemeters were used for characterisation of pulsed radiation fields generated by lasers within electron and proton acceleration experiments. Generally, passive, compared with active, systems have the disadvantage of a postponed read-out. However, behaviour of passive systems in the pulsed field seems to be more reliable. Still, results of this study suggest that it might be possible to use active systems under special conditions. Whereas EPDs are not able to reliably detect very short pulses at low repetition rates, their response is promising at higher repetition rates for off-beam locations. Finally, it appears that the definition of the source term of a laser-generated field is not as straightforward as was anticipated. Obtaining a more accurate source term definition for radioprotection purposes would require knowledge and combination of data of at least two sources: generated

  20. Attosecond laser pulse ionization of atoms and molecules

    International Nuclear Information System (INIS)

    Ionization dynamics of atoms and molecules under attosecond laser pulses with various photon energies and peak intensities have been investigated using the Time-Dependent Close-Coupling (TDCC) method. We predict the chirp effects on the triply differential probabilities for the ionized electrons of He produced by 450 and 135 asec pulses. In addition, we shall apply our generalized TDCC method to examine the four-body breakup dynamics of molecular hydrogen induced by these ultrashort pulses.

  1. Generation of a synchronized pulse of extraordinary precision using chirped pulse laser

    International Nuclear Information System (INIS)

    We have developed the generation system of synchronized pulses of high precision using chirped pulse laser. The PW laser is synchronized to Gekko XII beams within 10 picosecond by injecting part of the PW laser into the Gekko XII laser system. A part of the 3 ns/6 nm (pulse width/spectral width) output from the front end is stretched to 5.5 ns/5 nm and is then sliced to 1.1 ns/nm width and injected into Gekko XII system. We have obtained 2.5-kJ output energy at a 532-nm wavelength from 12 semi-Gaussian beams. The pulse width is 1.1 ± 0.1 ns (FWHM) and the conversion efficiency from 1 to 0.5 mm was 43%. (author)

  2. Pulsed laser ablation of GaAs using nano pulse length

    International Nuclear Information System (INIS)

    Ablation using very short pulses has shown a great promise in facilitating the growth of complex multi-element films with stoichiometries matching those of their parent materials. GaAs is an important material in the electronic and opto-electronic industries and due to its compound structure it is an intriguing candidate for pulsed laser deposition. This work investigates the effect of nanosecond laser pulse lengths on the ablation of GaAs in an inert atmosphere. The number of pulses was varied in order to find the optimal condition for nano particles formation in our setup. The deposited structures were studied by grazing incidence small angle X-ray scattering and atomic force microscopy. It is shown that the GaAs nanoparticle sizes and size distributions can be controlled partly by the number of laser pulses applied in their production.

  3. The effect of the laser wavelength on collinear double pulse laser induced breakdown spectroscopy (DP-LIBS)

    Science.gov (United States)

    Wang, Qi; Lin, Yanqing; Liu, Jing; Fan, Shuang; Xu, Zhuopin; Huang, Qing; Wu, Yuejin

    2016-05-01

    The pulsed lasers at wavelengths of 532 nm and 1064 nm were used as two beams of light for collinear double pulse laser induced breakdown spectroscopy (DP-LIBS). By changing the time sequence of two beams of different lasers, we studied the effect of the interval of two pulses of DP-LIBS on spectral signals compared with single pulsed (SP) LIBS.

  4. Mitigation technique for use of CMOS image sensors in megajoule class laser radiative environment

    OpenAIRE

    Goiffon, Vincent; Girard, Sylvain; Paillet, Philippe; Magnan, Pierre; Chabane, Aziouz; Rousseau, Adrien; Darbon, Stéphane; Cervantes, Paola; Bourgade, Jean-Luc

    2012-01-01

    Presented is a new mitigation technique to improve the radiation tolerance of CMOS image sensors to the radiation constraints associated to the fusion by inertial confinement experiments at megajoule class laser facilities. Using the global reset mode, results acquired at the OMEGA facility show the efficiency of this technique to reduce by more than 70% the number of white pixels induced by the mixed 14%MeV neutron and %-ray pulse.

  5. Mitigation technique for use of CMOS image sensors in mega-joule class laser radiative environment

    International Nuclear Information System (INIS)

    Presented is a new mitigation technique to improve the radiation tolerance of CMOS image sensors to the radiation constraints associated to the fusion by inertial confinement experiments at mega-joule class laser facilities. Using the global reset mode, results acquired at the OMEGA facility show the efficiency of this technique to reduce by more than 70% the number of white pixels induced by the mixed 14 MeV neutron and gamma-ray pulse. (authors)

  6. Synchronization of Sub-Picosecond Electron and Laser Pulses

    International Nuclear Information System (INIS)

    Sub-picosecond laser-electron synchronization is required to take full advantage of the experimental possibilities arising from the marriage of modern high intensity lasers and high brightness electron beams in the same laboratory. Two particular scenarios stand out in this regard, injection of ultra-short electron pulses in short wavelength laser-driven plasma accelerators, and Compton scattering of laser photons from short electron pulses. Both of these applications demand synchronization, which is subpicosecond, with tens of femtosecond synchronization implied for next-generation experiments. Typically, an RF electron accelerator is synchronized to a short pulse laser system by detecting the repetition signal of a laser oscillator, adjusted to an exact subharmonic of the linac RF frequency, and multiplying or phase locking this signal to produce the master RF clock. Pulse-to-pulse jitter characteristic of self-mode-locked laser oscillators represents a direct contribution to the ultimate timing jitter between a high intensity laser focus and electron beam at the interaction point, or a photocathode drive laser in an RF photoinjector. This timing jitter problem has been addressed most seriously in the context of the RF photoinjector, where the electron beam properties are sensitive functions of relative timing jitter. The timing jitter achieved in synchronized photocathode drive laser systems is near, or slightly below one picosecond. The ultimate time of arrival jitter of the beam at the photoinjector exit is typically a bit smaller than the photocathode drive-laser jitter due to velocity compression effects in the first RF cell of the gun. This tendency of the timing of the electron beam arrival at a given spatial point to lock to the RF lock is strongly reinforced by use of magnetic compression

  7. Theory and simulation of ultra-short pulse laser interactions

    Energy Technology Data Exchange (ETDEWEB)

    More, R.; Walling, R.; Price, D.; Guethlein, G.; Stewart, R.; Libby, S.; Graziani, F.; Levatin, J. [Lawrence Livermore National Lab., Livermore, CA (United States)

    1998-03-01

    This paper describes recent Livermore work aimed at building computational tools to describe ultra-short pulse laser plasmas. We discuss calculations of laser absorption, atomic data for high-charge ions, and a new idea for linear-response treatment of non-equilibrium phenomena near LTE. (author)

  8. Ion and neutral emission from pulsed laser irradiation of metals

    Czech Academy of Sciences Publication Activity Database

    Torrisi, L.; Andó, L.; Gammino, S.; Krása, Josef; Láska, Leoš

    2001-01-01

    Roč. 184, - (2001), s. 327-336. ISSN 0168-583X Institutional research plan: CEZ:AV0Z1010921 Keywords : pulse laser irradiation * ion neutral emission * plasma * time of flight Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.041, year: 2001

  9. DEVICE FOR INVESTIGATION OF MAGNETRON AND PULSED-LASER PLASMA

    Directory of Open Access Journals (Sweden)

    A. P. Burmakov

    2012-01-01

    Full Text Available Various modifications of complex pulsed laser and magnetron deposition thin-film structures unit are presented. They include joint and separate variants of layer deposition. Unit realizes the plasma parameters control and enhances the possibility of laser-plasma and magnetron methods of coatings deposition.

  10. Resonant infrared pulsed laser deposition of thin biodegradable polymer films

    DEFF Research Database (Denmark)

    Bubb, D.M.; Toftmann, B.; Haglund Jr., R.F.;

    2002-01-01

    Thin films of the biodegradable polymer poly(DL-lactide-co-glycolide) (PLGA) were deposited using resonant infrared pulsed laser deposition (RIR-PLD). The output of a free-electron laser was focused onto a solid target of the polymer, and the films were deposited using 2.90 (resonant with O...

  11. Precision machining of pig intestine using ultrafast laser pulses

    Science.gov (United States)

    Beck, Rainer J.; Góra, Wojciech S.; Carter, Richard M.; Gunadi, Sonny; Jayne, David; Hand, Duncan P.; Shephard, Jonathan D.

    2015-07-01

    Endoluminal surgery for the treatment of early stage colorectal cancer is typically based on electrocautery tools which imply restrictions on precision and the risk of harm through collateral thermal damage to the healthy tissue. As a potential alternative to mitigate these drawbacks we present laser machining of pig intestine by means of picosecond laser pulses. The high intensities of an ultrafast laser enable nonlinear absorption processes and a predominantly nonthermal ablation regime. Laser ablation results of square cavities with comparable thickness to early stage colorectal cancers are presented for a wavelength of 1030 nm using an industrial picosecond laser. The corresponding histology sections exhibit only minimal collateral damage to the surrounding tissue. The depth of the ablation can be controlled precisely by means of the pulse energy. Overall, the application of ultrafast lasers to ablate pig intestine enables significantly improved precision and reduced thermal damage to the surrounding tissue compared to conventional techniques.

  12. Ultrashort pulsed fiber laser welding and sealing of transparent materials.

    Science.gov (United States)

    Huang, Huan; Yang, Lih-Mei; Liu, Jian

    2012-05-20

    In this paper, methods of welding and sealing optically transparent materials using an ultrashort pulsed (USP) fiber laser are demonstrated which overcome the limit of small area welding of optical materials. First, the interaction of USP fiber laser radiation inside glass was studied and single line welding results with different laser parameters were investigated. Then multiline scanning was used to obtain successful area bonding. Finally, complete four-edge sealing of fused silica substrates with a USP laser was demonstrated and the hermetic seal was confirmed by water immersion test. This laser microwelding technique can be extended to various applications in the semiconductor industry and precision optic manufacturing. PMID:22614601

  13. Laser and intense pulsed light hair removal technologies

    DEFF Research Database (Denmark)

    Haedersdal, M; Beerwerth, F; Nash, J F

    2011-01-01

    Light-based hair removal (LHR) is one of the fastest growing, nonsurgical aesthetic cosmetic procedures in the United States and Europe. A variety of light sources including lasers, e.g. alexandrite laser (755 nm), pulsed diode lasers (800, 810 nm), Nd:YAG laser (1064 nm) and broad-spectrum intense...... devices have been sold directly to consumers for treatment in the home. In this review, we outline the principles underlying laser and IPL technologies and undertake an evidence-based assessment of the short- and long-term efficacy of the different devices available to the practising dermatologist...

  14. Photonic crystal Fano laser: terahertz modulation and ultrashort pulse generation.

    Science.gov (United States)

    Mork, J; Chen, Y; Heuck, M

    2014-10-17

    We suggest and analyze a laser with a mirror realized by Fano interference between a waveguide and a nanocavity. For small-amplitude modulation of the nanocavity resonance, the laser can be modulated at frequencies exceeding 1 THz, not being limited by carrier dynamics as for conventional lasers. For larger modulation, a transition from pure frequency modulation to the generation of ultrashort pulses is observed. The laser dynamics is analyzed by generalizing the field equation for conventional lasers to account for a dynamical mirror, described by coupled mode theory. PMID:25361259

  15. Pulse Selection Control for the IR FEL Photocathode Drive Laser

    Science.gov (United States)

    Jordan, K.; Evans, R.; Garza, O.; Hill, R.; Shinn, M.; Song, J.; Venhaus, D.

    1997-05-01

    The method for current control of the photocathode source is described. This device allows remote control of drive laser output pulses for resulting beam currents of less than 1 microamp to full current of 5 milliamps. The low current modes are accomplished by counting discrete micropulses and gating electro-optical cells. The higher current modes are done by varying both the photons per pulse and the frequency of the laser output pulses. Programmable Logic Devices (PLDs) provide the choice in micropulses per macropulse and the macropulse frequency. All macropulses are line locked to 60 Hz and have the ability to be slewed through a line cycle in discrete steps.

  16. Femtosecond laser pulse train interaction with dielectric materials

    CERN Document Server

    Caulier, O Dematteo; Chimier, B; Skupin, S; Bourgeade, A; Léger, C Javaux; Kling, R; Hönninger, C; Lopez, J; Tikhonchuk, V; Duchateau, G

    2015-01-01

    We investigate the interaction of trains of femtosecond microjoule laser pulses with dielectric materials by means of a multi-scale model. Our theoretical predictions are directly confronted with experimental observations in soda-lime glass. We show that due to the low heat conductivity, a significant fraction of the laser energy can be accumulated in the absorption region. Depending on the pulse repetition rate, the material can be heated to high temperatures even though the single pulse energy is too low to induce a significant material modification. Regions heated above the glass transition temperature in our simulations correspond very well to zones of permanent material modifications observed in the experiments.

  17. Bimodal Size Distribution of Gold Nanoparticles under Picosecond Laser Pulses.

    Science.gov (United States)

    Inasawa, Susumu; Sugiyama, Masakazu; Yamaguchi, Yukio

    2005-05-19

    The evolution of size distributions of gold nanoparticles under pulsed laser irradiation (Nd:YAG, lambda = 355 nm, pulse width 30 ps) was carefully observed by transmission electron microscopy. Interestingly, the initial monomodal size distribution of gold nanoparticles turned into a bimodal one, with two peaks in the number of particles, one at 6 nm and the other at 16-24 nm. The sizes for small particles depended very little on the irradiated laser energy. This change is attributed to laser-induced size reduction of the initial gold nanoparticles followed by the formation of small particles. In our analysis, we extracted a characteristic value for the size-reduction rate per one pulse and revealed that laser-induced size reduction of gold nanoparticles occurred even below the boiling point. When laser energy is insufficient for the boiling of particles, formation of gold vapor around liquid gold drops is thought to cause the phenomenon. With enough laser energy for the boiling, the formation of gold vapor around and inside liquid gold drops is responsible for the phenomenon. We also observed particles with gold strings after one pulse irradiation with a laser energy of 43 mJ cm(-2) pulse(-1), which is sufficient energy for the boiling. It is considered that such particles with gold strings are formed by the projection of gaseous gold from liquid gold drops with some volume of liquid gold around the bubble. On the basis of comparison with previous work, picosecond laser pulses are thought to be the most efficient way to cause laser-induced size reduction of gold nanoparticles. PMID:16852127

  18. Pulse-shaping mechanism in colliding-pulse mode-locked laser diodes

    DEFF Research Database (Denmark)

    Bischoff, Svend; Sørensen, Mads Peter; Mørk, J.;

    1995-01-01

    The large signal dynamics of passively colliding pulse mode-locked laser diodes is studied. We derive a model which explains modelocking via the interplay of gain and loss dynamics; no bandwidth limiting element is necessary for pulse formation. It is found necessary to have both fast and slow...

  19. Dynamical spin effects in ultra-relativistic laser pulses

    OpenAIRE

    Wen, Meng; Bauke, Heiko; Keitel, Christoph H.

    2014-01-01

    The dynamics of single laser-driven electrons and many particle systems with spin are investigated on the basis of a classical theory. We demonstrate that the spin forces can alter the electron dynamics in an ultra-relativistic laser field due to the coupling of the electron's spin degree of freedom to its kinematic momentum. High-energy electrons can acquire significant spin-dependent transverse momenta while passing through a counterpropagating ultra-relativistic infrared laser pulse. Numer...

  20. Irradiation experiment of textile materials by excimer laser pulses

    International Nuclear Information System (INIS)

    The results of the irradiation experiment of natural and synthetic textile materials by XeCl (excimer) laser pulses (emission wavelenght λ=0.308 μm) are presented. The friction, finish and look variations of the irradiated textiles are examined as a function of the laser radiation parameters (e. g. fluence and shots number). The possibility of using excimer laser systems on industrial bases is also discussed

  1. Toward attosecond electron pulses using ultra-intense lasers

    Science.gov (United States)

    Varin, Charles; Fortin, Pierre-Louis; Piché, Michel

    2008-06-01

    In many countries around the world, ultra-intense laser facilities are being built. These state-of-the-art lasers are intended for innovative medical and technological applications, as well as for basic experiments at the frontiers of fundamental science. Laser particle acceleration is a promising new endeavor. Recently developed schemes using radially polarized beams could help in reaching unprecedentedly short electron pulse durations, well in the attosecond range and potentially in the subattosecond range.

  2. Mathematical modelling of multiple pulsed laser percussion drilling

    OpenAIRE

    Suchatawat, Maturose

    2012-01-01

    In laser percussion drilling, a series of laser pulses with specified energies and durations irradiate the workpiece surface to gradually heat, melt, and vaporise material until a hole with required depth and diameter is achieved. Despite being the quickest technique for producing small diameter holes, laser percussion drilling regularly suffers from difficulties in controlling the hole quality such as hole circularity, hole taper and recast layer. Therefore, in order to produce holes to a sp...

  3. Deuterium Clusters Fusion Induced by the Intense Femtosecond Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    LIU Hong-Jie; CHEN Jia-Bin; WANG Hong-Bin; JIAO Chun-Ye; HE Ying-Ling; WEN Tian-Shu; WEN Xian-Lun; CHEN Ming; ZHENG Zhi-Jian; GU Yu-Qiu; ZHANG Bao-Han; RHEE Yong-Joo; NAM Sung-Mo; HAN Jae-Min; RHEE Yong-Woo; YEA Kwon-Hae

    2007-01-01

    Neutrons (2.45 MeV) from deuterium cluster fusion induced by the intense femtosecond (30 fs) laser pulse are experimentally demonstrated. The average neutron yield 103 per shot is obtained. It is found that the yield slightly increases with the increasing laser spot size. No neutron can be observed when the laser intensity Ⅰ <4.3×1015 W/cm2.

  4. Stoichiometric magnetite grown by infrared nanosecond pulsed laser deposition

    OpenAIRE

    Sanz, Mikel; Oujja, M.; Rebollar, Esther; Marco, J. F.; Figuera, Juan de la; Monti, Matteo; Bollero, A.; Camarero, J.; Pedrosa, Francisco J.; García-Hernández, M.; Castillejo, Marta

    2013-01-01

    Pulsed laser deposition (PLD) is a versatile technique for the fabrication of nanostructures due to the possibilities it offers to control size and shape of nanostructured deposits by varying the laser parameters. Magnetite nanostructures are currently promising materials to be used in computing, electronic devices and spintronic applications. For all these uses the fabrication of uniform nanostructured pure magnetite thin films is highly advantageous. In PLD of magnetite, the laser irradiati...

  5. Mechanism study of skin tissue ablation by nanosecond laser pulses

    Science.gov (United States)

    Fang, Qiyin

    Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to improve future design of the pulsed lasers for dermatology and plastic surgery. Multiple laser and optical configurations have been constructed to generate 9 to 12ns laser pulses with similar profiles at 1064. 532, 266 and 213nm for this study of skin tissue ablation. Through measurements of ablation depth as a function cf laser pulse energy, the 589nm spectral line in the secondary radiation from ablated skin tissue samples was identified as the signature of the occurrence of ablation. Subsequently, this spectral signature has been used to investigate the probabilistic process of the ablation near the threshold at the four wavelengths. Measurements of the ablation probability were conducted as a function of the electrical field strength of the laser pulse and the ablation thresholds in a wide spectral range from 1064nm to 213nm were determined. Histology analysis and an optical transmission method were applied in assessing of the ablation depth per pulse to study the ablation process at irradiance levels higher than threshold. Because more than 70% of the wet weight of the skin tissue is water, optical breakdown and backscattering in water was also investigated along with a nonlinear refraction index measurement using a z-scan technique. Preliminary studies on ablation of a gelatin based tissue phantom are also reported. The current theoretical models describing ablation of soft tissue ablation by short laser pulses were critically reviewed. Since none of the existing models was found capable of explaining the experimental results, a new plasma-mediated model was developed

  6. Propagation of intense, ultrashort laser pulses through preionized plasma slabs

    International Nuclear Information System (INIS)

    Relativistic self-focusing and channel formation induced by intense, ultrashort laser pulses in preionized targets is modeled for accessible experimental parameters. The stability of channel formation is limited by the nonparaxiality of the laser beam in regions of tight self-focusing. This issue is examined with recently developed nonparaxial theory. Channel formation is also characterized in terms of the transmitted pulse spectrum, the transmitted laser intensity profile, and the radial electron density distribution. Calculations indicate a signature spectral shift in transmission biased toward longer wavelengths, which is attributed to the rapid expulsion of electrons away from the propagation axis

  7. Interaction physics of multipicosecond Petawatt laser pulses with overdense plasma.

    Science.gov (United States)

    Kemp, A J; Divol, L

    2012-11-01

    We study the interaction of intense petawatt laser pulses with overdense plasma over several picoseconds, using two- and three-dimensional kinetic particle simulations. Sustained irradiation with non-diffraction-limited pulses at relativistic intensities yields conditions that differ qualitatively from what is experimentally available today. Nonlinear saturation of laser-driven density perturbations at the target surface causes recurrent emissions of plasma, which stabilize the surface and keep absorption continuously high. This dynamics leads to the acceleration of three distinct groups of electrons up to energies many times the laser ponderomotive potential. We discuss their energy distribution for applications like the fast-ignition approach to inertial confinement fusion. PMID:23215393

  8. Small rare gas clusters in XUV laser pulses

    CERN Document Server

    Bauer, D

    2003-01-01

    Semi-classical molecular dynamics simulations of small rare gas clusters in short laser pulses of 100 nm wavelength were performed. For comparison, the cluster response to 800 nm laser pulses was investigated as well. The inner ionization dynamics of the multi-electron atoms inside the cluster was treated explicitly. The simulation results underpin that at XUV wavelengths collisions play an important role in the energy absorption and the generation of the surprisingly high charge states of Xe atoms inside clusters, as they were observed in the free-electron laser experiment at DESY, Hamburg, Germany [Wabnitz et al., Nature 420, 482 (2002)].

  9. Propagation of intense laser pulses in strongly magnetized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Yang, X. H., E-mail: xhyang@nudt.edu.cn; Ge, Z. Y.; Xu, B. B.; Zhuo, H. B.; Ma, Y. Y.; Shao, F. Q. [College of Science, National University of Defense Technology, Changsha 410073 (China); Yu, W., E-mail: weiyu@mail.shcnc.ac.cn [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Xu, H. [School of Computer Science, National University of Defense Technology, Changsha 410073 (China); Yu, M. Y., E-mail: myyu@zju.edu.cn [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Institut für Theoretische Physik I, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Borghesi, M. [School of Mathematics and Physics, Queen' s University of Belfast, Belfast BT7 1NN (United Kingdom)

    2015-06-01

    Propagation of intense circularly polarized laser pulses in strongly magnetized inhomogeneous plasmas is investigated. It is shown that a left-hand circularly polarized laser pulse propagating up the density gradient of the plasma along the magnetic field is reflected at the left-cutoff density. However, a right-hand circularly polarized laser can penetrate up the density gradient deep into the plasma without cutoff or resonance and turbulently heat the electrons trapped in its wake. Results from particle-in-cell simulations are in good agreement with that from the theory.

  10. Laser ablation of iron: A comparison between femtosecond and picosecond laser pulses

    International Nuclear Information System (INIS)

    In this study, a comparison between femtosecond (fs) and picosecond (ps) laser ablation of electrolytic iron was carried out in ambient air. Experiments were conducted using a Ti:sapphire laser that emits radiation at 785 nm and at pulse widths of 110 ps and 130 fs, before and after pulse compression, respectively. Ablation rates were calculated from the depth of craters produced by multiple laser pulses incident normally to the target surface. Optical and scanning electron microscopy showed that picosecond laser pulses create craters that are deeper than those created by the same number of femtosecond laser pulses at the same fluence. Most of the ablated material was ejected from the ablation site in the form of large particles (few microns in size) in the case of picosecond laser ablation, while small particles (few hundred nanometers) were produced in femtosecond laser ablation. Thermal effects were apparent at high fluence in both femtosecond and picosecond laser ablation, but were less prevalent at low fluence, closer to the ablation threshold of the material. The quality of craters produced by femtosecond laser ablation at low fluence is better than those created at high fluence or using picosecond laser pulses

  11. Electroporation visualized under a multishot pulsed laser fluorescence microscope system

    Science.gov (United States)

    Itoh, Hiroyasu; Yu, Irene I. K.; Hibino, Masahiro; Hayakawa, Tsuyoshi; Kinosita, Kazuhiko, Jr.

    1993-10-01

    We describe a new fluorescence microscope system, which is the third generation of our pulsed-laser microscope systems developed for the purpose of capturing rapid cellular phenomena. Time resolution of this latest version is supported by the combination of a Q- switched Nd:YAG laser producing a burst of 4 pulses and a large format framing camera. We obtain series images at intervals on the order of 10 microsecond(s) with exposure times of 30 ns. With this multi-shot pulsed laser fluorescence microscope system, we examined the behavior of the transmembrane potential in a sea urchin egg under an intense electric field. Irreversible process of cell electroporation was revealed in serial images taken under a single electric pulse of microsecond duration.

  12. Xenon plasma sustained by pulse-periodic laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Rudoy, I. G.; Solovyov, N. G.; Soroka, A. M.; Shilov, A. O.; Yakimov, M. Yu., E-mail: yakimov@lantanlaser.ru [Russian Academy of Sciences, A. Ishlinsky Institute for Problems in Mechanics (Russian Federation)

    2015-10-15

    The possibility of sustaining a quasi-stationary pulse-periodic optical discharge (POD) in xenon at a pressure of p = 10–20 bar in a focused 1.07-μm Yb{sup 3+} laser beam with a pulse repetition rate of f{sub rep} ⩾ 2 kHz, pulse duration of τ ⩾ 200 μs, and power of P = 200–300 W has been demonstrated. In the plasma development phase, the POD pulse brightness is generally several times higher than the stationary brightness of a continuous optical discharge at the same laser power, which indicates a higher plasma temperature in the POD regime. Upon termination of the laser pulse, plasma recombines and is then reinitiated in the next pulse. The initial absorption of laser radiation in successive POD pulses is provided by 5p{sup 5}6s excited states of xenon atoms. This kind of discharge can be applied in plasma-based high-brightness broadband light sources.

  13. FY07 LDRD Final Report Precision, Split Beam, Chirped-Pulse, Seed Laser Technology

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, J W; Messerly, M J; Phan, H H; Crane, J K; Beach, R J; Siders, C W; Barty, C J

    2009-11-12

    The goal of this LDRD ER was to develop a robust and reliable technology to seed high-energy laser systems with chirped pulses that can be amplified to kilo-Joule energies and recompressed to sub-picosecond pulse widths creating extremely high peak powers suitable for petawatt class physics experiments. This LDRD project focused on the development of optical fiber laser technologies compatible with the current long pulse National Ignition Facility (NIF) seed laser. New technologies developed under this project include, high stability mode-locked fiber lasers, fiber based techniques for reduction of compressed pulse pedestals and prepulses, new compact stretchers based on chirped fiber Bragg gratings (CFBGs), new techniques for manipulation of chirped pulses prior to amplification and new high-energy fiber amplifiers. This project was highly successful and met virtually all of its goals. The National Ignition Campaign has found the results of this work to be very helpful. The LDRD developed system is being employed in experiments to engineer the Advanced Radiographic Capability (ARC) front end and the fully engineered version of the ARC Front End will employ much of the technology and techniques developed here.

  14. The interaction of intense subpicosecond laser pulses with underdense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Coverdale, C.A.

    1995-05-11

    Laser-plasma interactions have been of interest for many years not only from a basic physics standpoint, but also for their relevance to numerous applications. Advances in laser technology in recent years have resulted in compact laser systems capable of generating (psec), 10{sup 16} W/cm{sup 2} laser pulses. These lasers have provided a new regime in which to study laser-plasma interactions, a regime characterized by L{sub plasma} {ge} 2L{sub Rayleigh} > c{tau}. The goal of this dissertation is to experimentally characterize the interaction of a short pulse, high intensity laser with an underdense plasma (n{sub o} {le} 0.05n{sub cr}). Specifically, the parametric instability known as stimulated Raman scatter (SRS) is investigated to determine its behavior when driven by a short, intense laser pulse. Both the forward Raman scatter instability and backscattered Raman instability are studied. The coupled partial differential equations which describe the growth of SRS are reviewed and solved for typical experimental laser and plasma parameters. This solution shows the growth of the waves (electron plasma and scattered light) generated via stimulated Raman scatter. The dispersion relation is also derived and solved for experimentally accessible parameters. The solution of the dispersion relation is used to predict where (in k-space) and at what frequency (in {omega}-space) the instability will grow. Both the nonrelativistic and relativistic regimes of the instability are considered.

  15. Laser micro-processing of silicon using nanosecond pulse shaped fibre laser at 1 ?m wavelength

    OpenAIRE

    LI, Kun

    2012-01-01

    Processing of Si in the semiconductor and solar cell industry has been dominated by the Diode Pumped Solid State (DPSS) Ultraviolet (UV) laser. Recent advances in laser source technology have produced fibre lasers with Master Oscillator Power Amplifier (MOPA) architectures that offer high repetition rates, high operational efficiencies, and pulse modulation controls exceeding those of typical Q-switched DPSS lasers. The aim of this research is to investigate 1 ?m fibre laser machining of Si w...

  16. Space-selective laser joining of dissimilar transparent materials using femtosecond laser pulses

    International Nuclear Information System (INIS)

    We report on the joining of dissimilar transparent materials based on localized melting and resolidification of the materials only around the focal volume due to nonlinear absorption of focused femtosecond laser pulses. We demonstrate the joining of borosilicate glass and fused silica, whose coefficients of thermal expansion are different. The joint strength and the transmittance through joint volume were investigated by varying the translation velocity of the sample and the pulse energy of the irradiated laser pulses

  17. Envelope evolution of a laser pulse in an active medium

    International Nuclear Information System (INIS)

    The authors show that the envelope velocity, venv, of a short laser pulse can, via propagation in an active medium, be made less than, equal to, or even greater than c, the vacuum phase velocity of light. Simulation results, based on moving frame propagation equations coupling the laser pulse, active medium and plasma, are presented, as well as equations that determines the design value of super- and sub-luminous venv. In this simulation the laser pulse evolves in time in a moving frame as opposed to their earlier work where the profile was fixed. The elimination of phase slippage and pump depletion effects in the laser wakefield accelerator is discussed as a particular application. Finally they discuss media properties necessary for an experimental realization of this technique

  18. Medical applications of ultra-short pulse lasers

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B M; Marion, J E

    1999-06-08

    The medical applications for ultra short pulse lasers (USPLs) and their associated commercial potential are reviewed. Short pulse lasers offer the surgeon the possibility of precision cutting or disruption of tissue with virtually no thermal or mechanical damage to the surrounding areas. Therefore the USPL offers potential improvement to numerous existing medical procedures. Secondly, when USPLs are combined with advanced tissue diagnostics, there are possibilities for tissue-selective precision ablation that may allow for new surgeries that cannot at present be performed. Here we briefly review the advantages of short pulse lasers, examine the potential markets both from an investment community perspective, and from the view. of the technology provider. Finally nominal performance and cost requirements for the lasers, delivery systems and diagnostics and the present state of development will be addressed.

  19. Assessment and mitigation of radiation, EMP, debris and shrapnel impacts at megajoule-class laser facilities

    International Nuclear Information System (INIS)

    The generation of neutron/gamma radiation, electromagnetic pulses (EMP), debris and shrapnel at mega-Joule class laser facilities (NIF and LMJ) impacts experiments conducted at these facilities. The complex 3D numerical codes used to assess these impacts range from an established code that required minor modifications (MCNP - calculates neutron and gamma radiation levels in complex geometries), through a code that required significant modifications to treat new phenomena (EMSolve - calculates EMP from electrons escaping from laser targets), to a new code, ALE-AMR, that is being developed through a joint collaboration between LLNL, CEA, and UC (UCSD, UCLA, and LBL) for debris and shrapnel modelling.

  20. Complex Spectra Structure of an Attosecond Pulse Train Driven by Sub-5-fs Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    YUN Chen-Xia; TENG Hao; ZHANG Wei; WANG Li-Feng; ZHAN Min-Jie; HE Xin-Kui; WANG Bing-Bing; WEI Zhi-Yi

    2011-01-01

    We present the observation of the additional spectral components between the odd order harmonics in the harmonic spectrum generated from argon gas driven by sub-5-fs laser pulses.The theoretical analysis shows that the asymmetric laser field in both spatial and temporal domains leads to this complicated spectrum structure of high order harmonics.

  1. A Novel Femtosecond Laser System for Attosecond Pulse Generation

    Directory of Open Access Journals (Sweden)

    Jianqiang Zhu

    2012-01-01

    Full Text Available We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA. The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the KDP crystal as the gain medium to ensure the shortest pulse. After the completion, the laser will deliver about 8 J with pulse duration of about 10 femtoseconds, which should be beneficial to the attosecond pulse generation and other ultrafast experiments.

  2. Generation of ultrashort electron bunches by colliding laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, C.B.; Lee, P.B.; Wurtele, J.S. [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States); Esarey, E. [Beam Physics Branch, Plasma Physics Division, Navel Research Laboratory, Washington, District of Columbia 20375 (United States); Leemans, W.P. [Center for Beam Physics, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    1999-07-01

    A proposed laser-plasma based relativistic electron source [E. Esarey {ital et al.}, Phys. Rev. Lett. {bold 79}, 2682 (1997)] using laser triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counter-propagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses. {copyright} {ital 1999 American Institute of Physics.}

  3. Pulsed Single Frequency MOPA Laser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Latest advances in semiconductor optoelectronics makes it possible to develop compact light weight robust sources of coherent optical pulses, demanded for numerous...

  4. Self-pinching of pulsed laser beams during filamentary propagation

    International Nuclear Information System (INIS)

    Competing nonlinear optical effects that act on femtosecond laser pulses propagating in a self-generated light filament may give rise to a pronounced radial beam deformation, similar to the z-pinch contraction of pulsed high-current discharges. This self-generated spatial beam contraction is accompanied by a pulse break-up that can be beneficially exploited for on-axis temporal compression of the pulse. The pinching mechanism therefore explains the recently observed self-compression and the complicated spatio-temporal shapes typical for filament propagation experiments. (authors)

  5. Double-pulse laser ablation sampling: Enhancement of analyte emission by a second laser pulse at 213 nm

    International Nuclear Information System (INIS)

    For the purpose of devising methods for minimally destructive multi-element analysis, we compare the performance of a 266 nm–213 nm double-pulse scheme against that of the single 266 nm pulse scheme. The first laser pulse at 266 nm ablates a mica sample. Ten ns later, the second pulse at 213 nm and 64 mJ cm−2 orthogonally intercepts the gas plume to enhance the analyte signal. Emissions from aluminum, silicon, magnesium and sodium are simultaneously observed. At low 266 nm laser fluence when only sub-ng of sample mass is removed, the signal enhancement by the 213 nm pulse is especially apparent. The minimum detectable amount of aluminum is about 24 fmol; it will be a hundred times higher if the sample is analyzed by the 266 nm pulse alone. The minimum detectable mass for the other analytes is also reduced by about two orders of magnitude when the second pulse at 213 nm is introduced. The spectral and temporal properties of the enhanced signal are consistent with the mechanism of ultra-violet laser excited atomic fluorescence of dense plumes. - Highlights: • We devise a two-laser-pulse scheme to analyze the elemental composition of mica as test samples. • We compare the analytical performance of the single 266 nm pulse scheme against the 266 nm – 213 nm two pulse scheme. • The two pulse scheme improves the absolute LODs of the analytes by about a hundred times. • The spectral and temporal properties of the enhanced signal are consistent with the mechanism

  6. Double-pulse laser ablation sampling: Enhancement of analyte emission by a second laser pulse at 213 nm

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Bruno Yue [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong (China); Mao, Xianglei [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Hou, Huaming [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Ocean University of China, Qingdao (China); Zorba, Vassilia; Russo, Richard E. [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Cheung, Nai-Ho, E-mail: nhcheung@hkbu.edu.hk [Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong (China)

    2015-08-01

    For the purpose of devising methods for minimally destructive multi-element analysis, we compare the performance of a 266 nm–213 nm double-pulse scheme against that of the single 266 nm pulse scheme. The first laser pulse at 266 nm ablates a mica sample. Ten ns later, the second pulse at 213 nm and 64 mJ cm{sup −2} orthogonally intercepts the gas plume to enhance the analyte signal. Emissions from aluminum, silicon, magnesium and sodium are simultaneously observed. At low 266 nm laser fluence when only sub-ng of sample mass is removed, the signal enhancement by the 213 nm pulse is especially apparent. The minimum detectable amount of aluminum is about 24 fmol; it will be a hundred times higher if the sample is analyzed by the 266 nm pulse alone. The minimum detectable mass for the other analytes is also reduced by about two orders of magnitude when the second pulse at 213 nm is introduced. The spectral and temporal properties of the enhanced signal are consistent with the mechanism of ultra-violet laser excited atomic fluorescence of dense plumes. - Highlights: • We devise a two-laser-pulse scheme to analyze the elemental composition of mica as test samples. • We compare the analytical performance of the single 266 nm pulse scheme against the 266 nm – 213 nm two pulse scheme. • The two pulse scheme improves the absolute LODs of the analytes by about a hundred times. • The spectral and temporal properties of the enhanced signal are consistent with the mechanism.

  7. Pulse-to-pulse interaction analysis and parameter optimization for future-generation ophthalmic laser systems

    Science.gov (United States)

    Tinne, N.; Kaune, B.; Bleeker, S.; Lubatschowski, H.; Krüger, A.; Ripken, T.

    2014-02-01

    The immediate pulse-to-pulse interaction becomes more and more important for future-generation high-repetition rate ophthalmic laser systems. Therefore, we investigated the interaction of two laser pulses with different spatial and temporal separation by time-resolved photography. There are various different characteristic interaction mechanisms which are divided into 11 interaction scenarios. Furthermore, the parameter range has been constricted regarding the medical application; here, the efficiency was optimized to a maximum jet velocity along the scanning axis with minimum applied pulse energy as well as unwanted side effects at the same time. In conclusion, these results are of great interest for the prospective optimization of the ophthalmic surgical process with future-generation fs-lasers.

  8. Towards shorter wavelength x-ray lasers using a high power, short pulse pump laser

    International Nuclear Information System (INIS)

    A near-terawatt, KrF* laser system, focussable to power densities >1018 W/cm2 has been constructed for use as a pump laser in various schemes aimed at the development of x-ray lasing below 5nm. The laser system along with output characteristics such as the pulse duration, the focal spot size, and the percentage of amplified spontaneous emission (ASE) emitted along with the laser pulse will be presented. Schemes intended to lead to shorter wavelength x-ray emission will be described. The resultant requirements on the pump laser characteristics and the target design will be outlined. Results from recent solid target experiments and two-laser experiments, showing the interaction of a high-power, short pulse laser with a preformed plasma, will be presented. 13 refs., 5 figs

  9. Laser triggered injection of electrons in a laser wakefield accelerator with the colliding pulse method

    International Nuclear Information System (INIS)

    An injection scheme for a laser wakefield accelerator that employs a counter propagating laser (colliding with the drive laser pulse, used to generate a plasma wake) is discussed. The threshold laser intensity for electron injection into the wakefield was analyzed using a heuristic model based on phase-space island overlap. Analysis shows that the injection can be performed using modest counter propagating laser intensity a1 0 = 1.0. Preliminary experiments were preformed using a drive beam and colliding beam. Charge enhancement by the colliding pulse was observed. Increasing the signal-to-noise ratio by means of a preformed plasma channel is discussed

  10. Generation of high harmonics and attosecond pulses with ultrashort laser pulse filaments and conical waves

    Indian Academy of Sciences (India)

    A Couairon; A Lotti; D Faccio; P Di Trapani; D S Steingrube; E Schulz; T Binhammer; U Morgner; M Kovacev; M B Gaarde

    2014-08-01

    Results illustrating the nonlinear dynamics of ultrashort laser pulse filamentation in gases are presented, with particular emphasis on the filament properties useful for developing attosecond light sources. Two aspects of ultrashort pulse filaments are specifically discussed: (i) numerical simulation results on pulse self-compression by filamentation in a gas cell filled with noble gas. Measurements of high harmonics generated by the pulse extracted from the filament allows for the detection of intensity spikes and subcycle pulses generated within the filament. (ii) Simulation results on the spontaneous formation of conical wavepackets during filamentation in gases, which in turn can be used as efficient driving pulses for the generation of high harmonics and isolated attosecond pulses.

  11. Intense isolated few-cycle attosecond XUV pulses from overdense plasmas driven by tailored laser pulses

    Science.gov (United States)

    Chen, Zi-Yu; Li, Xiao-Ya; Chen, Li-Ming; Li, Yu-Tong; Zhu, Wen-Jun

    2014-06-01

    A method to generate an intense isolated few-cycle attosecond XUV pulse is demonstrated using particle-in-cell simulations. When a tailored laser pulse with a sharp edge irradiates a foil target, a strong transverse net current can be excited, which emits a few-cycle XUV pulse from the target rear side. The isolated pulse is ultrashort in the time domain with a duration of several hundred attoseconds. It also has a narrow bandwidth in the spectral domain compared to other XUV sources of high-order harmonics. It has most energy confined around the plasma frequency and no low-harmonic orders below the plasma frequency. It is also shown that XUV pulse of peak field strength up to $ 8\\times 10^{12} $ V$\\mathrm{m}^{-1}$ can be produced. Without the need for pulse selecting and spectral filtering, such an intense few-cycle XUV pulse is better suited to a number of applications.

  12. Intense isolated few-cycle attosecond XUV pulses from overdense plasmas driven by tailored laser pulses

    CERN Document Server

    Chen, Zi-Yu; Chen, Li-Ming; Li, Yu-Tong; Zhu, Wen-Jun

    2014-01-01

    A method to generate an intense isolated few-cycle attosecond XUV pulse is demonstrated using particle-in-cell simulations. When a tailored laser pulse with a sharp edge irradiates a foil target, a strong transverse net current can be excited, which emits a few-cycle XUV pulse from the target rear side. The isolated pulse is ultrashort in the time domain with a duration of several hundred attoseconds. It also has a narrow bandwidth in the spectral domain compared to other XUV sources of high-order harmonics. It has most energy confined around the plasma frequency and no low-harmonic orders below the plasma frequency. In addition, the peak electric field of the pulse is up to $ 8\\times 10^{12} $ V$\\mathrm{m}^{-1}$. Without the need for pulse selecting and spectral filtering, such an intense few-cycle XUV pulse is better suited to a number of applications.

  13. Nonlinear polarization rotation-induced pulse shaping in a stretched-pulse ytterbium-doped fiber laser

    Science.gov (United States)

    Bai, Dong-Bi; Li, Wen-Xue; Yang, Kang-Wen; Shen, Xu-Ling; Chen, Xiu-Liang; Zeng, He-Ping

    2014-10-01

    We report on controllable pulse shaping in a Yb-doped stretched-pulse fiber laser followed by a high-power chirped pulse amplifier. We demonstrate that the pulses after an extra-cavity grating pair change their intensity profile from Lorentz to Gaussian and then to sech2 shapes by adjusting the intra-cavity polarization through a quarter-wave plate inside the fiber laser cavity. The laser pulses with different pulse shapes exhibit pulse-to-pulse amplitude fluctuation of ~ 1.02%, while the sech2-shaped pulse train is provided with a more stable free-running repetition rate as a result of the stronger self-phase modulation in the fiber laser cavity than Lorentz- and Gaussian-shaped pulse trains.

  14. Pulsed DC accelerator for laser wakefield accelerator

    International Nuclear Information System (INIS)

    For the acceleration of ultra-short, high-brightness electron bunches, a pulsed DC accelerator was constructed. The pulser produced megavolt pulses of 1 ns duration in a vacuum diode. Results are presented from field emission of electrons in the diode. The results indicate that the accelerating gradient in the diode is approximately 1.5 GV/m

  15. COMPLIS: COllinear spectroscopy Measurements using a Pulsed Laser Ion Source

    CERN Multimedia

    2002-01-01

    A Pulsed Laser spectroscopy experiment has been installed for the study of hyperfine structure and isotope shift of refractory and daughter elements from ISOLDE beams. It includes decelerated ion-implantation, element-selective laser ionization, magnetic and time-of-flight mass separation. The laser spectroscopy has been performed on the desorbed atoms in a set-up at ISOLDE-3 but later on high resolution laser collinear spectroscopy with the secondary pulsed ion beam is planned for the Booster ISOLDE set-up. During the first operation time of ISOLDE-3 we restricted our experiments to Doppler-limited resonant ionization laser and $\\gamma$-$\\gamma$ nuclear spectroscopy on neutron deficient platinum isotopes of even mass number down to A~=~186 and A~=~179 respectively. These isotopes have been produced by implantation of radioactive Hg and their subsequent $\\beta$-decay.

  16. Wavelength dependence of soft tissue ablation by using pulsed lasers

    Institute of Scientific and Technical Information of China (English)

    Xianzeng Zhang; Shusen Xie; Qing Ye; Zhenlin Zhan

    2007-01-01

    Pulsed laser ablation of soft biological tissue was studied at 10.6-, 2.94-, and 2.08-μm wavelengths. The ablation effects were assessed by means of optical microscope, the ablation crater depths were measured with reading microscope. It was shown that Er:YAG laser produced the highest quality ablation with clear,sharp cuts following closely the patial contour of the incident beam and the lowest fluence threshold. The pulsed CO2 laser presented the moderate quality ablation with the highest ablation efficiency. The craters drilled with Ho:YAG laser were generally larger than the incident laser beam spot, irregular in shape, and clearly dependent on the local morphology of biotissue. The blation characteristics, including fluence threshold and ablation efficiency, varied substantially with wavelength. It is not evident that water is the only dominant chromophore in tissue.

  17. [Micromachining of Au film by femtosecond pulse laser].

    Science.gov (United States)

    Yuan, Dong-qing; Zhou, Ming; Cai, Lan; Shen, Jian

    2009-05-01

    Femtosecond laser micromachining of film is an emerging technology for fabrication of MEMS devices. A Ti: sapphire laser (130 fs, 1000 Hz)was used to irradiate the thin film with variations in process parameters such as pulse energy. The film thickness is about 4 microm which was measured by AFM. When we used single pulse to excite the film, the ablation diameter increased along with the energy ascending; when the energy of single pulse was invariable, the diameter had little change when altering the number of pulses. The single pulse threshold fluence of Au film was Fth = 0.7 J x cm(-2) at this ultrashort pulse-length in air. By changing the energy of excitation pulse it was found that when the energy was lower than the threshold, the line on the film was heaved; when the energy was higher than the threshold, the line was concave, which was detected by AFM. It was also found that the width of line decreased along with the increase in process speed when the pulse energy remained unchanged; the width of line increased along with the pulse energy ascending when the process speed was fixed. PMID:19650455

  18. Components for monolithic fiber chirped pulse amplification laser systems

    Science.gov (United States)

    Swan, Michael Craig

    The first portion of this work develops techniques for generating femtosecond-pulses from conventional fabry-perot laser diodes using nonlinear-spectral-broadening techniques in Yb-doped positive dispersion fiber ampliers. The approach employed an injection-locked fabry-perot laser diode followed by two stages of nonlinear-spectral-broadening to generate sub-200fs pulses. This thesis demonstrated that a 60ps gain-switched fabry-perot laser-diode can be injection-locked to generate a single-longitudinal-mode pulse and compressed by nonlinear spectral broadening to 4ps. Two problems have been identified that must be resolved before moving forward with this approach. First, gain-switched pulses from a standard diode-laser have a number of characteristics not well suited for producing clean self-phase-modulation-broadened pulses, such as an asymmetric temporal shape, which has a long pulse tail. Second, though parabolic pulse formation occurs for any arbitrary temporal input pulse profile, deviation from the optimum parabolic input results in extensively spectrally modulated self-phase-modulation-broadened pulses. In conclusion, the approach of generating self-phase-modulation-broadened pulses from pulsed laser diodes has to be modified from the initial approach explored in this thesis. The first Yb-doped chirally-coupled-core ber based systems are demonstrated and characterized in the second portion of this work. Robust single-mode performance independent of excitation or any other external mode management techniques have been demonstrated in Yb-doped chirally-coupled-core fibers. Gain and power efficiency characteristics are not compromised in any way in this novel fiber structure up to the 87W maximum power achieved. Both the small signal gain at 1064nm of 30.3dB, and the wavelength dependence of the small signal gain were comparable to currently deployed large-mode-area-fiber technology. The efficiencies of the laser and amplifier were measured to be 75% and 54

  19. Effect of sulfur on weld geometry in pulsed laser welds

    International Nuclear Information System (INIS)

    The primary goal of the present study was to determine whether compositional differences in a surface active element in austenitic stainless steel can alter the geometry of pulsed laser welds. Clearly, much less time is available during pulse laser welding for convection cells to form and influence heat transfer. A two-dimensional heat-transfer code has been developed for pulsed Nd:YAG laser welding that only incorporates heat transfer by conduction for the molten metal. For fluences that do not result in significant evaporation, this code generally yields good predictions of weld geometries, if appropriate corrections are made for surface absorptivity. At higher fluences, significant differences are found between predicted and observed weld pool shapes. This study is a portion of a larger program to determine the causes of these differences. Earlier work has produced direct experimental evidence that convection cells can develop during pulsed laser welding. However, experimental evidence that convection is present during welding is not sufficient to indicate whether convection is a dominant heat transfer mechanism. More recently, modeling of transient two-dimensional Marangoni flow in a pulsed laser weld pool was attempted

  20. Control of giant pulse duration in neodymium mini lasers with controllable cavity length and pulsed pumping

    International Nuclear Information System (INIS)

    In a solid-state laser incident on aLiNdP4O12 crystal, pumped by a short light pulse, giant pulse oscillation without the use of resonator Q switching is realized. Tuning of the oscillation pulse duration from 2 up to 20 ns is achieved by changing the cavity length from 24 to 3 mm, respectively. Our analysis of this mode of laser radiation is made on the basis of the rate equations. The factors influencing oscillation pulse duration a reinvestigated. It is shown that in a limiting case the minimal value of the pulse duration is limited by only the rate of excitation transfer from the pumping band to the metastable level

  1. Towards manipulating relativistic laser pulses with 3D printed materials

    CERN Document Server

    Ji, L L; Pukhov, A; Freeman, R R; Akli, K U

    2015-01-01

    Efficient coupling of intense laser pulses to solid-density matter is critical to many applications including ion acceleration for cancer therapy. At relativistic intensities, the focus has been mainly on investigating various laser beams irradiating initially flat interfaces with little or no control over the interaction. Here, we propose a novel approach that leverages recent advancements in 3D direct laser writing (DLW) of materials and high contrast lasers to manipulate the laser-matter interactions on the micro-scales. We demonstrate, via simulations, that usable intensities >10^23Wcm^(-2) could be achieved with current tabletop lasers coupled to 3D printed plasma lenses. We show that these plasma optical elements act not only as a lens to focus laser light, but also as an electromagnetic guide for secondary particle beams. These results open new paths to engineering light-matter interactions at ultra-relativistic intensities.

  2. Study of the plasma expansion produced on ultra-thin foil targets with a high intensity and ultrashort laser pulse

    Science.gov (United States)

    Gnedyuk, Semen; Fourmaux, Sylvain; Buffechoux, Sebastien; Albertazzi, Bruno; Martin, Francois; Kieffer, Jean Claude

    2011-10-01

    INRS-EMT, Université du Québec, 1650 Lionel Boulet, Varennes J3X 1S2, Québec, Canada LULI, UMR 7605, CNRS - CEA - Université Paris 6 - Ecole Polytechnique, Palaiseau, France Abstract: A high intensity ultrashort laser pulse, with an intensity of the order of 1019 W/cm2, focused onto a thin foil target generates a plasma and highly energetic ion (including proton) beams from its front and rear sides which propagate along the target normal. Another interest of laser plasma interaction with ultra-thin foil is the possibility to deposit energy in the entire laser absorption depth before any expansion thus enabling target isochoric heating. With a target thickness of 30 or 15 nm the laser pulse should interact in volume and enable to reach very high temperature while the target is still at solid density. The resulting cooling of the target will then be ultra-fast and potential X-ray emission should be ultrashort. The 100 TW class laser system at the Advanced Laser Light Source facility enables laser plasma interaction study with femtosecond laser pulses, ultra thin foil targets and high contrast laser pulse intensity ratio. We used a shadowgraph diagnostic with a femtosecond laser probe to characterize the plasma expansion.

  3. Diode-Pumped Nanosecond Pulsed Laser with Pulse-Transmission-Mode Q-Switch

    Institute of Scientific and Technical Information of China (English)

    CHEN Fei; HUO Yu-Jing; HE Shu-Fang; FENG Li-Chun

    2001-01-01

    Q-switched pulses at 1.064μm with a peak power of 5.02kW and a pulse width of2.8ns were obtained which were pumped by a 1 W laser diode on the Nd:YVO4 microchip at the 1 kHz repetition rate. These values were achieved by combining the techniques of aconsto-optic Q-switching and electro-optic pulse-transmission-mode Q-switching. The temporal characteristics of the pulses were analysed numerically. The experimental results are shown to be in good agreement with theoretical predictions.

  4. Electron-yield enhancement in a Laser-Wakefield accelerator driven by asymmetric laser pulses

    CERN Document Server

    Leemans, W P; Esarey, E; Geddes, C G R; Toth, C; Trines, R; Schroeder, C B; Shadwick, B A; Tilborg, J V; Faure, J

    2002-01-01

    The effect of asymmetric laser pulses on electron yield from a laser Wakefield accelerator has been experimentally studied using > 10 sup 1 sup 9 cm sup - sup 3 plasmas and a 10 TW, >45 fs, Ti:Al sub 2 O sub 3 laser. The laser pulse shape was controlled through nonlinear chirp with a grating pair compressor. Pulses (76 fs FWHM) with a steep rise and positive chirp were found to significantly enhance the electron yield compared to pulses with a gentle rise and negative chirp. Theory and simulation show that fast rising pulses can generate larger amplitude wakes that seed the growth of the self-modulation instability, and that frequency chirp is of minimal importance for the experimental parameters.

  5. Pulsed Mid-infrared Radiation from Spectral Broadening in Laser Wakefield Simulations

    OpenAIRE

    Zhu, W.; Palastro, J. P.; Antonsen, T. M.

    2013-01-01

    Spectral red-shifting of high power laser pulses propagating through underdense plasma can be a source of ultrashort mid-infrared (MIR) radiation. During propagation, a high power laser pulse drives large amplitude plasma waves, depleting the pulse energy. At the same time, the large amplitude plasma wave provides a dynamic dielectric response that leads to spectral shifting. The loss of laser pulse energy and the approximate conservation of laser pulse action imply that spectral red-shifts a...

  6. Single molecule imaging with longer x-ray laser pulses

    CERN Document Server

    Martin, Andrew V; Caleman, Carl; Quiney, Harry M

    2015-01-01

    In serial femtosecond crystallography, x-ray laser pulses do not need to outrun all radiation damage processes because Bragg diffraction exceeds the damage-induced background scattering for longer pulses ($\\sim$ 50--100 fs). This is due to a "self-gating pulse" effect whereby damage terminates Bragg diffraction prior to the pulse completing its passage through the sample, as if that diffraction were produced by a shorter pulse of equal fluence. We show here that a similar gating effect applies to single molecule diffraction with respect to spatially uncorrelated damage processes like ionization and ion diffusion. The effect is clearly seen in calculations of the diffraction contrast, by calculating the diffraction of average structure separately to the diffraction from statistical fluctuations of the structure due to damage ("damage noise"). Our results suggest that sub-nanometer single molecule imaging with longer pulses, like those produced at currently operating facilities, should not yet be ruled out. The...

  7. Modelling of noise-like pulses generated in fibre lasers

    Science.gov (United States)

    Smirnov, Sergey; Kobtsev, Sergey

    2016-03-01

    The present paper for the first time proposes and studies a relatively simple model of noise-like pulses that matches the experimental data well and suggests that there is a correlation between phases of adjacent spectral components of noiselike pulses. Comparison of a relatively basic model of `random' pulses with the results of noise-like pulse modelling in mode-locked fibre lasers based on coupled non-linear Schrödinger equations demonstrates that it adequately reproduces temporal and spectral properties of noise-like pulses as well as correlation between adjacent modes so that it's possible to use the proposed model for highly efficient simulations of promising applications of noise-like pulses, such as material processing, non-linear frequency conversion, microscopy, and others.

  8. Optimized laser pulse profile for efficient radiation pressure acceleration of ions

    OpenAIRE

    Bulanov, S. S.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

    2012-01-01

    The radiation pressure acceleration regime of laser ion acceleration requires high intensity laser pulses to function efficiently. Moreover the foil should be opaque for incident radiation during the interaction to ensure maximum momentum transfer from the pulse to the foil, which requires proper matching of the target to the laser pulse. However, in the ultrarelativistic regime, this leads to large acceleration distances, over which the high laser intensity for a Gaussian laser pulse must be...

  9. PIC simulations of SMLWFA for 35fs class lasers

    Science.gov (United States)

    Adam, J. C.; Tsung, F. S.; Ren, Chuang; Mori, W. B.; Fonseca, R. A.; Silva, L. O.

    2001-10-01

    In the self-modulated laser wakefield regime a laser pulse several to many 2 π c/ ωp long breaks up via Raman scattering type instabilities producing large wakes. In some cases these wakes can trap background electrons generating a beam of accelerated electrons with a large energy spread. PIC simulations have shown that this process is highly sensitive to the laser intensity, pulse length, and plasma density [K-C.Tzeng et al., PRL 76, 3332 (1996), K-C.Tzeng et al., PRL 79, 5258 (1997)]. There have been some recent experimental results in which 35fs laser pulses have been used. In this case the pulses are at most only a few 2 π c/ ωp long even for the highest densities 10**20 cm-3. We report here on 1D, 2D, and 3D PIC simulations using OSIRIS for parameters closely related to the LULI/LOA results [V.Malka et al., Phys. Plasmas 8, 2605 (2001)].

  10. Multiphoton ionization with femtosecond laser pulses

    International Nuclear Information System (INIS)

    There are a number of reasons to use subpicosecond pulses in multiphoton ionization experiments. Pulses with shorter risetimes make it possible to study processes with higher rates before one runs into the problem of depletion of target atoms. Furthermore, the momentum of the electron does not change between the point of ionization and the detector if the pulse expires before the electron has time to sample the spatial inhomogeneity of the light intensity. This makes it possible to identify the intensity at which an electron was formed from the energy with which it reaches the detector. Yet another advantage is the fact that the primary ionization products are subject to the ionizing radiation for only a short amount of time, thus reducing the probability of sequential ionization as compared to direct processes. In this paper the experimental results on the multiphoton ionization of xenon with pulses of 100 fs, that were obtained during the preceding year at ENSTA, Palaiseau, will be presented

  11. Energy deposition from focused terawatt laser pulses in air

    CERN Document Server

    Point, Guillaume; Mysyrowicz, André; Houard, Aurélien

    2015-01-01

    Laser filamentation is responsible for the deposition of a significant part of the laser pulse energy in the propagation medium. We found that using terawatt laser pulses and relatively tight focusing conditions in air, resulting in a bundle of co-propagating multifilaments, more than 50 % of the pulses energy is transferred to the medium, eventually degrading into heat. This results in a strong hydrodynamic reaction of air with the generation of shock waves and associated underdense channels for each short-scale filament. In the focal zone, where filaments are close to each other, these discrete channels eventually merge to form a single cylindrical low-density tube over a $\\sim 1~ \\mu\\mathrm{s}$ timescale. We measured the maximum lineic deposited energy to be more than 1 J/m.

  12. Generation and amplification of nanosecond pulses by iodine lasers

    Energy Technology Data Exchange (ETDEWEB)

    Zuev, V.S.; Katulin, V.A.; Nosach, V.Y.; Petrov, A.L.

    1982-12-01

    Results are reported of experimental investigations of high-power photodissociation iodine laser pumped by lamps and by radiation from high-current electric discharges. The basic parameters of the working medium, the parameters of both lamp-pumped and discharge-pumped lasers, and methods of shaping of a short pulse with diffraction directivity of the radiation are investigated. The possibility of effective amplification of a short pulse by an iodine amplifier pumped with an open high-current discharge is demonstrated. An iodine laser generating a pulse of duration 1 nsec, divergence 10/sup -4/ rad, and energy 100 J at a contrast 10/sup 8/ and 300 J at a contrast 10/sup 2/-10/sup 3/ is described.

  13. Laser short pulse heating of metal nano-wires

    Science.gov (United States)

    Yilbas, B. S.; Al-Dweik, A. Y.

    2012-11-01

    Non-equilibrium energy transfer takes place in a solid substrate during a short-pulse laser irradiation and temperature field can be obtained analytically in the irradiated region. In the present study, laser short-pulse heating of metal nano-wire is considered and the analytical solution for two-dimensional axisymmetric nano-wire is presented. Since the absorption of the incident beam takes place in the skin of the irradiated surface, a volumetric heat source resembling the absorption process is incorporated in the analysis. Three different nano-wire materials are introduced in the analysis for the comparison reason. These include silver, chromium, and copper. It is found that temperature decay is gradual on the surface vicinity and temporal variation of the surface temperature follows almost the laser pulse intensity profile at the irradiated center.

  14. Plasma shape control by pulsed solenoid on laser ion source

    International Nuclear Information System (INIS)

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS

  15. Plasma shape control by pulsed solenoid on laser ion source

    Science.gov (United States)

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-09-01

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

  16. Plasma shape control by pulsed solenoid on laser ion source

    Energy Technology Data Exchange (ETDEWEB)

    Sekine, M. [Tokyo Institute of Technology, Meguro-ku, Tokyo 2-12-1 (Japan); RIKEN, Wako, Saitama 351-0198 (Japan); Ikeda, S. [Tokyo Institute of Technology, Yokohama, Kanagawa 226-8502 (Japan); RIKEN, Wako, Saitama 351-0198 (Japan); Romanelli, M. [Cornell University, Ithaca, NY 14850 (United States); Kumaki, M. [RIKEN, Wako, Saitama 351-0198 (Japan); Waseda University, Shinjuku, Tokyo 169-0072 (Japan); Fuwa, Y. [RIKEN, Wako, Saitama 351-0198 (Japan); Kyoto University, Uji, Kyoto 611-0011 (Japan); Kanesue, T. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Hayashizaki, N. [Tokyo Institute of Technology, Meguro-ku, Tokyo 2-12-1 (Japan); Lambiase, R. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Okamura, M. [RIKEN, Wako, Saitama 351-0198 (Japan); Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2015-09-21

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

  17. Multiple Filamentation of Laser Pulses in a Glass

    Science.gov (United States)

    Apeksimov, D. V.; Bukin, O. A.; Golik, S. S.; Zemlyanov, A. A.; Iglakova, A. N.; Kabanov, A. M.; Kuchinskaya, O. I.; Matvienko, G. G.; Oshlakov, V. K.; Petrov, A. V.; Sokolova, E. B.

    2016-03-01

    Results are presented of experiments on investigation of the spatial characteristics of multi-filamentation region of giga- and terawatt pulses of a Ti:sapphire laser in a glass. Dependences are obtained of the coordinate of the beginning of filamentation region, number of filaments, their distribution along the laser beam axis, and length of filaments on the pulse power. It is shown that with increasing radiation power, the number of filaments in the multi-filamentation region decreases, whereas the filament diameter has a quasiconstant value for all powers realized in the experiments. It is shown that as a certain power of the laser pulse with Gauss energy density distribution is reached, the filamentation region acquires the shape of a hollow cone with apex directed toward the radiation source.

  18. Lipase biofilm deposited by Matrix Assisted Pulsed Laser Evaporation technique

    Energy Technology Data Exchange (ETDEWEB)

    Aronne, Antonio [Department of Chemical Engineering, Materials and Industrial Production, University of Naples “Federico II”, Napoli (Italy); Bloisi, Francesco, E-mail: bloisi@na.infn.it [SPIN – CNR, Naples (Italy); Department of Physics, University of Naples “Federico II”, Napoli (Italy); Calabria, Raffaela; Califano, Valeria [Istituto Motori – CNR, Naples (Italy); Depero, Laura E. [Department of Mechanical and Industrial Engineering, University of Brescia, Brescia (Italy); Fanelli, Esther [Department of Chemical Engineering, Materials and Industrial Production, University of Naples “Federico II”, Napoli (Italy); Federici, Stefania [Department of Mechanical and Industrial Engineering, University of Brescia, Brescia (Italy); Massoli, Patrizio [Istituto Motori – CNR, Naples (Italy); Vicari, Luciano R.M. [SPIN – CNR, Naples (Italy); Department of Physics, University of Naples “Federico II”, Napoli (Italy)

    2015-05-01

    Highlights: • A lipase film was deposited with Matrix Assisted Pulsed Laser Evaporation technique. • FTIR spectra show that laser irradiation do not damage lipase molecule. • Laser fluence controls the characteristics of complex structure generated by MAPLE. - Abstract: Lipase is an enzyme that finds application in biodiesel production and for detection of esters and triglycerides in biosensors. Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique derived from Pulsed Laser Deposition (PLD) for deposition of undamaged biomolecules or polymers, is characterized by the use of a frozen target obtained from a solution/suspension of the guest material (to be deposited) in a volatile matrix (solvent). The presence of the solvent avoids or at least reduces the potential damage of guest molecules by laser radiation but only the guest material reaches the substrate in an essentially solvent-free deposition. MAPLE can be used for enzymes immobilization, essential for industrial application, allowing the development of continuous processes, an easier separation of products, the reuse of the catalyst and, in some cases, enhancing enzyme properties (pH, temperature stability, etc.) and catalytic activity in non-aqueous media. Here we show that MAPLE technique can be used to deposit undamaged lipase and that the complex structure (due to droplets generated during extraction from target) of the deposited material can be controlled by changing the laser beam fluence.

  19. Evolution of short laser pulse in partially stripped plasma

    International Nuclear Information System (INIS)

    Intense laser pulses while propagating through neutral gases ionize them. If the intensity of the laser is not sufficiently high, the gases may not be completely ionized, hence giving rise to partially stripped plasma. The propagation medium for a laser beam in partially stripped plasma consists of a linear and a nonlinear plasma current due to free electrons as well as linear and nonlinear polarization field due to bound atomic electrons. Polarization fields can arise from a number of processes, the dominant process being electronic polarization arising due to modification of the atomic electron distribution by the optical field. The polarization field due to atoms in partially striped plasma can be expressed as a power series of the electric field of the laser. The present paper deals with the effect of nonlinear polarization field and plasma current density on the evolution characteristics of a laser pulse propagating in partially stripped plasma. The wave equation describing the laser field amplitude driven by plasma current density as well as polarization field of the bound atomic electrons is set up. Using a variational technique the equations governing the simultaneous evolution of the spot-size and length of a laser pulse propagating in partially stripped plasma are obtained and solved numerically. (author)

  20. Lipase biofilm deposited by Matrix Assisted Pulsed Laser Evaporation technique

    International Nuclear Information System (INIS)

    Highlights: • A lipase film was deposited with Matrix Assisted Pulsed Laser Evaporation technique. • FTIR spectra show that laser irradiation do not damage lipase molecule. • Laser fluence controls the characteristics of complex structure generated by MAPLE. - Abstract: Lipase is an enzyme that finds application in biodiesel production and for detection of esters and triglycerides in biosensors. Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique derived from Pulsed Laser Deposition (PLD) for deposition of undamaged biomolecules or polymers, is characterized by the use of a frozen target obtained from a solution/suspension of the guest material (to be deposited) in a volatile matrix (solvent). The presence of the solvent avoids or at least reduces the potential damage of guest molecules by laser radiation but only the guest material reaches the substrate in an essentially solvent-free deposition. MAPLE can be used for enzymes immobilization, essential for industrial application, allowing the development of continuous processes, an easier separation of products, the reuse of the catalyst and, in some cases, enhancing enzyme properties (pH, temperature stability, etc.) and catalytic activity in non-aqueous media. Here we show that MAPLE technique can be used to deposit undamaged lipase and that the complex structure (due to droplets generated during extraction from target) of the deposited material can be controlled by changing the laser beam fluence

  1. High power, short pulses ultraviolet laser for the development of a new x-ray laser

    International Nuclear Information System (INIS)

    A high power, short pulse ultraviolet laser system (Powerful Picosecond-Laser) has been developed at the Princeton Plasma Physics Laboratory (PPPL) as part of experiments designed to generate shorter wavelength x-ray lasers. With the addition of pulse compression and a final KrF amplifier the laser output is expected to have reached 1/3-1/2 TW (1012 watts) levels. The laser system, particularly the final amplifier, is described along with some initial soft x-ray spectra from laser-target experiments. The front end of the PP-Laser provides an output of 20--30 GW (109 watts) and can be focussed to intensities of /approximately/1016 W/cm2. Experiments using this output to examine the effects of a prepulse on laser-target interaction are described. 19 refs., 14 figs

  2. High power, short pulses ultraviolet laser for the development of a new x-ray laser

    Energy Technology Data Exchange (ETDEWEB)

    Meixler, L.; Nam, C.H.; Robinson, J.; Tighe, W.; Krushelnick, K.; Suckewer, S.; Goldhar, J.; Seely, J.; Feldman, U.

    1989-04-01

    A high power, short pulse ultraviolet laser system (Powerful Picosecond-Laser) has been developed at the Princeton Plasma Physics Laboratory (PPPL) as part of experiments designed to generate shorter wavelength x-ray lasers. With the addition of pulse compression and a final KrF amplifier the laser output is expected to have reached 1/3-1/2 TW (10/sup 12/ watts) levels. The laser system, particularly the final amplifier, is described along with some initial soft x-ray spectra from laser-target experiments. The front end of the PP-Laser provides an output of 20--30 GW (10/sup 9/ watts) and can be focussed to intensities of /approximately/10/sup 16/ W/cm/sup 2/. Experiments using this output to examine the effects of a prepulse on laser-target interaction are described. 19 refs., 14 figs.

  3. Development of pulsed UV lasers and their application in laser spectroscopy

    International Nuclear Information System (INIS)

    The application of two-photon laser spectroscopy to plasma diagnostics requires tuneable UV-laser spectrometers providing: some mJ pulse energy at ns time scale with spectral quality close to Fourier Transform Limit, good pulse to pulse reproducibility and tuning linearity. We report about two different systems, a first laser specially optimized for the radiation at 243 nm, which is required for the 1S-2S two photon transition of atomic hydrogen, and a second one generating 205 nm suited for the transition 1S - 3S/3D.

  4. The effect of laser pulse tailored welding of Inconel 718

    Science.gov (United States)

    Mccay, T. Dwayne; Mccay, Mary Helen; Sharp, C. Michael; Womack, Michael G.

    1990-01-01

    Pulse tailored laser welding has been applied to wrought, wrought grain grown, and cast Inconel 718 using a CO2 laser. Prior to welding, the material was characterized metallographically and the solid state transformation regions were identified using Differential Scanning Calorimetry and high temperature x-ray diffraction. Bead on plate welds (restrained and unrestrained) were then produced using a matrix of pulse duty cycles and pulsed average power. Subsequent characterization included heat affected zone width, penetration and underbead width, the presence of cracks, microfissures and porosity, fusion zone curvature, and precipitation and liquated region width. Pedigree welding on three selected processing conditions was shown by microstructural and dye penetrant analysis to produce no microfissures, a result which strongly indicates the viability of pulse tailored welding for microfissure free IN 718.

  5. Ultrafast Pulse Radiolysis Using a Terawatt Laser Wakefield Accelerator

    CERN Document Server

    Oulianov, D A; Gosztola, D J; Korovyanko, O J; Rey de Castro, R C; Shkrob, I A; Crowell, Robert A.; Gosztola, David J.; Korovyanko, Oleg J.; Oulianov, Dmitri A.; Rey-de-Castro, Roberto C.; Shkrob, Ilya A.

    2006-01-01

    We report the first ultrafast pulse radiolysis transient absorption spectroscopy measurements from the Terawatt Ultrafast High Field Facility (TUHFF) at Argonne National Laboratory. TUHFF houses a 20 TW Ti:sapphire laser system that generates 2.5 nC sub-picosecond pulses of multi-MeV electrons at 10 Hz using laser wakefield acceleration. The system has been specifically optimized for kinetic measurements in a pump-probe fashion. This requires averaging over many shots which necessitates stable, reliable generation of electron pulses. The latter were used to generate excess electrons in pulse radiolysis of liquid water and concentrated solutions of perchloric acid. The hydronium ions in the acidic solutions react with the hydrated electrons resulting in the rapid decay of the transient absorbance at 800 nm on the picosecond time scale. Time resolution of a few picoseconds has been demonstrated. The current time resolution is determined primarily by the physical dimensions of the sample and the detection sensit...

  6. Long-pulse-width narrow-bandwidth solid state laser

    Science.gov (United States)

    Dane, C. Brent; Hackel, Lloyd A.

    1997-01-01

    A long pulse laser system emits 500-1000 ns quasi-rectangular pulses at 527 nm with near diffraction-limited divergence and near transform-limited bandwidth. The system consists of one or more flashlamp-pumped Nd:glass zig-zag amplifiers, a very low threshold stimulated-Brillouin-scattering (SBS) phase conjugator system, and a free-running single frequency Nd:YLF master oscillator. Completely passive polarization switching provides eight amplifier gain passes. Multiple frequency output can be generated by using SBS cells having different pressures of a gaseous SBS medium or different SBS materials. This long pulse, low divergence, narrow-bandwidth, multi-frequency output laser system is ideally suited for use as an illuminator for long range speckle imaging applications. Because of its high average power and high beam quality, this system has application in any process which would benefit from a long pulse format, including material processing and medical applications.

  7. Numerical analysis of laser ablation and damage in glass with multiple picosecond laser pulses.

    Science.gov (United States)

    Sun, Mingying; Eppelt, Urs; Russ, Simone; Hartmann, Claudia; Siebert, Christof; Zhu, Jianqiang; Schulz, Wolfgang

    2013-04-01

    This study presents a novel numerical model for laser ablation and laser damage in glass including beam propagation and nonlinear absorption of multiple incident ultrashort laser pulses. The laser ablation and damage in the glass cutting process with a picosecond pulsed laser was studied. The numerical results were in good agreement with our experimental observations, thereby revealing the damage mechanism induced by laser ablation. Beam propagation effects such as interference, diffraction and refraction, play a major role in the evolution of the crater structure and the damage region. There are three different damage regions, a thin layer and two different kinds of spikes. Moreover, the electronic damage mechanism was verified and distinguished from heat modification using the experimental results with different pulse spatial overlaps. PMID:23571876

  8. Orienting coupled quantum rotors by ultrashort laser pulses

    OpenAIRE

    Shima, Hiroyuki; Nakayama, Tsuneyoshi

    2004-01-01

    We point out that the non-adiabatic orientation of quantum rotors, produced by ultrashort laser pulses, is remarkably enhanced by introducing dipolar interaction between the rotors. This enhanced orientation of quantum rotors is in contrast with the behavior of classical paired rotors, in which dipolar interactions prevent the orientation of the rotors. We demonstrate also that a specially designed sequence of pulses can most efficiently enhances the orientation of quantum paired rotors.

  9. Orienting coupled quantum rotors by ultrashort laser pulses

    OpenAIRE

    Shima, Hiroyuki; Nakayama, Tsuneyoshi

    2004-01-01

    We pointed out that the nonadiabatic orientation of quantum rotors, produced by ultrashort laser pulses, is remarkably enhanced by introducing dipolar interaction between the rotors. This enhanced orientation of quantum rotors is in contrast with the behavior of classical paired rotors, in which dipolar interactions prevent the orientation of the rotors. We demonstrate also that a specially designed sequence of pulses can most efficiently enhance the orientation of quantum paired rotors.

  10. Laser-Pulse/Fiber-Optic Liquid-Leak Detector

    Science.gov (United States)

    Padgett, M. E.

    1986-01-01

    Several potential leak sites monitored using single sensing fiber. Fluid systems monitored quickly for leaks in remote, hazardous, or inaccessible locations by system of compact, lightweight fiber-optic leak sensors presently undergoing development. Sensors installed at potential leak sites as joints, couplings, and fittings. Sensor read by sending laser pulse along fiber, then noting presence or relative amplitude of return pulse. Leak-monitoring technique applicable to wide range of fluid systems and minimizes human exposure to toxic or dangerous fluids.

  11. Pulsed laser ablation and deposition of niobium carbide

    Science.gov (United States)

    Sansone, M.; De Bonis, A.; Santagata, A.; Rau, J. V.; Galasso, A.; Teghil, R.

    2016-06-01

    NbC crystalline films have been deposited in vacuum by ultra-short pulsed laser deposition technique. The films have been characterized by transmission and scanning electron microscopies and by X-ray diffraction. To clarify the ablation-deposition mechanism, the plasma produced by the ablation process has been characterized by optical emission spectroscopy and fast imaging. A comparison of the results with those obtained by ns pulsed deposition of the same target has been carried out.

  12. Streak camera system for prompt display of laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Baumgart, J.S.; Justice, R.; Bender, S.

    1989-01-01

    The streak camera is a useful tool for doing imaging experiments. Its high bandwidth and large information carrying capacity provide great flexibility in data recording. This paper describes a streak system used to make two-dimensional measurements on a pulsed laser system. The streak system measures beam position, full width, relative intensity, and shape on multiple pulses in a single sweep. These measurements are analyzed in real time and displayed for user feedback. 18 figs.

  13. Pulsed ti: sapphire laser power amplifier

    International Nuclear Information System (INIS)

    We have demonstrated an all solid state Ti:Sapphire laser system consisting of a power oscillator and single pass amplifier. The electrical-to-optical efficiency far exceeds that of the current CW systems. The pump lasers have lower capital and operating costs than the Argon-ion laser. In the future, we plan to scale the output power to higher levels by adding a fourth pump laser and improving the output power of the current pump lasers. Modeling results suggest that a large increase in efficiency can be realized by improving the beam quality of the pump lasers, even at the cost of reduced output power. We will explore this option by adding apertures to the cavity and/or reducing the rod diameter along with optimizing the resonator design. Other improvements in efficiency which will be investigated include double passing the amplifier for better extraction. To complete this work, the laser system will be converted into a two-stage amplifier. A narrow band, lower power oscillator currently under development will be injected in to the amplifier to study the extraction and efficiency characteristics of the amplifier throughout the tuning range of Ti:Sapphire. Detailed beam quality measurements will also be made. Other work will include doubling the narrow band output for materials processing applications

  14. Detection of early dental caries with short pulse laser

    International Nuclear Information System (INIS)

    Differences in the optical properties of polarization and photoluminescence between caries lesion and noncaries (sound) enamel have been investigated by focusing a pulsed Nd:YAG laser of 532 nm on the surface of teeth. Significant difference in the polarization property of the scattered light from the surface can be observed with some carious samples. For photoluminescence spectral lines which appear at around 650 nm, the intensity of caries lesion has been approximately two times higher than that of sound one. A discussion is presented in which early are potentially detectable by the pulsed laser. (author)

  15. Pulsed Yb:KYW laser and UV generation

    OpenAIRE

    Tjörnhammar, Staffan

    2010-01-01

    In this master thesis project, a pulsed UV laser was designed and constructed. Also, the effects of absorption in a volume Bragg grating were investigated. The laser was diode pumped and constructed with Yb:KYW as gain medium. The lasing was at a wavelength of 1029.2 nm with a spectral bandwidth of 0.23 nm, locked by a volume Bragg grating that was used as input coupler for spectral control. Passive Q‑switching was used to generate pulses by placing a Cr:YAG saturable absorber inside the cavi...

  16. Plasma and cavitation dynamics during pulsed laser microsurgery in vivo

    CERN Document Server

    Hutson, M Shane

    2007-01-01

    We compare the plasma and cavitation dynamics underlying pulsed laser microsurgery in water and in fruit fly embryos (in vivo) - specifically for nanosecond pulses at 355 and 532 nm. We find two key differences. First, the plasma-formation thresholds are lower in vivo - especially at 355 nm - due to the presence of endogenous chromophores that serve as additional sources for plasma seed electrons. Second, the biological matrix constrains the growth of laser-induced cavitation bubbles. Both effects reduce the disrupted region in vivo when compared to extrapolations from measurements in water.

  17. Quantum quenching of radiation losses in short laser pulses

    CERN Document Server

    Harvey, Chris; Ilderton, Anton; Marklund, Mattias

    2016-01-01

    Accelerated charges radiate, and therefore must lose energy. The impact of this energy loss on particle motion, called radiation reaction, becomes significant in intense-laser matter interactions, where it can reduce collision energies, hinder particle acceleration schemes, and is seemingly unavoidable. Here we show that this common belief breaks down in short laser pulses, and that energy losses and radiation reaction can be controlled and effectively switched off by appropriate tuning of the pulse length. This "quenching" of emission is impossible in classical physics, but becomes possible in QED due to the discrete nature of quantum emissions.

  18. Interaction of nanosecond ultraviolet laser pulses with reactive dusty plasma

    Science.gov (United States)

    van de Wetering, F. M. J. H.; Oosterbeek, W.; Beckers, J.; Nijdam, S.; Gibert, T.; Mikikian, M.; Rabat, H.; Kovačević, E.; Berndt, J.

    2016-05-01

    Even though UV laser pulses that irradiate a gas discharge are small compared to the plasma volume (≲3%) and plasma-on time (≲6 × 10-6%), they are found to dramatically change the discharge characteristics on a global scale. The reactive argon-acetylene plasma allows the growth of nanoparticles with diameters up to 1 μm, which are formed inside the discharge volume due to spontaneous polymerization reactions. It is found that the laser pulses predominantly accelerate and enhance the coagulation phase and are able to suppress the formation of a dust void.

  19. Pulse laser irradiation into superconducting MgB2 detector

    International Nuclear Information System (INIS)

    We performed 20-ps pulse laser irradiation experiments on a MgB2 neutron detector to know a thermal-relaxation process for designing a MgB2 neutron detector. The membrane-type structured MgB2 device was fabricated to minimize the heat capacity of sensing part of a detector as well as to enhance its sensitivity. We successfully observed a thermal-relaxation signal resulting from pulse laser irradiation by developing a detection circuit. The response time was faster than 1 μs, meaning that the detector would be capable of counting neutrons at a rate of more than 106 events per second

  20. Nuclear fuel safety studies by laser pulse heating

    International Nuclear Information System (INIS)

    The behaviour of nuclear fuels under transient heating conditions is vital to nuclear safety. A laser pulse based heating system to simulate the transient heating conditions experienced by the fuel during reactor accidents like LOCA and RIA is under development at BARC, Mumbai. Some of the concepts used in this system are under testing in pilot studies. This paper describes the results of some pilot studies carried out on unirradiated UO2 specimens by laser pulse heating, followed by metallography and X-ray diffraction measurements. (author)

  1. Thermal diffusivity of diamond films using a laser pulse technique

    International Nuclear Information System (INIS)

    Polycrystalline diamond films were deposited using a microwave plasma-enhanced chemical vapor deposition process. A laser pulse technique was developed to measure the thermal diffusivity of diamond films deposited on a silicon substrate. The effective thermal diffusivity of a diamond film on silicon was measured by observing the phase and amplitude of the cyclic thermal waves generated by laser pulses. An analytical model is presented to calculate the effective inplane (face-parallel) diffusivity of a two-layer system. The model is used to reduce the effective thermal diffusivity of the diamond/silicon sample to a value for the thermal diffusivity and conductivity of the diamond film

  2. Plasma waveguides for high-intensity laser pulses

    International Nuclear Information System (INIS)

    This thesis documents the development of plasma waveguides for high-intensity laser pulses. Initial work concentrated on the development of the discharge-ablated capillary waveguide, based on the work of A. Zigler (Zigler, A., Y. Ehrlich, C. Cohen, J. Krall and P. Sprangle, J. Opt. Soc. Am. B 13, 68). The waveguide was shown to be capable of guiding picosecond laser pulses with an intensity of 1016 W cm-2 over a length of 10 mm. The pulse energy transmission of the capillary was increased from 48% to 70% when the discharge was fired. An interferometry-based measurement technique was developed, allowing measurement of the electron density profile formed in the capillary waveguide. These measurements were used as input to a numerical simulation that predicted the propagation of intense laser pulses through partially-ionised plasma waveguides. Numerical simulations accurately reproduced the picosecond pulse guiding results, and gave important insights into the properties and severe drawbacks of partially-ionised waveguides. Previous work on partially-ionised plasma waveguides has not fully explored the implications of the propagation of intense pulses through the partially-ionised plasma. For polypropylene waveguides, it was shown that for pulses with an intensity of 1016 W cm-2, the waveguide is not capable of high-quality guiding. However, for pulses with an intensity of greater than 1017 W cm-2, high-quality guiding is predicted through the partially-ionised waveguide in a new regime called 'quasi-matched guiding'. A novel gas-filled capillary discharge waveguide was designed and built. The device was shown to form a guiding channel inside a capillary pre-filled with gas. Interferometry measurements of the electron density profile formed in a hydrogen-filled capillary discharge waveguide showed that an approximately parabolic plasma waveguide could be formed in an essentially fully-ionised hydrogen plasma. The device was used to guide femtosecond laser pulses, with

  3. Curing of Epoxy Resin Induced by Femtosecond Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    LI Yubin; ZHANG Zuoguang

    2005-01-01

    The possibility of curing of epoxy resin induced by femtosecond laser beam was explored through choosing different initiators . Absorption spectroscopy, infrared spectroscopy (IR), stereomicroscopy and scanning electron microscopy (SEM) were applied to analyze the structure of epoxy resin systems after irradiation with a femtosecond laser beam. The experimental results show that the epoxy resin systems containing diaryliodonium salts can be cured by irradiation of Jemtosecond laser pulse, while the systems containing benzoin can not be cured. It is found that diaryliodonium salts decompose under the irradiation of femtosecond laser pulse through multi ( two ) -photon absorption, initiating the ring-opening polymerization of epoxy resin. And the appearance of cured area has a sheet structure consisting of many tiny lamellar structures.

  4. Interaction of Superintense Laser Pulses with Relativistic Ions

    Science.gov (United States)

    Chirilă, C. C.; Joachain, C. J.; Kylstra, N. J.; Potvliege, R. M.

    2004-12-01

    At high intensities, three-step recollision processes driven by low frequency laser pulses, such as high-order harmonic generation and high-order above-threshold ionization, are normally severely suppressed by the magnetic-field component of the laser field. It is shown that this suppression is not severe, even for ponderomotive energies well above 10keV, for multicharged ions moving at a sufficiently high relativistic velocity against a counterpropagating infrared laser pulse. Numerical results are presented for high-order harmonic emission by a single Ne9+ ion moving with a Lorentz factor γ=15 against a Nd:glass laser beam. The calculations are done within a Coulomb-corrected nondipole strong field approximation. The approximation is tested by comparing with accurate results.

  5. Interaction of superintense laser pulses with relativistic ions.

    Science.gov (United States)

    Chirilă, C C; Joachain, C J; Kylstra, N J; Potvliege, R M

    2004-12-10

    At high intensities, three-step recollision processes driven by low frequency laser pulses, such as high-order harmonic generation and high-order above-threshold ionization, are normally severely suppressed by the magnetic-field component of the laser field. It is shown that this suppression is not severe, even for ponderomotive energies well above 10 keV, for multicharged ions moving at a sufficiently high relativistic velocity against a counterpropagating infrared laser pulse. Numerical results are presented for high-order harmonic emission by a single Ne9+ ion moving with a Lorentz factor gamma=15 against a Nd:glass laser beam. The calculations are done within a Coulomb-corrected nondipole strong field approximation. The approximation is tested by comparing with accurate results. PMID:15697809

  6. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Brendel' , V M; Bukin, V V; Garnov, Sergei V; Bagdasarov, V Kh; Denisov, N N; Garanin, Sergey G; Terekhin, V A; Trutnev, Yurii A

    2012-12-31

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation. (laser technologies)

  7. Cutaneous effects of pulsed nitrogen gas laser irradiation

    International Nuclear Information System (INIS)

    The effects of pulsed nitrogen gas laser emission (337.1 nm wavelength) were studied on human skin. The laser provides high-intensity monochromatic UVA radiation and can elicit delayed erythema in an actual exposure time of about 1 msec (105,000 pulses, each lasting 10 nsec, delivered over 210 sec). The effects of nitrogen laser irradiation were compared clinically and histologically with conventional erythemogenic UVA and UVB exposures from xenon arc or mercury arc lamps and were found to be similar in many respects. The minimal erythema dose is comparable to that obtained using more conventional continuous light sources which have more than 100 times lower intensity. A phototoxicity comparison of oral and topically applied psoralens is presented, indicating that the laser may prove useful in comparing photosensitizing capacity of certain compounds

  8. Waveguide fabrication in phosphate glasses using femtosecond laser pulses

    International Nuclear Information System (INIS)

    We report on the response of glass to focused femtosecond (fs) laser pulses during waveguide fabrication in a commercial sodium aluminum phosphate glass (Schott IOG-1). Single-pass longitudinal translation of IOG-1 glass with respect to the focused laser beam at a rate of 20 μm/s and pulse energies of 3.5 μJ results in the formation of two waveguides located on opposite sides of the laser-exposed region, which itself does not guide light. This behavior is different from that of the more widely studied silica glass system. The precise location of the waveguides in IOG-1 glass depends on the relative tilt of the fs laser beam with respect to the sample translation direction. Fluorescence imaging of the modified glass using a confocal microscope setup reveals the formation of color center defects in the exposed region but not within the waveguides

  9. Ultrafast pulses from a mid-infrared fiber laser.

    Science.gov (United States)

    Hu, Tomonori; Jackson, Stuart D; Hudson, Darren D

    2015-09-15

    Ultrafast laser pulses at mid-infrared wavelengths (2-20 μm) interact strongly with molecules due to the resonance with their vibration modes. This enables their application in frequency comb-based sensing and laser tissue surgery. Fiber lasers are ideal to achieve these pulses, as they are compact, stable, and efficient. We extend the performance of these lasers with the production of 6.4 kW at a wavelength of 2.8 μm with complete electric field retrieval using frequency-resolved optical gating techniques. Contrary to the problems associated with achieving a high average power, fluoride fibers have now shown the capability of operating in the ultrafast, high-peak-power regime. PMID:26371902

  10. Multiple quantum wells for passive ultra short laser pulse generation

    CERN Document Server

    Quintero-Torres, R; Rodriguez-Rodriguez, E; Stintz, Andreas; Diels, Jean-Claude

    2007-01-01

    Solid state lasers are demanding independent control in the gain media and cavity loss to achieve ultra short laser pulses using passive mode-locking. Recently, laser mode-locking is achieved with a MBE structure with multiple quantum wells, designed to achieve two functions; Bragg mirror and changes in absorption to control the cavity dynamics. The use of an AlGaAs/AlAs Bragg mirror with a 15 nm GaAs saturable absorber used in a Cr:LiSAF tuneable laser proved to be effective to produce femtosecond pulses. The use of saturable absorbers thus far is a trial and error procedure that is changing due to the correlation with more predictive procedures.

  11. Droplet deformation and fragmentation by ultra-short laser pulses

    CERN Document Server

    Krivokorytov, M S; Sidelnikov, Yu V; Krivtsun, V M; Medvedev, V V; Kompanets, V O; Lash, A A; Koshelev, K N

    2016-01-01

    We report on the experimental studies of the deformation and fragmentation of liquid metal droplets by picosecond and subpicosecond laser pulses. The experiments were performed with laser irradiance varying in 10E13-10E15 W/cm^2 range. The observed evolution of the droplet shape upon the impact dramatically differs from the previously reported for nanosecond laser pulses. Instead of flattening the droplet undergoes rapid asymmetric expansion and transforms into a complex shape which can be interpreted as two conjunct spheroid shells and finally fragments. We explain the described hydrodynamic response to the ultra-short impact as a result of the propagation of the laser-induced convergent shockwave through the volume of droplet.

  12. Nanosecond laser-induced phase transitions in pulsed laser deposition-deposited GeTe films

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xinxing, E-mail: xinxing.sun@iom-leipzig.de; Thelander, Erik; Lorenz, Pierre; Gerlach, Jürgen W.; Decker, Ulrich; Rauschenbach, Bernd [Leibniz Institute of Surface Modification, Permoserstr. 15, D-04318, Leipzig (Germany)

    2014-10-07

    Phase transformations between amorphous and crystalline states induced by irradiation of pulsed laser deposition grown GeTe thin films with nanosecond laser pulses at 248 nm and pulse duration of 20 ns are studied. Structural and optical properties of the Ge-Te phase-change films were studied by X-ray diffraction and optical reflectivity measurements as a function of the number of laser pulses between 0 and 30 pulses and of the laser fluence up to 195 mJ/cm². A reversible phase transition by using pulse numbers ≥ 5 at a fluence above the threshold fluence between 11 and 14 mJ/cm² for crystallization and single pulses at a fluence between 162 and 182 mJ/cm² for amorphization could be proved. For laser fluences from 36 up to 130 mJ/cm², a high optical contrast of 14.7% between the amorphous and crystalline state is measured. A simple model is used that allows the discussion on the distribution of temperature in dependency on the laser fluence.

  13. Optical trapping of nanoparticles by ultrashort laser pulses.

    Science.gov (United States)

    Usman, Anwar; Chiang, Wei-Yi; Masuhara, Hiroshi

    2013-01-01

    Optical trapping with continuous-wave lasers has been a fascinating field in the optical manipulation. It has become a powerful tool for manipulating micrometer-sized objects, and has been widely applied in physics, chemistry, biology, material, and colloidal science. Replacing the continuous-wave- with pulsed-mode laser in optical trapping has already revealed some novel phenomena, including the stable trap, modifiable trapping positions, and controllable directional optical ejections of particles in nanometer scales. Due to two distinctive features; impulsive peak powers and relaxation time between consecutive pulses, the optical trapping with the laser pulses has been demonstrated to have some advantages over conventional continuous-wave lasers, particularly when the particles are within Rayleigh approximation. This would open unprecedented opportunities in both fundamental science and application. This Review summarizes recent advances in the optical trapping with laser pulses and discusses the electromagnetic formulations and physical interpretations of the new phenomena. Its aim is rather to show how beautiful and promising this field will be, and to encourage the in-depth study of this field. PMID:23738434

  14. Cooling of relativistic electron beams in chirped laser pulses

    CERN Document Server

    Yoffe, Samuel R; Kravets, Yevgen; Jaroszynski, Dino A

    2015-01-01

    The next few years will see next-generation high-power laser facilities (such as the Extreme Light Infrastructure) become operational, for which it is important to understand how interaction with intense laser pulses affects the bulk properties of a relativistic electron beam. At such high field intensities, we expect both radiation reaction and quantum effects to play a significant role in the beam dynamics. The resulting reduction in relative energy spread (beam cooling) at the expense of mean beam energy predicted by classical theories of radiation reaction depends only on the energy of the laser pulse. Quantum effects suppress this cooling, with the dynamics additionally sensitive to the distribution of energy within the pulse. Since chirps occur in both the production of high-intensity pulses (CPA) and the propagation of pulses in media, the effect of using chirps to modify the pulse shape has been investigated using a semi-classical extension to the Landau--Lifshitz theory. Results indicate that even la...

  15. Laser ablation of UHMWPE-polyethylene by 438 nm high energy pulsed laser

    International Nuclear Information System (INIS)

    Pulsed laser ablation of ultra-high-molecular-weight-polyethylene (UHMWPE) is investigated at Prague Asterix Laser System (PALS) Laboratory. The high ablation yield as a function of laser energy is presented at 438 nm laser wavelength. The mechanisms of the polymer ablation are studied on the base of ''in situ'' analysis, such as mass quadrupole spectrometry and time-of-flight measurements, and ''ex situ'' analysis, such as SEM investigations and Raman spectroscopy. Results show that the laser irradiation induces a strong polymer dehydrogenation and molecular emission due to different CxHy groups having high kinetic energy and high charge state. At a laser pulse energy of 150 J the H+, Cn+ ions (n=1 to 6) are emitted from the plasma with velocities of the order of 108 cm/s, while the CxHy groups and the carbon clusters, detected up to C16, have a velocity about one or two order magnitude lower. The laser ablation process produces a deep crater in the polymer, which depth depends on the laser pulse energy and it is of the order of 500 μm. The crater volume increases with the laser pulse energy. Results demonstrated that the laser radiation modifies the polymer chains because dehydrogenated material and carbon-like structures are detected in the crater walls and in the bottom of the crater, respectively. A comparison of the experimental results with the data available in literature is presented and discussed

  16. Vulnerability of CMOS image sensors in mega-joule class laser harsh environment

    International Nuclear Information System (INIS)

    CMOS image sensors (CIS) are promising candidates as part of optical imagers for the plasma diagnostics devoted to the study of fusion by inertial confinement. However, the harsh radiative environment of Megajoule Class Lasers threatens the performances of these optical sensors. In this paper, the vulnerability of CIS to the transient and mixed pulsed radiation environment associated with such facilities is investigated during an experiment at the OMEGA facility at the Laboratory for Laser Energetics (LLE), Rochester, NY, USA. The transient and permanent effects of the 14 MeV neutron pulse on CIS are presented. The behavior of the tested CIS shows that active pixel sensors (APS) exhibit a better hardness to this harsh environment than a CCD. A first order extrapolation of the reported results to the higher level of radiation expected for Megajoule Class Laser facilities (Laser Megajoule in France or National Ignition Facility in the USA) shows that temporarily saturated pixels due to transient neutron-induced single event effects will be the major issue for the development of radiation-tolerant plasma diagnostic instruments whereas the permanent degradation of the CIS related to displacement damage or total ionizing dose effects could be reduced by applying well known mitigation techniques. (authors)

  17. Demonstration of a self-pulsing photonic crystal Fano laser

    CERN Document Server

    Yu, Yi; Semenova, Elizaveta; Yvind, Kresten; Mork, Jesper

    2016-01-01

    Semiconductor lasers in use today rely on mirrors based on the reflection at a cleaved facet or Bragg reflection from a periodic stack of layers. Here, we demonstrate an ultra-small laser with a mirror based on the Fano resonance between a continuum of waveguide modes and the discrete resonance of a nanocavity. The Fano resonance leads to unique laser characteristics. Since the Fano mirror is very narrow-band compared to conventional lasers, the laser is single-mode and in particular, it can be modulated via the mirror. We show, experimentally and theoretically, that nonlinearities in the mirror may even promote the generation of a self-sustained train of pulses at gigahertz frequencies, an effect that was previously only observed in macroscopic lasers. Such a source is of interest for a number of applications within integrated photonics.

  18. PULSED MODE LASER CUTTING OF SHEETS FOR TAILORED BLANKS

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    1999-01-01

    This paper describes how the laser cutting process can be optimised in such a way that the cut sheets can subsequently be used to laser weld tailored blanks. In a number of systematic laboratory experiments the effect of cutting speed, assist gas pressure, average laser power and pulse energy was...... item for parameter optimisation of laser cut sheets used for tailored blanks. It was concluded that high quality cut edges with a squareness as small as 0.015 mm may be obtained. Such edges are well suited for subsequent laser welding....... analysed. For quality assessment the squareness, roughness and dross attachment of laser cut blanks were measured. In all tests, the medium strength steel GA 260 with a thickness of 1.8 mm was used. In this work it has been successfully demonstrated that the squareness of a cut can be used as a quality...

  19. Extensive angiokeratoma circumscriptum - successful treatment with 595-nm variable-pulse pulsed dye laser and 755-nm long-pulse pulsed alexandrite laser.

    Science.gov (United States)

    Baumgartner, Ján; Šimaljaková, Mária; Babál, Pavel

    2016-06-01

    Angiokeratomas are rare vascular mucocutaneous lesions characterized by small-vessel ectasias in the upper dermis with reactive epidermal changes. Angiokeratoma circumscriptum (AC) is the rarest among the five types in the current classification of angiokeratoma. We present a case of an extensive AC in 19-year-old women with Fitzpatrick skin type I of the left lower extremity, characterized by a significant morphological heterogeneity of the lesions, intermittent bleeding, and negative psychological impact. Histopathological examination after deep biopsy was consistent with that of angiokeratoma. The association with metabolic diseases (Fabry disease) was excluded by ophthalmological, biochemical, and genetic examinations. Nuclear magnetic resonance imaging has not detected deep vascular hyperplasia pathognomic for verrucous hemangioma. The combined treatment with 595-nm variable-pulse pulsed dye laser (VPPDL) and 755-nm long-pulse pulsed alexandrite laser (LPPAL) with dynamic cooling device led to significant removal of the pathological vascular tissue of AC. Only a slight degree of secondary reactions (dyspigmentations and texture changes) occurred. No recurrence was observed after postoperative interval of 9 months. We recommend VPPDL and LPPAL for the treatment of extensive AC. PMID:26736060

  20. Gain dynamics of a free-space nitrogen laser pumped by circularly polarized femtosecond laser pulses

    OpenAIRE

    Yao, Jinping; Xie, Hongqiang; Zeng, Bin; Chu, Wei; Li, Guihua; Ni, Jielei; Zhang, Haisu; Jing, Chenrui; Zhang, Chaojin; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan

    2014-01-01

    We experimentally demonstrate ultrafast dynamic of generation of a strong 337-nm nitrogen laser by injecting an external seed pulse into a femtosecond laser filament pumped by a circularly polarized laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the excited and ground states of N2 for the free-space 337-nm laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, ...

  1. An 11.5 W Yb:YAG planar waveguide laser fabricated via pulsed laser deposition

    OpenAIRE

    Grant-Jacob, James A.; Beecher, Stephen J.; Parsonage, Tina L.; Hua, Ping; Mackenzie, Jacob I.; Shepherd, David P.; Eason, Robert W.

    2016-01-01

    We present details of the homo-epitaxial growth of Yb:YAG onto a oriented YAG substrate by pulsed laser deposition. Material characterization and initial laser experiments are also reported, including the demonstration of laser action from the 15 µm-thick planar waveguide generating 11.5 W of output power with a slope efficiency of 48%. This work indicates that under appropriate conditions, high-quality single-crystal Yb:YAG growth via pulsed laser deposition is achievable with characteristi...

  2. Electrical properties of pulsed UV laser irradiated amorphous carbon

    OpenAIRE

    Y. Miyajima; Adikaari, AADT; Henley, SJ; Shannon, JM; Silva, SRP

    2008-01-01

    Amorphous carbon films containing no hydrogen were irradiated with a pulsed UV laser in vacuum. Raman spectroscopy indicates an increase in the quantity of sp(2) clustering with the highest laser energy density and a commensurate reduction in resistivity. The reduction of resistivity is explained to be associated with thermally induced graphitization of amorphous carbon films. The high field transport is consistent with a Poole-Frenkel type transport mechanism via neutral trapping centers rel...

  3. Polaritonic materials fabricated and tested with ultrashort-pulse lasers

    CERN Document Server

    Ward, D W; Feurer, T; Nelson, K A; Ward, David W.; Statz, Eric R.; Feurer, Thomas; Nelson, Keith A.

    2004-01-01

    Using femtosecond laser machining, we have fabricated photonic bandgap materials that influence propagation of phonon-polaritons in ferroelectric crystals. Broadband polaritons were generated with impulsive stimulated Raman scattering (ISRS) using an ultrashort laser pulse, and the spatial and temporal evolution of the polaritons were imaged as they propagated through the fabricated structures with polariton real-space imaging. These techniques offer a new approach to optical materials design.

  4. Modelling colliding-pulse mode-locked semiconductor lasers

    DEFF Research Database (Denmark)

    Bischoff, Svend

    determine the optimum operation conditions. The purpose of this thesis is to elucidate some of the physics of interest in the field of semiconductor laser modelling, semiconductor optics and fiber optics. To be more specific we will investigate: The Colliding-Pulse Mode-Locked (CPM) Quantum Well (QW) laser...... diode; the excitonic semiconductor response for varying material thickness in the case of linear optics; and modulational instability of electromagnetic waves in media with spatially varying non-linearity....

  5. Controlling energy coupling and particle ejection from aluminum surfaces irradiated with ultrashort laser pulses

    International Nuclear Information System (INIS)

    Hydrodynamic simulations are used to evaluate the potential of ultrashort laser pulses to localize energy at metallic surfaces, in our case aluminum. The emphasis is put on the dynamic sequence of laser energy deposition steps during the electron-ion nonequilibrium stage and the subsequent matter transformation phases. The simulations indicate correlated optical and thermodynamical states associated to specific electronic collisional mechanisms. The timescales of energy deposition deliver a guideline for using relevant relaxation times to improve the energy coupling into the material. We focus on a class of pump-probe experiments which investigate energy storage and particle emission from solids under ultrafast laser irradiation. Moreover, we have used our model to explain the experimentally observed optimization of energy coupling by tailoring temporal laser intensity envelopes and its subsequent influence on the ablation rate and on the composition of ablation products. Potential control for nanoparticle generation is discussed.

  6. Characterization of polymer thin films obtained by pulsed laser deposition

    International Nuclear Information System (INIS)

    The development of laser techniques for the deposition of polymer and biomaterial thin films on solid surfaces in a controlled manner has attracted great attention during the last few years. Here we report the deposition of thin polymer films, namely Polyepichlorhydrin by pulsed laser deposition. Polyepichlorhydrin polymer was deposited on flat substrate (i.e. silicon) using an NdYAG laser (266 nm, 5 ns pulse duration and 10 Hz repetition rate). The obtained thin films have been characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and spectroscopic ellipsometry. It was found that for laser fluences up to 1.5 J/cm2 the chemical structure of the deposited polyepichlorhydrin polymer thin layers resembles to the native polymer, whilst by increasing the laser fluence above 1.5 J/cm2 the polyepichlorohydrin films present deviations from the bulk polymer. Morphological investigations (atomic force microscopy and scanning electron microscopy) reveal continuous polyepichlorhydrin thin films for a relatively narrow range of fluences (1-1.5 J/cm2). The wavelength dependence of the refractive index and extinction coefficient was determined by ellipsometry studies which lead to new insights about the material. The obtained results indicate that pulsed laser deposition method is potentially useful for the fabrication of polymer thin films to be used in applications including electronics, microsensor or bioengineering industries.

  7. Impact of laser power density on tribological properties of Pulsed Laser Deposited DLC films

    International Nuclear Information System (INIS)

    Fabrication of wear resistant and low friction carbon films on the engineered substrates is considered as a challenging task for expanding the applications of diamond-like carbon (DLC) films. In this paper, pulsed laser deposition (PLD) technique is used to deposit DLC films on two different types of technologically important class of substrates such as silicon and AISI 304 stainless steel. Laser power density is one of the important parameter used to tailor the fraction of sp2 bonded amorphous carbon (a-C) and tetrahedral amorphous carbon (ta-C) made by sp3 domain in the DLC film. The I(D)/I(G) ratio decreases with the increasing laser power density which is associated with decrease in fraction of a-C/ta-C ratio. The fraction of these chemical components is quantitatively analyzed by EELS which is well supported to the data obtained from the Raman spectroscopy. Tribological properties of the DLC are associated with chemical structure of the film. However, the super low value of friction coefficient 0.003 is obtained when the film is predominantly constituted by a-C and sp2 fraction which is embedded within the clusters of ta-C. Such a particular film with super low friction coefficient is measured while it was deposited on steel at low laser power density of 2 GW/cm2. The super low friction mechanism is explained by low sliding resistance of a-C/sp2 and ta-C clusters. Combination of excellent physical and mechanical properties of wear resistance and super low friction coefficient of DLC films is desirable for engineering applications. Moreover, the high friction coefficient of DLC films deposited at 9GW/cm2 is related to widening of the intergrain distance caused by transformation from sp2 to sp3 hybridized structure

  8. Impact of laser power density on tribological properties of Pulsed Laser Deposited DLC films

    Directory of Open Access Journals (Sweden)

    S. Gayathri

    2013-12-01

    Full Text Available Fabrication of wear resistant and low friction carbon films on the engineered substrates is considered as a challenging task for expanding the applications of diamond-like carbon (DLC films. In this paper, pulsed laser deposition (PLD technique is used to deposit DLC films on two different types of technologically important class of substrates such as silicon and AISI 304 stainless steel. Laser power density is one of the important parameter used to tailor the fraction of sp2 bonded amorphous carbon (a-C and tetrahedral amorphous carbon (ta-C made by sp3 domain in the DLC film. The I(D/I(G ratio decreases with the increasing laser power density which is associated with decrease in fraction of a-C/ta-C ratio. The fraction of these chemical components is quantitatively analyzed by EELS which is well supported to the data obtained from the Raman spectroscopy. Tribological properties of the DLC are associated with chemical structure of the film. However, the super low value of friction coefficient 0.003 is obtained when the film is predominantly constituted by a-C and sp2 fraction which is embedded within the clusters of ta-C. Such a particular film with super low friction coefficient is measured while it was deposited on steel at low laser power density of 2 GW/cm2. The super low friction mechanism is explained by low sliding resistance of a-C/sp2 and ta-C clusters. Combination of excellent physical and mechanical properties of wear resistance and super low friction coefficient of DLC films is desirable for engineering applications. Moreover, the high friction coefficient of DLC films deposited at 9GW/cm2 is related to widening of the intergrain distance caused by transformation from sp2 to sp3 hybridized structure.

  9. Ablation and plasma emission produced by dual femtosecond laser pulses

    International Nuclear Information System (INIS)

    Pairs of 80 fs, 800 nm laser pulses were used to ablate Si, Cu, and CaF2 in air. The spectrally resolved plasma emission was measured as a function of laser fluence and pulse delay. After an initial dip, the fluorescence was found to increase monotonically with pulse delay, reaching a plateau after some tens of picoseconds, depending on the material and fluence. The enhancement ratio (defined as the ratio of the fluorescence produced by the pulse pair to that produced by a single pulse of the same total fluence) reaches a maximum value of 6 and 11 at a fluence of ∼6 J/cm2 for Si and Cu, respectively, and declines to a value below 2 at higher fluences. In contrast, the enhancement for CaF2 increases slowly from zero near threshold to a broad maximum value of 2 near 50 J/cm2. Using reflectivity and atomic force microscopy measurements as diagnostics, we interpret the Si and Cu behavior in terms of a two phase mechanism, in which the first pulse melts the surface of the crystal and the second pulse ablates the resulting liquid film. A qualitatively different mechanism initiated by multiphoton absorption is involved in CaF2 ablation

  10. Temporal laser pulse manipulation using multiple optical ring-cavities

    Science.gov (United States)

    Nguyen, Quang-Viet (Inventor); Kojima, Jun (Inventor)

    2010-01-01

    An optical pulse stretcher and a mathematical algorithm for the detailed calculation of its design and performance is disclosed. The optical pulse stretcher has a plurality of optical cavities, having multiple optical reflectors such that an optical path length in each of the optical cavities is different. The optical pulse stretcher also has a plurality of beam splitters, each of which intercepts a portion of an input optical beam and diverts the portion into one of the plurality of optical cavities. The input optical beam is stretched and a power of an output beam is reduced after passing through the optical pulse stretcher and the placement of the plurality of optical cavities and beam splitters is optimized through a model that takes into account optical beam divergence and alignment in the pluralities of the optical cavities. The optical pulse stretcher system can also function as a high-repetition-rate (MHz) laser pulse generator, making it suitable for use as a stroboscopic light source for high speed ballistic projectile imaging studies, or it can be used for high speed flow diagnostics using a laser light sheet with digital particle imaging velocimetry. The optical pulse stretcher system can also be implemented using fiber optic components to realize a rugged and compact optical system that is alignment free and easy to use.

  11. Laser fusion neutron source employing compression with short pulse lasers

    Science.gov (United States)

    Sefcik, Joseph A; Wilks, Scott C

    2013-11-05

    A method and system for achieving fusion is provided. The method includes providing laser source that generates a laser beam and a target that includes a capsule embedded in the target and filled with DT gas. The laser beam is directed at the target. The laser beam helps create an electron beam within the target. The electron beam heats the capsule, the DT gas, and the area surrounding the capsule. At a certain point equilibrium is reached. At the equilibrium point, the capsule implodes and generates enough pressure on the DT gas to ignite the DT gas and fuse the DT gas nuclei.

  12. Nonlinear 6-fold enhancement of laser drilling efficiency by double pulse mode: prospective in medicine application

    Science.gov (United States)

    Pershina, N. S.; Pershin, S. M.; Cech, M.; Prochazka, I.

    2009-05-01

    The efficiency of laser ablation drilling of metal and dielectric (ceramic, glasses, etc.) samples with single and multiple laser pulses per one laser shot was experimentally studied. The laser is operated on the fundamental (1064 nm) wavelength of Nd:YAG laser with 30 ns pulse length or its second (532 nm) and third (351 nm) harmonics, respectively. The laser shot repletion rate was 1 Hz. The pulses in train were separated by 25-45 μs interval. The crater depth and drilling speed dependence increasing on pulse number in multipulse train was studied. The laser ablation normalized per pulse energy in train dependence is not linear function. The strong ablation enhancement was observed. The optimal (in sense the total pulse energy using) drilling can be obtained with double pulse mode compared with 3 - 5 pulses. Nonlinear more than 6 fold increasing of crater depth produced by the second pulse in train was detected. The mechanism of selective increasing of the second pulse interaction efficiency with the hard target is discussed. Experimental results explained in terms of double pulse mode laser ablation model. Spectroscopy study of laser plasma was observed to confirm discussed model of high efficiency for two laser pulse laser ablation. Efficiency of double pulse mode compared with multipulse mode is discussed to be more perspective for various applications of laser ablation. The medicine (surgery, dentist, ophthalmology and so on) application is the most prospective, for instance, the teeth drilling or glaucoma perforation, can be done with smaller energy value.

  13. Microstructuring of fused silica by laser-induced backside wet etching using picosecond laser pulses

    International Nuclear Information System (INIS)

    The laser-induced backside wet etching (LIBWE) is an advanced laser processing method used for structuring transparent materials. LIBWE with nanosecond laser pulses has been successfully demonstrated for various materials, e.g. oxides (fused silica, sapphire) or fluorides (CaF2, MgF2), and applied for the fabrication of microstructures. In the present study, LIBWE of fused silica with mode-locked picosecond (tp = 10 ps) lasers at UV wavelengths (λ1 = 355 nm and λ2 = 266 nm) using a (pyrene) toluene solution was demonstrated for the first time. The influence of the experimental parameters, such as laser fluence, pulse number, and absorbing liquid, on the etch rate and the resulting surface morphology were investigated. The etch rate grew linearly with the laser fluence in the low and in the high fluence range with different slopes. Incubation at low pulse numbers as well as a nearly constant etch rate after a specific pulse number for example were observed. Additionally, the etch rate depended on the absorbing liquid used; whereas the higher absorption of the admixture of pyrene in the used toluene enhances the etch rate and decreases the threshold fluence. With a λ1 = 266 nm laser set-up, an exceptionally smooth surface in the etch pits was achieved. For both wavelengths (λ1 = 266 nm and λ2 = 355 nm), LIPSS (laser-induced periodic surface structures) formation was observed, especially at laser fluences near the thresholds of 170 and 120 mJ/cm2, respectively.

  14. Application of femtosecond ultrashort pulse laser to photodynamic therapy mediated by indocyanine green

    OpenAIRE

    Sawa, M; Awazu, K; Takahashi, T.; Sakaguchi, H; Horiike, H.; Ohji, M; Tano, Y

    2004-01-01

    Backgrounds/aims: To evaluate treatment with high peak power pulse energy by femtosecond ultrashort pulse laser (titanium sapphire laser) delivered at an 800 nm wavelength for corneal neovascularisation using photodynamic therapy (PDT) mediated by indocyanine green (ICG).

  15. Development of Nanosecond Short Pulse High Power KrF Laser System

    Institute of Scientific and Technical Information of China (English)

    SZATMAR; Sador; BOHUS; Janos

    2011-01-01

    Compression of short pulse laser is demanded by the physical experiments such as EOS for Heaven-I system. A nanosecond short pulse high power discharge pumping excimer laser system was developed under the frame of Science and Technology

  16. CO2 laser pulse switching by optically excited semiconductors

    International Nuclear Information System (INIS)

    The construction and the study of a semi-conductor optical switch used for generating short infrared pulses and to analyse the semiconductor characteristics, are presented. The switch response time depends on semiconductor and control laser characteristics. The results obtained using a Ge switch controlled by N2, NdYag and Dye lasers are presented. The response time was 50 ns limited by Ge recombination time. The reflectivity increased from 7% to 59% using N2 laser to control the switch. A simple model for semiconductor optical properties that explain very well the experimental results, is also presented. (author)

  17. Recent applications of pulsed lasers in advanced materials processing

    International Nuclear Information System (INIS)

    Pulsed laser sources are widely used for the micro-processing of materials from the structuring and patterning of surfaces to the direct machining of devices. This paper discusses laser micro-processing techniques for the fabrication of microstructures with high accuracy and precision over large areas. Techniques discussed include laser mask projection techniques, synchronised image scanning (SIS) and bow tie scanning (BTS) and direct beam micromachining. Examples of the application of these techniques in industrial production are discussed, including solar cell scribing, micro-optical device manufacture, inkjet printer nozzle drilling and plasma display panel patterning

  18. Physics of Giant ElectroMagnetic Pulse generation in short pulse laser experiments

    OpenAIRE

    Poyé, Alexandre; Hulin, Sébastien; Bailly-Grandvaux, Mathieu; Dubois, Jean-Luc; Ribolzi, Jérôme; Raffestin, Didier; Bardon, Matthieu; Lubrano-Lavaderci, Frédéric; D'Humières, Emmanuel; Santos, Joao Jorge; Nicolaï, Philippe; Tikhonchuk, Vladimir

    2015-01-01

    In this paper we describe the physical processes that lead to the generation of Giant Electro- Magnetic Pulses (GEMP) on powerful laser facilities. Our study is based on experimental mea- surements of both the charging of a solid target irradiated by an ultra-short, ultra-intense laser and the detection of the electromagnetic emission in the GHz domain. An unambiguous correlation between the neutralisation current in the target holder and the electromagnetic emission shows that the source of ...

  19. X-ray laser pulses from solids

    CERN Document Server

    Ivlev, Boris I

    2015-01-01

    In experiments on irradiation of metal surfaces by ions of keV energy, X-ray laser radiation was observed despite population inversion was unexpected. The radiation continued after the bombarding by ions was switched off. In this paper unusual properties of that X-ray radiation are analysed. Anomalous states are formed inside the metal. These states are associated with a narrow potential well created by the local reduction of zero point electromagnetic energy. This reminds the van der Waals potential well. States in the well are long-living which results in population inversion and the subsequent laser generation observed.

  20. Ablation of polymers by ultraviolet pulsed laser

    International Nuclear Information System (INIS)

    The surface modifications of different polymers treated by far UV-Excimer laser (λ = 193mn, 248, 308nm) are analysed by X-Ray Photoelectrons Spectroscopy. The main feature observed depends strongly on the absorption coefficients. For the high absorbing polymers such (PVC, PS, PI,...) the mechanism of the UV-Excimer Laser interaction appears to be governed by an ablative photodecomposition process (APD) with an APD threshold. In the other limit, i.e. low absorbing polymer the interaction leads to a photothermal process. (author). 51 refs, 24 figs, 7 tabs

  1. Optimised design of fibre-based pulse compressor for gain-switched DFB laser pulses at 1.5 µm

    OpenAIRE

    Barry, Liam P.; Benn C. Thomsen; Dudley, John M.; Harvey, John D.

    1999-01-01

    An optical-fibre based pulse compressor for gain-switched DFB laser pulses has been optimised using a systematic procedure based on the initial complete characterisation of the laser pulses, followed by numerical simulations of the pulse propagation in different types of fibre to determine the required lengths for optimum compression. Using both linear and nonlinear compression techniques, an optimum compression factor of 12 is achieved.

  2. Numeric modeling of synchronous laser pulsing and voltage pulsing field evaporation

    CERN Document Server

    Zhao, L; Houard, J; Blum, I; Delaroche, F; Vurpillot, F

    2016-01-01

    We have recently proposed an atom probe design based on a femtosecond time-resolved pump-probe setup. This setup unlocks the limitation of voltage pulsed mode atom probe thanks to the occurrence of local photoconductive switching effect . In this paper, we have used a numerical model to simulate the field evaporation process triggered by the synchronous two pulses. The model takes into account the local photoconductive effect and the temperature rise caused by the laser application and the voltage pulse distortion due to the RC effect.

  3. Pulsed pump: Thermal effects in solid state lasers under super-Gaussian pulses

    Indian Academy of Sciences (India)

    H Nadgaran; M Sabaian

    2006-12-01

    Solid state laser (SSL) powers can be realistically scaled when pumped by a real, efficient and multimode pulse. In this work, a fourth-order super-Gaussian pulse was assumed as a pump for SSL's and a complete analytical expression for the thermal phase shift is given. Moreover, the focal length of thermal lens in paraxial ray approximation regime was studied. The results when applied to a Ti : sapphire crystal show an appreciable correction for abberation compared to a top-hat pulse.

  4. Epitaxial thin films grown by pulsed laser deposition

    OpenAIRE

    Blank, D. H. A.

    2005-01-01

    In this paper, we present the pulsed laser deposition (PLD) technique to control the growth of metal oxide materials at atomic level using high-pressure reflective high-energy electron diffraction and ellipsometry. These developments have helped to make PLD a grown-up technique to fabricate complex materials and structures

  5. Ferroelectric thin films deposited by pulsed laser deposition

    Science.gov (United States)

    Dinu, Raluca; Vrejoiu, I.; Verardi, P.; Craciun, F.; Dinescu, Maria

    2001-06-01

    Influence of substrate and electrode on the properties of PbZr0.53Ti0.47O3 (PZT) thin films grown by pulsed laser deposition technique (1060 nm wavelength Nd:YAG laser light, 10 ns pulse duration, 10 Hz repetition rate, 0.35 J/pulse, 25 J/cm2 laser fluence, deposition rate about 1 angstrom/pulse) was studied. The substrate temperatures were in the range 380 degree(s)C-400 degree(s)C. Oriented crystalline PZT layers with 1-3 micrometers thickness were deposited on glass substrates plated with Au/Pt/NiCr electrodes, from a PZT commercial target in oxygen reactive atmosphere. The deposited PZT films with perovskite structure were preferentially oriented along the (111) direction as revealed from XRD spectra. Piezoelectric d33 coefficients up to 30 pC/N were obtained on as deposited films. Ferroelectric hysteresis loops at 100 Hz revealed a remanent polarization of 15 (mu) C/cm2 and a coercive field of 100 kV/cm. A comparison with properties of PZT films deposited using a KrF laser and with SrBi2Ta2O9 (SBT) films is reported.

  6. Modeling short-pulse laser excitation of dielectric materials

    DEFF Research Database (Denmark)

    Wædegaard, Kristian Juncher; Sandkamm, Ditte Både; Haahr-Lillevang, Lasse; Bay, Kathrine Glerup; Balling, Peter

    2014-01-01

    A theoretical description of ultrashort-pulse laser excitation of dielectric materials based on strong-field excitation in the Keldysh picture combined with a multiple-rateequation model for the electronic excitation including collisional processes is presented. The model includes light attenuation...

  7. Intense ion beams accelerated by ultra-intense laser pulses

    Science.gov (United States)

    Roth, Markus; Cowan, T. E.; Gauthier, J. C.; Vehn, J. Meyer-Ter; Allen, M.; Audebert, P.; Blazevic, A.; Fuchs, J.; Geissel, M.; Hegelich, M.; Karsch, S.; Pukhov, A.; Schlegel, T.

    2002-04-01

    The discovery of intense ion beams off solid targets irradiated by ultra-intense laser pulses has become the subject of extensive international interest. These highly collimated, energetic beams of protons and heavy ions are strongly depending on the laser parameters as well as on the properties of the irradiated targets. Therefore we have studied the influence of the target conditions on laser-accelerated ion beams generated by multi-terawatt lasers. The experiments were performed using the 100 TW laser facility at Laboratoire pour l'Utilisation des Laser Intense (LULI). The targets were irradiated by pulses up to 5×1019 W/cm2 (~300 fs,λ=1.05 μm) at normal incidence. A strong dependence on the surface conditions, conductivity, shape and purity was observed. The plasma density on the front and rear surface was determined by laser interferometry. We characterized the ion beam by means of magnetic spectrometers, radiochromic film, nuclear activation and Thompson parabolas. The strong dependence of the ion beam acceleration on the conditions on the target back surface was confirmed in agreement with predictions based on the target normal sheath acceleration (TNSA) mechanism. Finally shaping of the ion beam has been demonstrated by the appropriate tailoring of the target. .

  8. Ablation experiment and threshold calculation of titanium alloy irradiated by ultra-fast pulse laser

    OpenAIRE

    Buxiang Zheng; Gedong Jiang; Wenjun Wang; Kedian Wang; Xuesong Mei

    2014-01-01

    The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology...

  9. Analysis of boundary conditions and transient signal treatment in diffusivity measurements by laser pulse method

    OpenAIRE

    Pawlowski, L.; Fauchais, P.; Martin, C.

    1985-01-01

    A laser pulse method for diffusivity determination is analysed. The method which permits the measurement of the laser pulse energy distribution as well as its shape is developed. This method can be easily implanted into laser pulse diffusivity set-up and it allows to check periodically the pulse characteristics that is of primary importance for the accuracy of the diffusivity measurements. The corrections to the classical model of Parker et al. [1] due to the heat losses and finite pulse dura...

  10. Periodic dark pulse emission induced by delayed feedback in a quantum well semiconductor laser

    Directory of Open Access Journals (Sweden)

    L. Li

    2012-12-01

    Full Text Available We report the experimental observation of periodic dark pulse emission in a quantum-well semiconductor laser with delayed optical feedback. We found that under appropriate operation conditions the laser can also emit a stable train of dark pulses. The repetition frequency of the dark pulse is determined by the external cavity length. Splitting of the dark pulse was also observed. We speculate that the observed dark pulse is a kind of temporal cavity soliton formed in the laser.

  11. Generation of high-energy attosecond pulses by the relativistic-irradiance short laser pulse interacting with a thin foil

    International Nuclear Information System (INIS)

    When a thin foil target is irradiated by two laser pulses, or it is irradiated by one pulse under the condition when the charge separation electric field exceeds the laser field, the electron motion in the direction perpendicular to the target surface is suppressed. Electrons can only slide along the foil. Using an analytical model, we describe the new regime of attosecond pulse generation by the relativistic-irradiance short laser pulse interacting with the sliding mirror. Pulses with the duration of few hundred attoseconds can be generated with the conversion efficiency up to few percents

  12. Multiterawatt femtosecond laser system with kilohertz pulse repetition rate

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, V V; Pestryakov, E V; Laptev, A V; Petrov, V A; Kuptsov, G V; Trunov, V I; Frolov, S A [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2014-05-30

    The basic principles, layout and components are presented for a multiterawatt femtosecond laser system with a kilohertz pulse repetition rate f, based on their parametric amplification and laser amplification of picosecond radiation that pumps the stages of the parametric amplifier. The results of calculations for a step-by-step increase in the output power from the LBO crystal parametric amplifier channel up to the multiterawatt level are presented. By using the developed components in the pump channel of the laser system, the parameters of the regenerative amplifier with the output energy ∼1 mJ at the wavelength 1030 nm and with f = 1 kHz are experimentally studied. The optical scheme of the diode-pumped multipass cryogenic Yb:Y{sub 2}O{sub 3} laser ceramic amplifier is developed and its characteristics are determined that provide the output energy within the range 0.25 – 0.35 J. (lasers)

  13. Laser versus intense pulsed light: Competing technologies in dermatology.

    Science.gov (United States)

    Ross, E Victor

    2006-04-01

    Lasers have been competing with non-laser intense pulsed light (IPL) sources in the cosmetic arena over the past 10 years. Initially IPLs were somewhat cumbersome and accepted by a minority of "serious" practitioners. Recently, however, the popularity of full-face visible light skin rejuvenation, enhanced engineering of IPLs, and favorable cost versus many lasers, have lead to a proliferation of IPL devices. No longer a stepchild in the rejuvenation market, IPLs may overtake lasers as the devices of choice among most physicians. We review the pros and cons of lasers and IPLs within the context of design, cost, and other practical concerns for a typical office-based practice. PMID:16596659

  14. Efficient self-sustained pulsed CO laser

    NARCIS (Netherlands)

    Peters, P.J.M.

    1978-01-01

    In this paper a simple sealed-off TEA CO laser is described with a self-sustained discharge without an external UV preionization source. At 77 K this system yields more than 600 mJ from a lasing volume of about 60 cm3 CO-N2-He mixture (45 J/ℓ atm. with 15.6% efficiency).

  15. Pulse Compression Of An FM Chirped CO2 Laser

    Science.gov (United States)

    Henderson, D. M.; Halmos, M. J.; Duvall, R. L.

    1989-12-01

    FM chirp/pulse compression has long been used in conventional radar systems [1]. The main advantages of such a technique are: 1. Efficient use of the average power available at the transmitter. 2. Increased system accuracy, both in range and velocity measurements. 3. Reduction of jamming vulnerability. We have explored the use of this technique for laser radar systems and in this paper describe an electro-optically FM modulated CO2 waveguide with post detection pulse compression by a surface acoustic wave (SAW) com-pression filter. The CO2 laser has been FM chirp modulated by a CdTe intracavity modulator. A frequency deviation of 95 MHz in 2.1 psec was attained in this fashion. Following heterodyne detection, the chirped pulse was compressed to 15 nsec using a SAW compression filter. This corresponded to a compression factor of 130. The suppression of unwanted sidelobes with a weighting filter was also demonstrated.

  16. Analysis on volume grating induced by femtosecond laser pulses.

    Science.gov (United States)

    Zhou, Keya; Guo, Zhongyi; Ding, Weiqiang; Liu, Shutian

    2010-06-21

    We report on a kind of self-assembled volume grating in silica glass induced by tightly focused femtosecond laser pulses. The formation of the volume grating is attributed to the multiple microexplosion in the transparent materials induced by the femtosecond pulses. The first order diffractive efficiency is in dependence on the energy of the pulses and the scanning velocity of the laser greatly, and reaches as high as 30%. The diffraction pattern of the fabricated grating is numerically simulated and analyzed by a two dimensional FDTD method and the Fresnel Diffraction Integral. The numerical results proved our prediction on the formation of the volume grating, which agrees well with our experiment results. PMID:20588497

  17. Fluorescence of silicon nanoparticles prepared by nanosecond pulsed laser

    Directory of Open Access Journals (Sweden)

    Chunyang Liu

    2014-03-01

    Full Text Available A pulsed laser fabrication method is used to prepare fluorescent microstructures on silicon substrates in this paper. A 355 nm nanosecond pulsed laser micromachining system was designed, and the performance was verified and optimized. Fluorescence microscopy was used to analyze the photoluminescence of the microstructures which were formed using the pulsed laser processing technique. Photoluminescence spectra of the microstructure reveal a peak emission around 500 nm, from 370 nm laser irradiation. The light intensity also shows an exponential decay with irradiation time, which is similar to attenuation processes seen in porous silicon. The surface morphology and chemical composition of the microstructure in the fabricated region was also analyzed with multifunction scanning electron microscopy. Spherical particles are produced with diameters around 100 nm. The structure is compared with porous silicon. It is likely that these nanoparticles act as luminescence recombination centers on the silicon surface. The small diameter of the particles modifies the band gap of silicon by quantum confinement effects. Electron-hole pairs recombine and the fluorescence emission shifts into the visible range. The chemical elements of the processed region are also changed during the interaction between laser and silicon. Oxidation and carbonization play an important role in the enhancement of fluorescence emission.

  18. Surface ablation of transparent polymers with femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Florian, C.; Caballero-Lucas, F.; Fernández-Pradas, J.M., E-mail: jmfernandez@ub.edu; Morenza, J.L.; Serra, P.

    2014-05-01

    In this work, a study of the laser ablation on the surface of poly methyl-methacrylate (PMMA) is presented. Experiments were performed with a femtosecond laser delivering 450 fs pulses at a wavelength of 1027 nm. The laser beam energy was controlled through a polarizer based attenuator and measured by a calibrated photodiode energy meter. A focusing method called z-scan is used to place the sample on the beam waist. This method uses a second energy meter placed behind the sample, which was used to monitor the energy transmitted across the sample in situ. Thus, the absorption was evaluated by comparing the measurements of both energy meters. The z-scan method is evaluated by studying the laser ablation in three different positions between the sample and the laser beam waist. It is found that above a threshold energy that depends on the focusing conditions, the absorbance of the samples increases with the pulse energy. After irradiation, dimensional analysis of the craters produced at different pulse energies is performed in order to determine the best focusing conditions and the ablation threshold for ablation of PMMA samples.

  19. Precision resection of intestine using ultrashort laser pulses

    Science.gov (United States)

    Beck, Rainer J.; Gora, Wojciech S.; Jayne, David; Hand, Duncan P.; Shephard, Jonathan D.

    2016-03-01

    Endoscopic resection of early colorectal neoplasms typically employs electrocautery tools, which lack precision and run the risk of full thickness thermal injury to the bowel wall with subsequent perforation. We present a means of endoluminal colonic ablation using picosecond laser pulses as a potential alternative to mitigate these limitations. High intensity ultrashort laser pulses enable nonlinear absorption processes, plasma generation, and as a consequence a predominantly non-thermal ablation regimen. Robust process parameters for the laser resection are demonstrated using fresh ex vivo pig intestine samples. Square cavities with comparable thickness to early colorectal neoplasms are removed for a wavelength of 1030 nm and 515 nm using a picosecond laser system. The corresponding histology sections exhibit in both cases only minimal collateral damage to the surrounding tissue. The ablation depth can be controlled precisely by means of the pulse energy. Overall, the application of ultrafast lasers for the resection of intestine enables significantly improved precision and reduced thermal damage to the surrounding tissue compared to conventional electrocautery.

  20. Retinal hemorrhagic lesions from femtosecond visible laser pulses

    Science.gov (United States)

    Stein, Cindy D.; Toth, Cynthia A.; Cain, Clarence P.; Noojin, Gary D.; Stolarski, David J.; Rockwell, Benjamin A.; Roach, William P.

    1994-08-01

    We present our clinical evaluation of hemorrhagic and non-hemorrhagic 90 fs single pulses in rabbits and primates. The rabbit and primate eye present unique in vivo models for evaluation of retinal and choroidal laser induced hemorrhages with distinct differences in their retinal anatomy. We found two different hemorrhagic events to occur in the posterior pole with delivery of 90 fs pulses. First, in the Dutch Belted rabbit, we found large amounts of energy per pulse (from 20 to 60 times ED50) were required for formation of subretinal hemorrhages. Second, in the Rhesus monkey, we found significant numbers of small intraretinal hemorrhages from relatively low energy 90 fs pulses. Both the Dutch Belted rabbit and the Rhesus monkey failed to consistently show subretinal hemorrhagic lesions form very high pulse energies. Our findings suggest more energy absorption at the level of the retinal circulation than the choroidal circulation with our pulse parameters. The effects of the laser on the retinal circulation may be due to the use of a wavelength of 580 nm. At this wavelength the oxyhemoglobin to melanin absorption ratio is nearly at its peak (approximately 0.40), perhaps allowing improved absorption in the retinal vasculature. One precaution with this finding, however, are the distinct differences between primate and non-primate ocular systems. Further studies are required to resolve the differences in damage at the level of the RPE and choroid between rabbits and primates.

  1. Diode-pumped solid state laser. (Part V). ; Short pulse laser oscillation. Handotai laser reiki kotai laser. 5. ; Tan pulse hasshin

    Energy Technology Data Exchange (ETDEWEB)

    Kuwabara, M.; Bando, N. (Asahi Glass Co. Ltd., Tokyo (Japan))

    1991-12-25

    A semiconductor laser (LD) excited solid state laser using an LD as an excited light source is under discussion for its practical applications to measurements, processing, communications, office automation, and medical areas. This paper describes the discussions given on the short pulse transmission using AOQ switching elements in the LD excited solid state laser with a long wave length band (1.3{mu}m), which is expected of its application in the communications and measurements area. Based on a possibility of raising a measurements resolution by making the pluses in the LD excited solid state laser, and experiments were performed using Nd:YLF as a laser host. as a results, it was found that the smaller the effective mode volume V {sub eff},the smaller the pulse width, and that the ratio of number of initial inversion distribution (N{sub i}/N{sub t}), an important parameter to determine pulse widths, can be obtained from the ratio of the LD exciting light to the input power (P{sub in}/P{sub t}). 7 refs., 14 figs., 2 tabs.

  2. Experimental study on double-pulse laser ablation of steel upon multiple parallel-polarized ultrashort-pulse irradiations

    Science.gov (United States)

    Schille, Joerg; Schneider, Lutz; Kraft, Sebastian; Hartwig, Lars; Loeschner, Udo

    2016-07-01

    In this paper, double-pulse laser processing is experimentally studied with the aim to explore the influence of ultrashort pulses with very short time intervals on ablation efficiency and quality. For this, sequences of 50 double pulses of varied energy and inter-pulse delay, as adjusted between 400 fs and 18 ns by splitting the laser beam into two optical paths of different length, were irradiated to technical-grade stainless steel. The depth and the volume of the craters produced were measured in order to evaluate the efficiency of the ablation process; the crater quality was analyzed by SEM micrographs. The results obtained were compared with craters produced with sequences of 50 single pulses and energies equal to the double pulse. It is demonstrated that double-pulse processing cannot exceed the ablation efficiency of single pulses of optimal fluence, but the ablation crater surface formed smoother if inter-pulse delay was in the range between 10 ns and 18 ns. In addition, the influence of pulse duration and energy distribution between the individual pulses of the double pulse on ablation was studied. For very short inter-pulse delay, no significant effect of energy variation within the double pulse on removal rate was found, indicating that the double pulse acts as a big single pulse of equal energy. Further, the higher removal efficiency was achieved when double-pulse processing using femtosecond pulses instead of picosecond pulses.

  3. Thomson scattering in high-intensity chirped laser pulses

    International Nuclear Information System (INIS)

    We consider the Thomson scattering of an electron in an ultra-intense laser pulse. It is well known that at high laser intensities, the frequency and brilliance of the emitted radiation will be greatly reduced due to the electron losing energy before it reaches the peak field. In this work, we investigate the use of a small frequency chirp in the laser pulse in order to mitigate this effect of radiation reaction. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion of its original energy. This results in a significant enhancement of the frequency and intensity of the emitted radiation as compared to the case without chirping

  4. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    Science.gov (United States)

    Brendel', V. M.; Bukin, V. V.; Garnov, Sergei V.; Bagdasarov, V. Kh; Denisov, N. N.; Garanin, Sergey G.; Terekhin, V. A.; Trutnev, Yurii A.

    2012-12-01

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation.

  5. Pulsed laser excitation of phosphate stabilised silver nanoparticles

    Indian Academy of Sciences (India)

    Jyotirmayee Mohanty; Dipak K Palit; Laxminarayan V Shastri; Avinash V Sapre

    2000-02-01

    Laser flash photolysis studies were carried out on two types of silver nanoparticles prepared by -radiolysis of Ag+ solutions in the presence of polyphosphate as the stabiliser. Type I silver nanoparticles displayed a surface plasmon band at 390 nm. Type II silver nanoparticles showed a 390 nm surface plasmon band with a shoulder at 550 nm. On photoexcitation in the surface plasmon band region, using 35 picosecond laser pulses at 355 nm and 532 nm, the type II solutions showed transient bleaching and absorption signals in the 450-900 nm region, which did not decay appreciably up to 5 nanoseconds. These transient changes were found to get annealed in the interval where 5 ns < < 100 ns. Extended photolysis of the nanoparticle solutions with repetitive laser pulses resulted in a decrease in the values of the average particle size which were measured by employing the dynamic light scattering technique.

  6. PULSE: The Palomar Ultraviolet Laser for the Study of Exoplanets

    CERN Document Server

    Baranec, Christoph; Burruss, Rick S; Bowler, Brendan P; van Dam, Marcos; Riddle, Reed; Shelton, J Christopher; Truong, Tuan; Roberts, Jennifer; Milburn, Jennifer; Tesch, Jonathan

    2014-01-01

    The Palomar Ultraviolet Laser for the Study of Exoplanets (PULSE) will dramatically expand the science reach of PALM-3000, the facility high-contrast extreme adaptive optics system on the 5-meter Hale Telescope. By using an ultraviolet laser to measure the dominant high spatial and temporal order turbulence near the telescope aperture, one can increase the limiting natural guide star magnitude for exquisite correction from mV < 10 to mV < 16. Providing the highest near-infrared Strehl ratios from any large telescope laser adaptive optics system, PULSE uniquely enables spectroscopy of low-mass and more distant young exoplanet systems, essential to formulating a complete picture of exoplanet populations.

  7. Pulsed laser deposition of anatase thin films on textile substrates

    Science.gov (United States)

    Krämer, André; Kunz, Clemens; Gräf, Stephan; Müller, Frank A.

    2015-10-01

    Pulsed laser deposition (PLD) is a highly versatile tool to prepare functional thin film coatings. In our study we utilised a Q-switched CO2 laser with a pulse duration τ ≈ 300 ns, a laser wavelength λ = 10.59 μm, a repetition frequency frep = 800 Hz and a peak power Ppeak = 15 kW to deposit crystalline anatase thin films on carbon fibre fabrics. For this purpose, preparatory experiments were performed on silicon substrates to optimise the anatase deposition conditions including the influence of different substrate temperatures and oxygen partial pressures. Processing parameters were then transferred to deposit anatase on carbon fibres. Scanning electron microscopy, X-ray diffraction analyses, Raman spectroscopy and tactile profilometry were used to characterise the samples and to reveal the formation of phase pure anatase without the occurrence of a secondary rutile phase. Methanol conversion test were used to prove the photocatalytic activity of the coated carbon fibres.

  8. Trigonometric pulse envelopes for laser-induced quantum dynamics

    International Nuclear Information System (INIS)

    We relate powers of trigonometric functions to Gaussians by proving that properly truncated cosn functions converge to a Gaussian as n tends to infinity. For an application, we analyse the laser-induced population transfer |X1Σ+) → |A1Πx) in a two-level model system of aluminium monochloride (AlCl) with fixed nuclei. We apply linearly x-polarized ultraviolet laser pulses with a trigonometric envelope function, whose square has full width at half-maximum of 2.5 fs and 5.0 fs. Studying population dynamics and optimized laser parameters, we find that the optimal field amplitude for trigonometric pulses with n = 20 and n = 1000 has a relative difference of 1%, which is below experimental resolution.

  9. Laboratory Transferability of Optimally Shaped Laser Pulses for Quantum Control

    CERN Document Server

    Tibbetts, Katharine Moore; Rabitz, Herschel

    2013-01-01

    Optimal control experiments can readily identify effective shaped laser pulses, or "photonic reagents", that achieve a wide variety of objectives. For many practical applications, an important criterion is that a particular photonic reagent prescription still produce a good, if not optimal, target objective yield when transferred to a different system or laboratory, {even if the same shaped pulse profile cannot be reproduced exactly. As a specific example, we assess the potential for transferring optimal photonic reagents for the objective of optimizing a ratio of photoproduct ions from a family of halomethanes through three related experiments.} First, applying the same set of photonic reagents with systematically varying second- and third-order chirp on both laser systems generated similar shapes of the associated control landscape (i.e., relation between the objective yield and the variables describing the photonic reagents). Second, optimal photonic reagents obtained from the first laser system were found...

  10. Interaction of Repetitively Pulsed High Energy Laser Radiation With Matter

    Science.gov (United States)

    Hugenschmidt, Manfred

    1986-10-01

    The paper is concerned with laser target interaction processes involving new methods of improving the overall energy balance. As expected theoretically, this can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed by using a pulsed CO2 laser at mean powers up to 2 kW and repetition rates up to 100 Hz. The rates of temperature rise of aluminium for example were thereby increased by lore than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements were found for the overall absorptivities that were increased by this method by more than an order of magnitude.

  11. Laser ablation of CFRP using picosecond laser pulses at different wavelengths from UV to IR

    Science.gov (United States)

    Wolynski, Alexander; Herrmann, Thomas; Mucha, Patrick; Haloui, Hatim; L'huillier, Johannes

    Laser processing of carbon fibre reinforced plastics (CFRP) has a great industrial relevance for high performance structural parts in airplanes, machine tools and cars. Through-holes drilled by nanosecond laser pulses show thermal induced molten layers and voids. Recently, picosecond lasers have demonstrated the ability to drill high-efficient and high-quality rivet through-holes. In this paper a high-power picosecond laser system operating at different wavelengths (355 nm, 532 nm and 1064 nm) has been used for CFRP ablation experiments to study the influence of different laser parameters in terms of machining quality and processing time.

  12. Ultra-fast electron diffraction using electrons accelerated by intense femtosecond laser pulses

    International Nuclear Information System (INIS)

    We have demonstrated to use electron pulses accelerated by intense femtosecond laser pulses and self-compressed for ultrafast electron diffraction (UED). The electron pulses are generated by irradiating tightly focused terawatt femtosecond laser pulses on a polyethylene foil target, then, the pulses are compressed by using an achromatic bending magnet system. These femtosecond electron pulses have an intensity to demonstrate a single-shot diffraction pattern. (author)

  13. Single Ultrashort Attosecond Pulse Generation via Combination of Chirped Fundamental Laser and an Ultraviolet Controlling Pulse

    International Nuclear Information System (INIS)

    We theoretically study the high-order harmonic generation (HHG) from a hydrogen atom in an intense few-cycle chirped fundamental laser in combination with an ultraviolet (uv) controlling pulse. The high-order harmonic spectrum is calculated by solving the time-dependent Schroedinger equation using the split-operator method. In our calculation, we present the difference of the high-order harmonic spectrum from one-dimensional (1D) model hydrogen atom and three-dimensional (3D) real hydrogen atom. We found that the plateau of the high-order harmonic generation from the 1D case and 3D case are all extended effectively to Ip + 35Up due to the presence of the chirped laser pulse and the HHG supercontinuum spectrum is generated by adding an ultraviolet controlling pulse at a proper time, but the efficiency of the HHG for 3D case is more higher at the near cut-off region than the 1D case. Therefore, the generation of the attosecond pulse by synthesizing the harmonics near cut-off region have some slight differences between 1D and 3D simulations. As a real 3D case study, we show that an isolated 18 as pulse with a bandwidth of 232.5 eV is generated directly by optmizing the combination laser fields. (atomic and molecular physics)

  14. Manufacturing of Er:ZBLAN ridge waveguides by pulsed laser deposition and ultrafast laser micromachining for green integrated lasers

    Energy Technology Data Exchange (ETDEWEB)

    Gottmann, Jens [Lehrstuhl fuer Lasertechnik, RWTH Aachen University, Steinbachstr. 15, 52074 Aachen (Germany)], E-mail: jens.gottmann@llt.rwth-aachen.de; Moiseev, Leonid; Vasilief, Ion; Wortmann, Dirk [Lehrstuhl fuer Lasertechnik, RWTH Aachen University, Steinbachstr. 15, 52074 Aachen (Germany)

    2008-01-15

    Laser radiation is used both for the deposition of the laser active thin films and for the microstructuring to define wave guiding structures for the fabrication of waveguide lasers. Thin films of Er:ZBLAN (a fluoride glass consisting of ZrF{sub 4}, BaF{sub 2}, LaF{sub 3}, AlF{sub 3}, NaF, ErF{sub 3}) for green up-conversion lasers (545 nm) are produced by pulsed laser deposition using ArF excimer laser radiation (wavelength 193 nm). Manufacturing of the laser active waveguides by microstructuring is done using fs-laser ablation of the deposited films. The structural and optical properties of the films and the damping losses of the structured waveguides are determined in view of the design and the fabrication of compact and efficient diode pumped waveguide lasers. The resulting waveguides are polished, provided with resonator mirrors, pumped using diode lasers and characterized.

  15. Frequency conversion of high-intensity, femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Banks, P S

    1997-06-01

    Almost since the invention of the laser, frequency conversion of optical pulses via non- linear processes has been an area of active interest. However, third harmonic generation using ~(~1 (THG) in solids is an area that has not received much attention because of ma- terial damage limits. Recently, the short, high-intensity pulses possible with chirped-pulse amplification (CPA) laser systems allow the use of intensities on the order of 1 TW/cm2 in thin solids without damage. As a light source to examine single-crystal THG in solids and other high field inter- actions, the design and construction of a Ti:sapphire-based CPA laser system capable of ultimately producing peak powers of 100 TW is presented. Of special interest is a novel, all-reflective pulse stretcher design which can stretch a pulse temporally by a factor of 20,000. The stretcher design can also compensate for the added material dispersion due to propagation through the amplifier chain and produce transform-limited 45 fs pulses upon compression. A series of laser-pumped amplifiers brings the peak power up to the terawatt level at 10 Hz, and the design calls for additional amplifiers to bring the power level to the 100 TW level for single shot operation. The theory for frequency conversion of these short pulses is presented, focusing on conversion to the third harmonic in single crystals of BBO, KD*P, and d-LAP (deuterated I-arginine phosphate). Conversion efficiencies of up to 6% are obtained with 500 fs pulses at 1053 nm in a 3 mm thick BBO crystal at 200 GW/cm 2. Contributions to this process by unphasematched, cascaded second harmonic generation and sum frequency generation are shown to be very significant. The angular relationship between the two orders is used to measure the tensor elements of C = xt3)/4 with Crs = -1.8 x 1O-23 m2/V2 and .15Cri + .54Crs = 4.0 x 1O-23 m2/V2. Conversion efficiency in d-LAP is about 20% that in BBO and conversion efficiency in KD*P is 1% that of BBO. It is calculated

  16. Pulse shaping mechanism in mode-locked lasers

    Science.gov (United States)

    Horikis, Theodoros P.; Bakırtaş, İlkay; Antar, Nalan

    2016-06-01

    A pulse shaping mechanism applied to mode-locked lasers is proposed. By adding a linear (forcing) term in the power energy saturation model, we are able to control the resulting pulses in both energy and shape. In fact, this term also provides a focusing effect keeping most of the pulse’s energy confined within the width of the forcing. The appropriate condition for which mode-locking occurs is also derived and links the physical parameters of the system (gain, loss, filtering) to those of the pulse (amplitude, width, energy). Thus, given the desired pulse one only needs to fix the laser’s parameters accordingly, so as to obey this condition, and mode-locking will occur.

  17. Ab initio design of laser pulse for controlling photochemical reactions

    International Nuclear Information System (INIS)

    With high level ab initio description of molecule-field interaction, we have developed an optimal control algorithm for manipulating molecular transformation and quantum populations. High order molecule-field interactions are fully taken into account through the use of electric-nuclear Born-Oppenheimer (ENBO) approximation. The present algorithm is demonstrated on the control of molecular post-pulse (transient)alignment and orientation. High degrees of alignment and orientation are achieved in a vibrationally selective manner by optimized infrared laser pulses of duration on the order one rotational period of molecule. To reveal the control mechanism behind the complicated optimal pulses, an analytical pulse design method is developed within the ENBO approximation, which is based on a two-state treatment of the dynamics in a Floquet picture. This analytical method is also illustrated on the control of the alignment of homonuclear diatomics. (author)

  18. Hard-tissue drilling by short-pulse CO2 laser with controllable pulse-tail energy

    Science.gov (United States)

    Uno, Kazuyuki; Sasaki, Tatsufumi; Yamamoto, Takuya; Akitsu, Tetsuya; Jitsuno, Takahisa

    2016-02-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse with the almost same spike-pulse energy of about 0.8 mJ and the controllable pulse-tail energy of 0-21.26 mJ. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance and a spark-gap switch. In single-shot irradiation using these laser pulses, the dependence of the drilling depth of dry ivory samples on the fluence was investigated. The drilling depth increased with the fluence in the same laser pulse waveform. In this work, the effective short laser pulse for the hard tissue drilling was the laser pulse with the spike pulse energy of 0.87 mJ and the pulse tail energy of 6.33 mJ that produced the drilling depth of 28.1 μm at the fluence of 3.48 J/cm2 and the drilling depth per the fluence of 7.27 μm/J/cm2.

  19. Fraunhofer-type absorption line splitting and polarization in confocal double-pulse laser induced plasma

    International Nuclear Information System (INIS)

    Strong line splitting and polarization are observed in Fraunhofer-type absorption lines in Pb, Sn, Si, Cd, In, and Zn in confocal double-pulse laser induced plasma (DP-LIP) experiments. This effect is detectable using medium laser power densities: (∼ 1–2) × 1013 W/m2 for the first laser pulse and 1 × 1014 W/m2 for the second laser pulse. Polarization and splitting effects exist only during the second laser pulse (∼ 7 ns). Absorption line polarization and splitting phenomena may be explained by a high overall magnetic field and motional Stark effect caused by the second laser pulse inside the laser plasma created by the first pulse. - Highlights: • Certain Fraunhofer absorption lines in DP LIBS are polarized. • Certain Fraunhofer absorption lines in DP LIBS are split. • Those effects exist during laser pulse. • Effects take place in elements with ns2np2 and ns2 electron ground state

  20. Powerful laser pulse absorption in partly homogenized foam plasma

    Science.gov (United States)

    Cipriani, M.; Gus'kov, S. Yu.; De Angelis, R.; Andreoli, P.; Consoli, F.; Cristofari, G.; Di Giorgio, G.; Ingenito, F.; Rupasov, A. A.

    2016-03-01

    The internal volume structure of a porous medium of light elements determines unique features of the absorption mechanism of laser radiation; the characteristics of relaxation and transport processes in the produced plasma are affected as well. Porous materials with an average density larger than the critical density have a central role in enhancing the pressure produced during the ablation by the laser pulse; this pressure can exceed the one produced by target direct irradiation. The problem of the absorption of powerful laser radiation in a porous material is examined both analytically and numerically. The behavior of the medium during the process of pore filling in the heated region is described by a model of viscous homogenization. An expression describing the time and space dependence of the absorption coefficient of laser radiation is therefore obtained from the model. A numerical investigation of the absorption of a nanosecond laser pulse is performed within the present model. In the context of numerical calculations, porous media with an average density larger than the critical density of the laser-produced plasma are considered. Preliminary results about the inclusion of the developed absorption model into an hydrodynamic code are presented.

  1. Powerful laser pulse absorption in partly homogenized foam plasma

    International Nuclear Information System (INIS)

    The internal volume structure of a porous medium of light elements determines unique features of the absorption mechanism of laser radiation; the characteristics of relaxation and transport processes in the produced plasma are affected as well. Porous materials with an average density larger than the critical density have a central role in enhancing the pressure produced during the ablation by the laser pulse; this pressure can exceed the one produced by target direct irradiation. The problem of the absorption of powerful laser radiation in a porous material is examined both analytically and numerically. The behavior of the medium during the process of pore filling in the heated region is described by a model of viscous homogenization. An expression describing the time and space dependence of the absorption coefficient of laser radiation is therefore obtained from the model. A numerical investigation of the absorption of a nanosecond laser pulse is performed within the present model. In the context of numerical calculations, porous media with an average density larger than the critical density of the laser-produced plasma are considered. Preliminary results about the inclusion of the developed absorption model into an hydrodynamic code are presented

  2. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2011-08-01

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe2+ molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0×1014 W/cm2, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schrödinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe2+, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  3. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    International Nuclear Information System (INIS)

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe2+ molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0x1014 W/cm2, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schroedinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe2+, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  4. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Kai-Jun; Bandrauk, Andre D. [Laboratoire de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

    2011-08-15

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe{sup 2+} molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0x10{sup 14} W/cm{sup 2}, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schroedinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe{sup 2+}, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  5. Isolated attosecond pulse generation from atom radiated by a three-color laser pulse

    International Nuclear Information System (INIS)

    We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom in a three-color laser field, which is synthesized by 10 fs/800 nm Ti-sapphire laser and a two-color field consisting of 30 fs/532 nm and 30 fs/1330 nm pulses. Compared with harmonic spectrum generated by a monochromatic field, the harmonics generated from the synthesized three-color field show a supercontinuum spectrum with a bandwidth of 235 eV, ranging from the 154th to the 306th order harmonic. This phenomenon can be attributed to the fact that the ionization of atoms as well as motion of ionized electron can be effectively controlled in the three-color field. Therefore, an isolated 46-as pulse can be generated by superposing supercontinuum from the 160th to the 210th order harmonics. (atomic and molecular physics)

  6. Pulsed photothermal depth profiling of tattoos undergoing laser removal treatment

    Science.gov (United States)

    Milanic, Matija; Majaron, Boris

    2012-02-01

    Pulsed photothermal radiometry (PPTR) allows noninvasive determination of temperature depth profiles induced by pulsed laser irradiation of strongly scattering biological tissues and organs, including human skin. In present study, we evaluate the potential of this technique for investigational characterization and possibly quantitative evaluation of laser tattoo removal. The study involved 5 healthy volunteers (3 males, 2 females), age 20-30 years, undergoing tattoo removal treatment using a Q-switched Nd:YAG laser. There were four measurement and treatment sessions in total, separated by 2-3 months. Prior to each treatment, PPTR measurements were performed on several tattoo sites and one nearby healthy site in each patient, using a 5 ms Nd:YAG laser at low radiant exposure values and a dedicated radiometric setup. The laser-induced temperature profiles were then reconstructed by applying a custom numerical code. In addition, each tatoo site was documented with a digital camera and measured with a custom colorimetric system (in tristimulus color space), providing an objective evaluation of the therapeutic efficacy to be correlated with our PPTR results. The results show that the laser-induced temperature profile in untreated tattoos is invariably located at a subsurface depth of 300 μm. In tattoo sites that responded well to laser therapy, a significant drop of the temperature peak was observed in the profiles obtained from PPTR record. In several sites that appeared less responsive, as evidenced by colorimetric data, a progressive shift of the temperature profile deeper into the dermis was observed over the course of consecutive laser treatments, indicating that the laser tattoo removal was efficient.

  7. Protection of final optics in megajoule-class lasers by steering of UV beams using diffraction gratings

    International Nuclear Information System (INIS)

    In order to protect most the final optics hardware of megajoule-class lasers from the radiations produced by ignition shots, it is desirable to steer the laser beams after frequency conversion. Using a transmission grating etched in fused silica is an attractive solution for 3ω beam steering. The conceptual design of a focusing system based on this device is reviewed. The issues of pulse temporal shear and beam transport are addressed. The compatibility of 3ω gratings with other beam steering devices is assessed in view of possible evolution of the focusing system during the lifetime of the laser facility

  8. Interferometric characterization of pulse front tilt of spatiotemporally focused femtosecond laser pulses for three-dimensional micromachining application

    CERN Document Server

    Wang, Zhaohui; Ni, Jielei; Jing, Chenrui; Xie, Hongqiang; Zeng, Bin; Chu, Wei; Qiao, Lingling; Cheng, Ya

    2014-01-01

    We report on an experimental measurement of the pulse front tilt (PFT) of spatiotemporally focused femtosecond laser pulses in the focal plane in both air and bulk transparent materials, which is achieved by examination of the interference pattern between the spatiotemporally focused pulse and a conventional focused reference pulse as a function of time delay between the two pulses. Our simulation results agree well with the experimental observations.

  9. Multiple quasi-monoenergetic electron beams from laser-wakefield acceleration with spatially structured laser pulse

    International Nuclear Information System (INIS)

    By adjusting the focus geometry of a spatially structured laser pulse, single, double, and treble quasi-monoenergetic electron beams were generated, respectively, in laser-wakefield acceleration. Single electron beam was produced as focusing the laser pulse to a single spot. While focusing the laser pulse to two spots that are approximately equal in energy and size and intense enough to form their own filaments, two electron beams were produced. Moreover, with a proper distance between those two focal spots, three electron beams emerged with a certain probability owing to the superposition of the diffractions of those two spots. The energy spectra of the multiple electron beams are quasi-monoenergetic, which are different from that of the large energy spread beams produced due to the longitudinal multiple-injection in the single bubble

  10. Multiple quasi-monoenergetic electron beams from laser-wakefield acceleration with spatially structured laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y.; Li, M. H.; Li, Y. F.; Wang, J. G.; Tao, M. Z.; Han, Y. J.; Zhao, J. R.; Huang, K.; Yan, W. C.; Ma, J. L.; Li, Y. T. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080 (China); Chen, L. M., E-mail: lmchen@iphy.ac.cn [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080 (China); Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Li, D. Z. [Institute of High Energy Physics, CAS, Beijing 100049 (China); Chen, Z. Y. [Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621999 (China); Sheng, Z. M. [Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Zhang, J. [Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-08-15

    By adjusting the focus geometry of a spatially structured laser pulse, single, double, and treble quasi-monoenergetic electron beams were generated, respectively, in laser-wakefield acceleration. Single electron beam was produced as focusing the laser pulse to a single spot. While focusing the laser pulse to two spots that are approximately equal in energy and size and intense enough to form their own filaments, two electron beams were produced. Moreover, with a proper distance between those two focal spots, three electron beams emerged with a certain probability owing to the superposition of the diffractions of those two spots. The energy spectra of the multiple electron beams are quasi-monoenergetic, which are different from that of the large energy spread beams produced due to the longitudinal multiple-injection in the single bubble.

  11. Pulsed laser planarization of metal films for multilevel interconnects

    International Nuclear Information System (INIS)

    Multilevel interconnect schemes for integrated circuits generally require one or more planarization steps, in order to maintain an acceptably flat topography for lithography and thin-film step coverage on the higher levels. Traditional approaches have involved planarization of the interlevel insulation (dielectric) layers, either by spin-on application (e.g., polyimide), or by reflow (e.g., phosphosilicate glass). We have pursued an alternative approach, in which each metal level is melted (hence planarized) using a pulsed laser prior to patterning. Short (approx.1 μs) pulses are used to preclude undesirable metallurgical reactions between the film, adhesion or barrier layer, and dielectric layer. Laser planarization of metals is particularly well suited to multilevel systems which include ground or power planes. Results are presented for planarization of gold films on SiO2 dielectric layers using a flashlamp-pumped dye laser. The pulse duration is approx.1 μs, which allows the heat pulse to uniformly penetrate the gold while not penetrating substantially through the underlying SiO2 (hence not perturbing the lower levels of metal). Excellent planarization of the gold films is achieved (less than 0.1 μm surface roughness, even starting with extreme topographic variations), as well as improved conductivity. To demonstrate the process, numerous planarized two-layer structures (transmission lines under a ground plane) were fabricated and characterized. 9 refs., 2 figs

  12. Calculations of population transfer during intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Schafer, K.J.; Kulander, K.C.

    1993-08-01

    Recent experiments by several groups have examined the question of population transfer to resonantly excited states during intense short laser pulses, in particular the amount of population that remains ``trapped`` in excited states at the end of a laser pulse. In this chapter we present calculations of population transfer and resonant ionization in xenon at both 660 and 620 nm. At the longer wavelength, the seven photon channel closes at 2.5{times}10{sup 13} W/cm{sup 2}. Pulses with peak intensities higher than this result in ``Rydberg trapping``, the resonant transfer of population to a broad range of high-lying states. The amount of population transferred depends on both the peak intensity and pulse duration. At 620 mm there are numerous possible six photon resonances to states with p or f angular momentum. We have done a large number of calculations for 40 fs pulses at different peak intensities and have examined the population transferred to these low-lying resonant states as a function of the peak laser intensity. We do not have room to comment upon the resonantly enhanced ionized electron energy spectra that we also determine in the same calculations. Our calculations involve the direct numerical integration of the time-dependent Schroedinger equation for an atom interacting with a strong laser field. The time-dependent wave function of a given valence electron is calculated on a spatial grid using a one-electron pseudo potential. This single active electron approximation (SAE) has been shown to be a good approximation for the rare gases at the intensities and wavelengths that we will consider. The SAE potential we use has an explicit angular momentum dependence which allows us to reproduce all of the excited state energies for xenon quite well.

  13. Pulsed power for angular multiplexed laser fusion drivers

    International Nuclear Information System (INIS)

    The feasibility of using rare gas-halide lasers, in particular the KrF laser, as inertial confinement fusion (ICF) drivers has been assessed. These lasers are scalable to the required high energy (approx. =1-5 MJ) in a short pulse (approx. =10 ns) by optical angular multiplexing, and integration of the output from approx. =100 kJ laser amplifier subsystems. The e-beam current density (approx. =50A/cm2) and voltage (approx. =800 kV) required for these power amplifiers lead to an e-beam impedance of approx. =0.2Ω for approx. =300 ns pump time. This impedance level requires modularization of the large area e-gun, a) to achieve a diode inductance consistent with fast current risetime, b) to circumvent dielectric breakdown constraints in the pulse forming lines, and c) to reduce the requirement for guide magnetic fields. Pulsed power systems requirements, design concepts, scalability, tradeoffs, and performance projections are discussed in this paper

  14. Computational Design of Short Pulse Laser Driven Iron Opacity Experiments

    Science.gov (United States)

    Martin, Madison E.; London, Richard A.; Goluoglu, Sedat; Whitley, Heather D.

    2015-11-01

    Opacity is a critical parameter in the transport of radiation in systems such as inertial confinement fusion capsules and stars. The resolution of current disagreements between solar models and helioseismological observations would benefit from experimental validation of theoretical opacity models. Short pulse lasers can be used to heat targets to higher temperatures and densities than long pulse lasers and pulsed power machines, thus potentially enabling access to emission spectra at conditions relevant to solar models. In order to ensure that the relevant plasma conditions are accessible and that an emission measurement is practical, we use computational design of experiments to optimize the target characteristics and laser conditions. Radiation-hydrodynamic modeling, using HYDRA, is used to investigate the effects of modifying laser irradiance, target dimensions, and dopant dilution on the plasma conditions and emission of an iron opacity target. Several optimized designs reaching temperatures and densities relevant to the radiative zone of the sun will be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC.

  15. Pulsed laser ablation and deposition of ZnS:Cr

    International Nuclear Information System (INIS)

    We present a method to deposit films with a range of doping concentrations/dilute alloys, from a single target in pulsed laser deposition (PLD). Cr-doped ZnS films were deposited by ablating a target consisting Cr particles (diameter 20–100 μm) embedded in a ZnS:Cr matrix. The Cr content in the film was varied in the range 2.0–5.0 at.% simply by varying the laser fluence, or by varying the number of pre-ablation pulses. Such a doping/composition range is normally not achieved using a single target in PLD. Details of the target ablation study, which is needed prior to the deposition, are also presented. - Highlights: • ZnS:Cr films (2-5 %) were deposited by pulsed laser deposition using a single target. • Both the laser fluence and target pre-ablation affects the dopant concentration. • The non-stoichiometric transfer was controlled in a reproducible manner

  16. Pulsed laser ablation and deposition of ZnS:Cr

    Energy Technology Data Exchange (ETDEWEB)

    Nematollahi, Mohammadreza, E-mail: nematollahim@gmail.com; Yang, Xiaodong; Gibson, Ursula J.; Reenaas, Turid W.

    2015-09-01

    We present a method to deposit films with a range of doping concentrations/dilute alloys, from a single target in pulsed laser deposition (PLD). Cr-doped ZnS films were deposited by ablating a target consisting Cr particles (diameter 20–100 μm) embedded in a ZnS:Cr matrix. The Cr content in the film was varied in the range 2.0–5.0 at.% simply by varying the laser fluence, or by varying the number of pre-ablation pulses. Such a doping/composition range is normally not achieved using a single target in PLD. Details of the target ablation study, which is needed prior to the deposition, are also presented. - Highlights: • ZnS:Cr films (2-5 %) were deposited by pulsed laser deposition using a single target. • Both the laser fluence and target pre-ablation affects the dopant concentration. • The non-stoichiometric transfer was controlled in a reproducible manner.

  17. Modification of Cu surface with picosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Vincenc Oboňa, J. [Materials innovation institute M2i, Department of Applied Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Materials innovation institute M2i, Faculty of Engineering Technology, Chair of Applied Laser Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Ocelík, V., E-mail: v.ocelik@rug.nl [Materials innovation institute M2i, Department of Applied Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Rao, J.C. [Materials innovation institute M2i, Department of Applied Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Skolski, J.Z.P.; Römer, G.R.B.E. [Faculty of Engineering Technology, Chair of Applied Laser Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Huis in ‘t Veld, A.J. [Faculty of Engineering Technology, Chair of Applied Laser Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); TNO Technical Sciences, Mechatronics, Mechanics and Materials, De Rondom 1, 5600 HE, Eindhoven (Netherlands); Hosson, J. Th. M. De [Materials innovation institute M2i, Department of Applied Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands)

    2014-06-01

    High purity, mirror-polished polycrystalline Cu surface was treated with single picosecond laser pulses at fluence levels close to the single-pulse modification threshold. The induced surface topography and sub-surface changes were examined with scanning and transmission electron microscopy, respectively. The analysis showed an increased absorption of laser energy on the microscopic surface topography inhomogeneities, even at a fluence level below the modification threshold. Many features, like spikes, bubbles, spheres, as well as small periodic ripples at the bottom of scratches, reveal a significant influence of melting and eruptive relaxation of the absorbed laser energy on the final appearance of the surface. Further, it was found that thermal stresses result in twinning to a depth of few tens of nanometers under the surface. Voids at this depth have been observed as well. The results of the observations provide new insights into the early stages of the picosecond laser pulse modification of metals, especially metals with a weak electron–phonon coupling.

  18. Improved pulse contrast on the Texas Petawatt Laser

    Science.gov (United States)

    Gaul, E.; Toncian, T.; Martinez, M.; Gordon, J.; Spinks, M.; Dyer, G.; Truong, N.; Wagner, C.; Tiwari, G.; Donovan, M. E.; Ditmire, T.; Hegelich, B. M.

    2016-05-01

    We have completed a pulse contrast upgrade on the Texas Petawatt Laser. This improvement enables the use of thin and reduced mass targets for ion acceleration, and reduces pre-plasma effects on all experiments. The new design starts with two BBO-based OPCPA stages pumped by an optically synchronized 8-ps laser. These stages amplify slightly chirped few ps pulses by six orders of magnitude. Next there are two LBO-based OPCPA stages that are pumped by 4 ns pulses. With much less gain than before, parametric fluorescence has been reduced by about three orders of magnitude. Prior to the upgrade, lenses caused pencil beam prepulses. Since tilting or wedging lenses was not a viable option, we replaced all lenses in the glass amplifiers with off-axis parabolic mirrors. There are still weak prepulses that we attribute to surface scattering. We eliminated thin transmissive optics to avoid post pulses that would result in prepulses by nonlinear (B-integral) conversion. This required us to reduce from eight to four passes in the 64-mm glass amplifier and to add a two-pass 25-mm “booster amplifier.” As a final upgrade we added an Acousto-Optic Programmable Dispersive-Filter (AOPDF) to improve higher order dispersion and steepen the rising edge of the compressed pulse.

  19. Microencapsulation of silicon cavities using a pulsed excimer laser

    International Nuclear Information System (INIS)

    This work presents a novel low thermal-budget technique for sealing micromachined cavities in silicon. Cavities are sealed without deposition, similar to the silicon surface-migration sealing process. In contrast to the 1100 °C furnace anneal required for the migration process, the proposed technique uses short excimer laser pulses (24 ns), focused onto an area of 23 mm2, to locally heat the top few microns of the substrate, while the bulk substrate remains near ambient temperature. The treatment can be applied to selected regions of the substrate, without the need for special surface treatments or a controlled environment. This work investigates the effect of varying the laser pulse energy from 400 mJ cm−2 to 800 mJ cm−2, the pulse rate from 1 Hz to 50 Hz and the pulse count from 200 to 3000 pulses on sealing microfabricated cavities in silicon. An analytical model for the effect of holes on the surface temperature distribution is derived, which shows that much higher temperatures can be achieved by increasing the hole density. A mechanism for sealing the cavities is proposed, which indicates how complete sealing is feasible. (paper)

  20. Microencapsulation of silicon cavities using a pulsed excimer laser

    KAUST Repository

    Sedky, Sherif M.

    2012-06-07

    This work presents a novel low thermal-budget technique for sealing micromachined cavities in silicon. Cavities are sealed without deposition, similar to the silicon surface-migration sealing process. In contrast to the 1100°C furnace anneal required for the migration process, the proposed technique uses short excimer laser pulses (24ns), focused onto an area of 23mm 2, to locally heat the top few microns of the substrate, while the bulk substrate remains near ambient temperature. The treatment can be applied to selected regions of the substrate, without the need for special surface treatments or a controlled environment. This work investigates the effect of varying the laser pulse energy from 400 mJ cm 2to 800 mJ cm 2, the pulse rate from 1Hz to 50Hz and the pulse count from 200 to 3000 pulses on sealing microfabricated cavities in silicon. An analytical model for the effect of holes on the surface temperature distribution is derived, which shows that much higher temperatures can be achieved by increasing the hole density. A mechanism for sealing the cavities is proposed, which indicates how complete sealing is feasible. © 2012 IOP Publishing Ltd.

  1. Advances in laser technology for isolated attosecond pulse generation

    International Nuclear Information System (INIS)

    In this review we report on recent advances in laser technology, which have contributed to the fast development of attosecond science. In particular we will concentrate on two experimental methods for the generation of high-peak-power, few-optical-cycle laser pulses with controlled electric field, which are crucial for the generation of isolated attosecond pulses. The first method is the hollow-fiber compression technique, introduced in 1996 and now routinely used in several laboratories. So far, isolated attosecond pulses have been generated by using few-cycle pulses produced by such compression technique, in combination with active stabilization of the carrier-envelope phase. More recently, few-cycle pulses tunable in the infrared region have been generated by optical parametric amplification with passive stabilization of the carrier-envelope phase. Such parametric sources represent excellent drivers for the generation of harmonic radiation with an extended cutoff, and offer the possibility to extend attosecond science towards the soft-X rays region. Finally, we will briefly discuss the basic elements of attosecond metrology

  2. Double Ionization of Hydrogen Molecule by Intense Attosecond Laser Pulses

    Science.gov (United States)

    Lee, Teck-Ghee; Pindzola, M. S.; Robicheaux, F.

    2010-03-01

    Time-dependent close-coupling calculations within the fixed nuclei approximation are carried out for the double ionization of H2 induced by an intense attosecond laser pulse at a photon energy of 40 eV. We consider here the two-photon absorption processes and examine the response of the ejected electrons, particularly the single- and the double-electron energy distributions, to linearly and circularly polarized pulse at laser intensities between 10^15 W/cm^2 and 10^16 W/cm^2. We find that, for both the linearly and circularly polarized pulses, sequential peaks and non-sequential wells appear in both the single- and double-electron energy distributions that are generally akin to the analogous two electrons photoemission processes in He atom driven by a linearly polarized intense attosecond pulse [1,2]. Furthermore, a clear signature of the sequential double-electron above threshold ionization process can be seen in the single- and double-electron energy distributions when a linearly polarized pulse is being used.[4pt] [1] I. F. Barna, J. Wang, and J. Burgdorfer, Phys. Rev. A. 73, 023402 (2006) [0pt] [2] T-G Lee, M. S. Pindzola and F. Robicheaux, Phys. Rev. A. 79, 053420 (2009)

  3. Ionization of molecular hydrogen in ultrashort intense laser pulses

    International Nuclear Information System (INIS)

    A novel ab initio numerical approach is developed and applied that solves the time-dependent Schroedinger equation describing two-electron diatomic molecules (e.g. molecular hydrogen) exposed to an intense ultrashort laser pulse. The method is based on the fixed-nuclei and the non-relativistic dipole approximations and aims to accurately describe both correlated electrons in full dimensionality. The method is applicable for a wide range of the laser pulse parameters and is able to describe both few-photon and many-photon single ionization processes, also in a non-perturbative regime. A key advantage of the method is its ability to treat the strong-field response of the molecules with arbitrary orientation of the molecular axis with respect to the linear-polarized laser field. Thus, this work reports on the first successful orientation-dependent analysis of the multiphoton ionization of H2 performed by means of a full-dimensional numerical treatment. Besides the investigation of few-photon regime, an extensive numerical study of the ionization by ultrashort frequency-doubled Ti:sapphire laser pulses (400 nm) is presented. Performing a series of calculations for different internuclear separations, the total ionization yields of H2 and D2 in their ground vibrational states are obtained for both parallel and perpendicular orientations. A series of calculations for 800 nm laser pulses are used to test a popular simple interference model. Besides the discussion of the ab initio numerical method, this work considers different aspects related to the application of the strong-field approximation (SFA) for investigation of a strong-field response of an atomic and molecular system. Thus, a deep analysis of the gauge problem of SFA is performed and the quasistatic limit of the velocity-gauge SFA ionization rates is derived. The applications of the length-gauge SFA are examined and a recently proposed generalized Keldysh theory is criticized. (orig.)

  4. Ionization of molecular hydrogen in ultrashort intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Vanne, Yulian V.

    2010-03-18

    A novel ab initio numerical approach is developed and applied that solves the time-dependent Schroedinger equation describing two-electron diatomic molecules (e.g. molecular hydrogen) exposed to an intense ultrashort laser pulse. The method is based on the fixed-nuclei and the non-relativistic dipole approximations and aims to accurately describe both correlated electrons in full dimensionality. The method is applicable for a wide range of the laser pulse parameters and is able to describe both few-photon and many-photon single ionization processes, also in a non-perturbative regime. A key advantage of the method is its ability to treat the strong-field response of the molecules with arbitrary orientation of the molecular axis with respect to the linear-polarized laser field. Thus, this work reports on the first successful orientation-dependent analysis of the multiphoton ionization of H{sub 2} performed by means of a full-dimensional numerical treatment. Besides the investigation of few-photon regime, an extensive numerical study of the ionization by ultrashort frequency-doubled Ti:sapphire laser pulses (400 nm) is presented. Performing a series of calculations for different internuclear separations, the total ionization yields of H{sub 2} and D{sub 2} in their ground vibrational states are obtained for both parallel and perpendicular orientations. A series of calculations for 800 nm laser pulses are used to test a popular simple interference model. Besides the discussion of the ab initio numerical method, this work considers different aspects related to the application of the strong-field approximation (SFA) for investigation of a strong-field response of an atomic and molecular system. Thus, a deep analysis of the gauge problem of SFA is performed and the quasistatic limit of the velocity-gauge SFA ionization rates is derived. The applications of the length-gauge SFA are examined and a recently proposed generalized Keldysh theory is criticized. (orig.)

  5. A carrier-envelope-phase stabilized terawatt class laser at 1 kHz with a wavelength tunable option

    Science.gov (United States)

    Trallero, C. A.; Langdon, B.; Garlick, J.; Ren, X.; Wilson, D. J.; Summers, A. M.; Zigo, S.; Kling, M. F.; Lei, S.; Elles, C. G.; Poliakoff, E. D.; Carnes, K. D.; Kumarappan, V.; Ben-Itzhak, I.

    2015-05-01

    We demonstrate a chirped-pulse-amplified Ti:Sapphire laser system operating at 1 kHz, with 20 mJ pulse energy, 26 femtosecond pulse duration (0.77 terawatt), and excellent long term carrier-envelope-phase (CEP) stability. A new vibrational damping technique is implemented to significantly reduce vibrational noise on both the laser stretcher and compressor, thus enabling a single-shot CEP noise value of 250 mrad RMS over 1 hour and 300 mrad RMS over 9 hours. This is, to the best of our knowledge, the best long term CEP noise ever reported for any terawatt class laser. This laser is also used to pump a white-light-seeded optical parametric amplifier, producing 6 mJ of total energy in the signal and idler. Due to preservation of the CEP in the white-light generated signal and passive CEP stability in the idler, this laser system promises synthesized laser pulses spanning multi-octaves of bandwidth at an unprecedented energy scale. NSF-MRI grant No:1229672, DOD-DURIP grant No. FA2386-12-1-3014, DOE grant No. DE-FG02-86ER13491, NSF Fellowship DGE-1247193 (DJW), and NDSEG Fellowship (AMS).

  6. Multiterawatt femtosecond laser system with kilohertz pulse repetition rate

    Science.gov (United States)

    Petrov, V. V.; Pestryakov, E. V.; Laptev, A. V.; Petrov, V. A.; Kuptsov, G. V.; Trunov, V. I.; Frolov, S. A.

    2014-05-01

    The basic principles, layout and components are presented for a multiterawatt femtosecond laser system with a kilohertz pulse repetition rate f, based on their parametric amplification and laser amplification of picosecond radiation that pumps the stages of the parametric amplifier. The results of calculations for a step-by-step increase in the output power from the LBO crystal parametric amplifier channel up to the multiterawatt level are presented. By using the developed components in the pump channel of the laser system, the parameters of the regenerative amplifier with the output energy ~1 mJ at the wavelength 1030 nm and with f = 1 kHz are experimentally studied. The optical scheme of the diode-pumped multipass cryogenic Yb:Y2O3 laser ceramic amplifier is developed and its characteristics are determined that provide the output energy within the range 0.25 - 0.35 J.

  7. Simulation of intense short-pulse laser-plasma interaction

    International Nuclear Information System (INIS)

    We have completed the massive parallelization of a 2-dimensional giga-particle code and have achieved a 530-fold acceleration rate with 512 processing elements (PE's). Using this we have implemented a simulation of the interaction of a solid thin film and a high intensity laser and have discovered a phenomenon in which high quality short pulses from the far ultraviolet to soft X-rays are generated at the back surface of the thin layer. We have also introduced the atomic process database code (Hullac) and have the possibility for high precision simulations of X-ray laser radiation. With respect to laser acceleration we have the possibility to quantitatively evaluate relativistic self-focusing assumed to occur in higher intensity fields. Ion acceleration from a solid target and an underdense plasma irradiated by an intense and an ultra intense laser, respectively, has also been studied by particle-in-cell (PIC) simulations. (author)

  8. High power amplification of a tailored-pulse fiber laser

    Science.gov (United States)

    Saby, Julien; Sangla, Damien; Caplette, Stéphane; Boula-Picard, Reynald; Drolet, Mathieu; Reid, Benoit; Salin, François

    2013-02-01

    We demonstrate the amplification of a 1064nm pulse-programmable fiber laser with Large Pitch Rod-Type Fibers of various Mode field diameters from 50 to 70 μm. We have developed a high power fiber amplifier at 1064nm delivering up to 100W/1mJ at 15ns pulses and 30W/300μJ at 2ns with linearly polarized and diffraction limited output beam (M²LBO crystals leading to 50W at 532nm and 25W at 355nm with a diffraction limited output. Similar experiments performed at 1032nm are also reported.

  9. Materials processing with a tightly focused femtosecond laser vortex pulse.

    Science.gov (United States)

    Hnatovsky, Cyril; Shvedov, Vladlen G; Krolikowski, Wieslaw; Rode, Andrei V

    2010-10-15

    In this Letter we present the first (to our knowledge) demonstration of material modification using tightly focused single femtosecond laser vortex pulses. Double-charge femtosecond vortices were synthesized with a polarization-singularity beam converter based on light propagation in a uniaxial anisotropic medium and then focused using moderate- and high-NA optics (viz., NA=0.45 and 0.9) to ablate fused silica and soda-lime glass. By controlling the pulse energy, we consistently machine micrometer-size ring-shaped structures with <100nm uniform groove thickness. PMID:20967085

  10. Nonlinear Theory of Nonparaxial Laser Pulse Propagation in Plasma Channels

    International Nuclear Information System (INIS)

    Nonparaxial propagation of ultrashort, high-power laser pulses in plasma channels is examined. In the adiabatic limit, pulse energy conservation, nonlinear group velocity, damped betatron oscillations, self-steepening, self-phase modulation, and shock formation are analyzed. In the nonadiabatic limit, the coupling of forward Raman scattering (FRS) and the self-modulation instability (SMI) is analyzed and growth rates are derived, including regimes of reduced growth. The SMI is found to dominate FRS in most regimes of interest. (c) 2000 The American Physical Society

  11. Numerical modeling of ultrashort-pulse laser ablation of silicon

    International Nuclear Information System (INIS)

    Silicon ablation by a single ultrashort laser pulse is simulated through a computer model. The agreement between results obtained through the model and experimental data found in the literature supports the hypothesis made by the authors in considering thermal evaporation as the dominant ablation mechanism in silicon. Two distinctive thresholds are defined for the ablation procedure leading to a better interpretation of experimental data. The dependence of ablation fluence thresholds on both wavelength and pulse width is discussed. An approximate analytical model describing the crater formation process is proposed and indicative results are presented.

  12. Control of charge migration in molecules by ultrashort laser pulses

    CERN Document Server

    Golubev, Nikolay V

    2015-01-01

    Due to electronic many-body effects, the ionization of a molecule can trigger ultrafast electron dynamics appearing as a migration of the created hole charge throughout the system. Here we propose a scheme for control of the charge migration dynamics with a single ultrashort laser pulse. We demonstrate by fully ab initio calculations on a molecule containing a chromophore and an amine moieties that simple pulses can be used for stopping the charge-migration oscillations and localizing the charge on the desired site of the system. We argue that this control may be used to predetermine the follow-up nuclear rearrangement and thus the molecular reactivity.

  13. Short Intense Laser Pulse Collapse in Near-Critical Plasma

    OpenAIRE

    Sylla, F; Flacco, A.; Kahaly, S.; Veltcheva, M.; Lifschitz, A.; d'Humières, E; V. Tikhonchuk; Malka, V.

    2013-01-01

    It is observed that the interaction of an intense ultra-short laser pulse with an overdense gas jet results in the pulse collapse and the deposition of a significant part of energy in a small and well localized volume in the rising part of the gas jet, where the electrons are efficiently accelerated and heated. A collisionless plasma expansion over 150 microns at a sub-relativistic velocity (~c/3) has been optically monitored in time and space, and attributed to the quasistatic field ionizati...

  14. Short Intense Laser Pulse Collapse in Near-Critical Plasma

    CERN Document Server

    Sylla, F; Kahaly, S; Veltcheva, M; Lifschitz, A; d'Humières, E; Tikhonchuk, V; Malka, V

    2012-01-01

    It is observed that interaction of an intense ultra-short laser pulse with an overdense gas jet results in the pulse collapse and the deposition of a significant part of energy in a small and well localized volume in the rising part of the gas jet, where the electrons are efficiently accelerated and heated. The subsequent plasma expansion at a sub-relativistic velocity (~c/3) has been optically monitored in time and space, and attributed to the quasistatic field ionization of the gas associated to the hot electron current. Numerical simulations suggest the acceleration of hot electrons along with the excitation of a sizeable magnetic dipole in the collapse region.

  15. Polarization operator approach to pair creation in short laser pulses

    OpenAIRE

    Meuren, S.; Hatsagortsyan, K.; Keitel, C; Di Piazza, A.

    2014-01-01

    Short-pulse effects are investigated for the nonlinear Breit-Wheeler process, i.e. the production of an electron-positron pair induced by a gamma photon inside an intense plane-wave laser pulse. To obtain the total pair-creation probability we verify (to leading-order) the cutting rule for the polarization operator in the realm of strong-field QED by an explicit calculation. Using a double-integral representation for the leading-order contribution to the polarization operator, compact express...

  16. A Novel Femtosecond Laser System for Attosecond Pulse Generation

    OpenAIRE

    Jianqiang Zhu; Xinglong Xie; Meizhi Sun; Qunyu Bi; Jun Kang

    2012-01-01

    We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA). The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the K...

  17. Nanosecond length electron pulses from a laser-excited photocathode

    International Nuclear Information System (INIS)

    A photocathode made from polycrystalline lanthanum hexaboride (LaB6) has produced nanosecond length electron pulses when excited by an excimer laser at 308nm. Peak currents in excess of 1A have been observed, with quantum yields of 4 x 10-5 being measured. A method for extracting the electrons from an emission-limited cathode, plasma extraction, has been demonstrated. This technique uses a low power continuous discharge to provide the electric field needed to extract the photoelectrons. This technique may be useful in producing high repetition rate short pulse ion sources. 10 refs., 4 figs

  18. Laboratory transferability of optimally shaped laser pulses for quantum control

    International Nuclear Information System (INIS)

    Optimal control experiments can readily identify effective shaped laser pulses, or “photonic reagents,” that achieve a wide variety of objectives. An important additional practical desire is for photonic reagent prescriptions to produce good, if not optimal, objective yields when transferred to a different system or laboratory. Building on general experience in chemistry, the hope is that transferred photonic reagent prescriptions may remain functional even though all features of a shaped pulse profile at the sample typically cannot be reproduced exactly. As a specific example, we assess the potential for transferring optimal photonic reagents for the objective of optimizing a ratio of photoproduct ions from a family of halomethanes through three related experiments. First, applying the same set of photonic reagents with systematically varying second- and third-order chirp on both laser systems generated similar shapes of the associated control landscape (i.e., relation between the objective yield and the variables describing the photonic reagents). Second, optimal photonic reagents obtained from the first laser system were found to still produce near optimal yields on the second laser system. Third, transferring a collection of photonic reagents optimized on the first laser system to the second laser system reproduced systematic trends in photoproduct yields upon interaction with the homologous chemical family. These three transfers of photonic reagents are demonstrated to be successful upon paying reasonable attention to overall laser system characteristics. The ability to transfer photonic reagents from one laser system to another is analogous to well-established utilitarian operating procedures with traditional chemical reagents. The practical implications of the present results for experimental quantum control are discussed

  19. Studying the mechanism of micromachining by short pulsed laser

    Science.gov (United States)

    Gadag, Shiva

    The semiconductor materials like Si and the transparent dielectric materials like glass and quartz are extensively used in optoelectronics, microelectronics, and microelectromechanical systems (MEMS) industries. The combination of these materials often go hand in hand for applications in MEMS such as in chips for pressure sensors, charge coupled devices (CCD), and photovoltaic (PV) cells for solar energy generation. The transparent negative terminal of the solar cell is made of glass on one surface of the PV cell. The positive terminal (cathode) on the other surface of the solar cell is made of silicon with a glass negative terminal (anode). The digital watches and cell phones, LEDs, micro-lens, optical components, and laser optics are other examples for the application of silicon and or glass. The Si and quartz are materials extensively used in CCD and LED for digital cameras and CD players respectively. Hence, three materials: (1) a semiconductor silicon and transparent dielectrics,- (2) glass, and (3) quartz are chosen for laser micromachining as they have wide spread applications in microelectronics industry. The Q-switched, nanosecond pulsed lasers are most extensively used for micro-machining. The nanosecond type of short pulsed laser is less expensive for the end users than the second type, pico or femto, ultra-short pulsed lasers. The majority of the research work done on these materials (Si, SiO 2, and glass) is based on the ultra-short pulsed lasers. This is because of the cut quality, pin point precision of the drilled holes, formation of the nanometer size microstructures and fine features, and minimally invasive heat affected zone. However, there are many applications such as large surface area dicing, cutting, surface cleaning of Si wafers by ablation, and drilling of relatively large-sized holes where some associated heat affected zone due to melting can be tolerated. In such applications the nanosecond pulsed laser ablation of materials is very

  20. Gain dynamics of a free-space nitrogen laser pumped by circularly polarized femtosecond laser pulses

    Science.gov (United States)

    Yao, Jinping; Xie, Hongqiang; Zeng, Bin; Chu, Wei; Li, Guihua; Ni, Jielei; Zhang, Haisu; Jing, Chenrui; Zhang, Chaojin; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan

    2014-08-01

    We experimentally demonstrate ultrafast dynamic of generation of a strong 337-nm nitrogen laser by injecting an external seed pulse into a femtosecond laser filament pumped by a circularly polarized laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the excited and ground states of N2 for the free-space 337-nm laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the nitrogen gas pressure. By measuring the intensities of 337-nm signal from nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the nitrogen laser signal. Our experimental observations agree with the picture of electron-impact excitation.

  1. Gain dynamics of a free-space nitrogen laser pumped by circularly polarized femtosecond laser pulses

    CERN Document Server

    Yao, Jinping; Zeng, Bin; Chu, Wei; Li, Guihua; Ni, Jielei; Zhang, Haisu; Jing, Chenrui; Zhang, Chaojin; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan

    2015-01-01

    We experimentally demonstrate ultrafast dynamic of generation of a strong 337-nm nitrogen laser by injecting an external seed pulse into a femtosecond laser filament pumped by a circularly polarized laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the excited and ground states of N2 for the free-space 337-nm laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the nitrogen gas pressure. By measuring the intensities of 337-nm signal from nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the nitrogen laser signal. Our experimental observations agree with the picture of electron-impact excitation.

  2. Self-guiding of 100 TW Femtosecond Laser Pulses in Centimeter-scale Underdense Plasma

    CERN Document Server

    Chen, L M; Nakajima, K; Koga, J; Bulanov, S V; Tajima, T; Gu, Y Q; Peng, H S; Wang, X X; Wen, T S; Liu, H J; Jiao, C Y; Zhang, C G; Huang, X J; Guo, Y; Zhou, K N; Hua, J F; An, W M; Tang, C X; Lin, Y Z

    2006-01-01

    An experiment for studying laser self-guiding has been carried out for the high power ultrashort pulse laser interaction with an underdense plasma slab. Formation of an extremely long plasma channel and its bending are observed when the laser pulse power is much higher than the critical power for relativistic self-focusing. The long self-guiding channel formation is accompanied by electron acceleration with a low transverse emittance and high electric current. Particle-in-cell simulations show that laser bending occurs when the accelerated electrons overtake the laser pulse and modify the refractive index in the region in front of the laser pulse.

  3. Effects of laser fluence on the structural properties of pulsed laser deposited ruthenium thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Wai-Keat; Wong, Hin-Yong; Chan, Kah-Yoong; Tou, Teck-Yong [Multimedia University, Centre for Advanced Devices and Systems (CADS), Faculty of Engineering, Cyberjaya, Selangor (Malaysia); Yong, Thian-Khok [Universiti Tunku Abdul Rahman, Faculty of Engineering and Science, Setapak, Kuala Lumpur (Malaysia); Yap, Seong-Shan [Norwegian University of Science and Technology, Institute of Physics, Trondheim (Norway)

    2010-08-15

    Ruthenium (Ru) has received great interest in recent years for applications in microelectronics. Pulsed laser deposition (PLD) enables the growth of Ru thin films at low temperatures. In this paper, we report for the first time the characterization of pulsed laser deposited Ru thin films. The deposition processes were carried out at room temperature in vacuum environment for different durations with a pulsed Nd:YAG laser of 355-nm laser wavelength, employing various laser fluences ranging from 2 J/cm{sup 2} to 8 J/cm{sup 2}. The effect of the laser fluence on the structural properties of the deposited Ru films was investigated using surface profilometry, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Ru droplets, some spherical in shape and some flattened into round discs were found on the deposited Ru. The droplets were correlated to ripple formations on the target during the laser-induced ejection from the target. In addition, crystalline Ru with orientations of (100), (101), and (002) was observed in the XRD spectra and their intensities were found to increase with increasing laser fluence and film thickness. Grain sizes ranging from 20 nm to 35 nm were deduced using the Scherrer formula. Optical emission spectroscopy (OES) and energy-dispersive X-ray spectroscopy (EDS) show that the composition of the plume and the deposited Ru film was of high purity. (orig.)

  4. Effects of laser fluence on the structural properties of pulsed laser deposited ruthenium thin films

    International Nuclear Information System (INIS)

    Ruthenium (Ru) has received great interest in recent years for applications in microelectronics. Pulsed laser deposition (PLD) enables the growth of Ru thin films at low temperatures. In this paper, we report for the first time the characterization of pulsed laser deposited Ru thin films. The deposition processes were carried out at room temperature in vacuum environment for different durations with a pulsed Nd:YAG laser of 355-nm laser wavelength, employing various laser fluences ranging from 2 J/cm2 to 8 J/cm2. The effect of the laser fluence on the structural properties of the deposited Ru films was investigated using surface profilometry, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Ru droplets, some spherical in shape and some flattened into round discs were found on the deposited Ru. The droplets were correlated to ripple formations on the target during the laser-induced ejection from the target. In addition, crystalline Ru with orientations of (100), (101), and (002) was observed in the XRD spectra and their intensities were found to increase with increasing laser fluence and film thickness. Grain sizes ranging from 20 nm to 35 nm were deduced using the Scherrer formula. Optical emission spectroscopy (OES) and energy-dispersive X-ray spectroscopy (EDS) show that the composition of the plume and the deposited Ru film was of high purity. (orig.)

  5. Plasma plume induced during pulsed laser deposition of hydroxyapatite

    International Nuclear Information System (INIS)

    Pulsed laser deposition is well-established method of deposition of thin films on different substrates. The particles ablated from a target owing to laser radiation-target interaction form a plasma plume and subsequently are deposited on a substrate. The mechanism of plasma formation and expansion consists of three stages. During the interaction of the laser beam with a material the target is heated to the temperatures exceeding the boiling temperatures and sometimes also the critical temperatures. The characteristic time of the target temperature rise is from 1 nanosecond in the case of dielectrics to some hundreds nanoseconds in the case of metals case of metals. In the same time the process of ablation begins. In the second stage the ablated particles are heated by the laser beam to the temperatures of 10-20 kK and form a plasma plume. The characteristic time of plasma heating is 10-100 nanoseconds. This process depends on the intensity of the laser beam and energy of quanta. Next the laser radiation decays (laser pulse duration FWHM ∼ 20-50 ns) and plasma plume expands adiabatically. In this work plasma plume induced by ArF excimer laser ablation of a hydroxyapatite (Ca10(PO4)6(OH)2) target during deposition process has been studied in different ambient conditions., i.e in air or water vapour with the addition of oxygen. Hydroxyapatite is a biocompatible ceramic. It may be deposited onto orthopedic implants in order to increase the bone-implant contact or over a porous titanium coating where it is used to promote bone ingrowth. The process of deposition significantly depends on mechanisms of plasma plume formation and its expansion. ArF laser operated at the wavelength of 193 nm with the pulse energy of 300 mJ and 20 ns pulse duration. The emission spectra of the plasma plume were registered with the use of a spectrograph and a fast gate, micro-channel plate (MCP) image intensifier optically coupled to an Andor CCD camera. The emission spectra consist mainly

  6. 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.

  7. Selective gold nanoparticles formation by pulsed laser interference

    Science.gov (United States)

    Peláez, R. J.; Baraldi, G.; Afonso, C. N.; Riedel, S.; Boneberg, J.; Leiderer, P.

    2012-09-01

    Discontinuous Au films are prepared on glass substrates by pulsed laser deposition with two different metal coverages that lead to a film being formed by irregular coalesced nanoparticles (NPs) and to another film close to the percolation limit. The films are exposed to three interfering beams at different intensities produced by the fourth harmonic of a Nd:YAG laser (266 nm, 10 ns). Scanning electron microscopy and extinction spectra are used respectively to study the structural and optical properties before and after the laser structuring. Round metal NPs appear in the laser transformed areas due to melting followed by rapid solidification that is reflected in the extinction spectra by the appearance of a surface plasmon resonance around 530-540 nm. The areas with NPs are surrounded by non-transformed areas forming a periodic pattern that evolves from a 2D array to parallel lines when local laser intensity increases to cover the whole sample at high intensity. The accumulation of several pulses at low fluence can also transform the metal film almost completely by creating alternating areas having different NP dimensions. The accumulation of metal in some areas of the pattern is consistent with mass transport towards the lower temperature regions.

  8. Hybrid micromachining using a nanosecond pulsed laser and micro EDM

    International Nuclear Information System (INIS)

    Micro electrical discharge machining (micro EDM) is a well-known precise machining process that achieves micro structures of excellent quality for any conductive material. However, the slow machining speed and high tool wear are main drawbacks of this process. Though the use of deionized water instead of kerosene as a dielectric fluid can reduce the tool wear and increase the machine speed, the material removal rate (MRR) is still low. In contrast, laser ablation using a nanosecond pulsed laser is a fast and non-wear machining process but achieves micro figures of rather low quality. Therefore, the integration of these two processes can overcome the respective disadvantages. This paper reports a hybrid process of a nanosecond pulsed laser and micro EDM for micromachining. A novel hybrid micromachining system that combines the two discrete machining processes is introduced. Then, the feasibility and characteristics of the hybrid machining process are investigated compared to conventional EDM and laser ablation. It is verified experimentally that the machining time can be effectively reduced in both EDM drilling and milling by rapid laser pre-machining prior to micro EDM. Finally, some examples of complicated 3D micro structures fabricated by the hybrid process are shown

  9. Pulsed laser deposition of niobium nitride thin films

    International Nuclear Information System (INIS)

    Niobium nitride (NbNx) films were grown on Nb and Si(100) substrates using pulsed laser deposition. NbNx films were deposited on Nb substrates using PLD with a Q-switched Nd:YAG laser (λ = 1064 nm, ∼40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, nitrogen background pressures and deposition substrate temperatures. When all the fabrication parameters are fixed, except for the laser fluence, the surface roughness, nitrogen content, and grain size increase with increasing laser fluence. Increasing nitrogen background pressure leads to a change in the phase structure of the NbNx films from mixed β-Nb2N and cubic δ-NbN phases to single hexagonal β-Nb2N. The substrate temperature affects the preferred orientation of the crystal structure. The structural and electronic, properties of NbNx deposited on Si(100) were also investigated. The NbNx films exhibited a cubic δ-NbN with a strong (111) orientation. A correlation between surface morphology, electronic, and superconducting properties was found. The observations establish guidelines for adjusting the deposition parameters to achieve the desired NbNx film morphology and phase

  10. Pulsed laser deposition of niobium nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Farha, Ashraf Hassan, E-mail: ahass006@odu.edu; Elsayed-Ali, Hani E., E-mail: helsayed@odu.edu [Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23529 (United States); Applied Research Center, Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Department of Physics, Faculty of Science, Ain Shams University, Cairo 11566 (Egypt); Ufuktepe, Yüksel, E-mail: ufuk@cu.edu.tr [Department of Physics, University of Cukurova, 01330 Adana (Turkey); Myneni, Ganapati, E-mail: rao@jlab.org [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

    2015-12-04

    Niobium nitride (NbN{sub x}) films were grown on Nb and Si(100) substrates using pulsed laser deposition. NbN{sub x} films were deposited on Nb substrates using PLD with a Q-switched Nd:YAG laser (λ = 1064 nm, ∼40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, nitrogen background pressures and deposition substrate temperatures. When all the fabrication parameters are fixed, except for the laser fluence, the surface roughness, nitrogen content, and grain size increase with increasing laser fluence. Increasing nitrogen background pressure leads to a change in the phase structure of the NbN{sub x} films from mixed β-Nb{sub 2}N and cubic δ-NbN phases to single hexagonal β-Nb{sub 2}N. The substrate temperature affects the preferred orientation of the crystal structure. The structural and electronic, properties of NbN{sub x} deposited on Si(100) were also investigated. The NbN{sub x} films exhibited a cubic δ-NbN with a strong (111) orientation. A correlation between surface morphology, electronic, and superconducting properties was found. The observations establish guidelines for adjusting the deposition parameters to achieve the desired NbN{sub x} film morphology and phase.

  11. Epidermal cooling during pulsed laser treatment of selected dermatoses

    Science.gov (United States)

    Nelson, J. Stuart; Anvari, Bahman; Tanenbaum, B. S.; Milner, Thomas E.; Kimel, Sol; Svaasand, Lars O.

    1996-01-01

    The clinical objective in laser treatment of selected dermatoses such as port wine stain (PWS), hemangioma and telangiectasia is to maximize thermal damage to the blood vessels, while at the same time minimizing nonspecific injury to the normal overlying epidermis. 'Dynamic' cooling of skin, whereby a cryogen is sprayed onto the surface for an appropriately short period of time (on the order of tens of milliseconds), may offer an effective method for eliminating epidermal thermal injury during laser treatment. We present theoretical and experimental investigations of the thermal response of skin to dynamic cooling in conjunction with pulsed laser irradiation at 585 nm. Computed temperature distributions indicate that cooling the skin immediately prior to pulsed laser irradiation with a cryogen spurt of tetrafluoroethane is an effective method for eliminating epidermal thermal injury during laser treatment of PWS. Experimental results show rapid reduction of skin surface temperature is obtained when using tetrafluoroethane spurts of 20 - 100 ms duration. Successful blanching of PWS without thermal injury to the overlying epidermis is accomplished.

  12. Long-pulsed dye laser versus intense pulsed light for photodamaged skin: A randomized split-face trial with blinded response evaluation

    DEFF Research Database (Denmark)

    Jorgensen, G.F.; Hedelund, L.; Haedersdal, M.

    2008-01-01

    Objective: In a randomized controlled split-face trial to evaluate efficacy and adverse effects from rejuvenation with long-pulsed dye laser (LPDL) versus intense pulsed light (IPL). Materials and Methods: Twenty female volunteers with Fitzpatrick skin types I-III, classes I-II rhytids, and symme......Objective: In a randomized controlled split-face trial to evaluate efficacy and adverse effects from rejuvenation with long-pulsed dye laser (LPDL) versus intense pulsed light (IPL). Materials and Methods: Twenty female volunteers with Fitzpatrick skin types I-III, classes I-II rhytids......, and symmetrical split-face photodamage were included in the study. Subjects received a series of three treatments at 3-week intervals with half-face LPDL (V-beam Perfecta, 595 nm, Candela Laser Corporation) and half-face IPL (Ellipse Flex, Danish Dermatologic Development); the interventions being randomly.......75-5.5) treatments (Plaser and IPL equipments, which found LPDL rejuvenation advantageous to IPL rejuvenation due to superior vessel...

  13. Probing of chlorophyll a with pulsed tunable laser

    International Nuclear Information System (INIS)

    Probing with a tunable pulsed dye laser of a solution of chlorophyll a in pyridine is reported. Transmission studies at fixed wavelengths as function of laser intensity reveal that various levels within the singlet and triplet system become populated and the life-time of these excited states is determined. Fluorescence in the blue part of the electromagnetic spectrum is recorded and the spectrum is induced as a result of the consecutive absorption of two red photons. Using time resolved spectroscopical detection methods, the fluorescence spectra of dimers, free from interference of that due to the monomer, are recorded. (orig.)

  14. Two-pulse laser control of bond-selective fragmentation

    DEFF Research Database (Denmark)

    Amstrup, Bjarne; Henriksen, Niels Engholm

    1996-01-01

    We elaborate on a two-pulse (pump-pump) laser control scheme for selective bond-breaking in molecules [Amstrup and Henriksen, J. Chem. Phys. 97, 8285 (1992)]. We show, in particular, that with this scheme one can overcome the obstacle of intramolecular vibrational relaxation. As an example, we...... consider an ozone molecule with isotopic substitution, that is, (OOO)-O-16-O-16-O-18. It is shown that asymmetric bond stretching can be created in simple (intense) laser fields. We predict that an alternating high selectivity between the channels O-16+(OO)-O-16-O-18 and (OO)-O-16-O-16+ O-18 can be...

  15. Two-pulse laser control for selective photofragment orientation

    DEFF Research Database (Denmark)

    Machholm, Mette; Henriksen, Niels Engholm

    1999-01-01

    The nuclear wave packet dynamics in the potential well of a bound molecule can be controlled by an intense infrared (IR)-laser pulse. The phase of the nuclear wave packet motion is shown to depend on the phase of the laser field and the initial orientation of the molecule. We demonstrate, for...... diatomic heteronuclear molecules, that these spatial effects can be used to control the angular distribution of photofragments by selective dissociation of molecules with a given initial orientation from a sample of randomly oriented molecules. (C) 1999 American Institute of Physics. [S0021-9606(99)01131-9]....

  16. Short-Pulse Laser-Matter Computational Workshop Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Town, R; Tabak, M

    2004-11-02

    For three days at the end of August 2004, 55 plasma scientists met at the Four Points by Sheraton in Pleasanton to discuss some of the critical issues associated with the computational aspects of the interaction of short-pulse high-intensity lasers with matter. The workshop was organized around the following six key areas: (1) Laser propagation/interaction through various density plasmas: micro scale; (2) Anomalous electron transport effects: From micro to meso scale; (3) Electron transport through plasmas: From meso to macro scale; (4) Ion beam generation, transport, and focusing; (5) ''Atomic-scale'' electron and proton stopping powers; and (6) K{alpha} diagnostics.

  17. Entanglement generated between a single atom and a laser pulse

    OpenAIRE

    Silberfarb, Andrew; Deutsch, Ivan H.

    2003-01-01

    We quantify the entanglement generated between an atom and a laser pulse in free space. We find that the entanglement calculated using a simple closed-system Jaynes-Cummings Hamiltonian is in remarkable agreement with a full open-system calculation, even though the free-space geometry is far from the strong coupling regime of cavity QED. We explain this result using a simple model in which the atom couples weakly to the laser while coupling strongly to the vacuum. Additionally we place an upp...

  18. Testing of a femtosecond pulse laser in outer space

    OpenAIRE

    Joohyung Lee; Keunwoo Lee; Yoon-Soo Jang; Heesuk Jang; Seongheum Han; Sang-Hyun Lee; Kyung-In Kang; Chul-Woo Lim; Young-Jin Kim; Seung-Woo Kim

    2014-01-01

    We report a test operation of an Er-doped fibre femtosecond laser which was conducted for the first time in outer space. The fibre-based ultrashort pulse laser payload was designed to meet space-use requirements, undergone through ground qualification tests and finally launched into a low-earth orbit early in 2013. Test results obtained during a one-year mission lifetime confirmed stable mode-locking all the way through although the radiation induced attenuation (RIA) in the Er-doped gain fib...

  19. Modulation instability of laser pulse in magnetized plasma

    International Nuclear Information System (INIS)

    Modulation instability of a laser pulse propagating through transversely magnetized underdense plasma is studied. It is observed that interaction of laser radiation with plasma in the presence of uniform magnetic field results in an additional perturbed transverse plasma current density along with the relativistic and ponderomotive nonlinear current densities, thus affecting the modulational interaction. In the plane wave limit it is observed that modulational interaction is more stable for magnetized plasma as compared to the unmagnetized case. The analysis shows that there is a significant reduction in the growth rate of modulation instability over a given range of unstable wave numbers due to magnetization of plasma

  20. Fundamental Mechanisms of Pulsed Laser Ablation of Biological Tissue

    Science.gov (United States)

    Albagli, Douglas

    The ability to cut and remove biological tissue with short pulsed laser light, a process called laser ablation, has the potential to revolutionize many surgical procedures. Ablation procedures using short pulsed lasers are currently being developed or used in many fields of medicine, including cardiology, ophthalmology, dermatology, dentistry, orthopedics, and urology. Despite this, the underlying physics of the ablation process is not well understood. In fact, there is wide disagreement over whether the fundamental mechanism is primarily photothermal, photomechanical, or photochemical. In this thesis, both experimental and theoretical techniques are developed to explore this issue. The photothermal model postulates that ablation proceeds through vaporization of the target material. The photomechanical model asserts that ablation is initiated when the laser-induced tensile stress exceeds the ultimate tensile strength of the target. I have developed a three dimensional model of the thermoelastic response of tissue to short pulsed laser irradiation which allows the time dependent stress distribution to be calculated given the optical, thermal and mechanical properties of the target. A complimentary experimental technique has been developed to verify this model, measure the needed physical properties of the tissue, and record the thermoelastic response of the tissue at the onset of ablation. The results of this work have been widely disseminated to the international research community and have led to significant findings which support the photomechanical model of ablation of tissue. First, the energy deposited in tissue is an order of magnitude less than that required for vaporization. Second, unlike the one-dimensional thermoelastic model of laser-induced stress generation that has appeared in the literature, the full three-dimensional model predicts the development of significant tensile stresses on the surface of the target, precisely where ablation is observed to

  1. Laser-induced back-ablation of aluminum thin films using picosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    BULLOCK, A B

    1999-05-26

    Experiments were performed to understand laser-induced back-ablation of Al film targets with picosecond laser pulses. Al films deposited on the back surface of BK-7 substrates are ablated by picosecond laser pulses propagating into the Al film through the substrate. The ablated Al plume is transversely probed by a time-delayed, two-color sub-picoseond (500 fs) pulse, and this probe is then used to produce self-referencing interferograms and shadowgraphs of the Al plume in flight. Optical emission from the Al target due to LIBA is directed into a time-integrated grating spectrometer, and a time-integrating CCD camera records images of the Al plume emission. Ablated Al plumes are also redeposited on to receiving substrates. A post-experimental study of the Al target and recollected deposit characteristics was also done using optical microscopy, interferometry, and profilometry. In this high laser intensity regime, laser-induced substrate ionization and damage strongly limits transmitted laser fluence through the substrate above a threshold fluence. The threshold fluence for this ionization-based transmission limit in the substrate is dependent on the duration of the incident pulse. The substrate ionization can be used as a dynamic control of both transmitted spatial pulse profile and ablated Al plume shape. The efficiency of laser energy transfer between the laser pulse incident on the Al film and the ablated Al plume is estimated to be of order 5% and is a weak function of laser pulsewidth. The Al plume is highly directed. Low plume divergence ({theta}{sub divergence} < 5{sup o}) shows the ablated plume temperature to be very low at long time delays ( T << 0.5 eV at delays of 255 ns). Spectroscopic observations and calculations indicate that, in early time (t < 100 ps), the Al film region near the substrate/metal interface is at temperatures of order 0.5 eV. Interferograms of Al plumes produced with 0.1 {micro}m films show these plumes to be of high neutral atom

  2. Coupling coefficient for TEA CO2 laser propulsion with variable pulse repetition rate

    Institute of Scientific and Technical Information of China (English)

    Yijun Zheng; Rongqing Tan; Donglei Wang; Guang Zheng; Changjun Ke; Kuohai Zhang; Chongyi Wan; Jin Wu

    2006-01-01

    @@ Because pulse repetition rate affected directly the momentum coupling coefficient of transversely excited atmospheric (TEA) CO2 laser propulsion, a double pulse trigger, controlling high voltage switch of laser excitation circuit, was designed. The pulse interval ranged between 5 and 100 ms. The momentum coupling coefficient for air-breathing mode laser propulsion was studied experimentally. It was found that the momentum coupling coefficient decreased with the pulse repetition rate increasing.

  3. Photon Return On-Sky Test of Pulsed Sodium Laser Guide Star with D2b Repumping

    Science.gov (United States)

    Jin, Kai; Wei, Kai; Feng, Lu; Bo, Yong; Zuo, JunWei; Li, Min; Fu, HanChu; Dai, XiaoLin; Bian, Qi; Yao, Ji; Xu, Chang; Wang, ZhiChao; Peng, QingJun; Xue, XiangHui; Cheng, XueWu; Rao, ChangHui; Xu, ZuYan; Zhang, YuDong

    2015-08-01

    Sodium laser guide star (LGS) system has become one of the critical components in modern astronomical adaptive optics system (AOS), especially for the next-generation extremely large telescopes, such as the Thirty Meter Telescope and the European Extremely Large Telescope. Since the wavefront detection performance of AOS is directly related to the brightness of LGS, it is important for AOS to maximize its photon generation efficiency by all means. Sodium D2b line repumping is such a technique that can greatly increase the returned photons for either sodium continuous wave (CW) laser or pulsed laser. This technique has been studied theoretically and field tested with a 20 W CW laser by European Southern Observatory team. However, field test results of a 20 W class pulsed laser with D2b repumping have not been reported yet. In this paper, our latest field test results with theoretical comparison of D2b repumping with a 20 W quasi-continuous wave (QCW) pulsed laser will be presented. With a linearly polarized beam, approximate 40% photon return enhancement was achieved when 10% of laser power was detuned to D2b line, which agreed well with results from a rate equation-based Monte Carlo photon return simulation program. Both experiment and simulation results indicate that with a higher laser intensity projected at the sodium layer, the D2b repumping will be more effective.

  4. Long-laser-pulse method of producing thin films

    Science.gov (United States)

    Balooch, Mehdi; Olander, Donald K.; Russo, Richard E.

    1991-01-01

    A method of depositing thin films by means of laser vaporization employs a long-pulse laser (Nd-glass of about one millisecond duration) with a peak power density typically in the range 10.sup.5 -10.sup.6 W/cm.sup.2. The method may be used to produce high T.sub.c superconducting films of perovskite material. In one embodiment, a few hundred nanometers thick film of YBa.sub.2 Cu.sub.3 O.sub.7-x is produced on a SrTiO.sub.3 crystal substrate in one or two pulses. In situ-recrystallization and post-annealing, both at elevated temperature and in the presence of an oxidizing agen The invention described herein arose in the course of, or under, Contract No. DE-C03-76SF0098 between the United States Department of Energy and the University of California.

  5. Unitary model for atomic ionization by intense XUV laser pulses

    CERN Document Server

    Bustamante, M G

    2016-01-01

    A unitary model describing the electronic transitions in an atom subject to a strong high frequency laser pulse is proposed. The model fully accounts for the initial state coupling with the continuum spectrum. Continuum-continuum as well as discrete-discrete transitions are neglected. The model leads to a single integro-differential equation for the initial state amplitude. Exact numerical and approximate closed semi-analytical solutions of this equation are obtained. A comparison of present results with full time dependent Schr\\"odinger equation solution for Hydrogen atoms subject to a laser pulse is presented. The initial state time dependent population is rather well described by the model and two approximate solutions. The electron energy spectrum is also well reproduced by the model and by a new improved Weiskopf-Wigner related approximation.

  6. Breakdown of molecular oxygen by brief pulses of laser radiation

    International Nuclear Information System (INIS)

    We report a numerical analysis for the combined action of multi-photon (MPHI) and Cascade ionization (CI) processes in producing ionization and breakdown of molecular oxygen. The calculations were carried out at two different laser pulses of wavelengths 0.6943μm and 0.53μm with pulse durations 18ps and 25ps respectively, over a pressure range of 102-5x104 Torr. A reasonably good agreement has been obtained between the computed threshold intensities and the measured ones. Computations for nitrogen irradiated with 0.53μm are also given. This analysis shows that the model is capable to interpret gas breakdown experiments with short flashes of laser radiation. (author). 6 refs, 5 figs

  7. Regularization of an autoconvolution problem in ultrashort laser pulse characterization

    CERN Document Server

    Gerth, Daniel; Birkholz, Simon; Koke, Sebastian; Steinmeyer, Günter

    2013-01-01

    An ill-posed inverse problem of autoconvolution type is investigated. This inverse problem occurs in nonlinear optics in the context of ultrashort laser pulse characterization. The novelty of the mathematical model consists in a physically required extension of the deautoconvolution problem beyond the classical case usually discussed in literature: (i) For measurements of ultrashort laser pulses with the self-diffraction SPIDER method, a stable approximate solution of an autocovolution equation with a complex-valued kernel function is needed. (ii) The considered scenario requires complex functions both, in the solution and the rhs of the integral equation. Since, however, noisy data are available not only for amplitude and phase functions of the rhs, but also for the amplitude of the solution, the stable approximate reconstruction of the associated smooth phase function represents the main goal of the paper. An iterative regularization approach is described that is specifically adapted to the physical situati...

  8. Optical modulation of astrocyte network using ultrashort pulsed laser

    Science.gov (United States)

    Yoon, Jonghee; Ku, Taeyun; Chong, Kyuha; Ryu, Seung-Wook; Choi, Chulhee

    2012-03-01

    Astrocyte, the most abundant cell type in the central nervous system, has been one of major topics in neuroscience. Even though many tools have been developed for the analysis of astrocyte function, there has been no adequate tool that can modulates astrocyte network without pharmaceutical or genetic interventions. Here we found that ultrashort pulsed laser stimulation can induce label-free activation of astrocytes as well as apoptotic-like cell death in a dose-dependent manner. Upon irradiation with high intensity pulsed lasers, the irradiated cells with short exposure time showed very rapid mitochondria fragmentation, membrane blebbing and cytoskeletal retraction. We applied this technique to investigate in vivo function of astrocyte network in the CNS: in the aspect of neurovascular coupling and blood-brain barrier. We propose that this noninvasive technique can be widely applied for in vivo study of complex cellular network.

  9. Note: 15-fs, 15-μJ green pulses from two-stage temporal compressor of ytterbium laser pulses.

    Science.gov (United States)

    Konyashchenko, A V; Kostryukov, P V; Losev, L L; Tenyakov, S Yu

    2012-10-01

    15-fs, 15-μJ light pulses at the central wavelength of 515 nm were generated by two-stage nonlinear compression of 300-fs, 150-μJ ytterbium laser pulses. The compression was based on the pulse spectrum broadening by self-phase modulation in gas filled capillary and second harmonic generation in crystal. PMID:23126820

  10. High Intensity Particle Physics at PW-class laser facilities

    Science.gov (United States)

    Bulanov, Stepan; Schroeder, Carl; Esarey, Eric; Esirkepov, Timur; Kando, Masaki; Rosanov, Nikolay; Korn, Georg; Bulanov, Sergey V.; Leemans, Wim P.

    2015-11-01

    The processes typical for high intensity particle physics, i.e., the interactions of charged particles with strong electromagnetic fields, have attracted considerable interest recently. Some of these processes, previously believed to be of theoretical interest only, are now becoming experimentally accessible. High intensity electromagnetic (EM) fields significantly modify the interactions of particles and EM fields, giving rise to the phenomena that are not encountered either in classical or perturbative quantum theory of these interactions. One of such phenomena is the radiation reaction, which radically influences the electron motion in an electromagnetic standing wave formed by two super-intense counter-propagating laser pulses. Depending on the laser intensity and wavelength, either classical or quantum mode of radiation reaction prevail, or both are strong. When radiation reaction dominates, electron motion evolves to limit cycles and strange attractors. This creates a new framework for high energy physics experiments on an interaction of energetic charged particle beams and colliding super-intense laser pulses. Work supported by U.S. DOE under Contract No. DE-AC02-05CH11231.

  11. Multifunctional magnetic materials prepared by Pulsed Laser Deposition

    OpenAIRE

    Nagar, Sandeep

    2012-01-01

         Pulsed LASER deposition (PLD) is widely recognized as excellent deposition technique owing to stoichiometric transfer of target material, easy preparation and high quality. Thin films from few nanometers to micrometer regime can be fabricated with equal ease. Although a batch process is not suitable for mass scale industrial production, PLD is a versatile technique, efficient and convenient for high quality basic research.  This thesis illustrates the use of PLD technique to study the em...

  12. Modeling the early ionization of dielectrics by ultrashort laser pulses

    OpenAIRE

    Bourgeade, Antoine; Mézel, Candice; Saut, Olivier

    2010-01-01

    International audience In this paper, we present a model for propagation of intense and ultrashort laser pulses ionizing dielectrics. We consider early ion- ization so that this process is sufficiently weak to avoid requiring a complete description of the ionization process (e.g. the use of ki- netic equations which are very expensive from a computational point of view). As the intensity of the field is small, one photon ioniza- tion is neglected. Ionization may only occur through multi-ph...

  13. Growth of epitaxial thin films by pulsed laser ablation

    International Nuclear Information System (INIS)

    High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs

  14. Materials processing with a tightly focused femtosecond vortex laser pulse

    OpenAIRE

    Hnatovsky, Cyril; Shvedov, Vladlen G.; Krolikowski, Wieslaw; Rode, Andrei V.

    2010-01-01

    This letter is the first demonstration of material modification using tightly focused femtosecond laser vortex beams. Double-charge femtosecond vortices were synthesized with the polarization-singularity beam converter described in Ref [1] and then focused using moderate and high numerical aperture optics (viz., NA = 0.45 and 0.9) to ablate fused silica and soda-lime glasses. By controlling the pulse energy we consistently machine high-quality micron-size ring-shaped structures with less than...

  15. Photoionization in combined ultra short XUV and infrared laser pulses

    International Nuclear Information System (INIS)

    Multi-photon-double ionization of xenon by Ti:Sapphire laser pulses combined with their 25th harmonic has been studied by means of a momentum imaging spectrometer. The determination of the momenta of the emitted photoelectron pair and of its energy and angular correlation gives insight into the various mechanisms leading to double ionization. Although the conditions for non sequential direct multi-photon double ionization are met in the experiment, it is found that two-step sequential processes prevail.

  16. Semi-classical beam cooling in an intense laser pulse

    OpenAIRE

    Yoffe, Samuel R.; Kravets, Yevgen; Noble, Adam; Jaroszynski, Dino A.

    2014-01-01

    We present a novel technique for studying the evolution of a particle distribution using single particle dynamics such that the distribution can be accurately reconstructed using fewer particles than existing approaches. To demonstrate this, the Landau-Lifshiftz description of radiation reaction is adapted into a semi-classical model, for which the Vlasov equation is intractable. Collision between an energetic electron bunch and high-intensity laser pulses are then compared using the two theo...

  17. Short-pulse high intensity laser thin foil interaction

    Science.gov (United States)

    Audebert, Patrick

    2003-10-01

    The technology of ultrashort pulse laser generation has progressed to the point that optical pulses larger than 10 J, 300 fs duration or shorter are routinely produced. Such pulses can be focused to intensities exceeding 10^18 W/cm^2. With high contrast pulses, these focused intensities can be used to heat solid matter to high temperatures with minimal hydrodynamic expansion, producing an extremely high energy-density state of matter for a short period of time. This high density, high temperature plasma can be studied by x-ray spectroscopy. We have performed experiments on thin foils of different elements under well controlled conditions at the 100 Terawatt laser at LULI to study the characteristics X-ray emission of laser heated solids. To suppress the ASE effect, the laser was frequency doubled. S-polarized light with a peak intensity of 10^19W/cm^2 was used to minimize resonance absorption. To decrease the effect of longitudinal temperature gradients very thin (800 μ) aluminum foil targets were used. We have also studied the effect of radial gradient by limiting the measured x-ray emission zone using 50μ or 100μ pinhole on target. The spectra, in the range 7-8Å, were recorded using a conical crystal spectrometer coupled to a 800 fs resolution streak camera. A Fourier Domain Interferometry (FDI) of the back of the foil was also performed providing a measurement of the hydrodynamic expansion as function of time for each shot. To simulate the experiment, we used the 1D hydrodynamic code FILM with a given set of plasma parameter (ρ, Te) as initial conditions. The X-ray emission was calculated by post processing hydrodynamic results with a collisional-radiative model which uses super-configuration average atomic data. The simulation reproduces the main features of the experimental time resolved spectrum.

  18. Laser diagnostics on magnetically insulated flashover pulsed ion diodes

    International Nuclear Information System (INIS)

    Our recent experimental results on the characteristics of a flashover-type applied-B magnetically insulated pulsed ion diode are described. The main issues are to investigate the cause of impurity of the extracted beam and to examine the effect of neutral particles on the diode characteristics. In the experiment, our main efforts were placed on laser diagnostics of the diode gap behavior. (author)

  19. 3D sensor for indirect ranging with pulsed laser source

    Science.gov (United States)

    Bronzi, D.; Bellisai, S.; Villa, F.; Scarcella, C.; Bahgat Shehata, A.; Tosi, A.; Padovini, G.; Zappa, F.; Tisa, S.; Durini, D.; Weyers, S.; Brockherde, W.

    2012-10-01

    The growing interest for fast, compact and cost-effective 3D ranging imagers for automotive applications has prompted to explore many different techniques for 3D imaging and to develop new system for this propose. CMOS imagers that exploit phase-resolved techniques provide accurate 3D ranging with no complex optics and are rugged and costeffective. Phase-resolved techniques indirectly measure the round-trip return of the light emitted by a laser and backscattered from a distant target, computing the phase delay between the modulated light and the detected signal. Singlephoton detectors, with their high sensitivity, allow to actively illuminate the scene with a low power excitation (less than 10W with diffused daylight illumination). We report on a 4x4 array of CMOS SPAD (Single Photon Avalanche Diodes) designed in a high-voltage 0.35 μm CMOS technology, for pulsed modulation, in which each pixel computes the phase difference between the laser and the reflected pulse. Each pixel comprises a high-performance 30 μm diameter SPAD, an analog quenching circuit, two 9 bit up-down counters and memories to store data during the readout. The first counter counts the photons detected by the SPAD in a time window synchronous with the laser pulse and integrates the whole echoed signal. The second counter accumulates the number of photon detected in a window shifted with respect to the laser pulse, and acquires only a portion of the reflected signal. The array is readout with a global shutter architecture, using a 100 MHz clock; the maximal frame rate is 3 Mframe/s.

  20. Picosecond laser pulse induced damage in crystalline silicon

    International Nuclear Information System (INIS)

    Picosecond laser pulse irradiation of single crystalline Si can produce severe damage, including amorphisation. Morphology changes are studied by means of optical and high-voltage-electron microscopy and are found to depend on energy fluence, surface orientation, and wavelength. The detailed analysis of the damage distributions and thresholds lead to the conclusion that energy-confinement precedes the introduction of structural changes, which are formed by rapid quenching from the liquid state