WorldWideScience

Sample records for all-pm femtosecond yb-doped

  1. 1-MHz high power femtosecond Yb-doped fiber chirped-pulse amplifier

    Science.gov (United States)

    Hu, Zhong-Qi; Yang, Pei-Long; Teng, Hao; Zhu, Jiang-Feng; Wei, Zhi-Yi

    2018-01-01

    A practical femtosecond polarization-maintaining Yb-doped fiber amplifier enabling 153 fs transform-limited pulse duration with 32 μJ pulse energy at 1 MHz repetition rate corresponding to a peak power of 0.21 GW is demonstrated. The laser system based on chirped-pulse amplification (CPA) technique is seeded by a dispersion managed, nonlinear polarization evolution (NPE) mode-locked oscillator with spectrum bandwidth of 31 nm at 1040 nm and amplified by three fiber pre-amplifying stages and a rod type fiber main amplifying stage. The laser works with beam quality of M2 of 1.3 and power stability of 0.63% (root mean square, RMS) over 24 hours will be stable sources for industrial micromachining, medical therapy and scientific research.

  2. Monolithic all-PM femtosecond Yb-doped fiber laser using photonic bandgap fibers

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Lægsgaard, Jesper; Turchinovich, Dmitry

    2009-01-01

    We present a monolithic Yb fiber laser, dispersion managed by an all-solid photonic bandgap fiber, and pulse compressed in a hollow-core photonic crystal fiber. The laser delivers 9 nJ, 275-fs long pulses at 1035 nm.......We present a monolithic Yb fiber laser, dispersion managed by an all-solid photonic bandgap fiber, and pulse compressed in a hollow-core photonic crystal fiber. The laser delivers 9 nJ, 275-fs long pulses at 1035 nm....

  3. Development and applications of femtosecond monolithic Yb-doped fiber chirped-pulse amplifiers

    International Nuclear Information System (INIS)

    Zhu, L.

    2011-01-01

    In the past few years, compact and environmentally stable high-energy ultrashort pulse laser sources have been broadly utilized in many different applications. Fiber lasers offer big practical advantages over bulk solid-state laser systems in terms of flexibility, compactness, reliability, cost effectiveness and turn-key operability. Moreover, thermal effects are dramatically reduced due to the large surface-to-volume ratio of an optical fiber, and good spatial mode quality can be ensured by its waveguiding property. Therefore, a fiber-based laser system is considered to be the preferred laser architecture. The main theme of this thesis is the development of various femtosecond monolithic Yb-doped fiber chirped-pulse-amplification (FCPA) system and their applications. We demonstrate an ultrafast high-energy monolithic Yb-doped FCPA system in which the pulse fidelity is preserved by weakening the nonlinear effects via a substantial level of temporal stretching of the seed pulses and by using highly doped active fibers as amplifying media. The presented monolithic FCPA delivers up to ∼ 25 μJ diffraction-limited pulses that can be recompressed to sub-200 fs duration, and the pulse quality has been confirmed through the second-harmonic-generation (SHG) conversion efficiency of over 52%. Improved dispersion and nonlinearity management schemes of the FCPA system allowing substantial pulse energy scaling in the monolithic format as well as methods for overcoming a series of technological challenges are reported. Three different types of Yb-doped fiber oscillators have been developed and built in the course of this PhD work. First, we compare two oscillator types that are based on the all-normal-dispersion (ANDi) regime and the dispersion-managed (DM) regime. Both of them have been tested as the seed-pulse source of the monolithic Yb-doped FCPA system. Then we introduce another novel design based on higher-order-mode (HOM) dispersion management that competes with a

  4. A femtosecond Yb-doped fiber laser with generalized vector vortex beams output (Conference Presentation)

    Science.gov (United States)

    Huo, Tiancheng; Qi, Li; Zhang, Buyun; Chen, Zhongping

    2017-03-01

    Light carries both spin and orbital angular momentum (OAM) and the superpositions of these two dynamical properties have found many applications. Many techniques exist to create such light sources but none allow their creation at the femtosecond fiber laser. Here we report on a novel mode-locked Ytterbium-doped fiber laser that generates femtosecond pulses with generalized vector vortex states. The controlled generation of such pulses such as azimuthally and radially polarized light with definite orbital angular momentum modes are demonstrated. A unidirectional ring cavity constructed with the Yb-doped fiber placed at the end of the fiber section to reduces unnecessary nonlinear effects is employed for self-starting operation. Pairs of diffraction gratings are used for compensating the normal group velocity dispersion of the fiber and other elements. Mode-locked operation is achieved based on nonlinear polarization evolution, which is mainly implemented with the single mode fiber, the bulk wave plates and the variable spiral plates (q-plate with topological charge q=0.5). The conversion from spin angular momentum to the OAM and reverse inside the laser cavity are realized by means of a quarter-wave plate and a q-plate so that the polarization control was mapped to OAM mode control. The fiber laser is diode pumped by a wavelength-division multiplexing coupler, which leads to excellent stability and portability.

  5. Monolithic Highly Stable Yb-Doped Femtosecond Fiber Lasers for Applications in Practical Biophotonics

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Lægsgaard, Jesper; Turchinovich, Dmitry

    2012-01-01

    Operational and environmental stability of ultrafast laser systems is critical for their applications in practical biophotonics. Mode-locked fiber lasers show great promise in applications such as supercontinuum sources or multiphoton microscopy systems. Recently, substantial progress has been made...... in the development of all-fiber nonlinear-optical laser control schemes, which resulted in the demonstration of highly stable monolithic, i.e., not containing any free-space elements, lasers with direct fiber-end delivery of femtosecond pulses. This paper provides an overview of the progress in the development...

  6. Monolithic stabilized Yb-fiber All-PM laser directly delivering nJ-level femtosecond pulses

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Liu, Xiaomin; Lægsgaard, Jesper

    2008-01-01

    We present a monolithic, self-starting, all-PM, stabilized Yb-fiber laser, pulse-compressed in a hollow-core PM photonic crystal fiber, providing the 370 fs pulses of 4 nJ energy with high mode quality.......We present a monolithic, self-starting, all-PM, stabilized Yb-fiber laser, pulse-compressed in a hollow-core PM photonic crystal fiber, providing the 370 fs pulses of 4 nJ energy with high mode quality....

  7. Linearly polarized intracavity passive Q-switched Yb-doped ...

    Indian Academy of Sciences (India)

    2014-02-14

    Feb 14, 2014 ... ratio of active core area to inner cladding area, the pump light absorption is improved and smaller fibre length becomes possible. There are reports on the passive Q-switching in. Yb-doped LMA fibre lasers by using Cr4+:YAG crystal as a saturable absorber. Huang et al have reported maximum average ...

  8. Tunable femtosecond Cherenkov fiber laser

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Svane, Ask Sebastian; Lægsgaard, Jesper

    2014-01-01

    We demonstrate electrically-tunable femtosecond Cherenkov fiber laser output at the visible range. Using an all-fiber, self-starting femtosecond Yb-doped fiber laser as the pump source and nonlinear photonic crystal fiber link as the wave-conversion medium, ultrafast, milliwatt-level, tunable...

  9. Femtosecond pulse generation and amplification in Yb-doped fibre ...

    Indian Academy of Sciences (India)

    biomedical imaging [4], tissue processing [5], nanosurgery [6] and scientific appli- cations such as in nonlinear optics, metrology, spectroscopy and probing ultrafast dynamics. Even though it is clear that these emerging applications hold potential for major scientific and industrial impact, progress is hampered because of the ...

  10. Monolithic all-PM femtosecond Yb-fiber laser stabilized with a narrow-band fiber Bragg grating and pulse-compressed in a hollow-core photonic crystal fiber

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Liu, Xiaomin; Lægsgaard, Jesper

    2008-01-01

    We report on an environmentally stable self-starting monolithic (i.e. without any free-space coupling) all-polarization-maintaining (PM) femtosecond Yb-fiber laser, stabilized against Q-switching by a narrow-band fiber Bragg grating and modelocked using a semiconductor saturable absorber mirror....... The laser output is compressed in a spliced-on hollow-core PM photonic crystal fiber, thus providing direct end-of-the-fiber delivery of pulses of around 370 fs duration and 4 nJ energy with high mode quality. Tuning the pump power of the end amplifier of the laser allows for the control of output pulse...

  11. High-power Yb-doped continuous-wave and pulsed fibre lasers

    Indian Academy of Sciences (India)

    2014-01-05

    wave fibre laser; Q-switched fibre laser; nonlinearity; thermal effects; selfpulsing; Yb-doped fibre; nanosecond pulse ... Solid State Laser Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013, India ...

  12. Guided mode gain competition in Yb-doped rod-type photonic crystal fibers

    DEFF Research Database (Denmark)

    Poli, Federica; Passaro, Davide; Cucinotta, Annamaria

    2009-01-01

    The gain competition among the guided modes in Yb-doped rod-type photonic crystal fibers with a low refractive index core is investigated with a spatial model to demonstrate the fiber effective single-mode behaviour.......The gain competition among the guided modes in Yb-doped rod-type photonic crystal fibers with a low refractive index core is investigated with a spatial model to demonstrate the fiber effective single-mode behaviour....

  13. Mass fabrication of homogeneously Yb-doped silica nanoparticles and their spectroscopic properties

    International Nuclear Information System (INIS)

    Xiong Liangming; Sekiya, Edson H; Saito, Kazuya

    2009-01-01

    A large number of homogeneously Yb-doped silica nanoparticles were continually fabricated in a vapor synthesis route, in which the Yb doping level can be well controlled by varying either the heating temperature or the carrier gas flow rate of the Yb precursor. The sizes, shapes, and morphologies of the nanoparticles were examined, and no crystallites and no Yb 2 O 3 clusters were observed in the nanoparticles. These nanoparticles exhibit a clear Yb 3+ -derived absorption at around 973-975 nm and a dependence of the emission intensity and decay time on the doping level, much different from that of sintered pellets.

  14. High-power Yb-doped continuous-wave and pulsed fibre lasers

    Indian Academy of Sciences (India)

    2014-01-05

    Jan 5, 2014 ... Continuous-wave fibre laser; Q-switched fibre laser; nonlinearity; thermal effects; selfpulsing; Yb-doped fibre; nanosecond pulse ... intracore fibre Bragg gratings, low thermal problems due to large surface to volume ratio, diffraction-limited beam quality, compactness, reliability and fibre-optic beam delivery.

  15. Superconductivity at 31⋅3 K in Yb-doped La(O/F)FeAs ...

    Indian Academy of Sciences (India)

    Administrator

    43. *For correspondence. Superconductivity at 31⋅3 K in Yb-doped La(O/F)FeAs superconductors. J PRAKASH a. , S J SINGH b. , S PATNAIK b and A K GANGULI a,. * a. Department of Chemistry, Indian Institute of Technology, New Delhi 110 016 b. School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110 ...

  16. Assessment of effect of Yb3+ ion pairs on a highly Yb-doped double-clad fibre laser

    Science.gov (United States)

    Vallés, J. A.; Martín, J. C.; Berdejo, V.; Cases, R.; Álvarez, J. M.; Rebolledo, M. Á.

    2018-03-01

    Using a previously validated characterization method based on the careful measurement of the characteristic parameters and fluorescence emission spectra of a highly Yb-doped double-clad fibre, we evaluate the contribution of ion pair induced processes to the output power of a double-clad Yb-doped fibre ring laser. This contribution is proved to be insignificant, contrary to analysis by other authors, who overestimate the role of ion pairs.

  17. High-power Yb-doped continuous-wave and pulsed fibre lasers

    Indian Academy of Sciences (India)

    2014-01-05

    Jan 5, 2014 ... becomes a critical issue in scaling high output power from Yb-doped double clad fibres. Since polymer coating is used to .... Techniques to exploit self-pulsing to achieve reg- ular narrow pulses with .... a single order if the beam is incident at an angle equal to the Bragg angle (θB) given by sin θB = λ0. 2n0.

  18. Femtosecond all-polarization-maintaining fiber laser operating at 1028 nm

    DEFF Research Database (Denmark)

    Olsson, R.K.; Andersen, T.V.; Leick, Lasse

    2008-01-01

    We present an effective solution for an all-polarization-maintaining modelocked femtosecond fiber laser operating at the central wavelength of 1028 nm. The laser is based on an Yb-doped active fiber. Modelocking is enabled by a semiconductor saturable absorber mirror, and the central wavelength...

  19. Effects of rare-earth doping on femtosecond laser waveguide writing in zinc polyphosphate glass

    NARCIS (Netherlands)

    Fletcher, L.B.; Witcher, J.J.; Troy, N.; Reis, S.T.; Brow, R.K.; Krol, D.M.

    2012-01-01

    We have investigated waveguide writing in Er-Yb doped zinc polyphosphate glass using a femtosecond laser with a repetition rate of 1 KHz. We find that fabrication of good waveguides requires a glass composition with an O/P ratio of 3.25. The dependence on laser writing parameters including laser

  20. [Study on Spectral Characteristics of Two Kinds of Home-Made Novel Yb-Doped Fluoride Laser Crystals].

    Science.gov (United States)

    Xu, Wen-bin; Chai, Lu; Shi, Jun-kai; Song, You-jian; Hu, Ming-lie; Wang, Qing-yue; Su, Liang-bi; Jiang, Da-peng; Xu, Jun

    2015-09-01

    Yb-doped fluoride crystals are of important another Yb-doped laser materials besides Yb-doped oxide, which are becoming one of interests for developing tunable lasers and ultrafast lasers. In this paper, the systematic and contrastive experiments of the optical spectral characteristics are presented for two types of home-made novel Yb-doped fluoride laser crystals, namely, Yb-doped CaF2-SrF2 mixed crystal and co-doped Yb, Y:CaF2 single crystal. The fluorescent features of Yb-doped CaF2-SrF2 mixed crystal and co-doped Yb, Y:CaF2 single crystal are apparently different by the fluorescence experiment. The physical mechanism of these fluorescence spectra were analyzed and proposed. The influence of doping concentrations of active Yb(3+) ions or co-doping Y ions on the absorption of Yb-doped CaF2-SrF2 mixed crystal and co-doped Yb, Y:CaF2 single crystal was experimentally investigated, and the optimal values of doping concentrations of active Yb(3+) ions or co-doping Y ions in the two types of fluoride laser crystals were obtained. Continuous-wave laser operation for the two novel fluoride laser crystals has been achieved in three-mirror-folded resonator using a laser diode as the pump source. Therein, the laser operation for the co-doped Yb, Y:CaF2 crystal is demonstrated for the first time. For the two types of fluoride laser crystals (four samples), the input-output power relational curves, the optical slope efficiencies and the laser spectra were demonstrated by the laser experiments. By comparisons between the two types of fluoride laser crystals in the absorbability, fluorescence and laser spectra, laser threshold and slope efficiency of the continuous-wave laser operation, the results show that the best one of the four samples in spectral and laser characteristics is co-doped 3at%Yb, 6at% Y:CaF2 single crystal, which has an expected potential in the application. The research results provide available references for improving further laser performance of Yb-doped

  1. All-fiber femtosecond Cherenkov radiation source

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Lægsgaard, Jesper; Møller, Uffe

    2012-01-01

    An all-fiber femtosecond source of spectrally isolated Cherenkov radiation is reported, to the best of our knowledge, for the first time. Using a monolithic, self-starting femtosecond Yb-doped fiber laser as the pump source and the combination of photonic crystal fibers as the wave......-conversion medium, we demonstrate milliwatt-level, stable, and tunable Cherenkov radiation at visible wavelengths 580–630 nm, with pulse duration of sub-160-fs, and the 3 dB spectral bandwidth not exceeding 36 nm. Such an all-fiber Cherenkov radiation source is promising for practical applications in biophotonics...

  2. Monolithic Yb-fiber femtosecond laser with intracavity all-solid PBG fiber and ex-cavity HC-PCF

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Liu, Xiaomin; Lægsgaard, Jesper

    2010-01-01

    We demonstrate an all-fiber femtosecond master oscillator / power amplifier operating at the central wavelength of 1033 nm, based on Yb-doped fiber as gain medium, and two different kinds of photonic crystal fibers for dispersion control and stabilization. An all-solid (AS) polarization maintaini...

  3. Yb-doped aluminophosphosilicate ternary fiber with high efficiency and excellent laser stability

    Science.gov (United States)

    Li, Yuwei; Peng, Kun; Zhan, Huan; Liu, Shuang; Ni, Li; Wang, Yuying; Yu, Juan; Wang, Xiaolong; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

    2018-03-01

    By using chelate precursor doping technique and traditional modified chemical vapor deposition system, we fabricated Yb-doped aluminophosphosilicate (Al2O3-P2O5-SiO2, ternary Yb-APS) large-mode-area fiber and reported on its laser performance. The fiber preform was doped with Al, P and Yb with concentration of ∼8000 ppm, ∼1700 ppm and ∼400 ppm in molar percent, respectively. Tested with master oscillator power amplifier system, the home-made Yb-APS fiber was found to present 1.02 kW at 1061.1 nm with a high slope efficiency of 81.2% and excellent laser stability with power fluctuation less than ±1.1% for over 10 h. Compared with Yb-doped aluminosilicate (Al2O3-SiO2, binary Yb-AS) fiber, the introduction of P2O5 effectively suppressed photodarkening effect even the P/Al ratio is much less than 1, indicating that Yb-APS fiber is a better candidate for high power fiber lasers.

  4. Single-mode amplification in Yb-doped rod-type photonic crystal fibers for high brilliance lasers

    DEFF Research Database (Denmark)

    Poli, F.; Lægsgaard, Jesper; Passaro, D.

    2009-01-01

    to identify a proper ring characteristic that is width, position and refractive index. Then rod-type PCF designs have been optimized with a full-vector modal solver based on the finite-element method. Then, the amplification properties of the Yb-doped rod-type PCFs have been investigated by assuming a forward...

  5. Thermal effects in Yb-doped double-cladding Distributed Modal Filtering rod-type fibers

    DEFF Research Database (Denmark)

    Coscelli, Enrico; Poli, Federica; Jørgensen, Mette Marie

    2012-01-01

    The effects of thermally-induced refractive index change in Yb-doped Distributed Modal Filtering (DMF) photonic crystal fibers are investigated, where high-order mode suppression is obtained by resonant coupling with high index elements in the cladding. The temperature distribution on the fiber...... element method. A DMF fiber design, which is single-mode in the 1030 nm–1064 nm region, is considered, and the effects of thermal load on the transmission characteristics are evaluated. Results show a blue-shift of the single-mode window and the single-mode bandwidth narrowing as the absorbed pump power...... cross-section is calculated with an analytical model, for different pump power values. The consequent refractive index change, due to the thermo-optical effect, is applied to the cross-section of the DMF fiber, whose guiding properties are studied with a full-vector modal solver based on the finite...

  6. All-fiber Yb-doped fiber laser passively mode-locking by monolayer MoS2 saturable absorber

    Science.gov (United States)

    Zhang, Yue; Zhu, Jianqi; Li, Pingxue; Wang, Xiaoxiao; Yu, Hua; Xiao, Kun; Li, Chunyong; Zhang, Guangyu

    2018-04-01

    We report on an all-fiber passively mode-locked ytterbium-doped (Yb-doped) fiber laser with monolayer molybdenum disulfide (ML-MoS2) saturable absorber (SA) by three-temperature zone chemical vapor deposition (CVD) method. The modulation depth, saturation fluence, and non-saturable loss of this ML-MoS2 are measured to be 3.6%, 204.8 μJ/cm2 and 6.3%, respectively. Based on this ML-MoS2SA, a passively mode-locked Yb-doped fiber laser has been achieved at 979 nm with pulse duration of 13 ps and repetition rate of 16.51 MHz. A mode-locked fiber laser at 1037 nm is also realized with a pulse duration of 475 ps and repetition rate of 26.5 MHz. To the best of our knowledge, this is the first report that the ML-MoS2 SA is used in an all-fiber Yb-doped mode-locked fiber laser at 980 nm. Our work further points the excellent saturable absorption ability of ML-MoS2 in ultrafast photonic applications.

  7. Yb-doped phosphate double-cladding optical fiber for high-power laser applications

    Science.gov (United States)

    Mura, E.; Scarpignato, G. C.; Lousteau, J.; Boetti, N. G.; Abrate, S.; Milanese, D.

    2013-02-01

    A Yb-doped phosphate glass double cladding optical fiber was prepared using a custom designed glass composition (P2O5 - Al2O3 - Li2O - B2O3 - BaO - PbO - La2O3) for high-power amplifier and laser applications. The preform drawing method was followed, with the preform being fabricated using the rotational casting technique. This technique, previously developed for tellurite, fluoride or chalcogenide glass preforms is reported for the first time using rare earth doped phosphate glasses. The main challenge was to design an adequate numerical aperture between first and second cladding while maintaining similar thermo-mechanical properties in view of the fiber drawing process. The preform used for the fiber drawing was produced by rod-in-tube technique at a rotation speed of 3000 rpm. The rotational casting technique allowed the manufacturing of an optical fiber featuring high quality interfaces between core and internal cladding and between the internal and external cladding, respectively. Loss attenuation was measured using the cut-back method and lasing was demonstrated at 1022 nm by core pumping with a fiber pigtailed laser diode at the wavelength of 976 nm.

  8. Wavelength tunability of laser based on Yb-doped YGAG ceramics

    Science.gov (United States)

    Šulc, Jan; Jelínková, Helena; Jambunathan, Venkatesan; Miura, Taisuke; Endo, Akira; Lucianetti, Antonio; Mocek, TomáÅ.¡

    2015-02-01

    The wavelength tunability of diode pumped laser based on Yb-doped mixed garnet Y3Ga2Al3O12 (Yb:YGAG) ceramics was investigated. The tested Yb:YGAG sample (10% Yb/Y) was in the form of 2mm thick plane-parallel face-polished plate (without AR coatings). A fiber (core diameter 100 μm, NA= 0.22) coupled laser diode (LIMO, LIMO35-F100-DL980-FG-E) with emission at wavelength 969 nm, was used for longitudinal Yb:YGAG pumping. The laser diode was operating in the pulsed regime (2 ms pulse length, 10 Hz repetition rate). The duty-cycle 2% ensured a low thermal load even under the maximum diode pumping power amplitude 20W (ceramics sample was only air-cooled). The 145mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.01 - 1.09 μm, HT @ 0.97 μm) and curved (r = 150mm) output coupler with a reflectivity of ˜ 97% @ 1.01 - 1.09 μm. Wavelength tuning of the ytterbium laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle between the output coupler and the laser active medium. The laser was continuously tunable over ˜ 58nm (from 1022nm to 1080 nm) and the tuning band was mostly limited by the free spectral range of used birefringent filter. The maximum output power amplitude 3W was obtained at wavelength 1046nm for absorbed pump power amplitude 10.6W. The laser slope efficiency was 34%.

  9. Structural characterization and EXAFS wavelet analysis of Yb doped ZnO by wet chemistry route

    Energy Technology Data Exchange (ETDEWEB)

    Otal, Eugenio H., E-mail: eugenio.otal@citedef.gob.ar [Division of Porous Materials, UNIDEF, CITEDEF, CONICET, S.J.B de la Salle 4397, Villa Martelli (B1603ALO), Buenos Aires (Argentina); Laboratory for Materials Science and Technology, FRSC-UTN, Av. Inmigrantes 555, Río Gallegos 9400 (Argentina); Sileo, Elsa [INQUIMAE, Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Aguirre, Myriam H. [Dept. of Physics Condensed Matter, University of Zaragoza (Spain); Laboratory of Advanced Microscopy (LMA), Institute of Nanoscience of Aragón (INA), University of Zaragoza (Spain); Fabregas, Ismael O. [Division of Porous Materials, UNIDEF, CITEDEF, CONICET, S.J.B de la Salle 4397, Villa Martelli (B1603ALO), Buenos Aires (Argentina); Kim, Manuela [Division of Porous Materials, UNIDEF, CITEDEF, CONICET, S.J.B de la Salle 4397, Villa Martelli (B1603ALO), Buenos Aires (Argentina); Laboratory for Materials Science and Technology, FRSC-UTN, Av. Inmigrantes 555, Río Gallegos 9400 (Argentina)

    2015-02-15

    Highlights: • Optical and electrical properties of ZnO are influenced by lanthanide doping. • Optical and electrical properties of ZnO are influenced by lanthanide positioning. • Yb is incorporated in the O{sub h} sites of the wurtzite structure. • There is not Yb{sub 2}O{sub 3} clustering or segregation for treatments below 800 °C. - Abstract: Lanthanide doped ZnO are interesting materials for optical and electrical applications. The wide band gap of this semiconductor makes it transparent in the visible range (E{sub gap} = 3.2 eV), allowing a sharp emission from intra shell transition from the lanthanides. From the electrical side, ZnO is a widely used material in varistors and its electrical properties can be tailored by the inclusion of lanthanides. Both applications are influenced by the location of the lanthanides, grain boundaries or lattice inclusion. Yb doped ZnO samples obtained by wet chemistry route were annealed at different temperatures and characterized by Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Rietveld refinement of XRD data, and X-ray Absorption Fine Structure (XAFS). These techniques allowed to follow the changes occurred in the matrix and the Yb environment. The use of the Cauchy continuous wavelet transform allowed identifying a second coordination shell composed of Zn atoms, supporting the observations from XRD Rietveld refinement and XAFS fittings. The information obtained confirmed the incorporation of Yb in O{sub h} sites of the wurtzite structure without Yb{sub 2}O{sub 3} clustering in the lattice.

  10. Characterization of the lasing properties of a 5%Yb doped Lu.sub.2./sub.SiO.sub.5./sub. crystal along its three optical axes

    Czech Academy of Sciences Publication Activity Database

    Toci, G.; Pirri, A.; Beitlerová, Alena; Shoji, Y.; Yoshikawa, A.; Hybler, Jiří; Nikl, Martin; Vannini, M.

    2015-01-01

    Roč. 23, č. 10 (2015), s. 13210-13221 ISSN 1094-4087 Institutional support: RVO:68378271 Keywords : Lu 2 SiO 5 * Yb-doped * laser Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.148, year: 2015

  11. Single-pass waveguide amplifiers in Er-Yb doped zinc polyphosphate glass fabricated with femtosecond laser pulses.

    Science.gov (United States)

    Fletcher, Luke B; Witcher, Jon J; Troy, Neil; Brow, Richard K; Krol, Denise M

    2012-04-01

    We have investigated the direct fabrication of subsurface waveguide amplifiers in Er-Yb zinc polyphosphate glass by utilizing the relationship between the initial glass composition and the resulting changes to the network structure after modification by fs laser pulses. Waveguides, exhibiting internal gain of 1 dB/cm at 1.53 μm when pumped with 500 mW at 976 nm, were directly fabricated using a regenerative amplified Ti:sapphire 1 kHz, 180 fs laser system. Optical properties as well as insertion losses and internal gain are reported.

  12. Single-pass waveguide amplifiers in Er-Yb doped zinc polyphosphate glass fabricated with femtosecond laser pulses

    NARCIS (Netherlands)

    Fletcher, L.B.; Witcher, J.J.; Troy, N.; Brow, R.K.; Krol, D.M.

    2012-01-01

    We have investigated the direct fabrication of subsurface waveguide amplifiers in Er-Yb zinc polyphosphate glass by utilizing the relationship between the initial glass composition and the resulting changes to the network structure after modification by fs laser pulses. Waveguides, exhibiting

  13. Pulsed laser deposition and thermoelectric properties of In-and Yb-doped CoSb3 skutterudite thin films

    KAUST Repository

    Sarath Kumar, S. R.

    2011-07-29

    In-and Yb-doped CoSb3 thin films were prepared by pulsed laser deposition. Process optimization studies revealed that a very narrow process window exists for the growth of single-phase skutterudite films. The electrical conductivity and Seebeck coefficient measured in the temperature range 300-700 K revealed an irreversible change on the first heating cycle in argon ambient, which is attributed to the enhanced surface roughness of the films or trace secondary phases. A power factor of 0.68 W m-1 K-1 was obtained at ∼700 K, which is nearly six times lower than that of bulk samples. This difference is attributed to grain boundary scattering that causes a drop in film conductivity. Copyright © Materials Research Society 2011.

  14. Lattice dynamics and substrate-dependent transport properties of (In, Yb)-doped CoSb3 skutterudite thin films

    KAUST Repository

    Sarath Kumar, S. R.

    2011-10-24

    Lattice dynamics, low-temperature electrical transport, and high-temperature thermoelectric properties of (In, Yb)-doped CoSb3thin films on different substrates are reported. Pulsed laser deposition under optimized conditions yielded single-phase polycrystalline skutterudite films. Raman spectroscopy studies suggested that In and Yb dopants occupy the cage sites in the skutterudite lattice. Low-temperature electrical transport studies revealed the n-type semiconducting nature of the films with extrinsic and intrinsic conduction mechanisms, in sharp contrast to the degenerate nature reported for identical bulk samples. Calculations yielded a direct bandgap close to 50 meV with no evidence of an indirect gap. The carrier concentration of the films was identical to that reported for the bulk and increased with temperature beyond 250 K. The higher resistivity exhibited is attributed to the enhanced grain boundary scattering in films with a high concentration of grains. The maximum power factor of ∼0.68 W m−1 K−1 obtained at 660 K for the film on glass is found to be nearly four times smaller compared to that reported for the bulk. The observed difference in the power factors of the films on different substrates is explained on the basis of the diffusion of oxygen from the substrates and the formation of highly conducting CoSb2 phase upon the oxidation of CoSb3.

  15. Effects of rare-earth doping on femtosecond laser waveguide writing in zinc polyphosphate glass

    Energy Technology Data Exchange (ETDEWEB)

    Fletcher, Luke B.; Witcher, Jon J.; Troy, Neil; Krol, Denise M. [Department of Applied Science, University of California Davis, Davis, California 95616 (United States); Reis, Signo T.; Brow, Richard K. [Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States)

    2012-07-15

    We have investigated waveguide writing in Er-Yb doped zinc polyphosphate glass using a femtosecond laser with a repetition rate of 1 KHz. We find that fabrication of good waveguides requires a glass composition with an O/P ratio of 3.25. The dependence on laser writing parameters including laser fluence, focusing conditions, and scan speed is reported. Waveguide properties together with absorption and emission data indicate that these glasses can be used for the fabrication of compact, high gain amplifying devices.

  16. Effects of rare-earth doping on femtosecond laser waveguide writing in zinc polyphosphate glass

    International Nuclear Information System (INIS)

    Fletcher, Luke B.; Witcher, Jon J.; Troy, Neil; Krol, Denise M.; Reis, Signo T.; Brow, Richard K.

    2012-01-01

    We have investigated waveguide writing in Er-Yb doped zinc polyphosphate glass using a femtosecond laser with a repetition rate of 1 KHz. We find that fabrication of good waveguides requires a glass composition with an O/P ratio of 3.25. The dependence on laser writing parameters including laser fluence, focusing conditions, and scan speed is reported. Waveguide properties together with absorption and emission data indicate that these glasses can be used for the fabrication of compact, high gain amplifying devices.

  17. Synthesis and thermoelectric properties of rare earth Yb-doped Ba8−xYbxSi30Ga16 clathrates

    International Nuclear Information System (INIS)

    Liu, Lihua; Li, Feng; Wei, Yuping; Chen, Ning; Bi, Shanli; Qiu, Hongmei; Cao, Guohui; Li, Yang

    2014-01-01

    Highlights: • Samples with the chemical formula Ba8− x Yb x Si 30 Ga 16 (x = 0, 0.5, 0.7, 1 and 1.5) were prepared. • Some Yb atoms enter the clathrate lattice to replace Ba, while other Yb atoms are oxidized as Yb 2 O 3 . • The thermal conductivity decreases with Yb-doping. • Thermoelectric figure of merit ZT significantly increased. -- Abstract: The potential thermoelectric and magnetic application of clathrate materials with rare-earth doping is the focus of much of the recent research activity in the synthetic material physics and chemistry. A series of clathrate samples with the chemical formula Ba 8−x Yb x Si 30 Ga 16 (x = 0, 0.5, 0.7, 1 and 1.5) were prepared by combining arc melting, ball milling and spark plasma sintering (SPS) techniques. X-ray diffraction and scanning electronic microscopy combined with energy-dispersive X-ray spectroscopy (EDS) analysis showed the dominant phase to be the type-I clathrate. Whereas, X-ray structural refinement and EDS analysis indicated that some Yb atoms enter the clathrate lattice to replace Ba at 2a sites, while other Yb atoms are oxidized as Yb 2 O 3 precipitated around grain boundaries. The solid solubility of Yb into clathrate lattice yielded x ∼ 0.3. Comparative analysis between Yb-doped and Yb-free clathrates showed that the thermal conductivity decreases with Yb-doping. Consequently, thermoelectric figure of merit ZT significantly increased

  18. High power all-polarization-maintaining photonic crystal fiber monolithic femtosecond nonlinear chirped-pulse amplifier

    Science.gov (United States)

    Lv, Zhiguo; Yang, Zhi; Li, Feng; Yang, Xiaojun; Li, Qianglong; Zhang, Xin; Wang, Yishan; Zhao, Wei

    2018-03-01

    We report on an experimental study on fully fusion spliced high power all-polarization-maintaining Yb-doped photonic crystal fiber (PCF) femtosecond nonlinear chirped-pulse amplifier (CPA), which features large values of the positive third-order dispersion (TOD) superposed from the single-mode fiber stretcher (SMFs) and grating-pair compressor. Compensation of the TOD is realized by means of self-phase modulation (SPM) induced nonlinear phase shift during amplification. Up to 9.8 W of compressed average power at 275 kHz repetition rates with 36 μJ pulse energy and 495 fs pulse width has been obtained. To the best of our knowledge, this is the highest output power generated from the strictly all-fiber nonlinear CPA amplifier in femtosecond domain, which provides a possibility for the industrialized promotion and development of the high energy femtosecond fiber laser.

  19. Density-functional study on the robust ferromagnetism in rare-earth element Yb-doped SnO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kai-Cheng, E-mail: kczhang@yeah.net [College of Mathematics and Physics, Bohai University, Jinzhou 121013 (China); Li, Yong-Feng [Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal ResourcesInner Mongolia University of Science and Technology, Baotou 014010 (China); School of Mathematics, Physics and Biological Engineering, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Liu, Yong [State Key Laboratory of Metastable Materials Science and Technology and College of Science, Yanshan University, Qinhuangdao, Hebei 066004 (China); Chi, Feng [College of Engineering, Bohai University, Jinzhou 121013 (China)

    2014-06-01

    So far, little has been known about the ferromagnetism induced by p–f hybridization. We investigate the magnetic properties of Yb-doped SnO{sub 2} by first-principles calculations. We find that the doped system favors the ferromagnetic state and a room-temperature ferromagnetism can be expected in it. The origin of ferromagnetism can be attributed to the p–f hybridization between Yb impurity and its surrounding oxygen atoms. The formation energy of defect complex is calculated and the magnetic mediation of intrinsic vacancies is studied. Our results reveal that the formation energy of the defect complex with Sn vacancy is about 7.3 eV lower in energy than that with oxygen vacancy. This means Sn vacancy is much easier to form than oxygen vacancy in the presence of Yb substitution. The ferromagnetism of the doped system is greatly enhanced in the presence of Sn vacancies. - Highlights: • Room-temperature ferromagnetism can be expected in Yb-doped SnO{sub 2}. • The origin of ferromagnetism can be attributed to the p–f hybridization between Yb and O atoms. • Oxygen vacancies are much hard to form and contribute little to the ferromagnetism. • Sn vacancies are easy to form under oxygen-rich condition and stabilize the ferromagnetism effectively.

  20. Effect of cryogenic temperature on spectroscopic and laser properties of Er, Yb-doped potassium-lanthanum phosphate glass

    Science.gov (United States)

    Švejkar, Richard; Šulc, Jan; Němec, Michal; Jelínková, Helena; Nitsch, Karel; Cihlář, Antonín.; Král, Robert; Nejezchleb, Karel; Nikl, Martin

    2017-05-01

    Glass matrix doped with rare-earth ions is a promising laser active medium for high power laser systems. Due to amorphous structure of glasses the absorption and emission spectra lines are broader in comparison with crystalline materials thus pumping radiation can be absorbed efficiently, moreover much broader gain bandwidth is suitable for generation of ultra-short pulses. Another advantage of the glass matrix is the possibility to fabricate large volume ingots and simultaneously preservation of sufficient optical quality. The lower thermal conductivity of glasses can be compensated by geometry of the active medium for instance shaped into fibres or discs. We present temperature dependence of spectroscopic and laser properties of newly developed Er, Yb - doped potassium-lanthanum phosphate glass, which is appropriate for generation of radiation at 1.53 μm. The sample of Er,Yb:KLaP glassy mixture was cut into disc shape with dimensions of 2.5 mm (thickness) and 5 mm (diameter) and its faces were polished plan-parallelly without being anti-reflection coated. The temperature dependence of the transmission and emission spectra Er,Yb:KLaP together with the fluorescence decay time were measured the temperature range from 80 to 400 K. The fluorescence lifetime of manifold 4I13/2 (upper laser level) prolonged and the intensity of up-conversion radiation decreased with decreasing temperature. The longitudinal excitation of Er,Yb:KLaP was carried out by a fibre-coupled laser diode (pulse duration 2 ms, repetition rate 10 Hz, pump wavelength 969 nm). Laser resonator was hemispherical, with flat pumping mirror (HR @ 1.5 μm) and spherical output coupler (R = 98 % @ 1.5 - 1.6 μm). The Er,Yb:KLaP glass laser properties were investigated in the temperature range 80 - 300 K. The highest slope efficiency with respect to absorbed pumped power was 6.1 % at 80 K. The maximum output of peak amplitude power was 0.71 W at 80 K, i.e. 1.2 times higher than at 300 K. Tunability of laser

  1. Intervalence charge transfer luminescence: Interplay between anomalous and 5d − 4f emissions in Yb-doped fluorite-type crystals

    Energy Technology Data Exchange (ETDEWEB)

    Barandiarán, Zoila, E-mail: zoila.barandiaran@uam.es; Seijo, Luis [Departamento de Química, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Instituto Universitario de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid, 28049 Madrid (Spain)

    2014-12-21

    In this paper, we report the existence of intervalence charge transfer (IVCT) luminescence in Yb-doped fluorite-type crystals associated with Yb{sup 2+}–Yb{sup 3+} mixed valence pairs. By means of embedded cluster, wave function theory ab initio calculations, we show that the widely studied, very broad band, anomalous emission of Yb{sup 2+}-doped CaF{sub 2} and SrF{sub 2}, usually associated with impurity-trapped excitons, is, rather, an IVCT luminescence associated with Yb{sup 2+}–Yb{sup 3+} mixed valence pairs. The IVCT luminescence is very efficiently excited by a two-photon upconversion mechanism where each photon provokes the same strong 4f{sup 14}–1A{sub 1g}→ 4f{sup 13}({sup 2}F{sub 7/2})5de{sub g}–1T{sub 1u} absorption in the Yb{sup 2+} part of the pair: the first one, from the pair ground state; the second one, from an excited state of the pair whose Yb{sup 3+} moiety is in the higher 4f{sup 13}({sup 2}F{sub 5/2}) multiplet. The Yb{sup 2+}–Yb{sup 3+} → Yb{sup 3+}–Yb{sup 2+} IVCT emission consists of an Yb{sup 2+} 5de{sub g} → Yb{sup 3+} 4f{sub 7/2} charge transfer accompanied by a 4f{sub 7/2} → 4f{sub 5/2} deexcitation within the Yb{sup 2+} 4f{sup 13} subshell: [{sup 2}F{sub 5/2}5de{sub g},{sup 2}F{sub 7/2}] → [{sup 2}F{sub 7/2},4f{sup 14}]. The IVCT vertical transition leaves the oxidized and reduced moieties of the pair after electron transfer very far from their equilibrium structures; this explains the unexpectedly large band width of the emission band and its low peak energy, because the large reorganization energies are subtracted from the normal emission. The IVCT energy diagrams resulting from the quantum mechanical calculations explain the different luminescent properties of Yb-doped CaF{sub 2}, SrF{sub 2}, BaF{sub 2}, and SrCl{sub 2}: the presence of IVCT luminescence in Yb-doped CaF{sub 2} and SrF{sub 2}; its coexistence with regular 5d-4f emission in SrF{sub 2}; its absence in BaF{sub 2} and SrCl{sub 2}; the quenching of

  2. Controlling mode instabilities at 628 W average output power in an Yb-doped rod-type fiber amplifier by active modulation of the pump power

    Science.gov (United States)

    Stihler, Christoph; Jauregui, Cesar; Otto, Hans-Jürgen; Limpert, Jens; Tünnermann, Andreas

    2017-02-01

    The phenomenon of transverse mode instabilities (TMI) is currently the most limiting effect for the scaling of the average output power of fiber laser systems with nearly diffraction-limited beam quality. Thus, it is of high interest to develop efficient mitigation strategies to further enhance the performance of fiber laser systems. By actively modulating the pump power of an Yb-doped rod-type fiber amplifier, it was possible to weaken the thermally-induced refractive index grating along the fiber and, thus, to mitigate TMI to a large extent. A significant advantage of this approach is that it can be easily integrated in any existing fiber-laser system since no further optical components are needed. A function generator connected to the pump diode driver was used to achieve the modulation. With this setup we were able to extract a fully stabilized beam at 1.5 times above the TMI threshold. Furthermore, a stabilization of the beam was still feasible at an average output power of 628 W, which is more than three times higher than the free-running TMI threshold of that particular fiber under identical conditions (e.g. seed power). This is the highest average output power reported from a single-channel rod-type fiber amplifier with a high-quality stabilized beam, to the best of our knowledge.

  3. Direct generation of 2  W average-power and 232  nJ picosecond pulses from an ultra-simple Yb-doped double-clad fiber laser.

    Science.gov (United States)

    Huang, Yizhong; Luo, Zhengqian; Xiong, Fengfu; Li, Yingyue; Zhong, Min; Cai, Zhiping; Xu, Huiying; Fu, Hongyan

    2015-03-15

    We report the generation of 2.06 W average-power and 232 nJ picosecond mode-locked pulses directly from an ultra-simple Yb-doped fiber laser. A section of Yb-doped double-clad fiber pumped by a 976 nm laser diode provides the large gain, and the linear cavity is simply formed by a 1064 nm highly reflective fiber Bragg grating and a fiber loop mirror (FLM) using a 5/95 optical coupler. The asymmetric FLM not only acts as the output mirror for providing ∼20% optical feedback, but also equivalently behaves as a nonlinear optical loop mirror (NOLM) to initiate the mode-locking operation in this cavity. Stable mode-locking is therefore achieved over a pump power of 3.76 W. The mode-locked pulses show the dissipative soliton resonance (DSR), which has the pulse duration of 695 ps to ∼1  ns, and the almost unchanged peak power of ∼200  W as increasing the pump power. In particular, this laser can emit 232 nJ high-energy DSR pulses with an average output power of >2  W. This is, to the best of our knowledge, the first demonstration of such an ultra-simple, mode-locked fiber laser that enables watt-level, high energy, picosecond DSR pulses.

  4. New configurations for short-pulses high power solid-state lasers: conception and realization of highly doped waveguide amplifiers/lasers grown by liquid phase epitaxy and demonstration of Y2SiO5: Yb and Lu2SiO5: Yb femtosecond lasers

    International Nuclear Information System (INIS)

    Thibault, F.

    2006-04-01

    Yb-doped yttrium and lutetium ortho-silicates, Y 2 SiO 5 :Yb and Lu 2 SiO 5 :Yb respectively, exhibit spectroscopic properties favorable to an efficient laser operation in both high power cw and femtosecond regime. Their first diode-pumped femtosecond operation demonstration lead to exceptional performances in terms of output power and efficiency. In order to realize compact and efficient solid-state laser devices using those materials, we chose a configuration with an Yb-doped medium planar waveguide geometry, grown by liquid phase epitaxy, face-pumped by a single laser diode bar. The growth of highly doped Y 2 SiO 5 :Yb layers, within a large range of compositions and thicknesses, was demonstrated. The refractive index increase due to the substitution of the various dopants is analyzed. The layers spectroscopic properties are similar to the bulk ones, with an noticeably higher crystalline quality. The Yb ion lifetime evolution with respect to its doping shows up a particularly low decrease, proof of a low concentration of extrinsic quenching centers. The covered YSO:24%Yb waveguides exhibit lower than 0.3 dB/cm propagation losses, and provided up to 2.9 dB/cm net amplification at 1082 nm with a single mode output. The realization of the first diode-pumped monolithic cw waveguide lasers was also demonstrated. For a 4% output coupler, they provided up to 340 mW at 1082 nm with a 14% slope efficiency. (author)

  5. Femtosecond laser writing of waveguides in zinc phosphate glasses [Invited

    NARCIS (Netherlands)

    Fletcher, L.B.; Witcher, J.J.; Troy, N.; Reis, S.T.; Brow, R.K.; Martinez Vazquez, R.; Osellame, R.; Krol, D.M.|info:eu-repo/dai/nl/068370881

    2011-01-01

    We have studied the relationship between the initial glass composition and the structural changes associated with laser-induced refractive index modification in a series of Er-Yb doped and undoped zinc phosphate glasses. White light microscopy and waveguide experiments are used together with Raman

  6. Femtosecond Laser Filamentation

    CERN Document Server

    Chin, See Leang

    2010-01-01

    Femtosecond Laser Filamentation gives a comprehensive review of the physics of propagation of intense femtosecond laser pulses in optical media (principally air) and the applications and challenges of this new technique. This book presents the modern understanding of the physics of femtosecond laser pulse propagation, including unusual new effects such as the self-transformation of the pulse into a white light laser pulse, intensity clamping, the physics of multiple filamentation and competition, and how filaments’ ability to melt glass leads to wave guide writing. The potential applications of laser filamentation in atmospheric sensing and the generation of other electromagnetic pulses from the UV to the radio frequency are treated, together with possible future challenges in the excitation of super-excited states of molecules. Exciting new phenomena such as filament induced ultrafast birefringence and the excitation of molecular rotational wave packets and their multiple revivals in air (gases) will also ...

  7. Femtosecond laser spectroscopy

    CERN Document Server

    Hannaford, Peter

    2005-01-01

    As concepts and methodologies have evolved over the past two decades, the realm of ultrafast science has become vast and exciting and has impacted many areas of chemistry, biology and physics, and other fields such as materials science, electrical engineering, and optical communication. The field has recently exploded with the announcement of a series of remarkable new developments and advances. This volume surveys this recent growth in eleven chapters written by leading international researchers in the field. It includes sections on femtosecond optical frequency combs, soft x-ray femtosecond laser sources, and attosecond laser sources. In addition, the contributors address real-time spectroscopy of molecular vibrations with sub-5-fs pulses and multidimensional femtosecond coherent spectroscopies for studying molecular and electron dynamics. Novel methods for measuring and characterizing ultrashort laser pulses and ultrashort pulses of light are also described. The topics covered are revolutionizing the field...

  8. Femtosecond laser materials processing

    International Nuclear Information System (INIS)

    Stuart, B.C.

    1997-01-01

    The use femtosecond pulses for materials processing results in very precise cutting and drilling with high efficiency. Energy deposited in the electrons is not coupled into the bulk during the pulse, resulting in negligible shock or thermal loading to adjacent areas

  9. Femtosecond laser materials processing

    Energy Technology Data Exchange (ETDEWEB)

    Stuart, B. C., LLNL

    1998-06-02

    Femtosecond lasers enable materials processing of most any material with extremely high precision and negligible shock or thermal loading to the surrounding area Applications ranging from drilling teeth to cutting explosives to making high-aspect ratio cuts in metals with no heat-affected zone are made possible by this technology For material removal at reasonable rates, we developed a fully computer-controlled 15-Watt average power, 100-fs laser machining system.

  10. Femtosecond lasers for countermeasure applications

    NARCIS (Netherlands)

    Franssen, G.C.; Schleijpen, H.M.A.; Heuvel, J.C. van den; Buersing, H.; Eberle, B.; Walter, D.

    2009-01-01

    In recent years, much advance in the field of high-power femtosecond laser technology has been made. The high pulse power of femtosecond laser systems leads to various interesting phenomena, such as a very high power density and the formation of a plasma in the propagation medium, which is usually

  11. Femtosecond damage resistance of femtosecond multilayer and hybrid mirrors.

    Science.gov (United States)

    Csajbók, Viktória; Szikszai, Lőrinc; Nagy, Benedek J; Dombi, Péter

    2016-08-01

    Improving the laser-induced damage threshold of optical components is a basic endeavor in femtosecond technology. By testing more than 30 different femtosecond mirrors with 42 fs laser pulses at 1 kHz repetition rate, we found that a combination of high-bandgap dielectric materials and improved design and coating techniques enable femtosecond multilayer damage thresholds exceeding 2  J/cm2 in some cases. A significant ×2.5 improvement in damage resistance can also be achieved for hybrid Ag-multilayer mirrors exhibiting more than 1  J/cm2 threshold with a clear anticorrelation between damage resistance and peak field strength in the stack. Slight dependence on femtosecond pulse length and substantial decrease for high (megahertz) repetition rates are also observed.

  12. Effect of Sintering Temperature on Microstructure, Chemical Stability and Electrical Properties of Transition Metal or Yb-Doped BaZr0.1Ce0.7Y0.1M0.1O3-δ (M = Fe, Ni, Co and Yb

    Directory of Open Access Journals (Sweden)

    Behzad eMirfakhraei

    2014-03-01

    Full Text Available Perovskite-type BaZr0.1Ce0.7Y0.1M0.1O3-δ (M = Fe, Ni, Co and Yb (BZCY-M oxides were synthesized using the conventional solid-state reaction method at 1350-1550 oC in air in order to investigate the effect of dopants on sintering, crystal structure, chemical stability under CO2 and H2S, and electrical transport properties. The formation of the single-phase perovskite-type structure with an orthorhombic space group Imam was confirmed by Rietveld refinement using powder X-ray diffraction (PXRD for the Fe, Co, Ni and Yb-doped samples. The BZCY-Co and BZCY-Ni oxides show a total electrical conductivity of 0.01 and 8 × 10-3 Scm-1 at 600 oC in wet H2 with an activation energy of 0.36 and 0.41 eV, respectively. Scanning electron microscopy (SEM and energy-dispersive X-ray analysis (EDX revealed Ba and Co rich secondary phase at the grain-boundaries, which may explain the enhancement in the total conductivity of the BZCY-Co. However, ex-solution of Ni at higher sintering temperatures, especially at 1550 oC, decreases the total conductivity of the BZCY-Ni material. The Co and Ni dopants act as a sintering aid and form dense pellets at a lower sintering temperature of 1250 oC. The Fe, Co and Ni-doped BZCY-M samples synthesized at 1350 oC show stability in 30 ppm H2S/H2 at 800 oC, and increasing the firing temperature to 1550 oC, enhanced the chemical stability in CO2 / N2 (1: 2 at 25-900 oC. The BZCY-Co and Ni compounds with high conductivity in wet H2 could be considered as possible anodes for intermediate temperature solid oxide fuel cells (IT-SOFCs.

  13. Femtosecond optomagnetism in dielectric antiferromagnets

    Science.gov (United States)

    Bossini, D.; Rasing, Th

    2017-02-01

    Optical femtosecond manipulation of magnetic order is attractive for the development of new concepts for ultrafast magnetic recording. Theoretical and experimental investigations in this research area aim at establishing a physical understanding of magnetic media in light-induced non-equilibrium states. Such a quest requires one to adjust the theory of magnetism, since the thermodynamical concepts of elementary excitations and spin alignment determined by the exchange interaction are not applicable on the femtosecond time-scale after the photo-excitation. Here we report some key milestones concerning the femtosecond optical control of spins in dielectric antiferromagnets, whose spin dynamics is by nature faster than that of ferromagnets and can be triggered even without any laser heating. The recent progress of the opto-magnetic effect in the sub-wavelength regime makes this exciting research area even more promising, in terms of both fundamental breakthroughs and technological perspectives.

  14. Advances in femtosecond laser technology

    Directory of Open Access Journals (Sweden)

    Callou TP

    2016-04-01

    Full Text Available Thais Pinheiro Callou, Renato Garcia, Adriana Mukai, Natalia T Giacomin, Rodrigo Guimarães de Souza, Samir J Bechara Department of Ophthalmology, University of Sao Paulo, Sao Paulo, Brazil Abstract: Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures. Keywords: laser therapy, refractive surgical procedures, intracorneal ring, laser in situ keratomileusis, keratoplasty, presbyopia, cataract extraction, astigmatism surgery

  15. Linearly polarized intracavity passive Q-switched Yb-doped ...

    Indian Academy of Sciences (India)

    2014-02-14

    YAG crystal as a saturable absorber. An average output power of 9.4 W with pulse duration of 64 ns and pulse repetition rate of 57.4 kHz with a slope efficiency of 52% was achieved. Measured polarization extinction ratio (PER) ...

  16. Microchip laser operation of Yb-doped gallium garnets

    Czech Academy of Sciences Publication Activity Database

    Serres, J.M.; Jambunathan, Venkatesan; Loiko, P.; Mateos, X.; Yu, H.; Zhang, H.; Liu, J.; Lucianetti, Antonio; Mocek, Tomáš; Yumashev, K.; Griebner, U.; Petrov, V.; Aguilo, M.; Diaz, F.

    2016-01-01

    Roč. 6, č. 1 (2016), s. 46-57 ISSN 2159-3930 R&D Projects: GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.20.0143; GA ČR GA14-01660S Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143 Institutional support: RVO:68378271 Keywords : thermal - conductivity * crystal * temperature * Y 3 AL 5 O 12 * YAG * performance * CNGG Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 2.591, year: 2016

  17. Linearly polarized intracavity passive Q-switched Yb-doped ...

    Indian Academy of Sciences (India)

    2014-02-14

    Feb 14, 2014 ... Q-switched fibre lasers with high peak power have attracted a lot of attention due to many applications in the fields of industrial processing and medical treatments. For special applications of nonlinear frequency shifting like frequency doubling and optical paramet- ric oscillation, linearly polarized ...

  18. Nanoflow electrospinning serial femtosecond crystallography

    International Nuclear Information System (INIS)

    Sierra, Raymond G.; Laksmono, Hartawan; Kern, Jan; Tran, Rosalie; Hattne, Johan; Alonso-Mori, Roberto; Lassalle-Kaiser, Benedikt; Glöckner, Carina; Hellmich, Julia; Schafer, Donald W.; Echols, Nathaniel; Gildea, Richard J.; Grosse-Kunstleve, Ralf W.; Sellberg, Jonas; McQueen, Trevor A.; Fry, Alan R.; Messerschmidt, Marc M.; Miahnahri, Alan; Seibert, M. Marvin; Hampton, Christina Y.; Starodub, Dmitri; Loh, N. Duane; Sokaras, Dimosthenis; Weng, Tsu-Chien; Zwart, Petrus H.; Glatzel, Pieter; Milathianaki, Despina; White, William E.; Adams, Paul D.; Williams, Garth J.; Boutet, Sébastien; Zouni, Athina; Messinger, Johannes; Sauter, Nicholas K.; Bergmann, Uwe; Yano, Junko; Yachandra, Vittal K.; Bogan, Michael J.

    2012-01-01

    A low flow rate liquid microjet method for delivery of hydrated protein crystals to X-ray lasers is presented. Linac Coherent Light Source data demonstrates serial femtosecond protein crystallography with micrograms, a reduction of sample consumption by orders of magnitude. An electrospun liquid microjet has been developed that delivers protein microcrystal suspensions at flow rates of 0.14–3.1 µl min −1 to perform serial femtosecond crystallography (SFX) studies with X-ray lasers. Thermolysin microcrystals flowed at 0.17 µl min −1 and diffracted to beyond 4 Å resolution, producing 14 000 indexable diffraction patterns, or four per second, from 140 µg of protein. Nanoflow electrospinning extends SFX to biological samples that necessitate minimal sample consumption

  19. Nanoflow electrospinning serial femtosecond crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Sierra, Raymond G.; Laksmono, Hartawan [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Kern, Jan [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Tran, Rosalie; Hattne, Johan [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Alonso-Mori, Roberto [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Lassalle-Kaiser, Benedikt [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Glöckner, Carina; Hellmich, Julia [Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin (Germany); Schafer, Donald W. [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Echols, Nathaniel; Gildea, Richard J.; Grosse-Kunstleve, Ralf W. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Sellberg, Jonas [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Stockholm University, S-106 91 Stockholm (Sweden); McQueen, Trevor A. [Stanford University, Stanford, CA 94025 (United States); Fry, Alan R.; Messerschmidt, Marc M.; Miahnahri, Alan; Seibert, M. Marvin; Hampton, Christina Y.; Starodub, Dmitri; Loh, N. Duane; Sokaras, Dimosthenis; Weng, Tsu-Chien [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Zwart, Petrus H. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Glatzel, Pieter [European Synchrotron Radiation Facility, Grenoble (France); Milathianaki, Despina; White, William E. [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Adams, Paul D. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Williams, Garth J.; Boutet, Sébastien [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Zouni, Athina [Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin (Germany); Messinger, Johannes [Umeå Universitet, Umeå (Sweden); Sauter, Nicholas K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Bergmann, Uwe [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Yano, Junko; Yachandra, Vittal K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Bogan, Michael J., E-mail: mbogan@slac.stanford.edu [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States)

    2012-11-01

    A low flow rate liquid microjet method for delivery of hydrated protein crystals to X-ray lasers is presented. Linac Coherent Light Source data demonstrates serial femtosecond protein crystallography with micrograms, a reduction of sample consumption by orders of magnitude. An electrospun liquid microjet has been developed that delivers protein microcrystal suspensions at flow rates of 0.14–3.1 µl min{sup −1} to perform serial femtosecond crystallography (SFX) studies with X-ray lasers. Thermolysin microcrystals flowed at 0.17 µl min{sup −1} and diffracted to beyond 4 Å resolution, producing 14 000 indexable diffraction patterns, or four per second, from 140 µg of protein. Nanoflow electrospinning extends SFX to biological samples that necessitate minimal sample consumption.

  20. All-fiber femtosecond Cherenkov source

    Directory of Open Access Journals (Sweden)

    Tu H.

    2013-03-01

    Full Text Available An all-fiber femtosecond Cherenkov radiation source is demonstrated for the first time, to the best of our knowledge. Using a stable monolithic femtosecond Ybdoped fiber laser as the pump source, and the combination of photonic crystal fibers as the wave-conversion medium, we have generated tunable Cherenkov radiation at visible wavelengths 580 – 630 nm, with pulse duration of sub-160 fs, and the 3 dB spectral bandwidth not exceeding 36 nm. Such femtosecond source can find applications in practical biophotonics such as bio-imaging and microscopy.

  1. All-fiber femtosecond Cherenkov source

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Lægsgaard, Jesper; Møller, Uffe Visbech

    2013-01-01

    An all-fiber femtosecond Cherenkov radiation source is demonstrated for the first time, to the best of our knowledge. Using a stable monolithic femtosecond Ybdoped fiber laser as the pump source, and the combination of photonic crystal fibers as the wave-conversion medium, we have generated tunable...... Cherenkov radiation at visible wavelengths 580 - 630 nm, with pulse duration of sub-160 fs, and the 3 dB spectral bandwidth not exceeding 36 nm. Such femtosecond source can find applications in practical biophotonics such as bio-imaging and microscopy....

  2. Avant-garde femtosecond laser writing

    OpenAIRE

    Kazansky, Peter G.; Beresna, Martynas; Shimotsuma, Yasuhiko; Hirao, Kazuyuki; Svirko, Yuri P.; Aktürk, Selcuk

    2010-01-01

    Recently discovered phenomena of quill and non-reciprocal femtosecond laser writing in glasses and crystals are reviewed. Common beliefs that laser writing does not change when reversing beam scan or propagation direction are challenged.

  3. Generation of Femtosecond Electron and Photon Pulses

    CERN Document Server

    Thongbai, Chitrlada; Kangrang, Nopadol; Kusoljariyakul, Keerati; Rhodes, Michael W; Rimjaem, Sakhorn; Saisut, Jatuporn; Vilaithong, Thiraphat; Wichaisirimongkol, Pathom; Wiedemann, Helmut

    2005-01-01

    Femtosecond electron and photon pulses become a tool of interesting important to study dynamics at molecular or atomic levels. Such short pulses can be generated from a system consisting of an RF-gun with a thermionic cathode, an alpha magnet as a magnetic bunch compressor, and a linear accelerator. The femtosecond electron pulses can be used directly or used as sources to produce electromagnetic radiation of equally short pulses by choosing certain kind of radiation pruduction processes. At the Fast Neutron Research Facility (Thailand), we are especially interested in production of radiation in Far-infrared and X-ray regime. In the far-infrared wavelengths which are longer than the femtosecond pulse length, the radiation is emitted coherently producing intense radiation. In the X-ray regime, development of femtosecond X-ray source is crucial for application in ultrafast science.

  4. Femtosecond Optics: Advanced Devices and Ultrafast Phenomena

    Science.gov (United States)

    2007-05-31

    stability, the drift of the resonance frequency caused by temperature variations as well as drift in the PZT bias offset were minimal and a manual ...with a femtosecond laser," Optics Letters 21(21): 1729-31 (1996). [4] D. Homoelle, S. Wielandy, A. L. Gaeta, N. F. Borrelli , and C. Smith, "Infrared...Streltsov and N. F. Borrelli , "Fabrication and analysis of a directional coupler written in glass by nanojoule femtosecond laser pulses," Optics

  5. 2 micron femtosecond fiber laser

    Science.gov (United States)

    Liu, Jian; Wan, Peng; Yang, Lihmei

    2014-07-29

    Methods and systems for generating femtosecond fiber laser pulses are disclose, including generating a signal laser pulse from a seed laser oscillator; using a first amplifier stage comprising an input and an output, wherein the signal laser pulse is coupled into the input of the first stage amplifier and the output of the first amplifier stage emits an amplified and stretched signal laser pulse; using an amplifier chain comprising an input and an output, wherein the amplified and stretched signal laser pulse from the output of the first amplifier stage is coupled into the input of the amplifier chain and the output of the amplifier chain emits a further amplified, stretched signal laser pulse. Other embodiments are described and claimed.

  6. Femtosecond phacoemulsification: the business and the medicine.

    Science.gov (United States)

    Uy, Harvey S; Edwards, Keith; Curtis, Nick

    2012-01-01

    PURPOSE FOR REVIEW: Phacoemulsification is the preferred method for cataract surgery in the developed world. The number of phacoemulsification procedures performed annually is expected to increase as the population ages. Femtosecond cataract surgery offers several surgical advantages over conventional phacoemulsification and has already attained commercial application in some countries. The purpose of this review is to outline the benefits, risks and commercial issues of femtosecond lasers as applied to cataract surgery. Cataract surgeons are adopting femtosecond technology to perform laser capsulotomy, lens fragmentation, clear cornea incisions and limbal relaxing incisions. Femtosecond lasers clearly perform these surgical steps with greater precision and reproducibility. Further benefits such as improved postoperative refractive results and reduced complication rates are being investigated. Commercial issues have invariably arisen such as cost of installation and operation, value proposition and return on investment. Femtosecond cataract surgery is an evolving procedure that can potentially lead to better and safer surgical outcomes. This review presents the currently available scientific evidence and discusses some of the relevant financial issues concerning this technology.

  7. Femtosecond lasers for microsurgery of cornea

    Energy Technology Data Exchange (ETDEWEB)

    Vartapetov, Sergei K; Khudyakov, D V; Lapshin, Konstantin E; Obidin, Aleksei Z; Shcherbakov, Ivan A

    2012-03-31

    The review of femtosecond laser installations for medical applications is given and a new femtosecond ophthalmologic system for creation of a flap of corneal tissue during the LASIK operation is described. An all-fibre femtosecond laser emitting {approx}400-fs pulses at 1067 nm is used. The pulse repetition rate can vary from 200 kHz up to 1 MHz. The output energy of the femtosecond system does not exceed 1 {mu}J. A specially developed objective with small spherical and chromatic aberrations is applied to focus laser radiation to an area of an eye cornea. The size of the focusing spot does not exceed 3 {mu}m. To process the required area, scanning by a laser beam is applied with a speed no less than 5 m s{sup -1}. At a stage of preliminary tests of the system, the {Kappa}8 glass, organic PMMA glass and specially prepared agarose gels are used as a phantom of an eye. The femtosecond system is successfully clinically tested on a plenty of eyes of a pig and on several human eyes. The duration of the procedure of creation of a corneal flap does not exceed 20 s.

  8. Femtosecond Mode-locked Fiber Laser at 1 μm Via Optical Microfiber Dispersion Management.

    Science.gov (United States)

    Wang, Lizhen; Xu, Peizhen; Li, Yuhang; Han, Jize; Guo, Xin; Cui, Yudong; Liu, Xueming; Tong, Limin

    2018-03-16

    Mode-locked Yb-doped fiber lasers around 1 μm are attractive for high power applications and low noise pulse train generation. Mode-locked fiber lasers working in soliton and stretched-pulse regime outperform others in terms of the laser noise characteristics, mechanical stability and easy maintenance. However, conventional optical fibers always show a normal group velocity dispersion around 1 μm, leading to the inconvenience for necessary dispersion management. Here we show that optical microfibers having a large anomalous dispersion around 1 μm can be integrated into mode-locked Yb-doped fiber lasers with ultralow insertion loss down to -0.06 dB, enabling convenient dispersion management of the laser cavity. Besides, optical microfibers could also be adopted to spectrally broaden and to dechirp the ultrashort pulses outside the laser cavity, giving rise to a pulse duration of about 110 fs. We believe that this demonstration may facilitate all-fiber format high-performance ultrashort pulse generation at 1 μm and may find applications in precision measurements, large-scale facility synchronization and evanescent-field-based optical sensing.

  9. Femtosecond Laser Filamentation for Atmospheric Sensing

    Directory of Open Access Journals (Sweden)

    Huai Liang Xu

    2010-12-01

    Full Text Available Powerful femtosecond laser pulses propagating in transparent materials result in the formation of self-guided structures called filaments. Such filamentation in air can be controlled to occur at a distance as far as a few kilometers, making it ideally suited for remote sensing of pollutants in the atmosphere. On the one hand, the high intensity inside the filaments can induce the fragmentation of all matters in the path of filaments, resulting in the emission of characteristic fluorescence spectra (fingerprints from the excited fragments, which can be used for the identification of various substances including chemical and biological species. On the other hand, along with the femtosecond laser filamentation, white-light supercontinuum emission in the infrared to UV range is generated, which can be used as an ideal light source for absorption Lidar. In this paper, we present an overview of recent progress concerning remote sensing of the atmosphere using femtosecond laser filamentation.

  10. Flow induced by a femtosecond laser filament

    Science.gov (United States)

    Pouya, Shahram; Koochesfahani, Manoochehr

    2017-11-01

    Propagation of femtosecond pulsed lasers is of interest to a variety of applications in science and engineering. These laser sources also provide an attractive tool for molecular tagging velocimetry in air (e.g. FLEET). However, high power density of such short pulse lasers can potentially lead to flow perturbations. In this work we present PIV measurements in air around a high repetition rate (1 KHz) focused femtosecond laser beam and quantify the level of flow disturbances that it introduces in its vicinity. Results are shown for various pulse energy levels and the time scale for generation of flow disturbance. These results provide information about the measurement constraints when using femtosecond lasers in molecular tagging velocimetry. This work was supported by AFOSR Award Numbers FA9550-13-1-0034 and FA9550-15-1-0224.

  11. Laser-Induced Damage with Femtosecond Pulses

    Science.gov (United States)

    Kafka, Kyle R. P.

    The strong electric fields of focused femtosecond laser pulses lead to non-equilibrium dynamics in materials, which, beyond a threshold intensity, causes laser-induced damage (LID). Such a strongly non-linear and non-perturbative process renders important LID observables like fluence and intensity thresholds and damage morphology (crater) extremely difficult to predict quantitatively. However, femtosecond LID carries a high degree of precision, which has been exploited in various micro/nano-machining and surface engineering applications, such as human eye surgery and super-hydrophobic surfaces. This dissertation presents an array of experimental studies which have measured the damage behavior of various materials under femtosecond irradiation. Precision experiments were performed to produce extreme spatio-temporal confinement of the femtosecond laser-solid damage interaction on monocrystalline Cu, which made possible the first successful direct-benchmarking of LID simulation with realistic damage craters. A technique was developed to produce laser-induced periodic surface structures (LIPSS) in a single pulse (typically a multi-pulse phenomenon), and was used to perform a pump-probe study which revealed asynchronous LIPSS formation on copper. Combined with 1-D calculations, this new experimental result suggests more drastic electron heating than expected. Few-cycle pulses were used to study the LID performance and morphology of commercial ultra-broadband optics, which had not been systematically studied before. With extensive surface analysis, various morphologies were observed, including LIPSS, swelling (blisters), simple craters, and even ring-shaped structures, which varied depending on the coating design, number of pulses, and air/vacuum test environment. Mechanisms leading to these morphologies are discussed, many of which are ultrafast in nature. The applied damage behavior of multi-layer dielectric mirrors was measured and compared between long pulse (150 ps

  12. Amorphization of silicon by femtosecond laser pulses

    International Nuclear Information System (INIS)

    Jia, Jimmy; Li Ming; Thompson, Carl V.

    2004-01-01

    We have used femtosecond laser pulses to drill submicron holes in single crystal silicon films in silicon-on-insulator structures. Cross-sectional transmission electron microscopy and energy dispersive x-ray analysis of material adjacent to the ablated holes indicates the formation of a layer of amorphous Si. This demonstrates that even when material is ablated using femtosecond pulses near the single pulse ablation threshold, sufficient heating of the surrounding material occurs to create a molten zone which solidifies so rapidly that crystallization is bypassed

  13. Femtosecond tunneling response of surface plasmon polaritons

    DEFF Research Database (Denmark)

    Keil, Ulrich Dieter Felix; Ha, Taekjip; Jensen, Jacob Riis

    1998-01-01

    We obtain femtosecond (200 fs) time resolution using a scanning tunneling microscope on surface plasmon polaritons (SPPs) generated by two 100 fs laser beams in total internal reflection geometry. The tunneling gap dependence of the signal clearly indicates the tunneling origin of the signal...... and suggests that nanometer spatial resolution can be obtained together with femtosecond temporal resolution. This fast response, in contrast to the picosecond decay time of SPPs revealed by differential reflectivity measurements, can be attributed to a coherent superposition of SPPs rectified at the tunneling...... junction. (C) 1998 American Institute of Physics. [S0003-6951(98)02223-2]....

  14. Femtosecond laser ablation of dentin

    Science.gov (United States)

    Alves, S.; Oliveira, V.; Vilar, R.

    2012-06-01

    The surface morphology, structure and composition of human dentin treated with a femtosecond infrared laser (pulse duration 500 fs, wavelength 1030 nm, fluences ranging from 1 to 3 J cm-2) was studied by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The average dentin ablation threshold under these conditions was 0.6 ± 0.2 J cm-2 and the ablation rate achieved in the range 1 to 2 µm/pulse for an average fluence of 3 J cm-2. The ablation surfaces present an irregular and rugged appearance, with no significant traces of melting, deformation, cracking or carbonization. The smear layer was entirely removed by the laser treatment. For fluences only slightly higher than the ablation threshold the morphology of the laser-treated surfaces was very similar to the dentin fracture surfaces and the dentinal tubules remained open. For higher fluences, the surface was more porous and the dentin structure was partially concealed by ablation debris and a few resolidified droplets. Independently on the laser processing parameters and laser processing method used no sub-superficial cracking was observed. The dentin constitution and chemical composition was not significantly modified by the laser treatment in the processing parameter range used. In particular, the organic matter is not preferentially removed from the surface and no traces of high temperature phosphates, such as the β-tricalcium phosphate, were observed. The achieved results are compatible with an electrostatic ablation mechanism. In conclusion, the high beam quality and short pulse duration of the ultrafast laser used should allow the accurate preparation of cavities, with negligible damage of the underlying material.

  15. Femtosecond laser ablation of dentin

    International Nuclear Information System (INIS)

    Alves, S; Vilar, R; Oliveira, V

    2012-01-01

    The surface morphology, structure and composition of human dentin treated with a femtosecond infrared laser (pulse duration 500 fs, wavelength 1030 nm, fluences ranging from 1 to 3 J cm -2 ) was studied by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The average dentin ablation threshold under these conditions was 0.6 ± 0.2 J cm -2 and the ablation rate achieved in the range 1 to 2 µm/pulse for an average fluence of 3 J cm -2 . The ablation surfaces present an irregular and rugged appearance, with no significant traces of melting, deformation, cracking or carbonization. The smear layer was entirely removed by the laser treatment. For fluences only slightly higher than the ablation threshold the morphology of the laser-treated surfaces was very similar to the dentin fracture surfaces and the dentinal tubules remained open. For higher fluences, the surface was more porous and the dentin structure was partially concealed by ablation debris and a few resolidified droplets. Independently on the laser processing parameters and laser processing method used no sub-superficial cracking was observed. The dentin constitution and chemical composition was not significantly modified by the laser treatment in the processing parameter range used. In particular, the organic matter is not preferentially removed from the surface and no traces of high temperature phosphates, such as the β-tricalcium phosphate, were observed. The achieved results are compatible with an electrostatic ablation mechanism. In conclusion, the high beam quality and short pulse duration of the ultrafast laser used should allow the accurate preparation of cavities, with negligible damage of the underlying material. (paper)

  16. Development of a high power femtosecond laser

    CSIR Research Space (South Africa)

    Neethling, PH

    2010-10-01

    Full Text Available the pulses from the Coherent Mira/BMI amplified femtosecond laser at the LRI. Ideally the OPCPA stage should be pumped by a 100 ? 300 ps laser with tens of mJ pulse energy, matching the stretched pulse duration. This laser will be developed by the CSIR...

  17. Femtosecond laser control of chemical reactions

    CSIR Research Space (South Africa)

    Du Plessis, A

    2010-08-31

    Full Text Available Femtosecond laser control of chemical reactions is made possible through the use of pulse-shaping techniques coupled to a learning algorithm feedback loop – teaching the laser pulse to control the chemical reaction. This can result in controllable...

  18. Bending diamonds by femtosecond laser ablation

    DEFF Research Database (Denmark)

    Balling, Peter; Esberg, Jakob; Kirsebom, Kim

    2009-01-01

    We present a new method based on femtosecond laser ablation for the fabrication of statically bent diamond crystals. Using this method, curvature radii of 1 m can easily be achieved, and the curvature obtained is very uniform. Since diamond is extremely tolerant to high radiation doses, partly due...

  19. Aluminum alloy nanosecond vs femtosecond laser marking

    Indian Academy of Sciences (India)

    Femtosecond laser marking may bring con- sistent improvement in the visual and processing quality of the writing (Reif 2010), allowing micromachining with a ..... This paper was realized with the support of EURODOC. “Doctoral Scholarships for research performance at Euro- pean level” Project, financed by European ...

  20. Characteristics and Applications of Spatiotemporally Focused Femtosecond Laser Pulses

    Directory of Open Access Journals (Sweden)

    Chenrui Jing

    2016-12-01

    Full Text Available Simultaneous spatial and temporal focusing (SSTF of femtosecond laser pulses gives rise to strong suppression of nonlinear self-focusing during the propagation of the femtosecond laser beam. In this paper, we begin with an introduction of the principle of SSTF, followed by a review of our recent experimental results on the characterization and application of the spatiotemporally focused pulses for femtosecond laser micromachining. Finally, we summarize all of the results and give a future perspective of this technique.

  1. Use of the Femtosecond Lasers in Ophthalmology

    Science.gov (United States)

    Roszkowska, Anna M.; Urso, Mario; Signorino, Alberto; Aragona, Pasquale

    2018-01-01

    Femtosecond laser (FSL) is an infrared laser with a wavelength of 1053 nm. FS laser works producing photodisruption or photoionization of the optically transparent tissue such as cornea. Currently FS lasers have a wide range of applications in ophthalmic surgery. They are used above all in corneal surgery in refractive procedures and keratoplasty, and recently in cataract surgery. The use of the FSL in corneal refractive surgery includes LASIK flap creation, astigmatic keratotomy, Femtosecond Lenticule Extraction (FLEx), Small Incision Lenticule Extraction (SMILE) and channels creation for implantation of the intrastromal corneal rings. As to the corneal grafting, the FS lasers are used in laser-assisted anterior and posterior lamellar keratoplasty and customized trephination in the penetrating keratoplasty. FS Laser Assisted Cataract Surgery (FLACS) includes capsulorrhexis and nuclear fragmentation that enhance safety and efficacy of the procedure.

  2. Preliminary Design of a Femtosecond Oscilloscope

    CERN Document Server

    Gazazyan, Edmond D; Kalantaryan, Davit K; Laziev, Edouard; Margaryan, Amour

    2005-01-01

    The calculations on motion of electrons in a finite length electromagnetic field of linearly and circularly polarized laser beams have shown that one can use the transversal deflection of electrons on a screen at a certain distance after the interaction region for the measurement of the length and longitudinal particle distribution of femtosecond bunches. In this work the construction and preliminary parameters of various parts of a device that may be called femtosecond oscilloscope are considered. The influence of various factors, such as the energy spread and size of the electron bunches, are taken into account. For CO2 laser intensity 1016 W/cm2 and field free drift length 1m the deflection is 5.3 and 0.06 cm, while the few centimeters long interaction length between 2 mirrors requires assembling accuracy 6 mm and 1.3 micron for 20 MeV to 50 keV, respectively.

  3. Progress in Cherenkov femtosecond fiber lasers

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Svane, Ask Sebastian; Lægsgaard, Jesper

    2016-01-01

    We review the recent developments in the field of ultrafast Cherenkov fiber lasers. Two essential properties of such laser systems—broad wavelength tunability and high efficiency of Cherenkov radiation wavelength conversion are discussed. The exceptional performance of the Cherenkov fiber laser...... systems are highlighted—dependent on the realization scheme, the Cherenkov lasers can generate the femtosecond output tunable across the entire visible and even the UV range, and for certain designs more than 40% conversion efficiency from the pump to Cherenkov signal can be achieved. The femtosecond...... Cherenkov laser with all-fiber architecture is presented and discussed. Operating in the visible range, it delivers 100–200 fs wavelength-tunable pulses with multimilliwatt output power and exceptionally low noise figure an order of magnitude lower than the traditional wavelength tunable supercontinuumbased...

  4. Femtosecond laser additive manufacturing of YSZ

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jian; Bai, Shuang [PolarOnyx, Inc., San Jose, CA (United States)

    2017-04-15

    Laser additive manufacturing (LAM) of Yttria-Stabilized Zirconia (YSZ) is investigated using femtosecond (fs) fiber lasers. Various processing conditions are studied, which leads to desired characteristics in terms of morphology, porosity, hardness, microstructural and mechanical properties of the processed components. High-density (>99%) YSZ part with refined grain and increased hardness was obtained. Microstructure features of fabricated specimens were studied with SEM, EDX, the measured micro hardness is achieved as high as 18.84 GPa. (orig.)

  5. Femtosecond Laser Filamentation for Atmospheric Sensing

    OpenAIRE

    Huai Liang Xu; See Leang Chin

    2010-01-01

    Powerful femtosecond laser pulses propagating in transparent materials result in the formation of self-guided structures called filaments. Such filamentation in air can be controlled to occur at a distance as far as a few kilometers, making it ideally suited for remote sensing of pollutants in the atmosphere. On the one hand, the high intensity inside the filaments can induce the fragmentation of all matters in the path of filaments, resulting in the emission of characteristic fluorescence sp...

  6. Review: Femtosecond Laser Assisted Cataract Surgery (FLACS): An ...

    African Journals Online (AJOL)

    Age-related cataract is one of the most important causes of visual impairment, and cataract surgery is one of the commonest surgeries performed worldwide. Femtosecond laser assisted cataract surgery (FLACS) is a new and promising technology in the arena of cataract operations. Femtosecond lasers (FSL) are used in ...

  7. Parallel femtosecond laser processing with vector-wave control

    Directory of Open Access Journals (Sweden)

    Hayasaki Yoshio

    2013-11-01

    Full Text Available Parallel femtosecond laser processing with a computer-generated hologram displayed on a spatial light modulator, has the advantages of high throughput and high energy-use efficiency. for further increase of the processing efficiency, we demonstrated parallel femtosecond laser processing with vector-wave control that is based on polarization control using a pair of spatial light modulators.

  8. Femtosecond lasers in ophthalmology: clinical applications in anterior segment surgery

    Science.gov (United States)

    Juhasz, Tibor; Nagy, Zoltan; Sarayba, Melvin; Kurtz, Ronald M.

    2010-02-01

    The human eye is a favored target for laser surgery due to its accessibility via the optically transparent ocular tissue. Femtosecond lasers with confined tissue effects and minimized collateral tissue damage are primary candidates for high precision intraocular surgery. The advent of compact diode-pumped femtosecond lasers, coupled with computer controlled beam delivery devices, enabled the development of high precision femtosecond laser for ophthalmic surgery. In this article, anterior segment femtosecond laser applications currently in clinical practice and investigation are reviewed. Corneal procedures evolved first and remain dominant due to easy targeting referenced from a contact surface, such as applanation lenses placed on the eye. Adding a high precision imaging technique, such as optical coherence tomography (OCT), can enable accurate targeting of tissue beyond the cornea, such as the crystalline lens. Initial clinical results of femtosecond laser cataract surgery are discussed in detail in the latter portion part of the article.

  9. Optofluidic Microlasers based on Femtosecond Micromachining Technology

    Directory of Open Access Journals (Sweden)

    Simoni F.

    2017-08-01

    Full Text Available We present the different optofluidic lasers which have been realized using the Femtosecond Micromachining technique to fabricate the monolithic optofluidic structures in glass chips. We show how the great flexibility of this 3D technique allows getting different kind of optical cavities. The most recent devices fabricated by this technique as ring shaped and Fabry-Perot resonators show excellent emission performances.We also point out how the addition of the inkjet printing technique provides further opportunities in realizing optofluidic chips.

  10. Colorizing metals with femtosecond laser pulses

    International Nuclear Information System (INIS)

    Vorobyev, A. Y.; Guo Chunlei

    2008-01-01

    For centuries, it had been the dream of alchemists to turn inexpensive metals into gold. Certainly, it is not enough from an alchemist's point of view to transfer only the appearance of a metal to gold. However, the possibility of rendering a certain metal to a completely different color without coating can be very interesting in its own right. In this work, we demonstrate a femtosecond laser processing technique that allows us to create a variety of colors on a metal that ultimately leads us to control its optical properties from UV to terahertz

  11. Femtosecond laser studies of ultrafast intramolecular processes

    Energy Technology Data Exchange (ETDEWEB)

    Hayden, C. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    The goal of this research is to better understand the detailed mechanisms of chemical reactions by observing, directly in time, the dynamics of fundamental chemical processes. In this work femtosecond laser pulses are used to initiate chemical processes and follow the progress of these processes in time. The authors are currently studying ultrafast internal conversion and subsequent intramolecular relaxation in unsaturated hydrocarbons. In addition, the authors are developing nonlinear optical techniques to prepare and monitor the time evolution of specific vibrational motions in ground electronic state molecules.

  12. Femtosecond electron bunches, source and characterization

    International Nuclear Information System (INIS)

    Thongbai, C.; Kusoljariyakul, K.; Rimjaem, S.; Rhodes, M.W.; Saisut, J.; Thamboon, P.; Wichaisirimongkol, P.; Vilaithong, T.

    2008-01-01

    A femtosecond electron source has been developed at the Fast Neutron Research Facility (FNRF), Chiang Mai University, Thailand. So far, it has produced electron bunches as short as σ z ∼180 fs with (1-6)x10 8 electrons per microbunch. The system consists of an RF-gun with a thermionic cathode, an alpha-magnet as a magnetic bunch compressor, and a linear accelerator as a post acceleration section. Coherent transition radiation emitted at wavelengths equal to and longer than the bunch length is used in a Michelson interferometer to determine the bunch length by autocorrelation technique. The experimental setup and results of the bunch length measurement are described

  13. Preliminary observation of refractive cataract surgery assisted by femtosecond laser

    Directory of Open Access Journals (Sweden)

    Xiao-Li Wang

    2015-12-01

    Full Text Available AIM:To compare the differences of visual acuity and corneal astigmatism postoperatively between conventional refractive cataract surgery and that assisted by femtosecond laser.METHODS:Sixty patients(60 eyeswith age-related cataract and cornea astigmatism were divided into femtosecond group and conventional group randomly or voluntarily. The flat shaft, steep shaft and diopter of corneal astigmatism in patients in femtosecond group were inputted into the online vector calculators to get the location and width of the incision. Then femtosecond laser was used to make corneal releasing incision, the main and auxiliary incision. Phacoemulsification and aspheric multifocal intraocular lens implantation were undergone. Patients in conventional group received full-thickness relaxing incision by cornea paracentesis knife at the steepest meridian axis during phacoemulsification. Then aspheric multifocal intraocular lenses were implanted. Uncorrected distance visual acuity(UCDVA, uncorrected near visual acuity(UCNVAand cornea astigmatism were observed at 1d,1wk and 1mo postoperative. RESULTS:UCVA of patients in both groups was improved after the surgeries. UCDVA and UCNVA of femtosecond group were higher than those of conventional group, while the cornea astigmatism of femtosecond group was lower than that of conventional group.CONCLUSION:Refractile cataract surgery assisted by femtosecond laser canoffer better visual quality than conventional refractive cataract surgery because of lower cornea astigmatism and better visual acuity.

  14. Attomicroscopy: from femtosecond to attosecond electron microscopy

    Science.gov (United States)

    Hassan, Mohammed Th

    2018-02-01

    In the last decade, the development of ultrafast electron diffraction (UED) and microscopy (UEM) have enabled the imaging of atomic motion in real time and space. These pivotal table-top tools opened the door for a vast range of applications in different areas of science spanning chemistry, physics, materials science, and biology. We first discuss the basic principles and recent advancements, including some of the important applications, of both UED and UEM. Then, we discuss the recent advances in the field that have enhanced the spatial and temporal resolutions, where the latter, is however, still limited to a few hundreds of femtoseconds, preventing the imaging of ultrafast dynamics of matter lasting few tens of femtoseconds. Then, we present our new optical gating approach for generating an isolated 30 fs electron pulse with sufficient intensity to attain a temporal resolution on the same time scale. This achievement allows, for the first time, imaging the electron dynamics of matter. Finally, we demonstrate the feasibility of the optical gating approach to generate an isolated attosecond electron pulse, utilizing our recently demonstrated optical attosecond laser pulse, which paves the way for establishing the field of ‘Attomicroscopy’, ultimately enabling us to image the electron motion in action.

  15. Femtosecond laser's application in the corneal surgery

    Directory of Open Access Journals (Sweden)

    Shu-Liang Wang

    2015-10-01

    Full Text Available With the rapid development over the past two decades,femtosecond(10-15slasers(FShas become a new application in ophthalmic surgery. As laser power is defined as energy delivered per unit time, decreasing the pulse duration to femtosecond level(100fsnot only increases the power delivered but also decreases the fluence threshold for laser induced optical breakdown. In ablating tissue, FS has an edge over nanosecond lasers as there is minimal collateral damage from shock waves and heat conduction during surgical ablation. Thus, application of FS has been widely spread, from flap creation for laser-assisted in situ keratomileusis(LASIKsurgery, cutting of donor and recipient corneas in keratoplasty, creation of pockets for intracorneal ring implantation. FS applied in keratoplasty is mainly used in making graft and recipient bed, and can exactly cut different tissue of keratopathy. FS can also cut partial tissue of cornea, even if it is under the moderate corneal macula and corneal edema condition.

  16. Imaging femtosecond laser-induced electronic excitation in glass

    International Nuclear Information System (INIS)

    Mao Xianglei; Mao, Samuel S.; Russo, Richard E.

    2003-01-01

    While substantial progress has been achieved in understanding laser ablation on the nanosecond and picosecond time scales, it remains a considerable challenge to elucidate the underlying mechanisms during femtosecond laser material interactions. We present experimental observations of electronic excitation inside a wide band gap glass during single femtosecond laser pulse (100 fs, 800 nm) irradiation. Using a femtosecond time-resolved imaging technique, we measured the evolution of a laser-induced electronic plasma inside the glass and calculated the electron number density to be on the order of 10 19 cm -3

  17. Recent status on femtosecond laser-assisted cataract surgery

    Directory of Open Access Journals (Sweden)

    Xiao-Ming Wang

    2014-05-01

    Full Text Available Femtosecond laser-assisted cataract surgery performs the anterior capsulotomy, lens fragmentation, corneal incisions making and astigmatic limbal relaxing incision with femtosecond laser, which effectively reduces the complications of conventional phacoemulsification surgery and improves the postoperative visual quality of patients. It further improves the technology and effect of cataract surgery and has broad clinical application prospects. This paper compares pros and cons as well as the clinical values of femtosecond laser-assisted cataract surgery with conventional phacoemulsification surgery based on the overview of published articles.

  18. Femtosecond laser 3D micromachining for microfluidic and optofluidic applications

    CERN Document Server

    Sugioka, Koji

    2013-01-01

    Femtosecond lasers opened up new avenue in materials processing due to its unique features of ultrashort pulse width and extremely high peak intensity. One of the most important features of femtosecond laser processing is that strong absorption can be induced even by materials which are transparent to the femtosecond laser beam due to nonlinear multiphoton absorption. The multiphoton absorption allows us to perform not only surface but also three-dimensionally internal microfabrication of transparent materials such as glass. This capability makes it possible to directly fabricate three-dimensi

  19. Pico-femtosecond image-tube photography in quantum electronics

    International Nuclear Information System (INIS)

    Schelev, M Ya

    2001-01-01

    The possibility of experimental achievement of the time resolution of image-converter tubes (ICTs) corresponding to the theoretical limit of 10 fs is considered as applied to quantum electronics problems. A new generation of ICTs with a temporal resolution of 200 - 500 fs has been developed for recording femtosecond laser radiation. The entirely new devices based on time-analysing ICTs such as femtosecond photoelectronic diffractometers, have been created for studying the dynamics of phase transitions in substances using diffrac-tion of electrons with energies ranging from 20 to 40 keV. (femtosecond technologies)

  20. Multi-Parameter Measurement in Unseeded Flows using Femtosecond Lasers

    Data.gov (United States)

    National Aeronautics and Space Administration — Our approach is to use new turn-key femtosecond laser technology along with new high-speed CMOS camera technology to build a multi-parameter measurement system based...

  1. Unilateral keratectasia treated with femtosecond fashioned intrastromal corneal inlay

    Directory of Open Access Journals (Sweden)

    Khosrow Jadidi

    2017-01-01

    conclusion: Femtosecond laser–assisted pocket creation for the implantation of corneal inlays offers accuracy of pocket parameters, enhancing predictability, resulting in better final outcomes, and improving the safety of the procedure.

  2. Femtosecond laser induced phenomena in transparent solid materials

    DEFF Research Database (Denmark)

    Tan, D.Z.; Sharafudeen, K.N.; Yue, Yuanzheng

    2016-01-01

    The interaction of intense femtosecond laser pulses with transparent materials is a topic that has caused great interest of scientists over the past two decades. It will continue to be a fascinating field in the coming years. This is because many challenging fundamental problems have not been...... solved, especially concerning the interaction of strong, ultra-short electromagnetic pulses with matter, and also because potential advanced technologies will emerge due to the impressive capability of the intense femtosecond laser to create new material structures and hence functionalities. When......–matter interaction, and fabricate various integrated micro-devices. In recent years we have witnessed exciting development in understanding and applying femtosecond laser induced phenomena in transparent materials. The interaction of femtosecond laser pulses with transparent materials relies on non...

  3. Femtosecond Amplifiers and Microlasers in the Deep Ultraviolet

    Science.gov (United States)

    2013-11-19

    the ultraviolet (UV) and visible regions of the spectrum, as well as their applications in photochemistry and medical therapeutics. We believe that...FEMTOSECOND AMPLIFIERS AND MICROLASERS IN DEEP ULTRAVIOLET J GARY EDEN UNIVERSITY OF ILLINOIS 11/19/2013 Final Report DISTRIBUTION A: Distribution...Performance Report 15/08/2010 - 14/08/2013 Femtosecond Amplifiers and Microlasers in the Deep Ultraviolet FA9550-10-1-0456 Eden, James Gary Professor

  4. Cascaded Soliton Compression of Energetic Femtosecond Pulses at 1030 nm

    DEFF Research Database (Denmark)

    Bache, Morten; Zhou, Binbin

    2012-01-01

    We discuss soliton compression with cascaded second-harmonic generation of energetic femtosecond pulses at 1030 nm. We discuss problems encountered with soliton compression of long pulses and show that sub-10 fs compressed pulses can be achieved.......We discuss soliton compression with cascaded second-harmonic generation of energetic femtosecond pulses at 1030 nm. We discuss problems encountered with soliton compression of long pulses and show that sub-10 fs compressed pulses can be achieved....

  5. Femtosecond fiber laser welding of dissimilar metals.

    Science.gov (United States)

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

    2014-10-01

    In this paper, welding of dissimilar metals was demonstrated for the first time, to the best of our knowledge, by using a high-energy high-repetition-rate femtosecond fiber laser. Metallurgical and mechanical properties were investigated and analyzed under various processing parameters (pulse energy, repetition rate, and welding speed). Results showed that the formation of intermetallic brittle phases and welding defects could be effectively reduced. Strong welding quality with more than 210 MPa tensile strength for stainless steel-aluminum and 175 MPa tensile strength for stainless steel-magnesium has been demonstrated. A minimal heat affected zone and uniform and homogenous phase transformation in the welding region have been demonstrated. This laser-welding technique can be extended for various applications in semiconductor, automobile, aerospace, and biomedical industries.

  6. Femtosecond laser enabled keratoplasty for advanced keratoconus

    Directory of Open Access Journals (Sweden)

    Yathish Shivanna

    2013-01-01

    Full Text Available Purpose : To assess the efficacy and advantages of femtosecond laser enabled keratoplasty (FLEK over conventional penetrating keratoplasty (PKP in advanced keratoconus. Materials and Methods: Detailed review of literature of published randomized controlled trials of operative techniques in PKP and FLEK. Results: Fifteen studies were identified, analyzed, and compared with our outcome. FLEK was found to have better outcome in view of better and earlier stabilization uncorrected visual acuity (UCVA, best corrected visual acuity (BCVA, and better refractive outcomes with low astigmatism as compared with conventional PKP. Wound healing also was noticed to be earlier, enabling early suture removal in FLEK. Conclusions: Studies relating to FLEK have shown better results than conventional PKP, however further studies are needed to assess the safety and intraoperative complications of the procedure.

  7. Femtosecond Lasers in Ophthalmology: Surgery and Imaging

    Science.gov (United States)

    Bille, J. F.

    Ophthalmology has traditionally been the field with prevalent laser applications in medicine. The human eye is one of the most accessible human organs and its transparency for visible and near-infrared light allows optical techniques for diagnosis and treatment of almost any ocular structure. Laser vision correction (LVC) was introduced in the late 1980s. Today, the procedural ease, success rate, and lack of disturbing side-effects in laser assisted in-situ keratomileusis (LASIK) have made it the most frequently performed refractive surgical procedure (keratomileusis(greek): cornea-flap-cutting). Recently, it has been demonstrated that specific aspects of LVC can take advantage of unique light-matter interaction processes that occur with femtosecond laser pulses.

  8. 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.

  9. Femtosecond laser technologies for linear collider designs

    CERN Document Server

    Kobayashi, K

    2001-01-01

    A highly stabilized high-energy femtosecond laser system was developed for Compton X-ray experiments. The laser system is based on the chirped pulse amplification, and each component is actively or passively stabilized. A master oscillator with less than 100 fs timing jitter, two independent oscillators with 300 fs relative timing lag, a new measurement technique of timing fluctuation of low-repetition amplified pulse, and a special designed regenerative amplifier with high quality beam were developed. New technical options for linear collider are proposed based on these expertises. The options are temporally square pulse for low emittance electron generation, a timing stabilized seeder for CO sub 2 amplifier, and multi-pulse high-energy lasers for gamma-gamma collision and for multi-bunch electron generation.

  10. Pramana – Journal of Physics | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    ... Invited Papers. Femtosecond pulse generation and amplification in Yb-doped fibre oscillator–amplifier system .... On the operation of switch-less transversely excited atmosphere CO2 lasers in the oscillator and amplifier configurations .... Rate equation simulation of temporal characteristics of a pulsed dye laser oscillator.

  11. Femtosecond Carrier Dynamics and Modelocking in Monolithic CPM Lasers. [SB1

    DEFF Research Database (Denmark)

    Brorson, S.D.; Bischoff, Svend; MØrk, J.

    1996-01-01

    Femtosecond pump-probe measurements of the dynamics in both forward- and reverse-biased semiconductor optical waveguides arepresented. Slow (nanosecond) as well as ultrafast (femtosecond) dynamics are observed in both kinds of structures....

  12. Enhancement of peak intensity in a filament core with spatiotemporally focused femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Bin; Chu Wei; Li Guihua; Zhang Haisu; Ni Jielei [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Gao Hui; Liu Weiwei [Institute of Modern Optics, Nankai University, Tianjin, 300071 (China); Yao Jinping; Cheng Ya; Xu Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Chin, See Leang [Center for Optics, Photonics and Laser (COPL) and Department of Physics, Engineering Physics and Optics, Universite Laval, Quebec City, QC, G1V 0A6 (Canada)

    2011-12-15

    We demonstrate that the peak intensity in the filament core, which is inherently limited by the intensity clamping effect during femtosecond laser filamentation, can be significantly enhanced using spatiotemporally focused femtosecond laser pulses. In addition, the filament length obtained by spatiotemporally focused femtosecond laser pulses is {approx}25 times shorter than that obtained by a conventional focusing scheme, resulting in improved high spatial resolution.

  13. Design and analysis of X-band femtosecond linac

    Energy Technology Data Exchange (ETDEWEB)

    Uesaka, M.; Kozawa, T.; Takeshita, A.; Kobayashi, T.; Ueda, T.; Miya, K. [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab.

    1997-03-01

    Femtosecond quantum phenomena research project is proposed at Nuclear Engineering Research Laboratory, University of Tokyo. The research facility consists of an X-band (11.424GHz) femtosecond electron linac, a femtosecond wavelength tunable laser, two S-band (2.856GHz) picosecond electron linacs and measuring equipments. Especially, we aim to generate a 100 fs (FWHM) electron single bunch with more than 1 nC at the X-band femtosecond linac. Ultrafast processes in radiation physics, chemistry, material science and microscopic electromagnetic phenomena are going to be analyzed there. Here the design and analysis of an X-band femtosecond linac is presented. The simulation of electron dynamics is carried out including magnetic pulse compression by using PARMELA and SUPERFISH. It is found by the simulation that the 600 ps (tail-to-tail) electron emission from a 200 kV thermionic gun can be bunched and compressed to 110 fs (FWHM) with the charge of 0.8 nC which gives 7.3 kA. We plan to use one high power X-band klystron which can supply 60 MW with more than 200 ns pulse duration. The flatness of plateau of the pulse should be 0.2% for stable ultrashort bunch generation. (author)

  14. Mobile femtosecond laser platform for pediatric cataract surgery.

    Science.gov (United States)

    Fung, Simon S M; Brookes, John; Wilkins, Mark R; Adams, Gillian G W

    2017-10-26

    To describe the use of a mobile femtosecond laser platform in assisting paediatric cataract surgery. A mobile femtosecond laser was brought into the operating room and calibrated on the day of the surgery. After general anesthesia is induced, the femtosecond laser was docked onto the eyes with a liquid-filled interface, without any perioperative adaptations or additional surgical procedures. An anterior capsulotomy was created with the femtosecond laser, followed by conventional cataract extraction and intraocular lens implantation. Five eyes of 3 children with congenital cataracts were treated with this technique. Docking and capsulorhexis were successful in all cases. No perioperative or intraoperative complications were noted in any of the cases. At median follow-up of 15 months (range 6-18 months), all patients had improved best-corrected visual acuity. Using the mobile femtosecond laser platform, a perfectly sized anterior capsulotomy could be created with high precision and accuracy in paediatric cataract cases, while ensuring that perioperative care for the children undergoing the procedure was not compromised.

  15. Electrocatalytic methane dimerization with a Yb-doped SrCeO3 solid electrolyte

    International Nuclear Information System (INIS)

    Chiang, P.H.; Eng, D.; Stoukides, M.

    1991-01-01

    This paper reports on the electrocatalytic nonoxidative dimerization of methane to ethane and ethylene that was studied at 750 degrees C and 1 atm. The electrochemical cell used as Ag/SrCa 0.95 Yb 0.05 O 3 /Ag where the solid electrolyte was a proton conductor. By applying a current to the cell H + was pumped to or from the Ag electrodes. Under closed circuit the rate of methane dehydrogenation to ethane and ethylene could increase to as much as eight times the open-circuit rate. The electrolyte cell offers a promising advantage over conventional catalyst supports

  16. Highly Yb-doped KGd(WO4)2 thin-film amplifier

    NARCIS (Netherlands)

    Yong, Yean Sheng; Aravazhi, S.; Vázquez-Córdova, Sergio Andrés; García Blanco, Sonia Maria; Pollnau, Markus

    We report record-high small-signal gain of 1050 dB/cm at 981 nm wavelength in a KGd0.425Yb0.575(WO4)2 thin film. The sensitivity of gain to the shift of beam-focus position, which is critical under non-waveguiding conditions, is investigated.

  17. Gain-switched, Yb-doped, all-fiber laser with narrow bandwidth

    DEFF Research Database (Denmark)

    Larsen, Casper; Giesberts, Martin; Nyga, Sebastian

    2013-01-01

    We demonstrate that an all-fiber, narrow bandwidth, high pulse energy pulsed laser can be constructed from commercially available components by applying gain-switching. After single-stage amplification the pulses are frequency doubled in ppSLT with high efficiency.......We demonstrate that an all-fiber, narrow bandwidth, high pulse energy pulsed laser can be constructed from commercially available components by applying gain-switching. After single-stage amplification the pulses are frequency doubled in ppSLT with high efficiency....

  18. Tm-Yb Doped Optical Fiber Performance with Variation of Host-Glass Composition

    Directory of Open Access Journals (Sweden)

    Anirban Dhar

    2014-01-01

    Full Text Available The fabrication process of Thulium-Ytterbium doped optical fiber comprising different host glass through the Modified Chemical Vapor Deposition (MCVD coupled with solution doping technique is presented. The material and optical performance of different fibers are compared with special emphasis on their lasing efficiency for 2 µm application.

  19. Tunability of laser based on Yb-doped hot-pressed CaF2 ceramics

    Science.gov (United States)

    Sulc, Jan; Doroshenko, Maxim E.; Jelínková, Helena; Basiev, Tasoltan T.; Konyushkin, Vasilii A.; Osiko, Vyacheslav V.

    2012-06-01

    The aim of presented study was an investigation of tunability of diode pumped laser based on hot-pressed Yb:CaF2 ceramics. The tested Yb:CaF2 sample was in the form of 3.5mm thick plane-parallel face-polished plate (without AR coatings). The Yb3+ concentration was 5.5 %. A fiber (core diameter 200 μm, NA= 0.22) coupled laser diode (LIMO, HLU25F200-980) with emission at wavelength 976 nm, was used for longitudinal Yb:CaF2 pumping. The laser diode was operating in the pulsed regime (4 ms pulse length, 20 Hz repetition rate). The duty-cycle 8% ensured a low thermal load even under the maximum diode pumping power amplitude 10W (crystal sample was only air-cooled). This radiation was focused into the crystal (pumping beam waist diameter ~ 170 μm). The 145mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.01 - 1.09 μm, HT @ 0.97 μm) and curved (r = 150mm) output coupler with a reflectivity of ~ 98% @ 1.01 - 1.09 μm. Tuning of the ytterbium laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle between the output coupler and the laser active medium. The extremely broad and smooth tuning was obtained. The laser was continuously tunable over ~ 66nm (from 1015nm to 1081 nm) and the tuning band was mostly limited by free spectral range of used birefringent filter. The tunability FWHM was 40 nm corresponding bandwidth 10 THz results in Fourier limited gaussian pulse width ~ 40 fs (FWHM). The maximum output power amplitude 0.68W was obtained at wavelength 1054nm for absorbed pump power amplitude 6W. The laser slope efficiency was 15%.

  20. Properties of Er and Yb Doped Gallium nitride layers fabricated by magnetron sputtering

    Czech Academy of Sciences Publication Activity Database

    Prajzler, V.; Burian, Z.; Hüttel, I.; Špirková, J.; Hamáček, J.; Oswald, J.; Zavadil, Jiří; Peřina, Vratislav

    2006-01-01

    Roč. 46, č. 6 (2006), s. 49-55 ISSN 1210-2709 R&D Projects: GA ČR(CZ) GA102/06/0424 Institutional research plan: CEZ:AV0Z20670512; CEZ:AV0Z10480505 Keywords : fluorescence * gallium * rare earth compounds Subject RIV: BM - Solid Matter Physics ; Magnetism

  1. Growth and laser action of Yb: YVO4 crystals with low Yb doping concentration

    Science.gov (United States)

    Zhong, Degao; Teng, Bing; Li, Jianhong; Zhang, Shiming; Zhang, Bingtao; Wang, Chao; Tian, Xueping; Liu, Junhai

    2012-11-01

    Yb: YVO4 single crystals with low doping concentrations of Yb3+ less than 0.3 at% were grown using the Czochralski method. The polarized absorption spectra were measured at room temperature. Strong anisotropy exists in the absorption spectra, resulting in almost entirely different features for π-polarization and σ-polarization. The laser emission spectrum and relationship curve between the output power and absorbed pump power (Pabs) were measured. The continuous-wave laser action of Yb: YVO4 single crystal in a range of 1020.4-1026.3 nm was realized by using a high-power diode laser as the pump source.

  2. Synthesis of Er and Er : Yb doped sol–gel derived silica glass and ...

    Indian Academy of Sciences (India)

    Unknown

    doped samples showed enhanced absorption due to 2F7/2 → 2F5/2 transition. The absorption and ... Er3+ emission transition occurs within this wavelength ... reagent) grade. Calculated amount of dopant salts were poured in TEOS under stirring condition at room tem- perature. The molar ratio of TEOS : H2O : HCl was.

  3. Electrically tunable Yb-doped fiber laser based on a liquid crystal photonic bandgap fiber device

    DEFF Research Database (Denmark)

    Olausson, Christina Bjarnal Thulin; Scolari, Lara; Wei, Lei

    2010-01-01

    We demonstrate electrical tunability of a fiber laser using a liquid crystal photonic bandgap fiber. Tuning of the laser is achieved by combining the wavelength filtering effect of a tunable liquid crystal photonic bandgap fiber device with an ytterbium-doped photonic crystal fiber. We fabricate...... an all-spliced laser cavity based on the liquid crystal photonic bandgap fiber mounted on a silicon assembly, a pump/signal combiner with single-mode signal feed-through and an ytterbium-doped photonic crystal fiber. The laser cavity produces a single-mode output and is tuned in the range 1040-1065 nm...

  4. Electrical and microstructural properties of Yb-doped CeO2

    Directory of Open Access Journals (Sweden)

    B. Matović

    2014-06-01

    Full Text Available Nanopowdered Ce1−xYbxO2−δ solid solutions (0 ≤ x ≤ 0.2 were synthesized by a self-propagating room temperature synthesis. XRD and SEM were used to study the properties of these materials as well as the Yb solubility in CeO2 lattice. Results showed that all the obtained powders were solid solutions with a fluorite-type crystal structure and with nanometric particle size. The average size of Ce1−xYbxO2−δ particles was approximately 3 nm. Electrochemical impedance spectroscopy for the sintered pellets depicted that it was possible to separate Rbulk and Rgb in the temperature interval of 550–800 °C. The activation energy for the bulk conduction was 1.03 eV and for grain boundary conduction was 1.14 eV. Grain boundary resistivity dominates over the other resistivities. These measurements confirmed that Yb3+-doped CeO2 material had a potential as electrolyte for intermediate-temperature solid oxide fuel cell applications.

  5. High-power Yb-doped continuous-wave and pulsed fibre lasers

    Indian Academy of Sciences (India)

    2014-01-05

    14] A Suzuki, Y Takahashi, M Yoshida and M Nakazawa, IEEE Photonics Technol. Lett. 19, 1463. (2007). [15] B N Upadhyaya, Usha Chakravarty, A Kuruvilla, M R Shenoy, K Thyagarajan and A K Nath,. Opt. Commun. 281 ...

  6. Down conversion luminescence behavior of Er and Yb doped Y2O3 phosphor

    Directory of Open Access Journals (Sweden)

    Sadhana Agrawal

    2014-10-01

    Full Text Available We have studied downconversion luminescence behaviour of Y2O3 phosphor doped with Er 1 mol% and 1 mol% of Yb. The sample was prepared by modified solid state reaction method. Using inorganic material like (Y2O3, Flux Calcium Fluoride (CaF2 and Er2O3 as well as Yb2O3 with molar ratio 1 mol% of dopant. The prepared phosphor sample was characterized using Powder X-Ray Diffraction (PXRD, Field Emission Gun Scanning Electron Microscopy (FEGSEM, High Resolution Transmission Electron Microscopy (HRTEM, Photoluminescence (PL, Thermoluminescence (TL and CIE techniques. The obtained sample shows an intense greenish-white emission (ranging from 350 to 600 nm, centered at 565 nm under a wide range of UV light excitation (220–400 nm.

  7. Synthesis of Er and Er : Yb doped sol–gel derived silica glass and ...

    Indian Academy of Sciences (India)

    Unknown

    indicated in TGA curve). The weight loss at elevated tempe- ratures is probably due to removal of water during con-. Figure 1. Photograph of a gel sample sintered at 900°C. Figure 2. DTA curve for 1⋅0 mol% of Er2O3 doped silica gel. Figure 3.

  8. Thermal Properties of Transparent Yb-Doped YAG Ceramics at Elevated Temperatures

    Czech Academy of Sciences Publication Activity Database

    Hostaša, J.; Matějíček, Jiří; Nait-Ali, B.; Smith, D.S.; Pabst, W.; Esposito, L.

    2014-01-01

    Roč. 97, č. 8 (2014), s. 2602-2606 ISSN 0002-7820 Institutional support: RVO:61389021 Keywords : yttrium aluminium garnet * Yb:YAG * thermal diffusivity Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.610, year: 2014 http://onlinelibrary.wiley.com/doi/10.1111/jace.13015/abstract

  9. The all-fiber cladding-pumped Yb-doped gain-switched laser

    DEFF Research Database (Denmark)

    Larsen, Casper; Hansen, K. P.; Mattsson, Kent Erik

    2014-01-01

    Gain-switching is an alternative pulsing technique of fiber lasers, which is power scalable and has a low complexity. From a linear stability analysis of rate equations the relaxation oscillation period is derived and from it, the pulse duration is defined. Good agreement between the measured pul...

  10. A 98 W 1178 nm Yb-doped solid-core photonic bandgap fiber oscillator

    International Nuclear Information System (INIS)

    Fan, Xinyan; Chen, Mingchen; Shirakawa, Akira; Ueda, Ken-ichi; Olausson, Christina B; Broeng, Jes

    2013-01-01

    A high-power ytterbium-doped solid-core photonic bandgap fiber laser directly oscillating at 1178 nm is reported. The sharp-cut bandpass distributed filtering effect of photonic bandgap fiber can suppress amplified spontaneous emission (ASE) in the conventional high-gain spectral region. The oscillator is composed of a high reflection fiber Bragg grating spliced with a 39 m gain fiber and a Fresnel fiber end surface. A model based on rate equations is investigated numerically. A record output power of 98 W is achieved with a slope efficiency of 54%. The laser linewidth is 0.5 nm. The spectrum at 98 W indicates that ASE and parasitic lasing are suppressed effectively. (letter)

  11. Power-scalable long-wavelength Yb-doped photonic bandgap fiber sources

    DEFF Research Database (Denmark)

    Olausson, Christina Bjarnal Thulin; Shirakawa, Akira; Maurayama, Hiroki

    2010-01-01

    Ytterbium-doped photonic-bandgap fiber sources operationg at the long-wavelength edge of the ytterbium gain band are being investigated for high power amplification. Artificial shaping of the gain spectrum by the characteristic distributed filtering effect of the photonic bandgap enables spontane...

  12. Asymmetry in serial femtosecond crystallography data.

    Science.gov (United States)

    Sharma, Amit; Johansson, Linda; Dunevall, Elin; Wahlgren, Weixiao Y; Neutze, Richard; Katona, Gergely

    2017-03-01

    Serial crystallography is an increasingly important approach to protein crystallography that exploits both X-ray free-electron laser (XFEL) and synchrotron radiation. Serial crystallography recovers complete X-ray diffraction data by processing and merging diffraction images from thousands of randomly oriented non-uniform microcrystals, of which all observations are partial Bragg reflections. Random fluctuations in the XFEL pulse energy spectrum, variations in the size and shape of microcrystals, integrating over millions of weak partial observations and instabilities in the XFEL beam position lead to new types of experimental errors. The quality of Bragg intensity estimates deriving from serial crystallography is therefore contingent upon assumptions made while modeling these data. Here it is observed that serial femtosecond crystallography (SFX) Bragg reflections do not follow a unimodal Gaussian distribution and it is recommended that an idealized assumption of single Gaussian peak profiles be relaxed to incorporate apparent asymmetries when processing SFX data. The phenomenon is illustrated by re-analyzing data collected from microcrystals of the Blastochloris viridis photosynthetic reaction center and comparing these intensity observations with conventional synchrotron data. The results show that skewness in the SFX observations captures the essence of the Wilson plot and an empirical treatment is suggested that can help to separate the diffraction Bragg intensity from the background.

  13. Blackening of metals using femtosecond fiber laser.

    Science.gov (United States)

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

    2015-01-10

    This study presents an unprecedented high throughput processing for super-blackening and superhydrophobic/hydrophilic surface on both planar and nonplanar metals surfaces. By using a high pulse repetition rate femtosecond (fs) fiber laser, a light trapping microstructure and nanostructure is generated to absorb light from UV, visible to long-wave infrared spectral region. Different types of surface structures are produced with varying laser scanning conditions (scanning speed and pitch). The modified surface morphologies are characterized using scanning electron microscope and the blackening effect is investigated through spectral measurements. Spectral measurements show that the reflectance of the processed materials decreases sharply in a wide wavelength range and the decrease occurs at different rates for different scanning pitches and speeds. Above 98% absorption over the entire visible wavelength region and above 95% absorption over the near-infrared, middle-wave infrared and long-wave infrared regions range has been demonstrated for the surface structures, and the absorption for specific wavelengths can go above 99%. Furthermore, the processing efficiency of this fs fiber laser blackening technique is 1 order of magnitude higher than that of solid-state fs laser and 4 times higher than that of picosecond (ps) laser. Further increasing of the throughput is expected by using higher repetition and higher scanning speed. This technology offers the great potential in applications such as constructing sensitive detectors and sensors, solar energy absorber, and biomedicine.

  14. Berkeley Lab's ALS generates femtosecond synchrotron radiation

    CERN Document Server

    Robinson, A L

    2000-01-01

    A team at Berkeley's Advanced Light Source has shown how a laser time-slicing technique provides a path to experiments with ultrafast time resolution. A Lawrence Berkeley National Laboratory team has succeeded in generating 300 fs pulses of synchrotron radiation at the ALS synchrotron radiation machine. The team's members come from the Materials Sciences Division (MSD), the Center for Beam Physics in the Accelerator and Fusion Research Division and the Advanced Light Source (ALS). Although this proof-of principle experiment made use of visible light on a borrowed beamline, the laser "time-slicing" technique at the heart of the demonstration will soon be applied in a new bend magnet beamline that was designed specially for the production of femtosecond pulses of X-rays to study long-range and local order in condensed matter with ultrafast time resolution. An undulator beamline based on the same technique has been proposed that will dramatically increase the flux and brightness. The use of X-rays to study the c...

  15. Realization of phonon laser with femtosecond technology

    Science.gov (United States)

    Sun, Chi-Kuang; Huang, Yue-Kai; Chern, Gia-Wei

    2002-06-01

    One of the most desirable properties of phonon system is sound amplification by stimulated emission of phonon radiation, coined as SASER or called phonon laser or acoustic laser, which is the acoustic counterpart of LASER. Phonon stimulated emission, or sound amplification, has been previously observed fro several occasions in extremely low temperatures, however a lasing behavior of the phonon oscillators has never been established. It is also desirable to build a phonon laser operating at room temperature. Here we present an optically pumped nano-sized phonon laser with an output acoustic wavelength of 9.3 nm, operating at room temperature. The nano phonon laser is composed by InGaN/GaN multiple-quantum-wells (MQWs). By using femtosecond ultraviolet pulses as pumping sources, coherent acoustic phonon amplification with large acoustic gain was observed. When the induced acoustic gain is higher than the acoustic loss due to its traveling nature, a clear laser-like threshold behavior was observed, which resembles a pulsed optical laser. This demonstration will open a new way toward nano-ultrasonics.

  16. Large amplitude femtosecond electron dynamics in metal clusters

    CERN Document Server

    Daligault, J

    2003-01-01

    We present a theoretical model that allows us to study linear and non-linear aspects of the femtosecond electron dynamics in metal clusters. The theoretical approach consists in the classical limit of the time-dependent Kohn-Sham equations. The electrons are described by a phase-space distribution function which satisfies a Vlasov-like equation while the ions are treated classically. This allows simulations for clusters containing several hundreds of atoms and extending up to several hundreds of femtoseconds during which the description conserves the fermionic character of the electron distribution. This semi-quantal approach compares very well with the purely quantal treatment. As an application of this approach, we show the prominent role of the electron dynamics during and after the interaction with an intense femtosecond laser pulse.

  17. Femtosecond laser excitation drives ferromagnetic gadolinium out of magnetic equilibrium.

    Science.gov (United States)

    Carley, Robert; Döbrich, Kristian; Frietsch, Björn; Gahl, Cornelius; Teichmann, Martin; Schwarzkopf, Olaf; Wernet, Philippe; Weinelt, Martin

    2012-08-03

    The temporal evolution of the exchange-split Δ(2)-like Σ valence bands of the 4f-ferromagnet gadolinium after femtosecond laser excitation has been studied using angle-resolved photoelectron spectroscopy based on high-order harmonic generation. The ultrafast drop of the exchange splitting reflects the magnetic response seen in femtosecond magnetic dichroism experiments. However, while the minority valence band reacts immediately, the response of the majority counterpart is delayed by 1 picosecond and is only half as fast. These findings demonstrate that laser excitation drives the valence band structure out of magnetic equilibrium.

  18. Femtosecond pump-probe studies of zinc phthalocynine in DMSO

    CSIR Research Space (South Africa)

    Ombinda-Lemboumba, Saturnin

    2010-09-01

    Full Text Available .kashan.co.za] Femtosecond pump-probe studies of zinc phthalocynine in DMSO S OMBINDA-LEMBOUMBA1,2, A DU PLESSIS1, LR BOTHA1, EG ROHWER2 AND CM STEENKANP2 1CSIR National Laser Centre, PO Box 395, Pretoria, 0001 2Laser Research Institute, Department of Physics, University.... The excited state of the oxygen will lead to the destruction of the tumour. Figure 1: Energy transfer and energy level diagram of zinc phthalocyanine PUMP-PROBE TECHNIQUE Figure 2 indicates the Femtosecond pump-probe technique used to investigate...

  19. NOTE: Ultrasonic vibration-assisted femtosecond laser machining of microholes

    Science.gov (United States)

    Zheng, H. Y.; Huang, H.

    2007-08-01

    In this note, we describe a novel approach to improving laser hole drilling quality by exciting the work material with a high frequency ultrasonic vibrator during a femtosecond laser drilling process. It is found that both the aspect ratio (depth over diameter) and the wall surface finish of the microholes fabricated using the ultrasonic vibration (US) assisted laser drilling are improved, compared to those laser machined without US assistance. This is because the introduction of US into the femtosecond laser drilling process reduced the resolidified and redeposited particles on the wall surfaces.

  20. Unilateral Keratectasia Treated with Femtosecond Fashioned Intrastromal Corneal Inlay

    Science.gov (United States)

    Jadidi, Khosrow; Hasanpour, Hossein

    2017-01-01

    Purpose: In this case report, we describe the surgical procedure of corneal inlay preparation and corneal pocket creation using a femtosecond laser system. Case Report: A 7-year-old girl who presented with unilateral paracentral corneal thinning underwent the surgical procedure of corneal inlay. Preoperatively, the refraction was +10.00-6.00 × 170. One month after the procedure, astigmatism and hyperopia were decreased and the refraction was +5.00-1.25 × 110. Conclusion: Femtosecond laser–assisted pocket creation for the implantation of corneal inlays offers accuracy of pocket parameters, enhancing predictability, resulting in better final outcomes, and improving the safety of the procedure. PMID:28791068

  1. On femtosecond laser shock peening of stainless steel AISI 316

    Science.gov (United States)

    Hoppius, Jan S.; Kukreja, Lalit M.; Knyazeva, Marina; Pöhl, Fabian; Walther, Frank; Ostendorf, Andreas; Gurevich, Evgeny L.

    2018-03-01

    In this paper we report on the competition in metal surface hardening between the femtosecond shock peening on the one hand, and formation of laser-induced periodic surface structures (LIPSS) and surface oxidation on the other hand. Peening of the stainless steel AISI 316 due to shock loading induced by femtosecond laser ablation was successfully demonstrated. However, for some range of processing parameters, surface erosion due to LIPSS and oxidation seems to dominate over the peening effect. Strategies to increase the peening efficiency are discussed.

  2. Piecewise Adiabatic Passage with a Series of Femtosecond Pulses

    International Nuclear Information System (INIS)

    Shapiro, E. A.; Milner, V.; Menzel-Jones, C.; Shapiro, M.

    2007-01-01

    We develop a method of executing complete population transfers between quantum states in a piecewise manner using a series of femtosecond laser pulses. The method can be applied to a large class of problems as it benefits from the high peak powers and large spectral bandwidths afforded by femtosecond pulses. The degree of population transfer is robust to a wide variation in the absolute and relative intensities, durations, and time ordering of the pulses. The method is studied in detail for atomic sodium where piecewise adiabatic population transfer, as well as the induction of Ramsey-type interferences, is demonstrated

  3. Characterization and modulation of femtosecond laser pulse

    International Nuclear Information System (INIS)

    Dorrer, Christophe

    1999-01-01

    This work brings some solutions to the characterization and control of femtosecond laser pulses. Spectral interferometry has been extensively studied; whereas this is a rather old technique, it has found new specific applications to short pulses. Several important points concerning the experimental implementation of this technique are treated. Sources of errors have been tracked and simple solutions have been found to enhance its reliability. A recently demonstrated technique for the complete characterization of short pulses has been used to characterize short pulses from Chirped Pulse Amplification Systems. This transposition of shearing interferometry to the optical frequency domain, known as Spectral Phase Interferometry for Direct Electric-field Reconstruction (SPlDER), is conceptually very interesting: for example, the inversion from the experimental data to the electric field to be characterized is completely algebraic. A reliable tool for the characterization and optimization of Chirped pulse amplification systems has been built on this principle. This is the first single-shot real-time characterization implementation of this technique. An improvement of the method has also allowed the first single-shot real-time characterization of a short pulse using a single mono-dimensional integrative detector and an algebraic inversion of the experimental data. The control of these pulses is also of prior interest. Through a collaboration with Thomson CSF-LCR, the demonstration of the use of an optically addressed light valve at the Fourier plane of a zero-dispersion line for spectral phase modulation has been made. This device allows a high-resolution control of the spectral phase of a short pulse. It is a well-adapted tool for the correction of the residual spectral phase, at the output of Chirped Pulse Amplification systems and the temporal synthesis of shaped pulses for specific experiments. (author) [fr

  4. Nanospallation induced by a femtosecond laser pulse

    Science.gov (United States)

    Agranat, M. B.; Anisimov, S. I.; Ashitkov, S. I.; Zhakhovskii, V. V.; Inogamov, N. A.; Nishihara, K.; Petrov, Yu. V.

    2008-01-01

    In the present work phenomena are considered related to the interaction of ultra-short laser pulses, τ L~0.1 ps, with metallic targets. The absorption of laser pulse results in formation of thin layer of hot electrons strongly superheated (T e>>T i) relative to the ion temperature, T i. Initial thickness of the layer d heat is small, d heat~δ, where δ~10 nm is the skin layer thickness. Subsequent developments include the following stages: (1) Propagation of electron thermal wave which expands the hot layer d heat; (2) Cooling of electrons due to energy transfer to cold ions; (3) Onset of hydrodynamic motion that constitutes the rarefaction wave with positive pressure; (4) Further expansion of target material leading to the appearance of negative pressure; and (5) Long separation process which begins with nucleation of voids and goes on to the total separation of spallation plate. The thickness of the plate is ~10 nm (we call it nanospallation). Theoretical model involves two-temperature hydrodynamic equations with semiempirical EOS for a metal, electron heat conduction and electron-ion energy exchange. The decay of metastable strongly stretched matter is described by molecular dynamics (MD) simulation with extremely large number of atoms. The experimental setup includes femtosecond chromium-forsterite laser operating in the pump-probe regime. The experiments are performed with gold target. Measured ablation threshold for gold is 1.35 J/cm2 of incident pump light at inclination 45°, p-polarization. Calorimeter measurements give for the absorbed fluence F abs=0.3F inc, therefore the threshold value of F abs is 0.4 J/cm2.

  5. Pulse radiolysis based on a femtosecond electron beam and a femtosecond laser light with double-pulse injection technique

    International Nuclear Information System (INIS)

    Yang Jinfeng; Kondoh, Takafumi; Kozawa, Takahiro; Yoshida, Youichi; Tagawa, Seiichi

    2006-01-01

    A new pulse radiolysis system based on a femtosecond electron beam and a femtosecond laser light with oblique double-pulse injection was developed for studying ultrafast chemical kinetics and primary processes of radiation chemistry. The time resolution of 5.2 ps was obtained by measuring transient absorption kinetics of hydrated electrons in water. The optical density of hydrated electrons was measured as a function of the electron charge. The data indicate that the double-laser-pulse injection technique was a powerful tool for observing the transient absorptions with a good signal to noise ratio in pulse radiolysis

  6. Progress in sub-femtosecond control of electron localization in ...

    Indian Academy of Sciences (India)

    2014-01-04

    Jan 4, 2014 ... Home; Journals; Pramana – Journal of Physics; Volume 82; Issue 1. Progress in sub-femtosecond control of electron localization in molecules ... To highlight recent experimental progress, we explain how one can employ few-cycle IR pulses and different attosecond extreme ultraviolet (EUV) pulses in ...

  7. High Repetition Rate Femtosecond Lightsource for CARS Microscopy

    NARCIS (Netherlands)

    Potma, Eric O.; Boeij, Wim P. de; Pshenichnikov, Maxim S.; Wiersma, Douwe A.

    2000-01-01

    The use of femtosecond pulsed excitation in microscopy permits the application of nonlinear optical techniques to microscopic studies of biological samples. Among the these techniques, the method of coherent anti-Stokes Raman scattering (CARS) is particularly promising for biological imaging since

  8. Tesla coil discharges guided by femtosecond laser filaments in air

    OpenAIRE

    Brelet, Yohann; Houard, Aurélien; Arantchouk, Leonid; Forestier, Benjamin; Liu, Yi; Prade, Bernard; Carbonnel, Jérôme; André, Yves-Bernard; Mysyrowicz, André

    2012-01-01

    International audience; A Tesla coil generator was designed to produce high voltage pulses oscillating at 100 kHz synchronisable with a nanosecond temporal jitter. Using this compact high voltage generator, we demonstrate reproducible meter long discharges in air at a repetition rate of 1 Hz. Triggering and guiding of the discharges are performed in air by femtosecond laser filaments.

  9. Direct femtosecond laser waveguide writing inside zinc phosphate glass

    NARCIS (Netherlands)

    Fletcher, L.; Witcher, J.J.; Troy, N.; Reis, S.T.; Brow, R.K.; Krol, D.M.

    2011-01-01

    We report the relationship between the initial glass composition and the resulting microstructural changes after direct femtosecond laser waveguide writing with a 1 kHz repetition rate Ti:sapphire laser system. A zinc polyphosphate glass composition with an oxygen to phosphorus ratio of 3.25 has

  10. Thermal annealing of femtosecond laser written structures in silica glass

    NARCIS (Netherlands)

    Witcher, J.J.; Reichman, W.B.; Fletcher, L.B.; Troy, N.W.; Krol, D.M.

    2013-01-01

    We have investigated the thermal stability of femtosecond laser modification inside fused silica. Raman and FL spectroscopy show that fs-laser induced non-bridging oxygen hole center (NBOHC) defects completely disappear at 300 °C, whereas changes in Si-O ring structures only anneal out after heat

  11. Tracking Femtosecond Laser Pulses in Space and Time

    NARCIS (Netherlands)

    Balistreri, M.L.M.; Gersen, H.; Korterik, Jeroen P.; Kuipers, L.; van Hulst, N.F.

    2001-01-01

    We show that the propagation of a femtosecond laser pulse inside a photonic structure can be directly visualized and tracked as it propagates using a time-resolved photon scanning tunneling microscope. From the time-dependent and phase- sensitive measurements, both the group velocity and the phase

  12. Femtosecond electron-bunch dynamics in laser wakefields and vacuum

    NARCIS (Netherlands)

    Khachatryan, A.G.; Irman, A.; van Goor, F.A.; Boller, Klaus J.

    2007-01-01

    Recent advances in laser wakefield acceleration demonstrated the generation of extremely short (with a duration of a few femtoseconds) relativistic electron bunches with relatively low (of the order of couple of percent) energy spread. In this article we study the dynamics of such bunches in drift

  13. Femtosecond lasers as novel tool in dental surgery

    Science.gov (United States)

    Serbin, J.; Bauer, T.; Fallnich, C.; Kasenbacher, A.; Arnold, W. H.

    2002-09-01

    There is a proven potential of femtosecond lasers for medical applications like cornea shaping [1], ear surgery or dental surgery [2]. Minimal invasive treatment of carious tissue has become an increasingly important aspect in modern dentistry. State of the art methods like grinding using turbine-driven drills or ablation by Er:YAG lasers [3] generate mechanical and thermal stress, thus generating micro cracks of several tens of microns in the enamel [4]. These cracks are starting points for new carious attacks and have to be avoided for long term success of the dental treatment. By using femtosecond lasers (1 fs=10 -15 s) for ablating dental tissue, these drawbacks can be overcome. We have demonstrated that femtosecond laser ablation offers a tool for crack-free generation of cavities in dental tissue. Furthermore, spectral analysis of the laser induced plasma has been used to indicate carious oral tissue. Our latest results on femtosecond laser dentistry will be presented, demonstrating the great potential of this kind of laser technology in medicine.

  14. All-fiber femtosecond Cherenkov laser at visible wavelengths

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Lægsgaard, Jesper; Møller, Uffe Visbech

    2013-01-01

    -matching condition [1]. The resonant ultrafast wave conversion via the fiber-optic CR mechanism is instrumental for applications in biophotonics such as bio-imaging and microscopy [2]. In this work, we demonstrate a highly-stable all-fiber, fully monolithic CR system based on an Yb-fiber femtosecond laser, producing...

  15. Surface texturing of sialon ceramic by femtosecond pulsed laser

    CSIR Research Space (South Africa)

    Tshabalala, Lerato C

    2017-01-01

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

  16. Relaxation of femtosecond photoexcited electrons in a polar indirect ...

    Indian Academy of Sciences (India)

    A model calculation is given for the energy relaxation of a non-equilibrium distribution of hot electrons (holes) prepared in the conduction (valence) band of a polar indirect band-gap semiconductor, which has been subjected to homogeneous photoexcitation by a femtosecond laser pulse. The model assumes that the ...

  17. Influence of liquid environments on femtosecond laser ablation of silicon

    International Nuclear Information System (INIS)

    Liu Hewei; Chen Feng; Wang Xianhua; Yang Qing; Bian Hao; Si Jinhai; Hou Xun

    2010-01-01

    Liquid-assisted ablation of solids by femtosecond laser pulses has proved to be an efficient tool for highly precise microfabrication, which evokes numerous research interests in recent years. In this paper, we systematically investigate the interaction of femtosecond laser pulses with silicon wafer in water, alcohol, and as a comparison, in air. After producing a series of multiple-shot craters on a silicon wafer in the three types of environments, surface morphologies and femtosecond laser-induced periodic surface structures are comparatively studied via the scanning electron microscope investigations. Meanwhile, the influence of liquid mediums on ablation threshold fluence and ablation depth is also numerically analyzed. The experimental results indicate that the ablation threshold fluences of silicon are reduced by the presence of liquids (water/alcohol) and ablation depths of craters are deepened in ambient water. Furthermore, smoother surfaces tend to be obtained in alcohol-mediated ablation at smaller shot numbers. Finally, the evolution of the femtosecond laser-induced periodic surface structures in air, water and alcohol is also discussed.

  18. Correlation functions formed by a femtosecond pulse interferometer

    NARCIS (Netherlands)

    Cui, M.; Bhattacharya, N.; Urbach, H.P.; Van den berg, S.A.

    2008-01-01

    We experimentally demonstrate that a stabilized femtosecond frequency comb can be applied as a tool for distance measurement. The scheme is based on optical interference between individual pulses in a Michelson type interferometer. The cross-correlation functions between individual pulses with a

  19. Femtosecond carotenoid to retinal energy transfer in xanthorhodopsin

    Czech Academy of Sciences Publication Activity Database

    Polívka, Tomáš; Balashov, S.P.; Chábera, P.; Imasheva, E.S.; Yartsev, A.; Sundström, V.; Lanyi, J.K.

    2009-01-01

    Roč. 96, č. 6 (2009), s. 2268-2277 ISSN 0006-3495 R&D Projects: GA AV ČR IAA608170604 Institutional research plan: CEZ:AV0Z50510513 Keywords : energy transfer * carotenoids * femtosecond spectroscopy Subject RIV: BO - Biophysics Impact factor: 4.390, year: 2009

  20. Femtosecond laser-fabricated microstructures in bulk poly ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 75; Issue 6. Femtosecond laser-fabricated microstructures in bulk poly(methylmethacrylate) and poly(dimethylsiloxane) at 800 nm towards lab-on-a-chip applications. K L N Deepak S Venugopal Rao D Narayana Rao. Conributed Papers Volume 75 Issue 6 December ...

  1. Extended ABCD matrix formalism for the description of femtosecond diffraction patterns; application to femtosecond digital in-line holography with anamorphic optical systems.

    Science.gov (United States)

    Brunel, Marc; Shen, Huanhuan; Coetmellec, Sebastien; Lebrun, Denis

    2012-03-10

    We present a new model to predict diffraction patterns of femtosecond pulses through complex optical systems. The model is based on the extension of an ABCD matrix formalism combined with generalized Huygens-Fresnel transforms (already used in the CW regime) to the femtosecond regime. The model is tested to describe femtosecond digital in-line holography experiments realized in situ through a cylindrical Plexiglas pipe. The model allows us to establish analytical relations that link the holographic reconstruction process to the experimental parameters of the pipe and of the incident beam itself. Simulations and experimental results are in good concordance. Femtosecond digital in-line holography is shown to allow significant coherent noise reduction, and this model will be particularly efficient to describe a wide range of optical geometries. More generally, the model developed can be easily used in any experiment where the knowledge of the precise evolution of femtosecond transverse patterns is required.

  2. Evanescent-wave acceleration of femtosecond electron bunches

    CERN Document Server

    Zawadzka, J; Carey, J J; Wynne, K

    2000-01-01

    A 150-fs 800-nm 1-mu J laser was used to excited surface plasmons in the Kretschmann geometry in a 500-A silver film. Multiphoton excitation results in the emission of femtosecond electron bunches (40 fC) as had been seen before. The electron beam is highly directional and perpendicular to the prism surface. A time-of-flight setup has been used to measure the kinetic-energy distribution of the photoelectrons. Surprisingly, we find that this distribution extends to energies as high as 40 eV. Theoretical calculations show that these high energies may be due to acceleration in the evanescent laser field that extends from the silver film out into the vacuum. These results suggest that femtosecond pulses with more energy per pulse or longer wavelength may be used to accelerate electrons to the keV or even MeV level.

  3. Novel applications of femtosecond laser in missile countermeasures

    Science.gov (United States)

    Marquis, E.; Pocholle, J. P.

    2005-11-01

    Femtosecond lasers have been widely used in laboratories for years and are now suitable for industrial applications and new military ones. Due to their very short pulse duration, they have the capability to generate intense electric fields and plasmas in targeted materials. We present here a novel scheme of missile counter-measure that is using such an intense laser source to disrupt the operation of IR guidance systems. Classical lasers for missile defense are based on thermal effects on the target whereas photons are used as the kill vehicle [1,2]. In femtosecond countermeasure, the average power is quite low, but the very intense field creates ionization effects than can damage sensitive optics and also plasma that can be used as active decoys against IR homing electronics. As the recent systems are compact and portable, an airport protection scheme is proposed to eliminate manpads threats in the vicinity of a civilian airport.

  4. Rapid microfabrication of transparent materials using filamented femtosecond laser pulses

    Science.gov (United States)

    Butkus, S.; Gaižauskas, E.; Paipulas, D.; Viburys, Ž.; Kaškelyė, D.; Barkauskas, M.; Alesenkov, A.; Sirutkaitis, V.

    2014-01-01

    Microfabrication of transparent materials using femtosecond laser pulses has showed good potential towards industrial application. Maintaining pulse energies exceeding the critical self-focusing threshold by more than 100-fold produced filaments that were used for micromachining purposes. This article demonstrates two different micromachining techniques using femtosecond filaments generated in different transparent media (water and glass). The stated micromachining techniques are cutting and welding of transparent samples. In addition, cutting and drilling experiments were backed by theoretical modelling giving a deeper insight into the whole process. We demonstrate cut-out holes in soda-lime glass having thickness up to 1 mm and aspect ratios close to 20, moreover, the fabrication time is of the order of tens of seconds, in addition, grooves and holes were fabricated in hardened 1.1 mm thick glass (Corning Gorilla glass). Glass welding was made possible and welded samples were achieved after several seconds of laser fabrication.

  5. Origin of femtosecond laser induced periodic nanostructure on diamond

    Directory of Open Access Journals (Sweden)

    A. Abdelmalek

    2017-10-01

    Full Text Available We study the evolution of periodic nanostructures formed on the surface of diamond by femtosecond laser irradiation delivering 230 fs pulses at 1030 nm and 515 nm wavelengths with a repetition rate of 250 kHz. Using scanning electron microscopy, we observe a change in the periodicity of the nanostructures by varying the number of pulses overlapping in the laser focal volume. We simulate the evolution of the period of the high spatial frequency laser induced periodic surface structures at the two wavelengths as a function of number of pulses, accounting for the change in the optical properties of diamond via a generalized plasmonic model. We propose a hypothesis that describes the origin of the nanostructures and the principal role of plasmonic excitation in their formation during multipulse femtosecond laser irradiation.

  6. Surface treatment of CFRP composites using femtosecond laser radiation

    Science.gov (United States)

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

    2017-07-01

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

  7. Direct femtosecond laser waveguide writing inside zinc phosphate glass.

    Science.gov (United States)

    Fletcher, Luke B; Witcher, Jon J; Troy, Neil; Reis, Signo T; Brow, Richard K; Krol, Denise M

    2011-04-25

    We report the relationship between the initial glass composition and the resulting microstructural changes after direct femtosecond laser waveguide writing with a 1 kHz repetition rate Ti:sapphire laser system. A zinc polyphosphate glass composition with an oxygen to phosphorus ratio of 3.25 has demonstrated positive refractive index changes induced inside the focal volume of a focusing microscope objective for laser pulse energies that can achieve intensities above the modification threshold. The permanent photo-induced changes can be used for direct fabrication of optical waveguides using single scan writing techniques. Changes to the localized glass network structure that produce positive changes in the refractive index of zinc phosphate glasses upon femtosecond laser irradiation have been studied using scanning confocal micro-Raman and fluorescence spectroscopy.

  8. [Advantages and disadvantages of femtosecond laser assisted LASIK and SMILE].

    Science.gov (United States)

    Zhang, F J; Sun, M S

    2018-01-11

    With the development of excimer laser and femtosecond laser equipment, application of diversified and customized surgical decision in modern corneal refractive surgery has been an inevitable trend. However, how to make a personalized decision with an accurate surgical design to achieve better visual quality becomes the main focus in clinical applications. Small-incision lenticule extraction (SMILE) and femtosecond assisted laser in situ keratomileusis (FS-LASIK) have been commonly acknowledged as the mainstream of corneal refractive surgery for ametropia correction nowadays. Both methods have been verified by clinical practice for many years. This article compares and elaborates the different characteristics with advantages and disadvantages of the two methods so as to provide some reasonable treatment options for refractive surgery. (Chin J Ophthalmol, 2018, 54: 7-10) .

  9. Testing of a femtosecond pulse laser in outer space.

    Science.gov (United States)

    Lee, Joohyung; Lee, Keunwoo; Jang, Yoon-Soo; Jang, Heesuk; Han, Seongheum; Lee, Sang-Hyun; Kang, Kyung-In; Lim, Chul-Woo; Kim, Young-Jin; Kim, Seung-Woo

    2014-05-30

    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 fibre caused an 8.6% reduction in the output power. This successful test operation would help facilitate diverse scientific and technological applications of femtosecond lasers in space and earth atmosphere in the near future.

  10. Ultrafast phenomena in molecular sciences femtosecond physics and chemistry

    CERN Document Server

    Bañares, Luis

    2014-01-01

    This book presents the latest developments in Femtosecond Chemistry and Physics for the study of ultrafast photo-induced molecular processes. Molecular systems, from the simplest H2 molecule to polymers or biological macromolecules, constitute central objects of interest for Physics, Chemistry and Biology, and despite the broad range of phenomena that they exhibit, they share some common behaviors. One of the most significant of those is that many of the processes involving chemical transformation (nuclear reorganization, bond breaking, bond making) take place in an extraordinarily short time, in or around the femtosecond temporal scale (1 fs = 10-15 s). A number of experimental approaches - very particularly the developments in the generation and manipulation of ultrashort laser pulses - coupled with theoretical progress, provide the ultrafast scientist with powerful tools to understand matter and its interaction with light, at this spatial and temporal scale. This book is an attempt to reunite some of the ...

  11. Testing of a femtosecond pulse laser in outer space

    Science.gov (United States)

    Lee, Joohyung; Lee, Keunwoo; Jang, Yoon-Soo; Jang, Heesuk; Han, Seongheum; Lee, Sang-Hyun; Kang, Kyung-In; Lim, Chul-Woo; Kim, Young-Jin; Kim, Seung-Woo

    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 fibre caused an 8.6% reduction in the output power. This successful test operation would help facilitate diverse scientific and technological applications of femtosecond lasers in space and earth atmosphere in the near future. PMID:24875665

  12. Femtosecond laser etching of dental enamel for bracket bonding.

    Science.gov (United States)

    Kabas, Ayse Sena; Ersoy, Tansu; Gülsoy, Murat; Akturk, Selcuk

    2013-09-01

    The aim is to investigate femtosecond laser ablation as an alternative method for enamel etching used before bonding orthodontic brackets. A focused laser beam is scanned over enamel within the area of bonding in a saw tooth pattern with a varying number of lines. After patterning, ceramic brackets are bonded and bonding quality of the proposed technique is measured by a universal testing machine. The results are compared to the conventional acid etching method. Results show that bonding strength is a function of laser average power and the density of the ablated lines. Intrapulpal temperature changes are also recorded and observed minimal effects are observed. Enamel surface of the samples is investigated microscopically and no signs of damage or cracking are observed. In conclusion, femtosecond laser exposure on enamel surface yields controllable patterns that provide efficient bonding strength with less removal of dental tissue than conventional acid-etching technique.

  13. Desorption by Femtosecond Laser Pulses : An Electron-Hole Effect?

    OpenAIRE

    D. M., NEWNS; T. F., HEINZ; J. A., MISEWICH; IBM Research Division, T. J. Watson Research Center; IBM Research Division, T. J. Watson Research Center; IBM Research Division, T. J. Watson Research Center

    1992-01-01

    Desorption of molecules from metal surfaces induced by femtosecond visible laser pulses has been reported. Since the lattice temperature rise is insufficient to explain desorption, an electronic mechanism is clearly responsible. It is shown that a theory based on direct coupling between the center-of-mass degree of freedom of the adsorbate and the electron-hole excitations of the substrate provides a satisfactory explanation of the various experimental findings.

  14. Femtosecond Pulse Propagation in a Highly Nonlinear Photonic Crystal Fiber

    OpenAIRE

    J. F. Gabayno; C. A. Alonzo; W. O. Garcia

    2004-01-01

    Femtosecond pulses are launched into a highly nonlinear photonic crystal fiber (PCF). The input and output spectra were measured using a monochromator and streak camera. The spectrum of the output from a 50 cm PCF pumped at 794 nm for different pump powers features asymmetric side lobes due to intrapulse Raman scattering. Similar measurements on a 100 cm PCF pumped at 795 nm highlight the appearance of blueshifted peaks as a result of energy transfer of solitons to dispersive waves. Broadenin...

  15. Conical Double Frequency Emission by Femtosecond Laser Pulses from DKDP

    International Nuclear Information System (INIS)

    Xi-Peng, Zhang; Hong-Bing, Jiang; Shan-Chun, Tang; Qi-Huang, Gong

    2009-01-01

    Conical double frequency emission is investigated by femtosecond laser pulses at a wavelength of 800 nm in a DKDP crystal. It is demonstrated that the sum frequency of incident wave and its scattering wave accounts for the conical double frequency emission. The gaps on the conical rings are observed and they are very sensitive to the propagation direction, and thus could be used to detect the small angle deviation of surface direction. (fundamental areas of phenomenology (including applications))

  16. Lipidic cubic phase injector facilitates membrane protein serial femtosecond crystallography.

    Science.gov (United States)

    Weierstall, Uwe; James, Daniel; Wang, Chong; White, Thomas A; Wang, Dingjie; Liu, Wei; Spence, John C H; Bruce Doak, R; Nelson, Garrett; Fromme, Petra; Fromme, Raimund; Grotjohann, Ingo; Kupitz, Christopher; Zatsepin, Nadia A; Liu, Haiguang; Basu, Shibom; Wacker, Daniel; Han, Gye Won; Katritch, Vsevolod; Boutet, Sébastien; Messerschmidt, Marc; Williams, Garth J; Koglin, Jason E; Marvin Seibert, M; Klinker, Markus; Gati, Cornelius; Shoeman, Robert L; Barty, Anton; Chapman, Henry N; Kirian, Richard A; Beyerlein, Kenneth R; Stevens, Raymond C; Li, Dianfan; Shah, Syed T A; Howe, Nicole; Caffrey, Martin; Cherezov, Vadim

    2014-01-01

    Lipidic cubic phase (LCP) crystallization has proven successful for high-resolution structure determination of challenging membrane proteins. Here we present a technique for extruding gel-like LCP with embedded membrane protein microcrystals, providing a continuously renewed source of material for serial femtosecond crystallography. Data collected from sub-10-μm-sized crystals produced with less than 0.5 mg of purified protein yield structural insights regarding cyclopamine binding to the Smoothened receptor.

  17. Multiple filamentation generated by focusing femtosecond laser with axicon.

    Science.gov (United States)

    Sun, Xiaodong; Gao, Hui; Zeng, Bin; Xu, Shengqi; Liu, Weiwei; Cheng, Ya; Xu, Zhizhan; Mu, Guoguang

    2012-03-01

    Multiple filamentation has been observed when focusing a femtosecond laser pulse into a methanol solution with an axicon. It is found that multiple long filaments are located on the central spot and ring structures of the quasi-Bessel beam created by the axicon. Since the quasi-Bessel profile is determined by the axicon properties, the axicon has been suggested as a simple optics to control multiple filaments. © 2012 Optical Society of America

  18. Femtosecond laser fabrication of optofluidic devices for single cell manipulation

    Directory of Open Access Journals (Sweden)

    Bragheri Francesca

    2015-01-01

    Full Text Available In this work we fabricate and validate two optofludic devices for the manipulation and analysis of single cells. The chips are fabricated by femtosecond laser micromachining exploiting the 3D capabilities of the technique and the inherent perfect alignment between microfluidic channels and optical networks. Both devices have been validated by probing the mechanical properties of different cancer cell lines, which are expected to show different elasticity because of their different metastatic potential.

  19. Fiber inline Michelson interferometer fabricated by a femtosecond laser.

    Science.gov (United States)

    Yuan, Lei; Wei, Tao; Han, Qun; Wang, Hanzheng; Huang, Jie; Jiang, Lan; Xiao, Hai

    2012-11-01

    A fiber inline Michelson interferometer was fabricated by micromachining a step structure at the tip of a single-mode optical fiber using a femtosecond laser. The step structure splits the fiber core into two reflection paths and produces an interference signal. A fringe visibility of 18 dB was achieved. Temperature sensing up to 1000°C was demonstrated using the fabricated assembly-free device.

  20. Femtosecond photodissociation dynamics of I studied by ion imaging

    DEFF Research Database (Denmark)

    Larsen, J.J.; Bjerre, N.; Mørkbak, N.J.

    1998-01-01

    on imaging is employed to analyze the fragments from timed Coulomb explosion studies of femtosecond (fs) molecular dynamics. The technique provides high detection efficiency and direct recording of the two-dimensional velocity of all ionized fragments. We illustrate the approach by studying photo...... agreement with quantum mechanical wave packet simulations. We discuss the perspectives for extending the studies to photochemical reactions of small polyatomic molecules...

  1. Mercury Amalgam Diffusion in Human Teeth Probed Using Femtosecond LIBS.

    Science.gov (United States)

    Bello, Liciane Toledo; da Ana, Patricia Aparecida; Santos, Dário; Krug, Francisco José; Zezell, Denise Maria; Vieira, Nilson Dias; Samad, Ricardo Elgul

    2017-04-01

    In this work the diffusion of mercury and other elements from amalgam tooth restorations through the surrounding dental tissue (dentin) was evaluated using femtosecond laser-induced breakdown spectroscopy (fs-LIBS). To achieve this, seven deciduous and eight permanent extracted human molar teeth with occlusal amalgam restorations were half-sectioned and analyzed using pulses from a femtosecond laser. The measurements were performed from the amalgam restoration along the amalgam/dentin interface to the apical direction. It was possible to observe the presence of metallic elements (silver, mercury, copper and tin) emission lines, as well as dental constituent ones, providing fingerprints of each material and comparable data for checking the consistence of the results. It was also shown that the elements penetration depth values in each tooth are usually similar and consistent, for both deciduous and permanent teeth, indicating that all the metals diffuse into the dentin by the same mechanism. We propose that this diffusion mechanism is mainly through liquid dragging inside the dentin tubules. The mercury diffused further in permanent teeth than in deciduous teeth, probably due to the longer diffusion times due to the age of the restorations. It was possible to conclude that the proposed femtosecond-LIBS system can detect the presence of metals in the dental tissue, among the tooth constituent elements, and map the distribution of endogenous and exogenous chemical elements, with a spatial resolution that can be brought under 100 µm.

  2. Femtosecond laser direct writing of monocrystalline hexagonal silver prisms

    International Nuclear Information System (INIS)

    Vora, Kevin; Kang, SeungYeon; Moebius, Michael; Mazur, Eric

    2014-01-01

    Bottom-up growth methods and top-down patterning techniques are both used to fabricate metal nanostructures, each with a distinct advantage: One creates crystalline structures and the other offers precise positioning. Here, we present a technique that localizes the growth of metal crystals to the focal volume of a laser beam, combining advantages from both approaches. We report the fabrication of silver nanoprisms—hexagonal nanoscale silver crystals—through irradiation with focused femtosecond laser pulses. The growth of these nanoprisms is due to a nonlinear optical interaction between femtosecond laser pulses and a polyvinylpyrrolidone film doped with silver nitrate. The hexagonal nanoprisms have bases hundreds of nanometers in size and the crystal growth occurs over exposure times of less than 1 ms (8 orders of magnitude faster than traditional chemical techniques). Electron backscatter diffraction analysis shows that the hexagonal nanoprisms are monocrystalline. The fabrication method combines advantages from both wet chemistry and femtosecond laser direct-writing to grow silver crystals in targeted locations. The results presented in this letter offer an approach to directly positioning and growing silver crystals on a substrate, which can be used for plasmonic devices.

  3. Chalcogen doping of silicon via intense femtosecond-laser irradiation

    International Nuclear Information System (INIS)

    Sheehy, Michael A.; Tull, Brian R.; Friend, Cynthia M.; Mazur, Eric

    2007-01-01

    We have previously shown that doping silicon with sulfur via femtosecond-laser irradiation leads to near-unity absorption of radiation from ultraviolet wavelengths to below band gap short-wave infrared wavelengths. Here, we demonstrate that doping silicon with two other group VI elements (chalcogens), selenium and tellurium, also leads to near-unity broadband absorption. A powder of the chalcogen dopant is spread on the silicon substrate and irradiated with femtosecond-laser pulses. We examine and compare the resulting morphology, optical properties, and chemical composition for each chalcogen-doped substrate before and after thermal annealing. Thermal annealing reduces the absorption of below band gap radiation by an amount that correlates with the diffusivity of the chalcogen dopant used to make the sample. We propose a mechanism for the absorption of below band gap radiation based on defects in the lattice brought about by the femtosecond-laser irradiation and the presence of a supersaturated concentration of chalcogen dopant atoms. The selenium and tellurium doped samples show particular promise for use in infrared photodetectors as they retain most of their infrared absorptance even after thermal annealing-a necessary step in many semiconductor device manufacturing processes

  4. Femtosecond-laser experiment for Master II students: generation, measurement and control of femtoseconds pulses

    Science.gov (United States)

    Druon, Fréderic; Peyrot, Tom; Larrouy, Arthur; Courvoisier, Arnaud; Lejeune, Cédric; Avignon, Thierry

    2015-10-01

    In the framework of the experiment platform LEnsE (Laboratoire d'Enseignement Expérimental) of the Institut d'Optique Graduate School in Palaiseau, we present a new lab work dedicated to Master-­-II-­-level students. This lab work is integrated in the formation in the field of ultrashort-­-pulse lasers and its objective is to train students to this specific technology. The varied topics include generation, measurement and basic control of ultrashort pulses. Key concepts are studied, such as the time-­-frequency duality, nonlinear effects, the group velocity dispersion (GVD) and more generally managing spectral and temporal phase. The lab work is based on a totally accessible Ti:sapphire laser (Mira 800 from Coherent). It is used to understand crucial concepts in the generation process such as GVD and self-­-phase-­-modulation in the solitonic regime and Kerr lens mode-­-locking. Because the pulse measurement is a crucial issue to address in ultrafast optics, the lab work also studies different apparatus commonly used to fully characterize fs pulse train: photodiode, spectrometer, and more specifically second-­-order autocorrelator. The autocorrelation concept is detailed using a homemade accessible apparatus. For a simple manipulation of femtosecond pulses, we propose to realize a spectral-­-phase control with high-­-dispersive glass to temporally stretch the pulses. GTI mirrors then re-­-compress them. The three pillars generation-­-measurement-­-control will be described with a practical approach at the conference.

  5. Measurement of the density profile of pure and seeded molecular beams by femtosecond ion imaging

    NARCIS (Netherlands)

    Meng, C.; Janssen, M.H.M.

    2015-01-01

    Here, we report on femtosecond ion imaging experiments to measure the density profile of a pulsed supersonic molecular beam. Ion images are measured for both a molecular beam and bulk gas under identical experimental conditions via femtosecond multiphoton ionization of Xe atoms. We report the

  6. Selective Deactivation of M13 Bacteriophage in E. Coli using Femtosecond Laser Pulses

    CSIR Research Space (South Africa)

    Molukanele, P

    2010-09-01

    Full Text Available Deactivation of M13 Bacteriophage in E. Coli using Femtosecond Laser Pulses P. Molukanele 1, 3, A. Du Plessis 1, T. Roberts 1, L. Botha 1, M. Khati 2,3, W. Campos 2, 3 1CSIR National Laser Centre, Femtosecond Science group, Pretoria, South Africa 2CSIR...

  7. Development of a new picosecond pulse radiolysis system by using a femtosecond laser synchronized with a picosecond linac. A step to femtosecond pulse radiolysis

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Yoichi; Yamamoto, Tamotsu; Miki, Miyako; Seki, Shu; Okuda, Shuichi; Honda, Yoshihide; Kimura, Norio; Tagawa, Seiichi [Osaka Univ., Ibaraki (Japan). Inst. of Scientific and Industrial Research; Ushida, Kiminori

    1997-03-01

    A new picosecond pulse radiolysis system by using a Ti sapphire femtosecond laser synchronized with a 20 ps electron pulse from the 38 MeV L-band linac has been developed for the research of the ultra fast reactions in primary processes of radiation chemistry. The timing jitter in the synchronization of the laser pulse with the electron pulse is less than several picosecond. The technique can be used in the next femtosecond pulse radiolysis. (author)

  8. Femtosecond pulsed laser deposition of biological and biocompatible thin layers

    Energy Technology Data Exchange (ETDEWEB)

    Hopp, B. [Hungarian Academy of Sciences, University of Szeged, Research Group on Laser Physics, Dom ter 9, H-6720 Szeged (Hungary)]. E-mail: bhopp@physx.u-szeged.hu; Smausz, T. [Hungarian Academy of Sciences, University of Szeged, Research Group on Laser Physics, Dom ter 9, H-6720 Szeged (Hungary); Kecskemeti, G. [Department of Optics and Quantum Electronics, University of Szeged, Dom ter 9, H-6720 Szeged (Hungary); Klini, A. [Institute of Electronic Structure and Laser (I.E.S.L.), Foundation for Research and Technology-Hellas (F.O.R.T.H.), P.O. Box 1527, GR-711 10 Heraklion, Crete (Greece); Bor, Zs. [Department of Optics and Quantum Electronics, University of Szeged, Dom ter 9, H-6720 Szeged (Hungary)

    2007-07-31

    In our study we investigate and report the femtosecond pulsed laser deposition of biological and biocompatible materials. Teflon, polyhydroxybutyrate, polyglycolic-acid, pepsin and tooth in the form of pressed pellets were used as target materials. Thin layers were deposited using pulses from a femtosecond KrF excimer laser system (FWHM = 450 fs, {lambda} = 248 nm, f = 10 Hz) at different fluences: 0.6, 0.9, 1.6, 2.2, 2.8 and 3.5 J/cm{sup 2}, respectively. Potassium bromide were used as substrates for diagnostic measurements of the films on a FTIR spectrometer. The pressure in the PLD chamber was 1 x 10{sup -3} Pa, and in the case of tooth and Teflon the substrates were heated at 250 deg. C. Under the optimized conditions the chemical structure of the deposited materials seemed to be largely preserved as evidenced by the corresponding IR spectra. The polyglycolic-acid films showed new spectral features indicating considerable morphological changes during PLD. Surface structure and thickness of the layers deposited on Si substrates were examined by an atomic force microscopy (AFM) and a surface profilometer. An empirical model has been elaborated for the description of the femtosecond PLD process. According to this the laser photons are absorbed in the surface layer of target resulting in chemical dissociation of molecules. The fast decomposition causes explosion-like gas expansion generating recoil forces which can tear off and accelerate solid particles. These grains containing target molecules without any chemical damages are ejected from the target and deposited onto the substrate forming a thin layer.

  9. Investigation of diffractive optical element femtosecond laser machining

    Energy Technology Data Exchange (ETDEWEB)

    Chabrol, Grégoire R., E-mail: g.chabrol@ecam-strasbourg.eu [ECAM Strasbourg-Europe, Espace Européen de l’entreprise, 2, rue de Madrid – 67300 SCHILTIGHEIM, CS. 20013, 67012 Strasbourg CEDEX (France); Laboratoire des Sciences de l’Ingénieur, de l’Informatique et de l’Imagerie (ICube), UDS-CNRS, UMR 7357, 300 bld Sébastien Brant, CS 10413, 67412 Illkirch cedex (France); Ciceron, Adline [ECAM Strasbourg-Europe, Espace Européen de l’entreprise, 2, rue de Madrid – 67300 SCHILTIGHEIM, CS. 20013, 67012 Strasbourg CEDEX (France); Laboratoire des Sciences de l’Ingénieur, de l’Informatique et de l’Imagerie (ICube), UDS-CNRS, UMR 7357, 300 bld Sébastien Brant, CS 10413, 67412 Illkirch cedex (France); Twardowski, Patrice; Pfeiffer, Pierre [Laboratoire des Sciences de l’Ingénieur, de l’Informatique et de l’Imagerie (ICube), UDS-CNRS, UMR 7357, 300 bld Sébastien Brant, CS 10413, 67412 Illkirch cedex (France); Télécom Physique Strasbourg – Pôle API – 300 Bd Sébastien Brant – CS 10413, Illkirch Graffenstaden F 67400 (France); and others

    2016-06-30

    Highlights: • A method for rapid manufacturing of optical diffractive element in BK7 is proposed. • A binary grating in BK7 was successfully machined by femtosecond laser pulses. • Process relying on nonlinear absorption in the dielectric due to photoionization. • The binary grating was analysed by SEM and interferometric microscopy. • Simulations by Fourier modal method supported the measured diffractive efficiency. - Abstract: This paper presents an explorative study on the machining of diffractive optical elements (DOEs) in transparent materials using a femtosecond laser source. A simple form of DOE, a binary phase grating with a period of 20.85 μm (σ = 0.5 μm), a groove depth and width of 0.7 μm (σ = 0.2 μm) and 8.8 μm (σ = 0.5 μm) respectively, was successfully machined in BK7. The topographic characteristics were measured by white light interferometry and scanning electron microscopy (SEM). The processing was carried out on high precision stages with an ultrafast fibre laser (350 fs) emitting a 343 nm pulse focused onto the sample with a stationary microscope objective. A diffracted efficiency of 27%, obtained with a spectro goniometer, was corroborated by the theoretical results obtained by the Fourier modal method (FMM), taking into account the measured topographic values. These encouraging results demonstrate that high-speed femtosecond laser manufacturing of DOE in bulk glasses can be achieved, opening the way to rapid prototyping of multi-layered-DOEs.

  10. Initial evaluation of a femtosecond laser system in cataract surgery.

    Science.gov (United States)

    Chang, John S M; Chen, Ivan N; Chan, Wai-Man; Ng, Jack C M; Chan, Vincent K C; Law, Antony K P

    2014-01-01

    To report the early experience and complications during cataract surgery with a noncontact femtosecond laser system. Hong Kong Sanatorium and Hospital, Hong Kong Special Administrative Region, China. Retrospective case series. All patients had anterior capsulotomy or combined anterior capsulotomy and lens fragmentation using a noncontact femtosecond laser system (Lensar) before phacoemulsification. Chart and video reviews were performed retrospectively to determine the intraoperative complication rate. Risk factors associated with the complications were also analyzed. One hundred seventy eyes were included. Free-floating capsule buttons were found in 151 eyes (88.8%). No suction break occurred in any case. Radial anterior capsule tears occurred in 9 eyes (5.3%); they did not extend to the equator or posterior capsule. One eye (0.6%) had a posterior capsule tear. No capsular block syndrome developed, and no nuclei were dropped during irrigation/aspiration (I/A). Anterior capsule tags and miosis occurred in 4 eyes (2.4%) and 17 eyes (10.0%), respectively. Different severities of subconjunctival hemorrhages developed in 71 (43.8%) of 162 eyes after the laser procedure. The mean surgical time from the beginning to the end of suction was 6.72 minutes ± 4.57 (SD) (range 2 to 28 minutes). Cataract surgery with the noncontact femtosecond laser system was safe. No eye lost vision because of complications. Caution should be taken during phacoemulsification and I/A to avoid radial anterior capsule tears and posterior capsule tears. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  11. Femtosecond X-ray scattering in condensed matter

    Energy Technology Data Exchange (ETDEWEB)

    Korff Schmising, Clemens von

    2008-11-24

    This thesis investigates the manifold couplings between electronic and structural properties in crystalline Perovskite oxides and a polar molecular crystal. Ultrashort optical excitation changes the electronic structure and the dynamics of the connected reversible lattice rearrangement is imaged in real time by femtosecond X-ray scattering experiments. An epitaxially grown superlattice consisting of alternating nanolayers of metallic and ferromagnetic strontium ruthenate (SRO) and dielectric strontium titanate serves as a model system to study optically generated stress. In the ferromagnetic phase, phonon-mediated and magnetostrictive stress in SRO display similar sub-picosecond dynamics, similar strengths but opposite sign and different excitation spectra. The amplitude of the magnetic component follows the temperature dependent magnetization square, whereas the strength of phononic stress is determined by the amount of deposited energy only. The ultrafast, phonon-mediated stress in SRO compresses ferroelectric nanolayers of lead zirconate titanate in a further superlattice system. This change of tetragonal distortion of the ferroelectric layer reaches up to 2 percent within 1.5 picoseconds and couples to the ferroelectric soft mode, or ion displacement within the unit cell. As a result, the macroscopic polarization is reduced by up to 100 percent with a 500 femtosecond delay that is due to final elongation time of the two anharmonically coupled modes. Femtosecond photoexcitation of organic chromophores in a molecular, polar crystal induces strong changes of the electronic dipole moment via intramolecular charge transfer. Ultrafast changes of transmitted X-ray intensity evidence an angular rotation of molecules around excited dipoles following the 10 picosecond kinetics of the charge transfer reaction. Transient X-ray scattering is governed by solvation, masking changes of the chromophore's molecular structure. (orig.)

  12. Femtosecond X-ray scattering in condensed matter

    International Nuclear Information System (INIS)

    Korff Schmising, Clemens von

    2008-01-01

    This thesis investigates the manifold couplings between electronic and structural properties in crystalline Perovskite oxides and a polar molecular crystal. Ultrashort optical excitation changes the electronic structure and the dynamics of the connected reversible lattice rearrangement is imaged in real time by femtosecond X-ray scattering experiments. An epitaxially grown superlattice consisting of alternating nanolayers of metallic and ferromagnetic strontium ruthenate (SRO) and dielectric strontium titanate serves as a model system to study optically generated stress. In the ferromagnetic phase, phonon-mediated and magnetostrictive stress in SRO display similar sub-picosecond dynamics, similar strengths but opposite sign and different excitation spectra. The amplitude of the magnetic component follows the temperature dependent magnetization square, whereas the strength of phononic stress is determined by the amount of deposited energy only. The ultrafast, phonon-mediated stress in SRO compresses ferroelectric nanolayers of lead zirconate titanate in a further superlattice system. This change of tetragonal distortion of the ferroelectric layer reaches up to 2 percent within 1.5 picoseconds and couples to the ferroelectric soft mode, or ion displacement within the unit cell. As a result, the macroscopic polarization is reduced by up to 100 percent with a 500 femtosecond delay that is due to final elongation time of the two anharmonically coupled modes. Femtosecond photoexcitation of organic chromophores in a molecular, polar crystal induces strong changes of the electronic dipole moment via intramolecular charge transfer. Ultrafast changes of transmitted X-ray intensity evidence an angular rotation of molecules around excited dipoles following the 10 picosecond kinetics of the charge transfer reaction. Transient X-ray scattering is governed by solvation, masking changes of the chromophore's molecular structure. (orig.)

  13. Femtosecond laser fabrication of microspike-arrays on tungsten surface

    International Nuclear Information System (INIS)

    Sano, Tomokazu; Yanai, Masato; Ohmura, Etsuji; Nomura, Yasumitsu; Miyamoto, Isamu; Hirose, Akio; Kobayashi, Kojiro F.

    2005-01-01

    Microspike-arrays were fabricated by irradiating a femtosecond laser on a tungsten surface through a mask opening in air. The natural logarithms of the calculated intensity distributions diffracted at the edge of the mask opening were qualitatively consistent with the experimental results of the shape and arrays of microspikes fabricated. The shape and the array of microspikes depend on the intensity distribution diffracted at the edge of the mask opening. This microspike-array has the potential to be used as a source of micro emitter tips

  14. Femtosecond few-cycle mid-infrared laser pulses

    DEFF Research Database (Denmark)

    Liu, Xing

    The few-cycle pulses of mid-infrared (mid-IR, wavelength 2-10 microns) have attracted increasing attention owing to their great potentials for high order harmonic generation, time-resolved spectroscopy, precision of cutting and biomedical science.In this thesis, mid-IR frequency conversion.......2 - 5.5 μm with only one fixed pump wavelength, a feature absent in Kerr media. Finally, we experimentally observe supercontinuum generation spanning 1.5 octaves, generated in a 10 mm long silicon-rich nitride waveguide pumped by 100 pJ femtosecond pulses from an erbium fiber laser. The waveguide has...

  15. Femtosecond laser-assisted cataract surgery and implantable miniature telescope

    Directory of Open Access Journals (Sweden)

    Randal Pham

    2017-09-01

    Conclusions and importance: To our knowledge and confirmed by the manufacturer of the implantable miniature telescope this is the first case ever reported of a patient who has undergone femtosecond laser cataract surgery with corneal astigmatism correction and implantation of the implantable miniature telescope. This is also the first case report of the preoperative use of microperimetry and visual electrophysiology to evaluate a patient's postoperative potential visual acuity. The success of the procedure illustrated the importance of meticulous preoperative planning, the combined use of state-of-the-art technologies and the seamless teamwork in order to achieve the best clinical outcome for patients who undergo implantation of the implantable miniature telescope.

  16. Widely tunable femtosecond solitonic radiation in photonic crystal fiber cladding

    DEFF Research Database (Denmark)

    Peng, J. H.; Sokolov, A. V.; Benabid, F.

    2010-01-01

    We report on a means to generate tunable ultrashort optical pulses. We demonstrate that dispersive waves generated by solitons within the small-core features of a photonic crystal fiber cladding can be used to obtain femtosecond pulses tunable over an octave-wide spectral range. The generation...... process is highly efficient and occurs at the relatively low laser powers available from a simple Ti:sapphire laser oscillator. The described phenomenon is general and will play an important role in other systems where solitons are known to exist....

  17. Patterning of silicon differences between nanosecond and femtosecond laser pulses

    Science.gov (United States)

    Weingärtner, M.; Elschner, R.; Bostanjoglo, O.

    1999-01-01

    Si (100) surfaces were exposed to 8 ns and 100 fs laser pulses with fluences≤3 J/cm 2 and ≤0.5 J/cm 2, respectively. Transient stages and final patterns were investigated by pulsed photoelectron microscopy and scanning electron plus light interference microscopy. Though the pattern formation extends for both pulse lengths over the same time of some 10 ns, the patterns are different. Nanosecond pulses produce smooth craters and remove a covering oxide. Femtosecond pulses ablate an oxide-free Si surface and produce flat pits covered by nanodrops, whereas oxide-covered surfaces are converted to a foam, which solidifies to a blistered structure.

  18. Femtosecond Fiber Lasers Based on Dissipative Processes for Nonlinear Microscopy

    Science.gov (United States)

    Wise, Frank W.

    2012-01-01

    Recent progress in the development of femtosecond-pulse fiber lasers with parameters appropriate for nonlinear microscopy is reviewed. Pulse-shaping in lasers with only normal-dispersion components is briefly described, and the performance of the resulting lasers is summarized. Fiber lasers based on the formation of dissipative solitons now offer performance competitive with that of solid-state lasers, but with the benefits of the fiber medium. Lasers based on self-similar pulse evolution in the gain section of a laser also offer a combination of short pulse duration and high pulse energy that will be attractive for applications in nonlinear bioimaging. PMID:23869163

  19. Propagation delay of femtosecond pulses in an optical amplifier

    DEFF Research Database (Denmark)

    Poel, Mike van der; Mørk, Jesper; Hvam, Jørn Märcher

    of 2.6 THz, through a quantum-dot (QD) semiconductor amplifier (SOA) at room temperature. This extremely large bandwidth, on the other hand, is at the cost of a rather small group index change of ?ng=4*10-3. We have performed two types of femtosecond pulse slow-down and advancement experiments....... In the first experiment, we prepare a narrow peak or dip in the SOA gain spectrum by injection of a strong pump pulse4. The resulting dispersion feature is then probed by a weak pulse. In the second experiment, we measure self-slowdown or advancement as pulse energy isincreased5. In both cases, we perform...

  20. Postoperative Endophthalmitis Caused by Staphylococcus haemolyticus following Femtosecond Cataract Surgery

    OpenAIRE

    Wong, Margaret; Baumrind, Benjamin R.; Frank, James H.; Halpern, Robert L.

    2015-01-01

    A 53-year-old Caucasian man underwent femtosecond cataract surgery and then presented with pain and hand motions vision 1 day following surgery. Anterior segment examination showed a 2-mm-layered hypopyon, a well-centered intraocular lens in the sulcus, and an obscured view to the fundus. B-scan ultrasonography showed significant vitritis and that the retina was attached. A tap and an injection of vancomycin 1 mg per 0.1 ml and of ceftazidime 2.25 mg per 0.1 ml were performed. The tap eventua...

  1. Improvement of aluminum drilling efficiency and precision by shaped femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Ying; Qi, Hongxia; Chen, Anmin, E-mail: amchen@jlu.edu.cn; Hu, Zhan, E-mail: huzhan@jlu.edu.cn

    2014-10-30

    Highlights: • The ablation accuracy can be improved by the shaped femtosecond laser pulse. • The ablation rate can be improved by the shaped femtosecond laser pulse with higher laser fluence. • The results can be used to optimize femtosecond micromachining metal. - Abstract: Shaped femtosecond laser pulses with the plain phase (transform-limited pulse) and sine phase (A = 1.2566, T = 30, T = 10, and T = 5) were used to drill Al sheet in vacuum. Using different phase, the number of pulses required to drill through the sheet was different. With lower laser pulse energy, the ablation rate was the highest when plain phase (corresponding to transform limited pulse) was used. With higher laser energy, the optimized ablation rate can be achieved by increasing the time separation between the subpulses of pulse train produced from the sine phase function. And, with the shaped femtosecond laser, the diameter of ablation holes produced was smaller, the ablation precision was also improved. The results showed that shaped femtosecond laser pulse has great advantages in the context of femtosecond laser drilling.

  2. A novel inert crystal delivery medium for serial femtosecond crystallography

    Directory of Open Access Journals (Sweden)

    Chelsie E. Conrad

    2015-07-01

    Full Text Available Serial femtosecond crystallography (SFX has opened a new era in crystallography by permitting nearly damage-free, room-temperature structure determination of challenging proteins such as membrane proteins. In SFX, femtosecond X-ray free-electron laser pulses produce diffraction snapshots from nanocrystals and microcrystals delivered in a liquid jet, which leads to high protein consumption. A slow-moving stream of agarose has been developed as a new crystal delivery medium for SFX. It has low background scattering, is compatible with both soluble and membrane proteins, and can deliver the protein crystals at a wide range of temperatures down to 4°C. Using this crystal-laden agarose stream, the structure of a multi-subunit complex, phycocyanin, was solved to 2.5 Å resolution using 300 µg of microcrystals embedded into the agarose medium post-crystallization. The agarose delivery method reduces protein consumption by at least 100-fold and has the potential to be used for a diverse population of proteins, including membrane protein complexes.

  3. Continuous intracorneal ring implantation for keratoconus using a femtosecond laser.

    Science.gov (United States)

    Jabbarvand, Mahmoud; Salamatrad, Ahmad; Hashemian, Hesam; Mazloumi, Mehdi; Khodaparast, Mehdi

    2013-07-01

    To assess the clinical outcomes after continuous intracorneal ring (ICR) implantation for the management of keratoconus using femtosecond laser technology. Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran. Prospective nonrandomized consecutive case series. All patients presented with reduced visual acuity, contact lens intolerance, and a central corneal thickness of more than 360 μm. A Myoring ICR was inserted in an intrastromal pocket created by a femtosecond laser. The visual, refractive, aberrometric, and corneal biomechanical outcomes were measured preoperatively as well as 1, 3, and 6 months and 1 year postoperatively. The study comprised 98 keratoconic eyes of 98 patients with a mean age of 30.7 years ± 9.01 (SD). Fifteen eyes (15.3%) had grade I keratoconus, 37 eyes (37.7%) had grade II keratoconus, 24 eyes (24.5%) had grade III keratoconus, and 22 eyes (22.4%) had grade IV keratoconus. The uncorrected and corrected distance visual acuities and spherical and cylindrical errors improved 1 month after surgery (P.05). The mean keratometry and corneal astigmatism decreased 1 month after surgery (P.05). Primary coma decreased significantly (P=.03), and spherical aberrations increased significantly (P<.001) postoperatively. Continuous ICR implantation in keratoconus appears to be an acceptable substitute for keratoplasty in advanced keratoconus. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  4. Tracking ultrafast relaxation dynamics of furan by femtosecond photoelectron imaging

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yuzhu, E-mail: yuzhu.liu@gmail.com [School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Knopp, Gregor [Paul Scherrer Institute, Villigen 5232 (Switzerland); Qin, Chaochao [Department of Physics, Henan Normal University, Xinxiang 453007 (China); Gerber, Thomas [Paul Scherrer Institute, Villigen 5232 (Switzerland)

    2015-01-13

    Graphical abstract: - Highlights: • Relaxation dynamics of furan are tracked by femtosecond photoelectron imaging. • The mechanism for ultrafast formation of α-carbene and β-carbene is proposed. • Ultrafast internal conversion from S{sub 2} to S{sub 1} is observed. • The transient characteristics of the fragment ions are obtained. • Single-color multi-photon ionization dynamics at 800 nm are also studied. - Abstract: Ultrafast internal conversion dynamics of furan has been studied by femtosecond photoelectron imaging (PEI) coupled with photofragmentation (PF) spectroscopy. Photoelectron imaging of single-color multi-photon ionization and two-color pump–probe ionization are obtained and analyzed. Photoelectron bands are assigned to the related states. The time evolution of the photoelectron signal by pump–probe ionization can be well described by a biexponential decay: two rapid relaxation pathways with time constants of ∼15 fs and 85 (±11) fs. The rapid relaxation is ascribed to the ultrafast internal conversion (IC) from the S{sub 2} state to the vibrationally hot S{sub 1} state. The second relaxation process is attributed to the redistributions and depopulation of secondarily populated high vibronic S{sub 1} state and the formation of α-carbene and β-carbene by H immigration. Additionally, the transient characteristics of the fragment ions are also measured and discussed as a complementary understanding.

  5. Tracking ultrafast relaxation dynamics of furan by femtosecond photoelectron imaging

    International Nuclear Information System (INIS)

    Liu, Yuzhu; Knopp, Gregor; Qin, Chaochao; Gerber, Thomas

    2015-01-01

    Graphical abstract: - Highlights: • Relaxation dynamics of furan are tracked by femtosecond photoelectron imaging. • The mechanism for ultrafast formation of α-carbene and β-carbene is proposed. • Ultrafast internal conversion from S 2 to S 1 is observed. • The transient characteristics of the fragment ions are obtained. • Single-color multi-photon ionization dynamics at 800 nm are also studied. - Abstract: Ultrafast internal conversion dynamics of furan has been studied by femtosecond photoelectron imaging (PEI) coupled with photofragmentation (PF) spectroscopy. Photoelectron imaging of single-color multi-photon ionization and two-color pump–probe ionization are obtained and analyzed. Photoelectron bands are assigned to the related states. The time evolution of the photoelectron signal by pump–probe ionization can be well described by a biexponential decay: two rapid relaxation pathways with time constants of ∼15 fs and 85 (±11) fs. The rapid relaxation is ascribed to the ultrafast internal conversion (IC) from the S 2 state to the vibrationally hot S 1 state. The second relaxation process is attributed to the redistributions and depopulation of secondarily populated high vibronic S 1 state and the formation of α-carbene and β-carbene by H immigration. Additionally, the transient characteristics of the fragment ions are also measured and discussed as a complementary understanding

  6. Stress-induced birefringence control in femtosecond laser glass welding

    Science.gov (United States)

    Gstalter, M.; Chabrol, G.; Bahouka, A.; Serreau, L.; Heitz, J.-L.; Taupier, G.; Dorkenoo, K.-D.; Rehspringer, J.-L.; Lecler, S.

    2017-11-01

    Glass welding by femtosecond laser pulses causes microscopic structural modifications, affecting the refractive index due to residual stress. Locally induced birefringence is studied by photoelasticimetry using a polarized light microscope. The study is performed on borosilicate thin glass plates using an industrial femtosecond laser generating 300 fs pulses at 500 kHz, with a 100 mm focusing length F-theta lens allowing fast welding. For low-energy deposition, the principal birefringence axes are determined to be homogenous along the seam and perpendicular and parallel to the laser scanning direction. Tensile stress is induced in the laser scanning direction by the welding seams. The induced birefringence is determined to be equivalent for in-volume irradiated track and welding seams. An inhomogeneity of the birefringence within the seam is observed for the first time at high-energy deposition. The distribution of the birefringence can be controlled with the laser scanning patterns. The amount of residual stress is measured by compensating the local birefringence. The birefringence Δ n is estimated at 2.4 × 10^{-4}, corresponding to a residual stress amount around 59 MPa. The influence of the welding geometry is also illustrated.

  7. Review: Serial Femtosecond Crystallography: A Revolution in Structural Biology

    Science.gov (United States)

    Martin-Garcia, Jose M.; Conrad, Chelsie E.; Coe, Jesse; Roy-Chowdhury, Shatabdi; Fromme, Petra

    2016-01-01

    Macromolecular crystallography at synchrotron sources has proven to be the most influential method within structural biology, producing thousands of structures since its inception. While its utility has been instrumental in progressing our knowledge of structures of molecules, it suffers from limitations such as the need for large, well-diffracting crystals, and radiation damage that can hamper native structural determination. The recent advent of X-ray free electron lasers (XFELs) and their implementation in the emerging field of serial femtosecond crystallography (SFX) has given rise to a remarkable expansion upon existing crystallographic constraints, allowing structural biologists access to previously restricted scientific territory. SFX relies on exceptionally brilliant, micro-focused X-ray pulses, which are femtoseconds in duration, to probe nano/micrometer sized crystals in a serial fashion. This results in data sets comprised of individual snapshots, each capturing Bragg diffraction of single crystals in random orientations prior to their subsequent destruction. Thus structural elucidation while avoiding radiation damage, even at room temperature, can now be achieved. This emerging field has cultivated new methods for nanocrystallogenesis, sample delivery, and data processing. Opportunities and challenges within SFX are reviewed herein. PMID:27143509

  8. Serial Femtosecond Crystallography Opens New Avenues for Structural Biology

    Science.gov (United States)

    Coe, Jesse; Fromme, Petra

    2016-01-01

    Free electron lasers (FELs) provide X-ray pulses in the femtosecond time domain with up to 1012 higher photon flux than synchrotrons and open new avenues for the determination of difficult to crystallize proteins, like large complexes and human membrane proteins. While the X-ray pulses are so strong that they destroy any solid material, the crystals diffract before they are destroyed. The most successful application of FELs for biology has been the method of serial femtosecond crystallography (SFX) where nano or microcrystals are delivered to the FEL beam in a stream of their mother liquid at room temperature, which ensures the replenishment of the sample before the next X-ray pulse arrives. New injector technology allows also for the delivery of crystal in lipidic cubic phases or agarose, which reduces the sample amounts for an SFX data set by two orders of magnitude. Time-resolved SFX also allows for analysis of the dynamics of biomolecules, the proof of principle being recently shown for light-induced reactions in photosystem II and photoactive yellow protein. An SFX data sets consist of thousands of single crystal snapshots in random orientations, which can be analyzed now “on the fly” by data analysis programs specifically developed for SFX, but de-novo phasing is still a challenge, that might be overcome by two-color experiments or phasing by shape transforms. PMID:26786767

  9. Serial femtosecond crystallography: A revolution in structural biology.

    Science.gov (United States)

    Martin-Garcia, Jose M; Conrad, Chelsie E; Coe, Jesse; Roy-Chowdhury, Shatabdi; Fromme, Petra

    2016-07-15

    Macromolecular crystallography at synchrotron sources has proven to be the most influential method within structural biology, producing thousands of structures since its inception. While its utility has been instrumental in progressing our knowledge of structures of molecules, it suffers from limitations such as the need for large, well-diffracting crystals, and radiation damage that can hamper native structural determination. The recent advent of X-ray free electron lasers (XFELs) and their implementation in the emerging field of serial femtosecond crystallography (SFX) has given rise to a remarkable expansion upon existing crystallographic constraints, allowing structural biologists access to previously restricted scientific territory. SFX relies on exceptionally brilliant, micro-focused X-ray pulses, which are femtoseconds in duration, to probe nano/micrometer sized crystals in a serial fashion. This results in data sets comprised of individual snapshots, each capturing Bragg diffraction of single crystals in random orientations prior to their subsequent destruction. Thus structural elucidation while avoiding radiation damage, even at room temperature, can now be achieved. This emerging field has cultivated new methods for nanocrystallogenesis, sample delivery, and data processing. Opportunities and challenges within SFX are reviewed herein. Published by Elsevier Inc.

  10. Whole-pattern fitting technique in serial femtosecond nanocrystallography

    Directory of Open Access Journals (Sweden)

    Ruben A. Dilanian

    2016-03-01

    Full Text Available Serial femtosecond X-ray crystallography (SFX has created new opportunities in the field of structural analysis of protein nanocrystals. The intensity and timescale characteristics of the X-ray free-electron laser sources used in SFX experiments necessitate the analysis of a large collection of individual crystals of variable shape and quality to ultimately solve a single, average crystal structure. Ensembles of crystals are commonly encountered in powder diffraction, but serial crystallography is different because each crystal is measured individually and can be oriented via indexing and merged into a three-dimensional data set, as is done for conventional crystallography data. In this way, serial femtosecond crystallography data lie in between conventional crystallography data and powder diffraction data, sharing features of both. The extremely small sizes of nanocrystals, as well as the possible imperfections of their crystallite structure, significantly affect the diffraction pattern and raise the question of how best to extract accurate structure-factor moduli from serial crystallography data. Here it is demonstrated that whole-pattern fitting techniques established for one-dimensional powder diffraction analysis can be feasibly extended to higher dimensions for the analysis of merged SFX diffraction data. It is shown that for very small crystals, whole-pattern fitting methods are more accurate than Monte Carlo integration methods that are currently used.

  11. Facile synthesis of bimetallic nanoparticles by femtosecond laser irradiation method

    Directory of Open Access Journals (Sweden)

    Joseph Lik Hang Chau

    2017-02-01

    Full Text Available Bimetallic Pt–Au and Fe–Pt nanoparticles are successfully fabricated by high-intensity laser irradiation of aqueous solution without any chemical reducing agent. The mechanism of the formation of bimetallic nanoalloys by laser irradiation of the solution without using any reducing agent was mainly attributed to the optically induced decomposition of water molecule. When an intense femtosecond laser field is focused in an aqueous solution containing metal ions, the free electrons will be produced by the dissociation of water molecules, these free electrons and hydrogen radicals contained in the plasma might be caught by H+ or OH− ions to form the bubbles of H2 and O2 gases or they can be trapped by metal ions, resulting in the formation of metal atoms during the femtosecond laser irradiation process. The average size of the bimetallic nanoparticles increases with irradiation time. This technique is simple and ‘green’ process without using any chemicals except for metal salt and dispersing agent.

  12. Femtosecond electron-bunch dynamics in laser wakefields and vacuum

    Directory of Open Access Journals (Sweden)

    A. G. Khachatryan

    2007-12-01

    Full Text Available Recent advances in laser wakefield acceleration demonstrated the generation of extremely short (with a duration of a few femtoseconds relativistic electron bunches with relatively low (of the order of couple of percent energy spread. In this article we study the dynamics of such bunches in drift space (vacuum and in channel-guided laser wakefields. Analytical solutions were found for the transverse coordinate of an electron and for the bunch envelope in the wakefield in the case of arbitrary change in the energy. Our results show strong bunch dynamics already on a millimeter scale propagation distance both in plasma and in vacuum. When the bunch propagates in vacuum, its transverse sizes grow considerably; the same is observed for the normalized bunch emittance that worsens the focusability of the bunch. A scheme of two-stage laser wakefield accelerator with small drift space between the stages is proposed. It is found that fast longitudinal betatron phase mixing occurs in a femtosecond bunch when it propagates along the wakefield axis. When bunch propagates off axis, strong bunch decoherence and fast emittance degradation due to the finite bunch length was observed.

  13. Optical cell cleaning with NIR femtosecond laser pulses

    Science.gov (United States)

    Uchugonova, Aisada; Breunig, Hans Georg; Batista, Ana; König, Karsten

    2015-03-01

    Femtosecond laser microscopes have been used as both micro and nanosurgery tools. The optical knock-out of undesired cells in multiplex cell clusters shall be further reported on in this study. Femtosecond laser-induced cell death is beneficial due to the reduced collateral side effects and therefore can be used to selectively destroy target cells within monolayers, as well as within 3D tissues, all the while preserving cells of interest. This is an important characteristic for the application in stem cell research and cancer treatment. Non-precise damage compromises the viability of neighboring cells by inducing side effects such as stress to the cells surrounding the target due to the changes in the microenvironment, resulting from both the laser and laser-exposed cells. In this study, optimum laser parameters for optical cleaning by isolating single cells and cell colonies are exploited through the use of automated software control. Physiological equilibrium and cellular responses to the laser induced damages are also investigated. Cell death dependence on laser focus, determination and selectivity of intensity/dosage, controllable damage and cell recovery mechanisms are discussed.

  14. Influence of SOD on THG for femtosecond laser pulse

    Science.gov (United States)

    Trofimov, Vyacheslav A.; Sidorov, Pavel S.

    2017-02-01

    THG is used nowadays in many practical applications such as a substance diagnostics, and biological objects imaging, and etc. Therefore, THG features understanding are urgent problem and this problem attracts an attention of many researchers. In this paper we analyze THG efficiency of a femtosecond laser pulse. Consideration is based on computer simulation of the laser pulse propagation with taking into account a selfand cross- modulation of the interacting waves, and their SOD, and phase mismatching. Moreover, we analyze an influence of the non-homogeneous phase mismatching along laser pulse propagation coordinate. In this case, a phase matching occurs only in narrow area of longitudinal coordinate. Due to strong self- and crossmodulation of interacting waves it is possible to manage effective THG. Using the frame-work of long pulse duration approximation and plane wave approximation as well as an original approach we write the explicit solution of Schrödinger equations describing the frequency tripling of femtosecond pulse. It should be stressed, that the main feature of our approach consists in conservation laws using corresponding to wave interaction process.

  15. Optical Synchronization Systems for Femtosecond X-ray Sources

    International Nuclear Information System (INIS)

    Wilcox, Russell; Staples, John W.; Holzwarth, Ronald

    2004-01-01

    In femtosecond pump/probe experiments using short X-Ray and optical pulses, precise synchronization must be maintained between widely separated lasers in a synchrotron or FEL facility. We are developing synchronization systems using optical signals for applications requiring different ranges of timing error over 100 meter of glass fiber. For stabilization in the hundred femtosecond range a CW laser is amplitude modulated at 1 10 GHz, the signal retroreflected from the far end, and the relative phase used to correct the transit time with a piezoelectric phase modulator. For the sub-10 fsec range the laser frequency itself is upshifted 55 MHz with an acousto-optical modulator, retroreflected, upshifted again and phase compared at the sending end to a 110 MHz reference. Initial experiments indicate less than 1 fsec timing jitter. To lock lasers in the sub-10 fs range we will lock two single-frequency lasers separated by several tera Hertz to a master modelocked fiber laser, transmit the two frequencies over fiber, and lock two comb lines of a slave laser to these frequencies, thus synchronizing the two modelocked laser envelopes

  16. Femtosecond profiling of shaped x-ray pulses

    Science.gov (United States)

    Hoffmann, M. C.; Grguraš, I.; Behrens, C.; Bostedt, C.; Bozek, J.; Bromberger, H.; Coffee, R.; Costello, J. T.; DiMauro, L. F.; Ding, Y.; Doumy, G.; Helml, W.; Ilchen, M.; Kienberger, R.; Lee, S.; Maier, A. R.; Mazza, T.; Meyer, M.; Messerschmidt, M.; Schorb, S.; Schweinberger, W.; Zhang, K.; Cavalieri, A. L.

    2018-03-01

    Arbitrary manipulation of the temporal and spectral properties of x-ray pulses at free-electron lasers would revolutionize many experimental applications. At the Linac Coherent Light Source at Stanford National Accelerator Laboratory, the momentum phase-space of the free-electron laser driving electron bunch can be tuned to emit a pair of x-ray pulses with independently variable photon energy and femtosecond delay. However, while accelerator parameters can easily be adjusted to tune the electron bunch phase-space, the final impact of these actuators on the x-ray pulse cannot be predicted with sufficient precision. Furthermore, shot-to-shot instabilities that distort the pulse shape unpredictably cannot be fully suppressed. Therefore, the ability to directly characterize the x-rays is essential to ensure precise and consistent control. In this work, we have generated x-ray pulse pairs via electron bunch shaping and characterized them on a single-shot basis with femtosecond resolution through time-resolved photoelectron streaking spectroscopy. This achievement completes an important step toward future x-ray pulse shaping techniques.

  17. Formation of periodic nanostructures using a femtosecond laser to control cell spreading on titanium

    Science.gov (United States)

    Shinonaga, T.; Tsukamoto, M.; Kawa, T.; Chen, P.; Nagai, A.; Hanawa, T.

    2015-06-01

    Although titanium (Ti) is a common biomaterial, controlling cell spreading by forming periodic structures using a femtosecond laser should improve its biocompatibility. Herein we investigate the influence of periodic nanostructures formed on the surface of a Ti plate on cell spreading. Nanostructures with a periodicity of 590 nm are formed using a femtosecond laser with a wavelength of 775 nm. Cell spreading on the plate without period structures lacks a definite direction, whereas cell spreading on the Ti plate with periodic structures occurs along the grooves, suggesting that forming periodic structures via a femtosecond laser can control cell spreading.

  18. TiOx-based thin-film transistors prepared by femtosecond laser pre-annealing

    Science.gov (United States)

    Shan, Fei; Kim, Sung-Jin

    2018-02-01

    We report on thin-film transistors (TFTs) based on titanium oxide (TiOx) prepared using femtosecond laser pre-annealing for electrical application of n-type channel oxide transparent TFTs. Amorphous TFTs using TiOx semiconductors as an active layer have a low-temperature process and show remarkable electrical performance. And the femtosecond laser pre-annealing process has greater flexibility and development space for semiconductor production activity, with a fast preparation method. TFTs with a TiOx semiconductor pre-annealed via femtosecond laser at 3 W have a pinhole-free and smooth surface without crystal grains.

  19. Non-Linear Optical Studies of IR Materials with Infrared Femtosecond Laser

    Science.gov (United States)

    2016-12-15

    AFRL-RD-PS- AFRL-RD-PS- TR-2016-0055 TR-2016-0055 NON-LINEAR OPTICAL STUDIES OF IR MATERIALS WITH INFRARED FEMTOSECOND LASER Enam...TITLE AND SUBTITLE Non-Linear Optical Studies of IR Materials with Infrared Femtosecond Laser 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9451-14-1...femtosecond mid- IR (MIR) pulses from 2 - 4 micron wavelength at a 1 kHz repetition rate were used to explore nonlinear effects into various MIR materials

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

    Science.gov (United States)

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

    2008-09-29

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

  1. Femtosecond Laser Desorption of Thin Polymer Films from a Dielectric Surface

    Directory of Open Access Journals (Sweden)

    Mercadier L.

    2013-11-01

    Full Text Available We desorb polymer films from fused silica with a femtosecond laser and characterize the results by atomic force microscopy. Our study as a function of beam geometry and energy reveals two ways of achieving spatially controlled nanodesorption.

  2. Photo-transfection of mouse embryonic stem cells with plasmid DNA using femtosecond laser pulses

    CSIR Research Space (South Africa)

    Thobakgale, Lebogang

    2017-01-01

    Full Text Available This presentation is about the photo-transfection of mouse embryonic stem cells with plasmid DNA using femtosecond laser pulses. It outlines the background on embryonic stem cells (ES) and phototransfection....

  3. Volume gratings and welding of glass/plastic by femtosecond laser direct writing

    Science.gov (United States)

    Watanabe, Wataru

    2018-01-01

    Femtosecond laser direct writing is used to fabricate diffractive optical elements in three dimensions and to weld glass and/or plastic. In this paper, we review volume gratings in plastics and welding of glass/plastic by femtosecond laser direct writing. Volume gratings were embedded inside polymethyl methacrylate (PMMA) by femtosecond laser pulses. The diffraction efficiency of the gratings increased after fabrication and reached the maximum. After an initial slow decrease within first several days after the fabrication, the efficiency increased again. This phenomena was called regeneration of the grating. We also demonstrate welding of PMMA by dendrite pattern using femtosecond laser pulses. Laser pulses are focused at the interface of two PMMA substrates with an air gap and melted materials in laser-irradiated region spread within a gap of the substrates and dendrite morphology of melted PMMA was observed outside the laser irradiated area. Finally, we show welding of glass/plastic and metal.

  4. Selective deactivation of M13 bacteriophage in E. Coli using femtosecond laser pulses

    CSIR Research Space (South Africa)

    Molukanele, P

    2011-09-01

    Full Text Available Potential for the selective deactivation of viruses while leaving the sensitive material such as the host cell unharmed was studied using a femtosecond laser system, and preliminary results are reported....

  5. Mapping chemical bonding of reaction intermediates with femtosecond X-ray laser spectroscopy

    OpenAIRE

    Wernet, Ph.; Beye, Martin; Kunnus, K.; Leitner, T.; Mazza, T.; Meyer, M.; Nordlund, D.; Odelius, M.; Quevedo, W.; Radcliffe, P.; Rajkovic, I.; Schlotter, B.; de Groot, F.; Scholz, Mirko; Schreck, S.

    2013-01-01

    We determine the pathways in the photo-dissociation reactions of Fe(CO)$_5$ both in the gas phase and in solution by mapping the valence electronic structure of the reaction intermediates with femtosecond X-ray laser spectroscopy.

  6. Electrofluidics fabricated by space-selective metallization in glass microfluidic structures using femtosecond laser direct writing.

    Science.gov (United States)

    Xu, Jian; Wu, Dong; Hanada, Yasutaka; Chen, Chi; Wu, Sizhu; Cheng, Ya; Sugioka, Koji; Midorikawa, Katsumi

    2013-12-07

    Space-selective metallization of the inside of glass microfluidic structures using femtosecond laser direct-write ablation followed by electroless plating is demonstrated. Femtosecond laser direct writing followed by thermal treatment and successive chemical etching allows us to fabricate three-dimensional microfluidic structures inside photosensitive glass. Then, femtosecond laser ablation followed by electroless metal plating enables flexible deposition of patterned metal films on desired locations of not only the top and bottom walls but also the sidewalls of fabricated microfluidic structures. A volume writing scheme for femtosecond laser irradiation inducing homogeneous ablation on the sidewalls of microfluidic structures is proposed for sidewall metallization. The developed technique is used to fabricate electrofluidics in which microelectric components are integrated into glass microchannels. The fabricated electrofluidics are applied to control the temperature of liquid samples in the microchannels for the enhancement of chemical reactions and to manipulate the movement of biological samples in the microscale space.

  7. Enantioselective femtosecond laser photoionization spectrometry of limonene using photoelectron circular dichroism

    NARCIS (Netherlands)

    Rafiee Fanood, M.M.; Janssen, M.H.M.; Powis, I.

    2015-01-01

    Limonene is ionized by circularly polarized 420 nm femtosecond laser pulses. Ion mass and photoelectron energy spectra identify the dominant (2 + 1) multiphoton ionization mechanism, aided by TDDFT calculations of the Rydberg excitations. Photoelectron circular dichroism measurements on pure

  8. Two-Dimensional Fluorescence Spectroscopy for Measuring Uranium Isotopes in Femtosecond Laser Ablation

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Brumfield, Brian E.; Harilal, Sivanandan S.; Hartig, Kyle C.; Jovanovic, Igor

    2017-05-30

    We present the first two-dimensional fluorescence spectroscopy measurements of uranium isotopes in femtosecond laser ablation plasmas. A new method of signal normalization is presented to reduce noise in absorption-based measurements of laser ablation.

  9. Femtosecond dynamics of a spaser and unidirectional emission from a perfectly spherical nanoparticle

    KAUST Repository

    Gongora, J. S. Totero

    2015-01-01

    We investigate the femtosecond dynamics of the spaser emission by combining ab-initio simulations and thermodynamic analysis. Interestingly, the emission is characterized by rotational evolution, opening to the generation of unidirectional emission from perfectly spherical nanoparticles. © OSA 2015.

  10. Comparison of Heat Affected Zone due to nanosecond and femtosecond laser pulses using Transmission Electronic Microscopy

    OpenAIRE

    Le Harzic, Ronan; Huot, Nicolas; Audouard, Eric; Jonin, Christian; Laporte, Pierre; Valette, Stéphane; Fraczkievic, Anna; Fortunier, Roland

    2002-01-01

    International audience; This letter presents a method aimed at quantifying the dimensions of the heat-affected zone ~HAZ!, produced during nanosecond and femtosecond laser–matter interactions. According to this method, 0.1 mm thick Al samples were microdrilled and observed by a transmission electronic microscopy technique. The holes were produced at laser fluences above the ablation threshold in both nanosecond and femtosecond regimes ~i.e., 5 and 2 J/cm2, respectively!. The grain size in the...

  11. Periodic refractive index modifications inscribed in polymer optical fibre by focussed IR femtosecond pulses

    DEFF Research Database (Denmark)

    Stecher, Matthias; Williams, Robert J.; Bang, Ole

    Focussed femtosecond laser pulses were used to inscribe a periodic array of modifications in the core of a polymer optical fibre. Structural and refractive-index modifications have been observed at different pulse energies using DIC microscopy.......Focussed femtosecond laser pulses were used to inscribe a periodic array of modifications in the core of a polymer optical fibre. Structural and refractive-index modifications have been observed at different pulse energies using DIC microscopy....

  12. Femtosecond X-ray absorption and emission spectroscopy on zno nanoparticles in solution

    DEFF Research Database (Denmark)

    Penfold, Thomas J.; Szlachetko, Jakub; Gawelda, Wojciech

    2016-01-01

    We have performed femtosecond X-ray spectroscopy measurements after UV photoexcitation of a colloidal solution of ZnO nanoparticles. The results indicate sub-ps hole trapping at oxygen vacancies with shallowly-trapped electrons in the conduction band.......We have performed femtosecond X-ray spectroscopy measurements after UV photoexcitation of a colloidal solution of ZnO nanoparticles. The results indicate sub-ps hole trapping at oxygen vacancies with shallowly-trapped electrons in the conduction band....

  13. Laser photoionization of triacetone triperoxide (TATP) by femtosecond and nanosecond laser pulses

    Science.gov (United States)

    Mullen, Christopher; Huestis, David; Coggiola, Michael; Oser, Harald

    2006-05-01

    Laser ionization time-of-flight mass spectrometry has been applied to the study of triacetone triperoxide (TATP), an improvised explosive. Wavelength dependent mass spectra in two time regimes were acquired using nanosecond (5 ns) and femtosecond (130 fs) laser pulses. We find the major difference between the two time regimes to be the detection of the parent molecular ion when femtosecond laser pulses are employed.

  14. Undulators to FELs: Nanometers, Femtoseconds, Coherence and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Attwood, David [University of California Berkeley

    2011-11-30

    For scientists in many fields, from material science to the life sciences and archeology, synchrotron radiation, and in particular undulator radiation, has provide an intense source of x-rays which are tunable to the absorption edges of particular elements of interest, often permitting studies at high spatial and spectral resolution. Now a close cousin to the undulator, the x-ray free electron laser (XFEL) has emerged with improved spatial coherence and, perhaps more importantly, femtosecond pulse durations which permit dynamical studies. In the future attosecond x-ray capabilities are anticipated. In this colloqium we will describe some state of the art undulator studies, how undulators work, the evolution to FELs, their pulse and coherence properties, and the types of experiments envisioned.

  15. Serial femtosecond X-ray diffraction of enveloped virus microcrystals

    Directory of Open Access Journals (Sweden)

    Robert M. Lawrence

    2015-07-01

    Full Text Available Serial femtosecond crystallography (SFX using X-ray free-electron lasers has produced high-resolution, room temperature, time-resolved protein structures. We report preliminary SFX of Sindbis virus, an enveloped icosahedral RNA virus with ∼700 Å diameter. Microcrystals delivered in viscous agarose medium diffracted to ∼40 Å resolution. Small-angle diffuse X-ray scattering overlaid Bragg peaks and analysis suggests this results from molecular transforms of individual particles. Viral proteins undergo structural changes during entry and infection, which could, in principle, be studied with SFX. This is an important step toward determining room temperature structures from virus microcrystals that may enable time-resolved studies of enveloped viruses.

  16. Micro-hole drilling and cutting using femtosecond fiber laser

    Science.gov (United States)

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

    2014-05-01

    Micro-hole drilling and cutting in ambient air are presented by using a femtosecond fiber laser. At first, the micro-hole drilling was investigated in both transparent (glasses) and nontransparent (metals and tissues) materials. The shape and morphology of the holes were characterized and evaluated with optical and scanning electron microscopy. Debris-free micro-holes with good roundness and no thermal damage were demonstrated with the aspect ratio of 8∶1. Micro-hole drilling in hard and soft tissues with no crack or collateral thermal damage is also demonstrated. Then, trench micromachining and cutting were studied for different materials and the effect of the laser parameters on the trench properties was investigated. Straight and clean trench edges were obtained with no thermal damage.

  17. Femtosecond laser generated gold nanoparticles and their plasmonic properties

    International Nuclear Information System (INIS)

    Das, Rupali; Navas, M. P.; Soni, R. K.

    2016-01-01

    The pulsed laser ablation in liquid medium is now commonly used to generate stable colloidal nanoparticles (NPs) in absence of any chemical additives or stabilizer with diverse applications. In this paper, we report generation of gold NPs (Au NPs) by ultra-short laser pulses. Femtosecond (fs) laser radiation (λ = 800 nm) has been used to ablate a gold target in pure de-ionized water to produce gold colloids with smallsize distribution. The average size of the particles can be further controlled by subjecting to laser-induced post-irradiation providing a versatile physical method of size-selected gold nanoparticles. The optical extinction and morphological dimensions were investigated with UV-Vis spectroscopy and Transmission Electron Microscopy measurements, respectively. Finite difference time domain (FDTD) method is employed to calculate localized surface plasmon (LSPR) wavelength and the near-field generated by Au NPs and their hybrids.

  18. Polarization dependent nanostructuring of silicon with femtosecond vortex pulse

    Directory of Open Access Journals (Sweden)

    M. G. Rahimian

    2017-08-01

    Full Text Available We fabricated conical nanostructures on silicon with a tip dimension of ∼ 70 nm using a single twisted femtosecond light pulse carrying orbital angular momentum (ℓ=±1. The height of the nano-cone, encircled by a smooth rim, increased from ∼ 350 nm to ∼ 1 μm with the pulse energy and number of pulses, whereas the apex angle remained constant. The nano-cone height was independent of the helicity of the twisted light; however, it is reduced for linear polarization compared to circular at higher pulse energies. Fluid dynamics simulations show nano-cones formation when compressive forces arising from the radial inward motion of the molten material push it perpendicular to the surface and undergo re-solidification. Simultaneously, the radial outward motion of the molten material re-solidifies after reaching the cold boundary to form a rim. Overlapping of two irradiated spots conforms to the fluid dynamics model.

  19. Femtosecond laser written arrayed waveguide gratings with integrated photonic lanterns.

    Science.gov (United States)

    Douglass, G; Dreisow, F; Gross, S; Withford, M J

    2018-01-22

    We demonstrate for the first time functional arrayed waveguide gratings (AWGs) fabricated using the femtosecond laser direct-write technique. This fabrication technique is a mask-less alternative to lithography enabling design flexibility and rapid prototyping. It is ideal for customized small scale production for new applications. The devices were demonstrated in the visible region at 632.8 nm with a measured free spectral range (FSR) of 22.2 nm, and 1.35 nm resolution. To highlight the advantages of using a 3-dimensional fabrication technique, a 3-port photonic lantern was integrated with an AWG in a single monolithic chip. Integration of this type is not feasible with lithography-based AWG fabrication and can increase the functionality of AWGs for sensing applications.

  20. Theoretical Femtosecond Physics Atoms and Molecules in Strong Laser Fields

    CERN Document Server

    Grossmann, Frank

    2008-01-01

    Theoretical femtosecond physics is a new field of research. Theoretical investigations of atoms and molecules interacting with pulsed or continuous wave lasers of up to atomic field strengths are leading to an understanding of many challenging experimental discoveries. Laser-matter interaction is treated on a nonperturbative level in the book using approximate and numerical solutions of the time-dependent Schrödinger equation. The light field is treated classically. Physical phenomena, ranging from ionization of atoms to the ionization and dissociation of molecules and the control of chemical reactions are presented and discussed. Theoretical background for experiments with strong and short laser pulses is given. Several exercises are included in the main text. Some detailed calculations are performed in the appendices.

  1. Carrier dynamics in femtosecond-laser-excited bismuth telluride

    Science.gov (United States)

    Wang, J. L.; Guo, L.; Ling, C.; Song, Y. M.; Xu, X. F.; Ni, Z. H.; Chen, Y. F.

    2016-04-01

    The carrier dynamics of B i2T e3 is studied using the femtosecond pump-probe technique. Three distinct processes, including free carrier absorption, band filling, and electron-hole recombination, are found to contribute to the reflectivity changes. The two-temperature model is used to describe the intraband energy relaxation process of carriers, and the Drude contribution well explains the intensity dependence of the peak values of the nonoscillatory component in the reflectivity signal. The combined effects of free carrier absorption and band filling result in a reflection minimum at about 2 ps after laser excitation. The nonzero background signal increases linearly with the pump fluence, which is attributed to the electron-hole recombination. Finally, our results provide an illustration of investigating the carrier dynamics in semiconductors from the ultrafast reflectivity spectra.

  2. Microcrystal delivery by pulsed liquid droplet for serial femtosecond crystallography.

    Science.gov (United States)

    Mafuné, Fumitaka; Miyajima, Ken; Tono, Kensuke; Takeda, Yoshihiro; Kohno, Jun-ya; Miyauchi, Naoya; Kobayashi, Jun; Joti, Yasumasa; Nango, Eriko; Iwata, So; Yabashi, Makina

    2016-04-01

    A liquid-droplet injector has been developed that delivers pristine microcrystals to an X-ray irradiation area for conducting serial femtosecond crystallography (SFX) with an X-ray free-electron laser (XFEL). By finely tuning the pulsed liquid droplets in time and space, a high hit rate of the XFEL pulses to microcrystals in the droplets was achieved for measurements using 5 µm tetragonal lysozyme crystals, which produced 4265 indexable diffraction images in about 30 min. The structure was determined at a resolution of 2.3 Å from <0.3 mg of protein. With further improvements such as reduction of the droplet size, liquid droplets have considerable potential as a crystal carrier for SFX with low sample consumption.

  3. A Bright Future for Serial Femtosecond Crystallography with XFELs.

    Science.gov (United States)

    Johansson, Linda C; Stauch, Benjamin; Ishchenko, Andrii; Cherezov, Vadim

    2017-09-01

    X-ray free electron lasers (XFELs) have the potential to revolutionize macromolecular structural biology due to the unique combination of spatial coherence, extreme peak brilliance, and short duration of X-ray pulses. A recently emerged serial femtosecond (fs) crystallography (SFX) approach using XFEL radiation overcomes some of the biggest hurdles of traditional crystallography related to radiation damage through the diffraction-before-destruction principle. Intense fs XFEL pulses enable high-resolution room-temperature structure determination of difficult-to-crystallize biological macromolecules, while simultaneously opening a new era of time-resolved structural studies. Here, we review the latest developments in instrumentation, sample delivery, data analysis, crystallization methods, and applications of SFX to important biological questions, and conclude with brief insights into the bright future of structural biology using XFELs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Serial femtosecond crystallography datasets from G protein-coupled receptors.

    Science.gov (United States)

    White, Thomas A; Barty, Anton; Liu, Wei; Ishchenko, Andrii; Zhang, Haitao; Gati, Cornelius; Zatsepin, Nadia A; Basu, Shibom; Oberthür, Dominik; Metz, Markus; Beyerlein, Kenneth R; Yoon, Chun Hong; Yefanov, Oleksandr M; James, Daniel; Wang, Dingjie; Messerschmidt, Marc; Koglin, Jason E; Boutet, Sébastien; Weierstall, Uwe; Cherezov, Vadim

    2016-08-01

    We describe the deposition of four datasets consisting of X-ray diffraction images acquired using serial femtosecond crystallography experiments on microcrystals of human G protein-coupled receptors, grown and delivered in lipidic cubic phase, at the Linac Coherent Light Source. The receptors are: the human serotonin receptor 2B in complex with an agonist ergotamine, the human δ-opioid receptor in complex with a bi-functional peptide ligand DIPP-NH2, the human smoothened receptor in complex with an antagonist cyclopamine, and finally the human angiotensin II type 1 receptor in complex with the selective antagonist ZD7155. All four datasets have been deposited, with minimal processing, in an HDF5-based file format, which can be used directly for crystallographic processing with CrystFEL or other software. We have provided processing scripts and supporting files for recent versions of CrystFEL, which can be used to validate the data.

  5. Femtosecond time-resolved ERE-CARS of PM650

    Science.gov (United States)

    He, Ping; Fan, Rongwei; Chen, Deying; Li, Xiaohui; Xia, Yuanqin; Yu, Xin; Wang, Jialing; Jiang, Yugang

    2012-07-01

    We utilize femtosecond time-resolved electronic resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS) to investigate new information for pyrromethene 650 (PM650) dye molecules. For this purpose, the vibrational properties of PM650 are registered in diluted solutions of several organisms. We observe a strong Raman vibrational mode with a wavenumber difference of about 48 cm- 1 in its organic solutions. This may be linked to the intramolecular electron transfer (ICT) process from the aromatic ring to the cyano group in PM650. The influence of the solvent effects on the vibrational dynamics of PM650 is also investigated. The vibrational properties of PM650 dye molecules diluted in polar organic solutions are light solvent-dependent.

  6. 3 GHz, watt-level femtosecond Raman soliton source.

    Science.gov (United States)

    Lim, Jinkang; Chen, Hung-Wen; Xu, Shanhui; Yang, Zhongmin; Chang, Guoqing; Kärtner, Franz X

    2014-04-01

    We demonstrate a 3 GHz repetition rate, femtosecond Raman soliton source with its wavelength tunable from 1.15 to 1.35 μm. We investigate the dependence of Raman soliton formation on different photonic-crystal fibers (PCFs), input powers, and fiber lengths. To produce a Raman soliton peaking at the same wavelength, shorter PCFs demand higher input average powers and consequently generate stronger Raman soliton pulses. Using 30 cm PCF NL-3.2-945, the resulting Raman soliton pulse at 1.35 μm has 0.9 W average power. The integrated relative intensity noise of the Raman soliton pulse at 1.35 μm generated from the 54-cm PCF NL-3.2-945 is as low as 0.33% from 100 Hz to 10 MHz.

  7. Femtosecond Pulse Propagation in a Highly Nonlinear Photonic Crystal Fiber

    Directory of Open Access Journals (Sweden)

    J. F. Gabayno

    2004-12-01

    Full Text Available Femtosecond pulses are launched into a highly nonlinear photonic crystal fiber (PCF. The input and output spectra were measured using a monochromator and streak camera. The spectrum of the output from a 50 cm PCF pumped at 794 nm for different pump powers features asymmetric side lobes due to intrapulse Raman scattering. Similar measurements on a 100 cm PCF pumped at 795 nm highlight the appearance of blueshifted peaks as a result of energy transfer of solitons to dispersive waves. Broadening in the spectrum is observed and attributed to Raman-scattering-induced soliton self-frequency shift. Spectrograms of both input and output pulses into a 50 cm PCF are captured using a streak camera. The spectrum reveals that individual modes observed on the spectrogram are actually a decomposition of the input pulse.

  8. Filming Femtosecond Molecular Movies with X-ray Pulses

    DEFF Research Database (Denmark)

    Kjær, Kasper Skov

    This thesis describes the investigation of time-resolved phenomena using X-ray techniques, and in particular the new possibilities and challenges arising from the application of these techniques on the femtosecond time-scale. The thesis will review the processes following laser excitation...... of molecular species in solution, describing the interplay between electronic and structural dynamics, as well as the role of the solvent. This will be followed by an introduction of the three X-ray techniques used in this work, and it will be shown how the application of these techniques in a laser pump / X-ray...... probe framework can help elucidate the excited state dynamics. The theoretical information content of the X-ray techniques will be discussed, as well as the practical experimental considerations for their implementation. This is done in order to demonstrate the potential increase in information content...

  9. Luminescence response of synthetic opal under femtosecond laser pumping

    International Nuclear Information System (INIS)

    Vasnetsov, M.V.; Bazhenov, V.Yu.; Dmitruk, I.N.; Kudryavtseva, A.D.; Tcherniega, N.V.

    2015-01-01

    Synthetic opal is an artificial photonic metamaterial composed from spherical globules of amorphous silica (SiO 2 ) about 300 nm in diameter. We report, for the first time to our knowledge, the origin of a narrow luminescence spectral peak (4 nm HWHM) and optical second and third harmonic generation in synthetic opal samples under femtosecond laser excitation (800 nm) at liquid-nitrogen temperature. Stimulated-emission effects are discussed related to the possibility of nanocavity lasing at the condition of the first Mie resonance in a dielectric sphere. - Highlights: • Second harmonic generation in a synthetic opal (amorphous material composed from spherical SiO 2 globules) was observed. • Narrow luminescence peak which we assign to a Mie resonance in a globule was detected at liquid-nitrogen temperature

  10. Trapped electronic states in YAG crystal excited by femtosecond radiation

    Energy Technology Data Exchange (ETDEWEB)

    Zavedeev, E.V.; Kononenko, V.V.; Konov, V.I. [General Physics Institute of RAS, Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation)

    2017-07-15

    The excitation of an electronic subsystem of an yttrium aluminum garnet by 800 nm femtosecond radiation was studied theoretically and experimentally. The spatio-temporal dynamics of the refractive index (n) inside the beam waist was explored by means of the pump-probe interferometric technique with a submicron resolution. The observed increase in n indicated the formation of bound electronic states relaxed for ∝ 150 ps. We showed that the experimental data agreed with the computational simulation based on the numerical solution of the nonlinear Schroedinger equation only if these transient states were considered to arise from a direct light-induced process but not from the decay of radiatively generated free-electron-hole pairs. (orig.)

  11. Nanostructuring of ITO thin films through femtosecond laser ablation

    Science.gov (United States)

    Sahin, Ramazan; Kabacelik, Ismail

    2016-04-01

    Due to reduced thermal effects, tightly focused femtosecond laser beams can yield submicron resolution with minimal side effects. In laser direct writing applications, diffraction-free nature of the Bessel beams relaxes alignment of the sample and shortens the production time. Micron-sized central spots and long depth of focused beams can be simultaneously produced. We apply fs Bessel beam single-pulse ablation method to transparent conductive oxide films. We use laser of 1030 nm wavelength and two different axicons (base angles are 25° and 40°). Fabricated structures are characterized by optical microscope, atomic force microscope and scanning electron microscope. Laser beam shaping and virtues of non-diffracted Bessel beams provide periodic structures for scribing in the solar cells or high-resolution displays and reduce the process time.

  12. Effects of femtosecond and excimer lasers on implanted KAMRA corneal inlay in animal models.

    Science.gov (United States)

    Sammouh, F K; Baban, T A; Dandan, W N; Warrak, E L

    2017-05-01

    To evaluate the effect of femtosecond laser and excimer laser on an intracorneal inlay (KAMRA ® ) implanted in animal models. Femtosecond laser was used to create corneal intrastromal pockets at 250μm depth in five porcine eyes. Four intact KAMRA inlays, examined by slit-lamp biomicroscopy and light microscopy, were implanted in the pocket of four eyes. A standard LASIK flap was created above each implanted inlay in the four eyes using a femtosecond laser with flap thicknesses of 150μm, 130μm, 110μm and 90μm. In the fifth porcine eye, a LASIK flap was created using femtosecond laser at 110μm depth, and a fifth inlay was then implanted in the 250μm pocket. Excimer laser ablation was performed under the flap targeting a -3.00 refraction. The inlay was then explanted, examined and reimplanted in the same pocket followed by a second similar excimer laser ablation. Significant burn, shrinkage and distortion of microholes were noted in all the first four inlays following the femtosecond laser flap creation at all the various flap thicknesses. The damage was noted to be more prominent as the distance between the flap and inlay decreased. No apparent effect was noted on the fifth inlay following repeated excimer laser ablations. Unlike excimer laser, femtosecond laser appears to be hazardous and damaging to the intracorneal KAMRA inlay when applied above it. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  13. Simulation of condensed matter dynamics in strong femtosecond laser pulses

    International Nuclear Information System (INIS)

    Wachter, G.

    2014-01-01

    Ultrashort custom-tailored laser pulses can be employed to observe and control the motion of electrons in atoms and small molecules on the (sub-) femtosecond time scale. Very recently, efforts are underway to extend these concepts to solid matter. This monograph theoretically explores first applications of electron control by ultrashort laser pulses in three paradigmatic systems of solid-state density: a metal nano-structure (nanometric metal tip), a bulk dielectric (quartz glass), and the buckminsterfullerene molecule (C60) as arguably the smallest possible nano-particle. The electron motion is resolved on the atomic length and time scale by ab-initio simulations based on time-dependent density functional theory. Our quantum simulations are complemented by classical and semi-classical models elucidating the underlying mechanisms. We compare our results to experiments where already available and find good agreement. With increasing laser intensity, we find a transition from vertical photoexcitation to tunneling-like excitation. For nanostructures, that leads to temporally confined electron photoemission and thereby to quantum interferences in the energy spectra of emitted electrons. Similarly, tunneling can be induced between neighboring atoms inside an insulator. This provides a mechanism for ultrafast light-field controlled currents and modification of the optical properties of the solid, promising to eventually realize light-field electronic devices operating on the femtosecond time scale and nanometer length scale. Electron-electron interaction leads to near field enhancement and spatial localization of the non-linear response and is investigated both classically by solving the Maxwell equations near a nanostructure as well as quantum mechanically for the fullerene molecule. For the latter, we discuss scrutiny of the molecular near-field by the attosecond streaking technique. Our results demonstrate that ultrashort laser pulses can be employed to steer the

  14. Generation and patterning of Si nanoparticles by femtosecond laser pulses

    Science.gov (United States)

    Zywietz, Urs; Reinhardt, Carsten; Evlyukhin, Andrey B.; Birr, Tobias; Chichkov, Boris N.

    2014-01-01

    The unique optical properties of nanoparticles are highly sensitive in respect to particle shapes, sizes, and localization on a sample. This demands for a fully controlled fabrication process. The use of femtosecond laser pulses to generate and transfer nanoparticles from a bulk target towards a collector substrate is a promising approach. This process allows a controlled fabrication of spherical nanoparticles with a very smooth surface. Several process parameters can be varied to achieve the desired nanoparticle characteristics. In this paper, the influence of two of these parameters, i.e. the applied pulse energy and the laser beam shape, on the generation of Si nanoparticles from a bulk Si target are studied in detail. By changing the laser intensity distribution on the target surface one can influence the dynamics of molten material inducing its flow to the edges or to the center of the focal spot. Due to this dynamics of molten material, a single femtosecond laser pulse with a Gaussian beam shape generates multiple spherical nanoparticles from a bulk Si target. The statistical properties of this process, with respect to number of generated nanoparticles and laser pulse energy are investigated. We demonstrate for the first time that a ring-shaped intensity distribution on the target surface results in the generation of a single silicon nanoparticle with a controllable size. Furthermore, the generated silicon nanoparticles presented in this paper show strong electric and magnetic dipole resonances in the visible and near-infrared spectral range. Theoretical simulations as well as optical scattering measurements of single silicon nanoparticles are discussed and compared.

  15. Radially polarized and passively Q-switched Yb-doped fiber laser based on intracavity birefringent mode discrimination

    Science.gov (United States)

    Sun, Xuehuan; Wu, Yongxiao; Chen, Sanbin; Li, Jianlang

    2018-05-01

    In this paper, we demonstrated a passive Q-switched ytterbium-doped fiber laser with radially polarized beam emission by using a c-cut YVO4 birefringent crystal as the intracavity polarization discriminator, and a Cr4+:YAG crystal as the saturable absorber and output coupler. The maximum averaged laser power reached 3.89 W with a high slope efficiency of 66.5%. The laser pulse had a peak power of 161 W, 160 ns duration, and 151 kHz repetition rate at the absorbed pump power of 6.48 W. Such a radially polarized pulse would facilitate numerous applications.

  16. Luminescence and Electroluminescence of Nd, Tm and Yb Doped GaAs and some II-Vi Compounds

    Science.gov (United States)

    1994-02-28

    Gislason, B. Monemar, M.E. Pistol, P.J. Dean, D.C. Herbert , A. Kana’ah and B.C. Cavanett, Phys. Rev. B, 31, 3774, (1985). [8] H. P. Gislason, B. Monemar...published). 24C. Weishbuch, R. C. Miller, R. Dingle , A. C. Gossard, and 7M. Cardona and N. E. Christensen, Phys. Rev. B 37, 1011 W. Wiegmann, Solid

  17. Superconductivity at 31.3 K in Yb-doped La (O/F) FeAs ...

    Indian Academy of Sciences (India)

    The effect of ytterbium substitution at the lanthanum site on the superconducting properties of La1-YbO0.8F0.2FeAs ( = 0.10, 0.20 and 0.30) oxypnictides has been investigated. Powder X-ray diffraction studies show the presence of Yb2O3 and LaOF as secondary phases. The superconducting transition temperature ...

  18. Low-temperature growth and electronic structures of ambipolar Yb-doped zinc tin oxide transparent thin films

    Science.gov (United States)

    Oh, Seol Hee; Ferblantier, Gerald; Park, Young Sang; Schmerber, Guy; Dinia, Aziz; Slaoui, Abdelilah; Jo, William

    2018-05-01

    The compositional dependence of the crystal structure, optical transmittance, and surface electric properties of the zinc tin oxide (Zn-Sn-O, shortened ZTO) thin films were investigated. ZTO thin films with different compositional ratios were fabricated on glass and p-silicon wafers using radio frequency magnetron sputtering. The binding energy of amorphous ZTO thin films was examined by a X-ray photoelectron spectroscopy. The optical transmittance over 70% in the visible region for all the ZTO films was observed. The optical band gap of the ZTO films was changed as a result of the competition between the Burstein-Moss effect and renormalization. An electron concentration in the films and surface work function distribution were measured by a Hall measurement and Kelvin probe force microscopy, respectively. The mobility of the n- and p-type ZTO thin films have more than 130 cm2/V s and 15 cm2/V s, respectively. We finally constructed the band structure which contains band gap, work function, and band edges such as valence band maximum and conduction band minimum of ZTO thin films. The present study results suggest that the ZTO thin film is competitive compared with the indium tin oxide, which is a representative material of the transparent conducting oxides, regarding optoelectronic devices applications.

  19. Self-induced laser line sweeping in double-clad Yb-doped fiber-ring lasers

    Czech Academy of Sciences Publication Activity Database

    Peterka, Pavel; Navrátil, P.; Maria, J.; Dussardier, B.; Slavík, Radan; Honzátko, Pavel; Kubeček, V.

    2012-01-01

    Roč. 9, č. 6 (2012), s. 445-450 ISSN 1612-2011 R&D Projects: GA MŠk(CZ) ME10119 Institutional support: RVO:67985882 Keywords : fiber laser * tunable laser * ytterbium Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 7.714, year: 2012

  20. Mode-Selective Amplification in a Large Mode Area Yb-Doped Fiber Using a Photonic Lantern

    Science.gov (United States)

    2016-05-15

    Hawthorn, Opt. Express 22, 1036 (2014). 18. G. Lopez-Galmiche, Z. Sanjabi Eznaveh, L. A. Herrera Piad, A. M. Velazquez -Benitez, J. Rodriguez-Asomoza, E...M. Velazquez -Benitez, J. Alvarado-Zacarias, G. Lopez-Galmiche, J. E. Antonio-Lopez, J. Hernandez-Cordero, J. Sanchez-Mondragon, P. Sillard, C. M... Velazquez -Benitez, J. E. Antonio-Lopez, J. Alvarado-Zacarias, G. Lopez-Galmiche, P. Sillard, D. Van Ras, C. Okonkwo, H. Chen, R. Ryf, N. K. Fontaine, and

  1. Phosphate content influence on structural, spectroscopic, and lasing properties of Er,Yb-doped potassium-lanthanum phosphate glasses

    Czech Academy of Sciences Publication Activity Database

    Šulc, J.; Švejkar, R.; Jelínková, H.; Nejezchleb, K.; Nitsch, Karel; Cihlář, Antonín; Král, Robert; Ledinský, Martin; Fejfar, Antonín; Rodová, Miroslava; Zemenová, Petra; Nikl, Martin

    2016-01-01

    Roč. 55, č. 4 (2016), 1-10, č. článku 047102. ISSN 0091-3286 R&D Projects: GA ČR GAP204/12/0805 Institutional support: RVO:68378271 Keywords : erbium lasers * infrared lasers * laser materials modification * phosphate glass * diode-pumped eye -safe solid state laser Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.082, year: 2016

  2. Thermal effect-resilient design of large mode area double-cladding Yb-doped photonic crystal fibers

    DEFF Research Database (Denmark)

    Coscelli, Enrico; Poli, Federica; Johansen, Mette Marie

    2013-01-01

    The effects of thermally-induced refractive index change on the guiding properties of different large mode area fibers have been numerically analyzed. A simple but accurate model has been applied to obtain the refractive index change in the fiber cross-section, and a full-vector modal solver based...... on the finite-element method has been used to calculate the guided modes of the fibers operating at high power levels. The results demonstrate that resonant structures added to the fiber cross-section can be exploited to provide efficient suppression of high-order modes with a good resilience to thermal effects....

  3. Simulation of dissipative-soliton-resonance generation in a passively mode-locked Yb-doped fiber laser

    Science.gov (United States)

    Du, Wenxiong; Li, Heping; Liu, Cong; Shen, Shengnan; Zhang, Shangjian; Liu, Yong

    2017-10-01

    We present a numerical investigation of dissipative-soliton-resonance (DSR) generation in an all-normal-dispersion Ybdoped fiber laser mode-locked by a real saturable absorber (SA). In the simulation model, the SA includes both the saturable absorption and excited-state absorption (ESA) effects. The intra-cavity pulse evolution is numerically simulated with different transmission functions of SA. When omitting the ESA effect, the transmissivity of SA increases monotonically with the input pulse power. The noise-like pulse (NLP) operation in the cavity is obtained at high pump power, which is attributed to the spectral filtering effect. When the ESA effect is activated, higher instantaneous power part of pulse encounters larger loss induced by SA, causing that the pulse peak power is clamped at a certain fixed value. With increasing pump, the pulse starts to extend in the time domain while the pulse spectrum is considerably narrowed. In this case, the NLP operation state induced by the spectral filtering effect is avoided and the DSR is generated. Our simulation results indicate that the ESA effect in the SA plays a dominant role in generating the DSR pulses, which will be conducive to comprehending the mechanism of DSR generation in passively mode-locked fiber lasers.

  4. Q-Switched and Mode Locked Short Pulses from a Diode Pumped, YB-Doped Fiber Laser

    Science.gov (United States)

    2009-03-26

    polarization maintaining (PM) at a length of 8.7 ± 0.1 m. The surface area of the PANDA -style fiber is pictured in figure 3.3 (a) [46]. The core diameter was...diode- pumped c-cut Nd:GdVO4 laser,” Optics Communications 231 (2004) pg 365-369. 36. W. G. Wagner, B. A. Lengyel, "Evolution of the giant pulse in a

  5. Range extension in laser-induced breakdown spectroscopy using femtosecond-nanosecond dual-beam laser system

    Science.gov (United States)

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

    2017-06-01

    We extend the detection range of laser-induced breakdown spectroscopy by combining high-intensity femtosecond laser pulses with high-energy nanosecond CO2 laser pulses. The femtosecond laser pulses ionize the molecules and generate filament in air. The free electrons generated in the self-confined plasma channel by the femtosecond laser serve as the seed electrons which cause efficient avalanche ionization in the nanosecond CO2 laser field. We show that the detection distance has been extended by three times with the assistance of femtosecond laser filamentation.

  6. Femtosecond switching of magnetism via strongly correlated spin-charge quantum excitations.

    Science.gov (United States)

    Li, Tianqi; Patz, Aaron; Mouchliadis, Leonidas; Yan, Jiaqiang; Lograsso, Thomas A; Perakis, Ilias E; Wang, Jigang

    2013-04-04

    The technological demand to push the gigahertz (10(9) hertz) switching speed limit of today's magnetic memory and logic devices into the terahertz (10(12) hertz) regime underlies the entire field of spin-electronics and integrated multi-functional devices. This challenge is met by all-optical magnetic switching based on coherent spin manipulation. By analogy to femtosecond chemistry and photosynthetic dynamics--in which photoproducts of chemical and biochemical reactions can be influenced by creating suitable superpositions of molecular states--femtosecond-laser-excited coherence between electronic states can switch magnetic order by 'suddenly' breaking the delicate balance between competing phases of correlated materials: for example, manganites exhibiting colossal magneto-resistance suitable for applications. Here we show femtosecond (10(-15) seconds) photo-induced switching from antiferromagnetic to ferromagnetic ordering in Pr0.7Ca0.3MnO3, by observing the establishment (within about 120 femtoseconds) of a huge temperature-dependent magnetization with photo-excitation threshold behaviour absent in the optical reflectivity. The development of ferromagnetic correlations during the femtosecond laser pulse reveals an initial quantum coherent regime of magnetism, distinguished from the picosecond (10(-12) seconds) lattice-heating regime characterized by phase separation without threshold behaviour. Our simulations reproduce the nonlinear femtosecond spin generation and underpin fast quantum spin-flip fluctuations correlated with coherent superpositions of electronic states to initiate local ferromagnetic correlations. These results merge two fields, femtosecond magnetism in metals and band insulators, and non-equilibrium phase transitions of strongly correlated electrons, in which local interactions exceeding the kinetic energy produce a complex balance of competing orders.

  7. Femtosecond structural dynamics on the atomic length scale

    International Nuclear Information System (INIS)

    Zhang, Dongfang

    2014-03-01

    This thesis reports on the development and application of two different but complementary ultrafast electron diffraction setups built at the Max Planck Research Department for Structural Dynamics. One is an ultra-compact femtosecond electron diffraction (FED) setup (Egun300), which is currently operational (with a maximum electron energy of 150 keV) and provides ultrashort (∝300 fs) and bright (∝10 e/μm 2 ) electron bunches. The other one, named as Relativistic Electron Gun for Atomic Exploration (REGAE) is a radio frequency driven 2 to 5 MeV FED setup built in collaboration with different groups from DESY. REGAE was developed as a facility that will provide high quality diffraction with sufficient coherence to even address structural protein dynamics and with electron pulses as short as 20 fs (FWHM). As one of the first students in Prof. R.J. Dwayne Miller's group, I led the femtosecond (fs) laser sub-group at REGAE being responsible for the construction of different key optical elements required to drive both of aforementioned FED systems. A third harmonic generation (THG) and a nonlinear optical parametric amplifier (NOPA) have been used for the photo-generation of ultrashort electron bursts as well as sample laser excitation. Different diagnostic tools have been constructed to monitor the performance of the fs optical system. A fast autocorrelator was developed to provide on the fly pulse duration correction. A transient-grating frequency-resolved optical gating (TG-FROG) was built to obtain detail information about the characteristics of fs optical pulse, i.e. phase and amplitude of its spectral components. In addition to these optical setups, I developed a fs optical pump-probe system, which supports broadband probe pulses. This setup was successfully applied to investigate the semiconductor-to-metal photoinduced phase transition in VO 2 and the ultrafast photo-reduction mechanism of graphene oxide. In regard to FED setups, I have been deeply involved in

  8. Nonlinear femtosecond near infrared laser structuring in oxide glasses

    Science.gov (United States)

    Royon, Arnaud

    Three-dimensional femtosecond laser structuring has a growing interest because of its ease of implementation and the numerous possible applications in the domain of photonic components. Structures such as waveguides, diffraction gratings, optical memories or photonic crystals can be fabricated thanks to this technique. Its use with oxide glasses is promising because of several advantages; they are resistant to flux and ageing, their chemical composition can easily be changed to fit the well-defined requirements of an application. They can already be found in Raman amplifiers, optical fibers, fiber lasers, and other devices. This thesis is based on two axes. The first axis consists in characterizing the linear and nonlinear optical properties of bulk vitreous materials in order to optimize their composition with a particular application in view. Within this context, the nonlinear optical properties, their physical origins (electronic and nuclear) as well as their characteristic response times (from a few femtoseconds to a few hundreds of picoseconds) are described within the Born-Oppenheimer approximation. Fused silica and several sodium-borophosphate glasses containing different concentrations in niobium oxide have been studied. Results show that the nonlinear optical properties of fused silica are mainly from electronic origin, whereas in the sodium-borophosphate glasses, the contribution from nuclear origin becomes predominant when the concentration of niobium oxide exceeds 30%. The second axis is based on the structuring of materials. Three commercially available fused silica samples presenting different fabrication conditions (therefore distinct impurity levels) and irradiated with a near infrared femtosecond laser have been studied. The laser induced defects have been identified by means of several spectroscopic techniques. They show the formation of color centers as well as a densification inside the irradiated area. Their linear refractive index and

  9. Femtosecond pulse radiolysis based on photocathode electron accelerator

    International Nuclear Information System (INIS)

    Yoshida, Y.; Yang, Jinfeng; Kondoh, T.; Kozawa, T.; Tagawa, S.

    2006-01-01

    Pulse radiolysis is a powerful tool for studying chemical kinetics and primary processes or reactions of radiation chemistry. In the pulse radiolysis, a short electron beam, which is almost produced by radio-frequency (RF) electron linear accelerator with energy from a few MeV to a few tens MeV, is used as an irradiative source. The electron-induced reactions or phenomena in matter are analyzed by a short-pulse analyzing light (e.g. synchronized lasers) with the time-resolved stroboscopic technique. The time resolution of pulse radiolysis is not only dependent on the electron bunch length, the analyzing light pulse width, the time jitter between the electron bunch and the analyzing light, but also determined by degradation due to the velocity difference between light and the electron in the sample because of the refractive index. In order to improve the time resolution into femtosecond time region, we have develop a new pulse radiolysis based on a concept of 'Equivalent Velocity Spectroscopy (EVS)' to avoid the degradation of the time resolution caused by the velocity difference between the light and the electron beam in sample. In EVS as shown in Fig.1, a femtosecond electron beam produced by a photocathode electron linear accelerator was used, and a synchronized femtosecond laser was used as the analyzing light source. The electron beam and the laser light were injected into sample with an angle (θ), which is determined by the refractive index (n) of the sample. The electron bunch was also rotated with a same angle to make an overlap of the electron bunch with the laser pulse. The degradation of the time resolution caused by the velocity difference between the light and the electron beam can be calculated as g(L)=L[n/c-1/(vcos θ)], where L is the optical path length and v is the velocity of the electron in sample (we can assume v=c for a few tens MeV electron beam).We can thus obtained g(L)=0 by adjusting the incident angle to cos θ=1/n. However, the rotation

  10. Femtosecond structural dynamics on the atomic length scale

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Dongfang

    2014-03-15

    This thesis reports on the development and application of two different but complementary ultrafast electron diffraction setups built at the Max Planck Research Department for Structural Dynamics. One is an ultra-compact femtosecond electron diffraction (FED) setup (Egun300), which is currently operational (with a maximum electron energy of 150 keV) and provides ultrashort (∝300 fs) and bright (∝10 e/μm{sup 2}) electron bunches. The other one, named as Relativistic Electron Gun for Atomic Exploration (REGAE) is a radio frequency driven 2 to 5 MeV FED setup built in collaboration with different groups from DESY. REGAE was developed as a facility that will provide high quality diffraction with sufficient coherence to even address structural protein dynamics and with electron pulses as short as 20 fs (FWHM). As one of the first students in Prof. R.J. Dwayne Miller's group, I led the femtosecond (fs) laser sub-group at REGAE being responsible for the construction of different key optical elements required to drive both of aforementioned FED systems. A third harmonic generation (THG) and a nonlinear optical parametric amplifier (NOPA) have been used for the photo-generation of ultrashort electron bursts as well as sample laser excitation. Different diagnostic tools have been constructed to monitor the performance of the fs optical system. A fast autocorrelator was developed to provide on the fly pulse duration correction. A transient-grating frequency-resolved optical gating (TG-FROG) was built to obtain detail information about the characteristics of fs optical pulse, i.e. phase and amplitude of its spectral components. In addition to these optical setups, I developed a fs optical pump-probe system, which supports broadband probe pulses. This setup was successfully applied to investigate the semiconductor-to-metal photoinduced phase transition in VO{sub 2} and the ultrafast photo-reduction mechanism of graphene oxide. In regard to FED setups, I have been

  11. Femtosecond laser processing of photovoltaic and transparent materials

    Science.gov (United States)

    Ahn, Sanghoon

    The photovoltaic semiconducting and transparent dielectric materials are of high interest in current industry. Femtosecond laser processing can be an effective technique to fabricate such materials since non-linear photochemical mechanisms predominantly occur. In this series of studies, femtosecond (fs) laser processing techniques that include laser drilling on Si wafer, laser scribing on CIGS thin film, laser ablation on Lithium Niobate (LN) crystal, and fabrication of 3D structures in fused silica were studied. The fs laser drilling on Si wafer was performed to fabricate via holes for wrap-through PV devices. For reduction of the number of shots in fs laser drilling process, self-action of laser light in the air was initiated. To understand physical phenomena during laser drilling, scanning electron microscopy (SEM), emission, and shadowgraph images were studied. The result indicated the presence of two mechanisms that include fabrication by self-guided beam and wall-guided beam. Based on our study, we could fabricate ~16 micrometer circular-shaped via holes with ~200 laser pulses on 160-170 micrometer thick c- and mc-Si wafer. For the fs laser scribing on ink jet printed CIGS thin film solar cell, the effect of various parameters that include pulse accumulation, wavelength, pulse energy, and overlapping were elucidated. In our processing regime, the effect of wavelength could be diminished due to compensation between beam size, pulse accumulation, energy fluence, and the absorption coefficient. On the other hand, for high PRF fs laser processing, pulse accumulation effect cannot be ignored, while it can be negligible in low PRF fs laser processing. The result indicated the presence of a critical energy fluence for initiating delamination of CIGS layer. To avoid delamination and fabricate fine isolation lines, the overlapping method can be applied. With this method, ~1 micrometer width isolation lines were fabricated. The fs laser ablation on LN wafer was studied

  12. IL 12: Femtosecond x-ray powder diffraction

    International Nuclear Information System (INIS)

    Woerner, M.; Zamponi, F.; Rothhardt, P.; Ansari, Z.; Dreyer, J.; Freyer, B.; Premont-Schwarz, M.; Elsaesser, T.

    2010-01-01

    A chemical reaction generates new compounds out of one or more initial species. On a molecular level, the spatial arrangement of electrons and nuclei changes. While the structure of the initial and the product molecules can be measured routinely, the transient structures and molecular motions during a reaction have remained unknown in most cases. This knowledge, however, is a key element for the exact understanding of the reaction. The ultimate dream is a 'reaction microscope' which allows for an in situ imaging of the molecules during a reaction. We report on the first femtosecond x-ray powder diffraction experiment in which we directly map the transient electronic charge density in the unit cell of a crystalline solid with 30 pico-meter spatial and 100 femtosecond temporal resolution. X-ray diffraction from polycrystalline powder samples, the Debye Scherrer diffraction technique, is a standard method for determining equilibrium structures. The intensity of the Debye Scherrer rings is determined by the respective x-ray structure factor which represents the Fourier transform of the spatial electron density. In our experiments, the transient intensity and angular positions of up to 20 Debye Scherrer reactions from a polycrystalline powder are measured and unravel for the first time a concerted electron and proton transfer in hydrogen-bonded ionic (NH 4 ) 2 SO 4 crystals. Photoexcitation of ammonium sulfate induces a sub-100 fs electron transfer from the sulfate groups into a highly conned electron channel along the z-axis of the unit cell. The latter geometry is stabilized by transferring protons from the adjacent ammonium groups into the channel. Time-dependent charge density maps derived from the diffraction data display a periodic modulation of the channels charge density by low-frequency lattice motions with a concerted electron and proton motion between the channel and the initial proton binding site. A deeper insight into the underlying microscopic

  13. Evaluation of double-pass optical quality analysis system between SMILE and femtosecond LASIK for myopia

    Directory of Open Access Journals (Sweden)

    Wen-Jing Li

    2014-11-01

    Full Text Available AIM: To evaluate the visual quality between femtosecond laser small incision lenticule extraction(SMILEand femtosecond laser in situ keratomileusis(LASIKin the treatment of myopia. METHODS: This study comprised 22 eyes(11 patientsunderwent SMILE and 43 eyes(23 patientsreceived LASIK with femtosecond laser to correct myopia and myopic astigmatism. The two groups were recorded bydouble-pass optical quality analysis system(OQASat preoperative and postoperative 1mo. The two groups were compared: modulation transfer function cutoff frequency(MTF cutoff, strehl ratio(SR, objective scattering index(OSI. The early visual quality after operation between two groups were analyzed and evaluated.RESULTS: The MTF cutoff after operation one month were 34.835±10.113c/deg(SMILE groupand 38.362±10.623c/deg(LASIK group(t=0.925, P=0.362. The SR after operation one month were 0.204±0.077(SMILE groupand 0.218±0.072(LASIK group(t=0.557, P=0.582. The OSI after operation one month were 0.608±0.291(SMILE groupand 0.545±0.405(LASIK group(t=-0.473, P=0.640. CONCLUSION: The double-pass OQAS tell us that there was not statistically significant between femtosecond laser SMILE and femtosecond LASIK in the treatment of myopia.

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

    Science.gov (United States)

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

    2011-09-01

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

  15. Femtosecond Laser Assisted Deep Anterior Lamellar Keratoplasty Outcomes and Healing Patterns Compared to Manual Technique

    Directory of Open Access Journals (Sweden)

    Jorge L. Alio

    2015-01-01

    Full Text Available The purpose of the study is to report the visual, refractive, and wound healing pattern outcomes of femtosecond assisted deep anterior lamellar keratoplasty (DALK compared to the conventional manual technique. DALK was performed on 50 eyes of 47 advanced keratoconus patients. The patients were divided into two groups, 25 eyes each, depending on whether femtosecond assisted or manual DALK technique was performed for the side cut of the procedure only. Patients were followed up at 1 month, 6 months, and 1 year for visual acuity, clinical refraction, corneal cylinder, date of suture removal, and side cut corneal healing pattern according to new grading classification of the side cut scar (Grade 0 = transparent scar, 1 = faint healing opacity, 2 = evident healing opacity, 3 = significant opacity with some cosmetic imbalance, and 4 = highly significant opacity with very significant cosmetic imbalance. Outcomes are reported at one year. In conclusion, femtosecond assisted and manual DALK show comparable visual and refractive outcomes but femtosecond assisted DALK shows more evident corneal wound healing patterns at the side cut. This observation may indicate that an activated cornea wound healing might allow earlier suture removal when femtosecond technology is used to perform the side cut for DALK.

  16. Profitability analysis of a femtosecond laser system for cataract surgery using a fuzzy logic approach.

    Science.gov (United States)

    Trigueros, José Antonio; Piñero, David P; Ismail, Mahmoud M

    2016-01-01

    To define the financial and management conditions required to introduce a femtosecond laser system for cataract surgery in a clinic using a fuzzy logic approach. In the simulation performed in the current study, the costs associated to the acquisition and use of a commercially available femtosecond laser platform for cataract surgery (VICTUS, TECHNOLAS Perfect Vision GmbH, Bausch & Lomb, Munich, Germany) during a period of 5y were considered. A sensitivity analysis was performed considering such costs and the countable amortization of the system during this 5y period. Furthermore, a fuzzy logic analysis was used to obtain an estimation of the money income associated to each femtosecond laser-assisted cataract surgery (G). According to the sensitivity analysis, the femtosecond laser system under evaluation can be profitable if 1400 cataract surgeries are performed per year and if each surgery can be invoiced more than $500. In contrast, the fuzzy logic analysis confirmed that the patient had to pay more per surgery, between $661.8 and $667.4 per surgery, without considering the cost of the intraocular lens (IOL). A profitability of femtosecond laser systems for cataract surgery can be obtained after a detailed financial analysis, especially in those centers with large volumes of patients. The cost of the surgery for patients should be adapted to the real flow of patients with the ability of paying a reasonable range of cost.

  17. Theoretical femtosecond physics atoms and molecules in strong laser fields

    CERN Document Server

    Grossmann, Frank

    2018-01-01

    This textbook extends from the basics of femtosecond physics all the way to some of the latest developments in the field. In this updated edition, the chapter on laser-driven atoms is augmented by the discussion of two-electron atoms interacting with strong and short laser pulses, as well as by a review of ATI rings and low energy structures in photo-electron spectra. In the chapter on laser-driven molecules a discussion of 2D infrared spectroscopy is incorporated. Theoretical investigations of atoms and molecules interacting with pulsed lasers up to atomic field strengths on the order of 10^16 W/cm² are leading to an understanding of many challenging experimental discoveries. The presentation starts with a brief introduction to pulsed laser physics. The basis for the non-perturbative treatment of laser-matter interaction in the book is the time-dependent Schrödinger equation. Its analytical as well as numerical solution are laid out in some detail. The light field is treated classically and different possi...

  18. Femtosecond laser surface structuring of molybdenum thin films

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-10-30

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

  19. Wettability modification of porous PET by atmospheric femtosecond PLD

    Science.gov (United States)

    Assaf, Youssef; Forstmann, Guillaume; Kietzig, Anne-Marie

    2018-04-01

    In this study, porous structures were created on poly(ethylene terephthalate) (PET) by femtosecond (fs) laser micromachining. While such structures offer a texture that is desirable for several applications, their wettability does not always match the application in question. The aim of this investigation is to tune the wettability of such surfaces by incorporating a controlled amount of nanoparticles into the structure. The machined PET samples were thus used as substrates for fs pulsed laser deposition (PLD) of titanium under ambient conditions. The nanoparticles were deposited as nanochain clusters due to the formation of an oxide layer between individual nanoparticles. The stability of nanoparticle incorporation was tested by placing the samples in an ultrasonic ethanol bath. Results indicated that nanoparticles were still successfully incorporated into the microstructure after sonication. Nanoparticle surface coverage was observed to be controllable through the operating fluence. The dynamic contact angles of the resulting composite surface were observed to decrease with increasing titanium incorporation. Therefore, this work highlights atmospheric fs PLD as a method for wettability modification of high surface area microstructures without undermining their topology. In addition, this technique uses almost the same equipment as the machining process by which the microstructures are initially created, further highlighting its practicality.

  20. Volumetric graphics in liquid using holographic femtosecond laser pulse excitations

    Science.gov (United States)

    Kumagai, Kota; Hayasaki, Yoshio

    2017-06-01

    Much attention has been paid to the development of three-dimensional volumetric displays in the fields of optics and computer graphics, and it is a dream of we display researchers. However, full-color volumetric displays are challenging because many voxels with different colors have to be formed to render volumetric graphics in real three-dimensional space. Here, we show a new volumetric display in which microbubble voxels are three-dimensionally generated in a liquid by focused femtosecond laser pulses. Use of a high-viscosity liquid, which is the key idea of this system, slows down the movement of the microbubbles, and as a result, volumetric graphics can be displayed. This "volumetric bubble display" has a wide viewing angle and simple refresh and requires no addressing wires because it involves optical access to transparent liquid and achieves full-color graphics composed on light-scattering voxels controlled by illumination light sources. In addition, a bursting of bubble graphics system using an ultrasonic vibrator also has been demonstrated. This technology will open up a wide range of applications in three-dimensional displays, augmented reality and computer graphics.

  1. Efficacy of femtosecond lasers for application of acupuncture therapy.

    Science.gov (United States)

    Ohta, Mika; Hosokawa, Yoichiroh; Hatano, Naoya; Sugano, Aki; Ito, Akihiko; Takaoka, Yutaka

    2017-12-01

    Acupuncture treatment utilizes the stimulation of metal acupuncture needles that are manually inserted into a living body. In the last decades, laser light has been used as an alternative to needles to stimulate acupuncture points. We previously reported suppression of myostatin (Mstn) gene expression in skeletal muscle by means of femtosecond laser (FL) irradiation, after electroacupuncture, in which acupuncture needles are stimulated with a low-frequency microcurrent. The purpose of the study here was to investigate the efficacy of FL irradiation in mouse skeletal muscle with regard to protein synthesis. After irradiation of the hindlimbs, we first analyzed Mstn gene expression and Mstn protein level in the skeletal muscle. We then evaluated phosphorylation of the mammalian target of rapamycin (mTOR) and its downstream target 70-kDa ribosomal protein S6 kinase (p70S6K). The results showed that FL irradiation significantly reduced the amount of Mstn protein and enhanced the phosphorylation of p70S6K in of the mTOR/S6K signaling pathway. We suggest that FL irradiation activated the protein synthetic pathway in the skeletal muscle. In conclusion, we determined that FL irradiation can serve as an alternative for acupuncture needles and has the potential of being a new non-invasive acupuncture treatment of skeletal muscle.

  2. Femtosecond pulsed laser deposition of cobalt ferrite thin films

    Science.gov (United States)

    Dascalu, Georgiana; Pompilian, Gloria; Chazallon, Bertrand; Caltun, Ovidiu Florin; Gurlui, Silviu; Focsa, Cristian

    2013-08-01

    The insertion of different elements in the cobalt ferrite spinel structure can drastically change the electric and magnetic characteristics of CoFe2O4 bulks and thin films. Pulsed Laser Deposition (PLD) is a widely used technique that allows the growth of thin films with complex chemical formula. We present the results obtained for stoichiometric and Gadolinium-doped cobalt ferrite thin films deposited by PLD using a femtosecond laser with 1 kHz repetition rate. The structural properties of the as obtained samples were compared with other thin films deposited by ns-PLD. The structural characteristics and chemical composition of the samples were investigated using profilometry, Raman spectroscopy, X-Ray diffraction measurements and ToF-SIMS analysis. Cobalt ferrite thin films with a single spinel structure and a preferential growth direction have been obtained. The structural analysis results indicated the presence of internal stress for all the studied samples. By fs-PLD, uniform thin films were obtained in a short deposition time.

  3. Femtosecond laser ablation of polytetrafluoroethylene (Teflon) in ambient air

    International Nuclear Information System (INIS)

    Wang, Z.B.; Hong, M.H.; Lu, Y.F.; Wu, D.J.; Lan, B.; Chong, T.C.

    2003-01-01

    Teflon, polytetrafluorethylene (PTFE), is an important material in bioscience and medical application due to its special characteristics (bio-compatible, nonflammable, antiadhesive, and heat resistant). The advantages of ultrashort laser processing of Teflon include a minimal thermal penetration region and low processing temperatures, precision removal of material, and good-quality feature definition. In this paper, laser processing of PTFE in ambient air by a Ti:sapphire femtosecond laser (780 nm, 110 fs) is investigated. It is found that the pulse number on each irradiated surface area must be large enough for a clear edge definition and the ablated depth increases with the pulse number. The air ionization effect at high laser fluences not only degrades the ablated structures quality but also reduces the ablation efficiency. High quality microstructures are demonstrated with controlling laser fluence below a critical fluence to exclude the air ionization effect. The ablated microstructures show strong adhesion property to liquids and clear edges that are suitable for bio-implantation applications. Theoretical calculation is used to analyze the evolution of the ablated width and depth at various laser fluences

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-08-15

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

  5. Femtosecond Timekeeping: Slip-Free Clockwork for Optical Timescales

    Science.gov (United States)

    Herman, D.; Droste, S.; Baumann, E.; Roslund, J.; Churin, D.; Cingoz, A.; Deschênes, J.-D.; Khader, I. H.; Swann, W. C.; Nelson, C.; Newbury, N. R.; Coddington, I.

    2018-04-01

    The generation of true optical time standards will require the conversion of the highly stable optical-frequency output of an optical atomic clock to a high-fidelity time output. We demonstrate a comb-based clockwork that phase-coherently integrates ˜7 ×1020 optical cycles of an input optical frequency to create a coherent time output. We verify the underlying stability of the optical timing system by comparing two comb-based clockworks with a common input optical frequency and show time drift over the 37-day measurement period. Both clockworks also generate traditional timing signals including an optical pulse per second and a 10-MHz rf reference. The optical pulse-per-second time outputs remain synchronized to 240 attoseconds (240 as) at 1000 s. The phase-coherent 10-MHz rf outputs are stable to near a part in 1019 . Fault-free timekeeping from an optical clock to femtosecond level over months is an important step in replacing the current microwave time standard by an optical standard.

  6. Femtosecond electron diffraction: heralding the era of atomically resolved dynamics

    Science.gov (United States)

    Sciaini, Germán; Miller, R. J. Dwayne

    2011-09-01

    One of the great dream experiments in Science is to directly observe atomic motions as they occur. Femtosecond electron diffraction provided the first 'light' of sufficient intensity to achieve this goal by attaining atomic resolution to structural changes on the relevant timescales. This review covers the technical progress that made this new level of acuity possible and gives a survey of the new insights gained from an atomic level perspective of structural dynamics. Atomic level views of the simplest possible structural transition, melting, are discussed for a number of systems in which both thermal and purely electronically driven atomic displacements can be correlated with the degree of directional bonding. Optical manipulation of charge distributions and effects on interatomic forces/bonding can be directly observed through the ensuing atomic motions. New phenomena involving strongly correlated electron-lattice systems are also discussed in which optically induced changes in the potential energy landscape lead to ballistic structural changes. Concepts such as the structural order parameters are now directly observable at the atomic level of inspection to give a remarkable view of the extraordinary degree of cooperativity involved in strongly correlated electron-lattice systems. These recent examples, in combination with time-resolved real space imaging now possible with electron probes, are truly defining an emerging field that holds great promise to make a significant impact in how we understand structural dynamics. This article is dedicated to the memory of Professor David John Hugh Cockayne, a world leader in electron microscopy, who sadly passed away in December.

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

    Science.gov (United States)

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

    2014-08-08

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

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

    Directory of Open Access Journals (Sweden)

    Fang Liang

    2014-08-01

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

  9. Biomimetic surface structuring using cylindrical vector femtosecond laser beams

    Science.gov (United States)

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

    2017-03-01

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

  10. Acoustic Injectors for Drop-On-Demand Serial Femtosecond Crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Roessler, Christian G.; Agarwal, Rakhi; Allaire, Marc; Alonso-Mori, Roberto; Andi, Babak; Bachega, José F. R.; Bommer, Martin; Brewster, Aaron S.; Browne, Michael C.; Chatterjee, Ruchira; Cho, Eunsun; Cohen, Aina E.; Cowan, Matthew; Datwani, Sammy; Davidson, Victor L.; Defever, Jim; Eaton, Brent; Ellson, Richard; Feng, Yiping; Ghislain, Lucien P.; Glownia, James M.; Han, Guangye; Hattne, Johan; Hellmich, Julia; Héroux, Annie; Ibrahim, Mohamed; Kern, Jan; Kuczewski, Anthony; Lemke, Henrik T.; Liu, Pinghua; Majlof, Lars; McClintock, William M.; Myers, Stuart; Nelsen, Silke; Olechno, Joe; Orville, Allen M.; Sauter, Nicholas K.; Soares, Alexei S.; Soltis, S.  Michael; Song, Heng; Stearns, Richard G.; Tran, Rosalie; Tsai, Yingssu; Uervirojnangkoorn, Monarin; Wilmot, Carrie M.; Yachandra, Vittal; Yano, Junko; Yukl, Erik T.; Zhu, Diling; Zouni, Athina

    2016-04-01

    X-ray free-electron lasers (XFELs) provide very intense X-ray pulses suitable for macromolecular crystallography. Each X-ray pulse typically lasts for tens of femtoseconds and the interval between pulses is many orders of magnitude longer. Here we describe two novel acoustic injection systems that use focused sound waves to eject picoliter to nanoliter crystal-containing droplets out of microplates and into the X-ray pulse from which diffraction data are collected. The on-demand droplet delivery is synchronized to the XFEL pulse scheme, resulting in X-ray pulses intersecting up to 88% of the droplets. We tested several types of samples in a range of crystallization conditions, wherein the overall crystal hit ratio (e.g., fraction of images with observable diffraction patterns) is a function of the microcrystal slurry concentration. We report crystal structures from lysozyme, thermolysin, and stachydrine demethylase (Stc2). Additional samples were screened to demonstrate that these methods can be applied to rare samples.

  11. Clocking Femtosecond Collisional Dynamics via Resonant X-Ray Spectroscopy

    Science.gov (United States)

    van den Berg, Q. Y.; Fernandez-Tello, E. V.; Burian, T.; Chalupský, J.; Chung, H.-K.; Ciricosta, O.; Dakovski, G. L.; Hájková, V.; Hollebon, P.; Juha, L.; Krzywinski, J.; Lee, R. W.; Minitti, M. P.; Preston, T. R.; de la Varga, A. G.; Vozda, V.; Zastrau, U.; Wark, J. S.; Velarde, P.; Vinko, S. M.

    2018-02-01

    Electron-ion collisional dynamics is of fundamental importance in determining plasma transport properties, nonequilibrium plasma evolution, and electron damage in diffraction imaging applications using bright x-ray free-electron lasers (FELs). Here we describe the first experimental measurements of ultrafast electron impact collisional ionization dynamics using resonant core-hole spectroscopy in a solid-density magnesium plasma, created and diagnosed with the Linac Coherent Light Source x-ray FEL. By resonantly pumping the 1 s →2 p transition in highly charged ions within an optically thin plasma, we have measured how off-resonance charge states are populated via collisional processes on femtosecond time scales. We present a collisional cross section model that matches our results and demonstrates how the cross sections are enhanced by dense-plasma effects including continuum lowering. Nonlocal thermodynamic equilibrium collisional radiative simulations show excellent agreement with the experimental results and provide new insight on collisional ionization and three-body-recombination processes in the dense-plasma regime.

  12. Femtosecond probing of photodissociation dynamics in acyl cyanides

    Science.gov (United States)

    Lee, I.-Ren; Chung, Yu-Chieh; Chen, Wei-Kan; Hong, Xiu-Ping; Cheng, Po-Yuan

    2001-12-01

    The photodissociation of two acyl cyanide compounds, R-C(O)-CN, where R=methyl and tert-butyl groups, has been investigated using femtosecond time-resolved laser-induced fluorescence (LIF) spectroscopy. Both compounds were excited by two-photon excitation at a total energy of ˜6.4 eV and the formation of the free CN(X) radical products was probed in real time by monitoring the CN X→B LIF signal. The results revealed that the temporal evolution of the CN(X) formation can be well characterized by delayed biexponential rise functions with time constants in the picosecond time scale, indicating that the dissociation occurs via a complex-mode mechanism. We proposed a dissociation mechanism involving two discernable stages to account for the observed temporal behaviors as well as previous photofragment translational spectroscopic results reported by other groups. Our analyses suggested that the selectivity between the C-CN and C-R bond cleavage is determined by the competition between the adiabatic and nonadiabatic dynamics of the S2 state. The results also indicated that the adiabatic dissociation process occurring on the S2 surface is not statistical. We speculate that this nonstatistical dissociation behavior is due to an initial nonuniform phase space distribution and a slow intramolecular vibrational energy redistribution process that prevents the system from sampling the entire phase space before the reaction completes.

  13. Theoretical femtosecond physics atoms and molecules in strong laser fields

    CERN Document Server

    Grossmann, Frank

    2013-01-01

    Theoretical investigations of atoms and molecules interacting with pulsed or continuous wave lasers up to atomic field strengths on the order of 10^16 W/cm² are leading to an understanding of many challenging experimental discoveries. This book deals with the basics of femtosecond physics and goes up to the latest applications of new phenomena. The book presents an introduction to laser physics with mode-locking and pulsed laser operation. The solution of the time-dependent Schrödinger equation is discussed both analytically and numerically. The basis for the non-perturbative treatment of laser-matter interaction in the book is the numerical solution of the time-dependent Schrödinger equation. The light field is treated classically, and different possible gauges are discussed. Physical phenonema, ranging from Rabi-oscillations in two-level systems to the ionization of atoms, the generation of high harmonics, the ionization and dissociation of molecules as well as the control of chemical reactions are pre...

  14. Elaboration of submicron structures on PEEK polymer by femtosecond laser

    International Nuclear Information System (INIS)

    Hammouti, S.; Beaugiraud, B.; Salvia, M.; Mauclair, C.; Pascale-Hamri, A.; Benayoun, S.; Valette, S.

    2015-01-01

    Highlights: • We compare PEEK polymer under two crystalline forms: semi-crystalline and amorphous. • We assess topographical modifications of surface morphologies after femtosecond laser irradiation. • At low laser energy regime, there is an influence of the crystallinity rate on topographical features of surface morphologies. • At high laser energy regime, the contribution of the crystallinity tends to disappear. - Abstract: In this work, laser parameters initiating the emergence of periodic structures, so-called ripples on poly (ether ether ketone) (PEEK) surfaces, are investigated. PEEK was used in its semi-crystalline and amorphous forms. Polymer surfaces were treated locally by performing a matrix of laser impacts to highlight the influence of the crystallinity in ultrashort laser interaction. Different surface morphologies or ripples were analyzed by atomic force microscopy and optical interferometry. A map of the presence of these different morphologies according to the laser fluence and the number of pulses was established. Analysis by optical interferometry was carried out and led to the calculations of ablation efficiency. Some significant differences were demonstrated between amorphous and semi-crystalline surfaces. This work revealed topographical information on the local behavior of the irradiated material. Finally, the crystallinity rate of polymer surface seems to be a determinant factor for the periodic nanostructured appearance

  15. Elaboration of submicron structures on PEEK polymer by femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Hammouti, S., E-mail: sabrina.hammouti@ec-lyon.fr [LTDS, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France); Beaugiraud, B.; Salvia, M. [LTDS, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France); Mauclair, C. [LaHC, Université Jean Monnet, 18 rue du Professeur Benoît Lauras, 42000 Saint-Etienne (France); MANUTECH-USD, 20 rue du Professeur Benoît Lauras, 42000 Saint-Etienne (France); Pascale-Hamri, A. [MANUTECH-USD, 20 rue du Professeur Benoît Lauras, 42000 Saint-Etienne (France); Benayoun, S. [LTDS, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France); Valette, S. [LTDS, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France); MANUTECH-USD, 20 rue du Professeur Benoît Lauras, 42000 Saint-Etienne (France)

    2015-02-01

    Highlights: • We compare PEEK polymer under two crystalline forms: semi-crystalline and amorphous. • We assess topographical modifications of surface morphologies after femtosecond laser irradiation. • At low laser energy regime, there is an influence of the crystallinity rate on topographical features of surface morphologies. • At high laser energy regime, the contribution of the crystallinity tends to disappear. - Abstract: In this work, laser parameters initiating the emergence of periodic structures, so-called ripples on poly (ether ether ketone) (PEEK) surfaces, are investigated. PEEK was used in its semi-crystalline and amorphous forms. Polymer surfaces were treated locally by performing a matrix of laser impacts to highlight the influence of the crystallinity in ultrashort laser interaction. Different surface morphologies or ripples were analyzed by atomic force microscopy and optical interferometry. A map of the presence of these different morphologies according to the laser fluence and the number of pulses was established. Analysis by optical interferometry was carried out and led to the calculations of ablation efficiency. Some significant differences were demonstrated between amorphous and semi-crystalline surfaces. This work revealed topographical information on the local behavior of the irradiated material. Finally, the crystallinity rate of polymer surface seems to be a determinant factor for the periodic nanostructured appearance.

  16. Dissociative Ionization of Argon Dimer by Intense Femtosecond Laser Pulses.

    Science.gov (United States)

    Cheng, Qian; Xie, Xiguo; Yuan, Zongqiang; Zhong, Xunqi; Liu, Yunquan; Gong, Qihuang; Wu, Chengyin

    2017-05-25

    We experimentally and theoretically studied dissociative ionization of argon dimer driven by intense femtosecond laser pulses. In the experiment, we measured the ion yield and the angular distribution of fragmental ions generated from the dissociative ionization channels of (1,1) (Ar 2 2+ → Ar + + Ar + ) and (2,1) (Ar 2 3+ → Ar 2+ + Ar + ) using a cold target recoil ion momentum spectroscopy. The channel ratio of (2,1)/(1,1) is 4.5-7.5 times of the yield ratio of double ionization to single ionization of argon monomer depending on the laser intensity. The measurement verified that the ionization of Ar + is greatly enhanced if there exists a neighboring Ar + separated by a critical distance. In addition, the fragmental ions exhibit an anisotropic angular distribution with the peak along the laser polarization direction and the full width at half maximum becomes broader with increasing laser intensity. Using a full three-dimensional classical ensemble model, we calculated the angle-dependent multiple ionization probability of argon dimer in intense laser fields. The results show that the experimentally observed anisotropic angular distribution of fragmental ions can be attributed to the angle-dependent enhanced ionization of the argon dimer in intense laser fields.

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  18. Serial femtosecond crystallography of soluble proteins in lipidic cubic phase

    Energy Technology Data Exchange (ETDEWEB)

    Fromme, Raimund; Ishchenko, Andrii; Metz, Markus; Chowdhury, Shatabdi Roy; Basu, Shibom; Boutet, Sébastien; Fromme, Petra; White, Thomas A.; Barty, Anton; Spence, John C. H.; Weierstall, Uwe; Liu, Wei; Cherezov, Vadim

    2015-08-04

    Serial femtosecond crystallography (SFX) at X-ray free-electron lasers (XFELs) enables high-resolution protein structure determination using micrometre-sized crystals at room temperature with minimal effects from radiation damage. SFX requires a steady supply of microcrystals intersecting the XFEL beam at random orientations. An LCP–SFX method has recently been introduced in which microcrystals of membrane proteins are grown and delivered for SFX data collection inside a gel-like membrane-mimetic matrix, known as lipidic cubic phase (LCP), using a special LCP microextrusion injector. Here, it is demonstrated that LCP can also be used as a suitable carrier medium for microcrystals of soluble proteins, enabling a dramatic reduction in the amount of crystallized protein required for data collection compared with crystals delivered by liquid injectors. High-quality LCP–SFX data sets were collected for two soluble proteins, lysozyme and phycocyanin, using less than 0.1 mg of each protein.

  19. Optical Synchronization Systems for Femtosecond X-Ray Sources

    CERN Document Server

    Wilcox, Russell; Staples, John W

    2005-01-01

    In femtosecond pump/probe experiments using short x-ray and optical pulses, precise synchronization must be maintained between widely separated lasers in a synchrotron or FEL facility. We are developing synchronization systems using optical signals for applications requiring different ranges of timing error. For the sub-100fs range we use an amplitude modulated CW laser at 1GHz to transmit RF phase information, and control the delay through a 100m fiber by observing the retroreflected signal. Initial results show 40fs peak-to-peak error above 10Hz, and 200fs long term drift, mainly due to amplitude sensitivity in the analog mixers. For the sub-10fs range we will lock two single-frequency lasers separated by several teraHertz to a master modelocked fiber laser, transmit the two frequencies over fiber, and lock two comb lines of a slave laser to these frequencies, thus synchronizing the two modelocked laser envelopes. For attosecond synchronization we propose a stabilized, free space link using bulk lens wavegu...

  20. Spatially resolved nanostructural transformation in graphite under femtosecond laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Marcu, A., E-mail: aurelian.marcu@inflpr.ro [National Institute for Laser, Plasma and Radiation Physics, 077125 Bucharest (Romania); Avotina, L. [Institute of Chemical Physics, University of Latvia, Kronvalda 4, LV 1010 Riga (Latvia); Porosnicu, C. [National Institute for Laser, Plasma and Radiation Physics, 077125 Bucharest (Romania); Marin, A. [Ilie Murgulescu” Institute of Physical Chemistry, 202 Splaiul Independentei 060021, Bucharest (Romania); Grigorescu, C.E.A. [National Institute R& D for Optoelectronics INOE 2000, 077125 Bucharest (Romania); Ursescu, D. [National Institute for Laser, Plasma and Radiation Physics, 077125 Bucharest (Romania); Lungu, M. [National Institute of Materials Physics Atomistilor Str., 105 bis, 077125, Magurele (Romania); Demitri, N. [Hard X-ray Beamline and Structural Biology, Elettra-Sincrotrone Trieste, Strada Statale 14 - km 163,5 in AREA Science Park, 34149 Basovizza TS Italy (Italy); Lungu, C.P. [National Institute for Laser, Plasma and Radiation Physics, 077125 Bucharest (Romania)

    2015-11-15

    Graphical abstract: - Highlights: • Polycrystalline graphite was irradiated with a high power fs (IR) laser. • Presence of a diamond peak was detected by synchrotron XRD. • XPS and Raman showed in-depth sp{sup 3}% increase at tens of nm below the surface. • sp{sup 3}% is increasing with laser power density but it is independent of photon absorption rate. • Graphite crystallite size locally increase at tens of nanometers below the irradiated spots. - Abstract: A polycrystalline graphite target was irradiated using infrared (800 nm) femtosecond (120 fs) laser pulses of different energies. Increase of sp{sup 3} bonds percentage and possible diamond crystal formation were investigated ‘in-depth’ and on the irradiated surfaces. Synchrotron X-ray diffraction pattern have shown the presence of a diamond peak in one of the irradiated zones while X-ray photoelectron spectroscopy investigations have shown an increasing tendency of the sp{sup 3} percent in the low power irradiated areas and similarly ‘in the depth’ of the higher power irradiated zones. Multiple wavelength Micro-Raman investigations have confirmed this trend along with an ‘in-depth’ (but not on the surface) increase of the crystallite size. Based on the wavelength dependent photon absorption into graphite, the observed effects are correlated with high density photon per atom and attributed to the melting and recrystallization processes taking place tens of nanometers below the target surface.

  1. Spatially resolved nanostructural transformation in graphite under femtosecond laser irradiation

    International Nuclear Information System (INIS)

    Marcu, A.; Avotina, L.; Porosnicu, C.; Marin, A.; Grigorescu, C.E.A.; Ursescu, D.; Lungu, M.; Demitri, N.; Lungu, C.P.

    2015-01-01

    Graphical abstract: - Highlights: • Polycrystalline graphite was irradiated with a high power fs (IR) laser. • Presence of a diamond peak was detected by synchrotron XRD. • XPS and Raman showed in-depth sp 3 % increase at tens of nm below the surface. • sp 3 % is increasing with laser power density but it is independent of photon absorption rate. • Graphite crystallite size locally increase at tens of nanometers below the irradiated spots. - Abstract: A polycrystalline graphite target was irradiated using infrared (800 nm) femtosecond (120 fs) laser pulses of different energies. Increase of sp 3 bonds percentage and possible diamond crystal formation were investigated ‘in-depth’ and on the irradiated surfaces. Synchrotron X-ray diffraction pattern have shown the presence of a diamond peak in one of the irradiated zones while X-ray photoelectron spectroscopy investigations have shown an increasing tendency of the sp 3 percent in the low power irradiated areas and similarly ‘in the depth’ of the higher power irradiated zones. Multiple wavelength Micro-Raman investigations have confirmed this trend along with an ‘in-depth’ (but not on the surface) increase of the crystallite size. Based on the wavelength dependent photon absorption into graphite, the observed effects are correlated with high density photon per atom and attributed to the melting and recrystallization processes taking place tens of nanometers below the target surface.

  2. Femtosecond response time measurements of a Cs2Te photocathode

    Science.gov (United States)

    Aryshev, A.; Shevelev, M.; Honda, Y.; Terunuma, N.; Urakawa, J.

    2017-07-01

    Success in design and construction of a compact, high-brightness accelerator system is strongly related to the production of ultra-short electron beams. Recently, the approach to generate short electron bunches or pre-bunched beams in RF guns directly illuminating a high quantum efficiency semiconductor photocathode with femtosecond laser pulses has become attractive. The measurements of the photocathode response time in this case are essential. With an approach of the interferometer-type pulse splitter deep integration into a commercial Ti:Sa laser system used for RF guns, it has become possible to generate pre-bunched electron beams and obtain continuously variable electron bunch separation. In combination with a well-known zero-phasing technique, it allows us to estimate the response time of the most commonly used Cs2Te photocathode. It was demonstrated that the peak-to-peak rms time response of Cs2Te is of the order of 370 fs, and thereby, it is possible to generate and control a THz sequence of relativistic electron bunches by a conventional S-band RF gun. This result can also be applied for investigation of other cathode materials and electron beam temporal shaping and further opens a possibility to construct wide-range tunable, table-top THz free electron laser.

  3. Postoperative Endophthalmitis Caused by Staphylococcus haemolyticus following Femtosecond Cataract Surgery

    Directory of Open Access Journals (Sweden)

    Margaret Wong

    2015-12-01

    Full Text Available A 53-year-old Caucasian man underwent femtosecond cataract surgery and then presented with pain and hand motions vision 1 day following surgery. Anterior segment examination showed a 2-mm-layered hypopyon, a well-centered intraocular lens in the sulcus, and an obscured view to the fundus. B-scan ultrasonography showed significant vitritis and that the retina was attached. A tap and an injection of vancomycin 1 mg per 0.1 ml and of ceftazidime 2.25 mg per 0.1 ml were performed. The tap eventually yielded culture results positive for Staphylococcus haemolyticus, which was sensitive to vancomycin. We report a case of endophthalmitis that occurred on postoperative day 1 following complicated cataract surgery. This is an uncommon bacterium that is not widely reported in the literature as a cause of endophthalmitis in the postoperative period. We urge clinicians to consider S. haemolyticus as an offending agent, especially when the infection presents very early and aggressively in the postoperative period.

  4. Postoperative Endophthalmitis Caused by Staphylococcus haemolyticus following Femtosecond Cataract Surgery.

    Science.gov (United States)

    Wong, Margaret; Baumrind, Benjamin R; Frank, James H; Halpern, Robert L

    2015-01-01

    A 53-year-old Caucasian man underwent femtosecond cataract surgery and then presented with pain and hand motions vision 1 day following surgery. Anterior segment examination showed a 2-mm-layered hypopyon, a well-centered intraocular lens in the sulcus, and an obscured view to the fundus. B-scan ultrasonography showed significant vitritis and that the retina was attached. A tap and an injection of vancomycin 1 mg per 0.1 ml and of ceftazidime 2.25 mg per 0.1 ml were performed. The tap eventually yielded culture results positive for Staphylococcus haemolyticus, which was sensitive to vancomycin. We report a case of endophthalmitis that occurred on postoperative day 1 following complicated cataract surgery. This is an uncommon bacterium that is not widely reported in the literature as a cause of endophthalmitis in the postoperative period. We urge clinicians to consider S. haemolyticus as an offending agent, especially when the infection presents very early and aggressively in the postoperative period.

  5. Research on spectrum broadening covering visible light of a fiber femtosecond optical frequency comb for absolute frequency measurement

    Science.gov (United States)

    Xing, Shuai; Wu, Tengfei; Li, Shuyi; Xia, Chuanqing; Han, Jibo; Zhang, Lei; Zhao, Chunbo

    2018-03-01

    As a bridge connecting microwave frequency and optical frequency, femtosecond laser has important significance in optical frequency measurement. Compared with the traditional Ti-sapphire femtosecond optical frequency comb, with the advantages of compact structure, strong anti-interference ability and low cost, the fiber femtosecond optical frequency comb has a wider application prospect. An experiment of spectrum broadening in a highly nonlinear photonic crystal fiber pumped by an Er-fiber mode-locked femtosecond laser is studied in this paper. Based on optical amplification and frequency doubling, the central wavelength of the output spectrum is 780nm and the average power is 232mW. With the femtosecond pulses coupled into two different photonic crystal fibers, the coverage of visible spectrum is up to 500nm-960nm. The spectral shape and width can be optimized by changing the polarization state for satisfying the requirments of different optical frequencies measurement.

  6. Electron Bunch Timing with Femtosecond Precision in a Superconducting Free-Electron Laser

    International Nuclear Information System (INIS)

    Loehl, F.; Arsov, V.; Felber, M.; Hacker, K.; Lorbeer, B.; Ludwig, F.; Matthiesen, K.-H.; Schlarb, H.; Schmidt, B.; Winter, A.; Jalmuzna, W.; Schmueser, P.; Schulz, S.; Zemella, J.; Szewinski, J.

    2010-01-01

    High-gain free-electron lasers (FELs) are capable of generating femtosecond x-ray pulses with peak brilliances many orders of magnitude higher than at other existing x-ray sources. In order to fully exploit the opportunities offered by these femtosecond light pulses in time-resolved experiments, an unprecedented synchronization accuracy is required. In this Letter, we distributed the pulse train of a mode-locked fiber laser with femtosecond stability to different locations in the linear accelerator of the soft x-ray FEL FLASH. A novel electro-optic detection scheme was applied to measure the electron bunch arrival time with an as yet unrivaled precision of 6 fs (rms). With two beam-based feedback systems we succeeded in stabilizing both the arrival time and the electron bunch compression process within two magnetic chicanes, yielding a significant reduction of the FEL pulse energy jitter.

  7. Electron Bunch Timing with Femtosecond Precision in a Superconducting Free-Electron Laser

    Science.gov (United States)

    Löhl, F.; Arsov, V.; Felber, M.; Hacker, K.; Jalmuzna, W.; Lorbeer, B.; Ludwig, F.; Matthiesen, K.-H.; Schlarb, H.; Schmidt, B.; Schmüser, P.; Schulz, S.; Szewinski, J.; Winter, A.; Zemella, J.

    2010-04-01

    High-gain free-electron lasers (FELs) are capable of generating femtosecond x-ray pulses with peak brilliances many orders of magnitude higher than at other existing x-ray sources. In order to fully exploit the opportunities offered by these femtosecond light pulses in time-resolved experiments, an unprecedented synchronization accuracy is required. In this Letter, we distributed the pulse train of a mode-locked fiber laser with femtosecond stability to different locations in the linear accelerator of the soft x-ray FEL FLASH. A novel electro-optic detection scheme was applied to measure the electron bunch arrival time with an as yet unrivaled precision of 6 fs (rms). With two beam-based feedback systems we succeeded in stabilizing both the arrival time and the electron bunch compression process within two magnetic chicanes, yielding a significant reduction of the FEL pulse energy jitter.

  8. Experimental study of femtosecond laser-stimulated electrical discharges in small gaps and surface modifications

    International Nuclear Information System (INIS)

    Chen, J.; Farson, D. F.; Rokhlin, S. I.

    2009-01-01

    Femtosecond laser-stimulated discharges in nanoscale and microscale gaps between etched nanoprobe tip cathodes and gold film anodes with applied dc potential were experimentally studied to define parameter ranges for their controlled formation and resulting surface modifications. For appropriate values of gap length, applied potential, and laser irradiance, breakdown discharges could be reliably stimulated by femtosecond laser pulses and the mean breakdown field was approximately an order of magnitude smaller than for breakdown without laser stimulation. For 500 nm gaps, discharges were observed for applied potentials as small as 20 V and controllable gold film surface melting was detected for applied potential of 27.5 V. Minor cathode tip ablation could be observed for femtosecond laser pulses that reliably stimulated discharges, suggesting that cathode material played an important role in stimulation of breakdown discharges in nanoscale gaps. Surface melting produced features as small as 60 nm on gold film when discharge current was limited by 1 MΩ series resistor

  9. Fabrication of superconducting nanowire single-photon detectors by nonlinear femtosecond optical lithography

    Science.gov (United States)

    Minaev, N. V.; Tarkhov, M. A.; Dudova, D. S.; Timashev, P. S.; Chichkov, B. N.; Bagratashvili, V. N.

    2018-02-01

    This paper describes a new approach to the fabrication of superconducting nanowire single-photon detectors from ultrathin NbN films on SiO2 substrates. The technology is based on nonlinear femtosecond optical lithography and includes direct formation of the sensitive element of the detector (the meander) through femtosecond laser exposure of the polymethyl methacrylate resist at a wavelength of 525 nm and subsequent removal of NbN using plasma-chemical etching. The nonlinear femtosecond optical lithography method allows the formation of planar structures with a spatial resolution of ~50 nm. These structures were used to fabricate single-photon superconducting detectors with quantum efficiency no worse than 8% at a wavelength of 1310 nm and dark count rate of 10 s‑1 at liquid helium temperature.

  10. Photomechanical ablation of biological tissue induced by focused femtosecond laser and its application for acupuncture

    Science.gov (United States)

    Hosokawa, Yoichiroh; Ohta, Mika; Ito, Akihiko; Takaoka, Yutaka

    2013-03-01

    Photomechanical laser ablation due to focused femtosecond laser irradiation was induced on the hind legs of living mice, and its clinical influence on muscle cell proliferation was investigated via histological examination and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis to examine the expression of the gene encoding myostatin, which is a growth repressor in muscle satellite cells. The histological examination suggested that damage of the tissue due to the femtosecond laser irradiation was localized on epidermis and dermis and hardly induced in the muscle tissue below. On the other hand, gene expression of the myostatin of muscle tissue after laser irradiation was suppressed. The suppression of myostatin expression facilitates the proliferation of muscle cells, because myostatin is a growth repressor in muscle satellite cells. On the basis of these results, we recognize the potential of the femtosecond laser as a tool for noncontact, high-throughput acupuncture in the treatment of muscle disease.

  11. A new multifunctional device for femtosecond pulse characterization with a wide operating range

    International Nuclear Information System (INIS)

    Li, F J; Zhang, S X; Liu, Q F; Zhao, G K; Liu, J

    2014-01-01

    We demonstrate a novel and simple device for femtosecond pulse characterization, which combines the frequency-resolved optical gating (FROG) and the self-referenced spectral interferometry (SRSI) methods in the frequency-resolved optical gating and self-referenced spectral interferometry (FASI) method. It was found that the comparative advantages of FROG and SRSI can complement each other. Therefore FASI can be used to characterize femtosecond pulses in different conditions, which may need different devices when using either the FROG or the SRSI method independently. With our multifunctional FASI device, the TG-FROG, SHG-FROG and TG-SRSI methods were used to fully characterize femtosecond pulses at 800 nm with different dispersions. The experimental results obtained by all three methods were compared with each other and also with the calculated data. These results proved the reliability and the wide operating range of our FASI device. (letter)

  12. Achieving few-femtosecond time-sorting at hard X-ray free-electron lasers

    Science.gov (United States)

    Harmand, M.; Coffee, R.; Bionta, M. R.; Chollet, M.; French, D.; Zhu, D.; Fritz, D. M.; Lemke, H. T.; Medvedev, N.; Ziaja, B.; Toleikis, S.; Cammarata, M.

    2013-03-01

    Recently, few-femtosecond pulses have become available at hard X-ray free-electron lasers. Coupled with the available sub-10 fs optical pulses, investigations into few-femtosecond dynamics are not far off. However, achieving sufficient synchronization between optical lasers and X-ray pulses continues to be challenging. We report a `measure-and-sort' approach, which achieves sub-10 fs root-mean-squared (r.m.s.) error measurement at hard X-ray FELs, far beyond the 100-200 fs r.m.s. jitter limitations. This timing diagnostic, now routinely available at the Linac Coherent Light Source (LCLS), is based on ultrafast free-carrier generation in optically transparent materials. Correlation between two independent measurements enables unambiguous demonstration of ~6 fs r.m.s. error in reporting the optical/X-ray delay, with single shot error suggesting the possibility of reaching few-femtosecond resolution.

  13. A Comparison of Different Operating Systems for Femtosecond Lasers in Cataract Surgery.

    Science.gov (United States)

    Wu, B M; Williams, G P; Tan, A; Mehta, J S

    2015-01-01

    The introduction of femtosecond lasers is potentially a major shift in the way we approach cataract surgery. The development of increasingly sophisticated intraocular lenses (IOLs), coupled with heightened patient expectation of high quality postsurgical visual outcomes, has generated the need for a more precise, highly reproducible and standardized method to carry out cataract operations. As femtosecond laser-assisted cataract surgery (FLACS) becomes more commonplace in surgical centers, further evaluation of the potential risks and benefits needs to be established, particularly in the medium/long term effects. Healthcare administrators will also have to weigh and balance out the financial costs of these lasers relative to the advantages they put forth. In this review, we provide an operational overview of three of five femtosecond laser platforms that are currently commercially available: the Catalys (USA), the Victus (USA), and the LDV Z8 (Switzerland).

  14. Narrow-selection bandwith of femtosecond laser comb with application to changes in optical path distance

    Science.gov (United States)

    Šmíd, Radek; Ježek, Jan; Buchta, Zden"k.; Čížek, Martin; Lazar, Josef; Číp, Ondřej

    2010-05-01

    In this contribution we propose a scheme of Fabry-Perot interferometer measuring the absolute distance in atmosferic conditions using a femtosecond laser comb. The spacing of mirrors of the Fabry-Perot interferometer represents the length standard referenced to stable optical frequency of the femtosecond mode-locked laser. With the help of highly selective optical filter it is possible to get only a few of separate spectral components. By tuning and locking of the Fabry-Perot cavity to a selected single component it is possible to get a mechanical length standard with the uncertainty of the repetition frequency of the femtosecond laser. If the interferometer measures distance in atmospheric conditions, the absolute value of the laser wavelength fluctuates with a refractive index of air. Compairing the measurement in evacuated chamber with measurement in ambient air leads to enhanced precision in measurement of refrective index of air.

  15. Precise femtosecond laser ablation of dental hard tissue: preliminary investigation on adequate laser parameters

    International Nuclear Information System (INIS)

    Hikov, Todor; Pecheva, Emilia; Petrov, Todor; Montgomery, Paul; Antoni, Frederic; Leong-Hoi, Audrey

    2017-01-01

    This work aims at evaluating the possibility of introducing state-of-the-art commercial femtosecond laser system in restorative dentistry by maintaining well-known benefits of lasers for caries removal, but also in overcoming disadvantages such as thermal damage of irradiated substrate. Femtosecond ablation of dental hard tissue is investigated by changing the irradiation parameters (pulsed laser energy, scanning speed and pulse repetition rate), assessed for enamel and dentin. The femtosecond laser system used in this work may be suitable for cavity preparation in dentin and enamel, due to the expected effective ablation and low temperature increase when using ultra short laser pulses. If adequate laser parameters are selected, this system seems to be promising for promoting a laser-assisted, minimally invasive approach in restorative dentistry. (paper)

  16. Non-invasive bleaching of the human lens by femtosecond laser photolysis

    DEFF Research Database (Denmark)

    Kessel, L.; Eskildsen, Lars; Poel, Mike van der

    2010-01-01

    were susceptible to photobleaching by a non-invasive procedure and whether this would lead to optical rejuvenation of the lens. Methodology/Principal Findings: Nine human donor lenses were treated with an 800 nm infra-red femtosecond pulsed laser in a treatment zone measuring 1 x 1 x 0.52 mm. After...... laser treatment the age-induced yellow discoloration of the lens was markedly reduced and the transmission of light was increased corresponding to an optical rejuvenation of 3 to 7 years. Conclusions/Significance: The results demonstrate that the age-induced yellowing of the human lens can be bleached...... by a non-invasive procedure based on femtosecond laser photolysis. Cataract is a disease associated with old age. At the current technological stage, lens aging is delayed but with a treatment covering the entire lens volume complete optical rejuvenation is expected. Thus, femtosecond photolysis has...

  17. A stabilized optical frequency comb based on an Er-doped fiber femtosecond laser

    Science.gov (United States)

    Xia, Chuanqing; Wu, Tengfei; Zhao, Chunbo; Xing, Shuai

    2018-03-01

    An optical frequency comb based on a 250 MHz home-made Er-doped fiber femtosecond laser is presented in this paper. The Er-doped fiber laser has a ring cavity and operates mode-locked in femtosecond regime with the technique of nonlinear polarization rotation. The pulse duration is 118 fs and the spectral width is 30 nm. A part of the femtosecond laser is amplified in Er-doped fiber amplifier before propagating through a piece of highly nonlinear fiber for expanding the spectrum. The carrier-envelope offset frequency of the comb which has a signal-to-noise ratio more than 35 dB is extracted by means of f-2f beating. It demonstrates that both carrier-envelope offset frequency and repetition frequency keep phase locked to a Rubidium atomic clock simultaneously for 2 hours. The frequency stabilized fiber combs will be increasingly applied in optical metrology, attosecond pulse generation, and absolute distance measurement.

  18. Precise femtosecond laser ablation of dental hard tissue: preliminary investigation on adequate laser parameters

    Science.gov (United States)

    Hikov, Todor; Pecheva, Emilia; Montgomery, Paul; Antoni, Frederic; Leong-Hoi, Audrey; Petrov, Todor

    2017-01-01

    This work aims at evaluating the possibility of introducing state-of-the-art commercial femtosecond laser system in restorative dentistry by maintaining well-known benefits of lasers for caries removal, but also in overcoming disadvantages such as thermal damage of irradiated substrate. Femtosecond ablation of dental hard tissue is investigated by changing the irradiation parameters (pulsed laser energy, scanning speed and pulse repetition rate), assessed for enamel and dentin. The femtosecond laser system used in this work may be suitable for cavity preparation in dentin and enamel, due to the expected effective ablation and low temperature increase when using ultra short laser pulses. If adequate laser parameters are selected, this system seems to be promising for promoting a laser-assisted, minimally invasive approach in restorative dentistry.

  19. Porcine Model to Evaluate Real-Time Intraocular Pressure During Femtosecond Laser Cataract Surgery.

    Science.gov (United States)

    Ibarz, Marta; Hernández-Verdejo, José Luis; Bolívar, Gema; Tañá, Pedro; Rodríguez-Prats, José Luis; Teus, Miguel A

    2016-04-01

    To investigate the changes in intraocular pressure (IOP) in porcine eyes during femtosecond laser-assisted cataract surgery using a liquid-optic interface system. Femtosecond laser cataract surgery with the Catalys™ was performed on freshly enucleated porcine eyes in Oftalvist Moncloa, Madrid, Spain. Capsulorhexis and lens fragmentation were completed in all the eyes without complications. IOP was measured with a reusable blood pressure transducer connected by direct cannulation to the anterior chamber, recording data before suction (basal), at the beginning of the suction phase, every five seconds during femtosecond procedure and after the removal of the suction ring from the eye. Nine porcine eyes were used in this study. Basal IOP before suction was 5.67 ± 2.39 mmHg, rising to 20.33 ± 4.18 mmHg at the beginning of the suction phase (p < 0.001). During femtosecond procedure, pressure reached a value of 19.74 ± 4.31 mmHg, remaining stable during the entire process. The IOP recorded prior to removal of the suction ring was 21.00 ± 6.93 mmHg, returning to basal values in all the eyes after the suction ring was removed, with no statistical differences between basal and post-suction IOPs. Total femtosecond procedure time was 125.9 ±  15.9 s. Real-time IOP can be measured during surgery using a transducer connected to the anterior chamber. The results showed a significant increase in IOP during the procedure due to the pressure exerted by the suction ring but not by the effect of the femtosecond laser.

  20. Femtosecond lasers for LASIK flap creation: a report by the American Academy of Ophthalmology.

    Science.gov (United States)

    Farjo, Ayad A; Sugar, Alan; Schallhorn, Steven C; Majmudar, Parag A; Tanzer, David J; Trattler, William B; Cason, John B; Donaldson, Kendall E; Kymionis, George D

    2013-03-01

    To review the published literature to assess the safety, efficacy, and predictability of femtosecond lasers for the creation of corneal flaps for LASIK; to assess the reported outcomes of LASIK when femtosecond lasers are used to create corneal flaps; and to compare the differences in outcomes between femtosecond lasers and mechanical microkeratomes. Literature searches of the PubMed and Cochrane Library databases were last conducted on October 12, 2011, without language or date limitations. The searches retrieved a total of 636 references. Of these, panel members selected 58 articles that they considered to be of high or medium clinical relevance, and the panel methodologist rated each article according to the strength of evidence. Four studies were rated as level I evidence, 14 studies were rated as level II evidence, and the remaining studies were rated as level III evidence. The majority of published studies evaluated a single laser platform. Flap reproducibility varied by device and the generation of the device. Standard deviations in flap thicknesses ranged from 4 to 18.4 μm. Visual acuities and complications reported with LASIK flaps created using femtosecond lasers are within Food and Drug Administration safety and efficacy limits. Of all complications, diffuse lamellar keratitis is the most common after surgery but is generally mild and self-limited. Corneal sensation was reported to normalize by 1 year after surgery. Unique complications of femtosecond lasers included transient light-sensitivity syndrome, rainbow glare, opaque bubble layer, epithelial breakthrough of gas bubbles, and gas bubbles within the anterior chamber. Available evidence (levels I and II) indicates that femtosecond lasers are efficacious devices for creating LASIK flaps, with accompanying good visual results. Overall, femtosecond lasers were found to be as good as or better than mechanical microkeratomes for creating LASIK flaps. There are unique complications that can occur with

  1. Photofragmentation of colloidal solutions of gold nanoparticles under femtosecond laser pulses in IR and visible ranges

    International Nuclear Information System (INIS)

    Danilov, P A; Zayarnyi, D A; Ionin, A A; Kudryashov, S I; Makarov, S V; Rudenko, A A; Saraeva, I N; Yurovskikh, V I; Lednev, V N; Pershin, S M

    2015-01-01

    The specific features of photofragmentation of sols of gold nanoparticles under focused femtosecond laser pulses in IR (1030 nm) and visible (515 nm) ranges is experimentally investigated. A high photofragmentation efficiency of nanoparticles in the waist of a pulsed laser beam in the visible range (at moderate radiation scattering) is demonstrated; this efficiency is related to the excitation of plasmon resonance in nanoparticles on the blue shoulder of its spectrum, in contrast to the regime of very weak photofragmentation in an IR-laser field of comparable intensity. Possible mechanisms of femtosecond laser photofragmentation of gold nanoparticles are discussed. (extreme light fields and their applications)

  2. Reassembling Solid Materials by Femtosecond Laser Ablation: Case of Aluminum Nitride

    Science.gov (United States)

    Kobayashi, Tohru; Matsuo, Yukari

    2013-06-01

    Through atomization and ionization, we could completely alter the composition of a nonconductive material, aluminum nitride, by femtosecond laser ablation. Preferential production of pure aluminum cluster cations Aln+ (n≤32) reflects not only their higher energetic stability compared with mixed clusters AlnNm+ but also completion of thermal relaxation in ablation plasma. Observation of metastable dissociation of Aln+ indicates that cluster cations have still enough internal energy for dissociation to occur, although the process is much slower than the cluster formation. Almost no cluster formation has been observed after nanosecond laser ablation of aluminum nitride, which highlights the distinct nature of ablation plasma produced by femtosecond laser ablation.

  3. Cascaded quadratic soliton compression of high-power femtosecond fiber lasers in Lithium Niobate crystals

    DEFF Research Database (Denmark)

    Bache, Morten; Moses, Jeffrey; Wise, Frank W.

    2008-01-01

    The output of a high-power femtosecond fiber laser is typically 300 fs with a wavelength around $\\lambda=1030-1060$ nm. Our numerical simulations show that cascaded quadratic soliton compression in bulk LiNbO$_3$ can compress such pulses to below 100 fs.......The output of a high-power femtosecond fiber laser is typically 300 fs with a wavelength around $\\lambda=1030-1060$ nm. Our numerical simulations show that cascaded quadratic soliton compression in bulk LiNbO$_3$ can compress such pulses to below 100 fs....

  4. Astrocyte-to-neuron signaling in response to photostimulation with a femtosecond laser

    Science.gov (United States)

    Zhao, Yuan; Liu, Xiuli; Zhou, Wei; Zeng, Shaoqun

    2010-08-01

    Conventional stimulation techniques used in studies of astrocyte-to-neuron signaling are invasive or dependent on additional electrical devices or chemicals. Here, we applied photostimulation with a femtosecond laser to selectively stimulate astrocytes in the hippocampal neural network, and the neuronal responses were examined. The results showed that, after photostimulation, cell-specific astrocyte-to-neuron signaling was triggered; sometimes the neuronal responses were even synchronous. Since photostimulation with a femtosecond laser is noninvasive, agent-free, and highly precise, this method has been proved to be efficient in activating astrocytes for investigations of astrocytic functions in neural networks.

  5. In-line femtosecond common-path interferometer in reflection mode.

    Science.gov (United States)

    Chandezon, J; Rampnoux, J-M; Dilhaire, S; Audoin, B; Guillet, Y

    2015-10-19

    An innovative method to perform femtosecond time-resolved interferometry in reflection mode is proposed. The experiment consists in the combined use of a pump-probe setup and of a fully passive in-line femtosecond common-path interferometer. The originality of this interferometer relies on the use of a single birefringent crystal first to generate a pair of phase-locked pulses and second to recombine them to interfere. As predicted by analytical modeling, this interferometer measures the temporal derivative of the ultrafast changes of the complex optical reflection coefficient of the sample. Working conditions are illustrated through picosecond opto-acoustic experiments on a thin film.

  6. Probing the switching state of a surface-mounted azobenzene derivative using femtosecond XUV photoemission

    Science.gov (United States)

    Grunau, Jan; Heinemann, Nils; Rohwer, Timm; Zargarani, Dordaneh; Kuhn, Sonja; Jung, Ullrich; Kipp, Lutz; Magnussen, Olaf; Herges, Rainer; Bauer, Michael

    2012-03-01

    Photoemission spectroscopy using femtosecond XUV light pulses is applied to probe the isomerization state of the molecular switch 3-(4-(4-hexyl-phenylazo)-phenoxy)-propane-1-thiol deposited by liquid phase self-assembly on Au(111). Spectral shifts of valence-electronic signatures that we associate with the carbon C2s orbital enable us to distinguish the trans and the cis isomerization state of the adsorbed molecules. These preliminary results envision the potential to probe reversible switching processes of surface-mounted molecules in real time by tracking the temporal evolution of the electronic and nuclear degrees of freedom in a femtosecond XUV photoemission experiment.

  7. Ablation characteristics of aluminum oxide and nitride ceramics during femtosecond laser micromachining

    International Nuclear Information System (INIS)

    Kim, Sung Hoon; Sohn, Ik-Bu; Jeong, Sungho

    2009-01-01

    Femtosecond laser ablation of aluminum oxide (Al 2 O 3 ) and aluminum nitride (AlN) ceramics was performed under normal atmospheric conditions (λ = 785 nm, τ p = 185 fs, repetition rate = 1 kHz), and threshold laser fluencies for single- and multi-pulse ablation were determined. The ablation characteristics of the two ceramics showed similar trends except for surface morphologies, which revealed virtually no melting in Al 2 O 3 but clear evidence of melting for AlN. Based on subsequent X-ray photoelectron spectroscopy (XPS) analyses, the chemistry of these ceramics appeared to remain the same before and after femtosecond laser ablation.

  8. In-fiber whispering-gallery-mode resonator fabricated by femtosecond laser micromachining.

    Science.gov (United States)

    Shi, Leilei; Zhu, Tao; Huang, Dongmei; Liu, Min; Deng, Ming; Huang, Wei

    2015-08-15

    An in-fiber whispering-gallery-mode resonator fabricated by femtosecond laser micromachining is demonstrated. The cylinder resonator cavity is fabricated by scanning the D-fiber cladding with infrared femtosecond pulses along a cylindrical trace with a radius of 25 μm and height of 20 μm. Quality factor on the order of 10(3) is achieved by smoothing the cavity surface with an ultrasonic cleaner, which is mainly limited by the surface roughness of several hundred nanometers. Resonant characteristics and polarization dependence of the proposed resonator are also studied in detail. Our method takes a step forward in the integration of whispering-gallery-mode resonators.

  9. Fabrication of large-area hydrophobic surfaces with femtosecond-laser-structured molds

    Science.gov (United States)

    Wu, P. H.; Cheng, C. W.; Chang, C. P.; Wu, T. M.; Wang, J. K.

    2011-11-01

    Fast replication of large-area femtosecond-laser-induced surface micro/nanostructures on plastic parts by injection molding is demonstrated. An STAVAX steel mold insert is irradiated by femtosecond laser pulses with linear or circular polarization to form periodic-like nanostructures or nanostructure-covered conical microstructures. It was then used for the process of thermal injection molding. The process provides high-volume manufacturing means to generate hydrophobic enhanced plastic parts, which is expected to be widely used in consumables and chemical/biomedical device industries.

  10. Measurement of temperature rises in the femtosecond laser pulsed three-dimensional atom probe

    International Nuclear Information System (INIS)

    Cerezo, A.; Smith, G.D.W.; Clifton, P.H.

    2006-01-01

    A previous Letter [B. Gault et al., Appl. Phys. Lett. 86, 094101 (2005)] interpreted measurements of the field evaporation enhancement under femtosecond pulsed laser irradiation of a field emitter in terms of a direct electric field enhancement by the intrinsic field of the laser light. We show that, on the contrary, the field evaporation enhancement is predominantly a thermal heating effect. Indirect measurements of the peak specimen temperature under irradiation by femtosecond laser pulses are consistent with temperature rises obtained using longer laser pulses in a range of earlier work

  11. FAST TRACK COMMUNICATION: Inactivation of viruses with a very low power visible femtosecond laser

    Science.gov (United States)

    Tsen, K. T.; Tsen, Shaw-Wei D.; Chang, Chih-Long; Hung, Chien-Fu; Wu, T.-C.; Kiang, Juliann G.

    2007-08-01

    We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering. By using a very low power visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW cm-2. The inactivation of M13 phages was determined by plaque counts and depended on the pulse width as well as power density of the excitation laser.

  12. Inactivation of viruses with a very low power visible femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Tsen, K T [Department of Physics, Arizona State University, Tempe, AZ 85287 (United States); Tsen, Shaw-Wei D [Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21231 (United States); Chang, C.-L. [Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21231 (United States); Hung, C.-F. [Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21231 (United States); Wu, T-C [Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21231 (United States); Kiang, Juliann G [Scientific Research Department, Armed Forces Radiobiology Research Institute, Uniformed Services University of The Health Sciences, Bethesda, MD 20889-5603 (United States)

    2007-08-15

    We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering. By using a very low power visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW cm{sup -2}. The inactivation of M13 phages was determined by plaque counts and depended on the pulse width as well as power density of the excitation laser. (fast track communication)

  13. Microscopic and macroscopic modeling of femtosecond laser ablation of metals

    Energy Technology Data Exchange (ETDEWEB)

    Povarnitsyn, Mikhail E., E-mail: povar@ihed.ras.ru; Fokin, Vladimir B.; Levashov, Pavel R.

    2015-12-01

    Highlights: • We model laser ablation of aluminum using microscopic and macroscopic approaches. • We examine the domain of applicability for hydrodynamics and molecular dynamics. • Molecular dynamics describes ultra-fast processes of melting and fragmentation. • Hydrodynamics with a model of nucleation agrees well with molecular dynamics. • Both computational methods give similar ablation crater depths. - Abstract: Simulation of femtosecond laser ablation of a bulk aluminum target is performed using two complementary approaches. The first method is single-fluid two-temperature hydrodynamics (HD) completed with a two-temperature equation of state (EOS). The second approach is a combination of classical molecular dynamics (MD) and a continuum model of a free electron subsystem. In both methods, an identical and accurate description of optical and transport properties of the electron subsystem is based on wide-range models reproducing effects of electron heat wave propagation, electron–phonon/ion coupling and laser energy absorption on a time-dependent profile of the dielectric function. For simulation of homogeneous nucleation in a metastable liquid phase, a kinetic model of nucleation is implemented in the HD approach. The phase diagrams of the EOS and MD potential are in good agreement that gives opportunity to compare the dynamics of laser ablation obtained by both methods directly. Results of simulation are presented in the range of incident fluences 0.1–20 J/cm{sup 2} and match well with experimental findings for an ablation crater depth. The MD accurately reproduces nonequilibrium phase transitions and takes into account surface effects on nanoscale. The HD approach demonstrates good qualitative agreement with the MD method in the dynamics of phase explosion and spallation. Other advantages and disadvantages of both approaches are examined and discussed.

  14. Femtosecond transient absorption spectroscopy of silanized silicon quantum dots

    Science.gov (United States)

    Kuntermann, Volker; Cimpean, Carla; Brehm, Georg; Sauer, Guido; Kryschi, Carola; Wiggers, Hartmut

    2008-03-01

    Excitonic properties of colloidal silicon quantum dots (Si qdots) with mean sizes of 4nm were examined using stationary and time-resolved optical spectroscopy. Chemically stable silicon oxide shells were prepared by controlled surface oxidation and silanization of HF-etched Si qdots. The ultrafast relaxation dynamics of photogenerated excitons in Si qdot colloids were studied on the picosecond time scale from 0.3psto2.3ns using femtosecond-resolved transient absorption spectroscopy. The time evolution of the transient absorption spectra of the Si qdots excited with a 150fs pump pulse at 390nm was observed to consist of decays of various absorption transitions of photoexcited electrons in the conduction band which overlap with both the photoluminescence and the photobleaching of the valence band population density. Gaussian deconvolution of the spectroscopic data allowed for disentangling various carrier relaxation processes involving electron-phonon and phonon-phonon scatterings or arising from surface-state trapping. The initial energy and momentum relaxation of hot carriers was observed to take place via scattering by optical phonons within 0.6ps . Exciton capturing by surface states forming shallow traps in the amorphous SiOx shell was found to occur with a time constant of 4ps , whereas deeper traps presumably localized in the Si-SiOx interface gave rise to exciton trapping processes with time constants of 110 and 180ps . Electron transfer from initially populated, higher-lying surface states to the conduction band of Si qdots (>2nm) was observed to take place within 400 or 700fs .

  15. Optical microdevices fabricated using femtosecond laser processing (Conference Presentation)

    Science.gov (United States)

    Otuka, Adriano J. G.; Tomázio, Nathália B.; Tribuzi, Vinicius; Ferreira, Paulo Henrique D.; De Boni, Leonardo; Mendonça, Cleber R.

    2017-02-01

    Femtosecond laser processing techniques have been widely employed to produce micro or nanodevices with special features. These devices can be selectively doped with organic dyes, biological agents, nanoparticles or carbon nanotubes, increasing the range of applications. Acrylate polymers can be easily doped with various compounds, and therefore, they are interesting materials for laser fabrication techniques. In this work, we use multiphoton absorption polymerization (MAP) and laser ablation to fabricate polymeric microdevices for optical applications. The polymeric sample used in this work is composed in equal proportions of two three-acrylate monomers; while tris(2-hydroxyethyl)isocyanurate triacrylate gives hardness to the structure, the ethoxylated(6) trimethyl-lolpropane triacrylate reduces the shrinkage tensions upon polymerization. These monomers are mixed with a photoinitiator, the 2,4,6-trimetilbenzoiletoxifenil phosphine oxide, enabling the sample polymerization after laser irradiation. Using MAP, we fabricate three-dimensional structures doped with fluorescent dyes. These structures can be used in several optical applications, such as, RGB fluorescent microdevices or microresonators. Using azo compounds like dopant in the host resin, we can apply these structures in optical data storage devices. Using laser ablation technique, we can fabricate periodic microstructures inside polymeric bulks doped with xanthene dyes and single-walled carbon nanotubes, aiming applications in random laser experiments. In structured bulks we observed multi-narrow emission peaks over the xanthene fluorescence emission. Furthermore, in comparison with non-structured bulks, we observed that the periodic structure decreased the degree of randomness, reducing the number of peaks, but defining their position.

  16. Femtosecond laser processing in magneto-optical glasses

    Science.gov (United States)

    Liu, Qiang; Gross, Simon; Withford, M. J.; Steel, M. J.

    2014-03-01

    Femtosecond laser direct writing (FLDW) is developing rapidly but to date, there is no native optical isolator (needed to mitigate reflections in any optical system) for the platform. As a step towards integrated glass isolators, we have investigated FLDW in kHz and MHz pulse rate regimes for two magneto-optical glasses (TG20 and MR3-2) to ultimately create one-way structures based on the Faraday effect. Previously, we fabricated basic waveguides obtaining single-mode guidance at 632 nm (the Faraday effect is strongest near the Tb3+ resonance at 485 nm) in both regimes. kHz regime waveguides were isotropic but had high propagation loss due to associated photodarkening (which could be post-annealed). The propagation loss of the MHz regime waveguides was acceptable due to lower photodarkening, but the waveguides were too narrow to confine light properly because of the very strong focus of the writing beam. To try to combine the lower loss with larger waveguide width, we created overlapping structures using a series of superposed waveguides arranged in rings in MHz regime. The confinement in these multi-ring structures was indeed improved and the structure propagation loss was intermediate between that of one-path waveguides created in kHz and MHz regimes. For most other glasses, MHz FLDW systems operate in a heat-accumulation regime, producing waveguide diameters much larger than the writing laser spot size and superposed waveguides that merge into one by melting. Here, the sub-unit waveguides maintained their individual identity indicating that the heat-accumulation effect was absent.

  17. An Optical Streaking Method for Measuring Femtosecond Electron Bunches

    International Nuclear Information System (INIS)

    Ding, Yuantao

    2011-01-01

    The measurement of the ultra-short electron bunch length on the femtosecond time scale constitutes a very challenging problem. In the x-ray free electron laser facilities such as the Linac Coherent Light Source, generation of a sub-ten femtoseconds electron beam with 20pC charge is possible, but direct measurements are very difficult due to the resolution limit of the present diagnostics. We propose a new method here based on the measurement of the electron beam energy modulation induced from laser-electron interaction in a short wiggler. A typical optical streaking method requires a laser wavelength much longer than the electron bunch length. In this paper a laser with its wavelength shorter than the electron bunch length has been adopted, while the slope on the laser intensity envelope is used to distinguish the different periods. With this technique it is possible to reconstruct the bunch longitudinal profile from a single shot measurement. Generation of ultrashort x-ray pulses at femtoseconds (fs) scale is of great interest within synchrotron radiation and free electron laser (FEL) user community. One of the simple methods is to operate the FEL facility at low charge. At the Linac Coherent Light Source (LCLS), we have demonstrated the capability of generating ultrashort electron-beam (e-beam) with a duration of less than 10 fs fwhm using 20 pC charge. The x-ray pulses have been delivered to the x-ray users with a similar or even shorter pulse duration. However, The measurement of such short electron or x-ray pulse length at the fs time-scale constitutes a challenging problem. A standard method using an S-band radio-frequency (rf) transverse deflector has been established at LCLS, which works like a streak camera for electrons and is capable of resolving bunch lengths as short as 25 fs fwhm. With this device, the electrons are transversely deflected by the high-frequency time-variation of the deflecting fields. Increasing the deflecting voltage and rf frequency

  18. Histologic evaluation of in vivo femtosecond laser-generated capsulotomies reveals a potential cause for radial capsular tears.

    Science.gov (United States)

    Schultz, Tim; Joachim, Stephanie C; Tischoff, Iris; Dick, H Burkhard

    2015-01-01

    To compare histologically the size and appearance of capsule disks after femtosecond laser-assisted cataract surgery and conventional cataract surgery. In 100 eyes of 100 patients with visually significant cataracts, a femtosecond laser capsulotomy or a capsulorhexis with an aimed diameter of 5.0 mm was performed by one experienced surgeon. The diameter, area, circularity, and cut quality was histologically examined with light microscopy and scanning electron microscopy. The mean diameter of the manual and the femtosecond laser capsule disk group were not statistically significantly different (manual 4.91 ± 0.34; femtosecond: 4.93 ± 0.03; p = 0.58). The mean area of the capsule disks was 18.85 ± 2.69 mm2 in the manual and 19.03 ± 0.26 mm2 in the femtosecond group (p = 0.64). The capsules of the femtosecond group (0.95 ± 0.02) were significantly more circular than the ones of the manual group (0.81 ± 0.07; p<0.0001). The femtosecond laser capsule disks displayed a more saw blade-like structure created through the single laser spots. The histologic examination combined with prospective video analysis revealed respiratory movement of the eye during the capsulotomy as a potential risk factor for redial tears. Femtosecond laser can perform a capsulotomy with high reliability. In comparison to a highly experienced cataract surgeon, the achieved results in size are similar. In terms of circularity, the femtosecond laser was superior the manual procedure. Better refractive outcomes based on a 360°-degree optic overlap seem to be possible, especially for less experienced surgeons.

  19. Femtosecond-laser writing of photonic structures in zinc phosphate glasses

    Directory of Open Access Journals (Sweden)

    Krol Denise M.

    2013-11-01

    Full Text Available Good quality waveguides can be fabricated in zinc phosphate glasses with O/P ratios of 3.25 using the femtosecond-laser writing technique. Compositional effects, including the addition of Al2O3 and rare-earth doping, are discussed as well as results on the fabrication of active devices.

  20. Progressive evolution of silicon surface microstructures via femtosecond laser irradiation in ambient air

    International Nuclear Information System (INIS)

    Ma, Yuncan; Si, Jinhai; Sun, Xuehui; Chen, Tao; Hou, Xun

    2014-01-01

    Highlights: • Progressive evolution of the silicon surface microstructures has been demonstrated via the 800-nm femtosecond laser irradiation. • The formation and evolution mechanism of these microstructures was assigned to the modulated laser ablation. • The incorporation mechanism of foreign oxygen species into silicon material was attributed to femtosecond laser induced trapping effect of dangling bonds. - Abstract: Using 800-nm femtosecond laser irradiation, progressive evolution of the silicon surface microstructures has been demonstrated. Via the variation of laser irradiation parameters, four kinds of microstructures, such as: well-defined and clean nano-ripples, obscured nano-ripples with nano-protrusions and nano-holes, micro-spikes with nano-holes, and separated micro-spikes, have been produced. The morphology and chemical compositions of these microstructures have been characterized by a scanning electronic microscopy equipped with an energy dispersive x-ray spectroscopy. The formation and evolution mechanism of these microstructures have been systematically discussed. Meanwhile, the incorporation mechanism of foreign oxygen species into silicon materials has also been discussed on the basis of the femtosecond laser induced trapping effect of the dangling bonds

  1. Compression of XUV FEL pulses in the few-femtosecond regime

    International Nuclear Information System (INIS)

    Frassetto, Fabio; Giannessi, Luca; Poletto, Luca

    2008-01-01

    This work presents the design of a grating compressor for XUV FEL pulses able to compress chirped pulses from some hundreds to some tens of femtoseconds. The instrument adopts the conical diffraction mounts of gratings to reach high efficiency. We discuss the general design of the compressor and present an example of application to FEL emission at 13.5 nm

  2. Characterization and control of femtosecond electron and X-ray beams at free-electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Behrens, Christopher

    2012-11-15

    X-ray free-electron lasers (FELs) open up new frontiers in photon science, and in order to take full advantage of these unique accelerator-based light sources, the characterization and control of the femtosecond electron and X-ray beams is essential. Within this cumulative thesis, recent results achieved within the active research field of femtosecond electron and X-ray beams at FELs are reported.The basic principles of X-ray FELs are described, and concepts of longitudinal electron beam diagnostics with femtosecond accuracy are covered. Experimental results obtained with a transverse deflecting structure (TDS) and spectroscopy of coherent terahertz radiation are presented, and the suppression of coherent optical radiation effects, required for diagnostics utilizing a TDS, is demonstrated. Control of the longitudinal phase space by using multiple radio frequencies for longitudinal electron beam tailoring is presented, and a new technique of reversible electron beam heating with two TDSs is described. For the characterization of femtosecond X-ray pulses, a novel method based on dedicated longitudinal phase space diagnostics for electron beams is introduced, and recent measurements with a streaking technique using external terahertz fields are presented.

  3. Femtosecond laser surface structuring and oxidation of chromium thin coatings: Black chromium

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Mthunzi, P. [National Laser Centre, Council for Scientific and Industrial Research, 0001 Pretoria (South Africa); Muller, T.F.G. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Julies, B. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Manikandan, E. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Ramponi, R. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa)

    2014-12-01

    Highlights: • Oxidation of the chromium thin film to chromium oxide by femtosecond laser with a fundamental wavelength of 1064 nm. • Solar absorber from chromium oxide that low percentage reflectance. • Femtosecond laser oxidation, with a de-focused laser. • Chromium oxide formation by femtosecond laser in normal ambient. - Abstract: In view of their potential applications as selective solar absorbers, chromium coatings on float glass substrates were nano/micro structured by femtosecond laser in air. Raman and X-rays diffraction investigations confirmed the formation of an ultra-porous α-Cr{sub 2}O{sub 3} layer at the surface; higher is the input laser power, enhanced is the crystallinity of the α-Cr{sub 2}O{sub 3} layer. The α-Cr{sub 2}O{sub 3} layer with the Cr underneath it in addition to the photo-induced porosity acted as a classical ceramic–metal nano-composite making the reflectance to decrease significantly within the spectral range of 190–1100 nm. The average reflectance decreased from 70 to 2%.

  4. Elemental redistribution behavior in tellurite glass induced by high repetition rate femtosecond laser irradiation

    International Nuclear Information System (INIS)

    Teng, Yu; Zhou, Jiajia; Khisro, Said Nasir; Zhou, Shifeng; Qiu, Jianrong

    2014-01-01

    Highlights: • Abnormal elements redistribution behavior was observed in tellurite glass. • The refractive index and Raman intensity distribution changed significantly. • The relative glass composition remained unchanged while the glass density changed. • First time report on the abnormal element redistribution behavior in glass. • The glass network structure determines the elemental redistribution behavior. - Abstract: The success in the fabrication of micro-structures in glassy materials using femtosecond laser irradiation has proved its potential applications in the construction of three-dimensional micro-optical components or devices. In this paper, we report the elemental redistribution behavior in tellurite glass after the irradiation of high repetition rate femtosecond laser pulses. The relative glass composition remained unchanged while the glass density changed significantly, which is quite different from previously reported results about the high repetition rate femtosecond laser induced elemental redistribution in silicate glasses. The involved mechanism is discussed with the conclusion that the glass network structure plays the key role to determine the elemental redistribution. This observation not only helps to understand the interaction process of femtosecond laser with glassy materials, but also has potential applications in the fabrication of micro-optical devices

  5. Fresnel Lenses fabricated by femtosecond laser micromachining on Polymer 1D Photonic Crystal

    Directory of Open Access Journals (Sweden)

    Guduru Surya S.K.

    2013-11-01

    Full Text Available We report the fabrication of micro Fresnel lenses by femtosecond laser surface ablation on polymer 1D photonic crystals. This device is designed to focus the transmitted wavelength of the photonic crystal and filter the wavelengths corresponding to the photonic band gap region. Integration of such devices in a wavelength selective light harvesting and filtering microchip can be achieved.

  6. Femtosecond study of self-trapped vibrational excitons in crystalline acetanilide

    DEFF Research Database (Denmark)

    Edler, J.; Hamm, Peter; Scott, Alwyn C.

    2002-01-01

    Femtosecond IR spectroscopy of delocalized NH excitations of crystalline acetanilide confirms that self-trapping in hydrogen-bonded peptide units exists and does stabilize the excitation. Two phonons with frequencies of 48 and 76 cm(-1) are identified as the major degrees of freedom that mediate ...

  7. Characterization and control of femtosecond electron and X-ray beams at free-electron lasers

    International Nuclear Information System (INIS)

    Behrens, Christopher

    2012-11-01

    X-ray free-electron lasers (FELs) open up new frontiers in photon science, and in order to take full advantage of these unique accelerator-based light sources, the characterization and control of the femtosecond electron and X-ray beams is essential. Within this cumulative thesis, recent results achieved within the active research field of femtosecond electron and X-ray beams at FELs are reported.The basic principles of X-ray FELs are described, and concepts of longitudinal electron beam diagnostics with femtosecond accuracy are covered. Experimental results obtained with a transverse deflecting structure (TDS) and spectroscopy of coherent terahertz radiation are presented, and the suppression of coherent optical radiation effects, required for diagnostics utilizing a TDS, is demonstrated. Control of the longitudinal phase space by using multiple radio frequencies for longitudinal electron beam tailoring is presented, and a new technique of reversible electron beam heating with two TDSs is described. For the characterization of femtosecond X-ray pulses, a novel method based on dedicated longitudinal phase space diagnostics for electron beams is introduced, and recent measurements with a streaking technique using external terahertz fields are presented.

  8. Apparatus and method for nanoflow liquid jet and serial femtosecond x-ray protein crystallography

    Science.gov (United States)

    Bogan, Michael J.; Laksmono, Hartawan; Sierra, Raymond G.

    2016-03-01

    Techniques for nanoflow serial femtosecond x-ray protein crystallography include providing a sample fluid by mixing a plurality of a first target of interest with a carrier fluid and injecting the sample fluid into a vacuum chamber at a rate less than about 4 microliters per minute. In some embodiments, the carrier fluid has a viscosity greater than about 3 centipoise.

  9. Femtosecond Near Edge X-ray Absorption Measurement of the VO2 Phase Transition

    International Nuclear Information System (INIS)

    Cavalleri, A.; Chong, H.H.W.; Fourmaux, S.; Glover, T.E.; Heimann, P.A; Kieffer, J.C.; Padmore, H.A.; Schoenlein, R.W.

    2004-01-01

    The authors measure the insulator-to-metal transition in VO 2 using femtosecond Near-Edge X-ray Absorption. Sliced pulses of synchrotron radiation are used to detect the photo-induced dynamics at the 516-eV Vanadium L 3 edge

  10. [Hybrid (femtosecond laser-assisted) phaco surgery and the state of the macula].

    Science.gov (United States)

    Avetisov, K S; Bol'shunov, A V; Avetisov, S E; Yusef, Y N; Ivanov, M N; Sobol, E N; Sakalova, E D

    The review covers different aspects of the impact of femtosecond laser-assisted cataract surgery on the state of the macular zone of the retina. Literature search has revealed inconsistency of the published data and indicated the need for a more detailed study of this problem.

  11. Femtosecond X-ray Absorption Spectroscopy at a Hard X-ray Free Electron Laser

    DEFF Research Database (Denmark)

    Lemke, Henrik T.; Bressler, Christian; Chen, Lin X.

    2013-01-01

    -quality X-ray absorption data and we report femtosecond time-resolved X-ray absorption near-edge spectroscopy (XANES) measurements of a spin-crossover system, iron(II) tris(2,2'-bipyridine) in water. The data indicate that the low-spin to high-spin transition can be modeled by single-exponential kinetics...

  12. Femtosecond laser-induced cavitations in the lens of the human eye

    DEFF Research Database (Denmark)

    Kessel, Line; Nymand, Jose; Harbst, Michael

    2007-01-01

    Ultrafast femtosecond lasers are used increasingly for a wide range of medicai purposes. The immediate tissue response to pulses above a certain threshold is optically or laser induced breakdown, which is often visible as gas-filled cavities that persist for some time. In the present study, we at...

  13. Femtosecond laser surface structuring and oxidation of chromium thin coatings: black chromium.

    CSIR Research Space (South Africa)

    Kotsedi, L

    2014-12-01

    Full Text Available In view of their potential applications as selective solar absorbers, chromium coatings on float glass substrates were nano/micro structured by femtosecond laser in air. Raman and X-rays diffraction investigations confirmed the formation of an ultra...

  14. Single-Particle Time-of-Flight Mass Spectrometry Utilizing a Femtosecond Desorption and Ionization Laser.

    Science.gov (United States)

    Zawadowicz, Maria A; Abdelmonem, Ahmed; Mohr, Claudia; Saathoff, Harald; Froyd, Karl D; Murphy, Daniel M; Leisner, Thomas; Cziczo, Daniel J

    2015-12-15

    Single-particle time-of-flight mass spectrometry has now been used since the 1990s to determine particle-to-particle variability and internal mixing state. Instruments commonly use 193 nm excimer or 266 nm frequency-quadrupled Nd:YAG lasers to ablate and ionize particles in a single step. We describe the use of a femtosecond laser system (800 nm wavelength, 100 fs pulse duration) in combination with an existing single-particle time-of-flight mass spectrometer. The goal of this project was to determine the suitability of a femtosecond laser for single-particle studies via direct comparison to the excimer laser (193 nm wavelength, ∼10 ns pulse duration) usually used with the instrument. Laser power, frequency, and polarization were varied to determine the effect on mass spectra. Atmospherically relevant materials that are often used in laboratory studies, ammonium nitrate and sodium chloride, were used for the aerosol. Detection of trace amounts of a heavy metal, lead, in an ammonium nitrate matrix was also investigated. The femtosecond ionization had a large air background not present with the 193 nm excimer and produced more multiply charged ions. Overall, we find that femtosecond laser ablation and ionization of aerosol particles is not radically different than that provided by a 193 nm excimer.

  15. A higher-order-mode fiber delivery for Ti:Sapphire femtosecond lasers

    DEFF Research Database (Denmark)

    Jespersen, Kim Giessmann; Le, Tuan; Grüner-Nielsen, Lars Erik

    2010-01-01

    compressed in a quartz rod to nearly chirp-free 110fs pulses. Femtosecond pulse delivery is achieved by launching the laser output directly into the delivery fiber without any pre-chirping of the input pulse. The demonstrated pulse delivery scheme suggests scaling to >20meters for pulse delivery in harsh...

  16. Comparison of femtosecond and excimer laser platforms available for corneal refractive surgery.

    Science.gov (United States)

    Chen, Lisa Y; Manche, Edward E

    2016-07-01

    The evolution of laser technology has left today's refractive surgeon with a choice between multiple laser platforms. The purpose of this review is to compare currently available femtosecond and excimer laser platforms, providing a summary of current evidence. Femtosecond lasers create LASIK flaps with better accuracy, uniformity, and predictability than mechanical microkeratomes. Newer higher-frequency femtosecond platforms elicit less inflammation, producing better visual outcomes. SMILE achieved similar safety, efficacy, and predictability as LASIK with greater preservation of corneal nerves and biomechanical strength. The emergence of wavefront technology has resulted in improved excimer laser treatments. Comparisons of wavefront-guided and wavefront-optimized treatments suggest that there is an advantage to using wavefront-guided platforms in terms of visual acuity and quality of vision. Topography-guided ablations are another well tolerated and effective option, especially in eyes with highly irregular corneas. Advances in femtosecond and excimer laser technology have not only improved the safety and efficacy of refractive procedures, but have also led to the development of promising new treatment modalities, such as SMILE and the use of wavefront-guided and topography-guided ablation. Future studies and continued technological progress will help to better define the optimal use of these treatment platforms.

  17. Testing the energy conservation law in an optical parametric oscillator using phase-controlled femtosecond pulses.

    Science.gov (United States)

    Sun, Jinghua; Gale, Barry J S; Reid, Derryck T

    2007-04-02

    An experimental verification of energy conservation in a parametric oscillator is reported with an optical frequency precision of approximately 200 kHz (< 10(-6) nm). This high precision is made possible by simultaneously measuring the frequency offsets of the pump, signal and idler frequency combs in a singly-resonant femtosecond optical parametric oscillator system.

  18. Observation of enhanced soft x-ray emission using nitrogen clusters ionized by intense, femtosecond laser

    Czech Academy of Sciences Publication Activity Database

    Mocek, Tomáš; Park, J. J.; Kim, Ch. M.; Kim, H. T.; Lee, D. G.; Hong, K. H.; Nam, Ch. H.

    2003-01-01

    Roč. 93, č. 5 (2003), s. 3105-3107 ISSN 0021-8979 R&D Projects: GA MŠk LN00A100 Institutional research plan: CEZ:AV0Z1010921 Keywords : clusters * femtosecond laser s * x-ray spectroscopy Subject RIV: BH - Optics, Masers, Laser s Impact factor: 2.171, year: 2003

  19. Communication: The electronic structure of matter probed with a single femtosecond hard x-ray pulse

    Directory of Open Access Journals (Sweden)

    J. Szlachetko

    2014-03-01

    Full Text Available Physical, biological, and chemical transformations are initiated by changes in the electronic configuration of the species involved. These electronic changes occur on the timescales of attoseconds (10−18 s to femtoseconds (10−15 s and drive all subsequent electronic reorganization as the system moves to a new equilibrium or quasi-equilibrium state. The ability to detect the dynamics of these electronic changes is crucial for understanding the potential energy surfaces upon which chemical and biological reactions take place. Here, we report on the determination of the electronic structure of matter using a single self-seeded femtosecond x-ray pulse from the Linac Coherent Light Source hard x-ray free electron laser. By measuring the high energy resolution off-resonant spectrum (HEROS, we were able to obtain information about the electronic density of states with a single femtosecond x-ray pulse. We show that the unoccupied electronic states of the scattering atom may be determined on a shot-to-shot basis and that the measured spectral shape is independent of the large intensity fluctuations of the incoming x-ray beam. Moreover, we demonstrate the chemical sensitivity and single-shot capability and limitations of HEROS, which enables the technique to track the electronic structural dynamics in matter on femtosecond time scales, making it an ideal probe technique for time-resolved X-ray experiments.

  20. Long lifetime air plasma channel generated by femtosecond laser pulse sequence.

    Science.gov (United States)

    Liu, Xiao-Long; Lu, Xin; Ma, Jing-Long; Feng, Liu-Bin; Ge, Xu-Lei; Zheng, Yi; Li, Yu-Tong; Chen, Li-Ming; Dong, Quan-Li; Wang, Wei-Min; Wang, Zhao-Hua; Teng, Hao; Wei, Zhi-Yi; Zhang, Jie

    2012-03-12

    Lifetime of laser plasma channel is significantly prolonged using femtosecond laser pulse sequence, which is generated from a chirped pulse amplification laser system with pure multi-pass amplification chain. Time-resolved fluorescence images and electrical conductivity measurement are used to characterize the lifetime of the plasma channel. Prolongation of plasma channel lifetime up to microsecond level is observed using the pulse sequence.

  1. Inactivation of viruses by coherent excitations with a low power visible femtosecond laser

    Directory of Open Access Journals (Sweden)

    Wu T-C

    2007-06-01

    Full Text Available Abstract Background Resonant microwave absorption has been proposed in the literature to excite the vibrational states of microorganisms in an attempt to destroy them. But it is extremely difficult to transfer microwave excitation energy to the vibrational energy of microorganisms due to severe absorption of water in this spectral range. We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering. Results and discussion By using a very low power (as low as 0.5 nj/pulse visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width as well as power density of the excitation laser. Conclusion Our experimental findings lay down the foundation for an innovative new strategy of using a very low power visible femtosecond laser to selectively inactivate viruses and other microorganisms while leaving sensitive materials unharmed by manipulating and controlling with the femtosecond laser system.

  2. Compact 180-kV Marx generator triggered in atmospheric air by femtosecond laser filaments

    Science.gov (United States)

    Arantchouk, L.; Point, G.; Brelet, Y.; Larour, J.; Carbonnel, J.; André, Y.-B.; Mysyrowicz, A.; Houard, A.

    2014-03-01

    We developed a compact Marx generator triggered in atmospheric air by a single femtosecond laser beam undergoing filamentation. Voltage pulses of 180 kV could be generated with a subnanosecond jitter. The same laser beam was also used to initiate simultaneously guided discharges up to 21 cm long at the output of the generator.

  3. Structural Evolution in Photoactive Yellow Protein Studied by Femtosecond Stimulated Raman Spectroscopy

    Directory of Open Access Journals (Sweden)

    Yoshizawa M.

    2013-03-01

    Full Text Available Ultrafast structural evolution in photoactive yellow protein (PYP is studied by femtosecond stimulated Raman spectroscopy. A comparison between wild-type PYP and E46Q mutant reveals that the hydrogen-bonding network surrounding the chromophore of PYP is immediately rearranged in the electronic excited state.

  4. Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules

    DEFF Research Database (Denmark)

    Boll, Rebecca; Rouzee, Arnaud; Adolph, Marcus

    2014-01-01

    This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray Free-Electron Laser. We present results of two experiments aimed at measuring photoelectron angular...

  5. Monitoring of DNA molecules in a lab on a chip with femtosecond laser written waveguides

    NARCIS (Netherlands)

    Pollnau, Markus; Dongre, C.; Dekker, R; Dekker, R.; Hoekstra, Hugo; Martinez-Vazquez, R.; Osellame, R.; Ramponi, R.; Cerullo, G.; van Weeghel, R.; Besselink, G.A.J.; van den Vlekkert, H.H.

    Using femtosecond laser writing, optical waveguides were monolithically integrated into a commercial microfluidic lab-on-a-chip device, with the waveguides intersecting a microfluidic channel. Continuous-wave laser excitation through these optical waveguides confines the excitation window to a width

  6. Ultrafast Holographic Image Recording by Single Shot Femtosecond Spectral Hole Burning

    National Research Council Canada - National Science Library

    Rebane, Aleksander

    2001-01-01

    .... This allowed us to record image holograms with 150-fs duration pulses without need to accumulate the SHB effect from many exposures. Results of this research show that it is possible to perform optical recording of data in frequency-domain on ultrafast time scale. These results can be used also as a new diagnostic tool for femtosecond dynamics in various ultrafast optical interactions.

  7. Quantum Femtosecond Magnetism: Phase Transition in Step with Light in a Strongly Correlated Manganese Oxide

    Science.gov (United States)

    Wang, Jigang

    2014-03-01

    Research of non-equilibrium phase transitions of strongly correlated electrons is built around addressing an outstanding challenge: how to achieve ultrafast manipulation of competing magnetic/electronic phases and reveal thermodynamically hidden orders at highly non-thermal, femtosecond timescales? Recently we reveal a new paradigm called quantum femtosecond magnetism-photoinduced femtosecond magnetic phase transitions driven by quantum spin flip fluctuations correlated with laser-excited inter-atomic coherent bonding. We demonstrate an antiferromagnetic (AFM) to ferromagnetic (FM) switching during about 100 fs laser pulses in a colossal magneto-resistive manganese oxide. Our results show a huge photoinduced femtosecond spin generation, measured by magnetic circular dichroism, with photo-excitation threshold behavior absent in the picosecond dynamics. This reveals an initial quantum coherent regime of magnetism, while the optical polarization/coherence still interacts with the spins to initiate local FM correlations that compete with the surrounding AFM matrix. Our results thus provide a framework that explores quantum non-equilibrium kinetics to drive phase transitions between exotic ground states in strongly correlated elecrons, and raise fundamental questions regarding some accepted rules, such as free energy and adiabatic potential surface. This work is in collaboration with Tianqi Li, Aaron Patz, Leonidas Mouchliadis, Jiaqiang Yan, Thomas A. Lograsso, Ilias E. Perakis. This work was supported by the National Science Foundation (contract no. DMR-1055352). Material synthesis at the Ames Laboratory was supported by the US Department of Energy-Basic Energy Sciences (contract no. DE-AC02-7CH11358).

  8. Generation of electromagnetic pulses from plasma channels induced by femtosecond light strings

    OpenAIRE

    Cheng, Chung-Chieh; Wright, E. M.; Moloney, J. V.

    2000-01-01

    We present a model that elucidates the physics underlying the generation of an electromagnetic pulse from a femtosecond laser induced plasma channel. The radiation pressure force from the laser pulse spatially separates the ionized electrons from the heavier ions and the induced dipole moment subsequently oscillates at the plasma frequency and radiates an electromagnetic pulse.

  9. Femtosecond Bessel light pulse formation by a multi-circular diaphragm

    International Nuclear Information System (INIS)

    Ushakova, E.E.; Kurilkina, S.N.

    2010-01-01

    The dynamics of the envelope of a new type of light field, a femtosecond Bessel light pulse (FBLP) formed from a Gaussian pulsed beam by means of a multi-circular diaphragm, has been investigated theoretically. It is shown that the FBLP possesses a steady structure that features a narrow central maximum and significantly suppressed subordinate maxima. (authors)

  10. Influence of Nonlinear Environmental Properties on the Process of Pulse-Stimulated Compulsory Combined Scattering under Femtosecond Pumping Conditions

    Directory of Open Access Journals (Sweden)

    V.L. Dobryakov

    2017-12-01

    Full Text Available Impulsive stimulated Raman scattering (ISRS observed by pump-probe experiments was considered. The response from the model system for ISRS-process is calculated for femtosecond laser pump pulse. The response of the model system for the processes of the is-SRS type under the conditions of femtosecond pumping is calculated: the time behavior of the ISC signal is theoretically calculated, and also the frequency dependence of the amplitude of the oscillations excited by the laser pulse with a femtosecond duration. Qualitative agreement is demonstrated for the case of the experiment with the perylene molecule.

  11. Spatial and temporal dependence of interspark interactions in femtosecond-nanosecond dual-pulse laser-induced breakdown spectroscopy.

    Science.gov (United States)

    Scaffidi, Jon; Pearman, William; Lawrence, Marion; Carter, J Chance; Colston, Bill W; Angel, S Michael

    2004-09-20

    A femtosecond air spark has recently been combined with a nanosecond ablative pulse in order to map the spatial and temporal interactions of the two plasmas in femtosecond-nanosecond orthogonal preablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS). Good spatial and temporal correlation was found for reduced atomic emission from atmospheric species (nitrogen and oxygen) and increased atomic emission from ablated species (copper and aluminum) in the femtosecond-nanosecond plasma, suggesting a potential role for atmospheric pressure or nitrogen/oxygen concentration reduction following air spark formation in generating atomic emission enhancements in dual-pulse LIBS.

  12. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    Energy Technology Data Exchange (ETDEWEB)

    See, Tian Long, E-mail: tianlong.see@postgrad.manchester.ac.uk [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Liu, Zhu [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Li, Lin [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Zhong, Xiang Li [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom)

    2016-02-28

    Highlights: • Ablation threshold for excimer laser is lower compared to femtosecond laser. • Effective optical penetration depth for excimer laser is lower compared to femtosecond laser. • Two ablation characteristic regimes are observed for femtosecond laser ablation. • Reduction of C=C bond following excimer or fs laser ablation is observed. • Addition of oxygen- and nitrogen-rich functional groups is observed. - Abstract: This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser–material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (F{sub th} = 0.087 J/cm{sup 2}) than that for the femtosecond laser ablation of ABS (F{sub th} = 1.576 J/cm{sup 2}), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α{sup −1} = 223 nm) than that for femtosecond laser ablation (α{sup −1} = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the C=C bond completely through the chain scission process whereas

  13. Fabrication and Characterization of Linear and Nonlinear Photonic Devices in Fused Silica by Femtosecond Laser Writing

    Science.gov (United States)

    Ng, Jason Clement

    Femtosecond laser processing is a flexible, three-dimensional (3D) fabrication technique used to make integrated low-loss photonic devices in fused silica. My work expanded the suite of available optical devices through the design and optimization of linear optical components such as low-loss (70-nm spectral window. My work further complemented femtosecond laser processing with the development of nonlinear device capabilities. While thermal poling is a well known process, significant challenges had restricted the development of nonlinear devices in fused silica. The laser writing process would erase the induced nonlinearity (erasing) while a written waveguide core acted as a barrier to the thermal poling process (blocking). Using second harmonic (SH) microscopy, the effectiveness of thermal poling on laser-written waveguides was systematically analyzed leading to the technique of "double poling", which effectively overcomes the two challenges of erasing and blocking. In this new process the substrate is poled before and after waveguide writing to restore the induced nonlinearity within the vicinity of the waveguide to enable effective poling for inducing a second-order nonlinearity (SON) in fused silica. A new flexible, femtosecond laser based erasure process was also developed to enable quasi-phase matching and to form arbitrarily chirped gratings. Following this result, second harmonic generation (SHG) in a quasiphase-matched (QPM) femtosecond laser written waveguide device was demonstrated. SHG in a chirped QPM structure was also demonstrated to illustrate the flexibility of the femtosecond laser writing technique. These are the first demonstration of frequency doubling in an all-femtosecond-laser-written structure. A maximum SHG conversion efficiency of 1.3 +/- 0.1x10 -11/W-cm-2 was achieved for the fundamental wavelength of 1552.8 nm with a phase-matching bandwidth of 4.4 nm for a 10.0-mm-long waveguide. For a shorter sample, an effective SON of chi(2) = 0

  14. Femtosecond few- to single-electron point-projection microscopy for nanoscale dynamic imaging

    Science.gov (United States)

    Bainbridge, A. R.; Barlow Myers, C. W.; Bryan, W. A.

    2016-01-01

    Femtosecond electron microscopy produces real-space images of matter in a series of ultrafast snapshots. Pulses of electrons self-disperse under space-charge broadening, so without compression, the ideal operation mode is a single electron per pulse. Here, we demonstrate femtosecond single-electron point projection microscopy (fs-ePPM) in a laser-pump fs-e-probe configuration. The electrons have an energy of only 150 eV and take tens of picoseconds to propagate to the object under study. Nonetheless, we achieve a temporal resolution with a standard deviation of 114 fs (equivalent to a full-width at half-maximum of 269 ± 40 fs) combined with a spatial resolution of 100 nm, applied to a localized region of charge at the apex of a nanoscale metal tip induced by 30 fs 800 nm laser pulses at 50 kHz. These observations demonstrate real-space imaging of reversible processes, such as tracking charge distributions, is feasible whilst maintaining femtosecond resolution. Our findings could find application as a characterization method, which, depending on geometry, could resolve tens of femtoseconds and tens of nanometres. Dynamically imaging electric and magnetic fields and charge distributions on sub-micron length scales opens new avenues of ultrafast dynamics. Furthermore, through the use of active compression, such pulses are an ideal seed for few-femtosecond to attosecond imaging applications which will access sub-optical cycle processes in nanoplasmonics. PMID:27158637

  15. Femtosecond few- to single-electron point-projection microscopy for nanoscale dynamic imaging

    Directory of Open Access Journals (Sweden)

    A. R. Bainbridge

    2016-03-01

    Full Text Available Femtosecond electron microscopy produces real-space images of matter in a series of ultrafast snapshots. Pulses of electrons self-disperse under space-charge broadening, so without compression, the ideal operation mode is a single electron per pulse. Here, we demonstrate femtosecond single-electron point projection microscopy (fs-ePPM in a laser-pump fs-e-probe configuration. The electrons have an energy of only 150 eV and take tens of picoseconds to propagate to the object under study. Nonetheless, we achieve a temporal resolution with a standard deviation of 114 fs (equivalent to a full-width at half-maximum of 269 ± 40 fs combined with a spatial resolution of 100 nm, applied to a localized region of charge at the apex of a nanoscale metal tip induced by 30 fs 800 nm laser pulses at 50 kHz. These observations demonstrate real-space imaging of reversible processes, such as tracking charge distributions, is feasible whilst maintaining femtosecond resolution. Our findings could find application as a characterization method, which, depending on geometry, could resolve tens of femtoseconds and tens of nanometres. Dynamically imaging electric and magnetic fields and charge distributions on sub-micron length scales opens new avenues of ultrafast dynamics. Furthermore, through the use of active compression, such pulses are an ideal seed for few-femtosecond to attosecond imaging applications which will access sub-optical cycle processes in nanoplasmonics.

  16. Corneal tissue interactions of a new 345 nm ultraviolet femtosecond laser.

    Science.gov (United States)

    Hammer, Christian M; Petsch, Corinna; Klenke, Jörg; Skerl, Katrin; Paulsen, Friedrich; Kruse, Friedrich E; Seiler, Theo; Menzel-Severing, Johannes

    2015-06-01

    To assess the suitability of a new 345 nm ultraviolet (UV) femtosecond laser for refractive surgery. Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany. Experimental study. Twenty-five porcine corneas were used for stromal flap or lamellar bed creation (stromal depth, 150 μm) and 15 rabbit corneas for lamellar bed creation near the endothelium. Ultraviolet femtosecond laser cutting-line morphology, gas formation, and keratocyte death rate were evaluated using light and electron microscopy and compared with a standard infrared (IR) femtosecond laser. Endothelial cell survival was examined after application of a laser cut near the endothelium. Flaps created by the UV laser were lifted easily. Gas formation was reduced 4.2-fold compared with the IR laser (P = .001). The keratocyte death rate near the interface was almost doubled; however, the death zone was confined to a region within 38 μm ± 10 (SD) along the cutting line. Histologically and ultrastructurally, a distinct and continuous cutting line was not found after UV femtosecond laser application if flap lifting was omitted and standard energy parameters were used. Instead, a regular pattern of vertical striations, presumably representing self-focusing induced regions of optical tissue breakdown, were identified. Lamellar bed creation with standard energy parameters 50 μm from the endothelium rendered the endothelial cells intact and viable. The new 345 nm femtosecond laser is a candidate for pending in vivo trials and future high-precision flap creation, intrastromal lenticule extraction, and ultrathin Descemet-stripping endothelial keratoplasty. Mr. Klenke and Ms. Skerl were paid employees of Wavelight GmbH when the study was performed. Dr. Seiler is a scientific consultant to Wavelight GmbH. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  17. Measurement of the carrier envelope offset frequency of a femtosecond frequency comb using a Fabry-Perot interferometer

    International Nuclear Information System (INIS)

    Basnak, D V; Bikmukhametov, K A; Dmitrieva, N I; Dmitriev, Aleksandr K; Lugovoi, A A; Pokasov, P V; Chepurov, S V

    2010-01-01

    A method for measuring the carrier envelope offset (CEO) frequency of the femtosecond frequency comb with a bandwidth of less than one octave by using a Fabry-Perot interferometer is proposed and experimentally demonstrated. (laser components)

  18. Visualizing the non-equilibrium dynamics of photoinduced intramolecular electron transfer with femtosecond X-ray pulses

    DEFF Research Database (Denmark)

    Canton, Sophie E.; Kjær, Kasper S.; Vankó, György

    2015-01-01

    Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectrosc...

  19. Fusion of blastomeres in mouse embryos under the action of femtosecond laser radiation. Efficiency of blastocyst formation and embryo development

    Energy Technology Data Exchange (ETDEWEB)

    Osychenko, A A; Zalesskii, A D; Krivokharchenko, A S; Zhakhbazyan, A K; Nadtochenko, V A [N N Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow (Russian Federation); Ryabova, A V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2015-05-31

    Using the method of femtosecond laser surgery we study the fusion of two-cell mouse embryos under the action of tightly focused femtosecond laser radiation with the fusion efficiency reaching 60%. The detailed statistical analysis of the efficiency of blastomere fusion and development of the embryo up to the blastocyst stage after exposure of the embryos from different mice to a femtosecond pulse is presented. It is shown that the efficiency of blastocyst formation essentially depends on the biological characteristics of the embryo, namely, the strain and age of the donor mouse. The possibility of obtaining hexaploid embryonal cells using the methods of femtosecond laser surgery is demonstrated. (extreme light fields and their applications)

  20. Generating shaped femtosecond pulses in the far infrared using a spatial light modulator and difference frequency generation

    CSIR Research Space (South Africa)

    Botha, N

    2010-08-31

    Full Text Available Femtosecond pulse shaping can be done by different kinds of pulse shapers, such as liquid crystal spatial light modulators (LC SLM), acousto optic modulators (AOM) and deformable and movable mirrors. A few applications where pulse shaping...

  1. Femtosecond refractive-index tailoring of an optical fiber and phase retrieval from far-field measurements

    DEFF Research Database (Denmark)

    Savolainen, Juha-Matti; Grüner-Nielsen, Lars; Kristensen, Poul

    2013-01-01

    A refractive-index change is written inside an optical fiber close to the end face by femtosecond laser light. The induced phase change is measured by analyzing the far-field intensity profiles before and after the irradiation.......A refractive-index change is written inside an optical fiber close to the end face by femtosecond laser light. The induced phase change is measured by analyzing the far-field intensity profiles before and after the irradiation....

  2. Multi-image mosaic with SIFT and vision measurement for microscale structures processed by femtosecond laser

    Science.gov (United States)

    Wang, Fu-Bin; Tu, Paul; Wu, Chen; Chen, Lei; Feng, Ding

    2018-01-01

    In femtosecond laser processing, the field of view of each image frame of the microscale structure is extremely small. In order to obtain the morphology of the whole microstructure, a multi-image mosaic with partially overlapped regions is required. In the present work, the SIFT algorithm for mosaic images was analyzed theoretically, and by using multiple images of a microgroove structure processed by femtosecond laser, a stitched image of the whole groove structure could be studied experimentally and realized. The object of our research concerned a silicon wafer with a microgroove structure ablated by femtosecond laser. First, we obtained microgrooves at a width of 380 μm at different depths. Second, based on the gray image of the microgroove, a multi-image mosaic with slot width and slot depth was realized. In order to improve the image contrast between the target and the background, and taking the slot depth image as an example, a multi-image mosaic was then realized using pseudo color enhancement. Third, in order to measure the structural size of the microgroove with the image, a known width streak ablated by femtosecond laser at 20 mW was used as a calibration sample. Through edge detection, corner extraction, and image correction for the streak images, we calculated the pixel width of the streak image and found the measurement ratio constant Kw in the width direction, and then obtained the proportional relationship between a pixel and a micrometer. Finally, circular spot marks ablated by femtosecond laser at 2 mW and 15 mW were used as test images, and proving that the value Kw was correct, the measurement ratio constant Kh in the height direction was obtained, and the image measurements for a microgroove of 380 × 117 μm was realized based on a measurement ratio constant Kw and Kh. The research and experimental results show that the image mosaic, image calibration, and geometric image parameter measurements for the microstructural image ablated by

  3. Femtosecond-laser ablation dynamics of dielectrics: basics and applications for thin films

    DEFF Research Database (Denmark)

    Balling, P.; Schou, Jørgen

    2013-01-01

    ejected from the dielectric following the femtosecond-laser excitation can potentially be used for thin-film deposition. The deposition rate is typically much smaller than that for nanosecond lasers, but film production by femtosecond lasers does possess several attractive features. First, the strong......-field excitation makes it possible to produce films of materials that are transparent to the laser light. Second, the highly localized excitation reduces the emission of larger material particulates. Third, lasers with ultrashort pulses are shown to be particularly useful tools for the production of nanocluster...... films. The important question of the film stoichiometry relative to that of the target will be thoroughly discussed in relation to the films reported in the literature....

  4. Anomalous broadening and shift of emission lines in a femtosecond laser plasma filament in air

    Science.gov (United States)

    Ilyin, A. A.; Golik, S. S.; Shmirko, K. A.; Mayor, A. Yu.; Proschenko, D. Yu.

    2017-12-01

    The temporal evolution of the width and shift of N I 746.8 and O I 777.4 nm lines is investigated in a filament plasma produced by a tightly focused femtosecond laser pulse (0.9 mJ, 48 fs). The nitrogen line shift and width are determined by the joint action of electron impact shift and the far-off resonance AC Stark effect. The intensive (I = 1.2·1010 W/cm2) electric field of ASE (amplified spontaneous emission) and post-pulses result in a possible LS coupling break for the O I 3p 5P level and the generation of Rabi sidebands. The blueshifted main femtosecond pulse and Rabi sideband cause the stimulated emission of the N2 1+ system. The maximal widths of emission lines are approximately 6.7 times larger than the calculated Stark widths.

  5. Control of femtosecond multi-filamentation in glass by designable patterned optical fields

    Directory of Open Access Journals (Sweden)

    Ping-Ping Li

    2016-12-01

    Full Text Available We present a scheme for realizing femtosecond multi-filamentation with designable quantity and locations of filaments, based on the control of multi-focal spots formed by patterned optical fields (POFs composed of multiple individual optical fields (IOFs. A computer-controlled spatial light modulator is used to engineer the POFs. In particular, we introduce a blazed phase grating in any IOF, which increases a degree of freedom, making the engineering of multi-focal spots becomes more flexible. We achieve experimentally the aim controlling femtosecond multi-filamentation in a K9 glass. Our scheme has great flexibility and convenience in controlling the multi-filamentation in quantity and locations of filaments and strength of interaction between filaments.

  6. Adaptive control of lasers and their interactions with matter using femtosecond pulse shaping

    Science.gov (United States)

    Efimov, Anatoly

    Coherent control of chemical reactions, atomic and molecular systems, lattice dynamics, and electronic motion rely on femtosecond laser sources capable of producing programmable arbitrarily shaped waveforms. To enter the time scale of natural dynamic processes in many systems, femtosecond pulse shaping techniques must be extended to the ultrashort pulse domain (ISRS). We chose this material as a candidate for possible nonlinear oscillations regime for its wide band gap and superior optical properties allowing for high-energy excitation. To enter a nonlinear regime, however, complex asymmetric multiple-pulse excitation is required. Therefore, we make a detailed proposal of the experimental adaptive feedback implementation for optimization of phonon amplitude based on the coherent probe scattering and a novel phase mask calculation algorithm for the real-time asymmetric pulse train generation.

  7. Effects of emittance and space-charge in femtosecond bunch compression

    International Nuclear Information System (INIS)

    Kan, K.; Yang, J.; Kondoh, T.; Norizawa, K.; Yoshida, Y.

    2008-01-01

    Ultrashort electron bunches of the order of <100fs are essential for the study of ultrafast reactions and phenomena by means of time-resolved pump-probe experiments. In order to generate such an electron bunch, the effects of emittance, space-charge (SC) and coherent synchrotron radiation (CSR) on the bunch length in a femtosecond magnetic bunch compressor were studied theoretically. It was observed that the bunch length is dominated by the emittance, SC and CSR effects when the electron bunch is compressed into a femtosecond electron bunch. The increases in bunch length due to the transverse emittance, SC and CSR effects in the bunch compressor were 1.7 fs/mm mrad, 107 fs/nC and 72 fs/nC, respectively. Finally, the simulated bunch length was compared with the experimental results.

  8. Acceleration of a ground-state reaction by selective femtosecond-infrared-laser-pulse excitation

    Science.gov (United States)

    Stensitzki, Till; Yang, Yang; Kozich, Valeri; Ahmed, Ashour A.; Kössl, Florian; Kühn, Oliver; Heyne, Karsten

    2018-02-01

    Infrared (IR) excitation of vibrations that participate in the reaction coordinate of an otherwise thermally driven chemical reaction are believed to lead to its acceleration. Attempts at the practical realization of this concept have been hampered so far by competing processes leading to sample heating. Here we demonstrate, using femtosecond IR-pump IR-probe experiments, the acceleration of urethane and polyurethane formation due to vibrational excitation of the reactants for 1:1 mixtures of phenylisocyanate and cyclohexanol, and toluene-2,4-diisocyanate and 2,2,2-trichloroethane-1,1-diol, respectively. We measured reaction rate changes upon selective vibrational excitation with negligible heating of the sample and observed an increase of the reaction rate up to 24%. The observation is rationalized using reactant and transition-state structures obtained from quantum chemical calculations. We subsequently used IR-driven reaction acceleration to write a polyurethane square on sample windows using a femtosecond IR pulse.

  9. Local stimulation of cultured myocyte cells by femtosecond laser-induced stress wave

    Science.gov (United States)

    Kuo, Yung-En; Wu, Cheng-Chi; Hosokawa, Yoichiroh; Maezawa, Yasuyo; Okano, Kazunori; Masuhara, Hiroshi; Kao, Fu-Jen

    2010-12-01

    When an 800 nm femtosecond laser is tightly focused into cell culture medium a stress wave is generated at the laser focal point. Since the stress wave localizes in a few tens of μm, it is possible to locally stimulate single cells in vitro. In this work, several kinds of cultured mammalian cells, HeLa, PC12, P19CL6, and C2C12, were stimulated by the stress wave and the cell growth after the stress loading with the laser irradiation was investigated. In comparison with the control conditions, cell growth after the laser irradiation was enhanced for the cells of C2C12 and P19CL6, which can differentiate into myocytes, and suppressed for PC12 and HeLa cell lines. These results suggest a possibility of cell growth enhancement due to myogenic cells response to the femtosecond laser-induced stress.

  10. X-ray emission from stainless steel foils irradiated by femtosecond petawatt laser pulses

    Science.gov (United States)

    Alkhimova, M. A.; Faenov, A. Ya; Pikuz, T. A.; Skobelev, I. Yu; Pikuz, S. A.; Nishiuchi, M.; Sakaki, H.; Pirozhkov, A. S.; Sagisaka, S.; Dover, N. P.; Kondo, Ko; Ogura, K.; Fukuda, Y.; Kiriyama, H.; Esirkepov, T.; Bulanov, S. V.; Andreev, A.; Kando, M.; Zhidkov, A.; Nishitani, K.; Miyahara, T.; Watanabe, Y.; Kodama, R.; Kondo, K.

    2018-01-01

    We report about nonlinear growth of x-ray emission intensity emitted from plasma generated by femtosecond petawatt laser pulses irradiating stainless steel foils. X-ray emission intensity increases as ∼ I 4.5 with laser intensity I on a target. High spectrally resolved x-ray emission from front and rear surfaces of 5 μm thickness stainless steel targets were obtained at the wavelength range 1.7–2.1 Å, for the first time in experiments at femtosecond petawatt laser facility J-KAREN-P. Total intensity of front x-ray spectra three times dominates to rear side spectra for maximum laser intensity I ≈ 3.2×1021 W/cm2. Growth of x-ray emission is mostly determined by contribution of bremsstrahlung radiation that allowed estimating bulk electron plasma temperature for various magnitude of laser intensity on target.

  11. High repetition rate tunable femtosecond pulses and broadband amplification from fiber laser pumped parametric amplifier.

    Science.gov (United States)

    Andersen, T V; Schmidt, O; Bruchmann, C; Limpert, J; Aguergaray, C; Cormier, E; Tünnermann, A

    2006-05-29

    We report on the generation of high energy femtosecond pulses at 1 MHz repetition rate from a fiber laser pumped optical parametric amplifier (OPA). Nonlinear bandwidth enhancement in fibers provides the intrinsically synchronized signal for the parametric amplifier. We demonstrate large tunability extending from 700 nm to 1500 nm of femtosecond pulses with pulse energies as high as 1.2 muJ when the OPA is seeded by a supercontinuum generated in a photonic crystal fiber. Broadband amplification over more than 85 nm is achieved at a fixed wavelength. Subsequent compression in a prism sequence resulted in 46 fs pulses. With an average power of 0.5 W these pulses have a peak-power above 10 MW. In particular, the average power and pulse energy scalability of both involved concepts, the fiber laser and the parametric amplifier, will enable easy up-scaling to higher powers.

  12. Synchronized femtosecond laser pulse switching system based nano-patterning technology

    Science.gov (United States)

    Sohn, Ik-Bu; Choi, Hun-Kook; Yoo, Dongyoon; Noh, Young-Chul; Sung, Jae-Hee; Lee, Seong-Ku; Ahsan, Md. Shamim; Lee, Ho

    2017-07-01

    This paper demonstrates the design and development of a synchronized femtosecond laser pulse switching system and its applications in nano-patterning of transparent materials. Due to synchronization, we are able to control the location of each irradiated laser pulse in any kind of substrate. The control over the scanning speed and scanning step of the laser beam enables us to pattern periodic micro/nano-metric holes, voids, and/or lines in various materials. Using the synchronized laser system, we pattern synchronized nano-holes on the surface of and inside various transparent materials including fused silica glass and polymethyl methacrylate to replicate any image or pattern on the surface of or inside (transparent) materials. We also investigate the application areas of the proposed synchronized femtosecond laser pulse switching system in a diverse field of science and technology, especially in optical memory, color marking, and synchronized micro/nano-scale patterning of materials.

  13. Cylindrical shockwave-induced compression mechanism in femtosecond laser Bessel pulse micro-drilling of PMMA

    Science.gov (United States)

    Wang, Guoyan; Yu, Yanwu; Jiang, Lan; Li, Xiaowei; Xie, Qian; Lu, Yongfeng

    2017-04-01

    Femtosecond (fs) laser Bessel pulses can be employed for high-quality and high-speed fabrication of high-aspect-ratio uniform microhole arrays. This technique exhibits prominent potential in three-dimensional packaging, fluidic devices, fiber sensing, biomedical devices, and aeronautics. However, the fundamental mechanisms remain mysterious. Using the femtosecond time-resolved pump-probe shadowgraph technique, this study revealed that the generation of cylindrical shockwaves inside the bulk material and the corresponding compression mechanism play key roles in the formation of high-aspect-ratio microholes. The phenomena were observed in all experiments of Bessel beam drilling of polymethyl methacrylate. In the aforementioned cases, the compression mechanism was confirmed by measuring sample mass losses that were experimentally determined to be negligible. By contrast, neither cylindrical shockwave nor compression mechanism was observed when a fused silica or Gaussian laser beam was involved.

  14. Research on ultrasonic vibration aided femtosecond laser machining process of transparent materials

    Science.gov (United States)

    Dai, Yutang; Liu, Bin; Yin, Guanglin; Li, Tao; Karanja, Joseph M.

    2015-08-01

    A new process of femtosecond laser micromachining with ultrasonic vibration aided is proposed. An ultrasonic aided device has been designed, and the laser micromachining experiments of transparent materials have been carried out. The effects of the ultrasonic vibration with different power on surface quality and the drilling depth have been investigated, and the mechanism of the ultrasonic vibration aided laser machining has been analyzed. After introducing the ultrasonic vibration device, the residue debris on surface of the ablated trench is significantly reduced, and the drilling depth is increased. These results show that, ultrasonic vibration can effectively improve the surface quality of material processing, increase the depth of the drilling hole and promote the processing efficiency of the femtosecond laser.

  15. Femtosecond Pulse Characterization as Applied to One-Dimensional Photonic Band Edge Structures

    Science.gov (United States)

    Fork, Richard L.; Gamble, Lisa J.; Diffey, William M.

    1999-01-01

    The ability to control the group velocity and phase of an optical pulse is important to many current active areas of research. Electronically addressable one-dimensional photonic crystals are an attractive candidate to achieve this control. This report details work done toward the characterization of photonic crystals and improvement of the characterization technique. As part of the work, the spectral dependence of the group delay imparted by a GaAs/AlAs photonic crystal was characterized. Also, a first generation an electrically addressable photonic crystal was tested for the ability to electronically control the group delay. The measurement technique, using 100 femtosecond continuum pulses was improved to yield high spectral resolution (1.7 nanometers) and concurrently with high temporal resolution (tens of femtoseconds). Conclusions and recommendations based upon the work done are also presented.

  16. Femtosecond dynamics of excitons and hole-polarons in composite P3HT/PCBM nanoparticles.

    Science.gov (United States)

    Clafton, Scott N; Huang, David M; Massey, William R; Kee, Tak W

    2013-04-25

    The dynamics of charge separation in aqueous suspensions of regioregular P3HT nanoparticles containing PCBM were investigated for the first time using femtosecond transient absorption spectroscopy. This investigation is supported by the recently reported use of regioregular P3HT/PCBM nanoparticles as charge trapping and storage devices. In this study, the presence of excited-state and charge-separated species, including singlet excitons, polymer polarons and free charges, generated in rr-P3HT/PCBM nanoparticles was identified through visible pump and visible/near-infrared probe femtosecond transient absorption spectroscopy at a range of electron acceptor concentrations. The decrease of the singlet exciton lifetime by charge transfer to PCBM is well described by a one-dimensional diffusion model with a P3HT domain size of approximately 5 nm for 5-50 wt % PCBM. This model also indicates that bimolecular recombination is the dominant charge recombination mechanism at 20 wt % PCBM and above.

  17. Spectroscopie résolue en temps par continuum femtoseconde Applications en neurobiologie

    Science.gov (United States)

    Ramstein, S.; Mottin, S.

    2003-06-01

    La spectroscopie résolue en temps utilisant un laser blanc femtoseconde est appliquée à la mesure in vivo des principaux absorbeurs du cerveau. Après génération adéquate du continuum de lumière blanche femtoseconde (50mW/[580-756nm] à 1Hz), cette source se propage dans la calvaria, les méninges et le cortex chez le rat anesthésié. La transmission est étudiée sur 7mm de distance entre l'impact laser et la fibre optique de collection. Le signal transmis est analysé dans la fenêtre 580-760nm, par un spectromètre couplé à une caméra à balayage de fente permettant la décorrélation de l'absorption et de la diffusion.

  18. Synchronization of femtosecond UV-IR laser with electron beam for pulse radiolysis studies

    International Nuclear Information System (INIS)

    Saeki, Akinori; Kozawa, Takahiro; Kashiwagi, Shigeru; Okamoto, Kazumasa; Isoyama, Goro; Yoshida, Yoichi; Tagawa, Seiichi

    2005-01-01

    A picosecond stroboscopic pulse radiolysis system which consists of a femtosecond laser and a picosecond L-band linear accelerator (linac) is demonstrated. A newly installed femtosecond laser system operated at 960 Hz can cover a wide region of wavelength ranging from <300 nm to 10 μm, although the upper limit is 1.7 μm to date because of the sensitivity of photodetectors. In order to achieve a high accuracy of synchronization between the laser and the linac, a new timing and synchronization circuit was developed. A double pulse detection method was applied for the new system, resulting in doubling of the improvement in signal-to-noise ratio. The time resolution and time jitter were estimated from the rise time of hydrated electrons at 600 nm, and the transient absorption kinetics of electrons in n-dodecane was measured at 1300 nm

  19. Femtosecond laser based small incision lenticule extraction for moderate and high myopia

    DEFF Research Database (Denmark)

    Hjortdal, Jesper Østergaard; Asp, Sven; Ivarsen, Anders

    Femtosecond laser based small incision lenticule extraction for moderate and high myopia. Jesper Hjortdal, Sven Asp, Anders Ivarsen, Anders Vestergaard Department of Ophthalmology, Aarhus University Hospital, Denmark Purpose: ReLEx® smile is a new keratorefractive procedure whereby a stromal...... lenticule is cut by a femtosecond laser and manually extracted through a peripheral corneal tunnel. The purpose of the prospective quality study is to present our initial clinical experience with ReLEx smile for treatment of moderate and high myopia. Methods: 379 eyes (198 patients) were treated for myopia...... (spherical equivalent (SE) ranging from -13.13 to -1.63 D, mean -7.28 D) with ReLEx smile and followed for 3 months. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), proportion of eyes within ± 0.5/1.0 D, loss/gain of lines of CDVA, patient...

  20. Keratin film ablation for the fabrication of brick and mortar skin structure using femtosecond laser pulses

    Science.gov (United States)

    Haq, Bibi Safia; Khan, Hidayat Ullah; Dou, Yuehua; Alam, Khan; Attaullah, Shehnaz; Zari, Islam

    2015-09-01

    The patterning of thin keratin films has been explored to manufacture model skin surfaces based on the "bricks and mortar" view of the relationship between keratin and lipids. It has been demonstrated that laser light is capable of preparing keratin-based "bricks and mortar" wall structure as in epidermis, the outermost layer of the human skin. "Bricks and mortar" pattern in keratin films has been fabricated using an ArF excimer laser (193 nm wavelength) and femtosecond laser (800 and 400 nm wavelength). Due to the very low ablation threshold of keratin, femtosecond laser systems are practical for laser processing of proteins. These model skin structures are fabricated for the first time that will help to produce potentially effective moisturizing products for the protection of skin from dryness, diseases and wrinkles.

  1. Diffraction characteristics of spatial and temporal Gaussian-shaped femtosecond laser pulse by rectangle reflection grating.

    Science.gov (United States)

    Liu, Guohua; Xu, Rongrong; Yu, Wenbing; Wu, Hanping

    2011-02-20

    The exact intensity distribution expression for the spatial and temporal Gaussian-shaped femtosecond laser pulse diffracted by a rectangle reflection grating is derived. The spatial and temporal diffraction characteristics are theoretically investigated in detail, and a criterion for judging whether or not the diffraction pulse is just split into two independent pulses in the temporal domain is obtained. The results show that the diffraction intensity in the temporal domain consists of three parts: the intensity diffracted by the upper reflection surface of the grating, the intensity diffracted by the nether reflection surface, and their temporal coherent intensity. The temporal coherent intensity becomes weaker, even is zero, for the higher height from the nether surface to the upper surface of the grating. The principal maximum becomes more sharply bright for the bigger waist width of the femtosecond laser pulse in the spatial domain.

  2. Femtosecond optical transfection as a tool for genetic manipulation of human embryonic stem cells

    Science.gov (United States)

    Torres-Mapa, M. L.; Gardner, J.; Bradburn, H.; King, J.; Dholakia, K.; Gunn-Moore, F.

    2013-03-01

    We demonstrate the use of femtosecond optical transfection for the genetic manipulation of human embryonic stem cells. Using a system with an SLM combined with a scanning mirror allows poration of both single-cell and colony-formed human embryonic stem cells in a rapid and targeted manner. In this work, we show successful transfection of plasmid DNA tagged with fluorescent reporters into human embryonic stem cells using three doses of focused femtosecond laser. A significant number of transfected cells retained their undifferentiated morphological feature of large nucleus with high nucleus to cytoplasmic ratio, 48h after photoporation. Furthermore, DNA constructs driven by different types of promoters were also successfully transfected into human embryonic stem cells using this technique.

  3. Controllable assembly of silver nanoparticles induced by femtosecond laser direct writing

    International Nuclear Information System (INIS)

    Wang, Huan; Liu, Sen; Zhang, Yong-Lai; Wang, Jian-Nan; Wang, Lei; Xia, Hong; Chen, Qi-Dai; Sun, Hong-Bo; Ding, Hong

    2015-01-01

    We report controllable assembly of silver nanoparticles (Ag NPs) for patterning of silver microstructures. The assembly is induced by femtosecond laser direct writing (FsLDW). A tightly focused femtosecond laser beam is capable of trapping and driving Ag NPs to form desired micropatterns with a high resolution of ∼190 nm. Taking advantage of the ‘direct writing’ feature, three microelectrodes have been integrated with a microfluidic chip; two silver-based microdevices including a microheater and a catalytic reactor have been fabricated inside a microfluidic channel for chip functionalization. The FsLDW-induced programmable assembly of Ag NPs may open up a new way to the designable patterning of silver microstructures toward flexible fabrication and integration of functional devices. (focus issue paper)

  4. Fiber laser-microscope system for femtosecond photodisruption of biological samples.

    Science.gov (United States)

    Yavaş, Seydi; Erdogan, Mutlu; Gürel, Kutan; Ilday, F Ömer; Eldeniz, Y Burak; Tazebay, Uygar H

    2012-03-01

    We report on the development of a ultrafast fiber laser-microscope system for femtosecond photodisruption of biological targets. A mode-locked Yb-fiber laser oscillator generates few-nJ pulses at 32.7 MHz repetition rate, amplified up to ∼125 nJ at 1030 nm. Following dechirping in a grating compressor, ∼240 fs-long pulses are delivered to the sample through a diffraction-limited microscope, which allows real-time imaging and control. The laser can generate arbitrary pulse patterns, formed by two acousto-optic modulators (AOM) controlled by a custom-developed field-programmable gate array (FPGA) controller. This capability opens the route to fine optimization of the ablation processes and management of thermal effects. Sample position, exposure time and imaging are all computerized. The capability of the system to perform femtosecond photodisruption is demonstrated through experiments on tissue and individual cells.

  5. Fabrication of three-dimensional microdisk resonators in calcium fluoride by femtosecond laser micromachining

    Science.gov (United States)

    Lin, Jintian; Xu, Yingxin; Tang, Jialei; Wang, Nengwen; Song, Jiangxin; He, Fei; Fang, Wei; Cheng, Ya

    2014-09-01

    We report on fabrication of on-chip calcium fluoride (CaF2) microdisk resonators using water-assisted femtosecond laser micromachining. Focused ion beam (FIB) milling is used to create ultra-smooth sidewalls. The quality ( Q) factors of the fabricated microresonators are measured to be 4.2 × 104 at wavelengths near 1,550 nm. The Q factor is mainly limited by the scattering from the bottom surface of the disk whose roughness remains high due to the femtosecond laser micromachining process. This technique facilitates the formation of on-chip microresonators on various kinds of bulk crystalline materials, which can benefit a wide range of applications such as nonlinear optics, quantum optics, and chip-level integration of photonic devices.

  6. Size-controllable synthesis of bare gold nanoparticles by femtosecond laser fragmentation in water

    International Nuclear Information System (INIS)

    Maximova, Ksenia; Aristov, Andrei; Sentis, Marc; Kabashin, Andrei V

    2015-01-01

    We report a size-controllable synthesis of stable aqueous solutions of ultrapure low-size-dispersed Au nanoparticles by methods of femtosecond laser fragmentation from preliminary formed colloids. Such approach makes possible the tuning of mean nanoparticle size between a few nm and several tens of nm under the size dispersion lower than 70% by varying the fluence of pumping radiation during the fragmentation procedure. The efficient size control is explained by 3D geometry of laser fragmentation by femtosecond laser-induced white light super-continuum and plasma-related phenomena. Despite the absence of any protective ligands, the nanoparticle solutions demonstrate exceptional stability due to electric repulsion effect associated with strong negative charging of formed nanoparticles. Stable aqueous solutions of bare gold nanoparticles present a unique object with a variety of potential applications in catalysis, surface-enhanced Raman spectroscopy, photovoltaics, biosensing and biomedicine. (paper)

  7. Momentum distributions of selected rare-gas atoms probed by intense femtosecond laser pulses

    DEFF Research Database (Denmark)

    Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2011-01-01

    We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses. The cal......We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses....... The calculations are performed by solving the time-dependent Schrödinger equation within the single-active-electron approximation, and focal-volume effects are taken into account by appropriately averaging the results. The resulting momentum distributions are in quantitative agreement with the experimental...

  8. Femtosecond laser ablation of polymeric substrates for the fabrication of microfluidic channels

    International Nuclear Information System (INIS)

    Suriano, Raffaella; Kuznetsov, Arseniy; Eaton, Shane M.; Kiyan, Roman; Cerullo, Giulio; Osellame, Roberto; Chichkov, Boris N.; Levi, Marinella; Turri, Stefano

    2011-01-01

    This manuscript presents a study of physical and chemical properties of microchannels fabricated by femtosecond laser processing technology in thermoplastic polymeric materials, including poly(methyl methacrylate) (PMMA), polystyrene (PS) and cyclic olefin polymer (COP). By surface electron microscopy and optical profilometry, the dimensions of microchannels in the polymers were found to be easily tunable, with surface roughness values comparable to those obtained by standard prototyping techniques such as micromilling. Through colorimetric analysis and optical microscopy, PMMA was found to remain nearly transparent after ablation while COP and PS darkened significantly. Using infrared spectroscopy, the darkening in PS and COP was attributed to significant oxidation and dehydrogenation during laser ablation, unlike PMMA, which was found to degrade by a thermal depolymerization process. The more stable molecular structure of PMMA makes it the most viable thermoplastic polymer for femtosecond laser fabrication of microfluidic channels.

  9. Femtosecond laser ablation of polymeric substrates for the fabrication of microfluidic channels

    Energy Technology Data Exchange (ETDEWEB)

    Suriano, Raffaella, E-mail: raffaella.suriano@chem.polimi.it [Dipartimento di Chimica, Materiali e Ingegneria Chimica ' Giulio Natta' , Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Kuznetsov, Arseniy [Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover (Germany); Eaton, Shane M. [Istituto di Fotonica e Nanotecnologie (IFN)-CNR, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Kiyan, Roman [Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover (Germany); Cerullo, Giulio [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Osellame, Roberto [Istituto di Fotonica e Nanotecnologie (IFN)-CNR, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Chichkov, Boris N. [Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover (Germany); Levi, Marinella; Turri, Stefano [Dipartimento di Chimica, Materiali e Ingegneria Chimica ' Giulio Natta' , Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy)

    2011-05-01

    This manuscript presents a study of physical and chemical properties of microchannels fabricated by femtosecond laser processing technology in thermoplastic polymeric materials, including poly(methyl methacrylate) (PMMA), polystyrene (PS) and cyclic olefin polymer (COP). By surface electron microscopy and optical profilometry, the dimensions of microchannels in the polymers were found to be easily tunable, with surface roughness values comparable to those obtained by standard prototyping techniques such as micromilling. Through colorimetric analysis and optical microscopy, PMMA was found to remain nearly transparent after ablation while COP and PS darkened significantly. Using infrared spectroscopy, the darkening in PS and COP was attributed to significant oxidation and dehydrogenation during laser ablation, unlike PMMA, which was found to degrade by a thermal depolymerization process. The more stable molecular structure of PMMA makes it the most viable thermoplastic polymer for femtosecond laser fabrication of microfluidic channels.

  10. Neuroscience imaging enabled by new highly tunable and high peak power femtosecond lasers

    Science.gov (United States)

    Hakulinen, T.; Klein, J.

    2017-02-01

    Neuroscience applications benefit from recent developments in industrial femtosecond laser technology. New laser sources provide several megawatts of peak power at wavelength of 1040 nm, which enables simultaneous optogenetics photoactivation of tens or even hundreds of neurons using red shifted opsins. Another recent imaging trend is to move towards longer wavelengths, which would enable access to deeper layers of tissue due to lower scattering and lower absorption in the tissue. Femtosecond lasers pumping a non-collinear optical parametric amplifier (NOPA) enable the access to longer wavelengths with high peak powers. High peak powers of >10 MW at 1300 nm and 1700 nm allow effective 3-photon excitation of green and red shifted calcium indicators respectively and access to deeper, sub-cortex layers of the brain. Early results include in vivo detection of spontaneous activity in hippocampus within an intact mouse brain, where neurons express GCaMP6 activated in a 3-photon process at 1320 nm.

  11. Femtosecond Laser Microfabrication of an Integrated Device for Optical Release and Sensing of Bioactive Compounds

    Directory of Open Access Journals (Sweden)

    Giulio Cerullo

    2008-10-01

    Full Text Available Flash photolysis of caged compounds is one of the most powerful approaches to investigate the dynamic response of living cells. Monolithically integrated devices suitable for optical uncaging are in great demand since they greatly simplify the experiments and allow their automation. Here we demonstrate the fabrication of an integrated bio-photonic device for the optical release of caged compounds. Such a device is fabricated using femtosecond laser micromachining of a glass substrate. More in detail, femtosecond lasers are used both to cut the substrate in order to create a pit for cell growth and to inscribe optical waveguides for spatially selective uncaging of the compounds present in the culture medium. The operation of this monolithic bio-photonic device is tested using both free and caged fluorescent compounds to probe its capability of multipoint release and optical sensing. Application of this device to the study of neuronal network activity can be envisaged.

  12. 3D electrostatic actuator fabricated by non-ablative femtosecond laser exposure and chemical etching

    Directory of Open Access Journals (Sweden)

    Yang Tao

    2015-01-01

    Full Text Available We demonstrate the novel design of an electrostatic micro-actuator based on monolithic three-dimensional (3D shapes fabricated by non-ablative femtosecond laser exposure combined with chemical etching. Further, we present a single-scan stacking approach exploited in the fabrication of the 3D actuator to create crack-free, highcontrast, high fidelity and integrated micro-structures. Influential parameters: energy per pulse, polarization, scanning spacing and stacking directionwere systematically studied to predict and control the etching rate of 3D planes.Finally, we report the characterization of the actuator and its potential application in optomechanics to show a complete scenario of femtosecond laser machined integrated 3D micro-systems incorporating multiple functionalities.

  13. Few-femtosecond time-resolved measurements of X-ray free-electron lasers.

    Science.gov (United States)

    Behrens, C; Decker, F-J; Ding, Y; Dolgashev, V A; Frisch, J; Huang, Z; Krejcik, P; Loos, H; Lutman, A; Maxwell, T J; Turner, J; Wang, J; Wang, M-H; Welch, J; Wu, J

    2014-04-30

    X-ray free-electron lasers, with pulse durations ranging from a few to several hundred femtoseconds, are uniquely suited for studying atomic, molecular, chemical and biological systems. Characterizing the temporal profiles of these femtosecond X-ray pulses that vary from shot to shot is not only challenging but also important for data interpretation. Here we report the time-resolved measurements of X-ray free-electron lasers by using an X-band radiofrequency transverse deflector at the Linac Coherent Light Source. We demonstrate this method to be a simple, non-invasive technique with a large dynamic range for single-shot electron and X-ray temporal characterization. A resolution of less than 1 fs root mean square has been achieved for soft X-ray pulses. The lasing evolution along the undulator has been studied with the electron trapping being observed as the X-ray peak power approaches 100 GW.

  14. Theoretical and experimental analysis of the impact on ablation depth of microchannel milling using femtosecond laser

    Science.gov (United States)

    Lei, Chen; Pan, Zhang; Jianxiong, Chen; Tu, Yiliu

    2018-04-01

    The plasma brightness cannot be used as a direct indicator of ablation depth detection by femtosecond laser was experimentally demonstrated, which led to the difficulty of depth measurement in the maching process. The tests of microchannel milling on the silicon wafer were carried out in the micromachining center in order to obtain the influences of parameters on the ablation depth. The test results showed that the defocusing distance had no significant impact on ablation depth in LAV effective range. Meanwhile, the reason of this was explained in this paper based on the theoretical analysis and simulation calculation. Then it was proven that the ablation depth mainly depends on laser fluence, step distance and scanning velocity. Finally, a research was further carried out to study the laser parameters which relate with the microchannel ablation depth inside the quartz glass for more efficiency and less cost in processing by femtosecond laser.

  15. Femtosecond laser-assisted keratoplasty in a child with corneal opacity:case report

    Directory of Open Access Journals (Sweden)

    E. Yu. Markova

    2014-01-01

    Full Text Available Corneal opacities are the fourth cause of blindness world-wide. Over the past two centuries, various corneal transplantation (i.e., keratoplasty methods have been developed and improved. Nowadays, femtolaserssisted keratoplasty is one of most promising techniques. Femtosecond laser have several advantages that provide additional surgical benefits. Among them, no thermal injury, the ability to cut deeply on a single plane and to perform various corneal profiles should be mentioned. In children, corneal disorders are of special importance while femtosecondassisted keraatoplasty case reports are rare. Here, we describe femtosecond laserssisted penetrating keratoplasty in a girl with a rough central corneal opacity.

  16. Femtosecond single electron bunch generation by rotating longitudinal bunch phase space in magnetic field

    International Nuclear Information System (INIS)

    Yang, J.; Kondoh, T.; Kan, K.; Kozawa, T.; Yoshida, Y.; Tagawa, S.

    2006-01-01

    A femtosecond (fs) electron bunching was observed in a photoinjector with a magnetic compressor by rotating the bunch in longitudinal phase space. The bunch length was obtained by measuring Cherenkov radiation of the electron beam with a femtosecond streak camera technique. A single electron bunch with rms bunch length of 98 fs was observed for a 32 MeV electron beam at a charge of 0.17 nC. The relative energy spread and the normalized transverse emittance of the electron beam were 0.2% and 3.8 mm-mrad, respectively. The effect of space charge on the bunch compression was investigated experimentally for charges from 0.17 to 1.25 nC. The dependences of the relative energy spread and the normalized beam transverse emittance on the bunch charge were measured

  17. Transient photoconductivity and femtosecond nonlinear optical properties of a conjugated polymer-graphene oxide composite

    Energy Technology Data Exchange (ETDEWEB)

    Nalla, Venkatram; Ji Wei [Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Polavarapu, Lakshminarayana; Manga, Kiran Kumar; Goh, Bee Min; Loh, Kian Ping; Xu Qinghua, E-mail: chmxqh@nus.edu.sg, E-mail: phyjiwei@nus.edu.sg [Department of Chemistry, National University of Singapore, Singapore 117543 (Singapore)

    2010-10-15

    A water soluble conjugated thiophene polymer, sodium salt of poly[2-(3-thienyl)ethoxy-4-butylsulfonate] (TPP), and graphene oxide (GO) composite film (GO-TPP) device was prepared. Transient photoconductivity measurements were carried out on the GO-TPP composite film using 150 ns laser pulses of 527 nm wavelength. Highly efficient photocurrent generation was observed from the GO-TPP film. The relationships of the film photoconductivity, photocurrent decay time and electron decay times with the incident light intensity were investigated. The photoconductive gain of the film was determined to be greater than 40% and to be independent of the light intensity. Furthermore, the femtosecond nonlinear optical properties of the GO-TPP film were measured using 800 nm femtosecond laser pulses and the composite film exhibited high nonlinear absorption and nonlinear refraction coefficients.

  18. Mono-Cycle Photonics and Optical Scanning Tunneling Microscopy Route to Femtosecond Ångstrom Technology

    CERN Document Server

    Yamashita, Mikio; Morita, Ryuji

    2005-01-01

    "Mono-Cycle Photonics and Optical Scanning Tunneling Microscopy" deals with both the ultrashort laser-pulse technology in the few- to mono-cycle region and the laser-surface-controlled scanning-tunneling microscopy (STM) extending into the spatiotemporal extreme technology. The former covers the theory of nonlinear pulse propagation beyond the slowly-varing-envelope approximation, the generation and active chirp compensation of ultrabroadband optical pulses, the amplitude and phase characterization of few- to mono-cycle pulses, and the feedback field control for the mono-cycle-like pulse generation. In addition, the wavelength-multiplex shaping of ultrabroadband pulse is described. The latter covers the CW-laser-excitation STM, the femtosecond-time-resolved STM and atomic-level surface phenomena controlled by femtosecond pulses.

  19. Ultrafast conversions between hydrogen bonded structures in liquid water observed by femtosecond x-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Haidan; Huse, Nils; Schoenlein, Robert W.; Lindenberg, Aaron M.

    2010-05-01

    We present the first femtosecond soft x-ray spectroscopy in liquids, enabling the observation of changes in hydrogen bond structures in water via core-hole excitation. The oxygen K-edge of vibrationally excited water is probed with femtosecond soft x-ray pulses, exploiting the relation between different water structures and distinct x-ray spectral features. After excitation of the intramolecular OH stretching vibration, characteristic x-ray absorption changes monitor the conversion of strongly hydrogen-bonded water structures to more disordered structures with weaker hydrogen-bonding described by a single subpicosecond time constant. The latter describes the thermalization time of vibrational excitations and defines the characteristic maximum rate with which nonequilibrium populations of more strongly hydrogen-bonded water structures convert to less-bonded ones. On short time scales, the relaxation of vibrational excitations leads to a transient high-pressure state and a transient absorption spectrum different from that of statically heated water.

  20. Generation of a femtosecond electron microbunch train from a photocathode using twofold Michelson interferometer

    Science.gov (United States)

    Shevelev, M.; Aryshev, A.; Terunuma, N.; Urakawa, J.

    2017-10-01

    The interest in producing ultrashort electron bunches has risen sharply among scientists working on the design of high-gradient wakefield accelerators. One attractive approach generating electron bunches is to illuminate a photocathode with a train of femtosecond laser pulses. In this paper we describe the design and testing of a laser system for an rf gun based on a commercial titanium-sapphire laser technology. The technology allows the production of four femtosecond laser pulses with a continuously variable pulse delay. We also use the designed system to demonstrate the experimental generation of an electron microbunch train obtained by illuminating a cesium-telluride semiconductor photocathode. We use conventional diagnostics to characterize the electron microbunches produced and confirm that it may be possible to control the main parameter of an electron microbunch train.

  1. Generation of a femtosecond electron microbunch train from a photocathode using twofold Michelson interferometer

    Directory of Open Access Journals (Sweden)

    M. Shevelev

    2017-10-01

    Full Text Available The interest in producing ultrashort electron bunches has risen sharply among scientists working on the design of high-gradient wakefield accelerators. One attractive approach generating electron bunches is to illuminate a photocathode with a train of femtosecond laser pulses. In this paper we describe the design and testing of a laser system for an rf gun based on a commercial titanium-sapphire laser technology. The technology allows the production of four femtosecond laser pulses with a continuously variable pulse delay. We also use the designed system to demonstrate the experimental generation of an electron microbunch train obtained by illuminating a cesium-telluride semiconductor photocathode. We use conventional diagnostics to characterize the electron microbunches produced and confirm that it may be possible to control the main parameter of an electron microbunch train.

  2. Control of molecular breakup by an infrared pulse and a femtosecond pulse train

    Science.gov (United States)

    Singh, Kamal P.; Kenfack, A.; Rost, Jan M.; Pfeifer, Thomas

    2018-03-01

    We investigate the dissociation dynamics of diatomic molecules subjected to both a femtosecond infrared (IR) laser pulse and a femtosecond pulse train (FPT) within the framework of the Morse potential model. When the IR and FPT are phase delayed, we observe well-resolved oscillations in dissociation probability, corresponding to multiple integers of the IR period, exhibiting enhancement and suppression of bond dissociation. These oscillations reveal a rich dynamics as a function of the IR and FPT parameters including chaotic fields. A frequency-resolved profile of dressed molecular states shows that these oscillations are due to interference of many quantum paths analogous to the recently observed control of photoionization of atoms under IR and XUV pulses. By manipulating phases of FPTs we demonstrate an enhancement of molecular dissociation compared to the transform-limited case.

  3. Initial Atomic Motion Immediately Following Femtosecond-Laser Excitation in Phase-Change Materials.

    Science.gov (United States)

    Matsubara, E; Okada, S; Ichitsubo, T; Kawaguchi, T; Hirata, A; Guan, P F; Tokuda, K; Tanimura, K; Matsunaga, T; Chen, M W; Yamada, N

    2016-09-23

    Despite the fact that phase-change materials are widely used for data storage, no consensus exists on the unique mechanism of their ultrafast phase change and its accompanied large and rapid optical change. By using the pump-probe observation method combining a femtosecond optical laser and an x-ray free-electron laser, we substantiate experimentally that, in both GeTe and Ge_{2}Sb_{2}Te_{5} crystals, rattling motion of mainly Ge atoms takes place with keeping the off-center position just after femtosecond-optical-laser irradiation, which eventually leads to a higher symmetry or disordered state. This very initial rattling motion in the undistorted lattice can be related to instantaneous optical change due to the loss of resonant bonding that characterizes GeTe-based phase change materials. Based on the amorphous structure derived by first-principles molecular dynamics simulation, we infer a plausible ultrafast amorphization mechanism via nonmelting.

  4. High efficiency, monolithic fiber chirped pulse amplification system for high energy femtosecond pulse generation.

    Science.gov (United States)

    Peng, Xiang; Kim, Kyungbum; Mielke, Michael; Jennings, Stephen; Masor, Gordon; Stohl, Dave; Chavez-Pirson, Arturo; Nguyen, Dan T; Rhonehouse, Dan; Zong, Jie; Churin, Dmitriy; Peyghambarian, N

    2013-10-21

    A novel monolithic fiber-optic chirped pulse amplification (CPA) system for high energy, femtosecond pulse generation is proposed and experimentally demonstrated. By employing a high gain amplifier comprising merely 20 cm of high efficiency media (HEM) gain fiber, an optimal balance of output pulse energy, optical efficiency, and B-integral is achieved. The HEM amplifier is fabricated from erbium-doped phosphate glass fiber and yields gain of 1.443 dB/cm with slope efficiency >45%. We experimentally demonstrate near diffraction-limited beam quality and near transform-limited femtosecond pulse quality at 1.55 µm wavelength. With pulse energy >100 µJ and pulse duration of 636 fs (FWHM), the peak power is estimated to be ~160 MW. NAVAIR Public Release Distribution Statement A-"Approved for Public release; distribution is unlimited".

  5. Femtosecond Time-Resolved Resonance-Enhanced CARS of Gaseous Iodine at Room Temperature

    Science.gov (United States)

    He, Ping; Fan, Rong-Wei; Xia, Yuan-Qin; Yu, Xin; Yao, Yong; Chen, De-Ying

    2011-04-01

    Time-resolved resonance-enhanced coherent anti-Stokes Raman scattering (CARS) is applied to investigate molecular dynamics in gaseous iodine. 40 fs laser pulses are applied to create and monitor the high vibrational states of iodine at room temperature (corresponding to a vapor pressure as low as about 35 Pa) by femtosecond time-resolved CARS. Depending on the time delay between the probe pulse and the pump/Stokes pulse pairs, the high vibrational states both on the electronically ground states and the excited states can be detected as oscillations in the CARS transient signal. It is proved that the femtosecond time-resolved CARS technique is a promising candidate for investigating the molecular dynamics of a low concentration system and can be applied to environmental and atmospheric monitoring measurements.

  6. Noninvasive multiphoton imaging of cardiovascular structures using NIR femtosecond laser scanning microscopy

    Science.gov (United States)

    Schenke-Layland, Katja; Riemann, Iris; Stock, Ulrich A.; Konig, Karsten

    2004-07-01

    Near infrared (NIR) femtosecond laser scanning microscopy represents a novel and very promising medical diagnostic imaging technology for non-invasive cross-sectional analysis of living biological tissues. In this study multiphoton imaging has been performed to analyze the structural features of extracellular matrix (ECM) components, e.g. collagen and elastin, of living pulmonary and aortic heart valves. High-resolution autofluorescence and second harmonic generation (SHG) images of collagenous and elastic fibers were demonstrated using multifluorophore, multiphoton excitation at two different wavelengths and non-invasive optical sectioning, without the need of embedding or staining. The quality of the resulting three-dimensional images allowed exact differentiation of the ECM components. These experimental results indicated that NIR femtosecond laser scanning microscopy may prove to be a useful tool for the non-destructive monitoring and characterization of cardiovascular structures.

  7. Charge Carrier Dynamics in Transition Metal Oxides Studied by Femtosecond Transient Extreme Ultraviolet Absorption Spectroscopy

    OpenAIRE

    Jiang, Chang-Ming

    2015-01-01

    With the ability to disentangle electronic transitions that occur on different elements and local electronic structures, time-resolved extreme ultraviolet (XUV) spectroscopy has emerged as a powerful tool for studying ultrafast dynamics in condensed phase systems. In this dissertation, a visible-pump/XUV-probe transient absorption apparatus with femtosecond resolution was constructed to investigate the carrier relaxation dynamics in semiconductors after photo-excitation. This includes timesca...

  8. Fabrication of polycrystalline diamond refractive X-ray lens by femtosecond laser processing

    Energy Technology Data Exchange (ETDEWEB)

    Kononenko, T.V.; Ralchenko, V.G.; Ashkinazi, E.E.; Konov, V.I. [General Physics Institute of Russian Academy of Sciences, Moscow (Russian Federation); National Research Nuclear University ' ' MEPhI' ' , Moscow (Russian Federation); Polikarpov, M.; Ershov, P. [Immanuel Kant Baltic Federal University, Functional Nanomaterials, Kaliningrad (Russian Federation); Kuznetsov, S.; Yunkin, V. [Institute of Microelectronics Technology RAS, Chernogolovka, Moscow region (Russian Federation); Snigireva, I. [European Synchrotron Radiation Facility, Grenoble (France)

    2016-03-15

    X-ray planar compound refractive lenses were fabricated from a polycrystalline diamond plate grown by chemical vapor deposition, by precise through cutting with femtosecond laser pulses. The lens geometry and the surface morphology were investigated with optical and scanning electron microscopy, while the material structure modification was analyzed by Raman spectroscopy. The results of the preliminary lens test at 9.25-keV X-rays are presented. (orig.)

  9. Generation of coherent optical phonons in ZnO using femtosecond lasers

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Y. S. [Dept. of Applied Physics, Konkuk University, Chungju (Korea, Republic of); Lee, I. H.; Yee, K. J.; Lee, K. G.; Oh, E.; Kim, D. S. [School of Physics, Seoul National University, Seoul (Korea, Republic of)

    2002-07-01

    We report on coherent optical phonon oscillations in wuzite ZnO. The high- and low-frequency E{sub 2} modes are excited by the impulsive stimulated Raman scattering (ISRS), and detected through the electric sampling. The dephasing times at room temperature are measured to be 1.75 ps, 29.2 ps for high- and low-E{sub 2} mode, respectively. The relation of the coherent phonon amplitude with the spectral wide of femtosecond pump pulse is demonstrated.

  10. Channel waveguide lasers in Nd:GGG crystals fabricated by femtosecond laser inscription.

    Science.gov (United States)

    Zhang, Chao; Dong, Ningning; Yang, Jin; Chen, Feng; Vázquez de Aldana, Javier R; Lu, Qingming

    2011-06-20

    Buried channel waveguides have been fabricated in Nd:GGG crystals by using the femtosecond laser inscription. The waveguides are confined between two filaments with propagation losses of 2.0 dB/cm. Stable continuous wave laser oscillation at ~1061 nm has been demonstrated at room temperature. Under 808 nm optical excitation, a pump threshold of 29 mW and a slope efficiency of 25% have been obtained.

  11. Dual-pulse laser-induced breakdown spectroscopy with combinations of femtosecond and nanosecond laser pulses.

    Science.gov (United States)

    Scaffidi, Jon; Pender, Jack; Pearman, William; Goode, Scott R; Colston, Bill W; Carter, J Chance; Angel, S Michael

    2003-10-20

    Nanosecond and femtosecond laser pulses were combined in an orthogonal preablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS) configuration. Even without full optimization of interpulse alignment, ablation focus, large signal, signal-to-noise ratio, and signal-to-background ratio enhancements were observed for both copper and aluminum targets. Despite the preliminary nature of this study, these results have significant implications in the attempt to explain the sources of dual-pulse LIBS enhancements.

  12. [The pros and cons of femtosecond laser-assisted cataract surgery].

    Science.gov (United States)

    Li, Z H; Ye, Z

    2016-02-01

    Femtosecond laser-assisted cataract surgery (FLACS) is known as an innovative new technology. Compared with traditional surgical approach, FLACS is more accurate, more predictable and less energy used. However, in the current stage of development, there still may be intraoperative and postoperative complications, or even serious complications. FLACS has obvious advantages in certain surgical steps, but there are still clear disadvantages, so it still cannot completely replace the traditional phacoemulsification surgery.

  13. Photoluminescence and Terahertz Emission from Femtosecond Laser-Induced Plasma Channels

    Science.gov (United States)

    Hoyer, W.; Knorr, A.; Moloney, J. V.; Wright, E. M.; Kira, M.; Koch, S. W.

    2005-03-01

    Luminescence as a mechanism for terahertz emission from femtosecond laser-induced plasmas is studied. By using a fully microscopic theory, Coulomb scattering between electrons and ions is shown to lead to luminescence even for a spatially homogeneous plasma. The spectral features introduced by the rod geometry of laser-induced plasma channels in air are discussed on the basis of a generalized mode-function analysis.

  14. Fabrication of polycrystalline diamond refractive X-ray lens by femtosecond laser processing

    International Nuclear Information System (INIS)

    Kononenko, T.V.; Ralchenko, V.G.; Ashkinazi, E.E.; Konov, V.I.; Polikarpov, M.; Ershov, P.; Kuznetsov, S.; Yunkin, V.; Snigireva, I.

    2016-01-01

    X-ray planar compound refractive lenses were fabricated from a polycrystalline diamond plate grown by chemical vapor deposition, by precise through cutting with femtosecond laser pulses. The lens geometry and the surface morphology were investigated with optical and scanning electron microscopy, while the material structure modification was analyzed by Raman spectroscopy. The results of the preliminary lens test at 9.25-keV X-rays are presented. (orig.)

  15. Implementation of a single femtosecond optical frequency comb for rovibrational cooling

    OpenAIRE

    Shi, W.; Malinovskaya, S.

    2010-01-01

    We show that a single femtosecond optical frequency comb may be used to induce two-photon transitions between molecular vibrational levels to form ultracold molecules, e.g., KRb. The phase across an individual pulse in the pulse train is sinusoidally modulated with a carefully chosen modulation amplitude and frequency. Piecewise adiabatic population transfer is fulfilled to the final state by each pulse in the applied pulse train providing a controlled population accumulation in the final sta...

  16. Femtosecond spectroscopy on alkali-doped helium nanodroplets; Femtosekundenspektroskopie an alkalidotierten Helium-Nanotroepfchen

    Energy Technology Data Exchange (ETDEWEB)

    Claas, P.

    2006-01-15

    In the present thesis first studies on the short-time dynamics in alkali dimers and microclusters, which were bound on the surface of superfluid helium droplets, were presented. The experiments comprehended pump-probe measurements on the fs scale on the vibration dynamics on the dimers and on the fragmentation dynamics on the clusters. Generally by the studies it was shown that such extremely short slopes can also be observed on helium droplets by means of the femtosecond spectroscopy.

  17. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    Science.gov (United States)

    See, Tian Long; Liu, Zhu; Li, Lin; Zhong, Xiang Li

    2016-02-01

    This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser-material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (Fth = 0.087 J/cm2) than that for the femtosecond laser ablation of ABS (Fth = 1.576 J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α-1 = 223 nm) than that for femtosecond laser ablation (α-1 = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the Cdbnd C bond completely through the chain scission process whereas Cdbnd C bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the Cdbnd C bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (Csbnd O and Cdbnd O bond) and nitrogen-rich (Csbnd N) functional groups.

  18. Formation of array microstructures on silicon by multibeam interfered femtosecond laser pulses

    International Nuclear Information System (INIS)

    Zhao Quanzhong; Qiu Jianrong; Zhao Chongjun; Jiang Xiongwei; Zhu Congshan

    2005-01-01

    We report on an optical interference method to fabricate array microstructures on the surface of silicon wafers by means of five-beam interference of femtosecond laser pulses. Optical microscope and scanning electron microscope observations revealed microstructures with micrometer-order were fabricated. The diffraction characteristics of the fabricated structures were evaluated. The present technique allows one-step realization of functional optoelectronic devices on silicon surface

  19. Site Specificity in Femtosecond Laser Desorption of Neutral H Atoms from Graphite(0001)

    DEFF Research Database (Denmark)

    Frigge, R.; Hoger, T.; Siemer, B.

    2010-01-01

    Femtosecond laser excitation and density functional theory reveal site and vibrational state specificity in neutral atomic hydrogen desorption from graphite induced by multiple electronic transitions. Multimodal velocity distributions witness the participation of ortho and para pair states...... of chemisorbed hydrogen in the desorption process. Very slow velocities of 700 and 400  ms-1 for H and D atoms are associated with the desorption out of the highest vibrational state of a barrierless potential....

  20. Noncontact microsurgery of cell membranes using femtosecond laser pulses for optoinjection of specified substances into cells

    Science.gov (United States)

    Il'ina, I. V.; Ovchinnikov, A. V.; Chefonov, O. V.; Sitnikov, D. S.; Agranat, Mikhail B.; Mikaelyan, A. S.

    2013-04-01

    IR femtosecond laser pulses were used for microsurgery of a cell membrane aimed at local and short-duration change in its permeability and injection of specified extracellular substances into the cells. The possibility of noncontact laser delivery of the propidium iodide fluorescent dye and the pEGFP plasmid, encoding the green fluorescent protein, into the cells with preservation of the cell viability was demonstrated.

  1. Femtosecond Raman induced polarization spectroscopy studies of coherent rotational dynamics in molecular fluids

    Energy Technology Data Exchange (ETDEWEB)

    Morgen, Michael Mark [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1997-05-01

    We develop a polarization-sensitive femtosecond pump probe technique, Raman induced polarization spectroscopy (RIPS), to study coherent rotation in molecular fluids. By observing the collisional dephasing of the coherently prepared rotational states, we are able to extract information concerning the effects of molecular interactions on the rotational motion. The technique is quite sensitive because of the zero background detection method, and is also versatile due to its nonresonant nature.

  2. Efficacy of iris location to femtosecond-combined wavefront guided LASIK for myopia and astigmatism

    Directory of Open Access Journals (Sweden)

    Ke-Jie Lin

    2016-06-01

    Full Text Available AIM:To observe effect of the iris location to femtosecond-combined wavefront guided LASIK for myopia and astigmatism.METHODS:The patients with astigmatism >1.0D during the same time and followed up for 1a were selected. A total of 129 eyes in 67 patients were treated under iris location with femtosecond-combined wavefront guided LASIK(experimental groupand 161 eyes in 82 cases with femtosecond-combined wavefront guided LASIK(control group. Laser cutting went with the same laser machine. The uncorrected visual acuity(UCVA, best corrected visual acuity(BCVA, and wavefront aberration between the two groups were compared at 1, 3, 6mo and 1a after surgery. RESULTS:At 1 and 3mo after surgery, the number of patients with better postoperative UCVA than preoperative BCVA between the two group showed a statistically significant difference(χ2=6.423, P=0.011,χ2=14.431, P=0.01; at 1d and 1mo after surgery, the residual astigmatism showed a statistically significant difference between two groups(t=1.98, Pt=2.23, PP>0.05. At 6mo and 1a after surgery, the differences on UCVA between the two groups weren't significant(P>0.05. Until 1a after surgery, the root mean square(RMSof high order wavefront aberration of the two groups, spherical aberration and coma aberration(COMAwere all enhanced compared to before surgery(PPPCONCLUSION:Iris location technology applied in femtosecond-combined wavefront guided LASIK for myopia and astigmatism, can make the vision recovery faster, the RMS of high order and COMA increase less, the residual astigmatism less, show better and more stable treatment effect.

  3. Oval-like hollow intensity distribution of tightly focused femtosecond laser pulses in air.

    Science.gov (United States)

    Li, Y T; Xi, T T; Hao, Z Q; Zhang, Z; Peng, X Y; Li, K; Jin, Z; Zheng, Z Y; Yu, Q Z; Lu, X; Zhang, J

    2007-12-24

    The propagation of a tightly focused femtosecond laser pulse in air has been investigated. Unlike long-distance self-guided propagation of short laser pulses, a novel oval-like hollow distribution of the laser intensity is observed in the experiments and reproduced by the numerical simulations. The formation of the hollow structures can be explained by the interplay between ionization-induced refraction and Kerr self-focusing.

  4. How Plasmonic excitation influences the LIPSS formation on diamond during multipulse femtosecond laser irradiation ?

    Directory of Open Access Journals (Sweden)

    Abdelmalek Ahmed

    2017-01-01

    Full Text Available A generalized plasmonic model is proposed to calculate the nanostructure period induced by multipulse laser femtosecond on diamond at 800 nm wavelengths. We follow the evolution of LIPSS formation by changing diamond optical parameters in function of electron plasma excitation during laser irradiation. Our calculations shows that the ordered nanostructures can be observed only in the range of surface plasmon polariton excitation.

  5. Enhancement of third-order harmonic generation by interaction of two IR femtosecond filaments

    International Nuclear Information System (INIS)

    Liu, Z Y; Ding, P J; Shi, Y C; Lu, X; Liu, Q C; Sun, S H; Ding, B W; Hu, B T; Liu, X L

    2012-01-01

    Three orders of magnitude in the enhancement of the third-order harmonic (TH) generation induced by the interaction of two femtosecond filaments crossing with small angles in the air is achieved. The dependences of the TH generation on the time delay, the relative polarization, the input laser intensity ratios between the probe and pump beam are measured with the crossing angle of 3.5deg , and the results with quasi-vertical crossing angle are also shown for comparison

  6. Scaling of black silicon processing time by high repetition rate femtosecond lasers

    Directory of Open Access Journals (Sweden)

    Nava Giorgio

    2013-11-01

    Full Text Available Surface texturing of silicon substrates is performed by femtosecond laser irradiation at high repetition rates. Various fabrication parameters are optimized in order to achieve very high absorptance in the visible region from the micro-structured silicon wafer as compared to the unstructured one. A 70-fold reduction of the processing time is demonstrated by increasing the laser repetition rate from 1 kHz to 200 kHz. Further scaling up to 1 MHz can be foreseen.

  7. Formation of nanostructured TiO2 by femtosecond laser irradiation of titanium in O2

    International Nuclear Information System (INIS)

    Landis, Elizabeth C.; Phillips, Katherine C.; Mazur, Eric; Friend, Cynthia M.

    2012-01-01

    We used femtosecond laser irradiation of titanium metal in an oxidizing environment to form a highly stable surface layer of nanostructured amorphous titanium dioxide (TiO 2 ). We studied the influence of atmospheric composition on these surface structures and found that gas composition and pressure affect the chemical composition of the surface layer but not the surface morphology. Incorporation of nitrogen is only possible when no oxygen is present in the surrounding atmosphere.

  8. Femtosecond pulsed laser ablation to enhance drug delivery across the skin.

    Science.gov (United States)

    Garvie-Cook, Hazel; Stone, James M; Yu, Fei; Guy, Richard H; Gordeev, Sergey N

    2016-01-01

    Laser poration of the skin locally removes its outermost, barrier layer, and thereby provides a route for the diffusion of topically applied drugs. Ideally, no thermal damage would surround the pores created in the skin, as tissue coagulation would be expected to limit drug diffusion. Here, a femtosecond pulsed fiber laser is used to porate mammalian skin ex vivo. This first application of a hollow core negative curvature fiber (HC-NCF) to convey a femtosecond pulsed, visible laser beam results in reproducible skin poration. The effect of applying ink to the skin surface, prior to ultra-short pulsed ablation, has been examined and Raman spectroscopy reveals that the least, collateral thermal damage occurs in inked skin. Pre-application of ink reduces the laser power threshold for poration, an effect attributed to the initiation of plasma formation by thermionic electron emission from the dye in the ink. Poration under these conditions significantly increases the percutaneous permeation of caffeine in vitro. Dye-enhanced, plasma-mediated ablation of the skin is therefore a potentially advantageous approach to enhance topical/transdermal drug absorption. The combination of a fiber laser and a HC-NCF, capable of emitting and delivering femtosecond pulsed, visible light, may permit a compact poration device to be developed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Optical reprogramming of human cells in an ultrashort femtosecond laser microfluidic transfection platform.

    Science.gov (United States)

    Uchugonova, Aisada; Breunig, Hans Georg; Batista, Ana; König, Karsten

    2016-09-01

    Induced pluripotent stem cell (iPS cell) technology can be used to produce unlimited numbers of functional cells for both research and therapeutic purposes without ethical controversy. Typically, viruses are applied for efficient intracellular delivery of genes/transcription factors to generate iPS cells. However, the viral genomic integration may cause a risk of mutation as well as tumor formation therefore limits its clinical application. Here we demonstrate that spatially shaped extreme ultrashort laser pulses of sub-20 femtoseconds induce transient membrane permeabilisation which enables contamination-free transfection of cells in a microfluidic tube with multiple genes at the individual cell level in order to achieve optical reprogramming of large cell populations. We found that the ultrashort femtosecond laser-microfluidic cell transfection platform enhanced the efficacy of iPS-like colony-forming following merely a single transfection. Illustration of the spatially shaped femtosecond laser-assisted microfluidic cell transfection platform for production of iPS cell colonies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. The modification of generalized uncertainty principle applied in the detection technique of femtosecond laser

    Science.gov (United States)

    Li, Ziyi

    2017-12-01

    Generalized uncertainty principle (GUP), also known as the generalized uncertainty relationship, is the modified form of the classical Heisenberg’s Uncertainty Principle in special cases. When we apply quantum gravity theories such as the string theory, the theoretical results suggested that there should be a “minimum length of observation”, which is about the size of the Planck-scale (10-35m). Taking into account the basic scale of existence, we need to fix a new common form of Heisenberg’s uncertainty principle in the thermodynamic system and make effective corrections to statistical physical questions concerning about the quantum density of states. Especially for the condition at high temperature and high energy levels, generalized uncertainty calculations have a disruptive impact on classical statistical physical theories but the present theory of Femtosecond laser is still established on the classical Heisenberg’s Uncertainty Principle. In order to improve the detective accuracy and temporal resolution of the Femtosecond laser, we applied the modified form of generalized uncertainty principle to the wavelength, energy and pulse time of Femtosecond laser in our work. And we designed three typical systems from micro to macro size to estimate the feasibility of our theoretical model and method, respectively in the chemical solution condition, crystal lattice condition and nuclear fission reactor condition.

  11. Near-field enhanced femtosecond laser nano-drilling of glass substrate

    International Nuclear Information System (INIS)

    Zhou, Y.; Hong, M.H.; Fuh, J.Y.H.; Lu, L.; Lukyanchuk, B.S.; Wang, Z.B.

    2008-01-01

    Particle mask assisted near-field enhanced femtosecond laser nano-drilling of transparent glass substrate was demonstrated in this paper. A particle mask was fabricated by self-assembly of spherical 1 μm silica particles on the substrate surface. Then the samples were exposed to femtosecond laser (800 nm, 100 fs) and characterized by field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). The nano-hole array was found on the glass surface. The hole sizes were measured from 200 to 300 nm with an average depth of 150 nm and increased with laser fluence. Non-linear triple-photon absorption and near-field enhancement were the main mechanisms of the nano-feature formation. Calculations based on Mie theory shows an agreement with experiment results. More debris, however, was found at high laser fluence. This can be attributed to the explosion of silica particles because the focusing point is inside the 1 μm particle. The simulation predicts that the focusing point will move outside the particle if the particle size increases. The experiment performed under 6.84 μm silica particles verified that no debris was formed. And for all the samples, no cracks were found on the substrate surface because of ultra-short pulse width of femtosecond laser. This method has potential applications in nano-patterning of transparent glass substrate for nano-structure device fabrication

  12. Fiber-based 1150-nm femtosecond laser source for the minimally invasive harmonic generation microscopy

    Science.gov (United States)

    Huang, Jing-Yu; Guo, Lun-Zhang; Wang, Jing-Zun; Li, Tse-Chung; Lee, Hsin-Jung; Chiu, Po-Kai; Peng, Lung-Han; Liu, Tzu-Ming

    2017-03-01

    Harmonic generation microscopy (HGM) has become one unique tool of optical virtual biopsy for the diagnosis of cancer and the in vivo cytometry of leukocytes. Without labeling, HGM can reveal the submicron features of tissues and cells in vivo. For deep imaging depth and minimal invasiveness, people commonly adopt 1100- to 1300-nm femtosecond laser sources. However, those lasers are typically based on bulky oscillators whose performances are sensitive to environmental conditions. We demonstrate a fiber-based 1150-nm femtosecond laser source, with 6.5-nJ pulse energy, 86-fs pulse width, and 11.25-MHz pulse repetition rate. It was obtained by a bismuth borate or magnesium-doped periodically poled lithium niobate (MgO:PPLN) mediated frequency doubling of the 2300-nm solitons, generated from an excitation of 1550-nm femtosecond pulses on a large mode area photonic crystal fiber. Combined with a home-built laser scanned microscope and a tailor-made frame grabber, we achieve a pulse-per-pixel HGM imaging in vivo at a 30-Hz frame rate. This integrated solution has the potential to be developed as a stable HGM system for routine clinical use.

  13. Vibration-Assisted Femtosecond Laser Drilling with Controllable Taper Angles for AMOLED Fine Metal Mask Fabrication

    Directory of Open Access Journals (Sweden)

    Wonsuk Choi

    2017-02-01

    Full Text Available This study investigates the effect of focal plane variation using vibration in a femtosecond laser hole drilling process on Invar alloy fabrication quality for the production of fine metal masks (FMMs. FMMs are used in the red, green, blue (RGB evaporation process in Active Matrix Organic Light-Emitting Diode (AMOLED manufacturing. The taper angle of the hole is adjusted by attaching the objective lens to a micro-vibrator and continuously changing the focal plane position. Eight laser pulses were used to examine how the hole characteristics vary with the first focal plane’s position, where the first pulse is focused at an initial position and the focal planes of subsequent pulses move downward. The results showed that the hole taper angle can be controlled by varying the amplitude of the continuously operating vibrator during femtosecond laser hole machining. The taper angles were changed between 31.8° and 43.9° by adjusting the vibrator amplitude at a frequency of 100 Hz. Femtosecond laser hole drilling with controllable taper angles is expected to be used in the precision micro-machining of various smart devices.

  14. Trigger effect of infrared femtosecond laser irradiation on neoplasm in experimental cervical cancer

    Science.gov (United States)

    Gening, Tatyana; Voronova, Olga; Zolotovskii, Igor; Sysoliatin, Alexey; Dolgova, Dinara; Abakumova, Tatyana

    2013-02-01

    The present work discusses effect of infrared (IR) femtosecond laser irradiation on neoplasm of white mice with experimental cervical cancer- 5 (CC-5 on the 20th and 30th days after tumor transplantation). Tumor tissue was irradiated by femtosecond erbium doped fiber laser: the wavelength is 1.55 μm, average and peak powers are1,25 mW and 6kW, respectively, irradiation trials n=10. The average energy density (energy dose) on a tissue for two groups of animals was 0,24 J/cm2 and 0,36 J/cm2 for a single trial. Irradiation was followed by biochemical determination of LPO AOS parameters ("Lipid peroxidation-antioxidants" system): malondialdehyde (MDA), activity of superoxide dismutase (SOD), catalase and glutathione-reductase (GR), glutathione-S-transferase (GST). A subsequent morphological study of tumor tissue was performed. Mathematical analysis of data demonstrates a weak dependence of the studied parameters on energy dose. The latter implies the trigger effect of IR femtosecond laser irradiation on redox-dependent processes in neoplasm at experimental cervical cancer.

  15. Femtosecond laser machining for characterization of local mechanical properties of biomaterials: a case study on wood.

    Science.gov (United States)

    Jakob, Severin; Pfeifenberger, Manuel J; Hohenwarter, Anton; Pippan, Reinhard

    2017-01-01

    The standard preparation technique for micro-sized samples is focused ion beam milling, most frequently using Ga + ions. The main drawbacks are the required processing time and the possibility and risks of ion implantation. In contrast, ultrashort pulsed laser ablation can process any type of material with ideally negligible damage to the surrounding volume and provides 4 to 6 orders of magnitude higher ablation rates than the ion beam technique. In this work, a femtosecond laser was used to prepare wood samples from spruce for mechanical testing at the micrometre level. After optimization of the different laser parameters, tensile and compressive specimens were produced from microtomed radial-tangential and longitudinal-tangential sections. Additionally, laser-processed samples were exposed to an electron beam prior to testing to study possible beam damage. The specimens originating from these different preparation conditions were mechanically tested. Advantages and limitations of the femtosecond laser preparation technique and the deformation and fracture behaviour of the samples are discussed. The results prove that femtosecond laser processing is a fast and precise preparation technique, which enables the fabrication of pristine biological samples with dimensions at the microscale.

  16. High current table-top setup for femtosecond gas electron diffraction

    Directory of Open Access Journals (Sweden)

    Omid Zandi

    2017-07-01

    Full Text Available We have constructed an experimental setup for gas phase electron diffraction with femtosecond resolution and a high average beam current. While gas electron diffraction has been successful at determining molecular structures, it has been a challenge to reach femtosecond resolution while maintaining sufficient beam current to retrieve structures with high spatial resolution. The main challenges are the Coulomb force that leads to broadening of the electron pulses and the temporal blurring that results from the velocity mismatch between the laser and electron pulses as they traverse the sample. We present here a device that uses pulse compression to overcome the Coulomb broadening and deliver femtosecond electron pulses on a gas target. The velocity mismatch can be compensated using laser pulses with a tilted intensity front to excite the sample. The temporal resolution of the setup was determined with a streak camera to be better than 400 fs for pulses with up to half a million electrons and a kinetic energy of 90 keV. The high charge per pulse, combined with a repetition rate of 5 kHz, results in an average beam current that is between one and two orders of magnitude higher than previously demonstrated.

  17. Nano- and femtosecond UV laser pulses to immobilize biomolecules onto surfaces with preferential orientation

    Science.gov (United States)

    Lettieri, S.; Avitabile, A.; Della Ventura, B.; Funari, R.; Ambrosio, A.; Maddalena, P.; Valadan, M.; Velotta, R.; Altucci, C.

    2014-10-01

    By relying on the photonic immobilization technique of antibodies onto surfaces, we realized portable biosensors for light molecules based on the use of quartz crystal microbalances, given the linear dependence of the method on the laser pulse intensity. Here, we compare the quality of the anchoring method when using nanosecond (260 nm, 25 mJ/pulse, 5 ns, 10 Hz rep. rate) and femtosecond (258 nm, 25 μJ/pulse, 150 fs, 10 kHz rep. rate) laser source, delivering the same energy to the sample with the same average power. As a reference, we also tethered untreated antibodies by means of the passive adsorption. The results are striking: When the antibodies are irradiated with the femtosecond pulses, the deposition on the gold plate is much more ordered than in the other two cases. The effects of UV pulses irradiation onto the antibodies are also analyzed by measuring absorption and fluorescence and suggest the occurrence of remarkable degradation when nanosecond pulses are used likely induced by a larger thermal coupling. In view of the high average power required to activate the antibodies for the achievement of the photonic immobilization technique, we conclude that femtosecond rather than nanosecond laser pulses have to be used.

  18. Femtosecond laser micromachining of polylactic acid/graphene composites for designing interdigitated microelectrodes for sensor applications

    Science.gov (United States)

    Paula, Kelly T.; Gaál, Gabriel; Almeida, G. F. B.; Andrade, M. B.; Facure, Murilo H. M.; Correa, Daniel S.; Riul, Antonio; Rodrigues, Varlei; Mendonça, Cleber R.

    2018-05-01

    There is an increasing interest in the last years towards electronic applications of graphene-based materials and devices fabricated from patterning techniques, with the ultimate goal of high performance and temporal resolution. Laser micromachining using femtosecond pulses is an attractive methodology to integrate graphene-based materials into functional devices as it allows changes to the focal volume with a submicrometer spatial resolution due to the efficient nonlinear nature of the absorption, yielding rapid prototyping for innovative applications. We present here the patterning of PLA-graphene films spin-coated on a glass substrate using a fs-laser at moderate pulse energies to fabricate interdigitated electrodes having a minimum spatial resolution of 5 μm. Raman spectroscopy of the PLA-graphene films indicated the presence of multilayered graphene fibers. Subsequently, the PLA-graphene films were micromachined using a femtosecond laser oscillator delivering 50-fs pulses and 800 nm, where the pulse energy and scanning speed was varied in order to determine the optimum irradiation parameters (16 nJ and 100 μm/s) to the fabrication of microstructures. The micromachined patterns were characterized by optical microscopy and submitted to electrical measurements in liquid samples, clearly distinguishing all tastes tested. Our results confirm the femtosecond laser micromachining technique as an interesting approach to efficiently pattern PLA-graphene filaments with high precision and minimal mechanical defects, allowing the easy fabrication of interdigitated structures and an alternative method to those produced by conventional photolithography.

  19. Efficient femtosecond driven SOX 17 delivery into mouse embryonic stem cells: differentiation studies

    Science.gov (United States)

    Thobakgale, Lebogang; Manoto, Sello Lebohang; Lemboumba, Satuurnin Ombinda; Maaza, Malik; Mthunzi-Kufa, Patience

    2017-02-01

    Embryonic stem cells have great promise in regenerative medicine because of their ability to self-renew and differentiate into various cell types. Delivery of therapeutic genes into cells has already been achieved using of chemical agents and viral vectors with high transfection efficiencies. However, these methods have also been documented as toxic and in the latter case they can cause latent cell infections. In this study we use femtosecond laser pulses to optically deliver genetic material in mouse embryonic stem cells. Femtosecond laser pulses in contrast to the conventional approach, minimises the risk of unwanted side effects because photons are used to create transient pores on the membrane which allow free entry of molecules with no need for delivery agents. Using an Olympus microscope, fluorescence imaging of the samples post irradiation was performed and decreased expression of stage specific embryonic antigen one (SSEA-1) consistent with on-going cellular differentiation was observed. Our results also show that femtosecond laser pulses were effective in delivering SOX 17 plasmid DNA (pSOX17) which resulted in the differentiation of mouse embryonic stem cells into endoderm cells. We thus concluded that laser transfection of stem cells for the purpose of differentiation, holds potential for applications in tissue engineering as a method of generating new cell lines.

  20. Optimal Control of Atomic, Molecular and Electron Dynamics with Tailored Femtosecond Laser Pulses

    Science.gov (United States)

    Brixner, Tobias; Pfeifer, Thomas; Gerber, Gustav; Wollenhaupt, Matthias; Baumert, Thomas

    With the invention of the laser, the dream was realized to actively exert control over quantum systems. Active control over the dynamics of quantum mechanical systems is a fascinating perspective in modern physics. Cleavage and creation of predetermined chemical bonds, selective population transfer in atoms and molecules, and steering the dynamics of bound and free electrons have been important milestones along this way. A promising tool for this purpose is available with femtosecond laser technologies. In this chapter we review some of our work on adaptive femtosecond quantum control where a learning algorithm and direct experimental feedback signals are employed to optimize user-defined objectives. Femtosecond laser pulses are modified in frequency-domain pulse shapers, which apart from phase- and intensity-modulation can also modify the polarization state as a function of time. We will highlight the major advances in the field of optimal control by presenting our own illustrative experimental examples such as gas-phase and liquid-phase femtochemistry, control in weak and strong laser fields, and control of electron dynamics.

  1. Three-dimensional femtosecond laser processing for lab-on-a-chip applications

    Directory of Open Access Journals (Sweden)

    Sima Felix

    2018-02-01

    Full Text Available The extremely high peak intensity associated with ultrashort pulse width of femtosecond laser allows us to induce nonlinear interaction such as multiphoton absorption and tunneling ionization with materials that are transparent to the laser wavelength. More importantly, focusing the femtosecond laser beam inside the transparent materials confines the nonlinear interaction only within the focal volume, enabling three-dimensional (3D micro- and nanofabrication. This 3D capability offers three different schemes, which involve undeformative, subtractive, and additive processing. The undeformative processing preforms internal refractive index modification to construct optical microcomponents including optical waveguides. Subtractive processing can realize the direct fabrication of 3D microfluidics, micromechanics, microelectronics, and photonic microcomponents in glass. Additive processing represented by two-photon polymerization enables the fabrication of 3D polymer micro- and nanostructures for photonic and microfluidic devices. These different schemes can be integrated to realize more functional microdevices including lab-on-a-chip devices, which are miniaturized laboratories that can perform reaction, detection, analysis, separation, and synthesis of biochemical materials with high efficiency, high speed, high sensitivity, low reagent consumption, and low waste production. This review paper describes the principles and applications of femtosecond laser 3D micro- and nanofabrication for lab-on-a-chip applications. A hybrid technique that promises to enhance functionality of lab-on-a-chip devices is also introduced.

  2. Dynamics of photoprocesses induced by femtosecond infrared radiation in free molecules and clusters of iron pentacarbonyl

    International Nuclear Information System (INIS)

    Kompanets, V. O.; Lokhman, V. N.; Poydashev, D. G.; Chekalin, S. V.; Ryabov, E. A.

    2016-01-01

    The dynamics of photoprocesses induced by femtosecond infrared radiation in free Fe(CO) 5 molecules and their clusters owing to the resonant excitation of vibrations of CO bonds in the 5-μm range has been studied. The technique of infrared excitation and photoionization probing (λ = 400 nm) by femtosecond pulses has been used in combination with time-of-flight mass spectrometry. It has been found that an infrared pulse selectively excites vibrations of CO bonds in free molecules, which results in a decrease in the yield of the Fe(CO) 5 + molecular ion. Subsequent relaxation processes have been analyzed and the results have been interpreted. The time of the energy transfer from excited vibrations to other vibrations of the molecule owing to intramolecular relaxation has been measured. The dynamics of dissociation of [Fe(CO) 5 ] n clusters irradiated by femtosecond infrared radiation has been studied. The time dependence of the yield of free molecules has been measured under different infrared laser excitation conditions. We have proposed a model that well describes the results of the experiment and makes it possible, in particular, to calculate the profile of variation of the temperature of clusters within the “evaporation ensemble” concept. The intramolecular and intracluster vibrational relaxation rates in [Fe(CO) 5 ] n clusters have been estimated.

  3. Characteristics of calcium signaling in astrocytes induced by photostimulation with femtosecond laser

    Science.gov (United States)

    Zhao, Yuan; Zhang, Yuan; Zhou, Wei; Liu, Xiuli; Zeng, Shaoqun; Luo, Qingming

    2010-05-01

    Astrocytes have been identified to actively contribute to brain functions through Ca2+ signaling, serving as a bridge to communicate with neurons and other brain cells. However, conventional stimulation techniques are hard to apply to delicate investigations on astrocytes. Our group previously reported photostimulation with a femtosecond laser to evoke astrocytic calcium (Ca2+) waves, providing a noninvasive and efficient approach with highly precise targeting. In this work, detailed characteristics of astrocytic Ca2+ signaling induced by photostimulation are presented. In a purified astrocytic culture, after the illumination of a femtosecond laser onto one cell, a Ca2+ wave throughout the network with reduced speed is induced, and intracellular Ca2+ oscillations are observed. The intercellular propagation is pharmacologically confirmed to be mainly mediated by ATP through P2Y receptors. Different patterns of Ca2+ elevations with increased amplitude in the stimulated astrocyte are discovered by varying the femtosecond laser power, which is correspondingly followed by broader intercellular waves. These indicate that the strength of photogenerated Ca2+ signaling in astrocytes has a positive relationship with the stimulating laser power. Therefore, distinct Ca2+ signaling is feasibly available for specific studies on astrocytes by employing precisely controlled photostimulation.

  4. One-step fabrication of superhydrophobic hierarchical structures by femtosecond laser ablation

    International Nuclear Information System (INIS)

    Rukosuyev, Maxym V.; Lee, Jason; Cho, Seong Jin; Lim, Geunbae; Jun, Martin B.G.

    2014-01-01

    Highlights: • Superhydrophobic surface patterns by femtosecond laser ablation in open air. • Micron scale ridge-like structure with superimposed submicron convex features. • Hydrophobic or even superhydrophobic behavior with no additional silanization. - Abstract: Hydrophobic surface properties are sought after in many areas of research, engineering, and consumer product development. Traditionally, hydrophobic surfaces are produced by using various types of coatings. However, introduction of foreign material onto the surface is often undesirable as it changes surface chemistry and cannot provide a long lasting solution (i.e. reapplication is needed). Therefore, surface modification by transforming the base material itself can be preferable in many applications. Femtosecond laser ablation is one of the methods that can be used to create structures on the surface that will exhibit hydrophobic behavior. The goal of the presented research was to create micro and nano-scale patterns that will exhibit hydrophobic properties with no additional post treatment. As a result, dual scale patterned structures were created on the surface of steel aluminum and tungsten carbide samples. Ablation was performed in the open air with no subsequent treatment. Resultant surfaces appeared to be strongly hydrophobic or even superhydrophobic with contact angle values of 140° and higher. In conclusion, the nature of surface hydrophobicity proved to be highly dependent on surface morphology as the base materials used are intrinsically hydrophilic. It was also proven that the hydrophobicity inducing structures could be manufactured using femtosecond laser machining in a single step with no subsequent post treatment

  5. Selective ablation of dental enamel and dentin using femtosecond laser pulses

    International Nuclear Information System (INIS)

    Lizarelli, R F Z; Costa, M M; Carvalho-Filho, E; Bagnato, V S; Nunes, F D

    2008-01-01

    The study of the interaction of intense laser light with matter, as well as transient response of atoms and molecules is very appropriated because of the laser energy concentration in a femtosecond optical pulses. The fundamental problem to be solved is to find tools and techniques which allow us to observe and manipulate on a femtosecond time scale the photonics events on and into the matter. Six third human extracted molars were exposed to a femtosecond Ti:Sapphire Q-switched and mode locked laser (Libra-S, Coherent, Palo Alto, CA, USA), emitting pulses with 70 fs width, radiation wavelength of 801 nm, at a constant pulse repetition rate of 1 KHz. The laser was operated at different power levels (70 to 400 mW) with constant exposition time of 10 seconds, at focused and defocused mode. Enamel and dentin surfaces were evaluated concerned ablation rate and morphological aspects under scanning electron microscopic. The results in this present experiment suggest that at the focused mode and under higher average power, enamel tissues present microcavities with higher depth and very precise edges, but, while dentin shows a larger melt-flushing, lower depth and melting and solidification aspect. In conclusion, it is possible to choose hard or soft ablation, under lower and higher average power, respectively, revealing different aspects of dental enamel and dentin, depending on the average power, fluence and distance from the focal point of the ultra-short pulse laser on the tooth surface

  6. Vibration-Assisted Femtosecond Laser Drilling with Controllable Taper Angles for AMOLED Fine Metal Mask Fabrication

    Science.gov (United States)

    Choi, Wonsuk; Kim, Hoon Young; Jeon, Jin Woo; Chang, Won Seok; Cho, Sung-Hak

    2017-01-01

    This study investigates the effect of focal plane variation using vibration in a femtosecond laser hole drilling process on Invar alloy fabrication quality for the production of fine metal masks (FMMs). FMMs are used in the red, green, blue (RGB) evaporation process in Active Matrix Organic Light-Emitting Diode (AMOLED) manufacturing. The taper angle of the hole is adjusted by attaching the objective lens to a micro-vibrator and continuously changing the focal plane position. Eight laser pulses were used to examine how the hole characteristics vary with the first focal plane’s position, where the first pulse is focused at an initial position and the focal planes of subsequent pulses move downward. The results showed that the hole taper angle can be controlled by varying the amplitude of the continuously operating vibrator during femtosecond laser hole machining. The taper angles were changed between 31.8° and 43.9° by adjusting the vibrator amplitude at a frequency of 100 Hz. Femtosecond laser hole drilling with controllable taper angles is expected to be used in the precision micro-machining of various smart devices. PMID:28772571

  7. Three-dimensional femtosecond laser processing for lab-on-a-chip applications

    Science.gov (United States)

    Sima, Felix; Sugioka, Koji; Vázquez, Rebeca Martínez; Osellame, Roberto; Kelemen, Lóránd; Ormos, Pal

    2018-02-01

    The extremely high peak intensity associated with ultrashort pulse width of femtosecond laser allows us to induce nonlinear interaction such as multiphoton absorption and tunneling ionization with materials that are transparent to the laser wavelength. More importantly, focusing the femtosecond laser beam inside the transparent materials confines the nonlinear interaction only within the focal volume, enabling three-dimensional (3D) micro- and nanofabrication. This 3D capability offers three different schemes, which involve undeformative, subtractive, and additive processing. The undeformative processing preforms internal refractive index modification to construct optical microcomponents including optical waveguides. Subtractive processing can realize the direct fabrication of 3D microfluidics, micromechanics, microelectronics, and photonic microcomponents in glass. Additive processing represented by two-photon polymerization enables the fabrication of 3D polymer micro- and nanostructures for photonic and microfluidic devices. These different schemes can be integrated to realize more functional microdevices including lab-on-a-chip devices, which are miniaturized laboratories that can perform reaction, detection, analysis, separation, and synthesis of biochemical materials with high efficiency, high speed, high sensitivity, low reagent consumption, and low waste production. This review paper describes the principles and applications of femtosecond laser 3D micro- and nanofabrication for lab-on-a-chip applications. A hybrid technique that promises to enhance functionality of lab-on-a-chip devices is also introduced.

  8. High aspect ratio nanoholes in glass generated by femtosecond laser pulses with picosecond intervals

    Science.gov (United States)

    Ahn, Sanghoon; Choi, Jiyeon; Noh, Jiwhan; Cho, Sung-Hak

    2018-02-01

    Because of its potential uses, high aspect ratio nanostructures have been interested for last few decades. In order to generate nanostructures, various techniques have been attempted. Femtosecond laser ablation is one of techniques for generating nanostructures inside a transparent material. For generating nanostructures by femtosecond laser ablation, previous studies have been attempted beam shaping such as Bessel beam and temporal tailored beam. Both methods suppress electron excitation at near surface and initiate interference of photons at certain depth. Recent researches indicate that shape of nanostructures is related with temporal change of electron density and number of self-trapped excitons. In this study, we try to use the temporal change of electron density induced by femtosecond laser pulse for generating high aspect ratio nanoholes. In order to reveal the effect of temporal change of electron density, secondary pulses are irradiated from 100 to 1000 ps after the irradiation of first pulse. Our result shows that diameter of nanoholes is increasing and depth of nanoholes is decreasing as pulse to pulse interval is getting longer. With manipulating of pulse to pulse interval, we could generate high aspect ratio nanoholes with diameter of 250-350 nm and depth of 4∼6 μm inside a glass.

  9. Femtosecond timing distribution and control for next generation accelerators and light sources

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Li -Jin [Idesta Quantum Electronics, LLC, Newton, NJ (United States)

    2014-03-31

    Femtosecond Timing Distribution At LCLS Free-electron-lasers (FEL) have the capability of producing high photon flux from the IR to the hard x-ray wavelength range and to emit femtosecond and eventually even attosecond pulses. This makes them an ideal tool for fundamental as well as applied re-search. Timing precision at the Stanford Linear Coherent Light Source (LCLS) between the x-ray FEL (XFEL) and ultrafast optical lasers is currently no better than 100 fs RMS. Ideally this precision should be much better and could be limited only by the x-ray pulse duration, which can be as short as a few femtoseconds. An increasing variety of science problems involving electron and nuclear dynamics in chemical and material systems will become accessible as the timing improves to a few femtoseconds. Advanced methods of electron beam conditioning or pulse injection could allow the FEL to achieve pulse durations less than one femtosecond. The objective of the work described in this proposal is to set up an optical timing distribution system based on mode locked Erbium doped fiber lasers at LCLS facility to improve the timing precision in the facility and allow time stamping with a 10 fs precision. The primary commercial applications for optical timing distributions systems are seen in the worldwide accelerator facilities and next generation light sources community. It is reasonable to expect that at least three major XFELs will be built in the next decade. In addition there will be up to 10 smaller machines, such as FERMI in Italy and Maxlab in Sweden, plus the market for upgrading already existing facilities like Jefferson Lab. The total market is estimated to be on the order of a 100 Million US Dollars. The company owns the exclusive rights to the IP covering the technology enabling sub-10 fs synchronization systems. Testing this technology, which has set records in a lab environment, at LCLS, hence in a real world scenario, is an important corner stone of bringing the

  10. Highly effective 525 nm femtosecond laser crosslinking of collagen and strengthening of a human donor cornea

    Science.gov (United States)

    Shavkuta, B. S.; Gerasimov, M. Y.; Minaev, N. V.; Kuznetsova, D. S.; Dudenkova, V. V.; Mushkova, I. A.; Malyugin, B. E.; Kotova, S. L.; Timashev, P. S.; Kostenev, S. V.; Chichkov, B. N.; Bagratashvili, V. N.

    2018-01-01

    A two-photon laser femtosecond crosslinking process at the wavelength of 525 nm was studied in a human donor cornea in the presence of riboflavin using two-photon optical microscopy and nanoindentation. It was shown that such an approach results in efficient crosslinking of the corneal collagen and a significant (three-fold) increase in the Young’s modulus of the corneal structure. Application of a femtosecond laser with the wavelength of 525 nm allows a drastic enhancement of efficiency in the presence of riboflavin on human corneas and a 50-fold reduction of the laser treatment duration in comparison with the use of a femtosecond laser with the wavelength of 760 nm. We relate this effect to a significant growth in the coefficient of two-photon absorption due to the laser wavelength falling within the edge of the photoinitiator (riboflavin) absorption band. Our studies on a donor human cornea demonstrate the good potential for the clinical application of a femtosecond laser with the wavelength of 525 nm for increasing the cornea rigidity using the two-photon laser femtosecond crosslinking technique.

  11. Preclinical investigations of articular cartilage ablation with femtosecond and pulsed infrared lasers as an alternative to microfracture surgery

    Science.gov (United States)

    Su, Erica; Sun, Hui; Juhasz, Tibor; Wong, Brian J. F.

    2014-01-01

    Abstract. Microfracture surgery is a bone marrow stimulation technique for treating cartilage defects and injuries in the knee. Current methods rely on surgical skill and instrumentation. This study investigates the potential use of laser technology as an alternate means to create the microfracture holes. Lasers investigated in this study include an erbium:YAG laser (λ=2.94  μm), titanium:sapphire femtosecond laser system (λ=1700  nm), and Nd:glass femtosecond laser (λ=1053  nm). Bovine samples were ablated at fluences of 8 to 18  J/cm2 with the erbium:YAG laser, at a power of 300±15  mW with the titanium:sapphire femtosecond system, and at an energy of 3  μJ/pulse with the Nd:glass laser. Samples were digitally photographed and histological sections were taken for analysis. The erbium:YAG laser is capable of fast and efficient ablation; specimen treated with fluences of 12 and 18  J/cm2 experienced significant amounts of bone removal and minimal carbonization with saline hydration. The femtosecond laser systems successfully removed cartilage but not clinically significant amounts of bone. Precise tissue removal was possible but not to substantial depths due to limitations of the systems. With additional studies and development, the use of femtosecond laser systems to ablate bone may be achieved at clinically valuable ablation rates. PMID:25200394

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

    Science.gov (United States)

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

    2013-04-08

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

  13. Comparison of ultraviolet femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry analysis in glass, monazite, and zircon.

    Science.gov (United States)

    Poitrasson, Franck; Mao, Xianglei; Mao, Samuel S; Freydier, Rémi; Russo, Richard E

    2003-11-15

    We compared the analytical performance of ultraviolet femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). The benefit of ultrafast lasers was evaluated regarding thermal-induced chemical fractionation, that is otherwise well known to limit LA-ICPMS. Both lasers had a Gaussian beam energy profile and were tested using the same ablation system and ICPMS analyzer. Resulting crater morphologies and analytical signals showed more straightforward femtosecond laser ablation processes, with minimal thermal effects. Despite a less stable energy output, the ultrafast laser yielded elemental (Pb/U, Pb/Th) and Pb isotopic ratios that were more precise, repeatable, and accurate, even when compared to the best analytical conditions for the nanosecond laser. Measurements on NIST glasses, monazites, and zircon also showed that femtosecond LA-ICPMS calibration was less matrix-matched dependent and therefore more versatile.

  14. Temperature effects on the geometry during the formation of micro-holes fabricated by femtosecond laser in PMMA

    Science.gov (United States)

    Zhang, Fan; Dong, Xinran; Yin, Kai; Song, Yuxin; Tian, Yaxiang; Wang, Cong; Duan, Ji'an

    2018-03-01

    In this study, the temperature effects on hole geometry of the PMMA during micro-holes drilling by femtosecond laser has been studied under various pulse energy and number of pulse. The laser-induced hole's diameter is considerably increased by 73% as the temperature rises from 20 °C to 90 °C. Remarkable enhancement in the removal volume of micro-hole is also observed under high temperature. The possible mechanism for such changes is discussed in detail on account of optical absorption enhancement and higher density of surface plasma. The atomic percentage of oxygen obviously increases with the increase of temperature, which is beneficial to femtosecond laser fabrication of PMMA micro-hole. The spatter area of micro-hole has been found to tremendously extend with the increase of temperature, which is due to recoil pressure effect. These results demonstrate that temperature plays a crucial role to tailor micro-hole fabrication by femtosecond laser.

  15. Moorfields technique of donor cornea mounting for femtosecond-assisted keratoplasty: use of viscoelastic in the artificial anterior chamber.

    Science.gov (United States)

    Iovieno, Alfonso; Chowdhury, Vivek; Stevens, Julian D; Maurino, Vincenzo

    2012-07-01

    Appropriate mounting and cutting of the donor sclero-corneal cap is often cumbersome during femtosecond laser-assisted keratoplasty. The authors describe a technique for donor cornea femtosecond laser cutting using ophthalmic viscoelastic devices. The donor sclero-corneal cap is mounted on the artificial anterior chamber using a dispersive ophthalmic viscoelastic device instead of saline solution. The chances of artificial anterior chamber pressure loss, inadequate applanation, and fluid leaks are consistently reduced with the use of dispersive ophthalmic viscoelastic devices. The speed of donor femtosecond laser cutting is increased. The viscosity and elasticity of dispersive ophthalmic viscoelastic devices greatly assist the procedure with regard to ease of applanation, corneal endothelium protection, and decreased distortion of the applanated cornea. Copyright 2012, SLACK Incorporated.

  16. Kilohertz generation of high contrast polarization states for visible femtosecond pulses via phase-locked acousto-optic pulse shapers

    Energy Technology Data Exchange (ETDEWEB)

    Seiler, Hélène; Walsh, Brenna; Palato, Samuel; Kambhampati, Patanjali, E-mail: pat.kambhampati@mcgill.ca [Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8 (Canada); Thai, Alexandre; Forget, Nicolas [Fastlite, 1900 route des Crêtes, 06560 Valbonne (France); Crozatier, Vincent [Fastlite, Centre Scientifique d' Orsay, Bât.503, Plateau du Moulon, BP 45 Orsay (France)

    2015-09-14

    We present a detailed analysis of a setup capable of arbitrary amplitude, phase, and polarization shaping of broadband visible femtosecond pulses at 1 kHz via a pair of actively phase stabilized acousto-optic programmable dispersive filters arranged in a Mach-Zehnder interferometer geometry. The setup features phase stability values around λ/225 at 580 nm as well as degrees of polarization of at least 0.9 for any polarization state. Both numbers are important metrics to evaluate a setup's potential for applications based on polarization-shaped femtosecond pulses, such as fully coherent multi-dimensional electronic spectroscopy.

  17. Cell spreading on titanium periodic nanostructures with periods of 200, 300 and 600 nm produced by femtosecond laser irradiation

    Science.gov (United States)

    Tsukamoto, M.; Kawa, T.; Shinonaga, T.; Chen, P.; Nagai, A.; Hanawa, T.

    2016-02-01

    Titanium (Ti) is an important biomaterial. We have used femtosecond laser irradiation to form periodic nanostructures on Ti plate for control of the cell spreading. In this study, periodic nanostructures with periodicities of 200, 300 and 600 nm were formed on a Ti plates using a femtosecond laser with wavelengths of 258, 388 and 775 nm, respectively. Cell spreading on the Ti plate for periodic nanostructures with periodicity of 200 nm lacked a definite direction, whereas cell spreadings on the Ti plate for periodic nanostructures with periodicities of 300 and 600 nm occurred along the grooves.

  18. Generation of quantum beams in large clusters irradiated by Super-Intense, high - contrast femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Faenov, A.Ya.; Pikuz, T.A. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Kyoto (Japan); Joint Institute for High Temperatures RAS, Moscow (Russian Federation); Fukuda, Y.; Nakamura, T.; Bulanov, S.V.; Hayashi, Y.; Kotaki, H.; Pirozhkov, A.S.; Kawachi, T.; Kando, M. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Kyoto (Japan); Skobelev, I.Yu.; Fortov, V.E. [Joint Institute for High Temperatures RAS, Moscow (Russian Federation); Chen, L.M.; Zhang, L.; Yan, W.C.; Yuan, D.W.; Mao, J.Y.; Wang, Z.H.; Ma, J.L. [Institute of Physics, Chinese Academy of Sciences, Beijing (China); Kato, Y. [The Graduate School for the Creation of New Photonics Industries, Hamamatsu, Shizuoka (Japan)

    2013-02-15

    A short review of our experimental studies on generation of photon and particle beams in submicron clusters irradiated by intense, high-contrast ({proportional_to} 10{sup 8}-10{sup 10}) femtosecond laser pulses is presented. It is shown that highlyefficient laser-cluster interaction allows creating bright sources of X-ray, high-energy electron and ion beams. The examples of applications of femtosecond-laser-produced cluster plasmas (FLPCP) for X-ray and ion beams radiography are presented. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. A Real-Time Terahertz Time-Domain Polarization Analyzer with 80-MHz Repetition-Rate Femtosecond Laser Pulses

    Science.gov (United States)

    Watanabe, Shinichi; Yasumatsu, Naoya; Oguchi, Kenichi; Takeda, Masatoshi; Suzuki, Takeshi; Tachizaki, Takehiro

    2013-01-01

    We have developed a real-time terahertz time-domain polarization analyzer by using 80-MHz repetition-rate femtosecond laser pulses. Our technique is based on the spinning electro-optic sensor method, which we recently proposed and demonstrated by using a regenerative amplifier laser system; here we improve the detection scheme in order to be able to use it with a femtosecond laser oscillator with laser pulses of a much higher repetition rate. This improvement brings great advantages for realizing broadband, compact and stable real-time terahertz time-domain polarization measurement systems for scientific and industrial applications. PMID:23478599

  20. High-power femtosecond pulse generation in a passively mode-locked Nd:SrLaAlO4 laser

    Science.gov (United States)

    Liu, Shan-De; Dong, Lu-Lu; Zheng, Li-He; Berkowski, Marek; Su, Liang-Bi; Ren, Ting-Qi; Peng, Yan-Dong; Hou, Jia; Zhang, Bai-Tao; He, Jing-Liang

    2016-07-01

    A high optical quality Nd:SrLaAlO4 (Nd:SLA) crystal was grown using the Czochralski method and showed broad fluorescence spectrum with a full width at half maximum value of 34 nm, which is beneficial for generating femtosecond laser pulses. A stable diode-pumped passively mode-locked femtosecond Nd:SLA laser with 458 fs pulse duration was achieved for the first time at a central wavelength of 1077.9 nm. The average output power of the continuous-wave mode-locked laser was 520 mW and the repetition rate was 78.5 MHz.

  1. Efficient bragg grating fabrication in Ge-rich fibre by high-intensity femtosecond 264 mm irradation

    DEFF Research Database (Denmark)

    Slattery, S.A.; Nikogasyan, D.N.; Plougmann, Nikolai

    2004-01-01

    Fibre Bragg gratings (FBGs) are usually fabricated by UV laser light (typically, 248 nm radiation from a KrF* excimer laser), which spectrally coincides with the absorption band of defects in germanosilicate fibre core [1, 2]. Recently, it was demonstrated that the use of highintensity femtosecond...... silica glass and corresponding defects [5]. In this Letter we study FBG recording in a highly-nonlinear fibre (HNLF, OFS Denmark), employing 264 nm femtosecond pulses with a peak intensity of around 180 GW=cm2. refractive fluence, kJ/cm2....

  2. Femtosecond stimulated Raman spectroscopy as a tool to detect molecular vibrations in ground and excited electronic states

    Energy Technology Data Exchange (ETDEWEB)

    Gelin, Maxim F.; Domcke, Wolfgang [Department of Chemistry, Technische Universität München, D-85747 Garching (Germany); Rao, B. Jayachander [Departamento de Química and Centro de Química, Universidade de Coimbra, 3004-535 Coimbra (Portugal)

    2016-05-14

    We give a detailed theoretical analysis of the simplest variant of femtosecond stimulated Raman spectroscopy, where a picosecond Raman pump pulse and a femtosecond Raman probe pulse are applied resonantly to a chromophore in thermal equilibrium in the ground electronic state. We demonstrate that this technique is capable of the detection of dephasing-free Raman-like lines revealing vibrational modes not only in the electronic ground state but also in the excited electronic state of the chromophore. The analytical results obtained with simplifying assumptions for the shape of the laser pulses are substantiated by numerical simulations with realistic laser pulses, employing the equation-of-motion phase-matching approach.

  3. Femtosecond laser-assisted sutureless anterior lamellar keratoplasty for superficial corneal opacities.

    Science.gov (United States)

    Jabbarvand, Mahmoud; Hashemian, Hesam; Khodaparast, Mehdi; Ghadimi, Hadi; Khalilipour, Elias

    2014-11-01

    To evaluate the visual and refractive outcomes, endothelial cell count (ECC), ocular surface changes, corneal aberrations, and biomechanical profile changes after femtosecond laser-assisted anterior lamellar keratoplasty surgery for superficial corneal scars. Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran. Prospective case series. Patients with superficial corneal scars had femtosecond laser-assisted anterior lamellar keratoplasty. Visual and refractive results, ECC, ocular surface changes, corneal aberrations, and biomechanical profiles were assessed preoperatively and for 1 year postoperatively. Nineteen eyes (19 patients) were evaluated. A significant decline occurred in refractive astigmatism and corneal astigmatism after 1 year. There was a nonsignificant reduction in corneal hysteresis and the corneal resistance factor from preoperatively to 1 year postoperatively. The corneal-compensated intraocular pressure (IOP) and Goldmann-correlated IOP increased during the follow-up; the increase was not significant. A statistically insignificant reduction in the root mean square for trefoil and spherical aberrations occurred between 1 month and 1 year postoperatively (P=.1 and P=.4, respectively). The decreases in primary coma and total higher-order aberrations approached significance (P=.08 and P=.07, respectively). There were no significant changes in the central corneal thickness, ECC, or ocular surface parameters. No intraoperative complications occurred. Femtosecond laser-assisted anterior lamellar keratoplasty was an efficient and safe procedure for improving the quality of vision in patients with anterior corneal pathology, and the results remained stable during the 1-year follow-up. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  4. Multiparameter Flowfield Measurements in High-Pressure, Cryogenic Environments Using Femtosecond Lasers

    Science.gov (United States)

    Burns, Ross A.; Danehy, Paul M.; Peters, Christopher J.

    2016-01-01

    Femtosecond laser electronic excitation tagging (FLEET) and Rayleigh scattering (RS) from a femtosecond laser are demonstrated in the NASA Langley 0.3-m Transonic Cryogenic Tunnel (TCT). The measured signals from these techniques are examined for their thermodynamic dependencies in pure nitrogen. The FLEET signal intensity and signal lifetimes are found to scale primarily with the gas density, as does the RS signal. Several models are developed, which capture these physical behaviors. Notably, the FLEET and Rayleigh scattering intensities scale linearly with the flow density, while the FLEET signal decay rates are a more complex function of the thermodynamic state of the gas. The measurement of various flow properties are demonstrated using these techniques. While density was directly measured from the signal intensities and FLEET signal lifetime, temperature and pressure were measured using the simultaneous FLEET velocity measurements while assuming the flow had a constant total enthalpy. Measurements of density, temperature, and pressure from the FLEET signal are made with accuracies as high as 5.3 percent, 0.62 percent, and 6.2 percent, respectively, while precisions were approximately 10 percent, 0.26 percent, and 11 percent for these same quantities. Similar measurements of density from Rayleigh scattering showed an overall accuracy of 3.5 percent and a precision of 10.2 percent over a limited temperature range (T greater than 195 K). These measurements suggest a high degree of utility at using the femtosecond-laser based diagnostics for making multiparameter measurements in high-pressure, cryogenic environments such as large-scale TCT facilities.

  5. Measurements of transient electron density distributions by femtosecond X-ray diffraction

    International Nuclear Information System (INIS)

    Freyer, Benjamin

    2013-01-01

    This thesis concerns measurements of transient charge density maps by femtosecond X-ray diffraction. Different X-ray diffraction methods will be considered, particularly with regard to their application in femtosecond X-ray diffraction. The rotation method is commonly used in stationary X-ray diffraction. In the work in hand an X-ray diffraction experiment is demonstrated, which combines the method with ultrafast X-ray pulses. This experiment is the first implementation which makes use of the rotation method to map transient intensities of a multitude of Bragg reflections. As a prototype material Bismuth is used, which previously was studied frequently by femtosecond X-ray diffraction by measuring Bragg reflections successively. The experimental results of the present work are compared with the literature data. In the second part a powder-diffraction experiment will be presented, which is used to study the dynamics of the electron-density distribution on ultrafast time scales. The experiment investigates a transition metal complex after photoexcitation of the metal to ligand charge transfer state. Besides expected results, i. e. the change of the bond length between the metal and the ligand and the transfer of electronic charge from the metal to the ligand, a strong contribution of the anion to the charge transfer was found. Furthermore, the charge transfer has predominantly a cooperative character. That is, the excitation of a single complex causes an alteration of the charge density of several neighboring units. The results show that more than 30 transition-metal complexes and 60 anions contribute to the charge transfer. This collective response is a consequence of the strong coulomb interactions of the densely packed ions.

  6. Reduced myofibroblast differentiation on femtosecond laser treated 316LS stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Oberringer, Martin [Department of Trauma, Hand and Reconstructive Surgery, Saarland University, Homburg (Germany); Akman, Erhan [Laser Technologies Research and Application Center (LATARUM), Kocaeli University, Yenikoey/Kocaeli (Turkey); Lee, Juseok [CVD/Biosurfaces Division, INM - Leibniz Institute for New Materials, Saarbruecken (Germany); Metzger, Wolfgang [Department of Trauma, Hand and Reconstructive Surgery, Saarland University, Homburg (Germany); Akkan, Cagri Kaan [CVD/Biosurfaces Division, INM - Leibniz Institute for New Materials, Saarbruecken (Germany); Kacar, Elif [Laser Technologies Research and Application Center (LATARUM), Kocaeli University, Yenikoey/Kocaeli (Turkey); Demir, Arif [Laser Technologies Research and Application Center (LATARUM), Kocaeli University, Yenikoey/Kocaeli (Turkey); BEAM Ar-Ge Optic, Laser and Spectroscopy, KOU Technopark, Kocaeli, 41275 (Turkey); Abdul-Khaliq, Hashim [Clinic for Pediatric Cardiology, Saarland University Hospital, Homburg (Germany); Puetz, Norbert; Wennemuth, Gunther [Department of Anatomy and Cell Biology, Saarland University, Homburg (Germany); Pohlemann, Tim [Department of Trauma, Hand and Reconstructive Surgery, Saarland University, Homburg (Germany); Veith, Michael [CVD/Biosurfaces Division, INM - Leibniz Institute for New Materials, Saarbruecken (Germany); Aktas, Cenk, E-mail: cenk.aktas@inm-gmbh.de [CVD/Biosurfaces Division, INM - Leibniz Institute for New Materials, Saarbruecken (Germany)

    2013-03-01

    In-stent restenosis is a common complication after stent surgery which leads to a dangerous wall narrowing of a blood vessel. Laser assisted patterning is one of the effective methods to modify the stent surface to control cell-surface interactions which play a major role in the restenosis. In this current study, 316LS stainless steel substrates are structured by focusing a femtosecond laser beam down to a spot size of 50 {mu}m. By altering the laser induced spot density three distinct surfaces (low density (LD), medium density (MD) and high density (HD)) were prepared. While such surfaces are composed of primary microstructures, due to fast melting and re-solidification by ultra-short laser pulses, nanofeatures are also observed as secondary structures. Following a detailed surface characterization (chemical and physical properties of the surface), we used a well-established co-culture assay of human microvascular endothelial cells and human fibroblasts to check the cell compatibility of the prepared surfaces. The surfaces were analyzed in terms of cell adherence, proliferation, cell morphology and the differentiation of the fibroblast into the myofibroblast, which is a process indicating a general fibrotic shift within a certain tissue. It is observed that myofibroblast proliferation decreases significantly on laser treated samples in comparison to non-treated ones. On the other hand endothelial cell proliferation is not affected by the surface topography which is composed of micro- and nanostructures. Such surfaces may be used to modify stent surfaces for prevention or at least reduction of restenosis. - Highlights: Black-Right-Pointing-Pointer Reduced myofibroblast proliferation by micro- and nanotopography Black-Right-Pointing-Pointer Ultra-hydrophobic surfaces by femtosecond laser structuring Black-Right-Pointing-Pointer Micro- and nanostructuring of stainless steel surfaces by a femtosecond laser.

  7. Formation and metastable decomposition of unprotonated ammonia cluster ions upon femtosecond ionization

    International Nuclear Information System (INIS)

    Buzza, S.A.; Wei, S.; Purnell, J.; Castleman, A.W. Jr.

    1995-01-01

    The formation and metastable dissociation mechanism of unprotonated ammonia cluster ions, (NH 3 ) + n , produced by multiphoton ionization (MPI) at 624 nm and a nominal pulse width of 350 fs, are investigated through a reflectron time-of-flight (TOF) mass spectrometric technique. Detection of the unprotonated ions after femtosecond and nanosecond multiphoton ionization under various intensity conditions is explained. The role of the energy of the ionizing photons, and the observation of these ions after femtosecond MPI is examined. The formation of the unprotonated series is found to be a function of intensity in the case of ionization on the nanosecond time scale, but not so for the femtosecond time domain. The results can be explained in terms of ionization mechanisms and ionizing pulse durations. The findings of the present study suggest that the unprotonated ions are trapped behind the barrier to intracluster proton transfer and/or concomitant NH 2 loss. The studies of metastable decomposition also reveal that the unprotonated ammonia cluster ions dissociate in the field-free region of the TOF by losing an NH 2 radical rather than via the evaporative loss of NH 3 as occurs for protonated clusters. Additionally, isotopic investigations of the unimolecular decay reveal a strong dependence on the conditions of cluster formation. The cluster formation condition dependence of the unimolecular decay is further investigated by altering formation temperatures and observing the consequences reflected by changes in the spontaneous metastable decay rate constant. This is a unique example of a cluster system whose metastable dissociation does not obey an evaporative ensemble model

  8. High N-content a-C:N films elaborated by femtosecond PLD with plasma assistance

    Energy Technology Data Exchange (ETDEWEB)

    Maddi, C. [Université de Lyon, F-69003, Lyon, France, Université de Saint-Étienne, Laboratoire Hubert Curien (UMR 5516 CNRS) , 42000 Saint-Étienne (France); Donnet, C., E-mail: Christophe.Donnet@univ-st-etienne.fr [Université de Lyon, F-69003, Lyon, France, Université de Saint-Étienne, Laboratoire Hubert Curien (UMR 5516 CNRS) , 42000 Saint-Étienne (France); Loir, A.-S.; Tite, T. [Université de Lyon, F-69003, Lyon, France, Université de Saint-Étienne, Laboratoire Hubert Curien (UMR 5516 CNRS) , 42000 Saint-Étienne (France); Barnier, V. [Laboratoire Georges Friedel, Ecole Nationale Supérieure des Mines, 42023 Saint-Etienne (France); Rojas, T.C.; Sanchez-Lopez, J.C. [Instituto de Ciencia de Materiales de Sevilla (CSIC-US) , Avda. Américo Vespucio 49, 41092 Sevilla (Spain); Wolski, K. [Laboratoire Georges Friedel, Ecole Nationale Supérieure des Mines, 42023 Saint-Etienne (France); Garrelie, F. [Université de Lyon, F-69003, Lyon, France, Université de Saint-Étienne, Laboratoire Hubert Curien (UMR 5516 CNRS) , 42000 Saint-Étienne (France)

    2015-03-30

    Graphical abstract: - Highlights: • Nitrogen doped amorphous carbon films were deposited by DC reactive plasma femtosecond (fs) -PLD and conventional fs-PLD. • High nitrogen content in plasma assisted films. • More ordered sp2 rich graphitic clusters both in terms of structural and topological order. • Correlation length La of the clusters increases with nitrogen incorporation. • Formation of CN bonds at the expense of CC bonds with N content. • At the highest nitrogen concentration, terminal C≡N groups are incorporated in the film. • Correlation between film composition and plasma process. - Abstract: Amorphous carbon nitride (a-C:N) thin films are a interesting class of carbon-based electrode materials. Therefore, synthesis and characterization of these materials have found lot of interest in environmental analytical microsystems. Herein, we report the nitrogen-doped amorphous carbon thin film elaboration by femtosecond pulsed laser deposition (fs-PLD) both with and without a plasma assistance. The chemical composition and atomic bonding configuration of the films were investigated by multi-wavelength (MW) Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron energy-loss spectroscopy (EELS). The highest nitrogen content, 28 at.%, was obtained with plasma assistance. The I(D)/I(G) ratio and the G peak position increased as a function of nitrogen concentration, whereas the dispersion and full width at half maximum (FWHM) of G peak decreased. This indicates more ordered graphitic like structures in the films both in terms of topological and structural, depending on the nitrogen content. EELS investigations were correlated with MW Raman results. The interpretation of XPS spectra of carbon nitride films remains a challenge. Plasma assisted PLD in the femtosecond regime led to a significant high nitrogen concentration, which is highlighted on the basis of collisional processes in the carbon plasma plume interacting with the nitrogen

  9. Three-dimensional manipulation of femtosecond filament direction with an air bubble in water

    International Nuclear Information System (INIS)

    Cui, Qiannan; Yao, Jinping; Ni, Jielei; Cheng, Ya

    2012-01-01

    We experimentally reported a simple, novel method to manipulate the directions of femtosecond filaments in three-dimensional (3D) space taking advantage of an air bubble in water. When the air bubble is introduced to the path of filaments, it will change the propagation direction of filaments by reflection or refraction, acting as a curved mirror with a high damage threshold. In this way, we successfully realized 3D manipulation of the directions of both filaments and supercontinuum emission over a wide range of solid angles only by finely adjusting the position of the air bubble with respect to the filament. (paper)

  10. Tomographic measurement of femtosecond-laser induced stress changes in optical fibers

    International Nuclear Information System (INIS)

    Duerr, F.; Limberger, H.G.; Salathe, R.P.; Hindle, F.; Douay, M.; Fertein, E.; Przygodzki, C.

    2004-01-01

    The tomographic measurement of the residual stress profile in femtosecond-laser irradiated standard SMF-28 germanium-doped telecommunication fiber is demonstrated. The fiber is irradiated with weakly focused pulses to realize long-period fiber gratings. In the irradiated grating regions, an asymmetrical increase in axial core stress up to 6.2 kg/mm2 is found. The increase in stress is attributed to a densification of the irradiated glass matrix. The stress-induced anisotropic index distribution is calculated and related to the absolute index change in the irradiated regions

  11. Manipulation of Squeezed Two-Phonon Bound States using Femtosecond Laser Pulses

    Directory of Open Access Journals (Sweden)

    Nakamura Kazutaka G.

    2013-03-01

    Full Text Available Two-phonon bound states have been excited exclusively in ZnTe(110 via impulsive stimulated second-order Raman scattering, essentially being squeezed states due to phase coherent excitation of two identical components anticorrelated in the wave vector. By using coherent control technique with a pair of femtosecond laser pulses, the manipulation of squeezed states has been demonstrated in which both the amplitude and lifetime of coherent oscillations of squeezed states are modulated, indicating the feasibility to control the quantum noise and the quantum nature of phonon squeezed states, respectively.

  12. A femtosecond Raman generator for long wavelength two-photon and third harmonic generation imaging

    Directory of Open Access Journals (Sweden)

    J. Trägårdh

    2016-12-01

    Full Text Available We demonstrate a femtosecond single pass Raman generator based on an YVO4 crystal pumped by a high energy fiber laser at a wavelength of 1064 nm and a repetition rate of 1 MHz. The Raman generator shifts the pump wavelength to 1175 nm, in a broadband spectrum, making it suitable for multi-photon microscopy. We use the Raman generator for third harmonic generation imaging of live plant specimens as well as for two-photon fluorescence imaging of red fluorescent protein expressing HeLa cells. We demonstrate that the photo-damage to a live specimen is low.

  13. Magnetic field sensor based on fiber Bragg grating with a spiral microgroove ablated by femtosecond laser.

    Science.gov (United States)

    Dai, Yutang; Yang, Minghong; Xu, Gang; Yuan, Yinquan

    2013-07-15

    A novel magnetic field sensor based on Terfenol-D coated fiber Bragg grating with spiral microstructure was proposed and demonstrated. Through a specially-designed holder, the spiral microstructure was ablated into the fiber Bragg grating (FBG) cladding by femtosecond laser. Due to the spiral microstructure, the sensitivity of FBG coated with magnetostrictive film was enhanced greatly. When the spiral pitch is 50 μm and microgroove depth is 13.5 μm, the sensitivity of the magnetic field sensor is roughly 5 times higher than that of non-microstructured standard FBG. The response to magnetic field is reversible, and could be applicable for magnetic field detection.

  14. Extreme Environment Sensing Using Femtosecond Laser-Inscribed Fiber Bragg Gratings.

    Science.gov (United States)

    Mihailov, Stephen J; Grobnic, Dan; Hnatovsky, Cyril; Walker, Robert B; Lu, Ping; Coulas, David; Ding, Huimin

    2017-12-14

    The femtosecond laser-induced fiber Bragg grating is an effective sensor technology that can be deployed in harsh environments. Depending on the optical fiber chosen and the inscription parameters that are used, devices suitable for high temperature, pressure, ionizing radiation and strain sensor applications are possible. Such devices are appropriate for aerospace or energy production applications where there is a need for components, instrumentation and controls that can function in harsh environments. This paper will present a review of some of the more recent developments in this field.

  15. Femtosecond laser micromachining of compound parabolic concentrator fiber tipped glucose sensors

    DEFF Research Database (Denmark)

    Hassan, Hafeez Ul; Lacraz, Amédée; Kalli, Kyriacos

    2017-01-01

    We report on highly accurate femtosecond (fs) laser micromachining of a compound parabolic concentrator (CPC) fiber tip on a polymer optical fiber (POF). The accuracy is reflected in an unprecedented correspondence between the numerically predicted and experimentally found improvement in fluoresc.......5, which is only 11.6% from the predicted value. Earlier state-of-the-art fabrication of the CPC-shaped tip by fiber tapering was of so poor quality that the actual improvement was 43% lower than the predicted improvement of the ideal CPC shape....

  16. Femtosecond laser micro-inscription of optical coherence tomography resolution test artifacts.

    Science.gov (United States)

    Tomlins, Peter H; Smith, Graham N; Woolliams, Peter D; Rasakanthan, Janarthanan; Sugden, Kate

    2011-04-25

    Optical coherence tomography (OCT) systems are becoming more commonly used in biomedical imaging and, to enable continued uptake, a reliable method of characterizing their performance and validating their operation is required. This paper outlines the use of femtosecond laser subsurface micro-inscription techniques to fabricate an OCT test artifact for validating the resolution performance of a commercial OCT system. The key advantage of this approach is that by utilizing the nonlinear absorption a three dimensional grid of highly localized point and line defects can be written in clear fused silica substrates.

  17. Femtosecond laser-induced formation of submicrometer spikes on a semiconductor substrate

    Science.gov (United States)

    Mazur, Eric [Concord, MA; Shen, Mengyan [Arlington, MA

    2008-10-28

    The present invention generally provides semiconductor substrates having submicron-sized surface features generated by irradiating the surface with ultra short laser pulses. In one aspect, a method of processing a semiconductor substrate is disclosed that includes placing at least a portion of a surface of the substrate in contact with a fluid, and exposing that surface portion to one or more femtosecond pulses so as to modify the topography of that portion. The modification can include, e.g., generating a plurality of submicron-sized spikes in an upper layer of the surface.

  18. Experimental devices for the spatio-temporal characterization of femtosecond high-power laser chains

    International Nuclear Information System (INIS)

    Gallet, Valentin

    2014-01-01

    One of the advantages of high-power femtosecond lasers (TW-PW) is to obtain, at the focus of a focusing optic, very high intensities up to 10 22 W.cm -2 (i.e. an electric field of 2.7 PV.m -1 . Therefore, these lasers chains necessarily deliver beams with large diameter (up to 40 cm) and very short pulses (of the order of tens of femto-seconds). As a consequence, the spatial and temporal properties of the pulse are generally not independent. Such dependence, called spatial-temporal coupling has the effect of increasing the pulse duration and the size of the focal spot, which can lead to a significant reduction of the maximum intensity at the focus. Metrology devices commonly used on these high-power femtosecond lasers allow retrieving the spatial and temporal profiles of the pulse only in an independent manner. The aim of this thesis was to develop techniques for measuring spatio-temporal couplings in order to quantify their effect and correct them in order to obtain the maximum intensity at focus. First of all, we adapted an existing technique of spatio-temporal characterization to the measurement of TW lasers. To avoid the issues induced at the focus, such as those related to jittering, measurements were performed on the collimated beam. By adding a reference source to the original device, we managed to take into account the measurement artifacts due to thermal and mechanical variations affecting the interferometer. With this improvement, it was possible to reconstruct the complete spatio-temporal profile of the beam, particularly its wavefront. However, the limitations imposed by this technique led to the development of a new measurement device. Based on a cross-correlation, this technique consists of making the laser beam to interfere with a part of itself, small enough not to be spatio-temporally distorted. We have also implemented a variant of this device for a single-shot measurement along one transverse dimension of the pulse. Using these techniques, we

  19. The effect of femtosecond laser irradiation conditions on precipitation of silver nanoparticles in silicate glasses

    International Nuclear Information System (INIS)

    Zeng Huidan; Qiu Jianrong; Jiang Xiongwei; Zhu Congshan; Gan Fuxi

    2004-01-01

    We report the effect of femtosecond laser irradiation conditions on precipitation of silver nanoparticles in silicate glasses. Absorption spectra show that the intensity of the absorption peak due to the surface plasmon resonance of silver nanoparticles increases with increase of the light intensity of the laser beam, beam diameter in the focal plane, Rayleigh length of the focusing lens and shot number of the laser pulse. The position of the surface plasmon resonance peak remains constant regardless of the variation of the irradiation conditions. The influences of laser irradiation conditions on the size and spatial distribution of silver nanoparticles are discussed

  20. Flexible and rapidly configurable femtosecond pulse generation in the mid-IR.

    Science.gov (United States)

    Foreman, Seth M; Jones, David J; Ye, Jun

    2003-03-01

    We demonstrate a new experimental approach for flexible femtosecond pulse generation in the mid-IR by use of difference-frequency generation from two tightly synchronized Ti:sapphire lasers. The resultant mid-IR pulse train can be easily tuned, with an adjustable repetition frequency up to 100 MHz, a pulse energy of approximately 1.5 x 10(-13) J, and an intensity noise similar to that of the Ti:sapphire. Rapid switching of the mid-IR wavelength and programmable amplitude modulation are achieved by precision setting of the time delay between two original pulses.