Rapid prototyping of flexible intrafascicular electrode arrays by picosecond laser structuring.

Science.gov (United States)

Mueller, Matthias; de la Oliva, Natalia; Del Valle, Jaume; Delgado-Martínez, Ignacio; Navarro, Xavier; Stieglitz, Thomas

2017-12-01

Interfacing the peripheral nervous system can be performed with a large variety of electrode arrays. However, stimulating and recording a nerve while having a reasonable amount of channels limits the number of available systems. Translational research towards human clinical trial requires device safety and biocompatibility but would benefit from design flexibility in the development process to individualize probes. We selected established medical grade implant materials like precious metals and Parylene C to develop a rapid prototyping process for novel intrafascicular electrode arrays using a picosecond laser structuring. A design for a rodent animal model was developed in conjunction with an intrafascicular implantation strategy. Electrode characterization and optimization was performed first in saline solution in vitro before performance and biocompatibility were validated in sciatic nerves of rats in chronic implantation. The novel fabrication process proved to be suitable for prototyping and building intrafascicular electrode arrays. Electrochemical properties of the electrode sites were enhanced and tested for long-term stability. Chronic implantation in the sciatic nerve of rats showed good biocompatibility, selectivity and stable stimulation thresholds. Established medical grade materials can be used for intrafascicular nerve electrode arrays when laser structuring defines structure size in the micro-scale. Design flexibility reduces re-design cycle time and material certificates are beneficial support for safety studies on the way to clinical trials.

Rapid prototyping of flexible intrafascicular electrode arrays by picosecond laser structuring

Science.gov (United States)

Mueller, Matthias; de la Oliva, Natalia; del Valle, Jaume; Delgado-Martínez, Ignacio; Navarro, Xavier; Stieglitz, Thomas

2017-12-01

Objective. Interfacing the peripheral nervous system can be performed with a large variety of electrode arrays. However, stimulating and recording a nerve while having a reasonable amount of channels limits the number of available systems. Translational research towards human clinical trial requires device safety and biocompatibility but would benefit from design flexibility in the development process to individualize probes. Approach. We selected established medical grade implant materials like precious metals and Parylene C to develop a rapid prototyping process for novel intrafascicular electrode arrays using a picosecond laser structuring. A design for a rodent animal model was developed in conjunction with an intrafascicular implantation strategy. Electrode characterization and optimization was performed first in saline solution in vitro before performance and biocompatibility were validated in sciatic nerves of rats in chronic implantation. Main results. The novel fabrication process proved to be suitable for prototyping and building intrafascicular electrode arrays. Electrochemical properties of the electrode sites were enhanced and tested for long-term stability. Chronic implantation in the sciatic nerve of rats showed good biocompatibility, selectivity and stable stimulation thresholds. Significance. Established medical grade materials can be used for intrafascicular nerve electrode arrays when laser structuring defines structure size in the micro-scale. Design flexibility reduces re-design cycle time and material certificates are beneficial support for safety studies on the way to clinical trials.

The first picosecond terawatt CO2 laser at the Brookhaven Accelerator Test Facility

International Nuclear Information System (INIS)

Pogorelsky, I.V.; Ben-Zvi, I.; Babzien, M.

1998-02-01

The first terawatt picosecond CO 2 laser will be brought to operation at the Brookhaven Accelerator Test Facility in 1998. System consists of a single-mode TEA oscillator, picosecond semiconductor optical switch, multi-atmosphere. The authors report on design, simulation, and performance tests of the 10 atm final amplifier that allows for direct multi-joule energy extraction in a picosecond laser pulse

New and Advanced Picosecond Lasers for Tattoo Removal.

Science.gov (United States)

Adatto, Maurice A; Amir, Ruthie; Bhawalkar, Jayant; Sierra, Rafael; Bankowski, Richard; Rozen, Doran; Dierickx, Christine; Lapidoth, Moshe

2017-01-01

Early methods of tattoo removal ultimately resulted in unacceptable cosmetic outcomes. While the introduction of laser technology was an improvement over the existing chemical, mechanical, and surgical procedures, the use of nonselective tattoo removal with carbon dioxide and argon lasers led to scarring. Q-switched lasers with nanosecond (10-9) pulse domains were considered to have revolutionized tattoo treatment, by selectively heating the tattoo particles, while reducing the adverse sequelae to adjacent normal skin. Theoretical considerations of restricting pulse duration, to heat tattoo particles to higher temperatures, proposed the use of sub-nanosecond pulses to target particles with thermal relaxation times lower than the nanosecond pulses in Q-switched lasers. Initial studies demonstrated that picosecond (10-12) pulses were more effective than nanosecond pulses in clearing black tattoos. Advances in picosecond technology led to the development of commercially available lasers, incorporating several different wavelengths, to further refine pigment targeting. © 2017 S. Karger AG, Basel.

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

Science.gov (United States)

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

2013-04-08

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

Evidence of liquid phase during laser-induced periodic surface structures formation induced by accumulative ultraviolet picosecond laser beam

Energy Technology Data Exchange (ETDEWEB)

Huynh, T. T. D.; Petit, A.; Semmar, N., E-mail: nadjib.semmar@univ-orleans.fr [GREMI, UMR7344, CNRS/University of Orleans, 14 rue d' Issoudun, BP6744, 45067 Orleans Cedex 2 (France); Vayer, M. [ICMN, UMR 7374, CNRS/University of Orleans, 1b rue de la Ferollerie, CS 40059, 45071 Orleans Cedex (France); Sauldubois, A. [CME, UFR Sciences, University of Orleans, 1 Rue de Chartres, BP 6759, 45067 Orleans Cedex 2 (France)

2015-11-09

Laser-induced periodic surface structures (LIPSS) were formed on Cu/Si or Cu/glass thin films using Nd:YAG laser beam (40 ps, 10 Hz, and 30 mJ/cm{sup 2}). The study of ablation threshold is always achieved over melting when the variation of the number of pulses increases from 1 to 1000. But the incubation effect is leading to reduce the threshold of melting as increasing the number of laser pulse. Also, real time reflectivity signals exhibit typical behavior to stress the formation of a liquid phase during the laser-processing regime and helps to determine the threshold of soft ablation. Atomic Force Microscopy (AFM) analyses have shown the topology of the micro-crater containing regular spikes with different height. Transmission Electron Microscopy (TEM) allows finally to show three distinguished zones in the close region of isolated protrusions. The central zone is a typical crystallized area of few nanometers surrounded by a mixed poly-crystalline and amorphous area. Finally, in the region far from the protrusion zone, Cu film shows an amorphous structure. The real time reflectivity, AFM, and HR-TEM analyses evidence the formation of a liquid phase during the LIPSS formation in the picosecond regime.

Elemental fractionation in 785 nm picosecond and femtosecond laser ablation inductively coupled plasma mass spectrometry

International Nuclear Information System (INIS)

Shaheen, M.E.; Gagnon, J.E.; Fryer, B.J.

2015-01-01

Elemental fractionation and ICP-MS signal response were investigated for two different pulse width laser beams originating from the same laser system. Femtosecond and picosecond laser beams at pulse widths of 130 fs and 110 ps, respectively, and wavelength of 785 nm were used to ablate NIST 610 synthetic glass and SRM 1107 Naval Brass B at the same spot for 800 to 1000 laser pulses at different repetition rates (5 to 50 Hz). Elemental fractionation was found to depend on repetition rate and showed a trend with femtosecond laser ablation that is opposite to that observed in picosecond laser ablation for most measured isotopes. ICP-MS signal intensity was higher in femtosecond than picosecond LA-ICP-MS in both NIST 610 and naval brass when ablation was conducted under the same fluence and repetition rate. The differences in signal intensity were partly related to differences in particle size distribution between particles generated by femtosecond and picosecond laser pulses and the consequent differences in transport and ionization efficiencies. The main reason for the higher signal intensity resulting from femtosecond laser pulses was related to the larger crater sizes compared to those created during picosecond laser ablation. Elemental ratios measured using 66 Zn/ 63 Cu, 208 Pb/ 238 U, 232 Th/ 238 U, 66 Zn/ 232 Th and 66 Zn/ 208 Pb were found to change with the number of laser pulses with data points being more scattered in picosecond than femtosecond laser pulses. Reproducibility of replicate measurements of signal intensities, fractionation and elemental ratios was better for fs-LA-ICP-MS (RSD ~ 3 to 6%) than ps-LA-ICP-MS (RSD ~ 7 to 11%). - Highlights: • Fractionation and ICP-MS signal response were investigated for two different pulse widths using NIST 610 and Naval Brass. • Dependence of fractionation indices on repetition rate and pulse width. • Higher ablation rate was observed in picosecond compared to femtosecond laser ablation of NIST 610 and Brass

A novel dual-wavelength, Nd:YAG, picosecond-domain laser safely and effectively removes multicolor tattoos.

Science.gov (United States)

Bernstein, Eric F; Schomacker, Kevin T; Basilavecchio, Lisa D; Plugis, Jessica M; Bhawalkar, Jayant D

2015-07-14

Although nanosecond-domain lasers have been the mainstay of laser tattoo removal for decades, recent disruptive innovations in laser design have introduced a new class of commercial Q-switched lasers that generate picosecond-domain pulses. A picosecond-domain, Nd:YAG laser with a KTP frequency-doubling crystal was used to treat 31 decorative tattoos in 21 subjects. Safety and effectiveness were determined by blinded evaluation of digital images in this prospective clinical study. The average clearance overall as evaluated by blinded observers evaluating randomized digital photographs was 79 ± 0.9% (mean ± sem) after an average of 6.5 treatments. Of the 31 tattoos completing treatment, 6 had evidence of mild hyper- or hypo-pigmentation by evaluation of photographs. The 350 picosecond, 532 nm, and 450 picosecond 1,064 nm Nd:YAG laser is safe and effective for removing decorative tattoos. Lasers Surg. Med. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

Elemental fractionation in 785 nm picosecond and femtosecond laser ablation inductively coupled plasma mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Shaheen, M.E., E-mail: mshaheen73@science.tanta.edu.eg [Department of Physics, Faculty of Sciences, Tanta University, Tanta (Egypt); Gagnon, J.E.; Fryer, B.J. [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada); Department of Earth and Environmental Sciences, University of Windsor, Windsor, Ontario N9B 3P4 (Canada)

2015-05-01

Elemental fractionation and ICP-MS signal response were investigated for two different pulse width laser beams originating from the same laser system. Femtosecond and picosecond laser beams at pulse widths of 130 fs and 110 ps, respectively, and wavelength of 785 nm were used to ablate NIST 610 synthetic glass and SRM 1107 Naval Brass B at the same spot for 800 to 1000 laser pulses at different repetition rates (5 to 50 Hz). Elemental fractionation was found to depend on repetition rate and showed a trend with femtosecond laser ablation that is opposite to that observed in picosecond laser ablation for most measured isotopes. ICP-MS signal intensity was higher in femtosecond than picosecond LA-ICP-MS in both NIST 610 and naval brass when ablation was conducted under the same fluence and repetition rate. The differences in signal intensity were partly related to differences in particle size distribution between particles generated by femtosecond and picosecond laser pulses and the consequent differences in transport and ionization efficiencies. The main reason for the higher signal intensity resulting from femtosecond laser pulses was related to the larger crater sizes compared to those created during picosecond laser ablation. Elemental ratios measured using {sup 66}Zn/{sup 63}Cu, {sup 208}Pb/{sup 238}U, {sup 232}Th/{sup 238}U, {sup 66}Zn/{sup 232}Th and {sup 66}Zn/{sup 208}Pb were found to change with the number of laser pulses with data points being more scattered in picosecond than femtosecond laser pulses. Reproducibility of replicate measurements of signal intensities, fractionation and elemental ratios was better for fs-LA-ICP-MS (RSD ~ 3 to 6%) than ps-LA-ICP-MS (RSD ~ 7 to 11%). - Highlights: • Fractionation and ICP-MS signal response were investigated for two different pulse widths using NIST 610 and Naval Brass. • Dependence of fractionation indices on repetition rate and pulse width. • Higher ablation rate was observed in picosecond compared to

Laser Treatment of Professional Tattoos With a 1064/532-nm Dual-Wavelength Picosecond Laser.

Science.gov (United States)

Kauvar, Arielle N B; Keaney, Terrence C; Alster, Tina

2017-12-01

Picosecond-domain laser pulses improve the photomechanical disruption of tattoos. This study evaluates the efficacy and safety of a novel, dual-wavelength, 1,064/532-nm, picosecond-domain laser for tattoo clearance. This was a prospective, self-controlled, clinical study of 34 subjects with 39 tattoos treated at 2 sites with an interval of 4.8 ± 1.6 weeks and up to 10 treatments (mean, 7.5). Blinded evaluation and investigator assessment of serial digital images was performed to evaluate treatment efficacy in the 36 tattoos that received at least 3 treatments. Investigators also assessed efficacy before each treatment visit up to 10 treatments. Safety and tolerability was evaluated for all 39 tattoos that underwent at least 1 treatment. Blinded evaluation demonstrated that lightening of tattoos was achieved in all subjects, with 86% (31 of 36 tattoos) showing at least a 50% clearance after 3 treatments. Adverse events were few and transient in nature. Patient satisfaction and treatment tolerability were high. Treatment of single-colored and multicolored tattoos with this novel 1,064/532-nm picosecond laser is highly safe and effective.

High power industrial picosecond laser from IR to UV

Science.gov (United States)

Saby, Julien; Sangla, Damien; Pierrot, Simonette; Deslandes, Pierre; Salin, François

2013-02-01

Many industrial applications such as glass cutting, ceramic micro-machining or photovoltaic processes require high average and high peak power Picosecond pulses. The main limitation for the expansion of the picosecond market is the cost of high power picosecond laser sources, which is due to the complexity of the architecture used for picosecond pulse amplification, and the difficulty to keep an excellent beam quality at high average power. Amplification with fibers is a good technology to achieve high power in picosecond regime but, because of its tight confinement over long distances, light undergoes dramatic non linearities while propagating in fibers. One way to avoid strong non linearities is to increase fiber's mode area. Nineteen missing holes fibers offering core diameter larger than 80μm have been used over the past few years [1-3] but it has been shown that mode instabilities occur at approximately 100W average output power in these fibers [4]. Recently a new fiber design has been introduced, in which HOMs are delocalized from the core to the clad, preventing from HOMs amplification [5]. In these so-called Large Pitch Fibers, threshold for mode instabilities is increased to 294W offering robust single-mode operation below this power level [6]. We have demonstrated a high power-high efficiency industrial picosecond source using single-mode Large Pitch rod-type fibers doped with Ytterbium. Large Pitch Rod type fibers can offer a unique combination of single-mode output with a very large mode area from 40 μm up to 100μm and very high gain. This enables to directly amplify a low power-low energy Mode Locked Fiber laser with a simple amplification architecture, achieving very high power together with singlemode output independent of power level or repetition rate.

Multiphoton ionization of (Xe)n and (NO)n clusters using a picosecond laser

International Nuclear Information System (INIS)

Smith, D.B.; Miller, J.C.

1989-01-01

Mass-resolved multiphoton ionization (MPI) spectroscopy is an established technique for detecting and analyzing van der Waals molecules and larger clusters. MPI spectroscopy provides excellent detection sensitivity, moderately high resolution, and selectivity among cluster species. In addition to information provided by the analysis of photoions following MPI, photoelectron spectroscopy can reveal details regarding the structure of ionic states. Unfortunately, the technique is limited by its tendency to produce extensive fragmentation. Fragmentation is also a problem with other ionization techniques (e.g., electron impact ionization), but the intense laser beams required for MPI cause additional dissociation channels to become available. These channels include absorption of additional photons by parent ions (ion ladder mechanism), absorption of additional photons by fragment ions (ladder switching mechanism), and resonances with dissociative states in the neutral manifold. The existence of these dissociation channels can preclude the use of MPI spectroscopy in many situations. Recently, MPI studies of stable molecules using picosecond lasers (pulse length = 1 - 10 ps) have indicated that limitations due to fragmentation might be subdued. With picosecond lasers, dissociation mechanisms can be altered and in some cases fragmentation can be eliminated or reduced. Additional photon absorption competes effectively with dissociation channels when a very short laser pulse or, perhaps more importantly, a sufficiently high peak-power is used. In the case where ionic absorption and fragmentation occurs, it has been shown that picosecond MPI might favor the ion ladder mechanism rather than the ladder switching mechanism

Effect analysis of material properties of picosecond laser ablation for ABS/PVC

Science.gov (United States)

Tsai, Y. H.; Ho, C. Y.; Chiou, Y. J.

2017-06-01

This paper analytically investigates the picosecond laser ablation of ABS/PVC. Laser-pulsed ablation is a wellestablished tool for polymer. However the ablation mechanism of laser processing for polymer has not been thoroughly understood yet. This study utilized a thermal transport model to analyze the relationship between the ablation rate and laser fluences. This model considered the energy balance at the decomposition interface and Arrhenius law as the ablation mechanisms. The calculated variation of the ablation rate with the logarithm of the laser fluence agrees with the measured data. It is also validated in this work that the variation of the ablation rate with the logarithm of the laser fluence obeys Beer's law for low laser fluences. The effects of material properties and processing parameters on the ablation depth per pulse are also discussed for picosecond laser processing of ABS/PVC.

Improvements in picosecond chronography

International Nuclear Information System (INIS)

Arthurs, E.G.; Bradley, D.J.; Liddy, Brian; O'Neill, Fergus; Roddie, A.G.; Sibbett, Wilson; Sleat, W.E.

The durations of laser pulses as short as 1 picosecond have been measured with an electro-optical streak camera. The time resolution limit of the camera system has been directly and unambiguously demonstrated employing a flashlamp pumped mode-locked dye laser to reliably generate tunable-frequency pulses of duration between 1 and 2 psec. An argon laser pumped C.W. mode-locked dye laser has been developed using the streak camera as a diagnostic tool, to produce continuous streams of picosecond pulses. With the high light gain of the camera system, pulses of peak powers < 1 watt can be studied with picosecond time resolution. The build-up of picosecond pulses from the initial photon noise of the mode-locked laser has also been directly recorded for the first time

Emerging terawatt picosecond CO2 laser technology

International Nuclear Information System (INIS)

Pogorelsky, I.V.

1997-09-01

The first terawatt picosecond (TWps) CO 2 laser is under construction at the BNL Accelerator Test Facility (ATF). TWps-CO 2 lasers, having an order of magnitude longer wavelength than the well-known table-top terawatt solid state lasers, offer new opportunities for strong-field physics research. For laser wakefield accelerators (LWFA) the advantage of the new class of lasers is due to a gain of two orders of magnitude in the ponderomotive potential. The large average power of CO 2 lasers is important for the generation of hard radiation through Compton back-scattering of the laser off energetic electron beams. The authors discuss applications of TWps-CO 2 lasers for LWFA modules of a tentative electron-positron collider, for γ-γ (or γ-lepton) colliders, for a possible table-top source of high-intensity x-rays and gamma rays, and the generation of polarized positron beams

Iron plasma generation using a Nd:YAG laser pulse of several hundred picoseconds

Energy Technology Data Exchange (ETDEWEB)

Tamura, Jun, E-mail: jtamura@post.j-parc.jp [J-PARC Center, Japan Atomic Energy Agency, Ibaraki 319-1195 (Japan); Kumaki, Masafumi [Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Kondo, Kotaro [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Tokyo 152-8550 (Japan); Kanesue, Takeshi; Okamura, Masahiro [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2016-02-15

We investigated the high intensity plasma generated by using a Nd:YAG laser to apply a laser-produced plasma to the direct plasma injection scheme. The capability of the source to generate high charge state ions strongly depends on the power density of the laser irradiation. Therefore, we focused on using a higher power laser with several hundred picoseconds of pulse width. The iron target was irradiated with the pulsed laser, and the ion current of the laser-produced iron plasma was measured using a Faraday cup and the charge state distribution was investigated using an electrostatic ion analyzer. We found that higher charge state iron ions (up to Fe{sup 21+}) were obtained using a laser pulse of several hundred picoseconds in comparison to those obtained using a laser pulse of several nanoseconds (up to Fe{sup 19+}). We also found that when the laser irradiation area was relatively large, the laser power was absorbed mainly by the contamination on the target surface.

Fabrication of periodical surface structures by picosecond laser irradiation of carbon thin films: transformation of amorphous carbon in nanographite

Energy Technology Data Exchange (ETDEWEB)

Popescu, C.; Dorcioman, G. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, Magurele RO-077125 (Romania); Bita, B. [National Institute for Research and Development in Microtechnologies, 126A Erou Iancu Nicolae Street, Voluntari RO-077190 (Romania); Faculty of Physics, 405 Atomistilor Street, Magurele RO-077125 (Romania); Besleaga, C.; Zgura, I. [National Institute of Materials Physics, 105bis Atomistilor Street, Magurele RO-077125 (Romania); Himcinschi, C. [Institute of Theoretical Physics, TU Bergakademie Freiberg, Freiberg D-09596 (Germany); Popescu, A.C., E-mail: andrei.popescu@inflpr.ro [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, Magurele RO-077125 (Romania)

2016-12-30

Highlights: • Ripples obtained on carbon films after irradiation with visible ps laser pulses. • Amorphous carbon was transformed in nanographite following irradiation. • Ripples had a complex morphology, being made of islands of smaller ripples. • Hydrophilic carbon films became hydrophobic after surface structuring. - Abstract: Thin films of carbon were synthesized by ns pulsed laser deposition in vacuum on silicon substrates, starting from graphite targets. Further on, the films were irradiated with a picosecond laser source emitting in visible at 532 nm. After tuning of laser parameters, we obtained a film surface covered by laser induced periodical surface structures (LIPSS). They were investigated by optical, scanning electron and atomic force microscopy. It was observed that changing the irradiation angle influences the LIPSS covered area. At high magnification it was revealed that the LIPSS pattern was quite complex, being composed of other small LIPSS islands, interconnected by bridges of nanoparticles. Raman spectra for the non-irradiated carbon films were typical for a-C type of diamond-like carbon, while the LIPSS spectra were characteristic to nano-graphite. The pristine carbon film was hydrophilic, while the LIPSS covered film surface was hydrophobic.

Picosecond laser texturization of mc-silicon for photovoltaics: A comparison between 1064 nm, 532 nm and 355 nm radiation wavelengths

Energy Technology Data Exchange (ETDEWEB)

Binetti, Simona [Department of Materials Science and Milano-Bicocca Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milano (Italy); Le Donne, Alessia, E-mail: alessia.ledonne@mater.unimib.it [Department of Materials Science and Milano-Bicocca Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milano (Italy); Rolfi, Andrea [Department of Materials Science and Milano-Bicocca Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milano (Italy); Jäggi, Beat; Neuenschwander, Beat [Bern University of Applied Sciences, Engineering and Information Technology, Institute for Applied Laser, Photonics and Surface Technologies ALPS, Pestalozzistrasse 20, CH-3400 Burgdorf (Switzerland); Busto, Chiara [ENI Spa, Via Giacomo Fauser, 4, 28100 Novara (Italy); Frigeri, Cesare [CNR-IMEM Institute, Parco Area Delle Scienze 37/A, Fontanini, 43010 Parma (Italy); Scorticati, Davide; Longoni, Luca; Pellegrino, Sergio [Laserpoint Srl, Via Della Burrona 51, 20090 Vimodrone, Milano (Italy)

2016-05-15

Highlights: • Self-organized surface structures were produced by picosecond laser pulses on mc-Si. • Three laser wavelengths were used which effectively reduce Si reflectivity up to 8%. • The subsurface damage induced by the three lasers was studied in detail. • μ-Raman, PL and TEM proved that UV laser provides the lowest subsurface damage. • UV laser induced damage is located above the depletion region of the p–n junction. - Abstract: Self-organized surface structures were produced by picosecond laser pulses on multi-crystalline silicon for photovoltaic applications. Three different laser wavelengths were employed (i.e. 1064 nm, 532 nm and 355 nm) and the resulting morphologies were observed to effectively reduce the reflectivity of the samples after laser irradiation. Besides, a comparative study of the laser induced subsurface damage generated by the three different wavelengths was performed by confocal micro-Raman, photoluminescence and transmission electron microscopy. The results of both the structural and optical characterization showed that the mc-Si texturing performed with the laser at 355 nm provides surface reflectivity between 11% and 8% over the spectral range from 400 nm to 1 μm, while inducing the lowest subsurface damage, located above the depletion region of the p–n junction.

Spatial dynamics of picosecond CO2 laser pulses produced by optical switching in Ge

International Nuclear Information System (INIS)

Pogorelsky, I.; Fisher, A.S.; Veligdan, J.; Russell, P.

1991-01-01

The design, test and optimization of a picosecond CO 2 pulse-forming system are presented. The system switches a semiconductor's optical characteristics at 10 μm under the control of a synchronized 1.06-μm Nd:YAG picosecond laser pulse. An energy-efficient version of such a system using collimated beams is described. A simple, semi-empirical approach is used to simulate the switching process, specifically including the spatial distributions of the laser energy and phase, which are relevant for experiments in laser-driven electron acceleration. 11 refs., 7 figs

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)

Laser diagnostics in combustion. Elastic scattering and picosecond laser-induced fluorescence

Energy Technology Data Exchange (ETDEWEB)

Ossler, Frederik

1999-05-01

Elastic scattering and the Lorenz-Mie (LM) theory in particular is used for the characterization of sub-micron- and micron-sized droplets of organic fuels in sprays and aerosols. Calculations on the Lorenz-Mie theory show that backward-sideward scattered visible radiation can be used for unambiguous detection of ensembles of homogeneous droplets of organic substances with diameters around 1 micrometer (size parameter between 2 and 6). A backward feature in the polarization ratio appears with a value considerably higher than one, on the opposite to the case of the rainbow observed for larger droplets. A comparison between measurements and LM calculations showed that a large amount of droplets in aerosols and well-atomized sprays were smaller than one micrometer in diameter. The LM theory was also used to characterize different size groups in a burning spray. A 3 - D technique based on a picosecond laser and a streak camera was demonstrated for measurements of fast and turbulent biphase flows. The entire 3 - D information was obtained within a time-span of less than 15 nanoseconds. A 2 - D technique for lifetime measurements based on a picosecond laser and a streak camera has been demonstrated on static objects. An analysis indicates that the technique may be applied to measurements of lifetimes around or below one picosecond employing femtosecond lasers and femtosecond streak-cameras. The technique may in principle be used to study dynamic systems when two detectors are used. Fluorescence lifetime measurements on hydrogen and oxygen atoms in flames at atmospheric pressure demonstrate the need of lasers with suiting spectral properties such as jitter and linewidth and the need of detectors with high sensitivity in the near IR in the case of oxygen atoms. The fluorescence lifetimes of gas phase acetone and 3-pentanone at 266 nm excitation wavelength have been measured for mixtures with nitrogen and air at temperatures between 323 and 723 K and pressures between 0

A picosecond widely tunable deep-ultraviolet laser for angle-resolved photoemission spectroscopy

International Nuclear Information System (INIS)

Zhang Feng-Feng; Yang Feng; Zhang Shen-Jin; Xu Zhi; Wang Zhi-Min; Xu Feng-Liang; Peng Qin-Jun; Zhang Jing-Yuan; Xu Zu-Yan; Wang Xiao-Yang; Chen Chuang-Tian

2013-01-01

We develop a picosecond widely tunable laser in a deep-ultraviolet region from 175 nm to 210 nm, generated by two stages of frequency doubling of a 80-MHz mode-locked picosecond Ti:sapphire laser. A β-BaB 2 O 4 walk-off compensation configuration and a KBe 2 BO 3 F 2 prism-coupled device are adopted for the generation of second harmonic and fourth harmonics, respectively. The highest power is 3.72 mW at 193 nm, and the fluctuation at 2.85 mW in 130 min is less than ±2%

Pulsed-diode-pumped, all-solid-state, electro-optically controlled picosecond Nd:YAG lasers

International Nuclear Information System (INIS)

Gorbunkov, Mikhail V; Shabalin, Yu V; Konyashkin, A V; Kostryukov, P V; Olenin, A N; Tunkin, V G; Morozov, V B; Rusov, V A; Telegin, L S; Yakovlev, D V

2005-01-01

The results of the development of repetitively pulsed, diode-pumped, electro-optically controlled picosecond Nd:YAG lasers of two designs are presented. The first design uses the active-passive mode locking with electro-optical lasing control and semiconductor saturable absorber mirrors (SESAM). This design allows the generation of 15-50-ps pulses with an energy up to 0.5 mJ and a maximum pulse repetition rate of 100 Hz. The laser of the second design generates 30-ps pulses due to combination of positive and negative electro-optical feedback and the control of the electro-optical modulator by the photocurrent of high-speed semiconductor structures. (active media. lasers)

Picosecond electron probe for direct investigation of lattice temperature and structural phase transition

International Nuclear Information System (INIS)

Mourou, G.; Williamson, S.

1985-01-01

The authors have directly observed the laser-induced melt metamorphosis of thin aluminum films. The time required for the melt to evolve is dependent on the degree to which the Al specimen is superheated. The temperature of this superheated state can also be monitored on the picosecond time scale. The picosecond electron probe not only reveals information about the structure of a material but also about the lattice temperature. The change in lattice parameter that is observed as a shift in diffracted ring diameter is directly related to the thermal expansion coefficient. Also, based on the Debye-Waller effect, a reduction in the intensity of the diffraction rings can be observed due to increased lattice vibration. Presently, a 1-kHz-1-mJ/pulse Nd:YAG laser is being used to measure the temperature overshoot of laser-induced Al films. The high repetition rate permits signal averaging to be employed thereby increasing the sensitivity of the thermometric technique

Picosecond laser micro/nano surface texturing of nickel for superhydrophobicity

Science.gov (United States)

Wang, X. C.; Wang, B.; Xie, H.; Zheng, H. Y.; Lam, Y. C.

2018-03-01

A single step direct picosecond laser texturing process was demonstrated to be able to obtain a superhydrophobic surface on a nickel substrate, a key material for mold fabrication in the manufacture of various devices, including polymeric microfluidic devices. A two-scale hierarchical surface structure of regular 2D array micro-bumps with nano-ripples was produced on a nickel surface. The laser textured surface initially showed superhydrophilicity with almost complete wetting of the structured surface just after laser treatment, then quickly changed to nearly superhydrophobic with a water contact angle (WCA) of 140° in less than 1 d, and finally became superhydrophobic with a WCA of more than 150° and a contact angle hysteresis (CAH) of less than 5°. The mechanism involved in the process is discussed in terms of surface morphology and surface chemistry. The ultra-fast laser induced NiO catalytic effect was thought to play a key role in modifying the surface chemistry so as to lower the surface energy. The developed process has the potential to improve the performance of nickel mold in the fabrication of microfluidic devices.

Effects of Laser Operating Parameters on Piezoelectric Substrates Micromachining with Picosecond Laser

Directory of Open Access Journals (Sweden)

Lamia EL Fissi

2014-12-01

Full Text Available Ten picoseconds (200 kHz ultrafast laser micro-structuring of piezoelectric substrates including AT-cut quartz, Lithium Niobate and Lithium Tantalate have been studied for the purpose of piezoelectric devices application ranging from surface acoustic wave devices, e.g., bandpass filters, to photonic devices such as optical waveguides and holograms. The study examines the impact of changing several laser parameters on the resulting microstructural shapes and morphology. The micromachining rate has been observed to be strongly dependent on the operating parameters, such as the pulse fluence, the scan speed and the scan number. The results specifically indicate that ablation at low fluence and low speed scan tends to form a U-shaped cross-section, while a V-shaped profile can be obtained by using a high fluence and a high scan speed. The evolution of surface morphology revealed that laser pulses overlap in a range around 93% for both Lithium Niobate (LiNbO3 and Lithium Tantalate (LiTaO3 and 98% for AT-cut quartz can help to achieve optimal residual surface roughness.

Emerging terawatt picosecond CO{sub 2} laser technology

Energy Technology Data Exchange (ETDEWEB)

Pogorelsky, I V [Accelerator Test Facility, Brookhaven National Lab., Upton, NY (United States)

1998-03-01

The first terawatt picosecond (TWps) CO{sub 2} laser is under construction at the BNL Accelerator Test Facility (ATF). TWps-CO{sub 2} lasers, having an order of magnitude longer wavelength than the well-known table-top terawatt solid state lasers, offer new opportunities for strong-field physics research. For laser wakefield accelerators (LWFA) the advantage of the new class of lasers is due to a gain of two orders of magnitude in the ponderomotive potential. The large average power of CO{sub 2} lasers is important for the generation of hard radiation through Compton back-scattering of the laser off energetic electron beams. We discuss applications of TWps-CO{sub 2} lasers for LWFA modules of a tentative electron-positron collider, for {gamma}-{gamma} (or {gamma}-lepton) colliders, for a possible `table-top` source of high-intensity x-rays and gamma rays, and the generation of polarized positron beams. (author)

Femtosecond versus picosecond laser pulses for film-free laser bioprinting.

Science.gov (United States)

Petit, Stephane; Kérourédan, Olivia; Devillard, Raphael; Cormier, Eric

2017-11-01

We investigate the properties of microjets in the context of film-free laser induced forward transfer in the femtosecond and picosecond regimes. The influence of the pulse duration (ranging from 0.4 to 12 ps) and the energy (ranging from 6 to 12 μJ) is systematically studied on the height, diameter, speed, volume, and shape of the jets. The 400 fs pulses generate thin and stable jets compatible with bioprinting, while 14 ps pulses generate more unstable jets. A pulse duration around 8 ps seems, therefore, to be an interesting trade-off to cover many bio-applications of microjets generated by lasers.

Fast ion generation by a picosecond high-power laser

Czech Academy of Sciences Publication Activity Database

Badziak, J.; Parys, P.; Wolowski, J.; Hora, H.; Krása, Josef; Láska, Leoš; Rohlena, Karel

2005-01-01

Roč. 35, č. 1 (2005), s. 5-22 ISSN 0078-5466 R&D Projects: GA MŠk(CZ) ME 238 Grant - others:International Atomic Energy in Vienna(XE) 11535/RO; State Commitee for Scientific Research (KBN)(PL) 1 PO3B 082 19 and 1 PO3B 043 26 Institutional research plan: CEZ:AV0Z10100523 Keywords : fast ion * plasma * picosecond laser Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.459, year: 2005

The use of lasers for studying ultrahigh speed phenomena (picoseconds): equipement of a picosecond spectroscopy laboratory using synchronized mode lasers

International Nuclear Information System (INIS)

Goujon, P.; Pochon, E.; Clerc, M.

1975-01-01

The spectroscopy laboratory is equipped with a dye laser and a neodymium glass laser. Detection is one case is made by means of a streak picosecond camera capable of a 5 ps time interval. A second detection method uses a CS 2 Kerr cell switch based on the Duguay principle. The first qualitative results concerning the fluorescence of DODCI and chlorophyll in vivo as well as the bleaching and recovering of the absorption of the electron solvated in liquid ammonia, have shown that this equipment could effectively enable the observation of physical-chemical processes as brief as 5 ps [fr

Anomalous intensities of Ne-like ion resonance line in plasma produced by picosecond laser pulse

International Nuclear Information System (INIS)

Bryunetkin, B.A.; Skobelev, I.Yu.; Faenov, A.Ya.; Kalashnikov, M.P.; Nikles, P.; Shnyupep, M.

1995-01-01

An anomalous structure of intensities of spectral lines of CuXX and GeXXX Ne-like ions emitted by plasma produced by laser pulses of picosecond duration and up to 2x10 18 W/cm 2 flux density is recorded for the first time. It is shown that spectrum maximum of these ions is emitted from a plasma region whose density is significantly above the critical value of the length of heating laser radiation wave. 9 refs.; 3 figs

Plasma satellites of X-ray lines of ions in a picosecond laser plasma

International Nuclear Information System (INIS)

Belyaev, V.S.; Vinogradov, V.I.; Kurilov, A.S.; Matafonov, A.P.; Lisitsa, V.S.; Gavrilenko, V. P.; Faenov, A.Ya.; Pikuz, T.A.; Skobelev, I.Yu.; Magunov, A.I.; Pikuz, S.A. Jr.

2004-01-01

We present the results of our measurements of the spectra for multicharged ions in a plasma produced by moderately intense (about 10 17 W cm -2 ) picosecond laser pulses. They suggest the existence of intense plasma oscillations with a frequency appreciably lower than the frequency of the laser radiation. The observed spectrum for the plasma satellites of the Lyman Ly α doublet of the hydrogenic F IX ion in a dense plasma was modeled theoretically. The resulting doublet profile was shown to have a complex structure that depends nontrivially both on the plasma density and on the frequency and amplitude of the plasma oscillations. The positions of the satellites and their separations allowed them to be associated with intense electrostatic oscillations with an amplitude of (4-6) x 10 8 V cm -1 and a frequency near (0.7-1) x 10 15 s -1 . Assuming the oscillation frequency to be determined by the strength of the magnetic field B generated in the plasma, we obtained an estimate of B that is in reasonable agreement with other measurements and estimates of this quantity. Our theoretical analysis allowed explanation of the emission spectra observed when flat fluoroplastic targets were heated by intense picosecond laser pulses

Comparison of treatment with an Alexandrite picosecond laser and Nd:YAG nanosecond laser for removing blue-black Chinese eyeliner tattoos.

Science.gov (United States)

Zhang, Mengli; Huang, Yuqing; Lin, Tong; Wu, Qiuju

2018-02-28

To retrospectively evaluate the efficacy of an Alexandrite picosecond laser versus Nd:YAG nanosecond laser for removing blue-black eyeliner tattoos which have existed more than 10 years. A total of 40 patients were treated with an Alexandrite picosecond laser in our department from August 2015 to July 2017, with a fluence of 1.96-6.37J/cm 2 , spot size of 2.0-3.6 mm, and pulse width of 750 ps. Another 32 patients were treated with an Nd:YAG nanosecond laser, with a fluence of 2.80-7.00 J/cm 2 , spot size of 3 mm, and pulse width of 5-20 ns. All analysed patients completed at least one treatment and follow-up. The median number of treatment for all the patients was 1 (range, 1-4). After a single session, no difference was found between the two lasers for the eyeliner removal (p > 0.05). For the people who achieved an excellent response of tattoo clearance, there was still no difference between the two groups (p > 0.05). Transient side effects were observed in two groups, but neither group had significant adverse reactions. To treat blue-black Chinese eyeliner tattoos over 10 years, Alexandrite picosecond laser does not provide better clearance than the Nd:YAG nanosecond laser.

Si nanostructures grown by picosecond high repetition rate pulsed laser deposition

International Nuclear Information System (INIS)

Pervolaraki, M.; Komninou, Ph.; Kioseoglou, J.; Athanasopoulos, G.I.; Giapintzakis, J.

2013-01-01

One-step growth of n-doped Si nanostructures by picosecond ultra fast pulsed laser deposition at 1064 nm is reported for the first time. The structure and morphology of the Si nanostructures were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy. Transmission electron microscopy studies revealed that the shape of the Si nanostructures depends on the ambient argon pressure. Fibrous networks, cauliflower formations and Si rectangular crystals grew when argon pressure of 300 Pa, 30 Pa and vacuum (10 −3 Pa) conditions were used, respectively. In addition, the electrical resistance of the vacuum made material was investigated

Si nanostructures grown by picosecond high repetition rate pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Pervolaraki, M., E-mail: pervolaraki@ucy.ac.cy [Nanotechnology Research Center and Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Av., PO Box 20537, 1678 Nicosia (Cyprus); Komninou, Ph.; Kioseoglou, J. [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Athanasopoulos, G.I. [Nanotechnology Research Center and Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Av., PO Box 20537, 1678 Nicosia (Cyprus); Giapintzakis, J., E-mail: giapintz@ucy.ac.cy [Nanotechnology Research Center and Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Av., PO Box 20537, 1678 Nicosia (Cyprus)

2013-08-01

One-step growth of n-doped Si nanostructures by picosecond ultra fast pulsed laser deposition at 1064 nm is reported for the first time. The structure and morphology of the Si nanostructures were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy. Transmission electron microscopy studies revealed that the shape of the Si nanostructures depends on the ambient argon pressure. Fibrous networks, cauliflower formations and Si rectangular crystals grew when argon pressure of 300 Pa, 30 Pa and vacuum (10{sup −3} Pa) conditions were used, respectively. In addition, the electrical resistance of the vacuum made material was investigated.

Picosecond trigger system useful in mode-locked laser pulse measurements

International Nuclear Information System (INIS)

Cunin, B.; Miehe, J.A.; Sipp, B.; Thebault, J.

1976-01-01

A highly sensitive tunnel diode trigger useful in temporal intensity build-up measurements of mode-locked lasers has been developed; the device reduces notably the time walk due to the lack of repeatability in intensity of the laser output. The performance of the trigger have been established by means of a GHz wideband-0.1V/cm sensitive real-time oscilloscope and of an image converter camera having a picosecond resolution: the experimental results show that a variation of the amplitude of the laser pulse train of a factor 5 leads to a time jitter of less than 30 ps (Auth.)

In vivo multiphoton-microscopy of picosecond-laser-induced optical breakdown in human skin.

Science.gov (United States)

Balu, Mihaela; Lentsch, Griffin; Korta, Dorota Z; König, Karsten; Kelly, Kristen M; Tromberg, Bruce J; Zachary, Christopher B

2017-08-01

Improvements in skin appearance resulting from treatment with fractionated picosecond-lasers have been noted, but optimizing the treatment efficacy depends on a thorough understanding of the specific skin response. The development of non-invasive laser imaging techniques in conjunction with laser therapy can potentially provide feedback for guidance and optimizing clinical outcome. The purpose of this study was to demonstrate the capability of multiphoton microscopy (MPM), a high-resolution, label-free imaging technique, to characterize in vivo the skin response to a fractionated non-ablative picosecond-laser treatment. Two areas on the arm of a volunteer were treated with a fractionated picosecond laser at the Dermatology Clinic, UC Irvine. The skin response to treatment was imaged in vivo with a clinical MPM-based tomograph at 3 hours and 24 hours after treatment and seven additional time points over a 4-week period. MPM revealed micro-injuries present in the epidermis. Pigmented cells were particularly damaged in the process, suggesting that melanin is likely the main absorber for laser induced optical breakdown. Damaged individual cells were distinguished as early as 3 hours post pico-laser treatment with the 532 nm wavelength, and 24 hours post-treatment with both 532 and 1064 nm wavelengths. At later time points, clusters of cellular necrotic debris were imaged across the treated epidermis. After 24 hours of treatment, inflammatory cells were imaged in the proximity of epidermal micro-injuries. The epidermal injuries were exfoliated over a 4-week period. This observational and descriptive pilot study demonstrates that in vivo MPM imaging can be used non-invasively to provide label-free contrast for describing changes in human skin following a fractionated non-ablative laser treatment. The results presented in this study represent the groundwork for future longitudinal investigations on an expanded number of subjects to understand the response to treatment

Picosecond image-converter diagnostics

International Nuclear Information System (INIS)

Schelev, M.Ya.

1975-01-01

A brief review is presented of the improvements in picosecond image-converter diagnostics carried out since the previous Congress in 1972. The account is given under the following headings: picosecond image converter cameras for visible and x-ray radiation diagnostics; Nd:glass and ruby mode-locked laser measurements; x-ray plasma emission diagnostics; computer treatment of pictures produced by picosecond cameras. (U.K.)

Safety and efficacy of a novel diffractive lens array using a picosecond 755?nm alexandrite laser for treatment of wrinkles

OpenAIRE

Weiss, Robert A.; McDaniel, David H.; Weiss, Margaret A.; Mahoney, Anne Marie; Beasley, Karen L.; Halvorson, Christian R.

2016-01-01

Introduction Picosecond lasers have been reported to be effective for removal of tattoo pigment. This prospective study evaluated the efficacy and safety of the treatment of peri?oral and ?ocular wrinkles using a novel diffractive lens array coupled with a picosecond 755?nm alexandrite laser. Methods Forty female subjects presenting with wrinkles from photodamage were enrolled in an IRB approved study. Subjects received four picosecond diffractive lens array treatments to the full face at 1 m...

Radiation chemistry and advanced polymer materials studied by picosecond pulse radiolysis combined with femtosecond laser

International Nuclear Information System (INIS)

Tagawa, S.; Yoshida, Y.; Miki, M.; Yamamoto, T.; Ushida, K.; Izumi, Y.

1996-01-01

We have synchronized a single picosecond MeV electron pulse from L-band linear accelerator (linac) of The Institute of Scientific and Industrial Research of Osaka University to a single femtosecond laser pulse of Ti:Sapphire laser. It is an essential technique for the future femtosecond pulse radiolysis and is also applied to many kinds of combined application of more than two different beams from accelerators in very short time range. Radiation chemistry and new type of polymers have been studied by LL (laser-linac) twin picosecond pulse radiolysis. Especially the early events in radiation chemistry such as geminate recombination processes of electrons and radical cations are have been studied in both liquids and solids. (author)

Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

International Nuclear Information System (INIS)

Ortiz, Rocio; Quintana, Iban; Etxarri, Jon; Lejardi, Ainhoa; Sarasua, Jose-Ramon

2011-01-01

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

Energy Technology Data Exchange (ETDEWEB)

Ortiz, Rocio; Quintana, Iban; Etxarri, Jon [Manufacturing Processes Department, Fundacion TEKNIKER, Av. Otaola 20, 20600, Eibar, Guipuzcoa (Spain); Lejardi, Ainhoa; Sarasua, Jose-Ramon [Department of Mining and Metallurgy Engineering and Materials Science, School of Engineering, University of the Basque Country (EHU-UPV), Alameda de Urquijo s/n, 48013 Bilbao (Spain)

2011-11-01

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

Study of the laser-induced damage of reflective components in the sub-picosecond regime

International Nuclear Information System (INIS)

Sozet, Martin

2016-01-01

In this thesis, laser-induced damage phenomenon of reflective components is investigated in the sub-picosecond regime. These components, made of stacks of dielectric materials, are widely used in powerful laser facilities such as PETAL laser. PETAL laser has been built at the CEA-CESTA in France to deliver multi-kJ/500 fs pulses at 1053 nm and reach a power higher than 6 PW. For this kind of laser systems, reflective components are commonly used instead of optics operating in transmission to limit the accumulation of non-linear phase along the beam propagation due to the high intensities. Optical components irradiated by the highest power densities are the pulse compression gratings, transport mirrors and the focusing parabola, located at the end of the laser chain. Nowadays, laser-induced damage is the main factor that limits the overall performances of powerful laser systems. This manuscript presents three study axes to better understand and control damage phenomenon. The first one concerns the conception of reflective optics for the peta-watt applications. The design of new structures has been investigated to reach high diffraction efficiencies in the case of pulse compression gratings and a high reflectivity in the case of mirrors, while reducing the Electric-field enhancement which is one of the causes of the laser-induced damage. The second axis deals with the development of a precise damage metrology with new testing tools which brings new perspectives and a new viewpoint for the assessment of the laser resistance of optical components. Finally, the third axis concerns the study the damage growth after several irradiations in the sub-picosecond regime. The evolution of the damage area during growth sequences is observed and compared to numerical simulations. It enables to improve the understanding in the growth phenomenon. In the end, these studies will allow to develop predictive models of the laser-induced damage and new tools for the conception of

Amplification of picosecond pulse by electron-beam pumped KrF laser amplifiers. Denshi beam reiki KrF laser zofukuki ni yoru piko byo pulse no zofuku

Energy Technology Data Exchange (ETDEWEB)

Okuda, I.; Tomie, T.; Owadano, Y.; Yano, M. (Electrotechnical Laboratory, Tsukuba (Japan))

1991-08-20

Experiments on the amplification of a picosecond pulse by electron-beam pumped KrF laser amplifiers were carried out for the purpose of its application to the field such as excitation light source for soft X-ray laser which requires large energy besides peak power. The picosecond pulse was amplified by a discharge pumped KrF amplifier and two electron-beam pumped KrF amplifiers(at the middle stage and the final stage). The energy of 4J, which was the largest energy for short pulse excimer laser so far, was obtained by these devices. About 90% of the window area of the final amplifier with 29cm diameter was filled by the input beam, and energy density of the picosecond beam reached 3.9 times saturation energy density. Measured energy of amplified spontaneous emission(ASE) showed good agreement with the theoretically estimated value. Most of ASE was derived from the discharge pumped laser as the first amplifier. As for the focused power density, the power density ratio of the picosecond pulse to ASE was estimated to be as large as 10{sup 5}. 11 refs., 4 figs.

Picosecond Laser Pulse Interactions with Metallic and Semiconductor Surfaces.

Science.gov (United States)

1984-11-01

thermometric determination of plasma relaxation is by far more sensitive than direct optical measurements. The solid line in Fig. 4 shows the calculated...passively mode-locked Nd:yttrium aluminum garnet in Si, several researchers have used high picosecond or fem- laser was used to produce single 30-ps, 1.06...these targets to an aluminum backing plate with a silver-epoxy conducting glue (Ablestik). The conductivity of the targets was high enough to make

Mode-Locking in Broad-Area Semiconductor Lasers Enhanced by Picosecond-Pulse Injection

OpenAIRE

Kaiser, J; Fischer, I; Elsasser, W; Gehrig, E; Hess, O

2004-01-01

We present combined experimental and theoretical investigations of the picosecond emission dynamics of broad-area semiconductor lasers (BALs). We enhance the weak longitudinal self-mode-locking that is inherent to BALs by injecting a single optical 50-ps pulse, which triggers the output of a distinct regular train of 13-ps pulses. Modeling based on multimode Maxwell-Bloch equations illustrates how the dynamic interaction of the injected pulse with the internal laser field efficiently couples ...

Proton Radiography of Laser-Plasma Interactions with Picosecond Time Resolution

International Nuclear Information System (INIS)

Mackinnon, A J; Patel, P K; Town, R J; Hatchett, S P; Hicks, D; Phillips, T H; Wilks, S C; Price, D; Key, M H; Lasinski, B; Langdon, B; Borghesi, M; Romagnani, L; Kar, S

2005-01-01

Radiography of laser-produced plasmas with MeV protons has the potential to provide new information on plasma conditions in extreme states of matter. Protons with energies up to many hundreds MeV, produced by large scale accelerators have been recently been used to obtain mass density radiographs of the behavior of large samples which have been shocked on microsecond timescales with approximately mm spatial resolution. The recent discovery of laminar proton beams accelerated to multi-MeV energies by picosecond duration laser beams has provided the opportunity to probe dense plasmas with hitherto unparalleled temporal and spatial resolution

Fabrication and hydrophobic characteristics of micro / nanostructures on polydimethylsiloxane surface prepared by picosecond laser

Science.gov (United States)

Bin, Wang; Dong, Shiyun; Yan, Shixing; Gang, Xiao; Xie, Zhiwei

2018-03-01

Picosecond laser has ultrashort pulse width and ultrastrong peak power, which makes it widely used in the field of micro-nanoscale fabrication. polydimethylsiloxane (PDMS) is a typical silicone elastomer with good hydrophobicity. In order to further improve the hydrophobicity of PDMS, the picosecond laser was used to fabricate a grid-like microstructure on the surface of PDMS, and the relationship between hydrophobicity of PDMS with surface microstructure and laser processing parameters, such as processing times and cell spacing was studied. The results show that: compared with the unprocessed PDMS, the presence of surface microstructure significantly improved the hydrophobicity of PDMS. When the number of processing is constant, the hydrophobicity of PDMS decreases with the increase of cell spacing. However, when the cell spacing is fixed, the hydrophobicity of PDMS first increases and then decreases with the increase of processing times. In particular, when the times of laser processing is 6 and the cell spacing is 50μm, the contact angle of PDMS increased from 113° to 154°, which reached the level of superhydrophobic.

A High-Energy, 100 Hz, Picosecond Laser for OPCPA Pumping

Directory of Open Access Journals (Sweden)

Hongpeng Su

2017-09-01

Full Text Available A high-energy diode-pumped picosecond laser system centered at 1064 nm for optical parametric chirped pulse amplifier (OPCPA pumping was demonstrated. The laser system was based on a master oscillator power amplifier configuration, which contained an Nd:YVO4 mode-locked seed laser, an LD-pumped Nd:YAG regenerative amplifier, and two double-pass amplifiers. A reflecting volume Bragg grating with a 0.1 nm reflective bandwidth was used in the regenerative amplifier for spectrum narrowing and pulse broadening to suit the pulse duration of the optical parametric amplifier (OPA process. Laser pulses with an energy of 316.5 mJ and a pulse duration of 50 ps were obtained at a 100 Hz repetition rate. A top-hat beam distribution and a 0.53% energy stability (RMS were achieved in this system.

Prospective study of removing solar lentigines in Asians using a novel dual-wavelength and dual-pulse width picosecond laser.

Science.gov (United States)

Negishi, Kei; Akita, Hirotaka; Matsunaga, Yukiko

2018-04-02

Quality-switched (QS) lasers are known to be an effective treatment for removing solar lentigines, however, high incidence of post-inflammatory hyperpigmentation (PIH) is a concern in darker skin types. The objective of this study was to evaluate the efficacy and safety of a dual-wavelength and dual-pulse width picosecond Nd:YAG laser for removing solar lentigines in Asians. This was a prospective, IRB-approved study. Twenty cases with solar lentigines on the face were enrolled for treatment and evaluated at 1- and 3-month after the final treatment. Results were assessed by blinded evaluators using a 5-grade percentage improvement scale and Melanin index (MI) measured by a reflectance spectrophotometer. A patient self-assessment questionnaire was also administered using a 5-grade improvement scale. Additional treatment was performed if the improvement was less than 75% or the lentigo partially remained after 4 weeks. Histological evaluation was performed to compare the differences between the current picosecond laser and a QS Nd:YAG laser 532-nm using light and electron microscopy. Forty-three lesions in 20 females, skin type III or IV, age 53.7 ± 9.75 were treated and evaluated. The laser setting was: 532-nm, 750 picoseconds, average fluence of 0.35 ± 0.06 J/cm [2] using a spot size of 3 or 4 mm. Forty lesions (93.02%) achieved over 75% clearance with a single treatment and the other three lesions (6.98%) needed two treatments. PIH occurred only in 4.65% of lesions. The average score of the blinded evaluators' assessment was 4.77 and 4.58 on a 5-grade percentage improvement scale. The patients' self-assessment rating was 4.76 and 4.67 on a 5-grade scale at 1- and 3-month follow-up, respectively. The improvement rate of relative MI (MI in the lesion minus that of the normal area) was 77.60 ± 36.27% and 76.93 ± 20.95% at 1-and 3-month follow-up. Histology showed vacuolar formation by both lasers in the epidermis that were different sizes

Picosecond laser registration of interference pattern by oxidation of thin Cr films

Energy Technology Data Exchange (ETDEWEB)

Veiko, Vadim; Yarchuk, Michail [ITMO University, Kronverksky Ave. 49, St. Petersburg, 197101 (Russian Federation); Zakoldaev, Roman, E-mail: zakoldaev@gmail.com [ITMO University, Kronverksky Ave. 49, St. Petersburg, 197101 (Russian Federation); Gedvilas, Mindaugas; Račiukaitis, Gediminas [Center for Physical Sciences and Technology, Savanoriu Ave. 231, LT-02300, Vilnius (Lithuania); Kuzivanov, Michail; Baranov, Alexander [ITMO University, Kronverksky Ave. 49, St. Petersburg, 197101 (Russian Federation)

2017-05-15

Highlights: • Periodical patterning of thin films was achieved by combining two technologies. • Selective chemical etching was combined with laser-induced oxidation. • Formation of the protective oxide layer prevented of chromium film from etching. • 1D binary grating with the chromium stripe width of 750 nm was fabricated. - Abstract: The laser oxidation of thin metallic films followed by its selective chemical etching is a promising method for the formation of binary metal structures on the glass substrates. It is important to confirm that even a single ultrashort laser pulse irradiation is able to create the protective oxide layer that makes possible to imprint the thermochemical image. Results of the thermo-chemical treatment of thin chromium films irradiated by picosecond laser pulse utilizing two and four beam interference combined with the chemical etching are presented. The spatial resolution of this method can be high enough due to thermo-chemical sharpening and can be close to the diffraction limit. Micro-Raman spectroscopy was applied for characterization of the chemical composition of the protective oxide layers formed under atmospheric conditions on the surface of thin chromium films.

Multiphoton ionization of (Xe)/sub n/ and (NO)/sub n/ clusters using a picosecond laser

International Nuclear Information System (INIS)

Smith, D.B.; Miller, J.C.

1989-01-01

In an effort to extend the application of multiphoton ionization (MPI) spectroscopy to the study of weakly bound systems, we have begun a systematic investigation of picosecond MPI in van der Waals molecules and clusters. To our knowledge no previous picosecond MPI studies of weakly bound systems have been reported. We present here results of picosecond MPI of Xe/sub n/(n = 1-20) and (NO)/sub n/(n = 1-4) clusters. Previous MPI studies using nanosecond lasers have not detected the NO cluster series, presumably because of fast dissociation channels. The use of high peak-power allows resonant and non-resonant photon absorption to the ionization limit to compete effectively with fast dissociative processes. 10 refs., 2 figs

Environmentally stable picosecond Yb fiber laser with low repetition rate

Science.gov (United States)

Baumgartl, M.; Abreu-Afonso, J.; Díez, A.; Rothhardt, M.; Limpert, J.; Tünnermann, A.

2013-04-01

A SESAM-mode-locked, all-polarization-maintaining Ytterbium fiber laser producing picosecond pulses with narrow spectral bandwidth is presented. A simple linear all-fiber cavity without dispersion compensation is realized using a uniform fiber Bragg grating (FBG). Different cavity lengths are investigated and repetition rates down to 0.7 MHz are obtained. Bandwidth and pulse duration of the output pulses are mainly determined by the choice of FBG. Pulses between 30 and 200 ps are generated employing different FBGs with bandwidths between 17 and 96 pm. The experimental results are in good agreement with numerical simulations. The laser holds great potential for simple amplification setups without pulse picking.

Effect of different parameters on machining of SiC/SiC composites via pico-second laser

Energy Technology Data Exchange (ETDEWEB)

Li, Weinan; Zhang, Ruoheng [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an, Shaanxi 10068 (China); Liu, Yongsheng, E-mail: yongshengliu@nwpu.edu.cn [Science and technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China); Wang, Chunhui; Wang, Jing [Science and technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China); Yang, Xiaojun [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an, Shaanxi 10068 (China); Cheng, Laifei [Science and technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China)

2016-02-28

Graphical abstract: - Highlights: • The highlights of the manuscript include the following two aspects. • First, we found that the different machining modes (helical line scanning and single ring line scanning) and processing power of machining have remarkable effect on the surface morphology of the machined area, such as the shape, depth and the formation of different surface structures. • Secondly, we investigated that the debris consisted of C, Si and O was observed on the machined surface. • Some of the Si–C bonds of the SiC matrix and fibers would be transformed into Si–O bonds after machined, depending on the processing power. - Abstract: Pico-second laser plays an important role in modern machining technology, especially in machining high hardness materials. In this article, pico-second laser was utilized for irradiation on SiC/SiC composites, and effects of different processing parameters including the machining modes and laser power were discussed in detail. The results indicated that the machining modes and laser power had great effect on machining of SiC/SiC composites. Different types of surface morphology and structure were observed under helical line scanning and single ring line scanning, and the analysis of their formulation was discussed in detail. It was believed that the machining modes would be responsible to the different shapes of machining results at the same parameters. The processing power shall also influence the surface morphology and quality of machining results. In micro-hole drilling process, large amount of debris and fragments were observed within the micro-holes, and XPS analysis showed that there existed Si–O bonds and Si–C bonds, indicating that the oxidation during processing was incomplete. Other surface morphology, such as pores and pits were discussed as well.

Diode-pumped passively mode-locked sub-picosecond Yb:LuAG ceramic laser

International Nuclear Information System (INIS)

Zhu Jiang-Feng; Liu Kai; Wang Jun-Li; Yang Yu; Wang Hui-Bo; Gao Zi-Ye; Jiang Li; Xie Teng-Fei; Chao-Yu Li; Pan Yu-Bai; Wei Zhi-Yi

2017-01-01

In this paper the laser activities of a diode-pumped Yb:LuAG ceramic which was prepared by the solid-state reactive sintering method were reported. The maximum output power was 1.86 W in the continuous wave (CW) laser operation, corresponding to a slope efficiency of 53.6%. The CW laser could be tuned from 1030 to 1096 nm by inserting a prism in the cavity. With the assist of a semiconductor saturable absorber mirror (SESAM), passive mode-locking was realized, delivering sub-picosecond pulses with 933 fs duration and an average power of 532 mW at a repetition rate of 90.35 MHz. (paper)

Picosecond optical shutter for particle detection

International Nuclear Information System (INIS)

Fan, B.; Gee, C.M.; Shapiro, G.

1975-04-01

Characteristics of an optical shutter utilizing Kerr effect induced by picosecond laser pulses in carbon disulfide are studied experimentally. The shutter has a gate time of 4.5 to 5 ps full width at half-maximum and a transmission of approximately 15 percent at a wavelength 0.53 μm. Such an ultrafast shutter can be used as an optical signal gate in a sampling detection scheme that has picosecond time-resolution. The picosecond optical detection scheme is envisioned to have applications in experimental high-energy physics such as to time-resolve ultrashort Cherenkov or synchrotron radiation emitted by relativistic particles. Methods of synchronizing a laser-activated Kerr shutter with a particle accelerator or synchrotron are discussed

Picosecond spectroscopy: The first 20 years

International Nuclear Information System (INIS)

Rentzepis, P.M.

1987-01-01

Lasers were at first operating in the pulsed mode. That was the ruby, Cr/sup 3+/, emitting at 694.3 nm with a few kilowatts power, several microseconds time width, and a rather broad non-smooth-spiky-intensity profile. Even with such a primitive laser source, several noteworthy, novel experiments were performed such as two photon processes and second harmonic generation. The advent of Q-switch lasers by means of dyes, Kerr cells and electro-optic crystals introduced the era of high power lasers and laser spectroscopy. The high intensity and rather smooth intensity versus time profile pulses emitted by ruby and Nd/sup 3+//glass lasers provided excellent means for non-linear spectroscopy studies and nanosecond Raman spectroscopy, a field which flourished ten years later. In the mid-sixties, the He/Ne laser was mode locked, and shortly thereafter, the Nd/sup 3+//glass laser was also mode locked and shown to emit picosecond duration pulses. This paper presents what one observes on the screen of an oscilloscope once a laser is set up so as to generate picosecond pulses by use of either a saturable absorbing dye or solid state modulator. What is seen is, of course, a train of pulses. It is characteristic of these pulses that their intensity is extremely high, in the gigawatt region. In this particular case, the band width is approximately twenty to thirty wavenumbers. The method utilized to measure the picosecond pulses, initially, was the two photon method. This paper also gives a more graphic illustration how this technique operates. This same procedure provides an extremely simple technique which the author believes made possible the initial development of the picosecond spectroscopy field

Treatment of flat and elevated pigmented disorders with a 755-nm alexandrite picosecond laser: clinical and histological evaluation.

Science.gov (United States)

Alegre-Sanchez, Adrian; Jiménez-Gómez, Natalia; Moreno-Arrones, Óscar M; Fonda-Pascual, Pablo; Pérez-García, Bibiana; Jaén-Olasolo, Pedro; Boixeda, Pablo

2018-02-09

The novel picosecond lasers, initially developed for faster tattoo removal, have also shown great efficacy in endogenous pigmentary disorders. To describe the efficacy and safety profile of an alexandrite (755-nm) picosecond laser in a wide range of pigmented flat and elevated cutaneous lesions. A retrospective study was performed in which we collected all the clinical images of patients treated with the 755-nm alexandrite picosecond laser for 12 months (November 2016-November 2017). Clinical features were obtained from their medical charts. Patients treated for tattoo removal were excluded. All the images were analyzed by three blind physicians attending to a visual analogue scale (VAS) from 0 to 5 (0, no change; 1, 1-24% clearance; 2, 25-49% clearance; 3, 50-74% clearance; 4, 75-99% clearance; 5, complete clearance). Patient satisfaction was obtained from a subjective survey including four items: very satisfied, satisfied, non-satisfied, and totally dissatisfied. Thirty-seven patients were included (12 males; 25 females). The mean age of the study was 42.35 years. Twenty-five patients (68%) were treated for different pigmented flat disorders such as solar and mucosal lentigines (5), stasis dermatitis (4), or nevus of Ota (4), among other diagnoses. Twelve patients (32%) were treated for epidermal elevated lesions such as warts (5), epidermal nevi (2), and seborrheic keratosis (3), among other elevated lesions. Mean number of laser treatment was 3.02 sessions while mean follow-up after last laser treatment was 4.02 months. Mean VAS score of the three observers was 3.44 (61% of clearance) for pigmentary flat disorders and 3.60 (67%) for elevated lesions. Adverse effects reported were mild blistering in the first 2-5 days following laser treatment in some of the patients. Overall satisfaction among the patients included was high. The novel 755-nm picosecond alexandrite laser is effective not only for the resolution of pigmented flat lesions of different nature

Rewritable phase-change optical recording in Ge2Sb2Te5 films induced by picosecond laser pulses

International Nuclear Information System (INIS)

Siegel, J.; Schropp, A.; Solis, J.; Afonso, C.N.; Wuttig, M.

2004-01-01

The phase transformation dynamics induced in Ge 2 Sb 2 Te 5 films by picosecond laser pulses were studied using real-time reflectivity measurements with subnanosecond resolution. Evidence was found that the thermal diffusivity of the substrate plays a crucial role in determining the ability of the films to crystallize and amorphize. A film/substrate configuration with optimized heat flow conditions for ultrafast phase cycling with picosecond laser pulses was designed and produced. In this system, we achieved reversible phase transformations with large optical contrast (>20%) using single laser pulses with a duration of 30 ps within well-defined fluence windows. The amorphization (writing) process is completed within less than 1 ns, whereas crystallization (erasing) needs approximately 13 ns to be completed

Distributed-feedback dye laser for picosecond ultraviolet and visible spectroscopy

International Nuclear Information System (INIS)

Yaney, Perry P.; Kliner, Dahv A. V.; Schrader, Paul E.; Farrow, Roger L.

2000-01-01

We describe the design and operation of a tunable, picosecond laser system for use in time-resolved spectroscopic measurements in the visible and ultraviolet (UV) spectral region. The laser is designed for fine tuning and high wavelength stability. A Nd:YAG-pumped distributed-feedback dye laser (DFDL) generates pulses that are ∼100 ps in duration with a nearly transform-limited linewidth (∼5 GHz) at a 20 Hz repetition rate. The DFDL pulses are amplified in two bow-tie amplifiers, providing pulse energies of up to 3.0 mJ; the amplified pulses may be frequency doubled to the UV spectral region, providing up to 1.0 mJ. The DFDL wavelength is computer stabilized to within ±0.8 pm (±0.7 GHz, two standard deviations), allowing the wavelength to be stationed on a narrow atomic or molecular transition or permitting nearly continuous spectral scans. Application of the laser system to studies of OH energy transfer has been demonstrated; both laser-induced-fluorescence and degenerate-four-wave-mixing spectra have been recorded. (c) 2000 American Institute of Physics

Highlighting the nuances behind interaction of picosecond pulses with human skin: Relating distinct laser-tissue interactions to their potential in cutaneous interventions

Science.gov (United States)

Uzunbajakava, Natallia E.; Varghese, Babu; Botchkareva, Natalia V.; Verhagen, Rieko; Vogel, Alfred

2018-02-01

In recent years, several commercial systems relying on picosecond pulses have been introduced into the field of cutaneous interventions. In parallel with this development, a somewhat distinct research prototype also operating in the picosecond regime was described in literature. Albeit both market-available products and the investigational device employ laser beams of nearly the same pulse duration and were reported to cause laser-induced optical breakdown (LIOB), they are different in terms of wavelength, applied fluence, laser beam quality, optical architecture and related focusing optics, resulting in different histomorphological features (such as e.g. lesion size, location, expression of collagen). Understanding the differences between these systems in relation to implications for clinical results raises a need in highlighting the nuances behind interaction of picosecond pulses with biological tissue. To achieve this, we accentuate the interplay of irradiance levels of picosecond pulses in W/cm2 , absorption properties of a target tissue at a wavelength of a light source and resulting interaction mechanisms with biological object. We also relate these nuances to potential consequences for cutaneous interventions.

User issues at the Stanford picosecond free electron laser center

International Nuclear Information System (INIS)

Smith, T.I.

1995-01-01

Assembling a productive user facility around a Free Electron Laser (FEL) is a complex task. Reliable operation of the FEL is a necessary, but by no means sufficient, condition to ensure that the center will be able to attract and keep the interest of first rate researchers. Some other issues which are important include: center wavelength stability and ease of tuning, bandwidth control, amplitude and position stability, ability to select arbitrary sequences of micropulses, and real time availability of information of the FEL's important parameters (spectral width, center wavelength, micropulse length and energy, etc.). In addition, at the Stanford Center we have found that providing additional systems (conventional picosecond lasers synchronized to the FEL, an FTIR spectrometer, a confocal microscopy, ...) has been important. (author)

Design of a picosecond-laser-driven Ni-like Mo x-ray laser near 20 nm

International Nuclear Information System (INIS)

Nilsen, J.

1997-01-01

The gain is predicted for a solid molybdenum target illuminated by several joules of combined energy from a nanosecond laser pulse to create a preplasma followed by a picosecond laser pulse to drive the gain. Gains greater than 300cm -1 are predicted for the Ni-like Mo 4d 1 S 0 →4p 1 P 1 transition at 18.9 nm, which is driven by the monopole collisional excitation. High gain is also predicted for a self-photo-pumped 4f 1 P 1 →4d 1 P 1 transition at 22.0 nm and several other transitions driven by inner shell collisional ionization. copyright 1997 Optical Society of America

Towards crack-free ablation cutting of thin glass sheets with picosecond pulsed lasers

Science.gov (United States)

Sun, Mingying; Eppelt, Urs; Hartmann, Claudia; Schulz, Wolfgang; Zhu, Jianqiang; Lin, Zunqi

2017-08-01

We investigated the morphology and mechanism of laser-induced damage in the ablation cutting of thin glass sheets with picosecond laser. Two kinds of damage morphologies observed on the cross-section of the cut channel, are caused by high-density free-electrons and the temperature accumulation, respectively. Notches and micro-cracks can be observed on the top surface of the sample near the cut edge. The surface micro-cracks were related to high energy free-electrons and also the heat-affected zone. Heat-affected-zone and visible-cracks free conditions of glass cutting were achieved by controlling the repetition rate and spatial overlap of laser pulses.

A comparative study with a 755 nm picosecond Alexandrite laser with a diffractive lens array and a 532 nm/1064 nm Nd:YAG with a holographic optic.

Science.gov (United States)

Tanghetti Md, Emil; Jennings, John

2018-01-01

This study was performed to better understand the cutaneous effects of using a fractional picosecond laser at 755 nm with a diffractive lens array and a picosecond Nd:YAG laser at 532 mn and 1064 nm with a holographic optic. We characterized the injuries created by these devices on skin clinically and histologically over 24 hours. With this information we modeled the effects of these devices on a cutaneous target. Eight patients, representing Fitzpatrick skin types I-VI, were treated on their backs with a picosecond Alexandrite laser with a diffractive lens array, as well as a picosecond Nd:YAG laser at 532 nm and 1064 nm with a holographic optic. Photographs were taken 15 minutes and 24 hours after treatments. Punch biopsies were obtained at 24 hours and examined histologically. Treatment with the picosecond Nd:YAG laser at both 532 nm and 1064 nm with the holographic optic revealed erythema and small scatted areas of petechial hemorrhage areas immediately and in many cases at 24 hours after treatment. The 755 nm picosecond Alexandrite laser with diffractive lens array produced erythema immediately after treatment, which largely dissipated 24 hours later. Histologies revealed intra-epidermal vacuoles with all three wavelengths. Fractional picosecond Nd:YAG laser at 532 nm and 1064 nm with the holographic optic showed focal areas of dermal and intra-epidermal hemorrhage with areas of vascular damage in some patients. This study demonstrates that both fractional picosecond devices produce vacuoles in the skin, which are most likely due to areas of laser induced optical breakdown (LIOB). In the patients (skin type II-IV) we observed scatter areas of hemorrhage in the skin, due to vascular damage with the 532 nm and 1064 nm, but not with 755 nm wavelengths. Lasers Surg. Med. 50:37-44, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Second-harmonic generation in atomic vapor with picosecond laser pulses

International Nuclear Information System (INIS)

Kim, D.; Mullin, C.S.; Shen, Y.R.

1997-01-01

Picosecond laser pulses were used to study the highly forbidden resonant second-harmonic generation (SHG) in potassium vapor. The input intensity dependence, vapor density dependence, buffer-gas pressure dependence, and spatial profile of the SHG were measured. A pump - probe experiment was conducted to probe the time dependence of the SHG signal. The experimental results can be understood from an ionization-initiated dc-field-induced SHG model. A theory of a dc-field-induced SHG model is developed that takes into account the time development of the dc electric field in detail. This temporal buildup of the dc field along with transient coherent excitation between two-photon-allowed transitions can explain the experimental results quantitatively, including the previous vapor SHG results with nanosecond laser pulses. copyright 1997 Optical Society of America

Anti-biofouling superhydrophobic surface fabricated by picosecond laser texturing of stainless steel

Science.gov (United States)

Sun, Ke; Yang, Huan; Xue, Wei; He, An; Zhu, Dehua; Liu, Wenwen; Adeyemi, Kenneth; Cao, Yu

2018-04-01

Anti-biofouling technology is based on specifically designed materials and coatings. This is an enduring goal in the maritime industries, such as shipping, offshore oil exploration, and aquaculture. Recently, research of the relationship between wettability and antifouling effectiveness has attracted considerable attention, due to the anti-biofouling properties of the lotus leaf and shark skin. In this study, super-hydrophobic surfaces (SHSs) with controllable periodic structures were fabricated on AISI304 stainless steel by a picosecond laser, and their anti-biofouling performance were investigated by seawater immersion for five weeks in summertime. The results showed that the specimens with SHS demonstrate significant anti-biofouling effect as compared with the bare stainless steel plate. We observed that nearly 50% decrease of the average microbe attachment area ratio (Avg. MAAR) could be obtained. The micro-groove SHS with more abundant hierarchical micro-nano structures showed better anti-biofouling performance than the micro-pit SHS.

Picosecond camera

International Nuclear Information System (INIS)

Decroisette, Michel

A Kerr cell activated by infrared pulses of a model locked Nd glass laser, acts as an ultra-fast and periodic shutter, with a few p.s. opening time. Associated with a S.T.L. camera, it gives rise to a picosecond camera allowing us to study very fast effects [fr

A Polarization-Adjustable Picosecond Deep-Ultraviolet Laser for Spin- and Angle-Resolved Photoemission Spectroscopy

International Nuclear Information System (INIS)

Zhang Feng-Feng; Yang Feng; Zhang Shen-Jin; Wang Zhi-Min; Xu Feng-Liang; Peng Qin-Jun; Zhang Jing-Yuan; Xu Zu-Yan; Wang Xiao-Yang; Chen Chuang-Tian

2012-01-01

We report on a polarization-adjustable picosecond deep-ultraviolet (DUV) laser at 177.3 nm. The DUV laser was produced by second harmonic generation from a mode-locked laser at 355 nm in nonlinear optical crystal KBBF. The laser delivered a maximum average output power of 1.1 mW at 177.3 nm. The polarization of the 177.3 nm beam was adjusted with linear and circular polarization by means of λ/4 and λ/2 wave plates. To the best of our knowledge, the laser has been employed as the circularly polarized and linearly polarized DUV light source for a spin- and angle-resolved photoemission spectroscopy with high resolution for the first time. (fundamental areas of phenomenology(including applications))

Plasma ion emission from high intensity picosecond laser pulse interactions with solid targets

International Nuclear Information System (INIS)

Fews, A.P.; Norreys, P.A.; Beg, F.N.; Bell, A.R.; Dangor, A.E.; Danson, C.N.; Lee, P.; Rose, S.J.

1994-01-01

The fast ion emission from high intensity, picosecond laser plasmas has been measured to give the characteristic ion energy and the amount of laser energy transferred to ions with energies ≥100 keV/nucleon as a function of incident intensity. The characteristic ion energy varies from 0.2 to 1.3 MeV over the range 2.0x10 17 --2.0x10 18 W cm -2 . Ten percent of the laser energy is transferred into MeV ions at 2.0x10 18 W cm -2 . Calculations of stopping power in high density materials are presented that show that fast ions cannot be ignored in modeling fast ignitor schemes

Picosecond x-ray streak camera studies

International Nuclear Information System (INIS)

Kasyanov, Yu.S.; Malyutin, A.A.; Richardson, M.C.; Chevokin, V.K.

1975-01-01

Some initial results of direct measurement of picosecond x-ray emission from laser-produced plasmas are presented. A PIM-UMI 93 image converter tube, incorporating an x-ray sensitive photocathode, linear deflection, and three stages of image amplification was used to analyse the x-ray radiation emanating from plasmas produced from solid Ti targets by single high-intensity picosecond laser pulses. From such plasmas, the x-ray emission typically persisted for times of 60psec. However, it is shown that this detection system should be capable of resolving x-ray phenomena of much shorter duration. (author)

Antibacterial mechanisms of a novel type picosecond laser-generated silver-titanium nanoparticles and their toxicity to human cells

Directory of Open Access Journals (Sweden)

Korshed P

2017-12-01

Full Text Available Peri Korshed,1 Lin Li,2 Zhu Liu,3 Aleksandr Mironov,4 Tao Wang1 1School of Biological Science, Faculty of Biology, Medicine and Health, 2Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, 3School of Materials, 4Core Research Facilities, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK Abstract: In this study, we explored the antibacterial mechanisms for a novel type of Ag-TiO2 compound nanoparticles (NPs produced from an Ag-TiO2 alloy using a picosecond laser and evaluated the toxicity of the Ag-TiO2 NPs to a range of human cell types. Transmission electron microscopy was used to determine the morphology, shapes, and size distribution of the laser-generated Ag-TiO2 NPs. UV-visible spectrometer was used to confirm the shift of light absorbance of the NPs toward visible light wavelength. Results showed that the laser-generated Ag-TiO2 NPs had significant antibacterial activities against both Gram-negative and Gram-positive bacterial strains, including Escherichia coli, Pseudomonas aeruginosa, and the methicillin-resistant Staphylococcus aureus. Increased level of reactive oxygen species was produced by E. coli after exposure to the Ag-TiO2 NPs, which was accompanied with lipid peroxidation, glutathione depletion, disintegration of cell membrane and protein leakage, leading to the cell death. Five types of human cells originated from lung (A549, liver (HePG2, kidney (HEK293, endothelium cells (human coronary artery endothelial cells [hCAECs], and skin (human dermal fibroblast cells [HDFc] were used to evaluate the cytotoxicity of the laser-generated Ag-TiO2 NPs. A weak but statistically significant decrease in cell proliferation was observed for hCAECs, A549 and HDFc cells when co-cultured with 2.5 µg/mL or 20 µg/mL of the laser-generated Ag-TiO2 NPs for 48 hours. However, this effect was no longer apparent when a higher concentration of NPs (20 µg/mL was used after 72

Ultrafast high-repetition imaging of fuel sprays using picosecond fiber laser.

Science.gov (United States)

Purwar, Harsh; Wang, Hongjie; Tang, Mincheng; Idlahcen, Saïd; Rozé, Claude; Blaisot, Jean-Bernard; Godin, Thomas; Hideur, Ammar

2015-12-28

Modern diesel injectors operate at very high injection pressures of about 2000 bar resulting in injection velocities as high as 700 m/s near the nozzle outlet. In order to better predict the behavior of the atomization process at such high pressures, high-resolution spray images at high repetition rates must be recorded. However, due to extremely high velocity in the near-nozzle region, high-speed cameras fail to avoid blurring of the structures in the spray images due to their exposure time. Ultrafast imaging featuring ultra-short laser pulses to freeze the motion of the spray appears as an well suited solution to overcome this limitation. However, most commercial high-energy ultrafast sources are limited to a few kHz repetition rates. In the present work, we report the development of a custom-designed picosecond fiber laser generating ∼ 20 ps pulses with an average power of 2.5 W at a repetition rate of 8.2 MHz, suitable for high-speed imaging of high-pressure fuel jets. This fiber source has been proof tested by obtaining backlight images of diesel sprays issued from a single-orifice injector at an injection pressure of 300 bar. We observed a consequent improvement in terms of image resolution compared to standard white-light illumination. In addition, the compactness and stability against perturbations of our fiber laser system makes it particularly suitable for harsh experimental conditions.

Initiation of an early-stage plasma during picosecond laser ablation of solids

International Nuclear Information System (INIS)

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

2000-01-01

Picosecond time-resolved images of plasma initiation were recorded during pulsed-laser ablation of metal targets in an air atmosphere. An early-stage plasma was observed to form before the release of a material vapor plume. Close to the target surface, interferometry measurements indicate that the early-stage plasma has an electron number density on the order of 10 20 cm -3 . The longitudinal expansion of the ionization front for this plasma has a velocity 10 9 cm/s, during the laser pulse. In contrast, a material--vapor plume forms approximately 200 ps after the laser pulse, and it moves away from the target at 10 6 cm/s. The experimental observations of the early-stage plasma were simulated by using a theoretical model based on a two-fluids description of laser plasmas. The results indicate that the initiation of the plasma is due to air breakdown assisted by electron emission from the target

Multichannel, time-resolved picosecond laser ultrasound imaging and spectroscopy with custom complementary metal-oxide-semiconductor detector

International Nuclear Information System (INIS)

Smith, Richard J.; Light, Roger A.; Johnston, Nicholas S.; Pitter, Mark C.; Somekh, Mike G.; Sharples, Steve D.

2010-01-01

This paper presents a multichannel, time-resolved picosecond laser ultrasound system that uses a custom complementary metal-oxide-semiconductor linear array detector. This novel sensor allows parallel phase-sensitive detection of very low contrast modulated signals with performance in each channel comparable to that of a discrete photodiode and a lock-in amplifier. Application of the instrument is demonstrated by parallelizing spatial measurements to produce two-dimensional thickness maps on a layered sample, and spectroscopic parallelization is demonstrated by presenting the measured Brillouin oscillations from a gallium arsenide wafer. This paper demonstrates the significant advantages of our approach to pump probe systems, especially picosecond ultrasonics.

Multichannel, time-resolved picosecond laser ultrasound imaging and spectroscopy with custom complementary metal-oxide-semiconductor detector

Energy Technology Data Exchange (ETDEWEB)

Smith, Richard J.; Light, Roger A.; Johnston, Nicholas S.; Pitter, Mark C.; Somekh, Mike G. [Institute of Biophysics, Imaging and Optical Science, University of Nottingham, Nottinghamshire NG7 2RD (United Kingdom); Sharples, Steve D. [Applied Optics Group, Electrical Systems and Optics Research Division, University of Nottingham, Nottinghamshire NG7 2RD (United Kingdom)

2010-02-15

This paper presents a multichannel, time-resolved picosecond laser ultrasound system that uses a custom complementary metal-oxide-semiconductor linear array detector. This novel sensor allows parallel phase-sensitive detection of very low contrast modulated signals with performance in each channel comparable to that of a discrete photodiode and a lock-in amplifier. Application of the instrument is demonstrated by parallelizing spatial measurements to produce two-dimensional thickness maps on a layered sample, and spectroscopic parallelization is demonstrated by presenting the measured Brillouin oscillations from a gallium arsenide wafer. This paper demonstrates the significant advantages of our approach to pump probe systems, especially picosecond ultrasonics.

Picosecond X-ray streak camera dynamic range measurement

Energy Technology Data Exchange (ETDEWEB)

Zuber, C., E-mail: celine.zuber@cea.fr; Bazzoli, S.; Brunel, P.; Gontier, D.; Raimbourg, J.; Rubbelynck, C.; Trosseille, C. [CEA, DAM, DIF, F-91297 Arpajon (France); Fronty, J.-P.; Goulmy, C. [Photonis SAS, Avenue Roger Roncier, BP 520, 19106 Brive Cedex (France)

2016-09-15

Streak cameras are widely used to record the spatio-temporal evolution of laser-induced plasma. A prototype of picosecond X-ray streak camera has been developed and tested by Commissariat à l’Énergie Atomique et aux Énergies Alternatives to answer the Laser MegaJoule specific needs. The dynamic range of this instrument is measured with picosecond X-ray pulses generated by the interaction of a laser beam and a copper target. The required value of 100 is reached only in the configurations combining the slowest sweeping speed and optimization of the streak tube electron throughput by an appropriate choice of high voltages applied to its electrodes.

Picosecond laser damage of fused silica at 355 nm

International Nuclear Information System (INIS)

Meng Xiangjie; Liu Hongjie; Wang Fang; Zhang Zhen; An Xinyou; Huang Jin; Jiang Xiaodong; Wu Weidong; Ren Weiyi

2013-01-01

This paper studies the initiated damage threshold, the damage morphology and the subsequent damage growth on fused silica's input-surface and exit-surface under picosecond laser irradiation at 355 nm. Defects induced fluorescence on surface of the optical component is observed. The results demonstrate a significant dependence of the initiated damage on pulse duration and surface defects, and that of the damage growth on self-focusing, sub-surface defects. The damage-threshold is 3.98 J/cm 2 of input surface and 2.91 J/cm 2 of exit surface. The damage morphologies are quite different between input surface and exit surface. Slow growth behavior appears for the diameter of exit-surface and linear growth one for the depth of exit-surface in the lateral side of damage site with the increase of shot number. Defects have changed obviously compared with nanosecond laser damage in the damage area. Several main reasons such as electric intensification and self-focusing for the observed initiated damage and damage growth behavior are discussed. (authors)

Treatment of tattoos with a picosecond alexandrite laser: a prospective trial.

Science.gov (United States)

Saedi, Nazanin; Metelitsa, Andrei; Petrell, Kathleen; Arndt, Kenneth A; Dover, Jeffrey S

2012-12-01

OBJECTIVE To study a picosecond 755-nm alexandrite laser for the removal of tattoos to confirm the efficacy of this therapy, focusing on the effect of therapy on the target lesion as well as the surrounding tissues and quantifying the number of necessary treatments. DESIGN Fifteen patients with tattoos were enrolled. Treatments were scheduled approximately 6 ± 2 weeks apart. Standard photographs using 2-dimensional imaging were taken at baseline, before each treatment, and 1 month and 3 months after the last treatment. SETTING Dermatology clinic at SkinCare Physicians in Chestnut Hill, Massachusetts. PATIENTS Fifteen patients with darkly pigmented tattoos. MAIN OUTCOME MEASURES Treatment efficacy was assessed by the level of tattoo clearance in standard photographs. These photographs were assessed by a blinded physician evaluator and based on a 4-point scale. Efficacy was also assessed based on physician and patient satisfaction measured on a 4-point scale. RESULTS Twelve of 15 patients with tattoos (80%) completed the study. All 12 patients obtained greater than 75% clearance. Nine patients (75%) obtained greater than 75% clearance after having 2 to 4 treatments. The average number of treatment sessions needed to obtain this level of clearance was 4.25. All 12 patients (100%) were satisfied or extremely satisfied with the treatment. Adverse effects included pain, swelling, and blistering. Pain resolved immediately after therapy, while the swelling and blistering resolved within 1 week. Hypopigmentation and hyperpigmentation were reported at the 3-month follow-up. CONCLUSION The picosecond 755-nm alexandrite laser is a safe and very effective procedure for removing tattoo pigment.

Two-color pump-probe laser spectroscopy instrument with picosecond time-resolved electronic delay and extended scan range

Science.gov (United States)

Yu, Anchi; Ye, Xiong; Ionascu, Dan; Cao, Wenxiang; Champion, Paul M.

2005-11-01

An electronically delayed two-color pump-probe instrument was developed using two synchronized laser systems. The instrument has picosecond time resolution and can perform scans over hundreds of nanoseconds without the beam divergence and walk-off effects that occur using standard spatial delay systems. A unique picosecond Ti :sapphire regenerative amplifier was also constructed without the need for pulse stretching and compressing optics. The picosecond regenerative amplifier has a broad wavelength tuning range, which suggests that it will make a significant contribution to two-color pump-probe experiments. To test this instrument we studied the rotational correlation relaxation of myoglobin (τr=8.2±0.5ns) in water as well as the geminate rebinding kinetics of oxygen to myoglobin (kg1=1.7×1011s-1, kg2=3.4×107s-1). The results are consistent with, and improve upon, previous studies.

The first terawatt picosecond CO2 laser for advanced accelerator studies at the Brookhaven ATF

International Nuclear Information System (INIS)

Pogorelsky, I.V.; Ben-Zvi, I.; Skaritka, J.

1996-10-01

The first terawatt picosecond C0 2 laser system is under development at the Brookhaven Accelerator Test Facility. Presently operational 1 Joule 100-ps ATF laser will be upgraded with a 10 atm amplifier capable of delivery ∼ 15 Joules of laser energy in a 3 ps pulse. We describe the design of the x-ray preionized 10 atm amplifier of a 10 liter active volume energized by a 1 MV, 200 kA transverse electric discharge. The amplifier, equipped with internal optics, permits the accommodation of a regenerative stage and a multi-pass booster in a relatively compact single discharge volume. The ATF terawatt C0 2 laser shall become operational in 1997 to serve for laser acceleration, x-ray generation and other strong-field physics experiments

Monochromatic x-ray radiography of laser-driven spherical targets using high-energy, picoseconds LFEX laser

Science.gov (United States)

Sawada, Hiroshi; Fujioka, S.; Lee, S.; Arikawa, Y.; Shigemori, K.; Nagatomo, H.; Nishimura, H.; Sunahara, A.; Theobald, W.; Perez, F.; Patel, P. K.; Beg, F. N.

2015-11-01

Formation of a high density fusion fuel is essential in both conventional and advanced Inertial Confinement Fusion (ICF) schemes for the self-sustaining fusion process. In cone-guided Fast Ignition (FI), a metal cone is attached to a spherical target to maintain the path for the injection of an intense short-pulse ignition laser from blow-off plasma created when nanoseconds compression lasers drive the target. We have measured a temporal evolution of a compressed deuterated carbon (CD) sphere using 4.5 keV K-alpha radiography with the Kilo-Joule, picosecond LFEX laser at the Institute of Laser Engineering. A 200 μm CD sphere attached to the tip of a Au cone was directly driven by 9 Gekko XII beams with 300 J/beam in a 1.3 ns Gaussian pulse. The LFEX laser irradiated on a Ti foil to generate 4.51 Ti K-alpha x-ray. By varying the delay between the compression and backlighter lasers, the measured radiograph images show an increase of the areal density of the imploded target. The detail of the quantitative analyses to infer the areal density and comparisons to hydrodynamics simulations will be presented. This work was performed with the support and under the auspices of the NIFS Collaboration Research program (NIFS13KUGK072). H.S. was supported by the UNR's International Activities Grant program.

Generation of picosecond pulses and frequency combs in actively mode locked external ring cavity quantum cascade lasers

International Nuclear Information System (INIS)

Wójcik, Aleksander K.; Belyanin, Alexey; Malara, Pietro; Blanchard, Romain; Mansuripur, Tobias S.; Capasso, Federico

2013-01-01

We propose a robust and reliable method of active mode locking of mid-infrared quantum cascade lasers and develop its theoretical description. Its key element is the use of an external ring cavity, which circumvents fundamental issues undermining the stability of mode locking in quantum cascade lasers. We show that active mode locking can give rise to the generation of picosecond pulses and phase-locked frequency combs containing thousands of the ring cavity modes

Observation of asymmetric Stark profiles from plasmas created by a picosecond KrF laser

International Nuclear Information System (INIS)

Nam, C.H.; Tighe, W.; Suckewer, S.; Seely, J.F.; Feldman, U.; Woltz, L.A.

1987-10-01

High-resolution extreme ultraviolet (XUV) spectra from solid targets irradiated by a picosecond KrF* laser focused to 10 16 W/cm 2 have been recorded. The line profiles of transitions in Li-like fluorine and oxygen are asymmetric and up to 2 A in width. Calculations indicate the presence of transitions of the type 2p-3p and other forbidden Stark components. 11 refs., 6 figs

Measurements of Electron Transport in Foils Irradiated with a Picosecond Time Scale Laser Pulse

International Nuclear Information System (INIS)

Brown, C. R. D.; Hoarty, D. J.; James, S. F.; Swatton, D.; Hughes, S. J.; Morton, J. W.; Guymer, T. M.; Hill, M. P.; Chapman, D. A.; Andrew, J. E.; Comley, A. J.; Shepherd, R.; Dunn, J.; Chen, H.; Schneider, M.; Brown, G.; Beiersdorfer, P.; Emig, J.

2011-01-01

The heating of solid foils by a picosecond time scale laser pulse has been studied by using x-ray emission spectroscopy. The target material was plastic foil with a buried layer of a spectroscopic tracer material. The laser pulse length was either 0.5 or 2 ps, which resulted in a laser irradiance that varied over the range 10 16 -10 19 W/cm 2 . Time-resolved measurements of the buried layer emission spectra using an ultrafast x-ray streak camera were used to infer the density and temperature conditions as a function of laser parameters and depth of the buried layer. Comparison of the data to different models of electron transport showed that they are consistent with a model of electron transport that predicts the bulk of the target heating is due to return currents.

Picosecond mid-infrared amplifier for high average power.

CSIR Research Space (South Africa)

Botha, LR

2007-04-01

Full Text Available High pressure CO2 lasers are good candidates for amplifying picosecond mid infrared pulses. High pressure CO2 lasers are notorious for being unreliable and difficult to operate. In this paper a high pressure CO2 laser is presented based on well...

Pico-second laser spectroscopy and reaction dynamics in liquids

International Nuclear Information System (INIS)

Mialocq, Jean-Claude

1984-01-01

The dynamic relaxation of excited singlet states of molecules and ions in liquid solution is investigated using picosecond laser spectroscopy. The more efficient process for the deactivation of the first excited singlet state of pinacyanol is internal conversion S 1 → S 0 between iso-energetic states. At low viscosity, the rate constant is inversely proportional to the macroscopic viscosity and depends on the relaxation of the angle between the quinoline end groups around the polymethinic chain. Electron photodetachment by 265 nm excitation of the ferrocyanide and phenolate anions and photoionisation of neutral molecules, phenol, indole and tryptophan in polar solvents give rise to the solvated electron formation. The mono-or bi-photonic nature of the ejection process and the solvent relaxation around the excess electron are analyzed. (author) [fr

Relativistic Channeling of a Picosecond Laser Pulse in a Near-Critical Preformed Plasma

International Nuclear Information System (INIS)

Borghesi, M.; MacKinnon, A.J.; Barringer, L.; Gaillard, R.; Gizzi, L.; Meyer, C.; Willi, O.; Pukhov, A.; Meyer-ter-Vehn, J.

1997-01-01

Relativistic self-channeling of a picosecond laser pulse in a preformed plasma near critical density has been observed both experimentally and in 3D particle-in-cell simulations. Optical probing measurements indicate the formation of a single pulsating propagation channel, typically of about 5μm in diameter. The computational results reveal the importance in the channel formation of relativistic electrons traveling with the light pulse and of the corresponding self-generated magnetic field. copyright 1997 The American Physical Society

Laser surface texturing of cast iron steel: dramatic edge burr reduction and high speed process optimisation for industrial production using DPSS picosecond lasers

Science.gov (United States)

Bruneel, David; Kearsley, Andrew; Karnakis, Dimitris

2015-07-01

In this work we present picosecond DPSS laser surface texturing optimisation of automotive grade cast iron steel. This application attracts great interest, particularly in the automotive industry, to reduce friction between moving piston parts in car engines, in order to decrease fuel consumption. This is accomplished by partially covering with swallow microgrooves the inner surface of a piston liner and is currently a production process adopting much longer pulse (microsecond) DPSS lasers. Lubricated interface conditions of moving parts require from the laser process to produce a very strictly controlled surface topography around the laser formed grooves, whose edge burr height must be lower than 100 nm. To achieve such a strict tolerance, laser machining of cast iron steel was investigated using an infrared DPSS picosecond laser (10ps duration) with an output power of 16W and a repetition rate of 200 kHz. The ultrashort laser is believed to provide a much better thermal management of the etching process. All studies presented here were performed on flat samples in ambient air but the process is transferrable to cylindrical geometry engine liners. We will show that reducing significantly the edge burr below an acceptable limit for lubricated engine production is possible using such lasers and remarkably the process window lies at very high irradiated fluences much higher that the single pulse ablation threshold. This detailed experimental work highlights the close relationship between the optimised laser irradiation conditions as well as the process strategy with the final size of the undesirable edge burrs. The optimised process conditions are compatible with an industrial production process and show the potential for removing extra post)processing steps (honing, etc) of cylinder liners on the manufacturing line saving time and cost.

Antibacterial mechanisms of a novel type picosecond laser-generated silver-titanium nanoparticles and their toxicity to human cells.

Science.gov (United States)

Korshed, Peri; Li, Lin; Liu, Zhu; Mironov, Aleksandr; Wang, Tao

2018-01-01

In this study, we explored the antibacterial mechanisms for a novel type of Ag-TiO 2 compound nanoparticles (NPs) produced from an Ag-TiO 2 alloy using a picosecond laser and evaluated the toxicity of the Ag-TiO 2 NPs to a range of human cell types. Transmission electron microscopy was used to determine the morphology, shapes, and size distribution of the laser-generated Ag-TiO 2 NPs. UV-visible spectrometer was used to confirm the shift of light absorbance of the NPs toward visible light wavelength. Results showed that the laser-generated Ag-TiO 2 NPs had significant antibacterial activities against both Gram-negative and Gram-positive bacterial strains, including Escherichia coli, Pseudomonas aeruginosa , and the methicillin-resistant Staphylococcus aureus . Increased level of reactive oxygen species was produced by E. coli after exposure to the Ag-TiO 2 NPs, which was accompanied with lipid peroxidation, glutathione depletion, disintegration of cell membrane and protein leakage, leading to the cell death. Five types of human cells originated from lung (A549), liver (HePG2), kidney (HEK293), endothelium cells (human coronary artery endothelial cells [hCAECs]), and skin (human dermal fibroblast cells [HDFc]) were used to evaluate the cytotoxicity of the laser-generated Ag-TiO 2 NPs. A weak but statistically significant decrease in cell proliferation was observed for hCAECs, A549 and HDFc cells when co-cultured with 2.5 µg/mL or 20 µg/mL of the laser-generated Ag-TiO 2 NPs for 48 hours. However, this effect was no longer apparent when a higher concentration of NPs (20 µg/mL) was used after 72 hours of co-culture with human cells, suggesting a possible adaptive process in the cells had occurred. We conclude that picosecond laser-generated Ag-TiO 2 NPs have a broad spectrum of antibacterial effect, including against the drug-resistant strain, with multiple underlying molecular mechanisms and low human cell toxicity. The antimicrobial properties of the new type of

Quantitative study of the ionization-induced refraction of picosecond laser pulses in gas-jet targets

International Nuclear Information System (INIS)

Mackinnon, A.J.; Borghesi, M.; Iwase, A.; Jones, M.W.; Pert, G.J.; Rae, S.; Burnett, K.; Willi, O.

1996-01-01

A quantitative study of refractive whole beam defocusing and small scale breakup induced by optical ionization of subpicosecond and picosecond, 0.25 and 1 μm, laser pulses in gas-jet targets at densities above 1x10 19 cm -3 has been carried out. A significant reduction of the incident laser intensity was observed due to refraction from ionization-induced density gradients. The level of refraction measured with optical probing correlated well with the fraction of energy transmitted through the plasma. The numerical and analytical models were found to agree well with experimental observations. copyright 1996 The American Physical Society

Controlling dental enamel-cavity ablation depth with optimized stepping parameters along the focal plane normal using a three axis, numerically controlled picosecond laser.

Science.gov (United States)

Yuan, Fusong; Lv, Peijun; Wang, Dangxiao; Wang, Lei; Sun, Yuchun; Wang, Yong

2015-02-01

The purpose of this study was to establish a depth-control method in enamel-cavity ablation by optimizing the timing of the focal-plane-normal stepping and the single-step size of a three axis, numerically controlled picosecond laser. Although it has been proposed that picosecond lasers may be used to ablate dental hard tissue, the viability of such a depth-control method in enamel-cavity ablation remains uncertain. Forty-two enamel slices with approximately level surfaces were prepared and subjected to two-dimensional ablation by a picosecond laser. The additive-pulse layer, n, was set to 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70. A three-dimensional microscope was then used to measure the ablation depth, d, to obtain a quantitative function relating n and d. Six enamel slices were then subjected to three dimensional ablation to produce 10 cavities, respectively, with additive-pulse layer and single-step size set to corresponding values. The difference between the theoretical and measured values was calculated for both the cavity depth and the ablation depth of a single step. These were used to determine minimum-difference values for both the additive-pulse layer (n) and single-step size (d). When the additive-pulse layer and the single-step size were set 5 and 45, respectively, the depth error had a minimum of 2.25 μm, and 450 μm deep enamel cavities were produced. When performing three-dimensional ablating of enamel with a picosecond laser, adjusting the timing of the focal-plane-normal stepping and the single-step size allows for the control of ablation-depth error to the order of micrometers.

Investigation of Carbon Fiber Reinforced Plastics Machining Using 355 nm Picosecond Pulsed Laser

Science.gov (United States)

Hu, Jun; Zhu, Dezhi

2018-06-01

Carbon fiber reinforced plastics (CFRP) has been widely used in the aircraft industry and automobile industry owing to its superior properties. In this paper, a Nd:YVO4 picosecond pulsed system emitting at 355 nm has been used for CFRP machining experiments to determine optimum milling conditions. Milling parameters including laser power, milling speed and hatch distance were optimized by using box-behnken design of response surface methodology (RSM). Material removal rate was influenced by laser beam overlap ratio which affects mechanical denudation. The results in heat affected zones (HAZ) and milling quality were discussed through the machined surface observed with scanning electron microscope. A re-focusing technique based on the experiment with different focal planes was proposed and milling mechanism was also analyzed in details.

Investigation of Carbon Fiber Reinforced Plastics Machining Using 355 nm Picosecond Pulsed Laser

Science.gov (United States)

Hu, Jun; Zhu, Dezhi

2017-08-01

Carbon fiber reinforced plastics (CFRP) has been widely used in the aircraft industry and automobile industry owing to its superior properties. In this paper, a Nd:YVO4 picosecond pulsed system emitting at 355 nm has been used for CFRP machining experiments to determine optimum milling conditions. Milling parameters including laser power, milling speed and hatch distance were optimized by using box-behnken design of response surface methodology (RSM). Material removal rate was influenced by laser beam overlap ratio which affects mechanical denudation. The results in heat affected zones (HAZ) and milling quality were discussed through the machined surface observed with scanning electron microscope. A re-focusing technique based on the experiment with different focal planes was proposed and milling mechanism was also analyzed in details.

Picosecond and subpicosecond pulsed laser deposition of Pb thin films

Directory of Open Access Journals (Sweden)

F. Gontad

2013-09-01

Full Text Available Pb thin films were deposited on Nb substrates by means of pulsed laser deposition (PLD with UV radiation (248 nm, in two different ablation regimes: picosecond (5 ps and subpicosecond (0.5 ps. Granular films with grain size on the micron scale have been obtained, with no evidence of large droplet formation. All films presented a polycrystalline character with preferential orientation along the (111 crystalline planes. A maximum quantum efficiency (QE of 7.3×10^{-5} (at 266 nm and 7 ns pulse duration was measured, after laser cleaning, demonstrating good photoemission performance for Pb thin films deposited by ultrashort PLD. Moreover, Pb thin film photocathodes have maintained their QE for days, providing excellent chemical stability and durability. These results suggest that Pb thin films deposited on Nb by ultrashort PLD are a noteworthy alternative for the fabrication of photocathodes for superconductive radio-frequency electron guns. Finally, a comparison with the characteristics of Pb films prepared by ns PLD is illustrated and discussed.

Negative pressure and spallation in graphite targets under nano- and picosecond laser irradiation

Energy Technology Data Exchange (ETDEWEB)

Belikov, R S; Khishchenko, K V [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Krasyuk, I K; Semenov, A Yu; Stuchebryukhov, I A [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Rinecker, T; Schoenlein, A [Goethe University Frankfurt am Main (Germany); Rosmej, O N [GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany, 64291 Darmstadt, Planckstraße, 1 (Germany); Tomut, M [Technische Universität Darmstadt, Germany, 64289 Darmstadt, Karolinenplatz, 5 (Germany)

2015-05-31

We present the results of experiments on the spallation phenomena in graphite targets under shock-wave nano- and picosecond irradiation, which have been performed on Kamerton-T (GPI, Moscow, Russia) and PHELIX (GSI, Darmstadt, Germany) laser facilities. In the range of the strain rates of 10{sup 6} – 10{sup 7} s{sup -1}, the data on the dynamic mechanical strength of the material at rapure (spallation) have been for the first time obtained. With a maximal strain rate of 1.4 × 10{sup 7} s{sup -1}, the spall strength of 2.1 GPa is obtained, which constitutes 64% of the theoretical ultimate tensile strength of graphite. The effect of spallation is observed not only on the rear side of the target, but also on its irradiated (front) surface. With the use of optical and scanning electron microscopes, the morphology of the front and rear surfaces of the targets is studied. By means of Raman scattering of light, the graphite structure both on the target front surface under laser exposure and on its rear side in the spall zone is investigated. A comparison of the dynamic strength of graphite and synthetic diamond is performed. (extreme light fields and their applications)

Picosecond laser pulse-driven crystallization behavior of SiSb phase change memory thin films

International Nuclear Information System (INIS)

Huang Huan; Li Simian; Zhai Fengxiao; Wang Yang; Lai Tianshu; Wu Yiqun; Gan Fuxi

2011-01-01

Highlights: → We reported crystallization dynamics of a novel SiSb phase change material. → We measured optical constants of as-deposited and irradiated SiSb areas. → Optical properties of as-deposited and irradiated SiSb thin film were compared. → Crystallization of irradiated SiSb was confirmed by using AFM and micro-Raman spectra. → The heat conduction effect of lower metal layer of multi-layer films was studied. - Abstract: Transient phase change crystallization process of SiSb phase change thin films under the irradiation of picosecond (ps) laser pulse was studied using time-resolved reflectivity measurements. The ps laser pulse-crystallized domains were characterized by atomic force microscope, Raman spectra and ellipsometrical spectra measurements. A reflectivity contrast of about 15% can be achieved by ps laser pulse-induced crystallization. A minimum crystallization time of 11 ns was achieved by a low-fluence single ps laser pulse after pre-irradiation. SiSb was shown to be very promising for fast phase change memory applications.

Optoelectronic Picosecond Detection of Synchrotron X-rays

Energy Technology Data Exchange (ETDEWEB)

Durbin, Stephen M. [Purdue Univ., West Lafayette, IN (United States)

2017-08-04

The goal of this research program was to develop a detector that would measure x-ray time profiles with picosecond resolution. This was specifically aimed for use at x-ray synchrotrons, where x-ray pulse profiles have Gaussian time spreads of 50-100 ps (FWHM), so the successful development of such a detector with picosecond resolution would permit x-ray synchrotron studies to break through the pulse width barrier. That is, synchrotron time-resolved studies are currently limited to pump-probe studies that cannot reveal dynamics faster than ~50 ps, whereas the proposed detector would push this into the physically important 1 ps domain. The results of this research effort, described in detail below, are twofold: 1) the original plan to rely on converting electronic signals from a semiconductor sensor into an optical signal proved to be insufficient for generating signals with the necessary time resolution and sensitivity to be widely applicable; and 2) an all-optical method was discovered whereby the x-rays are directly absorbed in an optoelectronic material, lithium tantalate, which can then be probed by laser pulses with the desired picosecond sensitivity for detection of synchrotron x-rays. This research program has also produced new fundamental understanding of the interaction of x-rays and optical lasers in materials that has now created a viable path for true picosecond detection of synchrotron x-rays.

Study of photo-activated electron transfer reactions in the first excited singlet state by picosecond and nanosecond laser spectroscopy

International Nuclear Information System (INIS)

Doizi, Denis

1983-01-01

Picosecond laser spectroscopy has been used to study two photo-activated electron transfer reactions: - a bimolecular electron transfer reaction between a sensitizer, DODCI, and an electron acceptor, methylviologen. The two radical ions created with an electron transfer efficiency γ ≅ 0.07 have been identified in picosecond and nanosecond laser absorption spectroscopy by adding selective solutes such as para-benzoquinone (an electron acceptor) or L(+) ascorbic acid (an electron donor). - an intramolecular electron transfer reaction in a triad molecule consisting of a tetra-aryl-porphyrin covalently linked to both a carotenoid and a quinone. The photoinduced charge separation occurs within 30 ps and leads, with a yield of 25 pc, to the formation of a zwitterion whose half-life is 2.5 μs. The experimental results obtained in these two studies show an effective decrease in the recombination rate of the two radical ions created in the encounter pair. (author) [fr

ELYSE, a new picosecond electron accelerator at Orsay

International Nuclear Information System (INIS)

Belloni, J.D.; Gaillard, M.; Monard, H.; Larbre, J.-P.; Gobert, F.; Mostafavi, M.; Lampre, I.; Marignier, J.-L.

2003-01-01

ELYSE is a new instrument allowing to study fast kinetics processes at picosecond range by the complementary techniques of pulse radiolysis and laser photochemistry which was installed by the Laboratoire de Chimie Physique, University Paris-Sud, at Orsay. It was designed and constructed by the Linear Accelerator Laboratory, Orsay. The accelerator is a RF photocathode electron gun type which will deliver electron pulses of less than 5 ps FWHM. The Cs 2 Te cathode was chosen because of its high efficiency and long life time. Photoelectrons are generated by a picosecond synchronized laser system with a normal incidence. The charge per pulse is 1 nC with a dark current less than 1 % and a repetition frequency 1 to 50 Hz. Other detailed specifications of the accelerator, of the laser and of the optical spectroscopy detection set-up are described

Laser ablated micropillar energy directors for ultrasonic welding of microfluidic systems

DEFF Research Database (Denmark)

Poulsen, Carl Esben; Kistrup, Kasper; Andersen, Nis Korsgaard

2016-01-01

We present a new type of energy director (ED) for ultrasonic welding of microfluidic systems. These micropillar EDs are based on the replication of cone like protrusion structures introduced using a pico-second laser and may therefore be added to any mould surface accessible to a pico-second laser...

Pseudo-topotactic conversion of carbon nanotubes to T-carbon nanowires under picosecond laser irradiation in methanol.

Science.gov (United States)

Zhang, Jinying; Wang, Rui; Zhu, Xi; Pan, Aifei; Han, Chenxiao; Li, Xin; Dan Zhao; Ma, Chuansheng; Wang, Wenjun; Su, Haibin; Niu, Chunming

2017-09-25

Pseudo-topotactic conversion of carbon nanotubes into one-dimensional carbon nanowires is a challenging but feasible path to obtain desired diameters and morphologies. Here, a previously predicted but experimentally unobserved carbon allotrope, T-carbon, has been produced from pseudo-topotactic conversion of a multi-walled carbon nanotube suspension in methanol by picosecond pulsed-laser irradiation. The as-grown T-carbon nanowires have the same diameter distribution as pristine carbon nanotubes, and have been characterized by high-resolution transmission electron microscopy, fast Fourier transform, electron energy loss, ultraviolet-visible, and photoluminescence spectroscopies to possess a diamond-like lattice, where each carbon is replaced by a carbon tetrahedron, and a lattice constant of 7.80 Å. The change in entropy from carbon nanotubes to T-carbon reveals the phase transformation to be first order in nature. The computed electronic band structures and projected density of states are in good agreement with the optical absorption and photoluminescence spectra of the T-carbon nanowires.T-carbon is a previously predicted but so far unobserved allotrope of carbon, with a crystal structure similar to diamond, but with each atomic lattice position replaced by a carbon tetrahedron. Here, the authors produce T-carbon nanowires via laser-irradiating a suspension of carbon nanotubes in methanol.

Fabrication of superhydrophilic or superhydrophobic self-cleaning metal surfaces using picosecond laser pulses and chemical fluorination

Science.gov (United States)

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

2016-05-01

Bioinspired superhydrophilic/phobic self-cleaning surfaces have recently drawn a lot of interest in both fundamental and applied research. A hybrid method to produce the self-cleaning property of micro/nanostructured surface using ultra-fast laser pulses followed by chemical fluorination is proposed. The typical micro/nanocomposite structures that form from microporous arrays and microgroove groups have been processed by picosecond laser on titanium alloy surface. The surface hydrophilic/phobic and self-cleaning properties of micro/nanostructures before and after fluorination with fluoroalkyl-silane were investigated using surface contact angle measurements. The results indicate that surface properties change from hydrophilic to hydrophobic after fluorination, and the micro/nanostructured surface with increased roughness contributes to the improvement of surface hydrophobicity. The micro/nanomodification can make the original hydrophilic titanium alloy surface more hydrophilic or superhydrophilic. It also can make an originally hydrophobic fluorinated titanium alloy surface more hydrophobic or superhydrophobic. The produced micro/nanostructured titanium alloy surfaces show excellent self-cleaning properties regardless of the fluorination treatment, although the fluorinated surfaces have slightly better self-cleaning properties. It is found that surface treatment using ultra-fast laser pulses and subsequent chemical fluorination is an effective way to manipulate surface wettability and obtain self-cleaning properties.

Surface characterization of carbon fiber reinforced polymers by picosecond laser induced breakdown spectroscopy

Science.gov (United States)

Ledesma, Rodolfo; Palmieri, Frank; Connell, John; Yost, William; Fitz-Gerald, James

2018-02-01

Adhesive bonding of composite materials requires reliable monitoring and detection of surface contaminants as part of a vigorous quality control process to assure robust and durable bonded structures. Surface treatment and effective monitoring prior to bonding are essential in order to obtain a surface which is free from contaminants that may lead to inferior bond quality. In this study, the focus is to advance the laser induced breakdown spectroscopy (LIBS) technique by using pulse energies below 100 μJ (μLIBS) for the detection of low levels of silicone contaminants in carbon fiber reinforced polymer (CFRP) composites. Various CFRP surface conditions were investigated by LIBS using ∼10 ps, 355 nm laser pulses with pulse energies below 30 μJ. Time-resolved analysis was conducted to optimize the gate delay and gate width for the detection of the C I emission line at 247.9 nm to monitor the epoxy resin matrix of CFRP composites and the Si I emission line at 288.2 nm for detection of silicone contaminants in CFRP. To study the surface sensitivity to silicone contamination, CFRP surfaces were coated with polydimethylsiloxane (PDMS), the active ingredient in many mold release agents. The presence of PDMS was studied by inspecting the Si I emission lines at 251.6 nm and 288.2 nm. The measured PDMS areal densities ranged from 0.15 to 2 μg/cm2. LIBS measurements were performed before and after laser surface ablation. The results demonstrate the successful detection of PDMS thin layers on CFRP using picosecond μLIBS.

Micro-joule pico-second range Yb3+-doped fibre laser for medical applications in acupuncture

Science.gov (United States)

Alvarez-Chavez, J. A.; Rivera-Manrique, S. I.; Jacques, S. L.

2011-08-01

The work described here is based on the optical design, simulation and on-going implementation of a pulsed (Q-switch) Yb3+-doped, 1-um diffraction-limited fibre laser with pico-second, 10 micro-Joule-range energy pulses for producing the right energy pulses which could be of benefit for patients who suffer chronic headache, photophobia, and even nausea which could is sometimes triggered by a series of factors. The specific therapeutic effect known as acupunctural analgesia is the main objective of this medium-term project. It is a simple design on which commercially available software was employed for laser cavity design. Monte Carlo technique for skin light-transport, thermal diffusion and the possible thermal de-naturalization optical study and prediction will also be included in the presentation. Full optical characterization will be included and a complete set of recent results on the laser-skin interaction and the so called moxi-bustion from the laser design will be extensively described.

Synthesis by picosecond laser ablation of ligand-free Ag and Au nanoparticles for SERS applications

Science.gov (United States)

Fazio, Enza; Spadaro, Salvatore; Santoro, Marco; Trusso, Sebastiano; Lucotti, Andrea.; Tommasini, Matteo.; Neri, Fortunato; Maria Ossi, Paolo

2018-01-01

The morphological and optical properties of noble metal nanoparticles prepared by picosecond laser generated plasmas in water were investigated. First, the ablation efficiency was maximized searching the optimal focusing conditions. The nanoparticle size, measured by Scanning Transmission Electron Microscopy, strongly depends on the laser fluence, keeping fixed the other deposition parameters such as the target to scanner objective distance and laser repetition frequency. STEM images indicate narrow gradients of NP sizes. Hence the optimization of ablation parameters favours a fine tuning of nanoparticles. UV-Visible spectroscopy helped to determine the appropriate laser wavelength to resonantly excite the localized surface plasmon to carry out Surface Enhanced Raman Scattering (SERS) measurements. The SERS activity of Ag and Au substrates, obtained spraying the colloids synthesized in water, was tested using crystal violet as a probe molecule. The good SERS performance, observed at excitation wavelength 785 nm, is attributed to aggregation phenomena of nanoparticles sprayed on the support.

Picosecond Laser Treatment for Tattoos and Benign Cutaneous Pigmented Lesions (Secondary publication).

Science.gov (United States)

Kasai, Kenichiro

2017-12-31

The selective removal of tattoos and benign cutaneous pigmented lesions with laser energy evolved rapidly with the development of the nanosecond-domain Q-switched laser (ns-laser). Recently, however, a series of picosecond-domain lasers (ps-lasers) with pulsewidths less than 1 ns has become commercially available, enabling more efficient and faster removal of pigmented lesions in the field of dermatologic laser surgery. The efficacy of the ns-laser depended on the theory of selective photothermolysis, whereby an extremely short pulse width was delivered less than the thermal relaxation time (TRT) of a target. At sub-ns pulsewidths, i.e. in the ps-domain, this efficacy is dramatically extended through defeating the stress relaxation time (SRT) of a target allowing for even more effective pigment destruction with even less damage to the surrounding normal tissue. This will be discussed in detail. The ps-laser has been reported as achieving tattoo removal in fewer sessions than the ns-laser, with less in the way of unwanted side effects. Tattoos recalcitrant to ns-laser treatment have responded well to the ps-laser, and although true 'color blindness' is not yet completely achieved with the ps-domain pulses currently available, multicolored tattoos have also responded very favorably. The ability to limit damage precisely to the pigment target gives greater efficacy in treatment of epidermal lesions with less induction of post-inflammatory hyperpigmentation in the PIH-susceptible Asian skin, and dermal melanocytosis also respond very well to ps-laser treatment. Illustrative clinical examples from the author's experience are given. Current ps-lasers could be a revolutionary advance for laser tattoo removal but may be less effective for some specific aesthetic indications such as melasma and other cosmetic procedures. Manufacturers must make an effort to reduce the current comparatively long ps-domain pulsewidths to deliver a 'true' ps-domain laser, with more basic

Post-processing of 3D-printed parts using femtosecond and picosecond laser radiation

Science.gov (United States)

Mingareev, Ilya; Gehlich, Nils; Bonhoff, Tobias; Meiners, Wilhelm; Kelbassa, Ingomar; Biermann, Tim; Richardson, Martin C.

2014-03-01

Additive manufacturing, also known as 3D-printing, is a near-net shape manufacturing approach, delivering part geometry that can be considerably affected by various process conditions, heat-induced distortions, solidified melt droplets, partially fused powders, and surface modifications induced by the manufacturing tool motion and processing strategy. High-repetition rate femtosecond and picosecond laser radiation was utilized to improve surface quality of metal parts manufactured by laser additive techniques. Different laser scanning approaches were utilized to increase the ablation efficiency and to reduce the surface roughness while preserving the initial part geometry. We studied post-processing of 3D-shaped parts made of Nickel- and Titanium-base alloys by utilizing Selective Laser Melting (SLM) and Laser Metal Deposition (LMD) as additive manufacturing techniques. Process parameters such as the pulse energy, the number of layers and their spatial separation were varied. Surface processing in several layers was necessary to remove the excessive material, such as individual powder particles, and to reduce the average surface roughness from asdeposited 22-45 μm to a few microns. Due to the ultrafast laser-processing regime and the small heat-affected zone induced in materials, this novel integrated manufacturing approach can be used to post-process parts made of thermally and mechanically sensitive materials, and to attain complex designed shapes with micrometer precision.

Lasers in tattoo and pigmentation control: role of the PicoSure(®) laser system.

Science.gov (United States)

Torbeck, Richard; Bankowski, Richard; Henize, Sarah; Saedi, Nazanin

2016-01-01

The use of picosecond lasers to remove tattoos has greatly improved due to the long-standing outcomes of nanosecond lasers, both clinically and histologically. The first aesthetic picosecond laser available for this use was the PicoSure(®) laser system (755/532 nm). Now that a vast amount of research on its use has been conducted, we performed a comprehensive review of the literature to validate the continued application of the PicoSure(®) laser system for tattoo removal. A PubMed search was conducted using the term "picosecond" combined with "laser", "dermatology", and "laser tattoo removal". A total of 13 articles were identified, and ten of these met the inclusion criteria for this review. The majority of studies showed that picosecond lasers are an effective and safe treatment mode for the removal of tattoo pigments. Several studies also indicated potential novel applications of picosecond lasers in the removal of various tattoo pigments (eg, black, red, and yellow). Adverse effects were generally mild, such as transient hypopigmentation or blister formation, and were rarely more serious, such as scarring and/or textural change. Advancements in laser technologies and their application in cutaneous medicine have revolutionized the field of laser surgery. Computational modeling provides evidence that the optimal pulse durations for tattoo ink removal are in the picosecond domain. It is recommended that the PicoSure(®) laser system continue to be used for safe and effective tattoo removal, including for red and yellow pigments.

Lasers in tattoo and pigmentation control: role of the PicoSure® laser system

Directory of Open Access Journals (Sweden)

Torbeck R

2016-05-01

Full Text Available Richard Torbeck,1 Richard Bankowski,2 Sarah Henize,3 Nazanin Saedi,11Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 2Cynosure, Inc, Westford, MA, 3Huron Consulting Group, Chicago, IL, USABackground and objectives: The use of picosecond lasers to remove tattoos has greatly improved due to the long-standing outcomes of nanosecond lasers, both clinically and histologically. The first aesthetic picosecond laser available for this use was the PicoSure® laser system (755/532 nm. Now that a vast amount of research on its use has been conducted, we performed a comprehensive review of the literature to validate the continued application of the PicoSure® laser system for tattoo removal.Study design and methods: A PubMed search was conducted using the term "picosecond" combined with "laser", "dermatology", and "laser tattoo removal".Results: A total of 13 articles were identified, and ten of these met the inclusion criteria for this review. The majority of studies showed that picosecond lasers are an effective and safe treatment mode for the removal of tattoo pigments. Several studies also indicated potential novel applications of picosecond lasers in the removal of various tattoo pigments (eg, black, red, and yellow. Adverse effects were generally mild, such as transient hypopigmentation or blister formation, and were rarely more serious, such as scarring and/or textural change.Conclusion: Advancements in laser technologies and their application in cutaneous medicine have revolutionized the field of laser surgery. Computational modeling provides evidence that the optimal pulse durations for tattoo ink removal are in the picosecond domain. It is recommended that the PicoSure® laser system continue to be used for safe and effective tattoo removal, including for red and yellow pigments.Keywords: tattoo, removal, laser, picosecond 

Six-frame picosecond radiation camera based on hydrated electron photoabsorption phenomena

International Nuclear Information System (INIS)

Coutts, G.W.; Olk, L.B.; Gates, H.A.; St Leger-Barter, G.

1977-01-01

To obtain picosecond photographs of nanosecond radiation sources, a six-frame ultra-high speed radiation camera based on hydrated electron absorption phenomena has been developed. A time-dependent opacity pattern is formed in an acidic aqueous cell by a pulsed radiation source. Six time-resolved picosecond images of this changing opacity pattern are transferred to photographic film with the use of a mode-locked dye laser and six electronically gated microchannel plate image intensifiers. Because the lifetime of the hydrated electron absorption centers can be reduced to picoseconds, the opacity patterns represent time-space pulse profile images

Simulation of excitation and propagation of pico-second ultrasound

International Nuclear Information System (INIS)

Yang, Seung Yong; Kim, No Hyu

2016-01-01

This paper presents an analytic and numerical simulation of the generation and propagation of pico-second ultrasound with nano-scale wavelength, enabling the production of bulk waves in thin films. An analytic model of laser-matter interaction and elasto-dynamic wave propagation is introduced to calculate the elastic strain pulse in microstructures. The model includes the laser-pulse absorption on the material surface, heat transfer from a photon to the elastic energy of a phonon, and acoustic wave propagation to formulate the governing equations of ultra-short ultrasound. The excitation and propagation of acoustic pulses produced by ultra-short laser pulses are numerically simulated for an aluminum substrate using the finite-difference method and compared with the analytical solution. Furthermore, Fourier analysis was performed to investigate the frequency spectrum of the simulated elastic wave pulse. It is concluded that a pico-second bulk wave with a very high frequency of up to hundreds of gigahertz is successfully generated in metals using a 100-fs laser pulse and that it can be propagated in the direction of thickness for thickness less than 100 nm

Simulation of excitation and propagation of pico-second ultrasound

Energy Technology Data Exchange (ETDEWEB)

Yang, Seung Yong; Kim, No Hyu [Dept. of Mechanical Engineering, Korea University of Technology and Education, Chunan (Korea, Republic of)

2016-12-15

This paper presents an analytic and numerical simulation of the generation and propagation of pico-second ultrasound with nano-scale wavelength, enabling the production of bulk waves in thin films. An analytic model of laser-matter interaction and elasto-dynamic wave propagation is introduced to calculate the elastic strain pulse in microstructures. The model includes the laser-pulse absorption on the material surface, heat transfer from a photon to the elastic energy of a phonon, and acoustic wave propagation to formulate the governing equations of ultra-short ultrasound. The excitation and propagation of acoustic pulses produced by ultra-short laser pulses are numerically simulated for an aluminum substrate using the finite-difference method and compared with the analytical solution. Furthermore, Fourier analysis was performed to investigate the frequency spectrum of the simulated elastic wave pulse. It is concluded that a pico-second bulk wave with a very high frequency of up to hundreds of gigahertz is successfully generated in metals using a 100-fs laser pulse and that it can be propagated in the direction of thickness for thickness less than 100 nm.

Simulation of excitation and propagation of pico-second ultrasound

Energy Technology Data Exchange (ETDEWEB)

Yang, Seung Yong; Kim, No Kyu [Dept. of Mechanical Engineering, Korea University of Technology and Education, Chunan (Korea, Republic of)

2014-12-15

This paper presents an analytic and numerical simulation of the generation and propagation of pico-second ultrasound with nano-scale wavelength, enabling the production of bulk waves in thin films. An analytic model of laser-matter interaction and elasto-dynamic wave propagation is introduced to calculate the elastic strain pulse in microstructures. The model includes the laser-pulse absorption on the material surface, heat transfer from a photon to the elastic energy of a phonon, and acoustic wave propagation to formulate the governing equations of ultra-short ultrasound. The excitation and propagation of acoustic pulses produced by ultra-short laser pulses are numerically simulated for an aluminum substrate using the finite-difference method and compared with the analytical solution. Furthermore, Fourier analysis was performed to investigate the frequency spectrum of the simulated elastic wave pulse. It is concluded that a pico-second bulk wave with a very high frequency of up to hundreds of gigahertz is successfully generated in metals using a 100-fs laser pulse and that it can be propagated in the direction of thickness for thickness less than 100 nm.

Laser breakdown with millijoule trains of picosecond pulses transmitted through a hollow-core photonic-crystal fibre

CERN Document Server

Konorov, S O; Kolevatova, O A; Beloglasov, V I; Skibina, N B; Shcherbakov, A V; Wintner, E; Zheltikov, A M

2003-01-01

Sequences of picosecond pulses with a total energy in the pulse train of about 1 mJ are transmitted through a hollow-core photonic-crystal fibre with a core diameter of approximately 14 mu m. The fluence of laser radiation coupled into the core of the fibre under these conditions exceeds the breakdown threshold of fused silica by nearly an order of magnitude. The laser beam coming out of the fibre is then focused to produce a breakdown on a solid surface. Parameters of laser radiation were chosen in such a way as to avoid effects related to the excitation of higher order waveguide modes and ionization of the gas filling the fibre in order to provide the possibility to focus the output beam into a spot with a minimum diameter, thus ensuring the maximum spatial resolution and the maximum power density in the focal spot.

Debris-free rear-side picosecond laser ablation of thin germanium wafers in water with ethanol

International Nuclear Information System (INIS)

Zhang, Dongshi; Gökce, Bilal; Sommer, Steffen; Streubel, René; Barcikowski, Stephan

2016-01-01

Graphical abstract: - Highlights: • Picosecond laser cutting of fragile 150 μm thin germanium wafers (typically used for solar cell applications) in liquid results in debris-free surfaces. • Liquid-assisted laser cutting is much better than air-assisted laser cutting in terms of recast, debris and cleanness of the resultant grooves. • Laser cutting in ethanol–water mixtures result in better cut quality than those performed in pure water but lead to less cutting efficiency. • Low repetition rate (10 kHz), mixed solution (1 wt% ethanol in water) and moderate scanning speed (100 μm/s) are preferable for ultrafine high-quality debris-free cutting. - Abstract: In this paper, we perform liquid-assisted picosecond laser cutting of 150 μm thin germanium wafers from the rear side. By investigating the cutting efficiency (the ability to allow an one-line cut-through) and quality (characterized by groove morphologies on both sides), the pros and cons of this technique under different conditions are clarified. Specifically, with laser fluence fixed, repetition rate and scanning speed are varied to show quality and efficiency control by means of laser parameter modulation. It is found that low repetition rate ablation in liquid gives rise to a better cut quality on the front side than high repetition rate ablation since it avoids dispersed nanoparticles redeposition resulting from a bubble collapse, unlike the case of 100 kHz which leads to large nanorings near the grooves resulting from a strong interaction of bubbles and the case of 50 kHz which leads to random cutting due to the interaction of the former pulse induced cavitation bubble and the subsequent laser pulse. Furthermore, ethanol is mixed with pure distilled water to assess the liquid's impact on the cutting efficiency and cutting quality. The results show that increasing the ethanol fraction decreases the ablation efficiency but simultaneously, greatly improves the cutting quality. The improvement of

Debris-free rear-side picosecond laser ablation of thin germanium wafers in water with ethanol

Energy Technology Data Exchange (ETDEWEB)

Zhang, Dongshi; Gökce, Bilal [Technical Chemistry I and Center for Nanointegration, Duisburg-Essen (CENIDE), University of Duisburg-Essen, Universitaetsstrasse 7, 45141 Essen (Germany); Sommer, Steffen [Dausinger & Giesen GmbH, Rotebühlstrasse 87, 70178 Stuttgart (Germany); Streubel, René [Technical Chemistry I and Center for Nanointegration, Duisburg-Essen (CENIDE), University of Duisburg-Essen, Universitaetsstrasse 7, 45141 Essen (Germany); Barcikowski, Stephan, E-mail: stephan.barcikowski@uni-due.de [Technical Chemistry I and Center for Nanointegration, Duisburg-Essen (CENIDE), University of Duisburg-Essen, Universitaetsstrasse 7, 45141 Essen (Germany)

2016-03-30

Graphical abstract: - Highlights: • Picosecond laser cutting of fragile 150 μm thin germanium wafers (typically used for solar cell applications) in liquid results in debris-free surfaces. • Liquid-assisted laser cutting is much better than air-assisted laser cutting in terms of recast, debris and cleanness of the resultant grooves. • Laser cutting in ethanol–water mixtures result in better cut quality than those performed in pure water but lead to less cutting efficiency. • Low repetition rate (10 kHz), mixed solution (1 wt% ethanol in water) and moderate scanning speed (100 μm/s) are preferable for ultrafine high-quality debris-free cutting. - Abstract: In this paper, we perform liquid-assisted picosecond laser cutting of 150 μm thin germanium wafers from the rear side. By investigating the cutting efficiency (the ability to allow an one-line cut-through) and quality (characterized by groove morphologies on both sides), the pros and cons of this technique under different conditions are clarified. Specifically, with laser fluence fixed, repetition rate and scanning speed are varied to show quality and efficiency control by means of laser parameter modulation. It is found that low repetition rate ablation in liquid gives rise to a better cut quality on the front side than high repetition rate ablation since it avoids dispersed nanoparticles redeposition resulting from a bubble collapse, unlike the case of 100 kHz which leads to large nanorings near the grooves resulting from a strong interaction of bubbles and the case of 50 kHz which leads to random cutting due to the interaction of the former pulse induced cavitation bubble and the subsequent laser pulse. Furthermore, ethanol is mixed with pure distilled water to assess the liquid's impact on the cutting efficiency and cutting quality. The results show that increasing the ethanol fraction decreases the ablation efficiency but simultaneously, greatly improves the cutting quality. The improvement

Tailored optical vector fields for ultrashort-pulse laser induced complex surface plasmon structuring.

Science.gov (United States)

Ouyang, J; Perrie, W; Allegre, O J; Heil, T; Jin, Y; Fearon, E; Eckford, D; Edwardson, S P; Dearden, G

2015-05-18

Precise tailoring of optical vector beams is demonstrated, shaping their focal electric fields and used to create complex laser micro-patterning on a metal surface. A Spatial Light Modulator (SLM) and a micro-structured S-waveplate were integrated with a picosecond laser system and employed to structure the vector fields into radial and azimuthal polarizations with and without a vortex phase wavefront as well as superposition states. Imprinting Laser Induced Periodic Surface Structures (LIPSS) elucidates the detailed vector fields around the focal region. In addition to clear azimuthal and radial plasmon surface structures, unique, variable logarithmic spiral micro-structures with a pitch Λ ∼1μm, not observed previously, were imprinted on the surface, confirming unambiguously the complex 2D focal electric fields. We show clearly also how the Orbital Angular Momentum(OAM) associated with a helical wavefront induces rotation of vector fields along the optic axis of a focusing lens and confirmed by the observed surface micro-structures.

Diagnostics for the laser fusion program: plasma physics on the scale of microns and picoseconds

International Nuclear Information System (INIS)

Attwood, D.T.

1978-01-01

Laser induced fusion is the forerunner of a class of inertial confinement schemes in which hydrogen isotopes are heated to thermonuclear conditions in a very short period. The process is characterized by such short time scales that fuel confinement is achieved through its' own finite mass and expansion velocity, approaching 1 μm/psec for ignition temperatures of order 10 keV (10 8 0 K). With current laser powers limited to several terrawatts one readily estimates, on the basis of energy conservation, target mass, and expansion velocity, that target size and laser pulse duration are on the order of 100 μm and 100 psec, respectively. Within these constraints, targets have been heated and confined to the point where thermonuclear conditions have been achieved. This paper describes a sampling of diagnostic techniques with requisite resolution (microns and picoseconds) to accurately describe the dynamics of a laser driven compression. As discussed in each case cited, these in turn provide insight to and quantitative measure of, the physical processes dominating the implosion. The success of the inertial confinement fusion program is strongly dependent on the continued development of such diagnostics and the understanding they provide

Effects of picosecond laser repetition rate on ablation of Cr12MoV cold work mold steel

Energy Technology Data Exchange (ETDEWEB)

Wu, Baoye; Deng, Leimin; Liu, Peng; Zhang, Fei; Duan, Jun, E-mail: duans@hust.edu.cn; Zeng, Xiaoyan

2017-07-01

In this paper, the effects of pulse repetition rate on ablation efficiency and quality of Cr12MoV cold work mold steel have been studied using a picosecond (ps) pulse Nd:YVO{sub 4} laser system at λ= 1064 nm. The experimental results of area ablation on target surface reveal that laser repetition rate plays a significant role in controlling ablation efficiency and quality. Increasing the laser repetition rate, while keeping a constant mean power improves the ablation efficiency and quality. For each laser mean power, there is an optimal repetition rate to achieve a higher laser ablation efficiency with low surface roughness. A high ablation efficiency of 42.29, 44.11 and 47.52 μm{sup 3}/mJ, with surface roughness of 0.476, 0.463 and 0.706 μm could be achieved at laser repetition rate of 10 MHz, for laser mean power of 15, 17 and 19 W, respectively. Scanning electron microcopy images revels that the surface morphology evolves from rough with numerous craters, to flat without pores when we increased the laser repetition rate. The effects of laser repetition rate on the heat accumulation, plasma shield and ablation threshold were analyzed by numerical simulation, spectral analysis and multi-laser shot, respectively. The synergetic effects of laser repetition rate on laser ablation rate and machining quality were analyzed and discussed systemically in this paper.

Probing Dense Sprays with Gated, Picosecond, Digital Particle Field Holography

Directory of Open Access Journals (Sweden)

James Trolinger

2011-12-01

Full Text Available This paper describes work that demonstrated the feasibility of producing a gated digital holography system that is capable of producing high-resolution images of three-dimensional particle and structure details deep within dense particle fields of a spray. We developed a gated picosecond digital holocamera, using optical Kerr cell gating, to demonstrate features of gated digital holography that make it an exceptional candidate for this application. The Kerr cell gate shuttered the camera after the initial burst of ballistic and snake photons had been recorded, suppressing longer path, multiple scattered illumination. By starting with a CW laser without gating and then incorporating a picosecond laser and an optical Kerr gate, we were able to assess the imaging quality of the gated holograms, and determine improvement gained by gating. We produced high quality images of 50–200 μm diameter particles, hairs and USAF resolution charts from digital holograms recorded through turbid media where more than 98% of the light was scattered from the field. The system can gate pulses as short as 3 mm in pathlength (10 ps, enabling image-improving features of the system. The experiments lead us to the conclusion that this method has an excellent capability as a diagnostics tool in dense spray combustion research.

Picosecond ion pulses from an EN tandem created by a femtosecond Ti:sapphire laser

International Nuclear Information System (INIS)

Carnes, K.D.; Cocke, C.L.; Chang, Z.; Ben-Itzhak, I.; Needham, H.V.; Rankin, A.

2007-01-01

As the James R. Macdonald Laboratory at Kansas State University continues its transformation from an ion collisions facility to an ultrafast laser/ion collisions facility, we are looking for novel ways to combine our traditional accelerator expertise with our new laser capabilities. One such combination is to produce picosecond pulses of stripping gas ions in the high energy accelerating tube of our EN tandem by directing ∼100 fs, sub-milliJoule laser pulses up the high energy end of the tandem toward a focusing mirror at the terminal. Ion pulses from both stripping and residual gas have been produced and identified, with pulse widths thus far on the order of a nanosecond. This width represents an upper limit, as it is dominated by pulse-to-pulse jitter in the ion time-of-flight (TOF) and is therefore not a true representation of the actual pulse width. In this paper, we describe the development process and report on the results to date. Conditions limiting the minimum temporal pulse width, such as tandem terminal ripple, thermal motion of the gas and space charge effects, are also outlined

Note: Space qualified photon counting detector for laser time transfer with picosecond precision and stability.

Science.gov (United States)

Prochazka, Ivan; Kodet, Jan; Blazej, Josef

2016-05-01

The laser time transfer link is under construction for the European Space Agency in the frame of Atomic Clock Ensemble in Space. We have developed and tested the flying unit of the photon counting detector optimized for this space mission. The results are summarized in this Note. An extreme challenge was to build a detector package, which is rugged, small and which provides long term detection delay stability on picosecond level. The device passed successfully all the tests required for space missions on the low Earth orbits. The detector is extremely rugged and compact. Its long term detection delay stability is excellent, it is better than ±1 ps/day, in a sense of time deviation it is better than 0.5 ps for averaging times of 2000 s to several hours. The device is capable to operate in a temperature range of -55 °C up to +60 °C, the change of the detection delay with temperature is +0.5 ps/K. The device is ready for integration into the space structure now.

0.4 mJ quasi-continuously pumped picosecond Nd:GdVO4 laser with selectable pulse duration

International Nuclear Information System (INIS)

Kubeček, V; Jelínek, M; Čech, M; Hiršl, P; Diels, J-C

2010-01-01

A quasi-continuously pumped picosecond oscillator-amplifier Nd:GdVO 4 laser system based on two identical slabs in a single bounce geometry is reported. Pulse duration is from 160 to 55 ps resulting from the pulse shortening along the extended mode locked train from passively mode locked oscillator, which was measured directly from a single laser shot. The shortest 55 ps long cavity dumped single pulses from the oscillator with the energy of 15±1 μJ and the contrast better than 10 -3 were amplified to the energy of 150 μJ with the contrast better than 10 -3 after the single-pass amplification and to the energy of 400 μJ after the double-pass amplification

Enhanced optical confinement of dye-doped dielectric nanoparticles using a picosecond-pulsed near-infrared laser

International Nuclear Information System (INIS)

Kittiravechote, A; Chiang, W-Y; Usman, A; Liau, I; Masuhara, H

2014-01-01

We demonstrate a novel strategy to increase the capability of confining numerous dye-doped polymeric nanobeads (diameter 100 nm) with laser trapping. Unlike most classical works of optical trapping that address mainly the stiffness of the optical trap, our work concerns an increase in the number of particles confined near the laser focus. We developed an imaging system of light scattering in which a condenser lamp was employed to illuminate the focal plane of the objective lens, and the scattering of the incoherent light was specifically measured to determine the number of confined nanobeads. In contrast to preceding work that used mainly continuous-wave or femtosecond-pulsed lasers, we employed a picosecond-pulsed laser with the half-wavelength of the laser particularly falling within the absorption band of the dopant. Our results show that the number of doped nanobeads held by the laser is significantly greater than that of the bare nanobeads of the same dimension. In striking contrast, the confinement of the nanobeads of the two types was comparable when a continuous-wave laser of the same wavelength and power was employed. The number of confined dye-doped nanobeads increased nonlinearly with the power of the pulsed laser; this dependence was fitted satisfactorily with a second-order polynomial. Supported by theoretical analysis, we attribute the enhanced confinement of doped nanobeads in part to an increased effective refractive index resulting from two-photon resonance between the optical field of the laser and the dopant of the nanobead. We envisage that our findings would evoke applications that benefit from controlled confinement or aggregation of nanomaterials with the employment of near-infrared pulsed lasers. (letter)

Frequency-doubled green picosecond laser based on K3B6O10Br nonlinear optical crystal

Science.gov (United States)

Meng, Luping; Zhang, Ling; Hou, Zhanyu; Wang, Lirong; Xu, Hui; Shi, Meng; Wang, Lingwu; Yang, Yingying; Qi, Yaoyao; He, Chaojian; Yu, Haijuan; Lin, Xuechun; Su, Fufang; Xia, Mingjun; Li, Rukang

2018-05-01

We report a frequency-doubled green picosecond (ps) laser based on K3B6O10Br (KBB) nonlinear optical crystal with cutting angle of θ = 34.7° and φ = 30°. Through intracavity frequency doubling using a type I phase-matched KBB crystal with dimensions of 4 mm × 4 mm × 13.2 mm, the average output power of 185.00 mW green ps laser was obtained with a repetition rate of 80 MHz and pulse width of 25.0 ps. In addition, we present external frequency doubling using KBB crystal. The average output power of 3.00 W green ps laser was generated with a repetition rate of 10 kHz and pulse width of 38.1 ps, which corresponds to a pulse energy of 0.30 mJ and a peak power 7.89 MW, respectively. The experimental results show that KBB crystal is a promising nonlinear optical material.

Picosecond x-ray measurements from 100 eV to 30 keV

International Nuclear Information System (INIS)

Attwood, D.T.; Kauffman, R.L.; Stradling, G.L.

1980-01-01

Picosecond x-ray measurements relevant to the Livermore Laser Fusion Program are reviewed. Resolved to 15 picoseconds, streak camera detection capabilities extend from 100 eV to higher than 30 keV, with synchronous capabilities in the visible, near infrared, and ultraviolet. Capabilities include automated data retrieval using charge coupled devices (CCD's), absolute x-ray intensity levels, novel cathodes, x-ray mirror/reflector combinations, and a variety of x-ray imaging devices

Effect of laser absorption on picosecond laser ablation of Cr12MoV mold steel, 9Cr18 stainless steel and H13A cemented carbide

Science.gov (United States)

Wu, Baoye; Liu, Peng; Wang, Xizhao; Zhang, Fei; Deng, Leimin; Duan, Jun; Zeng, Xiaoyan

2018-05-01

Due to excellent properties, Cr12MoV mold steel, 9Cr18 stainless steel and H13A cemented carbide are widely used in industry. In this paper, the effect of absorption of laser light on ablation efficiency and roughness have been studied using a picosecond pulse Nd:YVO4 laser. The experimental results reveal that laser wavelength, original surface roughness and chemical composition play an important role in controlling ablation efficiency and roughness. Firstly, higher ablation efficiency with lower surface roughness is achieved on the ablation of 9Cr18 at 532, comparing with 1064 nm. Secondly, the ablation efficiency increases while the Ra of the ablated region decreases with the decrease of original surface roughness on ablation of Cr12MoV mold steel at 532 nm. Thirdly, the ablation efficiency of H13A cemented carbide is much higher than 9Cr18 stainless steel and Cr12MoV mold steel at 1064 nm. Scanning electron microscopy images reveals the formation of pores on the surface of 9Cr18 stainless steel and Cr12MoV mold steel at 532 nm while no pores are formed at 1064 nm. As to H13A cemented carbide, worm-like structure is formed at 1064 nm. The synergetic effects of the heat accumulation, plasma shielding and ablation threshold on laser ablation efficiency and machining quality were analyzed and discussed systematically in this paper.

On the use of a chirped Bragg grating as a cavity mirror of a picosecond Nd : YAG laser

Energy Technology Data Exchange (ETDEWEB)

Zubko, A E; Shashkov, E V; Smirnov, A V; Vorob' ev, N S [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Smirnov, V I [OptiGrate Corp., 562 South Econ Circle, Oviedo, Florida 32765-4311 (United States)

2016-02-28

The first experimental evidence is presented that the use of a chirped volume Bragg grating (CVBG) as a cavity mirror of a Q-switched picosecond Nd : YAG laser with self-mode-locking leads to significant changes in the temporal parameters of the laser output. Measurements have been performed at two positions of the CVBG: with the grating placed so that shorter wavelengths reflected from its front part lead longer wavelengths or with the grating rotated through 180°, so that longer wavelengths are reflected first. In the former case, the duration of individual pulses in a train increased from ∼35 to ∼300 ps, whereas the pulse train shape and duration remained the same as in the case of a conventional laser with a mirror cavity. In the latter case, the full width at half maximum of pulse trains increased from ∼70 ns (Nd : YAG laser with a mirror cavity) to ∼1 ms, and the duration of individual pulses increased from 35 ps to ∼1.2 ns, respectively, which is more typical of free-running laser operation. (laser crystals and braggg ratings)

Lasers in tattoo and pigmentation control: role of the PicoSure® laser system

Science.gov (United States)

Torbeck, Richard; Bankowski, Richard; Henize, Sarah; Saedi, Nazanin

2016-01-01

Background and objectives The use of picosecond lasers to remove tattoos has greatly improved due to the long-standing outcomes of nanosecond lasers, both clinically and histologically. The first aesthetic picosecond laser available for this use was the PicoSure® laser system (755/532 nm). Now that a vast amount of research on its use has been conducted, we performed a comprehensive review of the literature to validate the continued application of the PicoSure® laser system for tattoo removal. Study design and methods A PubMed search was conducted using the term “picosecond” combined with “laser”, “dermatology”, and “laser tattoo removal”. Results A total of 13 articles were identified, and ten of these met the inclusion criteria for this review. The majority of studies showed that picosecond lasers are an effective and safe treatment mode for the removal of tattoo pigments. Several studies also indicated potential novel applications of picosecond lasers in the removal of various tattoo pigments (eg, black, red, and yellow). Adverse effects were generally mild, such as transient hypopigmentation or blister formation, and were rarely more serious, such as scarring and/or textural change. Conclusion Advancements in laser technologies and their application in cutaneous medicine have revolutionized the field of laser surgery. Computational modeling provides evidence that the optimal pulse durations for tattoo ink removal are in the picosecond domain. It is recommended that the PicoSure® laser system continue to be used for safe and effective tattoo removal, including for red and yellow pigments. PMID:27194919

Ultrafast supercontinuum fiber-laser based pump-probe scanning magneto-optical Kerr effect microscope for the investigation of electron spin dynamics in semiconductors at cryogenic temperatures with picosecond time and micrometer spatial resolution.

Science.gov (United States)

Henn, T; Kiessling, T; Ossau, W; Molenkamp, L W; Biermann, K; Santos, P V

2013-12-01

We describe a two-color pump-probe scanning magneto-optical Kerr effect microscope which we have developed to investigate electron spin phenomena in semiconductors at cryogenic temperatures with picosecond time and micrometer spatial resolution. The key innovation of our microscope is the usage of an ultrafast "white light" supercontinuum fiber-laser source which provides access to the whole visible and near-infrared spectral range. Our Kerr microscope allows for the independent selection of the excitation and detection energy while avoiding the necessity to synchronize the pulse trains of two separate picosecond laser systems. The ability to independently tune the pump and probe wavelength enables the investigation of the influence of excitation energy on the optically induced electron spin dynamics in semiconductors. We demonstrate picosecond real-space imaging of the diffusive expansion of optically excited electron spin packets in a (110) GaAs quantum well sample to illustrate the capabilities of the instrument.

Picosecond 532-nm neodymium-doped yttrium aluminum garnet laser-a promising modality for the management of verrucous epidermal nevi.

Science.gov (United States)

Levi, Assi; Amitai, Dan Ben; Mimouni, Daniel; Leshem, Yael A; Arzi, Ofir; Lapidoth, Moshe

2018-04-01

The verrucous epidermal nevus (VEN) is the most common type of epidermal nevi. As lesions can be disfiguring, treatment is often sought. Many therapeutic approaches have been reported, with variable efficacy and safety. Picosecond (PS) lasers are novel laser devices designated to target small chromophores. A side effect of these lasers is blistering due to epidermal-dermal separation. We aimed to harness this side effect of the PS lasers to treat patients with VEN. The purpose of this study was to report our experience treating VEN using a PS 532-nm laser. We present a retrospective case series of six patients with large VEN who were treated using a PS 532-nm laser (2-6 treatments, 8-10 weeks apart). Response in clinical photographs was assessed by two independent dermatologists and graded on a scale of 0 (exacerbation) to 4 (76-100% improvement). Patient satisfaction was recorded on a scale of 1-5. All patients demonstrated significant improvement. Average improvement was 3.7 on the quartile scale of improvement. Patient satisfaction rate averaged 4.7. The PS 532-nm laser is a promising novel modality for the treatment of large VEN.

Characterisation of weld zone reactions in dissimilar glass-to-aluminium pulsed picosecond laser welds

Energy Technology Data Exchange (ETDEWEB)

Ciuca, Octav P., E-mail: octav.ciuca@manchester.ac.uk [School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom); Carter, Richard M. [Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS (United Kingdom); Prangnell, Philip B. [School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom); Hand, Duncan P. [Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS (United Kingdom)

2016-10-15

Precision welded joints, produced between fused silica glass and aluminium by a newly-developed picosecond-pulse laser technique, have been analysed for the first time using a full range of electron microscopy methods. The welds were produced as lap joints by focusing a 1.2 μm diameter laser beam through the transparent glass top sheet, slightly below the surface of the metal bottom sheet. Despite the extremely short interaction time, extensive reaction was observed in the weld zone, which involved the formation of nanocrystalline silicon and at least two transitional alumina phases, γ- and δ-Al{sub 2}O{sub 3}. The weld formation process was found to be complex and involved: the formation of a constrained plasma cavity at the joint interface, non-linear absorption in the glass, and the creation of multiple secondary keyholes in the metal substrate by beam scattering. The joint area was found to expand outside of the main interaction volume, as the energy absorbed into the low conductivity and higher melting point silica glass sheet melted the aluminium surface across a wider contact area. The reasons for the appearance of nanocrystalline Si and transitional alumina reaction products within the welds are discussed. - Highlights: •Pulsed laser welding of dissimilar materials causes extensive chemical reactivity. •Metastable Al{sub 2}O{sub 3} phases form due to laser-induced highly-transient thermal regime. •Fused silica is reduced by Al to form nanocrystalline Si. •Mechanism of joint formation is discussed.

Recent results on solvation dynamics of electron and spur reactions of solvated electron in polar solvents studied by femtosecond laser spectroscopy and picosecond pulse radiolysis

International Nuclear Information System (INIS)

Mostafavi, M.

2006-01-01

. Nevertheless, the results show that the effect of the molecular structure of the solvents on solvation dynamics of electron is not negligible. The first study of picosecond pulse radiolysis of neat tetrahydrofuran (THF) by pulse-probe method was performed using the ELYSE picosecond pulse electron facility. ELYSE is a laser triggered electron accelerator that delivers at repetition rate of 1-50 Hz, electron pulses with a duration 5-15 ps, a charge of 2-7 nC and a kinetic energy tuneable in the range 2-9 MeV. The pulse- probe study of neat THF shows a fast decay of absorbance at 790 nm within 2.5 ns (Figure 2). This decay is assigned to the solvated electron. From the decay we deduced the time dependent G-value of solvated electron in the picosecond time range. The ratio between the initial absorbance (at 30 ps) and at 2.5 ns is about 2. In similar conditions, the same ratio in water and in the alcohols is 1.15, 1.25, respectively. In fact, the G-value of solvated electron in THF is much more time dependent that those in polar solvents like water and alcohols. We compared the time dependent G value for solvated electron between two methods: direct time resolved measurement and scavenging method. The analysis suggests either that the initial yield in THF (at zero time) is lower than in water or that a very fast decay occurs within the electron pulse.Eventually, the first pulse radiolysis measurements at picosecond range and at elevated temperature in water is studied by pulse-probe method using a high temperature high pressure cell. This study is done in collaboration with the Radiolysis laboratory of CEA/Saclay. The kinetics of the hydrated electron are found to be temperature dependent (Figure 3) and are qualitatively in agreement with radiolytic yield values obtained at elevated temperature after spur reactions. Assuming the same initial G value at picosecond time range for different temperatures, we deduce that at 350 degree C the yield at nanosecond range becomes almost the

Generation and subsequent amplification of few-cycle femtosecond pulses from a picosecond pump laser

Science.gov (United States)

Mukhin, I. B.; Kuznetsov, I. I.; Palashov, O. V.

2018-04-01

Using a new approach, in which generation of femtosecond pulses as short as a few field cycles is implemented directly from the radiation of a picosecond pump laser, pulses with the microjoule energy, the repetition rate 10 kHz, and the duration less than 26 fs are generated in the spectral range 1.3 ‑ 1.4 μm. In the process of generating this radiation, use was made of a method providing passive phase stabilisation of the carrier oscillation of the electromagnetic field and its slow envelope. The radiation spectrum was converted into the range of parametric amplification in the BBO crystal by the broadband second harmonic generation; the pulse was parametrically amplified up to the microjoule level and compressed by chirped mirrors to a duration of 28 fs.

Accumulated surface damage on ZnS crystals produced by closely spaced pairs of picosecond laser pulses

International Nuclear Information System (INIS)

Chase, L.L.; Lee, H.W.H.

1988-12-01

Excitation of a transparent ZnS crystal by repetitive picosecond dye laser pulses causes an accumulated surface modification leading to optical damage. The onset of the damage is detected by an abrupt increase in the emission of neutral Zn (and possibly S 2 ) from the surface. Comparison of the neutral emission thresholds with pulse-pair and single-pulse excitation shows that linear absorption is the dominant laser-surface interaction. In general, this measurement technique shows considerable promise for investigating the possible influence of nonlinear absorption or excitation processes on damage mechanisms. The data suggest that heating of small absorbing regions produces the surface modification that leads to the observed surface ablation. The nature of the damage observed at fluences above the threshold suggests that it is caused by heating of a relatively large (/approximately/10 - 100 μm) surface region that has been modified by the accumulation pulses. 3 refs., 5 figs

Picosecond laser fabricated Ag, Au and Ag-Au nanoparticles for detecting ammonium perchlorate using a portable Raman spectrometer

Science.gov (United States)

Byram, Chandu; Moram, Sree Sathya Bharathi; Soma, Venugopal Rao

2018-04-01

In this paper, we present the results from fabrication studies of Ag, Au, and Ag-Au alloy nanoparticles (NPs) using picosecond laser ablation technique in the presence of liquid media. The alloy formation in the NPs was confirmed from UV-Visible measurements. The shape and crystallinity of NPs were investigated by using high resolution transmission electron microscopy (HRTEM), selected area diffraction pattern (SAED) and energy dispersive spectroscopy (EDS). The SERS effect of fabricated NPs was tested with methylene blue and an explosive molecule (ammonium perchlorate) using a portable Raman spectrometer and achieved EFs of ˜106.

Plasma satellites of X-ray spectral lines of ions in a plasma of solid-state targets, heated by a picosecond laser pulse

International Nuclear Information System (INIS)

Belyaev, V.S.; Vinogradov, V.I.; Kurilov, A.S.; Matafonov, A.P.; Lisitsa, V.S.; Gavrilenko, V.P.; Faenov, A.Ya.; Pikuz, T.A.; Skobelev, I.Yu.; Magunov, A.I.; Pikuz, S.A.

2003-01-01

The results of measuring the ions X-ray spectral lines by the interaction of the picosecond laser pulses with the solid-state target are presented. The spectra of the X-ray radiation were observed on the fluorine ion line. The spectral lines satellites, testifying to the availability, are identified. The position of the satellites and the distance between them make it possible to connect them with the intensive electrostatic oscillations with the amplitude, exceeding 10 8 V/cm, and the frequency close to 7 x 10 14 s -1 , substantially lower than the laser wave frequency. The experimental results are compared with the calculated data on the multicharge ions spectra [ru

Prediction of electromagnetic pulse generation by picosecond avalanches in high-pressure air

International Nuclear Information System (INIS)

Mayhall, D.J.; Yee, J.H.

1993-01-01

The gas avalanche switch is a laser-activated, high-voltage switch, consisting of a set of pulse-charged electrodes in a high-pressure gas. Induced electrons from a picosecond-scale laser pulse initiate an avalanche discharge between high-voltage and grounded electrodes. If the voltage, pressure, and dimensions are correct, the rapid avalanche, fueled by the immense number of electrons available in the gas, collapses the applied voltage in picoseconds and generates electromagnetic pulses with widths as short as 1-10 ps and 3 dB bandwidths of 20-120 GHz. With proper voltage or pressure detuning, wider pulses and lower bandwidths occur. In addition to picosecond electromagnetic pulse generation, application of this switch should result in ultra-fast Marx bank pulsers. A number of versions of the switch are possible. The simplest is a parallel plate capacitor, consisting of a gas between two parallel plate conductors. High voltage is applied across the two plates. A parallel plate, Blumlein geometry features a center electrode between two grounded parallel plates. This geometry emits a single pulse in each direction along the parallel plates. A frozen wave geometry with multiple, oppositely charged center electrodes will emit AC pulses. Series switches consisting of gas gaps between two electrodes are also possible

Picosecond energy relaxation in La0.67Ca0.33MnO3

International Nuclear Information System (INIS)

Dorosinets, Vladimir; Richter, Pablo; Mohler, Ernst; Roskos, Hartmut G.; Jakob, Gerhard

2005-01-01

Investigating the reflectance response dynamics of La 0.67 Ca 0.33 MnO 3 thin films after excitation by femtosecond laser pulses, we identify for the first time a picosecond relaxation step which only exists below the Curie temperature T C . The relaxation time increases from zero at T C to several picoseconds at low temperatures. The data can be explained with the existence of a magnetization-related effective energy gap, and assuming relaxation between these states to be mediated by a Frohlich-type electron-lattice interaction

Photonic Crystal Laser-Driven Accelerator Structures

International Nuclear Information System (INIS)

Cowan, Benjamin M.

2007-01-01

Laser-driven acceleration holds great promise for significantly improving accelerating gradient. However, scaling the conventional process of structure-based acceleration in vacuum down to optical wavelengths requires a substantially different kind of structure. We require an optical waveguide that (1) is constructed out of dielectric materials, (2) has transverse size on the order of a wavelength, and (3) supports a mode with speed-of-light phase velocity in vacuum. Photonic crystals---structures whose electromagnetic properties are spatially periodic---can meet these requirements. We discuss simulated photonic crystal accelerator structures and describe their properties. We begin with a class of two-dimensional structures which serves to illustrate the design considerations and trade-offs involved. We then present a three-dimensional structure, and describe its performance in terms of accelerating gradient and efficiency. We discuss particle beam dynamics in this structure, demonstrating a method for keeping a beam confined to the waveguide. We also discuss material and fabrication considerations. Since accelerating gradient is limited by optical damage to the structure, the damage threshold of the dielectric is a critical parameter. We experimentally measure the damage threshold of silicon for picosecond pulses in the infrared, and determine that our structure is capable of sustaining an accelerating gradient of 300 MV/m at 1550 nm. Finally, we discuss possibilities for manufacturing these structures using common microfabrication techniques

Laser-electron Compton interaction in plasma channels

International Nuclear Information System (INIS)

Pogorelsky, I.V.; Ben-Zvi, I.; Hirose, T.

1998-10-01

A concept of high intensity femtosecond laser synchrotron source (LSS) is based on Compton backscattering of focused electron and laser beams. The short Rayleigh length of the focused laser beam limits the length of interaction to a few picoseconds. However, the technology of the high repetition rate high-average power picosecond lasers required for high put through LSS applications is not developed yet. Another problem associated with the picosecond laser pulses is undesirable nonlinear effects occurring when the laser photons are concentrated in a short time interval. To avoid the nonlinear Compton scattering, the laser beam has to be split, and the required hard radiation flux is accumulated over a number of consecutive interactions that complicates the LSS design. In order to relieve the technological constraints and achieve a practically feasible high-power laser synchrotron source, the authors propose to confine the laser-electron interaction region in the extended plasma channel. This approach permits to use nanosecond laser pulses instead of the picosecond pulses. That helps to avoid the nonlinear Compton scattering regime and allows to utilize already existing technology of the high-repetition rate TEA CO 2 lasers operating at the atmospheric pressure. They demonstrate the advantages of the channeled LSS approach by the example of the prospective polarized positron source for Japan Linear Collider

Approach to compact terawatt CO2 laser system for particle acceleration

International Nuclear Information System (INIS)

Pogorelsky, I.V.; Kimura, W.D.; Fisher, C.H.; Kannari, F.

1994-01-01

A compact table-top 20-GW 50-ps CO 2 laser system is in operation for strong-field physics studies at the ATF. We propose scaling up of the picosecond CO 2 laser to a terawatt peak power level to meet the requirements of advanced laser accelerators. Computer modeling shows that a relatively compact single-beam picosecond CO 2 laser system with a high-pressure x-ray picosecond amplifier of a 10-cm aperture is potentially scalable to the ∼1-TW peak power level

Effect of focusing condition on molten area characteristics in micro-welding of borosilicate glass by picosecond pulsed laser

Energy Technology Data Exchange (ETDEWEB)

Nordin, I.H.W.; Okamoto, Y.; Okada, A.; Takekuni, T. [Okayama University, Graduate School of Natural Science and Technology, Okayama (Japan); Sakagawa, T. [Kataoka Corporation, Yokohama (Japan)

2016-05-15

The characteristics of the molten area are attributed not only by laser energy condition but also the focusing condition. In this study, a picosecond pulsed laser of 1064 nm in wavelength and 12.5 ps in pulse duration was used as a laser source for joining glass material. Influence of focusing condition on micro-welding of glasses was experimentally investigated by using an objective lens with and without spherical aberration correction, and its molten area was characterized. The usage of objective lens with spherical aberration correction led to a larger molten area inside the bulk material of glass even under the same pulse energy, which related to the efficient micro-welding of glass materials. In addition, an optical system with the spherical aberration correction led to a stable absorption of laser energy inside the bulk glass material, stabilizing the shape of molten area, which resulted in the reliable weld joint. On the other hand, breaking strength of the specimens with spherical aberration correction was higher than that without spherical aberration correction. Therefore, it is concluded that the focusing condition with spherical aberration correction led to the larger and stable molten area, which resulted in higher joining strength in micro-welding of glass materials. (orig.)

Direct observation of free-exciton thermalization in quantum-well structures

DEFF Research Database (Denmark)

Umlauff, M.; Hoffmann, J.; Kalt, H.

1998-01-01

We report on a direct observation of free-exciton thermalization in quantum-well structures. A narrow energy distribution of free 1s excitons is created in ZnSe-based quantum wells by emission of one LO phonon after optical excitation of the continuum stales with picosecond laser pulses. The subs......We report on a direct observation of free-exciton thermalization in quantum-well structures. A narrow energy distribution of free 1s excitons is created in ZnSe-based quantum wells by emission of one LO phonon after optical excitation of the continuum stales with picosecond laser pulses...

NATO Advanced Research Workshop on Applications of Picosecond Spectroscopy to Chemistry

CERN Document Server

1984-01-01

With the development of lasers that can generate light 11 14 pulses ranging from 10- - 10- sec duration, and capable of 13 peak powers in excess of 10 watts scientists have been able to investigate the interactions of light with matter in a time and power domain not previously possible. These ultrashort laser pulses provide a powerful tool for the study of chemical phenomena at the most fundamental level. Many of the elementary processes of importance in chemistry including energy dissipa­ tion, molecular motions, structural and chemical changes occur on a very short time scale and thus require special approaches. Th~ use of ultrashort laser pulses to perturb and to probe systems of interest affords a direct approach to the time reso­ lution of very rapid chemical phenomena. It was recognition of the impact of these relatively new approaches to chemical phenomena that motivated NATO to sponsor a meeting on the applications of picosecond spectroscopy in chemistry. The primary aim of the NATO workshop was to ...

Quench-free concentration measurements in high-temperature systems by picosecond LIF

International Nuclear Information System (INIS)

Buelter, A.; Rahmann, U.; Brockhinke, A.

2001-01-01

In the present work, a picosecond laser is used in conjunction with an intensified streak camera to study energy transfer processes in OH and to obtain quench-free results from the time-resolved spectra. Quantitative concentration profiles for OH and H are presented in a counterflow burner interacting with a vortex

Image-converter diagnostics of laser and laser plasma in pico-femtosecond region

International Nuclear Information System (INIS)

Schelev, M.Ya.

1979-01-01

In the present communication we would like to outline some new trends in development of pico-femtosecond image-converter diagnostics for laser and laser plasma research on the basis of the recent works done in P.N.Lebedev Physical Institute. The discussion of the following subjects will be included: new generation of picosecond image-converter tubes (ICT), pulsed control circuitry, late prototype of picosecond image-converter cameras (ICC), test installation consisting of Nd: glass and YAG lasers for production the ultra-short pulses and sinusoidally modulated radiation, methods and techniques for image tube and camera dynamic measurements in IR, visible and X-ray spectral regions. Also discussed are the image processing technique for pictures taken with picosecond ICC in order to correct the geometrical distortions, enhance pictures quality and evaluate parameters of the input signals through their recorded images. (author)

Four-wave-mixing and nonlinear cavity dumping of 280 picosecond 2nd Stokes pulse at 1.3 μm from Nd:SrMoO4 self-Raman laser

International Nuclear Information System (INIS)

Smetanin, S N; Ivleva, L I; Jelínek, M Jr; Kubeček, V; Jelínková, H; Shurygin, A S

2016-01-01

The 280 picosecond 2nd Stokes Raman pulses at 1.3 μm were generated directly from the miniature diode-pumped Nd:SrMoO 4 self-Raman laser. Using the 90° phase matching insensitive to the angular mismatch, the self-Raman laser allowed for the achievement of the four-wave-mixing generation of the 2nd Stokes Raman pulse directly in the active Nd:SrMoO 4 crystal at stimulated Raman scattering (SRS) self-conversion of the laser radiation. The passive Cr:YAG Q-switching and nonlinear cavity dumping was used without any phase locking device. (letter)

Zinc oxide nanocolloids prepared by picosecond pulsed laser ablation in water at different temperatures

Science.gov (United States)

D'Urso, Luisa; Spadaro, Salvatore; Bonsignore, Martina; Santangelo, Saveria; Compagnini, Giuseppe; Neri, Fortunato; Fazio, Enza

2018-01-01

Zinc oxide with wide direct band gap and high exciton binding energy is one of the most promising materials for ultraviolet (UV) light-emitting devices. It further exhibits good performance in the degradation of non-biodegradable pollutants under UV irradiation. In this work, zinc oxide (ZnO) and zinc oxide/gold (ZnO/Au) nanocolloids are prepared by picosecond pulsed laser ablation (ps-PLA), using a Zn and Au metallic targets in water media at room temperature (RT) and 80°C. ZnO and Au nanoparticles (NPs) with size in the 10-50 nm range are obtained at RT, while ZnO nanorods (NRs) are formed when water is maintained at 80°C during the ps-PLA process. Au NPs, added to ZnO colloids after the ablation process, decorate ZnO NRs. The crystalline phase of all ZnO nanocolloids is wurtzite. Methylene blue dye is used to investigate the photo-catalytic activity of all the synthesised nanocolloids, under UV light irradiation.

Efficient processing of CFRP with a picosecond laser with up to 1.4 kW average power

Science.gov (United States)

Onuseit, V.; Freitag, C.; Wiedenmann, M.; Weber, R.; Negel, J.-P.; Löscher, A.; Abdou Ahmed, M.; Graf, T.

2015-03-01

Laser processing of carbon fiber reinforce plastic (CFRP) is a very promising method to solve a lot of the challenges for large-volume production of lightweight constructions in automotive and airplane industries. However, the laser process is actual limited by two main issues. First the quality might be reduced due to thermal damage and second the high process energy needed for sublimation of the carbon fibers requires laser sources with high average power for productive processing. To achieve thermal damage of the CFRP of less than 10μm intensities above 108 W/cm² are needed. To reach these high intensities in the processing area ultra-short pulse laser systems are favored. Unfortunately the average power of commercially available laser systems is up to now in the range of several tens to a few hundred Watt. To sublimate the carbon fibers a large volume specific enthalpy of 85 J/mm³ is necessary. This means for example that cutting of 2 mm thick material with a kerf width of 0.2 mm with industry-typical 100 mm/sec requires several kilowatts of average power. At the IFSW a thin-disk multipass amplifier yielding a maximum average output power of 1100 W (300 kHz, 8 ps, 3.7 mJ) allowed for the first time to process CFRP at this average power and pulse energy level with picosecond pulse duration. With this unique laser system cutting of CFRP with a thickness of 2 mm an effective average cutting speed of 150 mm/sec with a thermal damage below 10μm was demonstrated.

Comparison of optical transients during the picosecond laser pulse-induced crystallization of GeSbTe and AgInSbTe phase-change thin films: Nucleation-driven versus growth-driven processes

Energy Technology Data Exchange (ETDEWEB)

Liang, Guangfei [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Li, Simian [State Key Laboratory of Optoelectronic Materials and Technology, Department of Physics, Sun Yat-Sen University, Guangzhou 510275 (China); Huang, Huan [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Wang, Yang, E-mail: ywang@siom.ac.cn [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Lai, Tianshu, E-mail: stslts@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technology, Department of Physics, Sun Yat-Sen University, Guangzhou 510275 (China); Wu, Yiqun [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

2013-09-01

Direct comparison of the real-time in-situ crystallization behavior of as-deposited amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} (GeSbTe) and Ag{sub 8}In{sub 14}Sb{sub 55}Te{sub 23} (AgInSbTe) phase-change thin films driven by picosecond laser pulses was performed by a time-resolved optical pump-probe technique with nanosecond resolution. Different optical transients showed various crystallization processes because of the dissimilar nucleation- and growth-dominated mechanisms of the two materials. The effects of laser pulse fluence, thermal conductive structure, and successive pulse irradiation on their crystallization dynamics were also discussed. A schematic was then established to describe the different crystallization processes beginning from the as-deposited amorphous state. The results may provide further insight into the phase-change mechanism under extra-non-equilibrium conditions and aid the development of ultrafast phase-change memory materials.

Picosecond multiphoton ionization of atomic and molecular clusters

International Nuclear Information System (INIS)

Miller, J.C.; Smith, D.B.

1990-01-01

High peak-power picosecond laser pulses have been used for the first time to effect nonresonant or resonant multiphoton ionization (MPI) of clusters generated in a supersonic nozzle expansion. The resulting ions are subsequently detected and characterized by time-of-flight mass spectroscopy. Specifically, we present results involving MPI of clusters of xenon and nitric oxide. Previous MPI studies of many molecular clusters using nanosecond lasers have not been successful in observing the parent ion, presumably due to fast dissociation channels. It is proposed that the present technique is a new and rather general ionization source for cluster studies which is complementary to electron impact but may, in addition, provide unique spectroscopic or dynamical information. 23 refs., 5 figs

Wavelength dependence of picosecond laser-induced periodic surface structures on copper

Czech Academy of Sciences Publication Activity Database

Maragkaki, S.; Derrien, Thibault; Levy, Yoann; Bulgakova, Nadezhda M.; Ostendorf, A.; Gurevich, E.L.

2017-01-01

Roč. 417, Sep (2017), s. 88-92 ISSN 0169-4332 R&D Projects: GA MŠk LO1602; GA MŠk EF15_003/0000445; GA MŠk LM2015086 EU Projects: European Commission(XE) 657424 - QuantumLaP Grant - others:OP VVV - BIATRI(XE) CZ.02.1.01/0.0/0.0/15_003/0000445 Institutional support: RVO:68378271 Keywords : irradiation * ablation * silicon * pulses * damage Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 3.387, year: 2016

CO2 laser technology for advanced particle accelerators

International Nuclear Information System (INIS)

Pogorelsky, I.V.

1996-06-01

Short-pulse, high-power CO 2 lasers open new prospects for development of ultra-high gradient laser-driven electron accelerators. The advantages of λ=10 μm CO 2 laser radiation over the more widely exploited solid state lasers with λ∼1 μm are based on a λ 2 -proportional ponderomotive potential, λ-proportional phase slippage, and λ-proportional scaling of the laser accelerator structures. We show how a picosecond terawatt CO 2 laser that is under construction at the Brookhaven Accelerator Test Facility may benefit the ATF's experimental program of testing far-field, near-field, and plasma accelerator schemes

Preliminary clinical results with the ISL laser

Science.gov (United States)

Hoppeler, Thomas; Gloor, Balder

1992-08-01

The ISL laser (Intelligent Surgical Lasers, Inc.), a Nd:YLF picosecond pulse laser, is currently being used under investigational device exemption to perform microsurgery of the anterior segment of the eye. At different study sites procedures for cataract fragmentation and iridotomy, as well as for posterior capsulotomy after cataract surgery, are under evaluation. Other potential applications include: sclerostomy ab interno, the cutting of membranes in the anterior and posterior segment of the eye; corneal incisions; and corneal intrastromal effects. We discuss various clinically relevant aspects of the use of this picosecond laser. An overview of different computer controlled laser patterns is given.

Study of polysilane mainchain electronic structure by picosecond pulse radiolysis

International Nuclear Information System (INIS)

Habara, H.; Saeki, A.; Kunimi, Y.; Seki, S.; Kozawa, T.; Yoshida, Y.; Tagawa, S.

2000-01-01

The electronic structure of a charged polysilane molecle is studied. The transient absorption spectroscopy was carried out for charged radicals of poly (methylphenylsilane): PMPS by pico-second and nanosecond pulse radiolysis technique. It was observed that the peak of the transient absorption spectra shifted to longer wavelength region within a few nsec, and an increase was observed in the optical density at 370 nm, which had been already assigned to the radical anions of PMPS. It is ascribed to inter-segment electron transfer (intra-molecular transfer) through polymer chain. The nanosecond pulse radiolysis experiments gave similar kinetic traces in near-UV and IR region. This suggests the presence of an interband level, that is, a polaron level occupied by an excess electron or a hole. (author)

High power all solid state VUV lasers

International Nuclear Information System (INIS)

Zhang, Shen-jin; Cui, Da-fu; Zhang, Feng-feng; Xu, Zhi; Wang, Zhi-min; Yang, Feng; Zong, Nan; Tu, Wei; Chen, Ying; Xu, Hong-yan; Xu, Feng-liang; Peng, Qin-jun; Wang, Xiao-yang; Chen, Chuang-tian; Xu, Zu-yan

2014-01-01

Highlights: • Polarization and pulse repetition rate adjustable ps 177.3 nm laser was developed. • Wavelength tunable ns, ps and fs VUV lasers were developed. • High power ns 177.3 nm laser with narrow linewidth was investigated. - Abstract: We report the investigation on the high power all solid state vacuum ultra-violet (VUV) lasers by means of nonlinear frequency conversion with KBe 2 BO 3 F 2 (KBBF) nonlinear crystal. Several all solid state VUV lasers have developed in our group, including polarization and pulse repetition rate adjustable picosecond 177.3 nm VUV laser, wavelength tunable nanosecond, picosecond and femtosecond VUV lasers, high power ns 177.3 nm laser with narrow linewidth. The VUV lasers have impact, accurate and precise advantage

CO2 laser technology for advanced particle accelerators. Revision

International Nuclear Information System (INIS)

Pogorelsky, I.V.

1996-06-01

Short-pulse, high-power CO 2 lasers open new prospects for development of ultra-high gradient laser-driven electron accelerators. The advantages of λ=10 μm CO 2 laser radiation over the more widely exploited solid state lasers with λ∼1 μm are based on a λ 2 -proportional ponderomotive potential, λ-proportional phase slippage distance, and λ-proportional scaling of the laser accelerator structures. We show how a picosecond terawatt CO 2 laser that is under construction at the Brookhaven Accelerator Test Facility may benefit the ATF's experimental program of testing far-field, near-field, and plasma accelerator schemes

Fluorescence imaging of lattice re-distribution on step-index direct laser written Nd:YAG waveguide lasers

Energy Technology Data Exchange (ETDEWEB)

Martínez de Mendívil, Jon; Pérez Delgado, Alberto; Lifante, Ginés; Jaque, Daniel [Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid 28049 (Spain); Ródenas, Airán [Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Tarragona 43007 (Spain); Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Benayas, Antonio, E-mail: antonio.benayas@emt.inrs.ca [Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid 28049 (Spain); Institut National de la Recherche Scientifique, Centre – Énergie Matériaux et Télécommunications, 1650, Boul. Lionel Boulet Varennes, Quebec J3X 1S2 (Canada); Aguiló, Magdalena; Diaz, Francesc [Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Tarragona 43007 (Spain); Kar, Ajoy K. [Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)

2015-01-14

The laser performance and crystalline micro-structural properties of near-infrared step-index channel waveguides fabricated inside Neodymium doped YAG laser ceramics by means of three-dimensional sub-picosecond pulse laser direct writing are reported. Fluorescence micro-mapping of the waveguide cross-sections reveals that an essential crystal lattice re-distribution has been induced after short pulse irradiation. Such lattice re-distribution is evidenced at the waveguide core corresponding to the laser written refractive index increased volume. The waveguides core surroundings also present diverse changes including slight lattice disorder and bi-axial strain fields. The step-index waveguide laser performance is compared with previous laser fabricated waveguides with a stress-optic guiding mechanism in absence of laser induced lattice re-distribution.

Time-resolved study of formate on Ni( 1 1 1 ) by picosecond SFG spectroscopy

Science.gov (United States)

Kusafuka, K.; Noguchi, H.; Onda, K.; Kubota, J.; Domen, K.; Hirose, C.; Wada, A.

2002-04-01

Time-resolved vibrational measurements were carried out on formate (HCOO) adsorbed on Ni(1 1 1) surface by combining the sum-frequency generation method and picosecond laser system (time resolution of 6 ps). Rapid intensity decrease (within the time resolution) followed by intensity recovery (time constant of several tens of ps) of CH stretching signal was observed when picosecond 800 nm pulse was irradiated on the sample surface. From the results of temperature and pump fluence dependences of temporal behaviour of signal intensity, we concluded that the observed intensity change was induced by non-thermal process. Mechanism of the temporal intensity change was discussed.

Measurement of Sub-Picosecond Electron Bunches via Electro-Optic Sampling of Coherent Transition Radiation

Energy Technology Data Exchange (ETDEWEB)

Maxwell, Timothy John [Northern Illinois U.

2012-01-01

Future collider applications as well as present high-gradient laser plasma wakefield accelerators and free-electron lasers operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation or the bunch wakefields with sub-picosecond time resolution. We present results on the single-shot electro-optic spectral decoding of coherent transition radiation from bunches generated at the Fermilab A0 photoinjector laboratory. A longitudinal double-pulse modulation of the electron beam is also realized by transverse beam masking followed by a transverse-to-longitudinal phase-space exchange beamline. Live profile tuning is demonstrated by upstream beam focusing in conjunction with downstream monitoring of single-shot electro-optic spectral decoding of the coherent transition radiation.

Laser ablated micropillar energy directors for ultrasonic welding of microfluidic systems

International Nuclear Information System (INIS)

Poulsen, Carl Esben; Kistrup, Kasper; Andersen, Nis Korsgaard; Taboryski, Rafael; Hansen, Mikkel Fougt; Wolff, Anders

2016-01-01

We present a new type of energy director (ED) for ultrasonic welding of microfluidic systems. These micropillar EDs are based on the replication of cone like protrusion structures introduced using a pico-second laser and may therefore be added to any mould surface accessible to a pico-second laser beam. The technology is demonstrated on an injection moulded microfluidic device featuring high-aspect ratio ( h   ×   w   =  2000 μ m  ×  550 μ m) and free-standing channel walls, where bonding is achieved with no detectable channel deformation. The bonding strength is similar to conventional EDs and the fabricated system can withstand pressures of over 9.5 bar. (technical note)

Investigation of the thermal and optical performance of a spatial light modulator with high average power picosecond laser exposure for materials processing applications

Science.gov (United States)

Zhu, G.; Whitehead, D.; Perrie, W.; Allegre, O. J.; Olle, V.; Li, Q.; Tang, Y.; Dawson, K.; Jin, Y.; Edwardson, S. P.; Li, L.; Dearden, G.

2018-03-01

Spatial light modulators (SLMs) addressed with computer generated holograms (CGHs) can create structured light fields on demand when an incident laser beam is diffracted by a phase CGH. The power handling limitations of these devices based on a liquid crystal layer has always been of some concern. With careful engineering of chip thermal management, we report the detailed optical phase and temperature response of a liquid cooled SLM exposed to picosecond laser powers up to 〈P〉  =  220 W at 1064 nm. This information is critical for determining device performance at high laser powers. SLM chip temperature rose linearly with incident laser exposure, increasing by only 5 °C at 〈P〉  =  220 W incident power, measured with a thermal imaging camera. Thermal response time with continuous exposure was 1-2 s. The optical phase response with incident power approaches 2π radians with average power up to 〈P〉  =  130 W, hence the operational limit, while above this power, liquid crystal thickness variations limit phase response to just over π radians. Modelling of the thermal and phase response with exposure is also presented, supporting experimental observations well. These remarkable performance characteristics show that liquid crystal based SLM technology is highly robust when efficiently cooled. High speed, multi-beam plasmonic surface micro-structuring at a rate R  =  8 cm2 s-1 is achieved on polished metal surfaces at 〈P〉  =  25 W exposure while diffractive, multi-beam surface ablation with average power 〈P〉  =100 W on stainless steel is demonstrated with ablation rate of ~4 mm3 min-1. However, above 130 W, first order diffraction efficiency drops significantly in accord with the observed operational limit. Continuous exposure for a period of 45 min at a laser power of 〈P〉  =  160 W did not result in any detectable drop in diffraction efficiency, confirmed afterwards by the efficient

Pockels cell shutter operating in the 100 picosecond range

International Nuclear Information System (INIS)

Blanchet, M.; Gex, J.P.

1975-01-01

The object of the first part of the statement is the study and the description of a 20 x 20mm section tranversal field shutter realized as a line transmission structure, acting as a roller-blind shutter acting within the limits of a subnanosecond. It is constituted by two appropriately cut, deuterized KDP electro-optical crystals, situated on either side of a birefringent plate having its neutral lines at a 45 0 angle to their optical axis, placed within a prtion of the dual plate transmission line. A resolution above 20 pairs of lines per millimetre, as well as a Transmission/Extinction ratio greater than 100 over all the optical section are obtained for a 250 picoseconds dynamic functioning. The second part of the statement deals with the application of this shutter to photography and hyper-rapid interferometry of plasmas created by lasers. (author)

High Power Picosecond Laser Surface Micro-texturing of H13 Tool Steel and Pattern Replication onto ABS Plastics via Injection Moulding

Science.gov (United States)

Otanocha, Omonigho B.; Li, Lin; Zhong, Shan; Liu, Zhu

2016-03-01

H13 tool steels are often used as dies and moulds for injection moulding of plastic components. Certain injection moulded components require micro-patterns on their surfaces in order to modify the physical properties of the components or for better mould release to reduce mould contamination. With these applications it is necessary to study micro-patterning to moulds and to ensure effective pattern transfer and replication onto the plastic component during moulding. In this paper, we report an investigation into high average powered (100 W) picosecond laser interactions with H13 tool steel during surface micro-patterning (texturing) and the subsequent pattern replication on ABS plastic material through injection moulding. Design of experiments and statistical modelling were used to understand the influences of laser pulse repetition rate, laser fluence, scanning velocity, and number of scans on the depth of cut, kerf width and heat affected zones (HAZ) size. The characteristics of the surface patterns are analysed. The process parameter interactions and significance of process parameters on the processing quality and efficiency are characterised. An optimum operating window is recommended. The transferred geometry is compared with the patterns generated on the dies. A discussion is made to explain the characteristics of laser texturing and pattern replication on plastics.

Utilization of the UV laser with picosecond pulses for the formation of surface microstructures on elastomeric plastics

Science.gov (United States)

Antoszewski, B.; Tofil, S.; Scendo, M.; Tarelnik, W.

2017-08-01

Elastomeric plastics belong to a wide range of polymeric materials with special properties. They are used as construction material for seals and other components in many branches of industry and, in particular, in the biomedical industry, mechatronics, electronics and chemical equipment. The micromachining of surfaces of these materials can be used to build micro-flow, insulating, dispensing systems and chemical and biological reactors. The paper presents results of research on the effects of micro-machining of selected elastomeric plastics using a UV laser emitting picosecond pulses. The authors see the prospective application of the developed technology in the sealing technique in particular to shaping the sealing pieces co-operating with the surface of the element. The result of the study is meant to show parameters of the UV laser’s performance when producing typical components such as grooves, recesses for optimum ablation in terms of quality and productivity.

Effect of the laser spot shape on spatial distribution of the ion bunch accelerated in a superstrong field

International Nuclear Information System (INIS)

Scientific research Institute for Optoelectronic Instrument Engineering, Leningrad region (Russian Federation))" data-affiliation=" (Public Limited Company Scientific research Institute for Optoelectronic Instrument Engineering, Leningrad region (Russian Federation))" >Komarov, V M; Scientific research Institute for Optoelectronic Instrument Engineering, Leningrad region (Russian Federation))" data-affiliation=" (Public Limited Company Scientific research Institute for Optoelectronic Instrument Engineering, Leningrad region (Russian Federation))" >Charukhchev, A V; S.I.Vavilov State Optical Institute (FSUE GOI), St.Petersburg (Russian Federation))" data-affiliation=" (Federal State Unitary Enterprise All-Russian Scientific Center S.I.Vavilov State Optical Institute (FSUE GOI), St.Petersburg (Russian Federation))" >Andreev, A A; S.I.Vavilov State Optical Institute (FSUE GOI), St.Petersburg (Russian Federation))" data-affiliation=" (Federal State Unitary Enterprise All-Russian Scientific Center S.I.Vavilov State Optical Institute (FSUE GOI), St.Petersburg (Russian Federation))" >Platonov, K Yu

2014-01-01

We have investigated the effect of the laser spot shape on the spatial distribution of accelerated ions on the front and back sides of a thin target irradiated by a picosecond laser pulse having the intensity of (3 – 4) × 10 18 W cm -2 . Experimental data are compared with numerical calculations. It is shown that the spatial structure of the ion bunch on the front side of the target resembles the laser spot structure rotated by 90°. (interaction of laser radiation with matter. laser plasma)

Effect of the laser spot shape on spatial distribution of the ion bunch accelerated in a superstrong field

Energy Technology Data Exchange (ETDEWEB)

Komarov, V M; Charukhchev, A V [Public Limited Company " Scientific research Institute for Optoelectronic Instrument Engineering" , Leningrad region (Russian Federation); Andreev, A A; Platonov, K Yu [Federal State Unitary Enterprise All-Russian Scientific Center " S.I.Vavilov State Optical Institute" (FSUE GOI), St.Petersburg (Russian Federation)

2014-12-31

We have investigated the effect of the laser spot shape on the spatial distribution of accelerated ions on the front and back sides of a thin target irradiated by a picosecond laser pulse having the intensity of (3 – 4) × 10{sup 18} W cm{sup -2}. Experimental data are compared with numerical calculations. It is shown that the spatial structure of the ion bunch on the front side of the target resembles the laser spot structure rotated by 90°. (interaction of laser radiation with matter. laser plasma)

High resolution laser patterning of ITO on PET substrate

Science.gov (United States)

Zhang, Tao; Liu, Di; Park, Hee K.; Yu, Dong X.; Hwang, David J.

2013-03-01

Cost-effective laser patterning of indium tin oxide (ITO) thin film coated on flexible polyethylene terephthalate (PET) film substrate for touch panel was studied. The target scribing width was set to the order of 10 μm in order to examine issues involved with higher feature resolution. Picosecond-pulsed laser and Q-switched nanosecond-pulsed laser at the wavelength of 532nm were applied for the comparison of laser patterning in picosecond and nanosecond regimes. While relatively superior scribing quality was achieved by picosecond laser, 532 nm wavelength showed a limitation due to weaker absorption in ITO film. In order to seek for cost-effective solution for high resolution ITO scribing, nanosecond laser pulses were applied and performance of 532nm and 1064nm wavelengths were compared. 1064nm wavelength shows relatively better scribing quality due to the higher absorption ratio in ITO film, yet at noticeable substrate damage. Through single pulse based scribing experiments, we inspected that reduced pulse overlapping is preferred in order to minimize the substrate damage during line patterning.

Comparison of three different laser systems for application in dentistry

Science.gov (United States)

Mindermann, Anja; Niemz, M. H.; Eisenmann, L.; Loesel, Frieder H.; Bille, Josef F.

1993-12-01

Three different laser systems have been investigated according to their possible application in dentistry: a free running and a Q-switched microsecond Ho:YAG laser, a free running microsecond Er:YAG laser and picosecond Nd:YLF laser system consisting of an actively mode locked oscillator and a regenerative amplifier. The experiments focused on the question if lasers can support or maybe replace ordinary drilling machines. For this purpose several cavities were generated with the lasers mentioned above. Their depth and quality were judged by light and electron microscopy. The results of the experiments showed that the picosecond Nd:YLF laser system has advantages compared to other lasers regarding their application in dentistry.

Onset and evolution of laser induced periodic surface structures on indium tin oxide thin films for clean ablation using a repetitively pulsed picosecond laser at low fluence

Science.gov (United States)

Farid, N.; Dasgupta, P.; O’Connor, G. M.

2018-04-01

The onset and evolution of laser induced periodic surface structures (LIPSS) is of key importance to obtain clean ablated features on indium tin oxide (ITO) thin films at low fluences. The evolution of subwavelength periodic nanostructures on a 175 nm thick ITO film, using 10 ps laser pulses at a wavelength of 1032 nm, operating at 400 kHz, is investigated. Initially nanoblisters are observed when a single pulse is applied below the damage threshold fluence (0.45 J cm‑2) the size and distribution of nanoblisters are found to depend on fluence. Finite difference time domain (FDTD) simulations support the hypothesis that conductive nanoblisters can enhance the local intensity of the applied electromagnetic field. The LIPSS are observed to evolve from regions where the electric field enhancement has occurred; LIPSS has a perpendicular orientation relative to the laser polarization for a small number (5) pulses, the orientation of the periodic structures appears to rotate and evolve to become aligned in parallel with the laser polarization at approximately the same periodicity. These orientation effects are not observed at higher fluence—due to the absence of the nanoblister-like structures; this apparent rotation is interpreted to be due to stress-induced fragmentation of the LIPSS structure. The application of subsequent pulses leads to clean ablation. LIPSS are further modified into features of a shorter period when laser scanning is used. Results provide evidence that the formation of conductive nanoblisters leads to the enhancement of the applied electromagnetic field and thereby can be used to precisely control laser ablation on ITO thin films.

40 W picosecond fiber amplifier with the large mode-area polarized crystal fiber

International Nuclear Information System (INIS)

Yu, H; Zhou, J; Wushouer, X; Yan, P; Wang, D; Gong, M

2009-01-01

We reported the 5W picosecond laser with pulse width of 30 ps and the repetition rate of 100 MHz, which was amplified to 40.2 W with the linear polarized Yb-doped photonic crystal fiber (PCF), with the slope efficiency of about 58%. As much as 17.3 W second-harmonic power was achieved corresponding to the conversion efficiency of 43%

Excitation and deexcitation of the Si-H stretching mode in a Si:H with picosecond free electron laser pulses

International Nuclear Information System (INIS)

Xu, Z.; Fauchet, M.; Rella, C.W.

1995-01-01

Hydrogen in amorphous and crystalline silicon has been the topic of intense theoretical and experimental investigations for more than one decade. To better understand how the Si-H bonds interact with the Si matrix and how they can be broken, it would be useful to excite selectively these bonds and monitor the energy flow from the Si-H bonds into the bulk Si modes. One attractive way of exciting the Si-H modes selectively is with an infrared laser tuned to a Si-H vibrational mode. Unfortunately, up to now, this type of experiment had not been possible because of the lack of a laser producing intense, ultrashort pulses that are tunable in the mid infrared. In this presentation, we report the first measurement where a 1 picosecond long laser pulse was used to excite the Si-H stretching modes near 2000 cm -1 and another identical laser pulse was used to measure the deexcitation from that specific vibrational mode. The laser was the Stanford free electron laser generating ∼1 ps-long pulses, tunable in the 5 μm region and focussed to an intensity of ∼1 GW/cm 2 . The pump-probe measurements were performed in transmission at room temperature on several 2 μm thick a-Si:H films deposited on c-Si. Samples with predominant Si-H 1 modes, predominant Si-H n>1 modes and with a mixture of modes were prepared. The laser was tuned on resonance with either of these modes. Immediately after excitation, we observe a bleaching of the infrared absorption, which can be attributed to excitation of the Si-H mode. Beaching is expected since, as a result of anharmonicity, the detuning between the (E 3 - E 2 ) resonance and the (E 2 - E 1 ) resonance is larger than the laser bandwidth. Note that despite the anharmonicity, it should be possible to climb the vibrational ladder due to power broadening

Self-cleaning effect in high quality percussion ablating of cooling hole by picosecond ultra-short pulse laser

Science.gov (United States)

Zhao, Wanqin; Yu, Zhishui

2018-06-01

Comparing with the trepanning technology, cooling hole could be processed based on the percussion drilling with higher processing efficiency. However, it is widely believed that the ablating precision of hole is lower for percussion drilling than for trepanning, wherein, the melting spatter materials around the hole surface and the recast layer inside the hole are the two main issues for reducing the ablating precision of hole, especially for the recast layer, it can't be eliminated completely even through the trepanning technology. In this paper, the self-cleaning effect which is a particular property just for percussion ablating of holes has been presented in detail. In addition, the reasons inducing the self-cleaning effect have been discussed. At last, based on the self-cleaning effect of percussion drilling, high quality cooling hole without the melting spatter materials around the hole surface and recast layer inside the hole could be ablated in nickel-based superalloy by picosecond ultra-short pulse laser.

Picosecond infrared activation of methanol in acid zeolites

NARCIS (Netherlands)

Bonn, Miacha; van Santen, Rutger A.; Lercher, J.A.; Kleyn, Aart W.; Bakker, H.J.; Bakker, Huib J.

1997-01-01

Highly porous, crystalline zeolite catalysts are used industrially to catalyze the conversion of methanol to gasoline. We have performed a picosecond spectroscopic study providing insights into both the structure and the dynamics of methanol adsorbed to acid zeolites. We reveal the adsorption

Luminescence from ZnSe excited by picosecond mid-infrared FEL pulses

International Nuclear Information System (INIS)

Mitsuyu, T.; Suzuki, T.; Tomimasu, T.

1998-01-01

We have observed blue band-edge emission from a ZnSe crystal under irradiation of mid-infrared picosecond free electron laser (FEL) pulses. The emission characteristics including spectrum, excitation power dependence, excitation wavelength dependence, and decay time have been investigated. The experimental results have indicated that it is difficult to understand the excitation process by multiphoton excitation, thermal excitation, or excitation through mid-gap levels. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Time-resolved SFG study of formate on a Ni( 1 1 1 ) surface under irradiation of picosecond laser pulses

Science.gov (United States)

Noguchi, H.; Okada, T.; Onda, K.; Kano, S. S.; Wada, A.; Domen, K.

2003-03-01

Time-resolved sum-frequency generation spectroscopy was carried out on a deuterated formate (DCOO) adsorbed on Ni(1 1 1) surface to investigate the surface reaction dynamics under instantaneous surface temperature jump induced by the irradiation by picosecond laser pulses. The irradiation of pump pulse (800 nm) caused the rapid intensity decrease of both CD and OCO stretching modes of bridged formate on Ni(1 1 1). Different temporal behaviors of intensity recovery between these two vibrational modes were observed, i.e., CD stretching mode recovered faster than OCO. This is the first result to show that the dynamics of adsorbates on metals strongly depends on the observed vibrational mode. From the results of temperature and pump fluence dependence, we concluded that the observed intensity change was not due to the decomposition or desorption, but was induced by a non-thermal process.

Fiber-laser-based, green-pumped, picosecond optical parametric oscillator using fan-out grating PPKTP.

Science.gov (United States)

Chaitanya Kumar, S; Parsa, S; Ebrahim-Zadeh, M

2016-01-01

We report a stable, Yb-fiber-laser-based, green-pumped, picosecond optical parametric oscillator (OPO) for the near-infrared based on periodically poled potassium titanyl phosphate (PPKTP) nonlinear crystal, using fan-out grating design and operating near room temperature. The OPO is continuously tunable across 726-955 nm in the signal and 1201-1998 nm in the idler, resulting in a total signal plus idler wavelength coverage of 1026 nm by grating tuning at a fixed temperature. The device generates up to 580 mW of average power in the signal at 765 nm and 300 mW in the idler at 1338 nm, with an overall extraction efficiency of up to 52% and a pump depletion >76%. The extracted signal at 765 nm and idler at 1746 nm exhibit excellent passive power stability better than 0.5% and 0.8% rms, respectively, over 1 h with good beam quality in TEM00 mode profile. The output signal pulses have a Gaussian temporal duration of 13.2 ps, with a FWHM spectral bandwidth of 3.4 nm at 79.5 MHz repetition rate. Power scaling limitations of the OPO due to the material properties of PPKTP are studied.

Study of 2ω and 3/2ω harmonics in ultrashort high-intensity laser ...

Indian Academy of Sciences (India)

Intense laser pulses from such laser systems may have many pre-pulses like picosecond ... ultrashort laser–matter interaction, as well as to control the source parameters. In situ monitoring of ultrashort ... central wavelength of 790 nm with a bandwidth of 16 ± 2 nm after the compressor. The picosecond intensity contrast ...

Characterization of Stone Cleaning by Nd:YAG Lasers with Different Pulse Duration

International Nuclear Information System (INIS)

Bartoli, L.; Siano, S.; Salimbeni, R.; Pouli, P.; Fotakis, C.

2006-01-01

The present work is a comparative study on the laser cleaning of stonework using Nd:YAG lasers at different pulse durations. The ablation rate, the degree of cleaning, and the appearance of the treated surface were studied irradiating a simulated sample and a real stone artefact using three different Nd:YAG laser systems with pulse duration of 90 microseconds, 15 nanoseconds, and 150 picoseconds. To our knowledge, the picosecond laser is here used for the first time in stone conservation. Differences in efficiency and in cleaning result are shown and discussed.

Investigation of the dynamic behavior in materials submitted to sub-picosecond laser driven shock

International Nuclear Information System (INIS)

Cuq-Lelandais, Jean-Paul

2010-01-01

Laser driven shocks allow to investigate materials behavior at high strain rate and present a great interest for research and industrial applications. The latest laser technologies evolutions provide an access to shorter regimes in duration, below the picosecond. This work, which results from a collaboration between the P' institute, the PIMM laboratory and the CEA-DAM, is dedicated to the characterization of the metallic material behavior in this ultra-short mode (aluminium, tantalum), leading to extreme dynamic solicitation in the target (>10 7 s -1 ). The study includes the validation of experimental results obtained on the LULI 100 TW facility by comparison with numerical model. First, the study is orientated to the femtosecond (fs) laser-matter interaction, which is different from what happens in nanosecond regime. Indeed, the characteristic duration scale is comparable to several molecular phenomena like non-equilibrium electrons-ions states. The aim is to determine the equivalent pressure loading induced by the laser pulse on the target. Then, the shock wave propagation within the target has been studied and particularly its pressure decay, notably strong in this regime. In this configuration, the spalls observed are thin, a few μm order, and show a planar rupture morphology. The results obtained by post-mortem observation show that the spall thickness is thinner if the target thickness is reduced. The spalls are characterized by the VISAR measurement. Within the framework of dynamic damage modeling and rupture criteria dimensioning, particularly those which have been validated in the ns regime as Kanel, shots with different thicknesses have been carried out to determine the damage properties in function of strain rate and validate the parameters by prolongation to the ultra-shorts modes. Then, the study has been generalized to the 2D propagation waves, which can explain the spall diameter evolutions. Meanwhile, microscopic simulations of ultra-short laser

Studies on linear, nonlinear optical and excited state dynamics of silicon nanoparticles prepared by picosecond laser ablation

Energy Technology Data Exchange (ETDEWEB)

Hamad, Syed; Nageswara Rao, S. V. S.; Pathak, A. P. [School of Physics, University of Hyderabad, Hyderabad 500046, Telangana (India); Krishna Podagatlapalli, G.; Mounika, R.; Venugopal Rao, S., E-mail: soma-venu@yahoo.com, E-mail: soma-venu@uohyd.ac.in [Advanced Center of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046, Telangana (India)

2015-12-15

We report results from our studies on the fabrication and characterization of silicon (Si) nanoparticles (NPs) and nanostructures (NSs) achieved through the ablation of Si target in four different liquids using ∼2 picosecond (ps) pulses. The consequence of using different liquid media on the ablation of Si target was investigated by studying the surface morphology along with material composition of Si based NPs. The recorded mean sizes of these NPs were ∼9.5 nm, ∼37 nm, ∼45 nm and ∼42 nm obtained in acetone, water, dichloromethane (DCM) and chloroform, respectively. The generated NPs were characterized by selected area electron diffraction (SAED), high resolution transmission microscopy (HRTEM), Raman spectroscopic techniques and Photoluminescence (PL) studies. SAED, HRTEM and Raman spectroscopy data confirmed that the material composition was Si NPs in acetone, Si/SiO{sub 2} NPs in water, Si-C NPs in DCM and Si-C NPs in chloroform and all of them were confirmed to be polycrystalline in nature. Surface morphological information of the fabricated Si substrates was obtained using the field emission scanning electron microscopic (FESEM) technique. FESEM data revealed the formation of laser induced periodic surface structures (LIPSS) for the case of ablation in acetone and water while random NSs were observed for the case of ablation in DCM and chloroform. Femtosecond (fs) nonlinear optical properties and excited state dynamics of these colloidal Si NPs were investigated using the Z-scan and pump-probe techniques with ∼150 fs (100 MHz) and ∼70 fs (1 kHz) laser pulses, respectively. The fs pump-probe data obtained at 600 nm consisted of single and double exponential decays which were tentatively assigned to electron-electron collisional relaxation (<1 ps) and non-radiative transitions (>1 ps). Large third order optical nonlinearities (∼10{sup −14} e.s.u.) for these colloids have been estimated from Z-scan data at an excitation wavelength of 680 nm

Studies on linear, nonlinear optical and excited state dynamics of silicon nanoparticles prepared by picosecond laser ablation

Directory of Open Access Journals (Sweden)

Syed Hamad

2015-12-01

Full Text Available We report results from our studies on the fabrication and characterization of silicon (Si nanoparticles (NPs and nanostructures (NSs achieved through the ablation of Si target in four different liquids using ∼2 picosecond (ps pulses. The consequence of using different liquid media on the ablation of Si target was investigated by studying the surface morphology along with material composition of Si based NPs. The recorded mean sizes of these NPs were ∼9.5 nm, ∼37 nm, ∼45 nm and ∼42 nm obtained in acetone, water, dichloromethane (DCM and chloroform, respectively. The generated NPs were characterized by selected area electron diffraction (SAED, high resolution transmission microscopy (HRTEM, Raman spectroscopic techniques and Photoluminescence (PL studies. SAED, HRTEM and Raman spectroscopy data confirmed that the material composition was Si NPs in acetone, Si/SiO2 NPs in water, Si-C NPs in DCM and Si-C NPs in chloroform and all of them were confirmed to be polycrystalline in nature. Surface morphological information of the fabricated Si substrates was obtained using the field emission scanning electron microscopic (FESEM technique. FESEM data revealed the formation of laser induced periodic surface structures (LIPSS for the case of ablation in acetone and water while random NSs were observed for the case of ablation in DCM and chloroform. Femtosecond (fs nonlinear optical properties and excited state dynamics of these colloidal Si NPs were investigated using the Z-scan and pump-probe techniques with ∼150 fs (100 MHz and ∼70 fs (1 kHz laser pulses, respectively. The fs pump-probe data obtained at 600 nm consisted of single and double exponential decays which were tentatively assigned to electron-electron collisional relaxation (1 ps. Large third order optical nonlinearities (∼10−14 e.s.u. for these colloids have been estimated from Z-scan data at an excitation wavelength of 680 nm suggesting that the colloidal Si NPs find

Enhancement of laser-induced breakdown spectroscopy (LIBS) Detection limit using a low-pressure and short-pulse laser-induced plasma process.

Science.gov (United States)

Wang, Zhen Zhen; Deguchi, Yoshihiro; Kuwahara, Masakazu; Yan, Jun Jie; Liu, Ji Ping

2013-11-01

Laser-induced breakdown spectroscopy (LIBS) technology is an appealing technique compared with many other types of elemental analysis because of the fast response, high sensitivity, real-time, and noncontact features. One of the challenging targets of LIBS is the enhancement of the detection limit. In this study, the detection limit of gas-phase LIBS analysis has been improved by controlling the pressure and laser pulse width. In order to verify this method, low-pressure gas plasma was induced using nanosecond and picosecond lasers. The method was applied to the detection of Hg. The emission intensity ratio of the Hg atom to NO (IHg/INO) was analyzed to evaluate the LIBS detection limit because the NO emission (interference signal) was formed during the plasma generation and cooling process of N2 and O2 in the air. It was demonstrated that the enhancement of IHg/INO arose by decreasing the pressure to a few kilopascals, and the IHg/INO of the picosecond breakdown was always much higher than that of the nanosecond breakdown at low buffer gas pressure. Enhancement of IHg/INO increased more than 10 times at 700 Pa using picosecond laser with 35 ps pulse width. The detection limit was enhanced to 0.03 ppm (parts per million). We also saw that the spectra from the center and edge parts of plasma showed different features. Comparing the central spectra with the edge spectra, IHg/INO of the edge spectra was higher than that of the central spectra using the picosecond laser breakdown process.

Resonance Raman spectroscopy in the picosecond time scale: the carboxyhemoglobin photointermediate

International Nuclear Information System (INIS)

Terner, J.; Spiro, T.G.; Nagumo, M.; Nicol, M.F.; El-Sayed, M.A.

1980-01-01

A picosecond resonance Raman detection technique is described. The technique is described as specifically applied to the analysis of carboxyhemoglobin (COHb). Irradiaton of COHb with a tightly focused laser produced three distinct bands between 1540 and 1620cm -1 that are distinct from bands of COHb or deoxyHb, and the bands are attributed to an intermediate in the photolysis of COHb which develops within 30ps of the excitation. Computer subtraction of the COHb spectrum yielded a spectrum of the photointermediate

Study on the Cross Plane Thermal Transport of Polycrystalline Molybdenum Nanofilms by Applying Picosecond Laser Transient Thermoreflectance Method

Directory of Open Access Journals (Sweden)

Tingting Miao

2014-01-01

Full Text Available Thin metal films are widely used as interconnecting wires and coatings in electronic devices and optical components. Reliable thermophysical properties of the films are required from the viewpoint of thermal management. The cross plane thermal transport of four polycrystalline molybdenum nanofilms with different thickness deposited on glass substrates has been studied by applying the picosecond laser transient thermoreflectance technique. The measurement is performed by applying both front pump-front probe and rear pump-front probe configurations with high quality signal. The determined cross plane thermal diffusivity of the Mo films greatly decreases compared to the corresponding bulk value and tends to increase as films become thicker, exhibiting significant size effect. The main mechanism responsible for the thermal diffusivity decrease of the present polycrystalline Mo nanofilms is the grain boundary scattering on the free electrons. Comparing the cross plane thermal diffusivity and inplane electrical conductivity indicates the anisotropy of the transport properties of the Mo films.

Optimization of InAs/GaAs quantum-dot structures and application to 1.3-μm mode-locked laser diodes

International Nuclear Information System (INIS)

Li Mi-Feng; Ni Hai-Qiao; Niu Zhi-Chuan; Ding Ying; David Bajek; Liang Kong; Ana Cataluna Maria

2014-01-01

The self-assembled growth of InAs/GaAs quantum dots by molecular beam epitaxy is conducted by optimizing several growth parameters, using a one-step interruption method after island formation. The dependence of photoluminescence on areal quantum-dot density is systematically investigated as a function of InAs deposition, growth temperature and arsenic pressure. The results of this investigation along with time-resolved photoluminescence measurements show that the combination of a growth temperature of 490 °C, with a deposition rate of 0.02 ML/s, under an arsenic pressure of 1 × 10 −6 Torr (1 Torr = 1.33322 × 10 2 Pa), provides the best compromise between high density and the photoluminescence of quantum dot structure, with a radiative lifetime of 780 ps. The applicability of this 5-layer quantum dot structure to high-repetition-rate pulsed lasers is demonstrated with the fabrication and characterization of a monolithic InAs/GaAs quantum-dot passively mode-locked laser operating at nearly 1300 nm. Picosecond pulse generation is achieved from a two-section laser, with a ∼ 19.7-GHz repetition rate. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Picosecond CO2 laser for relativistic particle acceleration

International Nuclear Information System (INIS)

Pogorelsky, I.; Ben-Zvi, I.; Kimura, W.D.; Kurnit, N.A.; Kannari, F.

1994-01-01

A table-top 20-GW 50-ps CO 2 laser system is under operation at the Brookhaven Accelerator Test Facility. We compare laser performance with model predictions. Extrapolations suggest the possibility of compact terawatt CO 2 laser systems suitable as laser accelerator drivers and for other strong-field applications. Latest progress on an Inverse Cherenkov Laser Accelerator experiment is reported

Picosecond, single pulse electron linear accelerator

International Nuclear Information System (INIS)

Kikuchi, Riichi; Kawanishi, Masaharu

1979-01-01

The picosecond, single pulse electron linear accelerators, are described, which were installed in the Nuclear Engineering Laboratory of the University of Tokyo and in the Nuclear Radiation Laboratory of the Osaka University. The purpose of the picosecond, single pulse electron linear accelerators is to investigate the very short time reaction of the substances, into which gamma ray or electron beam enters. When the electrons in substances receive radiation energy, the electrons get high kinetic energy, and the energy and the electric charge shift, at last to the quasi-stable state. This transient state can be experimented with these special accelerators very accurately, during picoseconds, raising the accuracy of the time of incidence of radiation and also raising the accuracy of observation time. The outline of these picosecond, single pulse electron linear accelerators of the University of Tokyo and the Osaka University, including the history, the systems and components and the output beam characteristics, are explained. For example, the maximum energy 30 -- 35 MeV, the peak current 1 -- 8 n C, the pulse width 18 -- 40 ps, the pulse repetition rate 200 -- 720 pps, the energy spectrum 1 -- 1.8% and the output beam diameter 2 -- 5 mm are shown as the output beam characteristics of the accelerators in both universities. The investigations utilizing the picosecond single pulse electron linear accelerators, such as the investigation of short life excitation state by pulsed radiation, the dosimetry study of pulsed radiation, and the investigation of the transforming mechanism and the development of the transforming technology from picosecond, single pulse electron beam to X ray, vacuum ultraviolet ray and visual ray, are described. (Nakai, Y.)

Photosensitivity of the Er/Yb-Codoped Schott IOG1 Phosphate Glass Using 248 nm, Femtosecond, and Picosecond Laser Radiation

International Nuclear Information System (INIS)

Pissadakis, S.; Michelakaki, I.

2009-01-01

The effect of 248 nm laser radiation, with pulse duration of 5 picoseconds, 500 femtosecond, and 120 femtosecond, on the optical properties and the Knoop hardness of a commercial Er/Yb-codoped phosphate glass is presented here. Refractive index changes of the order of few parts of 10-4 are correlated with optical absorption centers induced in the glass volume, using Kramers-Kroning relationship. Accordingly, substantially lower refractive index changes are measured in volume Bragg gratings inscribed in the glass, indicating that, in addition to the optical density changes, volume dilation changes of negative sign may also be associated with the 248 nm ultrafast irradiation. The Knoop hardness experimental results reveal that the glass matrix undergoes an observable initial hardening and then a reversing softening and volume dilation process for modest accumulated energy doses, where the Knoop hardness follows a nonmonotonic trend. Comparative results on the Knoop hardness trend are also presented for the case of 193 nm excimer laser radiation. The above findings denote that the positive or negative evolution of refractive index changes induced by the 248 0nm ultrafast radiation in the glass is dominated by the counteraction of the color center formation and the volume modification effects.

The use of laser beams for plasma diagnostics

International Nuclear Information System (INIS)

Gex, J.P.; Jolas, A.; Launspach, J.; Schirmann, D.

1975-01-01

The optical properties of lasers allow them to be a promising source for plasma diagnosis. The Q-switched lasers provide the opportunity to make observations in a very short time interval down to a few picoseconds. The laser space and time coherence properties allow interferometric measurements of plasma electron densities. Thus in the experiments of laser-matter interactions, the radiation obtained by frequency conversion of the Nd: glass laser emission is used for density measurements (up to 10 20 cm -3 ) in small scale plasmas (approximately equal to 1mm). Owing to the monochromaticity and high intensity of the Q-switched laser radiation, density fluctuations and microscopic instabilities of the plasma can be studied by Thompson scattering measurements. Finally, some statistically isotropic media become birefringent under the action of the strong electrical field of the laser beam radiation. This effect can be used for laser pulse duration measurements in a range not exceeding a few picoseconds [fr

Integrated laser-target interaction experiments on the RAL petawatt laser

International Nuclear Information System (INIS)

Patel, P K; Key, M H; Mackinnon, A J

2005-01-01

We review a recent experimental campaign to study the interaction physics of petawatt laser pulses incident at relativistic intensities on solid targets. The campaign was performed on the 500 J sub-picosecond petawatt laser at the Rutherford Appleton Laboratory. An extensive suite of optical, x-ray, and particle diagnostics was employed to characterise the processes of laser absorption, electron generation and transport, thermal and K-alpha x-ray generation, and proton acceleration

Picosecond rotationally resolved stimulated emission pumping spectroscopy of nitric oxide

International Nuclear Information System (INIS)

Tanjaroon, Chakree; Reeve, Scott W.; Ford, Alan; Murry, W. Dean; Lyon, Kevin; Yount, Bret; Britton, Dan; Burns, William A.; Allen, Susan D.; Bruce Johnson, J.

2012-01-01

Highlights: ► Stimulated emission pumping for nitric oxide was studied using picosecond lasers. ► Weak and tightly focused pulses provide sufficient energy for population transfer. ► Selective excitation at the bandhead yields strong fluorescence depletion signals. ► We observe 19% population transfer to v″ = 2 of the X 2 Π 1/2 ground electronic state. - Abstract: Stimulated emission pumping (SEP) experiments were performed on the nitric oxide molecule in a flow cell environment using lasers with pulse widths of 17–25 ps. A lambda excitation scheme, or ‘‘pump–dump” arrangement, was employed with the pump laser tuned to the T 00 vibronic band origin (λ pump =226.35(1)nm) of the A 2 Σ + (v′ = 0, J′) ← X 2 Π 1/2 (v″ = 0, J″) and the dump laser scanned from 246–248 nm within the A 2 Σ + (v′ = 0, J′) → X 2 Π 1/2 (v″ = 2, J″) transition. The rotationally resolved SEP spectra were measured by observing the total fluorescence within the A 2 Σ + (v′ = 0, J′) → X 2 Π 1/2 (v″ = 1, J″) transition between 235 nm and 237.2 nm while scanning the dump laser wavelengths. Multiple rotational states were excited due to the broad laser bandwidth. Measurements showed that the resolved rotational structure depended on the energy and bandwidth of the applied pump and dump laser pulses. Analysis of the observed fluorescence depletion signals yielded an average percent fluorescence depletion of about 19% when λ pump =226.35(1)nm and λ dump =247.91(1)nm. This value reflects the percent transfer of the NO population from the A 2 Σ + (V′ = 0, J′) excited electronic state to the X 2 Π 1/2 (v″ = 2, J″) ground electronic state. The maximum expected depletion is 50% in the limit of dump saturation. Selective excitation of NO at the bandhead provides good spectral discrimination from the background emission and noise and unambiguously confirms the identity of the emitter.

Excitation mechanisms in 1 mJ picosecond laser induced low pressure He plasma and the resulting spectral quality enhancement

Energy Technology Data Exchange (ETDEWEB)

Idris, Nasrullah; Lahna, Kurnia; Abdulmadjid, Syahrun Nur [Department of Physics, Faculty of Mathematics and Natural Sciences, Syiah Kuala University, Darussalam, Banda Aceh 23111, NAD (Indonesia); Ramli, Muliadi [Department of Chemistry, Faculty of Mathematics and Natural Sciences, Syiah Kuala University, Darussalam, Banda Aceh 23111, NAD (Indonesia); Suyanto, Hery [Department of Physics, Faculty of Mathematics and Natural Sciences, Udayana University, Kampus Bukit Jimbaran, Denpasar 80361, Bali (Indonesia); Marpaung, Alion Mangasi [Department of Physics, Faculty of Mathematics and Natural Sciences, Jakarta State University, 10 Rawamangun, Jakarta (Indonesia); Pardede, Marincan [Department of Electrical Engineering, University of Pelita Harapan, 1100 M.H. Thamrin Boulevard, Lippo Village, Tangerang 15811 (Indonesia); Jobiliong, Eric [Department of Industrial Engineering, University of Pelita Harapan, 1100 M.H. Thamrin Boulevard, Lippo Village, Tangerang 15811 (Indonesia); Hedwig, Rinda; Lie, Zener Sukra [Department of Computer Engineering, Bina Nusantara University, 9 K.H. Syahdan, Jakarta 14810 (Indonesia); Research Center of Maju Makmur Mandiri Foundation, 40/80 Srengseng Raya, Jakarta 11630 (Indonesia); Suliyanti, Maria Margaretha [Research Center for Physics, Indonesia Institute of Sciences, Kawasan PUSPIPTEK, Serpong, Tangerang Selatan 15314, Banten (Indonesia); Lie, Tjung Jie; Kurniawan, Koo Hendrik, E-mail: kurnia18@cbn.net.id [Research Center of Maju Makmur Mandiri Foundation, 40/80 Srengseng Raya, Jakarta 11630 (Indonesia); Kagawa, Kiichiro [Fukui Science Education Academy, Takagi Chuou 2 choume, Fukui 910-0804 (Japan); Tjia, May On [Research Center of Maju Makmur Mandiri Foundation, 40/80 Srengseng Raya, Jakarta 11630 (Indonesia); Physics of Magnetism and Photonics Group, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, 10 Ganesha, Bandung 40132 (Indonesia)

2015-06-14

We report in this paper the results of an experimental study on the spectral and dynamical characteristics of plasma emission induced by 1 mJ picoseconds (ps) Nd-YAG laser using spatially resolved imaging and time resolved measurement of the emission intensities of copper sample. This study has provided the experimental evidence concerning the dynamical characteristics of the excitation mechanisms in various stages of the plasma formation, which largely consolidate the basic scenarios of excitation processes commonly accepted so far. However, it is also clearly shown that the duration of the shock wave excitation process induced by ps laser pulses is much shorter than those observed in laser induced breakdown spectroscopy employing nanosecond laser at higher output energy. This allows the detection of atomic emission due exclusively to He assisted excitation in low pressure He plasma by proper gating of the detection time. Furthermore, the triplet excited state associated with He I 587.6 nm is shown to be the one most likely involved in the process responsible for the excellent spectral quality as evidenced by its application to spectrochemical analysis of a number of samples. The use of very low energy laser pulses also leads to minimal destructive effect marked by the resulted craters of merely about 10 μm diameter and only 10 nm deep. It is especially noteworthy that the excellent emission spectrum of deuterium detected from D-doped titanium sample is free of spectral interference from the undesirable ubiquitous water molecules without a precleaning procedure as applied previously and yielding an impressive detection limit of less than 10 μg/g. Finally, the result of this study also shows a promising application to depth profiling of impurity distribution in the sample investigated.

Surface and Bulk Nanostructuring of Insulators by Ultrashort Laser Pulses

Science.gov (United States)

2017-04-05

non perturbative effects leading to HHG. 15. SUBJECT TERMS Nanostructuring of bulk insulators, sub-picosecond electronic and structural events , photo...time, the charge density oscillations follow the time periodicity of the incident radiation. These transient charge oscillations are exclusively due...As in section II photoexcitation and the dielectric response of laser-irradiated diamond are treated in independent particle approximation based on the

Synchronizaiton Between Laser and Electron Beam at Photocathode RF Gun

CERN Document Server

Sakumi, Akira; Fukasawa, Atsushi; Kumagai, Noritaka; Muroya, Yusa; Tomizawa, Hiromitsu; Ueda, T; Uesaka, Mitsuru; Urakawa, Junji; Yoshii, K

2005-01-01

The chemical reactions of hot, room temperature and critical water in a time-range of picosecond and sub-picosecond have been carried out by the 18 MeV S-band linac and a Mg photocathode RF gun with the irradiation of third harmonic Ti: Sapphire laser, at Nuclear Engineering Research Laboratory (NERL), the University of Tokyo. Although this short bunch and 100 fs laser light are enough to perform the experiment of radiation chemistry in the time-range of sub-picosecond, the total time-resolution become worse by the instability of synchronization between laser and radio frequency of linac. We found that the fluctuation of room temperature causes the instability, particularly the cycle of turning on/off of the air-conditioner. It is shown that 0.3 °C (peak-to-peak) fluctuation of the laser-room temperature have approximately corresponded to the instability of 6 ps. We are trying to decrease the fluctuation of the room temperature, together with the local temperature stability of the Ti: Sapphire crysta...

Sweep devices for picosecond image-converter streak cameras

International Nuclear Information System (INIS)

Cunin, B.; Miehe, J.A.; Sipp, B.; Schelev, M.Ya.; Serduchenko, J.N.; Thebault, J.

1979-01-01

Four different sweep devices based on microwave tubes, avalanche transistors, krytrons, and laser-triggered spark gaps are treated in detail. These control circuits are developed for picosecond image-converter cameras and generate sweep pulses providing streak speeds in the range of 10 7 to 5x10 10 cm/sec with maximum time resolution better than 10 -12 sec. Special low-jitter triggering schemes reduce the jitter to less than 5x10 -11 sec. Some problems arising in the construction and matching of the sweep devices and image-streak tube are discussed. Comparative parameters of nanosecond switching elements are presented. The results described can be used by other authors involved in streak camera development

Short pulse generation in a passively mode-locked photonic crystal semiconductor laser

DEFF Research Database (Denmark)

Heuck, Mikkel; Blaaberg, Søren; Mørk, Jesper

2010-01-01

We present a new type of passively mode-locked laser with quantum wells embedded in photonic crystal waveguides operating in the slow light regime, which is capable of emitting sub picosecond pulses with widely controllable properties......We present a new type of passively mode-locked laser with quantum wells embedded in photonic crystal waveguides operating in the slow light regime, which is capable of emitting sub picosecond pulses with widely controllable properties...

High-power ultrashort fiber laser for solar cells micromachining

Science.gov (United States)

Lecourt, J.-B.; Duterte, C.; Liegeois, F.; Lekime, D.; Hernandez, Y.; Giannone, D.

2012-02-01

We report on a high-power ultra-short fiber laser for thin film solar cells micromachining. The laser is based on Chirped Pulse Amplification (CPA) scheme. The pulses are stretched to hundreds of picoseconds prior to amplification and can be compressed down to picosecond at high energy. The repetition rate is adjustable from 100 kHz to 1 MHz and the optical average output power is close to 13 W (before compression). The whole setup is fully fibred, except the compressor achieved with bulk gratings, resulting on a compact and reliable solution for cold ablation.

Prediction of picosecond voltage collapse and electromagnetic wave generation in gas avalanche switches

International Nuclear Information System (INIS)

Mayhall, D.J.; Yee, J.H.; Duong-Van, M.; Villa, F.

1988-01-01

A picosecond speed switch, the Gas Avalanche Switch (GAS), has been proposed for GeV linear accelerators. The medium is gas at high pressure (100 - 700 atm). An avalanche discharge is induced between pulse-charged high voltage electrodes by electron deposition from a fast laser pulse. Avalanche electrons move to the positive electrode, causing the applied voltage to collapse in picoseconds. A two-dimensional (2D) electromagnetic electron fluid computer code calculates the avalanche evolution and voltage collapse in air for an infinite parallel plate capacitor with a 0.1 mm spacing. Calculations are done for an accelerator switch geometry consisting of a 0.7 mm wide by 0.8 mm high, rectangular, high voltage center electrode (CE) between the grounded plates of a parallel plate line of 2 mm spacing. Several variations of CE elevation and initial electron deposition are investigated The 2D character of the outgoing TEM waves is shown

Guiding of laser pulses in plasma waveguides created by linearly-polarized femtosecond laser pulses

OpenAIRE

Lemos, N.; Cardoso, L.; Geada, J.; Figueira, G.; Albert, F.; Dias, J. M.

2018-01-01

We experimentally demonstrate that plasma waveguides produced with ultra-short laser pulses (sub-picosecond) in gas jets are capable of guiding high intensity laser pulses. This scheme has the unique ability of guiding a high-intensity laser pulse in a plasma waveguide created by the same laser system in the very simple and stable experimental setup. A hot plasma column was created by a femtosecond class laser that expands into an on-axis parabolic low density profile suitable to act as a wav...

Time-resolved x-ray laser induced photoelectron spectroscopy of isochoric heated copper

International Nuclear Information System (INIS)

Nelson, A.J.; Dunn, J.; Hunter, J.; Widmann, K.

2005-01-01

Time-resolved x-ray photoelectron spectroscopy is used to probe the nonsteady-state evolution of the valence band electronic structure of laser heated ultrathin (50 nm) copper. A metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.1-2.5 mJ laser energy focused in a large 500x700 μm 2 spot to create heated conditions of 0.07-1.8x10 12 W cm -2 intensity. Valence band photoemission spectra are presented showing the changing occupancy of the Cu 3d level with heating are presented. These picosecond x-ray laser induced time-resolved photoemission spectra of laser-heated ultrathin Cu foil show dynamic changes in the electronic structure. The ultrafast nature of this technique lends itself to true single-state measurements of shocked and heated materials

Ultrastable, high efficiency picosecond green light generation using K3B6O10Br series nonlinear optical crystals

Science.gov (United States)

Hou, Z. Y.; Xia, M. J.; Wang, L. R.; Xu, B.; Yan, D. X.; Meng, L. P.; Liu, L. J.; Xu, D. G.; Zhang, L.; Wang, X. Y.; Li, R. K.; Chen, C. T.

2017-09-01

Two perovskite-structure K3B6O10Br1-x Cl x (x  =  0 and 0.5) series nonlinear optical crystals were thoroughly investigated for their picosecond 532 nm laser pulses abilities and high power outputs were achieved via second harmonic generation (SHG) technique for the first time. SHG conversion efficiency of 57.3% with a 13.2 mm length K3B6O10Br (KBB) crystal was achieved using a laser source of pulse repetition rate of 10 Hz and pulse width of 25 ps, which is the highest conversion efficiency of ps visible laser based on KBB crystal. And by employing an 80 MHz, 10 ps fundamental laser beam, maximum power outputs of 12 W with K3B6O10Br0.5Cl0.5 (KBBC) and 11.86 W with KBB crystals were successfully demonstrated. Furthermore, the standard deviation jitters of the average power outputs are less than 0.6% and 1.17% by KBB and KBBC, respectively, showing ultrastable power stabilities favorable for practical applications. In addition, the other optical parameters including acceptance angle and temperature bandwidth were also investigated.

Laser techniques for spectroscopy of core-excited atomic levels

Science.gov (United States)

Harris, S. E.; Young, J. F.; Falcone, R. W.; Rothenberg, J. E.; Willison, J. R.

1982-01-01

We discuss three techniques which allow the use of tunable lasers for high resolution and picosecond time scale spectroscopy of core-excited atomic levels. These are: anti-Stokes absorption spectroscopy, laser induced emission from metastable levels, and laser designation of selected core-excited levels.

Photophysical and photochemical effects in ultrafast laser patterning of CVD graphene

International Nuclear Information System (INIS)

Bobrinetskiy, Ivan; Otero, Nerea; Romero, Pablo M; Emelianov, Aleksei; Komarov, Ivan; Nasibulin, Albert

2016-01-01

The micro-scale patterns in graphene on Si/SiO 2 substrate were fabricated using ultrashort 515 nm laser pulses. For both picosecond and femtosecond laser pulses two competitive processes, based on photo-thermal (ablation) and photochemical (oxidation/etching) effects, were observed. The laser-induced etching of graphene starts just below the threshold energy of graphene ablation: 1.7 nJ per 280 fs pulse and 2.7 µ J per 30 ps pulse. Whilst etching is not sensitive to thermal properties of graphene and provides uniform patterns, the ablation, in contrast, is highly affected by defects in the graphene structure like wrinkles and bilayer islands. The mechanisms of ultrafast laser interaction with graphene are discussed. (letter)

Investigation of laser plasma instabilities using picosecond laser pulses

International Nuclear Information System (INIS)

Kline, J L; Montgomery, D S; Yin, L; Flippo, K A; Shimada, T; Johnson, R P; Rose, H A; Albright, B J; Hardin, R A

2008-01-01

A new short-pulse version of the single-hot-spot configuration has been implemented to enhance the performance of experiments to understand Stimulated Raman Scattering. The laser pulse length was reduced from ∼200 to ∼3 ps. The reduced pulse length improves the experiment by minimizing effects such as plasma hydrodynamic evolution and ponderomotive filamentation of the interaction beam. In addition, the shortened laser pulses allow full length 2D particle-in-cell simulations of the experiments. Using the improved single-hot-spot configuration, a series of experiments to investigate kλ D scaling of SRS has been performed. Details of the experimental setup and initial results will be presented

Laser desorption ionization and peptide sequencing on laser induced silicon microcolumn arrays

Science.gov (United States)

Vertes, Akos [Reston, VA; Chen, Yong [San Diego, CA

2011-12-27

The present invention provides a method of producing a laser-patterned silicon surface, especially silicon wafers for use in laser desorption ionization (LDI-MS) (including MALDI-MS and SELDI-MS), devices containing the same, and methods of testing samples employing the same. The surface is prepared by subjecting a silicon substrate to multiple laser shots from a high-power picosecond or femtosecond laser while in a processing environment, e.g., underwater, and generates a remarkable homogenous microcolumn array capable of providing an improved substrate for LDI-MS.

Ultrafast Laser Diagnostics for Energetic-Material Ignition Mechanisms: Tools for Physics-Based Model Development.

Energy Technology Data Exchange (ETDEWEB)

Kearney, Sean Patrick; Jilek, Brook Anton; Kohl, Ian Thomas; Farrow, Darcie; Urayama, Junji

2014-11-01

We present the results of an LDRD project to develop diagnostics to perform fundamental measurements of material properties during shock compression of condensed phase materials at micron spatial scales and picosecond time scales. The report is structured into three main chapters, which each focus on a different diagnostic devel opment effort. Direct picosecond laser drive is used to introduce shock waves into thin films of energetic and inert materials. The resulting laser - driven shock properties are probed via Ultrafast Time Domain Interferometry (UTDI), which can additionally be used to generate shock Hugoniot data in tabletop experiments. Stimulated Raman scattering (SRS) is developed as a temperature diagnostic. A transient absorption spectroscopy setup has been developed to probe shock - induced changes during shock compressio n. UTDI results are presented under dynamic, direct - laser - drive conditions and shock Hugoniots are estimated for inert polystyrene samples and for the explosive hexanitroazobenzene, with results from both Sandia and Lawrence Livermore presented here. SRS a nd transient absorption diagnostics are demonstrated on static thin - film samples, and paths forward to dynamic experiments are presented.

Precision machining of pig intestine using ultrafast laser pulses

Science.gov (United States)

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

2015-07-01

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

Hematoporphyrin-sensitized degradation of deoxyribose and DNA in high intensity near-UV picosecond pulsed laser photolysis

International Nuclear Information System (INIS)

Gantchev, T.G.; Lier, J.E. van; Grabner, G.; Keskinova, E.; Angelov, D.

1995-01-01

The photosensitized degradation of deoxyribose and DNA, using hematoporphyrin (HP) and picosecond laser pulses at high intensities was studied. Aldehyde formation from 2-deoxy-D-ribose and long-chain double-stranded DNA, when analyzed as a function of light intensity, followed a non-linear dependence, suggesting the involvement of multiphoton light absorption by HP. The degradation mechanism was studied by analysis of the yield dependence on excitation intensity and the effect of added radical scavengers. The participation of OH radicals in the degradation process was confirmed by spin trapping techniques. At low light intensities, added N 2 O largely increased product formation, suggesting that HP photoionization predominates under these conditions. At higher intensities (I ≥ 3 GW/cm 2 ) the product yield was not affected by N 2 O which, combined with spin trapping data, suggested that OH radical formation occurred, but that neither HP photoionization nor peroxy formation was involved. Single and double strand breaks in supercoiled plasmid DNA (pBR 322) confirmed the generation of OH or OH-like radicals during high-intensity excitation of HP. A mechanism involving a multistep excitation of HP, followed by resonance energy transfer to H 2 O resulting in dissociation to yield OH and H atoms, is proposed. (author)

Face and labial rejuvenation with the new Nd-Yag 1064 picoseconds laser

Science.gov (United States)

Teixeira, Heitor; Teixeira, Carolina

2018-04-01

Lips are the component of the oral cavity which synthesizes more functions and emotions. The nonverbal communication is established by the body, every movement gesture, posture and facial expression which shows a willingness to communicate directly or subtly, consciously or unconsciously. The smile is one of the expressions that attract us the most, for its simplicity and mainly for its puzzle. In Lips aging implies a loss of mucous membranes' density; lips' dehydrate and resect themselves, reducing its' thickness which causes an appearance of aging of the all face. The demands of public opinion of being young and stay young are becoming more and more pressing, therefore it is necessary to meet this demand. The responsibility of achieving this task is up to the doctor, the anti-aging medicine and the actual existing physical means, which are available to correct and prevent this disease. Having the possibility of using the new picoseconds Nd-Yag Laser in Lips' rejuvenation we must use them together and in accordance between them and the guideline we presented what we believe to be the guideline which allows us to obtain good results in a new and simple effective treatment that can be proved by the major aspect of the lip and by evidence and monitoring that we went through for about ten month. Obtained results of labial cracks' disappearance inside of the red mucosa increase in lips' volume and contour and disappearance of oral wrinkles creates an aesthetic appearance witch is remarkable. This is a non invasive method with minimal complications with low morbidity and in our opinion superior results when compared to other traditional methods considered soft tissue augmentation including peelings, botox injections, injectable fillers such as hyaluronic acid injections temporary and permanent injectable bio-implants, bio- catalysts and even surgery of the upper lip.

Ultrafast disk lasers and amplifiers

Science.gov (United States)

Sutter, Dirk H.; Kleinbauer, Jochen; Bauer, Dominik; Wolf, Martin; Tan, Chuong; Gebs, Raphael; Budnicki, Aleksander; Wagenblast, Philipp; Weiler, Sascha

2012-03-01

Disk lasers with multi-kW continuous wave (CW) output power are widely used in manufacturing, primarily for cutting and welding applications, notably in the automotive industry. The ytterbium disk technology combines high power (average and/or peak power), excellent beam quality, high efficiency, and high reliability with low investment and operating costs. Fundamental mode picosecond disk lasers are well established in micro machining at high throughput and perfect precision. Following the world's first market introduction of industrial grade 50 W picosecond lasers (TruMicro 5050) at the Photonics West 2008, the second generation of the TruMicro series 5000 now provides twice the average power (100 W at 1030 nm, or 60 W frequency doubled, green output) at a significantly reduced footprint. Mode-locked disk oscillators achieve by far the highest average power of any unamplified lasers, significantly exceeding the 100 W level in laboratory set-ups. With robust long resonators their multi-microjoule pulse energies begin to compete with typical ultrafast amplifiers. In addition, significant interest in disk technology has recently come from the extreme light laser community, aiming for ultra-high peak powers of petawatts and beyond.

Passive mode locking in a multisegment laser diode with an external cavity

International Nuclear Information System (INIS)

Andreeva, E V; Magnitskiy, Sergey A; Koroteev, Nikolai I; Salik, E; Feinberg, J; Starodubov, D S; Shramenko, M V; Yakubovich, S D

1999-01-01

The structure and operating conditions of multisegment laser (GaAl)As diodes with passive locking of the modes of an external cavity (bulk and fibre) were optimised. Regular trains of optical single pulses of picosecond duration were generated in a spectral range 850 - 860 nm. The peak power of these pulses was several watts and the repetition rate was near 1 GHz. Under certain conditions these output pulses were linearly chirped, i.e. they were suitable for subpicosecond time compression. Laboratory prototypes were made of miniature light-emitting modules with these characteristics. (lasers)

Fast-electron-relaxation measurement for laser-solid interaction at relativistic laser intensities

International Nuclear Information System (INIS)

Chen, H.; Shepherd, R.; Chung, H. K.; Kemp, A.; Hansen, S. B.; Wilks, S. C.; Ping, Y.; Widmann, K.; Fournier, K. B.; Beiersdorfer, P.; Dyer, G.; Faenov, A.; Pikuz, T.

2007-01-01

We present measurements of the fast-electron-relaxation time in short-pulse (0.5 ps) laser-solid interactions for laser intensities of 10 17 , 10 18 , and 10 19 W/cm 2 , using a picosecond time-resolved x-ray spectrometer and a time-integrated electron spectrometer. We find that the laser coupling to hot electrons increases as the laser intensity becomes relativistic, and that the thermalization of fast electrons occurs over time scales on the order of 10 ps at all laser intensities. The experimental data are analyzed using a combination of models that include Kα generation, collisional coupling, and plasma expansion

Ultrashort pulse laser technology laser sources and applications

CERN Document Server

Schrempel, Frank; Dausinger, Friedrich

2016-01-01

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

Semiconductor laser diodes and the design of a D.C. powered laser diode drive unit

OpenAIRE

Cappuccio, Joseph C., Jr.

1988-01-01

Approved for public release; distribution is unlimited This thesis addresses the design, development and operational analysis of a D.C. powered semiconductor laser diode drive unit. A laser diode requires an extremely stable power supply since a picosecond spike of current or power supply switching transient could result in permanent damage. The design offers stability and various features for operational protection of the laser diode. The ability to intensity modulate (analog) and pulse m...

Laser tattoo removal: A clinical update

Directory of Open Access Journals (Sweden)

Stephanie GY Ho

2015-01-01

Full Text Available Techniques for tattoo removal have evolved significantly over the years. The commonly used Quality-switched (QS ruby, alexandrite, and Nd:YAG lasers are the traditional workhorses for tattoo removal. Newer strategies using combination laser treatments, multi-pass treatments, and picosecond lasers offer promising results. The tattoo color and skin type of the patient are important considerations when choosing the appropriate laser. Standard protocols can be developed for the effective and safe treatment of tattoos.

Laser Tattoo Removal: A Clinical Update

Science.gov (United States)

Ho, Stephanie GY; Goh, Chee Leok

2015-01-01

Techniques for tattoo removal have evolved significantly over the years. The commonly used Quality-switched (QS) ruby, alexandrite, and Nd:YAG lasers are the traditional workhorses for tattoo removal. Newer strategies using combination laser treatments, multi-pass treatments, and picosecond lasers offer promising results. The tattoo color and skin type of the patient are important considerations when choosing the appropriate laser. Standard protocols can be developed for the effective and safe treatment of tattoos. PMID:25949017

Picosecond dynamics of reactions in the liquid phase: studies of iodine photodissociation and development of new laser techniques

International Nuclear Information System (INIS)

Berg, M.A.

1985-09-01

Iodine photodissociation and recombination was studied as a model for processes common to chemical reaction in the liquid phase. Picosecond transient absorption measurements from 1000 to 295 nm were used to monitor the dynamics in a variety of solvents. Most of the atoms which undergo geminate recombination were found to do so in less than or equal to 15 ps, in agreement with the results of existing molecular dynamics simulations. Vibrational relaxation times vary from approx.15 ps near the middle of the ground state well to approx.150 ps for complete relaxation to v = 0. The prediction of strong resonant vibrational energy transfer to chlorinated methane solvents was not supported, but some evidence for this mechanism was found for alkane solvents. Current theory is unable to explain the large variation (65 to 2700 ps) of the excited A'-state lifetime in various solvents. The 10-Hz amplified, synchronously-pumped dye laser which was used in these studies is described and characterized. SERS (Stimulated Electronic Raman Scattering) and difference frequency mixing were used in the generation of the infrared and far-infrared, respectively. 54 refs., 38 figs., 3 tabs

Shock compression and flash-heating of molecular adsorbates on the picosecond time scale

Science.gov (United States)

Berg, Christopher Michael

An ultrafast nonlinear coherent laser spectroscopy termed broadband multiplex vibrational sum-frequency generation (SFG) with nonresonant suppression was employed to monitor vibrational transitions of molecular adsorbates on metallic substrates during laser-driven shock compression and flash-heating. Adsorbates were in the form of well-ordered self-assembled monolayers (SAMs) and included molecular explosive simulants, such as nitroaromatics, and long chain-length alkanethiols. Based on reflectance measurements of the metallic substrates, femtosecond flash-heating pulses were capable of producing large-amplitude temperature jumps with DeltaT = 500 K. Laser-driven shock compression of SAMs produced pressures up to 2 GPa, where 1 GPa ≈ 1 x 104 atm. Shock pressures were estimated via comparison with frequency shifts observed in the monolayer vibrational transitions during hydrostatic pressure measurements in a SiC anvil cell. Molecular dynamics during flash-heating and shock loading were probed with vibrational SFG spectroscopy with picosecond temporal resolution and sub-nanometer spatial resolution. Flash-heating studies of 4-nitrobenzenethiolate (NBT) on Au provided insight into effects from hot-electron excitation of the molecular adsorbates at early pump-probe delay times. At longer delay times, effects from the excitation of SAM lattice modes and lower-energy NBT vibrations were shown. In addition, flash-heating studies of alkanethiolates demonstrated chain disordering behaviors as well as interface thermal conductances across the Au-SAM junction, which was of specific interest within the context of molecular electronics. Shock compression studies of molecular explosive simulants, such as 4-nitrobenzoate (NBA), demonstrated the proficiency of this technique to observe shock-induced molecular dynamics, in this case orientational dynamics, on the picosecond time scale. Results validated the utilization of these refined shock loading techniques to probe the shock

Photoemission in nanosecond and picosecond regimes obtained from macro and micro cathodes

International Nuclear Information System (INIS)

Boussoukaya, M.; Bergeret, H.; Chehab, R.; Leblond, B.; Franco, M.

1987-03-01

For Lasertron studies at LAL, results obtained from tests on different photocathodes are given below. Using respectively two Nd: YAG lasers (a nanosecond one and a picosecond one) we have determined the level and the intensity of pulsed photoemission and the photoelectric yield in UV, green and infrared lights. We obtained a total current of more than 1 A with nanosecond width from a single W needle, and photoconversion yield of more than 1 was reached in green and UV lights. In classical pulsed photoemission, obtained photoconversion yield from LaB 6 photocathode was of about 10 -3 in higher fields

High performance mode locking characteristics of single section quantum dash lasers.

Science.gov (United States)

Rosales, Ricardo; Murdoch, S G; Watts, R T; Merghem, K; Martinez, Anthony; Lelarge, Francois; Accard, Alain; Barry, L P; Ramdane, Abderrahim

2012-04-09

Mode locking features of single section quantum dash based lasers are investigated. Particular interest is given to the static spectral phase profile determining the shape of the mode locked pulses. The phase profile dependence on cavity length and injection current is experimentally evaluated, demonstrating the possibility of efficiently using the wide spectral bandwidth exhibited by these quantum dash structures for the generation of high peak power sub-picosecond pulses with low radio frequency linewidths.

Picosecond pulse radiolysis study of primary reactions in solutions

International Nuclear Information System (INIS)

El-Omar, Abdel Karim

2013-01-01

Following the discovery of ionizing radiations and their chemical effects, it was important to study and comprehend the formation mechanisms of short lived free radicals and molecular products. In order to perform such studies, researchers and research groups worked on developing tools allowing both formation and detection of those species at short time scales. Nowadays, pulse radiolysis imposed itself as a fundamental and efficient tool allowing scientists to probe chemical effects as well as reaction mechanisms in studied media. The Laboratoire de Chimie Physique d'Orsay 'LCP' is an interdisciplinary laboratory hosting the platform of fast kinetics known as 'ELYSE'. Due to its femtosecond laser and its picosecond electron accelerator, we have the possibility to study chemical effects of ionizing radiations interaction with media at ultrashort times up to ∼5 ps.Knowing that we are interested in primary reactions induced in aqueous media by ionizing radiations, ELYSE represents the essential tool in performing our studies. The obtained results concern:- First direct determination of hydroxyl radical 'HO*' radiolytic yield as function of time at picosecond time scale;- Direct effect of ionizing radiation in highly concentrated aqueous solutions as well as investigation of the ultrafast electron transfer reaction between solute molecules and positive holes 'H 2 O*+' formed upon water radiolysis;- Study at room temperature of electron transfer reaction between solvated electron (electron donor) and organic solutes (electron acceptors) en viscous medium;- Study at room temperature of electron's solvation dynamics in ethylene glycol and 2-propanol. (author)

Pulsed laser-induced SEU in integrated circuits

International Nuclear Information System (INIS)

Buchner, S.; Kang, K.; Stapor, W.J.; Campbell, A.B.; Knudson, A.R.; McDonald, P.; Rivet, S.

1990-01-01

The authors have used a pulsed picosecond laser to measure the threshold for single event upset (SEU) and single event latchup (SEL) for two different kinds of integrated circuits. The relative thresholds show good agreement with published ion upset data. The consistency of the results together with the advantages of using a laser system suggest that the pulsed laser can be used for SEU/SEL hardness assurance of integrated circuits

Alignment of symmetric top molecules by short laser pulses

DEFF Research Database (Denmark)

Hamilton, Edward; Seideman, Tamar; Ejdrup, Tine

2005-01-01

-resolved photofragment imaging. Using methyliodide and tert-butyliodide as examples, we calculate and measure the alignment dynamics, focusing on the temporal structure and intensity of the revival patterns, including their dependence on the pulse duration, and their behavior at long times, where centrifugal distortion......Nonadiabatic alignment of symmetric top molecules induced by a linearly polarized, moderately intense picosecond laser pulse is studied theoretically and experimentally. Our studies are based on the combination of a nonperturbative solution of the Schrodinger equation with femtosecond time...

Dynamical test of Davydov-type solitons in acetanilide using a picosecond free-electron laser

Science.gov (United States)

Fann, Wunshain; Rothberg, Lewis; Roberson, Mark; Benson, Steve; Madey, John; Etemad, Shahab; Austin, Robert

1990-01-01

Picosecond infrared excitation experiments on acetanilide, an α-helix protein analog, indicate that the anomalous 1650-cm-1 band which appears on cooling of acetanilide crystals persists for at least several microseconds following rapid pulsed heating. The ground-state recovery time is 15+/-5 psec, consistent with a conventional mode strongly coupled to the phonon bath. We therefore suggest that the unusual temperature-dependent spectroscopy of acetanilide can be accounted for by slightly nondegenerate hydrogen atom configurations in the crystal.

Synchronisation of a femtosecond laser and a Q-switched laser to within 50 ps

International Nuclear Information System (INIS)

Katin, E V; Lozhkarev, V V; Palashov, O V; Khazanov, E A

2003-01-01

A Nd:YLF laser emitting 2-ns pulses synchronised with a femtosecond Cr:forsterite laser is built. The pulse duration and synchronisation are ensured by two Pockels cells, in which voltage pulses are synchronised with the femtosecond laser by fast emitter-coupled logic elements. One of the Pockels cells ensures Q-switching, while the other cuts a short pulse from a 15-ns Q-switched pulse. The experimental results show that the two-step scheme proposed for synchronisation of a Q-switched laser and a passively mode-locked laser provides quite simple and reliable synchronisation of these lasers with a jitter of a few tens of picoseconds. (control of laser radiation parameters)

The solid state detector technology for picosecond laser ranging

Science.gov (United States)

Prochazka, Ivan

1993-01-01

We developed an all solid state laser ranging detector technology, which makes the goal of millimeter accuracy achievable. Our design and construction philosophy is to combine the techniques of single photon ranging, ultrashort laser pulses, and fast fixed threshold discrimination while avoiding any analog signal processing within the laser ranging chain. The all solid state laser ranging detector package consists of the START detector and the STOP solid state photon counting module. Both the detectors are working in an optically triggered avalanche switching regime. The optical signal is triggering an avalanche current buildup which results in the generation of a uniform, fast risetime output pulse.

Demonstration of a transient high gain nickel-like xenon ion x-ray laser

International Nuclear Information System (INIS)

Lu, Peixiang; Kawachi, Tetsuya; Kishimoto, Maki

2003-01-01

We demonstrate a high gain nickel-like xenon ion x-ray laser using a picosecond-laser-irradiated gas puff target. The elongated x-ray laser plasma column was produced by irradiating the gas puff target with line-focused double picosecond laser pulses with a total energy of 18 J in a travelling-wave excitation scheme. Strong lasing at 9.98 nm was observed, and a high gain coefficient of 17.4 cm -1 was measured on the transient collisionally excited 4d-4p, J=0-1 transition for nickel-like xenon ion with target lengths up to 0.45 cm. A weak nickel-like lasing line at a shorter wavelength of 9.64 nm was also observed with a gain coefficient of 5.9 cm -1 . (author)

Picosecond radiolysis of ionic liquids

International Nuclear Information System (INIS)

Funston, A.M.; Wishart, J.F.; Neta, P.; Lall, S.I.; Engel, R.

2003-01-01

Ionic liquids (ILs) are a rapidly expanding family of condensed-phase media with important applications in nuclear fuel and waste processing, energy production, improving the efficiency and safety of industrial chemical processes, and pollution prevention. Ionic liquids are completely nonvolatile, noncombustible, highly conductive, recyclable and capable of dissolving a wide variety of materials. An understanding of the radiation chemistry of ionic liquids is important for development of their applications in radioactive material processing and for the application of pulse radiolysis techniques to the general study of chemical reactivity in ionic liquids. Kinetic studies with a picosecond electron accelerator, such as the BNL Laser-Electron Accelerator Facility (LEAF), allow one to observe primary radiation products and their reactions on short time scales. For example, the solvated electron lifetime in neat methyltributylammonium bis(trifluoromethylsulfonyl)imide is ∼300 ns and its absorption maximum is ∼1400 nm. Kinetic studies of primary radiolytic products and their reactivities will be described for several types of ionic liquids. Supported in part by the U.S. Department of Energy, Division of Chemical Sciences, Office of Basic Energy Sciences, under contract DE-AC02-98-CH1088

PLEIADES: A picosecond Compton scattering x-ray source for advanced backlighting and time-resolved material studies

International Nuclear Information System (INIS)

Gibson, David J.; Anderson, Scott G.; Barty, Christopher P.J.; Betts, Shawn M.; Booth, Rex; Brown, Winthrop J.; Crane, John K.; Cross, Robert R.; Fittinghoff, David N.; Hartemann, Fred V.; Kuba, Jaroslav; Le Sage, Gregory P.; Slaughter, Dennis R.; Tremaine, Aaron M.; Wootton, Alan J.; Hartouni, Edward P.; Springer, Paul T.; Rosenzweig, James B.

2004-01-01

The PLEIADES (Picosecond Laser-Electron Inter-Action for the Dynamical Evaluation of Structures) facility has produced first light at 70 keV. This milestone offers a new opportunity to develop laser-driven, compact, tunable x-ray sources for critical applications such as diagnostics for the National Ignition Facility and time-resolved material studies. The electron beam was focused to 50 μm rms, at 57 MeV, with 260 pC of charge, a relative energy spread of 0.2%, and a normalized emittance of 5 mm mrad horizontally and 13 mm mrad vertically. The scattered 820 nm laser pulse had an energy of 180 mJ and a duration of 54 fs. Initial x rays were captured with a cooled charge-coupled device using a cesium iodide scintillator; the peak photon energy was approximately 78 keV, with a total x-ray flux of 1.3x10 6 photons/shot, and the observed angular distribution found to agree very well with three-dimensional codes. Simple K-edge radiography of a tantalum foil showed good agreement with the theoretical divergence-angle dependence of the x-ray energy. Optimization of the x-ray dose is currently under way, with the goal of reaching 10 8 photons/shot and a peak brightness approaching 10 20 photons/mm 2 /mrad 2 /s/0.1% bandwidth

Microdrilling of metals with an inexpensive and compact ultra-short-pulse fiber amplified microchip laser

Energy Technology Data Exchange (ETDEWEB)

Ancona, A. [Friedrich-Schiller-Universitaet Jena, Institut fuer Angewandte Physik, Jena (Germany); CNR-INFM Regional Laboratory ' LIT3' , Dipartimento Interuniversitario di Fisica, Bari (Italy); Nodop, D.; Limpert, J.; Nolte, S. [Friedrich-Schiller-Universitaet Jena, Institut fuer Angewandte Physik, Jena (Germany); Tuennermann, A. [Friedrich-Schiller-Universitaet Jena, Institut fuer Angewandte Physik, Jena (Germany); Fraunhofer Institute for Applied Optics and Precision Engineering (IOF), Jena (Germany)

2009-01-15

We have investigated the ultra-fast microdrilling of metals using a compact and cheap fiber amplified passively Q-switched microchip laser. This laser system delivers 100-ps pulses with repetition rates higher than 100 kHz and pulse energies up to 80 {mu}J. The ablation process has been studied on metals with quite different thermal properties (copper, carbon steel and stainless steel). The dependence of the ablation depth per pulse on the pulse energy follows the same logarithmic scaling laws governing laser ablation with sub-picosecond pulses. Structures ablated with 100-ps laser pulses are accompanied only by a thin layer of melted material. Despite this, results with a high level of precision are obtained when using the laser trepanning technique. This simple and affordable laser system could be a valid alternative to nanosecond laser sources for micromachining applications. (orig.)

Nanosecond retinal structure changes in K-590 during the room-temperature bacteriorhodopsin photocycle: picosecond time-resolved coherent anti-stokes Raman spectroscopy

OpenAIRE

Weidlich, O.; Ujj, L.; Jäger, F.; Atkinson, G.H.

1997-01-01

Time-resolved vibrational spectra are used to elucidate the structural changes in the retinal chromophore within the K-590 intermediate that precedes the formation of the L-550 intermediate in the room-temperature (RT) bacteriorhodopsin (BR) photocycle. Measured by picosecond time-resolved coherent anti-Stokes Raman scattering (PTR/CARS), these vibrational data are recorded within the 750 cm-1 to 1720 cm-1 spectral region and with time delays of 50-260 ns after the RT/BR photocycle is optical...

Monoenergetic laser wakefield acceleration

Directory of Open Access Journals (Sweden)

N. E. Andreev

2000-02-01

Full Text Available Three dimensional test particle simulations are applied to optimization of the plasma-channeled laser wakefield accelerator (LWFA operating in a weakly nonlinear regime. Electron beam energy spread, emittance, and luminosity depend upon the proportion of the electron bunch size to the plasma wavelength. This proportion tends to improve with the laser wavelength increase. We simulate a prospective two-stage ∼1GeV LWFA with controlled energy spread and emittance. The input parameters correspond to realistic capabilities of the BNL Accelerator Test Facility that features a picosecond-terawatt CO_{2} laser and a high-brightness electron gun.

Narrow linewidth picosecond UV pulsed laser with mega-watt peak power.

Science.gov (United States)

Huang, Chunning; Deibele, Craig; Liu, Yun

2013-04-08

We demonstrate a master oscillator power amplifier (MOPA) burst mode laser system that generates 66 ps/402.5 MHz pulses with mega-watt peak power at 355 nm. The seed laser consists of a single frequency fiber laser (linewidth laser is operating in a 5-μs/10-Hz macropulse mode. The laser output has a transform-limited spectrum with a very narrow linewidth of individual longitudinal modes. The immediate application of the laser system is the laser-assisted hydrogen ion beam stripping for the Spallation Neutron Source (SNS).

Laser-induced bandgap collapse in GaAs

Science.gov (United States)

Siegal, Y.; Glezer, Eli N.; Huang, Li; Mazur, Eric

1994-05-01

We present recent time-resolved measurements of the linear dielectric constant of GaAs at 2.2 eV and 4.4 eV following femtosecond laser pulse excitation. In sharp contrast to predictions based on the widely used Drude model, the data show an interband absorption peak coming into resonance first with the 4.4 eV probe photon energy and then with the 2.2 eV probe photon energy, indicating major changes in the band structure. The time scale for these changes ranges from within 100 fs to a few picoseconds, depending on the incident pump pulse fluence.

Contribution of power lasers to fundamental physics

International Nuclear Information System (INIS)

Mainfray, G.

1997-01-01

The use of power lasers for studying the response of atoms that are perturbed by an intense laser electromagnetic field was considered at the CEA as soon as 1966, leading to a new research domain, atom multi-photonic ionization, and the analysis of the photon-matter interaction. The development of a new generation of compact laser delivering several terawatt in a few tenth of picoseconds resulting in illuminations superior to 10 18 W/cm 2 , enabled the shift to researches concerning photon-plasma interactions and the relativistic regime of the laser-plasma interaction

Incubation and nanostructure formation on n- and p-type Si(1 0 0) and Si(1 1 1) at various doping levels induced by sub-nanojoule femto- and picosecond near-infrared laser pulses

International Nuclear Information System (INIS)

Schüle, M.; Afshar, M.; Feili, D.; Seidel, H.; König, K.; Straub, M.

2014-01-01

Highlights: • Nanorifts, ripples of period 130 nm and randomly nanoporous surface structures were generated. • Such nanostructures emerged on heavily and lightly n- and p-doped Si(1 0 0) and Si(1 1 1) surfaces. • Strong incubation occurred irrespective of dopant type and concentration or surface orientation. • Incubation is attributed to photoexcitation from laser-induced defect states in the bandgap. • Aggregation of defects results in nanocracks, which turn into nanorift and nanoripple patterns. • Ablation involved predominantly single-photon processes but also multiphoton absorption. - Abstract: N- and p-doped Si(1 0 0) and Si(1 1 1) surfaces with dopant concentrations of 2 × 10 14 –1 × 10 19 cm −3 were irradiated by tightly focused 85-MHz repetition rate Ti:sapphire laser light (central wavelength 800 nm, bandwidth 120 nm) at pulse durations of 12 fs to 1.6 ps. Dependent on pulse peak intensity and exposure time nanorifts, ripples of period 130 nm as well as sponge-like randomly nanoporous surface structures were generated with water immersion and, thereafter, laid bare by etching off aggregated oxide nanoparticles. The same structure types emerged in air or water with transform-limited 100-fs pulses. At a pulse length of 12 fs pronounced incubation occurred with incubation coefficients S = 0.66–0.85, whereas incubation was diminished for picosecond pulses (S > 0.95). The ablation threshold strongly rose with dopant concentration. At similar doping level it was higher for n-type than for p-type samples and for Si(1 0 0) compared to Si(1 1 1) surfaces. These observations are attributed to laser-induced defect states in the bandgap which participate in photoexcitation, deactivation of dopants by complex formation, and different densities of interface states at the boundary with the ultrathin native silicon dioxide surface layer. The threshold increase with pulse length revealed predominant single-photon excitation as well as multiphoton

Deep-red semiconductor monolithic mode-locked lasers

International Nuclear Information System (INIS)

Kong, L.; Bajek, D.; White, S. E.; Forrest, A. F.; Cataluna, M. A.; Wang, H. L.; Pan, J. Q.; Wang, X. L.; Cui, B. F.; Ding, Y.

2014-01-01

A deep-red semiconductor monolithic mode-locked laser is demonstrated. Multi-section laser diodes based on an AlGaAs multi-quantum-well structure were passively mode-locked, enabling the generation of picosecond optical pulses at 752 nm, at pulse repetition rates of 19.37 GHz. An investigation of the dependence of the pulse duration as a function of reverse bias revealed a predominantly exponential decay trend of the pulse duration, varying from 10.5 ps down to 3.5 ps, which can be associated with the concomitant reduction of absorption recovery time with increasing applied field. A 30-MHz-tunability of the pulse repetition rate with bias conditions is also reported. The demonstration of such a compact, efficient and versatile ultrafast laser in this spectral region paves the way for its deployment in a wide range of applications such as biomedical microscopy, pulsed terahertz generation as well as microwave and millimeter-wave generation, with further impact on sensing, imaging and optical communications

A novel dual‐wavelength, Nd:YAG, picosecond‐domain laser safely and effectively removes multicolor tattoos

Science.gov (United States)

Schomacker, Kevin T.; Basilavecchio, Lisa D.; Plugis, Jessica M.; Bhawalkar, Jayant D.

2015-01-01

Background and Objectives Although nanosecond‐domain lasers have been the mainstay of laser tattoo removal for decades, recent disruptive innovations in laser design have introduced a new class of commercial Q‐switched lasers that generate picosecond‐domain pulses. Study A picosecond‐domain, Nd:YAG laser with a KTP frequency‐doubling crystal was used to treat 31 decorative tattoos in 21 subjects. Safety and effectiveness were determined by blinded evaluation of digital images in this prospective clinical study. Results The average clearance overall as evaluated by blinded observers evaluating randomized digital photographs was 79 ± 0.9% (mean ± sem) after an average of 6.5 treatments. Of the 31 tattoos completing treatment, 6 had evidence of mild hyper‐ or hypo‐pigmentation by evaluation of photographs. Conclusion The 350 picosecond, 532 nm, and 450 picosecond 1,064 nm Nd:YAG laser is safe and effective for removing decorative tattoos. Lasers Surg. Med. 47:542–548, 2015. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc. PMID:26175187

Spectral and Temporal Properties of the Alpha and Beta Subunits and (alpha Beta) Monomer Isolated from Nostoc SP. Using Picosecond Laser Spectroscopy.

Science.gov (United States)

Dagen, Aaron J.

1985-12-01

The fluorescence decay profiles, relative quantum yield and transmission of the (alpha), (beta) and ((alpha)(beta)) complexes from phycoerythrin isolated from the photosynthetic antenna system of Nostoc sp. and measured by single picosecond laser spectroscopic techniques is studied. The fluorescence decay profiles of all three complexes are found to be intensity independent for the intensity range investigated ((TURN)4 x 10('13) to (TURN)4 x 10('15) photons-cm('-2) per pulse). The apparent decrease in the relative quantum yield of all three complexes as intensity increases is offset by a corresponding increase in the relative transmission. This evidence, along with the intensity independent fluorescence kinetics, suggests that exciton annihilation is absent in these complexes. The decay profiles are fit to models assuming energy transfer amongst fluorescing chromophores. The intraprotein transfer rate is found to be 100 ps in the (alpha) subunit, 666 ps in the (beta) subunit. Constraining these rates to be identical in the monomer results in explaining the monomer kinetics by an increase in the nonradiative rate of the f(,(beta)) chromophore, an apparent result of aggregation effects.

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

International Nuclear Information System (INIS)

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

1989-04-01

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

Development of fiber lasers and devices for coherent Raman scattering microscopy

Science.gov (United States)

Lamb, Erin Stranford

As ultrafast laser technology has found expanding application in machining, spectroscopy, microscopy, surgery, and numerous other areas, the desire for inexpensive and robust laser sources has grown. Until recently, nonlinear effects in fiber systems due to the tight confinement of the light in the core have limited their performance. However, with advances in managing nonlinearity through pulse propagation physics and the use of large core fibers, the performance of fiber lasers can compete with that of their solid-state counterparts. As specific applications, such as coherent Raman scattering microscopy, emerge that stand to benefit from fiber technology, new performance challenges in areas such as laser noise are anticipated. This thesis studies nonlinear pulse propagation in fiber lasers and fiber parametric devices. Applications of dissipative solitons and self-similar pulse propagation to low-repetition rate oscillators that have the potential to simplify short-pulse amplification schemes will be examined. The rest of this thesis focuses on topics relevant to fiber laser development for coherent Raman scattering microscopy sources. Coherent pulse division and recombination inside the laser cavity will be introduced as an energy-scaling mechanism and demonstrated for a fiber soliton laser. The relative intensity noise properties of mode-locked fiber lasers, with a particular emphasis on normal dispersion lasers, will be explored in simulation and experiment. A fiber optical parametric oscillator will be studied in detail for low noise frequency conversion of picosecond pulses, and its utility for coherent Raman imaging will be demonstrated. Spectral compression of femtosecond pulses is used to generate picosecond pulses to pump this device, and this technique provides a route to future noise reduction in the system. Furthermore, this device forms a multimodal source capable of providing the picosecond pulses for coherent Raman scattering microscopy and the

Annealing of SnO2 thin films by ultra-short laser pulses

NARCIS (Netherlands)

Scorticati, D.; Illiberi, A.; Bor, T.; Eijt, S.W.H.; Schut, H.; Römer, G.R.B.E.; Lange, D.F. de; Huis In't Veld, A.J.

2014-01-01

Post-deposition annealing by ultra-short laser pulses can modify the optical properties of SnO2 thin films by means of thermal processing. Industrial grade SnO2 films exhibited improved optical properties after picosecond laser irradiation, at the expense of a slightly increased sheet resistance

Review on Recent Developments in Laser Driven Inertial Fusion

Directory of Open Access Journals (Sweden)

M. Ghoranneviss

2014-01-01

Full Text Available Discovery of the laser in 1960 hopes were based on using its very high energy concentration within very short pulses of time and very small volumes for energy generation from nuclear fusion as “Inertial Fusion Energy” (IFE, parallel to the efforts to produce energy from “Magnetic Confinement Fusion” (MCF, by burning deuterium-tritium (DT in high temperature plasmas to helium. Over the years the fusion gain was increased by a number of magnitudes and has reached nearly break-even after numerous difficulties in physics and technology had been solved. After briefly summarizing laser driven IFE, we report how the recently developed lasers with pulses of petawatt power and picosecond duration may open new alternatives for IFE with the goal to possibly ignite solid or low compressed DT fuel thereby creating a simplified reactor scheme. Ultrahigh acceleration of plasma blocks after irradiation of picosecond (PS laser pulses of around terawatt (TW power in the range of 1020 cm/s2 was discovered by Sauerbrey (1996 as measured by Doppler effect where the laser intensity was up to about 1018 W/cm2. This is several orders of magnitude higher than acceleration by irradiation based on thermal interaction of lasers has produced.

A re-evaluation of the initial yield of the hydrated electron in the picosecond time range

International Nuclear Information System (INIS)

Muroya, Yusa; Lin Mingzhang; Wu, Guozhong; Iijima, Hokuto; Yoshii, Koji; Ueda, Toru; Kudo, Hisaaki; Katsumura, Yosuke

2005-01-01

The yield of the hydrated electron in the picosecond time range has been re-evaluated with an ultrafast pulse radiolysis system using a laser photocathode RF-gun in combination with a conventional one, and a value of 4.1±0.2 per 100 eV of absorbed energy at 20 ps was derived. This is consistent with recent experimental results using a time correlation method [Bartels et al., J. Phys. Chem. A 104, 1686-1691 (2000)] and with Monte-Carlo calculations [Muroya et al., Can. J. Chem. 80 1367-1374 (2002)

Ultrafast laser pump X-ray probe experiments by means of asynchronous sampling

International Nuclear Information System (INIS)

Issenmann, D; Ibrahimkutty, S; Baumbach, T; Müller, A-S; Plech, A; Steininger, R; Göttlicher, J; Hiller, N

2013-01-01

A high time resolution in the picosecond range is required for the time-domain investigation of phonon dynamics in crystalline systems. Following a recently developed scheme in the visible spectrum, this resolution can be achieved by a method called asynchronous optical x-ray sampling (ASOXS). A pulsed femtosecond laser with high repetition rate is synchronized to the electron bunches in a storage ring. A slight frequency detuning changes the mutual delay continuously, resulting in a time-domain x-ray sampling of the laser-excited system. At the synchrotron radiation source ANKA a machine mode with low momentum compaction factor α c is available, which delivers ultra-short x-ray pulses in the picosecond range.

Fabrication of CVD graphene-based devices via laser ablation for wafer-scale characterization

DEFF Research Database (Denmark)

Mackenzie, David; Buron, Jonas Christian Due; Whelan, Patrick Rebsdorf

2015-01-01

Selective laser ablation of a wafer-scale graphene film is shown to provide flexible, high speed (1 wafer/hour) device fabrication while avoiding the degradation of electrical properties associated with traditional lithographic methods. Picosecond laser pulses with single pulse peak fluences of 140......-effect mobility, doping level, on–off ratio, and conductance minimum before and after laser ablation fabrication....

Picosecond resolution programmable delay line

International Nuclear Information System (INIS)

Suchenek, Mariusz

2009-01-01

The note presents implementation of a programmable delay line for digital signals. The tested circuit has a subnanosecond delay range programmable with a resolution of picoseconds. Implementation of the circuit was based on low-cost components, easily available on the market. (technical design note)

Broadly tunable picosecond ir source

International Nuclear Information System (INIS)

Campillo, A.J.; Hyer, R.C.; Shapiro, S.L.

1979-01-01

A completely grating tuned (1.9 to 2.4 μm) picosecond traveling wave IR generator capable of controlled spectral bandwidth operation down to the Fourier Transform limit is reported. Subsequent down conversion in CdSe extends tuning to 10 to 20 μm

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

Pico- and femtosecond laser-induced crosslinking of protein microstructures: evaluation of processability and bioactivity

Energy Technology Data Exchange (ETDEWEB)

Turunen, S; Kaepylae, E; Kellomaeki, M [Tampere University of Technology, Department of Biomedical Engineering, PO Box 692, 33101 Tampere (Finland); Terzaki, K; Fotakis, C; Farsari, M [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology Hellas (FORTH), N. Plastira 100, 70013, Heraklion, Crete (Greece); Viitanen, J, E-mail: elli.kapyla@tut.fi [VTT Technical Research Centre of Finland, PO Box 1300, 33101 Tampere (Finland)

2011-12-15

This study reports the pico- and femtosecond laser-induced photocrosslinking of protein microstructures. The capabilities of a picosecond Nd:YAG laser to promote multiphoton excited crosslinking of proteins were evaluated by fabricating 2D and 3D microstructures of avidin, bovine serum albumin (BSA) and biotinylated bovine serum albumin (bBSA). The multiphoton absorption-induced photocrosslinking of proteins was demonstrated here for the first time with a non-toxic biomolecule flavin mononucleotide (FMN) as the photosensitizer. Sub-micrometer and micrometer scale structures were fabricated from several different compositions of protein and photosensitizer by varying the average laser power and scanning speed in order to determine the optimal process parameters for efficient photocrosslinking. In addition, the retention of ligand-binding ability of the crosslinked protein structures was shown by fluorescence imaging of immobilized biotin or streptavidin conjugated fluorescence labels. The surface topography and the resolution of the protein patterns fabricated with the Nd:YAG laser were compared to the results obtained with a femtosecond Ti:Sapphire laser. Quite similar grain characteristics and comparable feature sizes were achieved with both laser sources, which demonstrates the utility of the low-cost Nd:YAG microlaser for direct laser writing of protein microstructures.

Pico- and femtosecond laser-induced crosslinking of protein microstructures: evaluation of processability and bioactivity

International Nuclear Information System (INIS)

Turunen, S; Kaepylae, E; Kellomaeki, M; Terzaki, K; Fotakis, C; Farsari, M; Viitanen, J

2011-01-01

This study reports the pico- and femtosecond laser-induced photocrosslinking of protein microstructures. The capabilities of a picosecond Nd:YAG laser to promote multiphoton excited crosslinking of proteins were evaluated by fabricating 2D and 3D microstructures of avidin, bovine serum albumin (BSA) and biotinylated bovine serum albumin (bBSA). The multiphoton absorption-induced photocrosslinking of proteins was demonstrated here for the first time with a non-toxic biomolecule flavin mononucleotide (FMN) as the photosensitizer. Sub-micrometer and micrometer scale structures were fabricated from several different compositions of protein and photosensitizer by varying the average laser power and scanning speed in order to determine the optimal process parameters for efficient photocrosslinking. In addition, the retention of ligand-binding ability of the crosslinked protein structures was shown by fluorescence imaging of immobilized biotin or streptavidin conjugated fluorescence labels. The surface topography and the resolution of the protein patterns fabricated with the Nd:YAG laser were compared to the results obtained with a femtosecond Ti:Sapphire laser. Quite similar grain characteristics and comparable feature sizes were achieved with both laser sources, which demonstrates the utility of the low-cost Nd:YAG microlaser for direct laser writing of protein microstructures.

Short-pulse generation in a diode-end-pumped solid-state laser

CSIR Research Space (South Africa)

Ngcobo, S

2010-09-01

Full Text Available , Development of High Average Power Picosecond Laser Systems, Opto- Electronic Devices, (2002). INTRODUCTION A Nd:YVO4 modelocked laser has been constructed using a resonator designed according to the theoretical parameters. The laser produced pulses... theoretical PQSML,th of 2.08W. Short-Pulse Generation in a Diode-End-Pumped Solid-State Laser S. Ngcobo1,2, C. Bollig1 and H. Von Bergmann2 1CSIR National Laser Centre, PO Box 395, Pretoria, 0001, South Africa 2Laser Research Center, University...

Laser-assisted vacuum arc extreme ultraviolet source: a comparison of picosecond and nanosecond laser triggering

Science.gov (United States)

Beyene, Girum A.; Tobin, Isaac; Juschkin, Larissa; Hayden, Patrick; O'Sullivan, Gerry; Sokell, Emma; Zakharov, Vassily S.; Zakharov, Sergey V.; O'Reilly, Fergal

2016-06-01

Extreme ultraviolet (EUV) light generation by hybrid laser-assisted vacuum arc discharge plasmas, utilizing Sn-coated rotating-disc-electrodes, was investigated. The discharge was initiated by localized ablation of the liquid tin coating of the cathode disc by a laser pulse. The laser pulse, at 1064 nm, was generated by Nd:YAG lasers with variable energy from 1 to 100 mJ per pulse. The impact of shortening the laser pulse from 7 ns to 170 ps on the EUV generation has been investigated in detail. The use of ps pulses resulted in an increase in emission of EUV radiation. With a fixed discharge energy of ~4 J, the EUV conversion efficiency tends to plateau at ~2.4  ±  0.25% for the ps laser pulses, while for the ns pulses, it saturates at ~1.7  ±  0.3%. Under similar discharge and laser energy conditions, operating the EUV source with the ps-triggering resulted also in narrower spectral profiles of the emission in comparison to ns-triggering. The results indicate an advantage in using ps-triggering in laser-assisted discharges to produce brighter plasmas required for applications such as metrology.

High-efficiency cavity-dumped micro-chip Yb:YAG laser

Science.gov (United States)

Nishio, M.; Maruko, A.; Inoue, M.; Takama, M.; Matsubara, S.; Okunishi, H.; Kato, K.; Kyomoto, K.; Yoshida, T.; Shimabayashi, K.; Morioka, M.; Inayoshi, S.; Yamagata, S.; Kawato, S.

2014-09-01

High-efficiency cavity-dumped ytterbium-doped yttrium aluminum garnet (Yb:YAG) laser was developed. Although the high quantum efficiency of ytterbium-doped laser materials is appropriate for high-efficiency laser oscillation, the efficiency is decreased by their quasi-three/four laser natures. High gain operation by high intensity pumping is suitable for high efficiency oscillation on the quasi-three/four lasers without extremely low temperature cooling. In our group, highest efficiency oscillations for continuous wave, nanosecond to picosecond pulse lasers were achieved at room temperature by the high gain operation in which pump intensities were beyond 100 kW/cm2.

Development of picosecond pulsed electron beam monitor. 2

International Nuclear Information System (INIS)

Hosono, Y.; Nakazawa, M.; Ueda, T.

1994-01-01

A picosecond pulsed electron beam monitor for a 35 MeV linear accelerator has been developed. The monitor consists of an electric SMA connector and aluminium pipe(inner diameter of 50mm). The following characteristics of this monitor were obtained, (a) the rise time is less than 17.5 ps (b) linearity of the monitor output voltage is proportional to the peak current of beam. It is shown that this monitor can be successfully used for bunch measurements of picosecond pulsed electron beam of 35 MeV linac. (author)

Laser System for Photoelectron and X-Ray Production in the PLEIADES Compton Light Source

CERN Document Server

Gibson, David J; Betts, S; Crane, John; Jovanovic, Igor

2005-01-01

The PLEIADES (Picosecond Laser-Electron Interaction for the Dynamic Evaluation of Structures) facility provides tunable short x-ray pulses with energies of 30-140 keV and pulse durations of 0.3 - 5 ps by scattering an intense, ultrashort laser pulse off a 35-75 MeV electron beam. Synchronization of the laser and electron beam is obtained by using a photoinjector gun, and using the same laser system to generate the electrons and the scattering laser. The Ti:Sapphire, chirped pulse amplification based 500 mJ, 50 fs, 810 nm scattering laser and the similar 300 μJ, 5 ps, 266 nm photoinjector laser systems are detailed. Additionally, an optical parametric chirped pulse amplification (OPCPA) system is studied as a replacement for part of the scattering laser front end. Such a change would significantly simplify the set-up the laser system by removing the need for active switching optics, as well as increase the pre-pulse contrast ratio which will be important when part of the scattering laser is used as a...

Novel Aspects of Materials Processing by Ultrafast Lasers: From Electronic to Biological and Cultural Heritage Applications

International Nuclear Information System (INIS)

Fotakis, C; Zorba, V; Stratakis, E; Athanassiou, A; Tzanetakis, P; Zergioti, I; Papagoglou, D G; Sambani, K; Filippidis, G; Farsari, M; Pouli, V; Bounos, G; Georgiou, S

2007-01-01

Materials processing by ultrafast lasers offers several distinct possibilities for micro/nano scale applications. This is due to the unique characteristics of the laser-matter interactions involved, when sub-picosecond pulses are employed. Prospects arising will be discussed in the context of surface and in bulk laser induced modifications. In particular, examples of diverse applications including the development and functionalization of laser engineered surfaces, the laser transfer of biomolecules and the functionalization of 3D structures constructed by three-photon stereolithography will be presented. Furthermore, the removal of molecular substrates by ultrafast laser ablation will be discussed with emphasis placed on assessing the photochemical changes induced in the remaining bulk material. The results indicate that in femtosecond laser processing of organic materials, besides the well acknowledged morphological advantages, a second fundamental factor responsible for its success pertains to the selective chemical effects. This is crucial for the laser cleaning of sensitive painted artworks

The chirped-pulse inverse free-electron laser: A high-gradient vacuum laser accelerator

International Nuclear Information System (INIS)

Hartemann, F.V.; Landahl, E.C.; Troha, A.L.; Van Meter, J.R.; Baldis, H.A.; Freeman, R.R.; Luhmann, N.C. Jr.; Song, L.; Kerman, A.K.; Yu, D.U.

1999-01-01

The inverse free-electron laser (IFEL) interaction is studied theoretically and computationally in the case where the drive laser intensity approaches the relativistic regime, and the pulse duration is only a few optical cycles long. The IFEL concept has been demonstrated as a viable vacuum laser acceleration process; it is shown here that by using an ultrashort, ultrahigh-intensity drive laser pulse, the IFEL interaction bandwidth and accelerating gradient are increased considerably, thus yielding large energy gains. Using a chirped pulse and negative dispersion focusing optics allows one to take further advantage of the laser optical bandwidth and produce a chromatic line focus maximizing the gradient. The combination of these novel ideas results in a compact vacuum laser accelerator capable of accelerating picosecond electron bunches with a high gradient (GeV/m) and very low energy spread. copyright 1999 American Institute of Physics

Observing Structure and Motion in Molecules with Ultrafast Strong Field and Short Wavelength Laser Radiation

Energy Technology Data Exchange (ETDEWEB)

Bucksbaum, Philip H

2011-04-13

The term "molecular movie" has come to describe efforts to track and record Angstrom-scale coherent atomic and electronic motion in a molecule. The relevant time scales for this range cover several orders of magnitude, from sub-femtosecond motion associated with electron-electron correlations, to 100-fs internal vibrations, to multi-picosecond motion associated with the dispersion and quantum revivals of molecular reorientation. Conventional methods of cinematography do not work well in this ultrafast and ultrasmall regime, but stroboscopic "pump and probe" techniques can reveal this motion with high fidelity. This talk will describe some of the methods and recent progress in exciting and controlling this motion, using both laboratory lasers and the SLAC Linac Coherent Light Source x-ray free electron laser, and will further try to relate the date to the goal of molecular movies.

The dynamics of the laser-induced metal-semiconductor phase transition of samarium sulfide (SmS)

International Nuclear Information System (INIS)

Kaempfer, Tino

2009-01-01

The present thesis is dedicated to the experimental study of the metal-semiconductor phase transition of samarium sulfide (SmS): Temperature- and time-resolved experiments on the characterization of the phase transition of mixed-valence SmS samples (M-SmS) are presented. The measurement of the dynamics of the laser-induced phase transition pursues via time-resolved ultrashort-time microscopy and by X-ray diffraction with sub-picosecond time resolution. The electronic and structural processes, which follow an excitation of M-SmS with infrared femtosecond laser pulses, are physically interpreted on the base of the results obtained in this thesis and model imaginations. [de

Using a cover layer to improve the damage resistance of gold-coated gratings induced by a picosecond pulsed laser

Science.gov (United States)

Xia, Zhilin; Wu, Yihan; Kong, Fanyu; Jin, Yunxia

2018-04-01

The chirped pulse amplification (CPA) technology is the main approach to achieve high-intensity short-pulse laser. Diffraction gratings are good candidates for stretching and compressing laser pulses in CPA. In this paper, a kind of gold-coated grating has been prepared and its laser damage experiment has been performed. The results reflect that the gratings laser damage was dominated by thermal ablation due to gold films or inclusions absorption and involved the deformation or eruption of the gold film. Based on these damage phenomena, a method of using a cover layer to prevent gold films from deforming and erupting has been adopted to improve the gold-coated gratings laser damage threshold. Since the addition of a cover layer changes the gratings diffraction efficiency, the gratings structure has been re-optimized. Furthermore, according to the calculated thermal stress distributions in gratings with optimized structures, the cover layer was demonstrated to be helpful for improving the gratings laser damage resistance if it is thick enough.

Laser milling of martensitic stainless steels using spiral trajectories

Science.gov (United States)

Romoli, L.; Tantussi, F.; Fuso, F.

2017-04-01

A laser beam with sub-picosecond pulse duration was driven in spiral trajectories to perform micro-milling of martensitic stainless steel. The geometry of the machined micro-grooves channels was investigated by a specifically conceived Scanning Probe Microscopy instrument and linked to laser parameters by using an experimental approach combining the beam energy distribution profile and the absorption phenomena in the material. Preliminary analysis shows that, despite the numerous parameters involved in the process, layer removal obtained by spiral trajectories, varying the radial overlap, allows for a controllable depth of cut combined to a flattening effect of surface roughness. Combining the developed machining strategy to a feed motion of the work stage, could represent a method to obtain three-dimensional structures with a resolution of few microns, with an areal roughness Sa below 100 nm.

Picosecond buildup and relaxation of intense stimulated emission in GaAs

International Nuclear Information System (INIS)

Ageeva, N. N.; Bronevoi, I. L.; Zabegaev, D. N.; Krivonosov, A. N.

2013-01-01

In support of the idea developed previously based on circumstantial evidence, we have found that stimulated emission emerges in GaAs and its intensity increases with a picosecond delay relative to the front of powerful picosecond optical pumping that produced a dense electron-hole plasma. The emission intensity relaxes with decreasing pumping with a characteristic time of ∼10 ps. We have derived the dependences of the delay time, the relaxation time, and the duration of the picosecond emission pulse on its photon energy. The estimates based on the fact that the relaxation of emission is determined by electron-hole plasma cooling correspond to the measured relaxation time.

Laser-mediated perforation of plant cells

Science.gov (United States)

Wehner, Martin; Jacobs, Philipp; Esser, Dominik; Schinkel, Helga; Schillberg, Stefan

2007-07-01

The functional analysis of plant cells at the cellular and subcellular levels requires novel technologies for the directed manipulation of individual cells. Lasers are increasingly exploited for the manipulation of plant cells, enabling the study of biological processes on a subcellular scale including transformation to generate genetically modified plants. In our setup either a picosecond laser operating at 1064 nm wavelength or a continuous wave laser diode emitting at 405 nm are coupled into an inverse microscope. The beams are focused to a spot size of about 1.5 μm and the tobacco cell protoplasts are irradiated. Optoporation is achieved when targeting the laser focal spot at the outermost edge of the plasma membrane. In case of the picosecond laser a single pulse with energy of about 0.4 μJ was sufficient to perforate the plasma membrane enabling the uptake of dye or DNA from the surrounding medium into the cytosol. When the ultraviolet laser diode at a power level of 17 mW is employed an irradiation time of 200 - 500 milliseconds is necessary to enable the uptake of macromolecules. In the presence of an EYFP encoding plasmid with a C-terminal peroxisomal signal sequence in the surrounding medium transient transformation of tobacco protoplasts could be achieved in up to 2% of the optoporated cells. Single cell perforation using this novel optoporation method shows that isolated plant cells can be permeabilized without direct manipulation. This is a valuable procedure for cell-specific applications, particularly where the import of specific molecules into plant cells is required for functional analysis.

The 1989 progress report: Laboratory for the Utilization of High-Intensity Laser

International Nuclear Information System (INIS)

Fabre, E.

1989-01-01

The 1989 progress report of the laboratory for the Utilization of High-Intensity Lasers of the Polytechnic School (France) is presented. The investigations reported were performed in the following fields: laser-matter interactions in fusion experiments, particles' laser acceleration, picoseconds and femtoseconds interactions, low-flux interactions, development of hydrodynamic codes, laser chocks simulation codes, x-ray lasers, generation of high pressures, implosion physics at 0.26 microns, dense plasmas, material's hardening by laser radiation. The published papers, the conferences and the Laboratory staff are listed [fr

Supercontinuum - broad as a lamp, bright as a laser, now in the mid-infrared

DEFF Research Database (Denmark)

Moselund, Peter M.; Petersen, Christian; Dupont, Sune

2012-01-01

Based on the experience gained developing our market leading visible spectrum supercontinuum sources NKT Photonics has built the first mid-infrared supercontinuum source based on modelocked picosecond fiber lasers. The source is pumped by a ≈ 2 um laser based on a combination of erbium and thuliu...

Advances in high power linearly polarized fiber laser and its application

Science.gov (United States)

Zhou, Pu; Huang, Long; Ma, Pengfei; Xu, Jiangming; Su, Rongtao; Wang, Xiaolin

2017-10-01

Fiber lasers are now attracting more and more research interest due to their advantages in efficiency, beam quality and flexible operation. Up to now, most of the high power fiber lasers have random distributed polarization state. Linearlypolarized (LP) fiber lasers, which could find wide application potential in coherent detection, coherent/spectral beam combining, nonlinear frequency conversion, have been a research focus in recent years. In this paper, we will present a general review on the achievements of various kinds of high power linear-polarized fiber laser and its application. The recent progress in our group, including power scaling by using power amplifier with different mechanism, high power linearly polarized fiber laser with diversified properties, and various applications of high power linear-polarized fiber laser, are summarized. We have achieved 100 Watt level random distributed feedback fiber laser, kilowatt level continuous-wave (CW) all-fiber polarization-maintained fiber amplifier, 600 watt level average power picosecond polarization-maintained fiber amplifier and 300 watt level average power femtosecond polarization-maintained fiber amplifier. In addition, high power linearly polarized fiber lasers have been successfully applied in 5 kilowatt level coherent beam combining, structured light field and ultrasonic generation.

Laser writing of nanostructures on bulk Al via its ablation in liquids

International Nuclear Information System (INIS)

Stratakis, E; Zorba, V; Barberoglou, M; Fotakis, C; Shafeev, G A

2009-01-01

Experimental results are presented on the formation of self-organized nanostructures (NSs) on a bulk Al target under its ablation in liquids-water and ethanol-with short laser pulses from 180 femtoseconds (fs) through 350 picoseconds (ps). NSs are characterized by atomic force microscopy, field emission scanning electron microscopy, optical absorption spectroscopy and x-ray diffraction. The period of NSs does not depend on the laser wavelength used from 248 through 800 nm and is approximately 200 nm. NSs on Al show the characteristic absorption peak in the near UV which has been attributed to plasmon oscillation of electrons. The wings of this peak, extending to the visible, lead to a distinct yellow coloration of the processed Al surface. Ultrafast laser structuring of bulk aluminum in liquids may be potentially a promising technique for efficient production of nanosized aluminum.

Material Engineering for Monolithic Semiconductor Mode-Locked Lasers

DEFF Research Database (Denmark)

Kulkova, Irina

This thesis is devoted to the materials engineering for semiconductor monolithic passively mode-locked lasers (MLLs) as a compact energy-efficient source of ultrashort optical pulses. Up to the present day, the achievement of low-noise sub-picosecond pulse generation has remained a challenge...

Time Evolution of the Excimer State of a Conjugated Polymer Laser

Directory of Open Access Journals (Sweden)

Wafa Musa Mujamammi

2017-11-01

Full Text Available An excited dimer is an important complex formed in nano- or pico-second time scales in many photophysics and photochemistry applications. The spectral and temporal profile of the excimer state of a laser from a new conjugated polymer, namely, poly (9,9-dioctylfluorenyl-2,7-diyl (PFO, under several concentrations in benzene were investigated. These solutions were optically pumped by intense pulsed third-harmonic Nd:YAG laser (355-nm to obtain the amplified spontaneous emission (ASE spectra of a monomer and an excimer with bandwidths of 6 and 7 nm, respectively. The monomer and excimer ASEs were dependent on the PFO concentration, pump power, and temperature. Employing a sophisticated picosecond spectrometer, the time evolution of the excimer state of this polymer, which is over 400 ps, can be monitored.

Robust optimization of the laser induced damage threshold of dielectric mirrors for high power lasers.

Science.gov (United States)

Chorel, Marine; Lanternier, Thomas; Lavastre, Éric; Bonod, Nicolas; Bousquet, Bruno; Néauport, Jérôme

2018-04-30

We report on a numerical optimization of the laser induced damage threshold of multi-dielectric high reflection mirrors in the sub-picosecond regime. We highlight the interplay between the electric field distribution, refractive index and intrinsic laser induced damage threshold of the materials on the overall laser induced damage threshold (LIDT) of the multilayer. We describe an optimization method of the multilayer that minimizes the field enhancement in high refractive index materials while preserving a near perfect reflectivity. This method yields a significant improvement of the damage resistance since a maximum increase of 40% can be achieved on the overall LIDT of the multilayer.

Stress assisted selective ablation of ITO thin film by picosecond laser

Science.gov (United States)

Farid, Nazar; Chan, Helios; Milne, David; Brunton, Adam; M. O'Connor, Gerard

2018-01-01

Fast selective pattering with high precession on 175 nm ITO thin film with IR ps lasers is investigated. Ablation parameters are optimized with detailed studies on the scribed depth, topography, and particle generation using AFM and SEM. A comparison of 10 and 150 ps laser revealed that the shorter pulse (10 ps) laser is more appropriate in selective and partial ablation; up to 20 nm resolution for controlled depth with multipulses having energy below the damage threshold is demonstrated. The experimental results are interpreted to involve stress assisted ablation mechanism for the 10 ps laser while thermal ablation along with intense melting occurs for 150 ps laser. The transition between these regimes is estimated to occur at approximately 30 ps.

[Glass Development Laser (GDL) Facility upgrade.] LLE Review. Quarterly report, October-December 1984. Volume 21

International Nuclear Information System (INIS)

Kim, H.

1984-01-01

This volume of the LLE Review contains articles on the upgrade of the GDL (Glass Development) system, theoretical advances in the laser fusion effort, improved target fabrication capabilities, x-ray laser research, developments in the picosecond optics research of the LLE advanced technology program, and on the National Laser Users Facility activities for October-December 1984. 56 refs., 31 figs., 3 tabs

High-Intensity Laser-to-Hot-Electron Conversion Efficiency from 1 to 2100 J Using the OMEGA EP Laser System

Science.gov (United States)

Nilson, P. M.

2010-11-01

Intense laser--matter interactions generate high-current electron beams. The laser-electron conversion efficiency is an important parameter for fast ignition and for developing intense x-ray sources for flash-radiography and x-ray-scattering experiments. These applications may require kilojoules of laser energy focused to greater than 10^18 W/cm^2 with pulse durations of tens of picoseconds. Previous experiments have measured the conversion efficiency with picosecond and subpicosecond laser pulses with energies up to ˜500 J. The research extends conversion-efficiency measurements to 1- to 10-ps laser pulses with energies up to 2100 J using the OMEGA EP Laser System and shows that the conversion efficiency is constant (20±10%) over the entire range The conversion efficiency is measured for interactions with finite-mass, thin-foil targets. A collimated electron jet exits the target rear surface and initiates rapid target charging, causing the majority of laser-accelerated electrons to recirculate (reflux) within the target. The total fast-electron energy is inferred from K-photon spectroscopy. Time-resolved x-ray emission data suggest that electrons are accelerated into the target over the entire laser-pulse duration with approximately constant conversion. This work provides significant insight into high-intensity laser--target interactions. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement Nos. DE-FC52-08NA28302 and DE-FC02-04ER54789. [4pt] In collaboration with R. Betti, A. A. Solodov (LLE/FSC), R. S. Craxton, J. A. Delettrez, C. Dorrer, L. Gao, P. A. Jaanimagi, J. H. Kelly, B. E. Kruschwitz, D. D. Meyerhofer, J. F. Myatt, T. C. Sangster, C. Stoeckl, W. Theobald, B. Yaakobi, J. D. Zuegel (LLE), A. J. MacKinnon, P. K. Patel (LLNL), K. U. Akli (General Atomics), L. Willingale, K. M. Krushelnick (U. of Michigan).

Depth-resolved sample composition analysis using laser-induced ablation-quadrupole mass spectrometry and laser-induced breakdown spectroscopy

Science.gov (United States)

Oelmann, J.; Gierse, N.; Li, C.; Brezinsek, S.; Zlobinski, M.; Turan, B.; Haas, S.; Linsmeier, Ch.

2018-06-01

Monitoring a sample's material composition became more and more important over the last years for both - industrial process control as well as for post mortem analysis in research and industrial development. Although material composition identification as well as a comparison with standard samples works fine, there is a lack of diagnostics which can provide quantitative information with depth resolution without any standard samples. We present a novel method utilizing a residual gas analysis with quadrupole mass spectrometry after picosecond laser-induced ablation and release of volatile species. In the present experiment, well characterized multilayer thin film solar cells (μc-Si:H and a-Si:D as p-i-n-junctions on ZnO:Al electrodes) are used as a set of well characterized material samples to demonstrate the capabilities of the new method. The linearity of the spectrometer signal to gas pressure simplifies its calibration and reduces its uncertainties in comparison with other analysis techniques, although high vacuum conditions (10-6 hPa to 10-7 hPa) are required to reach high sensitivity better than the percent-range. Moreover, the laser-ablation based sample analysis requires no preparation of the sample and is flexible regarding ablation rates. The application of a picosecond laser pulse ensures that the thermal penetration depth of the laser is in the same order of magnitude as the ablation rate, which enables to achieve depth resolutions in the order of 100 nm and avoids matrix mixing effects at the edge of the laser-induced crater in the sample.

Skin depth theory explaining anomalous picosecond-terawatt laser plasma interaction

Czech Academy of Sciences Publication Activity Database

Hora, H.; Osman, F.; Höpfl, R.; Badziak, J.; Parys, P.; Wolowski, J.; Woryna, E.; Boody, F.; Jungwirth, Karel; Králiková, Božena; Krása, Josef; Láska, Leoš; Pfeifer, Miroslav; Rohlena, Karel; Skála, Jiří; Ullschmied, Jiří

2002-01-01

Roč. 52, Suppl. D (2002), s. D349-D359 ISSN 0011-4626. [Plasma Physics and Technology. Prague, 10.06.2002-13.06.2002] R&D Projects: GA ČR GA202/00/1217 Institutional research plan: CEZ:AV0Z1010921 Keywords : laser plasma * ion acceleration Subject RIV: BH - Optics, Masers, Laser s Impact factor: 0.311, year: 2002

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

Science.gov (United States)

Wu, Mingtao; Guo, Bing; Zhao, Qingliang

2018-02-01

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

Proton- and x-ray beams generated by ultra-fast CO2 lasers for medical applications

Science.gov (United States)

Pogorelsky, Igor; Polyanskiy, Mikhail; Yakimenko, Vitaly; Ben-Zvi, Ilan; Shkolnikov, Peter; Najmudin, Zulfikar; Palmer, Charlotte A. J.; Dover, Nicholas P.; Oliva, Piernicola; Carpinelli, Massimo

2011-05-01

Recent progress in using picosecond CO2 lasers for Thomson scattering and ion-acceleration experiments underlines their potentials for enabling secondary radiation- and particle- sources. These experiments capitalize on certain advantages of long-wavelength CO2 lasers, such as higher number of photons per energy unit, and favorable scaling of the electrons' ponderomotive energy and critical plasma density. The high-flux x-ray bursts produced by Thomson scattering of the CO2 laser off a counter-propagating electron beam enabled high-contrast, time-resolved imaging of biological objects in the picosecond time frame. In different experiments, the laser, focused on a hydrogen jet, generated monoenergetic proton beams via the radiation-pressure mechanism. The strong power-scaling of this regime promises realization of proton beams suitable for laser-driven proton cancer therapy after upgrading the CO2 laser to sub-PW peak power. This planned improvement includes optimizing the 10-μm ultra-short pulse generation, assuring higher amplification in the CO2 gas under combined isotopic- and power-broadening effects, and shortening the postamplification pulse to a few laser cycles (150-200 fs) via chirping and compression. These developments will move us closer to practical applications of ultra-fast CO2 lasers in medicine and other areas.

Prototyping of Dental Structures Using Laser Milling

Science.gov (United States)

Andreev, A. O.; Kosenko, M. S.; Petrovskiy, V. N.; Mironov, V. D.

2016-02-01

The results of experimental studies of the effect of an ytterbium fiber laser radiation parameters on processing efficiency and quality of ZrO2 ceramics widely used in stomatology are presented. Laser operating conditions with optimum characteristics for obtaining high quality final surfaces and rapid material removal of dental structures are determined. The ability of forming thin-walled ceramic structures by laser milling technology (a minimum wall thickness of 50 μm) is demonstrated. The examples of three-dimensional dental structures created in computer 3D-models of human teeth using laser milling are shown.

Stable, high power, high efficiency picosecond ultraviolet generation at 355 nm in K3B6O10 Br crystal

Science.gov (United States)

Hou, Z. Y.; Wang, L. R.; Xia, M. J.; Yan, D. X.; Zhang, Q. L.; Zhang, L.; Liu, L. J.; Xu, D. G.; Zhang, D. X.; Wang, X. Y.; Li, R. K.; Chen, C. T.

2018-06-01

We demonstrate a high efficiency and high power picosecond ultraviolet source at 355 nm with stable output by sum frequency generation from a Nd:YAG laser using a type-I critically phase matched K3B6O10 Br crystal as nonlinear optical material. Conversion efficiency as high as 30.8% was achieved using a 25 ps laser at 1064 nm operated at 10 Hz. Similar work is done by using a 35 W 10 ps laser at 1064 nm as the pump source with a repetition rate of 80 MHz, and the highest average output power obtained was up to 5.3 W. In addition, the power stability of the 355 nm output power measurement shows that the standard deviation fluctuations of the average power are ±0.69% and ±0.91% at 3.0 W and 3.5 W, respectively.

Chirp of monolithic colliding pulse mode-locked diode lasers

DEFF Research Database (Denmark)

Hofmann, M.; Bischoff, S.; Franck, Thorkild

1997-01-01

Spectrally resolved streak camera measurements of picosecond pulses emitted by hybridly colliding pulse mode-locked (CPM) laser diodes are presented in this letter. Depending on the modulation frequency both blue-chirped (upchirped) and red-chirped (downchirped) pulses can be observed. The two...... different regimes and the transition between them are characterized experimentally and the behavior is explained on the basis of our model for the CPM laser dynamics. (C) 1997 American Institute of Physics....

PHELIX: A petawatt-class laser recently commissioned for experiments in plasma and atomic physics

International Nuclear Information System (INIS)

Bagnoud, V; Blazevic, A; Borneis, S; Eisenbarth, U; Fils, J; Goette, S; Kuehl, Th; Onkels, E; Stoehlker, T; Tauschwitz, A; Zimmer, D; Witte, K

2009-01-01

The PHELIX facility is available to users since 2008. Nanosecond pulses up to 500 J are utilized at present for experiments combining the heavy ions accelerated at the GSI LINAC facility, while sub-picosecond 200-TW pulses are used in laser stand-alone experiments. A review of the laser performance and future developments is shown.

PHELIX: A petawatt-class laser recently commissioned for experiments in plasma and atomic physics

Energy Technology Data Exchange (ETDEWEB)

Bagnoud, V; Blazevic, A; Borneis, S; Eisenbarth, U; Fils, J; Goette, S; Kuehl, Th; Onkels, E; Stoehlker, T; Tauschwitz, A; Zimmer, D; Witte, K, E-mail: v.bagnoud@gsi.d [GSI, Helmholtzzentrum fuer Schwerionenforschung mbH, Planckstr. 1, D-64291Darmstadt (Germany)

2009-11-01

The PHELIX facility is available to users since 2008. Nanosecond pulses up to 500 J are utilized at present for experiments combining the heavy ions accelerated at the GSI LINAC facility, while sub-picosecond 200-TW pulses are used in laser stand-alone experiments. A review of the laser performance and future developments is shown.

Laser parameters, focusing optics, and side effects in femtosecond laser corneal surgery

Science.gov (United States)

Plamann, Karsten; Nuzzo, Valeria; Peyrot, Donald A.; Deloison, Florent; Savoldelli, Michèle; Legeais, Jean-Marc

2008-02-01

Nowadays, femtosecond lasers are routinely used in refractive eye surgery. Until recently, commercialised clinical systems were exclusively based on ytterbium or neodymium-doped solid state lasers emitting sub-picosecond pulses at a wavelength of about 1 μm and repetition rates of a few 10 kHz. These systems use pulse energies in the μJ range and focussing optics of NA = 0.3 to 0.5. Recent developments have provided a variety of alternative and equally viable approaches: systems are now available using nJ pulses at high numerical apertures and MHz repetition rates - an approach so far only used for femtosecond cell surgery - and fibre laser technology is now being used for femtosecond laser corneal surgery. Recent research has also provided more insight in side effects occurring in present systems: self focusing phenomena and so far unexplained periodical structures have been observed even at high numerical apertures (NA >> 0.5) and moderate pulse energies. The interaction of femtosecond laser pulses with strongly scattering tissue has been studied in view of extending the application of femtosecond lasers to keratoplasty for opaque corneas and to glaucoma surgery. The use of new laser wavelengths and adaptive optics has been proposed. Despite the reputation of femtosecond surgical systems for their precision, repeatability and the absence of secondary effects or complications, a closer examination reveals the presence of subtle phenomena which merit further investigation. We present three of these phenomena: the influence of optical aberration on the quality of the incision, the occurrence of filamentation effects, and the deposit of microscopic glass fragments when performing penetrating incisions.

Multiphoton interactions in molecules with picosecond laser pulses. Progress report, July 15, 1985-July 14, 1986

International Nuclear Information System (INIS)

Kwok, H.S.

1986-01-01

The phenomena of superexcitation is discussed for C 2 F 5 Cl. This phenomena, which was first observed for SF 6 , is the excitation of very high levels of molecules by ultrashort pulses. For the same fluence, picosecond pulses were found to deposit more energy into the molecule than longer duration pulses. A second experimental result is discussed. The effect of collisions and pulse duration on the absorption spectrum of C 3 F 7 I. In this experiment it is observed that the linewidth decreases with pulse length. A red shift is observed with increased pressure. 2 refs., 2 figs

Production of ultrahigh ion current densities at skin-layer subrelativistic laser-plasma interaction

Czech Academy of Sciences Publication Activity Database

Badziak, J.; Glowacz, S.; Jablonski, S.; Parys, P.; Wolowski, J.; Hora, H.; Krása, Josef; Láska, Leoš; Rohlena, Karel

2005-01-01

Roč. 46, Suppl. 12B (2005), B541-B555 ISSN 0741-3335 Grant - others:International Atomic Energy Agency in Vienna(XE) 11535/RO; State Committee for Scientific Research (KBN)(PL) 1 PO3B 043 26 Institutional research plan: CEZ:AV0Z10100523 Keywords : high-intensity laser * multiply-charged ions * thin foil targets * picosecond laser * iodine laser * proton acceleration * energetic protons * Ag ions * generation * pulses Subject RIV: BH - Optics, Masers, Laser s Impact factor: 2.902, year: 2005

Dependence of Parameters of Laser-Produced Au Plasmas on the Incident Laser Energy of Sub-Nanosecond and Picosecond Laser Pulses

International Nuclear Information System (INIS)

Woryna, E.; Badziak, J.; Makowski, J.; Parys, P.; Vankov, A.B.; Wolowski, J.; Krasa, J.; Laska, L.; Rohlena, K.

2001-01-01

The parameters of Au plasma as functions of laser energy for ps pulses are presented and compared with the ones for sub-ns pulses at nearly the same densities of laser energy. The experiments were performed at the IPPLM with the use of CPA (chirped pulse amplification) Nd:glass laser system. Thick Au foil targets were irradiated by normally incident focused laser beams with maximum intensities of 8x10 16 and 2x10 14 W/cm 2 for ps and sub-ns laser pulses, respectively. The characteristics of ion streams were investigated with the use of ion diagnostics methods based on the time-of flight technique. In these experiments the laser energies were changed in the range from 90 to 700 mJ and the measurements were performed at a given focus position FP = 0 and along the target normal for both the laser pulses. The charge carried by the ions, the maximum ion velocities of fast and thermal ion groups, the maximum ion current density as well as the area of photopeak in dependence on the incident laser energy for sub-ns and ps pulses were investigated and discussed. (author)

Laser-induced band-gap collapse in GaAs

Science.gov (United States)

Glezer, E. N.; Siegal, Y.; Huang, L.; Mazur, E.

1995-03-01

We present experimentally determined values of the dielectric constant of GaAs at photon energies of 2.2 and 4.4 eV following excitation of the sample with 1.9-eV, 70-fs laser pulses spanning a fluence range from 0 to 2.5 kJ/m2. The data show that the response of the dielectric constant to the excitation is dominated by changes in the electronic band structure and not by the optical susceptibility of the excited free carriers. The behavior of the dielectric constant indicates a drop in the average bonding-antibonding splitting of GaAs following the laser-pulse excitation. This drop in the average splitting leads to a collapse of the band gap on a picosecond time scale for excitation at fluences near the damage threshold of 1.0 kJ/m2 and on a subpicosecond time scale at higher excitation fluences. The changes in the electronic band structure result from a combination of electronic screening of the ionic potential as well as structural deformation of the lattice caused by the destabilization of the covalent bonds.

Picosecond ballistic imaging of diesel injection in high-temperature and high-pressure air

Science.gov (United States)

Duran, Sean P.; Porter, Jason M.; Parker, Terence E.

2015-04-01

The first successful demonstration of picosecond ballistic imaging using a 15-ps-pulse-duration laser in diesel sprays at temperature and pressure is reported. This technique uses an optical Kerr effect shutter constructed from a CS2 liquid cell and a 15-ps pulse at 532 nm. The optical shutter can be adjusted to produce effective imaging pulses between 7 and 16 ps. This technique is used to image the near-orifice region (first 3 mm) of diesel sprays from a high-pressure single-hole fuel injector. Ballistic imaging of dodecane and methyl oleate sprays injected into ambient air and diesel injection at preignition engine-like conditions are reported. Dodecane was injected into air heated to 600 °C and pressurized to 20 atm. The resulting images of the near-orifice region at these conditions reveal dramatic shedding of the liquid near the nozzle, an effect that has been predicted, but to our knowledge never before imaged. These shedding structures have an approximate spatial frequency of 10 mm-1 with lengths from 50 to 200 μm. Several parameters are explored including injection pressure, liquid fuel temperature, air temperature and pressure, and fuel type. Resulting trends are summarized with accompanying images.

High peak power picosecond hybrid fiber and solid-state amplifier system

International Nuclear Information System (INIS)

Wushouer, X; Yan, P; Yu, H; Liu, Q; Fu, X; Yan, X; Gong, M

2010-01-01

We report the high peak power picosecond hybrid fiber and solid-state laser amplifier system. The passively mode-locked solid-state seed source produced an average power of 1.8 W with pulse width of 14 ps and repetition rate of 86 MHz. It was directly coupled into the first Yb-doped polarized photonic crystal fiber amplifier stage. To avoid the nonlinear effects in fiber, the output power from the first stage was merely amplified to 24 W with the narrow spectra broadening of 0.21 nm. For the improvement of the peak power, the dual-end pumped composite Nd:YVO 4 amplifier system has been chosen at the second stage. To reduce the serious thermal effect, the thermally bonded composite YVO 4 – Nd:YVO 4 – YVO 4 rod crystal was used as the gain medium. The 53 W TEM 00 mode with the peak power of 40 kW, beam quality of M 2 < 1.15, corresponding to the optical-optical efficiency of 42.4% was obtained at the hybrid amplifier laser system. The system allows using a low power seed source and demonstrates an increase in the peak power beyond a fiber master oscillator power amplifier's (MOPA's) limit

Picosecond anti-Stokes generation in a photonic-crystal fiber for interferometric CARS microscopy

DEFF Research Database (Denmark)

Keiding, Søren Rud

2006-01-01

We generate tunable picosecond anti-Stokes pulses by four-wave mixing of two picosecond pump and Stokes pulse trains in a photonic-crystal fiber. The visible, spectrally narrow anti-Stokes pulses with shifts over 150 nm are generated without generating other spectral features. As a demonstration,...

Picosecond electron bunches from GaAs/GaAsP strained superlattice photocathode

International Nuclear Information System (INIS)

Jin, Xiuguang; Matsuba, Shunya; Honda, Yosuke; Miyajima, Tsukasa; Yamamoto, Masahiro; Utiyama, Takashi; Takeda, Yoshikazu

2013-01-01

GaAs/GaAsP strained superlattices are excellent candidates for use as spin-polarized electron sources. In the present study, picosecond electron bunches were successfully generated from such a superlattice photocathode. However, electron transport in the superlattice was much slower than in bulk GaAs. Transmission electron microscopy observations revealed that a small amount of variations in the uniformity of the layers was present in the superlattice. These variations lead to fluctuations in the superlattice mini-band structure and can affect electron transport. Thus, it is expected that if the periodicity of the superlattice can be improved, much faster electron bunches can be produced. - Highlights: • GaAs/GaAsP strained superlattices are excellent candidates for spin-polarized electron beam. • Pulse spin-polarized electron beam is required for investigating the magnetic domain change. • Picosecond electron bunches were achieved from GaAs/GaAsP superlattice photocathode. • TEM observation revealed a small disorder of superlattice layers. • Improvement of superlattice periodicity can achieve much faster electron bunches

Laser Giant Ion Source and the Prepulse Effects for Picosecond Interaction for High Gain Laser Fusion

International Nuclear Information System (INIS)

Hora, Heinrich; Badziak, J.; Parys, P.; Wolowski, J.; Woryna, E.; Boody, F.P.; Hoepfl, R.; Jungwirth, K.; Ullschmied, J.; Kralikova, B.; Krasa, J.; Laska, L.; Pfeifer, M.; Rohlena, K.; Skala, J.; Perina, V.

2003-01-01

By studying laser driven ion sources which produce giant ion emission current densities exceeding the few mA/cm2 of classical ion sources (MEVVA or ECR) by more than six orders of magnitude, we unexpectedly measured an anomalous low ion energy with ps laser pulses.The emission is basically different from that with the fastest ion energies in the MeV to GeV range due to relativistic self focusing and from the second fastest ion group due to quiver-thermalization processes. We report on specifically designed experiments with gold targets where 0.5 ns laser pulses produce MeV Au-ions in accordance with relativistic self focusing in strong contrast to ps pulses where a 400 times higher intensity from TW pulses is needed to arrive at the same ion energies. These can be explained by a basically new model without self-focusing as a skin layer effect where the absence of a prepulse is essential. This has consequences for the application of laser driven ion sources and may improve the hitherto highest published laser fusion gains with 50 TW-ps laser pulses without the usual spherical precompression

Picosecond pulses from wavelength-swept continuous-wave Fourier domain mode-locked lasers.

Science.gov (United States)

Eigenwillig, Christoph M; Wieser, Wolfgang; Todor, Sebastian; Biedermann, Benjamin R; Klein, Thomas; Jirauschek, Christian; Huber, Robert

2013-01-01

Ultrafast lasers have a crucial function in many fields of science; however, up to now, high-energy pulses directly from compact, efficient and low-power semiconductor lasers are not available. Therefore, we introduce a new approach based on temporal compression of the continuous-wave, wavelength-swept output of Fourier domain mode-locked lasers, where a narrowband optical filter is tuned synchronously to the round-trip time of light in a kilometre-long laser cavity. So far, these rapidly swept lasers enabled orders-of-magnitude speed increase in optical coherence tomography. Here we report on the generation of ~60-70 ps pulses at 390 kHz repetition rate. As energy is stored optically in the long-fibre delay line and not as population inversion in the laser-gain medium, high-energy pulses can now be generated directly from a low-power, compact semiconductor-based oscillator. Our theory predicts subpicosecond pulses with this new technique in the future.

Laser-assisted shape selective fragmentation of nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Kazakevich, P.V. [Wave Research Center, General Physics Institute of the Russian Academy of Sciences, 38, Vavilov street, 117942 Moscow (Russian Federation); Simakin, A.V. [Wave Research Center, General Physics Institute of the Russian Academy of Sciences, 38, Vavilov street, 117942 Moscow (Russian Federation); Shafeev, G.A. [Wave Research Center, General Physics Institute of the Russian Academy of Sciences, 38, Vavilov street, 117942 Moscow (Russian Federation)]. E-mail: shafeev@kapella.gpi.ru; Viau, G. [ITODYS, UMR 7086, Universite Paris 7-Denis Diderot, case 7090, 2 place Jussieu, 75251 Paris Cedex 05 (France); Soumare, Y. [ITODYS, UMR 7086, Universite Paris 7-Denis Diderot, case 7090, 2 place Jussieu, 75251 Paris Cedex 05 (France); Bozon-Verduraz, F. [ITODYS, UMR 7086, Universite Paris 7-Denis Diderot, case 7090, 2 place Jussieu, 75251 Paris Cedex 05 (France)

2007-07-31

Experimental results are presented on laser-assisted fragmentation of gold-containing nanoparticles suspended in liquids (either ethanol or water). Two kinds of nanoparticles are considered: (i) elongated Au nanorods synthesized by laser ablation of a gold target immersed in liquid phase; (ii) gold-covered NiCo nanorods with high aspect ratio ({theta} {approx} 10) synthesized by wet chemistry processes. The shape selectivity induced by laser fragmentation of these nanorods is gained via tuning the wavelength of laser radiation into different parts of the spectrum of their plasmon resonance corresponding to different aspect ratios {theta}. Fragmentation is performed using three laser wavelengths, involving a Cu vapour laser (510 and 578 nm) and a Nd:YAG (1064 nm). Nanoparticles are characterized by UV-vis spectrometry, Transmission Electron Microscopy (TEM). The effect of laser pulse duration (nanosecond against picosecond range) is also studied in the case of fragmentation with an IR laser radiation.

Influence of organic solvent on optical and structural properties of ultra-small silicon dots synthesized by UV laser ablation in liquid.

Science.gov (United States)

Intartaglia, Romuald; Bagga, Komal; Genovese, Alessandro; Athanassiou, Athanassia; Cingolani, Roberto; Diaspro, Alberto; Brandi, Fernando

2012-11-28

Ultra small silicon nanoparticles (Si-NPs) with narrow size distribution are prepared in a one step process by UV picosecond laser ablation of silicon bulk in liquid. Characterization by electron microscopy and absorption spectroscopy proves Si-NPs generation with an average size of 2 nm resulting from an in situ photofragmentation effect. In this context, the current work aims to explore the liquid medium (water and toluene) effect on the Si-NPs structure and on the optical properties of the colloidal solution. Si-NPs with high pressure structure (s.g. Fm3m) and diamond-like structure (s.g. Fd3m), in water, and SiC moissanite 3C phase (s.g. F4[combining macron]3m) in toluene are revealed by the means of High-Resolution TEM and HAADF-STEM measurements. Optical investigations show that water-synthesized Si-NPs have blue-green photoluminescence emission characterized by signal modulation at a frequency of 673 cm(-1) related to electron-phonon coupling. The synthesis in toluene leads to generation of Si-NPs embedded in the graphitic carbon-polymer composite which has intrinsic optical properties at the origin of the optical absorption and luminescence of the obtained colloidal solution.

Computational and experimental progress on laser-activated gas avalanche switches for broadband, high-power electromagnetic pulse generation

International Nuclear Information System (INIS)

Mayhall, D.J.; Yee, J.H.; Villa, F.

1991-01-01

This paper discusses the gas avalanche switch, a high-voltage, picosecond-speed switch, which has been proposed. The basic switch consists of pulse-charged electrodes, immersed in a high-pressure gas. An avalanche discharge is induced in the gas between the electrodes by ionization from a picosecond-scale laser pulse. The avalanching electrons move toward the anode, causing the applied voltage to collapse in picoseconds. This voltage collapse, if rapid enough, generates electromagnetic waves. A two-dimensional (2D), finite difference computer code solves Maxwell's equations for transverse magnetic modes for rectilinear electrodes between parallel plate conductors, along with electron conservation equations for continuity, momentum, and energy. Collision frequencies for ionization and momentum and energy transfer to neutral molecules are assumed to scale linearly with neutral pressure. Electrode charging and laser-driven electron deposition are assumed to be instantaneous. Code calculations are done for a pulse generator geometry, consisting of an 0.7 mm wide by 0.8 mm high, beveled, rectangular center electrode between grounded parallel plates at 2 mm spacing in air

Stimulated Raman backscattering at high laser intensities

Energy Technology Data Exchange (ETDEWEB)

Skoric, M M [Vinca Inst. of Nuclear Sciences, Belgrade (Yugoslavia); Tajima, Toshiki; Sasaki, Akira; Maluckov, A; Jovanovic, M

1998-03-01

Signatures of Stimulated Raman backscattering of a short-pulse high-intensity laser interacting with an underdense plasma are discussed. We introduce a nonlinear three-wave interaction model that accounts for laser pump depletion and relativistic detuning. A mechanism is revealed based on a generic route to chaos, that predicts a progressive increase of the backscatter complexity with a growing laser intensity. Importance of kinetic effects is outlined and demonstrated in fluid-hybrid and particle simulations. As an application, we show that spectral anomalies of the backscatter, predicted by the above model, are consistent with recent sub-picosecond, high-intensity laser gas-target measurements at Livermore and elsewhere. Finally, a recently proposed scheme for generation of ultra-short, low-prepulse laser pulses by Raman backscattering in a thin foil target, is shown. (author)

Picosecond dissociation of amyloid fibrils with infrared laser: A nonequilibrium simulation study

Energy Technology Data Exchange (ETDEWEB)

Hoang Viet, Man; Roland, Christopher, E-mail: cmroland@ncsu.edu; Sagui, Celeste, E-mail: sagui@ncsu.edu [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202 (United States); Derreumaux, Philippe; Nguyen, Phuong H., E-mail: phuong.nguyen@ibpc.fr [Laboratoire de Biochimie Théorique, UPR 9080, CNRS Université Denis Diderot, Sorbonne Paris Cité IBPC, 13 rue Pierre et Marie Curie, 75005 Paris (France); Li, Mai Suan [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Institute for Computational Science and Technology, SBI Building, Quang Trung Software City, Tan Chanh Hiep Ward, District 12, Ho Chi Minh City (Viet Nam)

2015-10-21

Recently, mid-infrared free-electron laser technology has been developed to dissociate amyloid fibrils. Here, we present a theoretical framework for this type of experiment based on laser-induced nonequilibrium all-atom molecular dynamics simulations. We show that the fibril is destroyed due to the strong resonance between its amide I vibrational modes and the laser field. The effects of laser irradiation are determined by a balance between fibril formation and dissociation. While the overall rearrangements of the fibril finish over short time scales, the interaction between the peptides and the solvent continues over much longer times indicating that the waters play an important role in the dissociation process. Our results thus provide new insights into amyloid fibril dissociation by laser techniques and open up new venues to investigate the complex phenomena associated with amyloidogenesis.

Dissipative Structures At Laser-Solid Interactions

Science.gov (United States)

Nanai, Laszlo

1989-05-01

The questions which are discussed in this lecture refer to one of sections of laser-solid interactions, namely: to formation of different dissipative structures on the surface of metals and semiconductors when they are irradiated by intensive laser light in chemically active media (f.e.air). Some particular examples of the development at different spatial and time instabilities, periodic and stochastic structures, auto-wave processes are present-ed using testing materials vanadium metal and semiconducting V205 single crystals and light sources: cw and pulsed CO2 and YAG lasers.

Short-pulsed laser for the treatment of tattoos, pigmented lesions, scars and rejuvenation.

Science.gov (United States)

Tanghetti, Emil A; Hoffmann, Kristina Andrea; Hoffmann, Klaus

2017-12-01

This review describes the use of picosecond lasers for the treatment of tattoos, pigmented lesions, scars, and their use in rejuvenation. These devices have delivered enhanced efficacy for the treatment of tattoos and pigmented lesions when compared to the older 40-50 nanosecond devices. The fractional delivery with the picosecond devices have opened up a new method of rejuvenation for photodamaged skin and the treatment of scars. The delivery of these high-energy short pulses have created zones of injury in the skin referred to as areas of laser-induced optical breakdown. These areas of damage appear to produce cytokines and chemokines which result in epidermal and dermal repair and remodeling. The dual use of these devices with the flat and the fractional optics have made these devices useful in many ways that have been unanticipated. ©2017 Frontline Medical Communications.

High resolution X-ray spectromicroscopy of laser produced plasmas

Energy Technology Data Exchange (ETDEWEB)

Faenov, A.Ya. [Multi-charged Ions Spectra Data Center of VNIIFTRI (MISDC), Mendeleevo, Moscow region, (Russian Federation)

2000-01-01

In recent years new classes of X-ray spectroscopic instruments possessing both dispersive and focusing properties have been manufactured. Their principal advantage over more traditional instruments is that they combine very high luminosity with high spatial resolution, while preserving the highest possible spectral resolution of their dispersive elements. These instruments opened up the registration of plasmas in new regimes and surroundings. The measurements delivered new information about the properties of even previously studied traditional plasma objects (e.g. ns-laser produced plasmas). Also the detailed investigation of relatively new plasma laboratory sources with very small dimensions and low energy content (e.g. mJ fs-laser pulses) became possible. The purpose of this report is to give a short review of the experimental and theoretical results obtained in the past few years by MISDC (Multi-charged Ions Spectra Data Center) research team in the field of X-ray spectroscopy of a laser-produced plasma. Experimental spectra have been obtained at various laser installations with nanosecond, sub-nanosecond, picosecond and sub-picosecond pulses interacting with solid, gaseous or cluster targets in collaborations with research teams from Russia, USA, Germany, France, Poland, Belgium, Italy, China and Israel. Practically all results have been obtained with the help of spectrographs with spherically bent mica crystals operating in FSSR-1D, 2D schemes. (author)

Picosecond Soft-X-ray studies of Dense Plasma Regimes Progress Report (April 1, 2006 - March 31, 2007)

International Nuclear Information System (INIS)

Rocca, Jorge; Marconi, Mario; Shlyaptsev, Vyacheslav; Dunn, James; Moon, Stephen; Nilsen, Joseph

2007-01-01

The goal of this project is to investigate and characterize high-density converging plasma configurations using new soft x-ray laser based interferometric techniques. The results are used to verify and validate multi-dimensional hydrodynamic codes in plasma regimes which densities and size exceed those that can be probed with optical laser beams. The dynamics of converging plasmas created by laser irradiation of half-hohlraum cylindrical cavities targets was probed using a compact 46.9 nm soft x-ray laser. The results were used for comparison with extensive simulations conducted with the multi-dimensional hydrodynamic code HYDRA. As part of this study we have also investigated plasma regimes in which the index of refraction of the plasmas can not be defined solely based on the contribution of free electron, as is usually assumed for multiply ionized plasmas. Our results demonstrate the existence of plasma regimes in which the contribution of bound electrons from ions dominates the refractive index at soft x-ray wavelengths. We are also working in extending plasma interferometry to the sub 10 nm wavelength range. In the process we are advancing soft x-ray laser plasma diagnostics techniques to allow the measurement of large-scale, high-density plasmas with picosecond temporal resolution and micrometer spatial resolution, laying the foundations for future advanced diagnostics at high energy density DOE facilities. Dense plasma diagnostics, soft x-ray laser interferometry, converging plasmas

Laser-induced selective copper plating of polypropylene surface

Science.gov (United States)

Ratautas, K.; Gedvilas, M.; Stankevičiene, I.; JagminienÄ--, A.; Norkus, E.; Li Pira, N.; Sinopoli, S.; Emanuele, U.; Račiukaitis, G.

2016-03-01

Laser writing for selective plating of electro-conductive lines for electronics has several significant advantages, compared to conventional printed circuit board technology. Firstly, this method is faster and cheaper at the prototyping stage. Secondly, material consumption is reduced, because it works selectively. However, the biggest merit of this method is potentiality to produce moulded interconnect device, enabling to create electronics on complex 3D surfaces, thus saving space, materials and cost of production. There are two basic techniques of laser writing for selective plating on plastics: the laser-induced selective activation (LISA) and laser direct structuring (LDS). In the LISA method, pure plastics without any dopant (filler) can be used. In the LDS method, special fillers are mixed in the polymer matrix. These fillers are activated during laser writing process, and, in the next processing step, the laser modified area can be selectively plated with metals. In this work, both methods of the laser writing for the selective plating of polymers were investigated and compared. For LDS approach, new material: polypropylene with carbon-based additives was tested using picosecond and nanosecond laser pulses. Different laser processing parameters (laser pulse energy, scanning speed, the number of scans, pulse durations, wavelength and overlapping of scanned lines) were applied in order to find out the optimal regime of activation. Areal selectivity tests showed a high plating resolution. The narrowest width of a copper-plated line was less than 23 μm. Finally, our material was applied to the prototype of the electronic circuit board on a 2D surface.

Study, realisation and experimental test of an hyper frequency gun triggered by a subpicosecond laser (CANDELA)

International Nuclear Information System (INIS)

Travier, C.

1995-12-01

The photo-injector technique is the only one capable of generating very short ( picosecond range) electron pulses. A photocathode illuminated by short pulses of laser radiation (sapphire laser) is placed in a high frequency cavity resonator. The generated electrons can reach relativistic speeds in a few centimeters length, if an accelerating field of several MV / m (here 600 MV / m) is applied to extract them. CANDELA, designed thanks to Parmela code, is the only photo-injector triggered by a sub-picosecond laser. The first experimental results are in agreement with the design and prove that the gun is working properly. A maximum photo-emitted charge of two nano coulombs was obtained from a dispenser photocathode, with a quantum efficiency of one per mil, and a lifetime of a dozen hours. More detailed measurements have to check it works in complete agreement with computerized simulations. (D.L.). 657 refs., 123 figs., 20 tabs

Multi-pulse enhanced laser ion acceleration using plasma half cavity targets

International Nuclear Information System (INIS)

Scott, G. G.; Brenner, C. M.; Neely, D.; Green, J. S.; Robinson, A. P. L.; Spindloe, C.; Bagnoud, V.; Brabetz, C.; Zielbauer, B.; Carroll, D. C.; MacLellan, D. A.; McKenna, P.; Roth, M.; Wagner, F.

2012-01-01

We report on a plasma half cavity target design for laser driven ion acceleration that enhances the laser to proton energy conversion efficiency and has been found to modify the low energy region of the proton spectrum. The target design utilizes the high fraction of laser energy reflected from an ionized surface and refocuses it such that a double pulse interaction is attained. We report on numerical simulations and experimental results demonstrating that conversion efficiencies can be doubled, compared to planar foil interactions, when the secondary pulse is delivered within picoseconds of the primary pulse.

Multi-pulse enhanced laser ion acceleration using plasma half cavity targets

Energy Technology Data Exchange (ETDEWEB)

Scott, G. G.; Brenner, C. M.; Neely, D. [Central Laser Facility, STFC Rutherford Appleton Laboratory, OX11 0QX Didcot (United Kingdom); Department of Physics SUPA, University of Strathclyde, G4 0NG Glasgow (United Kingdom); Green, J. S.; Robinson, A. P. L.; Spindloe, C. [Central Laser Facility, STFC Rutherford Appleton Laboratory, OX11 0QX Didcot (United Kingdom); Bagnoud, V.; Brabetz, C.; Zielbauer, B. [PHELIX Group, Gesellschaft fuer Schwerionenforschung, D-64291 Darmstadt (Germany); Carroll, D. C.; MacLellan, D. A.; McKenna, P. [Department of Physics SUPA, University of Strathclyde, G4 0NG Glasgow (United Kingdom); Roth, M. [Fachbereich Physik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany); Wagner, F. [PHELIX Group, Gesellschaft fuer Schwerionenforschung, D-64291 Darmstadt (Germany); Fachbereich Physik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany)

2012-07-09

We report on a plasma half cavity target design for laser driven ion acceleration that enhances the laser to proton energy conversion efficiency and has been found to modify the low energy region of the proton spectrum. The target design utilizes the high fraction of laser energy reflected from an ionized surface and refocuses it such that a double pulse interaction is attained. We report on numerical simulations and experimental results demonstrating that conversion efficiencies can be doubled, compared to planar foil interactions, when the secondary pulse is delivered within picoseconds of the primary pulse.

Influence of different approaches for dynamical performance optimization of monolithic passive colliding-pulse mode-locked laser diodes emitting around 850 nm

Science.gov (United States)

Prziwarka, T.; Klehr, A.; Wenzel, H.; Fricke, J.; Bugge, F.; Weyers, M.; Knigge, A.; Tränkle, G.

2018-02-01

Monolithic laser diodes which generate short infrared pulses in the picosecond and sub-picosecond ranges with high peak power are ideal sources for many applications like e.g. THz-time-domain spectroscopy (TDS) scanning systems. The achievable THz bandwidth is limited by the length of the optical pulses. Due to the fact that colliding-pulse mode locking (CPM) leads to the shortest pulses which could reached by passive mode locking, we experimentally investigated in detail the dynamical and electro optical performance of InGaAsP based quantum well CPM laser diodes with well-established vertical layer structures. Simple design modifications whose implementation is technically easy were realized. Improvements of the device performance in terms of pulse duration, output power, and noise properties are presented in dependence on the different adaptions. From the results we extract an optimized configuration with which we have reached pulses with durations of ≍1.5 ps, a peak power of > 1 W and a pulse-to-pulse timing jitter < 200 fs. The laser diodes emit pulses at a wavelength around 850 nm with a repetition frequency of ≍ 12.4 GHz and could be used as pump source for GaAs antennas to generate THz-radiation. Approaches for reducing pulse width, increasing output power, and improving noise performance are described.

Diffractive sub-picosecond manipulation of x-rays

International Nuclear Information System (INIS)

Adams, B.

2004-01-01

A class of X-ray optical elements for the sub-picosecond manipulation of X-rays is proposed. The design of these elements is based upon a time-dependent dynamical diffraction theory that synthesizes the eikonal theory with the Takagi-Taupin theory. A brief outline of the theory is given

Fundamentals of laser pulse irradiation of silicon

International Nuclear Information System (INIS)

Rimini, E.; Baeri, P.; Russo, G.

1985-01-01

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

Laser-induced vibrational dynamics of ozone in solid argon

DEFF Research Database (Denmark)

Hansen, Flemming Yssing; Amstrup, B.; Henriksen, Niels Engholm

1997-01-01

We consider the vibrational dynamics, induced by an intense infrared laser pulse, in an ozone molecule with isotopic substitution, that is, (OOO)-O-16-O-16-O-18 and compare the dynamics in the gas phase and in solid ar on. not perturbed by argon on a time-scale of a few picoseconds and selective...

Picosecond laser machined designed patterns with anti-ice effect

NARCIS (Netherlands)

Del Cerro, D.A.; Römer, G.R.B.E.; Huis in 't Veld, A.J.

2010-01-01

Micromachining using ultra short laser pulses (USLP) has evolved over the past years as a versatile tool for introducing functional features in surfaces at a micrometric and even at a sub wavelength scale. Being able to control the surface topography at this level provides a method to change the

Method and apparatus for improving the quality and efficiency of ultrashort-pulse laser machining

Science.gov (United States)

Stuart, Brent C.; Nguyen, Hoang T.; Perry, Michael D.

2001-01-01

A method and apparatus for improving the quality and efficiency of machining of materials with laser pulse durations shorter than 100 picoseconds by orienting and maintaining the polarization of the laser light such that the electric field vector is perpendicular relative to the edges of the material being processed. Its use is any machining operation requiring remote delivery and/or high precision with minimal collateral dames.

Determination of Cross-Sectional Area of Focused Picosecond Gaussian Laser Beam

Science.gov (United States)

Ledesma, Rodolfo; Fitz-Gerald, James; Palmieri, Frank; Connell, John

2018-01-01

Measurement of the waist diameter of a focused Gaussian-beam at the 1/e(sup 2) intensity, also referred to as spot size, is key to determining the fluence in laser processing experiments. Spot size measurements are also helpful to calculate the threshold energy and threshold fluence of a given material. This work reports an application of a conventional method, by analyzing single laser ablated spots for different laser pulse energies, to determine the cross-sectional area of a focused Gaussian-beam, which has a nominal pulse width of approx. 10 ps. Polished tungsten was used as the target material, due to its low surface roughness and low ablation threshold, to measure the beam waist diameter. From the ablative spot measurements, the ablation threshold fluence of the tungsten substrate was also calculated.

Photodisruption in biological tissues using femtosecond laser pulses

Science.gov (United States)

Shen, Nan

Transparent materials do not ordinarily absorb visible or near-infrared light. However, the intensity of a tightly focused femtosecond laser pulse is great enough that nonlinear absorption of the laser energy takes place in transparent materials, leading to optical breakdown and permanent material modification. Because the absorption process is nonlinear, absorption and material modification are confined to the extremely small focal volume. Optical breakdown in transparent or semi-transparent biological tissues depends on intensity rather than energy. As a result, focused femtosecond pulses induce optical breakdown with significantly less pulse energy than is required with longer pulses. The use of femtosecond pulses therefore minimizes the amount of energy deposited into the targeted region of the sample, minimizing mechanical and thermal effects that lead to collateral damage in adjacent tissues. We demonstrate photodisruptive surgery in animal skin tissue and single cells using 100-fs laser pulses. In mouse skin, we create surface incisions and subsurface cavities with much less collateral damage to the surrounding tissue than is produced with picosecond pulses. Using pulses with only a few nanojoules of energy obtained from an unamplified femtosecond oscillator, we destroy single mitochondria in live cells without affecting cell viability, providing insights into the structure of the mitochondrial network. An apparatus is constructed to perform subcellular surgery and multiphoton 3D laser scanning imaging simultaneously with a single laser and objective lens.

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

Science.gov (United States)

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

2018-04-01

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

TECHNICAL DESIGN NOTE: Picosecond resolution programmable delay line

Science.gov (United States)

Suchenek, Mariusz

2009-11-01

The note presents implementation of a programmable delay line for digital signals. The tested circuit has a subnanosecond delay range programmable with a resolution of picoseconds. Implementation of the circuit was based on low-cost components, easily available on the market.

Generation of picosecond pulsed coherent state superpositions

DEFF Research Database (Denmark)

Dong, Ruifang; Tipsmark, Anders; Laghaout, Amine

2014-01-01

We present the generation of approximated coherent state superpositions-referred to as Schrodinger cat states-by the process of subtracting single photons from picosecond pulsed squeezed states of light. The squeezed vacuum states are produced by spontaneous parametric down-conversion (SPDC...... which exhibit non-Gaussian behavior. (C) 2014 Optical Society of America...

A non-linear optical ''photograph'' of picosecond pulses

Energy Technology Data Exchange (ETDEWEB)

Sukhorukova, A.K.; Sukhorukov, A.P.; Telegin, L.S.; Yankina, I.B.

1981-01-01

Results are given of experimental and theoretical studies on the conversion of the temporary structure of picosecond pulses into a spatial diagram with noncollinated lasing of the sum frequency. Correlations are found for the crystal parameters, the pumping emission and the interaction geometry, which are needed in measuring durations in a range from 10 /sup -10/ all the way up to 10 /sup -13/ seconds. The proposed optical recording circuit in the relatively simple experiment makes it possible to measure the duration of the super short pulses of weak signals.

[Experiments on the OMEGA Laser System]. LLE Review. Quarterly report, July-September 1985. Volume 24

International Nuclear Information System (INIS)

Skupsky, S.

1985-01-01

This volume of the LLE Review contains articles on the first 24-beam uv experiments on the OMEGA laser system, the use of absorption spectroscopy to diagnose high-density compressions, the development of a new target fabrication technique to coat mechanically unsupported laser-fusion targets with a parylene layer, the use of liquid crystals as laser-beam apodizers, the investigation of the process of melting using a subpicosecond probe, the development of a new picosecond oscilloscope, and the National Laser Users Facility activities for June-September 1985. 80 refs., 36 figs

Laser-pulsed relativistic electron gun

International Nuclear Information System (INIS)

Sherman, N.K.

1986-01-01

A relativistic (β ≅ 0.8) electron gun with good emittance and subnanosecond pulse duration which can be synchronized to picosecond laser pulses is being developed at NRC for use in studies of particle acceleration by lasers. Bursts of electron pulses exceeding 280 keV in energy have been extracted into air form a laser-driven vacuum photodiode. Trains of 5 ps pulses of ultraviolet UV light illuminate a magnesium cathode. Photoelectrons emitted from the cathode are accelerated in a graded electrostatic potential set up by a 360 kV Marx-generator. The UV pulses are obtained by doubling the frequency of a 606 nm dye laser modelocked at 160 MHz. Electron energies were measured by residual range in an echelon of Al foils. Total charge per burst was measured by picoammeter. Time structure of the bursts has been examined with plastic scintillator and a fast photomultiplier. Tests on a low voltage photodiode achieved a current density of 180 A/cm/sup 2/ from an Mg cathode, with quantum efficiency of 2.4 x 10/sup -6/ electron per UV photon. The brevity and intensity of the laser pulses cause the electric charge collected per pulse to increase linearly with bias voltage rather than according to the Langmuir-Child law. Gun emittance is about 150 mm-msr and beam brightness is about 1A/cm/sup 2/-sr. Estimated duration of individual electron pulses of a burst is about 400 ps with instantaneous current of about 0.1 mA. Energy spread within one pulse is expected to be about 15%. This gun has the potential to be a useful source of relativistic electrons for laser acceleration studies

Hydration and temperature interdependence of protein picosecond dynamics.

Science.gov (United States)

Lipps, Ferdinand; Levy, Seth; Markelz, A G

2012-05-14

We investigate the nature of the solvent motions giving rise to the rapid temperature dependence of protein picoseconds motions at 220 K, often referred to as the protein dynamical transition. The interdependence of picoseconds dynamics on hydration and temperature is examined using terahertz time domain spectroscopy to measure the complex permittivity in the 0.2-2.0 THz range for myoglobin. Both the real and imaginary parts of the permittivity over the frequency range measured have a strong temperature dependence at >0.27 h (g water per g protein), however the permittivity change is strongest for frequencies 1 THz, and 0.27 h for frequencies <1 THz. The data are consistent with the dynamical transition solvent fluctuations requiring only clusters of ~5 water molecules, whereas the enhancement of lowest frequency motions requires a fully spanning water network. This journal is © the Owner Societies 2012

High Harmonic Inverse Free-Electron-Laser Interaction at 800 NM

CERN Document Server

Sears, Chris M S; Colby, Eric R; Cowan, Benjamin; Plettner, Tomas; Siemann, Robert; Spencer, James

2005-01-01

The inverse Free Electron Laser (IFEL) interaction has recently been proposed and used as a short wavelength modulator forμbunching of beams for laser acceleration experiments*,**. These experiments utilized the fundamental of the interaction between the laser field and electron bunch. In the current experiment, we explore the higher order resonances of the IFEL interaction from a 3 period, 1.8 centimeter wavelength undulator with a picosecond, 0.25 mJ/pulse laser at 800 nm. The resonances are observed by adjusting the gap of the undulator while keeping the beam energy constant. We will also discuss diagnostics for obtaining beam overlap and statistical techniques used to account for machine drifts and analyze the data.

Modeling of high energy laser ignition of energetic materials

International Nuclear Information System (INIS)

Lee, Kyung-cheol; Kim, Ki-hong; Yoh, Jack J.

2008-01-01

We present a model for simulating high energy laser heating and ignition of confined energetic materials. The model considers the effect of irradiating a steel plate with long laser pulses and continuous lasers of several kilowatts and the thermal response of well-characterized high explosives for ignition. Since there is enough time for the thermal wave to propagate into the target and to create a region of hot spot in the high explosives, electron thermal diffusion of ultrashort (femto- and picosecond) lasing is ignored; instead, heat diffusion of absorbed laser energy in the solid target is modeled with thermal decomposition kinetic models of high explosives. Numerically simulated pulsed-laser heating of solid target and thermal explosion of cyclotrimethylenetrinitramine, triaminotrinitrobenzene, and octahydrotetranitrotetrazine are compared to experimental results. The experimental and numerical results are in good agreement

Watching proteins function with picosecond X-ray crystallography and molecular dynamics simulations.

Science.gov (United States)

Anfinrud, Philip

2006-03-01

Time-resolved electron density maps of myoglobin, a ligand-binding heme protein, have been stitched together into movies that unveil with molecular dynamics (MD) calculations and picosecond time-resolved X-ray structures provides single-molecule insights into mechanisms of protein function. Ensemble-averaged MD simulations of the L29F mutant of myoglobin following ligand dissociation reproduce the direction, amplitude, and timescales of crystallographically-determined structural changes. This close agreement with experiments at comparable resolution in space and time validates the individual MD trajectories, which identify and structurally characterize a conformational switch that directs dissociated ligands to one of two nearby protein cavities. This unique combination of simulation and experiment unveils functional protein motions and illustrates at an atomic level relationships among protein structure, dynamics, and function. In collaboration with Friedrich Schotte and Gerhard Hummer, NIH.

Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds Calculated Using Multiple Constraints

Science.gov (United States)

2015-12-10

Laboratory (Ret.), private communication. 33. S. Kou, Welding Metallurgy , 2nd Ed., John Wiley & Sons, Inc., 2003. DOI: 10.1002/0471434027. 34. J. K...Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--15-9665 Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds ...NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds Calculated Using Multiple

Laser ablation for the synthesis of carbon nanotubes

Science.gov (United States)

Holloway, Brian C.; Eklund, Peter C.; Smith, Michael W.; Jordan, Kevin C.; Shinn, Michelle

2010-04-06

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Laser ablation for the synthesis of carbon nanotubes

Science.gov (United States)

Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

2012-01-01

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Development of a picosecond time-of-flight system in the ATLAS experiment

International Nuclear Information System (INIS)

Grabas, Herve

2013-01-01

In this thesis, we present a study of the sensitivity to Beyond Standard Model physics brought by the design and installation of picosecond time-of-flight detectors in the forward region of the ATLAS experiment at the LHC. The first part of the thesis present a study of the sensitivity to the quartic gauge anomalous coupling between the photon and the W boson, using exclusive WW pair production in ATLAS. The event selection is built considering the semi-leptonic decay of WW pair and the presence of the AFP detector in ATLAS. The second part gives a description of large area picosecond photo-detectors design and time reconstruction algorithms with a special care given to signal sampling and processing for precision timing. The third part presents the design of SamPic: a custom picosecond readout integrated circuit. At the end, its first results are reported, and in particular a world-class 5 ps timing precision in measuring the delay between two fast pulses. (author) [fr

Second International Conference on 'Transient Chemical Structures in Dense Media' - TCSDM 2010. Book of Abstracts

International Nuclear Information System (INIS)

2010-01-01

A number of experimental techniques now exist that allow for the direct observation of temporally varying molecular geometries that occur during a chemical reaction. The most commonly used method is femtosecond laser spectroscopy. Another technique is picosecond pulse radiolysis, employing accelerator generated electron beams. Finally, highly promising new opportunities are provided by time-resolved X-ray diffraction/absorption: the pulses having duration of a few tens of picoseconds are generated by large synchrotron X-ray sources. Similar opportunities are being realized with the recent implementation of sub-picosecond electron diffraction. The recent advances in X-ray sources (SLAC and XFEL) enable the use of sub-picosecond pulse that will push forward our understanding of a chemical reaction. The use of those experimental techniques will certainly be fruitful in the fields of basic energy sciences and biochemistry. The conference will highlight such applications. Theoretical analysis of experimental data is based on statistical mechanics of nonlinear optical processes. Methods of molecular dynamics simulation, both classical and quantum mechanical, are also required. These methods have penetrated unequally in the three disciplines just mentioned: widely present in laser spectroscopy, they are less extensively used in pulsed radiolysis and in time resolved X-ray spectroscopy. We are currently at the edge of a new revolution in computing sciences that will enable the simulation of large quantum mechanical systems in dense media. Topics of the conference: - Femtosecond laser spectroscopy: Multidimensional spectroscopy, Raman spectroscopy, femto-chemistry in dense media and at interface. - Picosecond pulsed radiolysis: Time-resolved detection techniques, space distribution of absorbed energy, electron and proton transfer processes, micro-heterogeneous and polymeric systems. - New laser based sources for particle acceleration and X-ray experiments. - Ultrafast X

Picosecond x-ray streak cameras

Science.gov (United States)

Averin, V. I.; Bryukhnevich, Gennadii I.; Kolesov, G. V.; Lebedev, Vitaly B.; Miller, V. A.; Saulevich, S. V.; Shulika, A. N.

1991-04-01

The first multistage image converter with an X-ray photocathode (UMI-93 SR) was designed in VNIIOFI in 1974 [1]. The experiments carried out in IOFAN pointed out that X-ray electron-optical cameras using the tube provided temporal resolution up to 12 picoseconds [2]. The later work has developed into the creation of the separate streak and intensifying tubes. Thus, PV-003R tube has been built on base of UMI-93SR design, fibre optically connected to PMU-2V image intensifier carrying microchannel plate.

Ten-watt level picosecond parametric mid-IR source broadly tunable in wavelength

Science.gov (United States)

Vyvlečka, Michal; Novák, Ondřej; Roškot, Lukáscaron; Smrž, Martin; Mužík, Jiří; Endo, Akira; Mocek, Tomáš

2018-02-01

Mid-IR wavelength range (between 2 and 8 μm) offers perspective applications, such as minimally-invasive neurosurgery, gas sensing, or plastic and polymer processing. Maturity of high average power near-IR lasers is beneficial for powerful mid-IR generation by optical parametric conversion. We utilize in-house developed Yb:YAG thin-disk laser of 100 W average power at 77 kHz repetition rate, wavelength of 1030 nm, and about 2 ps pulse width for pumping of a ten-watt level picosecond mid-IR source. Seed beam is obtained by optical parametric generation in a double-pass 10 mm long PPLN crystal pumped by a part of the fundamental near-IR beam. Tunability of the signal wavelength between 1.46 μm and 1.95 μm was achieved with power of several tens of miliwatts. Main part of the fundamental beam pumps an optical parametric amplification stage, which includes a walk-off compensating pair of 10 mm long KTP crystals. We already demonstrated the OPA output signal and idler beam tunability between 1.70-1.95 μm and 2.18-2.62 μm, respectively. The signal and idler beams were amplified up to 8.5 W and 5 W, respectively, at 42 W pump without evidence of strong saturation. Thus, increase in signal and idler output power is expected for pump power increase.

Evaluation of laser-driven ion energies for fusion fast-ignition research

Science.gov (United States)

Tosaki, S.; Yogo, A.; Koga, K.; Okamoto, K.; Shokita, S.; Morace, A.; Arikawa, Y.; Fujioka, S.; Nakai, M.; Shiraga, H.; Azechi, H.; Nishimura, H.

2017-10-01

We investigate laser-driven ion acceleration using kJ-class picosecond (ps) laser pulses as a fundamental study for ion-assisted fusion fast ignition, using a newly developed Thomson-parabola ion spectrometer (TPIS). The TPIS has a space- and weight-saving design, considering its use in an laser-irradiation chamber in which 12 beams of fuel implosion laser are incident, and, at the same time, demonstrates sufficient performance with its detectable range and resolution of the ion energy required for fast-ignition research. As a fundamental study on laser-ion acceleration using a ps pulse laser, we show proton acceleration up to 40 MeV at 1 × 10^{19} W cm^{-2}. The energy conversion efficiency from the incident laser into protons higher than 6 MeV is 4.6%, which encourages the realization of fusion fast ignition by laser-driven ions.

Bibliography of Soviet Laser Developments: January - February 1988

Science.gov (United States)

1989-02-21

light in LiNbO(sub3), CsH(sub2)AsO(sub4) and Ba(sub2)NaNb(sub5)O(sub 15) crystals under synchronous pumping by a picosecond La (sub2)Be(sub2)O(sub5):Nd...Weber,T. 0 Determining the metrological characteristics of an He-Ne laser at 633 nm as a secondary standard of length (in Romanian). Metrologia

Laser-plasma harmonics with high-contrast pulses and designed prepulses

International Nuclear Information System (INIS)

Marjoribanks, R. S.; Zhao, L.; Budnik, F. W.; Kulcsar, G.; Vitcu, A.; Higaki, H.; Wagner, R.; Maksimchuk, A.; Umstadter, D.; Le Blanc, S. P.; Downer, M. C.

1998-01-01

One aspect of the complexity of mid- and high-harmonic generation in high-intensity laser-plasma interactions is that nonlinear hydrodynamics is virtually always folded together with the nonlinear optical conversion process. We have partly dissected this issue in picosecond and subpicosecond interactions with preformed plasma gradients, imaging and spectrally resolving low- and mid-order harmonics. We describe spatial breakup of the picosecond beam in preformed plasmas, concomitant broadening and breakup of the harmonic spectrum, presumably through self-phase modulation, together with data on the sensitivity of harmonics production efficiency to the gradient or extent of preformed plasma. Lastly, we show preliminary data of regular Stokes-like and anti-Stokes-like satellites to the harmonics, accompanied by modification of the forward-scattered beam

Picosecond relaxation of X-ray excited GaAs

Czech Academy of Sciences Publication Activity Database

Tkachenko, V.; Medvedev, Nikita; Lipp, V.; Ziaja, B.

2017-01-01

Roč. 24, Sep (2017), s. 15-21 ISSN 1574-1818 Institutional support: RVO:68378271 Keywords : GaAS * X-ray excitation * picosecond relaxation Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 0.908, year: 2016

Picosecond imaging of inertial confinement fusion plasmas using electron pulse-dilation

Science.gov (United States)

Hilsabeck, T. J.; Nagel, S. R.; Hares, J. D.; Kilkenny, J. D.; Bell, P. M.; Bradley, D. K.; Dymoke-Bradshaw, A. K. L.; Piston, K.; Chung, T. M.

2017-02-01

Laser driven inertial confinement fusion (ICF) plasmas typically have burn durations on the order of 100 ps. Time resolved imaging of the x-ray self emission during the hot spot formation is an important diagnostic tool which gives information on implosion symmetry, transient features and stagnation time. Traditional x-ray gated imagers for ICF use microchannel plate detectors to obtain gate widths of 40-100 ps. The development of electron pulse-dilation imaging has enabled a 10X improvement in temporal resolution over legacy instruments. In this technique, the incoming x-ray image is converted to electrons at a photocathode. The electrons are accelerated with a time-varying potential that leads to temporal expansion as the electron signal transits the tube. This expanded signal is recorded with a gated detector and the effective temporal resolution of the composite system can be as low as several picoseconds. An instrument based on this principle, known as the Dilation X-ray Imager (DIXI) has been constructed and fielded at the National Ignition Facility. Design features and experimental results from DIXI will be presented.

A kilohertz picosecond x-ray pulse generation scheme

International Nuclear Information System (INIS)

Guo, W.; Borland, M.; Harkay, K. C.; Wang, C.-X.; Yang, B.

2007-01-01

The duration of the x-ray pulse generated at a synchrotron light source is typically tens of picoseconds. Shorter pulses are highly desired by the users. In electron storage rings, the vertical beam size is usually orders of magnitude less than the bunch length due to radiation damping; therefore, a shorter pulse can be obtained by slitting the vertically tilted bunch. Zholents proposed tilting the bunch using rf deflection. We found that tilted bunches can also be generated by a dipole magnet kick. A vertical tilt is developed after the kick in the presence of nonzero chromaticity. The tilt was successfully observed and a 4.2-ps pulse was obtained from a 27-ps electron bunch at the Advanced Photon Source. Based on this principle we propose a short-pulse generation scheme that produces picosecond x-ray pulses at a repetition rate of 1 utilde2 kHz, which can be used for pump-probe experiments

Vibrational spectrum of the K-590 intermediate in the bacteriorhodopsin photocycle at room temperature: picosecond time-resolved resonance coherent anti-Raman spectroscopy

Science.gov (United States)

Ujj, L.; Jäger, F.; Popp, A.; Atkinson, G. H.

1996-12-01

The vibrational spectrum of the K-590 intermediate, thought to contribute significantly to the energy storage and transduction mechanism in the bacteriorhodopsin (BR) photocycle, is measured at room temperature using picosecond time-resolved resonance coherent anti-Stokes Raman scattering (PTR/CARS). The room-temperature BR photocycle is initiated by the 3 ps, 570 nm excitation of the ground-state species, BR-570, prepared in both H 2O and D 2O suspensions of BR. PTR/CARS data, recorded 50 ps after BR-570 excitation, at which time only BR-570 and K-590 are present, have an excellent S/N which provides a significantly more detailed view of the K-590 vibrational degrees of freedom than previously available. Two picosecond (6 ps FWHM) laser pulses, ω1 (633.4 nm) and ωS (675-700 nm), are used to record PTR/CARS data via electronic resonance enhancement in both BR-570 and K-590, each of which contains a distinct retinal structure (assigned as 13- rans, 15- anti, 13- cis, respectively). To obtain the vibrational spectrum of K-590 separately, the PTR/CARS spectra from the mixture of isomeric retinals is quantitatively analyzed in terms of third-order susceptibility ( η(3)) relationships. PTR/CARS spectra of K-590 recorded from both H 2O and D 2O suspensions of BR are compared with the analogous vibrational data obtained via spontaneous resonance Raman (RR) scattering at both low (77 K) and room temperature. Analyses of these vibrational spectra identify temperature-dependent effects and changes assignable to the substitution of deuterium at the Schiff-base nitrogen not previously reported.

kW-class picosecond thin-disc prepulse laser Perla for efficient EUV generation

Czech Academy of Sciences Publication Activity Database

Endo, Akira; Smrž, Martin; Mužík, Jiří; Novák, Ondřej; Chyla, Michal; Mocek, Tomáš

2017-01-01

Roč. 16, č. 4 (2017), s. 1-6, č. článku 041011. ISSN 1932-5150 R&D Projects: GA MŠk LO1602; GA ČR GA16-12960S; GA MŠk LM2015086 EU Projects: European Commission(XE) 739573 - HiLASE CoE Grant - others:OP VVV - HiLASE-CoE(XE) CZ.02.1.01/0.0/0.0/15_006/0000674 Institutional support: RVO:68378271 Keywords : EUV source * laser produced plasma * FEL * prepulse * thin-disc laser Subject RIV: BH - Optics, Masers, Laser s OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 1.350, year: 2016

Yb-fiber-pumped mid-infrared picosecond optical parametric oscillator tunable across 6.2-6.7 µm

Science.gov (United States)

Kumar, S. Chaitanya; Casals, J. Canals; Parsa, S.; Zawilski, K. T.; Schunemann, P. G.; Ebrahim-Zadeh, M.

2018-06-01

We report a high-average-power picosecond optical parametric oscillator (OPO) tunable in the mid-infrared (mid-IR) based on CdSiP2 synchronously pumped by an Yb-fiber laser at 80 MHz repetition rate. Successful operation of this high-repetition-rate singly-resonant picosecond OPO has been enabled by the improved CSP crystal quality over a long interaction length. The OPO can be tuned across 1264-1284 nm in the near-IR signal and 6205-6724 nm in the mid-IR idler by temperature tuning the CSP crystal over 39-134 °C. By deploying a 5% output coupler for the resonant signal, we have extracted up to 44 mW of average power in the near-IR and up to 95 mW of non-resonant idler power at 6205 nm at 6.3% total conversion efficiency, with > 50 mW over > 55% of the mid-IR tuning range. We have investigated temperature-tuning characteristics of the OPO and compared the data with the theoretical calculations using the recent Sellmeier and thermo-optic coefficients for CdSiP2. The signal pulses from the OPO exhibit a Gaussian pulse duration of 19 ps centered at 1284 nm. We have also studied the output power stability of the OPO, resulting in a passive stability better than 1.9% rms for the near-IR signal and 2.4% rms for the mid-IR idler, measured over > 17 h, with both beams in high spatial quality.

Interferometric studies of laser-created plasmas using compact soft x-ray lasers

International Nuclear Information System (INIS)

Dunn, J; Nilsen, J; Moon, S; Keenan, R; Jankowska, E; Maconi, M C; Hammarsten, E C; Filevich, J; Hunter, J R; Smith, R F; Shlyaptsev, V; Rocca, J J

2003-01-01

We summarize results of several successful dense plasma diagnostics experiments realized by combining two different kinds of table-top soft x-ray lasers with an amplitude division interferometer based on diffraction grating beam splitters. In the first set of experiments this robust high throughput diffraction grating interferometer (DGI) was used with a 46.9 nm portable capillary discharge laser to study the dynamics of line focus and point focus laser-created plasmas. The measured electron density profiles, which differ significantly from those expected from a classical expansion, unveil important two-dimensional effects of the dynamics of these plasmas. A second DGI customized to operate in combination with a 14.7 nm Ni-like Pd transient gain laser was used to perform interferometry of line focus laser-created plasmas with picosecond time resolution. These measurements provide valuable new benchmarks for complex hydrodynamic codes and help bring new understanding of the dynamics of dense plasmas. The instrumentation and methodology we describe is scalable to significantly shorter wavelengths, and constitutes a promising scheme for extending interferometry to the study of very dense plasmas such as those investigated for inertial confinement fusion

Growth and apoptosis of HeLa cells induced by intense picosecond pulsed electric field

Directory of Open Access Journals (Sweden)

Yuan-yuan HUA

2011-07-01

Full Text Available Objective To investigate the growth and apoptosis of HeLa cells induced by intense picosecond pulsed electric field(PEF in vitro.Methods HeLa cells cultured in vitro were divided into experimental group and control group(with or without intense picosecond PEF.With constant pulse width,frequency and voltage,the cells in experimental group were divided into 6 sub-groups according to the number of pulse(100,200,500,1000,1500,2000,the growth inhibition of HeLa cells by PEF and the dose-effect relationship were analyzed by MTT.Caspase 3 protein activity was detected in the cells in 500,1000 and 2000 sub-groups.Mitochondrial transmembrane potential was detected by rhodamine 123 staining with the cells in 2000 sub-groups.Results MTT assay demonstrated that intense picosecond PEF significantly inhibited the proliferation of HeLa cells in dose-dependent manner.The survival rates of cells declined along with the increase in pulse number,and were 96.23%±0.76%,94.11%±2.42%,90.31%±1.77%,64.59%±1.59%,32.95%±0.73%,23.85%±2.38% and 100%,respectively,in 100,200,500,1000,1500,2000 sub-groups and control group(P < 0.01.The Caspase 3 protein activity was significantly enhanced by intense picosecond PEF,and the absorbancy indexes(A were 0.174±0.012,0.232±0.017,0.365±0.016 and 0.122±0.011,respectively,in 500,1000,2000 sub-groups and control group(P < 0.05.The mitochondrial transmembrane potential of HeLa cells was significantly inhibited by intense picosecond PEF,and the fluorescence intensity in 2000 sub-group(76.66±13.38 was much lower than that in control group(155.81±2.33,P < 0.05.Conclusion Intense picosecond PEF may significantly inhibit the growth of HeLa cells,and induce cell apoptosis via mitochondrial pathway.

University of Hawaii Lure Observatory. [lunar laser ranging system construction

Science.gov (United States)

Carter, W. E.; Williams, J. D.

1973-01-01

The University of Hawaii's Institute for Astronomy is currently constructing a lunar laser ranging observatory at the 3050-meter summit of Mt. Haleakala, Hawaii. The Nd YAG laser system to be employed provides three pulses per second, each pulse being approximately 200 picoseconds in duration. The energy contained in one pulse at 5320 A lies in the range from 250 to 350 millijoules. Details of observatory construction are provided together with transmitter design data and information concerning the lunastat, the feed telescope, the relative pointing system, the receiver, and the event timer system.

Interferometrically enhanced sub-terahertz picosecond imaging utilizing a miniature collapsing-field-domain source

Science.gov (United States)

Vainshtein, Sergey N.; Duan, Guoyong; Mikhnev, Valeri A.; Zemlyakov, Valery E.; Egorkin, Vladimir I.; Kalyuzhnyy, Nikolay A.; Maleev, Nikolai A.; Näpänkangas, Juha; Sequeiros, Roberto Blanco; Kostamovaara, Juha T.

2018-05-01

Progress in terahertz spectroscopy and imaging is mostly associated with femtosecond laser-driven systems, while solid-state sources, mainly sub-millimetre integrated circuits, are still in an early development phase. As simple and cost-efficient an emitter as a Gunn oscillator could cause a breakthrough in the field, provided its frequency limitations could be overcome. Proposed here is an application of the recently discovered collapsing field domains effect that permits sub-THz oscillations in sub-micron semiconductor layers thanks to nanometer-scale powerfully ionizing domains arising due to negative differential mobility in extreme fields. This shifts the frequency limit by an order of magnitude relative to the conventional Gunn effect. Our first miniature picosecond pulsed sources cover the 100-200 GHz band and promise milliwatts up to ˜500 GHz. Thanks to the method of interferometrically enhanced time-domain imaging proposed here and the low single-shot jitter of ˜1 ps, our simple imaging system provides sufficient time-domain imaging contrast for fresh-tissue terahertz histology.

Ejection Regimes in Picosecond Laser-Induced Forward Transfer of Metals

NARCIS (Netherlands)

Pohl, Ralph; Visser, C.W.; Römer, Gerardus Richardus, Bernardus, Engelina; Lohse, Detlef; Sun, Chao; Huis in 't Veld, Bert

2015-01-01

Laser-induced forward transfer (LIFT) is a 3D direct-write method suitable for precision printing of various materials, including pure metals. To understand the ejection mechanism and thereby improve deposition, here we present visualizations of ejection events at high-spatial (submicrometer) and

Underwater laser cutting of metallic structures

International Nuclear Information System (INIS)

Alfille, J.P.; Schildknecht, J.; Ramaswami, V.S.

1993-01-01

In the frame of an european contract, the feasibility of the underwater cutting with a CO 2 laser power is studied. The aim of this work is the dismantling metallic structures of reactors pools. The paper analyzes the general concept of the experimental device, the underwater cutting head, the experimenting vessel, examples of cuttings in dismantling situation with a 500 W CO 2 laser, and examples of cuttings with a 5 kW CO 2 laser. (author). 2 refs., 9 figs., 2 tabs

Damage Mechanisms In Polymers Upon NIR Femtosecond Pulse Laser Irradiation: Sub-Threshold Processes And Their Implications For Laser Safety Applications

International Nuclear Information System (INIS)

Bonse, Joern; Krueger, Joerg; Solis, Javier; Spielmann, Christian; Lippert, Thomas

2010-01-01

This contribution investigates laser-induced damage of thin film and bulk polymer samples, with the focus on physical processes occurring close to the damage threshold. In-situ real-time reflectivity (RTR) measurements with picosecond (ps) and nanosecond (ns) temporal resolution were performed on thin polymer films on a timescale up to a few microseconds (μs). A model for polymer thin film damage is presented, indicating that irreversible chemical modification processes take place already below the fluence threshold for macroscopic damage. On dye-doped bulk polymer filters (as used for laser goggles), transmission studies using fs-and ps-laser pulses reveal the optical saturation behavior of the material and its relation to the threshold of permanent damage. Implications of the sub-threshold processes for laser safety applications will be discussed for thin film and bulk polymer damage.

Hybrid Laser Welding of Large Steel Structures

DEFF Research Database (Denmark)

Farrokhi, Farhang

Manufacturing of large steel structures requires the processing of thick-section steels. Welding is one of the main processes during the manufacturing of such structures and includes a significant part of the production costs. One of the ways to reduce the production costs is to use the hybrid...... laser welding technology instead of the conventional arc welding methods. However, hybrid laser welding is a complicated process that involves several complex physical phenomena that are highly coupled. Understanding of the process is very important for obtaining quality welds in an efficient way....... This thesis investigates two different challenges related to the hybrid laser welding of thick-section steel plates. Employing empirical and analytical approaches, this thesis attempts to provide further knowledge towards obtaining quality welds in the manufacturing of large steel structures....

X-ray laser related experiments and theory at Princeton

International Nuclear Information System (INIS)

Suckewer, S.

1989-04-01

This paper describes a new system for the development of an x-ray laser in the wavelength region from 5 nm to 1 nm utilizing a Powerful Sub-Picosecond Laser (PP-Laser) of expected peak power up to 0.5 TW in a 300 fs pulse. Soft x-ray spectra generated by the interaction of the PP-Laser beam with different targets are presented and compared to the spectra generated by a much less intense laser beam (20--30 GW). A theoretical model for the interaction of atoms with such a strong laser EM field is also briefly discussed. The development of additional amplifiers for the recombining soft x-ray laser and the design of a cavity are presented from the point of view of applications for x-ray microscopy and microlithography. This overview concludes with the presentation of recent results on the quenching of spontaneous emission radiation and its possible effect on the absolute intensity calibration of soft x-ray spectrometers. 26 refs., 18 figs

Thin disk amplifier-based 40 mJ, 1 kHz, picosecond laser at 515 nm

Czech Academy of Sciences Publication Activity Database

Novák, Jakub; Green, Jonathan T.; Metzger, T.; Mazanec, Tomáš; Himmel, Bedřich; Horáček, Martin; Hubka, Zbyněk; Boge, Robert; Antipenkov, Roman; Batysta, František; Naylon, Jack A.; Bakule, Pavel; Rus, Bedřich

2016-01-01

Roč. 24, č. 6 (2016), s. 5728-5733 ISSN 1094-4087 R&D Projects: GA MŠk ED1.1.00/02.0061; GA MŠk EE.2.3.20.0091 Grant - others:ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061; OP VK 1 Laser Sys(XE) CZ.1.07/2.3.00/20.0091 Institutional support: RVO:68378271 Keywords : laser amplifiers * laser s * pulsed * laser s * diode -pumped * laser s * frequency doubled * ultrafast laser s Subject RIV: BH - Optics, Masers, Laser s Impact factor: 3.307, year: 2016

A protection system for picosecond accelerator

International Nuclear Information System (INIS)

Cao Hongping; Chinese Academy of Sciences, Beijing; Chen Huanguang; Xu Ruinian; Tang Junlong; Li Deming

2006-01-01

A personnel and machine protection system for the picosecond accelerator has been built. The key of the system is to send on/off of three triggering signals which are those of electron gun, 2856 MHz and 476 MHz, respectively, to ensure the safety of users and the accelerator. This paper describes the emergencies interlocked by ADAM5511 and timing trigger processor, and some secondary functions which improve the efficiency of the protection system completed in upper layer software. (authors)

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

International Nuclear Information System (INIS)

Abdul Ghani, B.; Hammadi, M.

2004-08-01

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

Homogenization of tissues via picosecond-infrared laser (PIRL) ablation: Giving a closer view on the in-vivo composition of protein species as compared to mechanical homogenization.

Science.gov (United States)

Kwiatkowski, M; Wurlitzer, M; Krutilin, A; Kiani, P; Nimer, R; Omidi, M; Mannaa, A; Bussmann, T; Bartkowiak, K; Kruber, S; Uschold, S; Steffen, P; Lübberstedt, J; Küpker, N; Petersen, H; Knecht, R; Hansen, N O; Zarrine-Afsar, A; Robertson, W D; Miller, R J D; Schlüter, H

2016-02-16

Posttranslational modifications and proteolytic processing regulate almost all physiological processes. Dysregulation can potentially result in pathologic protein species causing diseases. Thus, tissue species proteomes of diseased individuals provide diagnostic information. Since the composition of tissue proteomes can rapidly change during tissue homogenization by the action of enzymes released from their compartments, disease specific protein species patterns can vanish. Recently, we described a novel, ultrafast and soft method for cold vaporization of tissue via desorption by impulsive vibrational excitation (DIVE) using a picosecond-infrared-laser (PIRL). Given that DIVE extraction may provide improved access to the original composition of protein species in tissues, we compared the proteome composition of tissue protein homogenates after DIVE homogenization with conventional homogenizations. A higher number of intact protein species was observed in DIVE homogenates. Due to the ultrafast transfer of proteins from tissues via gas phase into frozen condensates of the aerosols, intact protein species were exposed to a lesser extent to enzymatic degradation reactions compared with conventional protein extraction. In addition, total yield of the number of proteins is higher in DIVE homogenates, because they are very homogenous and contain almost no insoluble particles, allowing direct analysis with subsequent analytical methods without the necessity of centrifugation. Enzymatic protein modifications during tissue homogenization are responsible for changes of the in-vivo protein species composition. Cold vaporization of tissues by PIRL-DIVE is comparable with taking a snapshot at the time of the laser irradiation of the dynamic changes that occur continuously under in-vivo conditions. At that time point all biomolecules are transferred into an aerosol, which is immediately frozen. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Development of transient collisional excitation x-ray laser with ultra short-pulse laser

International Nuclear Information System (INIS)

Kado, Masataka; Kawachi, Tetsuya; Hasegawa, Noboru; Tanaka, Momoko; Sukegawa, Kouta; Nagashima, Keisuke; Kato, Yoshiaki

2001-01-01

We have observed lasing on Ne-like 3s-3p line from titanium (32.4 nm), Ni-like 4p-4d line from silver (13.9 nm) and tin (11.9 nm) with the transient collisional excitation (TCE) scheme that uses combination of a long pre-pulse (∼ns) and a short main pulse (∼ps). A gain coefficient of 23 cm -1 was measured for plasma length up to 4 mm with silver slab targets. We have also observed lasing on Ne-like and Ni-like lines with new TCE scheme that used pico-seconds laser pulse to generate plasma and observed strong improvement of x-ray laser gain coefficient. A gain coefficient of 14 cm -1 was measured for plasma length up to 6 mm with tin targets. (author)

[Alternatives to femtosecond laser technology: subnanosecond UV pulse and ring foci for creation of LASIK flaps].

Science.gov (United States)

Vogel, A; Freidank, S; Linz, N

2014-06-01

In refractive corneal surgery femtosecond (fs) lasers are used for creating LASIK flaps, dissecting lenticules and for astigmatism correction by limbal incisions. Femtosecond laser systems are complex and expensive and cutting precision is compromised by the large focal length associated with the commonly used infrared (IR) wavelengths. Based on investigations of the cutting dynamics, novel approaches for corneal dissection using ultraviolet A (UVA) picosecond (ps) pulses and ring foci from vortex beams are presented. Laser-induced bubble formation in corneal stroma was investigated by high-speed photography at 1-50 million frames/s. Using Gaussian and vortex beams of UVA pulses with durations between 200 and 850 ps the laser energy needed for easy removal of flaps created in porcine corneas was determined and the quality of the cuts by scanning electron microscopy was documented. Cutting parameters for 850 ps are reported also for rabbit eyes. The UV-induced and mechanical stress were evaluated for Gaussian and vortex beams. The results show that UVA picosecond lasers provide better cutting precision than IR femtosecond lasers, with similar processing times. Cutting energy decreases by >50 % when the laser pulse duration is reduced to 200 ps. Vortex beams produce a short, donut-shaped focus allowing efficient and precise dissection along the corneal lamellae which results in a dramatic reduction of the absorbed energy needed for cutting and of mechanical side effects as well as in less bubble formation in the cutting plane. A combination of novel approaches for corneal dissection provides the option to replace femtosecond lasers by compact UVA microchip laser technology. Ring foci are also of interest for femtosecond laser surgery, especially for improved lenticule excision.

The Effects of Slippage and Diffraction in Long-Wavelength Operation of a Free-Electron Laser

NARCIS (Netherlands)

Zhulin, V. I.; Haselhoff, E. H.; van Amersfoort, P. W.

1995-01-01

The Free-Electron Laser user facility FELIX produces picosecond optical pulses in the wavelength range of 5-110 mu m. The proposed installation of a new undulator with a larger magnetic period would allow extension towards considerably longer wavelengths. This would result in the production of

Coherent anti-Stokes Raman scattering spectroscope/microscope based on a widely tunable laser source

Science.gov (United States)

Dementjev, A.; Gulbinas, V.; Serbenta, A.; Kaucikas, M.; Niaura, G.

2010-03-01

We present a coherent anti-Stokes Raman scattering (CARS) microscope based on a robust and simple laser source. A picosecond laser operating in a cavity dumping regime at the 1 MHz repetition rate was used to pump a traveling wave optical parametric generator, which serves as a two-color excitation light source for the CARS microscope. We demonstrate the ability of the presented CARS microscope to measure CARS spectra and images by using several detection schemes.

Depth profiling of calcifications in breast tissue using picosecond Kerr-gated Raman spectroscopy.

Science.gov (United States)

Baker, Rebecca; Matousek, Pavel; Ronayne, Kate Louise; Parker, Anthony William; Rogers, Keith; Stone, Nicholas

2007-01-01

Breast calcifications are found in both benign and malignant lesions and their composition can indicate the disease state. Calcium oxalate (dihydrate) (COD) is associated with benign lesions, however calcium hydroxyapatite (HAP) is found mainly in proliferative lesions including carcinoma. The diagnostic practices of mammography and histopathology examine the morphology of the specimen. They can not reliably distinguish between the two types of calcification, which may indicate the presence of a cancerous lesion during mammography. We demonstrate for the first time that Kerr-gated Raman spectroscopy is capable of non-destructive probing of sufficient biochemical information from calcifications buried within tissue, and this information can potentially be used as a first step in identifying the type of lesion. The method uses a picosecond pulsed laser combined with fast temporal gating of Raman scattered light to enable spectra to be collected from a specific depth within scattering media by collecting signals emerging from the sample at a given time delay following the laser pulse. Spectra characteristic of both HAP and COD were obtained at depths of up to 0.96 mm, in both chicken breast and fatty tissue; and normal and cancerous human breast by utilising different time delays. This presents great potential for the use of Raman spectroscopy as an adjunct to mammography in the early diagnosis of breast cancer.

Generation of 46 W green-light by frequency doubling of 96 W picosecond unpolarized Yb-doped fiber amplifier

Science.gov (United States)

Qi, Yaoyao; Yu, Haijuan; Zhang, Jingyuan; Zhang, Ling; He, Chaojian; Lin, Xuechun

2018-05-01

We demonstrated a high efficiency and high average power picosecond green light source based on SHG (second harmonic generation) of an unpolarized ytterbium-doped fiber amplifier chain. Using single-pass frequency doubling in two temperature-tuned type-I phase-matching LBO crystals, we were able to generate 46 W, >70 ps pulses at 532 nm from a fundamental beam at 1064 nm, whose output is 96 W, 4.8 μJ, with a repetition frequency of 20 MHz and nearly diffraction limited. The optical conversion efficiency was ∼48% in a highly compact design. To the best of our knowledge, this is the first reported on ps green source through SHG of an unpolarized fiber laser with such a high output and high efficiency.

Injection moulding of optical functional micro structures using laser structured, PVD-coated mould inserts

Energy Technology Data Exchange (ETDEWEB)

Hopmann, Ch.; Weber, M.; Schöngart, M.; Schäfer, C., E-mail: weber@ikv-aachen.de [Institute of Plastics Processing (IKV) at RWTH Aachen University (Germany); Bobzin, K.; Bagcivan, N.; Brögelmann, T.; Theiß, S.; Münstermann, T. [Surface Engineering Institute (IOT), RWTH Aachen University, Aachen (Germany); Steger, M. [Fraunhofer Institute for Laser Technology (ILT), Aachen (Germany)

2015-05-22

Micro structured optical plastics components are intensively used i. e. in consumer electronics, for optical sensors in metrology, innovative LED-lighting or laser technology. Injection moulding has proven to be successful for the large-scale production of those parts. However, the production of those parts still causes difficulties due to challenges in the moulding and demoulding of plastics parts created with laser structured mould inserts. A complete moulding of the structures often leads to increased demoulding forces, which then cause a breaking of the structures and a clogging of the mould. An innovative approach is to combine PVD-coated (physical vapour deposition), laser structured inserts and a variothermal moulding process to create functional mic8iüro structures in a one-step process. Therefore, a PVD-coating is applied after the laser structuring process in order to improve the wear resistance and the anti-adhesive properties against the plastics melt. In a series of moulding trials with polycarbonate (PC) and polymethylmethacrylate (PMMA) using different coated moulds, the mould temperature during injection was varied in the range of the glass transition and the melt temperature of the polymers. Subsequently, the surface topography of the moulded parts is evaluated by digital 3D laser-scanning microscopy. The influence of the moulding parameters and the coating of the mould insert on the moulding accuracy and the demoulding behaviour are being analysed. It is shown that micro structures created by ultra-short pulse laser ablation can be successfully replicated in a variothermal moulding process. Due to the mould coating, significant improvements could be achieved in producing micro structured optical plastics components.

Picosecond transient absorption study of photodissociated carboxy hemoglobin and myoglobin

International Nuclear Information System (INIS)

Janes, S.M.; Dalickas, G.A.; Eaton, W.A.; Hochstrasser, R.M.

1988-01-01

The optical transient absorption spectra at 30 ps and 6.5 ns after photolysis are compared for both carboxy hemoglobin (HbCO) and carboxy myoglobin (MbCO). Both 355- and 532-nm excitation pulses were used. In all cases the shapes of the optical difference spectra thus generated are stationary over the complete time-scale studied. The photolysis spectra for MbCO are not significantly different from the equilibrium difference spectra generated on the same picosecond spectrometer when measured to an accuracy of +/- 0.5 nm. In addition, spectral parameters for delegated HbCO generated on the same spectrometer but detected by two different techniques, either by a Vidicon detector or point by point with photomultiplier tubes, are reported; the results are different from some of the previously reported picosecond experiments

Ultrafast laser pump/x-ray probe experiments

International Nuclear Information System (INIS)

Larsson, J.; Judd, E.; Schuck, P.J.

1997-01-01

In an ongoing project aimed at probing solids using x-rays obtained at the ALS synchrotron with a sub-picosecond time resolution following interactions with a 100 fs laser pulse, the authors have successfully performed pump-probe experiments limited by the temporal duration of ALS-pulse. They observe a drop in the diffraction efficiency following laser heating. They can attribute this to a disordering of the crystal. Studies with higher temporal resolution are required to determine the mechanism. The authors have also incorporated a low-jitter streakcamera as a diagnostic for observing time-dependant x-ray diffraction. The streakcamera triggered by a photoconductive switch was operated at kHz repetition rates. Using UV-pulses, the authors obtain a temporal response of 2 ps when averaging 5000 laser pulses. They demonstrate the ability to detect monochromatized x-ray radiation from a bend-magnet with the streak camera by measuring the pulse duration of a x-ray pulse to 70 ps. In conclusion, the authors show a rapid disordering of an InSb crystal. The resolution was determined by the duration of the ALS pulse. They also demonstrate that they can detect x-ray radiation from a synchrotron source with a temporal resolution of 2ps, by using an ultrafast x-ray streak camera. Their set-up will allow them to pursue laser pump/x-ray probe experiments to monitor structural changes in materials with ultrafast time resolution

Diode-pumped two-frequency lasers based on c-cut vanadate crystals

International Nuclear Information System (INIS)

Sirotkin, A A; Garnov, Sergei V; Zagumennyi, A I; Zavartsev, Yu D; Kutovoi, S A; Vlasov, V I; Shcherbakov, Ivan A

2009-01-01

The luminescent and lasing properties of the neo-dymium ion at the 4 F 3/2 - 4 I 11/2 transition in c-cut vanadate crystals (Nd:YVO 4 , Nd:GdVO 4 , and Nd:Gd 1-x Y x VO 4 ) are studied. Tuning of the laser radiation wavelength (Δλ = 5.4 nm) is demonstrated. Two-frequency laser schemes with the use of a Lyot filter, a Fabry-Perot etalon, and a Brewster prism as spectral selection elements are proposed and experimentally realised. Stable two-frequency lasing of a laser based on the c-cut Nd:GdVO 4 crystal was obtained in the cw, Q-switched (nanosecond pulses), and active acousto-optic mode-locked (picosecond pulses) regimes. (lasers)

Electron acceleration and generation of high-brilliance x-ray radiation in kilojoule, subpicosecond laser-plasma interactions

Directory of Open Access Journals (Sweden)

J. Ferri

2016-10-01

Full Text Available Petawatt, picosecond laser pulses offer rich opportunities in generating synchrotron x-rays. This paper concentrates on the regimes accessible with the PETAL laser, which is a part of the Laser Megajoule (LMJ facility. We explore two physically distinct scenarios through Particle-in-Cell simulations. The first one realizes in a dense plasma, such that the period of electron Langmuir oscillations is much shorter than the pulse duration. Hallmarks of this regime are longitudinal breakup (“self-modulation” of the picosecond-scale laser pulse and excitation of a rapidly evolving broken plasma wake. It is found that electron beams with a charge of several tens of nC can be obtained, with a quasi-Maxwellian energy distribution extending to a few-GeV level. In the second scenario, at lower plasma densities, the pulse is shorter than the electron plasma period. The pulse blows out plasma electrons, creating a single accelerating cavity, while injection on the density downramp creates a nC quasi-monoenergetic electron bunch within the cavity. This bunch accelerates without degradation beyond 1 GeV. The x-ray sources in the self-modulated regime offer a high number of photons (∼10^{12} with the slowly decaying energy spectra extending beyond 60 keV. In turn, quasimonoenergetic character of the electron beam in the blowout regime results in the synchrotron-like spectra with the critical energy around 10 MeV and a number of photons >10^{9}. Yet, much smaller source duration and transverse size increase the x-ray brilliance by more than an order of magnitude against the self-modulated case, also favoring high spatial and temporal resolution in x-ray imaging. In all explored cases, accelerated electrons emit synchrotron x-rays of high brilliance, B>10^{20}  photons/s/mm^{2}/mrad^{2}/0.1%BW. Synchrotron sources driven by picosecond kilojoule lasers may thus find an application in x-ray diagnostics on such facilities such as the LMJ or National

Demonstration of a neonlike argon soft-x-ray laser with a picosecond-laser-irradiated gas puff target.

Science.gov (United States)

Fiedorowicz, H; Bartnik, A; Dunn, J; Smith, R F; Hunter, J; Nilsen, J; Osterheld, A L; Shlyaptsev, V N

2001-09-15

We demonstrate a neonlike argon-ion x-ray laser, using a short-pulse laser-irradiated gas puff target. The gas puff target was formed by pulsed injection of gas from a high-pressure solenoid valve through a nozzle in the form of a narrow slit and irradiated with a combination of long, 600-ps and short, 6-ps high-power laser pulses with a total of 10 J of energy in a traveling-wave excitation scheme. Lasing was observed on the 3p (1)S(0)?3s (1)P(1) transition at 46.9 nm and the 3d (1)P(1)?3p (1)P(1) transition at 45.1 nm. A gain of 11 cm(-1) was measured on these transitions for targets up to 0.9 cm long.

Injection of harmonics generated in gas in a free-electron laser providing intense and coherent extreme-ultraviolet light

Energy Technology Data Exchange (ETDEWEB)

Lambert, G; Garzella, D; Labat, M; Carre, B; Bougeard, M; Salieres, P; Merdji, H; Gobert, O [CEA Saclay, DSM, DRECAM, Serv. Photons Atomes Mol., F-91191 Gif sur Yvette, (France); Lambert, G; Hara, T; Tanikawa, T; Kitamura, H; Shintake, T; Tanaka, Y; Tahara, K [RIKEN SPring Centre, Harima Inst., Hyogo 679-5148, (Japan); Lambert, G; Labat, M; Chubar, O; Couprie, M E [Groupe Magnetisme et Insertion, Synchrotron Soleil, F-91192 Gif sur Yvette, (France); Hara, T; Kitamura, H; Shintake, T; Inoue, S; Tanaka, Y [XFEL Project Head Office, RIKEN, Hyogo 679-5148, (Japan)

2008-07-01

Conventional synchrotron radiation sources enable the structure of matter to be studied at near-atomic spatial resolution and picosecond temporal resolution. Free-electron lasers promise to extend this down to femtosecond timescales. The process by which free-electron lasers amplify synchrotron light-known as self-amplified spontaneous emission - is only partially temporally coherent, but this can be improved by seeding it with an external laser. Here we explore the use of seed light produced by high-order harmonic generation in a gas, covering wavelengths from the ultraviolet to soft X-rays. Using the SPring-8 Compact SASE Source test accelerator, we demonstrate an increase of three orders of magnitude in the intensity of the fundamental radiation at 160 nm, halving of the free-electron laser saturation length, and the generation of nonlinear harmonics at 54 nm and 32 nm. The low seed level used in this demonstration suggests that nonlinear harmonic schemes should enable the generation of fully coherent soft X-rays at wavelengths down to the so-called 'water window', vital for the study of biological samples. (authors)

Formation of low time-bandwidth product, single-sided exponential optical pulses in free-electron laser oscillators

NARCIS (Netherlands)

MacLeod, A. M.; Yan, X.; Gillespie, W. A.; Knippels, G.M.H.; Oepts, D.; van der Meer, A. F. G.; Rella, C. W.; Smith, T. J.; Schwettman, H. A.

2000-01-01

The detailed shape of picosecond optical pulses from a free-electron laser (FEL) oscillator has been studied for various cavity detunings. For large values of the cavity detuning the optical pulse develops an exponential leading edge, with a time constant proportional to the applied cavity detuning

Laser-induced agglomeration of gold nanoparticles dispersed in a liquid

Science.gov (United States)

Serkov, A. A.; Shcherbina, M. E.; Kuzmin, P. G.; Kirichenko, N. A.

2015-05-01

Dynamics of gold nanoparticles (NPs) ensemble in dense aqueous solution under exposure to picosecond laser radiation is studied both experimentally and theoretically. Properties of NPs are examined by means of transmission electron microscopy, optical spectroscopy, and size-measuring disk centrifuge. Theoretical investigation of NPs ensemble behavior is based on the analytical model taking into account collisions and agglomeration of particles. It is shown that in case of dense NPs colloidal solutions (above 1014 particles per milliliter) the process of laser fragmentation typical for nanosecond laser exposure turns into laser-induced agglomeration which leads to formation of the particles with larger sizes. It is shown that there is a critical concentration of NPs: at higher concentrations agglomeration rate increases tremendously. The results of mathematical simulation are in compliance with experimental data.

Prepulse effect on intense femtosecond laser pulse propagation in gas

International Nuclear Information System (INIS)

Giulietti, Antonio; Tomassini, Paolo; Galimberti, Marco; Giulietti, Danilo; Gizzi, Leonida A.; Koester, Petra; Labate, Luca; Ceccotti, Tiberio; D'Oliveira, Pascal; Auguste, Thierry; Monot, Pascal; Martin, Philippe

2006-01-01

The propagation of an ultrashort laser pulse can be affected by the light reaching the medium before the pulse. This can cause a serious drawback to possible applications. The propagation in He of an intense 60-fs pulse delivered by a Ti:sapphire laser in the chirped pulse amplification (CPA) mode has been investigated in conditions of interest for laser-plasma acceleration of electrons. The effects of both nanosecond amplified spontaneous emission and picosecond pedestals have been clearly identified. There is evidence that such effects are basically of refractive nature and that they are not detrimental for the propagation of a CPA pulse focused to moderately relativistic intensity. The observations are fully consistent with numerical simulations and can contribute to the search of a stable regime for laser acceleration

Space- and time-resolved diagnostics of soft x-ray emission from laser plasmas

International Nuclear Information System (INIS)

Richardson, M.C.; Jaanimagi, P.A.; Chen, H.

1988-01-01

The analysis of soft x-ray emission from plasmas created by intense short-wavelength laser radiation can provide much useful information on the density, temperature and ionization distribution of the plasma. Until recently, limitations of sensitivity and the availability of suitable x-ray optical elements have restricted studies of soft x-ray emission from laser plasmas. In this paper, the authors describe novel instrumentation which provides high sensitivity in the soft x-ray spectrum with spatial and temporal resolution in the micron and picosecond ranges respectively. These systems exploit advances made in soft x-ray optic and electro-optic technology. Their application in current studies of laser fusion, x-ray lasers, and high density atomic physics are discussed

Retinal response of Macaca mulatta to picosecond laser pulses of varying energy and spot size.

Science.gov (United States)

Roach, William P; Cain, Clarence P; Narayan, Drew G; Noojin, Gary D; Boppart, Stephen A; Birngruber, Reginald; Fujimoto, James G; Toth, Cynthia A

2004-01-01

We investigate the relationship between the laser beam at the retina (spot size) and the extent of retinal injury from single ultrashort laser pulses. From previous studies it is believed that the retinal effect of single 3-ps laser pulses should vary in extent and location, depending on the occurrence of laser-induced breakdown (LIB) at the site of laser delivery. Single 3-ps pulses of 580-nm laser energy are delivered over a range of spot sizes to the retina of Macaca mulatta. The retinal response is captured sequentially with optical coherence tomography (OCT). The in vivo OCT images and the extent of pathology on final microscopic sections of the laser site are compared. With delivery of a laser pulse with peak irradiance greater than that required for LIB, OCT and light micrographs demonstrate inner retinal injury with many intraretinal and/or vitreous hemorrhages. In contrast, broad outer retinal injury with minimal to no choriocapillaris effect is seen after delivery of laser pulses to a larger retinal area (60 to 300 microm diam) when peak irradiance is less than that required for LIB. The broader lesions extend into the inner retina when higher energy delivery produces intraretinal injury. Microscopic examination of stained fixed tissues provide better resolution of retinal morphology than OCT. OCT provides less resolution but could be guided over an in vivo, visible retinal lesion for repeated sampling over time during the evolution of the lesion formation. For 3-ps visible wavelength laser pulses, varying the spot size and laser energy directly affects the extent of retinal injury. This again is believed to be partly due to the onset of LIB, as seen in previous studies. Spot-size dependence should be considered when comparing studies of retinal effects or when pursuing a specific retinal effect from ultrashort laser pulses. Copyright 2004 Society of Photo-Optical Instrumentation Engineers.

On the biphoton excitation of the fluorescence of the bacteriochlorophyll molecules of purple photosynthetic bacteria by powerful near IR femto-picosecond pulses

Energy Technology Data Exchange (ETDEWEB)

Borisov, A. Yu., E-mail: borissov@belozersky.msu.ru [Moscow State University, Belozersky Institute of Physicochemical Biology (Russian Federation)

2011-11-15

The authors of a number of experimental works detected nonresonance biphoton excitation of bacteriochlorophyll molecules, which represent the main pigment in the light-absorbing natural 'antenna' complexes of photosynthesizing purple bacteria, by femtosecond IR pulses (1250-1500 nm). They believe that IR quanta excite hypothetic forbidden levels of the pigments of these bacteria in the double frequency range 625-750 nm. We propose and ground an alternative triplet mechanism to describe this phenomenon. According to our hypothesis, the mechanism of biphoton excitation of molecules by IR quanta can manifest itself specifically, through high triplet levels of molecules in the high fields induced by femtosecond-picosecond laser pulses.

Development of a free-electron laser user facility for the extreme ultraviolet

International Nuclear Information System (INIS)

Newnam, B.E.

1987-01-01

A free-electron laser user facility for scientific experimentation in the extreme ultraviolet is being developed at Los Alamos. A series of laser oscillators and amplifiers, driven by a single, rf linear accelerator, will generate broadly tunable, picosecond-pulse, coherent radiation from 1 nm to 400 nm. The design and output parameters of this facility are described, comparison with synchrotron radiation sources is made, and recent progress in developing the three primary components (electron beam, undulator, and resonator mirrors) is reviewed, and various categories of scientific applications are indicated

Ultrafast, laser-based, x-ray science: the dawn of atomic-scale cinematography

International Nuclear Information System (INIS)

Barty, C.P.J.

2000-01-01

The characteristics of ultrafast chirped pulse amplification systems are reviewed. Application of ultrafast chirped pulse amplification to the generation of femtosecond, incoherent, 8-keV line radiation is outlined and the use of femtosecond laser-based, x-rays for novel time-resolved diffraction studies of crystalline dynamics with sub-picosecond temporal resolution and sub-picometer spatial resolution is reviewed in detail. Possible extensions of laser-based, x-ray technology and evaluation of alternative x-ray approaches for time-resolved studies of the atomic scale dynamics are given. (author)

Ultrafast, laser-based, x-ray science: the dawn of atomic-scale cinematography

Energy Technology Data Exchange (ETDEWEB)

Barty, C.P.J. [University of California, Department of Applied Mechanics and Engineering Science, Urey Hall, Mali Code 0339, San Diego, La Jolla, CA (United States)

2000-03-01

The characteristics of ultrafast chirped pulse amplification systems are reviewed. Application of ultrafast chirped pulse amplification to the generation of femtosecond, incoherent, 8-keV line radiation is outlined and the use of femtosecond laser-based, x-rays for novel time-resolved diffraction studies of crystalline dynamics with sub-picosecond temporal resolution and sub-picometer spatial resolution is reviewed in detail. Possible extensions of laser-based, x-ray technology and evaluation of alternative x-ray approaches for time-resolved studies of the atomic scale dynamics are given. (author)

Picosecond intersubband hole relaxation in p-type quantum wells

International Nuclear Information System (INIS)

Xu, Z.; Fauchet, P.M.; Rella, C.W.; Schwettman, H.A.

1995-01-01

We report the first direct measurement of the relaxation time of holes in p-type quantum wells using tunable, subpicosecond mid-infrared laser pulses in a pump-probe arrangement. The QW layers consisted of 50 In 0.5 Ga 0.5 As/Al 0.5 Ga 0.5 As periods. The In 0.5 Ga 0.5 As well was 4 nm wide and the Al 0.5 Ga 0.5 As barrier was 8 nm wide. The dopant concentration was 10 19 CM -3 which corresponds to a sheet density of 1.2 x 10 13 CM -2 . The room temperature IR spectrum showed a 50 meV wide absorption peak at 5.25 μm (220 meV). This energy agrees with the calculated n=1 heavy hole to n=1 light hole transition energy of 240 meV (150 meV for strain and 90 meV for confinement). The large absorption width results from hole-hole scattering and the difference in dispersion relations between the two subbands. The equal-wavelength pump-probe transmission measurements were performed using the Stanford free electron laser (FEL). The FEL pulses were tuned between 4 and 6 μ m and their duration was less than 1 ps. The measurements were performed as a function of temperature, pump wavelength and intensity (from 0.3 to 10 GW/cm 2 ). In all our experiments, we find an increase of transmission (decrease of absorption or bleaching) following photopumping, which recovers as a single exponential with a time constant (relaxation time) of the order of 1 picosecond. The maximum change in transmission is linear with pump 2 intensity below 1 GW/cm 2 and saturates to ∼3% with a saturation intensity I sat of 3 GW/cm 2 . As the saturation regime is entered, the relaxation time increases from 0.8 ps to 1.8 ps. This relaxation time depends on the temperature T: it increases from 0.8 ps to 1.3 ps as T decreases from 300 K to 77 K. Finally, when we tune the laser through the absorption band, the magnitude of the signal changes but its temporal behavior does not change, within the accuracy of the measurements

Picosecond laser krypton plasma emission in water window spectral range.

Czech Academy of Sciences Publication Activity Database

Vrba, Pavel; Vrbová, M.; Müller, M.; Mann, K.; Pánek, D.; Parkman, T.

2017-01-01

Roč. 24, č. 12 (2017), č. článku 123301. ISSN 1070-664X R&D Projects: GA MŠk LG15013 Institutional support: RVO:61389021 Keywords : laser plasma Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.115, year: 2016 http://aip.scitation.org/doi/10.1063/1.4998533

In-situ sequential laser transfer and laser reduction of graphene oxide films

Science.gov (United States)

Papazoglou, S.; Petridis, C.; Kymakis, E.; Kennou, S.; Raptis, Y. S.; Chatzandroulis, S.; Zergioti, I.

2018-04-01

Achieving high quality transfer of graphene on selected substrates is a priority in device fabrication, especially where drop-on-demand applications are involved. In this work, we report an in-situ, fast, simple, and one step process that resulted in the reduction, transfer, and fabrication of reduced graphene oxide-based humidity sensors, using picosecond laser pulses. By tuning the laser illumination parameters, we managed to implement the sequential printing and reduction of graphene oxide flakes. The overall process lasted only a few seconds compared to a few hours that our group has previously published. DC current measurements, X-Ray Photoelectron Spectroscopy, X-Ray Diffraction, and Raman Spectroscopy were employed in order to assess the efficiency of our approach. To demonstrate the applicability and the potential of the technique, laser printed reduced graphene oxide humidity sensors with a limit of detection of 1700 ppm are presented. The results demonstrated in this work provide a selective, rapid, and low-cost approach for sequential transfer and photochemical reduction of graphene oxide micro-patterns onto various substrates for flexible electronics and sensor applications.

High pulse energy sub-nanosecond Tm-doped fiber laser

Science.gov (United States)

Cserteg, Andras; Guillemet, Sebastien; Hernandez, Yves; Giannone, Domenico

2012-02-01

We report a core pumped thulium-doped fiber amplifier that generates 1.4 μJ pulses at 1980 nm with a repetition rate of 3.6 MHz preserving the original spectral bandwidth of the oscillator. The amplifier chain is seeded by a passively modelocked fiber laser with 5 mW output power and the pulses are stretched to 800 picoseconds. The amplifier is core pumped by a single mode erbium fiber laser. The slope efficiency is 35%. To the best of our knowledge, this is the first demonstration of sub nanosecond pulses with energies higher than 1 μJ coming out of a thulium-doped fiber amplifier.

Korea-China Joint R and D on High Energy Density Sciences using High Power Laser

International Nuclear Information System (INIS)

Kim, Cheol Jung; Nam, S. M.; Park, S. K.; Rhee, Y. J.; Lim, C. H.

2009-02-01

As to the high energy pico-second Peta Watt laser technology for fast ignition, the design of front-end and pre/main amplifier were pursued and the OPCPA technology to increase the aspect ratio by reducing the pre-pulse were developed. Furthermore, the tiled-grating technology to replace a large grating were obtained. As to the fast electron generation and propagation, a solid target was used to generate MeV class electron with TW femto-second laser and a gas cluster was also used to generate MeV class electron with PW femto-second laser at SIOM

Formation of periodic structures by laser ablation of metals in liquids

Energy Technology Data Exchange (ETDEWEB)

Kazakevich, P.V. [Wave Research Center of A.M. Prokhorov, General Physics Institute of the Russian Academy of Sciences, 38, Vavilov street, 119991 Moscow (Russian Federation)]. E-mail: pawel@kapella.gpi.ru; Simakin, A.V. [Wave Research Center of A.M. Prokhorov, General Physics Institute of the Russian Academy of Sciences, 38, Vavilov street, 119991 Moscow (Russian Federation); Shafeev, G.A. [Wave Research Center of A.M. Prokhorov, General Physics Institute of the Russian Academy of Sciences, 38, Vavilov street, 119991 Moscow (Russian Federation)

2006-04-30

Experimental results are presented on ablation of metals (W, Cu, brass and bronze) in a liquid environment (e.g., ethanol or water) by irradiation with either a pulsed copper vapor laser (0.51 {mu}m) or a pulsed Nd:YAG laser (1.06 {mu}m). The target material is ejected into surrounding liquid in the form of nanoparticles. In a certain range of laser parameters (fluence and number of laser shots) the surface of the solid target is composed of micro-cones having a regular structure. The distance between neighboring micro-cones in the structure depends on the laser spot size. The structures allow the observation of up-conversion of the laser frequency due to generation of the second harmonics in the eye retina.

Shaping of picosecond pulses for pumping optical parametric amplification

International Nuclear Information System (INIS)

Fueloep, J.A.; Krausz, F.; Major, Zs.; Horvath, B.

2006-01-01

Complete test of publication follows. The use of temporally shaped pump pulses for optical parametric amplification (OPA) is expected to facilitate an increase of efficiency and suppression of possible spectral distortions in this process, since the gain sensitively depends on the pump intensity. Our simulations confirmed such beneficial effect of temporally shaped pump pulses on the OPA process. With the aim to realize an optimized OPA stage pumped by shaped pulses, a novel method for passively shaping narrow band picosecond pulses has been developed. The method is based on the pulse-stacking principle, where replicas of the incoming pulse are created in a specially designed four-beam interferometer. The replicas are recombined with appropriate delays. The interferometer design allows for a unique flexibility in varying the pulse shape, since all relevant degrees of freedom, such as relative intensities and delays between the pulse replicas are independently adjustable. According to our calculations a pulse with a flat-top time profile would provide optimal conditions in the OPA process. Usually the pump pulse needs to be amplified in a conventional laser amplifier prior to the OPA. Our cross-correlation measurements showed that we are able to obtain shaped amplified pulses by shaping the amplifier input. Furthermore, by precompensating the distortions introduced by the amplifier we demonstrated our capability to produce amplified pulses with a flat-top time profile.

Laser-assisted patterning of double-sided adhesive tapes for optofluidic chip integration

Science.gov (United States)

Zamora, Vanessa; Janeczka, Christian; Arndt-Staufenbiel, Norbert; Havlik, George; Queisser, Marco; Schröder, Henning

2018-02-01

Portable high-sensitivity biosensors exhibit a growing demand in healthcare, food industry and environmental monitoring sectors. Optical biosensors based on photonic integration platforms are attractive candidates due to their high sensitivity, compactness and multiplexing capabilities. However, they need a low-cost and reliable integration with the microfluidic system. Laser-micropatterned double-sided biocompatible adhesive tapes are promising bonding layers for hybrid integration of an optofluidic biochip. As a part of the EU-PHOCNOSIS project, double-sided adhesive tapes have been proposed to integrate the polymer microfluidic system with the optical integrated waveguide sensor chip. Here the adhesive tape should be patterned in a micrometer scale in order to create an interaction between the sample that flows through the polymer microchannel and the photonic sensing microstructure. Three laser-assisted structuring methods are investigated to transfer microchannel patterns to the adhesive tape. The test structure design consists of a single channel with 400 μm wide, 30 mm length and two circular receivers with 3 mm radius. The best structuring results are found by using the picosecond UV laser where smooth and straight channel cross-sections are obtained. Such patterned tapes are used to bond blank polymer substrates to blank silicon substrates. As a proof of concept, the hybrid integration is tested using colored DI-water. Structuring tests related to the reduction of channel widths are also considered in this work. The use of this technique enables a simple and rapid manufacturing of narrow channels (50-60 μm in width) in adhesive tapes, achieving a cheap and stable integration of the optofluidic biochip.

Ultrashort pulse laser machining of metals and alloys

Science.gov (United States)

Perry, Michael D.; Stuart, Brent C.

2003-09-16

The invention consists of a method for high precision machining (cutting, drilling, sculpting) of metals and alloys. By using pulses of a duration in the range of 10 femtoseconds to 100 picoseconds, extremely precise machining can be achieved with essentially no heat or shock affected zone. Because the pulses are so short, there is negligible thermal conduction beyond the region removed resulting in negligible thermal stress or shock to the material beyond approximately 0.1-1 micron (dependent upon the particular material) from the laser machined surface. Due to the short duration, the high intensity (>10.sup.12 W/cm.sup.2) associated with the interaction converts the material directly from the solid-state into an ionized plasma. Hydrodynamic expansion of the plasma eliminates the need for any ancillary techniques to remove material and produces extremely high quality machined surfaces with negligible redeposition either within the kerf or on the surface. Since there is negligible heating beyond the depth of material removed, the composition of the remaining material is unaffected by the laser machining process. This enables high precision machining of alloys and even pure metals with no change in grain structure.

Detection of picosecond electrical transients in a scanning tunneling microscope

NARCIS (Netherlands)

Groeneveld, R.H.M.; Rasing, T.H.M.; Kaufmann, L.M.F.; Smalbrugge, E.; Wolter, J.H.; Melloch, M.R.; Kempen, van H.

1996-01-01

We have developed a scanning tunneling microscope using an optoelectronic switch which gates the tunneling tip current. The switch is fabricated within several tens of microns from the tip by photolithography and an accurate cleavage method. We demonstrate this approach by detecting picosecond

Dynamics of a broad-band quantum cascade laser: from chaos to coherent dynamics and mode-locking

Science.gov (United States)

Columbo, L. L.; Barbieri, S.; Sirtori, C.; Brambilla, M.

2018-02-01

The dynamics of a multimode Quantum Cascade Laser, is studied in a model based on effective semiconductor Maxwell-Bloch equations, encompassing key features for the radiationmedium interaction such as an asymmetric, frequency dependent, gain and refractive index as well as the phase-amplitude coupling provided by the Henry factor. By considering the role of the free spectral range and Henry factor, we develop criteria suitable to identify the conditions which allow to destabilize, close to threshold, the traveling wave emitted by the laser and lead to chaotic or regular multimode dynamics. In the latter case our simulations show that the field oscillations are associated to self-confined structures which travel along the laser cavity, bridging mode-locking and solitary wave propagation. In addition, we show how a RF modulation of the bias current leads to active mode-locking yielding high-contrast, picosecond pulses. Our results compare well with recent experiments on broad-band THz-QCLs and may help understanding the conditions for the generation of ultrashort pulses and comb operation in Mid-IR and THz spectral regions

Laser-based structural sensing and surface damage detection

Science.gov (United States)

Guldur, Burcu

Damage due to age or accumulated damage from hazards on existing structures poses a worldwide problem. In order to evaluate the current status of aging, deteriorating and damaged structures, it is vital to accurately assess the present conditions. It is possible to capture the in situ condition of structures by using laser scanners that create dense three-dimensional point clouds. This research investigates the use of high resolution three-dimensional terrestrial laser scanners with image capturing abilities as tools to capture geometric range data of complex scenes for structural engineering applications. Laser scanning technology is continuously improving, with commonly available scanners now capturing over 1,000,000 texture-mapped points per second with an accuracy of ~2 mm. However, automatically extracting meaningful information from point clouds remains a challenge, and the current state-of-the-art requires significant user interaction. The first objective of this research is to use widely accepted point cloud processing steps such as registration, feature extraction, segmentation, surface fitting and object detection to divide laser scanner data into meaningful object clusters and then apply several damage detection methods to these clusters. This required establishing a process for extracting important information from raw laser-scanned data sets such as the location, orientation and size of objects in a scanned region, and location of damaged regions on a structure. For this purpose, first a methodology for processing range data to identify objects in a scene is presented and then, once the objects from model library are correctly detected and fitted into the captured point cloud, these fitted objects are compared with the as-is point cloud of the investigated object to locate defects on the structure. The algorithms are demonstrated on synthetic scenes and validated on range data collected from test specimens and test-bed bridges. The second objective of

Picosecond excitation energy transfer of allophycocyanin studied in solution and in crystals.

Science.gov (United States)

Ranjbar Choubeh, Reza; Sonani, Ravi R; Madamwar, Datta; Struik, Paul C; Bader, Arjen N; Robert, Bruno; van Amerongen, Herbert

2018-03-01

Cyanobacteria perform photosynthesis with the use of large light-harvesting antennae called phycobilisomes (PBSs). These hemispherical PBSs contain hundreds of open-chain tetrapyrrole chromophores bound to different peptides, providing an arrangement in which excitation energy is funnelled towards the PBS core from where it can be transferred to photosystem I and/or photosystem II. In the PBS core, many allophycocyanin (APC) trimers are present, red-light-absorbing phycobiliproteins that covalently bind phycocyanobilin (PCB) chromophores. APC trimers were amongst the first light-harvesting complexes to be crystallized. APC trimers have two spectrally different PCBs per monomer, a high- and a low-energy pigment. The crystal structure of the APC trimer reveals the close distance (~21 Å) between those two chromophores (the distance within one monomer is ~51 Å) and this explains the ultrafast (~1 ps) excitation energy transfer (EET) between them. Both chromophores adopt a somewhat different structure, which is held responsible for their spectral difference. Here we used spectrally resolved picosecond fluorescence to study EET in these APC trimers both in crystallized and in solubilized form. We found that not all closely spaced pigment couples consist of a low- and a high-energy pigment. In ~10% of the cases, a couple consists of two high-energy pigments. EET to a low-energy pigment, which can spectrally be resolved, occurs on a time scale of tens of picoseconds. This transfer turns out to be three times faster in the crystal than in the solution. The spectral characteristics and the time scale of this transfer component are similar to what have been observed in the whole cells of Synechocystis sp. PCC 6803, for which it was ascribed to EET from C-phycocyanin to APC. The present results thus demonstrate that part of this transfer should probably also be ascribed to EET within APC trimers.

Short-pulse laser interactions with disordered materials and liquids

Energy Technology Data Exchange (ETDEWEB)

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

1995-12-31

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

Fast ion generation in femto- and picosecond laser plasma at low fluxes of heating radiation

International Nuclear Information System (INIS)

Faenov, A.Ya.; Pikuz, T.A.; Magunov, A.I.

2006-01-01

X-ray spectra from fluoroplastic targets irradiated by laser pulses with duration of 60 fs to 1 ps have been investigated experimentally. It is shown that, when the contrast of the laser pulse is sufficiently low, the effect of self-focusing of the main laser pulse in the plasma produced by the prepulse can significantly enhance the generation efficiency of fast particles. In this case, ions with energies as high as ∼1 MeV are observed at relatively low laser intensities [ru

Compact and high repetition rate Kerr-lens mode-locked 532 nm Nd:YVO4 laser

International Nuclear Information System (INIS)

Li, Zuohan; Peng, Jiying; Yuan, Ruixia; Yao, Jianquan; Zheng, Yi; Wang, Tongtong

2015-01-01

A compact and feasible CW Kerr-lens-induced mode-locked 532 nm Nd:YVO 4 laser system was experimentally demonstrated for the first time with theoretical analysis. Kerr-lens mode locking with intracavity second harmonic generation provides a promising method to generate a high-repetition-rate picosecond green laser. With an incident pump power of 6 W, the average output power of mode locking was 258 mW at a high repetition rate of 1.1 GHz. (paper)

Gas detectors for x-ray lasers

International Nuclear Information System (INIS)

Tiedtke, K.; Feldhaus, J.; Hahn, U.; Jastrow, U.; Nunez, T.; Tschentscher, T.; Bobashev, S. V.; Sorokin, A. A.; Hastings, J. B.; Moeller, S.; Cibik, L.; Gottwald, A.; Hoehl, A.; Kroth, U.; Krumrey, M.; Schoeppe, H.; Ulm, G.; Richter, M.

2008-01-01

We have developed different types of photodetectors that are based on the photoionization of a gas at a low target density. The almost transparent devices were optimized and tested for online photon diagnostics at current and future x-ray free-electron laser facilities on a shot-to-shot basis with a temporal resolution of better than 100 ns. Characterization and calibration measurements were performed in the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II in Berlin. As a result, measurement uncertainties of better than 10% for the photon-pulse energy and below 20 μm for the photon-beam position were achieved at the Free-electron LASer in Hamburg (FLASH). An upgrade for the detection of hard x-rays was tested at the Sub-Picosecond Photon Source in Stanford

Gas detectors for x-ray lasers

Science.gov (United States)

Tiedtke, K.; Feldhaus, J.; Hahn, U.; Jastrow, U.; Nunez, T.; Tschentscher, T.; Bobashev, S. V.; Sorokin, A. A.; Hastings, J. B.; Möller, S.; Cibik, L.; Gottwald, A.; Hoehl, A.; Kroth, U.; Krumrey, M.; Schöppe, H.; Ulm, G.; Richter, M.

2008-05-01

We have developed different types of photodetectors that are based on the photoionization of a gas at a low target density. The almost transparent devices were optimized and tested for online photon diagnostics at current and future x-ray free-electron laser facilities on a shot-to-shot basis with a temporal resolution of better than 100 ns. Characterization and calibration measurements were performed in the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II in Berlin. As a result, measurement uncertainties of better than 10% for the photon-pulse energy and below 20 μm for the photon-beam position were achieved at the Free-electron LASer in Hamburg (FLASH). An upgrade for the detection of hard x-rays was tested at the Sub-Picosecond Photon Source in Stanford.

Thermal annealing using ultra-short laser pulses to improve the electrical properties of Al:ZnO thin films

NARCIS (Netherlands)

Scorticati, D.; Illiberi, A.; Bor, Teunis Cornelis; Eijt, S.W.H.; Schut, H.; Römer, Gerardus Richardus, Bernardus, Engelina; Klein Gunnewiek, Michel; Lenferink, Aufrid T.M.; Kniknie, B.; Joy, R.M.; Dorenkamper, M.S.; de Lange, D.F.; Otto, Cornelis; Borsa, D.; Soppe, W.J.; Huis in 't Veld, Bert

2015-01-01

Industrial-grade Al:ZnO thin films, were annealed by UV picosecond laser irradiation in argon atmosphere. A remarkable increase of both the carrier density and electron mobility was measured, while the optical properties in the 400–1000 nm range did not change significantly. We studied the

Thermal annealing using ultra-short laser pulses to improve the electrical properties of Al:ZnO thin films

NARCIS (Netherlands)

Scorticati, D.; Illiberi, A.; Bor, T.C.; Eijt, S.W.H.; Schut, H.; Römer, G.R.B.E.; Klein Gunnewiek, M.; Lenferink, A.T.M.; Kniknie, B.J.; Mary Joy, R.; Dorenkamper, M.S.; Lange, D.F. de; Otto, C.; Borsa, D.; Soppe, W.J.; Huis in 't Veld, A.J.

2015-01-01

Abstract Industrial-grade Al:ZnO thin films, were annealed by UV picosecond laser irradiation in argon atmosphere. A remarkable increase of both the carrier density and electron mobility was measured, while the optical properties in the 400-1000 nm range did not change significantly. We studied the

Laser-matter structuration of optical and biological materials

Energy Technology Data Exchange (ETDEWEB)

Hallo, L., E-mail: hallo@celia.u-bordeaux1.fr [CELIA, Universite Bordeaux 1 (France); Mezel, C., E-mail: candice.mezel@cea.fr [CELIA, Universite Bordeaux 1 (France); CEA Le Ripault, 37260 Monts (France); Guillemot, F., E-mail: fabien.guillemot@inserm.fr [UMR 577 INSERM, Universite Bordeaux 2 (France); Chimier, B., E-mail: chimier@celia.u-bordeaux1.fr [CELIA, Universite Bordeaux 1 (France); Bourgeade, A., E-mail: antoine.bourgeade@cea.fr [CEA-CESTA, Le Barp (France); Regan, C., E-mail: regan@celia.u-bordeaux1.fr [CELIA, Universite Bordeaux 1 (France); Duchateau, G., E-mail: duchateau@celia.u-bordeaux1.fr [CELIA, Universite Bordeaux 1 (France); Souquet, A., E-mail: agnes.souquet@inserm.fr [UMR 577 INSERM, Universite Bordeaux 2 (France); Hebert, D., E-mail: david.hebert@cea.fr [CEA-CESTA, Le Barp (France)

2012-09-15

Highlights: Black-Right-Pointing-Pointer In this study we model nanomaterial structuring. Black-Right-Pointing-Pointer The laser energy deposition is discussed first. Black-Right-Pointing-Pointer Full and approximate models are discussed. Black-Right-Pointing-Pointer Dynamic material response is addressed via hydrodynamics. Black-Right-Pointing-Pointer Sild effects are accounted for - Abstract: Interaction of ultrafast laser, i.e. from the femtosecond (fs) to the nanosecond (ns) regime, with initially transparent matter may produce very high energy density hot spots in the bulk as well as at the material surface, depending on focusing conditions. In the fs regime, absorption is due to ionisation of the dielectric, which enables absorption process to begin, and then hydrodynamic to take place. In the ns regime both absorption and hydrodynamic are coupled to each other, which complexifies considerably the comprehension but matter structuration looks similar. A numerical tool including solution of 3D Maxwell equations and a rate equation for free electrons is first compared to some available simple models of laser energy absorption. Then, subsequent material deformation, i.e. structuration, is determined by solving hydrodynamic equations, including or not solid behaviour. We show that nature of the final structures strongly depends on the amount of deposited energy and on the shape of the absorption zone. Then we address some problems related to laser-matter structuration of optical and biological materials in the fs, ps and ns regimes.

Below-bandgap photoreflection spectroscopy of semiconductor laser structures

International Nuclear Information System (INIS)

Sotnikov, Aleksandr E; Chernikov, Maksim A; Ryabushkin, Oleg A; Trubenko, P; Moshegov, N; Ovchinnikov, A

2004-01-01

A new method of modulated light reflection - below-bandgap photoreflection, is considered. Unlike the conventional photoreflection method, the proposed method uses optical pumping by photons of energy smaller than the bandgap of any layer of a semiconductor structure under study. Such pumping allows one to obtain the modulated reflection spectrum for all layers of the structure without excitation of photoluminescence. This method is especially promising for the study of wide-gap semiconductors. The results of the study of semiconductor structures used in modern high-power multimode semiconductor lasers are presented. (laser applications and other topics in quantum electronics)

Selection of high-brightness, laser-driven cathodes for electron accelerators and FELS

International Nuclear Information System (INIS)

Oettinger, P.E.

1987-01-01

Very intense, low emittance pulsed beams of electrons can be generated from laser-driven cathodes either by thermionic- or photo-emission. Several hundreds of amperes of electrons per square centimeter were observed for pulse lengths up to 50 ns. A normalized beam brightness of 10 7 A/cm 2 /rad 2 has been measured. These beams can be emission-gated at the cathode surface by modulating the laser-beam. Such beam bunching will generate picosecond-to-microsecond-long pulses at the source. A variety of cathodes are described, and a method of selection for specific applications is presented

Laser measurements and nuclear structure

International Nuclear Information System (INIS)

Leander, G.A.

1982-01-01

The nuclear states amenable to laser studies are reviewed with respect to their structure. Systematic predictions are made, e.g., for magnetic moments of parity-mixed intrinsic orbitals in the Ac isotopes and for the shape of the known high-spin isomers in the Pb region

Measurements of magnetic fields generated in underdense plasmas by intense lasers

International Nuclear Information System (INIS)

Najmudin, Z.; Walton, B. R.; Mangles, S. P. D.; Dangor, A. E.; Krushelnick, K.; Fritzler, S.; Malka, V.; Faure, J.; Tatarakis, M.

2006-01-01

Measurements have been made of the magnetic field generated by the passage of high intensity short laser pulses through underdense plasmas. For a 30 fs, 1 J, 800 nm linearly-polarised laser pulse, an azimuthal magnetic field is observed at a radial extent of approximately 200 μm. The field is found to exceed 2.8 MG. For a 1 ps, 40 J, 1054 nm circularly-polarised laser pulse, a solenoidal field is observed that can exceed 7 MG. This solenoidal field is absent with linear polarised light, and hence can be considered as an Inverse Faraday effect. Both types of field are found to decay on the picosecond timescale. For both the azimuthal and solenoidal fields produced by such intense lasers, the production of energetic electrons by the interaction is thought to be vital for magnetic field generation

Ultra-intense, short pulse laser-plasma interactions with applications to the fast ignitor

International Nuclear Information System (INIS)

Wilks, S.C.; Kruer, W.L.; Young, P.E.; Hammer, J.; Tabak, M.

1995-04-01

Due to the advent of chirped pulse amplification (CPA) as an efficient means of creating ultra-high intensity laser light (I > 5x10 17 W/cm 2 ) in pulses less than a few picoseconds, new ideas for achieving ignition and gain in DT targets with less than 1 megajoule of input energy are currently being pursued. Two types of powerful lasers are employed in this scheme: (1) channeling beams and (2) ignition beams. The current state of laser-plasma interactions relating to this fusion scheme will be discussed. In particular, plasma physics issues in the ultra-intense regime are crucial to the success of this scheme. We compare simulation and experimental results in this highly nonlinear regime

UV laser cleaving of air-polymer structured fibre

NARCIS (Netherlands)

Canning, J.; Buckley, E.; Groothoff, N.; Luther-Davies, B.; Zagari, J.

2002-01-01

The demonstration of ultraviolet (UV) laser ablation technique for cleaving of air-polymer structure (APF) fiber was presented. ArF exciplex laser with an unstable resonator cavity with pulse-to-pulse intensity fluctuations was used for the study. The thermal diffusion time across a 200 µm diameter

Selective appearance of several laser-induced periodic surface structure patterns on a metal surface using structural colors produced by femtosecond laser pulses

Energy Technology Data Exchange (ETDEWEB)

Yao Jianwu; Zhang Chengyun; Liu Haiying; Dai Qiaofeng; Wu Lijun [Laboratory of Photonic Information Technology, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China); Lan, Sheng, E-mail: slan@scnu.edu.cn [Laboratory of Photonic Information Technology, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China); Gopal, Achanta Venu [Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Trofimov, Vyacheslav A.; Lysak, Tatiana M. [Department of Computational Mathematics and Cybernetics, M. V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation)

2012-07-15

Ripples with a subwavelength period were induced on the surface of a stainless steel (301 L) foil by femtosecond laser pulses. By optimizing the irradiation fluence of the laser pulses and the scanning speed of the laser beam, ripples with large amplitude ({approx}150 nm) and uniform period could be obtained, rendering vivid structural colors when illuminating the surface with white light. It indicates that these ripples act as a surface grating that diffracts light efficiently. The strong dependence of the ripple orientation on the polarization of laser light offers us the opportunity of decorating different regions of the surface with different types of ripples. As a result, different patterns can be selectively displayed with structural color when white light is irradiated on the surface from different directions. More interestingly, we demonstrated the possibility of decorating the same region with two or more types of ripples with different orientations. In this way, different patterns with spatial overlapping can be selectively displayed with structural color. This technique may find applications in the fields of anti-counterfeiting, color display, decoration, encryption and optical data storage.

Ultra-fast laser microprocessing of medical polymers for cell engineering applications

International Nuclear Information System (INIS)

Ortiz, R.; Moreno-Flores, S.; Quintana, I.; Vivanco, MdM; Sarasua, J.R.; Toca-Herrera, J.L.

2014-01-01

Picosecond laser micromachining technology (PLM) has been employed as a tool for the fabrication of 3D structured substrates. These substrates have been used as supports in the in vitro study of the effect of substrate topography on cell behavior. Different micropatterns were PLM-generated on polystyrene (PS) and poly-L-lactide (PLLA) and employed to study cellular proliferation and morphology of breast cancer cells. The laser-induced microstructures included parallel lines of comparable width to that of a single cell (which in this case is roughly 20 μm), and the fabrication of square-like compartments of a much larger area than a single cell (250,000 μm 2 ). The results obtained from this in vitro study showed that though the laser treatment altered substrate roughness, it did not noticeably affect the adhesion and proliferation of the breast cancer cells. However, pattern direction directly affected cell proliferation, leading to a guided growth of cell clusters along the pattern direction. When cultured in square-like compartments, cells remained confined inside these for eleven incubation days. According to these results, laser micromachining with ultra-short laser pulses is a suitable method to directly modify the cell microenvironment in order to induce a predefined cellular behavior and to study the effect of the physical microenvironment on cell proliferation. - Highlights: • Microstructuring of biocompatible polymers by ultra-short pulsed laser technology. • Contact guidance effect on a supracellular scale along microgrooved substrates. • Cell confinement inside square compartments. • Fabrication of a 3D microenvironment that induces predefined behavior of cells

Ultra-fast laser microprocessing of medical polymers for cell engineering applications

Energy Technology Data Exchange (ETDEWEB)

Ortiz, R. [Ultraprecision Processes Unit, Fundación IK4-TEKNIKER, Iñaki Goenaga 5, 20600, Eibar, Gipuzkoa (Spain); Moreno-Flores, S., E-mail: susana.moreno-flores@boku.ac.at [Biosurfaces Unit, CIC biomaGUNE, Po Miramón, 182, 20009, San Sebastián, Donostia (Spain); Quintana, I., E-mail: iban.quintana@tekniker.es [Ultraprecision Processes Unit, Fundación IK4-TEKNIKER, Iñaki Goenaga 5, 20600, Eibar, Gipuzkoa (Spain); Micro and Nanoengineering Unit, CIC microGUNE, Goiru Kalea 9, 20500, Arrasate-Mondragón, Gipuzkoa (Spain); Vivanco, MdM [Cell Biology and Stem Cells Unit, CIC bioGUNE, Technology Park of Bizkaia, Ed. 801A, 48160 Derio (Spain); Sarasua, J.R. [University of the Basque Country (EHU-UPV), School of Engineering, Department of Mining and Metallurgy Engineering and Materials Science, Alameda de Urquijo s/n, 48013 Bilbao (Spain); Toca-Herrera, J.L. [Biosurfaces Unit, CIC biomaGUNE, Po Miramón, 182, 20009, San Sebastián, Donostia (Spain); Micro and Nanoengineering Unit, CIC microGUNE, Goiru Kalea 9, 20500, Arrasate-Mondragón, Gipuzkoa (Spain)

2014-04-01

Picosecond laser micromachining technology (PLM) has been employed as a tool for the fabrication of 3D structured substrates. These substrates have been used as supports in the in vitro study of the effect of substrate topography on cell behavior. Different micropatterns were PLM-generated on polystyrene (PS) and poly-L-lactide (PLLA) and employed to study cellular proliferation and morphology of breast cancer cells. The laser-induced microstructures included parallel lines of comparable width to that of a single cell (which in this case is roughly 20 μm), and the fabrication of square-like compartments of a much larger area than a single cell (250,000 μm{sup 2}). The results obtained from this in vitro study showed that though the laser treatment altered substrate roughness, it did not noticeably affect the adhesion and proliferation of the breast cancer cells. However, pattern direction directly affected cell proliferation, leading to a guided growth of cell clusters along the pattern direction. When cultured in square-like compartments, cells remained confined inside these for eleven incubation days. According to these results, laser micromachining with ultra-short laser pulses is a suitable method to directly modify the cell microenvironment in order to induce a predefined cellular behavior and to study the effect of the physical microenvironment on cell proliferation. - Highlights: • Microstructuring of biocompatible polymers by ultra-short pulsed laser technology. • Contact guidance effect on a supracellular scale along microgrooved substrates. • Cell confinement inside square compartments. • Fabrication of a 3D microenvironment that induces predefined behavior of cells.

Quantum cascade laser combs: effects of modulation and dispersion.

Science.gov (United States)

Villares, Gustavo; Faist, Jérôme

2015-01-26

Frequency comb formation in quantum cascade lasers is studied theoretically using a Maxwell-Bloch formalism based on a modal decomposition, where dispersion is considered. In the mid-infrared, comb formation persists in the presence of weak cavity dispersion (500 fs2 mm-1) but disappears when much larger values are used (30'000 fs2 mm-1). Active modulation at the round-trip frequency is found to induce mode-locking in THz devices, where the upper state lifetime is in the tens of picoseconds. Our results show that mode-locking based on four-wave mixing in broadband gain, low dispersion cavities is the most promising way of achieving broadband quantum cascade laser frequency combs.

Pulsed Laser Interactions with Silicon Nano structures in Emitter Formation

International Nuclear Information System (INIS)

Huat, V.L.C.; Leong, C.S.; Kamaruzzaman Sopian, Saleem Hussain Zaidi

2015-01-01

Silicon wafer thinning is now approaching fundamental limits for wafer thickness owing to thermal expansion mismatch between Al and Si, reduced yields in wet-chemical processing as a result of fragility, and reduced optical absorption. An alternate manufacturing approach is needed to eliminate current manufacturing issues. In recent years, pulsed lasers have become readily available and costs have been significantly reduced. Pulsed laser interactions with silicon, in terms of micromachining, diffusions, and edge isolation, are well known, and have become industrial manufacturing tools. In this paper, pulsed laser interactions with silicon nano structures were identified as the most desirable solution for the fundamental limitations discussed above. Silicon nano structures have the capability for extremely high absorption that significantly reduces requirements for laser power, as well as thermal shock to the thinner wafer. Laser-assisted crystallization, in the presence of doping materials, leads to nano structure profiles that are highly desirable for sunlight absorption. The objective of this paper is the replacement of high temperature POCl_3 diffusion by laser-assisted phosphorus layers. With these improvements, complete low-temperature processing of thinner wafers was achievable with 3.7 % efficiency. Two-dimensional laser scanning was proved to be able to form uniformly annealed surfaces with higher fill factor and open-circuit voltage. (author)

Microsized structures assisted nanostructure formation on ZnSe wafer by femtosecond laser irradiation

International Nuclear Information System (INIS)

Wang, Shutong; Feng, Guoying; Zhou, Shouhuan

2014-01-01

Micro/nano patterning of ZnSe wafer is demonstrated by femtosecond laser irradiation through a diffracting pinhole. The irradiation results obtained at fluences above the ablation threshold are characterized by scanning electron microscopy. The microsized structure with low spatial frequency has a good agreement with Fresnel diffraction theory. Laser induced periodic surface structures and laser-induced periodic curvelet surface structures with high spatial frequency have been found on the surfaces of microsized structures, such as spikes and valleys. We interpret its formation in terms of the interference between the reflected laser field on the surface of the valley and the incident laser pulse

Ultrafast mid-IR laser scalpel: protein signals of the fundamental limits to minimally invasive surgery.

Science.gov (United States)

Amini-Nik, Saeid; Kraemer, Darren; Cowan, Michael L; Gunaratne, Keith; Nadesan, Puviindran; Alman, Benjamin A; Miller, R J Dwayne

2010-09-28

Lasers have in principle the capability to cut at the level of a single cell, the fundamental limit to minimally invasive procedures and restructuring biological tissues. To date, this limit has not been achieved due to collateral damage on the macroscale that arises from thermal and shock wave induced collateral damage of surrounding tissue. Here, we report on a novel concept using a specifically designed Picosecond IR Laser (PIRL) that selectively energizes water molecules in the tissue to drive ablation or cutting process faster than thermal exchange of energy and shock wave propagation, without plasma formation or ionizing radiation effects. The targeted laser process imparts the least amount of energy in the remaining tissue without any of the deleterious photochemical or photothermal effects that accompanies other laser wavelengths and pulse parameters. Full thickness incisional and excisional wounds were generated in CD1 mice using the Picosecond IR Laser, a conventional surgical laser (DELight Er:YAG) or mechanical surgical tools. Transmission and scanning electron microscopy showed that the PIRL laser produced minimal tissue ablation with less damage of surrounding tissues than wounds formed using the other modalities. The width of scars formed by wounds made by the PIRL laser were half that of the scars produced using either a conventional surgical laser or a scalpel. Aniline blue staining showed higher levels of collagen in the early stage of the wounds produced using the PIRL laser, suggesting that these wounds mature faster. There were more viable cells extracted from skin using the PIRL laser, suggesting less cellular damage. β-catenin and TGF-β signalling, which are activated during the proliferative phase of wound healing, and whose level of activation correlates with the size of wounds was lower in wounds generated by the PIRL system. Wounds created with the PIRL systsem also showed a lower rate of cell proliferation. Direct comparison of wound

Ultrafast mid-IR laser scalpel: protein signals of the fundamental limits to minimally invasive surgery.

Directory of Open Access Journals (Sweden)

Saeid Amini-Nik

2010-09-01

Full Text Available Lasers have in principle the capability to cut at the level of a single cell, the fundamental limit to minimally invasive procedures and restructuring biological tissues. To date, this limit has not been achieved due to collateral damage on the macroscale that arises from thermal and shock wave induced collateral damage of surrounding tissue. Here, we report on a novel concept using a specifically designed Picosecond IR Laser (PIRL that selectively energizes water molecules in the tissue to drive ablation or cutting process faster than thermal exchange of energy and shock wave propagation, without plasma formation or ionizing radiation effects. The targeted laser process imparts the least amount of energy in the remaining tissue without any of the deleterious photochemical or photothermal effects that accompanies other laser wavelengths and pulse parameters. Full thickness incisional and excisional wounds were generated in CD1 mice using the Picosecond IR Laser, a conventional surgical laser (DELight Er:YAG or mechanical surgical tools. Transmission and scanning electron microscopy showed that the PIRL laser produced minimal tissue ablation with less damage of surrounding tissues than wounds formed using the other modalities. The width of scars formed by wounds made by the PIRL laser were half that of the scars produced using either a conventional surgical laser or a scalpel. Aniline blue staining showed higher levels of collagen in the early stage of the wounds produced using the PIRL laser, suggesting that these wounds mature faster. There were more viable cells extracted from skin using the PIRL laser, suggesting less cellular damage. β-catenin and TGF-β signalling, which are activated during the proliferative phase of wound healing, and whose level of activation correlates with the size of wounds was lower in wounds generated by the PIRL system. Wounds created with the PIRL systsem also showed a lower rate of cell proliferation. Direct

Double pulse laser ablation and plasma: Laser induced breakdown spectroscopy signal enhancement

International Nuclear Information System (INIS)

Babushok, V.I.; DeLucia, F.C.; Gottfried, J.L.; Munson, C.A.; Miziolek, A.W.

2006-01-01

A review of recent results of the studies of double laser pulse plasma and ablation for laser induced breakdown spectroscopy applications is presented. The double pulse laser induced breakdown spectroscopy configuration was suggested with the aim of overcoming the sensitivity shortcomings of the conventional single pulse laser induced breakdown spectroscopy technique. Several configurations have been suggested for the realization of the double pulse laser induced breakdown spectroscopy technique: collinear, orthogonal pre-spark, orthogonal pre-heating and dual pulse crossed beam modes. In addition, combinations of laser pulses with different wavelengths, different energies and durations were studied, thus providing flexibility in the choice of wavelength, pulse width, energy and pulse sequence. The double pulse laser induced breakdown spectroscopy approach provides a significant enhancement in the intensity of laser induced breakdown spectroscopy emission lines up to two orders of magnitude greater than a conventional single pulse laser induced breakdown spectroscopy. The double pulse technique leads to a better coupling of the laser beam with the plasma plume and target material, thus providing a more temporally effective energy delivery to the plasma and target. The experimental results demonstrate that the maximum effect is obtained at some optimum separation delay time between pulses. The optimum value of the interpulse delay depends on several factors, such as the target material, the energy level of excited states responsible for the emission, and the type of enhancement process considered. Depending on the specified parameter, the enhancement effects were observed on different time scales ranging from the picosecond time level (e.g., ion yield, ablation mass) up to the hundred microsecond level (e.g., increased emission intensity for laser induced breakdown spectroscopy of submerged metal target in water). Several suggestions have been proposed to explain

Study of fast electron generation using multi beam of LFEX-class laser

International Nuclear Information System (INIS)

Hata, M; Nagatomo, H; Sakagami, H; Johzaki, T; Sentoku, Y

2016-01-01

Fast Ignition Realization Experiment project phase-I (FIREX-I) is being performed at Institute of Laser Engineering, Osaka University. In this project, the four-beam bundled high-energy Petawatt laser (LFEX) is being operated. LFEX laser provides great multi-beam irradiation flexibility, with the possibility of arrange the pulses in temporal sequence, spatially separate them in distinct spots of focus them in a single spot. In this paper, we study the two- beam interference effects on high-intensity picosecond laser-plasma interaction (LPI) by twodimensional relativistic Particle-In-Cell simulations. The interference causes surface perturbation, which enhances laser absorption and underdense plasma generation, increasing the accelerated electron number and their slope temperature. The laser-to-electron energy conversion efficiency for two-beam interference case is suitable for Fast Ignition (FI) compared to the single beam case, but the increment of fast electron divergence leads to lower energy coupling. To optimize the target design for FI, these interference effects should be taken into consideration. (paper)

Periodic thermodynamics of laser-driven molecular motor

International Nuclear Information System (INIS)

Li Dan; Zheng Wenwei; Wang Zhisong

2008-01-01

Operation of a laser-driven nano-motor inevitably generates a non-trivial amount of heat, which can possibly lead to instability or even hinder the motor's continual running. This work quantitatively examines the overheating problem for a recently proposed laser-operated molecular locomotive. We present a single-molecule cooling theory, in which molecular details of the locomotive system are explicitly treated. This theory is able to quantitatively predict cooling efficiency for various candidates of molecular systems for the locomotive, and also suggests concrete strategies for improving the locomotive's cooling. It is found that water environment is able to cool the hot locomotive down to room temperature within 100 picoseconds after photon absorption. This cooling time is a few orders of magnitude shorter than the typical time for laser operation, effectively preventing any overheating for the nano-locomotive. However, when the cooling is less effective in non-aqueous environment, residual heat may build up. A continuous running of the motor will then lead to a periodic thermodynamics, which is a common character of many laser-operated nano-devices

An injection modelocked Ti-sapphire laser for synchronous photoinjection

International Nuclear Information System (INIS)

Hovater, C.; Poelker, M.

1997-01-01

The CEBAF 4 GeV accelerator has recently begun delivering spin-polarized electrons for nuclear physics experiments. Spin-polarized electrons are emitted from a GaAs photocathode that is illuminated with pulsed laser light from a diode laser system synchronized to the injector chopping frequency (499 MHz). The present diode laser system is compact, reliable and relatively maintenance-free; however, output power is limited to less than 500 mW. In an effort to obtain higher average power and thereby prolong the effective operating lifetime of the source, they have constructed an injection modelocked Ti-sapphire laser with picosecond pulsewidths and gigahertz repetition rates. Modelocked operation is obtained through gain modulation within the Ti-sapphire crystal as a result of injection seeding with a gain-switched diode laser. Unlike conventional modelocked lasers, the pulse repetition rate of this laser can be discretely varied by setting the seed laser repetition rate equal to multiples of the Ti-sapphire laser cavity fundamental frequency. They observe pulse repetition rates from 223 MHz (fundamental) to 1,560 MHz (seventh harmonic) with average output power of 700 mW for all repetition rates. Pulsewidths ranged from 21 to 39 ps (FWHM) under various pump laser conditions

Measurements of plasma mirror reflectivity and focal spot quality for tens of picosecond laser pulses

Science.gov (United States)

Forestier-Colleoni, Pierre; Williams, Jackson; Scott, Graeme; Mariscal, Dereck. A.; McGuffey, Christopher; Beg, Farhat N.; Chen, Hui; Neely, David; Ma, Tammy

2017-10-01