WorldWideScience

Sample records for pulsed laser system

  1. Laser system using ultra-short laser pulses

    Science.gov (United States)

    Dantus, Marcos [Okemos, MI; Lozovoy, Vadim V [Okemos, MI; Comstock, Matthew [Milford, MI

    2009-10-27

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

  2. System for increasing laser pulse rate

    International Nuclear Information System (INIS)

    1980-01-01

    A technique of static elements is disclosed for combining a plurality of laser beams having time sequenced, pulsed radiation to achieve an augmented pulse rate. The technique may also be applied in a system for combining both time sequenced pulses and frequency distinct pulses for use in a system for isotope enrichment. (author)

  3. Short pulse laser systems for biomedical applications

    CERN Document Server

    Mitra, Kunal

    2017-01-01

    This book presents practical information on the clinical applications of short pulse laser systems and the techniques for optimizing these applications in a manner that will be relevant to a broad audience, including engineering and medical students as well as researchers, clinicians, and technicians. Short pulse laser systems are useful for both subsurface tissue imaging and laser induced thermal therapy (LITT), which hold great promise in cancer diagnostics and treatment. Such laser systems may be used alone or in combination with optically active nanoparticles specifically administered to the tissues of interest for enhanced contrast in imaging and precise heating during LITT. Mathematical and computational models of short pulse laser-tissue interactions that consider the transient radiative transport equation coupled with a bio-heat equation considering the initial transients of laser heating were developed to analyze the laser-tissue interaction during imaging and therapy. Experiments were first performe...

  4. Phase Noise Comparision of Short Pulse Laser Systems

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-12-01

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

  5. PHASE NOISE COMPARISON OF SHORT PULSE LASER SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-08-27

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

  6. New laser system for highly sensitive clinical pulse oximetry

    Science.gov (United States)

    Hamza, Mostafa; Hamza, Mohammad

    1996-04-01

    This paper describes the theory and design of a new pulse oximeter in which laser diodes and other compact laser sources are used for the measurement of oxygen saturation in patients who are at risk of developing hypoxemia. The technique depends upon illuminating special sites of the skin of the patient with radiation from modulated laser sources at selected wavelengths. The specific laser wavelengths are chosen based on the absorption characteristics of oxyhemoglobin, reduced hemoglobin and other interfering sources for obtaining more accurate measurements. The laser radiation transmitted through the tissue is detected and signal processing based on differential absorption laser spectroscopy is done in such a way to overcome the primary performance limitations of the conventionally used pulse oximetry. The new laser pulse oximeter can detect weak signals and is not affected by other light sources such as surgical lamps, phototherapy units, etc. The detailed description and operating characteristics of this system are presented.

  7. High Average Power, High Energy Short Pulse Fiber Laser System

    Energy Technology Data Exchange (ETDEWEB)

    Messerly, M J

    2007-11-13

    Recently continuous wave fiber laser systems with output powers in excess of 500W with good beam quality have been demonstrated [1]. High energy, ultrafast, chirped pulsed fiber laser systems have achieved record output energies of 1mJ [2]. However, these high-energy systems have not been scaled beyond a few watts of average output power. Fiber laser systems are attractive for many applications because they offer the promise of high efficiency, compact, robust systems that are turn key. Applications such as cutting, drilling and materials processing, front end systems for high energy pulsed lasers (such as petawatts) and laser based sources of high spatial coherence, high flux x-rays all require high energy short pulses and two of the three of these applications also require high average power. The challenge in creating a high energy chirped pulse fiber laser system is to find a way to scale the output energy while avoiding nonlinear effects and maintaining good beam quality in the amplifier fiber. To this end, our 3-year LDRD program sought to demonstrate a high energy, high average power fiber laser system. This work included exploring designs of large mode area optical fiber amplifiers for high energy systems as well as understanding the issues associated chirped pulse amplification in optical fiber amplifier systems.

  8. Feedback stabilization system for pulsed single longitudinal mode tunable lasers

    Science.gov (United States)

    Esherick, Peter; Raymond, Thomas D.

    1991-10-01

    A feedback stabilization system for pulse single longitudinal mode tunable lasers having an excited laser medium contained within an adjustable length cavity and producing a laser beam through the use of an internal dispersive element, including detection of angular deviation in the output laser beam resulting from detuning between the cavity mode frequency and the passband of the internal dispersive element, and generating an error signal based thereon. The error signal can be integrated and amplified and then applied as a correcting signal to a piezoelectric transducer mounted on a mirror of the laser cavity for controlling the cavity length.

  9. Components for monolithic fiber chirped pulse amplification laser systems

    Science.gov (United States)

    Swan, Michael Craig

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

  10. Ultrashort Laser Pulse Phenomena

    CERN Document Server

    Diels, Jean-Claude

    2006-01-01

    Ultrashort Laser Pulse Phenomena, 2e serves as an introduction to the phenomena of ultra short laser pulses and describes how this technology can be used to examine problems in areas such as electromagnetism, optics, and quantum mechanics. Ultrashort Laser Pulse Phenomena combines theoretical backgrounds and experimental techniques and will serve as a manual on designing and constructing femtosecond (""faster than electronics"") systems or experiments from scratch. Beyond the simple optical system, the various sources of ultrashort pulses are presented, again with emphasis on the basic

  11. Optimization of an Optical Parametric Chirped Pulse Amplification System for the OMEGA EP Laser System

    International Nuclear Information System (INIS)

    Begishev, I.; Bagnoud, V.; Guardalben, M.; Waxer, L.; Puth, J.; Zuegel, J.

    2003-01-01

    OAK B204 We report on the experimental achievements of the optical parametric chirped-pulse amplification (OPCPA) system, including 29% pump-to-signal conversion efficiency and 107 gain using two LBO crystals configured as a single amplification stage. Temporal and spatial shaping of the pump laser pulse is required to achieve both high-gain and high-conversion efficiency

  12. Atomic and Molecular Systems in Intense Ultrashort Laser Pulses

    Science.gov (United States)

    Saenz, A.

    2008-07-01

    The full quantum mechanical treatment of atomic and molecular systems exposed to intense laser pulses is a so far unsolved challenge, even for systems as small as molecular hydrogen. Therefore, a number of simplified qualitative and quantitative models have been introduced in order to provide at least some interpretational tools for experimental data. The assessment of these models describing the molecular response is complicated, since a comparison to experiment requires often a number of averages to be performed. This includes in many cases averaging of different orientations of the molecule with respect to the laser field, focal volume effects, etc. Furthermore, the pulse shape and even the peak intensity is experimentally not known with very high precision; considering, e.g., the exponential intensity dependence of the ionization signal. Finally, experiments usually provide only relative yields. As a consequence of all these averagings and uncertainties, it is possible that different models may successfully explain some experimental results or features, although these models disagree substantially, if their predictions are compared before averaging. Therefore, fully quantum-mechanical approaches at least for small atomic and molecular systems are highly desirable and have been developed in our group. This includes efficient codes for solving the time-dependent Schrodinger equation of atomic hydrogen, helium or other effective one- or two-electron atoms as well as for the electronic motion in linear (effective) one-and two-electron diatomic molecules like H_2.Very recently, a code for larger molecular systems that adopts the so-called single-active electron approximation was also successfully implemented and applied. In the first part of this talk popular models describing intense laser-field ionization of atoms and their extensions to molecules are described. Then their validity is discussed on the basis of quantum-mechanical calculations. Finally, some

  13. A 1J LD pumped Nd:YAG pulsed laser system

    Science.gov (United States)

    Yi, Xue-bin; Wang, Bin; Yang, Feng; Li, Jing; Liu, Ya-Ping; Li, Hui-Jun; Wang, Yu; Chen, Ren

    2017-11-01

    A 1J LD pumped Nd;YAG pulsed laser was designed. The laser uses an oscillation and two-staged amplification structure, and applies diode bar integrated array as side-pump. The TEC temperature control device combing liquid cooling system is organized to control the temperature of the laser system. This study also analyzed the theoretical threshold of working material, the effect of thermal lens and the basic principle of laser amplification. The results showed that the laser system can achieve 1J, 25Hz pulse laser output, and the laser pulse can be output at two width: 6-7ns and 10ns, respectively, and the original beam angle is 1.2mrad. The laser system is characterized by small size, light weight, as well as good stability, which make it being applied in varied fields such as photovoltaic radar platform and etc

  14. Ultrashort-pulse laser machining system employing a parametric amplifier

    Science.gov (United States)

    Perry, Michael D.

    2004-04-27

    A method and apparatus are provided for increasing the energy of chirped laser pulses to an output in the range 0.001 to over 10 millijoules at a repetition rate 0.010 to 100 kHz by using a two stage optical parametric amplifier utilizing a bulk nonlinear crystal wherein the pump and signal beam size can be independently adjusted in each stage.

  15. Study of laser pulses propagation through an ultrashort pulse amplifying systems for the development of an Offner temporal stretcher

    International Nuclear Information System (INIS)

    Cordeiro, Thiago da Silva

    2009-01-01

    The study of laser pulses propagation through an ultrashort pulses amplifying system containing dispersive and spectral modifying media was performed. The study emphasis was the development of an ultrashort pulse stretcher to replace the one inside a hybrid Ti:Sapphire/Cr:LiSAF CPA system operating at the Center for Lasers and Applications at IPEN/CNEN-SP. A spherical aberration free Offner stretcher was theoretically studied, aiming to obtain a stretching ratio larger than the one available in our system. The influence of the phase components in the amplified pulse final duration was also studied, and the bandwidth limiting elements of the system in operation were mapped, with the purpose of determining the conditions under which a new stretcher should be implemented. Based on the actual measurements, computing routines were implemented in order to determine the consequences of an ultrashort pulse travelling through a bandwidth limiting component. (author)

  16. High power ultrashort pulse lasers

    International Nuclear Information System (INIS)

    Perry, M.D.

    1994-01-01

    Small scale terawatt and soon even petawatt (1000 terawatt) class laser systems are made possible by application of the chirped-pulse amplification technique to solid-state lasers combined with the availability of broad bandwidth materials. These lasers make possible a new class of high gradient accelerators based on the large electric fields associated with intense laser-plasma interactions or from the intense laser field directly. Here, we concentrate on the laser technology to produce these intense pulses. Application of the smallest of these systems to the production of high brightness electron sources is also introduced

  17. High-power pulsed lasers

    International Nuclear Information System (INIS)

    Holzrichter, J.F.

    1980-01-01

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

  18. Pulsed Laser Shearography System for Defence Research and Education

    Science.gov (United States)

    2017-09-15

    RESEARCH AND EDUCATION PRINCIPAL INVESTIGATOR: V. ARANCHUK SECURITY CLASSIFICATION: UNCLASSIFIED 2 Table of Contents LONG-TERM GOALS...Defense Research and Education LONG-TERM GOALS The University of Mississippi purchased a pulsed digital shearography system for research...and education involving vibration analysis under the Defense University Research Instrumentation Program (DURIP). This system will be used to

  19. Synchronized femtosecond laser pulse switching system based nano-patterning technology

    Science.gov (United States)

    Sohn, Ik-Bu; Choi, Hun-Kook; Yoo, Dongyoon; Noh, Young-Chul; Sung, Jae-Hee; Lee, Seong-Ku; Ahsan, Md. Shamim; Lee, Ho

    2017-07-01

    This paper demonstrates the design and development of a synchronized femtosecond laser pulse switching system and its applications in nano-patterning of transparent materials. Due to synchronization, we are able to control the location of each irradiated laser pulse in any kind of substrate. The control over the scanning speed and scanning step of the laser beam enables us to pattern periodic micro/nano-metric holes, voids, and/or lines in various materials. Using the synchronized laser system, we pattern synchronized nano-holes on the surface of and inside various transparent materials including fused silica glass and polymethyl methacrylate to replicate any image or pattern on the surface of or inside (transparent) materials. We also investigate the application areas of the proposed synchronized femtosecond laser pulse switching system in a diverse field of science and technology, especially in optical memory, color marking, and synchronized micro/nano-scale patterning of materials.

  20. Multi-wavelength study of PPDs using an OPO tunable pulse laser microscope system

    International Nuclear Information System (INIS)

    Yoshimura, Koji; Nakamura, Isamu

    2012-01-01

    We have developed a new pulsed laser microscope system whose wavelength is continuously tunable from 410 nm to 2200 nm by using an optical parametric oscillator (OPO) laser system. The laser spot can be focused to ∼2μm diameter, small enough to measure pixel-by-pixel performance of PPDs (pixelated photon detectors). Using multi-wavelength laser light, we plan to probe PPDs at various depths, thanks to their different penetration lengths in the silicon layer. In this paper, details of the commissioning of the laser microscope system and pilot measurements on a PPD at several wavelengths will be presented.

  1. Multi-wavelength study of PPDs using an OPO tunable pulse laser microscope system

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimura, Koji, E-mail: koji.yoshimura@kek.jp [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Nakamura, Isamu [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2012-12-11

    We have developed a new pulsed laser microscope system whose wavelength is continuously tunable from 410 nm to 2200 nm by using an optical parametric oscillator (OPO) laser system. The laser spot can be focused to {approx}2{mu}m diameter, small enough to measure pixel-by-pixel performance of PPDs (pixelated photon detectors). Using multi-wavelength laser light, we plan to probe PPDs at various depths, thanks to their different penetration lengths in the silicon layer. In this paper, details of the commissioning of the laser microscope system and pilot measurements on a PPD at several wavelengths will be presented.

  2. 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)

  3. Diode-pumped, single frequency Nd:YLF laser for 60-beam OMEGA laser pulse-shaping system

    International Nuclear Information System (INIS)

    Okishev, A.V.; Seka, W.

    1997-01-01

    The operational conditions of the OMEGA pulse-shaping system require an extremely reliable and low-maintenance master oscillator. The authors have developed a diode-pumped, single-frequency, pulsed Nd:YLF laser for this application. The laser generates Q-switched pulses of ∼160-ns duration and ∼10-microJ energy content at the 1,053-nm wavelength with low amplitude fluctuations (<0.6% rms) and low temporal jitter (<7 ns rms). Amplitude and frequency feedback stabilization systems have been used for high long-term amplitude and frequency stability

  4. Laser pulse stacking method

    Science.gov (United States)

    Moses, E.I.

    1992-12-01

    A laser pulse stacking method is disclosed. A problem with the prior art has been the generation of a series of laser beam pulses where the outer and inner regions of the beams are generated so as to form radially non-synchronous pulses. Such pulses thus have a non-uniform cross-sectional area with respect to the outer and inner edges of the pulses. The present invention provides a solution by combining the temporally non-uniform pulses in a stacking effect to thus provide a more uniform temporal synchronism over the beam diameter. 2 figs.

  5. A photodiode amplifier system for pulse-by-pulse intensity measurement of an x-ray free electron laser.

    Science.gov (United States)

    Kudo, Togo; Tono, Kensuke; Yabashi, Makina; Togashi, Tadashi; Sato, Takahiro; Inubushi, Yuichi; Omodani, Motohiko; Kirihara, Yoichi; Matsushita, Tomohiro; Kobayashi, Kazuo; Yamaga, Mitsuhiro; Uchiyama, Sadayuki; Hatsui, Takaki

    2012-04-01

    We have developed a single-shot intensity-measurement system using a silicon positive-intrinsic-negative (PIN) photodiode for x-ray pulses from an x-ray free electron laser. A wide dynamic range (10(3)-10(11) photons/pulse) and long distance signal transmission (>100 m) were required for this measurement system. For this purpose, we developed charge-sensitive and shaping amplifiers, which can process charge pulses with a wide dynamic range and variable durations (ns-μs) and charge levels (pC-μC). Output signals from the amplifiers were transmitted to a data acquisition system through a long cable in the form of a differential signal. The x-ray pulse intensities were calculated from the peak values of the signals by a waveform fitting procedure. This system can measure 10(3)-10(9) photons/pulse of ~10 keV x-rays by direct irradiation of a silicon PIN photodiode, and from 10(7)-10(11) photons/pulse by detecting the x-rays scattered by a diamond film using the silicon PIN photodiode. This system gives a relative accuracy of ~10(-3) with a proper gain setting of the amplifiers for each measurement. Using this system, we succeeded in detecting weak light at the developmental phase of the light source, as well as intense light during lasing of the x-ray free electron laser. © 2012 American Institute of Physics

  6. Research on the optoacoustic communication system for speech transmission by variable laser-pulse repetition rates

    Science.gov (United States)

    Jiang, Hongyan; Qiu, Hongbing; He, Ning; Liao, Xin

    2018-06-01

    For the optoacoustic communication from in-air platforms to submerged apparatus, a method based on speech recognition and variable laser-pulse repetition rates is proposed, which realizes character encoding and transmission for speech. Firstly, the theories and spectrum characteristics of the laser-generated underwater sound are analyzed; and moreover character conversion and encoding for speech as well as the pattern of codes for laser modulation is studied; lastly experiments to verify the system design are carried out. Results show that the optoacoustic system, where laser modulation is controlled by speech-to-character baseband codes, is beneficial to improve flexibility in receiving location for underwater targets as well as real-time performance in information transmission. In the overwater transmitter, a pulse laser is controlled to radiate by speech signals with several repetition rates randomly selected in the range of one to fifty Hz, and then in the underwater receiver laser pulse repetition rate and data can be acquired by the preamble and information codes of the corresponding laser-generated sound. When the energy of the laser pulse is appropriate, real-time transmission for speaker-independent speech can be realized in that way, which solves the problem of underwater bandwidth resource and provides a technical approach for the air-sea communication.

  7. Aurora: A short-pulse multikilojoule KrF inertial fusion laser system

    International Nuclear Information System (INIS)

    Rosocha, L.A.

    1985-01-01

    Aurora is a laser system that serves as an operating technology demonstration prototype for large-scale high-energy KrF laser systems of interest for inertial fusion applications. This system will incorporate the following elements to achieve an end-to-end 248-nm laser fusion concept demonstration: an injection-locked oscillator-amplifier front end; an optical angular multiplexer to produce 96 encoded optical channels each of 5-nsec duration; a chain of four electron-beam-driven KrF laser amplifiers; automated alignment systems for beam alignment; a decoder to provide for pulse compression of some fraction of the total beam train to be delivered to target, and a target chamber to house and diagnose fusion targets. The front end configuration uses a stable resonator master oscillator to drive an injection-locked unstable resonator slave oscillator. An extension of existing technology has been used to develop an electrooptic switchout at 248 nm that produces a 5-nsec pulse from the longer slave oscillator pulse. This short pulse is amplified by a postamplifier. Using these discharge lasers, the front end then delivers at least 250 mJ of KrF laser light output to the optical encoder

  8. Method of high precision interval measurement in pulse laser ranging system

    Science.gov (United States)

    Wang, Zhen; Lv, Xin-yuan; Mao, Jin-jin; Liu, Wei; Yang, Dong

    2013-09-01

    Laser ranging is suitable for laser system, for it has the advantage of high measuring precision, fast measuring speed,no cooperative targets and strong resistance to electromagnetic interference,the measuremen of laser ranging is the key paremeters affecting the performance of the whole system.The precision of the pulsed laser ranging system was decided by the precision of the time interval measurement, the principle structure of laser ranging system was introduced, and a method of high precision time interval measurement in pulse laser ranging system was established in this paper.Based on the analysis of the factors which affected the precision of range measure,the pulse rising edges discriminator was adopted to produce timing mark for the start-stop time discrimination,and the TDC-GP2 high precision interval measurement system based on TMS320F2812 DSP was designed to improve the measurement precision.Experimental results indicate that the time interval measurement method in this paper can obtain higher range accuracy. Compared with the traditional time interval measurement system,the method simplifies the system design and reduce the influence of bad weather conditions,furthermore,it satisfies the requirements of low costs and miniaturization.

  9. Influence of Selected Parameters of XeCl Excimer Laser System on Characteristics of Radiation Pulses

    International Nuclear Information System (INIS)

    Pokora, L.; Iwanejko, L.

    1998-01-01

    We present the dependences of energy and duration of radiation pulses as well as efficiency of XeCl laser on selected parameters of the laser system such as: C 2 capacitance, the separating inductance, L S , the distance between electrodes in laser's chamber, d K and also the supply voltage, U 0 , composition, and pressure of the active-medium mixture of gases. Results of numerical computations relate to a three-component mixture of gases, He-Xe-HCl, of the active medium of the excimer laser. (author)

  10. Pulsed Blue and Ultraviolet Laser System for Fluorescence Diagnostics based on Nonlinear Frequency Conversion

    DEFF Research Database (Denmark)

    Cheng, Haynes Pak Hay

    The motivation for the current thesis work is to build a compact, efficient, pulsed, diode-pumped solid-state (DPSS) laser at 340 nm to be used for autofluorescence imaging and related cancer diagnostic experiments. By exciting endogenous fluorophores in the UV spectrum, autofluorescence imaging...... ns. Comparing this to the 9 ns relative jitter achieved in the passive system shows the performance penalty incurred in using the passive approach. Lastly, practical applications of compact semiconductor and DPSS lasers in the blue and UV spectral region are presented. A CW tapered diode at 808 nm...... applied to other wavelengths; specifically, those in the blue and UV spectral region. Using the passive synchronization technique and the optimization procedure reported for quasi-three-level lasers, a new generation of high peak power, pulsed, blue and UV laser light sources could be realized....

  11. Shaping of pulses in optical grating-based laser systems for optimal control of electrons in laser plasma wake-field accelerator

    International Nuclear Information System (INIS)

    Toth, Cs.; Faure, J.; Geddes, C.G.R.; Tilborg, J. van; Leemans, W.P.

    2003-01-01

    In typical chirped pulse amplification (CPA) laser systems, scanning the grating separation in the optical compressor causes the well know generation of linear chirp of frequency vs. time in a laser pulse, as well as a modification of all the higher order phase terms. By setting the compressor angle slightly different from the optimum value to generate the shortest pulse, a typical scan around this value will produce significant changes to the pulse shape. Such pulse shape changes can lead to significant differences in the interaction with plasmas such as used in laser wake-field accelerators. Strong electron yield dependence on laser pulse shape in laser plasma wake-field electron acceleration experiments have been observed in the L'OASIS Lab of LBNL [1]. These experiments show the importance of pulse skewness parameter, S, defined here on the basis of the ratio of the ''head-width-half-max'' (HWHM) and the ''tail-width-halfmax'' (TWHM), respectively

  12. Pulse radiolysis of liquid water using picosecond electron pulses produced by a table-top terawatt laser system

    International Nuclear Information System (INIS)

    Saleh, Ned; Flippo, Kirk; Nemoto, Koshichi; Umstadter, Donald; Crowell, Robert A.; Jonah, Charles D.; Trifunac, Alexander D.

    2000-01-01

    A laser based electron generator is shown, for the first time, to produce sufficient charge to conduct time resolved investigations of radiation induced chemical events. Electron pulses generated by focussing terawatt laser pulses into a supersonic helium gas jet are used to ionize liquid water. The decay of the hydrated electrons produced by the ionizing electron pulses is monitored with 0.3 μs time resolution. Hydrated electron concentrations as high as 22 μM were generated. The results show that terawatt lasers offer both an alternative to linear accelerators and a means to achieve subpicosecond time resolution for pulse radiolysis studies. (c) 2000 American Institute of Physics

  13. Laser beam diagnostics for kilowatt power pulsed YAG laser

    International Nuclear Information System (INIS)

    Liu, Yi; Leong, Keng H.

    1992-01-01

    There is a growing need for high power YAG laser beam diagnostics with the recent introduction of such lasers in laser material processing. In this paper, we will describe the use of a commercially available laser beam analyzer (Prometec) to profile the laser beam from a 1600 W pulsed Nd:YAG laser that has a 1 mm fiber optic beam delivery system. The selection of laser pulse frequency and pulse width for the measurement is discussed. Laser beam propagation parameters by various optical components such as fibers and lenses can be determined from measurements using this device. The importance of such measurements will be discussed

  14. High-Average-Power Diffraction Pulse-Compression Gratings Enabling Next-Generation Ultrafast Laser Systems

    Energy Technology Data Exchange (ETDEWEB)

    Alessi, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-11-01

    Pulse compressors for ultrafast lasers have been identified as a technology gap in the push towards high peak power systems with high average powers for industrial and scientific applications. Gratings for ultrashort (sub-150fs) pulse compressors are metallic and can absorb a significant percentage of laser energy resulting in up to 40% loss as well as thermal issues which degrade on-target performance. We have developed a next generation gold grating technology which we have scaled to the petawatt-size. This resulted in improvements in efficiency, uniformity and processing as compared to previous substrate etched gratings for high average power. This new design has a deposited dielectric material for the grating ridge rather than etching directly into the glass substrate. It has been observed that average powers as low as 1W in a compressor can cause distortions in the on-target beam. We have developed and tested a method of actively cooling diffraction gratings which, in the case of gold gratings, can support a petawatt peak power laser with up to 600W average power. We demonstrated thermo-mechanical modeling of a grating in its use environment and benchmarked with experimental measurement. Multilayer dielectric (MLD) gratings are not yet used for these high peak power, ultrashort pulse durations due to their design challenges. We have designed and fabricated broad bandwidth, low dispersion MLD gratings suitable for delivering 30 fs pulses at high average power. This new grating design requires the use of a novel Out Of Plane (OOP) compressor, which we have modeled, designed, built and tested. This prototype compressor yielded a transmission of 90% for a pulse with 45 nm bandwidth, and free of spatial and angular chirp. In order to evaluate gratings and compressors built in this project we have commissioned a joule-class ultrafast Ti:Sapphire laser system. Combining the grating cooling and MLD technologies developed here could enable petawatt laser systems to

  15. Pulse propagation properties in high-power CO2 laser system for laser fusion

    International Nuclear Information System (INIS)

    Daido, H.; Inoue, M.; Fujita, H.; Matoba, M.; Nakai, S.

    1981-01-01

    The simulation results of nonlinear propagation properties in the CO 2 laser system using a simulation model of the SF 6 saturable absorbers and the CO 2 laser amplifiers agree well with the experimental results. The technical problems of the simultaneous irradiation of the multi-beams to a target are also discussed. (author)

  16. Pulsed inductive HF laser

    Energy Technology Data Exchange (ETDEWEB)

    Razhev, A M; Kargapol' tsev, E S [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation); Churkin, D S; Demchuk, S V [Novosibirsk State University, Novosibirsk (Russian Federation)

    2016-03-31

    We report the results of experimentally investigated dependences of temporal, spectral and spatial characteristics of an inductive HF-laser generation on the pump conditions. Gas mixtures H{sub 2} – F{sub 2}(NF{sub 3} or SF6{sub 6}) and He(Ne) – H{sub 2} – F{sub 2}(NF{sub 3} or SF{sub 6}) were used as active media. The FWHM pulse duration reached 0.42 μs. This value corresponded to a pulsed power of 45 kW. For the first time, the emission spectrum of an inductive HF laser was investigated, which consisted of seven groups of bands with centres around the wavelengths of 2732, 2736, 2739, 2835, 2837, 2893 and 2913 nm. The cross section profile of the laser beam was a ring with a diameter of about 20 mm and width of about 5 mm. Parameters of laser operation in the repetitively pulsed regime were sufficiently stable. The amplitude instability of light pulses was no greater than 5% – 6%. (lasers)

  17. Pulsed atomic soliton laser

    International Nuclear Information System (INIS)

    Carr, L.D.; Brand, J.

    2004-01-01

    It is shown that simultaneously changing the scattering length of an elongated, harmonically trapped Bose-Einstein condensate from positive to negative and inverting the axial portion of the trap, so that it becomes expulsive, results in a train of self-coherent solitonic pulses. Each pulse is itself a nondispersive attractive Bose-Einstein condensate that rapidly self-cools. The axial trap functions as a waveguide. The solitons can be made robustly stable with the right choice of trap geometry, number of atoms, and interaction strength. Theoretical and numerical evidence suggests that such a pulsed atomic soliton laser can be made in present experiments

  18. Hohlraum glint and laser pre-pulse detector for NIF experiments using velocity interferometer system for any reflector.

    Science.gov (United States)

    Moody, J D; Clancy, T J; Frieders, G; Celliers, P M; Ralph, J; Turnbull, D P

    2014-11-01

    Laser pre-pulse and early-time laser reflection from the hohlraum wall onto the capsule (termed "glint") can cause capsule imprint and unwanted early-time shocks on indirect drive implosion experiments. In a minor modification to the existing velocity interferometer system for any reflector diagnostic on NIF a fast-response vacuum photodiode was added to detect this light. The measurements show evidence of laser pre-pulse and possible light reflection off the hohlraum wall and onto the capsule.

  19. Nano-pulsed laser irradiation scanning system for phase-change materials

    International Nuclear Information System (INIS)

    Kim, Sookyung; Li Xuezhe; Lee, Sangbin; Kim, Kyung-Ho; Lee, Seung-Yop

    2008-01-01

    Recently, the demand of a laser irradiation tester is increasing for phase change random access memory (PRAM) as well as conventional optical storage media. In this study, a nano-pulsed laser irradiation system is developed to characterize the optical property and writing performance of phase-change materials, based on a commercially available digital versatile disk (DVD) optical pick-up. The precisely controlled focusing and scanning on the material's surface are implemented using the auto-focusing mechanism and a voice coil motor (VCM) of the commercial DVD pick-up. The laser irradiation system provides various writing and reading functions such as adjustable laser power, pulse duration, recording pattern (spot, line and area), and writing/reading repetition, phase transition, and in situ reflectivity measurement before/after irradiation. Measurements of power time effect (PTE) diagram and reflectivity map of Ge 2 Sb 2 Te 5 samples show that the proposed laser irradiation system provides the powerful scanning tool to quantify the optical characteristics of phase-change materials

  20. Wavefront Tilt And Beam Walk Correction For A Pulsed Laser System

    Science.gov (United States)

    Bartosewcz, Mike; Tyburski, Joe

    1986-05-01

    The Lockheed Beam Alignment Assembly (BAA) is designed to be a space qualifiable, long life, low bandwidth beam stabilization system. The BAA will stabilize a wandering pulsed laser beam with an input beam tilt of ±750 microradians and translation of ±2.5 mm by two orders of magnitude at the bandwidth of interest. A bandwidth of three hertz was selected to remove laser and optical train thermal drifts and launch induced strain effects. The lambda over twenty RMS wavefront will be maintained in the optics at full power under vacuum test, to demonstrate space qualifiability and optical performance.

  1. Heat generation caused by ablation of dental hard tissues with an ultrashort pulse laser (USPL) system.

    Science.gov (United States)

    Braun, Andreas; Krillke, Raphael Franz; Frentzen, Matthias; Bourauel, Christoph; Stark, Helmut; Schelle, Florian

    2015-02-01

    Heat generation during the removal of dental hard tissues may lead to a temperature increase and cause painful sensations or damage dental tissues. The aim of this study was to assess heat generation in dental hard tissues following laser ablation using an ultrashort pulse laser (USPL) system. A total of 85 specimens of dental hard tissues were used, comprising 45 specimens of human dentine evaluating a thickness of 1, 2, and 3 mm (15 samples each) and 40 specimens of human enamel with a thickness of 1 and 2 mm (20 samples each). Ablation was performed with an Nd:YVO4 laser at 1,064 nm, a pulse duration of 9 ps, and a repetition rate of 500 kHz with an average output power of 6 W. Specimens were irradiated for 0.8 s. Employing a scanner system, rectangular cavities of 1-mm edge length were generated. A temperature sensor was placed at the back of the specimens, recording the temperature during the ablation process. All measurements were made employing a heat-conductive paste without any additional cooling or spray. Heat generation during laser ablation depended on the dental hard tissue (enamel or dentine) and the thickness of the respective tissue (p dental hard tissues, heat generation has to be considered. Especially during laser ablation next to pulpal tissues, painful sensations and potential thermal injury of pulp tissue might occur.

  2. Electra: Repetitively Pulsed Angularly Multiplexed KrF Laser System Performance

    Science.gov (United States)

    Wolford, Matthew; Myers, Matthew; Giuliani, John; Sethian, John; Burns, Patrick; Hegeler, Frank; Jaynes, Reginald

    2008-11-01

    As in a full size fusion power plant beam line, Electra is a multistage laser amplifier system. The multistage amplifier system consists of a commercial discharge laser and two doubled sided electron beam pumped amplifiers. Angular multiplexing is used in the optical layout to provide pulse length control and to maximize laser extraction from the amplifiers. Two angularly multiplexed beams have extracted 30 J of KrF laser light with an aperture 8 x 10 cm^2, which is sufficient to extract over 500 J from the main amplifier and models agree. The main amplifier of Electra in oscillator mode has demonstrated single shot and rep-rate laser energies exceeding 700 J with 100 ns pulsewidth at 248 nm with an aperture 29 x 29 cm^2. Continuous operation of the KrF electron beam pumped oscillator has lasted for more than 2.5 hours without failure at 1 Hz and 2.5 Hz. The measured intensity and pulse energy for durations greater than thousand shots are consistent at measurable rep-rates of 1 Hz, 2.5 Hz and 5 Hz.

  3. Evaluation of a high power submillimeter pulsed laser system

    International Nuclear Information System (INIS)

    Vander Sluis, K.L.; Hutchinson, D.P.; Staats, P.A.

    1980-01-01

    This report describes the selection, development, and testing of the system components and presents the power and frequency profiles achieved in tests made on the assembled system. These results, and knowledge gained through design and development work, have suggested improvements in design characteristics to be applied to future research on this diagnostic method

  4. Reactive pulsed laser deposition with gas jet

    International Nuclear Information System (INIS)

    Rakowski, R.; Bartnik, A.; Fiedorowicz, H.; Jarocki, R.; Kostecki, J.; Szczurek, M.

    2001-01-01

    Different metal (Sn, Al, steel, Cu, W) thin films were synthesized by reactive pulsed laser deposition on steel, copper and glass wafers. In our work pulsed Nd:glass (10 J, 800μs) laser system was used. Jet of gas was created by electromagnetic valve perpendicularly to the laser beam. Nitrogen, oxygen and argon were used. We used several to tens laser shots to obtain visible with the naked eye layers. Thin layers were observed under an optical microscope. (author)

  5. Evaluation of dynamic range for LLNL streak cameras using high contrast pulsed and pulse podiatry on the Nova laser system

    International Nuclear Information System (INIS)

    Richards, J.B.; Weiland, T.L.; Prior, J.A.

    1990-01-01

    This paper reports on a standard LLNL streak camera that has been used to analyze high contrast pulses on the Nova laser facility. These pulses have a plateau at their leading edge (foot) with an amplitude which is approximately 1% of the maximum pulse height. Relying on other features of the pulses and on signal multiplexing, we were able to determine how accurately the foot amplitude was being represented by the camera. Results indicate that the useful single channel dynamic range of the instrument approaches 100:1

  6. High energy HF pulsed lasers

    International Nuclear Information System (INIS)

    Patterson, E.L.; Gerber, R.A.

    1976-01-01

    Recent experiments show that pulsed HF lasers are capable of producing high energy with good efficiency. Preliminary experiments show that the laser radiation from the high-gain medium can be controlled with a low-power probe laser beam or with low-level feedback. These results indicate that the HF laser may have potential for second-generation laser fusion experiments

  7. Performance of a high repetition pulse rate laser system for in-gas-jet laser ionization studies with the Leuven laser ion source LISOL

    International Nuclear Information System (INIS)

    Ferrer, R.; Sonnenschein, V.T.; Bastin, B.; Franchoo, S.; Huyse, M.; Kudryavtsev, Yu.; Kron, T.; Lecesne, N.; Moore, I.D.; Osmond, B.; Pauwels, D.; Radulov, D.; Raeder, S.; Rens, L.

    2012-01-01

    The laser ionization efficiency of the Leuven gas cell-based laser ion source was investigated under on- and off-line conditions using two distinctly different laser setups: a low-repetition rate dye laser system and a high-repetition rate Ti:sapphire laser system. A systematic study of the ion signal dependence on repetition rate and laser pulse energy was performed in off-line tests using stable cobalt and copper isotopes. These studies also included in-gas-jet laser spectroscopy measurements on the hyperfine structure of 63 Cu. A final run under on-line conditions in which the radioactive isotope 59 Cu (T 1/2 = 81.5 s) was produced, showed a comparable yield of the two laser systems for in-gas-cell ionization. However, a significantly improved time overlap by using the high-repetition rate laser system for in-gas-jet ionization was demonstrated by an increase of the overall duty cycle, and at the same time, pointed to the need for a better shaped atomic jet to reach higher ionization efficiencies.

  8. Single- and dual-wavelength laser pulses induced modification in 10×(Al/Ti)/Si multilayer system

    Energy Technology Data Exchange (ETDEWEB)

    Salatić, B. [University of Belgrade, Institute of Physics Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Petrović, S., E-mail: spetro@vinca.rs [University of Belgrade, Institute of Nuclear Science-Vinča, POB 522, 11001 Belgrade (Serbia); Peruško, D. [University of Belgrade, Institute of Nuclear Science-Vinča, POB 522, 11001 Belgrade (Serbia); Čekada, M.; Panjan, P. [Jožef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Pantelić, D.; Jelenković, B. [University of Belgrade, Institute of Physics Belgrade, Pregrevica 118, 11080 Belgrade (Serbia)

    2016-01-01

    Graphical abstract: - Highlights: • Experimental and numerical study of laser-induced ablation and micro-sized crater formation. • Dual-wavelength pulses induce creation of wider and deeper craters due to synergies of two processes. • Sunflower-like structure formed by dual-wavelength pulses at low irradiance. • Numerical model of nanosecond pulsed laser ablation for complex (Al/Ti)/Si system has been developed. - Abstract: The surface morphology of the ablation craters created in the multilayer 10×(Al/Ti)/Si system by nanosecond laser pulses at single- and dual wavelength has been studied experimentally and numerically. A complex multilayer thin film including ten (Al/Ti) bilayers deposited by ion sputtering on Si(1 0 0) substrate to a total thickness of 260 nm were illuminated at different laser irradiance in the range 0.25–3.5 × 10{sup 9} W cm{sup −2}. Single pulse laser irradiation was done at normal incidence in air, with the single wavelength, either at 532 nm or 1064 nm or with both laser light simultaneously in the ratio of 1:10 for energy per pulse between second harmonic and 1064 nm. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the sample surface. The results show an increase in surface roughness, formation of specific nanostructures, appearance of hydrodynamic features and ablation of surface material with crater formation. Applying a small fraction (10%) of the second harmonic in dual-wavelength pulses, a modification of the 10×(Al/Ti)/Si system by a single laser pulse was reflected in the formation of wider and/or deeper craters. Numerical calculations show that the main physical mechanism in ablation process is normal evaporation without phase explosion. The calculated and experimental results agree relatively well for the whole irradiance range, what makes the model applicable to complex Al/Ti multilayer systems.

  9. Coaxial short pulsed laser

    Science.gov (United States)

    Nelson, M.A.; Davies, T.J.

    1975-08-01

    This invention relates to a laser system of rugged design suitable for use in a field environment. The laser itself is of coaxial design with a solid potting material filling the space between components. A reservoir is employed to provide a gas lasing medium between an electrode pair, each of which is connected to one of the coaxial conductors. (auth)

  10. 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.

  11. Development of novel solvent extraction system by utilizing the metal ions excitation with ultraviolet pulse laser

    International Nuclear Information System (INIS)

    Saeki, Morihisa; Sasaki, Yuji; Yokoyama, Atsushi

    2010-01-01

    Novel liquid-liquid extraction technique was developed using ultraviolet pulse laser. The liquid-liquid system was composed of pure water and the 1-octanol solution of EuCl 3 and TODGA (TODGA = N,N,N',N'-tetraoctyl-diglycolamide). The Eu 3+ ion, which was formed to be the Eu 3+ (TODGA) n complex in 1-octanol, was reduced to Eu 2+ by irradiation of fourth harmonic of Nd:YAG laser (266 nm). The Eu 2+ ion was stabilized by addition of 15-Crown-5 (15C5). The observation by in-situ emission spectroscopy showed that the Eu 2+ ion reduced by the 266 nm-laser irradiation resulted in back-extraction of Eu from the 1-octanol solution to the water. The emission spectrum observed in 1-octanol suggested the change from the Eu 3+ (TODGA) n to the Eu 2+ (15C5) m complex after the reduction by the 266 nm laser. Time dependence of the concentration of Eu 2+ (15C5) m was investigated at the aqueous phase, the organic one and their interface. The results suggest that (1) rapid formation of Eu 2+ (15C5) m in 1-octanol after the irradiation of the 266 nm laser, (2) slow diffusion of Eu 2+ (15C5) m in 1-octanol, and (3) existence of time-lag between the formation of Eu 2+ (15C5) m in 1-octanol and its back-extraction to the water. (author)

  12. Fast Prototyping of Sensorized Cell Culture Chips and Microfluidic Systems with Ultrashort Laser Pulses

    Directory of Open Access Journals (Sweden)

    Sebastian M. Bonk

    2015-03-01

    Full Text Available We developed a confined microfluidic cell culture system with a bottom plate made of a microscopic slide with planar platinum sensors for the measurement of acidification, oxygen consumption, and cell adhesion. The slides were commercial slides with indium tin oxide (ITO plating or were prepared from platinum sputtering (100 nm onto a 10-nm titanium adhesion layer. Direct processing of the sensor structures (approximately three minutes per chip by an ultrashort pulse laser facilitated the production of the prototypes. pH-sensitive areas were produced by the sputtering of 60-nm Si3N4 through a simple mask made from a circuit board material. The system body and polydimethylsiloxane (PDMS molding forms for the microfluidic structures were manufactured by micromilling using a printed circuit board (PCB milling machine for circuit boards. The microfluidic structure was finally imprinted in PDMS. Our approach avoided the use of photolithographic techniques and enabled fast and cost-efficient prototyping of the systems. Alternatively, the direct production of metallic, ceramic or polymeric molding tools was tested. The use of ultrashort pulse lasers improved the precision of the structures and avoided any contact of the final structures with toxic chemicals and possible adverse effects for the cell culture in lab-on-a-chip systems.

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

    Energy Technology Data Exchange (ETDEWEB)

    Galletti, Mario, E-mail: mario.gall22@gmail.com [INFN – LNF, Via Enrico Fermi 40, 00044 Frascati (Italy); Galimberti, Marco [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Hooker, Chris [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); University of Oxford, Oxford (United Kingdom); Chekhlov, Oleg; Tang, Yunxin [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Bisesto, Fabrizio Giuseppe [INFN – LNF, Via Enrico Fermi 40, 00044 Frascati (Italy); Curcio, Alessandro [INFN – LNF, Via Enrico Fermi 40, 00044 Frascati (Italy); Sapienza – University of Rome, P.le Aldo Moro, 2, 00185 Rome (Italy); Anania, Maria Pia [INFN – LNF, Via Enrico Fermi 40, 00044 Frascati (Italy); Giulietti, Danilo [Physics Department of the University and INFN, Pisa (Italy)

    2016-09-01

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

  14. Method for pulse control in a laser including a stimulated brillouin scattering mirror system

    Science.gov (United States)

    Dane, C. Brent; Hackel, Lloyd; Harris, Fritz B.

    2007-10-23

    A laser system, such as a master oscillator/power amplifier system, comprises a gain medium and a stimulated Brillouin scattering SBS mirror system. The SBS mirror system includes an in situ filtered SBS medium that comprises a compound having a small negative non-linear index of refraction, such as a perfluoro compound. An SBS relay telescope having a telescope focal point includes a baffle at the telescope focal point which blocks off angle beams. A beam splitter is placed between the SBS mirror system and the SBS relay telescope, directing a fraction of the beam to an alternate beam path for an alignment fiducial. The SBS mirror system has a collimated SBS cell and a focused SBS cell. An adjustable attenuator is placed between the collimated SBS cell and the focused SBS cell, by which pulse width of the reflected beam can be adjusted.

  15. UV saturable absorber for short-pulse KrF laser systems.

    Science.gov (United States)

    Nishioka, H; Kuranishi, H; Ueda, K; Takuma, H

    1989-07-01

    A derivative of the linear tricyclic compound, acridine, is shown to be useful as a saturable absorber for short-pulse KrF lasers. The saturation characteristics and absorption recovery of a methanol solution of acridine for a 20-psec KrF laser pulse are reported. We obtain a saturation fluence of 1.2 mJ/cm(2) and a ratio of the primary to the excited absorption cross section of 6.25:1.

  16. UV saturable absorber for short-pulse KrF laser systems

    Energy Technology Data Exchange (ETDEWEB)

    Nishioka, H.; Kuranishi, H.; Ueda, K.; Takuma, H.

    1989-07-01

    A derivative of the linear tricyclic compound, acridine, is shown to beuseful as a saturable absorber for short-pulse KrF lasers. The saturationcharacteristics and absorption recovery of a methanol solution of acridine for a20-psec KrF laser pulse are reported. We obtain a saturation fluence of 1.2mJ/cm/sup 2/ and a ratio of the primary to the excited absorption cross sectionof 6.25:1.

  17. 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...

  18. Propagating Characteristics of Pulsed Laser in Rain

    Directory of Open Access Journals (Sweden)

    Jing Guo

    2015-01-01

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

  19. Erbium:ytterbium fiber-laser system delivering watt-level femtosecond pulses using divided pulse amplification

    Science.gov (United States)

    Herda, Robert; Zach, Armin

    2015-03-01

    We present an Erbium:Ytterbium codoped fiber-amplifer system based on Divided-Pulses-Amplification (DPA) for ultrashort pulses. The output from a saturable-absorber mode-locked polarization-maintaining (PM) fiber oscillator is amplified in a PM normal-dispersion Erbium-doped fiber. After this stage the pulses are positively chirped and have a duration of 2.0 ps at an average power of 93 mW. A stack of 5 birefringent Yttrium-Vanadate crystals divides these pulses 32 times. We amplify these pulses using a double-clad Erbium:Ytterbium codoped fiber pumped through a multimode fiber combiner. The pulses double pass the amplifier and recombine in the crystals using non-reciprocal polarization 90° rotation by a Faraday rotating mirror. Pulses with a duration of 144 fs are obtained after separation from the input beam using a polarizing beam splitter cube. These pulses have an average power of 1.85 W at a repetition rate of 80 MHz. The generation of femtosecond pulses directly from the amplifier was enabled by a positively chirped seed pulse, normally dispersive Yttrium-Vanadate crystals, and anomalously dispersive amplifier fibers. Efficient frequency doubling to 780 nm with an average power of 725 mW and a pulse duration of 156 fs is demonstrated. In summary we show a DPA setup that enables the generation of femtosecond pulses at watt-level at 1560 nm without the need for further external dechirping and demonstrate a good pulse quality by efficient frequency doubling. Due to the use of PM fiber components and a Faraday rotator the setup is environmentally stable.

  20. Development of a yearlong maintenance-free terawatt Ti:Sapphire laser system with a 3D UV-pulse shaping system for THG

    International Nuclear Information System (INIS)

    Tomizawa, H; Dewa, H; Hanaki, H; Matsui, F

    2007-01-01

    Laser sources that feature a controlled pulse shape and long-term stability are required in a wide range of scientific fields. We developed a maintenance-free 3D-shaped UV-laser system for the photoinjector (RF gun photocathode) of an X-ray SASE free electron laser (FEL). The laser pulse-energy stability was improved to 0.2%-0.3% (rms, 10 pps, 0.4 TW in femtosecond operation) at the fundamental wavelength and to 0.7%-1.4% at the third-harmonic wavelength. This stability was continuously maintained for five months, 24 hours a day. Such improvement reflects an ability to stabilise the laser system in a humidity-controlled clean room. The pulse-energy stability of a mode-locked femtosecond oscillator was continuously held at 0.3% (p-p) for five months, 24 hours a day. In addition, the ideal spatial and temporal profiles of a shot-by-shot single UV-laser pulse are essential to suppress the emittance of the electron-beam pulse generated by the photocathode of the RF gun. We apply a deformable mirror that automatically shapes the spatial UV-laser profile with a feedback routine, based on a genetic algorithm, and a pulse stacker for temporal shaping at the same time. The 3D shape of the laser pulse is spatially top-hat (flattop) and temporally - a square stacked pulse. We apply the Q-scan method to evaluate the emittance of the electron beam generated by a 3D-shaped laser pulse. By using a 3D-shaped laser pulse of diameter 0.8 mm on the cathode and duration 10 ps (FWHM), we obtain a minimum horizontal normalised emittance of 1.4π mm mrad with beam energy of 26 MeV, holding its net charge to a 0.4 nC pulse -1 . At a higher net charge of 1.0 nC pulse -1 , the minimum beam emittance is 2.3π mm mrad with equivalent diameter and a longer pulse duration of 20 ps (FWHM). In this study, we demonstrate 3D shaping [both temporal (1D) and spatial (2D)] short pulse (5-20ps) laser beam as an ideal light source for yearlong stable generation of a low emittance electron beam with a

  1. Portable double-sided pulsed laser heating system for time-resolved geoscience and materials science applications.

    Science.gov (United States)

    Aprilis, G; Strohm, C; Kupenko, I; Linhardt, S; Laskin, A; Vasiukov, D M; Cerantola, V; Koemets, E G; McCammon, C; Kurnosov, A; Chumakov, A I; Rüffer, R; Dubrovinskaia, N; Dubrovinsky, L

    2017-08-01

    A portable double-sided pulsed laser heating system for diamond anvil cells has been developed that is able to stably produce laser pulses as short as a few microseconds with repetition frequencies up to 100 kHz. In situ temperature determination is possible by collecting and fitting the thermal radiation spectrum for a specific wavelength range (particularly, between 650 nm and 850 nm) to the Planck radiation function. Surface temperature information can also be time-resolved by using a gated detector that is synchronized with the laser pulse modulation and space-resolved with the implementation of a multi-point thermal radiation collection technique. The system can be easily coupled with equipment at synchrotron facilities, particularly for nuclear resonance spectroscopy experiments. Examples of applications include investigations of high-pressure high-temperature behavior of iron oxides, both in house and at the European Synchrotron Radiation Facility using the synchrotron Mössbauer source and nuclear inelastic scattering.

  2. A phase stabilized and pulse shaped Ti:Sapphire oscillator-amplifier laser system for the LCLS rf photoinjector

    International Nuclear Information System (INIS)

    Kotseroglou, T.; Alley, R.; Clendenin, J.; Fisher, A.; Frisch, J.

    1998-04-01

    The authors have designed a laser system for the Linac Coherent Light Source rf photoinjector consisting of a Ti:Sapphire oscillator and 2 amplifiers using Chirped Pulse Amplification. The output after tripling will be 0.5 mJ tunable UV pulses at 120 Hz, with wavelength around 260 nm, pulsewidth of 10 ps FWHM and 200 fs rise and fall times. Amplitude stability is expected to be 1% rms in the UV and timing jitter better than 500 fs rms

  3. Characterization of silicon microstrip sensors with a pulsed infrared laser system for the CBM experiment at FAIR

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Pradeep [Goethe Univ., Frankfurt (Germany); GSI (Germany); Eschke, Juergen [GSI (Germany); FAIR (Germany); Collaboration: CBM-Collaboration

    2014-07-01

    The Silicon Tracking System (STS) for the Compressed Baryonic Matter (CBM) experiment at FAIR will comprise more than 1200 double-sided silicon microstrip sensors. For the quality assurance of the prototype sensors a laser test system has been built up. The aim of the sensor scans with the pulsed infrared laser system is to determine the charge sharing between strips and to measure the uniformity of the sensor response over the whole active area. The laser system measures the sensor response in an automatized procedure at several thousand positions across the sensor with focused infrared laser light (σ∼15 μm, λ=1060 nm). The duration (5 ns) and power (few mW) of the laser pulses are selected such, that the absorption of the laser light in the 300 μm thick silicon sensors produces a number of about 24k electrons, which is similar to the charge created by minimum ionizing particles in these sensors. Results from the characterization of monolithic active pixel sensors, to understand the spot-size of the laser, and laser scans for different sensors are presented.

  4. Computer control of pulsed tunable dye lasers

    International Nuclear Information System (INIS)

    Thattey, S.S.; Dongare, A.S.; Suri, B.M.; Nair, L.G.

    1992-01-01

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

  5. Hybrid Pulsed Nd:YAG Laser

    Science.gov (United States)

    Miller, Sawyer; Trujillo, Skyler; Fort Lewis College Laser Group Team

    This work concerns the novel design of an inexpensive pulsed Nd:YAG laser, consisting of a hybrid Kerr Mode Lock (KLM) and Q-switch pulse. The two pulse generation systems work independently, non simultaneously of each other, thus generating the ability for the user to easily switch between ultra-short pulse widths or large energy density pulses. Traditionally, SF57 glass has been used as the Kerr medium. In this work, novel Kerr mode-locking mediums are being investigated including: tellurite compound glass (TeO2), carbon disulfide (CS2), and chalcogenide glass. These materials have a nonlinear index of refraction orders of magnitude,(n2), larger than SF57 glass. The Q-switched pulse will utilize a Pockels cell. As the two pulse generation systems cannot be operated simultaneously, the Pockels cell and Kerr medium are attached to kinematic mounts, allowing for quick interchange between systems. Pulse widths and repetition rates will vary between the two systems. A goal of 100 picosecond pulse widths are desired for the mode-locked system. A goal of 10 nanosecond pulse widths are desired for the Q-switch system, with a desired repetition rate of 50 Hz. As designed, the laser will be useful in imaging applications.

  6. Metal processing with ultrashort laser pulses

    Science.gov (United States)

    Banks, Paul S.; Felt, M. D.; Komashko, Aleksey M.; Perry, Michael D.; Rubenchik, Alexander M.; Stuart, Brent C.

    2000-08-01

    Femtosecond laser ablation has been shown to produce well-defined cuts and holes in metals with minimal heat effect to the remaining material. Ultrashort laser pulse processing shows promise as an important technique for materials processing. We will discuss the physical effects associated with processing based experimental and modeling results. Intense ultra-short laser pulse (USLP) generates high pressures and temperatures in a subsurface layer during the pulse, which can strongly modify the absorption. We carried out simulations of USLP absorption versus material and pulse parameters. The ablation rate as function of the laser parameters has been estimated. Since every laser pulse removes only a small amount of material, a practical laser processing system must have high repetition rate. We will demonstrate that planar ablation is unstable and the initially smooth crater bottom develops a corrugated pattern after many tens of shots. The corrugation growth rate, angle of incidence and the polarization of laser electric field dependence will be discussed. In the nonlinear stage, the formation of coherent structures with scales much larger than the laser wavelength was observed. Also, there appears to be a threshold fluence above which a narrow, nearly perfectly circular channel forms after a few hundred shots. Subsequent shots deepen this channel without significantly increasing its diameter. The role of light absorption in the hole walls will be discussed.

  7. 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.)

  8. Optical Emission Spectroscopy of Plasma in Hybrid Pulsed Laser Deposition System

    Czech Academy of Sciences Publication Activity Database

    Novotný, Michal; Jelínek, Miroslav; Bulíř, Jiří; Lančok, Ján; Jastrabík, Lubomír; Zelinger, Zdeněk

    2002-01-01

    Roč. 52, Suppl. D (2002), s. 292-298 ISSN 0011-4626 R&D Projects: GA AV ČR IAA1010110 Keywords : optical emission spectroscopy * pulsed laser deposition * RF discharge Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.311, year: 2002

  9. Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation

    Science.gov (United States)

    Kim, Beop-Min; Feit, Michael D.; Rubenchik, Alexander M.; Gold, David M.; Darrow, Christopher B.; Marion, John E., II; Da Silva, Luiz B.

    1998-05-01

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using an ultrashort pulse laser. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so bone tissue is selectively ablated while preserving the spinal cord.

  10. Pulse Synchronization System (PSS)

    International Nuclear Information System (INIS)

    1977-06-01

    This document is intended to serve as an operations manual, as well as a documentation of the backup analyses pertinent to the design as delivered. A history of earlier unsuccessful versions of the Pulse Synchronization System (PSS) is not included. The function of the PSS is to synchronize the time of arrival at the fusion target of laser pulses that are propagated through the 20 amplifier chains of the SHIVA laser. The positional accuracy requirement is +-1.5 mm (+-5 psec), and is obtained by the PSS with a wide margin factor

  11. Acousto-optic replication of ultrashort laser pulses

    Science.gov (United States)

    Yushkov, Konstantin B.; Molchanov, Vladimir Ya.; Ovchinnikov, Andrey V.; Chefonov, Oleg V.

    2017-10-01

    Precisely controlled sequences of ultrashort laser pulses are required in various scientific and engineering applications. We developed a phase-only acousto-optic pulse shaping method for replication of ultrashort laser pulses in a TW laser system. A sequence of several Fourier-transform-limited pulses is generated from a single femtosecond laser pulse by means of applying a piecewise linear phase modulation over the whole emission spectrum. Analysis demonstrates that the main factor which limits maximum delay between the pulse replicas is spectral resolution of the acousto-optic dispersive delay line used for pulse shaping. In experiments with a Cr:forsterite laser system, we obtained delays from 0.3 to 3.5 ps between two replicas of 190 fs transform-limited pulses at the central wavelength of laser emission, 1230 nm.

  12. Ultrashort pulsed laser technology development program

    Science.gov (United States)

    Manke, Gerald C.

    2014-10-01

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

  13. Regimes of self-pulsing in photonic crystal Fano lasers

    DEFF Research Database (Denmark)

    Rasmussen, Thorsten Svend; Yu, Yi; Mørk, Jesper

    2017-01-01

    Laser self-pulsing was a property exclusive to macroscopic laser systems until recently, where self-pulsing laser operation was demonstrated experimentally and theoretically in a microscopic photonic crystal Fano laser [1]. We now provide a detailed theoretical analysis of the self......-pulsing mechanism and laser characteristics with numerical simulations to demonstrate the parameter dependence of the self-pulsing regime and its limitations, indicating how the design may be optimised for applications in e.g. integrated on-chip communication systems....

  14. Comparative evaluation of long pulse Alexandrite laser and intense pulsed light systems for pseudofolliculitis barbae treatment with one year of follow up.

    Science.gov (United States)

    Leheta, Tahra M

    2009-01-01

    Existing remedies for controlling pseudofolliculitis barbae (PFB) are sometimes helpful; however the positive effects are often short lived. The only definitive cure for PFB is permanent removal of the hair follicle. Our aim was to compare the efficacy of the Alexandrite laser with the intense pulsed light system in the treatment of PFB and to follow up the recurrence. Twenty male patients seeking laser hair removal for the treatment of PFB were enrolled in this study. One half of the face was treated with the long-pulse Alexandrite laser and the other half was treated with the IPL system randomly. The treatment outcome and any complications were observed and followed up for one year. All patients exhibited a statistically significant decrease in the numbers of papules. Our results showed that the Alexandrite-treated side needed seven sessions to reach about 80% improvement, while the IPL-treated side needed 10-12 sessions to reach about 50% improvement. During the one year follow up period, the Alexandrite-treated side showed recurrence in very minimal areas, while the IPL-treated side showed recurrence in bigger areas. Our results showed that both systems might improve PFB but Alexandrite laser was more effective at reducing PFB than IPL.

  15. A new design of pulsed laser diode driver system for multistate quantum key distribution

    Science.gov (United States)

    Abdullah, M. S.; Jamaludin, M. Z.; Witjaksono, G.; Mokhtar, M. H. H.

    2011-07-01

    In this paper, we describe a new design of laser diode driver system based on MOSFET current mirror and digital signal controller (DSC). The system is designed to emit stream pairs of photons from three semiconductor laser diodes. The DSC is able to switch between the three laser diodes at constant rate. The duty cycle is maintained at 1% in order to reduce its thermal effect and thus prolong the laser diodes' life cycles. The MOSFET current mirror circuits are capable of delivering constant modulation current with peak current up to 58 mA to each laser diode. This laser driver system will allow the generating biphotons automatically with qubit rate around 8-13% for μ less than or equal to 1, thus making it practical for six-states quantum key distribution implementation.

  16. An ultrashort-pulse reconstruction software: GROG, applied to the FLAME laser system

    Science.gov (United States)

    Galletti, Mario

    2016-03-01

    The GRENOUILLE traces of FLAME Probe line pulses (60mJ, 10mJ after compression, 70fs, 1cm FWHM, 10Hz) were acquired in the FLAME Front End Area (FFEA) at the Laboratori Nazionali di Frascati (LNF), Instituto Nazionale di Fisica Nucleare (INFN). The complete characterization of the laser pulse parameters was made using a new algorithm: GRenouille/FrOG (GROG). A characterization with a commercial algorithm, QUICKFrog, was also made. The temporal and spectral parameters came out to be in great agreement for the two kinds of algorithms. In this experimental campaign the Probe line of FLAME has been completely characterized and it has been showed how GROG, the developed algorithm, works as well as QuickFrog algorithm with this type of pulse class.

  17. Self-compression of spatially limited laser pulses in a system of coupled light-guides

    Science.gov (United States)

    Balakin, A. A.; Litvak, A. G.; Mironov, V. A.; Skobelev, S. A.

    2018-04-01

    The self-action features of wave packets propagating in a 2D system of equidistantly arranged fibers are studied analytically and numerically on the basis of the discrete nonlinear Schrödinger equation. Self-consistent equations for the characteristic scales of a Gaussian wave packet are derived on the basis of the variational approach, which are proved numerically for powers P beams become filamented, and their amplitude is limited due to the nonlinear breaking of the interaction between neighboring light-guides. This makes it impossible to collect a powerful wave beam in a single light-guide. Variational analysis shows the possibility of the adiabatic self-compression of soliton-like laser pulses in the process of 3D self-focusing on the central light-guide. However, further increase of the field amplitude during self-compression leads to the development of longitudinal modulation instability and the formation of a set of light bullets in the central fiber. In the regime of hollow wave beams, filamentation instability becomes predominant. As a result, it becomes possible to form a set of light bullets in optical fibers located on the ring.

  18. Pulsed chemical laser

    International Nuclear Information System (INIS)

    Jacobson, T.V.; Kimbell, G.H.

    1975-01-01

    A hydrogen fluoride laser capable of operating super radiantly and at atmospheric pressure is described. A transverse electrical discharge is utilized to energize the reaction of a hydrogen donor to provide hydrogen fluoride in a metastable energy state which reverts to a stable state by laser action. A large range of hydrogen and fluorine donors is disclosed. A preferred pair of donors is sulphur hexafluoride and propane. Helium is frequently added to the gas mix to act as a buffer. (U.S.)

  19. Remote imaging laser-induced breakdown spectroscopy and laser-induced fluorescence spectroscopy using nanosecond pulses from a mobile lidar system.

    Science.gov (United States)

    Grönlund, Rasmus; Lundqvist, Mats; Svanberg, Sune

    2006-08-01

    A mobile lidar system was used in remote imaging laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) experiments. Also, computer-controlled remote ablation of a chosen area was demonstrated, relevant to cleaning of cultural heritage items. Nanosecond frequency-tripled Nd:YAG laser pulses at 355 nm were employed in experiments with a stand-off distance of 60 meters using pulse energies of up to 170 mJ. By coaxial transmission and common folding of the transmission and reception optical paths using a large computer-controlled mirror, full elemental imaging capability was achieved on composite targets. Different spectral identification algorithms were compared in producing thematic data based on plasma or fluorescence light.

  20. Repetitively pulsed, double discharge TEA CO/sub 2/ laser

    Energy Technology Data Exchange (ETDEWEB)

    Hamilton, D C; James, D J; Ramsden, S A

    1975-10-01

    The design and operation of a repetitively pulsed TEA CO/sub 2/ laser is described. Average powers of up to 400 W at a repetition frequency of 200 pulses/s have been obtained. The system has also been used to provide long pulses (over 20 ..mu..s) and tunable single axial mode pulses.

  1. Nova pulse power system description and status

    International Nuclear Information System (INIS)

    Holloway, R.W.; Whitham, K.; Merritt, B.T.; Gritton, D.G.; Oicles, J.A.

    1981-01-01

    The Nova laser system is designed to produce critical data in the nation's inertial confinement fusion effort. It is the world's largest peak power laser and presents various unique pulse power problems. In this paper, pulse power systems for this laser are described, the evolutionary points from prior systems are pointed out, and the current status of the hardware is given

  2. Ultrashort pulse laser deposition of thin films

    Science.gov (United States)

    Perry, Michael D.; Banks, Paul S.; Stuart, Brent C.

    2002-01-01

    Short pulse PLD is a viable technique of producing high quality films with properties very close to that of crystalline diamond. The plasma generated using femtosecond lasers is composed of single atom ions with no clusters producing films with high Sp.sup.3 /Sp.sup.2 ratios. Using a high average power femtosecond laser system, the present invention dramatically increases deposition rates to up to 25 .mu.m/hr (which exceeds many CVD processes) while growing particulate-free films. In the present invention, deposition rates is a function of laser wavelength, laser fluence, laser spot size, and target/substrate separation. The relevant laser parameters are shown to ensure particulate-free growth, and characterizations of the films grown are made using several diagnostic techniques including electron energy loss spectroscopy (EELS) and Raman spectroscopy.

  3. High-power noise-like pulse generation using a 1.56-µm all-fiber laser system.

    Science.gov (United States)

    Lin, Shih-Shian; Hwang, Sheng-Kwang; Liu, Jia-Ming

    2015-07-13

    We demonstrated an all-fiber, high-power noise-like pulse laser system at the 1.56-µm wavelength. A low-power noise-like pulse train generated by a ring oscillator was amplified using a two-stage amplifier, where the performance of the second-stage amplifier determined the final output power level. The optical intensity in the second-stage amplifier was managed well to avoid not only the excessive spectral broadening induced by nonlinearities but also any damage to the device. On the other hand, the power conversion efficiency of the amplifier was optimized through proper control of its pump wavelength. The pump wavelength determines the pump absorption and therefore the power conversion efficiency of the gain fiber. Through this approach, the average power of the noise-like pulse train was amplified considerably to an output of 13.1 W, resulting in a power conversion efficiency of 36.1% and a pulse energy of 0.85 µJ. To the best of our knowledge, these amplified pulses have the highest average power and pulse energy for noise-like pulses in the 1.56-µm wavelength region. As a result, the net gain in the cascaded amplifier reached 30 dB. With peak and pedestal widths of 168 fs and 61.3 ps, respectively, for the amplified pulses, the pedestal-to-peak intensity ratio of the autocorrelation trace remains at the value of 0.5 required for truly noise-like pulses.

  4. Possibilities of using pulsed lasers and copper-vapour laser system (CVL and CVLS) in modern technological equipment

    Science.gov (United States)

    Labin, N. A.; Bulychev, N. A.; Kazaryan, M. A.; Grigoryants, A. G.; Shiganov, I. N.; Krasovskii, V. I.; Sachkov, V. I.; Plyaka, P. S.; Feofanov, I. N.

    2015-12-01

    Research on CVL installations with an average power of 20-25 W of cutting and drilling has shown wide range of applications of these lasers for micromachining of metals and a wide range of non-metallic materials up to 1-2 mm. From the analysis indicated that peak power density in the focused light spot of 10-30 μm diameter must be 109 -1012 W/cm2 the productivity and quality micromachining, when the treatment material is preferably in the evaporative mode micro explosions, followed by the expansion of the superheated vapor and the liquid. To achieve such levels of power density, a minimum heat affected zone (5- 10 μm) and a minimum surface roughness of the cut (1-2 μm), the quality of the output beam of radiation should be as high. Ideally, to ensure the quality of the radiation, the structure of CVL output beam must be single-beam, diffraction divergence and have at duration pulses τi = 20-40 ns. The pulse energy should have low values of 0.1-1 mJ at pulse repetition rates of 10-20 kHz. Axis of the radiation beam instability of the pattern to be three orders of magnitude smaller than the diffraction limit of the divergence. The spot of the focused radiation beam must have a circular shape with clear boundary, and a Gaussian intensity distribution.

  5. Fabrication of polystyrene microfluidic devices using a pulsed CO2 laser system

    KAUST Repository

    Li, Huawei

    2013-10-10

    In this article, we described a simple and rapid method for fabrication of droplet microfluidic devices on polystyrene substrate using a CO2 laser system. The effects of the laser power and the cutting speed on the depth, width and aspect ratio of the microchannels fabricated on polystyrene were investigated. The polystyrene microfluidic channels were encapsulated using a hot press bonding technique. The experimental results showed that both discrete droplets and laminar flows could be obtained in the device.

  6. Fabrication of polystyrene microfluidic devices using a pulsed CO2 laser system

    KAUST Repository

    Li, Huawei; Fan, Yiqiang; Foulds, Ian G.; Kodzius, Rimantas

    2013-01-01

    In this article, we described a simple and rapid method for fabrication of droplet microfluidic devices on polystyrene substrate using a CO2 laser system. The effects of the laser power and the cutting speed on the depth, width and aspect ratio of the microchannels fabricated on polystyrene were investigated. The polystyrene microfluidic channels were encapsulated using a hot press bonding technique. The experimental results showed that both discrete droplets and laminar flows could be obtained in the device.

  7. Ex vivo evaluation of super pulse diode laser system with smart temperature feedback for contact soft-tissue surgery

    Science.gov (United States)

    Yaroslavsky, Ilya; Boutoussov, Dmitri; Vybornov, Alexander; Perchuk, Igor; Meleshkevich, Val; Altshuler, Gregory

    2018-02-01

    Until recently, Laser Diodes (LD) have been limited in their ability to deliver high peak power levels, which, in turn, limited their clinical capabilities. New technological developments made possible advent of "super pulse" LD (SPLD). Moreover, advanced means of smart thermal feedback enable precise control of laser power, thus ensuring safe and optimally efficacious application. In this work, we have evaluated a prototype SPLD system ex vivo. The device provided up to 25 W average and up to 150 W pulse power at 940 nm wavelength. The laser was operated in the thermal feedback-controlled mode, where power of the laser was varied automatically as a function of real-time thermal feedback to maintain constant tip temperature. The system was also equipped with a fiber tip initiated with advanced TiO2 /tungsten technique. Evaluation methods were designed to assess: 1) Speed and depth of cutting; 2) Dimensions of coagulative margin. The SPLD system was compared with industry-leading conventional diode and CO2 devices. The results indicate that the SPLD system provides increase in speed of controlled cutting by a factor of >2 in comparison with the conventional diode laser and approaching that of CO2 device. The produced ratio of the depth of cut to the thermal damage margin was significantly higher than conventional diodes and close to that of the CO2 system, suggesting optimal hemostasis conditions. SPLD technology with real-time temperature control has a potential for creating a new standard of care in the field of precision soft tissue surgery.

  8. Arbitrary temporal shape pulsed fiber laser based on SPGD algorithm

    Science.gov (United States)

    Jiang, Min; Su, Rongtao; Zhang, Pengfei; Zhou, Pu

    2018-06-01

    A novel adaptive pulse shaping method for a pulsed master oscillator power amplifier fiber laser to deliver an arbitrary pulse shape is demonstrated. Numerical simulation has been performed to validate the feasibility of the scheme and provide meaningful guidance for the design of the algorithm control parameters. In the proof-of-concept experiment, information on the temporal property of the laser is exchanged and evaluated through a local area network, and the laser adjusted the parameters of the seed laser according to the monitored output of the system automatically. Various pulse shapes, including a rectangular shape, ‘M’ shape, and elliptical shape are achieved through experimental iterations.

  9. Detection of calculus by laser-induced breakdown spectroscopy (LIBS) using an ultra-short pulse laser system (USPL)

    Science.gov (United States)

    Schelle, F.; Brede, O.; Krueger, S.; Oehme, B.; Dehn, C.; Frentzen, M.; Braun, A.

    2011-03-01

    The aim of this study was to assess the detection of calculus by Laser Induced Breakdown Spectroscopy (LIBS). The study was performed with an Nd:YVO4 laser, emitting pulses with a duration of 8 ps at a wavelength of 1064 nm. A repetition rate of 500 kHz at an average power of 5 W was used. Employing a focusing lense, intensities of the order of 1011 W/cm2 were reached on the tooth surface. These high intensities led to the generation of a plasma. The light emitted by the plasma was collimated into a fibre and then analyzed by an echelle spectroscope in the wavelength region from 220 nm - 900 nm. A total number of 15 freshly extracted teeth was used for this study. For each tooth the spectra of calculus and cementum were assessed separately. Comprising all single measurements median values were calculated for the whole spectrum, leading to two specific spectra, one for calculus and one for cementum. For further statistical analysis 28 areas of interest were defined as wavelength regions, in which the signal strength differed regarding the material. In 7 areas the intensity of the calculus spectrum differed statistically significant from the intensity of the cementum spectrum (p calculus. Further studies are necessary to verify that LIBS is a minimally invasive method allowing a safe application in laser-guided dentistry.

  10. Contribution to the study of an on line inspection system for pulsed Nd:YAG laser welding operations

    International Nuclear Information System (INIS)

    Charton, Stephane

    1999-01-01

    This thesis deals with the study of a on line inspection system for pulsed Nd 3+ :YAG laser welding operations. During a welding operation, laser-material interaction results in the emission of signals (optical, acoustical, electrical, thermal), characteristic of its behavior. On line inspection is based on the hypothesis that the signals evolutions, measured by sensors such as photodiodes, microphones.., may be correlated with the welding defects. Laser weld quality inspection can be done by the machine qualification (before and during welding), and by on line monitoring of the welding operation. The similarity of the signals produced by pulsed lasers (machine or interaction) has led us to develop a specific data acquisition and processing software. Signal processing tools utilization (Fourier and wavelets transforms) in conjunction with classification techniques (stress polytopes), introduces an innovating on line inspection approach. Discriminant parameters determination (signals/defect correlation) becomes thus automatic and non subjective. The developed prototype is not dedicated to the detection of a particular defect because the classification operator is a supervised one and needs a learning phase. lt has been validated on welding defects which are easy to deal with, and then applied to a precise production control at the Nuclear Fabrications and Technology Division of the Valduc Center of the French Atomic Energy Agency. (author) [fr

  11. Pulsed Power for Solid-State Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Gagnon, W; Albrecht, G; Trenholme, J; Newton, M

    2007-04-19

    Beginning in the early 1970s, a number of research and development efforts were undertaken at U.S. National Laboratories with a goal of developing high power lasers whose characteristics were suitable for investigating the feasibility of laser-driven fusion. A number of different laser systems were developed and tested at ever larger scale in pursuit of the optimum driver for laser fusion experiments. Each of these systems had associated with it a unique pulsed power option. A considerable amount of original and innovative engineering was carried out in support of these options. Ultimately, the Solid-state Laser approach was selected as the optimum driver for the application. Following this, the Laser Program at the Lawrence Livermore National Laboratory and the University of Rochester undertook aggressive efforts directed at developing the technology. In particular, at Lawrence Livermore National Laboratory, a series of laser systems beginning with the Cyclops laser and culminating in the present with the National Ignition Facility were developed and tested. As a result, a large amount of design information for solid-state laser pulsed power systems has been documented. Some of it is in the form of published papers, but most of it is buried in internal memoranda, engineering reports and LLNL annual reports. One of the goals of this book is to gather this information into a single useable format, such that it is easily accessed and understood by other engineers and physicists for use with future designs. It can also serve as a primer, which when seriously studied, makes the subsequent reading of original work and follow-up references considerably easier. While this book deals only with the solid-state laser pulsed power systems, in the bibliography we have included a representative cross section of papers and references from much of the very fine work carried out at other institutions in support of different laser approaches. Finally, in recent years, there has

  12. Characterization and modulation of femtosecond laser pulse

    International Nuclear Information System (INIS)

    Dorrer, Christophe

    1999-01-01

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

  13. Deep pulse fractional CO2 laser combined with a radiofrequency system: results of a case series.

    Science.gov (United States)

    Cannarozzo, Giovanni; Sannino, Mario; Tamburi, Federica; Chiricozzi, Andrea; Saraceno, Rosita; Morini, Cristiano; Nisticò, Steven

    2014-07-01

    The purpose of this study was evaluation of the safety and efficacy of this new combined technology that adds deep ablation to thermal stimulation. Minimally ablative or subablative lasers, such as fractional CO2 lasers, have been developed in an attempt to achieve the same clinical results observed with traditional ablative lasers, but with fewer side effects. Despite being an ablative laser, the system used in this study is able to produce a fractional supply of the beam of light. Fractional ablation of skin is performed through the development of microscopic vertical columns surrounded by spared areas of epidermis and dermis, ensuring rapid wound healing and minimum down time. Simultaneous synchronized delivery of a radiofrequency (RF) current to the deeper layers of the skin completes the therapeutic scenario, ensuring an effective skin tightening effect over the entire treated area. Nine adult patients were treated for wrinkles and acne scars using this new laser technology. An independent observer evaluated the improvement using a five point scale. All patients had good results in terms of improvement of skin texture, with mild and transitory side effects. This novel combined system produced improvement in wrinkles and acne scars, with progressive enhancement of skin tone and elasticity.

  14. Laser short-pulse heating of an aluminum thin film: Energy transfer in electron and lattice sub-systems

    Energy Technology Data Exchange (ETDEWEB)

    Bin Mansoor, Saad; Sami Yilbas, Bekir, E-mail: bsyilbas@kfupm.edu.sa

    2015-08-15

    Laser short-pulse heating of an aluminum thin film is considered and energy transfer in the film is formulated using the Boltzmann equation. Since the heating duration is short and the film thickness is considerably small, thermal separation of electron and lattice sub-systems is incorporated in the analysis. The electron–phonon coupling is used to formulate thermal communication of both sub-systems during the heating period. Equivalent equilibrium temperature is introduced to account for the average energy of all phonons around a local point when they redistribute adiabatically to an equilibrium state. Temperature predictions of the Boltzmann equation are compared with those obtained from the two-equation model. It is found that temperature predictions from the Boltzmann equation differ slightly from the two-equation model results. Temporal variation of equivalent equilibrium temperature does not follow the laser pulse intensity in the electron sub-system. The time occurrence of the peak equivalent equilibrium temperature differs for electron and lattice sub-systems, which is attributed to phonon scattering in the irradiated field in the lattice sub-system. In this case, time shift is observed for occurrence of the peak temperature in the lattice sub-system.

  15. Laser short-pulse heating of an aluminum thin film: Energy transfer in electron and lattice sub-systems

    International Nuclear Information System (INIS)

    Bin Mansoor, Saad; Sami Yilbas, Bekir

    2015-01-01

    Laser short-pulse heating of an aluminum thin film is considered and energy transfer in the film is formulated using the Boltzmann equation. Since the heating duration is short and the film thickness is considerably small, thermal separation of electron and lattice sub-systems is incorporated in the analysis. The electron–phonon coupling is used to formulate thermal communication of both sub-systems during the heating period. Equivalent equilibrium temperature is introduced to account for the average energy of all phonons around a local point when they redistribute adiabatically to an equilibrium state. Temperature predictions of the Boltzmann equation are compared with those obtained from the two-equation model. It is found that temperature predictions from the Boltzmann equation differ slightly from the two-equation model results. Temporal variation of equivalent equilibrium temperature does not follow the laser pulse intensity in the electron sub-system. The time occurrence of the peak equivalent equilibrium temperature differs for electron and lattice sub-systems, which is attributed to phonon scattering in the irradiated field in the lattice sub-system. In this case, time shift is observed for occurrence of the peak temperature in the lattice sub-system

  16. Quantitative TEM analysis of Al/Cu multilayer systems prepared by pulsed laser deposition

    DEFF Research Database (Denmark)

    Liu, Haihua; Pryds, Nini; Schou, Jørgen

    2010-01-01

    Thin films composed of alternating Al/Cu/Al layers were deposited on a (111) Si substrate using pulsed laser deposition (PLD). The thicknesses of the film and the individual layers, and the detailed internal structure within the layers were characterized by means of transmission electron microscopy...... for the formation of the first layer of nano-sized Al grains. The results demonstrate that the PLD technique is a powerful tool to produce nano-scale multilayered metal films with controllable thickness and grain sizes....... (TEM), high-resolution TEM (HRTEM), and energy-filtered TEM (EFTEM). Each Al or Cu layer consists of a single layer of nano-sized grains of different orientations. EFTEM results revealed a layer of oxide about 2 nm thick on the surface of the Si substrate, which is considered to be the reason...

  17. Laser-supported detonation waves and pulsed laser propulsion

    International Nuclear Information System (INIS)

    Kare, J.

    1990-01-01

    A laser thermal rocket uses the energy of a large remote laser, possibly ground-based, to heat an inert propellant and generate thrust. Use of a pulsed laser allows the design of extremely simple thrusters with very high performance compared to chemical rockets. The temperatures, pressures, and fluxes involved in such thrusters (10 4 K, 10 2 atmospheres, 10 7 w/cm 2 ) typically result in the creation of laser-supported detonation (LSD) waves. The thrust cycle thus involves a complex set of transient shock phenomena, including laser-surface interactions in the ignition of the LSD wave, laser-plasma interactions in the LSD wave itself, and high-temperature nonequilibrium chemistry behind the LSD wave. The SDIO Laser Propulsion Program is investigating these phenomena as part of an overall effort to develop the technology for a low-cost Earth-to-orbit laser launch system. We will summarize the Program's approach to developing a high performance thruster, the double-pulse planar thruster, and present an overview of some results obtained to date, along with a discussion of the many research question still outstanding in this area

  18. Pulsed power supplies for laser flashlamps. Final report

    International Nuclear Information System (INIS)

    Bird, W.L. Jr.; Driga, M.D.; Mayhall, D.J.T.; Brennan, M.

    1978-10-01

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

  19. Pulse generation and preamplification for long pulse beamlines of Orion laser facility.

    Science.gov (United States)

    Hillier, David I; Winter, David N; Hopps, Nicholas W

    2010-06-01

    We describe the pulse generation, shaping, and preamplification system for the nanosecond beamlines of the Orion laser facility. The system generates shaped laser pulses of up to approximately 1 J of 100 ps-5 ns duration with a programmable temporal profile. The laser has a 30th-power supergaussian spatial profile and is diffraction limited. The system is capable of imposing 2D smoothing by spectral dispersion upon the beam, which will produce a nonuniformity of 10% rms at the target.

  20. Optical pulse generation using fiber lasers and integrated optics

    International Nuclear Information System (INIS)

    Wilcox, R.B.; Browning, D.F.; Burkhart, S.C.; VanWonterghem, B.W.

    1995-01-01

    We have demonstrated an optical pulse forming system using fiber and integrated optics, and have designed a multiple-output system for a proposed fusion laser facility. Our approach is an advancement over previous designs for fusion lasers, and an unusual application of fiber lasers and integrated optics

  1. New methods of generation of ultrashort laser pulses for ranging

    Science.gov (United States)

    Jelinkova, Helena; Hamal, Karel; Kubecek, V.; Prochazka, Ivan

    1993-01-01

    To reach the millimeter satellite laser ranging accuracy, the goal for nineties, new laser ranging techniques have to be applied. To increase the laser ranging precision, the application of the ultrashort laser pulses in connection with the new signal detection and processing techniques, is inevitable. The two wavelength laser ranging is one of the ways to measure the atmospheric dispersion to improve the existing atmospheric correction models and hence, to increase the overall system ranging accuracy to the desired value. We are presenting a review of several nonstandard techniques of ultrashort laser pulses generation, which may be utilized for laser ranging: compression of the nanosecond pulses using stimulated Brillouin and Raman backscattering; compression of the mode-locked pulses using Raman backscattering; passive mode-locking technique with nonlinear mirror; and passive mode-locking technique with the negative feedback.

  2. Evaluation of dynamic range for LLNL streak cameras using high contrast pulses and pulse podiatry'' on the Nova laser system

    Energy Technology Data Exchange (ETDEWEB)

    Richards, J.B.; Weiland, T.L.; Prior, J.A.

    1990-07-01

    A standard LLNL streak camera has been used to analyze high contrast pulses on the Nova laser facility. These pulses have a plateau at their leading edge (foot) with an amplitude which is approximately 1% of the maximum pulse height. Relying on other features of the pulses and on signal multiplexing, we were able to determine how accurately the foot amplitude was being represented by the camera. Results indicate that the useful single channel dynamic range of the instrument approaches 100:1. 1 ref., 4 figs., 1 tab.

  3. Laser ablation comparison by picosecond pulses train and nanosecond pulse

    Science.gov (United States)

    Lednev, V. N.; Filippov, M. N.; Bunkin, A. F.; Pershin, S. M.

    2015-12-01

    A comparison of laser ablation by a train of picosecond pulses and nanosecond pulses revealed a difference in laser craters, ablation thresholds, plasma sizes and spectral line intensities. Laser ablation with a train of picosecond pulses resulted in improved crater quality while ablated mass decreased up to 30%. A reduction in laser plasma dimensions for picosecond train ablation was observed while the intensity of atomic/ionic lines in the plasma spectra was greater by a factor of 2-4 indicating an improved excitation and atomization in the plasma.

  4. FM-to-AM modulations induced by a weak residual reflection stack of sine-modulated pulses in inertial confinement fusion laser systems

    Science.gov (United States)

    Huang, Xiaoxia; Deng, Xuewei; Zhou, Wei; Hu, Dongxia; Guo, Huaiwen; Wang, Yuancheng; Zhao, Bowang; Zhong, Wei; Deng, Wu

    2018-02-01

    We report on frequency to amplitude modulation (FM-to-AM) conversion induced by a weak residual reflection stack of sine-modulated pulses in a complex laser system. Theoretical and experimental investigations reveal that when weak residual reflected pulses stack on the main pulse, the spectral intensity changes in the stacked region, which then converts to obvious AM. This kind of FM-to-AM effect often occurs in the tail of the pulse and cannot be eliminated by common compensation methods, which even enhance the modulation depth. Furthermore, the actual intensity modulation frequency and depth induced by the residual reflection stack are much higher and deeper than observed on the oscilloscope, which is harmful for safe operation of the laser facility and the driving power balance during inertial confinement fusion. To eliminate this kind of FM-to-AM effect, any possible on-axis and near-axis residual reflection in laser systems must be avoided.

  5. A Visualization Method for Corrosion Damage on Aluminum Plates Using an Nd:YAG Pulsed Laser Scanning System.

    Science.gov (United States)

    Lee, Inbok; Zhang, Aoqi; Lee, Changgil; Park, Seunghee

    2016-12-16

    This paper proposes a non-contact nondestructive evaluation (NDE) technique that uses laser-induced ultrasonic waves to visualize corrosion damage in aluminum alloy plate structures. The non-contact, pulsed-laser ultrasonic measurement system generates ultrasonic waves using a galvanometer-based Q-switched Nd:YAG laser and measures the ultrasonic waves using a piezoelectric (PZT) sensor. During scanning, a wavefield can be acquired by changing the excitation location of the laser point and measuring waves using the PZT sensor. The corrosion damage can be detected in the wavefield snapshots using the scattering characteristics of the waves that encounter corrosion. The structural damage is visualized by calculating the logarithmic values of the root mean square (RMS), with a weighting parameter to compensate for the attenuation caused by geometrical spreading and dispersion of the waves. An intact specimen is used to conduct a comparison with corrosion at different depths and sizes in other specimens. Both sides of the plate are scanned with the same scanning area to observe the effect of the location where corrosion has formed. The results show that the damage can be successfully visualized for almost all cases using the RMS-based functions, whether it formed on the front or back side. Also, the system is confirmed to have distinguished corroded areas at different depths.

  6. Pattern Laser Annealing by a Pulsed Laser

    Science.gov (United States)

    Komiya, Yoshio; Hoh, Koichiro; Murakami, Koichi; Takahashi, Tetsuo; Tarui, Yasuo

    1981-10-01

    Preliminary experiments with contact-type pattern laser annealing were made for local polycrystallization of a-Si, local evaporation of a-Si and local formation of Ni-Si alloy. These experiments showed that the mask patterns can be replicated as annealed regions with a resolution of a few microns on substrates. To overcome shortcomings due to the contact type pattern annealing, a projection type reduction pattern laser annealing system is proposed for resistless low temperature pattern forming processes.

  7. Pulsed laser triggered high speed microfluidic switch

    Science.gov (United States)

    Wu, Ting-Hsiang; Gao, Lanyu; Chen, Yue; Wei, Kenneth; Chiou, Pei-Yu

    2008-10-01

    We report a high-speed microfluidic switch capable of achieving a switching time of 10 μs. The switching mechanism is realized by exciting dynamic vapor bubbles with focused laser pulses in a microfluidic polydimethylsiloxane (PDMS) channel. The bubble expansion deforms the elastic PDMS channel wall and squeezes the adjacent sample channel to control its fluid and particle flows as captured by the time-resolved imaging system. A switching of polystyrene microspheres in a Y-shaped channel has also been demonstrated. This ultrafast laser triggered switching mechanism has the potential to advance the sorting speed of state-of-the-art microscale fluorescence activated cell sorting devices.

  8. Photoemission using femtosecond laser pulses

    International Nuclear Information System (INIS)

    Srinivasan-Rao, T.; Tsang, T.; Fischer, J.

    1991-10-01

    Successful operation of short wavelength FEL requires an electron bunch of current >100 A and normalized emittance < 1 mm-mrad. Recent experiments show that RF guns with photocathodes as the electron source may be the ideal candidate for achieving these parameters. To reduce the emittance growth due to space charge and RF dynamics effects, the gun may have to operate at high field gradient (hence at high RF frequency) and a spot size small compared to the aperture. This may necessitate the laser pulse duration to be in the subpicosecond regime to reduce the energy spread. We will present the behavior of metal photocathodes upon irradiation with femtosecond laser beams, comparison of linear and nonlinear photoemission, and scalability to high currents. Theoretical estimate of the intrinsic emittance at the photocathode in the presence of the anomalous heating of the electrons, and the tolerance on the surface roughness of the cathode material will be discussed

  9. 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

  10. Data acquisition and control system with a programmable logic controller (PLC) for a pulsed chemical oxygen-iodine laser

    Science.gov (United States)

    Yu, Haijun; Li, Guofu; Duo, Liping; Jin, Yuqi; Wang, Jian; Sang, Fengting; Kang, Yuanfu; Li, Liucheng; Wang, Yuanhu; Tang, Shukai; Yu, Hongliang

    2015-02-01

    A user-friendly data acquisition and control system (DACS) for a pulsed chemical oxygen -iodine laser (PCOIL) has been developed. It is implemented by an industrial control computer,a PLC, and a distributed input/output (I/O) module, as well as the valve and transmitter. The system is capable of handling 200 analogue/digital channels for performing various operations such as on-line acquisition, display, safety measures and control of various valves. These operations are controlled either by control switches configured on a PC while not running or by a pre-determined sequence or timings during the run. The system is capable of real-time acquisition and on-line estimation of important diagnostic parameters for optimization of a PCOIL. The DACS system has been programmed using software programmable logic controller (PLC). Using this DACS, more than 200 runs were given performed successfully.

  11. Analysis of picosecond pulsed laser melted graphite

    International Nuclear Information System (INIS)

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

    1986-01-01

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

  12. Laser cleaning of pulsed laser deposited rhodium films for fusion diagnostic mirrors

    International Nuclear Information System (INIS)

    Uccello, A.; Maffini, A.; Dellasega, D.; Passoni, M.

    2013-01-01

    Highlights: ► Pulsed laser deposition is exploited to produce Rh films for first mirrors. ► Pulsed laser deposition is exploited to produce tokamak-like C contaminants. ► Rh laser damage threshold has been evaluated for infrared pulses. ► Laser cleaning of C contaminated Rh films gives promising results. -- Abstract: In this paper an experimental investigation on the laser cleaning process of rhodium films, potentially candidates to be used as tokamak first mirrors (FMs), from redeposited carbon contaminants is presented. A relevant issue that lowers mirror's performance during tokamak operations is the redeposition of sputtered material from the first wall on their surface. Among all the possible techniques, laser cleaning, in which a train of laser pulses is launched to the surface that has to be treated, is a method to potentially mitigate this problem. The same laser system (Q-switched Nd:YAG laser with a fundamental wavelength of 1064-nm and 7-ns pulses) has been employed with three aims: (i) production by pulsed laser deposition (PLD) of Rh film mirrors, (ii) production by PLD of C deposits with controlled morphology, and (iii) investigation of the laser cleaning method onto C contaminated Rh samples. The evaluation of Rh films laser damage threshold, as a function of fluence and number of pulses, is discussed. Then, the C/Rh films have been cleaned by the laser beam. The exposed zones have been characterized by visual inspection and scanning electron microscopy (SEM), showing promising results

  13. Effect of laser pulse energies in laser induced breakdown spectroscopy in double-pulse configuration

    International Nuclear Information System (INIS)

    Benedetti, P.A.; Cristoforetti, G.; Legnaioli, S.; Palleschi, V.; Pardini, L.; Salvetti, A.; Tognoni, E.

    2005-01-01

    In this paper, the effect of laser pulse energy on double-pulse laser induced breakdown spectroscopy signal is studied. In particular, the energy of the first pulse has been changed, while the second pulse energy is held fixed. A systematic study of the laser induced breakdown spectroscopy signal dependence on the interpulse delay is performed, and the results are compared with the ones obtained with a single laser pulse of energy corresponding to the sum of the two pulses. At the same time, the crater formed at the target surface is studied by video-confocal microscopy, and the variation in crater dimensions is correlated to the enhancement of the laser induced breakdown spectroscopy signal. The results obtained are consistent with the interpretation of the double-pulse laser induced breakdown spectroscopy signal enhancement in terms of the changes in ambient gas pressure produced by the shock wave induced by the first laser pulse

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

    International Nuclear Information System (INIS)

    Ni Xiaochang; Wang Chingyue; Yang Li; Li Jianping; Chai Lu; Jia Wei; Zhang Ruobing; Zhang Zhigang

    2006-01-01

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

  15. Development of high power pulsed CO2 laser

    International Nuclear Information System (INIS)

    Nakai, Sadao; Matoba, Masafumi; Fujita, Hisanori; Daido, Hiroyuki; Inoue, Mitsuo

    1982-01-01

    The inertial nuclear fusion research using pellet implosion has rapidly progressed accompanying laser technique improvement and output increase. As the high output lasers for this purpose, Nd glass lasers or CO 2 lasers are used. The CO 2 lasers possess the characteristics required as reactor lasers, i.e., high efficiency, high frequency repetition, possibility of scale-up and economy. So, the technical development of high power CO 2 lasers assuming also as reactor drivers has been performed at a quick pace together with the research on the improvement of efficiency of pellet implosion by 10 μm laser beam. The Institute of Laser Engineering, Osaka University, stated to build a laser system LEKKO No. 8 of 8 beams and 10 kJ based on the experiences in laser systems LEKKO No. 1 and LEKKO No. 2, and the system LEKKO No. 8 was completed in March, 1981. The operation tests for one year since then has indicated as the laser characteristics that the system performance was as designed initially. This paper reviews the structure, problems and present status of the large scale CO 2 lasers. In other words, the construction of laser system, CO 2 laser proper, oscillator, booster amplifier, prevention of parasitic oscillation, non-linear pulse propagation and fairing of output pulse form, system control and beam alignment, and high power problems are described. The results obtained are to be reported in subsequent issues. (Wakatsuki, Y.)

  16. Numerical analysis of breakdown dynamics dependence on pulse width in laser-induced damage in fused silica: Role of optical system

    Science.gov (United States)

    Hamam, Kholoud A.; Gamal, Yosr E. E.-D.

    2018-06-01

    We report a numerical investigation of the breakdown and damage in fused silica caused by ultra-short laser pulses. The study based on a modified model (Gaabour et al., 2012) that solves the rate equation numerically for the electron density evolution during the laser pulse, under the combined effect of both multiphoton and electron impact ionization processes. Besides, electron loss processes due to diffusion out of the focal volume and recombination are also considered in this analysis. The model is applied to investigate the threshold intensity dependence on laser pulse width in the experimental measurements that are given by Liu et al. (2005). In this experiment, a Ti-sapphire laser source operating at 800 nm with pulse duration varies between 240 fs and 2.5 ps is used to irradiate a bulk of fused silica with dimensions 10 × 5 × 3 mm. The laser beam was focused into the bulk using two optical systems with effective numerical apertures (NA) 0.126 and 0.255 to give beam spot radius at the focus of the order 2.0 μm and 0.95 μm respectively. Reasonable agreement between the calculated thresholds and the measured ones is attained. Moreover, a study is performed to examine the respective role of the physical processes of the breakdown of fused silica in relation to the pulse width and focusing optical system. The analysis revealed a real picture of the location and size of the generated plasma.

  17. A ns-Pulse Laser Microthruster

    International Nuclear Information System (INIS)

    Phipps, Claude R.; Luke, James R.; Helgeson, Wesley; Johnson, Richard

    2006-01-01

    We have developed a prototype device which demonstrates the feasibility of using ns-duration laser pulses in a laser microthruster. Relative to the ms-duration thrusters which we have demonstrated in the past, this change offers the use of any target material, the use of reflection-mode target illumination, and adjustable specific impulse. Specific impulse is adjusted by varying laser intensity on target. In this way, we were able to vary specific impulse from 200s to 3,200s on gold. We used a Concepts Research, Inc. microchip laser with 170mW average optical power, 8kHz repetition rate and 20μJ pulse energy for many of the measurements. Thrust was in the 100nN - 1μN range for all the work, requiring development of an extremely sensitive, low-noise thrust stand. We will discuss the design of metallic fuel delivery systems. Ablation efficiency near 100% was observed. Results obtained on metallic fuel systems agreed with simulations. We also report time-of-flight measurements on ejected metal ions, which gave velocities up to 80km/s

  18. Development of subpicosecond pulse radiolysis system

    International Nuclear Information System (INIS)

    Kozawa, T.; Saeki, A.; Okamoto, K.; Numata, Y.; Kaseda, K.; Yamamoto, T.; Suemine, S.; Yoshida, Y.; Tagawa, S.

    2000-01-01

    Subpicosecond pulse radiolysis system was developed to elucidate the primary processes of radiation chemistry in the time region of femtosecond. The system consists of a femtosecond electron linac as an irradiation source, a femtosecond laser as an analyzing light and a jitter compensation system which was designed to reduce the effect of jitter between an electron pulse and a laser pulse on the time resolution. The time resolution of 800 fs was achieved. (author)

  19. Tracing explosive in solvent using quantum cascade laser with pulsed electric discharge system

    Energy Technology Data Exchange (ETDEWEB)

    Park, Seong-Wook; Tian, Chao; Martini, Rainer, E-mail: rmartini@stevens.edu [Department of Physics and Engineering Physics, Stevens Institute of Technology, 1 Castle Point on Hudson, Hoboken, New Jersey 07030 (United States); Chen, Gang [School of Optoelectronic Engineering, Chongqing University, Chongqing 400044 (China); Chen, I-chun Anderson [Newport Corporation/Oriel Instruments, 150 Long Beach Boulevard, Stratford, Connecticut 06615 (United States)

    2014-11-03

    We demonstrated highly sensitive detection of explosive dissolved in solvent with a portable spectroscopy system (Q-MACS) by tracing the explosive byproduct, N{sub 2}O, in combination with a pulsed electric discharge system for safe explosive decomposition. Using Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), the gas was monitored and analyzed by Q-MACS and the presence of the dissolved explosive clearly detected. While HMX presence could be identified directly in the air above the solutions even without plasma, much better results were achieved under the decomposition. The experiment results give an estimated detection limit of 10 ppb, which corresponds to a 15 pg of HMX.

  20. Tracing explosive in solvent using quantum cascade laser with pulsed electric discharge system

    International Nuclear Information System (INIS)

    Park, Seong-Wook; Tian, Chao; Martini, Rainer; Chen, Gang; Chen, I-chun Anderson

    2014-01-01

    We demonstrated highly sensitive detection of explosive dissolved in solvent with a portable spectroscopy system (Q-MACS) by tracing the explosive byproduct, N 2 O, in combination with a pulsed electric discharge system for safe explosive decomposition. Using Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), the gas was monitored and analyzed by Q-MACS and the presence of the dissolved explosive clearly detected. While HMX presence could be identified directly in the air above the solutions even without plasma, much better results were achieved under the decomposition. The experiment results give an estimated detection limit of 10 ppb, which corresponds to a 15 pg of HMX

  1. Effects of Femtosecond Terawatt Laser Pulses on Materials Similar to Porcine Skin

    National Research Council Canada - National Science Library

    Kumru, Semih S; Noojin, Gary D; Rockwell, Benjamin A

    2004-01-01

    As the laser technology advances and the availability of high power femtosecond pulsed laser systems increase, the urgency to have damage thresholds and ED50 data on these new laser systems becomes...

  2. Holograms made with a pulsed dye laser

    International Nuclear Information System (INIS)

    Fernandez-Guasti, M.; Iturbe-Castillo, D.; Silva-Perez, A.; Gil-Villegas, A.; Gonzalez-Torres, H.; Lopez-Guerrero, R.

    1989-01-01

    We report the obtention of holograms with a nitrogen pumped dye laser, whose source is inherently pulsed. We review the advantages and posibilities of holograms of moving objects which are impossible to make with CW lasers. The lasers used in these experiments were designed and built in the quantum optics laboratory at the Universidad Autonoma Metropolitana-Iztapalapa. (Author)

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  4. Numerical analysis of breakdown dynamics dependence on pulse width in laser-induced damage in fused silica: Role of optical system

    Directory of Open Access Journals (Sweden)

    Kholoud A. Hamam

    2018-06-01

    Full Text Available We report a numerical investigation of the breakdown and damage in fused silica caused by ultra-short laser pulses. The study based on a modified model (Gaabour et al., 2012 that solves the rate equation numerically for the electron density evolution during the laser pulse, under the combined effect of both multiphoton and electron impact ionization processes. Besides, electron loss processes due to diffusion out of the focal volume and recombination are also considered in this analysis. The model is applied to investigate the threshold intensity dependence on laser pulse width in the experimental measurements that are given by Liu et al. (2005. In this experiment, a Ti-sapphire laser source operating at 800 nm with pulse duration varies between 240 fs and 2.5 ps is used to irradiate a bulk of fused silica with dimensions 10 × 5 × 3 mm. The laser beam was focused into the bulk using two optical systems with effective numerical apertures (NA 0.126 and 0.255 to give beam spot radius at the focus of the order 2.0 μm and 0.95 μm respectively. Reasonable agreement between the calculated thresholds and the measured ones is attained. Moreover, a study is performed to examine the respective role of the physical processes of the breakdown of fused silica in relation to the pulse width and focusing optical system. The analysis revealed a real picture of the location and size of the generated plasma. Keywords: Ultra-short laser pulses, Ablation mechanisms, Electron density, Electron loss processes, Avalanche ionization, Breakdown threshold

  5. Synchronization of sub-picosecond electron and laser pulses

    International Nuclear Information System (INIS)

    Rosenzweig, J.B.; Le Sage, G.P.

    1999-01-01

    Sub-picosecond laser-electron synchronization is required to take full advantage of the experimental possibilities arising from the marriage of modern high intensity lasers and high brightness electron beams in the same laboratory. Two particular scenarios stand out in this regard, injection of ultra-short electron pulses in short wavelength laser-driven plasma accelerators, and Compton scattering of laser photons from short electron pulses. Both of these applications demand synchronization, which is sub-picosecond, with tens of femtosecond synchronization implied for next generation experiments. The design of a microwave timing modulator system is now being investigated in more detail. (AIP) copyright 1999 American Institute of Physics

  6. LASER PROCESSING ON SINGLE CRYSTALS BY UV PULSE LASER

    OpenAIRE

    龍見, 雅美; 佐々木, 徹; 高山, 恭宜

    2009-01-01

    Laser processing by using UV pulsed laser was carried out on single crystal such as sapphire and diamond in order to understand the fundamental laser processing on single crystal. The absorption edges of diamond and sapphire are longer and shorter than the wave length of UV laser, respectively. The processed regions by laser with near threshold power of processing show quite different state in each crystal.

  7. Shiva laser system performance

    International Nuclear Information System (INIS)

    Glaze, J.; Godwin, R.O.; Holzrichter, J.F.

    1978-01-01

    On November 18, 1977, after four years of experimentation, innovation, and construction, the Shiva High Energy Laser facility produced 10.2 kJ of focusable laser energy delivered in a 0.95 ns pulse. The Shiva laser, with its computer control system and delta amplifiers, demonstrated its versatility on May 18, 1978, when the first 20-beam target shot with delta amplifiers focused 26 TW on a target and produced a yield of 7.5 x 10 9 neutrons

  8. Measurement Issues In Pulsed Laser Propulsion

    International Nuclear Information System (INIS)

    Sinko, John E.; Scharring, Stefan; Eckel, Hans-Albert; Roeser, Hans-Peter; Sasoh, Akihiro

    2010-01-01

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

  9. Characterization of silicon micro-strip sensors with a pulsed infra-red laser system for the CBM experiment at FAIR

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Pradeep [Goethe University, Frankfurt am Main (Germany); GSI Helmholtz Center for Heavy Ion Research GmbH, Darmstadt (Germany); Eschke, Juergen [GSI Helmholtz Center for Heavy Ion Research GmbH, Darmstadt (Germany); Facility for Anti-proton and Ion Research, GmbH, Darmstadt (Germany); Collaboration: CBM-Collaboration

    2015-07-01

    The Silicon Tracking System (STS) of the CBM experiment at FAIR is composed of 8 tracking stations comprising of 1292 double-sided silicon micro-strip sensors. A Laser Test System (LTS) has been developed for the quality assurance of prototype sensors. The aim is to scan sensors with a pulsed infra-red laser driven by step motor to determine the charge sharing in-between strips and to measure qualitative uniformity of the sensor response over the whole active area. Several prototype sensors with strip pitch of 50 and 58 μm have been tested, as well as a prototype module with realistic mechanical arrangement of sensor and read-out cables. The LTS is designed to measure sensor response in an automatized procedure across the sensor with focused laser beam (spot-size ∼ 12 μm, wavelength = 1060 nm). The pulse with duration (∼ 10 ns) and power (∼ 5 mW) of the laser pulses is selected such, that the absorption of the laser light in the 300 μm thick silicon sensors produces a number of about 24000 electrons, which is similar to the charge created by minimum ionizing particles (MIP) in these sensors. Results from laser scans of prototype sensors and detector module are reported.

  10. Pulsed Laser Deposition: passive and active waveguides

    Czech Academy of Sciences Publication Activity Database

    Jelínek, Miroslav; Flory, F.; Escoubas, L.

    2009-01-01

    Roč. 34, č. 4 (2009), s. 438-449 ISSN 0268-1900 R&D Projects: GA ČR GA202/06/0216 Institutional research plan: CEZ:AV0Z10100522 Keywords : PLD * pulsed laser deposition * laser ablation * passive waveguides * active waveguides * waveguide laser * sensors * thin films * butane detection Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.384, year: 2009

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

    International Nuclear Information System (INIS)

    Fenstermacher, C.A.

    1979-01-01

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

  12. Traveling wave laser system

    International Nuclear Information System (INIS)

    Gregg, D.W.; Kidder, R.E.; Biehl, A.T.

    1975-01-01

    The invention broadly involves a method and means for generating a traveling wave laser pulse and is basically analogous to a single pass light amplifier system. However, the invention provides a traveling wave laser pulse of almost unlimited energy content, wherein a gain medium is pumped in a traveling wave mode, the traveling wave moving at essentially the velocity of light to generate an amplifying region or zone which moves through the medium at the velocity of light in the presence of directed stimulating radiation, thereby generating a traveling coherent, directed radiation pulse moving with the amplification zone through the gain medium. (U.S.)

  13. Switching waves dynamics in optical bistable cavity-free system at femtosecond laser pulse propagation in semiconductor under light diffraction

    Science.gov (United States)

    Trofimov, Vyacheslav A.; Egorenkov, Vladimir A.; Loginova, Maria M.

    2018-02-01

    We consider a propagation of laser pulse in a semiconductor under the conditions of an occurrence of optical bistability, which appears due to a nonlinear absorption of the semiconductor. As a result, the domains of high concentration of free charged particles (electrons and ionized donors) occur if an intensity of the incident optical pulse is greater than certain intensity. As it is well-known, that an optical beam must undergo a diffraction on (or reflection from) the domains boundaries. Usually, the beam diffraction along a coordinate of the optical pulse propagation does not take into account by using the slowly varying envelope approximation for the laser pulse interaction with optical bistable element. Therefore, a reflection of the beam from the domains with abrupt boundary does not take into account under computer simulation of the laser pulse propagation. However, the optical beams, reflected from nonhomogeneities caused by the domains of high concentration of free-charged particles, can essentially influence on a formation of switching waves in a semiconductor. We illustrate this statement by computer simulation results provided on the base of nonlinear Schrödinger equation and a set of PDEs, which describe an evolution of the semiconductor characteristics (concentrations of free-charged particles and potential of an electric field strength), and taking into account the longitudinal and transverse diffraction effects.

  14. Pulsed Laser Cladding of Ni Based Powder

    Science.gov (United States)

    Pascu, A.; Stanciu, E. M.; Croitoru, C.; Roata, I. C.; Tierean, M. H.

    2017-06-01

    The aim of this paper is to optimize the operational parameters and quality of one step Metco Inconel 718 atomized powder laser cladded tracks, deposited on AISI 316 stainless steel substrate by means of a 1064 nm high power pulsed laser, together with a Precitec cladding head manipulated by a CLOOS 7 axes robot. The optimization of parameters and cladding quality has been assessed through Taguchi interaction matrix and graphical output. The study demonstrates that very good cladded layers with low dilution and increased mechanical proprieties could be fabricated using low laser energy density by involving a pulsed laser.

  15. Superluminous laser pulse in an active medium

    International Nuclear Information System (INIS)

    Fisher, D.L.; Tajima, T.

    1993-12-01

    Physical conditions are obtained to make the propagation velocity of a laser pulse and thus the phase velocity of the excited wake be at any desired value, including that equal to or greater than the speed of light. The provision of an active-plasma laser medium with an appropriately shaped pulse allows not only replenishment of laser energy loss to the wakefield but also acceleration of the group velocity of photons. A stationary solitary solution in the accelerated frame is obtained from the model equations and simulations thereof for the laser, plasma and atoms. This approach has applications in photonics and telecommunications as well as wakefield accelerators

  16. A high pulse repetition frequency ultrasound system for the ex vivo measurement of mechanical properties of crystalline lenses with laser-induced microbubbles interrogated by acoustic radiation force

    International Nuclear Information System (INIS)

    Yoon, Sangpil; Emelianov, Stanislav; Aglyamov, Salavat; Karpiouk, Andrei

    2012-01-01

    A high pulse repetition frequency ultrasound system for an ex vivo measurement of mechanical properties of an animal crystalline lens was developed and validated. We measured the bulk displacement of laser-induced microbubbles created at different positions within the lens using nanosecond laser pulses. An impulsive acoustic radiation force was applied to the microbubble, and spatio-temporal measurements of the microbubble displacement were assessed using a custom-made high pulse repetition frequency ultrasound system consisting of two 25 MHz focused ultrasound transducers. One of these transducers was used to emit a train of ultrasound pulses and another transducer was used to receive the ultrasound echoes reflected from the microbubble. The developed system was operating at 1 MHz pulse repetition frequency. Based on the measured motion of the microbubble, Young’s moduli of surrounding tissue were reconstructed and the values were compared with those measured using the indentation test. Measured values of Young’s moduli of four bovine lenses ranged from 2.6 ± 0.1 to 26 ± 1.4 kPa, and there was good agreement between the two methods. Therefore, our studies, utilizing the high pulse repetition frequency ultrasound system, suggest that the developed approach can be used to assess the mechanical properties of ex vivo crystalline lenses. Furthermore, the potential of the presented approach for in vivo measurements is discussed. (paper)

  17. Short Pulse Laser Applications Design

    International Nuclear Information System (INIS)

    Town, R.J.; Clark, D.S.; Kemp, A.J.; Lasinski, B.F.; Tabak, M.

    2008-01-01

    We are applying our recently developed, LDRD-funded computational simulation tool to optimize and develop applications of Fast Ignition (FI) for stockpile stewardship. This report summarizes the work performed during a one-year exploratory research LDRD to develop FI point designs for the National Ignition Facility (NIF). These results were sufficiently encouraging to propose successfully a strategic initiative LDRD to design and perform the definitive FI experiment on the NIF. Ignition experiments on the National Ignition Facility (NIF) will begin in 2010 using the central hot spot (CHS) approach, which relies on the simultaneous compression and ignition of a spherical fuel capsule. Unlike this approach, the fast ignition (FI) method separates fuel compression from the ignition phase. In the compression phase, a laser such as NIF is used to implode a shell either directly, or by x rays generated from the hohlraum wall, to form a compact dense (∼300 g/cm 3 ) fuel mass with an areal density of ∼3.0 g/cm 2 . To ignite such a fuel assembly requires depositing ∼20kJ into a ∼35 (micro)m spot delivered in a short time compared to the fuel disassembly time (∼20ps). This energy is delivered during the ignition phase by relativistic electrons generated by the interaction of an ultra-short high-intensity laser. The main advantages of FI over the CHS approach are higher gain, a lower ignition threshold, and a relaxation of the stringent symmetry requirements required by the CHS approach. There is worldwide interest in FI and its associated science. Major experimental facilities are being constructed which will enable 'proof of principle' tests of FI in integrated subignition experiments, most notably the OMEGA-EP facility at the University of Rochester's Laboratory of Laser Energetics and the FIREX facility at Osaka University in Japan. Also, scientists in the European Union have recently proposed the construction of a new FI facility, called HiPER, designed to

  18. Characterization of silicon micro-strip sensors with a pulsed infra-red laser system for the CBM experiment at FAIR

    International Nuclear Information System (INIS)

    Ghosh, P.

    2015-01-01

    The Compressed Baryonic Matter (CBM) experiment at FAIR is composed of 8 tracking stations consisting of 1292 double sided silicon micro-strip sensors. For the quality assurance of produced prototype sensors a laser test system (LTS) has been developed. The aim of the LTS is to scan sensors with a pulsed infra-red laser driven by step motor to determine the charge sharing in-between strips and to measure qualitative uniformity of the sensor response over the whole active area. The prototype sensors which are tested with the LTS so far have 256 strips with a pitch of 50 μm on each side. They are read-out using a self-triggering prototype read-out electronic ASIC called n-XYTER. The LTS is designed to measure sensor response in an automatized procedure at several thousand positions across the sensor with focused infra-red laser light (spot size ≈ 12 μm , wavelength = 1060 nm). The pulse with duration (≈ 10 ns) and power (≈ 5 mW) of the laser pulses is selected such, that the absorption of the laser light in the 300 μm thick silicon sensors produces a number of about 24000 electrons, which is similar to the charge created by minimum ionizing particles (MIP) in these sensors. Laser scans different prototype sensors is reported

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

    International Nuclear Information System (INIS)

    Tighe, W.; Krushelnick, K.; Valeo, E.; Suckewer, S.

    1991-05-01

    A near-terawatt, KrF* laser system, focussable to power densities >10 18 W/cm 2 has been constructed for use as a pump laser in various schemes aimed at the development of x-ray lasing below 5nm. The laser system along with output characteristics such as the pulse duration, the focal spot size, and the percentage of amplified spontaneous emission (ASE) emitted along with the laser pulse will be presented. Schemes intended to lead to shorter wavelength x-ray emission will be described. The resultant requirements on the pump laser characteristics and the target design will be outlined. Results from recent solid target experiments and two-laser experiments, showing the interaction of a high-power, short pulse laser with a preformed plasma, will be presented. 13 refs., 5 figs

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

    Science.gov (United States)

    2014-01-30

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

  1. Laser transmitter system

    International Nuclear Information System (INIS)

    Dye, R.A.

    1975-01-01

    A laser transmitter system is disclosed which utilizes mechanical energy for generating an output pulse. The laser system includes a current developing device such as a piezoelectric crystal which charges a storage device such as a capacitor in response to a mechanical input signal. The capacitor is coupled to a switching device, such as a silicon controlled rectifier (SCR). The switching device is coupled to a laser transmitter such as a GaAs laser diode, which provides an output signal in response to the capacitor being discharged

  2. A compact three-electrode discharge system for long-pulse KrCl excimer lasers

    NARCIS (Netherlands)

    Casper, L.C.; Bastiaens, Hubertus M.J.; Peters, P.J.M.; Boller, Klaus J.; Hofstra, R.M.

    2008-01-01

    Spatially very homogeneous gas discharges with long-pulse duration have been realized in HCl-based rare-gas halide gas mixtures at over-atmospheric pressures. A low inductive three-electrode prepulse–mainpulse configuration with two discharge volumes has been used as excitation circuit. The energy

  3. Bringing Pulsed Laser Welding into Production

    DEFF Research Database (Denmark)

    Olsen, Flemmming Ove

    1996-01-01

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

  4. Survey on modern pulsed high power lasers

    International Nuclear Information System (INIS)

    Witte, K.J.

    1985-01-01

    The requirements to be met by lasers for particle acceleration are partially similar to those already known for fusion lasers. The power level wanted in both caes is up to 100 TW or even more. The pulse durations favourable for laser accelerators are in the range from 1 ps to 1000 ps whereas fusion lasers require several ns. The energy range for laser accelerators is thus correspondingly smaller than that for fusion lasers: 1-100 kJ versus several 100 kJ. The design criteria of lasers meeting the requirements are discussed in the following. The CO 2 , iodine, Nd:glass and excimer lasers are treated in detail. The high repetition rate aspect will not be particularly addressed since for the present generation of lasers the wanted rates of far above 1 Hz are completely out of scope. Moreover, for the demonstration of principle these rates are not needed. (orig./HSI)

  5. 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

  6. A pulsed laser polarization monitor for PEP

    International Nuclear Information System (INIS)

    Prescott, C.

    1975-01-01

    Back scattered circularly polarized laser photons are considered as a monitor for electron beam polarization. The up-down asymmetry of up to 10 percent can be measured using a wire ionization chamber with submillimeter resolution. With a pulsed laser backgrounds are to expected to be large

  7. Electromagnetically induced transparency with broadband laser pulses

    International Nuclear Information System (INIS)

    Yavuz, D. D.

    2007-01-01

    We suggest a scheme to slow and stop broadband laser pulses inside an atomic medium using electromagnetically induced transparency. Extending the suggestion of Harris et al. [Phys. Rev. Lett. 70, 552 (1993)], the key idea is to use matched Fourier components for the probe and coupling laser beams

  8. Laser Ablation of Biological Tissue Using Pulsed CO2 Laser

    International Nuclear Information System (INIS)

    Hashishin, Yuichi; Sano, Shu; Nakayama, Takeyoshi

    2010-01-01

    Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and the power reduction of a He-Ne laser beam. The aim of this study was to clarify the laser ablation mechanism by observing laser excision using the high-speed video camera and monitoring the power reduction of the He-Ne laser beam. We simulated laser excision of a biological tissue by irradiating gelatin (10 wt%) with radiation from a pulsed CO 2 laser (wavelength: 10.6 μm; pulse width: 80 ns). In addition, a microphone was used to measure the laser-induced sound. The first pulse caused ablation particles to be emitted in all directions; these particles were subsequently damped so that they formed a mushroom cloud. Furthermore, water was initially evaporated by laser irradiation and then tissue was ejected.

  9. 25 years of pulsed laser deposition

    Science.gov (United States)

    Lorenz, Michael; Ramachandra Rao, M. S.

    2014-01-01

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

  10. Frequency modulation of semiconductor disk laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Zolotovskii, I O; Korobko, D A; Okhotnikov, O G [Ulyanovsk State University, Ulyanovsk (Russian Federation)

    2015-07-31

    A numerical model is constructed for a semiconductor disk laser mode-locked by a semiconductor saturable absorber mirror (SESAM), and the effect that the phase modulation caused by gain and absorption saturation in the semiconductor has on pulse generation is examined. The results demonstrate that, in a laser cavity with sufficient second-order dispersion, alternating-sign frequency modulation of pulses can be compensated for. We also examine a model for tuning the dispersion in the cavity of a disk laser using a Gires–Tournois interferometer with limited thirdorder dispersion. (control of radiation parameters)

  11. 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

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

    International Nuclear Information System (INIS)

    De la Rosa, M I; Perez, C; Gruetzmacher, K; GarcIa, D; Bustillo, A

    2011-01-01

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

  13. Laser Megajoule synchronization system

    International Nuclear Information System (INIS)

    Luttmann, M.; Pastor, J.F; Drouet, V.; Prat, M.; Raimbourg, J.; Adolf, A.

    2011-01-01

    This paper describes the synchronisation system under development on the Laser Megajoule (LMJ) in order to synchronize the laser quads on the target to better than 40 ps rms. Our architecture is based on a Timing System (TS) which delivers trigger signals with jitter down to 15 ps rms coupled with an ultra precision timing system with 5 ps rms jitter. In addition to TS, a sensor placed at the target chamber center measures the arrival times of the 3 omega nano joule laser pulses generated by front end shots. (authors)

  14. Optically pumped laser systems

    International Nuclear Information System (INIS)

    DeMaria, A.J.; Mack, M.E.

    1975-01-01

    Laser systems which are pumped by an electric discharge formed in a gas are disclosed. The discharge is in the form of a vortex stabilized electric arc which is triggered with an auxiliary energy source. At high enough repetition rates residual ionization between successive pulses contributes to the pulse stabilization. The arc and the gain medium are positioned inside an optical pumping cavity where light from the arc is coupled directly into the gain medium

  15. Fast gas spectroscopy using pulsed quantum cascade lasers

    Science.gov (United States)

    Beyer, T.; Braun, M.; Lambrecht, A.

    2003-03-01

    Laser spectroscopy has found many industrial applications, e.g., control of automotive exhaust and process monitoring. The midinfrared region is of special interest because it has stronger absorption lines compared to the near infrared (NIR). However, in the NIR high quality reliable laser sources, detectors, and passive optical components are available. A quantum cascade laser could change this situation if fundamental advantages can be exploited with compact and reliable systems. It will be shown that, using pulsed lasers and available fast detectors, lower residual sensitivity levels than in corresponding NIR systems can be achieved. The stability is sufficient for industrial applications.

  16. Photo-switch of pulsed Nd:YAG laser

    International Nuclear Information System (INIS)

    Ketta, W.W.J.

    1989-01-01

    In this work passive Q-switching and its effect on the output laser beam from a pulsed Nd:YAG laser was studied. This was achieved using the photochemically stable (BDNI) dye after dissolving it in dichloroethane. The absorption spectra of the dye solution and how suitable to use with Nd:YAG laser was also dealt with. Cooling unit for the laser system, a detector to detect the output pulse, and an electronic counter to measure the pulse duration were constructed. In the free-running regime, the divergence angle was measured. The form of the output, its energy, and how it is affected by the pumping energy were also studied. In the Q-switching regime, the relation between output and pumping energies was studied and compared to the same relation under the free-running regime. 5 tabs.; 33 figs.; 57 refs

  17. Laser modification of silica, simulating pulse shape and length

    International Nuclear Information System (INIS)

    Corrales, L. Rene; Moore, Emily

    2009-01-01

    Computer simulations of instantaneous thermal heating due to a laser pulse is modeled as a pulse occurring over 1 or 100 fs, during which time the atoms within a cylinder are given excess kinetic energy to mimic the effect of adding energy locally to a system by a laser. The response of the material under conditions in which a similar amount of energy is dumped within 1 fs versus over a 100 fs pulse with two distinct shapes, square and Gaussian-like, is explored. Key physics disclosed is that with a pulse width of 100 fs, as the energy is being added it begins to dissipate away from region where it is added. With a 1 fs (instantaneous) pulse there is greater initial ballistic behavior than when it is dumped over a 100 fs period. In the latter, there are localized hot spots displaying ballistic behavior.

  18. The efficiency of photovoltaic cells exposed to pulsed laser light

    Science.gov (United States)

    Lowe, R. A.; Landis, G. A.; Jenkins, P.

    1993-01-01

    Future space missions may use laser power beaming systems with a free electron laser (FEL) to transmit light to a photovoltaic array receiver. To investigate the efficiency of solar cells with pulsed laser light, several types of GaAs, Si, CuInSe2, and GaSb cells were tested with the simulated pulse format of the induction and radio frequency (RF) FEL. The induction pulse format was simulated with an 800-watt average power copper vapor laser and the RF format with a frequency-doubled mode-locked Nd:YAG laser. Averaged current vs bias voltage measurements for each cell were taken at various optical power levels and the efficiency measured at the maximum power point. Experimental results show that the conversion efficiency for the cells tested is highly dependent on cell minority carrier lifetime, the width and frequency of the pulses, load impedance, and the average incident power. Three main effects were found to decrease the efficiency of solar cells exposed to simulated FEL illumination: cell series resistance, LC 'ringing', and output inductance. Improvements in efficiency were achieved by modifying the frequency response of the cell to match the spectral energy content of the laser pulse with external passive components.

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

    Energy Technology Data Exchange (ETDEWEB)

    Coverdale, Christine Ann [Univ. of California, Davis, CA (United States)

    1995-05-11

    Laser-plasma interactions have been of interest for many years not only from a basic physics standpoint, but also for their relevance to numerous applications. Advances in laser technology in recent years have resulted in compact laser systems capable of generating (psec), 1016 W/cm2 laser pulses. These lasers have provided a new regime in which to study laser-plasma interactions, a regime characterized by Lplasma ≥ 2LRayleigh > cτ. The goal of this dissertation is to experimentally characterize the interaction of a short pulse, high intensity laser with an underdense plasma (no ≤ 0.05ncr). Specifically, the parametric instability known as stimulated Raman scatter (SRS) is investigated to determine its behavior when driven by a short, intense laser pulse. Both the forward Raman scatter instability and backscattered Raman instability are studied. The coupled partial differential equations which describe the growth of SRS are reviewed and solved for typical experimental laser and plasma parameters. This solution shows the growth of the waves (electron plasma and scattered light) generated via stimulated Raman scatter. The dispersion relation is also derived and solved for experimentally accessible parameters. The solution of the dispersion relation is used to predict where (in k-space) and at what frequency (in ω-space) the instability will grow. Both the nonrelativistic and relativistic regimes of the instability are considered.

  20. Pulse power technology application to lasers

    International Nuclear Information System (INIS)

    Prestwich, K.R.

    1975-01-01

    Recent developments of intense relativistic electron beam accelerators and the associated pulse power technology are reviewed. The design of specific accelerators for gas laser excitation sources is discussed. A 3 MV, 800 kA, 24 ns electron beam accelerator under development for the electron beam fusion program is described along with the low jitter multichannel oil-dielectric rail switches developed for this application. This technology leads to the design of a 20 kJ, short pulse accelerator optimized gas laser excitation with radially converging electron beams. Other gas laser research requirements have led to the development of an accelerator that will produce a 0.5 MV, 20 kJ, 1 μs electron beam pulse. (auth)

  1. Pulsed laser illumination of photovoltaic cells

    Science.gov (United States)

    Yater, Jane A.; Lowe, Roland A.; Jenkins, Phillip P.; Landis, Geoffrey A.

    1995-01-01

    In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic receivers to provide remote power. Both the radio-frequency (RF) and induction FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL format.

  2. Excimer Pumped Pulsed Tunable Dye Laser

    Science.gov (United States)

    Littman, Michael G.

    1988-06-01

    It has been recently shown and reported for the first time at this meeting, that Excimer pumping of a single-mode, short-cavity, grazing-incidence, longitudinally-pumped pulsed dye laser is feasible. In this paper the key concepts upon which this latest development is based are presented and are in a somewhat unusual form. This manuscript describes five specific dye laser examples. The five examples represent a progression from the simplest type of dye laser to the single-mode version mentioned above. The examples thus serve as a tutorial introduction to potential users of dye lasers. The article is organized into five sections or STEPS, each of which describes a different pulsed dye laser. Since the subtle points about dye lasers are best appreciated only after one actually attempts to build a working model, a PROCEDURES category is included in which details about the construction of the particular form of laser are given. As one reads through this category, think of it as looking over the shoulder of the laser builder. The NOTES category which follows is a brief but essential discussion explaining why various components and procedures are used, as well as how laser performance specifications are obtained. This subsection can he viewed as a discussion with the laser builder concerning the reasons for specific actions and choices made in the assembly of the example laser. The last category contains COMMENTS which provide additional related information pertaining to the example laser that goes beyond the earlier annotated discussion. If you like, these are the narrator's comments. At the end of the article, after the five sequential forms of the laser have been presented, there is a brief summation.

  3. Molecular dynamics study of lubricant depletion by pulsed laser heating

    Science.gov (United States)

    Seo, Young Woo; Rosenkranz, Andreas; Talke, Frank E.

    2018-05-01

    In this study, molecular dynamics simulations were performed to numerically investigate the effect of pulsed laser heating on lubricant depletion. The maximum temperature, the lubricant depletion width, the number of evaporated lubricant beads and the number of fragmented lubricant chains were studied as a function of laser peak power, pulse duration and repetition rate. A continuous-wave laser and a square pulse laser were simulated and compared to a Gaussian pulse laser. With increasing repetition rate, pulsed laser heating was found to approach continuous-wave laser heating.

  4. 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.)

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

    DEFF Research Database (Denmark)

    Yu, Yi; Xue, Weiqi; Semenova, Elizaveta

    2017-01-01

    photonic and plasmonic systems(13,14). The Fano resonance leads to unique laser characteristics. In particular, because the Fano mirror is very narrowband compared to conventional laser mirrors, the laser is single mode and can be modulated via the mirror. We show, experimentally and theoretically......, that nonlinearities in the mirror may even promote the generation of a self-sustained train of pulses at gigahertz frequencies, an effect that has previously been observed only in macroscopic lasers(15-18). Such a source is of interest for a number of applications within integrated photonics....

  6. Nuclear fuel safety studies by laser pulse heating

    International Nuclear Information System (INIS)

    Viswanadham, C.S.; Kumar, Santosh; Dey, G.K.; Kutty, T.R.G.; Khan, K.B.; Kumar, Arun; Jathar, V.P.; Sahoo, K.C.

    2009-01-01

    The behaviour of nuclear fuels under transient heating conditions is vital to nuclear safety. A laser pulse based heating system to simulate the transient heating conditions experienced by the fuel during reactor accidents like LOCA and RIA is under development at BARC, Mumbai. Some of the concepts used in this system are under testing in pilot studies. This paper describes the results of some pilot studies carried out on unirradiated UO 2 specimens by laser pulse heating, followed by metallography and X-ray diffraction measurements. (author)

  7. In vitro studies with a pulsed neodymium/YAG laser.

    Science.gov (United States)

    Venkatesh, S; Guthrie, S; Foulds, W S; Lee, W R; Cruickshank, F R; Bailey, R T

    1985-02-01

    The relationships between the destructive effects of Q-switched Nd/YAG laser pulses and a number of experimental parameters were studied for various target materials including in particular excised, fixed samples of human trabecular meshwork. The laser parameters altered were the pulse energy, the convergence angle of the focused beam, and the position of the focus of the beam relative to the target's axial position. The main finding was that it was possible to make deep holes, of a diameter less than 100 micron, in virtually transparent samples of trabecular meshwork with a laser delivery system of 6 degrees convergence and pulse energies of 14 mJ or more. The relevance of this and the other experimental results to the development of a reliable system for performing internal trabeculotomies for the treatment of open-angle glaucoma is presented.

  8. Research on laser detonation pulse circuit with low-power based on super capacitor

    Science.gov (United States)

    Wang, Hao-yu; Hong, Jin; He, Aifeng; Jing, Bo; Cao, Chun-qiang; Ma, Yue; Chu, En-yi; Hu, Ya-dong

    2018-03-01

    According to the demand of laser initiating device miniaturization and low power consumption of weapon system, research on the low power pulse laser detonation circuit with super capacitor. Established a dynamic model of laser output based on super capacitance storage capacity, discharge voltage and programmable output pulse width. The output performance of the super capacitor under different energy storage capacity and discharge voltage is obtained by simulation. The experimental test system was set up, and the laser diode of low power pulsed laser detonation circuit was tested and the laser output waveform of laser diode in different energy storage capacity and discharge voltage was collected. Experiments show that low power pulse laser detonation based on super capacitor energy storage circuit discharge with high efficiency, good transient performance, for a low power consumption requirement, for laser detonation system and low power consumption and provide reference light miniaturization of engineering practice.

  9. Amorphization of silicon by femtosecond laser pulses

    International Nuclear Information System (INIS)

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

    2004-01-01

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

  10. Pulse to pulse klystron diagnosis system

    International Nuclear Information System (INIS)

    Nowak, J.; Davidson, V.; Genova, L.; Johnson, R.; Reagan, D.

    1981-03-01

    This report describes a system used to study the behavior of SLAC high powered klystrons operating with a twice normal pulse width of 5 μs. At present, up to eight of the klystrons installed along the accelerator can be operated with long pulses and monitored by this system. The report will also discuss some of the recent findings and investigations

  11. Pulsed laser deposition of hydroxyapatite thin films

    Czech Academy of Sciences Publication Activity Database

    Koch, C.F.; Johnson, S.; Kumar, D.; Jelínek, Miroslav; Chrisey, D.B.; Doraiswamy, A.; Jin, C.; Narayan, R.J.; Mihailescu, I. N.

    2007-01-01

    Roč. 27, - (2007), s. 484-494 ISSN 0928-4931 Institutional research plan: CEZ:AV0Z10100522 Keywords : hydroxyapatite * pulsed laser deposition * bioactive ceramic s Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.486, year: 2007

  12. Quantum Computation with Ultrafast Laser Pulse Shaping

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 10; Issue 6. Quantum Computation with Ultrafast Laser Pulse Shaping. Debabrata Goswami. General Article Volume 10 Issue 6 June 2005 pp 8-14. Fulltext. Click here to view fulltext PDF. Permanent link:

  13. Femtosecond laser pulse written Volume Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Richter Daniel

    2013-11-01

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

  14. Electron in the ultrashort laser pulse

    Czech Academy of Sciences Publication Activity Database

    Pardy, Miroslav

    2003-01-01

    Roč. 42, č. 1 (2003), s. 99-110 ISSN 0020-7748 R&D Projects: GA MŠk LN00A100 Institutional research plan: CEZ:AV0Z2043910 Keywords : laser pulse, Volkov solution, compton effect Subject RIV: BE - The oretical Physics Impact factor: 0.476, year: 2003

  15. Laser pulse heating of nuclear fuels for simulation of reactor power

    Indian Academy of Sciences (India)

    Laser applications; nuclear fuel elements; nuclear safety. ... accident (LOCA) and reactivity initiated accident (RIA), a laser pulse heating system is under ... As a prelude to work on irradiated nuclear fuel specimens, pilot studies on unirradiated ...

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

    International Nuclear Information System (INIS)

    Albin, S.; Winfree, W.P.; Crews, B.S.

    1990-01-01

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

  17. Closure phenomena in pinholes irradiated by Nd laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Auerbach, J.M.; Holmes, N.C.; Hunt, J.T.; Linford, G.J.

    1979-07-15

    An experimental investigation has been made on plasma closure in pinholes irradiated by Nd glass laser pulses; 300--500-..mu..m diam pinholes of various materials and thicknesses have been irradiated by 20--100-J 300-psec FWHM pulses on the Janus laser system. Calorimetry measurements have yielded data on pinhole energy transmission and intensity loading on the periphery of the pinhole. Ultrafast streak photography measurements indicate effective closure velocities of 2--5 x 10/sup 7/ cm/sec. Scattered light measurements have shown the transmission loss through a typical spatial filter configuration to be primarily refractive in nature.

  18. 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

  19. 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)

  20. Development of all solid-state, high average power ultra-short pulse laser for X-ray generation. High average power CPA system and wavefront control of ultra short laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Harayama, Sayaka; Akaoka, Katsuaki; Tei, Kazuyoku; Kato, Masaaki; Niwa, Yoshito; Maruyama, Yoichiro; Matoba, Toru; Arisawa, Takashi; Takuma, Hiroshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    We developed a prototype CPA laser system which is pumped by a all solid-state Nd:YAG laser. In a preliminary experiment, the output energy of 52mJ before compression was obtained when the pumping energy was 250mJ. To compensate the wavefront distortion, an adaptive optics has been developed. By using this wavefront control system, the laser beam with the distortion of 0.15{lambda} was obtained. (author)

  1. Double nanosecond pulses generation in ytterbium fiber laser

    Energy Technology Data Exchange (ETDEWEB)

    Veiko, V. P.; Samokhvalov, A. A., E-mail: samokhvalov.itmo@gmail.com; Yakovlev, E. B.; Zhitenev, I. Yu.; Kliushin, A. N. [Saint-Petersburg State University of Information Technologies, Mechanics and Optics, Kronverksky Pr. 49, Saint Petersburg (Russian Federation); Lednev, V. N. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, Moscow (Russian Federation); National University of Science and Technology MISiS, Leninskyave., 4, Moscow (Russian Federation); Pershin, S. M. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, Moscow (Russian Federation)

    2016-06-15

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

  2. Laser-Induced Damage with Femtosecond Pulses

    Science.gov (United States)

    Kafka, Kyle R. P.

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

  3. Pulse-power circuit diagnostics for the Nova laser

    International Nuclear Information System (INIS)

    Christie, D.J.; Dallum, G.E.; Gritton, D.G.; Merritt, B.T.; Whitham, K.; Berkbigler, L.W.

    1982-01-01

    The Nova laser will have a large pulse power system for driving laser amplifiers, incorporating approximately 1600 flashlamp circuits. An automated system has been designed for diagnosing the condition of these flashlamp circuits. It records digitized circuit current waveforms and detects current excursions above a given threshold. In addition, it is able to fire flashlamps at a low energy to ascertain the health of the system. Data from this system can be ploted for inspection by the operator, analyzed by the computer system and archived for future reference

  4. Efficient compression of the femtosecond pulses of an ytterbium laser in a gas-filled capillary

    International Nuclear Information System (INIS)

    Konyashchenko, Aleksandr V; Losev, Leonid L; Tenyakov, S Yu

    2011-01-01

    A 290-fs radiation pulse of an ytterbium laser system with a central wavelength of 1028 nm and an energy of 145 μJ was compressed to a 27-fs pulse with an energy of 75 μJ. The compression was realised on the basis of the effect of pulse spectrum broadening in a xenon-filled glass capillary for a pulse repetition rate of 3kHz. (control of laser radiation parameters)

  5. Repetitive output laser system and method using target reflectivity

    International Nuclear Information System (INIS)

    Johnson, R.R.

    1978-01-01

    An improved laser system and method for implosion of a thermonuclear fuel pellet is described in which that portion of a laser pulse reflected by the target pellet is utilized in the laser system to initiate a succeeding target implosion, and in which the energy stored in the laser system to amplify the initial laser pulse, but not completely absorbed thereby, is used to amplify succeeding laser pulses initiated by target refγlection

  6. A microprocessor controlled system for pulsed laser experiments nad its applications in two photon absorption spectroscopy of CaF2: Eu+2

    International Nuclear Information System (INIS)

    Nunes, L.A.O.; Matinaga, F.M.; Castro, J.C. de

    1986-01-01

    A very low cost data station for pulsed dye laser aplications is developed. The system employs a low cost single board microcomputer and low cost componenets. Details on the hardware configuration and sofware are presented. In order to demonstrate the power of this system we employed it to obtain a two photon absorption spectrum of some f→f transitions in europium ions present as impurity in CaF 2 . Flexibility of hardware and software allow other aplications, such as transient recording in the 10nsec per channel range and other real time data processing. (Author) [pt

  7. Laser-driven hydrothermal process studied with excimer laser pulses

    Science.gov (United States)

    Mariella, Raymond; Rubenchik, Alexander; Fong, Erika; Norton, Mary; Hollingsworth, William; Clarkson, James; Johnsen, Howard; Osborn, David L.

    2017-08-01

    Previously, we discovered [Mariella et al., J. Appl. Phys. 114, 014904 (2013)] that modest-fluence/modest-intensity 351-nm laser pulses, with insufficient fluence/intensity to ablate rock, mineral, or concrete samples via surface vaporization, still removed the surface material from water-submerged target samples with confinement of the removed material, and then dispersed at least some of the removed material into the water as a long-lived suspension of nanoparticles. We called this new process, which appears to include the generation of larger colorless particles, "laser-driven hydrothermal processing" (LDHP) [Mariella et al., J. Appl. Phys. 114, 014904 (2013)]. We, now, report that we have studied this process using 248-nm and 193-nm laser light on submerged concrete, quartzite, and obsidian, and, even though light at these wavelengths is more strongly absorbed than at 351 nm, we found that the overall efficiency of LDHP, in terms of the mass of the target removed per Joule of laser-pulse energy, is lower with 248-nm and 193-nm laser pulses than with 351-nm laser pulses. Given that stronger absorption creates higher peak surface temperatures for comparable laser fluence and intensity, it was surprising to observe reduced efficiencies for material removal. We also measured the nascent particle-size distributions that LDHP creates in the submerging water and found that they do not display the long tail towards larger particle sizes that we had observed when there had been a multi-week delay between experiments and the date of measuring the size distributions. This is consistent with transient dissolution of the solid surface, followed by diffusion-limited kinetics of nucleation and growth of particles from the resulting thin layer of supersaturated solution at the sample surface.

  8. Laser engineering of microbial systems

    Science.gov (United States)

    Yusupov, V. I.; Gorlenko, M. V.; Cheptsov, V. S.; Minaev, N. V.; Churbanova, E. S.; Zhigarkov, V. S.; Chutko, E. A.; Evlashin, S. A.; Chichkov, B. N.; Bagratashvili, V. N.

    2018-06-01

    A technology of laser engineering of microbial systems (LEMS) based on the method of laser-induced transfer of heterogeneous mixtures containing microorganisms (laser bioprinting) is described. This technology involves laser printing of soil microparticles by focusing near-infrared laser pulses on a specially prepared gel/soil mixture spread onto a gold-coated glass plate. The optimal range of laser energies from the point of view of the formation of stable jets and droplets with minimal negative impact on living systems of giant accelerations, laser pulse irradiation, and Au nanoparticles was found. Microsamples of soil were printed on glucose-peptone-yeast agar plates to estimate the LEMS process influence on structural and morphological microbial diversity. The obtained results were compared with traditionally treated soil samples. It was shown that LEMS technology allows significantly increasing the biodiversity of printed organisms and is effective for isolating rare or unculturable microorganisms.

  9. Crack imaging by pulsed laser spot thermography

    International Nuclear Information System (INIS)

    Li, T; Almond, D P; Rees, D A S; Weekes, B

    2010-01-01

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

  10. Pulse Compression Techniques for Laser Generated Ultrasound

    Science.gov (United States)

    Anastasi, R. F.; Madaras, E. I.

    1999-01-01

    Laser generated ultrasound for nondestructive evaluation has an optical power density limit due to rapid high heating that causes material damage. This damage threshold limits the generated ultrasound amplitude, which impacts nondestructive evaluation inspection capability. To increase ultrasound signal levels and improve the ultrasound signal-to-noise ratio without exceeding laser power limitations, it is possible to use pulse compression techniques. The approach illustrated here uses a 150mW laser-diode modulated with a pseudo-random sequence and signal correlation. Results demonstrate the successful generation of ultrasonic bulk waves in aluminum and graphite-epoxy composite materials using a modulated low-power laser diode and illustrate ultrasound bandwidth control.

  11. Pulsed laser radiation therapy of skin tumors

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, A.P.; Moskalik, K.G.

    1980-11-15

    Radiation from a neodymium laser was used to treat 846 patients with 687 precancerous lesions or benign tumors of the skin, 516 cutaneous carcinomas, 33 recurrences of cancer, 51 melanomas, and 508 metastatic melanomas in the skin. The patients have been followed for three months to 6.5 years. No relapses have been observed during this period. Metastases to regional lymph nodes were found in five patients with skin melanoma. Pulsed laser radiation may be successfully used in the treatment of precancerous lesions and benign tumors as well as for skin carcinoma and its recurrences, and for skin melanoma. Laser radiation is more effective in the treatment of tumors inaccessible to radiation therapy and better in those cases in which surgery may have a bad cosmetic or even mutilating effect. Laser beams can be employed in conjunction with chemo- or immunotherapy.

  12. Ultra-narrow band diode lasers with arbitrary pulse shape modulation (Conference Presentation)

    Science.gov (United States)

    Ryasnyanskiy, Aleksandr I.; Smirnov, Vadim; Mokhun, Oleksiy; Glebov, Alexei L.; Glebov, Leon B.

    2017-03-01

    Wideband emission spectra of laser diode bars (several nanometers) can be largely narrowed by the usage of thick volume Bragg gratings (VBGs) recorded in photo-thermo-refractive glass. Such narrowband systems, with GHz-wide emission spectra, found broad applications for Diode Pumped Alkali vapor Lasers, optically pumped rare gas metastable lasers, Spin Exchange Optical Pumping, atom cooling, etc. Although the majority of current applications of narrow line diode lasers require CW operation, there are a variety of fields where operation in a different pulse mode regime is necessary. Commercial electric pulse generators can provide arbitrary current pulse profiles (sinusoidal, rectangular, triangular and their combinations). The pulse duration and repetition rate however, have an influence on the laser diode temperature, and therefore, the emitting wavelength. Thus, a detailed analysis is needed to understand the correspondence between the optical pulse profiles from a diode laser and the current pulse profiles; how the pulse profile and duty cycle affects the laser performance (e.g. the wavelength stability, signal to noise ratio, power stability etc.). We present the results of detailed studies of the narrowband laser diode performance operating in different temporal regimes with arbitrary pulse profiles. The developed narrowband (16 pm) tunable laser systems at 795 nm are capable of operating in different pulse regimes while keeping the linewidth, wavelength, and signal-to-noise ratio (>20 dB) similar to the corresponding CW modules.

  13. Optical reprogramming with ultrashort femtosecond laser pulses

    Science.gov (United States)

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

    2015-03-01

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

  14. Brief review on pulse laser propulsion

    Science.gov (United States)

    Yu, Haichao; Li, Hanyang; Wang, Yan; Cui, Lugui; Liu, Shuangqiang; Yang, Jun

    2018-03-01

    Pulse laser propulsion (PLP) is an advanced propulsion concept can be used across a variety of fields with a wide range of applications. PLP reflects superior payload as well as decreased launch costs in comparison with other conventional methods of producing thrust, such as chemical propulsion or electric propulsion. Numerous researchers have attempted to exploit the potential applications of PLP. This paper first reviews concepts relevant to PLP, including the propulsion modes, breakdown regimes, and propulsion efficiency; the propulsion targets for different materials with the pulse laser are then discussed in detail, including the propulsion of solid and liquid microspheres. PLP applications such as the driven microsatellite, target surface particle removal, and orbital debris removal are also discussed. Although the PLP has been applied to a variety of fields, further research is yet warranted to establish its application in the aerospace field.

  15. Laser Pulse Heating of Spherical Metal Particles

    Directory of Open Access Journals (Sweden)

    Michael I. Tribelsky

    2011-12-01

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

  16. Pulsed laser damage to optical fibers

    International Nuclear Information System (INIS)

    Allison, S.W.; Gillies, G.T.; Magnuson, D.W.; Pagano, T.S.

    1985-01-01

    This paper describes some observations of pulsed laser damage to optical fibers with emphasis on a damage mode characterized as a linear fracture along the outer core of a fiber. Damage threshold data are presented which illustrate the effects of the focusing lens, end-surface preparation, and type of fiber. An explanation based on fiber-beam misalignment is given and is illustrated by a simple experiment and ray trace

  17. Laboratory transferability of optimally shaped laser pulses for quantum control

    International Nuclear Information System (INIS)

    Moore Tibbetts, Katharine; Xing, Xi; Rabitz, Herschel

    2014-01-01

    Optimal control experiments can readily identify effective shaped laser pulses, or “photonic reagents,” that achieve a wide variety of objectives. An important additional practical desire is for photonic reagent prescriptions to produce good, if not optimal, objective yields when transferred to a different system or laboratory. Building on general experience in chemistry, the hope is that transferred photonic reagent prescriptions may remain functional even though all features of a shaped pulse profile at the sample typically cannot be reproduced exactly. As a specific example, we assess the potential for transferring optimal photonic reagents for the objective of optimizing a ratio of photoproduct ions from a family of halomethanes through three related experiments. First, applying the same set of photonic reagents with systematically varying second- and third-order chirp on both laser systems generated similar shapes of the associated control landscape (i.e., relation between the objective yield and the variables describing the photonic reagents). Second, optimal photonic reagents obtained from the first laser system were found to still produce near optimal yields on the second laser system. Third, transferring a collection of photonic reagents optimized on the first laser system to the second laser system reproduced systematic trends in photoproduct yields upon interaction with the homologous chemical family. These three transfers of photonic reagents are demonstrated to be successful upon paying reasonable attention to overall laser system characteristics. The ability to transfer photonic reagents from one laser system to another is analogous to well-established utilitarian operating procedures with traditional chemical reagents. The practical implications of the present results for experimental quantum control are discussed

  18. Development of double-pulse lasers ablation system and electron paramagnetic resonance spectroscopy for direct spectral analysis of manganese doped PVA polymer

    Science.gov (United States)

    Khalil, A. A. I.; Morsy, M. A.; El-Deen, H. Z.

    2017-11-01

    Series of manganese-co-precipitated poly (vinyl alcohol) (PVA) polymer were quantitatively and qualitatively analyzed using laser ablation system (LAS) based on double-pulse laser induced breakdown spectroscopy (DP-LIBS) and electron paramagnetic resonance (EPR) spectroscopy. The collinear nanosecond laser beams of 266 and 1064 nm were optimized to focus on the surface of the PVA polymer target. Both laser beams were employed to estimate the natural properties of the excited Mn-PVA plasma, such as electron number density (Ne), electron temperature (Te), and Mn concentration. Individual transition lines of manganese (Mn), carbon (C), lithium (Li), hydrogen (H) and oxygen (O) atoms are identified based on the NIST spectral database. The results show better responses with DP-LIBS than the single-pulse laser induced breakdown spectroscopy (SP-LIBS). On the other hand, the EPR investigation shows characteristic broad peak of Mn-nano-particles (Mn-NPs) in the range of quantum dots of superparamagnetic materials. The line width (peak-to-peak, ΔHpp) and g-value of the observed Mn-EPR peak are ∼20 mT and 2.0046, respectively. The intensities of Mn-emission line at a wavelength 403.07 nm and the Mn-EPR absorption peak were used to accurate quantify the Mn-content in the polymer matrix. The results produce linear trends within the studied concentration range with regression coefficient (R2) value of ∼0.99, and limit of detection (LOD) of 0.026 mol.% and 0.016 mol.%, respectively. The LOD values are at a fold change of about -0.2 of the studied lowest mol.%. The proposed protocols of trace element detection are of significant advantage and can be applied to the other metal analysis.

  19. Physics of laser fusion. Volume III. High-power pulsed lasers

    International Nuclear Information System (INIS)

    Holzrichter, J.F.; Eimerl, D.; George, E.V.; Trenholme, J.B.; Simmons, W.W.; Hunt, J.T.

    1982-09-01

    High-power pulsed lasers can deliver sufficient energy on inertial-confinement fusion (ICF) time scales (0.1 to 10 ns) to heat and compress deuterium-tritium fuel to fusion-reaction conditions. Several laser systems have been examined, including Nd:glass, CO 2 , KrF, and I 2 , for their ICF applicability. A great deal of developmental effort has been applied to the Nd:glass laser and the CO 2 gas laser systems; these systems now deliver > 10 4 J and 20 x 10 12 W to ICF targets. We are constructing the Nova Nd:glass laser at LLNL to provide > 100 kJ and > 100 x 10 12 W of 1-μm radiation for fusion experimentation in the mid-1980s. For ICF target gain > 100 times the laser input, we expect that the laser driver must deliver approx. 3 to 5 MJ of energy on a time scale of 10 to 20 ns. In this paper we review the technological status of fusion-laser systems and outline approaches to constructing high-power pulsed laser drivers

  20. Heat effect of pulsed Er:YAG laser radiation

    Science.gov (United States)

    Hibst, Raimund; Keller, Ulrich

    1990-06-01

    Pulsed Er:YAG laser radiation has been found to be effective for dental enamel and dentin removal. Damage to the surrounding hard tissue is little, but before testing the Er:YAG laser clinically for the preparation of cavities, possible effects on the soft tissue of the pulp must be known. In order to estimate pulp damage , temperature rise in dentin caused by the laser radiation was measured by a thermocouple. Additionally, temperature distributions were observed by means of a thermal imaging system. The heat effect of a single Er:YAG laser pulse is little and limited to the vicinity of the impact side. Because heat energy is added with each additional pulse , the temperature distribution depends not only on the radiant energy, but also on the number of pulses and the repetition rate. Both irradiation conditions can be found , making irreversible pulp damage either likely or unlikely. The experimental observations can be explained qualitatively by a simple model of the ablation process.

  1. Aurora laser optical system

    International Nuclear Information System (INIS)

    Hanlon, J.A.; McLeod, J.

    1987-01-01

    Aurora is the Los Alamos short-pulse high-power krypton fluoride laser system. It is primarily an end-to-end technology demonstration prototype for large-scale UV laser systems of interest for short-wavelength inertial confinement fusion (ICF) investigations. The system is designed to employ optical angular multiplexing and aerial amplification by electron-beam-driven KrF laser amplifiers to deliver to ICF targets a stack of pulses with a duration of 5 ns containing several kilojoules at a wavelength of 248 nm. A program of high-energy density plasma physics investigations is now planned, and a sophisticated target chamber was constructed. The authors describe the design of the optical system for Aurora and report its status. This optical system was designed and is being constructed in two phases. The first phase carries only through the amplifier train and does not include a target chamber or any demultiplexing. Installation should be complete, and some performance results should be available. The second phase provides demultiplexing and carries the laser light to target. The complete design is reported

  2. Liquid Atomization Induced by Pulse Laser Reflection underneath Liquid Surface

    Science.gov (United States)

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

    2009-05-01

    We observed a novel effect of pulse laser reflection at the interface between transparent materials with different refractive indices. The electric field intensity doubles when a laser beam is completely reflected from a material with a higher refractive index to a material with a lower index. This effect appreciably reduces pulse laser ablation threshold of transparent materials. We performed experiments to observe the entire ablation process for laser incidence on the water-air interface using pulse laser shadowgraphy with high-resolution film; the minimum laser fluence for laser ablation at the water-air interface was approximately 12-16 J/cm2. We confirmed that this laser ablation occurs only when the laser beam is incident on the water-air interface from water. Many slender liquid ligaments extend like a milk crown and seem to be atomized at the tip. Their detailed structures can be resolved only by pulse laser photography using high-resolution film.

  3. Pulsed Nd-YAG laser in endodontics

    Science.gov (United States)

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

    1994-12-01

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

  4. 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

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  6. High power lasers & systems

    OpenAIRE

    Chatwin, Chris; Young, Rupert; Birch, Philip

    2015-01-01

    Some laser history;\\ud Airborne Laser Testbed & Chemical Oxygen Iodine Laser (COIL);\\ud Laser modes and beam propagation;\\ud Fibre lasers and applications;\\ud US Navy Laser system – NRL 33kW fibre laser;\\ud Lockheed Martin 30kW fibre laser;\\ud Conclusions

  7. Dye laser spectrometer for the analysis of pulsed vacuum arcs

    International Nuclear Information System (INIS)

    Hargis, P.J. Jr.; Robertson, M.M.

    1975-01-01

    A pulsed dye laser spectrometer which is used to obtain detailed single shot spectroscopic measurements of the plasma in a pulsed vacuum arc was developed. The capabilities of this spectrometer are indicated by the detection of laser induced fluorescence signals from 10 6 neutral Ti atoms in the plasma of a pulsed vacuum arc with a Ti anode. (U.S.)

  8. Drilling of Copper Using a Dual-Pulse Femtosecond Laser

    Directory of Open Access Journals (Sweden)

    Chung-Wei Cheng

    2016-02-01

    Full Text Available The drilling of copper using a dual-pulse femtosecond laser with wavelength of 800 nm, pulse duration of 120 fs and a variable pulse separation time (0.1–150 ps is investigated theoretically. A one-dimensional two-temperature model with temperature-dependent material properties is considered, including dynamic optical properties and the thermal-physical properties. Rapid phase change and phase explosion models are incorporated to simulate the material ablation process. Numerical results show that under the same total laser fluence of 4 J/cm2, a dual-pulse femtosecond laser with a pulse separation time of 30–150 ps can increase the ablation depth, compared to the single pulse. The optimum pulse separation time is 85 ps. It is also demonstrated that a dual pulse with a suitable pulse separation time for different laser fluences can enhance the ablation rate by about 1.6 times.

  9. Impact of pulse duration on Ho:YAG laser lithotripsy: fragmentation and dusting performance.

    Science.gov (United States)

    Bader, Markus J; Pongratz, Thomas; Khoder, Wael; Stief, Christian G; Herrmann, Thomas; Nagele, Udo; Sroka, Ronald

    2015-04-01

    In vitro investigations of Ho:YAG laser-induced stone fragmentation were performed to identify potential impacts of different pulse durations on stone fragmentation characteristics. A Ho:YAG laser system (Swiss LaserClast, EMS S.A., Nyon, Switzerland) with selectable long or short pulse mode was tested with regard to its fragmentation and laser hardware compatibility properties. The pulse duration is depending on the specific laser parameters. Fragmentation tests (hand-held, hands-free, single-pulse-induced crater) on artificial BEGO stones were performed under reproducible experimental conditions (fibre sizes: 365 and 200 µm; laser settings: 10 W through combinations of 0.5, 1, 2 J/pulse and 20, 10, 5 Hz, respectively). Differences in fragmentation rates between the two pulse duration regimes were detected with statistical significance for defined settings. Hand-held and motivated Ho:YAG laser-assisted fragmentation of BEGO stones showed no significant difference between short pulse mode and long pulse mode, neither in fragmentation rates nor in number of fragments and fragment sizes. Similarly, the results of the hands-free fragmentation tests (with and without anti-repulsion device) showed no statistical differences between long pulse and short pulse modes. The study showed that fragmentation rates for long and short pulse durations at identical power settings remain at a comparable level. Longer holmium laser pulse duration reduces stone pushback. Therefore, longer laser pulses may result in better clinical outcome of laser lithotripsy and more convenient handling during clinical use without compromising fragmentation effectiveness.

  10. Wavelength stabilisation during current pulsing of tapered laser

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin

    2009-01-01

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

  11. Detection of diamond in ore using pulsed laser Raman spectroscopy

    CSIR Research Space (South Africa)

    Lamprecht, GH

    2007-10-01

    Full Text Available is necessary for correcting for fluorescence of minerals and diamond itself. Various pulsed laser wavelengths from 266 to 1064 nm were used, as well as cw lasers for comparison. Wavelength scans of the regions of interest, indicated that pulsed lasers at 532...

  12. Theory of Self-pulsing in Photonic Crystal Fano Lasers

    DEFF Research Database (Denmark)

    Rasmussen, Thorsten Svend; Yu, Yi; Mørk, Jesper

    2017-01-01

    -dispersive Fano mirror, the laser frequency and the threshold gain. The model is based upon a combination of conventional laser rate equations and coupled-mode theory. The dynamical model is used to demonstrate how the laser has two regimes of operation, continuous-wave output and self-pulsing, and these regimes......Laser self-pulsing was a phenomenon exclusive to macroscopic lasers until recently, where self-starting laser pulsation in a microscopic photonic crystal Fano laser was reported. In this paper a theoretical model is developed to describe the Fano laser, including descriptions of the highly...

  13. Effects of laser wavelengths and pulse energy ratio on the emission enhancement in dual pulse LIBS

    International Nuclear Information System (INIS)

    Ahmed, Rizwan; Iqbal, Javed; Baig, M Aslam

    2015-01-01

    We present new studies on the effects of laser wavelengths, pulse energy ratio and interpulse delay between two laser pulses in the collinear dual pulse configuration of laser-induced breakdown spectroscopy (LIBS) on an iron sample in air using the fundamental (1064 nm) and the second harmonics (532 nm) of Nd:YAG lasers. In the dual pulse LIBS, an optimum value of interpulse delay with an appropriate combination of laser wavelengths, and laser pulse energy ratio, yields a 30 times signal intensity enhancement in the neutral iron lines as compared with single pulse LIBS. A comparison in the spatial variations of electron temperature along the axis of the plume expansion in single and double pulse LIBS has also been studied. (letter)

  14. Comparative study on Pulsed Laser Deposition and Matrix Assisted Pulsed Laser Evaporation of urease thin films

    International Nuclear Information System (INIS)

    Smausz, Tomi; Megyeri, Gabor; Kekesi, Renata; Vass, Csaba; Gyoergy, Eniko; Sima, Felix; Mihailescu, Ion N.; Hopp, Bela

    2009-01-01

    Urease thin films were produced by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed Laser Deposition from two types of targets: frozen water solutions of urease with different concentrations (1-10% m/v) and pure urease pellets. The fluence of the ablating KrF excimer laser was varied between 300 and 2200 mJ/cm 2 . Fourier transform infrared spectra of the deposited films showed no difference as compared to the original urease. Morphologic studies proved that the films consist of a smooth 'base' layer with embedded micrometer-sized droplets. Absorption-coefficient measurements contradicted the traditional 'absorptive matrix' model for MAPLE deposition. The laser energy was absorbed by urease clusters leading to a local heating-up and evaporation of the frozen matrix from the uppermost layer accompanied by the release of dissolved urease molecules. Significant enzymatic activity of urease was preserved only during matrix assisted transfer.

  15. Study of novel plasma devices generated by high power lasers coupled with a micro-pulse power technology

    International Nuclear Information System (INIS)

    Nishida, A; Chen, Z L; Jin, Z; Kondo, K; Nakagawa, M; Kodama, R; Arima, H; Yoneda, H

    2008-01-01

    The authors have proposed introducing a micro pulse power technology in high power laser plasma experiments to boost up the return current, resulting in efficiently guiding of energetic electrons. High current pulse power generators with a pulse laser trigger system generate high-density plasma that is well conductor. To efficiently guiding by using a micro pulse power, we estimated parameter of a micro pulse power system that is voltage of rise time, current, charging voltage and capacitance

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

    Energy Technology Data Exchange (ETDEWEB)

    Torrisi, L.; Gammino, S.; Mezzasalma, A.M.; Visco, A.M.; Badziak, J.; Parys, P.; Wolowski, J.; Woryna, E.; Krasa, J.; Laska, L.; Pfeifer, M.; Rohlena, K.; Boody, F.P

    2004-04-15

    Pulsed laser ablation of ultra-high-molecular-weight-polyethylene (UHMWPE) is investigated at Prague Asterix Laser System (PALS) Laboratory. The high ablation yield as a function of laser energy is presented at 438 nm laser wavelength. The mechanisms of the polymer ablation are studied on the base of ''in situ'' analysis, such as mass quadrupole spectrometry and time-of-flight measurements, and ''ex situ'' analysis, such as SEM investigations and Raman spectroscopy. Results show that the laser irradiation induces a strong polymer dehydrogenation and molecular emission due to different C{sub x}H{sub y} groups having high kinetic energy and high charge state. At a laser pulse energy of 150 J the H{sup +}, C{sup n+} ions (n=1 to 6) are emitted from the plasma with velocities of the order of 10{sup 8} cm/s, while the C{sub x}H{sub y} groups and the carbon clusters, detected up to C{sub 16}, have a velocity about one or two order magnitude lower. The laser ablation process produces a deep crater in the polymer, which depth depends on the laser pulse energy and it is of the order of 500 {mu}m. The crater volume increases with the laser pulse energy. Results demonstrated that the laser radiation modifies the polymer chains because dehydrogenated material and carbon-like structures are detected in the crater walls and in the bottom of the crater, respectively. A comparison of the experimental results with the data available in literature is presented and discussed.

  17. High-performance OPCPA laser system

    International Nuclear Information System (INIS)

    Zuegel, J.D.; Bagnoud, V.; Bromage, J.; Begishev, I.A.; Puth, J.

    2006-01-01

    Optical parametric chirped-pulse amplification (OPCPA) is ideally suited for amplifying ultra-fast laser pulses since it provides broadband gain across a wide range of wavelengths without many of the disadvantages of regenerative amplification. A high-performance OPCPA system has been demonstrated as a prototype for the front end of the OMEGA Extended Performance (EP) Laser System. (authors)

  18. High-performance OPCPA laser system

    Energy Technology Data Exchange (ETDEWEB)

    Zuegel, J.D.; Bagnoud, V.; Bromage, J.; Begishev, I.A.; Puth, J. [Rochester Univ., Lab. for Laser Energetics, NY (United States)

    2006-06-15

    Optical parametric chirped-pulse amplification (OPCPA) is ideally suited for amplifying ultra-fast laser pulses since it provides broadband gain across a wide range of wavelengths without many of the disadvantages of regenerative amplification. A high-performance OPCPA system has been demonstrated as a prototype for the front end of the OMEGA Extended Performance (EP) Laser System. (authors)

  19. 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...

  20. Extending ultra-short pulse laser texturing over large area

    Energy Technology Data Exchange (ETDEWEB)

    Mincuzzi, G., E-mail: girolamo.mincuzzi@alphanov.com; Gemini, L.; Faucon, M.; Kling, R.

    2016-11-15

    Highlights: • We carried out metal surface texturing (Ripples, micro grooves, Spikes) using a high power, high repetition rate, industrial, Ultra-short pulses laser. • Extremely Fast processing is shown (Laser Scan speed as high as 90 m/s) with a polygon scanner head. • Stainless steel surface blackening with Ultra-short pulses laser has been obtained with unprecedented scanspeed. • Full SEM surface characterization was carried out for all the different structures obtained. • Reflectance measurements were carried out to characterize surface reflectance. - Abstract: Surface texturing by Ultra-Short Pulses Laser (UPL) for industrial applications passes through the use of both fast beam scanning systems and high repetition rate, high average power P, UPL. Nevertheless unwanted thermal effects are expected when P exceeds some tens of W. An interesting strategy for a reliable heat management would consists in texturing with a low fluence values (slightly higher than the ablation threshold) and utilising a Polygon Scanner Heads delivering laser pulses with unrepeated speed. Here we show for the first time that with relatively low fluence it is possible over stainless steel, to obtain surface texturing by utilising a 2 MHz femtosecond laser jointly with a polygonal scanner head in a relatively low fluence regime (0.11 J cm{sup −2}). Different surface textures (Ripples, micro grooves and spikes) can be obtained varying the scan speed from 90 m s{sup −1} to 25 m s{sup −1}. In particular, spikes formation process has been shown and optimised at 25 m s{sup −1} and a full morphology characterization by SEM has been carried out. Reflectance measurements with integrating sphere are presented to compare reference surface with high scan rate textures. In the best case we show a black surface with reflectance value < 5%.

  1. Frequency conversion of high-intensity, femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Banks, P S

    1997-06-01

    Almost since the invention of the laser, frequency conversion of optical pulses via non- linear processes has been an area of active interest. However, third harmonic generation using ~(~1 (THG) in solids is an area that has not received much attention because of ma- terial damage limits. Recently, the short, high-intensity pulses possible with chirped-pulse amplification (CPA) laser systems allow the use of intensities on the order of 1 TW/cm2 in thin solids without damage. As a light source to examine single-crystal THG in solids and other high field inter- actions, the design and construction of a Ti:sapphire-based CPA laser system capable of ultimately producing peak powers of 100 TW is presented. Of special interest is a novel, all-reflective pulse stretcher design which can stretch a pulse temporally by a factor of 20,000. The stretcher design can also compensate for the added material dispersion due to propagation through the amplifier chain and produce transform-limited 45 fs pulses upon compression. A series of laser-pumped amplifiers brings the peak power up to the terawatt level at 10 Hz, and the design calls for additional amplifiers to bring the power level to the 100 TW level for single shot operation. The theory for frequency conversion of these short pulses is presented, focusing on conversion to the third harmonic in single crystals of BBO, KD*P, and d-LAP (deuterated I-arginine phosphate). Conversion efficiencies of up to 6% are obtained with 500 fs pulses at 1053 nm in a 3 mm thick BBO crystal at 200 GW/cm 2. Contributions to this process by unphasematched, cascaded second harmonic generation and sum frequency generation are shown to be very significant. The angular relationship between the two orders is used to measure the tensor elements of C = xt3)/4 with Crs = -1.8 x 1O-23 m2/V2 and .15Cri + .54Crs = 4.0 x 1O-23 m2/V2. Conversion efficiency in d-LAP is about 20% that in BBO and conversion efficiency in KD*P is 1% that of BBO. It is calculated

  2. Generation of 25-TW Femtosecond Laser Pulses at 515 nm with Extremely High Temporal Contrast

    Directory of Open Access Journals (Sweden)

    Marco Hornung

    2015-12-01

    Full Text Available We report on the frequency doubling of femtosecond laser pulses at 1030 nm center wavelength generated from the fully diode-pumped laser system POLARIS. The newly generated pulses at a center wavelength of 515 nm have a pulse energy of 3 J with a pulse duration of 120 fs. On the basis of initially ultra-high contrast seed pulses we expect a temporal intensity contrast better 10 17 200 ps before the peak of the main pulse. We analyzed the temporal intensity contrast from milliseconds to femtoseconds with a dynamic range covering more than 20 orders of magnitude. The pulses were focussed with a f/2-focussing parabola resulting in a peak intensity exceeding 10 20 W / cm 2 . The peak power and intensity are to the best of our knowledge the highest values for 515 nm-laser-pulses achieved so far.

  3. Advances on Polymer Optical Fiber Gratings Using a KrF Pulsed Laser System Operating at 248 nm

    Directory of Open Access Journals (Sweden)

    Carlos A. F. Marques

    2018-03-01

    Full Text Available This paper presents the achievements and progress made on the polymer optical fiber (POF gratings inscription in different types of Fiber Bragg Gratings (FBGs and long period gratings (LPGs. Since the first demonstration of POFBGs in 1999, significant progress has been made where the inscription times that were higher than 1 h have been reduced to 15 ns with the application of the krypton fluoride (KrF pulsed laser operating at 248 nm and thermal treatments such as the pre-annealing of fibers. In addition, the application of dopants such as benzyl dimethyl ketal (BDK has provided a significant decrease of the fiber inscription time. Furthermore, such improvements lead to the possibility of inscribing POF gratings in 850 nm and 600 nm, instead of only the 1550 nm region. The progress on the inscription of different types of polymer optical fiber Bragg gratings (POFBGs such as chirped POFBGs and phase-shifted POFBGs are also reported in this review.

  4. Scattering of Femtosecond Laser Pulses on the Negative Hydrogen Ion

    Science.gov (United States)

    Astapenko, V. A.; Moroz, N. N.

    2018-05-01

    Elastic scattering of ultrashort laser pulses (USLPs) on the negative hydrogen ion is considered. Results of calculations of the USLP scattering probability are presented and analyzed for pulses of two types: the corrected Gaussian pulse and wavelet pulse without carrier frequency depending on the problem parameters.

  5. Multiple pulse nanosecond laser induced damage threshold on hybrid mirrors

    Science.gov (United States)

    Vanda, Jan; Muresan, Mihai-George; Bilek, Vojtech; Sebek, Matej; Hanus, Martin; Lucianetti, Antonio; Rostohar, Danijela; Mocek, Tomas; Škoda, Václav

    2017-11-01

    So-called hybrid mirrors, consisting of broadband metallic surface coated with dielectric reflector designed for specific wavelength, becoming more important with progressing development of broadband mid-IR sources realized using parametric down conversion system. Multiple pulse nanosecond laser induced damage on such mirrors was tested by method s-on-1, where s stands for various numbers of pulses. We show difference in damage threshold between common protected silver mirrors and hybrid silver mirrors prepared by PVD technique and their variants prepared by IAD. Keywords: LIDT,

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-14

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

  7. Pulsed photothermal depth profiling of tattoos undergoing laser removal treatment

    Science.gov (United States)

    Milanic, Matija; Majaron, Boris

    2012-02-01

    Pulsed photothermal radiometry (PPTR) allows noninvasive determination of temperature depth profiles induced by pulsed laser irradiation of strongly scattering biological tissues and organs, including human skin. In present study, we evaluate the potential of this technique for investigational characterization and possibly quantitative evaluation of laser tattoo removal. The study involved 5 healthy volunteers (3 males, 2 females), age 20-30 years, undergoing tattoo removal treatment using a Q-switched Nd:YAG laser. There were four measurement and treatment sessions in total, separated by 2-3 months. Prior to each treatment, PPTR measurements were performed on several tattoo sites and one nearby healthy site in each patient, using a 5 ms Nd:YAG laser at low radiant exposure values and a dedicated radiometric setup. The laser-induced temperature profiles were then reconstructed by applying a custom numerical code. In addition, each tatoo site was documented with a digital camera and measured with a custom colorimetric system (in tristimulus color space), providing an objective evaluation of the therapeutic efficacy to be correlated with our PPTR results. The results show that the laser-induced temperature profile in untreated tattoos is invariably located at a subsurface depth of 300 μm. In tattoo sites that responded well to laser therapy, a significant drop of the temperature peak was observed in the profiles obtained from PPTR record. In several sites that appeared less responsive, as evidenced by colorimetric data, a progressive shift of the temperature profile deeper into the dermis was observed over the course of consecutive laser treatments, indicating that the laser tattoo removal was efficient.

  8. Development of short pulse laser pumped x-ray lasers

    International Nuclear Information System (INIS)

    Dunn, J; Osterheld, A L; Hunter, J R; Shlyaptsev, V N

    2000-01-01

    X-ray lasers have been extensively studied around the world since the first laboratory demonstration on the Novette laser at LLNL in 1984 [l]. The characteristic properties of short wavelength, high monochromaticity, collimation and coherence make x-ray lasers useful for various applications. These include demonstrations of biological imaging within the water window, interferometry of laser plasmas and radiography of laser-heated surfaces. One of the critical issues has been the high power pump required to produce the inversion. The power scaling as a function of x-ray laser wavelength follows a -k4 to law. The shortest x-ray laser wavelength of ∼ 35 (angstrom) demonstrated for Ni-like All was at the limit of Nova laser capabilities. By requiring large, high power lasers such as Nova, the shot rate and total number of shots available have limited the rapid development of x-ray lasers and applications. In fact over the last fifteen years the main thrust has been to develop more efficient, higher repetition rate x-ray lasers that can be readily scaled to shorter wavelengths. The recent state of progress in the field can be found in references. The objective of the project was to develop a soft x-ray laser (XRL) pumped by a short pulse laser of a few joules. In effect to demonstrate a robust, worlung tabletop x-ray laser at LLNL for the first time. The transient collisional scheme as proposed by Shlyaptsev et al [8, 9] was the candidate x-ray laser for study. The successful endeavour of any scientific investigation is often based upon prudent early decisions and the choice of this scheme was both sound and fruitful. It had been demonstrated very recently for Ne-like Ti at 326 A using a small tabletop laser [10] but had not yet reached its full potential. We chose this scheme for several reasons: (a) it was a collisional-type x-ray laser which has been historically the most robust; (b) it had the promise of high efficiency and low energy threshold for lasing; (c) the

  9. Coaxial monitoring of temperature field in selective pulsed laser melting

    Science.gov (United States)

    Liu, Che; Chen, Zhongyun; Cao, Hongzhong; Zhou, Jianhong

    2017-10-01

    Selective Laser Melting is a rapid manufacturing technology which produces complex parts layer by layer. The presence of thermal stress and thermal strain in the forming process often leads to defects in the formed parts. In order to detect fabricate errors and avoid failure which caused by thermal gradient in time. An infrared thermal imager and a high speed CCD camera were applied to build a coaxial optical system for real-time monitoring the temperature distribution and changing trend of laser affected zone in SLM forming process. Molten tracks were fabricated by SLM under different laser parameters such as frequency, pulse width. And the relationship between the laser parameters and the temperature distribution were all obtained and analyzed.

  10. Multiplex electric discharge gas laser system

    Science.gov (United States)

    Laudenslager, James B. (Inventor); Pacala, Thomas J. (Inventor)

    1987-01-01

    A multiple pulse electric discharge gas laser system is described in which a plurality of pulsed electric discharge gas lasers are supported in a common housing. Each laser is supplied with excitation pulses from a separate power supply. A controller, which may be a microprocessor, is connected to each power supply for controlling the application of excitation pulses to each laser so that the lasers can be fired simultaneously or in any desired sequence. The output light beams from the individual lasers may be combined or utilized independently, depending on the desired application. The individual lasers may include multiple pairs of discharge electrodes with a separate power supply connected across each electrode pair so that multiple light output beams can be generated from a single laser tube and combined or utilized separately.

  11. Pulsed laser planarization of metal films for multilevel interconnects

    International Nuclear Information System (INIS)

    Tuckerman, D.B.; Schmitt, R.L.

    1985-05-01

    Multilevel interconnect schemes for integrated circuits generally require one or more planarization steps, in order to maintain an acceptably flat topography for lithography and thin-film step coverage on the higher levels. Traditional approaches have involved planarization of the interlevel insulation (dielectric) layers, either by spin-on application (e.g., polyimide), or by reflow (e.g., phosphosilicate glass). We have pursued an alternative approach, in which each metal level is melted (hence planarized) using a pulsed laser prior to patterning. Short (approx.1 μs) pulses are used to preclude undesirable metallurgical reactions between the film, adhesion or barrier layer, and dielectric layer. Laser planarization of metals is particularly well suited to multilevel systems which include ground or power planes. Results are presented for planarization of gold films on SiO 2 dielectric layers using a flashlamp-pumped dye laser. The pulse duration is approx.1 μs, which allows the heat pulse to uniformly penetrate the gold while not penetrating substantially through the underlying SiO 2 (hence not perturbing the lower levels of metal). Excellent planarization of the gold films is achieved (less than 0.1 μm surface roughness, even starting with extreme topographic variations), as well as improved conductivity. To demonstrate the process, numerous planarized two-layer structures (transmission lines under a ground plane) were fabricated and characterized. 9 refs., 2 figs

  12. Pulsed hybrid dual wavelength Y-branch-DFB laser-tapered amplifier system suitable for water vapor detection at 965 nm with 16 W peak power

    Science.gov (United States)

    Vu, Thi N.; Klehr, Andreas; Sumpf, Bernd; Hoffmann, Thomas; Liero, Armin; Tränkle, Günther

    2016-03-01

    A master oscillator power amplifier system emitting alternatingly at two neighbored wavelengths around 965 nm is presented. As master oscillator (MO) a Y-branch DFB-laser is used. The two branches, which can be individually controlled, deliver the two wavelengths needed for a differential absorption measurement of water vapor. Adjusting the current through the DFB sections, the wavelength can be adjusted with respect to the targeted either "on" or "off" resonance, respectively wavelength λon or wavelength λoff. The emission of this laser is amplified in a tapered amplifier (TA). The ridge waveguide section of the TA acts as optical gate to generate short pulses with duration of 8 ns at a repetition rate of 25 kHz, the flared section is used for further amplification to reach peak powers up to 16 W suitable for micro-LIDAR (Light Detection and Ranging). The necessary pulse current supply user a GaN-transistor based driver electronics placed close to the power amplifier (PA). The spectral properties of the emission of the MO are preserved by the PA. A spectral line width smaller than 10 pm and a side mode suppression ratio (SMSR) of 37 dB are measured. These values meet the demands for water vapor absorption measurements under atmospheric conditions.

  13. Pulsed laser deposition—invention or discovery?

    International Nuclear Information System (INIS)

    Venkatesan, T

    2014-01-01

    The evolution of pulsed laser deposition had been an exciting process of invention and discovery, with the development of high T c superconducting films as the main driver. It has become the method of choice in research and development for rapid prototyping of multicomponent inorganic materials for preparing a variety of thin films, heterostructures and atomically sharp interfaces, and has become an indispensable tool for advancing oxide electronics. In this paper I will give a personal account of the invention and development of this process at Bellcore/Rutgers, the opportunity, challenges and mostly the extraordinary excitement that was generated, typical of any disruptive technology. (paper)

  14. Three-dimensional laser pulse intensity diagnostic for photoinjectors

    Directory of Open Access Journals (Sweden)

    Heng Li

    2011-11-01

    Full Text Available Minimizing the electron-beam emittance of photoinjectors is an important task for maximizing the brightness of the next-generation x-ray facilities, such as free-electron lasers and energy recovery linacs. Optimally shaped laser pulses can significantly reduce emittance. A reliable diagnostic for the laser pulse intensity is required for this purpose. We demonstrate measurement of three-dimensional spatiotemporal intensity profiles, with spatial resolution of 20  μm and temporal resolution of 130 fs. The capability is illustrated by measurements of stacked soliton pulses and pulses from a dissipative-soliton laser.

  15. Model of pulse extraction from a copper laser amplifier

    International Nuclear Information System (INIS)

    Boley, C.D.; Warner, B.E.

    1997-03-01

    A computational model of pulse propagation through a copper laser amplifier has been developed. The model contains a system of 1-D (in the axial direction), time-dependent equations for the laser intensity and amplified spontaneous emission (ASE), coupled to rate equations for the atomic levels. Detailed calculations are presented for a high-power amplifier at Lawrence Livermore National Laboratory. The extracted power agrees with experiment near saturation. At lower input power the calculation overestimates experiment, probably because of increased ASE effects. 6 refs., 6 figs

  16. Driver circuit for pulse modulation of a semiconductor laser

    International Nuclear Information System (INIS)

    Ueki, A.

    1975-01-01

    A pulse modulation driver circuit for a semiconductor laser is disclosed which discriminates among input pulse signals composed of binary codes to detect the occurrence of a pulse having a code of ''I'' following a pulse having a code of ''0''. Detection of this pattern is used to control the driver to increase either or both the width or peak value of the pulse having a code of 1. The effect of this is to eliminate a pattern effect in the light emitted by the semiconductor laser caused by an attenuation of the population inversion in the laser. (U.S.)

  17. Pulsed power for angular multiplexed laser fusion drivers

    International Nuclear Information System (INIS)

    Eninger, J.E.

    1983-01-01

    The feasibility of using rare gas-halide lasers, in particular the KrF laser, as inertial confinement fusion (ICF) drivers has been assessed. These lasers are scalable to the required high energy (approx. =1-5 MJ) in a short pulse (approx. =10 ns) by optical angular multiplexing, and integration of the output from approx. =100 kJ laser amplifier subsystems. The e-beam current density (approx. =50A/cm 2 ) and voltage (approx. =800 kV) required for these power amplifiers lead to an e-beam impedance of approx. =0.2Ω for approx. =300 ns pump time. This impedance level requires modularization of the large area e-gun, a) to achieve a diode inductance consistent with fast current risetime, b) to circumvent dielectric breakdown constraints in the pulse forming lines, and c) to reduce the requirement for guide magnetic fields. Pulsed power systems requirements, design concepts, scalability, tradeoffs, and performance projections are discussed in this paper

  18. Channeling and stability of laser pulses in plasmas

    International Nuclear Information System (INIS)

    Sprangle, P.; Krall, J.; Esarey, E.

    1995-01-01

    A laser pulse propagating in a plasma is found to undergo a combination of hose and modulation instabilities. The coupled equations for the laser beam envelope and centroid are derived and solved for a laser pulse of finite length propagating through either a uniform plasma or preformed plasma density channel. The laser envelope equation describes the pulse self-focusing and optical guiding in plasmas and is used to analyze the self-modulation instability. The laser centroid equation describes the transverse motion of the laser pulse (hosing) in plasmas. Significant coupling between the centroid and envelope motion as well as harmonic generation in the envelope can occur. In addition, the transverse profile of the generated wake field is strongly affected by the laser hose instability. Methods to reduce the laser hose instability are demonstrated. copyright 1995 American Institute of Physics

  19. Dynamics of laser-induced channel formation in water and influence of pulse duration on the ablation of biotissue under water with pulsed erbium-laser radiation

    Science.gov (United States)

    Ith, M.; Pratisto, H.; Altermatt, H. J.; Frenz, M.; Weber, H. P.

    1994-12-01

    The ability to use fiber-delivered erbium-laser radiation for non-contact arthroscopic meniscectomy in a liquid environment was studied. The laser radiation is transmitted through a water-vapor channel created by the leading part of the laser pulse. The dynamics of the channel formation around a submerged fiber tip was investigated with time-resolved flash photography. Strong pressure transients with amplitudes up to a few hundreds of bars measured with a needle hydrophone were found to accompany the channel formation process. Additional pressure transients in the range of kbars were observed after the laser pulse associated with the collapse of the vapor channel. Transmission measurements revealed that the duration the laser-induced channel stays open, and therefore the energy transmittable through it, is substantially determined by the laser pulse duration. The optimum pulse duration was found to be in the range between 250 and 350 µS. This was confirmed by histological evaluations of the laser incisions in meniscus: Increasing the pulse duration from 300 to 800 µs leads to a decrease in the crater depth from 1600 to 300 µm. A comparison of the histological examination after laser treatment through air and through water gave information on the influence of the vapor channel on the ablation efficiency, the cutting quality and the induced thermal damage in the adjacent tissue. The study shows that the erbium laser combined with an adequate fiber delivery system represents an effective surgical instrument liable to become increasingly accepted in orthopedic surgery.

  20. Instant recording of the duration of a single mode-locked Nd:YAG laser pulse

    International Nuclear Information System (INIS)

    Lompre, L.A.; Mainfray, G.; Thebault, J.

    1975-01-01

    An electro-optic streak camera incorporating a storage memory video system has been developed and used to instantly visualize and record the shape of a 1.06-μ-wavelength pulse generated by a mode-locked Nd:YAG laser. The duration of a single laser pulse (approximately 30 psec) has been directly measured with and without laser amplification. (U.S.)

  1. Cubic phase control of ultrashort laser pulses

    International Nuclear Information System (INIS)

    Mecseki, K.; Erdelyi, M.; Kovacs, A.P.; Szabo, G.

    2006-01-01

    Complete test of publication follows. The temporal shape of an ultrashort laser pulse may change upon propagating through a linear dispersive medium having a phase shift ψω. The change can be characterized by the Taylor-coefficients of the phase shift which are calculated around the central frequency ω 0 of the pulse. Measurements and independent control of the group delay dispersion (GDD, ψ'(ω 0 )) and the third order dispersion (TOD, ψ'(ω 0 )) are important in several research fields, particularly in the generation of ultrashort laser pulses by chirped pulse amplification (CPA) and pulse shaping for molecular control. The GDD and the TOD of an ideal pulse compressor are equal to the negative of the corresponding dispersion coefficients of the medium. However, in the case of prism-pair and grating-pair compressor is different from the ratio of the coefficients of the medium to be compensated for. Therefore it is necessary to develop so-called cubic compressors that are able to control the TOD of the pulse, yet, do not affect the GDD. In this paper a new cubic compressor setup is investigated theoretically and experimentally, which resembles the set-up proposed by White, however, we control the GDD and the TOD by the position of a birefringent, semi-cylinder crystal place around the focal point of an achromatic lens. For the evaluation of the phase shift introduced by the proposed cubic compressor, a ray tracing program was written. The program allows optimizing the compressor parameters, such as the radius of the crystal, magnification of the lens etc. Calcite was applied because it is a strong birefringent material. Calculations showed that there is a trajectory, along which shifting the crystal the TOD can be tuned independently of the GDD. The value of the TOD changed in a relatively wide range between -3.15 x 10 5 fs 3 and -1.67 x 10 5 fs 3 . Although the defocus also affects the angular dispersion of the pulse leaving the compressor, if does not exceed

  2. Laser and intense pulsed light hair removal technologies

    DEFF Research Database (Denmark)

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

    2011-01-01

    Light-based hair removal (LHR) is one of the fastest growing, nonsurgical aesthetic cosmetic procedures in the United States and Europe. A variety of light sources including lasers, e.g. alexandrite laser (755 nm), pulsed diode lasers (800, 810 nm), Nd:YAG laser (1064 nm) and broad-spectrum intense...

  3. Ionization of molecular hydrogen in ultrashort intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Vanne, Yulian V.

    2010-03-18

    A novel ab initio numerical approach is developed and applied that solves the time-dependent Schroedinger equation describing two-electron diatomic molecules (e.g. molecular hydrogen) exposed to an intense ultrashort laser pulse. The method is based on the fixed-nuclei and the non-relativistic dipole approximations and aims to accurately describe both correlated electrons in full dimensionality. The method is applicable for a wide range of the laser pulse parameters and is able to describe both few-photon and many-photon single ionization processes, also in a non-perturbative regime. A key advantage of the method is its ability to treat the strong-field response of the molecules with arbitrary orientation of the molecular axis with respect to the linear-polarized laser field. Thus, this work reports on the first successful orientation-dependent analysis of the multiphoton ionization of H{sub 2} performed by means of a full-dimensional numerical treatment. Besides the investigation of few-photon regime, an extensive numerical study of the ionization by ultrashort frequency-doubled Ti:sapphire laser pulses (400 nm) is presented. Performing a series of calculations for different internuclear separations, the total ionization yields of H{sub 2} and D{sub 2} in their ground vibrational states are obtained for both parallel and perpendicular orientations. A series of calculations for 800 nm laser pulses are used to test a popular simple interference model. Besides the discussion of the ab initio numerical method, this work considers different aspects related to the application of the strong-field approximation (SFA) for investigation of a strong-field response of an atomic and molecular system. Thus, a deep analysis of the gauge problem of SFA is performed and the quasistatic limit of the velocity-gauge SFA ionization rates is derived. The applications of the length-gauge SFA are examined and a recently proposed generalized Keldysh theory is criticized. (orig.)

  4. Ionization of molecular hydrogen in ultrashort intense laser pulses

    International Nuclear Information System (INIS)

    Vanne, Yulian V.

    2010-01-01

    A novel ab initio numerical approach is developed and applied that solves the time-dependent Schroedinger equation describing two-electron diatomic molecules (e.g. molecular hydrogen) exposed to an intense ultrashort laser pulse. The method is based on the fixed-nuclei and the non-relativistic dipole approximations and aims to accurately describe both correlated electrons in full dimensionality. The method is applicable for a wide range of the laser pulse parameters and is able to describe both few-photon and many-photon single ionization processes, also in a non-perturbative regime. A key advantage of the method is its ability to treat the strong-field response of the molecules with arbitrary orientation of the molecular axis with respect to the linear-polarized laser field. Thus, this work reports on the first successful orientation-dependent analysis of the multiphoton ionization of H 2 performed by means of a full-dimensional numerical treatment. Besides the investigation of few-photon regime, an extensive numerical study of the ionization by ultrashort frequency-doubled Ti:sapphire laser pulses (400 nm) is presented. Performing a series of calculations for different internuclear separations, the total ionization yields of H 2 and D 2 in their ground vibrational states are obtained for both parallel and perpendicular orientations. A series of calculations for 800 nm laser pulses are used to test a popular simple interference model. Besides the discussion of the ab initio numerical method, this work considers different aspects related to the application of the strong-field approximation (SFA) for investigation of a strong-field response of an atomic and molecular system. Thus, a deep analysis of the gauge problem of SFA is performed and the quasistatic limit of the velocity-gauge SFA ionization rates is derived. The applications of the length-gauge SFA are examined and a recently proposed generalized Keldysh theory is criticized. (orig.)

  5. Generation of Ultra-high Intensity Laser Pulses

    International Nuclear Information System (INIS)

    Fisch, N.J.; Malkin, V.M.

    2003-01-01

    Mainly due to the method of chirped pulse amplification, laser intensities have grown remarkably during recent years. However, the attaining of very much higher powers is limited by the material properties of gratings. These limitations might be overcome through the use of plasma, which is an ideal medium for processing very high power and very high total energy. A plasma can be irradiated by a long pump laser pulse, carrying significant energy, which is then quickly depleted in the plasma by a short counterpropagating pulse. This counterpropagating wave effect has already been employed in Raman amplifiers using gases or plasmas at low laser power. Of particular interest here are the new effects which enter in high power regimes. These new effects can be employed so that one high-energy optical system can be used like a flashlamp in what amounts to pumping the plasma, and a second low-power optical system can be used to extract quickly the energy from the plasma and focus it precisely. The combined system can be very compact. Thus, focused intensities more than 10 25 W/cm 2 can be contemplated using existing optical elements. These intensities are several orders of magnitude higher than what is currently available through chirped pump amplifiers

  6. 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).

  7. Ultra-short pulse, ultra-high intensity laser improvement techniques for laser-driven quantum beam science

    International Nuclear Information System (INIS)

    Kiriyama, Hiromitsu; Kando, Masaki

    2014-01-01

    Recent development activities of the Quantum Beam Research Team in JAEA are reported. The downsized, petawatt and femtosecond pulse laser is described at first. The process of the system development and utilization effort of so-called J-KAREN is explained with its time and space control system. For high contrast, OPCPA (Optical Parametric Chirped Pulse Amplification) preamplifier is adopted by using the titanium-sapphire laser system in which only the seed light pulses can be amplified. In addition, high contrast is obtained by adopting the high energy seed light to the amplifier. The system configuration of J-KAREN laser is illustrated. Typical spectra with and without OPCPA, as well as the spectra with OPCPA adjustment and without one are shown. The result of the recompressed pulses is shown in which the pulse width of 29.5 femtoseconds is close to the theoretical limit. Considering the throughput of the pulse compressor is 64 percent it is possible to generate high power laser beam of about 600 terawatts. In the supplementary budget of 2012, it has been approved to cope with the aging or obsoleteness of the system and at the same time to further sophisticate the laser using system. The upgraded laser system is named as J-KAREN-P in which the repetition rate is improved and another booster amplifier is added to increase the power. The system configuration of J-KAREN-P after the upgrading is illustrated. (S. Funahashi)

  8. Studying the mechanism of micromachining by short pulsed laser

    Science.gov (United States)

    Gadag, Shiva

    The semiconductor materials like Si and the transparent dielectric materials like glass and quartz are extensively used in optoelectronics, microelectronics, and microelectromechanical systems (MEMS) industries. The combination of these materials often go hand in hand for applications in MEMS such as in chips for pressure sensors, charge coupled devices (CCD), and photovoltaic (PV) cells for solar energy generation. The transparent negative terminal of the solar cell is made of glass on one surface of the PV cell. The positive terminal (cathode) on the other surface of the solar cell is made of silicon with a glass negative terminal (anode). The digital watches and cell phones, LEDs, micro-lens, optical components, and laser optics are other examples for the application of silicon and or glass. The Si and quartz are materials extensively used in CCD and LED for digital cameras and CD players respectively. Hence, three materials: (1) a semiconductor silicon and transparent dielectrics,- (2) glass, and (3) quartz are chosen for laser micromachining as they have wide spread applications in microelectronics industry. The Q-switched, nanosecond pulsed lasers are most extensively used for micro-machining. The nanosecond type of short pulsed laser is less expensive for the end users than the second type, pico or femto, ultra-short pulsed lasers. The majority of the research work done on these materials (Si, SiO 2, and glass) is based on the ultra-short pulsed lasers. This is because of the cut quality, pin point precision of the drilled holes, formation of the nanometer size microstructures and fine features, and minimally invasive heat affected zone. However, there are many applications such as large surface area dicing, cutting, surface cleaning of Si wafers by ablation, and drilling of relatively large-sized holes where some associated heat affected zone due to melting can be tolerated. In such applications the nanosecond pulsed laser ablation of materials is very

  9. Hybrid micromachining using a nanosecond pulsed laser and micro EDM

    International Nuclear Information System (INIS)

    Kim, Sanha; Chung, Do Kwan; Shin, Hong Shik; Chu, Chong Nam; Kim, Bo Hyun

    2010-01-01

    Micro electrical discharge machining (micro EDM) is a well-known precise machining process that achieves micro structures of excellent quality for any conductive material. However, the slow machining speed and high tool wear are main drawbacks of this process. Though the use of deionized water instead of kerosene as a dielectric fluid can reduce the tool wear and increase the machine speed, the material removal rate (MRR) is still low. In contrast, laser ablation using a nanosecond pulsed laser is a fast and non-wear machining process but achieves micro figures of rather low quality. Therefore, the integration of these two processes can overcome the respective disadvantages. This paper reports a hybrid process of a nanosecond pulsed laser and micro EDM for micromachining. A novel hybrid micromachining system that combines the two discrete machining processes is introduced. Then, the feasibility and characteristics of the hybrid machining process are investigated compared to conventional EDM and laser ablation. It is verified experimentally that the machining time can be effectively reduced in both EDM drilling and milling by rapid laser pre-machining prior to micro EDM. Finally, some examples of complicated 3D micro structures fabricated by the hybrid process are shown

  10. Technique for long and absolute distance measurement based on laser pulse repetition frequency sweeping

    Science.gov (United States)

    Castro Alves, D.; Abreu, Manuel; Cabral, A.; Jost, Michael; Rebordão, J. M.

    2017-11-01

    In this work we present a technique to perform long and absolute distance measurements based on mode-locked diode lasers. Using a Michelson interferometer, it is possible to produce an optical cross-correlation between laser pulses of the reference arm with the pulses from the measurement arm, adjusting externally their degree of overlap either changing the pulse repetition frequency (PRF) or the position of the reference arm mirror for two (or more) fixed frequencies. The correlation of the travelling pulses for precision distance measurements relies on ultra-short pulse durations, as the uncertainty associated to the method is dependent on the laser pulse width as well as on a highly stable PRF. Mode-locked Diode lasers are a very appealing technology for its inherent characteristics, associated to compactness, size and efficiency, constituting a positive trade-off with regard to other mode-locked laser sources. Nevertheless, main current drawback is the non-availability of frequency-stable laser diodes. The laser used is a monolithic mode-locked semiconductor quantum-dot (QD) laser. The laser PRF is locked to an external stabilized RF reference. In this work we will present some of the preliminary results and discuss the importance of the requirements related to laser PRF stability in the final metrology system accuracy.

  11. Stimulated brillouin backscatter of a short-pulse laser

    International Nuclear Information System (INIS)

    Hinkel, D.E.; Williams, E.A.; Berger, R.L.

    1994-01-01

    Stimulated Brillouin backscattering (SBBS) from a short-pulse laser, where the pulse length is short compared to the plasma length, is found to be qualitatively different than in the long pulse regime, where the pulse length is long compared to the plasma length. We find that after an initial transient of order the laser pulse length transit time, the instability reaches a steady state in the variables x' = x - V g t, t' = t, where V g is the pulse group velocity. In contrast, SBBS in a long pulse can be absolutely unstable and grows indefinitely, or until nonlinearities intervene. We find that the motion of the laser pulse induces Doppler related effects that substantially modify the backscattered spectrum at higher intensities, where the instability is strongly coupled (i.e. , has a growth rate large compared to the ion acoustic frequency)

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

    International Nuclear Information System (INIS)

    Yi, Jong Hoon; Horn, Roland; Wendt, K.

    2001-01-01

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

  13. Pulse laser ablation at water-air interface

    Science.gov (United States)

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

    2010-06-01

    We studied a new pulse laser ablation phenomenon on a liquid surface layer, which is caused by the difference between the refractive indices of the two materials involved. The present study was motivated by our previous study, which showed that laser ablation can occur at the interface between a transparent material and a gas or liquid medium when the laser pulse is focused through the transparent material. In this case, the ablation threshold fluence is reduced remarkably. In the present study, experiments were conducted in water and air in order to confirm this phenomenon for a combination of two fluid media with different refractive indices. This phenomenon was observed in detail by pulse laser shadowgraphy. A high-resolution film was used to record the phenomenon with a Nd:YAG pulse laser with 10-ns duration as a light source. The laser ablation phenomenon on the liquid surface layer caused by a focused Nd:YAG laser pulse with 1064-nm wavelength was found to be followed by the splashing of the liquid surface, inducing a liquid jet with many ligaments. The liquid jet extension velocity was around 1000 m/s in a typical case. The liquid jet decelerated drastically due to rapid atomization at the tips of the ligaments. The liquid jet phenomenon was found to depend on the pulse laser parameters such as the laser fluence on the liquid surface, laser energy, and laser beam pattern. The threshold laser fluence for the generation of a liquid jet was 20 J/cm2. By increasing the incident laser energy with a fixed laser fluence, the laser focused area increased, which eventually led to an increase in the size of the plasma column. The larger the laser energy, the larger the jet size and the longer the temporal behavior. The laser beam pattern was found to have significant effects on the liquid jet’s velocity, shape, and history.

  14. Electron acceleration by a self-diverging intense laser pulse

    International Nuclear Information System (INIS)

    Singh, K.P.; Gupta, D.N.; Tripathi, V.K.; Gupta, V.L.

    2004-01-01

    Electron acceleration by a laser pulse having a Gaussian radial and temporal profile of intensity has been studied. The interaction region is vacuum followed by a gas. The starting point of the gas region has been chosen around the point at which the peak of the pulse interacts with the electron. The tunnel ionization of the gas causes a defocusing of the laser pulse and the electron experiences the action of a ponderomotive deceleration at the trailing part of the pulse with a lower intensity rather than an acceleration at the rising part of the laser pulse with a high intensity, and thus gains net energy. The initial density of the neutral gas atoms should be high enough to properly defocus the pulse; otherwise the electron experiences some deceleration during the trailing part of the pulse and the net energy gain is reduced. The rate of tunnel ionization increases with the increase in the laser intensity and the initial density of neutral gas atoms, and with the decreases in the laser spot size, which causes more defocusing of the laser pulse. The required initial density of neutral gas atoms decreases with the increase in the laser intensity and also with the decrease in the laser spot size

  15. Development of subpicosecond pulse radiolysis system

    CERN Document Server

    Kozawa, T; Miki, M; Yamamoto, T; Suemine, S; Yoshida, Y; Tagawa, S

    2000-01-01

    The highest time resolution of the pulse radiolysis had remained about 30 ps since the late 1960s. To make clear the primary processes in the radiation chemistry and physics within 30 ps, we developed a stroboscopic pulse radiolysis system for the absorption spectroscopy with the time resolution of 2.0 ps (10-90% rise time). The time resolution of 2.0 ps was estimated from the time-dependent behavior of the hydrated electrons. The system consists of a subpicosecond electron linac as an irradiation source, a femtosecond laser as an analyzing light and a jitter compensation system.

  16. Ultrashort laser pulses and electromagnetic pulse generation in air and on dielectric surfaces

    International Nuclear Information System (INIS)

    Sprangle, P.; Penano, J.R.; Hafizi, B.; Kapetanakos, C.A.

    2004-01-01

    Intense, ultrashort laser pulses propagating in the atmosphere have been observed to emit sub-THz electromagnetic pulses (EMPS). The purpose of this paper is to analyze EMP generation from the interaction of ultrashort laser pulses with air and with dielectric surfaces and to determine the efficiency of conversion of laser energy to EMP energy. In our self-consistent model the laser pulse partially ionizes the medium, forms a plasma filament, and through the ponderomotive forces associated with the laser pulse, drives plasma currents which are the source of the EMP. The propagating laser pulse evolves under the influence of diffraction, Kerr focusing, plasma defocusing, and energy depletion due to electron collisions and ionization. Collective effects and recombination processes are also included in the model. The duration of the EMP in air, at a fixed point, is found to be a few hundred femtoseconds, i.e., on the order of the laser pulse duration plus the electron collision time. For steady state laser pulse propagation the flux of EMP energy is nonradiative and axially directed. Radiative EMP energy is present only for nonsteady state or transient laser pulse propagation. The analysis also considers the generation of EMP on the surface of a dielectric on which an ultrashort laser pulse is incident. For typical laser parameters, the power and energy conversion efficiency from laser radiation to EMP radiation in both air and from dielectric surfaces is found to be extremely small, -8 . Results of full-scale, self-consistent, numerical simulations of atmospheric and dielectric surface EMP generation are presented. A recent experiment on atmospheric EMP generation is also simulated

  17. Electron acceleration by laser produced wake field: Pulse shape effect

    Science.gov (United States)

    Malik, Hitendra K.; Kumar, Sandeep; Nishida, Yasushi

    2007-12-01

    Analytical expressions are obtained for the longitudinal field (wake field: Ex), density perturbations ( ne') and the potential ( ϕ) behind a laser pulse propagating in a plasma with the pulse duration of the electron plasma period. A feasibility study on the wake field is carried out with Gaussian-like (GL) pulse, rectangular-triangular (RT) pulse and rectangular-Gaussian (RG) pulse considering one-dimensional weakly nonlinear theory ( ne'/n0≪1), and the maximum energy gain acquired by an electron is calculated for all these three types of the laser pulse shapes. A comparative study infers that the RT pulse yields the best results: In its case maximum electron energy gain is 33.5 MeV for a 30 fs pulse duration whereas in case of GL (RG) pulse of the same duration the gain is 28.6 (28.8)MeV at the laser frequency of 1.6 PHz and the intensity of 3.0 × 10 18 W/m 2. The field of the wake and hence the energy gain get enhanced for the higher laser frequency, larger pulse duration and higher laser intensity for all types of the pulses.

  18. Simulation of eye-tracker latency, spot size, and ablation pulse depth on the correction of higher order wavefront aberrations with scanning spot laser systems.

    Science.gov (United States)

    Bueeler, Michael; Mrochen, Michael

    2005-01-01

    The aim of this theoretical work was to investigate the robustness of scanning spot laser treatments with different laser spot diameters and peak ablation depths in case of incomplete compensation of eye movements due to eye-tracker latency. Scanning spot corrections of 3rd to 5th Zernike order wavefront errors were numerically simulated. Measured eye-movement data were used to calculate the positioning error of each laser shot assuming eye-tracker latencies of 0, 5, 30, and 100 ms, and for the case of no eye tracking. The single spot ablation depth ranged from 0.25 to 1.0 microm and the spot diameter from 250 to 1000 microm. The quality of the ablation was rated by the postoperative surface variance and the Strehl intensity ratio, which was calculated after a low-pass filter was applied to simulate epithelial surface smoothing. Treatments performed with nearly ideal eye tracking (latency approximately 0) provide the best results with a small laser spot (0.25 mm) and a small ablation depth (250 microm). However, combinations of a large spot diameter (1000 microm) and a small ablation depth per pulse (0.25 microm) yield the better results for latencies above a certain threshold to be determined specifically. Treatments performed with tracker latencies in the order of 100 ms yield similar results as treatments done completely without eye-movement compensation. CONCWSIONS: Reduction of spot diameter was shown to make the correction more susceptible to eye movement induced error. A smaller spot size is only beneficial when eye movement is neutralized with a tracking system with a latency <5 ms.

  19. Dielectrophoretic focusing integrated pulsed laser activated cell sorting

    Science.gov (United States)

    Zhu, Xiongfeng; Kung, Yu-Chun; Wu, Ting-Hsiang; Teitell, Michael A.; Chiou, Pei-Yu

    2017-08-01

    We present a pulsed laser activated cell sorter (PLACS) integrated with novel sheathless size-independent dielectrophoretic (DEP) focusing. Microfluidic fluorescence activated cell sorting (μFACS) systems aim to provide a fully enclosed environment for sterile cell sorting and integration with upstream and downstream microfluidic modules. Among them, PLACS has shown a great potential in achieving comparable performance to commercial aerosol-based FACS (>90% purity at 25,000 cells sec-1). However conventional sheath flow focusing method suffers a severe sample dilution issue. Here we demonstrate a novel dielectrophoresis-integrated pulsed laser activated cell sorter (DEP-PLACS). It consists of a microfluidic channel with 3D electrodes laid out to provide a tunnel-shaped electric field profile along a 4cmlong channel for sheathlessly focusing microparticles/cells into a single stream in high-speed microfluidic flows. All focused particles pass through the fluorescence detection zone along the same streamline regardless of their sizes and types. Upon detection of target fluorescent particles, a nanosecond laser pulse is triggered and focused in a neighboring channel to generate a rapidly expanding cavitation bubble for precise sorting. DEP-PLACS has achieved a sorting purity of 91% for polystyrene beads at a throughput of 1,500 particle/sec.

  20. Active manipulation of the selective alignment by two laser pulses

    International Nuclear Information System (INIS)

    Zeng-Qiang, Yang; Zhi-Rong, Guo; Gui-Xian, Ge

    2010-01-01

    This paper solves numerically the full time-dependent Schrödinger equation based on the rigid rotor model, and proposes a novel strategy to determine the optimal time delay of the two laser pulses to manipulate the molecular selective alignment. The results illustrate that the molecular alignment generated by the first pulse can be suppressed or enhanced selectively, the relative populations of even and odd rotational states in the final rotational wave packet can be manipulated selectively by precisely inserting the peak of the second laser pulse at the time when the slope for the alignment parameter by the first laser locates a local maximum for the even rotational states and a local minimum for the odds, and vice versa. The selective alignment can be further optimised by selecting the intensity ratio of the two laser pulses on the condition that the total laser intensity and pulse duration are kept constant. (atomic and molecular physics)

  1. Ultrafast pulse lasers jump to macro applications

    Science.gov (United States)

    Griebel, Martin; Lutze, Walter; Scheller, Torsten

    2016-03-01

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

  2. Hose-Modulation Instability of Laser Pulses in Plasmas

    International Nuclear Information System (INIS)

    Sprangle, P.; Krall, J.; Esarey, E.

    1994-01-01

    A laser pulse propagating in a uniform plasma or a preformed plasma density channel is found to undergo a combination of hose and modulation instabilities, provided the pulse centroid has an initial tilt. Coupled equations for the laser centroid and envelope are derived and solved for a finite-length laser pulse. Significant coupling between the centroid and the envelope, harmonic generation in the envelope, and strong modification of the wake field can occur. Methods to reduce the growth rate of the laser hose instability are demonstrated

  3. Nonlinear laser pulse response in a crystalline lens.

    Science.gov (United States)

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

    2016-04-01

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

  4. Evaluation of cytogenetic effects of very short laser pulsed radiations

    International Nuclear Information System (INIS)

    Guedeney, G.; Courant, D.; Malarbet, J.-L.; Dolloy, M.-T.; Court, L.

    1992-01-01

    The aim of this study is to evaluate the capacity of a laser, delivering very short pulses in the near infrared spectrum with a high pulse ratio frequency, to induce genetic modification on biological tissues. Chromatid exchanges and chromosomal aberrations studies are used to test potential effect on human lymphocytes. The laser irradiation induces a significant increase of acentric fragments but the absence of dicentric suggests that a repetitive very short pulses irradiation has a relatively low capacity to induce genetic abnormalities. (author)

  5. Thermal Effect of Pulsed Laser on Human Skin

    OpenAIRE

    N. C. Majumdar; V. K. Kochhar

    1985-01-01

    An attempt has been made to derive from theoretical considerations, some idea about safety limits of exposure with regard to radiant energy skin burns. This may be regarded as a preliminary enquiry in respect of thermal tissue damage by pulsed laser radiation, since the effects of isolated single pulses from ruby laser only have been considered. The study needs to be extended to other wavelengths as well as to trains of pulses.

  6. 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....

  7. Water spray assisted ultrashort laser pulse ablation

    International Nuclear Information System (INIS)

    Silvennoinen, M.; Kaakkunen, J.J.J.; Paivasaari, K.; Vahimaa, P.

    2013-01-01

    Highlights: ► We show the novel method to use multibeam processing with ultrashort pulses efficiently. ► Sprayed thin water layer on ablation zone enhances ablation rate and quality. ► In some cases this method also enables ablation of the deeper and straighter holes compared to ones made without the water layer. ► Method also makes possible to directly write features without the self-organizing structures. - Abstract: We have studied femtosecond ablation under sprayed thin water film and its influence and benefits compared with ablation in the air atmosphere. These have been studied in case of the hole and the groove ablation using IR femtosecond laser. Water enhances the ablation rate and in some situations it makes possible to ablate the holes with a higher aspect ratio. While ablating the grooves, the water spray allows using the high fluences without the generation of the self-organized structures.

  8. Interaction of gold nanoparticles with nanosecond laser pulses: Nanoparticle heating

    International Nuclear Information System (INIS)

    Nedyalkov, N.N.; Imamova, S.E.; Atanasov, P.A.; Toshkova, R.A.; Gardeva, E.G.; Yossifova, L.S.; Alexandrov, M.T.; Obara, M.

    2011-01-01

    Theoretical and experimental results on the heating process of gold nanoparticles irradiated by nanosecond laser pulses are presented. The efficiency of particle heating is demonstrated by in-vitro photothermal therapy of human tumor cells. Gold nanoparticles with diameters of 40 and 100 nm are added as colloid in the cell culture and the samples are irradiated by nanosecond pulses at wavelength of 532 nm delivered by Nd:YAG laser system. The results indicate clear cytotoxic effect of application of nanoparticle as more efficient is the case of using particles with diameter of 100 nm. The theoretical analysis of the heating process of nanoparticle interacting with laser radiation is based on the Mie scattering theory, which is used for calculation of the particle absorption coefficient, and two-dimensional heat diffusion model, which describes the particle and the surrounding medium temperature evolution. Using this model the dependence of the achieved maximal temperature in the particles on the applied laser fluence and time evolution of the particle temperature is obtained.

  9. Interaction of gold nanoparticles with nanosecond laser pulses: Nanoparticle heating

    Science.gov (United States)

    Nedyalkov, N. N.; Imamova, S. E.; Atanasov, P. A.; Toshkova, R. A.; Gardeva, E. G.; Yossifova, L. S.; Alexandrov, M. T.; Obara, M.

    2011-04-01

    Theoretical and experimental results on the heating process of gold nanoparticles irradiated by nanosecond laser pulses are presented. The efficiency of particle heating is demonstrated by in-vitro photothermal therapy of human tumor cells. Gold nanoparticles with diameters of 40 and 100 nm are added as colloid in the cell culture and the samples are irradiated by nanosecond pulses at wavelength of 532 nm delivered by Nd:YAG laser system. The results indicate clear cytotoxic effect of application of nanoparticle as more efficient is the case of using particles with diameter of 100 nm. The theoretical analysis of the heating process of nanoparticle interacting with laser radiation is based on the Mie scattering theory, which is used for calculation of the particle absorption coefficient, and two-dimensional heat diffusion model, which describes the particle and the surrounding medium temperature evolution. Using this model the dependence of the achieved maximal temperature in the particles on the applied laser fluence and time evolution of the particle temperature is obtained.

  10. Characteristics and Applications of Spatiotemporally Focused Femtosecond Laser Pulses

    Directory of Open Access Journals (Sweden)

    Chenrui Jing

    2016-12-01

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

  11. Development of pulsed dye lasers for kidney stone fragmentation

    International Nuclear Information System (INIS)

    Hsia, J.

    1990-01-01

    The idea of using lasers to break stones inside the body was first proposed soon after the appearance of the pulsed ruby laser in 1960. Early work of pioneers in the field such as Mulvaney Pensel, and Tanahashi did not lead to a useful clinical protocol. In 1982, Dr. Graham Watson started a systematic search for the right laser. He soon came to the conclusion that CW lasers that relied on thermal effects were not clinically effective. Q-switched lasers such as ruby and Nd:YAG were eliminated because available optical fibers could not handle the high peak powers they emitted. Animal tests were completed and the first human was successfully treated at MGH by Dr. Stephen Dretler in October, 1985. This was soon followed by treatments at the Institute of Urology in London by Dr. Watson and Dr. Wickham. Today, lasertripsy is the treatment of choice for lower ureteral stones. In this paper the work leading to the development of the first clinically effective laser lithotripsy system is reviewed

  12. CO2 laser pulse shortening by laser ablation of a metal target

    International Nuclear Information System (INIS)

    Donnelly, T.; Mazoyer, M.; Lynch, A.; O'Sullivan, G.; O'Reilly, F.; Dunne, P.; Cummins, T.

    2012-01-01

    A repeatable and flexible technique for pulse shortening of laser pulses has been applied to transversely excited atmospheric (TEA) CO 2 laser pulses. The technique involves focusing the laser output onto a highly reflective metal target so that plasma is formed, which then operates as a shutter due to strong laser absorption and scattering. Precise control of the focused laser intensity allows for timing of the shutter so that different temporal portions of the pulse can be reflected from the target surface before plasma formation occurs. This type of shutter enables one to reduce the pulse duration down to ∼2 ns and to remove the low power, long duration tails that are present in TEA CO 2 pulses. The transmitted energy is reduced as the pulse duration is decreased but the reflected power is ∼10 MW for all pulse durations. A simple laser heating model verifies that the pulse shortening depends directly on the plasma formation time, which in turn is dependent on the applied laser intensity. It is envisaged that this plasma shutter will be used as a tool for pulse shaping in the search for laser pulse conditions to optimize conversion efficiency from laser energy to useable extreme ultraviolet (EUV) radiation for EUV source development.

  13. Concave pulse shaping of a circularly polarized laser pulse from non-uniform overdense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Hur, Min Sup [School of Natural Science, UNIST, BanYeon-Ri 100, Ulju-gun, Ulsan, 689-798 (Korea, Republic of); Kulagin, Victor V. [Sternberg Astronomical Institute, Moscow State University, Universitetsky prosp. 13, Moscow, 119992 (Russian Federation); Suk, Hyyong, E-mail: hysuk@gist.ac.kr [Department of Physics and Photon Science, GIST, 123 Cheomdan-gwangiro, Buk-gu, Gwangju, 500-712 (Korea, Republic of)

    2015-03-20

    Pulse shaping of circularly polarized laser pulses in nonuniform overdense plasmas are investigated numerically. Specifically we show by two-dimensional particle-in-cell simulations the generation of a concave pulse front of a circularly polarized, a few tens of petawatt laser pulse from a density-tapered, overdense plasma slab. The concept used for the transverse-directional shaping is the differential transmittance depending on the plasma density, and the laser intensity. For suitable selection of the slab parameters for the concave pulse shaping, we studied numerically the pulse transmittance, which can be used for further parameter design of the pulse shaping. The concavely shaped circularly polarized pulse is expected to add more freedom in controlling the ion-beam characteristics in the RPDA regime. - Highlights: • Laser pulse shaping for a concave front by non-uniform overdense plasma was studied. • Particle-in-cell (PIC) simulations were used for the investigation. • A laser pulse can be shaped by a density-tapered overdense plasma. • The concave and sharp pulse front are useful in many laser–plasma applications. • They are important for ion acceleration, especially in the radiation pressure dominant regime.

  14. Control of laser pulse waveform in longitudinally excited CO2 laser by adjustment of excitation circuit

    Science.gov (United States)

    Uno, Kazuyuki; Jitsuno, Takahisa

    2018-05-01

    In a longitudinally excited CO2 laser that had a 45 cm-long discharge tube with a 1:1:2 mixture of CO2/N2/He gas at a pressure of 3.0 kPa, we realized the generation of a short laser pulse with a spike pulse width of about 200 ns and a pulse tail length of several tens of microseconds, control of the energy ratio of the spike pulse part to the pulse tail part in the short laser pulse, the generation of a long laser pulse with a pulse width of several tens of microseconds, and control of the pulse width in the long laser pulse, by using four types of excitation circuits in which the capacitance was adjusted. In the short laser pulse, the energy ratio was in the range 1:14-1:112. In the long laser pulse, the pulse width was in the range 25.7-82.7 μs.

  15. CTS and CZTS for solar cells made by pulsed laser deposition and pulsed electron deposition

    DEFF Research Database (Denmark)

    Ettlinger, Rebecca Bolt

    This thesis concerns the deposition of thin films for solar cells using pulsed laser deposition (PLD) and pulsed electron deposition (PED). The aim was to deposit copper tin sulfide (CTS) and zinc sulfide (ZnS) by pulsed laser deposition to learn about these materials in relation to copper zinc tin...... time. We compared the results of CZTS deposition by PLD at DTU in Denmark to CZTS made by PED at IMEM-CNR, where CIGS solar cells have successfully been fabricated at very low processing temperatures. The main results of this work were as follows: Monoclinic-phase CTS films were made by pulsed laser...... deposition followed by high temperature annealing. The films were used to understand the double band gap that we and other groups observed in the material. The Cu-content of the CTS films varied depending on the laser fluence (the laser energy per pulse and per area). The material transfer from...

  16. Ultrafast population transfer in a Λ-configuration level system driven by few-cycle laser pulses

    International Nuclear Information System (INIS)

    Zhang Wen-Jing; Xie Xiao-Tao; Jin Lu-Ling; Bai Jin-Tao

    2013-01-01

    The feasibility of population transfer from a populated level via an intermediate state to the target level driven by few-cycle pulses is theoretically discussed. The processes of on- or far-resonance stimulated Raman scattering with sequential or simultaneous ultrashort pulses are investigated respectively. We find that the ultrashort pulses with about two optical cycles can be used to realize the population operation. This suggests that the population transfer can be completed in the femtosecond time scale. At the same time, our simulation shows that the signal of the carrier-envelope-phase-dependent effect can be enlarged due to quantum interference in some conditions. Our theoretic study may promote the research on the coherent control via ultrashort pulses in the related fields

  17. Pulsed laser dewetting of nickel catalyst for carbon nanofiber growth

    International Nuclear Information System (INIS)

    Guan, Y F; Pearce, R C; Simpson, M L; Rack, P D; Melechko, A V; Hensley, D K

    2008-01-01

    We present a pulsed laser dewetting technique that produces single nickel catalyst particles from lithographically patterned disks for subsequent carbon nanofiber growth through plasma enhanced chemical vapor deposition. Unlike the case for standard heat treated Ni catalyst disks, for which multiple nickel particles and consequently multiple carbon nanofibers (CNFs) are observed, single vertically aligned CNFs could be obtained from the laser dewetted catalyst. Different laser dewetting parameters were tested in this study, such as the laser energy density and the laser processing time measured by the total number of laser pulses. Various nickel disk radii and thicknesses were attempted and the resultant number of carbon nanofibers was found to be a function of the initial disk dimension and the number of laser pulses

  18. Characterization of Ultrafast Laser Pulses using a Low-dispersion Frequency Resolved Optical Grating Spectrometer

    Science.gov (United States)

    Whitelock, Hope; Bishop, Michael; Khosravi, Soroush; Obaid, Razib; Berrah, Nora

    2016-05-01

    A low dispersion frequency-resolved optical gating (FROG) spectrometer was designed to characterize ultrashort (non-colinear optical parametric amplifier. This instrument splits a laser pulse into two replicas with a 90:10 intensity ratio using a thin pellicle beam-splitter and then recombines the pulses in a birefringent medium. The instrument detects a wavelength-sensitive change in polarization of the weak probe pulse in the presence of the stronger pump pulse inside the birefringent medium. Scanning the time delay between the two pulses and acquiring spectra allows for characterization of the frequency and time content of ultrafast laser pulses, that is needed for interpretation of experimental results obtained from these ultrafast laser systems. Funded by the DoE-BES, Grant No. DE-SC0012376.

  19. Energy losses estimation during pulsed-laser seam welding

    Czech Academy of Sciences Publication Activity Database

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

    2014-01-01

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

  20. The Vulcan pulse generating system

    International Nuclear Information System (INIS)

    Danson, C.N.; Edwards, C.B.; Wyatt, R.W.W.

    1985-01-01

    During the past two years several changes have been made to the front end system on the VULCAN pulse generating system. These changes give greater flexibility and a wider choice of operating conditions. This note gives an updated description of the system capabilities, and gives users of the facility an idea of the various pulse combinations that are available. (author)

  1. An injection seeded single frequency Nd:YAG Q-switched laser with precisely controllable laser pulse firing time

    Science.gov (United States)

    Wu, Frank F.; Khizhnyak, Anatoliy; Markov, Vladimir

    2010-02-01

    We have realized a single frequency Q-switched Nd:YAG laser with precisely controllable lasing time and thus enabled synchronization of multi-laser systems. The use of injection seeding to the slave ring oscillator results in unidirectional Q-switched laser oscillation with suppression of bidirectional Q-switched oscillation that otherwise would be initiated from spontaneous emission if the seeding laser is not present. Under normal condition, the cavity is high in loss during the pumping period; then a Pockels cell opens the cavity to form the pulse build up, with a second Pockels cell to perform cavity dumping, generating the Q-switched pulse output with optimized characteristics. The two Pockels cells can be replaced by a single unit if an adjustable gated electrical pulse is applied to the Pockels cell in which the pulse front is used to open the cavity and the falling edge to dump the laser pulse. Proper selection of the pump parameters and Pockels-cell gating enables operation of the system in a mode in which the Q-switched pulse can be formed only under the seeding condition. The advantage of the realized regime is in stable laser operation with no need in adjustment of the seeded light wavelength and the mode of the cavity. It is found that the frequency of the Q-switched laser radiation matches well to the injected seeded laser mode. By using two-stage amplifiers, an output energy better than 300 mJ has been achieved in MOPA configuration without active control of the cavity length and with pulse width adjustability from several nanoseconds to 20 ns. The Q-switched oscillator operates not only at precisely controlled firing time but also can be tuned over wide range. This will enable multi-laser systems synchronization and frequency locking down each other if necessary.

  2. Explosive Nucleosynthesis Study Using Laser Driven γ-ray Pulses

    Directory of Open Access Journals (Sweden)

    Takehito Hayakawa

    2017-03-01

    Full Text Available We propose nuclear experiments using γ-ray pulses provided from high field plasma generated by high peak power laser. These γ-ray pulses have the excellent features of extremely short pulse, high intensity, and continuous energy distribution. These features are suitable for the study of explosive nucleosyntheses in novae and supernovae, such as the γ process and ν process. We discuss how to generate suitable γ-ray pulses and the nuclear astrophysics involved.

  3. Fragmentation dynamics of molecular hydrogen in strong ultrashort laser pulses

    International Nuclear Information System (INIS)

    Rudenko, A; Feuerstein, B; Zrost, K; Jesus, V L B de; Ergler, T; Dimopoulou, C; Schroeter, C D; Moshammer, R; Ullrich, J

    2005-01-01

    We present the results of a systematic experimental study of dissociation and Coulomb explosion of molecular hydrogen induced by intense ultrashort (7-25 fs) laser pulses. Using coincident recoil-ion momentum spectroscopy we can distinguish the contributions from dissociation and double ionization even if they result in the same kinetic energies of the fragments. The dynamics of all fragmentation channels drastically depends on the pulse duration, and for 7 fs pulses becomes extremely sensitive to the pulse shape

  4. Effect of laser pulse parameters on the size and fluorescence of nanodiamonds formed upon pulsed-laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Peikang [School of Materials Science and Engineering, North University of China, Taiyuan 030051 (China); Hu, Shengliang, E-mail: hsliang@yeah.net [Key Laboratory of Instrumentation Science and Dynamic Measurement (North University of China), Ministry of Education, National Key Laboratory Science and Technology on Electronic Test and Measurement, Taiyuan 030051 (China); School of Materials Science and Engineering, North University of China, Taiyuan 030051 (China); Zhang, Taiping; Sun, Jing [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Cao, Shirui [School of Materials Science and Engineering, North University of China, Taiyuan 030051 (China)

    2010-07-15

    The size of nanodiamonds formed upon laser irradiation could be easily controlled over simply adjusting laser pulse parameters. The stable size and structure of nanodiamonds were mostly determined by laser power density and pulse width. Both large nanodiamonds with multiply twinning structure (MTS) and small nanodiamonds with single crystalline structure (SCS) emitted strong visible light after surface passivation, and their fluorescence quantum yield (QY) was 4.6% and 7.1%, respectively.

  5. Effect of laser pulse parameters on the size and fluorescence of nanodiamonds formed upon pulsed-laser irradiation

    International Nuclear Information System (INIS)

    Bai, Peikang; Hu, Shengliang; Zhang, Taiping; Sun, Jing; Cao, Shirui

    2010-01-01

    The size of nanodiamonds formed upon laser irradiation could be easily controlled over simply adjusting laser pulse parameters. The stable size and structure of nanodiamonds were mostly determined by laser power density and pulse width. Both large nanodiamonds with multiply twinning structure (MTS) and small nanodiamonds with single crystalline structure (SCS) emitted strong visible light after surface passivation, and their fluorescence quantum yield (QY) was 4.6% and 7.1%, respectively.

  6. Generation and amplification of nanaosecond duration multiline hf laser pulses

    International Nuclear Information System (INIS)

    Getzinger, R.L.; Ware, K.D.; Carpenter, J.P.

    1976-01-01

    High-power, fast-rising pulses of hydrogen fluoride laser energy suitable for laser-fusion target interaction experiments can in principle be generated by directing an electro-optically shuttered oscillator pulse through one or more electron-beam driven amplifiers. A three-stage HF master oscillator-power amplifier (MOPA) configuration was constructed and tested using SF 6 -C 2 H 6 in which an E-O generated 4-ns-FWHM pulse was amplified in an electron-beam-excited third stage and subsequently isolated with a Brewster angle splitter. Independent experiments in which a 100-ns-FWHM pilot pulse interacted with the power amplifier demonstrated for the first time complete extraction of the available laser energy. These two results provide strong evidence that with upgrading to H 2 -F 2 , it should be possible to obtain nanosecond duration pulses with power levels sufficient for meaningful laser fusion target coupling experiments

  7. 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.

  8. 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

  9. Research on temperature characteristics of laser energy meter absorber irradiated by ms magnitude long pulse laser

    Science.gov (United States)

    Li, Nan; Qiao, Chunhong; Fan, Chengyu; Zhang, Jinghui; Yang, Gaochao

    2017-10-01

    The research on temperature characteristics for large-energy laser energy meter absorber is about continuous wave (CW) laser before. For the measuring requirements of millisecond magnitude long pulse laser energy, the temperature characteristics for absorber are numerically calculated and analyzed. In calculation, the temperature field distributions are described by heat conduction equations, and the metal cylinder cavity is used for absorber model. The results show that, the temperature of absorber inwall appears periodic oscillation with pulse structure, the oscillation period and amplitude respectively relate to the pulse repetition frequency and single pulse energy. With the wall deep increasing, the oscillation amplitude decreases rapidly. The temperature of absorber outerwall is without periodism, and rises gradually with time. The factors to affect the temperature rise of absorber are single pulse energy, pulse width and repetition frequency. When the laser irradiation stops, the temperature between absorber inwall and outerwall will reach agreement rapidly. After special technology processing to enhance the capacity of resisting laser damage for absorber inwall, the ms magnitude long pulse laser energy can be obtained with the method of measuring the temperature of absorber outerwall. Meanwhile, by optimization design of absorber structure, when the repetition frequency of ms magnitude pulse laser is less than 10Hz, the energy of every pulse for low repetition frequency pulse sequence can be measured. The work offers valuable references for the design of ms magnitude large-energy pulse laser energy meter.

  10. Pulse forming networks for fast pumping of high power electron-beam-controlled CO2 lasers

    International Nuclear Information System (INIS)

    Riepe, K.B.

    1975-01-01

    The transverse electric discharge is a widely used technique for pumping CO 2 lasers at high pressures for the generation, simply and efficiently, of very high power laser pulses. The development of the electron-beam-controlled discharge has allowed the application of the transverse discharge to large aperture, very high energy systems. LASL is now in the process of assembly and checkout of a CO 2 laser which is designed to generate a one nanosecond pulse containing 10 kilojoules, for use in laser fusion experiments. The front end of this laser consists of a set of preamplifiers and a mode locked oscillator with electro-optic single pulse switchout. The final amplifier stage consists of four parallel modules, each one consisting of a two-sided electron gun, and two 35 x 35 x 200 cm gas pumping regions operating at a pressure of 1800 torr with a 3/ 1 / 4 /1 (He/N 2 /CO 2 ) laser mix. (auth)

  11. Method and apparatus for obtaining very high energy laser pulses: photon cyclotron

    International Nuclear Information System (INIS)

    Vali, V.; Krogstad, R.S.; Goldstein, R.

    1975-01-01

    Apparatus is arranged in selected embodiments of several combinations, each sometimes being referred to as a system, and each embodiment establishing a large enclosable chamber containing a laser energy reacting medium through which a laser beam is created. When laser energy pulses of such a beam are created, they are guided in a continuous path using reflectors in this chamber, and they receive supplemental energy units from multiple spaced laser pumps. Each laser pump is effective in respect to its own inverted population laser energy source, and each laser pump is triggered by an overall excitation control system. The laser beam is thereby supplemented to a higher level at each laser pump. Yet at all times the laser energy reacting medium remains at a level below super radiance. A working unit or working pulse of a laser beam is allowed to escape from each large enclosable chamber through an escape exit only when a preselected very high energy level is reached. The escape exit of this chamber may be designed to be destroyed by the exiting high level pulse energy of the laser beam. Also an escape exit may be opened upon the operation of a piezoelectric decoupler. (U.S.)

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

    International Nuclear Information System (INIS)

    Wachter, G.

    2014-01-01

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

  13. Efficient delivery of 60 J pulse energy of long pulse Nd:YAG laser ...

    Indian Academy of Sciences (India)

    2014-02-09

    Feb 9, 2014 ... Most of today's industrial Nd:YAG lasers use fibre-optic beam delivery. ... optical fibre and successfully delivered up to 60 J of pulse energy with .... and electrical pump input to laser output conversion efficiency is about 5%. ... [3] W Koechner, Solid state laser engineering, 5th edn (Springer, Berlin, 1999).

  14. 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.

  15. Compression and heating of a cladding target by a partially profiled laser pulse

    International Nuclear Information System (INIS)

    Andreev, A.A.; Samsonov, A.G.; Solov'ev, N.A.

    1990-01-01

    The CLADDING-T semiempirical model and numerical calculations in accordance with the SPHERE program have been employed to show that the action of a partially profiled pulse on a simple cladding target raises the fuel compession degree and reduces the fuel temperature as compared to the action of a rectangular pulse (or a polynomial-shaped pulse) with the same energy. From the standpoint of the flash criterion the system composed of the profiled pulse and the simple (cladding) target is shown to be equivalent to that composed of a simple pulse and a dual-cascade (profiled) target. An analysis of the system composed of the laser and the simple target shows that the use of the partially profiled pulse and the simple target makes it possible to reduce requirements to the energy of laser systems

  16. 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

  17. Higher order harmonic generation in the intense laser pulse

    International Nuclear Information System (INIS)

    Parvizi, R.; Bahrampour, A.; Karimi, M.

    2006-01-01

    The high intensity pulse of laser field ionizes the atoms and electrons are going to the continuum states of atoms. electrons absorb energy from the strong laser field. The back ground electromagnetic field causes to come back the electrons to ground states of atoms and the absorbed energy is emitted as a high order odd harmonics of incident light. The intensity of emitted harmonics depends on the material atoms and the laser pulse shape. I this paper the effects of step pulse duration on the high order harmonic radiated by the Argon, Helium, and Hydrogen atoms are reported.

  18. Study of ultra-high gradient wakefield excitation by intense ultrashort laser pulses in plasma

    International Nuclear Information System (INIS)

    Kotaki, Hideyuki

    2002-12-01

    We investigate a mechanism of nonlinear phenomena in laser-plasma interaction, a laser wakefield excited by intense laser pulses, and the possibility of generating an intense bright electron source by an intense laser pulse. We need to understand and further employ some of these phenomena for our purposes. We measure self-focusing, filamentation, and the anomalous blueshift of the laser pulse. The ionization of gas with the self-focusing causes a broad continuous spectrum with blueshift. The normal blueshift depends on the laser intensity and the plasma density. We, however, have found different phenomenon. The laser spectrum shifts to fixed wavelength independent of the laser power and gas pressure above some critical power. We call the phenomenon 'anomalous blueshift'. The results are explained by the formation of filaments. An intense laser pulse can excite a laser wakefield in plasma. The coherent wakefield excited by 2 TW, 50 fs laser pulses in a gas-jet plasma around 10 18 cm -3 is measured with a time-resolved frequency domain interferometer (FDI). The density distribution of the helium gas is measured with a time-resolved Mach-Zehnder interferometer to search for the optimum laser focus position and timing in the gas-jet. The results show an accelerating wakefield excitation of 20 GeV/m with good coherency, which is useful for ultrahigh gradient particle acceleration in a compact system. This is the first time-resolved measurement of laser wakefield excitation in a gas-jet plasma. The experimental results are compared with a Particle-in-Cell (PIC) simulation. The pump-probe interferometer system of FDI and the anomalous blueshift will be modified to the optical injection system as a relativistic electron beam injector. In 1D PIC simulation we obtain the results of high quality intense electron beam acceleration. These results illuminate the possibility of a high energy and a high quality electron beam acceleration. (author)

  19. Some characteristics of isotopic separation laser systems

    International Nuclear Information System (INIS)

    Pochon, E.

    1988-01-01

    The principle of Laser Isotope Separation (LIS) is simple and based on either selective electronic photoexcitation and photoionization of atomic vapor, or selective vibrational photoexcitation and photodissociation of molecules in the gas phase. These processes, respectively called SILVA (AVLIS) and SILMO (MLIS) in France, both use specific laser systems with wavelengths spanning from infrared to ultraviolet. This article describes briefly some of the characteristics of a SILVA laser system. Following a three-step process, a SILVA laser system is based on dye copper vapor lasers. The pulse dye lasers provide the tunable laser light and are optically pumped by copper vapor laser operating at high repetition rates. In order to meet plant laser system requirements, the main improvements under way relate to copper vapor laser devices the power capability, efficiency, reliability and lifetime of which have to be increased. 1 fig

  20. Pulsed laser deposition to synthesize the bridge structure of artificial nacre: Comparison of nano- and femtosecond lasers

    Science.gov (United States)

    Melaibari, Ammar A.; Molian, Pal

    2012-11-01

    Nature offers inspiration to new adaptive technologies that allow us to build amazing shapes and structures such as nacre using synthetic materials. Consequently, we have designed a pulsed laser ablation manufacturing process involving thin film deposition and micro-machining to create hard/soft layered "brick-bridge-mortar" nacre of AlMgB14 (hard phase) with Ti (soft phase). In this paper, we report pulsed laser deposition (PLD) to mimic brick and bridge structures of natural nacre in AlMgB14. Particulate formation inherent in PLD is exploited to develop the bridge structure. Mechanical behavior analysis of the AlMgB14/Ti system revealed that the brick is to be 250 nm thick, 9 μm lateral dimensions while the bridge (particle) is to have a diameter of 500 nm for a performance equivalent to natural nacre. Both nanosecond (ns) and femtosecond (fs) pulsed lasers were employed for PLD in an iterative approach that involves varying pulse energy, pulse repetition rate, and target-to-substrate distance to achieve the desired brick and bridge characteristics. Scanning electron microscopy, x-ray photoelectron spectroscopy, and optical profilometer were used to evaluate the film thickness, particle size and density, stoichiometry, and surface roughness of thin films. Results indicated that both ns-pulsed and fs-pulsed lasers produce the desired nacre features. However, each laser may be chosen for different reasons: fs-pulsed laser is preferred for much shorter deposition time, better stoichiometry, uniform-sized particles, and uniform film thickness, while ns-pulsed laser is favored for industrial acceptance, reliability, ease of handling, and low cost.

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

    Science.gov (United States)

    Dowden, Paul C.; Jia, Quanxi

    2016-05-31

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

  2. 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)

  3. Lasertron, a pulsed RF-source using laser triggered photocathode

    International Nuclear Information System (INIS)

    Yoshioka, Masakazu.

    1988-12-01

    A new pulsed RF-source, 'Lasertron', are being developed as a possible RF-power source for future electron-positron linear colliders. In a series of systematic study, a prototype lasertron has been fabricated and tested. A peak power of 80 kW is attained at 2.856 GHz RF-frequency in 1-μs time duration. This paper describes the experimental results of the lasertron including the developments of the photocathode and the laser system. Test results are compared with the analysis of beam dynamics in the lasertron. (author)

  4. All-Fiber, Directly Chirped Laser Source for Chirped-Pulse-Amplification

    Science.gov (United States)

    Xin, Ran

    Chirped-pulse-amplification (CPA) technology is widely used to produce ultra-short optical pulses (sub picosecond to femtoseconds) with high pulse energy. A chirped pulse laser source with flexible dispersion control is highly desirable as a CPA seed. This thesis presents an all-fiber, directly chirped laser source (DCLS) that produces nanosecond, linearly-chirped laser pulses at 1053 nm for seeding high energy CPA systems. DCLS produces a frequency chirp on an optical pulse through direct temporal phase modulation. DCLS provides programmable control for the temporal phase of the pulse, high pulse energy and diffraction-limited beam performance, which are beneficial for CPA systems. The DCLS concept is first described. Its key enabling technologies are identified and their experimental demonstration is presented. These include high-precision temporal phase control using an arbitrary waveform generator, multi-pass phase modulation to achieve high modulation depth, regenerative amplification in a fiber ring cavity and a negative feedback system that controls the amplifier cavity dynamics. A few technical challenges that arise from the multi-pass architecture are described and their solutions are presented, such as polarization management and gain-spectrum engineering in the DCLS fiber cavity. A DCLS has been built and its integration into a high energy OPCPA system is demonstrated. DCLS produces a 1-ns chirped pulse with a 3-nm bandwidth. The temporal phase and group delay dispersion on the DCLS output pulse is measured using temporal interferometry. The measured temporal phase has an ˜1000 rad amplitude and is close to a quadratic shape. The chirped pulse is amplified from 0.9 nJ to 76 mJ in an OPCPA system. The amplified pulse is compressed to close to its Fourier transform limit, producing an intensity autocorrelation trace with a 1.5-ps width. Direct compressed-pulse duration control by adjusting the phase modulation drive amplitude is demonstrated. Limitation

  5. Hydroxyapatite thin films grown by pulsed laser deposition and matrix assisted pulsed laser evaporation: Comparative study

    Science.gov (United States)

    Popescu-Pelin, G.; Sima, F.; Sima, L. E.; Mihailescu, C. N.; Luculescu, C.; Iordache, I.; Socol, M.; Socol, G.; Mihailescu, I. N.

    2017-10-01

    Pulsed Laser Deposition (PLD) and Matrix Assisted Pulsed Laser Evaporation (MAPLE) techniques were applied for growing hydroxyapatite (HA) thin films on titanium substrates. All experiments were conducted in a reaction chamber using a KrF* excimer laser source (λ = 248 nm, τFWHM ≈ 25 ns). Half of the samples were post-deposition thermally treated at 500 °C in a flux of water vapours in order to restore crystallinity and improve adherence. Coating surface morphologies and topographies specific to the deposition method were evidenced by scanning electron, atomic force microscopy investigations and profilometry. They were shown to depend on deposition technique and also on the post-deposition treatment. Crystalline structure of the coatings evaluated by X-ray diffraction was improved after thermal treatment. Biocompatibility of coatings, cellular adhesion, proliferation and differentiation tests were conducted using human mesenchymal stem cells (MSCs). Results showed that annealed MAPLE deposited HA coatings were supporting MSCs proliferation, while annealed PLD obtained films were stimulating osteogenic differentiation.

  6. Laser sources for polarized electron beams in cw and pulsed accelerators

    CERN Document Server

    Hatziefremidis, A; Fraser, D; Avramopoulos, H

    1999-01-01

    We report the characterization of a high power, high repetition rate, mode-locked laser system to be used in continuous wave and pulsed electron accelerators for the generation of polarized electron beams. The system comprises of an external cavity diode laser and a harmonically mode-locked Ti:Sapphire oscillator and it can provide up to 3.4 W average power, with a corresponding pulse energy exceeding 1 nJ at 2856 MHz repetition rate. The system is tunable between 770-785 and 815-835 nm with two sets of diodes for the external cavity diode laser. (author)

  7. 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

  8. Pulsed-laser atom-probe field-ion microscopy

    International Nuclear Information System (INIS)

    Kellogg, G.L.; Tsong, T.T.

    1980-01-01

    A time-of-flight atom-probe field-ion microscope has been developed which uses nanosecond laser pulses to field evaporate surface species. The ability to operate an atom-probe without using high-voltage pulses is advantageous for several reasons. The spread in energy arising from the desorption of surface species prior to the voltage pulse attaining its maximum amplitude is eliminated, resulting in increased mass resolution. Semiconductor and insulator samples, for which the electrical resistivity is too high to transmit a short-duration voltage pulse, can be examined using pulsed-laser assisted field desorption. Since the electric field at the surface can be significantly smaller, the dissociation of molecular adsorbates by the field can be reduced or eliminated, permitting well-defined studies of surface chemical reactions. In addition to atom-probe operation, pulsed-laser heating of field emitters can be used to study surface diffusion of adatoms and vacancies over a wide range of temperatures. Examples demonstrating each of these advantages are presented, including the first pulsed-laser atom-probe (PLAP) mass spectra for both metals (W, Mo, Rh) and semiconductors (Si). Molecular hydrogen, which desorbs exclusively as atomic hydrogen in the conventional atom probe, is shown to desorb undissociatively in the PLAP. Field-ion microscope observations of the diffusion and dissociation of atomic clusters, the migration of adatoms, and the formation of vacancies resulting from heating with a 7-ns laser pulse are also presented

  9. 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.

  10. Transient thermal analysis of semiconductor diode lasers under pulsed operation

    Science.gov (United States)

    Veerabathran, G. K.; Sprengel, S.; Karl, S.; Andrejew, A.; Schmeiduch, H.; Amann, M.-C.

    2017-02-01

    Self-heating in semiconductor lasers is often assumed negligible during pulsed operation, provided the pulses are `short'. However, there is no consensus on the upper limit of pulse width for a given device to avoid-self heating. In this paper, we present an experimental and theoretical analysis of the effect of pulse width on laser characteristics. First, a measurement method is introduced to study thermal transients of edge-emitting lasers during pulsed operation. This method can also be applied to lasers that do not operate in continuous-wave mode. Secondly, an analytical thermal model is presented which is used to fit the experimental data to extract important parameters for thermal analysis. Although commercial numerical tools are available for such transient analyses, this model is more suitable for parameter extraction due to its analytical nature. Thirdly, to validate this approach, it was used to study a GaSb-based inter-band laser and an InP-based quantum cascade laser (QCL). The maximum pulse-width for less than 5% error in the measured threshold currents was determined to be 200 and 25 ns for the GaSb-based laser and QCL, respectively.

  11. Post-filament self-trapping of ultrashort laser pulses.

    Science.gov (United States)

    Mitrofanov, A V; Voronin, A A; Sidorov-Biryukov, D A; Andriukaitis, G; Flöry, T; Pugžlys, A; Fedotov, A B; Mikhailova, J M; Panchenko, V Ya; Baltuška, A; Zheltikov, A M

    2014-08-15

    Laser filamentation is understood to be self-channeling of intense ultrashort laser pulses achieved when the self-focusing because of the Kerr nonlinearity is balanced by ionization-induced defocusing. Here, we show that, right behind the ionized region of a laser filament, ultrashort laser pulses can couple into a much longer light channel, where a stable self-guiding spatial mode is sustained by the saturable self-focusing nonlinearity. In the limiting regime of negligibly low ionization, this post-filamentation beam dynamics converges to a large-scale beam self-trapping scenario known since the pioneering work on saturable self-focusing nonlinearities.

  12. Cutting and skin-ablative properties of pulsed mid-infrared laser surgery.

    Science.gov (United States)

    Kaufmann, R; Hartmann, A; Hibst, R

    1994-02-01

    Pulsed mid-infrared lasers allow a precise removal of soft tissues with only minimal thermal damage. To study the potential dermatosurgical usefulness of currently available systems at different wavelengths (2010-nm Thulium:YAG laser, 2100-nm Holmium:YAG laser, 2790-nm Erbium:YSGG laser, and 2940-nm Erbium:YAG laser) in vivo on pig skin. Immediate effects and wound healing of superficial laser-abrasions and incisions were compared with those of identical control lesions produced by dermabrasion, scalpel incisions, or laser surgery performed by a 1060-nm Nd:YAG and a 1060-nm CO2 laser (continuous and superpulsed mode). Best efficiency and least thermal injury was found for the pulsed Erbium:YAG laser, leading to ablative and incisional lesions comparable to those obtained by dermabrasion or superficial scalpel incisions, respectively. In contrast to other mid-infrared lasers tested, the 2940-nm Erbium:YAG laser thus provides a potential instrument for future applications in skin surgery, especially when aiming at a careful ablative removal of delicate superficial lesions with maximum sparing of adjacent tissue structures. However, in the purely incisional application mode pulsed mid-infrared lasers, though of potential usefulness in microsurgical indications (eg, surgery of the cornea), do not offer a suggestive alternative to simple scalpel surgery of the skin.

  13. Multi-Pulse Excitation for Underwater Analysis of Copper-Based Alloys Using a Novel Remote Laser-Induced Breakdown Spectroscopy (LIBS) System.

    Science.gov (United States)

    Guirado, Salvador; Fortes, Francisco J; Laserna, J Javier

    2016-04-01

    In this work, the use of multi-pulse excitation has been evaluated as an effective solution to mitigate the preferential ablation of the most volatile elements, namely Sn, Pb, and Zn, observed during laser-induced breakdown spectroscopy (LIBS) analysis of copper-based alloys. The novel remote LIBS prototype used in this experiments featured both single-pulse (SP-LIBS) and multi-pulse excitation (MP-LIBS). The remote instrument is capable of performing chemical analysis of submersed materials up to a depth of 50 m. Laser-induced breakdown spectroscopy analysis was performed at air pressure settings simulating the conditions during a real subsea analysis. A set of five certified bronze standards with variable concentration of Cu, As, Sn, Pb, and Zn were used. In SP-LIBS, signal emission is strongly sensitive to ambient pressure. In this case, fractionation effect was observed. Multi-pulse excitation circumvents the effect of pressure over the quantitative analysis, thus avoiding the fractionation phenomena observed in single pulse LIBS. The use of copper as internal standard minimizes matrix effects and discrepancies due to variation in ablated mass. © The Author(s) 2016.

  14. Pulsed hydrogen fluoride laser oscillator-amplifier experiments

    International Nuclear Information System (INIS)

    Schott, G.L.

    1975-01-01

    Pulsed HF chemical laser oscillator energies were scaled from millijoules to several kilojoules over the period 1970-1974, reaching approximately 10 J with SF 6 and transverse discharges, and using electron-beam initiation and elemental F 2 above 1000J. This demonstrated scalability to large energy with acceptable electrical efficiency is only one prerequisite for application of this gas laser in fusion; equally important matters are achievement of focusable, approximately 1 ns pulses, couplable to light-element targets, all from an affordable system. Exploratory MOPA experiments are reported which address control of HF laser beam focusability and pulse duration, using SF 6 -based experimental oscillator--amplifier sequences and Pockels' cell switching. Simultaneous multiline lasing with 2.6 less than or equal to lambda less than or equal to 3.1 μm and high specific gain and energy density are particularly important factors encountered with HF, where amplifier pumping and lasing occur in a substantially cw temporal relationship, even in less than 100 ns bursts. Time-resolved SF 6 --HI oscillator spectra contain 27 simultaneous lines from six vibrational bands. An apertured, SF 6 -hydrocarbon pin-discharge oscillator generates approximately 10 mJ of TEM 00 radiation, which is amplified to approximately 1 J in approximately 150 ns by a TEA amplifier and p []opagated tens of meters. A three-stage system coupling these elements through an approximately 1 ns electrooptic gate to a greater than 10 J, e-beam energized amplifier is under development. (auth)

  15. Spectroscopic and imaging diagnostics of pulsed laser deposition laser plasmas

    International Nuclear Information System (INIS)

    Thareja, Raj K.

    2002-01-01

    An overview of laser spectroscopic techniques used in the diagnostics of laser ablated plumes used for thin film deposition is given. An emerging laser spectroscopic imaging technique for the laser ablation material processing is discussed. (author)

  16. Determination of pulse profile characteristics of multi spot retinal photocoagulation lasers.

    Science.gov (United States)

    Clarkson, Douglas McG; Makhzoum, Osama; Blackburn, John

    2015-10-01

    A system is described for determination of discrete pulse train characteristics of multi spot laser delivery systems for retinal photocoagulation. While photodiodes provide an ideal detection mechanism, measurement artifacts can potentially be introduced by the spatial pattern of the delivered beam relative to a discrete photodiode element. This problem was overcome by use of an integrating sphere to produce a uniform light field at the site of the photodiode detector. A basic current driven photodiode detection circuit incorporating an operational amplifier was used to generate a signal captured by a commercially available USB interface device at a rate of 10 kHz. Studies were undertaken of a Topcon Pascal Streamline laser system with output at a wavelength of 577 nm (yellow). This laser features the proprietary feature of 'Endpoint Management' ™ where pulses can be delivered as 100% of set energy levels with visible reaction on the retina and also at a reduced energy level to create potentially non visible but clinically effective lesions. Using the pulse train measurement device it was identified that the 'Endpoint Management' ™ delivery mode of pulses of lower energy was achieved by reducing the pulse duration of pulses for non-visible effect pulses while maintaining consistent beam power levels within the delivered pulse profile. The effect of eye geometry in determining safety and effectiveness of multi spot laser delivery for retinal photocoagulation is discussed. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

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

    DEFF Research Database (Denmark)

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

    1995-01-01

    The large signal dynamics of passively colliding pulse mode-locked laser diodes is studied. We derive a model which explains modelocking via the interplay of gain and loss dynamics; no bandwidth limiting element is necessary for pulse formation. It is found necessary to have both fast and slow...... absorber dynamics to achieve mode-locking. Significant chirp is predicted for pulses emitted from long lasers, in agreement with experiment. The pulse width shows a strong dependence on both cavity and saturable absorber length. (C) 1995 American Institute of Physics....

  18. High Energy, Short Pulse Fiber Injection Lasers at Lawrence Livermore National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-09-10

    A short pulse fiber injection laser for the Advanced Radiographic Capability (ARC) on the National Ignition Facility (NIF) has been developed at Lawrence Livermore National Laboratory (LLNL). This system produces 100 {micro}J pulses with 5 nm of bandwidth centered at 1053 nm. The pulses are stretched to 2.5 ns and have been recompressed to sub-ps pulse widths. A key feature of the system is that the pre-pulse power contrast ratio exceeds 80 dB. The system can also precisely adjust the final recompressed pulse width and timing and has been designed for reliable, hands free operation. The key challenges in constructing this system were control of the signal to noise ratio, dispersion management and managing the impact of self phase modulation on the chirped pulse.

  19. Dynamics of plasma expansion in the pulsed laser material interaction

    Indian Academy of Sciences (India)

    at different ambient gas pressures using an adiabatic expansion model. ... Pulsed laser; plasma expansion; plasma ionization; plume dimension. 1. ...... De A, Shakhatov V A, Pascale De O 2001 Optical emission spectroscopy and modeling of.

  20. Fiber laser front end for high energy petawatt laser systems

    International Nuclear Information System (INIS)

    Dawson, J W; Messerly, M J; Phan, H; Mitchell, S; Drobshoff, A; Beach, R J; Siders, C; Lucianetti, A; Crane, J K; Barty, C J

    2006-01-01

    We are developing a fiber laser front end suitable for high energy petawatt laser systems on large glass lasers such as NIF. The front end includes generation of the pulses in a fiber mode-locked oscillator, amplification and pulse cleaning, stretching of the pulses to >3ns, dispersion trimming, timing, fiber transport of the pulses to the main laser bay and amplification of the pulses to an injection energy of 150 (micro)J. We will discuss current status of our work including data from packaged components. Design detail such as how the system addresses pulse contrast, dispersion trimming and pulse width adjustment and impact of B-integral on the pulse amplification will be discussed. A schematic of the fiber laser system we are constructing is shown in figure 1 below. A 40MHz packaged mode-locked fiber oscillator produces ∼1nJ pulses which are phase locked to a 10MHz reference clock. These pulses are down selected to 100kHz and then amplified while still compressed. The amplified compressed pulses are sent through a non-linear polarization rotation based pulse cleaner to remove background amplified spontaneous emission (ASE). The pulses are then stretched by a chirped fiber Bragg grating (CFBG) and then sent through a splitter. The splitter splits the signal into two beams. (From this point we follow only one beam as the other follows an identical path.) The pulses are sent through a pulse tweaker that trims dispersion imbalances between the final large optics compressor and the CFBG. The pulse tweaker also permits the dispersion of the system to be adjusted for the purpose of controlling the final pulse width. Fine scale timing between the two beam lines can also be adjusted in the tweaker. A large mode area photonic crystal single polarization fiber is used to transport the pulses from the master oscillator room to the main laser bay. The pulses are then amplified a two stage fiber amplifier to 150mJ. These pulses are then launched into the main amplifier

  1. Modeling pulsed excitation for gas-phase laser diagnostics

    International Nuclear Information System (INIS)

    Settersten, Thomas B.; Linne, Mark A.

    2002-01-01

    Excitation dynamics for pulsed optical excitation are described with the density-matrix equations and the rate equations for a two-level system. A critical comparison of the two descriptions is made with complete and consistent formalisms that are amenable to the modeling of applied laser-diagnostic techniques. General solutions, resulting from numerical integration of the differential equations describing the excitation process, are compared for collisional conditions that range from the completely coherent limit to the steady-state limit, for which the two formalisms are identical. This analysis demonstrates the failure of the rate equations to correctly describe the transient details of the excitation process outside the steady-state limit. However, reasonable estimates of the resultant population are obtained for nonsaturating (linear) excitation. This comparison provides the laser diagnostician with the means to evaluate the appropriate model for excitation through a simple picture of the breakdown of the rate-equation validity

  2. Closed cycle high-repetition-rate pulsed HF laser

    Science.gov (United States)

    Harris, Michael R.; Morris, A. V.; Gorton, Eric K.

    1997-04-01

    The design and performance of a closed cycle high repetition rate HF laser is described. A short pulse, glow discharge is formed in a 10 SF6:1 H2 gas mixture at a total pressure of approximately 110 torr within a 15 by 0.5 by 0.5 cm3 volume. Transverse, recirculated gas flow adequate to enable repetitive operation up to 3 kHz is imposed by a centrifugal fan. The fan also forces the gas through a scrubber cell to eliminate ground state HF from the gas stream. An automated gas make-up system replenishes spent gas removed by the scrubber. Typical mean laser output powers up to 3 W can be maintained for extended periods of operation.

  3. Production of quasi ellipsoidal laser pulses for next generation high brightness photoinjectors

    Energy Technology Data Exchange (ETDEWEB)

    Rublack, T., E-mail: Tino.Rublack@desy.de [DESY, Zeuthen (Germany); Good, J.; Khojoyan, M.; Krasilnikov, M.; Stephan, F. [DESY, Zeuthen (Germany); Hartl, I.; Schreiber, S. [DESY, Hamburg (Germany); Andrianov, A.; Gacheva, E.; Khazanov, E.; Mironov, S.; Potemkin, A.; Zelenogorskii, V.V. [IAP/RAS, Nizhny Novgorod (Russian Federation); Syresin, E. [JINR, Dubna (Russian Federation)

    2016-09-01

    The use of high brightness electron beams in Free Electron Laser (FEL) applications is of increasing importance. One of the most promising methods to generate such beams is the usage of shaped photocathode laser pulses. It has already demonstrated that temporal and transverse flat-top laser pulses can produce very low emittance beams [1]. Nevertheless, based on beam simulations further improvements can be achieved using quasi-ellipsoidal laser pulses, e.g. 30% reduction in transverse projected emittance at 1 nC bunch charge. In a collaboration between DESY, the Institute of Applied Physics of the Russian Academy of Science (IAP RAS) in Nizhny Novgorod and the Joint Institute of Nuclear Research (JINR) in Dubna such a laser system capable of producing trains of laser pulses with a quasi-ellipsoidal distribution, has been developed. The prototype of the system was installed at the Photo Injector Test facility at DESY in Zeuthen (PITZ) and is currently in the commissioning phase. In the following, the laser system will be introduced, the procedure of pulse shaping will be described and the last experimental results will be shown.

  4. Pulsed laser manipulation of an optically trapped bead: Averaging thermal noise and measuring the pulsed force amplitude

    DEFF Research Database (Denmark)

    Lindballe, Thue Bjerring; Kristensen, Martin V. G.; Keiding, Søren Rud

    2013-01-01

    An experimental strategy for post-eliminating thermal noise on position measurements of optically trapped particles is presented. Using a nanosecond pulsed laser, synchronized to the detection system, to exert a periodic driving force on an optically trapped 10 polystyrene bead, the laser pulse-bead...... interaction is repeated hundreds of times. Traces with the bead position following the prompt displacement from equilibrium, induced by each laser pulse, are averaged and reveal the underlying deterministic motion of the bead, which is not visible in a single trace due to thermal noise. The motion of the bead...... is analyzed from the direct time-dependent position measurements and from the power spectrum. The results show that the bead is on average displaced 208 nm from the trap center and exposed to a force amplitude of 71 nanoNewton, more than five orders of magnitude larger than the trapping forces. Our...

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

    Energy Technology Data Exchange (ETDEWEB)

    Franco, L. R.

    2016-08-01

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

  6. Ultra-short laser pulses. Petawatt and femtosecond

    International Nuclear Information System (INIS)

    Lemoine, P.

    1999-01-01

    This book deals with a series of new results obtained thanks to the use of ultra-short laser pulses. This branch of physics has made incredible progresses during the last 25 years. Ultra-short laser pulses offer the opportunity to explore the domain of ultra-high energies and of ultra-short duration events. Applications are various, from controlled nuclear fusion to eye surgery and to more familiar industrial applications such as electronics. (J.S.)

  7. Pulse propagation in tapered wiggler free electron lasers

    International Nuclear Information System (INIS)

    Goldstein, J.C.; Colson, W.B.

    1981-01-01

    The one-dimensional theory of short pulse propagation in free electron lasers is extended to tapered wiggler devices and is used to study the behavior of an oscillator with parameter values close to those expected in forthcoming experiments. It is found that stable laser output is possible only over a small range of optical cavity lengths. Optical pulse characteristcs are presented and are found to change considerably over this range

  8. Propagation of intense laser pulses in an underdense plasma

    International Nuclear Information System (INIS)

    Monot, P.; Auguste, T.; Gibbon, P.; Jakober, F.; Mainfray, G.

    1994-01-01

    Experiments carried out with a laser beam focused into a vacuum chamber onto a 3-mm long, pulsed hydrogen jet, at powers close to the critical power required for relativistic self focusing, have shown that an underdense plasma is able to significantly reduce the divergence of an intense laser pulse. The propagation mode is in good agreement with theoretical predictions of relativistic self focusing. 2 figs., 8 refs

  9. Supression of laser breakdown by pulsed nonequilibrium ns discharge

    Science.gov (United States)

    Starikovskiy, A. Y.; Semenov, I. E.; Shneider, M. N.

    2016-10-01

    The avalanche ionization induced by infrared laser pulses was investigated in a pre-ionized argon gas. Pre-ionization was created by a high-voltage pulsed nanosecond discharge developed in the form of a fast ionization wave. Then, behind the front of ionization wave additional avalanche ionization was initiated by the focused Nd-YAG laser pulse. It was shown that the gas pre-ionization inhibits the laser spark generation. It was demonstrated that the suppression of laser spark development in the case of strong gas pre-ionization is because of fast electron energy transfer from the laser beam focal region. The main mechanism of this energy transfer is free electrons diffusion.

  10. The role of lasers and intense pulsed light technology in dermatology

    Directory of Open Access Journals (Sweden)

    Husain Z

    2016-02-01

    Full Text Available Zain Husain,1 Tina S Alster1,2 1Department of Dermatology, Georgetown University Hospital, 2Washington Institute of Dermatologic Laser Surgery, Washington, DC, USA Abstract: The role of light-based technologies in dermatology has expanded dramatically in recent years. Lasers and intense pulsed light have been used to safely and effectively treat a diverse array of cutaneous conditions, including vascular and pigmented lesions, tattoos, scars, and undesired hair, while also providing extensive therapeutic options for cosmetic rejuvenation and other dermatologic conditions. Dermatologic laser procedures are becoming increasingly popular worldwide, and demand for them has fueled new innovations and clinical applications. These systems continue to evolve and provide enhanced therapeutic outcomes with improved safety profiles. This review highlights the important roles and varied clinical applications that lasers and intense pulsed light play in the dermatologic practice. Keywords: laser, intense pulsed light, treatment, dermatology, technology

  11. Numerical analysis of amplification of picosecond pulses in a THL-100 laser system with an increase in the pump energy of the XeF(C – A) amplifier

    Science.gov (United States)

    Yastremskii, A. G.; Ivanov, N. G.; Losev, V. F.

    2018-03-01

    Energy characteristics of laser radiation with a pulse width of 50 ps at an elevated pump energy of the XeF(C – A) amplifier of a hybrid THL-100 laser system are analysed numerically. The dynamics of the change in the energy and maximum intensity of laser radiation with an increase in the pump energy of the XeF(C – A) amplifier from 270 to 400 J is investigated. The results of studying the influence of the input beam divergence on the energy characteristics of the output beam are presented. It is shown that, for the existing system of mirrors, an increase in the pump energy to 400 J leads to an increase in the output energy from 3.2 to 5.5 J at a maximum radiation intensity of 57 GW cm-2. A system of amplifier mirrors with 27 laser beam passes and enlarged divergence angle of the amplified beam is considered. Theoretically, the proposed system of mirrors allows one to increase the laser pulse energy to 7.5 J at a maximum intensity of no more than 14.8 GW cm-2. The calculated efficiency of the conversion of the pump energy absorbed in the amplifier gas chamber into the lasing energy exceeds 3% in this regime.

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

    NARCIS (Netherlands)

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

    2012-01-01

    In this work, we studied the feasibility of surface texturing of thin molybdenum layers on a borosilicate glass substrate with Ultra-Short Laser Pulses (USLP). Large areas of regular diffraction gratings were produced consisting of Laserinduced periodic surface structures (LIPSS). A short pulsed

  13. Time dependent temperature distribution in pulsed Ti:sapphire lasers

    Science.gov (United States)

    Buoncristiani, A. Martin; Byvik, Charles E.; Farrukh, Usamah O.

    1988-01-01

    An expression is derived for the time dependent temperature distribution in a finite solid state laser rod for an end-pumped beam of arbitrary shape. The specific case of end pumping by circular (constant) or Gaussian beam is described. The temperature profile for a single pump pulse and for repetitive pulse operation is discussed. The particular case of the temperature distribution in a pulsed titanium:sapphire rod is considered.

  14. Laser and Plasma Parameters for Laser Pulse Amplification by Stimulated Brillouin Backscattering in the Strong Coupling Regime

    Science.gov (United States)

    Gangolf, Thomas; Blecher, Marius; Bolanos, Simon; Lancia, Livia; Marques, Jean-Raphael; Cerchez, Mirela; Prasad, Rajendra; Aurand, Bastian; Loiseau, Pascal; Fuchs, Julien; Willi, Oswald

    2017-10-01

    In the ongoing quest for novel techniques to obtain ever higher laser powers, plasma amplification has drawn much attention, benefiting from the fact that a plasma can sustain much higher energy densities than a solid state amplifier. As a plasma process, Stimulated Brillouin Backscattering in the strong coupling regime (sc-SBS) can be used to transfer energy from one laser pulse (pump) to another (seed), by a nonlinear ion oscillation forced by the pump laser. Here, we report on experimental results on amplification by sc-SBS using the ARCTURUS Ti:Sapphire multi-beam laser system at the University of Duesseldorf, Germany. Counter-propagating in a supersonic Hydrogen gas jet target, an ultrashort seed pulse with a pulse duration between 30 and 160 fs and an energy between 1 and 12 mJ was amplified by a high-energy pump pulse (1.7 ps, 700 mJ). For some of the measurements, the gas was pre-ionized with a separate laser pulse (780 fs, 460 mJ). Preliminary analysis shows that the amplification was larger for the longer seed pulses, consistent with theoretical predictions.

  15. Femtosecond and nanosecond pulsed laser deposition of silicon and germanium

    Energy Technology Data Exchange (ETDEWEB)

    Reenaas, Turid Worren [Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Lee, Yen Sian [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Chowdhury, Fatema Rezwana; Gupta, Manisha; Tsui, Ying Yin [Department of Electrical and Computer Engineering, University of Alberta (Canada); Tou, Teck Yong [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia); Yap, Seong Ling [Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Kok, Soon Yie [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia); Yap, Seong Shan, E-mail: seongshan@gmail.com [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2015-11-01

    Highlights: • Ge and Si were deposited by fs and ns laser at room temperature and at vacuum. • Ion of 10{sup 4} ms{sup −1} and 30–200 eV was obtained for ns ablation for Ge and Si. • Highly energetic ions of 10{sup 5} ms{sup −1} with 2–7 KeV were produced in fs laser ablation. • Nanocrystalline Si and Ge were deposited by using fs laser. • Nanoparticles < 10 nm haven been obtained by fs laser. - Abstract: 150 fs Ti:Sapphire laser pulsed laser deposition of Si and Ge were compared to a nanosecond KrF laser (25 ns). The ablation thresholds for ns lasers were about 2.5 J cm{sup −2} for Si and 2.1 J cm{sup −2} for Ge. The values were about 5–10 times lower when fs laser were used. The power densities were 10{sup 8}–10{sup 9} W cm{sup −2} for ns but 10{sup 12} W cm{sup −2} for fs. By using an ion probe, the ions emission at different fluence were measured where the emitting ions achieving the velocity in the range of 7–40 km s{sup −1} and kinetic energy in the range of 30–200 eV for ns laser. The ion produced by fs laser was measured to be highly energetic, 90–200 km s{sup −1}, 2–10 KeV. Two ion peaks were detected above specific laser fluence for both ns and fs laser ablation. Under fs laser ablation, the films were dominated by nano-sized crystalline particles, drastically different from nanosecond pulsed laser deposition where amorphous films were obtained. The ions characteristics and effects of pulse length on the properties of the deposited films were discussed.

  16. Pulse-forming and line-broadening in AM mode locking of the TEA-CO2laser

    NARCIS (Netherlands)

    Witteman, W.J.; Olbertz, A.H.M.

    1977-01-01

    The present paper describes AM mode locking for homogeneously broadened systems, a procedure for measuring linewidths under laser conditions, and finally, experimental results for a 1-atm CO2laser. Working in the frequency domain, analytic solutions are given for the pulse bandwidth and pulse shape

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

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

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

    Directory of Open Access Journals (Sweden)

    A. P. Burmakov

    2012-01-01

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

  19. Pulsed CO laser for isotope separation of uranium

    Energy Technology Data Exchange (ETDEWEB)

    Baranov, Igor Y.; Koptev, Andrey V. [Rocket-Space Technics Department, Baltic State Technical University, 1, 1st Krasnoarmeyskaya st.,St. Petersburg, 190005 (Russian Federation)

    2012-07-30

    This article proposes a technical solution for using a CO laser facility for the industrial separation of uranium used in the production of fuel for nuclear power plants, employing a method of laser isotope separation of uranium with condensation repression in a free jet. The laser operation with nanosecond pulse irradiation can provide an acceptable efficiency in the separating unit and a high efficiency of the laser with the wavelength of 5.3 {mu}m. In the present work we also introduce a calculation model and define the parameters of a mode-locked CO laser with a RF discharge in the supersonic stream. The average pulsed CO laser power of 3 kW is sufficient for efficient industrial isotope separation of uranium in one stage.

  20. 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.

  1. 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.

  2. Influence of laser pulse frequency on the microstructure of aluminum nitride thin films synthesized by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Antonova, K., E-mail: krasa@issp.bas.bg [Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784 (Bulgaria); Duta, L. [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, 077125 Magurele (Romania); Szekeres, A. [Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784 (Bulgaria); Stan, G.E. [National Institute of Materials Physics, 105 bis Atomistilor Street, 077125 Magurele (Romania); Mihailescu, I.N. [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, 077125 Magurele (Romania); Anastasescu, M.; Stroescu, H.; Gartner, M. [Institute of Physical Chemistry, “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania)

    2017-02-01

    Highlights: • Study of pulsed laser deposited AlN films at different laser pulse frequencies. • Higher laser pulse frequency promotes nanocrystallites formation at temperature 450 °C. • AFM and GIXRD detect randomly oriented wurtzite AlN structures. • Characterization of the nanocrystallites’ orientation by FTIR reflectance spectra. • Berreman effect is registered in p-polarised radiation at large incidence angles. - Abstract: Aluminum Nitride (AlN) thin films were synthesized on Si (100) wafers at 450 °C by pulsed laser deposition. A polycrystalline AlN target was multipulsed irradiated in a nitrogen ambient, at different laser pulse repetition rate. Grazing Incidence X-Ray Diffraction and Atomic Force Microscopy analyses evidenced nanocrystallites with a hexagonal lattice in the amorphous AlN matrix. The thickness and optical constants of the layers were determined by infrared spectroscopic ellipsometry. The optical properties were studied by Fourier Transform Infrared reflectance spectroscopy in polarised oblique incidence radiation. Berreman effect was observed around the longitudinal phonon modes of the crystalline AlN component. Angular dependence of the A{sub 1}LO mode frequency was analysed and connected to the orientation of the particles’ optical axis to the substrate surface normal. The role of the laser pulse frequency on the layers’ properties is discussed on this basis.

  3. Equipment for functional testing of the ALADIN TXA pulsed laser head

    Science.gov (United States)

    Emanuele, Stucchi; Franco, Trespidi; Enzo, Nava

    2017-11-01

    It is described a measurement instrument, used as Optical Ground Support Equipment, capable of performing the characterization of a pulsed laser beam. The instrument was developed for the functional testing of the EQM and FMs of the ALADIN laser transmitter (TXA). The performed measurements are: beam shaping, M2 measurement, beam angular stability, energy and wavelength measurements, pulse duration, polarization, pulse shape and spectral characterization, optical frequency stability measurement. The measurement system can work in automatic mode performing several measurements and providing automatic report generation.

  4. Possible applications of powerful pulsed CO2-Lasers in tokamak

    International Nuclear Information System (INIS)

    Nastoyashchii, A.F.; Morozov, I.N.; Hassanein, A.

    1998-01-01

    Applications of powerful pulsed CO 2 -lasers for injection of fuel tablets or creation of a protective screen from the vapor of light elements to protect against the destruction of plasma-facing components are discussed, and the corresponding laser parameters are determined. The possibility of using CO 2 -lasers in modelling the phenomena of powerful and energetic plasma fluxes interaction with a wall, as in the case of a plasma disruption, is considered. (author)

  5. SBS pulse compression applied to a commercial Q-switch Nd-YAG laser

    International Nuclear Information System (INIS)

    Aliaga-Rossel, R.; Bayley, J.; Mamin, A.; Nizienko, Y.

    1997-01-01

    In optical diagnosis of dense Z-pinches, sub-nanosecond laser pulses are required in order to freeze the movement of the plasma during the probing. Commercial lasers can provide such type of pulses but they are either very expensive, or they have a very low energy per pulse. A technique that uses Stimulated Brillouin Scattering (SBS) to compress a 8 ns pulse of a commercial Q-switched Nd-YAG laser is reported here. To carry out this passive compression technique, a frequency doubled laser pulse of 10 ns was focused into a single SBS gas cell, 2 m long, filled with a mixture of argon and sulphurhexafluoride (SF 6 ) at a total pressure of 40 bar. A shorter and high intensity pulse was reflected from the cell (created by SBS) and it travelled back along its original path until it was separated from its original direction by using a dichroic polariser. The pumping volume of the SBS cell, the convergence of the incident beam and the pressure of the gas cell, were optimised to maximise both temporal compression and the output energy. Pulses of 10 ns were compressed to less than 400 ps with a conversion efficiency of 80%. This SBS pulse compression system has been used to make most of the optical measurements of a dense fibre pinch plasma produced in the MAGPIE generator

  6. Development of pulse laser processing for mounting fiber Bragg grating

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, Aikihko; Shimada, Yukihiro; Yonemoto, Yukihiro; Suzuki, Hirokazu; Ishibashi, Hisayoshi [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 8-1-7 Umebidai Kidugawa Kyoto 619-0215 (Japan); Applied Laser Technology Institute, Tsuruga Head Office, Japan Atomic Energy Agency, 65-20 Kizaki Tsuruga Fukui 914-8585 (Japan); Technical Research and Development Institute, Kumagai Gumi Co., Ltd., 2-1 Tsukudo, Shinjuku Tokyo 162-8557 (Japan)

    2012-07-11

    Pulse laser processing has been developed for the application of industrial plants in monitoring and maintenance. Surface cleaning by nano-second laser ablation was demonstrated for decontamination of oxide layers of Cr contained steel. Direct writing by femtosecond processing induced a Bragg grating in optical fiber to make it a seismic sensor for structural health monitoring. Adhesive cement was used to fix the seismic sensor on the surface of reactor coolant pipe material. Pulse laser processing and its related technologies were presented to overcome the severe accidents of nuclear power plants.

  7. Visualization of cavitation bubbles induced by a laser pulse

    International Nuclear Information System (INIS)

    Testud-Giovanneschi, P.; Dufresne, D.; Inglesakis, G.

    1987-01-01

    The I.M.F.M. researchers working on Laser-Matter Interaction are studying the effects induced on matter by a pulsed radiation energy deposit. In this research, the emphasis is on the laser liquids interaction field and more particularly the cavitation induced by a laser pulse or ''optical-cavitation'' as termed by W. Lauterborn (1). For bubbles investigations, the visualizations form a basic diagnostic. This paper presents the experimental apparatus of formation of bubbles, the visualization apparatus and different typical examples of photographic recordings

  8. Controlling Plasma Channels through Ultrashort Laser Pulse Filamentation

    Science.gov (United States)

    Ionin, Andrey; Seleznev, Leonid; Sunchugasheva, Elena

    2013-09-01

    A review of studies fulfilled at the Lebedev Institute in collaboration with the Moscow State University and Institute of Atmospheric Optics in Tomsk on influence of various characteristics of ultrashort laser pulse on plasma channels formed under its filamentation is presented. Filamentation of high-power laser pulses with wavefront controlled by a deformable mirror, with cross-sections spatially formed by various diaphragms and with different wavelengths was experimentally and numerically studied. An application of plasma channels formed due to filamentation of ultrashort laser pulse including a train of such pulses for triggering and guiding long electric discharges is discussed. The research was supported by RFBR Grants 11-02-12061-ofi-m and 11-02-01100, and EOARD Grant 097007 through ISTC Project 4073 P

  9. Traveling wave laser system

    International Nuclear Information System (INIS)

    Gregg, D.W.; Kidder, R.E.; Biehl, A.T.

    1975-01-01

    A method is described for generating a traveling wave laser pulse of almost unlimited energy content wherein a gain medium is pumped into a traveling wave mode, the traveling wave moving at essentially the velocity of light to generate an amplifying region or zone which moves through the medium at the velocity of light in the presence of directed stimulating radiation, thereby generating a traveling coherent, directed radiation pulse moving with the amplification zone through the gain medium. (U.S.)

  10. Electron laser acceleration in vacuum by a quadratically chirped laser pulse

    International Nuclear Information System (INIS)

    Salamin, Yousef I; Jisrawi, Najeh M

    2014-01-01

    Single MeV electrons in vacuum subjected to single high-intensity quadratically chirped laser pulses are shown to gain multi-GeV energies. The laser pulses are modelled by finite-duration trapezoidal and cos  2 pulse-shapes and the equations of motion are solved numerically. It is found that, typically, the maximum energy gain from interaction with a quadratic chirp is about half of what would be gained from a linear chirp. (paper)

  11. Ablation of silicon with bursts of femtosecond laser pulses

    Science.gov (United States)

    Gaudiuso, Caterina; Kämmer, Helena; Dreisow, Felix; Ancona, Antonio; Tünnermann, Andreas; Nolte, Stefan

    2016-03-01

    We report on an experimental investigation of ultrafast laser ablation of silicon with bursts of pulses. The pristine 1030nm-wavelength 200-fs pulses were split into bursts of up to 16 sub-pulses with time separation ranging from 0.5ps to 4080ps. The total ablation threshold fluence was measured depending on the burst features, finding that it strongly increases with the number of sub-pulses for longer sub-pulse delays, while a slowly increasing trend is observed for shorter separation time. The ablation depth per burst follows two different trends according to the time separation between the sub-pulses, as well as the total threshold fluence. For delays shorter than 4ps it decreases with the number of pulses, while for time separations longer than 510ps, deeper craters were achieved by increasing the number of subpulses in the burst, probably due to a change of the effective penetration depth.

  12. The role of lasers and intense pulsed light technology in dermatology

    Science.gov (United States)

    Husain, Zain; Alster, Tina S

    2016-01-01

    The role of light-based technologies in dermatology has expanded dramatically in recent years. Lasers and intense pulsed light have been used to safely and effectively treat a diverse array of cutaneous conditions, including vascular and pigmented lesions, tattoos, scars, and undesired hair, while also providing extensive therapeutic options for cosmetic rejuvenation and other dermatologic conditions. Dermatologic laser procedures are becoming increasingly popular worldwide, and demand for them has fueled new innovations and clinical applications. These systems continue to evolve and provide enhanced therapeutic outcomes with improved safety profiles. This review highlights the important roles and varied clinical applications that lasers and intense pulsed light play in the dermatologic practice. PMID:26893574

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

    International Nuclear Information System (INIS)

    Fisher, D.L.; Tajima, T.; Downer, M.C.; Siders, C.W.

    1994-11-01

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

  14. 3D pulsed chaos lidar system.

    Science.gov (United States)

    Cheng, Chih-Hao; Chen, Chih-Ying; Chen, Jun-Da; Pan, Da-Kung; Ting, Kai-Ting; Lin, Fan-Yi

    2018-04-30

    We develop an unprecedented 3D pulsed chaos lidar system for potential intelligent machinery applications. Benefited from the random nature of the chaos, conventional CW chaos lidars already possess excellent anti-jamming and anti-interference capabilities and have no range ambiguity. In our system, we further employ self-homodyning and time gating to generate a pulsed homodyned chaos to boost the energy-utilization efficiency. Compared to the original chaos, we show that the pulsed homodyned chaos improves the detection SNR by more than 20 dB. With a sampling rate of just 1.25 GS/s that has a native sampling spacing of 12 cm, we successfully achieve millimeter-level accuracy and precision in ranging. Compared with two commercial lidars tested side-by-side, namely the pulsed Spectroscan and the random-modulation continuous-wave Lidar-lite, the pulsed chaos lidar that is in compliance with the class-1 eye-safe regulation shows significantly better precision and a much longer detection range up to 100 m. Moreover, by employing a 2-axis MEMS mirror for active laser scanning, we also demonstrate real-time 3D imaging with errors of less than 4 mm in depth.

  15. Femtosecond pulsed laser ablation of GaAs

    International Nuclear Information System (INIS)

    Trelenberg, T.W.; Dinh, L.N.; Saw, C.K.; Stuart, B.C.; Balooch, M.

    2004-01-01

    The properties of femtosecond-pulsed laser deposited GaAs nanoclusters were investigated. Nanoclusters of GaAs were produced by laser ablating a single crystal GaAs target in vacuum or in a buffer gas using a Ti-sapphire laser with a 150 fs minimum pulse length. For in-vacuum deposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) revealed that the average cluster size was approximately 7 nm for laser pulse lengths between 150 fs and 25 ps. The average cluster size dropped to approximately 1.5 nm at a pulse length of 500 ps. It was also observed that film thickness decreased with increasing laser pulse length. A reflective coating, which accumulated on the laser admission window during ablation, reduced the amount of laser energy reaching the target for subsequent laser shots and developed more rapidly at longer pulse lengths. This observation indicates that non-stoichiometric (metallic) ablatants were produced more readily at longer pulse lengths. The angular distribution of ejected material about the target normal was well fitted to a bi-cosine distribution of cos 47 θ+ cos 4 θ for ablation in vacuum using 150 fs pulses. XPS and AES revealed that the vacuum-deposited films contained excess amorphous Ga or As in addition to the stoichiometric GaAs nanocrystals seen with XRD. However, films containing only the GaAs nanocrystals were produced when ablation was carried out in the presence of a buffer gas with a pressure in excess of 6.67 Pa. At buffer gas pressure on the order of 1 Torr, it was found that the stoichiometry of the ablated target was also preserved. These experiments indicate that both laser pulse length and buffer gas pressure play important roles in the formation of multi-element nanocrystals by laser ablation. The effects of gas pressure on the target's morphology and the size of the GaAs nanocrystals formed will also be discussed

  16. Laser-pulsed Plasma Chemistry: Laser-initiated Plasma Oxidation Of Niobium

    OpenAIRE

    Marks R.F.; Pollak R.A.; Avouris Ph.; Lin C.T.; Thefaine Y.J.

    1983-01-01

    We report the first observation of the chemical modification of a solid surface exposed to an ambient gas plasma initiated by the interaction of laser radiation with the same surface. A new technique, which we designate laser-pulsed plasma chemistry (LPPC), is proposed for activating heterogeneous chemical reactions at solid surfaces in a gaseous ambient by means of a plasma initiated by laser radiation. Results for niobium metal in one atmosphere oxygen demonstrate single-pulse, self-limitin...

  17. National Ignition Facility system design requirements Laser System SDR002

    International Nuclear Information System (INIS)

    Larson, D.W.; Bowers, J.M.; Bliss, E.S.; Karpenko, V.P.; English, E.

    1996-01-01

    This System Design Requirement document establishes the performance, design, development, and test requirements for the NIP Laser System. The Laser System generates and delivers high-power optical pulses to the target chamber, and is composed of all optical puke creating and transport elements from Puke Generation through Final Optics as well as the special equipment that supports, energizes and controls them. The Laser System consists of the following WBS elements: 1.3 Laser System 1.4 Beam Transport System 1.6 Optical Components 1.7 Laser Control 1.8.7 Final Optics

  18. APPLICATION OF PULSE-PERIODICAL MODE FOR IMPROVEMENT OF LASER TREATMENT EFFICIENCY

    Directory of Open Access Journals (Sweden)

    V. V. Apollonov

    2014-01-01

    Full Text Available The purpose of the paper is to estimate an application of pulse-periodical mode for improvement of laser treatment efficiency. Laser technologies have been widely used in the processes of material treatment with the purpose to provide them the required surface properties and also for high accuracy cutting of sheet materials. Application of complex treatment is of great interest and especially when it is used for worn-out surfaces with formation of a coating by gas-flame laying of powder mixture of specific composition and subsequent laser fusion.Increase of laser unit capacity is very important task for higher efficiency of laser technology application in mechanical engineering. Nowadays technological processes using lasers with high average power (more than 100 W have been applying only sources that are working in two modes, namely: continuous and pulse- periodical (P-P with pulse repetition rate from some units to several hundred hertz and pulse duration within dozens to hundreds of microseconds and even within milliseconds. On the other hand, in some cases shielding effect of plasma cloud formed during laser alloying, cladding or welding reduces the efficiency of laser treatment up to 50 % depending on plasma composition and laser beam length. High frequency P-P laser systems with high average power working in mode of Q-factor modulation allow to realize principally other mechanism of irradiation interaction with materials that is an ablation. In this case it is possible to provide local energy release both in space and time.The performed analysis has revealed that P-P mode of laser operation for a majority of treatment processes is much better and more efficient from energetic point of view in comparison with the continuous mode. On the basis of the developments it is possible to make a conclusion that there is a possibility to create laser systems working in high frequency P-P mode with high average power above hundreds watt.

  19. Pulsed ultrasonic stir welding system

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    An ultrasonic stir welding system includes a welding head assembly having a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. During a welding operation, ultrasonic pulses are applied to the rod as it rotates about its longitudinal axis. The ultrasonic pulses are applied in such a way that they propagate parallel to the longitudinal axis of the rod.

  20. High beam quality and high energy short-pulse laser with MOPA

    Science.gov (United States)

    Jin, Quanwei; Pang, Yu; Jiang, JianFeng; Tan, Liang; Cui, Lingling; Wei, Bin; Sun, Yinhong; Tang, Chun

    2018-03-01

    A high energy, high beam quality short-pulse diode-pumped Nd:YAG master oscillator power-amplifier (MOPA) laser with two amplifier stages is demonstrated. The two-rod birefringence compensation was used as beam quality controlling methods, which presents a short-pulse energy of 40 mJ with a beam quality value of M2 = 1.2 at a repetition rate of 400Hz. The MOPA system delivers a short-pulse energy of 712.5 mJ with a pulse width of 12.4 ns.The method of spherical aberration compensation is improved the beam quality, a M2 factor of 2.3 and an optical-to-optical efficiency of 27.7% is obtained at the maximum laser out power.The laser obtained 1.4J out energy with polarization integration.

  1. A comparative study of pulsed dye laser versus long pulsed Nd:YAG laser treatment in recalcitrant viral warts.

    Science.gov (United States)

    Shin, Yo Sup; Cho, Eun Byul; Park, Eun Joo; Kim, Kwang Ho; Kim, Kwang Joong

    2017-08-01

    Viral warts are common infectious skin disease induced by human papillomavirus (HPV). But the treatment of recalcitrant warts is still challenging. In this study, we compared the effectiveness of pulsed dye laser (PDL) and long pulsed Nd:YAG (LPNY) laser in the treatment of recalcitrant viral warts. We retrospectively analyzed the medical records of patients with recalcitrant warts treated with laser therapy between January 2013 and February 2016. Seventy-two patients with recalcitrant warts were evaluated. Thirty-nine patients were treated with pulsed dye laser and thirty-three patients were treated with LPNY laser. The following parameters were used: PDL (spot size, 7 mm; pulse duration, 1.5 ms; and fluence, 10-14 J/cm 2 ) and LPNY (spot size, 5 mm; pulse duration, 20 ms; and fluence, 240-300 J/cm 2 ). Complete clearance of two patients (5.1%) in PDL group, and three patients (9.1%) in LPNY group were observed without significant side effects. The patients who achieved at least 50% improvement from baseline were 20 (51.3%) in PDL and 22 (66.7%) in LPNY, respectively. This research is meaningful because we compared the effectiveness of the PDL and LPNY in the recalcitrant warts. Both PDL and LPNY laser could be used as a safe and alternative treatment for recalcitrant warts.

  2. Direct measurement of the pulse duration and frequency chirp of seeded XUV free electron laser pulses

    Science.gov (United States)

    Azima, Armin; Bödewadt, Jörn; Becker, Oliver; Düsterer, Stefan; Ekanayake, Nagitha; Ivanov, Rosen; Kazemi, Mehdi M.; Lamberto Lazzarino, Leslie; Lechner, Christoph; Maltezopoulos, Theophilos; Manschwetus, Bastian; Miltchev, Velizar; Müller, Jost; Plath, Tim; Przystawik, Andreas; Wieland, Marek; Assmann, Ralph; Hartl, Ingmar; Laarmann, Tim; Rossbach, Jörg; Wurth, Wilfried; Drescher, Markus

    2018-01-01

    We report on a direct time-domain measurement of the temporal properties of a seeded free-electron laser pulse in the extreme ultraviolet spectral range. Utilizing the oscillating electromagnetic field of terahertz radiation, a single-shot THz streak-camera was applied for measuring the duration as well as spectral phase of the generated intense XUV pulses. The experiment was conducted at FLASH, the free electron laser user facility at DESY in Hamburg, Germany. In contrast to indirect methods, this approach directly resolves and visualizes the frequency chirp of a seeded free-electron laser (FEL) pulse. The reported diagnostic capability is a prerequisite to tailor amplitude, phase and frequency distributions of FEL beams on demand. In particular, it opens up a new window of opportunities for advanced coherent spectroscopic studies making use of the high degree of temporal coherence expected from a seeded FEL pulse.

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

    CERN Multimedia

    2002-01-01

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

  4. Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser

    OpenAIRE

    Liu, Ya; Zhao, Xin; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

    2016-01-01

    Dual-comb lasers from which asynchronous ultrashort pulses can be simultaneously generated have recently become an interesting research subject. They could be an intriguing alternative to the current dual-laser optical-frequency-comb source with highly sophisticated electronic control systems. If generated through a common light path traveled by all pulses, the common-mode noises between the spectral lines of different pulse trains could be significantly reduced. Therefore, coherent dual-comb...

  5. A Hybrid Fiber/Solid-State Regenerative Amplifier with Tunable Pulse Widths for Satellite Laser Ranging

    Science.gov (United States)

    Coyle, Barry; Poulios, Demetrios

    2013-01-01

    A fiber/solid-state hybrid seeded regenerative amplifier, capable of achieving high output energy with tunable pulse widths, has been developed for satellite laser ranging applications. The regenerative amplifier cavity uses a pair of Nd:YAG zigzag slabs oriented orthogonally to one another in order to make thermal lensing effects symmetrical and simplify optical correction schemes. The seed laser used is a fiber-coupled 1,064-nm narrowband (pumped by a single 120-W, pulsed 808-nm laser diode array. In this configuration, the average pump beam distribution in the slabs had a 1-D Gaussian shape, which matches the estimated cavity mode size. A half-wave plate between the slabs reduces losses from Fresnel reflections due to the orthogonal slabs Brewster-cut end faces. Successful "temporal" seeding of the regenerative amplifier cavity results in a cavity Q-switch pulse envelope segmenting into shorter pulses, each having the width of the input seed, and having a uniform temporal separation corresponding to the cavity round-trip time of approx. =10 ns. The pulse energy is allowed to build on successive passes in the regenerative amplifier cavity until a maximum is reached, (when cavity gains and losses are equal), after which the pulse is electro- optically switched out on the next round trip The overall gain of the amplifier is approx. =82 dB (or a factor of 1.26 million). After directing the amplified output through a LBO frequency doubling crystal, approx. = 2.1 W of 532-nm output (>1 mJ) was measured. This corresponds to a nonlinear conversion efficiency of >60%. Furthermore, by pulse pumping this system, a single pulse per laser shot can be created for the SLR (satellite laser ranging) measurement, and this can be ejected into the instrument. This is operated at the precise frequency needed by the measurement, as opposed to commercial short-pulsed, mode-locked systems that need to operate in a continuous fashion, or CW (continuous wave), and create pulses at many

  6. Laser pulse control of bridge mediated heterogeneous electron transfer

    International Nuclear Information System (INIS)

    Wang Luxia; May, Volkhard

    2009-01-01

    Ultrafast heterogeneous electron transfer from surface attached dye molecules into semiconductor band states is analyzed. The focus is on systems where the dye is separated from the surface by different bridge anchor groups. To simulate the full quantum dynamics of the transfer process a model of reduced dimensionality is used. It comprises the electronic levels of the dye, the bridge anchor group electronic levels and the continuum of semiconductor band states, all defined versus a single intramolecular vibrational coordinate. The effect of the bridge states is demonstrated, firstly, in studying the injection dynamics following an impulsive excitation of the dye. Then, by discussing different control tasks it is demonstrate in which way the charge injection process can be influenced by tailored laser pulses. To highlight the importance of electron wave function interference emphasis is put on asymmetric two-bridge molecule systems which are also characterized by different and complex valued electronic transfer matrix elements.

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

    International Nuclear Information System (INIS)

    Berenberg, Vladimir A.; Cervantes, Miguel A.; Terpugov, Vladimir S.

    2006-01-01

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

  8. Combined pulsed dye laser and fiberoptic Nd-YAG laser for the treatment of hypertrophic port wine stain.

    Science.gov (United States)

    Radmanesh, Mohammed; Radmanesh, Ramin

    2017-10-01

    The hypertrophic Port Wine Stain (PWS) is only partially and superficially treated with the Pulsed dye laser (PDL) because of its limited depth of penetration. We used combined PDL and fiberoptic 1444-nm Nd-YAG laser to treat a case with hypertrophic PWS. After tumescent anesthesia, few holes were made by a 16-gauge needle on different sides of the lesion. The fiberoptic tip of 1444-nm Nd-YAG laser was inserted within the holes and was pushed forward while triggering. In a fan pattern and by a back and forth movement, the subcutaneous and deep dermal areas were coagulated. The skin and outer mucosal surfaces were then treated by PDL. The fiberoptic system used was Accusculpt 1444-nm Nd-YAG laser (Lutronic lasers, South Korea), and the PDL used was 585 nm Nlite system (Chromogenex UK). The parameters used for PDL were fluence = 9 Joules/cm 2 and the spot size was 5 mm. The parameters used for fiberoptic 1444-nm Nd-YAG laser were: Pulse rate = 30 Hz, pulse energy = 300 mJ, power = 6 W, and the total energy = 4000 J for the whole face and mucosa. Little sign of regression and moderate purpura were detected immediately after combined fiberoptic Nd-YAG and PDL therapy. The lesion gradually regressed within 4 months with satisfactory color and volume change. Combined fiberoptic Nd-YAG laser and PDL can be used for the treatment of deeper and superficial layers of hypertrophic PWS.

  9. Pulsed Nd:YAG laser beam drilling: A review

    Science.gov (United States)

    Gautam, Girish Dutt; Pandey, Arun Kumar

    2018-03-01

    Laser beam drilling (LBD) is one of non contact type unconventional machining process that are employed in machining of stiff and high-strength materials, high strength temperature resistance materials such as; metal alloys, ceramics, composites and superalloys. Most of these materials are difficult-to-machine by using conventional machining methods. Also, the complex and precise holes may not be obtained by using the conventional machining processes which may be obtained by using unconventional machining processes. The laser beam drilling in one of the most important unconventional machining process that may be used for the machining of these materials with satisfactorily. In this paper, the attention is focused on the experimental and theoretical investigations on the pulsed Nd:YAG laser drilling of different categories of materials such as ferrous materials, non-ferrous materials, superalloys, composites and Ceramics. Moreover, the review has been emphasized by the use of pulsed Nd:YAG laser drilling of different materials in order to enhance productivity of this process without adverse effects on the drilled holes quality characteristics. Finally, the review is concluded with the possible scope in the area of pulsed Nd:YAG laser drilling. This review work may be very useful to the subsequent researchers in order to give an insight in the area of pulsed Nd:YAG laser drilling of different materials and research gaps available in this area.

  10. Laser spark distribution and ignition system

    Science.gov (United States)

    Woodruff, Steven [Morgantown, WV; McIntyre, Dustin L [Morgantown, WV

    2008-09-02

    A laser spark distribution and ignition system that reduces the high power optical requirements for use in a laser ignition and distribution system allowing for the use of optical fibers for delivering the low peak energy pumping pulses to a laser amplifier or laser oscillator. An optical distributor distributes and delivers optical pumping energy from an optical pumping source to multiple combustion chambers incorporating laser oscillators or laser amplifiers for inducing a laser spark within a combustion chamber. The optical distributor preferably includes a single rotating mirror or lens which deflects the optical pumping energy from the axis of rotation and into a plurality of distinct optical fibers each connected to a respective laser media or amplifier coupled to an associated combustion chamber. The laser spark generators preferably produce a high peak power laser spark, from a single low power pulse. The laser spark distribution and ignition system has application in natural gas fueled reciprocating engines, turbine combustors, explosives and laser induced breakdown spectroscopy diagnostic sensors.

  11. Laser cutting system

    Science.gov (United States)

    Dougherty, Thomas J

    2015-03-03

    A workpiece cutting apparatus includes a laser source, a first suction system, and a first finger configured to guide a workpiece as it moves past the laser source. The first finger includes a first end provided adjacent a point where a laser from the laser source cuts the workpiece, and the first end of the first finger includes an aperture in fluid communication with the first suction system.

  12. Influence of the laser pulse duration on laser-produced plasma properties

    International Nuclear Information System (INIS)

    Drogoff, B Le; Margot, J; Vidal, F; Laville, S; Chaker, M; Sabsabi, M; Johnston, T W; Barthelemy, O

    2004-01-01

    In the framework of laser-induced plasma spectroscopy (LIPS) applications, time-resolved characteristics of laser-produced aluminium plasmas in air at atmospheric pressure are investigated for laser pulse durations ranging from 100 fs to 270 ps. Measurements show that for delays after the laser pulse longer than ∼100 ns, the plasma temperature increases slightly with the laser pulse duration, while the electron density is independent of it. In addition, as the pulse duration increases, the plasma radiation emission lasts longer and the spectral lines arise later from the continuum emission. The time dependence of the continuum emission appears to be similar whatever the duration of the laser pulse is, while the temporal evolution of the line emission seems to be affected mainly by the plasma temperature. Finally, as far as spectrochemical applications (such as LIPS) of laser-produced plasmas are concerned, this study highlights the importance of the choice of appropriate temporal gating parameters for each laser pulse duration

  13. Magnetically switched power supply system for lasers

    Science.gov (United States)

    Pacala, Thomas J. (Inventor)

    1987-01-01

    A laser power supply system is described in which separate pulses are utilized to avalanche ionize the gas within the laser and then produce a sustained discharge to cause the gas to emit light energy. A pulsed voltage source is used to charge a storage device such as a distributed capacitance. A transmission line or other suitable electrical conductor connects the storage device to the laser. A saturable inductor switch is coupled in the transmission line for containing the energy within the storage device until the voltage level across the storage device reaches a predetermined level, which level is less than that required to avalanche ionize the gas. An avalanche ionization pulse generating circuit is coupled to the laser for generating a high voltage pulse of sufficient amplitude to avalanche ionize the laser gas. Once the laser gas is avalanche ionized, the energy within the storage device is discharged through the saturable inductor switch into the laser to provide the sustained discharge. The avalanche ionization generating circuit may include a separate voltage source which is connected across the laser or may be in the form of a voltage multiplier circuit connected between the storage device and the laser.

  14. Er:YAG laser pulse for small-dose splashback-free microjet transdermal drug delivery.

    Science.gov (United States)

    Park, Mi-ae; Jang, Hun-jae; Sirotkin, Fedir V; Yoh, Jack J

    2012-09-15

    The microjet injector system accelerates drugs and delivers them without a needle, which is shown to overcome the weaknesses of existing jet injectors. A significant increase in the delivered dose of drugs is reported with multiple pulses of laser beam at lower laser energy than was previously used in a Nd:YAG system. The new injection scheme uses the beam wavelength best absorbable by water at a longer pulse mode for elongated microjet penetration into a skin target. A 2.9 μm Er:YAG laser at 250 μs pulse duration is used for fluorescent staining of guinea pig skin and for injection controllability study. Hydrodynamic theory confirms the nozzle exit jet velocity obtained by the present microjet system.

  15. Complete elimination of nonlinear light-matter interactions with broadband ultrafast laser pulses

    DEFF Research Database (Denmark)

    Shu, Chuan-Cun; Dong, Daoyi; Petersen, Ian R.

    2017-01-01

    optical effects, however, the probability of pure single-photon absorption is usually very low, which is particularly pertinent in the case of strong ultrafast laser pulses with broad bandwidth. Here we demonstrate theoretically a counterintuitive coherent single-photon absorption scheme by eliminating...... nonlinear interactions of ultrafast laser pulses with quantum systems. That is, a completely linear response of the system with respect to the spectral energy density of the incident light at the transition frequency can be obtained for all transition probabilities between 0 and 100% in multilevel quantum...... systems. To that end, a multiobjective optimization algorithm is developed to find an optimal spectral phase of an ultrafast laser pulse, which is capable of eliminating all possible nonlinear optical responses while maximizing the probability of single-photon absorption between quantum states. This work...

  16. Applications of ultra-short pulsed laser ablation: thin films deposition and fs/ns dual-pulse laser-induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Teghil, R; De Bonis, A; Galasso, A; Santagata, A; Albano, G; Villani, P; Spera, D; Parisi, G P

    2008-01-01

    In this paper, we report a survey of two of the large number of possible practical applications of the laser ablation performed by an ultra-short pulse laser, namely pulsed laser deposition (PLD) and fs/ns dual-pulse laser-induced breakdown spectroscopy (DP-LIBS). These applications differ from those using just longer pulsed lasers as a consequence of the distinctive characteristics of the plasma produced by ultra-short laser beams. The most important feature of this plasma is the large presence of particles with nanometric size which plays a fundamental role in both applications.

  17. Interaction of high power ultrashort laser pulses with plasmas

    International Nuclear Information System (INIS)

    Geissler, M.

    2000-12-01

    The invention of short laser-pulses has opened a vast application range from testing ultra high-speed semiconductor devices to precision material processing, from triggering and tracing chemical reactions to sophisticated surgical applications in opthalmology and neurosurgery. In physical science, ultrashort light pulses enable researchers to follow ultrafast relaxation processes in the microcosm on time scale never before accessible and study light-matter-interactions at unprecedented intensity levels. The aim of this thesis is to investigate the interaction of ultrashort high power laser pulses with plasmas for a broad intensity range. First the ionization of atoms with intense laser fields is investigated. For sufficient strong and low frequent laser pulses, electrons can be removed from the core by a tunnel process through a potential barrier formed by the electric field of the laser. This mechanism is described by a well-established theory, but the interaction of few-cycle laser pulses with atoms can lead to regimes where the tunnel theory loses its validity. This regime is investigated and a new description of the ionization is found. Although the ionization plays a major role in many high-energy laser processes, there exist no simple and complete model for the evolution of laser pulses in field-ionizing media. A new propagation equation and the polarization response for field-ionizing media are presented and the results are compared with experimental data. Further the interaction of high power laser radiation with atoms result in nonlinear response of the electrons. The spectrum of this induced nonlinear dipole moment reaches beyond visible wavelengths into the x-ray regime. This effect is known as high harmonic generation (HHG) and is a promising tool for the generation of coherent shot wavelength radiation, but the conversions are still not efficient enough for most practical applications. Phase matching schemes to overcome the limitation are discussed

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

    International Nuclear Information System (INIS)

    Aronne, Antonio; Bloisi, Francesco; Calabria, Raffaela; Califano, Valeria; Depero, Laura E.; Fanelli, Esther; Federici, Stefania; Massoli, Patrizio; Vicari, Luciano R.M.

    2015-01-01

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

  19. 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)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-05-01

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

  1. The obtaining of giant laser pulses by optical pumping

    International Nuclear Information System (INIS)

    Briquet, Georges

    1970-12-01

    From coherent pumping studies a laser of short pulse duration was developed. Further study of laser effects in organic substances was envisaged. The first part of the work yielded awaited results, and led to the development of a single mode emitter (due to the small dimensions of the cavity). The principles of laser action were enumerated and the relative parameters defined. Various methods of obtaining pulses were discussed; the reasons behind the particular choice mode were given. A theoretical study was then made leading to the establishment of the fundamental equations defining the pulse formation process. An important part of the test deals with technical implications and the experimental results, which have arisen. The conclusion reviews possible applications. (author) [fr

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  3. Optimal control of quantum rings by terahertz laser pulses.

    Science.gov (United States)

    Räsänen, E; Castro, A; Werschnik, J; Rubio, A; Gross, E K U

    2007-04-13

    Complete control of single-electron states in a two-dimensional semiconductor quantum-ring model is established, opening a path into coherent laser-driven single-gate qubits. The control scheme is developed in the framework of optimal-control theory for laser pulses of two-component polarization. In terms of pulse lengths and target-state occupations, the scheme is shown to be superior to conventional control methods that exploit Rabi oscillations generated by uniform circularly polarized pulses. Current-carrying states in a quantum ring can be used to manipulate a two-level subsystem at the ring center. Combining our results, we propose a realistic approach to construct a laser-driven single-gate qubit that has switching times in the terahertz regime.

  4. Absorption of femtosecond laser pulses by atomic clusters

    International Nuclear Information System (INIS)

    Lin Jingquan; Zhang Jie; Li Yingjun; Chen Liming; Lu Tiezheng; Teng Hao

    2001-01-01

    Energy absorption by Xe, Ar, He atomic clusters are investigated using laser pulses with 5 mJ energy in 150 fs duration. Experimental results show that the size of cluster and laser absorption efficiency are strongly dependent on several factors, such as the working pressure of pulse valve, atomic number Z of the gas. Absorption fraction of Xe clusters is as high as 45% at a laser intensity of 1 x 10 15 W/cm 2 with 20 x 10 5 Pa gas jet backing pressure. Absorption of the atomic clusters is greatly reduced by introducing pre-pulses. Ion energy measurements confirm that the efficient energy deposition results in a plasma with very high ion temperature

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

    Science.gov (United States)

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

    2015-09-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-09-21

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

  7. A computerized pulse radiolysis system

    International Nuclear Information System (INIS)

    Eriksen, T.E.; Lind, J.; Reitberger, T.

    1976-01-01

    A computer based pulse radiolysis system for gathering and handling of transient optical absorption and electric conductivity data is presented. The system has been developed around a Biomation 8100 transient recorder and a PDP 11/40 (Digital Equipment Corp) computer. (author)

  8. LASER ABLATION OF MONOCRYSTALLINE SILICON UNDER PULSED-FREQUENCY FIBER LASER

    Directory of Open Access Journals (Sweden)

    V. P. Veiko

    2015-05-01

    Full Text Available Subject of research. The paper deals with research of the surface ablation for single-crystal silicon wafers and properties of materials obtained in response to silicon ablation while scanning beam radiation of pulse fiber ytterbium laser with a wavelenght λ = 1062 nm in view of variation of radiation power and scanning modes. Method. Wafers of commercial p-type conductivity silicon doped with boron (111, n-type conductivity silicon doped with phosphorus (100 have been under research with a layer of intrinsical silicon oxide having the thickness equal to several 10 s of nanometers and SiO2 layer thickness from 120 to 300 nm grown by thermal oxidation method. The learning system comprises pulse fiber ytterbium laser with a wavelenght λ = 1062 nm. The laser rated-power output is equal to 20 W, pulse length is 100 ns. Pulses frequency is in the range from 20 kHz to 100 kHz. Rated energy in the pulse is equal to 1.0 mJ. Scanning has been carried out by means of two axial scanning device driven by VM2500+ and controlled by personal computer with «SinMarkТМ» software package. Scanning velocity is in the range from 10 mm/s to 4000 mm/s, the covering varies from 100 lines per mm to 3000 lines per mm. Control of samples has been carried out by means of Axio Imager A1m optical microscope Carl Zeiss production with a high definition digital video camera. All experiments have been carried out in the mode of focused laser beam with a radiation spot diameter at the substrate equal to 50 μm. The change of temperature and its distribution along the surface have been evaluated by FLIR IR imager of SC7000 series. Main results. It is shown that ablation occurs without silicon melting and with plasma torch origination. The particles of ejected silicon take part in formation of silicon ions plasma and atmosphere gases supporting the plasmo-chemical growth of SiO2. The range of beam scanning modes is determined where the growth of SiO2 layer is observed

  9. 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

  10. 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.

  11. Programmable femtosecond laser pulses in the ultraviolet

    International Nuclear Information System (INIS)

    Hacker, M.; Feurer, T.; Sauerbrey, R.; Lucza, T.; Szabo, G.

    2001-01-01

    Using a combination of a zero-dispersion compressor and spectrally compensated sum-frequency generation, we have produced amplitude-modulated femtosecond pulses in the UV at 200 nm. [copyright] 2001 Optical Society of America

  12. Infrared laser system

    International Nuclear Information System (INIS)

    Cantrell, C.D.; Carbone, R.J.

    1977-01-01

    An infrared laser system and method for isotope separation may comprise a molecular gas laser oscillator to produce a laser beam at a first wavelength, Raman spin flip means for shifting the laser to a second wavelength, a molecular gas laser amplifier to amplify said second wavelength laser beam to high power, and optical means for directing the second wavelength, high power laser beam against a desired isotope for selective excitation thereof in a mixture with other isotopes. The optical means may include a medium which shifts the second wavelength high power laser beam to a third wavelength, high power laser beam at a wavelength coincidental with a corresponding vibrational state of said isotope and which is different from vibrational states of other isotopes in the gas mixture

  13. Boron distribution in silicon after multiple pulse excimer laser annealing

    International Nuclear Information System (INIS)

    Monakhov, E.V.; Svensson, B.G.; Linnarsson, M.K.; La Magna, A.; Italia, M.; Privitera, V.; Fortunato, G.; Cuscuna, M.; Mariucci, L.

    2005-01-01

    We have studied B redistribution in Si after excimer laser annealing (ELA) with multiple laser pulses. B was implanted with energies of 1 and 10 keV and doses of 1x10 14 and 1x10 15 cm -2 . ELA with the number of pulses from 1 to 100 was performed at room temperature and 450 deg. C in vacuum. Irrespective of the implantation parameters and the ELA conditions used, a pile-up in the B concentration is observed near the maximum melting depth after ten pulses of ELA. Moreover, a detailed study has revealed that B accumulates at the maximum melt depth gradually with the number of ELA pulses. Besides, an increase in the carrier concentration is observed at the maximum melt depth, suggesting electrical activity of the accumulated B. Formation of Si-B complexes and vacancy accumulation during multiple ELA are discussed as possible mechanisms for the B build-up

  14. Molecular photoelectron holography with circularly polarized laser pulses.

    Science.gov (United States)

    Yang, Weifeng; Sheng, Zhihao; Feng, Xingpan; Wu, Miaoli; Chen, Zhangjin; Song, Xiaohong

    2014-02-10

    We investigate the photoelectron momentum distribution of molecular-ion H2+driven by ultrashort intense circularly polarized laser pulses. Both numerical solutions of the time-dependent Schrödinger equation (TDSE) and a quasiclassical model indicate that the photoelectron holography (PH) with circularly polarized pulses can occur in molecule. It is demonstrated that the interference between the direct electron wave and rescattered electron wave from one core to its neighboring core induces the PH. Moreover, the results of the TDSE predict that there is a tilt angle between the interference pattern of the PH and the direction perpendicular to the molecular axis. Furthermore, the tilt angle is sensitively dependent on the wavelength of the driven circularly polarized pulse, which is confirmed by the quasiclassical calculations. The PH induced by circularly polarized laser pulses provides a tool to resolve the electron dynamics and explore the spatial information of molecular structures.

  15. UV and RIR matrix assisted pulsed laser deposition of organic MEH-PPV films

    International Nuclear Information System (INIS)

    Toftmann, B.; Papantonakis, M.R.; Auyeung, R.C.Y.; Kim, W.; O'Malley, S.M.; Bubb, D.M.; Horwitz, J.S.; Schou, J.; Johansen, P.M.; Haglund, R.F.

    2004-01-01

    A comparative study of thin film production based on gentle laser-ablation techniques has been carried out with the luminescent polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene]. Using a free-electron laser films were made by resonant infrared pulsed laser deposition (RIR-PLD). For the first time resonant infrared matrix assisted pulsed laser evaporation (RIR-MAPLE) was successfully demonstrated on a luminescent polymer system. In addition to this, an excimer laser has been used for UV-MAPLE depositions at 193 and 248-nm irradiation. Films deposited onto NaCl and quartz substrates were analyzed by Fourier transform infrared spectroscopy, UV-visible absorbance and photoluminescence. Photoluminescent material was deposited by RIR-MAPLE and 248-nm MAPLE, while the RIR-PLD and 193-nm-MAPLE depositions displayed the smoothest surfaces but did not show photoluminescence

  16. UV and RIR matrix assisted pulsed laser deposition of organic MEH-PPV films

    DEFF Research Database (Denmark)

    Christensen, Bo Toftmann; Papantonalis, M.R.; Auyeung, R.C.Y.

    2004-01-01

    -PLD). For the first time resonant infrared matrix assisted pulsed laser evaporation (RIR-MAPLE) was successfully demonstrated on a luminescent polymer system. In addition to this, an excimer laser has been used for UV-MAPLE depositions at 193 and 248-nm irradiation. Films deposited onto NaCl and quartz substrates......A comparative study of thin film production based on gentle laser-ablation techniques has been carried out with the luminescent polymer poly [2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene]. Using a free-electron laser films were made by resonant infrared pulsed laser deposition (RIR...... were analyzed by Fourier transform infrared spectroscopy, UV-visible absorbance and photoluminescence. Photoluminescent material was deposited by RIR-MAPLE and 248-nm MAPLE, while the RIR-PLD and 193-nm-MAPLE depositions displayed the smoothest surfaces but did not show photoluminescence. (C) 2003...

  17. Pulsed UV laser technologies for ophthalmic surgery

    International Nuclear Information System (INIS)

    Razhev, A M; Bagayev, S N; Churkin, D S; Kargapol’tsev, E S; Chernykh, V V; Iskakov, I A; Ermakova, O V

    2017-01-01

    The paper provides an overview of the results of multiyear joint researches of team of collaborators of Institute of Laser Physics SB RAS together with NF IRTC “Eye Microsurgery” for the period from 1988 to the present, in which were first proposed and experimentally realized laser medical technologies for correction of refractive errors of known today as LASIK, the treatment of ophthalmic herpes and open-angle glaucoma. It is proposed to carry out operations for the correction of refractive errors the use of UV excimer KrCl laser with a wavelength of 222 nm. The same laser emission is the most suitable for the treatment of ophthalmic herpes, because it has a high clinical effect, combined with many years of absence of recrudescence. A minimally invasive technique of glaucoma operations using excimer XeCl laser (λ=308 nm) is developed. Its wavelength allows perform all stages of glaucoma operations, while the laser head itself has high stability and lifetime, will significantly reduce operating costs, compared with other types of lasers. (paper)

  18. Cold cathode electron guns in the LASL high power short-pulse CO2 laser program

    International Nuclear Information System (INIS)

    Singer, S.; Ladish, J.S.; Nutter, M.J.

    1975-01-01

    The Electron Beam Controlled Discharge CO 2 Laser is now firmly established as the only high power short pulse laser amplifier that has been demonstrated to have scaling capabilities to large apertures and energies much greater than 100 J. These devices require a beam of energetic electrons to control the gas discharge that produces the required population inversion. Until recently, the electron source was usually a thermionic emitter, even for rather large lasers, whose heater requirements dwarfed the pulsed energies associated with the transient operation of the laser. With the advent of reliable cold-cathode electron guns, the operation of these lasers has been greatly simplified. At LASL, there are four electron beam controlled laser systems which are in operation, under construction, or in design: the 1 kJ system, now operational; the 2.5 kJ system; the 10 kJ system; and the 100 kJ system. Only the first uses thermionic-emitter electron guns; the remainder use or will use cold cathode sources. The operation of the 200 x 35 cm 2 two sided cold cathode electron gun used in the 2.5 kJ laser system and to be used in the 10 kJ laser is described

  19. Pulse laser irradiation into superconducting MgB2 detector

    International Nuclear Information System (INIS)

    Fujiwara, Daisuke; Miki, Shigehito; Satoh, Kazuo; Yotsuya, Tsutomu; Shimakage, Hisashi; Wang, Zhen; Okayasu, Satoru; Katagiri, Masaki; Machida, Masahiko; Kato, Masaru; Ishida, Takekazu

    2005-01-01

    We performed 20-ps pulse laser irradiation experiments on a MgB 2 neutron detector to know a thermal-relaxation process for designing a MgB 2 neutron detector. The membrane-type structured MgB 2 device was fabricated to minimize the heat capacity of sensing part of a detector as well as to enhance its sensitivity. We successfully observed a thermal-relaxation signal resulting from pulse laser irradiation by developing a detection circuit. The response time was faster than 1 μs, meaning that the detector would be capable of counting neutrons at a rate of more than 10 6 events per second

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  1. Multispectral photoacoustic microscopy of lipids using a pulsed supercontinuum laser.

    Science.gov (United States)

    Buma, Takashi; Conley, Nicole C; Choi, Sang Won

    2018-01-01

    We demonstrate optical resolution photoacoustic microscopy (OR-PAM) of lipid-rich tissue between 1050-1714 nm using a pulsed supercontinuum laser based on a large-mode-area photonic crystal fiber. OR-PAM experiments of lipid-rich samples show the expected optical absorption peaks near 1210 and 1720 nm. These results show that pulsed supercontinuum lasers are promising for OR-PAM applications such as label-free histology of lipid-rich tissue and imaging small animal models of disease.

  2. Phase selection during pulsed laser annealing of manganese

    International Nuclear Information System (INIS)

    Follstaedt, D.M.; Peercy, P.S.; Perepezko, J.H.

    1986-01-01

    Pulsed (25 ns) laser-induced heating of the α phase of Mn is found to be sufficiently rapid to bypass solid-state transformation to the high-temperature β, γ, and delta allotropes and thus produce melts that are calculated to be undercooled by approx. 120 K with respect to the equilibrium melting temperature of the delta phase. Nucleation of the γ phase in this highly undercooled melt is observed for sufficiently long melt durations. The experiments thus demonstrate that pulsed laser-induced melting of metals with allotropes permits the study of nucleation and growth in highly undercooled melts with calculable temperatures

  3. Method and system for communicating with a laser power driver

    Science.gov (United States)

    Telford, Steven

    2017-07-18

    A system for controlling a plurality of laser diodes includes an optical transmitter coupled to the laser diode driver for each laser diode. An optical signal including bi-phase encoded data is provided to each laser diode driver. The optical signal includes current level and pulse duration information at which each of the diodes is to be driven. Upon receiving a trigger signal, the laser diode drivers operate the laser diodes using the current level and pulse duration information to output a laser beam.

  4. Photoacoustic tweezers with a pulsed laser: theory and experiments

    International Nuclear Information System (INIS)

    Zharov, V P; Malinsky, T V; Kurten, R C

    2005-01-01

    A novel noninvasive optical technique for manipulating particles and cells is presented that utilizes laser-generated forces in an absorbing medium surrounding the particles or cells. In this technique, a laser pulse creates near-object acoustic waves, which during interaction with the objects lead to then being moved or trapped. The main optical schemes are considered, and a theory is presented for this new optical tool, namely photoacoustic (PA) tweezer with pulsed laser. The magnitudes of forces acting on polystyrene particles suspended in water were estimated as a function of the particles' properties for circular and ring geometries of the laser beam. Results of our preliminary experiments demonstrated proof that the manipulation, trapping and even rotation of cells is possible with PA tweezers

  5. Double-pulse standoff laser-induced breakdown spectroscopy for versatile hazardous materials detection

    Energy Technology Data Exchange (ETDEWEB)

    Gottfried, Jennifer L. [U.S. Army Research Laboratory, AMSRD-ARL-WM-BD, Aberdeen Proving Ground, MD, 21005-5069 (United States)], E-mail: jennifer.gottfried@arl.army.mil; De Lucia, Frank C.; Munson, Chase A.; Miziolek, Andrzej W. [U.S. Army Research Laboratory, AMSRD-ARL-WM-BD, Aberdeen Proving Ground, MD, 21005-5069 (United States)

    2007-12-15

    We have developed a double-pulse standoff laser-induced breakdown spectroscopy (ST-LIBS) system capable of detecting a variety of hazardous materials at tens of meters. The use of a double-pulse laser improves the sensitivity and selectivity of ST-LIBS, especially for the detection of energetic materials. In addition to various metallic and plastic materials, the system has been used to detect bulk explosives RDX and Composition-B, explosive residues, biological species such as the anthrax surrogate Bacillus subtilis, and chemical warfare simulants at 20 m. We have also demonstrated the discrimination of explosive residues from various interferents on an aluminum substrate.

  6. Electron heating enhancement by frequency-chirped laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Yazdani, E.; Afarideh, H., E-mail: hafarideh@aut.ac.ir [Department of Energy Engineering and Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Sadighi-Bonabi, R., E-mail: Sadighi@sharif.ir [Department of Physics, Sharif University of Technology, P.O. Box 11365-9567, Tehran (Iran, Islamic Republic of); Riazi, Z. [Physics and Accelerator School, Tehran (Iran, Islamic Republic of); Hora, H. [Department of Theoretical Physics, University of New South Wales, Sydney 2052 (Australia)

    2014-09-14

    Propagation of a chirped laser pulse with a circular polarization through an uprising plasma density profile is studied by using 1D-3V particle-in-cell simulation. The laser penetration depth is increased in an overdense plasma compared to an unchirped pulse. The induced transparency due to the laser frequency chirp results in an enhanced heating of hot electrons as well as increased maximum longitudinal electrostatic field at the back side of the solid target, which is very essential in target normal sheath acceleration regime of proton acceleration. For an applied chirp parameter between 0.008 and 0.01, the maximum amount of the electrostatic field is improved by a factor of 2. Furthermore, it is noticed that for a chirped laser pulse with a₀=5, because of increasing the plasma transparency length, the laser pulse can penetrate up to about n{sub e}≈6n{sub c}, where n{sub c} is plasma critical density. It shows 63% increase in the effective critical density compared to the relativistic induced transparency regime for an unchirped condition.

  7. Ionization of a multilevel atom by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Andreev, A. V.; Stremoukhov, S. Yu.; Shutova, O. A.

    2010-01-01

    Specific features of ionization of single atoms by laser fields of a near-atomic strength are investigated. Calculations are performed for silver atoms interacting with femtosecond laser pulses with wavelengths λ = 800 nm (Ti:Sapphire) and λ = 1.064 μm (Nd:YAG). The dependences of the probability of ionization and of the form of the photoelectron energy spectra on the field of laser pulses for various values of their duration are considered. It is shown that the behavior of the probability of ionization in the range of subatomic laser pulse fields is in good agreement with the Keldysh formula. However, when the field strength attains values close to the atomic field strength, the discrepancies in these dependences manifested in a decrease in the ionization rate (ionization stabilization effect) or in its increase (accelerated ionization) are observed. These discrepancies are associated with the dependence of the population dynamics of excited discrete energy levels of the atom on the laser pulse field amplitude.

  8. PULSED MODE LASER CUTTING OF SHEETS FOR TAILORED BLANKS

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    1999-01-01

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

  9. A trap-based pulsed positron beam optimised for positronium laser spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, B. S., E-mail: ben.cooper.13@ucl.ac.uk; Alonso, A. M.; Deller, A.; Wall, T. E.; Cassidy, D. B. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

    2015-10-15

    We describe a pulsed positron beam that is optimised for positronium (Ps) laser-spectroscopy experiments. The system is based on a two-stage Surko-type buffer gas trap that produces 4 ns wide pulses containing up to 5 × 10{sup 5} positrons at a rate of 0.5-10 Hz. By implanting positrons from the trap into a suitable target material, a dilute positronium gas with an initial density of the order of 10{sup 7} cm{sup −3} is created in vacuum. This is then probed with pulsed (ns) laser systems, where various Ps-laser interactions have been observed via changes in Ps annihilation rates using a fast gamma ray detector. We demonstrate the capabilities of the apparatus and detection methodology via the observation of Rydberg positronium atoms with principal quantum numbers ranging from 11 to 22 and the Stark broadening of the n = 2 → 11 transition in electric fields.

  10. Steady state ion acceleration by a circularly polarized laser pulse

    International Nuclear Information System (INIS)

    Zhang Xiaomei; Shen Baifei; Cang Yu; Li Xuemei; Jin Zhangying; Wang Fengchao

    2007-01-01

    The steady state ion acceleration at the front of a cold solid target by a circularly polarized flat-top laser pulse is studied with one-dimensional particle-in-cell (PIC) simulation. A model that ions are reflected by a steady laser-driven piston is used by comparing with the electrostatic shock acceleration. A stable profile with a double-flat-top structure in phase space forms after ions enter the undisturbed region of the target with a constant velocity

  11. Blue Diode Laser Absorption Spectroscopy of Pulsed Magnetron Discharge

    Czech Academy of Sciences Publication Activity Database

    Olejníček, Jiří; Do, H.T.; Hubička, Zdeněk; Hippler, R.; Jastrabík, Lubomír

    2006-01-01

    Roč. 45, 10B (2006), s. 8090-8094 ISSN 0021-4922 R&D Projects: GA AV ČR 1QS100100563; GA ČR GA202/05/2242 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z10100520 Keywords : laser absorption spectroscopy * pulsed magnetron * sputtering parameters Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.222, year: 2006

  12. Modelling colliding-pulse mode-locked semiconductor lasers

    DEFF Research Database (Denmark)

    Bischoff, Svend

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

  13. Identification of photoacoustic transients during pulsed laser ablation of the human temporal bone: an experimental model.

    Science.gov (United States)

    Wong, B J; Dickinson, M R; Berns, M W; Neev, J

    1996-12-01

    Laser ablation of hard tissues during neurotologic operations has been accomplished with continuous-wave (CW) lasers in the visible and midinfrared spectrum. The mechanism of ablation at these wavelengths is secondary to photothermal-induced tissue destruction. As a result, significant thermal damage to surrounding tissue may occur. Pulsed ultraviolet (UV) lasers have been suggested as an alternative to the argon, KTP-532, and CO2 lasers currently used in clinical practice. The pulse length of Excimer lasers are considerably shorter than the thermal diffusion time of bone tissue, and as a consequence thermal injury is minimal. This makes pulsed lasers an attractive tool for tissue ablation in the ear: in essence a "cold knife." However, the short pulse width of Excimer lasers (typically 10-150 ns) can create large thermoelastic stresses in the ablation specimen. This study identifies the presence of these photoacoustic waves during the Excimer laser treatment of the cadaveric human temporal bone. A XeCl (lambda = 308 nm, tau p = 12 ns) excimer laser was used to ablate hard tissue surrounding the oval window and facial ridge with energies of 75, 45, 25, and 12 mJ/pulse. Spot size was estimated to be 0.5 mm2. Custom high-frequency polyvinyldifluoride (PVDF) piezoelectric film transducers were fabricated and attached to the promontory, round window niche, and facial ridges. The signals were amplified using a low-noise preamplifier and recorded on a digitizing oscilloscope. Photoacoustic waves were clearly identified. Notably, large acoustic waves were measured on the promontory and on both sides of the facial ridge. The implications and clinical relevance of these findings is discussed and compared to findings obtained from a model system.

  14. Pulsed electron beam generation with fast repetitive double pulse system

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Surender Kumar; Deb, Pankaj; Shyam, Anurag, E-mail: surender80@gmail.com [Energetics and Electromagnetics Division, Bhabha Atomic Research Centre, Visakhapatnam (India); Sharma, Archana [Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Mumbai (India)

    2014-07-01

    Longer duration high voltage pulse (∼ 100 kV, 260 ns) is generated and reported using helical pulse forming line in compact geometry. The transmission line characteristics of the helical pulse forming line are also used to develop fast repetition double pulse system with very short inter pulse interval. It overcomes the limitations caused due to circuit parameters, power supplies and load characteristics for fast repetitive high voltage pulse generation. The high voltage double pulse of 100 kV, 100 ns with an inter pulse repetition interval of 30 ns is applied across the vacuum field emission diode for pulsed electron beam generation. The electron beam is generated from cathode material by application of negative high voltage (> 100 kV) across the diode by explosive electron emission process. The vacuum field emission diode is made of 40 mm diameter graphite cathode and SS mesh anode. The anode cathode gap was 6 mm and the drift tube diameter was 10 cm. The initial experimental results of pulsed electron beam generation with fast repetitive double pulse system are reported and discussed. (author)

  15. Single-pulse and multi-pulse femtosecond laser damage of optical single films

    International Nuclear Information System (INIS)

    Yuan Lei; Zhao Yuan'an; He Hongbo; Shao Jianda; Fan Zhengxiu

    2006-01-01

    Laser-induced damage of a single 500 nm HfO 2 film and a single 500 nm ZrO 2 film were studied with single- and multi-pulse femtosecond laser. The laser-induced damage thresholds (LIDT) of both samples by the 1-on-1 method and the 1000-on-1 method were reported. It was discovered that the LIDT of the HfO 2 single film was higher than that of the ZrO 2 single film by both test methods, which was explained by simple Keldysh's multiphoton ionization theory. The LIDT of multi-pulse was lower than that of single-pulse for both samples as a result of accumulative effect. (authors)

  16. Infantile hemangioma: pulsed dye laser versus surgical therapy

    Science.gov (United States)

    Remlova, E.; Dostalova, T.; Michalusova, I.; Vranova, J.; Jelinkova, H.; Hubacek, M.

    2014-05-01

    Hemangioma is a mesenchymal benign tumor formed by blood vessels. Anomalies affect up to 10% of children and they are more common in females than in males. The aim of our study was to compare the treatment efficacy, namely the curative effect and adverse events, such as loss of pigment and appearance of scarring, between classical surgery techniques and laser techniques. For that reason a group of 223 patients with hemangioma was retrospectively reviewed. For treatment, a pulsed dye laser (PDL) (Rhodamine G, wavelength 595 nm, pulsewidth between 0.45 and 40 ms, spot diameter 7 mm, energy density 9-11 J cm-2) was used and the results were compared with a control group treated with classical surgical therapy under general anesthesia. The curative effects, mainly number of sessions, appearance of scars, loss of pigment, and relapses were evaluated as a marker of successful treatment. From the results it was evident that the therapeutic effects of both systems are similar. The PDL was successful in all cases. The surgery patients had four relapses. Classical surgery is directly connected with the presence of scars, but the system is safe for larger hemangiomas. It was confirmed that the PDL had the optimal curative effect without scars for small lesions (approximately 10 mm). Surgical treatment under general anesthesia is better for large hemangiomas; the disadvantage is the presence of scars.

  17. Diffractive optics for reduction of hot cracking in pulsed mode Nd:YAG laser welding

    DEFF Research Database (Denmark)

    Bagger, Claus; Olesen, Søren; Roos, Sven-Olov

    2001-01-01

    In order to reduce the susceptibility to hot cracking in pulsed mode laser welding of austenitic stainless steel, an optical system for reduction of the cooling rate is sought developed. Based on intensive numerical simulations, an optical system producing three focused spots is made. In a number...

  18. Dynamics of pulsed holmium:YAG laser photocoagulation of albumen

    International Nuclear Information System (INIS)

    Pfefer, T.J.; Welch, A.J.

    2000-01-01

    The pulsed holmium:YAG laser (λ = 2.12 μm, τ p = 250 μs) has been investigated as a method for inducing localized coagulation for medical procedures, yet the dynamics of this process are not well understood. In this study, photocoagulation of albumen (egg white) was analysed experimentally and results compared with optical-thermal simulations to investigate a rate process approach to thermal damage and the role of heat conduction and dynamic changes in absorption. The coagulation threshold was determined using probit analysis, and coagulum dynamics were documented with fast flash photography. The nonlinear computational model, which included a Beer's law optical component, a finite difference heat transfer component and an Arrhenius equation-based damage calculation, was verified against data from the literature. Moderate discrepancies between simulation results and our experimental data probably resulted from the use of a laser beam with an irregular spatial profile. This profile produced a lower than expected coagulation threshold and an irregular damage distribution within a millisecond after laser onset. After 1 ms, heat conduction led to smoothing of the coagulum. Simulations indicated that dynamic changes in absorption led to a reduction in surface temperatures. The Arrhenius equation was shown to be effective for simulating transient albumen coagulation during pulsed holmium:YAG laser irradiation. Greater understanding of pulsed laser-tissue interactions may lead to improved treatment outcome and optimization of laser parameters for a variety of medical procedures. (author)

  19. Robot-laser system

    International Nuclear Information System (INIS)

    Akeel, H.A.

    1987-01-01

    A robot-laser system is described for providing a laser beam at a desired location, the system comprising: a laser beam source; a robot including a plurality of movable parts including a hollow robot arm having a central axis along which the laser source directs the laser beam; at least one mirror for reflecting the laser beam from the source to the desired location, the mirror being mounted within the robot arm to move therewith and relative thereto to about a transverse axis that extends angularly to the central axis of the robot arm; and an automatic programmable control system for automatically moving the mirror about the transverse axis relative to and in synchronization with movement of the robot arm to thereby direct the laser beam to the desired location as the arm is moved

  20. Attosecond pulse trains from long laser-gas interaction targets

    International Nuclear Information System (INIS)

    Hauri, C.P.; Lopez-Martens, R.; Varju, K.; Ruchon, T.; Gustafsson, E.; L'Huillier, A.

    2006-01-01

    Complete test of publication follows. Many experiments in attosecond physics require high XUV photon flux as well as a clean attosecond pulse train (APT) temporal structure. Temporal characterization of high-order harmonic generation (HHG) in long interaction targets is thus of high interest. HHG being a very inefficient process, a large effort has been made to increase the amount of XUV photons emitted per infrared laser pulse. Besides quasi phase-matching in a modulated capillary, loose driving laser focusing conditions and subsequent self-channeling have shown to significantly increase the conversion efficiency. We characterized the temporal structure of APTs generated during the self-channeling of an intense IR driving laser pulse. Our first results indicate, however, that the temporal structure of the APT generated during the HHG process might be affected by quantum path interference and spectral phase distortion due to the self-channeling process itself. In particular, our measurements show that the relative spectral phase between consecutive harmonics can strongly vary depending on the target length and the position of the laser focus with respect to the target. In general for short gas targets, no clean APT structure can be expected since the individual attosecond pulses carry significant chirp. For longer targets, however, we observe a flattening of the harmonic spectral phase, resulting in near-transform-limited attosecond pulse trains. A complete analysis of the process is complex and involves detailed knowledge of the spatial and temporal evolution of the self-channeling driver laser pulse throughout the gas target.

  1. Femtosecond and Subfemtosecond X-Ray Pulses from a SASE Based Free-Electron Laser

    Energy Technology Data Exchange (ETDEWEB)

    Emma, P

    2004-03-10

    We propose a novel method to generate femtosecond and sub-femtosecond photon pulses in a free electron laser by selectively spoiling the transverse emittance of the electron beam. Its merits are simplicity and ease of implementation. When the system is applied to the Linac Coherent Light Source, it can provide x-ray pulses the order of 1 femtosecond in duration containing about 1010 transversely coherent photons.

  2. Pulsed neutron porosity logging system

    International Nuclear Information System (INIS)

    Smith, H.D. Jr.; Smith, M.P.; Schultz, W.E.

    1978-01-01

    An improved pulsed neutron porosity logging system is provided in the present invention. A logging tool provided with a 14 MeV pulsed neutron source, an epithermal neutron detector, and a fast neutron detector is moved through a borehole. Repetitive bursts of neutrons irradiate the earth formations and, during the bursts, the fast neutron population is sampled. During the interval between bursts the epithermal neutron population is sampled along with background gamma radiation due to lingering thermal neutrons. The fast and epithermal neutron population measurements are combined to provide a measurement of formation porosity

  3. Experimental investigations of pulse shape control in passively mode-locked fiber lasers with net-normal dispersion

    International Nuclear Information System (INIS)

    Wang, L R; Han, D D

    2013-01-01

    Pulse shape control in passively mode-locked fiber lasers with net-normal dispersion is investigated experimentally. Three kinds of pulses with different spectral and temporal shapes are observed, and their pulse-shaping mechanisms are discussed. After a polarization-resolved system external to the cavity, the maximum intensity differences of the two polarization components for the rectangular-spectrum (RS), Gaussian-spectrum (GS), and super-broadband (SB) pulses are measured as ∼20 dB, ∼15 dB, and ∼1 dB, respectively. It is suggested that the equivalent saturable absorption effect plays an increasingly important role from the RS to GS and then to SB pulses in the pulse-shaping processes, while the spectral filtering effect declines. This work could help in systematically understanding pulse formation and proposing guidelines for the realization of pulses with better performance in fiber lasers. (paper)

  4. Tunable Landau-Zener transitions using continuous- and chirped-pulse-laser couplings

    Science.gov (United States)

    Sarreshtedari, Farrokh; Hosseini, Mehdi

    2017-03-01

    The laser coupled Landau-Zener avoided crossing has been investigated with an aim towards obtaining the laser source parameters for precise controlling of the state dynamics in a two-level quantum system. The conventional Landau-Zener equation is modified for including the interaction of the system with a laser field during a bias energy sweep and the obtained Hamiltonian is numerically solved for the investigation of the two-state occupation probabilities. We have shown that in the Landau-Zener process, using an additional laser source with controlled amplitude, frequency, and phase, the system dynamics could be arbitrarily engineered. This is while, by synchronous frequency sweeping of a chirped-pulse laser, the system could be guided into a resonance condition, which again gives the remarkable possibility for precise tuning and controlling of the quantum system dynamics.

  5. Determination of elemental composition of coffee using UV-pulsed laser induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Gondal, M. A.; Baig, Umair; Dastageer, M. A.; Sarwar, Mohsin

    2016-01-01

    A detection system based on laser induced breakdown spectroscopy (LIBS) was built using 266 nm wavelength pulsed laser from the fourth harmonic of Nd:YAG laser, 500 mm spectrograph and gated ICCD camera with built-in delay generator. The LIBS system was used to study the elemental composition in coffee available in the local market of Saudi Arabia for the detection of elements in coffee samples. The LIBS spectrum of coffee sample revealed the presence magnesium, calcium, aluminum, copper, sodium, barium, bromine, cobalt, chromium, cerium manganese and molybdenum. Atomic transition line of sodium is used to study the parametric dependence of LIBS signal. The study of the dependence of LIBS signal on the laser pulse energy is proven to be linear and the dependence of LIBS signal on the time delay between the excitation and data acquisition showed a typical increase, a peak value and a decrease with the optimum excitation – acquisition delay at 400 ns.

  6. Determination of elemental composition of coffee using UV-pulsed laser induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gondal, M. A., E-mail: magondal@kfupm.edu.sa; Baig, Umair; Dastageer, M. A.; Sarwar, Mohsin [Laser Research Group, Physics Department, King Fahd University of Petroleum and Minerals, P.O Box 5047, Dhahran 31261 (Saudi Arabia)

    2016-06-10

    A detection system based on laser induced breakdown spectroscopy (LIBS) was built using 266 nm wavelength pulsed laser from the fourth harmonic of Nd:YAG laser, 500 mm spectrograph and gated ICCD camera with built-in delay generator. The LIBS system was used to study the elemental composition in coffee available in the local market of Saudi Arabia for the detection of elements in coffee samples. The LIBS spectrum of coffee sample revealed the presence magnesium, calcium, aluminum, copper, sodium, barium, bromine, cobalt, chromium, cerium manganese and molybdenum. Atomic transition line of sodium is used to study the parametric dependence of LIBS signal. The study of the dependence of LIBS signal on the laser pulse energy is proven to be linear and the dependence of LIBS signal on the time delay between the excitation and data acquisition showed a typical increase, a peak value and a decrease with the optimum excitation – acquisition delay at 400 ns.

  7. Laser wakefield electron acceleration. A novel approach employing supersonic microjets and few-cycle laser pulses

    International Nuclear Information System (INIS)

    Schmid, Karl

    2011-01-01

    This thesis covers the few-cycle laser-driven acceleration of electrons in a laser-generated plasma. This process, known as laser wakefield acceleration (LWFA), relies on strongly driven plasma waves for the generation of accelerating gradients in the vicinity of several 100 GV/m, a value four orders of magnitude larger than that attainable by conventional accelerators. This thesis demonstrates that laser pulses with an ultrashort duration of 8 fs and a peak power of 6 TW allow the production of electron energies up to 50 MeV via LWFA. The special properties of laser accelerated electron pulses, namely the ultrashort pulse duration, the high brilliance, and the high charge density, open up new possibilities in many applications of these electron beams. (orig.)

  8. Laser pulses for coherent xuv Raman excitation

    Science.gov (United States)

    Greenman, Loren; Koch, Christiane P.; Whaley, K. Birgitta

    2015-07-01

    We combine multichannel electronic structure theory with quantum optimal control to derive femtosecond-time-scale Raman pulse sequences that coherently populate a valence excited state. For a neon atom, Raman target populations of up to 13% are obtained. Superpositions of the ground and valence Raman states with a controllable relative phase are found to be reachable with up to 4.5% population and arbitrary phase control facilitated by the pump pulse carrier-envelope phase. Analysis of the optimized pulse structure reveals a sequential mechanism in which the valence excitation is reached via a fast (femtosecond) population transfer through an intermediate resonance state in the continuum rather than avoiding intermediate-state population with simultaneous or counterintuitive (stimulated Raman adiabatic passage) pulse sequences. Our results open a route to coupling valence excitations and core-hole excitations in molecules and aggregates that locally address specific atoms and represent an initial step towards realization of multidimensional spectroscopy in the xuv and x-ray regimes.

  9. CO2 laser pulse switching by optically excited semiconductors

    International Nuclear Information System (INIS)

    Silva, V.L. da.

    1986-01-01

    The construction and the study of a semi-conductor optical switch used for generating short infrared pulses and to analyse the semiconductor characteristics, are presented. The switch response time depends on semiconductor and control laser characteristics. The results obtained using a Ge switch controlled by N 2 , NdYag and Dye lasers are presented. The response time was 50 ns limited by Ge recombination time. The reflectivity increased from 7% to 59% using N 2 laser to control the switch. A simple model for semiconductor optical properties that explain very well the experimental results, is also presented. (author) [pt

  10. LASER BIOLOGY AND MEDICINE: Effect of repetitive laser pulses on the electrical conductivity of intervertebral disc tissue

    Science.gov (United States)

    Omel'chenko, A. I.; Sobol', E. N.

    2009-03-01

    The thermomechanical effect of 1.56-μm fibre laser pulses on intervertebral disc cartilage has been studied using ac conductivity measurements with coaxial electrodes integrated with an optical fibre for laser radiation delivery to the tissue. The observed time dependences of tissue conductivity can be interpreted in terms of hydraulic effects and thermomechanical changes in tissue structure. The laserinduced changes in the electrical parameters of the tissue are shown to correlate with the structural changes, which were visualised using shadowgraph imaging. Local ac conductivity measurements in the bulk of tissue can be used to develop a diagnostic/monitoring system for laser regeneration of intervertebral discs.

  11. Computational model of dual q-switching and lasing processes of the pulsed Cr4+:YAG laser pumped by Nd-glass laser

    International Nuclear Information System (INIS)

    Abdul Ghani, B.; Hammadi, M.

    2007-01-01

    A mathematical model describing the absorption and oscillation processes of intracavity Cr 4+ : YAG crystal pumped by Nd-glass laser has been developed, in order to describe the temporal behavior of laser-absorber system. The model has been assumed that the Cr 4+ ions excited to a higher level by excited state absorption, followed by relaxation directly to the upper laser level through fast channel, and indirectly through slow proposed intermediate channel at different lifetimes. The model offers simple kinetic mechanisms for pulsed solid state lasers and also the influence of the variations of the laser input parameters (pumping rate, maximum amplification coefficient and loss coefficient) on the output pulse characteristics of the passive Q-switched Nd-glass and pulsed Cr 4+ : YAG lasers. The model estimates the temporal behavior of the population densities of different levels and laser beam densities as well as predicts the nanosecond output laser pulses of passive Q-switched Nd-glass laser and pulsed Cr 4+ : YAG laser. The calculated results are in good agreement with the available experimental and theoretical data in the literature. (author)

  12. Ablation of polymers by ultraviolet pulsed laser

    International Nuclear Information System (INIS)

    Brezini, A.; Benharrats, N.

    1993-08-01

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

  13. Pulsed-laser deposited ZnO for device applications

    NARCIS (Netherlands)

    King, S.L.; Gardeniers, Johannes G.E.; Boyd, I.W.

    1996-01-01

    The study investigates the growth by pulsed-laser deposition (PLD) of ZnO thin films for the eventual incorporation into piezo-electric actuators and other sensors being developed at the University of Twente. All films are purely c-axis oriented, and results are presented which suggest the

  14. RHEED study of titanium dioxide with pulsed laser deposition

    DEFF Research Database (Denmark)

    Rasmussen, Inge Lise; Pryds, Nini; Schou, Jørgen

    2009-01-01

    Reflection high-energy electron diffraction (RHEED) operated at high pressure has been used to monitor the growth of thin films of titanium dioxide (TiO2) on (1 0 0) magnesium oxide (MgO) substrates by pulsed laser deposition (PLD). The deposition is performed with a synthetic rutile TiO2 target...

  15. Direct Patterning of Oxides by Pulsed Laser Stencil Deposition

    NARCIS (Netherlands)

    te Riele, P.M.

    2008-01-01

    This thesis describes a detailed study of the application of stencil technology in the patterning of epitaxial oxide thin films by pulsed laser deposition (PLD). Stencil patterning has been applied in thin film sub-micron patterning of metals successfully for decades since it has several advantages

  16. Quantum energy duplication using super high output pulse laser

    International Nuclear Information System (INIS)

    Sugisaki, Kiwamu; Koyama, Kazuyoshi; Tanimoto, Mitsumori; Saito, Naoaki

    2000-01-01

    This study aims at elucidation on phenomena induced by strong electric field of super high output ultra short laser pulse to carry out development of basic technology required for promotion of a study on generation of high energy particle and photon using them, in order to contribute to application of super high output ultra short laser pulse and high energy plasma formed by it. In 1998 fiscal year of the last fiscal year in this study, by intending to increase the output by narrowing pulse width of the super high output laser, some basic experiments such as verification due to experiment on relativity theoretical self-convergence, generation of high energy particles, and so forth were carried out to establish a forecasting on future application. And, by conducting plasma generation experiment, self-guide and high energy particle formation experiment in plasma of super high intensity laser pulse important for its applications, and so forth, various technologies constituting foundation of future developments were developed, and more results could be obtained than those at proposal of this study. (G.K.)

  17. Dynamics of interaction of ultrashort laser pulses with solid targets

    International Nuclear Information System (INIS)

    Cang Yu; Wang Wei; Zhang Jie

    2001-01-01

    Using Saha equation, a simple model is proposed for the dynamics of interaction between ultrashort laser pulses and solid targets. An adiabatic expansion model is adopted to study the expansion phase after the heating phase. Temporal evolvement of the dynamics of the interaction is obtained, from which the electron temperature, density, ionization balances can be determined

  18. Laser-evaporated pulsed atomic beam and its application

    International Nuclear Information System (INIS)

    Zhang Yanping; Hu Qiquan; Su Haizheng; Lin Fucheng

    1986-01-01

    For the purpose of obtaining an atomic beam, laser-evaporated atomic vapor was studied experimentally. The signals of multiphoton ionization of refractory metal atoms obtained with the pulsed atomic beam were observed, and the problem associated with the detection of these signals was discussed

  19. Two-pulse laser control of nuclear and electronic motion

    DEFF Research Database (Denmark)

    Grønager, Michael; Henriksen, Niels Engholm

    1997-01-01

    We discuss an explicitly time-dependent two-pulse laser scheme for controlling where nuclei and electrons are going in unimolecular reactions. We focus on electronic motion and show, with HD+ as an example, that one can find non-stationary states where the electron (with some probability...

  20. Pulsed laser stereophotography of plasmas and dynamically moving surfaces

    International Nuclear Information System (INIS)

    Paisley, D.L.

    1987-01-01

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

  1. Ultrashort-pulse laser excitation and damage of dielectric materials

    DEFF Research Database (Denmark)

    Haahr-Lillevang, Lasse; Balling, Peter

    2015-01-01

    Ultrashort-pulse laser excitation of dielectrics is an intricate problem due to the strong coupling between the rapidly changing material properties and the light. In the present paper, details of a model based on a multiple-rate-equation description of the conduction band are provided. The model...

  2. Interaction of UV laser pulses with reactive dusty plasmas

    NARCIS (Netherlands)

    van de Wetering, F.M.J.H.; Beckers, J.; Nijdam, S.; Oosterbeek, W.; Kovacevic, E.; Berndt, J.

    2016-01-01

    This contribution deals with the effects of UV photons on the synthesis and transport of nanoparticles in reactive complex plasmas (capacitively coupled RF discharge). First measurements showed that the irradiation of a reactive acetylene-argon plasma with high-energy, ns UV laser pulses (355 nm, 75

  3. Modeling short-pulse laser excitation of dielectric materials

    DEFF Research Database (Denmark)

    Wædegaard, Kristian Juncher; Sandkamm, Ditte Både; Haahr-Lillevang, Lasse

    2014-01-01

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

  4. History and current status of commercial pulsed laser deposition equipment

    International Nuclear Information System (INIS)

    Greer, James A

    2014-01-01

    This paper will review the history of the scale-up of the pulsed laser deposition (PLD) process from small areas ∼1 cm 2 up to 10 m 2 starting in about 1987. It also documents the history of commercialization of PLD as various companies become involved in selling fully integrated laser deposition tools starting in 1989. The paper will highlight the current state of the art of commercial PLD equipment for R and D that is available on the market today from mainstream vendors as well as production-oriented applications directed at piezo-electric materials for microelectromechanical systems and high-temperature superconductors for coated-conductor applications. The paper clearly demonstrates that considerable improvements have been made to scaling this unique physical vapour deposition process to useful substrate sizes, and that commercial deposition equipment is readily available from a variety of vendors to address a wide variety of technologically important thin-film applications. (paper)

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

    Directory of Open Access Journals (Sweden)

    L. Li

    2012-12-01

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

  6. Efficient chirped-pulse amplification of sub-20 fs laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Matsuoka, Shinichi; Yamakawa, Koichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    We have developed a model for ultrabroadband and ultrashort pulse amplification including the effects of a pulse shaper for regenerative pulse shaping, gain narrowing and gain saturation in the amplifiers. Thin solid etalons are used to control both gain narrowing and gain saturation during amplification. This model has been used to design an optimized Ti:sapphire amplifier system for producing efficiently pulses of < 20-fs duration with approaching peak and average powers of 100 TW and 20 W. (author)

  7. Autofluorescence of pigmented skin lesions using a pulsed UV laser with synchronized detection: clinical results

    DEFF Research Database (Denmark)

    Cheng, Haynes Pak Hay; Svenmarker, Pontus; Tidemand-Lichtenberg, Peter

    2010-01-01

    signal, which may in turn produce high contrast images that improve diagnosis, even in the presence of ambient room light. The synchronized set-up utilizes a compact, diode pumped, pulsed UV laser at 355 nm which is coupled to a CCD camera and a liquid crystal tunable filter. The excitation and image......We report preliminary clinical results of autofluorescence imaging of malignant and benign skin lesions, using pulsed 355 nm laser excitation with synchronized detection. The novel synchronized detection system allows high signal-to-noise ratio to be achieved in the resulting autofluorescence...

  8. Histologic comparison of the pulsed dye laser and copper vapor laser effects on pig skin

    Energy Technology Data Exchange (ETDEWEB)

    Tan, O.T.; Stafford, T.J.; Murray, S.; Kurban, A.K. (Boston Univ. Medical Center, MA (USA))

    1990-01-01

    Albino pig skin was exposed to the copper vapor (CVL) and flash-lamp pulsed dye (PDL) lasers at 578 nm with a 3 mm diameter spotsize over a range of fluences until purpura and whitening were first established. The total irradiation time was the parameter that was varied in order for the CVL to reach the desired fluence. The lowest fluence producing each clinical endpoint was designated the threshold fluence: 34 J/cm{sup 2} was required to produce purpura using the CVL compared to 7.5 J/cm{sup 2} with the PDL laser. Histologically, skin exposed to purpura fluences from the CVL revealed the presence of constricted, disrupted papillary dermal blood vessels with trapped RBC's within them which were unlike those exposed to PDL where the irradiated vessels were dilated and packed with masses of intravascular agglutinated RBC's. The whitening threshold fluences for the CVL and PDL lasers were 67 J/cm{sup 2} and 29 J/cm{sup 2}, respectively. Streaming of epidermal cells and dermal collagen denaturation were observed in CVL irradiated skin, compared to occasional dyskeratotic epidermal cells and focal dermal collagen denaturation following PDL exposure. The mechanisms responsible for the clinical and histologic changes produced by the two laser systems are discussed.

  9. Laser repair welding of molds with various pulse shapes

    Directory of Open Access Journals (Sweden)

    M. Pleterski

    2010-01-01

    Full Text Available Repair welding of cold-work tool steels with conventional methods is very difficult due to cracking during remelting or cladding and is generally performed with preheating. As an alternative, repair welding with laser technology has recently been used. This paper presents the influence of different pulse shapes on welding of such tools with the pulsed Nd:YAG laser. Repair welding tests were carried out on AISI D2 tool steel, quenched and tempered to hardness of 56 HRc, followed by microstructural analysis and investigation of defects with scanning electron microscopy. Test results suggest that it is possible to obtain sound welds without preheating, with the right selection of welding parameters and appropriate pulse shape.

  10. Pulsed laser ablation and deposition of niobium carbide

    International Nuclear Information System (INIS)

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

    2016-01-01

    Highlights: • We have deposited in vacuum niobium carbide films by fs and ns PLD. • We have compared PLD performed by ultra-short and short laser pulses. • The films deposited by fs PLD of NbC are formed by nanoparticles. • The structure of the films produced by fs PLD at 500 °C corresponds to NbC. - Abstract: NbC crystalline films have been deposited in vacuum by ultra-short pulsed laser deposition technique. The films have been characterized by transmission and scanning electron microscopies and by X-ray diffraction. To clarify the ablation–deposition mechanism, the plasma produced by the ablation process has been characterized by optical emission spectroscopy and fast imaging. A comparison of the results with those obtained by ns pulsed deposition of the same target has been carried out.

  11. Short-pulse lasers for weather control

    Science.gov (United States)

    Wolf, J. P.

    2018-02-01

    Filamentation of ultra-short TW-class lasers recently opened new perspectives in atmospheric research. Laser filaments are self-sustained light structures of 0.1–1 mm in diameter, spanning over hundreds of meters in length, and producing a low density plasma (1015–1017 cm‑3) along their path. They stem from the dynamic balance between Kerr self-focusing and defocusing by the self-generated plasma and/or non-linear polarization saturation. While non-linearly propagating in air, these filamentary structures produce a coherent supercontinuum (from 230 nm to 4 µm, for a 800 nm laser wavelength) by self-phase modulation (SPM), which can be used for remote 3D-monitoring of atmospheric components by Lidar (Light Detection and Ranging). However, due to their high intensity (1013–1014 W cm‑2), they also modify the chemical composition of the air via photo-ionization and photo-dissociation of the molecules and aerosols present in the laser path. These unique properties were recently exploited for investigating the capability of modulating some key atmospheric processes, like lightning from thunderclouds, water vapor condensation, fog formation and dissipation, and light scattering (albedo) from high altitude clouds for radiative forcing management. Here we review recent spectacular advances in this context, achieved both in the laboratory and in the field, reveal their underlying mechanisms, and discuss the applicability of using these new non-linear photonic catalysts for real scale weather control.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-11-12

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

  13. Wavelength stabilized high pulse power laser diodes for automotive LiDAR

    Science.gov (United States)

    Knigge, A.; Klehr, A.; Wenzel, H.; Zeghuzi, A.; Fricke, J.; Maaßdorf, A.; Liero, A.; Tränkle, G.

    2018-03-01

    Diode lasers generating optical pulses with high peak power and lengths in the nanosecond range are key components of systems for free-space communication, metrology, material processing, spectroscopy, and light detection and ranging (LiDAR) as needed for object detection and autonomous driving. Automotive LiDAR systems demand additionally a good beam quality and low wavelength shift with temperature due to the wide operating temperature span. We present here internally wavelength stabilized lasers emitting ns optical pulses from an emission aperture between 30 μm and 100 μm with peak powers of tens of Watts at wavelengths around 905 nm. The vertical structure based on AlGaAs (confinement and cladding layers) and InGaAs (active quantum well) is especially optimized for pulsed operation with respect to the implementation of a surface Bragg grating with a high reflectivity. The fabricated 6 mm long distributed Bragg reflector (DBR) broad area (BA) lasers are electrically driven by an in-house developed high-speed unit generating 3 to 10 ns long nearly rectangular shaped current pulses with amplitudes of up to 250 A. Such lasers emit optical pulses with a peak power of more than 30 W at 95 A pulse current up to a temperature of 85°C with a wavelength shift as low as 65 pm/K and a lateral beam propagation factor less than 10. The influence of the lateral aperture width and the pulse length on the beam quality will be shown. A monolithic integration of 3 DBR BA lasers on a single chip whose emission can be combined into a single beam raises the output power to more than 100 W.

  14. Diode-pumped solid state laser. (Part V). ; Short pulse laser oscillation. Handotai laser reiki kotai laser. 5. ; Tan pulse hasshin

    Energy Technology Data Exchange (ETDEWEB)

    Kuwabara, M.; Bando, N. (Asahi Glass Co. Ltd., Tokyo (Japan))

    1991-12-25

    A semiconductor laser (LD) excited solid state laser using an LD as an excited light source is under discussion for its practical applications to measurements, processing, communications, office automation, and medical areas. This paper describes the discussions given on the short pulse transmission using AOQ switching elements in the LD excited solid state laser with a long wave length band (1.3{mu}m), which is expected of its application in the communications and measurements area. Based on a possibility of raising a measurements resolution by making the pluses in the LD excited solid state laser, and experiments were performed using Nd:YLF as a laser host. as a results, it was found that the smaller the effective mode volume V {sub eff},the smaller the pulse width, and that the ratio of number of initial inversion distribution (N{sub i}/N{sub t}), an important parameter to determine pulse widths, can be obtained from the ratio of the LD exciting light to the input power (P{sub in}/P{sub t}). 7 refs., 14 figs., 2 tabs.

  15. Study on laser welding of austenitic stainless steel by varying incident angle of pulsed laser beam

    Science.gov (United States)

    Kumar, Nikhil; Mukherjee, Manidipto; Bandyopadhyay, Asish

    2017-09-01

    In the present work, AISI 304 stainless steel sheets are laser welded in butt joint configuration using a robotic control 600 W pulsed Nd:YAG laser system. The objective of the work is of twofold. Firstly, the study aims to find out the effect of incident angle on the weld pool geometry, microstructure and tensile property of the welded joints. Secondly, a set of experiments are conducted, according to response surface design, to investigate the effects of process parameters, namely, incident angle of laser beam, laser power and welding speed, on ultimate tensile strength by developing a second order polynomial equation. Study with three different incident angle of laser beam 89.7 deg, 85.5 deg and 83 deg has been presented in this work. It is observed that the weld pool geometry has been significantly altered with the deviation in incident angle. The weld pool shape at the top surface has been altered from semispherical or nearly spherical shape to tear drop shape with decrease in incident angle. Simultaneously, planer, fine columnar dendritic and coarse columnar dendritic structures have been observed at 89.7 deg, 85.5 deg and 83 deg incident angle respectively. Weld metals with 85.5 deg incident angle has higher fraction of carbide and δ-ferrite precipitation in the austenitic matrix compared to other weld conditions. Hence, weld metal of 85.5 deg incident angle achieved higher micro-hardness of ∼280 HV and tensile strength of 579.26 MPa followed by 89.7 deg and 83 deg incident angle welds. Furthermore, the predicted maximum value of ultimate tensile strength of 580.50 MPa has been achieved for 85.95 deg incident angle using the developed equation where other two optimum parameter settings have been obtained as laser power of 455.52 W and welding speed of 4.95 mm/s. This observation has been satisfactorily validated by three confirmatory tests.

  16. Developing a Methodology for Elaborating a Pulsed Optical Safety Area for High Power Laser Diodes

    National Research Council Canada - National Science Library

    Yankov, Plamen

    2006-01-01

    The laser diodes are efficient sources of optical radiation. The maximum optical peak power depends on the pulse duration of the driving current pulse - reducing the pulse duration the safety peak power is increased...

  17. Propagation of an asymmetric relativistic laser pulse in plasma

    International Nuclear Information System (INIS)

    Garuchava, D.P.; Murusidze, I.G.; Suramlishvili, G.I.; Tsintsadze, N.L.; Tskhakaya, D.D.

    1997-01-01

    The interaction of a relativistically intense asymmetric laser pulse with a plasma has been studied. The asymmetric shape of the pulse implies that the rise time of the leading edge of the pulse is much greater than the fall time of the trailing edge. The numerical simulation of the propagation of such a pulse through an underdense plasma has shown that relativistic self-focusing enhances the effect of ponderomotive self-channeling. The radial ponderomotive force totally expels the electrons from the axis creating a density channel, that is, cavitation occurs. A very short fall time of the trailing edge (τ l ω p <1) causes a rapid increase in the amplitude of a laser driven longitudinal electric field to values of a few GV/cm at the back of the pulse. The numerical simulation also has shown that the channel as well as the large-amplitude longitudinal field can be sustained in the range immediately behind the pulse, thus creating favorable conditions to accelerate a trailing bunch of electrons to extremely high energies. According to our model, the accelerating electric field can reach the value 10 GV/cm. copyright 1997 The American Physical Society

  18. Selective photoionization of isotopic atoms with pulsed lasers

    International Nuclear Information System (INIS)

    Dai Changjian

    1994-01-01

    The dynamics of isotopically selective interactions between the radiation of three pulsed lasers and atoms with a four-levels scheme has been studied. Starting from the time-dependent Schroedinger equation with the rotating-wave approximation, authors applied Sylvester theorem to the dynamic equations associated with near-and off-resonant excitations, respectively. Authors obtained the explicit expressions for the four-levels occupation probabilities. The analytic treatment explored the properties of coherent oscillations occurred in the atomic excitation processes with intense monochromatic lasers. The conditions under which the population inversion takes place are derived from near-resonant excitations. The criteria to select the basic parameters of pulsed lasers involved in the process are also provided

  19. Interaction of Repetitively Pulsed High Energy Laser Radiation With Matter

    Science.gov (United States)

    Hugenschmidt, Manfred

    1986-10-01

    The paper is concerned with laser target interaction processes involving new methods of improving the overall energy balance. As expected theoretically, this can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed by using a pulsed CO2 laser at mean powers up to 2 kW and repetition rates up to 100 Hz. The rates of temperature rise of aluminium for example were thereby increased by lore than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements were found for the overall absorptivities that were increased by this method by more than an order of magnitude.

  20. Fiber Optic Cables for Transmission of High-Power Laser Pulses in Spaceflight Applications

    Science.gov (United States)

    Thomes, W. J., Jr.; Ott, M. N.; Chuska, R. F.; Switzer, R. C.; Blair, D. E.

    2010-01-01

    Lasers with high peak power pulses are commonly used in spaceflight missions for a wide range of applications, from LIDAR systems to optical communications. Due to the high optical power needed, the laser has to be located on the exterior of the satellite or coupled through a series of free space optics. This presents challenges for thermal management, radiation resistance, and mechanical design. Future applications will require multiple lasers located close together, which further complicates the design. Coupling the laser energy into a fiber optic cable allows the laser to be relocated to a more favorable position on the spacecraft. Typical fiber optic termination procedures are not sufficient for injection of these high-power laser pulses without catastrophic damage to the fiber endface. In the current study, we will review the causes of fiber damage during high-power injection and discuss our new manufacturing procedures that overcome these issues to permit fiber use with high reliability in these applications. We will also discuss the proper methods for launching the laser pulses into the fiber to avoid damage and how this is being implemented for current spaceflight missions.

  1. Fiber optic cables for transmission of high-power laser pulses in spaceflight applications

    Science.gov (United States)

    Thomes, W. J.; Ott, M. N.; Chuska, R. F.; Switzer, R. C.; Blair, D. E.

    2017-11-01

    Lasers with high peak power pulses are commonly used in spaceflight missions for a wide range of applications, from LIDAR systems to optical communications. Due to the high optical power needed, the laser has to be located on the exterior of the satellite or coupled through a series of free space optics. This presents challenges for thermal management, radiation resistance, and mechanical design. Future applications will require multiple lasers located close together, which further complicates the design. Coupling the laser energy into a fiber optic cable allows the laser to be relocated to a more favorable position on the spacecraft. Typical fiber optic termination procedures are not sufficient for injection of these high-power laser pulses without catastrophic damage to the fiber endface. In the current study, we will review the causes of fiber damage during high-power injection and discuss our new manufacturing procedures that overcome these issues to permit fiber use with high reliability in these applications. We will also discuss the proper methods for launching the laser pulses into the fiber to avoid damage and how this is being implemented for current spaceflight missions.

  2. Population dynamics of graphene driven by a few-cycle laser pulse

    Science.gov (United States)

    Ding, Chunling; Yu, Rong; Hao, Xiangying; Zhang, Duo; Zu, Fengxia

    2017-06-01

    We study the time evolution of the populations in a two-dimensional (2D) graphene system by employing a few-cycle laser pulse with a linear polarization. Specifically, we present a comparative numerical analysis of the population dynamics of graphene in three different model configurations. Our results show that the Rabi-like oscillations and intraband population inversion can be observed in the population spectrum, which originated from the periodicity of a few-cycle laser pulse and the intraband Coulomb scattering. Also, coherent population oscillations are produced across the Dirac point when the Rabi frequency of the laser field which is used to couple the interband transition is much larger than that couples the intraband transition, and vice versa. These investigations may be helpful to enhance the performance of graphene-based ultrafast electronic and optoelectronic devices, including light-emitting devices, touch screens, photodetectors, and ultrafast lasers.

  3. Characterization of ethylcellulose and hydroxypropyl methylcellulose thin films deposited by matrix-assisted pulsed laser evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Palla-Papavlu, A., E-mail: apalla@nipne.ro [National Institute for Lasers, Plasma and Radiation Physics, PO Box MG-36, Magurele, RO-077125 Bucharest (Romania); Rusen, L.; Dinca, V.; Filipescu, M. [National Institute for Lasers, Plasma and Radiation Physics, PO Box MG-36, Magurele, RO-077125 Bucharest (Romania); Lippert, T. [Paul Scherrer Institut, General Energy Research Department, 5232 Villigen PSI (Switzerland); Dinescu, M. [National Institute for Lasers, Plasma and Radiation Physics, PO Box MG-36, Magurele, RO-077125 Bucharest (Romania)

    2014-05-01

    In this study is reported the deposition of hydroxypropyl methylcellulose (HPMC) and ethylcellulose (EC) by matrix-assisted pulsed laser evaporation (MAPLE). Both HPMC and EC were deposited on silicon substrates using a Nd:YAG laser (266 nm, 5 ns laser pulse and 10 Hz repetition rate) and then characterized by atomic force microscopy and Fourier transform infrared spectroscopy. It was found that for laser fluences up to 450 mJ/cm{sup 2} the structure of the deposited HPMC and EC polymer in the thin film resembles to the bulk. Morphological investigations reveal island features on the surface of the EC thin films, and pores onto the HPMC polymer films. The obtained results indicate that MAPLE may be an alternative technique for the fabrication of new systems with desired drug release profile.

  4. Characterization of ethylcellulose and hydroxypropyl methylcellulose thin films deposited by matrix-assisted pulsed laser evaporation

    Science.gov (United States)

    Palla-Papavlu, A.; Rusen, L.; Dinca, V.; Filipescu, M.; Lippert, T.; Dinescu, M.

    2014-05-01

    In this study is reported the deposition of hydroxypropyl methylcellulose (HPMC) and ethylcellulose (EC) by matrix-assisted pulsed laser evaporation (MAPLE). Both HPMC and EC were deposited on silicon substrates using a Nd:YAG laser (266 nm, 5 ns laser pulse and 10 Hz repetition rate) and then characterized by atomic force microscopy and Fourier transform infrared spectroscopy. It was found that for laser fluences up to 450 mJ/cm2 the structure of the deposited HPMC and EC polymer in the thin film resembles to the bulk. Morphological investigations reveal island features on the surface of the EC thin films, and pores onto the HPMC polymer films. The obtained results indicate that MAPLE may be an alternative technique for the fabrication of new systems with desired drug release profile.

  5. Pulse-Flow Microencapsulation System

    Science.gov (United States)

    Morrison, Dennis R.

    2006-01-01

    The pulse-flow microencapsulation system (PFMS) is an automated system that continuously produces a stream of liquid-filled microcapsules for delivery of therapeutic agents to target tissues. Prior microencapsulation systems have relied on batch processes that involve transfer of batches between different apparatuses for different stages of production followed by sampling for acquisition of quality-control data, including measurements of size. In contrast, the PFMS is a single, microprocessor-controlled system that performs all processing steps, including acquisition of quality-control data. The quality-control data can be used as real-time feedback to ensure the production of large quantities of uniform microcapsules.

  6. Peculiarities of laser phase behavior associated with the accelerated electron in a chirped laser pulse

    International Nuclear Information System (INIS)

    Song, Q.; Wu, X. Y.; Wang, J. X.; Kawata, S.; Wang, P. X.

    2014-01-01

    In this paper, we qualitatively analyzed peculiarities of laser phase behavior associated with the accelerated electron in a chirped laser pulse. We unveiled the relationship between the changes in the orientation of the electron trajectory and the cusps in magnitude of the phase velocity of the optical field along the electron trajectory in a chirped laser pulse. We also explained how the chirp effect induced the singular point of the phase velocity. Finally, we discussed the phase velocity and phase witnessed by the electron in the particle's moving instantaneous frame

  7. A thermal model for nanosecond pulsed laser ablation of aluminum

    Directory of Open Access Journals (Sweden)

    Yu Zhang

    2017-07-01

    Full Text Available In order to simulate the nanosecond pulsed laser ablation of aluminum, a novel model was presented for the target ablation and plume expansion. The simulation of the target ablation was based on one-dimensional heat conduction, taking into account temperature dependent material properties, phase transition, dielectric transition and phase explosion. While the simulation of the plume expansion was based on one-dimensional gas-dynamical equation, taking into account ionization, plume absorption and shielding. By coupling the calculations of the target ablation and plume expansion, the characteristics of the target and plume were obtained. And the calculated results were in good agreement with the experimental data, in terms of ablation threshold and depth within the fluence range of the tested laser. Subsequently, investigations were carried out to analyze the mechanisms of nanosecond pulsed laser ablation. The calculated results showed that the maximum surface temperature remained at about 90% of the critical temperature (0.9Tc due to phase explosion. Moreover, the plume shielding has significant effects on the laser ablation, and the plume shielding proportion increase as the laser fluence increasing. The ambient pressure belows 100 Pa is more suitable for laser ablation, which can obtained larger ablation depth.

  8. The effect of benzyl alcohol on pulsed laser polymerization of styrene and methylmethacrylate

    NARCIS (Netherlands)

    O'Driscoll, K.F.; Monteiro, M.J.; Klumperman, B.

    1997-01-01

    The homo- and copolymerizations of styrene (STY) and methylmethacrylate (MMA) have been studied in the presence of several levels of benzyl alcohol (BA). From pulsed laser polymerizations it has been found that the apparent propagation rate constant increased with increasing BA for all systems. In

  9. Harmonic Dark Pulse Emission in Erbium-Doped Fiber Laser

    International Nuclear Information System (INIS)

    Zian, Cheak Tiu; Arman, Zarei; Sin, Jin Tan; Harith, Ahmad; Sulaiman, Wadi Harun

    2015-01-01

    A harmonic dark pulse generation in an erbium-doped fiber laser is demonstrated based on a figure-of-eight configuration. It is found that the harmonic dark pulse can be shifted from the fundamental to the 5"t"h order harmonic by increasing the pump power with an appropriate polarization controller orientation. The fundamental repetition rate of 20 kHz is obtained at the pump power of 29 mW. The highest pulse energy of 42.6 nJ is obtained at the fundamental repetition rate. The operating frequency of the dark pulse trains shifts to 2"n"d, 3"r"d, 4"t"h and 5"t"h harmonic as the pump powers are increased to 34 mW, 50 mW, 59 mW and 137 mW, respectively. (paper)

  10. Multiple quasi-monoenergetic electron beams from laser-wakefield acceleration with spatially structured laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y.; Li, M. H.; Li, Y. F.; Wang, J. G.; Tao, M. Z.; Han, Y. J.; Zhao, J. R.; Huang, K.; Yan, W. C.; Ma, J. L.; Li, Y. T. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080 (China); Chen, L. M., E-mail: lmchen@iphy.ac.cn [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080 (China); Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Li, D. Z. [Institute of High Energy Physics, CAS, Beijing 100049 (China); Chen, Z. Y. [Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621999 (China); Sheng, Z. M. [Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Zhang, J. [Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-08-15

    By adjusting the focus geometry of a spatially structured laser pulse, single, double, and treble quasi-monoenergetic electron beams were generated, respectively, in laser-wakefield acceleration. Single electron beam was produced as focusing the laser pulse to a single spot. While focusing the laser pulse to two spots that are approximately equal in energy and size and intense enough to form their own filaments, two electron beams were produced. Moreover, with a proper distance between those two focal spots, three electron beams emerged with a certain probability owing to the superposition of the diffractions of those two spots. The energy spectra of the multiple electron beams are quasi-monoenergetic, which are different from that of the large energy spread beams produced due to the longitudinal multiple-injection in the single bubble.

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

    Indian Academy of Sciences (India)

    2014-01-05

    Jan 5, 2014 ... In this article, a review of Yb-doped CW and pulsed fibre lasers along with our study on self-pulsing dynamics in CW fibre lasers to find its role in high-power fibre laser development and the physical ... Solid State Laser Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013, India ...

  12. High intensive short laser pulse interaction with submicron clusters media

    International Nuclear Information System (INIS)

    Faenov, A. Ya

    2008-01-01

    The interaction of short intense laser pulses with structured targets, such as clusters, exhibits unique features, stemming from the enhanced absorption of the incident laser light compared to solid targets. Due to the increased absorption, these targets are heated significantly, leading to enhanced emission of x rays in the keV range and generation of electrons and multiple charged ions with kinetic energies from tens of keV to tens of MeV. Possible applications of these targets can be an electron/ion source for a table top accelerator, a neutron source for a material damage study, or an x ray source for microscopy or lithography. The overview of recent results, obtained by the high intensive short laser pulse interaction with different submicron clusters media will be presented. High resolution K and L shell spectra of plasma generated by superintense laser irradiation of micron sized Ar, Kr and Xe clusters have been measured with intensity 10"17"-10"19"W/cm"2"and a pulse duration of 30-1000fs. It is found that hot electrons produced by high contrast laser pulses allow the isochoric heating of clusters and shift the ion balance toward the higher charge states, which enhances both the X ray line yield and the ion kinetic energy. Irradiation of clusters, produced from such gas mixture, by a fs Ti:Sa laser pulses allows to enhance the soft X ray radiation of Heβ(665.7eV)and Lyα(653.7eV)of Oxygen in 2-8 times compare with the case of using as targets pure CO"2"or N"2"O clusters and reach values 2.8x10"10"(∼3μJ)and 2.7x10"10"(∼2.9μJ)ph/(sr·pulse), respectively. Nanostructure conventional soft X ray images of 100nm thick Mo and Zr foils in a wide field of view (cm"2"scale)with high spatial resolution (700nm)are obtained using the LiF crystals as soft X ray imaging detectors. When the target used for the ion acceleration studies consists of solid density clusters embedded into the background gas, its irradiation by high intensity laser light makes the target

  13. Interaction of Rydberg atoms with two contrapropagating ultrashort laser pulses

    International Nuclear Information System (INIS)

    Lugovskoy, A. V.; Bray, I.

    2006-01-01

    In this paper we investigate how Rydberg atoms respond to perturbation by two contrapropagating ultrashort laser pulses. We consider the case where the durations of both pulses τ 1 and τ 2 are shorter than the inverse of the initial-state energy ε i -1 . When acting alone such a pulse passes through the atom without noticeable alteration in the atomic state. The situation is different if two such pulses interfere in the region of atom localization. In this case the atomic response is significantly enhanced. This is due to the nonzero momentum transferred to the electron by the interplay of the electric field of one pulse and the magnetic field of the other. The sudden perturbation approximation is used to evaluate the transition probabilities. They are shown to depend on the atom position with respect to the pulse interference region. This dependence is determined by the relationship between the atomic diameter d i and the interference-region size l=c(τ 1 +τ 2 ) (c is the speed of light). If d i i >>l the transition probabilities are sensitive to the electron density distribution along the propagation direction. The probabilities of the initial-state destruction and atom ionization drop as l/d i irrespective of the characteristics of the pulses

  14. Generation of short optical pulses for laser fusion. M.L. report No. 2451

    International Nuclear Information System (INIS)

    Kuizenga, D.J.

    1975-06-01

    This report considers some of the problems involved in generating the required short pulses for the laser-fusion program. Short pulses are required to produce the laser fusion, and pulses produced synchronously with this primary pulse are required for plasma diagnostics. The requirements of these pulses are first described. Several methods are considered in order to generate pulses at 1.064 μ to drive the Nd:Glass amplifiers to produce laser fusion. Conditions for optimum energy extraction per short pulse for Nd:YAG and Nd:Glass lasers are given. Four methods are then considered to produce these pulses: (1) using a fast switch to chop the required pulse out of a much longer Q-switched pulse; (2) active mode locking; (3) passive mode locking; and (4) a combination of active and passive mode locking. The use of cavity dumping is also considered to increase the energy per short pulse

  15. Design challenges for matrix assisted pulsed laser evaporation and infrared resonant laser evaporation equipment

    Science.gov (United States)

    Greer, James A.

    2011-11-01

    for several reasons. The first reason is that the polymer/solvent mix as well as the sample holder are both exposed to the humidity in the air which will coat the entire surface of the holder and target with water vapor. Some polymer and/or solvent materials may not react well with water vapor. Also, the layer of water vapor absorbed on the target surface may then absorb the incident laser radiation until it is removed from the surface. Thus, it may be unclear when the water vapor is fully removed from the polymer/solvent surface and the MAPLE deposition process actually occurs. This makes deposition of specific polymer thickness difficult to calculate. While it is well known that Quartz crystal microbalances do not work well for PLD of oxide materials it can be used for the deposition of MAPLE materials. However, with rastered laser beams the tooling factor becomes a dynamic number making interpretation of final thickness potentially difficult without careful pre-calibration. Another serious issue with the initial MAPLE process was related to the use of UV lasers such as an excimer operating at 193- or 248-nm or frequency tripled, Nd:YAG lasers at 355 nm. These lasers have high energy per photon (between about 6.4 to 3.5 eV) which can lead to a variety of deleterious photochemical mechanisms that can damage the polymer chains or organic structure. Such mechanisms can be direct photo-decomposition by photochemical bond breaking and photothermal effects. Alternative lasers, such as a Er:YAG laser operating at 2.9 microns produce photons with energy of ˜0.43 eV. Such longer wavelength lasers have been used for the IR-MAPLE process and may be very useful for future MAPLE systems. A third issue with the initial approach to MAPLE was that the process did not lend itself easily to growing multilayer films. Most standard pulsed laser deposition tools have "multi-target" carousels that allow for easy target changes and multilayer film growth. This is true for sputtering, MBE

  16. Morphological changes in skin tumors caused by pulsed laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Moskalik, K G; Lipova, V A; Neyshtadt, E L

    1979-01-01

    Morphological changes induced by treating melanomas, basaloma and flatcell skin cancers with a pulsed neodymium laser at 1060 nm, pulse length 1 msec and energy 250 to 500 J/cm/sup 2/, were studied using impressions and scrapings from the affected area. Nuclear pyknosis, nuclear and cellular elongation, vacuolization, frequent complete loss of cytoplasm, particulaly in the zone of direct irradiation, and loss of cellular structure were seen. These dystrophic changes increased with closeness to the zone of direct irradiation, culminating in necrosis. Formed and decomposed blood elements and melanin accumulated in the intracellular spaces, due to disruption of capillaries and small arteries and veins. Fewer and more aggregated melanoblasts were found after melanoma irradiation. Nuclear chromatin fusion, cytoplasmic changes and altered cell shape were observed. Basaloma cells were clustered and elongated after irradiation, with many fibrous structures and loss of cellular elements. Cytoplasmic vacuolization and lysis, bare nuclei, karyolysis, karyorrhexis and karyopyknosis were seen in corneous flat-cell cancer. In the few cases in which malignant cells were found under the scab from the first treatment the procedure was repeated. The morphological changes induced by pulsed laser irradiation are very similar to electrocoagulation necrosis, but are more localized. The ability of low and middle energy lasers to induce thrombosis and coagulation in vascular walls reduced the probability of hematogenic tumor cell dissemination. Cytological examination is highly effective in determining the degree of radical skin cancer healing due to laser treatment. 12 references, 2 figures.

  17. Generation of dual-wavelength, synchronized, tunable, high energy, femtosecond laser pulses with nearly perfect gaussian spatial profile

    Science.gov (United States)

    Wang, J.-K.; Siegal, Y.; Lü, C.; Mazur, E.

    1992-07-01

    We use self-phase modulation in a single-mode fiber to produce broadband femtosecond laser pulses. Subsequent amplification through two Bethune cells yields high-energy, tunable, pulses synchronized with the output of an amplified colliding-pulse-modelocked (CPM) laser. We routinely obtain tunable 200 μJ pulses of 42 fs (fwhm) duration with a nearly perfect gaussian spatial profile. Although self-phase modulation in a single-mode fiber is widely used in femtosecond laser systems, amplification of a fiber-generated supercontinuum in a Bethune cell amplifier is a new feature which maintains the high-quality spatial profile while providing high gain. This laser system is particularly well suited for high energy dual-wavelength pump=probe experiments and time-resolved four-wave mixing spectroscopy.

  18. Colorizing metals with femtosecond laser pulses

    International Nuclear Information System (INIS)

    Vorobyev, A. Y.; Guo Chunlei

    2008-01-01

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

  19. Phonon transport in a curved aluminum thin film due to laser short pulse irradiation

    Science.gov (United States)

    Mansoor, Saad Bin; Yilbas, Bekir Sami

    2018-05-01

    Laser short-pulse heating of a curved aluminum thin film is investigated. The Boltzmann transport equation is incorporated to formulate the heating situation. A Gaussian laser intensity distribution is considered along the film arc and time exponentially decaying of pulse intensity is incorporated in the analysis. The governing equations of energy transport in the electron and lattice sub-systems are coupled through the electron-phonon coupling parameter. To quantify the phonon intensity distribution in the thin film, equivalent equilibrium temperature is introduced, which is associated with the average energy of all phonons around a local point when the phonon energies are redistributed adiabatically to an equilibrium state. It is found the numerical simulations that electron temperature follows similar trend to the spatial distribution of the laser pulse intensity at the film edge. Temporal variation of electron temperature does not follow the laser pulse intensity distribution. The rise of temperature in the electron sub-system is fast while it remains slow in the lattice sub-system.

  20. Image digitizer system for bubble chamber laser

    International Nuclear Information System (INIS)

    Haggerty, H.

    1986-01-01

    An IBM PC-based image digitizer system has been assembled to monitor the laser flash used for holography at the 15 foot bubble chamber. The hardware and the operating software are outlined. For an operational test of the system, an array of LEDs was flashed with a 10 microsecond pulse and the image was grabbed by one of the operating programs and processed

  1. Injection of electrons by colliding laser pulses in a laser wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Hansson, M., E-mail: martin.hansson@fysik.lth.se; Aurand, B.; Ekerfelt, H.; Persson, A.; Lundh, O.

    2016-09-01

    To improve the stability and reproducibility of laser wakefield accelerators and to allow for future applications, controlling the injection of electrons is of great importance. This allows us to control the amount of charge in the beams of accelerated electrons and final energy of the electrons. Results are presented from a recent experiment on controlled injection using the scheme of colliding pulses and performed using the Lund multi-terawatt laser. Each laser pulse is split into two parts close to the interaction point. The main pulse is focused on a 2 mm diameter gas jet to drive a nonlinear plasma wave below threshold for self-trapping. The second pulse, containing only a fraction of the total laser energy, is focused to collide with the main pulse in the gas jet under an angle of 150°. Beams of accelerated electrons with low divergence and small energy spread are produced using this set-up. Control over the amount of accelerated charge is achieved by rotating the plane of polarization of the second pulse in relation to the main pulse. Furthermore, the peak energy of the electrons in the beams is controlled by moving the collision point along the optical axis of the main pulse, and thereby changing the acceleration length in the plasma. - Highlights: • Compact colliding pulse injection set-up used to produce low energy spread e-beams. • Beam charge controlled by rotating the polarization of injection pulse. • Peak energy controlled by point of collision to vary the acceleration length.

  2. Microencapsulation of silicon cavities using a pulsed excimer laser

    KAUST Repository

    Sedky, Sherif M.

    2012-06-07

    This work presents a novel low thermal-budget technique for sealing micromachined cavities in silicon. Cavities are sealed without deposition, similar to the silicon surface-migration sealing process. In contrast to the 1100°C furnace anneal required for the migration process, the proposed technique uses short excimer laser pulses (24ns), focused onto an area of 23mm 2, to locally heat the top few microns of the substrate, while the bulk substrate remains near ambient temperature. The treatment can be applied to selected regions of the substrate, without the need for special surface treatments or a controlled environment. This work investigates the effect of varying the laser pulse energy from 400 mJ cm 2to 800 mJ cm 2, the pulse rate from 1Hz to 50Hz and the pulse count from 200 to 3000 pulses on sealing microfabricated cavities in silicon. An analytical model for the effect of holes on the surface temperature distribution is derived, which shows that much higher temperatures can be achieved by increasing the hole density. A mechanism for sealing the cavities is proposed, which indicates how complete sealing is feasible. © 2012 IOP Publishing Ltd.

  3. Simulation of intense short-pulse laser-plasma interaction

    International Nuclear Information System (INIS)

    Yamagiwa, Mitsuru

    2000-01-01

    We have completed the massive parallelization of a 2-dimensional giga-particle code and have achieved a 530-fold acceleration rate with 512 processing elements (PE's). Using this we have implemented a simulation of the interaction of a solid thin film and a high intensity laser and have discovered a phenomenon in which high quality short pulses from the far ultraviolet to soft X-rays are generated at the back surface of the thin layer. We have also introduced the atomic process database code (Hullac) and have the possibility for high precision simulations of X-ray laser radiation. With respect to laser acceleration we have the possibility to quantitatively evaluate relativistic self-focusing assumed to occur in higher intensity fields. Ion acceleration from a solid target and an underdense plasma irradiated by an intense and an ultra intense laser, respectively, has also been studied by particle-in-cell (PIC) simulations. (author)

  4. Optical fiber link for transmission of 1-nJ femtosecond laser pulses at 1550 nm

    DEFF Research Database (Denmark)

    Eichhorn, Finn; Olsson, Rasmus Kjelsmark; Buron, Jonas Christian Due

    2010-01-01

    We report on numerical and experimental characterization of the performance of a fiber link optimized for the delivery of sub-100-fs laser pulses at 1550 nm over several meters of fiber. We investigate the power handling capacity of the link, and demonstrate all-fiber delivery of 1-nJ pulses over...... a distance of 5.3 m. The fiber link consists of dispersion-compensating fiber (DCF) and standard single-mode fiber. The optical pulses at different positions in the fiber link are measured using frequency-resolved optical gating (FROG). The results are compared with numerical simulations of the pulse...... propagation based on the generalized nonlinear Schrödinger equation. The high input power capacity of the fiber link allows the splitting and distribution of femtosecond pulses to an array of fibers with applications in multi-channel fiber-coupled terahertz time-domain spectroscopy and imaging systems. We...

  5. Interaction of few-cycle laser pulses in an isotropic nonlinear medium

    International Nuclear Information System (INIS)

    Oganesyan, D L; Vardanyan, A O

    2007-01-01

    The interaction of few-cycle laser pulses propagating in an isotropic nonlinear medium is studied theoretically. A system of nonlinear Maxwell's equations is integrated numerically with respect to time by the finite difference method. The interaction of mutually orthogonal linearly polarised 0.81-μm, 10-fs pulses is considered. Both the instant Kerr polarisation response and Raman inertial response of the medium in the nonlinear part of the medium are taken into account. The spectral shift of the probe pulse caused by the cross-action of the reference pulse is studied. The spectra of the interacting pulses are studied for different time delays between them and the shifts of these spectra are obtained as a function of the time delay. (nonlinear optical phenomena)

  6. Laser cutting of bone tissue under bulk water with a pulsed ps-laser at 532 nm.

    Science.gov (United States)

    Tulea, Cristian-Alexander; Caron, Jan; Gehlich, Nils; Lenenbach, Achim; Noll, Reinhard; Loosen, Peter

    2015-10-01

    Hard-tissue ablation was already investigated for a broad variety of pulsed laser systems, which cover almost the entire range of available wavelengths and pulse parameters. Most effective in hard-tissue ablation are Er:YAG and CO2 lasers, both utilizing the effect of absorption of infrared wavelengths by water and so-called explosive vaporization, when a thin water film or water–air spray is supplied. The typical flow rates and the water layer thicknesses are too low for surgical applications where bleeding occurs and wound flushing is necessary. We studied a 20 W ps-laser with 532 nm wavelength and a pulse energy of 1 mJ to effectively ablate bones that are submerged 14 mm under water. For these laser parameters, the plasma-mediated ablation mechanism is dominant. Simulations based on the blow-off model predict the cut depth and cross-sectional shape of the incision. The model is modified considering the cross section of the Gaussian beam, the incident angle, and reflections. The ablation rate amounts to 0.2  mm3/s, corresponding to an increase by at least 50% of the highest values published so far for ultrashort laser ablation of hard tissue.

  7. [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.

  8. Near and long term pulse power requirements for laser driven inertial confinement fusion

    International Nuclear Information System (INIS)

    Gagnon, W.L.

    1979-01-01

    At the Lawrence Livermore Laboraory, major emphasis has been placed upon the development of large, ND:glass laser systems in order to address the basic physics issues associated with light driven fusion targets. A parallel program is directed toward the development of lasers which exhibit higher efficiencies and shorter wavelengths and are thus more suitable as drivers for fusion power plants. This paper discusses the pulse power technology which has been developed to meet the near and far term needs of the laser fusion program at Livermore

  9. Femtosecond few-cycle mid-infrared laser pulses

    DEFF Research Database (Denmark)

    Liu, Xing

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

  10. 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...

  11. Nonlinear Theory of Nonparaxial Laser Pulse Propagation in Plasma Channels

    International Nuclear Information System (INIS)

    Esarey, E.; Schroeder, C. B.; Shadwick, B. A.; Wurtele, J. S.; Leemans, W. P.

    2000-01-01

    Nonparaxial propagation of ultrashort, high-power laser pulses in plasma channels is examined. In the adiabatic limit, pulse energy conservation, nonlinear group velocity, damped betatron oscillations, self-steepening, self-phase modulation, and shock formation are analyzed. In the nonadiabatic limit, the coupling of forward Raman scattering (FRS) and the self-modulation instability (SMI) is analyzed and growth rates are derived, including regimes of reduced growth. The SMI is found to dominate FRS in most regimes of interest. (c) 2000 The American Physical Society

  12. Powering laser diode systems

    CERN Document Server

    Trestman, Grigoriy A

    2017-01-01

    This Tutorial Text discusses the competent design and skilled use of laser diode drivers (LDDs) and power supplies (PSs) for the electrical components of laser diode systems. It is intended to help power-electronic design engineers during the initial design stages: the choice of the best PS topology, the calculation of parameters and components of the PS circuit, and the computer simulation of the circuit. Readers who use laser diode systems for research, production, and other purposes will also benefit. The book will help readers avoid errors when creating laser systems from ready-made blocks, as well as understand the nature of the "mystical failures" of laser diodes (and possibly prevent them).

  13. Effects of laser fluence on the structural properties of pulsed laser deposited ruthenium thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Wai-Keat; Wong, Hin-Yong; Chan, Kah-Yoong; Tou, Teck-Yong [Multimedia University, Centre for Advanced Devices and Systems (CADS), Faculty of Engineering, Cyberjaya, Selangor (Malaysia); Yong, Thian-Khok [Universiti Tunku Abdul Rahman, Faculty of Engineering and Science, Setapak, Kuala Lumpur (Malaysia); Yap, Seong-Shan [Norwegian University of Science and Technology, Institute of Physics, Trondheim (Norway)

    2010-08-15

    Ruthenium (Ru) has received great interest in recent years for applications in microelectronics. Pulsed laser deposition (PLD) enables the growth of Ru thin films at low temperatures. In this paper, we report for the first time the characterization of pulsed laser deposited Ru thin films. The deposition processes were carried out at room temperature in vacuum environment for different durations with a pulsed Nd:YAG laser of 355-nm laser wavelength, employing various laser fluences ranging from 2 J/cm{sup 2} to 8 J/cm{sup 2}. The effect of the laser fluence on the structural properties of the deposited Ru films was investigated using surface profilometry, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Ru droplets, some spherical in shape and some flattened into round discs were found on the deposited Ru. The droplets were correlated to ripple formations on the target during the laser-induced ejection from the target. In addition, crystalline Ru with orientations of (100), (101), and (002) was observed in the XRD spectra and their intensities were found to increase with increasing laser fluence and film thickness. Grain sizes ranging from 20 nm to 35 nm were deduced using the Scherrer formula. Optical emission spectroscopy (OES) and energy-dispersive X-ray spectroscopy (EDS) show that the composition of the plume and the deposited Ru film was of high purity. (orig.)

  14. Effects of laser fluence on the structural properties of pulsed laser deposited ruthenium thin films

    International Nuclear Information System (INIS)

    Lee, Wai-Keat; Wong, Hin-Yong; Chan, Kah-Yoong; Tou, Teck-Yong; Yong, Thian-Khok; Yap, Seong-Shan

    2010-01-01

    Ruthenium (Ru) has received great interest in recent years for applications in microelectronics. Pulsed laser deposition (PLD) enables the growth of Ru thin films at low temperatures. In this paper, we report for the first time the characterization of pulsed laser deposited Ru thin films. The deposition processes were carried out at room temperature in vacuum environment for different durations with a pulsed Nd:YAG laser of 355-nm laser wavelength, employing various laser fluences ranging from 2 J/cm 2 to 8 J/cm 2 . The effect of the laser fluence on the structural properties of the deposited Ru films was investigated using surface profilometry, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Ru droplets, some spherical in shape and some flattened into round discs were found on the deposited Ru. The droplets were correlated to ripple formations on the target during the laser-induced ejection from the target. In addition, crystalline Ru with orientations of (100), (101), and (002) was observed in the XRD spectra and their intensities were found to increase with increasing laser fluence and film thickness. Grain sizes ranging from 20 nm to 35 nm were deduced using the Scherrer formula. Optical emission spectroscopy (OES) and energy-dispersive X-ray spectroscopy (EDS) show that the composition of the plume and the deposited Ru film was of high purity. (orig.)

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

    Science.gov (United States)

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

    1987-12-01

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

  16. Numerical investigation of vessel heating using a copper vapor laser and a pulsed dye laser in treating vascular skin lesions

    Science.gov (United States)

    Pushkareva, A. E.; Ponomarev, I. V.; Isaev, A. A.; Klyuchareva, S. V.

    2018-02-01

    A computer simulation technique was employed to study the selective heating of a tissue vessel using emission from a pulsed copper vapor laser and a pulsed dye laser. The depth and size of vessels that could be selectively and safely removed were determined for the lasers under examination.

  17. Pulsed CH3OH terahertz laser radiation pumped by 9P(36) CO2 lasers

    International Nuclear Information System (INIS)

    Jiu Zhixian; Zuo Duluo; Miao Liang; Cheng Zuhai

    2011-01-01

    An efficient pulsed CH 3 OH terahertz (THz) laser pumped by a TEA CO 2 laser was investigated experimentally. A simple terahertz cavity and a TEA CO 2 laser for the optically pumped THz radiation were studied experimentally. To improve THz laser energy and photon conversion efficiency, two different TEA CO 2 lasers were developed to pump CH 3 OH. When CH 3 OH was pumped by the 9P(36) line with different powers of the CO 2 laser, the generation of terahertz radiation with energy as high as 0.307mJ and 23.75mJ were obtained, respectively. The corresponding photon conversion efficiencies were 0.29% and 2.4%. The photon conversion efficiency increases by a factor of about 8. Meanwhile, higher peak power of pump laser effectively improves the photon conversion efficiency. And the optimum THz laser pressure increases with narrower pulse width of pump laser because of increasing absorptive gases molecules of CH 3 OH with higher peak power of pump laser.

  18. A longitudinally-pumped laser (specifically, pulse-pumped lasers)

    Energy Technology Data Exchange (ETDEWEB)

    Wojtkowiak, J

    1979-10-15

    A laser is proposed that employs travelling-wave pumping, for which no less than four electrodes, interconnected with coaxial transmission lines with a feed network, are placed at specific distances from each other in a discharge channel filled with an active medium. An expression is given for determining the length of the coaxial sections.

  19. Realization of double-pulse laser irradiating scheme for laser ion sources

    International Nuclear Information System (INIS)

    Li Zhangmin; Jin Qianyu; Liu Wei; Zhang Junjie; Sha Shan; Zhao Huanyu; Sun Liangting; Zhang Xuezhen; Zhao Hongwei

    2015-01-01

    A double-pulse laser irradiating scheme has been designed and established for the production of highly charged ion beams at Institute of Modern Physics (IMP), Chinese Academy of Sciences. The laser beam output by a Nd : YAG laser is split and combined by a double of beam splitters, between which the split laser beams are transmitted along different optical paths to get certain time delay between each other. With the help of a quarter-wave plate before the first splitter, the energy ratio between the two laser pulses can be adjusted between 3 : 8 to 8 : 3. To testify its feasibility, a preliminary experiment was carried out with the new-developed double-pulse irradiating scheme to produce highly charged carbon ions. Comparing the results with those got from the previous single-pulse irradiating scheme, the differences in the time structure and Charge State Distribution (CSD) of the ion pulse were observed, but its mechanisms and optimization require further studies. (authors)

  20. Moderate high power 1 to 20μs and kHz Ho:YAG thin disk laser pulses for laser lithotripsy

    Science.gov (United States)

    Renz, Günther

    2015-02-01

    An acousto-optically or self-oscillation pulsed thin disk Ho:YAG laser system at 2.1 μm with an average power in the 10 W range will be presented for laser lithotripsy. In the case of cw operation the thin disk Ho:YAG is either pumped with InP diode stacks or with a thulium fiber laser which leads to a laser output power of 20 W at an optical-to-optical efficiency of 30%. For the gain switched mode of operation a modulated Tm-fiber laser is used to produce self-oscillation pulses. A favored pulse lengths for uric acid stone ablation is known to be at a few μs pulse duration which can be delivered by the thin disk laser technology. In the state of the art laser lithotripter, stone material is typically ablated with 250 to 750 μs pulses at 5 to 10 Hz and with pulse energies up to a few Joule. The ablation mechanism is performed in this case by vaporization into stone dust and fragmentation. With the thin disk laser technology, 1 to 20 μs-laser pulses with a repetition rate of a few kHz and with pulse energies in the mJ-range are available. The ablation mechanism is in this case due to a local heating of the stone material with a decomposition of the crystalline structure into calcium carbonate powder which can be handled by the human body. As a joint process to this thermal effect, imploding water vapor bubbles between the fiber end and the stone material produce sporadic shock waves which help clear out the stone dust and biological material.