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Sample records for picosecond uv pulses

  1. Picosecond, single pulse electron linear accelerator

    International Nuclear Information System (INIS)

    Kikuchi, Riichi; Kawanishi, Masaharu

    1979-01-01

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

  2. 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.

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

    Science.gov (United States)

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

    2017-08-01

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

  4. 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

  5. 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)

  6. Study of polysilane mainchain electronic structure by picosecond pulse radiolysis

    International Nuclear Information System (INIS)

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

    2000-01-01

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

  7. Development of picosecond pulsed electron beam monitor. 2

    International Nuclear Information System (INIS)

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

    1994-01-01

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

  8. A kilohertz picosecond x-ray pulse generation scheme

    International Nuclear Information System (INIS)

    Guo, W.; Borland, M.; Harkay, K. C.; Wang, C.-X.; Yang, B.

    2007-01-01

    The duration of the x-ray pulse generated at a synchrotron light source is typically tens of picoseconds. Shorter pulses are highly desired by the users. In electron storage rings, the vertical beam size is usually orders of magnitude less than the bunch length due to radiation damping; therefore, a shorter pulse can be obtained by slitting the vertically tilted bunch. Zholents proposed tilting the bunch using rf deflection. We found that tilted bunches can also be generated by a dipole magnet kick. A vertical tilt is developed after the kick in the presence of nonzero chromaticity. The tilt was successfully observed and a 4.2-ps pulse was obtained from a 27-ps electron bunch at the Advanced Photon Source. Based on this principle we propose a short-pulse generation scheme that produces picosecond x-ray pulses at a repetition rate of 1 utilde2 kHz, which can be used for pump-probe experiments

  9. 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

  10. High power industrial picosecond laser from IR to UV

    Science.gov (United States)

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

    2013-02-01

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

  11. Development of picosecond pulsed electron beam monitor

    International Nuclear Information System (INIS)

    Hosono, Y.; Nakazawa, M.; Ueda, T.; Kobayasi, T.; Yosida, Y.; Ohkuma, J.; Okuda, S.; Suemine, S.

    1993-01-01

    For the picosecond pulsed electron beam of a linear accelerator a simple monitor using an electric connector has been developed which is constructed with SMA, BNC, N type electric connector through pipe (inner diameter = 50 mm or 100 mm). Under the measurement conditions of peak current (26A-900A) and narrow pulse width (Pw = 10 ps(FWHM), Pw = 30 ps(FWHM)), the following characteristics of this monitor were obtained, (A) rise time is less than 25 ps (B) the amplitude of the monitor output pulse is proportional directly to the area of cross section of the electrode. (author)

  12. Picosecond and subpicosecond pulsed laser deposition of Pb thin films

    Directory of Open Access Journals (Sweden)

    F. Gontad

    2013-09-01

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

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

    International Nuclear Information System (INIS)

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

    1993-01-01

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

  14. Generation of picosecond pulsed coherent state superpositions

    DEFF Research Database (Denmark)

    Dong, Ruifang; Tipsmark, Anders; Laghaout, Amine

    2014-01-01

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

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

    Science.gov (United States)

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

    2018-01-01

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

  16. High current photoemission with 10 picosecond uv pulses

    International Nuclear Information System (INIS)

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

    1990-06-01

    The quantum efficiency and the optical damage threshold of various metals were explored with 10 ps, 266 nm, UV laser pulses. Efficiencies for Cu, Y, and Sm were: 1.4, 5, and 7 x 10 -4 , with damage thresholds about 100, 10, and 30 mJ/cm 2 . This would permit over 1 μC/cm 2 or current densities exceeding 100 kA/cm 2 . High charge and current densities of up to 66 kA/cm 2 were obtained on 0.25 mm diam cathodes, and 21 kA/cm 2 on a 3 mm diam yttrium cathode. The maximum currents were limited by space charge and the dc field. The experiments with small area illumination indicate that the emitted electrons spread transversely due to Coulomb repulsion and their initial transverse velocity. This increases the effective area above the cathode, reduces the space charge effect and increases emission density on the cathode. The quantum efficiency can be increased substantially by enhancing the field on the surface by either a suitable electrode geometry or microstructures on it. 14 refs., 12 figs., 3 tabs

  17. Generating picosecond x-ray pulses in synchrotron light sources using dipole kickers

    Directory of Open Access Journals (Sweden)

    W. Guo

    2007-02-01

    Full Text Available The duration of the x-ray pulse generated at a synchrotron light source is typically tens of picoseconds. Shorter pulses are highly desired by the users. In electron storage rings, the vertical beam size is usually orders of magnitude less than the bunch length due to radiation damping; therefore, a shorter pulse can be obtained by slitting the vertically tilted bunch. Zholents proposed tilting the bunch using rf deflection. We found that tilted bunches can also be generated by a dipole magnet kick. A vertical tilt is developed after the kick in the presence of nonzero chromaticity. The tilt was successfully observed and a 4.2-ps pulse was obtained from a 27-ps electron bunch at the Advanced Photon Source. Based on this principle, we propose a short-pulse generation scheme that produces picosecond x-ray pulses at a repetition rate of 1–2 kHz, which can be used for pump-probe experiments.

  18. Measurements of picosecond pulses of a high-current electron accelerator

    International Nuclear Information System (INIS)

    Zheltov, K.A.; Petrenko, A.N.; Turundaevskaya, I.G.; Shalimanov, V.F.

    1997-01-01

    The duration of a picosecond high-current accelerator electron beam pulse duration is measured and its shape is determined using a measuring line, comprising a Faraday cup, a radiofrequency cable of minor length and a wide-band SRG-7 oscillograph. The procedure of data reconstruction according to regularization method is applied to determine the actual shape of the pulse measured

  19. Picosecond chirped pulse compression in single-mode fibers

    International Nuclear Information System (INIS)

    Wenhua Cao; Youwei Zhang

    1995-01-01

    In this paper, the nonlinear propagation of picosecond chirped pulses in single mode fibers has been investigated both analytically and numerically. Results show that downchirped pulses can be compressed owing to normal group-velocity dispersion. The compression ratio depends both on the initial peak power and on the initial frequency chirp of the input pulse. While the compression ratio depends both on the initial peak power and on the initial frequency chirp of the input pulse. While the compression ratio increases with the negative frequency chirp, it decreases with the initial peak power of the input pulse. This means that the self-phase modulation induced nonlinear frequency chirp which is linear and positive (up-chirp) over a large central region of the pulse and tends to cancel the initial negative chirp of the pulse. It is also shown that, as the negative chirped pulse compresses temporally, it synchronously experiences a spectral narrowing

  20. Improvements in picosecond chronography

    International Nuclear Information System (INIS)

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

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

  1. Growth and apoptosis of HeLa cells induced by intense picosecond pulsed electric field

    Directory of Open Access Journals (Sweden)

    Yuan-yuan HUA

    2011-07-01

    Full Text Available Objective To investigate the growth and apoptosis of HeLa cells induced by intense picosecond pulsed electric field(PEF in vitro.Methods HeLa cells cultured in vitro were divided into experimental group and control group(with or without intense picosecond PEF.With constant pulse width,frequency and voltage,the cells in experimental group were divided into 6 sub-groups according to the number of pulse(100,200,500,1000,1500,2000,the growth inhibition of HeLa cells by PEF and the dose-effect relationship were analyzed by MTT.Caspase 3 protein activity was detected in the cells in 500,1000 and 2000 sub-groups.Mitochondrial transmembrane potential was detected by rhodamine 123 staining with the cells in 2000 sub-groups.Results MTT assay demonstrated that intense picosecond PEF significantly inhibited the proliferation of HeLa cells in dose-dependent manner.The survival rates of cells declined along with the increase in pulse number,and were 96.23%±0.76%,94.11%±2.42%,90.31%±1.77%,64.59%±1.59%,32.95%±0.73%,23.85%±2.38% and 100%,respectively,in 100,200,500,1000,1500,2000 sub-groups and control group(P < 0.01.The Caspase 3 protein activity was significantly enhanced by intense picosecond PEF,and the absorbancy indexes(A were 0.174±0.012,0.232±0.017,0.365±0.016 and 0.122±0.011,respectively,in 500,1000,2000 sub-groups and control group(P < 0.05.The mitochondrial transmembrane potential of HeLa cells was significantly inhibited by intense picosecond PEF,and the fluorescence intensity in 2000 sub-group(76.66±13.38 was much lower than that in control group(155.81±2.33,P < 0.05.Conclusion Intense picosecond PEF may significantly inhibit the growth of HeLa cells,and induce cell apoptosis via mitochondrial pathway.

  2. 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

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

    International Nuclear Information System (INIS)

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

    1996-01-01

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

  4. Studies on laser material processing with nanosecond and sub-nanosecond and picosecond and sub-picosecond pulses

    Science.gov (United States)

    Zhang, Jie; Tao, Sha; Wang, Brian; Zhao, Jay

    2016-03-01

    In this paper, laser ablation of widely used metal (Al, Cu. stainless-steel), semiconductor (Si), transparent material (glass, sapphire), ceramic (Al2O3, AlN) and polymer (PI, PMMA) in industry were systematically studied with pulse width from nanosecond (5-100ns), picosecond (6-10ps) to sub-picosecond (0.8-0.95ps). A critical damage zone (CDZ) of up to 100um with ns laser, efficiency were also investigated. This is to explore how to provide industry users the best laser solution for device micro-fabrication with best price. Our studies of cutting and drilling with ns, ps, and sub-ps lasers indicate that it is feasible to achieve user accepted quality and speed with cost-effective and reliable laser by optimizing processing conditions.

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

    Science.gov (United States)

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

    2017-11-01

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

  6. Structure of picosecond pulses of a Q-switched and mode-locked diode-pumped Nd:YAG laser

    Energy Technology Data Exchange (ETDEWEB)

    Donin, V I; Yakovin, D V; Gribanov, A V [Institute of Automation and Electrometry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2015-12-31

    The pulse duration of a diode-pumped Nd:YAG laser, in which Q-switching with mode-locking (QML regime) is achieved using a spherical mirror and a travelling-wave acousto-optic modulator, is directly measured with a streak camera. It is found that the picosecond pulses can have a non-single-pulse structure, which is explained by excitation of several competing transverse modes in the Q-switching regime with a pulse repetition rate of 1 kHz. In the case of cw mode-locking (without Q-switching), a new (auto-QML) regime is observed, in which the pulse train repetition rate is determined by the frequency of the relaxation oscillations of the laser field while the train contains single picosecond pulses. (control of laser radiation parameters)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-02-15

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

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

    OpenAIRE

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

    2004-01-01

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

  9. A five-picosecond electron pulse from ANL (Argonne National Laboratory) L-Band Linac

    International Nuclear Information System (INIS)

    Cox, G.L.; Jonah, C.D.; Ficht, D.T.; Mavrogenes, G.S.; Sauer, M.C. Jr.

    1989-01-01

    The pulse-compression system of the Argonne National Laboratory Chemistry Division L-Band Linac, presented at the 1986 Linear Accelerator Conference at Stanford, California, has been completed. A five-picosecond-wide electron pulse containing 6 x 10 -9 coulomb charge has been achieved. Acceleration parameters and the pulse-width measurement technique are discussed, and future plans for the utilization of this pulse in radiation chemistry studies are presented. 5 refs., 4 figs

  10. Optimally shaped narrowband picosecond pulses for femtosecond stimulated Raman spectroscopy.

    Science.gov (United States)

    Hoffman, David P; Valley, David; Ellis, Scott R; Creelman, Mark; Mathies, Richard A

    2013-09-09

    A comparison between a Fabry-Pérot etalon filter and a conventional grating filter for producing the picosecond (ps) Raman pump pulses for femtosecond stimulated Raman spectroscopy (FSRS) is presented. It is shown that for pulses of equal energy the etalon filter produces Raman signals twice as large as that of the grating filter while suppressing the electronically resonant background signal. The time asymmetric profile of the etalon-generated pulse is shown to be responsible for both of these observations. A theoretical discussion is presented which quantitatively supports this hypothesis. It is concluded that etalons are the ideal method for the generation of narrowband ps pulses for FSRS because of the optical simplicity, efficiency, improved FSRS intensity and reduced backgrounds.

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

    International Nuclear Information System (INIS)

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

    1987-03-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-08-20

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

  13. Photonic-band-gap gyrotron amplifier with picosecond pulses

    Science.gov (United States)

    Nanni, Emilio A.; Jawla, Sudheer; Lewis, Samantha M.; Shapiro, Michael A.; Temkin, Richard J.

    2017-12-01

    We report the amplification of 250 GHz pulses as short as 260 ps without observation of pulse broadening using a photonic-band-gap circuit gyrotron traveling-wave-amplifier. The gyrotron amplifier operates with a device gain of 38 dB and an instantaneous bandwidth of 8 GHz. The operational bandwidth of the amplifier can be tuned over 16 GHz by adjusting the operating voltage of the electron beam and the magnetic field. The amplifier uses a 30 cm long photonic-band-gap interaction circuit to confine the desired TE03-like operating mode while suppressing lower order modes which can result in undesired oscillations. The circuit gain is >55 dB for a beam voltage of 23 kV and a current of 700 mA. These results demonstrate the wide bandwidths and a high gain achievable with gyrotron amplifiers. The amplification of picosecond pulses of variable lengths, 260-800 ps, shows good agreement with the theory using the coupled dispersion relation and the gain-spectrum of the amplifier as measured with quasi-CW input pulses.

  14. Shaping of picosecond pulses for pumping optical parametric amplification

    International Nuclear Information System (INIS)

    Fueloep, J.A.; Krausz, F.; Major, Zs.; Horvath, B.

    2006-01-01

    Complete test of publication follows. The use of temporally shaped pump pulses for optical parametric amplification (OPA) is expected to facilitate an increase of efficiency and suppression of possible spectral distortions in this process, since the gain sensitively depends on the pump intensity. Our simulations confirmed such beneficial effect of temporally shaped pump pulses on the OPA process. With the aim to realize an optimized OPA stage pumped by shaped pulses, a novel method for passively shaping narrow band picosecond pulses has been developed. The method is based on the pulse-stacking principle, where replicas of the incoming pulse are created in a specially designed four-beam interferometer. The replicas are recombined with appropriate delays. The interferometer design allows for a unique flexibility in varying the pulse shape, since all relevant degrees of freedom, such as relative intensities and delays between the pulse replicas are independently adjustable. According to our calculations a pulse with a flat-top time profile would provide optimal conditions in the OPA process. Usually the pump pulse needs to be amplified in a conventional laser amplifier prior to the OPA. Our cross-correlation measurements showed that we are able to obtain shaped amplified pulses by shaping the amplifier input. Furthermore, by precompensating the distortions introduced by the amplifier we demonstrated our capability to produce amplified pulses with a flat-top time profile.

  15. Applications of picosecond lasers and pulse-bursts in precision manufacturing

    Science.gov (United States)

    Knappe, Ralf

    2012-03-01

    Just as CW and quasi-CW lasers have revolutionized the materials processing world, picosecond lasers are poised to change the world of micromachining, where lasers outperform mechanical tools due to their flexibility, reliability, reproducibility, ease of programming, and lack of mechanical force or contamination to the part. Picosecond lasers are established as powerful tools for micromachining. Industrial processes like micro drilling, surface structuring and thin film ablation benefit from a process, which provides highest precision and minimal thermal impact for all materials. Applications such as microelectronics, semiconductor, and photovoltaic industries use picosecond lasers for maximum quality, flexibility, and cost efficiency. The range of parts, manufactured with ps lasers spans from microscopic diamond tools over large printing cylinders with square feet of structured surface. Cutting glass for display and PV is a large application, as well. With a smart distribution of energy into groups of ps-pulses at ns-scale separation (known as burst mode) ablation rates can be increased by one order of magnitude or more for some materials, also providing a better surface quality under certain conditions. The paper reports on the latest results of the laser technology, scaling of ablation rates, and various applications in ps-laser micromachining.

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

    Science.gov (United States)

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

    2018-02-01

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

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

    International Nuclear Information System (INIS)

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

    2005-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1981-01-01

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

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

    International Nuclear Information System (INIS)

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

    1997-01-01

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

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

    International Nuclear Information System (INIS)

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

    2004-01-01

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

  1. UV spectroscopy. Ch. 16

    International Nuclear Information System (INIS)

    Stevens, Eugene S.

    1991-01-01

    The use of synchrotron radiation (SR) in the ultraviolet (UV) region by biophysics and biophysical chemists continues to increase as access improves and as awareness of its unique combination of properties grows. SR is continuously tunable, intense (even in the UV region), and pulsed. Pulse characteristics are comparable to those of picosecond lasers, but have the advantage of being independent of wavelength. Drawbacks are the continuous, but slow, decay of intensity arising from loss of particles in the ring, and the intrinsic limitation in pulse repetition rate. The particular combination of features that makes SR a superior light source depends upon the application. Spectroscopic techniques based on absorption and some techniques based on emission exploit its intensity and continuous tunability; time resolved techniques make use of its pulse characteristics. This chapter is a status report on two of the major biological applications of UV SR, circular dichroism and time-resolved fluorescence, covering mainly the published literature of the last five years. For the present purpose, the term UV is understood to include the vacuum ultraviolet region to 100 nm. (author). 83 refs.; 4 figs.; 6 tabs

  2. Distributed-feedback dye laser for picosecond ultraviolet and visible spectroscopy

    International Nuclear Information System (INIS)

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

    2000-01-01

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

  3. Luminescence from ZnSe excited by picosecond mid-infrared FEL pulses

    International Nuclear Information System (INIS)

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

    1998-01-01

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

  4. Second-harmonic generation in atomic vapor with picosecond laser pulses

    International Nuclear Information System (INIS)

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

    1997-01-01

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

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

    International Nuclear Information System (INIS)

    Kwok, H.S.

    1986-01-01

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

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

    International Nuclear Information System (INIS)

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

    1995-01-01

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

  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. Self-synchronization of the modulation of energy-levels population with electrons in GaAs induced by picosecond pulses of probe radiation and intrinsic stimulated emission

    Energy Technology Data Exchange (ETDEWEB)

    Ageeva, N. N.; Bronevoi, I. L., E-mail: bil@cplire.ru; Zabegaev, D. N.; Krivonosov, A. N. [Russian Academy of Sciences, Kotel’nikov Institute of Radioengineering and Electronics (Russian Federation)

    2016-10-15

    Picosecond optical pumping leads to the initiation of intrinsic picosecond stimulated emission in GaAs. As was established previously, due to the interaction of pulses of probe radiation with those of intrinsic emission, the dependence of the absorption α of the probe pulse on its delay τ with respect to the pump pulse is modulated with oscillations. It is found that the oscillatory dependences α(τ) have a similar shape only in the case of certain combinations of energies of the interacting pulses. As a result, it is assumed that the above interaction is, in fact, a synchronization of modulations (formed by pulses) of charge-carrier populations at energy levels; this synchronization occurs in the direction of the reconstruction of detailed equilibrium. The real-time picosecond self-modulation of the absorption α is measured for the first time. The characteristics of this self-modulation as well as absorption α and intrinsic emission self-modulation characteristics measured previously by correlation methods are now accounted for by the concept of synchronization.

  9. [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.

  10. Picosecond spectroscopy: The first 20 years

    International Nuclear Information System (INIS)

    Rentzepis, P.M.

    1987-01-01

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

  11. Si nanostructures grown by picosecond high repetition rate pulsed laser deposition

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  12. Si nanostructures grown by picosecond high repetition rate pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-08-01

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

  13. 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.

  14. Picosecond pulse radiolysis study of primary reactions in solutions

    International Nuclear Information System (INIS)

    El-Omar, Abdel Karim

    2013-01-01

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

  15. Picosecond camera

    International Nuclear Information System (INIS)

    Decroisette, Michel

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

  16. The picosecond laser for tattoo removal.

    Science.gov (United States)

    Hsu, Vincent M; Aldahan, Adam S; Mlacker, Stephanie; Shah, Vidhi V; Nouri, Keyvan

    2016-11-01

    The prevalence of tattoos continues to grow as modern society's stigma towards this form of body art shifts towards greater acceptance. Approximately one third of Americans aged 18-25 and 40 % of Americans aged 26-40 are tattooed. As tattoos continue to rise in popularity, so has the demand for an effective method of tattoo removal such as lasers. The various colors of tattoo inks render them ideal targets for specific lasers using the principle of selective photothermolysis. Traditional laser modalities employed for tattoo removal operate on pulse durations in the nanosecond domain. However, this pulse duration range is still too long to effectively break ink into small enough particles. Picosecond (10 -12 ) lasers have emerged at the forefront of laser tattoo removal due to their shorter pulse lengths, leading to quicker heating of the target chromophores, and consequently, more effective tattoo clearance. Recent studies have cited more effective treatment outcomes using picosecond lasers. Future comparative studies between picosecond lasers of various settings are necessary to determine optimal laser parameters for tattoo clearance.

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

    Science.gov (United States)

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

    2018-04-01

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

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

    International Nuclear Information System (INIS)

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

    2007-01-01

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

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

    DEFF Research Database (Denmark)

    Keiding, Søren Rud

    2006-01-01

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

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  1. Electric field measurements in a nanosecond pulse discharge by picosecond CARS/4-wave mixing

    Science.gov (United States)

    Goldberg, Ben; Shkurenkov, Ivan; Adamovich, Igor; Lempert, Walter

    2014-10-01

    Time-resolved electric field measurements in hydrogen by picosecond CARS/4-wave mixing are presented. Measurements are carried out in a high voltage nanosecond pulse discharge in hydrogen in plane-to-plane geometry, at pressures of up to several hundred Torr, and with a time resolution of 0.2 ns. Absolute calibration of the diagnostics is done using a sub-breakdown high voltage pulse of 12 kV/cm. A diffuse discharge is obtained by applying a peak high voltage pulse of 40 kV/cm between the electrodes. It is found that breakdown occurs at a lower field, 15--20 kV/cm, after which the field in the plasma is reduced rapidly due to plasma self shielding The experimental results are compared with kinetic modeling calculations, showing good agreement between the measured and the predicted electric field.

  2. Optoelectronic Picosecond Detection of Synchrotron X-rays

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-08-04

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

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  4. Pulse Distortion in Saturated Fiber Optical Parametric Chirped Pulse Amplification

    DEFF Research Database (Denmark)

    Lali-Dastjerdi, Zohreh; Da Ros, Francesco; Rottwitt, Karsten

    2012-01-01

    Fiber optical parametric chirped pulse amplification is experimentally compared for different chirped pulses in the picosecond regime. The amplified chirped pulses show distortion appearing as pedestals after recompression when the amplifier is operated in saturation.......Fiber optical parametric chirped pulse amplification is experimentally compared for different chirped pulses in the picosecond regime. The amplified chirped pulses show distortion appearing as pedestals after recompression when the amplifier is operated in saturation....

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

    International Nuclear Information System (INIS)

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

    1977-01-01

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

  6. Atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale

    Science.gov (United States)

    Pabst, Stefan

    2013-04-01

    Time-resolved investigations of ultrafast electronic and molecular dynamics were not possible until recently. The typical time scale of these processes is in the picosecond to attosecond realm. The tremendous technological progress in recent years made it possible to generate ultrashort pulses, which can be used to trigger, to watch, and to control atomic and molecular motion. This tutorial focuses on experimental and theoretical advances which are used to study the dynamics of electrons and molecules in the presence of ultrashort pulses. In the first part, the rotational dynamics of molecules, which happens on picosecond and femtosecond time scales, is reviewed. Well-aligned molecules are particularly suitable for angle-dependent investigations like x-ray diffraction or strong-field ionization experiments. In the second part, the ionization dynamics of atoms is studied. The characteristic time scale lies, here, in the attosecond to few-femtosecond regime. Although a one-particle picture has been successfully applied to many processes, many-body effects do constantly occur. After a broad overview of the main mechanisms and the most common tools in attosecond physics, examples of many-body dynamics in the attosecond world (e.g., in high-harmonic generation and attosecond transient absorption spectroscopy) are discussed.

  7. New and Advanced Picosecond Lasers for Tattoo Removal.

    Science.gov (United States)

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

    2017-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-05-15

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

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

    International Nuclear Information System (INIS)

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

    1995-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-05-01

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

  11. Picosecond optical shutter for particle detection

    International Nuclear Information System (INIS)

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

    1975-04-01

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

  12. 0.4 mJ quasi-continuously pumped picosecond Nd:GdVO4 laser with selectable pulse duration

    International Nuclear Information System (INIS)

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

    2010-01-01

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

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

    International Nuclear Information System (INIS)

    Mostafavi, M.

    2006-01-01

    Here, we report several studies done recently at ELYSE laboratory on the solvation dynamics of electron and on the kinetics of solvated electron in the spur reactions, performed by femtosecond laser spectroscopy and picosecond pulse radiolysis, respectively. Solvated electrons have been produced in polyol (1,2-Etanediol, 1,2-Propanediol and 1,3-Propanediol) by two-photon ionization of the solvent with 263 nm femtosecond laser pulses at room temperature. The two-photon absorption coefficient of these solvents at 263 nm has been determined. The dynamics of electron solvation in polyols has been studied by pump-probe transient absorption spectroscopy. So, time resolved absorption spectra ranging from 430 to 720 nm have been measured (Figure 1). A blue shift of the spectra is observed for the first tens of picoseconds. Using Bayesian data analysis method, the observed solvation dynamics are reconstructed with different models: stepwise mechanisms, continuous relaxation models or combinations of stepwise and continuous relaxation. That analysis clearly indicates that it is not obvious to select a unique model to describe the solvation dynamics of electron in diols. We showed that several models are able to reproduce correctly the data: a two-step model, a heterogeneous or bi-exponential continuous relaxation model and even a hybrid model with a stepwise transition and homogeneous continuous relaxation. Nevertheless, the best fits are given by the continuous spectral relaxation models. The fact that the time-evolution of the absorption spectrum of the solvated electron in diols can be accurately described by the temperature dependent absorption spectrum of the ground state solvated electron suggests that the spectral blue shift is mostly caused by the continuous relaxation of the electron trapped in a large distribution of solvent cages. Similar trends on electron solvation dynamics are observed in the cases of 1,2-ethanediol, 1,3-propanediol and 1,2 propanediol

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

    Science.gov (United States)

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

    2017-08-01

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

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

    International Nuclear Information System (INIS)

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

    1988-12-01

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

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  17. Dynamic Characterization of Fiber Optical Chirped Pulse Amplification for Sub-ps Pulses

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Rishøj, Lars Søgaard

    2013-01-01

    We investigate experimentally the propagation of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers, showing a significant broadening of the pulses from 450 fs up to 720 fs due to dispersion and self-phase modulation.......We investigate experimentally the propagation of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers, showing a significant broadening of the pulses from 450 fs up to 720 fs due to dispersion and self-phase modulation....

  18. Comparison of UV-C and Pulsed UV Light Treatments for Reduction of Salmonella, Listeria monocytogenes, and Enterohemorrhagic Escherichia coli on Eggs.

    Science.gov (United States)

    Holck, Askild L; Liland, Kristian H; Drømtorp, Signe M; Carlehög, Mats; McLEOD, Anette

    2018-01-01

    Ten percent of all strong-evidence foodborne outbreaks in the European Union are caused by Salmonella related to eggs and egg products. UV light may be used to decontaminate egg surfaces and reduce the risk of human salmonellosis infections. The efficiency of continuous UV-C (254 nm) and pulsed UV light for reducing the viability of Salmonella Enteritidis, Listeria monocytogenes, and enterohemorrhagic Escherichia coli on eggs was thoroughly compared. Bacterial cells were exposed to UV-C light at fluences from 0.05 to 3.0 J/cm 2 (10 mW/cm 2 , for 5 to 300 s) and pulsed UV light at fluences from 1.25 to 18.0 J/cm 2 , resulting in reductions ranging from 1.6 to 3.8 log, depending on conditions used. Using UV-C light, it was possible to achieve higher reductions at lower fluences compared with pulsed UV light. When Salmonella was stacked on a small area or shielded in feces, the pulsed UV light seemed to have a higher penetration capacity and gave higher bacterial reductions. Microscopy imaging and attempts to contaminate the interior of the eggs with Salmonella through the eggshell demonstrated that the integrity of the eggshell was maintained after UV light treatments. Only minor sensory changes were reported by panelists when the highest UV doses were used. UV-C and pulsed UV light treatments appear to be useful decontamination technologies that can be implemented in continuous processing.

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  20. Picosecond streak camera diagnostics of CO2 laser-produced plasmas

    International Nuclear Information System (INIS)

    Jaanimagi, P.A.; Marjoribanks, R.S.; Sancton, R.W.; Enright, G.D.; Richardson, M.C.

    1979-01-01

    The interaction of intense laser radiation with solid targets is currently of considerable interest in laser fusion studies. Its understanding requires temporal knowledge of both laser and plasma parameters on a picosecond time scale. In this paper we describe the progress we have recently made in analysing, with picosecond time resolution, various features of intense nanosecond CO 2 laser pulse interaction experiments. An infrared upconversion scheme, having linear response and <20 ps temporal resolution, has been utilized to characterise the 10 μm laser pulse. Various features of the interaction have been studied with the aid of picosecond IR and x-ray streak cameras. These include the temporal and spatial characteristics of high harmonic emission from the plasma, and the temporal development of the x-ray continuum spectrum. (author)

  1. ELYSE, a new picosecond electron accelerator at Orsay

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  2. Carcinogenesis related to intense pulsed light and UV exposure

    DEFF Research Database (Denmark)

    Hedelund, L; Lerche, C; Wulf, H C

    2006-01-01

    This study examines whether intense pulsed light (IPL) treatment has a carcinogenic potential itself or may influence ultraviolet (UV)-induced carcinogenesis. Secondly, it evaluates whether UV exposure may influence IPL-induced side effects. Hairless, lightly pigmented mice (n=144) received three...

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

    International Nuclear Information System (INIS)

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

    1998-02-01

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

  4. Simulation of excitation and propagation of pico-second ultrasound

    International Nuclear Information System (INIS)

    Yang, Seung Yong; Kim, No Hyu

    2016-01-01

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

  5. Simulation of excitation and propagation of pico-second ultrasound

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-12-15

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

  6. Simulation of excitation and propagation of pico-second ultrasound

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-12-15

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

  7. 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

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

    International Nuclear Information System (INIS)

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

    1996-01-01

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

  9. Picosecond x-ray streak camera studies

    International Nuclear Information System (INIS)

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

    1975-01-01

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

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

    Science.gov (United States)

    Hu, Jun; Zhu, Dezhi

    2018-06-01

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

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

    Science.gov (United States)

    Hu, Jun; Zhu, Dezhi

    2017-08-01

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

  12. 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

  13. 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).

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

    CERN Document Server

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

    2003-01-01

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

  15. Picosecond imaging of inertial confinement fusion plasmas using electron pulse-dilation

    Science.gov (United States)

    Hilsabeck, T. J.; Nagel, S. R.; Hares, J. D.; Kilkenny, J. D.; Bell, P. M.; Bradley, D. K.; Dymoke-Bradshaw, A. K. L.; Piston, K.; Chung, T. M.

    2017-02-01

    Laser driven inertial confinement fusion (ICF) plasmas typically have burn durations on the order of 100 ps. Time resolved imaging of the x-ray self emission during the hot spot formation is an important diagnostic tool which gives information on implosion symmetry, transient features and stagnation time. Traditional x-ray gated imagers for ICF use microchannel plate detectors to obtain gate widths of 40-100 ps. The development of electron pulse-dilation imaging has enabled a 10X improvement in temporal resolution over legacy instruments. In this technique, the incoming x-ray image is converted to electrons at a photocathode. The electrons are accelerated with a time-varying potential that leads to temporal expansion as the electron signal transits the tube. This expanded signal is recorded with a gated detector and the effective temporal resolution of the composite system can be as low as several picoseconds. An instrument based on this principle, known as the Dilation X-ray Imager (DIXI) has been constructed and fielded at the National Ignition Facility. Design features and experimental results from DIXI will be presented.

  16. Development and performance test of picosecond pulse x-ray excited streak camera system for scintillator characterization

    International Nuclear Information System (INIS)

    Yanagida, Takayuki; Fujimoto, Yutaka; Yoshikawa, Akira

    2010-01-01

    To observe time and wavelength-resolved scintillation events, picosecond pulse X-ray excited streak camera system is developed. The wavelength range spreads from vacuum ultraviolet (VUV) to near infrared region (110-900 nm) and the instrumental response function is around 80 ps. This work describes the principle of the newly developed instrument and the first performance test using BaF 2 single crystal scintillator. Core valence luminescence of BaF 2 peaking around 190 and 220 nm is clearly detected by our system, and the decay time turned out to be of 0.7 ns. These results are consistent with literature and confirm that our system properly works. (author)

  17. Laser diagnostics for picosecond e-beams

    International Nuclear Information System (INIS)

    Pogorelsky, I.; Ben-Zvi, I.

    1992-01-01

    We propose a novel approach to picosecond e-bunch/laser pulse synchronization and spatial alignment based upon refraction and reflection of a laser beam on a plasma column created by relativistic electrons traveling through a gas or solid optical material. The technique may be used in laser accelerators and for general subpicosecond e-beam diagnostics

  18. INACTIVATION OF PATHOGENIC BACTERIA USING PULSED UV-LIGHT AND ITS APPLICATION IN WATER DISINFECTION AND QUALITY CONTROL

    Directory of Open Access Journals (Sweden)

    M. K. Sharifi-Yazdi H. Darghahi

    2006-09-01

    Full Text Available The lethality of pulsed ultra-violet (UV rich light for the inactivation of pathogenic bacteria has been investigated. A low pressure xenon filled flash lamps that produced UV intensities have been used. The pulsed operation of the system enable the release of electrical energy stored in the capacitor into the flash lamp within a short time and produces the high current and high peak power required for emitting the intense UV flash. The flash frequency was adjusted to one pulse per second. Several types of bacteria were investigated for their susceptibility to pulsed UV illumination. The treated bacterial populations were reduced and determined by direct viable counts. Among the tested bacteria Pseudomonas aeruginosa was the most susceptible to the pulsed UV- light with a 8 log10 cfu/ml reduction after 11 pulses, while the spores of Bacillus megaterium was the most resistant and only 4 log10 cfu/ml reduction achieved after 50 pulses of illumination. The results of this study demonstrated that pulsed UV- light technology could be used as an effective method for the inactivation, of pathogenic bacteria in different environments such as drinking water.

  19. Formation of laser-induced periodic surface structures (LIPSS) on tool steel by multiple picosecond laser pulses of different polarizations

    Energy Technology Data Exchange (ETDEWEB)

    Gregorčič, Peter, E-mail: peter.gregorcic@fs.uni-lj.si [Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva 6, 1000 Ljubljana (Slovenia); Sedlaček, Marko; Podgornik, Bojan [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Reif, Jürgen [Brandenburgische Technische Universitaet – BTU Cottbus-Senftenberg, Platz der Deutschen Einheit 1, 03046 Cottbus (Germany)

    2016-11-30

    Highlights: • Low number of differently polarized ps laser pulses is superimposed on tool steel. • Last pulses determine the ripples orientation for single spot and coherent traces. • Previously formed structures are overridden by later incident pulses. • Ripples contrast depends on total exposure, independent on pulses’ polarization. • Weak role of pre-formed structures makes interference scenarios questionable. - Abstract: Laser-induced periodic surface structures (LIPSS) are produced on cold work tool steel by irradiation with a low number of picosecond laser pulses. As expected, the ripples, with a period of about 90% of the laser wavelength, are oriented perpendicular to the laser polarization. Subsequent irradiation with the polarization rotated by 45° or 90° results in a corresponding rotation of the ripples. This is visible already with the first pulse and becomes almost complete – erasing the previous orientation – after as few as three pulses. The phenomenon is not only observed for single-spot irradiation but also for writing long coherent traces. The experimental results strongly defy the role of surface plasmon-polaritons as the predominant key to LIPSS formation.

  20. 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.

  1. Picosecond buildup and relaxation of intense stimulated emission in GaAs

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  2. Carcinogenesis related to intense pulsed light and UV exposure

    DEFF Research Database (Denmark)

    Hedelund, L; Lerche, C; Wulf, H C

    2006-01-01

    This study examines whether intense pulsed light (IPL) treatment has a carcinogenic potential itself or may influence ultraviolet (UV)-induced carcinogenesis. Secondly, it evaluates whether UV exposure may influence IPL-induced side effects. Hairless, lightly pigmented mice (n=144) received three...... observation period. Side effects were evaluated clinically. No tumors appeared in untreated control mice or in just IPL-treated mice. Skin tumors developed in UV-exposed mice independently of IPL treatments. The time it took for 50% of the mice to first develop skin tumor ranged from 47 to 49 weeks...... in preoperative UV-exposed mice (p=0.94) and from 22 to 23 weeks in pre- and postoperative UV-exposed mice (p=0.11). IPL rejuvenation of lightly pigmented skin did not induce pigmentary changes (p=1.00). IPL rejuvenation of UV-pigmented skin resulted in an immediate increased skin pigmentation and a subsequent...

  3. Picosecond mid-infrared amplifier for high average power.

    CSIR Research Space (South Africa)

    Botha, LR

    2007-04-01

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

  4. Amplification of UV ultrashort pulse laser in e-beam pumped KrF amplifier

    CERN Document Server

    Tang Xiu Zhang; Gong Kun; Ma Wei Yi; Shan Yu Sheng; Wang Nai Yan

    2002-01-01

    Experimental investigations were performed for amplification of ultrashort pulse laser with Heaven-I e-beam pumped KrF amplifier in CIAE. A 50 mJ, 420 fs UV ultrashort pulse was amplified to 2-3 J energy, 1.2 ps pulse duration, and 2TW laser power. Experimental technique such as synchronization were describe, some parameters such as nonlinear absorb coefficient were measured in experiment. As a result, it is possible to achieve ultra-strong UV laser with intensity higher than 10 sup 1 sup 9 W/cm sup 2 in recently years

  5. Amplification of UV ultrashort pulse laser in e-beam pumped KrF amplifier

    International Nuclear Information System (INIS)

    Tang Xiuzhang; Zhang Haifeng; Gong Kun; Ma Weiyi; Shan Yusheng; Wang Naiyan

    2002-01-01

    Experimental investigations were performed for amplification of ultrashort pulse laser with Heaven-I e-beam pumped KrF amplifier in CIAE. A 50 mJ, 420 fs UV ultrashort pulse was amplified to 2-3 J energy, 1.2 ps pulse duration, and 2TW laser power. Experimental technique such as synchronization were describe, some parameters such as nonlinear absorb coefficient were measured in experiment. As a result, it is possible to achieve ultra-strong UV laser with intensity higher than 10 19 W/cm 2 in recently years

  6. On the biphoton excitation of the fluorescence of the bacteriochlorophyll molecules of purple photosynthetic bacteria by powerful near IR femto-picosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Borisov, A. Yu., E-mail: borissov@belozersky.msu.ru [Moscow State University, Belozersky Institute of Physicochemical Biology (Russian Federation)

    2011-11-15

    The authors of a number of experimental works detected nonresonance biphoton excitation of bacteriochlorophyll molecules, which represent the main pigment in the light-absorbing natural 'antenna' complexes of photosynthesizing purple bacteria, by femtosecond IR pulses (1250-1500 nm). They believe that IR quanta excite hypothetic forbidden levels of the pigments of these bacteria in the double frequency range 625-750 nm. We propose and ground an alternative triplet mechanism to describe this phenomenon. According to our hypothesis, the mechanism of biphoton excitation of molecules by IR quanta can manifest itself specifically, through high triplet levels of molecules in the high fields induced by femtosecond-picosecond laser pulses.

  7. Picosecond X-ray streak camera dynamic range measurement

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-09-15

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

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

    Science.gov (United States)

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

    2003-03-01

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

  9. Pulsed UV laser-induced modifications in optical and structural characteristics of alpha-irradiated PM-355 SSNTD.

    Science.gov (United States)

    Alghamdi, S S; Farooq, W A; Baig, M R; Algarawi, M S; Alrashidi, Talal Mohammed; Ali, Syed Mansoor; Alfaramawi, K

    2017-10-01

    Pre- and postalpha-exposed PM-355 detectors were irradiated using UV laser with different number of pulses (100, 150, 200, 300, and 400). UV laser beam energy of 20mJ per pulse with a pulse width of 9ns was incident on an area of 19.6mm 2 of the samples. XRD spectra indicated that for both reference and UV-irradiated samples, the structure is amorphous, but the crystallite size increases upon UV irradiation. The same results were obtained from SEM analysis. Optical properties of PM-355 polymeric solid-state nuclear track detectors were also investigated. Absorbance measurements for all PM-355 samples in the range of 200-400nm showed that the absorption edge had a blue shift up to a certain value, and then, it had an oscillating behavior. Photoluminescence spectra of PM-355 at 250nm revealed a decrease in the broadband peak intensity as a function of the number of UV pulses, while the wavelengths corresponding to the peaks had random shifts. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. The influence of the excitation pulse length on ultrafast magnetization dynamics in nickel

    Directory of Open Access Journals (Sweden)

    A. Fognini

    2015-03-01

    Full Text Available The laser-induced demagnetization of a ferromagnet is caused by the temperature of the electron gas as well as the lattice temperature. For long excitation pulses, the two reservoirs are in thermal equilibrium. In contrast to a picosecond laser pulse, a femtosecond pulse causes a non-equilibrium between the electron gas and the lattice. By pump pulse length dependent optical measurements, we find that the magnetodynamics in Ni caused by a picosecond laser pulse can be reconstructed from the response to a femtosecond pulse. The mechanism responsible for demagnetization on the picosecond time scale is therefore contained in the femtosecond demagnetization experiment.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  12. Detection of UV Pulse from Insulators and Application in Estimating the Conditions of Insulators

    Science.gov (United States)

    Wang, Jingang; Chong, Junlong; Yang, Jie

    2014-10-01

    Solar radiation in the band of 240-280 nm is absorbed by the ozone layer in the atmosphere, and corona discharges from high-voltage apparatus emit in air mainly in the 230-405 nm range of ultraviolet (UV), so the band of 240-280 nm is called UV Solar Blind Band. When the insulators in a string deteriorate or are contaminated, the voltage distribution along the string will change, which causes the electric fields in the vicinity of insulators change and corona discharge intensifies. An UV pulse detection method to check the conditions of insulators is presented based on detecting the UV pulse among the corona discharge, then it can be confirmed that whether there exist faulty insulators and whether the surface contamination of insulators is severe for the safe operation of power systems. An UV-I Insulator Detector has been developed, and both laboratory tests and field tests have been carried out which demonstrates the practical viability of UV-I Insulator Detector for online monitoring.

  13. Environmentally stable picosecond Yb fiber laser with low repetition rate

    Science.gov (United States)

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

    2013-04-01

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

  14. Influence of deposited nanoparticles on the spall strength of metals under the action of picosecond pulses of shock compression

    Science.gov (United States)

    Ebel, A. A.; Mayer, A. E.

    2018-01-01

    Molecular dynamic simulations of the generation and propagation of shock pulses of picosecond duration initiated by nanoscale impactors, and their interaction with the rear surface is carried out for aluminum and copper. It is shown that the presence of deposited nanoparticles on the rear surface increases the threshold value of the impact intensity leading to the rear spallation. The interaction of a shock wave with nanoparticles leads to severe plastic deformation in the surface layer of the metal including nanoparticles. A part of the compression pulse energy is expended on the plastic deformation, which suppresses the spall fracture. Spallation threshold substantially increases at large diameters of deposited nanoparticles, but instability develops on the rear surface of the target, which is accompanied by ejection of droplets. The instability disrupts the integrity of the rear surface, though the loss of integrity occurs through the ejection of mass, rather than a spallation.

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

    Science.gov (United States)

    Negishi, Kei; Akita, Hirotaka; Matsunaga, Yukiko

    2018-04-02

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

  16. Picosecond Laser Pulse Interactions with Metallic and Semiconductor Surfaces.

    Science.gov (United States)

    1984-11-01

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

  17. Acceleration of a solid-density plasma projectile to ultrahigh velocities by a short-pulse ultraviolet laser

    Energy Technology Data Exchange (ETDEWEB)

    Badziak, J.; Jablonski, S. [Institute of Plasma Physics and Laser Microfusion, Euratom Association, 01-497 Warsaw (Poland)

    2011-08-15

    It is shown by means of particle-in-cell simulations that a high-fluence ({>=}1 GJ/cm{sup 2}) solid-density plasma projectile can be accelerated up to sub-relativistic velocities by radiation pressure of an ultraviolet (UV) picosecond laser pulse of moderate values of dimensionless laser amplitude a{sub 0}{approx}10. The efficiency of acceleration by the UV laser is significantly higher than in the case of long-wavelength ({lambda} {approx} 1 {mu}m) driver of a comparable value of a{sub 0}, and the motion of the projectile is fairly well described by the ''Light Sail'' acceleration model.

  18. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-05-15

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

  20. Study of phonon propagation in water using picosecond ultrasonics

    International Nuclear Information System (INIS)

    Yang, F; Atay, T; Dang, C H; Grimsley, T J; Che, S; Ma, J; Zhang, Q; Nurmikko, A V; Maris, H J

    2007-01-01

    The propagation of ultra-short sound pulses in water is studied by using the picosecond ultrasonic technique. A sound pulse is generated when light is absorbed in a metal transducer film deposited onto a substrate. The sound propagates across a thin layer of water and is then reflected back to the surface at which it was generated. The efficiency of optoacoustic detection of the reflected sound is enhanced through the use of a resonant optical cavity. We show that the variation of the shape of the returning sound pulse with propagation distance agrees with that calculated by using the attenuation of sound in water that has been measured at lower frequencies

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

    Science.gov (United States)

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

    2017-06-01

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

  2. Experimental demonstration of novel cascaded SFG+DFG wavelength conversion of picosecond pulses in LiNbO 3 waveguides

    Science.gov (United States)

    Wang, Jian; Sun, Junqiang; Luo, Chuanhong

    2006-06-01

    A novel cascaded χ (2) wavelength conversion of picosecond pulses based on sum frequency generation and difference frequency generation (SFG+DFG) is proposed and experimentally demonstrated in LiNbO 3 waveguides. The signal pulse with 40-GHz repetition rate and 1.57-ps pulse width is adopted. First of all, high conversion efficiency about -18.93dB can be achieved with low power level required for both two pump lights, which is greatly enhanced approximately 8dB compared with the conventional cascaded second-order nonlinear interactions (SHG+DFG) with a single and much higher power pump. Secondly, the wavelength of the converted idler wave can be tuned from 1527.4 to 1540.5nm when the signal wavelength is changed from 1561.9 to 1548.4nm, and about 13.1nm converted idler bandwidth is achieved with the conversion efficiency higher than -31dB. Thirdly, two pump wavelengths can be separated as large as 17.3nm. Meanwhile, when one pump wavelength is fixed at 1549.1nm, the other can be tuned within a wide wavelength range about 7.6nm with the conversion efficiency higher than -34dB, which is much larger than that in the SHG+DFG situation. Finally, the temporal waveform of the converted idler pulse is observed with rather clear appearance achieved, and no obvious changes of the pulse shape and width are found compared with its corresponding original injected signal, showing that our proposed scheme exhibits a very good conversion performance.

  3. Development of high current electron source using photoemission from metals with ultrashort laser pulses

    International Nuclear Information System (INIS)

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

    1990-10-01

    We summarize the studies of photoemission from metal photocathodes using picosecond pulses in the UV (4.66 eV) wavelength and femtosecond laser pulses in the visible (2 eV) wavelengths. To achieve high current density yield from metal photocathodes, multiphoton photoemission using femtosecond laser pulses are suggested. Electron yield improvement incorporating surface photoemission and surface plasmon resonance in metals and metal films are demonstrated. We examine the possibility of the nonlinear photoemission process overtaking the linear process, and identity some possible complexity. To extract the large amount of electrons free of space charge, a pulsed high voltage is designed; the results of the preliminary test are presented. Finally, for the first time, the width of the electron temporal profiles are measured, utilizing the nonlinear photoelectric effect, to below 100 fsec time regime. The results indicated that the electron pulse duration follows the laser pulses and are not limited by the material. 8 refs., 15 figs

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-10-15

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

  5. Fiber Optical Parametric Chirped Pulse Amplification of Sub-Picosecond Pulses

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Da Ros, Francesco

    2013-01-01

    We demonstrate experimentally, for the first time to our knowledge, fiber optical parametric chirped pulse amplification of 400-fs pulses. The 400-fs signal is stretched, amplified by 26 dB and compressed back to 500 fs.......We demonstrate experimentally, for the first time to our knowledge, fiber optical parametric chirped pulse amplification of 400-fs pulses. The 400-fs signal is stretched, amplified by 26 dB and compressed back to 500 fs....

  6. Intense picosecond pulsed electric fields induce apoptosis through a mitochondrial-mediated pathway in HeLa cells

    Science.gov (United States)

    HUA, YUAN-YUAN; WANG, XIAO-SHU; ZHANG, YU; YAO, CHEN-GUO; ZHANG, XI-MING; XIONG, ZHENG-AI

    2012-01-01

    The application of pulsed electric fields (PEF) is emerging as a new technique for tumor therapy. Picosecond pulsed electric fields (psPEF) can be transferred to target deep tissue non-invasively and precisely, but the research of the biological effects of psPEF on cells is limited. Electric theory predicts that intense psPEF will target mitochondria and lead to changes in transmembrane potential, therefore, it is hypothesized that it can induce mitochondrial-mediated apoptosis. HeLa cells were exposed to psPEF in this study to investigate this hypothesis. MTT assay demonstrated that intense psPEF significantly inhibited the proliferation of HeLa cells in a dose-dependent manner. Typical characteristics of apoptosis in HeLa cells were observed, using transmission electron microscopy. Loss of mitochondrial transmembrane potential was explored using laser scanning confocal microscopy with Rhodamine-123 (Rh123) staining. Furthermore, the mitochondrial apoptotic events were also confirmed by western blot analysis for the release of cytochrome C and apoptosis-inducing factor from mitochondria into the cytosol. In addition, activation of caspase-3, caspase-9, upregulation of Bax, p53 and downregulation of Bcl-2 were observed in HeLa cells also indicating apoptosis. Taken together, these results demonstrate that intense psPEF induce cell apoptosis through a mitochondrial-mediated pathway. PMID:22307872

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

    Science.gov (United States)

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

    2016-05-01

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

  8. Removal of styrene vapor from atmospheric air using a pulsed corona discharge and UV-irridiation

    International Nuclear Information System (INIS)

    Shvedchikov, A.P.; Belousova, E.V.; Polyakova, A.V.; Ponizovskii, A.Z.; Goncharov, V.A.

    1993-01-01

    The authors have investigated processes for removal of styrene vapor from atmospheric air (volume content 0.007-0.06%) upon exposure to UV radiation and dc and pulsed corona discharges. The authors have studied the dependence of the degree of purification on various parameters (flow rate, temperature, composition, pulse frequency). It has been shown that the purification rate increases when UV radiation is combined with the discharge. A possible mechanism for the purification process is considered

  9. Temporal laser pulse shaping for RF photocathode guns: the cheap and easy way using UV birefringent crystals

    International Nuclear Information System (INIS)

    Power, J.G.; Jing, C.

    2009-01-01

    We report experimental investigations into a new technique for achieving temporal laser pulse shaping for RF photocathode gun applications using inexpensive UV birefringent crystals. Exploiting the group velocity mismatch between the two different polarizations of a birefringent crystal, a stack of UV pulses can be assembled into the desired temporal pulse shape. The scheme is capable of generating a variety of temporal pulse shapes including: (i) flat-top pulses with fast rise-time and variable pulse duration. (ii) microbunch trains, and (iii) ramped pulse generation. We will consider two applications for beam generation at the Argonne Wakefield Accelerator (AWA) including a flat-top laser pulse for low emittance production and matched bunch length for enhanced transformer ratio production. Streak camera measurements of the temporal profiles generated with a 2-crystal set and a 4-crystal set are presented.

  10. Picosecond energy relaxation in La0.67Ca0.33MnO3

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  11. The formation of ozone and UV radiation from high-power pulsed electric discharges

    Science.gov (United States)

    Piskarev, I. M.; Ushkanov, V. A.; Selemir, V. D.; Spirov, G. M.; Malevannaya Pikar', I. A.; Zuimach, E. A.

    2008-09-01

    High-power electric discharges with pulse energies of from 0.15 J to 4 kJ were studied. The yields of UV photons and ozone were found to be approximately equal, which led us to conclude that discharge conditions under which UV radiation and ozone fully destroyed each other were possible. If ozone formation was suppressed, as when a negative volume charge was created in the spark gap region, the flux of UV photons reached 3 × 1023 photons/(cm2 s).

  12. Picosecond laser ablation of porcine sclera

    Science.gov (United States)

    Góra, Wojciech S.; Harvey, Eleanor M.; Dhillon, Baljean; Parson, Simon H.; Maier, Robert R. J.; Hand, Duncan P.; Shephard, Jonathan D.

    2013-03-01

    Lasers have been shown to be successful in certain medical procedures and they have been identified as potentially making a major contribution to the development of minimally invasive procedures. However, the uptake is not as widespread and there is scope for many other applications where laser devices may offer a significant advantage in comparison to the traditional surgical tools. The purpose of this research is to assess the potential of using a picosecond laser for minimally invasive laser sclerostomy. Experiments were carried out on porcine scleral samples due to the comparable properties to human tissue. Samples were prepared with a 5mm diameter trephine and were stored in lactated Ringer's solution. After laser machining, the samples were fixed in 3% glutaraldehyde, then dried and investigated under SEM. The laser used in the experiments is an industrial picosecond TRUMPF TruMicro laser operating at a wavelength of 1030nm, pulse length of 6ps, repetition rate of 1 kHz and a focused spot diameter of 30μm. The laser beam was scanned across the samples with the use of a galvanometer scan head and various ablation patterns were investigated. Processing parameters (pulse energy, spot and line separation) which allow for the most efficient laser ablation of scleral tissue without introducing any collateral damage were investigated. The potential to create various shapes, such as linear incisions, square cavities and circular cavities was demonstrated.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  14. Enhanced detection of nitrogen dioxide via combined heating and pulsed UV operation of indium oxide nano-octahedra

    Directory of Open Access Journals (Sweden)

    Oriol Gonzalez

    2016-10-01

    Full Text Available We report on the use of combined heating and pulsed UV light activation of indium oxide gas sensors for enhancing their performance in the detection of nitrogen dioxide in air. Indium oxide nano-octahedra were synthesized at high temperature (900 °C via vapour-phase transport and screen-printed onto alumina transducers that comprised interdigitated electrodes and a heating resistor. Compared to the standard, constant temperature operation of the sensor, mild heating (e.g., 100 °C together with pulsed UV light irradiation employing a commercially available, 325 nm UV diode (square, 1 min period, 15 mA drive current signal, results in an up to 80-fold enhancement in sensitivity to nitrogen dioxide. Furthermore, this combined operation method allows for making savings in power consumption that range from 35% to over 80%. These results are achieved by exploiting the dynamics of sensor response under pulsed UV light, which convey important information for the quantitative analysis of nitrogen dioxide.

  15. Enhanced detection of nitrogen dioxide via combined heating and pulsed UV operation of indium oxide nano-octahedra.

    Science.gov (United States)

    Gonzalez, Oriol; Roso, Sergio; Vilanova, Xavier; Llobet, Eduard

    2016-01-01

    We report on the use of combined heating and pulsed UV light activation of indium oxide gas sensors for enhancing their performance in the detection of nitrogen dioxide in air. Indium oxide nano-octahedra were synthesized at high temperature (900 °C) via vapour-phase transport and screen-printed onto alumina transducers that comprised interdigitated electrodes and a heating resistor. Compared to the standard, constant temperature operation of the sensor, mild heating (e.g., 100 °C) together with pulsed UV light irradiation employing a commercially available, 325 nm UV diode (square, 1 min period, 15 mA drive current signal), results in an up to 80-fold enhancement in sensitivity to nitrogen dioxide. Furthermore, this combined operation method allows for making savings in power consumption that range from 35% to over 80%. These results are achieved by exploiting the dynamics of sensor response under pulsed UV light, which convey important information for the quantitative analysis of nitrogen dioxide.

  16. Formation of quasi-periodic nano- and microstructures on silicon surface under IR and UV femtosecond laser pulses

    International Nuclear Information System (INIS)

    Ionin, Andrei A; Golosov, E V; Kolobov, Yu R; Kudryashov, Sergei I; Ligachev, A E; Makarov, Sergei V; Novoselov, Yurii N; Seleznev, L V; Sinitsyn, D V

    2011-01-01

    Quasi-periodic nano- and microstructures have been formed on silicon surface using IR ( λ ≈ 744 nm) and UV ( λ ≈ 248 nm) femtosecond laser pulses. The influence of the incident energy density and the number of pulses on the structured surface topology has been investigated. The silicon nanostructurisation thresholds have been determined for the above-mentioned wavelengths. Modulation of the surface relief at the doubled spatial frequency is revealed and explained qualitatively. The periods of the nanostructures formed on the silicon surface under IR and UV femtosecond laser pulses are comparatively analysed and discussed.

  17. Picosecond image-converter diagnostics

    International Nuclear Information System (INIS)

    Schelev, M.Ya.

    1975-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Hongpeng Su

    2017-09-01

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

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-11-01

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

  1. Picosecond Electric-Field-Induced Threshold Switching in Phase-Change Materials.

    Science.gov (United States)

    Zalden, Peter; Shu, Michael J; Chen, Frank; Wu, Xiaoxi; Zhu, Yi; Wen, Haidan; Johnston, Scott; Shen, Zhi-Xun; Landreman, Patrick; Brongersma, Mark; Fong, Scott W; Wong, H-S Philip; Sher, Meng-Ju; Jost, Peter; Kaes, Matthias; Salinga, Martin; von Hoegen, Alexander; Wuttig, Matthias; Lindenberg, Aaron M

    2016-08-05

    Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag_{4}In_{3}Sb_{67}Te_{26}. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales-faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.

  2. Picosecond calorimetry

    DEFF Research Database (Denmark)

    Georgiou, Panayiotis; Vincent, Jonathan; Andersson, Magnus

    2006-01-01

    to rapidly heat liquid C H2 Cl2 using UV pulses of 100 fs duration. A significant x-ray diffraction signal is visible prior to the onset of thermal expansion, which characterizes a highly compressed superheated liquid. Liquid C H2 Cl2 then expands as a shock wave propagates through the sample...

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

    International Nuclear Information System (INIS)

    Grabas, Herve

    2013-01-01

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

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

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  5. Picosecond transient absorption study of photodissociated carboxy hemoglobin and myoglobin

    International Nuclear Information System (INIS)

    Janes, S.M.; Dalickas, G.A.; Eaton, W.A.; Hochstrasser, R.M.

    1988-01-01

    The optical transient absorption spectra at 30 ps and 6.5 ns after photolysis are compared for both carboxy hemoglobin (HbCO) and carboxy myoglobin (MbCO). Both 355- and 532-nm excitation pulses were used. In all cases the shapes of the optical difference spectra thus generated are stationary over the complete time-scale studied. The photolysis spectra for MbCO are not significantly different from the equilibrium difference spectra generated on the same picosecond spectrometer when measured to an accuracy of +/- 0.5 nm. In addition, spectral parameters for delegated HbCO generated on the same spectrometer but detected by two different techniques, either by a Vidicon detector or point by point with photomultiplier tubes, are reported; the results are different from some of the previously reported picosecond experiments

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

    International Nuclear Information System (INIS)

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

    1988-01-01

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

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

    Science.gov (United States)

    Zhao, Wanqin; Yu, Zhishui

    2018-06-01

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

  8. Contribution to the study of solvated electrons in water and alcohols and of radiolytic processes in organic carbonates by picosecond pulse radiolysis

    International Nuclear Information System (INIS)

    Torche, Faycal

    2012-01-01

    This work is part of the study area of the interaction of radiation with polar liquids. Using the picosecond electron accelerator ELYSE, studies were conducted using the techniques of pulse radiolysis combined with absorption spectrophotometry Time-resolved in the field of a picosecond. This work is divided into two separate chapters. The first study addresses the temporal variation of the radiolytic yield of solvated electron in water and simple alcohols. Due to original detection system mounted on the accelerator ELYSE, composed of a flash lamp specifically designed for the detection and a streak-camera used for the first time in absorption spectroscopy, it was possible to record the time-dependent radiolytic yields of the solvated electron from ten picoseconds to a few hundred nanoseconds. The scavenging of the electron solvated by methyl viologen, was utilized to reevaluate the molar extinction coefficient of the absorption spectrum of solvated electron in water and ethanol from isobestic points which corresponds to the intersection of the absorption spectra of solvated electron which disappears and methyl viologen which is formed during the reaction. The second chapter is devoted to the study of liquid organic carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC) and propylene carbonate (PC). This family of carbonate which compose the electrolytes lithium batteries, has never been investigated by pulse radiolysis. The studies were focused on the PC in the light of these physicochemical characteristics, including its very high dielectric constant and its strong dipole moment of 4.9 D. The first results were obtained on aqueous solutions containing propylene carbonate to observe the reactions of reduction and oxidation of PC by radiolytic species of water (solvated electron and OH radicals). Then, after the identification (spectral and kinetic) of the species formed by interaction with the OH radical as the PC* radical resulting from the

  9. Whole tumor antigen vaccination using dendritic cells: Comparison of RNA electroporation and pulsing with UV-irradiated tumor cells

    Directory of Open Access Journals (Sweden)

    Benencia Fabian

    2008-04-01

    Full Text Available Abstract Because of the lack of full characterization of tumor associated antigens for solid tumors, whole antigen use is a convenient approach to tumor vaccination. Tumor RNA and apoptotic tumor cells have been used as a source of whole tumor antigen to prepare dendritic cell (DC based tumor vaccines, but their efficacy has not been directly compared. Here we compare directly RNA electroporation and pulsing of DCs with whole tumor cells killed by ultraviolet (UV B radiation using a convenient tumor model expressing human papilloma virus (HPV E6 and E7 oncogenes. Although both approaches led to DCs presenting tumor antigen, electroporation with tumor cell total RNA induced a significantly higher frequency of tumor-reactive IFN-gamma secreting T cells, and E7-specific CD8+ lymphocytes compared to pulsing with UV-irradiated tumor cells. DCs electroporated with tumor cell RNA induced a larger tumor infiltration by T cells and produced a significantly stronger delay in tumor growth compared to DCs pulsed with UV-irradiated tumor cells. We conclude that electroporation with whole tumor cell RNA and pulsing with UV-irradiated tumor cells are both effective in eliciting antitumor immune response, but RNA electroporation results in more potent tumor vaccination under the examined experimental conditions.

  10. Formation of Porous Structure with Subspot Size under the Irradiation of Picosecond Laser Pulses

    Directory of Open Access Journals (Sweden)

    Bin Liu

    2013-01-01

    Full Text Available A study was presented in this paper on porous structure with microsize holes significantly smaller than laser spot on the stainless steel 304 target surface induced by a picosecond Nd:van regenerative amplified laser, operating at 1064 nm. The target surface variations were studied in air ambience. The estimated surface damage threshold was 0.15 J/cm2. The target specific surface changes and phenomena observed supported a complementary study on the formation and growth of the subspot size pit holes on metal surface with dependence of laser pulse number of 50–1000 and fluences of 0.8 and 1.6 J/cm2. Two kinds of porous structures were presented: periodic holes are formed from Coulomb Explosion during locally spatial modulated ablation, and random holes are formed from the burst of bubbles in overheated liquid during phase explosion. It can be concluded that it is effective to fabricate a large metal surface area of porous structure by laser scanning regime. Generally, it is also difficult for ultrashort laser to fabricate the microporous structures compared with traditional methods. These porous structures potentially have a number of important applications in nanotechnology, industry, nuclear complex, and so forth.

  11. 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

  12. 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...

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

    Science.gov (United States)

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

    2015-07-14

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

  14. Synchronization circuit for shaping electron beam picosecond pulses

    International Nuclear Information System (INIS)

    Pavlov, Yu.S.; Solov'ev, N.G.; Tomnikov, A.P.

    1985-01-01

    A fast response circuit of modulator trigger pulse synchronization of a deflector of the electron linear accelerator at 13 MeV with the given phase of HF-voltage is described. The circuit is constructed using K500 and K100 integrated emitter-coupled logics circuits. Main parameters of a synchropulse are duration of 20-50 ns, pulse rise time of 1-5 ns, pulse amplitude >=10 V, delay instability of a trigger pulse <=+-0.05 ns. A radiopulse with 3 μs duration, 5 V amplitude and 400 Hz frequency enters the circuit input. The circuit can operate at both pulsed operation and continuous modes

  15. Using the Transient Response of WO3 Nanoneedles under Pulsed UV Light in the Detection of NH3 and NO2

    Directory of Open Access Journals (Sweden)

    Oriol Gonzalez

    2018-04-01

    Full Text Available Here we report on the use of pulsed UV light for activating the gas sensing response of metal oxides. Under pulsed UV light, the resistance of metal oxides presents a ripple due to light-induced transient adsorption and desorption phenomena. This methodology has been applied to tungsten oxide nanoneedle gas sensors operated either at room temperature or under mild heating (50 °C or 100 °C. It has been found that by analyzing the rate of resistance change caused by pulsed UV light, a fast determination of gas concentration is achieved (ten-fold improvement in response time. The technique is useful for detecting both oxidizing (NO2 and reducing (NH3 gases, even in the presence of different levels of ambient humidity. Room temperature operated sensors under pulsed UV light show good response towards ammonia and nitrogen dioxide at low power consumption levels. Increasing their operating temperature to 50 °C or 100 °C has the effect of further increasing sensitivity.

  16. Compression of realistic laser pulses in hollow-core photonic bandgap fibers

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper; Roberts, John

    2009-01-01

    Dispersive compression of chirped few-picosecond pulses at the microjoule level in a hollow-core photonic bandgap fiber is studied numerically. The performance of ideal parabolic input pulses is compared to pulses from a narrowband picosecond oscillator broadened by self-phase modulation during...... amplification. It is shown that the parabolic pulses are superior for compression of high-quality femtosecond pulses up to the few-megawatts level. With peak powers of 5-10 MW or higher, there is no significant difference in power scaling and pulse quality between the two pulse types for comparable values...... of power, duration, and bandwidth. The same conclusion is found for the peak power and energy of solitons formed beyond the point of maximal compression. Long-pass filtering of these solitons is shown to be a promising route to clean solitonlike output pulses with peak powers of several MW....

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

    Science.gov (United States)

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

    2002-04-01

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

  18. Synchronization circuit for shaping picosecond accelerated-electron pulses

    International Nuclear Information System (INIS)

    Pavlov, Y.S.; Solov'ev, N.G.; Tomnikov, A.P.

    1986-01-01

    The authors discuss a high-speed circuit for synchronization of trigger pulses of the deflector modulator of an accelerator with a given phase of rf voltage of 200 MHz. The measured time instability between the output trigger pulses of the circuit and the input rf voltage is ≤ + or - 0.05 nsec. The circuit is implemented by ECL integrated circuits of series K100 and K500, and operates in both the pulse (pulse duration 3 μsec and repetition frequency 400 Hz) and continuous modes

  19. New theoretical approaches to atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale

    International Nuclear Information System (INIS)

    Pabst, Stefan Ulf

    2013-04-01

    The concept of atoms as the building blocks of matter has existed for over 3000 years. A revolution in the understanding and the description of atoms and molecules has occurred in the last century with the birth of quantum mechanics. After the electronic structure was understood, interest in studying the dynamics of electrons, atoms, and molecules increased. However, time-resolved investigations of these ultrafast processes were not possible until recently. The typical time scale of atomic and molecular processes is in the picosecond to attosecond realm. Tremendous technological progress in recent years makes it possible to generate light pulses on these time scales. With such ultrashort pulses, atomic and molecular dynamics can be triggered, watched, and controlled. Simultaneously, the need rises for theoretical models describing the underlying mechanisms. This doctoral thesis focuses on the development of theoretical models which can be used to study the dynamical behavior of electrons, atoms, and molecules in the presence of ultrashort light pulses. Several examples are discussed illustrating how light pulses can trigger and control electronic, atomic, and molecular motions. In the first part of this work, I focus on the rotational motion of asymmetric molecules, which happens on picosecond and femtosecond time scales. Here, the aim is to align all three axes of the molecule as well as possible. To investigate theoretically alignment dynamics, I developed a program that can describe alignment motion ranging from the impulsive to the adiabatic regime. The asymmetric molecule SO 2 is taken as an example to discuss strategies of optimizing 3D alignment without the presence of an external field (i.e., field-free alignment). Field-free alignment is particularly advantageous because subsequent experiments on the aligned molecule are not perturbed by the aligning light pulse. Wellaligned molecules in the gas phase are suitable for diffraction experiments. From the

  20. New theoretical approaches to atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale

    Energy Technology Data Exchange (ETDEWEB)

    Pabst, Stefan Ulf

    2013-04-15

    The concept of atoms as the building blocks of matter has existed for over 3000 years. A revolution in the understanding and the description of atoms and molecules has occurred in the last century with the birth of quantum mechanics. After the electronic structure was understood, interest in studying the dynamics of electrons, atoms, and molecules increased. However, time-resolved investigations of these ultrafast processes were not possible until recently. The typical time scale of atomic and molecular processes is in the picosecond to attosecond realm. Tremendous technological progress in recent years makes it possible to generate light pulses on these time scales. With such ultrashort pulses, atomic and molecular dynamics can be triggered, watched, and controlled. Simultaneously, the need rises for theoretical models describing the underlying mechanisms. This doctoral thesis focuses on the development of theoretical models which can be used to study the dynamical behavior of electrons, atoms, and molecules in the presence of ultrashort light pulses. Several examples are discussed illustrating how light pulses can trigger and control electronic, atomic, and molecular motions. In the first part of this work, I focus on the rotational motion of asymmetric molecules, which happens on picosecond and femtosecond time scales. Here, the aim is to align all three axes of the molecule as well as possible. To investigate theoretically alignment dynamics, I developed a program that can describe alignment motion ranging from the impulsive to the adiabatic regime. The asymmetric molecule SO{sub 2} is taken as an example to discuss strategies of optimizing 3D alignment without the presence of an external field (i.e., field-free alignment). Field-free alignment is particularly advantageous because subsequent experiments on the aligned molecule are not perturbed by the aligning light pulse. Wellaligned molecules in the gas phase are suitable for diffraction experiments. From the

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

    International Nuclear Information System (INIS)

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

    1989-01-01

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

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

    DEFF Research Database (Denmark)

    Heuck, Mikkel; Blaaberg, Søren; Mørk, Jesper

    2010-01-01

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

  3. Picosecond Water Radiolysis at High Temperature. Br- Oxidation - Experiments and MC-Simulations

    International Nuclear Information System (INIS)

    Baldacchino, G.; Saffre, D.; Jeunesse, J.P.; Schmidhammer, U.; Larbre, J.P.; Mostafavi, M.; Beuve, M.; Gervais, B.

    2012-09-01

    Acidic solutions of bromhydric acid have been irradiated by picosecond pulses of 7 MeV-electrons provided by ELYSE accelerator (LCP Orsay). At elevated temperatures up to 350 deg. C, salts like NaBr or KBr usually precipitate and organic compound are decomposed. Another choice of OH-scavenger may be acidic halogenates like HBr or HCl. In this situation, the processes involving H + and Br - must be considerate: while hydrated electrons are scavenged by H + , . OH reacts with Br - . Then the formations of BrOH . and Br 2 .- have been investigated by using a devoted picosecond pump-probe setup. A dedicated small-size high temperature optical flow cell has been developed for fitting the picosecond duration of the electron pulses. This cell replaces the one used also with nanosecond resolution. The picosecond time resolution remains roughly not affected by the material crossed by electrons (0.4 mm of Inconel 718) and by the white light continuum (20 mm of Sapphire windows and 6 mm of liquid solution). Depending on the concentration of HBr, the growing up of the signal can be attributed to mainly BrOH . or Br2 .- . Actually with a relatively low scavenging power ([HBr] = 25 mM), Br 2 .- is formed with a reaction between Br . and Br - which delays of around 4 ns the apparition of Br2 .- . In this particular case we then assume the absorbance is due to BrOH . . With higher and higher temperature, from 100 deg. C to 300 deg. C, the rate constant of this formation is lightly less and less. This observation must be associated to the fact that the formation of BrOH . is actually equilibrium with a lower and lower equilibrium constant value when temperature is increased. This presentation tries to explain this fact in detail by also considering Monte Carlo simulations. This will allows following all transient species from ps to μs. (authors)

  4. High-intensity coherent FIR radiation from sub-picosecond electron bunches

    International Nuclear Information System (INIS)

    Kung, P.H.; Lihn, Hung-chi; Wiedemann, H.; Bocek, D.

    1994-01-01

    A facility to generate high-intensity, ultra-short pulses of broad-band far-infrared radiation has been assembled and tested at Stanford. The device uses sub-picosecond relativistic electron bunches to generate coherent radiation through transition or synchrotron radiation in the far-infrared (FIR) regime between millimeter waves and wavelengths of about 100 μm and less. Experimental results show a peak radiation power of greater than 0.33 MW within a micro-bunch and an average FIR radiation power of 4 mW. The average bunch length of 2856 micro-bunches within a 1 μsec macro-pulse is estimated to be about 480 sec. Simulations experimental setup and results will be discussed

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

    Science.gov (United States)

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

    2015-02-01

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

  6. Ultrawide spectral broadening and compression of single extremely short pulses in the visible, uv-vuv, and middle infrared by high-order stimulated Raman scattering

    International Nuclear Information System (INIS)

    Kalosha, V. P.; Herrmann, J.

    2003-01-01

    We present the results of a comprehensive analytical and numerical study of ultrawide spectral broadening and compression of isolated extremely short visible, uv-vuv and middle infrared (MIR) pulses by high-order stimulated Raman scattering in hollow waveguides. Spectral and temporal characteristics of the output pulses and the mechanism of pulse compression using dispersion of the gas filling and output glass window are investigated without the slowly varying envelope approximation. Physical limitations due to phase mismatch, velocity walk off, and pump-pulse depletion as well as improvements through the use of pump-pulse sequences and dispersion control are studied. It is shown that phase-locked pulses as short as ∼2 fs in the visible and uv-vuv, and 6.5 fs in the MIR can be generated by coherent scattering in impulsively excited Raman media without the necessity of external phase control. Using pump-pulse sequences, shortest durations in the range of about 1 fs for visible and uv-vuv probe pulses are predicted

  7. Periodic nanostructures fabricated on GaAs surface by UV pulsed laser interference

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei; Huo, Dayun; Guo, Xiaoxiang; Rong, Chen; Shi, Zhenwu, E-mail: zwshi@suda.edu.cn; Peng, Changsi, E-mail: changsipeng@suda.edu.cn

    2016-01-01

    Graphical abstract: - Highlights: • Periodic nanostructures were fabricated on GaAs wafers by four-beam laser interference patterning which have potential applications in many fields. • Significant different results were obtained on epi-ready and homo-epitaxial GaAs substrate surfaces. • Two-pulse patterning was carried out on homo-epitaxial GaAs substrate, a noticeable morphology transformation induced by the second pulse was observed. • Temperature distribution on sample surface as a function of time and position was calculated by solving the heat diffusion equations. The calculation agrees well with the experiment results. - Abstract: In this paper, periodic nanostructures were fabricated on GaAs wafers by four-beam UV pulsed laser interference patterning. Significant different results were observed on epi-ready and homo-epitaxial GaAs substrate surfaces, which suggests GaAs oxide layer has an important effect on pulsed laser irradiation process. In the case of two-pulse patterning, a noticeable morphology transformation induced by the second pulse was observed on homo-epitaxial GaAs substrate. Based on photo-thermal mode, temperature distribution on sample surface as a function of time and position was calculated by solving the heat diffusion equations.

  8. Pattern analysis of laser-tattoo interactions for picosecond- and nanosecond-domain 1,064-nm neodymium-doped yttrium-aluminum-garnet lasers in tissue-mimicking phantom.

    Science.gov (United States)

    Ahn, Keun Jae; Zheng, Zhenlong; Kwon, Tae Rin; Kim, Beom Joon; Lee, Hye Sun; Cho, Sung Bin

    2017-05-08

    During laser treatment for tattoo removal, pigment chromophores absorb laser energy, resulting in fragmentation of the ink particles via selective photothermolysis. The present study aimed to outline macroscopic laser-tattoo interactions in tissue-mimicking (TM) phantoms treated with picosecond- and nanosecond-domain lasers. Additionally, high-speed cinematographs were captured to visualize time-dependent tattoo-tissue interactions, from laser irradiation to the formation of photothermal and photoacoustic injury zones (PIZs). In all experimental settings using the nanosecond or picosecond laser, tattoo pigments fragmented into coarse particles after a single laser pulse, and further disintegrated into smaller particles that dispersed toward the boundaries of PIZs after repetitive delivery of laser energy. Particles fractured by picosecond treatment were more evenly dispersed throughout PIZs than those fractured by nanosecond treatment. Additionally, picosecond-then-picosecond laser treatment (5-pass-picosecond treatment + 5-pass-picosecond treatment) induced greater disintegration of tattoo particles within PIZs than picosecond-then-nanosecond laser treatment (5-pass-picosecond treatment + 5-pass-nanosecond treatment). High-speed cinematography recorded the formation of PIZs after repeated reflection and propagation of acoustic waves over hundreds of microseconds to a few milliseconds. The present data may be of use in predicting three-dimensional laser-tattoo interactions and associated reactions in surrounding tissue.

  9. 40 W picosecond fiber amplifier with the large mode-area polarized crystal fiber

    International Nuclear Information System (INIS)

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

    2009-01-01

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

  10. UV laser micromachining of piezoelectric ceramic using a pulsed Nd:YAG laser

    International Nuclear Information System (INIS)

    Zeng, D.W.; Xie, C.S.; Li, K.; Chan, H.L.W.; Choy, C.L.; Yung, K.C.

    2004-01-01

    UV laser (λ=355 nm) ablation of piezoelectric lead zirconate titanate (PZT) ceramics in air has been investigated under different laser parameters. It has been found that there is a critical pulse number (N=750). When the pulse number is smaller than the critical value, the ablation rate decreases with increasing pulse number. Beyond the critical value, the ablation rate becomes constant. The ablation rate and concentrations of O, Zr and Ti on the ablated surface increase with the laser fluence, while the Pb concentration decreases due to the selective evaporation of PbO. The loss of the Pb results in the formation of a metastable pyrochlore phase. ZrO 2 was detected by XPS in the ablated zone. Also, the concentrations of the pyrochlore phase and ZrO 2 increase with increasing laser fluence. These results clearly indicate that the chemical composition and phase structure in the ablated zone strongly depend on the laser fluence. The piezoelectric properties of the cut PZT ceramic samples completely disappear due to the loss of the Pb and the existence of the pyrochlore phase. After these samples were annealed at 1150 C for 1 h in a PbO-controlled atmosphere, their phase structure and piezoelectric properties were recovered again. Finally, 1-3 and concentric-ring 2-2 PZT/epoxy composites were fabricated by UV laser micromachining and their thickness modes were measured by impedance spectrum analysis and a d 33 meter. Both composites show high piezoelectric properties. (orig.)

  11. 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...

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

    Science.gov (United States)

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

    2017-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-09-01

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

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

    Science.gov (United States)

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

    2005-11-01

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

  15. Studies of pulsed laser melting and rapid solidification using amorphous silicon

    International Nuclear Information System (INIS)

    Lowndes, D.H.; Wood, R.F.

    1984-06-01

    Pulsed-laser melting of ion implantation-amorphized silicon layers, and subsequent solidification were studied. Measurements of the onset of melting of amorphous silicon layers and of the duration of melting, and modified melting model calculations demonstrated that the thermal conductivity, K/sub a/, of amorphous silicon is very low (K/sub a/ approx. = 0.02 W/cm-K). K/sub a/ is also the dominant parameter determining the dynamical response of amorphous silicon to pulsed laser radiation. TEM indicates that bulk (volume) nucleation occurs directly from the highly undercooled liquid silicon that can be prepared by pulsed laser melting of amorphous silicon layers at low laser energy densities. A modified thermal melting model is presented. The model calculations demonstrate that the release of latent heat by bulk nucleation occurring during the melt-in process is essential to obtaining agreement with observed depths of melting. These calculations also show that this release of latent heat accompanying bulk nucleation can result in the existence of buried molten layers of silicon in the interior of the sample after the surface has solidified. The bulk nucleation implies that the liquid-to-amorphous phase transition (produced using picosecond or uv nanosecond laser pulses) cannot be explained using purely thermodynamic considerations

  16. 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.

  17. Pulsed EPR analysis of tooth enamel samples exposed to UV and {gamma}-radiations

    Energy Technology Data Exchange (ETDEWEB)

    Marrale, M., E-mail: marrale@unipa.it [Dipartimento di Fisica, Universita di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Gruppo V Sezione INFN, Catania, Italy and Unita CNISM, Palermo (Italy); Longo, A.; Brai, M. [Dipartimento di Fisica, Universita di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Gruppo V Sezione INFN, Catania (Italy) and Unita CNISM, Palermo (Italy); Barbon, A.; Brustolon, M. [Dipartimento di Scienze Chimiche, Universita degli Studi di Padova, Via Marzolo 1, 35131 Padova (Italy); Fattibene, P. [Istituto Superiore di Sanita, Viale Regina Elena 299, 00161 Rome (Italy)

    2011-09-15

    The electron paramagnetic resonance (EPR) spectroscopy is widely applied for retrospective dosimetric purposes by means of quantitative detection of radicals in tooth enamel and bone samples. In this work we report a study by cw and pulsed EPR on two samples of human tooth enamel respectively irradiated by UV (254 nm) and {gamma}-exposed. The continuous wave (cw) EPR spectra have shown the usual presence in both samples of two types of CO{sub 2}{sup -} radicals, with axial and orthorombic g tensors. We have obtained the electron spin echo detected EPR (ED-EPR) spectra at 80 K of the two samples, and we have shown that they are suitable to mark the difference between the effects produced by the different irradiations. At low temperature the contribution to the ED-EPR spectrum of the mobile radical with the axial g tensor is still present in the UV irradiated sample, but not in the {gamma}-irradiated one, where its dynamics is too slow to average the g tensor. We have moreover studied the two-pulse electron spin echo decay on varying the microwave power, a well established method for measuring the Instantaneous Diffusion. We have found that the spectral diffusion parameter is almost the same for both radiation types, whereas the Instantaneous Diffusion is significantly larger for {gamma}-exposed samples than for UV irradiated ones. This difference is due to a higher local microscopic concentration of free radicals for samples irradiated with {gamma} photons.

  18. Pulse properties of external cavity mode locked semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Kroh, Marcel; Mørk, Jesper

    2006-01-01

    picosecond duration with more than 30 dB trailing pulse suppression. The limiting factors to the device performance are investigated on the basis of a fully-distributed time-domain model.We find that ultrafast gain dynamics effectively reduce the pulse-shaping strength and inhibit the generation...

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

    International Nuclear Information System (INIS)

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

    1995-01-01

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

  20. Coherent Smith-Purcell radiation as a diagnostic for sub-picosecond electron bunch length

    International Nuclear Information System (INIS)

    Nguyen, D.C.

    1996-01-01

    We suggest a novel technique of measuring sub-picosecond electron bunch length base on coherent Smith-Purcell radiation (SPR) emitted when electrons pass close to the surface of a metal grating. With electron bunch lengths comparable to the grating period, we predict that coherent SPR will be emitted at large angles with respect to direction of beam propagation. As the bunch length shortens, the coherent SPR will be enhanced over the incoherent component that is normally observed at small angles. Furthermore, the angular distribution of the coherent SPR will be shifted toward smaller angles as the bunch length becomes much smaller than the grating period. By measuring the angular distribution of the coherent SPR, one can determine the bunch length of sub-picosecond electron pulses. This new technique is easy to implement and appears capable of measuring femtosecond electron bunch lengths

  1. 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

  2. Implementation of innovative pulsed xenon ultraviolet (PX-UV environmental cleaning in an acute care hospital

    Directory of Open Access Journals (Sweden)

    Fornwalt L

    2014-01-01

    Full Text Available Lori Fornwalt,1 Brad Riddell1,2 1Departments of Infection Prevention and Environmental Services, Trinity Medical Centre, Birmingham, AL, 2Environmental Services, Medical University of South Carolina, Charleston, SC, USA Abstract: It is widely acknowledged that the hospital environment is an important reservoir for many of the pathogenic microbes associated with health care-associated infections (HAIs. Environmental cleaning plays an important role in the prevention and containment of HAIs, in patient safety, and the overall experience of health care facilities. New technologies, such as pulsed xenon ultraviolet (PX-UV light systems are an innovative development for enhanced cleaning and decontamination of hospital environments. A portable PX-UV disinfection device delivers pulsed UV light to destroy microbial pathogens and spores, and can be used in conjunction with manual environmental cleaning. In addition, this technology facilitates thorough disinfection of hospital rooms in 10–15 minutes. The current study was conducted to evaluate whether the introduction of the PX-UV device had a positive impact on patient satisfaction. Satisfaction was measured using the Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS survey. In 2011, prior to the introduction of the PX-UV system, patient HCAHPS scores for cleanliness averaged 75.75%. In the first full quarter after enhanced cleaning of the facility was introduced, this improved to 83%. Overall scores for the hospital rose from 76% (first quarter, 2011 to 87.6% (fourth quarter, 2012. As a result of this improvement, the hospital received 1% of at-risk reimbursement from the inpatient prospective payment system as well as additional funding. Cleanliness of the hospital environment is one of the questions included in the HCAHPS survey and one measure of patient satisfaction. After the introduction of the PX-UV system, the score for cleanliness and the overall rating of the

  3. Hollow-core fibers for high power pulse delivery

    DEFF Research Database (Denmark)

    Michieletto, Mattia; Lyngsø, Jens K.; Jakobsen, Christian

    2016-01-01

    We investigate hollow-core fibers for fiber delivery of high power ultrashort laser pulses. We use numerical techniques to design an anti-resonant hollow-core fiber having one layer of non-touching tubes to determine which structures offer the best optical properties for the delivery of high power...... picosecond pulses. A novel fiber with 7 tubes and a core of 30 mu m was fabricated and it is here described and characterized, showing remarkable low loss, low bend loss, and good mode quality. Its optical properties are compared to both a 10 mu m and a 18 mu m core diameter photonic band gap hollow......-core fiber. The three fibers are characterized experimentally for the delivery of 22 picosecond pulses at 1032nm. We demonstrate flexible, diffraction limited beam delivery with output average powers in excess of 70W. (C) 2016 Optical Society of America...

  4. Technical design study. BESSY VSR. Variable pulse length Storage Ring. Upgrade of BESSY II

    International Nuclear Information System (INIS)

    2015-06-01

    BESSY-VSR is a novel approach to create in the Storage Ring BESSY II long and short photon pulses simultaneously for all beam lines through a pair of superconducting bunch compression cavities. Pulse-picking schemes will allow each individual user to freely switch between high average flux for X-ray spectroscopy, microscopy and scattering and picosecond pulses up to 500 MHz repetition rate for dynamic studies. Thus BESSY-VSR preserves the present average brilliance of BESSY II and adds the new capability of user accessible picosecond pulses at high repetition rate. In addition, high intensities for THz radiation with intrinsic synchronization of THz and X-ray pulses can be extracted from BESSY-VSR. For the scientific challenges of quantum materials for energy, future information technologies and basic energy science BESSY-VSR is the multi-user Synchrotron Radiation facility that allows with the flexible switching between high repetition rate for picosecond dynamics and high average brightness to move classical 3rd generation Synchrotron Radiation science from the observation of static properties and their quantum mechanical description towards the function and the control of materials properties, technologically relevant switching processes and chemical dynamics and kinetics on the picosecond time scale. Strategic relevance of BESSY-VSR for science with photons BESSY-VSR creates for the highly productive Synchrotron Radiation community a uniquely attractive multi user storage ring adding the soft X-ray picosecond dynamics at MHz repetition rate. In particular investigations on reversible dynamics and switching in molecular systems and materials are accessible in a non destructive way. The investigations with X-rays from BESSY-VSR are highly complementary and compatible to dynamic studies conducted by users with optical lasers at their home universities and laboratories. Technologically, the employed superconducting bunch compression cavities in BESSY-VSR are a

  5. Technical design study. BESSY VSR. Variable pulse length Storage Ring. Upgrade of BESSY II

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2015-06-15

    BESSY-VSR is a novel approach to create in the Storage Ring BESSY II long and short photon pulses simultaneously for all beam lines through a pair of superconducting bunch compression cavities. Pulse-picking schemes will allow each individual user to freely switch between high average flux for X-ray spectroscopy, microscopy and scattering and picosecond pulses up to 500 MHz repetition rate for dynamic studies. Thus BESSY-VSR preserves the present average brilliance of BESSY II and adds the new capability of user accessible picosecond pulses at high repetition rate. In addition, high intensities for THz radiation with intrinsic synchronization of THz and X-ray pulses can be extracted from BESSY-VSR. For the scientific challenges of quantum materials for energy, future information technologies and basic energy science BESSY-VSR is the multi-user Synchrotron Radiation facility that allows with the flexible switching between high repetition rate for picosecond dynamics and high average brightness to move classical 3rd generation Synchrotron Radiation science from the observation of static properties and their quantum mechanical description towards the function and the control of materials properties, technologically relevant switching processes and chemical dynamics and kinetics on the picosecond time scale. Strategic relevance of BESSY-VSR for science with photons BESSY-VSR creates for the highly productive Synchrotron Radiation community a uniquely attractive multi user storage ring adding the soft X-ray picosecond dynamics at MHz repetition rate. In particular investigations on reversible dynamics and switching in molecular systems and materials are accessible in a non destructive way. The investigations with X-rays from BESSY-VSR are highly complementary and compatible to dynamic studies conducted by users with optical lasers at their home universities and laboratories. Technologically, the employed superconducting bunch compression cavities in BESSY-VSR are a

  6. UV-Photochemistry of the Disulfide Bond: Evolution of Early Photoproducts from Picosecond X-ray Absorption Spectroscopy at the Sulfur K-Edge.

    Science.gov (United States)

    Ochmann, Miguel; Hussain, Abid; von Ahnen, Inga; Cordones, Amy A; Hong, Kiryong; Lee, Jae Hyuk; Ma, Rory; Adamczyk, Katrin; Kim, Tae Kyu; Schoenlein, Robert W; Vendrell, Oriol; Huse, Nils

    2018-05-30

    We have investigated dimethyl disulfide as the basic moiety for understanding the photochemistry of disulfide bonds, which are central to a broad range of biochemical processes. Picosecond time-resolved X-ray absorption spectroscopy at the sulfur K-edge provides unique element-specific insight into the photochemistry of the disulfide bond initiated by 267 nm femtosecond pulses. We observe a broad but distinct transient induced absorption spectrum which recovers on at least two time scales in the nanosecond range. We employed RASSCF electronic structure calculations to simulate the sulfur-1s transitions of multiple possible chemical species, and identified the methylthiyl and methylperthiyl radicals as the primary reaction products. In addition, we identify disulfur and the CH 2 S thione as the secondary reaction products of the perthiyl radical that are most likely to explain the observed spectral and kinetic signatures of our experiment. Our study underscores the importance of elemental specificity and the potential of time-resolved X-ray spectroscopy to identify short-lived reaction products in complex reaction schemes that underlie the rich photochemistry of disulfide systems.

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

    International Nuclear Information System (INIS)

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

    2004-01-01

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

  8. Photonic integrated circuit as a picosecond pulse timing discriminator.

    Science.gov (United States)

    Lowery, Arthur James; Zhuang, Leimeng

    2016-04-18

    We report the first experimental demonstration of a compact on-chip optical pulse timing discriminator that is able to provide an output voltage proportional to the relative timing of two 60-ps input pulses on separate paths. The output voltage is intrinsically low-pass-filtered, so the discriminator forms an interface between high-speed optics and low-speed electronics. Potential applications include timing synchronization of multiple pulse trains as a precursor for optical time-division multiplexing, and compact rangefinders with millimeter dimensions.

  9. 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...

  10. A rotationally symmetric electron beam chopper for picosecond pulses

    International Nuclear Information System (INIS)

    Oldfield, L.C.

    1976-01-01

    The chopper was designed for dynamic electron optical experiments where it is necessary to provide pulses of high quality with respect to both width and energy spread. The chopping action relies on the optical properties of a microwave cavity; these are exploited such that the time dependent space focusing causes a small circular aperture on the axis of rotational symmetry to transmit strongly for a single band of phase angles in each cycle of the excitation. Unless the pulses are to be used near the aperture plane, an 'energy correcting' cavity that operates in phase synchronism with the chopper is added to the system. The theoretical treatment is oriented towards computer display, and is novel in that it follows the progress of individual electron packets throughout the system. In contrast to conventional chopping and bunching theory, it is possible to analyse with ease the pulsing properties of a multicavity device. For a typical two-cavity design the pulse quality may range from 10 0 width and negligible energy spread, to 0.25% energy spread and negligible pulse width, depending on the second cavity excitation; in either situation 7.5% of the original steady beam is transmitted. (author)

  11. Sweep devices for picosecond image-converter streak cameras

    International Nuclear Information System (INIS)

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

    1979-01-01

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

  12. Picosecond multiphoton ionization of atomic and molecular clusters

    International Nuclear Information System (INIS)

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

    1990-01-01

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

  13. Avalanche mode of high-voltage overloaded p+–i–n+ diode switching to the conductive state by pulsed illumination

    International Nuclear Information System (INIS)

    Kyuregyan, A. S.

    2015-01-01

    A simple analytical theory of the picosecond switching of high-voltage overloaded p + –i–n + photodiodes to the conductive state by pulsed illumination is presented. The relations between the parameters of structure, light pulse, external circuit, and main process characteristics, i.e., the amplitude of the active load current pulse, delay time, and switching duration, are derived and confirmed by numerical simulation. It is shown that the picosecond light pulse energy required for efficient switching can be decreased by 6–7 orders of magnitude due to the intense avalanche multiplication of electrons and holes. This offers the possibility of using pulsed semiconductor lasers as a control element of optron pairs

  14. Influence of picosecond pulse electric field to invasive ability of cervical cancer

    Directory of Open Access Journals (Sweden)

    Li-mei WU

    2015-10-01

    Full Text Available Objective To investigate the influence of picosecond pulse electric field (psPEF to the invasive ability of cervical cancer. Methods The model of cervical cancer was reproduced in BALB/c nude mice (n=24, and they were randomly divided into four groups (n=6 when the xenografts had grown reaching a diameter of 0.8-1.0cm: control group (psPEF was not given, low field intensity group (50kV/cm, moderate field intensity group (60kV/cm and high field intensity group (70kV/cm. Seven days after the psPEF treatment, the histomorphological changes were observed with HE staining and transmission electron microscopy (TEM, the expressions of vascular endothelial growth factor (VEGF and matrix metalloproteinases-9 (MMP-9 were determined with immunohistochemical (IHC staining, and the changes in protein level of VEGF and MMP-9 were assessed with Western blotting. Results After psPEF treatment, the area of necrosis was found to be increased with an increase in psPEF intensity. With TEM different degrees of apoptosis and necrosis in tumor cells with an increase of psPEF intensity were found. IHC showed that the number of VEGF and MMP-9 positive cells in cancer tissue was decreased with an increase in psPEF intensity. The average optical density (AOD of VEGF and MMP-9 proteins decreased significantly in psPEF treatment groups compared with that in control group, and the AOD values in psPEF treatment groups decreased with an increase in psPEF intensity, and the decrease was statistically significant (P<0.05. Western blotting showed the expressive levels of VEGF and MMP-9 proteins declined gradually with an increase in psPEF intensity, and the difference between groups was statistically significant (P<0.05. Conclusion psPEF may have anti-cervical cancer effects by inhibiting the secretion of VEGF and MMP-9 and reducing the invasive ability of cervical cancer cells. DOI: 10.11855/j.issn.0577-7402.2015.09.03

  15. Modulated pumping in Cs with picosecond pulse trains

    International Nuclear Information System (INIS)

    Lehmitz, H.; Harde, H.; Kattau, W.

    1986-01-01

    Two different experimental arrangements were used for periodic excitation detection of coherence. Cs vapor in a gas cell was resonantly excited on the D 2 line by a train of ultrashort light pulses of circular polarization. To reduce transit-time broadening, additional buffer gas was contained in the cell and the light beam from a laser was expanded to a cross section of about 1.5 cm 2 . The resulting atomic coherence amplitude which was due to the periodic excitation of atoms could then be measured by different means. The experimental set-up is shown which takes advantage of the fact that atomic coherence gives rise to an oscillating optical anisotropy in the sample. The atomic splitting is measured by the 9th harmonic of the injection laser pulse rate with a width of less than 50 Hz. The experiments demonstrate the ultrahigh frequency resolution is possible with optical pulse train interference spectroscopy which allows one to sensitively detect small pressure shifts in the hyperfine frequency caused by buffer gases in the gas cell

  16. 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

  17. Disinfection and toxicological assessments of pulsed UV and pulsed-plasma gas-discharge treated-water containing the waterborne protozoan enteroparasite Cryptosporidium parvum.

    Science.gov (United States)

    Hayes, Jennifer; Kirf, Dominik; Garvey, Mary; Rowan, Neil

    2013-09-01

    We report for the first time on the comparative use of pulsed-plasma gas-discharge (PPGD) and pulsed UV light (PUV) for the novel destruction of the waterborne enteroparasite Cryptosporidium parvum. It also describes the first cyto-, geno- and ecotoxicological assays undertaken to assess the safety of water decontaminated using PPGD and PUV. During PPGD treatments, the application of high voltage pulses (16 kV, 10 pps) to gas-injected water (N2 or O2, flow rate 2.5L/min) resulted in the formation of a plasma that generated free radicals, ultraviolet light, acoustic shock waves and electric fields that killed ca. 4 log C. parvum oocysts in 32 min exposure. Findings showed that PPGD-treated water produced significant cytotoxic properties (as determined by MTT and neutral red assays), genotoxic properties (as determined by comet and Ames assays), and ecotoxic properties (as determined by Microtox™, Thamnotox™ and Daphnotox™ assays) that are representative of different trophic levels in aquatic environment (pozone (0.8 mg/L) and/or dissociated nitric and nitrous acid that contributed to the observed disinfection and toxicity. Chemical analysis of PPGD-treated water revealed increasing levels of electrode metals that were present at ≤ 30 times the tolerated respective values for EU drinking water. PUV-treated water did not exhibit any toxicity and was shown to be far superior to that of PPGD for killing C. parvum oocysts taking only 90 s of pulsing [UV dose of 6.29 μJ/cm(2)] to produce a 4-log reduction compared to a similar reduction level achieved after 32min PPGD treatment as determined by combined in vitro CaCo-2 cell culture-qPCR. © 2013. Published by Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

    Mourou, G.; Williamson, S.

    1985-01-01

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

  19. Picosecond absorption relaxation measured with nanosecond laser photoacoustics

    OpenAIRE

    Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin; Wang, Lihong V.

    2010-01-01

    Picosecond absorption relaxation—central to many disciplines—is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, b...

  20. A sub-picosecond pulsed 5 MeV electron beam system

    International Nuclear Information System (INIS)

    Farrell, J. Paul; Batchelor, K.; Meshkovsky, I.; Pavlishin, I.; Lekomtsev, V.; Dyublov, A.; Inochkin, M.; Srinivasan-Rao, T.

    2001-01-01

    Laser excited pulsed, electron beam systems that operate at energies from 1 MeV up to 5 MeV and pulse width from 0.1 to 100 ps are described. The systems consist of a high voltage pulser and a coaxial laser triggered gas or liquid spark gap. The spark gap discharges into a pulse forming line designed to produce and maintain a flat voltage pulse for 1 ns duration on the cathode of a photodiode. A synchronized laser is used to illuminate the photocathode with a laser pulse to produce an electron beam with very high brightness, short duration, and current at or near the space charge limit. Operation of the system is described and preliminary test measurements of voltages, synchronization, and jitter are presented for a 5 MeV system. Applications in chemistry, and accelerator research are briefly discussed

  1. 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

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

    Science.gov (United States)

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

    2018-02-28

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

  3. 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....

  4. Fabrication of sub-micron surface structures on copper, stainless steel and titanium using picosecond laser interference patterning

    Energy Technology Data Exchange (ETDEWEB)

    Bieda, Matthias, E-mail: matthias.bieda@iws.fraunhofer.de [Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Winterbergstr. 28, 01277 Dresden (Germany); Siebold, Mathias, E-mail: m.siebold@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstr. 400, 01328 Dresden (Germany); Lasagni, Andrés Fabián, E-mail: andres_fabian.lasagni@tu-dresden.de [Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Winterbergstr. 28, 01277 Dresden (Germany); Technische Universität Dresden, Institut für Fertigungstechnik, 01062 Dresden (Germany)

    2016-11-30

    Highlights: • Laser interference patterning is introduced to generate sub-micrometer surface pattern. • The two-temperature model is applied to ps-laser interference patterning of metals. • Line-like structures with a pitch of 0.7 μm were fabricated on SAE 304, Ti and Cu. • The process is governed by a photo-thermal mechanism for a pulse duration of 35 ps. • A “cold”-ablation process for metals requires a pulse duration shorter than 10 ps. - Abstract: Picosecond direct laser interference patterning (ps-DLIP) is investigated theoretically and experimentally for the bulk metals copper, stainless steel and titanium. While surface texturing with nanosecond pulses is limited to feature sizes in the micrometer range, utilizing picosecond pulses can lead to sub-micrometer structures. The modelling and simulation of ps-DLIP are based on the two-temperature model and were carried out for a pulse duration of 35 ps at 515 nm wavelength and a laser fluence of 0.1 J/cm{sup 2}. The subsurface temperature distribution of both electrons and phonons was computed for periodic line-like structures with a pitch of 0.8 μm. The increase in temperature rises for a lower absorption coefficient and a higher thermal conductivity. The distance, at which the maximum subsurface temperature occurs, increases for a small absorption coefficient. High absorption and low thermal conductivity minimize internal heating and give rise to a pronounced surface micro topography with pitches smaller than 1 μm. In order to confirm the computed results, periodic line-like surface structures were produced using two interfering beams of a Yb:YAG-Laser with 515 nm wavelength and a pulse duration of 35 ps. It was possible to obtain a pitch of 0.7 μm on the metallic surfaces.

  5. 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

  6. Avalanche mode of high-voltage overloaded p{sup +}–i–n{sup +} diode switching to the conductive state by pulsed illumination

    Energy Technology Data Exchange (ETDEWEB)

    Kyuregyan, A. S., E-mail: ask@vei.ru [Lenin All-Russia Electrical Engineering Institute (Russian Federation)

    2015-07-15

    A simple analytical theory of the picosecond switching of high-voltage overloaded p{sup +}–i–n{sup +} photodiodes to the conductive state by pulsed illumination is presented. The relations between the parameters of structure, light pulse, external circuit, and main process characteristics, i.e., the amplitude of the active load current pulse, delay time, and switching duration, are derived and confirmed by numerical simulation. It is shown that the picosecond light pulse energy required for efficient switching can be decreased by 6–7 orders of magnitude due to the intense avalanche multiplication of electrons and holes. This offers the possibility of using pulsed semiconductor lasers as a control element of optron pairs.

  7. GaN thin films growth and their application in photocatalytic removal of sulforhodamine B from aqueous solution under UV pulsed laser irradiation.

    Science.gov (United States)

    Gondal, Mohammed A; Chang, Xiao F; Yamani, Zain H; Yang, Guo F; Ji, Guang B

    2011-01-01

    Single-crystalline Gallium Nitride (GaN) thin films were fabricated and grown by metal organic chemical vapor deposition (MOCVD) method on c-plane sapphire substrates and then characterized by high resolution-X-ray diffraction (HR-XRD) and photoluminescence (PL) measurements. The photocatalytic decomposition of Sulforhodamine B (SRB) molecules on GaN thin films was investigated under 355 nm pulsed UV laser irradiation. The results demonstrate that as-grown GaN thin films exhibited efficient degradation of SRB molecules and exhibited an excellent photocatalytic-activity-stability under UV pulsed laser exposure.

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

    International Nuclear Information System (INIS)

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

    2000-01-01

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

  9. Bunch-shape monitor for a picosecond single-bunch beam of a 35 MeV electron linear accelerator

    International Nuclear Information System (INIS)

    Hosono, Yoneichi; Nakazawa, Masaharu; Iguchi, Tetsuo

    1995-01-01

    A non-interactive-type bunch-shape and beam intensity monitor for a 35 MeV electron linear accelerator (linac) has been developed. The monitor consists of an electric SMA-type connector and an Al pipe of 50 mm inner diameter. Test measurements of the present monitor have been made under the conditions of the accelerated charges of lower than 27 nC/pulse and the pulse width ranging from 6 to 30 ps (Full Width at Half Maximum). The results show that the present monitor is applicable to bunch-shape measurement of the picosecond single-bunch beam. The monitor output is also found to be proportional to the beam intensity of more than 0.05 nC/pulse. (author)

  10. Picosecond electron bunches from GaAs/GaAsP strained superlattice photocathode

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  11. NATO Advanced Research Workshop on Applications of Picosecond Spectroscopy to Chemistry

    CERN Document Server

    1984-01-01

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

  12. Upconversion imaging using short-wave infrared picosecond pulses

    DEFF Research Database (Denmark)

    Mathez, Morgan David; Rodrigo, Peter John; Tidemand-Lichtenberg, Peter

    2017-01-01

    beam diameter to upconvert a wider range of signal spatial frequencies in the crystal. The 1877 nm signal is converted into 849 nm—enabling an image to be acquired by a silicon CCD camera. The measured size of the smallest resolvable element of this imaging system is consistent with the value predicted...... repetition rate of 21.7 MHz. Due to synchronization of high peak-power pulses, efficient upconversion is achieved in a single-pass setup that employs a bulk lithium niobate crystal. Optimizing the temporal overlap of the pulses for high upconversion efficiency enables us to exploit a relatively large pump...... by an improved model that considers the combined image blurring effect due to finite pump beam size, thick nonlinear crystal, and polychromatic infrared illumination....

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

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, Timothy John [Northern Illinois U.

    2012-01-01

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

  14. Generation of fast-rise time, repetitive, (sub) nanosecond, high-voltage pulses

    NARCIS (Netherlands)

    Huiskamp, T.; Pemen, A.J.M.

    2017-01-01

    In this contribution we present our fast-rise time nanosecond pulse generator, capable of generating up to 50 kV (positive and negative) rectangular pulses at a repetition rate of up to 1 kHz and with a rise time of less than 200 picoseconds. We focus on the general concepts involved in the design

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

    Science.gov (United States)

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

    1990-01-01

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

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

    Directory of Open Access Journals (Sweden)

    James Trolinger

    2011-12-01

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

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

    International Nuclear Information System (INIS)

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

    1991-01-01

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

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

    International Nuclear Information System (INIS)

    Nilsen, J.

    1997-01-01

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

  19. Picosecond pulse radiolysis studies on geminate ion recombination in saturated hydrocarbon

    International Nuclear Information System (INIS)

    Tagawa, S.; Washio, M.; Kobayashi, H.; Katsumura, Y.; Tabata, Y.

    1983-01-01

    The geminate recombination kinetics of the excess electron and the electron hole are discussed, based on time-resolved data on picosecond and nanosecond time scales. The recombination times of the excess electron and the electron hole are evaluated to be 3 ps for cyclohexane on the basis of the comparison between the experimental and the calculated results. The spin correlation decay of the geminate ion pairs and the triplet state formation before the spin correlation loss have also been discussed. The rapidly decaying species with very broad absorption spectra, which are similar to the absorption spectra of the cation radicals of saturated hydrocarbons, have been observed in neat saturated hydrocarbons in the sub-nanosecond and a few nanosecond time regions. The identification of the rapidly decaying species were not definitely made but those species are tentatively assigned to the excited states and/or the tail of the geminate cation radicals of saturated hydrocarbons. (author)

  20. Characterestics of pico-second single bunch at the S-band linear accelerator

    International Nuclear Information System (INIS)

    Uesaka, Mitsuru; Kozawa, Takahiro; Kobayashi, Toshiaki; Ueda, Toru; Miya, Kenzo

    1994-01-01

    Measurement of the bunch structure of a pico-second single bunch was performed using a femto-second streak camera at the S-band linear accelerator of the University of Tokyo. The aim of this research is to investigate the feasibility of the generation of a femto-second single bunch at the S-band linac. The details of the bunch structure and energy spectrum of an original single bunch were precisely investigated in several operation modes where the RF phases in accelerating tubes and a prebuncher were varied. The femto-second streak camera was utilized to measure the bunch structure by one shot via Cherenkov radiation emitted by the electrons in the bunch. Next, an experiment for magnetic pulse compression of the original single bunch was carried out. Pulse shapes of the compressed bunchs for different energy modulation were also obtained by measuring Cherenkov radiation by one shot using the femto-second streak camera. Prior to the experiment, numerical tracking analysis to determine operating parameters for the magnetic pulse compression was also done. Measured pulse widths were compared with calculated ones. Finally, a 2 ps (full width at half maximum; FWHM) single bunch with an electric charge of 0.3 nC could be generated by the magnetic pulse compression. ((orig.))

  1. Studies of the mechanical properties of planar and patterned films with picosecond ultrasonics

    Science.gov (United States)

    Antonelli, George Andrew

    We describe a series of investigations of the mechanical properties of thin films and nanostructures. The experiments were performed with picosecond ultrasonics. In this method, sub-picosecond optical pulses are used to excite and detect acoustic phenomena. Several variations of the conventional experimental apparatus were developed and will be described. In the first study, we endeavor to analyze the vibrations of a nanostructure. From measurements of the change in the reflectivity, it is possible to determine the frequencies nun and damping rates Gamma n of a number of the normal modes of the structure. To understand the nature of these vibrations we developed a coarse-grained molecular dynamics model. By comparison of the measured nun and Gamma n with the frequencies and damping rates calculated from the computer simulation, we have been able to identify different normal modes and deduce their vibration patterns. We have also developed a new technique allowing the measurement of the transit time of an acoustic pulse in a thin film with great accuracy. This technique was applied to the study of elastic and anelastic effects in thin metal films. A strain was induced in the film either by heating the film-substrate system or bending the substrate. From measurements of these samples, we were able to extract a certain combination of second- and third-order elastic constants and detect the onset of plastic flow in the metal film. Finally, we describe a technique that can be used to generate high frequency surface waves. A transmission diffraction grating is formed on a transparent wafer, and then placed very close to the surface of the sample. A light pulse passing through the grating will give rise to a spatially-varying light intensity on the sample. This sets up a periodic thermal stress on the sample surface which in turn generates a standing surface acoustic wave.

  2. The wavelength dependence of gold nanorod-mediated optical breakdown during infrared ultrashort pulses

    Energy Technology Data Exchange (ETDEWEB)

    Davletshin, Yevgeniy R.; Kumaradas, J. Carl [Department of Physics, Ryerson University, Toronto, ON (Canada)

    2017-04-15

    This paper investigates the wavelength dependence of the threshold of gold nanorod-mediated optical breakdown during picosecond and femtosecond near infrared optical pulses. It was found that the wavelength dependence in the picosecond regime is governed solely by the changes of a nanorod's optical properties. On the other hand, the optical breakdown threshold during femtosecond pulse exposure falls within one of two regimes. When the ratio of the maximum electric field from the outside to the inside of the nanorod is less then 7 (the absorption regime) the seed electrons are initiated by photo-thermal emission, and the wavelength dependence in the threshold of optical breakdown is the result of optical properties of the nanoparticle. When the ratio is greater than 7 (the near-field regime) more seed electrons are initiated by multiphoton ionization, and the wavelength dependence of the threshold of optical breakdown results from a combination of nanorod's optical properties and transitions in the order of multiphoton ionization. The findings of this study can guide the design of nanoparticle based optical breakdown applications. This analysis also deepens the understanding of nanoparticle-mediated laser induced breakdown for picosecond and femtosecond pulses at near infrared wavelengths. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

    International Nuclear Information System (INIS)

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

    1994-01-01

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

  4. X-Ray Scattering Applications Using Pulsed X-Ray Sources

    Energy Technology Data Exchange (ETDEWEB)

    Larson, B.C.

    1999-05-23

    Pulsed x-ray sources have been used in transient structural phenomena investigations for over fifty years; however, until the advent of synchrotrons sources and the development of table-top picosecond lasers, general access to ligh temporal resolution x-ray diffraction was relatively limited. Advances in diffraction techniques, sample excitation schemes, and detector systems, in addition to IncEased access to pulsed sources, have ld tO what is now a diverse and growing array of pulsed-source measurement applications. A survey of time-resolved investigations using pulsed x-ray sources is presented and research opportunities using both present and planned pulsed x-ray sources are discussed.

  5. Picosecond absorption relaxation measured with nanosecond laser photoacoustics.

    Science.gov (United States)

    Danielli, Amos; Favazza, Christopher P; Maslov, Konstantin; Wang, Lihong V

    2010-10-18

    Picosecond absorption relaxation-central to many disciplines-is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, were measured at 576 nm. The added advantages in dispersion susceptibility, laser-wavelength availability, reflection sensing, and expense foster the study of natural-including strongly scattering and nonfluorescent-materials.

  6. Pulse radiolysis - new approaches to the classical technique

    Energy Technology Data Exchange (ETDEWEB)

    Zagorski, Z P [Institute of Nuclear Research, Warsaw (Poland)

    1973-01-01

    The present status of classical pulse radiolysis is described as well as trends in the further development of this technique (the investigation of radiolysis with nano- and picoseconds time resolution, new optica and electrochemical methods of intermediate species detection). The attention is concentrated on experimental difficulties of particular versions and the achievements are reviewed critically. This paper is the background for experiments being performed in the Institute of Nuclear Research on new techniques of pulse radiolysis.

  7. Short pulse mid-infrared amplifier for high average power

    CSIR Research Space (South Africa)

    Botha, LR

    2006-09-01

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

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

    Science.gov (United States)

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

    2018-03-01

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

  9. Dynamic characterization and amplification of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Rishøj, Lars Søgaard

    2013-01-01

    We show a first-time demonstration of amplification of 400 fs pulses in a fiber optical parametric amplifier. The 400 fs signal is stretched in time, amplified by 26 dB and compressed back to 500 fs. A significant broadening of the pulses is experimentally shown due to dispersion and limited gain...

  10. Chirped pulse amplification: Present and future

    International Nuclear Information System (INIS)

    Maine, P.; Strickland, D.; Pessot, M.; Squier, J.; Bado, P.; Mourou, G.; Harter, D.

    1988-01-01

    Short pulses with ultrahigh peak powers have been generated in Nd: glass and Alexandrite using the Chirped Pulse Amplification (CPA) technique. This technique has been successful in producing picosecond terawatt pulses with a table-top laser system. In the near future, CPA will be applied to large laser systems such as NOVA to produce petawatt pulses (1 kJ in a 1 ps pulse) with focused intensities exceeding 10/sup /plus/21/ W/cm 2 . These pulses will be associated with electric fields in excess of 100 e/a/sub o/ 2 and blackbody energy densities equivalent to 3 /times/ 10 10 J/cm 3 . This petawatt source will have important applications in x-ray laser research and will lead to fundamentally new experiments in atomic, nuclear, solid-state, plasma, and high-energy density physics. A review of present and future designs are discussed. 17 refs., 5 figs

  11. Dynamical equations and transport coefficients for the metals at high pulse electromagnetic fields

    International Nuclear Information System (INIS)

    Volkov, N B; Chingina, E A; Yalovets, A P

    2016-01-01

    We offer a metal model suitable for the description of fast electrophysical processes in conductors under influence of powerful electronic and laser radiation of femto- and picosecond duration, and also high-voltage electromagnetic pulses with picosecond front and duration less than 1 ns. The obtained dynamic equations for metal in approximation of one quasineutral liquid are in agreement with the equations received by other authors formerly. New wide-range expressions for the electronic conduction in strong electromagnetic fields are obtained and analyzed. (paper)

  12. Electro-optic sampling of THz pulses at the CTR source at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Wunderlich, Steffen

    2012-06-15

    Several applications in material science, non-linear optics and solid-state physics require short pulses with a high pulse energy of radiation in the far-infrared and in the terahertz (THz) regime in particular. As described in the following, coherent transition radiation generated by high-relativistic electron bunches at FLASH provides broadband single-cycle pulses of sub-picosecond length. The pulses are characterized using the quantitative and time-resolved technique of electro-optic sampling showing peak field strengths in the order of 1 MV/cm.

  13. Electro-optic sampling of THz pulses at the CTR source at FLASH

    International Nuclear Information System (INIS)

    Wunderlich, Steffen

    2012-06-01

    Several applications in material science, non-linear optics and solid-state physics require short pulses with a high pulse energy of radiation in the far-infrared and in the terahertz (THz) regime in particular. As described in the following, coherent transition radiation generated by high-relativistic electron bunches at FLASH provides broadband single-cycle pulses of sub-picosecond length. The pulses are characterized using the quantitative and time-resolved technique of electro-optic sampling showing peak field strengths in the order of 1 MV/cm.

  14. Formation of low time-bandwidth product, single-sided exponential optical pulses in free-electron laser oscillators

    NARCIS (Netherlands)

    MacLeod, A. M.; Yan, X.; Gillespie, W. A.; Knippels, G.M.H.; Oepts, D.; van der Meer, A. F. G.; Rella, C. W.; Smith, T. J.; Schwettman, H. A.

    2000-01-01

    The detailed shape of picosecond optical pulses from a free-electron laser (FEL) oscillator has been studied for various cavity detunings. For large values of the cavity detuning the optical pulse develops an exponential leading edge, with a time constant proportional to the applied cavity detuning

  15. DURATION LIMIT OF LASER PULSES EMITTED FROM A Ce-DOPED CRYSTAL SHORT CAVITY

    Directory of Open Access Journals (Sweden)

    Le Hoang Hai

    2017-11-01

    Full Text Available Based on the rate equation set for broadband cavities, the dependence of pulse duration on cavity and pumping parameters is analyzed. The cavity uses a Ce-doped crystal as a gain medium. Computation results show the variation of the pulse width with the change of cavity length, mirror reflectivity, pumping energy and pumping pulse duration. A significant influence of multiple-pulse operation in limiting pulse duration is realized and a pulse-width of the order 200 ps is found to be the limit for the direct generation of ultraviolet single picosecond pulses from a Ce:LLF short cavity.

  16. 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.

  17. Making ultracold molecules in a two color pump-dump photoassociation scheme using chirped pulses

    OpenAIRE

    Koch, Christiane P.; Luc-Koenig, Eliane; Masnou-Seeuws, Françoise

    2005-01-01

    This theoretical paper investigates the formation of ground state molecules from ultracold cesium atoms in a two-color scheme. Following previous work on photoassociation with chirped picosecond pulses [Luc-Koenig et al., Phys. Rev. A {\\bf 70}, 033414 (2004)], we investigate stabilization by a second (dump) pulse. By appropriately choosing the dump pulse parameters and time delay with respect to the photoassociation pulse, we show that a large number of deeply bound molecules are created in t...

  18. Picosecond radiolysis of ionic liquids

    International Nuclear Information System (INIS)

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

    2003-01-01

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

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

    International Nuclear Information System (INIS)

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

    2017-01-01

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

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

    Science.gov (United States)

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

    2011-08-01

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

  1. Repetitively pulsed UV radiation source based on a run-away electron preionised diffuse discharge in nitrogen

    Science.gov (United States)

    Baksht, E. Kh; Burachenko, A. G.; Lomaev, M. I.; Panchenko, A. N.; Tarasenko, V. F.

    2015-04-01

    An extended repetitively pulsed source of spontaneous UV radiation is fabricated, which may also be used for producing laser radiation. Voltage pulses with an incident wave amplitude of up to 30 kV, a half-amplitude duration of ~4 ns and a rise time of ~2.5 ns are applied to a gap with a nonuniform electric field. For an excitation region length of 35 cm and a nitrogen pressure of 30 - 760 Torr, a diffusive discharge up to a pulse repetition rate of 2 kHz is produced without using an additional system for gap preionisation. An investigation is made of the plasma of the run-away electron preionised diffuse discharge. Using a CCD camera it is found that the dense diffused plasma fills the gap in a time shorter than 1 ns. X-ray radiation is recorded from behind the foil anode throughout the pressure range under study; a supershort avalanche electron beam is recorded by the collector electrode at pressures below 100 Torr.

  2. UV laser-induced cross-linking in peptides

    Science.gov (United States)

    Leo, Gabriella; Altucci, Carlo; Bourgoin-Voillard, Sandrine; Gravagnuolo, Alfredo M.; Esposito, Rosario; Marino, Gennaro; Costello, Catherine E.; Velotta, Raffaele; Birolo, Leila

    2013-01-01

    RATIONALE The aim of this study was to demonstrate, and to characterize by high resolution mass spectrometry, that it is possible to preferentially induce covalent cross-links in peptides by using high energy femtosecond UV laser pulses. The cross-link is readily formed only when aromatic amino acids are present in the peptide sequence. METHODS Three peptides, xenopsin, angiotensin I, interleukin, individually or in combination, were exposed to high energy femtosecond UV laser pulses, either alone or in the presence of spin trapping molecules, the reaction products being characterized by high resolution mass spectrometry. RESULTS High resolution mass spectrometry and spin trapping strategies showed that cross-linking occurs readily, proceeds via a radical mechanism, and is the highly dominant reaction, proceeding without causing significant photo-damage in the investigated range of experimental parameters. CONCLUSIONS High energy femtosecond UV laser pulses can be used to induce covalent cross-links between aromatic amino acids in peptides, overcoming photo-oxidation processes, that predominate as the mean laser pulse intensity approaches illumination conditions achievable with conventional UV light sources. PMID:23754800

  3. A UV pre-ionized dual-wavelength short-pulse high-power CO{sub 2} laser facility for laser particle acceleration research

    Energy Technology Data Exchange (ETDEWEB)

    Ebrahim, N A; Mouris, J F; Davis, R W

    1994-12-01

    In this report we describe the Chalk River dual-wavelength, short-pulse, single-mode, high-power CO{sub 2} laser facility for research in laser particle acceleration and CANDU materials modifications. The facility is designed and built around UV-preionized transversely-excited atmospheric-pressure (TEA) Lumonics CO{sub 2} laser discharge modules. Peak focussed power densities of up to 2 x 10{sup 14} W/cm{sup 2} in 500 ps pulses have been obtained. (author). 10 refs., 9 figs.

  4. Proposed ultraviolet free-electron laser at Brookhaven National Laboratory: A source for time-resolved biochemical spectroscopy

    International Nuclear Information System (INIS)

    Johnson, E.D.; Sutherland, J.C.; Laws, W.R.

    1992-01-01

    Brookhaven National Laboratory is designing an ultraviolet free- electron laser (UV-FEL) user facility that will provide pico-second and sub-picosecond pulses of coherent ultraviolet radiation for wavelengths from 300 to 75 nm. Pulse width will be variable from abut 7 ps to ∼ 200 fs, with repetition rates as high as 10 4 Hz, single pulse energies > 1 mJ and hence peak pulse power >200 MW and average beam power > 10 W. The facility will be capable of ''pump-probe'' experiments utilizing the FEL radiation with: (1) synchronized auxiliary lasers, (2) a second, independently tunable FEL beam, or (3) broad-spectrum, high-intensity x-rays from the adjacent National Synchrotron Light Source. The UV-FEL consists of a high repetition rate recirculating superconducting linear accelerator which feeds pulses of electrons to two magnetic wigglers. Within these two devices, photons from tunable ''conventional'' laser would be frequency multiplied and amplified. By synchronously tuning the seed laser and modulating the energy of the electron beam, tuning of as much as 60% in wavelength is possible between alternating pulses supplied to different experimental stations, with Fourier transform limited resolution. Thus, up to four independent experiments may operate at one time, each with independent control of the wavelength and pulse duration. The UV-FEL will make possible new avenues of inquiry in time studies of diverse field including chemical, surface, and solid state physics, biology and materials science. The experimental area is scheduled to include a station dedicated to biological research. The complement of experimental and support facilities required by the biology station will be determined by the interests of the user community. 7 refs., 5 figs

  5. 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

  6. 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...

  7. Spatio-temporal imaging of voltage pulses with an ultrafast scanning tunneling microscope

    DEFF Research Database (Denmark)

    Jensen, Jacob Riis; Keil, Ulrich Dieter Felix; Hvam, Jørn Märcher

    1997-01-01

    Measurements on an ultrafast scanning tunneling microscope with simultaneous spatial and temporal resolution are presented. We show images of picosecond pulses propagating on a coplanar waveguide and resolve their mode structures. The influence of transmission line discontinuities on the mode...

  8. The effects of a picosecond pulsed electric field on angiogenesis in the cervical cancer xenograft models.

    Science.gov (United States)

    Wu, Limei; Yao, Chenguo; Xiong, Zhengai; Zhang, Ruizhe; Wang, Zhiliang; Wu, Yutong; Qin, Qin; Hua, Yuanyuan

    2016-04-01

    The application of picosecond pulsed electric field (psPEF) is a new biomedical engineering technique used in cancer therapy. However, its effects on cervical cancer angiogenesis are not clear. Therefore, the aim of the present study is to investigate the effects of psPEF on angiogenesis in cervical cancer xenograft models. Xenograft tumors were created by subcutaneously inoculating nude mice (athymic BALB/c nu/nu mice) with HeLa cells, then were placed closely between tweezer-type plate electrodes and subjected to psPEF with a gradually increased electric field intensity (0kV/cm, 50kV/cm, 60kV/cm, 70kV/cm). The direct effect on tumor tissue was observed by hematoxylin and eosin (H&E) staining and transmission electron microscopy (TEM). The changes of blood vessels and oxygen saturation (sO2) of tumors were monitored in vivo by photoacoustic tomography (PAT). The microvessel density (MVD), vascular endothelial growth factor (VEGF) and hypoxia-inducible transcription factors (HIF-1α and HIF-2α) were detected by immunohistochemical technique (IHC). Their protein expressions and gene transcription levels were evaluated using western blot (WB) and quantitative reverse transcription and polymerase chain reaction (RT-PCR). PsPEF induced obvious necrosis of cervical cancer tissue; with the increasing of electric field intensity, the MVD, vascular PA signal and sO2 values declined significantly. The protein expression and gene transcription levels of VEGF, HIF1α and HIF2α were significantly decreased at the same time. PsPEF exhibited dramatic anti-tumor and anti-angiogenesis effects in cervical cancer xenograft models by exerting direct effect on cancer cells and vascular endothelial cells and indirect effect on tumor angiogenesis-related factors. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. UV photoemission from metal cathodes for picosecond power switches

    International Nuclear Information System (INIS)

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

    1989-01-01

    Results are reported of photoemission studies using laser pulses of 10 ps duration and 4.66 eV photon energy on metal cathodes. These included thin wires, flat surfaces and an yttrium cathode with a grainy surface. The measurements of current density and quantum efficiency under low and high surface fields indicate that field assisted efficiencies exceeding 0.1% and current densities exceeding 10 5 A/cm 2 are obtainable. The results are compared to the requirements of switch power applications. 24 refs., 13 figs., 1 tab

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

    International Nuclear Information System (INIS)

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

    2012-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-07-09

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

  12. Yb-fiber-pumped mid-infrared picosecond optical parametric oscillator tunable across 6.2-6.7 µm

    Science.gov (United States)

    Kumar, S. Chaitanya; Casals, J. Canals; Parsa, S.; Zawilski, K. T.; Schunemann, P. G.; Ebrahim-Zadeh, M.

    2018-06-01

    We report a high-average-power picosecond optical parametric oscillator (OPO) tunable in the mid-infrared (mid-IR) based on CdSiP2 synchronously pumped by an Yb-fiber laser at 80 MHz repetition rate. Successful operation of this high-repetition-rate singly-resonant picosecond OPO has been enabled by the improved CSP crystal quality over a long interaction length. The OPO can be tuned across 1264-1284 nm in the near-IR signal and 6205-6724 nm in the mid-IR idler by temperature tuning the CSP crystal over 39-134 °C. By deploying a 5% output coupler for the resonant signal, we have extracted up to 44 mW of average power in the near-IR and up to 95 mW of non-resonant idler power at 6205 nm at 6.3% total conversion efficiency, with > 50 mW over > 55% of the mid-IR tuning range. We have investigated temperature-tuning characteristics of the OPO and compared the data with the theoretical calculations using the recent Sellmeier and thermo-optic coefficients for CdSiP2. The signal pulses from the OPO exhibit a Gaussian pulse duration of 19 ps centered at 1284 nm. We have also studied the output power stability of the OPO, resulting in a passive stability better than 1.9% rms for the near-IR signal and 2.4% rms for the mid-IR idler, measured over > 17 h, with both beams in high spatial quality.

  13. 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.

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

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  15. Subpicosecond pulse radiolysis in liquid methyl-substituted benzene derivatives

    International Nuclear Information System (INIS)

    Okamoto, Kazumasa; Kozawa, Takahiro; Saeki, Akinori; Yoshida, Yoichi; Tagawa, Seiichi

    2007-01-01

    The early processes of radiation chemistry in the picosecond time region in methyl-substituted benzene derivatives have been investigated using subpicosecond pulse radiolysis. In o-xylene, a fairly slow geminate ion recombination was observed within 50 ps after the electron beam irradiation; this is due to the smaller electron mobility. The kinetic traces were analyzed using the Smoluchowski equation with exponential and modified-Gaussian (YGP) functions as the distribution of thermalized electrons. Only exponential functions well reproduced the experimental data within 50 ps after the electron pulse

  16. Quantum coherent π-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

    Science.gov (United States)

    Mineo, Hirobumi; Fujimura, Yuichi

    2015-06-01

    We propose an ultrafast quantum switching method of π-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent π-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent π-electron ring current, and discussed ring current transfer between two aromatic rings.

  17. Development of optical parametric chirped-pulse amplifiers and their applications

    Energy Technology Data Exchange (ETDEWEB)

    Ishii, Nobuhisa

    2006-11-21

    In this work, optical pulse amplification by parametric chirped-pulse amplification (OPCPA) has been applied to the generation of high-energy, few-cycle optical pulses in the near-infrared (NIR) and infrared (IR) spectral regions. Amplification of such pulses is ordinarily difficult to achieve by existing techniques of pulse amplification based on standard laser gain media followed by external compression. Potential applications of few-cycle pulses in the IR have also been demonstrated. The NIR OPCPA system produces 0.5-terawatt (10 fs,5 mJ) pulses by use of noncollinearly phase-matched optical parametric amplification and a down-chirping stretcher and up-chirping compressor pair. An IR OPCPA system was also developed which produces 20-gigawatt (20 fs,350 {mu}J) pulses at 2.1 {mu}m. The IR seed pulse is generated by optical rectification of a broadband pulse and therefore it exhibits a self-stabilized carrier-envelope phase (CEP). In the IR OPCPA a common laser source is used to generate the pump and seed resulting in an inherent sub-picosecond optical synchronization between the two pulses. This was achieved by use of a custom-built Nd:YLF picosecond pump pulse amplifier that is directly seeded with optical pulses from a custom-built ultrabroadband Ti:sapphire oscillator. Synchronization between the pump and seed pulses is critical for efficient and stable amplification. Two spectroscopic applications which utilize these unique sources have been demonstrated. First, the visible supercontinuum was generated in a solid-state media by the infrared optical pulses and through which the carrier-envelope phase (CEP) of the driving pulse was measured with an f-to-3f interferometer. This measurement confirms the self-stabilization mechanism of the CEP in a difference frequency generation process and the preservation of the CEP during optical parametric amplification. Second, high-order harmonics with energies extending beyond 200 eV were generated with the few

  18. Repetitively pulsed UV radiation source based on a run-away electron preionised diffuse discharge in nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Baksht, E Kh; Burachenko, A G; Lomaev, M I; Panchenko, A N; Tarasenko, V F [Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation)

    2015-04-30

    An extended repetitively pulsed source of spontaneous UV radiation is fabricated, which may also be used for producing laser radiation. Voltage pulses with an incident wave amplitude of up to 30 kV, a half-amplitude duration of ∼4 ns and a rise time of ∼2.5 ns are applied to a gap with a nonuniform electric field. For an excitation region length of 35 cm and a nitrogen pressure of 30 – 760 Torr, a diffusive discharge up to a pulse repetition rate of 2 kHz is produced without using an additional system for gap preionisation. An investigation is made of the plasma of the run-away electron preionised diffuse discharge. Using a CCD camera it is found that the dense diffused plasma fills the gap in a time shorter than 1 ns. X-ray radiation is recorded from behind the foil anode throughout the pressure range under study; a supershort avalanche electron beam is recorded by the collector electrode at pressures below 100 Torr. (laser applications and other topics in quantum electronics)

  19. Fabrication of porous biopolymer substrates for cell growth by UV laser: The role of pulse duration

    International Nuclear Information System (INIS)

    Castillejo, Marta; Rebollar, Esther; Oujja, Mohamed; Sanz, Mikel; Selimis, Alexandros; Sigletou, Maria; Psycharakis, Stelios; Ranella, Anthi; Fotakis, Costas

    2012-01-01

    Highlights: ► UV laser-induced superficial foaming in biopolymer films with fs, ps and ns pulses. ► Reduction of photochemical and structural modifications by ultrashort fs irradiation. ► Successful cell culture on laser-induced foam structure generated in chitosan. - Abstract: Ultraviolet laser irradiation using pulses with duration from the nanosecond to the femtosecond range was investigated aiming at the generation of a foam layer on films of the biopolymers chitosan, starch and their blend. We report on the morphological characteristics of the foams obtained upon irradiation and on the accompanying laser induced photochemistry, assessed by on line monitoring of the laser induced fluorescence. We identify the laser conditions (pulse duration) at which foaming is produced and discuss the obtained results in reference to the material properties, particularly extinction coefficient and thermal parameters. This article also reports on successful cell culture on the laser induced foam structure generated in chitosan, as an illustrative example of the possibility of broader use of laser induced biopolymer foaming structures in biology.

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

    International Nuclear Information System (INIS)

    Sozet, Martin

    2016-01-01

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

  1. High pulse energy sub-nanosecond Tm-doped fiber laser

    Science.gov (United States)

    Cserteg, Andras; Guillemet, Sebastien; Hernandez, Yves; Giannone, Domenico

    2012-02-01

    We report a core pumped thulium-doped fiber amplifier that generates 1.4 μJ pulses at 1980 nm with a repetition rate of 3.6 MHz preserving the original spectral bandwidth of the oscillator. The amplifier chain is seeded by a passively modelocked fiber laser with 5 mW output power and the pulses are stretched to 800 picoseconds. The amplifier is core pumped by a single mode erbium fiber laser. The slope efficiency is 35%. To the best of our knowledge, this is the first demonstration of sub nanosecond pulses with energies higher than 1 μJ coming out of a thulium-doped fiber amplifier.

  2. Fast pulse beam generation systems for electron accelerators

    International Nuclear Information System (INIS)

    Koontz, R.F.

    1977-01-01

    The fast pulse beam generation system to supply the SLAC storage ring, SPEAR, by the two one nanosecond bunch electron beam pulses is described. Generation of these pulses is accomplished with a combination of a fast pulsed grided gun and a synchronized transverse beam chopper. Fast gun based on spherical cathode-grid assembly has output current up to 2As. Fast pulse amplifier system can handle trains of short pulses with repetition rates up to 40 MHz during the 1.6 μs normal accelerating time. Chopping deflector system consists of a resonant coaxial line with the deflecting plates. The resonator frequency is 39.667 MHz. A schematic diagram of the resonant system is shown. The fast beam pickup system has a one hundred picosecond rise time overrall. Fast beam generation and chopper systems permit to generate almost any short or single bunch beam profile needed for experiments

  3. Presence of UV-endonuclease sensitive sites in daughter DNA of UV-irradiated mammalian cells

    International Nuclear Information System (INIS)

    D'Ambrosio, S.; Setlow, R.B.

    1978-02-01

    Asynchronous Chinese hamster cells were irradiated with 10 Jm -2 uv radiation and 0.25 to 4 hours later pulse-labeled with [ 3 H]thymidine. Cells synchronized by shaking off mitotic and G 1 cells were irradiated in either the G 1 -phase or S-phase of the cell cycle and pulse-labeled with [ 3 H]thymidine in the S-phase. After a 12 to 14 hour chase in unlabeled medium, the DNA was extracted, incubated with Micrococcus luteus uv-endonuclease and sedimented in alkaline sucrose. The number of endonuclease sensitive sites decreased as the time between uv irradiation and pulse-labeling of daughter DNA increased. Further, there were significantly less endonuclease sensitive sites in the daughter DNA from cells irradiated in the G 1 -phase than in the S-phase. These data indicate that very few, if any, dimers are transferred from parental DNA to daughter DNA and that the dimers detected in daughter DNA may be due to the irradiation of replicating daughter DNA before labeling

  4. 100ps UV/x-ray framing camera

    International Nuclear Information System (INIS)

    Eagles, R.T.; Freeman, N.J.; Allison, J.M.; Sibbett, W.; Sleat, W.E.; Walker, D.R.

    1988-01-01

    The requirement for a sensitive two-dimensional imaging diagnostic with picosecond time resolution, particularly in the study of laser-produced plasmas, has previously been discussed. A temporal sequence of framed images would provide useful supplementary information to that provided by time resolved streak images across a spectral region of interest from visible to x-ray. To fulfill this requirement the Picoframe camera system has been developed. Results pertaining to the operation of a camera having S20 photocathode sensitivity are reviewed and the characteristics of an UV/x-ray sensitive version of the Picoframe system are presented

  5. Advances in High-Power, Ultrashort Pulse DPSSL Technologies at HiLASE

    Directory of Open Access Journals (Sweden)

    Martin Smrž

    2017-10-01

    Full Text Available The development of kW-class diode-pumped picosecond laser sources emitting at various wavelengths started at the HiLASE Center four years ago. A 500-W Perla C thin-disk laser with a diffraction limited beam and repetition rate of 50–100 kHz, a frequency conversion to mid-infrared (mid-IR, and second to fifth harmonic frequencies was demonstrated. We present an updated review on the progress in the development of compact picosecond and femtosecond high average power radiation sources covering the ultraviolet (UV to mid-IR spectral range at the HiLASE Center. We also report on thin-disk manufacturing by atomic diffusion bonding, which is a crucial technology for future high-power laser development.

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

    Science.gov (United States)

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

    2018-05-01

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

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

    Directory of Open Access Journals (Sweden)

    Lamia EL Fissi

    2014-12-01

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

  8. The EGFR family of receptors sensitizes cancer cells towards UV light

    DEFF Research Database (Denmark)

    Petersen, Steffen B.; Neves Petersen, Teresa; Olsen, Birgitte

    2008-01-01

    A combination of bioinformatics, biophysical, advanced laser studies and cell biology lead to the realization that laser-pulsed UV light stops cancer growth and induces apoptosis. We have previously shown that laser-pulsed UV (LP-UV) illumination of two different skin-derived cancer cell lines both...... bridges. The EGF receptor is often overexpressed in cancers and other proliferative skin disorders, it might be possible to significantly reduce the proliferative potential of these cells making them good targets for laser-pulsed UV-light treatment. The discovery that UV light can be used to open...... disulphide bridges in proteins upon illumination of nearby aromatic amino acids was the first step that lead to the hypothesis that UV light could modulate the structure and therefore the function of these key receptor proteins. The observation that membrane receptors (EGFR) contained exactly the motifs...

  9. Charge dynamics in aluminum oxide thin film studied by ultrafast scanning electron microscopy.

    Science.gov (United States)

    Zani, Maurizio; Sala, Vittorio; Irde, Gabriele; Pietralunga, Silvia Maria; Manzoni, Cristian; Cerullo, Giulio; Lanzani, Guglielmo; Tagliaferri, Alberto

    2018-04-01

    The excitation dynamics of defects in insulators plays a central role in a variety of fields from Electronics and Photonics to Quantum computing. We report here a time-resolved measurement of electron dynamics in 100 nm film of aluminum oxide on silicon by Ultrafast Scanning Electron Microscopy (USEM). In our pump-probe setup, an UV femtosecond laser excitation pulse and a delayed picosecond electron probe pulse are spatially overlapped on the sample, triggering Secondary Electrons (SE) emission to the detector. The zero of the pump-probe delay and the time resolution were determined by measuring the dynamics of laser-induced SE contrast on silicon. We observed fast dynamics with components ranging from tens of picoseconds to few nanoseconds, that fits within the timescales typical of the UV color center evolution. The surface sensitivity of SE detection gives to the USEM the potential of applying pump-probe investigations to charge dynamics at surfaces and interfaces of current nano-devices. The present work demonstrates this approach on large gap insulator surfaces. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Annealing of SnO2 thin films by ultra-short laser pulses

    NARCIS (Netherlands)

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

    2014-01-01

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

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

    Science.gov (United States)

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

    2018-04-01

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

  12. Improvement of chirped pulse contrast using electro-optic birefringence scanning filter method

    International Nuclear Information System (INIS)

    Zeng Shuguang; Wang Xianglin; Wang Qishan; Zhang Bin; Sun Nianchun; Wang Fei

    2013-01-01

    A method using scanning filter to improve the contrast of chirped pulse is proposed, and the principle of this method is analyzed. The scanning filter is compared with the existing pulse-picking technique and nonlinear filtering technique. The scanning filter is a temporal gate that is independent on the intensity of the pulses, but on the instantaneous wavelengths of light. Taking the electro-optic birefringence scanning filter as an example, the application of scanning filter methods is illustrated. Based on numerical simulation and experimental research, it is found that the electro-optic birefringence scanning filter can eliminate a prepulse which is several hundred picoseconds before the main pulse, and the main pulse can maintain a high transmissivity. (authors)

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

    Science.gov (United States)

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

    2013-01-01

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

  14. Laser system for a subpicosecond electron linac

    International Nuclear Information System (INIS)

    Crowell, R. A.

    1998-01-01

    At the Argonne Chemistry Division efforts are underway to develop a sub-picosecond electron beam pulse radiolysis facility for chemical studies. The target output of the accelerator is to generate electron pulses that can be adjusted from 3nC in .6ps to 100nC in 45ps. In conjunction with development of the accelerator a state-of-the-art ultrafast laser system is under construction that will drive the linac's photocathode and provide probe pulses that are tunable from the UV to IR spectral regions

  15. Study of graphitic microstructure formation in diamond bulk by pulsed Bessel beam laser writing

    Science.gov (United States)

    Kumar, S.; Sotillo, B.; Chiappini, A.; Ramponi, R.; Di Trapani, P.; Eaton, S. M.; Jedrkiewicz, O.

    2017-11-01

    The advantages of using Bessel beams for the generation of graphitic structures in diamond bulk are presented. We show that by irradiating the sample with a pulsed Bessel beam whose non-diffracting zone is of the same order of the sample thickness, it is possible to produce without any sample translation straight graphitic through-microstructures, whose size depends on the input pulse energy. The microstructure growth is investigated as a function of the number of irradiating pulses, and the femtosecond and picosecond regimes are contrasted.

  16. 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

  17. One nanosecond pulsed electron gun systems

    International Nuclear Information System (INIS)

    Koontz, R.F.

    1979-02-01

    At SLAC there has been a continuous need for the injection of very short bunches of electrons into the accelerator. Several time-of-flight experiments have used bursts of short pulses during a normal 1.6 micro-second rf acceleration period. Single bunch beam loading experiments made use of a short pulse injection system which included high power transverse beam chopping equipment. Until the equipment described in this paper came on line, the basic grid-controlled gun pulse was limited to a rise time of 7 nanoseconds and a pulse width of 10 nanoseconds. The system described here has a grid-controlled rise time of less than 500 pico-seconds, and a minimum pulse width of less than 1 nanosecond. Pulse burst repetition rate has been demonstrated above 20 MHz during a 1.6 microsecond rf accelerating period. The order-of-magnitude increase in gun grid switching speed comes from a new gun design which minimizes lead inductance and stray capacitance, and also increases gun grid transconductance. These gun improvements coupled with a newly designed fast pulser mounted directly within the gun envelope make possible subnanosecond pulsing of the gun

  18. Ultrafast geometric control of a single qubit using chirped pulses

    International Nuclear Information System (INIS)

    Hawkins, Patrick E; Malinovskaya, Svetlana A; Malinovsky, Vladimir S

    2012-01-01

    We propose a control strategy to perform arbitrary unitary operations on a single qubit based solely on the geometrical phase that the qubit state acquires after cyclic evolution in the parameter space. The scheme uses ultrafast linearly chirped pulses and provides the possibility of reducing the duration of a single-qubit operation to a few picoseconds.

  19. Picosecond chronography at x-ray wavelengths

    International Nuclear Information System (INIS)

    Bird, P.R.; Bradley, D.J.; Roddie, A.G.; Sibbett, W.; Key, M.H.; Lamb, M.J.; Lewis, C.L.S.

    1975-01-01

    An ultrafast streak camera for vacuum U-V to X-ray radiation is described. Preliminary measurements on laser-produced plasmas are presented with time resolution down to 150 psecs and space resolution down to 40μm for 1keV X-ray emission from a plasma generated by 2GW laser pulses focussed on a Cu target. High sensitivity and wide spectral bandwidth is due to front surface photoemission at oblique incidence. Time resolution capability of 40 psec and simultaneous spatial resolution down to a few microns is theoretically possible with this system. (author)

  20. Excimer UV curing in printing

    International Nuclear Information System (INIS)

    Mehnert, R.

    1999-01-01

    It is the aim of this study to investigate the potential of 308 run excimer UV curing in web and sheet fed offset printing and to discuss its present status. Using real-time FTIR-ATR and stationary or pulsed monochromatic (313 nm) irradiation chemical and physical factors affecting the curing speed of printing inks such as nature and concentration of photo-initiators, reactivity of the ink binding system, ink thickness and pigmentation, irradiance in the curing plane, oxygen concentration and nitrogen inerting, multiple pulse exposure, the photochemical dark reaction and temperature dependence were studied. The results were used to select optimum conditions for excimer UV curing in respect to ink reactivity, nitrogen inerting and UV exposure and to build an excimer UV curing unit consisting of two 50 W/cm 308 run excimer lamps, power supply, cooling and inerting unit. The excimer UV curing devices were tested under realistic conditions on a web offset press zirkon supra forte and a sheet fed press Heidelberg GTO 52. Maximum curing speeds of 300 m/min in web offset and 8000 sheets per hour in sheet fed offset were obtained

  1. Optimal initiation of electronic excited state mediated intramolecular H-transfer in malonaldehyde by UV-laser pulses

    Science.gov (United States)

    Nandipati, K. R.; Singh, H.; Nagaprasad Reddy, S.; Kumar, K. A.; Mahapatra, S.

    2014-12-01

    Optimally controlled initiation of intramolecular H-transfer in malonaldehyde is accomplished by designing a sequence of ultrashort (~80 fs) down-chirped pump-dump ultra violet (UV)-laser pulses through an optically bright electronic excited [ S 2 ( π π ∗)] state as a mediator. The sequence of such laser pulses is theoretically synthesized within the framework of optimal control theory (OCT) and employing the well-known pump-dump scheme of Tannor and Rice [D.J. Tannor, S.A. Rice, J. Chem. Phys. 83, 5013 (1985)]. In the OCT, the control task is framed as the maximization of cost functional defined in terms of an objective function along with the constraints on the field intensity and system dynamics. The latter is monitored by solving the time-dependent Schrödinger equation. The initial guess, laser driven dynamics and the optimized pulse structure (i.e., the spectral content and temporal profile) followed by associated mechanism involved in fulfilling the control task are examined in detail and discussed. A comparative account of the dynamical outcomes within the Condon approximation for the transition dipole moment versus its more realistic value calculated ab initio is also presented.

  2. Non-destructive evaluation of UV pulse laser-induced damage performance of fused silica optics.

    Science.gov (United States)

    Huang, Jin; Wang, Fengrui; Liu, Hongjie; Geng, Feng; Jiang, Xiaodong; Sun, Laixi; Ye, Xin; Li, Qingzhi; Wu, Weidong; Zheng, Wanguo; Sun, Dunlu

    2017-11-24

    The surface laser damage performance of fused silica optics is related to the distribution of surface defects. In this study, we used chemical etching assisted by ultrasound and magnetorheological finishing to modify defect distribution in a fused silica surface, resulting in fused silica samples with different laser damage performance. Non-destructive test methods such as UV laser-induced fluorescence imaging and photo-thermal deflection were used to characterize the surface defects that contribute to the absorption of UV laser radiation. Our results indicate that the two methods can quantitatively distinguish differences in the distribution of absorptive defects in fused silica samples subjected to different post-processing steps. The percentage of fluorescence defects and the weak absorption coefficient were strongly related to the damage threshold and damage density of fused silica optics, as confirmed by the correlation curves built from statistical analysis of experimental data. The results show that non-destructive evaluation methods such as laser-induced fluorescence and photo-thermal absorption can be effectively applied to estimate the damage performance of fused silica optics at 351 nm pulse laser radiation. This indirect evaluation method is effective for laser damage performance assessment of fused silica optics prior to utilization.

  3. Picosecond resolution programmable delay line

    International Nuclear Information System (INIS)

    Suchenek, Mariusz

    2009-01-01

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

  4. Broadly tunable picosecond ir source

    International Nuclear Information System (INIS)

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

    1979-01-01

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

  5. 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.

  6. Controlling semiconductor nanoparticle size distributions with tailored ultrashort pulses

    International Nuclear Information System (INIS)

    Hergenroeder, R; Miclea, M; Hommes, V

    2006-01-01

    The laser generation of size-controlled semiconductor nanoparticle formation under gas phase conditions is investigated. It is shown that the size distribution can be changed if picosecond pulse sequences of tailored ultra short laser pulses (<200 fs) are employed. By delivering the laser energy in small packages, a temporal energy flux control at the target surface is achieved, which results in the control of the thermodynamic pathway the material takes. The concept is tested with silicon and germanium, both materials with a predictable response to double pulse sequences, which allows deduction of the materials' response to complicated pulse sequences. An automatic, adaptive learning algorithm was employed to demonstrate a future strategy that enables the definition of more complex optimization targets such as particle size on materials less predictable than semiconductors

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

    Science.gov (United States)

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

    2015-04-01

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

  8. High-power picosecond pulse delivery through hollow core photonic band gap fibers

    DEFF Research Database (Denmark)

    Michieletto, Mattia; Johansen, Mette Marie; Lyngsø, Jens Kristian

    2015-01-01

    We demonstrated robust and bend insensitive fiber delivery of high power pulsed laser with diffraction limited beam quality for two different kind of hollow core photonic band gap fibers......We demonstrated robust and bend insensitive fiber delivery of high power pulsed laser with diffraction limited beam quality for two different kind of hollow core photonic band gap fibers...

  9. 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...

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

    Science.gov (United States)

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

    2018-02-01

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

  11. 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.

  12. Table-top instrumentation for time-resolved luminescence spectroscopy of solids excited by nanosecond pulse of soft X-ray source and/or UV laser

    International Nuclear Information System (INIS)

    Bruza, Petr; Fidler, Vlastimil; Nikl, Martin

    2011-01-01

    The practical applicability of the rare-earth doped scintillators in high-speed detectors is limited by the slow decay components in the temporal response of a scintillator. The study of origin and properties of material defects that induce the slow decay components is of major importance for the development of new scintillation materials. We present a table-top, time-domain UV-VIS luminescence spectrometer, featuring extended time and input sensitivity ranges and two excitation sources. The combination of both soft X-ray/XUV and UV excitation source allows the comparative measurements of luminescence spectra and decay kinetics of scintillators to be performed under the same experimental conditions. The luminescence of emission centers of a doped scintillator can be induced by conventional N 2 laser pulse, while the complete scintillation process can be initiated by a soft X-ray/XUV pulse excitation from the laser-produced plasma in gas puff target of 4 ns duration. In order to demonstrate the spectrometer, the UV-VIS luminescence spectra and decay kinetics of cerium doped Lu 3 Al 5 O 12 single crystal (LuAG:Ce) scintillator excited by XUV and UV radiation were acquired. Luminescence of the doped Ce 3+ ions was studied under 2.88 nm (430 eV) XUV excitation from the laser-produced nitrogen plasma, and compared with the luminescence under 337 nm (3.68 eV) UV excitation from nitrogen laser. In the former case the excitation energy is deposited in the LuAG host, while in the latter the 4f-5d 2 transition of Ce 3+ is directly excited. Furthermore, YAG:Ce and LuAG:Ce single crystals luminescence decay profiles are compared and discussed.

  13. Ultra-short laser processing of transparent material at the interface to liquid

    International Nuclear Information System (INIS)

    Boehme, R; Pissadakis, S; Ehrhardt, M; Ruthe, D; Zimmer, K

    2006-01-01

    Similarly to laser-induced backside wet etching (LIBWE) with nanosecond ultraviolet (ns UV) laser pulses, the irradiation of the solid/liquid interface of fused silica with sub-picosecond (sub-ps) UV and femtosecond near infrared (fs NIR) laser pulses results in etching of the fused silica surface and deposition of decomposition products from liquid. Furthermore, the etch threshold is reduced compared with both direct ablation with an fs laser in air and backside etching with UV ns pulses. Using 0.5 M pyrene/toluene as absorbing liquid, the thresholds were determined to be 70 mJ cm -2 (sub-ps UV) and 330 mJ cm -2 (fs NIR). Furthermore, an almost linear increase in the etch rate with increasing laser fluence was found. The roughness of surfaces backside etched with ultra-short pulses is higher in comparison with ns pulses but lower than that obtained using direct fs laser ablation. Hence a combination of processes involved in fs laser ablation and ns backside etching can be expected. The processes at the ultra-short pulse laser irradiated solid/liquid interface are discussed, considering the effects of ultra-fast heating, multi-photon absorption processes, as well as defect generation in the materials

  14. Kinetics of the reaction F+NO+M->FNO+M studied by pulse radiolysis combined with time-resolved IR and UV spectroscopy

    DEFF Research Database (Denmark)

    Pagsberg, Palle Bjørn; Sillesen, A.; Jodkowski, J.T.

    1996-01-01

    The title reaction was initiated by pulse radiolysis of SF6/NO gas mixtures, and the formation of FNO was studied by time-resolved IR and UV spectroscopy. At SF6 pressures of 10-320 mbar at 298 K, the formation of FNO was studied by infrared diode laser spectroscopy at 1857.324 cm(-1). Comparative...

  15. 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)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-05-15

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

  17. Thermal annealing using ultra-short laser pulses to improve the electrical properties of Al:ZnO thin films

    NARCIS (Netherlands)

    Scorticati, D.; Illiberi, A.; Bor, Teunis Cornelis; Eijt, S.W.H.; Schut, H.; Römer, Gerardus Richardus, Bernardus, Engelina; Klein Gunnewiek, Michel; Lenferink, Aufrid T.M.; Kniknie, B.; Joy, R.M.; Dorenkamper, M.S.; de Lange, D.F.; Otto, Cornelis; Borsa, D.; Soppe, W.J.; Huis in 't Veld, Bert

    2015-01-01

    Industrial-grade Al:ZnO thin films, were annealed by UV picosecond laser irradiation in argon atmosphere. A remarkable increase of both the carrier density and electron mobility was measured, while the optical properties in the 400–1000 nm range did not change significantly. We studied the

  18. Thermal annealing using ultra-short laser pulses to improve the electrical properties of Al:ZnO thin films

    NARCIS (Netherlands)

    Scorticati, D.; Illiberi, A.; Bor, T.C.; Eijt, S.W.H.; Schut, H.; Römer, G.R.B.E.; Klein Gunnewiek, M.; Lenferink, A.T.M.; Kniknie, B.J.; Mary Joy, R.; Dorenkamper, M.S.; Lange, D.F. de; Otto, C.; Borsa, D.; Soppe, W.J.; Huis in 't Veld, A.J.

    2015-01-01

    Abstract Industrial-grade Al:ZnO thin films, were annealed by UV picosecond laser irradiation in argon atmosphere. A remarkable increase of both the carrier density and electron mobility was measured, while the optical properties in the 400-1000 nm range did not change significantly. We studied the

  19. High Energy, Single-Mode, All-Solid-State and Tunable UV Laser Transmitter

    Science.gov (United States)

    Prasad, Narasimha S.; Singh, Upendra N.; Hovis, FLoyd

    2007-01-01

    A high energy, single mode, all solid-state Nd:YAG laser primarily for pumping an UV converter is developed. Greater than 1 J/pulse at 50 HZ PRF and pulse widths around 22 ns have been demonstrated. Higher energy, greater efficiency may be possible. Refinements are known and practical to implement. Technology Demonstration of a highly efficient, high-pulse-energy, single mode UV wavelength generation using flash lamp pumped laser has been achieved. Greater than 90% pump depletion is observed. 190 mJ extra-cavity SFG; IR to UV efficiency > 21% (> 27% for 1 mJ seed). 160 mJ intra-cavity SFG; IR to UV efficiency up to 24% Fluence laser is being refined to match or exceed the above UV converter results. Currently the Nd:YAG pump laser development is a technology demonstration. System can be engineered for compact packaging.

  20. High aspect ratio nanoholes in glass generated by femtosecond laser pulses with picosecond intervals

    Science.gov (United States)

    Ahn, Sanghoon; Choi, Jiyeon; Noh, Jiwhan; Cho, Sung-Hak

    2018-02-01

    Because of its potential uses, high aspect ratio nanostructures have been interested for last few decades. In order to generate nanostructures, various techniques have been attempted. Femtosecond laser ablation is one of techniques for generating nanostructures inside a transparent material. For generating nanostructures by femtosecond laser ablation, previous studies have been attempted beam shaping such as Bessel beam and temporal tailored beam. Both methods suppress electron excitation at near surface and initiate interference of photons at certain depth. Recent researches indicate that shape of nanostructures is related with temporal change of electron density and number of self-trapped excitons. In this study, we try to use the temporal change of electron density induced by femtosecond laser pulse for generating high aspect ratio nanoholes. In order to reveal the effect of temporal change of electron density, secondary pulses are irradiated from 100 to 1000 ps after the irradiation of first pulse. Our result shows that diameter of nanoholes is increasing and depth of nanoholes is decreasing as pulse to pulse interval is getting longer. With manipulating of pulse to pulse interval, we could generate high aspect ratio nanoholes with diameter of 250-350 nm and depth of 4∼6 μm inside a glass.

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

    Science.gov (United States)

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

    2013-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-02-28

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

  3. Making ultracold molecules in a two-color pump-dump photoassociation scheme using chirped pulses

    International Nuclear Information System (INIS)

    Koch, Christiane P.; Luc-Koenig, Eliane; Masnou-Seeuws, Francoise

    2006-01-01

    This theoretical paper investigates the formation of ground state molecules from ultracold cesium atoms in a two-color scheme. Following previous work on photoassociation with chirped picosecond pulses [Luc-Koenig et al., Phys. Rev. A, 70, 033414 (2004)], we investigate stabilization by a second (dump) pulse. By appropriately choosing the dump pulse parameters and time delay with respect to the photoassociation pulse, we show that a large number of deeply bound molecules are created in the ground triplet state. We discuss (i) broad-bandwidth dump pulses which maximize the probability to form molecules while creating a broad vibrational distribution as well as (ii) narrow-bandwidth pulses populating a single vibrational ground state level, bound by 113 cm -1 . The use of chirped pulses makes the two-color scheme robust, simple, and efficient

  4. Combined Yb/Nd driver for optical parametric chirped pulse amplifiers.

    Science.gov (United States)

    Michailovas, Kirilas; Baltuska, Andrius; Pugzlys, Audrius; Smilgevicius, Valerijus; Michailovas, Andrejus; Zaukevicius, Audrius; Danilevicius, Rokas; Frankinas, Saulius; Rusteika, Nerijus

    2016-09-19

    We report on the developed front-end/pump system for optical parametric chirped pulse amplifiers. The system is based on a dual output fiber oscillator/power amplifier which seeds and assures all-optical synchronization of femtosecond Yb and picosecond Nd laser amplifiers operating at a central wavelength of 1030 nm and 1064 nm, respectively. At the central wavelength of 1030 nm, the fiber oscillator generates partially stretched 4 ps pulses with the spectrum supporting a scaling currently is prevented by limited dimensions of the diffraction gratings, which, because of the fast progress in MLD grating manufacturing technologies is only a temporary obstacle.

  5. Method for single-shot measurement of picosecond laser pulse-lengths without electronic time dispersion

    International Nuclear Information System (INIS)

    Kyrala, G.A.

    1987-01-01

    A two-source shear pattern recording is proposed as a method for single-shot measurement of the pulse shape from nearly monochromatic sources whose pulse lengths are shorter than their coherence times. The basis of this method relies on the assertion that if two identical electromagnetic pulses are recombined with a time delay greater than the sum of their pulse widths, the recordable spatial pattern has no fringes in it. At an arbitrary delay, translated into an actual spatial recording position, the recorded modulated intensity will sample the corresponding laser intensity at that delay time, but with a modulation due to the coherence function of the electromagnetic pulse. Two arrangements are proposed for recording the pattern. The principles, the design parameters, and the methodologies of these arrangements are presented. Resolutions of the configurations and their limitations are given as well

  6. Picosecond laser damage of fused silica at 355 nm

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  7. Single flux pulses affecting the ensemble of superconducting qubits

    Science.gov (United States)

    Denisenko, M. V.; Klenov, N. V.; Satanin, A. M.

    2018-02-01

    The present study is devoted to development of a technique for numerical simulation of the wave function dynamics the single Josephson qubits and arrays of noninteracting qubits controlled by ultra-short pulses. We wish to demonstrate the feasibility of a new principle of basic logical operations on the picosecond timescale. The influence of the unipolar pulse ("fluxon") form on the evolution of the state during the execution of the quantum one-qubit operations - "NOT", "READ" and " √{N O T } " - is investigated in the presence of decoherence. In the array of non interacting qubits, the question of the influence of the spread of their energy parameters (tunnel constants) is studied. It is shown that a single unipolar pulse can control a huge array of artificial atoms with 10% spread of geometric parameters in the array.

  8. Autofluorescence of pigmented skin lesions using a pulsed UV laser with synchronized detection: clinical results

    Science.gov (United States)

    Cheng, Haynes P. H.; Svenmarker, Pontus; Xie, Haiyan; Tidemand-Lichtenberg, Peter; Jensen, Ole B.; Bendsoe, Niels; Svanberg, Katarina; Petersen, Paul Michael; Pedersen, Christian; Andersson-Engels, Stefan; Andersen, Peter E.

    2010-04-01

    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-tonoise ratio to be achieved in the resulting autofluorescence 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 capture is sampled at 5 kHz and the resulting autofluorescence is captured with the liquid crystal filter cycling through seven wavelengths between 420 nm and 580 nm. The clinical study targets pigmented skin lesions and evaluates the prospects of using autofluorescence as a possible means in differentiating malignant and benign skin tumors. Up to now, sixteen patients have participated in the clinical study. The autofluorescence images, averaged over the exposure time of one second, will be presented along with histopathological results. Initial survey of the images show good contrast and diagnostic results show promising agreement based on the histopathological results.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  10. Cavity-less sub-picosecond pulse generation for the demultiplexing of a 640 Gbaud OTDM signal

    DEFF Research Database (Denmark)

    Kong, Deming; Guan, Pengyu; Hu, Hao

    2015-01-01

    A 703 fs cavity-less pulse source based on pulse carving and pulse compression is demonstrated and utilized for demultiplexing a 640 Gbaud OTDM signal. Timing jitter is found to be the main limiting factor....

  11. Generation of frequency-chirped optical pulses with felix

    Energy Technology Data Exchange (ETDEWEB)

    Knippels, G.M.H.; Meer, A.F.G. van der; Mols, R.F.X.A.M. [FOM-Institute for Plasma Physics, Nieuwegein (Netherlands)] [and others

    1995-12-31

    Frequency-chirped optical pulses have been produced in the picosecond regime by varying the energy of the electron beam on a microsecond time scale. These pulses were then compressed close to their bandwidth limit by an external pulse compressor. The amount of chirp can be controlled by varying the sweep rate on the electron beam energy and by cavity desynchronisation. To examine the generated chirp we used the following diagnostics: a pulse compressor, a crossed beam autocorrelator, a multichannel electron spectrometer and multichannel optical spectrometer. The compressor is build entirely using reflective optics to permit broad band operation. The autocorrelator is currently operating from 6 {mu}m to 30 {mu}m with one single crystal. It has been used to measure pulses as short as 500 fs. All diagnostics are evacuated to prevent pulse shape distortion or pulse lengthening caused by absorption in ambient water vapour. Pulse length measurements and optical spectra will be presented for different electron beam sweep rates, showing the presence of a frequency chirp. Results on the compression of the optical pulses to their bandwidth limit are given for different electron sweep rates. More experimental results showing the dependence of the amount of chirp on cavity desynchronisation will be presented.

  12. QCL seeded, ns-pulse, multi-line, CO2 laser oscillator for laser-produced-plasma extreme-UV source

    Science.gov (United States)

    Nowak, Krzysztof Michał; Suganuma, Takashi; Kurosawa, Yoshiaki; Ohta, Takeshi; Kawasuji, Yasufumi; Nakarai, Hiroaki; Saitou, Takashi; Fujimoto, Junichi; Mizoguchi, Hakaru; Sumitani, Akira; Endo, Akira

    2017-01-01

    Successful merger of state-of-the-art, semiconductor quantum-cascade lasers (QCL), with the mature CO2 laser technology, resulted in a delivery of highly-desired qualities of CO2 laser output that were not available previously without much effort. These qualities, such as multi-line operation, excellent spectro-temporal stability and pulse waveform control, became available from a single device of moderate complexity. This paper describes the operation principle and the unique properties of the solid{state seeded CO2 laser, invented for an application in laser-produced-plasma (LPP), extreme-UV (EUV) light source.

  13. Picosecond wide-field time-correlated single photon counting fluorescence microscopy with a delay line anode detector

    Energy Technology Data Exchange (ETDEWEB)

    Hirvonen, Liisa M.; Le Marois, Alix; Suhling, Klaus, E-mail: klaus.suhling@kcl.ac.uk [Department of Physics, King' s College London, Strand, London WC2R 2LS (United Kingdom); Becker, Wolfgang; Smietana, Stefan [Becker & Hickl GmbH, Nahmitzer Damm 30, 12277 Berlin (Germany); Milnes, James; Conneely, Thomas [Photek Ltd., 26 Castleham Rd, Saint Leonards-on-Sea TN38 9NS (United Kingdom); Jagutzki, Ottmar [Institut für Kernphysik, Max-von-Laue-Str. 1, 60438 Frankfurt (Germany)

    2016-08-15

    We perform wide-field time-correlated single photon counting-based fluorescence lifetime imaging (FLIM) with a crossed delay line anode image intensifier, where the pulse propagation time yields the photon position. This microchannel plate-based detector was read out with conventional fast timing electronics and mounted on a fluorescence microscope with total internal reflection (TIR) illumination. The picosecond time resolution of this detection system combines low illumination intensity of microwatts with wide-field data collection. This is ideal for fluorescence lifetime imaging of cell membranes using TIR. We show that fluorescence lifetime images of living HeLa cells stained with membrane dye di-4-ANEPPDHQ exhibit a reduced lifetime near the coverslip in TIR compared to epifluorescence FLIM.

  14. Picosecond pulse radiolysis studies to understand the primary processes in radiolysis

    International Nuclear Information System (INIS)

    Jonah, C.D.; Lewis, M.A.

    1984-01-01

    The use of pulse radiolysis to learn about processes which occur before the beginning of chemical times is discussed. Two examples, the distance distribution of positive and negative ions in hydrocarbons, and the state of the dry electron are discussed in detail

  15. Picosecond pulse radiolysis studies to understand the primary processes in radiolysis

    Energy Technology Data Exchange (ETDEWEB)

    Jonah, C.D.; Lewis, M.A.

    1984-01-01

    The use of pulse radiolysis to learn about processes which occur before the beginning of chemical times is discussed. Two examples, the distance distribution of positive and negative ions in hydrocarbons, and the state of the dry electron are discussed in detail.

  16. Picosecond lasers for tattoo removal: a systematic review.

    Science.gov (United States)

    Reiter, Ofer; Atzmony, Lihi; Akerman, Lehavit; Levi, Assi; Kershenovich, Ruben; Lapidoth, Moshe; Mimouni, Daniel

    2016-09-01

    Given that the pigment particles in tattoos have a relaxation time of tattoo removal. To systematically review the evidence regarding the effectiveness and safety of picosecond lasers for tattoo removal, Pubmed, Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov, and reference lists were searched for relevant trials. The primary outcome was >70 % clearance of tattoo pigment. Secondary outcomes were 90-100 % clearance of tattoo pigment, number of laser sessions required, and adverse effects. Eight trials were included, six with human participants (160 participants) and 2 with animal models. Seven of the eight trials explored the usage of either 755, 758, 795, 1064, or 1064/532-nm picosecond lasers for black and blue ink tattoos. In the human trials, 69-100 % of tattoos showed over 70 % clearance of pigment after 1-10 laser treatments. Reported side effects included pain, hyperpigmentation and hypopigmentation, blister formation and transient erythema, edema, and pinpoint bleeding. Included articles varied in type of laser investigated, mostly non-comparative studies and with a medium to high risk of bias. There is sparse evidence that picosecond lasers are more effective than their nanosecond counterparts for mainly black and blue ink tattoo removal, with minor side effects.

  17. Diurnal changes in epidermal UV transmittance of plants in naturally high UV environments.

    Science.gov (United States)

    Barnes, Paul W; Flint, Stephan D; Slusser, James R; Gao, Wei; Ryel, Ronald J

    2008-06-01

    Studies were conducted on three herbaceous plant species growing in naturally high solar UV environments in the subalpine of Mauna Kea, Hawaii, USA, to determine if diurnal changes in epidermal UV transmittance (T(UV)) occur in these species, and to test whether manipulation of the solar radiation regime could alter these diurnal patterns. Additional field studies were conducted at Logan, Utah, USA, to determine if solar UV was causing diurnal T(UV) changes and to evaluate the relationship between diurnal changes in T(UV) and UV-absorbing pigments. Under clear skies, T(UV), as measured with a UV-A-pulse amplitude modulation fluorometer for leaves of Verbascum thapsus and Oenothera stricta growing in native soils and Vicia faba growing in pots, was highest at predawn and sunset and lowest at midday. These patterns in T(UV) closely tracked diurnal changes in solar radiation and were the result of correlated changes in fluorescence induced by UV-A and blue radiation but not photochemical efficiency (F(v)/F(m)) or initial fluorescence yield (F(o)). The magnitude of the midday reduction in T(UV) was greater for young leaves than for older leaves of Verbascum. Imposition of artificial shade eliminated the diurnal changes in T(UV) in Verbascum, but reduction in solar UV had no effect on diurnal T(UV) changes in Vicia. In Vicia, the diurnal changes in T(UV) occurred without detectable changes in the concentration of whole-leaf UV-absorbing compounds. Results suggest that plants actively control diurnal changes in UV shielding, and these changes occur in response to signals other than solar UV; however, the underlying mechanisms responsible for rapid changes in T(UV) remain unclear.

  18. Polycrystalline diamond film UV detectors for excimer lasers

    International Nuclear Information System (INIS)

    Ralchenko, V G; Savel'ev, A V; Konov, Vitalii I; Mazzeo, G; Spaziani, F; Conte, G; Polyakov, V I

    2006-01-01

    Photoresistive metal-semiconductor-metal detectors based on polycrystalline diamond films are fabricated for recording cw and pulsed UV radiation. The detectors have a high spectral selectivity (the UV-to-VIS response ratio is ∼10 5 ) and a temporal resolution of the order of 10 9 s. 'Solar-blind' photostable diamond detectors are promising for applications in UV lithography, laser micromachining, medicine, and space research. (letters)

  19. Bulk and surface laser damage of silica by picosecond and nanosecond pulses at 1064 nm

    International Nuclear Information System (INIS)

    Smith, Arlee V.; Do, Binh T.

    2008-01-01

    We measured bulk and surface dielectric breakdown thresholds of pure silica for 14 ps and 8 ns pulses of 1064 nm light. The thresholds are sharp and reproducible. For the 8 ns pulses the bulk threshold irradiance is 4.75 ± 0.25 kW/μm 2 . The threshold is approximately three times higher for 14 ps pulses. For 8 ns pulses the input surface damage threshold can be made equal to the bulk threshold by applying an alumina or silica surface polish

  20. Picosecond scale experimental verification of a globally convergent algorithm for a coefficient inverse problem

    International Nuclear Information System (INIS)

    Klibanov, Michael V; Pantong, Natee; Fiddy, Michael A; Schenk, John; Beilina, Larisa

    2010-01-01

    A globally convergent algorithm by the first and third authors for a 3D hyperbolic coefficient inverse problem is verified on experimental data measured in the picosecond scale regime. Quantifiable images of dielectric abnormalities are obtained. The total measurement timing of a 100 ps pulse for one detector location was 1.2 ns with 20 ps (=0.02 ns) time step between two consecutive readings. Blind tests have consistently demonstrated an accurate imaging of refractive indexes of dielectric abnormalities. At the same time, it is shown that a modified gradient method is inapplicable to this kind of experimental data. This inverse algorithm is also applicable to other types of imaging modalities, e.g. acoustics. Potential applications are in airport security, imaging of land mines, imaging of defects in non-distractive testing, etc

  1. Extended plasma channels created by UV laser in air and their application to control electric discharges

    International Nuclear Information System (INIS)

    Zvorykin, V. D.; Ionin, A. A.; Levchenko, A. O.; Seleznev, L. V.; Sinitsyn, D. V.; Smetanin, I. V.; Ustinovskii, N. N.; Shutov, A. V.

    2015-01-01

    Results are presented from a series of experimental and theoretical studies on creating weakly ionized extended plasma channels in atmospheric air by 248-nm UV laser radiation and their application to control long high-voltage discharges. The main mechanisms of air ionization by UV laser pulses with durations from 100 fs to 25 ns and intensities in the ranges of 3×10 11 –1.5×10 13 and 3×10 6 –3×10 11 W/cm 2 , respectively, which are below the threshold for optical gas breakdown, as well as the main relaxation processes in plasma with a density of 10 9 –10 17 cm −3 , are considered. It is shown that plasma channels in air can be efficiently created by amplitude-modulated UV pulses consisting of a train of subpicosecond pulses producing primary photoelectrons and a long UV pulse suppressing electron attachment and sustaining the density of free electrons in plasma. Different modes of the generation and amplification of trains of subterawatt subpicosecond pulses and amplitude-modulated UV pulses with an energy of several tens of joules were implemented on the GARPUN-MTW hybrid Ti:sapphire-KrF laser facility. The filamentation of such UV laser beams during their propagation in air over distances of up to 100 m and the parameters of the corresponding plasma channels were studied experimentally and theoretically. Laser initiation of high-voltage electric discharges and control of their trajectories by means of amplitude-modulated UV pulses, as well as the spatiotemporal structure of breakdowns in air gaps with length of up to 80 cm, were studied

  2. Lifetime testing UV LEDs for use in the LISA charge management system

    Science.gov (United States)

    Hollington, D.; Baird, J. T.; Sumner, T. J.; Wass, P. J.

    2017-10-01

    As a future charge management light source, UV light-emitting diodes (UV LEDs) offer far superior performance in a range of metrics compared to the mercury lamps used in the past. As part of a qualification program a number of short wavelength UV LEDs have been subjected to a series of lifetime tests for potential use on the laser interferometer space antenna (LISA) mission. These tests were performed at realistic output levels for both fast and continuous discharging in either a DC or pulsed mode of operation and included a DC fast discharge test spanning 50 days, a temperature dependent pulsed fast discharge test spanning 21 days and a pulsed continuous discharge test spanning 507 days. Two types of UV LED have demonstrated lifetimes equivalent to over 25 years of realistic mission usage with one type providing a baseline for LISA and the other offering a backup solution.

  3. Lifetime testing UV LEDs for use in the LISA charge management system

    International Nuclear Information System (INIS)

    Hollington, D; Baird, J T; Sumner, T J; Wass, P J

    2017-01-01

    As a future charge management light source, UV light-emitting diodes (UV LEDs) offer far superior performance in a range of metrics compared to the mercury lamps used in the past. As part of a qualification program a number of short wavelength UV LEDs have been subjected to a series of lifetime tests for potential use on the laser interferometer space antenna (LISA) mission. These tests were performed at realistic output levels for both fast and continuous discharging in either a DC or pulsed mode of operation and included a DC fast discharge test spanning 50 days, a temperature dependent pulsed fast discharge test spanning 21 days and a pulsed continuous discharge test spanning 507 days. Two types of UV LED have demonstrated lifetimes equivalent to over 25 years of realistic mission usage with one type providing a baseline for LISA and the other offering a backup solution. (paper)

  4. Synchronized and configurable source of electrical pulses for x-ray pump-probe experiments

    International Nuclear Information System (INIS)

    Strachan, J. P.; Chembrolu, V.; Yu, X. W.; Tyliszczak, T.; Acremann, Y.

    2007-01-01

    A method is described for the generation of software tunable patterns of nanosecond electrical pulses. The bipolar, high repetition rate (up to 250 MHz), fast rise time (<30 ps), square pulses are suitable for applications such as the excitation sequence in dynamic pump-probe experiments. Synchronization with the time structure of a synchrotron facility is possible as well as fine control of the relative delay in steps of 10 ps. The pulse generator described here is used to excite magnetic nanostructures with current pulses. Having an excitation system which can match the high repetition rate of a synchrotron allows for utilization of the full x-ray flux and is needed in experiments which require a large photon flux. The fast rise times allow for picosecond time resolution in pump-probe experiments. All pulse pattern parameters are configurable by software

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

    Science.gov (United States)

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

    2013-11-01

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

  6. Bactericidal effectiveness of modulated UV light

    International Nuclear Information System (INIS)

    Bank, H.L.; John, J.; Schmehl, M.K.; Dratch, R.J.

    1990-01-01

    Studies were designed to evaluate the effectiveness of pulsed modulated UV light waveforms for killing bacteria. Exposure of five strains of bacteria to the modulated information encoded in the light decreased the colony population from a confluent lawn to less than 20 colonies. However, approximately 2,000 colonies survived treatment with the same intensity and time of exposure to UV light lacking the modulated information

  7. Ultrafast pulse amplification in mode-locked vertical external-cavity surface-emitting lasers

    Energy Technology Data Exchange (ETDEWEB)

    Böttge, C. N., E-mail: boettge@optics.arizona.edu; Hader, J.; Kilen, I.; Moloney, J. V. [College of Optical Sciences, The University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721 (United States); Koch, S. W. [College of Optical Sciences, The University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721 (United States); Department of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg (Germany)

    2014-12-29

    A fully microscopic many-body Maxwell–semiconductor Bloch model is used to investigate the influence of the non-equilibrium carrier dynamics on the short-pulse amplification in mode-locked semiconductor microlaser systems. The numerical solution of the coupled equations allows for a self-consistent investigation of the light–matter coupling dynamics, the carrier kinetics in the saturable absorber and the multiple-quantum-well gain medium, as well as the modification of the light field through the pulse-induced optical polarization. The influence of the pulse-induced non-equilibrium modifications of the carrier distributions in the gain medium and the saturable absorber on the single-pulse amplification in the laser cavity is identified. It is shown that for the same structure, quantum wells, and gain bandwidth the non-equilibrium carrier dynamics lead to two preferred operation regimes: one with pulses in the (sub-)100 fs-regime and one with multi-picosecond pulses. The recovery time of the saturable absorber determines in which regime the device operates.

  8. Temporal resolution technology of a soft X-ray picosecond framing camera based on Chevron micro-channel plates gated in cascade

    Energy Technology Data Exchange (ETDEWEB)

    Yang Wenzheng [State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China)], E-mail: ywz@opt.ac.cn; Bai Yonglin; Liu Baiyu [State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); Bai Xiaohong; Zhao Junping; Qin Junjun [Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi' an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China)

    2009-09-11

    We describe a soft X-ray picosecond framing camera (XFC) based on Chevron micro-channel plates (MCPs) gated in cascade for ultra-fast process diagnostics. The micro-strip lines are deposited on both the input and the output surfaces of the Chevron MCPs and can be gated by a negative (positive) electric pulse on the first (second) MCP. The gating is controlled by the time delay T{sub d} between two gating pulses. By increasing T{sub d}, the temporal resolution and the gain of the camera are greatly improved compared with a single-gated MCP-XFC. The optimal T{sub d}, which results in the best temporal resolution, is within the electron transit time and transit time spread of the MCP. Using 250 ps, {+-}2.5 kV gating pulses, the temporal resolution of the double-gated Chevron MCPs camera is improved from 60 ps for the single-gated MCP-XFC to 37 ps for T{sub d}=350 ps. The principle is presented in detail and accompanied with a theoretic simulation and experimental results.

  9. UV laser cleaving of air-polymer structured fibre

    NARCIS (Netherlands)

    Canning, J.; Buckley, E.; Groothoff, N.; Luther-Davies, B.; Zagari, J.

    2002-01-01

    The demonstration of ultraviolet (UV) laser ablation technique for cleaving of air-polymer structure (APF) fiber was presented. ArF exciplex laser with an unstable resonator cavity with pulse-to-pulse intensity fluctuations was used for the study. The thermal diffusion time across a 200 µm diameter

  10. 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.)

  11. Picosecond Transient Photoconductivity in Functionalized Pentacene Molecular Crystals Probed by Terahertz Pulse Spectroscopy

    Science.gov (United States)

    Hegmann, F. A.; Tykwinski, R. R.; Lui, K. P.; Bullock, J. E.; Anthony, J. E.

    2002-11-01

    We have measured transient photoconductivity in functionalized pentacene molecular crystals using ultrafast optical pump-terahertz probe techniques. The single crystal samples were excited using 800nm, 100fs pulses, and the change in transmission of time-delayed, subpicosecond terahertz pulses was used to probe the photoconducting state over a temperature range from 10 to 300K. A subpicosecond rise in photoconductivity is observed, suggesting that mobile carriers are a primary photoexcitation. At times longer than 4ps, a power-law decay is observed consistent with dispersive transport.

  12. Coherent stacking of picosecond laser pulses in a high-Q optical cavity for accelerator applications

    International Nuclear Information System (INIS)

    Androsov, V.P.; Karnaukhov, I.M.; Telegin, Yu.N.

    2007-01-01

    We have performed the harmonic analysis of the steady-state coherent pulse-stacking process in a high-Q Fabry-Perot cavity. The expression for the stacked pulse shape is obtained as a function of both the laser cavity and pulse-stacking cavity parameters. We have also estimated the pulse power gains attainable in the laser-optical system of NESTOR storage ring, which is under development at Kharkov Institute of Physics and Technology. It is shown that high power gains (∼10 4 ) can be, in principle, achieved in a cavity, formed with low-absorption, high reflectivity (R ∼ 0.9999) mirrors, if the laser cavity length will differ exactly by half wavelength from the pulse-stacking cavity length. It implies development of the sophisticated frequency stabilization loop for maintaining the cavity length constant within a sub-nanometer range. At the same time, power gains of ∼10 3 can be obtained with medium reflectivity mirrors (R ∼ 0.999) at considerably lower cost

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

    International Nuclear Information System (INIS)

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

    1996-10-01

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

  14. 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.

  15. High efficiency single frequency 355 nm all-solid-state UV laser

    International Nuclear Information System (INIS)

    Xie, Xiaobing; Wei, Daikang; Ma, Xiuhua; Li, Shiguang; Liu, Jiqiao; Zhu, Xiaolei; Chen, Weibiao

    2016-01-01

    A novel conductively cooled high energy single-frequency 355 nm all-solid-state UV laser is presented based on sum-frequency mixing technique. In this system, a pulsed seeder laser at 1064 nm wavelength, modulated by an AOM, is directly amplified by the cascaded multi-stage hybrid laser amplifiers, and two LBO crystals are used for the SHG and SFG, finally a maximum UV pulse energy of 226 mJ at 355 nm wavelength is achieved with frequency-tripled conversion efficiency as high as 55%, the pulse width is around 12.2 ns at the repetition frequency of 30 Hz. The beam quality factor M 2 of the output UV laser is measured to be 2.54 and 2.98 respectively in two orthogonal directions. (paper)

  16. Picosecond high power laser systems and picosecond diagnostic technique in laser produced plasma

    International Nuclear Information System (INIS)

    Kuroda, Hiroto; Masuko, H.; Maekawa, Shigeru; Suzuki, Yoshiji; Sugiyama, Masaru.

    1979-01-01

    Highly repetitive, high power YAG and Glass laser systems have been developed and been successfully used for the studies of laser-plasma interactions. Various picosecond diagnostic techniques have been developed for such purposes in the regions from optical to X-ray frequency. Recently highly sensitive X-ray (1 - 10 KeV) streak camera for highly repetitive operations have been developed. Preliminary experiment shows the achievement of 28ps temporal resolution (100μm slit) and good sensitivity with detectable minimum number of 10E3-1KeV photons/shot/slit area. (author)

  17. Diffractive sub-picosecond manipulation of x-rays

    International Nuclear Information System (INIS)

    Adams, B.

    2004-01-01

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

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

    Science.gov (United States)

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

    2017-09-01

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

  19. Picosecond x-ray measurements from 100 eV to 30 keV

    International Nuclear Information System (INIS)

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

    1980-01-01

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

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

    Science.gov (United States)

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

    2015-12-28

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

  1. Simulations of a FIR Oscillator with Large Slippage parameter at Jefferson Lab for FIR/UV pump-probe experiments

    International Nuclear Information System (INIS)

    Benson, Stephen V.; Campbell, L. T.; McNeil, B.W.T.; Neil, George R.; Shinn, Michelle D.; Williams, Gwyn P.

    2014-01-01

    We previously proposed a dual FEL configuration on the UV Demo FEL at Jefferson Lab that would allow simultaneous lasing at FIR and UV wavelengths. The FIR source would be an FEL oscillator with a short wiggler providing diffraction-limited pulses with pulse energy exceeding 50 microJoules, using the exhaust beam from a UVFEL as the input electron beam. Since the UV FEL requires very short pulses, the input to the FIR FEL is extremely short compared to a slippage length and the usual Slowly Varying Envelope Approximation (SVEA) does not apply. We use a non-SVEA code to simulate this system both with a small energy spread (UV laser off) and with large energy spread (UV laser on)

  2. High speed micromachining with high power UV laser

    Science.gov (United States)

    Patel, Rajesh S.; Bovatsek, James M.

    2013-03-01

    Increasing demand for creating fine features with high accuracy in manufacturing of electronic mobile devices has fueled growth for lasers in manufacturing. High power, high repetition rate ultraviolet (UV) lasers provide an opportunity to implement a cost effective high quality, high throughput micromachining process in a 24/7 manufacturing environment. The energy available per pulse and the pulse repetition frequency (PRF) of diode pumped solid state (DPSS) nanosecond UV lasers have increased steadily over the years. Efficient use of the available energy from a laser is important to generate accurate fine features at a high speed with high quality. To achieve maximum material removal and minimal thermal damage for any laser micromachining application, use of the optimal process parameters including energy density or fluence (J/cm2), pulse width, and repetition rate is important. In this study we present a new high power, high PRF QuasarR 355-40 laser from Spectra-Physics with TimeShiftTM technology for unique software adjustable pulse width, pulse splitting, and pulse shaping capabilities. The benefits of these features for micromachining include improved throughput and quality. Specific example and results of silicon scribing are described to demonstrate the processing benefits of the Quasar's available power, PRF, and TimeShift technology.

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

    Science.gov (United States)

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

    2018-02-01

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

  4. Retinal response of Macaca mulatta to picosecond laser pulses of varying energy and spot size.

    Science.gov (United States)

    Roach, William P; Cain, Clarence P; Narayan, Drew G; Noojin, Gary D; Boppart, Stephen A; Birngruber, Reginald; Fujimoto, James G; Toth, Cynthia A

    2004-01-01

    We investigate the relationship between the laser beam at the retina (spot size) and the extent of retinal injury from single ultrashort laser pulses. From previous studies it is believed that the retinal effect of single 3-ps laser pulses should vary in extent and location, depending on the occurrence of laser-induced breakdown (LIB) at the site of laser delivery. Single 3-ps pulses of 580-nm laser energy are delivered over a range of spot sizes to the retina of Macaca mulatta. The retinal response is captured sequentially with optical coherence tomography (OCT). The in vivo OCT images and the extent of pathology on final microscopic sections of the laser site are compared. With delivery of a laser pulse with peak irradiance greater than that required for LIB, OCT and light micrographs demonstrate inner retinal injury with many intraretinal and/or vitreous hemorrhages. In contrast, broad outer retinal injury with minimal to no choriocapillaris effect is seen after delivery of laser pulses to a larger retinal area (60 to 300 microm diam) when peak irradiance is less than that required for LIB. The broader lesions extend into the inner retina when higher energy delivery produces intraretinal injury. Microscopic examination of stained fixed tissues provide better resolution of retinal morphology than OCT. OCT provides less resolution but could be guided over an in vivo, visible retinal lesion for repeated sampling over time during the evolution of the lesion formation. For 3-ps visible wavelength laser pulses, varying the spot size and laser energy directly affects the extent of retinal injury. This again is believed to be partly due to the onset of LIB, as seen in previous studies. Spot-size dependence should be considered when comparing studies of retinal effects or when pursuing a specific retinal effect from ultrashort laser pulses. Copyright 2004 Society of Photo-Optical Instrumentation Engineers.

  5. Fiscal 1997 R and D project under a consignment from NEDO. R and D of the femtosecond technology (R and D of the monitoring system using high-intensity X-ray pulse for power plants); 1997 nendo Shin energy Sangyo Gijutsu Sogo Kaihatsu Kiko itaku. Femto byo technology no kenkyu kaihatsu (kokido X sen pulse riyo hatsuden shisetsu monitoring system no kenkyu kaihatsu) seika hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    This paper reports the result on R and D of the femtosecond technology in fiscal 1997. Ultrahigh-speed electronic technology is indispensable for industrial basic technologies supporting the advanced information society in the 21st century. Control technology of photonic and electronic states in a femtosecond region is essential. In R and D of metrological technology using ultra-short light-pulses, study was made on generating and controlling technology for ultra- short light/electron beam pulses. Ti-sapphire mode-locked laser was prepared, and it was found that time-fluctuation of mode-locked laser pulses is measurable up to 100 femtosecond level. As measures against an instability of gain-switching semiconductor laser, light injection from the outside was effective. The stable directivity of laser beam was obtained by regenerative amplifier, while less temperature variation of an optical switch was necessary to stabilize energy. To generate femtosecond high-intensity X-ray pulse by collision of laser and electron beams, it was confirmed that sub- picosecond synchronization is possible by RF and picosecond laser synchronization circuit. 48 refs., 89 figs., 11 tabs.

  6. Controlled UV-C light-induced fusion of thiol-passivated gold nanoparticles.

    Science.gov (United States)

    Pocoví-Martínez, Salvador; Parreño-Romero, Miriam; Agouram, Said; Pérez-Prieto, Julia

    2011-05-03

    Thiol-passivated gold nanoparticles (AuNPs) of a relatively small size, either decorated with chromophoric groups, such as a phthalimide (Au@PH) and benzophenone (Au@BP), or capped with octadecanethiol (Au@ODCN) have been synthesized and characterized by NMR and UV-vis spectroscopy as well as transmission electron microscopy (TEM). These NPs were irradiated in chloroform at different UV-wavelengths using either a nanosecond laser (266 and 355 nm, ca. 12 mJ/pulse, 10 ns pulse) or conventional lamps (300 nm UV-vis spectroscopy, as well as by TEM. Laser irradiation at 355 nm led to NP aggregation and precipitation, while the NPs were photostable under UV-A lamp illumination. Remarkably, laser excitation at 266 nm induced a fast (minutes time-scale) increase in the size of the NPs, producing huge spherical nanocrystals, while lamp-irradiation at UV-C wavelengths brought about nanonetworks of partially fused NPs with a larger diameter than the native NPs.

  7. On red-shift of UV photoluminescence with decreasing size of silicon nanoparticles embedded in SiO2 matrix grown by pulsed laser deposition

    International Nuclear Information System (INIS)

    Chaturvedi, Amita; Joshi, M.P.; Rani, Ekta; Ingale, Alka; Srivastava, A.K.; Kukreja, L.M.

    2014-01-01

    Ensembles of silicon nanoparticles (Si-nps) embedded in SiO 2 matrix were grown by alternate ablation of Si and SiO 2 targets using KrF excimer laser based pulsed laser deposition (PLD). The sizes of Si-nps (mean size ranging from 1–5 nm) were controlled by varying the ablation time of silicon target. Transmission electron microscopy (TEM) along with selected area electron diffraction (SAED) and Raman spectroscopy were used to confirm the growth of silicon nanoparticles, its size variation with growth time and the crystalline quality of the grown nanoparticles. TEM analysis showed that mean size and size distribution of Si-nps increased with increase in the ablation time of Si target. Intense peaks ∼521 cm −1 in Raman analysis showed reasonably good crystalline quality of grown Si-nps. We observed asymmetric broadening of phonon line shapes which also redshift with decreasing size of Si-nps. Photoluminescence (PL) from these samples, obtained at room temperature, was broad band and consisted of three bands in UV and visible range. The intensity of PL band in UV spectral range (peak ∼3.2 eV) was strong compared to visible range bands (peaks ∼2.95 eV and ∼2.55 eV). We observed a small red-shift (∼0.07 eV) of peak position of UV range PL with the decrease in the mean sizes of Si-nps, while there was no appreciable size dependent shift of PL peak positions for other bands in the visible range. The width of UV PL band was also found to increase with decrease of Si-nps mean sizes. Based on the above observations of size dependent redshift of UV range PL band together with the PL lifetimes and PL excitation spectroscopy, the origin of UV PL band is attributed to the direct band transition at the Γ point of Si band structure. Visible range bands were ascribed as defect related transitions. The weak intensities of PL bands ∼2.95 eV and ∼2.55 eV suggested that Si nanoparticles grown by PLD were efficiently capped or passivated by SiO 2 with low density of

  8. UV light blocks EGFR signalling in human cancer cell lines

    DEFF Research Database (Denmark)

    Olsen, BB; Neves-Petersen, M T; Klitgaard, S

    2007-01-01

    UV light excites aromatic residues, causing these to disrupt nearby disulphide bridges. The EGF receptor is rich in aromatic residues near the disulphide bridges. Herein we show that laser-pulsed UV illumination of two different skin-derived cancer cell lines i.e. Cal-39 and A431, which both...... antibodies. There was a threshold level, below which the receptor could not be blocked. In addition, illumination caused the cells to upregulate the cyclin-dependent kinase inhibitor p21WAF1, irrespective of the p53 status. Since the EGF receptor is often overexpressed in cancers and other proliferative skin...... disorders, it might be possible to significantly reduce the proliferative potential of these cells making them good targets for laser-pulsed UV light treatment....

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

    Science.gov (United States)

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

    2001-01-01

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

  10. TECHNICAL DESIGN NOTE: Picosecond resolution programmable delay line

    Science.gov (United States)

    Suchenek, Mariusz

    2009-11-01

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

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

    Science.gov (United States)

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

    2017-12-01

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

  12. Ultraviolet germicidal efficacy as a function of pulsed radiation parameters studied by spore film dosimetry.

    Science.gov (United States)

    Bauer, Stefan; Holtschmidt, Hans; Ott, Günter

    2018-01-01

    Disinfection by pulsed ultraviolet (UV) radiation is a commonly used method, e.g. in industry or medicine and can be carried out either with lasers or broadband UV radiation sources. Detrimental effects to biological materials depending on parameters such as pulse duration τ or pulse repetition frequency f p are well-understood for pulsed coherent UV radiation, however, relatively little is known for its incoherent variant. Therefore, within this work, it is the first time that disinfection rates of pulsed and continuous (cw) incoherent UV radiation studied by means of spore film dosimetry are presented, compared with each other, and in a second step further investigated regarding two pulse parameters. After analyzing the dynamic range of the Bacillus subtilis spore films with variable cw radiant exposures H=5-100Jm -2 a validation of the Bunsen-Roscoe law revealed its restricted applicability and a 28% enhanced detrimental effect of pulsed compared to cw incoherent UV radiation. A radiant exposure H=50Jm -2 and an irradiance E=0.5Wm -2 were found to be suitable parameters for an analysis of the disinfection rate as a function of τ=0.5-10ms and f p =25-500Hz unveiling that shorter pulses and lower frequencies inactivate more spores. Finally, the number of applied pulses as well as the experiment time were considered with regard to spore film disinfection. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Effect of pulse width on near-infrared supercontinuum generation in nonlinear fiber amplifier

    Science.gov (United States)

    Song, Rui; Lei, Cheng-Min; Chen, Sheng-Ping; Wang, Ze-Feng; Hou, Jing

    2015-08-01

    The effect of pulse width on near-infrared supercontinuum generation in nonlinear fiber amplifier is investigated theoretically and experimentally. The complex Ginzburg-Landau equation and adaptive split-step Fourier method are used to simulate the propagation of pulses with different pulse widths in the fiber amplifier, and the results show that a longer pulse is more profitable in near-infrared supercontinuum generation if the central wavelength of the input laser lies in the normal dispersion region of the gain fiber. A four-stage master oscillator power amplifier configuration is adopted and the output spectra under picosecond and nanosecond input pulses are compared with each other. The experimental results are in good accordance with the simulations which can provide some guidance for further optimization of the system. Project supported by the National Natural Science Foundation of China (Grant Nos. 11404404 and 11274385) and the Outstanding Youth Fund Project of Hunan Province and the Fund of Innovation of National University of Defense Technology, China (Grant No. B120701).

  14. Interferometrically enhanced sub-terahertz picosecond imaging utilizing a miniature collapsing-field-domain source

    Science.gov (United States)

    Vainshtein, Sergey N.; Duan, Guoyong; Mikhnev, Valeri A.; Zemlyakov, Valery E.; Egorkin, Vladimir I.; Kalyuzhnyy, Nikolay A.; Maleev, Nikolai A.; Näpänkangas, Juha; Sequeiros, Roberto Blanco; Kostamovaara, Juha T.

    2018-05-01

    Progress in terahertz spectroscopy and imaging is mostly associated with femtosecond laser-driven systems, while solid-state sources, mainly sub-millimetre integrated circuits, are still in an early development phase. As simple and cost-efficient an emitter as a Gunn oscillator could cause a breakthrough in the field, provided its frequency limitations could be overcome. Proposed here is an application of the recently discovered collapsing field domains effect that permits sub-THz oscillations in sub-micron semiconductor layers thanks to nanometer-scale powerfully ionizing domains arising due to negative differential mobility in extreme fields. This shifts the frequency limit by an order of magnitude relative to the conventional Gunn effect. Our first miniature picosecond pulsed sources cover the 100-200 GHz band and promise milliwatts up to ˜500 GHz. Thanks to the method of interferometrically enhanced time-domain imaging proposed here and the low single-shot jitter of ˜1 ps, our simple imaging system provides sufficient time-domain imaging contrast for fresh-tissue terahertz histology.

  15. Picosecond infrared activation of methanol in acid zeolites

    NARCIS (Netherlands)

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

    1997-01-01

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

  16. Hydration and temperature interdependence of protein picosecond dynamics.

    Science.gov (United States)

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

    2012-05-14

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

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

    Science.gov (United States)

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

    2018-01-01

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

  18. Measurement techniques using ultrashort optical pulses. Final report, February 9-September 30, 1983

    International Nuclear Information System (INIS)

    Siegman, A.E.

    1983-12-01

    The very great potential contactless, very high speed, very flexible, on-chip testing, diagnostics and measurement of very fast semiconductor circuits and devices has led us to initiate a small program to investigate such applications, using our own familiarity with picosecond pulse techniques, in conjunction with the integrated circuits skills present in Stanford's Integrated Circuit Laboratory (ICL), Solid State Laboratory (SSL), and the newly established Center for Integrated Systems. We plan to carry out first a rather straightforward set of picosecond pulse measurements on polysilicon photodetectors or photoswitches, such as can be very conveniently fabricated onto silicon integrated circuits using standard IC techniques, to serve as on-chip, optically addressable test or diagnostic points. (Such test points may in fact be fabricated directly into the active portion of the IC, or as test points in the disposable Kerr region between chips, for access during initial fabrication only). We are therefore assembling the necessary laser system for these measurements, and in addition beginning the fabrication of silicon test devices in collaboration with Professor Robert Dutton of the Integrated Circuit Laboratory and CIS. While making these preparations we have also carried out a literature review of the current state-of-the-art in such electrooptic devices. Some of the results of this study are summarized

  19. Development of a non-thermal accelerated pulsed UV photolysis assisted digestion method for fresh and dried food samples

    International Nuclear Information System (INIS)

    Solis, C.; Lagunas-Solar, M.C.; Perley, B.P.; Pina, C.; Aguilar, L.F.; Flocchini, R.G.

    2002-01-01

    A simple, fast digestion procedure for fresh and dried foods, using high-power pulsed UV photolysis in the presence of hydrogen peroxide, is being developed. The homogenized food samples were mixed with H 2 O 2 or with a mixture of H 2 O 2 and HNO 3 , and irradiated for short times with a 248-nm UV excimer laser. After centrifugation, a clear, colorless solution was obtained and aliquots were deposited on Teflon filters for XRF and/or PIXE analyses. Standard reference materials (NIST Peach Leaves; Typical Diet) were also analyzed to compare recoveries and detection limits. Improvements in detection limits were observed, but a few trace elements (<1 ppm) were not reproducibly detected (Fe, Sr). This method proved to be practical for the accelerated digestion of food samples and preparing analytes in short-time intervals. In combination with PIXE and XRF, it allows high-sensitivity multi-elemental analyses for screening the nutritional elements and for food safety purposes regarding the potential presence of toxic elements. Further development to optimize and validate this procedure for a broader range of analytes is in progress

  20. Hydrodynamic simulation of X-UV laser-produced plasmas

    International Nuclear Information System (INIS)

    Fajardo, M.; Zeitoun, P.; Gauthier, J.C.

    2004-01-01

    With the construction of novel X-UV sources, such as V-UV FEL's (free-electron lasers), X-UV laser-matter interaction will become available at ultra-high intensities. But even table-top facilities such as X-UV lasers or High Harmonic Generation, are starting to reach intensities high enough to produce dense plasmas. X-UV laser-matter interaction is studied by a 1-dimensional hydrodynamic Lagrangian code with radiative transfer for a range of interesting X-UV sources. Heating is found to be very different for Z=12-14 elements having L-edges around the X-UV laser wavelength. Possible absorption mechanisms were investigated in order to explain this behaviour, and interaction with cold dense matter proved to be dominant. Plasma sensitivity to X-UV laser parameters such as energy, pulse duration, and wavelength was also studied, covering ranges of existing X-UV lasers. We found that X-UV laser-produced plasmas could be studied using table-top lasers, paving the way for future V-UV-FEL high intensity experiments. (authors)

  1. Depth profiling of calcifications in breast tissue using picosecond Kerr-gated Raman spectroscopy.

    Science.gov (United States)

    Baker, Rebecca; Matousek, Pavel; Ronayne, Kate Louise; Parker, Anthony William; Rogers, Keith; Stone, Nicholas

    2007-01-01

    Breast calcifications are found in both benign and malignant lesions and their composition can indicate the disease state. Calcium oxalate (dihydrate) (COD) is associated with benign lesions, however calcium hydroxyapatite (HAP) is found mainly in proliferative lesions including carcinoma. The diagnostic practices of mammography and histopathology examine the morphology of the specimen. They can not reliably distinguish between the two types of calcification, which may indicate the presence of a cancerous lesion during mammography. We demonstrate for the first time that Kerr-gated Raman spectroscopy is capable of non-destructive probing of sufficient biochemical information from calcifications buried within tissue, and this information can potentially be used as a first step in identifying the type of lesion. The method uses a picosecond pulsed laser combined with fast temporal gating of Raman scattered light to enable spectra to be collected from a specific depth within scattering media by collecting signals emerging from the sample at a given time delay following the laser pulse. Spectra characteristic of both HAP and COD were obtained at depths of up to 0.96 mm, in both chicken breast and fatty tissue; and normal and cancerous human breast by utilising different time delays. This presents great potential for the use of Raman spectroscopy as an adjunct to mammography in the early diagnosis of breast cancer.

  2. Development of transient collisional excitation x-ray laser with ultra short-pulse laser

    International Nuclear Information System (INIS)

    Kado, Masataka; Kawachi, Tetsuya; Hasegawa, Noboru; Tanaka, Momoko; Sukegawa, Kouta; Nagashima, Keisuke; Kato, Yoshiaki

    2001-01-01

    We have observed lasing on Ne-like 3s-3p line from titanium (32.4 nm), Ni-like 4p-4d line from silver (13.9 nm) and tin (11.9 nm) with the transient collisional excitation (TCE) scheme that uses combination of a long pre-pulse (∼ns) and a short main pulse (∼ps). A gain coefficient of 23 cm -1 was measured for plasma length up to 4 mm with silver slab targets. We have also observed lasing on Ne-like and Ni-like lines with new TCE scheme that used pico-seconds laser pulse to generate plasma and observed strong improvement of x-ray laser gain coefficient. A gain coefficient of 14 cm -1 was measured for plasma length up to 6 mm with tin targets. (author)

  3. Picosecond x-ray streak cameras

    Science.gov (United States)

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

    1991-04-01

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

  4. Picosecond rotationally resolved stimulated emission pumping spectroscopy of nitric oxide

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  5. Generation of 46 W green-light by frequency doubling of 96 W picosecond unpolarized Yb-doped fiber amplifier

    Science.gov (United States)

    Qi, Yaoyao; Yu, Haijuan; Zhang, Jingyuan; Zhang, Ling; He, Chaojian; Lin, Xuechun

    2018-05-01

    We demonstrated a high efficiency and high average power picosecond green light source based on SHG (second harmonic generation) of an unpolarized ytterbium-doped fiber amplifier chain. Using single-pass frequency doubling in two temperature-tuned type-I phase-matching LBO crystals, we were able to generate 46 W, >70 ps pulses at 532 nm from a fundamental beam at 1064 nm, whose output is 96 W, 4.8 μJ, with a repetition frequency of 20 MHz and nearly diffraction limited. The optical conversion efficiency was ∼48% in a highly compact design. To the best of our knowledge, this is the first reported on ps green source through SHG of an unpolarized fiber laser with such a high output and high efficiency.

  6. Picosecond relaxation of X-ray excited GaAs

    Czech Academy of Sciences Publication Activity Database

    Tkachenko, V.; Medvedev, Nikita; Lipp, V.; Ziaja, B.

    2017-01-01

    Roč. 24, Sep (2017), s. 15-21 ISSN 1574-1818 Institutional support: RVO:68378271 Keywords : GaAS * X-ray excitation * picosecond relaxation Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 0.908, year: 2016

  7. Type-I cascaded quadratic soliton compression in lithium niobate: Compressing femtosecond pulses from high-power fiber lasers

    DEFF Research Database (Denmark)

    Bache, Morten; Wise, Frank W.

    2010-01-01

    The output pulses of a commercial high-power femtosecond fiber laser or amplifier are typically around 300–500 fs with wavelengths of approximately 1030 nm and tens of microjoules of pulse energy. Here, we present a numerical study of cascaded quadratic soliton compression of such pulses in LiNbO3....... However, the strong group-velocity dispersion implies that the pulses can achieve moderate compression to durations of less than 130 fs in available crystal lengths. Most of the pulse energy is conserved because the compression is moderate. The effects of diffraction and spatial walk-off are addressed......, and in particular the latter could become an issue when compressing such long crystals (around 10 cm long). We finally show that the second harmonic contains a short pulse locked to the pump and a long multi-picosecond red-shifted detrimental component. The latter is caused by the nonlocal effects...

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

    Science.gov (United States)

    Berg, Christopher Michael

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

  9. Thin film beam splitter multiple short pulse generation for enhanced Ni-like Ag x-ray laser emission.

    Science.gov (United States)

    Cojocaru, Gabriel V; Ungureanu, Razvan G; Banici, Romeo A; Ursescu, Daniel; Delmas, Olivier; Pittman, Moana; Guilbaud, Olivier; Kazamias, Sophie; Cassou, Kevin; Demailly, Julien; Neveu, Olivier; Baynard, Elsa; Ros, David

    2014-04-15

    An alternative, novel multiple pulse generation scheme was implemented directly after the optical compressor output of an x-ray pump laser. The new method uses a polarization sensitive thin film beam splitter and a half-wavelength wave plate for tuning the energy ratio in the multiple short pulses. Based on this method, an extensive study was made of the running parameters for a grazing incidence pumped silver x-ray laser (XRL) pumped with a long pulse of 145 mJ in 6 ns at 532 nm and up to 1.45 J in few picoseconds at 810 nm. Fivefold enhancement in the emission of the silver XRL was demonstrated using the new pump method.

  10. Electromagnetic pulse-driven spin-dependent currents in semiconductor quantum rings.

    Science.gov (United States)

    Zhu, Zhen-Gang; Berakdar, Jamal

    2009-04-08

    We investigate the non-equilibrium charge and spin-dependent currents in a quantum ring with a Rashba spin-orbit interaction (SOI) driven by two asymmetric picosecond electromagnetic pulses. The equilibrium persistent charge and persistent spin-dependent currents are investigated as well. It is shown that the dynamical charge and the dynamical spin-dependent currents vary smoothly with a static external magnetic flux and the SOI provides a SU(2) effective flux that changes the phases of the dynamic charge and the dynamic spin-dependent currents. The period of the oscillation of the total charge current with the delay time between the pulses is larger in a quantum ring with a larger radius. The parameters of the pulse fields control to a certain extent the total charge and the total spin-dependent currents. The calculations are applicable to nanometre rings fabricated in heterojunctions of III-V and II-VI semiconductors containing several hundreds of electrons.

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

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  12. Single-mode, All-Solid-State Nd:YAG Laser Pumped UV Converter

    Science.gov (United States)

    Prasad, Narasimha S.; Armstrong, Darrell, J.; Edwards, William C.; Singh, Upendra N.

    2008-01-01

    In this paper, the status of a high-energy, all solid-state Nd:YAG laser pumped nonlinear optics based UV converter development is discussed. The high-energy UV transmitter technology is being developed for ozone sensing applications from space based platforms using differential lidar technique. The goal is to generate greater than 200 mJ/pulse with 10-50 Hz PRF at wavelengths of 308 nm and 320 nm. A diode-pumped, all-solid-state and single longitudinal mode Nd:YAG laser designed to provide conductively cooled operation at 1064 nm has been built and tested. Currently, this pump laser provides an output pulse energy of >1 J/pulse at 50 Hz PRF and a pulsewidth of 22 ns with an electrical-to-optical system efficiency of greater than 7% and a M(sup 2) value of UV converter arrangement basically consists of an IR Optical Parametric Oscillator (OPO) and a Sum Frequency Generator (SFG) setups that are pumped by 532 nm wavelength obtained via Second Harmonic Generation (SHG). In this paper, the operation of an inter cavity SFG with CW laser seeding scheme generating 320 nm wavelength is presented. Efforts are underway to improve conversion efficiency of this mJ class UV converter by modifying the spatial beam profile of the pump laser.

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

    Directory of Open Access Journals (Sweden)

    Korshed P

    2017-12-01

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

  14. Design and implementation of an optimal laser pulse front tilting scheme for ultrafast electron diffraction in reflection geometry with high temporal resolution

    Directory of Open Access Journals (Sweden)

    Francesco Pennacchio

    2017-07-01

    Full Text Available Ultrafast electron diffraction is a powerful technique to investigate out-of-equilibrium atomic dynamics in solids with high temporal resolution. When diffraction is performed in reflection geometry, the main limitation is the mismatch in group velocity between the overlapping pump light and the electron probe pulses, which affects the overall temporal resolution of the experiment. A solution already available in the literature involved pulse front tilt of the pump beam at the sample, providing a sub-picosecond time resolution. However, in the reported optical scheme, the tilted pulse is characterized by a temporal chirp of about 1 ps at 1 mm away from the centre of the beam, which limits the investigation of surface dynamics in large crystals. In this paper, we propose an optimal tilting scheme designed for a radio-frequency-compressed ultrafast electron diffraction setup working in reflection geometry with 30 keV electron pulses containing up to 105 electrons/pulse. To characterize our scheme, we performed optical cross-correlation measurements, obtaining an average temporal width of the tilted pulse lower than 250 fs. The calibration of the electron-laser temporal overlap was obtained by monitoring the spatial profile of the electron beam when interacting with the plasma optically induced at the apex of a copper needle (plasma lensing effect. Finally, we report the first time-resolved results obtained on graphite, where the electron-phonon coupling dynamics is observed, showing an overall temporal resolution in the sub-500 fs regime. The successful implementation of this configuration opens the way to directly probe structural dynamics of low-dimensional systems in the sub-picosecond regime, with pulsed electrons.

  15. Pulsed Raman fiber laser and multispectral imaging in three dimensions

    DEFF Research Database (Denmark)

    Andersen, Joachim F.; Busck, Jens; Heiselberg, Henning

    2006-01-01

    Raman scattering in single-mode optical fibers is exploited to generate multispectral light from a green nanolaser with high pulse repetition rate. Each pulse triggers a picosecond camera and measures the distance by time-of-flight in each of the 0.5 Mpixels. Three-dimensional images...... are then constructed with submillimeter accuracy for all visible colors. The generation of a series of Stokes peaks by Raman scattering in a Si fiber is discussed in detail and the laser radar technique is demonstrated. The data recording takes only a few seconds, and the high accuracy 3D color imaging works at ranges...... up to ∼200 m. Applications for optical tomography in highly scattering media such as water and human tissue are mentioned. © 2006 Optical Society of America....

  16. UV laser beam profile measurement by means of the photoelectric effect on the wires of a proportional chamber

    International Nuclear Information System (INIS)

    Prokoviev, O.; Seiler, P.G.

    1989-01-01

    A simple technique to measure the profiles of pulsed UV laser beams is described. Irradiating a cathode wire of a proportional chamber with UV laser shots results in signals from the anode wire whose amplitudes are proportional to the UV light intensity. Profile scanning is performed by shifting the chamber across the beam. The chamber can also be used with reversed polarities. This leads to avalanches developing outwardly from the signal wire. In this case we observe a quadratic dependence of the pulse height on the UV light intensity. (orig.)

  17. High-energy, high-repetition-rate picosecond pulses from a quasi-CW diode-pumped Nd:YAG system.

    Science.gov (United States)

    Noom, Daniel W E; Witte, Stefan; Morgenweg, Jonas; Altmann, Robert K; Eikema, Kjeld S E

    2013-08-15

    We report on a high-power quasi-CW pumped Nd:YAG laser system, producing 130 mJ, 64 ps pulses at 1064 nm wavelength with a repetition rate of 300 Hz. Pulses from a Nd:YVO(4) oscillator are first amplified by a regenerative amplifier to the millijoule level and then further amplified in quasi-CW diode-pumped Nd:YAG modules. Pulsed diode pumping enables a high gain at repetition rates of several hundred hertz, while keeping thermal effects manageable. Birefringence compensation and multiple thermal-lensing-compensated relay-imaging stages are used to maintain a top-hat beam profile. After frequency doubling, 75 mJ pulses are obtained at 532 nm. The intensity stability is better than 1.1%, which makes this laser an attractive pump source for a high-repetition-rate optical parametric amplification system.

  18. Ultra-intense, short pulse laser-plasma interactions with applications to the fast ignitor

    International Nuclear Information System (INIS)

    Wilks, S.C.; Kruer, W.L.; Young, P.E.; Hammer, J.; Tabak, M.

    1995-04-01

    Due to the advent of chirped pulse amplification (CPA) as an efficient means of creating ultra-high intensity laser light (I > 5x10 17 W/cm 2 ) in pulses less than a few picoseconds, new ideas for achieving ignition and gain in DT targets with less than 1 megajoule of input energy are currently being pursued. Two types of powerful lasers are employed in this scheme: (1) channeling beams and (2) ignition beams. The current state of laser-plasma interactions relating to this fusion scheme will be discussed. In particular, plasma physics issues in the ultra-intense regime are crucial to the success of this scheme. We compare simulation and experimental results in this highly nonlinear regime

  19. Time-Frequency (Wigner Analysis of Linear and Nonlinear Pulse Propagation in Optical Fibers

    Directory of Open Access Journals (Sweden)

    José Azaña

    2005-06-01

    Full Text Available Time-frequency analysis, and, in particular, Wigner analysis, is applied to the study of picosecond pulse propagation through optical fibers in both the linear and nonlinear regimes. The effects of first- and second-order group velocity dispersion (GVD and self-phase modulation (SPM are first analyzed separately. The phenomena resulting from the interplay between GVD and SPM in fibers (e.g., soliton formation or optical wave breaking are also investigated in detail. Wigner analysis is demonstrated to be an extremely powerful tool for investigating pulse propagation dynamics in nonlinear dispersive systems (e.g., optical fibers, providing a clearer and deeper insight into the physical phenomena that determine the behavior of these systems.

  20. A protection system for picosecond accelerator

    International Nuclear Information System (INIS)

    Cao Hongping; Chinese Academy of Sciences, Beijing; Chen Huanguang; Xu Ruinian; Tang Junlong; Li Deming

    2006-01-01

    A personnel and machine protection system for the picosecond accelerator has been built. The key of the system is to send on/off of three triggering signals which are those of electron gun, 2856 MHz and 476 MHz, respectively, to ensure the safety of users and the accelerator. This paper describes the emergencies interlocked by ADAM5511 and timing trigger processor, and some secondary functions which improve the efficiency of the protection system completed in upper layer software. (authors)

  1. 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

  2. Fundamental Scaling of Microplasmas and Tunable UV Light Generation.

    Energy Technology Data Exchange (ETDEWEB)

    Manginell, Ronald P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sillerud, Colin Halliday [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hopkins, Matthew M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Yee, Benjamin Tong [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Moorman, Matthew W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Schwindt, Peter [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Anderson, John Moses [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pfeifer, Nathaniel Bryant [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-11-01

    The temporal evolution of spectral lines from microplasma devices (MD) was studied, including impurity transitions. Long-wavelength emission diminishes more rapidly than deep UV with decreasing pulse width and RF operation. Thus, switching from DC to short pulsed or RF operation, UV emissions can be suppressed, allowing for real-time tuning of the ionization energy of a microplasma photo-ionization source, which is useful for chemical and atomic physics. Scaling allows MD to operate near atmospheric pressure where excimer states are efficiently created and emit down to 65 nm; laser emissions fall off below 200 nm, making MD light sources attractive for deep UV use. A first fully-kinetic three-dimensional model was developed that explicitly calculates electron-energy distribution function. This, and non-continuum effects, were studied with the model and how they are impacted by geometry and transient or DC operation. Finally, a global non-dimensional model was developed to help explain general trends MD physics.

  3. Formation of plasma channels in air under filamentation of focused ultrashort laser pulses

    International Nuclear Information System (INIS)

    Ionin, A A; Seleznev, L V; Sunchugasheva, E S

    2015-01-01

    The formation of plasma channels in air under filamentation of focused ultrashort laser pulses was experimentally and theoretically studied together with theoreticians of the Moscow State University and the Institute of Atmospheric Optics. The influence of various characteristics of ultrashort laser pulses on these plasma channels is discussed. Plasma channels formed under filamentation of focused laser beams with a wavefront distorted by spherical aberration (introduced by adaptive optics) and by astigmatism, with cross-section spatially formed by various diaphragms and with different UV and IR wavelengths, were experimentally and numerically studied. The influence of plasma channels created by a filament of a focused UV or IR femtosecond laser pulse (λ = 248 nm or 740 nm) on characteristics of other plasma channels formed by a femtosecond pulse at the same wavelength following the first one with varied nanosecond time delay was also experimentally studied. An application of plasma channels formed due to the filamentation of focused UV ultrashort laser pulses including a train of such pulses and a combination of ultrashort and long (∼100 ns) laser pulses for triggering and guiding long (∼1 m) electric discharges is discussed. (topical review)

  4. Femtosecond UV-laser pulses to unveil protein-protein interactions in living cells.

    Science.gov (United States)

    Itri, Francesco; Monti, Daria M; Della Ventura, Bartolomeo; Vinciguerra, Roberto; Chino, Marco; Gesuele, Felice; Lombardi, Angelina; Velotta, Raffaele; Altucci, Carlo; Birolo, Leila; Piccoli, Renata; Arciello, Angela

    2016-02-01

    A hallmark to decipher bioprocesses is to characterize protein-protein interactions in living cells. To do this, the development of innovative methodologies, which do not alter proteins and their natural environment, is particularly needed. Here, we report a method (LUCK, Laser UV Cross-linKing) to in vivo cross-link proteins by UV-laser irradiation of living cells. Upon irradiation of HeLa cells under controlled conditions, cross-linked products of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were detected, whose yield was found to be a linear function of the total irradiation energy. We demonstrated that stable dimers of GAPDH were formed through intersubunit cross-linking, as also observed when the pure protein was irradiated by UV-laser in vitro. We proposed a defined patch of aromatic residues located at the enzyme subunit interface as the cross-linking sites involved in dimer formation. Hence, by this technique, UV-laser is able to photofix protein surfaces that come in direct contact. Due to the ultra-short time scale of UV-laser-induced cross-linking, this technique could be extended to weld even transient protein interactions in their native context.

  5. A Mode Locked UV-FEL

    CERN Document Server

    Parvin, Parviz

    2004-01-01

    An appropriate resonator has been designed to generate femtosecond mode locked pulses in a UV FEL with the modulator performance based on the gain switching. The gain broadening due to electron energy spread affects on the gain parameters, small signal gain (γ0) and saturation intensity (Is), to determine the optimum output coupling as small.

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  7. Implementation of STUD Pulses at the Trident Laser and Initial Results

    Science.gov (United States)

    Johnson, R. P.; Shimada, T.; Montgomery, D. S.; Afeyan, B.; Hüller, S.

    2012-10-01

    Controlling and mitigating laser-plasma instabilities such as stimulated Brillouin scattering, stimulated Raman scattering, and crossed-beam energy transfer is important to achieve high-gain inertial fusion using laser drivers. Recent theory and simulations show that these instabilities can be largely controlled using laser pulses consisting of spike trains of uneven duration and delay (STUD) by modulating the laser on a picosecond time scale [1,2]. We have designed and implemented a STUD pulse generator at the LANL Trident Laser Facility using Fourier synthesis to produce a 0.5-ns envelope of psec-duration STUD pulses using a spatial light modulator. Initial results from laser propagation tests and measurements as well as initial laser-plasma characterization experiments will be presented.[4pt] [1] B. Afeyan and S. H"uller, ``Optimal Control of Laser Plasma Instabilities using STUD pulses,'' IFSA 2011, P.Mo.1, to appear in Euro. Phys. J. Web of Conf. (2012).[2] S. H"uller and B. Afeyan, ``Simulations of drastically reduced SBS with STUD pulses,'' IFSA 2011, O.Tu8-1, to appear in Euro. Phys. J. Web of Conf. (2012).

  8. Model of UV flashes due to gigantic blue jets

    International Nuclear Information System (INIS)

    Milikh, G M; Shneider, M N

    2008-01-01

    Analysis of UV flashes observed by the UV detector on board the 'Tatiana' microsatellite suggests, based on their location, pulse width and energy of the source of the photons, that the flashes were generated by gigantic blue jets (GBJs). Presented in this paper is a numerical model of UV flashes due to a bunch of long streamers which form a leader, a prong such as that observed in a GBJ. Using a previously developed model of upward propagation of a long streamer in the exponential atmosphere the paper describes temporal evolution of the UV flux generated by a bunch of long streamers, in the given spectral range 300-400 nm used by the UV detector on board 'Tatiana'. The model is in agreement with the observations.

  9. Development of a pump-probe facility with sub-picosecond time resolution combining a high-power ultraviolet regenerative FEL amplifier and a soft X-ray SASE FEL

    International Nuclear Information System (INIS)

    Faatz, B.; Fateev, A.A.; Feldhaus, J.; Krzywinski, J.; Pflueger, J.; Rossbach, J.; Saldin, E.L.; Schneidmiller, E.A.; Yurkov, M.V.

    2001-01-01

    This paper presents the conceptual design of a high power radiation source with laser-like characteristics in the ultraviolet spectral range at the TESLA Test Facility (TTF). The concept is based on the generation of radiation in a regenerative FEL amplifier (RAFEL). The RAFEL described in this paper covers a wavelength range of 200-400 nm and provides 200 fs pulses with 2 mJ of optical energy per pulse. The linac operates at 1% duty factor and the average output radiation power exceeds 100 W. The RAFEL will be driven by the spent electron beam leaving the soft X-ray FEL, thus providing minimal interference between these two devices. The RAFEL output radiation has the same time structure as the X-ray FEL and the UV pulses are naturally synchronized with the soft X-ray pulses from the TTF FEL. Therefore, it should be possible to achieve synchronization close to the duration of the radiation pulses (200 fs) for pump-probe techniques using either an UV pulse as a pump and soft X-ray pulse as a probe, or vice versa

  10. Comparison of femtosecond laser and continuous wave UV sources for protein-nucleic acid crosslinking.

    Science.gov (United States)

    Fecko, Christopher J; Munson, Katherine M; Saunders, Abbie; Sun, Guangxing; Begley, Tadhg P; Lis, John T; Webb, Watt W

    2007-01-01

    Crosslinking proteins to the nucleic acids they bind affords stable access to otherwise transient regulatory interactions. Photochemical crosslinking provides an attractive alternative to formaldehyde-based protocols, but irradiation with conventional UV sources typically yields inadequate product amounts. Crosslinking with pulsed UV lasers has been heralded as a revolutionary technique to increase photochemical yield, but this method had only been tested on a few protein-nucleic acid complexes. To test the generality of the yield enhancement, we have investigated the benefits of using approximately 150 fs UV pulses to crosslink TATA-binding protein, glucocorticoid receptor and heat shock factor to oligonucleotides in vitro. For these proteins, we find that the quantum yields (and saturating yields) for forming crosslinks using the high-peak intensity femtosecond laser do not improve on those obtained with low-intensity continuous wave (CW) UV sources. The photodamage to the oligonucleotides and proteins also has comparable quantum yields. Measurements of the photochemical reaction yields of several small molecules selected to model the crosslinking reactions also exhibit nearly linear dependences on UV intensity instead of the previously predicted quadratic dependence. Unfortunately, these results disprove earlier assertions that femtosecond pulsed laser sources provide significant advantages over CW radiation for protein-nucleic acid crosslinking.

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

    Science.gov (United States)

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

    2018-01-01

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

  12. Isomer-specific detection in the UV photodissociation of the propargyl radical by chirped-pulse mm-wave spectroscopy in a pulsed quasi-uniform flow.

    Science.gov (United States)

    Broderick, Bernadette M; Suas-David, Nicolas; Dias, Nureshan; Suits, Arthur G

    2018-02-21

    Isomer-specific detection and product branching fractions in the UV photodissociation of the propargyl radical is achieved through the use of chirped-pulse Fourier-transform mm-wave spectroscopy in a pulsed quasi-uniform flow (CPUF). Propargyl radicals are produced in the 193 nm photodissociation of 1,2-butadiene. Absorption of a second photon leads to H atom elimination giving three possible C 3 H 2 isomers: singlets cyclopropenylidene (c-C 3 H 2 ) and propadienylidene (l-C 3 H 2 ), and triplet propargylene ( 3 HCCCH). The singlet products and their appearance kinetics in the flow are directly determined by rotational spectroscopy, but due to the negligible dipole moment of propargylene, it is not directly monitored. However, we exploit the time-dependent kinetics of H-atom catalyzed isomerization to infer the branching to propargylene as well. We obtain the overall branching among H loss channels to be 2.9% (+1.1/-0.5) l-C 3 H 2 + H, 16.8% (+3.2/-1.3) c-C 3 H 2 + H, and 80.2 (+1.8/-4.2) 3 HCCCH + H. Our findings are qualitatively consistent with earlier RRKM calculations in that the major channel in the photodissociation of the propargyl radical at 193 nm is to 3 HCCCH + H; however, a greater contribution to the energetically most favorable isomer, c-C 3 H 2 + H is observed in this work. We do not detect the predicted HCCC + H 2 channel, but place an upper bound on its yield of 1%.

  13. Pulsed x-ray imaging of high-density objects using a ten picosecond high-intensity laser driver

    Science.gov (United States)

    Rusby, D. R.; Brenner, C. M.; Armstrong, C.; Wilson, L. A.; Clarke, R.; Alejo, A.; Ahmed, H.; Butler, N. M. H.; Haddock, D.; Higginson, A.; McClymont, A.; Mirfayzi, S. R.; Murphy, C.; Notley, M.; Oliver, P.; Allott, R.; Hernandez-Gomez, C.; Kar, S.; McKenna, P.; Neely, D.

    2016-10-01

    Point-like sources of X-rays that are pulsed (sub nanosecond), high energy (up to several MeV) and bright are very promising for industrial and security applications where imaging through large and dense objects is required. Highly penetrating X-rays can be produced by electrons that have been accelerated by a high intensity laser pulse incident onto a thin solid target. We have used a pulse length of 10ps to accelerate electrons to create a bright x-ray source. The bremsstrahlung temperature was measured for a laser intensity from 8.5-12×1018 W/cm2. These x-rays have sequentially been used to image high density materials using image plate and a pixelated scintillator system.

  14. Effect of absorbing coating on ablation of diamond by IR laser pulses

    Science.gov (United States)

    Kononenko, T. V.; Pivovarov, P. A.; Khomich, A. A.; Khmel'nitskii, R. A.; Konov, V. I.

    2018-03-01

    We study the possibility of increasing the efficiency and quality of laser ablation microprocessing of diamond by preliminary forming an absorbing layer on its surface. The laser pulses having a duration of 1 ps and 10 ns at a wavelength of 1030 nm irradiate the polycrystalline diamond surface coated by a thin layer of titanium or graphite. We analyse the dynamics of the growth of the crater depth as a function of the number of pulses and the change in optical transmission of the ablated surface. It is found that under irradiation by picosecond pulses the preliminary graphitisation allows one to avoid the laser-induced damage of the internal diamond volume until the appearance of a self-maintained graphitised layer. The absorbing coating (both graphite and titanium) much stronger affects ablation by nanosecond pulses, since it reduces the ablation threshold by more than an order of magnitude and allows full elimination of a laser-induced damage of deep regions of diamond and uncontrolled explosive ablation in the nearsurface layer.

  15. Porous nanostructured ZnO films deposited by picosecond laser ablation

    International Nuclear Information System (INIS)

    Sima, Cornelia; Grigoriu, Constantin; Besleaga, Cristina; Mitran, Tudor; Ion, Lucian; Antohe, Stefan

    2012-01-01

    Highlights: ► We deposite porous nanostructured ZnO films by picoseconds laser ablation (PLA). ► We examine changes of the films structure on the experimental parameter deposition. ► We demonstrate PLA capability to produce ZnO nanostructured films free of particulates. - Abstract: Porous nanostructured polycrystalline ZnO films, free of large particulates, were deposited by picosecond laser ablation. Using a Zn target, zinc oxide films were deposited on indium tin oxide (ITO) substrates using a picosecond Nd:YVO 4 laser (8 ps, 50 kHz, 532 nm, 0.17 J/cm 2 ) in an oxygen atmosphere at room temperature (RT). The morpho-structural characteristics of ZnO films deposited at different oxygen pressures (150–900 mTorr) and gas flow rates (0.25 and 10 sccm) were studied. The post-deposition influence of annealing (250–550 °C) in oxygen on the film characteristics was also investigated. At RT, a mixture of Zn and ZnO formed. At substrate temperatures above 350 °C, the films were completely oxidized, containing a ZnO wurtzite phase with crystallite sizes of 12.2–40.1 nm. At pressures of up to 450 mTorr, the porous films consisted of well-distinguished primary nanoparticles with average sizes of 45–58 nm, while at higher pressures, larger clusters (3.1–14.7 μm) were dominant, leading to thicker films; higher flow rates favored clustering.

  16. Measurements of plasma mirror reflectivity and focal spot quality for tens of picosecond laser pulses

    Science.gov (United States)

    Forestier-Colleoni, Pierre; Williams, Jackson; Scott, Graeme; Mariscal, Dereck. A.; McGuffey, Christopher; Beg, Farhat N.; Chen, Hui; Neely, David; Ma, Tammy

    2017-10-01

    The Advanced Radiographic Capability (ARC) laser at the NIF (LLNL) is high-energy ( 4 kJ) with a pulse length of 30ps, and is capable of focusing to an intensity of 1018W/cm2 with a 100 μm focal spot. The ARC laser is at an intensity which can be used to produce proton beams. However, for applications such as radiography and warm dense matter creation, a higher laser intensity may be desired to generate more energetic proton beams. One possibility to increase the intensity is to decrease the focused spot size by employing a smaller f-number optic. But it is difficult to implement such an optic or to bring the final focusing parabola closer to the target within the complicated NIF chamber geometry. A proposal is to use ellipsoidal plasma mirrors (PM) for fast focusing of the ARC laser light, thereby increasing the peak intensity. There is uncertainty, however, in the survivability and reflectivity of PM at such long pulse durations. Here, we show experimental results from the Titan laser to study the reflectivity of flat PM as a function of laser pulse length. A calorimeter was used to measure the PM reflectivity. We also observed degradation of the far and near field energy distribution of the laser after the reflection by the PM for pulse-lengths beyond 10ps. Contract DE-AC52-07NA27344. Funded by the LLNL LDRD program: tracking code 17-ERD-039.

  17. UV, visible and IR laser interaction with gelatine

    International Nuclear Information System (INIS)

    Oujja, M; Rebollar, E; Abrusci, C; Amo, A Del; Catalina, F; Castillejo, M

    2007-01-01

    In this work we investigate the effects on gelatine films of nanosecond pulsed laser irradiation at different laser wavelengths from the UV to the IR at 248, 266, 355, 532 and 1064 nm. We compared gelatines differing in gel strength values (Bloom 75 and 225) and in crosslinking degree. Formation of bubbles at the wavelengths in the UV (248 and 266 nm), melting and resolidification at 355 nm, and formation of craters by ablation in the VIS and IR (532 and 1064 nm) are the observed morphological changes. On the other hand, changes of the fluorescence behaviour of the films upon UV irradiation reveal chemical modifications of photolabile chromophores

  18. Response of YBa2Cu3O7-δ grain-boundary junctions to short light pulses

    International Nuclear Information System (INIS)

    Kaplan, S.B.; Chi, C.C.; Chaudhari, P.; Dimos, D.; Gross, R.; Gupta, A.; Koren, G.

    1991-01-01

    The electrical response of a single YBa 2 Cu 3 O 7-δ grain-boundary junction to visible light pulses was measured. Using an autocorrelation technique with picosecond laser pulses, no fast voltage transients were observed with the junction biased just above its critical current. Apparently, there are no relaxation times in the range of 7 ps to 14 ns. Using direct time-domain measurement with nanosecond pulses, three types of junction response were recorded: a nonexponential decay of 11 μs (90 to 10 % time) at temperatures near T c ; an inverse-time dependence of the order of 0.3 μs (100 to 50 % time) in the temperature range of 4.2 to 15 K; and an exponential decay time of 0.15 μs with the sample immersed in superfluid helium

  19. Ultra-intense, short pulse laser-plasma interactions with applications to the fast ignitor

    Energy Technology Data Exchange (ETDEWEB)

    Wilks, S.C.; Kruer, W.L.; Young, P.E.; Hammer, J.; Tabak, M.

    1995-04-01

    Due to the advent of chirped pulse amplification (CPA) as an efficient means of creating ultra-high intensity laser light (I > 5{times}10{sup 17} W/cm{sup 2}) in pulses less than a few picoseconds, new ideas for achieving ignition and gain in DT targets with less than 1 megajoule of input energy are currently being pursued. Two types of powerful lasers are employed in this scheme: (1) channeling beams and (2) ignition beams. The current state of laser-plasma interactions relating to this fusion scheme will be discussed. In particular, plasma physics issues in the ultra-intense regime are crucial to the success of this scheme. We compare simulation and experimental results in this highly nonlinear regime.

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

    Science.gov (United States)

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

    2016-09-01

    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 generation from a completely common-path, unidirectional lasing cavity would be an interesting territory to explore. In this paper, we demonstrate such a dual-comb lasing scheme based on a nanomaterial saturable absorber with additional pulse narrowing and broadening mechanisms concurrently introduced into a mode-locked fiber laser. The interactions between multiple soliton formation mechanisms result in unusual bifurcation into two-pulse states with quite different characteristics. Simultaneous oscillation of pulses with four-fold difference in pulsewidths and tens of Hz repetition rate difference is observed. The coherence between these spectral-overlapped, picosecond and femtosecond pulses is further verified by the corresponding asynchronous cross-sampling and dual-comb spectroscopy measurements.

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

    Science.gov (United States)

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

    2015-11-01

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

  2. Amplification and focusing of a picosecond chirped pulse to 20TW and 5x1017W/cm2

    International Nuclear Information System (INIS)

    Sauteret, C.; Husson, D.; Rouyer, C.; Seznec, S.; Gary, S.

    1991-01-01

    Pulses of 20 TW power have been generated at 1064 nm using the Chirped Pulse Amplification technique coupled to a 90 mm output aperture powerful Nd:silicate glass amplification line. This system delivers 60 J in a chirped pulse of 600 ps duration with a capacity of maintaining 3.5 nm output bandwidth. These chirped pulses have been compressed to 1.2 ps with an energy of 24J using large holographic diffraction gratings. After presenting the results we discuss the expected applications in atomic and plasma physics

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

    OpenAIRE

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

    2016-01-01

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

  4. Optical pulse dynamics for quantum-dot logic operations in a photonic-crystal waveguide

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Xun; John, Sajeev [Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7 Canada (Canada)

    2011-11-15

    We numerically demonstrate all-optical logic operations with quantum dots (QDs) embedded in a bimodal photonic-crystal waveguide using Maxwell-Bloch equations in a slowly varying envelope approximation (SVEA). The two-level QD excitation level is controlled by one or more femtojoule optical driving pulses passing through the waveguide. Specific logic operations depend on the relative pulse strengths and their detunings from an inhomogeneouslly broadened (about 1% for QD transitions centered at 1.5 {mu}m) QD transition. This excitation controlled two-level medium then determines passage of subsequent probe optical pulses. Envelope equations for electromagnetic waves in the linear dispersion and cutoff waveguide modes are derived to simplify solution of the coupled Maxwell-Bloch equations in the waveguide. These determine the quantum mechanical evolution of the QD excitation and its polarization, driven by classical electromagnetic (EM) pulses near a sharp discontinuity in the EM density of states of the bimodal waveguide. Different configurations of the driving pulses lead to distinctive relations between driving pulse strength and probe pulse passage, representing all-optical logic and, or, and not operations. Simulation results demonstrate that such operations can be done on picosecond time scales and within a waveguide length of about 10 {mu}m in a photonic-band-gap (PBG) optical microchip.

  5. Influence of picosecond multiple/single line ablation on copper nanoparticles fabricated for surface enhanced Raman spectroscopy and photonics applications

    International Nuclear Information System (INIS)

    Hamad, Syed; Tewari, Surya P; Podagatlapalli, G Krishna; Rao, S Venugopal

    2013-01-01

    A comprehensive study comprising fabrication of copper nanoparticles (NPs) using picosecond (ps) multiple/single line ablation in various solvents such as acetone, dichloromethane (DCM), acetonitrile (ACN) and chloroform followed by optical, nonlinear optical (NLO), and surface enhanced Raman spectroscopy (SERS) characterization was performed. The influence of surrounding liquid media and the writing conditions resulted in fabrication of Cu NPs in acetone, CuCl NPs in DCM, CuO NPs in ACN and CuCl 2 NPs in chloroform. Prepared colloids were characterized through transmission electron microscopy, energy dispersive x-ray spectra, selected area electron diffraction and UV-visible absorption spectra. A detailed investigation of the surface enhanced Raman scattering (SERS) activity and the ps NLO properties of the colloids prepared through multiple/single line ablation techniques revealed that the best performance was achieved by Cu NPs for SERS applications and CuCl 2 NPs for NLO applications. (paper)

  6. Control of the UV flux of a XeCl dielectric barrier discharge excilamp through its current variation

    Energy Technology Data Exchange (ETDEWEB)

    Piquet, H; Bhosle, S; Diez, R; Cousineau, M; Djibrillah, M; Le Thanh, D; Dagang, A N; Zissis, G

    2012-02-28

    The efficiency of the electrical power transfer to the gas mixture of a XeCl dielectric barrier discharge (DBD) exciplex lamp is analysed. An equivalent circuit model of the DBD is considered. It is shown that the excilamp power can be controlled by applying current to the lamp. This highly desired property is ensured by means of a specific power supply topology, whose concepts and design are discussed. The experimental prototype of a current-mode converter operating in the pulsed regime at pulse repetition rate of 50 kHz is presented and its capability to control the amount of energy transferred during each current pulse is demonstrated. The capability of this power supply to maintain specific operating conditions for the DBD lamp, with a very stable behaviour (even at a very low current, in the regime of a single discharge channel), is illustrated. The experimental results of a combined use of this converter and a XeCl excilamp are presented. The influence of the supply parameters on the 308-nm XeCl excilamp is analysed. The shape of the UV pulse of the lamp is experimentally shown to be similar to that of the current, which actually flows into the gas mixture. The UV radiation power is demonstrated to be tightly correlated to the current injected into the gas and controlled by the available degrees of freedom offered by the power supply. The measured UV output characteristics and performance of the system are discussed. Time resolved UV imaging of a XeCl DBD excilamp is used to analyse the mechanisms involved in the production of exciplexes at various power supply regimes. It is shown that a pulsed voltage source leads to formation of short high intensity UV peaks, while current pulses lead to formation of sustained discharge filaments. Based on the results of modelling of the above-mentioned operation conditions, the two power supply regimes are compared and analysed from the point of view of the UV power and radiative control.

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

    Science.gov (United States)

    Bruneel, David; Kearsley, Andrew; Karnakis, Dimitris

    2015-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-12-30

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

  9. Detection of picosecond electrical transients in a scanning tunneling microscope

    NARCIS (Netherlands)

    Groeneveld, R.H.M.; Rasing, T.H.M.; Kaufmann, L.M.F.; Smalbrugge, E.; Wolter, J.H.; Melloch, M.R.; Kempen, van H.

    1996-01-01

    We have developed a scanning tunneling microscope using an optoelectronic switch which gates the tunneling tip current. The switch is fabricated within several tens of microns from the tip by photolithography and an accurate cleavage method. We demonstrate this approach by detecting picosecond

  10. Few-cycle high energy mid-infrared pulse from Ho:YLF laser

    International Nuclear Information System (INIS)

    Murari, Krishna

    2017-04-01

    Over the past decade, development of high-energy ultrafast laser sources has led to important breakthroughs in attoscience and strong-field physics study in atoms and molecules. Coherent pulse synthesis of few-cycle high-energy laser pulse is a promising tool to generate isolated attosecond pulses via high harmonics generation (HHG). An effective way to extend the HHG cut-off energy to higher values is making use of long mid-infrared (MIR) driver wavelength, as the ponderomotive potential scales quadratically with wavelength. If properly scaled in energy to multi-mJ level and few-cycle duration, such pulses provide a direct path to intriguing attoscience experiments in gases and solids, which even permit the realization of bright coherent table-top HHG sources in the water-window and keV X-ray region. However, the generation of high-intensity long-wavelength MIR pulses has always remained challenging, in particular starting from high-energy picosecond 2-μm laser driver, that is suitable for further energy scaling of the MIR pulses to multi-mJ energies by utilizing optical parametric amplifiers (OPAs). In this thesis, a front-end source for such MIR OPA is presented. In particular, a novel and robust strong-field few-cycle 2-μm laser driver directly from picosecond Ho:YLF laser and utilizing Kagome fiber based compression is presented. We achieved: a 70-fold compression of 140-μJ, 3.3-ps pulses from Ho:YLF amplifier to 48 fs with 11 μJ energy. The work presented in this thesis demonstrates a straightforward path towards generation of few-cycle MIR pulses and we believe that in the future the ultrafast community will benefit from this enabling technology. The results are summarized in mainly four parts: The first part is focused on the development of a 2-μm, high-energy laser source as the front-end. Comparison of available technology in general and promising gain media at MIR wavelength are discussed. Starting from the basics of an OPA, the design criteria

  11. Few-cycle high energy mid-infrared pulse from Ho:YLF laser

    Energy Technology Data Exchange (ETDEWEB)

    Murari, Krishna

    2017-04-15

    Over the past decade, development of high-energy ultrafast laser sources has led to important breakthroughs in attoscience and strong-field physics study in atoms and molecules. Coherent pulse synthesis of few-cycle high-energy laser pulse is a promising tool to generate isolated attosecond pulses via high harmonics generation (HHG). An effective way to extend the HHG cut-off energy to higher values is making use of long mid-infrared (MIR) driver wavelength, as the ponderomotive potential scales quadratically with wavelength. If properly scaled in energy to multi-mJ level and few-cycle duration, such pulses provide a direct path to intriguing attoscience experiments in gases and solids, which even permit the realization of bright coherent table-top HHG sources in the water-window and keV X-ray region. However, the generation of high-intensity long-wavelength MIR pulses has always remained challenging, in particular starting from high-energy picosecond 2-μm laser driver, that is suitable for further energy scaling of the MIR pulses to multi-mJ energies by utilizing optical parametric amplifiers (OPAs). In this thesis, a front-end source for such MIR OPA is presented. In particular, a novel and robust strong-field few-cycle 2-μm laser driver directly from picosecond Ho:YLF laser and utilizing Kagome fiber based compression is presented. We achieved: a 70-fold compression of 140-μJ, 3.3-ps pulses from Ho:YLF amplifier to 48 fs with 11 μJ energy. The work presented in this thesis demonstrates a straightforward path towards generation of few-cycle MIR pulses and we believe that in the future the ultrafast community will benefit from this enabling technology. The results are summarized in mainly four parts: The first part is focused on the development of a 2-μm, high-energy laser source as the front-end. Comparison of available technology in general and promising gain media at MIR wavelength are discussed. Starting from the basics of an OPA, the design criteria

  12. 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.

  13. Studies on the pathogenesis and survival of different culture forms of Listeria monocytogenes to pulsed UV-light irradiation after exposure to mild-food processing stresses.

    Science.gov (United States)

    Bradley, Derek; McNeil, Brian; Laffey, John G; Rowan, Neil J

    2012-06-01

    The effects of mild conventional food-processing conditions on Listeria monocytogenes survival to pulsed UV (PUV) irradiation and virulence-associated characteristics were investigated. Specifically, this study describes the inability of 10 strains representative of 3 different culture forms or morphotypes of L. monocytogenes to adapt to normally lethal levels of PUV-irradiation after exposure to sub-lethal concentrations of salt (7.5% (w/v) NaCl for 1 h), acid (pH 5.5 for 1 h), heating (48 °C for 1 h) or PUV (UV dose 0.08 μJ/cm(2)). Findings showed that the order of increasing sensitivity of L. monocytogenes of non-adapted and stressed morphotypes to low pH (pH 3.5 for 5 h, adjusted with lactic), high salt (17.5% w/v NaCl for 5 h), heating (60 °C for 1 h) and PUV-irradiation (100 pulses at 7.2 J and 12.8 J, equivalent to UV doses of 2.7 and 8.4 μJ/cm(2) respectively) was typical wild-type smooth (S/WT), atypical filamentous rough (FR) and atypical multiple-cell-chain (MCR) variants. Exposure of L. monocytogenes cells to sub-lethal acid, salt or heating conditions resulted in similar or increased susceptibility to PUV treatments. Only prior exposure to mild heat stressing significantly enhanced invasion of Caco-2 cells, whereas subjection of L. monocytogenes cells to combined sub-lethal salt, acid and heating conditions produced the greatest reduction in invasiveness. Implications of these findings are discussed. This constitutes the first study to show that pre-exposure to mild conventional food-processing stresses enhances sensitivity of different culture morphotypes of L. monocytogenes to PUV, which is growing in popularity as an alternative or complementary approach for decontamination in the food environment. Copyright © 2011 Elsevier Ltd. All rights reserved.

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  15. 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.

  16. Measurements of Electric Field in a Nanosecond Pulse Discharge by 4-WAVE Mixing

    Science.gov (United States)

    Baratte, Edmond; Adamovich, Igor V.; Simeni Simeni, Marien; Frederickson, Kraig

    2017-06-01

    Picosecond four-wave mixing is used to measure temporally and Picosecond four-wave mixing is used to measure temporally and spatially resolved electric field in a nanosecond pulse dielectric discharge sustained in room air and in an atmospheric pressure hydrogen diffusion flame. Measurements of the electric field, and more precisely the reduced electric field (E/N) in the plasma is critical for determination rate coefficients of electron impact processes in the plasma, as well as for quantifying energy partition in the electric discharge among different molecular energy modes. The four-wave mixing measurements are performed using a collinear phase matching geometry, with nitrogen used as the probe species, at temporal resolution of about 2 ns . Absolute calibration is performed by measurement of a known electrostatic electric field. In the present experiments, the discharge is sustained between two stainless steel plate electrodes, each placed in a quartz sleeve, which greatly improves plasma uniformity. Our previous measurements of electric field in a nanosecond pulse dielectric barrier discharge by picosecond 4-wave mixing have been done in air at room temperature, in a discharge sustained between a razor edge high-voltage electrode and a plane grounded electrode (a quartz plate or a layer of distilled water). Electric field measurements in a flame, which is a high-temperature environment, are more challenging because the four-wave mixing signal is proportional to the to square root of the difference betwen the populations of N2 ground vibrational level (v=0) and first excited vibrational level (v=1). At high temperatures, the total number density is reduced, thus reducing absolute vibrational level populations of N2. Also, the signal is reduced further due to a wider distribution of N2 molecules over multiple rotational levels at higher temperatures, while the present four-wave mixing diagnostics is using spectrally narrow output of a ps laser and a high

  17. 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.

  18. Efficient all solid-state UV source for satellite-based lidar applications.

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, Darrell Jewell; Smith, Arlee Virgil

    2003-07-01

    A satellite-based UV-DIAL measurement system would allow continuous global monitoring of ozone concentration in the upper atmosphere. However such systems remain difficult to implement because aerosol-scattering return signals for satellite-based lidars are very weak. A suitable system must produce high-energy UV pulses at multiple wavelengths with very high efficiency. For example, a nanosecond system operating at 10 Hz must generate approximately 1 J per pulse at 308-320 nm. An efficient space-qualified wavelength-agile system based on a single UV source that can meet this requirement is probably not available using current laser technology. As an alternative, we're pursuing a multi-source approach employing all-solid-state modules that individually generate 300-320 nm light with pulse energies in the range of 50-200 mJ, with transform-limited bandwidths and good beam quality. Pulses from the individual sources can be incoherently summed to obtain the required single-pulse energy. These sources use sum-frequency mixing of the 532 nm second harmonic of an Nd:YAG pump laser with 731-803 nm light derived from a recently-developed, state-of-the-art, nanosecond optical parametric oscillator. Two source configurations are under development, one using extra-cavity sum-frequency mixing, and the other intra-cavity sum-frequency mixing. In either configuration, we hope to obtain sum-frequency mixing efficiency approaching 60% by carefully matching the spatial and temporal properties of the laser and OPO pulses. This ideal balance of green and near-IR photons requires an injection-seeded Nd:YAG pump-laser with very high beam quality, and an OPO exhibiting unusually high conversion efficiency and exceptional signal beam quality. The OPO employs a singly-resonant high-Fresnel-number image-rotating self-injection-seeded nonplanar-ring cavity that achieves pump depletion > 65% and produces signal beams with M{sup 2} {approx} 3 at pulse energies exceeding 50 mJ. Pump beam

  19. ASIC for time-of-flight measurements with picosecond timing resolution

    Energy Technology Data Exchange (ETDEWEB)

    Stankova, Vera; Shen, Wei; Harion, Tobias [Kirchhoff-Institute for Physics, Heidelberg Univ. (Germany)

    2015-07-01

    The Positron Emission Tomography (PET) images are especially affected by a high level of noise. This noise affects the potential to detect and discriminate the tumor in relation to the background. Including Time-of-Flight information, with picosecond time resolution, within the conventional PET scanners will improve the signal-to-noise ratio (SNR) and in sequence the quality of the medical images. A mix-mode ASIC (STIC3) has been developed for high precision timing measurements with Silicon Photomultipliers (SiPM). The STiC3 is 64-channel chip, with fully differential analog front-end for crosstalk and electronic noise immunity. It integrates Time to Digital Converters (TDC) with time binning of 50.2 ps for time and energy measurements. Measurements of the of the analog front-end show a time jitter less than 20 ps and jitter of the TDC together with the digital part is around 37 ps. Further the timing of a channel has been tested by injecting a pulse into two channels and measuring the time difference of the recorded timestamps. A Coincidence Time Resolution (CTR) of 215 ps FWHM has been obtained with 3.1 x 3.1 x 15 mm{sup 2} LYSO:Ce scintillator crystals and Hamamatsu SiPM matric (S12643-050CN(x)). Characterization measurements with the chip and its performances are presented.

  20. Multispectral UV imaging for determination of the tablet coating thickness

    DEFF Research Database (Denmark)

    Novikova, Anna; Carstensen, Jens Michael; Zeitler, J. Axel

    2017-01-01

    The applicability of off-line multispectral ultraviolet (UV) imaging in combination with multivariate data analysis was investigated to determine the coating thickness and its distribution on the tablet surface during lab scale coating. The UV imaging results were compared with the weight gain...... measured for each individual tablet and the corresponding coating thickness and its distribution measured by terahertz pulsed imaging (TPI). Three different tablet formulations were investigated, two of which contained UV active tablet cores. Three coating formulations were applied: Aquacoat® ECD (a mainly...... translucent coating) and Eudragit® NE (a turbid coating containing solid particles). It was shown that UV imaging is a fast and non-destructive method to predict individual tablet weight gain as well as coating thickness. The coating thickness distribution profiles determined by UV imaging correlated...

  1. Time-resolved UV spectroscopy on ammonia excited by a pulsed CO2 laser

    International Nuclear Information System (INIS)

    Holbach, H.

    1980-07-01

    This work investigates the excitation of ammonia by a pulsed CO 2 laser, in particular the processes associated with collisions with argon. It was prompted by two previous observations: the previously reported infrared multiphoton dissociation of NH 3 under nearly collisionless conditions, and the ill understood excitation mechanism of apparently nonresonant low vibrational levels in the presence of Ar. Based on recent spectroscopic data, all vibrational-rotational levels were determined which are simultaneously excited by different CO 2 laser lines. Transitions between the 1 + and 2 - vibrational levels were also taken into account. The linewidth in these calculations was dominated by power broadening, which generates a half width at half maximum of 0.36 cm -1 at the typical power density of 10 MW/cm 2 . In order to reproduce published experimental absorption data, it proved necessary to take account all transitions within a distance of 20 cm -1 from the laser line. This fact implies in most cases the simultaneous population of a large number of vibrational-rotational levels. The population of levels by absorption or by subsequent collisional processes was probed by time-resolved absorption measurement of vibrational bands and their rotational envelope in the near UV. Time resolution (5...10) was sufficient to observe rotational relaxation within individual vibrational levels. Characteristic differences were found for the various excitation lines. (orig.) [de

  2. Sintering of solution-based nano-particles by a UV laser pulse train

    Science.gov (United States)

    Zhang, Jie; Li, Ming; Morimoto, Kiyoshi

    2011-03-01

    Sintering of palladium (Pd) and silicon (Si) nano-particles (NPs) by a 266nm laser pulse train on ink-printed films was investigated. Organic Pd-ink, and organic Si-ink were used as precursors. A high repetition rate DPSS laser (up to 300 kHz, 25ns, 266nm, Coherent AVIA series), which produces a ns pulse train with 3.3 μs -33.3 μs interval of pulse-topulse, was used as the heating source. Highly electrically conductive Pd (Resistivity=~150μΩ.cm) thin film on PET substrate and semi-conductive Si (Resistivity=~23kΩ.cm) thin film on glass substrate were successfully obtained with this laser pulse train sintering process. The sintered films were characterized by AFM, SEM, TEM and Raman spectroscopy, respectively. The pulse train heating process was also numerically simulated.

  3. Increase in the temperature of a laser plasma formed by two-frequency UV - IR irradiation of metal targets

    International Nuclear Information System (INIS)

    Antipov, A A; Grasyuk, Arkadii Z; Efimovskii, S V; Kurbasov, Sergei V; Losev, Leonid L; Soskov, V I

    1998-01-01

    An experimental investigation was made of a laser plasma formed by successive irradiation of a metal target with 30-ps UV and IR laser pulses. The UV prepulse, of 266 nm wavelength, was of relatively low intensity (∼ 10 12 W cm -2 ), whereas the intensity of an IR pulse, of 10.6 μm wavelength, was considerably higher (∼3 x 10 14 W cm -2 ) and it was delayed by 0 - 6 ns (the optimal delay was 2 ns). Such two-frequency UV - IR irradiation produced a laser plasma with an electron temperature 5 times higher than that of a plasma created by singe-frequency IR pulses of the same (∼3 x 10 14 W cm -2 ) intensity. (interaction of laser radiation with matter. laser plasma)

  4. Silicon nanowire based high brightness, pulsed relativistic electron source

    Directory of Open Access Journals (Sweden)

    Deep Sarkar

    2017-06-01

    Full Text Available We demonstrate that silicon nanowire arrays efficiently emit relativistic electron pulses under irradiation by a high-intensity, femtosecond, and near-infrared laser (∼1018 W/cm2, 25 fs, 800 nm. The nanowire array yields fluxes and charge per bunch that are 40 times higher than those emitted by an optically flat surface, in the energy range of 0.2–0.5 MeV. The flux and charge yields for the nanowires are observed to be directional in nature unlike that for planar silicon. Particle-in-cell simulations establish that such large emission is caused by the enhancement of the local electric fields around a nanowire, which consequently leads to an enhanced absorption of laser energy. We show that the high-intensity contrast (ratio of picosecond pedestal to femtosecond peak of the laser pulse (10−9 is crucial to this large yield. We extend the notion of surface local-field enhancement, normally invoked in low-order nonlinear optical processes like second harmonic generation, optical limiting, etc., to ultrahigh laser intensities. These electron pulses, expectedly femtosecond in duration, have potential application in imaging, material modification, ultrafast dynamics, terahertz generation, and fast ion sources.

  5. A ZnO nanowire-based photo-inverter with pulse-induced fast recovery.

    Science.gov (United States)

    Raza, Syed Raza Ali; Lee, Young Tack; Hosseini Shokouh, Seyed Hossein; Ha, Ryong; Choi, Heon-Jin; Im, Seongil

    2013-11-21

    We demonstrate a fast response photo-inverter comprised of one transparent gated ZnO nanowire field-effect transistor (FET) and one opaque FET respectively as the driver and load. Under ultraviolet (UV) light the transfer curve of the transparent gate FET shifts to the negative side and so does the voltage transfer curve (VTC) of the inverter. After termination of UV exposure the recovery of photo-induced current takes a long time in general. This persistent photoconductivity (PPC) is due to hole trapping on the surface of ZnO NWs. Here, we used a positive voltage short pulse after UV exposure, for the first time resolving the PPC issue in nanowire-based photo-detectors by accumulating electrons at the ZnO/dielectric interface. We found that a pulse duration as small as 200 ns was sufficient to reach a full recovery to the dark state from the UV induced state, realizing a fast UV detector with a voltage output.

  6. Pulsed laser facilities operating from UV to IR at the Gas Laser Lab of the Lebedev Institute

    Science.gov (United States)

    Ionin, Andrei; Kholin, Igor; Vasil'Ev, Boris; Zvorykin, Vladimir

    2003-05-01

    Pulsed laser facilities developed at the Gas Lasers Lab of the Lebedev Physics Institute and their applications for different laser-matter interactions are discussed. The lasers operating from UV to mid-IR spectral region are as follows: e-beam pumped KrF laser (λ= 0.248 μm) with output energy 100 J; e-beam sustained discharge CO2(10.6 μm) and fundamental band CO (5-6 μm) lasers with output energy up to ~1 kJ; overtone CO laser (2.5-4.2 μm) with output energy ~ 50 J and N2O laser (10.9 μm) with output energy of 100 J; optically pumped NH3 laser (11-14 μm). Special attention is paid to an e-beam sustained discharge Ar-Xe laser (1.73 μm ~ 100 J) as a potential candidate for a laser-propulsion facility. The high energy laser facilities are used for interaction of laser radiation with polymer materials, metals, graphite, rocks, etc.

  7. Comparison of two picosecond lasers to a nanosecond laser for treating tattoos: a prospective randomized study on 49 patients.

    Science.gov (United States)

    Lorgeou, A; Perrillat, Y; Gral, N; Lagrange, S; Lacour, J-P; Passeron, T

    2018-02-01

    Q-switched nanosecond lasers demonstrated their efficacy in treating most types of tattoos, but complete disappearance is not always achieved even after performing numerous laser sessions. Picosecond lasers are supposed to be more efficient in clearing tattoos than nanosecond lasers, but prospective comparative data remain limited. To compare on different types of tattoos the efficacy of a nanosecond laser with two types of picosecond lasers. We conducted a prospective randomized study performed from December 2014 to June 2016 on adult patients with all types of tattoos. The tattoos were divided into two halves of equal size. After randomization, half of the tattoo was treated with a picosecond laser and the other half with a nanosecond laser. The evaluation was performed on standardized pictures performed before treatment and 2 months after the last session, by two physicians, not involved in the treatment, blinded on the type of treatments received. The main end point was a clearance above 75% of the tattoos. A total of 49 patients were included. Professional tattoos represented 85.7%, permanent make-up 8.2% and non-professional tattoo 6.1%. The majority were black or blue and 10.2% were polychromatic. No patient was lost during follow-up. A reduction of 75% or more of the colour intensity was obtained for 33% of the tattoos treated with the picosecond lasers compared to 14% with the nanosecond laser (P = 0.008). An improvement superior to 75% was obtained in 34% monochromic black or blue tattoos with the picosecond lasers compared to 9% for the nanosecond laser. Only one of the five polychromic tattoos achieved more than 75% of improvement with the two types of laser. Our results show a statistically significant superiority of the picosecond lasers compared to the nanosecond laser for tattoo clearance. However, they do not show better efficacy for polychromic tattoos and the difference in terms of side-effects was also minimal with a tendency of picosecond

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-09

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

  9. 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

  10. Probing ultrafast dynamics of solid-density plasma generated by high-contrast intense laser pulses

    Science.gov (United States)

    Jana, Kamalesh; Blackman, David R.; Shaikh, Moniruzzaman; Lad, Amit D.; Sarkar, Deep; Dey, Indranuj; Robinson, Alex P. L.; Pasley, John; Ravindra Kumar, G.

    2018-01-01

    We present ultrafast dynamics of solid-density plasma created by high-contrast (picosecond contrast ˜10-9), high-intensity (˜4 × 1018 W/cm2) laser pulses using time-resolved pump-probe Doppler spectrometry. Experiments show a rapid rise in blue-shift at early time delay (2-4.3 ps) followed by a rapid fall (4.3-8.3 ps) and then a slow rise in blue-shift at later time delays (>8.3 ps). Simulations show that the early-time observations, specifically the absence of any red-shifting of the reflected probe, can only be reproduced if the front surface is unperturbed by the laser pre-pulse at the moment that the high intensity pulse arrives. A flexible diagnostic which is capable of diagnosing the presence of low-levels of pre-plasma formation would be useful for potential applications in laser-produced proton and ion production, such as cancer therapy and security imaging.

  11. Luminescent Characteristics of a Pulsed Discharge Plasma in Xe-KBr Mixture

    Science.gov (United States)

    Heneral, A. A.; Zhmenyak, Y. V.

    2018-03-01

    A mixture of xenon with a nontoxic halogen carrier Xe-KBr is used to create a plasma radiation source at the 282-nm transition of the XeBr* molecule excited by a high-voltage pulsed-periodic discharge. The luminescence spectra of the plasma of a longitudinal pulsed-periodic discharge in the Xe-KBr mixture at low pressures are studied experimentally. The most intense UV bands of exciplex XeBr* molecules are recorded in the spectral range of 250-350 nm. The spectral, temporal, and energetic characteristics of the radiation source are presented, as well as the dependence of the XeBr* exciplex molecule formation efficiency on the discharge excitation conditions. The optimal conditions for the excitation of UV radiation in the pulsed-periodic discharge plasma are determined.

  12. Proposed uv-FEL user facility at BNL

    International Nuclear Information System (INIS)

    Ben-Zvi, I.; Di Mauro, L.F.; Krinsky, S.; White, M.G.; Yu, L.H.; Batchelor, K.; Friedman, A.; Fisher, A.S.; Halama, H.; Ingold, G.; Johnson, E.D.; Kramer, S.; Rogers, J.T.; Solomon, L.; Wachtel, J.; Zhang, X.

    1991-01-01

    The NSLS at Brookhaven National Laboratory is proposing the construction of a UV-FEL operating in the wavelength range from visible to 750 Angstrom. Nano-Coulomb electron pulses will be generated at a laser photo-cathode RF gun at a repetition rate of 10 KHz. The 6 ps pulses will be accelerated to 250 MeV in a superconducting linac. The FEL output will serve four stations with independent wavelength tuning, using two wigglers and two rotating mirror beam switches. Seed radiation for the FEL amplifiers will be provided by conventional tunable lasers, and the final frequency multiplication from the visible or near UV to the VUV will be carried out in the FEL itself. Each FEL will comprise of an initial wiggler resonant to the seed wavelength, a dispersion section, and a second wiggler resonant to the output wavelength. The facility will provide pump probe capability, FEL or FEL, and FEL on synchrotron light from an insersion device on the NSLS X-Ray ring. 15 refs., 2 figs., 3 tabs

  13. Ultra-fast pulse radiolysis: A review of the recent system progress and its application to study on initial yields and solvation processes of solvated electrons in various kinds of alcohols

    International Nuclear Information System (INIS)

    Muroya, Yusa; Lin Mingzhang; Han Zhenhui; Kumagai, Yuta; Sakumi, Akira; Ueda, Toru; Katsumura, Yosuke

    2008-01-01

    In order to study radiation-induced fast phenomena, a new pulse radiolysis system with higher time resolution based on pulse-and-probe method was developed and utilized for practical work. A few picosecond electron beam generated from a linear accelerator, in which a laser photocathode RF-gun is introduced, was synchronized with a femtosecond laser pulse which is employed as the analyzing light. The synchronization precision between them was suppressed within 1.6 ps (rms). Converting the fundamental laser into white light continuum or optical parametric amplification allows to measure in the wide wavelength from visible to infrared region

  14. Tracing temperature in a nanometer size region in a picosecond time period.

    Science.gov (United States)

    Nakajima, Kaoru; Kitayama, Takumi; Hayashi, Hiroaki; Matsuda, Makoto; Sataka, Masao; Tsujimoto, Masahiko; Toulemonde, Marcel; Bouffard, Serge; Kimura, Kenji

    2015-08-21

    Irradiation of materials with either swift heavy ions or slow highly charged ions leads to ultrafast heating on a timescale of several picosecond in a region of several nanometer. This ultrafast local heating result in formation of nanostructures, which provide a number of potential applications in nanotechnologies. These nanostructures are believed to be formed when the local temperature rises beyond the melting or boiling point of the material. Conventional techniques, however, are not applicable to measure temperature in such a localized region in a short time period. Here, we propose a novel method for tracing temperature in a nanometer region in a picosecond time period by utilizing desorption of gold nanoparticles around the ion impact position. The feasibility is examined by comparing with the temperature evolution predicted by a theoretical model.

  15. Fine structure of the CCl3 UV absorption spectrum and CCl3 kinetics

    DEFF Research Database (Denmark)

    Ellermann, T.

    1992-01-01

    The UV gas-phase spectrum of CCl3 was recorded in the range 220-300 nm using pulse radiolysis of CHCl3/SF6 or CCl4/Ar gas mixtures. The UV spectrum exhibits a pronounced vibrational fine structure which is assigned to transition into the (C2A1'(3s)) Rydberg state. The vibronic progression has...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-07-01

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

  17. Sensitive detection of chlorine in iron oxide by single pulse and dual pulse laser-induced breakdown spectroscopy

    Science.gov (United States)

    Pedarnig, J. D.; Haslinger, M. J.; Bodea, M. A.; Huber, N.; Wolfmeir, H.; Heitz, J.

    2014-11-01

    The halogen chlorine is hard to detect in laser-induced breakdown spectroscopy (LIBS) mainly due to its high excited state energies of 9.2 and 10.4 eV for the most intense emission lines at 134.72 nm and 837.59 nm, respectively. We report on sensitive detection of Cl in industrial iron oxide Fe2O3 powder by single-pulse (SP) and dual-pulse (DP) LIBS measurements in the near infrared range in air. In compacted powder measured by SP excitation (Nd:YAG laser, 532 nm) Cl was detected with limit of detection LOD = 440 ppm and limit of quantitation LOQ = 720 ppm. Orthogonal DP LIBS was studied on pressed Fe2O3 pellets and Fe3O4 ceramics. The transmission of laser-induced plasma for orthogonal Nd:YAG 1064 nm and ArF 193 nm laser pulses showed a significant dependence on interpulse delay time (ipd) and laser wavelength (λL). The UV pulses (λL = 193 nm) were moderately absorbed in the plasma and the Cl I emission line intensity was enhanced while IR pulses (λL = 1064 nm) were not absorbed and Cl signals were not enhanced at ipd = 3 μs. The UV laser enhancement of Cl signals is attributed to the much higher signal/background ratio for orthogonal DP excitation compared to SP excitation and to the increased plasma temperature and electron number density. This enabled measurement at a very short delay time of td ≥ 0.1 μs with respect to the re-excitation pulse and detection of the very rapidly decaying Cl emission with higher efficiency.

  18. 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

  19. Hypericin and pulsed laser therapy of squamous cell cancer in vitro.

    Science.gov (United States)

    Bublik, Michael; Head, Christian; Benharash, Peyman; Paiva, Marcos; Eshraghi, Adrian; Kim, Taiho; Saxton, Romaine

    2006-06-01

    This in vitro study compares continuous wave and pulsed laser light at longer wavelengths for activation of the phototoxic drug hypericin in human cancer cells. Two-photon pulsed laser light now allows high-resolution fluorescent imaging of cancer cells and should provide deeper tissue penetration with near infrared light for improved detection as well as phototoxicity in human tumors. Cultured Seoul National University (SNU)-1 tumor cells from a squamous cell carcinoma (SCC) were incubated with hypericin before photoirradiation at four laser wavelengths. Phototoxicity of hypericin sensitized SCC cells was measured by dimethyl thiazoldiphenyl (MTT) tetrazolium bromide cell viability assays and by confocal fluorescence microscopy via 532-nm and infrared two-photon pulsed laser light. Phototoxic response increased linearly with hypericin dose of 0.1-2 microM, light exposure time of 5-120 sec, and pulsed dye laser wavelengths of 514-593 nm. Light energy delivery for 50% cell phototoxicity (LD50) response was 9 joules at 514 nm, 3 joules at 550 nm, and less than 1 joule at the 593 nm hypericin light absorption maxima. Fluorescence confocal microscopy revealed membrane and perinuclear localization of hypericin in the SNU cells with membrane damage seen after excitation with visible 532 nm continuous wave light or two-photon 700-950 nm picosecond pulsed laser irradiation. Hypericin may be a powerful tumor targetting drug when combined with pulsed laser light in patients with recurrent head and neck SCC.

  20. Ultrafast Electric Field Pulse Control of Giant Temperature Change in Ferroelectrics

    Science.gov (United States)

    Qi, Y.; Liu, S.; Lindenberg, A. M.; Rappe, A. M.

    2018-01-01

    There is a surge of interest in developing environmentally friendly solid-state-based cooling technology. Here, we point out that a fast cooling rate (≈1011 K /s ) can be achieved by driving solid crystals to a high-temperature phase with a properly designed electric field pulse. Specifically, we predict that an ultrafast electric field pulse can cause a giant temperature decrease up to 32 K in PbTiO3 occurring on few picosecond time scales. We explain the underlying physics of this giant electric field pulse-induced temperature change with the concept of internal energy redistribution: the electric field does work on a ferroelectric crystal and redistributes its internal energy, and the way the kinetic energy is redistributed determines the temperature change and strongly depends on the electric field temporal profile. This concept is supported by our all-atom molecular dynamics simulations of PbTiO3 and BaTiO3 . Moreover, this internal energy redistribution concept can also be applied to understand electrocaloric effect. We further propose new strategies for inducing giant cooling effect with ultrafast electric field pulse. This Letter offers a general framework to understand electric-field-induced temperature change and highlights the opportunities of electric field engineering for controlled design of fast and efficient cooling technology.

  1. 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

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

    Science.gov (United States)

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

    2015-03-01

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

  3. Experimental installation for excitation of semiconductors and dielectrics by picosecond pulsed electron beam and electric field

    International Nuclear Information System (INIS)

    Nasibov, A.S.; Berezhnoj, K.V.; Shapkin, P.V.; Reutova, A.G.; Shunajlov, S.A.; Yalandin, M.I.

    2009-01-01

    The experimental facility for shaping high-voltage pulses with amplitudes of 30-250 kV and durations of 100-500 ps and electron beams with a current density of up to 1000 A/cm -2 is described. The facility was built using the principle of energy compression of a pulse from a nanosecond high-voltage generator accompanied by the subsequent pulse sharpening and cutting. The setup is equipped with two test coaxial chambers for radiation excitation in semiconductor crystals by an electron beam or an electric field in air at atmospheric pressure and T = 300 K. Generation of laser radiation in the visible range under field and electron pumping was attained in ZnSSe, ZnSe, ZnCdS, and CdS (462, 480, 515, and 525 nm, respectively). Under the exposure to an electric field (up to 10 6 V x cm -1 ), the laser generation region is as large as 300-500 μm. The radiation divergence was within 5 Deg C. The maximum integral radiation power (6 kW at λ = 480 nm) was obtained under field pumping of a zinc selenide sample with a single dielectric mirror [ru

  4. 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

  5. Pulsed cathodoluminescence of nanoscale aluminum oxide with different phase compositions

    International Nuclear Information System (INIS)

    Kortov, V.S.; Zvonarev, S.V.; Medvedev, A.I.

    2011-01-01

    The methods of pulsed cathodoluminescence have been used to study compacted powders and ceramics containing different phases of aluminum oxide. An intensive luminescence of the samples under study in the visible, NIR, and UV regions of the spectrum has been found. The luminescence bands are very broad and include a few components. The number of the bands depends on the phase composition of the samples. The oxygen vacancies, which capture one or two electrons, produce luminescence centers in the near UV region. The most probable in the visible region is the luminescence of aggregate defects, impurities, and surface centers. - Highlights: → We investigate pulsed cathodoluminescence spectra of nanoscale alumina. → We found the intensive luminescence in the visible, NIR, and UV regions. → The transformation of R-line structure depends on phase composition of alumina. → We substantiate the relation of luminescence bands with concrete centers.

  6. Picosecond intersubband hole relaxation in p-type quantum wells

    International Nuclear Information System (INIS)

    Xu, Z.; Fauchet, P.M.; Rella, C.W.; Schwettman, H.A.

    1995-01-01

    We report the first direct measurement of the relaxation time of holes in p-type quantum wells using tunable, subpicosecond mid-infrared laser pulses in a pump-probe arrangement. The QW layers consisted of 50 In 0.5 Ga 0.5 As/Al 0.5 Ga 0.5 As periods. The In 0.5 Ga 0.5 As well was 4 nm wide and the Al 0.5 Ga 0.5 As barrier was 8 nm wide. The dopant concentration was 10 19 CM -3 which corresponds to a sheet density of 1.2 x 10 13 CM -2 . The room temperature IR spectrum showed a 50 meV wide absorption peak at 5.25 μm (220 meV). This energy agrees with the calculated n=1 heavy hole to n=1 light hole transition energy of 240 meV (150 meV for strain and 90 meV for confinement). The large absorption width results from hole-hole scattering and the difference in dispersion relations between the two subbands. The equal-wavelength pump-probe transmission measurements were performed using the Stanford free electron laser (FEL). The FEL pulses were tuned between 4 and 6 μ m and their duration was less than 1 ps. The measurements were performed as a function of temperature, pump wavelength and intensity (from 0.3 to 10 GW/cm 2 ). In all our experiments, we find an increase of transmission (decrease of absorption or bleaching) following photopumping, which recovers as a single exponential with a time constant (relaxation time) of the order of 1 picosecond. The maximum change in transmission is linear with pump 2 intensity below 1 GW/cm 2 and saturates to ∼3% with a saturation intensity I sat of 3 GW/cm 2 . As the saturation regime is entered, the relaxation time increases from 0.8 ps to 1.8 ps. This relaxation time depends on the temperature T: it increases from 0.8 ps to 1.3 ps as T decreases from 300 K to 77 K. Finally, when we tune the laser through the absorption band, the magnitude of the signal changes but its temporal behavior does not change, within the accuracy of the measurements

  7. High impact ionization rate in silicon by sub-picosecond THz electric field pulses (Conference Presentation)

    DEFF Research Database (Denmark)

    Tarekegne, Abebe Tilahun; Iwaszczuk, Krzysztof; Hirori, Hideki

    2017-01-01

    Summary form only given. Metallic antenna arrays fabricated on high resistivity silicon are used to localize and enhance the incident THz field resulting in high electric field pulses with peak electric field strength reaching several MV/cm on the silicon surface near the antenna tips. In such high...... electric field strengths high density of carriers are generated in silicon through impact ionization process. The high density of generated carriers induces a change of refractive index in silicon. By measuring the change of reflectivity of tightly focused 800 nm light, the local density of free carriers...... near the antenna tips is measured. Using the NIR probing technique, we observed that the density of carriers increases by over 8 orders of magnitude in a time duration of approximately 500 fs with an incident THz pulse of peak electric field strength 700 kV/cm. This shows that a single impact...

  8. Pulse compression system for the ANL 20 MeV linac

    International Nuclear Information System (INIS)

    Mavrogenes, G.; Norem, J.; Simpson, J.

    1986-01-01

    This paper describes the pulse compression system being built on the Argonne 20 MeV electron linac. The system is designed to rotate the bunch from the present measured pulse length of 38 psec FWHM, to pulse lengths of 5 to 6 ps with the large instantaneous currents (1 to 4 kA) possible instantaneous current. This system was necessary to extend the study of reactive fragments of molecules to the time scale of a few picoseconds, in particular to examine the chemistry of electrons and ions before and during relaxation of the surrounding media. These experiments are not sensitive to the beam energy spread, High Energy Physics experiments studying wake fields have also been proposed using the short bunches and the facility was designed so that the wake field experiment could share the beam bunching system. The 20 MeV electron linac uses a double gap, 12th subharmonic prebuncher together with a one wavelength 1.3 Ghz prebuncher to produce a single pulse of 38 ps from one occupied rf bucket. Beam emittances of 15.7 mmmr have been measured for 40 nC of accelerated charge and 8 mmmr at 10 nC. The energy spread of dE/E = 1% (FWHM) has been measured at 40 nC. Thus the accelerated beam has excellent time structure, high current, and good emittance

  9. High-quality beam generation using an RF gun and a 150 MeV microtron

    Science.gov (United States)

    Kuroda, R.; Washio, M.; Kashiwagi, S.; Kobuki, T.; Ben-Zvi, I.; Wang, X. J.; Hori, T.; Sakai, F.; Tsunemi, A.; Urakawa, J.; Hirose, T.

    2000-11-01

    Low-emittance sub-picosecond electron pulses are expected to be used in a wide field, such as free electron laser, laser acceleration, femtosecond X-ray generation by Inverse Compton scattering, pulse radiolysis, etc. In order to produce the low-emittance sub-picosecond electron pulse, we are developing a compact Racetrack Microtron (RTM) with a new 5 MeV injection system adopting a laser photo cathode RF gun (Washio et al., Seventh China-Japan Bilateral Symposium on Radiation Chemistry, October 28, Cengdu, China, 1996). The operation of RTM has been kept under a steady state of beam loading for long pulse mode so far (Washio et al., J. Surf. Sci. Soc. Jpn. 19 (2) (1998) 23). In earlier work (Washio et al., PAC99, March 31, New York, USA, 1999), we have succeeded in the numerical simulation for the case of single short pulse acceleration. Finally, the modified RTM was demonstrated as a useful accelerator for a picosecond electron pulse generation under a transient state of beam loading. In the simulation, a picosecond electron pulse was accelerated to 149.6 MeV in RTM for the injection of 5 MeV electron bunch with a pulse length of 10 ps (FWHM), a charge of 1 nC per pulse, and an emittance of 3 πmm mrad.

  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. High-throughput machining using high average power ultrashort pulse lasers and ultrafast polygon scanner

    Science.gov (United States)

    Schille, Joerg; Schneider, Lutz; Streek, André; Kloetzer, Sascha; Loeschner, Udo

    2016-03-01

    In this paper, high-throughput ultrashort pulse laser machining is investigated on various industrial grade metals (Aluminium, Copper, Stainless steel) and Al2O3 ceramic at unprecedented processing speeds. This is achieved by using a high pulse repetition frequency picosecond laser with maximum average output power of 270 W in conjunction with a unique, in-house developed two-axis polygon scanner. Initially, different concepts of polygon scanners are engineered and tested to find out the optimal architecture for ultrafast and precision laser beam scanning. Remarkable 1,000 m/s scan speed is achieved on the substrate, and thanks to the resulting low pulse overlap, thermal accumulation and plasma absorption effects are avoided at up to 20 MHz pulse repetition frequencies. In order to identify optimum processing conditions for efficient high-average power laser machining, the depths of cavities produced under varied parameter settings are analyzed and, from the results obtained, the characteristic removal values are specified. The maximum removal rate is achieved as high as 27.8 mm3/min for Aluminium, 21.4 mm3/min for Copper, 15.3 mm3/min for Stainless steel and 129.1 mm3/min for Al2O3 when full available laser power is irradiated at optimum pulse repetition frequency.

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

    International Nuclear Information System (INIS)

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

    2001-01-01

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

  13. Pulse compressor with aberration correction

    Energy Technology Data Exchange (ETDEWEB)

    Mankos, Marian [Electron Optica, Inc., Palo Alto, CA (United States)

    2015-11-30

    In this SBIR project, Electron Optica, Inc. (EOI) is developing an electron mirror-based pulse compressor attachment to new and retrofitted dynamic transmission electron microscopes (DTEMs) and ultrafast electron diffraction (UED) cameras for improving the temporal resolution of these instruments from the characteristic range of a few picoseconds to a few nanoseconds and beyond, into the sub-100 femtosecond range. The improvement will enable electron microscopes and diffraction cameras to better resolve the dynamics of reactions in the areas of solid state physics, chemistry, and biology. EOI’s pulse compressor technology utilizes the combination of electron mirror optics and a magnetic beam separator to compress the electron pulse. The design exploits the symmetry inherent in reversing the electron trajectory in the mirror in order to compress the temporally broadened beam. This system also simultaneously corrects the chromatic and spherical aberration of the objective lens for improved spatial resolution. This correction will be found valuable as the source size is reduced with laser-triggered point source emitters. With such emitters, it might be possible to significantly reduce the illuminated area and carry out ultrafast diffraction experiments from small regions of the sample, e.g. from individual grains or nanoparticles. During phase I, EOI drafted a set of candidate pulse compressor architectures and evaluated the trade-offs between temporal resolution and electron bunch size to achieve the optimum design for two particular applications with market potential: increasing the temporal and spatial resolution of UEDs, and increasing the temporal and spatial resolution of DTEMs. Specialized software packages that have been developed by MEBS, Ltd. were used to calculate the electron optical properties of the key pulse compressor components: namely, the magnetic prism, the electron mirror, and the electron lenses. In the final step, these results were folded

  14. A new possibility for production of sub-picosecond x-ray pulses using a time dependent radio frequency orbit deflection

    Energy Technology Data Exchange (ETDEWEB)

    Zholents, A.

    2015-10-21

    It is shown that two radio frequency deflecting cavities with slightly different frequencies can be used to produce time-dependent orbit deflection to a few special electron bunches circulating in a synchrotron without affecting the majority of the electron bunches. These special bunches produce an x-ray pulse in which transverse position or angle, or both, are correlated with time. The x-ray pulse is then shortened, either with an asymmetrically cut crystal that acts as a pulse compressor, or with an angular aperture such as a narrow slit positioned downstream. The implementation of this technique creates a highly flexible environment for synchrotrons in which users of most beamlines will be able to easily select between the x-rays originated by the standard electron bunches and the short x-ray pulses originated by the special electron bunches carrying a time-dependent transverse correlation.

  15. A New Possibility for Production of Sub-picosecond X-ray Pulses using a Time Dependent Radio Frequency Orbit Deflection

    Energy Technology Data Exchange (ETDEWEB)

    Zholents, A. A. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2015-05-01

    It is shown that two radio frequency deflecting cavities with slightly different frequencies can be used to produce time-dependent orbit deflection to a few special electron bunches while keeping the majority of the electron bunches unaffected. These special bunches produce an x-ray pulse in which transverse position or angle, or both, are correlated with time. The x-ray pulses are then shortened, either with an asymmetrically cut crystal that acts as a pulse compressor, or with an angular aperture such as a narrow slit positioned downstream. The implementation of this technique creates a highly flexible environment for synchrotrons in which users of most beamlines will be able to easily select between the x-rays originated by the standard electron bunches and the short x-ray pulses originated by the special electron bunches carrying a time-dependent transverse correlation.

  16. Scattered UV irradiation during VISX excimer laser keratorefractive surgery.

    Science.gov (United States)

    Hope, R J; Weber, E D; Bower, K S; Pasternak, J P; Sliney, D H

    2008-04-01

    To evaluate the potential occupational health hazards associated with scattered ultraviolet (UV) radiation during photorefractive keratectomy (PRK) using the VISX Star S3 excimer laser. The Laser Vision Center, National Naval Medical Center, Bethesda, Maryland, USA. Intraoperative radiometric measurements were made with the Ophir Power/Energy Meter (LaserStar Model PD-10 with silicon detector) during PRK treatments as well as during required calibration procedures at a distance of 20.3 cm from the left cornea. These measurements were evaluated using a worst-case scenario for exposure, and then compared with the American Conference of Governmental Industrial Hygeinists (ACGIH) Threshold Value Limits (TVL) to perform a risk/hazard analysis. During the PRK procedures, the highest measured value was 248.4 nJ/pulse. During the calibration procedures, the highest measured UV scattered radiation level was 149.6 nJ/pulse. The maximum treatment time was 52 seconds. Using a worst-case scenario in which all treatments used the maximum power and time, the total energy per eye treated was 0.132 mJ/cm2 and the total UV radiation at close range (80 cm from the treated eye) was 0.0085 mJ/cm2. With a workload of 20 patients, the total occupational exposure at 80 cm to actinic UV radiation in an 8-hour period would be 0.425 mJ/cm2. The scattered actinic UV laser radiation from the VISX Star S3 excimer laser did not exceed occupational exposure limits during a busy 8-hour workday, provided that operating room personnel were at least 80 cm from the treated eye. While the use of protective eyewear is always prudent, this study demonstrates that the trace amounts of scattered laser emissions produced by this laser do not pose a serious health risk even without the use of protective eyewear.

  17. A pulse generator for xenon lamps

    CERN Document Server

    Janata, E

    2002-01-01

    A pulse generator is described, which enhances the analyzing light emitted from a xenon lamp as used in kinetic photospectrometry experiments. The lamp current is increased to 600 A for a duration of 3 ms; the current is constant within +-0.2% during a time interval of 2 ms. Because of instabilities of the lamp arc during pulsing, the use of the enhanced light source is limited to measuring times up to 500 mu s. The enhancement in light intensity depends on the wavelength and amounts to more than 400-fold in the UV-region.

  18. Demonstration of high-responsivity epitaxial β-Ga2O3/GaN metal–heterojunction-metal broadband UV-A/UV-C detector

    Science.gov (United States)

    Kalra, Anisha; Vura, Sandeep; Rathkanthiwar, Shashwat; Muralidharan, Rangarajan; Raghavan, Srinivasan; Nath, Digbijoy N.

    2018-06-01

    We demonstrate epitaxial β-Ga2O3/GaN-based vertical metal–heterojunction-metal (MHM) broadband UV-A/UV-C photodetectors with high responsivity (3.7 A/W) at 256 and 365 nm, UV-to-visible rejection >103, and a photo-to-dark current ratio of ∼100. A small (large) conduction (valence) band offset at the heterojunction of pulsed laser deposition (PLD)-grown β-Ga2O3 on metal organic chemical vapor deposition (MOCVD)-grown GaN-on-silicon with epitaxial registry, as confirmed by X-ray diffraction (XRD) azimuthal scanning, is exploited to realize detectors with an asymmetric photoresponse and is explained with one-dimensional (1D) band diagram simulations. The demonstrated novel vertical MHM detectors on silicon are fully scalable and promising for enabling focal plane arrays for broadband ultraviolet sensing.

  19. Dynamic View on Nanostructures: A Technique for Time Resolved Optical Luminescence Using Synchrotron Light Pulses at SRC, APS, and CLS

    International Nuclear Information System (INIS)

    Heigl, F.; Jurgensen, A.; Zhou, X.-T.; Lam, S.; Murphy, M.; Ko, J.Y.P.; Sham, T.K.; Rosenberg, R.A.; Gordon, R.; Brewe, D.; Regier, T.; Armelao, L.

    2007-01-01

    We present an experimental technique using the time structure of synchrotron radiation to study time resolved X-ray excited optical luminescence. In particular we are taking advantage of the bunched distribution of electrons in a synchrotron storage ring, giving short x-ray pulses (10-10 2 picoseconds) which are separated by non-radiating gaps on the nano- to tens of nanosecond scale - sufficiently wide to study a broad range of optical decay channels observed in advanced nanostructured materials.

  20. Microfabrication in free-standing gallium nitride using UV laser micromachining

    International Nuclear Information System (INIS)

    Gu, E.; Howard, H.; Conneely, A.; O'Connor, G.M.; Illy, E.K.; Knowles, M.R.H.; Edwards, P.R.; Martin, R.W.; Watson, I.M.; Dawson, M.D.

    2006-01-01

    Gallium nitride (GaN) and related alloys are important semiconductor materials for fabricating novel photonic devices such as ultraviolet (UV) light-emitting diodes (LEDs) and vertical cavity surface-emitting lasers (VCSELs). Recent technical advances have made free-standing GaN substrates available and affordable. However, these materials are strongly resistant to wet chemical etching and also, low etch rates restrict the use of dry etching. Thus, to develop alternative high-resolution processing for these materials is increasingly important. In this paper, we report the fabrication of microstructures in free-standing GaN using pulsed UV lasers. An effective method was first developed to remove the re-deposited materials due to the laser machining. In order to achieve controllable machining and high resolution in GaN, machining parameters were carefully optimised. Under the optimised conditions, precision features such as holes (through holes, blind or tapered holes) on a tens of micrometer length scale have been machined. To fabricate micro-trenches in GaN with vertical sidewalls and a flat bottom, different process strategies of laser machining were tested and optimised. Using this technique, we have successfully fabricated high-quality micro-trenches in free-standing GaN with various widths and depths. The approach combining UV laser micromachining and other processes is also discussed. Our results demonstrate that the pulsed UV laser is a powerful tool for fabricating precision microstructures and devices in gallium nitride

  1. Characterising and testing deep UV LEDs for use in space applications

    International Nuclear Information System (INIS)

    Hollington, D; Baird, J T; Sumner, T J; Wass, P J

    2015-01-01

    Deep ultraviolet (DUV) light sources are used to neutralise isolated test masses in highly sensitive space-based gravitational experiments. An example is the LISA Pathfinder charge management system, which uses low-pressure mercury lamps. A future gravitational-wave observatory such as eLISA will use UV light-emitting diodes (UV LEDs), which offer numerous advantages over traditional discharge lamps. Such devices have limited space heritage but are now available from a number of commercial suppliers. Here we report on a test campaign that was carried out to quantify the general properties of three types of commercially available UV LEDs and demonstrate their suitability for use in space. Testing included general electrical and UV output power measurements, spectral stability, pulsed performance and temperature dependence, as well as thermal vacuum, radiation and vibration survivability. (paper)

  2. Characterising and testing deep UV LEDs for use in space applications

    Science.gov (United States)

    Hollington, D.; Baird, J. T.; Sumner, T. J.; Wass, P. J.

    2015-12-01

    Deep ultraviolet (DUV) light sources are used to neutralise isolated test masses in highly sensitive space-based gravitational experiments. An example is the LISA Pathfinder charge management system, which uses low-pressure mercury lamps. A future gravitational-wave observatory such as eLISA will use UV light-emitting diodes (UV LEDs), which offer numerous advantages over traditional discharge lamps. Such devices have limited space heritage but are now available from a number of commercial suppliers. Here we report on a test campaign that was carried out to quantify the general properties of three types of commercially available UV LEDs and demonstrate their suitability for use in space. Testing included general electrical and UV output power measurements, spectral stability, pulsed performance and temperature dependence, as well as thermal vacuum, radiation and vibration survivability.

  3. 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)

  4. Higher pressure periodic CO/sub 2/ laser with non-self-sustaining discharge and UV ionization

    Energy Technology Data Exchange (ETDEWEB)

    Muratov, E A; Pismennyi, V D; Rakhimov, A T

    1979-02-01

    Stimulated emission was achieved in a CO/sub 2/ laser operating at 250 torr excited by a periodic non-self-sustaining discharge controlled by a spark source of UV radiation. Use of a UV source operating in periodic pulse regime is shown to permit quasicontinuous operation of the laser with characteristic radiating times up to several hundred microseconds.

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

    Science.gov (United States)

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

    2018-02-01

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

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

    International Nuclear Information System (INIS)

    Attwood, D.T.

    1978-01-01

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

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

    Indian Academy of Sciences (India)

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

  8. Ultrashort pulse laser machining of metals and alloys

    Science.gov (United States)

    Perry, Michael D.; Stuart, Brent C.

    2003-09-16

    The invention consists of a method for high precision machining (cutting, drilling, sculpting) of metals and alloys. By using pulses of a duration in the range of 10 femtoseconds to 100 picoseconds, extremely precise machining can be achieved with essentially no heat or shock affected zone. Because the pulses are so short, there is negligible thermal conduction beyond the region removed resulting in negligible thermal stress or shock to the material beyond approximately 0.1-1 micron (dependent upon the particular material) from the laser machined surface. Due to the short duration, the high intensity (>10.sup.12 W/cm.sup.2) associated with the interaction converts the material directly from the solid-state into an ionized plasma. Hydrodynamic expansion of the plasma eliminates the need for any ancillary techniques to remove material and produces extremely high quality machined surfaces with negligible redeposition either within the kerf or on the surface. Since there is negligible heating beyond the depth of material removed, the composition of the remaining material is unaffected by the laser machining process. This enables high precision machining of alloys and even pure metals with no change in grain structure.

  9. Development of an electron momentum spectrometer for time-resolved experiments employing nanosecond pulsed electron beam

    Science.gov (United States)

    Tang, Yaguo; Shan, Xu; Liu, Zhaohui; Niu, Shanshan; Wang, Enliang; Chen, Xiangjun

    2018-03-01

    The low count rate of (e, 2e) electron momentum spectroscopy (EMS) has long been a major limitation of its application to the investigation of molecular dynamics. Here we report a new EMS apparatus developed for time-resolved experiments in the nanosecond time scale, in which a double toroidal energy analyzer is utilized to improve the sensitivity of the spectrometer and a nanosecond pulsed electron gun with a repetition rate of 10 kHz is used to obtain an average beam current up to nA. Meanwhile, a picosecond ultraviolet laser with a repetition rate of 5 kHz is introduced to pump the sample target. The time zero is determined by photoionizing the target using a pump laser and monitoring the change of the electron beam current with time delay between the laser pulse and electron pulse, which is influenced by the plasma induced by the photoionization. The performance of the spectrometer is demonstrated by the EMS measurement on argon using a pulsed electron beam, illustrating the potential abilities of the apparatus for investigating the molecular dynamics in excited states when employing the pump-probe scheme.

  10. Pulsed lasers versus continuous light sources in capillary electrophoresis and fluorescence detection studies: Photodegradation pathways and models

    International Nuclear Information System (INIS)

    Boutonnet, Audrey; Morin, Arnaud; Petit, Pierre; Vicendo, Patricia; Poinsot, Véréna; Couderc, François

    2016-01-01

    Pulsed lasers are widely used in capillary electrophoresis (CE) studies to provide laser induced fluorescence (LIF) detection. Unfortunately pulsed lasers do not give linear calibration curves over a wide range of concentrations. While this does not prevent their use in CE/LIF studies, the non-linear behavior must be understood. Using 7-hydroxycoumarin (7-HC) (10–5000 nM), Tamra (10–5000 nM) and tryptophan (1–200 μM) as dyes, we observe that continuous lasers and LEDs result in linear calibration curves, while pulsed lasers give polynomial ones. The effect is seen with both visible light (530 nm) and with UV light (355 nm, 266 nm). In this work we point out the formation of byproducts induced by pulsed laser upon irradiation of 7-HC. Their separation by CE using two Zeta LIF detectors clearly shows that this process is related to the first laser detection. All of these photodegradation products can be identified by an ESI-/MS investigation and correspond to at least two 7HC dimers. By using the photodegradation model proposed by Heywood and Farnsworth (2010) and by taking into account the 7-HC results and the fact that in our system we do not have a constant concentration of fluorophore, it is possible to propose a new photochemical model of fluorescence in LIF detection. The model, like the experiment, shows that it is difficult to obtain linear quantitation curves with pulsed lasers while UV-LEDs used in continuous mode have this advantage. They are a good alternative to UV pulsed lasers. An application involving the separation and linear quantification of oligosaccharides labeled with 2-aminobezoic acid is presented using HILIC and LED (365 nm) induced fluorescence. - Highlights: • No linear calibration curves are obtained in CE/Pulsed-LIF detection. • Photodegradation and photodimerisation are responsible of this non linearity. • A mathematical model of this phenomenon is presented. • 7 hydroxycoumarin in CE/LIF is used to verify the

  11. Fast ion generation by a picosecond high-power laser

    Czech Academy of Sciences Publication Activity Database

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

    2005-01-01

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

  12. Time-resolved terahertz spectroscopy of semiconductor nanostructures

    DEFF Research Database (Denmark)

    Porte, Henrik

    This thesis describes time-resolved terahertz spectroscopy measurements on various semiconductor nanostructures. The aim is to study the carrier dynamics in these nanostructures on a picosecond timescale. In a typical experiment carriers are excited with a visible or near-infrared pulse and by me......This thesis describes time-resolved terahertz spectroscopy measurements on various semiconductor nanostructures. The aim is to study the carrier dynamics in these nanostructures on a picosecond timescale. In a typical experiment carriers are excited with a visible or near-infrared pulse...... and by measuring the transmission of a terahertz probe pulse, the photoconductivity of the excited sample can be obtained. By changing the relative arrival time at the sample between the pump and the probe pulse, the photoconductivity dynamics can be studied on a picosecond timescale. The rst studied semiconductor...

  13. The regrowth of phytoplankton cultures after UV disinfection

    International Nuclear Information System (INIS)

    Martínez, Lucía F.; Mahamud, Manuel M.; Lavín, Antonio G.; Bueno, Julio L.

    2013-01-01

    Highlights: ► Phytoplankton cultures were placed in a rich medium after UV-C irradiation. ► Flow cytometry and PAM were used for determining cell viability. ► The behavior differs from that of cultures kept in their original environment. ► Chlorella autotrophica recovers between 5 and 10 days after the treatment. ► Phaeocystis globosa shows only a slight recovery for low-dose UV-radiation exposure. - Abstract: This study addresses how cultures of three phytoplankton species –Chaetoceros calcitrans, Chlorella autotrophica and Phaeocystis globosa – can recover from the effects of UV-C exposure if the cells are placed in a rich medium. Flow cytometry and pulse amplitude modulation (PAM) were used to determine cell recovery after UV treatment. The recovery of C. calcitrans was complete 9 days after treatment. For C. autotrophica, the recovery was noticeable 5 days after treatment. P. globosa only recovered if the UV dose did not exceed 7.3 × 10 5 μWs/cm 2 . The recovery of the UV-treated cultures introduced to a regrowth medium, compared with the recovery of the irradiated cultures kept in their original environment, had two main characteristics: cell recovery was slower but was more efficient. This pattern of recovery has very important implications for real ballast water management systems because such systems discharge treated water into the environment

  14. 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)

  15. Passive mode locking of a femtosecond Ti:sapphire laser with pulsed synchronous pumping by a finite train of picosecond pulses

    International Nuclear Information System (INIS)

    Borisevich, N A; Buganov, O V; Tikhomirov, S A; Tolstorozhev, G B; Shkred, G L

    1999-01-01

    An analysis is made, with the aid of the self-consistent nonlinear ABCD matrix method, of the specific features of the mechanism of passive mode locking of a femtosecond Ti:sapphire laser under conditions of pulsed synchronous pumping. The conditions of stable laser operation are studied. It is proposed to use an additional aperture as an element of negative feedback for the stabilisation of passive mode locking. Practical recommendations concerning the optimisation of a femtosecond laser are given. (control of laser radiation parameters)

  16. Multispectral UV Imaging for Determination of the Tablet Coating Thickness.

    Science.gov (United States)

    Novikova, Anna; Carstensen, Jens M; Zeitler, J Axel; Rades, Thomas; Leopold, Claudia S

    2017-06-01

    The applicability of off-line multispectral UV imaging in combination with multivariate data analysis was investigated to determine the coating thickness and its distribution on the tablet surface during lab-scale coating. The UV imaging results were compared with the weight gain measured for each individual tablet and the corresponding coating thickness and its distribution measured by terahertz pulsed imaging (TPI). Three different tablet formulations were investigated, 2 of which contained UV-active tablet cores. Three coating formulations were applied: Aquacoat® ECD (a mainly translucent coating) and Eudragit® NE (a turbid coating containing solid particles). It was shown that UV imaging is a fast and nondestructive method to predict individual tablet weight gain as well as coating thickness. The coating thickness distribution profiles determined by UV imaging correlated to the results of the TPI measurements. UV imaging appears to hold a significant potential as a process analytical technology tool for determination of the tablet coating thickness and its distribution resulting from its high measurement speed, high molar absorptivity, and a high scattering coefficient, in addition to relatively low costs. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

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

    International Nuclear Information System (INIS)

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

    1975-01-01

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

  18. Spectroscopic studies on diamond like carbon films synthesized by pulsed laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Panda, Madhusmita; Krishnan, R., E-mail: krish@igcar.gov.in; Ravindran, T. R.; Das, Arindam; Mangamma, G.; Dash, S.; Tyagi, A. K. [Material Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam - 603102, Tamil Nadu (India)

    2016-05-23

    Hydrogen free Diamond like Carbon (DLC) thin films enriched with C-C sp{sup 3} bonding were grown on Si (111) substrates at laser pulse energies varying from 100 to 400 mJ (DLC-100, DLC-200, DLC-300, DLC-400), by Pulsed Laser Ablation (PLA) utilizing an Nd:YAG laser operating at fundamental wavelength. Structural, optical and morphological evolutions as a function of laser pulse energy were studied by micro Raman, UV-Vis spectroscopic studies and Atomic Force Microscopy (AFM), respectively. Raman spectra analysis provided critical clues for the variation in sp{sup 3} content and optical energy gap. The sp{sup 3} content was estimated using the FWHM of the G peak and found to be in the range of 62-69%. The trend of evolution of sp{sup 3} content matches well with the evolution of I{sub D}/I{sub G} ratio with pulse energy. UV-Vis absorption study of DLC films revealed the variation of optical energy gap with laser pulse energy (1.88 – 2.23 eV), which matches well with the evolution of G-Peak position of the Raman spectra. AFM study revealed that roughness, size and density of particulate in DLC films increase with laser pulse energy.

  19. Analysis of material modifications caused by nanosecond pulsed UV laser processing of SiC and GaN

    Energy Technology Data Exchange (ETDEWEB)

    Krueger, Olaf; Wernicke, Tim; Wuerfl, Joachim; Traenkle, Guenther [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Berlin (Germany); Hergenroeder, Roland [ISAS-Institute for Analytical Sciences, Dortmund (Germany)

    2008-10-15

    The effects of direct UV laser processing on single crystal SiC in ambient air were investigated by cross-sectional transmission electron microscopy, Auger electron spectroscopy, and measurements of the electrical resistance using the transfer length method (TLM). Scanning electron microscopy was applied to study the morphology and dimensions of the laser-treated regions. After laser processing using a nanosecond pulsed solid-state laser the debris consisting of silicon oxide was removed by etching in buffered hydrofluoric acid. A layer of resolidified material remains at the surface indicating the thermal impact of the laser process. The Si/C ratio is significantly disturbed at the surface of the resolidified layer and approaches unity in a depth of several tens of nanometers. A privileged oxidation of carbon leaves elementary resolidified silicon at the surface, where nanocrystalline silicon was detected. Oxygen and nitrogen were detected near the surface down to a depth of some tens of nanometers. A conductive surface film is formed, which is attributed to the thermal impact causing the formation of the silicon-rich surface layer and the incorporation of nitrogen as dopant. No indications for microcrack or defect formation were found beneath the layer of resolidified material. (orig.)

  20. Phase change dynamics in a polymer thin film upon femtosecond and picosecond laser irradiation

    International Nuclear Information System (INIS)

    Bonse, J.; Wiggins, S.M.; Solis, J.; Lippert, T.

    2005-01-01

    The influence of the pulse duration on the laser-induced changes in a thin triazenepolymer film on a glass substrate has been investigated for single, near-infrared (800 nm) Ti:sapphire laser pulses with durations ranging from 130 fs up to 2.6 ps. Post-irradiation optical microscopy has been used to quantitatively determine the damage threshold fluence. The latter decreases from ∼800 mJ/cm 2 for a 2.6 ps laser pulse to ∼500 mJ/cm 2 for a pulse duration of 130 fs. In situ real-time reflectivity (RTR) measurements have been performed using a ps-resolution streak camera set-up to study the transformation dynamics upon excitation with single pulses of duration of 130 fs and fluences close to the damage threshold. Very different reflectivity transients have been observed above and below the damage threshold fluence. Above the damage threshold, an extremely complicated behaviour with oscillations of up to 100% in the transient reflectivity has been observed. Below the damage threshold, the transient reflectivity decreases by as much as 70% within 1 ns with a subsequent recovery to the initial level occurring on the ms timescale. No apparent damage could be detected by optical microscopy under these irradiation conditions. Furthermore, within the 395-410 mJ/cm 2 fluence range, the transient reflectivity increases by ∼10%. The analysis of these results indicates that the observed transformations are thermal in nature, in contrast to the known photochemical decomposition of this triazenepolymer under UV irradiation

  1. Morphology of IR and UV Laser-induced Structural Changes on Silicon Surfaces

    International Nuclear Information System (INIS)

    Jimenez-Jarquin, J.; Haro-Poniatowski, E.; Fernandez-Guasti, M.; Hernandez-Pozos, J.L.

    2005-01-01

    Using scanning electronic microscopy, we analyze the structural changes induced in silicon (100) wafers by focused IR (1064 nm) and UV (355 nm) nanosecond laser pulses. The experiments were performed in the laser ablation regime. When a silicon surface is irradiated by laser pulses in an O2 atmosphere conical microstructures are obtained. The changes in silicon surface morphology depend both on the incident radiation wavelength and the environmental atmosphere. We have patterned Si surfaces with a single focused laser spot and, in doing the experiments with IR or UV this reveals significant differences in the initial surface cracking and pattern formation, however the final result consist of an array of microcones when the experiment is carried out in oxygen. We employ a random scanning technique to irradiate silicon surfaces over large areas. In this form we have obtained large patterned areas

  2. UV Lidar Receiver Analysis for Tropospheric Sensing of Ozone

    Science.gov (United States)

    Pliutau, Denis; DeYoung, Russell J.

    2013-01-01

    A simulation of a ground based Ultra-Violet Differential Absorption Lidar (UV-DIAL) receiver system was performed under realistic daytime conditions to understand how range and lidar performance can be improved for a given UV pulse laser energy. Calculations were also performed for an aerosol channel transmitting at 3 W. The lidar receiver simulation studies were optimized for the purpose of tropospheric ozone measurements. The transmitted lidar UV measurements were from 285 to 295 nm and the aerosol channel was 527-nm. The calculations are based on atmospheric transmission given by the HITRAN database and the Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological data. The aerosol attenuation is estimated using both the BACKSCAT 4.0 code as well as data collected during the CALIPSO mission. The lidar performance is estimated for both diffuseirradiance free cases corresponding to nighttime operation as well as the daytime diffuse scattered radiation component based on previously reported experimental data. This analysis presets calculations of the UV-DIAL receiver ozone and aerosol measurement range as a function of sky irradiance, filter bandwidth and laser transmitted UV and 527-nm energy

  3. Pulsed Plasma Polymerization of Perfluorooctyl Ethylene for Transparent Hydrophobic Thin Coatings

    International Nuclear Information System (INIS)

    Liu Xiaojun; Wang Lei; Hao Jie; Chu Liqiang

    2015-01-01

    Herein we report on the deposition of transparent hydrophobic thin coatings by radio frequency plasma polymerization (PP) of perfluorooctyl ethylene (PFOE) in both pulsed and continuous wave (CW) modes. The chemical compositions of the resulting PP-PFOE coatings were confirmed by means of Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The thicknesses and surface morphologies of the coatings were examined using surface plasmon resonance spectroscopy and atomic force microscopy. The surface wetting properties and optical transmittance were measured using a water contact angle goniometer and UV-vis spectroscopy. The FT-IR and XPS data showed that the PP-PFOE coatings deposited in the pulsed mode had a higher retention of CF 2 groups compared to those from the CW mode. While the water contact angle of the freshly deposited PP-PFOE from the pulsed mode showed a decrease from 120 degrees to 111 degrees in the first two days, it then remained almost unchanged up to 45 days. The UV-vis data indicated that a PP-PFOE coating 30.6 nm thick had a light transmittance above 90% in the UV and visible ranges. The deposition rates under various plasma conditions are also discussed. (paper)

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

    Science.gov (United States)

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

    2016-01-01

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

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-02-15

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

  7. Two-electron time-delay interference in atomic double ionization by attosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Rescigno, Thomas N

    2009-10-04

    A two-color two-photon atomic double ionization experiment using subfemtosecond UV pulses can be designed such that the sequential two-color process dominates and one electron is ejected by each pulse. Nonetheless, ab initio calculations show that, for sufficiently short pulses, a prominent interference pattern in the joint energy distribution of the sequentially ejected electrons can be observed that is due to their indistinguishability and the exchange symmetry of the wave function.

  8. Two-Electron Time-Delay Interference in Atomic Double Ionization by Attosecond Pulses

    International Nuclear Information System (INIS)

    Palacios, A.; Rescigno, T. N.; McCurdy, C. W.

    2009-01-01

    A two-color two-photon atomic double ionization experiment using subfemtosecond uv pulses can be designed such that the sequential two-color process dominates and one electron is ejected by each pulse. Nonetheless, ab initio calculations show that, for sufficiently short pulses, a prominent interference pattern in the joint energy distribution of the sequentially ejected electrons can be observed that is due to their indistinguishability and the exchange symmetry of the wave function.

  9. The role of morphology and coupling of gold nanoparticles in optical breakdown during picosecond pulse exposures

    Directory of Open Access Journals (Sweden)

    Yevgeniy R. Davletshin

    2016-06-01

    Full Text Available This paper presents a theoretical study of the interaction of a 6 ps laser pulse with uncoupled and plasmon-coupled gold nanoparticles. We show how the one-dimensional assembly of particles affects the optical breakdown threshold of its surroundings. For this purpose we used a fully coupled electromagnetic, thermodynamic and plasma dynamics model for a laser pulse interaction with gold nanospheres, nanorods and assemblies, which was solved using the finite element method. The thresholds of optical breakdown for off- and on-resonance irradiated gold nanosphere monomers were compared against nanosphere dimers, trimers, and gold nanorods with the same overall size and aspect ratio. The optical breakdown thresholds had a stronger dependence on the optical near-field enhancement than on the mass or absorption cross-section of the nanostructure. These findings can be used to advance the nanoparticle-based nanoscale manipulation of matter.

  10. High power all-solid-state fourth harmonic generation of 266 nm at the pulse repetition rate of 100 kHz

    International Nuclear Information System (INIS)

    Liu, Q; Yan, X P; Fu, X; Gong, M; Wang, D S

    2009-01-01

    14.8 W UV laser at 266 nm was reported with the extra cavity frequency quartered configuration. The fundamental frequency IR source is a high-power high-beam-quality acoustic-optic Q-switched Nd:YVO 4 master-oscillator-power-amplifier laser. The type-I phase-matched LBO and type-I phase-matched BBO crystals were used as the extra-cavity frequency doubled and quartered crystal respectively. 14.8 W UV laser of 266 nm was obtained at the pulse repetition rate of 100 kHz with the conversion efficiency of 18.3% from green to UV, and the pulse duration of the UV laser was 10 ns corresponding to the pulse peak power of 14.8 kW. At 150 kHz, 11.5 W power output was obtained. The highest peak power of 21 kW was also achieved at 80 kHz with the average output power of 14.5 W

  11. UV-visible spectrum of the phenyl radical and kinetics of its reaction with NO in the gas phase

    DEFF Research Database (Denmark)

    Wallington, T.J.; Egsgaard, H.; Nielsen, O.J.

    1998-01-01

    Pulse radiolysis transient UV-visible absorption spectroscopy was used to study the UV-visible absorption spectrum (225-575 nm) of the phenyl radical, C6H5(.), and kinetics of its reaction with NO. Phenyl radicals have a strong broad featureless absorption in the region of 225-340 nm...

  12. Challenges of UV light processing of low UVT foods and beverages

    Science.gov (United States)

    Koutchma, Tatiana

    2010-08-01

    Ultraviolet (UV) technology holds promise as a low cost non-thermal alternative to heat pasteurization of liquid foods and beverages. However, its application for foods is still limited due to low UV transmittance (LUVT). LUVT foods have a diverse range of chemical (pH, Brix, Aw), physical (density and viscosity) and optical properties (absorbance and scattering) that are critical for systems and process designs. The commercially available UV sources tested for foods include low and medium pressure mercury lamps (LPM and MPM), excimer and pulsed lamps (PUV). The LPM and excimer lamps are monochromatic sources whereas emission of MPM and PUV is polychromatic. The optimized design of UV-systems and UV-sources with parameters that match to specific product spectra have a potential to make UV treatments of LUVT foods more effective and will serve its further commercialization. In order to select UV source for specific food application, processing effects on nutritional, quality, sensorial and safety markers have to be evaluated. This paper will review current status of UV technology for food processing along with regulatory requirements. Discussion of approaches and results of measurements of chemico-physical and optical properties of various foods (fresh juices, milk, liquid whey proteins and sweeteners) that are critical for UV process and systems design will follow. Available UV sources did not prove totally effective either resulting in low microbial reduction or UV over-dosing of the product thereby leading to sensory changes. Beam shaping of UV light presents new opportunities to improve dosage uniformity and delivery of UV photons in LUVT foods.

  13. UV action spectroscopy of protonated PAH derivatives. Methyl substituted quinolines

    DEFF Research Database (Denmark)

    Klærke, Benedikte; Holm, Anne; Andersen, Lars Henrik

    2011-01-01

    using the electrostatic storage ring ELISA, an electrospray ion source and 3 ns UV laser pulses. Results. It is shown that the absorption profile is both redshifted and broadened when moving the methyl group from the heterocycle containing nitrogen to the homoatomic ring. The absorption profiles......Aims. We investigate the production of molecular photofragments upon UV excitation of PAH derivatives, relevant for the interstellar medium. Methods. The action absorption spectra of protonated gas-phase methyl-substituted quinolines (CH3−C9H7NH+) have been recorded in the 215–338 nm spectral range...

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

    Science.gov (United States)

    Kasai, Kenichiro

    2017-12-31

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

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

    Science.gov (United States)

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

    2014-03-01

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

  16. Extreme nonlinear terahertz electro-optics in diamond for ultrafast pulse switching

    Science.gov (United States)

    Shalaby, Mostafa; Vicario, Carlo; Hauri, Christoph P.

    2017-03-01

    Polarization switching of picosecond laser pulses is a fundamental concept in signal processing [C. Chen and G. Liu, Annu. Rev. Mater. Sci. 16, 203 (1986); V. R. Almeida et al., Nature 431, 1081 (2004); and A. A. P. Pohl et al., Photonics Sens. 3, 1 (2013)]. Conventional switching devices rely on the electro-optical Pockels effect and work at radio frequencies. The ensuing gating time of several nanoseconds is a bottleneck for faster switches which is set by the performance of state-of-the-art high-voltage electronics. Here we show that by substituting the electric field of several kV/cm provided by modern electronics by the MV/cm field of a single-cycle THz laser pulse, the electro-optical gating process can be driven orders of magnitude faster, at THz frequencies. In this context, we introduce diamond as an exceptional electro-optical material and demonstrate a pulse gating time as fast as 100 fs using sub-cycle THz-induced Kerr nonlinearity. We show that THz-induced switching in the insulator diamond is fully governed by the THz pulse shape. The presented THz-based electro-optical approach overcomes the bandwidth and switching speed limits of conventional MHz/GHz electronics and establishes the ultrafast electro-optical gating technology for the first time in the THz frequency range. We finally show that the presented THz polarization gating technique is applicable for advanced beam diagnostics. As a first example, we demonstrate tomographic reconstruction of a THz pulse in three dimensions.

  17. 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

  18. Formation of nanograting in fused silica by temporally delayed femtosecond double-pulse irradiation

    Science.gov (United States)

    Wang, Haodong; Song, Juan; Li, Qin; Zeng, Xianglong; Dai, Ye

    2018-04-01

    A 1 kHz femtosecond double-pulse sequence irradiation is used to study the temporal evolution of nanograting in fused silica by controlling the delay times and polarization combinations of two independent beams from a Mach–Zehnder interferometer. A lateral laser-scan experiment with speed at 5 µm s‑1 and each pulse energy of 1 µJ is firstly performed with the delay time from sub-picosecond to 10 ps, and then the written nanostructures are systematically studied under a cross-polarized microscope because the intensity of birefringence signal nearly corresponds to optical retardance and development level of the induced nanograting. The trend shows that the induced nanogratings can continue developing with a decrease of delay time in the case of the linear polarization pulse arriving before. In another vertical laser-scan experiment at the same speed and pulse energy, the morphologies of nanogratings embedded in the lines are characterized by scanning electron microscope after mechanical polishing and chemical etching. The self-organized patterns have a commonly spatial period of 200–300 nm and the orientation is always perpendicular to the polarization of the first laser pulse, and the second pulse in each sequence seems to promote the as-formed nanograting developing further even if the polarized direction is different from the previous pulse. These new findings verify again that a localized memory effect can make positive feedback to reinforce the patterned nanostripes. In that process, the impact ionization from the seed electrons left by the first pulse excitation and the photoionization of self-trapped excitons with lower ionization threshold results in an increase of the re-excited carriers during the second pulse irradiation and the subsequent development of the as-formed nanograting. Our result provides further proofs for understanding the physical mechanism of nanograting strongly connection with the interplay on multiple ionization channels.

  19. Generation of stable Ps, mJ pulses at high repetition rate for ultrafast diagnostic experiments: Final report

    International Nuclear Information System (INIS)

    Mourou, G.

    1986-10-01

    Nd:Glass amplifiers have very good energy storage capabilities (5 J/cm 2 ), but, the energy extraction is extremely inefficient for short-pulse amplification. At relatively high peak intensities of ∼ 10 GW/cm 2 , nonlinear phase shifts occur, leading to beam wavefront distortion which can result in filamentation and irreversible damage. In order that the peak intensity in the amplifier remain below this damage level, a picosecond pulse can be amplified only to an energy density of ∼ 10 mJ/cm 2 , two orders of magnitude less than the stored energy level of 5 J/cm 2 . We have developed an amplification system, which uses an optical pulse compression technique to circumvent this peak power limitation. This technique is analogous to a method developed over forty years ago for the amplification of radar pulses. Briefly: a long optical pulse is deliberately produced by stretching a short, low-energy pulse, amplified and then compressed. The frequency chirp and the temporal broadening are produced by propagating a high-intensity pulse along a single-mode fiber. At the beginning of the fiber, the pulse undergoes self-phase modulation which produces a frequncy chirp. The chirp is then linearized by the group-velocity dispersion of the fiber. This long, frequency-chirped, pulse is amplified, and then compressed to a pulsewidth approximately equal to 1/Δf, where Δf is the chirped bandwidth. With this system, short pulses can reach the high saturation energy levels, with moderately low peak power levels being maintained in the amplifying medium

  20. Advances in high-power, Ultrashort pulse DPSSL technologies at HiLASE

    Czech Academy of Sciences Publication Activity Database

    Smrž, Martin; Novák, Ondřej; Mužík, Jiří; Turčičová, Hana; Chyla, Michal; Nagisetty, Siva S.; Vyvlečka, Michal; Roškot, Lukáš; Miura, Taisuke; Černohorská, Jitka; Sikocinski, Pawel; Chen, Liyuan; Huynh, Jaroslav; Severová, Patricie; Pranovich, Alina; Endo, Akira; Mocek, Tomáš

    2017-01-01

    Roč. 7, č. 10 (2017), s. 1-12, č. článku 1016. ISSN 2076-3417 R&D Projects: GA MŠk LO1602; GA ČR GA16-12960S; GA MŠk LM2015086; GA TA ČR(CZ) TG02010056 EU Projects: European Commission(XE) 739573 Grant - others:OP VVV - HiLASE-CoE(XE) CZ.02.1.01/0.0/0.0/15_006/0000674 Institutional support: RVO:68378271 Keywords : diode-pumped solid- state lasers (DPSSL) * high average power lasers * higher harmonic generation * Yb:YAG * mid-infrared radiation * thin-disk laser * picosecond pulses Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 1.679, year: 2016