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Sample records for repetition rate stability

  1. Very high repetition-rate electro-optical cavity-dumped Nd: YVO4 laser with optics and dynamics stabilities

    NASA Astrophysics Data System (ADS)

    Liu, Xuesong; Shi, Zhaohui; Huang, Yutao; Fan, Zhongwei; Yu, Jin; Zhang, Jing; Hou, Liqun

    2015-02-01

    In this paper, a very high repetition-rate, short-pulse, electro-optical cavity-dumped Nd: YVO4 laser is experimentally and theoretically investigated. The laser performance is optimized from two aspects. Firstly, the laser resonator is designed for a good thermal stability under large pump power fluctuation through optics methods. Secondly, dynamics simulation as well as experiments verifies that cavity dumping at very high repetition rate has better stability than medium/high repetition rate. At 30 W, 880 nm pump power, up to 500 kHz, constant 5 ns, stable 1064 nm fundamental-mode laser pulses can be obtained with 10 W average output power.

  2. High Repetition Rate and Frequency Stabilized Ho:YLF Laser for CO2 Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Petros, M.; Petzar, Pau; Trieu, Bo; Lee, Hyung; Singh, U.

    2009-01-01

    High repetition rate operation of an injection seeded Ho:YLF laser has been demonstrated. For 1 kHz operation, the output pulse energy reaches 5.8mJ and the optical-to-optical efficiency is 39% when the pump power is 14.5W.

  3. Repetition rate stabilization of an erbium-doped all-fiber laser via opto-mechanical control of the intracavity group velocity

    SciTech Connect

    Shen, Xuling; He, Boqu; Zhao, Jian; Liu, Yang; Bai, Dongbi; Wang, Chao; Liu, Geping; Luo, Daping; Liu, Fengjiang; Li, Wenxue; Zeng, Heping; Yang, Kangwen; Hao, Qiang

    2015-01-19

    We present a method for stabilizing the repetition rate of an erbium-doped all-fiber laser by inserting an electronic polarization controller (EPC) in the fiber laser cavity. The device exhibited good integration, low cost, and convenient operation. Such a repetition rate stabilization may facilitate an all-fiber laser comb system with high integration. The repetition rate was phase-locked to a Rb reference more than 72 h with a low feedback voltage applied to one channel of the EPC. The repetition rate was 74.6 MHz. The standard deviation and the repetition rate linewidth were 1.4 and 1.7 mHz, respectively.

  4. Fast repetition rate (FRR) flasher

    DOEpatents

    Kolber, Zbigniew; Falkowski, Paul

    1997-02-11

    A fast repetition rate (FRR) flasher suitable for high flash photolysis including kinetic chemical and biological analysis. The flasher includes a power supply, a discharge capacitor operably connected to be charged by the power supply, and a flash lamp for producing a series of flashes in response to discharge of the discharge capacitor. A triggering circuit operably connected to the flash lamp initially ionizes the flash lamp. A current switch is operably connected between the flash lamp and the discharge capacitor. The current switch has at least one insulated gate bipolar transistor for switching current that is operable to initiate a controllable discharge of the discharge capacitor through the flash lamp. Control means connected to the current switch for controlling the rate of discharge of the discharge capacitor thereby to effectively keep the flash lamp in an ionized state between Successive discharges of the discharge capacitor. Advantageously, the control means is operable to discharge the discharge capacitor at a rate greater than 10,000 Hz and even up to a rate greater than about 250,000 Hz.

  5. Fast repetition rate (FRR) flasher

    DOEpatents

    Kolber, Z.; Falkowski, P.

    1997-02-11

    A fast repetition rate (FRR) flasher is described suitable for high flash photolysis including kinetic chemical and biological analysis. The flasher includes a power supply, a discharge capacitor operably connected to be charged by the power supply, and a flash lamp for producing a series of flashes in response to discharge of the discharge capacitor. A triggering circuit operably connected to the flash lamp initially ionizes the flash lamp. A current switch is operably connected between the flash lamp and the discharge capacitor. The current switch has at least one insulated gate bipolar transistor for switching current that is operable to initiate a controllable discharge of the discharge capacitor through the flash lamp. Control means connected to the current switch for controlling the rate of discharge of the discharge capacitor thereby to effectively keep the flash lamp in an ionized state between successive discharges of the discharge capacitor. Advantageously, the control means is operable to discharge the discharge capacitor at a rate greater than 10,000 Hz and even up to a rate greater than about 250,000 Hz. 14 figs.

  6. High repetition rate plasma mirror device for attosecond science

    SciTech Connect

    Borot, A.; Douillet, D.; Iaquaniello, G.; Lefrou, T.; Lopez-Martens, R.; Audebert, P.; Geindre, J.-P.

    2014-01-15

    This report describes an active solid target positioning device for driving plasma mirrors with high repetition rate ultra-high intensity lasers. The position of the solid target surface with respect to the laser focus is optically monitored and mechanically controlled on the nm scale to ensure reproducible interaction conditions for each shot at arbitrary repetition rate. We demonstrate the target capabilities by driving high-order harmonic generation from plasma mirrors produced on glass targets with a near-relativistic intensity few-cycle pulse laser system operating at 1 kHz. During experiments, residual target surface motion can be actively stabilized down to 47 nm (root mean square), which ensures sub-300-as relative temporal stability of the plasma mirror as a secondary source of coherent attosecond extreme ultraviolet radiation in pump-probe experiments.

  7. High repetition rate plasma mirror device for attosecond science

    NASA Astrophysics Data System (ADS)

    Borot, A.; Douillet, D.; Iaquaniello, G.; Lefrou, T.; Audebert, P.; Geindre, J.-P.; Lopez-Martens, R.

    2014-01-01

    This report describes an active solid target positioning device for driving plasma mirrors with high repetition rate ultra-high intensity lasers. The position of the solid target surface with respect to the laser focus is optically monitored and mechanically controlled on the nm scale to ensure reproducible interaction conditions for each shot at arbitrary repetition rate. We demonstrate the target capabilities by driving high-order harmonic generation from plasma mirrors produced on glass targets with a near-relativistic intensity few-cycle pulse laser system operating at 1 kHz. During experiments, residual target surface motion can be actively stabilized down to 47 nm (root mean square), which ensures sub-300-as relative temporal stability of the plasma mirror as a secondary source of coherent attosecond extreme ultraviolet radiation in pump-probe experiments.

  8. High repetition rate plasma mirror device for attosecond science.

    PubMed

    Borot, A; Douillet, D; Iaquaniello, G; Lefrou, T; Audebert, P; Geindre, J-P; Lopez-Martens, R

    2014-01-01

    This report describes an active solid target positioning device for driving plasma mirrors with high repetition rate ultra-high intensity lasers. The position of the solid target surface with respect to the laser focus is optically monitored and mechanically controlled on the nm scale to ensure reproducible interaction conditions for each shot at arbitrary repetition rate. We demonstrate the target capabilities by driving high-order harmonic generation from plasma mirrors produced on glass targets with a near-relativistic intensity few-cycle pulse laser system operating at 1 kHz. During experiments, residual target surface motion can be actively stabilized down to 47 nm (root mean square), which ensures sub-300-as relative temporal stability of the plasma mirror as a secondary source of coherent attosecond extreme ultraviolet radiation in pump-probe experiments. PMID:24517742

  9. 1-kHz-repetition-rate femtosecond Raman laser

    NASA Astrophysics Data System (ADS)

    Didenko, N. V.; Konyashchenko, A. V.; Kostryukov, P. V.; Losev, L. L.; Pazyuk, V. S.; Tenyakov, S. Yu

    2016-07-01

    A femtosecond Raman laser utilising compressed hydrogen is experimentally investigated under pumping by radiation from a 1-kHz-repetition-rate Ti : sapphire laser. In the regime of double-pulse pumping, the conditions are determined, which correspond to the minimal energy dispersion of Stokes pulses. The optical scheme is realised, which is capable of ensuring the long-term stability of the average power of the first Stokes component with a variation of less than 2%. The Stokes pulses are produced with a pulse duration of 60 fs and energy of 0.26 mJ at a conversion efficiency of 14%.

  10. Properties of water surface discharge at different pulse repetition rates

    NASA Astrophysics Data System (ADS)

    Ruma, Hosseini, S. H. R.; Yoshihara, K.; Akiyama, M.; Sakugawa, T.; Lukeš, P.; Akiyama, H.

    2014-09-01

    The properties of water surface discharge plasma for variety of pulse repetition rates are investigated. A magnetic pulse compression (MPC) pulsed power modulator able to deliver pulse repetition rates up to 1000 Hz, with 0.5 J per pulse energy output at 25 kV, was used as the pulsed power source. Positive pulse with a point-to-plane electrode configuration was used for the experiments. The concentration and production yield of hydrogen peroxide (H2O2) were quantitatively measured and orange II organic dye was treated, to evaluate the chemical properties of the discharge reactor. Experimental results show that the physical and chemical properties of water surface discharge are not influenced by pulse repetition rate, very different from those observed for under water discharge. The production yield of H2O2 and degradation rate per pulse of the dye did not significantly vary at different pulse repetition rates under a constant discharge mode on water surface. In addition, the solution temperature, pH, and conductivity for both water surface and underwater discharge reactors were measured to compare their plasma properties for different pulse repetition rates. The results confirm that surface discharge can be employed at high pulse repetition rates as a reliable and advantageous method for industrial and environmental decontamination applications.

  11. Properties of water surface discharge at different pulse repetition rates

    SciTech Connect

    Ruma,; Yoshihara, K.; Hosseini, S. H. R. Sakugawa, T.; Akiyama, H.; Akiyama, M.; Lukeš, P.

    2014-09-28

    The properties of water surface discharge plasma for variety of pulse repetition rates are investigated. A magnetic pulse compression (MPC) pulsed power modulator able to deliver pulse repetition rates up to 1000 Hz, with 0.5 J per pulse energy output at 25 kV, was used as the pulsed power source. Positive pulse with a point-to-plane electrode configuration was used for the experiments. The concentration and production yield of hydrogen peroxide (H₂O₂) were quantitatively measured and orange II organic dye was treated, to evaluate the chemical properties of the discharge reactor. Experimental results show that the physical and chemical properties of water surface discharge are not influenced by pulse repetition rate, very different from those observed for under water discharge. The production yield of H₂O₂ and degradation rate per pulse of the dye did not significantly vary at different pulse repetition rates under a constant discharge mode on water surface. In addition, the solution temperature, pH, and conductivity for both water surface and underwater discharge reactors were measured to compare their plasma properties for different pulse repetition rates. The results confirm that surface discharge can be employed at high pulse repetition rates as a reliable and advantageous method for industrial and environmental decontamination applications.

  12. High-pulse-repetition-rate UV lasers with the inductance-capacitance discharge stabilisation

    SciTech Connect

    Andramanov, A V; Kabaev, S A; Lazhintsev, B V; Nor-Arevyan, V A; Pisetskaya, A V; Selemir, Victor D

    2009-02-28

    Compact high-pulse-repetition-rate XeF and KrF excimer lasers and an N{sub 2} laser with plate electrodes and the inductive-capacitance discharge stabilisation are studied. The composition and pressure of the active medium of lasers are optimised for obtaining the maximum output energy and maximum pulse repetition rate at comparatively low (no more than 19 m s{sup -1}) active-medium flow rates in the interelectrode gap. The pulse repetition rate achieved 4-5 kHz for the relative root-mean-square deviation of the laser pulse energy less than 2%. It is found that the energy of the N{sub 2}-laser pulses changes periodically under the action of acoustic perturbations appearing at high pulse repetition rates. It is shown that the use of the inductance-capacitance stabilisation of the discharge provides the increase in the maximum pulse repetition rate by 0.5-1.5 kHz (depending on the active medium type). It is found that the stability of the output energy and maximum pulse repetition rate depend on the location of preionisation sparks with respect to the gas flow direction. Some ways for the development of the technology of plate electrodes and inductance-capacitance discharge stabilisation are proposed. (lasers)

  13. Flexible high-repetition-rate ultrafast fiber laser

    PubMed Central

    Mao, Dong; Liu, Xueming; Sun, Zhipei; Lu, Hua; Han, Dongdong; Wang, Guoxi; Wang, Fengqiu

    2013-01-01

    High-repetition-rate pulses have widespread applications in the fields of fiber communications, frequency comb, and optical sensing. Here, we have demonstrated high-repetition-rate ultrashort pulses in an all-fiber laser by exploiting an intracavity Mach-Zehnder interferometer (MZI) as a comb filter. The repetition rate of the laser can be tuned flexibly from about 7 to 1100 GHz by controlling the optical path difference between the two arms of the MZI. The pulse duration can be reduced continuously from about 10.1 to 0.55 ps with the spectral width tunable from about 0.35 to 5.7 nm by manipulating the intracavity polarization controller. Numerical simulations well confirm the experimental observations and show that filter-driven four-wave mixing effect, induced by the MZI, is the main mechanism that governs the formation of the high-repetition-rate pulses. This all-fiber-based laser is a simple and low-cost source for various applications where high-repetition-rate pulses are necessary. PMID:24226153

  14. High-repetition-rate short-pulse gas discharge.

    PubMed

    Tulip, J; Seguin, H; Mace, P N

    1979-09-01

    A high-average-power short-pulse gas discharge is described. This consists of a volume-preionized transverse discharge of the type used in gas lasers driven by a Blumlein energy storage circuit. The Blumlein circuit is fabricated from coaxial cable, is pulse-charged from a high-repetition-rate Marx-bank generator, and is switched by a high-repetition-rate segmented rail gap. The operation of this discharge under conditions typical of rare-gas halide lasers is described. A maximum of 900 pps was obtained, giving a power flow into the discharge of 30 kW. PMID:18699678

  15. Short-cavity high-repetition-rate CO2 laser

    NASA Astrophysics Data System (ADS)

    Klopper, Wouter; Bagrova, Kalina; du Pisanie, Johan; Ronander, Einar; Meyer, Jan A.; von Bergmann, Hubertus M.

    1994-09-01

    We report on the construction and optimization of a TEA CO2 laser with a discharge volume of 15 cm3 and cavity length of 20 cm. Such a short cavity facilitates single longitudinal mode operation. A roots blower is employed to achieve the necessary gas flow rate for high-repetition-frequency operation in a compact design. Output has been obtained at 1 kHz and a stable discharge to a repetition rate of 2 kHz has been demonstrated. The laser is part of a program aimed at the development of an efficient laser system for molecular laser isotope separation. Additional applications in materials processing are envisioned.

  16. A gigawatt level repetitive rate adjustable magnetic pulse compressor.

    PubMed

    Li, Song; Gao, Jing-Ming; Yang, Han-Wu; Qian, Bao-Liang; Li, Ze-Xin

    2015-08-01

    In this paper, a gigawatt level repetitive rate adjustable magnetic pulse compressor is investigated both numerically and experimentally. The device has advantages of high power level, high repetitive rate achievability, and long lifetime reliability. Importantly, dominate parameters including the saturation time, the peak voltage, and even the compression ratio can be potentially adjusted continuously and reliably, which significantly expands the applicable area of the device and generators based on it. Specifically, a two-stage adjustable magnetic pulse compressor, utilized for charging the pulse forming network of a high power pulse generator, is designed with different compression ratios of 25 and 18 through an optimized design process. Equivalent circuit analysis shows that the modification of compression ratio can be achieved by just changing the turn number of the winding. At the same time, increasing inductance of the grounded inductor will decrease the peak voltage and delay the charging process. Based on these analyses, an adjustable compressor was built and studied experimentally in both the single shot mode and repetitive rate mode. Pulses with peak voltage of 60 kV and energy per pulse of 360 J were obtained in the experiment. The rise times of the pulses were compressed from 25 μs to 1 μs and from 18 μs to 1 μs, respectively, at repetitive rate of 20 Hz with good repeatability. Experimental results show reasonable agreement with analyses. PMID:26329219

  17. A gigawatt level repetitive rate adjustable magnetic pulse compressor

    NASA Astrophysics Data System (ADS)

    Li, Song; Gao, Jing-Ming; Yang, Han-Wu; Qian, Bao-Liang; Li, Ze-Xin

    2015-08-01

    In this paper, a gigawatt level repetitive rate adjustable magnetic pulse compressor is investigated both numerically and experimentally. The device has advantages of high power level, high repetitive rate achievability, and long lifetime reliability. Importantly, dominate parameters including the saturation time, the peak voltage, and even the compression ratio can be potentially adjusted continuously and reliably, which significantly expands the applicable area of the device and generators based on it. Specifically, a two-stage adjustable magnetic pulse compressor, utilized for charging the pulse forming network of a high power pulse generator, is designed with different compression ratios of 25 and 18 through an optimized design process. Equivalent circuit analysis shows that the modification of compression ratio can be achieved by just changing the turn number of the winding. At the same time, increasing inductance of the grounded inductor will decrease the peak voltage and delay the charging process. Based on these analyses, an adjustable compressor was built and studied experimentally in both the single shot mode and repetitive rate mode. Pulses with peak voltage of 60 kV and energy per pulse of 360 J were obtained in the experiment. The rise times of the pulses were compressed from 25 μs to 1 μs and from 18 μs to 1 μs, respectively, at repetitive rate of 20 Hz with good repeatability. Experimental results show reasonable agreement with analyses.

  18. The Effect of Syllable Repetition Rate on Vocal Characteristics

    ERIC Educational Resources Information Center

    Topbas, Oya; Orlikoff, Robert F.; St. Louis, Kenneth O.

    2012-01-01

    This study examined whether mean vocal fundamental frequency ("F"[subscript 0]) or speech sound pressure level (SPL) varies with changes in syllable repetition rate. Twenty-four young adults (12 M and 12 F) repeated the syllables/p[inverted v]/,/p[inverted v]t[schwa]/, and/p[inverted v]t[schwa]k[schwa]/at a modeled "slow" rate of approximately one…

  19. New high repetition rate, high energy 308 nm excimer laser for material processing

    NASA Astrophysics Data System (ADS)

    Herbst, Ludolf; Klaft, Ingo; Schmidt, Kai; Bragin, Igor; Albrecht, Hans-Stephan

    2007-02-01

    High power excimer lasers are well established as work horses for various kinds of micro material processing. The applications are ranging from drilling holes, trench formation, thin film ablation to the crystallization of amorphous-Si into polycrystalline-Si. All applications use the high photon energy and large pulse power of the excimer technology. The increasing demand for micro scale products has let to the demand for UV lasers which support high throughput production. We report the performance parameters of a newly developed XeCl excimer laser with doubled repetition rate compared to available lasers. The developed laser system delivers up to 900 mJ stabilized pulse energy at 600 Hz repetition rate. The low jitter UV light source operates with excellent energy stability. The outstanding energy stability was reached by using a proprietary solid-state pulser discharge design.

  20. A Dynamic Feedback Model for High Repetition Rate LINAC-Driven FELS

    SciTech Connect

    Mellado Munoz, M.; Doolittle, L.; Emma, P.; Huang, G.; Ratti, A.; Serrano, C.; Byrd, J. M.

    2012-05-20

    One of the concepts for the next generation of linacdriven FELs is a CW superconducting linac driving an electron beam with MHz repetition rates. One of the challenges for next generation FELs is improve the stability of the xray pulses by improving the shot-to-shot stability of the energy, charge, peak current, and timing jitter of the electron beam. A high repetition rate FEL with a CW linac presents an opportunity to use a variety of broadband feedbacks to stabilize the beam parameters. To understand the performance of such a feedback system, we are developing a dynamic model of the machine with a focus on the longitudinal beam properties. The model is being developed as an extension of the LITrack code and includes the dynamics of the beam-cavity interaction, RF feedback, beam-based feedback, and multibunch effects. In this paper, we present a detailed description of this model.

  1. High-pulse-repetition-rate HF laser with plate electrodes

    SciTech Connect

    Andramanov, A V; Kabaev, S A; Lazhintsev, B V; Nor-Arevyan, V A; Pisetskaya, A V; Selemir, Victor D

    2006-03-31

    A high-pulse-repetition-rate electric-discharge HF laser with inductive-capacitive discharge stabilisation in the active H{sub 2}-SF{sub 6}-He mixture is studied. The multisectional discharge gap with a total length of 250 mm is formed by pairs of anode-cathode plates arranged in a zigzag pattern. The width of the discharge gap between each pair of plates is {approx}1 mm and its height is {approx}12 mm. The laser-beam cross section at the output cavity mirror is {approx}9 mm x 11 mm. The maximum laser pulse energy and the maximum laser efficiency for the H{sub 2}-SF{sub 6} mixture are 14.3 mJ and 2.1%, respectively. The addition of He to the mixture reduced the laser pulse energy by 10%-15%. The maximum gas velocity in the gap between the electrodes achieves 20 m s{sup -1}. The limiting pulse repetition rate f{sub lim} for which a decrease in the laser pulse energy is still not observed is {approx}2kHz for the H{sub 2}-SF{sub 6} mixture and {approx}2.4kHz for the H{sub 2}-SF{sub 6}-He mixture. The average output power {approx}27 W is obtained for a pulse repetition rate of 2.4 kHz. (lasers)

  2. Bipolar high-repetition-rate high-voltage nanosecond pulser

    SciTech Connect

    Tian Fuqiang; Wang Yi; Shi Hongsheng; Lei Qingquan

    2008-06-15

    The pulser designed is mainly used for producing corona plasma in waste water treatment system. Also its application in study of dielectric electrical properties will be discussed. The pulser consists of a variable dc power source for high-voltage supply, two graded capacitors for energy storage, and the rotating spark gap switch. The key part is the multielectrode rotating spark gap switch (MER-SGS), which can ensure wider range modulation of pulse repetition rate, longer pulse width, shorter pulse rise time, remarkable electrical field distortion, and greatly favors recovery of the gap insulation strength, insulation design, the life of the switch, etc. The voltage of the output pulses switched by the MER-SGS is in the order of 3-50 kV with pulse rise time of less than 10 ns and pulse repetition rate of 1-3 kHz. An energy of 1.25-125 J per pulse and an average power of up to 10-50 kW are attainable. The highest pulse repetition rate is determined by the driver motor revolution and the electrode number of MER-SGS. Even higher voltage and energy can be switched by adjusting the gas pressure or employing N{sub 2} as the insulation gas or enlarging the size of MER-SGS to guarantee enough insulation level.

  3. Novel self-switched high-repetition-rate HF(DF) laser

    NASA Astrophysics Data System (ADS)

    Harris, Michael R.; Jackson, David J.; Milsom, Philip K.

    1998-05-01

    We present results obtained from a new class of self- switching, high repetition rate, HF (DF) laser. The laser utilizes a magnetically stabilized longitudinal discharge, transverse to a high velocity gas flow. The gas mixture is pre-mixed, and consists of He, SF6 and H2(D2) in the ratio 1000:9:2 at a total pressure of around 52 torr. A centrifugal fan recirculates the gas and provides a linear flow velocity of 80 ms-1 in the gain region. Permanent magnets provide the stabilizing magnetic field of approximately 1400 Gauss. This magnetic field ensures that the discharge and optic axes are co-linear. The discharge length is 30 cm, and the gas flow channel 0.5 cm in height. Conventional stable resonators were used to extract the laser energy. We show that the self-switching behavior is a result of the negative I-V characteristic in the positive column of a constricted SF6 discharge, coupled with the current limitations imposed by the external electrical circuit. It is found that the switching frequency, and therefore lasing repetition rate, can be controlled via either the applied discharge current or the RC time constant for the external circuit. Higher discharge currents and shorter time constants both result in higher pulse repetition frequencies. We have demonstrated self-switched lasing at repetition rates from 400 Hz up to 17 kHz.

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

    NASA Astrophysics Data System (ADS)

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

    1997-04-01

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

  5. Laser stimulation of auditory neurons at high repetition rate

    NASA Astrophysics Data System (ADS)

    Izzo, Agnella D.; Littlefield, Philip; Walsh, Joseph T., Jr.; Webb, Jim; Ralph, Heather; Bendett, Mark; Jansen, E. Duco; Richter, Claus-Peter

    2007-02-01

    Pulsed, mid-infrared lasers can evoke neural activity from motor as well as sensory neurons in vivo. Lasers allow more selective spatial resolution of stimulation than the conventional electrical stimulation. To date, few studies have examined pulsed, mid-infrared neural stimulation and very little of the available optical parameter space has been studied. We found that pulse durations as short as 20 ?s elicit a compound action potential from the gerbil cochlea. Moreover, stimulation thresholds are not a function of absolute energy or absolute power deposited. Compound action potential peak-to-peak amplitude remained constant over extended periods of stimulation. Stimulation occurred up six hours continuously and up to 50 Hz in repetition rate. Single fiber experiments were made using repetition rates of up to 1 kHz. Action potentials occurred 2.5-4 ms after the laser pulse. Maximum rates of discharge were up to 250 action potentials per second. With increasing stimulation rate (300 Hz), the action potentials did not respond strictly after the light pulse. The results from these experiments are important for designing the next generation of neuroprostheses, specifically cochlear implants.

  6. High voltage high repetition rate pulse using Marx topology

    NASA Astrophysics Data System (ADS)

    Hakki, A.; Kashapov, N.

    2015-06-01

    The paper describes Marx topology using MOSFET transistors. Marx circuit with 10 stages has been done, to obtain pulses about 5.5KV amplitude, and the width of the pulses was about 30μsec with a high repetition rate (PPS > 100), Vdc = 535VDC is the input voltage for supplying the Marx circuit. Two Ferrite ring core transformers were used to control the MOSFET transistors of the Marx circuit (the first transformer to control the charging MOSFET transistors, the second transformer to control the discharging MOSFET transistors).

  7. High-repetition-rate CF/sub 4/ laser

    SciTech Connect

    Telle, J.

    1981-01-01

    A 16 ..mu..m CF/sub 4/ laser oscillator has operated at 1 kHz in a cooled static cell. Threshold pump energies required from the low pressure, Q-switched, cw discharge CO/sub 2/ laser were as low as 60 ..mu..J. The laser cavity employed the multiple-pass off-axis path resonator in a ring configuration. CF/sub 4/ laser power at 615 cm/sup -1/ and a 1 kHz repetition rate exceeded 300 ..mu..W.

  8. A Simulation of the Effects of Varying Repetition Rate and Pulse Width of Nanosecond Discharges on Premixed Lean Methane-Air Combustion

    DOE PAGESBeta

    Bak, Moon Soo; Cappelli, Mark A.

    2012-01-01

    Two-dimensional kinetic simulation has been carried out to investigate the effects of repetition rate and pulse width of nanosecond repetitively pulsed discharges on stabilizing premixed lean methane-air combustion. The repetition rate and pulse width are varied from 10 kHz to 50 kHz and from 9 ns to 2 ns while the total power is kept constant. The lower repetition rates provide larger amounts of radicals such as O, H, and OH. However, the effect on stabilization is found to be the same for all of the tested repetition rates. The shorter pulse width is found to favor the production of species in higher electronicmore » states, but the varying effects on stabilization are also found to be small. Our results indicate that the total deposited power is the critical element that determines the extent of stabilization over this range of discharge properties studied.« less

  9. Compact, high-repetition-rate OPCPA system for high harmonic generation

    NASA Astrophysics Data System (ADS)

    Matyschok, Jan; Binhammer, Thomas; Lang, Tino; Prochnow, Oliver; Rausch, Stefan; Rudawski, Piotr; Harth, Anne; Miranda, Miguel; Guo, Chen; Lorek, Eleonora; Mauritsson, Johan; Arnold, Cord L.; L'Huillier, Anne; Morgner, Uwe

    2014-03-01

    A compact, high-repetition rate optical parametric chirped pulse amplifier system emitting CEP-stable, few-cycle pulses with 10 μJ of pulse energy is reported for the purpose of high-order harmonic generation. The system is seeded from a commercially available, CEP-stabilized Ti:sapphire oscillator, delivering an octave-spanning spectrum from 600-1200 nm. The oscillator output serves on the one hand as broadband signal for the parametric amplification process and on the other hand as narrowband seed for an Ytterbium-based fiber preamplifier with subsequent main amplifiers and frequency doubling. Broadband parametric amplification up to 17 μJ at 200 kHz repetition rate was achieved in two 5 mm BBO crystals using non-collinear phase matching in the Poynting-vector-walk-off geometry. Efficient pulse compression down to 6.3 fs is achieved with chirped mirrors leading to a peak power exceeding 800 MW. We observed after warm-up time a stability of < 0.5 % rms over 100 min. Drifts of the CE-phase in the parametric amplifier part could be compensated by a slow feedback to the set point of the oscillator phase lock. The CEP stability was measured to be better than 80 mrad over 15 min (3 ms integration time). The experimentally observed output spectra and energies could be well reproduced by simulations of the parametric amplification process based on a (2+1)-dimensional nonlinear propagation code, providing important insight for future repetition rate scaling of OPCPA systems. The system is well-suited for attosecond science experiments which benefit from the high repetition rate. First results for high-order harmonic generation in argon will be presented.

  10. Final Report, Photocathodes for High Repetition Rate Light Sources

    SciTech Connect

    Ben-Zvi, Ilan

    2014-04-20

    This proposal brought together teams at Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL) and Stony Brook University (SBU) to study photocathodes for high repetition rate light sources such as Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). The work done under this grant comprises a comprehensive program on critical aspects of the production of the electron beams needed for future user facilities. Our program pioneered in situ and in operando diagnostics for alkali antimonide growth. The focus is on development of photocathodes for high repetition rate Free Electron Lasers (FELs) and Energy Recovery Linacs (ERLs), including testing SRF photoguns, both normal-conducting and superconducting. Teams from BNL, LBNL and Stony Brook University (SBU) led this research, and coordinated their work over a range of topics. The work leveraged a robust infrastructure of existing facilities and the support was used for carrying out the research at these facilities. The program concentrated in three areas: a) Physics and chemistry of alkali-antimonide cathodes b) Development and testing of a diamond amplifier for photocathodes c) Tests of both cathodes in superconducting RF photoguns and copper RF photoguns

  11. Multiterawatt femtosecond laser system with kilohertz pulse repetition rate

    SciTech Connect

    Petrov, V V; Pestryakov, E V; Laptev, A V; Petrov, V A; Kuptsov, G V; Trunov, V I; Frolov, S A

    2014-05-30

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

  12. Multiterawatt femtosecond laser system with kilohertz pulse repetition rate

    NASA Astrophysics Data System (ADS)

    Petrov, V. V.; Pestryakov, E. V.; Laptev, A. V.; Petrov, V. A.; Kuptsov, G. V.; Trunov, V. I.; Frolov, S. A.

    2014-05-01

    The basic principles, layout and components are presented for a multiterawatt femtosecond laser system with a kilohertz pulse repetition rate f, based on their parametric amplification and laser amplification of picosecond radiation that pumps the stages of the parametric amplifier. The results of calculations for a step-by-step increase in the output power from the LBO crystal parametric amplifier channel up to the multiterawatt level are presented. By using the developed components in the pump channel of the laser system, the parameters of the regenerative amplifier with the output energy ~1 mJ at the wavelength 1030 nm and with f = 1 kHz are experimentally studied. The optical scheme of the diode-pumped multipass cryogenic Yb:Y2O3 laser ceramic amplifier is developed and its characteristics are determined that provide the output energy within the range 0.25 - 0.35 J.

  13. Heart rate variability with repetitive exposure to music.

    PubMed

    Iwanaga, Makoto; Kobayashi, Asami; Kawasaki, Chie

    2005-09-01

    Previous studies of physiological responses to music showed inconsistent results, which might be attributable to methodological differences. Heart rate variability has been used to assess activation of the sympathetic and the parasympathetic nervous systems. The present study aimed to examine heart rate variability with repetitive exposure to sedative or excitative music. The participants were 13 undergraduate or graduate students who were each exposed to three conditions sedative music (SM), excitative music (EM), and no music (NM) on different days. Each participant underwent four sessions of one condition in a day. Sedative music and no music each induced both high relaxation and low tension subjectively. However, excitative music decreased perceived tension and increased perceived relaxation as the number of sessions increased. The low-frequency (LF) component of heart rate variability (HRV) and the LF/HF (high-frequency) ratio increased during SM and EM sessions but decreased during NM sessions. The HF component of HRV during SM was higher than that during EM but the same as that during NM. These findings suggest that excitative music decreased the activation of the parasympathetic nervous system. PMID:16038775

  14. High repetition rate fiber amplifier pumped sub-20 fs optical parametric amplifier.

    PubMed

    Rothhardt, J; Hädrich, S; Schimpf, D N; Limpert, J; Tünnermann, A

    2007-12-10

    We report on a high repetition rate noncollinear optical parametric amplifier system (NOPA) based on a cavity dumped Ti:Sapphire oscillator providing the signal, and an Ytterbium-doped fiber amplifier pumping the device. Temporally synchronized NOPA pump pulses are created via soliton generation in a highly nonlinear photonic crystal fiber. This soliton is fiber amplified to high pulse-energies at high repetition rates. The broadband Ti:Sapphire laser pulses are parametrically amplified either directly or after additional spectral broadening. The approach of fiber-based pump-pulse generation from a femtosecond laser, that emits in the spectral region of NOPA-gain, offers enhanced long-term stability and pulse quality compared to conventional techniques, such as signal pulse generation from a high power laser system via filamentation in bulk media. The presented system produces high-energy ultra-short pulses with pulse-durations down to 15.6 fs and pulse-energies up to 500 nJ at a repetition rate as high as 2 MHz. PMID:19550960

  15. Broadly tunable, low timing jitter, high repetition rate optoelectronic comb generator

    PubMed Central

    Metcalf, A. J.; Quinlan, F.; Fortier, T. M.; Diddams, S. A.; Weiner, A. M.

    2016-01-01

    We investigate the low timing jitter properties of a tunable single-pass optoelectronic frequency comb generator. The scheme is flexible in that both the repetition rate and center frequency can be continuously tuned. When operated with 10 GHz comb spacing, the integrated residual pulse-to-pulse timing jitter is 11.35 fs (1 Hz to 10 MHz) with no feedback stabilization. The corresponding phase noise at 1 Hz offset from the photodetected 10 GHz carrier is −100 dBc/Hz. PMID:26865734

  16. Adjustable high-repetition-rate pulse trains in a passively-mode-locked fiber laser

    NASA Astrophysics Data System (ADS)

    Si Fodil, Rachid; Amrani, Foued; Yang, Changxi; Kellou, Abdelhamid; Grelu, Ph.

    2016-07-01

    We experimentally investigate multipulse regimes obtained within a passively-mode-locked fiber laser that includes a Mach-Zehnder (MZ) interferometer. By adjusting the time delay imbalance of the MZ, ultrashort pulse trains at multi-GHz repetition rates are generated. We compare the observed dynamics with high-harmonic mode locking, and show that the multi-GHz pulse trains display an inherent instability, which has been overlooked. By using a recirculation loop containing the MZ, we demonstrate a significant improvement of the pulse train stability.

  17. Fast repetition rate (FRR) fluorometer and method for measuring fluorescence and photosynthetic parameters

    DOEpatents

    Kolber, Z.; Falkowski, P.

    1995-06-20

    A fast repetition rate fluorometer device and method for measuring in vivo fluorescence of phytoplankton or higher plants chlorophyll and photosynthetic parameters of phytoplankton or higher plants is revealed. The phytoplankton or higher plants are illuminated with a series of fast repetition rate excitation flashes effective to bring about and measure resultant changes in fluorescence yield of their Photosystem II. The series of fast repetition rate excitation flashes has a predetermined energy per flash and a rate greater than 10,000 Hz. Also, disclosed is a flasher circuit for producing the series of fast repetition rate flashes. 14 figs.

  18. Fast repetition rate (FRR) fluorometer and method for measuring fluorescence and photosynthetic parameters

    DOEpatents

    Kolber, Zbigniew; Falkowski, Paul

    1995-06-20

    A fast repetition rate fluorometer device and method for measuring in vivo fluorescence of phytoplankton or higher plants chlorophyll and photosynthetic parameters of phytoplankton or higher plants by illuminating the phytoplankton or higher plants with a series of fast repetition rate excitation flashes effective to bring about and measure resultant changes in fluorescence yield of their Photosystem II. The series of fast repetition rate excitation flashes has a predetermined energy per flash and a rate greater than 10,000 Hz. Also, disclosed is a flasher circuit for producing the series of fast repetition rate flashes.

  19. Extreme-ultraviolet ultrafast ARPES at high repetition rates

    NASA Astrophysics Data System (ADS)

    Buss, Jan; Wang, He; Xu, Yiming; Stoll, Sebastian; Zeng, Lingkun; Ulonska, Stefan; Denlinger, Jonathan; Hussain, Zahid; Jozwiak, Chris; Lanzara, Alessandra; Kaindl, Robert

    Time- and angle-resolved photoemission spectroscopy (trARPES) represents a powerful approach to resolve the electronic structure and quasiparticle dynamics in complex materials, yet is often limited in either momentum space (incident photon energy), probe sensitivity (pulse repetition rate), or energy resolution. We demonstrate a novel table-top trARPES setup that combines a bright 50-kHz source of narrowband, extreme ultraviolet (XUV) pulses at 22.3 eV with UHV photoemission instrumentation to sensitively access dynamics for a large momentum space. The output of a high-power Ti:sapphire amplifier is split to provide the XUV probe and intense photoexcitation (up to mJ/cm2) . A vacuum beamline delivers spectral and flux characterization, differential pumping, as well as XUV beam steering and toroidal refocusing onto the sample with high incident flux of 3x1011 ph/s. Photoemission studies are carried out in a customized UHV chamber equipped with a hemispherical analyzer (R4000), six-axis sample cryostat, and side chambers for sample loading, storage and preparation. An ARPES energy resolution down to 70 meV with the direct XUV output is demonstrated. We will discuss initial applications of this setup including Fermi surface mapping and trARPES of complex materials.

  20. Method for generating high-energy and high repetition rate laser pulses from CW amplifiers

    DOEpatents

    Zhang, Shukui

    2013-06-18

    A method for obtaining high-energy, high repetition rate laser pulses simultaneously using continuous wave (CW) amplifiers is described. The method provides for generating micro-joule level energy in pico-second laser pulses at Mega-hertz repetition rates.

  1. High-repetition-rate, recirculating hydrogen fluoride/deuterium fluoride laser

    SciTech Connect

    Rudko, R.I.; Drozdowicz, Z.; Linhares, S.; Bua, D.

    1982-04-01

    A compact, gas-efficient, pulsed chemical laser operated with HF, DF, or HF and DF simultaneously, is described. This laser produced over 1 mJ/pulse up to over 4000 pps repetition rates with maximum average power over 4.5 W. Maximum repetition rate was 10 000 pulse/s.

  2. Mode locking of fiber lasers at high repetition rates

    NASA Astrophysics Data System (ADS)

    Usechak, Nicholas G.

    Mode-locked fiber lasers have become indispensable tools in many fields as their use is no longer relegated to the optics community. In the future, their size will decrease and their applications will become far more prevalent than they are today. At present, the field is undergoing a cardinal shift as these devices have become commercially available in the last decade. This has put an emphasis on long-term performance and reliability as these devices are beginning to be integrated into complex systems in areas as diverse as medical optics, micro-machining, forensics, and tracking as well as their obvious use as laboratory tools or sources in telecommunications. This is also resulting in a transition from research to engineering. Since the field of mode-locked lasers has been extensively studied for over forty years, one may expect that little has been overlooked. However, since the mode-locking phenomena is governed by nonlinear partial differential equations, a rich degree of effects exist and the field has not yet been exhausted. During the past two decades, the main emphasis has been on short-pulse generation; however, the main thrust of research is likely to change to producing high-power devices, which will result in limiting effects and thermal issues that are currently ignored for low-power sources. Finally, detailed studies have generally been performed numerically as analytic solutions only exist in limiting cases. In this thesis, mode-locked fiber lasers are studied experimentally, numerically, and theoretically. The experimental work focuses on high-repetition rate, mode-locked cavities, which are then modeled numerically. A semi-analytic tool, which goes beyond the prior theories and includes all of the effects experienced by steady-state, mode-locked pulses as they propagate in a laser cavity, is also derived. The only caveats to this approach are an assumption of the pulse shape and the requirement that it not change during propagation through the

  3. Self-mode-locked all-fibre erbium laser with a low repetition rate and high pulse energy

    SciTech Connect

    Denisov, Vladimir I; Nyushkov, B N; Pivtsov, V S

    2010-01-31

    Self-starting mode locking is demonstrated for the first time in an all-fibre erbium laser with a cavity length above 1 km and high positive (normal) intracavity dispersion. The unconventional cavity design, with polarisation instability compensation, ensures stable operation and good frequency stability. The laser generates pulses with a record low repetition rate (82.4 kHz) and record high energy (564.3 nJ). (lasers)

  4. Octave-spanning Ti:sapphire laser with a repetition rate >1 ghz for optical frequency measurements and comparisons.

    PubMed

    Fortier, T M; Bartels, A; Diddams, S A

    2006-04-01

    We demonstrate a self-referenced, octave-spanning, mode-locked Ti:sapphire laser with a scalable repetition rate (550 MHz - 1.35 GHz). We use the frequency comb output of the laser, without additional broadening in optical fiber, for simultaneous measurements against atomic optical standards at 534, 578, 563, and 657 nm and to stabilize the laser offset frequency. PMID:16599240

  5. High-power 355 nm ultraviolet lasers operating at ultrahigh repetition rate

    NASA Astrophysics Data System (ADS)

    Chen, H.; Liu, Q.; Yan, P.; Gong, M.

    2013-02-01

    In this letter, we demonstrate a novel 355 nm ultraviolet (UV) laser operating at ultrahigh repetition rate from 300 kHz to 1 MHz. The hybrid fiber-MOPA-bulk amplifiers based IR source exhibits a high average power of 105 W with near-diffraction-limited beam quality, narrow linewidth and high polarization extinction ratio. Two-cascaded LBO crystals are employed for high efficiency frequency tripling, and a maximum 43.7 W of average UV power is achieved at 400 kHz, corresponding to a conversion efficiency as high as 41.6%. The pulse duration of the UV pulse can be tuned from 5 to 10 ns with good pulse peak stability (better than 2.2% (RMS)).

  6. Pathway to a lower cost high repetition rate ignition facility

    SciTech Connect

    Obenschain, S.P.; Colombant, D.G.; Schmitt, A.J.; Sethian, J.D.; McGeoch, M. W.

    2006-05-15

    An approach to a high-repetition ignition facility based on direct drive with the krypton-fluoride laser is presented. The objective is development of a 'Fusion Test Facility' that has sufficient fusion power to be useful as a development test bed for power plant materials and components. Calculations with modern pellet designs indicate that laser energies well below a megajoule may be sufficient. A smaller driver would result in an overall smaller, less complex and lower cost facility. While this facility might appear to have most direct utility to inertial fusion energy, the high flux of neutrons would also be able to address important issues concerning materials and components for other approaches to fusion energy. The physics and technological basis for the Fusion Test Facility are presented along with a discussion of its applications.

  7. Coherent quasi-CW 153-nm light source at high repetition rate

    NASA Astrophysics Data System (ADS)

    Nomura, Yutaka; Ito, Yoshiaki; Ozawa, Akira; Wang, Xiaoyang; Chen, Chuangtian; Shin, Shik; Watanabe, Shuntaro; Kobayashi, Yohei

    2012-02-01

    We present a quasi-cw laser in vacuum ultraviolet region at megahertz repetition rate. The narrowband pulses generated from an ytterbium-fiber laser system at 33 MHz repetition rate at the central wavelength of 1074 nm is frequency-converted by successive stages of LBO crystals and KBBF crystals. The generated radiation at 153 nm has the shortest wavelength achieved through phase-matched frequency conversion processes in nonlinear optical crystals to our knowledge.

  8. Slow Ca2+ wave stimulation using low repetition rate femtosecond pulsed irradiation

    NASA Astrophysics Data System (ADS)

    Iwanaga, S.; Smith, N. I.; Fujita, K.; Kawata, S.

    2006-01-01

    We demonstrated stimulation of Ca2+ in living cells by near-infrared laser pulses operated at sub-MHz repetition rates. HeLa cells were exposed to focused 780 nm femtosecond pulses, generated by a titanium-sapphire laser and adjusted by an electro-optical modulator. We found that the laser-induced Ca2+ waves could be generated over three orders of magnitude in repetition rates, with required laser pulse energy varying by less than one order of magnitude. Ca2+ wave speed and gradients were reduced with repetition rate, which allows the technique to be used to modulate the strength and speed of laser-induced effects. By lowering the repetition rate, we found that the laser-induced Ca2+ release is partially mediated by reactive oxygen species (ROS). Inhibition of ROS was successful only at low repetition rates, with the implication that ROS scavengers may in general be depleted in experiments using high repetition rate laser irradiation.

  9. High rate PLD of diamond-like-carbon utilizing high repetition rate visible lasers

    SciTech Connect

    McLean, W. II; Fehring, E.J.; Dragon, E.P.; Warner, B.E.

    1994-09-15

    Pulsed Laser Deposition (PLD) has been shown to be an effective method for producing a wide variety of thin films of high-value-added materials. The high average powers and high pulse repetition frequencies of lasers under development at LLNL make it possible to scale-up PLD processes that have been demonstrated in small systems in a number of university, government, and private laboratories to industrially meaningful, economically feasible technologies. A copper vapor laser system at LLNL has been utilized to demonstrate high rate PLD of high quality diamond-like-carbon (DLC) from graphite targets. The deposition rates for PLD obtained with a 100 W laser were {approx} 2000 {mu}m{center_dot}cm{sup 2}/h, or roughly 100 times larger than those reported by chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods. Good adhesion of thin (up to 2 pm) films has been achieved on a small number of substrates that include SiO{sub 2} and single crystal Si. Present results indicate that the best quality DLC films can be produced at optimum rates at power levels and wavelengths compatible with fiber optic delivery systems. If this is also true of other desirable coating systems, this PLD technology could become an extremely attractive industrial tool for high value added coatings.

  10. Design of a low emittance and high repetition rate S-band photoinjector

    NASA Astrophysics Data System (ADS)

    Han, Jang-Hui

    2014-09-01

    As an electron beam injector of X-ray free-electron lasers (FELs), photoinjectors have been developed for the past few decades. Such an injector starting with a photocathode RF gun provides high brightness beams and therefore it is being adopted as an injector of X-ray FELs. In this paper we show how to improve photoinjector performance in terms of emittance and repetition rates by means of injector components optimization, especially with the gun. Transverse emittance at the end of an injector is reduced by optimizing the gun design, gun solenoid position, and accelerating section position. The repetition rate of an injector mainly depends on the gun. It is discussed that a repetition rate of 1 kHz at a normal-conducting S-band photoinjector is feasible by adopting a coaxial RF coupler and improving cooling-water channels surrounding the gun.

  11. Near- infrared, mode-locked waveguide lasers with multi-GHz repetition rates

    NASA Astrophysics Data System (ADS)

    Choudhary, A.; Lagatsky, A. A.; Zhang, Z. Y.; Zhou, K. J.; Wang, Q.; Hogg, R. A.; Pradeesh, K.; Rafailov, E. U.; Resan, B.; Oehler, A. E. H.; Weingarten, K. J.; Sibbett, W.; Brown, C. T. A.; Shepherd, D. P.

    2014-02-01

    In this work, we discuss mode-locking results obtained with low-loss, ion-exchanged waveguide lasers. With Yb3+-doped phosphate glass waveguide lasers, a repetition rate of up to 15.2 GHz was achieved at a wavelength of 1047 nm with an average power of 27 mW and pulse duration of 811 fs. The gap between the waveguide and the SESAM introduced negative group velocity dispersion via the Gires Tournois Interferometer (GTI) effect which allowed the soliton mode-locking of the device. A novel quantum dot SESAM was used to mode-lock Er3+, Yb3+-doped phosphate glass waveguide lasers around 1500 nm. Picosecond pulses were achieved at a maximum repetition rate of 6.8 GHz and an average output power of 30 mW. The repetition rate was tuned by more than 1 MHz by varying the pump power.

  12. 3.5-GHz intra-burst repetition rate ultrafast Yb-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Akçaalan, Önder; Ilday, F. Ömer

    2016-05-01

    We report on an all-fiber Yb laser amplifier system with an intra-burst repetition rate of 3.5 GHz. The system is able to produce minimum of 15-ns long bursts containing approximately 50 pulses with a total energy of 215 μJ at a burst repetition rate of 1 kHz. The individual pulses are compressed down to the subpicosecond level. The seed signal from a 108 MHz fiber oscillator is converted to approximately 3.5 GHz by a multiplier consisting of six cascaded 50/50 couplers, and then amplified in ten stages. The highly cascaded amplification suppresses amplified spontaneous emission at low repetition rates. Nonlinear interactions between overlapping pulses within a burst is also discussed.

  13. Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Petzar, Paul; Petros, M.; Chen, Songsheng; Trieu, Bo; Lee, Nyung; Singh, U.

    2009-01-01

    Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.

  14. Ultrafast, high repetition rate, ultraviolet, fiber-laser-based source: application towards Yb+ fast quantum-logic.

    PubMed

    Hussain, Mahmood Irtiza; Petrasiunas, Matthew Joseph; Bentley, Christopher D B; Taylor, Richard L; Carvalho, André R R; Hope, Joseph J; Streed, Erik W; Lobino, Mirko; Kielpinski, David

    2016-07-25

    Trapped ions are one of the most promising approaches for the realization of a universal quantum computer. Faster quantum logic gates could dramatically improve the performance of trapped-ion quantum computers, and require the development of suitable high repetition rate pulsed lasers. Here we report on a robust frequency upconverted fiber laser based source, able to deliver 2.5 ps ultraviolet (UV) pulses at a stabilized repetition rate of 300.00000 MHz with an average power of 190 mW. The laser wavelength is resonant with the strong transition in Ytterbium (Yb+) at 369.53 nm and its repetition rate can be scaled up using high harmonic mode locking. We show that our source can produce arbitrary pulse patterns using a programmable pulse pattern generator and fast modulating components. Finally, simulations demonstrate that our laser is capable of performing resonant, temperature-insensitive, two-qubit quantum logic gates on trapped Yb+ ions faster than the trap period and with fidelity above 99%. PMID:27464118

  15. Advances in high repetition rate, ultra-short, gigawatt laser systems for time-resolved spectroscopy

    SciTech Connect

    DiMauro, L.F.

    1991-12-31

    The objective of this article is to emphasize the current advances in the development of high-repetition rate amplifier pumps. Although this review highlights amplifier pump development, any recent data from achieved outputs via the tunable amplifier section is also discussed. The first section describes desirable parameters attributable to the pump amplifier while the rest of the article deals with specific examples for various options. The pump amplifiers can be characterized into two distinct classes; those achieving operation in the hundred hertz regime and those performing at repetition rates {ge}1kHz. 23 refs., 4 figs.

  16. Advances in high repetition rate, ultra-short, gigawatt laser systems for time-resolved spectroscopy

    SciTech Connect

    DiMauro, L.F.

    1991-01-01

    The objective of this article is to emphasize the current advances in the development of high-repetition rate amplifier pumps. Although this review highlights amplifier pump development, any recent data from achieved outputs via the tunable amplifier section is also discussed. The first section describes desirable parameters attributable to the pump amplifier while the rest of the article deals with specific examples for various options. The pump amplifiers can be characterized into two distinct classes; those achieving operation in the hundred hertz regime and those performing at repetition rates {ge}1kHz. 23 refs., 4 figs.

  17. High power, high repetition rate, few picosecond Nd:LuVO₄ oscillator with cavity dumping.

    PubMed

    Gao, Peng; Guo, Jie; Li, Jinfeng; Lin, Hua; Yu, Haohai; Zhang, Huaijin; Liang, Xiaoyan

    2015-12-28

    We investigate the potential use of Nd:LuVO4 in high average power, high repetition rate ultrafast lasers. Maximum mode-locked average power of 28 W is obtained at the repetition rate of 58 MHz. The shortest pulse duration is achieved at 4 ps without dispersion compensation. With a cavity dumping technique, the pulse energy is scaling up to 40.7 μJ at 300 kHz and 14.3 μJ at 1.5 MHz. PMID:26831955

  18. High-order harmonic generation at a repetition rate of 100 kHz

    SciTech Connect

    Lindner, F.; Stremme, W.; Schaetzel, M. G.; Grasbon, F.; Paulus, G. G.; Walther, H.; Hartmann, R.; Strueder, L.

    2003-07-01

    We report high-order harmonic generation (HHG) in rare gases using a femtosecond laser system with a very high repetition rate (100 kHz) and low pulse energy (7 {mu}J). To our knowledge, this is the highest repetition rate reported to date for HHG. The tight focusing geometry required to reach sufficiently high intensities implies low efficiency of the process. Harmonics up to the 45th order are nevertheless generated and detected. We show evidence of clear separation and selection of quantum trajectories by moving the gas jet with respect to the focus, in agreement with the theoretical predictions of the semiclassical model of HHG.

  19. Fibre laser with a subterahertz repetition rate of ultrashort pulses in the telecom range

    NASA Astrophysics Data System (ADS)

    Andrianov, A. V.; Mylnikov, V. M.; Koptev, M. Yu; Muravyev, S. V.; Kim, A. V.

    2016-04-01

    We have investigated a new fibre laser configuration for the generation of ultrashort pulses at a repetition rate far exceeding the fundamental cavity frequency. The laser configuration includes a nonlinear amplifying mirror as an artificial saturable absorber for mode locking and a spectral comb filter for pulse separation stabilisation. Generation of trains and sequences of ultrashort pulses at a repetition rate tunable in the range 8 – 200 GHz has been demonstrated experimentally. The pulses generated by the laser have been shown to retain an ordered, equidistant structure on a nanosecond timescale.

  20. A contactless microwave-based diagnostic tool for high repetition rate laser systems

    SciTech Connect

    Braggio, C.; Borghesani, A. F.

    2014-02-15

    We report on a novel electro-optic device for the diagnostics of high repetition rate laser systems. It is composed of a microwave receiver and of a second order nonlinear crystal, whose irradiation with a train of short laser pulses produces a time-dependent polarization in the crystal itself as a consequence of optical rectification. This process gives rise to the emission of microwave radiation that is detected by a receiver and is analyzed to infer the repetition rate and intensity of the pulses. We believe that this new method may overcome some of the limitations of photodetection techniques.

  1. Injector Beam Dynamics for a High-Repetition Rate 4th-Generation Light Source

    SciTech Connect

    Papadopoulos, C. F.; Corlett, J.; Emma, P.; Filippetto, D.; Penn, G.; Qiang, J.; Reinsch, M.; Sannibale, F.; Steier, C.; Venturini, M.; Wells, R.

    2013-05-20

    We report on the beam dynamics studies and optimization methods for a high repetition rate (1 MHz) photoinjector based on a VHF normal conducting electron source. The simultaneous goals of beamcompression and reservation of 6-dimensional beam brightness have to be achieved in the injector, in order to accommodate a linac driven FEL light source. For this, a parallel, multiobjective optimization algorithm is used. We discuss the relative merits of different injector design points, as well as the constraints imposed on the beam dynamics by technical considerations such as the high repetition rate.

  2. Picosecond supercontinuum laser with consistent emission parameters over variable repetition rates from 1 to 40 MHz

    NASA Astrophysics Data System (ADS)

    Schönau, Thomas; Siebert, Torsten; Härtel, Romano; Klemme, Dietmar; Lauritsen, Kristian; Erdmann, Rainer

    2013-02-01

    An freely triggerable picosecond visible supercontinuum laser source is presented that allows for a uniform spectral profile and equivalent pulse characteristics over variable repetition rates from 1 to 40MHz. The system features PM Yb3+-doped fiber amplification of a picosecond gain-switched seed diode at 1062 nm. The pump power in the multi-stage amplifier is actively adjusted by a microcontroller for a consistent peak power of the amplified signal in the full range of repetition rates. The length of the PCF is scaled to deliver a homogeneous spectrum and minimized distortion of the temporal pulse shape.

  3. High-average-power 100-Hz repetition rate table-top soft x-ray lasers

    NASA Astrophysics Data System (ADS)

    Rocca, Jorge J.; Reagan, Brendan A.; Wernsing, Keith; Wang, Yong; Yin, Liang; Wang, Shoujun; Berrill, Mark; Woolston, Mark R.; Curtis, Alden H.; Furch, Federico J. A.; Shlyaptsev, Vyacheslav N.; Luther, Brad M.; Patel, Dinesh; Marconi, Mario C.; Menoni, Carmen S.

    2013-09-01

    The table-top generation of high average power coherent soft x-ray radiation in a compact set up is of high interest for numerous applications. We have demonstrated the generation of bright soft x-ray laser pulses at 100 Hz repetition rate with record-high average power from compact plasma amplifiers excited by an ultrafast diode-pumped solid state laser. Results of compact λ=18.9nm Ni-like Mo and λ=13.9nm Ni-like Ag lasers operating at 100 Hz repetition rate are discussed.

  4. Electron diffraction using ultrafast electron bunches from a laser-wakefield accelerator at kHz repetition rate

    NASA Astrophysics Data System (ADS)

    He, Z.-H.; Thomas, A. G. R.; Beaurepaire, B.; Nees, J. A.; Hou, B.; Malka, V.; Krushelnick, K.; Faure, J.

    2013-02-01

    We show that electron bunches in the 50-100 keV range can be produced from a laser wakefield accelerator using 10 mJ, 35 fs laser pulses operating at 0.5 kHz. It is shown that using a solenoid magnetic lens, the electron bunch distribution can be shaped. The resulting transverse and longitudinal coherence is suitable for producing diffraction images from a polycrystalline 10 nm aluminum foil. The high repetition rate, the stability of the electron source, and the fact that its uncorrelated bunch duration is below 100 fs make this approach promising for the development of sub-100 fs ultrafast electron diffraction experiments.

  5. [INVITED] Laser welding of glasses at high repetition rates - Fundamentals and prospects

    NASA Astrophysics Data System (ADS)

    Richter, Sören; Zimmermann, Felix; Tünnermann, Andreas; Nolte, Stefan

    2016-09-01

    We report on the welding of various glasses with ultrashort laser pulses. Femtosecond laser pulses at repetition rates in the MHz range are focused at the interface between two substrates, resulting in multiphoton absorption and heat accumulation from successive pulses. This leads to local melting and subsequent resolidification which can be used to weld the glasses. The fundamental interaction process was studied using an in-situ micro Raman setup to measure the laser induced temperature distribution and its temporal decay. The induced network changes were analyzed by Raman spectrocopy identifying an increase of three and four membered silicon rings within the laser irradiated area. In order to determine the stability of the laser welded samples a three point bending test was used. Thereby, we identified that the maximal achievable breaking strength is limited by laser induced stress surrounding the modified material. To minimize the amount of stress bursts of laser pulses or an post processing annealing step can be applied. Besides fused silica, we welded borosilicate glasses and glasses with a low thermal expansion coefficient. Even the welding of different glass combinations is possible demonstrating the versatility of ultrashort pulse induced laser welding.

  6. High repetition rate femtosecond laser forming sub-10 µm diameter interconnection vias

    NASA Astrophysics Data System (ADS)

    Tan, B; Panchatsharam, S; Venkatakrishnan, K

    2009-03-01

    Laser ablative microvia formation has been widely accepted as an effective manufacturing method for interconnect via formation. Current conventional nanosecond laser microvia formation has reached its limit in terms of minimum via diameter and machining quality. Femtosecond laser has been investigated intensively for its superior machining quality and capability of producing much smaller features. However, the traditional femtosecond laser has very low power and is thus unable to meet the throughput requirement. In this paper we report ablative microvia formation using femtosecond lasers at megahertz repetition rates. Laser ablation was demonstrated for the first time for sub-10 µm interconnection via drilling at a throughput of 10 000 vias per second. A systematic study of the influence of a high repetition rate in femtosecond laser micromachining of silicon was carried out. The experiments were performed using an Yb-doped fibre amplified/oscillator laser with 1030 nm wavelength in an air environment. The effects of a high repetition rate on microvia formation were observed at ~300 fs for silicon substrates. Laser parameters along with threshold energy, via diameter, ablation depth, ablation rate and via quality were studied in detail to accentuate the need of femtosecond lasers for forming sub-10 µm diameter microvias. The experimental results show that femtosecond laser pulses with high repetition rates show unequivocally the advantages of short-pulse laser ablation for high-precision applications in micrometre-scale dimensions.

  7. Spectral distortion of dual-comb spectrometry due to repetition rate fluctuation

    NASA Astrophysics Data System (ADS)

    Hong-Lei, Yang; Hao-Yun, Wei; Yan, Li

    2016-04-01

    Dual-comb spectrometry suffers the fluctuations of parameters in combs. We demonstrate that the repetition rate is more important than any other parameter, since the fluctuation of the repetition rate leads to a change of difference in the repetition rate between both combs, consequently causing the conversion factor variation and spectral frequency misalignment. The measured frequency noise power spectral density of the repetition rate exhibits an integrated residual frequency modulation of 1.4 Hz from 1 Hz to 100 kHz in our system. This value corresponds to the absorption peak fluctuation within a root mean square value of 0.19 cm‑1 that is verified by both simulation and experimental result. Further, we can also simulate spectrum degradation as the fluctuation varies. After modifying misaligned spectra and averaging, the measured result agrees well with the simulated spectrum based on the GEISA database. Project supported by the State Key Laboratory of Precision Measurement Technology & Instruments of Tsinghua University and the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61205147).

  8. Multipass dye-cell amplifier for high-repetition-rate femtosecond optical pulses

    SciTech Connect

    Nickel, D.; Kuehlke, D.; von der Linde, D.

    1989-01-01

    We describe a dye-cell amplifier pumped by a copper-vapor laser at a 8.4-kHz repetition rate. This system avoids possible problems and restrictions arising from nozzle performance in commonly used jet-stream amplifiers. We obtained a nearly diffraction-limited beam with pulses of 60 fsec and energies of up to 50 ..mu..J.

  9. Effect of the pulse repetition rate on fiber-assisted tissue ablation

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook

    2016-07-01

    The effect of the pulse repetition rate on ablation performance was evaluated ex vivo at various fiber sweeping speeds for an effective 532-nm laser prostatectomy. Three pulse repetition rates (7.5, 15, and 30 kHz) at 100 W were delivered to bovine liver tissue at three sweeping speeds (2, 4, and 6 mm/s) to achieve bulky tissue removal. Ablation performance was quantitatively compared in terms of the ablation volume and the coagulation thickness. The lowest pulse repetition rate of 7.5 kHz attained the highest ablation volume (101.5 ± 12.0 mm3) and the thinnest coagulation (0.7 ± 0.1 mm) along with superficial carbonization. The highest pulse repetition rate of 30 kHz was associated with the least tissue removal (65.8 ± 5.0 mm3) and the deepest thermal denaturation (1.1 ± 0.2 mm). Quantitative evaluations of laser parameters can be instrumental in facilitating ablation efficiency and maintaining hemostatic coagulation during treatment of large-sized benign prostate hyperplasia.

  10. Wide-field medium-repetition-rate multiphoton microscopy reduces photodamage of living cells.

    PubMed

    Macias-Romero, C; Zubkovs, V; Wang, S; Roke, S

    2016-04-01

    Demands of higher spatial and temporal resolutions in linear and nonlinear imaging keep pushing the limits of optical microscopy. We showed recently that a multiphoton microscope with 200 kHz repetition rate and wide-field illumination has a 2-3 orders of magnitude improved throughput compared to a high repetition rate confocal scanning microscope. Here, we examine the photodamage mechanisms and thresholds in live cell imaging for both systems. We first analyze theoretically the temperature increase in an aqueous solution resulting from illuminating with different repetition rates (keeping the deposited energy and irradiated volume constant). The analysis is complemented with photobleaching experiments of a phenolsulfonphthalein (phenol red) solution. Combining medium repetition rates and wide-field illumination promotes thermal diffusivity, which leads to lower photodamage and allows for higher peak intensities. A three day proliferation assay is also performed on living cells to confirm these results: dwell times can be increased by a factor of 3×10(6) while still preserving cell proliferation. By comparing the proliferation data with the endogenous two-photon fluorescence decay, we propose to use the percentage of the remaining endogenous two-photon fluorescence after exposure as a simple in-situ viability test. These findings enable the possibility of long-term imaging and reduced photodamage. PMID:27446668

  11. Wide-field medium-repetition-rate multiphoton microscopy reduces photodamage of living cells

    PubMed Central

    Macias-Romero, C.; Zubkovs, V.; Wang, S.; Roke, S.

    2016-01-01

    Demands of higher spatial and temporal resolutions in linear and nonlinear imaging keep pushing the limits of optical microscopy. We showed recently that a multiphoton microscope with 200 kHz repetition rate and wide-field illumination has a 2–3 orders of magnitude improved throughput compared to a high repetition rate confocal scanning microscope. Here, we examine the photodamage mechanisms and thresholds in live cell imaging for both systems. We first analyze theoretically the temperature increase in an aqueous solution resulting from illuminating with different repetition rates (keeping the deposited energy and irradiated volume constant). The analysis is complemented with photobleaching experiments of a phenolsulfonphthalein (phenol red) solution. Combining medium repetition rates and wide-field illumination promotes thermal diffusivity, which leads to lower photodamage and allows for higher peak intensities. A three day proliferation assay is also performed on living cells to confirm these results: dwell times can be increased by a factor of 3×106 while still preserving cell proliferation. By comparing the proliferation data with the endogenous two-photon fluorescence decay, we propose to use the percentage of the remaining endogenous two-photon fluorescence after exposure as a simple in-situ viability test. These findings enable the possibility of long-term imaging and reduced photodamage.

  12. Estimation of Promotion, Repetition and Dropout Rates for Learners in South African Schools

    ERIC Educational Resources Information Center

    Uys, Daniël Wilhelm; Alant, Edward John Thomas

    2015-01-01

    A new procedure for estimating promotion, repetition and dropout rates for learners in South African schools is proposed. The procedure uses three different data sources: data from the South African General Household survey, data from the Education Management Information Systems, and data from yearly reports published by the Department of Basic…

  13. Multi-gigahertz repetition rate ultrafast waveguide lasers mode-locked with graphene saturable absorbers

    NASA Astrophysics Data System (ADS)

    Obraztsov, P. A.; Okhrimchuk, A. G.; Rybin, M. G.; Obraztsova, E. D.; Garnov, S. V.

    2016-08-01

    We report the development of an approach to build compact waveguide lasers that operate in the stable fundamental mode-locking regime with multigigahertz repetition rates. The approach is based on the use of depressed cladding multi- or single-mode waveguides fabricated directly in the active laser crystal using the femtosecond laser inscription method and a graphene saturable absorber. Using this approach we achieve the stable self-starting mode-locking operation of a diode-pumped waveguide Nd:YAG laser that delivers picosecond pulses at a repetition rate of up to 11.5 GHz with an average power of 12 mW at a central wavelength of 1064 nm. The saturable absorbers are formed through the chemical vapor deposition of single-layer graphene on the output coupler mirror or directly on the end facet of the laser crystal. The stable self-starting mode-locking operation is achieved by controlling the group delay dispersion in the laser cavity with an intracavity interferometer. The method developed for the creation of compact ultrashort pulse laser generators with gigahertz repetition rates can be extended further and applied for the development of compact high-repetition rate lasers that operate at a wide range of IR wavelengths.

  14. High-repetition-rate oscillators based on athermal glass rods and on birefringence correction techniques

    NASA Astrophysics Data System (ADS)

    Jackel, Steven M.; Kaufman, Alon; Lallouz, Raphael

    1994-09-01

    A high-repetition-rate oscillator, based on a flashlamp-pumped Q-100- clad athermal phosphate glass rod in a stable cavity, was developed to act as the driver for a high-repetition-rate Nd:glass laser system. Although the athermal properties compensated to a large extent for thermal lensing, birefringence losses in a conventional linear cavity containing a polarizer, as required for Q-switched operation, reduced pulse energy by up to a factor of 3 when the repetition rate was increased from single shot to 50% of fracture-limit pump conditions. Several birefringence compensation techniques were evaluated with the best results obtained in a reentrant (Y-cavity) design, with a Faraday rotator to partially compensate for birefringence and a mirror to reinsert polarizer-rejected light, so that the light quadruple passed the laser head per cavity round-trip and egressed through the output mirror (the only oscillator exit port). Birefringence losses were then reduced to 20%. High-repetition-rate TEM 00 operation was obtained by using a long (223-cm) cavity, and by placing the Faraday rotator/laser head together with a large mode selection aperture next to the curved back mirror.

  15. Operation and thermal modeling of the ISIS H- source from 50 to 2 Hz repetition rates

    NASA Astrophysics Data System (ADS)

    Pereira, H.; Faircloth, D.; Lettry, J.

    2013-02-01

    CERN's Linac4 accelerator H- ion source, currently under construction, will operate at a 2 Hz repetition rate, with pulse length of 0.5 ms and a beam current of 80 mA. Its reliability must exceed 99 % with a mandatory 3 month uninterrupted operation period. A Penning ion source is successfully operated at ISIS; at 50 Hz repetition rate it reliably provides 55 mA H- pulses of 0.25 ms duration over 1 month. The discharge plasma ignition is very sensitive to the temperatures of the discharge region, especially of its cathode. The investigation by modeling and measurement of operation parameters suitable for arc ignition and H- production at 2 Hz is of paramount importance and must be understood prior to the implementation of discharge ion sources in the Linac4 accelerator. In its original configuration, the ISIS H- source delivers beam only if the repetition rate is above 12.5 Hz, this paper describes the implementation of a temperature control of the discharge region aiming at lower repetition rate operation. The experimental results of the modified source successfully operated down to 1.6 Hz and providing 30 mA H- pulses of 0.75 ms duration are presented. A thermal modeling of the ISIS ion source gives insight to the relevant parameters. The analysis demonstrates the adaptability of discharge sources for the operating conditions of the Linac4.

  16. Long pulse and high repetition rate operation of a relativistic klystron amplifier

    SciTech Connect

    Levine, J.S.; Harteneck, B.D.

    1994-12-31

    The authors are developing an L-band (1.3 GHz) high current relativistic klystron amplifier for both long pulse ({ge} 500 ns) and high repetition rate ({ge} 200 pps) capabilities. In repetitive operation, it has produced 3.3 kW of average power in 80 ns FWHM pulses of 250 MW peak power at 200 pps. They are currently transferring this same klystron to a single-shot, long-pulse driver to demonstrate its operation with a {ge} 500 ns electrical pulse.

  17. High-energy, high-repetition-rate picosecond pulses from a quasi-CW diode-pumped Nd:YAG system.

    PubMed

    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. PMID:24104637

  18. 115 kHz tuning repetition rate ultrahigh-speed wavelength-swept semiconductor laser

    PubMed Central

    Oh, W. Y.; Yun, S. H.; Tearney, G. J.; Bouma, B. E.

    2009-01-01

    We demonstrate an ultrahigh-speed wavelength-swept semiconductor laser using a polygon-based wavelength scanning filter. With a polygon rotational speed of 900 revolutions per second, a continuous wavelength tuning rate of 9200 nm/ms and a tuning repetition rate of 115 kHz were achieved. The wavelength tuning range of the laser was 80 nm centered at 1325 nm, and the average polarized output power was 23 mW. PMID:16350273

  19. High-power high-repetition-rate single-mode Er-Yb-doped fiber laser system.

    PubMed

    Pavlov, Ihor; Ilbey, Emrah; Dülgergil, Ebru; Bayri, Alper; Ilday, F Ömer

    2012-04-23

    We demonstrate an all-fiber-integrated, high-power chirped-pulse-amplification system operating at 1550 nm. The seed source is a soliton fiber laser with 156 MHz repetition rate. Two-stage single mode amplifier provides an amplification of more than 40 dB without significant spontaneous amplified emission. The power amplifier is based on cladding-pumped 10 µm-core Er-Yb co-doped fiber, the output of which was spliced into standard singlemode fiber. We obtain 10 W average power in a strictly singlemode operation. After dechirping with a grating compressor, near transform-limited, 450 fs-long pulses are obtained. The laser source exhibits excellent short and long-term intensity stability, with relative intensity noise measurements characterizing the short-term stability. PMID:22535037

  20. A four kHz repetition rate compact TEA CO2 laser

    NASA Astrophysics Data System (ADS)

    Zheng, Yijun; Tan, Rongqing

    2013-09-01

    A compact transversely excited atmospheric (TEA) CO2 laser with high repetition-rate was reported. The size of the laser is 380 mm×300 mm×200 mm, and the discharge volume is 12×103 mm3. The laser cavity has a length of 320mm and consists of a totally reflective concave mirror with a radius of curvature of 4 m (Cu metal substrate coated with Au) and a partially reflecting mirror. The ultraviolet preionization makes the discharge even and stable,the output energy can be as high as 28 mJ under the circumstance of free oscillation, and the width of the light pulse is 60ns.To acquire the high wind velocity, a turbocharger is used in the system of the fast-gas flow cycle. When the wind speed is 100m/s, the repetition rate of the transversely excited atmospheric CO2 laser is up to 2 kHz. On this basis, a dual modular structure with two sets of the gas discharge unit is adopted to obtain a higher pulse repetition frequency output. The dual discharge unit composed two sets of electrodes and two sets of turbo fan. Alternate trigger technology is used to make the two sets of discharge module work in turn with repetition frequency of 2 kHz, the discharge interval of two sets of the gas discharge unit can be adjusted continuously from 20 microseconds to 250 microseconds. Under the conditions of maintaining the other parameters constant, the repetition frequency of the laser pulse is up to 4 kHz. The total size of laser with dual modular structure is 380mm×520mm×200mm, and the discharge volume is 24×103 mm3 with the cavity length of 520mm.

  1. Design and Development of High-Repetition-Rate Satellite Laser Ranging System

    NASA Astrophysics Data System (ADS)

    Choi, Eun-Jung; Bang, Seong-Cheol; Sung, Ki-Pyoung; Lim, Hyung-Chul; Jung, Chan-Gyu; Kim, In-Yeung; Choi, Jae-Seung

    2015-09-01

    The Accurate Ranging System for Geodetic Observation ? Mobile (ARGO-M) was successfully developed as the first Korean mobile Satellite Laser Ranging (SLR) system in 2012, and has joined in the International Laser Ranging Service (ILRS) tracking network, DAEdeoK (DAEK) station. The DAEK SLR station was approved as a validated station in April 2014, through the ILRS station ¡°data validation¡± process. The ARGO-M system is designed to enable 2 kHz laser ranging with millimeter-level precision for geodetic, remote sensing, navigation, and experimental satellites equipped with Laser Retroreflector Arrays (LRAs). In this paper, we present the design and development of a next generation high-repetition-rate SLR system for ARGO-M. The laser ranging rate up to 10 kHz is becoming an important issue in the SLR community to improve ranging precision. To implement high-repetition-rate SLR system, the High-repetition-rate SLR operation system (HSLR-10) was designed and developed using ARGO-M Range Gate Generator (A-RGG), so as to enable laser ranging from 50 Hz to 10 kHz. HSLR-10 includes both hardware controlling software and data post-processing software. This paper shows the design and development of key technologies of high-repetition-rate SLR system. The developed system was tested successfully at DAEK station and then moved to Sejong station, a new Korean SLR station, on July 1, 2015. HSLR-10 will begin normal operations at Sejong station in the near future.

  2. The influence of the repetition rate on the nanosecond pulsed pin-to-pin microdischarges

    NASA Astrophysics Data System (ADS)

    Huang, Bang-Dou; Takashima, Keisuke; Zhu, Xi-Ming; Pu, Yi-Kang

    2014-10-01

    The effect of repetition rate on a nanosecond atmospheric pressure discharge is investigated. The discharge is generated between two pins in a mixture of Ne and Ar. The voltage, current, power waveforms and the temporally and spatially resolved electron density and an ‘effective’ electron temperature are measured, with a pulse interval between 1.5 and 200 µs. It is found that not only does the repetition rate have a strong influence on the breakdown voltage and the peak discharge power, but it can also affect the rise rate of the volume averaged electron density and its peak value. Temporally and spatially resolved measurement of the electron density and the effective electron temperature show that the spatial distributions of both quantities are also influenced by the repetition rate. In the initial discharge period of all cases, the sharp rise of the electron density correlates with the drastic drop of the effective electron temperature. It is suggested that the residual charges have a strong impact on the axial distribution of the electric field and energetic electrons between the electrodes during the breakdown period, as illustrated by a simple sheath model.

  3. Optical breakdown of multilayer thin-films induced by ultrashort pulses at MHz repetition rates.

    PubMed

    Angelov, Ivan B; von Pechmann, Maximilian; Trubetskov, Michael K; Krausz, Ferenc; Pervak, Vladimir

    2013-12-16

    Multilayer coatings composed of TiO(2), Ta(2)O(5), HfO(2), or Al(2)O(3) as high-index materials and SiO(2) as low-index material were investigated for laser-induced damage using 1 ps, 5 µJ pulses generated by a mode-locked Yb:YAG thin-disk oscillator operating at a wavelength of 1030 nm and repetition rate of 11.5 MHz. Previously reported linear band gap dependence of damage threshold at kHz repetition rates was confirmed also for the MHz regime. Additionally, we studied the effect of electric field distribution inside of the layer stack. We did not observe any significant influence of thermal effects on the laser-induced damage threshold in this regime. PMID:24514719

  4. High repetition rate gain-switched Er:YAG ceramic laser at 1645 nm

    NASA Astrophysics Data System (ADS)

    Chen, B. H.; Zhang, J. N.; Zhao, Y. G.; Zhang, J.; Tang, D. Y.; Shen, D. Y.

    2016-02-01

    We report on a gain-switched Er:YAG ceramic laser resonantly pumped by an acousto-optically modulated Er, Yb co-doped fiber laser at 1532 nm. The laser produced stable pulse trains at 1645 nm with pulse repetition rate tunable between 13-100 kHz and corresponding pulse width of 480-450 ns under a pump power-level of 8.7 W. At the 100 kHz of repetition rate, over 2.2 W of average output power was generated for 6.5 W of incident pump power, corresponding to a slope efficiency of 40% with respect to incident pump power.

  5. Single-pass high-harmonic generation at 20.8 MHz repetition rate.

    PubMed

    Vernaleken, Andreas; Weitenberg, Johannes; Sartorius, Thomas; Russbueldt, Peter; Schneider, Waldemar; Stebbings, Sarah L; Kling, Matthias F; Hommelhoff, Peter; Hoffmann, Hans-Dieter; Poprawe, Reinhart; Krausz, Ferenc; Hänsch, Theodor W; Udem, Thomas

    2011-09-01

    We report on single-pass high-harmonic generation (HHG) with amplified driving laser pulses at a repetition rate of 20.8 MHz. An Yb:YAG Innoslab amplifier system provides 35 fs pulses with 20 W average power at 1030 nm after external pulse compression. Following tight focusing into a xenon gas jet, we observe the generation of high-harmonic radiation of up to the seventeenth order. Our results show that state-of-the-art amplifier systems have become a promising alternative to cavity-assisted HHG for applications that require high repetition rates, such as frequency comb spectroscopy in the extreme UV. PMID:21886233

  6. Demonstration of a desk-top size high repetition rate soft x-ray laser.

    PubMed

    Heinbuch, S; Grisham, M; Martz, D; Rocca, J J

    2005-05-30

    We have demonstrated a new type of high repetition rate 46.9 nm capillary discharge laser that fits on top of a small desk and that it does not require a Marx generator for its excitation. The relatively low voltage required for its operation allows a reduction of nearly one order of magnitude in the size of the pulsed power unit relative to previous capillary discharge lasers. Laser pulses with an energy of ~ 13 microJ are generated at repetition rates up to 12 Hz. About (2-3) x 10 4 laser shots can be generated with a single capillary. This new type of portable laser is an easily accessible source of intense short wavelength laser light for applications. PMID:19495315

  7. Continuous high-repetition-rate operation of collisional soft-x-ray lasers with solid targets.

    PubMed

    Weith, A; Larotonda, M A; Wang, Y; Luther, B M; Alessi, D; Marconi, M C; Rocca, J J; Dunn, J

    2006-07-01

    We have generated a laser average output power of 2 microW at a wavelength of 13.9 nm by operating a tabletop laser-pumped Ni-like Ag laser at a 5 Hz repetition rate, using a solid helicoidal target that is continuously rotated and advanced to renew the target surface between shots. More than 2 x 10(4) soft-x-ray laser shots were obtained by using a single target. Similar results were obtained at 13.2 nm in Ni-like Cd with a Cd-coated target. This scheme will allow uninterrupted operation of laser-pumped tabletop collisional soft-x-ray lasers at a repetition rate of 10 Hz for a period of hours, enabling the generation of continuous high average soft-x-ray powers for applications. PMID:16770410

  8. High Repetition Rate, LINAC-Based Nuclear Resonance Fluorescence FY 2008 Final Report

    SciTech Connect

    Scott M Watson; Mathew T Kinlaw; James L Jones; Alan W. Hunt; Glen A. Warren

    2008-12-01

    This summarizes the first year of a multi-laboratory/university, multi-year effort focusing on high repetition rate, pulsed LINAC-based nuclear resonance fluorescence (NRF) measurements. Specifically, this FY2008 effort centered on experimentally assessing NRF measurements using pulsed linear electron accelerators, operated at various repetition rates, and identifying specific detection requirements to optimize such measurements. Traditionally, interest in NRF as a detection technology, which continues to receive funding from DHS and DOE/NA-22, has been driven by continuous-wave (CW), Van de Graff-based bremsstrahlung sources. However, in addition to the relatively sparse present-day use of Van de Graff sources, only limited NRF data from special nuclear materials has been presented; there is even less data available regarding shielding effects and photon source optimization for NRF measurements on selected nuclear materials.

  9. Comparison of two high-repetition-rate pulsed CO/sub 2/ laser discharge geometries

    SciTech Connect

    Faszer, W.; Tulip, J.; Seguin, H.

    1980-11-01

    Two discharge geometries are commonly used for pumping high-repetition-rate transversely excited atmosphere (TEA) lasers. One uses solid electrodes with preionization provided by downstream spark pins. The other uses a solid electrode and a screen electrode with preionization provided by an auxiliary discharge behind the screen. In this study the performance of the two systems was compared. The repetition rate at which arcing occurs was found to increase linearly with flow velocity but decrease with increasing energy density. It was also dependent on system geometry and the spark pin preionized system performed better than the auxiliary discharge preionized system. Data are given for discharges in N/sub 2/, CO/sub 2/, He, and a CO/sub 2/ laser mixture.

  10. Group velocity locked vector dissipative solitons in a high repetition rate fiber laser.

    PubMed

    Luo, Yiyang; Li, Lei; Liu, Deming; Sun, Qizhen; Wu, Zhichao; Xu, Zhilin; Tang, Dingyuan; Fu, Songnian; Zhao, Luming

    2016-08-01

    Vectorial nature of dissipative solitons (DSs) with high repetition rate is studied for the first time in a normal-dispersion fiber laser. Despite the fact that the formed DSs are strongly chirped and the repetition rate is greater than 100 MHz, polarization locked and polarization rotating group velocity locked vector DSs can be formed under 129.3 MHz fundamental mode-locking and 258.6 MHz harmonic mode-locking of the fiber laser, respectively. The two orthogonally polarized components of these vector DSs possess distinctly different central wavelengths and travel together at the same group velocity in the laser cavity, resulting in a gradual spectral edge and small steps on the optical spectrum, which can be considered as an auxiliary indicator of the group velocity locked vector DSs. Moreover, numerical simulations well confirm the experimental observations and further reveal the impact of the net cavity birefringence on the properties of the formed vector DSs. PMID:27505834

  11. A simple sub-nanosecond ultraviolet light pulse generator with high repetition rate and peak power.

    PubMed

    Binh, P H; Trong, V D; Renucci, P; Marie, X

    2013-08-01

    We present a simple ultraviolet sub-nanosecond pulse generator using commercial ultraviolet light-emitting diodes with peak emission wavelengths of 290 nm, 318 nm, 338 nm, and 405 nm. The generator is based on step recovery diode, short-circuited transmission line, and current-shaping circuit. The narrowest pulses achieved have 630 ps full width at half maximum at repetition rate of 80 MHz. Optical pulse power in the range of several hundreds of microwatts depends on the applied bias voltage. The bias voltage dependences of the output optical pulse width and peak power are analysed and discussed. Compared to commercial UV sub-nanosecond generators, the proposed generator can produce much higher pulse repetition rate and peak power. PMID:24007048

  12. A simple sub-nanosecond ultraviolet light pulse generator with high repetition rate and peak power

    NASA Astrophysics Data System (ADS)

    Binh, P. H.; Trong, V. D.; Renucci, P.; Marie, X.

    2013-08-01

    We present a simple ultraviolet sub-nanosecond pulse generator using commercial ultraviolet light-emitting diodes with peak emission wavelengths of 290 nm, 318 nm, 338 nm, and 405 nm. The generator is based on step recovery diode, short-circuited transmission line, and current-shaping circuit. The narrowest pulses achieved have 630 ps full width at half maximum at repetition rate of 80 MHz. Optical pulse power in the range of several hundreds of microwatts depends on the applied bias voltage. The bias voltage dependences of the output optical pulse width and peak power are analysed and discussed. Compared to commercial UV sub-nanosecond generators, the proposed generator can produce much higher pulse repetition rate and peak power.

  13. Upscaling of X-Ray Laser Repetition Rate Using an OPCPA Architecture

    NASA Astrophysics Data System (ADS)

    Jia, Fei; Staub, Felix; Balmer, Jürg

    We present a novel design of a hybrid amplification chain for pumping a Sn target producing ˜μJ coherent soft-X-ray pulses at few-Hz repetition rate. The driver aims to generate multi-joule energy at the central wavelength of 1053 nm and consists of optical-parametric chirped-pulse amplification (OPCPA) combined with diode-pumped Nd:YLF amplifiers. The soft-X-ray laser at the wavelength of 11.9 nm is produced by focusing the infrared beam into a line focus on a solid Sn target. Benefiting from this hybrid pump scheme and grazing-incidence pump geometry (GRIP), such a system has the potential to upscale the repetition rate of soft-X-ray lasers from single shot to the few-Hz region.

  14. High-order harmonic generation using a high-repetition-rate turnkey laser.

    PubMed

    Lorek, E; Larsen, E W; Heyl, C M; Carlström, S; Paleček, D; Zigmantas, D; Mauritsson, J

    2014-12-01

    We generate high-order harmonics at high pulse repetition rates using a turnkey laser. High-order harmonics at 400 kHz are observed when argon is used as target gas. In neon, we achieve generation of photons with energies exceeding 90 eV (∼13 nm) at 20 kHz. We measure a photon flux of up to 4.4 × 10(10) photons per second per harmonic in argon at 100 kHz. Many experiments employing high-order harmonics would benefit from higher repetition rates, and the user-friendly operation opens up for applications of coherent extreme ultra-violet pulses in new research areas. PMID:25554271

  15. High-order harmonic generation using a high-repetition-rate turnkey laser

    SciTech Connect

    Lorek, E. Larsen, E. W.; Heyl, C. M.; Carlström, S.; Mauritsson, J.; Paleček, D.; Zigmantas, D.

    2014-12-15

    We generate high-order harmonics at high pulse repetition rates using a turnkey laser. High-order harmonics at 400 kHz are observed when argon is used as target gas. In neon, we achieve generation of photons with energies exceeding 90 eV (∼13 nm) at 20 kHz. We measure a photon flux of up to 4.4 × 10{sup 10} photons per second per harmonic in argon at 100 kHz. Many experiments employing high-order harmonics would benefit from higher repetition rates, and the user-friendly operation opens up for applications of coherent extreme ultra-violet pulses in new research areas.

  16. An optical parametric chirped-pulse amplifier for seeding high repetition rate free-electron lasers

    SciTech Connect

    Höppner, H.; Tanikawa, T.; Schulz, M.; Riedel, R.; Teubner, U.; Faatz, B.; Tavella, F.

    2015-05-15

    High repetition rate free-electron lasers (FEL), producing highly intense extreme ultraviolet and x-ray pulses, require new high power tunable femtosecond lasers for FEL seeding and FEL pump-probe experiments. A tunable, 112 W (burst mode) optical parametric chirped-pulse amplifier (OPCPA) is demonstrated with center frequencies ranging from 720–900 nm, pulse energies up to 1.12 mJ and a pulse duration of 30 fs at a repetition rate of 100 kHz. Since the power scalability of this OPCPA is limited by the OPCPA-pump amplifier, we also demonstrate a 6.7–13.7 kW (burst mode) thin-disk OPCPA-pump amplifier, increasing the possible OPCPA output power to many hundreds of watts. Furthermore, third and fourth harmonic generation experiments are performed and the results are used to simulate a seeded FEL with high-gain harmonic generation.

  17. A High Power and High Repetition Rate Modelocked Ti-Sapphire Laser for Photoinjectors

    SciTech Connect

    J. Hansknecht; M. Poelker

    2001-07-01

    A high power cw mode-locked Ti-sapphire laser has been constructed to drive the Jefferson Lab polarized photoinjector and provide > 500 mW average power with 50 ps pulsewidths at 499 MHz or 1497 MHz pulse repetition rates. This laser allows efficient, high current synchronous photoinjection for extended periods of time before intrusive steps must be taken to restore the quantum efficiency of the strained layer GaAs photocathode. The use of this laser has greatly enhanced the maximum high polarization beam current capability and operating lifetime of the Jefferson Lab photoinjector compared with previous performance using diode laser systems. A novel modelocking technique provides a simple means to phase-lock the optical pulse train of the laser to the accelerator and allows for operation at higher pulse repetition rates to {approx} 3 GHz without modification of the laser cavity. The laser design and characteristics are described below.

  18. 503MHz repetition rate femtosecond Yb: fiber ring laser with an integrated WDM collimator.

    PubMed

    Wang, Aimin; Yang, Hongyu; Zhang, Zhigang

    2011-12-01

    We demonstrate 503MHz fundamental high repetition rate operation in a ring cavity passively mode-locked Yb:fiber laser incorporating a novel wavelength-division-multiplexing collimator and a piece of all-solid photonic bandgap fiber. The Yb doped fiber was directly fabricated as one fiber pigtail into the functional collimator, greatly shortening the cavity length and facilitating the splicing operation. A 5cm long photonic bandgap fiber with abnormal dispersion at the lasing wavelength (centered at 1030nm) decreases the net dispersion for shorter output pulses. The spectral bandwidth of the pulse was 34nm. The direct output pulse was measured to be 156fs and the dechirped pulse was about 76fs. With this innovative Yb:fiber pigtailed WDM collimator, the ring cavity laser has the potential to work at a repetition rate up to GHz. PMID:22273932

  19. Studies of a Linac Driver for a High Repetition Rate X-Ray FEL

    SciTech Connect

    Venturini, M.; Corlett, J.; Doolittle, L.; Filippetto, D.; Papadopoulos, C.; Penn, G.; Prosnitz, D.; Qiang, J.; Reinsch, M.; Ryne, R.; Sannibale, F.; Staples, J.; Wells, R.; Wurtele, J.; Zolotorev, M.; Zholents, A.

    2011-06-01

    We report on on-going studies of a superconducting CW linac driver intended to support a high repetition rate FEL operating in the soft x-rays spectrum. We present a pointdesign for a 1.8 GeV machine tuned for 300 pC bunches and delivering low-emittance, low-energy spread beams as needed for the SASE and seeded beamlines.

  20. Temporal dynamics of repetition suppression to individual faces presented at a fast periodic rate.

    PubMed

    Nemrodov, Dan; Jacques, Corentin; Rossion, Bruno

    2015-10-01

    Periodic presentation of visual stimuli leads to a robust electrophysiological response on the human scalp exactly at the periodic stimulation frequency, a response defined as a "steady-state visual evoked potential" (SSVEP, Regan, 1966). However, recent studies have shown that SSVEPs over the (right) occipito-temporal cortex are reduced when the same individual face is repeated at periodic rates of 3 to 9 Hz compared to when different faces are presented (Rossion, 2014). Here, we characterized the temporal dynamics of this repetition suppression effect. We presented different face identities at a rate of 5.88 Hz (stimulus onset asynchrony of 170 ms) for 15 s, followed by the repetition of the exact same face at this rate for 35 s. Compared to a stimulation sequence with different faces only, there was a large and specific decrease of the 5.88 Hz response when the same face was repeated at that rate. This effect was observed over the left and right occipito-temporal cortex, but not over medial occipital electrode sites where SSVEPs are typically measured. In the right hemisphere, this decrease occurred abruptly, i.e., within half a second following the introduction of the same-identity stimulation, with no further decrease until the end of the stimulation. These observations indicate that the SSVEP recorded over high-level visual areas to periodic stimulation is not steady but rather adapts immediately and fully following the repetition of the same individual face, supporting a bottom-up, stimulus-driven account of repetition suppression effects. PMID:26113059

  1. Dual-color three-dimensional STED microscopy with a single high-repetition-rate laser

    PubMed Central

    Han, Kyu Young; Ha, Taekjip

    2016-01-01

    We describe a dual-color three-dimensional stimulated emission depletion (3D-STED) microscopy employing a single laser source with a repetition rate of 80 MHz. Multiple excitation pulses synchronized with a STED pulse were generated by a photonic crystal fiber and the desired wavelengths were selected by an acousto-optic tunable filter with high spectral purity. Selective excitation at different wavelengths permits simultaneous imaging of two fluorescent markers at a nanoscale resolution in three dimensions. PMID:26030581

  2. Steady State Microbunching for High Brilliance and High Repetition Rate Storage Ring-Based Light Sources

    SciTech Connect

    Chao, Alex; Ratner, Daniel; Jiao, Yi; /Beijing, Inst. High Energy Phys.

    2012-09-06

    Electron-based light sources have proven to be effective sources of high brilliance, high frequency radiation. Such sources are typically either linac-Free Electron Laser (FEL) or storage ring types. The linac-FEL type has high brilliance (because the beam is microbunched) but low repetition rate. The storage ring type has high repetition rate (rapid beam circulation) but comparatively low brilliance or coherence. We propose to explore the feasibility of a microbunched beam in a storage ring that promises high repetition rate and high brilliance. The steady-state-micro-bunch (SSMB) beam in storage ring could provide CW sources for THz, EUV, or soft X-rays. Several SSMB mechanisms have been suggested recently, and in this report, we review a number of these SSMB concepts as promising directions for high brilliance, high repetition rate light sources of the future. The trick of SSMB lies in the RF system, together with the associated synchrotron beam dynamics, of the storage ring. Considering various different RF arrangements, there could be considered a number of scenarios of the SSMB. In this report, we arrange these scenarios more or less in order of the envisioned degree of technical challenge to the RF system, and not in the chronological order of their original references. Once the stored beam is steady-state microbunched in a storage ring, it passes through a radiator repeatedly every turn (or few turns). The radiator extracts a small fraction of the beam energy as coherent radiation with a wavelength corresponding to the microbunched period of the beam. In contrast to an FEL, this radiator is not needed to generate the microbunching (as required e.g. by SASE FELs or seeded FELs), so the radiator can be comparatively simple and short.

  3. High-repetition-rate high-power variable-bandwidth dye laser

    SciTech Connect

    Lavi, S.; Amit, M.; Bialolanker, G.; Miron, E.; Levin, L.A.

    1985-07-01

    An efficient high-repetition-rate dye laser is described which has a bandwidth that can be tailored to match typical atomic inhomogeneous linewidths. The dye laser is pumped by a 4-kHz 2--6 mJ/pulse copper vapor laser. The total efficiency of the dye laser (oscillator and amplifier) is 45% for rhodamine 6G and 30% for rhodamine B.

  4. The role of excitation parameters in high repetition-rate N2-TE lasers

    NASA Astrophysics Data System (ADS)

    Kukhlevsky, S. V.; Kozma, L.

    1993-09-01

    We have studied the effects of decreasing the excitation duration on the pulse-repetition-rate (PRR) capabilities of a low-pressure ( P<200 Torr) N2-TE laser. It was found that maximum PRR increases with decreasing duration of the discharge current. PRR as high as 1000 Hz has been obtained in the sealed-off non-flowing regime of laser operation. These findings are adequately explained by the time dependence of the arc-discharge formation.

  5. Effects of shifts in the rate of repetitive stimulation on sustained attention

    NASA Technical Reports Server (NTRS)

    Krulewitz, J. E.; Warm, J. S.; Wohl, T. H.

    1975-01-01

    The effects of shifts in the rate of presentation of repetitive neutral events (background event rate) were studied in a visual vigilance task. Four groups of subjects experienced either a high (21 events/min) or a low (6 events/min) event rate for 20 min and then experienced either the same or the alternate event rate for an additional 40 min. The temporal occurrence of critical target signals was identical for all groups, irrespective of event rate. The density of critical signals was 12 signals/20 min. By the end of the session, shifts in event rate were associated with changes in performance which resembled contrast effects found in other experimental situations in which shift paradigms were used. Relative to constant event rate control conditions, a shift from a low to a high event rate depressed the probability of signal detections, while a shift in the opposite direction enhanced the probability of signal detections.

  6. All-optical repetition rate multiplication of pseudorandom bit sequences by employing power coupler and equalizer

    NASA Astrophysics Data System (ADS)

    Sun, Zhenchao; Wang, Zhi; Wu, Chongqing; Wang, Fu; Li, Qiang

    2015-10-01

    A scheme for all-optical repetition rate multiplication of pseudorandom bit sequences (PRBS) is demonstrated with a precision delay feedback loop cascaded with a terahertz optical asymmetric demultiplexer (TOAD)-based power equalizer. Its feasibility has been verified by experiments, which show a multiplication for PRBS at cycle 2^7-1 from 2.5 to 10 Gb/s. This scheme can be employed for the rate multiplication of a much longer cycle PRBS at a much higher bit rate over 40 Gb/s if the time-delay, the loss, and the dispersion of an optical delay line are all precisely managed.

  7. High repetition rate laser-induced breakdown spectroscopy using acousto-optically gated detection

    NASA Astrophysics Data System (ADS)

    Pořízka, Pavel; Klessen, Benjamin; Kaiser, Jozef; Gornushkin, Igor; Panne, Ulrich; Riedel, Jens

    2014-07-01

    This contribution introduces a new type of setup for fast sample analysis using laser-induced breakdown spectroscopy (LIBS). The novel design combines a high repetition rate laser (up to 50 kHz) as excitation source and an acousto-optical modulator (AOM) as a fast switch for temporally gating the detection of the emitted light. The plasma radiation is led through the active medium of the AOM where it is diffracted on the transient ultrasonic Bragg grid. The diffracted radiation is detected by a compact Czerny-Turner spectrometer equipped with a CCD line detector. Utilizing the new combination of high repetition rate lasers and AOM gated detection, rapid measurements with total integration times of only 10 ms resulted in a limit of detection (LOD) of 0.13 wt.% for magnesium in aluminum alloys. This short integration time corresponds to 100 analyses/s. Temporal gating of LIP radiation results in improved LODs and consecutively higher sensitivity of the LIBS setup. Therefore, an AOM could be beneficially utilized to temporally detect plasmas induced by high repetition rate lasers. The AOM in combination with miniaturized Czerny-Turner spectrometers equipped with CCD line detectors and small footprint diode pumped solid state lasers results in temporally gateable compact LIBS setups.

  8. High repetition rate laser-induced breakdown spectroscopy using acousto-optically gated detection

    SciTech Connect

    Pořízka, Pavel; Kaiser, Jozef

    2014-07-15

    This contribution introduces a new type of setup for fast sample analysis using laser-induced breakdown spectroscopy (LIBS). The novel design combines a high repetition rate laser (up to 50 kHz) as excitation source and an acousto-optical modulator (AOM) as a fast switch for temporally gating the detection of the emitted light. The plasma radiation is led through the active medium of the AOM where it is diffracted on the transient ultrasonic Bragg grid. The diffracted radiation is detected by a compact Czerny-Turner spectrometer equipped with a CCD line detector. Utilizing the new combination of high repetition rate lasers and AOM gated detection, rapid measurements with total integration times of only 10 ms resulted in a limit of detection (LOD) of 0.13 wt.% for magnesium in aluminum alloys. This short integration time corresponds to 100 analyses/s. Temporal gating of LIP radiation results in improved LODs and consecutively higher sensitivity of the LIBS setup. Therefore, an AOM could be beneficially utilized to temporally detect plasmas induced by high repetition rate lasers. The AOM in combination with miniaturized Czerny-Turner spectrometers equipped with CCD line detectors and small footprint diode pumped solid state lasers results in temporally gateable compact LIBS setups.

  9. High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

    NASA Astrophysics Data System (ADS)

    Green, B.; Kovalev, S.; Asgekar, V.; Geloni, G.; Lehnert, U.; Golz, T.; Kuntzsch, M.; Bauer, C.; Hauser, J.; Voigtlaender, J.; Wustmann, B.; Koesterke, I.; Schwarz, M.; Freitag, M.; Arnold, A.; Teichert, J.; Justus, M.; Seidel, W.; Ilgner, C.; Awari, N.; Nicoletti, D.; Kaiser, S.; Laplace, Y.; Rajasekaran, S.; Zhang, L.; Winnerl, S.; Schneider, H.; Schay, G.; Lorincz, I.; Rauscher, A. A.; Radu, I.; Mährlein, S.; Kim, T. H.; Lee, J. S.; Kampfrath, T.; Wall, S.; Heberle, J.; Malnasi-Csizmadia, A.; Steiger, A.; Müller, A. S.; Helm, M.; Schramm, U.; Cowan, T.; Michel, P.; Cavalleri, A.; Fisher, A. S.; Stojanovic, N.; Gensch, M.

    2016-02-01

    Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.

  10. High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

    PubMed Central

    Green, B.; Kovalev, S.; Asgekar, V.; Geloni, G.; Lehnert, U.; Golz, T.; Kuntzsch, M.; Bauer, C.; Hauser, J.; Voigtlaender, J.; Wustmann, B.; Koesterke, I.; Schwarz, M.; Freitag, M.; Arnold, A.; Teichert, J.; Justus, M.; Seidel, W.; Ilgner, C.; Awari, N.; Nicoletti, D.; Kaiser, S.; Laplace, Y.; Rajasekaran, S.; Zhang, L.; Winnerl, S.; Schneider, H.; Schay, G.; Lorincz, I.; Rauscher, A. A.; Radu, I.; Mährlein, S.; Kim, T. H.; Lee, J. S.; Kampfrath, T.; Wall, S.; Heberle, J.; Malnasi-Csizmadia, A.; Steiger, A.; Müller, A. S.; Helm, M.; Schramm, U.; Cowan, T.; Michel, P.; Cavalleri, A.; Fisher, A. S.; Stojanovic, N.; Gensch, M.

    2016-01-01

    Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution. PMID:26924651

  11. High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter.

    PubMed

    Green, B; Kovalev, S; Asgekar, V; Geloni, G; Lehnert, U; Golz, T; Kuntzsch, M; Bauer, C; Hauser, J; Voigtlaender, J; Wustmann, B; Koesterke, I; Schwarz, M; Freitag, M; Arnold, A; Teichert, J; Justus, M; Seidel, W; Ilgner, C; Awari, N; Nicoletti, D; Kaiser, S; Laplace, Y; Rajasekaran, S; Zhang, L; Winnerl, S; Schneider, H; Schay, G; Lorincz, I; Rauscher, A A; Radu, I; Mährlein, S; Kim, T H; Lee, J S; Kampfrath, T; Wall, S; Heberle, J; Malnasi-Csizmadia, A; Steiger, A; Müller, A S; Helm, M; Schramm, U; Cowan, T; Michel, P; Cavalleri, A; Fisher, A S; Stojanovic, N; Gensch, M

    2016-01-01

    Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution. PMID:26924651

  12. High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

    DOE PAGESBeta

    Green, B.; Kovalev, S.; Asgekar, V.; Geloni, G.; Lehnert, U.; Golz, T.; Kuntzsch, M.; Bauer, C.; Hauser, J.; Voigtlaender, J.; et al

    2016-02-29

    Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields andmore » the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. In conclusion, we benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.« less

  13. Effects of repetition rate and impulsiveness of simulated helicopter rotor noise on annoyance

    NASA Technical Reports Server (NTRS)

    Powell, C. A.; Mccurdy, D. A.

    1982-01-01

    Annoyance judgements were obtained for computer generated stimuli simulative of helicopter impulsive rotor noise to investigate effects of repetition rate and impulsiveness. Each of the 82 different stimuli was judged at 3 sound pressure levels by 48 subjects. Impulse repetition rates covered a range from 10 Hz to 115 Hz; crest factors covered a range from 3.2 dB to 19.3 dB. Increases in annoyance with increases in repetition rate were found which were not predicted by common loudness or annoyance metrics and which were independent of noise level. The ability to predict effects of impulsiveness varied between the noise metrics and was found to be dependent on noise level. The ability to predict the effects of impulsiveness was not generally improved by any of several proposed impulsiveness corrections. Instead, the effects of impulsiveness were found to be systematically related to the frequency content of the stimuli. A modified frequency weighting was developed which offers improved annoyance prediction.

  14. Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve.

    PubMed

    Zourdos, Michael C; Klemp, Alex; Dolan, Chad; Quiles, Justin M; Schau, Kyle A; Jo, Edward; Helms, Eric; Esgro, Ben; Duncan, Scott; Garcia Merino, Sonia; Blanco, Rocky

    2016-01-01

    The primary aim of this study was to compare rating of perceived exertion (RPE) values measuring repetitions in reserve (RIR) at particular intensities of 1 repetition maximum (RM) in experienced (ES) and novice squatters (NS). Furthermore, this investigation compared average velocity between ES and NS at the same intensities. Twenty-nine individuals (24.0 ± 3.4 years) performed a 1RM squat followed by a single repetition with loads corresponding to 60, 75, and 90% of 1RM and an 8-repetition set at 70% 1RM. Average velocity was recorded at 60, 75, and 90% 1RM and on the first and last repetitions of the 8-repetition set. Subjects reported an RPE value that corresponded to an RIR value (RPE-10 = 0-RIR, RPE-9 = 1-RIR, and so forth). Subjects were assigned to one of the 2 groups: (a) ES (n = 15, training age: 5.2 ± 3.5 years) and (b) NS (n = 14, training age: 0.4 ± 0.6 years). The mean of the average velocities for ES was slower (p ≤ 0.05) than NS at 100% and 90% 1RM. However, there were no differences (p > 0.05) between groups at 60, 75%, or for the first and eighth repetitions at 70% 1RM. In addition, ES recorded greater RPE at 1RM than NS (p = 0.023). In ES, there was a strong inverse relationship between average velocity and RPE at all percentages (r = -0.88, p < 0.001), and a strong inverse correlation in NS between average velocity and RPE at all intensities (r = -0.77, p = 0.001). Our findings demonstrate an inverse relationship between average velocity and RPE/RIR. Experienced squatter group exhibited slower average velocity and higher RPE at 1RM than NS, signaling greater efficiency at high intensities. The RIR-based RPE scale is a practical method to regulate daily training load and provide feedback during a 1RM test. PMID:26049792

  15. Characteristics of a velvet cathode under high repetition rate pulse operation

    SciTech Connect

    Xun Tao; Zhang Jiande; Yang Hanwu; Zhang Zicheng; Fan Yuwei

    2009-10-15

    As commonly used material for cold cathodes, velvet works well in single shot and low repetition rate (rep-rate) high-power microwave (HPM) sources. In order to determine the feasibility of velvet cathodes under high rep-rate operation, a series of experiments are carried out on a high-power diode, driven by a {approx}300 kV, {approx}6 ns, {approx}100 {omega}, and 1-300 Hz rep-rate pulser, Torch 02. Characteristics of vacuum compatibility and cathode lifetime under different pulse rep-rate are focused on in this paper. Results of time-resolved pressure history, diode performance, shot-to-shot reproducibility, and velvet microstructure changes are presented. As the rep-rate increases, the equilibrium pressure grows hyperlinearly and the velvet lifetime decreases sharply. At 300 Hz, the pressure in the given diode exceeded 1 Pa, and the utility shots decreased to 2000 pulses for nonstop mode. While, until the velvet begins to degrade, the pulse-to-pulse instability of diode voltage and current is quite small, even under high rep-rate conditions. Possible reasons for the operation limits are discussed, and methods to improve the performance of a rep-rate velvet cathode are also suggested. These results may be of interest to the repetitive HPM systems with cold cathodes.

  16. Research of narrow pulse width, high repetition rate, high output power fiber lasers for deep space exploration

    NASA Astrophysics Data System (ADS)

    Tang, Yan-feng; Li, Hong-zuo; Wang, Yan; Hao, Zi-qiang; Xiao, Dong-Ya

    2013-08-01

    As human beings expand the research in unknown areas constantly, the deep space exploration has become a hot research topic all over the world. According to the long distance and large amount of information transmission characteristics of deep space exploration, the space laser communication is the preferred mode because it has the advantages of concentrated energy, good security, and large information capacity and interference immunity. In a variety of laser source, fibre-optical pulse laser has become an important communication source in deep space laser communication system because of its small size, light weight and large power. For fiber lasers, to solve the contradiction between the high repetition rate and the peak value power is an important scientific problem. General Q technology is difficult to obtain a shorter pulse widths, This paper presents a DFB semiconductor laser integrated with Electro-absorption modulator to realize the narrow pulse width, high repetition rate of the seed source, and then using a two-cascaded high gain fiber amplifier as amplification mean, to realize the fibre-optical pulse laser with pulse width 3ns, pulse frequency 200kHz and peak power 1kW. According to the space laser atmospheric transmission window, the wavelength selects for 1.06um. It is adopted that full fibre technology to make seed source and amplification, pumping source and amplification of free-space coupled into fiber-coupled way. It can overcome that fibre lasers are vulnerable to changes in external conditions such as vibration, temperature drift and other factors affect, improving long-term stability. The fiber lasers can be modulated by PPM mode, to realize high rate modulation, because of its peak power, high transmission rate, narrow pulse width, high frequency stability, all technical indexes meet the requirements of the exploration of deep space communication technology.

  17. Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser by sweeping the pulse repetition rate.

    PubMed

    Lee, Keunwoo; Lee, Joohyung; Jang, Yoon-Soo; Han, Seongheum; Jang, Heesuk; Kim, Young-Jin; Kim, Seung-Woo

    2015-01-01

    Femtosecond lasers allow for simultaneous detection of multiple absorption lines of a specimen over a broad spectral range of infrared or visible light with a single spectroscopic measurement. Here, we present an 8-THz bandwidth, 0.5-GHz resolution scheme of Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser. A resolving power of 1.6 × 10(4) about a 1560-nm center wavelength is achieved by sweeping the pulse repetition rate of the light source on a fiber Mach-Zehnder interferometer configured to capture interferograms with a 0.02-fs temporal sampling accuracy through a well-stabilized 60-m unbalance arm length. A dual-servo mechanism is realized by combining a mechanical linear stage with an electro-optic modulator (EOM) within the fiber laser cavity, enabling stable sweeping control of the pulse repetition rate over a 1.0-MHz scan range with 0.4-Hz steps with reference to the Rb clock. Experimental results demonstrate that the P-branch lines of the H(13)CN reference cell can be observed with a signal-to-noise ratio reaching 350 for the most intense line. PMID:26503257

  18. Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser by sweeping the pulse repetition rate

    NASA Astrophysics Data System (ADS)

    Lee, Keunwoo; Lee, Joohyung; Jang, Yoon-Soo; Han, Seongheum; Jang, Heesuk; Kim, Young-Jin; Kim, Seung-Woo

    2015-10-01

    Femtosecond lasers allow for simultaneous detection of multiple absorption lines of a specimen over a broad spectral range of infrared or visible light with a single spectroscopic measurement. Here, we present an 8-THz bandwidth, 0.5-GHz resolution scheme of Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser. A resolving power of 1.6 × 104 about a 1560-nm center wavelength is achieved by sweeping the pulse repetition rate of the light source on a fiber Mach-Zehnder interferometer configured to capture interferograms with a 0.02-fs temporal sampling accuracy through a well-stabilized 60-m unbalance arm length. A dual-servo mechanism is realized by combining a mechanical linear stage with an electro-optic modulator (EOM) within the fiber laser cavity, enabling stable sweeping control of the pulse repetition rate over a 1.0-MHz scan range with 0.4-Hz steps with reference to the Rb clock. Experimental results demonstrate that the P-branch lines of the H13CN reference cell can be observed with a signal-to-noise ratio reaching 350 for the most intense line.

  19. High-repetition-rate chirped-pulse-amplification thin-disk laser system with joule-level pulse energy.

    PubMed

    Tümmler, J; Jung, R; Stiel, H; Nickles, P V; Sandner, W

    2009-05-01

    We are reporting on the development of a diode-pumped chirped-pulse-amplification (CPA) laser system based on Yb:YAG thin-disk technology with a repetition rate of 100 Hz and output pulse energy in the joule range. The focus lies with the first results of the preamplifier--a regenerative amplifier (RA) and a multipass amplifier (MP). The system consists of a front end including the CPA stretcher followed by an amplifier chain based on Yb:YAG thin-disk amplifiers and the CPA compressor. It is developed in the frame of our x-ray laser (XRL) program and fulfills all requirements for pumping a plasma-based XRL in grazing incidence pumping geometry. Of course it can also be used for other interesting applications. With the RA pulse energies of more than 165 mJ can be realized. At a repetition rate of 100 Hz a stability of 0.8% (1sigma) over a period of more than 45 min has been measured. The optical-to-optical efficiency is 14%. The following MP amplifier can increase the pulse energy to more than 300 mJ. A nearly bandwidth-limited recompression to less than 2 ps could be demonstrated. PMID:19412278

  20. High-power, highly stable KrF laser with a 4-kHz pulse repetition rate

    NASA Astrophysics Data System (ADS)

    Borisov, V. M.; El'tsov, A. V.; Khristoforov, O. B.

    2015-08-01

    An electric-discharge KrF laser (248 nm) with an average output power of 300 W is developed and studied. A number of new design features are related to the use of a laser chamber based on an Al2O3 ceramic tube. A high power and pulse repetition rate are achieved by using a volume discharge with lateral preionisation by the UV radiation of a creeping discharge in the form of a homogeneous plasma sheet on the surface of a plane sapphire plate. Various generators for pumping the laser are studied. The maximum laser efficiency is 3.1%, the maximum laser energy is 160 mJ pulse-1, and the pulse duration at half maximum is 7.5 ns. In the case of long-term operation at a pulse repetition rate of 4 kHz and an output power of 300 W, high stability of laser output energy (σ <= 0.7%) is achieved using an all-solid-state pump system.

  1. Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser by sweeping the pulse repetition rate

    PubMed Central

    Lee, Keunwoo; Lee, Joohyung; Jang, Yoon-Soo; Han, Seongheum; Jang, Heesuk; Kim, Young-Jin; Kim, Seung-Woo

    2015-01-01

    Femtosecond lasers allow for simultaneous detection of multiple absorption lines of a specimen over a broad spectral range of infrared or visible light with a single spectroscopic measurement. Here, we present an 8-THz bandwidth, 0.5-GHz resolution scheme of Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser. A resolving power of 1.6 × 104 about a 1560-nm center wavelength is achieved by sweeping the pulse repetition rate of the light source on a fiber Mach-Zehnder interferometer configured to capture interferograms with a 0.02-fs temporal sampling accuracy through a well-stabilized 60-m unbalance arm length. A dual-servo mechanism is realized by combining a mechanical linear stage with an electro-optic modulator (EOM) within the fiber laser cavity, enabling stable sweeping control of the pulse repetition rate over a 1.0-MHz scan range with 0.4-Hz steps with reference to the Rb clock. Experimental results demonstrate that the P-branch lines of the H13CN reference cell can be observed with a signal-to-noise ratio reaching 350 for the most intense line. PMID:26503257

  2. Optimization of graffiti removal on natural stone by means of high repetition rate UV laser

    NASA Astrophysics Data System (ADS)

    Fiorucci, M. P.; López, A. J.; Ramil, A.; Pozo, S.; Rivas, T.

    2013-08-01

    The use of laser for graffiti removal is a promising alternative to conventional cleaning methods, though irradiation parameters must be carefully selected in order to achieve the effective cleaning without damaging the substrate, especially when referring to natural stone. From a practical point of view, once a safe working window is selected, it is necessary to determine the irradiation conditions to remove large paint areas, with minimal time consumption. The aim of this paper is to present a systematic procedure to select the optimum parameters for graffiti removal by means of the 3rd harmonic of a high repetition rate nanosecond Nd:YVO4 laser. Ablation thresholds of four spray paint colors were determined and the effect of pulse repetition frequency, beam diameter and line scan separation was analyzed, obtaining a set of values which optimize the ablation process.

  3. Front end for high-repetition rate thin disk-pumped OPCPA beamline at ELI-beamlines

    NASA Astrophysics Data System (ADS)

    Green, Jonathan T.; Novák, Jakub; Antipenkov, Roman; Batysta, František; Zervos, Charalampos; Naylon, Jack A.; Mazanec, TomáÅ.¡; Horáček, Martin; Bakule, Pavel; Rus, Bedřich

    2015-02-01

    The ELI-Beamlines facility, currently under construction in Prague, Czech Republic, will house multiple high power laser systems with varying pulse energies, pulse durations, and repetition rates. Here we present the status of a high repetition rate beamline currently under construction with target parameters of 20 fs pulse duration, 100 mJ pulse energy, and 1 kHz repetition rate. Specifically we present the Yb:YAG thin disk lasers which are intended to pump picosecond OPCPA, synchronization between pump and signal pulses in the OPCPA, and the first stages of OPCPA.

  4. Solid-state YVO4/Nd:YVO4/KTP green laser system for the generation of subnanosecond pulses with adjustable kilohertz repetition rate.

    PubMed

    Zhang, Haijuan; Zhao, Shengzhi; Yang, Kejian; Li, Guiqiu; Li, Dechun; Zhao, Jia; Wang, Yonggang

    2013-09-20

    A solid-state green laser generating subnanosecond pulses with adjustable kilohertz repetition rate is presented. This pulse laser system is composed of a Q-switched and mode-locked YVO(4)/Nd:YVO(4)/KTP laser simultaneously modulated by an electro-optic (EO) modulator and a central semiconductor saturable absorption mirror. Because the repetition rate of the Q-switched envelope in this laser depends on the modulation frequency of the EO modulator, so long as the pulsewidth of the Q-switched envelope is shorter than the cavity roundtrip transmit time, i.e., the time interval of two neighboring mode-locking pulses, only one mode-locking pulse exists underneath a Q-switched envelope, resulting in the generation of subnanosecond pulses with kilohertz repetition rate. The experimental results show that the pulsewidth of subnanosecond pulses decreases with increasing pump power and the shortest pulse generated at 1 kHz was 450 ps with pulse energy as high as 252 μJ, corresponding to a peak power of 560 kW. In addition, this laser was confirmed to have high stability, and the pulse repetition rate could be freely adjusted from 1 to 4 kHz. PMID:24085177

  5. Ultrashort pulse high repetition rate laser system for biological tissue processing

    DOEpatents

    Neev, J.; Da Silva, L.B.; Matthews, D.L.; Glinsky, M.E.; Stuart, B.C.; Perry, M.D.; Feit, M.D.; Rubenchik, A.M.

    1998-02-24

    A method and apparatus are disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment. 8 figs.

  6. Ultrashort pulse high repetition rate laser system for biological tissue processing

    DOEpatents

    Neev, Joseph; Da Silva, Luiz B.; Matthews, Dennis L.; Glinsky, Michael E.; Stuart, Brent C.; Perry, Michael D.; Feit, Michael D.; Rubenchik, Alexander M.

    1998-01-01

    A method and apparatus is disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment.

  7. 100 Hz repetition rate, high average power, plasma-based soft x-ray lasers

    NASA Astrophysics Data System (ADS)

    Reagan, Brendan; Wernsing, Keith; Baumgarten, Cory; Berrill, Mark; Durivage, Leon; Furch, Federico; Curtis, Alden; Luther, Bradley; Patel, Dinesh; Menoni, Carmen; Shlyaptsev, Vyacheslav; Rocca, Jorge

    2013-10-01

    Numerous applications demand high average power / high repetition rate compact sources of coherent soft x-ray radiation. We report the demonstration table-top soft x-ray lasers at wavelengths ranging from 10.9 nm to 18.9 nm from plasmas created at 100 Hz repetition rate. Results includes a record average power of 0.15 mW at λ = 18.9 nm from a laser-produced Mo plasma and 0.1 mW average power at λ = 13.9 nm from a Ag plasma. These soft x-ray lasers are driven by collisional electron impact excitation in elongated line focus plasmas a few mm in length heated by a compact, directly diode-pumped, chirped pulse amplification Yb:YAG laser that produces 1 J pulses of ps duration at 100 Hz repetition rate. Pulses from this laser irradiate the surface of polished metal targets producing transient population inversions on the 4d1S0 --> 4p1P1 transition of Ni-like ions. Tailoring of the temporal profile of the driver laser pulse is observed to significantly increase soft x-ray laser output power as well as allow the generation of shorter wavelength lasers with reduced pump energy. Work was supported by the NSF ERC for Extreme Ultraviolet Science and Technology using equipment developed under NSF Award MRI-ARRA 09-561, and by the AMOS program of the Office of Basic Energy Sciences, US Department of Energy.

  8. All-optical repetition rate multiplication of pseudorandom bit sequences based on cascaded TOADs

    NASA Astrophysics Data System (ADS)

    Sun, Zhenchao; Wang, Zhi; Wu, Chongqing; Wang, Fu; Li, Qiang

    2016-03-01

    A scheme for all-optical repetition rate multiplication of pseudorandom bit sequences (PRBS) is demonstrated with all-optical wavelength conversion and optical logic gate 'OR' based on cascaded Tera-Hertz Optical Asymmetric Demultiplexers (TOADs). Its feasibility is verified by multiplication experiments from 500 Mb/s to 4 Gb/s for 23-1 PRBS and from 1 Gb/s to 4 Gb/s for 27-1 PRBS. This scheme can be employed for rate multiplication for much longer cycle PRBS at much higher bit rate over 40 Gb/s when the time-delay, the loss and the dispersion of the optical delay line are all precisely managed. The upper limit of bit rate will be restricted by the recovery time of semiconductor optical amplifier (SOA) finally.

  9. Plasmon-enhanced photocathode for high brightness and high repetition rate x-ray sources.

    PubMed

    Polyakov, A; Senft, C; Thompson, K F; Feng, J; Cabrini, S; Schuck, P J; Padmore, H A; Peppernick, S J; Hess, W P

    2013-02-15

    In this Letter, we report on the efficient generation of electrons from metals using multiphoton photoemission by use of nanostructured plasmonic surfaces to trap, localize, and enhance optical fields. The plasmonic surface increases absorption over normal metals by more than an order of magnitude, and due to the localization of fields, this results in over 6 orders of magnitude increase in effective nonlinear quantum yield. We demonstrate that the achieved quantum yield is high enough for use in rf photoinjectors operating as electron sources for MHz repetition rate x-ray free electron lasers. PMID:25166390

  10. High repetition rate optical switch using an electroabsorption modulator in TOAD configuration

    NASA Astrophysics Data System (ADS)

    Huo, Li; Yang, Yanfu; Lou, Caiyun; Gao, Yizhi

    2007-07-01

    A novel optical switch featured with high repetition rate, short switching window width, and high contrast ratio is proposed and demonstrated for the first time by placing an electroabsorption modulator (EAM) in a terahertz optical asymmetric demultiplexer (TOAD) configuration. The feasibility and main characteristics of the switch are investigated by numerical simulations and experiments. With this EAM-based TOAD, an error-free return-to-zero signal wavelength conversion with 0.62 dB power penalty at 20 Gbit/s is demonstrated.

  11. Optimal repetition rates of excitation pulses in a Tm-vapour laser

    NASA Astrophysics Data System (ADS)

    Gerasimov, V. A.; Gerasimov, V. V.; Pavlinskii, A. V.

    2011-01-01

    The optimal excitation pulse repetition rates (PRRs) for a gas-discharge Tm-vapour laser with indirect population of upper laser levels are determined. It is shown that, under the same excitation conditions, the optimal PRRs increase with a decrease in the energy defect between the upper laser acceptor level and the nearest resonant donor level. The reasons for the limitation of the optimal PRRs in Tm-vapour laser are discussed. It is shown that the maximum average power of Tm-vapour laser radiation may exceed several times the Cu-vapour laser power under the same excitation conditions and in identical gas-discharge tubes.

  12. High repetition rate Q-switched radially polarized laser with a graphene-based output coupler

    NASA Astrophysics Data System (ADS)

    Li, Lifei; Zheng, Xinliang; Jin, Chenjie; Qi, Mei; Chen, Xiaoming; Ren, Zhaoyu; Bai, Jintao; Sun, Zhipei

    2014-12-01

    We demonstrate a Q-switched radially polarized all-solid-state laser by transferring a graphene film directly onto an output coupler. The laser generates Q-switched radially polarized beam (QRPB) with a pulse width of 192 ns and 2.7 W average output power. The corresponding single pulse energy is up to 16.2 μJ with a high repetition rate of 167 kHz. The M2 factor and the polarization purity are ˜2.1 and 96%, respectively. Our QRPB source is a simple and low-cost source for a variety of applications, such as industrial material processing, optical trapping, and microscopy.

  13. High-repetition-rate Cr:Nd:GSGG active-mirror amplifier.

    PubMed

    Kelly, J H; Smith, D L; Lee, J C; Jacobs, S D; Smith, D J; Lambropoulos, J C; Shoup Iii, M J

    1987-12-01

    We have designed, constructed, and operated a 3.8-cm clear-aperture Cr:Nd:GSGG active-mirror amplifier. We believe this to be the first active mirror that uses a crystalline host and the largest-aperture Cr:Nd:GSGG amplifier yet reported. We have measured a small-signal gain of 1.6. The wave front has been measured and found to be less than three waves of defocus at repetition rates of up to 10 Hz. Surface displacements were measured and compared with theory. Depolarization was less than 2.5% at maximum power at any location in the clear aperture. PMID:19741940

  14. Power scaling of supercontinuum seeded megahertz-repetition rate optical parametric chirped pulse amplifiers.

    PubMed

    Riedel, R; Stephanides, A; Prandolini, M J; Gronloh, B; Jungbluth, B; Mans, T; Tavella, F

    2014-03-15

    Optical parametric chirped-pulse amplifiers with high average power are possible with novel high-power Yb:YAG amplifiers with kW-level output powers. We demonstrate a compact wavelength-tunable sub-30-fs amplifier with 11.4 W average power with 20.7% pump-to-signal conversion efficiency. For parametric amplification, a beta-barium borate crystal is pumped by a 140 W, 1 ps Yb:YAG InnoSlab amplifier at 3.25 MHz repetition rate. The broadband seed is generated via supercontinuum generation in a YAG crystal. PMID:24690803

  15. Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training

    PubMed Central

    Cronin, John; Storey, Adam; Zourdos, Michael C.

    2016-01-01

    ABSTRACT RATINGS OF PERCEIVED EXERTION ARE A VALID METHOD OF ESTIMATING THE INTENSITY OF A RESISTANCE TRAINING EXERCISE OR SESSION. SCORES ARE GIVEN AFTER COMPLETION OF AN EXERCISE OR TRAINING SESSION FOR THE PURPOSES OF ATHLETE MONITORING. HOWEVER, A NEWLY DEVELOPED SCALE BASED ON HOW MANY REPETITIONS ARE REMAINING AT THE COMPLETION OF A SET MAY BE A MORE PRECISE TOOL. THIS APPROACH ADJUSTS LOADS AUTOMATICALLY TO MATCH ATHLETE CAPABILITIES ON A SET-TO-SET BASIS AND MAY MORE ACCURATELY GAUGE INTENSITY AT NEAR-LIMIT LOADS. THIS ARTICLE OUTLINES HOW TO INCORPORATE THIS NOVEL SCALE INTO A TRAINING PLAN. PMID:27531969

  16. 85.7 MHz repetition rate mode-locked semiconductor disk laser: fundamental and soliton bound states.

    PubMed

    Butkus, M; Viktorov, E A; Erneux, T; Hamilton, C J; Maker, G; Malcolm, G P A; Rafailov, E U

    2013-10-21

    Mode-locked optically pumped semiconductor disk lasers (SDLs) are in strong demand for applications in bio-medical photonics, chemistry, space communications and non-linear optics. However, the wider spread of SDLs was constrained as they are operated in high repetition rates above 200 MHz due to short carrier lifetimes in the semiconductors. Here we demonstrate experimentally and theoretically that it is possible to overcome the limitation of fast carrier relaxation and show significant reduction of repetition rate down to 85.7 MHz by exploiting phase-amplitude coupling effect. In addition, a low repetition rate SDL serves as a test-bed for bound soliton state previously unknown for semiconductor devices. The breakthrough to sub-100 MHz repetition rate will open a whole new window of development opportunities. PMID:24150392

  17. High-repetition-rate plate-electrode CO{sub 2} laser

    SciTech Connect

    Andramanov, Aleksandr V; Voevodin, Denis D; Vysotskii, Andrei V; Kabaev, Sergei A; Lazhintsev, Boris V; Nor-Arevyan, Vladimir A; Pisetskaya, Anastasiya V; Selemir, Victor D

    2009-12-31

    A high-repetition-rate CO{sub 2} laser with the inductive-capacitive discharge stabilisation is studied for the first time. A multisection discharge gap of length 250 mm was formed by pairs of anode - cathode plates arranged in the form of a broken line. The width of the discharge region between each pair of the plates was {approx} 1.3 mm and height {approx} 12 mm. The cross section of the laser beam on the output mirror of the resonator was {approx} 6 x 8 mm. The maximum output energy of the laser using the CO{sub 2}:N{sub 2}:He=32:32:96 Torr mixture was 15.9 mJ, the lasing efficiency being 1.7%. For a relatively low gas flow rate of 19 m s{sup -1}, a CO{sub 2} laser pulse repetition rate of 3 kHz was achieved, the relative root-mean-square deviation of the pulse energy being within 5%. The average output power of the laser was {approx} 40 W. (lasers)

  18. High Repetition Rate Pulsed 2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Uprendra N.; Bai, Yingxin; Yu, Jirong; Petros, Mulugeta; Petzar, Paul J.; Trieu, Bo C.; Lee, Hyung

    2009-01-01

    A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed at NASA Langley Research Center. Such a laser transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of approximately 50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. The measured standard deviation of the laser frequency jitter is about 3 MHz.

  19. BEAM DYNAMICS STUDIES OF A HIGH-REPETITION RATE LINAC-DRIVER FOR A 4TH GENERATION LIGHT SOURCE

    SciTech Connect

    Ventturini, M.; Corlett, J.; Emma, P.; Papadopoulos, C.; Penn, G.; Placidi, M.; Qiang, J.; Reinsch, M.; Sannibale, F.; Steier, C.; Sun, C.; Wells, R.

    2012-05-18

    We present recent progress toward the design of a super-conducting linac driver for a high-repetition rate FEL-based soft x-ray light source. The machine is designed to accept beams generated by the APEX photo-cathode gun operating with MHz-range repetition rate and deliver them to an array of SASE and seeded FEL beamlines. We review the current baseline design and report results of beam dynamics studies.

  20. Experimental study on GaP surface damage threshold induced by a high repetition rate femtosecond laser

    SciTech Connect

    Li Yi; Liu Feng; Li Yanfeng; Chai Lu; Xing Qirong; Hu Minglie; Wang Chingyue

    2011-05-01

    The surface damage threshold of undoped bulk <110> GaP induced by a high repetition rate femtosecond pulse at 1040 nm with a duration of 61 fs was studied. The threshold value was obtained by a linear fit of the incident single pulse fluence and was confirmed with a breakdown test around the threshold level. The result will be useful in high intensity, high repetition rate laser applications and ultrafast processes.

  1. The effects of laser repetition rate on femtosecond laser ablation of dry bone: a thermal and LIBS study.

    PubMed

    Gill, Ruby K; Smith, Zachary J; Lee, Changwon; Wachsmann-Hogiu, Sebastian

    2016-01-01

    The aim of this study is to understand the effect of varying laser repetition rate on thermal energy accumulation and dissipation as well as femtosecond Laser Induced Breakdown Spectroscopy (fsLIBS) signals, which may help create the framework for clinical translation of femtosecond lasers for surgical procedures. We study the effect of repetition rates on ablation widths, sample temperature, and LIBS signal of bone. SEM images were acquired to quantify the morphology of the ablated volume and fsLIBS was performed to characterize changes in signal intensity and background. We also report for the first time experimentally measured temperature distributions of bone irradiated with femtosecond lasers at repetition rates below and above carbonization conditions. While high repetition rates would allow for faster cutting, heat accumulation exceeds heat dissipation and results in carbonization of the sample. At repetition rates where carbonization occurs, the sample temperature increases to a level that is well above the threshold for irreversible cellular damage. These results highlight the importance of the need for careful selection of the repetition rate for a femtosecond laser surgery procedure to minimize the extent of thermal damage to surrounding tissues and prevent misclassification of tissue by fsLIBS analysis. PMID:26260774

  2. Long-pulse high-repetition-rate transversely excited CO2 laser for material processing

    NASA Astrophysics Data System (ADS)

    Okita, Yuji; Yasuoka, Koichi; Ishii, Akira; Tamagawa, Tohru

    1994-05-01

    Using a TE-CO2 laser, we could obtain a long-pulsed laser beam of low initial spike by controlling the discharge current by a pulse forming network and optimizing the gas composition, discharge length to resonator length ratio, and output mirror reflectivity. The maximum laser output was 1.1 J; the initial spike energy, 100 kW; the tail output, 56 kW; and the 16 (mu) sec (FWHM). The maximum repetition rate was 500 Hz. A new type of circuit with small pre-ionization current made it possible to operate the laser at a high repetition rate so as to prolong the laser life. When a 5-inch lens was used, the laser power density at the focal point was 1*108 W/cm2, making it possible to use the laser with an unusually high energy density without causing the breakdown of air insulation. In fact, we succeeded in fine- cutting a 0.5 mm thick alumina ceramic with the laser. It was found that unlike other working methods, the newly developed laser does not cause cracks in ceramic work pieces.

  3. A high repetition rate laser-heavy water based neutron source

    NASA Astrophysics Data System (ADS)

    Hah, Jungmoo; He, Zhaohan; Nees, John; Krushelnick, Karl; Thomas, Alexander; CenterUltrafast Optical Science Team

    2015-11-01

    Neutrons have numerous applications in diverse areas, such as medicine, security, and material science. For example, sources of MeV neutrons may be used for active interrogation for nuclear security applications. Recently, alternative ways to generate neutron flux have been studied. Among them, ultrashort laser pulse interactions with dense plasma have attracted significant attention as compact, pulse sources of neutrons. To generate neutrons using a laser through fusion reactions, thin solid density targets have been used in a pitcher-catcher arrangement, using deuterated plastic for example. However, the use of solid targets is limited for high-repetition rate operation due to the need to refresh the target for every laser shot. Here, we use a free flowing heavy water target with a high repetition rate (500 Hz) laser without a catcher. From the interaction between a 10 micron scale diameter heavy water stream with the Lambda-cubed laser system at the Univ. of Michigan (12mJ, 800nm, 35fs), deuterons collide with each other resulting in D-D fusion reactions generating 2.45 MeV neutrons. Under best conditions a time average of ~ 105 n/s of neutrons are generated.

  4. An optical parametric chirped-pulse amplifier for seeding high repetition rate free-electron lasers

    DOE PAGESBeta

    Höppner, H.; Hage, A.; Tanikawa, T.; Schulz, M.; Riedel, R.; Teubner, U.; Prandolini, M. J.; Faatz, B.; Tavella, F.

    2015-05-15

    High repetition rate free-electron lasers (FEL), producing highly intense extreme ultraviolet and x-ray pulses, require new high power tunable femtosecond lasers for FEL seeding and FEL pump-probe experiments. A tunable, 112 W (burst mode) optical parametric chirped-pulse amplifier (OPCPA) is demonstrated with center frequencies ranging from 720–900 nm, pulse energies up to 1.12 mJ and a pulse duration of 30 fs at a repetition rate of 100 kHz. Since the power scalability of this OPCPA is limited by the OPCPA-pump amplifier, we also demonstrate a 6.7–13.7 kW (burst mode) thin-disk OPCPA-pump amplifier, increasing the possible OPCPA output power to manymore » hundreds of watts. Furthermore, third and fourth harmonic generation experiments are performed and the results are used to simulate a seeded FEL with high-gain harmonic generation.« less

  5. Ultrafast XUV Pulses at High Repetition Rate for Time Resolved Photoelectron Spectroscopy of Surface Dynamics

    NASA Astrophysics Data System (ADS)

    Corder, Christopher; Zhao, Peng; Li, Xinlong; Muraca, Amanda R.; Kershis, Matthew D.; White, Michael G.; Allison, Thomas K.

    2016-05-01

    Ultrafast photoelectron studies of surface dynamics are often limited by low repetition rates. At Stony Brook we have built a cavity-enhanced high-harmonic generation XUV source that delivers ultrafast pulses to a surface science apparatus for photoelectron spectroscopy. We begin with a Ytterbium fiber laser at a repetition rate of 78 MHz and up to 90 W of average power. After compression the pulses have μJ's of energy with < 180 fs pulse width. We then use an enhancement cavity with a finesse of a few hundred to build up to the peak intensity required for high harmonic generation. The enhancement cavity is a six mirror double folded bow-tie geometry with a focus of 15 μm at a Krypton gas jet, followed by a Sapphire crystal at Brewster's angle for the fundamental to allow outcoupling of the harmonics. A single harmonic is selected using a time-preserving monochromator to maintain the short pulses, and is sent to an ultra high vacuum chamber with sample preparation and diagnostic tools as well as an electron energy spectrometer. This allows us to study the electronic dynamics of semiconductor surfaces and their interfaces with adsorbed molecules which enable various charge transfer effects. Supported by AFOSR.

  6. EUV emission of Xe-clusters excited by a high-repetition rate burst mode laser

    NASA Astrophysics Data System (ADS)

    Stiel, Holger; Vogt, Ulrich; Ter-Avetisyan, Sargis; Schnurer, Matthias; Will, Ingo; Nickles, Peter V.

    2002-10-01

    In this contribution we describe a laser plasma source for Extreme Ultraviolet Lithography (EUVL) based on a Xe-cluster target. Although Xe-clusters as target systems for EUVL are known for some time, no attempts have been made for a systematic study of the influence of the laser parameters on the EUV-emission at a well defined Xe-aggregation. The MBI burst mode laser used offers some unique features: Within one burst (duration 800 μs) the repetition rate of single laser pulses can be adjusted between 30 and 1000 kHz. The average power per burst is about 5 kW at the maximum energy of 4 J/burst. The pulse duration of a single pulse can be adjusted from the ps- to ns-range. We have examined the EUV-emission from the Xe-cluster target within one burst of the laser as a function of single pulse intensity and repetition rate. Based on the measured EUV-spectra the conversion efficiency at 13.4 nm wavelength in dependence on pulse duration in the range from 30 ps to 3 ns were estimated.

  7. Coherent dual-comb interferometry with quasi-integer-ratio repetition rates.

    PubMed

    Hébert, Nicolas Bourbeau; Boudreau, Sylvain; Genest, Jérôme; Deschênes, Jean-Daniel

    2014-11-17

    We demonstrate a generalized method for dual-comb interferometry that involves the use of two frequency combs with quasi-integer-ratio repetition rates. We use a 16.67 MHz comb to probe an 80-cm-long ring cavity and a 100 MHz comb to asynchronously sample its impulse response. The resulting signal can be seen as six time-multiplexed independent interferograms. We perform a deconvolution of the photodetector's impulse response to prevent any crosstalk between these multiplexed data sets. The measurement is then demultiplexed and corrected with referencing signals. We obtain a measurement with a spectral point spacing of 16.67 MHz and a spectral SNR of 55 dB by averaging 15,000 interferograms, corresponding to a measurement time of 500 s. Compared to conventional dual-comb spectroscopy, this generalized technique allows to either reduce the spectral point spacing or the acquisition time by changing the repetition rate of only one of the combs. PMID:25402154

  8. Diagnostic for a high-repetition rate electron photo-gun and first measurements

    NASA Astrophysics Data System (ADS)

    Filippetto, D.; Doolittle, L.; Huang, G.; Norum, E.; Portmann, G.; Qian, H.; Sannibale, F.

    2015-05-01

    The APEX electron source at LBNL combines the high-repetition-rate with the high beam brightness typical of photoguns, delivering low emittance electron pulses at MHz frequency. Proving the high beam quality of the beam is an essential step for the success of the experiment, opening the doors of the high average power to brightness-hungry applications as X-Ray FELs, MHz ultrafast electron diffraction etc.. As first step, a complete characterization of the beam parameters is foreseen at the Gun beam energy of 750 keV. Diagnostics for low and high current measurements have been installed and tested, and measurements of cathode lifetime and thermal emittance in a RF environment with mA current performed. The recent installation of a double slit system, a deflecting cavity and a high precision spectrometer, allow the exploration of the full 6D phase space. Here we discuss the present layout of the machine and future upgrades, showing the latest results at low and high repetition rate, together with the tools and techniques used.

  9. Comparison of high repetition rate Q-switched 355nm ultraviolet lasers with EOM and AOM

    NASA Astrophysics Data System (ADS)

    Lu, Tingting; Li, Xiaolei; Zang, Huaguo; Zhu, Xiaolei

    2013-05-01

    Two kinds of Q-switched ultraviolet lasers using an acousto-optic modulator and an electro-optic modulator in the same cavity structure are demonstrated, with type I phase-matched LBO as second harmonic generation crystal and type II phase-matched LBO as third harmonic generation crystal. For acousto-optic Q-switched UV laser-a maximum average power of 6.3W with the shortest pulse width of 12 ns was obtained at the repetition rate of 22 kHz when the pump power reached 52.4 W. The optical conversion efficiency was up to 12%. Then we used a La3Ga5SiO14 crystal electro-optic modulator to replace the acousto-optic modulator. The 1.29W output power at 355nm wavelength was obtained at the repetition rate of 10 kHz when the pump power was increased to 20.4W, and the UV laser pulse width was as short as 9.6ns.The optical conversion efficiency was up to 6.3%.

  10. Compact Pulsed X-Ray Generator Operated At High Repetitive Rates

    NASA Astrophysics Data System (ADS)

    Isobe, Hiroshi; Sato, Eiichi; Kimura, Shingo; Tamakawa, Yoshiharu; Yanagisawa, Toru

    1990-01-01

    A repetitive pulsed x-ray generator achieved with a compact diode utilizing a new type of cathode for biomedical radiography is described. This generator consisted of the following components: a high-voltage power supply, two ceramic condensers of about 850pF, a repetitive impulse switching system, a turbo molecular pump, and an x-ray tube. Since the high-voltage pulser employed a modified Marx circuit, this pulser produced twice the potential of the condenser charging voltage. The x-ray tube was of the demountable-diode type which was connected to the turbo molecular pump and consisted of the following components: a rod-shaped anode tip made of tungsten, a plane cathode made of aluminum and carbon, and a vacuum vessel made of glass with a diameter of 50mm. Two condensers were charged from 30 to 100kV, and the output of this pulser ranged from 50 to 180kV. The x-ray pulse widths primarily increased according to increases in the anode-cathode (A-C space) and their values ranged from 20 to 100ns. The repetitive rate was determined by the condenser capacity, the charging voltage, and the current capacity of the power supply, and its maximum value was about 100Hz. The time integrated x-ray intensities were less than 4.0pC/kg at 0.5m per pulse when the discharge capacity of about 430pF (Marx Circuit) was employed. The effective focal spot size was determined by the diameter of anode tip and its value ranged from 0.5 to 3.0mm in diameter.

  11. Stability Reliability of the Behavior Rating Profile.

    ERIC Educational Resources Information Center

    Ellers, Robert A.; And Others

    1989-01-01

    Examined test-retest stability of Behavior Rating Profile for students grades l-12 (N=198), parents (N=212), and teachers (N=176) on 3 norm-referenced scales. Found Teacher Rating scale reliable across all grades for screening and eligibility, Parent Rating scale reliable for Grade 3-12 screening and Grade 3-6,ll, and l2, eligibility. Found…

  12. A frequency-locked and frequency-doubled, hybrid Q-switched Yb:KYW laser at 515 nm with a widely adjustable repetition rate

    NASA Astrophysics Data System (ADS)

    Tjörnhammar, S.; Zukauskas, A.; Canalias, C.; Pasiskevicius, V.; Laurell, F.

    2015-09-01

    We demonstrate a compact wavelength-stabilized, frequency-doubled Yb-doped double-tungstate laser with widely tunable repetition rate, spanning from 35 Hz to 3 kHz obtained by hybrid Q-switching. The Q-switching unit consisted of a combination of a passive Cr:YAG crystal and an opto-mechanical active intensity modulator. The fundamental wavelength was locked at 1029 nm with a volume Bragg grating, and the pulse length and energy were 42 ns and 250 µJ, respectively. As the laser was stabilized with the VBG and the opto-mechanical modulator, the frequency instability was reduced six times from free running down to 0.29 %. Frequency doubling was done extra-cavity in PPKTP, and a repetition rate-independent conversion efficiency of 63 % was obtained. The controllable repetition rate together with stable temporal and spatial characteristics makes this laser a suitable candidate in many biology-related experiments, as a pump source for in vivo excitation of fluorophores, e.g., pumping of "living lasers" and matrix-assisted laser desorption/ionization mass spectroscopy.

  13. Coupling effects of the number of pulses, pulse repetition rate and fluence during laser PMMA ablation

    NASA Astrophysics Data System (ADS)

    Liu, Z. Q.; Feng, Y.; Yi, X.-S.

    2000-10-01

    Poly(methyl methacrylate) (PMMA) was ablated using a 248-nm long-pulsed KrF excimer laser operating at a pulse repetition rate (PRR) of 2 and 10 Hz, and fluence varying from 0.4 to 2 J/cm 2. The coupling effects of multiple shots, PRR, and fluence are found and discussed on the etching depth data and topography of PMMA. An increase in either PRR, or fluence or the number of pulses can accelerate the etching efficiency in terms of ablation rate, as a result of strengthened thermal effects. Quality of the craters such as roughness, porosity and contamination is sensitively dependent on the specific laser operating conditions. Basically, increasing the PRR and the number of pulses gives rise to a crater with smoother and less porous bottom.

  14. High-repetition-rate single-frequency electro-optic Q-switched Nd:YAG laser with feedback controlled prelase

    NASA Astrophysics Data System (ADS)

    Dai, Shutao; Shi, Fei; Huang, Jianhong; Deng, Jing; Zheng, Hui; Liu, Huagang; Wu, Hongchun; Weng, Wen; Ge, Yan; Li, Jinhui; Lin, Wenxiong

    2015-10-01

    A stable high-repetition-rate, high pulse energy and single-frequency electro-optic Q-switched laser has been developed and demonstrated in this paper. The prelase technique has been used in this single-frequency laser. And a PID feedback control electronics is applied to stabilize the prelase. Meanwhile, a two-plate resonant reflector take the place of traditional dielectric output coupler mirror to enhance the single-axial-mode selection. And a Cr:YAG saturable absorber is also inserted in the cavity to improve single-axial-mode selection. Output laser power over 2 W with 10 ns pulse duration has been obtained at a repetition rate of 1 kHz. And the single-axial-mode probability was 100% in one hour without any manual adjustments. The experimental results show that the prelase technique is reliable to attain single-frequency operation.

  15. Autonomic Nervous System Reactivity During Speech Repetition Tasks: Heart Rate Variability and Skin Conductance.

    PubMed

    Mackersie, Carol L; Calderon-Moultrie, Natalie

    2016-01-01

    Cognitive and emotional challenges may elicit a physiological stress response that can include arousal of the sympathetic nervous system (fight or flight response) and withdrawal of the parasympathetic nervous system (responsible for recovery and rest). This article reviews studies that have used measures of electrodermal activity (skin conductance) and heart rate variability (HRV) to index sympathetic and parasympathetic activity during auditory tasks. In addition, the authors present results from a new study with normal-hearing listeners examining the effects of speaking rate on changes in skin conductance and high-frequency HRV (HF-HRV). Sentence repetition accuracy for normal and fast speaking rates was measured in noise using signal to noise ratios that were adjusted to approximate 80% accuracy (+3 dB fast rate; 0 dB normal rate) while monitoring skin conductance and HF-HRV activity. A significant increase in skin conductance level (reflecting sympathetic nervous system arousal) and a decrease in HF-HRV (reflecting parasympathetic nervous system withdrawal) were observed with an increase in speaking rate indicating sensitivity of both measures to increased task demand. Changes in psychophysiological reactivity with increased auditory task demand may reflect differences in listening effort, but other person-related factors such as motivation and stress may also play a role. Further research is needed to understand how psychophysiological activity during listening tasks is influenced by the acoustic characteristics of stimuli, task demands, and by the characteristics and emotional responses of the individual. PMID:27355761

  16. Producing ultrashort Terahertz to UV photons at high repetition rates for research into materials

    SciTech Connect

    G. R. Neil; C. Behre; S. V. Benson; G. Biallas; J. Boyce; L.A. Dillon-Townes; D. Douglas; H. F. Dylla; R. Evans; A. Grippo; D. Gruber; J. Gubeli; C. Hernandez-Garcia; K. Jordan; M. J. Kelley; L. Merminga; J. Mammosser; N. Nishimori; J. Preble; R. Rimmer; Michelle D. Shinn; T. Siggins; R. Walker; G. P. Williams; and S. Zhang

    2005-11-01

    A new THz/IR/UV photon source at Jefferson Lab is the first of a new generation of light sources based on a Energy-Recovered, (superconducting) Linac (ERL). The machine has a 160 MeV electron beam and an average current of 10 mA in 75 MHz repetition rate hundred femtosecond bunches. These electron bunches pass through a magnetic chicane and therefore emit synchrotron radiation. For wavelengths longer than the electron bunch the electrons radiate coherently a broadband THz {approx} half cycle pulse whose average brightness is > 5 orders of magnitude higher than synchrotron IR sources. Previous measurements showed 20 W of average power extracted[1]. The new facility offers simultaneous synchrotron light from the visible through the FIR along with broadband THz production of 100 fs pulses with >200 W of average power (see G. P. Williams, this conference). The FELs also provide record-breaking laser power [2]: up to 10 kW of average power in the IR from 1 to 14 microns in 400 fs pulses at up to 74.85 MHz repetition rates and soon will produce similar pulses of 300-1000 nm light at up to 3 kW of average power from the UV FEL. These ultrashort pulses are ideal for maximizing the interaction with material surfaces. The optical beams are Gaussian with nearly perfect beam quality. See www.jlab.org/FEL for details of the operating characteristics; a wide variety of pulse train configurations are feasible from 10 microseconds long at high repetition rates to continuous operation. The THz and IR system has been commissioned. The UV system is to follow in 2005. The light is transported to user laboratories for basic and applied research. Additional lasers synchronized to the FEL are also available. Past activities have included production of carbon nanotubes, studies of vibrational relaxation of interstitial hydrogen in silicon, pulsed laser vapor deposition, nitriding of metals, and energy flow in proteins. This paper will present the status of the system and discuss some of

  17. Design of laser beam expander in underwater high-repetition-rate range-gated imaging system

    NASA Astrophysics Data System (ADS)

    Zhong, Wei; Zhang, Xiaohui

    2015-10-01

    Active underwater imaging systems, using an artificial light source for underwater target illumination, have preferable practical value in military and civil domain. Back-scattering of water impacts imaging system performance by reducing image contrast, and this is especially bad when the light source is close to the camera. Range-gated technique can effectively rejecting the back-scattering of water and improve the range of underwater target detection, while it can only collect image at certain distance for every laser impulse. High-repetition-rate green laser is a better light source in underwater range-gated imaging system. It has smaller pulse energy, while it can improve the imaging result. In order to illuminate the proper area underwater according to the different distance between the laser source and targets, there must be a magnifying-ratio variable beam expander to adjust the divergent angle of the laser. Challenges associated with magnifying-ratio computation and designing of beam expander are difficult to overcome due to the obvious refraction and forward-scattering of water. An efficiency computing method is presented to obtain the magnifying-ratio of beam expander. The illuminating area of laser beam can be computed according to the refraction index and beam spread function (BSF) which has already considered forward-scattering process. The magnifying-ratio range of beam expander should be 0.925~3.09 in order to obtain about φ1m illuminating area when the distance between laser and target is 10~40m. A magnifying-ratio variable beam expander is designed according to computation. Underwater experiments show that this beam expander plays an effective role on illuminating in underwater high-repetition-rate range-rated Imaging system.

  18. High power fiber amplifier with adjustable repetition rate for use in all-fiber supercontinuum light sources

    NASA Astrophysics Data System (ADS)

    Baselt, T.; Taudt, Ch.; Hartmann, P.

    2014-03-01

    In recent years the use of supercontinuum light sources has encouraged the development of various optical measurement techniques, like microscopy and optical coherence-tomography. Some disadvantages of common supercontinuum solutions, in particular the rather poor stability and the absence of modulation abilities limit the application potential of this technique. We present a directly controllable all-fiber laser source with appropriate parameters in order to generate a broad supercontinuum spectrum with the aid of microstructured fibers. Through the application of a laser seed-diode, which is driven by a custom built controller to generate nanosecond pulses with repetition rates in the MHz range in a reproducible manner, a direct control of the laser system is enabled. The seedsignal is amplified to the appropriate power level in a 2-step amplification stage. Wide supercontinuum is finally generated by launching the amplified laser pulses into different microstructured fibers. The system has been optimized in terms of stability, power-output, spectral width and beam-quality by employing different laser pulse parameters and several different microstructured fibers. Finally, the system as a whole has been characterized in reference to common solid state-laser-based supercontinuum light sources

  19. Variable Thickness Liquid Crystal Films for High Repetition Rate Laser Applications

    NASA Astrophysics Data System (ADS)

    Poole, Patrick; Willis, Christopher; Cochran, Ginevra; Hanna, Randall; Andereck, C. David; Schumacher, Douglass

    2015-05-01

    The presentation of a clean target or target substrate at high repetition rates is of importance to a number of photoelectron spectroscopy and free electron laser applications, often in high vacuum environments. Additionally, high intensity laser facilities are approaching the 10 Hz shot rate at petawatt powers, but are currently unable to insert targets at these rates. We have developed liquid crystal films to address this need for high rep rate targets while preserving the planar geometry advantageous to many applications. The molecular ordering of liquid crystal is variable with temperature and can be manipulated to form a layered thin film. In this way temperature and volume control can be used to vary film thickness in vacuo and on-demand between 10 nm and over 10 μm. These techniques were previously applied to a single-shot ion acceleration experiment in, where target thickness critically determines the physics of the acceleration. Here we present an automatic film formation device that utilizes a linear sliding rail to form liquid crystal films within the aforementioned range at rates up to 0.1 Hz. The design ensures film formation location within 2 μm RMS, well within the Rayleigh range of even short f-number systems. Details of liquid crystal films and this target formation device will be shown as well as recent experimental data from the Scarlet laser facility at OSU. This work was supported by DARPA through a grant from AMRDEC.

  20. Repetition rate operation of an improved magnetically insulated transmission line oscillator

    SciTech Connect

    Fan Yuwei; Zhong Huihuang; Li Zhiqiang; Shu Ting; Yang Hanwu; Zhou Heng; Yuan Chengwei; Zhou Weihong; Luo Ling

    2008-08-15

    In order to investigate the performances of repetition rate (rep-rate) operation of an improved magnetically insulated transmission line oscillator (MILO), a series of experiments are carried out on the improved MILO device, which is driven by a 40 {omega}, 50 ns rep-rate pulser, TORCH-01. Polymer velvet and graphite cathodes are tested, respectively, in the experiments, whose diameters and lengths are the same. The results of experimental comparison between them are presented in the paper. Both cathodes are tested at electric field strengths of about 300 kV/cm. The applied voltage has 60 ns duration with a rise time of 10 ns. This paper focuses on the performance of the voltage and current characteristics, the shot-to-shot reproducibility, the pressure evolution of the diode, and the lifetime of the cathodes, not upon the radiated microwave power. The experimental results show that the graphite cathode is superior to the velvet cathode in the lifetime and the shot-to-shot reproducibility during the rep-rate operation, and it is a promising cathode for the MILO device under the rep-rate conditions.

  1. Pump-seed synchronization for MHz repetition rate, high-power optical parametric chirped pulse amplification.

    PubMed

    Fattahi, Hanieh; Teisset, Catherine Yuriko; Pronin, Oleg; Sugita, Atsushi; Graf, Roswitha; Pervak, Vladimir; Gu, Xun; Metzger, Thomas; Major, Zsuzsanna; Krausz, Ferenc; Apolonski, Alexander

    2012-04-23

    We report on an active synchronization between two independent mode-locked lasers using a combined electronic-optical feedback. With this scheme, seed pulses at MHz repetition rate were amplified in a non-collinear optical parametric chirped pulse amplifier (OPCPA). The amplifier was seeded with stretched 1.5 nJ pulses from a femtosecond Ti:Sapphire oscillator, while pumped with the 1 ps, 2.9 µJ frequency-doubled output of an Yb:YAG thin-disk oscillator. The residual timing jitter between the two oscillators was suppressed to 120 fs (RMS), allowing for an efficient and broadband amplification at 11.5 MHz to a pulse energy of 700 nJ and an average power of 8 W. First compression experiment with 240 nJ amplified pulse energy resulted in a pulse duration of ~10 fs. PMID:22535076

  2. Picosecond supercontinuum light source for stroboscopic white-light interferometry with freely adjustable pulse repetition rate.

    PubMed

    Novotny, Steffen; Durairaj, Vasuki; Shavrin, Igor; Lipiäinen, Lauri; Kokkonen, Kimmo; Kaivola, Matti; Ludvigsen, Hanne

    2014-06-01

    We present a picosecond supercontinuum light source designed for stroboscopic white-light interferometry. This source offers a potential for high-resolution characterization of vibrational fields in electromechanical components with frequencies up to the GHz range. The light source concept combines a gain-switched laser diode, the output of which is amplified in a two-stage fiber amplifier, with supercontinuum generation in a microstructured optical fiber. Implemented in our white-light interferometer setup, optical pulses with optimized spectral properties and below 310 ps duration are used for stroboscopic illumination at freely adjustable repetition rates. The performance of the source is demonstrated by characterizing the surface vibration field of a square-plate silicon MEMS resonator at 3.37 MHz. A minimum detectable vibration amplitude of less than 100 pm is reached. PMID:24921556

  3. Role of the optical pulse repetition rate in the efficiency of terahertz emitters

    NASA Astrophysics Data System (ADS)

    Reklaitis, Antanas

    2016-07-01

    Excitation of n-GaAs and p-InAs terahertz emitters by the series of optical pulses is studied by ensemble Monte Carlo simulations. It is found that the spatial separation of photoexcited electrons and holes dramatically reduces the recombination intensity in n-GaAs emitter, the operation of which is based on the surface field effect. The spatial separation of carriers does not affect the recombination intensity in p-InAs emitter, the operation of which is based on the photo-Dember effect. Therefore, the recovery time of equilibrium state after optical pulse in n-GaAs emitter significantly exceeds the corresponding recovery time in p-InAs emitter. This fact leads to a substantial reduction of photocurrent amplitude in n-GaAs emitter excited by the optical pulse series at high repetition rate.

  4. Luminescence of black silicon fabricated by high-repetition rate femtosecond laser pulses

    SciTech Connect

    Chen Tao; Si Jinhai; Hou Xun; Kanehira, Shingo; Miura, Kiyotaka; Hirao, Kazuyuki

    2011-10-01

    We studied the photoluminescence (PL) from black silicon that was fabricated using an 800 nm, 250 kHz femtosecond laser in air. By changing the scan velocity and the fluence of the femtosecond laser, the formation of the PL band between the orange (600 nm) and red bands (near 680 nm) could be controlled. The red band PL from the photoinduced microstructures on the black silicon was observed even without annealing due to the thermal accumulation of high-repetition rate femtosecond laser pulses. The orange band PL was easily quenched under 532 nm cw laser irradiation, whereas the red band PL was more stable; this can be attributed to ''defect luminescence'' and ''quantum confinement'', respectively.

  5. Generation of Electron Bunches at Low Repetition Rates Using a Beat-Frequency Technique

    SciTech Connect

    Poelker, Matt; Grames, Joseph; Hansknecht, John; Kazimi, Reza; Musson, John

    2007-05-01

    Even at a continuous wave facility such as CEBAF at Jefferson Lab, an electron beam with long time intervals (tens of ns) between individual bunches can be useful, for example to isolate sources of background via time of flight detection or to measure the energy of neutral particles that cannot be separated with a magnetic field. This paper describes a demonstrated method to quickly and easily deliver bunches with repetition rates of 20 to 100 MHz corresponding to time intervals between 10 to 50 ns (respectively). This is accomplished by changing the ON/OFF frequency of the RF-pulsed drive laser by a small amount (f/f < 20%), resulting in a bunch frequency equal to the beat frequency between the radio frequencies of the drive laser and the photoinjector chopper system.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  7. Femtosecond-induced micostructures in Magnesium- doped Lithium Niobate crystals with high repetition rate

    NASA Astrophysics Data System (ADS)

    Kan, Hongli; Zhang, Shuanggen; Zhai, Kaili; Ma, Xiurong; Luo, Yiming; Hu, Minglie; Wang, Qingyue

    2016-02-01

    In this paper, heat accumulation effect of MgO: LN crystal irradiated by femtosecond pulses was analyzed by a developed thermal conduction model in terms of the spatial and temporal distribution of the absorbed laser energy. Using the focused femtosecond pulses about 61 fs at 1040 nm with a repetition rate of 52 MHz, ablation morphologies under different exposure time and average power were obtained experimentally. The measured laser-induced damage threshold of X-, Y- and Z-cut MgO: LN crystals are 0.82 mJ/cm2, 0.74 mJ/cm2 and 0.76 mJ/cm2, respectively, and based on the measurement achieved in the Lab the differences in the ablation morphologies were analyzed in detail.

  8. Femtosecond pump/supercontinuum-probe setup with 20 kHz repetition rate.

    PubMed

    Auböck, Gerald; Consani, Cristina; Monni, Roberto; Cannizzo, Andrea; van Mourik, Frank; Chergui, Majed

    2012-09-01

    We developed a fast multichannel detection system for pump-probe spectroscopy, capable of detecting single shot super-continuum spectra at the repetition rate (10-50 kHz) of an amplified femtosecond laser system. By tandem pumping the amplifier with three pump lasers we obtain very low noise operation, with less than 0.1% rms intensity fluctuations at the output of the amplifier. We also propose an alternative way of chopping the pump beam. With a synchronized scanning mirror two spots in the sample are illuminated by the train of pump pulses in an alternating fashion, such that when both spots are interrogated by the probe pulse, the duty cycle of the experiment is doubled. PMID:23020360

  9. Thyratron characteristics under high di/dt and high-repetition-rate operation

    SciTech Connect

    Ball, D.; Hill, J.; Kan, T.

    1981-05-11

    Power conditioning systems for high peak and average power, high repetition rate discharge excited lasers involve operation of modulator components in unconventional regimes. Reliable operation of switches and energy storage elements under high voltage and high di/dt conditions is a pacing item for laser development at the present time. To test and evaluate these components a Modulator Component Test Facility (MCTF) was constructed. The MCTF consists of a command charge system, energy storage capacitors, thyratron switch with inverse thyratron protection, and a resistive load. The modulator has initially been operated at voltages up to 60 kV at 600 Hz. Voltage, current, and calorimetric diagnostics are provided for major modulator components. Measurements of thyratron characteristics under high di/dt operation are presented. Commutation energy loss and di/dt have been measured as functions of the tube hydrogen pressure.

  10. High-power, high-repetition-rate femtosecond pulses tunable in the visible.

    PubMed

    Ellingson, R J; Tang, C L

    1993-03-15

    We demonstrate a Ti:sapphire-pumped intracavity-doubled optical parametric oscillator (OPO) that generates a total of up to 240 mW of sub-100-fs pulses tunable in the visible. The OPO consists of a 1.5-mm-thick KTiPO(4) (KTP) crystal configured in a ring cavity that is synchronously pumped by a self-mode-locked Ti:sapphire laser operating at an 81-MHz repetition rate and 2.1-W average power, producing 115-fs pulses at lambda = 790 nm. Intracavity doubling of the OPO is accomplished by inserting a 47-microm-thick beta-BaB(2)O(4) crystal into an additional focus in the OPO cavity. We demonstrate continuous tuning of the second-harmonic output from 580 to 657 nm. The potential tuning range of this intracavity-doubled KTP OPO is approximately 500 to 800 nm. PMID:19802161

  11. Saturated 13.2 nm high-repetition-rate laser in nickellike cadmium

    NASA Astrophysics Data System (ADS)

    Rocca, J. J.; Wang, Y.; Larotonda, M. A.; Luther, B. M.; Berrill, M.; Alessi, D.

    2005-10-01

    We report gain-saturated operation of a 13.2 nm tabletop laser in Ni-like Cd at a 5 Hz repetition rate. A gain-length product G×L=17.6 was obtained by heating a precreated plasma with 8 ps duration Ti:sapphire laser pulses with an energy of only 1 J impinging at a grazing angle of 23°. With an average power of ˜1 µW, this laser is an attractive coherent source for at-wavelength metrology of extreme UV lithography optics and other applications. [Note: Due to a production error in the print version abstract, the value "1 µW" is incorrectly stated as "1 mW." This value is stated correctly in the online PDF.

  12. New results on spin determination of nanosatellite BLITS from High Repetition Rate SLR data

    NASA Astrophysics Data System (ADS)

    Kucharski, D.; Kirchner, G.; Lim, H.-C.; Koidl, F.

    2013-03-01

    The nanosatellite BLITS (Ball Lens In The Space) demonstrates a successful design of the new spherical lens type satellite for Satellite Laser Ranging (SLR). The spin parameters of the satellite were calculated from more than 1000 days of SLR data collected from 6 High Repetition Rate (HRR) systems: Beijing, Changchun, Graz, Herstmonceux, Potsdam, Shanghai.Analysis of the 892 passes (September 26, 2009-June 18, 2012) shows precession of the spin axis around orientation of the along track vector calculated at the launch epoch of the satellite RA = 9h16m39s, Dec = 43.1°. The spin period of BLITS remains stable with the mean value Tmean = 5.613 s, RMS = 11 ms. The incident angle between the spin axis and the symmetry axis of the body changes within 60° range.

  13. High-power high-repetition-rate copper-vapor-pumped dye laser

    SciTech Connect

    Singh, S.; Dasgupta, K.; Kumar, S.; Manohar, K.G.; Nair, L.G.; Chatterjee, U.K. . Laser and Plasma Technology Div.)

    1994-06-01

    The design and development of an efficient high average power dye laser oscillator-amplifier system developed at the Laser and Plasma Technology Division, Bhabha Atomic Research Centre, is reported. The dye laser is pumped by a 6.5-kHz repetition rate copper vapor laser. The signal beam to the dye amplifier is obtained from an efficient narrow-band grazing incidence grating (GIG) dye laser oscillator incorporating a multiple prism beam expander. Amplifier extraction efficiency up to 40% was obtained in a single amplifier stage, using rhodamine 6G (Rh6G) in ethanol. The authors have also demonstrated simultaneous amplification of two laser beams at different wavelengths in the same dye amplifier cell.

  14. High repetition rate frequency-doubled Nd:YAG laser for airborne bathymetry

    NASA Astrophysics Data System (ADS)

    Northam, D. B.; Guerra, M. A.; Mack, M. E.; Itzkan, I.; Deradourian, C.

    1981-03-01

    A flashlamp pumped frequency-doubled Nd:YAG laser producing 7-nsec 2.8-mJ pulses at 530 nm and 400 pps has been developed for use in airborne bathymetry. A flashlamp gas mixture of krypton and xenon provides efficient laser operation and rapid lamp recovery. Pulse transmission mode operation is used to achieve a narrow pulse width. Thermally induced lensing and birefringence in the rod are compensated for in the optical resonator. Rapid, high repetition rate Pockels cell switching is accomplished with a thyratron driver. A CD(asterisk)A crystal cut for 85 deg phase matching at 55 C is used to provide high conversion efficiency second harmonic generation.

  15. Design Studies for a High-Repetition-Rate FEL Facility at LBNL.

    SciTech Connect

    CORLETT, J.; BELKACEM, A.; BYRD, J. M.; FAWLEY, W.; KIRZ, J.; LIDIA, S.; MCCURDY, W.; PADMORE, H.; PENN, G.; POGORELOV, I.; QIANG, J.; ROBIN, D.; SANNIBALE, F.; SCHOENLEIN, R.; STAPLES, J.; STEIER, C.; VENTURINI, M.; WAN, W.; WILCOX, R.; ZHOLENTS, A.

    2007-10-04

    Lawrence Berkeley National Laboratory (LBNL) is working to address the needs of the primary scientific Grand Challenges now being considered by the U.S. Department of Energy, Office of Basic Energy Sciences: we are exploring scientific discovery opportunities, and new areas of science, to be unlocked with the use of advanced photon sources. A partnership of several divisions at LBNL is working to define the science and instruments needed in the future. To meet these needs, we propose a seeded, high-repetition-rate, free-electron laser (FEL) facility. Temporally and spatially coherent photon pulses, of controlled duration ranging from picosecond to sub-femtosecond, are within reach in the vacuum ultraviolet (VUV) to soft X-ray regime, and LBNL is developing critical accelerator physics and technologies toward this goal. We envision a facility with an array of FELs, each independently configurable and tunable, providing a range of photon-beam properties with high average and peak flux and brightness.

  16. High repetition rate Q-switched radially polarized laser with a graphene-based output coupler

    SciTech Connect

    Li, Lifei; Jin, Chenjie; Qi, Mei; Chen, Xiaoming; Ren, Zhaoyu E-mail: rzy@nwu.edu.cn; Zheng, Xinliang E-mail: rzy@nwu.edu.cn; Bai, Jintao; Sun, Zhipei

    2014-12-01

    We demonstrate a Q-switched radially polarized all-solid-state laser by transferring a graphene film directly onto an output coupler. The laser generates Q-switched radially polarized beam (QRPB) with a pulse width of 192 ns and 2.7 W average output power. The corresponding single pulse energy is up to 16.2 μJ with a high repetition rate of 167 kHz. The M{sup 2} factor and the polarization purity are ∼2.1 and 96%, respectively. Our QRPB source is a simple and low-cost source for a variety of applications, such as industrial material processing, optical trapping, and microscopy.

  17. Detector response to high repetition rate ultra-short laser pulses. I

    NASA Astrophysics Data System (ADS)

    Zakharova, I. K.; Rafailov, Michael K.

    2015-05-01

    Optical nonlinearities in semiconductors and semiconductor detectors have been widely investigated and exploited for many scientific and industrial applications. The correlation of optical and electronic characteristics in these detector materials under exposure of ultra-short laser pulses at high pulse repetition rates is still not very well known. These effects may be quite beneficial for many applications ranging from chemical and biological sensing to light-induced superconductivity. In this paper, we discuss the effect of extended bleaching in order to demonstrate sensing applications of such phenomenon as an example. Pump-probe measurements in bulk semiconductors will be presented to quantify the transient absorption dynamics and relate this to the electronic response of the detector devices. This effect is not limited semiconductors and may affect other matter states and electronic structures, like dielectrics.

  18. A high repetition rate passively Q-switched microchip laser for controllable transverse laser modes

    NASA Astrophysics Data System (ADS)

    Dong, Jun; Bai, Sheng-Chuang; Liu, Sheng-Hui; Ueda, Ken-Ichi; Kaminskii, Alexander A.

    2016-05-01

    A Cr4+:YAG passively Q-switched Nd:YVO4 microchip laser for versatile controllable transverse laser modes has been demonstrated by adjusting the position of the Nd:YVO4 crystal along the tilted pump beam direction. The pump beam diameter-dependent asymmetric saturated inversion population inside the Nd:YVO4 crystal governs the oscillation of various Laguerre-Gaussian, Ince-Gaussian and Hermite-Gaussian modes. Controllable transverse laser modes with repetition rates over 25 kHz and up to 183 kHz, depending on the position of the Nd:YVO4 crystal, have been achieved. The controllable transverse laser beams with a nanosecond pulse width and peak power over hundreds of watts have been obtained for potential applications in optical trapping and quantum computation.

  19. Laser system generating 250-mJ bunches of 5-GHz repetition rate, 12-ps pulses.

    PubMed

    Agnesi, Antonio; Braggio, Caterina; Carrà, Luca; Pirzio, Federico; Lodo, Stefano; Messineo, Giuseppe; Scarpa, Daniele; Tomaselli, Alessandra; Reali, Giancarlo; Vacchi, Carla

    2008-09-29

    We report on a high-energy solid-state laser based on a master-oscillator power-amplifier system seeded by a 5-GHz repetition-rate mode-locked oscillator, aimed at the excitation of the dynamic Casimir effect by optically modulating a microwave resonator. Solid-state amplifiers provide up to 250 mJ at 1064 nm in a 500-ns (macro-)pulse envelope containing 12-ps (micro-)pulses, with a macro/micropulse format and energy resembling that of near-infrared free-electron lasers. Efficient second-harmonic conversion allowed synchronous pumping of an optical parametric oscillator, obtaining up to 40 mJ in the range 750-850 nm. PMID:18825218

  20. Repetition rate switching in a passively mode-locked fibre laser

    NASA Astrophysics Data System (ADS)

    Tian, X. L.; Tang, M.; Gong, Y. D.; Shum, P.

    2006-09-01

    Here we demonstrated a dispersion stretched passively mode-locked fiber laser. The laser was mode-locked by nonlinear polarization rotation (NPR) technical. Both dispersion managed soliton and noise-like pulses were observed in the experiment. Harmonic mode-locked noise-like pulses were observed. By changing the pump power or rotating the waveplates, noise-like pulse could split and always form equally spaced pulse train, thus the repetition rate of the output pulse could be switched among different orders of harmonic frequency. The experiment results were analyzed. We found that peak power clamping caused by NPR module led to pulse splitting, the pulse interaction through the Raman light drives the pulse to space equally.

  1. Modeling and optimization of single-pass laser amplifiers for high-repetition-rate laser pulses

    SciTech Connect

    Ozawa, Akira; Udem, Thomas; Zeitner, Uwe D.; Haensch, Theodor W.; Hommelhoff, Peter

    2010-09-15

    We propose a model for a continuously pumped single-pass amplifier for continuous and pulsed laser beams. The model takes into account Gaussian shape and focusing geometry of pump and seed beam. As the full-wave simulation is complex we have developed a largely simplified numerical method that can be applied to rotationally symmetric geometries. With the tapered-shell model we treat (focused) propagation and amplification of an initially Gaussian beam in a gain crystal. The implementation can be done with a few lines of code that are given in this paper. With this code, a numerical parameter optimization is straightforward and example results are shown. We compare the results of our simple model with those of a full-wave simulation and show that they agree well. A comparison of model and experimental data also shows good agreement. We investigate in detail different regimes of amplification, namely the unsaturated, the fully saturated, and the intermediate regime. Because the amplification process is affected by spatially varying saturation and exhibits a nonlinear response against pump and seed power, no analytical expression for the expected output is available. For modeling of the amplification we employ a four-level system and show that if the fluorescence lifetime of the gain medium is larger than the inverse repetition rate of the seed beam, continuous-wave amplification can be employed to describe the amplification process of ultrashort pulse trains. We limit ourselves to this regime, which implies that if titanium:sapphire is chosen as gain medium the laser repetition rate has to be larger than a few megahertz. We show detailed simulation results for titanium:sapphire for a large parameter set.

  2. 200 ps FWHM and 100 MHz repetition rate ultrafast gated camera for optical medical functional imaging

    NASA Astrophysics Data System (ADS)

    Uhring, Wilfried; Poulet, Patrick; Hanselmann, Walter; Glazenborg, René; Zint, Virginie; Nouizi, Farouk; Dubois, Benoit; Hirschi, Werner

    2012-04-01

    The paper describes the realization of a complete optical imaging device to clinical applications like brain functional imaging by time-resolved, spectroscopic diffuse optical tomography. The entire instrument is assembled in a unique setup that includes a light source, an ultrafast time-gated intensified camera and all the electronic control units. The light source is composed of four near infrared laser diodes driven by a nanosecond electrical pulse generator working in a sequential mode at a repetition rate of 100 MHz. The resulting light pulses, at four wavelengths, are less than 80 ps FWHM. They are injected in a four-furcated optical fiber ended with a frontal light distributor to obtain a uniform illumination spot directed towards the head of the patient. Photons back-scattered by the subject are detected by the intensified CCD camera; there are resolved according to their time of flight inside the head. The very core of the intensified camera system is the image intensifier tube and its associated electrical pulse generator. The ultrafast generator produces 50 V pulses, at a repetition rate of 100 MHz and a width corresponding to the 200 ps requested gate. The photocathode and the Micro-Channel-Plate of the intensifier have been specially designed to enhance the electromagnetic wave propagation and reduce the power loss and heat that are prejudicial to the quality of the image. The whole instrumentation system is controlled by an FPGA based module. The timing of the light pulses and the photocathode gating is precisely adjustable with a step of 9 ps. All the acquisition parameters are configurable via software through an USB plug and the image data are transferred to a PC via an Ethernet link. The compactness of the device makes it a perfect device for bedside clinical applications.

  3. High repetition rate sealed CO2 TEA lasers using heterogeneous catalysts

    NASA Technical Reports Server (NTRS)

    Price, H. T.; Shaw, S. R.

    1987-01-01

    The significant operational advantages offered by CO2 lasers, operating in the 10.6 micron region of the spectrum, over current solid state lasers, emitting in the near IR region, have prompted increased interest in the development of compact, reliable, rugged CO2 laser sources. Perhaps the most critical aspect associated with achieving a laser compatible with military use is the development of lasers which require no gas replenishment. Sealed, single shot, CO2 TEA lasers have been available for a number of years. Stark et al were first to demonstrate reliable sealed operation in single shot CO2 TEA lasers in 1975 using gas catalysis. GEC Avionics reported the compact, environmentally qualified, MKIII CO2 TEA laser with a pulse life of greater than 10 to the 6th power pulses in 1980. A sealed laser lifetime of greater than 10 to the 6th power pulses is acceptable for single shot cases, such as direct detection rangefinders for tank laser sights. However, in many other applications, such as tracking of fast moving targets, it is essential that a repetition rate of typically 30Hz to 100Hz is employed. In such cases, a pulse lifetime of 10 to the 6th power pulses is no longer sufficient and a minimum pulse lifetime 10 to the 7th power pulses is essential to ensure a useful service life. In 1983 Stark el al described a sealed, 100Hz CO2 TEA laser, with a life of greater than 2.6 x 10 to the 6th power, which employed heterogeneous catalysis. Following this pioneering work, GEC Avionics has been engaged in the development of sealed high repetition rate lasers with a pulse lifetime of 20 million pulses.

  4. Continuous multigram nanoparticle synthesis by high-power, high-repetition-rate ultrafast laser ablation in liquids.

    PubMed

    Streubel, René; Barcikowski, Stephan; Gökce, Bilal

    2016-04-01

    Utilizing a novel laser system consisting of a 500 W, 10 MHz, 3 ps laser source which is fully synchronized with a polygon scanner reaching scanning speeds up to 500 m/s, we explore the possibilities to increase the productivity of nanoparticle synthesis by laser ablation in liquids. By exploiting the high scanning speed, laser-induced cavitation bubbles are spatially bypassed at high repetition rates and continuous multigram ablation rates up to 4 g/h are demonstrated for platinum, gold, silver, aluminum, copper, and titanium. Furthermore, the applicable, ablation-effective repetition rate is increased by two orders of magnitude. The ultrafast ablation mechanisms are investigated for different laser fluences, repetition rates, interpulse distances, and ablation times, while the resulting trends are successfully described by validating a model developed for ultrafast laser ablation in air to hold in liquids as well. PMID:27192268

  5. NOx diesel exhaust treatment using a pulsed corona discharge: the pulse repetition rate effect

    NASA Astrophysics Data System (ADS)

    Yankelevich, Y.; Wolf, M.; Baksht, R.; Pokryvailo, A.; Vinogradov, J.; Rivin, B.; Sher, E.

    2007-05-01

    The pulsed corona offers real promise for degradation of pollutants in gas and water streams. This paper presents a study of NOx removal from diesel exhaust. Special emphasis is laid on the investigation of the dependence of the NO removal rate and efficiency on the pulse repetition rate (PRR). A nanosecond solid state power supply (45 kV, 60 ns, up to 1 kHz) was used for driving the corona reactor. A Mitsubishi 10 kW 3-cylinder diesel-generator engine with a total volume of 1300 cm3 was used as a source of exhaust gas. At an NO removal rate of 35% the NO removal efficiency was 53 g kW-1h-1 for PRR = 500 Hz and the initial NO concentration was 375 ppm. A semi-empirical expression for the corona reactor removal efficiency related both to PRR and to the residence time is presented. The removal efficiency decreases with increasing PRR at constant flow rate or constant residence time. This expression demonstrates reasonable agreement between the calculation results and the experimental data.

  6. Continuous hydroxyl radical planar laser imaging at 50 kHz repetition rate.

    PubMed

    Hammack, Stephen; Carter, Campbell; Wuensche, Clemens; Lee, Tonghun

    2014-08-10

    This study demonstrates high-repetition-rate planar laser-induced fluorescence (PLIF) imaging of hydroxyl radicals (OH) in flames at a continuous framing rate of 50 kHz. A frequency-doubled dye laser is pumped by the second harmonic of an Nd:YAG laser to generate laser radiation near 283 nm with a pulse width of 8 ns and rate of 50 kHz. Fluorescence is recorded by a two-stage image intensifier and complementary metal-oxide-semiconductor camera. The average power of the 283 nm beam reaches 7 W, yielding a pulse energy of 140 μJ. Both a Hencken burner and a DC transient-arc plasmatron are used to produce premixed CH4/air flames to evaluate the OH PLIF system. The average signal-to-noise ratio for the Hencken burner flame is greater than 20 near the flame front and greater than 10 further downstream in a region of the flame near equilibrium. Image sequences of the DC plasmatron discharge clearly illustrate development and evolution of flow features with signal levels comparable to those in the Hencken burner. The results are a demonstration of the ability to make high-fidelity OH PLIF measurements at 50 kHz using a Nd:YAG-pumped, frequency-doubled dye laser. PMID:25320935

  7. Formation of crystalline dots and lines in lanthanum borogermanate glass by the low pulse repetition rate femtosecond laser

    NASA Astrophysics Data System (ADS)

    Lipateva, Tatiana O.; Lotarev, Sergey V.; Lipatiev, Alexey S.; Kazansky, Peter G.; Sigaev, Vladimir N.

    2015-01-01

    Femtosecond lasers have become a powerful tool for 3D space-selective crystallization of glasses. A laser-induced cumulative heating effect required for crystal growth is usually considered to take place only at pulse repetition rate over 100 or 200 kHz and 200 kHz is known as the lowest repetition rate at which femtosecond laser-induced crystallization has been reported so far. We for the first time demonstrate precipitation of LaBGeO5 crystals in lanthanum borogermanate glass using a femtosecond laser emitting 1030 nm, 300 fs, 110 μJ pulses with adjustable repetition rate below 100 kHz. For the applied laser, minimal repetition rate enabling nucleation of ferroelectric LaBGeO5 crystals inside the glass was shown to be 9 kHz at maximal pulse energy of 110 μJ and growth of a crystalline line from the formed seed crystal was obtained starting from 8 kHz though smooth homogeneous oriented line which might be regarded as quasi-single-crystalline could be grown at 25 kHz or higher and corresponding pulse energy of 18 μJ. Thus, the pulse repetition rate sufficient for a cumulative heating effect and a stable crystal growth was reduced by an order of magnitude as compared to earlier publications due to relatively high pulse energy. Possibility and efficiency of cumulative heating and crystal growth and average time required for forming the seed crystal have been studied for various combinations of the pulse energy and the repetition rate. Obtained crystalline features have been studied by micro-Raman spectroscopy and Raman mapping which confirmed growth of stillwellite-like LaBGeO5 phase and orientation of its polar axis along the direction of the crystalline line.

  8. Yb:YAG Innoslab amplifier: efficient high repetition rate subpicosecond pumping system for optical parametric chirped pulse amplification.

    PubMed

    Schulz, M; Riedel, R; Willner, A; Mans, T; Schnitzler, C; Russbueldt, P; Dolkemeyer, J; Seise, E; Gottschall, T; Hädrich, S; Duesterer, S; Schlarb, H; Feldhaus, J; Limpert, J; Faatz, B; Tünnermann, A; Rossbach, J; Drescher, M; Tavella, F

    2011-07-01

    We report on a Yb:YAG Innoslab laser amplifier system for generation of subpicsecond high energy pump pulses for optical parametric chirped pulse amplification (OPCPA) at high repetition rates. Pulse energies of up to 20 mJ (at 12.5 kHz) and repetition rates of up to 100 kHz were attained with pulse durations of 830 fs and average power in excess of 200 W. We further investigate the possibility to use subpicosecond pulses to derive a stable continuum in a YAG crystal for OPCPA seeding. PMID:21725443

  9. Study of filamentation with a high power high repetition rate ps laser at 1.03 µm.

    PubMed

    Houard, A; Jukna, V; Point, G; André, Y-B; Klingebiel, S; Schultze, M; Michel, K; Metzger, T; Mysyrowicz, A

    2016-04-01

    We study the propagation of intense, high repetition rate laser pulses of picosecond duration at 1.03 µm central wavelength through air. Evidence of filamentation is obtained from measurements of the beam profile as a function of distance, from photoemission imaging and from spatially resolved sonometric recordings. Good agreement is found with numerical simulations. Simulations reveal an important self shortening of the pulse duration, suggesting that laser pulses with few optical cycles could be obtained via double filamentation. An important lowering of the voltage required to induce guided electric discharges between charged electrodes is measured at high laser pulse repetition rate. PMID:27137034

  10. A Real-Time Terahertz Time-Domain Polarization Analyzer with 80-MHz Repetition-Rate Femtosecond Laser Pulses

    PubMed Central

    Watanabe, Shinichi; Yasumatsu, Naoya; Oguchi, Kenichi; Takeda, Masatoshi; Suzuki, Takeshi; Tachizaki, Takehiro

    2013-01-01

    We have developed a real-time terahertz time-domain polarization analyzer by using 80-MHz repetition-rate femtosecond laser pulses. Our technique is based on the spinning electro-optic sensor method, which we recently proposed and demonstrated by using a regenerative amplifier laser system; here we improve the detection scheme in order to be able to use it with a femtosecond laser oscillator with laser pulses of a much higher repetition rate. This improvement brings great advantages for realizing broadband, compact and stable real-time terahertz time-domain polarization measurement systems for scientific and industrial applications. PMID:23478599

  11. 1.4-MHz repetition rate electro-optic Q-switched Nd:YVO4 laser.

    PubMed

    Horiuchi, Ryusuke; Adachi, Koji; Watanabe, Goro; Tei, Kazuyoku; Yamaguchi, Shigeru

    2008-10-13

    An electro-optic (EO) deflector was used for Q-switching of a laser cavity with a Nd-doped yttrium vanadate (Nd:YVO(4)), enabling a short pulse width and a high peak power to be achieved at a high repetition rate of over 1 MHz. The EO deflector has a low optical loss during Q-switching without polarizers and can be used to form a short laser cavity. A repetition rate of 1.4 MHz with a pulse width of 39 ns was achieved. An output power of 2.7 W was obtained at a pump power of 6.5 W. PMID:18852782

  12. A rapidly-tuned, short-pulse-length, high-repetition-rate CO{sub 2} laser for IR dial

    SciTech Connect

    Zaugg, T.; Thompson, D.; Leland, W.T.; Busch, G.

    1997-08-01

    Analysis of noise sources in Differential Absorption LIDAR (DIAL) in the infrared region of the spectrum indicates that the signal-to-noise ratio for direct detection can be improved if multiple-wavelength, short-pulse-length beams are transmitted and received at high repetition rates. Atmospheric effects can be minimized, albedo can be rapidly scanned, and uncorrelated speckle can be acquired at the maximum possible rate. A compact, rugged, RF-excited waveguide laser can produce 15 nanosecond pulses at a 100 kHz rate with sufficient energy per pulse to reach the speckle limit of the signal-to-noise ratio. A high-repetition-rate laser has been procured and will be used to verify these signal and noise scaling relationships at high repetition rates. Current line-tuning devices are mechanical and are capable of switching lines at a rate up to a few hundred Hertz. Acousto-optic modulators, deflectors or tunable filters can be substituted for these mechanical devices in the resonator of a CO{sub 2} laser and used to rapidly line-tune the laser across the 9 and 10 micron bands at a rate as high as 100 kHz. Several configurations for line tuning using acousto-optic and electro-optic devices with and without gratings are presented. The merits of and constraints on each design are also discussed. A pair of large aperture, acousto-optic deflectors has been purchased and the various line-tuning designs will be evaluated in a conventional, glass tube, CO{sub 2} laser, with a view to incorporation into the high-repetition-rate, waveguide laser. A computer model of the dynamics of an RF-excited, short-pulse-length, high-repetition-rate waveguide laser has been developed. The model will be used to test the consequences of various line-tuning designs.

  13. Fast repetition rate (FRR) fluorometer for making in situ measurements of primary productivity

    SciTech Connect

    Kolber, Z.S.; Falkowski, P.G.

    1992-01-01

    Understanding the ocean carbon cycle and predicting how climate-induced changes in ocean circulation will affect ocean productivity requires that (a) primary productivity be measured with high spatial and temporal resolution, and (b) natural variability in primary productivity be parameterized with regardto environmental factors such as nutrient availabuity, irradiance, and temperature. Instrumentation to measure primary productivity from the stimulated in vivo fluoresence of phytoplankton chlorophyll is currendy being developed at Brookhaven National Laboratory. The instrumentation is based on fast repetition rate (FRR) fluorometry, and provides a robust technique for deriving the photosynthetic rates in situ. Moreover, the FRR methodology directly measures several photosynthetic parameters such as effective absorption cross- section, photo-conversion efficiency, and turnover time of photosynthesis, and relate them to primary productivity. Since photosynthetic parameters are affected by environmental factors such as fight and nutrient availability, the relationship between these parameters and primary productivity can be established. By understanding such relationships, prognostic models of primary productivity can be developed and parameterized.

  14. Fast repetition rate (FRR) fluorometer for making in situ measurements of primary productivity

    SciTech Connect

    Kolber, Z.S.; Falkowski, P.G.

    1992-10-01

    Understanding the ocean carbon cycle and predicting how climate-induced changes in ocean circulation will affect ocean productivity requires that (a) primary productivity be measured with high spatial and temporal resolution, and (b) natural variability in primary productivity be parameterized with regardto environmental factors such as nutrient availabuity, irradiance, and temperature. Instrumentation to measure primary productivity from the stimulated in vivo fluoresence of phytoplankton chlorophyll is currendy being developed at Brookhaven National Laboratory. The instrumentation is based on fast repetition rate (FRR) fluorometry, and provides a robust technique for deriving the photosynthetic rates in situ. Moreover, the FRR methodology directly measures several photosynthetic parameters such as effective absorption cross- section, photo-conversion efficiency, and turnover time of photosynthesis, and relate them to primary productivity. Since photosynthetic parameters are affected by environmental factors such as fight and nutrient availability, the relationship between these parameters and primary productivity can be established. By understanding such relationships, prognostic models of primary productivity can be developed and parameterized.

  15. Laser ranging system and measurement analysis for space debris with high repetition rate

    NASA Astrophysics Data System (ADS)

    Wu, Zhibo; Zhang, Haifeng; Meng, Wendong; Li, Pu; Deng, Huarong; Tang, Kai; Ding, Renjie; Zhang, Zhongping

    2016-01-01

    Laser measurement technology is inherently high accurate and will play an important role in precise orbit determination, accurate catalog, surveillance to space debris. Shanghai Astronomical Observatory (SHAO) has been developing the technology of laser measurement to space debris for several years. Based on the first successful laser ranging measurement to space debris in country, by applying one new set of high power 532nm wavelength laser system with 200Hz repetition rate, and adopting low dark noise APD detector with high quantum efficiency and high transmissivity of narrow bandwidth spectral filter, SHAO have achieved hundreds of passes of laser data from space debris in 2014, and the measured objects with distance between 500km and 2200km, Radar Cross Section (RCS) of >10m2 to <0.5m2 at the precision of <1m RMS for small RCS targets ,and the success rate of measured passes of up to 80%. The results show that laser ranging technology in China can routinely measure space debris and provide enough measurement data with high accuracy to space debris applications and researches such as surveillance activities in the future.

  16. Improved repetition rate mixed isotope CO{sub 2} TEA laser

    SciTech Connect

    Cohn, D. B.

    2014-09-15

    A compact CO{sub 2} TEA laser has been developed for remote chemical detection that operates at a repetition rate of 250 Hz. It emits 700 mJ/pulse at 10.6 μm in a multimode beam with the {sup 12}C{sup 16}O{sub 2} isotope. With mixed {sup 12}C{sup 16}O{sub 2} plus {sup 13}C{sup 16}O{sub 2} isotopes it emits multiple lines in both isotope manifolds to improve detection of a broad range of chemicals. In particular, output pulse energies are 110 mJ/pulse at 9.77 μm, 250 mJ/pulse at 10 μm, and 550 mJ/pulse at 11.15 μm, useful for detection of the chemical agents Sarin, Tabun, and VX. Related work shows capability for long term sealed operation with a catalyst and an agile tuner at a wavelength shift rate of 200 Hz.

  17. Sentence comprehension in Alzheimer's disease: effects of grammatical complexity, speech rate, and repetition.

    PubMed

    Small, J A; Kemper, S; Lyons, K

    1997-03-01

    Caregivers of patients diagnosed with Alzheimer's disease (AD) are often advised to modify their speech to facilitate the patients' sentence comprehension. Three common recommendations are to (a) speak in simple sentences, (b) speak slowly, and (c) repeat one's utterance, using the same words. These three speech modifications were experimentally manipulated in order to investigate their individual and combined effects on sentence comprehension in AD. Fifteen patients with mild to moderate AD and 20 healthy older persons were tested on a sentence comprehension task with sentences varying in terms of (a) degree of grammatical complexity, (b) rate of presentation (normal vs. slow), and (c) form of repetition (verbatim vs. paraphrase). The results indicated a significant decline in sentence comprehension for the AD group. Sentence comprehension improved, however, after the sentence was repeated in either verbatim or parapharsed form. However, the patients' comprehension did not improve for sentences presented at the slow speech rate. This pattern of results is explained via-à-vis the patients' working memory loss. The findings challenge the appropriateness of several clinical recommendations. PMID:9100263

  18. GHz repetition rate tabletop X-band photoinjector for free-electron laser applications

    SciTech Connect

    Le Sage, G.P.; Fochs, S.N.; Feng, H.X.C.

    1995-12-31

    A 1-1/2 cell {pi}-mode X-bend (8.568 GHz) photoinjector system capable of producing trains of up to one hundred, 1 nC, 1ps, 5 MeV, {epsilon}{sub n} < 2.5 {pi} mm-mrad photoelectron bunches, at a micropulse repetition rate of 1-10 Hz, is currently under development at LLNL, in the UC Davis DAS coherent millimeter-wave group. The system is powered by a 20 MW, 8.568 GHz SLAC development klystron. The system also uses a Cs{sub 2}Te (Cesium Telluride) photocathode which has a quantum efficiency > 5% in the UV (210 nm). The compact UV laser system is composed of a synchronously modelocked AlGaAs semiconductor laser oscillator which produces pulses with a duration of 250 fs and 100 pJ energy at 830 nm, at a repetion rate of 2.142 GHz with less 400 is jitter, a 5 GHz bandwidth Lithium Niobate Mach-Zender fiber modulator, an 8-pass, 10{sup 6} gain, TiAl{sub 2}O{sub 3} (Titanium:Sapphire) chirped pulse amplifier, and 2 BBO frequency doublers in series to quadruple the laser frequency into the UV (207 nm).

  19. Reliable, high repetition rate thyratron grid driver used with a magnetic modulator

    SciTech Connect

    Hill, J.V.; Ball, D.G.; Garrett, D.N.

    1991-06-14

    The Atomic Vapor Laser Isotope Separation (AVLIS) Program at Lawrence Livermore National Laboratory uses a magnetic modulator switched by a high voltage thyratron to drive a gas discharge laser. The thyratron trigger source must provide an extremely reliable, low jitter, high- rep-rate grid pulse. This paper describes a thyratron grid driver which delivers a 1.2 kV, 80 ns rise time grid pulse into a 50 ohm load at up to 4.5 kHz repetition rate and has demonstrated approximately 10,000 hours MTBF. Since the thyratron is used with a magnetic compression circuit having a delay time of 1.4 ms this grid driver incorporates a jitter compensation circuit to adjust the trigger timing of the thyratron to provide overall modulator/laser jitter of less than {plus minus} 2 ns. The specific grid driver requirements will be discussed followed by a description of the circuit design and theory of operation. Construction comments will be followed by performance data (for a specific thyratron and magnetic compression circuit), including pulse shape, jitter, and lifetime. 1 ref., 10 figs.

  20. Reliable, high repetition rate thyratron grid driver used with a magnetic modulator

    NASA Astrophysics Data System (ADS)

    Hill, J. V.; Ball, D. G.; Garrett, D. N.

    1991-06-01

    The Atomic Vapor Laser Isotope Separation (AVLIS) Program at Lawrence Livermore National Laboratory uses a magnetic modulator switched by a high voltage thyratron to drive a gas discharge laser. The thyratron trigger source must provide an extremely reliable, low jitter, high-rep-rate grid pulse. This paper describes a thyratron grid driver which delivers a 1.2 kV, 80 ns rise time grid pulse into a 50 ohm load at up to 4.5 kHz repetition rate and has demonstrated approximately 10,000 hours MTBF. Since the thyratron is used with a magnetic compression circuit having a delay time of 1.4 ms, this grid driver incorporates a jitter compensation circuit to adjust the trigger timing of the thyratron to provide overall modulator/laser jitter of less than +/- 2 ns. The specific grid driver requirements will be discussed followed by a description of the circuit design and theory of operation. Construction comments will be followed by performance data (for a specific thyratron and magnetic compression circuit), including pulse shape, jitter, and lifetime.

  1. Design of a liquid membrane target for high repetition rate neutron generation

    NASA Astrophysics Data System (ADS)

    Poole, Patrick; Andereck, C. David; Storm, Mike; Schumacher, Douglass

    2013-10-01

    Ultra-bright, pulsed, spatially-small sources of energetic neutrons have applications in radiography and non-destructive remote sensing. Neutrons can be generated by a process wherein ions accelerated from a laser-irradiated primary target subsequently bombard a converter material, causing neutron-producing nuclear reactions, such as 7Li(d,n)8Be. Deuterons from this process are suppressed by contamination that builds up on the rear of the solid primary target. To eliminate this issue we propose a self-replenishing liquid membrane target consisting of heavy water and deuterated surfactant, formed in-vacuum within a moveable wire frame. In addition to removing issues associated with solid target positioning and collateral damage, this apparatus provides flow rate and target thickness control, and allows for the high repetition rates required to generate desired neutron fluxes with a portable laser-based system. The apparatus design will be presented, as well as a novel interferometric method that measures the membrane thickness using tightly-focused light. This work was performed with support from DARPA.

  2. A pulsed, high repetition rate 2-micron laser transmitter for coherent CO2 DIAL

    NASA Astrophysics Data System (ADS)

    Yu, J.; Bai, Y.; Petzar, P.; Petros, M.; Chen, S.; Trieu, B.; Koch, G. J.; Kavaya, M. J.; Singh, U. N.

    2009-12-01

    A Holmium solid-state 2-µm pulsed laser, end-pumped by a Thulium fiber laser, is being developed for coherent CO2 Differential Absorption Lidar (DIAL). It combines the advantages of high efficient fiber laser technology with the mature high energy solid state laser technology to produce desired energy levels at a high repetition rate. To obtain high beam quality that is required by coherent detection technique, the effect of “spatial hole burning” in the laser gain medium must be prevented. This is achieved by the use of ring cavity configuration in which the laser light is forced to travel in one direction, so that no standing waves are formed. The pump beam and laser beam are mode-matched in the laser crystals to improve the laser efficiency. At the pumping power of 13.25W, optical-to-optical efficiency of 52% was obtained with the pulse repetition rate of 1.25 kHz, which gives the energy per pulse of ~5.5mJ. The pulse energy can be scaled by increasing the pump power or by reducing the pulse repetition rate. The pulse length of this laser is at ~50ns. The wavelengths of the Ho pulse laser are tunable over several characteristic absorption lines of CO2. The exact wavelengths of the Ho pulse laser are controlled by well-controlled continuous wave (CW) seed lasers to provide the required sequential, on-and-off line wavelength pulses for DIAL applications. Three CW lasers were used to provide the accurate on-and-off wavelengths. The first CW laser is locked to the center of a characteristic CO2 absorption line through a CO2 cell by the frequency modulation technique. The frequency of the second CW laser was shifted related to the first CW laser by a few GHz to the wing of the CO2 absorption line, and used as the on-line frequency of the CO2 DIAL. This frequency shift is necessary to obtain a better weighting function for the CO2 measurement. The standard deviation of the CW on-line frequency can be controlled within 250 KHz. The third CW laser provides the off

  3. Effects of water spray and repetition rate on the temperature elevation during Er:YAG laser ablation of dentine

    NASA Astrophysics Data System (ADS)

    Hibst, Raimund; Keller, Ulrich

    1996-01-01

    The Er:YAG is currently used as an alternative instrument for the removal of dental decay. Safe laser parameters have been found, but in order to increase the preparation speed also higher pulse energies or repetition rates are under consideration. To investigate systematically the temperature effect of these parameters and of water spray, slices of dentine were perforated with the laser radiation, exactly towards a thermocouple placed in a hole at the back side. During and after preparation temperature was monitored, and maximum temperature rise reached at the moment of perforation (Tm) was evaluated. For preparation without water irrigation Tm was in the range of 30 to 40 K, increasing slightly with pulse repetition rate (prr). For low prr (2 Hz) the same was observed for the radiant energy, however for high prr (10 Hz) the effect was inverse. When moistening the slices during preparation by a fine water spray, Tm decreases. The temperature reduction is very pronounced for low prr, leading to a temperature rise of only 2 K at 2 Hz (200 mJ). When prr is enhanced the spray becomes less effective, even when higher flow rates are chosen. With respect to temperature, combinations of low pulse energy and high repetition rate are least favorable. For safe preparations in dentine low pulse repetition rates are recommended.

  4. Use of spatial time-division repetition rate multiplication of mode-locked laser pulses to generate microwave radiation from optoelectronic switches

    NASA Astrophysics Data System (ADS)

    Mooradian, A.

    1984-09-01

    An all-optical technique is described which can substantially increase the pulse repetition rate of the output from any mode-locked laser. Multiplication of the repetition rate by a factor of 16 has been demonstrated. A mode-locked laser pulse train multiplied up to a 2-GHz repetition rate has been used to generate microwave radiation by means of a GaAs avalanche photodiode as well as an Fe:InP optoelectronic switch.

  5. Heart Rate Variability and Skin Conductance During Repetitive TMS Course in Children with Autism.

    PubMed

    Wang, Yao; Hensley, Marie K; Tasman, Allan; Sears, Lonnie; Casanova, Manuel F; Sokhadze, Estate M

    2016-03-01

    Autism spectrum disorder (ASD) is a developmental disorder marked by difficulty in social interactions and communication. ASD also often present symptoms of autonomic nervous system (ANS) functioning abnormalities. In individuals with autism the sympathetic branch of the ANS presents an over-activation on a background of the parasympathetic activity deficits, creating an autonomic imbalance, evidenced by a faster heart rate with little variation and increased tonic electrodermal activity. The objective of this study was to explore the effect of 12 sessions of 0.5 Hz repetitive transcranial magnetic stimulation (rTMS) over dorsolateral prefrontal cortex (DLPFC) on autonomic activity in children with ASD. Electrocardiogram and skin conductance level (SCL) were recorded and analyzed during each session of rTMS. The measures of interest were time domain (i.e., R-R intervals, standard deviation of cardiac intervals, NN50-cardio-intervals >50 ms different from preceding interval) and frequency domain heart rate variability (HRV) indices [i.e., power of high frequency (HF) and low frequency (LF) components of HRV spectrum, LF/HF ratio]. Based on our prior pilot studies it was proposed that the course of 12 weekly inhibitory low-frequency rTMS bilaterally applied to the DLPFC will improve autonomic balance probably through improved frontal inhibition of the ANS activity, and will be manifested in an increased length of cardiointervals and their variability, and in higher frequency-domain HRV in a form of increased HF power, decreased LF power, resulting in decreased LF/HF ratio, and in decreased SCL. Our post-12 TMS results showed significant increases in cardiac intervals variability measures and decrease of tonic SCL indicative of increased cardiac vagal control and reduced sympathetic arousal. Behavioral evaluations showed decreased irritability, hyperactivity, stereotype behavior and compulsive behavior ratings that correlated with several autonomic variables. PMID

  6. High energy, high repetition rate, second harmonic generation in large aperture DKDP, YCOB, and LBO crystals.

    PubMed

    Phillips, Jonathan P; Banerjee, Saumyabrata; Smith, Jodie; Fitton, Mike; Davenne, Tristan; Ertel, Klaus; Mason, Paul; Butcher, Thomas; De Vido, Mariastefania; Greenhalgh, Justin; Edwards, Chris; Hernandez-Gomez, Cristina; Collier, John

    2016-08-22

    We report on type-I phase-matched second harmonic generation (SHG) in three nonlinear crystals: DKDP (98% deuteration), YCOB (XZ plane), and LBO (XY plane), of 8 J, 10 Hz cryogenic gas cooled Yb:YAG laser operating at 1029.5 nm. DKDP exhibited an efficiency of 45% at a peak fundamental intensity of 0.24 GW/cm2 for 10 Hz operation at 10 ns. At the same intensity and repetition rate, YCOB and LBO showed 50% and 65% conversion efficiencies, respectively. Significant improvement in conversion efficiency, to a maximum of 82%, was demonstrated in LBO at 0.7 GW/cm2 and 10 Hz, generating output energy of 5.6 J at 514.75 nm, without damage or degradation. However, no improvement in conversion efficiency was recorded for YCOB at this increased intensity. Additionally, we present theoretically calculated temperature maps for both 10 J and 100 J operation at 10 Hz, and discuss the suitability of these three crystals for frequency conversion of a 100 J, 10 Hz diode pumped solid state laser (DPSSL). PMID:27557246

  7. Cavity-Enhanced Field-Free Molecular Alignment at a High Repetition Rate

    NASA Astrophysics Data System (ADS)

    Benko, Craig; Hua, Linqiang; Allison, Thomas K.; Labaye, François; Ye, Jun

    2015-04-01

    Extreme ultraviolet frequency combs are a versatile tool with applications including precision measurement, strong-field physics, and solid-state physics. Here we report on an application of extreme ultraviolet frequency combs and their driving lasers for studying strong-field effects in molecular systems. We perform field-free molecular alignment and high-order harmonic generation with aligned molecules in a gas jet at a repetition rate of 154 MHz using a high-powered optical frequency comb inside a femtosecond enhancement cavity. The cavity-enhanced system provides a means to reach suitable intensities to study field-free molecular alignment and enhance the observable effects of the molecule-field interaction. We observe modulations of the driving field, arising from the nature of impulsive stimulated Raman scattering responsible for coherent molecular rotations. We foresee the impact of this work on the study of molecule-based strong-field physics, with improved precision and a more fundamental understanding of the interaction effects on both the field and molecules.

  8. Choppers to optimise the repetition rate multiplication technique on a direct geometry neutron chopper spectrometer

    SciTech Connect

    Vickery, A.; Deen, P. P.

    2014-11-15

    In recent years the use of repetition rate multiplication (RRM) on direct geometry neutron spectrometers has been established and is the common mode of operation on a growing number of instruments. However, the chopper configurations are not ideally optimised for RRM with a resultant 100 fold flux difference across a broad wavelength band. This paper presents chopper configurations that will produce a relative constant (RC) energy resolution and a relative variable (RV) energy resolution for optimised use of RRM. The RC configuration provides an almost uniform ΔE/E for all incident wavelengths and enables an efficient use of time as the entire dynamic range is probed with equivalent statistics, ideal for single shot measurements of transient phenomena. The RV energy configuration provides an almost uniform opening time at the sample for all incident wavelengths with three orders of magnitude in time resolution probed for a single European Spallation Source (ESS) period, which is ideal to probe complex relaxational behaviour. These two chopper configurations have been simulated for the Versatile Optimal Resolution direct geometry spectrometer, VOR, that will be built at ESS.

  9. Resolving range ambiguities in high-repetition rate airborne lidar applications

    NASA Astrophysics Data System (ADS)

    Rieger, Peter; Ullrich, Andreas

    2011-11-01

    Correctly determining a measurement range in LIDAR instruments, based on time-of-flight measurements on laser pulses, requires the allocation of each received echo pulse to its causative emitted laser pulse. Without further precautions this definite allocation is only possible under specific conditions constraining the usability of range finders and laser scanners with very high measurement rates. Losing the unambiguity of ranges in high repetition systems is well known in RADAR and the term "multiple time around" (MTA) has been coined. However because of fundamental differences between scanning LIDAR and RADAR, with respect to MTA processing, new approaches for resolving range ambiguities in LIDAR are possible. In this paper we compare known and novel techniques for avoiding or even resolving range ambiguities without any further user interaction required. Such techniques may be based upon measures affecting hardware (e.g. spatial multiplexing or modulation of consecutive laser pulses), software (e.g. assumptions about the true measurement range based on a rough DTM) or both hard- and soft-ware in order to achieve a high probability of correctly resolved range ambiguities. Furthermore a comparison of different approaches is given, discussing their specific (dis-) advantages and their current status of implementation.

  10. Cavity-enhanced field-free molecular alignment at a high repetition rate.

    PubMed

    Benko, Craig; Hua, Linqiang; Allison, Thomas K; Labaye, François; Ye, Jun

    2015-04-17

    Extreme ultraviolet frequency combs are a versatile tool with applications including precision measurement, strong-field physics, and solid-state physics. Here we report on an application of extreme ultraviolet frequency combs and their driving lasers for studying strong-field effects in molecular systems. We perform field-free molecular alignment and high-order harmonic generation with aligned molecules in a gas jet at a repetition rate of 154 MHz using a high-powered optical frequency comb inside a femtosecond enhancement cavity. The cavity-enhanced system provides a means to reach suitable intensities to study field-free molecular alignment and enhance the observable effects of the molecule-field interaction. We observe modulations of the driving field, arising from the nature of impulsive stimulated Raman scattering responsible for coherent molecular rotations. We foresee the impact of this work on the study of molecule-based strong-field physics, with improved precision and a more fundamental understanding of the interaction effects on both the field and molecules. PMID:25933311

  11. Design of a high repetition rate S-band photocathode gun

    NASA Astrophysics Data System (ADS)

    Han, Jang-Hui; Cox, Matthew; Huang, Houcheng; Pande, Shivaji

    2011-08-01

    Photocathode RF guns have been developed in many laboratories for generating high quality electron beams for free-electron lasers based on linear accelerators. Such guns can generate electron beams with an exceptionally high peak current as well as a small transverse emittance. Their applications have been recently expanded for ultrafast electron diffraction, coherent terahertz radiation, and X-ray or γ-ray radiation by Compton scattering. In this paper, we design an S-band normal-conducting gun with capabilities of high quality beam generation and high repetition rate operation. The RF design and thermal analysis of the gun cavity and coupler are introduced. Optimal position of the gun focusing solenoid for low emittance beam generation is found by performing particle tracking simulations. Then, the gun system is designed to be able to afford the optimal solenoid position. The cooling-water channel surrounding the gun cavity and coupler is designed and analyzed numerically. The pressure in the gun is simulated with a vacuum model containing the detailed inner structure of the gun. An injector for a free-electron laser application is designed by using this gun and the beam dynamics simulation is shown. A cold test with a prototype gun for confirmation of the RF design is reported.

  12. Design of a VHF-band RF Photoinjector with Megahertz BeamRepetition Rate

    SciTech Connect

    Staples, J.W.; Baptiste, K.M.; Corlett, J.N.; Kwiatkowski, S.; Lidia, S.M.; Qiang, J.; Sannibale, F.; Sonnad, K.G.; Virostek, S.P.; Wells, R.P.

    2007-06-01

    New generation accelerator-based X-ray light sources require high quality beams with high average brightness. Normal conducting L- and S-band photoinjectors are limited in repetition rate and D-C (photo)injectors are limited in field strength at the cathode. We propose a low frequency normal-conducting cavity, operating at 50 to 100MHz CW, to provide beam bunches of up to the cavity frequency. The photoinjector uses a re-entrant cavity structure, requiring less than 100 kW CW, with a peak wall power density less than 10 W/cm{sup 2}. The cavity will support a vacuum down to 10 picoTorr, with a load-lock mechanism for easy replacement of photocathodes. The photocathode can be embedded in a magnetic field to provide correlations useful for emittance exchange. Beam dynamics simulations indicate that normalized emittances smaller than 1 mm-mrad are possible with gap voltage of 750 kV, with fields up to 20 MV/m at the photocathode, for 1 nanocoulomb charge per bunch after acceleration and emittance compensation. Long-bunch operation (10's of picosecond) is made possible by the low cavity frequency, permitting low bunch current at the 750 kV gap voltage.

  13. Experiments and Simulations on Magnetically Driven Implosions in High Repetition Rate Dense Plasma Focus

    NASA Astrophysics Data System (ADS)

    Caballero Bendixsen, Luis; Bott-Suzuki, Simon; Cordaro, Samuel; Krishnan, Mahadevan; Chapman, Stephen; Coleman, Phil; Chittenden, Jeremy

    2015-11-01

    Results will be shown on coordinated experiments and MHD simulations on magnetically driven implosions, with an emphasis on current diffusion and heat transport. Experiments are run at a Mather-type dense plasma focus (DPF-3, Vc: 20 kV, Ip: 480 kA, E: 5.8 kJ). Typical experiments are run at 300 kA and 0.33 Hz repetition rate with different gas loads (Ar, Ne, and He) at pressures of ~ 1-3 Torr, usually gathering 1000 shots per day. Simulations are run at a 96-core HP blade server cluster using 3GHz processors with 4GB RAM per node.Preliminary results show axial and radial phase plasma sheath velocity of ~ 1x105 m/s. These are in agreement with the snow-plough model of DPFs. Peak magnetic field of ~ 1 Tesla in the radial compression phase are measured. Electron densities on the order of 1018 cm-3 anticipated. Comparison between 2D and 3D models with empirical results show a good agreement in the axial and radial phase.

  14. High-repetition rate laser ablation coupled to dielectric barrier discharge postionization for ambient mass spectrometry.

    PubMed

    Bierstedt, Andreas; Riedel, Jens

    2016-07-15

    Most ambient sample introduction and ionization techniques for native mass spectrometry are highly selective for polar agents. To achieve a more general sensitivity for a wider range of target analytes, a novel laser ablation dielectric barrier discharge (LA DBD) ionization scheme was developed. The approach employs a two-step mechanism with subsequent sample desorption and post-ionization. Effective ablation was achieved by the second harmonic output (λ=532nm) of a diode pumped Nd:YVO4 laser operating at a high-repetition rate of several kHz and pulse energies below 100μJ. The ejected analyte-containing aerosol was consecutively vaporized and ionized in the afterglow of a DBD plasma jet. Depending on their proton affinity the superexcited helium species in this afterglow produced analyte ions as protonated and ammoniated species, as well as radical cations. The optimization procedure could corroborate underlying conceptual consideration on the ablation, desorption and ionization mechanisms. A successful detection of a variety of target molecules could be shown from the pharmaceutical ibuprofen, urea, the amino acids l-arginine, l-lysine, the polymer polyethylene glycol, the organometallic compound ferrocene and the technical mixture wild mint oil. For a reliable evaluation of the introduced detection procedure spectra from the naturally abundant alkaloid capsaicin in dried capsicum fruits were recorded. PMID:26851554

  15. Advances in generation of high-repetition-rate burst mode laser output.

    PubMed

    Jiang, Naibo; Webster, Matthew C; Lempert, Walter R

    2009-02-01

    It is demonstrated that the incorporation of variable pulse duration flashlamp power supplies into an Nd:YAG burst mode laser system results in very substantial increases in the realizable energy per pulse, the total pulse train length, and uniformity of the intensity envelope. As an example, trains of 20 pulses at burst frequencies of 50 and 20 kHz are demonstrated with individual pulse energy at 1064 nm of 220 and 400 mJ, respectively. Conversion efficiency to the second- (532 nm) and third- (355 nm) harmonic wavelengths of approximately 50% and 35-40%, respectively, is also achieved. Use of the third-harmonic output of the burst mode laser as a pump source for a simple, home built optical parametric oscillator (OPO) produces pulse trains of broadly wavelength tunable output. Sum-frequency mixing of OPO signal output at 622 nm with residual output from the 355 nm pump beam is shown to produce uniform bursts of tunable output at approximately 226 nm, with individual pulse energy of approximately 0.5 mJ. Time-correlated NO planar laser induced fluorescence (PLIF) image sequences are obtained in a Mach 3 wind tunnel at 500 kHz, representing, to our knowledge, the first demonstration of NO PLIF imaging at repetition rates exceeding tens of hertz. PMID:19183578

  16. Choppers to optimise the repetition rate multiplication technique on a direct geometry neutron chopper spectrometer

    NASA Astrophysics Data System (ADS)

    Vickery, A.; Deen, P. P.

    2014-11-01

    In recent years the use of repetition rate multiplication (RRM) on direct geometry neutron spectrometers has been established and is the common mode of operation on a growing number of instruments. However, the chopper configurations are not ideally optimised for RRM with a resultant 100 fold flux difference across a broad wavelength band. This paper presents chopper configurations that will produce a relative constant (RC) energy resolution and a relative variable (RV) energy resolution for optimised use of RRM. The RC configuration provides an almost uniform ΔE/E for all incident wavelengths and enables an efficient use of time as the entire dynamic range is probed with equivalent statistics, ideal for single shot measurements of transient phenomena. The RV energy configuration provides an almost uniform opening time at the sample for all incident wavelengths with three orders of magnitude in time resolution probed for a single European Spallation Source (ESS) period, which is ideal to probe complex relaxational behaviour. These two chopper configurations have been simulated for the Versatile Optimal Resolution direct geometry spectrometer, VOR, that will be built at ESS.

  17. Optical Parameter Variability in Laser Nerve Stimulation: A Study of Pulse Duration, Repetition Rate, and Wavelength

    PubMed Central

    Walsh, Joseph T.; Jansen, E. Duco; Bendett, Mark; Webb, Jim; Ralph, Heather; Richter, Claus-Peter

    2012-01-01

    Pulsed lasers can evoke neural activity from motor as well as sensory neurons in vivo. Lasers allow more selective spatial resolution of stimulation than the conventional electrical stimulation. To date, few studies have examined pulsed, mid-infrared laser stimulation of nerves and very little of the available optical parameter space has been studied. In this study, a pulsed diode laser, with wavelength between 1.844–1.873 μm, was used to elicit compound action potentials (CAPs) from the auditory system of the gerbil. We found that pulse durations as short as 35 μs elicit a CAP from the cochlea. In addition, repetition rates up to 13 Hz can continually stimulate cochlear spiral ganglion cells for extended periods of time. Varying the wavelength and, therefore, the optical penetration depth, allowed different populations of neurons to be stimulated. The technology of optical stimulation could significantly improve cochlear implants, which are hampered by a lack of spatial selectivity. PMID:17554829

  18. Modeling transient gain dynamics in a cladding-pumped Yb-doped fiber ampliefier pulsed at low repetition rates

    NASA Technical Reports Server (NTRS)

    Valley, G. C.; Wright, M.

    2001-01-01

    Simulations of 1-50 kHz repetition rate, pulsed Yb-fiber amplifiers show peak powers to 10 kW with half-widths < 30 ns, consistent with commercial amplifier performance. This device is a potential source for deep space-communication.

  19. High Repetition Rate Table-Top Soft X-Ray Lasers in Capillary Discharges and Laser-Created Plasmas

    SciTech Connect

    Rocca, J.J.; Luther, B.M.; Heinbuch, S.; Larotonda, M.A.; Wang, Y.; Alessi, D.; Berrill, M.; Marconi, M.C.; Menoni, C.S.; Shlyaptsev, V.N.

    2006-01-05

    We discuss very recent advances in high repetition rate soft x-ray lasers resulting from the use of two different types of hot dense plasmas: fast capillary discharges and laser-created plasmas. We have demonstrated a new high repetition rate 46.9 nm capillary discharge laser that fits onto the surface area of a small desk and that operates at a relatively low voltage, therefore not requiring a Marx generator. Laser pulses with an energy of {approx} 13 {mu}J are generated at repetition rates up to 12 Hz. About (2-3)x104 laser shots can be generated with a single capillary. This new type of portable laser is an easily accessible source of intense short wavelength laser light for applications. We also discuss the demonstration of 5 Hz repetition rate table-top soft x-ray lasers producing microwatt average powers at wavelengths ranging from 13.2 to 33 nm. The results were obtained by collisional electron excitation of Ni-like and Ne-like ions in plasmas efficiently heated with a picosecond optical laser pulse impinging at grazing incidence onto a pre-created plasma. Efficient deposition of the pump beam into the gain region allows for the excitation of soft x-ray lasers in this wavelength range with a short pulse pump energy of only 1 J.

  20. High-repetition-rate Q-modulation in solid-state laser using fast saturable absorber V:YAG

    NASA Astrophysics Data System (ADS)

    Ma, Jia-Sai; Wang, Feng; Li, Pei-Xin; Hu, Wei-Wei; Yin, Chun-Hao; Xu, Jin-Long

    2015-07-01

    A high-repetition-rate Q-modulation operation in a solid-state Nd:GdVO4 laser with a V3+:YAG saturable absorber has been demonstrated in this paper. The V3+:YAG crystal behaves as a fast saturable absorber in this laser because of its very short lifetime of 22 ns. Taking advantage of such fast bleaching recovery and effective cooling of the V:YAG by a home-made copper holder, we realized a pulse repetition rate of 2.4 MHz, which is, to our best knowledge, the maximum among the reported passively Q-switched lasers. The corresponding average output power and pulse width were 1.28 W and 170 ns, respectively, giving a slope efficiency of 15.9% and a pulse energy of 0.53 µJ. This compact high-repetition-rate Q-switched laser offers a potential application in the construction of low-cost, integrated and portable sensing detection equipment which needs a high laser pulse repetition rate.

  1. High-repetition-rate optical delay line using a micromirror array and galvanometer mirror for a terahertz system.

    PubMed

    Kitahara, Hideaki; Tani, Masahiko; Hangyo, Masanori

    2009-07-01

    We developed a high-repetition-rate optical delay line based on a micromirror array and galvanometer mirror for terahertz time-domain spectroscopy. The micromirror array is fabricated by using the x-ray lithographic technology. The measurement of terahertz time-domain waveforms with the new optical delay line is demonstrated successfully up to 25 Hz. PMID:19655989

  2. Ultrashort pulse laser drilling of metals using a high-repetition rate high average power fiber CPA system

    NASA Astrophysics Data System (ADS)

    Ancona, A.; Jauregui, C.; Döring, S.; Röser, F.; Limpert, J.; Nolte, S.; Tünnermann, A.

    2009-02-01

    We present an experimental study of the drilling of metal targets with ultrashort laser pulses with pulse durations from 800 fs to 19 ps at repetition rates up to 1 MHz, average powers up to 70 Watts, using an Ytterbium-doped fiber CPA system. Particle shielding and heat accumulation have been found to influence the drilling efficiency at high repetition rates. Particle shielding causes an increase in the number of pulses for breakthrough. It occurs at a few hundred kHz, depending on the pulse energy and duration. The heat accumulation effect is noticed at higher repetition rates. Although it overbalances the particle shielding thus making the drilling process faster, heat accumulation is responsible for the formation of a large amount of molten material that limits the hole quality. The variations of the pulse duration reveal that heat accumulation starts at higher repetition rates for shorter pulse lengths. This is in agreement with the observed higher ablation efficiency with shorter pulse duration. Thus, the shorter pulses might be advantageous if highest precision and processing speed is required.

  3. Status of MBI activities: Will a transient collisional x-ray laser with high repetition rate come soon?

    NASA Astrophysics Data System (ADS)

    Nickles, Peter V.; Janulewicz, Karol A.; Priebe, Gerd; Lucianetti, Antonio; Kroemer, Robert K.; Gerlitzke, Anne-Kathrin; Sandner, Wolfgang

    2003-12-01

    Some prospects for development of collisional X-ray lasers with a high repetition rate based on the output characteristics of a transient Ni-like Ag soft X-ray laser pumped by a single picosecond laser pulse are analysed. Such problems as target technology, new driver development and the active medium parameters are discussed.

  4. Operation of the pulse-burst laser system for high-repetition-rate Thomson scattering on MST

    NASA Astrophysics Data System (ADS)

    Harris, W. S.; den Hartog, D. J.; Hurst, N. C.

    2011-10-01

    A custom pulse-burst laser system has been developed for high-repetition-rate Thomson scattering measurements on MST. The laser system is a master-oscillator power-amplifier (MOPA) design with five flashlamp-pumped amplifier stages. A diode-pumped, Q-switched Nd:YVO4 master oscillator (1064 nm) operates at pulse repetition rates between 5-250 kHz. The first four amplifier stages are Nd:YAG; the final amplifier is Nd:glass (silicate). Amplifier flashlamp drive is extremely flexible, ranging from short (250 μs) high-power pump pulses to long (10 ms) lower-power pulses. The entire laser system is computer controlled. Single pulse energies of the laser system are up to 5.5 J. Operation of the system with a short, high-power flashlamp discharge delivers a burst of up to 25 Q-switched laser pulses at 250 kHz repetition rate. For long flashlamp discharges, the laser system can deliver a burst of up to 50 pulses at a 5 kHz repetition rate. This work is supported by the U. S. DOE and NSF.

  5. High-repetition-rate pulse-burst laser for Thomson scattering on the MST reversed-field pinch

    NASA Astrophysics Data System (ADS)

    Young, W. C.; Morton, L. A.; Parke, E.; Den Hartog, D. J.

    2013-11-01

    A new, high-repetition-rate pulse-burst laser system for the MST Thomson scattering diagnostic has operated with 2 J pulses at repetition rates up to 75 kHz within a burst. The 1064 nm laser currently employs a q-switched, diode pumped Nd:YVO4 master oscillator, four Nd:YAG amplifier stages, and a Nd:glass amplifier, with plans for an additional Nd:glass amplifier. The laser can maintain 1.5-2 J pulses in two operating modes: either at a uniform repetition rate of 5-10 kHz (sustained for 5-8 ms), or reach rates of up to 75 kHz in pulse-burst operation (for 10 bursts of 15 pulses each), limited by flashlamp explosion energy and wall loading. The full system, including an additional Nd:glass amplifier, is designed to produce bursts of 2 J pulses at a repetition rate of at least 250 kHz. Custom programmable square-pulse power supplies drive the amplifier flashlamps, providing fine control of pulse timing, duration, and repetition, and allow for pulse-burst operation. The new laser system integrates with the same collection optics and detectors as used by the previous MST Thomson laser: 21 spatial points across the MST minor radius, filter polychromators with 6 to 8 channels (10 eV-5 keV range), avalanche photodiode detectors, and 1 GSample/s/channel digitization. Use of the previous pulse-burst laser continues concurrently with new laser development. Additional notes on optimization of flashlamp simmering will also be covered, showing that an increase in simmer currents can improve pulse-to-pulse energy consistency on both the new and older lasers.

  6. High-power, high-repetition-rate performance characteristics of β-BaB₂O₄ for single-pass picosecond ultraviolet generation at 266 nm.

    PubMed

    Kumar, S Chaitanya; Casals, J Canals; Wei, Junxiong; Ebrahim-Zadeh, M

    2015-10-19

    We report a systematic study on the performance characteristics of a high-power, high-repetition-rate, picosecond ultraviolet (UV) source at 266 nm based on β-BaB2O4 (BBO). The source, based on single-pass fourth harmonic generation (FHG) of a compact Yb-fiber laser in a two-crystal spatial walk-off compensation scheme, generates up to 2.9 W of average power at 266 nm at a pulse repetition rate of ~80 MHz with a single-pass FHG efficiency of 35% from the green to UV. Detrimental issues such as thermal effects have been studied and confirmed by performing relevant measurements. Angular and temperature acceptance bandwidths in BBO for FHG to 266 nm are experimentally determined, indicating that the effective interaction length is limited by spatial walk-off and thermal gradients under high-power operation. The origin of dynamic color center formation due to two-photon absorption in BBO is investigated by measurements of intensity-dependent transmission at 266 nm. Using a suitable theoretical model, two-photon absorption coefficients as well as the color center densities have been estimated at different temperatures. The measurements show that the two-photon absorption coefficient in BBO at 266 nm is ~3.5 times lower at 200°C compared to that at room temperature. The long-term power stability as well as beam pointing stability is analyzed at different output power levels and focusing conditions. Using cylindrical optics, we have circularized the generated elliptic UV beam to a circularity of >90%. To our knowledge, this is the first time such high average powers and temperature-dependent two-photon absorption measurements at 266 nm are reported at repetition rates as high as ~80 MHz. PMID:26480467

  7. Micro-processing of polymers and biological materials using high repetition rate femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Ding, Li

    High repetition rate femtosecond laser micro-processing has been applied to ophthalmological hydrogel polymers and ocular tissues to create novel refractive and diffractive structures. Through the optimization of laser irradiation conditions and material properties, this technology has become feasible for future industrial applications and clinical practices. A femtosecond laser micro-processing workstation has been designed and developed. Different experimental parameters of the workstation such as laser pulse duration, focusing lens, and translational stages have been described and discussed. Diffractive gratings and three-dimensional waveguides have been fabricated and characterized in hydrogel polymers, and refractive index modifications as large as + 0.06 have been observed within the laser-irradiated region. Raman spectroscopic studies have shown that our femtosecond laser micro-processing induces significant thermal accumulation, resulting in a densification of the polymer network and increasing the localized refractive index of polymers within the laser irradiated region. Different kinds of dye chromophores have been doped in hydrogel polymers to enhance the two-photon absorption during femtosecond laser micro-processing. As the result, laser scanning speed can be greatly increased while the large refractive index modifications remain. Femtosecond laser wavelength and pulse energy as well as water and dye concentration of the hydrogels are optimized. Lightly fixed ocular tissues such as corneas and lenses have been micro-processed by focused femtosecond laser pulses, and refractive index modifications without any tissue-breakdown are observed within the stromal layer of the corneas and the cortex of the lenses. Living corneas are doped with Sodium Fluorescein to increase the two-photon absorption during the laser micro-processing, and laser scanning speed can be greatly increased while inducing large refractive index modifications. No evidence of cell death

  8. Nonword Repetition by Children with Cochlear Implants: Accuracy Ratings from Normal-Hearing Listeners.

    ERIC Educational Resources Information Center

    Dillon, Caitlin M.; Burkholder, Rose A.; Cleary, Miranda; Pisoni, David B.

    2004-01-01

    Seventy-six children with cochlear implants completed a nonword repetition task. The children were presented with 20 nonword auditory patterns over a loudspeaker and were asked to repeat them aloud to the experimenter. The children's responses were recorded on digital audiotape and then played back to normal-hearing adult listeners to obtain…

  9. Rapid micromachining of high aspect ratio holes in fused silica glass by high repetition rate picosecond laser

    NASA Astrophysics Data System (ADS)

    Karimelahi, Samira; Abolghasemi, Ladan; Herman, Peter R.

    2014-01-01

    We present multiple methods of high aspect ratio hole drilling in fused silica glass, taking advantage of high power and high repetition rate picosecond lasers and flexible beam delivery methods to excise deep holes with minimal collateral damage. Combinations of static and synchronous scanning of laser focus were explored over a range of laser repetition rates and burst-train profiles that dramatically vary laser plume interaction dynamics, heat-affected zone, and heat accumulation physics. Chemically assisted etching of picosecond laser modification tracks are also presented as an extension from femtosecond laser writing of volume nanograting to form high aspect ratio (77) channels. Processing windows are identified for the various beam delivery methods that optimize the laser exposure over energy, wavelength, and repetition rate to reduce microcracking and deleterious heating effects. The results show the benefits of femtosecond laser interactions in glass extend into the picosecond domain, where the attributes of higher power further yield wide processing windows and significantly faster fabrication speed. High aspect ratio holes of 400 μm depth were formed over widely varying rates of 333 holes per second for mildly cracked holes in static-focal positioning through to one hole per second for low-damage and taper free holes in synchronous scanning.

  10. Low-Pump-Power, Low-Phase-Noise, and Microwave to Millimeter-Wave Repetition Rate Operation in Microcombs

    NASA Astrophysics Data System (ADS)

    Li, Jiang; Lee, Hansuek; Chen, Tong; Vahala, Kerry J.

    2012-12-01

    Microresonator-based frequency combs (microcombs or Kerr combs) can potentially miniaturize the numerous applications of conventional frequency combs. A priority is the realization of broadband (ideally octave spanning) spectra at detectable repetition rates for comb self-referencing. However, access to these rates involves pumping larger mode volumes and hence higher threshold powers. Moreover, threshold power sets both the scale for power per comb tooth and also the optical pump. Along these lines, it is shown that a class of resonators having surface-loss-limited Q factors can operate over a wide range of repetition rates with minimal variation in threshold power. A new, surface-loss-limited resonator illustrates the idea. Comb generation on mode spacings ranging from 2.6 to 220 GHz with overall low threshold power (as low as 1 mW) is demonstrated. A record number of comb lines for a microcomb (around 1900) is also observed with pump power of 200 mW. The ability to engineer a wide range of repetition rates with these devices is also used to investigate a recently observed mechanism in microcombs associated with dispersion of subcomb offset frequencies. We observe high-coherence phase locking in cases where these offset frequencies are small enough so as to be tuned into coincidence. In these cases, a record-low microcomb phase noise is reported at a level comparable to an open-loop, high-performance microwave oscillator.

  11. 1  J, 0.5  kHz repetition rate picosecond laser.

    PubMed

    Baumgarten, Cory; Pedicone, Michael; Bravo, Herman; Wang, Hanchen; Yin, Liang; Menoni, Carmen S; Rocca, Jorge J; Reagan, Brendan A

    2016-07-15

    We report the demonstration of a diode-pumped chirped pulse amplification Yb:YAG laser that produces λ=1.03  μm pulses of up to 1.5 J energy compressible to sub-5 ps duration at a repetition rate of 500 Hz (750 W average power). Amplification to high energy takes place in cryogenically cooled Yb:YAG active mirrors designed for kilowatt average power laser operation. This compact laser system will enable new advances in high-average-power ultrashort-pulse lasers and high-repetition-rate tabletop soft x-ray lasers. As a first application, the laser was used to pump a 400 Hz λ=18.9  nm laser. PMID:27420530

  12. Ytterbium fiber-based, 270 fs, 100 W chirped pulse amplification laser system with 1 MHz repetition rate

    NASA Astrophysics Data System (ADS)

    Zhao, Zhigang; Kobayashi, Yohei

    2016-01-01

    A 100 W Yb-doped, fiber-based, femtosecond, chirped pulse amplification laser system was developed with a repetition rate of 1 MHz, corresponding to a pulse energy of 100 µJ. Large-scale, fused-silica transmission gratings were used for both the pulse stretcher and compressor, with a compression throughput efficiency of ∼85%. A pulse duration of 270 fs was measured by second harmonic generation frequency-resolved optical gating (SHG-FROG). To the best of our knowledge, this is the shortest pulse duration ever achieved by a 100-W-level fiber chirped pulse amplification laser system at a repetition rate of few megahertz, without any special post-compression manipulation.

  13. 1 MHz repetition rate hollow fiber pulse compression to sub-100-fs duration at 100 W average power.

    PubMed

    Rothhardt, Jan; Hädrich, Steffen; Carstens, Henning; Herrick, Nicholas; Demmler, Stefan; Limpert, Jens; Tünnermann, Andreas

    2011-12-01

    We report on nonlinear pulse compression at very high average power. A high-power fiber chirped pulse amplification system based on a novel large pitch photonic crystal fiber delivers 700 fs pulses with 200 μJ pulse energy at a 1 MHz repetition rate, resulting in 200 W of average power. Subsequent spectral broadening in a xenon-filled hollow-core fiber and pulse compression with chirped mirrors is employed for pulse shortening and peak power enhancement. For the first time, to our knowledge, more than 100 W of average power are transmitted through a noble-gas-filled hollow fiber. After pulse compression of 81 fs, 93 μJ pulses are obtained at a 1 MHz repetition rate. PMID:22139257

  14. Neodymium glass laser with a pulse energy of 220 J and a pulse repetition rate of 0.02 Hz

    SciTech Connect

    Kuzmin, A A; Kulagin, O V; Khazanov, Efim A; Shaykin, A A

    2013-07-31

    A compact neodymium glass laser with a pulse energy of 220 J and a record-high pulse repetition rate of 0.02 Hz (pulse duration 30 ns) is developed. Thermally induced phase distortions are compensated using wave phase conjugation. The integral depolarisation of radiation is decreased to 0.4% by using linear compensation schemes. The second harmonic of laser radiation can be used for pumping Ti : sapphire multipetawatt complexes. (letters)

  15. Breaking the trade-off: rainforest bats maximize bandwidth and repetition rate of echolocation calls as they approach prey

    PubMed Central

    Schmieder, Daniela A.; Kingston, Tigga; Hashim, Rosli; Siemers, Björn M.

    2010-01-01

    Both mammals and birds experience a performance trade-off between producing vocalizations with high bandwidths and at high repetition rate. Echolocating bats drastically increase repetition rate from 2–20 calls s−1 up to about 170 calls s−1 prior to intercepting airborne prey in order to accurately track prey movement. In turn, bandwidth drops to about 10–30 kHz for the calls of this ‘final buzz’. We have now discovered that Southeast Asian rainforest bats (in the vespertilionid subfamilies Kerivoulinae and Murininae) are able to maintain high call bandwidths at very high repetition rates throughout approach to prey. Five species of Kerivoula and Phoniscus produced call bandwidths of between 78 and 170 kHz at repetition rates of 140–200 calls s−1 and two of Murina at 80 calls s−1. The ‘typical’ and distinct drop in call frequency was present in none of the seven species. This stands in striking contrast to our present view of echolocation during approach to prey in insectivorous bats, which was established largely based on European and American members of the same bat family, the Vespertilionidae. Buzz calls of Kerivoula pellucida had mean bandwidths of 170 kHz and attained maximum starting frequencies of 250 kHz which makes them the most broadband and most highly pitched tonal animal vocalization known to date. We suggest that the extreme vocal performance of the Kerivoulinae and Murininae evolved as an adaptation to echolocating and tracking arthropods in the dense rainforest understorey. PMID:20356884

  16. High average power, high repetition rate table-top soft x-ray lasers for applications in nanoscience and nanotechnology

    NASA Astrophysics Data System (ADS)

    Reagan, Brendan; Wernsing, Keith; Baumgarten, Cory; Durivage, Leon; Berrill, Mark; Curtis, Alden; Furch, Federico; Luther, Brad; Woolston, Mark; Patel, Dinesh; Menoni, Carmen; Shlyaptsev, Vyacheslav; Rocca, Jorge

    2014-03-01

    There is great interest in table-top sources of bright coherent soft x-ray radiation for nanoscale applications. We report the demonstration of a compact, high repetition rate soft x-ray laser operating at wavelengths between 10.9nm to 18.9nm, including the generation of 0.15mW average power at λ = 18.9nm and 0.1mW average power at λ = 13.9nm. These short wavelength lasers were driven by an all diode pumped, chirped pulse amplification laser based on cryogenically-cooled Yb:YAG amplifiers that produces 1 Joule, picosecond duration pulses at 100 Hz repetition rate. Irradiation of solid targets results in the production of plasmas with large transient population inversions on the 4d1S0 --> 4p1P1 transition of Ni-like ions. Optimization of this high repetition rate laser combined with the development of high shot capacity, rotating targets has allowed the uninterrupted operation of this soft x-ray laser for hundreds of thousands of consecutive shots, making it suitable for a number of applications requiring high photon flux at short wavelengths. Work was supported by the NSF ERC for Extreme Ultraviolet Science and Technology using equipment developed under NSF Award MRI-ARRA 09-561, and by the AMOS program of the Office of Basic Energy Sciences, US Department of Energy.

  17. MAPLE-deposited PFO films: influence of the laser fluence and repetition rate on the film emission and morphology

    NASA Astrophysics Data System (ADS)

    Caricato, A. P.; Anni, M.; Cesaria, M.; Lattante, S.; Leggieri, G.; Leo, C.; Martino, M.; Perulli, A.; Resta, V.

    2015-06-01

    The Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique is emerging as an alternative route to the conventional methods for depositing organic materials, although the MAPLE-deposited films very often present high surface roughness and characteristic morphological features. Films of the blue-emitting polymer, poly(9,9-dioctylfluorene)—PFO, have been deposited by MAPLE to investigate the influence of the laser fluence and repetition rate on both their topography and emission properties. The laser fluence has been changed from 150 up to 450 mJ/cm2, while laser repetition rates of 2 and 10 Hz have been considered. The interplay/relationship between the topography and the emission properties of the MAPLE-deposited films has been studied by confocal microscopy, photoluminescence spectrometry and atomic force microscopy. It has been found that under high irradiation (fluence of 450 mJ/cm2) conditions, the sample surface is characterized by bubbles presenting the intrinsic PFO blue emission. Instead, while improvements in the film morphology can be observed for lowered fluence and laser repetition rate, green emission becomes predominant in such conditions. Such result is very interesting to better understand the MAPLE ablation mechanism, which is discussed in this study.

  18. High speed laser drilling of metals using a high repetition rate, high average power ultrafast fiber CPA system.

    PubMed

    Ancona, A; Röser, F; Rademaker, K; Limpert, J; Nolte, S; Tünnermann, A

    2008-06-01

    We present an experimental study on the drilling of metal targets with ultrashort laser pulses at high repetition rates (from 50 kHz up to 975 kHz) and high average powers (up to 68 Watts), using an ytterbium-doped fiber CPA system. The number of pulses to drill through steel and copper sheets with thicknesses up to 1 mm have been measured as a function of the repetition rate and the pulse energy. Two distinctive effects, influencing the drilling efficiency at high repetition rates, have been experimentally found and studied: particle shielding and heat accumulation. While the shielding of subsequent pulses due to the ejected particles leads to a reduced ablation efficiency, this effect is counteracted by heat accumulation. The experimental data are in good qualitative agreement with simulations of the heat accumulation effect and previous studies on the particle emission. However, for materials with a high thermal conductivity as copper, both effects are negligible for the investigated processing parameters. Therefore, the full power of the fiber CPA system can be exploited, which allows to trepan high-quality holes in 0.5mm-thick copper samples with breakthrough times as low as 75 ms. PMID:18545607

  19. Efficient high repetition rate electro-optic Q-switched laser with an optically active langasite crystal.

    PubMed

    Ma, Shihui; Yu, Haohai; Zhang, Huaijin; Han, Xuekun; Lu, Qingming; Ma, Changqin; Boughton, Robert I; Wang, Jiyang

    2016-01-01

    With an optically active langasite (LGS) crystal as the electro-optic Q-switch, we demonstrate an efficient Q-switched laser with a repetition rate of 200 kHz. Based on the theoretical analysis of the interaction between optical activity and electro-optic property, the optical activity of the crystal has no influence on the birefringence during Q-switching if the quarter wave plate used was rotated to align with the polarization direction. With a Nd:LuVO4 crystal possessing a large emission cross-section and a short fluorescence lifetime as the gain medium, a stable LGS Q-switched laser was designed with average output power of 4.39 W, corresponding to a slope efficiency of 29.4% and with a minimum pulse width of 5.1 ns. This work represents the highest repetition rate achieved so far in a LGS Q-switched laser and it can provide a practical Q-switched laser with a tunable high repetition rates for many applications, such as materials processing, laser ranging, medicine, military applications, biomacromolecule materials, remote sensing, etc. PMID:27461819

  20. All-fiberized SBS-based high repetition rate sub-nanosecond Yb fiber laser for supercontinuum generation

    NASA Astrophysics Data System (ADS)

    Hua, Dacheng; Su, Jianjia; Cui, Wei; Yan, Yaxi; Jiang, Peipei

    2014-12-01

    We report an all-fiberized SBS-based high repetition rate sub-nanosecond Yb fiber laser for supercontinuum generation. The high repetition rate ns laser pulses were produced from a fiber Bragg grating (FBG)-constructed fiber laser cavity consisting of a piece of double cladding Yb fiber as the gain medium and a short piece of Bi/Cr-doped fiber as a saturable absorber (SA). By optimizing the fiber length of the Bi/Cr-doped fiber and the reflectivity of the FBG, the Q-switching state of the fiber laser can be adjusted so that the energy storing condition within the fiber cavity can assure the start of stimulated Brillouin scattering (SBS) and as a result, compress the laser pulse duration. The fiber laser had an average laser power output of 1.2 W at 1064 nm with pulse repetition rate of about 80 kHz, almost four times the reported results. The pulse duration was about 1 ns with peak power of about 15 kW. After one stage of amplification, the laser power was raised to about 3 W and was used to pump a 20 m long photonic crystal fiber (PCF). Supercontiuum (SC) laser output was obtained with average power up to 1.24 W and spectrum spanning from 550 to 2200 nm.

  1. Efficient high repetition rate electro-optic Q-switched laser with an optically active langasite crystal

    PubMed Central

    Ma, Shihui; Yu, Haohai; Zhang, Huaijin; Han, Xuekun; Lu, Qingming; Ma, Changqin; Boughton, Robert I.; Wang, Jiyang

    2016-01-01

    With an optically active langasite (LGS) crystal as the electro-optic Q-switch, we demonstrate an efficient Q-switched laser with a repetition rate of 200 kHz. Based on the theoretical analysis of the interaction between optical activity and electro-optic property, the optical activity of the crystal has no influence on the birefringence during Q-switching if the quarter wave plate used was rotated to align with the polarization direction. With a Nd:LuVO4 crystal possessing a large emission cross-section and a short fluorescence lifetime as the gain medium, a stable LGS Q-switched laser was designed with average output power of 4.39 W, corresponding to a slope efficiency of 29.4% and with a minimum pulse width of 5.1 ns. This work represents the highest repetition rate achieved so far in a LGS Q-switched laser and it can provide a practical Q-switched laser with a tunable high repetition rates for many applications, such as materials processing, laser ranging, medicine, military applications, biomacromolecule materials, remote sensing, etc. PMID:27461819

  2. Performance of large aperture tapered fiber phase conjugate mirror with high pulse energy and 1-kHz repetition rate.

    PubMed

    Zhao, Zhigang; Dong, Yantao; Pan, Sunqiang; Liu, Chong; Chen, Jun; Tong, Lixin; Gao, Qingsong; Tang, Chun

    2012-01-16

    A large aperture fused silica tapered fiber phase conjugate mirror is presented with a maximum 70% stimulated Brillouin scattering (SBS) reflectivity, which is obtained with 1 kHz repetition rate, 15 ns pulse width and 38 mJ input pulse energy. To the best of our knowledge, this is the highest SBS reflectivity ever reported by using optical fiber as a phase conjugate mirror for such high pulse repetition rate (1 kHz) and several tens of millijoule (mJ) input pulse energy. The influences of fiber end surface quality and pump pulse widths on SBS reflectivity are investigated experimentally. The results show that finer fiber end surface quality and longer input pulse widths are preferred for obtaining higher SBS reflectivity with higher input pulse energy. Double passing amplification experiments are also performed. 52 mJ pulse energy is achieved at 1 kHz repetition rate, with a reflected SBS pulse width of 1.5 ns and a M(2) factor of 2.3. The corresponding peak power reaches 34.6 MW. Obvious beam quality improvement is observed. PMID:22274534

  3. Efficient high repetition rate electro-optic Q-switched laser with an optically active langasite crystal

    NASA Astrophysics Data System (ADS)

    Ma, Shihui; Yu, Haohai; Zhang, Huaijin; Han, Xuekun; Lu, Qingming; Ma, Changqin; Boughton, Robert I.; Wang, Jiyang

    2016-07-01

    With an optically active langasite (LGS) crystal as the electro-optic Q-switch, we demonstrate an efficient Q-switched laser with a repetition rate of 200 kHz. Based on the theoretical analysis of the interaction between optical activity and electro-optic property, the optical activity of the crystal has no influence on the birefringence during Q-switching if the quarter wave plate used was rotated to align with the polarization direction. With a Nd:LuVO4 crystal possessing a large emission cross-section and a short fluorescence lifetime as the gain medium, a stable LGS Q-switched laser was designed with average output power of 4.39 W, corresponding to a slope efficiency of 29.4% and with a minimum pulse width of 5.1 ns. This work represents the highest repetition rate achieved so far in a LGS Q-switched laser and it can provide a practical Q-switched laser with a tunable high repetition rates for many applications, such as materials processing, laser ranging, medicine, military applications, biomacromolecule materials, remote sensing, etc.

  4. Repetitive flash x-ray generator operated at low-dose rates for a medical x-ray television system

    NASA Astrophysics Data System (ADS)

    Sato, Eiichi; Isobe, Hiroshi; Takahashi, Kei; Tamakawa, Yoshiharu; Yanagisawa, Toru

    1991-04-01

    The fundamental studies for the repetitive flash x-ray generator operated at lowdose rates for a medical x-ray television system are described. This x-ray generator consisted of the following components: a high-voltage power supply, an energy storage condenser of lOOnF, a coaxial cable condenser with a capacity of l000pF, a repetitive impulse switching system, a turbo molecular pump, and an x-ray tube having a cold cathode. The condenser was charged from 40 to 70kV by a power supply, and the electric charges stored in the condenser were discharged repetitively by using a trigger electrode operated by an impulse switching system. The x-ray tube was of the triode-type which was connected to the turbo molecular pump and had a large discharge impedance in order to prevent the damped oscillations of the tube current and voltage. The maximum tube voltage was equivalent to the initial charged voltage, and the peak current was less than 70A. The durations were about 2ps, and the x-ray intensities were less than 1. OpC/kg at 0. 5m per pulse. The repetition frequency was less than 50Hz, and the effective focal spot size was equivalent to the anode diameter of 3. 0mm. For the x-ray television system used in conjunction with this repetitive pulsed x-ray generator, since the electromagnetic noise primarily caused by the high tube current was decreased, noise-free stroboscopic radiography performed by the television system could be realized.

  5. LD pumped high-repetition-rate high-power 532nm Nd:YAG/LBO solid state laser

    NASA Astrophysics Data System (ADS)

    Li, Pingxue; Liu, Dongyu; Chi, Junjie; Yang, Chun; Zhao, Ziqiang; Hu, Haowei; Zhang, Guangju; Yao, Yifei

    2013-09-01

    Diode pumped solid state 532 nm green laser is widely required for many industrial, medical and scientific applications. Among most of these applications, high power quasi-continuous-wave (QCW) green laser output is demanded. This can be efficiently achieved through a diode-side-pumped acoustic-optic Q-switched Nd:YAG laser with an intracavity second harmonic generation (SHG). In our experiment, LBO crystal is used for the second harmonic generation of high-average-power lasers of near infrared (NIR) range, though its effective NLO coefficient deff is relatively small. It is because of its high damage threshold (greater than 2.5 GW/cm2), large acceptance angle, small walk-off angle, and the nonhygroscopic characteristic. In this paper, we reported a high-repetition-rate high-power diode-side-pumped AO Q-switched Nd:YAG 532 nm laser. A plane-plane cavity with two rods, two AO Q-switches and the type II critical phase-matched LBO at room temperature were employed. Under the LD pump power of 480 W, 95.86 W at 1064 nm wavelength was achieved when the repetition rate was 15 kHz, and the 532 nm average output power of 44.77 W was obtained, with a pulse width of 111.7 ns, corresponding to an optical to optical conversion efficiency of 46.7% from 1064 nm to 532 nm. The 532 nm average output power was 40.10 W at a repetition rate of 10 kHz with a pulse width of 78.65 ns. The output characteristics of the SHG varying with the pumping current and the pulse repetition frequency (PRF) of the laser were also investigated. Further improvement of the SHG is under study.

  6. Laser-diode pumped self-mode-locked praseodymium visible lasers with multi-gigahertz repetition rate.

    PubMed

    Zhang, Yuxia; Yu, Haohai; Zhang, Huaijin; Di Lieto, Alberto; Tonelli, Mauro; Wang, Jiyang

    2016-06-15

    We demonstrate efficient laser-diode pumped multi-gigahertz (GHz) self-mode-locked praseodymium (Pr3+) visible lasers with broadband spectra from green to deep red for the first time to our knowledge. With a Pr3+-doped GdLiF4 crystal, stable self-mode-locked visible pulsed lasers at the wavelengths of 522 nm, 607 nm, 639 nm, and 720 nm have been obtained with the repetition rates of 2.8 GHz, 3.1 GHz, 3.1 GHz, and 3.0 GHz, respectively. The maximum output power was 612 mW with the slope efficiency of 46.9% at 639 nm. The mode-locking mechanism was theoretically analyzed. The stable second-harmonic mode-locking with doubled repetition frequency was also realized based on the Fabry-Perot effect formed in the laser cavity. In addition, we find that the polarization directions were turned with lasing wavelengths. This work may provide a new way for generating efficient ultrafast pulses with high- and changeable-repetition rates in the visible range. PMID:27304265

  7. Oral-diadochokinetic rates for Hebrew-speaking school-age children: real words vs. non-words repetition.

    PubMed

    Icht, Michal; Ben-David, Boaz M

    2015-02-01

    Oral-diadochokinesis (DDK) tasks are a common tool for evaluating speech disorders. Usually, these tasks involve repetitions of non-words. It has been suggested that repeating real words can be more suitable for preschool children. But, the impact of using real words with elementary school children has not been studied yet. This study evaluated oral-DDK rates for Hebrew-speaking elementary school children using non-words and real words. The participants were 60 children, 9-11 years old, with normal speech and language development, who were asked to repeat "pataka" (non-word) and "bodeket" (Hebrew real word). Data replicate the advantage generally found for real word repetition with preschoolers. Children produced real words faster than non-words for all age groups, and repetition rates were higher for the older children. The findings suggest that adding real words to the standard oral-DDK task with elementary school children may provide a more comprehensive picture of oro-motor function. PMID:25259403

  8. Low-noise, low repetition rate, semiconductor-based mode-locked laser source suitable for high bandwidth photonic analog-digital conversion.

    PubMed

    Mandridis, Dimitrios; Ozdur, Ibrahim; Quinlan, Franklyn; Akbulut, Mehmetcan; Plant, Jason J; Juodawlkis, Paul W; Delfyett, Peter J

    2010-05-20

    A semiconductor-based mode-locked laser source with low repetition rate, ultralow amplitude, and phase noise is introduced. A harmonically mode-locked semiconductor-based ring laser is time demultiplexed at a frequency equal to the cavity fundamental frequency (80MHz), resulting in a low repetition rate pulse train having ultralow amplitude and phase noise, properties usually attributed to multigigahertz repetition rate lasers. The effect of time demultiplexing on the phase noise of harmonically mode-locked lasers is analyzed and experimentally verified. PMID:20490247

  9. High-peak-power optically pumped AlGaInAs eye-safe laser at 500-kHz repetition rate with an intracavity diamond heat spreader

    NASA Astrophysics Data System (ADS)

    Chen, Y.-F.; Su, K. W.; Chen, W. L.; Huang, K. F.; Chen, Y. F.

    2012-08-01

    We report on a compact efficient high-repetition-rate (>100 kHz) optically pumped AlGaInAs nanosecond eye-safe laser at 1525 nm. A diamond heat spreader bonded to the gain chip is employed to improve the heat removal. At a pump power of 13.3 W, the average output power at a repetition rate 200 kHz is up to 3.12 W, corresponding to a peak output power of 560 W. At a repetition rate 500 kHz, the maximum average power and peak power are found to be 2.32 W and 170 W, respectively.

  10. 3.7 GHz repetition rate operated narrow-bandwidth picosecond pulsed Yb fiber amplifier with an all-fiber multiplier

    NASA Astrophysics Data System (ADS)

    Wei, K. H.; Wen, R. H.; Guo, Y.

    2016-04-01

    A high power picosecond pulsed Yb fiber amplifier with a pulse repetition rate of 3.7 GHz is experimentally demonstrated. The seed is a gain switched distributed Bragg reflection (DBR) structured laser diode (LD) with a pulse duration of 130 ps and a repetition rate of 460 MHz. The pulse repetition rate is increased to 3.7 GHz by introducing an all-fiber multiplier, which is composed of four 2  ×  2 structured fiber couplers. The multiplied pulse train is amplified to 81 W through two stage Yb fiber amplifiers.