WorldWideScience

Sample records for average power femtosecond

  1. 16.2-W average power from a diode-pumped femtosecond Yb:YAG thin disk laser.

    Science.gov (United States)

    Aus der Au, J; Spühler, G J; Südmeyer, T; Paschotta, R; Hövel, R; Moser, M; Erhard, S; Karszewski, M; Giesen, A; Keller, U

    2000-06-01

    We demonstrate a power-scalable concept for high-power all-solid-state femtosecond lasers, based on passive mode locking of Yb:YAG thin disk lasers with semiconductor saturable-absorber mirrors. We obtained 16.2 W of average output power in pulses with 730-fs duration, 0.47-muJ pulse energy, and 560-kW peak power. This is to our knowledge the highest average power reported for a laser oscillator in the subpicosecond regime. Single-pass frequency doubling through a 5-mm-long lithium triborate crystal (LBO) yields 8-W average output power of 515-nm radiation. PMID:18064208

  2. High-average-power femtosecond pulse generation in the blue using BiB3O6

    Science.gov (United States)

    Ghotbi, M.; Ebrahim-Zadeh, M.; Majchrowski, A.; Michalski, E.; Kityk, I. V.

    2004-11-01

    Efficient generation of tunable femtosecond pulses in the blue is reported in the nonlinear crystal BiB3O6. By use of fundamental pulses from a mode-locked Ti:sapphire laser at 76 MHz, single-pass second-harmonic average powers of as much as 830 mW have been generated at 50% conversion efficiency, and a tunable range of 375-435 nm in the blue is demonstrated. Temporal measurements using cross correlation of the fundamental and second-harmonic pulses in a 100-µm-thick ß-BaB2O4 crystal result in blue pulse durations of 220 fs for 130-fs fundamental pulses. Direct experimental comparison with ß-BaB2O4 confirms the superior performance BiB3O6 for second-harmonic generation of femtosecond pulses.

  3. High average power, high energy, femto-second fiber chirped pulse amplification system

    OpenAIRE

    He, F.; Price, J.H.V.; De Malinowski, A.; Piper, A.; Ibsen, M; D.J.Richardson; Dawson, J.W.; Siders, C.W.; Britten, J.A.; Barty, C.P.J.

    2007-01-01

    We have demonstrated an Yb-fiber laser system incorporating a CFBG stretcher, bandwidth optimised amplifiers and dielectric grating compressor. The system produced 135 W average power with pulse energy of 13.5 µJ. The recompressed pulse duration was 360 fs.

  4. Diode-pumped high-average power femtosecond fiber laser systems

    OpenAIRE

    Fermann, M. E.; Galvanauskas, A.; Harter, D; Minelly, J. D.; Caplen, J.E.; Chen, Z.J.; Payne, D. N.

    1996-01-01

    The recent progress in femtosecond laser technology is currently driven by the prospect of fully diode pumped systems, which promise the eventual replacement of the well-established Ti:sapphire laser in the field of ultrafast optics. Apart from more traditional diode-pumped solid-state lasers, fiber-based systems have received an increasing amount of attention due to the uniquely compact assemblies possible with fiber lasers. However, to date fiber lasers have replaced Ti:sapphire-based syste...

  5. Femtosecond pulse generation at 50 W average powers from an Yb:KYW-Yb:YAG planar-waveguide MOPA

    Directory of Open Access Journals (Sweden)

    Baker H. J.

    2013-03-01

    Full Text Available An Yb:YAG planar-waveguide power amplifier seeded by an Yb:KYW master oscillator is reported. The system produced 700-fs pulses at 1032 nm at average output powers of 50 W and a frequency of 53 MHz.

  6. Air-clad chirally-coupled-core Yb-fiber femtosecond oscillator with >10W average power

    Directory of Open Access Journals (Sweden)

    Ma Xiuquan

    2013-03-01

    Full Text Available We demonstrate high-power (> 10 W, 300-fs mode-locked oscillators at 83-MHz repetition rate using air-clad Chirally-Coupled-Core Yb-fiber with 37-µm central-core diameter, corresponding to a 30-µm mode-field-diameter.

  7. Diode-pumped continuous-wave and femtosecond Cr:LiCAF lasers with high average power in the near infrared, visible and near ultraviolet

    OpenAIRE

    Demirbas, Umit; Baali, Ilyes; Acar, Durmus Alp Emre; Leitenstorfer, Alfred

    2015-01-01

    We demonstrate continuous-wave (cw), cw frequency-doubled, cw mode-locked and Q-switched mode-locked operation of multimode diode-pumped Cr:LiCAF lasers with record average powers. Up to 2.54 W of cw output is obtained around 805 nm at an absorbed pump power of 5.5 W. Using intracavity frequency doubling with a BBO crystal, 0.9 W are generated around 402 nm, corresponding to an optical-to-optical conversion efficiency of 12%. With an intracavity birefringent tuning plate, the fundamental and ...

  8. Diode-pumped continuous-wave and femtosecond Cr:LiCAF lasers with high average power in the near infrared, visible and near ultraviolet.

    Science.gov (United States)

    Demirbas, Umit; Baali, Ilyes; Acar, Durmus Alp Emre; Leitenstorfer, Alfred

    2015-04-01

    We demonstrate continuous-wave (cw), cw frequency-doubled, cw mode-locked and Q-switched mode-locked operation of multimode diode-pumped Cr:LiCAF lasers with record average powers. Up to 2.54 W of cw output is obtained around 805 nm at an absorbed pump power of 5.5 W. Using intracavity frequency doubling with a BBO crystal, 0.9 W are generated around 402 nm, corresponding to an optical-to-optical conversion efficiency of 12%. With an intracavity birefringent tuning plate, the fundamental and frequency-doubled laser output is tuned continuously in a broad wavelength range from 745 nm to 885 nm and from 375 to 440 nm, respectively. A saturable Bragg reflector is used to initiate and sustain mode locking. In the cw mode-locked regime, the Cr:LiCAF laser produces 105-fs long pulses near 810 nm with an average power of 0.75 W. The repetition rate is 96.4 MHz, resulting in pulse energies of 7.7 nJ and peak powers of 65 kW. In Q-switched mode-locked operation, pulses with energies above 150 nJ are generated.

  9. Diode-pumped continuous-wave and femtosecond Cr:LiCAF lasers with high average power in the near infrared, visible and near ultraviolet.

    Science.gov (United States)

    Demirbas, Umit; Baali, Ilyes; Acar, Durmus Alp Emre; Leitenstorfer, Alfred

    2015-04-01

    We demonstrate continuous-wave (cw), cw frequency-doubled, cw mode-locked and Q-switched mode-locked operation of multimode diode-pumped Cr:LiCAF lasers with record average powers. Up to 2.54 W of cw output is obtained around 805 nm at an absorbed pump power of 5.5 W. Using intracavity frequency doubling with a BBO crystal, 0.9 W are generated around 402 nm, corresponding to an optical-to-optical conversion efficiency of 12%. With an intracavity birefringent tuning plate, the fundamental and frequency-doubled laser output is tuned continuously in a broad wavelength range from 745 nm to 885 nm and from 375 to 440 nm, respectively. A saturable Bragg reflector is used to initiate and sustain mode locking. In the cw mode-locked regime, the Cr:LiCAF laser produces 105-fs long pulses near 810 nm with an average power of 0.75 W. The repetition rate is 96.4 MHz, resulting in pulse energies of 7.7 nJ and peak powers of 65 kW. In Q-switched mode-locked operation, pulses with energies above 150 nJ are generated. PMID:25968727

  10. JAERI femtosecond pulsed and tens-kilowatts average-powered free-electron lasers and their applications of large-scaled non-thermal manufacturing in nuclear energy industry

    International Nuclear Information System (INIS)

    We first reported the novel method that femto-second (fs) lasers of the low average power Ti: Sapphire one, the JAERI high average power free-electron laser, excimer laser, fiber laser and so on could peel off and remove both stress corrosion cracking (SCC) origins of the cold-worked (CW) and very crack-susceptible material, and residual tensile stress in the hardened surface of low-carbon stainless steel cubic samples for nuclear reactor internals as a proof of principle experiment except for the last and third origin of corrosive environment. Because it has been successfully demonstrated that the fs lasers could clearly remove the two SCC origins, we could resultantly prevent the cold-worked SCC in many field near future. The SCC is a well known phenomenon in modern material sciences, technologies, and industries, and defined as an insidious failure mechanism that is caused by the corrosive environment, and the crack-susceptible material and the surface residual tensile stress simultaneously. There are a large number of famous SCC examples for damaging stainless steels, aluminum alloys, brass and other alloy metals in many different cases. In many boiling light-water reactor (BWR) nuclear power plants and a few pressurized light water reactor (PWR) ones in Japan and the world up to now, a large number of the deep and wide cracks have been recently found in the reactor-grade low-carbon stainless steel components of core shroud, control-blade handle, re-circulating pipes, sheath and other internals in the reactor vessel under very low or no applied stresses. These cracks have been thought to be initiated from the crack-susceptible like very small-sized cracks, pinholes, concentrated dislocation defects and so on in the hardened surface, which were originated from cold-work machining processes in reactor manufacturing factories, and to be insidiously penetrated widely into the deep inside under the residual tensile stress and corrosive environment, and under no

  11. High average power supercontinuum sources

    Indian Academy of Sciences (India)

    J C Travers

    2010-11-01

    The physical mechanisms and basic experimental techniques for the creation of high average spectral power supercontinuum sources is briefly reviewed. We focus on the use of high-power ytterbium-doped fibre lasers as pump sources, and the use of highly nonlinear photonic crystal fibres as the nonlinear medium. The most common experimental arrangements are described, including both continuous wave fibre laser systems with over 100 W pump power, and picosecond mode-locked, master oscillator power fibre amplifier systems, with over 10 kW peak pump power. These systems can produce broadband supercontinua with over 50 and 1 mW/nm average spectral power, respectively. Techniques for numerical modelling of the supercontinuum sources are presented and used to illustrate some supercontinuum dynamics. Some recent experimental results are presented.

  12. Power convergence of Abel averages

    OpenAIRE

    Kozitsky, Yuri; Shoikhet, David; Zemanek, Jaroslav

    2012-01-01

    Necessary and sufficient conditions are presented for the Abel averages of discrete and strongly continuous semigroups, $T^k$ and $T_t$, to be power convergent in the operator norm in a complex Banach space. These results cover also the case where $T$ is unbounded and the corresponding Abel average is defined by means of the resolvent of $T$. They complement the classical results by Michael Lin establishing sufficient conditions for the corresponding convergence for a bounded $T$.

  13. High-power synchronously pumped femtosecond Raman fiber laser.

    Science.gov (United States)

    Churin, D; Olson, J; Norwood, R A; Peyghambarian, N; Kieu, K

    2015-06-01

    We report a high-power synchronously pumped femtosecond Raman fiber laser operating in the normal dispersion regime. The Raman laser is pumped by a picosecond Yb(3+)-doped fiber laser. It produces highly chirped pulses with energy up to 18 nJ, average power of 0.76 W and 88% efficiency. The pulse duration is measured to be 147 fs after external compression. We observed two different regimes of operation of the laser: coherent and noise-like regime. Both regimes were experimentally characterized. Numerical simulations are in a good agreement with experimental results. PMID:26030549

  14. High-power Yb:YAG single-crystal fiber amplifiers for femtosecond lasers

    Science.gov (United States)

    Lesparre, Fabien; Martial, Igor; Didierjean, Julien; Gomes, Jean Thomas; Pallmann, Wolfgang; Resan, Bojan; Loescher, André; Negel, Jan-Phillipp; Graf, Thomas; Abdou Ahmed, Marwan; Balembois, François; Georges, Patrick

    2015-02-01

    We describe a multi-stages single crystal fiber (SCF) amplifier for the amplification of femtosecond pulses with radial or azimuthal polarization in view of high speed material processing (surface structuring, drilling). We demonstrate a three stages diode-pumped Yb:YAG single crystal fiber amplifier to achieve femtosecond pulses at an average power of 85W at 20 MHz in radial and azimuthal polarization.

  15. High average-power induction linacs

    Energy Technology Data Exchange (ETDEWEB)

    Prono, D.S.; Barrett, D.; Bowles, E.; Caporaso, G.J.; Chen, Yu-Jiuan; Clark, J.C.; Coffield, F.; Newton, M.A.; Nexsen, W.; Ravenscroft, D.

    1989-03-15

    Induction linear accelerators (LIAs) are inherently capable of accelerating several thousand amperes of /approximately/ 50-ns duration pulses to > 100 MeV. In this paper we report progress and status in the areas of duty factor and stray power management. These technologies are vital if LIAs are to attain high average power operation. 13 figs.

  16. HIGH AVERAGE POWER OPTICAL FEL AMPLIFIERS

    International Nuclear Information System (INIS)

    Historically, the first demonstration of the optical FEL was in an amplifier configuration at Stanford University [l]. There were other notable instances of amplifying a seed laser, such as the LLNL PALADIN amplifier [2] and the BNL ATF High-Gain Harmonic Generation FEL [3]. However, for the most part FELs are operated as oscillators or self amplified spontaneous emission devices. Yet, in wavelength regimes where a conventional laser seed can be used, the FEL can be used as an amplifier. One promising application is for very high average power generation, for instance FEL's with average power of 100 kW or more. The high electron beam power, high brightness and high efficiency that can be achieved with photoinjectors and superconducting Energy Recovery Linacs (ERL) combine well with the high-gain FEL amplifier to produce unprecedented average power FELs. This combination has a number of advantages. In particular, we show that for a given FEL power, an FEL amplifier can introduce lower energy spread in the beam as compared to a traditional oscillator. This properly gives the ERL based FEL amplifier a great wall-plug to optical power efficiency advantage. The optics for an amplifier is simple and compact. In addition to the general features of the high average power FEL amplifier, we will look at a 100 kW class FEL amplifier is being designed to operate on the 0.5 ampere Energy Recovery Linac which is under construction at Brookhaven National Laboratory's Collider-Accelerator Department

  17. Scalability of components for kW-level average power few-cycle lasers.

    Science.gov (United States)

    Hädrich, Steffen; Rothhardt, Jan; Demmler, Stefan; Tschernajew, Maxim; Hoffmann, Armin; Krebs, Manuel; Liem, Andreas; de Vries, Oliver; Plötner, Marco; Fabian, Simone; Schreiber, Thomas; Limpert, Jens; Tünnermann, Andreas

    2016-03-01

    In this paper, the average power scalability of components that can be used for intense few-cycle lasers based on nonlinear compression of modern femtosecond solid-state lasers is investigated. The key components of such a setup, namely, the gas-filled waveguides, laser windows, chirped mirrors for pulse compression and low dispersion mirrors for beam collimation, focusing, and beam steering are tested under high-average-power operation using a kilowatt cw laser. We demonstrate the long-term stable transmission of kW-level average power through a hollow capillary and a Kagome-type photonic crystal fiber. In addition, we show that sapphire substrates significantly improve the average power capability of metal-coated mirrors. Ultimately, ultrabroadband dielectric mirrors show negligible heating up to 1 kW of average power. In summary, a technology for scaling of few-cycle lasers up to 1 kW of average power and beyond is presented.

  18. Scalability of components for kW-level average power few-cycle lasers.

    Science.gov (United States)

    Hädrich, Steffen; Rothhardt, Jan; Demmler, Stefan; Tschernajew, Maxim; Hoffmann, Armin; Krebs, Manuel; Liem, Andreas; de Vries, Oliver; Plötner, Marco; Fabian, Simone; Schreiber, Thomas; Limpert, Jens; Tünnermann, Andreas

    2016-03-01

    In this paper, the average power scalability of components that can be used for intense few-cycle lasers based on nonlinear compression of modern femtosecond solid-state lasers is investigated. The key components of such a setup, namely, the gas-filled waveguides, laser windows, chirped mirrors for pulse compression and low dispersion mirrors for beam collimation, focusing, and beam steering are tested under high-average-power operation using a kilowatt cw laser. We demonstrate the long-term stable transmission of kW-level average power through a hollow capillary and a Kagome-type photonic crystal fiber. In addition, we show that sapphire substrates significantly improve the average power capability of metal-coated mirrors. Ultimately, ultrabroadband dielectric mirrors show negligible heating up to 1 kW of average power. In summary, a technology for scaling of few-cycle lasers up to 1 kW of average power and beyond is presented. PMID:26974623

  19. Industrial Applications of High Average Power FELS

    CERN Document Server

    Shinn, Michelle D

    2005-01-01

    The use of lasers for material processing continues to expand, and the annual sales of such lasers exceeds $1 B (US). Large scale (many m2) processing of materials require the economical production of laser powers of the tens of kilowatts, and therefore are not yet commercial processes, although they have been demonstrated. The development of FELs based on superconducting RF (SRF) linac technology provides a scaleable path to laser outputs above 50 kW in the IR, rendering these applications economically viable, since the cost/photon drops as the output power increases. This approach also enables high average power ~ 1 kW output in the UV spectrum. Such FELs will provide quasi-cw (PRFs in the tens of MHz), of ultrafast (pulsewidth ~ 1 ps) output with very high beam quality. This talk will provide an overview of applications tests by our facility's users such as pulsed laser deposition, laser ablation, and laser surface modification, as well as present plans that will be tested with our upgraded FELs. These upg...

  20. High-power femtosecond pulse generation in a passively mode-locked Nd:SrLaAlO4 laser

    Science.gov (United States)

    Liu, Shan-De; Dong, Lu-Lu; Zheng, Li-He; Berkowski, Marek; Su, Liang-Bi; Ren, Ting-Qi; Peng, Yan-Dong; Hou, Jia; Zhang, Bai-Tao; He, Jing-Liang

    2016-07-01

    A high optical quality Nd:SrLaAlO4 (Nd:SLA) crystal was grown using the Czochralski method and showed broad fluorescence spectrum with a full width at half maximum value of 34 nm, which is beneficial for generating femtosecond laser pulses. A stable diode-pumped passively mode-locked femtosecond Nd:SLA laser with 458 fs pulse duration was achieved for the first time at a central wavelength of 1077.9 nm. The average output power of the continuous-wave mode-locked laser was 520 mW and the repetition rate was 78.5 MHz.

  1. Extended femtosecond laser wavelength range to 330 nm in a high power LBO based optical parametric oscillator.

    Science.gov (United States)

    Fan, Jintao; Gu, Chenglin; Wang, Chingyue; Hu, Minglie

    2016-06-13

    We experimentally demonstrate a compact tunable, high average power femtosecond laser source in the ultraviolet (UV) regime. The laser source is based on intra-cavity frequency doubling of a temperature-tuned lithium tribotate (LBO) optical parametric oscillator (OPO), synchronously pumped at 520 nm by a frequency-doubled, Yb-fiber femtosecond laser amplifier system. By adjusting crystal temperature, the OPO can provide tunable visible to near-infrared (NIR) signal pulse, which have a wide spectral tuning range from 660 to 884 nm. Using a β-barium borate (BBO) crystal for intra-cavity frequency doubling, tunable femtosecond UV pulse are generated across 330~442 nm with up to 364 mW at 402 nm.

  2. Extended femtosecond laser wavelength range to 330 nm in a high power LBO based optical parametric oscillator.

    Science.gov (United States)

    Fan, Jintao; Gu, Chenglin; Wang, Chingyue; Hu, Minglie

    2016-06-13

    We experimentally demonstrate a compact tunable, high average power femtosecond laser source in the ultraviolet (UV) regime. The laser source is based on intra-cavity frequency doubling of a temperature-tuned lithium tribotate (LBO) optical parametric oscillator (OPO), synchronously pumped at 520 nm by a frequency-doubled, Yb-fiber femtosecond laser amplifier system. By adjusting crystal temperature, the OPO can provide tunable visible to near-infrared (NIR) signal pulse, which have a wide spectral tuning range from 660 to 884 nm. Using a β-barium borate (BBO) crystal for intra-cavity frequency doubling, tunable femtosecond UV pulse are generated across 330~442 nm with up to 364 mW at 402 nm. PMID:27410342

  3. High-power Yb:YAG single-crystal fiber amplifiers for femtosecond lasers in cylindrical polarization

    OpenAIRE

    Lesparre, Fabien; GOMES, Jean Thomas; Delen, Xavier; Martial, Igor; Didierjean, Julien; Pallmann, Wolfgang; Resan, Bojan; Eckerle, Michael; Graf, Thomas; Abdou Ahmed, Marwan; Druon, Frédéric; Balembois, François; Georges, Patrick

    2015-01-01

    International audience We demonstrate a three-stage diode-pumped Yb:YAG single-crystal-fiber amplifier to generate femtosecond pulses at high average powers with linear or cylindrical (i.e., radial or azimuthal) polarization. At a repetition rate of 20 MHz, 750-fs pulses were obtained at an average power of 85 W in cylindrical polarization and at 100 W in linear polarization. The report includes investigations on the use of Yb:YAG single-crystal fibers with different length/doping ratio an...

  4. New generation of high average power industry grade ultrafast ytterbium fiber lasers

    Science.gov (United States)

    Yusim, Alex; Samartsev, Igor; Shkurikhin, Oleg; Myasnikov, Daniil; Bordenyuk, Andrey; Platonov, Nikolai; Kancharla, Vijay; Gapontsev, Valentin

    2016-03-01

    We report an industrial grade picosecond and femtosecond pulse Yb fiber lasers with >100 μJ pulse energy and hundreds of Watts of average power for improved laser machining speed of sapphire and glass. This highly efficient laser offers >25% wall plug efficiency within a compact 3U rack-mountable configuration plus a long >2m fiber delivery cable. Reconfigurable features such as controllable repetition rate, fine pulse duration control, burst mode operation and adjustable pulse energy permit the customer to tailor the laser to their application.

  5. Energetic sub-2-cycle laser with 216  W average power.

    Science.gov (United States)

    Hädrich, Steffen; Kienel, Marco; Müller, Michael; Klenke, Arno; Rothhardt, Jan; Klas, Robert; Gottschall, Thomas; Eidam, Tino; Drozdy, András; Jójárt, Péter; Várallyay, Zoltán; Cormier, Eric; Osvay, Károly; Tünnermann, Andreas; Limpert, Jens

    2016-09-15

    Few-cycle lasers are essential for many research areas such as attosecond physics that promise to address fundamental questions in science and technology. Therefore, further advancements are connected to significant progress in the underlying laser technology. Here, two-stage nonlinear compression of a 660 W femtosecond fiber laser system is utilized to achieve unprecedented average power levels of energetic ultrashort or even few-cycle laser pulses. In a first compression step, 408 W, 320 μJ, 30 fs pulses are achieved, which can be further compressed to 216 W, 170 μJ, 6.3 fs pulses in a second compression stage. To the best of our knowledge, this is the highest average power few-cycle laser system presented so far. It is expected to significantly advance the fields of high harmonic generation and attosecond science. PMID:27628390

  6. Energetic sub-2-cycle laser with 216  W average power.

    Science.gov (United States)

    Hädrich, Steffen; Kienel, Marco; Müller, Michael; Klenke, Arno; Rothhardt, Jan; Klas, Robert; Gottschall, Thomas; Eidam, Tino; Drozdy, András; Jójárt, Péter; Várallyay, Zoltán; Cormier, Eric; Osvay, Károly; Tünnermann, Andreas; Limpert, Jens

    2016-09-15

    Few-cycle lasers are essential for many research areas such as attosecond physics that promise to address fundamental questions in science and technology. Therefore, further advancements are connected to significant progress in the underlying laser technology. Here, two-stage nonlinear compression of a 660 W femtosecond fiber laser system is utilized to achieve unprecedented average power levels of energetic ultrashort or even few-cycle laser pulses. In a first compression step, 408 W, 320 μJ, 30 fs pulses are achieved, which can be further compressed to 216 W, 170 μJ, 6.3 fs pulses in a second compression stage. To the best of our knowledge, this is the highest average power few-cycle laser system presented so far. It is expected to significantly advance the fields of high harmonic generation and attosecond science.

  7. Time-dependent wave packet averaged vibrational frequencies from femtosecond stimulated Raman spectra

    Science.gov (United States)

    Wu, Yue-Chao; Zhao, Bin; Lee, Soo-Y.

    2016-02-01

    Femtosecond stimulated Raman spectroscopy (FSRS) on the Stokes side arises from a third order polarization, P(3)(t), which is given by an overlap of a first order wave packet, |" separators=" Ψ2 ( 1 ) ( p u , t ) > , prepared by a narrow band (ps) Raman pump pulse, Epu(t), on the upper electronic e2 potential energy surface (PES), with a second order wave packet, resembles the zeroth order wave packet |" separators=" Ψ1 ( 0 ) ( t ) > on the lower PES spatially, but with a force on |" separators=" Ψ2 ( 1 ) ( p u , t ) > along the coordinates of the reporter modes due to displacements in the equilibrium position, so that . The observable FSRS Raman gain is related to the imaginary part of P(3)(ω). The imaginary and real parts of P(3)(ω) are related by the Kramers-Kronig relation. Hence, from the FSRS Raman gain, we can obtain the complex P(3)(ω), whose Fourier transform then gives us the complex P(3)(t) to analyze for ω ¯ j ( t ) . We apply the theory, first, to a two-dimensional model system with one conformational mode of low frequency and one reporter vibrational mode of higher frequency with good results, and then we apply it to the time-resolved FSRS spectra of the cis-trans isomerization of retinal in rhodopsin [P. Kukura et al., Science 310, 1006 (2005)]. We obtain the vibrational frequency up-shift time constants for the C12-H wagging mode at 216 fs and for the C10-H wagging mode at 161 fs which are larger than for the C11-H wagging mode at 127 fs, i.e., the C11-H wagging mode arrives at its final frequency while the C12-H and C10-H wagging modes are still up-shifting to their final values, agreeing with the findings of Yan et al. [Biochemistry 43, 10867 (2004)].

  8. High-power single-mode all-fiber femtosecond laser system and its use in continuum generation

    Science.gov (United States)

    Nicholson, Jeffrey W.; Yan, Man F.; Yablon, Andrew D.; Westbrook, Paul S.; Feder, Ken S.

    2004-10-01

    We present a source of high power femtosecond pulses at 1550 nm generating compressed pulses at the end of a single mode fiber pigtail. The system generates sub 35 femtosecond pulses at a repetition rate of 50 MHz, with average powers greater than 400 mW. The pulses are generated in a passively modelocked, erbium doped fiber laser, and amplified in a short, erbium doped amplifier. The output of the fiber amplifier consists of highly chirped picosecond pulses. These picosecond pulses are then compressed in standard single mode fiber. While the compressed pulses in the SMF pigtail do show a low pedestal that could be avoided with the use of bulk-optic compression the desire to compress the pulses in SMF is motivated by the ability to splice the single mode fiber to a nonlinear fiber, for continuum generation applications. We demonstrate that with highly nonlinear dispersion shifted fiber (HNLF) fusion spliced directly to the amplifier output, we generate a supercontinuum spectrum that spans more than an octave, with an average power 350 mW. Such a high power, all-fiber supercontinuum source has many important applications including frequency metrology and biomedical imaging.

  9. High power, single mode, all-fiber source of femtosecond pulses at 1550 nm and its use in supercontinuum generation

    Science.gov (United States)

    Nicholson, Jeffrey W.; Yablon, A. D.; Westbrook, P. S.; Feder, K. S.; Yan, M. F.

    2004-06-01

    We present a source of high power femtosecond pulses at 1550 nm with compressed pulses at the end of a single mode fiber (SMF) pigtail. The system generates 34 femtosecond pulses at a repetition rate of 46 MHz, with average powers greater than 400 mW. The pulses are generated in a passively modelocked, erbium-doped fiber laser, and amplified in a short, erbium-doped fiber amplifier. The output of the fiber amplifier consists of highly chirped picosecond pulses. These picosecond pulses are then compressed in standard single mode fiber. While the compressed pulses in the SMF pigtail do show a low pedestal that could be avoided with the use of bulk-optic compression, the desire to compress the pulses in SMF is motivated by the ability to splice the single mode fiber to a nonlinear fiber, for continuum generation applications. We demonstrate that with highly nonlinear dispersion shifted fiber (HNLF) fusion spliced directly to the amplifier output, we generate a supercontinuum spectrum that spans more than an octave, with an average power 400 mW. Such a high power, all-fiber supercontinuum source has many important applications including frequency metrology and bio-medical imaging.

  10. Process optimization in high-average-power ultrashort pulse laser microfabrication: how laser process parameters influence efficiency, throughput and quality

    Science.gov (United States)

    Schille, Joerg; Schneider, Lutz; Loeschner, Udo

    2015-09-01

    In this paper, laser processing of technical grade stainless steel and copper using high-average-power ultrashort pulse lasers is studied in order to gain deeper insight into material removal for microfabrication. A high-pulse repetition frequency picosecond and femtosecond laser is used in conjunction with high-performance galvanometer scanners and an in-house developed two-axis polygon scanner system. By varying the processing parameters such as wavelength, pulse length, fluence and repetition rate, cavities of standardized geometry are fabricated and analyzed. From the depths of the cavities produced, the ablation rate and removal efficiency are estimated. In addition, the quality of the cavities is evaluated by means of scanning electron microscope micrographs or rather surface roughness measurements. From the results obtained, the influence of the machining parameters on material removal and machining quality is discussed. In addition, it is shown that both material removal rate and quality increase by using femtosecond compared to picosecond laser pulses. On stainless steel, a maximum throughput of 6.81 mm3/min is achieved with 32 W femtosecond laser powers; if using 187 W picosecond laser powers, the maximum is 15.04 mm3/min, respectively. On copper, the maximum throughputs are 6.1 mm3/min and 21.4 mm3/min, obtained with 32 W femtosecond and 187 W picosecond laser powers. The findings indicate that ultrashort pulses in the mid-fluence regime yield most efficient material removal. In conclusion, from the results of this analysis, a range of optimum processing parameters are derived feasible to enhance machining efficiency, throughput and quality in high-rate micromachining. The work carried out here clearly opens the way to significant industrial applications.

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

    DEFF Research Database (Denmark)

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

    2008-01-01

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

  12. Inactivation of viruses by coherent excitations with a low power visible femtosecond laser

    Directory of Open Access Journals (Sweden)

    Wu T-C

    2007-06-01

    Full Text Available Abstract Background Resonant microwave absorption has been proposed in the literature to excite the vibrational states of microorganisms in an attempt to destroy them. But it is extremely difficult to transfer microwave excitation energy to the vibrational energy of microorganisms due to severe absorption of water in this spectral range. We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering. Results and discussion By using a very low power (as low as 0.5 nj/pulse visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width as well as power density of the excitation laser. Conclusion Our experimental findings lay down the foundation for an innovative new strategy of using a very low power visible femtosecond laser to selectively inactivate viruses and other microorganisms while leaving sensitive materials unharmed by manipulating and controlling with the femtosecond laser system.

  13. HIGH AVERAGE POWER UV FREE ELECTRON LASER EXPERIMENTS AT JLAB

    Energy Technology Data Exchange (ETDEWEB)

    Douglas, David; Evtushenko, Pavel; Gubeli, Joseph; Hernandez-Garcia, Carlos; Legg, Robert; Neil, George; Powers, Thomas; Shinn, Michelle D; Tennant, Christopher

    2012-07-01

    Having produced 14 kW of average power at {approx}2 microns, JLAB has shifted its focus to the ultraviolet portion of the spectrum. This presentation will describe the JLab UV Demo FEL, present specifics of its driver ERL, and discuss the latest experimental results from FEL experiments and machine operations.

  14. High average power supercontinuum generation in a fluoroindate fiber

    Science.gov (United States)

    Swiderski, J.; Théberge, F.; Michalska, M.; Mathieu, P.; Vincent, D.

    2014-01-01

    We report the first demonstration of Watt-level supercontinuum (SC) generation in a step-index fluoroindate (InF3) fiber pumped by a 1.55 μm fiber master-oscillator power amplifier (MOPA) system. The SC is generated in two steps: first ˜1 ns amplified laser diode pulses are broken up into soliton-like sub-pulses leading to initial spectrum extension and then launched into a fluoride fiber to obtain further spectral broadening. The pump MOPA system can operate at a changeable repetition frequency delivering up to 19.2 W of average power at 2 MHz. When the 8-m long InF3 fiber was pumped with 7.54 W at 420 kHz, output average SC power as high as 2.09 W with 27.8% of slope efficiency was recorded. The achieved SC spectrum spread from 1 to 3.05 μm.

  15. Thermal effects in high average power optical parametric amplifiers.

    Science.gov (United States)

    Rothhardt, Jan; Demmler, Stefan; Hädrich, Steffen; Peschel, Thomas; Limpert, Jens; Tünnermann, Andreas

    2013-03-01

    Optical parametric amplifiers (OPAs) have the reputation of being average power scalable due to the instantaneous nature of the parametric process (zero quantum defect). This Letter reveals serious challenges originating from thermal load in the nonlinear crystal caused by absorption. We investigate these thermal effects in high average power OPAs based on beta barium borate. Absorption of both pump and idler waves is identified to contribute significantly to heating of the nonlinear crystal. A temperature increase of up to 148 K with respect to the environment is observed and mechanical tensile stress up to 40 MPa is found, indicating a high risk of crystal fracture under such conditions. By restricting the idler to a wavelength range far from absorption bands and removing the crystal coating we reduce the peak temperature and the resulting temperature gradient significantly. Guidelines for further power scaling of OPAs and other nonlinear devices are given. PMID:23455291

  16. Thermal effects in high average power optical parametric amplifiers.

    Science.gov (United States)

    Rothhardt, Jan; Demmler, Stefan; Hädrich, Steffen; Peschel, Thomas; Limpert, Jens; Tünnermann, Andreas

    2013-03-01

    Optical parametric amplifiers (OPAs) have the reputation of being average power scalable due to the instantaneous nature of the parametric process (zero quantum defect). This Letter reveals serious challenges originating from thermal load in the nonlinear crystal caused by absorption. We investigate these thermal effects in high average power OPAs based on beta barium borate. Absorption of both pump and idler waves is identified to contribute significantly to heating of the nonlinear crystal. A temperature increase of up to 148 K with respect to the environment is observed and mechanical tensile stress up to 40 MPa is found, indicating a high risk of crystal fracture under such conditions. By restricting the idler to a wavelength range far from absorption bands and removing the crystal coating we reduce the peak temperature and the resulting temperature gradient significantly. Guidelines for further power scaling of OPAs and other nonlinear devices are given.

  17. Database of average-power damage thresholds at 1064 nm

    International Nuclear Information System (INIS)

    We have completed a database of average-power, laser-induced, damage thresholds at 1064 nm on a variety of materials. Measurements were made with a newly constructed laser to provide design input for moderate and high average-power laser projects. The measurements were conducted with 16-ns pulses at pulse-repetition frequencies ranging from 6 to 120 Hz. Samples were typically irradiated for time ranging from a fraction of a second up to 5 minutes (36,000 shots). We tested seven categories of samples which included antireflective coatings, high reflectors, polarizers, single and multiple layers of the same material, bare and overcoated metal surfaces, bare polished surfaces, and bulk materials. The measured damage threshold ranged from 2 for some metals to > 46 J/cm2 for a bare polished glass substrate. 4 refs., 7 figs., 1 tab

  18. Power Efficiency Improvements through Peak-to-Average Power Ratio Reduction and Power Amplifier Linearization

    Directory of Open Access Journals (Sweden)

    Zhou G Tong

    2007-01-01

    Full Text Available Many modern communication signal formats, such as orthogonal frequency-division multiplexing (OFDM and code-division multiple access (CDMA, have high peak-to-average power ratios (PARs. A signal with a high PAR not only is vulnerable in the presence of nonlinear components such as power amplifiers (PAs, but also leads to low transmission power efficiency. Selected mapping (SLM and clipping are well-known PAR reduction techniques. We propose to combine SLM with threshold clipping and digital baseband predistortion to improve the overall efficiency of the transmission system. Testbed experiments demonstrate the effectiveness of the proposed approach.

  19. Optical Parametric Amplification for High Peak and Average Power

    Energy Technology Data Exchange (ETDEWEB)

    Jovanovic, I

    2001-11-26

    Optical parametric amplification is an established broadband amplification technology based on a second-order nonlinear process of difference-frequency generation (DFG). When used in chirped pulse amplification (CPA), the technology has been termed optical parametric chirped pulse amplification (OPCPA). OPCPA holds a potential for producing unprecedented levels of peak and average power in optical pulses through its scalable ultrashort pulse amplification capability and the absence of quantum defect, respectively. The theory of three-wave parametric interactions is presented, followed by a description of the numerical model developed for nanosecond pulses. Spectral, temperature and angular characteristics of OPCPA are calculated, with an estimate of pulse contrast. An OPCPA system centered at 1054 nm, based on a commercial tabletop Q-switched pump laser, was developed as the front end for a large Nd-glass petawatt-class short-pulse laser. The system does not utilize electro-optic modulators or multi-pass amplification. The obtained overall 6% efficiency is the highest to date in OPCPA that uses a tabletop commercial pump laser. The first compression of pulses amplified in highly nondegenerate OPCPA is reported, with the obtained pulse width of 60 fs. This represents the shortest pulse to date produced in OPCPA. Optical parametric amplification in {beta}-barium borate was combined with laser amplification in Ti:sapphire to produce the first hybrid CPA system, with an overall conversion efficiency of 15%. Hybrid CPA combines the benefits of high gain in OPCPA with high conversion efficiency in Ti:sapphire to allow significant simplification of future tabletop multi-terawatt sources. Preliminary modeling of average power limits in OPCPA and pump laser design are presented, and an approach based on cascaded DFG is proposed to increase the average power beyond the single-crystal limit. Angular and beam quality effects in optical parametric amplification are modeled

  20. Using Bayes Model Averaging for Wind Power Forecasts

    Science.gov (United States)

    Preede Revheim, Pål; Beyer, Hans Georg

    2014-05-01

    For operational purposes predictions of the forecasts of the lumped output of groups of wind farms spread over larger geographic areas will often be of interest. A naive approach is to make forecasts for each individual site and sum them up to get the group forecast. It is however well documented that a better choice is to use a model that also takes advantage of spatial smoothing effects. It might however be the case that some sites tends to more accurately reflect the total output of the region, either in general or for certain wind directions. It will then be of interest giving these a greater influence over the group forecast. Bayesian model averaging (BMA) is a statistical post-processing method for producing probabilistic forecasts from ensembles. Raftery et al. [1] show how BMA can be used for statistical post processing of forecast ensembles, producing PDFs of future weather quantities. The BMA predictive PDF of a future weather quantity is a weighted average of the ensemble members' PDFs, where the weights can be interpreted as posterior probabilities and reflect the ensemble members' contribution to overall forecasting skill over a training period. In Revheim and Beyer [2] the BMA procedure used in Sloughter, Gneiting and Raftery [3] were found to produce fairly accurate PDFs for the future mean wind speed of a group of sites from the single sites wind speeds. However, when the procedure was attempted applied to wind power it resulted in either problems with the estimation of the parameters (mainly caused by longer consecutive periods of no power production) or severe underestimation (mainly caused by problems with reflecting the power curve). In this paper the problems that arose when applying BMA to wind power forecasting is met through two strategies. First, the BMA procedure is run with a combination of single site wind speeds and single site wind power production as input. This solves the problem with longer consecutive periods where the input data

  1. Femtosecond Optical Trapping of Cells: Efficiency and Viability

    Institute of Scientific and Technical Information of China (English)

    GONG Jixian; LI Fang; XING Qirong

    2009-01-01

    The femtosecond optical trapping capability and the effect of femtosecond laser pulses on cell viability were studied. The maximum lateral velocity at which the particles just failed to be trapped, together with the measured average trapping power, were used to calculate the lateral trapping force(Q-value). The viability of the cells after femtosecond laser trapping was ascertained by vital staining. Measurement of the Q-values shows that femtosecond optical tweezers are just as effective as continuous wave optical tweezers. The experiments demonstrate that there is a critical limit for expo-sure time at each corresponding laser power of femtosecond optical tweezers, and femtosecond laser tweezers are safe for optical trapping at low power with short exposure time.

  2. Potential of high-average-power solid state lasers

    International Nuclear Information System (INIS)

    We discuss the possibility of extending solid state laser technology to high average power and of improving the efficiency of such lasers sufficiently to make them reasonable candidates for a number of demanding applications. A variety of new design concepts, materials, and techniques have emerged over the past decade that, collectively, suggest that the traditional technical limitations on power (a few hundred watts or less) and efficiency (less than 1%) can be removed. The core idea is configuring the laser medium in relatively thin, large-area plates, rather than using the traditional low-aspect-ratio rods or blocks. This presents a large surface area for cooling, and assures that deposited heat is relatively close to a cooled surface. It also minimizes the laser volume distorted by edge effects. The feasibility of such configurations is supported by recent developments in materials, fabrication processes, and optical pumps. Two types of lasers can, in principle, utilize this sheet-like gain configuration in such a way that phase and gain profiles are uniformly sampled and, to first order, yield high-quality (undistorted) beams. The zig-zag laser does this with a single plate, and should be capable of power levels up to several kilowatts. The disk laser is designed around a large number of plates, and should be capable of scaling to arbitrarily high power levels

  3. Femtosecond laser materials processing

    Energy Technology Data Exchange (ETDEWEB)

    Stuart, B. C., LLNL

    1998-06-02

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

  4. Femtosecond laser materials processing

    Energy Technology Data Exchange (ETDEWEB)

    Stuart, B

    1998-08-05

    Femtosecond lasers enable materials processing of most any material with extremely high precision and negligible shock or thermal loading to the surrounding area. Applications ranging from drilling teeth to cutting explosives to precision cuts in composites are possible by using this technology. For material removal at reasonable rates, we have developed a fully computer-controlled 15-Watt average power, 100-fs laser machining system.

  5. Ultrafast green laser exceeding 400 W of average power

    Science.gov (United States)

    Gronloh, Bastian; Russbueldt, Peter; Jungbluth, Bernd; Hoffmann, Hans-Dieter

    2014-05-01

    We present the world's first laser at 515 nm with sub-picosecond pulses and an average power of 445 W. To realize this beam source we utilize an Yb:YAG-based infrared laser consisting of a fiber MOPA system as a seed source, a rod-type pre-amplifier and two Innoslab power amplifier stages. The infrared system delivers up to 930 W of average power at repetition rates between 10 and 50 MHz and with pulse durations around 800 fs. The beam quality in the infrared is M2 = 1.1 and 1.5 in fast and slow axis. As a frequency doubler we chose a Type-I critically phase-matched Lithium Triborate (LBO) crystal in a single-pass configuration. To preserve the infrared beam quality and pulse duration, the conversion was carefully modeled using numerical calculations. These take dispersion-related and thermal effects into account, thus enabling us to provide precise predictions of the properties of the frequency-doubled beam. To be able to model the influence of thermal dephasing correctly and to choose appropriate crystals accordingly, we performed extensive absorption measurements of all crystals used for conversion experiments. These measurements provide the input data for the thermal FEM analysis and calculation. We used a Photothermal Commonpath Interferometer (PCI) to obtain space-resolved absorption data in the bulk and at the surfaces of the LBO crystals. The absorption was measured at 1030 nm as well as at 515 nm in order to take into account the different absorption behavior at both occurring wavelengths.

  6. Experimental devices for the spatio-temporal characterization of femtosecond high-power laser chains

    International Nuclear Information System (INIS)

    One of the advantages of high-power femtosecond lasers (TW-PW) is to obtain, at the focus of a focusing optic, very high intensities up to 1022 W.cm-2 (i.e. an electric field of 2.7 PV.m-1. Therefore, these lasers chains necessarily deliver beams with large diameter (up to 40 cm) and very short pulses (of the order of tens of femto-seconds). As a consequence, the spatial and temporal properties of the pulse are generally not independent. Such dependence, called spatial-temporal coupling has the effect of increasing the pulse duration and the size of the focal spot, which can lead to a significant reduction of the maximum intensity at the focus. Metrology devices commonly used on these high-power femtosecond lasers allow retrieving the spatial and temporal profiles of the pulse only in an independent manner. The aim of this thesis was to develop techniques for measuring spatio-temporal couplings in order to quantify their effect and correct them in order to obtain the maximum intensity at focus. First of all, we adapted an existing technique of spatio-temporal characterization to the measurement of TW lasers. To avoid the issues induced at the focus, such as those related to jittering, measurements were performed on the collimated beam. By adding a reference source to the original device, we managed to take into account the measurement artifacts due to thermal and mechanical variations affecting the interferometer. With this improvement, it was possible to reconstruct the complete spatio-temporal profile of the beam, particularly its wavefront. However, the limitations imposed by this technique led to the development of a new measurement device. Based on a cross-correlation, this technique consists of making the laser beam to interfere with a part of itself, small enough not to be spatio-temporally distorted. We have also implemented a variant of this device for a single-shot measurement along one transverse dimension of the pulse. Using these techniques, we

  7. High-power MIXSEL: an integrated ultrafast semiconductor laser with 6.4 W average power.

    Science.gov (United States)

    Rudin, B; Wittwer, V J; Maas, D J H C; Hoffmann, M; Sieber, O D; Barbarin, Y; Golling, M; Südmeyer, T; Keller, U

    2010-12-20

    High-power ultrafast lasers are important for numerous industrial and scientific applications. Current multi-watt systems, however, are based on relatively complex laser concepts, for example using additional intracavity elements for pulse formation. Moving towards a higher level of integration would reduce complexity, packaging, and manufacturing cost, which are important requirements for mass production. Semiconductor lasers are well established for such applications, and optically-pumped vertical external cavity surface emitting lasers (VECSELs) are most promising for higher power applications, generating the highest power in fundamental transverse mode (>20 W) to date. Ultrashort pulses have been demonstrated using passive modelocking with a semiconductor saturable absorber mirror (SESAM), achieving for example 2.1-W average power, sub-100-fs pulse duration, and 50-GHz pulse repetition rate. Previously the integration of both the gain and absorber elements into a single wafer was demonstrated with the MIXSEL (modelocked integrated external-cavity surface emitting laser) but with limited average output power (design combined with an improved thermal management by wafer removal and mounting of the 8-µm thick MIXSEL structure directly onto a CVD-diamond heat spreader. The simple straight cavity with only two components has generated 28-ps pulses at 2.5-GHz repetition rate and an average output power of 6.4 W, which is higher than for any other modelocked semiconductor laser. PMID:21197032

  8. Compact and high-power broadband terahertz source based on femtosecond photonic crystal fiber amplifier

    Institute of Scientific and Technical Information of China (English)

    Feng Liu; Lu Chai; Qirong Xing; Chingyue Wang; Weili Zhang; Xiaokun Hu; Jiang Li; Changlei Wang; Yi Li; Yanfeng Li; YoujianSong; Bowen Liu; Minglie Hu

    2011-01-01

    Terahertz (THz) waves,generally defined in the 0.1-10 THz range are finding growing applications in various important fields[1-4] such as imaging,food and pharmaceutical quality coutrol,security screening,and standoff detection of bio-threat species,among which THz timedomain spectroscopy (THz-TDS)[5] is particularly appealing.However,the low conversion efficiency and low power of typical broadband THz sources severely hinder the utility and realization of the full potential of THzTDS.Recently,there have been efforts to generate THz pulses using compact pump sources in fiber format[6,7].%We present a review of the development of a compact and high-power broadband terahertz (THz) source optically excited by a femtosecond photonic crystal fiber (PCF) amplifier. The large mode area of the PCF and the stretcher-free configuration make the pump source compact and very efficient. Broadband THz pulseg of 150 μW extending from 0.1 to 3.5 TH2 are generated from a 3-mm-thick GaP crystal through optical rectification of 12-W pump pulses with duration of 66 & and a repetition rate of 52 MHz. A strong saturation effect is observed, which is attributed to pump pulse absorption; a Z-scan measurement shows that three-photon absorption dominates the nonlinear absorption when the crystal is pumped by femtosecond pulses at 1040 run. A further scale-up of the THz source power is expected to find important applications in THz nonlinear optics and nonlinear THz spectroscope

  9. High average power lasers for future particle accelerators

    Science.gov (United States)

    Dawson, Jay W.; Crane, John K.; Messerly, Michael J.; Prantil, Matthew A.; Pax, Paul H.; Sridharan, Arun K.; Allen, Graham S.; Drachenberg, Derrek R.; Phan, Henry H.; Heebner, John E.; Ebbers, Christopher A.; Beach, Raymond J.; Hartouni, Edward P.; Siders, Craig W.; Spinka, Thomas M.; Barty, C. P. J.; Bayramian, Andrew J.; Haefner, Leon C.; Albert, Felicie; Lowdermilk, W. Howard; Rubenchik, Alexander M.; Bonanno, Regina E.

    2012-12-01

    Lasers are of increasing interest to the accelerator community and include applications as diverse as stripping electrons from hydrogen atoms, sources for Compton scattering, efficient high repetition rate lasers for dielectric laser acceleration, peta-watt peak power lasers for laser wake field and high energy, short pulse lasers for proton and ion beam therapy. The laser requirements for these applications are briefly surveyed. State of the art of laser technologies with the potential to eventually meet those requirements are reviewed. These technologies include diode pumped solid state lasers (including cryogenic), fiber lasers, OPCPA based lasers and Ti:Sapphire lasers. Strengths and weakness of the various technologies are discussed along with the most important issues to address to get from the current state of the art to the performance needed for the accelerator applications. Efficiency issues are considered in detail as in most cases the system efficiency is a valuable indicator of the actual ability of a given technology to deliver the application requirements.

  10. Spatio-temporal characterization techniques of high-power femtosecond laser chains

    Science.gov (United States)

    Gallet, Valentin; Pariente, Gustave; Kahaly, Subhendu; Gobert, Olivier; Quéré, Fabien

    2014-03-01

    In this letter, we propose two techniques capable of spatio-temporally characterizing high-power femtosecond laser chains. We demonstrate a new implementation of SEA TADPOLE. To avoid the problems induced by the the significant spatial jittering of the focal spot on high-power laser chains, our setup is adapted to collimated beams. In addition, a fibered light source is also used to correct the phase fluctuations. This experimental setup allows identifying any spatiotemporal distortions such as the pulse front tilt for instance. In this paper, to the best of our knowledge, we present the very first spatio-temporal characterization done on a TW laser. However, a SEA TADPOLE measurement is not immediate since it requires scanning the beam over the two transverse dimensions which prevent us from studying the shot-to-shot laser fluctuations. This is why, we developed MUFFIN, a single-shot technique capable of spatio-temporally characterizing a laser pulse along its two transverse dimensions. First experimental results obtained with this technique are presented here.

  11. Average incore axial power distribution measurement by a multi excore detector

    International Nuclear Information System (INIS)

    French 1300 MWe reactors Protection System against DNB and excessive linear power is based on the average incore axial power distribution continuous measurement by multi-excore detectors. This paper describes the main results obtained during the first power escalation of PALUEL Unit 1 and 2, first units of 1300 MWe reactors and shows some INCORE/EXCORE power distribution comparisons. (author)

  12. High power mode-locked rod-type fiber femtosecond laser with micro-joule energy

    Science.gov (United States)

    Lv, Zhiguo; Teng, Hao; Wang, Lina; Wang, Rui; Wang, Junli; Wei, Zhiyi

    2016-07-01

    We report a high power all-normal-dispersion (ANDi) mode-locked laser based on nonlinear polarization evolution (NPE) technique using rod-type fiber with polarization maintaining (PM) characteristic. With 85 μm gain core diameter, 31 W of average power at repetition rates of 57.93 MHz, which corresponds to the pulse energy of 0.53 μJ, is demonstrated under a pump power of 93 W. The pulse duration of 124 fs after compressor is obtained at the central wavelength of 1033 nm as well as the measured power jitter of 0.3% over a period of 2 h.

  13. Peak to Average Power Ratio Reduction in OFDM System by Clipping and Filtering

    Directory of Open Access Journals (Sweden)

    Dr. O.P. Sahu

    2012-05-01

    Full Text Available This paper results clipping and filtering technique for peak to average power ratio (PAPR reduction in orthogonal frequency division multiplexing (OFDM. Our simulation results show that this technique removes inband and out of band distortion along with 1dB reduction in peak to average power ratio when crest ratio changes from 1.4 to 1.2.

  14. Energy and average power scalable optical parametric chirped-pulse amplification in yttrium calcium oxyborate.

    Science.gov (United States)

    Liao, Zhi M; Jovanovic, Igor; Ebbers, Chris A; Fei, Yiting; Chai, Bruce

    2006-05-01

    Optical parametric chirped-pulse amplification (OPCPA) in nonlinear crystals has the potential to produce extremes of peak and average power but is limited either in energy by crystal growth issues or in average power by crystal thermo-optic characteristics. Recently, large (7.5 cm diameter x 25 cm length) crystals of yttrium calcium oxyborate (YCOB) have been grown and utilized for high-average-power second-harmonic generation. Further, YCOB has the necessary thermo-optic properties required for scaling OPCPA systems to high peak and average power operation for wavelengths near 1 microm. We report what is believed to be the first use of YCOB for OPCPA. Scalability to higher peak and average power is addressed.

  15. Highly Efficient Self-Starting Femtosecond Cr:Forsterite Laser

    Institute of Scientific and Technical Information of China (English)

    ZHOU Bin-Sin; ZHANG Yong-Dong; ZHONG Xin; WEI Zhi-Yi

    2008-01-01

    We report a highly efficient and high power self-starting femtosecond Cr:forsterite laser pumped by a 1064-nm Yb doped fibre laser. Five chirped mirrors are used to compensate for the intra-cavity group-delay dispersion,and the mode-locking is initiated by a semiconductor saturable absorber mirror (SESAM). Under pump power of 7.9 W, stable femtosecond laser pulses with average power of 760mW are obtained, yielding a pump power slope efficiency of 12.3%. The measured pulse duration and spectral bandwidth (FWHM) are 46 fs and 45 nm;the repetition rate is 82 MHz.

  16. Influence on natural circulation nuclear thermal coupling average power under rolling motion

    International Nuclear Information System (INIS)

    By performing simulation computations of single-phase flow natural circulation considering nuclear thermal coupling under rolling motion conditions, the influence factors which have great effect on the average heating power of this circulation system were studied. The analysis results indicate that under rolling motion conditions, the average heating power which considers the nuclear thermal coupling effect is in direct proportion to the average flow rate and average heat transfer coefficient, while it has an inverse relationship with the ratio between temperature-feedback coefficient of moderator and that of fuel. The effect of rolling parameters on the average heating power is related with the ratio between temperature-feedback coefficient of moderator and that of fuel. When the effect of the variation of the average heat transfer coefficient on the reactivity plays a leading role in the process, the stronger the rolling motion is, the higher the average heating power is. However, when the effect of the variation for the average friction coefficient on the reactivity takes the lead, the stronger the rolling motion is, the lower the average heating power is. (authors)

  17. High-power mid-infrared frequency comb source based on a femtosecond Er:fiber oscillator.

    Science.gov (United States)

    Zhu, Feng; Hundertmark, Holger; Kolomenskii, Alexandre A; Strohaber, James; Holzwarth, Ronald; Schuessler, Hans A

    2013-07-01

    We report on a high-power mid-infrared (MIR) frequency comb source based on a femtosecond (fs) Er:fiber oscillator with a stabilized repetition rate of 250 MHz. The MIR frequency comb is produced through difference frequency generation in a periodically poled MgO-doped lithium niobate crystal. The output power is about 120 mW, with a pulse duration of about 80 fs and spectrum coverage from 2.9 to 3.6 μm, and the single comb mode power is larger than 0.3 μW over the range of 700 nm. The coherence properties of the produced high-power broadband MIR frequency comb are maintained, which was verified by heterodyne measurements. As the first application, the spectrum of a ~200 ppm methane-air mixture in a short 20 cm glass cell at ambient atmospheric pressure and temperature was measured. PMID:23811928

  18. Kilowatt high average power narrow-linewidth nanosecond all-fiber laser

    Institute of Scientific and Technical Information of China (English)

    Rongtao; Su; Pu; Zhou; Xiaolin; Wang; Rumao; Tao; Xiaojun; Xu

    2014-01-01

    A high power narrow-linewidth nanosecond all-fiber laser based on the master oscillator power amplifier(MOPA)configuration is demonstrated. A pulsed seed with high repetition rate of 10 MHz was generated by modulating a continuous-wave(CW) single-frequency fiber laser at ~1064 nm by using an electro-optic intensity modulator(EOIM).After multi-stage cascaded power amplification, the average power was boosted to be kilowatt level. The pulses from the main amplifier had a pulse width of ~3 ns and an average/peak power of 913 W/28.6 kW. Further power scaling of the pulses was limited by stimulated Raman scattering(SRS) for the moment, method for SRS suppression and further power scaling was briefly discussed.

  19. A Comparison Between Two Average Modelling Techniques of AC-AC Power Converters

    OpenAIRE

    Pawel Szczesniak

    2015-01-01

    In this paper, a comparative evaluation of two modelling tools for switching AC-AC power converters is presented. Both of them are based on average modelling techniques. The first approach is based on the circuit averaging technique and consists in the topological manipulations, applied to a converters states. The second approach makes use of state-space averaged model of the converter and is based on analytical manipulations using the different state representations of a converter. The two m...

  20. A Hybrid Islanding Detection Technique Using Average Rate of Voltage Change and Real Power Shift

    DEFF Research Database (Denmark)

    Mahat, Pukar; Chen, Zhe; Bak-Jensen, Birgitte

    2009-01-01

    technique is proposed to solve this problem. An average rate of voltage change (passive technique) has been used to initiate a real power shift (active technique), which changes the eal power of distributed generation (DG), when the passive technique cannot have a clear discrimination between islanding...

  1. Performance and production requirements for the optical components in a high-average-power laser system

    Energy Technology Data Exchange (ETDEWEB)

    Chow, R.; Doss, F.W.; Taylor, J.R.; Wong, J.N.

    1999-07-02

    Optical components needed for high-average-power lasers, such as those developed for Atomic Vapor Laser Isotope Separation (AVLIS), require high levels of performance and reliability. Over the past two decades, optical component requirements for this purpose have been optimized and performance and reliability have been demonstrated. Many of the optical components that are exposed to the high power laser light affect the quality of the beam as it is transported through the system. The specifications for these optics are described including a few parameters not previously reported and some component manufacturing and testing experience. Key words: High-average-power laser, coating efficiency, absorption, optical components

  2. High-power mid-infrared frequency comb source based on a femtosecond Er:fiber oscillator

    CERN Document Server

    Zhu, Feng; Kolomenskii, Alexandre A; Strohaber, James; Holzwarth, Ronald; Schuessler, Hans A

    2013-01-01

    We report on a high-power mid-infrared frequency comb source based on a femtosecond Er:fiber oscillator with a stabilized repetition rate at 250 MHz. The mid-infrared frequency comb is produced through difference frequency generation in a periodically poled MgO-doped lithium niobate crystal. The output power is about 120 mW with a pulse duration of about 80 fs, and spectrum coverage from 2.9 to 3.6 um. The coherence properties of the produced high-power broadband mid-infrared frequency comb are maintained, which was verified by heterodyne measurements. As the first application, the spectrum of a ~200 ppm methane-air mixture in a short 20 cm glass cell at ambient atmospheric pressure and temperature was measured.

  3. Recent advances in the development of high average power induction accelerators for industrial and environmental applications

    International Nuclear Information System (INIS)

    Short-pulse accelerator technology developed during time period from the early 60's through the late 80's is now being extended to high average power systems capable of being used in industrial and environmental applications. Processes requiring high dose levels and/or high volume throughput may require systems with beam power levels from several hundreds of kilowatts to megawatts. Processes may include chemical waste mitigation, flue gas cleanup, food pasteurization, and new forms of materials preparation and treatment. This paper will address the present status of high average power systems now in operation that use combinations of semiconductor and saturable core magnetic switches with inductive voltage adders to achieve MeV beams of electrons or x-rays over areas of 10,000 cm2 or more. Similar high average power technology is also being used below 1 MeV to drive repetitive ion beam sources for treatment of material surfaces

  4. Generation and parametric amplification of femtosecond radiation up to terawatt power in the mid-infrared

    Science.gov (United States)

    Trunov, V. I.; Frolov, S. A.; Pestryakov, E. V.

    2015-11-01

    Nonlinear optical schemes for generation of terawatt femtosecond pulses in the range of 2-10 μm using multiterawatt laser radiation of the two-channel system created in the ILP SB RAS are presented and discussed. It is shown that the use of large aperture LBO crystals and AgGaGeS4 for difference frequency generation and parametric amplification enables to generate a wideband radiation in the range of 2-10 μm.

  5. Nonlinear propagation of a high-power focused femtosecond laser pulse in air under atmospheric and reduced pressure

    International Nuclear Information System (INIS)

    This paper examines the propagation of focused femtosecond gigawatt laser pulses in air under normal and reduced pressure in the case of Kerr self-focusing and photoionisation of the medium. The influence of gas density on the beam dimensions and power and the electron density in the plasma column in the nonlinear focus zone of the laser beam has been studied experimentally and by numerical simulation. It has been shown that, in rarefied air, the radiation-induced reduction in the rate of plasma formation diminishes the blocking effect of the plasma on the growth of the beam intensity in the case of tight focusing. This allows higher power densities of ultrashort laser pulses to be reached in the focal waist region in comparison with beam self-focusing under atmospheric pressure.

  6. Self-compression of femtosecond pulses in argon with a power close to the self-focusing threshold

    Institute of Scientific and Technical Information of China (English)

    Chen Xiao-Wei; Zeng Zhi-Nan; Dai Jun; Li Xiao-Fang; Li Ru-Xin; Xu Zhi-Zhan

    2008-01-01

    Self-compression of femtosecond pulses in noble gases with an input power close to the self-focusing threshold has been investigated experimentally and theoretically.It is demonstrated that either multiphoton ionization (MPI) or space-time focusing and self-steepening effects can induce pulse shortening,but they predominate at different beam intensities during the propagation.The latter effects play a key role in the final pulse self-compression.By choosing an appropriate focusing parameter,action distance of the space-time focusing and self-steepening effects can be lengthened,which can promote a shock pulse structure with a duration as short as two optical cycles.It is also found that,for our calculation eases in which an input pulse power is close to the self-focusing threshold,either group velocity dispersion(GVD) or multiphoton absorption (MPA) has a negligible influence on pulse characteristics in the propagation process.

  7. MOX Average Power Test 30 GWd/MT PIE: Quick Look

    Energy Technology Data Exchange (ETDEWEB)

    MORRIS, RN

    2001-02-14

    This report summarizes the early results of the post irradiation examination of the 30 GWd/MT MOX Average Power Test Capsules (numbers 3 and 10). The purpose of this preliminary examination is to document and monitor the progress of the MOX Average Power Test Irradiation. The capsules and their fuel pins were found to be in excellent condition. Measurement of the fission gas release fraction (about 1.50 to 2.26%), preliminary fuel stack gamma scan measurements, and preliminary fuel pin diameter measurements indicate that the fuel is behaving as expected.

  8. High-average-power narrow-line-width sum frequency generation 589 nm laser

    Science.gov (United States)

    Lu, Yanhua; Fan, Guobin; Ren, Huaijin; Zhang, Lei; Xu, Xiafei; Zhang, Wei; Wan, Min

    2015-10-01

    An 81 W average-power all-solid-state sodium beacon laser at 589 nm with a repetition rate of 250 Hz is introduced, which is based on a novel sum frequency generation idea between two high-energy, different line widths, different beam quality infrared lasers (a 1064 nm laser and a 1319 nm laser). The 1064 nm laser, which features an external modulated CW single frequency seed source and two stages of amplifiers, can provide average-power of 150 W, beam quality M2 of ~1.8 with ultra-narrow line width (beacon laser ever reported.

  9. Numerical Investigation of Thermal Effect in Plasma Electrode Pockels Cell for High Average Power

    Institute of Scientific and Technical Information of China (English)

    CAO Ding-Xiang; ZHANG Xiong-Jun; ZHENG Wan-Guo; HE Shao-Bo; SUI Zhan

    2006-01-01

    @@ The average power of a Pockels cell is limited by thermal effects arising from the optical absorption of the laser pulse. These thermal effects can be managed by configuring the switch as a plasma-electrode thin plate Pockels cell, which works under heat-capacity operation. Simulation results show that, based on KD*P (in thickness 0.5cm) at an average power loading of 1 kW, the aperture integrated depolarization loss at 1.06 um is less than 10% in 5min working time.

  10. Average power scaling of UV excimer lasers drives flat panel display and lidar applications

    Science.gov (United States)

    Herbst, Ludolf; Delmdahl, Ralph F.; Paetzel, Rainer

    2012-03-01

    Average power scaling of 308nm excimer lasers has followed an evolutionary path over the last two decades driven by diverse industrial UV laser microprocessing markets. Recently, a new dual-oscillator and beam management concept for high-average power upscaling of excimer lasers has been realized, for the first time enabling as much as 1.2kW of stabilized UV-laser average output power at a UV wavelength of 308nm. The new dual-oscillator concept enables low temperature polysilicon (LTPS) fabrication to be extended to generation six glass substrates. This is essential in terms of a more economic high-volume manufacturing of flat panel displays for the soaring smartphone and tablet PC markets. Similarly, the cost-effective production of flexible displays is driven by 308nm excimer laser power scaling. Flexible displays have enormous commercial potential and can largely use the same production equipment as is used for rigid display manufacturing. Moreover, higher average output power of 308nm excimer lasers aids reducing measurement time and improving the signal-to-noise ratio in the worldwide network of high altitude Raman lidar stations. The availability of kW-class 308nm excimer lasers has the potential to take LIDAR backscattering signal strength and achievable altitude to new levels.

  11. High average power quasi-CW single-mode green and UV fiber lasers

    Science.gov (United States)

    Avdokhin, Alexey; Gapontsev, Valentin; Kadwani, Pankaj; Vaupel, Andreas; Samartsev, Igor; Platonov, Nicholai; Yusim, Alex; Myasnikov, Daniil

    2015-02-01

    Kilowatt-level narrow-linewidth SM ytterbium fiber laser operating in high-repetition-rate QCW regime was used to obtain 700 W average power at 532 nm with single-mode beam quality and wall-plug efficiency of over 23 %. To the best of our knowledge, this is ~60 % higher power than previously reported for single-mode green lasers based on other platforms, and also is ~30 % increase comparing to the previous result obtained by our group on the base of similar fiber laser platform. We have also experimentally proved that the same type of fiber laser can be used for generating of world-record levels of power at other wavelengths of visible and UV spectral ranges by employing cascaded non-linear frequency conversion. Thus, utilizing frequency tripling in 2 LBO crystals, we achieved over 160 W average power of nearly single-mode UV light at 355 nm with THG efficiency of more than 25 %. As far as we know, this is the highest output power ever reported for UV laser with nearly diffraction limited beam quality. We also conducted some preliminary experiments to demonstrate suitability of our approach for generating longer wavelengths of the visible spectrum. By pre-shifting fundamental emission wavelength in fiber Raman converter, followed by frequency doubling in NCPM LBO, we obtained average powers of 36 W at 589 nm and 27 W at 615 nm. These proof-of-concept experiments were performed with low-power pump laser and were not fully optimized with respect to frequency conversion. Our analysis indicates that employing kW-level QCW ytterbium laser with optimized SRS and SHG converters we can achieve hundreds of Watts of average power in red and orange color with single-mode beam quality.

  12. Cryogenic Yb:YAG picosecond laser with high average power visible and ultraviolet harmonic generation

    Science.gov (United States)

    Brown, D. C.; Kowalewski, K.; Envid, V.; Zembek, J.; Canale, B.; Kolis, J. W.; McMillen, C. D.; Geisber, H.

    2012-06-01

    Cryogenic Yb:YAG lasers operating at 1029 nm have been demonstrated at Snake Creek Lasers with high average power CW and ultrafast output powers, and provide near diffraction-limited output beams that are ideal for applications in harmonic generation. We describe experiments that have produced high average power green output power at 515 nm as well as preliminary experiments producing UV output power at 257.25 nm. Frequency doubling experiments used a 20 mm long non-critically phase-matched LBO crystal mounted in a constant temperature oven. A mode-locked Yb fiber laser operating at 50 MHz was used to drive a two Yb:YAG cryogenic amplifier system, producing hundreds of watts of average power output with a FWHM pulsewidth of 12 ps. Doubling efficiencies of > 50 % have been observed. For frequency quadrupling, we have used hydrothermally grown KTTP crystals grown at Clemson University and Advanced Photonic Crystals. KBBF offers unprecedented UV transmission down to 155 nm, and was used in a Type I phasematching configuration. The properties of KBBF will be discussed, as well as the experimental results observed and conversion efficiency.

  13. Power scaling from buried depressed-cladding waveguides realized in Nd:YVO4 by femtosecond-laser beam writing

    Science.gov (United States)

    Salamu, Gabriela; Pavel, Nicolaie

    2016-10-01

    We report on output power performances obtained by diode-laser pumping of buried cladding-waveguides that were inscribed with a femtosecond-laser beam writing technique in several Nd:YVO4 media. Continuous-wave output power of 3.4 W at 1.06 μm for an absorbed pump power at 808 nm of 10.3 W was obtained from a circular waveguide of 100-μm diameter that was realized in a 6.9-mm long, 0.5-at% Nd:YVO4 crystal; the slope efficiency with respect to the absorbed pump power was 0.36. The pump at 880 nm, directly into the 4F3/2 emitting level, was used to improve the waveguide output characteristics. With an absorbed pump power of 9.8 W at 880 nm, the same waveguide yielded 4.4 W at 1.06 μm, whereas for emission at 1.34 μm the output power reached 1.7 W; the slope efficiency improved to 0.47 for laser emission at 1.06 μm and reached 0.24 for operation at 1.34 μm. Results recorded from similar waveguides that were inscribed in 0.7-at% Nd:YVO4 and 1.0-at% Nd:YVO4 crystals are presented.

  14. Estimating ensemble average power delivered by a piezoelectric patch actuator to a non-deterministic subsystem

    Science.gov (United States)

    Muthalif, Asan G. A.; Wahid, Azni N.; Nor, Khairul A. M.

    2014-02-01

    Engineering systems such as aircraft, ships and automotive are considered built-up structures. Dynamically they are taught of as being fabricated from many components that are classified as 'deterministic subsystems' (DS) and 'non-deterministic subsystems' (Non-DS). Structures' response of the DS is deterministic in nature and analysed using deterministic modelling methods such as finite element (FE) method. The response of Non-DS is statistical in nature and estimated using statistical modelling technique such as statistical energy analysis (SEA). SEA method uses power balance equation, in which any external input to the subsystem must be represented in terms of power. Often, input force is taken as point force and ensemble average power delivered by point force is already well-established. However, the external input can also be applied in the form of moments exerted by a piezoelectric (PZT) patch actuator. In order to be able to apply SEA method for input moments, a mathematical representation for moment generated by PZT patch in the form of average power is needed, which is attempted in this paper. A simply-supported plate with attached PZT patch is taken as a benchmark model. Analytical solution to estimate average power is derived using mobility approach. Ensemble average of power given by the PZT patch actuator to the benchmark model when subjected to structural uncertainties is also simulated using Lagrangian method and FEA software. The analytical estimation is compared with the Lagrangian model and FE method for validation. The effects of size and location of the PZT actuators on the power delivered to the plate are later investigated.

  15. Image registration and averaging of low laser power two-photon fluorescence images of mouse retina.

    Science.gov (United States)

    Alexander, Nathan S; Palczewska, Grazyna; Stremplewski, Patrycjusz; Wojtkowski, Maciej; Kern, Timothy S; Palczewski, Krzysztof

    2016-07-01

    Two-photon fluorescence microscopy (TPM) is now being used routinely to image live cells for extended periods deep within tissues, including the retina and other structures within the eye . However, very low laser power is a requirement to obtain TPM images of the retina safely. Unfortunately, a reduction in laser power also reduces the signal-to-noise ratio of collected images, making it difficult to visualize structural details. Here, image registration and averaging methods applied to TPM images of the eye in living animals (without the need for auxiliary hardware) demonstrate the structural information obtained with laser power down to 1 mW. Image registration provided between 1.4% and 13.0% improvement in image quality compared to averaging images without registrations when using a high-fluorescence template, and between 0.2% and 12.0% when employing the average of collected images as the template. Also, a diminishing return on image quality when more images were used to obtain the averaged image is shown. This work provides a foundation for obtaining informative TPM images with laser powers of 1 mW, compared to previous levels for imaging mice ranging between 6.3 mW [Palczewska G., Nat Med.20, 785 (2014) Sharma R., Biomed. Opt. Express4, 1285 (2013)]. PMID:27446697

  16. GENERATION OF HIGH-AVERAGE-POWER ULTRABROAD-BAND INFRARED PULSES

    Science.gov (United States)

    This paper summarizes the results of analytical and numerical studies on a novel technique that is capable of providing high average power ultra broadband radiation that extends from approximately 2 to 16 m. Such a spectrum has several potential applications, including telecommu...

  17. Image registration and averaging of low laser power two-photon fluorescence images of mouse retina.

    Science.gov (United States)

    Alexander, Nathan S; Palczewska, Grazyna; Stremplewski, Patrycjusz; Wojtkowski, Maciej; Kern, Timothy S; Palczewski, Krzysztof

    2016-07-01

    Two-photon fluorescence microscopy (TPM) is now being used routinely to image live cells for extended periods deep within tissues, including the retina and other structures within the eye . However, very low laser power is a requirement to obtain TPM images of the retina safely. Unfortunately, a reduction in laser power also reduces the signal-to-noise ratio of collected images, making it difficult to visualize structural details. Here, image registration and averaging methods applied to TPM images of the eye in living animals (without the need for auxiliary hardware) demonstrate the structural information obtained with laser power down to 1 mW. Image registration provided between 1.4% and 13.0% improvement in image quality compared to averaging images without registrations when using a high-fluorescence template, and between 0.2% and 12.0% when employing the average of collected images as the template. Also, a diminishing return on image quality when more images were used to obtain the averaged image is shown. This work provides a foundation for obtaining informative TPM images with laser powers of 1 mW, compared to previous levels for imaging mice ranging between 6.3 mW [Palczewska G., Nat Med.20, 785 (2014) Sharma R., Biomed. Opt. Express4, 1285 (2013)].

  18. The LUCIA project: a high average power ytterbium diode pumped solid state laser chain

    Science.gov (United States)

    Bourdet, Gilbert L.; Chanteloup, Jean-Christophe; Fulop, A.; Julien, Y.; Migus, Arnold

    2004-04-01

    With the goal to set up a high average power Diode Pumped Solid State Laser (100 Joules/10 Hz/10 ns), the Laboratory for Use of Intense Laser (LULI) is now studying various solutions concerning the amplifier medium, the cooling, the pumping and the extraction architectures. In this paper, we present the last states of these developments and the solutions already chosen.

  19. Competition between multiphoton/tunnel ionization and filamentation induced by powerful femtosecond laser pulses in air

    Institute of Scientific and Technical Information of China (English)

    W. Liu; Q. Luo; S. L. Chin

    2003-01-01

    In this work we present experiments by focusing 42 femtosecond laser pulses in air using three different focal length lenses: f=100, 30 and 5 cm. For the longest focal length, only the filament, which is a weak plasma column, is observed. When the shorter focal length lens is used, a high density plasma is generated near the geometrical focus and coexists with a weak plasma channel of the filament. Under the tightest focusing condition, filamentation is prevented and only a strong plasma volume appears at the geometrical focus.

  20. High average power of Q-switched Tm:YAG slab laser

    Science.gov (United States)

    Jin, Lin; Liu, Pian; Liu, Xuan; Huang, Haitao; Yao, Weichao; Shen, Deyuan

    2016-08-01

    A laser-diode end-pumped Tm:YAG single crystal slab laser in acousto-optic Q-switched operation was demonstrated. For Q-switched operation, the average output power of 20.7 W at 1 kHz was achieved under the absorbed pump power of 83.6 W, corresponding to the slope efficiency of 36.1%, the shortest pulse width of 84 ns and the maximum pulse energy of 20.7 mJ with peak power of 250 kW were obtained.

  1. High-power directly diode-pumped femtosecond Yb:KGW lasers with optimized parameters

    Science.gov (United States)

    Kim, G. H.; Yang, J.; Kulik, A. V.; Sall, E. G.; Chizhov, S. A.; Yashin, V. E.; Kang, U.

    2014-02-01

    We report a diode-pumped Yb:KGW laser that is capable of operating as a Q-switched oscillator or as a regenerative amplifier with average power of more than 20 W. The laser is based on a dual-crystal configuration where the pump thermal load is distributed over relatively long two crystals. It permits a sufficiently large number of passes with low passive losses and maximizes the energy extraction efficiency. The amplification bandwidth was extended by spectral combining of two Yb:KGW crystals with spectrally shifted gain maxima, that allows to mitigate spectral gain narrowing and provides pulse length down to 200 fs after compression in a stretcher-compressor module. The output power saturated with increasing pump power and output beam quality was defined by aberration of thermal lenses. Optimization of laser cavity allows us to compensate thermal lens partially and provide output beams with quality M2BBO crystal. Second or third harmonic generation with respective conversion efficiency of 55% or 24% was achieved in a single-pass configuration.

  2. Two-crystal, synchronously pumped, femtosecond optical parametric oscillator

    OpenAIRE

    Ramaiah-Badarla, V.; Esteban-Martin, A.; Ebrahim-Zadeh, Majid

    2015-01-01

    We demonstrate a femtosecond optical parametric oscillator based on two nonlinear crystals synchronously pumped by a single ultrafast laser for efficient intracavity signal amplification and output power enhancement. By deploying two identical MgO:PPLN crystals in a single standing-wave cavity, and two pump pulse trains of similar average power from the same Kerr-lens-mode-locked Ti:sapphire laser, a minimum enhancement of 56% in the extracted signal power is achieved, with un-opt...

  3. Average Minimum Transmit Power to achieve SINR Targets: Performance Comparison of Various User Selection Algorithms

    CERN Document Server

    Salim, Umer

    2010-01-01

    In multi-user communication from one base station (BS) to multiple users, the problem of minimizing the transmit power to achieve some target guaranteed performance (rates) at users has been well investigated in the literature. Similarly various user selection algorithms have been proposed and analyzed when the BS has to transmit to a subset of the users in the system, mostly for the objective of the sum rate maximization. We study the joint problem of minimizing the transmit power at the BS to achieve specific signal-to-interference-and-noise ratio (SINR) targets at users in conjunction with user scheduling. The general analytical results for the average transmit power required to meet guaranteed performance at the users' side are difficult to obtain even without user selection due to joint optimization required over beamforming vectors and power allocation scalars. We study the transmit power minimization problem with various user selection algorithms, namely semi-orthogonal user selection (SUS), norm-based...

  4. High power multi-color OPCPA source with simultaneous femtosecond deep-UV to mid-IR outputs.

    Science.gov (United States)

    Baudisch, M; Wolter, B; Pullen, M; Hemmer, M; Biegert, J

    2016-08-01

    Many experimental investigations demand synchronized pulses at various wavelengths, ideally with very short pulse duration and high repetition rate. Here we describe a femtosecond multi-color optical parametric chirped pulse amplifier (OPCPA) with simultaneous outputs from the deep-UV to the mid-IR with optical synchronization. The high repetition rate of 160 kHz is well suited to compensate for low interaction probability or low cross section in strong-field interactions. Our source features high peak powers in the tens to hundreds of MW regime with pulse durations below 110 fs, which is ideal for pump-probe experiments of nonlinear and strong-field physics. We demonstrate its utility by strong-field ionization experiments of xenon in the near- to mid-IR. PMID:27472624

  5. High-average-power actively-mode-locked Tm3+ fiber lasers

    Science.gov (United States)

    Eckerle, Michael; Kieleck, Christelle; Hübner, Philipp; Świderski, Jacek; Jackson, Stuart D.; Mazé, Gwenael; Eichhorn, Marc

    2012-02-01

    Fiber lasers emitting in the 2 μm wavelength range doped with thulium ions can be used as highly efficient pump sources for nonlinear converters to generate mid-infrared radiation. For spectroscopic purposes, illumination and countermeasures, a broad mid-infrared emission spectrum is advantageous. This can be reached by supercontinuum generation in fibers, e.g. fluoride fibers, which up to now has, however, only been presented with either low average power, complex Raman-shifted 1.55 μm pump sources or multi-stage amplifier pump schemes. Here we present recent results of a new actively-mode-locked single-oscillator scheme that can provide the high-repetition rate sub-ns pump pulses needed for pumping supercontinuum generators. A thulium-doped silica fiber laser is presented that provides > 11 W of average power CW-mode-locked pulses at 38 MHz repetition rate at ~ 38 ps pulse width. Upgrading the setup to allow Q-switched mode-locked operation yields mode-locked 40 MHz pulses arranged in 60 kHz bunched Q-switch envelopes and thus increases further the available peak power. In this Q-switched mode-locked regime over 5 W of average power has been achieved.

  6. High-average-power water window soft X-rays from an Ar laser plasma

    Science.gov (United States)

    Amano, Sho

    2016-07-01

    A high average power of 140 mW and high conversion efficiency of 14% were demonstrated in “water window” soft X-rays generated using a laser plasma source developed in-house, when a solid Ar target was irradiated by a commercial Nd:YAG Q-switched laser with an energy of 1 J at a repetition rate of 1 Hz. This soft X-ray power compared favorably with that produced using a synchrotron radiation source, and the developed laser plasma source can be used in various applications, such as soft X-ray microscopy, in place of synchrotron facilities.

  7. 28W average power hydrocarbon-free rubidium diode pumped alkali laser.

    Science.gov (United States)

    Zweiback, Jason; Krupke, William F

    2010-01-18

    We present experimental results for a high-power diode pumped hydrocarbon-free rubidium laser with a scalable architecture. The laser consists of a liquid cooled, copper waveguide which serves to both guide the pump light and to provide a thermally conductive surface near the gain volume to remove heat. A laser diode stack, with a linewidth narrowed to approximately 0.35 nm with volume bragg gratings, is used to pump the cell. We have achieved 24W average power output using 4 atmospheres of naturally occurring helium ((4)He) as the buffer gas and 28W using 2.8 atmospheres of (3)He.

  8. Metal micro drilling combining high power femtosecond laser and trepanning head

    Science.gov (United States)

    Kling, R.; Dijoux, M.; Romoli, L.; Tantussi, F.; Sanabria, J.; Mottay, E.

    2013-03-01

    Trepanning heads are well known to be efficient in high aspect drilling and to provide a precise control of the hole geometry. Secondly, femtosecond lasers enable to minimize the heat effects and the recast layer on sidewalls but are typically used on thin sheet. The combination of both present a high potential for industrial applications such as injector or cooling holes where the bore sidewall topology has a major influence on the dynamics of the gas flow. In this paper we present results using this combination. The effect of pulse energy, repetition rate and revolution speed of the head on both geometry and roughness are discussed. The quality of the sidewall is checked by roughness measurement and by metallographic analysis (SEM; chemical etching, micro hardness).

  9. Femtosecond stabilization of optical fiber links based on RF power detection

    International Nuclear Information System (INIS)

    X-ray light sources like the free electron laser FLASH in Hamburg or the future XFEL generate light pulses with durations in the order of a few ten femtoseconds. To fulfill the requirements for the synchronisation of various components on this timescale, optical synchronisation systems are already successfully used. In this diploma thesis a novel photodiode-based, detection principle for the measurement of drifts in the optical links of such a synchronisation system is developed. The detection principle is nearly drift-free and highly robust. It is demonstrated that the long term stability of the assembled detector over 33 h is below 5 fs (peak to peak) at a standard deviation of 0.86 fs. Furthermore, an active stabilisation of a fibre link using this detector is successfully achieved. (orig.)

  10. Efficient nonlinear companding scheme for substantial reduction in peak-to-average power ratio of OFDM

    Institute of Scientific and Technical Information of China (English)

    Kasun Bandara,Atul Sewaiwar,; Yeon-Ho Chung

    2015-01-01

    Orthogonal frequency division multiplexing (OFDM) produces a high peak-to-average power ratio (PAPR) that ad-versely affects high-speed OFDM data transmission. In order to reduce the high PAPR, an efficient nonlinear companding trans-form (NCT) function is proposed. With the proposed NCT function, the compression and expansion weights can be applied indepen-dently with suitably chosen function parameter values. As a re-sult, the proposed function can easily maintain the average signal power approximately unchanged during the companding process. In this regard, the proposed function is superior to previously pro-posed schemes. Also, the simulations show the outstanding PAPR reduction performance of the proposed function. It is demonstrated that the proposed scheme performs wel with nonlinear transmitter amplifiers and delivers superior error performance, compared with error function and exponential function based schemes.

  11. Constellation Compaction Design to Reduce Both PAPR and Average Power in OFDM Systems

    Directory of Open Access Journals (Sweden)

    Al-Shaikhi Ali

    2010-01-01

    Full Text Available This paper proposes a novel way to compact the constellation points in QAM modulation schemes and exploits this compaction to reduce the peak to average power ratio (PAPR in orthogonal frequency division multiplexing (OFDM systems. The compaction is accomplished using one dimensional product code (PC. Significant PAPR reduction is achieved by carefully mapping the points in the compact version of the constellation to their radial symmetric points and choosing for transmission signalling points which result in lower PAPRs. Specifically, the complementary cumulative distribution function (CCDF of the modified OFDM signal shows about five dB improvement in PAPR at a clipping probability of 10−4 over the original OFDM signal. This performance is comparable to that in similar PAPR reduction schemes; however, it is achieved using simple single parity check (SPC product code and at lower average power.

  12. A Comparison Between Two Average Modelling Techniques of AC-AC Power Converters

    Directory of Open Access Journals (Sweden)

    Pawel Szczesniak

    2015-03-01

    Full Text Available In this paper, a comparative evaluation of two modelling tools for switching AC-AC power converters is presented. Both of them are based on average modelling techniques. The first approach is based on the circuit averaging technique and consists in the topological manipulations, applied to a converters states. The second approach makes use of state-space averaged model of the converter and is based on analytical manipulations using the different state representations of a converter. The two modelling techniques are applied to a same AC-AC converter called matrix-reactance frequency converter based on buck-boost topology. These techniques are compared on the basis of their rapidity, quantity of calculations and transformations and its limitations.

  13. Thermal distortion and birefringence in repetition-rate plasma electrode Pockels cell for high average power

    Institute of Scientific and Technical Information of China (English)

    Dingxiang Cao; Xiongjun Zhang; Wanguo Zheng; Shaobo He; Zhan Sui

    2007-01-01

    We numerically study thermally induced birefringence and distortion in plasma electrode Pockels cell based on KD*P as the electro-optic material. This device can repetitively operate under the heat capacity mode.Simulation results indicate that the excellent switching performances and low wave-front distortion are achieved within several tens seconds working time at average power in excess of 1 kW.

  14. Atmospheric propagation simulations and Boeing's high average power free electron laser

    OpenAIRE

    Ramos, Luis de, llib.

    1995-01-01

    The development of a high average power FEL for military applications, whether shipboard or not, represents a significant advancement in technology over present weapons systems design. The FEL has significant advantages over conventional kinetic systems and other classical high-energy laser systems. The rapid response, wavelength tunability, and infinite magazine make the FEL a highly desirable shipboard weapon system. The initial pan of this thesis examines the advantages of a FEL over a con...

  15. High-average-power normal-mode Cr:Nd:GSGG lasers

    International Nuclear Information System (INIS)

    Several recent studies have shown the laser host material gadolinium scandium gallium garnet (GSGG) doped with Nd/sup 3+/ and sensitized by Cr/sup 3+/ to be a more efficient laser than the well-known commonly used Nd:YAG. However, all these studies have been performed at relatively low average pump power. To evaluate Nd:GSGG as a high-average-power laser material, the authors measured absorption efficiency, heat deposition rate, and thermally induced stress in 4- and 6.3-mm diam GSGG laser rods up to 2-KW pumping levels and compared these values, as well as laser output powers, to the results of similar experiments in Nd:YAG. In this work, 79-mm long Cr:Nd:GSGG rods have been tested using a silver-plated elliptical pump reflector which housed a xenon flashlamp running at a 6-Hz repetition rate with a pulse duration of ≅500 μs. The authors used the frequency-doubled output from a cw Nd:YAG laser at 532 nm as a probe beam to measure average thermal focal length and thermally induced birefringence

  16. Temperature-insensitive frequency tripling for generating high-average power UV lasers.

    Science.gov (United States)

    Zhong, Haizhe; Yuan, Peng; Wen, Shuangchun; Qian, Liejia

    2014-02-24

    Aimed for generating high-average power ultraviolet (UV) lasers via third-harmonic generation (THG) consisting of frequency doubling and tripling stages, we numerically and experimentally demonstrate a novel frequency tripling scheme capable of supporting temperature-insensitive phase-matching (PM). Two cascaded tripling crystals, with opposite signs of the temperature derivation of phase-mismatch, are proposed and theoretically studied for improving the temperature-acceptance of PM. The proof-of-principle tripling experiment using two crystals of LBO and BBO shows that the temperature acceptance can be ~1.5 times larger than that of using a single tripling crystal. In addition, the phase shift caused by air dispersion, along with its influence on the temperature-insensitive PM, are also discussed. To illustrate the potential applications of proposed two-crystal tripling design in the high-average-power regime, full numerical simulations for the tripling process, are implemented based on the realistic crystals. The demonstrated two-crystal tripling scheme may provide a promising route to high-average-power THG in the UV region.

  17. Temperature-insensitive frequency tripling for generating high-average power UV lasers.

    Science.gov (United States)

    Zhong, Haizhe; Yuan, Peng; Wen, Shuangchun; Qian, Liejia

    2014-02-24

    Aimed for generating high-average power ultraviolet (UV) lasers via third-harmonic generation (THG) consisting of frequency doubling and tripling stages, we numerically and experimentally demonstrate a novel frequency tripling scheme capable of supporting temperature-insensitive phase-matching (PM). Two cascaded tripling crystals, with opposite signs of the temperature derivation of phase-mismatch, are proposed and theoretically studied for improving the temperature-acceptance of PM. The proof-of-principle tripling experiment using two crystals of LBO and BBO shows that the temperature acceptance can be ~1.5 times larger than that of using a single tripling crystal. In addition, the phase shift caused by air dispersion, along with its influence on the temperature-insensitive PM, are also discussed. To illustrate the potential applications of proposed two-crystal tripling design in the high-average-power regime, full numerical simulations for the tripling process, are implemented based on the realistic crystals. The demonstrated two-crystal tripling scheme may provide a promising route to high-average-power THG in the UV region. PMID:24663750

  18. High average power CO II laser MOPA system for Tin target LPP EUV light source

    Science.gov (United States)

    Ariga, Tatsuya; Hoshino, Hideo; Endo, Akira

    2007-02-01

    Extreme ultraviolet lithography (EUVL) is the candidate for next generation lithography to be introduced by the semiconductor industry to HVM (high volume manufacturing) in 2013. The power of the EUVL light source has to be at least 115W at a wavelength of 13.5nm. A laser produced plasma (LPP) is the main candidate for this light source but a cost effective laser driver is the key requirement for the realization of this concept. We are currently developing a high power and high repetition rate CO II laser system to achieve 50 W intermediate focus EUV power with a Tin droplet target. We have achieved CE of 2.8% with solid Tin wire target by a transversely excited atmospheric (TEA) CO II laser MOPA system with pulse width, pulse energy and pulse repetition rate as 10~15 ns, 30 mJ and 10 Hz, respectively. A CO II laser system with a short pulse length less than 15 ns, a nominal average power of a few kW, and a repetition rate of 100 kHz, based on RF-excited, fast axial flow CO II laser amplifiers is under development. Output power of about 3 kW has been achieved with a pulse length of 15 ns at 130 kHz repletion rate in a small signal amplification condition with P(20) single line. The phase distortion of the laser beam after amplification is negligible and the beam can be focused to about 150μm diameter in 1/e2. The CO II laser system is reported on short pulse amplification performance using RF-excited fast axial flow lasers as amplifiers. And the CO II laser average output power scaling is shown towards 5~10 kW with pulse width of 15 ns from a MOPA system.

  19. Experimental studies of high average power CO2-laser-induced thermomechanical processes

    Science.gov (United States)

    Hugenschmidt, Manfred

    1990-04-01

    Pulsed high average power CO2 lasers allow for a most efficient conversion of coherence IR laser radiation into thermal and mechanical energies. Investigations using a specially developed repetitively pulsed high energy CO2 laser are presented. This powerful device provides mean powers of several kW and peak powers of the individual pulses in the multi-MW range. Studies were performed to obtain information on the transient behavior of the fast energy transfer mechanisms that occur at peak power densities near or above the surface plasma ignition thresholds. As shown, these plasma waves are periodically building up, expanding and recombining during the short time intervals between subsequent pulses, even in the case of the highest repetition rates that are presently limited to 100 Hz. Besides the efficient thermal energy transfer through plasma enhanced thermal coupling mechanisms, the simultaneously induced mechanical pressure waves are providing an additional impulsive loading of the targets. These pressures were investigated by using PVDF gauges. The experiments reveal that these effects are also responsible for improvements, concerning the energy balance, in most manufacturing processes such as in cutting or in drilling, where these fast thermomechanically coupled processes, for example, contribute to increase the mass removal rates.

  20. Experimental studies of high-average-power pulsed CO2-laser-induced thermomechanical processes

    Science.gov (United States)

    Hugenschmidt, Manfred

    1990-10-01

    Pulsed high average power C02-lasers allow for a most efficient conversion of coherent IR-laser radiation into thermal and mechanical energies. This paper is concerned with investigations using a specially developed repetitively pulsed high energy C02-laser. This powerful device provides mean powers of several kW and peak powers of the individual pulses in the multi-MW range. Studies were performed to obtain information on the transient behaviour of the fast energy transfer mechanisms that occur at peak power densities near or above the surface plasma ignition thresholds. As shown, these plasma waves are periodically building up, expanding and recombining during the short time intervals between subsequent pulses, even in case of the highest repetition rates that are presently limited to 100 Hz. Besides the efficient thermal energy transfer through plasma-enhanced thermal coupling mechanisms, the simultaneously induced mechanical pressure waves are providing an additional impulsive loading of the targets. These pressures were investigated by using PVDF gauges. The experiments reveal that these effects too are responsible for improvements, concerning the energy balance, in most manufacturing processes such as in cutting or in drilling, where these fast thermo-mechanically coupled processes, for example, contribute to increase the mass removal rates.

  1. High-throughput machining using high average power ultrashort pulse lasers and ultrafast polygon scanner

    Science.gov (United States)

    Schille, Joerg; Schneider, Lutz; Streek, André; Kloetzer, Sascha; Loeschner, Udo

    2016-03-01

    In this paper, high-throughput ultrashort pulse laser machining is investigated on various industrial grade metals (Aluminium, Copper, Stainless steel) and Al2O3 ceramic at unprecedented processing speeds. This is achieved by using a high pulse repetition frequency picosecond laser with maximum average output power of 270 W in conjunction with a unique, in-house developed two-axis polygon scanner. Initially, different concepts of polygon scanners are engineered and tested to find out the optimal architecture for ultrafast and precision laser beam scanning. Remarkable 1,000 m/s scan speed is achieved on the substrate, and thanks to the resulting low pulse overlap, thermal accumulation and plasma absorption effects are avoided at up to 20 MHz pulse repetition frequencies. In order to identify optimum processing conditions for efficient high-average power laser machining, the depths of cavities produced under varied parameter settings are analyzed and, from the results obtained, the characteristic removal values are specified. The maximum removal rate is achieved as high as 27.8 mm3/min for Aluminium, 21.4 mm3/min for Copper, 15.3 mm3/min for Stainless steel and 129.1 mm3/min for Al2O3 when full available laser power is irradiated at optimum pulse repetition frequency.

  2. High-power femtosecond-terahertz pulse induces a wound response in mouse skin

    Science.gov (United States)

    Kim, Kyu-Tae; Park, Jaehun; Jo, Sung Jin; Jung, Seonghoon; Kwon, Oh Sang; Gallerano, Gian Piero; Park, Woong-Yang; Park, Gun-Sik

    2013-08-01

    Terahertz (THz) technology has emerged for biomedical applications such as scanning, molecular spectroscopy, and medical imaging. Although a thorough assessment to predict potential concerns has to precede before practical utilization of THz source, the biological effect of THz radiation is not yet fully understood with scant related investigations. Here, we applied a femtosecond-terahertz (fs-THz) pulse to mouse skin to evaluate non-thermal effects of THz radiation. Analysis of the genome-wide expression profile in fs-THz-irradiated skin indicated that wound responses were predominantly mediated by transforming growth factor-beta (TGF-β) signaling pathways. We validated NFκB1- and Smad3/4-mediated transcriptional activation in fs-THz-irradiated skin by chromatin immunoprecipitation assay. Repeated fs-THz radiation delayed the closure of mouse skin punch wounds due to up-regulation of TGF-β. These findings suggest that fs-THz radiation initiate a wound-like signal in skin with increased expression of TGF-β and activation of its downstream target genes, which perturbs the wound healing process in vivo.

  3. Application of Bayesian model averaging to measurements of the primordial power spectrum

    CERN Document Server

    Parkinson, David

    2010-01-01

    Cosmological parameter uncertainties are often stated assuming a particular model, neglecting the model uncertainty, even when Bayesian model selection is unable to identify a conclusive best model. Bayesian model averaging is a method for assessing parameter uncertainties in situations where there is also uncertainty in the underlying model. We apply model averaging to the estimation of the parameters associated with the primordial power spectra of curvature and tensor perturbations. We use CosmoNest and MultiNest to compute the model Evidences and posteriors, using cosmic microwave data from WMAP, ACBAR, BOOMERanG and CBI, plus large-scale structure data from the SDSS DR7. We find that the model-averaged 95% credible interval for the spectral index using all of the data is 0.940 < n_s < 1.000, where n_s is specified at a pivot scale 0.015 Mpc^{-1}. For the tensors model averaging can tighten the credible upper limit, depending on prior assumptions.

  4. Dual-scale turbulence in filamenting laser beams at high average power

    CERN Document Server

    Schubert, Elise; Mongin, Denis; Kasparian, Jérôme; Wolf, Jean-Pierre; Klingebiel, Sandro; Schultze, Marcel; Metzger, Thomas; Michel, Knut

    2016-01-01

    We investigate the self-induced turbulence of high repetition rate laser filaments over a wide range of average powers (1 mW to 100 W) and its sensitivity to external atmospheric turbulence. Although both externally-imposed and self-generated turbulences can have comparable magnitudes, they act on different temporal and spatial scales. While the former drives the shot-to-shot motion at the millisecond time scale, the latter acts on the 0.5 s scale. As a consequence, their effects are decoupled, preventing beam stabilization by the thermally-induced low-density channel produced by the laser filaments.

  5. A self-organizing power system stabilizer using Fuzzy Auto-Regressive Moving Average (FARMA) model

    Energy Technology Data Exchange (ETDEWEB)

    Park, Y.M.; Moon, U.C. [Seoul National Univ. (Korea, Republic of). Electrical Engineering Dept.; Lee, K.Y. [Pennsylvania State Univ., University Park, PA (United States). Electrical Engineering Dept.

    1996-06-01

    This paper presents a self-organizing power system stabilizer (SOPSS) which use the Fuzzy Auto-Regressive Moving Average (FARMA) model. The control rules and the membership functions of the proposed logic controller are generated automatically without using any plant model. The generated rules are stored in the fuzzy rule space and updated on-line by a self-organizing procedure. To show the effectiveness of the proposed controller, comparison with a conventional controller for one-machine infinite-bus system is presented.

  6. New material for high average power laser based on silica glass

    International Nuclear Information System (INIS)

    We are developing high average power laser materials based on silica glass. The uniform dispersion of rare earth ions in SiO2 glass, which is the most difficult thing to make laser material, was achieved by using rare earth distributed Zeolite X. Nd doped SiO2 glass shows enough properties as a laser material, but its spectroscopic properties are weaker than commonly used phosphate glass. Some trial for improving the spectroscopic properties are done and it is shown that the co-doping effect in supercage of Zeolite X and phosphoric acid treatment are useful. (orig.)

  7. Method and system for modulation of gain suppression in high average power laser systems

    Science.gov (United States)

    Bayramian, Andrew James

    2012-07-31

    A high average power laser system with modulated gain suppression includes an input aperture associated with a first laser beam extraction path and an output aperture associated with the first laser beam extraction path. The system also includes a pinhole creation laser having an optical output directed along a pinhole creation path and an absorbing material positioned along both the first laser beam extraction path and the pinhole creation path. The system further includes a mechanism operable to translate the absorbing material in a direction crossing the first laser beam extraction laser path and a controller operable to modulate the second laser beam.

  8. Peak-to-Average Power Ratio Reduction in NC-OFDM based Cognitive Radio

    Directory of Open Access Journals (Sweden)

    Mohammad Zavid Parvez

    2012-04-01

    Full Text Available This paper presents a novel technique for reducing the peak-to-average power ratio (PAPR innon-contiguous bands spectrum of Orthogonal Frequency Division Multiplexing (OFDM basedCognitive Radio (CR. The proposed system exposed is to carry the earlier period channelinformation as well as the spectrum sensing to utilize the radio spectrum to achieve anappropriate PAPR reduction. It is maintaining end-to-end throughput performance by using a setof approaches in the current CR environment. The simulation results for PAPR reduction hasshown that higher constellation modulation schemes are better compared to lower constellationmodulation schemes.

  9. Peak-to-Average Power Ratio Reduction in NC-OFDM based Cognitive Radio.

    Directory of Open Access Journals (Sweden)

    Mohammad Zavid Parvez

    2012-04-01

    Full Text Available This paper presents a novel technique for reducing the peak-to-average power ratio (PAPR in non-contiguous bands spectrum of Orthogonal Frequency Division Multiplexing (OFDM based Cognitive Radio (CR. The proposed system exposed to carry the past channel information and the spectrum sensing to utilize the radio spectrum as well as achieving an appropriate PAPR reduction and maintaining end-to-end throughput performance by using a set of approaches in the current CR environment. The simulation results for PAPR reduction has shown that higher constellation modulation schemes are better compared to lower constellation modulation schemes.

  10. Clustering monthly average global insolation for the determination of solar thermal power plants potential sites

    International Nuclear Information System (INIS)

    The insolation level represents a very specific aspect when selecting solar thermal power plants sites. Sites with high insolation level, especially high direct solar radiation, reduce the amount of fossil fuel to be consumed for a given operation strategy of the plant. In this paper, a neural network-based method is proposed to cluster the monthly average daily global insolation of different sites. A Self-Organizing Feature Map SOM is applied to cluster insolation data of two systems as two case studies. As a result, sites with similar radiation conditions are identified in a self-organized fashion; they build independent clusters. The resulting clusters centers represent typical radiation conditions of the analyzed system. The proposed method presents a very helpful tool for intelligent radiation data analysis and is helpful for the decision making process of the site selection for the application of solar thermal power plants. (Author)

  11. Peak to Average Power Ratio Reduction of OFDM Signal by Combining Clipping with Walsh Hadamard Transform

    Directory of Open Access Journals (Sweden)

    Lavish Kansal

    2013-03-01

    Full Text Available Wireless communications have been developed widelyand rapidly in the modern world especially duringthe last decade. Orthogonal Frequency Division Multiplexing (OFDM has grown to a popularcommunication technique for high speed communication. Besides of the advantages, one of maindisadvantage of OFDM is high peak to average powerratio (PAPR. In this paper, a PAPR reductionmethod is proposed that is based on combining clipping with Walsh Hadamard Transform (WHT.WHT isa precoding technique which is having less complexity compared to the other existing power reductiontechniques and also it can reduce PAPR considerablyand results in no distortion. The performance of theproposed scheme is examined through computer simulations and it is found that power reductions areobtained.

  12. Non-chain pulsed DF laser with an average power of the order of 100 W

    Science.gov (United States)

    Pan, Qikun; Xie, Jijiang; Wang, Chunrui; Shao, Chunlei; Shao, Mingzhen; Chen, Fei; Guo, Jin

    2016-07-01

    The design and performance of a closed-cycle repetitively pulsed DF laser are described. The Fitch circuit and thyratron switch are introduced to realize self-sustained volume discharge in SF6-D2 mixtures. The influences of gas parameters and charging voltage on output characteristics of non-chain pulsed DF laser are experimentally investigated. In order to improve the laser power stability over a long period of working time, zeolites with different apertures are used to scrub out the de-excitation particles produced in electric discharge. An average output power of the order of 100 W was obtained at an operating repetition rate of 50 Hz, with amplitude difference in laser pulses 50 Hz.

  13. Welding of transparent polymers using femtosecond laser

    Science.gov (United States)

    Roth, Gian-Luca; Rung, Stefan; Hellmann, Ralf

    2016-02-01

    Based on nonlinear absorption, we report on laser welding of cycloolefin copolymers without any additional absorption layer employing infrared femtosecond laser. To the best of our knowledge, this is the first report of ultrashort laser welding of this material class, revealing a remarkable high processing speed of 20 mm/s in a single pass mode. Using a 1028 nm laser having a pulse duration of 220 fs at a repetition rate of 571 kHz leads to a welding seam width between 38 and 137 μm, depending on the applied laser average power. The welded joint is characterized by a maximum shear strength of 40 MPa. The experimental results are compared to those reported for femtosecond laser welding of PMMA and to those published for using a Thulium fiber laser.

  14. Intensity noise reduction of a high-power nonlinear femtosecond fiber amplifier based on spectral-breathing self-similar parabolic pulse evolution

    Science.gov (United States)

    Wang, Sijia; Liu, Bowen; Song, Youjian; Hu, Minglie

    2016-04-01

    We report on a simple passive scheme to reduce the intensity noise of high-power nonlinear fiber amplifiers by use of the spectral-breathing parabolic evolution of the pulse amplification with an optimized negative initial chirp. In this way, the influences of amplified spontaneous emission (ASE) on the amplifier intensity noise can be efficiently suppressed, owing to the lower overall pulse chirp, shorter spectral broadening distance, as well as the asymptotic attractive nature of self-similar pulse amplification. Systematic characterizations of the relative intensity noise (RIN) of a free-running nonlinear Yb-doped fiber amplifier are performed over a series of initial pulse parameters. Experiments show that the measured amplifier RIN increases respect to the decreased input pulse energy, due to the increased amount of ASE noise. For pulse amplification with a proper negative initial chirp, the increase of RIN is found to be smaller than with a positive initial chirp, confirming the ASE noise tolerance of the proposed spectral-breathing parabolic amplification scheme. At the maximum output average power of 27W (25-dB amplification gain), the incorporation of an optimum negative initial chirp (-0.84 chirp parameter) leads to a considerable amplifier root-mean-square (rms) RIN reduction of ~20.5% (integrated from 10 Hz to 10 MHz Fourier frequency). The minimum amplifier rms RIN of 0.025% (integrated from 1 kHz to 5 MHz Fourier frequency) is obtained along with the transform-limited compressed pulse duration of 55fs. To our knowledge, the demonstrated intensity noise performance is the lowest RIN level measured from highpower free-running femtosecond fiber amplifiers.

  15. Effect of Carbohydrate Solutions with Different level of Sugar on Average Anaerobic power and Fatigue index of karate Players

    OpenAIRE

    AMINIAN, Ensiyeh

    2015-01-01

    Abstract. Main aim of this research was investigating effect of carbohydrate solutions with different level of sager on average anaerobic power and fatigue index of karate players. Statistical sample of this research was 72 karate players of Khorasa Razavi province and 48 people were selected randomly. Average age, weight, height, and BMI were measures Average age of athletes was 22.23, average height 175cm and average weight 72.77. We used frequency distribution tables and indexes of the cen...

  16. A method for the estimation of p-mode parameters from averaged solar oscillation power spectra

    CERN Document Server

    Reiter, J; Kosovichev, A G; Schou, J; Scherrer, P H; Larson, T P

    2015-01-01

    A new fitting methodology is presented which is equally well suited for the estimation of low-, medium-, and high-degree mode parameters from $m$-averaged solar oscillation power spectra of widely differing spectral resolution. This method, which we call the "Windowed, MuLTiple-Peak, averaged spectrum", or WMLTP Method, constructs a theoretical profile by convolving the weighted sum of the profiles of the modes appearing in the fitting box with the power spectrum of the window function of the observing run using weights from a leakage matrix that takes into account both observational and physical effects, such as the distortion of modes by solar latitudinal differential rotation. We demonstrate that the WMLTP Method makes substantial improvements in the inferences of the properties of the solar oscillations in comparison with a previous method that employed a single profile to represent each spectral peak. We also present an inversion for the internal solar structure which is based upon 6,366 modes that we ha...

  17. Green sub-ps laser exceeding 400 W of average power

    Science.gov (United States)

    Gronloh, Bastian; Russbueldt, Peter; Jungbluth, Bernd; Hoffmann, Hans-Dieter

    2014-02-01

    We present the world's first laser at 515 nm with sub-picosecond pulses and an average power of 445 W. To realize this beam source we utilize an Yb:YAG-based infrared laser consisting of a fiber MOPA system as a seed source, a rod-type pre-amplifier and two Innoslab power amplifier stages. The infrared system delivers up to 930 W of average power at repetition rates between 10 and 50 MHz and with pulse durations around 800 fs. The beam quality in the infrared is M² = 1.1 and 1.5 in fast and slow axis. As a frequency doubler we chose a Type-I critically phase-matched Lithium Triborate (LBO) crystal in a single-pass configuration. To preserve the infrared beam quality and pulse duration, the conversion was carefully modeled using numerical calculations. These take dispersion-related and thermal effects into account, thus enabling us to provide precise predictions of the properties of the frequency-doubled beam. To be able to model the influence of thermal dephasing correctly and to choose appropriate crystals accordingly, we performed extensive absorption measurements of all crystals used for conversion experiments. These measurements provide the input data for the thermal FEM analysis and calculation. We used a Photothermal Commonpath Interferometer (PCI) to obtain space-resolved absorption data in the bulk and at the surfaces of the LBO crystals. The absorption was measured at 1030 nm as well as at 515 nm in order to take into account the different absorption behavior at both occurring wavelengths.

  18. On type I cascaded quadratic soliton compression in lithium niobate: Compressing femtosecond pulses from high-power fiber lasers

    CERN Document Server

    Bache, Morten

    2009-01-01

    The output pulses of a commercial high-power femtosecond fiber laser or amplifier are typically around 300-500 fs with a wavelength around 1030 nm and 10s of $\\mu$J pulse energy. Here we present a numerical study of cascaded quadratic soliton compression of such pulses in LiNbO$_3$ using a type I phase matching configuration. We find that because of competing cubic material nonlinearities compression can only occur in the nonstationary regime, where group-velocity mismatch induced Raman-like nonlocal effects prevent compression to below 100 fs. However, the strong group velocity dispersion implies that the pulses can achieve moderate compression to sub-130 fs duration in available crystal lengths. Most of the pulse energy is conserved because the compression is moderate. The effects of diffraction and spatial walk-off is addressed, and in particular the latter could become an issue when compressing in such long crystals (around 10 cm long). We finally show that the second harmonic contains a short pulse locke...

  19. Peak to Average Power Ratio Reduction of OFDM Signals Using Clipping and Iterative Processing Methods

    Directory of Open Access Journals (Sweden)

    Ahmed K. Hassan

    2008-01-01

    Full Text Available One of the serious problems in any wireless communication system using multi carrier modulation technique like Orthogonal Frequency Division Multiplexing (OFDM is its Peak to Average Power Ratio (PAPR.It limits the transmission power due to the limitation of dynamic range of Analog to Digital Converter and Digital to Analog Converter (ADC/DAC and power amplifiers at the transmitter, which in turn sets the limit over maximum achievable rate.This issue is especially important for mobile terminals to sustain longer battery life time. Therefore reducing PAPR can be regarded as an important issue to realize efficient and affordable mobile communication services.This paper presents an efficient PAPR reduction method for OFDM signal. This method is based on clipping and iterative processing. Iterative processing is performed to limit PAPR in time domain but the subtraction process of the peak that over PAPR threshold with the original signal is done in frequency domain, not in time like usual clipping technique. The results of this method is capable of reducing the PAPR significantly with minimum bit error rate (BER degradation.

  20. Thermally induced distortion of a high-average-power laser system by an optical transport system

    Science.gov (United States)

    Chow, Robert; Ault, Linda E.; Taylor, John R.; Jedlovec, Don

    1999-11-01

    The atomic vapor laser isotope separation process uses high- average power lasers that have the commercial potential to enrich uranium for the electric power utilities. The transport of the laser beam through the laser system to the separation chambers requires high performance optical components, most of which have either fused silica or Zerodur as the substrate material. One of the requirements of the optical components is to preserve the wavefront quality of the laser beam that propagate over long distances. Full aperture tests with the high power process lasers and finite element analysis (FEA) have been performed on the transport optics. The wavefront distortions of the various sections of the transport path were measured with diagnostic Hartmann sensor packages. The FEA results were derived from an in-house thermal-structural- optical code which is linked to the commercially available CodeV program. In comparing the measured and predicted results, the bulk absorptance of fused silica was estimated to about 50 ppm/cm in the visible wavelength regime. Wavefront distortions will be reported on optics made from fused silica and Zerodur substrate materials.

  1. Sub-100 fs high average power directly blue-diode-laser-pumped Ti:sapphire oscillator

    Science.gov (United States)

    Rohrbacher, Andreas; Markovic, Vesna; Pallmann, Wolfgang; Resan, Bojan

    2016-03-01

    Ti:sapphire oscillators are a proven technology to generate sub-100 fs (even sub-10 fs) pulses in the near infrared and are widely used in many high impact scientific fields. However, the need for a bulky, expensive and complex pump source, typically a frequency-doubled multi-watt neodymium or optically pumped semiconductor laser, represents the main obstacle to more widespread use. The recent development of blue diodes emitting over 1 W has opened up the possibility of directly diode-laser-pumped Ti:sapphire oscillators. Beside the lower cost and footprint, a direct diode pumping provides better reliability, higher efficiency and better pointing stability to name a few. The challenges that it poses are lower absorption of Ti:sapphire at available diode wavelengths and lower brightness compared to typical green pump lasers. For practical applications such as bio-medicine and nano-structuring, output powers in excess of 100 mW and sub-100 fs pulses are required. In this paper, we demonstrate a high average power directly blue-diode-laser-pumped Ti:sapphire oscillator without active cooling. The SESAM modelocking ensures reliable self-starting and robust operation. We will present two configurations emitting 460 mW in 82 fs pulses and 350 mW in 65 fs pulses, both operating at 92 MHz. The maximum obtained pulse energy reaches 5 nJ. A double-sided pumping scheme with two high power blue diode lasers was used for the output power scaling. The cavity design and the experimental results will be discussed in more details.

  2. PEAK-TO-AVERAGE POWER RATIO REDUCTION USING CODING AND HYBRID TECHNIQUES FOR OFDM SYSTEM

    Directory of Open Access Journals (Sweden)

    Bahubali K. Shiragapur

    2016-03-01

    Full Text Available In this article, the research work investigated is based on an error correction coding techniques are used to reduce the undesirable Peak-to-Average Power Ratio (PAPR quantity. The Golay Code (24, 12, Reed-Muller code (16, 11, Hamming code (7, 4 and Hybrid technique (Combination of Signal Scrambling and Signal Distortion proposed by us are used as proposed coding techniques, the simulation results shows that performance of Hybrid technique, reduces PAPR significantly as compared to Conventional and Modified Selective mapping techniques. The simulation results are validated through statistical properties, for proposed technique’s autocorrelation value is maximum shows reduction in PAPR. The symbol preference is the key idea to reduce PAPR based on Hamming distance. The simulation results are discussed in detail, in this article.

  3. Simulation on Peak-to-Average Power Ratio for Orthogonal Frequency Division Multiplexing

    Institute of Scientific and Technical Information of China (English)

    SHAN Weifeng; MENG Baohong; LIU Ningning; LI Hui; ZHANG Hongwei

    2006-01-01

    Clipping is a simple and convenient PAPR (peak-to-average power ratio) reduction method for high speed OFDM (orthogonal frequency division multiplexing) communication system. In this paper, we propose a new PAPR reduction method for Wireless-MAN(metropolitan area network)-OFDM system based on IEEE 802.16, which is over-sampling clipping arithmetic. Simulation and performance of the over-samples clipping's PAPR reduction capability, BER effect is given. The simulation indicates that the PAPR of at least 99.9% OFDM symbol is below 6dB after 2 Nyquist rate clipping, and the performance of BER has 1dB SNR(signal noise ratio) loss. The results prove that this method has better capacity to reducing PAPR. So it can be well used in WMAN-OFDM system.

  4. A Method for the Estimation of p-Mode Parameters from Averaged Solar Oscillation Power Spectra

    Science.gov (United States)

    Reiter, J.; Rhodes, E. J., Jr.; Kosovichev, A. G.; Schou, J.; Scherrer, P. H.; Larson, T. P.

    2015-04-01

    A new fitting methodology is presented that is equally well suited for the estimation of low-, medium-, and high-degree mode parameters from m-averaged solar oscillation power spectra of widely differing spectral resolution. This method, which we call the “Windowed, MuLTiple-Peak, averaged-spectrum” or WMLTP Method, constructs a theoretical profile by convolving the weighted sum of the profiles of the modes appearing in the fitting box with the power spectrum of the window function of the observing run, using weights from a leakage matrix that takes into account observational and physical effects, such as the distortion of modes by solar latitudinal differential rotation. We demonstrate that the WMLTP Method makes substantial improvements in the inferences of the properties of the solar oscillations in comparison with a previous method, which employed a single profile to represent each spectral peak. We also present an inversion for the internal solar structure, which is based upon 6366 modes that we computed using the WMLTP method on the 66 day 2010 Solar and Heliospheric Observatory/MDI Dynamics Run. To improve both the numerical stability and reliability of the inversion, we developed a new procedure for the identification and correction of outliers in a frequency dataset. We present evidence for a pronounced departure of the sound speed in the outer half of the solar convection zone and in the subsurface shear layer from the radial sound speed profile contained in Model S of Christensen-Dalsgaard and his collaborators that existed in the rising phase of Solar Cycle 24 during mid-2010.

  5. Peak-to-average power ratio reduction in interleaved OFDMA systems

    KAUST Repository

    Al-Shuhail, Shamael

    2015-12-07

    Orthogonal frequency division multiple access (OFDMA) systems suffer from several impairments, and communication system engineers use powerful signal processing tools to combat these impairments and to keep up with the capacity/rate demands. One of these impairments is high peak-to-average power ratio (PAPR) and clipping is the simplest peak reduction scheme. However, in general, when multiple users are subjected to clipping, frequency domain clipping distortions spread over the spectrum of all users. This results in compromised performance and hence clipping distortions need to be mitigated at the receiver. Mitigating these distortions in multiuser case is not simple and requires complex clipping mitigation procedures at the receiver. However, it was observed that interleaved OFDMA presents a special structure that results in only self-inflicted clipping distortions (i.e., the distortions of a particular user do not interfere with other users). In this work, we prove analytically that distortions do not spread over multiple users (while utilizing interleaved carrier assignment in OFDMA) and construct a compressed sensing system that utilizes the sparsity of the clipping distortions and recovers it on each user. We provide numerical results that validate our analysis and show promising performance for the proposed clipping recovery scheme.

  6. 7.5 MeV High Average Power Linear Accelerator System for Food Irradiation Applications

    International Nuclear Information System (INIS)

    In December 2004 the US Food and Drug Administration (FDA) approved the use of 7.5 MeV X-rays for irradiation of food products. The increased efficiency for treatment at 7.5 MeV (versus the previous maximum allowable X-ray energy of 5 MeV) will have a significant impact on processing rates and, therefore, reduce the per-package cost of irradiation using X-rays. Titan Pulse Sciences Division is developing a new food irradiation system based on this ruling. The irradiation system incorporates a 7.5 MeV electron linear accelerator (linac) that is capable of 100 kW average power. A tantalum converter is positioned close to the exit window of the scan horn. The linac is an RF standing waveguide structure based on a 5 MeV accelerator that is used for X-ray processing of food products. The linac is powered by a 1300 MHz (L-Band) klystron tube. The electrical drive for the klystron is a solid state modulator that uses inductive energy store and solid-state opening switches. The system is designed to operate 7000 hours per year. Keywords: Rf Accelerator, Solid state modulator, X-ray processing

  7. Development of high average power industrial Nd:YAG laser with peak power of 10 kW class

    International Nuclear Information System (INIS)

    We developed and commercialized an industrial pulsed Nd:YAG laser with peak power of 10 kW class for fine cutting and drilling applications. Several commercial models have been investigated in design and performance. We improved its quality to the level of commercial Nd:YAG laser by an endurance test for each parts of laser system. The maximum peak power and average power of our laser were 10 kW and 250 W, respectively. Moreover, the laser pulse width could be controlled from 0.5 msec to 20 msec continuously. Many optical parts were localized and lowered much in cost. Only few parts were imported and almost 90% in cost were localized. Also, to accellerate the commercialization by the joint company, the training and transfer of technology were pursued in the joint participation in design and assembly by company researchers from the early stage. Three Nd:YAG lasers have been assembled and will be tested in industrial manufacturing process to prove the capability of developed Nd:YAG laser with potential users. (Author)

  8. High Average Power Free-Electron Lasers - A New Source for Materials Processing

    International Nuclear Information System (INIS)

    Material processing with lasers has grown greatly in the previous decade, with annual sales in excess of $1 B (US). In general, the processing consists of material removal steps such as drilling, cutting, as well as joining. Here lasers that are either cw or pulsed with pulsewidths in the mu-s time regime have done well. Some applications, such as the surface processing of polymers to improve look and feel, or treating metals to improve corrosion resistance, require the economical production of laser powers of the tens of kilowatts, and therefore are not yet commercial processes. The development of FELs based on superconducting RF (SRF) linac technology provides a scaleable path to laser outputs above 50 kW, rendering these applications economically viable, since the cost/photon drops as the output power increases. Such FELs will provide quasi-cw (PRFs in the tens of MHz), of ultrafast (pulsewidth ∼ 1 ps) output with very high beam quality. The first example of such an FEL is the IR Demo FEL at the Thomas Jefferson National Accelerator Facility (Jefferson Lab), which produces nearly 2 kW of high average power on a routine basis. Housed in a multilaboratory user facility, we as well as members of our user community have started materials process studies in the areas mentioned earlier. I will present some of the first results of these studies. I will also briefly discuss the status of our DOD-funded project to upgrade the FEL to 10 kW in the mid IR

  9. The monotonic increasing relationship between average powers of CMOS VLSI circuits with and without delay and its applications

    Institute of Scientific and Technical Information of China (English)

    骆祖莹; 闵应骅; 杨士元; 李晓维

    2002-01-01

    The authors theoretically describe the monotonic increasing relationship between averagepowers of a CMOS VLSI circuit with and without delay. The power of an ideal circuit without delay, whichcan be fast computed, has been used as the evaluation criterion for the power of a practical circuit withdelay, which needs more computing time, in such fields as fast estimation for the average power and themaximum power, and fast optimization for the Iow test power. The authors propose a novel simulationapproach that uses delay-free power to compact a long input vector pair sequence into a short sequenceand then, uses the compacted one to fast simulate the average (or maximum) power for a CMOS circuit. Incomparison with the traditional simulation approach that uses an un-compacted input sequence to simu-late the average (or maximum) power, experiment results demonstrate that in the field of fast estimationfor the average power, the present approach can be 6-10 times faster without significant loss in accuracy(less than 3.5% on average), and in the field of fast estimation for the maximum power, this approach canbe 6-8 times faster without significant loss in accuracy (less than 5% on average). In the field of fast op-timization for the test power, the authors propose a novel delay-free power optimization approach for thetest power. Experiment results demonstrate that, in comparison with the approach of direct optimizationand the approach of Hamming distance optimization, this approach is of the highest optimization effi-ciency because it needs shorter time (16.84%) to obtain a better optimization effect (reducing 35.11% testpower).

  10. Synchronously pumped femtosecond optical parametric oscillator at 1053 nm

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A femtosecond optical parametric oscillator synchronously pumped by a Ti:Sapphire oscillator is reported.By the cavity length tuning,the signal wavelength is continuously tuned from 1000 to 1200 nm.The average output power of 32 mW is obtained at 1053 nm.The pulse width is measured to be 342 fs by intensity autocorrelation method.In addition,we observed bichromatic emission during the cavity length tuning process.

  11. Synchronously pumped femtosecond optical parametric oscillator at 1053 nm

    Institute of Scientific and Technical Information of China (English)

    ZHONG Xin; ZHU JiangFeng; ZHOU BinBin; WEI ZhiYi

    2009-01-01

    A femtosecond optical parametric oscillator synchronously pumped by a Ti:Sapphire oscillator is re-ported. By the cavity length tuning, the signal wavelength is continuously tuned from 1000 to 1200 nm. The average output power of 32 mW is obtained at 1053 nm. The pulse width is measured to be 342 fs by intensity autocorrelation method. In addition, we observed bichromatic emission during the cavity length tuning process.

  12. Gas-dynamic explosion of water microparticles under action high-power femtosecond laser pulses

    Science.gov (United States)

    Zemlyanov, Alexander A.; Geints, Yuri E.; Apeksimov, Dmitrii V.

    2006-02-01

    Among the broad audience of problems of atmospheric nonlinear optics the important place is occupied with a problem about interaction of intensive laser radiation with water microparticles. Drops, being in a field of powerful light radiation, owing to effects of evaporation or explosion change the optical characteristics and influence on the optical properties of an environment. It results to that process and the distribution of intensive laser radiation in a particle is characterized by self-influence and is capable to change the internal power of a drop due to occurrence of areas of optical breakdown. In the report the model of destruction of water microparticles under action of supershort laser radiation is submitted. The physical contents of model is the effect of shock boiling up of a liquid at it gas-dynamic expansion from areas subject to optical breakdown.

  13. Femtosecond optical parametric oscillators: a practical approach for power scaling and pulse-shape control

    OpenAIRE

    O'Connor, M.V.; Shepherd, D. P.; Hanna, D.C.

    2004-01-01

    The synchronously pumped optical parametric oscillator (SPOPO) has undergone major developments in the past decade. Quasi-phase-matched nonlinear materials, such as periodically-poled lithium niobate (PPLN) and the availability of higher pump power have led to SPOPO demonstrations with additional functionality including extended tuning ranges throughout the infrared with greater spectral control and frequency tuning agility. In addition, two demonstrations of extended wavelength performance ...

  14. Industrial applications of high-average power high-peak power nanosecond pulse duration Nd:YAG lasers

    Science.gov (United States)

    Harrison, Paul M.; Ellwi, Samir

    2009-02-01

    Within the vast range of laser materials processing applications, every type of successful commercial laser has been driven by a major industrial process. For high average power, high peak power, nanosecond pulse duration Nd:YAG DPSS lasers, the enabling process is high speed surface engineering. This includes applications such as thin film patterning and selective coating removal in markets such as the flat panel displays (FPD), solar and automotive industries. Applications such as these tend to require working spots that have uniform intensity distribution using specific shapes and dimensions, so a range of innovative beam delivery systems have been developed that convert the gaussian beam shape produced by the laser into a range of rectangular and/or shaped spots, as required by demands of each project. In this paper the authors will discuss the key parameters of this type of laser and examine why they are important for high speed surface engineering projects, and how they affect the underlying laser-material interaction and the removal mechanism. Several case studies will be considered in the FPD and solar markets, exploring the close link between the application, the key laser characteristics and the beam delivery system that link these together.

  15. A ROBUST CLUSTER HEAD SELECTION BASED ON NEIGHBORHOOD CONTRIBUTION AND AVERAGE MINIMUM POWER FOR MANETs

    Directory of Open Access Journals (Sweden)

    S.Balaji

    2015-06-01

    Full Text Available Mobile Adhoc network is an instantaneous wireless network that is dynamic in nature. It supports single hop and multihop communication. In this infrastructure less network, clustering is a significant model to maintain the topology of the network. The clustering process includes different phases like cluster formation, cluster head selection, cluster maintenance. Choosing cluster head is important as the stability of the network depends on well-organized and resourceful cluster head. When the node has increased number of neighbors it can act as a link between the neighbor nodes which in further reduces the number of hops in multihop communication. Promisingly the node with more number of neighbors should also be available with enough energy to provide stability in the network. Hence these aspects demand the focus. In weight based cluster head selection, closeness and average minimum power required is considered for purging the ineligible nodes. The optimal set of nodes selected after purging will compete to become cluster head. The node with maximum weight selected as cluster head. Mathematical formulation is developed to show the proposed method provides optimum result. It is also suggested that weight factor in calculating the node weight should give precise importance to energy and node stability.

  16. Peak-To-Average Power Reduction In Mimo-Ofdm Systems Using Sub-Optimal Algorithm

    Directory of Open Access Journals (Sweden)

    K Srinivasarao

    2012-06-01

    Full Text Available Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM technology is one of the most attractive candidates for fourth generation (4G mobile radio communication. It effectively combats the multipath fading channel and improves the bandwidth efficiency. At the same time, it also increases system capacity so as to provide a reliable transmission. However, the main drawback of MIMO-OFDM system is high peak-to-average power ratio (PAPR for large number of sub-carriers, which result in many restrictions for practical applications. Coding, phase rotation and clipping are among many PAPR reduction schemes that have been proposed to overcome this problem. In this paper, we mainly investigate the PAPR reduction performance with two different PAPR reduction methods: partial transmit sequence (PTS and selective mapping (SLM. These two methods are sub-entities of phase rotation scheme. We propose an algorithm, Sub-Optimal algorithm that shows better PAPR reduction compared to the existing algorithms. Results are verified using MATLAB software.

  17. Industrial applications of a fiber-based high-average-power picosecond laser

    Science.gov (United States)

    Moorhouse, Colin

    2009-02-01

    Presently lasers are well established tools for materials processing due to advantages such as (i) the non-contact nature of the laser-material interaction, (ii) the high precision achievable and (iii) no requirement for high vacuum equipment or costly chemicals. Now, industrial laser users demand improvements in order to achieve higher quality features with reduced heat affected zones and so it is increasingly necessary to use shorter pulse durations. To satisfy these needs, there has been significant research into ultrafast laser technology for decades, however at this time, these lasers have yet to be adopted by industry for mass production. Recent developments have shown that the combination of a fibre seed oscillator and Diode Pumped Solid State (DPSS) amplifying technology can offer high average power, picosecond pulses (~10ps) in an industrially-rugged package. The significant laser design aspects are outlined here, along with the advantages this technology offers for applications such as silicon via drilling, thin film patterning and the machining of wide bandgap materials.

  18. NEO-LISP: Deflecting near-earth objects using high average power, repetitively pulsed lasers

    Energy Technology Data Exchange (ETDEWEB)

    Phipps, C.R. [Los Alamos National Lab., NM (United States). Chemical Science and Technology Div.; Michaelis, M.M. [Univ. of Natal, Durban (South Africa). Physics Dept.

    1994-10-01

    Several kinds of Near-Earth objects exist for which one would like to cause modest orbit perturbations, but which are inaccessible to normal means of interception because of their number, distance or the lack of early warning. For these objects, LISP (Laser Impulse Space Propulsion) is an appropriate technique for rapidly applying the required mechanical impulse from a ground-based station. In order of increasing laser energy required, examples are: (1) repositioning specially prepared geosynchronous satellites for an enhanced lifetime, (2) causing selected items of space junk to re-enter and burn up in the atmosphere on a computed trajectory, and (3) safely deflecting Earth-directed comet nuclei and earth-crossing asteroids (ECA`s) a few tens of meters in size (the most hazardous size). They will discuss each of these problems in turn and show that each application is best matched by its own matrix of LISP laser pulse width, pulse repetition rate, wavelength and average power. The latter ranges from 100W to 3GW for the cases considered. They will also discuss means of achieving the active beam phase error correction during passage through the atmosphere and very large exit pupil in the optical system which are required in each of these cases.

  19. COMPLEMENT BLOCK CODING SCHEME FOR REDUCING PEAK-TO-AVERAGE POWER RATIO OF OFDM SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Jiang Tao; Zhu Guangxi

    2004-01-01

    A new scheme termed as Complement Block Coding (CBC) technique is proposed to reduce the Peak-to-Average Power Ratio (PAPR) of OFDM signals. Utilizing the complement bits which are added to the original information bits,this method can effectively reduce the PAPR of OFDM systems with random frame size N and the coding rate R ≤ (N - k)/N, where kis a positive integer and k ≤ N/2. The performance results obtained with CBC are given and compared with that of some well known schemes, such as Simple Block Coding (SBC), Modified Simple Block Coding (MSBC) and Simple Odd Parity Code (SOPC) for the same purpose. The results show that, at the same coding rate 3/4, the CBC can achieve almost the same performance as SBC, MSBC, but with lower complexity, and that the same performance can be obtained with higher coding rate by using CBC. At the same coding rate (N - 1)/N, the PAPR reduction of CBC is almost the twice as that of SOPC when N ≥ 16. Further more, the PAPR reductions with coding rate (N - 1)/N are almost the same as that with coding rate less than (N - 1)/N,so the proposed scheme CBC is more suitable for the large frame size with high coding rate and can provide error detection.

  20. An Effective Algorithm for Average Power Estimation of CMOS Sequential Chircuit

    Institute of Scientific and Technical Information of China (English)

    LIYueping; TANGPushan; ZHAOWenqing

    2003-01-01

    An incremental probabilistic algorithm is proposed for estimating average power of CMOS sequential circuit.We facilitate the flrst-order Taylor expansion to consider the spatial and temporal correlation among the internal nodes of the seauential circuits.Regarding finite state machines as non-decomposable and aperiodic Markov Chains,the steady-state probabilities exist.Consequently there have the steady probabilities of state lines.Thus the signal probability and switching activity of state line can be gotten through Picard-Peano iteration method.Sequential modules are separated from the whole circuit to shorten the runtime of our algorithm.We unroll the sequential module to accurately estimate the signal probability of state lines.Unilke the algorithms bassed on global BDD,the runtime of computing signal probability and switching activity of our algorithm does not depend on the circuit size.Experimental results show that our algorithm is much faster than the Monte-Carlo simulation method with the error below 10%.

  1. Design of a high average-power FEL driven by an existing 20 MV electrostatic-accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kimel, I.; Elias, L.R. [Univ. of Central Florida, Orlando, FL (United States)

    1995-12-31

    There are some important applications where high average-power radiation is required. Two examples are industrial machining and space power-beaming. Unfortunately, up to date no FEL has been able to show more than 10 Watts of average power. To remedy this situation we started a program geared towards the development of high average-power FELs. As a first step we are building in our CREOL laboratory, a compact FEL which will generate close to 1 kW in CW operation. As the next step we are also engaged in the design of a much higher average-power system based on a 20 MV electrostatic accelerator. This FEL will be capable of operating CW with a power output of 60 kW. The idea is to perform a high power demonstration using the existing 20 MV electrostatic accelerator at the Tandar facility in Buenos Aires. This machine has been dedicated to accelerate heavy ions for experiments and applications in nuclear and atomic physics. The necessary adaptations required to utilize the machine to accelerate electrons will be described. An important aspect of the design of the 20 MV system, is the electron beam optics through almost 30 meters of accelerating and decelerating tubes as well as the undulator. Of equal importance is a careful design of the long resonator with mirrors able to withstand high power loading with proper heat dissipation features.

  2. 53 W average power few-cycle fiber laser system generating soft x rays up to the water window.

    Science.gov (United States)

    Rothhardt, Jan; Hädrich, Steffen; Klenke, Arno; Demmler, Stefan; Hoffmann, Armin; Gotschall, Thomas; Eidam, Tino; Krebs, Manuel; Limpert, Jens; Tünnermann, Andreas

    2014-09-01

    We report on a few-cycle laser system delivering sub-8-fs pulses with 353 μJ pulse energy and 25 GW of peak power at up to 150 kHz repetition rate. The corresponding average output power is as high as 53 W, which represents the highest average power obtained from any few-cycle laser architecture so far. The combination of both high average and high peak power provides unique opportunities for applications. We demonstrate high harmonic generation up to the water window and record-high photon flux in the soft x-ray spectral region. This tabletop source of high-photon flux soft x rays will, for example, enable coherent diffractive imaging with sub-10-nm resolution in the near future.

  3. A Simple Instant-Estimation Method for Time-Average Quantities of Single-Phase Power and Application to Single-Phase Power Grid Connection by Inverter

    Science.gov (United States)

    Shinnaka, Shinji

    This paper presents and analyzes a new simple instant-estimation method for time-average quantities such as rms-values of voltage and current, active and reactive powers, and power factor for single-phase power with the fundamental component of constant or nearly-constant frequency by measuring instantaneous values of voltage and current. According to the analyses, the method can instantly estimate time average values with accuracy of the fundamental frequency, and estimation accuracy of power factor is about two times better than that of voltage, current, and powers. The instant-estimation method is simple and can be easily applied to single-phase power control systems that are expected to control instantly and continuously power factor on a single-phase grid by inverter. Based on the proposed instant-estimation method, two-methods for such power control systems are also proposed and their usefulness is verified through simulations.

  4. Efficient Spectral Broadening in the 100-W Average Power Regime Using Gas Filled Kagome HC-PCF and Pulse Compression

    CERN Document Server

    Emaury, Florian; Debord, Benoit; Ghosh, Debashri; Diebold, Andreas; Gerome, Frederic; Suedmeyer, Thomas; Benabid, Fetah; Keller, Ursula

    2014-01-01

    We present nonlinear pulse compression of a high-power SESAM-modelocked thin-disk laser (TDL) using an Ar-filled hypocycloid-core Kagome Hollow-Core Photonic Crystal Fiber (HC-PCF). The output of the modelocked Yb:YAG TDL with 127 W average power, a pulse repetition rate of 7 MHz, and a pulse duration of 740 fs was spectrally broadened 16-fold while propagating in a Kagome HC-PCF containing 13 bar of static Argon gas. Subsequent compression tests performed using 8.4% of the full available power resulted in a pulse duration as short as 88 fs using the spectrally broadened output from the fiber. Compressing the full transmitted power through the fiber (118 W) could lead to a compressed output of >100 W of average power and >100 MW of peak power with an average power compression efficiency of 88%. This simple laser system with only one ultrafast laser oscillator and a simple single-pass fiber pulse compressor, generating both high peak power >100 MW and sub-100-fs pulses at megahertz repetition rate, is very int...

  5. 23-kW peak power femtosecond pulses from a mode-locked fiber ring laser at 2.8 μm

    Science.gov (United States)

    Duval, Simon; Olivier, Michel; Fortin, Vincent; Bernier, Martin; Piché, Michel; Vallée, Réal

    2016-03-01

    The recent development of soliton femtosecond fiber lasers emitting at 2.8 μm opens a new avenue for the generation of ultrashort pulses in the mid-infrared spectral region. In this paper, we investigate the peak power scalability of such lasers. By optimizing the output coupling ratio and the length of the Er3+: fluoride fiber in the cavity, we demonstrate the generation of 270-fs pulses with an energy of 7 nJ and an estimated peak power of 23 kW. These record performances at 2.8 μm surpass by far those obtained from standard soliton lasers at 1.55 μm. A numerical model of the laser including the effect of the intracavity atmospheric absorption is also presented. Numerical simulations agree well with the experimental results and suggest that the atmospheric propagation in the cavity could prevent the laser from self-starting in a mode-locked regime. This femtosecond laser could be the building block for simple and compact mid-infrared frequency combs and supercontinuum sources.

  6. Femtosecond laser ablation properties of transparent materials: impact of the laser process parameters on the machining throughput

    Science.gov (United States)

    Matylitsky, V. V.; Hendricks, F.; Aus der Au, J.

    2013-03-01

    High average power, high repetition rate femtosecond lasers with μJ pulse energies are increasingly used for bio-medical and material processing applications. With the introduction of femtosecond laser systems such as the SpiritTM platform developed by High Q Lasers and Spectra-Physics, micro-processing of solid targets with femtosecond laser pulses have obtained new perspectives for industrial applications [1]. The unique advantage of material processing with subpicosecond lasers is efficient, fast and localized energy deposition, which leads to high ablation efficiency and accuracy in nearly all kinds of solid materials. The study on the impact of the laser processing parameters on the removal rate for transparent substrate using femtosecond laser pulses will be presented. In particular, examples of micro-processing of poly-L-lactic acid (PLLA) - bio-degradable polyester and XensationTM glass (Schott) machined with SpiritTM ultrafast laser will be shown.

  7. Analysis of the scalability of diffraction-limited fiber lasers and amplifiers to high average power.

    Science.gov (United States)

    Dawson, Jay W; Messerly, Michael J; Beach, Raymond J; Shverdin, Miroslav Y; Stappaerts, Eddy A; Sridharan, Arun K; Pax, Paul H; Heebner, John E; Siders, Craig W; Barty, C P J

    2008-08-18

    We analyze the scalability of diffraction-limited fiber lasers considering thermal, non-linear, damage and pump coupling limits as well as fiber mode field diameter (MFD) restrictions. We derive new general relationships based upon practical considerations. Our analysis shows that if the fiber's MFD could be increased arbitrarily, 36 kW of power could be obtained with diffraction-limited quality from a fiber laser or amplifier. This power limit is determined by thermal and non-linear limits that combine to prevent further power scaling, irrespective of increases in mode size. However, limits to the scaling of the MFD may restrict fiber lasers to lower output powers. PMID:18711562

  8. High average power harmonic mode-locking of a Raman fiber laser based on nonlinear polarization evolution

    Science.gov (United States)

    Liu, J.; Zhao, C. J.; Gao, Y. X.; Fan, D. Y.

    2016-03-01

    We experimentally demonstrate the operation of a stable harmonically mode-locked Raman fiber laser based on the nonlinear polarization rotation technique. A maximum average output power of up to 235 mW is achieved at the repetition rate of 466.2 MHz, corresponding to the 1665th order harmonic mode-locking. The temporal width of the mode-locked pulse train is 450 ps. The experimental results should shed some light on the design of wavelength versatile ultrashort lasers with high repetition rate and average output power.

  9. Design study of high average power (20-100 watts) pulsed nitrogen lasers at lambda = 3371 A

    International Nuclear Information System (INIS)

    The purpose of this design study is to assess the feasibility of building high average power nitrogen lasers with a goal of identifying data which must be obtained and technology which must be developed for the venture to succeed. The report consists of four sections which treats respectively; (1) laser modeling, (2) mode-control and energy extraction, (3) electrical pulser technology, and (4) gas flow. The conclusion reached is that the feasibility of high average power nitrogen lasers is very positive. Conceptual designs for 20 and 100 W nitrogen lasers are presented in (5). (U.S.)

  10. Observer design for DC/DC power converters with bilinear averaged model

    NARCIS (Netherlands)

    Spinu, V.; Dam, M.C.A.; Lazar, M.

    2012-01-01

    Increased demand for high bandwidth and high efficiency made full state-feedback control solutions very attractive to power-electronics community. However, full state measurement is economically prohibitive for a large range of applications. Moreover, state measurements in switching power converters

  11. Diode-pumped self-Q-switched Cr,Nd:YAG laser with 7-W average output power

    Institute of Scientific and Technical Information of China (English)

    Yuxian Shi; Sumei Wang; Qinan Li; Jing Zhang; Dongxiang Zhang; Baohua Feng; Zhiguo Zhang; Shiwen Zhang

    2009-01-01

    @@ We report a diode-pumped self-Q-switched 1064-nm Cr,Nd:YAG laser with pulse duration in the range of 16-18 ns.The maximum average output power up to 7 W, corresponding to a slope efiiciency of 33%, is obtained in a simple and compact linear cavity by using a plane-concave output coupler with a transmittance of 15%.The laser operates at TEM00 mode with a pump power of 14.2 W.

  12. Time-variant power spectral analysis of heart-rate time series by autoregressive moving average (ARMA) method

    Indian Academy of Sciences (India)

    V P S Naidu; M R S Reddy

    2003-12-01

    Frequency domain representation of a short-term heart-rate time series (HRTS) signal is a popular method for evaluating the cardiovascular control system. The spectral parameters, viz. percentage power in low frequency band (%PLF), percentage power in high frequency band (%PHF), power ratio of low frequency to high frequency (PRLH), peak power ratio of low frequency to high frequency (PPRLH) and total power (TP) are extrapolated from the averaged power spectrum of twenty-five healthy subjects, and 16 acute anterior-wall and nine acute inferior-wall myocardial infarction (MI) patients. It is observed that parasympathetic activity predominates in healthy subjects. From this observation we conclude that during acute myocardial infarction, the anterior wall MI has stimulated sympathetic activity, while the acute inferior wall MI has stimulated parasympathetic activity. Results obtained from ARMA-based analysis of heart-rate time series signals are capable of complementing the clinical examination results.

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

    Science.gov (United States)

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

    2015-03-01

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

  14. High repetition rate tunable femtosecond pulses and broadband amplification from fiber laser pumped parametric amplifier.

    Science.gov (United States)

    Andersen, T V; Schmidt, O; Bruchmann, C; Limpert, J; Aguergaray, C; Cormier, E; Tünnermann, A

    2006-05-29

    We report on the generation of high energy femtosecond pulses at 1 MHz repetition rate from a fiber laser pumped optical parametric amplifier (OPA). Nonlinear bandwidth enhancement in fibers provides the intrinsically synchronized signal for the parametric amplifier. We demonstrate large tunability extending from 700 nm to 1500 nm of femtosecond pulses with pulse energies as high as 1.2 muJ when the OPA is seeded by a supercontinuum generated in a photonic crystal fiber. Broadband amplification over more than 85 nm is achieved at a fixed wavelength. Subsequent compression in a prism sequence resulted in 46 fs pulses. With an average power of 0.5 W these pulses have a peak-power above 10 MW. In particular, the average power and pulse energy scalability of both involved concepts, the fiber laser and the parametric amplifier, will enable easy up-scaling to higher powers.

  15. High-average-power and high-beam-quality Innoslab picosecond laser amplifier.

    Science.gov (United States)

    Xu, Liu; Zhang, Hengli; Mao, Yefei; Yan, Ying; Fan, Zhongwei; Xin, Jianguo

    2012-09-20

    We demonstrated a laser-diode, end-pumped picosecond amplifier. With effective shaping of the seed laser, we achieved 73 W amplified laser output at the pump power of 255 W, and the optical-optical efficiency was about 28%. The beam propagation factors M(2) measured at the output power of 60 W in the horizontal direction and the vertical direction were 1.5 and 1.4, respectively.

  16. Significance of power average of sinusoidal and non-sinusoidal periodic excitations in nonlinear non-autonomous system

    Indian Academy of Sciences (India)

    VENKATESH P R; VENKATESAN A

    2016-07-01

    Additional sinusoidal and different non-sinusoidal periodic perturbations applied to the periodically forced nonlinear oscillators decide the maintainance or inhibitance of chaos. It is observed that the weak amplitude of the sinusoidal force without phase is sufficient to inhibit chaos rather than the other non-sinusoidal forces and sinusoidal force with phase. Apart from sinusoidal force without phase, i.e., from various non-sinusoidal forces and sinusoidal force with phase, square force seems to be an effective weak perturbation to suppress chaos. The effectiveness of weak perturbation for suppressing chaos is understood with the total power average of the external forces applied to the system. In any chaotic system, the total power average of the external forces isconstant and is different for different nonlinear systems. This total power average decides the nature of the force to suppress chaos in the sense of weak perturbation. This has been a universal phenomenon for all the chaoticnon-autonomous systems. The results are confirmed by Melnikov method and numerical analysis. With the help of the total power average technique, one can say whether the chaos in that nonlinear system is to be supppressed or not.

  17. Generation of high-power femtosecond supercontinua in the near-IR spectral range using broadband parametric frequency conversion in LBO and DCDA crystals pumped at λ = 620 nm

    Science.gov (United States)

    Podshivalov, A. A.; Potemkin, F. V.; Sidorov-Biryukov, D. A.

    2014-09-01

    The pump wavelength of parametric amplifiers based on CLBO, DCDA and LBO crystals and pumped by the second harmonic of a femtosecond Cr : forsterite laser (620 nm) is close to optimal for broadband amplification because of the proximity of group velocities of interacting pulses. Injection of a broadband continuum into the range of the signal-wave gain in LBO and DCDA parametric amplifiers, pumped at λ = 620 nm, leads to generation of broadband femtosecond pulses with a spectrum ranging from 1050 to 1600 nm and peak powers up to 20 MW.

  18. Investigation of laser diode face-pumped high average power heat capacity laser

    Institute of Scientific and Technical Information of China (English)

    Shenjin Zhang; Shouhuan Zhou; Xiaojun Tang; Guojiang Bi; Huachang LV

    2006-01-01

    The three-dimensional (3D) pump intensity distribution in medium of the laser diode (LD) pumped highaverage power heat capacity laser is simulated by the ray tracing method, and the divergence characteristicsof fast axis and slow axis of LD are simultaneously considered. The transient 3D temperature and stressdistributions are also simulated by the finite element method (FEM) with considering the uneven heatsource distribution in medium. A LD face-pumped Nd:GGG heat capacity laser is designed. The averageoutput power is 1.49 kW with an optical-optical efficiency of 24.1%.

  19. Development of high average power DPSSL for laser fusion driver and industrial application

    International Nuclear Information System (INIS)

    Laser fusion is one of the most feasible approach in the fusion energy development. The goal of inertial fusion energy (IFE) development is to prove that fusion energy can be available to society as electric power source. Recent progress of laser fusion research and development enable the authors to examine technical and economical feasibility, and to plan the realistic strategy and program to the commercial power plant. The most important key issue for IFE is driver technologies. The development of the laser fusion driver may establish new industrial technologies based on the photon processes and is attracting attentions in wide industrial fields

  20. Femtosecond pulse amplification in cladding-pumped fibers

    OpenAIRE

    Minelly, J. D.; Galvanauskas, A.; Fermann, M. E.; Harter, D.; Caplen, J.E.; Chen, Z.J.; Payne, D. N.

    1995-01-01

    Femtosecond pulse amplification in a cladding-pumped fiber amplifier is demonstrated for the first time to our knowledge. Using a cladding-pumped erbium-doped fiber power amplifier and a passively mode-locked fiber seed oscillator in conjunction with an all-fiber chirped-pulse amplification system, we obtain 380-fs near-bandwidth-limited pulses with an average power of 260 mW. The pulse repetition rate is varied between 5 and 50 MHz, and pulse energies as high as 20 nJ are generated.

  1. Program THEK energy production units of average power and using thermal conversion of solar radiation

    Science.gov (United States)

    1978-01-01

    General studies undertaken by the C.N.R.S. in the field of solar power plants have generated the problem of building energy production units in the medium range of electrical power, in the order of 100 kW. Among the possible solutions, the principle of the use of distributed heliothermal converters has been selected as being, with the current status of things, the most advantageous solution. This principle consists of obtaining the conversion of concentrated radiation into heat by using a series of heliothermal conversion modules scattered over the ground; the produced heat is collected by a heat-carrying fluid circulating inside a thermal loop leading to a device for both regulation and storage.

  2. Beyond Gaussian averages: redirecting international business and management research toward extreme events and power laws

    OpenAIRE

    Pierpaolo Andriani; Bill McKelvey

    2007-01-01

    Practicing managers live in a world of ‘extremes’, but international business and management research is based on Gaussian statistics that rule out such extremes. On occasion, positive feedback processes among interactive data points cause extreme events characterized by power laws. They seem ubiquitous; we list 80 kinds of them – half each among natural and social phenomena. We use imposed tension and Per Bak's ‘self-organized criticality’ to argue that Pareto-based science and statistics (b...

  3. Average current control of DC-DC Cuk Converters as Power Factor Corrector

    OpenAIRE

    Ashima Kulshreshtha; Anmol R. Saxena

    2015-01-01

    The era of electronic devices in all loads due to the manufacturing technologies replaced many conventional electrical or mechanical loads including lighting loads where Light Emitting Diodes (LEDs) is becoming an emerging technique with many advantages. High frequency switching dc-dc converter is a new technology to control the load and the supply side simultaneously. Due to additional harmonics generated by these switching converters power factor correction has become a necessit...

  4. High-power Femtosecond Optical Parametric Amplification at 1 kHz in BiB(3)O(6) pumped at 800 nm.

    Science.gov (United States)

    Petrov, Valentin; Noack, Frank; Tzankov, Pancho; Ghotbi, Masood; Ebrahim-Zadeh, Majid; Nikolov, Ivailo; Buchvarov, Ivan

    2007-01-22

    Substantial power scaling of a travelling-wave femtosecond optical parametric amplifier, pumped near 800 nm by a 1 kHz Ti:sapphire laser amplifier, is demonstrated using monoclinic BiB(3)O(6) in a two stage scheme with continuum seeding. Total energy output (signal plus idler) exceeding 1 mJ is achieved, corresponding to an intrinsic conversion efficiency of approximately 32% for the second stage. The tunability extends from 1.1 to 2.9 microm. The high parametric gain and broad amplification bandwidth of this crystal allowed the maintenance of the pump pulse duration, leading to pulse lengths less than 140 fs, both for the signal and idler pulses, even at such high output levels.

  5. Power- and polarization-dependent supercontinuum generation in α -BaB2O4 crystals by intense, near-infrared, femtosecond laser pulses

    Science.gov (United States)

    Vasa, Parinda; Dota, Krithika; Singh, Mamraj; Kushavah, Dushyant; Singh, Bhanu P.; Mathur, Deepak

    2015-05-01

    We report generation of a broadband supercontinuum (SC) in a birefringent crystal upon irradiation by intense, near-infrared, femtosecond laser pulses and investigate its dependence on incident laser power and the initial laser polarization. We choose as our sample α -BaB2O4 (α -BBO), a material in which the third order is the lowest order of nonvanishing nonlinear optical susceptibility. Three different SC generation mechanisms are identified under our experimental conditions; these are found to depend upon the pump power Pp u. Close to the critical power for self-focusing (Pp u˜5 MW), the spectrum is dominated by Kerr nonlinearity or self-phase modulation, whereas at intermediate pumping Pp u˜125 MW, Raman amplification on the Stokes side is a dominating mechanism. At higher pump power ˜300 MW, significant asymmetric broadening extending up to ˜570 nm is observed due to the coherent anti-Stokes Raman scattering. Our study provides an intuitive explanation for the observed power- and polarization-dependent SC generation in α -BBO crystals.

  6. High-repetition rate industrial TEA CO2 laser with average output power of 1.5 kW

    Science.gov (United States)

    Wan, Chongyi; Liu, Shiming; Zhou, Jinwen; Qi, Jilan; Yang, Xiaola; Wu, Jin; Tan, Rongqing; Wang, Lichun; Mei, Qichu

    1995-03-01

    High power high repetition rate TEA CO2 laser has potential importance in material processing such as shock hardening, glazing, drilling, welding, and cutting for high damage threshold materials, as well as in chemical reaction and isotope separation. This paper describes a transverse-flow closed-cycle UV-preionized TEA CO2 laser with peak pulse power of 20 MW, maximum average power of 1.5 KW at repetition rate of 300 HZ. The laser has compact constructure of gas flow circulation system using tangential fans. With addition of small amounts of H2 and CO to the normal CO2-N2-He gas mixture, one filling sealed operating lifetime is up to millions of pulses. A novel spark gap switch has been developed for very high repetition rate laser discharge in the condition of high pulse power.

  7. SM green fiber laser operating in CW and QCW regimes and producing over 550W of average output power

    Science.gov (United States)

    Gapontsev, Valentin; Avdokhin, Alexey; Kadwani, Pankaj; Samartsev, Igor; Platonov, Nikolai; Yagodkin, Roman

    2014-02-01

    We report a single-mode (SM) green laser based on single-pass frequency doubling of a linearly-polarized narrowlinewidth Yb fiber laser in LBO crystal, and configured to operate in a range of regimes from continuous-wave (CW) to high-repetition-rate quasi-continuous-wave (QCW). Adjusting the duty cycle, we maintained high second harmonic generation (SHG) efficiency for various output powers. Average powers of over 550W in QCW and over 350W in CW regimes were obtained with the wall-plug efficiency up to 15%, opening the possibility to creating new class of simple, compact and efficient single-mode green lasers with output power up to 1kW and above. The same approach could also be used to create high-power lasers operating at other wavelengths in ultraviolet and visible spectral ranges.

  8. Development of a 16 kHz repetition rate, 110 W average power copper HyBrID laser

    Indian Academy of Sciences (India)

    R Biswal; P K Agrawal; G K Mishra; S V Nakhe; S K Dixit; J K Mittal

    2010-11-01

    This paper presents the design and performance analysis of an indigenously developed 110 W average output power copper HyBrID laser operating at 16 kHz pulse repetition rate. The laser active medium was confined within a fused silica tube of ∼ 6 cm diameter and ∼ 200 cm active length. An in-house developed high-power (∼ 10 kW) solid-state pulser was used as the electrical excitation source. A simple estimation of deposited electrical power, at the laser head, was carried out and based on it, the laser tube efficiency was found to be 2.9% at 70 W and 2.2% at 110 W laser power levels.

  9. High energy, high average power solid state green or UV laser

    Science.gov (United States)

    Hackel, Lloyd A.; Norton, Mary; Dane, C. Brent

    2004-03-02

    A system for producing a green or UV output beam for illuminating a large area with relatively high beam fluence. A Nd:glass laser produces a near-infrared output by means of an oscillator that generates a high quality but low power output and then multi-pass through and amplification in a zig-zag slab amplifier and wavefront correction in a phase conjugator at the midway point of the multi-pass amplification. The green or UV output is generated by means of conversion crystals that follow final propagation through the zig-zag slab amplifier.

  10. Efficient Spectral Broadening in the 100-W Average Power Regime Using Gas Filled Kagome HC-PCF and Pulse Compression

    OpenAIRE

    Emaury, Florian; Saraceno, Clara J.; Debord, Benoit; Ghosh, Debashri; Diebold, Andreas; Gerome, Frederic; Suedmeyer, Thomas; Benabid, Fetah; Keller, Ursula

    2014-01-01

    We present nonlinear pulse compression of a high-power SESAM-modelocked thin-disk laser (TDL) using an Ar-filled hypocycloid-core Kagome Hollow-Core Photonic Crystal Fiber (HC-PCF). The output of the modelocked Yb:YAG TDL with 127 W average power, a pulse repetition rate of 7 MHz, and a pulse duration of 740 fs was spectrally broadened 16-fold while propagating in a Kagome HC-PCF containing 13 bar of static Argon gas. Subsequent compression tests performed using 8.4% of the full available pow...

  11. New Tone Reservation Technique for Peak to Average Power Ratio Reduction

    Science.gov (United States)

    Wilharm, Joachim; Rohling, Hermann

    2014-09-01

    In Orthogonal Frequency Division Multiplexing (OFDM) the transmit signals have a highly fluctuating, non-constant envelope which is a technical challenge for the High Power Amplifier (HPA). Without any signal processing procedures the amplitude peaks of the transmit signal will be clipped by the HPA resulting in out-ofband radiation and in bit error rate (BER) performance degradation. The classical Tone Reservation (TR) technique calculates a correction signal in an iterative way to reduce the amplitude peaks. However this step leads to a high computational complexity. Therefore, in this paper an alternative TR technique is proposed. In this case a predefined signal pattern is shifted to any peak position inside the transmit signal and reduces thereby all amplitude peaks. This new procedure is able to outperform the classical TR technique and has a much lower computational complexity.

  12. Diode Pumped Alkali Vapor Lasers - A New Pathway to High Beam Quality at High Average Power

    Energy Technology Data Exchange (ETDEWEB)

    Page, R H; Boley, C D; Rubenchik, A M; Beach, R J

    2005-05-06

    Resonance-transition alkali-vapor lasers have only recently been demonstrated [1] but are already attracting considerable attention. Alkali-atom-vapor gain media are among the simplest possible systems known, so there is much laboratory data upon which to base performance predictions. Therefore, accurate modeling is possible, as shown by the zero- free-parameter fits [2] to experimental data on alkali-vapor lasers pumped with Ti:sapphire lasers. The practical advantages of two of the alkali systems--Rb and Cs--are enormous, since they are amenable to diode-pumping [3,4]. Even without circulating the gas mixture, these lasers can have adequate cooling built-in owing to the presence of He in their vapor cells. The high predicted (up to 70%) optical-to-optical efficiency of the alkali laser, the superb (potentially 70% or better) wall-plug efficiency of the diode pumps, and the ability to exhaust heat at high temperature (100 C) combine to give a power-scalable architecture that is lightweight. A recent design exercise [5] at LLNL estimated that the system ''weight-to-power ratio'' figure of merit could be on the order of 7 kg/kW, an unprecedented value for a laser of the 100 kW class. Beam quality is expected to be excellent, owing to the small dn/dT value of the gain medium. There is obviously a long way to go, to get from a small laser pumped with a Ti:sapphire or injection-seeded diode system (of near-perfect beam quality, and narrow linewidth) [1, 4] to a large system pumped with broadband, multimode diode- laser arrays. We have a vision for this technology-development program, and have already built diode-array-pumped Rb lasers at the 1 Watt level. A setup for demonstrating Diode-array-Pumped Alkali vapor Lasers (DPALs) is shown in Figure 1. In general, use of a highly-multimode, broadband pump source renders diode-array-based experiments much more difficult than the previous ones done with Ti:sapphire pumping. High-NA optics, short focal

  13. Yb-fiber-laser-based, 1.8 W average power, picosecond ultraviolet source at 266 nm.

    Science.gov (United States)

    Chaitanya Kumar, S; Canals Casals, J; Sanchez Bautista, E; Devi, K; Ebrahim-Zadeh, M

    2015-05-15

    We report a compact, stable, high-power, picosecond ultraviolet (UV) source at 266 nm based on simple single-pass two-step fourth-harmonic generation (FHG) of a mode-locked Yb-fiber laser at 79.5 MHz in LiB3O5 (LBO) and β-BaB2O4. Using a 30-mm-long LBO crystal for single-pass second-harmonic generation, we achieve up to 9.1 W of average green power at 532 nm for 16.8 W of Yb-fiber power at a conversion efficiency of 54% in 16.2 ps pulses with a TEM00 spatial profile and passive power stability better than 0.5% rms over 16 h. The generated green radiation is then used for single-pass FHG into the UV, providing as much as 1.8 W of average power at 266 nm under the optimum focusing condition in the presence of spatial walk-off, at an overall FHG conversion efficiency of ∼11%. The generated UV output exhibits passive power stability better than 4.6% rms over 1.5 h and beam pointing stability better than 84 μrad over 1 h. The UV output beam has a circularity of >80% in high beam quality with the TEM00 mode profile. To the best of our knowledge, this is the first report of picosecond UV generation at 266 nm at megahertz repetition rates. PMID:26393749

  14. The Mercury Laser System-A scaleable average-power laser for fusion and beyond

    International Nuclear Information System (INIS)

    Nestled in a valley between the whitecaps of the Pacific and the snowcapped crests of the Sierra Nevada, Lawrence Livermore National Laboratory (LLNL) is home to the nearly complete National Ignition Facility (NIF). The purpose of NIF is to create a miniature star-on demand. An enormous amount of laser light energy (1.8 MJ in a pulse that is 20 ns in duration) will be focused into a small gold cylinder approximately the size of a pencil eraser. Centered in the gold cylinder (or hohlraum) will be a nearly perfect sphere filled with a complex mixture of hydrogen gas isotopes that is similar to the atmosphere of our Sun. During experiments, the laser light will hit the inside of the gold cylinder, heating the metal until it emits X-rays (similar to how your electric stove coil emits visible red light when heated). The X-rays will be used to compress the hydrogen-like gas with such pressure that the gas atoms will combine or 'fuse' together, producing the next heavier element (helium) and releasing energy in the form of energetic particles. 2010 will mark the first credible attempt at this world-changing event: the achievement of fusion energy 'break-even' on Earth using NIF, the world's largest laser NIF is anticipated to eventually perform this immense technological accomplishment once per week, with the capability of firing up to six shots per day - eliminating the need for continued underground testing of our nation's nuclear stockpile, in addition to opening up new realms of science. But what about the day after NIF achieves ignition? Although NIF will achieve fusion energy break-even and gain, the facility is not designed to harness the enormous potential of fusion for energy generation. A fusion power plant, as opposed to a world-class engineering research facility, would require that the laser deliver drive pulses nearly 100,000 times more frequently - a rate closer to 10 shots per second as opposed to several shots per day.

  15. The Mercury Laser System-A scaleable average-power laser for fusion and beyond

    Energy Technology Data Exchange (ETDEWEB)

    Ebbers, C A; Moses, E I

    2008-03-26

    Nestled in a valley between the whitecaps of the Pacific and the snowcapped crests of the Sierra Nevada, Lawrence Livermore National Laboratory (LLNL) is home to the nearly complete National Ignition Facility (NIF). The purpose of NIF is to create a miniature star-on demand. An enormous amount of laser light energy (1.8 MJ in a pulse that is 20 ns in duration) will be focused into a small gold cylinder approximately the size of a pencil eraser. Centered in the gold cylinder (or hohlraum) will be a nearly perfect sphere filled with a complex mixture of hydrogen gas isotopes that is similar to the atmosphere of our Sun. During experiments, the laser light will hit the inside of the gold cylinder, heating the metal until it emits X-rays (similar to how your electric stove coil emits visible red light when heated). The X-rays will be used to compress the hydrogen-like gas with such pressure that the gas atoms will combine or 'fuse' together, producing the next heavier element (helium) and releasing energy in the form of energetic particles. 2010 will mark the first credible attempt at this world-changing event: the achievement of fusion energy 'break-even' on Earth using NIF, the world's largest laser! NIF is anticipated to eventually perform this immense technological accomplishment once per week, with the capability of firing up to six shots per day - eliminating the need for continued underground testing of our nation's nuclear stockpile, in addition to opening up new realms of science. But what about the day after NIF achieves ignition? Although NIF will achieve fusion energy break-even and gain, the facility is not designed to harness the enormous potential of fusion for energy generation. A fusion power plant, as opposed to a world-class engineering research facility, would require that the laser deliver drive pulses nearly 100,000 times more frequently - a rate closer to 10 shots per second as opposed to several shots per day.

  16. High average current 2-MeV electron accelerator for a high-power free-electron laser

    CERN Document Server

    Lee Byung Cheol; Cho, S O; Lee, J; Miginsky, S V; Kulipanov, G N

    1999-01-01

    A high average current CW RF electron accelerator has been developed for the free electron laser programs at KAERI. The accelerator is composed of a 300-keV electron gun, one RF bunching cavity, and two RF acceleration cavities. The kinetic energy of the electron beam is 1.5 MeV nominally and 2 MeV at maximum. The duration of a pulse is 350 ps and its repetition rate is variable from a single pulse to 22.5 MHz. The peak current is 6 A, and the average current, at the maximum repetition rate, is 45 mA. The resonant frequency of the RF cavities is 180 MHz. The energy gain of an RF acceleration cavity is 0.6 MeV nominally and 0.85 MeV at maximum. The total RF power supplied into the RF cavities is 262 kW. A millimeter-wave FEL driven by the 2-MeV accelerator is under design. The 2-MeV accelerator will be used as an injector of a high-average-power infrared FEL.

  17. Selective ablation of dental enamel and dentin using femtosecond laser pulses

    International Nuclear Information System (INIS)

    The study of the interaction of intense laser light with matter, as well as transient response of atoms and molecules is very appropriated because of the laser energy concentration in a femtosecond optical pulses. The fundamental problem to be solved is to find tools and techniques which allow us to observe and manipulate on a femtosecond time scale the photonics events on and into the matter. Six third human extracted molars were exposed to a femtosecond Ti:Sapphire Q-switched and mode locked laser (Libra-S, Coherent, Palo Alto, CA, USA), emitting pulses with 70 fs width, radiation wavelength of 801 nm, at a constant pulse repetition rate of 1 KHz. The laser was operated at different power levels (70 to 400 mW) with constant exposition time of 10 seconds, at focused and defocused mode. Enamel and dentin surfaces were evaluated concerned ablation rate and morphological aspects under scanning electron microscopic. The results in this present experiment suggest that at the focused mode and under higher average power, enamel tissues present microcavities with higher depth and very precise edges, but, while dentin shows a larger melt-flushing, lower depth and melting and solidification aspect. In conclusion, it is possible to choose hard or soft ablation, under lower and higher average power, respectively, revealing different aspects of dental enamel and dentin, depending on the average power, fluence and distance from the focal point of the ultra-short pulse laser on the tooth surface

  18. Cooperative AF Relaying in Spectrum-Sharing Systems: Performance Analysis under Average Interference Power Constraints and Nakagami-m Fading

    KAUST Repository

    Xia, Minghua

    2012-06-01

    Since the electromagnetic spectrum resource becomes more and more scarce, improving spectral efficiency is extremely important for the sustainable development of wireless communication systems and services. Integrating cooperative relaying techniques into spectrum-sharing cognitive radio systems sheds new light on higher spectral efficiency. In this paper, we analyze the end-to-end performance of cooperative amplify-and-forward (AF) relaying in spectrum-sharing systems. In order to achieve the optimal end-to-end performance, the transmit powers of the secondary source and the relays are optimized with respect to average interference power constraints at primary users and Nakagami-$m$ fading parameters of interference channels (for mathematical tractability, the desired channels from secondary source to relay and from relay to secondary destination are assumed to be subject to Rayleigh fading). Also, both partial and opportunistic relay-selection strategies are exploited to further enhance system performance. Based on the exact distribution functions of the end-to-end signal-to-noise ratio (SNR) obtained herein, the outage probability, average symbol error probability, diversity order, and ergodic capacity of the system under study are analytically investigated. Our results show that system performance is dominated by the resource constraints and it improves slowly with increasing average SNR. Furthermore, larger Nakagami-m fading parameter on interference channels deteriorates system performance slightly. On the other hand, when interference power constraints are stringent, opportunistic relay selection can be exploited to improve system performance significantly. All analytical results are corroborated by simulation results and they are shown to be efficient tools for exact evaluation of system performance.

  19. TECATE - a code for anisotropic thermoelasticity in high-average-power laser technology. Phase 1 final report

    International Nuclear Information System (INIS)

    This report describes a totally Eulerian code for anisotropic thermoelasticity (code name TECATE) which may be used in evaluations of prospective crystal media for high-average-power lasers. The present TECATE code version computes steady-state distributions of material temperatures, stresses, strains, and displacement fields in 2-D slab geometry. Numerous heat source and coolant boundary condition options are available in the TECATE code for laser design considerations. Anisotropic analogues of plane stress and plane strain evaluations can be executed for any and all crystal symmetry classes. As with all new and/or large physics codes, it is likely that some code imperfections will emerge at some point in time

  20. Peak-to-Average-Power-Ratio (PAPR) reduction in WiMAX and OFDM/A systems

    Science.gov (United States)

    Khademi, Seyran; Svantesson, Thomas; Viberg, Mats; Eriksson, Thomas

    2011-12-01

    A peak to average power ratio (PAPR) reduction method is proposed that exploits the precoding or beamforming mode in WiMAX. The method is applicable to any OFDM/A systems that implements beamforming using dedicated pilots which use the same beamforming antenna weights for both pilots and data. Beamforming performance depends on the relative phase shift between antennas, but is unaffected by a phase shift common to all antennas. PAPR, on the other hand, changes with a common phase shift and this paper exploits that property. An effective optimization technique based on sequential quadratic programming is proposed to compute the common phase shift. The proposed technique has several advantages compared with traditional PAPR reduction techniques in that it does not require any side-information and has no effect on power and bit-error-rate while providing better PAPR reduction performance than most other methods.

  1. Relationship Between Selected Strength and Power Assessments to Peak and Average Velocity of the Drive Block in Offensive Line Play.

    Science.gov (United States)

    Jacobson, Bert H; Conchola, Eric C; Smith, Doug B; Akehi, Kazuma; Glass, Rob G

    2016-08-01

    Jacobson, BH, Conchola, EC, Smith, DB, Akehi, K, and Glass, RG. Relationship between selected strength and power assessments to peak and average velocity of the drive block in offensive line play. J Strength Cond Res 30(8): 2202-2205, 2016-Typical strength training for football includes the squat and power clean (PC) and routinely measured variables include 1 repetition maximum (1RM) squat and 1RM PC along with the vertical jump (VJ) for power. However, little research exists regarding the association between the strength exercises and velocity of an actual on-the-field performance. The purpose of this study was to investigate the relationship of peak velocity (PV) and average velocity (AV) of the offensive line drive block to 1RM squat, 1RM PC, the VJ, body mass (BM), and body composition. One repetition maximum assessments for the squat and PC were recorded along with VJ height, BM, and percent body fat. These data were correlated with PV and AV while performing the drive block. Peal velocity and AV were assessed using a Tendo Power and Speed Analyzer as the linemen fired, from a 3-point stance into a stationary blocking dummy. Pearson product analysis yielded significant (p ≤ 0.05) correlations between PV and AV and the VJ, the squat, and the PC. A significant inverse association was found for both PV and AV and body fat. These data help to confirm that the typical exercises recommended for American football linemen is positively associated with both PV and AV needed for the drive block effectiveness. It is recommended that these exercises remain the focus of a weight room protocol and that ancillary exercises be built around these exercises. Additionally, efforts to reduce body fat are recommended.

  2. Continuously tunable Yb:KYW femtosecond oscillator based on a tunable highly dispersive semiconductor mirror.

    Science.gov (United States)

    Wnuk, P; Wasylczyk, P; Zinkiewicz, Ł; Dems, M; Hejduk, K; Regiński, K; Wójcik-Jedlińska, A; Jasik, A

    2014-07-28

    The optimized nonuniform growth process was used to achieve spatially dependent reflectivity and dispersions characteristics in a highly dispersive semiconductor mirror. The mirror, together with a semiconductor saturable absorber mirror (SESAM), was used to demonstrate a tunable femtosecond Yb:KYW oscillator. In the passive modelocking regime the laser could be continuously tuned over 3.5 nm spectral band around 1032 nm with high resolution, maintaining the average output power above 140 mW. PMID:25089448

  3. Sub-300-femtosecond operation from a MIXSEL.

    Science.gov (United States)

    Mangold, Mario; Golling, Matthias; Gini, Emilio; Tilma, Bauke W; Keller, Ursula

    2015-08-24

    Peak power scaling of semiconductor disk lasers is important for many applications, but their complex pulse formation mechanism requires a rigorous pulse characterization to confirm stable fundamental modelocking. Here we fully confirm sub-300-fs operation of Modelocked Integrated eXternal-cavity Surface Emitting Lasers (MIXSELs) with record high peak power at gigahertz pulse repetition rates. A strain-compensated InGaAs quantum well gain section enables an emission wavelength in the range of Yb-doped amplifiers at ≈1030 nm. We demonstrate the shortest pulses from a MIXSEL with a duration of 253 fs with 240 W of peak power, the highest peak power generated from any MIXSEL to date. This peak power performance is comparable to conventional SESAM-modelocked VECSELs for the first time. At a 10-GHz pulse repetition rate we still obtained 279-fs pulses with 310 mW of average output power, which is currently the highest output power of any femtosecond MIXSEL. Continuous tuning of the pulse repetition rate has been demonstrated with sub-400-fs pulse durations and >225 mW of average output power between 2.9 and 3.4 GHz. The strain-compensated MIXSEL chip allowed for more detailed parameter studies with regards to different heat sink temperatures, pump power, and epitaxial homogeneity of the MIXSEL chip for the first time. We discuss in detail, how the critical temperature balance between quantum well gain and quantum well absorber, the partially saturated absorber and a limited epitaxial growth quality influence the overall device efficiency. PMID:26368179

  4. Study on Network Remote Controlling Huge-Power Chopping Cascade Speed Regulation System Based on State-Space Averaging Model

    Directory of Open Access Journals (Sweden)

    Zhuo Zhang

    2014-07-01

    Full Text Available This paper deals with the modeling of DC-DC boost chopping circuit in a huge-power chopping cascade speed regulation system while the motor power level is over 1 megawatt. The model involves the Insulated Gate Bipolar Translator(IGBT & Free-Wheel Diode(FWD based on a state-space averaging method. It solves the problems of thedesigning of a control system in the chopping cascade speed regulation system when the controlling motor has a huge power. The system can be remote controlled through the industrial field network, and it has a good interface of human-computer interaction.The experiments show that the dual closed-loop control system is reliable and stable, it also has the better steady-state and dynamic characteristics and higher power factor compared with traditional cascade speed regulation systems. Based on this dual closed-loop control system, several devices with remarkable energy-saving effect have been running very well in the industrial sites. 

  5. Fabrication of Micro -Optical Devices by a Femtosecond Laser

    Institute of Scientific and Technical Information of China (English)

    Kazuyuki; Hirao

    2003-01-01

    Femtosecond laser is a perfect laser source for materials processing when high accuracy and small structure size are required. Due to the ultra short interaction time and the high peak power, the process is generally characterized by the absence of heat diffusion and, consequently molten layers. Various induced structures have been observed in materials after the femtosecond laser irradiation. Here, we report on fabrication of micro-optical devices by the femtosecond laser. 1) formation of optical waveg...

  6. The acute effect of lower-body training on average power output measured by loaded half-squat jump exercise

    Directory of Open Access Journals (Sweden)

    Matúš Krčmár

    2015-09-01

    Full Text Available Background: High muscular power output is required in many athletic endeavors in order for success to be achieved. In the scientific community postactivation potentiation and its effect on performance are often discussed. There are many studies where the effect of resistance exercise on motor performance (such as vertical jump performance and running speed has been investigated but only a few of them studied power output. Objective: The purpose of this study was to determine the acute responses to a 2 set loaded half-squat jumps and 2 set loaded back half-squat protocols designed to induce the acute maximum average power output during loaded half-squat jumps. Methods: A randomized cross-over design was used. 11 participants of this study performed 3 trials in randomized order separated by at least 48 hours where maximum average power output was measured. The specific conditioning activities were comprised of 2 sets and 4 repetitions of half-squat jumps, 2 sets and 4 repetitions of back half-squat exercises and a control protocol without an intervention by specific a conditioning activity. Participants were strength trained athletes with different sport specializations (e.g. ice-hockey, volleyball. Mean age of the athletes was 22 ± 1.8 years, body mass 80 ± 7.1 kg and body height 185 ± 6.5 cm. Analysis of variance with repeated measures was used to determine differences between pre- and post-condition in each protocol, as well as between conditioning protocols, and also effect size was used to evaluate practical significance. Results: Maximum average power was significantly enhanced after application of the half-squat jump condition protocol (1496.2 ± 194.5 to 1552 ± 196.1 W, Δ ~ 3.72%, p < .001 and after application of the back half-squat protocol (1500.7 ± 193.2 to 1556 ± 191.2 W, Δ ~ 3.68%, p < .001 after 10 min of rest. Power output after control protocol was

  7. Compact Source of Electron Beam with Energy of 200 kEv and Average Power of 2 kW

    CERN Document Server

    Kazarezov, Ivan; Balakin, Vladimir E; Bryazgin, Alex; Bulatov, Alexandre; Glazkov, Ivan; Kokin, Evgeny; Krainov, Gennady; Kuznetsov, Gennady I; Molokoedov, Andrey; Tuvik, Alfred

    2005-01-01

    The paper describes a compact electron beam source with average electron energy of 200 keV. The source operates with pulse power up to 2 MW under average power not higher than 2 kW, pulsed beam current up to 10 A, pulse duration up to 2 mks, and repetition rate up to 5 kHz. The electron beam is extracted through aluminium-beryllium alloy foil. The pulse duration and repetition rate can be changed from control desk. High-voltage generator for the source with output voltage up to 220 kV is realized using the voltage-doubling circuit which consists of 30 sections. The insulation type - gas, SF6 under pressure of 8 atm. The cooling of the foil supporting tubes is provided by a water-alcohol mixture from an independent source. The beam output window dimensions are 180?75 mm, the energy spread in the beam +10/-30%, the source weight is 80 kg.

  8. A Study on Estimation of Average Power Output Fluctuation of Clustered Photovoltaic Power Generation Systems in Urban District of a Few km2

    Science.gov (United States)

    Kato, Takeyoshi; Suzuoki, Yasuo

    The fluctuation of the total power output of clustered PV systems would be smaller than that of single PV system because of the time difference in the power output fluctuation among PV systems at different locations. This effect, so called smoothing-effect, must be taken into account properly when the impact of clustered PV systems on electric power system is assessed. If the average power output of clustered PV systems can be estimated from the power output of single PV system, it is very useful and helpful for the impact assessment. In this study, we propose a simple method to estimate the total power output fluctuation of clustered PV systems. In the proposed method, a smoothing effect is assumed to be caused as a result of two factors, i.e. time difference of overhead clouds passing among PV systems and the random change in the size and/or shape of clouds. The first one is formulated as a low-pass filter, assuming that output fluctuation is transmitted to the same direction as the wind direction at the constant speed. The second one is taken into account by using a Fourier transform surrogate data. The parameters in the proposed method were selected, so that the estimated fluctuation can be similar with that of ensemble average fluctuation of data observed at 5 points used as a training data set. Then, by using the selected parameters, the fluctuation property was estimated for other data set. The results show that the proposed method is useful for estimating the total power output fluctuation of clustered PV systems.

  9. Study on high coupling efficiency Er-doped fiber laser for femtosecond optical frequency comb

    Science.gov (United States)

    Pang, Lihui; Liu, Wenjun; Han, Hainian; Wei, Zhiyi

    2016-09-01

    The femtosecond laser is crucial to the operation of the femtosecond optical frequency comb. In this paper, a passively mode-locked erbium-doped fiber laser is presented with 91.4 fs pulse width and 100.8 MHz repetition rate, making use of the nonlinear polarized evolution effect. Using a 976 nm pump laser diode, the average output power is 16 mW from the coupler and 27 mW from the polarization beam splitter at the pump power of 700 mW. The proposed fiber laser can offer excellent temporal purity in generated pulses with high power, and provide a robust source for fiber-based frequency combs and supercontinuum generation well suited for industrial applications.

  10. Low-power CMOS fully-folding ADC with a mixed-averaging distributed T/H circuit

    Institute of Scientific and Technical Information of China (English)

    Liu Zhen; Jia Song; Wang Yuan; Ji Lijiu; Zhang Xing

    2009-01-01

    This paper describes an 8-bit 125 Mhzlow-powerCMOS fully-foldinganalog-to-digital converter(ADC).A novel mixed-averaging distributed T/H circuit is proposed to improve the accuracy. Folding circuits are not only used in the fine converter but also in the coarse one and in the bit synchronization block to reduce the number of comparators for low power. This ADC is implemented in 0.5μm CMOS technology and occupies a die area of 2 × 1.5 mm~2. The measured differential nonlinearity and integral nonlinearity are 0.6 LSB/-0.8 LSB and 0.9 LSB/-1.2 LSB, respectively. The ADC exhibits 44.3 dB of signal-to-noise plus distortion ratio and 53.5 dB of spurious-free dynamic range for 1 MHz input sine-wave. The power dissipation is 138 mW at a sampling rate of 125 MHz at a 5 V supply.

  11. 180W at 1kHz, 532nm SHG from LBO crystals using high average power Nd:YAG laser

    Science.gov (United States)

    Tamaoki, Yoshinori; Kato, Yoshinori; Iyama, Koichi; Kawashima, Toshiyuki; Miyanaga, Noriaki

    2014-02-01

    We have developed high average power MOPA laser system with SHG unit on the table top size (3 × 1.5m). At the wavelength 1064nm has been obtained the max average output power of 715W. We have achieved the average power 180W at the wavelength 532nm, the pulse width of about 100ns, the frequency of 1kHz. And the power efficiency of the SHG from the wavelength of 1064nm to 532nm was obtained about 25.6%.

  12. Femtosecond single-electron diffraction

    Directory of Open Access Journals (Sweden)

    S. Lahme

    2014-05-01

    Full Text Available Ultrafast electron diffraction allows the tracking of atomic motion in real time, but space charge effects within dense electron packets are a problem for temporal resolution. Here, we report on time-resolved pump-probe diffraction using femtosecond single-electron pulses that are free from intra-pulse Coulomb interactions over the entire trajectory from the source to the detector. Sufficient average electron current is achieved at repetition rates of hundreds of kHz. Thermal load on the sample is avoided by minimizing the pump-probe area and by maximizing heat diffusion. Time-resolved diffraction from fibrous graphite polycrystals reveals coherent acoustic phonons in a nanometer-thick grain ensemble with a signal-to-noise level comparable to conventional multi-electron experiments. These results demonstrate the feasibility of pump-probe diffraction in the single-electron regime, where simulations indicate compressibility of the pulses down to few-femtosecond and attosecond duration.

  13. High average power Yb:CaF2 femtosecond amplifier with integrated simultaneous spatial and temporal focusing for laser material processing

    Science.gov (United States)

    Squier, J.; Thomas, J.; Block, E.; Durfee, C.; Backus, S.

    2014-01-01

    A watt level, 10-kz repetition rate chirped pulse amplification system that has an integrated simultaneous spatial and temporal focusing (SSTF) processing system is demonstrated for the first time. SSTF significantly reduces nonlinear effects normally detrimental to beam control enabling the use of a low numerical aperture focus to quickly treat optically transparent materials over a large area. The integrated SSTF system has improved efficiency compared to previously reported SSTF designs, which combined with the high-repetition rate of the laser, further optimizes its capability to provide rapid, large volume processing.

  14. Design and development of a 6 MW peak, 24 kW average power S-band klystron

    International Nuclear Information System (INIS)

    A 6 MW peak, 24 kW average power S-band Klystron is under development at CEERI, Pilani under an MoU between BARC and CEERI. The design of the klystron has been completed. The electron gun has been designed using TRAK and MAGIC codes. RF cavities have been designed using HFSS and CST Microwave Studio while the complete beam wave interaction simulation has been done using MAGIC code. The thermal design of collector and RF window has been done using ANSYS code. A Gun Collector Test Module (GCTM) was developed before making actual klystron to validate gun perveance and thermal design of collector. A high voltage solid state pulsed modulator has been installed for performance valuation of the tube. The paper will cover the design aspects of the tube and experimental test results of GCTM and klystron. (author)

  15. Plasma wakefield excitation by incoherent laser pulses: a path towards high-average power laser-plasma accelerators

    CERN Document Server

    Benedetti, C; Esarey, E; Leemans, W P

    2014-01-01

    In a laser plasma accelerator (LPA), a short and intense laser pulse propagating in a plasma drives a wakefield (a plasma wave with a relativistic phase velocity) that can sustain extremely large electric fields, enabling compact accelerating structures. Potential LPA applications include compact radiation sources and high energy linear colliders. We propose and study plasma wave excitation by an incoherent combination of a large number of low energy laser pulses (i.e., without constraining the pulse phases). We show that, in spite of the incoherent nature of electromagnetic fields within the volume occupied by the pulses, the excited wakefield is regular and its amplitude is comparable or equal to that obtained using a single, coherent pulse with the same energy. These results provide a path to the next generation of LPA-based applications, where incoherently combined multiple pulses may enable high repetition rate, high average power LPAs.

  16. MODIFIED CLIPPING AND FILTERING TECHNIQUE FOR PEAK-TO-AVERAGE POWER RATIO REDUCTION OF OFDM SIGNALS USED IN WLAN.

    Directory of Open Access Journals (Sweden)

    P.K.Sharma

    2010-10-01

    Full Text Available Orthogonal Frequency Division Multiplexing (OFDM has several attributes which make it a preferred modulation scheme for high speed wireless communication. However, the increased Peak-to-Average Power Ratio (PAPR of the signal is a significant drawback for OFDM systems since it restricts the efficiency of the transmitter. This paper is focused in the domain of PAPR reduction of OFDM signals. The main idea is to use a combination of data interleaving with clipping and filtering and use of optimum clipping ratio (Υ in order to increase the overall performance of the system and the PAPR and BER is valuated in AWGN channel. The main advantage of the proposed combination lies in reducing PAPR and significantly reduction in BER in the presence of AWGN channel.

  17. High-Average-Power Third Harmonic Generation at 355 nm with CsB3O5 Crystal

    Institute of Scientific and Technical Information of China (English)

    WU Yi-Cheng; CHANG Feng; FU Pei-Zhen; CHEN Chuang-Tian; WANG Gui-Ling; GENG Ai-Cong; BO Yong; CUI Da-Fu; XU Zu-Yan

    2005-01-01

    @@ A 17.7W average power output at 355nm by the third harmonic generation (THG) of 1064nm light has been obtained with the nonlinear optical crystal CsB3O5 (CBO). The fundamental light source is a diode-pumped Nd:YAG laser with a pulse duration of 70ns and a repetition rate of 7kHz. A CBO crystal cut for type-ⅡPM angles is used in the experiment. The THG energy conversion efficiency with CBO is twice as large as that with LBO. As a THG crystal, CBO has better performance than that of LiB3O5 crystal (LBO).

  18. Femtosecond laser-electron x-ray source

    Science.gov (United States)

    Hartemann, Frederic V.; Baldis, Hector A.; Barty, Chris P.; Gibson, David J.; Rupp, Bernhard

    2004-04-20

    A femtosecond laser-electron X-ray source. A high-brightness relativistic electron injector produces an electron beam pulse train. A system accelerates the electron beam pulse train. The femtosecond laser-electron X-ray source includes a high intra-cavity power, mode-locked laser and an x-ray optics system.

  19. Characterizing THz Coherent Synchrotron Radiation at Femtosecond Linear Accelerator

    Institute of Scientific and Technical Information of China (English)

    LIN Xu-Ling; ZHANG Jian-Bing; LU YU; LUO Feng; LU Shan-Liang; YU Tie-Min; DAI Zhi-Min

    2009-01-01

    The generation and observation of coherent THz synchrotron radiation from femtosecond electron bunches in the Shanghai Institute of Applied Physics femtosecond accelerator device is reported.We describe the experiment setup and present the first result of THz radiation properties such as power and spectrum.

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

    Science.gov (United States)

    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

  1. Tunable femtosecond laser in the visible range with an intracavity frequency-doubled optical parametric oscillator

    Science.gov (United States)

    Zhu, Jiang-Feng; Xu, Liang; Lin, Qing-Feng; Zhong, Xin; Han, Hai-Nian; Wei, Zhi-Yi

    2013-05-01

    We demonstrated experimentally a synchronously pumped intracavity frequency-doubled femtosecond optical parametric oscillator (OPO) using a periodically-poled lithium niobate (PPLN) as the nonlinear material in combination with a lithium triborate (LBO) as the doubling crystal. A Kerr-lens-mode-locked (KLM) Ti:sapphire oscillator at the wavelength of 790 nm was used as the pump source, which was capable of generating pulses with a duration as short as 117 fs. A tunable femtosecond laser covering the 624-672 nm range was realized by conveniently adjusting the OPO cavity length. A maximum average output power of 260 mW in the visible range was obtained at the pump power of 2.2 W, with a typical pulse duration of 205 fs assuming a sech2 pulse profile.

  2. A 18-W Signal Average Power Nanosecond LiB3O5 Optical Parametric Oscillator around 860 nm and the Beam Quality

    Institute of Scientific and Technical Information of China (English)

    LI Hui-Qing; GENG Ai-Cong; BO Yong; PENG Qin-Jun; CUI Da-Fu; XU Zu-Yan

    2005-01-01

    @@ We report a compact high average power optical parametric oscillator (OPO) pumped by an all-solid-state nanosecond 532-nm laser. Based on the merit of non-critically phase-matched crystals without walk-off effect, a 60-mm-long LiB3O5 (LBO) crystal is used as the OPO nonlinear crystal to enhance the conversion efficiency and to increase the output power. The maximum average power of signal output is up to 18 W at 860nm for pump power of 65 W. This is the highest signal average power generated by a nanosecond OPO in single bulk LBO,to the best of our knowledge. The dynamic characteristics of beam quality are investigated. Our experimental results demonstrate that good OPO conversion efficiency and high output power can be obtained even with relatively poor pump beam quality.

  3. High-average-power 2 μm few-cycle optical parametric chirped pulse amplifier at 100 kHz repetition rate.

    Science.gov (United States)

    Shamir, Yariv; Rothhardt, Jan; Hädrich, Steffen; Demmler, Stefan; Tschernajew, Maxim; Limpert, Jens; Tünnermann, Andreas

    2015-12-01

    Sources of long wavelengths few-cycle high repetition rate pulses are becoming increasingly important for a plethora of applications, e.g., in high-field physics. Here, we report on the realization of a tunable optical parametric chirped pulse amplifier at 100 kHz repetition rate. At a central wavelength of 2 μm, the system delivered 33 fs pulses and a 6 W average power corresponding to 60 μJ pulse energy with gigawatt-level peak powers. Idler absorption and its crystal heating is experimentally investigated for a BBO. Strategies for further power scaling to several tens of watts of average power are discussed. PMID:26625047

  4. High-average-power 2 μm few-cycle optical parametric chirped pulse amplifier at 100 kHz repetition rate.

    Science.gov (United States)

    Shamir, Yariv; Rothhardt, Jan; Hädrich, Steffen; Demmler, Stefan; Tschernajew, Maxim; Limpert, Jens; Tünnermann, Andreas

    2015-12-01

    Sources of long wavelengths few-cycle high repetition rate pulses are becoming increasingly important for a plethora of applications, e.g., in high-field physics. Here, we report on the realization of a tunable optical parametric chirped pulse amplifier at 100 kHz repetition rate. At a central wavelength of 2 μm, the system delivered 33 fs pulses and a 6 W average power corresponding to 60 μJ pulse energy with gigawatt-level peak powers. Idler absorption and its crystal heating is experimentally investigated for a BBO. Strategies for further power scaling to several tens of watts of average power are discussed.

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

    International Nuclear Information System (INIS)

    Highlights: • Oxidation of the chromium thin film to chromium oxide by femtosecond laser with a fundamental wavelength of 1064 nm. • Solar absorber from chromium oxide that low percentage reflectance. • Femtosecond laser oxidation, with a de-focused laser. • Chromium oxide formation by femtosecond laser in normal ambient. - Abstract: In view of their potential applications as selective solar absorbers, chromium coatings on float glass substrates were nano/micro structured by femtosecond laser in air. Raman and X-rays diffraction investigations confirmed the formation of an ultra-porous α-Cr2O3 layer at the surface; higher is the input laser power, enhanced is the crystallinity of the α-Cr2O3 layer. The α-Cr2O3 layer with the Cr underneath it in addition to the photo-induced porosity acted as a classical ceramic–metal nano-composite making the reflectance to decrease significantly within the spectral range of 190–1100 nm. The average reflectance decreased from 70 to 2%

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-12-01

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

  7. Development of a 33 kV, 20 A long pulse converter modulator for high average power klystron.

    Science.gov (United States)

    Reghu, T; Mandloi, V; Shrivastava, Purushottam

    2014-05-01

    Research, design, and development of high average power, long pulse modulators for the proposed Indian Spallation Neutron Source are underway at Raja Ramanna Centre for Advanced Technology. With this objective, a prototype of long pulse modulator capable of delivering 33 kV, 20 A at 5 Hz repetition rate has been designed and developed. Three Insulated Gate Bipolar Transistors (IGBT) based switching modules driving high frequency, high voltage transformers have been used to generate high voltage output. The IGBT based switching modules are shifted in phase by 120° with respect to each other. The switching frequency is 25 kHz. Pulses of 1.6 ms pulse width, 80 μs rise time, and 70 μs fall time have been achieved at the modulator output. A droop of ±0.6% is achieved using a simple segmented digital droop correction technique. The total fault energy transferred to the load during fault has been measured by conducting wire burn tests and is found to be within 3.5 J. PMID:24880410

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

    Science.gov (United States)

    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.

  9. Development of a 33 kV, 20 A long pulse converter modulator for high average power klystron

    Energy Technology Data Exchange (ETDEWEB)

    Reghu, T.; Mandloi, V.; Shrivastava, Purushottam [Pulsed High Power Microwave Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India)

    2014-05-15

    Research, design, and development of high average power, long pulse modulators for the proposed Indian Spallation Neutron Source are underway at Raja Ramanna Centre for Advanced Technology. With this objective, a prototype of long pulse modulator capable of delivering 33 kV, 20 A at 5 Hz repetition rate has been designed and developed. Three Insulated Gate Bipolar Transistors (IGBT) based switching modules driving high frequency, high voltage transformers have been used to generate high voltage output. The IGBT based switching modules are shifted in phase by 120° with respect to each other. The switching frequency is 25 kHz. Pulses of 1.6 ms pulse width, 80 μs rise time, and 70 μs fall time have been achieved at the modulator output. A droop of ±0.6% is achieved using a simple segmented digital droop correction technique. The total fault energy transferred to the load during fault has been measured by conducting wire burn tests and is found to be within 3.5 J.

  10. Development of a 33 kV, 20 A long pulse converter modulator for high average power klystron

    Science.gov (United States)

    Reghu, T.; Mandloi, V.; Shrivastava, Purushottam

    2014-05-01

    Research, design, and development of high average power, long pulse modulators for the proposed Indian Spallation Neutron Source are underway at Raja Ramanna Centre for Advanced Technology. With this objective, a prototype of long pulse modulator capable of delivering 33 kV, 20 A at 5 Hz repetition rate has been designed and developed. Three Insulated Gate Bipolar Transistors (IGBT) based switching modules driving high frequency, high voltage transformers have been used to generate high voltage output. The IGBT based switching modules are shifted in phase by 120° with respect to each other. The switching frequency is 25 kHz. Pulses of 1.6 ms pulse width, 80 μs rise time, and 70 μs fall time have been achieved at the modulator output. A droop of ±0.6% is achieved using a simple segmented digital droop correction technique. The total fault energy transferred to the load during fault has been measured by conducting wire burn tests and is found to be within 3.5 J.

  11. Advanced high-power optical parametric oscillators synchronously pumped by ultrafast fibre-based sources

    OpenAIRE

    Kienle, Florian

    2012-01-01

    This thesis is concerned with investigating the generation of ultra short, tunable pulses at high average power and / or high pulse energy using synchronously pumped optical parametric oscillators (OPO) and appropriate power-scalable fibre-amplifier pump sources. Two types of pump sources with average powers up to ? 100W are considered: (1) a picosecond, all-fiberised, high-power, variable-repetition-rate, Yb:fibre-amplified, gain-switched laser diode system and (2) a femtosecond, high-power,...

  12. Critical femtosecond laser parameters for the fabrication of optimal reflecting diffraction gratings on Invar36

    Science.gov (United States)

    Mohammad Hossein, Goudarzi; Meng-Jyun, Lin; Ji-Bin, Horng; Jeng-Ywan, Jeng

    2016-06-01

    This paper discusses the effect of femtosecond laser parameters on Invar36, and the efficiency of reflecting diffraction gratings on the alloy. Several gratings were made with different laser parameters in two regimes: constant repetition rates and constant average laser power on the Invar surface. The efficiency of diffraction gratings is measured in an off-plane configuration by determining the power of diffracted points. With the constant average power technique, an increase in laser influence decreased the ablation depth of lines and increased the line widths. The discoloration of line edges from increasing the laser influence more than 0.57 J /cm2 decreased the grating efficiency by over 49%. It was also found that increasing the repetition rate enhanced the grating efficiency and increasing the average power decreased the efficiency. In addition, the ablation threshold of Invar is 0.122 J /cm2 when the number of pulses (NOP) equals 389.

  13. Octave-spanning OPCPA system delivering CEP-stable few-cycle pulses and 22 W of average power at 1 MHz repetition rate.

    Science.gov (United States)

    Rothhardt, Jan; Demmler, Stefan; Hädrich, Steffen; Limpert, Jens; Tünnermann, Andreas

    2012-05-01

    We report on an OPCPA system delivering CEP-stable pulses with a pulse duration of only 1.7 optical cycles at 880 nm wavelength. This pulse duration is achieved by the generation, optical parametric amplification and compression of a full optical octave of bandwidth. The system is pumped by a high average power Yb-fiber laser system, which allows for operation of the OPCPA at up to 1 MHz repetition rate and 22 W of average output power. Further scaling towards single-cycle pulses, higher energy and output power is discussed. PMID:22565712

  14. Energy scaling of a carbon nanotube saturable absorber mode-locked femtosecond bulk laser

    OpenAIRE

    Baylam, Işınsu; Çankaya, Hüseyin; Sennaroğlu, Alphan; Ozharar, S.; Choi, S. Y.; Kim, K.; Rotermund, F.; Griebner, U.; Petrov, V.

    2012-01-01

    We report successful energy scaling of a room-temperature femtosecond Cr4+: forsterite laser by using a single-walled carbon nanotube saturable absorber (SWCNT-SA). By incorporating a q-preserving multipass cavity, a repetition rate of 4.51 MHz was realized, and the oscillator produced 121 fs, 10 nJ pulses at 1247 nm, with an average output power of 46 mW. To the best of our knowledge, the peak power of 84 kW is the highest generated to date from a SWCNT-SA mode-locked oscillator. Furthermore...

  15. State Averages

    Data.gov (United States)

    U.S. Department of Health & Human Services — A list of a variety of averages for each state or territory as well as the national average, including each quality measure, staffing, fine amount and number of...

  16. Nonlinear Femtosecond Pulse Reshaping in Waveguide Arrays

    OpenAIRE

    Darren D. Hudson; Shish, Kimberlee; Schibli, Thomas R.; Kutz, J. Nathan; Christodoulides, Demetrios N.; Morandotti, Roberto; Cundiff, Steven T.

    2008-01-01

    We observe nonlinear pulse reshaping of femtosecond pulses in a waveguide array due to coupling between waveguides. Amplified pulses from a mode-locked fiber laser are coupled to an AlGaAs core waveguide array structure. The observed power-dependent pulse reshaping agrees with theory, including shortening of the pulse in the central waveguide.

  17. Fabrication of Micro -Optical Devices by a Femtosecond Laser

    Institute of Scientific and Technical Information of China (English)

    Jianrong Qiu; Kazuyuki Hirao

    2003-01-01

    Femtosecond laser is a perfect laser source for materials processing when high accuracy and small structure size are required. Due to the ultra short interaction time and the high peak power, the process is generally characterized by the absence of heat diffusion and, consequently molten layers. Various induced structures have been observed in materials after the femtosecond laser irradiation. Here, we report on fabrication of micro-optical devices by the femtosecond laser. 1) formation of optical waveguide with internal loss less than 0.5dB/cm in the wavelength region from 1.2 to 1.6 mm, by translating a silica glass perpendicular to the axis of the focused femtosecond laser beam; 2) nano-scale valence state manipulation of active ions inside transparent materials; 3) space-selective precipitation and control of metal nanoparticles inside transparent materials; The mechanisms and applications of the femtosecond laser induced phenomena were also discussed.

  18. Efficient spectral broadening in the 100-W average power regime using gas-filled kagome HC-PCF and pulse compression.

    Science.gov (United States)

    Emaury, Florian; Saraceno, Clara J; Debord, Benoit; Ghosh, Debashri; Diebold, Andreas; Gèrôme, Frederic; Südmeyer, Thomas; Benabid, Fetah; Keller, Ursula

    2014-12-15

    We present nonlinear pulse compression of a high-power SESAM-modelocked thin-disk laser (TDL) using an Ar-filled hypocycloid-core kagome hollow-core photonic crystal fiber (HC-PCF). The output of the modelocked Yb:YAG TDL with 127 W average power, a pulse repetition rate of 7 MHz, and a pulse duration of 740 fs was spectrally broadened 16-fold while propagating in a kagome HC-PCF containing 13 bar of static argon gas. Subsequent compression tests performed using 8.4% of the full available power resulted in a pulse duration as short as 88 fs using the spectrally broadened output from the fiber. Compressing the full transmitted power through the fiber (118 W) could lead to a compressed output of >100  W of average power and >100  MW of peak power with an average power compression efficiency of 88%. This simple laser system with only one ultrafast laser oscillator and a simple single-pass fiber pulse compressor, generating both high peak power >100  MW and sub-100-fs pulses at megahertz repetition rate, is very interesting for many applications such as high harmonic generation and attosecond science with improved signal-to-noise performance.

  19. Femtosecond Laser Filamentation for Atmospheric Sensing

    Directory of Open Access Journals (Sweden)

    Huai Liang Xu

    2010-12-01

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

  20. Quaternion Averaging

    Science.gov (United States)

    Markley, F. Landis; Cheng, Yang; Crassidis, John L.; Oshman, Yaakov

    2007-01-01

    Many applications require an algorithm that averages quaternions in an optimal manner. For example, when combining the quaternion outputs of multiple star trackers having this output capability, it is desirable to properly average the quaternions without recomputing the attitude from the the raw star tracker data. Other applications requiring some sort of optimal quaternion averaging include particle filtering and multiple-model adaptive estimation, where weighted quaternions are used to determine the quaternion estimate. For spacecraft attitude estimation applications, derives an optimal averaging scheme to compute the average of a set of weighted attitude matrices using the singular value decomposition method. Focusing on a 4-dimensional quaternion Gaussian distribution on the unit hypersphere, provides an approach to computing the average quaternion by minimizing a quaternion cost function that is equivalent to the attitude matrix cost function Motivated by and extending its results, this Note derives an algorithm that deterniines an optimal average quaternion from a set of scalar- or matrix-weighted quaternions. Rirthermore, a sufficient condition for the uniqueness of the average quaternion, and the equivalence of the mininiization problem, stated herein, to maximum likelihood estimation, are shown.

  1. Trigger effect of infrared femtosecond laser irradiation on neoplasm in experimental cervical cancer

    Science.gov (United States)

    Gening, Tatyana; Voronova, Olga; Zolotovskii, Igor; Sysoliatin, Alexey; Dolgova, Dinara; Abakumova, Tatyana

    2013-02-01

    The present work discusses effect of infrared (IR) femtosecond laser irradiation on neoplasm of white mice with experimental cervical cancer- 5 (CC-5 on the 20th and 30th days after tumor transplantation). Tumor tissue was irradiated by femtosecond erbium doped fiber laser: the wavelength is 1.55 μm, average and peak powers are1,25 mW and 6kW, respectively, irradiation trials n=10. The average energy density (energy dose) on a tissue for two groups of animals was 0,24 J/cm2 and 0,36 J/cm2 for a single trial. Irradiation was followed by biochemical determination of LPO AOS parameters ("Lipid peroxidation-antioxidants" system): malondialdehyde (MDA), activity of superoxide dismutase (SOD), catalase and glutathione-reductase (GR), glutathione-S-transferase (GST). A subsequent morphological study of tumor tissue was performed. Mathematical analysis of data demonstrates a weak dependence of the studied parameters on energy dose. The latter implies the trigger effect of IR femtosecond laser irradiation on redox-dependent processes in neoplasm at experimental cervical cancer.

  2. Compton Scattering and Its Applications: The PLEIADES Femtosecond X-ray Source at LLNL

    Energy Technology Data Exchange (ETDEWEB)

    Hartemann, F V; Brown, W J; Anderson, S G; Barty, C P J; Betts, S M; Booth, R; Crane, J K; Cross, R R; Fittinghoff, D N; Gibson, D J; Kuba, J; Rupp, B; Tremaine, A M; Springer, P T

    2003-05-01

    Remarkable developments in critical technologies including terawatt-class lasers using chirped-pulse amplification, high brightness photoinjectors, high-gradient accelerators, and superconducting linacs make it possible to design and operate compact, tunable, subpicosecond Compton scattering x-ray sources with a wide variety of applications. In such novel radiation sources, the collision between a femtosecond laser pulse and a low emittance relativistic electron bunch in a small ({micro}m{sup 3}) interaction volume produces Doppler-upshifted scattered photons with unique characteristics: the energy is tunable in the 5-500 keV range, the angular divergence of the beam is small (mrad), and the pulses are ultrashort (10 fs - 10 ps). Two main paths are currently being followed in laboratories worldwide: high peak brightness, using ultrahigh intensity femtosecond lasers at modest repetition rates, and high average brightness, using superconducting linac and high average power laser technology at MHz repetition rates. Targeted applications range from x-ray protein crystallography and high contrast medical imaging to femtosecond pump-probe and diffraction experiments. More exotic uses of such sources include the {gamma}-{gamma} collider, NIF backlighting, nonlinear Compton scattering, and high-field QED. Theoretical considerations and experimental results will be discussed within this context.

  3. Femtosecond laser microchannels fabrication based on electrons dynamics control using temporally or spatially shaped pulses

    Science.gov (United States)

    Yan, Xueliang; Hu, Jie; Li, Xiaowei; Xia, Bo; Liu, Pengjun; Lu, Yongfeng; Jiang, Lan

    2014-11-01

    With ultrashort pulse durations and ultrahigh power densities, femtosecond laser presents unique advantages of high precision and high quality fabrication of microchannels in transparent materials. In our study, by shaping femtosecond laser pulse energy distribution in temporal or spatial domains, localized transient electrons dynamics and the subsequent processes, such as phase changes, can be controlled, leading to the dramatic increases in the capability of femtosecond laser microchannels fabrication. The temporally shaped femtosecond laser pulse trains can significantly enhance the material removal rate in both water-assisted femtosecond laser drilling and femtosecond laser irradiation followed by chemical etching. Besides, high-aspect-ratio and small-diameter microchannels are drilled by spatially shaped femtosecond laser pulses.

  4. Long range prospect of the electric power demand in FY 2,000. Total demand: 8. 38 trillion KWh, annual average increase: 2. 3%

    Energy Technology Data Exchange (ETDEWEB)

    1988-01-05

    The Agency of Natural Resources and Energy, the Ministry of International Trade and Industry held meetings of the Committee on Demand and Supply of the Electric Utility Industrial Council in October, 1987. This article is the Committee's interim report and establishes the prospect of the electric power supply and demand in Japan in FY 1995 and FY 2000. Total power demand in FY 1995 is about 7.38 trillion KWh and in FY 2000, about 8.38 trillion KWh. Average annual growth is about 2.6% during the period of FY 1995 through FY 2000. Among the above, the public demand will increase and occupy 50.2% of the total power demand in the year of 2000. The industrial demand will increase about 1.4% in terms of annual rate during the period of FY 1995 through FY 2000 due to the demand increase by new industries, etc. against continued rationalization of power utilization. The maximum electric power demand is around 163 million KW in FY 2000. The target of electric power supply in FY 2000 is 53 million KW from atomic power generation, 23 million KW from coal burning thermal power generation, 43 million KW from LNG, 21 million KW from hydro power generation and 52 million KW from oil and LPG. Hereafter, electric load leveling, more efficient electric power supply and strengthening of the basis of electric power utilization are necessary. (1 photo, 3 tabs)

  5. Femtosecond Fiber Lasers

    Science.gov (United States)

    Bock, Katherine J.

    This thesis focuses on research I have done on ytterbium-doped femtosecond fiber lasers. These lasers operate in the near infrared region, lasing at 1030 nm. This wavelength is particularly important in biomedical applications, which includes but is not limited to confocal microscopy and ablation for surgical incisions. Furthermore, fiber lasers are advantageous compared to solid state lasers in terms of their cost, form factor, and ease of use. Solid state lasers still dominate the market due to their comparatively high energy pulses. High energy pulse generation in fiber lasers is hindered by either optical wave breaking or by multipulsing. One of the main challenges for fiber lasers is to overcome these limitations to achieve high energy pulses. The motivation for the work done in this thesis is increasing the output pulse peak power and energy. The main idea of the work is that decreasing the nonlinearity that acts on the pulse inside the cavity will prevent optical wave breaking, and thus will generate higher energy pulses. By increasing the output energy, ytterbium-doped femtosecond fiber lasers can be competitive with solid state lasers which are used commonly in research. Although fiber lasers tend to lack the wavelength tuning ability of solid state lasers, many biomedical applications take advantage of the 1030 microm central wavelength of ytterbium-doped fiber lasers, so the major limiting factor of fiber lasers in this field is simply the output power. By increasing the output energy without resorting to external amplification, the cavity is optimized and cost can remain low and economical. During verification of the main idea, the cavity was examined for possible back-reflections and for components with narrow spectral bandwidths which may have contributed to the presence of multipulsing. Distinct cases of multipulsing, bound pulse and harmonic mode-locking, were observed and recorded as they may be of more interest in the future. The third

  6. High-average power THG of a diode-pumped Nd:YAG laser at 355 nm generated by LiB3O5 crystal

    Institute of Scientific and Technical Information of China (English)

    Yong Bi(毕勇); Yan Feng(冯衍); Huarong Gong(巩华荣); Hongbo Zhang(张鸿博); Zuyan Xu(许祖彦)

    2003-01-01

    More than 6 W average power ultraviolet radiation at 355 nm was generated in LiB3O5 (LBO) crystalthrough the frequency mixing of the fundamental and second harmonic radiation of a Nd:YAG laser. Thisperformance was achieved with 38% optical-to-optical conversion efficiency (532 nm to 355 nm).

  7. High-average-power green laser using Nd:YAG amplifier with stimulated Brillouin scattering phase-conjugate pulse-cleaning mirror.

    Science.gov (United States)

    Tsubakimoto, Koji; Yoshida, Hidetsugu; Miyanaga, Noriaki

    2016-06-13

    We present a high-average-power green laser based on second harmonic conversion of a laser diode-pumped master oscillator Nd:YAG power amplifier system. The power amplifier chain includes a stimulated Brillouin scattering (SBS) cell that was used a phase-conjugate mirror to double-pass scheme. That suppresses the thermal phase distortion and compresses the pulse duration. The fundamental beam output power was 670 W with a pulse width of 7.9 ns. A second harmonic power of 335 W with a 4.8-ns pulse width and 80-mJ pulse energy was produced using a LiB3O5 (LBO) crystal. PMID:27410277

  8. Computations of longitudinal electron dynamics in the recirculating cw RF accelerator-recuperator for the high average power FEL

    Science.gov (United States)

    Sokolov, A. S.; Vinokurov, N. A.

    1994-03-01

    The use of optimal longitudinal phase-energy motion conditions for bunched electrons in a recirculating RF accelerator gives the possibility to increase the final electron peak current and, correspondingly, the FEL gain. The computer code RECFEL, developed for simulations of the longitudinal compression of electron bunches with high average current, essentially loading the cw RF cavities of the recirculator-recuperator, is briefly described and illustrated by some computational results.

  9. Optical data storage in nonphotosensitive media by femtosecond laser pulses

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Ultrashort lasers have become powerful tools by inducing extremely nonlinear effects in a wide variety of materials.Femtosecond laser data storage in non-photosensitive media is promising for its high density and fast retrieval. We reviewed the progress of three types of femtosecond laser storage in transparent materials: three-dimensional bit-oriented storage by micro-voids, holographic data storage by two beam interference and storage by computer-generated holograms.

  10. Femtosecond optical studies of cuprates

    Science.gov (United States)

    Schneider, Michael L.; Rast, S.; Onellion, Marshall; Demsar, Jure; Taylor, Antoinette J.; Glinka, Yu D.; Tolk, Norman H.; Ren, Yuhang; Luepke, Gunter; Klimov, A.; Xu, Ying; Sobolewski, Roman; Si, Weidong; Zeng, X. H.; Soukiassian, A.; Xi, Xiaoxing; Abrecht, M.; Ariosa, Daniel; Pavuna, Davor; Manzke, Recardo; Printz, J. O.; Parkhurst, D. K.; Downum, K. E.; Guptasarma, P.; Bozovic, Ivan

    2002-11-01

    Femtosecond optical reflectivity measurements of La2-xSrxCuO4, La2CuO4+y, Bi2Sr2CuO6+z and Bi2Sr2CaCu2O8+δ thin films and single crystal samples indicate qualitative changes with fluence. At the lowest fluencies, there is a power law divergence in the relaxation time. The divergence has an onset temperature of 55+/-15K, independent of whether the sample is in the superconducting or normal states. At slightly higher fluencies, still perturbative, the additional response does not exhibit this power law divergence. At quite high fluencies- no longer perturbative- the metallic samples exhibit oscillations in the reflectivity amplitude. The period of these oscillations varies with the probe wavelength but not with the pump wavelength. The oscillations exhibit a decay time as long as 10 nsec.

  11. Femtosecond Laser Filamentation

    CERN Document Server

    Chin, See Leang

    2010-01-01

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

  12. Femtosecond laser spectroscopy

    CERN Document Server

    Hannaford, Peter

    2005-01-01

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

  13. Peak torque and average power at flexion/extension of the shoulder and knee when using a mouth guard in adults with mild midline discrepancy.

    Science.gov (United States)

    Lee, Sang-Yeol; Hong, Min-Ho; Choi, Seung-Jun

    2014-07-01

    [Purpose] This study was conducted to investigate the changes in torque and power during flexion and extension of the shoulder and the knee joints caused by midline correction using mouth guards made from different materials in adults with mild midline discrepancy. [Subjects] The subjects of this study were males (n=12) in their 20s who showed a 3-5 mm difference between the midlines of the upper and lower teeth but had normal masticatory function. [Methods] The torque and average power of the lower limb and upper limb were measured during flexion and extension according to various types of mouth guard. [Results] There were significant differences in relative torque and average power between three conditions (no mouth guard, soft-type mouth guard, and hard-type mouth guard) at shoulder flexion and extension. There were no significant differences in relative torque and average power between the three conditions at knee flexion and extension. [Conclusions] These results suggest that use of a mouth guard is a method by which people with a mild midline discrepancy can improve the stability of the entire body.

  14. Femtosecond pulse generation and amplification in Yb-doped fibre oscillator–amplifier system

    Indian Academy of Sciences (India)

    P K Mukhopadhyay

    2010-11-01

    In recent times ytterbium (Yb) doped fibre-based mode-locked master oscillator and power amplifier have attracted a great deal of interest because of their inherent advantages like flexibility, reliability, compactness, high power handling capability and diffraction limited output beam quality as compared to the solid-state counterpart. But, to successfully develope of high-power femtosecond oscillator–amplifier system based on Yb- doped fibre, an appropriate choice of the mode-locking regime and the amplifier geometry are required. Development of an all-fibre integrated high-power Yb-doped fibre oscillator–amplifier system in which the advantages of a fibre-based system can be fully exploited remained a challenge as it requires the careful optimization of dispersion, nonlinearity, gain and ASE contribution. In this article, femto-second pulse generation in Yb-doped fibre oscillator in different mode-locking regimes are reviewed and the details of development and characterization of an all-fibre, high-power, low-noise amplifier system seeded by an all-normal-dispersion mode-locked Yb-doped fibre laser oscillator is described. More than 10 W of average power is obtained from the fibre oscillator–amplifier system at a repetition rate of 43 MHz with diffraction-limited beam quality. Amplified pulses are de-chirped to sub-160 fs duration in a grating compressor. This is the first 10 W-level source of femtosecond pulses with completely fibre-integrated amplification comprised of commercially available components.

  15. Yb-fiber-laser-based, 1.8  W average power, picosecond ultraviolet source at 266  nm

    OpenAIRE

    S Chaitanya Kumar; Canals Casals, J.; Sanchez Bautista, E.; Devi, K; Ebrahim-Zadeh, M.

    2015-01-01

    We report a compact, stable, high-power, picosecond ultraviolet (UV) source at 266 nm based on simple single-pass two-step fourth-harmonic generation (FHG) of a mode-locked Yb-fiber laser at 79.5 MHz in LiB3O5 (LBO) and β-BaB2O4. Using a 30-mm-long LBO crystal for single-pass second-harmonic generation, we achieve up to 9.1 W of average green power at 532 nm for 16.8 W of Yb-fiber power at a conversion efficiency of 54% in 16.2 ps pulses with a TEM00 spatial profile and passive power stabilit...

  16. High average/peak power linearly polarized all-fiber picosecond MOPA seeded by mode-locked noise-like pulses

    Science.gov (United States)

    Yu, H. L.; Ma, P. F.; Tao, R. M.; Wang, X. L.; Zhou, P.; Chen, J. B.

    2015-06-01

    The characteristics of mode-locked noise-like pulses generated from a passively mode-locked fiber oscillator are experimentally investigated. By carefully adjusting the two polarization controllers, stable mode-locked noise-like pulse emission with a high radio frequency signal/noise ratio of  >55 dB is successfully achieved, ensuring the safety and possibility of high power amplification. To investigate the amplification characteristics of such pulses, one all-fiber master oscillator power amplifier (MOPA) is built to boost the power and energy of such pulses. Amplified noise-like pulses with average output power of 423 W, repetition rate of 18.71 MHz, pulse energy of 22.61 μJ, pulse duration of 72.1 ps and peak power of 314 kW are obtained. Near diffraction-limited beam is also demonstrated with M2 factor measured at full power operation of ~1.2 in the X and Y directions. The polarization extinction ratio at output power of 183 W is measured to be ~13 dB. To the best of our knowledge, this is the first demonstration of high-power amplification of noise-like pulses and the highest peak power ever reported in all-fiber picosecond MOPAs. The temporal self-compression process of such pulses and high peak power when amplified make it an ideal pump source for generation of high-power supercontinuum. Other potential applications, such as material processing and optical coherent tomography, could also be foreseen.

  17. Development of laser diode-pumped high average power solid-state laser for the pumping of Ti:sapphire CPA system

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

    Laser diode pumped all solid state, high repetition frequency (PRF) and high energy Nd:YAG laser using zigzag slab crystals has been developed for the pumping source of Ti:sapphire CPA system. The pumping laser installs two main amplifiers which compose ring type amplifier configuration. The maximum amplification gain of the amplifier system is 140 and the condition of saturated amplification is achieved with this high gain. The average power of fundamental laser radiation is 250 W at the PRF of 200 Hz and the pulse duration is around 20 ns. The average power of second harmonic is 105 W at the PRF of 170 Hz and the pulse duration is about 16 ns. The beam profile of the second harmonic is near top hat and will be suitable for the pumping of Ti:sapphire laser crystal. The wall plug efficiency of the laser is 2.0 %. (author)

  18. Peak to Average Power Ratio Reduction using a Hybrid of Bacterial Foraging and Modified Cuckoo Search Algorithm in MIMO-OFDM System

    OpenAIRE

    R. Manjith; M. Suganthi

    2014-01-01

    The Partial Transmit Sequence which reduces the PAPR (Peak-to-Average Power Ratio) in Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system using a novel optimization algorithm is proposed in this study. This novel optimization algorithm is based on a hybrid of Bacterial Foraging Optimization (BFO) and Modified Cuckoo Search algorithm (MCS) and is thus called HBFOMCS. In HBFOMCS, reproduction of individuals in a new generation is created, not only by swi...

  19. Investigation on repetition rate and pulse duration influences on ablation efficiency of metals using a high average power Yb-doped ultrafast laser

    Directory of Open Access Journals (Sweden)

    Lopez J.

    2013-11-01

    Full Text Available Ultrafast lasers provide an outstanding processing quality but their main drawback is the low removal rate per pulse compared to longer pulses. This limitation could be overcome by increasing both average power and repetition rate. In this paper, we report on the influence of high repetition rate and pulse duration on both ablation efficiency and processing quality on metals. All trials have been performed with a single tunable ultrafast laser (350 fs to 10ps.

  20. All-fiber high-average power nanosecond-pulsed master-oscillator power amplifier at 2  μm with mJ-level pulse energy.

    Science.gov (United States)

    Wang, Xiong; Jin, Xiaoxi; Zhou, Pu; Wang, Xiaolin; Xiao, Hu; Liu, Zejin

    2016-03-10

    We present a high-power nanosecond-pulsed Tm-doped fiber amplifier at 1.971 μm based on a master-oscillator power amplifier (MOPA) configuration. When the repetition rate is 500 kHz and the pulse width is 63.3 ns, the average power reaches 238 W, the peak power reaches 7.06 kW, and the pulse energy is 0.477 mJ. When the pulse train's repetition rate is 300 kHz with a pulse width of 63.7 ns, the average power reaches 197 W, the peak power reaches 9.73 kW, and the pulse energy is 0.66 mJ. When the pulse train's repetition rate is 200 kHz with a pulse width of 58.2 ns, the average power reaches 150 W, the peak power reaches 12.1 kW, and the pulse energy is 0.749 mJ. The spectral linewidths of the pulse trains are 0.15, 0.14, and 0.10 nm for 500 kHz repetition rate, 300 kHz repetition rate, and 200 kHz repetition rate, respectively. To the best of our knowledge, this is the first demonstration of high-power nanosecond-pulsed MOPA at 2 μm with the maximum average power reaching 238 W, the maximum peak power reaching 12.1 kW, and the maximum pulse energy reaching 0.749 mJ.

  1. The Influence of the Age, the Years of Training, and the BMI on the Average Muscle Power in Male and Female Rowers.

    Science.gov (United States)

    Mogus, Mate; Fric, Vlasta Orsić; Atalić, Bruno

    2015-12-01

    The aim of the study was to evaluate the influence of the age, the body mass index (BMI), and the years of training on the average muscle power in male and female rowers. The analysis of the testing results of the members of the Rowing club Iktus from Osijek in Croatia was performed. Results were obtained during the regular yearly testing on the rowing ergometer for the rowing season of 2009. Members of the Rowing club Iktus were divided into two subgroups according to their sex. The obtained results were analysed in accordance with the age, the BMI, and the years of training independently for the each of the two subgroups. The results have showed that the average muscle power is independent of all the three parameters in the male rowers, while it is dependent on the age and the years of training in the female rowers. It seems that the BMI does not play any role at all in the average muscle power. As a conclusion, it could be stated that while one can suggest to female rowers to improve their performance with prolonged training, there is a need for a further research in order to formulate a suitable advice for male rowers. PMID:26987157

  2. The final power calibration of the IPEN/MB-01 nuclear reactor for various configurations obtained from the measurements of the absolute average neutron flux

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Alexandre Fonseca Povoa da, E-mail: alexandre.povoa@mar.mil.br [Centro Tecnologico da Marinha em Sao Paulo (CTMSP), Sao Paulo, SP (Brazil); Bitelli, Ulysses d' Utra; Mura, Luiz Ernesto Credidio; Lima, Ana Cecilia de Souza; Betti, Flavio; Santos, Diogo Feliciano dos, E-mail: ubitelli@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    The use of neutron activation foils is a widely spread technique applied to obtain nuclear parameters then comparing the results with those calculated using specific methodologies and available nuclear data. By irradiation of activation foils and subsequent measurement of its induced activity, it is possible to determine the neutron flux at the position of irradiation. The power level during operation of the reactor is a parameter which is directly proportional to the average neutron flux throughout the core. The objective of this work is to gather data from irradiation of gold foils symmetrically placed along a cylindrically configured core which presents only a small excess reactivity in order to derive the power generated throughout the spatial thermal and epithermal neutron flux distribution over the core of the IPEN/MB-01 Nuclear Reactor, eventually lending to a proper calibration of its nuclear channels. The foils are fixed in a Lucite plate then irradiated with and without cadmium sheaths so as to obtain the absolute thermal and epithermal neutron flux. The correlation between the average power neutron flux resulting from the gold foils irradiation, and the average power digitally indicated by the nuclear channel number 6, allows for the calibration of the nuclear channels of the reactor. The reactor power level obtained by thermal neutron flux mapping was (74.65 ± 2.45) watts to a mean counting per seconds of 37881 cps to nuclear channel number 10 a pulse detector, and 0.719.10{sup -5} ampere to nuclear linear channel number 6 (a non-compensated ionization chamber). (author)

  3. Phase transformation and nanograting structure on TiO2 rutile single crystal induced by infrared femtosecond laser

    Institute of Scientific and Technical Information of China (English)

    Ma Hong-Liang; Yang Jun-Yi; Lu Bo; Ma Guo-Hong

    2007-01-01

    In this paper, Titanium dioxide (TiO2) rutile single crystal was irradiated by infrared femtosecond laser pulses with repetition rate of 250 kHz. For a P-polarized femtosecond laser, the periodic nanograting structure on the ablation crater surface was formed. The periodicity is much less than the laser wavelength. The direction of nanograting alignment depends on the polarization laser beam. Micro-Raman spectra show that the intensity of Eg Raman vibrating mode of rutile phase increases and that of Alg Raman vibrating mode decreases apparently within the ablation crater. With the increase of irradiation time and laser average power, the Raman vibrating modes of anatase phase emerged. Rutile phase of TiO2 single crystal is partly transformed into anatase phase.

  4. Generation of calcium waves in living cells induced by 1 kHz femtosecond laser protuberance microsurgery

    Science.gov (United States)

    Zhou, M.; Zhao, E. L.; Yang, H. F.; Gong, A. H.; di, J. K.; Zhang, Z. J.

    2009-07-01

    We have demonstrated that intracellular calcium waves in a living olfactory ensheathing cell (OEC) can be induced by femtosecond laser surgery on cellular protuberance. In this paper, calcium wave generation mechanisms are further investigated using different culture mediums and protuberance diameters. The protuberances of living OECs are cut by home-made 1 kHz femtosecond laser surgery system with 130 fs pulsewidth and 800 nm wavelength, and the average power of 200 μW is chosen for stable and effective cell surgery. Whether the cells are cultured in mediums with Ca2+ or not, intracellular calcium waves can be induced after cell surgery. The generation of calcium waves is independent on the dimension of protuberance diameter. Based on these results, we analyze generation mechanisms of calcium wave and conclude that shockwave-induced mechanical force and laser-induced cytoskeleton depolymerization are two key factors.

  5. Giantically blue-shifted visible light in femtosecond mid-IR filament in fluorides

    CERN Document Server

    Dormidonov, A E; Chekalin, S V; Kandidov, V P

    2015-01-01

    A giant blue shift of an isolated visible band of supercontinuum was discovered and studied in the single filament regime of Mid-IR femtosecond laser pulse at powers slightly exceeding critical power for self-focusing in fluorides.

  6. Femtosecond laser machining of electrospun membranes

    Energy Technology Data Exchange (ETDEWEB)

    Wu Yiquan, E-mail: wuyiquan@me.rochester.edu [Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627 (United States); Vorobyev, A.Y. [Institute of Optics, University of Rochester, Rochester, NY 14627 (United States); Clark, Robert L. [Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627 (United States); Guo Chunlei [Institute of Optics, University of Rochester, Rochester, NY 14627 (United States)

    2011-01-15

    We demonstrate that a femtosecond laser can be used to machine arbitrary patterns and pattern arrays into free-standing electrospun polycaprolactone (PCL) membranes. We also examine the influence of various laser irradiation settings on the final microstructure of electrospun membranes. A beam fluence of 0.6 J/cm{sup 2} is used to ablate holes in 100 {mu}m thick PCL membranes. The machined holes have an average diameter of 436 {mu}m and a center-to-center spacing of 1000 {mu}m. Based on these results, the femtosecond ablation of electrospun membranes shows great potential for fabricating a variety of functional tissue scaffolds. This technique will advance scaffold design by providing the ability to rapidly tailor surface morphology, while minimizing and controlling the deformation of the electrospun fibers.

  7. Femtosecond stabilization of optical fiber links based on RF power detection; Femtosekundengenaue Stabilisierung von optischen Glasfaserstrecken basierend auf HF-Leistungsmessung

    Energy Technology Data Exchange (ETDEWEB)

    Lamb, Thorsten

    2011-01-15

    X-ray light sources like the free electron laser FLASH in Hamburg or the future XFEL generate light pulses with durations in the order of a few ten femtoseconds. To fulfill the requirements for the synchronisation of various components on this timescale, optical synchronisation systems are already successfully used. In this diploma thesis a novel photodiode-based, detection principle for the measurement of drifts in the optical links of such a synchronisation system is developed. The detection principle is nearly drift-free and highly robust. It is demonstrated that the long term stability of the assembled detector over 33 h is below 5 fs (peak to peak) at a standard deviation of 0.86 fs. Furthermore, an active stabilisation of a fibre link using this detector is successfully achieved. (orig.)

  8. 高平均功率电能激光器研究进展%Research progress of high average power electric-energy laser

    Institute of Scientific and Technical Information of China (English)

    吴武明; 冷进勇; 周朴; 吴慧云; 许晓军

    2011-01-01

    High average power electric-energy laser possesses some advantages such as high conversion efficiency, compact configuration, convenient heat management and advantageous logistic services.Therefore, considerable attention has been paid to the technology because of potential applications in laser material processing, orient power transmission, national military, laser drilling etc.Firstly, the research progress of high average power electric-energy laser were summarized, which included solid-state laser, fiber laser, liquid laser, free-electron laser, alkali-vapor laser, carbon dioxide laser.Secondly, coherent beam combinations of solid-state laser, fiber laser, diode laser were discussed.Meanwhile, incoherent and spectral beam combinations multiple laser beams were also investigated.Finally, based on the different principles and key technologies of high average power electric-energy laser, the technical challenge and development tendency of high average power electric-energy laser were analyzed.%高平均功率电能激光器在工业加工和定向能量传输、国防军事、激光钻油井等领域具有重要的应用前景.而且有效率高、结构紧凑灵活、热管理方便、后勤保障容易等优点.广泛关注了近几年来国外高平均功率电能激光器的研究进展,包括固体激光器、光纤激光器、液体激光器、自由电子激光器、碱金属蒸汽激光器、二氧化碳激光器及基于固体和光纤、半导体激光器的相干合成、非相干合成、光谱合成.在介绍了各种激光器工作原理和关键技术的基础上,详细分析了高平均功率电能激光器面临的技术挑战及未来的发展趋势.

  9. Tunable femtosecond Cherenkov fiber laser

    DEFF Research Database (Denmark)

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

    2014-01-01

    We demonstrate electrically-tunable femtosecond Cherenkov fiber laser output at the visible range. Using an all-fiber, self-starting femtosecond Yb-doped fiber laser as the pump source and nonlinear photonic crystal fiber link as the wave-conversion medium, ultrafast, milliwatt-level, tunable...... and spectral isolated Cherenkov radiation at visible wavelengths are reported. Such a femtosecond Cherenkov laser source is promising for practical biophotonics applications....

  10. Development of a kilowatt-class, joule-level ultrafast laser for driving compact high average power coherent EUV/soft x-ray sources

    Science.gov (United States)

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

    2016-03-01

    Our recent progress in the development of high energy / high average power, chirped pulse amplification laser systems based on diode-pumped, cryogenically-cooled Yb:YAG amplifiers is discussed, including the demonstration of a laser that produces 1 Joule, sub-10 picosecond duration, λ = 1.03μm pulses at 500 Hz repetition rate. This compact, all-diodepumped laser combines a mode-locked Yb:KYW oscillator and a water-cooled Yb:YAG preamplifer with two cryogenic power amplification stages to produce 1.5 Joule pulses with high beam quality which are subsequently compressed. This laser system occupies an optical table area of less than 1.5x3m2. This laser was employed to pump plasma-based soft x-ray lasers at λ = 10-20nm at repetition rates >=100 Hz. To accomplish this, temporally-shaped pulses were focused at grazing incidence into a high aspect ratio line focus using cylindrical optics on a high shot capacity rotating metal target. This results in an elongated plasma amplifier that produces microjoule pulses at several narrow-linewidth EUV wavelengths between λ = 109Å and 189Å. The resulting fraction of a milliwatt average powers are the highest reported to date for a compact, coherent source operating at these wavelengths, to the best of our knowledge.

  11. 直觉模糊Power交叉影响算子及其应用%Intuitionistic fuzzy power interaction averaging operator and its application to group decision making

    Institute of Scientific and Technical Information of China (English)

    何迎东; 陈华友; 周礼刚; 刘金培

    2015-01-01

    Considering that there may exist some interactions between membership function and non-membership func-tion of different intuitionistic fuzzy sets,this paper generalizes the Power operator to intuitionistic fuzzy environment and presents the intuitionistic fuzzy power interaction average operator.The properties of the operator are investigated.An example is illustrated to show the feasibility and validity of the new operator in the application of group decision making problems. It makes a comparison on stability between the proposed operator and the existing intuitionistic fuzzy power averaging operator.%将Power算子推广到直觉模糊环境中,提出了直觉模糊Power交叉影响平均算子,考虑了不同直觉模糊集的隶属度与非隶属度之间可能存在的交叉影响,根据数学归纳法得到了其具体计算公式,并研究了其性质。实例说明了新的集成算子在多属性群决策应用中的有效性。将提出的算子与现存的直觉模糊Power平均算子做了稳定性比较。

  12. Generation of 1.5 W average power, 18 kHz repetition rate coherent mid-ultraviolet radiation at 271.2 nm.

    Science.gov (United States)

    Biswal, Ramakanta; Agrawal, Praveen K; Dixit, Sudhir K; Nakhe, Shankar V

    2015-11-10

    This paper presents to our knowledge a first time study on the generation of 1.5 W average power, 18 kHz repetition rate coherent mid-ultraviolet (UV) radiation at 271.2 nm. The work is based on frequency summing of coherent green (G: 510.6 nm) and yellow (Y: 578.2 nm) radiations of a copper-HBr laser in a β-barium borate crystal. Average and peak sum frequency conversion efficiencies of about 13% and 16%, respectively, are obtained. The sum frequency results are experimentally analyzed in terms of the extent of matching of green and yellow pump radiations in space, time, and frequency domains. The result is of high significance for many applications in photonics components fabrication, semiconductor technology, and spectroscopy. PMID:26560794

  13. Femtosecond laser cataract surgery

    OpenAIRE

    Nagy, Zoltan Z.; McAlinden, Colm

    2015-01-01

    Femtosecond laser (FSL) cataract surgery is in its infancy but is rapidly gaining popularity due to the improved consistency and predictability for corneal incisions and anterior capsulorhexis. It enables subsequently less phacoemulsification energy and time to be employed, which has gains in terms of reduced corneal oedema. In addition, the FSL allows better circularity of the anterior capsulotomy, capsule overlap, intraocular lens (IOL) placement and centration of the IOL. These advantages ...

  14. Inter-antenna and subblock shifting and inversion for peak-to-average power ratio reduction in MIMO-OFDM systems

    Institute of Scientific and Technical Information of China (English)

    WANG Yi; TAO Xiao-feng

    2007-01-01

    In this article, an inter-antenna inter-subblock shifting and inversion (IASSI) scheme is proposed to reduce the peak-to-average power ratio (PAPR) in multi-input multi- output orthogonal frequency division multiplexing (MIMO- OFDM) systems. It exploits multiple antennas and subblocks to provide additional degrees of freedom to benefit the system. To reduce the implementation complexity of the proposed scheme, two simple suboptimal schemes are further presented based on the minimum current maximum criterion; one adopts sequential search and the other employs random binary grouping. The simulation results exhibit the effectiveness of these proposed schemes.

  15. Performance of MgO:PPLN, KTA, and KNbO₃ for mid-wave infrared broadband parametric amplification at high average power.

    Science.gov (United States)

    Baudisch, M; Hemmer, M; Pires, H; Biegert, J

    2014-10-15

    The performance of potassium niobate (KNbO₃), MgO-doped periodically poled lithium niobate (MgO:PPLN), and potassium titanyl arsenate (KTA) were experimentally compared for broadband mid-wave infrared parametric amplification at a high repetition rate. The seed pulses, with an energy of 6.5 μJ, were amplified using 410 μJ pump energy at 1064 nm to a maximum pulse energy of 28.9 μJ at 3 μm wavelength and at a 160 kHz repetition rate in MgO:PPLN while supporting a transform limited duration of 73 fs. The high average powers of the interacting beams used in this study revealed average power-induced processes that limit the scaling of optical parametric amplification in MgO:PPLN; the pump peak intensity was limited to 3.8  GW/cm² due to nonpermanent beam reshaping, whereas in KNbO₃ an absorption-induced temperature gradient in the crystal led to permanent internal distortions in the crystal structure when operated above a pump peak intensity of 14.4  GW/cm². PMID:25361089

  16. Performance of MgO:PPLN, KTA, and KNbO₃ for mid-wave infrared broadband parametric amplification at high average power.

    Science.gov (United States)

    Baudisch, M; Hemmer, M; Pires, H; Biegert, J

    2014-10-15

    The performance of potassium niobate (KNbO₃), MgO-doped periodically poled lithium niobate (MgO:PPLN), and potassium titanyl arsenate (KTA) were experimentally compared for broadband mid-wave infrared parametric amplification at a high repetition rate. The seed pulses, with an energy of 6.5 μJ, were amplified using 410 μJ pump energy at 1064 nm to a maximum pulse energy of 28.9 μJ at 3 μm wavelength and at a 160 kHz repetition rate in MgO:PPLN while supporting a transform limited duration of 73 fs. The high average powers of the interacting beams used in this study revealed average power-induced processes that limit the scaling of optical parametric amplification in MgO:PPLN; the pump peak intensity was limited to 3.8  GW/cm² due to nonpermanent beam reshaping, whereas in KNbO₃ an absorption-induced temperature gradient in the crystal led to permanent internal distortions in the crystal structure when operated above a pump peak intensity of 14.4  GW/cm².

  17. Amplified spontaneous emission and thermal management on a high average-power diode-pumped solid-state laser - the Lucia laser system

    International Nuclear Information System (INIS)

    The development of the laser triggered the birth of numerous fields in both scientific and industrial domains. High intensity laser pulses are a unique tool for light/matter interaction studies and applications. However, current flash-pumped glass-based systems are inherently limited in repetition-rate and efficiency. Development within recent years in the field of semiconductor lasers and gain media drew special attention to a new class of lasers, the so-called Diode Pumped Solid State Laser (DPSSL). DPSSLs are highly efficient lasers and are candidates of choice for compact, high average-power systems required for industrial applications but also as high-power pump sources for ultra-high intense lasers. The work described in this thesis takes place in the context of the 1 kilowatt average-power DPSSL program Lucia, currently under construction at the 'Laboratoire d'Utilisation des Laser Intenses' (LULI) at the Ecole Polytechnique, France. Generation of sub-10 nanosecond long pulses with energies of up to 100 joules at repetition rates of 10 hertz are mainly limited by Amplified Spontaneous Emission (ASE) and thermal effects. These limitations are the central themes of this work. Their impact is discussed within the context of a first Lucia milestone, set around 10 joules. The developed laser system is shown in detail from the oscillator level to the end of the amplification line. A comprehensive discussion of the impact of ASE and thermal effects is completed by related experimental benchmarks. The validated models are used to predict the performances of the laser system, finally resulting in a first activation of the laser system at an energy level of 7 joules in a single-shot regime and 6.6 joules at repetition rates up to 2 hertz. Limitations and further scaling approaches are discussed, followed by an outlook for the further development. (author)

  18. Wave-front correction of a femtosecond laser using a deformable mirror

    Science.gov (United States)

    Daly, Elizabeth; Dainty, Christopher; O'Connor, Gerard; Glynn, Thomas

    2005-04-01

    Typical applications of ultra-high-power femtosecond lasers include precision drilling and surface micro-machining of metals, and micro-structuring of transparent materials. However, high peak-power pulsed lasers are difficult to focus close to the diffraction limit because of aberrations that induce deviations from a perfect spatial wave-front. The sources of these aberrations include thermally induced and nonlinear optical distortions, as well as static distortions such as those introduced by gratings used in chirped-pulse amplification (CPA). A spatially clean beam is desirable to achieve the highest possible intensity on-target, and to minimize the energy deposited outside the central focus. One way to achieve this is to correct the wave-front using an adaptive optical element such as a deformable mirror, a more cost-effective solution than increasing peak intensity by providing further pulse amplification. The wave-front of the femtosecond system is measured using a Hartmann-Shack wave-front sensor, and corrected with a 37-channel deformable membrane mirror used slightly off-axis. The deformable mirror has been tested with a FISBA OPTIK μPhase HR digital interferometer, which is also used to calibrate the performance of the wave-front sensor. The influence of fluctuations of the laser on the measurement is minimised by averaging the centroid positions obtained from several consecutive frames. The distorted wave-front is compared to a reference flat wave-front which is obtained from a collimated laser diode operating at the same wavelength as the femtosecond system. The voltages on the deformable mirror actuators are then set to minimise the difference between the measured and reference wave-fronts using a simple least squares approach. Wave-front sensor and correction software is implemented in Matlab.

  19. Implications of the focal beam profile in serial femtosecond crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Galli, Lorenzo [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Chapman, Henry N. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Metcalf, Peter [Univ. of Auckland (New Zealand)

    2015-05-12

    The photon density profile of an X-ray free-electron laser (XFEL) beam at the focal position is a critical parameter for serial femtosecond crystallography (SFX), but is difficult to measure because of the destructive power of the beam. A novel high intensity radiation induced phasing method (HIRIP) has been proposed as a general experimental approach for protein structure determination, but has proved to be sensitive to variations of the X-ray intensity, with uniform incident fluence desired for best performance. Here we show that experimental SFX data collected at the nano-focus chamber of the Coherent X-ray Imaging end-station at the Linac Coherent Light Source using crystals with a limited size distribution suggests an average profile of the X-ray beam that has a large variation of intensity. We propose a new method to improve the quality of high fluence data for HI-RIP, by identifying and removing diffraction patterns from crystals exposed to the low intensity region of the beam. The method requires crystals of average size comparable to the width of the focal spot.

  20. Application of femtosecond ultrashort pulse laser to photodynamic therapy mediated by indocyanine green

    OpenAIRE

    Sawa, M; Awazu, K; Takahashi, T.; Sakaguchi, H; Horiike, H.; Ohji, M; Tano, Y

    2004-01-01

    Backgrounds/aims: To evaluate treatment with high peak power pulse energy by femtosecond ultrashort pulse laser (titanium sapphire laser) delivered at an 800 nm wavelength for corneal neovascularisation using photodynamic therapy (PDT) mediated by indocyanine green (ICG).

  1. Frequency doubled femtosecond Ti:sapphire laser with an assisted enhancement cavity

    Science.gov (United States)

    Jin-Wei, Zhang; Hai-Nian, Han; Lei, Hou; Long, Zhang; Zi-Jiao, Yu; De-Hua, Li; Zhi-Yi, Wei

    2016-01-01

    We report an enhancement cavity for femtosecond Ti:sapphire laser at the repetition rate of 170 MHz. An enhancement factor of 24 is obtained when the injecting pulses have an average power of 1 W and a pulse duration of 80 fs. By placing a BBO crystal at the focus of the cavity, we obtain a 392-mW intracavity doubled-frequency laser, corresponding to a conversion efficiency of 43%. The output power has a long-term stability with a root mean square (RMS) of 0.036%. Project supported by the National Basic Research Program of China (Grant Nos. 2013CB922401 and 2012CB821304) and the National Natural Science Foundation of China (Grant No. 61378040).

  2. Pump-tuned deep-infrared femtosecond optical parametric oscillator across 6-7  μm based on CdSiP2.

    Science.gov (United States)

    Chaitanya Kumar, S; Esteban-Martin, A; Santana, A; Zawilski, K T; Schunemann, P G; Ebrahim-Zadeh, M

    2016-07-15

    We report on a high-power femtosecond optical parametric oscillator (OPO) at 80 MHz repetition rate, tunable across 6318-7061 nm in the deep-infrared (deep-IR) using pump wavelength tuning. The OPO, based on CdSiP2 (CSP), is synchronously pumped by a commercial Ti:sapphire-pumped femtosecond OPO in the near-IR, enabling rapid static tuning of the CSP OPO with minimal adjustments to its cavity length. The deep-IR CSP OPO provides as much as 32 mW of average idler power at 6808 nm with spectral bandwidth >1000  nm (at -10  dB level) across the tuning range. By implementing intracavity dispersion control, near-transform-limited signal pulses of ∼100  fs duration with smooth single-peak spectrum are achieved at 1264 nm, corresponding to an idler wavelength at 6440 nm. To the best of our knowledge, this is the first time such practical idler powers in the deep-IR have been generated from a dispersion-compensated CSP femtosecond OPO at sub-100 MHz repetition rate.

  3. Design and analysis of X-band femtosecond linac

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-03-01

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

  4. Compact femtosecond fiber laser with integrated optical components

    International Nuclear Information System (INIS)

    A compact femtosecond ytterbium-doped fiber laser has been developed with integrated optical components. The femtosecond fiber laser oscillator was miniaturized by integrating the intracavity wavelength division multiplexer and optical isolator with collimators, and placing a quarter-wave plate before a transmission grating pair to get light retroflection from the intracavity dispersive delay line. Stretched-pulse mode-locking could be self-started at a repetition rate of 65 MHz with pump power as low as 100 mW. The compact femtosecond fiber laser oscillator could be optimized to generate 86 fs pulse duration and 0.5 nJ pulse energy. (paper)

  5. Femtosecond laser ablation of dentin

    International Nuclear Information System (INIS)

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

  6. Detection Techniques of Femtosecond Lasers

    Institute of Scientific and Technical Information of China (English)

    LIU Li-peng; ZHOU Ming; DAI Qi-xun; CAI Lan

    2004-01-01

    The measurement techniques of femtosecond spectroscopy are effective method to investigate ultrafast dynamics, they are widely used in the fields of physics, chemistry and biology. In this paper, the principle, experiment setup and the approaches to deal with the experiment data were presented. Then different measurement techniques such as transient absorption spectroscopy, photon echoes, optical Kerr effect and degenerate four-wave mixing were explained with special examples. At last, the application prospect of measurement techniques of femtosecond spectroscopy was forecasted.

  7. Femtosecond Stimulated Raman Spectroscopy.

    Science.gov (United States)

    Dietze, Daniel R; Mathies, Richard A

    2016-05-01

    Femtosecond stimulated Raman spectroscopy (FSRS) is an ultrafast nonlinear optical technique that provides vibrational structural information with high temporal (sub-50 fs) precision and high spectral (10 cm(-1) ) resolution. Since the first full demonstration of its capabilities ≈15 years ago, FSRS has evolved into a mature technique, giving deep insights into chemical and biochemical reaction dynamics that would be inaccessible with any other technique. It is now being routinely applied to virtually all possible photochemical reactions and systems spanning from single molecules in solution to thin films, bulk crystals and macromolecular proteins. This review starts with an historic overview and discusses the theoretical and experimental concepts behind this technology. Emphasis is put on the current state-of-the-art experimental realization and several variations of FSRS that have been developed. The unique capabilities of FSRS are illustrated through a comprehensive presentation of experiments to date followed by prospects. PMID:26919612

  8. Long-term optical phase locking between femtosecond Ti:sapphire and Cr:forsterite lasers

    Science.gov (United States)

    Kobayashi, Yohei; Yoshitomi, Dai; Kakehata, Masayuki; Takada, Hideyuki; Torizuka, Kenji

    2005-09-01

    Long-term optical phase-coherent two-color femtosecond pulses were generated by use of passively timing-synchronized Ti:sapphire and Cr:forsterite lasers. The relative carrier-envelope phase relation was fixed by an active feedback loop. The accumulated phase noise from 10 mHz to 1 MHz of the locked beat note was 0.43 rad, showing tight phase locking. The optical frequency fluctuation between two femtosecond combs was submillihertz, with a 1 s averaged counter measurement over 3400 s, leading to a long-term femtosecond frequency-comb connection.

  9. Ultrafast laser with an average power of 120 W at 515 nm and a highly dynamic repetition rate in the MHz range for novel applications in micromachining

    Science.gov (United States)

    Harth, F.; Piontek, M. C.; Herrmann, T.; L'huillier, J. A.

    2016-03-01

    A new generation of resonant scanners in the kHz-range shows ultra-high deflection speeds of more than 1000m/s but suffer from an inherent nonlinear mirror oscillation. If this oscillation is not compensated, a typical bitmap, written point by point, would be strongly distorted because of the decreasing spot distance at the turning point of the scanning mirror. However, this can be avoided by a dynamic adaption of the repetition rate (RR) of the ultrafast laser. Since resonant scanners are operated in the 10 kHz-range, this means that the RR has to be continuously swept up to several 10 000 times per second between e.g. 5MHz and 10 MHz. High-speed continuous adaption of the RR could also optimize laser micromachining of narrow curved geometries, where nowadays a time consuming approximation with numerous vectors is required. We present a laser system, which is capable of sweeping the RR more than 32 000 times per second between 5MHz and 10MHz at an average output power of more than 120W at 515nm with a pulse duration of about 40 ps. The laser consists of a semiconductor oscillator, a 3-stage fiber pre-amplifier, a solid state InnoSlab power amplifier and a SHG stage. We systematically analyzed the dynamic of the laser system as well as the spectral and temporal behavior of the optical pulses. Switching the repetition rate typically causes a varying pulse energy, which could affect the machining quality over one scanning line. This effect will be analyzed and discussed. Possible techniques to compensate or avoid this effect will be considered.

  10. Optimization of X-ray sources from a high-average-power ND:Glass laser-produced plasma for proximity lithography

    Energy Technology Data Exchange (ETDEWEB)

    Celliers, P.; Da Silva, L.B.; Dane, C.B. [and others

    1996-06-01

    The concept of a laser-based proximity lithography system for electronic microcircuit production has advanced to the point where a detailed design of a prototype system capable of exposing wafers at 40 wafer levels per hr is technically feasible with high-average-power laser technology. In proximity x-ray lithography, a photoresist composed of polymethyl- methacrylate (PMMA) or similar material is exposed to x rays transmitted through a mask placed near the photoresist, a procedure which is similar to making a photographic contact print. The mask contains a pattern of opaque metal features, with line widths as small as 0.12 {mu}m, placed on a thin (1-{mu}m thick) Si membrane. During the exposure, the shadow of the mask projected onto the resist produces in the physical and chemical properties of the resist a pattern of variation with the same size and shape as the features contained in the metal mask. This pattern can be further processed to produce microscopic structures in the Si substrate. The main application envisioned for this technology is the production of electronic microcircuits with spatial features significantly smaller than currently achievable with conventional optical lithographic techniques (0.12 {micro}m vs 0.25 {micro}m). This article describes work on optimizing a laser-produced plasma x-ray source intended for microcircuit production by proximity lithography.

  11. Combined peak-to-average power ratio reduction and physical layer security enhancement in optical orthogonal frequency division multiplexing visible-light communication systems

    Science.gov (United States)

    Wang, Zhongpeng; Chen, Shoufa

    2016-07-01

    A physical encryption scheme for discrete Hartley transform (DHT) precoded orthogonal frequency division multiplexing (OFDM) visible-light communication (VLC) systems using frequency domain chaos scrambling is proposed. In the scheme, the chaos scrambling, which is generated by a modified logistic mapping, is utilized to enhance the physical layer of security, and the DHT precoding is employed to reduce of OFDM signal for OFDM-based VLC. The influence of chaos scrambling on peak-to-average power ratio (PAPR) and bit error rate (BER) of systems is studied. The experimental simulation results prove the efficiency of the proposed encryption method for DHT-precoded, OFDM-based VLC systems. Furthermore, the influence of the proposed encryption to the PAPR and BER of systems is evaluated. The experimental results show that the proposed security scheme can protect the DHT-precoded, OFDM-based VLC from eavesdroppers, while keeping the good BER performance of DHT-precoded systems. The BER performance of the encrypted and DHT-precoded system is almost the same as that of the conventional DHT-precoded system without encryption.

  12. Plasma wakefields driven by an incoherent combination of laser pulses: a path towards high-average power laser-plasma accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Benedetti, C.; Schroeder, C.B.; Esarey, E.; Leemans, W.P.

    2014-05-01

    he wakefield generated in a plasma by incoherently combining a large number of low energy laser pulses (i.e.,without constraining the pulse phases) is studied analytically and by means of fully-self-consistent particle-in-cell simulations. The structure of the wakefield has been characterized and its amplitude compared with the amplitude of the wake generated by a single (coherent) laser pulse. We show that, in spite of the incoherent nature of the wakefield within the volume occupied by the laser pulses, behind this region the structure of the wakefield can be regular with an amplitude comparable or equal to that obtained from a single pulse with the same energy. Wake generation requires that the incoherent structure in the laser energy density produced by the combined pulses exists on a time scale short compared to the plasma period. Incoherent combination of multiple laser pulses may enable a technologically simpler path to high-repetition rate, high-average power laser-plasma accelerators and associated applications.

  13. Peak to Average Power Ratio Reduction using a Hybrid of Bacterial Foraging and Modified Cuckoo Search Algorithm in MIMO-OFDM System

    Directory of Open Access Journals (Sweden)

    R. Manjith

    2014-05-01

    Full Text Available The Partial Transmit Sequence which reduces the PAPR (Peak-to-Average Power Ratio in Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM system using a novel optimization algorithm is proposed in this study. This novel optimization algorithm is based on a hybrid of Bacterial Foraging Optimization (BFO and Modified Cuckoo Search algorithm (MCS and is thus called HBFOMCS. In HBFOMCS, reproduction of individuals in a new generation is created, not only by swim and tumble operation as in BFO, but also by MCS. The natural reproduction step of BFO is swapped by the concept of searching best solutions as in MCS which then increases the possibility of generating the elite individuals for next generation. These enhanced reproduction step constitute the ready-to-perform population for the new generation once the initial population is performed by swim and tumble operation. Afterwards, discover probability is applied to abandon the worst solution due to the nature of MCS. HBFOMCS is applied to optimize the best combination from a set of allowed phase factors in Partial Transmit Sequence (PTS technique. The performance of HBFOMCS is compared with BFO, Cuckoo Search (CS and Modified cuckoo search MCS in the PAPR reduction in MIMO-OFDM system, accordingly proving its proficiency.

  14. Numerical research on flow and thermal transport in cooling pool of electrical power station using three depth-averaged turbulence models

    Institute of Scientific and Technical Information of China (English)

    Li-ren YU; Jun YU

    2009-01-01

    This paper describes a numerical simulation of thermal discharge in the cooling pool of an electrical power station,aiming to develop general-purpose computational programs for grid generation and flow/pollutant transport in the complex domains of natural and artificial waterways.Three depth-averaged two-equation closure turbulence models,(k)-(ε),(k)-(w),and (k)-(ω),were used to close the quasi three-dimensional hydrodynamic model.The (k)-(ω) model was recently established by the authors and is still in the testing process.The general-purpose computational programs and turbulence models will be involved in a software that is under development.The SIMPLE (Semi-Implicit Method for Pressure-Linked Equation) algorithm and multi-grid iterative method are used to solve the hydrodynamic fundamental governing equations,which are discretized on non-orthogonal boundary-fitted grids with a variable collocated arrangement.The results calculated with the three turbulence models were compared with one another.In addition to the steady flow and thermal transport simulation,the unsteady process of waste heat inpouring and development in the cooling pool was also investigated.

  15. An Overview of Peak-to-Average Power Ratio Reduction Techniques for O-OFDM System%O-OFDM系统PAPR抑制方法综述

    Institute of Scientific and Technical Information of China (English)

    彭程; 石紫娟; 朱思瑾

    2014-01-01

    For the high peak-to-average power ration (PAPR) of optical orthogonal frequency division multiplexing (O-OFDM) system, the main schemes and their strengths and weaknesses are introduced, including pre-distortion techniques, coding techniques, and probability techniques. The principles of clipping and PTS algorithms are expounded. In addition, their PAPR reduction validity is analyzed by simulation.%针对光正交频分复用(O-OFDM)系统具有较高的峰值平均功率比(PAPR)问题,介绍了目前降低光OFDM系统PAPR的主要方法及其优缺点,包括预畸变类技术、编码类技术和概率类技术。阐述了限幅方法和部分传输序列(PTS)方法的基本原理,并对其PAPR抑制效果进行了仿真分析。

  16. Femtosecond laser processing and spatial light modulator

    Science.gov (United States)

    Paivasaari, Kimmo; Silvennoinen, Martti; Kaakkunen, Jarno; Vahimaa, Pasi

    2014-03-01

    The use of the femtosecond laser enables generation of small spot sizes and ablation features. Ablation of the small features usually requires only a small amount of laser power to be delivered to the ablation spot. When using only a one beam for the ablation of the small features this process is bound to be time consuming. The spatial light modulator (SLM) together with the computer generated holograms (CGH) can be used for manipulating and shaping of the laser beam in various applications. In laser micromachining, when using laser with relatively high power, the original beam can be divided up to hundreds beams and still have the energy of the individual beam above the ablation threshold of the material. This parallel laser processing enables more efficient use of the laser power regardless of the machining task.

  17. Preparation Femtosecond Laser Prevention for the Cold-Worked Stress Corrosion Crackings on Reactor Grade Low Carbon Stainless Steel

    CERN Document Server

    John Minehara, Eisuke

    2004-01-01

    We report here that the femtosecond lasers like low average power Ti:Sapphire lasers, the JAERI high average power free-electron laser and others could peel off and remove two stress corrosion cracking (SCC) origins of the cold-worked and the cracking susceptible material, and residual tensile stress in hardened and stretched surface of low-carbon stainless steel cubic samples for nuclear reactor internals as a proof of principle experiment except for the third origin of corrosive environment. Because a 143 °C and 43% MgCl2 hot solution SCC test was performed for the samples to simulate the cold-worked SCC phenomena of the internals to show no crack at the laser-peered off strip on the cold-worked side and ten-thousands of cracks at the non-peeled off on the same side, it has been successfully demonstrated that the femtosecond lasers could clearly remove the two SCC origins and could resultantly prevent the cold-worked SCC.

  18. Femtosecond laser induced microripple on PDMS surface

    Institute of Scientific and Technical Information of China (English)

    Jin Xie; Changhe Zhou; Wei Wang; Tengfei Wu

    2009-01-01

    laser pulses and the subsequent cool-down solidification of the melting PDMS along with the movement of the femtosecond laser spot. This result will be helpful to understand the interaction between the femtosecond laser and the polymer.

  19. Bragg gratings inscription in step-index PMMA optical fiber by femtosecond laser pulses at 400 nm

    Science.gov (United States)

    Hu, X.; Kinet, D.; Chah, K.; Mégret, P.; Caucheteur, C.

    2016-05-01

    In this paper, we report photo-inscription of uniform Bragg gratings in trans-4-stilbenemethanol-doped photosensitive step-index polymer optical fiber. Gratings were produced at ~1575 nm by the phase mask technique with a femtosecond laser emitting at 400 nm with different average optical powers (8 mW, 13 mW and 20 mW). The grating growth dynamics in transmission were monitored during the manufacturing process, showing that the grating grows faster with higher power. Using 20 mW laser beam power, the reflectivity reaches 94 % (8 dB transmission loss) in 70 seconds. Finally, the gratings were characterized in temperature in the range 20 - 45 °C. The thermal sensitivity has been computed equal to - 86.6 pm/°C.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-12-15

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

  1. Experiment Safety Assurance Package for Mixed Oxide Fuel Irradiation in an Average Power Position (I-24) in the Advanced Test Reactor

    Energy Technology Data Exchange (ETDEWEB)

    J. M . Ryskamp; R. C. Howard; R. C. Pedersen; S. T. Khericha

    1998-10-01

    The Fissile Material Disposition Program Light Water Reactor Mixed Oxide Fuel Irradiation Test Project Plan details a series of test irradiations designed to investigate the use of weapons-grade plutonium in MOX fuel for light water reactors (LWR) (Cowell 1996a, Cowell 1997a, Thoms 1997a). Commercial MOX fuel has been successfully used in overseas reactors for many years; however, weapons-derived test fuel contains small amounts of gallium (about 2 parts per million). A concern exists that the gallium may migrate out of the fuel and into the clad, inducing embrittlement. For preliminary out-of-pile experiments, Wilson (1997) states that intermetallic compound formation is the principal interaction mechanism between zircaloy cladding and gallium. This interaction is very limited by the low mass of gallium, so problems are not expected with the zircaloy cladding, but an in-pile experiment is needed to confirm the out-of-pile experiments. Ryskamp (1998) provides an overview of this experiment and its documentation. The purpose of this Experiment Safety Assurance Package (ESAP) is to demonstrate the safe irradiation and handling of the mixed uranium and plutonium oxide (MOX) Fuel Average Power Test (APT) experiment as required by Advanced Test Reactor (ATR) Technical Safety Requirement (TSR) 3.9.1 (LMITCO 1998). This ESAP addresses the specific operation of the MOX Fuel APT experiment with respect to the operating envelope for irradiation established by the Upgraded Final Safety Analysis Report (UFSAR) Lockheed Martin Idaho Technologies Company (LMITCO 1997a). Experiment handling activities are discussed herein.

  2. Ultrafast thin-disk multipass laser amplifier delivering 1.4 kW (4.7 mJ, 1030 nm) average power converted to 820 W at 515 nm and 234 W at 343 nm.

    Science.gov (United States)

    Negel, Jan-Philipp; Loescher, André; Voss, Andreas; Bauer, Dominik; Sutter, Dirk; Killi, Alexander; Ahmed, Marwan Abdou; Graf, Thomas

    2015-08-10

    We report on an Yb:YAG thin-disk multipass laser amplifier delivering sub-8 ps pulses at a wavelength of 1030 nm with 1420 W of average output power and 4.7 mJ of pulse energy. The amplifier is seeded by a regenerative amplifier delivering 6.5 ps pulses with 300 kHz of repetition rate and an average power of 115 W. The optical efficiency of the multipass amplifier was measured to be 48% and the beam quality factor was better than M2 = 1.4. Furthermore we report on the external second harmonic generation from 1030 nm to 515 nm using an LBO crystal leading to an output power of 820 W with 2.7 mJ of energy per pulse. This corresponds to a conversion efficiency of 70%. Additionally, 234 W of average power were obtained at the third harmonic with a wavelength of 343 nm. PMID:26367957

  3. Efficient, high-speed ablation of soft tissue with few-microjoule, femtosecond pulse bursts

    CERN Document Server

    Kerse, Can; Kalaycıoğlu, Hamit; Aşık, Mehmet D; Akçaalan, Önder; Ilday, F Ömer

    2014-01-01

    Femtosecond pulses hold great promise for high-precision tissue removal. However, ablation rates are severely limited by the need to keep average laser power low to avoid collateral damage due to heat accumulation. Furthermore, previously reported pulse energies preclude delivery in flexible fibers, hindering in vivo operation. Both of these problems can be addressed through use of groups of high-repetition-rate pulses, or bursts. Here, we report a novel fiber laser and demonstrate ultrafast burst-mode ablation of brain tissue at rates approaching 1 mm$^3$/min, an order of magnitude improvement over previous reports. Burst mode operation is shown to be superior in terms of energy required and avoidance of thermal effects, compared to uniform repetition rates. These results can pave the way to in vivo operation at medically relevant speeds, delivered via flexible fibers to surgically hard-to-reach targets, or with simultaneous magnetic resonance imaging.

  4. Mid-infrared supercontinuum generation spanning 1.8 octaves using step-index indium fluoride fiber pumped by a femtosecond fiber laser near 2 µm.

    Science.gov (United States)

    Salem, Reza; Jiang, Zack; Liu, Dongfeng; Pafchek, Robert; Gardner, David; Foy, Paul; Saad, Mohammed; Jenkins, Doug; Cable, Alex; Fendel, Peter

    2015-11-30

    A nearly two-octave wide coherent mid-infrared supercontinuum is demonstrated in a dispersion-engineered step-index indium fluoride fiber pumped near 2 µm. The pump source is an all-fiber femtosecond laser with 100 fs pulse width, 570 mW average power and 50 MHz repetition rate. The supercontinuum spectrum spans from 1.25 µm to 4.6 µm. Numerical modelling of the supercontinuum spectra show good agreement with the measurements. The coherence of the supercontinuum is calculated using a numerical model and shows a high degree of coherence across the generated bandwidth allowing it to be used for frequency comb applications. PMID:26698692

  5. Deuterium Clusters Fusion Induced by the Intense Femtosecond Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    LIU Hong-Jie; CHEN Jia-Bin; WANG Hong-Bin; JIAO Chun-Ye; HE Ying-Ling; WEN Tian-Shu; WEN Xian-Lun; CHEN Ming; ZHENG Zhi-Jian; GU Yu-Qiu; ZHANG Bao-Han; RHEE Yong-Joo; NAM Sung-Mo; HAN Jae-Min; RHEE Yong-Woo; YEA Kwon-Hae

    2007-01-01

    Neutrons (2.45 MeV) from deuterium cluster fusion induced by the intense femtosecond (30 fs) laser pulse are experimentally demonstrated. The average neutron yield 103 per shot is obtained. It is found that the yield slightly increases with the increasing laser spot size. No neutron can be observed when the laser intensity Ⅰ <4.3×1015 W/cm2.

  6. Holographic vector-wave femtosecond laser processing

    Science.gov (United States)

    Hayasaki, Yoshio; Hasegawa, Satoshi

    2016-03-01

    Arbitrary and variable beam shaping of femtosecond pulses by a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM) have been applied to femtosecond laser processing. The holographic femtosecond laser processing has been widely used in many applications such as two-photon polymerization, optical waveguide fabrication, fabrication of volume phase gratings in polymers, and surface nanostructuring. A vector wave that has a spatial distribution of polarization states control of femtosecond pulses gives good performances for the femtosecond laser processing. In this paper, an in- system optimization of a CGH for massively-parallel femtosecond laser processing, a dynamic control of spatial spectral dispersion to improve the focal spot shape, and the holographic vector-wave femtosecond laser processing are demonstrated.

  7. Monitoring femtosecond laser microscopic photothermolysis with multimodal microscopy (Conference Presentation)

    Science.gov (United States)

    Huang, Yimei; Lui, Harvey; Zhao, Jianhua; McLean, David I.; Zeng, Haishan

    2016-02-01

    Photothermolysis induced by femtosecond (fs) lasers may be a promising modality in dermatology because of its advantages of high precision due to multiphoton absorption and deeper penetration due to the use of near infrared wavelengths. Although multiphoton absorption nonlinear effects are capable of precision targeting, the femtosecond laser photothermolysis could still have effects beyond the targeted area if a sufficiently high dose of laser light is used. Such unintended effects could be minimized by real time monitoring photothermolysis during the treatment. Targeted photothermolytic treatment of ex vivo mouse skin dermis was performed with tightly focused fs laser beams. Images of reflectance confocal microscopy (RCM), second harmonic generation (SHG), and two-photon fluorescence (TPF) of the mouse skins were obtained with integrated multimodal microscopy before, during, and after the laser treatment. The RCM, SHG, and TPF signal intensities of the treatment areas changed after high power femtosecond laser irradiation. The intensities of the RCM and SHG signals decreased when the tissue was damaged, while the intensity of the TPF signal increased when the photothermolysis was achieved. Moreover, the TPF signal was more susceptible to the degree of the photothermolysis than the RCM and SHG signals. The results suggested that multimodal microscopy is a potentially useful tool to monitor and assess the femtosecond laser treatment of the skin to achieve microscopic photothermolysis with high precision.

  8. Investigation of interaction femtosecond laser pulses with skin and eyes mathematical model

    Science.gov (United States)

    Rogov, P. U.; Smirnov, S. V.; Semenova, V. A.; Melnik, M. V.; Bespalov, V. G.

    2016-08-01

    We present a mathematical model of linear and nonlinear processes that takes place under the action of femtosecond laser radiation on the cutaneous covering. The study is carried out and the analytical solution of the set of equations describing the dynamics of the electron and atomic subsystems and investigated the processes of linear and nonlinear interaction of femtosecond laser pulses in the vitreous of the human eye, revealed the dependence of the pulse duration on the retina of the duration of the input pulse and found the value of the radiation power density, in which there is a self-focusing is obtained. The results of the work can be used to determine the maximum acceptable energy, generated by femtosecond laser systems, and to develop Russian laser safety standards for femtosecond laser systems.

  9. Experiment of C-Band Wavelength Conversion in a Silicon Waveguide Pumped by Dispersed Femtosecond Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    GAO Shi-Ming; TIEN En-Kuang; SONG Qi; HUANG Yue-Wang; Salih Kagan KALYONCU

    2010-01-01

    @@ We experimentally demonstrate the C-band wavelength conversion using four-wave mixing in a 17-mm-long silicon-on-insulator waveguide pumped by a dispersed mode-locked femtosecond laser pulse.The idler can be observed with an incident average pump power lower than 4 dBm,and about 35 nm of conversion bandwidth from 1530 nm to 1565 nm js measured by using a 1550-nm pump wavelength.The pulse-pumped efficiency is demonstrated to be higher,by more than 22 dB,than the ew-pumped efficiency.The conversion efficiency variations with respect to the pump and signal powers are also investigated.

  10. Fast femtosecond laser ablation for efficient cutting of sintered alumina substrates

    Science.gov (United States)

    Oosterbeek, Reece N.; Ward, Thomas; Ashforth, Simon; Bodley, Owen; Rodda, Andrew E.; Simpson, M. Cather

    2016-09-01

    Fast, accurate cutting of technical ceramics is a significant technological challenge because of these materials' typical high mechanical strength and thermal resistance. Femtosecond pulsed lasers offer significant promise for meeting this challenge. Femtosecond pulses can machine nearly any material with small kerf and little to no collateral damage to the surrounding material. The main drawback to femtosecond laser machining of ceramics is slow processing speed. In this work we report on the improvement of femtosecond laser cutting of sintered alumina substrates through optimisation of laser processing parameters. The femtosecond laser ablation thresholds for sintered alumina were measured using the diagonal scan method. Incubation effects were found to fit a defect accumulation model, with Fth,1=6.0 J/cm2 (±0.3) and Fth,∞=2.5 J/cm2 (±0.2). The focal length and depth, laser power, number of passes, and material translation speed were optimised for ablation speed and high quality. Optimal conditions of 500 mW power, 100 mm focal length, 2000 μm/s material translation speed, with 14 passes, produced complete cutting of the alumina substrate at an overall processing speed of 143 μm/s - more than 4 times faster than the maximum reported overall processing speed previously achieved by Wang et al. [1]. This process significantly increases processing speeds of alumina substrates, thereby reducing costs, making femtosecond laser machining a more viable option for industrial users.

  11. Patterned birefringent polarization converters fabricated by femtosecond laser direct writing

    OpenAIRE

    Gertus, T.; Kazansky, P. G.

    2014-01-01

    Under certain exposure conditions, focused femtosecond light pulses can induce self-assembled nanogratings inside bulk of fused silica glass. Orientation of nanogratings is always perpendicular to incident light polarization. Induced nanograting period varies from 140 nm to 320 nm. By changing incident light power and polarization orientation we can control induced retardance and slow axis of fabricated birefringent patterns. Induced nanogratings exhibit birefringence that provide retardance ...

  12. On the interferometric coherent structures in femtosecond supercontinuum generation

    Science.gov (United States)

    Dinda, Sirshendu; Bandyopadhyay, Soumendra Nath; Goswami, Debabrata

    2016-05-01

    We report structured interferometric features in femtosecond supercontinuum generation (FSG) with incident laser powers that are near threshold for FSG. We argue that near threshold, these structures arise from the coherent superposition of pulses that are split initially into two daughter pulses during FSG process. Increase in the input pulse energy generates multiple daughter fragments in the temporal domain to an extent that correlated interference structures are not measurable.

  13. Multiphoton imaging with high peak power VECSELs

    Science.gov (United States)

    Mirkhanov, Shamil; Quarterman, Adrian H.; Swift, Samuel; Praveen, Bavishna B.; Smyth, Conor J. C.; Wilcox, Keith G.

    2016-03-01

    Multiphoton imaging (MMPI) has become one of thee key non-invasive light microscopy techniques. This technique allows deep tissue imaging with high resolution and less photo-damage than conventional confocal microscopy. MPI is type of laser-scanning microscopy that employs localized nonlinear excitation, so that fluorescence is excited only with is scanned focal volume. For many years, Ti: sapphire femtosecond lasers have been the leading light sources for MPI applications. However, recent developments in laser sources and new types of fluorophores indicate that longer wavelength excitation could be a good alternative for these applications. Mode-locked VECSEELs have the potential to be low cost, compact light sources for MPI systems, with the additional advantage of broad wavelength coverage through use of different semiconductor material systems. Here, we use a femtosecond fibber laser to investigate the effect average power and repetition rate has on MPI image quality, to allow us to optimize our mode-locked VVECSELs for MPI.

  14. An investigation of the effectiveness of blending (averaging) brown coal for state regional electric power plants (GRES). Issledovaniye effektivnosti usredneniya burykh ugley dlya GRES

    Energy Technology Data Exchange (ETDEWEB)

    Varshavskiy, A.M.

    1985-01-01

    The variability of the ash content of coal effects the specific expenditure of fuel by a state regional electric power plant for producing electric power. The studies were conducted at the Aleksandriyskiy thermal power plant (TeTs) number three and at the Zaporozhye, Yermakovskiy and Nazarovskiy state regional thermal power plants. It is established that a reduction in the mean square deviation of the hourly volumes of coal from 3 to 0.5 leads to a savings of 3.2 to 3.8 percent of coal and 2.4 to 2.9 percent brown coal. Regression equations are acquired. Correlation factors are calculated which do not exceed 0.7 percent of the reliable association between indicators.

  15. Femtosecond laser in laser in situ keratomileusis

    OpenAIRE

    Salomão, Marcella Q.; Wilson, Steven E.

    2010-01-01

    Flap creation is a critical step in laser in situ keratomileusis (LASIK). Efforts to improve the safety and predictability of the lamellar incision have fostered the development of femtosecond lasers. Several advantages of the femtosecond laser over mechanical microkeratomes have been reported in LASIK surgery. In this article, we review common considerations in management and complications of this step in femtosecond laser–LASIK and concentrate primarily on the IntraLase laser because most p...

  16. High-efficiency diode-pumped femtosecond Yb:YAG ceramic laser

    DEFF Research Database (Denmark)

    Zhou, Binbin; Wei, Z.Y.; Zou, Y.W.;

    2010-01-01

    A highly efficient diode-end-pumped femtosecond Yb:yttrium aluminum garnet (YAG) ceramic laser was demonstrated. Pumped by a 968 nm fiber-coupled diode laser, 1.9 W mode-locked output power at a repetition rate of 64.27 MHz was obtained with 3.5 W absorbed pump power, corresponding to a slope eff...

  17. Femtosecond Photon-Counting Receiver

    Science.gov (United States)

    Krainak, Michael A.; Rambo, Timothy M.; Yang, Guangning; Lu, Wei; Numata, Kenji

    2016-01-01

    An optical correlation receiver is described that provides ultra-precise distance and/or time/pulse-width measurements even for weak (single photons) and short (femtosecond) optical signals. A new type of optical correlation receiver uses a fourth-order (intensity) interferometer to provide micron distance measurements even for weak (single photons) and short (femtosecond) optical signals. The optical correlator uses a low-noise-integrating detector that can resolve photon number. The correlation (range as a function of path delay) is calculated from the variance of the photon number of the difference of the optical signals on the two detectors. Our preliminary proof-of principle data (using a short-pulse diode laser transmitter) demonstrates tens of microns precision.

  18. Nanoflow electrospinning serial femtosecond crystallography

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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.

  1. Nanoflow electrospinning serial femtosecond crystallography.

    Science.gov (United States)

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

    2012-11-01

    An electrospun liquid microjet has been developed that delivers protein microcrystal suspensions at flow rates of 0.14-3.1 µl min(-1) to perform serial femtosecond crystallography (SFX) studies with X-ray lasers. Thermolysin microcrystals flowed at 0.17 µl min(-1) and diffracted to beyond 4 Å resolution, producing 14,000 indexable diffraction patterns, or four per second, from 140 µg of protein. Nanoflow electrospinning extends SFX to biological samples that necessitate minimal sample consumption. PMID:23090408

  2. Discrete Cosine Transform-II for Reduction in Peak to Average Power Ratio of OFDM Signals Through μ-Law Companding Technique

    Directory of Open Access Journals (Sweden)

    Navneet Kaur

    2013-05-01

    Full Text Available Orthogonalfrequency Division multiplexing (OFDM is the most familiar word intelecommunicationand wireless communication systems as it provides enhanced spectral efficiency than Frequency divisionmultiplexing (FDM.Although itissustaininganorthogonal relationbetweencarriers but highpeak toaverage power ratio (PAPRis oneof the main disadvantages of OFDMsystem.Various PAPR reductiontechniques have beenused,including techniques based oncompanding. Incompanding,-Lawcompandinghas potential toreducethePAPRof OFDMsignals.-Law Compandingtechniquepreserves thedynamic range of samples at low amplitudes.Anew methodnamed as precoding which ishaving less complexity compared to the other power reductiontechniquesis proposed to reduce PAPR.This paper put forward combinationof two existing techniques namely-LawCompanding Transformand Discrete Cosine Transform-IIprecoding technique.The simulationresults show that, the proposedcombinedscheme givesbetter result for PAPR Reductionand resultsin no distortion

  3. In-situ x-ray free-electron laser diffraction under femtosecond laser-driven shock compression of solids

    International Nuclear Information System (INIS)

    We have succeeded in quenching metastable high-pressure phases which are not quenchable using conventional compression methods or forming dense lattice defects in solids using femtosecond laser-driven shock wave. In-situ X-ray diffraction (XRD) under femtosecond laser-driven shock compression of solids using X-ray Free Electron Laser (XFEL) is one of the powerful tools to directly image the lattice dynamics to make clear the mechanism. In this report we review the femtosecond laser-driven shock compression of solids and introduce some experiments performed at XFEL facility in Japan 'SACLA (SPring-8 Angstrom Compact Free Electron Laser).' (author)

  4. Graphene mode-locked multipass-cavity femtosecond Cr4+: forsterite laser

    OpenAIRE

    Baylam, Işınsu; Çizmeciyan, Melisa Natali; Sennaroğlu, Alphan; Ozharar, Sarper; Balcı, Osman; Pince, Ercag; Kocabaş, Coşkun

    2013-01-01

    We report, for the first time to our knowledge, the use of graphene as a saturable absorber in an energy-scaled femtosecond Cr4+: forsterite laser. By incorporating a multipass cavity, the repetition rate of the original short resonator was reduced to 4.51 MHz, which resulted in the generation of 100 fs, nearly transform-limited pulses at 1252 nm with a peak power of 53 kW. To the best of our knowledge, this is the highest peak power obtained from a room-temperature, femtosecond Cr4+: forster...

  5. Overview of the Lucia laser program: toward 100-Joules, nanosecond-pulse, kW averaged power based on ytterbium diode-pumped solid state laser

    Science.gov (United States)

    Chanteloup, J.-C.; Yu, H.; Bourdet, G.; Dambrine, C.; Ferre, S.; Fulop, A.; Le Moal, S.; Pichot, A.; Le Touze, G.; Zhao, Z.

    2005-04-01

    We present the current status of the Lucia laser being built at the LULI laboratory, the national civil facility for intense laser matter interaction in France. This diode pumped laser will deliver a 100 Joules, 10 ns, 10 Hz pulse train from Yb:YAG using 4400 power diode laser bars. We first focus on the amplifier stage by describing the reasons for selecting our extraction architecture. Thermal issues and solutions for both laser and pumping heads are then described. Finally, we emphasize more specifically the need for long-lifetime high-laser-damage-threshold coatings and optics.

  6. Production Planning with Respect to Uncertainties. Simulator Based Production Planning of Average Sized Combined Heat and Power Production Plants; Produktionsplanering under osaekerhet. Simulatorbaserad produktionsplanering av medelstora kraftvaermeanlaeggningar

    Energy Technology Data Exchange (ETDEWEB)

    Haeggstaahl, Daniel [Maelardalen Univ., Vaesteraas (Sweden); Dotzauer, Erik [AB Fortum, Stockholm (Sweden)

    2004-12-01

    Production planning in Combined Heat and Power (CHP) systems is considered. The focus is on development and use of mathematical models and methods. Different aspects on production planning are discussed, including weather and load predictions. Questions relevant on the different planning horizons are illuminated. The main purpose with short-term (one week) planning is to decide when to start and stop the production units, and to decide how to use the heat storage. The main conclusion from the outline of pros and cons of commercial planning software are that several are using Mixed Integer Programming (MIP). In that sense they are similar. Building a production planning model means that the planning problem is formulated as a mathematical optimization problem. The accuracy of the input data determines the practical detail level of the model. Two alternatives to the methods used in today's commercial programs are proposed: stochastic optimization and simulator-based optimization. The basic concepts of mathematical optimization are outlined. A simulator-based model for short-term planning is developed. The purpose is to minimize the production costs, depending on the heat demand in the district heating system, prices of electricity and fuels, emission taxes and fees, etc. The problem is simplified by not including any time-linking conditions. The process model is developed in IPSEpro, a heat and mass-balance software from SimTech Simulation Technology. TOMLAB, an optimization toolbox in MATLAB, is used as optimizer. Three different solvers are applied: glcFast, glcCluster and SNOPT. The link between TOMLAB and IPSEpro is accomplished using the Microsoft COM technology. MATLAB is the automation client and contains the control of IPSEpro and TOMLAB. The simulator-based model is applied to the CHP plant in Eskilstuna. Two days are chosen and analyzed. The optimized production is compared to the measured. A sensitivity analysis on how variations in outdoor

  7. A passively mode-locked intracavity frequency doubled Nd:YVO4 femtosecond green laser based on graphene

    Science.gov (United States)

    Shi, R. P.; Bai, Y.; Qi, M.; Chen, X. M.; Wei, H. D.; Ren, Z. Y.; Bai, J. T.

    2014-02-01

    By using an atmospheric-pressure chemical vapor deposition (APCVD) method with a C2H2 carbon source, seven-layer graphene films as saturable absorbers are fabricated and transferred to an anti-reflective mirror of 1064 nm wavelength range. Based on this transmission-type graphene saturable absorber mirror (GSAM), a continuous wave (CW) passively mode-locked femtosecond green laser is achieved by 808 nm laser diode (LD) end-pumped Nd:YVO4 crystal and type-I critical phase-matched LBO crystal intracavity frequency doubling for the first time. Stable ultrashort green laser pulses as short as 374 fs are measured with a repetition rate of 71.4 MHz and an average output power of 117 mW at a central wavelength of 531.7 nm.

  8. High pulse energy femtosecond large-mode-area photonic crystal fiber laser

    Institute of Scientific and Technical Information of China (English)

    SONG YouJian; HU MingLie; ZHANG Chi; CHAI Lu; WANG ChingYue

    2008-01-01

    A high pulse energy femtosecond fiber laser based on a large-mode-area photonic crystal fiber is demonstrated. A segment of Yb-doped single-polarization large-mode-area photonic crystal fiber with extremely low nonlinearity is explored as gain media of this fiber laser, resulting in intrinsically environmentally stability. The fiber laser is based on a linear cavity with dispersion compensation free configuration, and the stable mode-locking is obtained by a semiconductor saturable absorber mirror (SESAM). The fiber laser directly generates 2.5 W of average power at a repetition rate of 51.4 MHz,corresponding to a single pulse energy of 50 nJ. The output pulse duration is 4.2 ps, which is dechirped to 410 fs after extracavity dispersion compensation. The nonlinear absorption of SESAM determines the pulse shaping at low output power, while the mode-locking mechanism is under the balance between spectrum broadening from self-phase-modulation and gain filtering at the high output power.

  9. Light bullets and supercontinuum spectrum during femtosecond pulse filamentation under conditions of anomalous group-velocity dispersion in fused silicalicati

    Energy Technology Data Exchange (ETDEWEB)

    Chekalin, Sergei V; Kompanets, V O; Smetanina, E O; Kandidov, V P

    2013-04-30

    We report the results of theoretical and experimental research on spectrum transformation and spatiotemporal distribution of the femtosecond laser radiation intensity during filamentation in fused silica. The formation of light bullets with a high power density is first observed in a femtosecond laser pulse in the anomalous group velocity dispersion regime at a wavelength of 1800 nm. The minimum duration of the light bullet is about two oscillation cycles of the light field. (extreme light fields and their applications)

  10. Neutron resonance averaging

    International Nuclear Information System (INIS)

    The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs

  11. Fabrication of Long-Period Fibre Gratings Using 800 nm Femtosecond Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    ZHANG Nan; YANG Jian-Jun; WANG Ming-Wei; ZHU Xiao-Nong

    2006-01-01

    Long-period fibre gratings inside standard single-mode optical communication fibres are successfully fabricated with infrared femtosecond laser pulses. The refractive index perturbations are well confined within the fibre core by choosing the proper laser focusing parameters and translation speed of the fibre during the direct laser writing process. With the self-focusing effect considered and at a constant average irradiation dose of 1.62 ×103 J/(cm2 μm), the threshold intensity for fabricating long-period gratings with infrared femtosecond laser pulses is determined to be 5.13 × 1013 W/cm2.

  12. Averaging anisotropic cosmologies

    International Nuclear Information System (INIS)

    We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of anisotropic pressure-free models. Adopting the Buchert scheme, we recast the averaged scalar equations in Bianchi-type form and close the standard system by introducing a propagation formula for the average shear magnitude. We then investigate the evolution of anisotropic average vacuum models and those filled with pressureless matter. In the latter case we show that the backreaction effects can modify the familiar Kasner-like singularity and potentially remove Mixmaster-type oscillations. The presence of nonzero average shear in our equations also allows us to examine the constraints that a phase of backreaction-driven accelerated expansion might put on the anisotropy of the averaged domain. We close by assessing the status of these and other attempts to define and calculate 'average' spacetime behaviour in general relativity

  13. Compact fixed wavelength femtosecond oscillators as an add-on for tunable Ti:sapphire lasers extend the range of applications towards multimodal imaging and optogenetics

    Science.gov (United States)

    Hakulinen, T.; Klein, J.

    2016-03-01

    Two-photon (2P) microscopy based on tunable Ti:sapphire lasers has become a widespread tool for 3D imaging with sub-cellular resolution in living tissues. In recent years multi-photon microscopy with simpler fixed-wavelength femtosecond oscillators using Yb-doped tungstenates as gain material has raised increasing interest in life-sciences, because these lasers offer one order of magnitude more average power than Ti:sapphire lasers in the wavelength range around 1040 nm: Two-photon (2P) excitation of mainly red or yellow fluorescent dyes and proteins (e.g. YFP, mFruit series) simultaneously has been proven with a single IR laser wavelength. A new approach is to extend the usability of existing tunable Titanium sapphire lasers by adding a fixed IR wavelength with an Yb femtosecond oscillator. By that means a multitude of applications for multimodal imaging and optogenetics can be supported. Furthermore fs Yb-lasers are available with a repetition rate of typically 10 MHz and an average power of typically 5 W resulting in pulse energy of typically 500 nJ, which is comparably high for fs-oscillators. This makes them an ideal tool for two-photon spinning disk laser scanning microscopy and holographic patterning for simultaneous photoactivation of large cell populations. With this work we demonstrate that economical, small-footprint Yb fixed-wavelength lasers can present an interesting add-on to tunable lasers that are commonly used in multiphoton microscopy. The Yb fs-lasers hereby offer higher power for imaging of red fluorescent dyes and proteins, are ideally enhancing existing Ti:sapphire lasers with more power in the IR, and are supporting pulse energy and power hungry applications such as spinning disk microscopy and holographic patterning.

  14. Ultra-compact (palm-top size) low-cost maintenance-free (>3000 h) diode-pumped femtosecond (160 fs) solid state laser source for multiphoton microscopy

    Science.gov (United States)

    Yamazoe, S.; Katou, M.; Kasamatsu, T.

    2009-02-01

    We propose and demonstrate a novel practical femtosecond laser source, which is to our knowledge, the smallest size and potentially low cost. The innovation is the simple linear cavity design utilizing soliton mode-locking induced by precise group velocity dispersion control. Average output power of 680 mW and pulse width of 162 fs were obtained at around 1045 nm from a diode-pumped Yb3+:KY(WO4)2 laser. The pulse repetition rate was 2.8 GHz, leading to a pulse peak power of 1.5 kW, which is sufficient for biomedical imaging. The laser module including the laser diode pump system has a footprint of 8×4 cm2. Under automatic current control condition, stable operation of 3000-hour was observed with an average power fluctuation of less than +/-10 %. Furthermore, under automatic power control condition, stable operation of 2000-hour was observed with an average power fluctuation of less than +/-1 %. Using this laser module, we successfully obtained clear two-photon fluorescence images of muntjac skin fibroblast cells stained with a combination of fluorescent stains (Alexa Fluor 488 phalloidin and Alexa Flour 555 goat anti-mouse lgG).

  15. FY2005 Progress Summary and FY2006 Program Plan Statement of Work and Deliverables for Development of High Average Power Diode-Pumped Solid State Lasers, and Complementary Technologies, for Applications in Energy and Defense

    Energy Technology Data Exchange (ETDEWEB)

    Ebbers, C

    2006-03-24

    The primary focus this year was to operate the system with two amplifiers populated with and pumped by eight high power diode arrays. The system was operated for extended run periods which enabled average power testing of components, diagnostics, and controls. These tests were highly successful, with a demonstrated energy level of over 55 joules for 4 cumulative hours at a repetition rate of 10 Hz (average power 0.55 kW). In addition, high average power second harmonic generation was demonstrated, achieving 227 W of 523.5 nm light (22.7 J, 10 Hz, 15 ns, 30 minutes) Plans to achieve higher energy levels and average powers are in progress. The dual amplifier system utilizes a 4-pass optical arrangement. The Yb:S-FAP slabs were mounted in aerodynamic aluminum vane structures to allow turbulent helium gas flow across the faces. Diagnostic packages that monitored beam performance were deployed during operation. The laser experiments involved injecting a seed beam from the front end into the system and making four passes through both amplifiers. Beam performance diagnostics monitored the beam on each pass to assess system parameters such as gain and nearfield intensity profiles. This year, an active mirror and wavefront sensor were procured and demonstrated in an off-line facility. The active mirror technology can correct for low order phase distortions at user specified operating conditions (such as repetition rates different than 10 Hz) and is a complementary technology to the static phase plates used in the system for higher order distortions. A picture of the laser system with amplifier No.2 (foreground) and amplifier No.1 (background) is shown in Fig. 1.0.1.1. The control system and diagnostics were recently enhanced for faster processing and allow remote operation of the system. The growth and fabrication of the Yb:S-FAP slabs constituted another major element of our program objectives. Our goal was to produce at least fourteen 4x6 cm2 crystalline slabs. These

  16. All-fiber femtosecond Cherenkov source

    OpenAIRE

    Tu H.; Møller U.; Lægsgaard J.; Liu X.; Boppart S. A.; Turchinovich D.

    2013-01-01

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

  17. All-fiber femtosecond Cherenkov source

    Directory of Open Access Journals (Sweden)

    Tu H.

    2013-03-01

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

  18. All-fiber femtosecond Cherenkov source

    DEFF Research Database (Denmark)

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

    2013-01-01

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

  19. Large-mode-area erbium-ytterbium-doped photonic-crystal fiber amplifier for high-energy femtosecond pulses at 1.55 microm.

    Science.gov (United States)

    Shirakawa, Akira; Ota, Jun; Musha, Mitsuru; Nakagawa, Ken'ichi; Ueda, Ken-Ichi; Folkenberg, Jacob Riis; Broeng, Jes

    2005-02-21

    We report a high-energy femtosecond fiber amplifier based on an air-cladded single-transverse-mode erbium-ytterbium-codoped photonic-crystal fiber with a 26-microm mode-field-diameter. 700-fs, 47-MHz pulses at 1557 nm were amplified and compressed to near-transform-limited 100-fs, 7.4-nJ pulses with 54-kW peak powers without chirped-pulse amplification. A linearly polarized output with an extinction ratio exceeding 42 dB was obtained by double-pass configuration. As an application, supercontinuum spanning from 1000 to 2500 nm was generated by a successive 2-m high-nonlinear fiber with a 140-mW average power. PMID:19494992

  20. Large-mode-area erbium-ytterbium-doped photonic-crystal fiber amplifier for high-energy femtosecond pulses at 1.55 µm

    Science.gov (United States)

    Shirakawa, Akira; Ota, Jun; Musha, Mitsuru; Nakagawa, Ken'Ichi; Ueda, Ken-Ichi; Riis Folkenberg, Jacob; Broeng, Jes

    2005-02-01

    We report a high-energy femtosecond fiber amplifier based on an air-cladded single-transverse-mode erbium-ytterbium-codoped photonic-crystal fiber with a 26-µm mode-field-diameter. 700-fs, 47-MHz pulses at 1557 nm were amplified and compressed to near-transform-limited 100-fs, 7.4-nJ pulses with 54-kW peak powers without chirped-pulse amplification. A linearly polarized output with an extinction ratio exceeding 42 dB was obtained by double-pass configuration. As an application, supercontinuum spanning from 1000 to 2500 nm was generated by a successive 2-m high-nonlinear fiber with a 140-mW average power.

  1. High repetition TEA CO2 laser with average output power of 3.3 kW%平均功率3.3kW高重复频率TEA CO2激光器

    Institute of Scientific and Technical Information of China (English)

    文康; 谭荣清; 张阔海; 刘世明; 朱玉峰; 徐程; 王东蕾; 卢远添; 赵志龙

    2011-01-01

    研制了一台平均功率3.3 kW横向激励大气压(TEA)CO2激光器.激光器采用单节放电体积为5 cm×4 cm×90 cm的两节腔体串连的形式,印刷板电路预电离结构和闸流管开关放电电路,实现了激光器单脉冲能量输出,高重复频率工作.在重复频率150 Hz条件下,获得了3.3 kW平均输出功率.获得32.8 J单脉冲输出能量,电光转换效率达到15.4%.%A high average power TEA CO2 laser has been developed. Average output power of 3.3 kW is achieved at a repetition of 150 Hz. The TEA CO2 laser consists of two same laser modules, each of which has a 5 cm x 4 cm× 90 cm discharge volume. Several special technologies including Printed Circuit Board (PCB) pre-ionization and thyratron switch discharging circuit are employed. The laser realized large energy output, high repetition operating and high average power output. Laser output pulse energy is measured. The relationship between laser pulse energy and voltage at different gas pressures is obtained. The maximum of output pulse energy is 32.8 J. Electro-optical efficiency is calculated and the maximum of electro-optical efficiency is 15.4%. The laser pulse waveforms are measured at different gas pressures.

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

    DEFF Research Database (Denmark)

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

    2010-01-01

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

  3. Theoretical research on period microstructure induced by femtosecond laser in transparent dielectric

    Science.gov (United States)

    Fan, Shuwei; Zhang, Yan

    2014-11-01

    In this paper, we do some research on the interior period microstructure of transparent materials induced by a femtosecond laser of 800-nm wavelength. By adopting a nonlinear propagation physical model of femtosecond laser pulses and considering the spherical aberration effect(SA), we analyze the influence of nonlinear effects such an self-focusing, GDV, MPA, plasma defocusing and interface aberration on femtosecond laser propagation in transparent materials. Meantime, in the case with nonlinear effects and interface aberration, we research the influence of fs laser power, pulse width, numerical aperture and focusing depth on period microvoid. Simultaneously, compared with simulating results in different focusing lens numerical aperture, we find that big numerical aperature and deep focusing more easily produced period voids.

  4. Stable,efficient diode-pumped femtosecond Yb:KGW laser through optimization of energy density on SESAM

    Institute of Scientific and Technical Information of China (English)

    Jinfeng Li; Xiaoyan Liang; Jinping He; Hua Lin

    2011-01-01

    An efficient high-power diode-pumped femtosecond Yb:KGW laser is repored.Through optimization of energy density by semiconductor saturable absorber mirror,output power achieved 2.4 W with pulse duration of 350 fs and repetition rate of 53 MHz at a pump power of 12.5 W,corresponding to an optical-to-optical efficiency of 19.2%. We believe that it is the highest optical-to-optical efficiency for single-diode-pumped bulk Yb:KGW femtosecond lasers to date.

  5. The art of femtosecond laser writing

    OpenAIRE

    Kazansky, Peter G.; Yang, Weijia; Shimotsuma, Yasuhiko; Hirao, Kazuyuki; Arai, Alan; Svirko, Yuri P.

    2009-01-01

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

  6. Avant-garde femtosecond laser writing

    OpenAIRE

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

    2010-01-01

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

  7. Average-energy games

    OpenAIRE

    Bouyer, Patricia; Markey, Nicolas; Randour, Mickael; Larsen, Kim G.; Laursen, Simon

    2015-01-01

    Two-player quantitative zero-sum games provide a natural framework to synthesize controllers with performance guarantees for reactive systems within an uncontrollable environment. Classical settings include mean-payoff games, where the objective is to optimize the long-run average gain per action, and energy games, where the system has to avoid running out of energy. We study average-energy games, where the goal is to optimize the long-run average of the accumulated energy. We show that this ...

  8. Bi-Plasma Interactions on Femtosecond Time-Scales

    Energy Technology Data Exchange (ETDEWEB)

    2011-06-22

    Ultrafast THz radiation has important applications in materials science studies, such as characterizing transport properties, studying the vibrational response of materials, and in recent years, controlling materials and elucidating their response in intense electromagnetic fields. THz fields can be generated in a lab setting using various plasma-based techniques. This study seeks to examine the interaction of two plasmas in order to better understand the fundamental physics associated with femtosecond filamentation processes and to achieve more efficient THz generation in a lab setting. The intensity of fluorescence in the region of overlap was measured as a function of polarization, power, and relative time delay of the two plasma-generating laser beams. Results of time dependent intensity studies indicate strikingly similar behaviors across polarizations and power levels; a sudden intensity spike was observed at time-zero, followed by a secondary maxima and subsequent decay to the initial plasma intensity. Dependence of the intensity on the power through either beam arm was also observed. Spectral studies of the enhanced emission were also carried out. Although this physical phenomenon is still not fully understood, future studies, including further spectral analysis of the fluorescence overlap, could yield new insight into the ultrafast processes occurring at the intersection of femtosecond filaments, and would provide a better understanding of the mechanisms for enhanced THz production.

  9. Spatial filters for high average power lasers

    Science.gov (United States)

    Erlandson, Alvin C

    2012-11-27

    A spatial filter includes a first filter element and a second filter element overlapping with the first filter element. The first filter element includes a first pair of cylindrical lenses separated by a first distance. Each of the first pair of cylindrical lenses has a first focal length. The first filter element also includes a first slit filter positioned between the first pair of cylindrical lenses. The second filter element includes a second pair of cylindrical lenses separated by a second distance. Each of the second pair of cylindrical lenses has a second focal length. The second filter element also includes a second slit filter positioned between the second pair of cylindrical lenses.

  10. Femtosecond Laser Induced Underwater Superoleophobic Surfaces

    OpenAIRE

    Yong Jiale; Chen Feng; Yang Qing

    2015-01-01

    Femtosecond laser microfabrication has been recently utilized in interface science to modify the liquid wettability of solid surfaces. Silicon surface with hierarchical micro/nanostructure is fabricated by a femtosecond laser. Similar to the fish’s scales, the laser-induced surface shows superhydrophilicity in air and superoleophobicity underwater. The oil contact angles can reach up to 159.4 ± 1° for the 1,2-dichloroethane droplets in water. Besides, the surface exhibits ultralow oil-adhesio...

  11. Massively parallel femtosecond laser processing.

    Science.gov (United States)

    Hasegawa, Satoshi; Ito, Haruyasu; Toyoda, Haruyoshi; Hayasaki, Yoshio

    2016-08-01

    Massively parallel femtosecond laser processing with more than 1000 beams was demonstrated. Parallel beams were generated by a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM). The key to this technique is to optimize the CGH in the laser processing system using a scheme called in-system optimization. It was analytically demonstrated that the number of beams is determined by the horizontal number of pixels in the SLM NSLM that is imaged at the pupil plane of an objective lens and a distance parameter pd obtained by dividing the distance between adjacent beams by the diffraction-limited beam diameter. A performance limitation of parallel laser processing in our system was estimated at NSLM of 250 and pd of 7.0. Based on these parameters, the maximum number of beams in a hexagonal close-packed structure was calculated to be 1189 by using an analytical equation. PMID:27505815

  12. 2 micron femtosecond fiber laser

    Science.gov (United States)

    Liu, Jian; Wan, Peng; Yang, Lihmei

    2014-07-29

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

  13. Averaged extreme regression quantile

    OpenAIRE

    Jureckova, Jana

    2015-01-01

    Various events in the nature, economics and in other areas force us to combine the study of extremes with regression and other methods. A useful tool for reducing the role of nuisance regression, while we are interested in the shape or tails of the basic distribution, is provided by the averaged regression quantile and namely by the average extreme regression quantile. Both are weighted means of regression quantile components, with weights depending on the regressors. Our primary interest is ...

  14. On the Averaging Principle

    OpenAIRE

    Fibich, Gadi; Gavious, Arieh; Solan, Eilon

    2012-01-01

    Typically, models with a heterogeneous property are considerably harder to analyze than the corresponding homogeneous models, in which the heterogeneous property is replaced with its average value. In this study we show that any outcome of a heterogeneous model that satisfies the two properties of differentiability and interchangibility is O(\\epsilon^2) equivalent to the outcome of the corresponding homogeneous model, where \\epsilon is the level of heterogeneity. We then use this averaging pr...

  15. Average Angular Velocity

    OpenAIRE

    Van Essen, H.

    2004-01-01

    This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li (1989) of separation of the energy of overall rotation in an arbitrary (non-linear) $N$-particle system. It generalizes the so called Koenig's theorem on the two parts of the kinetic energy (center of mass plus internal) to th...

  16. On Averaging Rotations

    DEFF Research Database (Denmark)

    Gramkow, Claus

    1999-01-01

    In this article two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very offten the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...... approximations to the Riemannian metric, and that the subsequent corrections are inherient in the least squares estimation. Keywords: averaging rotations, Riemannian metric, matrix, quaternion...

  17. Averaging anisotropic cosmologies

    CERN Document Server

    Barrow, J D; Barrow, John D.; Tsagas, Christos G.

    2006-01-01

    We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of pressure-free Bianchi-type models. Adopting the Buchert averaging scheme, we identify the kinematic backreaction effects by focussing on spacetimes with zero or isotropic spatial curvature. This allows us to close the system of the standard scalar formulae with a propagation equation for the shear magnitude. We find no change in the already known conditions for accelerated expansion. The backreaction terms are expressed as algebraic relations between the mean-square fluctuations of the models' irreducible kinematical variables. Based on these we investigate the early evolution of averaged vacuum Bianchi type $I$ universes and those filled with pressureless matter. In the latter case we show that the backreaction effects can modify the familiar Kasner-like singularity and potentially remove Mixmaster-type oscillations. We also discuss the possibility of accelerated expansion due to ...

  18. Average Angular Velocity

    CERN Document Server

    Essén, H

    2003-01-01

    This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li (1989) of separation of the energy of overall rotation in an arbitrary (non-linear) $N$-particle system. It generalizes the so called Koenig's theorem on the two parts of the kinetic energy (center of mass plus internal) to three parts: center of mass, rotational, plus the remaining internal energy relative to an optimally translating and rotating frame.

  19. On sparsity averaging

    CERN Document Server

    Carrillo, Rafael E; Wiaux, Yves

    2013-01-01

    Recent developments in Carrillo et al. (2012) and Carrillo et al. (2013) introduced a novel regularization method for compressive imaging in the context of compressed sensing with coherent redundant dictionaries. The approach relies on the observation that natural images exhibit strong average sparsity over multiple coherent frames. The associated reconstruction algorithm, based on an analysis prior and a reweighted $\\ell_1$ scheme, is dubbed Sparsity Averaging Reweighted Analysis (SARA). We review these advances and extend associated simulations establishing the superiority of SARA to regularization methods based on sparsity in a single frame, for a generic spread spectrum acquisition and for a Fourier acquisition of particular interest in radio astronomy.

  20. High-peak-power single-oscillator actively Q-switched mode-locked Tm3+-doped fiber laser and its application for high-average output power mid-IR supercontinuum generation in a ZBLAN fiber.

    Science.gov (United States)

    Kneis, Christian; Donelan, Brenda; Manek-Hönninger, Inka; Robin, Thierry; Cadier, Benoît; Eichhorn, Marc; Kieleck, Christelle

    2016-06-01

    A single-oscillator actively Q-switched mode-locked (QML) thulium-doped silica fiber laser is presented and used to pump a ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber for mid-infrared (mid-IR) supercontinuum (SC) generation. The fiber laser provided high-peak-power levels directly from the oscillator delivering single mode-locked pulse energies up to 48 μJ, being 2-4 orders of magnitude higher than conventional continuous wave mode-locked lasers. By pumping a ZBLAN fiber specially designed for high-output-power SC generation, 7.8 W have been achieved in all spectral bands with a spectrum extending to 4.2 μm. PMID:27244410

  1. High-peak-power single-oscillator actively Q-switched mode-locked Tm3+-doped fiber laser and its application for high-average output power mid-IR supercontinuum generation in a ZBLAN fiber.

    Science.gov (United States)

    Kneis, Christian; Donelan, Brenda; Manek-Hönninger, Inka; Robin, Thierry; Cadier, Benoît; Eichhorn, Marc; Kieleck, Christelle

    2016-06-01

    A single-oscillator actively Q-switched mode-locked (QML) thulium-doped silica fiber laser is presented and used to pump a ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber for mid-infrared (mid-IR) supercontinuum (SC) generation. The fiber laser provided high-peak-power levels directly from the oscillator delivering single mode-locked pulse energies up to 48 μJ, being 2-4 orders of magnitude higher than conventional continuous wave mode-locked lasers. By pumping a ZBLAN fiber specially designed for high-output-power SC generation, 7.8 W have been achieved in all spectral bands with a spectrum extending to 4.2 μm.

  2. FY2002 Progress Summary Program Plan, Statement of Work and Deliverables for Development of High Average Power Diode-Pumped Solid State Lasers, and Complementary Technologies, for Applications in Energy and Defense

    Energy Technology Data Exchange (ETDEWEB)

    Bayramian, A; Bibeau, C; Beach, R; Behrendt, B; Ebbers, C; Latkowski, J; Meier, W; Payne, S; Perkins, J; Schaffers, K; Skulina, K; Ditmire, T; Kelly, J; Waxer, L; Rudi, P; Randles, M; Witter, D; Meissner, H; Merissner, O

    2001-12-13

    The High Average Power Laser Program (HAPL) is a multi-institutional, coordinated effort to develop a high-energy, repetitively pulsed laser system for Inertial Fusion Energy and other DOE and DOD applications. This program is building a laser-fusion energy base to complement the laser-fusion science developed by DOE Defense programs over the past 25 years. The primary institutions responsible for overseeing and coordinating the research activities are the Naval Research Laboratory (NRL) and LLNL. The current LLNL proposal is a companion proposal to that submitted by NRL, for which the driver development element is focused on the krypton fluoride excimer laser option. Aside from the driver development aspect, the NRL and LLNL companion proposals pursue complementary activities with the associated rep-rated laser technologies relating to target fabrication, target injection, final optics, fusion chamber, materials and power plant economics. This report requests continued funding in FY02 to support LLNL in its program to build a 1kW, 100J, diode-pumped, crystalline laser. In addition, research in high gain laser target design, fusion chamber issues and survivability of the final optic element will be pursued. These technologies are crucial to the feasibility of inertial fusion energy power plants and also have relevance in rep-rated stewardship experiments.

  3. On Averaging Rotations

    DEFF Research Database (Denmark)

    Gramkow, Claus

    2001-01-01

    In this paper two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very often the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...

  4. Site-Selective Field Emission Source by Femtosecond Laser Pulses and Its Emission Mechanism

    OpenAIRE

    Yanagisawa, Hirofumi

    2012-01-01

    Recent experimental and theoretical investigations on asymmetric field emission induced by weak femtosecond laser pulses and also its emission mechanisms are briefly reviewed. The emission mechanisms are discussed further for a wider range of DC fields and laser power. It appears that firstly photo-assisted field emission from lower-excitation order grows in the higher DC fields and secondly our simulations can be applied only for lower laser power.

  5. Switchable dual-pulse-shape mode-locked figure-eight all-PM fibre master oscillator with 0.5 W-level average output

    Science.gov (United States)

    Kobtsev, Sergey; Ivanenko, Aleksey; Fedotov, Yurii; Smirnov, Sergey V.; Golubtsov, Artur; Khripunov, Sergey

    2016-03-01

    For the first time a method for switching between generation of single- and double-scale pulses has been demonstrated in a mode-locked figure-eight NALM-based all-PM-fibre Yb master oscillator by adjustment of two pumps power. Introduction into a F8 configuration of a non-linear amplifying loop mirror with two active media not only ensured relatively high average output power of the master oscillator (> 0.5 W at 22-MHz repetition rate), but also allowed switching laser operation from one pulse type (single-scale with duration of <10 ps) to another - femtosecond clusters with envelope width of 16 ps and sub-pulse duration <200 fs.

  6. Green Laser with High Energy, Narrow Pulse Width and High Average Power%大能量窄脉宽高平均功率绿光激光器

    Institute of Scientific and Technical Information of China (English)

    李欣荣; 孙琦

    2011-01-01

    A green laser system with high average power output is developed with high energy and narrow pulse width. With diode laser pumped Nd :! YAG crystal, RTP electro-optic Q-switching and power dividing by master oscillator power amplifying (MOPA), the 532 nm green laser output with high energy, narrow pulse width and high repetition rate is realized. For the fundamental frequency output at 1064 nm, the average pulse energy is 213 mj, the operating frequency is 100 Hz and the optical-optical conversion efficiency is 12%. While a type H phase matching high gray track resistance KTP crystal is used for extra cavity frequency doubling, an green light output at 532 nm can be obtained, with the average pulse energy of 127 Mj, the operating frequency of 100 Hz, the pulse width of 7 .2 ns, the beam quality of 20 mm · Mrad and the total wall plug efficiency of 2,1% .%研制了在大能量窄脉宽情况下实现高平均功率输出的绿光激光系统.利用激光二极管抽运Nd∶YAG晶体,采用RTP晶体电光调Q和主振荡功率放大的功率分摊技术,实现大能量窄脉宽高重复频率532 nm绿光激光输出.输出基频光波长1064 nm,脉冲平均能量213 mJ,工作频率100 Hz,光-光转换效率12%.采用Ⅱ类相位匹配高抗灰迹KTP晶体腔外倍频,输出绿光波长532 nm,脉冲平均能量127 mJ,工作频率100 Hz,脉冲宽度7.2 ns,光束质量20mm· mrad,532 nm插头效率2.1%.

  7. Femtosecond x-ray pulses from a synchrotron

    OpenAIRE

    Schoenlein, R. W.; Chong, H. H. W.; Glover, T. E.; Heimann, P. A.; Shank, C. V.; Zholents, A.A.; Zolotorev, M.S.

    2000-01-01

    An important frontier in ultrafast science is the application of femtosecond x-ray pulses to the study of structural dynamics in condensed matter. We show that femtosecond laser pulses can be used to generate high-brightness, tunable, femtosecond x-ray pulses from a synchrotron. Performance of existing and proposed femtosecond x-ray beamlines at the Advanced Light Source synchrotron are discussed.

  8. 一种教学用简易飞秒光纤激光器的研制%Construction of a femtosecond fiber laser for teaching

    Institute of Scientific and Technical Information of China (English)

    朱海波; 朱晓农

    2011-01-01

    介绍了一种适合于日常高校光学或光电技术专业的研究生和高年级本科生熟悉、了解飞秒激光教学实验用的飞秒光纤激光器.该飞秒激光光源基于非线性旋转偏振效应被动锁模原理,输出脉冲宽度为440 fs、脉宽带宽积为0.362、中心波长在1560 nm附近、平均输出功率为12mW、脉冲重复频率为31.15MHz.%It is shown that a femtosecond fiber laser with a pulse repetition rate of 31 MHz, pulse width of 440 fs, central wavelength of 1560 nm and 12 mW average output power is successfully constructed. Such a laser source shows excellent stability with little frequency chirp, and it is compact, robust, lightweight, inexpensive, and easy to operate and maintain. With all these advantages, this laser is very suitable for both graduate and undergraduate students to study and experiment on femtosecond lasers.

  9. Coherent electron - hole state and femtosecond cooperative emission in bulk GaAs

    International Nuclear Information System (INIS)

    The conditions for obtaining a collective coherent electron - hole state in semiconductors are discussed. The results of the experimental study of the regime of cooperative recombination of high-density electrons and holes (more than 3 x 1018 cm-3) in bulk GaAs at room temperature are presented. It is shown that the collective pairing of electrons and holes and their condensation cause the formation of a short-living coherent electron - hole BCS-like state, which exhibits radiative recombination in the form of high-power femtosecond optical pulses. It is experimentally demonstrated that almost all of the electrons and holes available are condensed at the very bottoms of the bands and are at the cooperative state. The average lifetime of this state is measured to be of about 300 fs. The dependences of the order parameter (the energy gap of the spectrum of electrons and holes) and the Fermi energy of the coherent BCS state on the electron - hole concentration are obtained. (special issue devoted to the 80th anniversary of academician n g basov's birth)

  10. The averaging principle

    OpenAIRE

    Fibich, Gadi; Gavious, Arieh; Solan, Eilon

    2012-01-01

    Typically, models with a heterogeneous property are considerably harder to analyze than the corresponding homogeneous models, in which the heterogeneous property is replaced with its average value. In this study we show that any outcome of a heterogeneous model that satisfies the two properties of \\emph{differentiability} and \\emph{interchangibility}, is $O(\\epsilon^2)$ equivalent to the outcome of the corresponding homogeneous model, where $\\epsilon$ is the level of heterogeneity. We then us...

  11. Femtosecond lasers for microsurgery of cornea

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-03-31

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

  12. Whole-pattern fitting technique in serial femtosecond nanocrystallography

    Science.gov (United States)

    Dilanian, Ruben A.; Williams, Sophie R.; Martin, Andrew V.; Streltsov, Victor A.; Quiney, Harry M.

    2016-01-01

    Serial femtosecond X-ray crystallography (SFX) has created new opportunities in the field of structural analysis of protein nanocrystals. The intensity and timescale characteristics of the X-ray free-electron laser sources used in SFX experiments necessitate the analysis of a large collection of individual crystals of variable shape and quality to ultimately solve a single, average crystal structure. Ensembles of crystals are commonly encountered in powder diffraction, but serial crystallography is different because each crystal is measured individually and can be oriented via indexing and merged into a three-dimensional data set, as is done for conventional crystallography data. In this way, serial femtosecond crystallography data lie in between conventional crystallography data and powder diffraction data, sharing features of both. The extremely small sizes of nanocrystals, as well as the possible imperfections of their crystallite structure, significantly affect the diffraction pattern and raise the question of how best to extract accurate structure-factor moduli from serial crystallography data. Here it is demonstrated that whole-pattern fitting techniques established for one-dimensional powder diffraction analysis can be feasibly extended to higher dimensions for the analysis of merged SFX diffraction data. It is shown that for very small crystals, whole-pattern fitting methods are more accurate than Monte Carlo integration methods that are currently used. PMID:27006776

  13. Whole-pattern fitting technique in serial femtosecond nanocrystallography

    Directory of Open Access Journals (Sweden)

    Ruben A. Dilanian

    2016-03-01

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

  14. Femtosecond laser ablation of enamel

    Science.gov (United States)

    Le, Quang-Tri; Bertrand, Caroline; Vilar, Rui

    2016-06-01

    The surface topographical, compositional, and structural modifications induced in human enamel by femtosecond laser ablation is studied. The laser treatments were performed using a Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs and 1030 nm) and fluences up to 14 J/cm2. The ablation surfaces were studied by scanning electron microscopy, grazing incidence x-ray diffraction, and micro-Raman spectroscopy. Regardless of the fluence, the ablation surfaces were covered by a layer of resolidified material, indicating that ablation is accompanied by melting of hydroxyapatite. This layer presented pores and exploded gas bubbles, created by the release of gaseous decomposition products of hydroxyapatite (CO2 and H2O) within the liquid phase. In the specimen treated with 1-kHz repetition frequency and 14 J/cm2, thickness of the resolidified material is in the range of 300 to 900 nm. The micro-Raman analysis revealed that the resolidified material contains amorphous calcium phosphate, while grazing incidence x-ray diffraction analysis allowed detecting traces of a calcium phosphate other than hydroxyapatite, probably β-tricalcium phosphate Ca3), at the surface of this specimen. The present results show that the ablation of enamel involves melting of enamel's hydroxyapatite, but the thickness of the altered layer is very small and thermal damage of the remaining material is negligible.

  15. Average sampling theorems for shift invariant subspaces

    Institute of Scientific and Technical Information of China (English)

    孙文昌; 周性伟

    2000-01-01

    The sampling theorem is one of the most powerful results in signal analysis. In this paper, we study the average sampling on shift invariant subspaces, e.g. wavelet subspaces. We show that if a subspace satisfies certain conditions, then every function in the subspace is uniquely determined and can be reconstructed by its local averages near certain sampling points. Examples are given.

  16. A Harmonics Detection Method Based on Average Power Theory in Single-phase Circuit%基于平均有功功率的单相电路谐波和无功电流检测方法

    Institute of Scientific and Technical Information of China (English)

    丁菊霞; 康莉; 张华俊; 张秀峰

    2011-01-01

    In order to meet the demand of detecting harmonics and reactive currents when the voltage distortion, a detecting method based on average active power definition is drawn in this paper. Testified through analysis and simulation, this method is proved to detect instantaneous reactive currents, fundamental reactive current and harmonics in single-phase circuit, and without PLL in the detection of only instantaneous reactive currents. Compared with other methods based on the theory of instantaneous reactive power, this method is simpler and easier.%为解决电网电压畸变时单相电路谐波和无功电流检测问题,本文提出了基于平均有功功率的单相电路谐波和无功电流检测方法.理论分析和仿真验证表明,该方法能够实时检测出单相电路瞬时无功电流、基波无功电流及谐波电流,并且在只检测瞬时无功电流时无需锁相环电路.与基于瞬时无功功率理论的检测方法及有功电流分离法相比,该检测方法概念更清晰、算法更简单、更容易实现.

  17. Polarization maintaining linear cavity Er-doped fiber femtosecond laser

    Science.gov (United States)

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

    2015-10-01

    We present a polarization-maintaining (PM) type of Er-doped fiber linear oscillator designed to produce femtosecond laser pulses with high operational stability. Mode locking is activated using a semiconductor saturable absorber mirror (SESAM) attached to one end of the linear PM oscillator. To avoid heat damage, the SESAM is mounted on a copper-silicon-layered heat sink and connected to the linear oscillator through a fiber buffer dissipating the residual pump power. A long-term stability test is performed to prove that the proposed oscillator design maintains a soliton-mode single-pulse operation without breakdown of mode locking over a week period. With addition of an Er-doped fiber amplifier, the output power is raised to 180 mW with 60 fs pulse duration, from which an octave-spanning supercontinuum is produced.

  18. Synchronously pumped femtosecond optical parametric oscillator with broadband chirped mirrors

    Science.gov (United States)

    Stankevičiūte, Karolina; Melnikas, Simas; Kičas, Simonas; Trišauskas, Lukas; Vengelis, Julius; Grigonis, Rimantas; Vengris, Mikas; Sirutkaitis, Valdas

    2015-05-01

    We present results obtained during investigation of synchronously pumped optical parametric oscillator (SPOPO) with broadband complementary chirped mirror pairs (CMP). The SPOPO based on β-BBO nonlinear crystal is pumped by second harmonic of femtosecond Yb:KGW laser and provides signal pulses tunable over spectral range from 625 to 980 nm. More than 500 mW are generated in the signal beam, giving up to 27 % pump power to signal power conversion efficiency. The plane SPOPO cavity mirror pairs were specially designed to provide 99 % reflection in broad spectral range corresponding to signal wavelength tuning (630-1030 nm) and to suppress group delay dispersion (GDD) oscillations down to +/-10 fs2. Dispersion properties of designed mirrors were tested with white light interferometer (WLI) and attributed to the SPOPO tuning behaviour.

  19. Femtosecond fabricated surfaces for cell biology

    Science.gov (United States)

    Day, Daniel; Gu, Min

    2010-08-01

    Microfabrication using femtosecond pulse lasers is enabling access to a range of structures, surfaces and materials that was not previously available for scientific and engineering applications. The ability to produce micrometre sized features directly in polymer and metal substrates is demonstrated with applications in cell biology. The size, shape and aspect ratio of the etched features can be precisely controlled through the manipulation of the fluence of the laser etching process with respect to the properties of the target material. Femtosecond laser etching of poly(methyl methacrylate) and aluminium substrates has enabled the production of micrometre resolution moulds that can be accurately replicated using soft lithography. The moulded surfaces are used in the imaging of T cells and demonstrate the improved ability to observe biological events over time periods greater than 10 h. These results indicate the great potential femtosecond pulse lasers may have in the future manufacturing of microstructured surfaces and devices.

  20. April 25, 2003, FY2003 Progress Summary and FY2002 Program Plan, Statement of Work and Deliverables for Development of High Average Power Diode-Pumped Solid State Lasers,and Complementary Technologies, for Applications in Energy and Defense

    Energy Technology Data Exchange (ETDEWEB)

    Meier, W; Bibeau, C

    2005-10-25

    The High Average Power Laser Program (HAPL) is a multi-institutional, synergistic effort to develop inertial fusion energy (IFE). This program is building a physics and technology base to complement the laser-fusion science being pursued by DOE Defense programs in support of Stockpile Stewardship. The primary institutions responsible for overseeing and coordinating the research activities are the Naval Research Laboratory (NRL) and Lawrence Livermore National Laboratory (LLNL). The current LLNL proposal is a companion document to the one submitted by NRL, for which the driver development element is focused on the krypton fluoride excimer laser option. The NRL and LLNL proposals also jointly pursue complementary activities with the associated rep-rated laser technologies relating to target fabrication, target injection, final optics, fusion chamber, target physics, materials and power plant economics. This proposal requests continued funding in FY03 to support LLNL in its program to build a 1 kW, 100 J, diode-pumped, crystalline laser, as well as research into high gain fusion target design, fusion chamber issues, and survivability of the final optic element. These technologies are crucial to the feasibility of inertial fusion energy power plants and also have relevance in rep-rated stewardship experiments. The HAPL Program pursues technologies needed for laser-driven IFE. System level considerations indicate that a rep-rated laser technology will be needed, operating at 5-10 Hz. Since a total energy of {approx}2 MJ will ultimately be required to achieve suitable target gain with direct drive targets, the architecture must be scaleable. The Mercury Laser is intended to offer such an architecture. Mercury is a solid state laser that incorporates diodes, crystals and gas cooling technologies.

  1. Negative Average Preference Utilitarianism

    Directory of Open Access Journals (Sweden)

    Roger Chao

    2012-03-01

    Full Text Available For many philosophers working in the area of Population Ethics, it seems that either they have to confront the Repugnant Conclusion (where they are forced to the conclusion of creating massive amounts of lives barely worth living, or they have to confront the Non-Identity Problem (where no one is seemingly harmed as their existence is dependent on the “harmful” event that took place. To them it seems there is no escape, they either have to face one problem or the other. However, there is a way around this, allowing us to escape the Repugnant Conclusion, by using what I will call Negative Average Preference Utilitarianism (NAPU – which though similar to anti-frustrationism, has some important differences in practice. Current “positive” forms of utilitarianism have struggled to deal with the Repugnant Conclusion, as their theory actually entails this conclusion; however, it seems that a form of Negative Average Preference Utilitarianism (NAPU easily escapes this dilemma (it never even arises within it.

  2. Femtosecond tunneling response of surface plasmon polaritons

    DEFF Research Database (Denmark)

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

    1998-01-01

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

  3. All-fiber femtosecond Cherenkov radiation source.

    Science.gov (United States)

    Liu, Xiaomin; Lægsgaard, Jesper; Møller, Uffe; Tu, Haohua; Boppart, Stephen A; Turchinovich, Dmitry

    2012-07-01

    An all-fiber femtosecond source of spectrally isolated Cherenkov radiation is reported, to the best of our knowledge, for the first time. Using a monolithic, self-starting femtosecond Yb-doped fiber laser as the pump source and the combination of photonic crystal fibers as the wave-conversion medium, we demonstrate milliwatt-level, stable, and tunable Cherenkov radiation at visible wavelengths 580-630 nm, with pulse duration of sub-160-fs, and the 3 dB spectral bandwidth not exceeding 36 nm. Such an all-fiber Cherenkov radiation source is promising for practical applications in biophotonics such as bioimaging and microscopy. PMID:22743523

  4. All-fiber femtosecond Cherenkov radiation source

    OpenAIRE

    Liu, Xiaomin; Lægsgaard, Jesper; Møller, Uffe; Tu, Haohua; Boppart, Stephen A.; Turchinovich, Dmitry

    2012-01-01

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

  5. Femtosecond laser collagen cross-linking without traditional photosensitizers

    Science.gov (United States)

    Guo, Yizang; Wang, Chao; Celi, Nicola; Vukelic, Sinisa

    2015-03-01

    Collagen cross-linking in cornea has the capability of enhancing its mechanical properties and thereby providing an alternative treatment for eye diseases such as keratoconus. Currently, riboflavin assisted UVA light irradiation is a method of choice for cross-link induction in eyes. However, ultrafast pulsed laser interactions may be a powerful alternative enabling in-depth treatment while simultaneously diminishing harmful side effects such as, keratocyte apoptosis. In this study, femtosecond laser is utilized for treatment of bovine cornea slices. It is hypothesized that nonlinear absorption of femtosecond laser pulses plays a major role in the maturation of immature cross-links and the promotion of their growth. Targeted irradiation with tightly focused laser pulses allows for the absence of a photosensitizing agent. Inflation test was conducted on half treated porcine cornea to identify the changes of mechanical properties due to laser treatment. Raman spectroscopy was utilized to study subtle changes in the chemical composition of treated cornea. The effects of treatment are analyzed by observing shifts in Amide I and Amide III bands, which suggest deformation of the collagen structure in cornea due to presence of newly formed cross-links.

  6. Wavelength-dependent femtosecond pulse amplification in wideband tapered-waveguide quantum well semiconductor optical amplifiers.

    Science.gov (United States)

    Xia, Mingjun; Ghafouri-Shiraz, H

    2015-12-10

    In this paper, we study the wavelength-dependent amplification in three different wideband quantum well semiconductor optical amplifiers (QWAs) having conventional, exponentially tapered, and linearly tapered active region waveguide structures. A new theoretical model for tapered-waveguide QWAs considering the effect of lateral carrier density distribution and the strain effect in the quantum well is established based on a quantum well transmission line modeling method. The temporal and spectral characteristics of amplified femtosecond pulse are analyzed for each structure. It was found that, for the amplification of a single femtosecond pulse, the tapered-waveguide QWA provides higher saturation gain, and the output spectra of the amplified pulse in all three structures exhibit an apparent redshift and bandwidth narrowing due to the reduction of carrier density; however, the output spectrum in the tapered-waveguide amplifier is less distorted and exhibits smaller bandwidth narrowing. For the simultaneous amplification of two femtosecond pulses with different central frequencies, in all the three structures, two peaks appear in the output spectra while the peak at the frequency closer to the peak frequency of the QWA gain spectrum receives higher amplification due to the frequency (wavelength) dependence of the QWA gain. At a low peak power level of the input pulse, the bandwidth of each window in the tapered structure is larger than that of the conventional waveguide structure, which aggravates the spectrum alias in the amplification of femtosecond pulses with different central frequencies. As the peak powers of the two pulses increase, the spectrum alias in the conventional waveguide becomes more serious while there are small changes in the tapered structures. Also, we have found that in the amplification of a femtosecond pulse train, the linear-tapered QWAs exhibit the fastest gain recovery as compared with the conventional and exponentially tapered QWAs.

  7. Femtosecond laser-assisted deep anterior lamellar keratoplasty for keratoconus and keratectasia

    Institute of Scientific and Technical Information of China (English)

    Yan; Lu; Yu-Hua; Shi; Li-Ping; Yang; Yi-Rui; Ge; Xiang-Fei; Chen; Yan; Wu; Zhen-Ping; Huang

    2014-01-01

    ·AIM: To describe the initial outcomes and safety of femtosecond laser-assisted deep anterior lamellar keratoplasty(DALK) for keratoconus and post-LASIK keratectasia.·METHODS: In this non-comparative case series, 10 eyes of 9 patients underwent DALK procedures with a femtosecond laser(Carl Zeiss Meditec AG, Jena,Germany). Of the 9 patients, 7 had keratoconus and 2had post-LASIK keratectasia. A 500 kHz VisuMax femtosecond laser was used to perform corneal cuts on both donor and recipient corneas. The outcome measures were the uncorrected visual acuity(UCVA),best-corrected visual acuity(BCVA), corneal thickness,astigmatism, endothelial density count(EDC), and corneal power.·RESULTS: All eyes were successfully treated. Early postoperative evaluation showed a clear graft in all cases. Intraoperative complications included one case of a small Descemet’s membrane perforation.Postoperatively, there was one case of stromal rejection,one of loosened sutures, and one of wound dehiscence.A normal corneal pattern topography and transparency were restored, UCVA and BCVA improved significantly,and astigmatism improved slightly. There was no statistically significant decrease in EDC.· CONCLUSION: Our early results indicate that femtosecond laser-assisted deep anterior lamellar keratoplasty could improve UCVA and BCVA in patients with anterior corneal pathology. This approach shows promise as a safe and effective surgical choice in the treatment of keratoconus and post-LASIK keratectasia.

  8. Femtosecond laser generated gold nanoparticles and their plasmonic properties

    Science.gov (United States)

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

    2016-05-01

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

  9. Power

    OpenAIRE

    Samuel Bowles; Herbert Gintis

    2007-01-01

    We consider the exercise of power in competitive markets for goods, labour and credit. We offer a definition of power and show that if contracts are incomplete it may be exercised either in Pareto-improving ways or to the disadvantage of those without power. Contrasting conceptions of power including bargaining power, market power, and consumer sovereignty are considered. Because the exercise of power may alter prices and other aspects of exchanges, abstracting from power may miss essential a...

  10. Fragmentation of CO in Femtosecond Laser Fields

    International Nuclear Information System (INIS)

    Fragmentation of CO in a linearly polarized femtosecond laser field within the intensity order of 1014 W cm−2 at 820nm is investigated experimentally by using velocity mapping technique. According to the observed kinetic energy and angular distributions of different charged fragment ions, fragmentation channels of CO are proposed. The angular distributions provide helpful information for assigning the dissociation channels

  11. Microstructuring of electrospun mats employing femtosecond laser

    Directory of Open Access Journals (Sweden)

    Erika Adomavičiūtė

    2015-03-01

    Full Text Available Electrospun mats from nano/micro-fibers with control porosity and pore shape may be ideal candidate for tissue engineering scaffolds. In this study three type of poly(vinyl alcohol (PVA mats of 48-65 µm thickness with different nano/micro-fibers diameters mostly of 100-200 nm were deposited by electrospinning process. Controlled density porosity in the electrospun mats was introduced by Yb:KGW femtosecond laser micromachining system. The influence of electrospun mat micro structure, the distance between the adjacent laser ablation points, the number of femtosecond laser pulses on quality and structure of laser irradiated holes were investigated. It was demonstrated that the quality of irradiated holes depend on structure of electrospun mats (diameter of nano/micro-fibers, thickness of mats and femtosecond laser processing parameters. Varying the distance between points and number of applied femtosecond laser pulses it is possible to fabricate electrospun mats with pores of 22-36 μm diameter.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.10249

  12. Fragmentation of CO in Femtosecond Laser Fields

    Institute of Scientific and Technical Information of China (English)

    GUO Wei; ZHU Jing-Yi; WANG Bing-Xing; WANG Yan-Qiu; WANG Li

    2009-01-01

    Fragmentation of CO in a linearly polarized femtosecond laser field within the intensity order of 1014 W.cm-2 at 82Onto is investigated experimentally by using velocity mapping technique. According to the observed kinetic energy and angular distributions of different charged fragment ions, fragmentation channels of CO are proposed. The angular distributions provide helpful information for assigning the dissociation channels.

  13. Bending diamonds by femtosecond laser ablation

    DEFF Research Database (Denmark)

    Balling, Peter; Esberg, Jakob; Kirsebom, Kim;

    2009-01-01

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

  14. Atmospheric pressure femtosecond laser imaging mass spectrometry

    Science.gov (United States)

    Coello, Yves; Gunaratne, Tissa C.; Dantus, Marcos

    2009-02-01

    We present a novel imaging mass spectrometry technique that uses femtosecond laser pulses to directly ionize the sample. The method offers significant advantages over current techniques by eliminating the need of a laser-absorbing sample matrix, being suitable for atmospheric pressure sampling, and by providing 10μm resolution, as demonstrated here with a chemical image of vegetable cell walls.

  15. Femtosecond laser microstructuring of zirconia dental implants

    NARCIS (Netherlands)

    Delgado-Ruiz, R. A.; Calvo-Guirado, J. L.; Moreno, P.; Guardia, J.; Gomez-Moreno, G.; Mate-Sanchez, J. E.; Ramirez-Fernandez, P.; Chiva, F.

    2011-01-01

    This study evaluated the suitability of femtosecond laser for microtexturizing cylindrical zirconia dental implants surface. Sixty-six cylindrical zirconia implants were used and divided into three groups: Control group (with no laser modification), Group A (microgropored texture), and Group 13 (mic

  16. [Micro- and nano-structures on metal induced by femtosecond laser radiation].

    Science.gov (United States)

    Zhou, Ming; Yuan, Dong-Qing; Li, Jian; Fan, Xiao-Meng; Dai, Juan; Shen, Jian; Wang, Hui; Li, Bao-Jia; Cai, Lan

    2009-06-01

    In the present study the authors performed surface treatment of stainless steel 65Mn (the thickness is 60 microm) by femtosecond laser (pulse duration 148 fs, wavelength 775 nm). The single-pulse threshold could be obtained directly to be about 0. 2 J x cm(-2). The authors found that the femtosecond laser produced a large number of micro-structures such as nano-pores and nano-protrusions. Then the authors discussed the influence of pulse power and the number of shots on the formed surface structures. The authors found that with the change in the power and the number of pulses, the period of multiple parallel grooved surface patterns remained unchanged, which is about on the sub-micron level. Finally the authors processed the array of holes and the lines with different speed and number of pulses. PMID:19810507

  17. 语言值区间二元组能量平均算子及其应用%Linguistic interval 2-tuple power average operator and its application

    Institute of Scientific and Technical Information of China (English)

    晏力; 阮艳丽; 裴峥

    2013-01-01

    针对决策中的不确定性,提出了语言值区间二元组表示和语言值区间二元组能量平均(LI2TPA)算子,讨论了该语言聚合算子的性质.在LI2TPA算子中,分析了被聚合对象之间的相互支持测度,所以该算子可减弱过高或过低语言评价值对综合语言评价结果的影响,实例说明了LI2TPA算子在语言决策中的有效性.%Due to the uncertainty of decision making, a linguistic interval 2-tuple representation and a linguistic interval 2-tuple power average (LI2TPA) operator were proposed, and some desired properties of the developed operator were also studied. Because the support measure between two aggregated objects was analyzed in LI2TPA operator, this operator could relieve the influence of unduly high or unduly low evaluation values on the collective linguistic evaluation result. A numerical example showed the effectiveness of the new operator in linguistic decision making.

  18. Multi-modal label-free imaging based on a femtosecond fiber laser

    OpenAIRE

    Xie, Ruxin; Su, Jue; Rentchler, Eric C.; Zhang, Ziyan; Johnson, Carey K.; Shi, Honglian; Hui, Rongqing

    2014-01-01

    We demonstrate multi-mode microscopy based on a single femtosecond fiber laser. Coherent anti-Stokes Raman scattering (CARS), stimulated Raman scattering (SRS) and photothermal images can be obtained simultaneously with this simplified setup. Distributions of lipid and hemoglobin in sliced mouse brain samples and blood cells are imaged. The dependency of signal amplitude on the pump power and pump modulation frequency is characterized, which allows to isolate the impact from different contrib...

  19. Ultrafast Strong-Field Vibrational Dynamics Studied by Femtosecond Extreme-Ultraviolet Transient Absorption Spectroscopy

    OpenAIRE

    Hosler, Erik Robert

    2013-01-01

    Femtosecond time-resolved extreme-ultraviolet core-level absorption spectroscopy has developed into a powerful tool for investigating chemical dynamics due to its sensitivity for detecting changes in electronic structure. By probing the core-levels of atoms and molecules, dynamics may be monitored with elemental specificity, as well as localized sensitivity to the oxidation state around the atomic absorber. Previous experiments with this technique demonstrated the capability to quantitatively...

  20. Self-seeded lasing in ionized air pumped by 800 nm femtosecond laser pulses

    OpenAIRE

    Liu, Yi; Brelet, Yohann; Point, Guillaume; Houard, Aurélien; Mysyrowicz, André

    2013-01-01

    We report on the lasing in air and pure nitrogen gas pumped by a single 800 nm femtosecond laser pulse. Depending on gas pressure, incident laser power and beam convergence, different lasing lines are observed in the forward direction with rapid change of their relative intensities. The lines are attributed to transitions between vibrational and rotational levels of the first negative band of the singly charged nitrogen molecule-ion. We show that self-seeding plays an important role in the ob...

  1. Sub-diffraction-Limit Voids in Bulk Quartz Induced by Femtosecond Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    王丹翎; 李呈德; 罗乐; 杨宏; 龚旗煌

    2001-01-01

    When a powerful femtosecond laser pulse was tightly focused into a bulk quartz, plasma generation occurred only in a very small focal volume. This extremely confined interaction led to an explosive expansion and generated a sub-micrometre void with a diameter as small as 200-300nm. The dependence of the size of the void on the laser energy or pulse duration was investigated and the mechanism of this process was associated dominantly with the multiphoton ionization.

  2. Study on multiphoton ionization mass spectra of 3-picoline in femtosecond laser field

    International Nuclear Information System (INIS)

    Using 800 nm femtosecond laser as excitation source, the processes and mechanism of multiphoton ionization and dissociation of 3-picoline is studied, and find the process is ionization before dissociation, the possible dissociation channels are analyzed. At B3LYP/6-311 G + + (d, p) level, we calculate the energy of every dissociation channel, the result is consistent with the laser power index of ions based on the experiment. (authors)

  3. STATISTICAL ANALYSIS OF FEMTOSECOND PULSES LASER ON HOLE DRILLING OF SILICON WAFER

    OpenAIRE

    Jiao, L; E. Y. K. Ng; Zheng, H.; Wee, L.M.

    2011-01-01

    This study investigated the relationship and parameters interactions between five independent variables in laser percussion drilling of micro-hole. Experiments were conducted on single crystal silicon wafer with material thickness of 725 μm using femtosecond (fs) laser with wavelength of 775 nm and pulse duration of 200 fs. Laser power, focus position, number of pulses, workpiece temperature and assist liquid were selected as independent process variables. Taguchi L18 orthogonal array was app...

  4. Preclinical investigations of articular cartilage ablation with femtosecond and pulsed infrared lasers as an alternative to microfracture surgery

    Science.gov (United States)

    Su, Erica; Sun, Hui; Juhasz, Tibor; Wong, Brian J. F.

    2014-09-01

    Microfracture surgery is a bone marrow stimulation technique for treating cartilage defects and injuries in the knee. Current methods rely on surgical skill and instrumentation. This study investigates the potential use of laser technology as an alternate means to create the microfracture holes. Lasers investigated in this study include an erbium:YAG laser (λ=2.94 μm), titanium:sapphire femtosecond laser system (λ=1700 nm), and Nd:glass femtosecond laser (λ=1053 nm). Bovine samples were ablated at fluences of 8 to 18 J/cm2 with the erbium:YAG laser, at a power of 300±15 mW with the titanium:sapphire femtosecond system, and at an energy of 3 μJ/pulse with the Nd:glass laser. Samples were digitally photographed and histological sections were taken for analysis. The erbium:YAG laser is capable of fast and efficient ablation; specimen treated with fluences of 12 and 18 J/cm2 experienced significant amounts of bone removal and minimal carbonization with saline hydration. The femtosecond laser systems successfully removed cartilage but not clinically significant amounts of bone. Precise tissue removal was possible but not to substantial depths due to limitations of the systems. With additional studies and development, the use of femtosecond laser systems to ablate bone may be achieved at clinically valuable ablation rates.

  5. Replication of nano/micro-scale features using bulk metallic glass mold prepared by femtosecond laser and imprint processes

    International Nuclear Information System (INIS)

    This study describes the replication of nano/micro-scale features using a Pd40Ni40P20 bulk metallic glass (BMG) mold prepared using a femtosecond laser and nanoimprinting process. The use of the beam shaper feature of the femtosecond laser enabled the rapid fabrication of periodic nanostripes over an area of ∼5 × 4 mm2 on the BMG mold following a single pulse of irradiation. The ablation pitch of the nanostructure irradiated with 100 mW of femtosecond laser power was determined to be 175.8 nm. The imprinting results demonstrate the applicability of Pd-based BMG in the replication of mold features ranging from 100 µm to 90 nm. Additionally, Pd-based BMG can itself be used as a mold to transfer features onto Au-based BMG and polydimethylsiloxane, where the results could be used to ascertain the workability of BMG for molding in a nano/micro-imprint process. (paper)

  6. Multiterawatt femtosecond laser system with kilohertz pulse repetition rate

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, V V; Pestryakov, E V; Laptev, A V; Petrov, V A; Kuptsov, G V; Trunov, V I; Frolov, S A [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

    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)

  7. Multiterawatt femtosecond laser system with kilohertz pulse repetition rate

    Science.gov (United States)

    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.

  8. Hole drilling on glass optical fibers by a femtosecond laser

    Science.gov (United States)

    Hamasaki, Masayuki; Gouya, Kenji; Watanabe, Kazuhiro

    2012-01-01

    A novel optical fiber sensor has been developed for gaseous material detection by means of a femto-second laser which has ultrashort pulse and ultrahigh peak power. This sensor has attractive sensor potion consisted of drilling holes array which is machined on the glass optical fiber. Additionally, the sensor potion is coated with thin gold film. This work expects that an interaction could be induced between transmitted light through fiber core and a bottom of the drilled holes which reaches the fiber core. The interaction could induce near-field optical phenomenon excited by transmitted light through the fiber core. This scheme could make it possible to detect gaseous-material phase substances around the optical fiber. In this study, we found that localized surface plasmon (LSP) was excited by the transmitted light through the fiber core. This paper shows experiment to obtain optimum irradiation conditions and investigation for sensor principle for the development of a novel fiber sensor.

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

    Directory of Open Access Journals (Sweden)

    J. F. Gabayno

    2004-12-01

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

  10. X-ray laser–induced electron dynamics observed by femtosecond diffraction from nanocrystals of Buckminsterfullerene

    Science.gov (United States)

    Abbey, Brian; Dilanian, Ruben A.; Darmanin, Connie; Ryan, Rebecca A.; Putkunz, Corey T.; Martin, Andrew V.; Wood, David; Streltsov, Victor; Jones, Michael W. M.; Gaffney, Naylyn; Hofmann, Felix; Williams, Garth J.; Boutet, Sébastien; Messerschmidt, Marc; Seibert, M. Marvin; Williams, Sophie; Curwood, Evan; Balaur, Eugeniu; Peele, Andrew G.; Nugent, Keith A.; Quiney, Harry M.

    2016-01-01

    X-ray free-electron lasers (XFELs) deliver x-ray pulses with a coherent flux that is approximately eight orders of magnitude greater than that available from a modern third-generation synchrotron source. The power density of an XFEL pulse may be so high that it can modify the electronic properties of a sample on a femtosecond time scale. Exploration of the interaction of intense coherent x-ray pulses and matter is both of intrinsic scientific interest and of critical importance to the interpretation of experiments that probe the structures of materials using high-brightness femtosecond XFEL pulses. We report observations of the diffraction of extremely intense 32-fs nanofocused x-ray pulses by a powder sample of crystalline C60. We find that the diffraction pattern at the highest available incident power significantly differs from the one obtained using either third-generation synchrotron sources or XFEL sources operating at low output power and does not correspond to the diffraction pattern expected from any known phase of crystalline C60. We interpret these data as evidence of a long-range, coherent dynamic electronic distortion that is driven by the interaction of the periodic array of C60 molecular targets with intense x-ray pulses of femtosecond duration.

  11. Angle-dependent lubricated tribological properties of stainless steel by femtosecond laser surface texturing

    Science.gov (United States)

    Wang, Zhuo; Li, Yang-Bo; Bai, Feng; Wang, Cheng-Wei; Zhao, Quan-Zhong

    2016-07-01

    Lubricated tribological properties of stainless steel were investigated by femtosecond laser surface texturing. Regular-arranged micro-grooved textures with different spacing and micro-groove inclination angles (between micro-groove path and sliding direction) were produced on AISI 304L steel surfaces by an 800 nm femtosecond laser. The spacing of micro-groove was varied from 25 to 300 μm, and the inclination angles of micro-groove were measured as 90° and 45°. The tribological properties of the smooth and textured surfaces with micro-grooves were investigated by reciprocating ball-on-flat tests against Al2O3 ceramic balls under starved oil lubricated conditions. Results showed that the spacing of micro-grooves significantly affected the tribological property. With the increase of micro-groove spacing, the average friction coefficients and wear rates of textured surfaces initially decreased then increased. The tribological performance also depended on the inclination angles of micro-grooves. Among the investigated patterns, the micro-grooves perpendicular to the sliding direction exhibited the lowest average friction coefficient and wear rate to a certain extent. Femtosecond laser-induced surface texturing may remarkably improve friction and wear properties if the micro-grooves were properly distributed.

  12. Dissociating Averageness and Attractiveness: Attractive Faces Are Not Always Average

    Science.gov (United States)

    DeBruine, Lisa M.; Jones, Benedict C.; Unger, Layla; Little, Anthony C.; Feinberg, David R.

    2007-01-01

    Although the averageness hypothesis of facial attractiveness proposes that the attractiveness of faces is mostly a consequence of their averageness, 1 study has shown that caricaturing highly attractive faces makes them mathematically less average but more attractive. Here the authors systematically test the averageness hypothesis in 5 experiments…

  13. Polyatomic molecules under intense femtosecond laser irradiation.

    Science.gov (United States)

    Konar, Arkaprabha; Shu, Yinan; Lozovoy, Vadim V; Jackson, James E; Levine, Benjamin G; Dantus, Marcos

    2014-12-11

    Interaction of intense laser pulses with atoms and molecules is at the forefront of atomic, molecular, and optical physics. It is the gateway to powerful new tools that include above threshold ionization, high harmonic generation, electron diffraction, molecular tomography, and attosecond pulse generation. Intense laser pulses are ideal for probing and manipulating chemical bonding. Though the behavior of atoms in strong fields has been well studied, molecules under intense fields are not as well understood and current models have failed in certain important aspects. Molecules, as opposed to atoms, present confounding possibilities of nuclear and electronic motion upon excitation. The dynamics and fragmentation patterns in response to the laser field are structure sensitive; therefore, a molecule cannot simply be treated as a "bag of atoms" during field induced ionization. In this article we present a set of experiments and theoretical calculations exploring the behavior of a large collection of aryl alkyl ketones when irradiated with intense femtosecond pulses. Specifically, we consider to what extent molecules retain their molecular identity and properties under strong laser fields. Using time-of-flight mass spectrometry in conjunction with pump-probe techniques we study the dynamical behavior of these molecules, monitoring ion yield modulation caused by intramolecular motions post ionization. The set of molecules studied is further divided into smaller sets, sorted by type and position of functional groups. The pump-probe time-delay scans show that among positional isomers the variations in relative energies, which amount to only a few hundred millielectronvolts, influence the dynamical behavior of the molecules despite their having experienced such high fields (V/Å). High level ab initio quantum chemical calculations were performed to predict molecular dynamics along with single and multiphoton resonances in the neutral and ionic states. We propose the

  14. 18 CFR 301.7 - Average System Cost methodology functionalization.

    Science.gov (United States)

    2010-04-01

    ... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Average System Cost... REGULATORY COMMISSION, DEPARTMENT OF ENERGY REGULATIONS FOR FEDERAL POWER MARKETING ADMINISTRATIONS AVERAGE... ACT § 301.7 Average System Cost methodology functionalization. (a) Functionalization of each...

  15. EXPERIMENTAL STUDY OF THE GENERATION OF FEMTOSECOND ULTRAVIOLET LASER PULSE FROM THE HARMONICS OF Ti:sapphire%飞秒紫外激光脉冲振荡的实验研究

    Institute of Scientific and Technical Information of China (English)

    陈国夫; 王屹山; 于连君; 赵尚弘; 王贤华

    2001-01-01

    本文讨论了采用空间光脉冲光谱的啁啾特性和选择聚焦透镜焦距相结合的技术大大提高二次谐波转换效率和产生紫外飞秒光脉冲的实验研究.采用一类相位匹配的BBO晶体,当飞秒钛宝石光脉冲平均功率为560mW时,二次谐波输出功率为352mW,二次谐波转换效率高达63%;采用一类相位匹配的LBO晶体时,获得高光束质量的倍频蓝光输出,输出平均功率为170mW,转换效率大于30%.运用LBO倍频产生的蓝光脉冲和剩余的基频光脉冲进行了三次谐波的振荡研究.三倍频晶体采用BBO,通过优化设计倍频光与基频光之间的空间模匹配及精确时间延迟,得到飞秒紫外光输出,输出功率为2mW,中心波长约为280nm,重复率为100MHz%The SHG and THG experimental research is made,using home-madefemtosecond Ti:sapphire KLM laser.The SHG conversion efficiency is raised greatly when using the technique of the combination of space dispersion chirp and suitable lens.When the average power of femtosecond Ti:sapphire laser is 560mW,the SHG output power is 352mW with type I phase matching BBO crystal.The SHG conversion efficiency is 63%.Under the same condition,although the average power of femtosecond frequency-doubling laser pulse is 170mW wiht bype I phase matching LBO crystal,femtoseond blue pulse beam has good beam quality.This is advantageous for the generation of more harmonics of femtosecond Ti:sapphire laser.The THG study is made using the femtosecond blue pulse from frequency-doubling of LBO crystal and residual fundamental Ti:sapphire pulse.The femtosecond ultraviolet laser pulse is obtained,using THG BBO crystal.The ultraviolet average power is 2mW.The cetral wavelength is 280nm.The repetition is about 100MHz

  16. Micromachining soda-lime glass by femtosecond laser pulses

    Science.gov (United States)

    Jia, Wei; Yu, Jian; Chai, Lu; Wang, Ching-Yue

    2015-08-01

    The physical process of forming a modified region in soda-lime glass was investigated using 1 kHz intense femtosecond laser pulses from a Ti: sapphire laser at 775 nm. Through the modifications induced by the femtosecond laser radiation using selective chemical etching techniques, we fabricated reproducible and defined microstructures and further studied their morphologies and etching properties. Moreover, a possible physical mechanism for the femtosecond laser modification in soda-lime glass was proposed.

  17. Effects of femtosecond laser radiation on the skin

    Science.gov (United States)

    Rogov, P. Yu; Bespalov, V. G.

    2016-08-01

    A mathematical model of linear and nonlinear processes is presented occurring under the influence of femtosecond laser radiation on the skin. There was held an analysis and the numerical solution of an equation system describing the dynamics of the electron and phonon subsystems were received. The results can be used to determine the maximum permissible levels of energy generated by femtosecond laser systems and the establishment of Russian laser safety standards for femtosecond laser systems.

  18. Virtual Averaging Making Nonframe-Averaged Optical Coherence Tomography Images Comparable to Frame-Averaged Images

    OpenAIRE

    Chen, Chieh-Li; Ishikawa, Hiroshi; Wollstein, Gadi; Bilonick, Richard A.; Kagemann, Larry; Schuman, Joel S.

    2016-01-01

    Purpose Developing a novel image enhancement method so that nonframe-averaged optical coherence tomography (OCT) images become comparable to active eye-tracking frame-averaged OCT images. Methods Twenty-one eyes of 21 healthy volunteers were scanned with noneye-tracking nonframe-averaged OCT device and active eye-tracking frame-averaged OCT device. Virtual averaging was applied to nonframe-averaged images with voxel resampling and adding amplitude deviation with 15-time repetitions. Signal-to...

  19. Micromachining with femtosecond laser written radial polarization converter

    OpenAIRE

    Beresna, M.; Gecevičius, M.; Kazansky, P. G.; Bellouard, Y.; Champion, A.

    2012-01-01

    Structures for microfluidics are fabricated with radially polarized femtosecond laser beam. Radial polarization is produced using birefringent optical element. Omnidirectional etching can be achieved using cylindrically symmetric polarization.

  20. Broadening and Amplification of an Infrared Femtosecond Pulse for Optical Parametric Chirped-Pulse Amplification

    Institute of Scientific and Technical Information of China (English)

    WANG He-Lin; YANG Ai-Jun; LENG Yu-Xin

    2011-01-01

    A high-average-power diode-pumped narrowband regenerative chirped pulse amplifier is developed using the thin-rod Nd:YAG laser architecture for optical parametric chirped-pulse amplification (OPCPA).The effect of the etalons on the amplified pulse in the regenerative cavity is studied experimentally and theoretically.By inserting glass etalons of thickness 1 mm and 5 mm into the regenerative cavity,the pre-stretching pulse from an (O)ffner stretcher is further broadened to above 200ps,which matches the amplification windows of the signal pulses in OPCPA and is suitable for use as a pump source in the OPCPA system.The bandwidth of the amplified pulse is 1.5 nm,and an output energy of 2mJ is achieved at a repetition rate of 10 Hz.Optical parametric chirped pulse amplification (OPCPA)[1-4] has attracted a great deal of attention as the most promising technique for generating ultrashort ultrahigh-peak-power laser pulses because of its very broad gain bandwidth,negligible thermal load on the nonlinear crystal,and extremely high singlepass gain as compared to amplifiers based on laser gain media.For efficient amplification and high fidelity of dispersion compensation in OPCPA,a femtosecond seed pulse is first stretched to several tens of picoseconds with a bulk grating stretcher or a fiber stretcher.%A high-average-power diode-pumped narrowband regenerative chirped pulse amplifier is developed using the thin-rod Nd:YAG laser architecture for optical parametric chirped-pulse amplification (OPCPA). The effect of the etalons on the amplified pulse in the regenerative cavity is studied experimentally and theoretically. By inserting glass etalons of thickness 1 mm and 5 mm into the regenerative cavity, the pre-stretching pulse from an (O)finer stretcher is further broadened to above 200 ps, which matches the amplification windows of the signal pulses in OPCPA and is suitable for use as a pump source in the OPCPA system. The bandwidth of the amplified pulse is 1.5 nm, and an

  1. Cutting NiTi with Femtosecond Laser

    Directory of Open Access Journals (Sweden)

    L. Quintino

    2013-01-01

    Full Text Available Superelastic shape memory alloys are difficult to machine by thermal processes due to the facility for Ti oxidation and by mechanical processes due to their superelastic behavior. In this study, femtosecond lasers were tested to analyze the potential for machining NiTi since femtosecond lasers allow nonthermal processing of materials by ablation. The effect of processing parameters on machining depth was studied, and material removal rates were computed. Surfaces produced were analyzed under SEM which shows a resolidified thin layer with minimal heat affected zones. However, for high cutting speeds, that is, for short interaction times, this layer was not observed. A depletion of Ni was seen which may be beneficial in biomedical applications since Ni is known to produce human tissue reactions in biophysical environments.

  2. Femtosecond electron microscopy using photocathode RF gun

    International Nuclear Information System (INIS)

    The revealing and understanding of ultrafast structural-change induced dynamics are essential not only in physics, chemistry and biology, but also are indispensable for the development of new materials, new devices and applications. Both new RF gun based ultrafast relativistic electron diffraction and microscopy (UED and UEM) have being developed in Osaka University to probe directly structural changes at the atomic scale with sub-100 fs temporal resolution in materials. The first prototype of relativistic-energy UEM using a femtosecond photocathode RF gun has been developed. Both ultrafast diffraction and image measurements have been succeeded using a femtosecond electron beam. In this paper, the development of the UEM prototype and the first experiments of relativistic-energy electron imaging will be reported. (author)

  3. Lipidic phase membrane protein serial femtosecond crystallography

    OpenAIRE

    Johansson, LC; Arnlund, D.; White, TA; Katona, G.; DePonte, DP; Weierstall, U.; Doak, RB; Shoeman, RL; Lomb, L; Malmerberg, E.; Davidsson, J; Nass, K.; Liang, MN; Andreasson, J.; Dell'Aquila, A.

    2012-01-01

    X-ray free electron laser (X-FEL)-based serial femtosecond crystallography is an emerging method with potential to rapidly advance the challenging field of membrane protein structural biology. Here we recorded interpretable diffraction data from micrometer-sized lipidic sponge phase crystals of the Blastochloris viridis photosynthetic reaction center delivered into an X-FEL beam using a sponge phase micro-jet.

  4. Femtosecond Photodissociation of Molecules Facilitated by Noise

    OpenAIRE

    Singh, Kamal P.; Kenfack, Anatole; Rost, Jan M

    2007-01-01

    We investigate the dynamics of diatomic molecules subjected to both a femtosecond mid-infrared laser pulse and Gaussian white noise. The stochastic Schr\\"odinger equation with a Morse potential is used to describe the molecular vibrations under noise and the laser pulse. For weak laser intensity, well below the dissociation threshold, it is shown that one can find an optimum amount of noise that leads to a dramatic enhancement of the dissociation probability. The enhancement landscape which i...

  5. Characteristics of calcium signaling in astrocytes induced by photostimulation with femtosecond laser

    Science.gov (United States)

    Zhao, Yuan; Zhang, Yuan; Zhou, Wei; Liu, Xiuli; Zeng, Shaoqun; Luo, Qingming

    2010-05-01

    Astrocytes have been identified to actively contribute to brain functions through Ca2+ signaling, serving as a bridge to communicate with neurons and other brain cells. However, conventional stimulation techniques are hard to apply to delicate investigations on astrocytes. Our group previously reported photostimulation with a femtosecond laser to evoke astrocytic calcium (Ca2+) waves, providing a noninvasive and efficient approach with highly precise targeting. In this work, detailed characteristics of astrocytic Ca2+ signaling induced by photostimulation are presented. In a purified astrocytic culture, after the illumination of a femtosecond laser onto one cell, a Ca2+ wave throughout the network with reduced speed is induced, and intracellular Ca2+ oscillations are observed. The intercellular propagation is pharmacologically confirmed to be mainly mediated by ATP through P2Y receptors. Different patterns of Ca2+ elevations with increased amplitude in the stimulated astrocyte are discovered by varying the femtosecond laser power, which is correspondingly followed by broader intercellular waves. These indicate that the strength of photogenerated Ca2+ signaling in astrocytes has a positive relationship with the stimulating laser power. Therefore, distinct Ca2+ signaling is feasibly available for specific studies on astrocytes by employing precisely controlled photostimulation.

  6. Two-photon lithography and nanoprocessing with picojoule extreme ultrashort 12 femtosecond laser pulses

    Science.gov (United States)

    König, Karsten; Uchugonova, Aisada; Schug, Michael; Zhang, Huijing; Saremi, Sumarie; Feili, Dara; Seidel, Helmut

    2010-02-01

    A compact ultra-broadband femtosecond laser scanning microscope with 12 femtoseconds pulse width at the focal plane of a high NA objective has been employed in material nanoprocessing. The laser works at 85 MHz with an M-shaped emission spectrum with maxima at 770 nm and 827 nm. Different motorized setups based on the introduction of chirped mirrors, flint glass wedges, and glass blocks have been realized to vary the in situ pulse length from 12 femtoseconds up to 3 picoseconds. Nanoprocessing was performed in silica, photoresists, glass, polymers, and biological structures. Mean powers as low as 2 mW were sufficient to realize plasma-mediated cutting effects in human chromosomes with sub-80 nm cut width. Using a mean power of 7-9 mW, transient nanoholes were "drilled" in the cellular membrane for targeted transfection of stem cells and the introduction of μRNA probes. Region of interest (ROI) scanning have been used for optical cleaning of human adult stem cell populations and blood cell suspensions. 3D two-photon nanolithography based on the ultrabroad band laser pulses was realized with the photoresist SU-8. Multiphoton sub-20fs microscopes may become novel non-invasive 3D tools for highly precise nanoprocessing of inorganic and organic targets.

  7. Hemifusion of cells using femtosecond laser pulses

    Science.gov (United States)

    Katchinskiy, Nir; Godbout, Roseline; Goez, Helly R.; Elezzabi, Abdulhakem Y.

    2015-03-01

    Attachment of single cells via hemifusion of cellular membranes using femtosecond laser pulses is reported in this manuscript. This is a method to attach single cells using sub-10 femtosecond laser pulses, with 800 nm central wavelength delivered from a Ti:Sapphire laser is described. A fluorescent dye, Calcein AM, was used to verify that the cell's cytoplasm did not migrate from a dyed cell to a non-dyed cell, in order to ascertain that the cells did not go through cell-fusion process. An optical tweezer was used in order to assess the mechanical integrity of the attached joint membranes. Hemifusion of cellular membranes was successful without initiating full cell fusion. Attachment efficiency of 95% was achieved, while the cells' viability was preserved. The attachment was performed via the delivery of one to two trains of sub-10 femtosecond laser pulses lasting 15 milliseconds each. An ultrafast reversible destabilization of the phospholipid molecules in the cellular membranes was induced due to a laser-induced ionization process. The inner phospholipid cell membrane remained intact during the attachment procedure, and cells' cytoplasm remained isolated from the surrounding medium. The unbounded inner phospholipid molecules bonded to the nearest free phospholipid molecule, forming a joint cellular membrane at the connection point. The cellular membrane hemifusion technique can potentially provide a platform for the creation of engineered tissue and cell cultures.

  8. Femtosecond Laser Induced Underwater Superoleophobic Surfaces

    Directory of Open Access Journals (Sweden)

    Yong Jiale

    2015-01-01

    Full Text Available Femtosecond laser microfabrication has been recently utilized in interface science to modify the liquid wettability of solid surfaces. Silicon surface with hierarchical micro/nanostructure is fabricated by a femtosecond laser. Similar to the fish’s scales, the laser-induced surface shows superhydrophilicity in air and superoleophobicity underwater. The oil contact angles can reach up to 159.4 ± 1° for the 1,2-dichloroethane droplets in water. Besides, the surface exhibits ultralow oil-adhesion. In the oil/water/solid three-phase system, water can be trapped in the hierarchical rough structure and forms a repulsive oil layer according to underwater Cassie’s theory. The contact area between the asprepared surface and oil droplet is significantly reduced, resulting in superoleophobicity and ultralow oil-adhesion in water. In addition, transparent underwater superoleophobic and anti-oil surfaces are achieved on silica glass surfaces by femtosecond laser ablation. This transparent property is attributed to the presence of the water environment because scattering and refraction are effectively weakened. The presented method is simple and can accurately control the processing location, which may have widely potential applications in, for instance, microfluidics, biotechnologies, and antifouling coatings.

  9. Femtosecond Laser Microfabrication of an Integrated Device for Optical Release and Sensing of Bioactive Compounds

    Science.gov (United States)

    Ghezzi, Diego; Vazquez, Rebeca Martinez; Osellame, Roberto; Valtorta, Flavia; Pedrocchi, Alessandra; Valle, Giuseppe Della; Ramponi, Roberta; Ferrigno, Giancarlo; Cerullo, Giulio

    2008-01-01

    Flash photolysis of caged compounds is one of the most powerful approaches to investigate the dynamic response of living cells. Monolithically integrated devices suitable for optical uncaging are in great demand since they greatly simplify the experiments and allow their automation. Here we demonstrate the fabrication of an integrated bio-photonic device for the optical release of caged compounds. Such a device is fabricated using femtosecond laser micromachining of a glass substrate. More in detail, femtosecond lasers are used both to cut the substrate in order to create a pit for cell growth and to inscribe optical waveguides for spatially selective uncaging of the compounds present in the culture medium. The operation of this monolithic bio-photonic device is tested using both free and caged fluorescent compounds to probe its capability of multipoint release and optical sensing. Application of this device to the study of neuronal network activity can be envisaged.

  10. Webcam autofocus mechanism used as a delay line for the characterization of femtosecond pulses

    Science.gov (United States)

    Castro-Marín, Pablo; Kapellmann-Zafra, Gabriel; Garduño-Mejía, Jesús; Rosete-Aguilar, Martha; Román-Moreno, Carlos J.

    2015-08-01

    In this work, we present an electromagnetic focusing mechanism (EFM), from a commercial webcam, implemented as a delay line of a femtosecond laser pulse characterization system. The characterization system consists on a second order autocorrelator based on a two-photon-absorption detection. The results presented here were performed for two different home-made femtosecond oscillators: Ti:sapph @ 820 nm and highly chirped pulses generated with an Erbium Doped Fiber @ 1550 nm. The EFM applied as a delay line represents an excellent alternative due its performance in terms of stability, resolution, and long scan range up to 3 ps. Due its low power consumption, the device can be connected through the Universal Serial Bus (USB) port. Details of components, schematics of electronic controls, and detection systems are presented.

  11. Femtosecond Laser Microfabrication of an Integrated Device for Optical Release and Sensing of Bioactive Compounds

    Directory of Open Access Journals (Sweden)

    Giulio Cerullo

    2008-10-01

    Full Text Available Flash photolysis of caged compounds is one of the most powerful approaches to investigate the dynamic response of living cells. Monolithically integrated devices suitable for optical uncaging are in great demand since they greatly simplify the experiments and allow their automation. Here we demonstrate the fabrication of an integrated bio-photonic device for the optical release of caged compounds. Such a device is fabricated using femtosecond laser micromachining of a glass substrate. More in detail, femtosecond lasers are used both to cut the substrate in order to create a pit for cell growth and to inscribe optical waveguides for spatially selective uncaging of the compounds present in the culture medium. The operation of this monolithic bio-photonic device is tested using both free and caged fluorescent compounds to probe its capability of multipoint release and optical sensing. Application of this device to the study of neuronal network activity can be envisaged.

  12. Webcam autofocus mechanism used as a delay line for the characterization of femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Castro-Marín, Pablo; Kapellmann-Zafra, Gabriel; Garduño-Mejía, Jesús, E-mail: jesus.garduno@ccadet.unam.mx; Rosete-Aguilar, Martha; Román-Moreno, Carlos J. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, A. P. 70-186, CP 04510 México D.F. (Mexico)

    2015-08-15

    In this work, we present an electromagnetic focusing mechanism (EFM), from a commercial webcam, implemented as a delay line of a femtosecond laser pulse characterization system. The characterization system consists on a second order autocorrelator based on a two-photon-absorption detection. The results presented here were performed for two different home-made femtosecond oscillators: Ti:sapph @ 820 nm and highly chirped pulses generated with an Erbium Doped Fiber @ 1550 nm. The EFM applied as a delay line represents an excellent alternative due its performance in terms of stability, resolution, and long scan range up to 3 ps. Due its low power consumption, the device can be connected through the Universal Serial Bus (USB) port. Details of components, schematics of electronic controls, and detection systems are presented.

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

    Directory of Open Access Journals (Sweden)

    Marco Hornung

    2015-12-01

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

  14. Peak to Average Power Ratio Reduction with Low Computational Complexity in FrFT-OFDM System%FrFT-OFDM系统的低复杂度峰均功率比抑制技术研究

    Institute of Scientific and Technical Information of China (English)

    赵越; 王腾; 陶然; 时鹏飞; 蒋政国

    2014-01-01

    This paper proposes a low-complexity Peak to Average Power Ratio (PAPR) reduction method in Orthogonal Frequency Division Multiplexing (OFDM) system based on the Fractional Fourier Transform (FrFT). The method reduces PAPR effectively through periodic extension of random phase sequence to the length of FrFT-OFDM symbol, weighting it with phase factors and multiplying transmitted data vector. Only one Inverse Discrete Fractional Fourier Transform (IDFrFT) operation is performed in the proposed method, and the signal candidates can be calculated in time domain via weighted summation of the chirp circularly shifted FrFT-OFDM symbols. The simulation results show that, in the case that all the methods have 32 candidates, the proposed method has almost the same performance, when compared with the SeLecting Mapping (SLM) and performs even better than the Partial Transmit Sequence (PTS). More importantly, the proposed method has lower computational complexity compared with SLM and PTS.%针对基于分数阶Fourier变换的OFDM系统(简称FrFT-OFDM系统)的高峰均功率比(PAPR)问题,该文提出一种低复杂度的峰均比抑制算法。通过对随机相位序列采用周期延拓至FrFT-OFDM符号长度,相位因子加权后与子载波调制前的数据相乘的方式,实现对高峰均比的有效抑制。该算法只需要一次逆离散分数阶Fourier变换(IDFrFT),所有备选信号直接通过时域chirp圆周移位的加权和得到。仿真结果表明,当备选信号个数相同时,该算法与选择映射(SeLecting Mapping, SLM)算法的PAPR抑制性能相当,比部分传输序列(Partial Transmit Sequence, PTS)算法具有更好的PAPR抑制性能,同时,该算法较SLM和PTS算法的运算量降低。

  15. Normal dispersion femtosecond fiber optical parametric oscillator.

    Science.gov (United States)

    Nguyen, T N; Kieu, K; Maslov, A V; Miyawaki, M; Peyghambarian, N

    2013-09-15

    We propose and demonstrate a synchronously pumped fiber optical parametric oscillator (FOPO) operating in the normal dispersion regime. The FOPO generates chirped pulses at the output, allowing significant pulse energy scaling potential without pulse breaking. The output average power of the FOPO at 1600 nm was ∼60  mW (corresponding to 1.45 nJ pulse energy and ∼55% slope power conversion efficiency). The output pulses directly from the FOPO were highly chirped (∼3  ps duration), and they could be compressed outside of the cavity to 180 fs by using a standard optical fiber compressor. Detailed numerical simulation was also performed to understand the pulse evolution dynamics around the laser cavity. We believe that the proposed design concept is useful for scaling up the pulse energy in the FOPO using different pumping wavelengths. PMID:24104828

  16. Normal dispersion femtosecond fiber optical parametric oscillator.

    Science.gov (United States)

    Nguyen, T N; Kieu, K; Maslov, A V; Miyawaki, M; Peyghambarian, N

    2013-09-15

    We propose and demonstrate a synchronously pumped fiber optical parametric oscillator (FOPO) operating in the normal dispersion regime. The FOPO generates chirped pulses at the output, allowing significant pulse energy scaling potential without pulse breaking. The output average power of the FOPO at 1600 nm was ∼60  mW (corresponding to 1.45 nJ pulse energy and ∼55% slope power conversion efficiency). The output pulses directly from the FOPO were highly chirped (∼3  ps duration), and they could be compressed outside of the cavity to 180 fs by using a standard optical fiber compressor. Detailed numerical simulation was also performed to understand the pulse evolution dynamics around the laser cavity. We believe that the proposed design concept is useful for scaling up the pulse energy in the FOPO using different pumping wavelengths.

  17. Femtosecond laser pulses for chemical-free embryonic and mesenchymal stem cell differentiation

    Science.gov (United States)

    Mthunzi, Patience; Dholakia, Kishan; Gunn-Moore, Frank

    2011-10-01

    Owing to their self renewal and pluripotency properties, stem cells can efficiently advance current therapies in tissue regeneration and/or engineering. Under appropriate culture conditions in vitro, pluripotent stem cells can be primed to differentiate into any cell type some examples including neural, cardiac and blood cells. However, there still remains a pressing necessity to answer the biological questions concerning how stem cell renewal and how differentiation programs are operated and regulated at the genetic level. In stem cell research, an urgent requirement on experimental procedures allowing non-invasive, marker-free observation of growth, proliferation and stability of living stem cells under physiological conditions exists. Femtosecond (fs) laser pulses have been reported to non-invasively deliver exogenous materials, including foreign genetic species into both multipotent and pluripotent stem cells successfully. Through this multi-photon facilitated technique, directly administering fs laser pulses onto the cell plasma membrane induces transient submicrometer holes, thereby promoting cytosolic uptake of the surrounding extracellular matter. To display a chemical-free cell transfection procedure that utilises micro-litre scale volumes of reagents, we report for the first time on 70 % transfection efficiency in ES-E14TG2a cells using the enhanced green fluorescing protein (EGFP) DNA plasmid. We also show how varying the average power output during optical transfection influences cell viability, proliferation and cytotoxicity in embryonic stem cells. The impact of utilizing objective lenses of different numerical aperture (NA) on the optical transfection efficiency in ES-E14TG2a cells is presented. Finally, we report on embryonic and mesenchymal stem cell differentiation. The produced specialized cell types could thereafter be characterized and used for cell based therapies.

  18. Using femtosecond lasers to modify sizes of gold nanoparticles

    Science.gov (United States)

    da Silva Cordeiro, Thiago; Almeida de Matos, Ricardo; Silva, Flávia Rodrigues de Oliveira; Vieira, Nilson D.; Courrol, Lilia C.; Samad, Ricardo E.

    2016-04-01

    Metallic nanoparticles are important on several scientific, medical and industrial areas. The control of nanoparticles characteristics has fundamental importance to increase the efficiency on the processes and applications in which they are employed. The metallic nanoparticles present specific surface plasmon resonances (SPR). These resonances are related with the collective oscillations of the electrons presents on the metallic nanoparticle. The SPR is determined by the potential defined by the nanoparticle size and geometry. There are several methods of producing gold nanoparticles, including the use of toxic chemical polymers. We already reported the use of natural polymers, as for example, the agar-agar, to produce metallic nanoparticles under xenon lamp irradiation. This technique is characterized as a "green" synthesis because the natural polymers are inoffensive to the environment. We report a technique to produce metallic nanoparticles and change its geometrical and dimensional characteristics using a femtosecond laser. The 1 ml initial solution was irradiate using a laser beam with 380 mW, 1 kHz and 40 nm of bandwidth centered at 800 nm. The setup uses an Acousto-optic modulator, Dazzler, to change the pulses spectral profiles by introduction of several orders of phase, resulting in different temporal energy distributions. The use of Dazzler has the objective of change the gold nanoparticles average size by the changing of temporal energy distributions of the laser pulses incident in the sample. After the laser irradiation, the gold nanoparticles average diameter were less than 15 nm.

  19. Average Convexity in Communication Situations

    NARCIS (Netherlands)

    Slikker, M.

    1998-01-01

    In this paper we study inheritance properties of average convexity in communication situations. We show that the underlying graph ensures that the graphrestricted game originating from an average convex game is average convex if and only if every subgraph associated with a component of the underlyin

  20. Autocorrelation measurement of femtosecond laser pulses based on two-photon absorption in GaP photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Chong, E. Z.; Watson, T. F.; Festy, F., E-mail: frederic.festy@kcl.ac.uk [Biomaterials, Biomimetics and Biophotonics Division, King' s College London—Dental Institute, SE1 9RT London (United Kingdom)

    2014-08-11

    Semiconductor materials which exhibit two-photon absorption characteristic within a spectral region of interest can be useful in building an ultra-compact interferometric autocorrelator. In this paper, we report on the evidence of a nonlinear absorption process in GaP photodiodes which was exploited to measure the temporal profile of femtosecond Ti:sapphire laser pulses with a tunable peak wavelength above 680 nm. The two-photon mediated conductivity measurements were performed at an average laser power of less than a few tenths of milliwatts. Its suitability as a single detector in a broadband autocorrelator setup was assessed by investigating the nonlinear spectral sensitivity bandwidth of a GaP photodiode. The highly favourable nonlinear response was found to cover the entire tuning range of our Ti:sapphire laser and can potentially be extended to wavelengths below 680 nm. We also demonstrated the flexibility of GaP in determining the optimum compensation value of the group delay dispersion required to restore the positively chirped pulses inherent in our experimental optical system to the shortest pulse width possible. With the rise in the popularity of nonlinear microscopy, the broad two-photon response of GaP and the simplicity of this technique can provide an alternative way of measuring the excitation laser pulse duration at the focal point of any microscopy systems.

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

    Science.gov (United States)

    Ding, Li

    has been observed in or around the laser-induced refractive index modification regions. These results support the notion that femtosecond laser micro-processing method may be an excellent means of altering the refraction or higher order aberration content of corneal tissue without cell death and short-term tissue damage, and has been named as Intra-tissue Refractive Index Shaping (IRIS). The femtosecond laser micro-processing workstation has also been employed for laser transfection of single defined cells. Some preliminary results suggest that this method can be used to trace individual cells and record their biological and morphological evolution, which is quite promising in many biomedical applications especially in immunology science. In conclusion, high repetition rate femtosecond laser micro-processing has been employed to fabricate microstructures in ophthalmological hydrogels and ocular tissues. Its unique three-dimensional capability over transparent materials and biological media makes it a powerful tool and will greatly impact the future of laser material-processing.

  2. Microstructure and chemical bond evolution of diamond-like carbon films machined by femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-06-15

    Highlights: • The machining depth was essentially proportional to the laser power. • The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. And the number of nanoparticles increased with the processing power as well. • It revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. • It showed that a great decrease of sp{sup 3}/sp{sup 2} after laser treatment. - Abstract: Femtosecond laser is of great interest for machining high melting point and hardness materials such as diamond-like carbon, SiC ceramic, et al. In present work, the microstructural and chemical bond evolution of diamond-like carbon films were investigated using electron microscopy and spectroscopy techniques after machined by diverse femtosecond laser power in air. The results showed the machining depth was essentially proportional to the laser power. The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. Considering the D and G Raman band parameters on the laser irradiation, it revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. X-ray photoelectron spectroscopy analysis showed a great decrease of sp{sup 3}/sp{sup 2} after laser treatment.

  3. Microstructure and chemical bond evolution of diamond-like carbon films machined by femtosecond laser

    International Nuclear Information System (INIS)

    Highlights: • The machining depth was essentially proportional to the laser power. • The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. And the number of nanoparticles increased with the processing power as well. • It revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. • It showed that a great decrease of sp3/sp2 after laser treatment. - Abstract: Femtosecond laser is of great interest for machining high melting point and hardness materials such as diamond-like carbon, SiC ceramic, et al. In present work, the microstructural and chemical bond evolution of diamond-like carbon films were investigated using electron microscopy and spectroscopy techniques after machined by diverse femtosecond laser power in air. The results showed the machining depth was essentially proportional to the laser power. The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. Considering the D and G Raman band parameters on the laser irradiation, it revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. X-ray photoelectron spectroscopy analysis showed a great decrease of sp3/sp2 after laser treatment

  4. Power

    DEFF Research Database (Denmark)

    Elmholdt, Claus Westergård; Fogsgaard, Morten

    2016-01-01

    In this chapter, we will explore the dynamics of power in processes of creativity, and show its paradoxical nature as both a bridge and a barrier to creativity in organisations. Recent social psychological experimental research (Slighte, de Dreu & Nijstad, 2011) on the relation between power...... and creativity suggests that when managers give people the opportunity to gain power and explicate that there is reason to be more creative, people will show a boost in creative behaviour. Moreover, this process works best in unstable power hierarchies, which implies that power is treated as a negotiable...... and floating source for empowering people in the organisation. We will explore and discuss here the potentials, challenges and pitfalls of power in relation to creativity in the life of organisations today. The aim is to demonstrate that power struggles may be utilised as constructive sources of creativity...

  5. Parallel femtosecond laser processing with vector-wave control

    Directory of Open Access Journals (Sweden)

    Hayasaki Yoshio

    2013-11-01

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

  6. The difference between alternative averages

    Directory of Open Access Journals (Sweden)

    James Vaupel

    2012-09-01

    Full Text Available BACKGROUND Demographers have long been interested in how compositional change, e.g., change in age structure, affects population averages. OBJECTIVE We want to deepen understanding of how compositional change affects population averages. RESULTS The difference between two averages of a variable, calculated using alternative weighting functions, equals the covariance between the variable and the ratio of the weighting functions, divided by the average of the ratio. We compare weighted and unweighted averages and also provide examples of use of the relationship in analyses of fertility and mortality. COMMENTS Other uses of covariances in formal demography are worth exploring.

  7. Photoimaging of the multiple filamentation of femtosecond laser pulses in poly(methyl methacrylate) doped with 2,2-difluoro-4-(9-anthracyl)-6-methyl-1,3,2-dioxaborine

    Energy Technology Data Exchange (ETDEWEB)

    Kulchin, Yu N; Vitrik, O B; Chekhlenok, A A; Zhizhchenko, A Yu; Proschenko, D Yu [Institute for Automation and Control Processes, Far-Eastern Branch, Russian Academy of Sciences, Vladivostok (Russian Federation); Mirochnik, A G [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok (Russian Federation); Lyu Guohui [Electronic Engineering College, Heilongjiang University (China)

    2013-12-31

    We have studied the filamentation of femtosecond laser pulses (λ = 800 nm, ∼42 fs pulse duration) in poly(methyl methacrylate) doped with 2,2-difluoro-4-(9-anthracyl)-6-methyl-1,3,2- dioxaborine and the associated photomodification of the material. The results demonstrate that multiple filamentation occurs at pulse energies above 5 μJ. At a pulse energy of 1.5 mJ, it is accompanied by supercontinuum generation. The average filament length in PMMA is 9 mm and the filament diameter is ∼10 μm. An incident power density of ∼10{sup 12} W cm{sup -2} ensures inscription of the filament pattern owing to two-photon photochemical processes. Preliminary exposure to continuous light at λ = 400 nm enables an ordered filament pattern to be written. (interaction of laser radiation with matter)

  8. Femtosecond parabolic pulse shaping in normally dispersive optical fibers.

    Science.gov (United States)

    Sukhoivanov, Igor A; Iakushev, Sergii O; Shulika, Oleksiy V; Díez, Antonio; Andrés, Miguel

    2013-07-29

    Formation of parabolic pulses at femtosecond time scale by means of passive nonlinear reshaping in normally dispersive optical fibers is analyzed. Two approaches are examined and compared: the parabolic waveform formation in transient propagation regime and parabolic waveform formation in the steady-state propagation regime. It is found that both approaches could produce parabolic pulses as short as few hundred femtoseconds applying commercially available fibers, specially designed all-normal dispersion photonic crystal fiber and modern femtosecond lasers for pumping. The ranges of parameters providing parabolic pulse formation at the femtosecond time scale are found depending on the initial pulse duration, chirp and energy. Applicability of different fibers for femtosecond pulse shaping is analyzed. Recommendation for shortest parabolic pulse formation is made based on the analysis presented.

  9. Power

    OpenAIRE

    Hafford-Letchfield, Trish

    2015-01-01

    This chapter looks at the concept of power in social work by focusing on what this means as a ‘professional’ and theorizes competing discourses of empowerment in social work and its key concepts, drawing in particular on the explanatory powers of critical theorist Michel Foucault (1991). The chapter problematizes the concept of power by explicitly drawing on both users’ and carers’ accounts from the literature to demonstrate different external and internal influences on the root causes of dis...

  10. Noncontact microsurgery and micromanipulation of living cells with combined system femtosecond laser scalpel-optical tweezers

    Science.gov (United States)

    Il'ina, Inna V.; Sitnikov, Dmitry S.; Ovchinnikov, Andrey V.; Agranat, Mikhail B.; Khramova, Yulia V.; Semenova, Maria L.

    2012-06-01

    We report on the results of using self-developed combined laser system consisting of a femtosecond laser scalpel (Cr:Forsterite seed oscillator and a regenerative amplifier, 620 nm, 100 fs, 10 Hz) and optical tweezers (cw laser, 1064 nm) for performing noncontact laser-mediated polar body (PB) and trophectoderm (TE) biopsy of early mammalian embryos. To perform PB biopsy the femtosecond laser scalpel was initially used to drill an opening in the zona pellucida, and then the PB was extracted out of the zygote with the optical tweezers. Unlike PB biopsy, TE biopsy allows diagnosing maternally-derived as well as paternally-derived defects. Moreover, as multiple TE cells can be taken from the embryo, more reliable diagnosis can be done. TE biopsy was performed by applying laser pulses to dissect the desired amount of TE cells that had just left the zona pellucida during the hatching. Optical tweezers were then used to trap and move the dissected TE cells in a prescribed way. Laser power in optical tweezers and energy of femtosecond laser pulses were thoroughly optimized to prevent cell damage and obtain high viability rates. In conclusion, the proposed techniques of laser-based embryo biopsy enable accurate, contamination-free, simple and quick microprocessing of living cells.

  11. Femtosecond laser surface ablation of transparent solids: understanding the bulk filamentation damage

    Science.gov (United States)

    Kudryashov, Sergey I.; Joglekar, A.; Mourou, G.; Ionin, A. A.; Zvorykin, V. D.; Hunt, A. J.

    2007-06-01

    Direct SEM examination reveals a complex nanoscale structure of deep narrow central channels within shallow wide external craters produced by single-shot high-intensity femtosecond laser radiation on Corning 0211 glass and sapphire surfaces. These internal narrow channels are not expected from ordinary surface melt spallation and expulsion processes characteristic of the external surface nanocraters, but exhibit nearly the same appearance threshold. Surprisingly, the nanochannel radiuses rapidly saturate versus incident laser intensity indicating bulk rather than surface character of laser energy deposition, in contrast to the external craters extending versus laser intensity in a regular manner. These facts may be explained by channeling of electromagnetic radiation by near-surface ablative filamentary propagation of intense femtosecond laser pulses in the highly electronically excited dielectrics, by spherical aberrations in the surface layer, or deep drilling of the samples by short-wavelength Bremsstrahlung radiation of relatively hot surface electron-hole or electron-ion plasma. The double structure of ablated surface nano-features is consistent with similar structures observed for bulk damage features fabricated by femtosecond laser pulses at supercritical laser powers, but much lower laser intensities.

  12. Femtosecond pulsed laser ablation to enhance drug delivery across the skin.

    Science.gov (United States)

    Garvie-Cook, Hazel; Stone, James M; Yu, Fei; Guy, Richard H; Gordeev, Sergey N

    2016-01-01

    Laser poration of the skin locally removes its outermost, barrier layer, and thereby provides a route for the diffusion of topically applied drugs. Ideally, no thermal damage would surround the pores created in the skin, as tissue coagulation would be expected to limit drug diffusion. Here, a femtosecond pulsed fiber laser is used to porate mammalian skin ex vivo. This first application of a hollow core negative curvature fiber (HC-NCF) to convey a femtosecond pulsed, visible laser beam results in reproducible skin poration. The effect of applying ink to the skin surface, prior to ultra-short pulsed ablation, has been examined and Raman spectroscopy reveals that the least, collateral thermal damage occurs in inked skin. Pre-application of ink reduces the laser power threshold for poration, an effect attributed to the initiation of plasma formation by thermionic electron emission from the dye in the ink. Poration under these conditions significantly increases the percutaneous permeation of caffeine in vitro. Dye-enhanced, plasma-mediated ablation of the skin is therefore a potentially advantageous approach to enhance topical/transdermal drug absorption. The combination of a fiber laser and a HC-NCF, capable of emitting and delivering femtosecond pulsed, visible light, may permit a compact poration device to be developed.

  13. Model propagation of a femtosecond laser radiation in the vitreous of the human eye

    Science.gov (United States)

    Rogov, P. Y.; Bespalov, V. G.

    2016-04-01

    The paper presents a mathematical model of linear and nonlinear processes occurring due to propagation of femtosecond laser pulses in vitreous of the human eye. By methods of numerical simulation, we have solved a nonlinear spectral equation describing dynamics of two-dimensional TE-polarized radiation. The solution was performed in a homogeneous isotropic medium with instantaneous cubic nonlinearity without using slowly varying envelope approximation. For simulation we used medium with parameters close to the optical media of the eye. The model of femtosecond radiation takes into account the dynamics of the process of dispersion pulse broadening in time and occurrence of self-focusing of the retina when passing through vitreous body of the eye. The dependence between pulse duration on the retina and duration of the input pulse was found, as well as the values of power density at which self-focusing occurs. It was shown that the main mechanism of radiation damage caused while using Ti-sapphire laser is photoionization. The results coincide with the results obtained by other scientists. They can be used to create Russian laser safety standards for femtosecond laser systems.

  14. Femtosecond laser in refractive and cataract surgeries

    Institute of Scientific and Technical Information of China (English)

    Han-Han; Liu; Ying; Hu; Hong-Ping; Cui

    2015-01-01

    In the past few years, 9 unique laser platforms have been brought to the market. As femtosecond(FS) laserassisted ophthalmic surgery potentially improves patient safety and visual outcomes, this new technology indeed provides ophthalmologists a reliable new option. But this new technology also poses a range of new clinical and financial challenges for surgeons. We provide an overview of the evolution of FS laser technology for use in refractive and cataract surgeries. This review describes the available laser platforms and mainly focuses on discussing the development of ophthalmic surgery technologies.

  15. Direct-write waveplates using femtosecond lasers

    CERN Document Server

    McMillen, Ben; Bellouard, Yves

    2016-01-01

    The use of femtosecond lasers to introduce controlled stress states has recently been demonstrated in silica glass. We use this principle in combination with chemical etching to demonstrate direct-write wave plates with precisely tailored retardance levels. In this work, we achieve sufficient retardance to act as a quarter-wave plate, producing a broadband device with a clear aperture free of any laser modifications. We analyze and model the stress distribution within the clear aperture, providing a generic template that can be applied to form multiple retardance levels within the same substrate.

  16. Femtosecond laser studies of ultrafast intramolecular processes

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-12-01

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

  17. Physical Theories with Average Symmetry

    CERN Document Server

    Alamino, Roberto C

    2013-01-01

    This Letter probes the existence of physical laws invariant only in average when subjected to some transformation. The concept of a symmetry transformation is broadened to include corruption by random noise and average symmetry is introduced by considering functions which are invariant only in average under these transformations. It is then shown that actions with average symmetry obey a modified version of Noether's Theorem with dissipative currents. The relation of this with possible violations of physical symmetries, as for instance Lorentz invariance in some quantum gravity theories, is briefly commented.

  18. High-Energy Ions Emitted from Ar Clusters Irradiated by Intense Femtosecond Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    LI Zhong; LEI An-Le; NI Guo-Quan; XU Zhi-Zhan

    2000-01-01

    We have experimentally studied the energy spectra of Ar ions emitted from Ar clusters irradiated by intense femtosecond laser pulses. The Ar clusters were produced in the adiabatic expansion of Ar gas into vacuum at high backing pressures. The laser peak intensity was about 2×106 W/cm2 with a pulse duration of 45 fs. The maximum and the average energies of Ar ions are 0.2 MeV and 15kev at a backing pressure of 2. S MPa, respectively. They are almost independent of the backing pressures in the range of 0.6 to 4.5 MPa.

  19. Momentum distributions of selected rare-gas atoms probed by intense femtosecond laser pulses

    DEFF Research Database (Denmark)

    Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2011-01-01

    We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses. The...... calculations are performed by solving the time-dependent Schrödinger equation within the single-active-electron approximation, and focal-volume effects are taken into account by appropriately averaging the results. The resulting momentum distributions are in quantitative agreement with the experimental...

  20. Ultrafast electron diffraction from non-equilibrium phonons in femtosecond laser heated Au films

    Energy Technology Data Exchange (ETDEWEB)

    Chase, T. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Department of Applied Physics, Stanford University, Stanford, California 94305, USA; Trigo, M. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Reid, A. H. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Li, R. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Vecchione, T. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Shen, X. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Weathersby, S. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Coffee, R. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Hartmann, N. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Reis, D. A. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Department of Applied Physics, Stanford University, Stanford, California 94305, USA; PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Wang, X. J. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA; Dürr, H. A. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA

    2016-01-25

    We use ultrafast electron diffraction to detect the temporal evolution of non-equilibrium phonons in femtosecond laser-excited ultrathin single-crystalline gold films. From the time-dependence of the Debye-Waller factor, we extract a 4.7 ps time-constant for the increase in mean-square atomic displacements. The observed increase in the diffuse scattering intensity demonstrates that the energy transfer from laser-heated electrons to phonon modes near the X and K points in the Au fcc Brillouin zone proceeds with timescales of 2.3 and 2.9 ps, respectively, faster than the Debye-Waller average mean-square displacement.

  1. Femtosecond Transient Absorption Microspectroscopy of Benzil Confined Into a Single Bead of Porous Glass

    OpenAIRE

    Porter, Christopher F.; Tamai, Naoto; Masuhara, Hiroshi

    1996-01-01

    The photophysical properties of benzil dissolved in free solution and in solution confined into a single bead of porous glasses (size < 100 μm) were investigated by femtosecond transient absorption microspectroscopy. In nonpolar solvent, cyclohexane, the rate of conformational change from the skewed to the near trans-planar form was reduced from 2.2 × 1012s-1 in free solution to 9.1 × 1011s-1 in porous glasses with an average pore diameter of 26 nm. In polar solvent, DMF, however, there was l...

  2. MACHINE PROTECTION FOR HIGH AVERAGE CURRENT LINACS

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, Kevin; Allison, Trent; Evans, Richard; Coleman, James; Grippo, Albert

    2003-05-01

    A fully integrated Machine Protection System (MPS) is critical to efficient commissioning and safe operation of all high current accelerators. The Jefferson Lab FEL [1,2] has multiple electron beam paths and many different types of diagnostic insertion devices. The MPS [3] needs to monitor both the status of these devices and the magnet settings which define the beam path. The matrix of these devices and beam paths are programmed into gate arrays, the output of the matrix is an allowable maximum average power limit. This power limit is enforced by the drive laser for the photocathode gun. The Beam Loss Monitors (BLMs), RF status, and laser safety system status are also inputs to the control matrix. There are 8 Machine Modes (electron path) and 8 Beam Modes (average power limits) that define the safe operating limits for the FEL. Combinations outside of this matrix are unsafe and the beam is inhibited. The power limits range from no beam to 2 megawatts of electron beam power.

  3. "Pricing Average Options on Commodities"

    OpenAIRE

    Kenichiro Shiraya; Akihiko Takahashi

    2010-01-01

    This paper proposes a new approximation formula for pricing average options on commodities under a stochastic volatility environment. In particular, it derives an option pricing formula under Heston and an extended lambda-SABR stochastic volatility models (which includes an extended SABR model as a special case). Moreover, numerical examples support the accuracy of the proposed average option pricing formula.

  4. Quantized average consensus with delay

    NARCIS (Netherlands)

    Jafarian, Matin; De Persis, Claudio

    2012-01-01

    Average consensus problem is a special case of cooperative control in which the agents of the network asymptotically converge to the average state (i.e., position) of the network by transferring information via a communication topology. One of the issues of the large scale networks is the cost of co

  5. Optical measurement on quantum cascade lasers using femtosecond pulses

    Science.gov (United States)

    Cai, Hong

    Quantum cascade lasers (QCLs) as the state-of-the-art mid-infrared (mid-IR) coherent sources have been greatly developed in aspects such as output power, energy efficiency and spectral purity. However, there are additional applications of QCLs in high demand, namely mode-locking, mid-IR modulation, etc. The inherent optical properties and ultrafast carrier dynamics can lead to solutions to these challenges. In this dissertation, we further characterize QCLs using mid-IR femtosecond (fs) pulses generated from a laser system consisting of a Ti:sapphire oscillator, a Ti:sapphire regenerative amplifier, an optical parametric amplifier and a difference frequency generator. We study the Kerr nonlinearity of QCLs by coupling resonant and off-resonant mid-IR fs pulses into an active QCL waveguide. We observe an increase in the spectral width of the transmitted fs pulses as the coupled mid-IR pulse power increases. This is explained by the self-phase modulation effect due to the large Kerr nonlinearity of QCL waveguides. We further confirm this effect by observing the intensity dependent far-field profile of the transmitted mid-IR pulses, showing the pulses undergo self-focusing as they propagate through the active QCL due to the intensity dependent refractive index. The finite-difference time-domain simulations of QCL waveguides with Kerr nonlinearity incorporated show similar behavior to the experimental results. The giant Kerr nonlinearity investigated here may be used to realize ultrafast pulse generation in QCLs. In addition, we temporally resolved the ultrafast mid-infrared transmission modulation of QCLs using a near-infrared pump/mid-infrared probe technique at room temperature. Two different femtosecond wavelength pumps are used with photon energy above and below the quantum well (QW) bandgap. The shorter wavelength pump modulates the mid-infrared probe transmission through interband transition assisted mechanisms, resulting in a high transmission modulation depth

  6. Optical gene transfer by femtosecond laser pulses

    Science.gov (United States)

    Konig, Karsten; Riemann, Iris; Tirlapur, Uday K.

    2003-07-01

    Targeted transfection of cells is an important technique for gene therapy and related biomedical applications. We delineate how high-intensity (1012 W/cm2) near-infrared (NIR) 80 MHz nanojoule femtosecond laser pulses can create highly localised membrane perforations within a minute focal volume, enabling non-invasive direct transfection of mammalian cells with DNA. We suspended Chinese hamster ovarian (CHO), rat kangaroo kidney epithelial (PtK2) and rat fibroblast cells in 0.5 ml culture medium in a sterile miniaturized cell chamber (JenLab GmbH, Jena, Germany) containing 0.2 μg plasmid DNA vector pEGFP-N1 (4.7 kb), which codes for green fluorescent protein (GFP). The NIR laser beam was introduced into a femtosecond laser scanning microscope (JenLab GmbH, Jena, Germany; focussed on the edge of the cell membrane of a target cell for 16 ms. The integration and expression efficiency of EGFP were assessed in situ by two-photon fluorescence-lifetime imaging using time-correlated single photon counting. The unique capability to transfer foreign DNA safely and efficiently into specific cell types (including stem cells), circumventing mechanical, electrical or chemical means, will have many applications, such as targeted gene therapy and DNA vaccination.

  7. Matrix averages relating to Ginibre ensembles

    Energy Technology Data Exchange (ETDEWEB)

    Forrester, Peter J [Department of Mathematics and Statistics, University of Melbourne, Victoria 3010 (Australia); Rains, Eric M [Department of Mathematics, California Institute of Technology, Pasadena, CA 91125 (United States)], E-mail: p.forrester@ms.unimelb.edu.au

    2009-09-25

    The theory of zonal polynomials is used to compute the average of a Schur polynomial of argument AX, where A is a fixed matrix and X is from the real Ginibre ensemble. This generalizes a recent result of Sommers and Khoruzhenko (2009 J. Phys. A: Math. Theor. 42 222002), and furthermore allows analogous results to be obtained for the complex and real quaternion Ginibre ensembles. As applications, the positive integer moments of the general variance Ginibre ensembles are computed in terms of generalized hypergeometric functions; these are written in terms of averages over matrices of the same size as the moment to give duality formulas, and the averages of the power sums of the eigenvalues are expressed as finite sums of zonal polynomials.

  8. Resolving photon-shortage mystery in femtosecond magnetism

    CERN Document Server

    Si, M S

    2010-01-01

    For nearly a decade, it has been a mystery why the small average number of photons absorbed per atom from an ultrashort laser pulse is able to induce a strong magnetization within a few hundred femtoseconds. Here we resolve this mystery by directly computing the number of photons per atom layer by layer as the light wave propagates inside the sample. We find that for all the 24 experiments considered here, each atom has more than one photon. The so-called photon shortage does not exist. By plotting the relative demagnetization change versus the number of photons absorbed per atom, we show that depending on the experimental condition, 0.1 photon can induce about 4% to 72% spin moment change. Our perturbation theory reveals that the demagnetization depends linearly on the amplitude of laser field. In addition, we find that the transition frequency of a sample may also play a role in magnetization processes. As far as the intensity is not zero, the intensity of the laser field only affects the matching range of ...

  9. Resolving photon-shortage mystery in femtosecond magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Si, M S; Zhang, G P, E-mail: gpzhang@indstate.ed [Department of Physics, Indiana State University, Terre Haute, IN 47809 (United States)

    2010-02-24

    For nearly a decade, it has been a mystery why the small average number of photons absorbed per atom from an ultrashort laser pulse is able to induce a strong magnetization within a few hundred femtoseconds. Here we resolve this mystery by directly computing the number of photons per atom layer by layer as the light wave propagates inside the sample. We find that for all the 24 experiments considered here, each atom has more than one photon. The so-called photon shortage does not exist. By plotting the relative demagnetization change versus the number of photons absorbed per atom, we show that, depending on the experimental condition, 0.1 photon can induce about 4%-72% spin moment change. Our perturbation theory reveals that the demagnetization depends linearly on the amplitude of the laser field. In addition, we find that the transition frequency of a sample may also play a role in magnetization processes. As long as the intensity is not zero, the intensity of the laser field only affects the matching range of the transition frequencies, but not whether the demagnetization can happen or not.

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

    CERN Document Server

    Sugioka, Koji

    2013-01-01

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

  11. Femtosecond photodissociation dynamics of I studied by ion imaging

    DEFF Research Database (Denmark)

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

    1998-01-01

    on imaging is employed to analyze the fragments from timed Coulomb explosion studies of femtosecond (fs) molecular dynamics. The technique provides high detection efficiency and direct recording of the two-dimensional velocity of all ionized fragments. We illustrate the approach by studying...... photodissociation of iodine initiated by a weak femtosecond pump pulse and probed by an intense, delayed femtosecond pulse. The ion images, recorded as a function of the pump-probe delay, reveal the evolution of the internuclear separation of the dissociating I2 molecule. The experimental results are in good...

  12. Native sulfur/chlorine SAD phasing for serial femtosecond crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Nakane, Takanori [The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Song, Changyong [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); POSTECH, Pohang 790-784 (Korea, Republic of); Suzuki, Mamoru [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871 (Japan); Nango, Eriko; Kobayashi, Jun [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Masuda, Tetsuya [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Inoue, Shigeyuki [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Mizohata, Eiichi [Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Nakatsu, Toru [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Kyoto University, 46-29 Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501 (Japan); Tanaka, Tomoyuki; Tanaka, Rie [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Shimamura, Tatsuro [Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501 (Japan); Tono, Kensuke; Joti, Yasumasa; Kameshima, Takashi [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Hatsui, Takaki; Yabashi, Makina [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Nureki, Osamu [The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Iwata, So [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501 (Japan); Sugahara, Michihiro, E-mail: msuga@spring8.or.jp [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)

    2015-11-27

    Sulfur SAD phasing facilitates the structure determination of diverse native proteins using femtosecond X-rays from free-electron lasers via serial femtosecond crystallography. Serial femtosecond crystallography (SFX) allows structures to be determined with minimal radiation damage. However, phasing native crystals in SFX is not very common. Here, the structure determination of native lysozyme from single-wavelength anomalous diffraction (SAD) by utilizing the anomalous signal of sulfur and chlorine at a wavelength of 1.77 Å is successfully demonstrated. This sulfur SAD method can be applied to a wide range of proteins, which will improve the determination of native crystal structures.

  13. Gaussian moving averages and semimartingales

    DEFF Research Database (Denmark)

    Basse-O'Connor, Andreas

    2008-01-01

    In the present paper we study moving averages (also known as stochastic convolutions) driven by a Wiener process and with a deterministic kernel. Necessary and sufficient conditions on the kernel are provided for the moving average to be a semimartingale in its natural filtration. Our results...... are constructive - meaning that they provide a simple method to obtain kernels for which the moving average is a semimartingale or a Wiener process. Several examples are considered. In the last part of the paper we study general Gaussian processes with stationary increments. We provide necessary and sufficient...

  14. Effects on Organic Photovoltaics Using Femtosecond-Laser-Treated Indium Tin Oxides.

    Science.gov (United States)

    Chen, Mei-Hsin; Tseng, Ya-Hsin; Chao, Yi-Ping; Tseng, Sheng-Yang; Lin, Zong-Rong; Chu, Hui-Hsin; Chang, Jan-Kai; Luo, Chih-Wei

    2016-09-28

    The effects of femtosecond-laser-induced periodic surface structures (LIPSS) on an indium tin oxide (ITO) surface applied to an organic photovoltaic (OPV) system were investigated. The modifications of ITO induced by LIPPS in OPV devices result in more than 14% increase in power conversion efficiency (PCE) and short-circuit current density relative to those of the standard device. The basic mechanisms for the enhanced short-circuit current density are attributed to better light harvesting, increased scattering effects, and more efficient charge collection between the ITO and photoactive layers. Results show that higher PCEs would be achieved by laser-pulse-treated electrodes.

  15. Self-seeded lasing in ionized air pumped by 800 nm femtosecond laser pulses

    CERN Document Server

    Liu, Yi; Point, Guillaume; Houard, Aurélien; Mysyrowicz, André

    2013-01-01

    We report on the lasing in air and pure nitrogen gas pumped by a single 800 nm femtosecond laser pulse. Depending on gas pressure, incident laser power and beam convergence, different lasing lines are observed in the forward direction with rapid change of their relative intensities. The lines are attributed to transitions between vibrational and rotational levels of the first negative band of the singly charged nitrogen molecule-ion. We show that self-seeding plays an important role in the observed intensity changes.

  16. Three-dimensional direct cell patterning in collagen hydrogels with near-infrared femtosecond laser

    Science.gov (United States)

    Hribar, Kolin C.; Meggs, Kyle; Liu, Justin; Zhu, Wei; Qu, Xin; Chen, Shaochen

    2015-11-01

    We report a methodology for three-dimensional (3D) cell patterning in a hydrogel in situ. Gold nanorods within a cell-encapsulating collagen hydrogel absorb a focused near-infrared femtosecond laser beam, locally denaturing the collagen and forming channels, into which cells migrate, proliferate, and align in 3D. Importantly, pattern resolution is tunable based on writing speed and laser power, and high cell viability (>90%) is achieved using higher writing speeds and lower laser intensities. Overall, this patterning technique presents a flexible direct-write method that is applicable in tissue engineering systems where 3D alignment is critical (such as vascular, neural, cardiac, and muscle tissue).

  17. Ultrahigh resolution optical coherence tomography with femtosecond Ti:sapphire laser and photonic crystal fiber

    Institute of Scientific and Technical Information of China (English)

    XUE Ping; James G FUJIMOTO

    2008-01-01

    Optical coherence tomography (OCT) with ultrahigh axial resolution was achieved by the super-contin- uum generated by coupling femtosecond pulses from a commercial Ti :sapphire laser into an air-silica microstructure fiber. The visible spectrum of the super-continuum from 450 to 700 nm centered at 540 nm can be generated. A free-space axial OCT resolution of 0.64 IJm was achieved. The sensitivity of OCT system was 108 dB with incident light power 3 mW at sample, only 7dB below the theoretical limit. Subcellular OCT imaging was also demonstrated, showing great potential for biomedical application.

  18. Absorption of laser radiation by femtosecond laser-induced plasma of air and its emission characteristics

    Science.gov (United States)

    Ilyin, A. A.; Golik, S. S.; Shmirko, K. A.

    2015-11-01

    The energy absorbed by femtosecond laser plasma has nonlinear dependence on incident laser energy. The threshold power for plasma formation is 5.2 GW. Emission of nitrogen molecule, nitrogen molecule ion, atomic oxygen (unresolved triplet O I 777 nm) and nitrogen (triplet N I 742.4, 744.3 and 746.8 nm) lines is detected. Molecular emission consists of second positive and firs negative systems of nitrogen. Time-resolved spectroscopy of plasmas shows short molecular line emission (up to 1 ns) and long atomic line emission (up to 150 ns).

  19. Diamond photonics platform enabled by femtosecond laser writing

    CERN Document Server

    Sotillo, Belen; Hadden, J P; Sakakura, Masaaki; Chiappini, Andrea; Fernandez, Toney Teddy; Longhi, Stefano; Jedrkiewicz, Ottavia; Shimotsuma, Yasuhiko; Criante, Luigino; Osellame, Roberto; Galzerano, Gianluca; Ferrari, Maurizio; Miura, Kiyotaka; Ramponi, Roberta; Barclay, Paul E; Eaton, Shane Michael

    2016-01-01

    We demonstrate the first buried optical waveguides in diamond using focused femtosecond laser pulses. The properties of nitrogen vacancy centers are preserved in the waveguides, making them promising for diamond-based magnetometers or quantum information systems.

  20. New science and art of femtosecond laser writing

    OpenAIRE

    Kazansky, Peter G.

    2009-01-01

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

  1. Femtosecond soliton diode on heterojunction Bragg-grating structure

    CERN Document Server

    Deng, Zhigui; Li, Hongji; Fu, Shenhe; Liu, Yikun; Xiang, Ying; Li, Yongyao

    2016-01-01

    We numerically propose a scheme for realizing an all-optical femtosecond soliton diode based on a tailored heterojunction Bragg grating, which is designed by two spatially asymmetric chirped cholesteric liquid crystals. Our simulations demonstrate that with the consideration of optical nonlinearity, not only the femtosecond diode effect with nonreciprocal transmission ratio up to 120 can be achieved, but also the optical pulse evolving into soliton which maintains its shape during propagation through the sample is observed. Further, the influence of pulse width and the carrier wavelength to the femtosecond diode effect is also discussed in detail. Our demonstrations might suggest a new direction for experimentally realizing the femtosecond soliton diode based on the cholesteric liquid crystals.

  2. Monitor and control of neuronal activities with femtosecond pulse laser

    Institute of Scientific and Technical Information of China (English)

    ZHOU Wei; LIU XiuLi; L(U) XiaoHua; LI JiaSong; LUO QingMing; ZENG ShaoQun

    2008-01-01

    Combined with the fluorescence labeling technique, two-photon microscopy excited with femtosecond pulse laser has become an important tool for neuroscience research. In this research, the calcium signals from neurons in rat cortex slice were monitored by a custom-built two-photon microscopy, and the spontaneous calcium signals and the pharmacological responses as well as the responses to femtosecond pulse laser stimulation were recorded. The results showed that the amplitude of the cal-cium signals increased in direct proportion to the corresponding electrical activities. Glutamate induced a calcium transient, but continuous application resulted in smaller response. Simultaneous monitoring of neuronal populations distinguished the neurons of different microcircuits. The femtosecond pulse laser induced local or global calcium signals in the pyramidal neurons. The approach of interrogation and control of neural activities using femtosecond pulse laser is non-contact, nondestructive, repeatable, and without any additional substrates, which will contribute to the development of neuroscience.

  3. Femtosecond laser embedded grating micromachining of flexible PDMS plates

    Science.gov (United States)

    Cho, Sung-Hak; Chang, Won-Seok; Kim, Kwang-Ryul; Hong, Jong Wook

    2009-04-01

    We report on the femtosecond laser micromachining of photo-induced embedded diffraction grating in flexible Poly (Dimethly Siloxane) (PDMS) plates using a high-intensity femtosecond (130 fs) Ti: sapphire laser ( λp = 800 nm). The refractive index modifications with diameters ranging from 2 μm to 5 μm were photo-induced after the irradiation with peak intensities of more than 1 × 10 11 W/cm 2. The graded refractive index profile was fabricated to be a symmetric around from the center of the point at which femtosecond laser was focused. The maximum refractive index change (Δ n) was estimated to be 2 × 10 -3. By the X- Y- Z scanning of sample, the embedded diffraction grating in PDMS plate was fabricated successfully using a femtosecond laser.

  4. Carrier dynamics and terahertz photoconductivity of doped silicon measured by femtosecond pump-terahertz probe spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The carrier dynamics and terahertz photoconductivity in the n-type silicon (n-Si) as well as in the p-type Silicon (p-Si) have been investigated by using femtosecond pump-terahertz probe technique. The measurements show that the relative change of terahertz transmission of p-Si at low pump power is slightly smaller than that of n-Si,due to the lower carrier density induced by the recombination of original holes in the p-type material and the photogenerated electrons. At high pump power,the bigger change of terahertz transmission of p-Si originates from the greater mobility of the carriers compared to n-Si. The transient photoconductivities are calculated and fit well with the Drude-Smith model,showing that the mobility of the photogenerated carriers decreases with the increasing pump power. The obtained results indicate that femtosecond pump-terahertz probe technique is a promising method to investigate the carrier dynamics of semiconductors.

  5. Vocal attractiveness increases by averaging.

    Science.gov (United States)

    Bruckert, Laetitia; Bestelmeyer, Patricia; Latinus, Marianne; Rouger, Julien; Charest, Ian; Rousselet, Guillaume A; Kawahara, Hideki; Belin, Pascal

    2010-01-26

    Vocal attractiveness has a profound influence on listeners-a bias known as the "what sounds beautiful is good" vocal attractiveness stereotype [1]-with tangible impact on a voice owner's success at mating, job applications, and/or elections. The prevailing view holds that attractive voices are those that signal desirable attributes in a potential mate [2-4]-e.g., lower pitch in male voices. However, this account does not explain our preferences in more general social contexts in which voices of both genders are evaluated. Here we show that averaging voices via auditory morphing [5] results in more attractive voices, irrespective of the speaker's or listener's gender. Moreover, we show that this phenomenon is largely explained by two independent by-products of averaging: a smoother voice texture (reduced aperiodicities) and a greater similarity in pitch and timbre with the average of all voices (reduced "distance to mean"). These results provide the first evidence for a phenomenon of vocal attractiveness increases by averaging, analogous to a well-established effect of facial averaging [6, 7]. They highlight prototype-based coding [8] as a central feature of voice perception, emphasizing the similarity in the mechanisms of face and voice perception.

  6. Vocal attractiveness increases by averaging.

    Science.gov (United States)

    Bruckert, Laetitia; Bestelmeyer, Patricia; Latinus, Marianne; Rouger, Julien; Charest, Ian; Rousselet, Guillaume A; Kawahara, Hideki; Belin, Pascal

    2010-01-26

    Vocal attractiveness has a profound influence on listeners-a bias known as the "what sounds beautiful is good" vocal attractiveness stereotype [1]-with tangible impact on a voice owner's success at mating, job applications, and/or elections. The prevailing view holds that attractive voices are those that signal desirable attributes in a potential mate [2-4]-e.g., lower pitch in male voices. However, this account does not explain our preferences in more general social contexts in which voices of both genders are evaluated. Here we show that averaging voices via auditory morphing [5] results in more attractive voices, irrespective of the speaker's or listener's gender. Moreover, we show that this phenomenon is largely explained by two independent by-products of averaging: a smoother voice texture (reduced aperiodicities) and a greater similarity in pitch and timbre with the average of all voices (reduced "distance to mean"). These results provide the first evidence for a phenomenon of vocal attractiveness increases by averaging, analogous to a well-established effect of facial averaging [6, 7]. They highlight prototype-based coding [8] as a central feature of voice perception, emphasizing the similarity in the mechanisms of face and voice perception. PMID:20129047

  7. Materials processing with a tightly focused femtosecond vortex laser pulse

    OpenAIRE

    Hnatovsky, Cyril; Shvedov, Vladlen G.; Krolikowski, Wieslaw; Rode, Andrei V.

    2010-01-01

    This letter is the first demonstration of material modification using tightly focused femtosecond laser vortex beams. Double-charge femtosecond vortices were synthesized with the polarization-singularity beam converter described in Ref [1] and then focused using moderate and high numerical aperture optics (viz., NA = 0.45 and 0.9) to ablate fused silica and soda-lime glasses. By controlling the pulse energy we consistently machine high-quality micron-size ring-shaped structures with less than...

  8. Materials processing with tightly focused femtosecond vortex laser beams

    OpenAIRE

    Hnatovsky, Cyril; Shvedov, Vladlen G.; Krolikowski, Wieslaw; Rode, Andrei V.

    2010-01-01

    This letter is the first demonstration of material modification using tightly focused femtosecond laser vortex beams. Double-charge femtosecond vortices were synthesized with the polarization-singularity beam converter described in Ref [1] and then focused using moderate and high numerical aperture optics (viz., NA = 0.45 and 0.9) to ablate fused silica and soda-lime glasses. By controlling the pulse energy we consistently machine high-quality micron-size ring-shaped structures with less than...

  9. Femtosecond laser processing of photovoltaic and transparent materials

    OpenAIRE

    Sanghoon AHN

    2013-01-01

    The photovoltaic semiconducting and transparent dielectric materials are of high interest in current industry. Femtosecond laser processing can be an effective technique to fabricate such materials since non-linear photochemical mechanisms predominantly occur. In this series of studies, femtosecond (fs) laser processing techniques that include laser drilling on Si wafer, laser scribing on CIGS thin film, laser ablation on Lithium Niobate (LN) crystal, and fabrication of 3D structures in fused...

  10. Femtosecond Laser Fabrication of Monolithically Integrated Microfluidic Sensors in Glass

    OpenAIRE

    Fei He; Yang Liao; Jintian Lin; Jiangxin Song; Lingling Qiao; Ya Cheng; Koji Sugioka

    2014-01-01

    Femtosecond lasers have revolutionized the processing of materials, since their ultrashort pulse width and extremely high peak intensity allows high-quality micro- and nanofabrication of three-dimensional (3D) structures. This unique capability opens up a new route for fabrication of microfluidic sensors for biochemical applications. The present paper presents a comprehensive review of recent advancements in femtosecond laser processing of glass for a variety of microfluidic sensor applicatio...

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

    DEFF Research Database (Denmark)

    Bache, Morten; Zhou, Binbin

    2012-01-01

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

  12. Femtosecond fiber laser additive manufacturing of tungsten

    Science.gov (United States)

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

    2016-04-01

    Additive manufacturing (AM) is promising to produce complex shaped components, including metals and alloys, to meet requirements from different industries such as aerospace, defense and biomedicines. Current laser AM uses CW lasers and very few publications have been reported for using pulsed lasers (esp. ultrafast lasers). In this paper, additive manufacturing of Tungsten materials is investigated by using femtosecond (fs) fiber lasers. Various processing conditions are studied, which leads to desired characteristics in terms of morphology, porosity, hardness, microstructural and mechanical properties of the processed components. Fully dense Tungsten part with refined grain and increased hardness was obtained and compared with parts made with different pulse widths and CW laser. The results are evidenced that the fs laser based AM provides more dimensions to modify mechanical properties with controlled heating, rapid melting and cooling rates compared with a CW or long pulsed laser. This can greatly benefit to the make of complicated structures and materials that could not be achieved before.

  13. Femtosecond fiber laser welding of dissimilar metals.

    Science.gov (United States)

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

    2014-10-01

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

  14. Femtosecond laser enabled keratoplasty for advanced keratoconus

    Directory of Open Access Journals (Sweden)

    Yathish Shivanna

    2013-01-01

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

  15. Femtosecond fiber laser welding of dissimilar metals.

    Science.gov (United States)

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

    2014-10-01

    In this paper, welding of dissimilar metals was demonstrated for the first time, to the best of our knowledge, by using a high-energy high-repetition-rate femtosecond fiber laser. Metallurgical and mechanical properties were investigated and analyzed under various processing parameters (pulse energy, repetition rate, and welding speed). Results showed that the formation of intermetallic brittle phases and welding defects could be effectively reduced. Strong welding quality with more than 210 MPa tensile strength for stainless steel-aluminum and 175 MPa tensile strength for stainless steel-magnesium has been demonstrated. A minimal heat affected zone and uniform and homogenous phase transformation in the welding region have been demonstrated. This laser-welding technique can be extended for various applications in semiconductor, automobile, aerospace, and biomedical industries. PMID:25322246

  16. Optical reprogramming with ultrashort femtosecond laser pulses

    Science.gov (United States)

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

    2015-03-01

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

  17. Femtosecond laser technologies for linear collider designs

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, K. E-mail: kty_kobayashi@shi.co.jp; Endo, A

    2001-10-11

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

  18. Femtosecond laser technologies for linear collider designs

    CERN Document Server

    Kobayashi, K

    2001-01-01

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

  19. Sparsity Averaging for Compressive Imaging

    CERN Document Server

    Carrillo, Rafael E; Van De Ville, Dimitri; Thiran, Jean-Philippe; Wiaux, Yves

    2012-01-01

    We propose a novel regularization method for sparse image reconstruction from compressive measurements. The approach relies on the conjecture that natural images exhibit strong average sparsity over multiple coherent frames. The associated reconstruction algorithm, based on an analysis prior and a reweighted $\\ell_1$ scheme, is dubbed Sparsity Averaging Reweighted Analysis (SARA). We test our prior and the associated algorithm through extensive numerical simulations for spread spectrum and Gaussian acquisition schemes suggested by the recent theory of compressed sensing with coherent and redundant dictionaries. Our results show that average sparsity outperforms state-of-the-art priors that promote sparsity in a single orthonormal basis or redundant frame, or that promote gradient sparsity. We also illustrate the performance of SARA in the context of Fourier imaging, for particular applications in astronomy and medicine.

  20. Femtosecond excitation transfer processes in biliprotein trimers

    Science.gov (United States)

    Sharkov, A. V.; Khoroshilov, E. V.; Kryukov, I. V.; Palsson, Lars-Olof; Kryukov, P. G.; Fischer, R.; Scheer, Hella-Christin; Gillbro, Tomas

    1993-06-01

    Femtosecond processes in allophycocyanin, C-phycocyanin and phycoerythrocyanin trimers and monomers have been examined by means of polarization pump-probe technique. No femtosecond kinetics were observed in monomeric preparations. The isotropic absorption recovery kinetics with (tau) equals 440 +/- 50 fs which is not accompanied by anisotropy decay kinetics was obtained in allophycocyanin trimers at 612 nm. The conclusion about energy transfer between neighboring (alpha) 84 and (beta) 84 chromophores with different absorption spectra was made. The proposed model takes into account a stabilizing role of the linker peptide. Spectral and kinetic measurements were made in the 635 - 690 nm spectral region where the proposed acceptor should absorb. The bleaching of the 650-nm band occurs with a delay relative to the bleaching at 615 nm. Only a rise term was observed at 658 nm in consistence with the proposed model. Anisotropy values calculated around 650 nm at 3 ps after excitation are in the range 0.1 - 0.25 corresponding to an angle of 30 degree(s) - 45 degree(s) between the donor and acceptor transition dipole moments. A 500-fs absorption recovery and anisotropy decay process was obtained for C-phycocyanin trimers and explained by Forster energy transfer over 20.8 angstroms between neighboring (alpha) 84 and (beta) 84 chromophores of different monomeric subunits having similar absorption spectra and with a 65 degree(s) angle between their orientations. Energy transfer between violobilin ((alpha) 84) and phycocyanobilin ((beta) 84) chromophores was examined in donor and acceptor spectral regions of phycoerythrocyanin trimers, and was found to take 400 fs.

  1. Lasing of ambient air with microjoule pulse energy pumped by a multi terawatt IR femtosecond laser

    CERN Document Server

    Point, Guillaume; Brelet, Yohann; Mitryukovskiy, Sergey; Ding, Pengji; Houard, Aurélien; Mysyrowicz, André

    2014-01-01

    We report on the lasing action of atmospheric air pumped by an 800 nm femtosecond laser pulse with peak power up to 4 TW. Lasing emission at 428 nm increases rapidly over a small range of pump laser power, followed by saturation above ~ 1.5 TW. The maximum lasing pulse energy is measured to be 2.6 uJ corresponding to an emission power in the MW range, while a maximum conversion efficiency of is measured at moderate pump pulse energy. The optical gain inside the filament plasma is estimated to be excess of 0.7/cm. The lasing emission shows a doughnut profile, reflecting the spatial distribution of the pump-generated white-light continuum that acts as a seed for the lasing. We attribute the pronounced saturation to the defocusing of the seed in the plasma amplifying region and to the saturation of the seed intensity.

  2. Analysis of Femtosecond Timing Noise and Stability in Microwave Components

    Energy Technology Data Exchange (ETDEWEB)

    Whalen, Michael R.; /Stevens Tech. /SLAC

    2011-06-22

    To probe chemical dynamics, X-ray pump-probe experiments trigger a change in a sample with an optical laser pulse, followed by an X-ray probe. At the Linac Coherent Light Source, LCLS, timing differences between the optical pulse and x-ray probe have been observed with an accuracy as low as 50 femtoseconds. This sets a lower bound on the number of frames one can arrange over a time scale to recreate a 'movie' of the chemical reaction. The timing system is based on phase measurements from signals corresponding to the two laser pulses; these measurements are done by using a double-balanced mixer for detection. To increase the accuracy of the system, this paper studies parameters affecting phase detection systems based on mixers, such as signal input power, noise levels, temperature drift, and the effect these parameters have on components such as the mixers, splitters, amplifiers, and phase shifters. Noise data taken with a spectrum analyzer show that splitters based on ferrite cores perform with less noise than strip-line splitters. The data also shows that noise in specific mixers does not correspond with the changes in sensitivity per input power level. Temperature drift is seen to exist on a scale between 1 and 27 fs/{sup o}C for all of the components tested. Results show that any components using more metallic conductor tend to exhibit more noise as well as more temperature drift. The scale of these effects is large enough that specific care should be given when choosing components and designing the housing of high precision microwave mixing systems for use in detection systems such as the LCLS. With these improvements, the timing accuracy can be improved to lower than currently possible.

  3. Transient localized electron dynamics simulation during femtosecond laser tunnel ionization of diamond

    International Nuclear Information System (INIS)

    Highlights: ► A first-principles calculation of nonlinear electron–photon interactions when tunnel ionization dominates is presented. ► TDDFT is applied for the description of transient localized electrons dynamics. ► The relationships among average absorbed energy, Keldysh parameter and laser intensity are revealed. -- Abstract: A real-time and real-space time-dependent density-functional theory (TDDFT) is applied to simulate the nonlinear electron–photon interactions during femtosecond laser processing of diamond when tunnel ionization dominates. The transient localized electron dynamics including the electron excitation, energy absorption and electron density evolution are described in this Letter. In addition, the relationships among average absorbed energy, Keldysh parameter and laser intensity are revealed when the laser frequency is fixed.

  4. Ultrafast thin-disk multipass amplifier with 1.4 kW average power and 4.7 mJ pulse energy at 1030 nm converted to 820 W and 2.7 mJ at 515 nm

    Science.gov (United States)

    Negel, Jan-Philipp; Loescher, André; Voss, Andreas; Bauer, Dominik; Sutter, Dirk H.; Killi, Alexander; Abdou Ahmed, Marwan; Graf, Thomas

    2015-02-01

    In recent years, there has been a growing interest in increasing the output power of ultrafast lasers to the kW-range. This allows higher productivity for laser material processing, e.g. for cutting of carbon-fiber reinforced plastics (CFRP) or for micro-machining. We developed an Yb:YAG thin-disk multipass amplifier delivering sub-8 ps pulses with 1.4 kW average power which is - to the best of our knowledge - the highest output power reported for a sub-100 ps ultrafast laser system so far. The amplifier is seeded by a regenerative amplifier with 6.5 ps pulses and 115 W of average power at a repetition rate of 300 kHz. Taking this repetition rate into account, the energy of the amplified pulses is as high as 4.7 mJ. This was achieved using a scheme with 40 mirrors in an array to geometrically fold the seed beam 40 times over the thin-disk. The beam quality was measured to be better than M2=1.4. This system was used in first experiments to cut CFRP with very good quality and with unprecedented efficiency. Additionally, the output beam of the amplifier was frequency-doubled in an LBO crystal to 820 W (70 % conversion efficiency) output power at the second harmonic wavelength (515 nm) and 106 W (26.5 % conversion efficiency) at the third harmonic wavelength (343 nm). Both results are record output powers for ultrafast laser systems at the respective wavelengths. In the presentation, we will show concepts on further power scaling of the system.

  5. Sparsity averaging for radio-interferometric imaging

    CERN Document Server

    Carrillo, Rafael E; Wiaux, Yves

    2014-01-01

    We propose a novel regularization method for compressive imaging in the context of the compressed sensing (CS) theory with coherent and redundant dictionaries. Natural images are often complicated and several types of structures can be present at once. It is well known that piecewise smooth images exhibit gradient sparsity, and that images with extended structures are better encapsulated in wavelet frames. Therefore, we here conjecture that promoting average sparsity or compressibility over multiple frames rather than single frames is an extremely powerful regularization prior.

  6. Two-dimensional model for femtosecond pulse conversion and compression using high-order stimulated Raman scattering in solid hydrogen

    International Nuclear Information System (INIS)

    We present a numerical model for the interaction of a femtosecond probe pulse with a Raman medium excited by two nanosecond laser pulses in solid hydrogen. The model consists of a solution of a system of Bloch equations (for the medium state) and of the two-dimensional wave equation (for the field propagation). It is shown that by optimizing the tilt angle between the two driving pulses and the interaction length, the power of the probe pulse can be converted either into a quasicontinuous broadband spectrum or into a selected high-order sideband. The first situation can be used for generation of subfemtosecond pulses. The second situation can be used for the wavelength conversion of a femtosecond probe pulse from the infrared to the ultraviolet region. Due to the transfer of energy from the driving pulses, the energy conversion efficiency of these processes (with respect to the probe pulse) can be larger than unity

  7. Dependability in Aggregation by Averaging

    CERN Document Server

    Jesus, Paulo; Almeida, Paulo Sérgio

    2010-01-01

    Aggregation is an important building block of modern distributed applications, allowing the determination of meaningful properties (e.g. network size, total storage capacity, average load, majorities, etc.) that are used to direct the execution of the system. However, the majority of the existing aggregation algorithms exhibit relevant dependability issues, when prospecting their use in real application environments. In this paper, we reveal some dependability issues of aggregation algorithms based on iterative averaging techniques, giving some directions to solve them. This class of algorithms is considered robust (when compared to common tree-based approaches), being independent from the used routing topology and providing an aggregation result at all nodes. However, their robustness is strongly challenged and their correctness often compromised, when changing the assumptions of their working environment to more realistic ones. The correctness of this class of algorithms relies on the maintenance of a funda...

  8. Stochastic Approximation with Averaging Innovation

    CERN Document Server

    Laruelle, Sophie

    2010-01-01

    The aim of the paper is to establish a convergence theorem for multi-dimensional stochastic approximation in a setting with innovations satisfying some averaging properties and to study some applications. The averaging assumptions allow us to unify the framework where the innovations are generated (to solve problems from Numerical Probability) and the one with exogenous innovations (market data, output of "device" $e.g.$ an Euler scheme) with stationary or ergodic properties. We propose several fields of applications with random innovations or quasi-random numbers. In particular we provide in both setting a rule to tune the step of the algorithm. At last we illustrate our results on five examples notably in Finance.

  9. Controllable generation of reactive oxygen species by femtosecond-laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Wei; He, Hao, E-mail: haohe@tju.edu.cn; Wang, Yintao; Wang, Yisen; Hu, Minglie; Wang, Chingyue [Ultrafast Laser Laboratory, Key Laboratory of Optoelectronic Information Technology (Ministry of Education), College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin (China)

    2014-02-24

    Femtosecond lasers have been advancing Biophotonics research in the past two decades with multiphoton microscopy, microsurgery, and photodynamic therapy. Nevertheless, laser irradiation is identified to bring photodamage to cells via reactive oxygen species (ROS) generation with unclear mechanism. Meanwhile, currently in biological researches, there is no effective method to provide controllable ROS production precisely, which originally is leaked from mitochondria during respiration and plays a key role in a lot of important cellular processes and cellular signaling pathways. In this study, we show the process of how the tightly focused femtosecond-laser induces ROS generation solely in mitochondria at the very beginning and then release to cytosol if the stimulus is intense enough. At certain weak power levels, the laser pulses induce merely moderate Ca{sup 2+} release but this is necessary for the laser to generate ROS in mitochondria. Cellular original ROS are also involved with a small contribution. When the power is above a threshold, ROS are then released to cytosol, indicating photodamage overwhelming cellular repair ability. The mechanisms in those two cases are quite different. Those results clarify parts of the mechanism in laser-induced ROS generation. Hence, it is possible to further this optical scheme to provide controllable ROS generation for ROS-related biological researches including mitochondrial diseases and aging.

  10. Controllable generation of reactive oxygen species by femtosecond-laser irradiation

    Science.gov (United States)

    Yan, Wei; He, Hao; Wang, Yintao; Wang, Yisen; Hu, Minglie; Wang, Chingyue

    2014-02-01

    Femtosecond lasers have been advancing Biophotonics research in the past two decades with multiphoton microscopy, microsurgery, and photodynamic therapy. Nevertheless, laser irradiation is identified to bring photodamage to cells via reactive oxygen species (ROS) generation with unclear mechanism. Meanwhile, currently in biological researches, there is no effective method to provide controllable ROS production precisely, which originally is leaked from mitochondria during respiration and plays a key role in a lot of important cellular processes and cellular signaling pathways. In this study, we show the process of how the tightly focused femtosecond-laser induces ROS generation solely in mitochondria at the very beginning and then release to cytosol if the stimulus is intense enough. At certain weak power levels, the laser pulses induce merely moderate Ca2+ release but this is necessary for the laser to generate ROS in mitochondria. Cellular original ROS are also involved with a small contribution. When the power is above a threshold, ROS are then released to cytosol, indicating photodamage overwhelming cellular repair ability. The mechanisms in those two cases are quite different. Those results clarify parts of the mechanism in laser-induced ROS generation. Hence, it is possible to further this optical scheme to provide controllable ROS generation for ROS-related biological researches including mitochondrial diseases and aging.

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

    DEFF Research Database (Denmark)

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

    1996-01-01

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

  12. The JLab high power ERL light source

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-03-19

    A new THz/IR/UV photon source at Jefferson Lab is the first of a new generation of light sources based on an 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. 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 deposition and ablation, nitriding of metals, and energy flow in proteins. This paper will present the status of the system and discuss some of the discoveries we have made

  13. Michel Parameters averages and interpretation

    International Nuclear Information System (INIS)

    The new measurements of Michel parameters in τ decays are combined to world averages. From these measurements model independent limits on non-standard model couplings are derived and interpretations in the framework of specific models are given. A lower limit of 2.5 tan β GeV on the mass of a charged Higgs boson in models with two Higgs doublets can be set and a 229 GeV limit on a right-handed W-boson in left-right symmetric models (95 % c.l.)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-12-15

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

  15. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

    OpenAIRE

    Ya. Faenov, A.; Colgan, J.; S. B. Hansen; Zhidkov, A.; Pikuz, T. A.; Nishiuchi, M; Pikuz, S. A.; Yu. Skobelev, I.; Abdallah, J.; Sakaki, H.; Sagisaka, A.; Pirozhkov, A. S.; Ogura, K.; Y. Fukuda; Kanasaki, M

    2015-01-01

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021  W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E 4–5 of its power. The non-linear power growth occurs far earli...

  16. Holographic femtosecond laser manipulation for advanced material processing

    Science.gov (United States)

    Hasegawa, Satoshi; Hayasaki, Yoshio

    2016-02-01

    Parallel femtosecond laser processing using a computer-generated hologram displayed on a spatial light modulator, known as holographic femtosecond laser processing, provides the advantages of high throughput and high-energy use efficiency. Therefore, it has been widely used in many applications, including laser material processing, two-photon polymerization, two-photon microscopy, and optical manipulation of biological cells. In this paper, we review the development of holographic femtosecond laser processing over the past few years from the perspective of wavefront and polarization modulation. In particular, line-shaped and vector-wave femtosecond laser processing are addressed. These beam-shaping techniques are useful for performing large-area machining in laser cutting, peeling, and grooving of materials and for high-speed fabrication of the complex nanostructures that are applied to material-surface texturing to control tribological properties, wettability, reflectance, and retardance. Furthermore, issues related to the nonuniformity of diffraction light intensity in optical reconstruction and wavelength dispersion from a computer-generated hologram are addressed. As a result, large-scale holographic femtosecond laser processing over 1000 diffraction spots was successfully demonstrated on a glass sample.

  17. Femtosecond laser fabrication of monolithically integrated microfluidic sensors in glass.

    Science.gov (United States)

    He, Fei; Liao, Yang; Lin, Jintian; Song, Jiangxin; Qiao, Lingling; Cheng, Ya; Sugioka, Koji

    2014-01-01

    Femtosecond lasers have revolutionized the processing of materials, since their ultrashort pulse width and extremely high peak intensity allows high-quality micro- and nanofabrication of three-dimensional (3D) structures. This unique capability opens up a new route for fabrication of microfluidic sensors for biochemical applications. The present paper presents a comprehensive review of recent advancements in femtosecond laser processing of glass for a variety of microfluidic sensor applications. These include 3D integration of micro-/nanofluidic, optofluidic, electrofluidic, surface-enhanced Raman-scattering devices, in addition to fabrication of devices for microfluidic bioassays and lab-on-fiber sensors. This paper describes the unique characteristics of femtosecond laser processing and the basic concepts involved in femtosecond laser direct writing. Advanced spatiotemporal beam shaping methods are also discussed. Typical examples of microfluidic sensors fabricated using femtosecond lasers are then highlighted, and their applications in chemical and biological sensing are described. Finally, a summary of the technology is given and the outlook for further developments in this field is considered. PMID:25330047

  18. Femtosecond Laser Fabrication of Monolithically Integrated Microfluidic Sensors in Glass

    Directory of Open Access Journals (Sweden)

    Fei He

    2014-10-01

    Full Text Available Femtosecond lasers have revolutionized the processing of materials, since their ultrashort pulse width and extremely high peak intensity allows high-quality micro- and nanofabrication of three-dimensional (3D structures. This unique capability opens up a new route for fabrication of microfluidic sensors for biochemical applications. The present paper presents a comprehensive review of recent advancements in femtosecond laser processing of glass for a variety of microfluidic sensor applications. These include 3D integration of micro-/nanofluidic, optofluidic, electrofluidic, surface-enhanced Raman-scattering devices, in addition to fabrication of devices for microfluidic bioassays and lab-on-fiber sensors. This paper describes the unique characteristics of femtosecond laser processing and the basic concepts involved in femtosecond laser direct writing. Advanced spatiotemporal beam shaping methods are also discussed. Typical examples of microfluidic sensors fabricated using femtosecond lasers are then highlighted, and their applications in chemical and biological sensing are described. Finally, a summary of the technology is given and the outlook for further developments in this field is considered.

  19. Femtosecond X-ray protein nanocrystallography

    Energy Technology Data Exchange (ETDEWEB)

    Chapman, Henry N. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Univ. of Hamburg (Germany); Barty, Anton [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; White, Thomas A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Aquila, Andrew [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Schulz, Joachim [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; DePonte, Daniel P. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Martin, Andrew V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Coppola, Nicola [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Liang, Mengning [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Caleman, Carl [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Gumprecht, Lars [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Stern, Stephan [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Nass, Karol [Univ. of Hamburg (Germany); Fromme, Petra [Arizona State Univ., Tempe, AZ (United States). Dept. of Chemistry and Biochemistry; Hunter, Mark S. [Arizona State Univ., Tempe, AZ (United States). Dept. of Chemistry and Biochemistry; Grotjohann, Ingo [Arizona State Univ., Tempe, AZ (United States). Dept. of Chemistry and Biochemistry; Fromme, Raimund [Arizona State Univ., Tempe, AZ (United States). Dept. of Chemistry and Biochemistry; Kirian, Richard A. [Arizona State Univ., Tempe, AZ (United States). Dept. of Physics; Weierstall, Uwe [Arizona State Univ., Tempe, AZ (United States). Dept. of Physics; Doak, R. Bruce [Arizona State Univ., Tempe, AZ (United States). Dept. of Physics; Schmidt, Kevin E. [Arizona State Univ., Tempe, AZ (United States). Dept. of Physics; Wang, Xiaoyu [Arizona State Univ., Tempe, AZ (United States). Dept. of Physics; Spence, John C. H. [Arizona State Univ., Tempe, AZ (United States). Dept. of Physics; Schlichting, Ilme [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Medizinische Forschung, Heidelberg (Germany); Epp, Sascha W. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Kernphysik, Heidelberg (Germany); Rolles, Daniel [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Medizinische Forschung, Heidelberg (Germany); Rudenko, Artem [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Kernphysik, Heidelberg (Germany); Foucar, Lutz [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Medizinische Forschung, Heidelberg (Germany); Rudek, Benedikt [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Kernphysik, Heidelberg (Germany); Erk, Benjamin [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Kernphysik, Heidelberg (Germany); Schmidt, Carlo [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Kernphysik, Heidelberg (Germany); Hömke, André [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Kernphysik, Heidelberg (Germany); Strüder, Lothar [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Society Semiconductor Lab., Munich (Germany); Ullrich, Joachim [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Kernphysik, Heidelberg (Germany); Krasniqi, Faton [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science, Max Planck Advanced Study Group; Max Planck Inst. fur Medizinische Forschung, Heidelberg (Germany); Lomb, Lukas [Max Planck Inst. fur Medizinische Forschung, Heidelberg (Germany); Shoeman, Robert L. [Max Planck Inst. fur Medizinische Forschung, Heidelberg (Germany); Bott, Mario [Max Planck Inst. fur Medizinische Forschung, Heidelberg (Germany); Barends, Thomas R. M. [Max Planck Inst. fur Medizinische Forschung, Heidelberg (Germany); Kuhnel, Kai-Uwe [Max Planck Inst. fur Kernphysik, Heidelberg (Germany); Schroter, Claus-Dieter [Max Planck Inst. fur Kernphysik, Heidelberg (Germany); Hartmann, Robert [PNSensor GmbH, Munich (Germany); Holl, Peter [PNSensor GmbH, Munich (Germany); Reich, Christian [PNSensor GmbH, Munich (Germany); Soltau, Heike [PNSensor GmbH, Munich (Germany); Kimmel, Nils [Max Planck Society Semiconductor Lab., Munich (Germany); Weidenspointner, Georg [Max Planck Society Semiconductor Lab., Munich (Germany); Max Planck Inst. fur Extraterrestrische Physik, Garching (Germany); Pietschner, Daniel [Max Planck Society Semiconductor Lab., Munich (Germany); Hauser, Günter [Max Planck Society Semiconductor Lab., Munich (Germany); Herrmann, Sven [Max Planck Society Semiconductor Lab., Munich (Germany); Schaller, Gerhard [Max Planck Society Semiconductor Lab., Munich (Germany); Schopper, Florian [Max Planck Society Semiconductor Lab., Munich (Germany); Andritschke, Robert [Max Planck Society Semiconductor Lab., Munich (Germany); Boutet, Sébastien [SLAC National Accelerator Lab., Menlo Park, CA (United States). Linac Coherent Light Source (LCLS); Krzywinski, Jacek [SLAC National Accelerator Lab., Menlo Park, CA (United States). Linac Coherent Light Source (LCLS); Bostedt, Christoph [SLAC National Accelerator Lab., Menlo Park, CA (United States). Linac Coherent Light Source (LCLS); Messerschmidt, Marc [SLAC National Accelerator Lab., Menlo Park, CA (United States). Linac Coherent Light Source (LCLS); Bozek, John D. [SLAC National Accelerator Lab., Menlo Park, CA (United States). Linac Coherent Light Source (LCLS); Williams, Garth J. [SLAC National Accelerator Lab., Menlo Park, CA (United States). Linac Coherent Light Source (LCLS); Bogan, Michael J. [SLAC National Accelerator Lab., Menlo Park, CA (United States). Photon Ultrafast Laser Science and Engineering Inst. (PULSE); Hampton, Christina Y. [SLAC National Accelerator Lab., Menlo Park, CA (United States). Photon Ultrafast Laser Science and Engineering Inst. (PULSE); Sierra, Raymond G. [SLAC National Accelerator Lab., Menlo Park, CA (United States). Photon Ultrafast Laser Science and Engineering Inst. (PULSE); Starodub, Dmitri [SLAC National Accelerator Lab., Menlo Park, CA (United States). Photon Ultrafast Laser Science and Engineering Inst. (PULSE); Gorke, Hubert [Forschungszentrum Julich (Germany); Hau-Riege, Stefan P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Frank, Matthias [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Maia, Filipe R. N. C. [Uppsala Univ. (Sweden). Dept. of Cell and Molecular Biology, Lab. of Molecular Biophysics; Hajdu, Janos [Uppsala Univ. (Sweden). Dept. of Cell and Molecular Biology, Lab. of Molecular Biophysics; Timneanu, Nicusor [Uppsala Univ. (Sweden). Dept. of Cell and Molecular Biology, Lab. of Molecular Biophysics; Seibert, M. Marvin [Uppsala Univ. (Sweden). Dept. of Cell and Molecular Biology, Lab. of Molecular Biophysics; Andreasson, Jakob [Uppsala Univ. (Sweden). Dept. of Cell and Molecular Biology, Lab. of Molecular Biophysics; Rocker, Andrea [Uppsala Univ. (Sweden). Dept. of Cell and Molecular Biology, Lab. of Molecular Biophysics; Jönsson, Olof [Uppsala Univ. (Sweden). Dept. of Cell and Molecular Biology, Lab. of Molecular Biophysics; Svenda, Martin [Uppsala Univ. (Sweden). Dept. of Cell and Molecular Biology, Lab. of Molecular Biophysics; Holton, James M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS); Marchesini, Stefano [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS); Neutze, Richard [Univ. of Gothenburg (Sweden). Dept. of Chemistry, Biochemistry and Biophysics; Schorb, Sebastian [Technische Univ. Berlin (Germany). Inst. fur Optik und Atomare Physik (IOAP); Rupp, Daniela [Technische Univ. Berlin (Germany). Inst. fur Optik und Atomare Physik (IOAP); Adolph, Marcus [Technische Univ. Berlin (Germany). Inst. fur Optik und Atomare Physik (IOAP); Gorkhover, Tais [Technische Univ. Berlin (Germany). Inst. fur Optik und Atomare Physik (IOAP); Andersson, Inger [Swedish Univ. of Agricultural Sciences, Uppsala Biomedical Centre, Uppsala, (Sweden). Dept. of Molecular Biology; Barthelmess, Miriam [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Photon Science; Bajt, Saša [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Photon Science; Hirsemann, Helmut [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Photon Science; Potdevin, Guillaume [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Photon Science; Graafsma, Heinz [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Photon Science; Nilsson, Björn [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Photon Science

    2011-02-03

    X-ray crystallography provides the vast majority of macromolecular structures, but the success of the method relies on growing crystals of sufficient size. In conventional measurements, the necessary increase in X-ray dose to record data from crystals that are too small leads to extensive damage before a diffraction signal can be recorded. It is particularly challenging to obtain large, well-diffracting crystals of membrane proteins, for which fewer than 300 unique structures have been determined despite their importance in all living cells. Here we present a method for structure determination where single-crystal X-ray diffraction ‘snapshots’ are collected from a fully hydrated stream of nanocrystals using femtosecond pulses from a hard-X-ray free-electron laser, the Linac Coherent Light Source. We prove this concept with nanocrystals of photosystem I, one of the largest membrane protein complexes. More than 3,000,000 diffraction patterns were collected in this study, and a three-dimensional data set was assembled from individual photosystem I nanocrystals (~200 nm to 2 μm in size). We mitigate the problem of radiation damage in crystallography by using pulses briefer than the timescale of most damage processes. This offers a new approach to structure determination of macromolecules that do not yield crystals of sufficient size for studies using conventional radiation sources or are particularly sensitive to radiation damage.

  20. Giantically blue-shifted visible light in femtosecond mid-IR filament in fluorides.

    Science.gov (United States)

    Dormidonov, A E; Kompanets, V O; Chekalin, S V; Kandidov, V P

    2015-11-01

    A giant blue shift (more than 3000 nm) of an isolated visible band of supercontinuum was discovered and studied in the single filament regime of Mid-IR femtosecond laser pulse at powers slightly exceeding critical power for self-focusing in fluorides. At the pulse central wavelength increasing from 3000 nm to 3800 nm the spectral maximum of the visible band is shifted from 570 nm and 520 nm up to 400 nm and 330 nm for BaF(2) and CaF(2), respectively, its spectral width (FWHM) being reduced from 50 - 70 nm to 14 nm. It is shown that the formation of this narrow visible wing is a result of the interference of the supercontinuum components in the anomalous group velocity dispersion regime. PMID:26561190