WorldWideScience

Sample records for average power femtosecond

  1. Industry-grade high average power femtosecond light source

    Science.gov (United States)

    Heckl, O. H.; Weiler, S.; Fleischhaker, R.; Gebs, R.; Budnicki, A.; Wolf, M.; Kleinbauer, J.; Russ, S.; Kumkar, M.; Sutter, D. H.

    2014-03-01

    Ultrashort pulses are capable of processing practically any material with negligible heat affected zone. Typical pulse durations for industrial applications are situated in the low picosecond-regime. Pulse durations of 5 ps or below are a well established compromise between the electron-phonon interaction time of most materials and the need for pulses long enough to suppress detrimental effects such as nonlinear interaction with the ablated plasma plume. However, sub-picosecond pulses can further increase the ablation efficiency for certain materials, depending on the available average power, pulse energy and peak fluence. Based on the well established TruMicro 5000 platform (first release in 2007, third generation in 2011) an Yb:YAG disk amplifier in combination with a broadband seed laser was used to scale the output power for industrial femtosecond-light sources: We report on a subpicosecond amplifier that delivers a maximum of 160 W of average output power at pulse durations of 750 fs. Optimizing the system for maximum peak power allowed for pulse energies of 850 μJ at pulse durations of 650 fs. Based on this study and the approved design of the TruMicro 5000 product-series, industrygrade, high average power femtosecond-light sources are now available for 24/7 operation. Since their release in May 2013 we were able to increase the average output power of the TruMicro 5000 FemtoEdition from 40 W to 80 W while maintaining pulse durations around 800 fs. First studies on metals reveal a drastic increase of processing speed for some micro processing applications.

  2. 275 W average output power from a femtosecond thin disk oscillator operated in a vacuum environment.

    Science.gov (United States)

    Saraceno, Clara J; Emaury, Florian; Heckl, Oliver H; Baer, Cyrill R E; Hoffmann, Martin; Schriber, Cinia; Golling, Matthias; Südmeyer, Thomas; Keller, Ursula

    2012-10-01

    We present an ultrafast thin disk laser that generates an average output power of 275 W, which is higher than any other modelocked laser oscillator. It is based on the gain material Yb:YAG and operates at a pulse duration of 583 fs and a repetition rate of 16.3 MHz resulting in a pulse energy of 16.9 μJ and a peak power of 25.6 MW. A SESAM designed for high damage threshold initiated and stabilized soliton modelocking. We reduced the nonlinearity of the atmosphere inside the cavity by several orders of magnitude by operating the oscillator in a vacuum environment. Thus soliton modelocking was achieved at moderate amounts of self-phase modulation and negative group delay dispersion. Our approach opens a new avenue for power scaling femtosecond oscillators to the kW level. PMID:23188316

  3. 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

  4. Femtosecond Innoslab amplifier with 300W average power and pulse energies in the mJ-regime

    Science.gov (United States)

    Mans, T.; Graf, R.; Dolkemeyer, J.; Schnitzler, C.

    2014-02-01

    We demonstrate a femtosecond Yb:YAG InnoSlab laser amplifier producing powers High energy and high average power could be obtained with the use of chirped pulse amplification on the power amplifier end. The laser setup consists of a seed laser with 10mW average power at pulse repetition rates of 100kHz to 1MHz, a pre-amplifier stage, a highpower InnoSlab-amplifier stage and a grating based pulse compressor. This laser source is suited for pumping of OPCPA setups und parallelisation of applications in materials processing.

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

    OpenAIRE

    He, F.; Price, J.H.V.; Malinowski, A.; Piper, A.; Ibsen, M.; Richardson, D.J.; 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.

  6. 275 W average output power from a femtosecond thin disk oscillator operated in a vacuum environment

    OpenAIRE

    Clara J. Saraceno; Emaury, Florian; Heckl, Oliver H.; Baer, Cyrill R. E.; Hoffmann, Martin; Schriber, Cinia; Golling, Matthias; Südmeyer, Thomas; Keller, Ursula

    2012-01-01

    We present an ultrafast thin disk laser that generates an average output power of 275 W, which is higher than any other modelocked laser oscillator. It is based on the gain material Yb:YAG and operates at a pulse duration of 583 fs and a repetition rate of 16.3 MHz resulting in a pulse energy of 16.9 µJ and a peak power of 25.6 MW. A SESAM designed for high damage threshold initiated and stabilized soliton modelocking. We reduced the nonlinearity of the atmosphere inside the cavity by several...

  7. 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...

  8. Investigation of the thermally induced laser beam distortion associated with vacuum compressor gratings in high energy and high average power femtosecond laser systems

    OpenAIRE

    Fourmaux, S.; Serbanescu, C.; Lecherbourg, L; S. Payeur; Martin, F.; Kieffer, J.C.

    2009-01-01

    We report successful compensation of the thermally induced laser beam distortion associated with high energy 110 mJ and high average power femtosecond laser system of 11 Watts operated with vacuum compressor gratings. To enhance laser-based light source brightness requires development of laser systems with higher energy and higher average power. Managing the high thermal loading on vacuum optical components is a key issue in the implementation of this approach. To our knowledge this is the fi...

  9. Femtosecond pulses at 50-W average power from an Yb:YAG planar waveguide amplifier seeded by an Yb:KYW oscillator.

    Science.gov (United States)

    Leburn, Christopher G; Ramírez-Corral, Cristtel Y; Thomson, Ian J; Hall, Denis R; Baker, Howard J; Reid, Derryck T

    2012-07-30

    We report the demonstration of a high-power single-side-pumped Yb:YAG planar waveguide amplifier seeded by an Yb:KYW femtosecond laser. Five passes through the amplifier yielded 700-fs pulses with average powers of 50 W at 1030 nm. A numerical simulation of the amplifier implied values for the laser transition saturation intensity, the small-signal intensity gain coefficient and the gain bandwidth of 10.0 kW cm(-2), 1.6 cm(-1), and 3.7 nm respectively, and identified gain-narrowing as the dominant pulse-shaping mechanism. PMID:23038288

  10. Nonlinear femtosecond pulse compression at high average power levels by use of a large-mode-area holey fiber.

    Science.gov (United States)

    Südmeyer, T; Brunner, F; Innerhofer, E; Paschotta, R; Furusawa, K; Baggett, J C; Monro, T M; Richardson, D J; Keller, U

    2003-10-15

    We demonstrate that nonlinear fiber compression is possible at unprecedented average power levels by use of a large-mode-area holey (microstructured) fiber and a passively mode-locked thin disk Yb:YAG laser operating at 1030 nm. We broaden the optical spectrum of the 810-fs pump pulses by nonlinear propagation in the fiber and remove the resultant chirp with a dispersive prism pair to achieve 18 W of average power in 33-fs pulses with a peak power of 12 MW and a repetition rate of 34 MHz. The output beam is nearly diffraction limited and is linearly polarized. PMID:14587786

  11. 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 ...

  12. Production of high power femtosecond terahertz radiation

    Science.gov (United States)

    Neil, George R.; Carr, G. L.; Gubeli, Joseph F.; Jordan, K.; Martin, Michael C.; McKinney, Wayne R.; Shinn, Michelle; Tani, Masahiko; Williams, G. P.; Zhang, X.-C.

    2003-07-01

    The terahertz (THz) region of the electromagnetic spectrum is attracting interest for a broad range of applications ranging from diagnosing electron beams to biological imaging. Most sources of short pulse THz radiation utilize excitation of biased semiconductors or electro-optic crystals by high peak power lasers. For example, this was done by using an un-doped InAs wafer irradiated by a femtosecond free-electron laser (FEL) at the Thomas Jefferson National Accelerator Facility. Microwatt levels of THz radiation were detected when excited with FEL pulses at 1.06 μm wavelength and 10 W average power. Recently substantially higher powers of femtosecond THz pulses produced by synchrotron emission were extracted from the electron beamline. Calculations and measurements confirm the production of coherent broadband THz radiation from relativistic electrons with an average power of nearly 20 W, a world record in this wavelength range by a factor of 10,000. We describe the source, presenting theoretical calculations and their experimental verification. Potential applications of this exciting new source include driving new non-linear phenomena, performing pump-probe studies of dynamical properties of novel materials, and studying molecular vibrations and rotations, low frequency protein motions, phonons, superconductor bandgaps, electronic scattering, collective electronic excitations (e.g., charge density waves), and spintronics.

  13. 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

  14. 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

  15. High-average-power lasers

    International Nuclear Information System (INIS)

    The goals of the High-Average-Power Laser Program at LLNL are to develop a broad technology base for solid state lasers and to demonstrate high-average-power laser operation with more efficiency and higher beam quality than has been possible with current technology. Major activities are the zig-zag laser testbed and the gas-cooled-slab laser test bed. This section describes these activities as well as discussion of material development; nonlinear optics; laser materials, and applications

  16. 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.

  17. 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 $T$.

  18. 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

  19. 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.

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

    OpenAIRE

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

    2014-01-01

    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.

  1. High-Average Power Facilities

    Energy Technology Data Exchange (ETDEWEB)

    Dowell, David H.; /SLAC; Power, John G.; /Argonne

    2012-09-05

    There has been significant progress in the development of high-power facilities in recent years yet major challenges remain. The task of WG4 was to identify which facilities were capable of addressing the outstanding R&D issues presently preventing high-power operation. To this end, information from each of the facilities represented at the workshop was tabulated and the results are presented herein. A brief description of the major challenges is given, but the detailed elaboration can be found in the other three working group summaries.

  2. High average power induction accelerators

    International Nuclear Information System (INIS)

    The induction accelerator is discussed with respect to general background and concept, beam transport, scaling, pulse power technology, and the electron beam injector. A discussion of the factors which affect the scaling of the intensity of the beam is given. Limiting factors include collective forces in the beam, virtual cathode formation, surroundings, and beam breakup instability. 24 refs., 11 figs

  3. High Average Power Yb:YAG Laser

    Energy Technology Data Exchange (ETDEWEB)

    Zapata, L E; Beach, R J; Payne, S A

    2001-05-23

    We are working on a composite thin-disk laser design that can be scaled as a source of high brightness laser power for tactical engagement and other high average power applications. The key component is a diffusion-bonded composite comprising a thin gain-medium and thicker cladding that is strikingly robust and resolves prior difficulties with high average power pumping/cooling and the rejection of amplified spontaneous emission (ASE). In contrast to high power rods or slabs, the one-dimensional nature of the cooling geometry and the edge-pump geometry scale gracefully to very high average power. The crucial design ideas have been verified experimentally. Progress this last year included: extraction with high beam quality using a telescopic resonator, a heterogeneous thin film coating prescription that meets the unusual requirements demanded by this laser architecture, thermal management with our first generation cooler. Progress was also made in design of a second-generation laser.

  4. High average-power induction linacs

    International Nuclear Information System (INIS)

    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

  5. 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

  6. 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

  7. High average power laser for EUV lithography

    Energy Technology Data Exchange (ETDEWEB)

    Kania, D.R.; Gaines, D.P.; Hermann, M.; Honig, J.; Hostetler, R.; Levesque, R.; Sommargren, G.E.; Spitzer, R.C.; Vernon, S.P.

    1995-01-19

    We have demonstrated the operation of a high average power, all solid state laser and target system for EUV lithography. The laser operates at 1.06 {mu}m with a pulse repetition rate of 200 Hz. Each pulse contains up to 400 mJ of energy and is less than 10 ns in duration. The ELTV conversion efficiency measured with the laser is independent of the laser repetition rate. Operating at 200 Hz, the laser has been used for lithography using a 3 bounce Kohler illuminator.

  8. High average power solid state laser power conditioning system

    International Nuclear Information System (INIS)

    The power conditioning system for the High Average Power Laser program at Lawrence Livermore National Laboratory (LLNL) is described. The system has been operational for two years. It is high voltage, high power, fault protected, and solid state. The power conditioning system drives flashlamps that pump solid state lasers. Flashlamps are driven by silicon control rectifier (SCR) switched, resonant charged, (LC) discharge pulse forming networks (PFNs). The system uses fiber optics for control and diagnostics. Energy and thermal diagnostics are monitored by computers

  9. 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...

  10. 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.

  11. High-average-power solid state lasers

    International Nuclear Information System (INIS)

    In 1987, a broad-based, aggressive R ampersand D program aimed at developing the technologies necessary to make possible the use of solid state lasers that are capable of delivering medium- to high-average power in new and demanding applications. Efforts were focused along the following major lines: development of laser and nonlinear optical materials, and of coatings for parasitic suppression and evanescent wave control; development of computational design tools; verification of computational models on thoroughly instrumented test beds; and applications of selected aspects of this technology to specific missions. In the laser materials areas, efforts were directed towards producing strong, low-loss laser glasses and large, high quality garnet crystals. The crystal program consisted of computational and experimental efforts aimed at understanding the physics, thermodynamics, and chemistry of large garnet crystal growth. The laser experimental efforts were directed at understanding thermally induced wave front aberrations in zig-zag slabs, understanding fluid mechanics, heat transfer, and optical interactions in gas-cooled slabs, and conducting critical test-bed experiments with various electro-optic switch geometries. 113 refs., 99 figs., 18 tabs

  12. 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

  13. 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.

  14. 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...

  15. 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.

  16. 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.

  17. 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.

  18. 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....

  19. 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.

  20. High average power diode pumped solid state lasers for CALIOPE

    International Nuclear Information System (INIS)

    Diode pumping of solid state media offers the opportunity for very low maintenance, high efficiency, and compact laser systems. For remote sensing, such lasers may be used to pump tunable non-linear sources, or if tunable themselves, act directly or through harmonic crystals as the probe. The needs of long range remote sensing missions require laser performance in the several watts to kilowatts range. At these power performance levels, more advanced thermal management technologies are required for the diode pumps. The solid state laser design must now address a variety of issues arising from the thermal loads, including fracture limits, induced lensing and aberrations, induced birefringence, and laser cavity optical component performance degradation with average power loading. In order to highlight the design trade-offs involved in addressing the above issues, a variety of existing average power laser systems are briefly described. Included are two systems based on Spectra Diode Laboratory's water impingement cooled diode packages: a two times diffraction limited, 200 watt average power, 200 Hz multi-rod laser/amplifier by Fibertek, and TRW's 100 watt, 100 Hz, phase conjugated amplifier. The authors also present two laser systems built at Lawrence Livermore National Laboratory (LLNL) based on their more aggressive diode bar cooling package, which uses microchannel cooler technology capable of 100% duty factor operation. They then present the design of LLNL's first generation OPO pump laser for remote sensing. This system is specified to run at 100 Hz, 20 nsec pulses each with 300 mJ, less than two times diffraction limited, and with a stable single longitudinal mode. The performance of the first testbed version will be presented. The authors conclude with directions their group is pursuing to advance average power lasers. This includes average power electro-optics, low heat load lasing media, and heat capacity lasers

  1. High-average-power diode-pumped Yb: YAG lasers

    International Nuclear Information System (INIS)

    A scaleable diode end-pumping technology for high-average-power slab and rod lasers has been under development for the past several years at Lawrence Livermore National Laboratory (LLNL). This technology has particular application to high average power Yb:YAG lasers that utilize a rod configured gain element. Previously, this rod configured approach has achieved average output powers in a single 5 cm long by 2 mm diameter Yb:YAG rod of 430 W cw and 280 W q-switched. High beam quality (M(sup 2)= 2.4) q-switched operation has also been demonstrated at over 180 W of average output power. More recently, using a dual rod configuration consisting of two, 5 cm long by 2 mm diameter laser rods with birefringence compensation, we have achieved 1080 W of cw output with an M(sup 2) value of 13.5 at an optical-to-optical conversion efficiency of 27.5%. With the same dual rod laser operated in a q-switched mode, we have also demonstrated 532 W of average power with an M(sup 2) and lt; 2.5 at 17% optical-to-optical conversion efficiency. These q-switched results were obtained at a 10 kHz repetition rate and resulted in 77 nsec pulse durations. These improved levels of operational performance have been achieved as a result of technology advancements made in several areas that will be covered in this manuscript. These enhancements to our architecture include: (1) Hollow lens ducts that enable the use of advanced cavity architectures permitting birefringence compensation and the ability to run in large aperture-filling near-diffraction-limited modes. (2) Compound laser rods with flanged-nonabsorbing-endcaps fabricated by diffusion bonding. (3) Techniques for suppressing amplified spontaneous emission (ASE) and parasitics in the polished barrel rods

  2. High-average-power diode-pumped Yb: YAG lasers

    Energy Technology Data Exchange (ETDEWEB)

    Avizonis, P V; Beach, R; Bibeau, C M; Emanuel, M A; Harris, D G; Honea, E C; Monroe, R S; Payne, S A; Skidmore, J A; Sutton, S B

    1999-10-01

    A scaleable diode end-pumping technology for high-average-power slab and rod lasers has been under development for the past several years at Lawrence Livermore National Laboratory (LLNL). This technology has particular application to high average power Yb:YAG lasers that utilize a rod configured gain element. Previously, this rod configured approach has achieved average output powers in a single 5 cm long by 2 mm diameter Yb:YAG rod of 430 W cw and 280 W q-switched. High beam quality (M{sup 2} = 2.4) q-switched operation has also been demonstrated at over 180 W of average output power. More recently, using a dual rod configuration consisting of two, 5 cm long by 2 mm diameter laser rods with birefringence compensation, we have achieved 1080 W of cw output with an M{sup 2} value of 13.5 at an optical-to-optical conversion efficiency of 27.5%. With the same dual rod laser operated in a q-switched mode, we have also demonstrated 532 W of average power with an M{sup 2} < 2.5 at 17% optical-to-optical conversion efficiency. These q-switched results were obtained at a 10 kHz repetition rate and resulted in 77 nsec pulse durations. These improved levels of operational performance have been achieved as a result of technology advancements made in several areas that will be covered in this manuscript. These enhancements to our architecture include: (1) Hollow lens ducts that enable the use of advanced cavity architectures permitting birefringence compensation and the ability to run in large aperture-filling near-diffraction-limited modes. (2) Compound laser rods with flanged-nonabsorbing-endcaps fabricated by diffusion bonding. (3) Techniques for suppressing amplified spontaneous emission (ASE) and parasitics in the polished barrel rods.

  3. 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.

  4. 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

  5. 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

  6. An Advanced Time Averaging Modelling Technique for Power Electronic Circuits

    Science.gov (United States)

    Jankuloski, Goce

    For stable and efficient performance of power converters, a good mathematical model is needed. This thesis presents a new modelling technique for DC/DC and DC/AC Pulse Width Modulated (PWM) converters. The new model is more accurate than the existing modelling techniques such as State Space Averaging (SSA) and Discrete Time Modelling. Unlike the SSA model, the new modelling technique, the Advanced Time Averaging Model (ATAM) includes the averaging dynamics of the converter's output. In addition to offering enhanced model accuracy, application of linearization techniques to the ATAM enables the use of conventional linear control design tools. A controller design application demonstrates that a controller designed based on the ATAM outperforms one designed using the ubiquitous SSA model. Unlike the SSA model, ATAM for DC/AC augments the system's dynamics with the dynamics needed for subcycle fundamental contribution (SFC) calculation. This allows for controller design that is based on an exact model.

  7. Gas cooled disk amplifier approach to solid state average power

    International Nuclear Information System (INIS)

    Disk amplifiers have been used on almost all solid state laser systems of high energy, and, in principle, one simply has to cool the device to operate it at average power. To achieve the desired waste heat removal, gas is flowed across the disk surface. The authors show the basic gas flow geometry. They computationally and experimentally characterize the flow and its optical implications over regimes which far exceed the envisioned operating requirements of a working amplifier

  8. 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.

  9. Nonlinear femtosecond pump-probe spectroscopy using a power-encoded soliton delay line.

    Science.gov (United States)

    Saint-Jalm, Sarah; Andresen, Esben Ravn; Bendahmane, Abdelkrim; Kudlinski, Alexandre; Rigneault, Hervé

    2016-01-01

    We show femtosecond time-resolved nonlinear pump-probe spectroscopy using a fiber soliton as the probe pulse. Furthermore, we exploit soliton dynamics to record an entire transient trace with a power-encoded delay sweep. The power-encoded delay line takes advantage of the dependency of the soliton trajectory in the (λ,z) space upon input power; the difference in accumulated group delay between trajectories converts a fast power sweep into a fast delay sweep. We demonstrate the concept by performing transient absorption spectroscopy in a test sample and validate it against a conventional pump-probe setup. PMID:26696172

  10. Yb:YAG single crystal fiber power amplifier for femtosecond sources.

    Science.gov (United States)

    Délen, Xavier; Zaouter, Yoann; Martial, Igor; Aubry, Nicolas; Didierjean, Julien; Hönninger, Clemens; Mottay, Eric; Balembois, François; Georges, Patrick

    2013-01-15

    We demonstrate a versatile femtosecond power amplifier using a Yb:YAG single crystal fiber operating from 10 kHz to 10 MHz. For a total pump power of 75 W, up to 30 W is generated from the double-pass power amplifier. At a repetition rate of 10 kHz, an output energy of 1 mJ is obtained after recompression. In this configuration, the pulse duration is 380 fs, corresponding to a peak power of 2.2 GW. The M2 beam quality factor is better than 1.1 for investigated parameters. PMID:23454931

  11. Yb:YAG single crystal fiber power amplifier for femtosecond sources

    OpenAIRE

    Délen, Xavier; Zaouter, Yoann; Martial, Igor; Aubry, Nicolas; Didierjean, Julien; Hönninger, Clemens; Mottay, Eric; Balembois, François; Georges, Patrick

    2013-01-01

    We demonstrate a versatile femtosecond power amplifier using a Yb:YAG single crystal fiber operating from 10 kHz to 10 MHz. For a total pump power of 75 W, up to 30 W is generated from the double-pass power amplifier. At a repetition rate of 10 kHz, an output energy of 1 mJ is obtained after recompression. In this configuration, the pulse duration is 380 fs, corresponding to a peak power of 2.2 GW. The M2 beam quality factor is better than 1.1 for investigated parameters.

  12. 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

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. Correlation of average scaling coefficient with asymmetric parameter and average power index with quadrupole deformation parameter

    International Nuclear Information System (INIS)

    The nuclear structure of even-even nuclei in ground state band and other excited bands with non zero band head is collectively built. The level energy in medium mass region deviates below the ideal rotor energy formula EI = AI(I+1). The average scaling coefficient with asymmetric parameter and bAV rises for Er-Os nuclei when N increases from 88 to 104

  20. 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

  1. Third-generation femtosecond technology

    OpenAIRE

    Fattahi, Hanieh

    2015-01-01

    Chirped pulse amplification in solid-state lasers is currently the method of choice for producing high-energy ultrashort pulses, having surpassed the performance of dye lasers over 20 years ago. The third generation of femtosecond technology based on short-pulse-pumped optical parametric chirped pulse amplification (OPCPA) holds promise for providing few-cycle pulses with terawatt-scale peak powers and kilowatt-scale-average powers simultaneously, heralding the next wave of ...

  2. 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

  3. 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

  4. Development of High Average Power Lasers for the Photon Collider

    Energy Technology Data Exchange (ETDEWEB)

    Gronberg, Jeff; /LLNL, Livermore; Stuart, Brent; /LLNL, Livermore; Seryi, Andrei; /SLAC

    2012-07-05

    The laser and optics system for the photon collider seeks to minimize the required laser power by using an optical stacking cavity to recirculate the laser light. An enhancement of between 300 to 400 is desired. In order to achieve this the laser pulses which drive the cavity must precisely match the phase of the pulse circulating within the cavity. We report on simulations of the performance of a stacking cavity to various variations of the drive laser in order to specify the required tolerances of the laser system.

  5. Stand-off detection and classification of CBRNe using a Lidar system based on a high power femtosecond laser

    Science.gov (United States)

    Izawa, Jun; Yokozawa, Takeshi; Kurata, Takao; Yoshida, Akihiro; Mastunaga, Yasushi; Somekawa, Toshihiro; Eto, Shuzo; Manago, Naohiro; Horisawa, Hideyuki; Yamaguchi, Shigeru; Fujii, Takashi; Kuze, Hiroaki

    2014-10-01

    We propose a stand-off system that enables detection and classification of CBRNe (Chemical, Biological, Radioactive, Nuclear aerosol and explosive solids). The system is an integrated lidar using a high-power (terawatt) femtosecond laser. The detection and classification of various hazardous targets with stand-off distances from several hundred meters to a few kilometers are achieved by means of laser-induced breakdown spectroscopy (LIBS) and two-photon fluorescence (TPF) techniques. In this work, we report on the technical considerations on the system design of the present hybrid lidar system consisting of a nanosecond laser and a femtosecond laser. Also, we describe the current progress in our laboratory experiments that have demonstrated the stand-off detection and classification of various simulants. For the R and N detection scheme, cesium chloride aerosols have successfully been detected by LIBS using a high-power femtosecond laser. For the B detection scheme, TPF signals of organic aerosols such as riboflavin have clearly been recorded. In addition, a compact femtosecond laser has been employed for the LIBS classification of organic plastics employed as e-simulants.

  6. Development of High Average Power Lasers for the Photon Collider

    Energy Technology Data Exchange (ETDEWEB)

    Gronberg, J; Stuart, B; Seryi, A

    2010-05-17

    The laser and optics system for the photon collider seeks to minimize the required laser power by using an optical stacking cavity to recirculate the laser light. An enhancement of between 300 to 400 is desired. In order to achieve this the laser pulses which drive the cavity must precisely match the phase of the pulse circulating within the cavity. We report on simulations of the performance of a stacking cavity to various variations of the drive laser in order to specify the required tolerances of the laser system. We look at the behavior of a simple four mirror cavity as shown in Fig. 1. As a unit input pulse is applied to the coupling mirror a pulse begins to build up in the interior of the cavity. If the drive pulses and the interior pulse arrive at the coupling mirror in phase the interior pulse will build up to a larger value. The achievable enhancement is a strong function of the reflectivity of the cavities. The best performance if attained when the reflectivities of the input coupler is matched to the internal reflectivities of the cavity. In Fig. 2 we show the build up of the internal pulse after a certain number of drive pulses, assuming the input coupler has a reflectivity of 0.996 and the interior mirrors have 0.998 reflectivity. With these parameters the cavity will reach an enhancement factor of 450. Reducing the coupler reflectivity gives a faster cavity loading rate but with a reduced enhancement of the internal pulse. The enhancement as a function of coupler reflectivity and total internal cavity reflectivity is shown in Fig. 3. The best enhancement is achieved when the coupling mirror is matched to the reflectivity of the cavity. A coupler reflectivity just below the internal cavity reflectivity minimizes the required laser power.

  7. 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)

  8. 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.

  9. 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)

  10. Demonstration of a 10 kW average power 94 GHz gyroklystron amplifier

    Science.gov (United States)

    Blank, M.; Danly, B. G.; Levush, B.; Calame, J. P.; Nguyen, K.; Pershing, D.; Petillo, J.; Hargreaves, T. A.; True, R. B.; Theiss, A. J.; Good, G. R.; Felch, K.; James, B. G.; Borchard, P.; Cahalan, P.; Chu, T. S.; Jory, H.; Lawson, W. G.; Antonsen, T. M.

    1999-12-01

    The experimental demonstration of a high average power W-band (75-110 GHz) gyroklystron amplifier is reported. The gyroklystron has produced 118 AW peak output power and 29.5% electronic efficiency in the TE011 mode using a 66.7 kV, 6 A electron beam at 0.2% rf duty factor. At this operating point, the instantaneous full width at half-maximum (FWHM) bandwidth is 600 MHz. At 11% rf duty factor, the gyroklystron has produced up to 10.1 kW average power at 33% electronic efficiency with a 66 kV, 4.15 A electron beam. This represents world record performance for an amplifier at this frequency. At the 10.1 kW average power operating point, the FWHM bandwidth is 420 MHz. At higher magnetic fields and lower beam voltages, larger bandwidths can be achieved at the expense of peak and average output power.

  11. 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.

  12. Improved performance of high average power semiconductor arrays for applications in diode pumped solid state lasers

    International Nuclear Information System (INIS)

    The average power performance capability of semiconductor diode laser arrays has improved dramatically over the past several years. These performance improvements, combined with cost reductions pursued by LLNL and others in the fabrication and packaging of diode lasers, have continued to reduce the price per average watt of laser diode radiation. Presently, we are at the point where the manufacturers of commercial high average power solid state laser systems used in material processing applications can now seriously consider the replacement of their flashlamp pumps with laser diode pump sources. Additionally, a low cost technique developed and demonstrated at LLNL for optically conditioning the output radiation of diode laser arrays has enabled a new and scalable average power diode-end-pumping architecture that can be simply implemented in diode pumped solid state laser systems (DPSSL's). This development allows the high average power DPSSL designer to look beyond the Nd ion for the first time. Along with high average power DPSSL's which are appropriate for material processing applications, low and intermediate average power DPSSL's are now realizable at low enough costs to be attractive for use in many medical, electronic, and lithographic applications

  13. 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...

  14. 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.

  15. 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

  16. High average power picoseconds fiber amplifier with 20 μm core YDF

    International Nuclear Information System (INIS)

    In this letter we report a simple single-stage amplifier realized as high as 62 W average power output at 1064 nm wavelength, 40 picoseconds pulse width and 80 MHz repetition from 0.7 W seed laser based on backward pumped master-oscillator fiber power amplifier (MOPA) system. It is can stable operation in 57.6 W output for hours. We applied a semiconductor saturable absorber mirror (SESAM) passive mode-lock Nd:YVO4 oscillator as seed source and 6m long 20 μm core double-cladding Yb-doped fiber (YDF) as gain medium. To the best of our knowledge, 62 W average power is the highest output of single-stage ps-pulse amplifier with 20 μm-core fiber. None amplified spontaneous emission (ASE) and stimulated Raman scattering (SRS) nonlinear phenomenon was observed in 57.6 W high average power output

  17. 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

  18. New design of a high-power femtosecond 800-nm laser

    International Nuclear Information System (INIS)

    A new simple design of a femtosecond laser is proposed, which consists of a 1550-nm erbium-doped fibre laser, a fibre stretcher, a BBO crystal parametric amplifier converting the input radiation to the 800-nm radiation, a Ti:sapphire or a BBO amplifier, and a diffraction grating compressor. (lasers)

  19. A high average power single-stage picosecond double-clad fiber amplifier

    International Nuclear Information System (INIS)

    In this paper, we report 38.8 W average power output through a single-stage fiber amplifier, with emission of 1064 nm wavelength with 80 MHz repetition and 35 ps pulse width amplified from a 2.15 W SESAM passively mode-locked Nd:YVO4 laser oscillator. The high power fiber amplification is through a coupled 60.8 W 976 nm backward unidirectional pump power into a 2 m long 30/250 μm Yb-doped inner cladding. No obvious nonlinear effects arise in the high power output. To our knowledge this is the highest average power output with 2 m 30/250 μm Yb-doped double-clad fiber in a single-stage picosecond fiber amplifier. (paper)

  20. 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.

  1. High-power wavelength-tunable photonic-crystal-fiber-based oscillator-amplifier-frequency-shifter femtosecond laser system and its applications for material microprocessing

    International Nuclear Information System (INIS)

    A high-power wavelength-tunable femtosecond fiber laser source is developed based on photonic-crystal fiber technology. Laser oscillator and amplifier stages in this system employ diode-pumped ytterbium-doped single-polarization large-mode-area photonic-crystal fibers in a stretcher-free configuration, delivering laser pulses with an average power of 10.4 W, a pulse width of 52 fs, and a peak power of 4 MW at a repetition rate of 50 MHz after pulse compression. Nonlinear transformation of such laser pulses in a highly nonlinear photonic-crystal fiber yields light pulses smoothly tunable within the range of wavelengths from 1.0 to 1.4 μm and allows the generation of supercontinuum stretching from 450 to at least 1750 nm. We report experiments on silicon microprocessing and chromium nanofilm patterning at a high repetition rate, demonstrating the potential of the developed fiber-laser source for fast micromachining, microfabrication, and microprocessing

  2. 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.

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

    Science.gov (United States)

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

    2013-09-01

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

  4. Diode-Pumped High Energy and High Average Power All-Solid-State Picosecond Amplifier Systems

    OpenAIRE

    Jiaxing Liu; Wei Wang; Zhaohua Wang; Zhiguo Lv; Zhiyuan Zhang; Zhiyi Wei

    2015-01-01

    We present our research on the high energy picosecond laser operating at a repetition rate of 1 kHz and the high average power picosecond laser running at 100 kHz based on bulk Nd-doped crystals. With diode-pumped solid state (DPSS) hybrid amplifiers consisting of a picosecond oscillator, a regenerative amplifier, end-pumped single-pass amplifiers, and a side-pumped amplifier, an output energy of 64.8 mJ at a repetition rate of 1 kHz was achieved. An average power of 37.5 W at a repetition ra...

  5. 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.

  6. 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.

  7. Diode-Pumped High Energy and High Average Power All-Solid-State Picosecond Amplifier Systems

    Directory of Open Access Journals (Sweden)

    Jiaxing Liu

    2015-12-01

    Full Text Available We present our research on the high energy picosecond laser operating at a repetition rate of 1 kHz and the high average power picosecond laser running at 100 kHz based on bulk Nd-doped crystals. With diode-pumped solid state (DPSS hybrid amplifiers consisting of a picosecond oscillator, a regenerative amplifier, end-pumped single-pass amplifiers, and a side-pumped amplifier, an output energy of 64.8 mJ at a repetition rate of 1 kHz was achieved. An average power of 37.5 W at a repetition rate of 100 kHz pumped by continuous wave laser diodes was obtained. Compact, stable and high power DPSS laser amplifier systems with good beam qualities are excellent picosecond sources for high power optical parametric chirped pulse amplification (OPCPA and high-efficiency laser processing.

  8. 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.

  9. 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.

  10. Simulation of performance of wavefront correction using deformable mirror in high-average-power laser systems

    Czech Academy of Sciences Publication Activity Database

    Pilař, Jan; Divoký, Martin; Sikocinski, Pawel; Kmetík, V.; Slezák, Ondřej; Lucianetti, Antonio; Bonora, S.; Mocek, Tomáš

    Bellingham: SPIE, 2013 - (Hein, J.; Korn, G.; Silva, L.), s. 878011. (Proceedings of SPIE. 8780). ISBN 978-0-8194-9582-2. ISSN 0277-786X. [High-Power, High-Energy, and High-Intensity Laser Technology; and Research Using Extreme Light - Entering New Frontiers with Petawatt-Class Lasers. Praha (CZ), 15.04.2013-17.04.2013] Institutional support: RVO:68378271 Keywords : high-average-power laser * adaptive optics * deformable mirror * wavefront correction Subject RIV: BH - Optics, Masers, Lasers

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  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. LD pumped Yb:YAG regenerative amplifier for high average power short-pulse generation

    International Nuclear Information System (INIS)

    A diode pumped Yb:YAG regenerative amplifier has been developed for short pulse generation. High gain and efficient cooling characteristics were achieved in the laser gain module using a thin square-rod laser structure. Average output power of 10 W was realized at a pulse repetition rate of 100 kHz with 6.2 ps pulse width

  18. 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.

  19. 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.

  20. 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 <8 %. And under the action of micropore alkaline zeolites, the average power fell by 20 % after the laser continuing working 100 s at repetition frequency of 50 Hz.

  1. 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...

  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. Measurement of the absorption of nonlinear crystals used for high-average-power frequency doubling

    Science.gov (United States)

    Mann, Guido; Seidel, Stefan

    1997-07-01

    The absorption coefficients of nonlinear crystals for fundamental and second harmonic wave are of great importance for high average power second harmonic generation. A practical method to measure low absorption coefficients for high average power second harmonic generation. A practical method to measure low absorption coefficients is to use an interferometric laser calorimeter with high power lasers. Therefore Q-switched Nd:YAG laser systems with intracavity second harmonic generation are used. The measurements are made with optical powers up to 300 W and 45 W, respectively. Because of the high power, the resolution limit for the absorption coefficients is 0.001 percent/cm. The absorption coefficients of KTP and LBO crystals of different manufacturers are determined. The results are used for a numerical model which takes into account the decrease of conversion efficiency due to thermal effects caused by the absorption of laser power in the nonlinear crystal. This model describes saturation effects which appear in the range of 100 W in the green using a KTP crystal. A new idea for compensation of thermal effects will be presented.

  4. 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.

  5. A novel Generalized State-Space Averaging (GSSA) model for advanced aircraft electric power systems

    International Nuclear Information System (INIS)

    Highlights: • A study model is developed for aircraft electric power systems. • A novel GSSA model is developed for the interconnected power grid. • The system’s dynamics are characterized under various conditions. • The averaged results are compared and verified with the actual model. • The obtained measured values are validated with available aircraft standards. - Abstract: The growing complexity of Advanced Aircraft Electric Power Systems (AAEPS) has made conventional state-space averaging models inadequate for systems analysis and characterization. This paper presents a novel Generalized State-Space Averaging (GSSA) model for the system analysis, control and characterization of AAEPS. The primary objective of this paper is to introduce a mathematically elegant and computationally simple model to copy the AAEPS behavior at the critical nodes of the electric grid. Also, to reduce some or all of the drawbacks (complexity, cost, simulation time…, etc) associated with sensor-based monitoring and computer aided design software simulations popularly used for AAEPS characterization. It is shown in this paper that the GSSA approach overcomes the limitations of the conventional state-space averaging method, which fails to predict the behavior of AC signals in a circuit analysis. Unlike conventional averaging method, the GSSA model presented in this paper includes both DC and AC components. This would capture the key dynamic and steady-state characteristics of the aircraft electric systems. The developed model is then examined for the aircraft system’s visualization and accuracy of computation under different loading scenarios. Through several case studies, the applicability and effectiveness of the GSSA method is verified by comparing to the actual real-time simulation model obtained from Powersim 9 (PSIM9) software environment. The simulations results represent voltage, current and load power at the major nodes of the AAEPS. It has been demonstrated that

  6. 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.

  7. 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.

  8. Pulsed operation of a high average power Yb:YAG thin-disk multipass amplifier.

    Science.gov (United States)

    Schulz, M; Riedel, R; Willner, A; Düsterer, S; Prandolini, M J; Feldhaus, J; Faatz, B; Rossbach, J; Drescher, M; Tavella, F

    2012-02-27

    An Yb:YAG thin-disk multipass laser amplifier system was developed operating in a 10 Hz burst operation mode with 800 µs burst duration and 100 kHz intra-burst repetition rate. Methods for the suppression of parasitic amplified spontaneous emission are presented. The average output pulse energy is up to 44.5 mJ and 820 fs compressed pulse duration. The average power of 4.45 kW during the burst is the highest reported for this type of amplifier. PMID:22418308

  9. Generation of coherent attosecond pulses from a nano-tube array illuminated by a high-power femtosecond laser

    International Nuclear Information System (INIS)

    A method to generate an isolated single-cycle attosecond pulse from the interaction of a high-power femtosecond laser pulse with a nano-tube array is demonstrated using a two-dimensional relativistic particle-in-cell simulation. The radiation mechanism is relativistic nonlinear Thomson scattering from the electrons in a target material. Coherent radiation is emitted in the direction of specular reflection for the incident laser pulse while the electrons make a bunch size smaller than a wavelength of the laser pulse. Maintaining the coherence of the radiation from the electrons is essential to get an intense attosecond duration, which is achieved by using a nano-tube array target and a sharply increasing laser pulse. Optimal conditions for attosecond pulse generation are investigated by parameter scanning over plasma density, target thickness and laser pulse duration. (paper)

  10. Reasons for above average operating results at Beznau and Muehleberg nuclear power stations

    International Nuclear Information System (INIS)

    The operational performance of a nuclear power station is determined by the interaction of many different factors. Consequently no simple or plausible reasons can be quoted for the above average operating results of the first three Swiss nucelar power plants, Beznau I, Beznau II und Muehleberg. Various points, which, according to the opinion of the author, have the greatest influence on the operating results, are indicated. Theses aspects include quality of plant, design features, qualifications and trainung of personnel, organization, operational management, maintenance planning, applicability of the state of technology and supervision by the authorities. (orig.)

  11. Composite Thin-Disk Laser Scaleable to 100 kW Average Power Output and Beyond

    Energy Technology Data Exchange (ETDEWEB)

    Zapata, L.; Beach, R.; Payne, S.

    2000-06-01

    By combining newly developed technologies to engineer composite laser components with state of the art diode laser pump delivery technologies, we are in a position to demonstrate high beam quality, continuous wave, laser radiation at scaleable high average powers. The crucial issues of our composite thin disk laser technology were demonstrated during a successful first light effort. The high continuous wave power levels that are now within reach make this system of high interest to future DoD initiatives in solid-state laser technology for the laser weapon arena.

  12. 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.

  13. 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.

  14. 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.

  15. 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...

  16. Use of induction linacs with nonlinear magnetic drive as high average power accelerators

    International Nuclear Information System (INIS)

    The marriage of induction linac technology with Nonlinear Magnetic Modulators has produced some unique capabilities. It appears possible to produce electron beams with average currents measured in amperes, at gradients exceeding 1 Mev/meter, and with power efficiencies approaching 50%. A 2 MeV, 5 kA electron accelerator is under construction at Lawrence Livermore National Laboratory (LLNL) to allow us to demonstrate some of these concepts. Progress on this project is reported here

  17. 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

  18. 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

  19. Femtosecond laser 3D micromachining: a powerful tool for the fabrication of microfluidic, optofluidic, and electrofluidic devices based on glass.

    Science.gov (United States)

    Sugioka, Koji; Xu, Jian; Wu, Dong; Hanada, Yasutaka; Wang, Zhongke; Cheng, Ya; Midorikawa, Katsumi

    2014-09-21

    Femtosecond lasers have unique characteristics of ultrashort pulse width and extremely high peak intensity; however, one of the most important features of femtosecond laser processing is that strong absorption can be induced only at the focus position inside transparent materials due to nonlinear multiphoton absorption. This exclusive feature makes it possible to directly fabricate three-dimensional (3D) microfluidic devices in glass microchips by two methods: 3D internal modification using direct femtosecond laser writing followed by chemical wet etching (femtosecond laser-assisted etching, FLAE) and direct ablation of glass in water (water-assisted femtosecond laser drilling, WAFLD). Direct femtosecond laser writing also enables the integration of micromechanical, microelectronic, and microoptical components into the 3D microfluidic devices without stacking or bonding substrates. This paper gives a comprehensive review on the state-of-the-art femtosecond laser 3D micromachining for the fabrication of microfluidic, optofluidic, and electrofluidic devices. A new strategy (hybrid femtosecond laser processing) is also presented, in which FLAE is combined with femtosecond laser two-photon polymerization to realize a new type of biochip termed the ship-in-a-bottle biochip. PMID:25012238

  20. An efficient erbium doped phosphate laser glass for high average power pumping

    International Nuclear Information System (INIS)

    An efficient Er-doped phosphate laser glass CrE5 designed for high average power pumping laser operating at 1540 nm, especially for eye-safe laser surgery, was developed. This glass possesses high thermal shock resistance and excellent laser properties. The CrE5 glass can withstand 1.6 times more flashlamp pump power than ordinary phosphate glass. The ion-exchange surface strengthened glass can further endure >45% more pump power. Laser slope efficiency of 1.71% and output energy of 3.03 J were achieved at 1 Hz. The calculated laser output energy density was 15.4 J/cm2. The laser output energy was only limited by the available pump energy in this work, and not by the thermal damage of the laser glass.

  1. 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.)

  2. 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).

  3. 100 Hz repetition rate, high average power, plasma-based soft x-ray lasers

    Science.gov (United States)

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

    2013-10-01

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

  4. 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.

  5. 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.

  6. Femtosecond oscillator on Yb:KYW crystal pumped by laser diode with fiber output

    Science.gov (United States)

    Kim, G. H.; Kang, U.; Heo, D.; Yashin, V. E.; Kulik, A. V.; Sall', E. G.; Chizhov, S. A.

    2010-05-01

    A femtosecond laser based on an Yb:KYW crystal with direct longitudinal pumping by a high-power semiconductor injection laser with a fiber output is described. Femtosecond pulses were generated in the self-longitudinal-mode-locking operating condition due to the use of a semiconductor saturable absorber. The average power of the oscillator was as high as 3.5 W at a central wavelength of 1035 nm, the pulse length and pulse repetition rate being 200 fs and 85.5 MHz, respectively. The product of the pulse length and the radiation spectrum width was 1.3 times higher than the theoretical limit for the pulse shape described by the function sech2. The designed master oscillator can be also used as a stand-alone source of femtosecond radiation pulses for material microprocessing and primary source for femtosecond laser amplification systems.

  7. 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...

  8. The influence of seat configuration on maximal average crank power during pedaling: a simulation study.

    Science.gov (United States)

    Rankin, Jeffery W; Neptune, Richard R

    2010-11-01

    Manipulating seat configuration (i.e., seat tube angle, seat height and pelvic orientation) alters the bicycle-rider geometry, which influences lower extremity muscle kinematics and ultimately muscle force and power generation during pedaling. Previous studies have sought to identify the optimal configuration, but isolating the effects of specific variables on rider performance from the confounding effect of rider adaptation makes such studies challenging. Of particular interest is the influence of seat tube angle on rider performance, as seat tube angle varies across riding disciplines (e.g., road racers vs. triathletes). The goals of the current study were to use muscle-actuated forward dynamics simulations of pedaling to 1) identify the overall optimal seat configuration that produces maximum crank power and 2) systematically vary seat tube angle to assess how it influences maximum crank power. The simulations showed that a seat height of 0.76 m (or 102% greater than trochanter height), seat tube angle of 85.1 deg, and pelvic orientation of 20.5 deg placed the major power-producing muscles on more favorable regions of the intrinsic force-length-velocity relationships to generate a maximum average crank power of 981 W. However, seat tube angle had little influence on crank power, with maximal values varying at most by 1% across a wide range of seat tube angles (65 to 110 deg). The similar power values across the wide range of seat tube angles were the result of nearly identical joint kinematics, which occurred using a similar optimal seat height and pelvic orientation while systematically shifting the pedal angle with increasing seat tube angles. PMID:21245509

  9. Full Rank Solutions for the MIMO Gaussian Wiretap Channel With an Average Power Constraint

    Science.gov (United States)

    Fakoorian, S. Ali. A.; Swindlehurst, A. Lee

    2013-05-01

    This paper considers a multiple-input multiple-output (MIMO) Gaussian wiretap channel model, where there exists a transmitter, a legitimate receiver and an eavesdropper, each equipped with multiple antennas. In this paper, we first revisit the rank property of the optimal input covariance matrix that achieves the secrecy capacity of the multiple antenna MIMO Gaussian wiretap channel under the average power constraint. Next, we obtain necessary and sufficient conditions on the MIMO wiretap channel parameters such that the optimal input covariance matrix is full-rank, and we fully characterize the resulting covariance matrix as well. Numerical results are presented to illustrate the proposed theoretical findings.

  10. 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.

  11. 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.

  12. 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.)

  13. Development of high-average-power-laser medium based on silica glass

    International Nuclear Information System (INIS)

    We have developed a high-average-power laser material based on silica glass. A new method using Zeolite X is effective for homogeneously dispersing rare earth ions in silica glass to get a high quantum yield. High quality medium, which is bubbleless and quite low refractive index distortion, must be required for realization of laser action, and therefore, we have carefully to treat the gelation and sintering processes, such as, selection of colloidal silica, pH value of for hydrolysis of tetraethylorthosilicate, and sintering history. The quality of the sintered sample and the applications are discussed. (author)

  14. 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.

  15. Cryogenic Yb:YAG composite-thin-disk for high energy and average power amplifiers

    OpenAIRE

    Zapata, Luis E.; Lin, Hua; Calendron, Anne-Laure; Cankaya, Huseyin; Hemmer, Michael; Reichert, Fabian; Huang, W. Ronny; Granados, Eduardo; Hong, Kyung-Han; Kärtner, Franz X.

    2015-01-01

    A cryogenic composite-thin-disk amplifier with amplified spontaneous emission (ASE) rejection is implemented that overcomes traditional laser system problems in high-energy pulsed laser drivers of high average power. A small signal gain of 8 dB was compared to a 1.5 dB gain for an uncapped thin-disk without ASE mitigation under identical pumping conditions. A strict image relayed 12-pass architecture using an off-axis vacuum telescope and polarization switching extracted 100 mJ at 250 Hz in h...

  16. 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)

  17. 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.

  18. 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...

  19. The ETA-II induction linac as a high-average-power FEL driver

    Science.gov (United States)

    Nexsen, W. E.; Atkinson, D. P.; Barrett, D. M.; Chen, Y.-J.; Clark, J. C.; Griffith, L. V.; Kirbie, H. C.; Newton, M. A.; Paul, A. C.; Sampayan, S.; Throop, A. L.; Turner, W. C.

    1990-10-01

    The Experimental Test Accelerator II (ETA-II) is the first induction linac designed specifically to FEL requirements. It is primarily intended to demonstrate induction accelerator technology for high-average-power, high-brightness electron beams, and will be used to drive a 140 and 250 GHz microwave FEL for plasma heating experiments in the Microwave Tokamak Experiment (MTX) at LLNL. Its features include high-vacuum design which allows the use of an intrinsically bright dispenser cathode, induction cells designed to minimize BBU growth rate, and careful attention to magnetic alignment to minimize radial sweep due to beam corkscrew. The use of magnetic switches allows high-average-power operation. At present ETA-II is being used to drive 140 GHz plasma heating experiments. These experiments require nominal beam parameters of 6 MeV energy, 2 kA current, 20 ns pulse width and a brightness of 1 × 108 A/(m rad)2 at the wiggler with a pulse repetition frequency (prf) of 0.5 Hz. Future 250 GHz experiments require beam parameters of 10 MeV energy, 3 kA current, 50 ns pulse width and a brightness of 1 × 108 A/(m rad)2 with a 5 kHz prf for 0.5 s. In this paper we discuss the present status of ETA-II parameters and the phased development program necessary to satisfy these future requirements.

  20. 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.

  1. The relevance of averaging period to wind power measurements and efficiency of Wind Energy Conversion Systems (WECS)

    Science.gov (United States)

    Mengelkamp, H. T.

    The 10 min averages of wind speed, wind speed cubed, and power output are used for the determination of power curves and power coefficient of wind energy conversion systems and turbulence intensity. It is shown that the turbulent part of the air flow at the Pellworm (Germany) test field contains 16% of the mean flow energy. Neglecting the turbulent part in determining the power coefficient or power curve leads to an error in the calculation of the mean energy output at locations with a different turbulence intensity. Averaging the third power of the instantaneous wind speed is recommended.

  2. 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.

  3. A picosecond thin-rod Yb:YAG regenerative laser amplifier with the high average power of 20 W

    International Nuclear Information System (INIS)

    A high-average-power, laser-diode-pumped, picosecond-pulse regenerative amplifier was developed using the thin-rod Yb:YAG (yttrium aluminum garnet) laser architecture. This architecture has a complete set of favorable properties for the cost-effective, high-average-power, and high-peak-power lasers. These include low amplified spontaneous emission with high gain and high repetition rate. For the amplifier system, an average output power of 20 W was achieved at a pulse repetition rate of 100 kHz, which corresponds to an output pulse energy of 200 μJ with an output pulse width of 2 ps. (letter)

  4. A picosecond thin-rod Yb:YAG regenerative laser amplifier with the high average power of 20 W

    Science.gov (United States)

    Matsubara, S.; Tanaka, M.; Takama, M.; Hitotsuya, H.; Kobayashi, T.; Kawato, S.

    2013-05-01

    A high-average-power, laser-diode-pumped, picosecond-pulse regenerative amplifier was developed using the thin-rod Yb:YAG (yttrium aluminum garnet) laser architecture. This architecture has a complete set of favorable properties for the cost-effective, high-average-power, and high-peak-power lasers. These include low amplified spontaneous emission with high gain and high repetition rate. For the amplifier system, an average output power of 20 W was achieved at a pulse repetition rate of 100 kHz, which corresponds to an output pulse energy of 200 μJ with an output pulse width of 2 ps.

  5. Development of linear proton accelerators with the high average beam power

    CERN Document Server

    Bomko, V A; Egorov, A M

    2001-01-01

    Review of the current situation in the development of powerful linear proton accelerators carried out in many countries is given. The purpose of their creation is solving problems of safe and efficient nuclear energetics on a basis of the accelerator-reactor complex. In this case a proton beam with the energy up to 1 GeV, the average current of 30 mA is required. At the same time there is a needed in more powerful beams,for example, for production of tritium and transmutation of nuclear waste products. The creation of accelerators of such a power will be followed by the construction of linear accelerators of 1 GeV but with a more moderate beam current. They are intended for investigation of many aspects of neutron physics and neutron engineering. Problems in the creation of efficient constructions for the basic and auxiliary equipment, the reliability of the systems, and minimization of the beam losses in the process of acceleration will be solved.

  6. Design and component specifications for high average power laser optical systems

    International Nuclear Information System (INIS)

    Laser imaging and transport systems are considered in the regime where laser-induced damage and/or thermal distortion have significant design implications. System design and component specifications are discussed and quantified in terms of the net system transport efficiency and phase budget. Optical substrate materials, figure, surface roughness, coatings, and sizing are considered in the context of visible and near-ir optical systems that have been developed at Lawrence Livermore National Laboratory for laser isotope separation applications. In specific examples of general applicability, details of the bulk and/or surface absorption, peak and/or average power damage threshold, coating characteristics and function, substrate properties, or environmental factors will be shown to drive the component size, placement, and shape in high-power systems. To avoid overstressing commercial fabrication capabilities or component design specifications, procedures will be discussed for compensating for aberration buildup, using a few carefully placed adjustable mirrors. By coupling an aggressive measurements program on substrates and coatings to the design effort, an effective technique has been established to project high-power system performance realistically and, in the process, drive technology developments to improve performance or lower cost in large-scale laser optical systems. 13 refs

  7. Design and component specifications for high average power laser optical systems

    Energy Technology Data Exchange (ETDEWEB)

    O' Neil, R.W.; Sawicki, R.H.; Johnson, S.A.; Sweatt, W.C.

    1987-01-01

    Laser imaging and transport systems are considered in the regime where laser-induced damage and/or thermal distortion have significant design implications. System design and component specifications are discussed and quantified in terms of the net system transport efficiency and phase budget. Optical substrate materials, figure, surface roughness, coatings, and sizing are considered in the context of visible and near-ir optical systems that have been developed at Lawrence Livermore National Laboratory for laser isotope separation applications. In specific examples of general applicability, details of the bulk and/or surface absorption, peak and/or average power damage threshold, coating characteristics and function, substrate properties, or environmental factors will be shown to drive the component size, placement, and shape in high-power systems. To avoid overstressing commercial fabrication capabilities or component design specifications, procedures will be discussed for compensating for aberration buildup, using a few carefully placed adjustable mirrors. By coupling an aggressive measurements program on substrates and coatings to the design effort, an effective technique has been established to project high-power system performance realistically and, in the process, drive technology developments to improve performance or lower cost in large-scale laser optical systems. 13 refs.

  8. 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.

  9. 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.

  10. Status of HiLASE project: High average power pulsed DPSSL systems for research and industry

    Science.gov (United States)

    Mocek, T.; Divoky, M.; Smrz, M.; Sawicka, M.; Chyla, M.; Sikocinski, P.; Vohnikova, H.; Severova, P.; Lucianetti, A.; Novak, J.; Rus, B.

    2013-11-01

    We introduce the Czech national R&D project HiLASE which focuses on strategic development of advanced high-repetition rate, diode pumped solid state laser (DPSSL) systems that may find use in research, high-tech industry and in the future European large-scale facilities such as HiPER and ELI. Within HiLASE we explore two major concepts: thin-disk and cryogenically cooled multislab amplifiers capable of delivering average output powers above 1 kW level in picosecond-to-nanosecond pulsed regime. In particular, we have started a programme of technology development to demonstrate the scalability of multislab concept up to the kJ level at repetition rate of 1-10 Hz.

  11. 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.

  12. Status of HiLASE project: High average power pulsed DPSSL systems for research and industry

    Directory of Open Access Journals (Sweden)

    Mocek T.

    2013-11-01

    Full Text Available We introduce the Czech national R&D project HiLASE which focuses on strategic development of advanced high-repetition rate, diode pumped solid state laser (DPSSL systems that may find use in research, high-tech industry and in the future European large-scale facilities such as HiPER and ELI. Within HiLASE we explore two major concepts: thin-disk and cryogenically cooled multislab amplifiers capable of delivering average output powers above 1 kW level in picosecond-to-nanosecond pulsed regime. In particular, we have started a programme of technology development to demonstrate the scalability of multislab concept up to the kJ level at repetition rate of 1–10 Hz.

  13. Status of HiLASE project: High average power pulsed DPSSL systems for research and industry

    International Nuclear Information System (INIS)

    We introduce the Czech national RandD project HiLASE which focuses on strategic development of advanced high-repetition rate, diode pumped solid state laser (DPSSL) systems that may find use in research, high-tech industry and in the future European large-scale facilities such as HiPER and ELI. Within HiLASE we explore two major concepts: thin-disk and cryogenically cooled multi-slab amplifiers capable of delivering average output powers above 1 kW level in picosecond-to-nanosecond pulsed regime. In particular, we have started a programme of technology development to demonstrate the scalability of multi-slab concept up to the kJ level at repetition rate of 1-10 Hz. (authors)

  14. Increases in the average power output of wave energy converters using quiescent period predictive control

    Energy Technology Data Exchange (ETDEWEB)

    Belmont, M.R. [Exeter Marine Dynamics Group, School of Engineering, Mathematics, Computer Science and Physics, North Part Rd., Exeter, Devon EX4 4QF (United Kingdom)

    2010-12-15

    The potential of controlling wave energy converters, (WEC), by deterministic prediction of large damaging waves is introduced and shown to offer very substantial increases in the annual average power output of such devices. Results obtained for idealised WEC models show that the potential exists for this increase to be at least a factor of two. Numerical simulations of actual dynamical models for both point absorbers and directionally sensitive devices employing practical control strategies show that most of this potential can actually be realised. The control of large scale wave farms using quiescent period predictive control is likely to be most cost effective using master/slave WEC systems. To achieve the computational savings that will allow this strategy analytic approximations are required for the response of WECs with time varying coefficients, preliminary forms of these have also been introduced. (author)

  15. 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.

  16. High average power CW FELs [Free Electron Laser] for application to plasma heating: Designs and experiments

    International Nuclear Information System (INIS)

    A short period wiggler (period ∼ 1 cm), sheet beam FEL has been proposed as a low-cost source of high average power (1 MW) millimeter-wave radiation for plasma heating and space-based radar applications. Recent calculation and experiments have confirmed the feasibility of this concept in such critical areas as rf wall heating, intercepted beam (''body'') current, and high voltage (0.5 - 1 MV) sheet beam generation and propagation. Results of preliminary low-gain sheet beam FEL oscillator experiments using a field emission diode and pulse line accelerator have verified that lasing occurs at the predicted FEL frequency. Measured start oscillation currents also appear consistent with theoretical estimates. Finally, we consider the possibilities of using a short-period, superconducting planar wiggler for improved beam confinement, as well as access to the high gain, strong pump Compton regime with its potential for highly efficient FEL operation

  17. 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.

  18. 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.

  19. 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

  20. 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)

  1. 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

  2. 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).

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Femtosecond mode-locked holmium fiber laser pumped by semiconductor disk laser.

    Science.gov (United States)

    Chamorovskiy, A; Marakulin, A V; Ranta, S; Tavast, M; Rautiainen, J; Leinonen, T; Kurkov, A S; Okhotnikov, O G

    2012-05-01

    We report on a 2085 nm holmium-doped silica fiber laser passively mode-locked by semiconductor saturable absorber mirror and carbon nanotube absorber. The laser, pumped by a 1.16 μm semiconductor disk laser, produces 890 femtosecond pulses with the average power of 46 mW and the repetition rate of 15.7 MHz. PMID:22555700

  10. 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.

  11. 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 ...

  12. 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.

  13. The Application of Cryogenic Laser Physics to the Development of High Average Power Ultra-Short Pulse Lasers

    OpenAIRE

    Brown, David C.; Sten Tornegård; Joseph Kolis; Colin McMillen; Cheryl Moore; Liurukara Sanjeewa; Christopher Hancock

    2016-01-01

    Ultrafast laser physics continues to advance at a rapid pace, driven primarily by the development of more powerful and sophisticated diode-pumping sources, the development of new laser materials, and new laser and amplification approaches such as optical parametric chirped-pulse amplification. The rapid development of high average power cryogenic laser sources seems likely to play a crucial role in realizing the long-sought goal of powerful ultrafast sources that offer concomitant high peak a...

  14. High-power femtosecond fiber-feedback optical parametric oscillator based on periodically poled stoichiometric LiTaO3.

    Science.gov (United States)

    Südmeyer, T; Innerhofer, E; Brunner, F; Paschotta, R; Usami, T; Ito, H; Kurimura, S; Kitamura, K; Hanna, D C; Keller, U

    2004-05-15

    We demonstrate a synchronously pumped high-gain optical parametric oscillator with feedback through a fiber, using a passively mode-locked Yb:YAG thin-disk laser as a pump source. We obtain as much as 19-W average signal power at a wavelength of 1.45 microm in 840-fs pulses and 7.8 W of idler power at 3.57 microm. The repetition rate of the pulses is 56 MHz, and the transverse beam quality of the generated signal is M2 < 1.6. PMID:15182002

  15. High sustained average power cw and ultrafast Yb:YAG near-diffraction-limited cryogenic solid-state laser.

    Science.gov (United States)

    Brown, David C; Singley, Joseph M; Kowalewski, Katie; Guelzow, James; Vitali, Victoria

    2010-11-22

    We report what we believe to be record performance for a high average power Yb:YAG cryogenic laser system with sustained output power. In a CW oscillator-single-pass amplifier configuration, 963 W of output power was measured. In a second configuration, a two amplifier Yb:YAG cryogenic system was driven with a fiber laser picosecond ultrafast oscillator at a 50 MHz repetition rate, double-passed through the first amplifier and single-passed through the second, resulting in 758 W of average power output. Pulses exiting the system have a FWHM pulsewidth of 12.4 ps, an energy/pulse of 15.2 μJ, and a peak power of 1.23 MW. Both systems are force convection-cooled with liquid nitrogen and have been demonstrated to run reliably over long time periods. PMID:21164825

  16. 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...

  17. 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.

  18. Development of an all-solid-state exciter for a high average-power TEA CO2 laser

    International Nuclear Information System (INIS)

    An all-solid-state exciter with a three-stage magnetic pulse compressor has been designed and constructed for a high repetition-rate transversely excited atmospheric CO2 laser. An average laser power of 1.5 kW was obtained at a repetition rate of 200 pps, with an overall efficiency of 7.3%. This is the first time that the average CO2 laser power of more than 1 kW has been demonstrated by an all-solid-state exciter. (author)

  19. 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.)

  20. Analysis of thermal effects of high average power Nd:YAG laser as a pump laser of wavelength tunable laser

    International Nuclear Information System (INIS)

    For AVLIS (Atomic Vapor Laser Isotope Separation), high average power frequency tunable laser is required to excite and ionize 235U. To realize such a tunable laser, a pump laser with high pulse repetition rate and high average power is inevitable. A copper vapor laser was thought to be a pump laser and had been developed. However, it is thought that all solid state Nd:YAG laser, pumped by laser diode array can reduce separation energy because of its high efficiency. And high average power Nd:YAG laser has been developing. In a laser crystal of such Nd:YAG laser, a part of pumping energy is converted to thermal energy, and thermal gradient is generated. As a result, thermal stress is caused and the effects of thermal lensing and depolarization of laser radiation are generated. These effects decrease output power and deteriorate laser beam quality. Therefore, analysis of thermal characteristics of laser crystal is carried out for laser crystals with the pulse repetition rate of around 2 kHz. As a result, a prospect of realizing high average power Nd:YAG is obtained. (author)

  1. 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.

  2. 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.

  3. 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.

  4. In-situ optical phase distortion measurement of Yb:YAG thin disk in high average power regenerative amplifier

    Czech Academy of Sciences Publication Activity Database

    Miura, Taisuke; Chyla, Michal; Smrž, Martin; Nagisetty, Siva S.; Severová, Patricie; Novák, Ondřej; Endo, Akira; Mocek, Tomáš

    Bellingham: SPIE, 2013 - (Dorsch, F.), s. 860303. (Proceedings of SPIE. 8603). ISBN 978-0-8194-9372-9. ISSN 0277-786X. [High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications II. San Francisco (US), 05.02.2013-07.02.2013] Institutional support: RVO:68378271 Keywords : thin disk laser * high energy * high average power * OPD measurement Subject RIV: BH - Optics, Masers, Lasers

  5. 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

  6. 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.

  7. 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.

  8. Femtosecond Laser--Pumped Source of Entangled Photons for Quantum Cryptography Applications

    International Nuclear Information System (INIS)

    We present an experimental setup for generation of entangled-photon pairs via spontaneous parametric down-conversion, based on the femtosecond-pulsed laser. Our entangled-photon source utilizes a 76-MHz-repetition-rate, 100-fs-pulse-width, mode-locked, ultrafast femtosecond laser, which can produce, on average, more photon pairs than a cw laser of an equal pump power. The resulting entangled pairs are counted by a pair of high-quantum-efficiency, single-photon, silicon avalanche photodiodes. Our apparatus s intended as an efficient source/receiver system for the quantum communications and quantum cryptography applications

  9. 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.

  10. Westinghouse seeks to resume gains in average availability [power plant performance

    International Nuclear Information System (INIS)

    After significant gains during the previous three years, the average availability of Westinghouse PWRs operating in the United States dropped from more than 77 per cent in 1985 to 71 per cent in 1986. The causes of unavailability of the PWRs are discussed. It is expected that the improvements in availability will resume. (U.K.)

  11. Averages in the electro-power stations and its influence on the high-pressure pipelines

    International Nuclear Information System (INIS)

    In the paper the problems connected with the influence of the emergency subsidence on the safety of the power units during exploitation are done. The problem is described on the real example. (authors)

  12. Different cooling configurations for a high average power longitudinally diode-pumped Yb:YAG amplifier.

    Science.gov (United States)

    Yu, Haiwu; Bourdet, Gilbert

    2006-08-20

    We analyze the temperature distribution in several Yb:YAG longitudinally pumped amplifier crystals by using various cooling configurations. The crystal designs are (i) a composite crystal made of a thin sheet of high-doped Yb:YAG bonded on a bulk piece of undoped YAG and (ii) a thick piece of low-doped Yb:YAG crystal. The cooling configurations investigated here include those both from the rear face or from the rear and side faces together. In every case we determine the average temperature rise, the longitudinal and radial temperature gradient, and the resulting crystal bending and optical phase distortion. We optimize the best cooling configuration and crystal design by compromising the average temperature, thermodeformation, and optical phase distortion. The experimental results also indicate that a thin sheet of gain medium (1.6 mm thick at 10 at. % doping) suffers from a notable bending deformation, which results in an unexpected decrease of the output energy. PMID:16892125

  13. Absorptance behavior of optical coatings for high-average-power laser applications

    International Nuclear Information System (INIS)

    A modified photothermal deformation technique is used to measure the absorptance behaviors of optical multilayered dielectric coatings for a high-power laser system. The surface thermal-lensing modification uses an enlarged probe beam to facilitate alignment of the laser beam and data acquisition. The coatings, both reflective and transmissive types, are made by a physical vapor-deposition process. Coating absorptances are observed to depend on the laser's exposure time and power density. Time-dependent absorptance defect models are proposed. Also, micrometer-sized sites of high absorptance and an area with physical damage can be found during the spatial scans. It is proposed that absorptance values reported for coatings in high-repetition-rate or cw-laser systems include time- and power-dependent behaviors in addition to other relevant irradiation parameters. (c) 2000 Optical Society of America

  14. 2-kW Average Power CW Phase-Conjugate Solid-State Laser

    OpenAIRE

    Zakharenkov, Yuri A.; Clatterbuck, Todd O.; Shkunov, Vladimir V.; Betin, Alexander A.; Filgas, David M.; Ostby, Eric P.; Strohkendl, Friederich P.; Rockwell, David A.; Baltimore, Robert S.

    2007-01-01

    We have demonstrated stable operation of a 2-kW Yb:YAG phase-conjugate master oscillator power amplifier (PC-MOPA) laser system with a loop phase-conjugate mirror (LPCM). This is the first demonstration of a continuous wave (CW)-input LPCM MOPA operating at a power greater than 1 kW with a nearly diffraction-limited output beam. The single-pass beam quality incident on the LPCM varied with the specific operating conditions, but it was typically ${sim}20$ times diffraction-limited (XDL). The m...

  15. 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

  16. 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%.

  17. 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.

  18. 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.

  19. 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.

  20. Current status on high average power and energy diode pumped solid state lasers

    International Nuclear Information System (INIS)

    With ongoing efforts in Europe, the United States, and Asia on power production through inertial fusion, intense work has been focused on proposing and studying Diode Pumped Solid State Lasers (DPSSLs). Such drivers should be able to deliver 1 to 10 kJ at a repetition rate in the 10-Hz range and a wall-plug efficient nearing 10%. Recent achievements will be presented with emphasis on 100 J-class prototypes, which are currently being built. (authors)

  1. 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...

  2. 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...

  3. 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.

  4. 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.

  5. Mode-locked Yb:YAG thin-disk oscillator with 41 µJ pulse energy at 145 W average infrared power and high power frequency conversion.

    Science.gov (United States)

    Bauer, Dominik; Zawischa, Ivo; Sutter, Dirk H; Killi, Alexander; Dekorsy, Thomas

    2012-04-23

    We demonstrate the generation of 1.1 ps pulses containing more than 41 µJ of energy directly out of an Yb:YAG thin-disk without any additional amplification stages. The laser oscillator operates in ambient atmosphere with a 3.5 MHz repetition rate and 145 W of average output power at a fundamental wavelength of 1030 nm. An average output power of 91.5 W at 515 nm was obtained by frequency doubling with a conversion efficiency exceeding 65%. Third harmonic generation resulted in 34 W at 343 nm at 34% efficiency. PMID:22535061

  6. Mode-locked Yb:YAG thin-disk oscillator with 41 µJ pulse energy at 145 W average infrared power and high power frequency conversion

    OpenAIRE

    Bauer, Dominik; Zawischa, Ivo; Sutter, Dirk H.; Killi, Alexander; Dekorsy, Thomas

    2012-01-01

    We demonstrate the generation of 1.1 ps pulses containing more than 41 µJ of energy directly out of an Yb:YAG thin-disk without any additional amplification stages. The laser oscillator operates in ambient atmosphere with a 3.5 MHz repetition rate and 145 W of average output power at a fundamental wavelength of 1030 nm. An average output power of 91.5 W at 515 nm was obtained by frequency doubling with a conversion efficiency exceeding 65%. Third harmonic generation resulted in 34 W at 343 nm...

  7. 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...

  8. 60-W average power in 810-fs pulses from a thin-disk Yb:YAG laser.

    Science.gov (United States)

    Innerhofer, E; Südmeyer, T; Brunner, F; Häring, R; Aschwanden, A; Paschotta, R; Hönninger, C; Kumkar, M; Keller, U

    2003-03-01

    We demonstrate a passively mode-locked diode-pumped thin-disk Yb:YAG laser generating 810-fs pulses at 1030 nm with as much as 60 W of average output power (without using an amplifier). At a pulse repetition rate of 34.3 MHz, the pulse energy is 1.75 microJ and the peak power is as high as 1.9 MW. The beam quality is close to the diffraction limit, with M2 < 1.1. PMID:12659446

  9. Spatial distribution of average charge state and deposition rate in high power impulse magnetron sputtering of copper

    OpenAIRE

    Horwat, David

    2008-01-01

    The spatial distribution of copper ions and atoms in high power impulse magnetron sputtering (HIPIMS) discharges was determined by (i) measuring the ion current to electrostatic probes and (ii) measuring the film thickness by profilometry. A set of electrostatic and collection probes were placed at different angular positions and distances from the target surface. The angular distribution of the deposition rate and the average charge state of the copper species (including ions and neutrals)...

  10. High-average-power, 100-Hz-repetition-rate, tabletop soft-x-ray lasers at sub-15-nm wavelengths

    Energy Technology Data Exchange (ETDEWEB)

    Reagan, Brendon [Colorado State University, Fort Collins; Berrill, Mark A [ORNL; Wernsing, Keith [Colorado State University, Fort Collins; Baumgarten, Cory [Colorado State University, Fort Collins; Woolston, Mark [Colorado State University, Fort Collins; Rocca, Jorge [Colorado State University, Fort Collins

    2014-01-01

    Efficient excitation of dense plasma columns at 100-Hz repetition rate using a tailored pump pulse profile produced a tabletop soft-x-ray laser average power of 0.1 mW at = 13.9 nm and 20 W at = 11.9 nm from transitions of Ni-like Ag and Ni-like Sn, respectively. Lasing on several other transitions with wavelengths between 10.9 and 14.7 nm was also obtained using 0.9-J pump pulses of 5-ps duration from a compact diode-pumped chirped pulse amplification Yb:YAG laser. Hydrodynamic and atomic plasma simulations show that the pump pulse profile, consisting of a nanosecond ramp followed by two peaks of picosecond duration, creates a plasma with an increased density of Ni-like ions at the time of peak temperature that results in a larger gain coefficient over a temporally and spatially enlarged space leading to a threefold increase in the soft-x-ray laser output pulse energy. The high average power of these compact soft-x-ray lasers will enable applications requiring high photon flux. These results open the path to milliwatt-average-power tabletop soft-x-ray lasers.

  11. High-average-power, 100-Hz-repetition-rate, tabletop soft-x-ray lasers at sub-15-nm wavelengths

    Science.gov (United States)

    Reagan, Brendan A.; Berrill, Mark; Wernsing, Keith A.; Baumgarten, Cory; Woolston, Mark; Rocca, Jorge J.

    2014-05-01

    Efficient excitation of dense plasma columns at 100-Hz repetition rate using a tailored pump pulse profile produced a tabletop soft-x-ray laser average power of 0.1 mW at λ = 13.9 nm and 20 μW at λ = 11.9 nm from transitions of Ni-like Ag and Ni-like Sn, respectively. Lasing on several other transitions with wavelengths between 10.9 and 14.7 nm was also obtained using 0.9-J pump pulses of 5-ps duration from a compact diode-pumped chirped pulse amplification Yb:YAG laser. Hydrodynamic and atomic plasma simulations show that the pump pulse profile, consisting of a nanosecond ramp followed by two peaks of picosecond duration, creates a plasma with an increased density of Ni-like ions at the time of peak temperature that results in a larger gain coefficient over a temporally and spatially enlarged space leading to a threefold increase in the soft-x-ray laser output pulse energy. The high average power of these compact soft-x-ray lasers will enable applications requiring high photon flux. These results open the path to milliwatt-average-power tabletop soft-x-ray lasers.

  12. Thin-disk multipass amplifier for ultrashort laser pulses with kilowatt average output power and mJ pulse energies

    Science.gov (United States)

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

    2014-05-01

    We report on a Yb:YAG thin-disk multipass amplifier for ultrashort laser pulses delivering an average output power of 1.1 kW which to the best of our knowledge is the highest output power reported from such a system so far. A modified commercial TruMicro5050 laser delivers the seed pulses with an average power of 80 W at a wavelength of 1030 nm, a pulse duration of 6.5 ps and a repetition rate of 800 kHz. These pulses are amplified to 1.38 mJ of pulse energy with a duration of 7.3 ps. To achieve this, we developed a scheme in which an array of 40 plane mirrors is used to geometrically fold the seed beam over the pumped thin-disk crystal. Exploiting the incoming linear polarization, an overall number of 40 double-passes through the disk was realized by using the backpath through the amplifier with the orthogonal linear polarization state. Thermal issues on the disk were mitigated by zero-phonon line pumping at a wavelength of 969 nm directly into the upper laser level and by employing a retroreflective mirror pair. The amplifier exhibits an optical efficiency of 44 % and a slope efficiency of 46 %. The beam quality was measured to be better than M2=1.25 at all power levels. As this system can deliver high pulse energies and high average output powers at the same time without the need of a CPA technique, it can be very suitable for high productivity material processing with ultrashort laser pulses.

  13. 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.

  14. 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

  15. 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

  16. Progress of high average power, short-pulse laser technology for the Compton X-ray source

    International Nuclear Information System (INIS)

    Recent progress is reported in the development of high average power, short-pulse laser technology, which is relevant toward achieving a high X-ray flux in a Compton X-ray source for use in various applications. The Yb-based laser material is suitable for high-pulse energy in a picosecond pulse length. The thin disc amplifier technology is now close to operating continuously with 1 J, 2 ps, at a 100 Hz repetition rate with a multi-pass amplification scheme. The average power is 100 W at a 1030 nm wavelength. The laser beam quality is fine enough to focus on the bunched electron beam from a photocathode/S-band linac single-pass accelerator and to generate an X-ray flux of 109 photons/s at 100 Hz. The short-pulse carbon dioxide (CO2) laser has an advantage for a Compton X-ray source in high X-ray flux applications. The short-pulse amplification of the CO2 laser pulse has been demonstrated, at a power level of more than 10 kW at a 100 kHz repetition rate in a single laser beam, for application in the plasma generation for an extreme ultraviolet light source, using a commercially available RF-pumped laser module. The pulse length is now limited to around 1 ns because of the bandwidth of the low-pressure gain medium. The additional pulse compression scheme makes a high average power, pulsed CO2 laser ideal for various applications of the Compton X-ray source.

  17. 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.

  18. 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.

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

    International Nuclear Information System (INIS)

    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

  20. Chirped-beam two-stage free-electron laser for high-power femtosecond x-ray pulse generation

    International Nuclear Information System (INIS)

    A method for generating femtosecond-duration x-ray pulses with a free-electron laser is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequency-chirped x-ray pulse by self-amplified spontaneous emission. A short temporal pulse is created by use of a monochromator to select a narrow radiation bandwidth. A second undulator is used to amplify the short-duration radiation. The radiation characteristics produced by a chirped-beam two-stage free-electron laser are calculated, and the performance of the chirped-beam two-stage option for the Linac Coherent Light Source is considered

  1. Optimal dynamic vibration absorber design for minimizing the band-averaged input power using the residue theorem

    Science.gov (United States)

    D`Amico, R.; Koo, K.; Claeys, C. C.; Pluymers, B.; Desmet, W.

    2015-03-01

    This paper deals with an efficient strategy to improve the vibro-acoustic behavior of a structure over frequency bands. Genetic Algorithms are used to identify the optimal resonance frequency and location of Dynamic Vibration Absorbers (DVAs) which minimize the band-averaged input power into a plate, leading to an indirect reduction of the radiated acoustic power and global vibration. Instead of classic numerical quadrature schemes, the residue theorem is used to evaluate the band-averaged input power. This results into a considerable reduction of computational effort, as it requires only few function evaluations at complex frequencies, regardless of the analyzed bandwidth. The structural response is simulated by using the Wave Based Method (WBM). Besides an increased convergence rate as compared to classical element-based techniques, the WBM is also free in determining the optimal position of the DVAs, not restricting it to nodal grid locations. Moreover, when point connections are taken into account, only a small part of the WB matrices needs to be recomputed at each iteration, resulting in a strong reduction of the computation time. Numerical examples illustrate the benefits and the efficiency of the proposed optimization strategy.

  2. 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.

  3. 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

  4. 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

  5. In-situ optical phase distortion measurement of Yb:YAG thin disk in high average power regenerative amplifier

    Science.gov (United States)

    Miura, Taisuke; Chyla, Michal; Smrž, Martin; Nagisetty, Siva Sankar; Severová, Patricie; Novák, Ondřej; Endo, Akira; Mocek, TomáÅ.¡

    2013-02-01

    We are developing one kilohertz picosecond Yb:YAG thin disk regenerative amplifier with 500-W average power for medical and industrial applications. In case of high energy pulse amplification, a large area mode matching in gain media, which is drastically degenerated by the optical phase distortion, is required to avoid optical damage. We designed in-situ thin disk deformation measurement based on the combination of a precise wavefront sensor and a single mode probe beam. In contrast to a conventional interferometric measurement, this measurement is compact, easy-to-align, and is less affected by mechanical vibrations.

  6. 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.

  7. 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. 

  8. Construction of a femtosecond laser microsurgery system

    OpenAIRE

    Steinmeyer, Joseph D; Gilleland, Cody L.; Pardo-Martin, Carlos; Angel, Matthew; Rohde, Christopher B.; Scott, Mark A.; Yanik, Mehmet Fatih

    2010-01-01

    Femtosecond laser microsurgery is a powerful method for studying cellular function, neural circuits, neuronal injury and neuronal regeneration because of its capability to selectively ablate sub-micron targets in vitro and in vivo with minimal damage to the surrounding tissue. Here, we present a step-by-step protocol for constructing a femtosecond laser microsurgery setup for use with a widely available compound fluorescence microscope. The protocol begins with the assembly and alignment of b...

  9. 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.

  10. Wavelength and average power density dependency of the recrystallization of tooth dentin using a MIR-FEL

    Science.gov (United States)

    Heya, Manabu; Awazu, Kunio

    2002-04-01

    Recrystallization of tooth dentin by the application of mid- infrared (MIR) pulsed-laser irradiation is one candidate for a novel, non-invasive treatment for the prevention of tooth decay. Recrystallized dentin functions in a similar way to dental enamel. To recrystallize the dentin effectively and non-invasively it is essential to estimate quantitatively and qualitatively the laser parameters, such as the wavelength and the average power density, required for recrystallization. The laser-tissue interaction is initiated effectively by selective excitation of phosphate acid ions (PO4) in the dentin. Using a tunable, MIR Free Electron Laser (FEL) in the wavelength region of 8.8- 10.6micrometers , corresponding to intense absorption bands due to PO4 vibration modes, we have investigated macroscopically extent of surface modification of dentin, and we have obtained experimental results related to the ablation depth, the MIR absorption spectrum, and the elemental chemical composition. From these results, it was found that (1) the laser parameters at which efficient surface modification, without enhanced ablation effects, occurred were estimated to be approximately in the wavelength and average power density regions of ~9.4- 10.3micrometers and ~10-20 W/cm2, and that (2) in this region PO4 vibration modes with lower binding energy were preferentially excluded from the dentin.

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

    Science.gov (United States)

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

    2014-03-01

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

  12. 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

  13. 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

  14. 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%.

  15. 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...

  16. 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.

  17. 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.

  18. Overview of the HiLASE project: high average power pulsed DPSSL systems for research and industry

    Czech Academy of Sciences Publication Activity Database

    Divoký, Martin; Smrž, Martin; Chyla, Michal; Sikocinski, Pawel; Severová, Patricie; Novák, Ondřej; Huynh, Jaroslav; Nagisetty, Siva S.; Miura, Taisuke; Pilař, Jan; Slezák, Jiří; Sawicka, Magdalena; Jambunathan, Venkatesan; Vanda, Jan; Endo, Akira; Lucianetti, Antonio; Rostohar, Danijela; Mason, P.D.; Phillips, P.J.; Ertel, K.; Banerjee, S.; Hernandez-Gomez, C.; Collier, J.L.; Mocek, Tomáš

    2014-01-01

    Roč. 2, SI (2014), s. 1-10. ISSN 2095-4719 R&D Projects: GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.20.0143; GA MŠk EE2.3.30.0057 Grant ostatní: HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143; OP VK 4 POSTDOK(XE) CZ.1.07/2.3.00/30.0057 Institutional support: RVO:68378271 Keywords : DPSSL * Yb3C:YAG * thin-disk * multi-slab * pulsed high average power laser Subject RIV: BH - Optics, Masers, Lasers

  19. 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.

  20. 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).

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

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, L.M.; Meena, Rakesh; Nangru, Subhash; Kant, Deepender; Pal, Debashis; Lamba, O.S.; Jindal, Vishnu; Jangid, Sushil Kumar, E-mail: joslm@rediffmail.com [Central Electronics Engineering Research Institute, Council of Scientific and Industrial Research, Pilani (India); Chakravarthy, D.P.; Dixit, Kavita [Bhabha Atomic Research Centre, Mumbai (India)

    2011-07-01

    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)

  2. 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)

  3. A high-average power tapered FEL amplifier at submillimeter frequencies using sheet electron beams and short-period wigglers

    International Nuclear Information System (INIS)

    A high-average-power FEL amplifier operating at submillimeter frequencies is under development at the University of Maryland. Program goals are to produce a CW, ∼1 MW, FEL amplifier source at frequencies between 280 GHz and 560 GHz. To this end, a high-gain, high-efficiency, tapered FEL amplifier using a sheet electron beam and a short-period (superconducting) wiggler has been chosen. Development of this amplifier is progressing in three stages: (1) beam propagation through a long length (∼1 m) of short period (λω = 1 cm) wiggler, (2) demonstration of a proof-of-principle amplifier experiment at 98 GHz, and (3) designs of a superconducting tapered FEL amplifier meeting the ultimate design goal specifications. 17 refs., 1 fig., 1 tab

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

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

    International Nuclear Information System (INIS)

    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

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. Femtosecond laser's application in the corneal surgery

    OpenAIRE

    Shu-Liang Wang; Zhi-Fang Qiu; Hong-Li Li; Qin Hu

    2015-01-01

    With the rapid development over the past two decades,femtosecond(10-15s)lasers(FS)has become a new application in ophthalmic surgery. As laser power is defined as energy delivered per unit time, decreasing the pulse duration to femtosecond level(100fs)not only increases the power delivered but also decreases the fluence threshold for laser induced optical breakdown. In ablating tissue, FS has an edge over nanosecond lasers as there is minimal collateral damage from shock waves and heat conduc...

  17. 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,...

  18. 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%.

  19. 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%

  20. 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.

  1. 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

  2. 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...

  3. 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...

  4. 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. PMID:25503011

  5. 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.

  6. Femtosecond Generation of Nano-Fibers

    Directory of Open Access Journals (Sweden)

    Richardson Martin

    2013-11-01

    Full Text Available A new approach to making extremely large aspect ratio glass nano-fibers with diameters typically 20 – 40 nm is described. The fabrication process utilizes a novel phenomenon occurring with the interaction of focused high power femtosecond laser radiation with transparent media.

  7. Diode-pumped Kerr-lens mode-locked femtosecond Yb:YAG ceramic laser

    Science.gov (United States)

    Zi-Ye, Gao; Jiang-Feng, Zhu; Ke, Wang; Jun-Li, Wang; Zhao-Hua, Wang; Zhi-Yi, Wei

    2016-02-01

    We experimentally demonstrated a diode-pumped Kerr-lens mode-locked femtosecond laser based on an Yb:YAG ceramic. Stable laser pulses with 97-fs duration, 2.8-nJ pulse energy, and 320-mW average power were obtained. The femtosecond oscillator operated at a central wavelength of 1049 nm and a repetition rate of 115 MHz. To the best of our knowledge, this is the first demonstration of a Kerr-lens mode-locked operation in a diode-pumped Yb:YAG ceramic laser with sub-100 fs pulse duration. Project supported by the National Major Scientific Instrument Development Project of China (Grant No. 2012YQ120047), the National Natural Science Foundation of China (Grant No. 61205130), and the Fundamental Research Funds for the Central Universities, China (Grant No. JB140502).

  8. Design and operation of high-energy and high-average-power diode-pumped single Nd:YAG amplifier with stimulated-Brillouin-scattering phase conjugate mirror

    International Nuclear Information System (INIS)

    We describe a compact laser-diode-pumped, phase conjugate Nd:YAG master oscillator power amplifier system with a reduced number of components in the single slab amplifier geometry. This system is readily suited for pumping a Ti:sapphire amplifier, making it possible to construct a compact, high-repetition-rate, terawatt-peak-power chirped-pulse amplification system. An average infrared power of 362 W at a repetition rate of 1 kHz in a 29 ns pulse has been produced with an optical-to-optical efficiency of 14%. With a KTiOPO4 frequency-doubling crystal, as average green output power of 132 W at a repetition rate of 1 kHz has also been generated when pumped at an input incident power of 222 W, corresponding to a second-harmonic energy conversion efficiency of 60%. The average power at both infrared and green wavelengths represents a record performance for a single-amplifier system. We discuss in detail the design, performance and operation of the system including output power, optical efficiency, beam quality and stability. (author)

  9. 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.

  10. 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.

  11. Towards a compact thin-disk-based femtosecond XUV source

    OpenAIRE

    Pronin, Oleg

    2012-01-01

    The goal of this thesis is to develop a compact high-power solid-state oscillator capable of superseding existing ultrafast technology based on low-power Ti:sapphire oscillators. Different applications such as extra- or intra-cavity XUV generation, seeding of high-energy low-repetition-rate amplifier systems and femtosecond enhancement cavities can be dramatically influenced by the availability of such a reliable, compact femtosecond source. We applied, for the first time, Kerr-lens mode-...

  12. 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.

  13. Design of a thin disk amplifier with extraction during pumping for high peak and average power Ti:Sa systems (EDP-TD).

    Science.gov (United States)

    Chvykov, Vladimir; Nagymihaly, Roland S; Cao, Huabao; Kalashnikov, Mikhail; Osvay, Karoly

    2016-02-22

    Combination of the scheme of extraction during pumping (EDP) and the Thin Disk (TD) technology is presented to overcome the limitations associated with thermal cooling of crystal and transverse amplified spontaneous emission in high average power laser systems based on Ti:Sa amplifiers. The optimized design of high repetition rate 1-10 PW Ti:Sapphire EDP-TD power amplifiers are discussed, including their thermal dynamic behavior. PMID:26907029

  14. 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).

  15. 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.

  16. 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

  17. Average Interest

    OpenAIRE

    George Chacko; Sanjiv Ranjan Das

    1997-01-01

    We develop analytic pricing models for options on averages by means of a state-space expansion method. These models augment the class of Asian options to markets where the underlying traded variable follows a mean-reverting process. The approach builds from the digital Asian option on the average and enables pricing of standard Asian calls and puts, caps and floors, as well as other exotica. The models may be used (i) to hedge long period interest rate risk cheaply, (ii) to hedge event risk (...

  18. 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...

  19. 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.

  20. 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.

  1. 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...

  2. 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 ...

  3. 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.

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

    International Nuclear Information System (INIS)

    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)

  5. 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)

  6. 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.

  7. 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.

  8. 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...

  9. 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

  10. 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)

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

    International Nuclear Information System (INIS)

    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 0.719.10-5 ampere to nuclear linear channel number 6 (a non-compensated ionization chamber). (author)

  12. Terbium gallium garnet ceramic-based Faraday isolator with compensation of thermally induced depolarization for high-energy pulsed lasers with kilowatt average power

    International Nuclear Information System (INIS)

    A scalable aperture Faraday isolator for high-energy pulsed lasers with kW-level average power was demonstrated using terbium gallium garnet ceramics with water cooling and compensation of thermally induced depolarization in a magnetic field. An isolation ratio of 35 dB (depolarization ratio γ of 3.4 × 10−4) was experimentally observed at a maximum laser power of 740 W. By using this result, we estimated that this isolator maintains an isolation ratio of 30 dB for laser powers of up to 2.7 kW. Our results provide the solution for achieving optical isolation in high-energy (100 J to kJ) laser systems with a repetition rate greater than 10 Hz

  13. 250  W average power, 100  kHz repetition rate cryogenic Yb:YAG amplifier for OPCPA pumping.

    Science.gov (United States)

    Zapata, L E; Reichert, F; Hemmer, M; Kärtner, F X

    2016-02-01

    A cryogenically cooled, bulk Yb:YAG, four-pass amplifier delivering up to 250 W average power at 100 kHz repetition rate is reported. The 2.5 mJ amplified optical pulses show a sub-20 ps duration before temporal compression and a spectrum supporting a transform-limited duration of 3.6 ps. The power instabilities were measured to be <0.5% rms over 30 min at full power, and the spatial intensity profile showed a flat-top distribution and near diffraction-limited beam quality. This compact amplifier is an ideal source for pumping either near-IR or mid-IR optical parametric chirped pulse amplifiers. PMID:26907405

  14. High-average-power (15-W) 255-nm source based on second-harmonic generation of a copper laser master oscillator power amplifier system in cesium lithium borate

    Science.gov (United States)

    Brown, Daniel J. W.; Withford, Michael J.

    2001-12-01

    We have generated 15 W of UV (255-nm) radiation with an optical conversion efficiency of 28% by frequency doubling the 510.6-nm output of a high-beam-quality, high-power copper laser system in cesium borate lithium (CLBO). We found that the superior performance of CLBO relative to β-barium borate is attributable largely to the small UV absorption and wide temperature acceptance bandwidth of CLBO, which reduces thermal dephasing during high-power UV generation.

  15. The ETA-II linear induction accelerator and IMP wiggler: A high-average-power millimeter-wave free-electron laser for plasma heating

    International Nuclear Information System (INIS)

    The authors have constructed a 140-GHz free-electron laser to generate high-average-power microwaves for heating the MTX tokamak plasma. A 5.5-m steady-state wiggler (Intense Microwave, Prototype-IMP) has been installed at the end of the upgraded 60-cell ETA-II accelerator, and is configured as an FEL amplifier for the output of a 140-GHz long-pulse gyrotron. Improvements in the ETA-II accelerator include a multicable-feed power distribution network, better magnetic alignment using a stretched-wire alignment technique (SWAT), and a computerized tuning algorithm that directly minimizes the transverse sweep (corkscrew motion) of the electron beam. The upgrades were first tested on the 20-cell, 3-MeV front end of ETA-II and resulted in greatly improved energy flatness and reduced corkscrew motion. The upgrades were then incorporated into the full 60-cell configuration of ETA-II, along with modifications to allow operation in 50-pulse bursts at pulse repetition frequencies up to 5 kHz. The pulse power modifications were developed and tested on the High Average Power Test Stand (HAPTS), and have significantly reduced the voltage and timing jitter of the MAG 1D magnetic pulse compressors. The 2-3 kA, 6-7 MeV beam from ETA-II is transported to the IMP wiggler, which has been reconfigured as a laced wiggler, with both permanent magnets and electromagnets, for high magnetic field operation. Tapering of the wiggler magnetic field is completely computer controlled and can be optimized based on the output power. The microwaves from the FEL are transmitted to the MTX tokamak by a windowless quasi-optical microwave transmission system. Experiments at MTX are focused on studies of electron-cyclotron-resonance heating (ECRH) of the plasma. The authors summarize here the accelerator and pulse power modifications, and describe the status of ETA-II, IMP, and MTX operations

  16. 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.

  17. 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.

  18. 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.

  19. 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。

  20. Femtosecond laser machining of electrospun membranes

    Science.gov (United States)

    Wu, Yiquan; Vorobyev, A. Y.; Clark, Robert L.; Guo, Chunlei

    2011-01-01

    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/cm2 is used to ablate holes in 100 μm thick PCL membranes. The machined holes have an average diameter of 436 μm and a center-to-center spacing of 1000 μm. 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.

  1. 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.

  2. 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

  3. 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.)

  4. Setting of scaling factors and average radioactivity concentration on container-filled and solidified waste packages generated from Kashiwazaki Kariwa Nuclear Power Plants Unit 1-5

    International Nuclear Information System (INIS)

    The report evaluates the appropriateness of the point of view addressed from Japan Nuclear Fuel Co., an enterprise in charge of radioactive waste disposal. The low-level radioactive wastes produced from Kashiwazaki Kariwa Power Plants Unit 1 - 5 as in container-filled and solidified packages in 200L drums were investigated for adequateness of using the same scaling factors and confirming the average radioactivity concentration of H-3, C-14, Co-60, Ni-59, Ni-63, Sr-90, Nb-94, Tc-99, I-129, Cs-137, and total alpha-emitting nuclei before sending to Rokkasho radioactive waste storing center. (S. Ohno)

  5. 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....

  6. Continuous-wave seeded mid-IR parametric system pumped by the high-average-power picosecond Yb:YAG thin-disk laser

    Science.gov (United States)

    Novák, Ondřej; Smrž, Martin; Miura, Taisuke; Turčičová, Hana; Endo, Akira; Mocek, Tomáś

    2015-05-01

    Mid-IR wavelength range offers variety of interesting applications. Down-conversion in the optical parametric devices is promising to generate high average power mid-IR beam due to inherently low thermal load of the nonlinear crystals if a powerful and high quality pump beam is available. We developed 100 kHz pump laser of 100-W level average power. The stretched pulses of Yb-fiber laser oscillator at 1030 nm wavelength are injected into the regenerative amplifier with an Yb:YAG thin-disk. Diode pumping at zero phonon line at wavelength of 969 nm significantly reduces its thermal load and increases conversion efficiency and stability. We obtained the beam with power of 80 W and 2 ps compressed pulsewidth. We are developing a watt level mid-IR picosecond light source pumped by a beam of the thin disk regenerative amplifier. Part of the beam pumps PPLN, which is seeded by a continuous wave laser diode at 1.94 μm to decrease the generation threshold and determine the amplified spectrum. The 3 W pumping gave output of 30 mW, which is by up to two orders higher compared to unseeded operation. The gain of about 107 was achieved in the PPLN in the temporal window of the pump pulse. The spectrum and beam of the generated idler pulses in the mid-IR was measured. We obtained an amplified signal from the second stage with the KTP crystal. We expect watt level mid-IR output for initial 50-W pumping. The generation of longer wavelengths is discussed.

  7. Tunable mid-IR parametric conversion system pumped by a high-average-power picosecond Yb:YAG thin-disk laser

    Science.gov (United States)

    Novák, Ondřej; Miura, Taisuke; Smrž, Martin; Huynh, Jaroslav; Severová, Patricie; Endo, Akira; Mocek, TomáÅ.¡

    2014-05-01

    The mid-IR wavelength range has gained increased interest due to its applications in gas sensing, medicine, defense, and others. Optical parametric devices play an important role in the generation of radiation in the mid-IR. Low thermal load of nonlinear crystals promises high average power outputs if powerful pump laser is available. We have developed 75-W average power pump laser operating at 100 kHz repetition rate. The pulses of Yb-fiber laser oscillator at 1030-nm wavelength are stretched by a chirped volume Bragg grating from 5 ps to 180 ps and inserted into a cavity of regenerative amplifier with an Yb:YAG thin-disk. The amplified pulses are compressed by a chirped volume Bragg grating with an 88% efficiency. We have proposed a wavelength conversion system generating picosecond pulses tunable between 2 and 3 μm. The seed signal radiation is acquired by the optical parametric generation in the first nonlinear crystal. Signal pulse energy is increased in the subsequent optical parametric amplifiers. Each amplification stage consists of a crystal pair in the walkoff compensating arrangement. The wavelength of the signal beam is tunable between 1.6 and 2.1 μm. The 2.1 - 3 μm tunable source will be the idler beam taken from the last amplification stage. Calculations show the output power of ten watt can be achieved for 100 W pump. The results of preliminary experiments with seeded optical parametric generation and subsequent amplification are presented and discussed.

  8. Femtosecond Laser Nonlinear Lithography

    OpenAIRE

    Nishiyama, Hiroaki; Hirata, Yoshinori

    2010-01-01

    In this chapter, we presented the fundamentals of femtosecond laser nonlinear lithography and demonstrated the fabrication of three-dimensional surfaces of inorganic materials using FLAM. We can write complex structures directly inside resists using TPA. Simultaneously, high spatial resolution below the diffraction limit was achievable in spite of low-NA focusing. Using such unique properties, the semiconductor fabrication technology was extended to microfabrication on non-flat substrates. Op...

  9. 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 ...

  10. femtosecond laser ablation

    OpenAIRE

    Margetic, Vanja

    2003-01-01

    Femtosecond laser ablation was investigated as a solid sampling method for elemental chemical analysis. In comparison to the sampling with longer laser pulses, two aspects could be improved by using ultrashort pulses: elimination of the elemental fractionation from the ablation crater, which is necessary for an accurate quantitative analysis, and better control of the material removal (especially for metals), which increases the spatial resolution of microanalysis. Basic aspects of ultrashort...

  11. 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

  12. 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)

  13. High-average-power 1-{mu}m performance and frequency conversion of a diode-end-pumped Yb:YAG laser

    Energy Technology Data Exchange (ETDEWEB)

    Bibeau, C.; Beach, R.J.; Mitchell, S.C.; Emanuel, M.A.; Skidmore, J.; Ebbers, C.A.; Sutton, S.B.; Jancaitis, K.S. [Lawrence Livermore National Lab., CA (United States)

    1998-10-01

    Using a diode-end-pumped technology, a Yb:YAG laser capable of delivering up to 434 W of CW power has been demonstrated. The system incorporates a unique composite rod design which allows for high-average-power operation while simultaneously suppressing parasitic oscillations. Modeling and experimental data to support the quenching of parasitics are discussed. Beam quality measurements for CW operation with several cavity configurations are presented. In particular, beam quality measurements at 340-W CW yielded a beam quality factor of M{sup 2} = 21. Predictions of a quasi-three-level model are compared with the experimental data for several output coupler reflectivities. An observed dependence of the cavity mode fill as a function of output coupler reflectivity is discussed. Employing a single acoustooptical switch, the system was Q-switched at 10 kHz and generated output powers up to 280 W with a measured beam quality of M{sup 2} = 6.8 at 212 W. With an external dual-KTP crystal configuration, the Q-switched output was frequency converted to 515 nm and produced up to 76 W at 10 kHz in a 30-ns pulse length.

  14. Advances in femtosecond laser technology

    Science.gov (United States)

    Callou, Thais Pinheiro; Garcia, Renato; Mukai, Adriana; Giacomin, Natalia T; de Souza, Rodrigo Guimarães; Bechara, Samir J

    2016-01-01

    Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures. PMID:27143847

  15. Generation of Red Light Femtosecond Pulses from an Intra-Cavity Frequency-Doubled Cr4+: Forsterite Laser

    International Nuclear Information System (INIS)

    We demonstrate the generation of red light femtosecond laser pulses from an intra-cavity frequency-doubled Cr4+ :forsterite laser. An average output power of 75 mW is obtained at the central wavelength of 647 nm with a pulse width of 55 fs by inserting a 500-μm-thick BBO crystal in the laser cavity. The bandwidth of the spectrum of second harmonic pulses is 9 nm, corresponding to a time-bandwidth product of 0.355

  16. Femtosecond laser cataract surgery.

    Science.gov (United States)

    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 have resulted in improved visual and refractive outcomes in the short term. Complication rates are low which reduce with surgeon experience. This review article focuses on the Alcon LenSx system. PMID:26605364

  17. 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).

  18. Highly versatile confocal microscopy system based on a tunable femtosecond Er:fiber source.

    Science.gov (United States)

    Träutlein, D; Adler, F; Moutzouris, K; Jeromin, A; Leitenstorfer, A; Ferrando-May, E

    2008-03-01

    The performance of a confocal microscopy setup based on a single femtosecond fiber system is explored over a broad range of pump wavelengths for both linear and nonlinear imaging techniques. First, the benefits of a laser source in linear fluorescence excitation that is continuously tunable over most of the visible spectrum are demonstrated. The influences of subpicosecond pulse durations on the bleaching behavior of typical fluorophores are discussed. We then utilize the tunable near-infrared output of the femtosecond system in connection with a specially designed prism compressor for dispersion control. Pulses as short as 33 fs are measured in the confocal region. As a consequence, 2 mW of average power are sufficient for two-photon microscopy in an organotypic sample from the mouse brain. This result shows great prospect for deep-tissue imaging in the optimum transparency window around 1100 nm. In a third experiment, we prove that our compact setup is powerful enough to exploit even higher-order nonlinearities such as three-photon absorption that we use to induce spatially localized photodamage in DNA. PMID:19343635

  19. 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).

  20. 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)

  1. 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)

  2. 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.

  3. 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)

  4. 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.

  5. 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.

  6. 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。

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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

  13. Terahertz generation in an actively controlled femtosecond enhancement cavity

    International Nuclear Information System (INIS)

    We report on terahertz generation by Cherenkov-type optical rectification in lithium niobate using an actively controlled femtosecond pumped enhancement cavity. In this way a much higher pump power is available inside the cavity and an increased terahertz output power is obtained. The advantages of terahertz generation in the Cherenkov geometry are verified by comparing it with other types of emitters by means of electro-optical detection as well as by bolometer measurements

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

    International Nuclear Information System (INIS)

    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.

  15. 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.

  16. Dual echelon femtosecond single-shot spectroscopy

    International Nuclear Information System (INIS)

    We have developed a femtosecond single-shot spectroscopic technique to measure irreversible changes in condensed phase materials in real time. Crossed echelons generate a two-dimensional array of time-delayed pulses with one femtosecond probe pulse. This yields 9 ps of time-resolved data from a single laser shot, filling a gap in currently employed measurement methods. We can now monitor ultrafast irreversible dynamics in solid-state materials or other samples that cannot be flowed or replenished between laser shots, circumventing limitations of conventional pump-probe methods due to sample damage or product buildup. Despite the absence of signal-averaging in the single-shot measurement, an acceptable signal-to-noise level has been achieved via background and reference calibration procedures. Pump-induced changes in relative reflectivity as small as 0.2%−0.5% are demonstrated in semimetals, with both electronic and coherent phonon dynamics revealed by the data. The optical arrangement and the space-to-time conversion and calibration procedures necessary to achieve this level of operation are described. Sources of noise and approaches for dealing with them are discussed

  17. Harmonically mode-locked femtosecond fiber laser using non-uniform, WS2-particle deposited side-polished fiber

    Science.gov (United States)

    Lee, Junsu; Park, June; Koo, Joonhoi; Jhon, Young Min; Lee, Ju Han

    2016-03-01

    We investigated the feasibility of using a WS2-deposited side-polished fiber as a harmonic mode-locker to produce a femtosecond fiber laser with a frequency of 1.51 GHz. Our work focuses on using a side-polished fiber platform with non-uniform WS2 particles prepared through liquid phase exfoliation method without centrifugation. Femtosecond optical pulses were generated from an all-fiberized erbium-doped fiber-based ring cavity by increasing the pump power to achieve a tunable pulse repetition rate from 14.57 MHz to 1.51 GHz (104th harmonic). The characteristics of the output pulse were systematically investigated to analyze the pulse repetition rate, harmonic order, average output power, pulse energy, and pulse width as a function of the pump power. The output performance of the laser was compared to that of a laser based on a microfiber-based WS2 film SA described in (Yan et al 2015 Opt. Mater. Express 5 479-89). This experimental demonstration reaffirms that a side-polished fiber is an effective platform to implement an ultrafast harmonic mode-locker, and non-uniform WS2 particles prepared via simple liquid phase exfoliation method without centrifugation provide a suitable saturable absorption response at 1.55 μm.

  18. 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.

  19. Microstructure of the multiple-filamentation zone formed by femtosecond laser radiation in a solid dielectric

    Science.gov (United States)

    Geints, Yu E.; Golik, S. S.; Zemlyanov, A. A.; Kabanov, A. M.; Petrov, A. V.

    2016-02-01

    The regularities of multiple filamentation of gigawatt femtosecond laser pulses in a solid dielectric (optical glass) have been considered. The fine spatial structure of the plasma region that is formed under glass photoionisation and accompanies the formation of light filaments is analysed experimentally and by means of numerical simulation. The dependence of the number, position, and extension of individual 'generations' of plasma channels on the laser pulse energy has been investigated for the first time. It is found that the distribution of the number of plasma channels over the length of a dielectric sample has a maximum, the position of which correlates well with the position of the nonlinear focus of the light beam as a whole; at the same time, the average channel length decreases with increasing pulse power, whereas the number of successive channel 'generations', on the contrary, increases.

  20. Femtosecond laser Kerr microscopy

    International Nuclear Information System (INIS)

    We present a new femtosecond laser Kerr microscope which has both scanning and full-field imaging capabilities. This instrument combines a lateral resolution in the sub-micrometer regime with a temporal resolution of better than 100 fs. The magnetic sample is thermally pumped by the fundamental beam and probed by the frequency-doubled beam via the magneto-optical Kerr effect (MOKE) in polar or longitudinal geometry. Double lock-in technique using a photo-elastic modulator (50 kHz) and an optical chopper (80 Hz) leads to very high sensitivity. In the scanning mode a three-axis piezo stage with a sub-nanometer resolution and 400 μm scan range in all directions is used. Full-field Kerr microscopy is possible by destroying the lateral coherence of the laser light with a rotating disc and detecting the image with a CCD camera. A cryostat allows measurements in the temperature range from 3.5 to 450 K. Instrument controlling software, developed on Visual Studio.Net, enables multi-dimensional scans, e.g., the MOKE signal can be recorded for arbitrary combination of six parameters (sample position, magnetic field, pump-probe delay time, and temperature). First time-resolved studies on Fe/Gd, Co/Ni and Co/Pt multilayer systems are presented

  1. 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

  2. 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.

  3. Advances in femtosecond laser technology

    Directory of Open Access Journals (Sweden)

    Callou TP

    2016-04-01

    Full Text Available Thais Pinheiro Callou, Renato Garcia, Adriana Mukai, Natalia T Giacomin, Rodrigo Guimarães de Souza, Samir J Bechara Department of Ophthalmology, University of Sao Paulo, Sao Paulo, Brazil Abstract: Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures. Keywords: laser therapy, refractive surgical procedures, intracorneal ring, laser in situ keratomileusis, keratoplasty, presbyopia, cataract extraction, astigmatism surgery

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 250  W average power, 100  kHz repetition rate cryogenic Yb:YAG amplifier for OPCPA pumping

    OpenAIRE

    Zapata, Luis E.; Reichert, Fabian; Hemmer, M.; Kärtner, F. X.

    2016-01-01

    A cryogenically cooled, bulk Yb:YAG, four-pass amplifier delivering up to 250Waverage power at 100 kHz repetition rate is reported. The 2.5 mJ amplified optical pulses show a sub-20 ps duration before temporal compression and a spectrum supporting a transform-limited duration of 3.6 ps. The power instabilities were measured to be

  9. 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.

  10. 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.

  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. An all-digital spike-based ultra-low-power IR-UWB dynamic average threshold crossing scheme for muscle force wireless transmission

    OpenAIRE

    Demarchi, Danilo; Martina, Maurizio; Masera, Guido

    2015-01-01

    We introduce an Impulse Radio Ultra-Wide Band (IR-UWB) radio transmission scheme for miniaturized biomed-ical applications based on a dynamic and adaptive voltage thresholding of surface Electro Myo Graphy (sEMG) signals. The amplified sEMG signal is compared to a DAC-generated threshold computed from the previous 1-bit history by custom digital control logic running at 2kHz clock and implementing an ad-hoc algorithm (Dynamic Average Threshold Crossing, D-ATC). The resulting events and the as...

  14. 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...

  15. 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

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

    DEFF Research Database (Denmark)

    Zhou, Binbin; Wei, Z.Y.; Zou, Y.W.; Zhang, Y.D.; Zhong, X.; Bourdet, G.L.; Wang, J.L.

    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...

  18. 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.

  19. 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

  20. Designing the femtosecond optical oscilloscope

    Science.gov (United States)

    Toneyan, H.; Sukiasyan, M.; Zeytunyan, A.; Tsakanov, V.; Mouradian, L.

    2016-01-01

    We present the results of our recent experimental and numerical studies on femtosecond pulse spectrotemporal imaging in a similariton-induced temporal lens aimed to designing a femtosecond optical oscilloscope [1]. We have studied nonlinear and dispersive peculiarities of modern high-tech materials, such as photonic crystal fibers, hollow-core fibers etc, to use them in the scheme, and to provide compactness and reliability of the device. The use of hollow-core fibers, as a dispersive medium instead of a pair of prisms or gratings, is of special importance for constructing the industrial tool. Additionally, we are experimenting on the method of dispersive Fourier transformation, using the effect of chromo-modal dispersion in multimode fibers [2], to provide real-time performance of the device.

  1. 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.

  2. 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.

  3. 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

  4. Femtosecond Laser Cutting of Graphene

    OpenAIRE

    Zhang, Wen

    2012-01-01

    Graphene is a single atomic layer 2D graphite that has unusual properties that would open up wide industrial applications. As graphite is the toughest material on earth, challenges exist to cut and shape the materials. This MPhil thesis presents the outcome of femtosecond laser micro-patterning of single layer graphene on a glass substrate, which has resulted in a journal publication. A literature review was carried out to understand the process, basic characteristics and challenges in laser ...

  5. Longitudinal temperature distribution in an end-pumped solid-state amplifier medium: application to a high average power diode pumped Yb:YAG thin disk amplifier.

    Science.gov (United States)

    Bourdet, Gilbert L; Yu, Haiwu

    2007-08-10

    We propose a simple analytical derivation making it possible to compute a one-dimensional temperature variation in an end-pumped solid-state laser. This derivation takes into account the pump intensity variation along the crystal, the doping concentration, and temperature dependence of the thermal conductivity. We then compare this simulation with the one usually used, which does not take into account any of these dependences. The results show that, at room temperature, the two methods are in good agreement, but at a cryogenic temperature where the thermal conductivity varies fast with temperature, a large discrepancy is found, and the conventional computations underestimate both the average temperature and the longitudinal gradient. PMID:17694159

  6. Stack and dump: Peak-power scaling by coherent pulse addition in passive cavities. Review

    OpenAIRE

    Breitkopf, S.; T. Eidam; Klenke, A.; Carstens, H.; S. Holzberger; Fill, E.; Schreiber, T.; Krausz, F.; Tünnermann, A.; Pupeza, I.; Limpert, J.

    2015-01-01

    During the last decades femtosecond lasers have proven their vast benefit in both scientific and technological tasks. Nevertheless, one laser feature bearing the tremendous potential for high-field applications, delivering extremely high peak and average powers simultaneously, is still not accessible. This is the performance regime several upcoming applications such as laser particle acceleration require, and therefore, challenge laser technology to the fullest. On the one hand, some state-of...

  7. Pulsed 1.645 μm Er3+:YAG laser with increased average output power and diffraction limited beam quality

    International Nuclear Information System (INIS)

    An actively Q-switched Er3+:YAG laser operating at the wavelength of 1645 nm was developed. The system was TIR (total internal reflection), resonantly diode-pumped at the wavelength of 1532 nm with a repetition rate of 100 Hz. For ∼305 mJ of incident pump pulse energy, output pulse energy of 24 mJ was generated with almost 8% of optical-to-optical efficiency. At maximum pumping power the M2 parameter of the generated beam was 1. (letter)

  8. 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.

  9. Tunable sub-20 fs pulses from a 500 kHz OPCPA with 15 W average power based on an all-ytterbium laser

    OpenAIRE

    Puppin, Michele; Deng, Yunpei; Prochnow, Oliver; Ahrens, Jan; Binhammer, Thomas; Morgner, Uwe; Krenz, Marcel; Wolf, Martin; Ernstorfer, Ralph

    2014-01-01

    An optical parametric chirped pulse amplifier fully based on Yb lasers at 500 kHz is described. Passive optical-synchronization is achieved between a fiber laser-pumped white-light and a 515 nm pump produced with a 200 W picosecond Yb:YAG InnoSlab amplifier. An output power up to 19.7 W with long-term stability of 0.3% is demonstrated for wavelength tunable pulses between 680 nm and 900 nm and spectral stability of 0.2%; 16.5 W can be achieved with a bandwidth supporting 5.4 fs pulses. We dem...

  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. A diode-pumped Q-switched a-cut Tm:YAP laser with an average output power of 13 W

    International Nuclear Information System (INIS)

    We report experimental results on a highly efficient Q-switched a-cut Tm:YAP laser working at 1.99 µm. A fiber-coupled laser diode (LD) working at 795 nm was used to pump a Tm:YAP (diameter 5 mm × 9 mm) crystal with 3% Tm3+ doping. Under the input pump power of 44.5 W, it delivered a polarized pulsed laser output with a repetition rate of 10 kHz at 1.99 µm. The maximum output power was 13.29 W, corresponding to a slope efficiency of 36.5% and optical-to-optical conversion efficiency of 29.9%. The influences of curvature and transmittance of the output mirror on the laser output are analyzed and validated by experiments, and the results are of benefit for optimization of the laser cavity. (paper)

  12. Theoretical and experimental study of a high average power, high repetition rate solid-state laser with a good beam quality

    International Nuclear Information System (INIS)

    Technological progress in power lasers requires a better understanding of the thermal effects in solid-state lasers. This work aims at contributing to this issue through the designing of an extreme ultra violet (EUV) source involving 6 laser beams focusing on a liquid xenon target. In the first chapter we show that the best configuration that complies with the EUV source specifications is that involving side-pumped rod lasers. Rod lasers being prone to thermal effects, we present in the second chapter the thermal effects that are: thermal lensing, bi-focus effect and spherical aberration. The third and fourth chapters presents a characterization of laser amplifying media through numerical simulations and their experimental validation. The two last chapters present the impact of the thermal effects on the laser performance and their compensation through simple but efficient devices. Two devices have been proposed to counter-balance the spherical aberration: a pure spherical aberration phase blade and an a-focal system made of 2 identical short focal lenses. It is shown that these 2 devices have improved notably (but less than theoretically expected) the laser output power. (A.C.)

  13. 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)

  14. 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

  15. Single shot depth sensitivity using femtosecond Laser Induced Breakdown Spectroscopy

    International Nuclear Information System (INIS)

    Depth profiling measurement using multiple pulse Laser Induced Breakdown Spectroscopy (LIBS) can be used to determine the characteristics of buried layers. However for femtosecond pulses the emission spectra does not necessarily reflect the average depth composition for the single shot case and instead has much higher sensitivity for the surface layer of the ablation region. We introduce a concept of “depth sensitivity” to characterize this behavior for single shot LIBS depth profiling. Experiments were carried out using 800 nm femtosecond laser pulses irradiating layered targets while monitoring the plasma emission with a spectrometer system. Laser induced plasma formed at the surface layer exhibits a strong LIBS signature while deeper ablated region contributes very little to the emission spectrum. The sensitive depth region, the source of the major part of the emission, is much less than the ablation crater depth and is shown to be of the order of 3 nm in the case of actual crater depths of 100's of nm. A two temperature model has been used to determine the lattice temperature profile versus depth which qualitatively predicts the observed behavior. - Highlights: • Depth dependence of LIBS emission within a single 800 nm femtosecond laser shot. • LIBS emission spectra dominated by only a thin surface layer. • Depth sensitivity, a new concept, is ∼3 nm when actual crater depth ∼100’s of nm. • Qualitative agreement with TTM model of lattice temperature versus depth and time

  16. Tunable sub-20 fs pulses from a 500 kHz OPCPA with 15 W average power based on an all-ytterbium laser

    CERN Document Server

    Puppin, Michele; Prochnow, Oliver; Ahrens, Jan; Binhammer, Thomas; Morgner, Uwe; Krenz, Marcel; Wolf, Martin; Ernstorfer, Ralph

    2014-01-01

    An optical parametric chirped pulse amplifier fully based on Yb lasers at 500 kHz is described. Passive optical-synchronization is achieved between a fiber laser-pumped white-light and a 515 nm pump produced with a 200 W picosecond Yb:YAG InnoSlab amplifier. An output power up to 19.7 W with long-term stability of 0.3% is demonstrated for wavelength tunable pulses between 680 nm and 900 nm and spectral stability of 0.2%; 16.5 W can be achieved with a bandwidth supporting 5.4 fs pulses. We demonstrate compression of 30 microjoule pulses to sub-20 fs duration with a prism compressor, suitable for high harmonic generation.

  17. 500 kHz OPCPA delivering tunable sub-20 fs pulses with 15 W average power based on an all-ytterbium laser.

    Science.gov (United States)

    Puppin, Michele; Deng, Yunpei; Prochnow, Oliver; Ahrens, Jan; Binhammer, Thomas; Morgner, Uwe; Krenz, Marcel; Wolf, Martin; Ernstorfer, Ralph

    2015-01-26

    An optical parametric chirped pulse amplifier fully based on Yb lasers at 500 kHz is described. Passive optical-synchronization is achieved between a fiber laser-pumped white-light and a 515 nm pump produced with a 200 W picosecond Yb:YAG InnoSlab amplifier. An output power up to 19.7 W with long-term stability of 0.3% is demonstrated for wavelength tunable pulses between 680 nm and 900 nm and spectral stability of 0.2%; 16.5 W can be achieved with a bandwidth supporting 5.4 fs pulses. We demonstrate compression of 30 µJ pulses to sub-20 fs duration with a prism compressor, suitable for high harmonic generation. PMID:25835905

  18. 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...

  19. 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

  20. 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.

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

    International Nuclear Information System (INIS)

    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. (letter)

  2. 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.

  3. Simple Yb:YAG femtosecond booster amplifier using divided-pulse amplification.

    Science.gov (United States)

    Pouysegur, Julien; Weichelt, Birgit; Guichard, Florent; Zaouter, Yoann; Hönninger, Clemens; Mottay, Eric; Druon, Frédéric; Georges, Patrick

    2016-05-01

    A hybrid-system approach using a low-gain Yb:YAG single crystal booster amplifier behind a state-of-the-art industrial high-power femtosecond fiber system is studied to significantly increase the output pulse energy of the fiber amplifier. With this system, more than 60 W of average power is demonstrated at 100 kHz for pulse duration of 400 fs, corresponding to an energy per pulse of 600 µJ. Reducing the repetition rate, the energy is increased up to 2.5 mJ (before compression), which corresponds to the limitation due to laser damage threshold of the optical coatings. To scale further the energy, passive divided-pulse amplification is then implemented at the entrance of the bulk amplifier. Using this geometry, a safe nominal operating point is presented with output pulse energies of 3 mJ before and 2.3 mJ after compression and with a pulse duration of 520 fs, corresponding to a peak power of 4.4 GW. PMID:27137601

  4. Molecular fragmentation induced by a femtosecond laser

    Science.gov (United States)

    Kosmidis, Constantine E.; Ledingham, Kenneth W. D.; Kilic, H. S.; McCanny, T.; Singhal, Raghunandan P.; Smith, D.; Langley, Andrew J.

    1998-07-01

    The 90 femtosecond laser induced fragmentation at 375 nm for a number of different nitro-molecules is compared to that induced by a nanosecond laser at the same wavelength by means of time-of-flight mass spectrometry. The potential of femtosecond laser mass spectrometry for analytical purposes is discussed.

  5. Micromachining of Silicon Carbide using femtosecond lasers

    Energy Technology Data Exchange (ETDEWEB)

    Farsari, M [Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, PO Box 1527, 71110 Heraklion, Crete (Greece); Filippidis, G [Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, PO Box 1527, 71110 Heraklion, Crete (Greece); Zoppel, S [Vienna University of Technology, Photonics Institute, Gusshausstr. 27-29/387, 1040 Vienna (Austria); Reider, G A [Vienna University of Technology, Photonics Institute, Gusshausstr. 27-29/387, 1040 Vienna (Austria); Fotakis, C [Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, PO Box 1527, 71110 Heraklion, Crete (Greece)

    2007-04-15

    We have demonstrated micromachining of bulk 3C silicon carbide (3C- SiC) wafers by employing 1028nm wavelength femtosecond laser pulses of energy less than 10 nJ directly from a femtosecond laser oscillator, thus eliminating the need for an amplified system and increasing the micromachining speed by more than four orders of magnitude.

  6. Micromachining of Silicon Carbide using femtosecond lasers

    International Nuclear Information System (INIS)

    We have demonstrated micromachining of bulk 3C silicon carbide (3C- SiC) wafers by employing 1028nm wavelength femtosecond laser pulses of energy less than 10 nJ directly from a femtosecond laser oscillator, thus eliminating the need for an amplified system and increasing the micromachining speed by more than four orders of magnitude

  7. Single-step synthesis of graphene quantum dots by femtosecond laser ablation of graphene oxide dispersions

    Science.gov (United States)

    Russo, Paola; Liang, Robert; Jabari, Elahe; Marzbanrad, Ehsan; Toyserkani, Ehsan; Zhou, Y. Norman

    2016-04-01

    In the last few years, graphene quantum dots (GQDs) have attracted the attention of many research groups for their outstanding properties, which include low toxicity, chemical stability and photoluminescence. One of the challenges of GQD synthesis is finding a single-step, cheap and sustainable approach for synthesizing these promising nanomaterials. In this study, we demonstrate that femtosecond laser ablation of graphene oxide (GO) dispersions could be employed as a facile and environmentally friendly synthesis method for GQDs. With the proper control of laser ablation parameters, such as ablation time and laser power, it is possible to produce GQDs with average sizes of 2-5 nm, emitting a blue luminescence at 410 nm. We tested the feasibility of the synthesized GQDs as materials for electronic devices by aerosol-jet printing of an ink that is a mixture of water dispersion of laser synthesized GQDs and silver nanoparticle dispersion, which resulted in lower resistivity of the final printed patterns. Preliminary results showed that femtosecond laser synthesized GQDs can be mixed with silver nanoparticle dispersion to fabricate a hybrid material, which can be employed in printing electronic devices by either printing patterns that are more conductive and/or reducing costs of the ink by decreasing the concentration of silver nanoparticles (AgNPs) in the ink.In the last few years, graphene quantum dots (GQDs) have attracted the attention of many research groups for their outstanding properties, which include low toxicity, chemical stability and photoluminescence. One of the challenges of GQD synthesis is finding a single-step, cheap and sustainable approach for synthesizing these promising nanomaterials. In this study, we demonstrate that femtosecond laser ablation of graphene oxide (GO) dispersions could be employed as a facile and environmentally friendly synthesis method for GQDs. With the proper control of laser ablation parameters, such as ablation time and

  8. 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)

  9. 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.

  10. 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

  11. 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.

  12. 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).

  13. 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.

  14. Design of a tunable parametric wavelength conversion system between 2 and 3 μm pumped by a high-average-power Yb:YAG thin-disk laser

    Science.gov (United States)

    Novák, Ondřej; Miura, Taisuke; Severová, Patricie; Endo, Akira; Mocek, Tomáš

    2013-05-01

    With increasing energy densities of laser pulses the laser induced damage threshold (LIDT) testing becomes an important characterization of optical components. The emission wavelength of several laser materials is in the 2 - 3 μm wavelength-range. We propose a wavelength conversion system generating tunable sub-ns pulses for LIDT measurements in this IR spectral range. The pump beam of the conversion system will be based on the thin-disk laser technology. The Yb-fiber-laser seeded CPA system with high-energy Yb:YAG thin-disk regenerative amplifier will produce uncompressed pulses of 0.5 ns width, 130 mJ energy, at wavelength of 1030 nm with 1 kHz repetition rate giving 130 W of average power. Output of the thin-disk regenerative amplifier will pump an optical parametric generator (OPG) and subsequent optical parametric amplifiers (OPA). The tunable output wavelength of the OPG will be between 1.5 μm - 2.1 μm for the signal beam and between 2.1 μm - 3 μm for the idler beam. The signal will be amplified in the OPAs because the optics and diagnostics is more easily available below 2 μm wavelength. The tunable multi-millijoule source above 2.1 μm will be the idler beam taken from the last amplification stage. High-average output power of 10 W at 1 kHz repetition rate will be unique among 2 - 3 μm tunable systems. Operation of the amplifiers at high-intensities and high-average powers limits the system performance. The thermal load of crystals caused by the partial beam absorption will be studied. Further, the damage threshold of optical components, transmission range of nonlinear crystals, and amplifiers bandwidths will be addressed.

  15. 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 ...

  16. Compressive auto-indexing in femtosecond nanocrystallography

    International Nuclear Information System (INIS)

    Ultrafast nanocrystallography has the potential to revolutionize biology by enabling structural elucidation of proteins for which it is possible to grow crystals with 10 or fewer unit cells on the side. The success of nanocrystallography depends on robust orientation-determination procedures that allow us to average diffraction data from multiple nanocrystals to produce a three-dimensional (3D) diffraction data volume with a high signal-to-noise ratio. Such a 3D diffraction volume can then be phased using standard crystallographic techniques. 'Indexing' algorithms used in crystallography enable orientation determination of diffraction data from a single crystal when a relatively large number of reflections are recorded. Here we show that it is possible to obtain the exact lattice geometry from a smaller number of measurements than standard approaches using a basis pursuit solver. -- Research Highlights: → Femtosecond nanocrystallography relies on orientation-determination procedures to sort data. → Standard approaches using Fourier transforms fail when the number of reflections is small. → Basis pursuit algorithms enable orientation determination using fewer reflections than before.

  17. 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

  18. 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.

  19. On Averaging Rotations

    DEFF Research Database (Denmark)

    Gramkow, Claus

    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...... natural approximations to the Riemannian metric, and that the subsequent corrections are inherient in the least squares estimation. Keywords: averaging rotations, Riemannian metric, matrix, quaternion...

  20. 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...

  1. 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...

  2. 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...... natural approximations to the Riemannian metric, and that the subsequent corrections are inherient in the least squares estimation. Keywords: averaging rotations, Riemannian metric, matrix, quaternion...

  3. 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 ...

  4. 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....

  5. 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.

  6. 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...

  7. Femtosecond laser surface structuring technique for making human enamel and dentin surfaces superwetting

    Science.gov (United States)

    Vorobyev, A. Y.; Guo, Chunlei

    2013-12-01

    It is known that good wettability of enamel and dentin surfaces is a key factor in enhancing adhesion of restorative materials in dentistry. Here, we report on a femtosecond laser surface texturing approach that makes both the enamel and dentine surfaces superwetting. In contrast to the traditional chemical etching that yields random surface structures, this new approach produces engineered surface structures. The surface structure engineered and tested here is an array of femtosecond laser-produced parallel microgrooves that generates a strong capillary force. Due to the powerful capillary action, water is rapidly sucked into this engineered surface structure and spreads even on a vertical surface.

  8. 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....

  9. Focal spot of femtosecond laser pulse under tight focusing condition

    Czech Academy of Sciences Publication Activity Database

    Jeong, Tae Moon; Weber, Stefan A.; Le Garrec, Bruno; Margarone, Daniele; Mocek, Tomáš; Korn, Georg

    Bellingham: SPIE, 2015 - (Korn, G.; Silva, L.), "95150I-1"-"95150I-6". (Proceedings of SPIE. 9515). ISBN 978-1-62841-636-7. ISSN 0277-786X. [Research Using Extreme Light - Entering New Frontiers with Petawatt-Class Lasers II. Praha (CZ), 13.04.2015-15.04.2015] R&D Projects: GA MŠk ED1.1.00/02.0061 Grant ostatní: ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061 Institutional support: RVO:68378271 Keywords : femtosecond * high-power laser * relativistic * focal spot Subject RIV: BL - Plasma and Gas Discharge Physics

  10. All-fiber femtosecond Cherenkov laser at visible wavelengths

    DEFF Research Database (Denmark)

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

    2013-01-01

    -matching condition [1]. The resonant ultrafast wave conversion via the fiber-optic CR mechanism is instrumental for applications in biophotonics such as bio-imaging and microscopy [2]. In this work, we demonstrate a highly-stable all-fiber, fully monolithic CR system based on an Yb-fiber femtosecond laser, producing...... conversion [5]. Bridge fibers are used in the CR link to enhance the conversion efficiency. Fig. 1(b) shows the far-field saturated visible images of the CR emitted from the laser system, generated as the pump power increases in the range 150 mW - 300 mW. The emitted CR spectra corresponding to different...

  11. 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.

  12. Valence state change and defect centers induced by infrared femtosecond laser in Yb:YAG crystals

    Science.gov (United States)

    Wang, Xinshun; Liu, Yang; Zhao, Panjuan; Guo, Zhongyi; Li, Yan; Qu, Shiliang

    2015-04-01

    The broad band upconversion luminescence in Yb3+:YAG crystal has been observed in experiments under the irradiation of focused infrared femtosecond laser. The dependence of the fluorescence intensity on the pump power shows that the upconversion luminescence is due to simultaneous two-photon absorption process, which indicates that the broad emission bands at 365 and 463 nm could be assigned to the 5d → 4f transitions of Yb2+ ions and the one at 692 nm could be attributed to the electron-hole recombination process on (Yb2+-F+) centers. The absorption spectra of the Yb:YAG crystal samples before and after femtosecond laser irradiation, and after further annealing reveal that permanent valence state change of Yb ions from Yb3+ to Yb2+ and (Yb2+-F+) centers have been induced by infrared femtosecond laser irradiation in Yb3+:YAG crystal.

  13. Valence state change and defect centers induced by infrared femtosecond laser in Yb:YAG crystals

    International Nuclear Information System (INIS)

    The broad band upconversion luminescence in Yb3+:YAG crystal has been observed in experiments under the irradiation of focused infrared femtosecond laser. The dependence of the fluorescence intensity on the pump power shows that the upconversion luminescence is due to simultaneous two-photon absorption process, which indicates that the broad emission bands at 365 and 463 nm could be assigned to the 5d → 4f transitions of Yb2+ ions and the one at 692 nm could be attributed to the electron-hole recombination process on (Yb2+-F+) centers. The absorption spectra of the Yb:YAG crystal samples before and after femtosecond laser irradiation, and after further annealing reveal that permanent valence state change of Yb ions from Yb3+ to Yb2+ and (Yb2+-F+) centers have been induced by infrared femtosecond laser irradiation in Yb3+:YAG crystal

  14. 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 ...

  15. All-fiber femtosecond Cherenkov radiation source

    DEFF Research Database (Denmark)

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

    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 med......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...

  16. 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

  17. 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

  18. Generation of Femtosecond Electron and Photon Pulses

    CERN Document Server

    Thongbai, Chitrlada; Kangrang, Nopadol; Kusoljariyakul, Keerati; Rhodes, Michael W; Rimjaem, Sakhorn; Saisut, Jatuporn; Vilaithong, Thiraphat; Wichaisirimongkol, Pathom; Wiedemann, Helmut

    2005-01-01

    Femtosecond electron and photon pulses become a tool of interesting important to study dynamics at molecular or atomic levels. Such short pulses can be generated from a system consisting of an RF-gun with a thermionic cathode, an alpha magnet as a magnetic bunch compressor, and a linear accelerator. The femtosecond electron pulses can be used directly or used as sources to produce electromagnetic radiation of equally short pulses by choosing certain kind of radiation pruduction processes. At the Fast Neutron Research Facility (Thailand), we are especially interested in production of radiation in Far-infrared and X-ray regime. In the far-infrared wavelengths which are longer than the femtosecond pulse length, the radiation is emitted coherently producing intense radiation. In the X-ray regime, development of femtosecond X-ray source is crucial for application in ultrafast science.

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  3. 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.

  4. 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

  5. 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 to...

  6. 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.

  7. 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

  8. 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%.

  9. 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.

  10. Covariant approximation averaging

    CERN Document Server

    Shintani, Eigo; Blum, Thomas; Izubuchi, Taku; Jung, Chulwoo; Lehner, Christoph

    2014-01-01

    We present a new class of statistical error reduction techniques for Monte-Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in $N_f=2+1$ lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte-Carlo calculations over conventional methods for the same cost.

  11. 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...

  12. Calibration of femtosecond optical tweezers as a sensitive thermometer

    Science.gov (United States)

    Mondal, Dipankar; Goswami, Debabrata

    2015-08-01

    We present cumulative perturbation effects of femtosecond laser pulses on an optical tweezer. Our experiments involve a dual wavelength high repetition rate femtosecond laser, one at the non-heating wavelength of 780 nm while the other at 1560 nm to cause heating in the trapped volume under low power (100-800 μW) conditions. The 1560 nm high repetition rate laser acts as a resonant excitation source for the vibrational combination band of the hydroxyl group (OH) of water, which helps create the local heating effortlessly within the trapping volume. With such an experimental system, we are the first to observe direct effect of temperature on the corner frequency deduced from power spectrum. We can, thus, control and measure temperature precisely at the optical trap. This observation has lead us to calculate viscosity as well as temperature in the vicinity of the trapping zone. These experimental results also support the well-known fact that the nature of Brownian motion is the response of the optically trapped bead from the temperature change of surroundings. Temperature rise near the trapping zone can significantly change the viscosity of the medium. However, we notice that though the temperature and viscosity are changing as per our corner frequency calculations, the trap stiffness remains the same throughout our experiments within the temperature range of about 20 K.

  13. 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.

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

    Science.gov (United States)

    Zhou, Binbin; Wei, Zhiyi; Zou, Yuwan; Zhang, Yongdong; Zhong, Xin; Bourdet, G L; Wang, Junli

    2010-02-01

    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 efficiency of 76%. Our measurement showed that the pulse duration was 418 fs with the central wavelength of 1048 nm. PMID:20125697

  15. 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.

  16. Robust Averaging Level Control

    OpenAIRE

    Rosander, Peter; Isaksson, Alf; Löfberg, Johan; Forsman, Krister

    2011-01-01

    Frequent inlet flow changes typically cause problems for averaging level controllers. For a frequently changing inlet flow the upsets do not occur when the system is in steady state and the tank level at its set-point. For this reason the tuning of the level controller gets quite complicated, since not only the size of the upsets but also the time in between them relative to the hold up of the tank have to be considered. One way to obtain optimal flow filtering while directly accounting for futur...

  17. 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.

  18. Mid-infrared upconversion spectroscopy based on a Yb:fiber femtosecond laser

    CERN Document Server

    Johnson, Todd A

    2011-01-01

    We present a system for molecular spectroscopy using a broadband mid-infrared laser with near infrared detection. Difference frequency generation of a Yb:fiber femtosecond laser produced a mid-infrared (MIR) source tunable from 2100-3700 cm^-1 (2.7-4.7 microns) with average power up to 40 mW. The MIR spectrum was upconverted to near-infrared wavelengths for broadband detection using a two-dimensional dispersion imaging technique. Absorption measurements were performed over bandwidths of 240 cm^-1 (7.2 THz) with 0.048 cm^-1 (1.4 GHz) resolution, and absolute frequency scale uncertainty was better than 0.005 cm^-1 (150 MHz). The minimum detectable absorption coefficient per spectral element was determined to be 4.4 x 10^-7 cm^-1 from measurements in low pressure CH_4, leading to a detection limit of 2 parts-per-billion. The spectral range, resolution, and frequency accuracy of this system show promise for determination of trace concentrations in gas mixtures containing both narrow and broad overlapping spectral...

  19. 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)

  20. 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.

  1. 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

  2. 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.

  3. 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

    International Nuclear Information System (INIS)

    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 ∼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

  4. 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.

  5. 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.

  6. Average nuclear surface properties

    International Nuclear Information System (INIS)

    The definition of the nuclear surface energy is discussed for semi-infinite matter. This definition is extended also for the case that there is a neutron gas instead of vacuum on the one side of the plane surface. The calculations were performed with the Thomas-Fermi Model of Syler and Blanchard. The parameters of the interaction of this model were determined by a least squares fit to experimental masses. The quality of this fit is discussed with respect to nuclear masses and density distributions. The average surface properties were calculated for different particle asymmetry of the nucleon-matter ranging from symmetry beyond the neutron-drip line until the system no longer can maintain the surface boundary and becomes homogeneous. The results of the calculations are incorporated in the nuclear Droplet Model which then was fitted to experimental masses. (orig.)

  7. 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.

  8. 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.

  9. Femtosecond laser micromachining of fused silica molds.

    Science.gov (United States)

    Madani-Grasset, Frédéric; Bellouard, Yves

    2010-10-11

    The use of low-energy femtosecond laser beam combined with chemical etching has been proven to be an efficient method to fabricate three-dimensional structures in fused silica. For high-volume application, this technology--like other serial processes--suffers from a moderate production rate. Here, we show that femtosecond laser can also be employed to fabricate silica molds and other patterned surfaces, including surfaces with high aspect ratio features (> 10). Through appropriate tailoring of silica's surface property and subsequent creation of, for instance, simple elastomeric molding, new opportunities for the indirect 3D, multi-scale spatial characterization of deep laser-fabricated microstructures come along. We demonstrate that those moldings are characterized by a high fidelity (down to the nanometer scale) to the silica mold. These results further advance the applicability of femtosecond laser processing to glass. PMID:20941083

  10. 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...

  11. Femtosecond laser sintering of copper nanoparticles

    Science.gov (United States)

    Cheng, C. W.; Chen, J. K.

    2016-04-01

    The ultrafast melting of copper nanoparticles (NPs) induced by a femtosecond laser pulse with duration of 100 fs and wavelength of 800 nm is investigated theoretically and experimentally. The Cu pattern fabricated from sintering of a Cu NP-dispersed film by the femtosecond laser at a repetition rate of 80 MHz is experimentally studied. A one-dimensional two-temperature model with temperature-dependent material properties, including the extended Drude model for dynamic optical properties and the thermophysical properties, is employed to simulate the particles ultrafast melting and re-solidification process.

  12. 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

  13. 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. ...

  14. Generating long sequences of high-intensity femtosecond pulses

    CERN Document Server

    Bitter, Martin

    2015-01-01

    We present an approach to create pulse sequences extending beyond 150~picoseconds in duration, comprised of $100~\\mu$J femtosecond pulses. A quarter of the pulse train is produced by a high-resolution pulse shaper, which allows full controllability over the timing of each pulse. Two nested Michelson interferometers follow to quadruple the pulse number and the sequence duration. To boost the pulse energy, the long train is sent through a multi-pass Ti:Sapphire amplifier, followed by an external compressor. A periodic sequence of 84~pulses of 120~fs width and an average pulse energy of 107~$\\mu$J, separated by 2~ps, is demonstrated as a proof of principle.

  15. Generating long sequences of high-intensity femtosecond pulses.

    Science.gov (United States)

    Bitter, M; Milner, V

    2016-02-01

    We present an approach to creating pulse sequences extending beyond 150 ps in duration, comprised of 100 μJ femtosecond pulses. A quarter of the pulse train is produced by a high-resolution pulse shaper, which allows full controllability over the timing of each pulse. Two nested Michelson interferometers follow to quadruple the pulse number and the sequence duration. To boost the pulse energy, the long train is sent through a multipass Ti:sapphire amplifier, followed by an external compressor. A periodic sequence of 84 pulses of 120 fs width and an average pulse energy of 107 μJ, separated by 2 ps, is demonstrated as a proof of principle. PMID:26836087

  16. 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.

  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. Power

    OpenAIRE

    Bowles, Samuel; Gintis, Herbert

    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...

  19. Femtosecond laser pulse written Volume Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Richter Daniel

    2013-11-01

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

  20. 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

  1. 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...

  2. 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

  3. [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

  4. 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...

  5. 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)

  6. 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...

  7. 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...

  8. 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...

  9. 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.

  10. 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...

  11. Efficient waveguide lasers in femtosecond laser inscribed double-cladding waveguides of Yb:YAG ceramics

    OpenAIRE

    Jia, Yuechen; R. Vázquez de Aldana, Javier; Chen, Feng

    2013-01-01

    We report on the fabrication of depressed double-cladding waveguides in Yb:YAG ceramics by using femtosecond (fs) laser inscription. The double-cladding structures consist of tubular central structures with 30 μm diameter and concentric larger size tubular claddings with diameters of 100-200 μm. Continuous wave laser oscillations at wavelength of 1030 nm have been realized at room temperature through optical pump at 946 nm. The obtained maximum output power of the double-...

  12. 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.

  13. Stack and dump: Peak-power scaling by coherent pulse addition in passive cavities

    Science.gov (United States)

    Breitkopf, S.; Eidam, T.; Klenke, A.; Carstens, H.; Holzberger, S.; Fill, E.; Schreiber, T.; Krausz, F.; Tünnermann, A.; Pupeza, I.; Limpert, J.

    2015-10-01

    During the last decades femtosecond lasers have proven their vast benefit in both scientific and technological tasks. Nevertheless, one laser feature bearing the tremendous potential for high-field applications, delivering extremely high peak and average powers simultaneously, is still not accessible. This is the performance regime several upcoming applications such as laser particle acceleration require, and therefore, challenge laser technology to the fullest. On the one hand, some state-of-the-art canonical bulk amplifier systems provide pulse peak powers in the range of multi-terawatt to petawatt. On the other hand, concepts for advanced solid-state-lasers, specifically thin disk, slab or fiber systems have shown their capability of emitting high average powers in the kilowatt range with a high wall-plug-efficiency while maintaining an excellent spatial and temporal quality of the output beam. In this article, a brief introduction to a concept for a compact laser system capable of simultaneously providing high peak and average powers all along with a high wall-plug efficiency will be given. The concept relies on the stacking of a pulse train emitted from a high-repetitive femtosecond laser system in a passive enhancement cavity, also referred to as temporal coherent combining. In this manner, the repetition rate is decreased in favor of a pulse energy enhancement by the same factor while the average power is almost preserved. The key challenge of this concept is a fast, purely reflective switching element that allows for the dumping of the enhanced pulse out of the cavity. Addressing this challenge could, for the first time, allow for the highly efficient extraction of joule-class pulses at megawatt average power levels and thus lead to a whole new area of applications for ultra-fast laser systems.

  14. 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)

  15. 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.

  16. 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)

  17. 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.

  18. 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.

  19. Femtosecond Laser Micromachining Photonic and Microfluidic Devices in Transparent Materials

    CERN Document Server

    Cerullo, Giulio; Ramponi, Roberta

    2012-01-01

    Femtosecond laser micromachining of transparent material is a powerful and versatile technology. In fact, it can be applied to several materials. It is a maskless technology that allows rapid device prototyping, has intrinsic three-dimensional capabilities and can produce both photonic and microfluidic devices. For these reasons it is ideally suited for the fabrication of complex microsystems with unprecedented functionalities. The book is mainly focused on micromachining of transparent materials which, due to the nonlinear absorption mechanism of ultrashort pulses, allows unique three-dimensional capabilities and can be exploited for the fabrication of complex microsystems with unprecedented functionalities.This book presents an overview of the state of the art of this rapidly emerging topic with contributions from leading experts in the field, ranging from principles of nonlinear material modification to fabrication techniques and applications to photonics and optofluidics.

  20. 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

  1. 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.

  2. Femtosecond laser electronic excitation tagging for quantitative velocity imaging in air

    International Nuclear Information System (INIS)

    Time-accurate velocity measurements in unseeded air are made by tagging nitrogen with a femtosecond-duration laser pulse and monitoring the displacement of the molecules with a time-delayed, fast-gated camera. Centimeter-long lines are written through the focal region of a ∼1 mJ, 810 nm laser and are produced by nonlinear excitation and dissociation of nitrogen. Negligible heating is associated with this interaction. The emission arises from recombining nitrogen atoms and lasts for tens of microseconds in natural air. It falls into the 560 to 660 nm spectral region and consists of multiple spectral lines associated with first positive nitrogen transitions. The feasibility of this concept is demonstrated with lines written across a free jet, yielding instantaneous and averaged velocity profiles. The use of high-intensity femtosecond pulses for flow tagging allows the accurate determination of velocity profiles with a single laser system and camera.

  3. 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

  4. Synthesis of nanocrystalline cubic zirconia using femtosecond laser ablation

    International Nuclear Information System (INIS)

    We report on the synthesis of nanocrystalline zirconia in liquid using femtosecond laser ablation. Nanocrystalline cubic zirconia has been prepared by femtosecond laser ablation of zirconium in ammonia, while nanocrystalline tetragonal and monoclinic zirconia was synthesized in water. The physical and chemical mechanisms of the formation of nanocrystalline metastable zirconia are discussed. The intrinsic properties of femtosecond laser ablation in liquid and OH−1 may be responsible for the synthesis of cubic zirconia. It is suggested that the femtosecond laser pulse can create higher temperature and pressure conditions at a localized area in the liquid than the nanosecond laser pulse and the cooling is also faster in the femtosecond laser ablation process, which determined the difference between the products synthesized with femtosecond and nanosecond-pulsed laser ablation.

  5. 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.

  6. 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

  7. 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.

  8. Titanium alloy nanosecond vs. femtosecond laser marking

    International Nuclear Information System (INIS)

    Highlights: ► We analyze nanosecond (commercial) and femtosecond laser marks, using SEM and EDAX. ► Elevated repetitive thermal gradients leads to structural defects for double crosses. ► Femtolaser engraving forms amorphous structures, composed of spherical particles. ► We conduct X-ray diffractometry to detect internal micro and residual stresses. ► No internal stresses modification occurred for nano and femtosecond laser marking. - Abstract: There are few papers which aim to analyze the effects of laser marking for traceability on various materials; therefore, the present paper proposes a study of the influences of such radiation processing on a titanium alloy, a vastly used material base within several industry fields. For the novelty impact, femtolaser marking has been carried out, besides the commercial nanosecond standard engraving. All marks have been analyzed using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometry.

  9. 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)

  10. Femtosecond dynamics of molecules and clusters

    OpenAIRE

    Baumert, Thomas,; Thalweiser, Rainer; Weiss, V.; Wiedenmann, Ernst; Gerber, Gustav

    1994-01-01

    The real-time dynamics of multiphoton ionization and fragmentation of molecules - Na_2 , Na_3 - and clusters - Na_n, Hg_n - has been studied in molecular beam experiments employing ion and electron spectroscopy together with femtosecond pump-probe techniques. Experiments with Na_2 and Na_3 reveal unexpected features of the dynamics of the absorption of several photons as seen in the one- and three dimensional vibrational wave packet motion in different potential surfaces and...

  11. Encoding and decoding of femtosecond pulses.

    Science.gov (United States)

    Weiner, A M; Heritage, J P; Salehi, J A

    1988-04-01

    We demonstrate the spreading of femtosecond optical pulses into picosecond-duration pseudonoise bursts. Spreading is accomplished by encoding pseudorandom binary phase codes onto the optical frequency spectrum. Subsequent decoding of the spectral phases restores the original pulse. We propose that frequency-domain encoding and decoding of coherent ultrashort pulses could form the basis for a rapidly reconfigurable, code-division multiple-access optical telecommunications network. PMID:19745879

  12. 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...

  13. Femtosecond protein nanocrystallography—data analysis methods

    OpenAIRE

    Kirian, R. A.; X. Wang; Weierstall, U.; Schmidt, K. E.; Spence, J. C. H.; Hunter, M; Fromme, P.; White, Thomas; Chapman, H. N.; Holton, J

    2010-01-01

    X-ray diffraction patterns may be obtained from individual submicron protein nanocrystals using a femtosecond pulse from a free-electron X-ray laser. Many “single-shot” patterns are read out every second from a stream of nanocrystals lying in random orientations. The short pulse terminates before significant atomic (or electronic) motion commences, minimizing radiation damage. Simulated patterns for Photosystem I nanocrystals are used to develop a method for recovering structure factors from ...

  14. 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.

  15. Remotely manageable system for stabilizing femtosecond lasers

    Czech Academy of Sciences Publication Activity Database

    Čížek, Martin; Hucl, Václav; Šmíd, Radek; Mikel, Břetislav; Lazar, Josef; Číp, Ondřej

    Bellingham: SPIE, 2014, 913527:1-6. ISBN 9781628410839. ISSN 0277-786X. [Laser Sources and Applications /2./. Brussels (BE), 14.04.2014-17.04.2014] R&D Projects: GA ČR GAP102/10/1813; GA MŠk ED3.1.00/12.0232; GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : femtosecond lasers * lasers * signal processing * frequency combs * laser spectroscopy * clocks * digital signal processing Subject RIV: BH - Optics, Masers, Lasers

  16. Beam Characterizations at Femtosecond Electron Beam Facility

    CERN Document Server

    Rimjaem, Sakhorn; Kangrang, Nopadol; Kusoljariyakul, Keerati; Rhodes, Michael W; Saisut, Jatuporn; Thongbai, Chitrlada; Vilaithong, Thiraphat; Wichaisirimongkol, Pathom; Wiedemann, Helmut

    2005-01-01

    The SURIYA project at the Fast Neutron Research Facility (FNRF) has been established and is being commissioning to generate femtosecond electron pulses. Theses short pulses are produced by a system consisting of an S-band thermionic cathode RF-gun, an alpha magnet as a magnetic bunch compressor, and a linear accelerator. The characteristics of its major components and the beam characterizations as well as the preliminary experimental results will be presented and discussed.

  17. 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.

  18. Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

    Science.gov (United States)

    Ilgner, Justus F. R.; Wehner, Martin M.; Lorenzen, Johann; Bovi, Manfred; Westhofen, Martin

    2006-01-01

    We evaluate the feasibility of nanosecond-pulsed and femtosecond-pulsed lasers for otologic surgery. The outcome parameters are cutting precision (in micrometers), ablation rate (in micrometers per second), scanning speed (in millimeters per second), and morphological effects on human middle ear ossicles. We examine single-spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG laser (355 nm, beam diameter 10µm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. A similar system (355 nm, beam diameter 20µm, pulse rate 10 kHz, power 160-1500 mW) and a femtosecond-pulsed CrLi:SAF-Laser (850 nm, pulse duration 100 fs, pulse energy 40 µJ, beam diameter 36 µm, pulse rate 1 kHz) are coupled to a scanner to perform bone surface ablation over a defined area. In our setups 1 and 2, marginal carbonization is visible in all single-spot ablations of 1-s exposures and longer: With an exposure time of 0.5 s, precise cutting margins without carbonization are observed. Cooling with saline solution result is in no carbonization at 1500 mW and a scan speed of 500 mm/s. Our third setup shows no carbonization but greater cutting precision, although the ablation volume is lower. Nanosecond- and femtosecond-pulsed laser systems bear the potential to increase cutting precision in otologic surgery.

  19. 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.

  20. 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.