Sample records for subpicosecond laser pulse

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

    Directory of Open Access Journals (Sweden)

    F. Gontad


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

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

    Energy Technology Data Exchange (ETDEWEB)

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


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

  3. All-Optical Switching of Magnetic Tunnel Junctions with Single Subpicosecond Laser Pulses (United States)

    Chen, Jun-Yang; He, Li; Wang, Jian-Ping; Li, Mo


    The magnetic tunnel junction (MTJ) is one of the most important building blocks of spintronic logic and memory components for beyond-CMOS computation and communication. Although switching of MTJs without magnetic field has been achieved by charge and spin current injection, the operation speed is limited fundamentally by the spin-precession time to many picoseconds. We report the demonstration of ultrafast all-optical switching of an MTJ using single subpicosecond infrared laser pulses. This optically switchable MTJ uses ferrimagnetic Gd(Fe,Co) as the free layer and its switching is read out by measuring its tunneling magnetoresistance with a Δ R /R ratio of 0.6%. A switching repetition rate at MHz has been demonstrated, but the fundamental upper limit should be higher than tens of GHz rate. This result represents an important step toward integrated optospintronic devices that combines spintronics and photonics technologies to enable ultrafast conversion between fundamental information carriers of electron spins and photons.

  4. Subpicosecond, high-brightness excimer laser systems

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, A.J.; Gosnell, T.R.; Roberts, J.P.; Lester, C.S.; Gibson, R.B.; Harper, S.E.; Tallman, C.R.


    Subpicosecond, high-brightness excimer laser systems are being used to explore the interaction of intense coherent ultraviolet radiation with matter. Applications of current systems include generation of picosecond x-ray pulses, investigation of possible x-ray laser pumping schemes, studies of multiphoton phenomena in atomic species, and time-resolved photochemistry. These systems, based on the amplification of subpicosecond pulses in small aperture (/approximately/1 cm/sup 2/) XeCl or KrF amplifiers, deliver focal spot intensities of /approximately/10/sup 17/ W/cm/sup 2/. Scaling to higher intensities, however, will require an additional large aperture amplifier which preserves near-diffraction-limited beam quality and subpicosecond pulse duration. We describe here both a small aperture KrF system which routinely provides intensities >10/sup 17/ W/cm/sup 2/ to several experiments, and a large aperture XeCl system designed to deliver /approximately/1 J subpicosecond pulses and yield intensities on target in excess of 10/sup 19/W/cm/sup 2/. We also discuss the effects of two-photon absorption on large-aperture, high-brightness excimer lasers. 4 refs., 2 figs.

  5. Time-resolved electron thermal conduction by probing of plasma formation in transparent solids with high power subpicosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Vu, Brian -Tinh Van [Univ. of California, Davis, CA (United States)


    This dissertation work includes a series of experimental measurements in a search for better understanding of high temperature (104-106K) and high density plasmas (1022-1024cm-3) produced by irradiating a transparent solid target with high intensity (1013 - 1015W/cm2) and subpicosecond (10-12-10-13s) laser pulses. Experimentally, pump and probe schemes with both frontside (vacuum-plasma side) and backside (plasma-bulk material side) probes are used to excite and interrogate or probe the plasma evolution, thereby providing useful insights into the plasma formation mechanisms. A series of different experiments has been carried out so as to characterize plasma parameters and the importance of various nonlinear processes. Experimental evidence shows that electron thermal conduction is supersonic in a time scale of the first picosecond after laser irradiation, so fast that it was often left unresolved in the past. The experimental results from frontside probing demonstrate that upon irradiation with a strong (pump) laser pulse, a thin high temperature (~40eV) super-critical density (~1023/cm3) plasma layer is quickly formed at the target surface which in turn becomes strongly reflective and prevents further transmission of the remainder of the laser pulse. In the bulk region behind the surface, it is also found that a large sub-critical (~1018/cm3) plasma is produced by inverse Bremsstrahlung absorption and collisional ionization. The bulk underdense plasma is evidenced by large absorption of the backside probe light. A simple and analytical model, modified from the avalanche model, for plasma evolution in transparent materials is proposed to explain the experimental results. Elimination of the bulk plasma is then experimentally illustrated by using targets overcoated with highly absorptive films.

  6. Elastic and magnetic dynamics of nanomagnet-ordered arrays impulsively excited by subpicosecond laser pulses. (United States)

    Comin, A; Giannetti, C; Samoggia, G; Vavassori, P; Grando, D; Colombi, P; Bontempi, E; Depero, L E; Metlushko, V; Ilic, B; Parmigiani, F


    This Letter reports on the first observation of elastic and magnetic dynamics of ordered arrays of permalloy nanodots excited by low-intensity 120 fs light pulses. The first order of the diffraction pattern, generated by the probe beam in a pump-probe configuration, is used for time-resolved reflectivity and time-resolved magneto-optical Kerr effect measurements. The nonadiabatical absorption of the pump triggers an acoustic standing wave, detected by the reflected probe signal, with a frequency related to the array wave vector. Instead, the magneto-optical signal exhibits, on the nanosecond time scale, the signature of the heat-exchange diffusion processes. In addition, a clear oscillation of the magnetic signal, at a frequency close to the frequency of the acoustic wave, is unambiguously detected. Finally, the interplay between the elastic and magnetic dynamics is analyzed and interpreted.

  7. Transient interference implications on the subpicosecond laser damage of multidielectrics (United States)

    Gallais, Laurent; Mangote, Benoît; Commandré, Mireille; Melninkaitis, Andrius; Mirauskas, Julius; Jeskevic, Maksim; Sirutkaitis, Valdas


    Laser-induced damage in optical thin films with subpicosecond pulses is investigated. A model dedicated to optical interference coatings and based on the rate equation for free electron generation is introduced. It takes into account the transient interference effects induced by changes in the dielectric function during the laser pulse and its feedback effect on the electron density distribution in the multilayer stack. Simulations are compared to experiments on HfO2 and Ta2O5 films with pulses ranging from 45 fs to 1 ps. It is shown that this approach can improve the interpretation of femtosecond and picosecond laser induced damage in thin films.

  8. Sub-picosecond pulse and terahertz optical frequency comb generation by monolithically integrated linear mode-locked laser (United States)

    Lo, Mu-Chieh; Guzmán, Robinson; Ali, Muhsin; Santos, Rui; Augustin, Luc; Carpintero, Guillermo


    We report on a record broad 3-dB bandwidth of 14 nm ( 1.8 THz around 1532 nm) optical frequency comb generated from a passively mode-locked quantum-well (QW) laser in the form of photonic integrated circuits through an InP generic photonic integration technology platform. This 21.5-GHz colliding-pulse mode-locked laser cavity is defined by two on-chip reflectors incorporating intracavity phase modulators followed by an out-of-cavity SOA as booster. Under certain operating conditions, an ultra-wide spectral bandwidth is achieved along with an autocorrelation trace confirming the mode locking nature exhibiting a pulse width of 0.35 ps. The beat note RF spectrum has a linewidth of sub-MHz and 35-dB SNR.

  9. Ultrashort X-ray pulse generation using subpicosecond electron linac

    CERN Document Server

    Harano, H; Yoshii, K; Ueda, T; Okita, S; Uesaka, M


    As a promising tool for ultrafast material analyses, we propose to utilize the X-ray pulse which may be generated in a quite simple manner using subpicosecond electron linacs. The properties of the X-ray were numerically studied with the EGS4 code. Verification of the X-ray generation was also conducted at the Nuclear Engineering Research Laboratory (NERL) linac and clear diffraction patterns of characteristic X-ray were obtained for typical single crystals.

  10. Hybrid Particle-In-Cell (PIC) simulation of heat transfer and ionization balance in overdense plasmas irradiated by subpicosecond pulse lasers

    Energy Technology Data Exchange (ETDEWEB)

    Zhidkov, A.; Sasaki, Akira [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment


    A 1D hybrid electromagnetic particle-in-cell code with new methods to include particle collisions and atomic kinetics is developed and applied to ultra-short-pulse laser plasma interaction. Using the Langevin equation to calculate the Coulomb collision term, the present code is shown to be fast and stable in calculating the particle motion in the PIC simulation. Furthermore, by noting that the scale length of the change of atomic kinetics is much longer than the Debye radius, we calculate ionization and X-ray emission on kinetics cells, which are determined by averaging plasma parameters such as the electron density and energy over number of PIC cells. The absorption of short-pulse laser by overdense plasmas is calculated in self-consistent manner, including the effect of rapid change of density and temperature caused by instantaneous heating and successive fast ionization of the target material. The calculated results agree well with those obtained from the Fokker-Planck simulation as well as experiments, for non-local heat transport in plasmas with steep temperature gradient, and for the absorption of a short laser pulse by solid density targets. These results demonstrate usefulness of the code and the computational method therein for understanding of physics of short pulse laser plasma interaction experiments, and for application to the gain calculation of short-pulse laser excited X-ray laser as well. (author)

  11. Invited article: a test-facility for large-area microchannel plate detector assemblies using a pulsed sub-picosecond laser. (United States)

    Adams, Bernhard; Chollet, Matthieu; Elagin, Andrey; Oberla, Eric; Vostrikov, Alexander; Wetstein, Matthew; Obaid, Razib; Webster, Preston


    The Large Area Picosecond Photodetector Collaboration is developing large-area fast photodetectors with time resolution detector systems. The facility consists of a pulsed Ti:Sapphire laser with a pulse duration ≈100 fs, an optical system allowing the laser to be scanned in two dimensions, and a computer-controlled data-acquisition system capable of reading out 60 channels of anode signals with a sampling rate of over 10 GS/s. The laser can scan on the surface of a sealed large-area photodetector, or can be introduced into a large vacuum chamber for tests on bare 8 in.-square MCP plates or into a smaller chamber for tests on 33-mm circular substrates. We present the experimental setup, detector calibration, data acquisition, analysis tools, and typical results demonstrating the performance of the test facility.

  12. Single-shot measurement of subpicosecond KrF pulse width by three-photon fluorescence of the XeF visible transition. (United States)

    Sarukura, N; Watanabe, M; Endoh, A; Watanabe, S


    The intensity of the XeF C-A transition induced by a subpicosecond KrF laser is shown to have a cubic dependence on KrF laser intensity. The third-order autocorrelation technique for measuring the duration of a single KrF subpicosecond pulse has been developed utilizing this visible transition. A pulse width of 220 fsec was successfully measured with a high contrast of ~10. The visible fluorescence is more useful to researchers than vacuum-UV fluorescences. Furthermore, this simple technique may be applied over a wide UV wavelength region from 204 to 306 nm.

  13. Subpicosecond-pulse generation through cross-phase-modulation-induced modulational instability in optical fibers. (United States)

    Gouveia-Neto, A S; Faldon, M E; Sombra, A S; Wigley, P G; Taylor, J R


    We report subpicosecond-pulse generation at 1.319 microm in a single-mode optical fiber by modulational instability induced through cross-phase modulation by 1.06-microm pulses propagating in the normal dispersion regime. Pulse-repetition rates approaching 300 GHz were achieved.

  14. Sub-picosecond snapshots of fast electrons from high intensity laser-matter interactions. (United States)

    Pompili, R; Anania, M P; Bisesto, F; Botton, M; Castellano, M; Chiadroni, E; Cianchi, A; Curcio, A; Ferrario, M; Galletti, M; Henis, Z; Petrarca, M; Schleifer, E; Zigler, A


    The interaction of a high-intensity short-pulse laser with thin solid targets produces electron jets that escape the target and positively charge it, leading to the formation of the electrostatic potential that in turn governs the ion acceleration. The typical timescale of such phenomena is on the sub-picosecond level. Here we show, for the first time, temporally-resolved measurements of the first released electrons that escaped from the target, so-called fast electrons. Their total charge, energy and temporal profile are provided by means of a diagnostics based on Electro-Optical Sampling with temporal resolution below 100 fs.

  15. Time- and space-resolved X-ray absorption spectroscopy of aluminum irradiated by a subpicosecond high-power laser (United States)

    Tzortzakis, S.; Audebert, P.; Renaudin, P.; Bastiani-Ceccotti, S.; Geindre, J. P.; Chenais-Popovics, C.; Nagels, V.; Gary, S.; Shepherd, R.; Girard, F.; Matsushima, I.; Peyrusse, O.; Gauthier, J.-C.


    The ionization and recombination dynamics of transient aluminum plasmas was measured using point projection K-shell absorption spectroscopy. An aluminum plasma was produced with a subpicosecond beam of the 100-TW laser at the LULI facility and probed at different times with a picosecond X-ray backlighter created with a synchronized subpicosecond laser beam. Fourier-Domain-Interferometry (FDI) was used to measure the electron temperature at the peak of the heating laser pulse. Absorption X-ray spectra at early times are characteristic of a dense and rather homogeneous plasma, with limited longitudinal gradients as shown by hydrodynamic simulations. The shift of the Al K-edge was measured in the cold dense plasma located at the edge of the heated plasma. From the 1s 2p absorption spectra, the average ionization was measured as a function of time and was also modeled with a collisional-radiative atomic physics code coupled with hydrodynamic simulations.

  16. Time- and space-resolved X-ray absorption spectroscopy of aluminum irradiated by a subpicosecond high-power laser

    Energy Technology Data Exchange (ETDEWEB)

    Tzortzakis, S. [Laboratoire pour l' Utilisation des Lasers Intenses (LULI), UMR 7605, CNRS-CEA-Universite Paris VI-Ecole Polytechnique, 91128 Palaiseau (France)]. E-mail:; Audebert, P. [Laboratoire pour l' Utilisation des Lasers Intenses (LULI), UMR 7605, CNRS-CEA-Universite Paris VI-Ecole Polytechnique, 91128 Palaiseau (France); Renaudin, P. [Commissariat a l' Energie Atomique, 91680 Bruyeres-le-Chatel Cedex (France); Bastiani-Ceccotti, S. [Laboratoire pour l' Utilisation des Lasers Intenses (LULI), UMR 7605, CNRS-CEA-Universite Paris VI-Ecole Polytechnique, 91128 Palaiseau (France); Geindre, J.P. [Laboratoire pour l' Utilisation des Lasers Intenses (LULI), UMR 7605, CNRS-CEA-Universite Paris VI-Ecole Polytechnique, 91128 Palaiseau (France); Chenais-Popovics, C. [Laboratoire pour l' Utilisation des Lasers Intenses (LULI), UMR 7605, CNRS-CEA-Universite Paris VI-Ecole Polytechnique, 91128 Palaiseau (France); Nagels, V. [Laboratoire pour l' Utilisation des Lasers Intenses (LULI), UMR 7605, CNRS-CEA-Universite Paris VI-Ecole Polytechnique, 91128 Palaiseau (France); Gary, S. [Commissariat a l' Energie Atomique, 91680 Bruyeres-le-Chatel Cedex (France); Shepherd, R. [Lawrence Livermore National Laboratory, University of California, Livermore, CA 94550 (United States); Girard, F. [Commissariat a l' Energie Atomique, 91680 Bruyeres-le-Chatel Cedex (France); Matsushima, I. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 3058568 (Japan); Peyrusse, O. [CELIA, UMR 5107, CNRS-CEA-Universite Bordeaux 1, 33405 Talence (France); Gauthier, J.-C. [CELIA, UMR 5107, CNRS-CEA-Universite Bordeaux 1, 33405 Talence (France)


    The ionization and recombination dynamics of transient aluminum plasmas was measured using point projection K-shell absorption spectroscopy. An aluminum plasma was produced with a subpicosecond beam of the 100-TW laser at the LULI facility and probed at different times with a picosecond X-ray backlighter created with a synchronized subpicosecond laser beam. Fourier-Domain-Interferometry (FDI) was used to measure the electron temperature at the peak of the heating laser pulse. Absorption X-ray spectra at early times are characteristic of a dense and rather homogeneous plasma, with limited longitudinal gradients as shown by hydrodynamic simulations. The shift of the Al K-edge was measured in the cold dense plasma located at the edge of the heated plasma. From the 1s-2p absorption spectra, the average ionization was measured as a function of time and was also modeled with a collisional-radiative atomic physics code coupled with hydrodynamic simulations.

  17. Sub-picosecond pulse break-up in an InGaAsP optical amplifier

    DEFF Research Database (Denmark)

    Romstad, Francis Pascal

    For high-speed optical communication systems with data speed higher than 200 Gb/s sub-picosecond pulse dynamics, coherent effects become important. We have, experimentally and theoretically, investigated the pulse distortion of a 150 fs pulse due to amplification in a 250 μm long InGaAsP ridge...... broadening and eventual break-up for input pulse energies on the order of picoJoules. This break-up is present in the gain region (6-14 dB), while for absorption (-6 dB9 and transparency, pulse narrowing by a factor of two is evidenced. We observe that not only the amplitude is modulated, but also the linear...

  18. Sub-picosecond pulse break-up in an InGaAsP optical amplifier

    DEFF Research Database (Denmark)

    Romstad, Francis Pascal


    For high speed optical communication system with data speed higher than 200 Gb/s sub-picosecond pulse dynamics, coherent effects become important.We have, experimentally and theoretically, investigated the pulse distortion of an 150 fs pulse due to amplification in a 250 ìm long InGaAsP ridge...... broadening and eventual break-up for input pulse energies on the order of picoJoules. This break-up is present in the gain region (6-14 dB), while for absorption (-6 dB) and transparency, pulse narrowing by a factor of two is evidenced. We observe that not only the amplitude is modulated, but also the linear...

  19. Pulse properties of external cavity mode locked semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Kroh, Marcel; Mørk, Jesper


    The performance of an external-cavity mode-locked semiconductor laser is investigated both theoretically and experimentally. The optimization analysis focuses on the regimes of stable mode locking and the generation of sub-picosecond optical pulses. We demonstrate stable output pulses down to one...

  20. Sub-picosecond x-ray streak camera development for laser fusion diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Lieber, A.J.; Sutphin, H.D.; Webb, C.B.; Williams, A.H.


    In laser-fusion interactions the effectiveness of coupling laser energy into target compression can be followed by obtaining spatial and temporal information on x-radiation emitted by the target. Microballoon targets now used require temporal resolution of better than a few picoseconds to track accurately target collapse and disassembly. Instabilities of two picoseconds or less are predicted for the process. Most streak cameras are based upon a sector-focused streak tube, which in the design limit is capable of only about 10 ps x-ray resolution. Therefore, a new tube, based upon the proximity-focused or wafer intensifier was developed as a laser-fusion diagnostic capable in the design limit of delivering truly sub-picosecond x-ray resolution. A new power supply was also developed to drive the streak tube. Together, a camera has resulted with true picosecond capability, small size, high sensitivity, broad dynamic range, high spatial resolution, and very low jitter. The system has proved 98 percent reliable in over 300 laser shots providing data on the collapse of microballoons when irradiated by a dual beam Nd:YAG laser. Theoretical predictions of 2.5 to 3 ps resolution are consistent with experimental data. A visible variant of the design now under construction is expected to give sub-picosecond resolution with advantages similar to the x-ray system.

  1. Subpicosecond laser ablation of copper and fused silica: Initiation threshold and plasma expansion

    Energy Technology Data Exchange (ETDEWEB)

    Axente, E., E-mail: [Lasers Department, National Institute for Lasers, Plasma, and Radiation Physics, P.O. Box MG 36, RO-77125, Bucharest-Magurele (Romania); Laboratoire LP3, CNRS - Universite Aix-Marseille II, Luminy, 13288 Marseille (France); Noel, S.; Hermann, J.; Sentis, M. [Laboratoire LP3, CNRS - Universite Aix-Marseille II, Luminy, 13288 Marseille (France); Mihailescu, I.N. [Lasers Department, National Institute for Lasers, Plasma, and Radiation Physics, P.O. Box MG 36, RO-77125, Bucharest-Magurele (Romania)


    We investigated the subpicosecond laser ablation of copper and fused silica under 100 fs laser irradiation at 800 nm in vacuum by means of fast plume imaging and time- and space-resolved optical emission spectroscopy. We found that, to the difference of copper ablation, the laser-generated plasma from a fused silica target exhibited one 'main' component only. The 'slow' plasma component, observed during copper ablation and usually assigned to optical emission from nanoparticles was not detected by either plasma fast imaging or optical emission spectroscopy even when fused silica targets were submitted to the highest incident fluences used in our experiments. The characteristic expansion velocity of this unique component was about three times larger than the velocity of the fast plume component observed during copper ablation. The dependence of laser fluence on both plasma expansion and ablation rate was investigated and discussed in terms of ablation efficiency and initiation mechanisms.

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

    DEFF Research Database (Denmark)

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


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

  3. In-Fiber Subpicosecond Pulse Shaping for Nonlinear Optical Telecommunication Data Processing at 640 Gbit/s

    DEFF Research Database (Denmark)

    Azaña, J.; Oxenløwe, Leif Katsuo; Palushani, Evarist


    We review recent work on all-fiber (long-period fiber grating) devices for optical pulse shaping, particularly flat-top pulse generation, down to the subpicosecond range and their application for nonlinear switching (demultiplexing) of optical time-division multiplexed (OTDM) data signals in fiber...... benefits in the demultiplexing process, including a significantly increased timing-jitter tolerance (up to ~500 fs, i.e., 30% of the bit period) and the associated improvement in the bit-error-rate performance (e.g., with a sensitivity increase of up to ~13 dB as compared with the use of Gaussian...

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

    DEFF Research Database (Denmark)

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


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

  5. Electronically driven adsorbate excitation mechanism in femtosecond-pulse laser desorption

    DEFF Research Database (Denmark)

    Brandbyge, Mads; Hedegård, Per; Heinz, T. F.


    Femtosecond-pulse laser desorption is a process in which desorption is driven by a subpicosecond temperature pulse of order 5000 K in the substrate-adsorbate electron system, whose energy is transferred into the adsorbate center-of-mass degrees of freedom by a direct coupling mechanism. We presen...

  6. Subpicosecond Nd:glass CPA laser system for kilovolt x-ray generation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, T.; Sharma, L.B.; Daido, H.; Uematsu, H.; Ninomiya, S.; Murai, K.; Kato, Y.; Nakatsuka, M.; Izawa, Y.; Nakai, S. [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565 (Japan); Kitada, T. [The Kansai Electric Power Co., Inc., 3-11-20 Naoji, Amagasaki 661 (Japan); Yamanaka, C. [Institute for Laser Technology, 1-8-4 Utsubohonmachi, Nishiku Osaka 550 (Japan)


    We describe an experiment on second-harmonic generation of a picosecond Nd:glass laser pulse with time predelay at intensities of up to 200 GW/cm{sup 2} and a wavelength of 1.053 {mu}m. Duration of the second-harmonic pulse was reduced to 0.6 ps from 1.5 ps width of the fundamental pulse at an optimum intensity of 50 GW/cm{sup 2}. The spatial profile of the laser beam is not degraded by self-focusing at an input intensity of {approximately}50 GW/cm{sup 2}. {copyright} {ital 1996 American Institute of Physics.}

  7. In-Fiber Subpicosecond Pulse Shaping for Nonlinear Optical Telecommunication Data Processing at 640 Gbit/s

    Directory of Open Access Journals (Sweden)

    J. Azaña


    Full Text Available We review recent work on all-fiber (long-period fiber grating devices for optical pulse shaping, particularly flat-top pulse generation, down to the subpicosecond range and their application for nonlinear switching (demultiplexing of optical time-division multiplexed (OTDM data signals in fiber-optic telecommunication links operating up to 640 Gbit/s. Experiments are presented demonstrating error-free 640-to-10 Gbit/s demultiplexing of the 64 tributary channels using the generated flat-top pulses for temporal gating in a Kerr-effect-based nonlinear optical loop mirror. The use of flat-top pulses has critical benefits in the demultiplexing process, including a significantly increased timing-jitter tolerance (up to ~500 fs, i.e., 30% of the bit period and the associated improvement in the bit-error-rate performance (e.g., with a sensitivity increase of up to ~13 dB as compared with the use of Gaussian-like gating pulses. Long-period fiber grating pulse shapers with reduced polarization dependence are fabricated and successfully used for polarization-independent 640-to-10 Gbit/s demultiplexing experiments.

  8. Short-pulse laser interactions with disordered materials and liquids

    Energy Technology Data Exchange (ETDEWEB)

    Phinney, L.M.; Goldman, C.H.; Longtin, J.P.; Tien, C.L. [Univ. of California, Berkeley, CA (United States)


    High-power, short-pulse lasers in the picosecond and subpicosecond range are utilized in an increasing number of technologies, including materials processing and diagnostics, micro-electronics and devices, and medicine. In these applications, the short-pulse radiation interacts with a wide range of media encompassing disordered materials and liquids. Examples of disordered materials include porous media, polymers, organic tissues, and amorphous forms of silicon, silicon nitride, and silicon dioxide. In order to accurately model, efficiently control, and optimize short-pulse, laser-material interactions, a thorough understanding of the energy transport mechanisms is necessary. Thus, fractals and percolation theory are used to analyze the anomalous diffusion regime in random media. In liquids, the thermal aspects of saturable and multiphoton absorption are examined. Finally, a novel application of short-pulse laser radiation to reduce surface adhesion forces in microstructures through short-pulse laser-induced water desorption is presented.

  9. Ultrashort Laser Pulse Phenomena

    CERN Document Server

    Diels, Jean-Claude


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

  10. A passively mode-locked sub-picosecond Ho3+,Pr3+-doped fluoride fiber laser operating at 2.86 µm(Conference Presentation) (United States)

    Antipov, Sergei; Jackson, Stuart D.; Withford, Michael J.; Fürbach, Alexander


    We demonstrate a passively mode-locked holmium-praseodymium co-doped ring fiber laser that produces an estimated 950 fs pulsewidth and peak power of 4.3 kW at a pulse repetition rate of 74 MHz. The measured center wavelength was 2.86 µm which overlaps more strongly with liquid water whilst better avoiding atmospheric water vapor which overlaps more strongly with previously reported ultrafast Er3+ fiber lasers operating at 2.8. Thus the present system should display better long term stability compared to the Er3+-based system and at the same time, be a more practical tool for interaction with biological tissues. The laser was constructed using a 1.2 m long double-clad fluoride fiber doped with Ho3+ and Pr3+ ions and arranged into a unidirectional ring resonator that was resistant to instabilities associated with back reflections. Two semiconductor 1150 nm laser diodes with the maximum combined output of 7.5 W were used to pump the fiber. Mode-locking was achieved using the combination of two techniques: sub-picosecond pulses were produced by nonlinear polarization evolution after longer pulses were initially obtained using an in-cavity GaAs saturable absorber having a modulation depth of 90% and a relaxation time of 10 ps. A standard arrangement employing two waveplates and an optical isolator was introduced into the resonator to carry out nonlinear polarization rotation. The average power of the mode-locked laser reached 350 mW after the 50% outcoupling mirror. The RF signal-to-noise ratio reached 67 dB for the first peak at the resolution bandwidth of 10 kHz.

  11. Fiber-Optical Parametric Amplification of Sub-Picosecond Pulses for High-Speed Optical Communications

    DEFF Research Database (Denmark)

    Lali-Dastjerdi, Zohreh; Cristofori, Valentina; Rottwitt, Karsten


    This article reviews recent results of amplification of short optical pulses using fiber-optical parametric amplifiers. This includes chirped-pulse amplification of 400 fs pulses, error-free amplification of a 640-Gbit/s optical time-division multiplexed signal with less than a 1-dB power penalty...

  12. Long Wavelength Electromagnetic Light Bullets Generated by a 10.6 micron CO2 Ultrashort Pulsed Source (United States)


    studying atmospheric propagation of a high energy Joule-level few picosecond to sub-picosecond pulsed CO2 laser system being planned within a new DOD... high energy Joule- level few picosecond to sub-picosecond pulsed CO2 laser system being planned within a new DOD joint initiative of AFOSR, AFRL and...provide a basic research support infrastructure for, a high energy Joule-level few picosecond to sub-picosecond pulsed few cycle CO2 laser system

  13. High impact ionization rate in silicon by sub-picosecond THz electric field pulses (Conference Presentation)

    DEFF Research Database (Denmark)

    Tarekegne, Abebe Tilahun; Iwaszczuk, Krzysztof; Hirori, Hideki


    Summary form only given. Metallic antenna arrays fabricated on high resistivity silicon are used to localize and enhance the incident THz field resulting in high electric field pulses with peak electric field strength reaching several MV/cm on the silicon surface near the antenna tips. In such hi...... carrier dynamics in other semiconductors....

  14. Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement. (United States)

    Rakhman, Abdurahim; Wang, Yang; Garcia, Frances; Long, Cary; Huang, Chunning; Takeda, Yasuhiro; Liu, Yun


    A compact multifunctional optical correlator system for pulse width measurement of ultrashort ultraviolet (UV) pulses has been designed and experimentally demonstrated. Both autocorrelation and cross-correlation functions are measured using a single nonlinear crystal, and the switching between two measurements requires no adjustment of phase matching and detector. The system can measure UV pulse widths from sub-picoseconds to 100 ps, and it involves no auxiliary pulse in the measurement. The measurement results on a burst-mode picosecond UV laser show a high-quality performance on speed, accuracy, resolution, and dynamic range. The proposed correlator can be applied to measure any ultrashort UV pulses produced through sum-frequency generation or second-harmonic generation.

  15. Nanofabrication with Pulsed Lasers

    Directory of Open Access Journals (Sweden)

    Kabashin AV


    Full Text Available Abstract An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3, is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser–matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics.

  16. Comparison Between Geometrically Focused Pulses Versus Filaments in Femtosecond Laser Ablation of Steel and Titanium Alloys (Reprint) (United States)


    titanium samples are ablated by filaments and by sharply focused sub-picosecond laser pulses. We then performed metrology on the samples to compare the...sub-picosecond laser pulses. We then performed metrology on the samples to compare the ablation features in addition to modeling of the plasma...versus filaments 491 123 12 1 DEFENSE TECHNICAL ( PDF ) INFORMATION CTR DTIC OCA 2 DIRECTOR ( PDF ) US ARMY RESEARCH LAB RDRL CIO LL

  17. Pulsed laser ablation of copper (United States)

    Jordan, R.; Cole, D.; Lunney, J. G.; Mackay, K.; Givord, D.


    The laser ablation of copper with a 532 nm, 6 ns laser has been investigated in the regime normally used for pulsed laser deposition. The ablation depth per pulse and the flux and energy distribution of the ions in the plume were measured and compared to the deposition rate as measured by a quartz microbalance. These measurements were compared with an analytic model of ablation via a laser sustained plasma. It is shown that self-sputtering of the growing film is significant.

  18. High power ultrashort pulse lasers

    Energy Technology Data Exchange (ETDEWEB)

    Perry, M.D.


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

  19. Plasma mediated ablation of biological tissues with ultrashort laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Oraevsky, A.A. [Lawrence Livermore National Lab., CA (United States)]|[Rice Univ., Houston, TX (United States). Dept. of Electrical Engineering; DaSilva, L.B.; Feit, M.D. [Lawrence Livermore National Lab., CA (United States)] [and others


    Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range from 350 fs to 1 ns at 1,053 nm wavelength. A time resolved stress detection technique was employed to measure transient stress profiles and amplitudes. Optical microscopy was used to characterize ablation craters qualitatively, while a wide band acoustic transducer helped to quantify tissue mechanical response and the ablation threshold. The ablation threshold was measured as a function of laser pulse duration and linear absorption coefficient. For nanosecond pulses the ablation threshold was found to have a strong dependence on the linear absorption coefficient of the material. As the pulse length decreased into the subpicosecond regime the ablation threshold became insensitive to the linear absorption coefficient. The ablation efficiency was found to be insensitive to both the laser pulse duration and the linear absorption coefficient. High quality ablation craters with no thermal or mechanical damage to surrounding material were obtained with 350 fs laser pulses. The mechanism of optical breakdown at the tissue surface was theoretically investigated. In the nanosecond regime, optical breakdown proceeds as an electron collisional avalanche ionization initiated by thermal seed electrons. These seed electrons are created by heating of the tissue by linear absorption. In the ultrashort pulse range, optical breakdown is initiated by the multiphoton ionization of the irradiated medium (6 photons in case of tissue irradiated at 1,053 nm wavelength), and becomes less sensitive to the linear absorption coefficient. The energy deposition profile is insensitive to both the laser pulse duration and the linear absorption coefficient.

  20. Laser system using ultra-short laser pulses (United States)

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


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

  1. Optical pulses, lasers, measuring techniques

    CERN Document Server

    Früngel, Frank B A


    High Speed Pulse Technology: Volume II: Optical Pulses - Lasers - Measuring Techniques focuses on the theoretical and engineering problems that result from the capacitor discharge technique.This book is organized into three main topics: light flash production from a capacitive energy storage; signal transmission and ranging systems by capacitor discharges and lasers; and impulse measuring technique. This text specifically discusses the air spark under atmospheric conditions, industrial equipment for laser flashing, and claims for light transmitting system. The application of light impulse sign

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

    DEFF Research Database (Denmark)

    Kong, Deming; Guan, Pengyu; Hu, Hao


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

  3. Electron acceleration and generation of high-brilliance x-ray radiation in kilojoule, subpicosecond laser-plasma interactions

    Directory of Open Access Journals (Sweden)

    J. Ferri


    Full Text Available Petawatt, picosecond laser pulses offer rich opportunities in generating synchrotron x-rays. This paper concentrates on the regimes accessible with the PETAL laser, which is a part of the Laser Megajoule (LMJ facility. We explore two physically distinct scenarios through Particle-in-Cell simulations. The first one realizes in a dense plasma, such that the period of electron Langmuir oscillations is much shorter than the pulse duration. Hallmarks of this regime are longitudinal breakup (“self-modulation” of the picosecond-scale laser pulse and excitation of a rapidly evolving broken plasma wake. It is found that electron beams with a charge of several tens of nC can be obtained, with a quasi-Maxwellian energy distribution extending to a few-GeV level. In the second scenario, at lower plasma densities, the pulse is shorter than the electron plasma period. The pulse blows out plasma electrons, creating a single accelerating cavity, while injection on the density downramp creates a nC quasi-monoenergetic electron bunch within the cavity. This bunch accelerates without degradation beyond 1 GeV. The x-ray sources in the self-modulated regime offer a high number of photons (∼10^{12} with the slowly decaying energy spectra extending beyond 60 keV. In turn, quasimonoenergetic character of the electron beam in the blowout regime results in the synchrotron-like spectra with the critical energy around 10 MeV and a number of photons >10^{9}. Yet, much smaller source duration and transverse size increase the x-ray brilliance by more than an order of magnitude against the self-modulated case, also favoring high spatial and temporal resolution in x-ray imaging. In all explored cases, accelerated electrons emit synchrotron x-rays of high brilliance, B>10^{20}  photons/s/mm^{2}/mrad^{2}/0.1%BW. Synchrotron sources driven by picosecond kilojoule lasers may thus find an application in x-ray diagnostics on such facilities such as the LMJ or National

  4. Pulsed Scophony laser projection system (United States)

    Lowry, J. B.; Welford, W. T.; Humphries, M. R.


    A novel laser TV projection display has been developed by PA Technology employing the Scophony system with acousto-optic modulators and pulsed lasers. This results in a projection system with greater optical simplicity, higher reliability and reduced power and cooling requirements over similar laser projectors. The technique has been successfully implemented in British Aerospace's Microdome missile training simulator. This paper describes the underlying principles of the design, its operational features and its implementation in the Microdome.

  5. EUV emission stimulated by use of dual laser pulses from continus liquid microjet targets (United States)

    Higashiguchi, Takeshi; Rajyaguru, Chirag; Sasaki, Wataru; Kubodera, Shoichi


    A continuous water-jet or water-jet mixed with LiF with several tens μm diameter was formed in a vacuum chamber through a small capillary nozzle. Usage of two laser pulses is an efficient way to produce EUV emission, since a density and temperature of a plasma formed by the first laser pulse are regulated by the second laser pulse. By adjusting the delay of the second pulse, one could maximize the EUV emission. A subpicosecond Ti:Sapphire laser at a wavelength of 800 nm produced a maximum energy around 30 mJ. The beam was divided by a Michelson interferometer, which produced two laser pulses with energies of 5 mJ. The pulse duration was adjusted around 300 fs (FWHM). Both beams were focused on a micro-jet using a lens with a focal length of 15 cm. The delay time between the two pulses was varied from 100 to 800 ps by use of an optical delay line. Clear enhancement of the EUV emission yield was observed when the delay between the two pulses was around 500 ps. The experimentally observed delay agrees reasonably well with that of a plasma to expand to its critical density of 10^21 cm-3.

  6. Ultrashort Laser Pulses in Biology and Medicine

    CERN Document Server

    Braun, Markus; Zinth, Wolfgang


    Sources of ultrashort laser pulses are nowadays commercially available and have entered many areas of research and development. This book gives an overview of biological and medical applications of these laser pulses. The briefness of these laser pulses permits the tracing of the fastest processes in photo-active bio-systems, which is one focus of the book. The other focus is applications that rely on the high peak intensity of ultrashort laser pulses. Examples covered span non-linear imaging techniques, optical tomography, and laser surgery.

  7. Pulsed laser deposition: metal versus oxide ablation

    NARCIS (Netherlands)

    Doeswijk, L.M.; Rijnders, Augustinus J.H.M.; Blank, David H.A.


    We present experimental results of pulsed laser interaction with metal (Ni, Fe, Nb) and oxide (TiO2, SrTiO3, BaTiO3) targets. The influence of the laser fluence and the number of laser pulses on the resulting target morphology are discussed. Although different responses for metal and oxide targets

  8. Long-period fiber-brating-based filter for generation of picosecond and subpicosecond transform-limited flat-top pulses

    Czech Academy of Sciences Publication Activity Database

    Slavík, Radan; Park, Y.; Azana, J.


    Roč. 20, č. 10 (2008), s. 806-808 ISSN 1041-1135 R&D Projects: GA AV ČR(CZ) KJB200670601; GA ČR(CZ) GA102/07/0999 Institutional research plan: CEZ:AV0Z20670512 Keywords : optical fibre filters * passive filters * optical pulse shaping Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.173, year: 2008

  9. FY07 LDRD Final Report Precision, Split Beam, Chirped-Pulse, Seed Laser Technology

    Energy Technology Data Exchange (ETDEWEB)

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


    The goal of this LDRD ER was to develop a robust and reliable technology to seed high-energy laser systems with chirped pulses that can be amplified to kilo-Joule energies and recompressed to sub-picosecond pulse widths creating extremely high peak powers suitable for petawatt class physics experiments. This LDRD project focused on the development of optical fiber laser technologies compatible with the current long pulse National Ignition Facility (NIF) seed laser. New technologies developed under this project include, high stability mode-locked fiber lasers, fiber based techniques for reduction of compressed pulse pedestals and prepulses, new compact stretchers based on chirped fiber Bragg gratings (CFBGs), new techniques for manipulation of chirped pulses prior to amplification and new high-energy fiber amplifiers. This project was highly successful and met virtually all of its goals. The National Ignition Campaign has found the results of this work to be very helpful. The LDRD developed system is being employed in experiments to engineer the Advanced Radiographic Capability (ARC) front end and the fully engineered version of the ARC Front End will employ much of the technology and techniques developed here.

  10. Pulsed Laser Spectroscopy: An Inexpensive Approach (United States)

    Daly, J. G.; Hastings, R.; Schmidt, J. A.


    The assembly of a pulsed laser spectroscopy laboratory is presented. The authors describe how they constructed pulsed lasers, fast photodetectors, a boxcar signal averager, and associated equipment. A molecular nitrogen laser operating up to 50 Hz with an ultraviolet (337.1 nm) 700 kW pulse was used to optically pump an organic dye laser. The resulting output could be tuned from 360.0 to 680.0 nm. This pulse was typically 30 kW and 8 nsec, which makes it ideally suited to selective excitation and fluorescence studies. By constructing this equipment, it is estimated that the investment was one-tenth the cost of commercial components.

  11. Ultrashort pulse laser technology laser sources and applications

    CERN Document Server

    Schrempel, Frank; Dausinger, Friedrich


    Ultrashort laser pulses with durations in the femtosecond range up to a few picoseconds provide a unique method for precise materials processing or medical applications. Paired with the recent developments in ultrashort pulse lasers, this technology is finding its way into various application fields. The book gives a comprehensive overview of the principles and applications of ultrashort pulse lasers, especially applied to medicine and production technology. Recent advances in laser technology are discussed in detail. This covers the development of reliable and cheap low power laser sources as well as high average power ultrashort pulse lasers for large scale manufacturing. The fundamentals of laser-matter-interaction as well as processing strategies and the required system technology are discussed for these laser sources with respect to precise materials processing. Finally, different applications within medicine, measurement technology or materials processing are highlighted.

  12. One laser pulse generates two photoacoustic signals

    CERN Document Server

    Gao, Fei; Zheng, Yuanjin


    Photoacoustic sensing and imaging techniques have been studied widely to explore optical absorption contrast based on nanosecond laser illumination. In this paper, we report a long laser pulse induced dual photoacoustic (LDPA) nonlinear effect, which originates from unsatisfied stress and thermal confinements. Being different from conventional short laser pulse illumination, the proposed method utilizes a long square-profile laser pulse to induce dual photoacoustic signals. Without satisfying the stress confinement, the dual photoacoustic signals are generated following the positive and negative edges of the long laser pulse. More interestingly, the first expansion-induced photoacoustic signal exhibits positive waveform due to the initial sharp rising of temperature. On the contrary, the second contraction-induced photoacoustic signal exhibits exactly negative waveform due to the falling of temperature, as well as pulse-width-dependent, signal amplitude which is caused by the concurrent heat accumulation and ...

  13. Energy coupling in short pulse laser solid interactions and its impact for space debris removal. (United States)

    Neely, David; Allott, Ric; Bingham, Bob; Collier, John; Greenhalgh, Justin; Michaelis, Max; Phillips, Jonathan; Phipps, Claude R; McKenna, Paul


    Significant advances have been made over the last decade to improve the performance, efficiency, and contrast of high peak and average power laser systems, driven by their use in a wide variety of fields, from the industrial to the scientific. As the contrast of the lasers has improved, interactions with contrasts of 1012 are now routinely undertaken. At such high contrasts, there is negligible preplasma formation and the ionized surface layer created by subpicosecond-duration pulses typically forms a highly reflective "plasma mirror" capable of reflecting between 70% and 90% of the incident energy. Although such interactions are of significant interest for applications such as harmonic source production and to enable the underlying physics to be studied, their low absorption can limit their usefulness for applications such as space debris removal.

  14. Femtosecond Laser Pulses Principles and Experiments

    CERN Document Server

    Rullière, Claude


    This smooth introduction for advanced undergraduates starts with the fundamentals of lasers and pulsed optics. Thus prepared, the student is introduced to short and ultrashort laser pulses, and learns how to generate, manipulate, and measure them. Spectroscopic implications are also discussed. The second edition has been completely revised and includes two new chapters on some of the most promising and fast-developing applications in ultrafast phenomena: coherent control and attosecond pulses.

  15. Dark pulse quantum dot diode laser. (United States)

    Feng, Mingming; Silverman, Kevin L; Mirin, Richard P; Cundiff, Steven T


    We describe an operating regime for passively mode-locked quantum dot diode laser where the output consists of a train of dark pulses, i.e., intensity dips on a continuous background. We show that a dark pulse train is a solution to the master equation for mode-locked lasers. Using simulations, we study stability of the dark pulses and show they are consistent with the experimental results.

  16. Femtosecond laser pulses principles and experiments

    CERN Document Server


    This smooth introduction for advanced undergraduate students starts with the fundamentals of lasers and pulsed optics Thus prepared, the student learns how to generate short and ultrashort laser pulses, how to manipulate them, and how to measure them Finally, spectroscopic implications are discussed This rounded text gives the student an up-to-date introduction to one of the most exciting fields in laser physics

  17. Short pulse laser systems for biomedical applications

    CERN Document Server

    Mitra, Kunal


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

  18. Pulsed Laser Annealing of Carbon (United States)

    Abrahamson, Joseph P.

    This dissertation investigates laser heating of carbon materials. The carbon industry has been annealing carbon via traditional furnace heating since at least 1800, when Sir Humphry Davy produced an electric arc with carbon electrodes made from carbonized wood. Much knowledge has been accumulated about carbon since then and carbon materials have become instrumental both scientifically and technologically. However, to this day the kinetics of annealing are not known due to the slow heating and cooling rates of furnaces. Additionally, consensus has yet to be reached on the cause of nongraphitizability. Annealing trajectories with respect to time at temperature are observed from a commercial carbon black (R250), model graphitizable carbon (anthracene coke) and a model nongraphitizable carbon (sucrose char) via rapid laser heating. Materials were heated with 1064 nm and 10.6 im laser radiation from a Q-switched Nd:YAG laser and a continuous wave CO2 laser, respectively. A pulse generator was used reduce the CO2 laser pulse width and provide high temporal control. Time-temperature-histories with nanosecond temporal resolution and temperature reproducibility within tens of degrees Celsius were determined by spectrally resolving the laser induced incandescence signal and applying multiwavelength pyrometry. The Nd:YAG laser fluences include: 25, 50, 100, 200, 300, and 550 mJ/cm2. The maximum observed temperature ranged from 2,400 °C to the C2 sublimation temperature of 4,180 °C. The CO2 laser was used to collect a series of isothermal (1,200 and 2,600 °C) heat treatments versus time (100 milliseconds to 30 seconds). Laser heated samples are compared to furnace annealing at 1,200 and 2,600 °C for 1 hour. The material transformation trajectory of Nd:YAG laser heated carbon is different than traditional furnace heating. The traditional furnace annealing pathway is followed for CO2 laser heating as based upon equivalent end structures. The nanostructure of sucrose char

  19. Controlling magnetism by ultrashort laser pulses: from fundamentals to nanoscale engineering (United States)

    Bossini, D.; Rasing, Th.


    From the discovery of sub-picosecond demagnetization over a decade ago [1] to the recent demonstration of magnetization reversal by a single 40 femtosecond laser pulse [2], the manipulation of spins by ultra-short laser pulses has become a fundamentally challenging topic with a potentially high impact for future spintronics, data storage and manipulation and quantum computation [3]. It was realized that the femtosecond laser induced all-optical switching (AOS) as observed in ferrimagnets exploits the laser induced strongly non-equilibrium dynamics and the antiferromagnetic exchange interaction between their sublattices [4-6]. This opens the way to engineer new magnetic materials for AOS [7,8], though for real applications nanoscale control of inhomogeneities appears to be relevant [9]. Besides the intruiging technological implications of these observations, they broadened remarkably the frontiers of our fundamental knowledge of magnetic phenomena. The laser driven out-of-equilibrium states cannot be described in term of the well-established thermodynamical approach, which is based on the concepts of equilibrium and adiabatic transformations. Theoretical efforts, although in their infancy, have already demonstrated [5,6] that light-induced spin dynamics on the (sub)-picosecond time scale results in phenomena utterly forbidden in a thermodynamical framework. Another challenge is how to bring the optical manipulation of magnetic media to the required nanoscale. This is clearly a key element for the perspectives in terms of magnetic recording. In addition, it would allow to explore a novel regime of spin dynamics, since the investigation of magnets on the femtosecond time-scale and the nanometer length-scale simultaneously is unexplored. One experimental approach which may be successful makes use of wave-shaping techniques [10]. Recent results with engineered hybrid magnetic materials and nanofocusing via a plasmonic antenna showed the practical potential of AOS: the

  20. Observation of neutron spectrum from deuterated plastic irradiated by 100 picosecond and sub-picosecond ultra-intense laser. (United States)

    Izumi, N.; Miyoshi, K.; Takahashi, K.; Habara, H.; Kodama, R.; Sentoku, S.; Fujita, H.; Kitagawa, Y.; Katou, Y.; Mima, K.; Tanaka, K. A.


    For understanding of the fundamental physics of the fast ignition, it is crucial to investigate the fast ion production in a high density plasma irradiated by an ultra-intense laser. The energy spectrum of the neutrons produced in the deuterated target reflects the energy spectrum of fast deuterons accelerated in the interacting region. Due to high penetration ability of fast neutron, the neutron spectra directly bring out the information of the hot ions from the high density plasma. We have observed 10^6 of the DD neutrons produced in a deuterated polystyrene (C8D8)x target irradiated by the 500-fs intense laser (up to 10^19 W/cm^2). The fast neutron spectra were measured by multi-channel time-of-flight neutron spectrometer (MANDALA) at the GEKKO XII laser facility of Osaka University. The spectrometer has two sets of 421 channel detector arrays which were located at 90 and 54.7 degrees with respect to the irradiation axis. The observed spectral width of DD neutrons were 1.35 MeV in full width of half maximum. This spectrum result from the fusion reaction created by accelerated ions which have energy about 300 keV. We report the details of the experimental results and the quantitative analysis using particle in cell code.

  1. Propagating Characteristics of Pulsed Laser in Rain

    Directory of Open Access Journals (Sweden)

    Jing Guo


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

  2. Conceptual design of a laser wakefield acceleration experiment with external bunch injection

    NARCIS (Netherlands)

    Khachatryan, A.G.; Luttikhof, M.J.H.; Irman, A.; van Goor, F.A.; Verschuur, Jeroen W.J.; Bastiaens, Hubertus M.J.; Boller, Klaus J.


    We present a conceptual design of a laser wakefield acceleration experiment where a sub-picosecond electron bunch from a photo-cathode RF linac is injected into a plasma channel just before a laser pulse. The pulse overtakes the bunch which is then trapped, compressed and accelerated in the laser

  3. Laser Pulses Characterization with Pyroelectric Sensors


    Malka, V.; J. Faure; Y. Gauduel


    There are many industrial and medical applications of CO2 (λ=10.6 μm) and Nd:YAG (λ=1.06 μm) infrared lasers for which the quality of the process are tightly connected to the characteristic of the laser pulse. These two types of lasers deliver pulses with duration, repetition frequency and power that can be controlled by means of a programmable electronic control unit. An open-loop control generally optimize the process performances by availing of a laser system model. How...

  4. Sub-picosecond timing fluctuation suppression in laser-based atmospheric transfer of microwave signal using electronic phase compensation (United States)

    Chen, Shijun; Sun, Fuyu; Bai, Qingsong; Chen, Dawei; Chen, Qiang; Hou, Dong


    We demonstrated a timing fluctuation suppression in outdoor laser-based atmospheric radio-frequency transfer over a 110 m one-way free-space link using an electronic phase compensation technique. Timing fluctuations and Allan Deviation are both measured to characterize the instability of transferred frequency incurred during the transfer process. With transferring a 1 GHz microwave signal over a timing fluctuation suppressed transmission link, the total root-mean-square (rms) timing fluctuation was measured to be 920 femtoseconds in 5000 s, with fractional frequency instability on the order of 1 × 10-12 at 1 s, and order of 2 × 10-16 at 1000 s. This atmospheric frequency transfer scheme with the timing fluctuation suppression technique can be used to fast build an atomic clock-based frequency free-space transmission link since its stability is superior to a commercial Cs and Rb clock.

  5. Evolution Strategies for Laser Pulse Compression

    NARCIS (Netherlands)

    Monmarché, Nicolas; Fanciulli, Riccardo; Willmes, Lars; Talbi, El-Ghazali; Savolainen, Janne; Collet, Pierre; Schoenauer, Marc; van der Walle, P.; Lutton, Evelyne; Back, Thomas; Herek, Jennifer Lynn


    This study describes first steps taken to bring evolutionary optimization technology from computer simulations to real world experimentation in physics laboratories. The approach taken considers a well understood Laser Pulse Compression problem accessible both to simulation and laboratory

  6. Pulse growth dynamics in laser mode locking (United States)

    Popov, Mark; Gat, Omri


    We analyze theoretically and numerically the nonlinear process of pulse formation in mode-locked lasers, starting from a perturbation of a continuous wave. Focusing on weak-to-moderate dispersion systems, we show that pulse growth is initially slow, dominated by a cascade of energy from low to high axial modes, followed by fast strongly nonlinear growth, and finally relaxation to the stable pulse wave form. The pulse grows initially by condensing a fixed amount of energy into a decreasing time interval, with peak power growing toward a finite-time singularity that is checked when the gain bandwidth is saturated by the pulse.

  7. Bringing Pulsed Laser Welding into Production

    DEFF Research Database (Denmark)

    Olsen, Flemmming Ove


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

  8. Sub-picosecond Graphene-based Harmonically Mode-Locked Fiber Laser With Repetition Rates up to 2.22 GHz

    Directory of Open Access Journals (Sweden)

    Abramski K.M.


    Full Text Available Passive harmonic-mode locking (PHML of erbium-doped fiber laser with multilayer graphene is presented. The laser could operate at several harmonics (from 2nd to 21st of the fundamental repetition frequency of the ring resonator (106 MHz. The highest achieved repetition rate was 2.22 GHz (which corresponds to the 21st harmonic with 900 fs pulse duration and 50 dB of the supermode noise suppression. The saturable absorber was formed by multilayer graphene, mechanically exfoliated from pure graphite block through Scotch-tape and deposited on the fiber ferrule.

  9. Decoration of silica nanowires with gold nanoparticles through ultra-short pulsed laser deposition (United States)

    Gontad, F.; Caricato, A. P.; Cesaria, M.; Resta, V.; Taurino, A.; Colombelli, A.; Leo, C.; Klini, A.; Manousaki, A.; Convertino, A.; Rella, R.; Martino, M.; Perrone, A.


    The ablation of a metal target at laser energy densities in the range of 1-10 TW/cm2 leads to the generation of nanoparticles (NP) of the ablated material. This aspect is of particular interest if the immobilization of NPs on three-dimensional (3D) substrates is necessary as for example in sensing applications. In this work the deposition of Au NP by irradiation of a Au bulk target with a sub-picosecond laser beam (500 fs; 248 nm; 10 Hz) on 2D (silica and Si(100)) and 3D substrates (silica nanowire forests) is reported for different number of laser pulses (500, 1000, 1500, 2000, 2500). A uniform coverage of small Au NPs (with a diameter of few nm) on both kinds of substrates has been obtained using a suitable number of laser pulses. The presence of spherical droplets, with a diameter ranging from tens of nm up to few μm was also detected on the substrate surface and their presence can be explained by the weak electron-phonon coupling of Au. The optical characterization of the samples on 2D and 3D substrates evidenced the surface plasmon resonance peak characteristic of the Au NPs although further improvements of the size-distribution are necessary for future applications in sensing devices.

  10. Hybrid Pulsed Nd:YAG Laser (United States)

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

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

  11. RF synchronized short pulse laser ion source

    Energy Technology Data Exchange (ETDEWEB)

    Fuwa, Yasuhiro, E-mail:; Iwashita, Yoshihisa; Tongu, Hiromu; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Okamura, Masahiro [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Yamazaki, Atsushi [Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603 (Japan)


    A laser ion source that produces shortly bunched ion beam is proposed. In this ion source, ions are extracted immediately after the generation of laser plasma by an ultra-short pulse laser before its diffusion. The ions can be injected into radio frequency (RF) accelerating bucket of a subsequent accelerator. As a proof-of-principle experiment of the ion source, a RF resonator is prepared and H{sub 2} gas was ionized by a short pulse laser in the RF electric field in the resonator. As a result, bunched ions with 1.2 mA peak current and 5 ns pulse length were observed at the exit of RF resonator by a probe.

  12. Phase recovery by using optical fiber dispersion and pulse pre-stretching (United States)

    Cuadrado-Laborde, C.; Brotons-Gisbert, M.; Serafino, G.; Bogoni, A.; Pérez-Millán, P.; Andrés, M. V.


    In this work, the applicability of a recently proposed phase recovery technique is extended, by using temporal pulse pre-stretching. As a proof of concept, the light pulses emitted by a two-stage laser system consisting of a sub-picosecond passively mode-locked fiber laser followed by an erbium-doped fiber amplifier were experimentally analyzed. These results were successfully compared with two indirect phase recovery techniques, both based on the Gerchberg-Saxton recursive algorithm and with the intensity autocorrelation when sub-picosecond light pulses were analyzed.

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

    DEFF Research Database (Denmark)

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


    Laser self-pulsing was a property exclusive to macroscopic laser systems until recently, where self-pulsing laser operation was demonstrated experimentally and theoretically in a microscopic photonic crystal Fano laser [1]. We now provide a detailed theoretical analysis of the self-pulsing mechan......Laser self-pulsing was a property exclusive to macroscopic laser systems until recently, where self-pulsing laser operation was demonstrated experimentally and theoretically in a microscopic photonic crystal Fano laser [1]. We now provide a detailed theoretical analysis of the self...

  14. Ophthalmic applications of ultrashort pulsed lasers (United States)

    Juhasz, Tibor; Spooner, Greg; Sacks, Zachary S.; Suarez, Carlos G.; Raksi, Ferenc; Zadoyan, Ruben; Sarayba, Melvin; Kurtz, Ronald M.


    Ultrashort laser pulses can be used to create high precision incision in transparent and translucent tissue with minimal damage to adjacent tissue. These performance characteristics meet important surgical requirements in ophthalmology, where femtosecond laser flap creation is becoming a widely used refractive surgery procedure. We summarize clinical findings with femtosecond laser flaps as well as early experiments with other corneal surgical procedures such as corneal transplants. We also review laser-tissue interaction studies in the human sclera and their consequences for the treatment of glaucoma.

  15. Drop shaping by laser-pulse impact

    CERN Document Server

    Klein, Alexander L; Visser, Claas Willem; Lhuissier, Henri; Sun, Chao; Snoeijer, Jacco H; Villermaux, Emmanuel; Lohse, Detlef; Gelderblom, Hanneke


    We study the hydrodynamic response of a falling drop hit by a laser pulse. Combining high-speed with stroboscopic imaging we report that a millimeter-sized dyed water drop hit by a milli-Joule nanosecond laser-pulse deforms and propels forward at several meters per second, until it eventually fragments. We show that the drop motion results from the recoil momentum imparted at the drop surface by water vaporization. We measure the propulsion speed and the time-deformation law of the drop, complemented by boundary integral simulations. We explain the drop propulsion and shaping in terms of the laser pulse energy and drop surface tension. These findings are crucial for the generation of extreme ultraviolet (EUV) light in lithography machines.

  16. Pulsed laser illumination of photovoltaic cells (United States)

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


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

  17. Ultrashort laser pulse driven inverse free electron laser accelerator experiment

    Directory of Open Access Journals (Sweden)

    J. T. Moody


    Full Text Available In this paper we discuss the ultrashort pulse high gradient inverse free electron laser accelerator experiment carried out at the Lawrence Livermore National Laboratory which demonstrated gradients exceeding 200  MV/m using a 4 TW 100 fs long 800 nm Ti:Sa laser pulse. Due to the short laser and electron pulse lengths, synchronization was determined to be one of the main challenges in this experiment. This made necessary the implementation of a single-shot, nondestructive, electro-optic sampling based diagnostics to enable time-stamping of each laser accelerator shot with <100  fs accuracy. The results of this experiment are expected to pave the way towards the development of future GeV-class IFEL accelerators.

  18. Laser breakdown in air at ultrahigh laser pulse repetition rates

    Energy Technology Data Exchange (ETDEWEB)

    Kononenko, Vitalii V; Kononenko, Taras V; Pashinin, V P; Gololobov, V M; Konov, Vitalii I [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)


    Some specific features of interaction of intense femtosecond laser pulses with air at ultrahigh pulse repetition rates have been experimentally studied. Data on the dynamics of plasma cloud expansion and the plasma electron density on time intervals no longer than 10 ns are obtained by femtosecond interferometry. These data are interpreted in terms of the most likely mechanisms of ionised gas recombination. The effect of ultrahigh-frequency laser radiation on a medium was modelled by double-pulse irradiation with a short delay {Delta}t between the pulses: from 1 ps to 11 ns. A nonmonotonic dependence of the degree of air ionisation by the second pulse on the delay time {Delta}t is found; possible mechanisms of these dependences are discussed in terms of the processes of femtosecond radiation absorption in the residual plasma. (extreme light fields and their applications)

  19. New pulsed laser data-acquisition system (United States)

    Singer, K. D.; Merlin, M. S.; Grossman, C. H.; Garito, A. F.


    A new pulsed laser data-acquisition system which can perform the normal operations of boxcar integrators is described. The system is based on a CAMAC standard photocurrent charge-sensitive integrator which is coupled to a laboratory minicomputer. The charge-sensitive integrator is triggered by a gate pulse which is optically synchronized to the laser output. This greatly reduces asynchronous noise. Details of the hardware configuration, the trigger gate circuit, and data averaging software are presented. Flexibility of hardware and software allow for other applications, such as multichannel analysis and other real time data processing.

  20. Quantum Computation with Ultrafast Laser Pulse Shaping

    Indian Academy of Sciences (India)

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

  1. A New Possibility for Production of Sub-picosecond X-ray Pulses using a Time Dependent Radio Frequency Orbit Deflection

    Energy Technology Data Exchange (ETDEWEB)

    Zholents, A. A. [Argonne National Lab. (ANL), Argonne, IL (United States)


    It is shown that two radio frequency deflecting cavities with slightly different frequencies can be used to produce time-dependent orbit deflection to a few special electron bunches while keeping the majority of the electron bunches unaffected. These special bunches produce an x-ray pulse in which transverse position or angle, or both, are correlated with time. The x-ray pulses are then shortened, either with an asymmetrically cut crystal that acts as a pulse compressor, or with an angular aperture such as a narrow slit positioned downstream. The implementation of this technique creates a highly flexible environment for synchrotrons in which users of most beamlines will be able to easily select between the x-rays originated by the standard electron bunches and the short x-ray pulses originated by the special electron bunches carrying a time-dependent transverse correlation.

  2. Group velocity and pulse lengthening of mismatched laser pulses in plasma channels

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Carl; Benedetti, Carlo; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim


    Analytic solutions are presented to the non-paraxial wave equation describing an ultra-short, low-power, laser pulse propagating in aplasma channel. Expressions for the laser pulse centroid motion and laser group velocity are derived, valid for matched and mismatchedpropagation in a parabolic plasma channel, as well as in vacuum, for an arbitrary Laguerre-Gaussian laser mode. The group velocity of amismatched laser pulse, for which the laser spot size is strongly oscillating, is found to be independent of propagation distance andsignificantly less than that of a matched pulse. Laser pulse lengthening of a mismatched pulse owing to laser mode slippage isexamined and found to dominate over that due to dispersive pulse spreading for sufficiently long pulses. Analytic results are shown tobe in excellent agreement with numerical solutions of the full Maxwell equations coupled to the plasma response. Implications for plasmachannel diagnostics are discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, Timothy John [Northern Illinois U.


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

  4. Laser-Induced Damage with Femtosecond Pulses (United States)

    Kafka, Kyle R. P.

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

  5. Pulsed Power for Solid-State Lasers

    Energy Technology Data Exchange (ETDEWEB)

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


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

  6. Selective laser melting of copper using ultrashort laser pulses (United States)

    Kaden, Lisa; Matthäus, Gabor; Ullsperger, Tobias; Engelhardt, Hannes; Rettenmayr, Markus; Tünnermann, Andreas; Nolte, Stefan


    Within the field of laser-assisted additive manufacturing, the application of ultrashort pulse lasers for selective laser melting came into focus recently. In contrast to conventional lasers, these systems provide extremely high peak power at ultrashort interaction times and offer the potential to control the thermal impact at the vicinity of the processed region by tailoring the pulse repetition rate. Consequently, materials with extremely high melting points such as tungsten or special composites such as AlSi40 can be processed. In this paper, we present the selective laser melting of copper using 500 fs laser pulses at MHz repetition rates emitted at a center wavelength of about 1030 nm. To identify an appropriate processing window, a detailed parameter study was performed. We demonstrate the fabrication of bulk copper parts as well as the realization of thin-wall structures featuring thicknesses below 100 {μ }m. With respect to the extraordinary high thermal conductivity of copper which in general prevents the additive manufacturing of elements with micrometer resolution, this work demonstrates the potential for sophisticated copper products that can be applied in a wide field of applications extending from microelectronics functionality to complex cooling structures.

  7. Characterization of short-pulse laser-produced x-rays for diagnosing magnetically driven cylindrical isentropic compression (United States)

    Sawada, Hiroshi; Daykin, Tyler; Bauer, Bruno; Beg, Farhat


    We have developed an experimental platform to study material properties of magnetically compressed cylinder using a 1 MA pulsed power generator Zebra and a 50 TW subpicosecond short-pulse laser Leopard at the UNR's Nevada Terawatt Facility. According to a MHD simulation, strong magnetic fields generated by 100 ns rise time Zebra current can quasi-isentropically compress a material to the strongly coupled plasma regime. Taking advantage of the cylindrical geometry, a metal rod can be brought to higher pressures than that in the planar geometry. To diagnose the compressed rod with high precision x-ray measurements, an initial laser-only experiment was carried out to characterize laser-produced x-rays. Interaction of a high-intensity, short-pulse laser with solids produces broadband and monochromatic x-rays with photon energies high enough to probe dense metal rods. Bremsstrahlung was measured with Imaging plate-based filter stack spectrometers and monochromatic 8.0 keV Cu K-alpha was recorded with an absolutely calibrated Bragg crystal spectrometer. The broadband x-ray source was applied to radiography of thick metal objects and different filter materials were tested. The experimental results and a design of a coupled experiment will be presented.

  8. Laser-Material Interaction of Powerful Ultrashort Laser Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Komashko, A


    Laser-material interaction of powerful (up to a terawatt) ultrashort (several picoseconds or shorter) laser pulses and laser-induced effects were investigated theoretically in this dissertation. Since the ultrashort laser pulse (USLP) duration time is much smaller than the characteristic time of the hydrodynamic expansion and thermal diffusion, the interaction occurs at a solid-like material density with most of the light energy absorbed in a thin surface layer. Powerful USLP creates hot, high-pressure plasma, which is quickly ejected without significant energy diffusion into the bulk of the material, Thus collateral damage is reduced. These and other features make USLPs attractive for a variety of applications. The purpose of this dissertation was development of the physical models and numerical tools for improvement of our understanding of the process and as an aid in optimization of the USLP applications. The study is concentrated on two types of materials - simple metals (materials like aluminum or copper) and wide-bandgap dielectrics (fused silica, water). First, key physical phenomena of the ultrashort light interaction with metals and the models needed to describe it are presented. Then, employing one-dimensional plasma hydrodynamics code enhanced with models for laser energy deposition and material properties at low and moderate temperatures, light absorption was self-consistently simulated as a function of laser wavelength, pulse energy and length, angle of incidence and polarization. Next, material response on time scales much longer than the pulse duration was studied using the hydrocode and analytical models. These studies include examination of evolution of the pressure pulses, effects of the shock waves, material ablation and removal and three-dimensional dynamics of the ablation plume. Investigation of the interaction with wide-bandgap dielectrics was stimulated by the experimental studies of the USLP surface ablation of water (water is a model of

  9. Analysis of data transmission technique based on pulsed laser (United States)

    Drozd, T.; Zygmunt, M.; Knysak, P.; Wojtanowski, J.


    Pulsed lasers are used mainly in lidar systems as sources of short and highly energetic light pulses. In data transmission systems continuous wave lasers are typically applied, however it is also possible to use pulsed lasers in such systems. Such approach seems to be especially reasonable for devices where a pulsed laser is applied anyway and executes another function (rangefinding). The article discusses a data transmission concept based on a pulsed laser technology. Advantages and limits of such a transmission method are described. Influence of individual transmission elements on the effective data transmission speed is analysed.

  10. Emission from Vertical-Cavity Surface-Emitting Lasers after Femtosecond Pulse Injection (United States)

    Zhang, Botao; Heberle, Albert


    Vertical-cavity surface-emitting lasers (VCSEL's) are important devices for optical communication and sensing. Many applications require single-mode operation, which can be achieved by suppressing multiple lateral modes with emission apertures of 10 micrometers or less and by restricting emission to one polarization by reduction of symmetry. Such single-mode lasers still can produce multi-mode emission when subject to high pump currents or high-frequency modulation. Here we will discuss the emission dynamics of single-mode VCSEL's after resonant optical injection of femtosecond pulses from a mode-locked Ti:sapphire laser. The VCSEL emission is time and polarization resolved by cross correlation on a nonlinear optical crystal. This all-optical technique gives access to the VCSEL dynamics without limitation from electronics. Our measurements show dynamics in the 10 GHz range stemming from ordinary and from polarization relaxation oscillations. Interference beats above 100 GHz show the importance of dynamic multi-mode behavior. The decay of these beats gives direct information on the roundtrip gain of the dynamically excited modes. Polarization resolved measurements show the feasibility of polarization switching on a subpicosecond time scale.

  11. Pulsed lasers in speckle photography: error owing to pulse width. (United States)

    Joenathan, C; Blair, S M; Ganesan, A R


    The effect of the pulse width of a pulsed laser in the studies of speckle velocimetry and transient vibration analysis is discussed. Because of the motion of the object during an exposure, a sine function is obtained by using the pointwise filtering method. This function modulates the halo along with the Young's fringes. It is shown that for high object velocities the sinc function modifies the halo distribution; as a result, the error in calculating the fringe position increases. An aperture geometry for which the autocorrelation halo is made constant in certain regions is proposed in which the intensity variation in this region is the result of the modulating sinc function only. A closed-form solution for the shift in the position of the fringes in this region is obtained. Experimental results of the simulation are presented.

  12. Plasma generated during underwater pulsed laser processing (United States)

    Hoffman, Jacek; Chrzanowska, Justyna; Moscicki, Tomasz; Radziejewska, Joanna; Stobinski, Leszek; Szymanski, Zygmunt


    The plasma induced during underwater pulsed laser ablation of graphite is studied both experimentally and theoretically. The results of the experiment show that the maximum plasma temperature of 25000 K is reached 20 ns from the beginning of the laser pulse and decreases to 6500 K after 1000 ns. The observed OH absorption band shows that the plasma plume is surrounded by the thin layer of dissociated water vapour at a temperature around 5500 K. The hydrodynamic model applied shows similar maximum plasma temperature at delay times between 14 ns and 30 ns. The calculations show also that already at 14th ns, the plasma electron density reaches 0.97·1027 m-3, which is the critical density for 1064 nm radiation. At the same time the plasma pressure is 2 GPa, which is consisted with earlier measurements of the peak pressure exerted on a target in similar conditions.

  13. Laser Pulse Heating of Spherical Metal Particles

    Directory of Open Access Journals (Sweden)

    Michael I. Tribelsky


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

  14. Pulsed laser deposition of rare earth compounds

    CERN Document Server

    Stone, L A


    Magnetostrictive thin films have been deposited using various techniques such as sputtering and evaporation but the use of laser deposition has been limited. This research presents the results from pulsed laser deposition (PLD) of TbFe sub 2 , DyFe sub 2 and Terfenol-D thin films using an infra red Transversely Excited Atmospheric (TEA) CO sub 2 laser at lambda approx 10.6 mu m and an ultra violet Argon-Fluoride (ArF) excimer laser at lambda approx 193 nm. Results have showed that the TEA CO sub 2 laser under the range of conditions studied is not suitable for the production of magnetostrictive films. The problems experienced are a mixture of mostly fracture debris at low fluences (F approx 20 Jcm sup - sup 2) and melt droplets at high fluences (F approx 60 Jcm sup - sup 2). In all cases the destruction of the target is a major problem, with the Terfenol-D targets being the worst affected. Thin films produced were all iron rich. The use of an excimer laser has proved more successful in providing stoichiometri...

  15. Ultrafast laser pulses for medical applications (United States)

    Lubatschowski, Holger; Heisterkamp, Alexander; Will, Fabian; Serbin, Jesper; Bauer, Thorsten; Fallnich, Carsten; Welling, Herbert; Mueller, Wiebke; Schwab, Burkard; Singh, Ajoy I.; Ertmer, Wolfgang


    Ultrafast lasers have become a promising tool for micromachining and extremely precise ablation of all kinds of materials. Due to the low energy threshold, thermal and mechanical side effects are limited to the bu micrometers range. The neglection of side effects enables the use of ultrashort laser pulses in a broad field of medical applications. Moreover, the interaction process based on nonlinear absorption offers the opportunity to process transparent tissue three dimensionally inside the bulk. We demonstrate the feasibility of surgical procedures in different fields of medical interest: in ophthalmology intrastromal cutting and preparing of cornael flaps for refractive surgery in living animals is presented. Besides, the very low mechanical side effects enables the use of fs- laser in otoralyngology to treat ocecular bones. Moreover, the precise cutting quality can be used in fields of cardiovascular surgery for the treatment of arteriosklerosis as well as in dentistry to remove caries from dental hard tissue.

  16. Pulsed Nd-YAG laser in endodontics (United States)

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


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

  17. Pulsed pump: Thermal effects in solid state lasers under super ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 67; Issue 6. Pulsed ... Pulse pump; thermal effects; thermal lensing; phase shift; diode-pumped solid state laser; super-Gaussian pump profile. Abstract. Solid state laser (SSL) powers can be realistically scaled when pumped by a real, efficient and multimode pulse.

  18. Corneal and skin laser exposures from 1540-nm laser pulses (United States)

    Johnson, Thomas E.; Mitchell, Michael A.; Rico, Pedro J.; Fletcher, David J.; Eurell, Thomas E.; Roach, William P.


    Mechanisms of tissue damage are investigated for skin and cornea exposures from 1540 nm ('eye safe') laser single pulses of 0.8 milli-seconds. New skin model data point out the advantages of using the Yucatan mini-pig versus the Yorkshire pig for in-vivo skin laser exposures. Major advantages found include similarities in thickness and melanin content when compared with human skin. Histology from Yucatan mini-pig skin exposures and the calculation of an initial ED50 threshold indicate that the main photon tissue interaction may not be solely due to water absorption. In-vitro corneal equivalents compared well with in-vivo rabbit cornea exposure under similar laser conditions. In-vivo and in-vitro histology show that initial energy deposition leading to damage occurs intrastromally, while epithelial cells show no direct injury due to laser light absorption.

  19. Synchronization of picosecond laser pulses to the target X-ray pulses at SPring-8

    CERN Document Server

    Tanaka, Y; Kitamura, H; Ishikawa, T


    Synchronization system between an intense picosecond laser and the target X-ray pulses has been developed at SPring-8. The intense laser pulses were obtained by amplification of the pulses picked up from a mode-locked Ti:sapphire laser synchronized with the radio frequency of the storage ring. The repetition rate of amplified laser pulses was controlled to be 1/n of the RF, where n is a multiple of the number of RF buckets in the ring, so that the laser pulses meet the SR pulses originated from a particular electron bunch in partial filling patterns. The temporal overlap of the laser and the target X-ray pulses was achieved as monitored with a streak camera in synchroscan and repetitive single shot operation modes, and was stable with a precision of a few ps for several hours.

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

    Energy Technology Data Exchange (ETDEWEB)

    Smausz, Tomi, E-mail: tomi@physx.u-szeged.h [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged, P.O. Box 406 (Hungary); Megyeri, Gabor; Kekesi, Renata; Vass, Csaba [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged, P.O. Box 406 (Hungary); Gyoergy, Eniko; Sima, Felix; Mihailescu, Ion N. [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, PO Box MG-54, RO-77125, Bucharest-Magurele (Romania); Hopp, Bela [Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6701 Szeged, P.O. Box 406 (Hungary)


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

  1. Pulsed laser fluorometry for environmental monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Saunders, G. C.; Martin, J. C.; Jett, J. H.; Wilder, M. E.; Martinez, A.; Bentley, B. F.; Lopez, J.; Hutson, L.


    A compact pulsed laser fluorometer has been incorporated into a continuous flow system developed to detect acetylcholinesterase (AChE) inhibitors and/or primary amine compounds in air and water. A pulsed nitrogen laser pumped dye laser excites fluorescent reactants which flow continuously through a quartz flow cell. Data are collected, analyzed, and displayed using a Macintosh II personal computer. For detection of cholinesterase inhibitors the fluorogenic substrate N methylindoxyl acetate is used to monitor the activity of immobilized enzyme. Presence of inhibitors results in a decrease of steady state fluorescence. Detection of compounds containing primary amines is based on their reaction with fluorescamine to rapidly produce intensely fluorescent products. Compounds of interest to our research were amino acids, peptides, and proteins. An increase in steady state fluorescence could be cause to evaluate the reasons for the change. The detection limit of the protein, bovine serum albumin (BSA) in water is 10 ppT. Nebulized BSA concentrated by the LANL air sampler can be detected at sub ppT original air concentration. 16 refs., 14 figs., 3 tabs.

  2. Pulse Front Tilt and Laser Plasma Acceleration (United States)

    Mittelberger, Daniel; Thévenet, Maxence; Nakamura, Kei; Lehe, Remi; Gonsalves, Anthony; Benedetti, Carlo; Leemans, Wim


    Pulse front tilt (PFT) is potentially present in any CPA laser system, but its effects may be overlooked because spatiotemporal pulse characterization is considerably more involved than measuring only spatial or temporal profile. PFT is particularly important for laser plasma accelerators (LPA) because it influences electron beam injection and steering. In this work, experimental results from the BELLA Center will be presented that demonstrate the effect of optical grating misalignment and optical compression, resulting in PFT, on accelerator performance. Theoretical models of laser and electron beam steering will be introduced based on particle-in-cell simulations showing distortion of the plasma wake. Theoretical predictions will be compared with experiments and complimentary simulations, and tolerances on PFT and optical compressor alignment will be developed as a function of LPA performance requirements. This work was supported by the Office of High Energy Physics, Office of Science, US Department of Energy under Contract DE-AC02-05CH11231 and the National Science Foundation under Grant PHY-1415596.

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

    Energy Technology Data Exchange (ETDEWEB)

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


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

  4. Three-dimensional laser pulse intensity diagnostic for photoinjectors

    Directory of Open Access Journals (Sweden)

    Heng Li


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

  5. Histological difference between pulsed wave laser and continuous wave laser in endovenous laser ablation. (United States)

    Kansaku, Rei; Sakakibara, Naoki; Amano, Atsushi; Endo, Hisako; Shimabukuro, Takashi; Sueishi, Michiaki


    Endovenous laser ablation to saphenous veins has been popular as a minimally invasive treatment for chronic venous insufficiency. However, adverse effects after endovenous laser ablation using continuous wave laser still remain. Pulsed wave with enough short pulse duration and sufficiently long thermal relaxation time may avoid the excess energy delivery, which leads to the perforation of the vein wall. (1) Free radiation: Laser is radiated in blood for 10 s. (2) Endovenous laser ablation: Veins were filled with blood and placed in saline. Endovenous laser ablations were performed. (1) There were clots on the fiber tips with continuous wave laser while no clots with pulsed wave laser. (2) In 980-nm continuous wave, four of 15 specimens had ulcers and 11 of 15 had perforation. In 1470-nm continuous wave with 120 J/cm of linear endovenous energy density, two of three presented ulcers and one of three showed perforation. In 1470-nm continuous wave with 60 J/cm of linear endovenous energy density, two of four had ulcers and two of four had perforation. In 1320-nm pulsed wave, there were neither ulcers nor perforation in the specimens. While endovenous laser ablation using continuous wave results in perforation in many cases, pulsed wave does not lead to perforation. © The Author(s) 2014.

  6. Design and implementation of an optimal laser pulse front tilting scheme for ultrafast electron diffraction in reflection geometry with high temporal resolution

    Directory of Open Access Journals (Sweden)

    Francesco Pennacchio


    Full Text Available Ultrafast electron diffraction is a powerful technique to investigate out-of-equilibrium atomic dynamics in solids with high temporal resolution. When diffraction is performed in reflection geometry, the main limitation is the mismatch in group velocity between the overlapping pump light and the electron probe pulses, which affects the overall temporal resolution of the experiment. A solution already available in the literature involved pulse front tilt of the pump beam at the sample, providing a sub-picosecond time resolution. However, in the reported optical scheme, the tilted pulse is characterized by a temporal chirp of about 1 ps at 1 mm away from the centre of the beam, which limits the investigation of surface dynamics in large crystals. In this paper, we propose an optimal tilting scheme designed for a radio-frequency-compressed ultrafast electron diffraction setup working in reflection geometry with 30 keV electron pulses containing up to 105 electrons/pulse. To characterize our scheme, we performed optical cross-correlation measurements, obtaining an average temporal width of the tilted pulse lower than 250 fs. The calibration of the electron-laser temporal overlap was obtained by monitoring the spatial profile of the electron beam when interacting with the plasma optically induced at the apex of a copper needle (plasma lensing effect. Finally, we report the first time-resolved results obtained on graphite, where the electron-phonon coupling dynamics is observed, showing an overall temporal resolution in the sub-500 fs regime. The successful implementation of this configuration opens the way to directly probe structural dynamics of low-dimensional systems in the sub-picosecond regime, with pulsed electrons.

  7. Proton acceleration by radially polarized chirped laser pulses

    Directory of Open Access Journals (Sweden)

    Jin-Lu Liu (刘晋陆


    Full Text Available Within the framework of plane-wave angular spectrum analysis of electromagnetic fields, a solution for the field of a tightly focused radially polarized (RP chirped laser pulse is presented. With this solution, direct laser acceleration of protons by this kind of RP laser pulses is investigated numerically. It is found that a RP laser pulse with proper negative frequency chirps can lead to efficient proton acceleration, reaching sub-GeV at the laser intensity of 10^{22}  W/cm^{2} from its injection energy of 45 MeV.

  8. 25 years of pulsed laser deposition (United States)

    Lorenz, Michael; Ramachandra Rao, M. S.


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

  9. Laser and intense pulsed light hair removal technologies

    DEFF Research Database (Denmark)

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


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

  10. Laser and intense pulsed light hair removal technologies

    DEFF Research Database (Denmark)

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


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

  11. Pulse-burst operation of standard Nd:YAG lasers

    Energy Technology Data Exchange (ETDEWEB)

    Den Hartog, D J; Borchardt, M T; Reusch, J A; Yang, Y M [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Ambuel, J R; Robl, P E, E-mail: djdenhar@wisc.ed [Physical Sciences Laboratory, University of Wisconsin-Madison, Stoughton, Wisconsin 53589 (United States)


    Two standard commercial flashlamp-pumped Nd:YAG lasers have been upgraded to 'pulse-burst' capability. Each laser produces a burst of up to fifteen 2 J Q-switched pulses (1064 nm) at repetition rates 1-12.5 kHz. Variable pulse-width drive (0.15-0.39 ms) of the flashlamps is accomplished by IGBT (insulated gate bipolar transistor) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinch to study the dynamic evolution of the electron temperature.

  12. Repetitive pulses and laser-induced retinal injury thresholds (United States)

    Lund, David J.


    Experimental studies with repetitively pulsed lasers show that the ED 50, expressed as energy per pulse, varies as the inverse fourth power of the number of pulses in the exposure, relatively independently of the wavelength, pulse duration, or pulse repetition frequency of the laser. Models based on a thermal damage mechanism cannot readily explain this result. Menendez et al. proposed a probability-summation model for predicting the threshold for a train of pulses based on the probit statistics for a single pulse. The model assumed that each pulse is an independent trial, unaffected by any other pulse in the train of pulses and assumes that the probability of damage for a single pulse is adequately described by the logistic curve. The requirement that the effect of each pulse in the pulse train be unaffected by the effects of other pulses in the train is a showstopper when the end effect is viewed as a thermal effect with each pulse in the train contributing to the end temperature of the target tissue. There is evidence that the induction of cell death by microcavitation bubbles around melanin granules heated by incident laser irradiation can satisfy the condition of pulse independence as required by the probability summation model. This paper will summarize the experimental data and discuss the relevance of the probability summation model given microcavitation as a damage mechanism.

  13. Pulsed laser deposition of pepsin thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kecskemeti, G. [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dom ter 9 (Hungary)]. E-mail:; Kresz, N. [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dom ter 9 (Hungary); Smausz, T. [Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6720 Szeged, Dom ter 9 (Hungary); Hopp, B. [Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6720 Szeged, Dom ter 9 (Hungary); Nogradi, A. [Department of Ophthalmology, University of Szeged, H-6720, Szeged, Koranyi fasor 10-11 (Hungary)


    Pulsed laser deposition (PLD) of organic and biological thin films has been extensively studied due to its importance in medical applications among others. Our investigations and results on PLD of a digestion catalyzing enzyme, pepsin, are presented. Targets pressed from pepsin powder were ablated with pulses of an ArF excimer laser ({lambda} = 193 nm, FWHM = 30 ns), the applied fluence was varied between 0.24 and 5.1 J/cm{sup 2}. The pressure in the PLD chamber was 2.7 x 10{sup -3} Pa. The thin layers were deposited onto glass and KBr substrates. Our IR spectroscopic measurements proved that the chemical composition of deposited thin films is similar to that of the target material deposited at 0.5 and 1.3 J/cm{sup 2}. The protein digesting capacity of the transferred pepsin was tested by adapting a modified 'protein cube' method. Dissolution of the ovalbumin sections proved that the deposited layers consisted of catalytically active pepsin.

  14. Pulsed laser ablation of solids basics, theory and applications

    CERN Document Server

    Stafe, Mihai; Puscas, Niculae N


    The book introduces ‘the state of the art' of pulsed laser ablation and its applications. It is based on recent theoretical and experimental studies. The book reaches from the basics to advanced topics of pulsed laser ablation. Theoretical and experimental fundamental phenomena involved in pulsed laser ablation are discussed with respect to material properties, laser wavelength, fluence and intensity regime of the light absorbed linearly or non-linearly in the target material. The energy absorbed by the electrons leads to atom/molecule excitation, ionization and/or direct chemical bond breaking and is also transferred to the lattice leading to material heating and phase transitions. Experimental  non-invasive optical methods for analyzing these phenomena in real time are described. Theoretical models for pulsed laser ablation and phase transitions induced by laser beams and laser-vapour/plasma interaction during the plume expansion above the target are also presented. Calculations of the ablation speed and...

  15. Nanospallation induced by a femtosecond laser pulse (United States)

    Agranat, M. B.; Anisimov, S. I.; Ashitkov, S. I.; Zhakhovskii, V. V.; Inogamov, N. A.; Nishihara, K.; Petrov, Yu. V.


    In the present work phenomena are considered related to the interaction of ultra-short laser pulses, τ L~0.1 ps, with metallic targets. The absorption of laser pulse results in formation of thin layer of hot electrons strongly superheated (T e>>T i) relative to the ion temperature, T i. Initial thickness of the layer d heat is small, d heat~δ, where δ~10 nm is the skin layer thickness. Subsequent developments include the following stages: (1) Propagation of electron thermal wave which expands the hot layer d heat; (2) Cooling of electrons due to energy transfer to cold ions; (3) Onset of hydrodynamic motion that constitutes the rarefaction wave with positive pressure; (4) Further expansion of target material leading to the appearance of negative pressure; and (5) Long separation process which begins with nucleation of voids and goes on to the total separation of spallation plate. The thickness of the plate is ~10 nm (we call it nanospallation). Theoretical model involves two-temperature hydrodynamic equations with semiempirical EOS for a metal, electron heat conduction and electron-ion energy exchange. The decay of metastable strongly stretched matter is described by molecular dynamics (MD) simulation with extremely large number of atoms. The experimental setup includes femtosecond chromium-forsterite laser operating in the pump-probe regime. The experiments are performed with gold target. Measured ablation threshold for gold is 1.35 J/cm2 of incident pump light at inclination 45°, p-polarization. Calorimeter measurements give for the absorbed fluence F abs=0.3F inc, therefore the threshold value of F abs is 0.4 J/cm2.

  16. Pulse front adaptive optics: a new method for control of ultrashort laser pulses. (United States)

    Sun, Bangshan; Salter, Patrick S; Booth, Martin J


    Ultrafast lasers enable a wide range of physics research and the manipulation of short pulses is a critical part of the ultrafast tool kit. Current methods of laser pulse shaping are usually considered separately in either the spatial or the temporal domain, but laser pulses are complex entities existing in four dimensions, so full freedom of manipulation requires advanced forms of spatiotemporal control. We demonstrate through a combination of adaptable diffractive and reflective optical elements - a liquid crystal spatial light modulator (SLM) and a deformable mirror (DM) - decoupled spatial control over the pulse front (temporal group delay) and phase front of an ultra-short pulse was enabled. Pulse front modulation was confirmed through autocorrelation measurements. This new adaptive optics technique, for the first time enabling in principle arbitrary shaping of the pulse front, promises to offer a further level of control for ultrafast lasers.

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

    DEFF Research Database (Denmark)

    Ettlinger, Rebecca Bolt

    This thesis concerns the deposition of thin films for solar cells using pulsed laser deposition (PLD) and pulsed electron deposition (PED). The aim was to deposit copper tin sulfide (CTS) and zinc sulfide (ZnS) by pulsed laser deposition to learn about these materials in relation to copper zinc tin......, which make them promising alternatives to the commercially successful solar cell material copper indium gallium diselenide (CIGS). Complementing our group's work on pulsed laser deposition of CZTS, we collaborated with IMEM-CNR in Parma, Italy, to deposit CZTS by pulsed electron deposition for the first...... of using pulsed electron deposition was to make CZTS at a low processing temperature, avoiding the 570 °C annealing step used for our pulsed laser deposited solar cells. Preliminary solar cells had an efficiency of 0.2 % with a 300 °C deposition step without annealing. Further process control is needed...

  18. Nonlinear interaction of ultraintense laser pulse with relativistic thin ...

    Indian Academy of Sciences (India)

    momentum acquired by the ions as a result of the ultraintense laser pulse focussed on a thin plasma layer in the radiation pressuredominant(RPD) regime. In the RPD regime, the plasma foil is pushed by ultraintense laser pulse when the radiation ...

  19. Property change during nanosecond pulse laser annealing of ...

    Indian Academy of Sciences (India)

    Keywords. SMA; NiTi; pulse laser; thin film; crystallization. Abstract. Nanosecond lasers of different intensities were pulsed into sputter-deposited amorphous thin films of near equiatomic Ni/Ti composition to produce partially crystallized highly sensitive -phase spots surrounded by amorphous regions. Scanning electron ...

  20. Modelling multiple laser pulses for port wine stain treatment

    NARCIS (Netherlands)

    Verkruysse, W.; van Gemert, M. J.; Smithies, D. J.; Nelson, J. S.


    Many port wine stains (PWS) are still resistant to pulsed dye laser treatment. However, anecdotal information suggests that multiple-pulse laser irradiation improves patient outcome. Our aims in this note are to explain the underlying mechanism and estimate the possible thermal effects of multiple

  1. Spectral compression of single-photon-level laser pulse (United States)

    Li, Yuanhua; Xiang, Tong; Nie, Yiyou; Sang, Minghuang; Chen, Xianfeng


    We experimentally demonstrate that the bandwidth of single photons laser pulse is compressed by a factor of 58 in a periodically poled lithium niobate (PPLN) waveguide chip. A positively chirped single photons laser pulse and a negatively chirped classical laser pulse are employed to produce a narrowband single photon pulse with new frequency through sum-frequency generation. In our experiment, the frequency and bandwidth of single photons at 1550 nm are simultaneously converted. Our results mark a critical step towards the realization of coherent photonic interface between quantum communication at 1550 nm and quantum memory in the near-visible window.

  2. Generation And Measurement Of High Contrast Ultrashort Intense Laser Pulses

    CERN Document Server

    Konoplev, O A


    In this thesis, the generation and measurement of high contrast, intense, ultrashort pulses have been studied. Various factors affecting the contrast and pulse shape of ultrashort light pulses from a chirped pulse amplification (CPA) laser system are identified. The level of contrast resulting from influence of these factors is estimated. Methods for improving and controlling the pulse shape and increasing the contrast are discussed. Ultrahigh contrast, 1-ps pulses were generated from a CPA system with no temporal structure up to eleven orders of magnitude. This is eight orders of magnitude higher contrast than the original pulse. This contrast boost was achieved using two techniques. One is the optical pulse cleaning based on the nonlinear birefringence of the chirping fiber and applied to the pulses before amplification. The other is the fast saturable absorber. The fast saturable absorber was placed after amplification and compression of the pulse. The measurements of high-contrast, ultrashort pulse with h...

  3. Chirp of monolithic colliding pulse mode-locked diode lasers

    DEFF Research Database (Denmark)

    Hofmann, M.; Bischoff, S.; Franck, Thorkild


    Spectrally resolved streak camera measurements of picosecond pulses emitted by hybridly colliding pulse mode-locked (CPM) laser diodes are presented in this letter. Depending on the modulation frequency both blue-chirped (upchirped) and red-chirped (downchirped) pulses can be observed. The two...

  4. Accuracy of laser measurements improved by pulse autocorrelator electronic system (United States)

    Campanella, S. J.


    Pulse autocorrelator electronic system discriminates between the dispersion effect of a disturbed laser signal and background noise by detecting multipath arrivals of Gaussian-shaped signal pulses. The autocorrelation function is time-dependent and can be determined by integrating the product of a received pulse and its delayed replicas.

  5. Pulse compression in synchronously pumped mode locked Raman lasers. (United States)

    Granados, Eduardo; Spence, David J


    We explain a pulse compression mechanism reported in picosecond Raman lasers pumped by continuous trains of mode-locked pulses. Our theoretical model is based on transient Raman scattering equations, and shows good agreement with the experimental results. The model reveals that the compression effect is produced by a combination of group velocity walk-off and strong pump pulse depletion. We predict the possibilities and the limitations of this technique for constructing highly efficient, low cost, ultrafast Raman lasers in the visible.

  6. Ultra-short pulsed laser engineered metal-glass nanocomposites

    CERN Document Server

    Stalmashonak, Andrei; Abdolvand, Amin


    Glasses containing metallic nanoparticles exhibit very promising linear and nonlinear optical properties, mainly due to the surface plasmon resonances (SPRs) of the nanoparticles. The spectral position in the visible and near-infrared range and polarization dependence of the SPR are characteristically determined by the nanoparticles’ shapes. The focus of Ultra-Short Pulsed Laser Engineered Metal-Glass Nanocomposites is the interaction of intense ultra-short laser pulses with glass containing silver nanoparticles embedded in soda-lime glass, and nanostructural modifications in metal-glass nanocomposites induced by such laser pulses. In order to provide a comprehensive physical picture of the processes leading to laser-induced persistent shape transformation of the nanoparticles, series of experimental results investigating the dependences of laser assisted shape modifications of nanoparticles with laser pulse intensity, excitation wavelength, temperature are considered. In addition, the resulting local opti...

  7. Fast heating of fuel assembled in a spherical deuterated polystyrene shell target by counter-irradiating tailored laser pulses delivered by a HAMA 1 Hz ICF driver (United States)

    Mori, Y.; Nishimura, Y.; Hanayama, R.; Nakayama, S.; Ishii, K.; Kitagawa, Y.; Sekine, T.; Takeuchi, Y.; Kurita, T.; Satoh, N.; Kawashima, T.; Komeda, O.; Nishi, T.; Azuma, H.; Hioki, T.; Motohiro, T.; Sunahara, A.; Sentoku, Y.; Miura, E.


    Fast heating is a method of heating an assembled high-density plasma into a hot state by irradiating it with short-duration (sub-picosecond), high-intensity (> 1018 W cm-2 ) laser pulses before the plasma expands and dissolves hydrodynamically. In this paper, we present detailed experimental results of fast heating fuel assembled in a spherical deuterated polystyrene shell target of 500 μ m diameter and 7 μm thickness with counterbeam illumination by using a HAMA 1 Hz, 5.9 J inertial confinement fusion laser driver with pulse tailoring. These tailored pulses contain three pulses in sequence: a ‘foot’ pulse of 2.4 J/25 ns, a ‘spike’ pulse of 0.5 J/300 ps and a ‘heater’ pulse of 0.4 J/110 fs; these pulses are designed to assemble the fuel and heat it. By varying the energy of the foot pulse, we find that fast heating the fuel is achieved only if the fuel is weakly ablated by the foot pulse and then shock-assembled by the spike pulse into the target centre so that the heater pulse can access the fuel with a focal intensity greater than 1018 W cm-2 . Without a foot pulse, the heater pulse contributes to assembling the fuel. For higher foot-pulse energies, the heater pulse drives a hydrodynamic motion with speeds of the order 107 cm s-1 with intensities of the order 1017 W cm-2 , resulting in re-assembling and additional heating of the pre-assembled fuel. Once a shock-assembled core is achieved at the target centre, we succeed qualitatively in fast heating the core for shots in sequence with variations of laser energy within 18%. The coupling efficiency from the heating laser to the core is inferred to be (10 +/- 2) % in total: (8 +/- 1.6) % for the ionized bulk electrons and (2 +/- 0.4) % for the bulk ions. The fusion neutron spectrum detected on the laser axis exhibits peaks at 1.0 MeV, 1.7 MeV and 3.8 MeV. These peaks are attributed to the C(d, n){\\hspace{0pt}}13 N and d(d, n){\\hspace{0pt}}3 He reactions induced by counterpropagating fast deuterons

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

    Indian Academy of Sciences (India)


    Feb 9, 2014 ... In this work, we have put efforts to efficiently deliver the laser output of 'ceramic reflector'-based long pulse Nd:YAG laser through a 200 m core diameter optical fibre and successfully delivered up to 60 J of pulse energy with 90% transmission efficiency, using a GRADIUM (axial gradient) plano-convex ...

  9. Pulsed laser Doppler measurements of wind shear (United States)

    Dimarzio, C.; Harris, C.; Bilbro, J. W.; Weaver, E. A.; Burnham, D. C.; Hallock, J. N.


    There is a need for a sensor at the airport that can remotely detect, identify, and track wind shears near the airport in order to assure aircraft safety. To determine the viability of a laser wind-shear system, the NASA pulsed coherent Doppler CO2 lidar (Jelalian et al., 1972) was installed in a semitrailer van with a rooftop-mounted hemispherical scanner and was used to monitor thunderstorm gust fronts. Wind shears associated with the gust fronts at the Kennedy Space Center (KSC) between 5 July and 4 August 1978 were measured and tracked. The most significant data collected at KSC are discussed. The wind shears were clearly visible in both real-time velocity vs. azimuth plots and in postprocessing displays of velocities vs. position. The results indicate that a lidar system cannot be used effectively when moderate precipitation exists between the sensor and the region of interest.

  10. Production of picosecond, kilojoule, petawatt laser pulses via Raman amplification of nanosecond pulses

    CERN Document Server

    Trines, R; Bingham, R; Fonseca, R A; Silva, L O; Cairns, R A; Norreys, P A


    Raman amplification in plasma has been promoted as a means of compressing picosecond optical laser pulses to femtosecond duration to explore the intensity frontier. Here we show for the first time that it can be used, with equal success, to compress laser pulses from nanosecond to picosecond duration. Simulations show up to 60% energy transfer from pump to probe pulses, implying that multi-kiloJoule ultra-violet petawatt laser pulses can be produced using this scheme. This has important consequences for the demonstration of fast-ignition inertial confinement fusion.

  11. Characteristics and Applications of Spatiotemporally Focused Femtosecond Laser Pulses

    Directory of Open Access Journals (Sweden)

    Chenrui Jing


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

  12. Laser pulse heating of surfaces and thermal stress analysis

    CERN Document Server

    Yilbas, Bekir S; Al-Aqeeli, Nasser; Al-Qahtani, Hussain M


    This book introduces laser pulse heating and thermal stress analysis in materials surface. Analytical temperature treatments and stress developed in the surface region are also explored. The book will help the reader analyze the laser induced stress in the irradiated region and presents solutions for the stress field. Detailed thermal stress analysis in different laser pulse heating situations and different boundary conditions are also presented. Written for surface engineers.

  13. CO{sub 2} laser pulse shortening by laser ablation of a metal target

    Energy Technology Data Exchange (ETDEWEB)

    Donnelly, T.; Mazoyer, M.; Lynch, A.; O' Sullivan, G.; O' Reilly, F.; Dunne, P.; Cummins, T. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)


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

  14. Electron guns at the Budker Institute of Nuclear Physics SB RAS: prospects for the use of photocathodes with nanosecond and subpicosecond laser drivers (United States)

    Vinokurov, N. A.; Barnyakov, A. M.; Volkov, V. N.; Kolobanov, E. I.; Kuznetsov, G. I.; Kurkin, G. Ya; Levichev, A. E.; Logachev, P. V.; Nikiforov, D. A.; Petrov, V. M.; Starostenko, D. A.; Tribendis, A. G.


    The problem of producing high-current electron beams with relatively small lateral sizes and small velocity spread is more than a hundred years old. The continuous improvement of near-ultraviolet electromagnetic radiation sources (lasers with harmonics generators) allows significantly improving the parameters of existing electron guns. This paper discusses some problems in the development of electron guns with photocathodes and considers possible ways of using laser photocathodes in the electron guns designed at the Budker INP SB RAS.

  15. Energy losses estimation during pulsed-laser seam welding

    Czech Academy of Sciences Publication Activity Database

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


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


    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove


    This paper describes how the laser cutting process can be optimised in such a way that the cut sheets can subsequently be used to laser weld tailored blanks. In a number of systematic laboratory experiments the effect of cutting speed, assist gas pressure, average laser power and pulse energy was...

  17. Picosecond pulses of coherent MM-wave radiation in a photoinjector-driven waveguide free-selected laser

    Energy Technology Data Exchange (ETDEWEB)

    Fochs, S.N.; Le Sage, G.P.; Feng, L. [Univ. of California, Davis, CA (United States)] [and others


    A 5 MeV, high repetition rate (2.142 GHz in burst mode), high brightness, tabletop photoinjector is currently under construction at the UC Davis Department of Applied Science, on the LLNL site. Ultrashort pulses of coherent synchrotron radiation can be generated by transversally accelerating the electron beam with a wiggler in either metallic or dielectric-loaded waveguide FEL structures. This interaction is investigated theoretically and experimentally. Subpicosecond photoelectron bunches will be produced in the photoinjector by irradiating a high quantum efficiency Cs{sub 2}Te (Cesium Telluride) photocathode with a train of 100 UV (210 nm), ultra-short (250 fs) laser pulses. These bunches will be accelerated in a 1-1/2 cell {pi}-mode X-band RF gun e energized by a 20 MW, 8,568 GHz SLAC klystron. The peak current is 0.25 kA (0.25 nC, 1 ps), with a normalized beam emittance {epsilon}{sub n}<2.5 {pi} mm-mrad. This prebunched electron beam is then transversally accelerated in a cylindrical waveguide by a 30-mm period, 10 period long helical wiggler. The peak wiggler field is adjusted to 8.5 kG, so that the group velocity of the radiated electromagnetic waves matches the axial velocity of the electron bunch (grazing condition, zero slippage). Chirped output pulses in excess of 2 MW power are predicted, with an instantaneous bandwidth extending from 125 GHz to 225 GHz and a pulse duration of 15 ps (HWHM). To produce even shorter pulses, a dielectric-loaded waveguide can be used. The dispersion relation of this waveguide structure has an inflection point (zero group velocity dispersion). If the grazing condition is satisfied at this point, the final output pulse duration is no longer determined by slippage, or by group velocity dispersion and bandwidth, but by higher-order dispersive effects yielding transform-limited pulses.

  18. Role of laser pre-pulse wavelength and inter-pulse delay on signal enhancement in collinear double-pulse laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Diwakar, P.K., E-mail:; Harilal, S.S.; Freeman, J.R.; Hassanein, A.


    Dual-pulse (DP) laser-induced breakdown spectroscopy (LIBS) provides significant improvement in signal intensity as compared to conventional single-pulse LIBS. We investigated collinear DPLIBS experimental performance using various laser wavelength combinations employing 1064 nm, 532 nm, and 266 nm Nd:YAG lasers. In particular, the role of the pre-pulse laser wavelength, inter-pulse delay times, and energies of the reheating pulses on LIBS sensitivity improvements is studied. Wavelengths of 1064 nm, 532 nm, and 266 nm pulses were used for generating pre-pulse plasma while 1064 nm pulse was used for reheating the pre-formed plasma generated by the pre-pulse. Significant emission intensity enhancement is noticed for all reheated plasma regardless of the pre-pulse excitation beam wavelength compared to single pulse LIBS. A dual peak in signal enhancement was observed for different inter-pulse delays, especially for 1064:1064 nm combinations, which is explained based on temperature measurement and shockwave expansion phenomenon. Our results also show that 266 nm:1064 nm combination provided maximum absolute signal intensity as compared to 1064 nm:1064 nm or 532 nm:1064 nm. - Highlights: • Role of pre-pulse wavelength and inter-pulse delay on LIBS sensitivity was studied. • For NIR:NIR combination, dual peaks in signal enhancement were observed. • UV:NIR combination resulted in maximum absolute signal intensity. • Persistence of neutral species was increased for double pulse.

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

    Energy Technology Data Exchange (ETDEWEB)

    Rudenko, A; Feuerstein, B; Zrost, K; Jesus, V L B de; Ergler, T; Dimopoulou, C; Schroeter, C D; Moshammer, R; Ullrich, J [Max-Planck-Institut fuer Kernphysik, D-69029 Heidelberg (Germany)


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

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

    Directory of Open Access Journals (Sweden)

    Takehito Hayakawa


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

  1. Pulse-burst laser systems for fast Thomson scattering (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Den Hartog, D. J. [Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706 (United States); Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Ambuel, J. R.; Holly, D. J.; Robl, P. E. [Physical Sciences Laboratory, University of Wisconsin-Madison, 3725 Schneider Drive, Stoughton, Wisconsin 53589 (United States); Borchardt, M. T.; Falkowski, A. F.; Harris, W. S.; Parke, E.; Reusch, J. A.; Stephens, H. D.; Yang, Y. M. [Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706 (United States)


    Two standard commercial flashlamp-pumped Nd:YAG (YAG denotes yttrium aluminum garnet) lasers have been upgraded to ''pulse-burst'' capability. Each laser produces a burst of up to 15 2 J Q-switched pulses (1064 nm) at repetition rates of 1-12.5 kHz. Variable pulse-width drive (0.15-0.39 ms) of the flashlamps is accomplished by insulated gate bipolar transistor (IGBT) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinch to record the dynamic evolution of the electron temperature profile and temperature fluctuations. To further these investigations, a custom pulse-burst laser system with a maximum pulse repetition rate of 250 kHz is now being commissioned.

  2. Application of ultrashort laser pulses for intrastromal refractive surgery. (United States)

    Lubatschowski, H; Maatz, G; Heisterkamp, A; Hetzel, U; Drommer, W; Welling, H; Ertmer, W


    Recently, laser systems have become available which generate ultrashort laser pulses with a duration of 100-200 femtoseconds (fs). By generating micro-plasmas inside the corneal stroma with fs pulses, it is possible to achieve a cutting effect inside the tissue while leaving the anterior layers intact. The energy threshold to generate a micro-plasma with fs pulses is some orders of magnitude lower than it is for picosecond or nanosecond pulses. This results in a strong reduction of the thermal and mechanical damage of the surrounding tissue. With a titanium:sapphire fs laser system, the cutting effect on corneal tissue from freshly enucleated porcine eye globes was investigated with different pulse energies. The irradiated samples were examined by light and electron microscopy. The laser-induced pressure transients and the laser-induced bubble formation were analysed with a broadband acoustic transducer and by flash photography. With fs laser pulses, the extent of thermal and mechanical damage of the adjacent tissue is in the order of 1 microm or below and therefore comparable with the tissue alterations after ArF excimer laser ablation. Using pulse energies of approximately 1-2 microJ and a spot diameter of 5-10 microm, intrastromal cuts can be performed very precisely in order to prepare corneal flaps and lenticules. Femtosecond photodisruption has the potential to become an attractive tool for intrastromal refractive surgery.

  3. Non-Contact Cardiac Activity Monitoring using Pulsed Laser Vibrometer

    Directory of Open Access Journals (Sweden)

    Chen Chia WANG


    Full Text Available We demonstrate experimentally the detection of detailed human cardiac mechanical activity in a remote, non-contacting, and non-ionizing manner using a pulsed laser vibrometer. The highly sensitive pulsed laser vibrometer allows the detection of the temporally-phased mechanical events occurring in individual cardiac cycles even from the surface of clothing-covered extremities of the subjects. Fine structures of the detected cardiac traces are identified with their meanings assigned and corroborated using accelerometer and electrocardiogram measurements obtained concurrently with the pulsed laser vibrometer studies.

  4. Optimisation study of the synthesis of vanadium oxide nanostructures using pulsed laser deposition

    CSIR Research Space (South Africa)

    Masina, BN


    Full Text Available . For the case of the nanosecond, long pulse laser ablation, the plasma expands isothermally during the laser pulse followed by adiabatic expansion after the laser pulse termination [7, 8]. During the isothermal regime process, initially the laser interacts... and plasma plume expansion during a pulsed laser deposition process of synthesising the VO2 nanostructures thin films. In pulsed laser deposition (PLD) process, it is important to control the plume dynamics in order to obtain good quality and correct...

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

    DEFF Research Database (Denmark)

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


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

  6. Optimization and control of electron beams from laser wakefield accelerations using asymmetric laser pulses (United States)

    Gopal, K.; Gupta, D. N.


    Optimization and control of electron beam quality in laser wakefield acceleration are explored by using a temporally asymmetric laser pulse of the sharp rising front portion. The temporally asymmetric laser pulse imparts stronger ponderomotive force on the ambient plasma electrons. The stronger ponderomotive force associated with the asymmetric pulse significantly affects the injection of electrons into the wakefield and consequently the quality of the injected bunch in terms of injected charge, mean energy, and emittance. Based on particle-in-cell simulations, we report to generate a monoenergetic electron beam with reduced emittance and enhanced charge in laser wakefield acceleration using an asymmetric pulse of duration 30 fs.

  7. Hydroxyapatite thin films grown by pulsed laser deposition and matrix assisted pulsed laser evaporation: Comparative study (United States)

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


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

  8. Excitation and Control of Plasma Wakefields by Multiple Laser Pulses (United States)

    Cowley, J.; Thornton, C.; Arran, C.; Shalloo, R. J.; Corner, L.; Cheung, G.; Gregory, C. D.; Mangles, S. P. D.; Matlis, N. H.; Symes, D. R.; Walczak, R.; Hooker, S. M.


    We demonstrate experimentally the resonant excitation of plasma waves by trains of laser pulses. We also take an important first step to achieving an energy recovery plasma accelerator by showing that a plasma wave can be damped by an out-of-resonance trailing laser pulse. The measured laser wakefields are found to be in excellent agreement with analytical and numerical models of wakefield excitation in the linear regime. Our results indicate a promising direction for achieving highly controlled, GeV-scale laser-plasma accelerators operating at multikilohertz repetition rates.

  9. Phase-coherent optical pulse synthesis from separate femtosecond lasers. (United States)

    Shelton, R K; Ma, L S; Kapteyn, H C; Murnane, M M; Hall, J L; Ye, J


    We generated a coherently synthesized optical pulse from two independent mode-locked femtosecond lasers, providing a route to extend the coherent bandwidth available for ultrafast science. The two separate lasers (one centered at 760 nanometers wavelength, the other at 810 nanometers) are tightly synchronized and phase-locked. Coherence between the two lasers is demonstrated via spectral interferometry and second-order field cross-correlation. Measurements reveal a coherently synthesized pulse that has a temporally narrower second-order autocorrelation width and that exhibits a larger amplitude than the individual laser outputs. This work represents a new and flexible approach to the synthesis of coherent light.

  10. Parabolic similariton Yb-fiber laser with triangular pulse evolution (United States)

    Wang, Sijia; Wang, Lei


    We propose a novel mode-locked fiber laser design which features a passive nonlinear triangular pulse formation and self-similar parabolic pulse amplification intra cavity. Attribute to the nonlinear reshaping progress in the passive fiber, a triangular-profiled pulse with negative-chirp is generated and paved the way for rapid and efficient self-similar parabolic evolution in a following short-length high-gain fiber. In the meanwhile, the accompanied significantly compressed narrow spectrum from this passive nonlinear reshaping also gives the promise of pulse stabilization and gain-shaping robustness without strong filtering. The resulting short average intra-cavity pulse duration, low amplified spontaneous emission (ASE) and low intra-cavity power loss are essential for the low-noise operation. Simulations predict this modelocked fiber laser allows for high-energy ultra-short transform-limited pulse generation exceeding the gain bandwidth. The output pulse has a de-chirped duration (full-width at half maximum, FWHM) of 27 fs. In addition to the ultrafast laser applications, the proposed fiber laser scheme can support low-noise parabolic and triangular pulse trains at the same time, which are also attractive in optical pulse shaping, all-optical signal processing and high-speed communication applications.

  11. Continuous and Pulsed THz generation with molecular gas lasers and photoconductive antennas gated by femtosecond pulses (United States)

    Cruz, Flavio C.; Nogueira, T.; Costa, Leverson F. L.; Jarschel, Paulo F.; Frateschi, Newton C.; Viscovini, Ronaldo C.; Vieira, Bruno R. B.; Guevara, Victor M. B.; Pereira, Daniel


    We report THz generation based on two systems: 1) continuous-wave (cw) laser generation in molecular gas lasers, and 2) short pulse generation in photoconductive antennas, gated by femtosecond near-infrared Ti:sapphire lasers. With the first system, we have generated tens of monochromatic cw laser lines over the last years, extending roughly from 40 microns to several hundred microns. This is done by optical pumping of gas lasers based on polar molecules such as methanol and its isotopes. In the second system, under development, pulsed THz radiation is generated by a photoconductive antenna built in a semi-insulating GaAs substrate excited by femtosecond pulses from a near-infrared (800 nm) Ti:sapphire laser.

  12. Metal Processing with Ultra-Short Laser Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Banks, P S; Feit, M D; Komashko, A M; Perry, M D; Rubenchik, A M; Stuart, B C


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

  13. Fundamental studies of pulsed laser ablation

    CERN Document Server

    Claeyssens, F


    dopant) have resulted in a coherent view of the resulting plume, which exhibits a multi-component structure correlated with different regimes of ablation, which are attributed to ejection from ZnO and ablation from a Zn melt. OES measurements show that the emitting Zn component within the plume accelerates during expansion in vacuum - an observation attributable to the presence of hot, fast electrons in the plume. The same acceleration behaviour is observed in the case of Al atomic emissions resulting from ablation of an Al target in vacuum. Deposition conditions, substrate temperature and background gas pressure were all varied in a quest for optimally aligned, high quality ZnO thin films. Initial ab initio calculations were performed also, to aid in understanding the stability of these c-axis aligned films. The pulsed ultraviolet (lambda = 193, 248 nm) laser ablation of graphite, polycrystalline diamond and ZnO targets has been investigated. Characteristics of the resulting plumes of ablated material have b...

  14. Miniature, Rugged, Pulsed Laser Source for LIDAR Application Project (United States)

    National Aeronautics and Space Administration — Princeton Optronics proposes to develop a high energy pulsed laser source based on a novel approach. The approach consists of a technique to combine a large number...

  15. 20 W High Efficiency 1550 nm Pulsed Fiber Laser Project (United States)

    National Aeronautics and Space Administration — High peak power short pulsed lasers have been considered to be an enabling technology to build high power transmitters for future deep space high rate space...

  16. Reduction of the pulse duration of the ultrafast laser pulses of the Two-Photon Laser Scanning Microscopy (2PLSM

    Directory of Open Access Journals (Sweden)

    Reshak Ali


    Full Text Available Abstract Background We provide an update of our two-photon laser scanning microscope by compressing or reducing the broadening of the pulse width of ultrafast laser pulses for dispersion precompensation, to enable the pulses to penetrate deeply inside the sample. Findings The broadening comes as the pulses pass through the optical elements. We enhanced and modified the quality and the sharpness of images by enhancing the resolution using special polarizer namely Glan Laser polarizer GL10. This polarizer consists of two prisms separated by air space. This air separation between the two prisms uses to delay the red wavelength when the light leaves the first prism to the air then to second prism. We note a considerable enhancing with using the GL polarizer, and we can see the details of the leaf structure in early stages when we trying to get focus through z-stacks of images in comparison to exactly the same measurements without using GL polarizer. Hence, with this modification we able to reduce the time of exposure the sample to the laser radiation thereby we will reduce the probability of photobleaching and phototoxicity. When the pulse width reduced, the average power of the laser pulses maintained at a constant level. Significant enhancement is found between the two kinds of images of the Two-Photon Excitation Fluorescence (TPEF. Conclusion In summary reduction the laser pulse width allowed to collect more diffraction orders which will used to form the images. The more diffraction orders the higher resolution images.

  17. Carbon dioxide laser with a variable output pulse duration

    Energy Technology Data Exchange (ETDEWEB)

    Apollonov, V.V.; Akhunov, N.; Derzhavin, S.I.; Kononov, I.K.; Sirotkin, A.A.; Firsov, K.N.; Yamshchikov, V.A.


    A report is given of the construction of a CO/sub 2/ laser in which the exciting discharge was stabilized by adding readily ionized organic substances to the mixture. The temporal characteristics of the laser emission pulses were investigated for a wide range of active mixtures and pulse durations from 10 to 150 nsec. A discussion is given of improvements in the output energy distribution over the beam cross section.

  18. Non-Contact Cardiac Activity Monitoring using Pulsed Laser Vibrometer


    Chen Chia WANG; Sudhir TRIVEDI; Susan KUTCHER; Ponciano RODRIGUEZ; Feng JIN; V. SWAMINATHAN; Frank WALTERS; Narasimha S. PRASAD


    We demonstrate experimentally the detection of detailed human cardiac mechanical activity in a remote, non-contacting, and non-ionizing manner using a pulsed laser vibrometer. The highly sensitive pulsed laser vibrometer allows the detection of the temporally-phased mechanical events occurring in individual cardiac cycles even from the surface of clothing-covered extremities of the subjects. Fine structures of the detected cardiac traces are identified with their meanings assigned and corrobo...

  19. Ultrashort Laser Pulse Heating of Nanoparticles: Comparison of Theoretical Approaches

    Directory of Open Access Journals (Sweden)

    Renat R. Letfullin


    Full Text Available The interaction between nanoparticles and ultrashort laser pulses holds great interest in laser nanomedicine, introducing such possibilities as selective cell targeting to create highly localized cell damage. Two models are studied to describe the laser pulse interaction with nanoparticles in the femtosecond, picosecond, and nanosecond regimes. The first is a two-temperature model using two coupled diffusion equations: one describing the heat conduction of electrons, and the other that of the lattice. The second model is a one-temperature model utilizing a heat diffusion equation for the phonon subsystem and applying a uniform heating approximation throughout the particle volume. A comparison of the two modeling strategies shows that the two-temperature model gives a good approximation for the femtosecond mode, but fails to accurately describe the laser heating for longer pulses. On the contrary, the simpler one-temperature model provides an adequate description of the laser heating of nanoparticles in the femtosecond, picosecond, and nanosecond modes.

  20. Supression of laser breakdown by pulsed nonequilibrium ns discharge (United States)

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


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

  1. Role of laser pre-pulse wavelength and inter-pulse delay on signal enhancement in collinear double-pulse laser-induced breakdown spectroscopy (United States)

    Diwakar, P. K.; Harilal, S. S.; Freeman, J. R.; Hassanein, A.


    Dual-pulse (DP) laser-induced breakdown spectroscopy (LIBS) provides significant improvement in signal intensity as compared to conventional single-pulse LIBS. We investigated collinear DPLIBS experimental performance using various laser wavelength combinations employing 1064 nm, 532 nm, and 266 nm Nd:YAG lasers. In particular, the role of the pre-pulse laser wavelength, inter-pulse delay times, and energies of the reheating pulses on LIBS sensitivity improvements is studied. Wavelengths of 1064 nm, 532 nm, and 266 nm pulses were used for generating pre-pulse plasma while 1064 nm pulse was used for reheating the pre-formed plasma generated by the pre-pulse. Significant emission intensity enhancement is noticed for all reheated plasma regardless of the pre-pulse excitation beam wavelength compared to single pulse LIBS. A dual peak in signal enhancement was observed for different inter-pulse delays, especially for 1064:1064 nm combinations, which is explained based on temperature measurement and shockwave expansion phenomenon. Our results also show that 266 nm:1064 nm combination provided maximum absolute signal intensity as compared to 1064 nm:1064 nm or 532 nm:1064 nm.

  2. Pulse Duration of Seeded Free-Electron Lasers (United States)

    Finetti, Paola; Höppner, Hauke; Allaria, Enrico; Callegari, Carlo; Capotondi, Flavio; Cinquegrana, Paolo; Coreno, Marcello; Cucini, Riccardo; Danailov, Miltcho B.; Demidovich, Alexander; De Ninno, Giovanni; Di Fraia, Michele; Feifel, Raimund; Ferrari, Eugenio; Fröhlich, Lars; Gauthier, David; Golz, Torsten; Grazioli, Cesare; Kai, Yun; Kurdi, Gabor; Mahne, Nicola; Manfredda, Michele; Medvedev, Nikita; Nikolov, Ivaylo P.; Pedersoli, Emanuele; Penco, Giuseppe; Plekan, Oksana; Prandolini, Mark J.; Prince, Kevin C.; Raimondi, Lorenzo; Rebernik, Primoz; Riedel, Robert; Roussel, Eleonore; Sigalotti, Paolo; Squibb, Richard; Stojanovic, Nikola; Stranges, Stefano; Svetina, Cristian; Tanikawa, Takanori; Teubner, Ulrich; Tkachenko, Victor; Toleikis, Sven; Zangrando, Marco; Ziaja, Beata; Tavella, Franz; Giannessi, Luca


    The pulse duration, and, more generally, the temporal intensity profile of free-electron laser (FEL) pulses, is of utmost importance for exploring the new perspectives offered by FELs; it is a nontrivial experimental parameter that needs to be characterized. We measured the pulse shape of an extreme ultraviolet externally seeded FEL operating in high-gain harmonic generation mode. Two different methods based on the cross-correlation of the FEL pulses with an external optical laser were used. The two methods, one capable of single-shot performance, may both be implemented as online diagnostics in FEL facilities. The measurements were carried out at the seeded FEL facility FERMI. The FEL temporal pulse characteristics were measured and studied in a range of FEL wavelengths and machine settings, and they were compared to the predictions of a theoretical model. The measurements allowed a direct observation of the pulse lengthening and splitting at saturation, in agreement with the proposed theory.

  3. Diagnostics of pulse contrast for petawatt laser in SGII (United States)

    Ouyang, Xiaoping; Liu, Daizhong; Zhu, Baoqiang; Zhu, Jian; Zhu, Jianqiang


    Pulse contrast is an important parameter for ultrafast pulses. It shall be 108 or higher in order to avoid effect from noise before main pulse. Diagnostics with cross-correlation can achieve high temporal resolution such as ~7fs. Cross-correlation has advantage in pulse contrast measurement than autocorrelation because it can distinguish noise before or after main pulse. High dynamic range is also essential in pulse contrast measurement. Cross-correlation signal from a single shot is converted into a signal series through fiber array, which can be analyzed by a set of a PMT and an oscilloscope. Noise from nonlinear crystal and scatter needs decrease to improve dynamic range. And pulse power is also discussed in pulse contrast experiments. Time delay τ is generated by travel stage in measurement for repetition pulses. Then energy instability will generate error in this measurement. In measurement for single shot pulse, time delay τ is generated by slant angle of beams. The scanning procession is completed with thousands parts of beam section within a single shot, and error will generated from no uniformity in near field. Performance test of pulse contrast measurement is introduced in subsequent sections. Temporal resolution is testified by self-calibration. Dynamic range is judged by a parallel flat. At last pulse contrast of petawatt laser is diagnosed by a single shot cross-correlator with high confidence. The ratio is 10-6 at 50ps before main pulse, and 10-4 at 10ps before main pulse.

  4. Filamentation of ultrashort laser pulses of different wavelengths in ...

    Indian Academy of Sciences (India)

    We investigate the filaments formed by the ultrashort laser pulses with different wavelengths of 400 nm, 586 nm and 800 nm propagating in argon. Numerical results show that, when the input power or the ratio of the input power to the critical power is given, the pulse with 400 nm wavelength has the largest on-axis intensity, ...

  5. Imposed layer by layer growth by pulsed laser interval deposition

    NARCIS (Netherlands)

    Koster, Gertjan; Rijnders, Augustinus J.H.M.; Blank, David H.A.; Rogalla, Horst


    Pulsed laser deposition has become an important technique to fabricate novel materials. Although there is the general impression that, due to the pulsed deposition, the growth mechanism differs partially from continuous physical and chemical deposition techniques, it has hardly been used. Here, we

  6. Advanced pulse generator and preamplifier for the HELEN laser (United States)

    Norman, Michael J.; Harvey, E. J.; Hopps, N. W.; Nolan, J. R.; Smith, W. F. E.


    A replacement for the HELEN laser has been proposed that would involve a considerable increase in performance up to 100 TW from 32 beams. The design for the new laser is to be based on the technology being developed for the US National Ignition Facility. The pulse generation and preamplification stages employ novel technologies and represent a significant departure from previous designs. As part of the laser replacement development program a pulse generator and preamplifier have been built and installed on the HELEN laser at AWE, based on those employed on the Beamlet laser physics demonstration facility at Lawrence Livermore National Laboratory. As well as providing experience of the technologies involved, this system represents a significant enhancement of the performance of HELEN. Initial pulses are generated by a diode-pumped Q-switched Neodymium-doped Yttrium Lithium Fluoride ring oscillator. These are then launched into optical fiber and transported to a series of two integrated optics amplitude modulators for pulse shaping. The resulting pulses are then transported by optical fibers to a ring regenerative preamplifier for amplification to a level suitable for input to the HELEN laser. We describe this system, its performance and the enhanced capabilities of the HELEN laser resulting from its installation.

  7. Time dependent temperature distribution in pulsed Ti:sapphire lasers (United States)

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


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

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

    Energy Technology Data Exchange (ETDEWEB)

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


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

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

    Energy Technology Data Exchange (ETDEWEB)

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


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


    Directory of Open Access Journals (Sweden)

    A. P. Burmakov


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

  11. Precision machining of pig intestine using ultrafast laser pulses (United States)

    Beck, Rainer J.; Góra, Wojciech S.; Carter, Richard M.; Gunadi, Sonny; Jayne, David; Hand, Duncan P.; Shephard, Jonathan D.


    Endoluminal surgery for the treatment of early stage colorectal cancer is typically based on electrocautery tools which imply restrictions on precision and the risk of harm through collateral thermal damage to the healthy tissue. As a potential alternative to mitigate these drawbacks we present laser machining of pig intestine by means of picosecond laser pulses. The high intensities of an ultrafast laser enable nonlinear absorption processes and a predominantly nonthermal ablation regime. Laser ablation results of square cavities with comparable thickness to early stage colorectal cancers are presented for a wavelength of 1030 nm using an industrial picosecond laser. The corresponding histology sections exhibit only minimal collateral damage to the surrounding tissue. The depth of the ablation can be controlled precisely by means of the pulse energy. Overall, the application of ultrafast lasers to ablate pig intestine enables significantly improved precision and reduced thermal damage to the surrounding tissue compared to conventional techniques.

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

    Energy Technology Data Exchange (ETDEWEB)

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


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

  13. Autocorrelation measurement of fast electron pulses emitted through the interaction of femtosecond laser pulses with a solid target. (United States)

    Inoue, Shunsuke; Tokita, Shigeki; Otani, Kazuto; Hashida, Masaki; Hata, Masayasu; Sakagami, Hitoshi; Taguchi, Toshihiro; Sakabe, Shuji


    We report the first direct measurement of the emission duration of laser-accelerated fast electrons from the surface of a solid target irradiated by a high-intensity femtosecond laser pulse. The emission duration is determined by autocorrelation measurement using the Coulomb repulsive forces that act on two equivalent electron pulses. The emission duration depends on the laser pulse duration for laser pulses of 200-690 fs. Numerical modeling of three-dimensional charged particle dynamics indicates that the emission duration of fast electrons is almost equal to the duration of the laser pulse.

  14. Effect of laser pulse duration on damage to metal mirrors for laser IFE (United States)

    Pulsifer, John E.; Tillack, Mark S.; Harilal, S. S.


    A Grazing Incidence Metal Mirror (GIMM) is a chief candidate for beam delivery for Inertial Fusion Energy (IFE). The goal for GIMM survival is greater than 3×10 8 laser pulses with 5 J/cm2 laser fluence normal to the incident beam. Laser-induced damage to metal mirrors is primarily a thermomechanical process. Long-term exposure leads to microstructural evolution analogous to fatigue. We have performed laser-induced damage experiments on high damage threshold aluminum mirrors using commercial KrF excimer (248 nm) lasers. We have studied mirror response to standard, 25 ns long-pulses as well as to IFE prototypic, 5 ns short-pulses achieved using a Pockels Cell. Short-pulse damage fluence was found to be better than predicted using simple thermal diffusion scaling from long-pulse results.

  15. Mechanism study of skin tissue ablation by nanosecond laser pulses (United States)

    Fang, Qiyin

    Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to improve future design of the pulsed lasers for dermatology and plastic surgery. Multiple laser and optical configurations have been constructed to generate 9 to 12ns laser pulses with similar profiles at 1064. 532, 266 and 213nm for this study of skin tissue ablation. Through measurements of ablation depth as a function cf laser pulse energy, the 589nm spectral line in the secondary radiation from ablated skin tissue samples was identified as the signature of the occurrence of ablation. Subsequently, this spectral signature has been used to investigate the probabilistic process of the ablation near the threshold at the four wavelengths. Measurements of the ablation probability were conducted as a function of the electrical field strength of the laser pulse and the ablation thresholds in a wide spectral range from 1064nm to 213nm were determined. Histology analysis and an optical transmission method were applied in assessing of the ablation depth per pulse to study the ablation process at irradiance levels higher than threshold. Because more than 70% of the wet weight of the skin tissue is water, optical breakdown and backscattering in water was also investigated along with a nonlinear refraction index measurement using a z-scan technique. Preliminary studies on ablation of a gelatin based tissue phantom are also reported. The current theoretical models describing ablation of soft tissue ablation by short laser pulses were critically reviewed. Since none of the existing models was found capable of explaining the experimental results, a new plasma-mediated model was developed

  16. Development of pulse laser processing for mounting fiber Bragg grating (United States)

    Nishimura, Aikihko; Shimada, Yukihiro; Yonemoto, Yukihiro; Suzuki, Hirokazu; Ishibashi, Hisayoshi


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

  17. Interaction physics of multipicosecond Petawatt laser pulses with overdense plasma. (United States)

    Kemp, A J; Divol, L


    We study the interaction of intense petawatt laser pulses with overdense plasma over several picoseconds, using two- and three-dimensional kinetic particle simulations. Sustained irradiation with non-diffraction-limited pulses at relativistic intensities yields conditions that differ qualitatively from what is experimentally available today. Nonlinear saturation of laser-driven density perturbations at the target surface causes recurrent emissions of plasma, which stabilize the surface and keep absorption continuously high. This dynamics leads to the acceleration of three distinct groups of electrons up to energies many times the laser ponderomotive potential. We discuss their energy distribution for applications like the fast-ignition approach to inertial confinement fusion.

  18. Xenon plasma sustained by pulse-periodic laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Rudoy, I. G.; Solovyov, N. G.; Soroka, A. M.; Shilov, A. O.; Yakimov, M. Yu., E-mail: [Russian Academy of Sciences, A. Ishlinsky Institute for Problems in Mechanics (Russian Federation)


    The possibility of sustaining a quasi-stationary pulse-periodic optical discharge (POD) in xenon at a pressure of p = 10–20 bar in a focused 1.07-μm Yb{sup 3+} laser beam with a pulse repetition rate of f{sub rep} ⩾ 2 kHz, pulse duration of τ ⩾ 200 μs, and power of P = 200–300 W has been demonstrated. In the plasma development phase, the POD pulse brightness is generally several times higher than the stationary brightness of a continuous optical discharge at the same laser power, which indicates a higher plasma temperature in the POD regime. Upon termination of the laser pulse, plasma recombines and is then reinitiated in the next pulse. The initial absorption of laser radiation in successive POD pulses is provided by 5p{sup 5}6s excited states of xenon atoms. This kind of discharge can be applied in plasma-based high-brightness broadband light sources.

  19. The efficiency of photovoltaic cells exposed to pulsed laser light (United States)

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


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

  20. High stability breakdown of noble gases with femtosecond laser pulses. (United States)

    Heins, A M; Guo, Chunlei


    In the past, laser-induced breakdown spectroscopy (LIBS) signals have been reported to have a stability independent of the pulse length in solids. In this Letter, we perform the first stability study of femtosecond LIBS in gases (to our best knowledge) and show a significant improvement in signal stability over those achieved with longer pulses. Our study shows that ultrashort-pulse LIBS has an intrinsically higher stability in gas compared to nanosecond-pulse LIBS because of a deterministic ionization process at work in the femtosecond pulse. Relative standard deviations below 1% are demonstrated and are likely only limited by our laser output fluctuations. This enhanced emission stability may open up possibilities for a range of applications, from monitoring rapid gas dynamics to high-quality broadband light sources.

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

    Energy Technology Data Exchange (ETDEWEB)

    Corrales, L. Rene [Departments of Materials Science and Engineering, and Chemistry, University of Arizona, Tucson, Arizona 85721 (United States)], E-mail:; Moore, Emily [Departments of Materials Science and Engineering, and Chemistry, University of Arizona, Tucson, Arizona 85721 (United States)


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

  2. 100J Pulsed Laser Shock Driver for Dynamic Compression Research (United States)

    Wang, X.; Sethian, J.; Bromage, J.; Fochs, S.; Broege, D.; Zuegel, J.; Roides, R.; Cuffney, R.; Brent, G.; Zweiback, J.; Currier, Z.; D'Amico, K.; Hawreliak, J.; Zhang, J.; Rigg, P. A.; Gupta, Y. M.


    Logos Technologies and the Laboratory for Laser Energetics (LLE, University of Rochester) - in partnership with Washington State University - have designed, built and deployed a one of a kind 100J pulsed UV (351 nm) laser system to perform real-time, x-ray diffraction and imaging experiments in laser-driven compression experiments at the Dynamic Compression Sector (DCS) at the Advanced Photon Source, Argonne National Laboratory. The laser complements the other dynamic compression drivers at DCS. The laser system features beam smoothing for 2-d spatially uniform loading of samples and four, highly reproducible, temporal profiles (total pulse duration: 5-15 ns) to accommodate a wide variety of scientific needs. Other pulse shapes can be achieved as the experimental needs evolve. Timing of the laser pulse is highly precise (<200 ps) to allow accurate synchronization of the x-rays with the dynamic compression event. Details of the laser system, its operating parameters, and representative results will be presented. Work supported by DOE/NNSA.

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


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


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

  4. Laser photoionization of triacetone triperoxide (TATP) by femtosecond and nanosecond laser pulses (United States)

    Mullen, Christopher; Huestis, David; Coggiola, Michael; Oser, Harald


    Laser ionization time-of-flight mass spectrometry has been applied to the study of triacetone triperoxide (TATP), an improvised explosive. Wavelength dependent mass spectra in two time regimes were acquired using nanosecond (5 ns) and femtosecond (130 fs) laser pulses. We find the major difference between the two time regimes to be the detection of the parent molecular ion when femtosecond laser pulses are employed.

  5. Pulsed Single Frequency MOPA Laser Project (United States)

    National Aeronautics and Space Administration — Latest advances in semiconductor optoelectronics makes it possible to develop compact light weight robust sources of coherent optical pulses, demanded for numerous...

  6. Surface modification of collagen-based biomaterial induced by pulse width variable femtosecond laser pulses (United States)

    Daskalova, A.; Selimis, A.; Manousaki, A.; Gray, D.; Ranella, A.; Fotakis, C.


    The ability to produce idealized cellular constructs is essential for understanding and controlling intercellular processes and ultimately for producing engineered tissue replacements. Preliminary results have been obtained on collagen modification by irradiation with single and multiple pulses of femtosecond laser with variable pulse duration. Irradiation of collagen thin film by single pulses of femtosecond duration results in creation of foam layer with micrometer thickness. The structure and thickness of the layer strongly depends on the number of the applied laser pulses. The surface properties of collagen thin films before and after Ti-sapphire irradiation with 800 nm were investigated by means of the technique Field Emission Scanning Electron Microscope (FESEM). Based on the FESEM results, it was possible to identify an energy density range as the ablation threshold for collagen thin films. The laser-induced foam formation was characterized over the intensity range 3 - 4.2x1011 W/cm2. The results of the field emission scanning electron microscopy, showed that by tailoring the laser pulse duration, improved the uniformity of the pore network. Examination of the interaction of ultra-short laser pulses with collagen films is useful for controlling the chemical and microstructural modification of the created foam layer.

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

    CERN Multimedia


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

  8. Pathogen reduction in human plasma using an ultrashort pulsed laser. (United States)

    Tsen, Shaw-Wei D; Kingsley, David H; Kibler, Karen; Jacobs, Bert; Sizemore, Sara; Vaiana, Sara M; Anderson, Jeanne; Tsen, Kong-Thon; Achilefu, Samuel


    Pathogen reduction is a viable approach to ensure the continued safety of the blood supply against emerging pathogens. However, the currently licensed pathogen reduction techniques are ineffective against non-enveloped viruses such as hepatitis A virus, and they introduce chemicals with concerns of side effects which prevent their widespread use. In this report, we demonstrate the inactivation of both enveloped and non-enveloped viruses in human plasma using a novel chemical-free method, a visible ultrashort pulsed laser. We found that laser treatment resulted in 2-log, 1-log, and 3-log reductions in human immunodeficiency virus, hepatitis A virus, and murine cytomegalovirus in human plasma, respectively. Laser-treated plasma showed ≥70% retention for most coagulation factors tested. Furthermore, laser treatment did not alter the structure of a model coagulation factor, fibrinogen. Ultrashort pulsed lasers are a promising new method for chemical-free, broad-spectrum pathogen reduction in human plasma.

  9. Pathogen reduction in human plasma using an ultrashort pulsed laser.

    Directory of Open Access Journals (Sweden)

    Shaw-Wei D Tsen

    Full Text Available Pathogen reduction is a viable approach to ensure the continued safety of the blood supply against emerging pathogens. However, the currently licensed pathogen reduction techniques are ineffective against non-enveloped viruses such as hepatitis A virus, and they introduce chemicals with concerns of side effects which prevent their widespread use. In this report, we demonstrate the inactivation of both enveloped and non-enveloped viruses in human plasma using a novel chemical-free method, a visible ultrashort pulsed laser. We found that laser treatment resulted in 2-log, 1-log, and 3-log reductions in human immunodeficiency virus, hepatitis A virus, and murine cytomegalovirus in human plasma, respectively. Laser-treated plasma showed ≥70% retention for most coagulation factors tested. Furthermore, laser treatment did not alter the structure of a model coagulation factor, fibrinogen. Ultrashort pulsed lasers are a promising new method for chemical-free, broad-spectrum pathogen reduction in human plasma.

  10. Study of laser die release by Q-switched Nd:YAG laser pulses

    NARCIS (Netherlands)

    Karlitskaya, N.; de Lange, D.F.; Meijer, J.; Sanders, Rene; Phipps, Claude R.


    A new laser-assisted process called "Laser Die Transfer" is developed for high speed assembling of miniature electronic components. Silicon dies, fabricated on an optically transparent carrier are released using a laser pulse. This process has the potential to offer major advantages compared to

  11. Computer modeling of pulsed CO2 lasers for lidar applications (United States)

    Spiers, Gary D.


    The object of this effort is to develop code to enable the accurate prediction of the performance of pulsed transversely excited (TE) CO2 lasers prior to their construction. This is of particular benefit to the NASA Laser Atmospheric Wind Sounder (LAWS) project. A benefit of the completed code is that although developed specifically for the pulsed CO2 laser much of the code can be modified to model other laser systems of interest to the lidar community. A Boltzmann equation solver has been developed which enables the electron excitation rates for the vibrational levels of CO2 and N2, together with the electron ionization and attachment coefficients to be determined for any CO2 laser gas mixture consisting of a combination of CO2, N2, CO, He and CO. The validity of the model has been verified by comparison with published material. The results from the Boltzmann equation solver have been used as input to the laser kinetics code which is currently under development. A numerical code to model the laser induced medium perturbation (LIMP) arising from the relaxation of the lower laser level has been developed and used to determine the effect of LIMP on the frequency spectrum of the LAWS laser output pulse. The enclosed figures show representative results for a laser operating at 0.5 atm. with a discharge cross-section of 4.5 cm to produce a 20 J pulse with aFWHM of 3.1 microns. The first four plots show the temporal evolution of the laser pulse power, energy evolution, LIMP frequency chirp and electric field magnitude. The electric field magnitude is taken by beating the calculated complex electric field and beating it with a local oscillator signal. The remaining two figures show the power spectrum and energy distribution in the pulse as a function of the varying pulse frequency. The LIMP theory has been compared with experimental data from the NOAA Windvan Lidar and has been found to be in good agreement.

  12. Towards manipulating relativistic laser pulses with 3D printed materials

    CERN Document Server

    Ji, L L; Pukhov, A; Freeman, R R; Akli, K U


    Efficient coupling of intense laser pulses to solid-density matter is critical to many applications including ion acceleration for cancer therapy. At relativistic intensities, the focus has been mainly on investigating various laser beams irradiating initially flat interfaces with little or no control over the interaction. Here, we propose a novel approach that leverages recent advancements in 3D direct laser writing (DLW) of materials and high contrast lasers to manipulate the laser-matter interactions on the micro-scales. We demonstrate, via simulations, that usable intensities >10^23Wcm^(-2) could be achieved with current tabletop lasers coupled to 3D printed plasma lenses. We show that these plasma optical elements act not only as a lens to focus laser light, but also as an electromagnetic guide for secondary particle beams. These results open new paths to engineering light-matter interactions at ultra-relativistic intensities.

  13. Electron yield enhancement in a laser wakefield accelerator driven by asymmetric laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Leemans, W.P.; Catravas, P.; Esarey, E.; Geddes, C.G.R.; Toth, C.; Trines, R.; Schroeder, C.B.; Shadwick, B.A.; van Tilborg, J.; Faure, J.


    The effect of asymmetric laser pulses on electron yield from a laser wakefield accelerator has been experimentally studied using > 10{sup 19} cm{sup -3} plasmas and a 10 TW, > 45 fs, Ti:Al{sub 2}O{sub 3} laser. Laser pulse shape was controlled through non-linear chirp with a grating pair compressor. Pulses (76 fs FWHM) with a steep rise and positive chirp were found to significantly enhance the electron yield compared to pulses with a gentle rise and negative chirp. Theory and simulation show that fast rising pulses can generate larger amplitude wakes that seed the growth of the self-modulation instability and that frequency chirp is of minimal importance for the experimental parameters.

  14. Free space optical communication based on pulsed lasers (United States)

    Drozd, Tadeusz; Mierczyk, Zygmunt; Zygmunt, Marek; Wojtanowski, Jacek


    Most of the current optical data transmission systems are based on continuous wave (cw) lasers. It results from the tendency to increase data transmission speed, and from the simplicity in implementation (straightforward modulation). Pulsed lasers, which find many applications in a variety of industrial, medical and military systems, in this field are not common. Depending on the type, pulsed lasers can generate instantaneous power which is many times greater when compared with cw lasers. As such, they seem to be very attractive to be used in data transmission technology, especially due to the potentially larger ranges of transmission, or in adverse atmospheric conditions where low power cw-lasersbased transmission is no longer feasible. It is also a very practical idea to implement data transmission capability in the pulsed laser devices that have been around and already used, increasing the functionality of this type of equipment. At the Institute of Optoelectronics at Military University of Technology, a unique method of data transmission based on pulsed laser radiation has been developed. This method is discussed in the paper in terms of both data transmission speed and transmission range. Additionally, in order to verify the theoretical assumptions, modules for voice and data transmission were developed and practically tested which is also reported, including the measurements of Bit Error Rate (BER) and performance vs. range analysis.

  15. Pulsed Nd:YAG laser beam drilling: A review (United States)

    Gautam, Girish Dutt; Pandey, Arun Kumar


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

  16. Laser scar revision: comparison of CO2 laser vaporization with and without simultaneous pulsed dye laser treatment. (United States)

    Alster, T S; Lewis, A B; Rosenbach, A


    Over the past decade, the 585-nm pulsed dye laser (PDL) has been used successfully to treat a variety of cutaneous vascular lesions as well as hypertrophic scars. Laser scar revision has been revolutionized by the recent development of high-energy, pulsed carbon dioxide (CO2) laser systems. These new CO2 lasers allow controlled vaporization of thin layers of skin while minimizing damage to surrounding dermal structures. To determine the effect of a high-energy, pulsed CO2 laser alone and in combination with a 585-nm PDL on nonerythematous hypertrophic scars. Twenty patients with nonerythematous hypertrophic scars were treated with a high-energy, pulsed CO2 laser. One-half of each scar was additionally treated with the 585-nm PDL laser. Sequential clinical and photographic analyses were performed independently by two blinded assessors. In addition, erythema reflectance spectrometry measurements were obtained from the scars before and at regular postoperative intervals. Global assessment scores and erythema spectrometry measurements were significantly improved after laser treatment. Combination CO2 and PDL laser treatment resulted in more significant improvement than CO2 laser irradiation alone. Concomitant use of the high-energy, pulsed CO2 and PDL laser systems was superior to CO2 laser vaporization alone for revision of nonerythematous hypertrophic scars. Once again, the vascular specificity of the 585-nm PDL has been linked to improvement in hypertrophic scar tissue.

  17. A comparative study of pulsed Nd:YAG and CO2 laser effect on cardiovascular tissue


    Yova, D.; Papadakis, E.; Kassis, K.; Agapitos, E.; Kavantzas, N.; Koutsouris, D.; Serafetinidis, A.


    Percutaneous laser angioplasty is receiving increasing attention, as laser ablation of atheromatous plaque presents advantages to direct surgery or balloon angioplasty. One of the main prerequisites of using powerful pulsed lasers in angioplasty is the optimum choice of the irradiation parameters (the wavelength, the pulse shape and duration, the energy parameters e.t.c.). Infrared lasers have numerous applications in surgery. Among them the pulsed CO2 laser emitting at 10.6 µm and the pulsed...

  18. Energy deposition from focused terawatt laser pulses in air

    CERN Document Server

    Point, Guillaume; Mysyrowicz, André; Houard, Aurélien


    Laser filamentation is responsible for the deposition of a significant part of the laser pulse energy in the propagation medium. We found that using terawatt laser pulses and relatively tight focusing conditions in air, resulting in a bundle of co-propagating multifilaments, more than 50 % of the pulses energy is transferred to the medium, eventually degrading into heat. This results in a strong hydrodynamic reaction of air with the generation of shock waves and associated underdense channels for each short-scale filament. In the focal zone, where filaments are close to each other, these discrete channels eventually merge to form a single cylindrical low-density tube over a $\\sim 1~ \\mu\\mathrm{s}$ timescale. We measured the maximum lineic deposited energy to be more than 1 J/m.

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

    Energy Technology Data Exchange (ETDEWEB)

    Aronne, Antonio [Department of Chemical Engineering, Materials and Industrial Production, University of Naples “Federico II”, Napoli (Italy); Bloisi, Francesco, E-mail: [SPIN – CNR, Naples (Italy); Department of Physics, University of Naples “Federico II”, Napoli (Italy); Calabria, Raffaela; Califano, Valeria [Istituto Motori – CNR, Naples (Italy); Depero, Laura E. [Department of Mechanical and Industrial Engineering, University of Brescia, Brescia (Italy); Fanelli, Esther [Department of Chemical Engineering, Materials and Industrial Production, University of Naples “Federico II”, Napoli (Italy); Federici, Stefania [Department of Mechanical and Industrial Engineering, University of Brescia, Brescia (Italy); Massoli, Patrizio [Istituto Motori – CNR, Naples (Italy); Vicari, Luciano R.M. [SPIN – CNR, Naples (Italy); Department of Physics, University of Naples “Federico II”, Napoli (Italy)


    Highlights: • A lipase film was deposited with Matrix Assisted Pulsed Laser Evaporation technique. • FTIR spectra show that laser irradiation do not damage lipase molecule. • Laser fluence controls the characteristics of complex structure generated by MAPLE. - Abstract: Lipase is an enzyme that finds application in biodiesel production and for detection of esters and triglycerides in biosensors. Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique derived from Pulsed Laser Deposition (PLD) for deposition of undamaged biomolecules or polymers, is characterized by the use of a frozen target obtained from a solution/suspension of the guest material (to be deposited) in a volatile matrix (solvent). The presence of the solvent avoids or at least reduces the potential damage of guest molecules by laser radiation but only the guest material reaches the substrate in an essentially solvent-free deposition. MAPLE can be used for enzymes immobilization, essential for industrial application, allowing the development of continuous processes, an easier separation of products, the reuse of the catalyst and, in some cases, enhancing enzyme properties (pH, temperature stability, etc.) and catalytic activity in non-aqueous media. Here we show that MAPLE technique can be used to deposit undamaged lipase and that the complex structure (due to droplets generated during extraction from target) of the deposited material can be controlled by changing the laser beam fluence.

  20. Seeded QED cascades in counterpropagating laser pulses. (United States)

    Grismayer, T; Vranic, M; Martins, J L; Fonseca, R A; Silva, L O


    The growth rates of seeded QED cascades in counterpropagating lasers are calculated with first-principles two- and three-dimensional QED-PIC (particle-in-cell) simulations. The dependence of the growth rate on the laser polarization and intensity is compared with analytical models that support the findings of the simulations. The models provide insight regarding the qualitative trend of the cascade growth when the intensity of the laser field is varied. A discussion about the cascade's threshold is included, based on the analytical and numerical results. These results show that relativistic pair plasmas and efficient conversion from laser photons to γ rays can be observed with the typical intensities planned to operate on future ultraintense laser facilities such as ELI or Vulcan.

  1. High power, short pulses ultraviolet laser for the development of a new x-ray laser

    Energy Technology Data Exchange (ETDEWEB)

    Meixler, L.; Nam, C.H.; Robinson, J.; Tighe, W.; Krushelnick, K.; Suckewer, S.; Goldhar, J.; Seely, J.; Feldman, U.


    A high power, short pulse ultraviolet laser system (Powerful Picosecond-Laser) has been developed at the Princeton Plasma Physics Laboratory (PPPL) as part of experiments designed to generate shorter wavelength x-ray lasers. With the addition of pulse compression and a final KrF amplifier the laser output is expected to have reached 1/3-1/2 TW (10/sup 12/ watts) levels. The laser system, particularly the final amplifier, is described along with some initial soft x-ray spectra from laser-target experiments. The front end of the PP-Laser provides an output of 20--30 GW (10/sup 9/ watts) and can be focussed to intensities of /approximately/10/sup 16/ W/cm/sup 2/. Experiments using this output to examine the effects of a prepulse on laser-target interaction are described. 19 refs., 14 figs.

  2. Numerical analysis of laser ablation and damage in glass with multiple picosecond laser pulses. (United States)

    Sun, Mingying; Eppelt, Urs; Russ, Simone; Hartmann, Claudia; Siebert, Christof; Zhu, Jianqiang; Schulz, Wolfgang


    This study presents a novel numerical model for laser ablation and laser damage in glass including beam propagation and nonlinear absorption of multiple incident ultrashort laser pulses. The laser ablation and damage in the glass cutting process with a picosecond pulsed laser was studied. The numerical results were in good agreement with our experimental observations, thereby revealing the damage mechanism induced by laser ablation. Beam propagation effects such as interference, diffraction and refraction, play a major role in the evolution of the crater structure and the damage region. There are three different damage regions, a thin layer and two different kinds of spikes. Moreover, the electronic damage mechanism was verified and distinguished from heat modification using the experimental results with different pulse spatial overlaps.

  3. Application of laser pulse stretching scheme for efficiently delivering laser energy in photoacoustic imaging (United States)

    Wang, Tianheng; Kumavor, Patrick D.; Zhu, Quing


    High-energy and short-duration laser pulses are desirable to improve the photoacoustic image quality when imaging deeply seated lesions. In many clinical applications, the high-energy pulses are coupled to tissue using optical fibers. These pulses can damage fibers if the damage threshold is exceeded. While keeping the total energy under the Food and Drug Administration limit for avoiding tissue damage, it is necessary to reduce the peak intensity and increase the pulse duration for minimizing fiber damage and delivering sufficient light for imaging. We use laser-pulse-stretching to address this problem. An initial 17-ns pulse was stretched to 27 and 37 ns by a ring-cavity laser-pulse-stretching system. The peak power of the 37-ns stretched pulse reduced to 42% of the original, while the fiber damage threshold was increased by 1.5-fold. Three ultrasound transducers centered at 1.3-, 3.5-, and 6-MHz frequencies were simulated, and the results showed that the photoacoustic signal of a 0.5-mm-diameter target obtained with 37-ns pulse was about 98, 91, and 80%, respectively, using the same energy as the 17-ns pulse. Simulations were validated using a broadband hydrophone. Quantitative comparisons of photoacoustic images obtained with three corresponding transducers showed that the image quality was not affected by stretching the pulse.

  4. Short infrared laser pulses block action potentials in neurons (United States)

    Walsh, Alex J.; Tolstykh, Gleb P.; Martens, Stacey L.; Ibey, Bennett L.; Beier, Hope T.


    Short infrared laser pulses have many physiological effects on cells including the ability to stimulate action potentials in neurons. Here we show that short infrared laser pulses can also reversibly block action potentials. Primary rat hippocampal neurons were transfected with the Optopatch2 plasmid, which contains both a blue-light activated channel rhodopsin (CheRiff) and a red-light fluorescent membrane voltage reporter (QuasAr2). This optogenetic platform allows robust stimulation and recording of action potential activity in neurons in a non-contact, low noise manner. For all experiments, QuasAr2 was imaged continuously on a wide-field fluorescent microscope using a Krypton laser (647 nm) as the excitation source and an EMCCD camera operating at 1000 Hz to collect emitted fluorescence. A co-aligned Argon laser (488 nm, 5 ms at 10Hz) provided activation light for CheRiff. A 200 mm fiber delivered infrared light locally to the target neuron. Reversible action potential block in neurons was observed following a short infrared laser pulse (0.26-0.96 J/cm2; 1.37-5.01 ms; 1869 nm), with the block persisting for more than 1 s with exposures greater than 0.69 J/cm2. Action potential block was sustained for 30 s with the short infrared laser pulsed at 1-7 Hz. Full recovery of neuronal activity was observed 5-30s post-infrared exposure. These results indicate that optogenetics provides a robust platform for the study of action potential block and that short infrared laser pulses can be used for non-contact, reversible action potential block.

  5. Pulsed-Laser Irradiation Space Weathering Of A Carbonaceous Chondrite (United States)

    Thompson, M. S.; Keller, L. P.; Christoffersen, R.; Loeffler, M. J.; Morris, R. V.; Graff, T. G.; Rahman, Z.


    Grains on the surfaces of airless bodies experience irradiation from solar energetic particles and melting, vaporization and recondensation processes associated with micrometeorite impacts. Collectively, these processes are known as space weathering and they affect the spectral properties, composition, and microstructure of material on the surfaces of airless bodies, e.g. Recent efforts have focused on space weathering of carbonaceous materials which will be critical for interpreting results from the OSIRIS-REx and Hayabusa2 missions targeting primitive, organic-rich asteroids. In addition to returned sample analyses, space weathering processes are quantified through laboratory experiments. For example, the short-duration thermal pulse from hypervelocity micrometeorite impacts have been simulated using pulsed-laser irradiation of target material e.g. Recent work however, has shown that pulsed-laser irradiation has variable effects on the spectral properties and microstructure of carbonaceous chondrite samples. Here we investigate the spectral characteristics of pulsed-laser irradiated CM2 carbonaceous chondrite, Murchison, including the vaporized component. We also report the chemical and structural characteristics of specific mineral phases within the meteorite as a result of pulsed-laser irradiation.

  6. Interaction of nanosecond ultraviolet laser pulses with reactive dusty plasma

    Energy Technology Data Exchange (ETDEWEB)

    Wetering, F. M. J. H. van de; Oosterbeek, W.; Beckers, J.; Nijdam, S. [Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Gibert, T.; Mikikian, M.; Rabat, H.; Kovačević, E.; Berndt, J. [GREMI, UMR7344, CNRS & Université d' Orléans, Orléans (France)


    Even though UV laser pulses that irradiate a gas discharge are small compared to the plasma volume (≲3%) and plasma-on time (≲6 × 10{sup −6}%), they are found to dramatically change the discharge characteristics on a global scale. The reactive argon–acetylene plasma allows the growth of nanoparticles with diameters up to 1 μm, which are formed inside the discharge volume due to spontaneous polymerization reactions. It is found that the laser pulses predominantly accelerate and enhance the coagulation phase and are able to suppress the formation of a dust void.

  7. Two-pulse laser control of nuclear and electronic motion

    DEFF Research Database (Denmark)

    Grønager, Michael; Henriksen, Niels Engholm


    We discuss an explicitly time-dependent two-pulse laser scheme for controlling where nuclei and electrons are going in unimolecular reactions. We focus on electronic motion and show, with HD+ as an example, that one can find non-stationary states where the electron (with some probability) oscilla......We discuss an explicitly time-dependent two-pulse laser scheme for controlling where nuclei and electrons are going in unimolecular reactions. We focus on electronic motion and show, with HD+ as an example, that one can find non-stationary states where the electron (with some probability...

  8. Correlated Multielectron Dynamics in Ultrafast Laser Pulse Interactions with Atoms (United States)

    Rudenko, A.; Zrost, K.; Feuerstein, B.; de Jesus, V. L.; Schröter, C. D.; Moshammer, R.; Ullrich, J.


    We present the results of the detailed experimental study of multiple ionization of Ne and Ar by 25 and 7fs laser pulses. Whereas in multiple ionization of Ar different mechanisms, involving field ionization steps and recollision-induced excitations, play a role, for Ne only one channel, where the highly correlated instantaneous emission of up to four electrons is triggered by a recollisional electron impact, is found to be important. Using few-cycle pulses we are able to suppress those processes that occur on time scales longer than one laser cycle.

  9. Plasma high-order-harmonic generation from ultraintense laser pulses (United States)

    Tang, Suo; Kumar, Naveen; Keitel, Christoph H.


    Plasma high-order-harmonic generation from an extremely intense short-pulse laser is explored by including the effects of ion motion, electron-ion collisions, and radiation reaction force in the plasma dynamics. The laser radiation pressure induces plasma ion motion through the hole-boring effect, resulting in frequency shifting and widening of the harmonic spectra. The classical radiation reaction force slightly mitigates the frequency broadening caused by the ion motion. Based on the results and physical considerations, parameter maps highlighting the optimum regions for generating a single intense attosecond pulse and coherent XUV radiation are presented.

  10. Detection of early dental caries with short pulse laser

    Energy Technology Data Exchange (ETDEWEB)

    Okubo, Nahoko; Goto, Shigeru [Osada Research Inst., Ltd., Tokyo (Japan); Tanaka, Hiroshi; Ohzu, Akira; Arisawa, Takashi [Japan Atomic Energy Research Inst., Kansai Research Establishment, Advanced Photon Research Center, Kyoto (Japan)


    Differences in the optical properties of polarization and photoluminescence between caries lesion and noncaries (sound) enamel have been investigated by focusing a pulsed Nd:YAG laser of 532 nm on the surface of teeth. Significant difference in the polarization property of the scattered light from the surface can be observed with some carious samples. For photoluminescence spectral lines which appear at around 650 nm, the intensity of caries lesion has been approximately two times higher than that of sound one. A discussion is presented in which early are potentially detectable by the pulsed laser. (author)

  11. Absorption of a laser light pulse in a dense plasma. (United States)

    Mehlman-Balloffet, G.


    An experimental study of the absorption of a laser light pulse in a transient, high-density, high-temperature plasma is presented. The plasma is generated around a metallic anode tip by a fast capacitive discharge occurring in vacuum. The amount of transmitted light is measured for plasmas made of different metallic ions in the regions of the discharge of high electronic density. Variation of the transmission during the laser pulse is also recorded. Plasma electrons are considered responsible for the very high absorption observed.

  12. Relativistic Electron Acceleration with Ultrashort Mid-IR Laser Pulses (United States)

    Feder, Linus; Woodbury, Daniel; Shumakova, Valentina; Gollner, Claudia; Miao, Bo; Schwartz, Robert; Pugžlys, Audrius; Baltuška, Andrius; Milchberg, Howard


    We report the first results of laser plasma wakefield acceleration driven by ultrashort mid-infrared laser pulses (λ = 3.9 μm , pulsewidth 100 fs, energy width, as well as trends in the accelerated beam profiles, charge and energy spectra which are supported by 3D particle-in-cell simulations. These results extend earlier work with sub-TW self-modulated laser wakefield acceleration using near IR drivers to the Mid-IR, and enable us to capture time-resolved images of relativistic self-focusing of the laser pulse. This work supported by DOE (DESC0010706TDD, DESC0015516); AFOSR(FA95501310044, FA95501610121); NSF(PHY1535519); DHS.

  13. Influence of laser pulse frequency on the microstructure of aluminum nitride thin films synthesized by pulsed laser deposition (United States)

    Antonova, K.; Duta, L.; Szekeres, A.; Stan, G. E.; Mihailescu, I. N.; Anastasescu, M.; Stroescu, H.; Gartner, M.


    Aluminum Nitride (AlN) thin films were synthesized on Si (100) wafers at 450 °C by pulsed laser deposition. A polycrystalline AlN target was multipulsed irradiated in a nitrogen ambient, at different laser pulse repetition rate. Grazing Incidence X-Ray Diffraction and Atomic Force Microscopy analyses evidenced nanocrystallites with a hexagonal lattice in the amorphous AlN matrix. The thickness and optical constants of the layers were determined by infrared spectroscopic ellipsometry. The optical properties were studied by Fourier Transform Infrared reflectance spectroscopy in polarised oblique incidence radiation. Berreman effect was observed around the longitudinal phonon modes of the crystalline AlN component. Angular dependence of the A1LO mode frequency was analysed and connected to the orientation of the particles' optical axis to the substrate surface normal. The role of the laser pulse frequency on the layers' properties is discussed on this basis.


    Energy Technology Data Exchange (ETDEWEB)

    Filip, C V


    The influence of the active gain medium on the spectral amplitude and phase of amplified pulses in a CPA system is studied. Results from a 10-PW example based on Nd-doped mixed glasses are presented. In conclusion, this study shows that, by using spectral shaping and gain saturation in a mixed-glass amplifier, it is possible to produce 124 fs, 1.4 kJ laser pulses. One detrimental effect, the pulse distortion due to resonant amplification medium, has been investigated and its magnitude as well as its compensation calculated.

  15. Characterization of polymer thin films obtained by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Palla-Papavlu, A., E-mail: [NILPRP, National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-16, Zip RO-077125, Magurele, Bucharest (Romania); Dinca, V.; Ion, V.; Moldovan, A.; Mitu, B.; Luculescu, C.; Dinescu, M. [NILPRP, National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-16, Zip RO-077125, Magurele, Bucharest (Romania)


    The development of laser techniques for the deposition of polymer and biomaterial thin films on solid surfaces in a controlled manner has attracted great attention during the last few years. Here we report the deposition of thin polymer films, namely Polyepichlorhydrin by pulsed laser deposition. Polyepichlorhydrin polymer was deposited on flat substrate (i.e. silicon) using an NdYAG laser (266 nm, 5 ns pulse duration and 10 Hz repetition rate). The obtained thin films have been characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and spectroscopic ellipsometry. It was found that for laser fluences up to 1.5 J/cm{sup 2} the chemical structure of the deposited polyepichlorhydrin polymer thin layers resembles to the native polymer, whilst by increasing the laser fluence above 1.5 J/cm{sup 2} the polyepichlorohydrin films present deviations from the bulk polymer. Morphological investigations (atomic force microscopy and scanning electron microscopy) reveal continuous polyepichlorhydrin thin films for a relatively narrow range of fluences (1-1.5 J/cm{sup 2}). The wavelength dependence of the refractive index and extinction coefficient was determined by ellipsometry studies which lead to new insights about the material. The obtained results indicate that pulsed laser deposition method is potentially useful for the fabrication of polymer thin films to be used in applications including electronics, microsensor or bioengineering industries.

  16. Characterization of polymer thin films obtained by pulsed laser deposition (United States)

    Palla-Papavlu, A.; Dinca, V.; Ion, V.; Moldovan, A.; Mitu, B.; Luculescu, C.; Dinescu, M.


    The development of laser techniques for the deposition of polymer and biomaterial thin films on solid surfaces in a controlled manner has attracted great attention during the last few years. Here we report the deposition of thin polymer films, namely Polyepichlorhydrin by pulsed laser deposition. Polyepichlorhydrin polymer was deposited on flat substrate (i.e. silicon) using an NdYAG laser (266 nm, 5 ns pulse duration and 10 Hz repetition rate). The obtained thin films have been characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and spectroscopic ellipsometry. It was found that for laser fluences up to 1.5 J/cm 2 the chemical structure of the deposited polyepichlorhydrin polymer thin layers resembles to the native polymer, whilst by increasing the laser fluence above 1.5 J/cm 2 the polyepichlorohydrin films present deviations from the bulk polymer. Morphological investigations (atomic force microscopy and scanning electron microscopy) reveal continuous polyepichlorhydrin thin films for a relatively narrow range of fluences (1-1.5 J/cm 2). The wavelength dependence of the refractive index and extinction coefficient was determined by ellipsometry studies which lead to new insights about the material. The obtained results indicate that pulsed laser deposition method is potentially useful for the fabrication of polymer thin films to be used in applications including electronics, microsensor or bioengineering industries.

  17. Dynamics of pulsed holmium:YAG laser photocoagulation of albumen

    Energy Technology Data Exchange (ETDEWEB)

    Pfefer, T.J. [Biomedical Engineering Program, The University of Texas at Austin, Austin, TX 78712 (United States). E-mail: jpfefer at; Chan, K.F.; Hammer, D.X. [Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712 (United States); Welch, A.J. [Biomedical Engineering Program, The University of Texas at Austin, Austin, TX 78712 (United States); Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712 (United States)


    The pulsed holmium:YAG laser ({lambda} = 2.12 {mu}m, {tau}{sub p} = 250 {mu}s) has been investigated as a method for inducing localized coagulation for medical procedures, yet the dynamics of this process are not well understood. In this study, photocoagulation of albumen (egg white) was analysed experimentally and results compared with optical-thermal simulations to investigate a rate process approach to thermal damage and the role of heat conduction and dynamic changes in absorption. The coagulation threshold was determined using probit analysis, and coagulum dynamics were documented with fast flash photography. The nonlinear computational model, which included a Beer's law optical component, a finite difference heat transfer component and an Arrhenius equation-based damage calculation, was verified against data from the literature. Moderate discrepancies between simulation results and our experimental data probably resulted from the use of a laser beam with an irregular spatial profile. This profile produced a lower than expected coagulation threshold and an irregular damage distribution within a millisecond after laser onset. After 1 ms, heat conduction led to smoothing of the coagulum. Simulations indicated that dynamic changes in absorption led to a reduction in surface temperatures. The Arrhenius equation was shown to be effective for simulating transient albumen coagulation during pulsed holmium:YAG laser irradiation. Greater understanding of pulsed laser-tissue interactions may lead to improved treatment outcome and optimization of laser parameters for a variety of medical procedures. (author)

  18. Modeling of ablation threshold dependence on pulse duration for dielectrics with ultrashort pulsed laser (United States)

    Sun, Mingying; Zhu, Jianqiang; Lin, Zunqi


    We present a numerical model of plasma formation in ultrafast laser ablation on the dielectrics surface. Ablation threshold dependence on pulse duration is predicted with the model and the numerical results for water agrees well with the experimental data for pulse duration from 140 fs to 10 ps. Influences of parameters and approximations of photo- and avalanche-ionization on the ablation threshold prediction are analyzed in detail for various pulse lengths. The calculated ablation threshold is strongly dependent on electron collision time for all the pulse durations. The complete photoionization model is preferred for pulses shorter than 1 ps rather than the multiphoton ionization approximations. The transition time of inverse bremsstrahlung absorption needs to be considered when pulses are shorter than 5 ps and it can also ensure the avalanche ionization (AI) coefficient consistent with that in multiple rate equations (MREs) for pulses shorter than 300 fs. The threshold electron density for AI is only crucial for longer pulses. It is reasonable to ignore the recombination loss for pulses shorter than 100 fs. In addition to thermal transport and hydrodynamics, neglecting the threshold density for AI and recombination could also contribute to the disagreements between the numerical and the experimental results for longer pulses.

  19. Temporal laser pulse manipulation using multiple optical ring-cavities (United States)

    Nguyen, Quang-Viet (Inventor); Kojima, Jun (Inventor)


    An optical pulse stretcher and a mathematical algorithm for the detailed calculation of its design and performance is disclosed. The optical pulse stretcher has a plurality of optical cavities, having multiple optical reflectors such that an optical path length in each of the optical cavities is different. The optical pulse stretcher also has a plurality of beam splitters, each of which intercepts a portion of an input optical beam and diverts the portion into one of the plurality of optical cavities. The input optical beam is stretched and a power of an output beam is reduced after passing through the optical pulse stretcher and the placement of the plurality of optical cavities and beam splitters is optimized through a model that takes into account optical beam divergence and alignment in the pluralities of the optical cavities. The optical pulse stretcher system can also function as a high-repetition-rate (MHz) laser pulse generator, making it suitable for use as a stroboscopic light source for high speed ballistic projectile imaging studies, or it can be used for high speed flow diagnostics using a laser light sheet with digital particle imaging velocimetry. The optical pulse stretcher system can also be implemented using fiber optic components to realize a rugged and compact optical system that is alignment free and easy to use.

  20. Polycrystalline ZnTe thin film on silicon synthesized by pulsed laser deposition and subsequent pulsed laser melting (United States)

    Xu, Menglei; Gao, Kun; Wu, Jiada; Cai, Hua; Yuan, Ye; Prucnal, S.; Hübner, R.; Skorupa, W.; Helm, M.; Zhou, Shengqiang


    ZnTe thin films on Si substrates have been prepared by pulsed laser deposition and subsequent pulsed laser melting (PLM) treatment. The crystallization during PLM is confirmed by Raman scattering, x-ray diffraction and room temperature photoluminescence (PL) measurements. The PL results show a broad peak at 574 nm (2.16 eV), which can be assigned to the transitions from the conduction band to the acceptor level located at 0.145 eV above the valence band induced by zinc-vacancy ionization. Our work provides an applicable approach to low temperature preparation of crystalline ZnTe thin films.

  1. Electron optical injection with head-on and countercrossing colliding laser pulses. (United States)

    Kotaki, H; Daito, I; Kando, M; Hayashi, Y; Kawase, K; Kameshima, T; Fukuda, Y; Homma, T; Ma, J; Chen, L-M; Esirkepov, T Zh; Pirozhkov, A S; Koga, J K; Faenov, A; Pikuz, T; Kiriyama, H; Okada, H; Shimomura, T; Nakai, Y; Tanoue, M; Sasao, H; Wakai, D; Matsuura, H; Kondo, S; Kanazawa, S; Sugiyama, A; Daido, H; Bulanov, S V


    A high stability electron bunch is generated by laser wakefield acceleration with the help of a colliding laser pulse. The wakefield is generated by a laser pulse; the second laser pulse collides with the first pulse at 180 degrees and at 135 degrees realizing optical injection of an electron bunch. The electron bunch has high stability and high reproducibility compared with single pulse electron generation. In the case of 180 degrees collision, special measures have been taken to prevent damage. In the case of 135 degrees collision, since the second pulse is countercrossing, it cannot damage the laser system.


    Directory of Open Access Journals (Sweden)

    I. V. Guk,


    Full Text Available The article deals with theoreticalmodeling results of the combined influence of nonlinear absorptivity and absorption coefficient on the spatial and temporal distribution of the electron-hole plasma and the dynamics of the specific absorption flux in silicon under femtosecond laser pulse. It is shown thatincreased absorption of the hot electron gas makes the main contribution to the change in specific absorption flux. Obtained results were compared with the known views about the polariton mechanism,which is usedfor the interpretation of femtosecond laser silicon microstructuring. There aredemonstratedThe need to consider absorption capacity dynamics in the regimes assessment of ultra short laser semiconductor processing.

  3. Nitridation of Nb surface by nanosecond and femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Farha, Ashraf Hassan [Department of Electrical and Computer Engineering and the Applied Research Center, Old Dominion University, Norfolk, VA 23529 (United States); Department of Physics, Faculty of Science, Ain Shams University, Cairo 11566 (Egypt); Ozkendir, Osman Murat [Tarsus Technology Faculty, Mersin University, Tarsus 33480 (Turkey); Koroglu, Ulas; Ufuktepe, Yüksel [Department of Physics, Cukurova University, Adana 01330 (Turkey); Elsayed-Ali, Hani E., E-mail: [Department of Electrical and Computer Engineering and the Applied Research Center, Old Dominion University, Norfolk, VA 23529 (United States)


    Highlights: • Laser nitridation of niobium is performed with nanosecond and femtosecond pulses. • Formation of NbN{sub x} with mixed α, β and δ phases was observed. • For femtosecond laser processed samples, laser induced ripple patterns oriented parallel to the beam polarization were formed. • X-ray absorption near edge structure show formation of Nb{sub 2}O{sub 5} on the surface of the samples. - Abstract: Niobium nitride samples were prepared by laser nitridation in a reactive nitrogen gas environment at room temperature using a Q-switched Nd:YAG nanosecond laser and a Ti:sapphire femtosecond laser. The effects of laser fluence on the formed phase, surface morphology, and electronic properties of the NbN{sub x} were investigated. The samples were prepared at different nanosecond laser fluences up to 5.0 ± 0.8 J/cm{sup 2} at fixed nitrogen pressure of ∼2.7 × 10{sup 4} Pa formed NbN{sub x} with mainly the cubic δ-NbN phase. Femtosecond laser nitrided samples were prepared using laser fluences up to 1.3 ± 0.3 mJ/cm{sup 2} at ∼4.0 × 10{sup 4} Pa nitrogen pressure. Laser induced ripple patterns oriented parallel to the beam polarization were formed with spacing that increases with the laser fluence. To achieve a laser-nitrided surface with desired crystal orientation the laser fulence is an important parameter that needs to be properly adjusted.

  4. Effect of aging on copper nanoparticles synthesized by pulsed laser ...

    Indian Academy of Sciences (India)

    Effect of aging on copper nanoparticles synthesized by pulsed laser ablation of copper plate in water was studied. By characterization studies of the aged nanoparticles, it is found that copper nanoparticles converted into Cu@Cu2O nanostructure. The synthesized nanomaterial is characterized with UV-Visible absorption, ...

  5. Two-pulse laser control of bond-selective fragmentation

    DEFF Research Database (Denmark)

    Amstrup, Bjarne; Henriksen, Niels Engholm


    We elaborate on a two-pulse (pump-pump) laser control scheme for selective bond-breaking in molecules [Amstrup and Henriksen, J. Chem. Phys. 97, 8285 (1992)]. We show, in particular, that with this scheme one can overcome the obstacle of intramolecular vibrational relaxation. As an example, we...

  6. Tracing the phase of focused broadband laser pulses (United States)

    Hoff, Dominik; Krüger, Michael; Maisenbacher, Lothar; Sayler, A. M.; Paulus, Gerhard G.; Hommelhoff, Peter


    Precise knowledge of the behaviour of the phase of light in a focused beam is fundamental to understanding and controlling laser-driven processes. More than a hundred years ago, an axial phase anomaly for focused monochromatic light beams was discovered and is now commonly known as the Gouy phase. Recent theoretical work has brought into question the validity of applying this monochromatic phase formulation to the broadband pulses becoming ubiquitous today. Based on electron backscattering at sharp nanometre-scale metal tips, a method is available to measure light fields with sub-wavelength spatial resolution and sub-optical-cycle time resolution. Here we report such a direct, three-dimensional measurement of the spatial dependence of the optical phase of a focused, 4-fs, near-infrared pulsed laser beam. The observed optical phase deviates substantially from the monochromatic Gouy phase--exhibiting a much more complex spatial dependence, both along the propagation axis and in the radial direction. In our measurements, these significant deviations are the rule and not the exception for focused, broadband laser pulses. Therefore, we expect wide ramifications for all broadband laser-matter interactions, such as in high-harmonic and attosecond pulse generation, femtochemistry, ophthalmological optical coherence tomography and light-wave electronics.

  7. Deep-ultraviolet quantum interference metrology with ultrashort laser pulses

    NARCIS (Netherlands)

    Witte, S.; Zinkstok, R.T.; Ubachs, W.M.G.; Hogervorst, W.; Eikema, K.S.E.


    Precision spectroscopy at ultraviolet and shorter wavelengths has been hindered by the poor access of narrow-band lasers to that spectral region. We demonstrate high-accuracy quantum interference metrology on atomic transitions with the use of an amplified train of phase-controlled pulses from a

  8. Modeling short-pulse laser excitation of dielectric materials

    DEFF Research Database (Denmark)

    Wædegaard, Kristian Juncher; Sandkamm, Ditte Både; Haahr-Lillevang, Lasse


    A theoretical description of ultrashort-pulse laser excitation of dielectric materials based on strong-field excitation in the Keldysh picture combined with a multiple-rateequation model for the electronic excitation including collisional processes is presented. The model includes light attenuation...

  9. Epitaxial oxide thin films by pulsed laser deposition: Retrospect and ...

    Indian Academy of Sciences (India)


    Among the large number of processes to fabricate thin films of materials, pulsed laser deposition (PLD) has emerged as a ... It is important to recognize that highly stoichiometric, nearly single crystal like epitaxial film is aimed for in the PLD .... This new class of Josephson junctions is attractive for novel phase devices.

  10. RHEED study of titanium dioxide with pulsed laser deposition

    DEFF Research Database (Denmark)

    Rasmussen, Inge Lise; Pryds, Nini; Schou, Jørgen


    Reflection high-energy electron diffraction (RHEED) operated at high pressure has been used to monitor the growth of thin films of titanium dioxide (TiO2) on (1 0 0) magnesium oxide (MgO) substrates by pulsed laser deposition (PLD). The deposition is performed with a synthetic rutile TiO2 target...

  11. Surface melting of copper by ultrashort laser pulses

    NARCIS (Netherlands)

    Oboňa, J.V.; Ocelík, V.; De Hosson, J.T.M.; Skolski, J.Z.P.; Mitko, V.S.; Römer, G.R.B.E.; Huis in 't Veld, A.J.


    The main advantage of ultrashort laser pulses in manufacturing technology is their very high removal rate of material and high quality of microstructures with the smallest dimensions at 1 μm level. The accuracy is mainly due to an almost absence of thermal diffusion into bulk material. In this paper

  12. Non-stoichiometry in sulfides produced by pulsed laser deposition

    DEFF Research Database (Denmark)

    Canulescu, Stela; Cazzaniga, Andrea Carlo; Ettlinger, Rebecca Bolt

    Pulsed laser deposition or PLD is known as a technique by which complex materials can be stoichiometrically transferred from a target to a substrate, providing that the ablation threshold is exceeded. For a multi-target component, it frequently happens that there is loss of the lightest and the m...

  13. Design of optimal laser pulses to control molecular rovibrational ...

    Indian Academy of Sciences (India)

    Abstract. Optimal control theory in combination with time-dependent quantum dynamics is employed to design laser pulses which can perform selective vibrational and rotational excitations in a heteronuclear diatomic system. We have applied the conjugate gradient method for the constrained optimization of a suit-.

  14. Treatment of lupus erythematosus with pulsed dye laser. (United States)

    Baniandrés, Ofelia; Boixeda, Pablo; Belmar, Paulina; Pérez, Alejandro


    The treatment of cutaneous lupus erythematosus (CLE) with dye and argon laser has been evaluated in a number of articles in recent years. The improvement of telangiectasias and chronic erythema of the cutaneous lesions was based on the selective photothermolysis ablation of the dilated capillaries and venules. We describe the results of the treatment of cutaneous lesions of 14 patients; eight with discoid lupus erythematosus (DLE) and six with systemic lupus erythematosus (SLE). Three patients received a treatment with flashlamp pulsed dye laser (FPDL) (585 nm, 450 microseconds) with fluences in the range from 5 to 7.75 J/cm(2); the other 11 patients were treated with long pulsed dye laser (LPDL) (595 nm, 1.5-10 milliseconds) with fluences in the range from 6 to 13 J/cm(2) depending on the pulse duration. During a median follow-up of 10 months, we observed an average improvement in over 60% of the lesions. A few side effects were observed in all patients: four had transient hyperpigmentation and one patient had light scarring. Three patients had a relapse after more than 1 year; they were then offered conventional treatment. We confirm that pulsed dye laser is a good alternative treatment for the erythema in active cutaneous lesions of lupus erythematosus (LE). Copyright 2003 Wiley-Liss, Inc.

  15. Design of optimal laser pulses to control molecular rovibrational ...

    Indian Academy of Sciences (India)

    Optimal control theory in combination with time-dependent quantum dynamics is employed to design laser pulses which can perform selective vibrational and rotational excitations in a heteronuclear diatomic system. We have applied the conjugate gradient method for the constrained optimization of a suitably designed ...

  16. Tracking Femtosecond Laser Pulses in Space and Time

    NARCIS (Netherlands)

    Balistreri, M.L.M.; Gersen, H.; Korterik, Jeroen P.; Kuipers, L.; van Hulst, N.F.


    We show that the propagation of a femtosecond laser pulse inside a photonic structure can be directly visualized and tracked as it propagates using a time-resolved photon scanning tunneling microscope. From the time-dependent and phase- sensitive measurements, both the group velocity and the phase

  17. Influence of SOD on THG for femtosecond laser pulse (United States)

    Trofimov, Vyacheslav A.; Sidorov, Pavel S.


    THG is used nowadays in many practical applications such as a substance diagnostics, and biological objects imaging, and etc. Therefore, THG features understanding are urgent problem and this problem attracts an attention of many researchers. In this paper we analyze THG efficiency of a femtosecond laser pulse. Consideration is based on computer simulation of the laser pulse propagation with taking into account a selfand cross- modulation of the interacting waves, and their SOD, and phase mismatching. Moreover, we analyze an influence of the non-homogeneous phase mismatching along laser pulse propagation coordinate. In this case, a phase matching occurs only in narrow area of longitudinal coordinate. Due to strong self- and crossmodulation of interacting waves it is possible to manage effective THG. Using the frame-work of long pulse duration approximation and plane wave approximation as well as an original approach we write the explicit solution of Schrödinger equations describing the frequency tripling of femtosecond pulse. It should be stressed, that the main feature of our approach consists in conservation laws using corresponding to wave interaction process.

  18. Formation of ultrasmooth thin silver films by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, I. A.; Garaeva, M. Ya.; Mamichev, D. A., E-mail:; Grishchenko, Yu. V.; Zanaveskin, M. L. [NBIC Center, National Research Centre ' Kurchatov Institute' (Russian Federation)


    Ultrasmooth thin silver films have been formed on a quartz substrate with a buffer yttrium oxide layer by pulsed laser deposition. The dependence of the surface morphology of the film on the gas (N{sub 2}) pressure in the working chamber and laser pulse energy is investigated. It is found that the conditions of film growth are optimal at a gas pressure of 10{sup -2} Torr and lowest pulse energy. The silver films formed under these conditions on a quartz substrate with an initial surface roughness of 0.3 nm had a surface roughness of 0.36 nm. These films can be used as a basis for various optoelectronics and nanoplasmonics elements.

  19. Efficient self-sustained pulsed CO laser

    NARCIS (Netherlands)

    Peters, P.J.M.


    In this paper a simple sealed-off TEA CO laser is described with a self-sustained discharge without an external UV preionization source. At 77 K this system yields more than 600 mJ from a lasing volume of about 60 cm3 CO-N2-He mixture (45 J/ℓ atm. with 15.6% efficiency).

  20. Short-pulse lasers for weather control (United States)

    Wolf, J. P.


    Filamentation of ultra-short TW-class lasers recently opened new perspectives in atmospheric research. Laser filaments are self-sustained light structures of 0.1–1 mm in diameter, spanning over hundreds of meters in length, and producing a low density plasma (1015–1017 cm‑3) along their path. They stem from the dynamic balance between Kerr self-focusing and defocusing by the self-generated plasma and/or non-linear polarization saturation. While non-linearly propagating in air, these filamentary structures produce a coherent supercontinuum (from 230 nm to 4 µm, for a 800 nm laser wavelength) by self-phase modulation (SPM), which can be used for remote 3D-monitoring of atmospheric components by Lidar (Light Detection and Ranging). However, due to their high intensity (1013–1014 W cm‑2), they also modify the chemical composition of the air via photo-ionization and photo-dissociation of the molecules and aerosols present in the laser path. These unique properties were recently exploited for investigating the capability of modulating some key atmospheric processes, like lightning from thunderclouds, water vapor condensation, fog formation and dissipation, and light scattering (albedo) from high altitude clouds for radiative forcing management. Here we review recent spectacular advances in this context, achieved both in the laboratory and in the field, reveal their underlying mechanisms, and discuss the applicability of using these new non-linear photonic catalysts for real scale weather control.

  1. Short-pulse lasers for weather control. (United States)

    Wolf, J P


    Filamentation of ultra-short TW-class lasers recently opened new perspectives in atmospheric research. Laser filaments are self-sustained light structures of 0.1-1 mm in diameter, spanning over hundreds of meters in length, and producing a low density plasma (1015-1017 cm-3) along their path. They stem from the dynamic balance between Kerr self-focusing and defocusing by the self-generated plasma and/or non-linear polarization saturation. While non-linearly propagating in air, these filamentary structures produce a coherent supercontinuum (from 230 nm to 4 µm, for a 800 nm laser wavelength) by self-phase modulation (SPM), which can be used for remote 3D-monitoring of atmospheric components by Lidar (Light Detection and Ranging). However, due to their high intensity (1013-1014 W cm-2), they also modify the chemical composition of the air via photo-ionization and photo-dissociation of the molecules and aerosols present in the laser path. These unique properties were recently exploited for investigating the capability of modulating some key atmospheric processes, like lightning from thunderclouds, water vapor condensation, fog formation and dissipation, and light scattering (albedo) from high altitude clouds for radiative forcing management. Here we review recent spectacular advances in this context, achieved both in the laboratory and in the field, reveal their underlying mechanisms, and discuss the applicability of using these new non-linear photonic catalysts for real scale weather control.

  2. Pulsed laser deposition of anatase thin films on textile substrates

    Energy Technology Data Exchange (ETDEWEB)

    Krämer, André; Kunz, Clemens; Gräf, Stephan; Müller, Frank A.


    Highlights: • Anatase thin films were grown on carbon fibre fabrics by pulsed laser deposition. • A novel Q-switched CO{sub 2} laser was utilised as radiation source. • Coated fibres exhibit photocatalytic activity and are resistant against bending. - Abstract: Pulsed laser deposition (PLD) is a highly versatile tool to prepare functional thin film coatings. In our study we utilised a Q-switched CO{sub 2} laser with a pulse duration τ ≈ 300 ns, a laser wavelength λ = 10.59 μm, a repetition frequency f{sub rep} = 800 Hz and a peak power P{sub peak} = 15 kW to deposit crystalline anatase thin films on carbon fibre fabrics. For this purpose, preparatory experiments were performed on silicon substrates to optimise the anatase deposition conditions including the influence of different substrate temperatures and oxygen partial pressures. Processing parameters were then transferred to deposit anatase on carbon fibres. Scanning electron microscopy, X-ray diffraction analyses, Raman spectroscopy and tactile profilometry were used to characterise the samples and to reveal the formation of phase pure anatase without the occurrence of a secondary rutile phase. Methanol conversion test were used to prove the photocatalytic activity of the coated carbon fibres.

  3. Making Relativistic Positrons Using Ultra-Intense Short Pulse Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Chen, H; Wilks, S; Bonlie, J; Chen, C; Chen, S; Cone, K; Elberson, L; Gregori, G; Liang, E; Price, D; Van Maren, R; Meyerhofer, D D; Mithen, J; Murphy, C V; Myatt, J; Schneider, M; Shepherd, R; Stafford, D; Tommasini, R; Beiersdorfer, P


    This paper describes a new positron source produced using ultra-intense short pulse lasers. Although it has been studied in theory since as early as the 1970s, the use of lasers as a valuable new positron source was not demonstrated experimentally until recent years, when the petawatt-class short pulse lasers were developed. In 2008 and 2009, in a series of experiments performed at Lawrence Livermore National Laboratory, a large number of positrons were observed after shooting a millimeter thick solid gold target. Up to 2 x 10{sup 10} positrons per steradian ejected out the back of {approx}mm thick gold targets were detected. The targets were illuminated with short ({approx}1 ps) ultra-intense ({approx}1 x 10{sup 20} W/cm{sup 2}) laser pulses. These positrons are produced predominantly by the Bethe-Heitler process, and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. For a wide range of applications, this new laser based positron source with its unique characteristics may complements the existing sources using radioactive isotopes and accelerators.

  4. Free Electron Laser Pulse Control by Acousto Optic Modulators

    CERN Document Server

    Kanai, T; Yoshihashi-Suzuki, S


    Free Electron Laser (FEL) at Osaka University can be continuously varied in the range of 5.0-20.0 μm. A FEL has a double pulse structure. The structure consists of a train of macropulses of the pulse width 15 μs, and each macropulse contains a train of 330 micropulses of the pulse width 5 ps. The tunability and short pulse afford new medical applications such as investigation of protein dynamics and ablation of soft tissues. Precise control of micropulse train is very important for medical applications using FEL because macropulse with long pulse duration sometimes leads to undesirable thermal effects. FEL pulse control system using an acousto optic modulators (AOM) was developed in order to investigate of non-thermal effect between the FEL and tissue. This system provide a very good efficiency (~60 %) and a fast switching speed (>200 ns). A phosphorylated protein was irradiated with FEL that controlled the pulse. These result confirmed that the thermal effect is controlled by pulse durat...

  5. Laser Cooling with Ultrafast Pulse Trains (United States)


    unprecedented agreement between ab initio theory and experiment in this field by investigating ionisation of atomic hydrogen with few-cycle pulses [1]. Figure 1...Abeln, K Bartschat, I Ivanov, A Kheifets, HM Quiney, IV Litvinyuk, RT Sang, and D Kielpinski, “Above threshold ionisation of atomic hydrogen using few...Grzhimailo, B Abeln, K Bartschat, I Ivanov, A Kheifets, HM Quiney, IV Litvinyuk, RT Sang, and D Kielpinski, “Above threshold ionisation of atomic

  6. Power supplied for pulsed laser systems (United States)

    Ed Strickland, B.; Nelms, R. Mark


    Conventional DC power supplies are normally designed for loads with constant or near constant power requirements and do not perform well under the wide range of load variations involved in repetitively charging an energy storage capacitor from zero volts to a maximum voltage. This paper will discuss a family of capacitor charging power supplies developed in a collaborative effort between Auburn University and Maxwell Laboratories in San Diego, California. These supplies utilize resonant technology and a patented pulse-width modulation scheme.

  7. Laser pulse detection method and apparatus (United States)

    Goss, W.; Janesick, J. R.


    A sensor is described for detecting the difference in phase of a pair of returned light pulse components, such as two components of a light pulse of an optical gyro. In an optic gyro, the two light components have passed in opposite directions through a coil of optical fiber, with the difference in phase of the returned light components determining the intensity of light shining on the sensor. The sensor includes a CCD (charge coupled device) that receives the pair of returned light components to generate a charge proportional to the number of photons in the received light. The amount of the charge represents the phase difference between the two light components. At a time after the transmission of the light pulse and before the expected time of arrival of the interfering light components, charge accumulating in the CCD as a result of reflections from components in the system, are repeatedly removed from the CCD, by transferring out charges in the CCD and dumping these charges.

  8. Diode-pumped solid state laser. (Part V). ; Short pulse laser oscillation. Handotai laser reiki kotai laser. 5. ; Tan pulse hasshin

    Energy Technology Data Exchange (ETDEWEB)

    Kuwabara, M.; Bando, N. (Asahi Glass Co. Ltd., Tokyo (Japan))


    A semiconductor laser (LD) excited solid state laser using an LD as an excited light source is under discussion for its practical applications to measurements, processing, communications, office automation, and medical areas. This paper describes the discussions given on the short pulse transmission using AOQ switching elements in the LD excited solid state laser with a long wave length band (1.3{mu}m), which is expected of its application in the communications and measurements area. Based on a possibility of raising a measurements resolution by making the pluses in the LD excited solid state laser, and experiments were performed using Nd:YLF as a laser host. as a results, it was found that the smaller the effective mode volume V {sub eff},the smaller the pulse width, and that the ratio of number of initial inversion distribution (N{sub i}/N{sub t}), an important parameter to determine pulse widths, can be obtained from the ratio of the LD exciting light to the input power (P{sub in}/P{sub t}). 7 refs., 14 figs., 2 tabs.

  9. Evidence of femtosecond-laser pulse induced cell membrane nanosurgery (United States)

    Katchinskiy, Nir; Godbout, Roseline; Elezzabi, Abdulhakem Y.


    The mechanism of femtosecond laser nanosurgical attachment is investigated in the following article. Using sub-10 femtosecond laser pulses with 800 nm central wavelength were used to attach retinoblastoma cells. During the attachment process the cell membrane phospholipid bilayers hemifuse into one shared phospholipid bilayer, at the location of attachment. Transmission electron microscopy was used in order to verify the above hypothesis. Based on the imaging results, it was concluded that the two cell membrane coalesce to form one single shared membrane. The technique of cell-cell attachment via femtosecond laser pulses could potentially serve as a platform for precise cell membrane manipulation. Manipulation of the cellular membrane is valuable for studying diseases such as cancer; where the expression level of plasma proteins on the cell membrane is altered.

  10. Medical and biological applications for ultrafast laser pulses (United States)

    Lubatschowski, Holger; Heisterkamp, Alexander; Will, Fabian; Singh, Ajoy I.; Serbin, Jesper; Ostendorf, Andreas; Kermani, Omid; Heermann, R.; Welling, Herbert; Ertmer, Wolfgang


    Due to the low energy threshold of photodisruption with fs laser pulses, thermal and mechanical side effects are limited to the sub μm range. The neglection of side effects enables the use of ultrashort laser pulses in a broad field of medical applications. Moreover, the interaction process based on nonlinear absorption offers the opportunity to process transparent tissue three dimensionally inside the bulk. We demonstrate the feasibility of surgical procedures in different fields of medical interest: In ophthalmology intrastromal cutting and preparing of corneal flaps for refractive surgery in living animals is presented. Besides, the very low mechanical side effects enables the use of fs-laser in otoralyngology to treat ocecular bones. Moreover, the precise cutting quality can be used in fields of cardiovascular surgery for the treatment of arteriosclerosis as well as in dentistry to remove caries from dental hard tissue.

  11. Interaction of Repetitively Pulsed High Energy Laser Radiation With Matter (United States)

    Hugenschmidt, Manfred


    The paper is concerned with laser target interaction processes involving new methods of improving the overall energy balance. As expected theoretically, this can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed by using a pulsed CO2 laser at mean powers up to 2 kW and repetition rates up to 100 Hz. The rates of temperature rise of aluminium for example were thereby increased by lore than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements were found for the overall absorptivities that were increased by this method by more than an order of magnitude.

  12. Shadowgraphic imaging of material removal during laser drilling with a long pulse eximer laser

    NARCIS (Netherlands)

    Schoonderbeek, A.; Biesheuvel, C.A.; Hofstra, R.M.; Boller, Klaus J.; Meijer, J.


    After the development of a novel XeCl excimer laser with a nearly diffraction-limited beam and 175 ns pulse length, research was done on different industrial applications of this laser. Hole drilling, one of these applications, was studied extensively. A better understanding of the drilling process

  13. A New Kind of Laser Microphone Using High Sensitivity Pulsed Laser Vibrometer (United States)

    Wang, Chen-Chia; Trivedi, Sudhir; Jin, Feng; Swaminathan, V.; Prasad, Narasimha S.


    We demonstrate experimentally a new kind of laser microphone using a highly sensitive pulsed laser vibrometer. By using the photo-electromotive-force (photo-EMF) sensors, we present data indicating the real-time detection of surface displacements as small as 4 pm.

  14. Laser surface and subsurface modification of sapphire using femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Eberle, G., E-mail: [Institute of Machine Tools and Manufacturing, ETH Zurich, Leonhardstrasse 21, 8092 Zurich (Switzerland); Schmidt, M. [Chair of Photonic Technologies, University of Erlangen-Nuremberg, Konrad-Zuse-Strasse 3-5, 91052 Erlangen (Germany); Pude, F. [Inspire AG, Technoparkstrasse 1, 8005 Zurich (Switzerland); Wegener, K. [Institute of Machine Tools and Manufacturing, ETH Zurich, Leonhardstrasse 21, 8092 Zurich (Switzerland); Inspire AG, Technoparkstrasse 1, 8005 Zurich (Switzerland)


    Highlights: • Single and multipulse ablation threshold of aluminium oxide is determined. • Laser ablation, and in-volume modification followed by wet etching are demonstrated. • Quality following laser processing and laser-material interactions are studied. - Abstract: Two methods to process sapphire using femtosecond laser pulses are demonstrated, namely ablation (surface), and in-volume laser modification followed by wet etching (subsurface). Firstly, the single and multipulse ablation threshold is determined and compared with previous literature results. A unique application of ablation is demonstrated by modifying the entrance aperture of water jet orifices. Laser ablation exhibits advantages in terms of geometric flexibility and resolution, however, defects in the form of edge outbreaks and poor surface quality are evident. Secondly, the role of material transformation, polarisation state and formation of multi-focus structures after in-volume laser modification is investigated in order to explain their influence during the wet etching process. Laser scanning and electron microscopy as well as electron backscatter diffraction measurements supported by ion beam polishing are used to better understand quality and laser-material interactions of the two demonstrated methods of processing.

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

    Energy Technology Data Exchange (ETDEWEB)

    Mincuzzi, G., E-mail:; Gemini, L.; Faucon, M.; Kling, R.


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

  16. 80 GHz AlGaInAs/InP colliding-pulse mode-locked laser with high pulse power (United States)

    Zhao, Pengchao; Liu, Anjin; Zheng, Wanhua


    We theoretically analyze the impact of a saturable absorber (SA) length on the pulse power of a semiconductor mode-locked laser and find that in the range of the SA length from 1.5 to 7%, a laser with a longer SA can generate pulses with a higher power. Based on the simulation, we demonstrate a colliding-pulse mode-locked laser with an 80 µm SA. The device generates pulses at 80 GHz, with a pulse width of 1.75 ps, peak power of 188 mW, pulse energy of 0.33 pJ, and time-bandwidth product of 0.51. The results provide new possibilities for the design of high-repetition frequency high-pulse power mode-locked lasers.

  17. Laser-pulsed plasma chemistry: Laser-initiated plasma oxidation of niobium (United States)

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


    We report the first observation of the chemical modification of a solid surface exposed to an ambient gas plasma initiated by the interaction of laser radiation with the same surface. A new technique, which we designate laser-pulsed plasma chemistry (LPPC), is proposed for activating heterogeneous chemical reactions at solid surfaces in a gaseous ambient by means of a plasma initiated by laser radiation. Results for niobium metal in one atmosphere oxygen demonstrate single-pulse, self-limiting oxide growth induced by a pulsed CO2 laser. X-ray photoelectron spectroscopy (XPS or ESCA) was used to monitor surface chemical composition changes and thickness control of thin (1 to 5 nm) reaction product layers. The dependence of single-pulse oxide growth upon laser fluence is observed to be monotonic for oxide thicknesses up to 5 nm. Composition of the oxide Nb2O5-δ, formed by such an optically driven plasma, is similar to that formed by low-temperature oxidation processes such as rf plasma oxidation; however, the valence defect δ of the LPPC oxide is a least two to five times lower. Interdiffusion at the oxide/metal interface becomes important at higher irradiances and is activated by direct optical coupling with the solid or by plasma-mediated thermal coupling. Under ultrahigh vacuum, CO2 laser irradiances greater than 0.9 J cm-2 per pulse thin the surface oxide.

  18. Pulsed photothermal depth profiling of tattoos undergoing laser removal treatment (United States)

    Milanic, Matija; Majaron, Boris


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

  19. Real-time energy measurement of high repetition rate ultrashort laser pulses using pulse integration and FPGA processing (United States)

    Tang, Qi-jie; Yang, Dong-xu; Wang, Jian; Feng, Yi; Zhang, Hong-fei; Chen, Teng-yun


    Real-time energy measurement using pulse integration method for high repetition rate ultrashort laser pulses based on FPGA (Field-Programmable Gate Array) and high-speed pipeline ADC (Analog-to-Digital Convertor) is introduced in this paper. There are two parts contained in this method: pulse integration and real-time data processing. The pulse integration circuit will convert the pulse to the step type signals which are linear to the laser pulse energy. Through the real-time data processing part, the amplitude of the step signals will be obtained by ADC sampling and conducting calculation in real time in FPGA. The test result shows that the method with good linearity (4.770%) and without pulse measurement missing is suitable for ultrashort laser pulses with high repetition rate up to 100 MHz.

  20. Ultracold and ultrafast: Probing quantum gases with femtosecond laser pulses (United States)

    Wessels, Philipp; Ruff, Bernhard; Kroker, Tobias; Pehmöller, Steffen; Simonet, Juliette; Drescher, Markus; Sengstock, Klaus


    Ultrafast lasers open new pathways for probing and manipulating ultracold atomic systems in order to address fundamental questions in quantum physics. The short pulses act as a highly localized instantaneous trigger to drive complex dynamics and enable access to coherence properties in macroscopic quantum targets and superfluid matter. We report on first experiments exploring ultracold 87Rb atoms and Bose-Einstein condensates (BEC) exposed to ultrashort laser pulses of 280 fs duration. The intense light pulses create ions within the focal region via strong-field ionization and the remaining atoms are detected by absorption imaging. Additionally, we quantify the momentum transferred to the atoms by the femtosecond laser pulse. Since the amount of generated ions is tunable, a tool with the potential to create hybrid quantum systems of few ions immersed in the trapped cloud is provided. First results already indicate the formation of a long-lived ultracold plasma state. Analyzing the charged fragments after ionization promises further insight so that we discuss perspectives on detecting ions and electrons in a new experimental setup to investigate coherence transfer from a macroscopic wave function to its microscopic constituents.

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

    DEFF Research Database (Denmark)

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


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

  2. Charging and plasma effects under ultrashort pulsed laser ablation (United States)

    Bulgakova, N. M.; Bulgakov, A. V.; Zhukov, V. P.; Marine, W.; Vorobyev, A. Y.; Guo, Chunlei


    Based on experiments and a theoretical analysis, we raise questions on two fundamental mechanisms of femtosecond laser desorption/ablation of solids, namely Coulomb explosion (CE) and plasma etching. The effects of laser-induced ionization and surface charging are analyzed which can be responsible for ultrafast ions observed in time-of-flight mass-spectra under ultrashort laser irradiation of solids. The importance of surface charging in formation of velocity distributions of desorbed/ablated species has been revealed for conditions when the CE mechanism is inhibited. The influence of ambient plasma formation on the dynamics of heating of metallic targets by femtosecond laser pulses is studied based on 2D modeling of laser-induced target heating and dynamics of the ambient plasma. The calculations show an intriguing picture of the laser-induced ambient gas motion. We propose a model of laser-induced breakdown of an ambient gas in a region in front of the irradiated target and analyze plasma-chemical processes which can affect laser processing of surfaces in the presence of air or highly reactive media.

  3. Calculations of population transfer during intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Schafer, K.J.; Kulander, K.C.


    Recent experiments by several groups have examined the question of population transfer to resonantly excited states during intense short laser pulses, in particular the amount of population that remains ``trapped`` in excited states at the end of a laser pulse. In this chapter we present calculations of population transfer and resonant ionization in xenon at both 660 and 620 nm. At the longer wavelength, the seven photon channel closes at 2.5{times}10{sup 13} W/cm{sup 2}. Pulses with peak intensities higher than this result in ``Rydberg trapping``, the resonant transfer of population to a broad range of high-lying states. The amount of population transferred depends on both the peak intensity and pulse duration. At 620 mm there are numerous possible six photon resonances to states with p or f angular momentum. We have done a large number of calculations for 40 fs pulses at different peak intensities and have examined the population transferred to these low-lying resonant states as a function of the peak laser intensity. We do not have room to comment upon the resonantly enhanced ionized electron energy spectra that we also determine in the same calculations. Our calculations involve the direct numerical integration of the time-dependent Schroedinger equation for an atom interacting with a strong laser field. The time-dependent wave function of a given valence electron is calculated on a spatial grid using a one-electron pseudo potential. This single active electron approximation (SAE) has been shown to be a good approximation for the rare gases at the intensities and wavelengths that we will consider. The SAE potential we use has an explicit angular momentum dependence which allows us to reproduce all of the excited state energies for xenon quite well.

  4. Short electron bunches generated by perpendicularly crossing laser pulses (United States)

    Horný, Vojtěch; Petržílka, Václav; Klimo, Ondřej; Krůs, Miroslav


    Optical injection of electrons into a laser wakefield accelerator by a low intensity orthogonally colliding laser pulse is investigated using 2D particle-in-cell simulations. The collision of the main laser pulse driving the plasma wave in the cavitated regime and the low intensity injection pulse affects the trajectories of electrons in the crossing region. As a consequence, some electrons are ejected into the front part of the bubble, and these electrons are subsequently trapped in the rear part of the bubble. The injected and accelerated electron bunch reaches a peak energy of 630 MeV after 8 ps of acceleration being as short as 7.0 fs and is quasimonoenergetic with a low energy spread of 20 MeV (3.8%), having a charge of several dozens of pC and a relatively large emittance of 2.27 π . mm . mrad. Two main injection mechanisms—crossing beatwave injection and injection by laser field preacceleration—were identified.

  5. Longitudinally excited CO2 laser with short laser pulse operating at high repetition rate (United States)

    Li, Jianhui; Uno, Kazuyuki; Akitsu, Tetsuya; Jitsuno, Takahisa


    A short-pulse longitudinally excited CO2 laser operating at a high repetition rate was developed. The discharge tube was made of a 45 cm-long or 60 cm-long dielectric tube with an inner diameter of 16 mm and two metallic electrodes at the ends of the tube. The optical cavity was formed by a ZnSe output coupler with a reflectivity of 85% and a high-reflection mirror. Mixed gas (CO2:N2:He = 1:1:2) was flowed into the discharge tube. A high voltage of about 33 kV with a rise time of about 200 ns was applied to the discharge tube. At a repetition rate of 300 Hz and a gas pressure of 3.4 kPa, the 45 cm-long discharge tube produced a short laser pulse with a laser pulse energy of 17.5 mJ, a spike pulse energy of 0.2 mJ, a spike width of 153 ns, and a pulse tail length of 90 μs. The output power was 5.3 W. The laser pulse waveform did not depend on the repetition rate, but the laser beam profile did. At a low repetition rate of less than 50 Hz, the laser beam had a doughnut-like shape. However, at a high repetition rate of more than 150 Hz, the discharge concentrated at the center of the discharge tube, and the intensity at the center of the laser beam was higher. The laser beam profile depended on the distribution of the discharge. An output power of 7.0 W was achieved by using the 60 cm-long tube.

  6. Determination of the temporal structure of femtosecond laser pulses by means of laser-induced air plasma (United States)

    Zhang, Nan; Bao, Wen-Xia; Yang, Jing-Hui; Zhu, Xiao-Nong


    A new approach is presented to reveal the temporal structure of femtosecond laser pulses by recording the corresponding time-resolved shadowgraphs of the laser-induced air plasma. It is shown that the temporal structures of femtosecond laser pulses, normally not observable by the ordinary intensity autocorrelator, can be detected through intuitively analyzing the ultrafast evolution process of the air plasma induced by the femtosecond laser pulses under examination. With this method, existence of pre- and post-pulses has been clearly unveiled within the time window of ±150 fs in reference with the main 50-fs laser pulses output from a commercial 1-kHz femtosecond laser amplifier. The unique advantage of the proposed method is that it can directly provide valuable information about the pulse temporal structures' effect on the laser-induced ionization or material ablation.

  7. Picosecond lasers: the next generation of short-pulsed lasers. (United States)

    Freedman, Joshua R; Kaufman, Joely; Metelitsa, Andrea I; Green, Jeremy B


    Selective photothermolysis, first discussed in the context of targeted microsurgery in 1983, proposed that the optimal parameters for specific thermal damage rely critically on the duration over which energy is delivered to the tissue. At that time, nonspecific thermal damage had been an intrinsic limitation of all commercially available lasers, despite efforts to mitigate this by a variety of compensatory cooling mechanisms. Fifteen years later, experimental picosecond lasers were first reported in the dermatological literature to demonstrate greater efficacy over their nanosecond predecessors in the context of targeted destruction of tattoo ink. Within the last 4 years, more than a decade after those experiments, the first commercially available cutaneous picosecond laser unit became available (Cynosure, Westford, Massachusetts), and several pilot studies have demonstrated its utility in tattoo removal. An experimental picosecond infrared laser has also recently demonstrated a nonthermal tissue ablative capability in soft tissue, bone, and dentin. In this article, we review the published data pertaining to dermatology on picosecond lasers from their initial reports to the present as well as discuss forthcoming technology.

  8. Microencapsulation of silicon cavities using a pulsed excimer laser

    KAUST Repository

    Sedky, Sherif M.


    This work presents a novel low thermal-budget technique for sealing micromachined cavities in silicon. Cavities are sealed without deposition, similar to the silicon surface-migration sealing process. In contrast to the 1100°C furnace anneal required for the migration process, the proposed technique uses short excimer laser pulses (24ns), focused onto an area of 23mm 2, to locally heat the top few microns of the substrate, while the bulk substrate remains near ambient temperature. The treatment can be applied to selected regions of the substrate, without the need for special surface treatments or a controlled environment. This work investigates the effect of varying the laser pulse energy from 400 mJ cm 2to 800 mJ cm 2, the pulse rate from 1Hz to 50Hz and the pulse count from 200 to 3000 pulses on sealing microfabricated cavities in silicon. An analytical model for the effect of holes on the surface temperature distribution is derived, which shows that much higher temperatures can be achieved by increasing the hole density. A mechanism for sealing the cavities is proposed, which indicates how complete sealing is feasible. © 2012 IOP Publishing Ltd.

  9. Ionization of molecular hydrogen in ultrashort intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Vanne, Yulian V.


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

  10. Studying the mechanism of micromachining by short pulsed laser (United States)

    Gadag, Shiva

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

  11. Simulation of intense short-pulse laser-plasma interaction

    Energy Technology Data Exchange (ETDEWEB)

    Yamagiwa, Mitsuru [Advanced Photon Research Center, Kansai Research Establishment, Japan Atomic Energy Research Inst., Kizu, Kyoto (Japan)


    We have completed the massive parallelization of a 2-dimensional giga-particle code and have achieved a 530-fold acceleration rate with 512 processing elements (PE's). Using this we have implemented a simulation of the interaction of a solid thin film and a high intensity laser and have discovered a phenomenon in which high quality short pulses from the far ultraviolet to soft X-rays are generated at the back surface of the thin layer. We have also introduced the atomic process database code (Hullac) and have the possibility for high precision simulations of X-ray laser radiation. With respect to laser acceleration we have the possibility to quantitatively evaluate relativistic self-focusing assumed to occur in higher intensity fields. Ion acceleration from a solid target and an underdense plasma irradiated by an intense and an ultra intense laser, respectively, has also been studied by particle-in-cell (PIC) simulations. (author)

  12. Femtosecond few-cycle mid-infrared laser pulses

    DEFF Research Database (Denmark)

    Liu, Xing

    The few-cycle pulses of mid-infrared (mid-IR, wavelength 2-10 microns) have attracted increasing attention owing to their great potentials for high order harmonic generation, time-resolved spectroscopy, precision of cutting and biomedical science.In this thesis, mid-IR frequency conversion.......2 - 5.5 μm with only one fixed pump wavelength, a feature absent in Kerr media. Finally, we experimentally observe supercontinuum generation spanning 1.5 octaves, generated in a 10 mm long silicon-rich nitride waveguide pumped by 100 pJ femtosecond pulses from an erbium fiber laser. The waveguide has...

  13. Energy effective dual-pulse bispectral laser for EUV lithography (United States)

    Zhevlakov, A. P.; Seisyan, R. P.; Bespalov, V. G.; Elizarov, V. V.; Grishkanich, A. S.; Kascheev, S. V.; Sidorov, I. S.


    The power consumption in the two-pulse bispectral primary source could be substantially decreased by replacing the SRS converters from 1.06 μm into 10.6 μm wavelength as the preamplifier cascades in CO2 laser channel at the same efficiency radiation of EUV source. The creation of high volume manufacturing lithography facilities with the technological standard of 10-20 nm is related to the implementation of resist exposure modes with pulse repetition rate of 100 kHz. Low power consumption of the proposed scheme makes it promising for the creation of LPP EUV sources.

  14. Alignment of symmetric top molecules by short laser pulses

    DEFF Research Database (Denmark)

    Hamilton, Edward; Seideman, Tamar; Ejdrup, Tine


    Nonadiabatic alignment of symmetric top molecules induced by a linearly polarized, moderately intense picosecond laser pulse is studied theoretically and experimentally. Our studies are based on the combination of a nonperturbative solution of the Schrodinger equation with femtosecond time......-resolved photofragment imaging. Using methyliodide and tert-butyliodide as examples, we calculate and measure the alignment dynamics, focusing on the temporal structure and intensity of the revival patterns, including their dependence on the pulse duration, and their behavior at long times, where centrifugal distortion...

  15. Time-resolved beam profiler for pulsed lasers (United States)

    Klick, David I.; Knight, Frederick K.


    A high-speed imaging device based on a streak camera has been demonstrated, which provides multiple images from non-repeatable transient events of time scale >= 1 ns. It can be employed for pulsed laser beam diagnostics, measuring laser beam spatial and temporal structure on a single-pulse basis. The system currently has angular resolution of 16 X 16 pixels, with a time resolution of 250 ps. The laser beam width is sized to fill the input optic, and the image is dissected by a square array of optical fibers. At the other end of the fiber optic image converter, the 256 fibers form a line array, which is input to the slit of a streak camera. The streak camera sweeps the input line across the output phosphor screen so that position is directly proportional to time. The resulting 2-D image (fiber position vs. time) at the phosphor is read by an intensified (SIT) vidicon TV tube, and the image is digitized and stored. A computer subsequently decodes the image, unscrambling the linear pixels into an angle-angle image at each time. We are left with a series of snapshots, each one depicting the laser beam spatial profile (intensity cross-section) at succeeding moments in time. The system can currently record several hundred images over a span of 25 to 400 ns. This detector can study lasers of pulse width >= 1 ns and with a visible wavelength (200 - 900 nm). Candidate lasers include doubled Nd:YAG, excimer, ruby, nitrogen, metal vapor, and Ti:Sapphire. The system could also be simply configured as an 8 X 8 element wavefront sensor to record the cross-sectional distribution of phase, as well as amplitude. Finally, suggestions for system improvement are detailed, and the ultimate limitations of the method in terms of spatial and temporal resolution are discussed.

  16. Gain dynamics of a free-space nitrogen laser pumped by circularly polarized femtosecond laser pulses. (United States)

    Yao, Jinping; Xie, Hongqiang; Zeng, Bin; Chu, Wei; Li, Guihua; Ni, Jielei; Zhang, Haisu; Jing, Chenrui; Zhang, Chaojin; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan


    We experimentally demonstrate ultrafast dynamic of generation of the 337-nm nitrogen laser by injecting an external seed pulse into a femtosecond laser filament pumped by a circularly polarized laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the C(3)Π(u) and B(3)Π(g) states of N(2) for the free-space 337-nm laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the nitrogen gas pressure. By measuring the intensities of 337-nm signal from nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the nitrogen laser signal. Our experimental observations agree with the picture of electron-impact excitation.

  17. INTERACTION OF LASER RADIATION WITH MATTER: Influence of a target on operation of a pulsed CO2 laser emitting microsecond pulses (United States)

    Baranov, V. Yu; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.


    The profile of pulses emitted by a TEA CO2 laser with an unstable resonator changed as a result of interaction of laser radiation with the surface of a metal in the presence of a breakdown plasma. This influence of a target on laser operation and its possible applications in laser processing of materials are analyzed.

  18. Tunable CO2 laser system with subnanosecond-pulse-train output (United States)

    Kimura, W. D.


    A CO2 laser system has been demonstrated that generates a train of subnanosecond pulses tunable over the P and R branches of the CO2 laser spectrum at 9-11 μm. It utilizes optical free induction decay to generate a single 100-ps laser pulse from a tunable transverse-excited-atmospheric CO2 laser. This laser pulse is injection-seeded into a high-pressure CO2 oscillator whose output consists of a train of amplified 100-ps pulses with maximum pulse energy of 30 mJ, corresponding to a peak power of 300 MW. The 100-ps, tunable, infrared laser pulses are needed for a new technique to remotely detect atmospheric gaseous molecules, which relies on the train of CO2 laser pulses selectively exciting the target molecules whose presence is then revealed using a separate terahertz probe beam.

  19. Numerical investigation of vessel heating using a copper vapor laser and a pulsed dye laser in treating vascular skin lesions (United States)

    Pushkareva, A. E.; Ponomarev, I. V.; Isaev, A. A.; Klyuchareva, S. V.


    A computer simulation technique was employed to study the selective heating of a tissue vessel using emission from a pulsed copper vapor laser and a pulsed dye laser. The depth and size of vessels that could be selectively and safely removed were determined for the lasers under examination.

  20. Pulsed laser deposition of niobium nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Farha, Ashraf Hassan, E-mail:; Elsayed-Ali, Hani E., E-mail: [Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23529 (United States); Applied Research Center, Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Department of Physics, Faculty of Science, Ain Shams University, Cairo 11566 (Egypt); Ufuktepe, Yüksel, E-mail: [Department of Physics, University of Cukurova, 01330 Adana (Turkey); Myneni, Ganapati, E-mail: [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)


    Niobium nitride (NbN{sub x}) films were grown on Nb and Si(100) substrates using pulsed laser deposition. NbN{sub x} films were deposited on Nb substrates using PLD with a Q-switched Nd:YAG laser (λ = 1064 nm, ∼40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, nitrogen background pressures and deposition substrate temperatures. When all the fabrication parameters are fixed, except for the laser fluence, the surface roughness, nitrogen content, and grain size increase with increasing laser fluence. Increasing nitrogen background pressure leads to a change in the phase structure of the NbN{sub x} films from mixed β-Nb{sub 2}N and cubic δ-NbN phases to single hexagonal β-Nb{sub 2}N. The substrate temperature affects the preferred orientation of the crystal structure. The structural and electronic, properties of NbN{sub x} deposited on Si(100) were also investigated. The NbN{sub x} films exhibited a cubic δ-NbN with a strong (111) orientation. A correlation between surface morphology, electronic, and superconducting properties was found. The observations establish guidelines for adjusting the deposition parameters to achieve the desired NbN{sub x} film morphology and phase.

  1. High pulse energy, high beam quality microsecond-pulse Ti:sapphire laser at 819.7 nm (United States)

    Xu, Chang; Guo, Chuan; Yu, Hai-Bo; Wang, Zhi-Min; Zuo, Jun-Wei; Xia, Yuan-Qin; Bian, Qi; Bo, Yong; Gao, Hong-Wei; Guo, Ya-Ding; Zhang, Sheng; Cui, Da-Fu; Peng, Qin-Jun; Xu, Zu-Yan


    In this letter, a high pulse energy and high beam quality 819.7 nm Ti:sapphire laser pumped by a frequency-doubled Nd:YAG laser is demonstrated. At incident pump energy of 774 mJ, the maximum output energy of 89 mJ at 819.7 nm with a pulse width of 100 μs is achieved at a repetition rate of 5 Hz. To the best of our knowledge, this is the highest pulse energy at 819.7 nm with pulse width of hundred microseconds for a Ti:sapphire laser. The beam quality factor M 2 is measured to be 1.18. This specific wavelength with the high pulse energy and high beam quality at 819.7 nm is a promising light source to create a polychromatic laser guide star together with a home-made 589 nm laser via exciting the sodium atoms in the mesospheric atmosphere.

  2. Picosecond Laser Pulse Optical Density of Three 1060-NM Filters. (United States)


    pul- ses. These included a dyed glass plate (Schott KG-3), a polymethyl methacrylate plate ( PMMA ) developed for the Air Force for 1060-nm- specific...Schott KG-3), a polymethyl methacrylate plate ( PMMA ) developed for the Air Force for 1060-nm-specific visors, and a dielectric-coated laser cavity... Ocular tissue damage due to ultrashort 1060-nm light pulses from a mode-locked Nd:glass laser. Appl Opt 14:1759-1761 (1975). 4. Taboada, J., and D. D

  3. Two-pulse laser control for selective photofragment orientation

    DEFF Research Database (Denmark)

    Machholm, Mette; Henriksen, Niels Engholm


    The nuclear wave packet dynamics in the potential well of a bound molecule can be controlled by an intense infrared (IR)-laser pulse. The phase of the nuclear wave packet motion is shown to depend on the phase of the laser field and the initial orientation of the molecule. We demonstrate......, for diatomic heteronuclear molecules, that these spatial effects can be used to control the angular distribution of photofragments by selective dissociation of molecules with a given initial orientation from a sample of randomly oriented molecules. (C) 1999 American Institute of Physics. [S0021-9606(99)01131-9]....

  4. Resonant infrared pulsed laser deposition of thin biodegradable polymer films

    DEFF Research Database (Denmark)

    Bubb, D.M.; Toftmann, B.; Haglund Jr., R.F.


    Thin films of the biodegradable polymer poly(DL-lactide-co-glycolide) (PLGA) were deposited using resonant infrared pulsed laser deposition (RIR-PLD). The output of a free-electron laser was focused onto a solid target of the polymer, and the films were deposited using 2.90 (resonant with O...... absorbance spectrum of the films is nearly identical with that of the native polymer, the average molecular weight of the films is a little less than half that of the starting material. Potential strategies for defeating this mass change are discussed....

  5. Short-Pulse Laser-Matter Computational Workshop Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Town, R; Tabak, M


    For three days at the end of August 2004, 55 plasma scientists met at the Four Points by Sheraton in Pleasanton to discuss some of the critical issues associated with the computational aspects of the interaction of short-pulse high-intensity lasers with matter. The workshop was organized around the following six key areas: (1) Laser propagation/interaction through various density plasmas: micro scale; (2) Anomalous electron transport effects: From micro to meso scale; (3) Electron transport through plasmas: From meso to macro scale; (4) Ion beam generation, transport, and focusing; (5) ''Atomic-scale'' electron and proton stopping powers; and (6) K{alpha} diagnostics.

  6. Wetting ability modifications in biocompatible polymers induced by pulsed lasers (United States)

    Scolaro, C.; Torrisi, L.; Cutroneo, M.; Velardi, L.


    Wetting ability was measured in the surface of different biocompatible polymers, such as mylar, polyethylene, poly-methyl-methacrylate and teflon. Nanosecond pulse lasers at intensities of the order of 108 W/cm2 were employed at different doses to irradiate the polymeric surfaces and to induce wetting ability modifications due to the chemical and physical surface changes vs. irradiation time and laser wavelength. In particular, the contact angle as a function of the surface roughness was investigated, as will be presented and discussed.

  7. Femtosecond Timing Distribution Using Optical Pulses

    CERN Document Server

    Winter, A; Winter, A


    Fourth-generation light sources, such as the European X-ray Free Electron Laser (XFEL) require timing signals distributed over distances of several kilometers with a stability in the order of femtoseconds. A promising approach is the use of a mode-locked laser that generates sub-picosecond pulses which are distributed in timing stabilized optical fiber links. A good candidate for a laser master oscillator (LMO) is a mode-locked Erbium-doped fiber laser, featuring extremely low phase noise far from the carrier. Results on the development of the LMO locked to an external reference microwave oscillator to suppress low frequency jitter, the distribution via timing stabilized optical fiber links and the reconversion of the optical pulses to a low phase noise microwave RF signals with overall femtosecond stability are presented.

  8. Laser-induced back-ablation of aluminum thin films using picosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)



    Experiments were performed to understand laser-induced back-ablation of Al film targets with picosecond laser pulses. Al films deposited on the back surface of BK-7 substrates are ablated by picosecond laser pulses propagating into the Al film through the substrate. The ablated Al plume is transversely probed by a time-delayed, two-color sub-picoseond (500 fs) pulse, and this probe is then used to produce self-referencing interferograms and shadowgraphs of the Al plume in flight. Optical emission from the Al target due to LIBA is directed into a time-integrated grating spectrometer, and a time-integrating CCD camera records images of the Al plume emission. Ablated Al plumes are also redeposited on to receiving substrates. A post-experimental study of the Al target and recollected deposit characteristics was also done using optical microscopy, interferometry, and profilometry. In this high laser intensity regime, laser-induced substrate ionization and damage strongly limits transmitted laser fluence through the substrate above a threshold fluence. The threshold fluence for this ionization-based transmission limit in the substrate is dependent on the duration of the incident pulse. The substrate ionization can be used as a dynamic control of both transmitted spatial pulse profile and ablated Al plume shape. The efficiency of laser energy transfer between the laser pulse incident on the Al film and the ablated Al plume is estimated to be of order 5% and is a weak function of laser pulsewidth. The Al plume is highly directed. Low plume divergence ({theta}{sub divergence} < 5{sup o}) shows the ablated plume temperature to be very low at long time delays ( T << 0.5 eV at delays of 255 ns). Spectroscopic observations and calculations indicate that, in early time (t < 100 ps), the Al film region near the substrate/metal interface is at temperatures of order 0.5 eV. Interferograms of Al plumes produced with 0.1 {micro}m films show these plumes to be of high neutral atom

  9. Preface to the Special Issue on short pulse fiber lasers (United States)

    Delavaux, Jean-Marc P.; Grelu, Philippe; Pu, Wang; Ilday, Fatih Ömer


    In the last two decades the fiber laser has evolved from a laboratory curiosity to a viable tool in an increasing number of applications in such diverse areas as material processing, atmospheric monitoring, high energy physics, medicine, telecommunications, and defense. The reasons for the growing acceptance of fiber lasers lie in the combination of their many attractive features. Indeed, fiber lasers are together power efficient, compact, light weight, versatile and reliable. Initially, the development of fiber laser technology was led to challenge the dominance of well entrenched solid state lasers used in the lucrative manufacturing industry. Traditionally, the emission wavelength band of interest was mostly limited to the near infrared (NIR) region (i.e. from 1 to 1.6 μm). More recently, extensive fiber laser R&D advances have extended the laser applications to a broader spectrum, from the ultra violet (UV) to the mid-infrared (Mid-IR) wavelength region, and investigated the specific advantages associated with different pulse widths, from ns to fs, and different operating regimes.

  10. Note: 15-fs, 15-μJ green pulses from two-stage temporal compressor of ytterbium laser pulses. (United States)

    Konyashchenko, A V; Kostryukov, P V; Losev, L L; Tenyakov, S Yu


    15-fs, 15-μJ light pulses at the central wavelength of 515 nm were generated by two-stage nonlinear compression of 300-fs, 150-μJ ytterbium laser pulses. The compression was based on the pulse spectrum broadening by self-phase modulation in gas filled capillary and second harmonic generation in crystal.

  11. Rapid microfabrication of transparent materials using filamented femtosecond laser pulses (United States)

    Butkus, S.; Gaižauskas, E.; Paipulas, D.; Viburys, Ž.; Kaškelyė, D.; Barkauskas, M.; Alesenkov, A.; Sirutkaitis, V.


    Microfabrication of transparent materials using femtosecond laser pulses has showed good potential towards industrial application. Maintaining pulse energies exceeding the critical self-focusing threshold by more than 100-fold produced filaments that were used for micromachining purposes. This article demonstrates two different micromachining techniques using femtosecond filaments generated in different transparent media (water and glass). The stated micromachining techniques are cutting and welding of transparent samples. In addition, cutting and drilling experiments were backed by theoretical modelling giving a deeper insight into the whole process. We demonstrate cut-out holes in soda-lime glass having thickness up to 1 mm and aspect ratios close to 20, moreover, the fabrication time is of the order of tens of seconds, in addition, grooves and holes were fabricated in hardened 1.1 mm thick glass (Corning Gorilla glass). Glass welding was made possible and welded samples were achieved after several seconds of laser fabrication.

  12. Optical modulation of astrocyte network using ultrashort pulsed laser (United States)

    Yoon, Jonghee; Ku, Taeyun; Chong, Kyuha; Ryu, Seung-Wook; Choi, Chulhee


    Astrocyte, the most abundant cell type in the central nervous system, has been one of major topics in neuroscience. Even though many tools have been developed for the analysis of astrocyte function, there has been no adequate tool that can modulates astrocyte network without pharmaceutical or genetic interventions. Here we found that ultrashort pulsed laser stimulation can induce label-free activation of astrocytes as well as apoptotic-like cell death in a dose-dependent manner. Upon irradiation with high intensity pulsed lasers, the irradiated cells with short exposure time showed very rapid mitochondria fragmentation, membrane blebbing and cytoskeletal retraction. We applied this technique to investigate in vivo function of astrocyte network in the CNS: in the aspect of neurovascular coupling and blood-brain barrier. We propose that this noninvasive technique can be widely applied for in vivo study of complex cellular network.

  13. Intrastromal refractive sugery with ultrashort laser pulses in living animals (United States)

    Heisterkamp, Alexander; Mamom, Thanongsak; Kermani, Omid; Drommer, Wolfgang; Welling, Herbert; Ertmer, Wolfgang; Lubatschowski, Holger


    In order to perform refractive surgery, fs-laser pulses of 130-fs pulse duration were focused into animal cornea. By focusing the radiation down to spot-sizes of 5 micrometers , very precise cuts could be achieved inside the treated eyes, accompanied with minimum collateral damage to the tissue by thermal or mechanical effects. Due to these low side effects, micrometers -cutting precisions at preparing of corneal flaps and lenticules can be achieved. Thus, animal studies with 8 living rabbits were performed, in which intrastromal lenticules and flaps were created and extracted. Wound healing reactions were studied by histo- pathological analysis of the treated eyes in intervals at one, 7, 14 and 28 days after surgery. The treated eyes showed mild wound healing reactions with comparable results to what is known from Excimer-LASIK. Moreover the use of the fs-laser offered new possibilities in preparation of corneal flaps, providing advantages to the use of the mechanical keratome.

  14. Nonlinear electron emission in ultrashort laser pulses and rescattering suppression (United States)

    Mikhin, E. A.; Preobrazhenskii, M. A.; Golovinski, P. A.


    The process of nonlinear electron emission from a metal surface under the action of femtosecond laser pulse with moderate intensity ~1011 W/cm2 is considered. One-dimensional model is formulated, taking into account the advantage of the p-polarized light in the nonlinear emission. The time dependent Schrödinger equation with fixed equilibrium boundary conditions is solved in the half-space using the Laplace transform technique. The energy spectrum of emitted electrons is presented, including analysis of dependence on the laser pulse parameters. In the framework of classical mechanics, the impact of additional dc electric field on the rescattering of emitted electron on the metal surface is investigated. The model reproduces the fiches of electron energy distribution and can be used at arbitrary Keldysh parameters.

  15. [A clinical observation of pericoronitis treatment with pulse semiconductor laser]. (United States)

    Lu, Shan; Fang, Yuan


    In order to valuate the effect of pericoronitis treated with pulse semiconductor laser. As a treatment group, 24 ones drawn ramdomly from 48 cases of pericoronitis were given periodontal radiation, point-radiation therapy and pharmacotherapy as well. While another 24 cases as a contrast group were given pharmacotherapy only. On the 3rd day and the 5th day the degree of pain and restriction of mouth opening of the two groups were graded, contrasted and processed by Ridit statistics. Result, The therapy group gained more notable effect in pain-relieving and mouth-opening-improving than the contrast group. Because of no damage, handy and can be done easily, be definite in curative effect, Pulse semiconductor laser treatment pericoronitis deserves popularizing.

  16. Photoconductive Semiconductor Switch Technology for Short Pulse Electromagnetics and Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Denison, Gary J.; Helgeson, Wesley D.; Hjalmarson, Harold P.; Loubriel, Guillermo M.; Mar, Alan; O' Malley, Martin W.; Zutavern, Fred J.


    High gain photoconductive semiconductor switches (PCSS) are being used to produce high power electromagnetic pulses foc (1) compact, repetitive accelerators, (2) ultra-wide band impulse sources, (3) precision gas switch triggers, (4) optically-activated firesets, and (5) high power optical pulse generation and control. High power, sub-nanosecond optical pulses are used for active optical sensors such as compact optical radars and range-gated hallistic imaging systems. Following a brief introduction to high gain PCSS and its general applications, this paper will focus on PCSS for optical pulse generation and control. PCSS technology can be employed in three distinct approaches to optical pulse generation and control: (1) short pulse carrier injection to induce gain-switching in semiconductor lasers, (2) electro-optical Q-switching, and (3) optically activated Q-switching. The most significant PCSS issues for these applications are switch rise time, jitter, and longevity. This paper will describe both the requirements of these applications and the most recent results from PCSS technology. Experiments to understand and expand the limitations of high gain PCSS will also be described.

  17. Short-pulse high intensity laser thin foil interaction (United States)

    Audebert, Patrick


    The technology of ultrashort pulse laser generation has progressed to the point that optical pulses larger than 10 J, 300 fs duration or shorter are routinely produced. Such pulses can be focused to intensities exceeding 10^18 W/cm^2. With high contrast pulses, these focused intensities can be used to heat solid matter to high temperatures with minimal hydrodynamic expansion, producing an extremely high energy-density state of matter for a short period of time. This high density, high temperature plasma can be studied by x-ray spectroscopy. We have performed experiments on thin foils of different elements under well controlled conditions at the 100 Terawatt laser at LULI to study the characteristics X-ray emission of laser heated solids. To suppress the ASE effect, the laser was frequency doubled. S-polarized light with a peak intensity of 10^19W/cm^2 was used to minimize resonance absorption. To decrease the effect of longitudinal temperature gradients very thin (800 μ) aluminum foil targets were used. We have also studied the effect of radial gradient by limiting the measured x-ray emission zone using 50μ or 100μ pinhole on target. The spectra, in the range 7-8Å, were recorded using a conical crystal spectrometer coupled to a 800 fs resolution streak camera. A Fourier Domain Interferometry (FDI) of the back of the foil was also performed providing a measurement of the hydrodynamic expansion as function of time for each shot. To simulate the experiment, we used the 1D hydrodynamic code FILM with a given set of plasma parameter (ρ, Te) as initial conditions. The X-ray emission was calculated by post processing hydrodynamic results with a collisional-radiative model which uses super-configuration average atomic data. The simulation reproduces the main features of the experimental time resolved spectrum.

  18. Desorption by Femtosecond Laser Pulses : An Electron-Hole Effect?


    D. M., NEWNS; T. F., HEINZ; J. A., MISEWICH; IBM Research Division, T. J. Watson Research Center; IBM Research Division, T. J. Watson Research Center; IBM Research Division, T. J. Watson Research Center


    Desorption of molecules from metal surfaces induced by femtosecond visible laser pulses has been reported. Since the lattice temperature rise is insufficient to explain desorption, an electronic mechanism is clearly responsible. It is shown that a theory based on direct coupling between the center-of-mass degree of freedom of the adsorbate and the electron-hole excitations of the substrate provides a satisfactory explanation of the various experimental findings.

  19. Pulsed laser deposition and characterisation of thin superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Morone, A. [CNR, zona industriale di Tito Scalo, Potenza (Italy). Istituto per i Materiali Speciali


    Same concepts on pulsed laser deposition of thin films will be discussed and same examples of high transition temperature (HTc) BiSrCaCuO (BISCO) and low transition temperature NbN/MgO/NbN multilayers will be presented. X-ray and others characterizations of these films will be reported and discussed. Electrical properties of superconducting thin films will be realized as a function of structural and morphological aspect.

  20. Dielectrophoretic focusing integrated pulsed laser activated cell sorting (United States)

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


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

  1. Extreme dynamic compression with a low energy laser pulse (United States)

    Armstrong, Michael R.; Crowhurst, Jonathan C.; Zaug, Joseph M.; Radousky, Harry B.


    Here we review the scaling of pulse energy with duration for sub-ns laser-driven dynamic compression experiments, which suggests that extreme pressures (multiple Mbar) might be achieved in rapidly equilibrating materials with substantially lower energy than used in traditional experiments. For instance, conventional scaling of pressure with laser intensity indicates that pressures well into the multiple Mbar range should be accessible by compressing with a hundreds of picosecond duration drive pulse with some tens of mJ of energy - orders of magnitude less than required for conventional experiments. Via a related scaling argument, we also show that the throughput of time-resolved pulsed x-ray dynamic compression experiments (such as those performed at x-ray free electron lasers) varies as the inverse square of the time scale of the experiment. The strong variation of throughput with the scale of the experiment should be a significant consideration in the design of such experiments - to obtain high throughput, the time scale of compression should be no longer than required (via material equilibration) to achieve the desired final material state.

  2. Phonatory outcome of 585 nm/pulsed-dye laser in the management of glottic leukoplakia. (United States)

    Park, Young Min; Jo, Kwang Hee; Hong, Hyun Jun; Choi, Hong-Shik


    Vocal cord mucosectomy using pulsed-dye laser was assessed for its ability to completely remove lesions without deterioration of vocal quality in cases of vocal cord leukoplakia. To confirm the validity of a pulsed-dye laser, we retrospectively analyzed the treatment outcomes of patients who received surgery preceded by pulsed-dye laser and compared these with the outcomes of patients who received vocal cord mucosectomy using CO2 laser. Between February 2007 and June 2012, 36 patients were enrolled. Seventeen patients received vocal cord treatment with a CO2 laser and 19 patients received operation with a pulsed-dye laser. To evaluate voice status, acoustic wave form analysis and electroglottography were done, and voice handicap index was measured before and after the operation. The entire lesion was removed in all patients. Compared to preoperative vocal parameters, the postoperative values for jitter were only improved in the pulsed-dye laser group. On stroboscopic findings, a diminution or lack of mucosal wave was observed in more CO2 laser cases than pulsed-dye laser cases. Significant improvement in voice handicap index results was only observed in the pulsed-dye laser group. Although long-term results with more patients are required to establish the validity of pulsed-dye laser, this study confirmed the merits of pulsed-dye laser for the en-bloc removal of vocal cord leukoplakia and improved voice outcome. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  3. LASER PHYSICS: Self-stabilization of ultrashort pulses emitted by a neodymium phosphate glass laser (United States)

    Mavritskiĭ, O. B.; Petrovskiĭ, A. N.


    An investigation was made of the emission spectra of a neodymium phosphate glass laser during various stages of formation of ultrashort pulses. The kinetics of the spectrum of free lasing with passive mode locking was observed first. Considerable changes in the spectrum were observed for successive free-lasing spikes, which made it impossible to achieve self-stabilization of the ultrashort pulse duration. The spectrum of ultrashort pulses varied with the point of selection of a pulse in a train. The results were explained allowing for the simultaneous influence of burning of spectral holes in the population inversion and phase self-modulation on the operation of a laser with passive mode locking.

  4. Submicro foaming in biopolymers by UV pulsed laser irradiation (United States)

    Oujja, Mohamed; Rebollar, Esther; Gaspard, Solenne; Abrusci, Concepción; Catalina, Fernando; Lazare, Sylvain; Castillejo, Marta


    Microstructuring of polymers and biopolymers is of application in medical technology and biotechnology. Using different fabrication techniques three-dimensionally shaped and micro structured constructs can be developed for drug release and tissue engineering. As an alternative method, laser microstructuring offers a series of advantages including high resolution capability, low heat deposition in the substrate and high level of flexibility. In this work we present evidence of laser microfoam formation in collagen and gelatine by nanosecond pulsed laser irradiation in the UV at 248 and 266 nm. Irradiation at 355 nm produces melting followed by resolidification of the substrate, whereas irradiation at 532 and 1064 nm induces the formation of craters of irregular contours. Single pulse irradiation of a collagen film with an homogenized KrF microbeam yields a 20 μm thick expanded layer, which displays the interesting features of a nanofibrous 3-dimensional network with open cells. In gelatine, irradiation at 248 and 266 nm produces similar morphological modifications. The effect of the structural properties of the substrate on the laser induced microfoam is studied by comparing gelatines differing in gel strength (Bloom values 225 and 75) and in crosslinking degree. While results are discussed on the basis of thermal and photomechanical mechanisms and of the role played by the water content of the substrates, it is thought that such structures could have a biomimic function in future 3D cell culture devices for research.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nedyalkov, N.N., E-mail: [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Imamova, S.E.; Atanasov, P.A. [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Toshkova, R.A.; Gardeva, E.G.; Yossifova, L.S.; Alexandrov, M.T. [Institute of Experimental Pathology and Parasitology, Bulgarian Academy of Sciences, G. Bonchev Street, bl. 25, Sofia 1113 (Bulgaria); Obara, M. [Department of Electronics and Electrical Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)


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

  6. Copper bromide vapour laser with an output pulse duration of up to 320 ns

    Energy Technology Data Exchange (ETDEWEB)

    Gubarev, F A; Fedorov, K V; Evtushenko, G S [National Research Tomsk Polytechnic University, Tomsk (Russian Federation); Fedorov, V F; Shiyanov, D V [V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation)


    We report the development of a copper bromide vapour laser with an output pulse duration of up to 320 ns. To lengthen the pulse, the discharge current was limited using a compound switch comprising a pulsed hydrogen thyratron and a tacitron. This technique permits limiting the excitation of the working levels at the initial stage of the discharge development to lengthen the inversion lifetime. The longest duration of a laser pulse was reached in tubes 25 and 50 mm in diameter for a pulse repetition rate of 2 – 4 kHz. (lasers and laser beams)

  7. Controlling laser-ion acceleration with chirped pulses (United States)

    Mackenroth, Felix; Gonoskov, Arkady; Marklund, Mattias


    The recently proposed novel laser-ion acceleration scheme Chirped-standing-wave acceleration (CSWA) makes use of chirped high-intensity laser pulses to gain enhanced control over the accelerated ions' phase space distribution. The first proof-of-principle analysis of this scheme promised favorable scaling properties of ion energies and densities while simultaneously offering unprecedented spatial and temporal control over the ion beam itself. In this talk we provide an extended analysis of the schemes' further capabilities accessible through, e.g., customized laser chirps and targets. We provide quantitative estimates for existing and upcoming experimental facilities to highlight the scheme's versatility. Furthermore, we benchmark the newly proposed scheme against conventional laser-ion acceleration schemes. To this end we use the accelerated ions' flux as a measure for the conversion efficiency of laser energy into ion kinetic energy and provide a systematic comparison of the theoretically achievable performances of the most common laser-ion acceleration schemes. We find CSWA to be highly competitive in terms of reachable ion energies and fluxes.

  8. Injection of electrons by colliding laser pulses in a laser wakefield accelerator

    CERN Document Server

    Hansson, Martin; Ekerfelt, Henrik; Persson, Anna; Lundh, Olle


    To improve the stability and reproducibility of laser wakefield accelerators and to allow for future applications, controlling the injection of electrons is of great importance. This allows us to control the amount of charge in the beams of accelerated electrons and final energy of the electrons. Results are presented from a recent experiment on controlled injection using the scheme of colliding pulses and performed using the Lund multi-terawatt laser. Each laser pulse is split into two parts close to the interaction point. The main pulse is focused on a 2 mm diameter gas jet to drive a nonlinear plasma wave below threshold for self-trapping. The second pulse, containing only a fraction of the total laser energy, is focused to collide with the main pulse in the gas jet under an angle of 150°. Beams of accelerated electrons with low divergence and small energy spread are produced using this set-up. Control over the amount of accelerated charge is achieved by rotating the plane of polarization of the second p...

  9. Femtosecond laser pulse induced desorption: A molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Lončarić, Ivor, E-mail: [Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), P. Manuel de Lardizabal 5, 20018 San Sebastián (Spain); Alducin, Maite [Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), P. Manuel de Lardizabal 5, 20018 San Sebastián (Spain); Donostia International Physics Center DIPC, P. Manuel de Lardizabal 4, 20018 San Sebastián (Spain); Saalfrank, Peter [Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam (Germany); Donostia International Physics Center DIPC, P. Manuel de Lardizabal 4, 20018 San Sebastián (Spain); Juaristi, J. Iñaki [Departamento de Física de Materiales, Facultad de Químicas, Universidad del País Vasco (UPV/EHU), Apartado 1072, 20080 San Sebastián (Spain); Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), P. Manuel de Lardizabal 5, 20018 San Sebastián (Spain); Donostia International Physics Center DIPC, P. Manuel de Lardizabal 4, 20018 San Sebastián (Spain)


    In recent simulations of femtosecond laser induced desorption of molecular oxygen from the Ag(110) surface, it has been shown that depending on the properties (depth and electronic environment) of the well in which O{sub 2} is adsorbed, the desorption can be either induced dominantly by hot electrons or via excitations of phonons. In this work we explore whether the ratios between the desorption yields from different adsorption wells can be tuned by changing initial surface temperature and laser pulse properties. We show that the initial surface temperature is an important parameter, and that by using low initial surface temperatures the electronically mediated process can be favored. In contrast, laser properties seem to have only a modest influence on the results.

  10. Drug delivery with microsecond laser pulses into gelatin (United States)

    Shangguan, Hanqun; Casperson, Lee W.; Shearin, Alan; Gregory, Kenton W.; Prahl, Scott A.


    Photoacoustic drug delivery is a technique for localized drug delivery by laser-induced hydrodynamic pressure following cavitation bubble expansion and collapse. Photoacoustic drug delivery was investigated on gelatin-based thrombus models with planar and cylindrical geometries by use of one microsecond laser pulses. Solutions of a hydrophobic dye in mineral oil permitted monitoring of delivered colored oil into clear gelatin-based thrombus models. Cavitation bubble development and photoacoustic drug delivery were visualized with flash photography. This study demonstrated that cavitation is the governing mechanism for photoacoustic drug delivery, and the deepest penetration of colored oil in gels followed the bubble collapse. Spatial distribution measurements revealed that colored oil could be driven a few millimeters into the gels in both axial and radial directions, and the penetration was less than 500 mu m when the gelatin structure was not fractured. localized drug delivery, cavitation bubble, laser thrombolysis.

  11. Testing of a femtosecond pulse laser in outer space (United States)

    Lee, Joohyung; Lee, Keunwoo; Jang, Yoon-Soo; Jang, Heesuk; Han, Seongheum; Lee, Sang-Hyun; Kang, Kyung-In; Lim, Chul-Woo; Kim, Young-Jin; Kim, Seung-Woo


    We report a test operation of an Er-doped fibre femtosecond laser which was conducted for the first time in outer space. The fibre-based ultrashort pulse laser payload was designed to meet space-use requirements, undergone through ground qualification tests and finally launched into a low-earth orbit early in 2013. Test results obtained during a one-year mission lifetime confirmed stable mode-locking all the way through although the radiation induced attenuation (RIA) in the Er-doped gain fibre caused an 8.6% reduction in the output power. This successful test operation would help facilitate diverse scientific and technological applications of femtosecond lasers in space and earth atmosphere in the near future. PMID:24875665

  12. Testing of a femtosecond pulse laser in outer space. (United States)

    Lee, Joohyung; Lee, Keunwoo; Jang, Yoon-Soo; Jang, Heesuk; Han, Seongheum; Lee, Sang-Hyun; Kang, Kyung-In; Lim, Chul-Woo; Kim, Young-Jin; Kim, Seung-Woo


    We report a test operation of an Er-doped fibre femtosecond laser which was conducted for the first time in outer space. The fibre-based ultrashort pulse laser payload was designed to meet space-use requirements, undergone through ground qualification tests and finally launched into a low-earth orbit early in 2013. Test results obtained during a one-year mission lifetime confirmed stable mode-locking all the way through although the radiation induced attenuation (RIA) in the Er-doped gain fibre caused an 8.6% reduction in the output power. This successful test operation would help facilitate diverse scientific and technological applications of femtosecond lasers in space and earth atmosphere in the near future.

  13. Pulse-periodic iodine photodissociation laser pumped with radiation from magnetoplasma compressors (United States)

    Kashnikov, G. N.; Orlov, V. K.; Panin, A. N.; Piskunov, A. K.; Reznikov, V. A.


    The design and operation of an iodine photodissociation laser, pumped by radiation from magnetoplasma compressors, are described. The laser uses a closed-circulation system with C3F7I as the working gas. Repetitive-pulse operation has been achieved with an interval between pulses of 1 minute, a lasing energy of 110 J, and a pulse duration of 30 microseconds.

  14. Influence of laser pulse duration on extreme ultraviolet and ion emission features from tin plasmas (United States)

    Roy, A.; Harilal, S. S.; Polek, M. P.; Hassan, S. M.; Endo, A.; Hassanein, A.


    We investigated the role of laser pulse duration and intensity on extreme ultraviolet (EUV) generation and ion emission from a laser produced Sn plasma. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm Nd:YAG laser pulses with varying pulse duration (5-20 ns) and intensity. Experimental results performed at CMUXE indicate that the conversion efficiency (CE) of the EUV radiation strongly depend on laser pulse width and intensity, with a maximum CE of ˜2.0% measured for the shortest laser pulse width used (5 ns). Faraday Cup ion analysis of Sn plasma showed that the ion flux kinetic profiles are shifted to higher energy side with the reduction in laser pulse duration and narrower ion kinetic profiles are obtained for the longest pulse width used. However, our initial results showed that at a constant laser energy, the ion flux is more or less constant regardless of the excitation laser pulse width. The enhanced EUV emission obtained at shortest laser pulse duration studied is related to efficient laser-plasma reheating supported by presence of higher energy ions at these pulse durations.

  15. Influence of laser pulse duration on extreme ultraviolet and ion emission features from tin plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Roy, A., E-mail:, E-mail: [HiLASE Project, Department of Diode-Pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague (Czech Republic); School of Nuclear Engineering and Center for Materials Under Extreme Environment (CMUXE), Purdue University, West Lafayette, Indiana 47907 (United States); Harilal, S. S.; Polek, M. P.; Hassan, S. M.; Hassanein, A. [School of Nuclear Engineering and Center for Materials Under Extreme Environment (CMUXE), Purdue University, West Lafayette, Indiana 47907 (United States); Endo, A. [HiLASE Project, Department of Diode-Pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague (Czech Republic)


    We investigated the role of laser pulse duration and intensity on extreme ultraviolet (EUV) generation and ion emission from a laser produced Sn plasma. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm Nd:YAG laser pulses with varying pulse duration (5–20 ns) and intensity. Experimental results performed at CMUXE indicate that the conversion efficiency (CE) of the EUV radiation strongly depend on laser pulse width and intensity, with a maximum CE of ∼2.0% measured for the shortest laser pulse width used (5 ns). Faraday Cup ion analysis of Sn plasma showed that the ion flux kinetic profiles are shifted to higher energy side with the reduction in laser pulse duration and narrower ion kinetic profiles are obtained for the longest pulse width used. However, our initial results showed that at a constant laser energy, the ion flux is more or less constant regardless of the excitation laser pulse width. The enhanced EUV emission obtained at shortest laser pulse duration studied is related to efficient laser-plasma reheating supported by presence of higher energy ions at these pulse durations.

  16. Magnus expansion for laser-matter interaction: Application to generic few-cycle laser pulses

    DEFF Research Database (Denmark)

    Klaiber, Michael; Dimitrovski, Darko; Briggs, John S.


    We treat the interaction of an atom with a short intense few-cycle laser pulse by the use of the Magnus expansion of the time-evolution operator. Terms of the Magnus expansion up to the third order in the pulse duration are evaluated explicitly, and expressions for the transition probability...... of the Magnus approximation are in excellent agreement with time-dependent transition probabilities obtained from accurate ab initio numerical calculations. However, the limitation of the Magnus expansion for pulses having both vanishing momentum and position shifts is demonstrated also....

  17. High-power pulsed and CW diode-pumped mode-locked Nd:YAG lasers (United States)

    Marshall, Larry R.; Hays, A. D.; Kaz, Alex; Kasinski, Jeff; Burnham, R. L.


    The operation of both pulsed and CW diode-pumped mode-locked Nd:YAG lasers are presented. The pulsed laser produced 1.0 mJ with pulsewidths of 90 psec at 20 Hz. The CW pumped laser produced 6 W output at 1.064 microns and 3 W output at 532 nm.

  18. Effect of surface-breakdown plasma on metal drilling by pulsed CO2-laser radiation (United States)

    Arutiunian, P. V.; Baranov, V. Iu.; Bobkov, I. V.; Bol'Shakov, L. A.; Dolgov, V. A.


    The effect of low-threshold surface breakdown produced by short (5-microsec) CO2-laser pulses on the metal drilling process is investigated. Data on the interaction of metals with laser pulses having the same duration but different shape are shown to be different. The effect of the ambient atmospheric pressure on the laser drilling process is investigated.

  19. Novel oral applications of ultra-short laser pulses (United States)

    Wieger, V.; Wernisch, J.; Wintner, E.


    In the past decades, many efforts have been made to replace mechanical tools in oral applications by various laser systems. The reasons therefore are manifold: i) Friction causes high temperatures damaging adjacent tissue. ii) Smear layers and rough surfaces are produced. iii) Size and shape of traditional tools are often unsuitable for geometrically complicated incisions and for minimum invasive treatment. iv) Mechanical damage of the remaining tissue occurs. v) Online diagnosis for feedback is not available. Different laser systems in the µs and sub-&mrgs-pulse regime, among them Erbium lasers, have been tested in the hope to overcome the mentioned drawbacks and, to some extent, they represent the current state of the art with respect to commercial and hence practical application. In the present work the applicability of scanned ultrashort pulse lasers (USPLs) for biological hard tissue as well as dental restoration material removal was tested. It is shown that cavities with features superior to mechanically treated or Erbium laser ablated cavities can be generated if appropriate scan algorithms and optimum laser parameters are matched. Smooth cavity rims, no microcracks, melting or carbonisation and precise geometry are the advantages of scanned USLP ablation. For bone treatment better healing conditions are expected as the natural structure remains unaffected by the preparation procedure. The novelty of this work is represented by a comprehensive compilation of various experimental results intended to assess the performance of USPLs. In this context, various pulse durations in the picosecond and femtosecond regime were applied to dental and bone tissue as well as dental restoration materials which is considered to be indispensable for a complete assessment. Parameters like ablation rates describing the efficiency of the ablation process, and ablation thresholds were determined - some of them for the first time - and compared to the corresponding Erbium

  20. Experimental study of laser-induced plasma: Influence of laser fluence and pulse duration

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Xueshi; Ma, Qianli; Perrier, Maxime; Motto-Ros, Vincent [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne cedex (France); Sabourdy, David; Nguyen, Luc; Jalocha, Alain [CILAS Laser Company, Photonics Department, 45000 Orléans (France); Yu, Jin, E-mail: [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne cedex (France)


    Influence of laser fluence and pulse duration on the morphology and the internal structure of plasma induced by infrared nanosecond laser pulse on an aluminum target placed in an argon ambient gas of one atmosphere pressure was experimentally studied. Dual-wavelength differential spectroscopic imaging was used in the experiment, which allowed observing the detailed structure inside of the ablation plume with distributions of species evaporated from the target as well as contributed by the ambient gas. Different regimes of post-ablation interaction were investigated using different laser fluences and pulse durations. We demonstrate in particular that plasma shielding due to various species localized in different zones inside of the plume leads to different morphologies and internal structures of the plasma. At moderate fluence, the plasma shielding due to the ablation vapor localized in the central part of the plume leads to its nearly spherical expansion with a layered structure of the distribution of different species. At higher fluence, the plasma shielding becomes strongly contributed by ionized ambient gas localized in the propagation front of the plume. An elongated morphology of the plume is observed with a zone of mixing between different species evaporated from the target or contributed by the ambient gas. Finally with extremely strong plasma shielding by ionized ambient gas in the case of a long duration pulse at high fluence, a delayed evaporation from the target is observed due to the ejection of melted material by splashing. - Highlights: • Morphology and internal structure of a plasma were experimentally determined. • Laser fluence and pulse duration are critical parameters for plasma structure. • Plasma shielding due to various species leads to different plasma structures. • Different regimes of laser-support absorption wave are used for interpretation. • Splashing ejection is observed for strong plasma shielding with long pulse.

  1. Route to the minimum pulse duration in normal-dispersion fiber lasers (United States)

    Chong, Andy; Renninger, William H.; Wise, Frank W.


    The factors that control the pulse duration in all-normal-dispersion lasers are identified. To minimize the pulse duration, the cavity dispersion should be as small as possible. For fixed dispersion, increasing pulse energy leads to shorter, but more-structured, pulses. Experiments performed with ordinary single-mode fiber at 1 μm wavelength agree reasonably with numerical simulations, and produce clean ~80-fs pulses. The simulations indicate that 30-fs pulses can be reached at higher energies. PMID:19015693

  2. Synthesis of silver nanoparticles by laser ablation in ethanol: A pulsed photoacoustic study

    Energy Technology Data Exchange (ETDEWEB)

    Valverde-Alva, M.A., E-mail: [Posgrado en Ciencia e Ingeniería de Materiales, Universidad Nacional Autónoma de México (UNAM), México D.F., C.P. 04510, México (Mexico); García-Fernández, T. [Universidad Autónoma de la Ciudad de México (UACM), Prolongación San Isidro 151, Col. San Lorenzo Tezonco, México D.F., C.P. 09790, México (Mexico); Villagrán-Muniz, M.; Sánchez-Aké, C.; Castañeda-Guzmán, R. [CCADET Universidad Nacional Autónoma de México (UNAM), México D.F., C.P. 04510, México (Mexico); Esparza-Alegría, E. [Facultad de Ciencias, Universidad Nacional Autónoma de México (UNAM), México D.F., C.P. 04510, México (Mexico); Sánchez-Valdés, C.F. [Instituto Potosino de Investigación Científica y Tecnológica A.C., Camino a la Presa San José 2055, Col. Lomas 4a sección, San Luis Potosí, S.L.P., C.P. 78216, México (Mexico); and others


    Graphical abstract: - Highlights: • Pulsed photoacoustic technique allowed to determine the production rate of NPs. • Pulsed photoacoustic technique allows to determine the Ag concentration in colloids. • The nanoparticles production rate drops quickly during the first laser pulses. • Nanoparticles production rate is almost constant after few hundreds of laser shots. • Photoacoustic signal amplitude was proportional to fluence on the target surface. - Abstract: The pulsed photoacoustic (PA) technique was used to study the synthesis by laser ablation of silver nanoparticles (Ag-NPs) in ethanol. PA technique allowed to determine the production rate per laser pulse and concentration of synthesized Ag-NPs. The samples were produced by using a pulsed Nd:YAG laser with 1064 nm of wavelength and 7 ns of pulse duration. The laser pulse energy varied from 10 to 100 mJ. Transmission electron microscopy micrographs demonstrated that the obtained nanoparticles were spherical with an average size close to 10 nm. The absorption spectra of the colloids showed a plasmon absorption peak around 400 nm. The PA analyses showed a significant reduction of the production rate of Ag-NPs during the first hundreds of laser pulses. For a higher number of pulses this rate was kept almost constant. Finally, we found that the root mean square (RMS) value of the PA signal was proportional to the laser pulse fluence on the target surface. Thus PA technique was useful to monitor the ablation process.

  3. Fatigue Testing of Materials by UV Pulsed Laser Irradiation

    CERN Document Server

    Calatroni, S; Taborelli, M


    The energy dissipated by the RF currents in the cavities of pulsed high-power linacs induces cycles of the surface temperature. In the case of the CLIC main linac the expected amplitude of the thermal cycles is above fifty degrees, for a total number of pulses reaching 1011. The differential thermal expansion due to the temperature gradient in the material creates a cyclic stress that can result in surface break-up by fatigue. The materials for cavity fabrication must therefore be selected in order to withstand such constraints whilst maintaining an acceptable surface state. The fatigue behaviour of Cu and CuZr alloy has been tested by inducing larger surface peak temperatures, thus reducing the number of cycles to failure, irradiating the surface with 40 ns pulses of UV light (308 nm) from an excimer laser. Surface break-up is observed after different number of laser shots as a function of the peak temperature. CuZr appears to withstand a much larger number of cycles than Cu, for equal peak temperature. The ...

  4. Thin film surface processing by ultrashort laser pulses (USLP) (United States)

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


    In this work, we studied the feasibility of surface texturing of thin molybdenum layers on a borosilicate glass substrate with Ultra-Short Laser Pulses (USLP). Large areas of regular diffraction gratings were produced consisting of Laserinduced periodic surface structures (LIPSS). A short pulsed laser source (230 fs-10 ps) was applied using a focused Gaussian beam profile (15-30 μm). Laser parameters such as fluence, overlap (OL) and Overscans (OS), repetition frequency (100-200 kHz), wavelength (1030 nm, 515 nm and 343 nm) and polarization were varied to study the effect on periodicity, height and especially regularity of LIPSS obtained in layers of different thicknesses (150-400 nm). The aim was to produce these structures without cracking the metal layer and with as little ablation as possible. It was found that USLP are suitable to reach high power densities at the surface of the thin layers, avoiding mechanical stresses, cracking and delamination. A possible photovoltaic (PV) application could be found in texturing of thin film cells to enhance light trapping mechanisms.

  5. The effects of pulsed laser parameters on the photoacoustic detection of glucose aqueous solution (United States)

    Ren, Zhong; Liu, Guodong; Huang, Zhen; Zeng, Lvming


    In this study, the photoacoustic detection system was established based on the Q switched Nd: YAG 532nm pumped optical parametric oscillator pulsed laser and the ultrasonic detector. Based on the established photoacoustic detection system, the effects of pulsed laser on the photoacoustic detection of glucose aqueous solutions were experimentally studied. The photoacoustic peak-to-peak values of glucose and pure water were obtained at different output energy of pulsed laser and at the wavelengths from 1300nm to 2200nm. Experimental results show that the photoacoustic peak-to-peak values of glucose linearly increase with the increasing of the output energy of pulsed laser. The photoacoustic peak-to-peak values were compensated because the output energy of pulsed laser exponentially decreased with the increasing of the wavelengths of pulsed laser. The characteristic wavelengths of glucose were determined according to the difference spectral between the compensated photoacoustic peak-to-peak values of glucose aqueous solution and pure water.

  6. Femtosecond laser ablation of silver foil with single and double pulses

    CSIR Research Space (South Africa)

    Roberts, DE


    Full Text Available The average ablation depth per pulse of silver foil by 130 fs laser pulses has been measured in vacuum over a range of three orders of magnitude of pulse fluence up to 900 J cm_2. In addition, double pulses with separations up to 3.4 ns have been...

  7. Femtosecond laser ablation of silver foil with single and double pulses

    CSIR Research Space (South Africa)

    Roberts, DE


    Full Text Available The average ablation depth per pulse of silver foil by 130 fs laser pulses has been measured in vacuum over a range of three orders of magnitude of pulse fluence up to 900 J cm-2. In addition, double pulses with separations up to 3.4 ns have been...

  8. Investigations on fibers for high-peak power pulsed Nd:YAG-lasers for laser detonator (United States)

    Gao, Yang; Zhao, Xing-hai; Su, Wei; Cheng, Yong-sheng; Xu, Mei-jian; Duan, Wen-tao; Yu, Hai-wu


    For laser detonator application, high-peak power pulsed Nd:YAG laser is transmitted through all-silica optical fiber. The transmission properties of step-index fibers are investigated, using a high-peak power pulsed Nd: YAG rod laser with beyond 1MW power and Q-switch mode. The fibers are step-index multimode fibers with 400 or 600 μm core diameters, 440 or 660 μm cladding diameters. The power delivery characteristics were studied by theory and experiments. The results show that the fiber core diameter, NA, length and so on affect the transmission efficiency for high power laser. When the laser power is beyond a certain threshold, the SRS and SBS will be serious; the quantity of fiber end-face limits to the raising of laser power passing through fibers; the zero-probability damage threshold is calculated according to ISO/DIS standard 11254-1.2, which is 58.6J/cm2. Energy distribution of output beam from fibers will be uniform. Even the fiber end-face was partly damaged, laser power is still deliverable, and the transmission efficiency is related to the fiber damage grade.

  9. Effects of pulse width and repetition rate of pulsed laser on kinetics and production of singlet oxygen luminescence

    Directory of Open Access Journals (Sweden)

    Defu Chen


    Full Text Available Pulsed and continuous-wave (CW lasers have been widely used as the light sources for photodynamic therapy (PDT treatment. Singlet oxygen (1O2 is known to be a major cytotoxic agent in type-II PDT and can be directly detected by its near-infrared luminescence at 1270nm. As compared to CW laser excitation, the effects of pulse width and repetition rate of pulsed laser on the kinetics and production of 1O2 luminescence were quantitatively studied during photosensitization of Rose Bengal. Significant difference in kinetics of 1O2 luminescence was found under the excitation with various pulse widths of nanosecond, microsecond and CW irradiation with power of 20mW. The peak intensity and duration of 1O2 production varied with the pulse widths for pulsed laser excitation, while the 1O2 was generated continuously and its production reached a steady state with CW excitation. However, no significant difference (P>0.05 in integral 1O2 production was observed. The results suggest that the PDT efficacy using pulsed laser may be identical to the CW laser with the same wavelength and the same average fluence rate below a threshold in solution.

  10. Experimental set-up for a pulsed CO2 laser rangefinder with heterodyne detection (United States)

    Bloem, J.


    The creation of a pulsed CO2 laser range finder with heterodyne detection is described. The range finder uses a hybrid CW-TEA (Continuous Wave-Transversely Excited Atmospheric pressure) laser as emitter and an RF laser as local oscillator. The laser stabilization is described. The frequency offset between the transmitted laser pulse and the local oscillator laser is locked at 20 MHz. The long term (20 to 30 min) variation of this offset frequency is limited to 50 kHz. The effects of pulsing on this stabilization were eliminated. The signal processing was started. A rough model of the laser pulse and its frequency characteristics was developed. An AM demodulator was developed to determine the envelope of the reflected pulses. The system created can be used to measure the range to (and in the future also the speed of) diffuse reflecting targets.

  11. Short energetic electron bunches from laser wakefield accelerator with orthogonally polarized perpendicularly crossed laser pulses (United States)

    Horný, Vojtěch; Petržílka, Václav; Klimo, Ondřej; Krůs, Miroslav


    Electron acceleration with optical injection by a perpendicularly propagating and orthogonally polarized low intensity laser pulse into a nonlinear plasma wave driven by a short intense laser pulse was explored by particle- in-cell simulations. The scheme presented here provides an energetic electron bunch in the first ion cavity with a low energy spread. The electron bunch short and compact, with the mean energy about 400 MeV and a low energy spread about 10 MeV in time of 6 ps of acceleration. The injected charge is several tens of pC for the low intensity of the injection pulse. Initial positions of electrons forming the energetic bunch are shown and then these electrons are followed during the simulation in order to understand the injection process and determine electron bunch properties.

  12. REVIEW ARTICLE: Spatio-temporal couplings in ultrashort laser pulses (United States)

    Akturk, Selcuk; Gu, Xun; Bowlan, Pamela; Trebino, Rick


    The electric field of an ultrashort laser pulse often fails to separate into a product of purely temporal and purely spatial factors. These so-called spatio-temporal couplings constitute a broad range of physical effects, which often become important in applications. In this review, we compile some recent experimental and theoretical work on the understanding, avoidance and applications of these effects. We first present a discussion of the characteristics of pulses containing spatio-temporal couplings, including their sources, a mathematical description and the interdependence of different couplings. We then review different experimental methods for their characterization. Finally, we describe different applications of spatio-temporal couplings and suggest further schemes for their exploitation and avoidance.

  13. Short intense laser pulse collapse in near-critical plasma. (United States)

    Sylla, F; Flacco, A; Kahaly, S; Veltcheva, M; Lifschitz, A; Malka, V; d'Humières, E; Andriyash, I; Tikhonchuk, V


    It is observed that the interaction of an intense ultrashort laser pulse with a near-critical gas jet results in the pulse collapse and the deposition of a significant fraction of the energy. This deposition happens in a small and well-localized volume in the rising part of the gas jet, where the electrons are efficiently accelerated and heated. A collisionless plasma expansion over ~ 150 μm at a subrelativistic velocity (~ c/3) has been optically monitored in time and space, and attributed to the quasistatic field ionization of the gas associated with the hot electron current. Numerical simulations in good agreement with the observations suggest the acceleration in the collapse region of relativistic electrons, along with the excitation of a sizable magnetic dipole that sustains the electron current over several picoseconds.

  14. Production of color centers in PMMA by ultrashort laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Elgul Samad, Ricardo, E-mail: [Instituto de Pesquisas Energeticas e Nucleares, IPEN-CNEN/SP, Av. Prof. Lineu Prestes 2242, Cidade universitaria 05508-000, Sao Paulo, SP (Brazil); Coronato Courrol, Lilia [Departamento de Ciencias Exatas e da Terra, UNIFESP, Diadema, SP (Brazil); Benevolo Lugao, Ademar; Zanardi Freitas, Anderson de; Dias Vieira, Nilson [Instituto de Pesquisas Energeticas e Nucleares, IPEN-CNEN/SP, Av. Prof. Lineu Prestes 2242, Cidade universitaria 05508-000, Sao Paulo, SP (Brazil)


    We report here the creation of color centers in commercial, transparent PMMA samples by ultrashort pulses from a Ti:Sapphire laser emitting at 800 nm, with spatial control. Although the 800 nm photon energy is not sufficient to ionize the polymer, the centers are created following a multiphotonic absorption that causes the ionization. We propose that the free electrons quivering motion on the pulse electric field displaces atoms from its equilibrium positions, creating free radicals and double bonds that coalesce into color centers. The absorption and emission spectra of the centers were measured, but a dose-like curve could not be built due to the presence of damages created along with the centers that scatter the excitation and emission lights due to the commercial sample's poor optical quality.

  15. Robust Short-Pulse, High-Peak-Power Laser Transmitter for Optical Communications (United States)

    Wright, Malcolm W.


    We report on a pulsed fiber based master oscillator power amplifier laser at 1550 nm to support moderate data rates with high peak powers in a compact package suitable for interplanetary optical communications. To accommodate pulse position modulation, the polarization maintaining laser transmitter generates pulses from 0.1 to 1 ns with variable duty cycle over a pulse repetition frequency range of 10 to 100 MHz.

  16. Formation of hexagonal-wurtzite germanium by pulsed laser ablation (United States)

    Zhang, Y.; Iqbal, Z.; Vijayalakshmi, S.; Qadri, S.; Grebel, H.


    A stable phase of relatively large hexagonal-wurtzite germanium (lonsdaleite) crystals (up to 10 μm) was formed when germanium was directly deposited at low pressure using pulsed ultraviolet laser ablation. Films were grown on various substrates at room temperature from a single crystal, cubic germanium target. Crystallites of the hexagonal-wurtzite phase of germanium were clearly identified using selected area electron diffraction. Further characterizations of the films were made using X-ray diffraction and confocal scanning micro-Raman spectroscopy.

  17. Frequency doubling of ultrashort laser pulses in biological tissues

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Beop-Min [Medical Technology Program, Lawrence Livermore National Laboratory, 7000 East Avenue L-399, Livermore, California 94550 (United States); Eichler, Juergen [Technische Fachhochschule Berlin, University of Applied Sciences, Seestrasse 63, 13347 Berlin, (Germany); Da Silva, Luiz B. [Medical Technology Program, Lawrence Livermore National Laboratory, 7000 East Avenue L-399, Livermore, California 94550 (United States)


    Theoretical and experimental studies of second-harmonic generation (SHG) in biological tissues was performed by use of ultrashort laser pulses (<1 ps). A simplified one-dimensional model for the generation and the propagation of frequency-doubled light inside tissue was developed. This model was tested in vitro against measurements of pig and chicken tissue and human tooth. The experimental results indicate that the intensity of SHG varies significantly among tissues types and between test sites in individual tissue. Possibilities of using this nonlinear tissue property in imaging and diagnostics are discussed. (c) 1999 Optical Society of America.

  18. Metallic Light Absorbers Produced by Femtosecond Laser Pulses

    Directory of Open Access Journals (Sweden)

    Anatoliy Y. Vorobyev


    Full Text Available Using high-intensity femtosecond laser pulses for surface structuring, technologically important metallic light absorbers (dark Au, W, and Ti alloy with absorption of about 85–95% over a broad wavelength range from ultraviolet to infrared were produced. It was found that the enhanced absorption of the dark metals is caused by a rich variety of nano-/microscale surface structures. The dark metals produced in this study may find a variety of applications in the fields of renewable energy and energy efficiency, such as thermophotovoltaics, solar energy absorbers, thermal radiation sources, and radiative heat transfer devices.

  19. Ultrashort-pulse laser excitation and damage of dielectric materials

    DEFF Research Database (Denmark)

    Haahr-Lillevang, Lasse; Balling, Peter


    Ultrashort-pulse laser excitation of dielectrics is an intricate problem due to the strong coupling between the rapidly changing material properties and the light. In the present paper, details of a model based on a multiple-rate-equation description of the conduction band are provided. The model...... is verified by comparison with recent experimental measurements of the transient optical properties in combination with ablation-depth determinations. The excitation process from the first creation of conduction-band electrons at low intensities to the formation of a highly-excited plasma and associated...

  20. Experimental investigations and statistical analysis of pulsed laser bending of AISI 304 stainless steel sheet (United States)

    Maji, Kuntal; Pratihar, D. K.; Nath, A. K.


    This paper presents experimental investigations on pulsed laser bending of sheet metal and statistical analysis to study the effects of process parameters. Laser power, scan speed, spot diameter and pulsed duration were taken as input variables and bending angle was considered as the output. Response surface methodology was used for modeling and optimization of the pulsed laser bending process. The performance of the developed model was validated through the experiments. All the input variables were found to have significant influence on the bending angle. Bending angle increased with the increase of laser power and pulse duration and decreased with the increase of scan speed and spot diameter. The optimum process parameters for the maximum bending angle were also found and verified with experimental data. The effects of pulse frequency, pulse width and pulse energy on bending angle were also investigated through experiments. Bending angle was found to be the maximum for a certain value of pulse frequency. With the increase of pulse width, bending angle increased at constant laser power but decreased at constant pulse energy. Bending angle was seen to increase with the increase of spatial overlapping and decrease with the increase of gap at constant laser power, but it showed optimal values for both the cases at constant line energy. A comparative study between continuous and pulsed laser bending was carried out to study the process efficiency in terms of energy input and produced deformation.

  1. Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers (United States)

    Yao, B. C.; Rao, Y. J.; Wang, Z. N.; Wu, Y.; Zhou, J. H.; Wu, H.; Fan, M. Q.; Cao, X. L.; Zhang, W. L.; Chen, Y. F.; Li, Y. R.; Churkin, D.; Turitsyn, S.; Wong, C. W.


    Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses.

  2. Bioactive glass thin films synthesized by advanced pulsed laser techniques (United States)

    Mihailescu, N.; Stan, George E.; Ristoscu, C.; Sopronyi, M.; Mihailescu, Ion N.


    Bioactive materials play an increasingly important role in the biomaterials industry, and are extensively used in a range of applications, including biodegradable metallic implants. We report on Bioactive Glasses (BG) films deposition by pulsed laser techniques onto biodegradable substrates. The BG coatings were obtained using a KrF* excimer laser source (λ= 248 nm, τFWHM ≤ 25 ns).Their thickness has been determined by Profilometry measurements, whilst their morphology has been analysed by Scanning Electron Microscopy (SEM). The obtained coatings fairly preserved the targets composition and structure, as revealed by Energy Dispersive X-Ray Spectroscopy, Grazing Incidence X-Ray Diffraction, and Fourier Transform Infra-Red Spectroscopy analyses.

  3. History and current status of commercial pulsed laser deposition equipment (United States)

    Greer, James A.


    This paper will review the history of the scale-up of the pulsed laser deposition (PLD) process from small areas ∼1 cm2 up to 10 m2 starting in about 1987. It also documents the history of commercialization of PLD as various companies become involved in selling fully integrated laser deposition tools starting in 1989. The paper will highlight the current state of the art of commercial PLD equipment for R&D that is available on the market today from mainstream vendors as well as production-oriented applications directed at piezo-electric materials for microelectromechanical systems and high-temperature superconductors for coated-conductor applications. The paper clearly demonstrates that considerable improvements have been made to scaling this unique physical vapour deposition process to useful substrate sizes, and that commercial deposition equipment is readily available from a variety of vendors to address a wide variety of technologically important thin-film applications.

  4. Growth modes of pentacene films obtained by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wisz, G., E-mail: [Institute of Physics, University of Rzeszow, Rejtana 16a, 35-309 Rzeszow (Poland); Kuzma, M.; Virt, I.; Sagan, P. [Institute of Physics, University of Rzeszow, Rejtana 16a, 35-309 Rzeszow (Poland); Rudyj, I. [Lviv University of Technology, Bandery 12, 90-646 Lviv (Ukraine)


    Thin pentacene films were deposited on KCl and ITO/glass substrates by the pulsed laser deposition method (PLD) using a YAG:Nd{sup 3+} laser with a second harmonic ({lambda} = 532 nm). We compared the structure of the layer on differently oriented substrates with respect to the pentacene plasma plume - vertical and parallel orientation. The structure of the layers formed was examined using SEM, RHEED and THEED methods. The lattice parameters of the layer deposited on KCl were determined from THEED pattern (a = 5.928 A, b 7.874 A, c = 14,98 A, {alpha} = 76.54{sup o}, {beta} 75.17{sup o}, {gamma} = 89.20{sup o}). The preferred direction [11-bar 0] of the layer growth on KCl substrate was addressed. The effect of the substrate orientation results in a different growth mode of the layers.

  5. Bulk diamond optical waveguides fabricated by focused femtosecond laser pulses (United States)

    Hadden, J. P.; Sotillo, Belén.; Bharadwaj, Vibhav; Rampini, Stefano; Bosia, Federico; Picollo, Federico; Sakakura, Masaaki; Chiappini, Andrea; Fernandez, Toney T.; Osellame, Roberto; Miura, Kiyotaka; Ferrari, Maurizio; Ramponi, Roberta; Olivero, Paolo; Barclay, Paul E.; Eaton, Shane M.


    Diamond's nitrogen-vacancy (NV) centers show great promise in sensing applications and quantum computing due to their long electron spin coherence time and their ability to be located, manipulated and read out using light. The electrons of the NV center, largely localized at the vacancy site, combine to form a spin triplet, which can be polarized with 532- nm laser light, even at room temperature. The NV's states are isolated from environmental perturbations making their spin coherence comparable to trapped ions. An important breakthrough would be in connecting, using waveguides, multiple diamond NVs together optically. However, the inertness of diamond is a significant hurdle for the fabrication of integrated optics similar to those that revolutionized silicon photonics. In this work we show the possibility of buried waveguide fabrication in diamond, enabled by focused femtosecond high repetition rate laser pulses. We use μRaman spectroscopy to gain better insight into the structure and refractive index profile of the optical waveguides.

  6. Modeling laser pulse evolution in ionizing gas and plasma with application to laser wakefield acceleration (United States)

    Cooley, James Hamilton

    The interaction of high intensity laser pulses with matter is of current research interest not only for potential applications but also due to the interesting non-linear process that can occur with current experimental facilities. Understanding many of the non-linear processes requires significant modeling and simulation effort. We explore several aspects of laser pulse evolution and plasma response in simulations ranging from modeling laser wakefield accelerators to modeling basic ionization processes. First, we present a model that describes the onset and growth of axial modulation found experimentally during the formation of plasma channels formed using an axicon lens. We provide a systematic development that describes this new type of parametric instability and explains the pressure dependence and the mechanism for formation of these axial modulations in the channel. Next, we describe details of a new three-dimensional laser pulse evolution code that we have developed to model propagation in tenuous gas and plasma and we provide relevant information about the validation and testing of the code. We then use this new code to examine the three-dimensional structure of the laser pulse evolving in the presence of ionizing gas. In particular we present results from the first three-dimensional study of the ionization scattering instability. Finally, we examine injecting electrons into laser wakefield accelerators. We examine in detail the injection and trapping characteristics for an electron beam with an initially broad energy distribution and look at the effect of beam loading on the trapping efficiency. We present estimates for the maximum charge that can be trapped from a low energy beam with a Boltzmann type energy distribution.

  7. Fast Micromachining Using Spatial Light Modulator and Galvanometer Scanner with Infrared Pulsed Nanosecond Fiber Laser

    National Research Council Canada - National Science Library

    Jarno J J Kaakkunen; Ilkka Vanttaja; Petri Laakso


    ...) and a galvanometer scanner with an infrared nanosecond fiber lasers is studied. Here, the SLM is used as a computer generated hologram which can be applied to modify laser pulses intensity distribution virtually almost arbitrary...

  8. Reliability of High Power Laser Diode Arrays Operating in Long Pulse Mode (United States)

    Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.; Baker, Nathaniel R.


    Reliability and lifetime of quasi-CW laser diode arrays are greatly influenced by their thermal characteristics. This paper examines the thermal properties of laser diode arrays operating in long pulse duration regime.

  9. An informal teaching of light and lasers through the CSIR-NLC PULSE programme

    CSIR Research Space (South Africa)

    Shikwambana, L


    Full Text Available The PULSE programme of the CSIR relates to the public understanding of laser science and engineering and the awareness of laser science and engineering to schools and tertiary institutions....

  10. Noncollinear SHG with compensation of phase mismatch by controlling frequency chirp and tilted pulse fronts of femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Aoyama, Makoto; Nakano, Fumihiko; Akahane, Yutaka; Yamakawa, Koichi [Japan Atomic Energy Research Inst., Kizu, Kyoto (Japan). Kansai Research Establishment; Harimoto, Tetsuo [Yamanashi Univ., Faculty of Engineering, Yamanashi (Japan)


    In order to achieve efficient second-harmonic generation with femtosecond laser pulses, we studied noncollinear second-harmonic generation with tilted pulse fronts and a suitable frequency chirp of fundamental pulses. We discussed the compensation of a phase-mismatch by controlling the frequency chirp of fundamental pulses and an improvement of the energy conversion efficiency using our method. When the energy conversion efficiency was less than 0.4% under a phase-mismatch condition, we experimentally obtained a 30% energy conversion efficiency with a proper frequency chirp of fundamental pulses. (author)

  11. Treatment of rosacea with long-pulsed Nd: YAG laser

    Directory of Open Access Journals (Sweden)

    Ekin Meşe Say


    Full Text Available Background and Design: Rosacea is a chronic inflammatory disorder of the face. There is no curative treatment for the disease. Facial flushing and vascular lesions due to rosacea may significantly affect a patient’s quality of life. Topical and oral antibiotics are not effective for treating rosacea. Currently, laser treatment of vascular lesions has been reported in the literature. We aimed to investigate the efficacy of long-pulse 1064-nm neodymium: YAG (Nd: YAG laser in the treatment of vascular lesions (erythema and telangiectasia in rosacea patients. Materials and Methods: Thirty-nine patients (29 women, 10 men with erythematotelangiectatic rosacea (ETR were recruited into the study. Severity of the disease (ETR-score: 0-3 was assessed for all patients. We used long-pulsed Nd: YAG laser for vascular lesions at 3-4 weeks intervals. The face was divided into seven anatomic regions for evaluation. Assessment was made by comparing pretreatment and posttreatment photographs by using ETR-scores. For evaluating patient satisfaction, a scale of 0 to 3 was used. Results: The patients were divided into three groups according to the ETR scores [ETR-1 (n=12, ETR-2 (n=9, ETR-3 (n=18]. Following an average of 3.95 (2-8 sessions laser treatments, the clinical improvement was statistically significant in all groups (p<0.05. The mean reduction of ETR-score was 91.70% in patients with ETR-1 and. the clinical improvement was to be decreased in severe forms of ETR. The most common sites for the lesions were the malar region, ala nasi and the nasal dorsum, respectively. The lesions on the ala nasi were more recalcitrant to the treatment than those on the other areas. Regarding to physician assessment of treatment’s success, 97% of the patients was associated with moderate and excellent improvement. According to physicians’ assessment, excellent improvement was noticed in 43.58% and, 61.5% of patients reported a high degree of satisfaction with this

  12. Broadband and high power terahertz pulse generation beyond excitation bandwidth limitation via chi2 cascaded processes in LiNbO3. (United States)

    Nagai, Masaya; Jewariya, Mukesh; Ichikawa, Yuki; Ohtake, Hideyuki; Sugiura, Toshiharu; Uehara, Yuzuru; Tanaka, Koichiro


    We proposed a novel THz generation technique beyond the limitation of the input optical pulse width, based on phase modulation via cascaded chi((2)) process. When intense THz electric field generated by optical rectification lies in electro-optic (EO) crystal, emitted THz field gives phase modulation to the optical excitation pulse. The phase modulation causes excitation pulse narrowing and consequently gives rise to the enhancement of conversion efficiency and THz wave bandwidth broadening. We experimentally realize this generation technique with high chi((2)) EO crystal LiNbO(3) and with subpicosecond pulse from Yb-doped fiber laser. It opens new concept of THz technologies.

  13. Computational design of short pulse laser driven iron opacity experiments (United States)

    Martin, M. E.; London, R. A.; Goluoglu, S.; Whitley, H. D.


    The resolution of current disagreements between solar parameters calculated from models and observations would benefit from the experimental validation of theoretical opacity models. Iron's complex ionic structure and large contribution to the opacity in the radiative zone of the sun make iron a good candidate for validation. Short pulse lasers can be used to heat buried layer targets to plasma conditions comparable to the radiative zone of the sun, and the frequency dependent opacity can be inferred from the target's measured x-ray emission. Target and laser parameters must be optimized to reach specific plasma conditions and meet x-ray emission requirements. The HYDRA radiation hydrodynamics code is used to investigate the effects of modifying laser irradiance and target dimensions on the plasma conditions, x-ray emission, and inferred opacity of iron and iron-magnesium buried layer targets. It was determined that plasma conditions are dominantly controlled by the laser energy and the tamper thickness. The accuracy of the inferred opacity is sensitive to tamper emission and optical depth effects. Experiments at conditions relevant to the radiative zone of the sun would investigate the validity of opacity theories important to resolving disagreements between solar parameters calculated from models and observations.

  14. Impact of pulse duration on Ho:YAG laser lithotripsy: fragmentation and dusting performance. (United States)

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


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

  15. The effect of laser contrast on generation of highly charged Fe ions by ultra-intense femtosecond laser pulses (United States)

    Faenov, Anatoly Ya.; Alkhimova, Maria A.; Pikuz, Tatiana A.; Skobelev, Igor Yu.; Nishiuchi, Mamiko; Sakaki, Hironao; Pirozhkov, Alexander S.; Sagisaka, Akito; Dover, Nicholas P.; Kondo, Kotaro; Ogura, Koichi; Fukuda, Yuji; Kiriyama, Hiromitsu; Andreev, Alexander; Nishitani, Keita; Miyahara, Takumi; Watanabe, Yukinobu; Pikuz, Sergey A.; Kando, Masaki; Kodama, Ruosuke; Kondo, Kiminori


    Experimental studies on the formation of highly charged ions of medium-Z elements using femtosecond laser pulses with different contrast levels were carried out. Multiply charged Fe ions were generated by laser pulses with 35 fs duration and an intensity exceeding 1021 W/cm2. Using high-resolution X-ray spectroscopic methods, bulk electron temperature of the generated plasma has been identified. It is shown that the presence of a laser pre-pulse at a contrast level of 105-106 with respect to the main pulse drastically decreases the degree of Fe ionization. We conclude that an effective source of energetic, multiply charged moderate and high- Z ions based on femtosecond laser-plasma interactions can be created only using laser pulses of ultra-high contrast.

  16. Clinical laser angioplasty with a pulsed neodymium:YAG laser: long-term followup (United States)

    Lawrence, Roy N.; Michaels, Jonathan A.; Cross, Frank W.; Raphael, Michael; Adiseshiah, M.; Marston, A.


    Since December 1986, 140 laser angioplasty procedures have been carried out using a pulsed Nd:YAG laser (Lumonics Ltd. Rugby, UK). The laser produces 100 microsecond(s) ec pulses at a wavelength of 1064 nm and a repetition rate of 10 Hz. All procedures were carried out for critical ischaemia or severe claudication in patients who had complete occlusion of the superficial femoral artery (SFA). All occlusions were over 5 cm in length or previous failures of balloon angioplasty and would otherwise have proceeded to bypass surgery. The occlusion was approached percutaneously via the ipsilateral femoral artery and successful recanalization was followed by balloon dilatation. Problems with access were encountered in 18% of the procedures, about half of which were subsequently repeated with successful access. There was failure of recanalization in 26% of the cases, five due to vessel perforation. These did not result in clinical sequelae. Early occlusion (procedure (range 3 - 47 months). Of the 19 patients who reoccluded, (mean 12.1 months, range 1 - 26 months), seven had bypass grafts, three underwent amputation (all three presented with rest pain), two had repeat laser procedures, and seven were treated conservatively. Thirteen percent of the patients have died, chiefly from cardiovascular disease elsewhere. Overall, continued patency has been achieved in 32% of limbs considered for laser treatment, but this rises to 60% of all initially successful procedures. In conclusion, laser angioplasty may avoid the need for vascular surgery in a significant number of patients.



    D. S. Ivanov; V. P. Veiko; Y. B. Yakovlev; M. E. Carcia; Rethfeld, B.


    The process of laser ablation under the influence of ultra short laser pulses on metals is investigated by methods of molecular dynamics. The validity and applicability of the hybrid atomistic-continuous model for the estimation of optimum modes of ultra short laser pulses processing are explored. Combination of atomistic model of laser-induced non-equilibrium process of a phase transition at the atomic level with continuous two-temperature model for describing the dynamics of photo-excitatio...

  18. Effects of Beam Size and Pulse Duration on the Laser Drilling Process

    CERN Document Server

    Afrin, Nazia; Chen, J K; Zhang, Yuwen


    A two-dimensional axisymmetric transient laser drilling model is used to analyze the effects of laser beam diameter and laser pulse duration on the laser drilling process. The model includes conduction and convection heat transfer, melting, solidification and vaporization, as well as material removal resulting from the vaporization and melt ejection. The validated model is applied to study the effects of laser beam size and pulse duration on the geometry of the drilled hole. It is found that the ablation effect decrease with the increasing beam diameter due to the effect of increased vaporization rate, and deeper hole is observed for the larger pulse width due to the higher thermal ablation efficiency.

  19. Shadowgraphic imaging of metal drilling with a long pulse excimer laser

    NARCIS (Netherlands)

    Schoonderbeek, A.; Biesheuvel, C.A.; Hofstra, R.M.; Boller, Klaus J.; Meijer, J.; Miyamoto, Isamu; Ostendorf, Andreas; Sugioka, Koji; Helvajian, Henry


    A shadowgraphic imaging technique is used for studying the interaction between the laser beam and the material during laser drilling. The used laser is a XeCl excimer laser with a nearly diffraction limited beam and 175 ns pulse length. We studied how and when the material is removed. Holes are

  20. First-principles electron dynamics control simulation of diamond under femtosecond laser pulse train irradiation. (United States)

    Wang, Cong; Jiang, Lan; Wang, Feng; Li, Xin; Yuan, Yanping; Xiao, Hai; Tsai, Hai-Lung; Lu, Yongfeng


    A real-time and real-space time-dependent density functional is applied to simulate the nonlinear electron-photon interactions during shaped femtosecond laser pulse train ablation of diamond. Effects of the key pulse train parameters such as the pulse separation, spatial/temporal pulse energy distribution and pulse number per train on the electron excitation and energy absorption are discussed. The calculations show that photon-electron interactions and transient localized electron dynamics can be controlled including photon absorption, electron excitation, electron density, and free electron distribution by the ultrafast laser pulse train.

  1. Femtosecond KCl:Li and RbCl:Li color-center lasers near 2.8 microm with a HgCdTe multiple-quantum-well saturable absorber. (United States)

    Cesar, C L; Islam, M N; Soccolich, C E; Feldman, R D; Austin, R F; German, K R


    We have used HgCdTe multiple-quantum-well saturable absorbers to passively mode lock KCl:Li and RbCl:Li color-center lasers and have generated pedestal-free pulses as short as 120 fsec near 2.8 microm. To our knowledge, these are the shortest pulses in this wavelength range, and our laser is the only direct source of subpicosecond pulses in the mid-infrared region. Our results generalize the semiconductor passive mode-locking technique to different wavelength ranges, saturable absorber materials, and laser systems and are consistent with a model in which LO phonon collisions determine the fast saturable absorber behavior.

  2. Effect of pressure relaxation during the laser heating and electron-ion relaxation stages

    Energy Technology Data Exchange (ETDEWEB)

    Chimier, B.; Tikhonchuk, V.T.; Hallo, L. [Univ Bordeaux 1, CEA, CNRS, CELIA, UMR 5107, 33 - Talence (France)


    The multi-phase equation of state by Bushman et al. (Sov. Tech. Rev. 5:1-44, 2008) is modified to describe states with different electron and ion temperatures and it is applied to the non-equilibrium evolution of an aluminum sample heated by a subpicosecond laser pulse. The sample evolution is described by the two-temperature model for the electron and ion temperatures, while the pressure and density are described by a simplified relaxation equation. The pressure relaxation in the heating stage reduces the binding energy and facilitates the electron-driven ablation. The model is applied to estimate the ablation depth of an Al target irradiated by a subpicosecond laser pulse. It improves the agreement with the experimental data and provides a new explanation of the ablation process. (authors)

  3. Temporal structure of X-ray radiation pulses of picosecond laser plasma

    Energy Technology Data Exchange (ETDEWEB)

    Belyaev, V S; Kovkov, D V; Matafonov, A P; Karabadzhak, G F; Raikunov, G G [Central Research Institute of Machine Building, Korolev, Moscow region (Russian Federation); Faenov, A Ya; Pikuz, S A; Skobelev, I Yu; Pikuz, T A; Fokin, D A; Fortov, V E [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Ignat' ev, G N; Kapitanov, S V; Krapiva, P S; Korotkov, K E [All-Russian Institute of Automatics, Moscow (Russian Federation)


    The shape of the X-ray pulse generated by picosecond laser plasma is experimentally studied. The unusual phenomenon was experimentally observed for the first time for targets made of moderate-heavy chemical elements, namely, the pulse of hard X-ray radiation generated by laser plasma at the laser radiation flux of ∼10{sup 18} W cm{sup -2} had a longer duration than the pulse of softer X-ray radiation. A simple kinetic model is suggested for explaining this fact. We have suggested a method for controlling the temporal shape of X-ray pulse emitted by laser plasma by varying the contrast of laser pulse. (interaction of laser radiation with matter)

  4. Novel doped hydroxyapatite thin films obtained by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Duta, L. [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, 409 Atomistilor Street, Magurele (Romania); Oktar, F.N. [Department of Bioengineering, Faculty of Engineering, Marmara University, Goztepe, Istanbul 34722 (Turkey); Department of Medical Imaging Technics, Vocational School of Health Services, Marmara University, Uskudar, Istanbul 34668 (Turkey); Nanotechnology and Biomaterials Application and Research Centre, Marmara University, Istanbul (Turkey); Stan, G.E. [National Institute of Materials Physics, 105 Bis Atomistilor Street, Magurele (Romania); Popescu-Pelin, G.; Serban, N.; Luculescu, C. [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, 409 Atomistilor Street, Magurele (Romania); Mihailescu, I.N., E-mail: [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, 409 Atomistilor Street, Magurele (Romania)


    Highlights: Black-Right-Pointing-Pointer HA coatings synthesized by pulsed laser deposition. Black-Right-Pointing-Pointer Comparative study of commercial vs. animal origin materials. Black-Right-Pointing-Pointer HA coatings of animal origin were rougher and more adherent to substrates. Black-Right-Pointing-Pointer Animal origin films can be considered as promising candidates for implant coatings. - Abstract: We report on the synthesis of novel ovine and bovine derived hydroxyapatite thin films on titanium substrates by pulsed laser deposition for a new generation of implants. The calcination treatment applied to produce the hydroxyapatite powders from ovine/bovine bones was intended to induce crystallization and to prohibit the transmission of diseases. The deposited films were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy. Pull-off adherence and profilometry measurements were also carried out. X-ray diffraction ascertained the polycrystalline hydroxyapatite nature of the powders and films. Fourier transform infrared spectroscopy evidenced the vibrational bands characteristic to a hydroxyapatite material slightly carbonated. The micrographs of the films showed a uniform distribution of spheroidal particulates with a mean diameter of {approx}2 {mu}m. Pull-off measurements demonstrated excellent bonding strength values between the hydroxyapatite films and the titanium substrates. Because of their physical-chemical properties and low cost fabrication from renewable resources, we think that these new coating materials could be considered as a prospective competitor to synthetic hydroxyapatite used for implantology applications.

  5. Single and double long pulse laser ablation of aluminum induced in air and water ambient

    Energy Technology Data Exchange (ETDEWEB)

    Akbari Jafarabadi, Marzieh; Mahdieh, Mohammad Hossein, E-mail:


    Highlights: • Laser ablation of aluminum target by single and double pulse (∼ 5 ns delay) in ambient air and distilled water • Comparing with air, in ambient water, plasma confinement results in higher crater depth. • In comparison with single pulse laser ablation, the absorption of the laser pulse energy is higher for double pulse regime. • As a result of ablated material expansion, the crater depth is decreased if the target is placed at lower depth. - Abstract: In this paper, single pulse and double pulse laser ablation of an aluminum target in two interaction ambient was investigated experimentally. The interaction was performed by nanosecond Nd:YAG laser beam in air and four depths (i.e. 9, 13, 17, and 21 mm) of distilled water ambient. The irradiation was carried out in single and collinear double pulse configurations in both air and liquid ambient. Crater geometry (depth and diameter) was measured by an optical microscope. The results indicated that the crater geometry strongly depends on both single pulse and double pulse configurations and interaction ambient. In single pulse regime, the crater diameter is higher for all water depths compared to that of air. However, the crater depth, depend on water depth, is higher or lower than the crater depth in air. In double pulse laser ablation, there are greater values for both crater diameters and crater depths in the water.

  6. Ablation experiment and threshold calculation of titanium alloy irradiated by ultra-fast pulse laser

    Directory of Open Access Journals (Sweden)

    Buxiang Zheng


    Full Text Available The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology and feature sizes, including ablation crater width (i.e. diameter, ablation depth, ablation area, ablation volume, single pulse ablation rate, and so forth, of the titanium alloy were studied, and their ablation distributions were obtained. The experimental results show that titanium alloy irradiated by a picosecond pulse infrared laser with a 1064 nm wavelength has better ablation morphology than that of the green picosecond pulse laser with a 532 nm wavelength. The feature sizes are approximately linearly dependent on the laser pulse energy density at low energy density and the monotonic increase in laser pulse energy density. With the increase in energy density, the ablation feature sizes are increased. The rate of increase in the feature sizes slows down gradually once the energy density reaches a certain value, and gradually saturated trends occur at a relatively high energy density. Based on the linear relation between the laser pulse energy density and the crater area of the titanium alloy surface, and the Gaussian distribution of the laser intensity on the cross section, the ablation threshold of titanium alloy irradiated by an ultra-fast pulse laser was calculated to be about 0.109 J/cm2.

  7. Sub-picosecond dynamics in liquid Si

    Energy Technology Data Exchange (ETDEWEB)

    Hosokawa, S [Institut fuer Physikalische-, Kern-, und Makromolekulare Chemie, Philipps Universitaet Marburg, D-35032 Marburg (Germany); Pilgrim, W-C [Institut fuer Physikalische-, Kern-, und Makromolekulare Chemie, Philipps Universitaet Marburg, D-35032 Marburg (Germany); Kawakita, Y [Department of Physics, Faculty of Sciences, Kyushu University, Fukuoka 810-8560 (Japan); Ohshima, K [Department of Physics, Faculty of Sciences, Kyushu University, Fukuoka 810-8560 (Japan); Takeda, S [Department of Physics, Faculty of Sciences, Kyushu University, Fukuoka 810-8560 (Japan); Ishikawa, D [SPring-8, Hyogo 679-5198 (Japan); Tsutsui, S [SPring-8, Hyogo 679-5198 (Japan); Tanaka, Y [SPring-8, Hyogo 679-5198 (Japan); Baron, A Q R [SPring-8, Hyogo 679-5198 (Japan)


    We are the first group to succeed in measuring the dynamic structure factor S(Q,{omega}) of liquid Si close to melting using high-resolution inelastic x-ray scattering. The spectra clearly demonstrate the existence of propagating short wavelength modes in the melt with a Q-{omega} relation similar to those in other liquid metal systems. A specific variation of the quasi-elastic line shape with increasing Q is observed close to the structure factor maximum. This observation is related to the onset of atomic correlations on the sub-picosecond timescale in the vicinity of a metal-to-insulator transition. Such observations have been made previously only in computer simulations of metallic systems with increasing covalent character. Our data provide the first experimental evidence for these ultrashort density correlations. (letter to the editor)

  8. Comparison of 2 pulsed lasers for lithotripsy of ureteral calculi: report on 154 patients. (United States)

    Benizri, E; Wodey, J; Amiel, J; Toubol, J


    Extracorporeal lithotripsy does not always provide satisfactory results for the treatment of ureteral stones. Such cases appear to be excellent indications for endocorporeal lithotripsy based on an association of ureteroscopy and laser. To compare the performances of 2 pulsed lasers, the pulsed dye laser (Candela) and solid Q switched laser (HMT), for the treatment of these calculi 161 ureteral stones were treated successively from November 1990 to March 1992 by a combination of ureteroscopy and laser. Endocorporeal lithotripsy was performed in 102 cases with the Candela laser, in 47 with the HMT laser and in 7 with both lasers. With a stable success rate greater than 90%, both lasers demonstrated equivalent performances regardless of the location of the stone along the ureter. However, while stone fragmentation was more rapid with the Candela laser, the HMT laser appeared to be more effective for dark stones (monohydrate calcium oxidate).

  9. Enhancement mechanism of femtosecond double-pulse laser-induced Cu plasma spectroscopy (United States)

    Zhang, Dan; Chen, Anmin; Wang, Xiaowei; Li, Suyu; Wang, Ying; Sui, Laizhi; Jiang, Yuanfei; Jin, Mingxing


    A dual-wavelength femtosecond double-pulse laser is used to induce the Cu plasma spectroscopy in air. The laser wavelengths are a fundamental wavelength (800 nm) and a second harmonic wavelength (400 nm) from Ti:sapphire laser. The inter-pulse delay of double-pulse is from -300 ps to 160 ps. The observed spectral intensity is dependent on the inter-pulse delay of the dual-wavelength femtosecond double-pulse. We analyze the characteristics of the plasma temperature and the electron number density on the inter-pulse delay of double-pulse with two different wavelengths. For 800 nm + 400 nm, the spectral emission enhancement is based on more material ablation. For 400 nm + 800 nm, the enhanced mechanism is plasma reheating effect. This study will provide a better way to understand the mechanism of femtosecond double-pulse LIBS.

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

    Directory of Open Access Journals (Sweden)

    Marco Hornung


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

  11. Laser Energy Monitor for Double-Pulsed 2-Micrometer IPDA Lidar Application (United States)

    Refaat, Tamer F.; Petros, Mulugeta; Remus, Ruben; Yu, Jirong; Singh, Upendra N.


    Integrated path differential absorption (IPDA) lidar is a remote sensing technique for monitoring different atmospheric species. The technique relies on wavelength differentiation between strong and weak absorbing features normalized to the transmitted energy. 2-micron double-pulsed IPDA lidar is best suited for atmospheric carbon dioxide measurements. In such case, the transmitter produces two successive laser pulses separated by short interval (200 microseconds), with low repetition rate (10Hz). Conventional laser energy monitors, based on thermal detectors, are suitable for low repetition rate single pulse lasers. Due to the short pulse interval in double-pulsed lasers, thermal energy monitors underestimate the total transmitted energy. This leads to measurement biases and errors in double-pulsed IPDA technique. The design and calibration of a 2-micron double-pulse laser energy monitor is presented. The design is based on a high-speed, extended range InGaAs pin quantum detectors suitable for separating the two pulse events. Pulse integration is applied for converting the detected pulse power into energy. Results are compared to a photo-electro-magnetic (PEM) detector for impulse response verification. Calibration included comparing the three detection technologies in single-pulsed mode, then comparing the pin and PEM detectors in double-pulsed mode. Energy monitor linearity will be addressed.

  12. Ultraviolet pulsed laser irradiation of multi-walled carbon nanotubes in nitrogen atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Pérez del Pino, Ángel, E-mail:; Cabana, Laura; Tobias, Gerard [Instituto de Ciencia de Materiales de Barcelona, Consejo Superior de Investigaciones Científicas (ICMAB-CSIC), Campus UAB, 08193 Bellaterra (Spain); György, Enikö [Instituto de Ciencia de Materiales de Barcelona, Consejo Superior de Investigaciones Científicas (ICMAB-CSIC), Campus UAB, 08193 Bellaterra (Spain); National Institute for Lasers, Plasma and Radiation Physics, P. O. Box MG 36, 76900 Bucharest V (Romania); Ballesteros, Belén [ICN2—Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra, Barcelona (Spain)


    Laser irradiation of randomly oriented multi-walled carbon nanotube (MWCNT) networks has been carried out using a pulsed Nd:YAG UV laser in nitrogen gas environment. The evolution of the MWCNT morphology and structure as a function of laser fluence and number of accumulated laser pulses has been studied using electron microscopies and Raman spectroscopy. The observed changes are discussed and correlated with thermal simulations. The obtained results indicate that laser irradiation induces very fast, high temperature thermal cycles in MWCNTs which produce the formation of different nanocarbon forms, such as nanodiamonds. Premelting processes have been observed in localized sites by irradiation at low number of laser pulses and low fluence values. The accumulation of laser pulses and the increase in the fluence cause the full melting and amorphization of MWCNTs. The observed structural changes differ from that of conventional high temperature annealing treatments of MWCNTs.

  13. Infrared Pulse-laser Long-path Absorption Measurement of Carbon Dioxide Using a Raman-shifted Dye Laser (United States)

    Minato, Atsushi; Sugimoto, Nobuo; Sasano, Yasuhiro


    A pulsed laser source is effective in infrared laser long-path absorption measurements when the optical path length is very long or the reflection from a hard target is utilized, because higher signal-to-noise ratio is obtained in the detection of weak return signals. We have investigated the performance of a pulse-laser long-path absorption system using a hydrogen Raman shifter and a tunable dye laser pumped by a Nd:YAG laser, which generates second Stokes radiation in the 2-micron region.

  14. Femtosecond pulsed laser deposition of biological and biocompatible thin layers

    Energy Technology Data Exchange (ETDEWEB)

    Hopp, B. [Hungarian Academy of Sciences, University of Szeged, Research Group on Laser Physics, Dom ter 9, H-6720 Szeged (Hungary)]. E-mail:; Smausz, T. [Hungarian Academy of Sciences, University of Szeged, Research Group on Laser Physics, Dom ter 9, H-6720 Szeged (Hungary); Kecskemeti, G. [Department of Optics and Quantum Electronics, University of Szeged, Dom ter 9, H-6720 Szeged (Hungary); Klini, A. [Institute of Electronic Structure and Laser (I.E.S.L.), Foundation for Research and Technology-Hellas (F.O.R.T.H.), P.O. Box 1527, GR-711 10 Heraklion, Crete (Greece); Bor, Zs. [Department of Optics and Quantum Electronics, University of Szeged, Dom ter 9, H-6720 Szeged (Hungary)


    In our study we investigate and report the femtosecond pulsed laser deposition of biological and biocompatible materials. Teflon, polyhydroxybutyrate, polyglycolic-acid, pepsin and tooth in the form of pressed pellets were used as target materials. Thin layers were deposited using pulses from a femtosecond KrF excimer laser system (FWHM = 450 fs, {lambda} = 248 nm, f = 10 Hz) at different fluences: 0.6, 0.9, 1.6, 2.2, 2.8 and 3.5 J/cm{sup 2}, respectively. Potassium bromide were used as substrates for diagnostic measurements of the films on a FTIR spectrometer. The pressure in the PLD chamber was 1 x 10{sup -3} Pa, and in the case of tooth and Teflon the substrates were heated at 250 deg. C. Under the optimized conditions the chemical structure of the deposited materials seemed to be largely preserved as evidenced by the corresponding IR spectra. The polyglycolic-acid films showed new spectral features indicating considerable morphological changes during PLD. Surface structure and thickness of the layers deposited on Si substrates were examined by an atomic force microscopy (AFM) and a surface profilometer. An empirical model has been elaborated for the description of the femtosecond PLD process. According to this the laser photons are absorbed in the surface layer of target resulting in chemical dissociation of molecules. The fast decomposition causes explosion-like gas expansion generating recoil forces which can tear off and accelerate solid particles. These grains containing target molecules without any chemical damages are ejected from the target and deposited onto the substrate forming a thin layer.

  15. Laser dynamics of a mode-locked thulium/holmium fiber laser in the solitonic and the stretched pulse regimes (United States)

    Kadel, Rajesh

    Mode-locked lasers that produce short optical pulses in the mid-infrared wavelength region have been sought out for a wide range of applications such as free space communication, molecular spectroscopy, medical diagnostics, and remote sensing. Here, a thulium and holmium (Tm/Ho) co-doped fiber laser that mode-locks in both the solitonic and stretched-pulse regimes is used to produce ultra-short pulses in the 2 mum region. Nonlinear polarization rotation technique is used where fiber nonlinearity is responsible to mode-lock the laser. The anomalous group velocity dispersion of both the single mode and gain fibers used limit the laser operation in the solitonic regime where spectral bandwidth is 10 nm and hence the pulse duration is limited to 996 fs. In order to increase the spectral bandwidth and hence get the shorter pulses the anomalous dispersion of these fibers has to compensate using normal group velocity dispersion fiber in the laser cavity. High numerical aperture fibers, which have normal group velocity dispersion around 2 mum due to its large and positive waveguide dispersion, can be used to compensate the anomalous dispersion of the gain and single mode fibers. We used a high numerical aperture fiber called UHNA4 in the laser cavity in order to compensate the anomalous dispersion of other fibers and mode-locked the laser in stretched pulse regime. The spectral bandwidth of the laser increased to 31 nm with corresponding pulse duration of 450 fs measured from the interferometric autocorrelation. The laser dynamics of the Tm/Ho co-doped fiber laser is also studied while going from the stretched-pulse to solitonic regime by fiber cut-back measurements of normal dispersion fiber. It was clearly observed that both the spectral bandwidth and the pulse duration changed significantly going from one region to the other.

  16. Effects of laser wavelength and fluence on the growth of ZnO thin films by pulsed laser deposition

    NARCIS (Netherlands)

    Craciun, V.; Amirhaghi, S.; Craciun, D.; Elders, J.; Gardeniers, Johannes G.E.; Boyd, Ian W.

    Transparent, electrically conductive and c-axis oriented ZnO thin films have been grown by the pulsed laser deposition (PLD) technique on silicon and Corning glass substrates employing either a KrF excimer laser (λ = 248 nm) or a frequency-doubled Nd:YAG laser (λ = 532 nm). The crystalline

  17. Fluorescence imaging of lattice re-distribution on step-index direct laser written Nd:YAG waveguide lasers

    Energy Technology Data Exchange (ETDEWEB)

    Martínez de Mendívil, Jon; Pérez Delgado, Alberto; Lifante, Ginés; Jaque, Daniel [Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid 28049 (Spain); Ródenas, Airán [Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Tarragona 43007 (Spain); Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Benayas, Antonio, E-mail: [Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid 28049 (Spain); Institut National de la Recherche Scientifique, Centre – Énergie Matériaux et Télécommunications, 1650, Boul. Lionel Boulet Varennes, Quebec J3X 1S2 (Canada); Aguiló, Magdalena; Diaz, Francesc [Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Tarragona 43007 (Spain); Kar, Ajoy K. [Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)


    The laser performance and crystalline micro-structural properties of near-infrared step-index channel waveguides fabricated inside Neodymium doped YAG laser ceramics by means of three-dimensional sub-picosecond pulse laser direct writing are reported. Fluorescence micro-mapping of the waveguide cross-sections reveals that an essential crystal lattice re-distribution has been induced after short pulse irradiation. Such lattice re-distribution is evidenced at the waveguide core corresponding to the laser written refractive index increased volume. The waveguides core surroundings also present diverse changes including slight lattice disorder and bi-axial strain fields. The step-index waveguide laser performance is compared with previous laser fabricated waveguides with a stress-optic guiding mechanism in absence of laser induced lattice re-distribution.

  18. Measurement of weldpiece distortion during pulsed laser welding using rapid laser profilometry


    Gorkič, Aleš; Jezeršek, Matija; Možina, Janez; Diaci, Janez


    The present paper reports a new setup for acquisition of shape data for weldpieces during pulsed laser welding. The setup is based on illumination of the weldpiece surface by laser light, which is structured as multiple light planes, and acquisition of the image of the illuminated surface by a digital camera. The position of the optical system is fixed relative to the measured weldpiece. The acquired image is fed into a personal computer where it is processed to obtain the three-dimensional s...

  19. Laser Ion Acceleration from the Interaction of Ultra-Intense laser Pulse with thi foils

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Matthew Mark [Univ. of California, Berkeley, CA (United States)


    The discovery that ultra-intense laser pulses (I > 1018 W/cm2) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies > 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I > 1018 W/cm2), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by Up = ([1 + Iλ2/1.3 x 1018]1/2 - 1) moc2, where Iλ2 is the irradiance in Wμm2/cm2 and moc2 is the electron rest mass.At laser irradiance of Iλ2 ~ 1018 Wμm2/cm2, the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the front surface of the target to energies up to tens of MeV. Another model, known as Target Normal Sheath Acceleration (TNSA), describes the mechanism as an electrostatic sheath on the back surface of the laser target. According to the TNSA model, relativistic hot electrons created at the laser-solid interaction penetrate the foil where a few escape to infinity. The remaining hot electrons are retained by the target potential and establish an electrostatic sheath on the back surface of the target.

  20. Planar waveguide devices fabricated by pulsed laser deposition

    CERN Document Server

    Barrington, S J


    buried Nd:GGG waveguide laser has been fabricated for the first time by PLD and has achieved lasing action at a threshold of 14.8 mW of absorbed power. Comparison of the lasing threshold to that of similar uncapped devices demonstrate that the capped layer has a highly beneficial effect on the lasing threshold when the particulate density in the film is high. This thesis is intended to be a comprehensive study on using pulsed laser deposition to fabricate planar waveguide devices. As such a thorough review into the state of art of current activities in this area is initially presented. A versatile technique has been developed to efficiently and homogeneously heat substrates using a raster scanned CO sub 2 laser. Use of this device has virtually eliminated the occurrence of substrate fracture and has greatly reduced the turn-around time for depositions of crystalline films. The heating homogeneity achievable with this system is ultimately limited to speed at which it is able to scan the substrate. Growth of ph...

  1. Pulsed Laser Interactions with Space Debris: Target Shape Effects

    CERN Document Server

    Liedahl, D A; Libby, S B; Nikolaev, S; Phipps, C R


    Among the approaches to the proposed mitigation and remediation of the space debris problem is the de-orbiting of objects in low Earth orbit through irradiation by ground-based high-intensity pulsed lasers. Laser ablation of a thin surface layer causes target recoil, resulting in the depletion of orbital angular momentum and accelerated atmospheric re-entry. However, both the magnitude and direction of the recoil are shape dependent, a feature of the laser-based remediation concept that has received little attention. Since the development of a predictive capability is desirable, we have investigated the dynamical response to ablation of objects comprising a variety of shapes. We derive and demonstrate a simple analytical technique for calculating the ablation-driven transfer of linear momentum, emphasizing cases for which the recoil is not exclusively parallel to the incident beam. For the purposes of comparison and contrast, we examine one case of momentum transfer in the low-intensity regime, where photon p...

  2. Near-infrared laser-induced fluorescence detection in column liquid chromatography. A comparison of various lasers and detection systems. II*. Pulsed lasers.

    NARCIS (Netherlands)

    Mank, A.J.G.; Velthorst, N.H.; Brinkman, U.A.T.; Gooijer, C.


    The applicability of two pulsed lasers, a XeCl-excimer/dye laser and a Nd:YAG/dye laser combination, as excitation sources for near-infrared (NIR) laser-induced fluorescence (LIF) detection in column liquid chromatography (LC) is studied. Using gradient LC, the best detection limit for the model

  3. Laser-induced retinal damage threshold for repetitive-pulse exposure to 100-μs pulses (United States)

    Lund, Brian J.; Lund, David J.; Edsall, Peter R.; Gaines, Victor D.


    The laser-induced retinal injury thresholds for repetitive-pulse exposures to 100-μs-duration pulses at a wavelength of 532 nm have been determined for exposures of up to 1000 pulses in an in vivo model. The ED50 was measured for pulse repetition frequencies of 50 and 1000 Hz. Exposures to collimated beams producing a minimal retinal beam spot and to divergent beams producing a 100-μm-diameter retinal beam spot were considered. The ED50 for a 100-μs exposure was measured to be 12.8 μJ total intraocular energy for a minimal retinal beam spot exposure and 18.1 μJ total intraocular energy for a 100-μm-diameter retinal beam spot. The threshold for exposures to N>1 pulse was found to be the same for both pulse repetition frequencies. The variation of the ED50 with the number of pulses is described well by the probability summation model, in which each pulse is considered an independent event. This is consistent with a threshold-level damage mechanism of microcavitation for single-pulse 100-μs-duration exposures. The data support the maximum permissible exposure levels for repetitive-pulse exposure promulgated in the most recent laser safety guidelines.

  4. Effect of double-pulse-laser polarization and time delay on laser-assisted etching of fused silica (United States)

    Chu, Dongkai; Sun, Xiaoyan; Dong, Xinran; Yin, Kai; Luo, Zhi; Chen, Guowei; Duan, Ji-An; Hu, Youwang; Zhao, Xinyu


    High-aspect-ratio microchannels were fabricated by femtosecond-double-pulse-laser-assisted polarization-selective etching. The etching rate and uniformity of the microchannels were mainly determined by the double-pulse polarization and time delay. We found that when the two sub-pulses had a different polarization (one linear, the other circular), the microchannel etching rate increased by a factor of 10 compared to when both sub-pulses were linearly polarized. The maximum etching rate was obtained when the polarization combination was circular for the first sub-pulse and vertical for the second one. In this case, the etching rate was independent from the time delay. Laser confocal microscopy images showed that when the polarization was circular, the area modified by the laser was larger than when the polarization was linear, explaining the higher etching rate value obtained after irradiation with circularly polarized laser light.

  5. Stimulated Raman backscattering at high laser intensities

    Energy Technology Data Exchange (ETDEWEB)

    Skoric, M.M. [Vinca Inst. of Nuclear Sciences, Belgrade (Yugoslavia); Tajima, Toshiki; Sasaki, Akira; Maluckov, A.; Jovanovic, M.


    Signatures of Stimulated Raman backscattering of a short-pulse high-intensity laser interacting with an underdense plasma are discussed. We introduce a nonlinear three-wave interaction model that accounts for laser pump depletion and relativistic detuning. A mechanism is revealed based on a generic route to chaos, that predicts a progressive increase of the backscatter complexity with a growing laser intensity. Importance of kinetic effects is outlined and demonstrated in fluid-hybrid and particle simulations. As an application, we show that spectral anomalies of the backscatter, predicted by the above model, are consistent with recent sub-picosecond, high-intensity laser gas-target measurements at Livermore and elsewhere. Finally, a recently proposed scheme for generation of ultra-short, low-prepulse laser pulses by Raman backscattering in a thin foil target, is shown. (author)

  6. In vivo photoacoustic imaging of blood vessels with a pulsed laser diode

    NARCIS (Netherlands)

    Kolkman, R.G.M.; Steenbergen, Wiendelt; van Leeuwen, Ton


    Photoacoustic imaging is a hybrid imaging modality that is based on the detection of acoustic waves generated by absorption of pulsed light by tissue chromophores such as hemoglobin in blood. For this technique, usually large and costly Q-switched Nd:YAG lasers are used. These lasers provide a pulse

  7. Properties of pulsed laser deposited NiO/MWCNT thin films

    CSIR Research Space (South Africa)

    Yalisi, B


    Full Text Available Pulsed laser deposition (PLD) is a thin-film deposition technique, which uses short and intensive laser pulses to evaporate target material. The technique has been used in this work to produce selective solar absorber (SSA) thin film composites...

  8. Pondermotive absorption of a short intense laser pulse in a non-uniform plasma

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, A.A.; Platonov, K.Yu. [Inst. for Laser Physics, SC `Vavilov State Optical Inst.` 12, Birzhevaya line, St Petersburg (Russian Federation); Tanaka, K.A.


    An analytical description of the pondermotive absorption mechanism at a short high intense laser pulse interaction with a strong inhomogeneous plasma is presented. The optimal conditions for the maximum of resonance absorption of laser pulse interaction with non-uniform plasma at normal incidence are founded. (author)

  9. Foam Au driven by 4ω-2ω ignition laser pulse for inertial confinement fusion (United States)

    Lan, Ke; Song, Peng


    Green light (2ω) has the potential to drive ignition target for laser fusion with significantly more energy than blue light (3ω) and a relatively higher damage threshold for the optic components in the final optic assembly, but it has issues of a relatively low laser to x-ray conversion efficiency and a hard x-ray spectrum as compared to 3ω. In this paper, we propose to drive a foam hohlraum wall with an ignition laser pulse by taking a 4ω laser at the pre-pulse and a 2ω laser at the main-pulse, called as 4ω-2ω ignition pulse. This novel design has the following advantages: (1) benefiting from 2ω of its relatively high energy output and low damage threshold during main-pulse; (2) benefiting from foam in its relatively high laser to x-ray conversion efficiency and relatively low M-band fraction in re-emission; (3) benefiting from 4ω of its low LPI and low M-band fraction during pre-pulse. From our one-dimensional simulations with the Au material, the laser to x-ray conversion in a foam driven by 4ω-2ω pulse has an increase of 28% as compared to a solid target driven by 3ω with the same pulse shape. The relatively thin optical depth of foam is one of the main reasons for the increase of laser to x-ray conversion efficiency inside a foam target.

  10. Fast- and ultra-fast laser pulse induced reactions between carbon dioxide and methane

    CSIR Research Space (South Africa)

    Kotze, FJ


    Full Text Available in pressure. Results from this study showed that carbon dioxide and methane can be activated successfully using nanosecond laser pulses at 2000 nm and femtosecond laser pulses at 795 or 2000 nm and that these activated species react to form CO and C...

  11. Optimization Performance of a CO[subscript 2] Pulsed Tuneable Laser (United States)

    Ribeiro, J. H. F.; Lobo, R. F. M.


    In this paper, a procedure is presented that will allow (i) the power and (ii) the energy of a pulsed and tuneable TEA CO[subscript 2] laser to be optimized. This type of laser represents a significant improvement in performance and portability. Combining a pulse mode with a grating tuning facility, it enables us to scan the working wavelength…

  12. Temperature response of biological materials to pulsed non-ablative CO2 laser irradiation

    NARCIS (Netherlands)

    Brugmans, M. J.; Kemper, J.; Gijsbers, G. H.; van der Meulen, F. W.; van Gemert, M. J.


    This paper presents surface temperature responses of various tissue phantoms and in vitro and in vivo biological materials in air to non-ablative pulsed CO2 laser irradiation, measured with a thermocamera. We studied cooling off behavior of the materials after a laser pulse, to come to an

  13. Modeling of High Efficiency Solar Cells Under Laser Pulse for Power Beaming Applications (United States)

    Jain, Raj K.; Landis, Geoffrey A.


    Solar cells may be used as receivers for laser power beaming. To understand the behavior of solar cells when illuminated by a pulsed laser, the time response of gallium arsenide and silicon solar cells to pulsed monochromatic input has been modeled using a finite element solar cell model.

  14. High precision laser direct microstructuring system based on bursts of picosecond pulses (United States)

    Mur, Jaka; Petelin, Jaka; Osterman, Natan; Petkovšek, Rok


    We have developed an efficient, high precision system for direct laser microstructuring using fiber laser generated bursts of picosecond pulses. An advanced opto-mechanical system for beam deflection and sample movement, precise pulse energy control, and a custom built fiber laser with the pulse duration of 65 ps have been combined in a compact setup. The setup allows structuring of single-micrometer sized objects with a nanometer resolution of the laser beam positioning due to a combination of acousto-optical laser beam deflection and tight focusing. The precise synchronization of the fiber laser with the pulse burst repetition frequency of up to 100 kHz allowed a wide range of working parameters, including a tuneable number of pulses in each burst with the intra-burst repetition frequency of 40 MHz and delivering exactly one burst of pulses to every chosen position. We have demonstrated that tightly focused bursts of pulses significantly increase the ablation efficiency during the microstructuring of a copper layer and shorten the typical processing time compared to the single pulse per spot regime. We have used a simple short-pulse ablation model to describe our single pulse ablation data and developed an upgrade to the model to describe the ablation with bursts. Bursts of pulses also contribute to a high quality definition of structure edges and sides. The increased ablation efficiency at lower pulse energies compared to the single pulse per spot regime opens a window to utilize compact fiber lasers designed to operate at lower pulse energies, reducing the overall system complexity and size.

  15. Resonance enhanced high-order harmonic generation in H2+ by two sequential laser pulses. (United States)

    Wang, Baoning; He, Lixin; Wang, Feng; Yuan, Hua; Zhu, Xiaosong; Lan, Pengfei; Lu, Peixiang


    We investigate high-order harmonic generation in H2+ by using two sequential laser pulses, which consist of a 800-nm pump pulse and a time-delayed 1600-nm probe pulse. Based on the solution of the time-dependent Schrödinger equation, we demonstrate that the harmonic cutoff in our two-pulse scheme is significantly extended compared to that in the 1600-nm probe pulse alone. Meanwhile, the harmonic efficiency is enhanced by 2-3 orders of magnitude due to charge-resonance-enhanced ionization steered by the 800-nm pump pulse. By using a probe pulse with longer wavelength, our scheme can be used for efficient high harmonic generation in the water window region. In addition, the influence of the intensity of the pump pulse and the relative time delay of the two laser pulses on the harmonic generation are also investigated.

  16. Pulsed-laser atom probe studies of a precipitation hardened maraging TRIP steel

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O., E-mail: [Max-Planck-Institute for Iron Research, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Choi, P., E-mail: [Max-Planck-Institute for Iron Research, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Gerstl, S.S.A. [Imago Scientific Instruments, Madison, WI 53711 (United States); Ponge, D.; Raabe, D. [Max-Planck-Institute for Iron Research, Max-Planck-Str. 1, 40237 Duesseldorf (Germany)


    A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected. -- Research highlights: {yields} Changing the laser pulse energy in pulsed-laser atom probe could induce some changes in the analysis results of complex steels. {yields} Decreases in the evaporation fields and the ++/+ charge state ratios were detected with raising laser energy. {yields} Chemical composition of the intermetallic precipitates and the interface sharpness were not influenced by changing the laser energy.

  17. Capillary compressor of femtosecond laser pulses with nonlinear rotation of polarisation ellipse

    Energy Technology Data Exchange (ETDEWEB)

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


    The process of nonlinear rotation of the polarisation ellipse of laser radiation, occurring simultaneously with the broadening of the pulse spectrum due to nonlinear self-phase modulation in a gas-filled capillary, is studied. It is shown that the maximal rotation of the polarisation ellipse is experienced by the spectral components, shifted towards the short-wavelength side with respect to the central wavelength of the initial laser pulse. Using the effect of polarisation ellipse rotation, an eightfold increase in the energy contrast ratio of a 28-fs light pulse, obtained by compression of the radiation pulse from an ytterbium laser with the duration 290 fs, is implemented.

  18. Wavelength-tunable and pulse-width variable Fourier domain mode-locking lasers. (United States)

    Lee, Eung Je; Kim, Yong Pyung


    In this study, wavelength-tunable and pulse-width variable Fourier domain mode-locking lasers were developed with a repetition rate of 60.9 kHz. A spectral laser tuning range of over 100 nm was achieved by tuning the offset voltage to a fiber Fabry-Perot tunable filter (FFP-TF). The pulse width variation was achieved with amplitude modulation of the driving voltage to the FFP-TF. The pulse width ranged from 6.2 μs to 55 ns. The linewidth of the laser changed, from 0.109 to 0.083 nm, according to the pulse width variation.

  19. A compact plasma pre-ionized TEA-CO2 laser pulse clipper for material processing (United States)

    Gasmi, Taieb


    An extra-laser cavity CO2-TEA laser pulse clipper using gas breakdown techniques for high spatial resolution material processing and shallow material engraving and drilling processes is presented. Complete extinction of the nitrogen tail, that extends the pulse width, is obtained at pressures from 375 up to 1500 torr for nitrogen and argon gases. Excellent energy stability and pulse repeatability were further enhanced using high voltage assisted preionized plasma gas technique. Experimental data illustrates the direct correlation between laser pulse width and depth of engraving in aluminum and alumina materials.

  20. Development of a new picosecond pulse radiolysis system by using a femtosecond laser synchronized with a picosecond linac. A step to femtosecond pulse radiolysis

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Yoichi; Yamamoto, Tamotsu; Miki, Miyako; Seki, Shu; Okuda, Shuichi; Honda, Yoshihide; Kimura, Norio; Tagawa, Seiichi [Osaka Univ., Ibaraki (Japan). Inst. of Scientific and Industrial Research; Ushida, Kiminori


    A new picosecond pulse radiolysis system by using a Ti sapphire femtosecond laser synchronized with a 20 ps electron pulse from the 38 MeV L-band linac has been developed for the research of the ultra fast reactions in primary processes of radiation chemistry. The timing jitter in the synchronization of the laser pulse with the electron pulse is less than several picosecond. The technique can be used in the next femtosecond pulse radiolysis. (author)

  1. Quantum interference effects in a Λ-type atom interacting with two short laser pulse trains (United States)

    Buica, Gabriela


    We study the quantum interference between the excitation pathways in a three-level Λ-type atom interacting with two short laser pulse trains under the conditions of electromagnetically induced transparency. The probability amplitude equations which describe the interaction of a three-level Λ-type atom with two laser pulse trains are numerically solved. We derive analytical expressions for the population of the upper excited state for resonant laser pulse trains with a rectangular temporal profile. By varying the parameters of the laser pulse trains such as area of a single pulse, detuning, repetition period, and number of individual pulses, we analyze the quantum interference between the excitation pathways in terms of the upper excited state population.

  2. Pulse-spacing manipulation in a passively mode-locked multipulse fiber laser. (United States)

    Yu, Ying; Wei, Xiaoming; Kang, Jiqiang; Li, Bowen; Wong, Kenneth K Y


    Passively mode-locked fiber lasers have been intensively applied in various research fields. However, the passive mode-locking typically operates in free-running regime, which easily produces messy multiple pulses due to the fruitful nonlinear effects involved in optical fibers. Actively controlling those disordered pulses in a passively mode-locked laser is of great interest but rarely studied. In this work, we experimentally investigate a flexible pulse-spacing manipulation in the passively mode-locked multipulse fiber laser by both intracavity and extracavity methods. A tuning range of pulse spacing up to 1.5 ns is achieved. More importantly, continuous pulse-spacing modulation is successfully demonstrated through external optical injection. It is anticipated that the results can contribute to the understanding of laser nonlinear dynamics and pursuing the optimal performance of passively mode-locked fiber lasers for practical applications.

  3. Nuclear-state engineering in tripod systems using x-ray laser pulses (United States)

    Nedaee-Shakarab, B.; Saadati-Niari, M.; Zolfagharpour, F.


    Coherent superposition of nuclear states in tripod systems using three x-ray laser pulses is investigated theoretically. The laser pulses transfer the population from one ground state to an arbitrary superposition of other ground states using coincident pulses and stimulated Raman adiabatic passage techniques. The short wavelengths needed in the frame of the nuclei are achieved by envisaging an accelerated nucleus interacting with three x-ray laser pulses. This study exploits the Morris-shore transformation to reduce the tripod system into a coupled three-state Λ -like system and a noncoupled state. We calculated the required laser intensities which satisfy the conditions of coincident pulses and adiabatic passage techniques. Considering the spontaneous emission from excited state |4 〉 and unstable ground states (|2 〉,|3 〉 ) to other states, we have used a master equation for numerical study, and the final fidelity of desired states with respect to the tolerance of laser intensities is studied numerically.

  4. 17-fs pulses from a self-mode-locked Ti:sapphire laser. (United States)

    Huang, C P; Asaki, M T; Backus, S; Murnane, M M; Kapteyn, H C; Nathel, H


    We have generated sub-17-fs-duration pulses directly from a self-mode-locked Ti:sapphire laser. These pulses are near transform limited, with a wavelength centered at 817 nm, a pulse repetition rate of 80 MHz, and an average power of 500 mW. By minimizing the amount of material inside the laser cavity and choosing the correct glass for the intracavity prism pair, third-order dispersion in the laser can be significantly reduced compared with that in previous designs. Extracavity compensation for group-velocity dispersion in the output coupler and autocorrelator optics is necessary to measure this pulse width. To our knowledge this laser generates pulses substantially shorter than any other laser to date.

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

    Directory of Open Access Journals (Sweden)

    David C. Brown


    Full Text Available 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 and average powers. In this paper, we review the optical, thermal, thermo-optic and laser parameters important to cryogenic laser technology, recently achieved laser and laser materials progress, the progression of cryogenic laser technology, discuss the importance of cryogenic laser technology in ultrafast laser science, and what advances are likely to be achieved in the near-future.

  6. Pulsed laser deposition of thin refractory metal nitride films (United States)

    Fernandez, Manuel; Bereznai, M.; Caricato, A. P.; D'Anna, Emilia; Juhasz, A.; Leggieri, Gilberto; Luches, Armando; Majni, Guiseppe; Martino, Maurizio; Mengucci, Paolo; Nagy, P. M.; Nanai, Laszlo; Toth, Zsolt


    We report on the deposition of thin transition metal nitride (TMN) films by ablating Mo, Ta, V and W targets in low-pressure (1, 10 and 100 Pa) nitrogen atmosphere by KrF excimer laser pulses, and on their characterization. The targets were foils of high purity (99.8%). 3" Si(111) wafers wre used as substrates. Film characteristics (composition, crystalline structure, hardness) were studied as a function of N2 pressure, KrF laser fluence (4.5-19 J/cm2), substrate temperature (20-750°C) and target to substrate distance (30-70 mm). Rutherford backscattering spectrometery (RBS) was used to calculate thickness of the films and identification of the composition. TMN films ar formed already at low N2 ambient pressures (1 Pa) and laser fluences (6 J/cm2) on substrates at room temperature. XRD investigations show that films deposited at elevated temperatures are mostly polycrystalline. While Mo, W and Ta nitrides show respectively a γ-Mo2N, β-W2N and δ-TaN phase in almost any deposition condition, vanadium nitride shows a prevalent phase of δ-VN at N2 pressures of 1-10 Pa, while at higher pressures (100 Pa) and at relatively high laser fluences (16-19 J/cm2) the dominant phase is β-V2N. Generally the crystallinity of the films improves by increasing the substrate temperature. Well-crystallinzed films are obtained on substrates heated at 500°C. Surface morphology, microhardness and electrical resistivity of the films are discussed as a function of both the nitrogen pressure and substrate temperature.

  7. 197 nm femtosecond laser-pulse duration: comparison of autocorrelation measurements (United States)

    Heisel, P.-C.; Bergmann, J.; Paa, W.; Triebel, W.; Zeuner, T.; Stafast, H.


    An easy and reliable way is presented to measure the duration of UV femtosecond laser pulses of λ autocorrelation techniques are based on two-photon absorption (TPA) in different TPA media, especially calcium fluoride (CaF2). For 197 nm, the laser-pulse energy transmission and the laser-induced fluorescence of self-trapped excitons at 278 nm are applied. Both methods yield nearly the same second-order autocorrelation functions allowing to analyze the investigated laser pulse and obtain its duration of fs.

  8. Selection of CO laser single nanosecond pulse by electro-optic CdTe shutter (United States)

    Ionin, A. A.; Kinyaevskiy, I. O.; Klimachev, Yu. M.; Kotkov, A. A.; Kozlov, A. Yu.; Kryuchkov, D. S.


    To select a single laser pulse from a train of nanosecond pulses emitted by a mode-locked CO laser with wavelengths from ∼5 to 6 μm, an electro-optic shutter based on CdTe Pockels cell was developed. A contrast between the selected pulse and unselected laser emission was equal to 20 and twice as much decreased in a CO laser power amplifier. To increase the contrast, a feasibility of applying a narrow-gap semiconductor as a saturable absorber is discussed.

  9. Effective way to minimize the initial spike energy in a pulsed TE CO2 laser (United States)

    Wu, Jin; Wang, Donglei; Wan, Chongyi; Liu, Shiming


    A novel method is provided in conventional TE CO2 laser configuration by utilizing a specially designed small capacitance in the UV preionization scheme and a carefully optimized pulser/sustainer discharge circuitry so that the initial spike energy in the laser pulse profile induced by gain-switch effect can be greatly reduced. An experimental illustration is given in which the initial spike energy in the laser pulse is suppressed to less than 3.5% of the total pulse energy while stable laser performance is maintained.


    Directory of Open Access Journals (Sweden)

    D. S. Ivanov


    Full Text Available The process of laser ablation under the influence of ultra short laser pulses on metals is investigated by methods of molecular dynamics. The validity and applicability of the hybrid atomistic-continuous model for the estimation of optimum modes of ultra short laser pulses processing are explored. Combination of atomistic model of laser-induced non-equilibrium process of a phase transition at the atomic level with continuous two-temperature model for describing the dynamics of photo-excitation of free media is proposed. Applicability of laser ablation model on the example of aluminum films and gold under exposure to pulses with different energy density and duration is shown. It is indicated that, depending on the ratio of the laser pulse duration and the characteristic time of electron-phonon material interaction, photothermal and photomechanical modes of destruction are implemented that determine the quality and performance of the laser processing. It is established that at the duration of laser pulse less than the time of electron-phonon interaction high-performance photomechanical type of destruction is implemented by internal stresses arising in the area of exposure. This is confirmed by a linear dependence of the ablation rate from the absorbed energy. At the duration of laser pulse greater than the time of electron-phonon interaction inefficient photothermal mode of destruction is implemented. The results may be useful for specialists engaged in the development of laser technologies

  11. Comparison of pulsed dye laser versus combined pulsed dye laser and Nd:YAG laser in the treatment of inflammatory acne vulgaris. (United States)

    Salah El Din, Manal Mohamed; Samy, Nevien Ahmed; Salem, Amira Eid


    Both pulsed dye laser and combined 585/1064-nm (sequential dual-wavelength PDL and Nd:YAG) laser improves inflammatory skin disorders including acne vulgaris. To compare the efficacy of 585-nm pulsed dye laser versus sequential dual-wavelength PDL and Nd:YAG in treatment of acne vulgaris. Thirty patients with acne vulgaris were treated by PDL alone on half of the face while contra lateral half was treated by combined 585/1064 nm laser. The study showed that inflammatory acne lesions count was significantly reduced by 82.5% (p 0.0001) on PDL sides and by 83.5% (p 0.00001) on combined 585/1064-nm side after 8 weeks, while reduction of non-inflammatory acne lesions was observed at 8 weeks by 58.4% and 71.5% respectively. However, difference between the two modalities was not statistically significant. PDL and combined PDL/Nd:YAG laser treatment were found to be an effective, safe and well-tolerated treatment option for inflammatory and non-inflammatory acne vulgaris.

  12. Flashlamp pumped Ti-sapphire laser for ytterbium glass chirped pulse amplification

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, Akihiko; Ohzu, Akira; Sugiyama, Akira [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment] [and others


    A flashlamp pumped Ti:sapphire laser is designed for ytterbium glass chirped pulse amplification. A high quality Ti:sapphire rod and a high energy long pulse discharging power supply are key components. The primary step is to produce the output power of 10 J per pulse at 920 nm. (author)

  13. Comparison of the quantitative analysis performance between pulsed voltage atom probe and pulsed laser atom probe. (United States)

    Takahashi, J; Kawakami, K; Raabe, D


    The difference in quantitative analysis performance between the voltage-mode and laser-mode of a local electrode atom probe (LEAP3000X HR) was investigated using a Fe-Cu binary model alloy. Solute copper atoms in ferritic iron preferentially field evaporate because of their significantly lower evaporation field than the matrix iron, and thus, the apparent concentration of solute copper tends to be lower than the actual concentration. However, in voltage-mode, the apparent concentration was higher than the actual concentration at 40K or less due to a detection loss of matrix iron, and the concentration decreased with increasing specimen temperature due to the preferential evaporation of solute copper. On the other hand, in laser-mode, the apparent concentration never exceeded the actual concentration, even at lower temperatures (20K), and this mode showed better quantitative performance over a wide range of specimen temperatures. These results indicate that the pulsed laser atom probe prevents both detection loss and preferential evaporation under a wide range of measurement conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. BRIEF COMMUNICATIONS: Pulse-periodic iodine photodissociation laser pumped with radiation from magnetoplasma compressors (United States)

    Kashnikov, G. N.; Orlov, V. K.; Panin, A. N.; Piskunov, A. K.; Reznikov, Vladimir A.


    A study was made of the characteristics of an iodine photodissociation laser pumped by radiation emitted from magnetoplasma compressors. A closed system for circulating the working gas C3F7I was employed in this laser. Pulse-periodic operation with an interval of 1 min between the pulses was achieved; the output energy was 110 J and the pulse duration was 30 μ sec.

  15. Influence of electrical Field on Pulsed Laser beam welding of Stainless Steel (304)


    FAWZİ, Salah A. H.; ARİF, RAZ N.


    Pulsed laser beam welding experiment were carried out on stainless steel (SUS 304), using vertical and horizontal electric fields of different intensities to study its effectiveness on the welding process, regarding depth and weld quality. Pulsed Nd: YAG laser emitting 10 ms pulses in the TEM00 mode at 1.06 m m wave length was employed, microstructure of welded zone and defect were investigated using optical and scanning electron microscopes. Tensile test and microhardness measuremen...

  16. Pulse dynamics of a passively mode-locked Bi-doped fiber laser. (United States)

    Kivistö, Samuli; Puustinen, Janne; Guina, Mircea; Herda, Robert; Marcinkevicius, Saulius; Dianov, Evgueny M; Okhotnikov, Oleg G


    The pulse evolution in Bi-doped soliton fiber laser with slow and fast saturable absorber has been studied both experimentally and numerically. Semiconductor saturable absorbers with balanced slow and fast absorption recovery mechanisms exhibit a bi-temporal recovery dynamics which permits both reliable start-up of passive mode-locking and short pulse generation and stabilization. The pulse dynamics within the Bi fiber laser cavity have been investigated.

  17. Three types of pulses delivered from a nanotube-mode-locked fiber laser (United States)

    Yao, X. K.


    Three types of pulses are experimentally investigated in a switchable normal-dispersion nanotube-mode-locked fiber laser by adjusting polarizer controller and pump power. They are a standard dissipative-soliton (DS), conventional soliton (CS)-like pulse, and noiselike pulse, which correspond to three mode-locking states. The standard DS with a rectangular spectrum possesses a Gaussian-shape pulse. The CS-like operation has a Lorenz shape, and the spectrum involves several sidebands similar to the CS case. For the noiselike pulse with a bell-shaped spectrum, a 317 fs peak rides upon the 132.5 ps pedestal in the autocorrelation trace. The spectra of these three pulse operations are centered at three close wavelengths. The generation of three such different types of pulses in one identical normal- dispersion laser cavity may find an important application for the future of mode-locked laser research.

  18. Single laser pulse compression via strongly coupled stimulated Brillouin scattering in plasma

    Energy Technology Data Exchange (ETDEWEB)

    Peng, H.; Wu, Z. H.; Zhang, Z. M. [Laser Fusion Research Center, China Academy of Engineering Physics, P.O. Box 919-988, Mianyang 621900 (China); Science and Technology on Plasma Physics Laboratory, P.O. Box 919-988, Mianyang 621900 (China); Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiaotong University, Shanghai 200240 (China); Zuo, Y. L.; Zhou, K. N.; Su, J. Q., E-mail: [Laser Fusion Research Center, China Academy of Engineering Physics, P.O. Box 919-988, Mianyang 621900 (China); Science and Technology on Plasma Physics Laboratory, P.O. Box 919-988, Mianyang 621900 (China)


    Laser amplification in plasma, including stimulated Raman scattering amplification and strongly coupled stimulated Brillouin scattering (sc-SBS) amplification, is very promising to generate ultrahigh-power and ultrashort laser pulses. But both are quite complex in experiments: at least three different laser pulses must be prepared; temporal delay and spatial overlap of these three pulses are difficult. We propose a single pulse compression scheme based on sc-SBS in plasma. Only one moderately long laser is applied, the front part of which ionizes the gas to produced plasma, and gets reflected by a plasma mirror at the end of the gas channel. The reflected front quickly depletes the remaining part of the laser by sc-SBS in the self-similar regime. The output laser is much stronger and shorter. This scheme is at first considered theoretically, then validated by using 1D PIC simulations.

  19. Long-pulsed dye laser versus long-pulsed dye laser-assisted photodynamic therapy for acne vulgaris: A randomized controlled trial

    DEFF Research Database (Denmark)

    Haedersdal, M.; Togsverd, K.; Wiegell, S.R.


    Background: Long-pulsed dye laser (LPDL)-assisted photodynamic therapy has been suggested to be superior to laser alone for acne vulgaris but no evidence is available. Objective: To evaluate the efficacy and safety of LPDL alone versus LPDL in photodynamic therapy with methylaminolevulinic acid (...

  20. Resonant infrared pulsed laser deposition of a polyimide precursor

    Energy Technology Data Exchange (ETDEWEB)

    Dygert, N L; Schriver, K E; Jr, R F Haglund [Department of Physics and Astronomy and W M Keck Foundation Free-Electron Laser Centre, Vanderbilt University, Nashville TN 37235 (United States)


    Poly(amic acid) (PAA), a precursor to polyimide, was successfully deposited on substrates without reaching curing temperature, by resonant infrared pulsed laser ablation. The PAA was prepared by dissolving pyromellitic dianhydride and 4, 4' oxidianiline in the polar solvent Nmethyl pyrrolidinone (NMP). The PAA was deposited in droplet-like morphologies when ablation occurred in air, and in string-like moieties in the case of ablation in vacuum. In the as-deposited condition, the PAA was easily removed by washing with NMP; however, once cured thermally for thirty minutes, the PAA hardened, indicating the expected thermosetting property. Plume shadowgraphy showed very clear contrasts in the ablation mechanism between ablation of the solvent alone and the ablation of the PAA, even at low concentrations. A Wavelength dependence in plume velocity was also observed.

  1. Effects of an external magnetic field in pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, T. [Universidad Autonoma de la Ciudad de Mexico (UACM), Prolongacion San Isidro 151, Col. San Lorenzo Tezonco, C.P. 09790, Mexico DF (Mexico)], E-mail:; Posada, E. de [CINVESTAV-IPN Unidad Merida, Applied Physics Department, A.P. 73, Cordemex, C.P. 97130 Merida, Yuc. (Mexico); Villagran, M. [CCADET, Universidad Nacional Autonoma de Mexico (UNAM), A.P. 70-186, C.P. 04510, Mexico DF (Mexico); Ll, J.L. Sanchez [Laboratorio de Magnetismo, Facultad de Fisica-IMRE, Universidad de La Habana, La Habana 10400 (Cuba); Bartolo-Perez, P.; Pena, J.L. [CINVESTAV-IPN Unidad Merida, Applied Physics Department, A.P. 73, Cordemex, C.P. 97130 Merida, Yuc. (Mexico)


    Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation of a sintered ceramic SrFe{sub 12}O{sub 19} target with and without the presence of a nonhomogeneous magnetic field of {mu}{sub 0}H = 0.4 T perpendicular to substrate plane and parallel to the plasma expansion axis. The field was produced by a rectangular-shaped Nd-Fe-B permanent magnet and the substrate was just placed on the magnet surface (Aurora method). An appreciable increment of optical emission due to the presence of the magnetic field was observed, but no film composition change or thickness increment was obtained. It suggests that the increment of the optical emission is due mainly to the electron confinement rather than confinement of ionic species.

  2. A Case of Lymphangioma Circumscriptum Treated with Pulsed Dye Laser

    Directory of Open Access Journals (Sweden)

    Turna İlknur


    Full Text Available Lymphangioma circumscriptum (LS is a superficial lymphatic malformation which consists of dilated lymphatic channels. Clinically, it presents as grouped translucent vesicles, which usually contain clear lymph fluid but may also contain red blood cells due to hemorrhage. It has been suggested that pulsed dye laser (PDL, which efficacy is known in vascular lesions, has also been successfully used for such lympangiomas with hemorrhagic character. In the literature, two patients who had LS and whose lesions responded well to PDL treatment have been reported. Here, we describe a 14-year-old woman with LS who had vesicles on her left shoulder some of which showed hemorrhagic character and who gave an inadequate partial response to the treatment with PDL.

  3. Matrix assisted pulsed laser deposition of melanin thin films (United States)

    Bloisi, F.; Pezzella, A.; Barra, M.; Chiarella, F.; Cassinese, A.; Vicari, L.


    Melanins constitute a very important class of organic pigments, recently emerging as a potential material for a new generation of bioinspired biocompatible electrically active devices. In this paper, we report about the deposition of synthetic melanin films starting from aqueous suspensions by matrix assisted pulsed laser evaporation (MAPLE). In particular, we demonstrate that it is possible to deposit melanin films by MAPLE even if melanin (a) is not soluble in water and (b) absorbs light from UV to IR. AFM images reveal that the film surface features are highly depending on the deposition parameters. UV-VIS and FTIR spectra show both the optical properties and the molecular structure typical of melanins are preserved.

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

    CERN Document Server

    Kotaki, H


    We investigate a mechanism of nonlinear phenomena in laser-plasma interaction, a laser wakefield excited by intense laser pulses, and the possibility of generating an intense bright electron source by an intense laser pulse. We need to understand and further employ some of these phenomena for our purposes. We measure self-focusing, filamentation, and the anomalous blueshift of the laser pulse. The ionization of gas with the self-focusing causes a broad continuous spectrum with blueshift. The normal blueshift depends on the laser intensity and the plasma density. We, however, have found different phenomenon. The laser spectrum shifts to fixed wavelength independent of the laser power and gas pressure above some critical power. We call the phenomenon 'anomalous blueshift'. The results are explained by the formation of filaments. An intense laser pulse can excite a laser wakefield in plasma. The coherent wakefield excited by 2 TW, 50 fs laser pulses in a gas-jet plasma around 10 sup 1 sup 8 cm sup - sup 3 is mea...

  5. Mesoscale Laser Processing using Excimer and Short-Pulse Ti: Sapphire Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Shirk, M D; Rubenchik, A M; Gilmer, G H; Stuart, B C; Armstrong, J P; Oberhelman, S K; Baker, S L; Nikitin, A J; Mariella, R P


    Targets to study high-energy density physics and inertial confinement fusion processes have very specific and precise tolerances that are pushing the state-of-the-art in mesoscale microsculpting technology. A significant effort is required in order to advance the capabilities to make these targets with very challenging geometries. Ultrashort pulsed (USP) Ti:Sapphire lasers and excimer lasers are proving to be very effective tools in the fabrication of the very small pieces that make up these targets. A brief description of the dimensional and structural requirements of these pieces will be presented, along with theoretical and experimental results that demonstrate to what extent these lasers are achieving the desired results, which include sub-{mu}m precision and RMS surface values well below 100 nm. This work indicates that excimer lasers are best at sculpting the polymer pieces and that the USP lasers work quite well on metal and aerogel surfaces, especially for those geometries that cannot be produced using diamond machining and where material removal amounts are too great to do with focused ion beam milling in a cost effective manner. In addition, the USP laser may be used as part of the procedure to fill target capsules with fusion fuel, a mixture of deuterium and tritium, without causing large perturbations on the surface of the target by keeping holes drilled through 125 {micro}m of beryllium below 5 {micro}m in diameter.

  6. LIGHT SOURCE: Terahertz emission in tenuous gases irradiated by ultrashort laser pulses (United States)

    Wang, Wei-Min; Sheng, Zheng-Ming; Wit, Hui-Chun; Chen, Min; Li, Chun; Zhang, Jie; Mima, K.


    Mechanism of terahertz (THz) pulse generation in gases irradiated by ultrashort laser pulses is investigated theoretically. Quasi-static transverse currents produced by laser field ionization of gases and the longitudinal modulation in formed plasmas are responsible for the THz emission at the electron plasma frequency, as demonstrated by particle-in-cell simulations including field ionization. The THz field amplitude scaling with the laser amplitude within a large range is also discussed.

  7. Interaction between pulsed infrared laser and carbon fiber reinforced polymer composite laminates (United States)

    Liu, Yan-Chi; Wu, Chen-Wu; Song, Hong-Wei; Huang, Chen-Guang


    The Laser drilling processes, in particular the interaction between the pulsed infrared Laser and the target materials were investigated on the CFRP composite laminate. The incremental freezing method was designed to reveal experimentally the temporal patterns of the ablation profiles in the CFRP composite laminates subjected to pulsed Laser irradiation. The temperature characteristics of the specimens were analyzed with Finite Element Method (FEM) and the phase change history studied. The theoretical results match well with the experimental outcome.

  8. Bi-wavelength operation of a short-pulse Ti:sapphire laser

    Energy Technology Data Exchange (ETDEWEB)

    Barros, M.R.X. de; Becker, P.C. [AT and T Bell Labs., Murray Hill, NJ (United States)


    The authors have demonstrated a femtosecond mode locked Ti:sapphire laser that simultaneously generates synchronous and colinear near transform limited two color pulses. The two color operating was obtained from a single laser cavity and the separation between the two wavelengths can be tuned from 55 to 90 nm. This laser is ideally suited for the generation of femtosecond mid-infrared pulses by difference frequency mixing.

  9. High power pulsed fiber laser development for Co2 space based dial system (United States)

    Canat, Guillaume; Le Gouët, Julien; Lombard, Laurent; Bresson, Alexandre; Goular, Didier; Dolfi-Bouteyre, Agnès.; Duzellier, Sophie; Boivin, Denis; Nilsson, Johan; Sahu, Jayata; Bordais, Sylvain


    High energy fiber lasers emitting around 1579nm is seen as a possible technology for the laser unit of a spaceborn CO2 DIAL system. We are developing an all fiber system with the following expected performances: pulse energy of 260μJ, pulse duration 150ns, beam quality M2 laser stability 200 kHz. One of our main concerns has been the radiation induced attenuation mitigation. Various fiber compositions have been investigated.

  10. White light continuum generation in sapphire using two-coloured femtosecond laser pulses


    Čepėnas, Augustas


    A wide spectrum of laser radiation is useful for two reasons: wider spectrum allows generation of shorter laser pulses, meanwhile, in pump-probe spectroscopy it is prefered to cover the largest possible spectral range with the same source. This work explores white light continuum generation using two-colored (wavelength of 1030 nm and 515 nm) femtosecond laser pulses. Combining these two white light continuums should expand radiation spectrum. However, this research shows that white light con...

  11. Construction and Characterization of a Nanosecond Nd:YAG Laser Pumped Distributed Feedback Dye Laser Generating Picosecond Pulses (United States)

    Clark, Timothy; Weckerly, Chris; Ujj, Laszlo


    We have constructed a Distributed Feedback Dye Laser (DFDL) using interferometric pumping. DFDL works according to the dynamic modulation of the gain medium creating short pulses. Shortening of the pulses, stability, and dynamic range of the DFDL were investigated. Pulses were measured with the help of a photodiode with a 30 picosecond response time. Traces were recorded with a Tektronics DSA73304D (33GHz) digital serial analyser. The gain medium contains an ethanol solution of Rhodamine 590 dye and DODCI saturable absorber. Increasing the concentration of DODCI saturable absorber resulted in significant pulse shortening (150 to 54 picoseconds). Single pulse generation was achieved when the power of the pump laser was adjusted 10 percent above the laser threshold. The central wavelength of the laser pulses was 587 nm. The mathematical modeling, optical layout of the DFDL, and the results of the temporal and spectral characterization of the laser are presented on the poster. The development of the DFDL will lead to an extensive investigation of short pulse dye lasers for educational purposes and for applications in nonlinear spectroscopy. Financial support from University of West Florida is acknowledged.

  12. Analysis of THG modes for femtosecond laser pulse (United States)

    Trofimov, Vyacheslav A.; Sidorov, Pavel S.


    THG is used nowadays in many practical applications such as a substance diagnostics, and biological objects imaging, and etc. With developing of new materials and technology (for example, photonic crystal) an attention to THG process analysis grow. Therefore, THG features understanding are a modern problem. Early we have developed new analytical approach based on using the problem invariant for analytical solution construction of the THG process. It should be stressed that we did not use a basic wave non-depletion approximation. Nevertheless, a long pulse duration approximation and plane wave approximation has applied. The analytical solution demonstrates, in particular, an optical bistability property (and may other regimes of frequency tripling) for the third harmonic generation process. But, obviously, this approach does not reflect an influence of a medium dispersion on the frequency tripling. Therefore, in this paper we analyze THG efficiency of a femtosecond laser pulse taking into account a second order dispersion affect as well as self- and crossmodulation of the interacting waves affect on the frequency conversion process. Analysis is made using a computer simulation on the base of Schrödinger equations describing the process under consideration.

  13. Variable pulsewidth erbium:YAG laser ablation of the ureter and urethra in vitro and in vivo: optimization of the laser fluence, pulse duration, and pulse repetition rate (United States)

    Fried, Nathaniel M.; Tesfaye, Zelalem; Ong, Albert M.; Rha, Koon H.; Hejazi, Pooya


    Stricture recurrence frequently occurs due to mechanical or thermal insult during endourologic treatment of ureteral and urethral strictures. Optimization of the Er:YAG laser for precise incision of strictures was conducted using ureteral and urethral tisssue samples, ex vivo, and a laparoscopic porcine ureteral model with exposed ureter, in vivo. Erbium:YAG laser radiation with a wavelength of 2.94 microns, pulse lengths of 8, 70, and 220 microseconds, output energies of 2 - 35 mJ, fluences of 1 - 25 J/cm2, and pulse repetition rates of 5 - 30 Hz, was delivered through germanium oxide optical fibers in contact with the tissue. Incision of the ureteral wall was achieved in vivo with less than 20 pulses at a laser fluence of 4 J/cm2. Thermal damage was reduced from 30 - 60 microns to 10 - 20 microns by shortening the laser pulse duration from 220 to 70 microseconds. Pulse repetition rates above 20 Hz resulted in larger thermal damage zones ranging from 60 - 120 microns. The Er:YAG laser, operating at a pulse duration of approximately 70 microseconds, a fluence of 4 J/cm2 or greater, and a repetition rate less than 20 Hz, is capable of rapidly incising urethral and ureteral tissues, in vivo, with minimal thermal and mechanical side-effects.

  14. Accelerating protons to therapeutic energies with ultraintense, ultraclean, and ultrashort laser pulses (United States)

    Bulanov, Stepan S.; Brantov, Andrei; Bychenkov, Valery Yu.; Chvykov, Vladimir; Kalinchenko, Galina; Matsuoka, Takeshi; Rousseau, Pascal; Reed, Stephen; Yanovsky, Victor; Krushelnick, Karl; Litzenberg, Dale William; Maksimchuk, Anatoly


    Proton acceleration by high-intensity laser pulses from ultrathin foils for hadron therapy is discussed. With the improvement of the laser intensity contrast ratio to 10−11 achieved on the Hercules laser at the University of Michigan, it became possible to attain laser-solid interactions at intensities up to 1022 W∕cm2 that allows an efficient regime of laser-driven ion acceleration from submicron foils. Particle-in-cell (PIC) computer simulations of proton acceleration in the directed Coulomb explosion regime from ultrathin double-layer (heavy ions∕light ions) foils of different thicknesses were performed under the anticipated experimental conditions for the Hercules laser with pulse energies from 3 to 15 J, pulse duration of 30 fs at full width half maximum (FWHM), focused to a spot size of 0.8 μm (FWHM). In this regime heavy ions expand predominantly in the direction of laser pulse propagation enhancing the longitudinal charge separation electric field that accelerates light ions. The dependence of the maximum proton energy on the foil thickness has been found and the laser pulse characteristics have been matched with the thickness of the target to ensure the most efficient acceleration. Moreover, the proton spectrum demonstrates a peaked structure at high energies, which is required for radiation therapy. Two-dimensional PIC simulations show that a 150–500 TW laser pulse is able to accelerate protons up to 100–220 MeV energies. PMID:18561651

  15. Bone tissue heating and ablation by short and ultrashort laser pulses (United States)

    Letfullin, Renat R.; Rice, Colin E. W.; George, Thomas F.


    Biological hard tissues, such as those found in bone and teeth, are complex tissues that build a strong mineral structure over an organic matrix framework. The laser-matter interaction for bone hard tissues holds great interest to laser surgery and laser dentistry; the use of short/ultrashort pulses, in particular, shows interesting behaviors not seen in continuous wave lasers. High laser energy densities in ultrashort pulses can be focused on a small irradiated surface (spot diameter is 10-50 μm) leading to rapid temperature rise and thermal ablation of the bone tissue. Ultrashort pulses, specifically those in the picosecond and femtosecond ranges, impose several challenges in modeling bone tissue response. In the present paper we perform time-dependent thermal simulations of short and ultrashort pulse laser-bone interactions in singlepulse and multipulse (set of ultrashort pulses) modes of laser heating. A comparative analysis for both radiation modes is discussed for laser heating of different types of the solid bone on the nanosecond, picosecond and femtosecond time scales. It is shown that ultrashort laser pulses with high energy densities can ablate bone tissue without heating tissues bordering the ablation creator. This reaction is particularly desirable as heat accumulation and thermal damage are the main factors affecting tissue regrowth rates, and thus patient recovery times.



    Wang, X.C.; G. C. Lim; F. L. NG; W.; Liu; Chua, S. J.


    The formation of femtosecond pulsed laser-induced periodic surface structure on GaN is reported for the first time (to our knowledge) in this paper. It has been found that the formation of the laser-induced ripples is very much dependent and quite sensitive to the laser conditions of the incident laser beam energy fluence and pulse numbers. Possibly due to the unique property of high-defect density of GaN material, the process window for laser-induced ripple formation is quite narrow compared...

  17. Ultra-short pulse reconstruction software in high power laser system

    Energy Technology Data Exchange (ETDEWEB)

    Galletti, M. [Physics Department of the University and INFN, Pisa (Italy); Galimberti, M. [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Giulietti, D. [Physics Department of the University and INFN, Pisa (Italy)


    An ultra-short pulse reconstruction software, validated through a set of experimental measurements on the front-end of the Vulcan laser at the RAL Central Laser Facility is presented. The measurements were acquired in Target Area Petawatt of the Vulcan laser, both using a conventional autocorrelation technique and the GRENOUILLE technique in order to compare the results. The FWHM of the laser pulses considered came out to be comparable for the two techniques. In this experimental campaign for the first time a technique different from the autocorrelation one has been used for a PW class laser as Vulcan.

  18. Ultra-short pulse reconstruction software in high power laser system (United States)

    Galletti, M.; Galimberti, M.; Giulietti, D.


    An ultra-short pulse reconstruction software, validated through a set of experimental measurements on the front-end of the Vulcan laser at the RAL Central Laser Facility is presented. The measurements were acquired in Target Area Petawatt of the Vulcan laser, both using a conventional autocorrelation technique and the GRENOUILLE technique in order to compare the results. The FWHM of the laser pulses considered came out to be comparable for the two techniques. In this experimental campaign for the first time a technique different from the autocorrelation one has been used for a PW class laser as Vulcan.

  19. Ultrafast, laser-based, x-ray science: the dawn of atomic-scale cinematography

    Energy Technology Data Exchange (ETDEWEB)

    Barty, C.P.J. [University of California, Department of Applied Mechanics and Engineering Science, Urey Hall, Mali Code 0339, San Diego, La Jolla, CA (United States)


    The characteristics of ultrafast chirped pulse amplification systems are reviewed. Application of ultrafast chirped pulse amplification to the generation of femtosecond, incoherent, 8-keV line radiation is outlined and the use of femtosecond laser-based, x-rays for novel time-resolved diffraction studies of crystalline dynamics with sub-picosecond temporal resolution and sub-picometer spatial resolution is reviewed in detail. Possible extensions of laser-based, x-ray technology and evaluation of alternative x-ray approaches for time-resolved studies of the atomic scale dynamics are given. (author)

  20. Laser beam welding of titanium nitride coated titanium using pulse-shaping

    Directory of Open Access Journals (Sweden)

    Milton Sergio Fernandes de Lima


    Full Text Available A new welding method which allows the assembly of two titanium nitride coated titanium parts is proposed. The welding procedure utilizes the possibility for pulse-shaping in order to change the energy distribution profile during the laser pulse. The pulse-shaping is composed of three elements: a a short high power pulse for partial ablation at the surface; b a long pulse for thermal penetration; and c a quenching slope for enhanced weldability. The combination of these three elements produces crack-free welds. The weld microstructure is changed in comparison to normal welding, i.e. with a rectangular pulse, as the nitrogen and the microhardness are more homogenously distributed in the weld under pulse-shaping conditions. This laser pulse dissolves the TiN layer and allows nitrogen to diffuse into the melt pool, also contributing to an enhanced weldability by providing suitable thermal conditions.


    Directory of Open Access Journals (Sweden)

    V. P. Veiko


    Full Text Available Subject of research. The paper deals with research of the surface ablation for single-crystal silicon wafers and properties of materials obtained in response to silicon ablation while scanning beam radiation of pulse fiber ytterbium laser with a wavelenght λ = 1062 nm in view of variation of radiation power and scanning modes. Method. Wafers of commercial p-type conductivity silicon doped with boron (111, n-type conductivity silicon doped with phosphorus (100 have been under research with a layer of intrinsical silicon oxide having the thickness equal to several 10 s of nanometers and SiO2 layer thickness from 120 to 300 nm grown by thermal oxidation method. The learning system comprises pulse fiber ytterbium laser with a wavelenght λ = 1062 nm. The laser rated-power output is equal to 20 W, pulse length is 100 ns. Pulses frequency is in the range from 20 kHz to 100 kHz. Rated energy in the pulse is equal to 1.0 mJ. Scanning has been carried out by means of two axial scanning device driven by VM2500+ and controlled by personal computer with «SinMarkТМ» software package. Scanning velocity is in the range from 10 mm/s to 4000 mm/s, the covering varies from 100 lines per mm to 3000 lines per mm. Control of samples has been carried out by means of Axio Imager A1m optical microscope Carl Zeiss production with a high definition digital video camera. All experiments have been carried out in the mode of focused laser beam with a radiation spot diameter at the substrate equal to 50 μm. The change of temperature and its distribution along the surface have been evaluated by FLIR IR imager of SC7000 series. Main results. It is shown that ablation occurs without silicon melting and with plasma torch origination. The particles of ejected silicon take part in formation of silicon ions plasma and atmosphere gases supporting the plasmo-chemical growth of SiO2. The range of beam scanning modes is determined where the growth of SiO2 layer is observed

  2. Antibacterial polymeric coatings grown by matrix assisted pulsed laser evaporation (United States)

    Paun, Irina Alexandra; Moldovan, Antoniu; Luculescu, Catalin Romeo; Dinescu, Maria


    We report on a simple and environmental friendly method to produce composite biocompatible antibacterial coatings consisting of silver nanoparticles (AgNPs, size 40 nm) combined with polymer blends (polyethylene glycol/poly(lactide-co-glycolide), PEG/PLGA blends). The PEG/PLGA&AgNPs coatings were produced by Matrix Assisted Pulsed Laser Evaporation, using a Nd:YAG laser with λ=266 nm. The AgNPs were deposited either on top of a PEG/PLGA layer (i.e., bilayered coating), or simultaneously with the polymers (i.e., blended coating). In both cases, chemical analysis indicated that the polymers preserved their integrity, with no evidence of chemical interaction with the AgNPs. Morphological investigations evidenced homogenous distribution of individual AgNPs on the surface of the coatings, with no signs of aggregation. The size of the AgNPs was ˜40 nm, consistent with size of the as-received ones. The presence of AgNPs in the coatings was confirmed by the absorption band at ˜420 nm and their stability was checked by monitoring this absorption versus time. After exposure to air, the AgNPs from the bilayered coating showed signs of oxidation. In the blended coating, the oxidation of the AgNPs was prevented by the neighboring polymer molecules. Finally, preliminary investigations confirmed the bacterial killing activity of the coatings against Escherichia coli.

  3. Infantile hemangioma: pulsed dye laser versus surgical therapy (United States)

    Remlova, E.; Dostalova, T.; Michalusova, I.; Vranova, J.; Jelinkova, H.; Hubacek, M.


    Hemangioma is a mesenchymal benign tumor formed by blood vessels. Anomalies affect up to 10% of children and they are more common in females than in males. The aim of our study was to compare the treatment efficacy, namely the curative effect and adverse events, such as loss of pigment and appearance of scarring, between classical surgery techniques and laser techniques. For that reason a group of 223 patients with hemangioma was retrospectively reviewed. For treatment, a pulsed dye laser (PDL) (Rhodamine G, wavelength 595 nm, pulsewidth between 0.45 and 40 ms, spot diameter 7 mm, energy density 9-11 J cm-2) was used and the results were compared with a control group treated with classical surgical therapy under general anesthesia. The curative effects, mainly number of sessions, appearance of scars, loss of pigment, and relapses were evaluated as a marker of successful treatment. From the results it was evident that the therapeutic effects of both systems are similar. The PDL was successful in all cases. The surgery patients had four relapses. Classical surgery is directly connected with the presence of scars, but the system is safe for larger hemangiomas. It was confirmed that the PDL had the optimal curative effect without scars for small lesions (approximately 10 mm). Surgical treatment under general anesthesia is better for large hemangiomas; the disadvantage is the presence of scars.

  4. Collective behavior of silver plasma during pulsed laser ablation (United States)

    Dildar, I. M.; Rehman, S.; Khaleeq-ur-Rahman, M.; Bhatti, K. A.; Shuaib, A.


    The present work reports an electrical investigation of silver plasma using a self-fabricated Langmuir probe in air and under a low vacuum (~10-3 torr). A silver target was irradiated with a Q-switched Nd:YAG laser with the wavelength 1.064 µm, energy 10 mJ, pulse duration 9-14 ns and power 1.1 MW. The collective behavior of a silver plasma plume is studied using a Langmuir probe as an electrical diagnostic technique. By applying different positive and negative voltages to the probe, the respective signals are collected on a four channels digital storage oscilloscope having a frequency of 500 MHz. An I-V curve helps to measure electron temperature and electron density directly and plasma frequency, response time, Debye length and number of particles in ‘Debye’s sphere’ indirectly using the theory of Langmuir probe and mathematical formulas. The floating potential is measured as negative for laser induced silver plasma in air and vacuum, following the theory of plasma.

  5. Engineering plasmonic nanostructured surfaces by pulsed laser deposition (United States)

    Ghidelli, Matteo; Mascaretti, Luca; Bricchi, Beatrice Roberta; Zapelli, Andrea; Russo, Valeria; Casari, Carlo Spartaco; Li Bassi, Andrea


    The synthesis and the optical response of gold nanoparticles (NPs) and thin nanostructured films grown by pulsed laser deposition (PLD) are here studied. Different PLD process parameters - including background gas pressure and the number of laser shots as well as post-deposition annealing treatments - have been varied to control the growth of Au NPs and films, thus tuning the surface plasmon characteristics. The mechanisms of NPs and film growth have been explored performing a morphological characterization by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), and the correlation with the optical behavior is investigated. We show that the size distribution and the morphology of the as deposited Au NPs depend on growth mechanisms which are controlled by tuning the deposition process, while the optical behavior is strongly affected by the average size and surface density of NPs or by the length of percolated Au domains. Furthermore, nucleation in gas phase has been reported at high (1000 Pa Ar) background pressures, enabling independent control of NP size and coverage, contrary to surface driven NP growth by diffusion and aggregation on substrate.

  6. Properties of pulsed laser deposited fluorinated hydroxyapatite films on titanium

    Energy Technology Data Exchange (ETDEWEB)

    Rau, J.V., E-mail: [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Smirnov, V.V. [A.A. Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Leninsky Prospect 49, 119991 Moscow (Russian Federation); Laureti, S. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via Salaria km 29.300, 00016 Monterotondo Scalo (RM) (Italy); Generosi, A. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Varvaro, G. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via Salaria km 29.300, 00016 Monterotondo Scalo (RM) (Italy); Fosca, M. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Ferro, D.; Cesaro, S. Nunziante [Istituto per lo Studio dei Materiali Nanostrutturati, Consiglio Nazionale delle Ricerche, Piazzale Aldo Moro 5, 00185 Rome (Italy); Albertini, V. Rossi [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Barinov, S.M. [A.A. Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Leninsky Prospect 49, 119991 Moscow (Russian Federation)


    Fluorinated hydroxyapatite coated titanium was investigated for application as implant coating for bone substitute materials in orthopaedics and dentistry. Pulsed laser deposition technique was used for films preparation. Fluorinated hydroxyapatite target composition, Ca{sub 10}(PO{sub 4}){sub 6}F{sub 1.37}(OH){sub 0.63}, was maintained at 2 J/cm{sup 2} of laser fluence and 500-600 {sup o}C of the substrate temperature. Prepared films had a compact microstructure, composed of spherical micrometric-size aggregates. The average surface roughness resulted to be of 3 nm for the film grown at 500 {sup o}C and of 10 nm for that grown at 600 {sup o}C, showing that the temperature increase did not favour the growth of a more fine granulated surface. The films were polycrystalline with no preferential growth orientation. The films grown at 500-600 {sup o}C were about 8 {mu}m thick and possessed a hardness of 12-13 GPa. Lower or higher substrate temperature provides the possibility to obtain coatings with different fine texture and roughness, thus tayloring them for various applications.

  7. Pulsed laser kinetic studies of liquids under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Eyring, E.M.


    Experiments have been developed for measuring the rates of chemical reactions liquids and in supercritical Co[sub 2]. A pulsed (Q-switch) Nd:YAG laser at 355 nm was the pump beam for laser flash photolysis studies of molybdenum and tungsten hexacarbonyls undergoing ligand displacement reactions by bidentate chelating agents such as 2,2[prime]-bipyridine in toluene. Experiments were carried out at 0.1 to 150 MPa. In the case of molybdenum complexes, the reaction mechanism for thermal ring closure is found from activation volumes to change from associative interchange to dissociative interchange as substituents on the 2,2[prime]-bipyridine ligands become bulkier. In a similar study of more rigid, substituted phenanthroline bidentate ligands it was found that substituent bulkiness had little effect on the thermal ring closure mechanism. Similar high pressure flash photolysis experiments with tungsten hexacarbonyl have also been completed. The concentration dependence of the fluorescence and nonradiative decay quantum yields for cresyl violet in several solvent have been reported as well as stability constants for the complexation of lithium ion by four different crown ethers dissolved in a room temperature molten salt.

  8. Benefits of cryogenic cooling on the operation of a pulsed CO2 laser

    Indian Academy of Sciences (India)


    Jan 5, 2014 ... The paper presents results of a theoretical model of a pulsed electron beam controlled CO2 laser (EBCL) to investigate the effect of cooling on the laser gas mixture. It is shown that cryogenic cooling can significantly improve the performance of the laser. The efficiency of an EBCL improved from 20% to ...

  9. Benefits of cryogenic cooling on the operation of a pulsed CO2 laser

    Indian Academy of Sciences (India)


    Jan 5, 2014 ... Abstract. The paper presents results of a theoretical model of a pulsed electron beam controlled. CO2 laser (EBCL) to investigate the effect of cooling on the laser gas mixture. It is shown that cryogenic cooling can significantly improve the performance of the laser. The efficiency of an. EBCL improved from ...

  10. Enhanced performance of a repetitively pulsed 130 mJ KrF laser ...

    Indian Academy of Sciences (India)


    Jan 5, 2014 ... Studies related to the effect of pre-ionizer on laser output energy of a repetitively pulsed KrF laser are presented. The dependence of laser output energy, spectral width and beam spot homogeneity on pre-ionization parameters, namely its current and voltage rise time are reported here. Here, effectiveness ...

  11. Ultra short pulse laser generated surface textures for anti-ice applications in aviation

    NARCIS (Netherlands)

    Römer, G.W.; Del Cerro, D.A.; Sipkema, R.C.J.; Groenendijk, M.N.W.; Huis in 't Veld, A.J.


    By laser ablation with ultra short laser pulses in the pico- and femto-second range, well controlled dual scaled micro- and nano-scaled surface textures can be obtained. The micro-scale of the texture is mainly determined by the dimensions of the laser spot, whereas the superimposed nano-structure

  12. Laser-induced fluorescence analysis of plasmas for epitaxial growth of YBiO3 films with pulsed laser deposition

    National Research Council Canada - National Science Library

    Orsel, K; Groenen, Rik; Bastiaens, Hubertus M.J; Koster, Gertjan; Rijnders, Augustinus J.H.M; Boller, Klaus J


    ... the influence of oxygen present in the background gas during pulsed laser deposition to the oxidation of plasma species as well as the formation of epitaxial YBiO 3 films. With spatiotemporal LIF mapping of ...

  13. Degree of compression and energy efficiency of a capillary compressor of femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

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


    A relation between the degree of pulse compression and energy efficiency is derived for femtosecond laser pulse compressors that utilise spectral broadening of pulses in a gas-filled capillary. We show that the degree of compression has a maximum at an energy efficiency from 15% to 30%. A 15-fold compression of a 290-fs pulse with an energy efficiency of 24% is demonstrated.

  14. Narrow linewidth picosecond UV pulsed laser with mega-watt peak power. (United States)

    Huang, Chunning; Deibele, Craig; Liu, Yun


    We demonstrate a master oscillator power amplifier (MOPA) burst mode laser system that generates 66 ps/402.5 MHz pulses with mega-watt peak power at 355 nm. The seed laser consists of a single frequency fiber laser (linewidth laser is operating in a 5-μs/10-Hz macropulse mode. The laser output has a transform-limited spectrum with a very narrow linewidth of individual longitudinal modes. The immediate application of the laser system is the laser-assisted hydrogen ion beam stripping for the Spallation Neutron Source (SNS).

  15. Forward-backward asymmetry of photoemission in C60 excited by few-cycle laser pulses (United States)

    Gao, C.-Z.; Dinh, P. M.; Reinhard, P.-G.; Suraud, E.; Meier, C.


    We theoretically analyze angle-resolved photoelectron spectra (ARPES) generated by the interaction of C60 with intense, short laser pulses. In particular, we focus on the impact of the carrier-envelope phase (CEP) onto the angular distribution. The electronic dynamics is described by time-dependent density functional theory, and the ionic background of C60 is approximated by a particularly designed jellium model. Our results show a clear dependence of the angular distributions onto the CEP for very short pulses covering only very few laser cycles, which disappears for longer pulses. For the specific laser parameters used in recent experiments, a very good agreement is obtained. Furthermore, the asymmetry is found to depend on the energy of the emitted photoelectrons. The strong influence of the angular asymmetry of electron emission onto the CEP and pulse duration suggests using this sensitivity as a means to analyze the structure of few-cycle laser pulses.

  16. Multielectron dissociative ionization of methane and formaldehyde molecules with optimally tailored intense femtosecond laser pulses (United States)

    Irani, E.; Anvari, A.; Sadighi-Bonabi, R.; Monfared, M.


    The multielectron dissociative ionization of CH4 and CH2O molecules has been investigated using optimum convolution of different dual tailored short laser pulses. Based on three dimensional molecular dynamics simulations and TDDFT approach, the dissociation probability is enhanced by designing the dual chirped-chirped laser pulses and chirped-ordinary laser pulses for formaldehyde molecule. However, it is interesting to notice that the sensitivity of enhanced dissociation probability into different tailored laser pulses is not significant for methane molecule. In this presented modifications, time variation of bond length, velocity, time dependent electron localization function and evolution of the efficient occupation states are presented to analyze the time evolution of molecular dynamics. This work is proved to be a potential way to reduce the controlling costs with a currently available pulse shaping technology.

  17. Multiphoton photoemission from a copper cathode illuminated by ultrashort laser pulses in an RF photoinjector. (United States)

    Musumeci, P; Cultrera, L; Ferrario, M; Filippetto, D; Gatti, G; Gutierrez, M S; Moody, J T; Moore, N; Rosenzweig, J B; Scoby, C M; Travish, G; Vicario, C


    In this Letter we report on the use of ultrashort infrared laser pulses to generate a copious amount of electrons by a copper cathode in an rf photoinjector. The charge yield verifies the generalized Fowler-Dubridge theory for multiphoton photoemission. The emission is verified to be prompt using a two pulse autocorrelation technique. The thermal emittance associated with the excess kinetic energy from the emission process is comparable with the one measured using frequency tripled uv laser pulses. In the high field of the rf gun, up to 50 pC of charge can be extracted from the cathode using a 80 fs long, 2 microJ, 800 nm pulse focused to a 140 mum rms spot size. Taking into account the efficiency of harmonic conversion, illuminating a cathode directly with ir laser pulses can be the most efficient way to employ the available laser power.

  18. Transient analytical solution of temperature distribution and fracture limits in pulsed solid-state laser rod

    Directory of Open Access Journals (Sweden)

    Shibib Khalid S.


    Full Text Available The exact analytical solution of axis-symmetry transient temperature and Tresca failure stress in pulsed mode solid-state laser rod is derived using integral transform method. The result obtained from this work is compared with previously published data and good agreement is found. The effect of increasing period is studied, and it is found that at constant pulse width as the period is increased, the allowable pumping power is increased too. Furthermore, the effect of changing pulse width with a constant period is studied, and it is found that as the pulse width is increased, the allowable pumping power is decreased. The effect of duty cycle is studied also and it is found that as duty cycle is increased the allowable pumping power is decreased. This work permits proper selection of pulse width, period and duty cycle to avoid laser rod fracture while obtaining maximum output laser power in the designing of laser system.

  19. Forward voltage short-pulse technique for measuring high power laser array junction temperature (United States)

    Meadows, Byron L. (Inventor); Amzajerdian, Frazin (Inventor); Barnes, Bruce W. (Inventor); Baker, Nathaniel R. (Inventor)


    The present invention relates to a method of measuring the temperature of the P-N junction within the light-emitting region of a quasi-continuous-wave or pulsed semiconductor laser diode device. A series of relatively short and low current monitor pulses are applied to the laser diode in the period between the main drive current pulses necessary to cause the semiconductor to lase. At the sufficiently low current level of the monitor pulses, the laser diode device does not lase and behaves similar to an electronic diode. The voltage across the laser diode resulting from each of these low current monitor pulses is measured with a high degree of precision. The junction temperature is then determined from the measured junction voltage using their known linear relationship.

  20. Influence of consecutive picosecond pulses at 532 nm wavelength on laser ablation of human teeth (United States)

    Mirdan, Balsam M.; Antonelli, Luca; Batani, Dimitri; Jafer, Rashida; Jakubowska, Katarzyna; Tarazi, Saad al; Villa, Anna Maria; Vodopivec, Bruno; Volpe, Luca


    The interaction of 40 ps pulse duration laser emitting at 532 nm wavelength with human dental tissue (enamel, dentin, and dentin-enamel junction) has been investigated. The crater profile and the surface morphology have been studied by using a confocal auto-fluorescence microscope (working in reflection mode) and a scanning electron microscope. Crater profile and crater morphology were studied after applying consecutive laser pulses and it was found that the ablation depth increases with the number of consecutive pulses, leaving the crater diameter unchanged. We found that the thermal damage is reduced by using short duration laser pulses, which implies an increased retention of restorative material. We observe carbonization of the irradiated samples, which does not imply changes in the chemical composition. Finally, the use of 40 ps pulse duration laser may become a state of art in conservative dentistry.

  1. Observation of enhanced field-free molecular alignment by two laser pulses

    DEFF Research Database (Denmark)

    Bisgaard, Christer; Poulsen, Mikael Dahlerup; Peronne, Emmanuel


    We show experimentally that field-free alignment of iodobenzene molecules, induced by a single, intense, linearly polarized 1.4-ps-long laser pulse, can be strongly enhanced by dividing the pulse into two optimally synchronized pulses of the same duration. For a given total energy of the two-puls......-pulse sequence the degree of alignment is maximized with an intensity ratio of 1:3 and by sending the second pulse near the time where the alignment created by the first pulse peaks....

  2. Sensitive detection of chlorine in iron oxide by single pulse and dual pulse laser-induced breakdown spectroscopy (United States)

    Pedarnig, J. D.; Haslinger, M. J.; Bodea, M. A.; Huber, N.; Wolfmeir, H.; Heitz, J.


    The halogen chlorine is hard to detect in laser-induced breakdown spectroscopy (LIBS) mainly due to its high excited state energies of 9.2 and 10.4 eV for the most intense emission lines at 134.72 nm and 837.59 nm, respectively. We report on sensitive detection of Cl in industrial iron oxide Fe2O3 powder by single-pulse (SP) and dual-pulse (DP) LIBS measurements in the near infrared range in air. In compacted powder measured by SP excitation (Nd:YAG laser, 532 nm) Cl was detected with limit of detection LOD = 440 ppm and limit of quantitation LOQ = 720 ppm. Orthogonal DP LIBS was studied on pressed Fe2O3 pellets and Fe3O4 ceramics. The transmission of laser-induced plasma for orthogonal Nd:YAG 1064 nm and ArF 193 nm laser pulses showed a significant dependence on interpulse delay time (ipd) and laser wavelength (λL). The UV pulses (λL = 193 nm) were moderately absorbed in the plasma and the Cl I emission line intensity was enhanced while IR pulses (λL = 1064 nm) were not absorbed and Cl signals were not enhanced at ipd = 3 μs. The UV laser enhancement of Cl signals is attributed to the much higher signal/background ratio for orthogonal DP excitation compared to SP excitation and to the increased plasma temperature and electron number density. This enabled measurement at a very short delay time of td ≥ 0.1 μs with respect to the re-excitation pulse and detection of the very rapidly decaying Cl emission with higher efficiency.

  3. Simulations of Laser Pulse Coupling and Transmission Efficiency in Plasma Channels

    CERN Document Server

    Giacone, Rodolfo; Cary, John R; Dimitrov, Dimitre; Esarey, Eric; Geddes, Cameron G R; Leemans, Wim; Messmer, Peter


    Optical guiding of the laser pulse in a laser wakefield accelerator (LWFA) via plasma channels can greatly increase the interaction length and, hence, the maximun energy of trapped electrons.* Energy efficient coupling of laser pulses from vacuum into plasma channels is very important for optimal LWFA performance. We present 2D particle-in-cell simulations of this problem using the VORPAL code.** Some of the mechanisms considered are enhanced leakage of laser energy transversely through the channel walls, enhanced refraction due to tunneling ionization of neutral gas on the periphery of the gas jet, ionization of neutral gas by transverse wings of the laser pulse and effect of the pulse being off axis of the channel. Using power spectral diagnostics,*** we are able to differentiate between pump depletion and leakage from the channel. The results from our simulations show that for short (≈λp

  4. Plasma optical modulation for lasers based on the plasma induced by femtosecond pulses. (United States)

    Tan, Chao; Fu, Xiquan; Hu, Yonghua; Deng, Yangbao; Shi, Xiaohui; Zhan, Shiping; Xi, Zaifang


    We present a theoretical and experimental study of plasma optical modulation for probe lasers based on the plasma induced by pump pulses. This concept relies on two co-propagating laser pulses in carbon disulfide, where a drive laser pulse first excites plasma channels while a following carrier laser pulse is modulated by the plasma. The modulation on the probe beam can be conveniently adjusted through electron density, plasma width, propagation distance of plasma, the power of pump lasers, or the pump beam's profile. The experimental results and theoretical solutions are very consistent, which fully illustrates that this method for plasma optical modulation is reasonable. This pump-probe method is also a potential measurement technique for inferring the on-axis plasma density shape.

  5. Exploring the ultrashort pulse laser parameter space for membrane permeabilisation in mammalian cells. (United States)

    Rudhall, Andrew P; Antkowiak, Maciej; Tsampoula, Xanthi; Mazilu, Michael; Metzger, Nikolaus K; Gunn-Moore, Frank; Dholakia, Kishan


    The use of ultrashort femtosecond pulsed lasers to effect membrane permeabilisation and initiate both optoinjection and transfection of cells has recently seen immense interest. We investigate femtosecond laser-induced membrane permeabilisation in mammalian cells as a function of pulse duration, pulse energy and number of pulses, by quantifying the efficiency of optoinjection for these parameters. Depending on pulse duration and pulse energy we identify two distinct membrane permeabilisation regimes. In the first regime a nonlinear dependence of order 3.4-9.6 is exhibited below a threshold peak power of at least 6 kW. Above this threshold peak power, the nonlinear dependence is saturated resulting in linear behaviour. This indicates that the membrane permeabilisation mechanism requires efficient multiphoton absorption to produce free electrons but once this process saturates, linear absorption dominates. Our experimental findings support a previously proposed theoretical model and provide a step towards the optimisation of laser-mediated gene delivery into mammalian cells.

  6. Studies of the confinement at laser-induced backside dry etching using infrared nanosecond laser pulses (United States)

    Ehrhardt, M.; Lorenz, P.; Bayer, L.; Han, B.; Zimmer, K.


    In the present study, laser-induced backside etching of SiO2 at an interface to an organic material using laser pulses with a wavelength of λ = 1064 nm and a pulse length of τ = 7 ns have been performed in order to investigate selected processes involved in etching of the SiO2 at confined ablation conditions with wavelengths well below the band gap of SiO2. Therefore, in between the utilized metallic absorber layer and the SiO2 surface, a polymer interlayer with a thickness between 20 nm to 150 nm was placed with the aim, to separate the laser absorption process in the metallic absorber layer from the etching process of the SiO2 surface due to the provided organic interlayer. The influence of the confinement of the backside etching process was analyzed by the deposition of different thick polymer layers on top of the metallic absorber layer. In particular, it was found that the SiO2 etching depth decreases with higher polymer interlayer thickness. However, the etching depth increases with increasing the confinement layer thickness. SEM images of the laser processed areas show that the absorber and confinement layers are ruptured from the sample surface without showing melting, and suggesting a lift off process of these films. The driving force for the layers lift off and the etching of the SiO2 is probably the generated laser-induce plasma from the confined ablation that provides the pressure for lift off, the high temperatures and reactive organic species that can chemically attack the SiO2 surface at these conditions.

  7. Photocoagulation of dermal blood vessels with multiple laser pulses in an in vivo microvascular model. (United States)

    Jia, Wangcun; Tran, Nadia; Sun, Victor; Marinček, Marko; Majaron, Boris; Choi, Bernard; Nelson, J Stuart


    Current laser therapy of port wine stain (PWS) birthmarks with a single laser pulse (SLP) does not produce complete lesion removal in the majority of patients. To improve PWS therapeutic efficacy, we evaluated the performance of an approach based on multiple laser pulses (MLP) to enhance blood vessel photocoagulation. The hamster dorsal window chamber model was used. Radiant exposure (RE), pulse repetition rate (f(r)), total number of pulses (n(p)), and length of vessel irradiated were varied. Blood vessels in the window were irradiated with either SLP with RE of 4-7 J/cm(2) or MLP with RE per pulse of 1.4-5.0 J/cm(2), f(r) of 0.5-26.0 Hz, and n(p) of 2-5. The laser wavelength was 532 nm and pulse duration was 1 ms. Either a 2 mm vessel segment or entire vessel branch was irradiated. Digital photographs and laser speckle images of the window were recorded before and at specific time points after laser irradiation to monitor laser-induced blood vessel structural and functional changes, respectively. We found that: (1) for a SLP approach, the RE required to induce blood vessel photocoagulation was 7 J/cm(2) as compared to only 2 J/cm(2) per pulse for the MLP approach; (2) for MLP, two pulses at a repetition rate of 5 Hz and a RE of 3 J/cm(2) can induce photocoagulation of more than 80% of irradiated blood vessel; and (3) irradiation of a longer segment of blood vessel resulted in lower reperfusion rate. The MLP approach can induce blood vessel photocoagulation at much lower RE per pulse as compared to SLP. The 5 Hz f(r) and the need for two pulses are achievable with modern laser technology, which makes the MLP approach practical in the clinical management of PWS birthmarks. Copyright © 2012 Wiley Periodicals, Inc.

  8. Elimination of cracking during UV laser ablation of SrTiO 3 single crystals by employing a femtosecond laser (United States)

    Zoppel, S.; Gray, D.; Farsari, M.; Merz, R.; Reider, G. A.; Fotakis, C.


    We have performed a comparative study of UV laser ablation of SrTiO 3 with nanosecond- and sub-picosecond sources, respectively. The experiments were performed with lasers at a wavelength of 248 nm and pulse durations of 34 ns and 500 fs. Femtosecond ablation turns out to be more efficient by one order of magnitude and eliminated the known problem of cracking of SrTiO 3 during laser machining with longer pulses. In addition, the cavities ablated with femtosecond pulses display a smoother surface with no indication of melting and well-defined, sharp edges. These effects can be explained by the reduced thermal shock effect on the material by using ultrashort pulses.

  9. Enhanced 5-aminolevulinic acid-gold nanoparticle conjugate-based photodynamic therapy using pulse laser (United States)

    Xu, Hao; Yao, Cuiping; Wang, Jing; Chang, Zhennan; Zhang, Zhenxi


    The low bioavailability is a crucial limitation for the application of 5-aminolevulinic acid (ALA) in theranostics. In this research, 5-aminolevulinic acid and gold nanoparticle conjugates (ALA-GNPs) were synthesized to improve the bioavailability of ALA and to investigate the impact of ALA photodynamic therapy (ALA-PDT) in Hela cells. A 532 nm pulse laser and light-emitting diode (central wavelengths 502 nm) were jointly used as light sources in PDT research. The results show a 532 nm pulse laser can control ALA release from ALA-GNPs by adjusting the pulse laser dose. This laser control release may be attributed to the heat generation from GNPs under pulse laser irradiation, which indicates accurately adjusting the pulse laser dose to control the drug release in the cell interior can be considered as a new cellular surgery modality. Furthermore, the PDT results in Hela cells indicate the enhancement of ALA release by pulse laser before PDT can promote the efficacy of cell eradication in the light-emitting diode PDT (LED-PDT). This laser mediated drug release system can provide a new online therapy approach in PDT and it can be utilized in the optical monitor technologies based individual theranostics.

  10. Generation of a passively Q-switched mode-locked pulse from a laser diode pumped Nd:YAG laser

    CERN Document Server

    Jeong, T M; Kim, C J; Nam, C H


    A passively Q-switched, mode-locked pulse was generated from a laser diode pumped Nd:YAG laser. The passive Q-switching was performed by using a Cr sup 4 sup + :YAG saturable absorber. The mode-locked pulse inside the Q-switched pulse was obtained by using a nonlinear mirror mode-locking without any tight focusing geometry. With a Cr sup 4 sup + :YAG saturable absorber and a nonlinear mirror mode locking method, a mode-locked pulse with a pulse width of less than 600 ps and a repetition rate of 714 MHz was obtained inside a Q-switched pulse envelope with a temporal duration of 80 ns and a repetition rate of about 2 kHz.

  11. Numerical investigation on the effects of the laser energy and focal position on the multi-pulses laser propulsion

    Energy Technology Data Exchange (ETDEWEB)

    Song Junling [College of Postgraduate, the Academy of Equipment Command and Technology, Post Box 3380-86, Huairou Dis. Beijing, 101416 (China); Hong Yanji; Wen Ming, E-mail:, E-mail:, E-mail: [Department of Basic theories, the Academy of Equipment Command and Technology, Post Box 3380-86, Huairou Dis. Beijing, 101416 (China)


    A detailed parametric study on the air-breathing laser propulsive performance is carried out for multi-pulses. Based on the finite volume scheme, the detailed evolving process of the inner and outer flow fluids is simulated. The numerical models with different focal positions and laser energies are employed to analyze the parameters effect on the multi-pulses impulse coupling coefficient C{sub m}. Moreover, the laser frequency is discussed and compared with those calculations. The simulation results indicate that the focal position is one of the main factors to influence the multi-pulses C{sub m} at low frequency. For high frequency, it is beneficial to replenish the air in the nozzle when the focal position locates near the nozzle exit. The influence of the laser energy is similar to the single pulse at low frequency, but at high frequency, the partial filling air in the nozzle causes low C{sub m} by high laser energy. The multi-pulses C{sub m} is lower than that of a single pulse. In the same calculative time, the higher the laser frequency, the higher the impulse value, but the lower the C{sub m}.

  12. Externally Controlled Injection of Electrons by a Laser Pulse in a Laser Wakefield Electron Accelerator

    CERN Document Server

    Chen Szu Yuan; Chen Wei Ting; Chien, Ting-Yei; Lee, Chau-Hwang; Lin, Jiunn-Yuan; Wang, Jyhpyng


    Spatially and temporally localized injection of electrons is a key element for development of plasma-wave electron accelerator. Here we report the demonstration of two different schemes for electron injection in a self-modulated laser wakefield accelerator (SM-LWFA) by using a laser pulse. In the first scheme, by implementing a copropagating laser prepulse with proper timing, we are able to control the growth of Raman forward scattering and the production of accelerated electrons. We found that the stimulated Raman backward scattering of the prepulse plays the essential role of injecting hot electrons into the fast plasma wave driven by the pump pulse. In the second scheme, by using a transient density ramp we achieve self-injection of electrons in a SM-LWFA with spatial localization. The transient density ramp is produced by a prepulse propagating transversely to drill a density depression channel via ionization and expansion. The same mechanism of injection with comparable efficiency is also demonstrated wi...

  13. 15-THz pulse generation arising from modulation instability oscillation in a colliding-pulse mode-locking dye laser. (United States)

    Wang, C Y; Baldeck, P L; Budansky, Y; Alfano, R R


    15-THz trains of a few-tens-of-femtoseconds optical pulses were generated by modulation instability oscillation in a colliding-pulse mode-locked dye laser. A repeatable and stable modulation instability regime was obtained with the laser operating in the anomalous-dispersion regime and with a low saturable-absorber concentration. Autocorrelation measurements indicate that subpulses were completely separated in real time. Variations of the modulation with the pump power and the amount of dispersion in the cavity are in good agreement with modulation instability theory.

  14. Pulse-by-pulse multi-beam-line operation for x-ray free-electron lasers


    Toru Hara; Kenji Fukami; Takahiro Inagaki; Hideaki Kawaguchi; Ryota Kinjo; Chikara Kondo; Yuji Otake; Yasuyuki Tajiri; Hideki Takebe; Kazuaki Togawa; Tatsuya Yoshino; Hitoshi Tanaka; Tetsuya Ishikawa


    The parallel operation of plural undulator beam lines is an important means of improving the efficiency and usability of x-ray free-electron laser facilities. After the installation of a second undulator beam line (BL2) at SPring-8 Angstrom compact free-electron laser (SACLA), pulse-by-pulse switching between two beam lines was tested using kicker and dc twin-septum magnets. To maintain a compact size, all undulator beam lines at SACLA are designed to be placed within the same undulator hall ...

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

    DEFF Research Database (Denmark)

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


    is analyzed from the direct time-dependent position measurements and from the power spectrum. The results show that the bead is on average displaced 208 nm from the trap center and exposed to a force amplitude of 71 nanoNewton, more than five orders of magnitude larger than the trapping forces. Our......An experimental strategy for post-eliminating thermal noise on position measurements of optically trapped particles is presented. Using a nanosecond pulsed laser, synchronized to the detection system, to exert a periodic driving force on an optically trapped 10 polystyrene bead, the laser pulse...

  16. Repetitively pulsed SPER laser using transitions in Cd atoms. [Segmented plasma source of metal vapor

    Energy Technology Data Exchange (ETDEWEB)

    Apollonov, V.V.; Sirotkin, A.A. (Institut Obshchei Fiziki, Moscow (USSR))


    The repetitively pulsed operation of a laser with a segmented plasma source of metal vapor using transitions in Cd I atoms (at wavelengths of 1.43 and 3.955 microns) is reported. The mean power of laser radiation at the pump pulse repetition rate of 2 kHz amounted to 36 and 20 mW for 1.43 and 3.955 microns, respectively. Mechanisms which limit the maximum pulse repetition rate are considered, and ways to enhance the laser output energy characteristics are proposed. 7 refs.

  17. Effects of wavelength filtering on pulse dynamics in a tunable, actively Q-switched fiber laser (United States)

    Srivastava, Manas; Venkitesh, Deepa; Srinivasan, Balaji


    We present a numerical simulation, validated by experimental analysis, of the effect of wavelength filtering on pulse dynamics of a wavelength-tunable Erbium-doped fiber Q-switched laser in a ring configuration. Travelling wave time-dependent model is implemented using finite difference time domain (FDTD) method to accurately simulate the population dynamics and the pulse evolution in the ring laser. Such a model is experimentally validated for a wavelength tunable Q-switched fiber laser and stable Q-switched pulses are obtained over a wavelength tuning range of ∼30 nm in the C-band.

  18. Comparison of soft and hard tissue ablation with sub-ps and ns pulse lasers

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva, L.B.; Stuart, B.C.; Celliers, P.M.; Feit, M.D.; Glinsky, M.E.; Heredia, N.J.; Herman, S.; Lane, S.M.; London, R.A.; Matthews, D.L.; Perry, M.D.; Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Chang, T.D. [Veterans Administration Hospital, Martinez, CA (United States); Neev, J. [Beckman Laser Inst. and Medical Clinic, Irvine, CA (United States)


    Tissue ablation with ultrashort laser pulses offers several unique advantages. The nonlinear energy deposition is insensitive to tissue type, allowing this tool to be used for soft and hard tissue ablation. The localized energy deposition lead to precise ablation depth and minimal collateral damage. This paper reports on efforts to study and demonstrate tissue ablation using an ultrashort pulse laser. Ablation efficiency and extent of collateral damage for 0.3 ps and 1000 ps duration laser pulses are compared. Temperature measurements of the rear surface of a tooth section is also presented.

  19. Layout of NALM fiber laser with adjustable peak power of generated pulses. (United States)

    Smirnov, Sergey; Kobtsev, Sergey; Ivanenko, Alexey; Kokhanovskiy, Alexey; Kemmer, Anna; Gervaziev, Mikhail


    The Letter proposes a new layout of a passively mode-locked fiber laser based on a nonlinear amplifying loop mirror (NALM) with two stretches of active fiber and two independently controlled pump modules. In contrast with conventional NALM configurations using a single piece of active fiber that yields virtually constant peak power, the proposed novel laser features larger than a factor of 2 adjustment range of peak power of generated pulses. The proposed layout also provides independent adjustment of duration and peak power of generated pulses as well as power-independent control of generated pulse spectral width impossible in NALM lasers with a single piece of active fiber.

  20. Femtosecond-pulse laser ablation of dental hydroxyapatite and single-crystalline fluoroapatite (United States)

    Krüger, J.; Kautek, W.; Newesely, H.

    Laser microdrilling of healthy human enamel and dentine using 300 fs pulses at a wavelength of 615 nm and 3 Hz repetition rate leads to an enhanced structuring quality in comparison with nanosecond-laser results. Microcracking and damage to neighboring tissue can be reduced. Ablation threshold fluences for 100 laser pulses of 0.3 Jcm-2 (human dentine), 0.6 Jcm-2 (human enamel) and 0.8 Jcm-2 (single crystalline fluoroapatite) could be determined. Ablation depths per pulse below 1 μm were observed.

  1. High-power ns-pulse fiber laser sources for remote sensors (United States)

    Di Teodoro, Fabio; Belden, Paul; Ionov, Pavel; Werner, Nicolette


    The development of fiber-based laser sources for space-borne remote sensors must meet many concurrent requirements including high pulse energy/peak power, excellent beam quality, narrow spectral linewidth, simple thermal management, small volume and mass, low power consumption, rugged packaging, and long-term reliability. To address these requirements, many aspects of pulse fiber laser technology must be advanced beyond the state of the art of traditional optical sources used in telecommunications and materials processing. In this article, we discuss component and solutions that enable pulsed fiber laser sources to support remote sensing from space. We also describe several examples of such sources and characterize their performance.

  2. Decoupling Electronic versus Nuclear Photoresponse of Isolated Green Fluorescent Protein Chromophores Using Short Laser Pulses (United States)

    Kiefer, Hjalte V.; Pedersen, Henrik B.; Bochenkova, Anastasia V.; Andersen, Lars H.


    The photophysics of a deprotonated model chromophore for the green fluorescent protein is studied by femtosecond laser pulses in an electrostatic ion-storage ring. The laser-pulse duration is much shorter than the time for internal conversion, and, hence, contributions from sequential multiphoton absorption, typically encountered with ns-laser pulses, are avoided. Following single-photon excitation, the action-absorption maximum is shown to be shifted within the S0 to S1 band from its origin at about 490 to 450 nm, which is explained by the different photophysics involved in the detected action.

  3. Analysis of thermodynamic effect in Si irradiated by pulsed-laser (United States)

    Guo, Ming; Jin, Guangyong; Li, Mingxin; Ma, Yao; Yuan, Boshi; Yu, Huadong


    According to the heat conduction equation, thermoelastic equation and boundary conditions of finite, using the finite element method(FEM), established the three-dimensional finite element calculation model of thermal elastic ,numerical simulation the transient temperature field and stress field distribution of the single crystal silicon materials by the pulsing laser irradiation, and analytic solution the temperature distribution and stress distribution of laser irradiation on the silicon material , and analyzes the different parameters such as laser energy, pulse width, pulse number influence on temperature and stress, and the intrinsic damage mechanism of pulsed laser irradiation on silicon were studied. The results show that the silicon material is mainly in hot melt under the action of ablation damage.According to the irradiation of different energy and different pulse laser ,we can obtain the center temperature distribution, then get the law of the change of temperature with the variation of laser energy and pulse width in silicon material; according to the principal stress and shear stress distribution in 110 direction with different energy and different pulse, we can get the law of the change of stress distribution with the variation of laser energy and pulse width ;according to the principal stress distribution of single pulse and pulse train in 110 direction, we can get the law of the change of stress with pulse numbers in silicon.When power density of laser on optical material surface (or energy density) is the damage threshold, the optical material surface will form a spontaneous, periodic, and permanent surface ripple, it is called periodic surface structure laser induced (LIPSS).It is the condensed optical field of work to generate low dimensional quantum structures by laser irradiation on Si samples. The pioneering work of research and development and application of low dimensional quantum system has important academic value.The result of this paper

  4. Feasibility of depth profiling of animal tissue by ultrashort pulse laser ablation. (United States)

    Milasinovic, Slobodan; Liu, Yaoming; Bhardwaj, Chhavi; Blaze M T, Melvin; Gordon, Robert J; Hanley, Luke


    Experiments were performed to examine the feasibility of mass spectrometry (MS) depth profiling of animal tissue by ~75 fs, 800 nm laser pulses to expose underlying layers of tissue for subsequent MS analysis. Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) was used to analyze phospholipids and proteins from both intact bovine eye lens tissue and tissue ablated by ultrashort laser pulses. Laser desorption postionization mass spectrometry (LDPI-MS) with 10.5 eV single photon ionization was also used to analyze cholesterol and other small molecules in the tissue before and after laser ablation. Scanning electron microscopy was applied to examine the ablation patterns in the tissue and estimate the depth of the ablation craters. Ultrashort pulse laser ablation was found to be able to remove a layer of several tens of micrometers from the surface of eye lens tissue while leaving the underlying tissue relatively undamaged for subsequent MS analysis. MS analysis of cholesterol, phospholipids, peptides, and various unidentified species did not reveal any chemical damage caused by ultrashort pulse laser ablation for analytes smaller than ~6 kDa. However, a drop in intensity of larger protein ions was detected by MALDI-MS following laser ablation. An additional advantage was that ablated tissue displayed up to an order of magnitude higher signal intensities than intact tissue when subsequently analyzed by MS. These results support the use of ultrashort pulse laser ablation in combination with MS analysis to permit depth profiling of animal tissue.

  5. Transient magnetized plasma as an optical element for high power laser pulses

    Directory of Open Access Journals (Sweden)

    Nobuhiko Nakanii


    Full Text Available Underdense plasma produced in gas jets by low intensity laser prepulses in the presence of a static magnetic field, B∼0.3  T, is shown experimentally to become an optical element allowing steering of tightly focused high power femtosecond laser pulses within several degrees along with essential enhancement of pulse’s focusability. Strong laser prepulses form a density ramp perpendicularly to magnetic field direction and, owing to the light refraction, main laser pulses propagate along the magnetic field even if it is tilted from the laser axis. Electrons generated in the laser pulse wake are well collimated and follow in the direction of the magnetic field; their characteristics are measured to be not sensitive to the tilt of magnetic field up to angles ±5°.

  6. Pulsed laser Raman spectroscopy in the laser-heated diamond anvil cell

    Energy Technology Data Exchange (ETDEWEB)

    Goncharov, A F; Crowhurst, J C


    We describe the design and operation of a spatially-filtered Raman/fluorescence spectrometer that incorporates a pulsed 532 nm laser excitation source and a synchronized and electronically gated CCD detector. This system permits the suppression of undesired continuous radiation from various sources by a factor of up to 50,000 providing the possibility of acquiring Raman signals at temperatures exceeding 5,000 K. We present performance comparisons of this system with that of a state-of-the-art conventional CW system using a 458 nm excitation source. We also demonstrate that the pulsed system is capable of suppressing an impurity-induced (single nitrogen defects) fluorescence in diamond, and further suggest that this capability can be used to suppress the stress-induced fluorescence in diamond that may appear at pressures near or above 150 GPa.

  7. A pulsed single-longitudinal-mode fiber laser based on gain control of pulse-injection-locked cavity (United States)

    Wan, Hongdan; Wu, Zhongwei; Sun, Xiaohan


    We achieve a pulsed fiber laser based on injecting a pulsed-seed into a high power fiber ring cavity consisting of two-stage amplifier chain. Through gain control of the fiber amplifier chain and adjustment of a variable optical coupler in the cavity, locking condition is satisfied which produce mode-hopping free, single-longitudinal-mode optical spectrum with 38 dB optical signal to noise ratio. The noise-free lasing RF spectrum has a 7.0 kHz 3 dB linewidth. The nanosecond lasing pulses are jittering-free with 40 W peak power at 1550 nm wavelength.

  8. Retina damage potential by ultra-short laser pulses in refractive surgery


    Sander, Meike


    Since the beginning of the 1990s, laser in situ keratomileusis procedure (LASIK) has been successfully implemented in refractive eye surgery to correct ametropia. Nowadays this long time commanding treatment method is enhanced by implementing a new laser technology. It is based on correcting ametropia by applying ultrashort laser pulses in the fs-regime without using mechanical effect. Within this new technique the cutting process inside the cornea is achieved by a laser induced break...

  9. Plasma channels during filamentation of a femtosecond laser pulse with wavefront astigmatism in air

    Energy Technology Data Exchange (ETDEWEB)

    Dergachev, A A; Kandidov, V P; Shlenov, S A [Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation); Ionin, A A; Mokrousova, D V; Seleznev, L V; Sinitsyn, D V; Sunchugasheva, E S; Shustikova, A P [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)


    We have demonstrated experimentally and numerically the possibility of controlling parameters of plasma channels formed during filamentation of a femtosecond laser pulse by introducing astigmatism in the laser beam wavefront. It is found that weak astigmatism increases the length of the plasma channel in comparison with the case of aberration-free focusing and that strong astigmatism can cause splitting of the plasma channel into two channels located one after another on the filament axis. (interaction of laser radiation with matter. laser plasma)

  10. Design and simulation of laser wakefield acceleration with external electron bunch injection in front of the laser pulse

    NARCIS (Netherlands)

    Irman, A.; Luttikhof, M.J.H.; Khachatryan, A.G.; van Goor, F.A.; Verschuur, Jeroen W.J.; Bastiaens, Hubertus M.J.; Boller, Klaus J.


    In this article we present a theoretical investigation on an experimental design of a laser wakefield accelerator in which electron bunches from a photocathode radio frequency linac are injected into a capillary discharge plasma channel just in front of a few tens of terawatt drive laser pulse. The

  11. Three-dimensional time and frequency-domain theory of femtosecond x-ray pulse generation through Thomson scattering

    Directory of Open Access Journals (Sweden)

    Winthrop J. Brown


    Full Text Available The generation of high intensity, ultrashort x-ray pulses enables exciting new experimental capabilities, such as femtosecond pump-probe experiments used to temporally resolve material structural dynamics on atomic time scales. Thomson backscattering of a high intensity laser pulse with a bright relativistic electron bunch is a promising method for producing such high-brightness x-ray pulses in the 10–100 keV range within a compact facility. While a variety of methods for producing subpicosecond x-ray bursts by Thomson scattering exist, including compression of the electron bunch to subpicosecond bunch lengths and/or colliding a subpicosecond laser pulse in a side-on geometry to minimize the interaction time, a promising alternative approach to achieving this goal while maintaining ultrahigh brightness is the production of a time-correlated (or chirped x-ray pulse in conjunction with pulse slicing or compression. We present the results of a complete analysis of this process using a recently developed 3D time and frequency-domain code for analyzing the spatial, temporal, and spectral properties an x-ray beam produced by relativistic Thomson scattering. Based on the relativistic differential cross section, this code has the capability to calculate time and space dependent spectra of the x-ray photons produced from linear Thomson scattering for both bandwidth-limited and chirped incident laser pulses. Spectral broadening of the scattered x-ray pulse resulting from the incident laser bandwidth, laser focus, and the transverse and longitudinal phase space of the electron beam were examined. Simulations of chirped x-ray pulse production using both a chirped electron beam and a chirped laser pulse are presented. Required electron beam and laser parameters are summarized by investigating the effects of beam emittance, energy spread, and laser bandwidth on the scattered x-ray spectrum. It is shown that sufficient temporal correlation in the scattered

  12. Ultrafast switching dynamics of nonlasing modes of vertical-cavity surface-emitting lasers (United States)

    Zhang, Botao; Snoke, David W.; Heberle, Albert P.


    Single-mode vertical-cavity surface-emitting lasers (VCSELs) have been investigated with ultrafast optical modulation. After injection of a subpicosecond laser pulse into the VCSEL cavity, nonlasing modes were excited and produced optical beating in the emission of the VCSEL. After these oscillations have died down, when the VCSEL is operating at high power and when the injected laser pulses exceed a power threshold as well, the injected laser pulses can induce the lasing to switch to a normally nonlasing mode with crossed polarization. Our measurements of the decay time of the nonlasing modes at low injected pulse energy are consistent with the interpretation of this switching as enabled by increased lifetime of the nonlasing modes at high power.

  13. University of Illinois nuclear pumped laser program. [experiments with a TRIGA pulsed reactor with a broad pulse and a low peak flux (United States)

    Miley, G. H.


    The development of nuclear pumped lasers with improved efficiency, energy storage capability, and UF6 volume pumping is reviewed. Results of nuclear pumped laser experiments using a TRIGA-type pulsed reactor are outlined.

  14. Precision and resolution in laser direct microstructuring with bursts of picosecond pulses (United States)

    Mur, Jaka; Petkovšek, Rok


    Pulsed laser sources facilitate various applications, including efficient material removal in different scientific and industrial applications. Commercially available laser systems in the field typically use a focused laser beam of 10-20 μm in diameter. In line with the ongoing trends of miniaturization, we have developed a picosecond fiber laser-based system combining fast beam deflection and tight focusing for material processing and optical applications. We have predicted and verified the system's precision, resolution, and minimum achievable feature size for material processing applications. The analysis of the laser's performance requirements for the specific applications of high-precision laser processing is an important aspect for further development of the technique. We have predicted and experimentally verified that maximal edge roughness of single-micrometer-sized features was below 200 nm, including the laser's energy and positioning stability, beam deflection, the effect of spot spacing, and efficient isolation of mechanical vibrations. We have demonstrated that a novel fiber laser operating regime in bursts of pulses increases the laser energy stability. The results of our research improve the potential of fiber laser sources for material processing applications and facilitate their use through enabling the operation at lower pulse energies in bursts as opposed to single pulse regimes.

  15. Characterization of pulsed laser deposited chalcogenide thin layers

    Energy Technology Data Exchange (ETDEWEB)

    Petkova, T. [Institute of Electrochemistry and Energy Systems (IEES), Bulgarian Academy of Sciences, Sofia (Bulgaria)], E-mail:; Popov, C. [Institute of Nanostructure Technologies and Analytics (INA), University of Kassel (Germany); Hineva, T.; Petkov, P. [Laboratory of Thin Film Technology, Department of Physics, University of Chemical Technology and Metallurgy, Sofia (Bulgaria); Socol, G.; Axente, E.; Mihailescu, C.N.; Mihailescu, I.N. [National Institute for Lasers, Plasma, and Radiation Physics, Bucharest-Magurele (Romania); Reithmaier, J.P. [Institute of Nanostructure Technologies and Analytics (INA), University of Kassel (Germany)


    In this work we report on pulsed laser deposition (PLD) of chalcogenide thin films from the systems (AsSe){sub 100-x}AgI{sub x} and (AsSe){sub 100-x}Ag{sub x} for sensing applications. A KrF* excimer laser ({lambda} = 248 nm; {tau}{sub FWHM} = 25 ns) was used to ablate the targets that had been prepared from the synthesised chalcogenide materials. The films were deposited in either vacuum (4 x 10{sup -4} Pa) or argon (5 Pa) on silicon and glass substrates kept at room temperature. The basic properties of the films, including their morphology, topography, structure, and composition were characterised by complementary techniques. Investigations by X-ray diffraction (XRD) confirmed the amorphous nature of the films, as no strong diffraction reflections were found. The film composition was studied by energy dispersive X-ray (EDX) spectroscopy. The morphology of the films investigated by scanning electron microscopy (SEM), revealed a particulate-covered homogeneous surface, typical of PLD. Topographical analyses by atomic force microscopy (AFM) showed that the particulate size was slightly larger in Ar than in vacuum. The uniform surface areas were rather smooth, with root mean square (rms) roughness increasing up to several nanometers with the AgI or Ag doping. Based upon the results from the comprehensive investigation of the basic properties of the chalcogenide films prepared by PLD and their dependence on the process parameters, samples with appropriate sorption properties can be selected for possible applications in cantilever gas sensors.

  16. Pyramidal growth of ceria nanostructures by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Bârcă, E.S. [Pitesti University, Faculty of Mechanics and Technology, 110040 Pitesti, Arges (Romania); Filipescu, M., E-mail: [National Institute for Lasers, Plasma and Radiation Physics, 077125 Magurele (Romania); Luculescu, C.; Birjega, R.; Ion, V.; Dumitru, M. [National Institute for Lasers, Plasma and Radiation Physics, 077125 Magurele (Romania); Nistor, L.C. [National Institute of Materials Physics, 077125 Magurele, Ilfov (Romania); Stanciu, G. [National Institute for Lasers, Plasma and Radiation Physics, 077125 Magurele (Romania); University Politehnica of Bucharest, Faculty of Applied Chemistry and Material Science, 011061 Bucharest (Romania); Abrudeanu, M. [Pitesti University, Faculty of Mechanics and Technology, 110040 Pitesti, Arges (Romania); Munteanu, C. [Technical University “Gheorghe Asachi” of Iasi, Faculty of Mechanics, 700050, Iasi (Romania); Dinescu, M. [National Institute for Lasers, Plasma and Radiation Physics, 077125 Magurele (Romania)


    Graphical abstract: - Highlights: • Growth of ceria thin films with pyramidal morphology suitable for catalytic and sensor applications. • Ceria thin films with hierarchical structures combination of columnar and dendritic growth and crystalline cubic structure are obtained by pulsed laser deposition. • High substrate temperature influences the appearance of these hierarchical structures. - Abstract: We report in this paper on the deposition and characterization of CeO{sub 2} nanostructured thin films with hierarchical morphology. Micro-sized ceria powder (CeO{sub 2}, 99.9% purity) was pressed to obtain a ceramic target. An ArF laser working at 193 nm irradiated the target in controlled oxygen gas flow at constant pressure (0.1 mbar). Silicon wafers used as substrates for thin films were heated at different temperatures, up to 773 K. The influence of substrate temperature on the structure and surface morphology of ceria thin films was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and scanning electron microscopy (SEM). The refractive indices and information about roughness and thickness were revealed by spectroellipsometry. Crystalline cubic ceria thin films exhibiting a hierarchical structure that combines columnar and dendritic growth were obtained at temperatures above 473 K. For the samples obtained at 773 K, columns ending in pyramidal formations with sharp edges and sizes of hundreds of nanometers were observed, indicating a high crystallinity of the layer. XRD analysis reveals a consistent increase of the X-ray coherence length/crystallite size along the [111] direction with increasing temperature. Using a semi-empirical formula, Raman crystallites sizes were calculated and it was found that size increases with the temperature increasing. The spectroellipsometry investigations evidenced the increasing of refractive index with the substrate temperature increase. High surface roughness and pyramidal

  17. Modeling and laser-based sensing of pulsed detonation engines (United States)

    Barbour, Ethan A.

    This work is concerned with two major aspects of pulse detonation engines (PDE) research: modeling and laser-based sensing. The modeling addresses both ideal and real considerations relevant to PDE design. First, an ideal nozzle model is developed which provides a tool for choosing area ratios for fixed-geometry converging, diverging, or converging-diverging nozzles. Next, losses associated with finite-rate chemistry are investigated. It was found that PDEs can experience up to 10% reduction in specific impulse from this effect if 02 is used as the oxidizer, whereas the losses are negligible for air-breathing applications. Next, heat transfer and friction losses were investigated and found to be greater than the losses from simple straight-tube PDEs. These losses are most pronounced (˜15%) when converging nozzles are used. The second portion of this work focuses on laser-based absorption sensing for PDEs. The mid-infrared was chosen as the best way to address the challenges of signal-to-noise ratio, sensitivity, robustness, and sensor bandwidth. A water vapor sensor was developed and applied to the PDE at the Naval Postgraduate School. This sensor provided improvements in temperature accuracy, and it revealed that water (generated by the vitiator) inhibited performance of the engine. Next, a JP-10 absorption sensor was developed and applied to the same engine. This sensor provided thermometry data at a higher temporal resolution than the water sensor. The sensor also provided crucial information on equivalence ratio and fuel arrival time which enabled the engine to be successfully operated on JP-10 and air for the first time.

  18. Modeling crater formation in femtosecond-pulse laser damage from basic principles. (United States)

    Mitchell, Robert A; Schumacher, Douglass W; Chowdhury, Enam A


    We present the first fundamental simulation method for the determination of crater morphology due to femtosecond-pulse laser damage. To this end we have adapted the particle-in-cell (PIC) method commonly used in plasma physics for use in the study of laser damage and developed the first implementation of a pair potential for PIC codes. We find that the PIC method is a complementary approach to modeling laser damage, bridging the gap between fully ab-initio molecular dynamics approaches and empirical models. We demonstrate our method by modeling a femtosecond-pulse laser incident on a flat copper slab for a range of intensities.

  19. Synthesis and Properties of Platinum Nanoparticles by Pulsed Laser Ablation in Liquid

    Directory of Open Access Journals (Sweden)

    Maria Isabel Mendivil Palma


    Full Text Available Platinum (Pt nanoparticles were synthesized by pulsed laser ablation in liquid (PLAL technique in different liquids (acetone, ethanol, and methanol. Ablation was performed using a Q-switched Nd:YAG laser with output energy of 230 mJ/pulse for 532 nm wavelength. Ablation time and laser energy fluence were varied for all the liquids. Effects of laser energy fluence, ablation time, and nature of the liquid were reported. The mean size, size distributions, shape, elemental composition, and optical properties of Pt nanoparticles synthesized by PLAL were examined by transmission electron microscopy (TEM, X-ray photoelectron spectroscopy (XPS, and UV-Visible absorption spectroscopy.

  20. Metal oxide hollow nanoparticles formation by a single nanosecond pulsed laser ablation in liquid (United States)

    Zhang, Tao; Wang, Zhen; Hwang, David J.


    In this study, the trend of metal oxide hollow nanoparticles formation is experimentally inspected by a single nanosecond pulsed laser ablation of a bulk metal material in water and/or ethanol. Analysis results by transmission electron microscope indicate that the hollow formation can be completed or initiated by a single nanosecond laser pulse, dictated by the diffusive thermo-chemical and/or bubble-assisted assembly mechanisms, depending on the surrounding liquid medium and laser parameters. The results not only provide experimental clues to unveiling complex mechanisms involved with the hollow formation by the multiple laser shots but also will contribute to improving the hollow particle production efficiency.