WorldWideScience

Sample records for ultrashort laser fields

  1. Ultrashort Laser Pulse Phenomena

    CERN Document Server

    Diels, Jean-Claude

    2006-01-01

    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

  2. Effects of nuclear vibration on the ionization process of H2+ in ultrashort intense laser field

    International Nuclear Information System (INIS)

    Phan, Ngoc-Loan; Nguyen, Ngoc-Ty; Truong, Tran-Chau

    2015-01-01

    By numerically solving the time-dependent Schrödinger equation, we calculate the ionization probability of a vibrating H 2 + exposed to ultrashort intense laser fields. The results show that the ionization probability increases by time and gets a saturation value. We also find that with some first vibration levels, the ionization probability from a higher vibration level is larger than that from a lower one. However, with higher vibration levels, at a certain level the ionization probability will take maximum and decrease with next levels. (paper)

  3. Fields of an ultrashort tightly focused radially polarized laser pulse in a linear response plasma

    Science.gov (United States)

    Salamin, Yousef I.

    2017-10-01

    Analytical expressions for the fields of a radially polarized, ultrashort, and tightly focused laser pulse propagating in a linear-response plasma are derived and discussed. The fields are obtained from solving the inhomogeneous wave equations for the vector and scalar potentials, linked by the Lorenz gauge, in a plasma background. First, the scalar potential is eliminated using the gauge condition, then the vector potential is synthesized from Fourier components of an initial uniform distribution of wavenumbers, and the inverse Fourier transformation is carried out term-by-term in a truncated series (finite sum). The zeroth-order term in, for example, the axial electric field component is shown to model a pulse much better than its widely used paraxial approximation counterpart. Some of the propagation characteristics of the fields are discussed and all fields are shown to have manifested the expected limits for propagation in a vacuum.

  4. Ultrashort pulse laser technology laser sources and applications

    CERN Document Server

    Schrempel, Frank; Dausinger, Friedrich

    2016-01-01

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

  5. Double ionization of molecule H2 in intense ultrashort laser fields

    International Nuclear Information System (INIS)

    Le, Thu-Thuy; Nguyen, Ngoc-Ty

    2015-01-01

    By solving numerically the time-dependent Schrödinger equation (TDSE), we have calculated the double ionization probability when a vibrating hydrogen molecule interacts with intense ultrashort laser pulses. The results show that in the case of vibrating nuclei the double ionization probability is higher than that of the fixed nuclei. Additionally, the double ionization probability is larger if the molecule is vibrating in a higher level. This is due to the decreasing of ionization potential when the inter-nuclei separation increases. (paper)

  6. Superintense fields from multiple ultrashort laser pulses retroreflected in circular geometry

    Science.gov (United States)

    Ooi, C. H. Raymond

    2010-02-01

    Laser field with superintensity beyond 1029 W/cm2 can be generated by coherent superposition of multiple 100 fs laser pulses in circular geometry setup upon retroreflection by a ring mirror. We have found the criteria for attaining such intensities using broadband ring mirror within the practical damage threshold and paraxial focusing regime. Simple expressions for the intensity enhancement factor are obtained, providing insight for achieving unlimited laser intensity. Higher intensities can be achieved by using few-cycle laser pulses.

  7. Metal processing with ultrashort laser pulses

    Science.gov (United States)

    Banks, Paul S.; Felt, M. D.; Komashko, Aleksey M.; Perry, Michael D.; Rubenchik, Alexander M.; Stuart, Brent C.

    2000-08-01

    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.

  8. Near-field marking of gold nanostars by ultrashort pulsed laser irradiation: experiment and simulations

    Science.gov (United States)

    Møller, Søren H.; Vester-Petersen, Joakim; Nazir, Adnan; Eriksen, Emil H.; Julsgaard, Brian; Madsen, Søren P.; Balling, Peter

    2018-02-01

    Quantitative measurements of the electric near-field distribution of star-shaped gold nanoparticles have been performed by femtosecond laser ablation. Measurements were carried out on and off the plasmon resonance. A detailed comparison with numerical simulations of the electric fields is presented. Semi-quantitative agreement is found, with slight systematic differences between experimentally observed and simulated near-field patterns close to strong electric-field gradients. The deviations are attributed to carrier transport preceding ablation.

  9. Laser-based terahertz-field-driven streak camera for the temporal characterization of ultrashort processes

    International Nuclear Information System (INIS)

    Schuette, Bernd

    2011-09-01

    In this work, a novel laser-based terahertz-field-driven streak camera is presented. It allows for a pulse length characterization of femtosecond (fs) extreme ultraviolet (XUV) pulses by a cross-correlation with terahertz (THz) pulses generated with a Ti:sapphire laser. The XUV pulses are emitted by a source of high-order harmonic generation (HHG) in which an intense near-infrared (NIR) fs laser pulse is focused into a gaseous medium. The design and characterization of a high-intensity THz source needed for the streak camera is also part of this thesis. The source is based on optical rectification of the same NIR laser pulse in a lithium niobate crystal. For this purpose, the pulse front of the NIR beam is tilted via a diffraction grating to achieve velocity matching between NIR and THz beams within the crystal. For the temporal characterization of the XUV pulses, both HHG and THz beams are focused onto a gas target. The harmonic radiation creates photoelectron wavepackets which are then accelerated by the THz field depending on its phase at the time of ionization. This principle adopted from a conventional streak camera and now widely used in attosecond metrology. The streak camera presented here is an advancement of a terahertz-field-driven streak camera implemented at the Free Electron Laser in Hamburg (FLASH). The advantages of the laser-based streak camera lie in its compactness, cost efficiency and accessibility, while providing the same good quality of measurements as obtained at FLASH. In addition, its flexibility allows for a systematic investigation of streaked Auger spectra which is presented in this thesis. With its fs time resolution, the terahertz-field-driven streak camera thereby bridges the gap between attosecond and conventional cameras. (orig.)

  10. Laser-based terahertz-field-driven streak camera for the temporal characterization of ultrashort processes

    Energy Technology Data Exchange (ETDEWEB)

    Schuette, Bernd

    2011-09-15

    In this work, a novel laser-based terahertz-field-driven streak camera is presented. It allows for a pulse length characterization of femtosecond (fs) extreme ultraviolet (XUV) pulses by a cross-correlation with terahertz (THz) pulses generated with a Ti:sapphire laser. The XUV pulses are emitted by a source of high-order harmonic generation (HHG) in which an intense near-infrared (NIR) fs laser pulse is focused into a gaseous medium. The design and characterization of a high-intensity THz source needed for the streak camera is also part of this thesis. The source is based on optical rectification of the same NIR laser pulse in a lithium niobate crystal. For this purpose, the pulse front of the NIR beam is tilted via a diffraction grating to achieve velocity matching between NIR and THz beams within the crystal. For the temporal characterization of the XUV pulses, both HHG and THz beams are focused onto a gas target. The harmonic radiation creates photoelectron wavepackets which are then accelerated by the THz field depending on its phase at the time of ionization. This principle adopted from a conventional streak camera and now widely used in attosecond metrology. The streak camera presented here is an advancement of a terahertz-field-driven streak camera implemented at the Free Electron Laser in Hamburg (FLASH). The advantages of the laser-based streak camera lie in its compactness, cost efficiency and accessibility, while providing the same good quality of measurements as obtained at FLASH. In addition, its flexibility allows for a systematic investigation of streaked Auger spectra which is presented in this thesis. With its fs time resolution, the terahertz-field-driven streak camera thereby bridges the gap between attosecond and conventional cameras. (orig.)

  11. High power ultrashort pulse lasers

    International Nuclear Information System (INIS)

    Perry, M.D.

    1994-01-01

    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

  12. Tailored optical vector fields for ultrashort-pulse laser induced complex surface plasmon structuring.

    Science.gov (United States)

    Ouyang, J; Perrie, W; Allegre, O J; Heil, T; Jin, Y; Fearon, E; Eckford, D; Edwardson, S P; Dearden, G

    2015-05-18

    Precise tailoring of optical vector beams is demonstrated, shaping their focal electric fields and used to create complex laser micro-patterning on a metal surface. A Spatial Light Modulator (SLM) and a micro-structured S-waveplate were integrated with a picosecond laser system and employed to structure the vector fields into radial and azimuthal polarizations with and without a vortex phase wavefront as well as superposition states. Imprinting Laser Induced Periodic Surface Structures (LIPSS) elucidates the detailed vector fields around the focal region. In addition to clear azimuthal and radial plasmon surface structures, unique, variable logarithmic spiral micro-structures with a pitch Λ ∼1μm, not observed previously, were imprinted on the surface, confirming unambiguously the complex 2D focal electric fields. We show clearly also how the Orbital Angular Momentum(OAM) associated with a helical wavefront induces rotation of vector fields along the optic axis of a focusing lens and confirmed by the observed surface micro-structures.

  13. The time resolved measurement of ultrashort terahertz-band electric fields without an ultrashort probe

    International Nuclear Information System (INIS)

    Walsh, D. A.; Snedden, E. W.; Jamison, S. P.

    2015-01-01

    The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG (frequency resolved optical gating) measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe, and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators

  14. Laser system using ultra-short laser pulses

    Science.gov (United States)

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

    2009-10-27

    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.

  15. Laser-assisted electron scattering in strong-field ionization of dense water vapor by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Wilke, M; Al-Obaidi, R; Moguilevski, A; Kothe, A; Engel, N; Metje, J; Kiyan, I Yu; Aziz, E F

    2014-01-01

    We report on strong-field ionization of dense water gas in a short infrared laser pulse. By employing a unique combination of photoelectron spectroscopy with a liquid micro-jet technique, we observe how the character of electron emission at high kinetic energies changes with the increase of the medium density. This change is associated with the process of laser-assisted electron scattering (LAES) on neighboring particles, which becomes a dominant mechanism of hot electron emission at higher medium densities. The manifestation of this mechanism is found to require densities that are orders of magnitude lower than those considered for heating the laser-generated plasmas via the LAES process. The experimental results are supported by simulations of the LAES yield with the use of the Kroll–Watson theory. (paper)

  16. Ultra-short laser pulses. Petawatt and femtosecond

    International Nuclear Information System (INIS)

    Lemoine, P.

    1999-01-01

    This book deals with a series of new results obtained thanks to the use of ultra-short laser pulses. This branch of physics has made incredible progresses during the last 25 years. Ultra-short laser pulses offer the opportunity to explore the domain of ultra-high energies and of ultra-short duration events. Applications are various, from controlled nuclear fusion to eye surgery and to more familiar industrial applications such as electronics. (J.S.)

  17. Supercomputations and big-data analysis in strong-field ultrafast optical physics: filamentation of high-peak-power ultrashort laser pulses

    Science.gov (United States)

    Voronin, A. A.; Panchenko, V. Ya; Zheltikov, A. M.

    2016-06-01

    High-intensity ultrashort laser pulses propagating in gas media or in condensed matter undergo complex nonlinear spatiotemporal evolution where temporal transformations of optical field waveforms are strongly coupled to an intricate beam dynamics and ultrafast field-induced ionization processes. At the level of laser peak powers orders of magnitude above the critical power of self-focusing, the beam exhibits modulation instabilities, producing random field hot spots and breaking up into multiple noise-seeded filaments. This problem is described by a (3  +  1)-dimensional nonlinear field evolution equation, which needs to be solved jointly with the equation for ultrafast ionization of a medium. Analysis of this problem, which is equivalent to solving a billion-dimensional evolution problem, is only possible by means of supercomputer simulations augmented with coordinated big-data processing of large volumes of information acquired through theory-guiding experiments and supercomputations. Here, we review the main challenges of supercomputations and big-data processing encountered in strong-field ultrafast optical physics and discuss strategies to confront these challenges.

  18. Cubic phase control of ultrashort laser pulses

    International Nuclear Information System (INIS)

    Mecseki, K.; Erdelyi, M.; Kovacs, A.P.; Szabo, G.

    2006-01-01

    Complete test of publication follows. The temporal shape of an ultrashort laser pulse may change upon propagating through a linear dispersive medium having a phase shift ψω. The change can be characterized by the Taylor-coefficients of the phase shift which are calculated around the central frequency ω 0 of the pulse. Measurements and independent control of the group delay dispersion (GDD, ψ'(ω 0 )) and the third order dispersion (TOD, ψ'(ω 0 )) are important in several research fields, particularly in the generation of ultrashort laser pulses by chirped pulse amplification (CPA) and pulse shaping for molecular control. The GDD and the TOD of an ideal pulse compressor are equal to the negative of the corresponding dispersion coefficients of the medium. However, in the case of prism-pair and grating-pair compressor is different from the ratio of the coefficients of the medium to be compensated for. Therefore it is necessary to develop so-called cubic compressors that are able to control the TOD of the pulse, yet, do not affect the GDD. In this paper a new cubic compressor setup is investigated theoretically and experimentally, which resembles the set-up proposed by White, however, we control the GDD and the TOD by the position of a birefringent, semi-cylinder crystal place around the focal point of an achromatic lens. For the evaluation of the phase shift introduced by the proposed cubic compressor, a ray tracing program was written. The program allows optimizing the compressor parameters, such as the radius of the crystal, magnification of the lens etc. Calcite was applied because it is a strong birefringent material. Calculations showed that there is a trajectory, along which shifting the crystal the TOD can be tuned independently of the GDD. The value of the TOD changed in a relatively wide range between -3.15 x 10 5 fs 3 and -1.67 x 10 5 fs 3 . Although the defocus also affects the angular dispersion of the pulse leaving the compressor, if does not exceed

  19. Optical reprogramming with ultrashort femtosecond laser pulses

    Science.gov (United States)

    Uchugonova, Aisada; Breunig, Hans G.; Batista, Ana; König, Karsten

    2015-03-01

    The use of sub-15 femtosecond laser pulses in stem cell research is explored with particular emphasis on the optical reprogramming of somatic cells. The reprogramming of somatic cells into induced pluripotent stem (iPS) cells can be evoked through the ectopic expression of defined transcription factors. Conventional approaches utilize retro/lenti-viruses to deliver genes/transcription factors as well as to facilitate the integration of transcription factors into that of the host genome. However, the use of viruses may result in insertional mutations caused by the random integration of genes and as a result, this may limit the use within clinical applications due to the risk of the formation of cancer. In this study, a new approach is demonstrated in realizing non-viral reprogramming through the use of ultrashort laser pulses, to introduce transcription factors into the cell so as to generate iPS cells.

  20. Ultrashort electromagnetic clusters formation by two-stream superheterodyne free electron lasers

    DEFF Research Database (Denmark)

    Kulish, Viktor V.; Lysenko, Alexander V.; Volk, Iurii I.

    2016-01-01

    A cubic nonlinear self-consistent theory of multiharmonic two-stream superheterodyne free electron lasers (TSFEL) of a klystron type, intended to form powerful ultrashort clusters of an electromagnetic field is constructed. Plural three-wave parametric resonant interactions of wave harmonics have...... been taken into account. An amplitude, phase and spectral analyses of the processes occurring in such devices have been carried out. The conditions necessary for the forming of the ultrashort clusters of an electromagnetic field have been found out. The possibility of the ultrashort electromagnetic...

  1. Water spray assisted ultrashort laser pulse ablation

    International Nuclear Information System (INIS)

    Silvennoinen, M.; Kaakkunen, J.J.J.; Paivasaari, K.; Vahimaa, P.

    2013-01-01

    Highlights: ► We show the novel method to use multibeam processing with ultrashort pulses efficiently. ► Sprayed thin water layer on ablation zone enhances ablation rate and quality. ► In some cases this method also enables ablation of the deeper and straighter holes compared to ones made without the water layer. ► Method also makes possible to directly write features without the self-organizing structures. - Abstract: We have studied femtosecond ablation under sprayed thin water film and its influence and benefits compared with ablation in the air atmosphere. These have been studied in case of the hole and the groove ablation using IR femtosecond laser. Water enhances the ablation rate and in some situations it makes possible to ablate the holes with a higher aspect ratio. While ablating the grooves, the water spray allows using the high fluences without the generation of the self-organized structures.

  2. Ionization of molecular hydrogen in ultrashort intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Vanne, Yulian V.

    2010-03-18

    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.)

  3. Ionization of molecular hydrogen in ultrashort intense laser pulses

    International Nuclear Information System (INIS)

    Vanne, Yulian V.

    2010-01-01

    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 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 2 and D 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.)

  4. Post-filament self-trapping of ultrashort laser pulses.

    Science.gov (United States)

    Mitrofanov, A V; Voronin, A A; Sidorov-Biryukov, D A; Andriukaitis, G; Flöry, T; Pugžlys, A; Fedotov, A B; Mikhailova, J M; Panchenko, V Ya; Baltuška, A; Zheltikov, A M

    2014-08-15

    Laser filamentation is understood to be self-channeling of intense ultrashort laser pulses achieved when the self-focusing because of the Kerr nonlinearity is balanced by ionization-induced defocusing. Here, we show that, right behind the ionized region of a laser filament, ultrashort laser pulses can couple into a much longer light channel, where a stable self-guiding spatial mode is sustained by the saturable self-focusing nonlinearity. In the limiting regime of negligibly low ionization, this post-filamentation beam dynamics converges to a large-scale beam self-trapping scenario known since the pioneering work on saturable self-focusing nonlinearities.

  5. 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)

    1998-03-01

    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)

  6. New methods of generation of ultrashort laser pulses for ranging

    Science.gov (United States)

    Jelinkova, Helena; Hamal, Karel; Kubecek, V.; Prochazka, Ivan

    1993-01-01

    To reach the millimeter satellite laser ranging accuracy, the goal for nineties, new laser ranging techniques have to be applied. To increase the laser ranging precision, the application of the ultrashort laser pulses in connection with the new signal detection and processing techniques, is inevitable. The two wavelength laser ranging is one of the ways to measure the atmospheric dispersion to improve the existing atmospheric correction models and hence, to increase the overall system ranging accuracy to the desired value. We are presenting a review of several nonstandard techniques of ultrashort laser pulses generation, which may be utilized for laser ranging: compression of the nanosecond pulses using stimulated Brillouin and Raman backscattering; compression of the mode-locked pulses using Raman backscattering; passive mode-locking technique with nonlinear mirror; and passive mode-locking technique with the negative feedback.

  7. Plasma discreteness effects in the presence of an intense, ultrashort laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Savchenko, V.I.; Fisch, N.J.

    1996-03-01

    Discrete effects of the plasma irradiated by an ultrashort, intense laser pulse are investigated. Although, for most plasmas of interest, the damping of the laser pulse is due to collective plasma effects, in certain regimes the energy absorbed in the plasma microfields can be important. A scattering matrix is derived for an electron scattering off an ion in the presence of an intense laser field.

  8. Plasma discreteness effects in the presence of an intense, ultrashort laser pulse

    International Nuclear Information System (INIS)

    Savchenko, V.I.; Fisch, N.J.

    1996-03-01

    Discrete effects of the plasma irradiated by an ultrashort, intense laser pulse are investigated. Although, for most plasmas of interest, the damping of the laser pulse is due to collective plasma effects, in certain regimes the energy absorbed in the plasma microfields can be important. A scattering matrix is derived for an electron scattering off an ion in the presence of an intense laser field

  9. Optical third-harmonic generation using ultrashort laser pulses

    International Nuclear Information System (INIS)

    Stoker, D.; Keto, J.W.; Becker, M.F.

    2005-01-01

    To better predict optical third-harmonic generation (THG) in transparent dielectrics, we model a typical ultrashort pulsed Gaussian beam, including both group velocity mismatch and phase mismatch of the fundamental and harmonic fields. We find that competition between the group velocity mismatch and phase mismatch leads to third-harmonic generation that is sensitive only to interfaces. In this case, the spatial resolution is determined by the group velocity walk-off length. THG of modern femtosecond lasers in optical solids is a bulk process, without a surface susceptibility, but bears the signature of a surface enhancement effect in z-scan measurements. We demonstrate the accuracy of the model, by showing the agreement between the predicted spectral intensity and the measured third-harmonic spectrum from a thin sapphire crystal

  10. Acousto-optic replication of ultrashort laser pulses

    Science.gov (United States)

    Yushkov, Konstantin B.; Molchanov, Vladimir Ya.; Ovchinnikov, Andrey V.; Chefonov, Oleg V.

    2017-10-01

    Precisely controlled sequences of ultrashort laser pulses are required in various scientific and engineering applications. We developed a phase-only acousto-optic pulse shaping method for replication of ultrashort laser pulses in a TW laser system. A sequence of several Fourier-transform-limited pulses is generated from a single femtosecond laser pulse by means of applying a piecewise linear phase modulation over the whole emission spectrum. Analysis demonstrates that the main factor which limits maximum delay between the pulse replicas is spectral resolution of the acousto-optic dispersive delay line used for pulse shaping. In experiments with a Cr:forsterite laser system, we obtained delays from 0.3 to 3.5 ps between two replicas of 190 fs transform-limited pulses at the central wavelength of laser emission, 1230 nm.

  11. Interaction of high power ultrashort laser pulses with plasmas

    International Nuclear Information System (INIS)

    Geissler, M.

    2000-12-01

    The invention of short laser-pulses has opened a vast application range from testing ultra high-speed semiconductor devices to precision material processing, from triggering and tracing chemical reactions to sophisticated surgical applications in opthalmology and neurosurgery. In physical science, ultrashort light pulses enable researchers to follow ultrafast relaxation processes in the microcosm on time scale never before accessible and study light-matter-interactions at unprecedented intensity levels. The aim of this thesis is to investigate the interaction of ultrashort high power laser pulses with plasmas for a broad intensity range. First the ionization of atoms with intense laser fields is investigated. For sufficient strong and low frequent laser pulses, electrons can be removed from the core by a tunnel process through a potential barrier formed by the electric field of the laser. This mechanism is described by a well-established theory, but the interaction of few-cycle laser pulses with atoms can lead to regimes where the tunnel theory loses its validity. This regime is investigated and a new description of the ionization is found. Although the ionization plays a major role in many high-energy laser processes, there exist no simple and complete model for the evolution of laser pulses in field-ionizing media. A new propagation equation and the polarization response for field-ionizing media are presented and the results are compared with experimental data. Further the interaction of high power laser radiation with atoms result in nonlinear response of the electrons. The spectrum of this induced nonlinear dipole moment reaches beyond visible wavelengths into the x-ray regime. This effect is known as high harmonic generation (HHG) and is a promising tool for the generation of coherent shot wavelength radiation, but the conversions are still not efficient enough for most practical applications. Phase matching schemes to overcome the limitation are discussed

  12. Thin film surface processing by ultrashort laser pulses (USLP)

    NARCIS (Netherlands)

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

    2012-01-01

    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

  13. Dynamics of interaction of ultrashort laser pulses with solid targets

    International Nuclear Information System (INIS)

    Cang Yu; Wang Wei; Zhang Jie

    2001-01-01

    Using Saha equation, a simple model is proposed for the dynamics of interaction between ultrashort laser pulses and solid targets. An adiabatic expansion model is adopted to study the expansion phase after the heating phase. Temporal evolvement of the dynamics of the interaction is obtained, from which the electron temperature, density, ionization balances can be determined

  14. Ultrashort-pulse laser excitation and damage of dielectric materials

    DEFF Research Database (Denmark)

    Haahr-Lillevang, Lasse; Balling, Peter

    2015-01-01

    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...

  15. Magnetization reversal in ultrashort magnetic field pulses

    International Nuclear Information System (INIS)

    Bauer, M.; Lopusnik, R.; Fassbender, J.; Hillebrands, B.

    2000-01-01

    We report the switching properties of a thin magnetic film subject to an ultrashort, laterally localized magnetic field pulse, obtained by numerical investigations. The magnetization distribution in the film is calculated on a grid assuming Stoner-like coherent rotation within the grid square size. Perpendicularly and in-plane magnetized films exhibit a magnetization reversal due to a 4 ps magnetic field pulse. Outside the central region the pulse duration is short compared to the precession period. In this area the evolution of the magnetization during the field pulse does not depend strongly on magnetic damping and/or pulse shape. However, the final magnetization distribution is affected by the magnetic damping. Although the pulse duration is short compared to the precession period, the time needed for the relaxation of the magnetization to the equilibrium state is rather large. The influence of the different magnetic anisotropy contributions and the magnetic damping parameter enters into the magnetization reversal process. Comparing the case of perpendicular anisotropy with different kinds of in-plane anisotropies, a principal difference is found due to the symmetry of the shape anisotropy with respect to the anisotropy in question

  16. Simple formula for photoprocesses in ultrashort electromagnetic field

    International Nuclear Information System (INIS)

    Astapenko, V.A.

    2010-01-01

    Within the framework of the perturbation theory, a simple formula for the probability of a photoprocess for the whole time of action of an ultrashort electromagnetic pulse has been derived, when the concept of spectral intensity of radiation and probability per unit time is inapplicable. In the obtained formula the total probability is expressed in terms of the cross-section of a photoprocess in a monochromatic field and the Fourier transform of electric field strength. The advanced approach is applied for the analysis of photoabsorption of an atom and a metal nanosphere under the action of a subcycle laser pulse with a changeable value of the carrier-envelope phase. The expressions for probability and energy of photoabsorption in the limit of a zero pulse duration have been obtained.

  17. Controlling Plasma Channels through Ultrashort Laser Pulse Filamentation

    Science.gov (United States)

    Ionin, Andrey; Seleznev, Leonid; Sunchugasheva, Elena

    2013-09-01

    A review of studies fulfilled at the Lebedev Institute in collaboration with the Moscow State University and Institute of Atmospheric Optics in Tomsk on influence of various characteristics of ultrashort laser pulse on plasma channels formed under its filamentation is presented. Filamentation of high-power laser pulses with wavefront controlled by a deformable mirror, with cross-sections spatially formed by various diaphragms and with different wavelengths was experimentally and numerically studied. An application of plasma channels formed due to filamentation of ultrashort laser pulse including a train of such pulses for triggering and guiding long electric discharges is discussed. The research was supported by RFBR Grants 11-02-12061-ofi-m and 11-02-01100, and EOARD Grant 097007 through ISTC Project 4073 P

  18. Interaction of Rydberg atoms with two contrapropagating ultrashort laser pulses

    International Nuclear Information System (INIS)

    Lugovskoy, A. V.; Bray, I.

    2006-01-01

    In this paper we investigate how Rydberg atoms respond to perturbation by two contrapropagating ultrashort laser pulses. We consider the case where the durations of both pulses τ 1 and τ 2 are shorter than the inverse of the initial-state energy ε i -1 . When acting alone such a pulse passes through the atom without noticeable alteration in the atomic state. The situation is different if two such pulses interfere in the region of atom localization. In this case the atomic response is significantly enhanced. This is due to the nonzero momentum transferred to the electron by the interplay of the electric field of one pulse and the magnetic field of the other. The sudden perturbation approximation is used to evaluate the transition probabilities. They are shown to depend on the atom position with respect to the pulse interference region. This dependence is determined by the relationship between the atomic diameter d i and the interference-region size l=c(τ 1 +τ 2 ) (c is the speed of light). If d i i >>l the transition probabilities are sensitive to the electron density distribution along the propagation direction. The probabilities of the initial-state destruction and atom ionization drop as l/d i irrespective of the characteristics of the pulses

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

    International Nuclear Information System (INIS)

    Rudenko, A; Feuerstein, B; Zrost, K; Jesus, V L B de; Ergler, T; Dimopoulou, C; Schroeter, C D; Moshammer, R; Ullrich, J

    2005-01-01

    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. Extending ultra-short pulse laser texturing over large area

    Energy Technology Data Exchange (ETDEWEB)

    Mincuzzi, G., E-mail: girolamo.mincuzzi@alphanov.com; Gemini, L.; Faucon, M.; Kling, R.

    2016-11-15

    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%.

  1. Ultrashort pulse laser deposition of thin films

    Science.gov (United States)

    Perry, Michael D.; Banks, Paul S.; Stuart, Brent C.

    2002-01-01

    Short pulse PLD is a viable technique of producing high quality films with properties very close to that of crystalline diamond. The plasma generated using femtosecond lasers is composed of single atom ions with no clusters producing films with high Sp.sup.3 /Sp.sup.2 ratios. Using a high average power femtosecond laser system, the present invention dramatically increases deposition rates to up to 25 .mu.m/hr (which exceeds many CVD processes) while growing particulate-free films. In the present invention, deposition rates is a function of laser wavelength, laser fluence, laser spot size, and target/substrate separation. The relevant laser parameters are shown to ensure particulate-free growth, and characterizations of the films grown are made using several diagnostic techniques including electron energy loss spectroscopy (EELS) and Raman spectroscopy.

  2. High-power ultrashort fiber laser for solar cells micromachining

    Science.gov (United States)

    Lecourt, J.-B.; Duterte, C.; Liegeois, F.; Lekime, D.; Hernandez, Y.; Giannone, D.

    2012-02-01

    We report on a high-power ultra-short fiber laser for thin film solar cells micromachining. The laser is based on Chirped Pulse Amplification (CPA) scheme. The pulses are stretched to hundreds of picoseconds prior to amplification and can be compressed down to picosecond at high energy. The repetition rate is adjustable from 100 kHz to 1 MHz and the optical average output power is close to 13 W (before compression). The whole setup is fully fibred, except the compressor achieved with bulk gratings, resulting on a compact and reliable solution for cold ablation.

  3. Ultra-Short Laser Absorption In Solid Targets

    International Nuclear Information System (INIS)

    Harfouche, A.; Bendib, A.

    2008-01-01

    With the rapid development and continuously improving technology of subpicosecond laser pulse generation, new interesting physical problems are now investigated. Among them the laser light absorption in solid targets. During the interaction with solid targets, high intensity laser pulses are absorbed by electrons in optical skin depths, leading to rapid ionization before that significant ablation of solid material takes place. The ultra-short laser is absorbed in the overdense plasma through the electron-ion collisions (normal skin effect) or collisionless mechanisms (anomalous skin effect or sheath inverse bremsstrahlung). These two regimes depend on the laser intensity, the plasma temperature and the ionization state Z. In this work we solve numerically the Fokker-Planck equation to compute the electron distribution function in the skin layer. In the second step we compute the surface impedance and we deduce the absorption coefficient.

  4. International Conference on the Interaction of atoms, molecules and plasmas with intense ultrashort laser pulses. Book of abstracts

    International Nuclear Information System (INIS)

    2006-01-01

    International Conference on the Interaction of atoms, molecules and plasmas with intense ultrashort laser pulses was held in Hungary in 2006. This conference which joined the ULTRA COST activity ('Laser-matter interactions with ultra-short pulses, high-frequency pulses and ultra-intense pulses. From attophysics to petawatt physics') and the XTRA ('Ultrashort XUV Pulses for Time-Resolved and Non-Linear Applications') Marie-Curie Research Training Network, intends to offer a possibility to the members of both of these activities to exchange ideas on recent theoretical and experimental results on the interaction of ultrashort laser pulses with matter giving a broad view from theoretical models to practical and technical applications. Ultrashort laser pulses reaching extra high intensities open new windows to obtain information about molecular and atomic processes. These pulses are even able to penetrate into atomic scalelengths not only by generating particles of ultrahigh energy but also inside the spatial and temporal atomic scalelengths. New regimes of laser-matter interaction were opened in the last decade with an increasing number of laboratories and researchers in these fields. (S.I.)

  5. Generation of ultra-short relativistic-electron-bunch by a laser wakefield

    NARCIS (Netherlands)

    Khachatryan, A.G.; Boller, Klaus J.; van Goor, F.A.

    2003-01-01

    The possibility of the generation of an ultra-short (about one micron long) relativistic (up to a few GeVs) electron-bunch in a moderately nonlinear laser wakefield excited in an underdense plasma by an intense laser pulse is investigated. The ultra-short bunch is formed by trapping, effective

  6. Study of 2ω and 3/2ω harmonics in ultrashort high-intensity laser ...

    Indian Academy of Sciences (India)

    Intense laser pulses from such laser systems may have many pre-pulses like picosecond ... ultrashort laser–matter interaction, as well as to control the source parameters. In situ monitoring of ultrashort ... central wavelength of 790 nm with a bandwidth of 16 ± 2 nm after the compressor. The picosecond intensity contrast ...

  7. Electron in the ultrashort laser pulse

    Czech Academy of Sciences Publication Activity Database

    Pardy, Miroslav

    2003-01-01

    Roč. 42, č. 1 (2003), s. 99-110 ISSN 0020-7748 R&D Projects: GA MŠk LN00A100 Institutional research plan: CEZ:AV0Z2043910 Keywords : laser pulse, Volkov solution, compton effect Subject RIV: BE - The oretical Physics Impact factor: 0.476, year: 2003

  8. Ultrashort pulsed laser technology development program

    Science.gov (United States)

    Manke, Gerald C.

    2014-10-01

    The Department of Navy has been pursuing a technology development program for advanced, all-fiber, Ultra Short Pulsed Laser (USPL) systems via Small Business Innovative Research (SBIR) programs. Multiple topics have been published to promote and fund research that encompasses every critical component of a standard USPL system and enable the demonstration of mJ/pulse class systems with an all fiber architecture. This presentation will summarize published topics and funded programs.

  9. Nonlinear propagation of ultrashort laser pulses in transparent media

    International Nuclear Information System (INIS)

    Vincotte, A.

    2006-10-01

    We present different aspects of the propagation of ultrashort laser pulses in transparent media. First, we derive the propagation equations starting from the Maxwell equations. We remind of the main physical phenomena undergone by ultrashort and powerful laser pulses. First self-focusing occurs, owing to the Kerr response of the medium. This self-focusing is stopped by plasma generation from the laser-induced ionization of the ambient atoms. The propagation of the wave generates a super-continuum through self-phase modulation. We recall the main results concerning the simple and multiple filamentation of an intense wave, induced by the beam inhomogeneities and which take place as soon as the beam power is above critical. In a second part, we investigate the influence of high-order nonlinearities on the propagation of the beam and especially on its filamentation pattern. To control the multi-filamentation process, we investigate in a third part the propagation of beams with special designs, namely; Gradient- and vortex-shaped beams. We justify the robustness of this latter kind of optical objects. Eventually, we investigate multi-filamentation patterns of femtosecond pulses in a fog tube and in cells of ethanol doped with coumarin, for different beam configurations. (author)

  10. Strong field laser physics

    CERN Document Server

    2008-01-01

    Since the invention of the laser in the 1960s, people have strived to reach higher intensities and shorter pulse durations. High intensities and ultrashort pulse durations are intimately related. Recent developments have shown that high intensity lasers also open the way to realize pulses with the shortest durations to date, giving birth to the field of attosecond science (1 asec = 10-18s). This book is about high-intensity lasers and their applications. The goal is to give an up to date introduction to the technology behind these laser systems and to the broad range of intense laser applications. These applications include AMO (atomic molecular and optical) physics, x-ray science, attosecond science, plasma physics and particle acceleration, condensed matter science and laser micromachining, and finally even high-energy physics.

  11. Nonlinear scattering in hard tissue studied with ultrashort laser pulses

    International Nuclear Information System (INIS)

    Eichler, J.; Kim, B.M.

    2002-01-01

    The back-scattered spectrum of ultrashort laser pulses (800 nm, 0.2 ps) was studied in human dental and other hard tissues in vitro below the ablation threshold. Frequency doubled radiation (SHG), frequency tripled radiation and two-photon fluorescence were detected. The relative yield for these processes was measured for various pulse energies. The dependence of the SHG signal on probe thickness was determined in forward and back scattering geometry. SHG is sensitive to linear polarization of the incident laser radiation. SHG in human teeth was studied in vitro showing larger signals in dentin than in cementum and enamel. In carious areas no SHG signal could be detected. Possible applications of higher harmonic radiation for diagnostics and microscopy are discussed. (orig.)

  12. Multiphoton photoemission from a copper cathode illuminated by ultrashort laser pulses in an RF photoinjector.

    Science.gov (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

    2010-02-26

    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.

  13. Multiphoton Photoemission from a Copper Cathode Illuminated by Ultrashort Laser Pulses in an rf Photoinjector

    International Nuclear Information System (INIS)

    Musumeci, P.; Gutierrez, M. S.; Moody, J. T.; Moore, N.; Rosenzweig, J. B.; Scoby, C. M.; Travish, G.; Cultrera, L.; Ferrario, M.; Filippetto, D.; Gatti, G.; Vicario, C.

    2010-01-01

    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 μJ, 800 nm pulse focused to a 140 μm 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.

  14. Plasma lenses for ultrashort multi-petawatt laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Palastro, J. P.; Gordon, D.; Hafizi, B.; Johnson, L. A.; Peñano, J.; Hubbard, R. F.; Helle, M.; Kaganovich, D. [Naval Research Laboratory, Washington DC 20375-5346 (United States)

    2015-12-15

    An ideal plasma lens can provide the focusing power of a small f-number, solid-state focusing optic at a fraction of the diameter. An ideal plasma lens, however, relies on a steady-state, linear laser pulse-plasma interaction. Ultrashort multi-petawatt (MPW) pulses possess broad bandwidths and extreme intensities, and, as a result, their interaction with the plasma lens is neither steady state nor linear. Here, we examine nonlinear and time-dependent modifications to plasma lens focusing, and show that these result in chromatic and phase aberrations and amplitude distortion. We find that a plasma lens can provide enhanced focusing for 30 fs pulses with peak power up to ∼1 PW. The performance degrades through the MPW regime, until finally a focusing penalty is incurred at ∼10 PW.

  15. Interaction of intense ultrashort pulse lasers with clusters

    International Nuclear Information System (INIS)

    Petrov, G. M.; Davis, J.

    2008-01-01

    The dynamics of clusters composed of different material irradiated by a high-intensity ultrashort pulse laser was studied using a fully relativistic three-dimensional molecular dynamics model. Key parameters of the cluster evolution such as particle positions, energy absorption, and cluster explosion were simulated. By a direct comparison of these parameters for clusters of equal initial radius but made of different material (deuterium, neon, argon, and xenon), the main stages and attributes of cluster evolution were elucidated. The simulations showed that clusters made of different material act alike, especially those of heavy elements. Clusters made of heavy elements (neon, argon, and xenon) differentiate from clusters made of light elements (deuterium) by the magnitude of the absorbed energy per cluster and the final mean energy of exploding ions. What most distinguishes clusters composed of different material is the amount of emitted radiation and its spectral range

  16. Optimization And Single-Shot Characterization Of Ultrashort Thz Pulses From A Laser Wakefield Accelerator

    International Nuclear Information System (INIS)

    Plateau, G.R.; Matlis, N.H.; van Tilborg, J.; Geddes, C.G.R.; Toth, Cs.; Schroeder, C.B.; Leemans, W.P.

    2009-01-01

    We present spatiotemporal characterization of μJ-class ultrashort THz pulses generated from a laser wakefield accelerator (LWFA). Accelerated electrons, resulting from the interaction of a high-intensity laser pulse with a plasma, emit high-intensity THz pulses as coherent transition radiation. Such high peak-power THz pulses, suitable for high-field (MV/cm) pump-probe experiments, also provide a non-invasive bunch-length diagnostic and thus feedback for the accelerator. The characterization of the THz pulses includes energy measurement using a Golay cell, 2D sign-resolved electro-optic measurement and single-shot spatiotemporal electric-field distribution retrieval using a new technique, coined temporal electric-field cross-Correlation (TEX). All three techniques corroborate THz pulses of ∼ 5 μJ, with peak fields of 100's of kV/cm and ∼ 0.4 ps rms duration.

  17. Interaction of ultra-short ultra-intense laser pulses with under-dense plasmas

    International Nuclear Information System (INIS)

    Solodov, A.

    2000-12-01

    Different aspects of interaction of ultra-short ultra-intense laser pulses with underdense plasmas are studied analytically and numerically. These studies can be interesting for laser-driven electron acceleration in plasma, X-ray lasers, high-order harmonic generation, initial confinement fusion with fast ignition. For numerical simulations a fully-relativistic particle code WAKE was used, developed earlier at Ecole Polytechnique. It was modified during the work on the thesis in the part of simulation of ion motion, test electron motion, diagnostics for the field and plasma. The studies in the thesis cover the problems of photon acceleration in the plasma wake of a short intense laser pulse, phase velocity of the plasma wave in the Self-Modulated Laser Wake-Field Accelerator (SM LWFA), relativistic channeling of laser pulses with duration of the order of a plasma period, ion dynamics in the wake of a short intense laser pulse, plasma wave breaking. Simulation of three experiments on the laser pulse propagation in plasma and electron acceleration were performed. Among the main results of the thesis, it was found that reduction of the plasma wave phase velocity in the SM LWFA is crucial for electron acceleration, only if a plasma channel is used for the laser pulse guiding. Self-similar structures describing relativistic guiding of short laser pulses in plasmas were found and relativistic channeling of initially Gaussian laser pulses of a few plasma periods in duration was demonstrated. It was shown that ponderomotive force of a plasma wake excited by a short laser pulse forms a channel in plasma and plasma wave breaking in the channel was analyzed in detail. Effectiveness of electron acceleration by the laser field and plasma wave was compared and frequency shift of probe laser pulses by the plasma waves was found in conditions relevant to the current experiments. (author)

  18. Investigation of ultrashort-pulsed laser on dental hard tissue

    Science.gov (United States)

    Uchizono, Takeyuki; Awazu, Kunio; Igarashi, Akihiro; Kato, Junji; Hirai, Yoshito

    2007-02-01

    Ultrashort-pulsed laser (USPL) can ablate various materials with precious less thermal effect. In laser dentistry, to solve the problem that were the generation of crack and carbonized layer by irradiating with conventional laser such as Er:YAG and CO II laser, USPL has been studied to ablate dental hard tissues by several researchers. We investigated the effectiveness of ablation on dental hard tissues by USPL. In this study, Ti:sapphire laser as USPL was used. The laser parameter had the pulse duration of 130 fsec, 800nm wavelength, 1KHz of repetition rate and the average power density of 90~360W/cm2. Bovine root dentin plates and crown enamel plates were irradiated with USPL at 1mm/sec using moving stage. The irradiated samples were analyzed by SEM, EDX, FTIR and roughness meter. In all irradiated samples, the cavity margin and wall were sharp and steep, extremely. In irradiated dentin samples, the surface showed the opened dentin tubules and no smear layer. The Ca/P ratio by EDX measurement and the optical spectrum by FTIR measurement had no change on comparison irradiated samples and non-irradiated samples. These results confirmed that USPL could ablate dental hard tissue, precisely and non-thermally. In addition, the ablation depths of samples were 10μm, 20μm, and 60μm at 90 W/cm2, 180 W/cm2, and 360 W/cm2, approximately. Therefore, ablation depth by USPL depends on the average power density. USPL has the possibility that can control the precision and non-thermal ablation with depth direction by adjusting the irradiated average power density.

  19. Ultra-short laser interactions with nanoparticles in different media: from electromagnetic to thermal and electrostatic effects

    Science.gov (United States)

    Itina, Tatiana E.

    2017-02-01

    Key issues of the controlled synthesis of nanoparticles and nanostructures, as well as laser-particle interactions are considered in the context of the latest applications appearing in many fields such as photonics, medicine, 3D printing, etc. The results of a multi-physics numerical study of laser interaction with nanoparticles will be presented in the presence of several environments. In particular, attention will be paid to the numerical study of laser interactions with heterogeneous materials (eg. colloidal liquids and/or nanoparticles in a dielectric medium) and the aggregation/sintering/fragmentation processes induced by ultra-short laser pulses.

  20. Surface Texturing of CVD Diamond Assisted by Ultrashort Laser Pulses

    Directory of Open Access Journals (Sweden)

    Daniele M. Trucchi

    2017-11-01

    Full Text Available Diamond is a wide bandgap semiconductor with excellent physical properties which allow it to operate under extreme conditions. However, the technological use of diamond was mostly conceived for the fabrication of ultraviolet, ionizing radiation and nuclear detectors, of electron emitters, and of power electronic devices. The use of nanosecond pulse excimer lasers enabled the microstructuring of diamond surfaces, and refined techniques such as controlled ablation through graphitization and etching by two-photon surface excitation are being exploited for the nanostructuring of diamond. On the other hand, ultrashort pulse lasers paved the way for a more accurate diamond microstructuring, due to reduced thermal effects, as well as an effective surface nanostructuring, based on the formation of periodic structures at the nanoscale. It resulted in drastic modifications of the optical and electronic properties of diamond, of which “black diamond” films are an example for future high-temperature solar cells as well as for advanced optoelectronic platforms. Although experiments on diamond nanostructuring started almost 20 years ago, real applications are only today under implementation.

  1. Selective laser melting of hypereutectic Al-Si40-powder using ultra-short laser pulses

    Science.gov (United States)

    Ullsperger, T.; Matthäus, G.; Kaden, L.; Engelhardt, H.; Rettenmayr, M.; Risse, S.; Tünnermann, A.; Nolte, S.

    2017-12-01

    We investigate the use of ultra-short laser pulses for the selective melting of Al-Si40-powder to fabricate complex light-weight structures with wall sizes below 100 μ {m} combined with higher tensile strength and lower thermal expansion coefficient in comparison to standard Al-Si alloys. During the cooling process using conventional techniques, large primary silicon particles are formed which impairs the mechanical and thermal properties. We demonstrate that these limitations can be overcome using ultra-short laser pulses enabling the rapid heating and cooling in a non-thermal equilibrium process. We analyze the morphology characteristics and micro-structures of single tracks and thin-walled structures depending on pulse energy, repetition rate and scanning velocity utilizing pulses with a duration of 500 {fs} at a wavelength of 1030 {nm}. The possibility to specifically change and optimize the microstructure is shown.

  2. Theoretical analysis of supercontinuum and coloured conical emission produced during ultrashort laser pulse interaction with gases

    International Nuclear Information System (INIS)

    Semak, V V; Shneider, M N

    2014-01-01

    We use a conceptually new approach to theoretical modelling of self-focusing in which we integrated diffractive and geometrical optics in order to explain and predict emission of white light and coloured rings observed in ultrashort laser pulse interaction. In our approach, laser beam propagation is described by blending the solution of the linear Maxwell's equation and a correction term that represents nonlinear field perturbation expressed in terms of paraxial ray-optics (eikonal) equation. No attempt is made to create an appearance of exhaustive treatment via use of complex mathematical models. Rather, emphasis is placed on elegance of the formulations leading to fundamental understanding of the underlying physics and, eventually, to an accurate practical numerical model capable of simulating white light generation and conical emission of coloured rings produced around the filament. (paper)

  3. Two-dimensional angular energy spectrum of electrons accelerated by the ultra-short relativistic laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Borovskiy, A. V. [Department of Computer Science and Cybernetics, Baikal State University of Economics and Law, 11 Lenin Street, Irkutsk 664003 (Russian Federation); Galkin, A. L. [Coherent and Nonlinear Optics Department, A.M. Prokhorov General Physics Institute of the RAS, 38 Vavilov Street, Moscow 119991 (Russian Federation); Department of Physics of MBF, Pirogov Russian National Research Medical University, 1 Ostrovitianov Street, Moscow 117997 (Russian Federation); Kalashnikov, M. P., E-mail: galkin@kapella.gpi.ru [Max-Born-Institute for Nonlinear Optics and Short-Time Spectroscopy, 2a Max-Born-Strasse, Berlin 12489 (Germany)

    2015-04-15

    The new method of calculating energy spectra of accelerated electrons, based on the parameterization by their initial coordinates, is proposed. The energy spectra of electrons accelerated by Gaussian ultra-short relativistic laser pulse at a selected angle to the axis of the optical system focusing the laser pulse in a low density gas are theoretically calculated. The two-peak structure of the electron energy spectrum is obtained. Discussed are the reasons for its appearance as well as an applicability of other models of the laser field.

  4. Laser-Bioplasma Interaction: The Blood Type Transmutation Induced by Multiple Ultrashort Wavelength Laser Beams

    Science.gov (United States)

    Stefan, V. Alexander

    2015-11-01

    The interaction of ultrashort wavelength multi laser beams with the flowing blood thin films leads to the transmutation of the blood types A, B, and AB into O type. This is a novel mechanism of importance for the transfusion medicine. Laser radiation is in resonance with the eigen-frequency modes of the antigen proteins and forces the proteins to parametrically oscillate until they get kicked out from the surface. The stripping away of antigens is done by the scanning-multiple-lasers of a high repetition rate in the blue-purple frequency domain. The guiding-lasers are in the red-green frequency domain. The laser force, (parametric interaction with the antigen eigen-oscillation), upon the antigen protein molecule must exceed its weight. The scanning laser beam is partially reflected as long as the antigen(s) is not eliminated. The process of the protein detachment can last a few minutes. Supported by Nikola Tesla Labs., Stefan University.

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

    CERN Document Server

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

    2002-01-01

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

  6. Control of the hyperbolic dispersion of dielectrics by an ultrashort laser pulse

    Science.gov (United States)

    Zhang, Xiaoqin; Wang, Feng; Zhang, Fengshou; Yao, Yugui

    2018-01-01

    An idea of controlling hyperbolic dispersion of dielectric materials by an ultrashort laser pulse is proposed. Taking the diamond as a concrete example and using time-dependent density functional theory calculations, we show that the permittivity tensor of the material can be effectively tuned by an ultrashort laser pulse, serving as a transient hyperbolic medium with wide working frequency window. With easily tunable laser parameters, the material can even be switched by reversal of both elliptic and hyperbolic for a particular light frequency. Our result points out a route toward transient hyperbolic materials, and it offers methods to achieve tunable hyperbolic dispersion with great potential for ultrafast device applications.

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

    International Nuclear Information System (INIS)

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

    2002-01-01

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

  8. Temporal characterization of ultrashort linearly chirped electron bunches generated from a laser wakefield accelerator

    Directory of Open Access Journals (Sweden)

    C. J. Zhang

    2016-06-01

    Full Text Available A new method for diagnosing the temporal characteristics of ultrashort electron bunches with linear energy chirp generated from a laser wakefield accelerator is described. When the ionization-injected bunch interacts with the back of the drive laser, it is deflected and stretched along the direction of the electric field of the laser. Upon exiting the plasma, if the bunch goes through a narrow slit in front of the dipole magnet that disperses the electrons in the plane of the laser polarization, it can form a series of bunchlets that have different energies but are separated by half a laser wavelength. Since only the electrons that are undeflected by the laser go through the slit, the energy spectrum of the bunch is modulated. By analyzing the modulated energy spectrum, the shots where the bunch has a linear energy chirp can be recognized. Consequently, the energy chirp and beam current profile of those bunches can be reconstructed. This method is demonstrated through particle-in-cell simulations and experiment.

  9. Ultra-short laser pulses: review of the 3. physics talks, September 17-18, 1998

    International Nuclear Information System (INIS)

    Lemoine, P.

    1999-01-01

    This book deals with the operation of lasers with ultra-short pulses and with the laser beam-matter interaction. The applications in concern are: the acceleration of particles, the production of X-ray or photon sources, the micro-machining, the fast ignition in thermonuclear fusion, the production of thin films and the surgery of cornea. (J.S.)

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

    NARCIS (Netherlands)

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

    2014-01-01

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

  11. Ion acceleration in electrostatic field of charged cavity created by ultra-short laser pulses of 1020-1021 W/cm2

    Science.gov (United States)

    Bychenkov, V. Yu.; Singh, P. K.; Ahmed, H.; Kakolee, K. F.; Scullion, C.; Jeong, T. W.; Hadjisolomou, P.; Alejo, A.; Kar, S.; Borghesi, M.; Ter-Avetisyan, S.

    2017-01-01

    Ion acceleration resulting from the interaction of ultra-high intensity and ultra-high contrast (˜10-10) laser pulses with thin A l foil targets at 30° angle of laser incidence is studied. Proton maximum energies of 30 and 18 MeV are measured along the target normal rear and front sides, respectively, showing intensity scaling as Ib . For the target front bf r o n t= 0.5-0.6 and for the target rear br e a r= 0.7-0.8 is observed in the intensity range 1020-1021 W/cm2. The fast scaling from the target rear ˜I0.75 can be attributed enhancement of laser energy absorption as already observed at relatively low intensities. The backward acceleration of the front side protons with intensity scaling as ˜I0.5 can be attributed to the to the formation of a positively charged cavity at the target front via ponderomotive displacement of the target electrons at the interaction of relativistic intense laser pulses with a solid target. The experimental results are in a good agreement with theoretical predictions.

  12. Optical and electrical properties of SnO2 thin films after ultra-short pulsed laser annealing

    NARCIS (Netherlands)

    Scorticati, D.; Illiberi, A.; Römer, G.R.B.E.; Bor, T.; Ogieglo, W.; Klein Gunnewiek, M.; Lenferink, A.; Otto, C.; Skolski, J.Z.P.; Grob, F.; Lange, D.F. de; Huis in 't Veld, A.J.

    2013-01-01

    Ultra-short pulsed laser sources, with pulse durations in the ps and fs regime, are commonly exploited for cold ablation. However, operating ultra-short pulsed laser sources at fluence levels well below the ablation threshold allows for fast and selective thermal processing. The latter is especially

  13. Modification of transparent materials with ultrashort laser pulses: What is energetically and mechanically meaningful?

    Energy Technology Data Exchange (ETDEWEB)

    Bulgakova, Nadezhda M., E-mail: nadezhda.bulgakova@hilase.cz [HiLASE Centre, Institute of Physics ASCR, Za Radnicí 828, 25241 Dolní Břežany (Czech Republic); Institute of Thermophysics SB RAS, 1 Lavrentyev Ave., 630090 Novosibirsk (Russian Federation); Zhukov, Vladimir P. [Institute of Computational Technologies SB RAS, 6 Lavrentyev Ave., 630090 Novosibirsk (Russian Federation); Novosibirsk State Technical University, 20 Karl Marx Ave., 630073, Novosibirsk (Russian Federation); Sonina, Svetlana V. [Novosibirsk State University, 1 Koptuga Ave., 630090 Novosibirsk (Russian Federation); Meshcheryakov, Yuri P. [Design and Technology Branch of Lavrentyev Institute of Hydrodynamics SB RAS, Tereshkovoi street 29, 630090 Novosibirsk (Russian Federation)

    2015-12-21

    A comprehensive analysis of laser-induced modification of bulk glass by single ultrashort laser pulses is presented which is based on combination of optical Maxwell-based modeling with thermoelastoplastic simulations of post-irradiation behavior of matter. A controversial question on free electron density generated inside bulk glass by ultrashort laser pulses in modification regimes is addressed on energy balance grounds. Spatiotemporal dynamics of laser beam propagation in fused silica have been elucidated for the regimes used for direct laser writing in bulk glass. 3D thermoelastoplastic modeling of material relocation dynamics under laser-induced stresses has been performed up to the microsecond timescale when all motions in the material decay. The final modification structure is found to be imprinted into material matrix already at sub-nanosecond timescale. Modeling results agree well with available experimental data on laser light transmission through the sample and the final modification structure.

  14. Ultra-short X-ray sources generated through laser-matter interaction and their applications

    International Nuclear Information System (INIS)

    Rousse, A.

    2004-04-01

    This work is dedicated to the sources of ultra-short X-rays. The K α source, the non-linear Thomson source, the betatron source and the X-γ source are presented. We show that a pump-probe experiment where the pump is a laser excitation and the probe is the X-K α ultra-short radiation, can be used to study the dynamics of material structure with a time resolution of 100 femtosecond. We describe 2 applications that have been achieved in the field of solid physics by using the diffraction technique with a time resolution in the range of the femtosecond. The first application has permitted the observation and characterization of the ultra-quick solid-phase transition that occurs on the surface of a semiconductor crystal. The second experiment deals with the role of optical phonons in the antecedent processes that lead to such ultra-quick solid-phase transitions. (A.C.)

  15. Ionization of a multilevel atom by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Andreev, A. V.; Stremoukhov, S. Yu.; Shutova, O. A.

    2010-01-01

    Specific features of ionization of single atoms by laser fields of a near-atomic strength are investigated. Calculations are performed for silver atoms interacting with femtosecond laser pulses with wavelengths λ = 800 nm (Ti:Sapphire) and λ = 1.064 μm (Nd:YAG). The dependences of the probability of ionization and of the form of the photoelectron energy spectra on the field of laser pulses for various values of their duration are considered. It is shown that the behavior of the probability of ionization in the range of subatomic laser pulse fields is in good agreement with the Keldysh formula. However, when the field strength attains values close to the atomic field strength, the discrepancies in these dependences manifested in a decrease in the ionization rate (ionization stabilization effect) or in its increase (accelerated ionization) are observed. These discrepancies are associated with the dependence of the population dynamics of excited discrete energy levels of the atom on the laser pulse field amplitude.

  16. The interaction of super-intense ultra-short laser pulse and micro-clusters with large atomic clusters

    International Nuclear Information System (INIS)

    Miao Jingwei; Yang Chaowen; An Zhu; Yuan Xuedong; Sun Weiguo; Luo Xiaobing; Wang Hu; Bai Lixing; Shi Miangong; Miao Lei; Zhen Zhijian; Gu Yuqin; Liu Hongjie; Zhu Zhouseng; Sun Liwei; Liao Xuehua

    2007-01-01

    The fusion mechanism of large deuterium clusters (100-1000 Atoms/per cluster) in super-intense ultra-short laser pulse field, Coulomb explosions of micro-cluster in solids, gases and Large-size clusters have been studied using the interaction of a high-intensity femtosecond laser pulses with large deuterium clusters, collision of high-quality beam of micro-cluster from 2.5 MV van de Graaff accelerator with solids, gases and large clusters. The experimental advance of the project is reported. (authors)

  17. Formation of plasma channels in air under filamentation of focused ultrashort laser pulses

    International Nuclear Information System (INIS)

    Ionin, A A; Seleznev, L V; Sunchugasheva, E S

    2015-01-01

    The formation of plasma channels in air under filamentation of focused ultrashort laser pulses was experimentally and theoretically studied together with theoreticians of the Moscow State University and the Institute of Atmospheric Optics. The influence of various characteristics of ultrashort laser pulses on these plasma channels is discussed. Plasma channels formed under filamentation of focused laser beams with a wavefront distorted by spherical aberration (introduced by adaptive optics) and by astigmatism, with cross-section spatially formed by various diaphragms and with different UV and IR wavelengths, were experimentally and numerically studied. The influence of plasma channels created by a filament of a focused UV or IR femtosecond laser pulse (λ = 248 nm or 740 nm) on characteristics of other plasma channels formed by a femtosecond pulse at the same wavelength following the first one with varied nanosecond time delay was also experimentally studied. An application of plasma channels formed due to the filamentation of focused UV ultrashort laser pulses including a train of such pulses and a combination of ultrashort and long (∼100 ns) laser pulses for triggering and guiding long (∼1 m) electric discharges is discussed. (topical review)

  18. Laser mass spectrometry of chemical warfare agents using ultrashort laser pulses

    International Nuclear Information System (INIS)

    Weickhardt, C.; Grun, C.; Grotemeyer, J.

    1998-01-01

    Fast relaxation processes in excited molecules such as IC, ISC, and fragmentation are observed in many environmentally and technically relevant substances. They cause severe problems to resonance ionization mass spectrometry because they reduce the ionization yield and lead to mass spectra which do not allow the identification of the compound. By the use of ultrashort laser pulses these problems can be overcome and the advantages of REMPI over conventional ionization techniques in mass spectrometry can be regained. This is demonstrated using soil samples contaminated with a chemical warfare agent

  19. Magnetic Field Effect on Ultrashort Two-dimensional Optical Pulse Propagation in Silicon Nanotubes

    Science.gov (United States)

    Konobeeva, N. N.; Evdokimov, R. A.; Belonenko, M. B.

    2018-05-01

    The paper deals with the magnetic field effect which provides a stable propagation of ultrashort pulses in silicon nanotubes from the viewpoint of their waveform. The equation is derived for the electromagnetic field observed in silicon nanotubes with a glance to the magnetic field for two-dimensional optical pulses. The analysis is given to the dependence between the waveform of ultrashort optical pulses and the magnetic flux passing through the cross-sectional area of the nanotube.

  20. Printed organic smart devices characterized by ultra-short laser pulses

    DEFF Research Database (Denmark)

    Pastorelli, Francesco

    Resume: In this study, we demonstrate that nonlinear optical microscopy is a promising technique to characterize organic printed electronics. Using ultrashort laser pulses we stimulate two-photon absorption in a roll coated polymer semiconductor and map the resulting two-photon induced...

  1. Thin film surface processing by UltraShort Laser Pulses (USLP)

    NARCIS (Netherlands)

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

    2012-01-01

    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

  2. On the surface topography of ultrashort laser pulse treated steel surfaces

    NARCIS (Netherlands)

    Obona, J. Vincenc; Ocelik, V.; Skolski, J. Z. P.; Mitko, V. S.; Romer, G. R. B. E.; in't Veld, A. J. Huis; De Hosson, J. Th M.; Römer, G.R.B.E.; Huis in’t Veld, A.J.

    2011-01-01

    This paper concentrates on observations of the surface topography by scanning electron microscopy (SEM) on alloyed and stainless steels samples treated by ultrashort laser pulses with duration of 210 fs and 6.7 ps. Globular-like and jet-like objects were found depending on the various levels of the

  3. On the surface topography of ultrashort laser pulse treated steel surface

    NARCIS (Netherlands)

    Vincenc Obona, J.; Ocelik, V.; Skolski, J.Z.P.; Mitko, V.S.; Mitko, S.; Römer, Gerardus Richardus, Bernardus, Engelina; Huis in 't Veld, Bert; de Hosson, J.Th.M.

    2011-01-01

    This paper concentrates on observations of the surface topography by scanning electron microscopy (SEM) on alloyed and stainless steels samples treated by ultrashort laser pulses with duration of 210 fs and 6.7 ps. Globular-like and jet-like objects were found depending on the various levels of the

  4. Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation

    Science.gov (United States)

    Kim, Beop-Min; Feit, Michael D.; Rubenchik, Alexander M.; Gold, David M.; Darrow, Christopher B.; Marion, John E., II; Da Silva, Luiz B.

    1998-05-01

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using an ultrashort pulse laser. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so bone tissue is selectively ablated while preserving the spinal cord.

  5. Optical and electrical properties of SnO2 thin films after ultra-short pulsed laser annealing

    OpenAIRE

    Scorticati, D.; Illiberi, A.; Römer, G.R.B.E.; Bor, T.; Ogieglo, W.; Klein Gunnewiek, M.; Lenferink, A.; Otto, C.; Skolski, J.Z.P.; Grob, F.; Lange, D.F. de; Huis in 't Veld, A.J.

    2013-01-01

    Ultra-short pulsed laser sources, with pulse durations in the ps and fs regime, are commonly exploited for cold ablation. However, operating ultra-short pulsed laser sources at fluence levels well below the ablation threshold allows for fast and selective thermal processing. The latter is especially advantageous for the processing of thin films. A precise control of the heat affected zone, as small as tens of nanometers, depending on the material and laser conditions, can be achieved. It enab...

  6. Electron emission from insulator surfaces by ultra-short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Acuna, M; Gravielle, M S, E-mail: mario@iafe.uba.a, E-mail: msilvia@iafe.uba.a [Institutes de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina)

    2009-11-01

    Photoelectron emission from insulator surfaces induced by ultra-short laser pulses is studied within a time-dependent distorted wave method. The proposed approach combines the Volkov phase, which takes into account the laser interaction, with a simple representation of the unperturbed surface states, given by the Tight-binding method. The model is applied to evaluate the photoelectron emission from a LiF(001) surface, finding effects of interference produced by the crystal lattice.

  7. Heat wave propagation in a thin film irradiated by ultra-short laser pulses

    International Nuclear Information System (INIS)

    Yoo, Jae Gwon; Kim, Cheol Jung; Lim, C. H.

    2004-01-01

    A thermal wave solution of a hyperbolic heat conduction equation in a thin film is developed on the basis of the Green's function formalism. Numerical computations are carried out to investigate the temperature response and the propagation of the thermal wave inside a thin film due to a heat pulse generated by ultra-short laser pulses with various laser pulse durations and thickness of the film

  8. Triggering and guiding high-voltage large-scale leader discharges with sub-joule ultrashort laser pulses

    International Nuclear Information System (INIS)

    Pepin, H.; Comtois, D.; Vidal, F.; Chien, C.Y.; Desparois, A.; Johnston, T.W.; Kieffer, J.C.; La Fontaine, B.; Martin, F.; Rizk, F.A.M.; Potvin, C.; Couture, P.; Mercure, H.P.; Bondiou-Clergerie, A.; Lalande, P.; Gallimberti, I.

    2001-01-01

    The triggering and guiding of leader discharges using a plasma channel created by a sub-joule ultrashort laser pulse have been studied in a megavolt large-scale electrode configuration (3-7 m rod-plane air gap). By focusing the laser close to the positive rod electrode it has been possible, with a 400 mJ pulse, to trigger and guide leaders over distances of 3 m, to lower the leader inception voltage by 50%, and to increase the leader velocity by a factor of 10. The dynamics of the breakdown discharges with and without the laser pulse have been analyzed by means of a streak camera and of electric field and current probes. Numerical simulations have successfully reproduced many of the experimental results obtained with and without the presence of the laser plasma channel

  9. Bright ultrashort x-rays from intense subpicosecond laser-plasma interactions

    International Nuclear Information System (INIS)

    Umstadter, D.

    1995-01-01

    Short-pulse, high-intensity lasers interacting with solid targets make possible the study of a new class of laser-plasma interactions. They are unique because during the ultrashort laser pulse relatively little expansion occurs, and the density scale length remains much less than the laser wavelength. This makes possible the direct deposition of a significant amount of the laser energy at close to solid density. Steep plasma temperature and density gradients subsequently cause rapid cooling, resulting in highly non-equilibrium conditions and the concurrent emission of extremely bright ultrashort x-ray pulses. In this study, the latter are investigated experimentally with temporally and spectrally resolved soft x-ray diagnostics. The emitted x-ray spectra from solid targets with various atomic numbers are characterized for a laser pulse width τ l ∼ 400 fs. These ultrashort x rays may be used as (1) a diagnostic of solid-density plasma conditions, (2) a tool for the study of radiation hydrodynamics in a parameter regime that is otherwise inaccessible, and (3) a source for time-resolved diffraction, spectroscopy, or microscopy studies of transient chemical, biological or physical phenomena

  10. Ultrashort laser pulses and electromagnetic pulse generation in air and on dielectric surfaces

    International Nuclear Information System (INIS)

    Sprangle, P.; Penano, J.R.; Hafizi, B.; Kapetanakos, C.A.

    2004-01-01

    Intense, ultrashort laser pulses propagating in the atmosphere have been observed to emit sub-THz electromagnetic pulses (EMPS). The purpose of this paper is to analyze EMP generation from the interaction of ultrashort laser pulses with air and with dielectric surfaces and to determine the efficiency of conversion of laser energy to EMP energy. In our self-consistent model the laser pulse partially ionizes the medium, forms a plasma filament, and through the ponderomotive forces associated with the laser pulse, drives plasma currents which are the source of the EMP. The propagating laser pulse evolves under the influence of diffraction, Kerr focusing, plasma defocusing, and energy depletion due to electron collisions and ionization. Collective effects and recombination processes are also included in the model. The duration of the EMP in air, at a fixed point, is found to be a few hundred femtoseconds, i.e., on the order of the laser pulse duration plus the electron collision time. For steady state laser pulse propagation the flux of EMP energy is nonradiative and axially directed. Radiative EMP energy is present only for nonsteady state or transient laser pulse propagation. The analysis also considers the generation of EMP on the surface of a dielectric on which an ultrashort laser pulse is incident. For typical laser parameters, the power and energy conversion efficiency from laser radiation to EMP radiation in both air and from dielectric surfaces is found to be extremely small, -8 . Results of full-scale, self-consistent, numerical simulations of atmospheric and dielectric surface EMP generation are presented. A recent experiment on atmospheric EMP generation is also simulated

  11. Photoelectron emission from metal surfaces by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Faraggi, M. N.; Gravielle, M. S.; Silkin, V. M.

    2006-01-01

    Electron emission from metal surfaces produced by short laser pulses is studied within the framework of the distorted-wave formulation. The proposed approach, named surface-Volkov (SV) approximation, makes use of the band-structure based (BSB) model and the Volkov phase to describe the interaction of the emitted electron with the surface and the external electric field, respectively. The BSB model provides a realistic representation of the surface, based on a model potential that includes the main features of the surface band structure. The SV method is applied to evaluate the photoelectron emission from the valence band of Al(111). Angular and energy distributions are investigated for different parameters of the laser pulse, keeping in all cases the carrier frequency larger than the plasmon one

  12. A high-order corrected description of ultra-short and tightly focused laser pulses, and their electron acceleration in vacuum

    International Nuclear Information System (INIS)

    Zhang, J.T.; Wang, P.X.; Kong, Q.; Chen, Z.; Ho, Y.K.

    2007-01-01

    Field expressions are derived for ultra-short, tightly focused laser pulses up to the second-order temporal correction and seventh-order spatial correction. To evaluate the importance of these corrections, we simulate these fields and investigate the final energy of the accelerated electrons. We vary the order of the corrected expressions, the pulse duration, and the beam waist. We find that electron capture is still an important and generic phenomenon in ultra-short, tightly focused laser pulses. While small differences in the electron acceleration are obtained for various orders of the corrected field equations relative to the paraxial field equations, there is no qualitative difference in the behavior of the electron. Furthermore, the temporal and spatial corrections are found to be correlated

  13. Nonponderomotive electron acceleration in ultrashort surface-plasmon fields

    Energy Technology Data Exchange (ETDEWEB)

    Racz, Peter; Dombi, Peter [Wigner Research Centre for Physics, Konkoly-Thege M. ut 29-33, H-1121 Budapest (Hungary)

    2011-12-15

    We investigate the nonponderomotive nature of ultrafast plasmonic electron acceleration in strongly decaying electromagnetic fields generated by few-cycle and single-cycle femtosecond laser pulses. We clearly identify the conditions contributing to nonponderomotive acceleration and establish fundamental scaling laws and carrier-envelope phase effects. These all-optically accelerated compact, femtosecond electron sources can be utilized in contemporary ultrafast methods.

  14. Atomic and Molecular Systems in Intense Ultrashort Laser Pulses

    Science.gov (United States)

    Saenz, A.

    2008-07-01

    The full quantum mechanical treatment of atomic and molecular systems exposed to intense laser pulses is a so far unsolved challenge, even for systems as small as molecular hydrogen. Therefore, a number of simplified qualitative and quantitative models have been introduced in order to provide at least some interpretational tools for experimental data. The assessment of these models describing the molecular response is complicated, since a comparison to experiment requires often a number of averages to be performed. This includes in many cases averaging of different orientations of the molecule with respect to the laser field, focal volume effects, etc. Furthermore, the pulse shape and even the peak intensity is experimentally not known with very high precision; considering, e.g., the exponential intensity dependence of the ionization signal. Finally, experiments usually provide only relative yields. As a consequence of all these averagings and uncertainties, it is possible that different models may successfully explain some experimental results or features, although these models disagree substantially, if their predictions are compared before averaging. Therefore, fully quantum-mechanical approaches at least for small atomic and molecular systems are highly desirable and have been developed in our group. This includes efficient codes for solving the time-dependent Schrodinger equation of atomic hydrogen, helium or other effective one- or two-electron atoms as well as for the electronic motion in linear (effective) one-and two-electron diatomic molecules like H_2.Very recently, a code for larger molecular systems that adopts the so-called single-active electron approximation was also successfully implemented and applied. In the first part of this talk popular models describing intense laser-field ionization of atoms and their extensions to molecules are described. Then their validity is discussed on the basis of quantum-mechanical calculations. Finally, some

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  16. Ultrashort megaelectronvolt positron beam generation based on laser-accelerated electrons

    Science.gov (United States)

    Xu, Tongjun; Shen, Baifei; Xu, Jiancai; Li, Shun; Yu, Yong; Li, Jinfeng; Lu, Xiaoming; Wang, Cheng; Wang, Xinliang; Liang, Xiaoyan; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan

    2016-03-01

    Experimental generation of ultrashort MeV positron beams with high intensity and high density using a compact laser-driven setup is reported. A high-density gas jet is employed experimentally to generate MeV electrons with high charge; thus, a charge-neutralized MeV positron beam with high density is obtained during laser-accelerated electrons irradiating high-Z solid targets. It is a novel electron-positron source for the study of laboratory astrophysics. Meanwhile, the MeV positron beam is pulsed with an ultrashort duration of tens of femtoseconds and has a high peak intensity of 7.8 × 1021 s-1, thus allows specific studies of fast kinetics in millimeter-thick materials with a high time resolution and exhibits potential for applications in positron annihilation spectroscopy.

  17. Axisymmetric modeling of ultrashort-pulse laser interactions with thin metal film

    Directory of Open Access Journals (Sweden)

    E. Majchrzak

    2011-10-01

    Full Text Available The hyperbolic two-temperature model is used in order to describe the heat propagation in metal film subjected to an ultrashort-pulse laser heating. An axisymmetric heat soureceewith Gaussian temporeal and spatial distributions has been taken into account. At the stage of numerical computations the finite difference method is used. In the final part of the paper the examples of computations are shown.

  18. Ultrashort laser-pulse diagnostics for detection of ordering within an ion beam

    International Nuclear Information System (INIS)

    Calabrese, R.; Guidi, V.; Lenisa, P.; Mariotti, E.

    1996-01-01

    A novel diagnostic method to detect ordering within one-dimensional ion beams in a storage ring is presented. The ions are simultaneously excited by a ultrashort pulsed laser (≅1 ps) at two different locations along the beam and fluorescence is detected by a group of four photomultipliers. Correlation in fluorescence signals is a firm indication that the ion beam has an ordered structure. (orig.)

  19. Effect of group velocity mismatch on acousto-optic interaction of ultrashort laser pulses

    International Nuclear Information System (INIS)

    Yushkov, K B; Molchanov, V Ya

    2011-01-01

    Equations describing acousto-optic diffraction of ultrashort laser pulses in an anisotropic medium are derived, taking into account the group velocity mismatch of optical eigenmodes. It is shown that the solution of the modified coupled-mode equations taking into account the group delay is characterised by an increase in the pulse duration, a decrease in diffraction efficiency, a change in the shape of the wave packet envelope, as well as by an increase in the width of the transmission function.

  20. A plasma microlens for ultrashort high power lasers

    Science.gov (United States)

    Katzir, Yiftach; Eisenmann, Shmuel; Ferber, Yair; Zigler, Arie; Hubbard, Richard F.

    2009-07-01

    We present a technique for generation of miniature plasma lens system that can be used for focusing and collimating a high intensity femtosecond laser pulse. The plasma lens was created by a nanosecond laser, which ablated a capillary entrance. The spatial configuration of the ablated plasma focused a high intensity femtosecond laser pulse. This configuration offers versatility in the plasma lens small f-number for extremely tight focusing of high power lasers with no damage threshold restrictions of regular optical components.

  1. A plasma microlens for ultrashort high power lasers

    International Nuclear Information System (INIS)

    Katzir, Yiftach; Eisenmann, Shmuel; Ferber, Yair; Zigler, Arie; Hubbard, Richard F.

    2009-01-01

    We present a technique for generation of miniature plasma lens system that can be used for focusing and collimating a high intensity femtosecond laser pulse. The plasma lens was created by a nanosecond laser, which ablated a capillary entrance. The spatial configuration of the ablated plasma focused a high intensity femtosecond laser pulse. This configuration offers versatility in the plasma lens small f-number for extremely tight focusing of high power lasers with no damage threshold restrictions of regular optical components.

  2. How to optimize ultrashort pulse laser interaction with glass surfaces in cutting regimes?

    Energy Technology Data Exchange (ETDEWEB)

    Bulgakova, Nadezhda M., E-mail: bulgakova@fzu.cz [HiLASE Centre, Institute of Physics ASCR, Za Radnicí 828, 25241 Dolní Břežany (Czech Republic); Institute of Thermophysics SB RAS, 1 Lavrentyev Ave., Novosibirsk 630090 (Russian Federation); Zhukov, Vladimir P. [Institute of Computational Technologies SB RAS, 6 Lavrentyev Ave., 630090 Novosibirsk (Russian Federation); Novosibirsk State Technical University, 20 Karl Marx Ave., 630073 Novosibirsk (Russian Federation); Collins, Adam R. [NCLA, NUI Galway, Galway (Ireland); Rostohar, Danijela; Derrien, Thibault J.-Y.; Mocek, Tomáš [HiLASE Centre, Institute of Physics ASCR, Za Radnicí 828, 25241 Dolní Břežany (Czech Republic)

    2015-05-01

    Highlights: • The factors influencing laser micromachining of transparent materials are analyzed. • Important role of ambient gas in laser processing is shown by numerical simulations. • The large potential of bi-wavelength laser processing is demonstrated. - Abstract: The interaction of short and ultrashort pulse laser radiation with glass materials is addressed. Particular attention is paid to regimes which are important in industrial applications such as laser cutting, drilling, functionalization of material surfaces, etc. Different factors influencing the ablation efficiency and quality are summarized and their importance is illustrated experimentally. The effects of ambient gas ionization in front of the irradiated target are also analyzed. A possibility to enhance laser coupling with transparent solids by bi-wavelength irradiation is discussed.

  3. Interaction of ultrashort laser pulses and silicon solar cells under short circuit conditions

    Energy Technology Data Exchange (ETDEWEB)

    Mundus, M., E-mail: markus.mundus@ise.fraunhofer.de; Giesecke, J. A.; Fischer, P.; Hohl-Ebinger, J.; Warta, W. [Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstraße 2, 79110 Freiburg (Germany)

    2015-02-28

    Ultrashort pulse lasers are promising tools for numerous measurement purposes. Among other benefits their high peak powers allow for efficient generation of wavelengths in broad spectral ranges and at spectral powers that are orders of magnitude higher than in conventional light sources. Very recently this has been exploited for the establishment of sophisticated measurement facilities for electrical characterization of photovoltaic (PV) devices. As the high peak powers of ultrashort pulses promote nonlinear optical effects they might also give rise to nonlinear interactions with the devices under test that possibly manipulate the measurement outcome. In this paper, we present a comprehensive theoretical and experimental study of the nonlinearities affecting short circuit current (I{sub SC}) measurements of silicon (Si) solar cells. We derive a set of coupled differential equations describing the radiation-device interaction and discuss the nonlinearities incorporated in those. By a semi-analytical approach introducing a quasi-steady-state approximation and integrating a Green's function we solve the system of equations and obtain simulated I{sub SC} values. We validate the theoretical model by I{sub SC} ratios obtained from a double ring resonator setup capable for reproducible generation of various ultrashort pulse trains. Finally, we apply the model to conduct the most prominent comparison of I{sub SC} generated by ultrashort pulses versus continuous illumination. We conclude by the important finding that the nonlinearities induced by ultrashort pulses are negligible for the most common I{sub SC} measurements. However, we also find that more specialized measurements (e.g., of concentrating PV or Si-multijunction devices as well as highly localized electrical characterizations) will be biased by two-photon-absorption distorting the I{sub SC} measurement.

  4. New techniques of time-resolved infrared and Raman spectroscopy using ultrashort laser pulses

    International Nuclear Information System (INIS)

    Laubereau, A.

    1986-01-01

    Considerable progress has been made in recent years in the field of spectroscopic applications of ultrashort laser pulses. This paper examines two approaches toward studying ultrafast relaxation processes in condensed matter: an IR technique which complements coherent Raman scattering; and a Fourier Raman method with high frequency resolution. The time domain IR spectroscopy technique has been applied to various vibration-rotation transitions of pure HCl gas and in mixtures with Ar buffer gas. The advantage of the time domain measurements instead of frequency spectroscopy is readily visualized when one recalls that a frequency resolution of 10 -3 cm -1 corresponds to time observations over 10 -8 , which are readily feasible. As a first demonstration of the FT-Raman technique the author presents experimental data on the Q-branch of the v 1 -vibrational mode of methane. An example for the experimental data obtained approximately 2 mm behind the nozzle is presented; the coherent anti-Stokes Raman signal is plotted versus delay time. A complicated beating structure and the decay of the signal envelope are readily seen. The desired spectroscopic information is obtained by numerical Fourier transformation of the experimental points presented

  5. High repetition rate ultrashort laser cuts a path through fog

    Science.gov (United States)

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

    2016-12-01

    We experimentally demonstrate that the transmission of a 1030 nm, 1.3 ps laser beam of 100 mJ energy through fog increases when its repetition rate increases to the kHz range. Due to the efficient energy deposition by the laser filaments in the air, a shockwave ejects the fog droplets from a substantial volume of the beam, at a moderate energy cost. This process opens prospects for applications requiring the transmission of laser beams through fogs and clouds.

  6. Applications of ultra-short pulsed laser ablation: thin films deposition and fs/ns dual-pulse laser-induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Teghil, R; De Bonis, A; Galasso, A; Santagata, A; Albano, G; Villani, P; Spera, D; Parisi, G P

    2008-01-01

    In this paper, we report a survey of two of the large number of possible practical applications of the laser ablation performed by an ultra-short pulse laser, namely pulsed laser deposition (PLD) and fs/ns dual-pulse laser-induced breakdown spectroscopy (DP-LIBS). These applications differ from those using just longer pulsed lasers as a consequence of the distinctive characteristics of the plasma produced by ultra-short laser beams. The most important feature of this plasma is the large presence of particles with nanometric size which plays a fundamental role in both applications.

  7. X-ray emission as a potential hazard during ultrashort pulse laser material processing

    Science.gov (United States)

    Legall, Herbert; Schwanke, Christoph; Pentzien, Simone; Dittmar, Günter; Bonse, Jörn; Krüger, Jörg

    2018-06-01

    In laser machining with ultrashort laser pulses unwanted X-ray radiation in the keV range can be generated when a critical laser intensity is exceeded. Even if the emitted X-ray dose per pulse is low, high laser repetition rates can lead to an accumulation of X-ray doses beyond exposure safety limits. For 925 fs pulse duration at a center wavelength of 1030 nm, the X-ray emission was investigated up to an intensity of 2.6 × 1014 W/cm2. The experiments were performed in air with a thin disk laser at a repetition rate of 400 kHz. X-ray spectra and doses were measured for various planar target materials covering a wide range of the periodic table from aluminum to tungsten. Without radiation shielding, the measured radiation doses at this high repetition rate clearly exceed the regulatory limits. Estimations for an adequate radiation shielding are provided.

  8. Yb3+:Sr3Y2(BO3)4: A potential ultrashort pulse laser crystal

    International Nuclear Information System (INIS)

    Sun, Shijia; Xu, Jinlong; Wei, Qi; Lou, Fei; Huang, Yisheng; Yuan, Feifei; Zhang, Lizhen; Lin, Zhoubin; He, Jingliang; Wang, Guofu

    2015-01-01

    Highlights: • A Yb 3+ :Sr 3 Y 2 (BO 3 ) 4 crystal was grown successfully by Czochralski method. • The crystal has wide absorption and emission bandwidth. • 3.47 W continuous wave laser output with a slope efficiency of 29% was obtained. • The results show that the crystal is a promising ultrashort pulse laser material. - Abstract: A Yb 3+ :Sr 3 Y 2 (BO 3 ) 4 crystal was grown successfully by the Czochralski method. The polarized spectral properties and continuous wave laser output of this crystal were investigated in detail. The crystal has larger absorption and emission cross sections compared with many mature Yb 3+ -doped borate crystals. The full width at half maximum of the emission bands around 1023 nm are 69 nm (E//a), 61 nm (E//b) and 65 nm (E//c). 3.47 W continuous wave laser output with a slope efficiency of 29% and an optical conversion efficiency of 24% was obtained. The results reveal that Yb 3+ :Sr 3 Y 2 (BO 3 ) 4 crystal is an excellent candidate for ultrashort pulse laser crystal

  9. Electron Hole Plasma in Solids Induced by Ultrashort XUV Laser Pulses

    International Nuclear Information System (INIS)

    Rethfeld, B.; Medvedev, N.

    2013-01-01

    Irradiation of solids with ultrashort XUV laser pulses leads to an excitation of electrons from the valence band and deeper shells to the conduction band leading to a nonequilibrium highly energetic electron hole plasma. We investigate the transient electron dynamics in a solid semiconductor and metal (silicon and aluminum, respectively) under irradiation with a femtosecond VUV to XUV laser pulse as used in experiments with the Free Electron Laser FLASH at DESY in Hamburg, Germany. Applying the Asymptotical Trajectory Monte-Carlo technique, we obtain the transient energy distribution of the excited and ionized electrons within the solid. Photon absorption by electrons in different bands and secondary excitation and ionization processes are simulated event by event. The method was extended in order to take into account the electronic band structure and Pauli's principle for electrons in the conduction band. In this talk we review our results on the dynamics of the transient electron-hole plasma, in particular its transient density and energy distribution in dependence on laser and material parameters. For semiconductors we introduce the concept of an ''effective energy gap'' for collective electronic excitation, which can be applied to estimate the free electron density after high-intensity ultrashort XUV laser pulse irradiation. For aluminum we demonstrate that the electronic spectra depend on the relaxation kinetics of the excited electronic subsystem. Experimentally observed spectra of emitted photons from irradiated aluminum can be explained well with our results. (author)

  10. Ultra-short laser pulse ablation using shear-force feedback: Femtosecond laser induced breakdown spectroscopy feasibility study

    International Nuclear Information System (INIS)

    Samek, Ota; Kurowski, Andre; Kittel, Silke; Kukhlevsky, Sergei; Hergenroeder, Roland

    2005-01-01

    This work reports on a feasibility study of proximity ablation using femtosecond pulses. Ultra-short pulses were launched to a bare tapered optical fiber and delivered to the sample. The tip-sample distance was controlled by means of shear-force feedback. Consequently, ablation craters with submicrometer dimensions were obtained. Potential analytical applications for Laser Induced Breakdown Spectroscopy (LIBS) technique, such as e.g. inclusions in steel or bio cells, are suggested

  11. Ultrashort pulse laser processing of hard tissue, dental restoration materials, and biocompatibles

    Science.gov (United States)

    Yousif, A.; Strassl, M.; Beer, F.; Verhagen, L.; Wittschier, M.; Wintner, E.

    2007-07-01

    During the last few years, ultra-short laser pulses have proven their potential for application in medical tissue treatment in many ways. In hard tissue ablation, their aptitude for material ablation with negligible collateral damage provides many advantages. Especially teeth representing an anatomically and physiologically very special region with less blood circulation and lower healing rates than other tissues require most careful treatment. Hence, overheating of the pulp and induction of microcracks are some of the most problematic issues in dental preparation. Up till now it was shown by many authors that the application of picosecond or femtosecond pulses allows to perform ablation with very low damaging potential also fitting to the physiological requirements indicated. Beside the short interaction time with the irradiated matter, scanning of the ultra-short pulse trains turned out to be crucial for ablating cavities of the required quality. One main reason for this can be seen in the fact that during scanning the time period between two subsequent pulses incident on the same spot is so much extended that no heat accumulation effects occur and each pulse can be treated as a first one with respect to its local impact. Extension of this advantageous technique to biocompatible materials, i.e. in this case dental restoration materials and titanium plasma-sprayed implants, is just a matter of consequence. Recently published results on composites fit well with earlier data on dental hard tissue. In case of plaque which has to be removed from implants, it turns out that removal of at least the calcified version is harder than tissue removal. Therefore, besides ultra-short lasers, also Diode and Neodymium lasers, in cw and pulsed modes, have been studied with respect to plaque removal and sterilization. The temperature increase during laser exposure has been experimentally evaluated in parallel.

  12. Nonlinear Thomson scattering of a relativistically strong tightly focused ultrashort laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Vais, O. E.; Bochkarev, S. G., E-mail: bochkar@sci.lebedev.ru; Bychenkov, V. Yu. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2016-09-15

    The problem of nonlinear Thomson scattering of a relativistically strong linearly polarized ultrashort laser pulse tightly focused into a spot with a diameter of D{sub F} ≳ λ (where λ is the laser wavelength) is solved. The energy, spectral, and angular distributions of radiation generated due to Thomson scattering from test electrons located in the focal region are found. The characteristics of scattered radiation are studied as functions of the tightness of laser focusing and the initial position of test particles relative to the center of the focal region for a given laser pulse energy. It is demonstrated that the ultratight focusing is not optimal for obtaining the brightest and hardest source of secondary electromagnetic radiation. The hardest and shortest radiation pulse is generated when the beam waist diameter is ≃10λ.

  13. On the surface topography of ultrashort laser pulse treated steel surfaces

    International Nuclear Information System (INIS)

    Vincenc Obona, J.; Ocelík, V.; Skolski, J.Z.P.; Mitko, V.S.; Römer, G.R.B.E.; Huis in’t Veld, A.J.; De Hosson, J.Th.M.

    2011-01-01

    This paper concentrates on observations of the surface topography by scanning electron microscopy (SEM) on alloyed and stainless steels samples treated by ultrashort laser pulses with duration of 210 fs and 6.7 ps. Globular-like and jet-like objects were found depending on the various levels of the fluence applied. It is shown that these features appear due to solid-liquid and liquid-gas transitions within surface layer irradiated by intense laser light. The observations are confronted to the theory of short-pulsed laser light-matter interactions, including interference, excitation of electrons, electron-phonon coupling as well as subsequent ablation. It is shown that the orientation of small ripples does not always depend on the direction of the polarization of laser light.

  14. Anterior capsulotomy with an ultrashort-pulse laser.

    Science.gov (United States)

    Tackman, Ramon Naranjo; Kuri, Jorge Villar; Nichamin, Louis D Skip; Edwards, Keith

    2011-05-01

    To assess the precision of laser anterior capsulotomy compared with that of manual continuous curvilinear capsulorhexis (CCC). Asociación Para Evitar La Ceguera en México IAP, Hospital Dr. Luis Sánchez Bulnes, Mexico City, Mexico. Nonrandomized single-center clinical trial. In patients presenting for cataract surgery, the LensAR Laser System was used to create a laser anterior capsulotomy of the surgeon's desired size. Capsule buttons were retrieved and measured and then compared with buttons retrieved from eyes having a manually torn CCC. Deviation from the intended diameter and the regularity of shape were assessed. When removing the capsule buttons at the start of surgery, the surgeon rated the ease of removal on a scale of 1 to 10 (1 = required manual capsulorhexis around the whole diameter; 10 = button free floating or required no manual detachment from remaining capsule during removal). The mean deviation from the intended diameter was 0.16 mm ± 0.17 (SD) for laser anterior capsulotomy and 0.42 ± 0.54 mm for CCC (P=.03). The mean absolute deviation from the intended diameter was 0.20 ± 0.12 mm and 0.49 ± 0.47 mm, respectively (P=.003). The mean of the average squared residuals was 0.01 ± 0.03 and 0.02 ± 0.04, respectively (P=.09). The median rating of the ease of removal was 9 (range 5 to 10). Laser anterior capsulotomy created a more precise capsule opening than CCC, and the buttons created by the laser procedure were easy to remove at the beginning of cataract surgery. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  15. Surface and Bulk Nanostructuring of Insulators by Ultrashort Laser Pulses

    Science.gov (United States)

    2017-04-05

    non perturbative effects leading to HHG. 15. SUBJECT TERMS Nanostructuring of bulk insulators, sub-picosecond electronic and structural events , photo...time, the charge density oscillations follow the time periodicity of the incident radiation. These transient charge oscillations are exclusively due...As in section II photoexcitation and the dielectric response of laser-irradiated diamond are treated in independent particle approximation based on the

  16. Ultrashort-pulse laser machining system employing a parametric amplifier

    Science.gov (United States)

    Perry, Michael D.

    2004-04-27

    A method and apparatus are provided for increasing the energy of chirped laser pulses to an output in the range 0.001 to over 10 millijoules at a repetition rate 0.010 to 100 kHz by using a two stage optical parametric amplifier utilizing a bulk nonlinear crystal wherein the pump and signal beam size can be independently adjusted in each stage.

  17. Prospects for a novel ultrashort pulsed laser technology for pathogen inactivation

    Directory of Open Access Journals (Sweden)

    Tsen Shaw-Wei D

    2012-07-01

    Full Text Available Abstract The threat of emerging pathogens and microbial drug resistance has spurred tremendous efforts to develop new and more effective antimicrobial strategies. Recently, a novel ultrashort pulsed (USP laser technology has been developed that enables efficient and chemical-free inactivation of a wide spectrum of viral and bacterial pathogens. Such a technology circumvents the need to introduce potentially toxic chemicals and could permit safe and environmentally friendly pathogen reduction, with a multitude of possible applications including the sterilization of pharmaceuticals and blood products, and the generation of attenuated or inactivated vaccines.

  18. Modelling of the energy density deposition profiles of ultrashort laser pulses focused in optical media

    International Nuclear Information System (INIS)

    Vidal, F; Lavertu, P-L; Bigaouette, N; Moore, F; Brunette, I; Giguere, D; Kieffer, J-C; Olivie, G; Ozaki, T

    2007-01-01

    The propagation of ultrashort laser pulses in dense optical media is investigated theoretically by solving numerically the nonlinear Schroedinger equation. It is shown that the maximum energy density deposition as a function of the pulse energy presents a well-defined threshold that increases with the pulse duration. As a consequence of plasma defocusing, the maximum energy density deposition is generally smaller and the size of the energy deposition zone is generally larger for shorter pulses. Nevertheless, significant values of the energy density deposition can be obtained near threshold, i.e., at lower energy than for longer pulses

  19. Self-oscillations in cw solid-state ultrashort-pulse-generating lasers with mode locking by self-focusing

    International Nuclear Information System (INIS)

    Kalashnikov, V L; Krimer, D O; Mejid, F; Poloiko, I G; Mikhailov, V P

    1999-01-01

    Steady-state and transient regimes of ultrashort pulse generation are studied for cw solid-state lasers with mode locking by self-focusing. It is shown that the control parameter, which governs the nature of lasing, is the relationship between self-phase-modulation and the saturation intensity of an efficient shutter, induced by the Kerr self-focusing. Numerical modelling based on mapping the parameters of a quasi-soliton ultrashort pulse, considered in the aberration-free approximation, yields results in good agreement with experiments. (control of laser radiation parameters)

  20. Chromium carbide thin films deposited by ultra-short pulse laser deposition

    International Nuclear Information System (INIS)

    Teghil, R.; Santagata, A.; De Bonis, A.; Galasso, A.; Villani, P.

    2009-01-01

    Pulsed laser deposition performed by a laser with a pulse duration of 250 fs has been used to deposit films from a Cr 3 C 2 target. Due to the different processes involved in the laser ablation when it is performed by an ultra-short pulse source instead of a conventional short pulse one, it has been possible to obtain in vacuum films containing only one type of carbide, Cr 3 C 2 , as shown by X-ray photoelectron spectroscopy. On the other hand, Cr 3 C 2 is not the only component of the films, since a large amount of amorphous carbon is also present. The films, deposited at room temperature, are amorphous and seem to be formed by the coalescence of a large number of particles with nanometric size. The film composition can be explained in terms of thermal evaporation from particles ejected from the target.

  1. Ultrashort pulse laser machining of metals and alloys

    Science.gov (United States)

    Perry, Michael D.; Stuart, Brent C.

    2003-09-16

    The invention consists of a method for high precision machining (cutting, drilling, sculpting) of metals and alloys. By using pulses of a duration in the range of 10 femtoseconds to 100 picoseconds, extremely precise machining can be achieved with essentially no heat or shock affected zone. Because the pulses are so short, there is negligible thermal conduction beyond the region removed resulting in negligible thermal stress or shock to the material beyond approximately 0.1-1 micron (dependent upon the particular material) from the laser machined surface. Due to the short duration, the high intensity (>10.sup.12 W/cm.sup.2) associated with the interaction converts the material directly from the solid-state into an ionized plasma. Hydrodynamic expansion of the plasma eliminates the need for any ancillary techniques to remove material and produces extremely high quality machined surfaces with negligible redeposition either within the kerf or on the surface. Since there is negligible heating beyond the depth of material removed, the composition of the remaining material is unaffected by the laser machining process. This enables high precision machining of alloys and even pure metals with no change in grain structure.

  2. Mimicking lizard-like surface structures upon ultrashort laser pulse irradiation of inorganic materials

    Science.gov (United States)

    Hermens, U.; Kirner, S. V.; Emonts, C.; Comanns, P.; Skoulas, E.; Mimidis, A.; Mescheder, H.; Winands, K.; Krüger, J.; Stratakis, E.; Bonse, J.

    2017-10-01

    Inorganic materials, such as steel, were functionalized by ultrashort laser pulse irradiation (fs- to ps-range) to modify the surface's wetting behavior. The laser processing was performed by scanning the laser beam across the surface of initially polished flat sample material. A systematic experimental study of the laser processing parameters (peak fluence, scan velocity, line overlap) allowed the identification of different regimes associated with characteristic surface morphologies (laser-induced periodic surface structures, grooves, spikes, etc.). Analyses of the surface using optical as well as scanning electron microscopy revealed morphologies providing the optimum similarity to the natural skin of lizards. For mimicking skin structures of moisture-harvesting lizards towards an optimization of the surface wetting behavior, additionally a two-step laser processing strategy was established for realizing hierarchical microstructures. In this approach, micrometer-scaled capillaries (step 1) were superimposed by a laser-generated regular array of small dimples (step 2). Optical focus variation imaging measurements finally disclosed the three dimensional topography of the laser processed surfaces derived from lizard skin structures. The functionality of these surfaces was analyzed in view of wetting properties.

  3. Interaction of ultrashort pulses with molecules and solids: Physics ...

    Indian Academy of Sciences (India)

    2014-07-26

    energy materials. Abstract. The interaction of ultrashort laser pulses with molecules and solids is an extremely complex area of science research encompassing the fields of physics, chemistry, and materials science. The physics ...

  4. Study of laser pulses propagation through an ultrashort pulse amplifying systems for the development of an Offner temporal stretcher

    International Nuclear Information System (INIS)

    Cordeiro, Thiago da Silva

    2009-01-01

    The study of laser pulses propagation through an ultrashort pulses amplifying system containing dispersive and spectral modifying media was performed. The study emphasis was the development of an ultrashort pulse stretcher to replace the one inside a hybrid Ti:Sapphire/Cr:LiSAF CPA system operating at the Center for Lasers and Applications at IPEN/CNEN-SP. A spherical aberration free Offner stretcher was theoretically studied, aiming to obtain a stretching ratio larger than the one available in our system. The influence of the phase components in the amplified pulse final duration was also studied, and the bandwidth limiting elements of the system in operation were mapped, with the purpose of determining the conditions under which a new stretcher should be implemented. Based on the actual measurements, computing routines were implemented in order to determine the consequences of an ultrashort pulse travelling through a bandwidth limiting component. (author)

  5. Fast Prototyping of Sensorized Cell Culture Chips and Microfluidic Systems with Ultrashort Laser Pulses

    Directory of Open Access Journals (Sweden)

    Sebastian M. Bonk

    2015-03-01

    Full Text Available We developed a confined microfluidic cell culture system with a bottom plate made of a microscopic slide with planar platinum sensors for the measurement of acidification, oxygen consumption, and cell adhesion. The slides were commercial slides with indium tin oxide (ITO plating or were prepared from platinum sputtering (100 nm onto a 10-nm titanium adhesion layer. Direct processing of the sensor structures (approximately three minutes per chip by an ultrashort pulse laser facilitated the production of the prototypes. pH-sensitive areas were produced by the sputtering of 60-nm Si3N4 through a simple mask made from a circuit board material. The system body and polydimethylsiloxane (PDMS molding forms for the microfluidic structures were manufactured by micromilling using a printed circuit board (PCB milling machine for circuit boards. The microfluidic structure was finally imprinted in PDMS. Our approach avoided the use of photolithographic techniques and enabled fast and cost-efficient prototyping of the systems. Alternatively, the direct production of metallic, ceramic or polymeric molding tools was tested. The use of ultrashort pulse lasers improved the precision of the structures and avoided any contact of the final structures with toxic chemicals and possible adverse effects for the cell culture in lab-on-a-chip systems.

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

    Indian Academy of Sciences (India)

    2017-01-17

    Jan 17, 2017 ... and alluring application prospects of filament are dis- covered, e.g. control of a ... (1) are the linear effects, accounting for the spatial diffraction and the ... The input electric field envelope is modelled by a. Gaussian profile with ...

  7. Ultra-short pulse delivery at high average power with low-loss hollow core fibers coupled to TRUMPF's TruMicro laser platforms for industrial applications

    Science.gov (United States)

    Baumbach, S.; Pricking, S.; Overbuschmann, J.; Nutsch, S.; Kleinbauer, J.; Gebs, R.; Tan, C.; Scelle, R.; Kahmann, M.; Budnicki, A.; Sutter, D. H.; Killi, A.

    2017-02-01

    Multi-megawatt ultrafast laser systems at micrometer wavelength are commonly used for material processing applications, including ablation, cutting and drilling of various materials or cleaving of display glass with excellent quality. There is a need for flexible and efficient beam guidance, avoiding free space propagation of light between the laser head and the processing unit. Solid core step index fibers are only feasible for delivering laser pulses with peak powers in the kW-regime due to the optical damage threshold in bulk silica. In contrast, hollow core fibers are capable of guiding ultra-short laser pulses with orders of magnitude higher peak powers. This is possible since a micro-structured cladding confines the light within the hollow core and therefore minimizes the spatial overlap between silica and the electro-magnetic field. We report on recent results of single-mode ultra-short pulse delivery over several meters in a lowloss hollow core fiber packaged with industrial connectors. TRUMPF's ultrafast TruMicro laser platforms equipped with advanced temperature control and precisely engineered opto-mechanical components provide excellent position and pointing stability. They are thus perfectly suited for passive coupling of ultra-short laser pulses into hollow core fibers. Neither active beam launching components nor beam trackers are necessary for a reliable beam delivery in a space and cost saving packaging. Long term tests with weeks of stable operation, excellent beam quality and an overall transmission efficiency of above 85 percent even at high average power confirm the reliability for industrial applications.

  8. Nonlinear dynamics in integrated coupled DFB lasers with ultra-short delay.

    Science.gov (United States)

    Liu, Dong; Sun, Changzheng; Xiong, Bing; Luo, Yi

    2014-03-10

    We report rich nonlinear dynamics in integrated coupled lasers with ultra-short coupling delay. Mutually stable locking, period-1 oscillation, frequency locking, quasi-periodicity and chaos are observed experimentally. The dynamic behaviors are reproduced numerically by solving coupled delay differential equations that take the variation of both frequency detuning and coupling phase into account. Moreover, it is pointed out that the round-trip frequency is not involved in the above nonlinear dynamical behaviors. Instead, the relationship between the frequency detuning Δν and the relaxation oscillation frequency νr under mutual injection are found to be critical for the various observed dynamics in mutually coupled lasers with very short delay.

  9. Fullerene-reduced graphene oxide composites obtained by ultrashort laser ablation of fullerite in water

    Energy Technology Data Exchange (ETDEWEB)

    De Bonis, A., E-mail: angela.debonis@unibas.it [Dipartimento di Scienze, Università degli Studi della Basilicata, Viale dell’Ateneo Lucano, 10-85100, Potenza (Italy); Curcio, M. [Dipartimento di Scienze, Università degli Studi della Basilicata, Viale dell’Ateneo Lucano, 10-85100, Potenza (Italy); Santagata, A. [CNR-ISM, U.O.S. Tito Scalo, Zona Industriale, 85050, Tito Scalo (PZ) (Italy); Rau, J.V. [CNR-ISM, Via del Fosso del Cavaliere, 100-00133, Rome (Italy); Galasso, A.; Teghil, R. [Dipartimento di Scienze, Università degli Studi della Basilicata, Viale dell’Ateneo Lucano, 10-85100, Potenza (Italy)

    2015-05-01

    Highlights: • Laser ablation of a fullerite target in water performed by an ultra-short laser source has been reported. • The formation of reduced graphene oxide has been described considering the laser ablation in liquid mechanism. • Fullerene-reduced graphene oxide composite, in the form of self assembled microtubes, has been described. - Abstract: The laser ablation in liquid of carbon-based solid targets is of particular interest thanks to the possibility of obtaining different carbon allotropes by varying the experimental parameters employed. The ablation of a fullerite target in water using a frequency-doubled Nd:glass laser source with a pulse duration of 250 fs and a frequency repetition rate of 10 Hz is presented. The obtained products have been characterized by transmission electron and atomic force microscopies and by X-ray photoelectron and micro-Raman spectroscopies. During the femtosecond laser ablation, the collapse of fullerene cages has been considered with the consequent formation of graphene oxide (GO) and its successive hydrogenation. The process of self-assembling in microtube structures of the formed reduced graphene oxide-fullerene composites has then been reported.

  10. Self-Guiding of Ultrashort Relativistically Intense Laser Pulses to the Limit of Nonlinear Pump Depletion

    International Nuclear Information System (INIS)

    Ralph, J. E.; Marsh, K. A.; Pak, A. E.; Lu, W.; Clayton, C. E.; Fang, F.; Joshi, C.; Tsung, F. S.; Mori, W. B.

    2009-01-01

    A study of self-guiding of ultra short, relativistically intense laser pulses is presented. Here, the laser pulse length is on the order of the nonlinear plasma wavelength and the normalized vector potential is greater than one. Self-guiding of ultrashort laser pulses over tens of Rayliegh lengths is possible when driving a highly nonlinear wake. In this case, self-guiding is limited by nonlinear pump depletion. Erosion of the pulse due to diffraction at the head of the laser pulse is minimized for spot sizes close to the blow-out radius. This is due to the slowing of the group velocity of the photons at the head of the laser pulse. Using an approximately 10 TW Ti:Sapphire laser with a pulse length of approximately 50 fs, experimental results are presented showing self-guiding over lengths exceeding 30 Rayliegh lengths in various length Helium gas jets. Fully explicit 3D PIC simulations supporting the experimental results are also presented.

  11. On-the-fly depth profiling during ablation with ultrashort laser pulses: A tool for accurate micromachining and laser surgery

    International Nuclear Information System (INIS)

    Lausten, Rune; Balling, Peter

    2001-01-01

    A method for accurate depth profiling of a region subjected to ablation with ultrashort laser pulses is demonstrated. Time-gated imaging of the backscattered radiation from the ablation region is performed in a geometry, which allows the depth along a chosen axis on the sample to be determined with a single measurement. The profiling system has a spatial resolution of a few micrometers and applications are promoted by the fact that the measurement is performed with the same pulse that undertakes ablation. This also indicates that the method is inherently suited for in situ on-the-fly measurements. Copyright 2001 American Institute of Physics

  12. Additional external electromagnetic fields for laser microprocessing of metals.

    Science.gov (United States)

    Schütz, V; Bischoff, K; Brief, S; Koch, J; Suttmann, O; Overmeyer, L

    2016-11-14

    Ultra-short pulsed laser processing is a potent tool for microstructuring of a lot of materials. At certain laser parameters, particular periodical and/or quasi-periodical µm-size surface structures evolve apparently during processing. With extended plasmonics theory, it is possible to predict the structure formation, and a systematic technology can be derived to alter the surface for laser processing. In this work, we have demonstrated the modification of the laser processing with applying tailored dynamic surface electro-magnetic fields. Possible improvement in applications is seen in the fields of process efficiency of laser ablation and a superior control of the surface topography.

  13. Table-top laser-driven ultrashort electron and X-ray source: the CIBER-X source project

    Science.gov (United States)

    Girardeau-Montaut, Jean-Pierre; Kiraly, Bélà; Girardeau-Montaut, Claire; Leboutet, Hubert

    2000-09-01

    We report on the development of a new laser-driven table-top ultrashort electron and X-ray source, also called the CIBER-X source . X-ray pulses are produced by a three-step process which consists of the photoelectron emission from a thin metallic photocathode illuminated by 16 ps duration laser pulses at 213 nm. The e-gun is a standard Pierce diode electrode type, in which electrons are accelerated by a cw electric field of ˜11 MV/m up to a hole made in the anode. The photoinjector produces a train of 70-80 keV electron pulses of ˜0.5 nC and 20 A peak current at a repetition rate of 10 Hz. The electrons are then transported outside the diode along a path of 20 cm length, and are focused onto a target of thullium by magnetic fields produced by two electromagnetic coils. X-rays are then produced by the impact of electrons on the target. Simulations of geometrical, electromagnetic fields and energetic characteristics of the complete source were performed previously with the assistance of the code PIXEL1 also developed at the laboratory. Finally, experimental electron and X-ray performances of the CIBER-X source as well as its application to very low dose imagery are presented and discussed. source Compacte d' Impulsions Brèves d' Electrons et de Rayons X

  14. Table-top laser-driven ultrashort electron and X-ray source: the CIBER-X source project

    Energy Technology Data Exchange (ETDEWEB)

    Girardeau-Montaut, J.-P. E-mail: jean-pierre.girardeau@univ-lyonl.fr; Kiraly, Bela; Girardeau-Montaut, Claire; Leboutet, Hubert

    2000-09-21

    We report on the development of a new laser-driven table-top ultrashort electron and X-ray source, also called the CIBER-X source . X-ray pulses are produced by a three-step process which consists of the photoelectron emission from a thin metallic photocathode illuminated by 16 ps duration laser pulses at 213 nm. The e-gun is a standard Pierce diode electrode type, in which electrons are accelerated by a cw electric field of {approx}11 MV/m up to a hole made in the anode. The photoinjector produces a train of 70-80 keV electron pulses of {approx}0.5 nC and 20 A peak current at a repetition rate of 10 Hz. The electrons are then transported outside the diode along a path of 20 cm length, and are focused onto a target of thulium by magnetic fields produced by two electromagnetic coils. X-rays are then produced by the impact of electrons on the target. Simulations of geometrical, electromagnetic fields and energetic characteristics of the complete source were performed previously with the assistance of the code PIXEL1 also developed at the laboratory. Finally, experimental electron and X-ray performances of the CIBER-X source as well as its application to very low dose imagery are presented and discussed.

  15. Mode-locking peculiarities in an all-fiber erbium-doped ring ultrashort pulse laser with a highly-nonlinear resonator

    Science.gov (United States)

    Dvoretskiy, Dmitriy A.; Sazonkin, Stanislav G.; Kudelin, Igor S.; Orekhov, Ilya O.; Pnev, Alexey B.; Karasik, Valeriy E.; Denisov, Lev K.

    2017-12-01

    Today ultrashort pulse (USP) fiber lasers are in great demand in a frequency metrology field, THz pulse spectroscopy, optical communication, quantum optics application, etc. Therefore mode-locked (ML) fiber lasers have been extensively investigated over the last decade due the number of scientific, medical and industrial applications. It should be noted, that USP fiber lasers can be treated as an ideal platform to expand future applications due to the complex ML nonlinear dynamics in a laser resonator. Up to now a series of novel ML regimes have been investigated e.g. self-similar pulses, noise-like pulses, multi-bound solitons and soliton rain generation. Recently, we have used a highly nonlinear germanosilicate fiber (with germanium oxides concentration in the core 50 mol. %) inside the resonator for more reliable and robust launching of passive mode-locking based on the nonlinear polarization evolution effect in fibers. In this work we have measured promising and stable ML regimes such as stretched pulses, soliton rain and multi-bound solitons formed in a highly-nonlinear ring laser and obtained by intracavity group velocity dispersion (GVD) variation in slightly negative region. As a result, we have obtained the low noise ultrashort pulse generation with duration 59 dB) and relative intensity noise <-101 dBc / Hz.

  16. Fabrication of Nb/Pb structures through ultrashort pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gontad, Francisco; Lorusso, Antonella, E-mail: antonella.lorusso@le.infn.it; Perrone, Alessio [Dipartimento di Matematica e Fisica “E. De Giorgi,” Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Klini, Argyro; Fotakis, Costas [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), 100 N. Plastira St., GR 70013 Heraklion, Crete (Greece); Broitman, Esteban [Thin Film Physics Division, IFM, Linköping University, 581-83 Linköping (Sweden)

    2016-07-15

    This work reports the fabrication of Nb/Pb structures with an application as photocathode devices. The use of relatively low energy densities for the ablation of Nb with ultrashort pulses favors the reduction of droplets during the growth of the film. However, the use of laser fluences in this ablation regime results in a consequent reduction in the average deposition rate. On the other hand, despite the low deposition rate, the films present a superior adherence to the substrate and an excellent coverage of the irregular substrate surface, avoiding the appearance of voids or discontinuities on the film surface. Moreover, the low energy densities used for the ablation favor the growth of nanocrystalline films with a similar crystalline structure to the bulk material. Therefore, the use of low ablation energy densities with ultrashort pulses for the deposition of the Nb thin films allows the growth of very adherent and nanocrystalline films with adequate properties for the fabrication of Nb/Pb structures to be included in superconducting radiofrequency cavities.

  17. Heat generation caused by ablation of dental hard tissues with an ultrashort pulse laser (USPL) system.

    Science.gov (United States)

    Braun, Andreas; Krillke, Raphael Franz; Frentzen, Matthias; Bourauel, Christoph; Stark, Helmut; Schelle, Florian

    2015-02-01

    Heat generation during the removal of dental hard tissues may lead to a temperature increase and cause painful sensations or damage dental tissues. The aim of this study was to assess heat generation in dental hard tissues following laser ablation using an ultrashort pulse laser (USPL) system. A total of 85 specimens of dental hard tissues were used, comprising 45 specimens of human dentine evaluating a thickness of 1, 2, and 3 mm (15 samples each) and 40 specimens of human enamel with a thickness of 1 and 2 mm (20 samples each). Ablation was performed with an Nd:YVO4 laser at 1,064 nm, a pulse duration of 9 ps, and a repetition rate of 500 kHz with an average output power of 6 W. Specimens were irradiated for 0.8 s. Employing a scanner system, rectangular cavities of 1-mm edge length were generated. A temperature sensor was placed at the back of the specimens, recording the temperature during the ablation process. All measurements were made employing a heat-conductive paste without any additional cooling or spray. Heat generation during laser ablation depended on the dental hard tissue (enamel or dentine) and the thickness of the respective tissue (p dental hard tissues, heat generation has to be considered. Especially during laser ablation next to pulpal tissues, painful sensations and potential thermal injury of pulp tissue might occur.

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

    Science.gov (United States)

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

    2016-03-01

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

  19. Dynamics of atomic clusters in intense optical fields of ultrashort ...

    Indian Academy of Sciences (India)

    J. Chem. Sci. Vol. 124, No. 1, January 2012, pp. 75–81. c Indian Academy of Sciences. ... Consequently, exposure of atoms and molecules to such intense pulses inevitably leads to single and multiple ... Coulomb explosion, giving rise to ejection of fast Ar-ions. .... intense laser pulses of only a few femtoseconds dura-.

  20. Detection of hydrodynamic expansion in ultrashort pulse laser ellipsometric pump-probe experiments

    International Nuclear Information System (INIS)

    Morikami, Hidetoshi; Yoneda, Hitoki; Ueda, Ken-ichi; More, Richard M.

    2004-01-01

    In ultrashort-pulse laser interaction with solid target materials, the target rapidly heats, melts, evaporates, and begins to expand as a vapor or plasma. The onset of hydrodynamic expansion following surface evaporation is a switching point, where the dominant physics changes from temperature dependence of the solid dielectric function to refraction by the dense vapor cloud. We propose and demonstrate a method to analyze reflection data to identify this onset of target expansion. We use two of the Stokes parameters obtained from ellipsometric pump-probe measurements to determine a dielectric function with an assumption of no expansion. We use this dielectric function to predict the full set of reflectivity measurements. If there is a sharply defined target interface, this method reproduces the experimental data. When the plasma expansion is no longer negligible, the prediction deviates from the experimental measurements. This comparison shows when the plasma expansion is no longer negligible

  1. Non-destructive testing of ceramic materials using mid-infrared ultrashort-pulse laser

    Science.gov (United States)

    Sun, S. C.; Qi, Hong; An, X. Y.; Ren, Y. T.; Qiao, Y. B.; Ruan, Liming M.

    2018-04-01

    The non-destructive testing (NDT) of ceramic materials using mid-infrared ultrashort-pulse laser is investigated in this study. The discrete ordinate method is applied to solve the transient radiative transfer equation in 2D semitransparent medium and the emerging radiative intensity on boundary serves as input for the inverse analysis. The sequential quadratic programming algorithm is employed as the inverse technique to optimize objective function, in which the gradient of objective function with respect to reconstruction parameters is calculated using the adjoint model. Two reticulated porous ceramics including partially stabilized zirconia and oxide-bonded silicon carbide are tested. The retrieval results show that the main characteristics of defects such as optical properties, geometric shapes and positions can be accurately reconstructed by the present model. The proposed technique is effective and robust in NDT of ceramics even with measurement errors.

  2. Influence of dispersion stretching of ultrashort UV laser pulse on the critical power for self-focusing

    Science.gov (United States)

    Ionin, A. A.; Mokrousova, D. V.; Piterimov, D. A.; Seleznev, L. V.; Sinitsyn, D. V.; Sunchugasheva, E. S.

    2018-04-01

    The critical power for self-focusing in air for ultrashort ultraviolet laser pulses, stretched due to dispersion from 90 to 730 fs, was experimentally measured. It was shown that the pulse duration enhancement due to its propagation in condensed media leads to an almost linear decrease in the critical power for self-focusing. It was also observed that when the pulse peak power exceeds the critical one, the maximum of linear plasma distribution along the ultraviolet laser filament does not shift in the direction opposite to the laser pulse propagation, as observed for infrared laser filaments, but remains at the geometrical focus.

  3. Exotic behavior of molecules in intense laser light fields. New research directions

    Energy Technology Data Exchange (ETDEWEB)

    Yamanouchi, Kaoru [Tokyo Univ., Department of Chemistry, Tokyo (Japan)

    2002-08-01

    The recent investigation of the dynamical behavior of molecules and clusters in intense laser fields has afforded us invaluable opportunities to understand fundamentals of the interaction between molecular species and light fields as well as to manipulate molecules and their dynamical pathways by taking advantage of characteristics of coherent ultrashort laser light fields. In the present report, new directions of this rapidly growing interdisciplinary research fields called molecular science in intense laser fields are discussed by referring to our recent studies. (author)

  4. Selective ablation of a titanium nitride film on tungsten carbide substrate using ultrashort laser pulses

    International Nuclear Information System (INIS)

    Oliveira, Eduardo Spinelli

    2017-01-01

    Surface coatings are applied to many cutting tools in the metallurgical industry in order to improve cutting efficiency and extend its useful life. In this work, tests were performed to remove the coating of titanium aluminum nitride (TiAlN) on tungsten carbide (WC-Co) pellets, using an ultrashort laser pulses beam. After determination of the damage thresholds of the film and the substrate, were ablated on the surface of the coating lines using two ablation conditions, it was initially operated on the low fluence regime for the film, and later on the low fluence regime of the substrate, far below the threshold of the film, applying high overlapping pulses. A laser induced breakdown spectroscopy (LIBS) system was set up to monitor the materials present in the plasma generated by the laser, but the system did not present sufficient sensitivity to read the low intensity of the plasma generated in the process and was not used. After the analysis of the traces by electron microscopy, optical profilometer and X-ray fluorescence spectroscopy, it was not possible to determine a safe process to carry out the selective removal of the film in question, however, due to the data obtained and observations of the results in some traces, new possibilities were raised, opening the discussion for future work. (author)

  5. Texturing in titanium grade 2 surface irradiate with ultrashort pulse laser

    International Nuclear Information System (INIS)

    Nogueira, Alessandro Francelino

    2015-01-01

    The texturing laser micromachining is an important alternative to improve the bonding adhesion between composites and titanium, which are applied to structural components in the aerospace industry. The texturing running on titanium plates is due to the fact that the preferred joining technique for many composite materials is the adhesive bonding. In this work, titanium plates were texturized using laser ultrashort pulses temporal widths of femtoseconds. This process resulted in minimal heat transfer to the material, avoiding deformation of the titanium plate surface as well as the formation of resolidified material in the ablated region. These drawbacks have occurred with the use of nanoseconds pulses. Were performed three types of texturing using laser with femtosecond pulses, with variations in the distances between the machined lines. The analysis of the obtained surfaces found that the wettability increases when there is the increased distance between the texturing lines. Advancing in the analysis by optical profilometry of textured surfaces was observed that there is substantial increase in the volume available for penetration of structural adhesive when the distances between the textured lines are diminished. In tensile tests conducted it was observed that there is an increase in shear strength of the adhesive joint by reducing the distance between the textured lines. (author)

  6. Two-temperature hydrodynamics of laser-generated ultrashort shock waves in elasto-plastic solids

    International Nuclear Information System (INIS)

    Ilnitsky, Denis K; Migdal, Kirill P; Khokhlov, Viktor A; Inogamov, Nail A; Petrov, Yurii V; Anisimov, Sergey I; Zhakhovsky, Vasily V; Khishchenko, Konstantin V

    2014-01-01

    Shock-wave generation by ultrashort laser pulses opens new doors for study of hidden processes in materials happened at an atomic-scale spatiotemporal scales. The poorly explored mechanism of shock generation is started from a short-living two-temperature (2T) state of solid in a thin surface layer where laser energy is deposited. Such 2T state represents a highly non-equilibrium warm dense matter having cold ions and hot electrons with temperatures of 1-2 orders of magnitude higher than the melting point. Here for the first time we present results obtained by our new hybrid hydrodynamics code combining detailed description of 2T states with a model of elasticity together with a wide-range equation of state of solid. New hydro-code has higher accuracy in the 2T stage than molecular dynamics method, because it includes electron related phenomena including thermal conduction, electron-ion collisions and energy transfer, and electron pressure. From the other hand the new code significantly improves our previous version of 2T hydrodynamics model, because now it is capable of reproducing the elastic compression waves, which may have an imprint of supersonic melting like as in MD simulations. With help of the new code we have solved a difficult problem of thermal and dynamic coupling of a molten layer with an uniaxially compressed elastic solid. This approach allows us to describe the recent femtosecond laser experiments.

  7. Optical reprogramming of human somatic cells using ultrashort Bessel-shaped near-infrared femtosecond laser pulses

    Science.gov (United States)

    Uchugonova, Aisada; Breunig, Hans Georg; Batista, Ana; König, Karsten

    2015-11-01

    We report a virus-free optical approach to human cell reprogramming into induced pluripotent stem cells with low-power nanoporation using ultrashort Bessel-shaped laser pulses. Picojoule near-infrared sub-20 fs laser pulses at a high 85 MHz repetition frequency are employed to generate transient nanopores in the membrane of dermal fibroblasts for the introduction of four transcription factors to induce the reprogramming process. In contrast to conventional approaches which utilize retro- or lentiviruses to deliver genes or transcription factors into the host genome, the laser method is virus-free; hence, the risk of virus-induced cancer generation limiting clinical application is avoided.

  8. Scheme for the fabrication of ultrashort channel metal-oxide-semiconductor field-effect transistors

    International Nuclear Information System (INIS)

    Appenzeller, J.; Martel, R.; Solomon, P.; Chan, K.; Avouris, Ph.; Knoch, J.; Benedict, J.; Tanner, M.; Thomas, S.; Wang, K. L.

    2000-01-01

    We present a scheme for the fabrication of ultrashort channel length metal-oxide-semiconductor field-effect transistors (MOSFETs) involving nanolithography and molecular-beam epitaxy. The active channel is undoped and is defined by a combination of nanometer-scale patterning and anisotropic etching of an n ++ layer grown on a silicon on insulator wafer. The method is self-limiting and can produce MOSFET devices with channel lengths of less than 10 nm. Measurements on the first batch of n-MOSFET devices fabricated with this approach show very good output characteristics and good control of short-channel effects. (c) 2000 American Institute of Physics

  9. Ultrashort Channel Length Black Phosphorus Field-Effect Transistors.

    Science.gov (United States)

    Miao, Jinshui; Zhang, Suoming; Cai, Le; Scherr, Martin; Wang, Chuan

    2015-09-22

    This paper reports high-performance top-gated black phosphorus (BP) field-effect transistors with channel lengths down to 20 nm fabricated using a facile angle evaporation process. By controlling the evaporation angle, the channel length of the transistors can be reproducibly controlled to be anywhere between 20 and 70 nm. The as-fabricated 20 nm top-gated BP transistors exhibit respectable on-state current (174 μA/μm) and transconductance (70 μS/μm) at a VDS of 0.1 V. Due to the use of two-dimensional BP as the channel material, the transistors exhibit relatively small short channel effects, preserving a decent on-off current ratio of 10(2) even at an extremely small channel length of 20 nm. Additionally, unlike the unencapsulated BP devices, which are known to be chemically unstable in ambient conditions, the top-gated BP transistors passivated by the Al2O3 gate dielectric layer remain stable without noticeable degradation in device performance after being stored in ambient conditions for more than 1 week. This work demonstrates the great promise of atomically thin BP for applications in ultimately scaled transistors.

  10. Excitation of hydrogen atom by ultrashort laser pulses in optically dense plasma

    Energy Technology Data Exchange (ETDEWEB)

    Calisti, A. [Aix Marseille Universite, CNRS, PIIM, Marseille (France); Astapenko, V.A. [Moscow Institute of Physics and Technology, Dolgoprudnyi (Russian Federation); Lisitsa, V.S. [Moscow Institute of Physics and Technology, Dolgoprudnyi (Russian Federation); Russian Research Center ' ' Kurchatov Institute' ' , Moscow (Russian Federation); National Research Nuclear University MEPhI, Moscow (Russian Federation)

    2017-10-15

    The features of excitation of a hydrogen atom by ultrashort laser pulses (USP) with a Gaussian envelope in optically dense plasma at a Lyman-beta transition are studied theoretically. The problem is of interest for diagnostics of optically dense media. USP have two doubtless advantages over conventional laser excitation: (a) the USP carrier frequency is shifted to the region of short wavelengths allowing exciting atoms from the ground state and (b) the wide spectrum of USP allows them to penetrate into optically dense media to much longer distances as compared with monochromatic radiation. As actual realistic cases, two examples are considered: hot rarefied plasma (the coronal limit) and dense cold plasma (the Boltzmann equilibrium). Universal expressions for the total probability of excitation of the transition under consideration are obtained in view of absorption of radiation in a medium. As initial data for the spectral form of a line, the results of calculations by methods of molecular dynamics are used. The probability of excitation of an atom is analysed for different values of problem parameters: the pulse duration, the optical thickness of a medium, and the detuning of the pulse carrier frequency from the eigenfrequency of an electron transition. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Proceedings of the first JAERI-Kansai international workshop on ultrashort-pulse ultrahigh-power lasers and simulation for laser-plasma interactions

    International Nuclear Information System (INIS)

    1998-03-01

    Records of the First JAERI-Kansai International Workshop, which focused on the subject of 'Ultrashort-Pulse Ultrahigh-Power Lasers and Simulation for Laser-Plasma Interactions', are contained in this issue. The First JAERI-Kansai International Workshop was held as Joint ICFA/JAERI-Kansai International Workshop '97 with International Committee for Future Accelerators (ICFA). This report consists of 24 contributed papers. (J.P.N.)

  12. Proceedings of the first JAERI-Kansai international workshop on ultrashort-pulse ultrahigh-power lasers and simulation for laser-plasma interactions

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    Records of the First JAERI-Kansai International Workshop, which focused on the subject of `Ultrashort-Pulse Ultrahigh-Power Lasers and Simulation for Laser-Plasma Interactions`, are contained in this issue. The First JAERI-Kansai International Workshop was held as Joint ICFA/JAERI-Kansai International Workshop `97 with International Committee for Future Accelerators (ICFA). This report consists of 24 contributed papers. (J.P.N.)

  13. Investigation of Temperature Change under Influence of Ultrashort Laser Pulses Taking into Account Relaxation Properties of Materials

    Science.gov (United States)

    Eremin, A. V.; Kudinov, V. A.; Stefanyuk, E. V.; Kudinov, I. V.

    2018-03-01

    By using the modified Fourier law’s formula considering the relaxation of heat flow and temperature gradient, a mathematical model of the local non-equilibrium process of plate heating with ultrashort laser pulses was developed. The research showed that consideration of non-locality results in the delayed plate heat up irrespective of the laser radiation flow intensity. It was also shown that in consideration of the relaxation phenomena, the boundary conditions may not be fulfilled immediately – they may be set only within a definite range of the initial time.

  14. Controlled laser biochemistry in room-temperature polar liquids by ultrashort laser pulses

    DEFF Research Database (Denmark)

    Gruzdev, Vitaly; Korkin, Dmitry; Mooney, Brian P.

    2018-01-01

    Traditional laser methods to control chemical modifications of biomolecules are not applicable under biologically relevant conditions. We report controlled modifications of peptides and insulin by femtosecond laser in water, methanol, and acetonitrile at room temperature...

  15. Characterization of ultrashort laser pulses employing self-phase modulation dispersion-scan technique

    Science.gov (United States)

    Sharba, A. B.; Chekhlov, O.; Wyatt, A. S.; Pattathil, R.; Borghesi, M.; Sarri, G.

    2018-03-01

    We present a new phase characterization technique for ultrashort laser pulses that employs self-phase modulation (SPM) in the dispersion scan approach. The method can be implemented by recording a set of nonlinearly modulated spectra generated with a set of known chirp values. The unknown phase of the pulse is retrieved by linking the recorded spectra to the initial spectrum of the pulse via a phase function guessed by a function minimization iterative algorithm. This technique has many advantages over the dispersion scan techniques that use frequency conversion processes. Mainly, the use of SPM cancels out the phase and group velocity mismatch errors and dramatically widens the spectral acceptance of the nonlinear medium and the range of working wavelength. The robustness of the technique is demonstrated with smooth and complex phase retrievals using numerical examples. The method is shown to be not affected by the spatial distribution of the beam or the presence of nonlinear absorption process. In addition, we present an efficient method for phase representation based on a summation of a set of Gaussian functions. The independence of the functions from each other prevents phase coupling of any kind and facilitates a flexible phase representation.

  16. Direct pumping of ultrashort Ti:sapphire lasers by a frequency doubled diode laser

    DEFF Research Database (Denmark)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika

    2011-01-01

    electro-optical efficiency of the diode laser. Autocorrelation measurements show that pulse widths of less than 20 fs can be expected with an average power of 52 mW when using our laser. These results indicate the high potential of direct diode laser pumped Ti: sapphire lasers to be used in applications....... When using our diode laser system, the optical conversion efficiencies from green to near-infrared light reduces to 75 % of the values achieved with the commercial pump laser. Despite this reduction the overall efficiency of the Ti: sapphire laser is still increased by a factor > 2 due to the superior...... like retinal optical coherence tomography (OCT) or pumping of photonic crystal fibers for CARS (coherent anti-stokes Raman spectroscopy) microscopy....

  17. Ultrashort pulsed laser ablation for decollation of solid state lithium-ion batteries

    Science.gov (United States)

    Hördemann, C.; Anand, H.; Gillner, A.

    2017-08-01

    Rechargeable lithium-ion batteries with liquid electrolytes are the main energy source for many electronic devices that we use in our everyday lives. However, one of the main drawbacks of this energy storage technology is the use of liquid electrolyte, which can be hazardous to the user as well as the environment. Moreover, lithium-ion batteries are limited in voltage, energy density and operating temperature range. One of the most novel and promising battery technologies available to overcome the above-mentioned drawbacks is the Solid-State Lithium-Ion Battery (SSLB). This battery type can be produced without limitations to the geometry and is also bendable, which is not possible with conventional batteries1 . Additionally, SSLBs are characterized by high volumetric and gravimetric energy density and are intrinsically safe since no liquid electrolyte is used2-4. Nevertheless, the manufacturing costs of these batteries are still high. The existing production-technologies are comparable to the processes used in the semiconductor industry and single cells are produced in batches with masked-deposition at low deposition rates. In order to decrease manufacturing costs and to move towards continuous production, Roll2Roll production methods are being proposed5, 6. These methods offer the possibility of producing large quantities of substrates with deposited SSLB-layers. From this coated substrate, single cells can be cut out. For the flexible decollation of SSLB-cells from the substrate, new manufacturing technologies have to be developed since blade-cutting, punching or conventional laser-cutting processes lead to short circuiting between the layers. Here, ultra-short pulsed laser ablation and cutting allows the flexible decollation of SSLBs. Through selective ablation of individual layers, an area for the cutting kerf is prepared to ensure a shortcut-free decollation.

  18. Development of high repetition rate ultra-short pulse solid state lasers pumped by laser diodes

    International Nuclear Information System (INIS)

    Ueda, Ken-ichi; Lu, Jianren; Takaichi, Kazunori; Yagi, Hideki; Yanagitani, Takakimi; Kaminskii, Alexander; Kawanaka, Junji

    2004-01-01

    A novel technique for ceramic lasers has been developed recently. Self-energy-driven sintering of nano-and micro particles created the fully transparent Nd:YAG ceramics. The ceramic YAG demonstrated high efficiency operation (optical-to-optical conversion of 60% in end pumping) and solid-phase crystals growth and the possible scaling were investigated principally. Typical performance of ceramic YAG laser has been reviewed. The present status and future prospect of the ceramic lasers technologies were discussed. (author)

  19. Polarized spectral properties of Yb3+ : Li2Gd4(MoO4)7 crystal: a candidate for tunable and ultrashort pulse lasers

    International Nuclear Information System (INIS)

    Zhu Haomiao; Chen Yujin; Lin Yanfu; Gong Xinghong; Liao Jinsheng; Chen Xueyuan; Luo Zundu; Huang Yidong

    2007-01-01

    Detailed polarized spectral properties of a 3.2 at.% Yb 3+ : Li 2 Gd 4 (MoO 4 ) 7 crystal, including absorption cross-section, emission cross-section, up-conversion spectrum and intrinsic fluorescence lifetime, were investigated. The laser potentiality was also evaluated and the results show that this crystal is a good candidate for tunable and ultrashort pulse lasers

  20. Interaction of ultra-short ultra-intense laser pulses with under-dense plasmas; Interaction d'impulsions laser ultra-courtes et ultra-intenses avec des plasmas sous denses

    Energy Technology Data Exchange (ETDEWEB)

    Solodov, A

    2000-12-15

    Different aspects of interaction of ultra-short ultra-intense laser pulses with underdense plasmas are studied analytically and numerically. These studies can be interesting for laser-driven electron acceleration in plasma, X-ray lasers, high-order harmonic generation, initial confinement fusion with fast ignition. For numerical simulations a fully-relativistic particle code WAKE was used, developed earlier at Ecole Polytechnique. It was modified during the work on the thesis in the part of simulation of ion motion, test electron motion, diagnostics for the field and plasma. The studies in the thesis cover the problems of photon acceleration in the plasma wake of a short intense laser pulse, phase velocity of the plasma wave in the Self-Modulated Laser Wake-Field Accelerator (SM LWFA), relativistic channeling of laser pulses with duration of the order of a plasma period, ion dynamics in the wake of a short intense laser pulse, plasma wave breaking. Simulation of three experiments on the laser pulse propagation in plasma and electron acceleration were performed. Among the main results of the thesis, it was found that reduction of the plasma wave phase velocity in the SM LWFA is crucial for electron acceleration, only if a plasma channel is used for the laser pulse guiding. Self-similar structures describing relativistic guiding of short laser pulses in plasmas were found and relativistic channeling of initially Gaussian laser pulses of a few plasma periods in duration was demonstrated. It was shown that ponderomotive force of a plasma wake excited by a short laser pulse forms a channel in plasma and plasma wave breaking in the channel was analyzed in detail. Effectiveness of electron acceleration by the laser field and plasma wave was compared and frequency shift of probe laser pulses by the plasma waves was found in conditions relevant to the current experiments. (author)

  1. Determination of ultra-short laser induced damage threshold of KH2PO4 crystal: Numerical calculation and experimental verification

    Directory of Open Access Journals (Sweden)

    Jian Cheng

    2016-03-01

    Full Text Available Rapid growth and ultra-precision machining of large-size KDP (KH2PO4 crystals with high laser damage resistance are tough challenges in the development of large laser systems. It is of high interest and practical significance to have theoretical models for scientists and manufacturers to determine the laser-induced damage threshold (LIDT of actually prepared KDP optics. Here, we numerically and experimentally investigate the laser-induced damage on KDP crystals in ultra-short pulse laser regime. On basis of the rate equation for free electron generation, a model dedicated to predicting the LIDT is developed by considering the synergistic effect of photoionization, impact ionization and decay of electrons. Laser damage tests are performed to measure the single-pulse LIDT with several testing protocols. The testing results combined with previously reported experimental data agree well with those calculated by the model. By taking the light intensification into consideration, the model is successfully applied to quantitatively evaluate the effect of surface flaws inevitably introduced in the preparation processes on the laser damage resistance of KDP crystals. This work can not only contribute to further understanding of the laser damage mechanisms of optical materials, but also provide available models for evaluating the laser damage resistance of exquisitely prepared optical components used in high power laser systems.

  2. Advances in high field laser physics

    CERN Document Server

    Sheng, Zhengming; Chen, Liming; Lu, Wei; Shen, Baifei

    2019-01-01

    High field laser physics emerged with the advent of ultrashort intense lasers about 25 years ago. It has developed into a frontier of cross-disciplinary studies, covering attosecond X-ray physics, particle accelerator physics, and physics of inertial confined fusion, etc., with prospects of wide applications. Because this is a new and rapidly developing field, so far there are only 2-3 related books available. There are a few review articles in some journals, which are limited to specific topics in high field physics. There are quite a few conference proceedings in this field, which are the collections of papers presented at conferences. In this book, a few leading experts working on different subjects in this field are invited to introduce the key topics in high field laser physics, which cover the involved fundamental physics, the recent advances, as well as the prospects of future applications. It shall be very useful to graduate students, young researchers, and people who want to have an overview of thi...

  3. Atomistic simulations of ultra-short pulse laser ablation of aluminum: validity of the Lambert-Beer law

    Science.gov (United States)

    Eisfeld, Eugen; Roth, Johannes

    2018-05-01

    Based on hybrid molecular dynamics/two-temperature simulations, we study the validity of the application of Lambert-Beer's law, which is conveniently used in various modeling approaches of ultra-short pulse laser ablation of metals. The method is compared to a more rigorous treatment, which involves solving the Helmholtz wave equation for different pulse durations ranging from 100 fs to 5 ps and a wavelength of 800 nm. Our simulations show a growing agreement with increasing pulse durations, and we provide appropriate optical parameters for all investigated pulse durations.

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

    Science.gov (United States)

    Stuart, Brent C.; Nguyen, Hoang T.; Perry, Michael D.

    2001-01-01

    A method and apparatus for improving the quality and efficiency of machining of materials with laser pulse durations shorter than 100 picoseconds by orienting and maintaining the polarization of the laser light such that the electric field vector is perpendicular relative to the edges of the material being processed. Its use is any machining operation requiring remote delivery and/or high precision with minimal collateral dames.

  5. High-throughput machining using a high-average power ultrashort pulse laser and high-speed polygon scanner

    Science.gov (United States)

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

    2016-09-01

    High-throughput ultrashort pulse laser machining is investigated on various industrial grade metals (aluminum, copper, and stainless steel) and Al2O3 ceramic at unprecedented processing speeds. This is achieved by using a high-average power picosecond laser in conjunction with a unique, in-house developed polygon mirror-based biaxial scanning system. Therefore, different concepts of polygon scanners are engineered and tested to find the best architecture for high-speed and precision laser beam scanning. In order to identify the optimum conditions for efficient processing when using high-average laser powers, the depths of cavities made in the samples by varying the processing parameter settings are analyzed and, from the results obtained, the characteristic removal values are specified. For overlapping pulses of optimum fluence, the removal rate is as high as 27.8 mm3/min for aluminum, 21.4 mm3/min for copper, 15.3 mm3/min for stainless steel, and 129.1 mm3/min for Al2O3, when a laser beam of 187 W average laser powers irradiates. On stainless steel, it is demonstrated that the removal rate increases to 23.3 mm3/min when the laser beam is very fast moving. This is thanks to the low pulse overlap as achieved with 800 m/s beam deflection speed; thus, laser beam shielding can be avoided even when irradiating high-repetitive 20-MHz pulses.

  6. Studies on widely tunable ultra-short laser pulses using energy transfer distributed feedback dye laser

    International Nuclear Information System (INIS)

    Ahamed, M.B.; Ramalingam, A.; Palanisamy, P.K.

    2003-01-01

    This paper presents both theoretical and experimental study of the characteristics of Nd: YAG laser pumped energy transfer distributed feedback dye laser (ETDFDL). Using theoretical model proposed, the behavior of ETDFDL such as the characteristics of donor DFDL, the acceptor DFDL, the dependence of their pulse width and output power on donor-acceptor concentrations and pump power are studied for dye mixture Rhodamine 6G and Cresyl Violet in detail. Experimentally using prism-dye cell configuration, the ETDFDL output is obtained and the output energy of DFDL is measured at the emission peaks of donor and acceptor dyes for different pump powers and donor-acceptor concentrations. In addition, the DFDL linewidth measurement has been carried out at the lasing wavelengths of the donor and acceptor dyes using Fabry-Perot etalon and the tunability of DFDL is measured to be in the wavelength range of 545-680 nm

  7. ANALYSIS OF PERIODIC NANOSTRUCTURES FORMATION ON A GOLD SURFACE UNDER EXPOSURE TO ULTRASHORT LASER PULSES NEAR THE MELTING THRESHOLD

    Directory of Open Access Journals (Sweden)

    D. S. Ivanov

    2015-11-01

    Full Text Available Subject of Study. The mechanism of surface restructuring by ultrashort laser pulses involves a lot of fast, non-equilibrium, and interrelated processes while the solid is in a transient state. As a result, the analysis of the experimental data cannot cover all the mechanisms of nanostructuring. We present a direct comparison of a simulation and experimental results of surface nanomodification induced by a single laser pulse. Method. The experimental results were obtained by using a mask projection setup with a laser wavelength equal to 248 nm and a pulse length equal to 1.6 ps. This setup is used to produce an intensity grating on a gold surface with a sinusoidal shape and a period of 500 nm. The formed structures were analyzed by a scanning and transmission electron microscope, respectively. Then a hybrid atomistic-continuum model capable of capturing the essential mechanisms responsible for the nanostructuring process was used for modeling the interaction of the laser pulse with a thick gold target. Main Results. A good agreement between simulation and experimental data justifies the proposed approach as a powerful tool revealing the physics behind the nanostructuring process at a gold surface and providing a microscopic insight into the dynamics of the structuring processes of metals in general. The presented model, therefore, is an important step towards a new computational tool in predicting materials response to an ultrashort laser pulse on the atomic scale and properties of the modified surfaces. Practical Relevance. This detailed understanding of the dynamics of the process will pave the way towards pre-designed topologies for functionalized surfaces on the nano- and micro-scales.

  8. Femtosecond timing-jitter between photo-cathode laser and ultra-short electron bunches by means of hybrid compression

    CERN Document Server

    Pompili, Riccardo; Bellaveglia, M; Biagioni, A; Castorina, G; Chiadroni, E; Cianchi, A; Croia, M; Di Giovenale, D; Ferrario, M; Filippi, F; Gallo, A; Gatti, G; Giorgianni, F; Giribono, A; Li, W; Lupi, S; Mostacci, A; Petrarca, M; Piersanti, L; Di Pirro, G; Romeo, S; Scifo, J; Shpakov, V; Vaccarezza, C; Villa, F

    2017-01-01

    The generation of ultra-short electron bunches with ultra-low timing-jitter relative to the photo-cathode (PC) laser has been experimentally proved for the first time at the SPARC_LAB test-facility (INFN-LNF, Frascati) exploiting a two-stage hybrid compression scheme. The first stage employs RF-based compression (velocity-bunching), which shortens the bunch and imprints an energy chirp on it. The second stage is performed in a non-isochronous dogleg line, where the compression is completed resulting in a final bunch duration below 90 fs (rms). At the same time, the beam arrival timing-jitter with respect to the PC laser has been measured to be lower than 20 fs (rms). The reported results have been validated with numerical simulations.

  9. Femtosecond timing-jitter between photo-cathode laser and ultra-short electron bunches by means of hybrid compression

    International Nuclear Information System (INIS)

    Pompili, R; Anania, M P; Bellaveglia, M; Biagioni, A; Castorina, G; Chiadroni, E; Croia, M; Giovenale, D Di; Ferrario, M; Gallo, A; Gatti, G; Cianchi, A; Filippi, F; Giorgianni, F; Giribono, A; Lupi, S; Mostacci, A; Petrarca, M; Piersanti, L; Li, W

    2016-01-01

    The generation of ultra-short electron bunches with ultra-low timing-jitter relative to the photo-cathode (PC) laser has been experimentally proved for the first time at the SPARC-LAB test-facility (INFN-LNF, Frascati) exploiting a two-stage hybrid compression scheme. The first stage employs RF-based compression (velocity-bunching), which shortens the bunch and imprints an energy chirp on it. The second stage is performed in a non-isochronous dogleg line, where the compression is completed resulting in a final bunch duration below 90 fs (rms). At the same time, the beam arrival timing-jitter with respect to the PC laser has been measured to be lower than 20 fs (rms). The reported results have been validated with numerical simulations. (paper)

  10. Enhanced proton acceleration by ultrashort laser pulse interaction with nanostructured thin films

    International Nuclear Information System (INIS)

    Mondal, Angana; Dalui, Malay; Tata, Sheroy; Sarkar, Subhrangshu; Jha, Jagannath; Lad, Amit; Krishnamurthy, M.; Ayyub, P.; Wang, W m; Sheng, Z m

    2015-01-01

    Enhancement of local electromagnetic field in nanostructured targets as opposed to plain polished targets has been experimentally observed and studied. This increase in field strength leads to enhanced hot electron generation, which gives rise to highly energetic ions through Target Normal Sheath Acceleration. As the laser energy coupled to the electrons increases, the sheath magnitude is expected to increase, leading to an enhancement in ion acceleration. We investigate energy enhancements in ions generated as a result of intense femtosecond laser interaction with nanostructured thin film targets, comprising 2 μm Ta foil coated with 100-200 nm diameter Ta clusters. The optimum nanoparticle size of 100 nm corresponding to maximum laser energy absorption has been predetermined through PIC simulations. The accelerated ions have been studied using Thompson parabola spectrometer at a laser intensity of 15 x 10 19 W/cm 2 at the TIFR high contrast 100 TW Ti:Sapphire laser facility. The proton cut-off energy is observed to increase rapidly with increasing cluster density till a saturation is reached. The enhancement in the proton cut-off energy is observed to be three-fold as compared to the proton cut-off energy for unstructured foils. (author)

  11. Quasi-monoenergetic proton acceleration from cryogenic hydrogen microjet by ultrashort ultraintense laser pulses

    Science.gov (United States)

    Sharma, A.; Tibai, Z.; Hebling, J.; Fülöp, J. A.

    2018-03-01

    Laser-driven proton acceleration from a micron-sized cryogenic hydrogen microjet target is investigated using multi-dimensional particle-in-cell simulations. With few-cycle (20-fs) ultraintense (2-PW) laser pulses, high-energy quasi-monoenergetic proton acceleration is predicted in a new regime. A collisionless shock-wave acceleration mechanism influenced by Weibel instability results in a maximum proton energy as high as 160 MeV and a quasi-monoenergetic peak at 80 MeV for 1022 W/cm2 laser intensity with controlled prepulses. A self-generated strong quasi-static magnetic field is also observed in the plasma, which modifies the spatial distribution of the proton beam.

  12. Zero photon dissociation of CS2+ in intense ultrashort laser pulses

    Science.gov (United States)

    Severt, Travis; Betsch, K. J.; Zohrabi, M.; Ablikim, U.; Jochim, Bethany; Carnes, K. D.; Esry, B. D.; Ben-Itzhak, I.

    2013-05-01

    We measured the dissociation of a CS2+ molecular ion beam in intense laser pulses ( C+ + S+. We speculate that a pump-dump process occurs whereby the vibrational wavepacket in the electronic ground state of CS2+ is pumped into the electronic first excited state's continuum by a single photon during the laser pulse. Once this continuum vibrational wavepacket passes the potential barrier in the ground electronic potential, the emission of a second photon is stimulated by the same laser pulse, most likely when the wavepacket moves through the internuclear distance where the two electronic states are in resonance with the driving field. A comparison is made to ZPD and ATD in the isovalent CO2+ species. Curiously, ATD is the favored mechanism in CO2+. The underlying molecular structure and dynamics determining this preference will be discussed. Supported by Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

  13. Histological observation on dental hard tissue irradiated by ultrashort-pulsed laser

    Science.gov (United States)

    Uchizono, Takeyuki; Awazu, Kunio; Igarashi, Akihiro; Kato, Junji; Hirai, Yoshito

    2006-04-01

    In the field of dentistry, effectiveness of USPL irradiation is researched because USPL has less thermal side effect to dental hard tissue. In this paper, we observed morphological change and optical change of dental hard tissue irradiated by USPL for discussing the safety and effectiveness of USPL irradiation to dental hard tissues. Irradiated samples were crown enamel and root dentin of bovine teeth. Lasers were Ti:sapphire laser, which had pulse duration (P d)of 130 fsec and pulse repetition rate (f) of 1kHz and wavelength (l) of 800nm, free electron laser (FEL), which had P d of 15 μsec and f of 10Hz and wavelength of 9.6μm, and Er:YAG laser, which had P d of 250 μsec and f of 10Hz and wavelength of 2.94μm. After laser irradiation, the sample surfaces and cross sections were examined with SEM and EDX. The optical change of samples was observed using FTIR. In SEM, the samples irradiated by USPL had sharp and accurate ablation with no crack and no carbonization. But, in FEL and Er:YAG laser, the samples has rough ablation with crack and carbonization. It was cleared that the P/Ca ratio of samples irradiated by USPL had same value as non-irradiated samples. There was no change in the IR absorption spectrum between samples irradiated by USPL and non-irradiated sample. But, they of samples irradiated by FEL and Er:YAG laser, however, had difference value as non-irradiated samples. These results showed that USPL might be effective to ablate dental hard tissue without thermal damage.

  14. Dynamic control of laser driven proton beams by exploiting self-generated, ultrashort electromagnetic pulses

    Energy Technology Data Exchange (ETDEWEB)

    Kar, S., E-mail: s.kar@qub.ac.uk; Ahmed, H.; Nersisyan, G.; Hanton, F.; Naughton, K.; Lewis, C. L. S.; Borghesi, M. [Centre for Plasma Physics, School of Mathematics and Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); Brauckmann, S.; Giesecke, A. L.; Willi, O. [Institut für Laser-und Plasmaphysik, Heinrich-Heine-Universität, Düsseldorf (Germany)

    2016-05-15

    As part of the ultrafast charge dynamics initiated by high intensity laser irradiations of solid targets, high amplitude EM pulses propagate away from the interaction point and are transported along any stalks and wires attached to the target. The propagation of these high amplitude pulses along a thin wire connected to a laser irradiated target was diagnosed via the proton radiography technique, measuring a pulse duration of ∼20 ps and a pulse velocity close to the speed of light. The strong electric field associated with the EM pulse can be exploited for controlling dynamically the proton beams produced from a laser-driven source. Chromatic divergence control of broadband laser driven protons (upto 75% reduction in divergence of >5 MeV protons) was obtained by winding the supporting wire around the proton beam axis to create a helical coil structure. In addition to providing focussing and energy selection, the technique has the potential to post-accelerate the transiting protons by the longitudinal component of the curved electric field lines produced by the helical coil lens.

  15. Time-dependent H-like and He-like Al lines produced by ultra-short pulse laser

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Takako; Kato, Masatoshi [National Inst. for Fusion Science, Nagoya (Japan); Shepherd, R; Young, B; More, R; Osterheld, Al

    1998-03-01

    We have performed numerical modeling of time-resolved x-ray spectra from thin foil targets heated by the LLNL Ultra-short pulse (USP) laser. The targets were aluminum foils of thickness ranging from 250 A to 1250 A, heated with 120 fsec pulses of 400 nm light from the USP laser. The laser energy was approximately 0.2 Joules, focused to a 3 micron spot size for a peak intensity near 2 x 10{sup 19} W/cm{sup 2}. Ly{alpha} and He{alpha} lines were recorded using a 900 fsec x-ray streak camera. We calculate the effective ionization, recombination and emission rate coefficients including density effects for H-like and He-like aluminum ions using a collisional radiative model. We calculate time-dependent ion abundances using these effective ionization and recombination rate coefficients. The time-dependent electron temperature and density used in the calculation are based on an analytical model for the hydrodynamic expansion of the target foils. During the laser pulse the target is ionized. After the laser heating stops, the plasma begins to recombine. Using the calculated time dependent ion abundances and the effective emission rate coefficients, we calculate the time dependent Ly{alpha} and He{alpha} lines. The calculations reproduce the main qualitative features of the experimental spectra. (author)

  16. Ultrashort x-ray pulse generation by nonlinear Thomson scattering of a relativistic electron with an intense circularly polarized laser pulse

    Directory of Open Access Journals (Sweden)

    F. Liu

    2012-07-01

    Full Text Available The nonlinear Thomson scattering of a relativistic electron with an intense laser pulse is calculated numerically. The results show that an ultrashort x-ray pulse can be generated by an electron with an initial energy of 5 MeV propagating across a circularly polarized laser pulse with a duration of 8 femtosecond and an intensity of about 1.1×10^{21}  W/cm^{2}, when the detection direction is perpendicular to the propagation directions of both the electron and the laser beam. The optimal values of the carrier-envelop phase and the intensity of the laser pulse for the generation of a single ultrashort x-ray pulse are obtained and verified by our calculations of the radiation characteristics.

  17. Inelastic processes in interaction of an atom with ultrashort pulse of an electromagnetic field

    International Nuclear Information System (INIS)

    Matveev, V.I.; Gusarevich, E.S.; Pashev, I.N.

    2005-01-01

    Electron transitions occurring when a heavy relativistic atom interacts with a spatially inhomogeneous ultrashort electromagnetic pulse are considered. Transition probabilities are expressed in terms of the known inelastic atomic form factors. By way of example, the inelastic processes accompanying the interaction of ultrashort pulses with hydrogen-like atoms are considered. The probabilities of ionization and production of a bound-free electron-positron pair on a bare nucleus, which are accompanied by the formation of a hydrogen-like atom in the final state and a positron in the continuum, are calculated. The developed technique makes it possible to take into exact account magnetic interaction besides spatial inhomogeneity of an ultrashort electromagnetic pulse [ru

  18. The noise of ultrashort pulse mode-locked lasers beyond the slowly varying envelope approximation

    International Nuclear Information System (INIS)

    Takushima, Y; Haus, H A; Kaertner, F X

    2004-01-01

    The zero-point fluctuations in an L-C circuit of finite Q are revisited. The zero-point energy is shown to approach the value of hbarω 0 /2 only in the limit of an infinite Q. A Fabry-Perot resonator, on the other hand, has bounded zero-point energies of its modes that are equal to hbarω n /2 for each resonance. Based on the Fabry-Perot resonator with broadband noise, we analyse the noise of an ultrafast mode-locked laser when the slowly varying envelope approximation (SVEA) is not valid. This is achieved by reinterpreting the quantized form of the master equation of mode locking as an equation of motion for the electric field rather than for the creation operator of a photon. It is found that in this formulation quantum correlations exist that are not present in the SVEA. The correlations become evident in the spectrum of the zero-point fluctuations and therefore in the background noise of the laser. This behaviour can be detected by homodyne detection of the laser output. The linewidth of the frequency comb generated by the mode-locked laser is not affected by these correlations and is given by the Schawlow-Townes linewidth of an equivalent continuous wave taking the additional intracavity loss due to the mode locking process into account

  19. Birefringence profile adjustment by spatial overlap of nanogratings induced by ultra-short laser pulses inside fused silica

    Science.gov (United States)

    Arabanian, Atoosa Sadat; Najafi, Somayeh; Ajami, Aliasghar; Husinsky, Wolfgang; Massudi, Reza

    2018-02-01

    We have succeeded in realizing a method to control the spatial distribution of optical retardation as a result of nanogratings in bulk-fused silica induced by ultrashort laser pulses. A colorimetry-based retardation measurement (CBRM) based on the Michel-Levy interference color chart using a polarization microscope is used to determine the profiles of the optical retardation. Effects of the spatial overlap of written regions as well as the energy and polarization of the writing pulses on the induced retardations are studied. It has been found that the spatial overlap of lines written by pulse trains with different energies and polarizations can result in an adjustment of the induced birefringence in the overlap region. This approach offers the possibility of designing polarization-sensitive components with a desired birefringence profile.

  20. Retrieving molecular structural information and tracking HNC/HCN isomerization process with high harmonic generation by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Nguyen Ngoc Ty; Le Van Hoang; Vu Ngoc Tuoc; Le Anh Thu

    2010-01-01

    We investigate the possibility of applying the iterative method, suggested in our previous work, for HCN molecule and its HNC isomer. We found that the high-order harmonic generation (HHG) spectra are quite insensitive to the change of H-C (or H-N) bond length so that only the inter-nuclear C-N distance can be retrieved from the high-order harmonic spectra using ultrashort intense lasers. Furthermore, by analyzing the HHG spectra emitted by HCN during the chemical reaction path of isomerization we identify the intensity peaks nearby the stable, metastable and transition states. this finding can be useful for tracking the HNC/HNC isomerization process. (author)

  1. Two-temperature hydrodynamic expansion and coupling of strong elastic shock with supersonic melting front produced by ultrashort laser pulse

    International Nuclear Information System (INIS)

    Inogamov, Nail A; Khokhlov, Viktor A; Zhakhovsky, Vasily V; Khishchenko, Konstantin V; Demaske, Brian J; Oleynik, Ivan I

    2014-01-01

    Ultrafast processes, including nonmonotonic expansion of material into vacuum, supersonic melting and generation of super-elastic shock wave, in a surface layer of metal irradiated by an ultrashort laser pulse are discussed. In addition to the well-established two-temperature (2T) evolution of heated layer a new effect of electron pressure gradient on early stage of material expansion is studied. It is shown that the expanding material experiences an unexpected jump in flow velocity in a place where stress exceeds the effective tensile strength provided by used EoS of material. Another 2T effect is that supersonic propagation of homogeneous melting front results in distortion of spatial profile of ion temperature, which later imprints on ion pressure profile transforming in a super-elastic shock wave with time.

  2. Limitations of the strong field approximation in ionization of the hydrogen atom by ultrashort pulses

    International Nuclear Information System (INIS)

    Arbo, D.G.; Toekesi, K.; Miraglia, J.E.; FCEN, University of Buenos Aires

    2008-01-01

    Complete text of publication follows. We presented a theoretical study of the ionization of hydrogen atoms as a result of the interaction with an ultrashort external electric field. Doubly-differential momentum distributions and angular momentum distributions of ejected electrons calculated in the framework of the Coulomb-Volkov and strong field approximations, as well as classical calculations are compared with the exact solution of the time dependent Schroedinger equation. We have shown that the Coulomb-Volkov approximation (CVA) describes the quantum atomic ionization probabilities exactly when the external field is described by a sudden momentum transfer [1]. The velocity distribution of emitted electrons right after ionization by a sudden momentum transfer is given through the strong field approximation (SFA) within both the CVA and CTMC methods. In this case, the classical and quantum time dependent evolutions of an atom subject to a sudden momentum transfer are identical. The difference between the classical and quantum final momentum distributions resides in the time evolution of the escaping electron under the subsequent action of the Coulomb field. Furthermore, classical mechanics is incapable of reproducing the quantum angular momentum distribution due to the improper initial radial distribution used in the CTMC calculations, i.e., the microcanonical ensemble. We find that in the limit of high momentum transfer, based on the SFA, there is a direct relation between the cylindrical radial distribution dP/dρ and the final angular momentum distribution dP/dL. This leads to a close analytical expression for the partial wave populations (dP/dL) SFA-Q given by dP SFA-Q / dL = 4Z 3 L 2 / (Δp) 3 K 1 (2ZL/Δp) which, together with the prescription L = l + 1/2, reproduces quite accurately the quantum (CVA) results. Considering the inverse problem, knowing the final angular momentum distribution can lead to the inference of the initial probability distribution

  3. Linear and non-linear carrier-envelope phase difference effects in interactions of ultra-short laser pulses with a metal nano-layer

    International Nuclear Information System (INIS)

    Varro, S.

    2006-01-01

    Complete test of publication follows. On the basis of classical electrodynamics the reflection and transmission of an ultra-short laser pulse impinging on a metal nano-layer have been analysed. The thickness of the layer was assumed to be of the order of 2-10 nm, and the metallic electrons were represented by a surface current density at the plane boundary of a dielectric substrate. It has been shown that in the scattered fields a non-oscillatory wake-field appears following the main pulse with an exponential decay and with a definite sign of the electric and magnetic fields. The characteristic time of these wake-fields is inversely proportional to the square of the plasma frequency and to the thickness of the metal nano-layer, and can be of order or larger then the original pulse duration. The magnitude of these wake-fields is proportional with the incoming field strength - so this is a linear effect - and the definite sign of them is governed by the cosine of the carrier-envelope phase difference of the incoming ultrashort laser pulse. As a consequence, when we let such a wake-field excite the electrons of a secondary target - say a plasma, a metal surface or a gas - we obtain 100 percent modulation depth in the electron signal in a given direction. This scheme can perhaps serve as a basis for the construction of a robust linear carrier-envelope phase difference mater. At relativistic laser intensities the target becomes a plasma layer generated, e.g. by the rising part of the incoming laser pulse. An approximate analytic solution has been given for the system of the coupled Maxwell-Lorentz equations describing the dynamics of the surface current (representing the plasma electrons) and the composite radiation field. With the help of these solutions the Fourier components of the reflected and transmitted radiation have been calculated. The nonlinearities stemming from the relativistic kinematics lead to the appearance of higher-order harmonics in the scattered

  4. Ultra-short X-ray sources generated through laser-matter interaction and their applications; Sources de rayonnement X ultrabref generees par interaction laser-matiere et leurs applications

    Energy Technology Data Exchange (ETDEWEB)

    Rousse, A

    2004-04-15

    This work is dedicated to the sources of ultra-short X-rays. The K{sub {alpha}} source, the non-linear Thomson source, the betatron source and the X-{gamma} source are presented. We show that a pump-probe experiment where the pump is a laser excitation and the probe is the X-K{sub {alpha}} ultra-short radiation, can be used to study the dynamics of material structure with a time resolution of 100 femtosecond. We describe 2 applications that have been achieved in the field of solid physics by using the diffraction technique with a time resolution in the range of the femtosecond. The first application has permitted the observation and characterization of the ultra-quick solid-phase transition that occurs on the surface of a semiconductor crystal. The second experiment deals with the role of optical phonons in the antecedent processes that lead to such ultra-quick solid-phase transitions. (A.C.)

  5. Highlighting the DNA damage response with ultrashort laser pulses in the near infrared and kinetic modeling

    Directory of Open Access Journals (Sweden)

    Elisa eFerrando-May

    2013-07-01

    Full Text Available Our understanding of the mechanisms governing the response to DNA damage in higher eucaryotes crucially depends on our ability to dissect the temporal and spatial organization of the cellular machinery responsible for maintaining genomic integrity. To achieve this goal, we need experimental tools to inflict DNA lesions with high spatial precision at pre-defined locations, and to visualize the ensuing reactions with adequate temporal resolution. Near-infrared femtosecond laser pulses focused through high-aperture objective lenses of advanced scanning microscopes offer the advantage of inducing DNA damage in a 3D-confined volume of subnuclear dimensions. This high spatial resolution results from the highly nonlinear nature of the excitation process. Here we review recent progress based on the increasing availability of widely tunable and user-friendly technology of ultrafast lasers in the near infrared. We present a critical evaluation of this approach for DNA microdamage as compared to the currently prevalent use of UV or VIS laser irradiation, the latter in combination with photosensitizers. Current and future applications in the field of DNA repair and DNA-damage dependent chromatin dynamics are outlined. Finally, we discuss the requirement for proper simulation and quantitative modeling. We focus in particular on approaches to measure the effect of DNA damage on the mobility of nuclear proteins and consider the pros and cons of frequently used analysis models for FRAP and photoactivation and their applicability to nonlinear photoperturbation experiments.

  6. Plasma heating by ultrashort laser pulse in the regime of anomalous skin-effect

    International Nuclear Information System (INIS)

    Gamaly, E.G.; Kiselev, A.E.; Tikhonchuk, V.T.

    1991-01-01

    The problem of interaction of short laser pulse (light frequency ω 0 pulse duration, τ s /V Ti ; 1 s , skin depth, V Ti , ion velocity) with dense (ω 0 much-lt ω pe ) semi-infinite plasm was solved. The authors formulated the self-consistent problem of obtaining the electron distribution function and space dependence of electric field in skin layer, and solved the problem for the case of absence of the energy losses from the skin layer. The authors found self-similar nonstationary electron distribution function and space dependence of electric field in this case, and basing on these solutions, have calculated mean electron energy, absorption coefficient, bremsstrahlung radiation, time dependent skin depth. This paper discusses the limitations of our theory

  7. Dynamics of ultra-short electromagnetic pulses in the system of chiral carbon nanotube waveguides in the presence of external alternating electric field

    Energy Technology Data Exchange (ETDEWEB)

    Konobeeva, N.N., E-mail: yana_nn@inbox.ru [Volgograd State University, University Avenue 100, Volgograd 400062 (Russian Federation); Belonenko, M.B. [Volgograd Institute of Business, Uzhno-ukrainskaya str., Volgograd 400048 (Russian Federation)

    2014-04-01

    The paper addresses the propagation of ultra-short optical pulses in chiral carbon nanotubes in the presence of external alternating electric field. Following the assumption that the considered optical pulses are represented in the form of discrete solitons, we analyze the wave equation for the electromagnetic field and consider the dynamics of pulses in external field, their initial amplitudes and frequencies.

  8. Signatures of collective electron dynamics in the angular distributions of electrons ejected during ultrashort laser pulse interactions with C+

    International Nuclear Information System (INIS)

    Lysaght, M A; Hutchinson, S; Van der Hart, H W

    2009-01-01

    We use the time-dependent R-matrix approach to investigate an ultrashort pump-probe scheme to observe collective electron dynamics in C + driven by the repulsion of two equivalent p electrons. By studying the two-dimensional momentum distributions of the ejected electron as a function of the time-delay between an ultrashort pump pulse and an ionizing ultrashort probe pulse it is possible to track the collective dynamics inside the C + ion in the time domain.

  9. Graphics-processing-unit-accelerated finite-difference time-domain simulation of the interaction between ultrashort laser pulses and metal nanoparticles

    Science.gov (United States)

    Nikolskiy, V. P.; Stegailov, V. V.

    2018-01-01

    Metal nanoparticles (NPs) serve as important tools for many modern technologies. However, the proper microscopic models of the interaction between ultrashort laser pulses and metal NPs are currently not very well developed in many cases. One part of the problem is the description of the warm dense matter that is formed in NPs after intense irradiation. Another part of the problem is the description of the electromagnetic waves around NPs. Description of wave propagation requires the solution of Maxwell’s equations and the finite-difference time-domain (FDTD) method is the classic approach for solving them. There are many commercial and free implementations of FDTD, including the open source software that supports graphics processing unit (GPU) acceleration. In this report we present the results on the FDTD calculations for different cases of the interaction between ultrashort laser pulses and metal nanoparticles. Following our previous results, we analyze the efficiency of the GPU acceleration of the FDTD algorithm.

  10. Effects of ultrashort laser pulses on angular distributions of photoionization spectra.

    Science.gov (United States)

    Ooi, C H Raymond; Ho, W L; Bandrauk, A D

    2017-07-27

    We study the photoelectron spectra by intense laser pulses with arbitrary time dependence and phase within the Keldysh framework. An efficient semianalytical approach using analytical transition matrix elements for hydrogenic atoms in any initial state enables efficient and accurate computation of the photoionization probability at any observation point without saddle point approximation, providing comprehensive three dimensional photoelectron angular distribution for linear and elliptical polarizations, that reveal the intricate features and provide insights on the photoionization characteristics such as angular dispersions, shift and splitting of photoelectron peaks from the tunneling or above threshold ionization(ATI) regime to non-adiabatic(intermediate) and multiphoton ionization(MPI) regimes. This facilitates the study of the effects of various laser pulse parameters on the photoelectron spectra and their angular distributions. The photoelectron peaks occur at multiples of 2ħω for linear polarization while  odd-ordered peaks are suppressed in the direction perpendicular to the electric field. Short pulses create splitting and angular dispersion where the peaks are strongly correlated to the angles. For MPI and elliptical polarization with shorter pulses the peaks split into doublets and the first peak vanishes. The carrier envelope phase(CEP) significantly affects the ATI spectra while the Stark effect shifts the spectra of intermediate regime to higher energies due to interference.

  11. Generalized bipolariton model. propagation of a ultrashort laser pulse through a thin semiconductor film in the conditions of two-photon generation of biexcitons

    International Nuclear Information System (INIS)

    Igor Beloussov

    2013-01-01

    A generalized bipolariton model is proposed. Bipolaritons is formed from virtual excitons of four kinds. There exists both attractive and repulsive interaction between these excitons, though only excitons of a specific type can interact with light. A substantial difference between conventional and our models is shown for the case of nonlinear transmission/reflection of ultrashort laser pulses by a thin semiconductor film under two-photon generation of biexcitons. (author)

  12. K-shell spectra from hot dense aluminum layers buried in carbon and heated by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Eidmann, K.; Andiel, U.; Pisani, F.; Hakel, P.; Mancini, R.C.; Junkel-Vives, G.C.; Abdallah, J.; Witte, K.

    2003-01-01

    Ultrashort laser pulses allow for the generation of hot plasmas near solid state densities. For this purpose a Ti:Sapphire laser was used, which delivers after frequency doubling, pulses of high contrast with an energy of about 60 mJ and a duration of 150 fs at 395 nm. The typical intensity on the target was a few 10 17 W/cm 2 . To achieve a high degree of uniformity we used targets consisting of a 25 nm thin Al tracer layer buried at different depths up to 400 nm in solid carbon. Time-integrated Al K-shell spectra are presented. Characteristic features of the spectra are significant high-order satellite line emission, strong line broadening and a center-of-mass line shift to the red, which was observed in transitions from principal quantum number n=2 or 3 to 1. Accurate measurement of the shift was made possible by using the cold Si K α line as an absolute wavelength calibration. In addition to time-integrated measurements, we used an ultrafast X-ray streak camera to obtain time and spectrally resolved spectra. Typical durations of the Ly α and He α lines are in the range 2-4 ps. The experimental results are compared with a time-dependent model, which combines hydrodynamic simulations, time-dependent atomic kinetics, detailed spectral line shapes including line shifts, and radiation transport

  13. Study of ultra-high gradient wakefield excitation by intense ultrashort laser pulses in plasma

    International Nuclear Information System (INIS)

    Kotaki, Hideyuki

    2002-12-01

    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 18 cm -3 is measured with a time-resolved frequency domain interferometer (FDI). The density distribution of the helium gas is measured with a time-resolved Mach-Zehnder interferometer to search for the optimum laser focus position and timing in the gas-jet. The results show an accelerating wakefield excitation of 20 GeV/m with good coherency, which is useful for ultrahigh gradient particle acceleration in a compact system. This is the first time-resolved measurement of laser wakefield excitation in a gas-jet plasma. The experimental results are compared with a Particle-in-Cell (PIC) simulation. The pump-probe interferometer system of FDI and the anomalous blueshift will be modified to the optical injection system as a relativistic electron beam injector. In 1D PIC simulation we obtain the results of high quality intense electron beam acceleration. These results illuminate the possibility of a high energy and a high quality electron beam acceleration. (author)

  14. Electron transport phenomena and dense plasmas produced by ultra-short pulse laser interaction

    International Nuclear Information System (INIS)

    More, R.M.

    1994-01-01

    Recent experiments with femtosecond lasers provide a test bed for theoretical ideas about electron processes in hot dense plasmas. We briefly review aspects of electron conduction theory likely to prove relevant to femtosecond laser absorption. We show that the Mott-Ioffe-Regel limit implies a maximum inverse bremsstrahlung absorption of about 50% at temperatures near the Fermi temperature. We also propose that sheath inverse bremsstrahlung leads to a minimum absorption of 7-10% at high laser intensity

  15. Impacts of ambient and ablation plasmas on short- and ultrashort-pulse laser processing of surfaces

    Czech Academy of Sciences Publication Activity Database

    Bulgakova, Nadezhda M.; Panchenko, A.N.; Zhukov, V.P.; Kudryashov, S.I.; Pereira, A.; Marine, W.; Mocek, Tomáš; Bulgakov, A.V.

    2014-01-01

    Roč. 5, č. 4 (2014), s. 1344-1372 ISSN 2072-666X R&D Projects: GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.20.0143 Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143 Institutional support: RVO:68378271 Keywords : pulsed laser ablation * laser material processing * laser plasma * ambient gas breakdown * material redeposition * plasma pipe formation * microstructures Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.269, year: 2014

  16. How to optimize ultrashort pulse laser interaction with glass surfaces in cutting regimes?

    Czech Academy of Sciences Publication Activity Database

    Bulgakova, Nadezhda M.; Zhukov, V.P.; Collins, A.R.; Rostohar, Danijela; Derrien, Thibault; Mocek, Tomáš

    2015-01-01

    Roč. 336, May (2015), s. 364-374 ISSN 0169-4332 R&D Projects: GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.20.0143 Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143 Institutional support: RVO:68378271 Keywords : laser material processing * high power lasers * glass cutting * laser-matter interaction * biwave length irradiation * ambient gas ionization Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.150, year: 2015

  17. Analytical performances of laser-induced micro-plasma of Al samples with single and double ultrashort pulses in air and with Ar-jet: A comparative study

    International Nuclear Information System (INIS)

    Semerok, A.; Dutouquet, C.

    2014-01-01

    Ultrashort pulse laser microablation coupled with optical emission spectroscopy was under study to obtain several micro-LIBS analytical features (shot-to-shot reproducibility, spectral line intensity and lifetime, calibration curves, detection limits). Laser microablation of Al matrix samples with known Cu- and Mg-concentrations was performed by single and double pulses of 50 fs and 1 ps pulse duration in air and with Ar-jet. The micro-LIBS analytical features obtained under different experimental conditions were characterized and compared. The highest shot-to-shot reproducibility and gain in plasma spectral line intensity were obtained with double pulses with Ar-jet for both 50 fs and 1 ps pulse durations. The best calibration curves were obtained with 1 ps pulse duration with Ar-jet. Micro-LIBS with ultrashort double pulses may find its effective application for surface elemental microcartography. - Highlights: • Analytical performances of micro-LIBS with ultrashort double pulses were studied. • The maximal line intensity gain of 20 was obtained with double pulses and Ar-jet. • LIBS gain was obtained without additional ablation of a sample by the second pulse. • LIBS properties were almost the same for both 50 fs and 1 ps pulses. • The micro-LIBS detection limit was around 35 ppm

  18. Ultrashort Generation Regimes in the All-Fiber Kerr Mode-Locked Erbium-Doped Fiber Ring Laser for Terahertz Pulsed Spectroscopy

    Directory of Open Access Journals (Sweden)

    V. S. Voropaev

    2015-01-01

    Full Text Available Many femtosecond engineering applications require for a stable generation of ultrashort pulses. Thus, in the terahertz pulsed spectroscopy a measurement error in the refractive index is strongly dependent on the pulse duration stability with allowable variation of few femtoseconds. The aim of this work is to study the ultrashort pulses (USP regimes stability in the all – fiber erbium doped ring laser with Kerr mode-locking. The study was conducted at several different values of the total resonator intra-cavity dispersion. Three laser schemes with the intra-cavity dispersion values from -1.232 ps2 to +0.008 ps2 have been studied. In the experiment there were two regimes of generation observed: the stretched pulse generation and ordinary soliton generation. Main attention is focused on the stability of regimes under study. The most stable regime was that of the stretched pulse generation with a spectrum form of sech2 , possible pulse duration of 490 fs at least, repetition rate of 2.9 MHz, and average output power of 17 mW. It is worth noting, that obtained regimes had characteristics suitable for the successful use in the terahertz pulsed spectroscopy. The results may be useful in the following areas of science and technology: a high-precision spectroscopy, optical frequency standards, super-continuum generation, and terahertz pulsed spectroscopy. The future system development is expected to stabilize duration and repetition rate of the obtained regime of ultra-short pulse generation.

  19. 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

    2016-01-01

    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.

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

    Science.gov (United States)

    Zhao, Wanqin; Yu, Zhishui

    2018-06-01

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

  1. Quantum interference metrology at deep-UV wavelengths using phase-controlled ultrashort laser pulses

    NARCIS (Netherlands)

    Zinkstok, R. Th; Witte, S.; Ubachs, W.; Hogervorst, W.; Eikema, K. S E

    2005-01-01

    High-resolution metrology at wavelengths shorter than ultraviolet is in general hampered by a limited availability of appropriate laser sources. It is demonstrated that this limitation can be overcome by quantum-interference metrology with frequency up-converted ultrafast laser pulses. The required

  2. Study of 2ω and 3/2ω harmonics in ultrashort high-intensity laser ...

    Indian Academy of Sciences (India)

    An experimental study is presented on measurements of optical spectrum of the laser light scattered from solid surface irradiated by Ti:sapphire laser pulses up to an intensity of 1.2 × 1018 W cm-2. The spectrum has well-defined peaks at wavelengths corresponding to 2 and 3/2 radiations. The spectral features vary with ...

  3. Controlled modification of biomolecules by ultrashort laser pulses in polar liquids

    DEFF Research Database (Denmark)

    Gruzdev, Vitaly; Korkin, Dmitry; Mooney, Brian P.

    2017-01-01

    Targeted chemical modification of peptides and proteins by laser pulses in a biologically relevant environment, i.e. aqueous solvent at room temperature, allows for accurate control of biological processes. However, the traditional laser methods of control of chemical reactions are applicable onl...

  4. Impacts of Ambient and Ablation Plasmas on Short- and Ultrashort-Pulse Laser Processing of Surfaces

    Directory of Open Access Journals (Sweden)

    Nadezhda M. Bulgakova

    2014-12-01

    Full Text Available In spite of the fact that more than five decades have passed since the invention of laser, some topics of laser-matter interaction still remain incompletely studied. One of such topics is plasma impact on the overall phenomenon of the interaction and its particular features, including influence of the laser-excited plasma re-radiation, back flux of energetic plasma species, and massive material redeposition, on the surface quality and processing efficiency. In this paper, we analyze different plasma aspects, which go beyond a simple consideration of the well-known effect of plasma shielding of laser radiation. The following effects are considered: ambient gas ionization above the target on material processing with formation of a “plasma pipe”; back heating of the target by both laser-driven ambient and ablation plasmas through conductive and radiative heat transfer; plasma chemical effects on surface processing including microstructure growth on liquid metals; complicated dynamics of the ablation plasma flow interacting with an ambient gas that can result in substantial redeposition of material around the ablation spot. Together with a review summarizing our main to-date achievements and outlining research directions, we present new results underlining importance of laser plasma dynamics and photoionization of the gas environment upon laser processing of materials.

  5. Controlling the porosity of collagen, gelatin and elastin biomaterials by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Daskalova, A.; Nathala, Chandra S.R.; Bliznakova, I.; Stoyanova, E.; Zhelyazkova, A.; Ganz, T.; Lueftenegger, S.; Husinsky, W.

    2014-01-01

    We report on the structural investigation of self-organized micropores generated in thin gelatin, collagen, and collagen–elastin films after single and multishot irradiation with pulse durations ranging from 30–100 fs at 800 nm. We systematically studied the effect of laser parameters: laser energy, number of pulses, and pulse duration on the development of the micropores. This work showed that applying laser pulses at different rates significantly modified the thin film surface. The results clearly revealed that femtosecond laser treatment of thin films of biomaterials: gelatin, collagen and collagen–elastin, results in creation of micro/nanopores with different size of cavity formations. Experimentally, it is demonstrated that it is possible to influence the dimensions of the pore sizes, ranging from 100 nm to 2 μm by tuning the laser parameters. We are currently further exploring the possibility of structuring these biomaterials by applying a time delay between separate pulses. First results from cell culture experiments on laser created surface foam of collagen–elastin were successfully obtained, showing the potential of the method to cultivate cells on superficial porous substrates and the preferable selectivity of the cells to proliferate on the laser modified parts of the biopolymer substrate.

  6. Controlling the porosity of collagen, gelatin and elastin biomaterials by ultrashort laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Daskalova, A., E-mail: a_daskalova@code.bg [Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee blvd., 1784 Sofia (Bulgaria); Nathala, Chandra S.R. [IAP, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna (Austria); Femtolasers Productions GmbH, Fernkorngasse10, 1100 Vienna (Austria); Bliznakova, I. [Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee blvd., 1784 Sofia (Bulgaria); Stoyanova, E. [IBIR, Department of Molecular Immunology, Bulgarian Academy of Sciences, 73, Tzarigradsko Chaussee blvd., 1113 Sofia (Bulgaria); Zhelyazkova, A. [Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee blvd., 1784 Sofia (Bulgaria); Ganz, T. [Femtolasers Productions GmbH, Fernkorngasse10, 1100 Vienna (Austria); Lueftenegger, S.; Husinsky, W. [IAP, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna (Austria)

    2014-02-15

    We report on the structural investigation of self-organized micropores generated in thin gelatin, collagen, and collagen–elastin films after single and multishot irradiation with pulse durations ranging from 30–100 fs at 800 nm. We systematically studied the effect of laser parameters: laser energy, number of pulses, and pulse duration on the development of the micropores. This work showed that applying laser pulses at different rates significantly modified the thin film surface. The results clearly revealed that femtosecond laser treatment of thin films of biomaterials: gelatin, collagen and collagen–elastin, results in creation of micro/nanopores with different size of cavity formations. Experimentally, it is demonstrated that it is possible to influence the dimensions of the pore sizes, ranging from 100 nm to 2 μm by tuning the laser parameters. We are currently further exploring the possibility of structuring these biomaterials by applying a time delay between separate pulses. First results from cell culture experiments on laser created surface foam of collagen–elastin were successfully obtained, showing the potential of the method to cultivate cells on superficial porous substrates and the preferable selectivity of the cells to proliferate on the laser modified parts of the biopolymer substrate.

  7. Texturing in titanium grade 2 surface irradiate with ultrashort pulse laser; Texturizacao em superficies de titanio grau 2 irradiadas com laser com pulsos ultracurtos

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira, Alessandro Francelino

    2015-07-01

    The texturing laser micromachining is an important alternative to improve the bonding adhesion between composites and titanium, which are applied to structural components in the aerospace industry. The texturing running on titanium plates is due to the fact that the preferred joining technique for many composite materials is the adhesive bonding. In this work, titanium plates were texturized using laser ultrashort pulses temporal widths of femtoseconds. This process resulted in minimal heat transfer to the material, avoiding deformation of the titanium plate surface as well as the formation of resolidified material in the ablated region. These drawbacks have occurred with the use of nanoseconds pulses. Were performed three types of texturing using laser with femtosecond pulses, with variations in the distances between the machined lines. The analysis of the obtained surfaces found that the wettability increases when there is the increased distance between the texturing lines. Advancing in the analysis by optical profilometry of textured surfaces was observed that there is substantial increase in the volume available for penetration of structural adhesive when the distances between the textured lines are diminished. In tensile tests conducted it was observed that there is an increase in shear strength of the adhesive joint by reducing the distance between the textured lines. (author)

  8. Laser injection of ultra-short electron bursts for the diagnosis of Hall thruster plasma

    International Nuclear Information System (INIS)

    Albarede, L; Gibert, T; Lazurenko, A; Bouchoule, A

    2006-01-01

    The present developments of Hall thrusters for satellite control and space mission technologies represent a new step towards their routine use in place of conventional thermal thrusters. In spite of their long R and D history, the complex physics of the E x B discharge at work in these structures has prevented, up to now, the availability of predictive simulations. The electron transport in the accelerating layers of these thrusters is one of the remaining challenges in this direction. From the experimental point of view, any diagnostics of electron transport and electric field in this critical layer would be welcome for comparison with code predictions. Appropriate diagnostics are difficult, due to the very aggressive local plasma conditions. This paper presents the first step in the development of a new tool for characterization of the plasma electric field in the very near exhaust thruster plume and comparison with simulation code predictions. The main idea is to use very short bursts of electrons, probing local electron dynamics in this critical plume area. Such bursts can be obtained through photoelectric emission induced by a UV pulsed laser beam on a convenient target. A specific study, devoted to the characterization of the electron burst emission, is presented in the first section of the paper; the implementation and testing of the injection of electrons in the critical layer of Hall thruster plasma is described in the second section. The design and testing of a fast and sensitive system for characterizing the transport of injected bursts will be the next step of this program. It requires a preliminary evaluation of electron trajectories which was achieved by using simulation code. Simulation data are presented in the last section of the paper, with the full diagnostic design to be tested in the near future, when runs will be available in the renewed PIVOINE facility. The same electron burst injection could also be a valuable input in the present

  9. Inertial displacement of a domain wall excited by ultra-short circularly polarized laser pulses

    Czech Academy of Sciences Publication Activity Database

    Janda, Tomáš; Roy, P.E.; Otxoa, R.M.; Šobáň, Zbyněk; Ramsay, A.; Irvine, A.C.; Trojánek, F.; Surynek, M.; Campion, R. P.; Gallagher, B. L.; Němec, P.; Jungwirth, Tomáš; Wunderlich, Joerg

    2017-01-01

    Roč. 8, May (2017), 1-7, č. článku 15226. ISSN 2041-1723 R&D Projects: GA MŠk LM2015087; GA ČR GB14-37427G EU Projects: European Commission(XE) 610115 - SC2 Institutional support: RVO:68378271 Keywords : spintronics * domain walls Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 12.124, year: 2016

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

    International Nuclear Information System (INIS)

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

    1990-10-01

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

  11. Soft x-ray generation in gases with an ultrashort pulse laser

    Energy Technology Data Exchange (ETDEWEB)

    Ditmire, Todd Raymond [Univ. of California, Davis, CA (United States)

    1996-01-08

    An experimental investigation of soft x-ray production resulting from the interaction of intense near infra-red laser radiation with gases is presented in this thesis. Specifically, soft x-ray generation through high order harmonic generation or exploiting intense inverse bremsstrahlung heating is examined. Most of these studies are conducted with femtosecond, terawatt class Cr:LiSrAlF6 (LiSAF) laser, though results derived from studies with other laser systems are presented as well. The majority of this work is devoted to experimental investigations, however, theoretical and computational models are developed to interpret the data. These studies are motivated by the possibility of utilizing the physics of intense laser/matter interactions as a potential compact source of bright x-rays. Consequently, the thrust of many of the experiments conducted is aimed at characterizing the x-rays produced for possible use in applications. In general, the studies of this manuscript fall into three categories. First, a unique 130 fs, 8 TW laser that is based on chirped pulse amplification, is described, and its performance is evaluated. The generation of x-rays through high order harmonics is then discussed with emphasis on characterizing and optimizing harmonic generation. Finally, the generation of strong, incoherent x-ray radiation by the intense irradiation of large (>1,000 atom) clusters in gas jets, is explored. The physics of laser energy absorption by clusters illuminated with intensities of 1015 to 1017 W/cm2 is considered in detail. X-ray spectroscopy of the hot plasmas that result from the irradiation of the clusters is conducted, and energy transport and kinetics issues in these plasmas are discussed.

  12. Modification of transparent materials with ultrashort laser pulses: what is energetically and mechanically meaningful?

    Czech Academy of Sciences Publication Activity Database

    Bulgakova, Nadezhda M.; Zhukov, V.P.; Sonina, S.V.; Meshcheryakov, Y.P.

    2015-01-01

    Roč. 118, č. 23 (2015), 1-17, č. článku 233108. ISSN 0021-8979 R&D Projects: GA MŠk ED2.1.00/01.0027 Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027 Institutional support: RVO:68378271 Keywords : bulk fused-silica * femtosecond-laser * wave-guides * structural modifications * induced nanogratings * repetition rate * amorphous sio2 * light-pulses * glass Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.101, year: 2015

  13. Ultrashort pulse laser ablation of dielectrics: thresholds, mechanisms, role of breakdown

    Czech Academy of Sciences Publication Activity Database

    Mirza, M. Inam; Bulgakova, Nadezhda M.; Tomáštík, J.; Michálek, Václav; Haderka, O.; Fekete, Ladislav; Mocek, Tomáš

    2016-01-01

    Roč. 6, Dec (2016), 1-11, č. článku 39133. ISSN 2045-2322 R&D Projects: GA MŠk LO1602; GA MŠk LM2015086; GA MŠk LO1409; GA MŠk LM2015088 Grant - others:FUNBIO(XE) CZ.2.16/3.1.00/21568 Institutional support: RVO:68378271 Keywords : laser material processing * surfaces * interfaces * thin films Subject RIV: BH - Optics, Masers, Lasers Impact factor: 4.259, year: 2016

  14. Determination of ultra-short laser induced damage threshold of KH{sub 2}PO{sub 4} crystal: Numerical calculation and experimental verification

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Jian [Center for Precision Engineering, School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Department of Physics, The Ohio State University, 191 W. Woodruff Ave, Columbus, OH 43210 (United States); Chen, Mingjun, E-mail: chenmj@hit.edu.cn, E-mail: chowdhury.24@osu.edu; Wang, Jinghe; Xiao, Yong [Center for Precision Engineering, School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Kafka, Kyle; Austin, Drake; Chowdhury, Enam, E-mail: chenmj@hit.edu.cn, E-mail: chowdhury.24@osu.edu [Department of Physics, The Ohio State University, 191 W. Woodruff Ave, Columbus, OH 43210 (United States)

    2016-03-15

    Rapid growth and ultra-precision machining of large-size KDP (KH{sub 2}PO{sub 4}) crystals with high laser damage resistance are tough challenges in the development of large laser systems. It is of high interest and practical significance to have theoretical models for scientists and manufacturers to determine the laser-induced damage threshold (LIDT) of actually prepared KDP optics. Here, we numerically and experimentally investigate the laser-induced damage on KDP crystals in ultra-short pulse laser regime. On basis of the rate equation for free electron generation, a model dedicated to predicting the LIDT is developed by considering the synergistic effect of photoionization, impact ionization and decay of electrons. Laser damage tests are performed to measure the single-pulse LIDT with several testing protocols. The testing results combined with previously reported experimental data agree well with those calculated by the model. By taking the light intensification into consideration, the model is successfully applied to quantitatively evaluate the effect of surface flaws inevitably introduced in the preparation processes on the laser damage resistance of KDP crystals. This work can not only contribute to further understanding of the laser damage mechanisms of optical materials, but also provide available models for evaluating the laser damage resistance of exquisitely prepared optical components used in high power laser systems.

  15. Propagation of ultrashort laser pulses in water: linear absorption and onset of nonlinear spectral transformation.

    Science.gov (United States)

    Sokolov, Alexei V; Naveira, Lucas M; Poudel, Milan P; Strohaber, James; Trendafilova, Cynthia S; Buck, William C; Wang, Jieyu; Strycker, Benjamin D; Wang, Chao; Schuessler, Hans; Kolomenskii, Alexandre; Kattawar, George W

    2010-01-20

    We study propagation of short laser pulses through water and use a spectral hole filling technique to essentially perform a sensitive balanced comparison of absorption coefficients for pulses of different duration. This study is motivated by an alleged violation of the Bouguer-Lambert-Beer law at low light intensities, where the pulse propagation is expected to be linear, and by a possible observation of femtosecond optical precursors in water. We find that at low intensities, absorption of laser light is determined solely by its spectrum and does not directly depend on the pulse duration, in agreement with our earlier work and in contradiction to some work of others. However, as the laser fluence is increased, interaction of light with water becomes nonlinear, causing energy exchange among the pulse's spectral components and resulting in peak-intensity dependent (and therefore pulse-duration dependent) transmission. For 30 fs pulses at 800 nm center wavelength, we determine the onset of nonlinear propagation effects to occur at a peak value of about 0.12 mJ/cm(2) of input laser energy fluence.

  16. Decoration of silica nanowires with gold nanoparticles through ultra-short pulsed laser deposition

    Science.gov (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.

    2017-10-01

    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.

  17. Dynamics of laser ablation at the early stage during and after ultrashort pulse

    International Nuclear Information System (INIS)

    Ilnitsky, D K; Zhakhovsky, V V; Migdal, K P; Inogamov, N A; Khokhlov, V A; Petrov, Yu V

    2016-01-01

    Study of material flow in two-temperature states is needed for a fundamental understanding the physics of femtosecond laser ablation. To explore phenomena at a very early stage of laser action on a metallic target our in-house two-temperature hydrodynamics code is used here. The early stage covers duration of laser pulse with next first few picoseconds. We draw attention to the difference in behavior at this stage between the cases: (i) of an ultrathin film (thickness of order of skin depth d skin or less), (ii) thin films (thickness of a film is 4-7 of d skin for gold), and (iii) bulk targets (more than 10 d skin for gold). We demonstrate that these differences follow from a competition among conductive cooling of laser excited electrons in a skin layer, electron-ion coupling, and hydrodynamics of unloading caused by excess of pressure of excited free electrons. Conductive cooling of the skin needs a heat sink, which is performed by the cold material outside the skin. Such sink is unavailable in the ultrathin films. (paper)

  18. Structure modifications in silikon irradiated by ultra-short pulses of XUV free electron laser

    Czech Academy of Sciences Publication Activity Database

    Pelka, J. B.; Andrejczuk, A.; Reniewicz, H.; Schell, N.; Krzywinski, J.; Sobierajski, R.; Wawro, A.; Zytkiewicz, Z. R.; Klinger, D.; Juha, Libor

    2004-01-01

    Roč. 382, - (2004), s. 264-270 ISSN 0925-8388 R&D Projects: GA MŠk 1P04LA235; GA MŠk LN00A100 Institutional research plan: CEZ:AV0Z1010914 Keywords : XUV ablation * free electron laser Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.562, year: 2004

  19. Technical advantages of disk laser technology in short and ultrashort pulse processes

    Science.gov (United States)

    Graham, P.; Stollhof, J.; Weiler, S.; Massa, S.; Faisst, B.; Denney, P.; Gounaris, E.

    2011-03-01

    This paper demonstrates that disk-laser technology introduces advantages that increase efficiency and allows for high productivity in micro-processing in both the nanosecond (ns) and picosecond (ps) regimes. Some technical advantages of disk technology include not requiring good pump beam quality or special wavelengths for pumping of the disk, high optical efficiencies, no thermal lensing effects and a possible scaling of output power without an increase of pump beam quality. With cavity-dumping, the pulse duration of the disk laser can be specified between 30 and hundreds of nanoseconds, but is independent of frequency, thus maintaining process stability. TRUMPF uses this technology in the 750 watts average power laser TruMicro 7050. High intensity, along with fluency, is important for high ablation rates in thinfilm removal. Thus, these ns lasers show high removal rates, above 60 cm2/s, in thin-film solar cell production. In addition, recent results in paint-stripping of aerospace material prove the green credentials and high processing rates inherent with this technology as it can potentially replace toxic chemical processes. The ps disk technology meanwhile is used in, for example, scribing of solar cells, wafer dicing and drilling injector nozzles, as the pulse duration is short enough to minimize heat input in the laser-matter interaction. In the TruMicro Series 5000, the multi-pass regenerative amplifier stage combines high optical-optical efficiencies together with excellent output beam quality for pulse durations of only 6 ps and high pulse energies of up to 0.25 mJ.

  20. Atom dynamics in laser fields

    International Nuclear Information System (INIS)

    Jang, Su; Mi, No Gin

    2004-12-01

    This book introduces coherent dynamics of internal state, spread of atoms wave speed, semiclassical atoms density matrix such as dynamics equation in both still and moving atoms, excitation of atoms in movement by light, dipole radiating power, quantum statistical mechanics by atoms in movement, semiclassical atoms in movement, atoms in movement in the uniform magnetic field including effects of uniform magnetic field, atom cooling using laser such as Doppler cooling, atom traps using laser and mirrors, radiant heat which particles receive, and near field interactions among atoms in laser light.

  1. Effects of laser wavelength and density scale length on absorption of ultrashort intense lasers on solid-density targets

    Energy Technology Data Exchange (ETDEWEB)

    Susumu, Kato; Eiichi, Takahashi; Tatsuya, Aota; Yuji, Matsumoto; Isao, Okuda; Yoshiro, Owadano [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki (Japan)

    2004-07-01

    The interaction of intense laser pulses with overdense plasmas has attracted much interest for the fast igniter concept in inertial fusion energy. Hot electron temperatures and electron energy spectra in the course of interaction between intense laser pulse and overdense plasmas are reexamined from a viewpoint of the difference in laser wavelength. The hot electron temperature measured by a particle-in-cell simulation is scaled by I rather than I{lambda}{sup 2} at the interaction with overdense plasmas with fixed ions, where I and {lambda} are the laser intensity and wavelength, respectively. (authors)

  2. Strong-field QED processes in short laser pulses. One- and two-photon Compton scattering

    Energy Technology Data Exchange (ETDEWEB)

    Seipt, Daniel

    2012-12-20

    The purpose of this thesis is to advance the understanding of strong-field QED processes in short laser pulses. The processes of non-linear one-photon and two-photon Compton scattering are studied, that is the scattering of photons in the interaction of relativistic electrons with ultra-short high-intensity laser pulses. These investigations are done in view of the present and next generation of ultra-high intensity optical lasers which are supposed to achieve unprecedented intensities of the order of 10{sup 24} W/cm{sup 2} and beyond, with pulse lengths in the order of some femtoseconds. The ultra-high laser intensity requires a non-perturbative description of the interaction of charged particles with the laser field to allow for multi-photon interactions, which is beyond the usual perturbative expansion of QED organized in powers of the fine structure constant. This is achieved in strong-field QED by employing the Furry picture and non-perturbative solutions of the Dirac equation in the presence of a background laser field as initial and final state wave functions, as well as the laser dressed Dirac-Volkov propagator. The primary objective is a realistic description of scattering processes with regard to the finite laser pulse duration beyond the common approximation of infinite plane waves, which is made necessary by the ultra-short pulse length of modern high-intensity lasers. Non-linear finite size effects are identified, which are a result of the interplay between the ultra-high intensity and the ultra-short pulse length. In particular, the frequency spectra and azimuthal photon emission spectra are studied emphasizing the differences between pulsed and infinite laser fields. The proper description of the finite temporal duration of the laser pulse leads to a regularization of unphysical infinities (due to the infinite plane-wave description) of the laser-dressed Dirac-Volkov propagator and in the second-order strong-field process of two-photon Compton

  3. Time-resolved measurements with intense ultrashort laser pulses: a 'molecular movie' in real time

    International Nuclear Information System (INIS)

    Rudenko, A; Ergler, Th; Feuerstein, B; Zrost, K; Schroeter, C D; Moshammer, R; Ullrich, J

    2007-01-01

    We report on the high-resolution multidimensional real-time mapping of H 2 + and D 2 + nuclear wave packets performed employing time-resolved three-dimensional Coulomb explosion imaging with intense laser pulses. Exploiting a combination of a 'reaction microscope' spectrometer and a pump-probe setup with two intense 6-7 fs laser pulses, we simultaneously visualize both vibrational and rotational motion of the molecule, and obtain a sequence of snapshots of the squared ro-vibrational wave function with time-step resolution of ∼ 0.3 fs, allowing us to reconstruct a real-time movie of the ultrafast molecular motion. We observe fast dephasing, or 'collapse' of the vibrational wave packet and its subsequent revival, as well as signatures of rotational excitation. For D 2 + we resolve also the fractional revivals resulting from the interference between the counter-propagating parts of the wave packet

  4. Oxygen-assisted multipass cutting of carbon fiber reinforced plastics with ultra-short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Kononenko, T. V.; Komlenok, M. S.; Konov, V. I. [Natural Sciences Center, General Physics Institute, Vavilov str. 38, 119991 Moscow (Russian Federation); National Research Nuclear University, “MEPhI,” Kashirskoye shosse 31, 115409 Moscow (Russian Federation); Freitag, C. [Universität Stuttgart, Institut für Strahlwerkzeuge (IFSW), Pfaffenwaldring 43, 70569 Stuttgart (Germany); GSaME Graduate School of Excellence Advanced Manufacturing Engineering, Nobelstrasse 12, 70569 Stuttgart (Germany); Onuseit, V.; Weber, R.; Graf, T. [Universität Stuttgart, Institut für Strahlwerkzeuge (IFSW), Pfaffenwaldring 43, 70569 Stuttgart (Germany)

    2014-03-14

    Deep multipass cutting of bidirectional and unidirectional carbon fiber reinforced plastics (CFRP) with picosecond laser pulses was investigated in different static atmospheres as well as with the assistance of an oxygen or nitrogen gas flow. The ablation rate was determined as a function of the kerf depth and the resulting heat affected zone was measured. An assisting oxygen gas flow is found to significantly increase the cutting productivity, but only in deep kerfs where the diminished evaporative ablation due to the reduced laser fluence reaching the bottom of the kerf does not dominate the contribution of reactive etching anymore. Oxygen-supported cutting was shown to also solve the problem that occurs when cutting the CFRP parallel to the fiber orientation where a strong deformation and widening of the kerf, which temporarily slows down the process speed, is revealed to be typical for processing in standard air atmospheres.

  5. Oxygen-assisted multipass cutting of carbon fiber reinforced plastics with ultra-short laser pulses

    International Nuclear Information System (INIS)

    Kononenko, T. V.; Komlenok, M. S.; Konov, V. I.; Freitag, C.; Onuseit, V.; Weber, R.; Graf, T.

    2014-01-01

    Deep multipass cutting of bidirectional and unidirectional carbon fiber reinforced plastics (CFRP) with picosecond laser pulses was investigated in different static atmospheres as well as with the assistance of an oxygen or nitrogen gas flow. The ablation rate was determined as a function of the kerf depth and the resulting heat affected zone was measured. An assisting oxygen gas flow is found to significantly increase the cutting productivity, but only in deep kerfs where the diminished evaporative ablation due to the reduced laser fluence reaching the bottom of the kerf does not dominate the contribution of reactive etching anymore. Oxygen-supported cutting was shown to also solve the problem that occurs when cutting the CFRP parallel to the fiber orientation where a strong deformation and widening of the kerf, which temporarily slows down the process speed, is revealed to be typical for processing in standard air atmospheres

  6. Electron Acceleration and the Propagation of Ultrashort High-Intensity Laser Pulses in Plasmas

    International Nuclear Information System (INIS)

    Wang, Xiaofang; Krishnan, Mohan; Saleh, Ned; Wang, Haiwen; Umstadter, Donald

    2000-01-01

    Reported are interactions of high-intensity laser pulses (λ=810 nm and I≤3x10 18 W /cm 2 ) with plasmas in a new parameter regime, in which the pulse duration (τ=29 fs ) corresponds to 0.6-2.6 plasma periods. Relativistic filamentation is observed to cause laser-beam breakup and scattering of the beam out of the vacuum propagation angle. A beam of megaelectronvolt electrons with divergence angle as small as 1 degree sign is generated in the forward direction, which is correlated to the growth of the relativistic filamentation. Raman scattering, however, is found to be much less than previous long-pulse results. (c) 2000 The American Physical Society

  7. An ultrashort pulse ultra-violet radiation undulator source driven by a laser plasma wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Anania, M. P. [SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); INFN, Laboratori Nazionali di Frascati, I-00044 Frascati (Italy); Brunetti, E.; Wiggins, S. M.; Grant, D. W.; Welsh, G. H.; Issac, R. C.; Cipiccia, S.; Shanks, R. P.; Manahan, G. G.; Aniculaesei, C.; Jaroszynski, D. A., E-mail: d.a.jaroszynski@strath.ac.uk [SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Geer, S. B. van der; Loos, M. J. de [Pulsar Physics, Burghstraat 47, 5614 BC Eindhoven (Netherlands); Poole, M. W.; Shepherd, B. J. A.; Clarke, J. A. [ASTeC, STFC, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Gillespie, W. A. [SUPA, School of Engineering, Physics and Mathematics, University of Dundee, Dundee DD1 4HN (United Kingdom); MacLeod, A. M. [School of Computing and Creative Technologies, University of Abertay Dundee, Dundee DD1 1HG (United Kingdom)

    2014-06-30

    Narrow band undulator radiation tuneable over the wavelength range of 150–260 nm has been produced by short electron bunches from a 2 mm long laser plasma wakefield accelerator based on a 20 TW femtosecond laser system. The number of photons measured is up to 9 × 10{sup 6} per shot for a 100 period undulator, with a mean peak brilliance of 1 × 10{sup 18} photons/s/mrad{sup 2}/mm{sup 2}/0.1% bandwidth. Simulations estimate that the driving electron bunch r.m.s. duration is as short as 3 fs when the electron beam has energy of 120–130 MeV with the radiation pulse duration in the range of 50–100 fs.

  8. Ultrashort Pulsed Laser Ablation of Magnesium Diboride: Plasma Characterization and Thin Films Deposition

    Directory of Open Access Journals (Sweden)

    Angela De Bonis

    2015-01-01

    Full Text Available A MgB2 target has been ablated by Nd:glass laser with a pulse duration of 250 fs. The plasma produced by the laser-target interaction, showing two temporal separated emissions, has been characterized by time and space resolved optical emission spectroscopy and ICCD fast imaging. The films, deposited on silicon substrates and formed by the coalescence of particles with nanometric size, have been analyzed by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. The first steps of the films growth have been studied by Transmission Electron Microscopy. The films deposition has been studied by varying the substrate temperature from 25 to 500°C and the best results have been obtained at room temperature.

  9. Generation of ultra-intense and ultra-short laser pulses with high temporal contrast

    International Nuclear Information System (INIS)

    Julien, A.

    2006-03-01

    The topic of this thesis work concerns the design and the characterization of an efficient device devoted to the temporal contrast improvement for ultra-intense femtosecond laser pulses. The contrast is defined as the intensity ratio between the main femtosecond pulse and its nanosecond pedestal. This pedestal is the amplified spontaneous emission (ASE), inherent with laser amplification mechanism. The ASE background has dramatic effects for laser-matter interactions on a solid target. The presented work consists in the theoretical and experimental study of a temporal filter based on a third order nonlinear effect acting on the pulse polarization. We have studied several kinds of nonlinear filters. The selected device is based on the process of cross-polarized wave generation (XPW) in crystals with an anisotropic third-order nonlinear susceptibility. This nonlinear filter has been experimented on various femtosecond systems. It allows a contrast improvement of several orders of magnitude, as demonstrated by temporal profiles measurements on a large intensity dynamic. A device to improve the nonlinear process conversion efficiency, it means the filter transmission, has also been achieved. This method is based on constructive interferences between XPW signals generated in different crystals. This setup has made it possible to reach experimentally the maximum theoretical efficiency ( >20%) and in the same time ensures the system stability. At least, we have demonstrated that the filter preserves, or even improves, spectral and spatial qualities of the laser pulse. These results are thus particularly promising and allow contemplating the implementation of the filter in current femtosecond systems. (author)

  10. High density ultrashort relativistic positron beam generation by laser-plasma interaction

    Czech Academy of Sciences Publication Activity Database

    Gu, Yanjun; Klimo, Ondřej; Weber, Stefan A.; Korn, Georg

    2016-01-01

    Roč. 18, č. 11 (2016), 1-7, č. článku 113023. ISSN 1367-2630 R&D Projects: GA MŠk EF15_008/0000162 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : radation reaction effect * pair creation * laser-plasma interaction Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.786, year: 2016

  11. Field enhancement induced laser ablation

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kjelstrup-Hansen, Jakob

    Sub-diffraction spatially resolved, quantitative mapping of strongly localized field intensity enhancement on gold nanostructures via laser ablation of polymer thin films is reported. Illumination using a femtosecond laser scanning microscope excites surface plasmons in the nanostructures....... The accompanying field enhancement substantially lowers the ablation threshold of the polymer film and thus creates local ablation spots and corresponding topographic modifications of the polymer film. Such modifications are quantified straightforwardly via scanning electron and atomic force microscopy. Thickness...

  12. Dynamics of the spectral behaviour of an ultrashort laser pulse in an argon-gas-filled capillary discharge-preformed plasma channel

    Directory of Open Access Journals (Sweden)

    Sakai S.

    2013-11-01

    Full Text Available We have reported the argon plasma waveguide produced in an alumina (Al2O3 capillary discharge and used to guide ultrashort laser pulses at intensities of the order of 1016  W/cm2. A one-dimensional magnetohydrodynamic (MHD code was used to evaluate the average degree of ionization of Ar in the preformed plasma channel. The spectrum of the propagated laser pulse in the Ar plasma waveguide was not modified and was well reproduced by a particle-in-cell (PIC simulation under initial ion charge state of Ar3+ in the preformed plasma waveguide. The optimum timing for the laser pulse injection was around 150 ns after initiation of a discharge with a peak current of 200 A.

  13. Spectral characteristics of ultra-short laser pulses in plasma amplifiers

    Czech Academy of Sciences Publication Activity Database

    Riconda, C.; Weber, Stefan A.; Lancia, L.; Marquès, J.-R.; Mourou, G.A.; Fuchs, J.

    2013-01-01

    Roč. 20, č. 8 (2013), "083115-1"-"083115-10" ISSN 1070-664X R&D Projects: GA MŠk ED1.1.00/02.0061; GA MŠk EE2.3.20.0279 Grant - others:ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061; OPVK 3 Laser Zdroj(XE) CZ.1.07/2.3.00/20.0279 Program:EE Institutional support: RVO:68378271 Keywords : amplification * compression * generation * intensity * extreme * optics * light Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.249, year: 2013

  14. Self-guiding of high-intensity laser pulses for laser wake field acceleration

    International Nuclear Information System (INIS)

    Umstader, D.; Liu, X.

    1992-01-01

    A means of self-guiding an ultrashort and high-intensity laser pulse is demonstrated both experimentally and numerically. Its relevance to the laser wake field accelerator concept is discussed. Self-focusing and multiple foci formation are observed when a high peak power (P>100 GW), 1 μm, subpicosecond laser is focused onto various gases (air or hydrogen). It appears to result from the combined effects of self-focusing by the gas, and de-focusing both by diffraction and the plasma formed in the central high-intensity region. Quasi-stationary computer simulations show the same multiple foci behavior as the experiments. The results suggest much larger nonlinear electronic susceptibilities of a gas near or undergoing ionization in the high field of the laser pulse. Although self-guiding of a laser beam by this mechanism appears to significantly extend its high-intensity focal region, small-scale self-focusing due to beam non-uniformity is currently a limitation

  15. Optical transmission control in graphene oxide and its organic composites with ultrashort laser pulses

    International Nuclear Information System (INIS)

    Bala Murali Krishna, M; Narayana Rao, D; Venkatramaiah, N

    2014-01-01

    Nonlinear optical transmission of graphene oxide–(Cu, Zn, Sn, H 2 ) porphyrin composites was investigated using the Z-scan technique at 532 nm with picosecond (ps) and 800 nm with femtosecond laser pulses. Pure porphyrins show saturable absorption (SA) in reverse saturable absorption (RSA) behaviour and graphene oxide shows complete RSA behaviour, observed in an open aperture Z-scan curve. Interestingly, composites have shown a switch-over from reverse RSA to SA and back to RSA behaviour, observed with variation of intensity towards the focus, due to strong two-photon absorption as well as excited state absorption in the ps regime. This switching behaviour was interpreted as due to long lifetimes and saturation of the excited states. This may find application in optical switching. (paper)

  16. An ultrashort-pulse reconstruction software: GROG, applied to the FLAME laser system

    Science.gov (United States)

    Galletti, Mario

    2016-03-01

    The GRENOUILLE traces of FLAME Probe line pulses (60mJ, 10mJ after compression, 70fs, 1cm FWHM, 10Hz) were acquired in the FLAME Front End Area (FFEA) at the Laboratori Nazionali di Frascati (LNF), Instituto Nazionale di Fisica Nucleare (INFN). The complete characterization of the laser pulse parameters was made using a new algorithm: GRenouille/FrOG (GROG). A characterization with a commercial algorithm, QUICKFrog, was also made. The temporal and spectral parameters came out to be in great agreement for the two kinds of algorithms. In this experimental campaign the Probe line of FLAME has been completely characterized and it has been showed how GROG, the developed algorithm, works as well as QuickFrog algorithm with this type of pulse class.

  17. Ultra-short pulse, ultra-high intensity laser improvement techniques for laser-driven quantum beam science

    International Nuclear Information System (INIS)

    Kiriyama, Hiromitsu; Kando, Masaki

    2014-01-01

    Recent development activities of the Quantum Beam Research Team in JAEA are reported. The downsized, petawatt and femtosecond pulse laser is described at first. The process of the system development and utilization effort of so-called J-KAREN is explained with its time and space control system. For high contrast, OPCPA (Optical Parametric Chirped Pulse Amplification) preamplifier is adopted by using the titanium-sapphire laser system in which only the seed light pulses can be amplified. In addition, high contrast is obtained by adopting the high energy seed light to the amplifier. The system configuration of J-KAREN laser is illustrated. Typical spectra with and without OPCPA, as well as the spectra with OPCPA adjustment and without one are shown. The result of the recompressed pulses is shown in which the pulse width of 29.5 femtoseconds is close to the theoretical limit. Considering the throughput of the pulse compressor is 64 percent it is possible to generate high power laser beam of about 600 terawatts. In the supplementary budget of 2012, it has been approved to cope with the aging or obsoleteness of the system and at the same time to further sophisticate the laser using system. The upgraded laser system is named as J-KAREN-P in which the repetition rate is improved and another booster amplifier is added to increase the power. The system configuration of J-KAREN-P after the upgrading is illustrated. (S. Funahashi)

  18. Ablation by ultrashort laser pulses: Atomistic and thermodynamic analysis of the processes at the ablation threshold

    International Nuclear Information System (INIS)

    Upadhyay, Arun K.; Inogamov, Nail A.; Rethfeld, Baerbel; Urbassek, Herbert M.

    2008-01-01

    Ultrafast laser irradiation of solids may ablate material off the surface. We study this process for thin films using molecular-dynamics simulation and thermodynamic analysis. Both metals and Lennard-Jones (LJ) materials are studied. We find that despite the large difference in thermodynamical properties between these two classes of materials--e.g., for aluminum versus LJ the ratio T c /T tr of critical to triple-point temperature differs by more than a factor of 4--the values of the ablation threshold energy E abl normalized to the cohesion energy, ε abl =E abl /E coh , are surprisingly universal: all are near 0.3 with ±30% scattering. The difference in the ratio T c /T tr means that for metals the melting threshold ε m is low, ε m abl , while for LJ it is high, ε m >ε abl . This thermodynamical consideration gives a simple explanation for the difference between metals and LJ. It explains why despite the universality in ε abl , metals thermomechanically ablate always from the liquid state. This is opposite to LJ materials, which (near threshold) ablate from the solid state. Furthermore, we find that immediately below the ablation threshold, the formation of large voids (cavitation) in the irradiated material leads to a strong temporary expansion on a very slow time scale. This feature is easily distinguished from the acoustic oscillations governing the material response at smaller intensities, on the one hand, and the ablation occurring at larger intensities, on the other hand. This finding allows us to explain the puzzle of huge surface excursions found in experiments at near-threshold laser irradiation

  19. Multifunctional gold nanorods for selective plasmonic photothermal therapy in pancreatic cancer cells using ultra-short pulse near-infrared laser irradiation.

    Science.gov (United States)

    Patino, Tania; Mahajan, Ujjwal; Palankar, Raghavendra; Medvedev, Nikolay; Walowski, Jakob; Münzenberg, Markus; Mayerle, Julia; Delcea, Mihaela

    2015-03-12

    Gold nanorods (AuNRs) have attracted considerable attention in plasmonic photothermal therapy for cancer treatment by exploiting their selective and localized heating effect due to their unique photophysical properties. Here we describe a strategy to design a novel multifunctional platform based on AuNRs to: (i) specifically target the adenocarcinoma MUC-1 marker through the use of the EPPT-1 peptide, (ii) enhance cellular uptake through a myristoylated polyarginine peptide (MPAP) and (iii) selectively induce cell death by ultra-short near infrared laser pulses. We used a biotin-avidin based approach to conjugate EPPT-1 and MPAP to AuNRs. Dual-peptide (EPPT-1+MPAP) labelled AuNRs showed a significantly higher uptake by pancreatic ductal adenocarcinoma cells when compared to their single peptide or avidin conjugated counterparts. In addition, we selectively induced cell death by ultra-short near infrared laser pulses in small target volumes (∼1 μm3), through the creation of plasmonic nanobubbles that lead to the destruction of a local cell environment. Our approach opens new avenues for conjugation of multiple ligands on AuNRs targeting cancer cells and tumors and it is relevant for plasmonic photothermal therapy.

  20. The Use of Ultrashort Picosecond Laser Pulses to Generate Quantum Optical Properties of Single Molecules in Biophysics

    Science.gov (United States)

    Ly, Sonny

    Generation of quantum optical states from ultrashort laser-molecule interactions have led to fascinating discoveries in physics and chemistry. In recent years, these interactions have been extended to probe phenomena in single molecule biophysics. Photons emitted from a single fluorescent molecule contains important properties about how the molecule behave and function in that particular environment. Analysis of the second order coherence function through fluorescence correlation spectroscopy plays a pivotal role in quantum optics. At very short nanosecond timescales, the coherence function predicts photon antibunching, a purely quantum optical phenomena which states that a single molecule can only emit one photon at a time. Photon antibunching is the only direct proof of single molecule emission. From the nanosecond to microsecond timescale, the coherence function gives information about rotational diffusion coefficients, and at longer millisecond timescales, gives information regarding the translational diffusion coefficients. In addition, energy transfer between molecules from dipole-dipole interaction results in FRET, a highly sensitive method to probe conformational dynamics at nanometer distances. Here I apply the quantum optical techniques of photon antibunching, fluorescence correlation spectroscopy and FRET to probe how lipid nanodiscs form and function at the single molecule level. Lipid nanodiscs are particles that contain two apolipoprotein (apo) A-I circumventing a lipid bilayer in a belt conformation. From a technological point of view, nanodiscs mimics a patch of cell membrane that have recently been used to reconstitute a variety of membrane proteins including cytochrome P450 and bacteriorhodopsin. They are also potential drug transport vehicles due to its small and stable 10nm diameter size. Biologically, nanodiscs resemble to high degree, high density lipoproteins (HDL) in our body and provides a model platform to study lipid-protein interactions

  1. Photoionization of atoms and molecules by intense EUV-FEL pulses and FEL seeded by high-order harmonic of ultrashort laser pulses

    International Nuclear Information System (INIS)

    Iwasaki, Atsushi; Owada, Shigeki; Yamanouchi, Kaoru; Sato, Takahiro; Nagasono, Mitsuru; Yabashi, Makina; Ishikawa, Tetsuya; Togashi, Tadashi; Takahashi, Eiji J.; Midorikawa, Katsumi; Aoyama, Makoto; Yamakawa, Koichi; Kannari, Fumihiko; Yagishita, Akira

    2012-01-01

    The advantages of SPring-8 Compact SASE Source as a light source for spectroscopic measurements in the extreme ultraviolet (EUV) wavelength region are introduced by referring to our recent study of non-linear photoionization processes of He, in which the absolute two-photon ionization cross sections of He at four different wavelengths in the 54 - 62 nm region were determined using intense pulses of the free-election laser (FEL). In addition, our recent effort to generate intense full-coherent EUV light pulses are introduced, in which significant amplification of the 13th harmonic of ultrashort laser pulses at 800 nm was achieved by FEL seeded with the 13th harmonic. (author)

  2. Lasers plasmas and magnetic field

    International Nuclear Information System (INIS)

    Albertazzi, Bruno

    2014-01-01

    We studied the coupling between a laser produced plasmas and a magnetic field in two cases: 1) in the context of Inertial Fusion Confinement (ICF), we first studied how magnetic fields are self generated during the interaction between a target and a laser, then 2) to progress in the understanding of the large-scale shaping of astrophysical jets, we studied the influence of an externally applied magnetic field on the dynamics of a laser-produced plasma expanding into vacuum. The first part of this thesis is thus dedicated to a numerical and experimental study of the self generated magnetic fields that are produced following the irradiation of a solid target by a high power laser (having pulse duration in the nanosecond and picosecond regimes). These fields play an important role in the frame of ICF since they influence the dynamics of the electrons produced during the laser-matter interaction, and thus condition the success of ICF experiments. The second part of this thesis is a numerical and experimental study of the influence of an externally applied magnetic field on the morphology of a laser produced plasma freely otherwise expanding into vacuum. This work aims at better understanding the observed large-scale collimation of astrophysical jets which cannot be understood in the frame of existing models. We notably show that a purely axial magnetic field can force an initially isotropic laboratory flow, scaled to be representative of a flow emerging from a Young Star Object, in a re-collimation shock, from which emerges a narrow, well collimated jet. We also show that the plasma heating induced at the re-collimation point could explain the 'puzzling' observations of stationary X ray emission zones embedded within astrophysical jets. (author) [fr

  3. Detection of calculus by laser-induced breakdown spectroscopy (LIBS) using an ultra-short pulse laser system (USPL)

    Science.gov (United States)

    Schelle, F.; Brede, O.; Krueger, S.; Oehme, B.; Dehn, C.; Frentzen, M.; Braun, A.

    2011-03-01

    The aim of this study was to assess the detection of calculus by Laser Induced Breakdown Spectroscopy (LIBS). The study was performed with an Nd:YVO4 laser, emitting pulses with a duration of 8 ps at a wavelength of 1064 nm. A repetition rate of 500 kHz at an average power of 5 W was used. Employing a focusing lense, intensities of the order of 1011 W/cm2 were reached on the tooth surface. These high intensities led to the generation of a plasma. The light emitted by the plasma was collimated into a fibre and then analyzed by an echelle spectroscope in the wavelength region from 220 nm - 900 nm. A total number of 15 freshly extracted teeth was used for this study. For each tooth the spectra of calculus and cementum were assessed separately. Comprising all single measurements median values were calculated for the whole spectrum, leading to two specific spectra, one for calculus and one for cementum. For further statistical analysis 28 areas of interest were defined as wavelength regions, in which the signal strength differed regarding the material. In 7 areas the intensity of the calculus spectrum differed statistically significant from the intensity of the cementum spectrum (p calculus. Further studies are necessary to verify that LIBS is a minimally invasive method allowing a safe application in laser-guided dentistry.

  4. Atoms in strong laser fields

    International Nuclear Information System (INIS)

    L'Huillier, A.

    2002-01-01

    When a high-power laser focuses into a gas of atoms, the electromagnetic field becomes of the same magnitude as the Coulomb field which binds a 1s electron in a hydrogen atom. 3 highly non-linear phenomena can happen: 1) ATI (above threshold ionization): electrons initially in the ground state absorb a large number of photons, many more than the minimum number required for ionization; 2) multiple ionization: many electrons can be emitted one at a time, in a sequential process, or simultaneously in a mechanism called direct or non-sequential; and 3) high order harmonic generation (HHG): efficient photon emission in the extreme ultraviolet range, in the form of high-order harmonics of the fundamental laser field can occur. The theoretical problem consists in solving the time dependent Schroedinger equation (TDSE) that describes the interaction of a many-electron atom with a laser field. A number of methods have been proposed to solve this problem in the case of a hydrogen atom or a single-active electron atom in a strong laser field. A large effort is presently being devoted to go beyond the single-active approximation. The understanding of the physics of the interaction between atoms and strong laser fields has been provided by a very simple model called ''simple man's theory''. A unified view of HHG, ATI, and non-sequential ionization, originating from the simple man's model and the strong field approximation, expressed in terms of electrons trajectories or quantum paths is slowly emerging. (A.C.)

  5. Electrons and atoms in intense laser fields

    International Nuclear Information System (INIS)

    Davidovich, L.

    1982-01-01

    Several non-linear effects that show up when electrons and atoms interact with strong laser fields are considered. Thomson scattering, electron potential scattering in the presence of a laser beam, atomic ionization by strong laser fields, the refraction of electrons by laser beams and the Kapitza-Dirac effect are discussed. (Author) [pt

  6. Electrons and atoms in intense laser fields

    International Nuclear Information System (INIS)

    Davidovich, L.

    1982-11-01

    Several non-linear effects that show up when electrons and atoms interact with strong laser fields are considered. Thomson scattering, electron potential scattering in the presence of a laser beam, atomic ionization by strong laser fields, the refraction of electrons by laser beams and the Kapitza-Dirac effect are discussed. (Author) [pt

  7. Muonic atoms in super-intense laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Shahbaz, Atif

    2009-01-28

    Nuclear effects in hydrogenlike muonic atoms exposed to intense high-frequency laser fields have been studied. Systems of low nuclear charge number are considered where a nonrelativistic description applies. By comparing the radiative response for different isotopes we demonstrate characteristic signatures of the finite nuclear mass, size and shape in the high-harmonic spectra. Cutoff energies in the MeV domain can be achieved, offering prospects for the generation of ultrashort coherent {gamma}-ray pulses. Also, the nucleus can be excited while the laser-driven muon moves periodically across it. The nuclear transition is caused by the time-dependent Coulomb field of the oscillating charge density of the bound muon. A closed-form analytical expression for electric multipole transitions is derived within a fully quantum mechanical approach and applied to various isotopes. The excitation probabilities are in general very small. We compare the process with other nuclear excitation mechanisms through coupling with atomic shells and discuss the prospects to observe it in experiment. (orig.)

  8. Muonic atoms in super-intense laser fields

    International Nuclear Information System (INIS)

    Shahbaz, Atif

    2009-01-01

    Nuclear effects in hydrogenlike muonic atoms exposed to intense high-frequency laser fields have been studied. Systems of low nuclear charge number are considered where a nonrelativistic description applies. By comparing the radiative response for different isotopes we demonstrate characteristic signatures of the finite nuclear mass, size and shape in the high-harmonic spectra. Cutoff energies in the MeV domain can be achieved, offering prospects for the generation of ultrashort coherent γ-ray pulses. Also, the nucleus can be excited while the laser-driven muon moves periodically across it. The nuclear transition is caused by the time-dependent Coulomb field of the oscillating charge density of the bound muon. A closed-form analytical expression for electric multipole transitions is derived within a fully quantum mechanical approach and applied to various isotopes. The excitation probabilities are in general very small. We compare the process with other nuclear excitation mechanisms through coupling with atomic shells and discuss the prospects to observe it in experiment. (orig.)

  9. Nonlinear quantum electrodynamic and electroweak processes in strong laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Meuren, Sebastian

    2015-06-24

    Various nonlinear electrodynamic and electroweak processes in strong plane-wave laser fields are considered with an emphasis on short-pulse effects. In particular, the momentum distribution of photoproduced electron-positron pairs is calculated numerically and a semiclassical interpretation of its characteristic features is established. By proving the optical theorem, compact double-integral expressions for the total pair-creation probability are obtained and numerically evaluated. The exponential decay of the photon wave function in a plane wave is included by solving the Schwinger-Dyson equations to leading-order in the quasistatic approximation. In this respect, the polarization operator in a plane wave is investigated and its Ward-Takahashi identity verified. A classical analysis indicates that a photoproduced electron-positron pair recollides for certain initial conditions. The contributions of such recollision processes to the polarization operator are identified and calculated both analytically and numerically. Furthermore, the existence of nontrivial electron-spin dynamics induced by quantum fluctuations is verified for ultra-short laser pulses. Finally, the exchange of weak gauge bosons is considered, which is essential for neutrino-photon interactions. In particular, the axial-vector-vector coupling tensor is calculated and the so-called Adler-Bell-Jackiw (ABJ) anomaly investigated.

  10. Development of a high brightness ultrafast Transmission Electron Microscope based on a laser-driven cold field emission source.

    Science.gov (United States)

    Houdellier, F; Caruso, G M; Weber, S; Kociak, M; Arbouet, A

    2018-03-01

    We report on the development of an ultrafast Transmission Electron Microscope based on a cold field emission source which can operate in either DC or ultrafast mode. Electron emission from a tungsten nanotip is triggered by femtosecond laser pulses which are tightly focused by optical components integrated inside a cold field emission source close to the cathode. The properties of the electron probe (brightness, angular current density, stability) are quantitatively determined. The measured brightness is the largest reported so far for UTEMs. Examples of imaging, diffraction and spectroscopy using ultrashort electron pulses are given. Finally, the potential of this instrument is illustrated by performing electron holography in the off-axis configuration using ultrashort electron pulses. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Emission of ultrashort electromagnetic pulses from electron bunches formed and accelerated by laser beams with tilted amplitude fronts

    International Nuclear Information System (INIS)

    Galkin, A.L.; Korobkin, V.V.; Romanovsky, M.Yu.; Shiryaev, O.B.; Trofimov, V.A.

    2013-01-01

    The dynamics of an electron in a standing wave generated by a pair of counterpropagating linearly polarized relativistically intense laser pulses and the emission of electromagnetic radiation by the electron are analyzed. The pulses are assumed to have tilted amplitude fronts and asymmetric focal spots. The analysis of the dynamics is performed by solving numerically the Newton equation with the corresponding Lorentz force, and the emission of radiation is simulated based on the Lienard-Wiechert potentials. The electrons are accelerated by the direct action of the standing wave field and are shown to form a small short bunch. For relativistic intensities, the energies gained by the electrons reach several GeV. It is demonstrated that the radiation emitted by the electrons in the bunch is a single electromagnetic pulse confined to a narrow solid angle and having an attosecond duration. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. ILIAS. Ion and laser beam interaction and application studies. Progress report no. 3 of the PHELIX theory group

    Energy Technology Data Exchange (ETDEWEB)

    Mulser, P. (ed.)

    2008-04-15

    The following topics are dealt with: The PHELIX laser-plasma facility, coupling of nuclear matter to intense photon fields, QED effects in strong laser fields, relativistic critical density increase in a linearly polarized laser beam, absorption of ultrashort laser pulses in strongly overdense targets, Coulomb focusing in electron-ion collisions in a strong laser field, quasiperiodic waves in relativistic plasmas, high-energy-density physics studied by intense particle beams, heavy ions in a high-power laser beam, Monte-Carlo study of electron dynamics in silicon during irradiation with an ultrashort VUV laser pulse. (HSI)

  13. ILIAS. Ion and laser beam interaction and application studies. Progress report no. 3 of the PHELIX theory group

    International Nuclear Information System (INIS)

    Mulser, P.

    2008-04-01

    The following topics are dealt with: The PHELIX laser-plasma facility, coupling of nuclear matter to intense photon fields, QED effects in strong laser fields, relativistic critical density increase in a linearly polarized laser beam, absorption of ultrashort laser pulses in strongly overdense targets, Coulomb focusing in electron-ion collisions in a strong laser field, quasiperiodic waves in relativistic plasmas, high-energy-density physics studied by intense particle beams, heavy ions in a high-power laser beam, Monte-Carlo study of electron dynamics in silicon during irradiation with an ultrashort VUV laser pulse. (HSI)

  14. Low-level ultrahigh-frequency and ultrashort-pulse blue laser irradiation enhances osteoblast extracellular calcification by upregulating proliferation and differentiation via transient receptor potential vanilloid 1.

    Science.gov (United States)

    Mikami, Risako; Mizutani, Koji; Aoki, Akira; Tamura, Yukihiko; Aoki, Kazuhiro; Izumi, Yuichi

    2018-04-01

    Low-level laser irradiation (LLLI) exerts various biostimulative effects, including promotion of wound healing and bone formation; however, few studies have examined biostimulation using blue lasers. The purpose of this study was to investigate the effects of low-level ultrahigh-frequency (UHF) and ultrashort-pulse (USP) blue laser irradiation on osteoblasts. The MC3T3-E1 osteoblast cell line was used in this study. Following LLLI with a 405 nm newly developed UHF-USP blue laser (80 MHz, 100 fs), osteoblast proliferation, and alkaline phosphatase (ALP) activity were assessed. In addition, mRNA levels of the osteoblast differentiation markers, runt-related transcription factor 2 (Runx2), osterix (Osx), alkaline phosphatase (Alp), and osteopontin (Opn) was evaluated, and extracellular calcification was quantified. To clarify the involvement of transient receptor potential (TRP) channels in LLLI-induced biostimulation, cells were treated prior to LLLI with capsazepine (CPZ), a selective inhibitor of TRP vanilloid 1 (TRPV1), and subsequent proliferation and ALP activity were measured. LLLI with the 405 nm UHF-USP blue laser significantly enhanced cell proliferation and ALP activity, compared with the non-irradiated control and LLLI using continuous-wave mode, without significant temperature elevation. LLLI promoted osteoblast proliferation in a dose-dependent manner up to 9.4 J/cm 2 and significantly accelerated cell proliferation in in vitro wound healing assay. ALP activity was significantly enhanced at doses up to 5.6 J/cm 2 , and expression of Osx and Alp mRNAs was significantly increased compared to that of the control on days 3 and 7 following LLLI at 5.6 J/cm 2 . The extent of extracellular calcification was also significantly higher as a result of LLLI 3 weeks after the treatment. Measurement of TRPV1 protein expression on 0, 3, and 7 days post-irradiation revealed no differences between the LLLI and control groups; however, promotion of cell

  15. Ablation of burned skin with ultra-short pulses laser to promote healing: evaluation by optical coherence tomography, histology, μATR-FTIR and Nonlinear Microscopy

    International Nuclear Information System (INIS)

    Santos, Moises Oliveira dos

    2012-01-01

    Burns cause changes in the anatomical structure of the skin associated with trauma. The severity of the burn injury is divided into first, second and third-degree burns. The third-degree burns have been a major focus of research in search of more conservative treatments and faster results in repair for a functional and cosmetically acceptable. The conventional treatment is the use of topical natural or synthetic skin graft. An alternative therapy is the laser ablation process for burned tissue necrosis removal due to the no mechanical contact, fast application and access to difficult areas. The purpose of this study is to evaluate the feasibility of using high intensity femtosecond lasers as an adjunct treatment of burned patients. For this study, 65 Wistar rats were divided into groups of five animals: healthy skin, burned skin, two types of treatment (surgical debridement or femtosecond laser ablation) and four different times in the healing process monitoring. Three regions of the back of the animals were exposed to steam source causing third-degree burn. On the third day after the burn, one of the regions was ablated with high intensity ultrashort laser pulses (λ = 785 nm, 90 fs, 2 kHz and 10 μJ/ pulse), the other received surgical debridement, and the last was considered the burn control. The regions were analyzed by optical coherence tomography (OCT), histology, attenuated total reflectance infrared spectroscopy using Fourier transform (μ-ATR-FTIR), two-photon excitation fluorescence microscopy (TPEFM) and second harmonic generation technique (SHG) on days 3, 5, 7 and 14 pos-treatments. The results showed that with the laser irradiation conditions used it was possible to remove debris from third degree burn. The techniques used to characterize the tissue allowed to verify that all treatments promoted wound healing. On the fourteenth day, the regeneration curve showed that the attenuation coefficient of laser ablated tissue converges to the values of

  16. Dissociation and ionization of molecular ions by ultra-short intense laser pulses probed by coincidence 3D momentum imaging

    International Nuclear Information System (INIS)

    Ben-Itzhak, Itzik; Wang, Pengqian; Xia, Jiangfan; Max Sayler, A.; Smith, Mark A.; Maseberg, J.W.; Carnes, Kevin D.; Esry, Brett D.

    2005-01-01

    We have experimentally explored laser-induced dissociation and ionization of diatomic molecular ions using coincidence 3D momentum imaging. The vibrationally excited molecular ion beam (4-8 keV) is crossed by an ultrafast intense laser beam (28-200 fs, 10 13 -10 14 W/cm 2 ). The resulting fragments are recorded in coincidence by a time and position-sensitive detector. Complete angular distributions and kinetic energy release maps are reconstructed from the measured dissociation-momentum vectors. The angular distribution of the H + + H fragments was found to be strongly correlated to their kinetic energy release upon dissociation. Low KER was associated with very narrow angular distributions and high KER with distributions peaking away from the laser polarization. Ionization was found to be smaller than dissociation and increased with laser intensity. The H + + H + fragments have a very narrow angular distribution along the laser polarization

  17. Near-field enhanced femtosecond laser nano-drilling of glass substrate

    International Nuclear Information System (INIS)

    Zhou, Y.; Hong, M.H.; Fuh, J.Y.H.; Lu, L.; Lukyanchuk, B.S.; Wang, Z.B.

    2008-01-01

    Particle mask assisted near-field enhanced femtosecond laser nano-drilling of transparent glass substrate was demonstrated in this paper. A particle mask was fabricated by self-assembly of spherical 1 μm silica particles on the substrate surface. Then the samples were exposed to femtosecond laser (800 nm, 100 fs) and characterized by field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). The nano-hole array was found on the glass surface. The hole sizes were measured from 200 to 300 nm with an average depth of 150 nm and increased with laser fluence. Non-linear triple-photon absorption and near-field enhancement were the main mechanisms of the nano-feature formation. Calculations based on Mie theory shows an agreement with experiment results. More debris, however, was found at high laser fluence. This can be attributed to the explosion of silica particles because the focusing point is inside the 1 μm particle. The simulation predicts that the focusing point will move outside the particle if the particle size increases. The experiment performed under 6.84 μm silica particles verified that no debris was formed. And for all the samples, no cracks were found on the substrate surface because of ultra-short pulse width of femtosecond laser. This method has potential applications in nano-patterning of transparent glass substrate for nano-structure device fabrication

  18. Resonant multiphoton ionization of caesium atoms by ultra-short laser pulses at 1.06 μm

    International Nuclear Information System (INIS)

    Lompre, L.A.; Mainfray, G.; Manus, C.; Thebault, J.

    1978-01-01

    This paper reports the four-photon ionization of caesium atoms when the laser frequency is tuned through the resonant three-photon transition 6S → 6F. This experiment was performed by using a tunable-wavelength bandwidth-limited subnanosecond laser pulse at 1.06 μm, in the 10 8 -10 9 W.cm -2 laser intensity range. Pulse widths of 1.5 ns, 50 ps, and 15 ps were used. The resonant character of the multiphoton ionization process was observed, even with the shortest pulse of 15 ps. Nevertheless the influence of a temporal effect is demonstrated according to theoretical predictions. The resonance shift ΔE of the 6S → 6F transition energy was found to be linear with the laser intensity I within the range 10 8 -10 9 W.cm -2 . ΔE = αI, with α = 2 cm -1 /GW.cm -2 . This results confirms previous measurements performed with single-mode 35 ns laser pulses and is in very good agreement with calculated resonance shifts

  19. Investigation of ultrashort pulse laser ablation of solid targets by measuring the ablation-generated momentum using a torsion pendulum.

    Science.gov (United States)

    Zhang, Nan; Wang, Wentao; Zhu, Xiaonong; Liu, Jiansheng; Xu, Kuanhong; Huang, Peng; Zhao, Jiefeng; Li, Ruxin; Wang, Mingwei

    2011-04-25

    50 fs - 12 ps laser pulses are employed to ablate aluminum, copper, iron, and graphite targets. The ablation-generated momentum is measured with a torsion pendulum. Corresponding time-resolved shadowgraphic measurements show that the ablation process at the optimal laser fluence achieving the maximal momentum is primarily dominated by the photomechanical mechanism. When laser pulses with specific laser fluence are used and the pulse duration is tuned from 50 fs to 12 ps, the generated momentum firstly increases and then remains almost constant, which could be attributed to the change of the ablation mechanism involved from atomization to phase explosion. The investigation of the ablation-generated momentum also reveals a nonlinear momentum-energy conversion scaling law, namely, as the pulse energy increases, the momentum obtained by the target increases nonlinearly. This may be caused by the effective reduction of the dissipated energy into the surrounding of the ablation zone as the pulse energy increases, which indicates that for femtosecond laser the dissipated energy into the surrounding target is still significant.

  20. Ultra-fast Movies Resolve Ultra-short Pulse Laser Ablation and Bump Formation on Thin Molybdenum Films

    Science.gov (United States)

    Domke, Matthias; Rapp, Stephan; Huber, Heinz

    For the monolithic serial interconnection of CIS thin film solar cells, 470 nm molybdenum films on glass substrates must be separated galvanically. The single pulse ablation with a 660 fs laser at a wavelength of 1053 nm is investigated in a fluence regime from 0.5 to 5.0 J/cm2. At fluences above 2.0 J/cm2 bump and jet formation can be observed that could be used for creating microstructures. For the investigation of the underlying mechanisms of the laser ablation process itself as well as of the bump or jet formation, pump probe microscopy is utilized to resolve the transient ablation behavior.

  1. Single-pass, efficient type-I phase-matched frequency doubling of high-power ultrashort-pulse Yb-fiber laser using LiB_3O_5

    Science.gov (United States)

    Shukla, Mukesh Kumar; Kumar, Samir; Das, Ritwick

    2016-05-01

    We report 48 % efficient single-pass second harmonic generation of high-power ultrashort-pulse ({≈ }250 fs) Yb-fiber laser by utilizing type-I phase matching in LiB_3O_5 (LBO) crystal. The choice of LBO among other borate crystals for high-power frequency doubling is essentially motivated by large thermal conductivity, low birefringence and weak group velocity dispersion. By optimally focussing the beam in a 4-mm-long LBO crystal, we have generated about 2.3 W of average power at 532 nm using 4.8 W of available pump power at 1064 nm. The ultrashort green pulses were found out to be near-transform limited sech^2 pulses with a pulse width of Δ τ ≈ 150 fs and being delivered at 78 MHz repetition rate. Due to appreciably low spatial walk-off angle for LBO ({≈ }0.4°), we obtain M^2beam which signifies marginal distortion in comparison with the pump beam (M^2<1.15). We also discuss the impact of third-order optical nonlinearity of the LBO crystal on the generated ultrashort SH pulses.

  2. Study and realisation of a femtosecond dye laser operating at different wavelengths. Ultrashort pulses compression and amplification

    International Nuclear Information System (INIS)

    Georges, Patrick

    1989-01-01

    We present the study and the realization of a passively mode-locked dye laser producing pulses shorter than 100 femto-seconds (10 -13 s). In a ring cavity with an amplifier medium (Rhodamine 60) and a saturable absorber (DODCI), a sequence of four prisms controls the group velocity dispersion and allows the generation of very short pulses. Then we have studied the production of femtosecond pulses at other wavelengths directly from the femtosecond dye laser. For the first rime, 60 fs pulses at 685 nm and pulses shorter than 50 fs between 775 nm and 800 nm have been produced by passive mode locking. These near infrared pulses have been used to study the absorption saturation kinetics in semiconductors multiple quantum wells GaAs/GaAlAs. We have observed a singular behavior of the laser operating at 685 nm and analyzed the produced pulses in terms of optical solitons. To perform time resolved spectroscopy with shortest pulses, we have studied a pulse compressor and a multipass amplifier to increase the pulses energy. Pulses of 20 fs and 10 micro-joules (peak power: 0.5 GW) have been obtained at low repetition rate (10 Hz) and pulses of 16 fs and 0.6 micro-joules pulses have been generated at high repetition rate (11 kHz) using a copper vapor laser. These pulses have been used to study the absorption saturation kinetics of an organic dye (the Malachite Green). (author) [fr

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

    NARCIS (Netherlands)

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

    2015-01-01

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

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

    NARCIS (Netherlands)

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

    2015-01-01

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

  5. Vacuum ultraviolet Ar2*laser pumped by a high-intensity laser

    International Nuclear Information System (INIS)

    Kubodera, Shoichi; Kaku, Masanori; Higashiguchi, Takeshi

    2004-01-01

    We observed a small-signal gain of Ar 2 * emission at 126 nm by use of an Ar-filled hollow fiber to guide the ultrashort-pulse high-intensity laser propagation. The small signal gain coefficient was measured to be 0.05 cm -1 at 126 nm. Kinetic analysis revealed that the electrons produced by the high-intensity laser through an optical-field ionization process initiated the Ar 2 * production process. This laser scheme could be combined with high harmonic radiation of the pump laser in the vacuum ultraviolet (VUV), leading to the production of amplified ultrashort VUV pulses. (author)

  6. Holding molecular dications together in strong laser fields

    International Nuclear Information System (INIS)

    Guo Chunlei

    2006-01-01

    Metastable channel of doubly ionized carbon monoxide, CO 2+ , was scantly seen in previous strong-field experiments at the visible wavelength region, but was commonly observed using single high-energy photon or electron excitation. For the first time with near-IR ultrashort-pulse radiation, we observe an abundance of CO 2+ . We show that CO 2+ results from nonsequential double ionization, while its dissociation counterpart, C + +O + , results from sequential processes, and CO 2+ can be obtained through either single high-energy photon or electron excitation or multiphoton ionization with ultrashort pulses before a critical internuclear distance is reached. Our study demonstrates the experimental conditions to converge the outcomes from two vastly different regimes, namely, multiphoton excitation and ionization in strong fields and single high-energy photon or electron excitation and ionization in weak fields

  7. High field laser heated solenoids

    International Nuclear Information System (INIS)

    Hoffman, A.L.

    1979-01-01

    A 10 kJ pulsed CO 2 laser and 3.8 cm bore, 15 T, 8 μs rise time, 1-m long fast solenoid facility has been constructed to demonstrate the feasibility of using long wavelength lasers to heat magnetically confined plasmas. The most critical physics requirement is the necessity of creating and maintaining an on-axis electron density minimum to trap the axially directed laser beam. Satisfaction of this requirement has been demonstrated by heating 1.5 Torr deuterium fill plasmas in 2.7 cm bore plasma tubes to line energies of approximately 1 kJ/m. (Auth.)

  8. Study on the drain bias effect on negative bias temperature instability degradation of an ultra-short p-channel metal-oxide-semiconductor field-effect transistor

    International Nuclear Information System (INIS)

    Yan-Rong, Cao; Xiao-Hua, Ma; Yue, Hao; Shi-Gang, Hu

    2010-01-01

    This paper studies the effect of drain bias on ultra-short p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) degradation during negative bias temperature (NBT) stress. When a relatively large gate voltage is applied, the degradation magnitude is much more than the drain voltage which is the same as the gate voltage supplied, and the time exponent gets larger than that of the NBT instability (NBTI). With decreasing drain voltage, the degradation magnitude and the time exponent all get smaller. At some values of the drain voltage, the degradation magnitude is even smaller than that of NBTI, and when the drain voltage gets small enough, the exhibition of degradation becomes very similar to the NBTI degradation. When a relatively large drain voltage is applied, with decreasing gate voltage, the degradation magnitude gets smaller. However, the time exponent becomes larger. With the help of electric field simulation, this paper concludes that the degradation magnitude is determined by the vertical electric field of the oxide, the amount of hot holes generated by the strong channel lateral electric field at the gate/drain overlap region, and the time exponent is mainly controlled by localized damage caused by the lateral electric field of the oxide in the gate/drain overlap region where hot carriers are produced. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  9. Heating of a dense plasma by an ultrashort laser pulse in the anomalous skin-effect regime

    International Nuclear Information System (INIS)

    Andreev, A.A.; Gamalii, E.G.; Novikov, V.N.; Semakhin, A.N.; Tikhonchuk, V.T.

    1992-01-01

    The absorption of laser light in an overdense plasma with a sharp boundary and the heating of the plasma under conditions corresponding to the anomalous skin effect are studied. Heat transfer from the absorption region near the surface into the interior of the plasma is studied in the kinetic approximation. At high intensities of the laser pulse, the electron distribution function is deformed, and the plasma is heated at a rate tens of times that predicted by classical heat-transfer theory, because of the severe limitation on thermal conductivity. The anisotropy of the electron distribution function in the skin layer leads to an increase in the absorption coefficient. The angular distribution and the polarization dependence of the absorption coefficient are discussed

  10. X-ray emission spectra of the plasma produced by an ultrashort laser pulse in cluster targets

    International Nuclear Information System (INIS)

    Stenz, C; Bagnoud, V; Blasco, F; Roche, J R; Salin, F; Faenov, A Ya; Skobelev, I Yu; Magunov, A I; Pikuz, T A

    2000-01-01

    The first observation of x-ray emission spectra of multiply charged ions in the plasma produced by a 35-fs laser pulse with an intensity up to 10 17 W cm -2 in CO 2 and Kr gas jet targets is reported. The emission in the wavelength ranges of the 1snp-1s 2 (n=3-6) transitions of O VII ions and the Ly α line of O VIII ions, as well as of the (2s 1/2 2p 6 3p 3/2 ) 1 -2s 2 2p 6 1 S 0 and (2s 1/2 2p 6 3p 1/2 ) 1 -2s 2 2p 6 1 S 0 lines of Ne-like KrXXVII ions testifies that the highly ionised plasma is formed by collision processes in clusters. Modelling the shape of the spectral lines of oxygen ions by including the principal mechanisms of broadening and absorption in optically dense plasmas reveals that the main contribution to the time-integrated intensity is made by the plasma with the parameters N e =(2-20)x10 20 cm -3 and T e =100 - 115 eV. (interaction of laser radiation with matter. laser plasma)

  11. Evanescent fields of laser written waveguides

    Science.gov (United States)

    Jukić, Dario; Pohl, Thomas; Götte, Jörg B.

    2015-03-01

    We investigate the evanescent field at the surface of laser written waveguides. The waveguides are written by a direct femtosecond laser writing process into fused silica, which is then sanded down to expose the guiding layer. These waveguides support eigenmodes which have an evanescent field reaching into the vacuum above the waveguide. We study the governing wave equations and present solution for the fundamental eigenmodes of the modified waveguides.

  12. Magnetic fields in laser heated plasmas

    International Nuclear Information System (INIS)

    Amiranoff, F.; Brackbill, J.; Colombant, D.; Grandjouan, N.

    1984-01-01

    With a fixed-ion code for the study of self-generated magentic fields in laser heated plasmas, the inhibition of thermal transport and the effect of the Nernst term are modeled for a KrF laser. For various values of the flux limiter, the response of a foil to a focused laser is calculated without a magnetic field and compared with the response calculated with a magnetic field. The results are: The Nernst term convects the magnetic field to densities above critical as found by Nishiguchi et al. (1984), but the field does not strongly inhibit transport into the foil. The field is also transported to sub-critical densities, where it inhibits thermal diffusion and enhance lateral transport by convection

  13. Innovation: study of 'ultra-short' time reactions

    International Nuclear Information System (INIS)

    Anon.

    2001-01-01

    This short article presents the new Elyse facility of Orsay-Paris 11 university for the study of ultra-short chemical and biochemical phenomena. Elyse uses the 'pump-probe' technique which consists in two perfectly synchronized electron and photon pulses. It comprises a 3 to 9 MeV electron accelerator with a HF gun photo-triggered with a laser. Elyse can initiate reactions using ultra-short electron pulses (radiolysis) or ultra-short photon pulses (photolysis). (J.S.)

  14. Four-photon parametric light scattering of ultrashort laser pulses in water in case of weak self-phase modulation

    International Nuclear Information System (INIS)

    Babenko, V A; Sychev, Andrei A

    2009-01-01

    The hyper-Raman scattering (HRS) of light in water is detected reliably by the active spectroscopy method of coherent light scattering, in particular, by the method of four-photon parametric light scattering in a medium in which HRS is a 'signal' wave in the parametric process involving simultaneously two high-power laser photons and IR photons of an 'idler' wave. Hyper-Raman scattering by libration vibrations of water molecules, which virtually cannot be detected by conventional methods of Raman scattering, was observed. (nonlinear optical phenomena)

  15. Layer-by-layer modification of thin-film metal-semiconductor multilayers with ultrashort laser pulses

    Science.gov (United States)

    Romashevskiy, S. A.; Tsygankov, P. A.; Ashitkov, S. I.; Agranat, M. B.

    2018-05-01

    The surface modifications in a multilayer thin-film structure (50-nm alternating layers of Si and Al) induced by a single Gaussian-shaped femtosecond laser pulse (350 fs, 1028 nm) in the air are investigated by means of atomic-force microscopy (AFM), scanning electron microscopy (SEM), and optical microscopy (OM). Depending on the laser fluence, various modifications of nanometer-scale metal and semiconductor layers, including localized formation of silicon/aluminum nanofoams and layer-by-layer removal, are found. While the nanofoams with cell sizes in the range of tens to hundreds of nanometers are produced only in the two top layers, layer-by-layer removal is observed for the four top layers under single pulse irradiation. The 50-nm films of the multilayer structure are found to be separated at their interfaces, resulting in a selective removal of several top layers (up to 4) in the form of step-like (concentric) craters. The observed phenomenon is associated with a thermo-mechanical ablation mechanism that results in splitting off at film-film interface, where the adhesion force is less than the bulk strength of the used materials, revealing linear dependence of threshold fluences on the film thickness.

  16. Applications of ultrashort laser pulses in science and technology; Proceedings of the Meeting, The Hague, Netherlands, Mar. 12, 13, 1990

    Science.gov (United States)

    Antonetti, Andre (Editor)

    1990-01-01

    Topics discussed are on the generation of high-intensity femtosecond lasers, the high-repetition and infrared femtosecond pulses, and physics of semiconductors and applications. Papers are presented on the femtosecond pulse generation at 193 nm; the generation of intense subpicosecond and femtosecond pulses; intense tunable subpicosecond and femtosecond pulses in the visible and infrared, generated by optical parametric oscillators; a high-efficiency high-energy optical amplifier for femtosecond pulses; and the generation of solitons, periodic pulsing, and nonlinearities in GaAs. Other papers are on ultrafast relaxation dynamics of photoexcited carriers in GaAs, high-order optical nonlinear susceptibilities of transparent glasses, subnanosecond risetime high-power pulse generation using photoconductive bulk GaAs devices, femtosecond studies of plasma formation in crystalline and amorphous silicon, and subpicosecond dynamics of hot carrier relaxation in InP and GaAs.

  17. Strong field interaction of laser radiation

    International Nuclear Information System (INIS)

    Pukhov, Alexander

    2003-01-01

    The Review covers recent progress in laser-matter interaction at intensities above 10 18 W cm -2 . At these intensities electrons swing in the laser pulse with relativistic energies. The laser electric field is already much stronger than the atomic fields, and any material is instantaneously ionized, creating plasma. The physics of relativistic laser-plasma is highly non-linear and kinetic. The best numerical tools applicable here are particle-in-cell (PIC) codes, which provide the most fundamental plasma model as an ensemble of charged particles. The three-dimensional (3D) PIC code Virtual Laser-Plasma Laboratory runs on a massively parallel computer tracking trajectories of up to 10 9 particles simultaneously. This allows one to simulate real laser-plasma experiments for the first time. When the relativistically intense laser pulses propagate through plasma, a bunch of new physical effects appears. The laser pulses are subject to relativistic self-channelling and filamentation. The gigabar ponderomotive pressure of the laser pulse drives strong currents of plasma electrons in the laser propagation direction; these currents reach the Alfven limit and generate 100 MG quasistatic magnetic fields. These magnetic fields, in turn, lead to the mutual filament attraction and super-channel formation. The electrons in the channels are accelerated up to gigaelectronvolt energies and the ions gain multi-MeV energies. We discuss different mechanisms of particle acceleration and compare numerical simulations with experimental data. One of the very important applications of the relativistically strong laser beams is the fast ignition (FI) concept for the inertial fusion energy (IFE). Petawatt-class lasers may provide enough energy to isochorically ignite a pre-compressed target consisting of thermonuclear fuel. The FI approach would ease dramatically the constraints on the implosion symmetry and improve the energy gain. However, there is a set of problems to solve before the FI

  18. Laser ion source with solenoid field

    International Nuclear Information System (INIS)

    Kanesue, Takeshi; Okamura, Masahiro; Fuwa, Yasuhiro; Kondo, Kotaro

    2014-01-01

    Pulse length extension of highly charged ion beam generated from a laser ion source is experimentally demonstrated. The laser ion source (LIS) has been recognized as one of the most powerful heavy ion source. However, it was difficult to provide long pulse beams. By applying a solenoid field (90 mT, 1 m) at plasma drifting section, a pulse length of carbon ion beam reached 3.2 μs which was 4.4 times longer than the width from a conventional LIS. The particle number of carbon ions accelerated by a radio frequency quadrupole linear accelerator was 1.2 × 10 11 , which was provided by a single 1 J Nd-YAG laser shot. A laser ion source with solenoid field could be used in a next generation heavy ion accelerator

  19. Laser ion source with solenoid field

    Energy Technology Data Exchange (ETDEWEB)

    Kanesue, Takeshi, E-mail: tkanesue@bnl.gov; Okamura, Masahiro [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Fuwa, Yasuhiro [Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-7501 (Japan); RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Kondo, Kotaro [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8550 (Japan)

    2014-11-10

    Pulse length extension of highly charged ion beam generated from a laser ion source is experimentally demonstrated. The laser ion source (LIS) has been recognized as one of the most powerful heavy ion source. However, it was difficult to provide long pulse beams. By applying a solenoid field (90 mT, 1 m) at plasma drifting section, a pulse length of carbon ion beam reached 3.2 μs which was 4.4 times longer than the width from a conventional LIS. The particle number of carbon ions accelerated by a radio frequency quadrupole linear accelerator was 1.2 × 10{sup 11}, which was provided by a single 1 J Nd-YAG laser shot. A laser ion source with solenoid field could be used in a next generation heavy ion accelerator.

  20. Laser ion source with solenoid field

    Science.gov (United States)

    Kanesue, Takeshi; Fuwa, Yasuhiro; Kondo, Kotaro; Okamura, Masahiro

    2014-11-01

    Pulse length extension of highly charged ion beam generated from a laser ion source is experimentally demonstrated. The laser ion source (LIS) has been recognized as one of the most powerful heavy ion source. However, it was difficult to provide long pulse beams. By applying a solenoid field (90 mT, 1 m) at plasma drifting section, a pulse length of carbon ion beam reached 3.2 μs which was 4.4 times longer than the width from a conventional LIS. The particle number of carbon ions accelerated by a radio frequency quadrupole linear accelerator was 1.2 × 1011, which was provided by a single 1 J Nd-YAG laser shot. A laser ion source with solenoid field could be used in a next generation heavy ion accelerator.

  1. Recent progress on laser acceleration research

    International Nuclear Information System (INIS)

    Nakajima, Kazuhisa; Dewa, Hideki; Hosokai, Tomonao; Kanazawa, Shuhei; Kando, Masaki; Kondoh, Shuji; Kotaki, Hideyuki

    2000-01-01

    Recently there has been a tremendous experimental progress in ultrahigh field particle acceleration driven by ultraintense laser pulses in plasmas. A design of the laser wakefield accelerators aiming at GeV energy gains is discussed by presenting our recent progress on the laser wakefield acceleration experiments, the developments of high quality electron beam injectors and the capillary plasma waveguide for optical guiding of ultrashort intense laser pulses. (author)

  2. Aligning molecules with intense nonresonant laser fields

    DEFF Research Database (Denmark)

    Larsen, J.J.; Safvan, C.P.; Sakai, H.

    1999-01-01

    Molecules in a seeded supersonic beam are aligned by the interaction between an intense nonresonant linearly polarized laser field and the molecular polarizability. We demonstrate the general applicability of the scheme by aligning I2, ICl, CS2, CH3I, and C6H5I molecules. The alignment is probed...... by mass selective two dimensional imaging of the photofragment ions produced by femtosecond laser pulses. Calculations on the degree of alignment of I2 are in good agreement with the experiments. We discuss some future applications of laser aligned molecules....

  3. Femtosecond laser spectroscopy

    CERN Document Server

    Hannaford, Peter

    2005-01-01

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

  4. Multi-Chromatic Ultrashort Pulse Filamentation and Bulk Modification in Dielectrics

    Science.gov (United States)

    2016-05-05

    AFRL-AFOSR-VA-TR-2016-0194 Multi- Chromatic Ultrashort Pulse Filamentation and Bulk Modification in Dielectrics Jeremy Gulley KENNESAW STATE...Jan 2016 4. TITLE AND SUBTITLE Multi- chromatic Ultrashort Pulse Filamentation and Bulk Modification in Dielectrics 5a. CONTRACT NUMBER 5b. GRANT...in, and modification of, dielectric solids by multi- chromatic ultrashort laser pulses. It was a theoretical effort to develop models of multi

  5. Ultrashort X-ray pulse science

    Energy Technology Data Exchange (ETDEWEB)

    Chin, Alan Hap [Univ. of California, Berkeley, CA (US). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    1998-05-01

    A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by 90° Thomson scattering between terawatt laser pulses and relativistic electrons. Using this technique, the author generated ~ 300 fs, 30 keV (0.4 Å) x-ray pulses. These x-ray pulses are absolutely synchronized with ultrashort laser pulses, allowing femtosecond optical pump/x-ray probe experiments to be performed. Using the right-angle Thomson scattering x-ray source, the author performed time-resolved x-ray diffraction studies of laser-perturbated InSb. These experiments revealed a delayed onset of lattice expansion. This delay is due to the energy relaxation from a dense electron-hole plasma to the lattice. The dense electron-hole plasma first undergoes Auger recombination, which reduces the carrier concentration while maintaining energy content. Longitudinal-optic (LO) phonon emission then couples energy to the lattice. LO phonon decay into acoustic phonons, and acoustic phonon propagation then causes the growth of a thermally expanded layer. Source characterization is instrumental in utilizing ultrashort x-ray pulses in time-resolved x-ray spectroscopies. By measurement of the electron beam diameter at the generation point, the pulse duration of the Thomson scattered x-rays is determined. Analysis of the Thomson scattered x-ray beam properties also provides a novel means of electron bunch characterization. Although the pulse duration is inferred for the Thomson scattering x-ray source, direct measurement is required for other x-ray pulse sources. A method based on the laser-assisted photoelectric effect (LAPE) has been demonstrated as a

  6. Ultrashort X-ray pulse science

    International Nuclear Information System (INIS)

    Chin, A.H.; Lawrence Berkeley National Lab., CA

    1998-01-01

    A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by 90 o Thomson scattering between terawatt laser pulses and relativistic electrons. Using this technique, the author generated ∼ 300 fs, 30 keV (0.4 (angstrom)) x-ray pulses. These x-ray pulses are absolutely synchronized with ultrashort laser pulses, allowing femtosecond optical pump/x-ray probe experiments to be performed. Using the right-angle Thomson scattering x-ray source, the author performed time-resolved x-ray diffraction studies of laser-perturbated InSb. These experiments revealed a delayed onset of lattice expansion. This delay is due to the energy relaxation from a dense electron-hole plasma to the lattice. The dense electron-hole plasma first undergoes Auger recombination, which reduces the carrier concentration while maintaining energy content. Longitudinal-optic (LO) phonon emission then couples energy to the lattice. LO phonon decay into acoustic phonons, and acoustic phonon propagation then causes the growth of a thermally expanded layer. Source characterization is instrumental in utilizing ultrashort x-ray pulses in time-resolved x-ray spectroscopies. By measurement of the electron beam diameter at the generation point, the pulse duration of the Thomson scattered x-rays is determined. Analysis of the Thomson scattered x-ray beam properties also provides a novel means of electron bunch characterization. Although the pulse duration is inferred for the Thomson scattering x-ray source, direct measurement is required for other x-ray pulse sources. A method based on the laser-assisted photoelectric effect (LAPE) has been

  7. Coherent Control of Multiphoton Transitions in the Gas and Condensed Phases with Shaped Ultrashort Pulses

    International Nuclear Information System (INIS)

    Dantus, Marcos

    2008-01-01

    Controlling laser-molecule interactions has become an integral part of developing devices and applications in spectroscopy, microscopy, optical switching, micromachining and photochemistry. Coherent control of multiphoton transitions could bring a significant improvement of these methods. In microscopy, multi-photon transitions are used to activate different contrast agents and suppress background fluorescence; coherent control could generate selective probe excitation. In photochemistry, different dissociative states are accessed through two, three, or more photon transitions; coherent control could be used to select the reaction pathway and therefore the yield-specific products. For micromachining and processing a wide variety of materials, femtosecond lasers are now used routinely. Understanding the interactions between the intense femtosecond pulse and the material could lead to technologically important advances. Pulse shaping could then be used to optimize the desired outcome. The scope of our research program is to develop robust and efficient strategies to control nonlinear laser-matter interactions using ultrashort shaped pulses in gas and condensed phases. Our systematic research has led to significant developments in a number of areas relevant to the AMO Physics group at DOE, among them: generation of ultrashort phase shaped pulses, coherent control and manipulation of quantum mechanical states in gas and condensed phases, behavior of isolated molecules under intense laser fields, behavior of condensed phase matter under intense laser field and implications on micromachining with ultrashort pulses, coherent control of nanoparticles their surface plasmon waves and their nonlinear optical behavior, and observation of coherent Coulomb explosion processes at 10 16 W/cm 2 . In all, the research has resulted in 36 publications (five journal covers) and nine invention disclosures, five of which have continued on to patenting

  8. Ultrashort pulse energy distribution for propulsion in space

    Science.gov (United States)

    Bergstue, Grant Jared

    This thesis effort focuses on the development of a novel, space-based ultrashort pulse transmission system for spacecraft. The goals of this research include: (1) ultrashort pulse transmission strategies for maximizing safety and efficiency; (2) optical transmission system requirements; (3) general system requirements including control techniques for stabilization; (4) optical system requirements for achieving effective ablative propulsion at the receiving spacecraft; and (5) ultrashort pulse transmission capabilities required for future missions in space. A key element of the research is the multiplexing device required for aligning the ultrashort pulses from multiple laser sources along a common optical axis for transmission. This strategy enables access to the higher average and peak powers required for useful missions in space.

  9. Progress in Ultrafast Intense Laser Science VIII

    CERN Document Server

    Nisoli, Mauro; Hill, Wendell; III, III

    2012-01-01

    The PUILS series delivers up-to-date reviews of progress in Ultrafast Intense Laser Science, a newly emerging interdisciplinary research field spanning atomic and molecular physics, molecular science and optical science which has been stimulated by the recent developments in ultrafast laser technologies. Each volume compiles peer-reviewed articles authored by researchers at the forefront of each their own subfields of UILS. Every chapter opens with an overview of the topics to be discussed, so that researchers unfamiliar to the subfield as well as graduate students can grasp the importance and attractions of the research topic at hand. These are followed by reports of cutting-edge discoveries. This eighth volume covers a broad range of topics from this interdisciplinary research field, focusing on molecules interacting with ultrashort and intense laser fields, advanced technologies for the characterization of ultrashort laser pulses and their applications, laser plasma formation and laser acceleration.

  10. Spin and radiation in intense laser fields

    International Nuclear Information System (INIS)

    Walser, M.W.; Urbach, D.J.; Hatsagortsyan, K.Z.; Hu, S.X.; Keitel, C.H.

    2002-01-01

    The spin dynamics and its reaction on the particle motion are investigated for free and bound electrons in intense linearly polarized laser fields. Employing both classical and quantum treatments we analytically evaluate the spin oscillation of free electrons in intense laser fields and indicate the effect of spin-orbit coupling on the motion of the electron. In Mott scattering an estimation for the spin oscillation is derived. In intense laser ion dynamics spin signatures are studied in detail with emphasis on high-order harmonic generation in the tunneling regime. First- and second-order calculations in the ratio of electron velocity and the speed of light show spin signatures in the radiation spectrum and spin-orbit effects in the electron polarization

  11. Cyclotron resonance cooling by strong laser field

    International Nuclear Information System (INIS)

    Tagcuhi, Toshihiro; Mima, Kunioka

    1995-01-01

    Reduction of energy spread of electron beam is very important to increase a total output radiation power in free electron lasers. Although several cooling systems of particle beams such as a stochastic cooling are successfully operated in the accelerator physics, these cooling mechanisms are very slow and they are only applicable to high energy charged particle beams of ring accelerators. We propose here a new concept of laser cooling system by means of cyclotron resonance. Electrons being in cyclotron motion under a strong magnetic field can resonate with circular polarized electromagnetic field, and the resonance take place selectively depending on the velocity of the electrons. If cyclotron frequency of electrons is equal to the frequency of the electromagnetic field, they absorb the electromagnetic field energy strongly, but the other electrons remain unchanged. The absorbed energy will be converted to transverse kinetic energy, and the energy will be dumped into the radiation energy through bremastrahlung. To build a cooling system, we must use two laser beams, where one of them is counter-propagating and the other is co-propagating with electron beam. When the frequency of the counter-propagating laser is tuned with the cyclotron frequency of fast electrons and the co-propagating laser is tuned with the cyclotron frequency of slow electrons, the energy of two groups will approach and the cooling will be achieved. We solve relativistic motions of electrons with relativistic radiation dumping force, and estimate the cooling rate of this mechanism. We will report optimum parameters for the electron beam cooling system for free electron lasers

  12. Laser heating of field-reversed configurations

    International Nuclear Information System (INIS)

    Carson, R.S.; Vlases, G.C.

    1983-01-01

    The experimental facility is a 21-cm-long solenoid with a 5.5-cm bore. The 4-cm ID quartz tube is filled with slowly flowing H 2 to 0.5-3.0 torr. Fields up to 6.5 T in 3.7 μsec are produced, with reverse-bias fields up -1.9 T. Preionization is by 40kA axial discharge 4.5 μsec before field-reversal is begun. The CO 2 laser used produces 300 to 400 J in 2 μsec, in an annular beam that can be defocused for preheating the outer edges of the plasma, or focused tightly for central-column heating and beam propagation during formation. The focusing system includes a return mirror for multiple passing of the laser energy. Diagnostics include compensated, diamagnetic flux loops, internal field probes, cross-tube and axial interferometers, fast photography, and spectroscopy

  13. Ambient fields generated by a laser spark

    Czech Academy of Sciences Publication Activity Database

    Rohlena, Karel; Mašek, Martin

    2016-01-01

    Roč. 61, č. 2 (2016), s. 119-124 ISSN 0029-5922 R&D Projects: GA MŠk(CZ) LD14089; GA MŠk(CZ) LG13031 Institutional support: RVO:68378271 Keywords : laser spark * radiation chemistry * field generation Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.760, year: 2016

  14. Phosphorene in ultrafast laser field

    Science.gov (United States)

    Nematollahi, Fatemeh; Apalkov, Vadym; Stockman, Mark I.

    2018-01-01

    We study numerically interaction of phosphorene monolayer with a strong femtosecond-long optical pulse. For such a short pulse, the electron dynamics is coherent and can be described by the time-dependent Schrödinger equation. Strong optical field of the pulse causes redistribution of electrons between the conduction and valence bands. Such interband dynamics is highly irreversible, i.e., the conduction band population after the pulse is large and comparable to the maximum conduction band during the pulse. The conduction band population distribution in the reciprocal space shows high contrast hot spots, which are due to large interband coupling at the Γ point. The optical pulse also causes the net charge transfer through the phosphorene monolayer. The direction of the transfer is the same as the direction of the field maximum.

  15. Ultrafast transmission electron microscopy using a laser-driven field emitter: Femtosecond resolution with a high coherence electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Feist, Armin; Bach, Nora; Rubiano da Silva, Nara; Danz, Thomas; Möller, Marcel; Priebe, Katharina E.; Domröse, Till; Gatzmann, J. Gregor; Rost, Stefan; Schauss, Jakob; Strauch, Stefanie; Bormann, Reiner; Sivis, Murat; Schäfer, Sascha, E-mail: sascha.schaefer@phys.uni-goettingen.de; Ropers, Claus, E-mail: claus.ropers@uni-goettingen.de

    2017-05-15

    We present the development of the first ultrafast transmission electron microscope (UTEM) driven by localized photoemission from a field emitter cathode. We describe the implementation of the instrument, the photoemitter concept and the quantitative electron beam parameters achieved. Establishing a new source for ultrafast TEM, the Göttingen UTEM employs nano-localized linear photoemission from a Schottky emitter, which enables operation with freely tunable temporal structure, from continuous wave to femtosecond pulsed mode. Using this emission mechanism, we achieve record pulse properties in ultrafast electron microscopy of 9 Å focused beam diameter, 200 fs pulse duration and 0.6 eV energy width. We illustrate the possibility to conduct ultrafast imaging, diffraction, holography and spectroscopy with this instrument and also discuss opportunities to harness quantum coherent interactions between intense laser fields and free-electron beams. - Highlights: • First implementation of an ultrafast TEM employing a nanoscale photocathode. • Localized single photon-photoemission from nanoscopic field emitter yields low emittance ultrashort electron pulses. • Electron pulses focused down to ~9 Å, with a duration of 200 fs and an energy width of 0.6 eV are demonstrated. • Quantitative characterization of ultrafast electron gun emittance and brightness. • A range of applications of high coherence ultrashort electron pulses is shown.

  16. Steering neutral atoms in strong laser fields

    International Nuclear Information System (INIS)

    Eilzer, S; Eichmann, U

    2014-01-01

    The seminal strong-field tunnelling theory introduced by L V Keldysh plays a pivotal role. It has shaped our understanding of atomic strong-field processes, where it represents the first step in complex ionisation dynamics and provides reliable tunnelling rates. Tunnelling rates, however, cannot be necessarily equated with ionisation rates. Taking into account the electron dynamics in the Coulomb potential following the tunnelling process, the process of frustrated tunnelling ionisation has been found to lead to excited Rydberg atoms. Here, we excite He atoms in the strong-field tunnelling regime into Rydberg states. A high percentage of these Rydberg atoms survive in high intensity laser fields. We exploit this fact together with their high polarisability to kinematically manipulate the Rydberg atoms with a second elliptically polarised focused strong laser field. By varying the spatial overlap of the two laser foci, we are able to selectively control the deflection of the Rydberg atoms. The results of semi-classical calculations, which are based on the frustrated tunnelling model and on the ponderomotive acceleration, are in accord with our experimental data. (paper)

  17. Variational analysis of self-focusing of intense ultrashort pulses in gases

    International Nuclear Information System (INIS)

    Arevalo, E.; Becker, A.

    2005-01-01

    By using perturbation theory we derive an expression for the electrical field of a Gaussian laser beam propagating in a gas medium. This expression is used as a trial solution in a variational method to get quasianalytical solutions for the width, intensity, and self-focusing distance. The approximation gives a better agreement with results of numerical simulations for a broad range of values of the input power than previous analytical results available in the literature. The results apply in the case of ultrashort pulses too

  18. Ultra fast imaging of a laser wake field accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Saevert, Alexander; Schnell, Michael; Nicolai, Maria; Reuter, Maria; Schwab, Matthew B.; Moeller, Max [Friedrich-Schiller-Universitaet, Jena (Germany); Mangles, Stuart P.D.; Cole, Jason M.; Poder, Kristjan; Najmudin, Zulfikar [The John Adams Institute Imperial College, London (United Kingdom); Jaeckel, Oliver; Paulus, Gerhard G.; Spielmann, Christian; Kaluza, Malte C. [Friedrich-Schiller-Universitaet, Jena (Germany); Helmholtz Institut Jena, Jena (Germany)

    2014-07-01

    Ultra intense laser pulses are known to excite plasma waves with a relativistic phase velocity. By harnessing these waves it is possible to generate quasi-monoenergetic, ultra-short electron pulses with kinetic energies from 0.1 to 2 GeV by guiding the laser pulse over several Rayleigh lengths. To further improve the stability of these particle pulses and ultimately to be able to tailor the energy spectrum toward their suitability for various applications, the physics underlying the different acceleration scenarios need to be understood as completely as possible. To be able to resolve the acceleration process diagnostics well-suited for this plasma environment need to be designed and realized. By using sub-10 fs probe pulses we were able to freeze the transient accelerating structure in the plasma. We will present the first results of an experiment which was carried out with the 30 TW JETi Laser and a few cycle probe pulse at the Institute of Optics and Quantum Electronics Jena. The resulting snapshots show unprecedented details from the laser plasma interaction and allow a direct comparison to computer simulations.

  19. Curved laser microjet in near field.

    Science.gov (United States)

    Kotlyar, Victor V; Stafeev, Sergey S; Kovalev, Alexey A

    2013-06-20

    With the use of the finite-difference time-domain-based simulation and a scanning near-field optical microscope that has a metal cantilever tip, the diffraction of a linearly polarized plane wave of wavelength λ by a glass corner step of height 2λ is shown to generate a low divergence laser jet of a root-parabolic form: over a distance of 4.7λ on the optical axis, the beam path is shifted by 2.1λ. The curved laser jet of the FWHM length depth of focus=9.5λ has the diameter FWHM=1.94λ over the distance 5.5λ, and the intensity maximum is 5 times higher than the incident wave intensity. The discrepancy between the analytical and the experimental results amounts to 11%.

  20. Study of helium and beryllium atoms with strong and short laser field; Etude des atomes d'helium et de beryllium en champ laser intense et bref

    Energy Technology Data Exchange (ETDEWEB)

    Laulan, St

    2004-09-01

    We present a theoretical study of the interaction between a two-active electron atom and an intense (10{sup 14} to 10{sup 15} W/cm{sup 2}) and ultrashort (from a few 10{sup -15} to a few 10{sup -18} s) laser field. In the first part, we describe the current experimental techniques able to produce a coherent radiation of high power in the UV-XUV regime and with femtosecond time duration. A theoretical model of a laser pulse is defined with such characteristics. Then, we develop a numerical approach based on B-spline functions to describe the atomic structure of the two-active electron system. A spectral non perturbative method is proposed to solve the time dependent Schroedinger equation. We focalize our attention on the description of the atomic double continuum states. Finally, we expose results on the double ionization of helium and beryllium atoms with intense and short laser field. In particular, we present total cross section calculations and ejected electron energy distributions in the double continuum after one- and two-photon absorption. (author)

  1. Spectral coherent combination of ultrashort pulses

    International Nuclear Information System (INIS)

    Ursescu, D.; Banici, R.; Ionel, L.; Rusen, L.; Sandel, S.; Blanaru, C.

    2010-01-01

    Complete text of publication follows. The coherent beam combination was chosen in several laser systems, including ELI, as a solution to increase the final attainable intensity. However, the coherent beam combination it is also a difficult technique while it has to combine coherently in space and in time several beams amplified in different laser chains. That means in particular that the beams should be in phase in every point of the amplified beam so the spatial beam profiling techniques have to be mastered with high accuracy for all the combined beams. Here it is proposed an alternative coherent beam combination than the use of identical ultrashort pulses. The idea is to spectrally combine laser pulses with complementary spectra. Collinear and non-collinear approaches have been modelled. Ongoing experimental development, including the demonstration of the rephasing for two spectrally complementary ultrashort pulses will be presented. Acknowledgements. The research leading to these results has received funding from the EC's Seventh Framework Programme (LASERLAB-EUROPE, grant agreement no. 228334).

  2. Reversed Cherenkov emission of terahertz waves from an ultrashort laser pulse in a sandwich structure with nonlinear core and left-handed cladding.

    Science.gov (United States)

    Bakunov, M I; Mikhaylovskiy, R V; Bodrov, S B; Luk'yanchuk, B S

    2010-01-18

    We propose a scheme for an experimental verification of the reversed Cherenkov effect in left-handed media. The scheme uses optical-to-terahertz conversion in a planar sandwichlike structure that consists of a nonlinear core cladded with a material that exhibits left-handedness at terahertz frequencies. The focused into a line femtosecond laser pulse propagates in the core and emits Cherenkov wedge of terahertz waves in the cladding. We developed a theory that describes terahertz generation in such a structure and calculated spatial distribution of the generated terahertz field, its energy spectrum, and optical-to-terahertz conversion efficiency. The proposed structure can be a useful tool for characterization of the electromagnetic properties of metamaterials in the terahertz frequency range.

  3. Laser Processing and Chemistry

    CERN Document Server

    Bäuerle, Dieter

    2011-01-01

    This book gives an overview of the fundamentals and applications of laser-matter interactions, in particular with regard to laser material processing. Special attention is given to laser-induced physical and chemical processes at gas-solid, liquid-solid, and solid-solid interfaces. Starting with the background physics, the book proceeds to examine applications of lasers in “standard” laser machining and laser chemical processing (LCP), including the patterning, coating, and modification of material surfaces. This fourth edition has been enlarged to cover the rapid advances in the understanding of the dynamics of materials under the action of ultrashort laser pulses, and to include a number of new topics, in particular the increasing importance of lasers in various different fields of surface functionalizations and nanotechnology. In two additional chapters, recent developments in biotechnology, medicine, art conservation and restoration are summarized. Graduate students, physicists, chemists, engineers, a...

  4. Real-time full-field characterization of transient dissipative soliton dynamics in a mode-locked laser

    Science.gov (United States)

    Ryczkowski, P.; Närhi, M.; Billet, C.; Merolla, J.-M.; Genty, G.; Dudley, J. M.

    2018-04-01

    Dissipative solitons are remarkably localized states of a physical system that arise from the dynamical balance between nonlinearity, dispersion and environmental energy exchange. They are the most universal form of soliton that can exist, and are seen in far-from-equilibrium systems in many fields, including chemistry, biology and physics. There has been particular interest in studying their properties in mode-locked lasers, but experiments have been limited by the inability to track the dynamical soliton evolution in real time. Here, we use simultaneous dispersive Fourier transform and time-lens measurements to completely characterize the spectral and temporal evolution of ultrashort dissipative solitons as their dynamics pass through a transient unstable regime with complex break-up and collisions before stabilization. Further insight is obtained from reconstruction of the soliton amplitude and phase and calculation of the corresponding complex-valued eigenvalue spectrum. These findings show how real-time measurements provide new insights into ultrafast transient dynamics in optics.

  5. Ultrafast lasers for precise and corrosion free marking on chirurgical steels

    Science.gov (United States)

    Neugebauer, Christoph; Aalderink, Dennis; Maurer, Erich; Faisst, Birgit; Budnicki, Aleksander

    2017-02-01

    The unique properties of ultrashort laser pulses and the decrease of invest pave the way to numerous novel applications. Even in the very price sensitive field of laser marking, ultrashort laser can compete due to a new cost structure and remarkable properties of the marking results. In this study we concentrated on industrial marking of medical equipment by using IR ultrashort lasers and compared the results with common marking laser systems. We demonstrate the benefits of ultrashort lasers marking on chirurgical devices, observing the influence of pulse energy, pulse duration, scanning velocity in respect to the visibility, corrosion resistance and long term durability under clinical conditions. Nowadays many parts and products are marked for the purpose of identification and traceability. One kind of laser marking is the well known annealing of stainless steel by nanosecond marking lasers. When annealing occurs a colored oxide layer grows due to the local heating of the material surface. Compared to the raw material, the annealed marking shows increased corrosion sensitivity. Regarding the traceability, the poor durability of the ns marking resulting in contrast reduction and the corrosion susceptibility are a huge problem. Therefore three different laser sources with ns-psfs pulse duration were observed. The focus rests on the realization of parameter studies (various lasers) and their effect on the corrosion and passivation behavior. Furthermore analysis of the oxide layers by use of EDX and XRD were performed to obtain further information on the composition and structure of the markings.

  6. Interaction between laser-produced plasma and guiding magnetic field

    International Nuclear Information System (INIS)

    Hasegawa, Jun; Takahashi, Kazumasa; Ikeda, Shunsuke; Nakajima, Mitsuo; Horioka, Kazuhiko

    2013-01-01

    Transportation properties of laser-produced plasma through a guiding magnetic field were examined. A drifting dense plasma produced by a KrF laser was injected into an axisymmetric magnetic field induced by permanent ring magnets. The plasma ion flux in the guiding magnetic field was measured by a Faraday cup at various distances from the laser target. Numerical analyses based on a collective focusing model were performed to simulate plasma particle trajectories and then compared with the experimental results. (author)

  7. Near-field mapping by laser ablation of PMMA coatings

    DEFF Research Database (Denmark)

    Fiutowski, J.; Maibohm, C.; Kostiucenko, O.

    2011-01-01

    The optical near-field of lithography-defined gold nanostructures, arranged into regular arrays on a gold film, is characterized via ablation of a polymer coating by laser illumination. The method utilizes femto-second laser pulses from a laser scanning microscope which induces electrical field...... that the different stages in the ablation process can be controlled and characterized making the technique suitable for characterizing optical near-fields of metal nanostructures....

  8. Source of ultra-short laser pulses at 1,55μm in vertical-external-cavity for linear optical sampling applications

    International Nuclear Information System (INIS)

    Khadour, A.

    2009-12-01

    The objectives of this thesis were, in a first step, to develop and implement VECSEL structures containing an active zone formed by GaAlInAs/InP quantum wells located at the anti-nodes of the resonant electric field, positioned on a Bragg mirror, all this being bonded to a substrate of good thermal conductivity. For this, we have designed structures optimizing the evacuation of heat generated in the active zone. This has greatly improved the VECSEL performances, especially their output power. The VECSEL performances were evaluated in a simple cavity with two mirrors (plane-concave). The second point was to develop and implement SESAM structures which, owing to their nonlinear characteristics, would allow a passively mode-locked laser operation. The structures contained InGaAsN/GaAs quantum wells. The studied parameters were the number of quantum wells, and the resonant or anti-resonant behavior of the structure. The linear and nonlinear optical characterizations were used to optimize the SESAM structure and estimate their performances. Finally, the compatibility between the VECSEL and SESAM structures, in terms of modulation depth and resonance wavelength, made it possible to obtain the passive mode locking operation. The obtained pulses show two different behaviors depending on the dispersion properties of the structures. With low dispersion, we have made the first demonstration of a passively mode-locked VECSEL at 1550 nm, operating at room temperature. An all-optical sampling device implementing the linear optical sampling technique using short laser pulses has been realized and tested. This device will allow displaying eye diagrams and constellation diagrams with an expected sensitivity around -20 dBm of average power. Testing the device allowed to visualize the acquisition of very high repetition rate signals (40 Gb/s). (author)

  9. Atomic processes in strong bichromatic elliptically polarized laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Odžak, S., E-mail: senad.odzak@gmail.com; Hasović, E.; Gazibegović-Busuladžić, A.; Čerkić, A., E-mail: anercerkic@yahoo.com; Fetić, B. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegovina); Kramo, A. [BHANSA, Aeronautical Meteorology Department, Kurta Schorka 36, 71000 Sarajevo (Bosnia and Herzegovina); Busuladžić, M. [Medical Faculty, University of Sarajevo, Čekaluša 90, 71000 Sarajevo (Bosnia and Herzegovina); Milošević, D. B. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegovina); Academy of Sciences and Arts of Bosnia and Herzegovina, Bistrik 7, 71000 Sarajevo (Bosnia and Herzegovina); Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin (Germany)

    2016-03-25

    Nonlinear quantum-mechanical phenomena in strong laser fields, such as high-order harmonic generation (HHG) and above-threshold ionization (ATI) are significantly modified if the applied laser field is bichromatic and/or elliptically polarized. Numerical results obtained within the strong-field approximation are presented for two special cases. We show results for HHG by plasma ablation in a bichromatic linearly polarized laser field. We also consider the ATI process in bicircular field which consists of two coplanar counter-rotating circularly polarized fields.

  10. Imaging photoelectrons formed in strong laser fields

    International Nuclear Information System (INIS)

    Helm, H.; Dyer, M.J.; Saeed, M.; Huestis, D.L.

    1993-01-01

    An instrument capable of characterizing the angular correlation and energy distribution of products from photoionization of single atoms or molecules will be described. An external electric field is used to project individual charged particles generated in multiphoton ionization from the focal volume onto two-dimensional detectors. Digital images are recorded for each laser shot and summed. These images provide a direct view of the angular nodal plants of the photoelectrons and they can be analyzed to represent the spatial and energy distributions in the form of a polar plot, f(E,Θ). We discuss the application of this instrument to short pulse photoionization of rare gases and molecular hydrogen at visible and UV wavelengths at intensities ranging from 10 13 to 10 15 W/cm 2

  11. Radial focusing and energy compression of a laser-produced proton beam by a synchronous rf field

    Directory of Open Access Journals (Sweden)

    Masahiro Ikegami

    2009-06-01

    Full Text Available The dynamics of a MeV laser-produced proton beam affected by a radio frequency (rf electric field has been studied. The proton beam was emitted normal to the rear surface of a thin polyimide target irradiated with an ultrashort pulsed laser with a power density of 4×10^{18}  W/cm^{2}. The energy spread was compressed to less than 11% at the full width at half maximum (FWHM by an rf field. Focusing and defocusing effects of the transverse direction were also observed. These effects were analyzed and reproduced by Monte Carlo simulations. The simulation results show that the transversely focused protons had a broad continuous spectrum, while the peaks in the proton spectrum were defocused. Based on this new information, we propose that elimination of the continuous energy component of laser-produced protons is possible by utilizing a focal length difference between the continuous spectral protons and the protons included in the spectral peak.

  12. Abstracts of the 5. International Conference on Lasers and their Applications

    International Nuclear Information System (INIS)

    1985-01-01

    New results have been presented in the fields of laser physics and laser applications including the development of new laser light sources, new laser frequencies in the UV and VUV spectral regions using anti-Stokes Raman scattering, nonlinear optical effects for the formation of ultrashort optical pulses, laser spectroscopy, collisionless multiphoton excitation processes using molecular beams, selective generation of free radicals by laser, laser applications in medicine, plasma diagnostics analysing X-ray spectra for studying laser fusion problems, coherence properties in phase-sampling interferometric techniques, and fundamental problems in quantum physics and nonlinear processes

  13. Atomic stabilization in superintense laser fields

    International Nuclear Information System (INIS)

    Gavrila, Mihai

    2002-01-01

    Atomic stabilization is a highlight of superintense laser-atom physics. A wealth of information has been gathered on it; established physical concepts have been revised in the process; points of contention have been debated. Recent technological breakthroughs are opening exciting perspectives of experimental study. With this in mind, we present a comprehensive overview of the phenomenon. We discuss the two forms of atomic stabilization identified theoretically. The first one, 'quasistationary (adiabatic) stabilization' (QS), refers to the limiting case of plane-wave monochromatic radiation. QS characterizes the fact that ionization rates, as calculated from single-state Floquet theory, decrease with intensity (possibly in an oscillatory manner) at high values of the field. We present predictions for QS from various forms of Floquet theory: high frequency (that has led to its discovery and offers the best physical insight), complex scaling, Sturmian, radiative close coupling and R-matrix. These predictions all agree quantitatively, and high-accuracy numerical results have been obtained for hydrogen. Predictions from non-Floquet theories are also discussed. Thereafter, we analyse the physical origin of QS. The alternative form of stabilization, 'dynamic stabilization' (DS), is presented next. This expresses the fact that the ionization probability at the end of a laser pulse of fixed shape and duration does not approach unity as the peak intensity is increased, but either starts decreasing with the intensity (possibly in an oscillatory manner), or flattens out at a value smaller than unity. We review the extensive research done on one-dimensional models, that has provided valuable insights into the phenomenon; two- and three-dimensional models are also considered. Full three-dimensional Coulomb calculations have encountered severe numerical handicaps in the past, and it is only recently that a comprehensive mapping of DS could be made for hydrogen. An adiabatic

  14. Modeling short-pulse laser excitation of dielectric materials

    DEFF Research Database (Denmark)

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

    2014-01-01

    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...

  15. Control and dynamics of attosecond electron wave packets in strong laser fields

    International Nuclear Information System (INIS)

    Johnsson, P.; Remetter, T.; Varju, K.; L'Huillier; Lopez-Martens, R.; Valentin, C.; Balcou, P.; Kazamias, S.; Mauritsson, J.; Gaarde, M.B.; Schafer, K.J.; Mairess, Y.; Wabnitz, H.; Boutu, W.; Salieres, P.

    2005-01-01

    Full text: Trains of attosecond pulses, emerging from the phase-locking of high-order harmonics generated in a strong laser field are now being routinely produced and characterized in a few laser laboratories. Attosecond pulse trains (APTs) are flexible attosecond sources, since the amplitude and relative phase of the spectral components (the harmonics) can be tailored, allowing us to vary both the duration and the carrier frequency of the pulses. Attosecond pulses interacting with a gas of atoms generate electron wave packets (EWPs), which are temporally localized with approximately the same duration as the attosecond pulses. In contrast to the tunneling electron wave packets giving rise to processes such as high-order harmonic generation and above-threshold-ionization (ATI), the properties of these EWPs are inherited from the attosecond pulses through the single-photon ionization step. Thus the energy and temporal characteristics of the EWPs can be varied independently of the process under investigation, by controlling the properties of the attosecond pulses. This talk will describe two recent experiments done in Lund. First we report on the generation, compression and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. The APT is synthesized from the 13 th to 35 th harmonics of a 35 fs Ti:sapphire laser. The harmonics are generated by focusing the laser beam into a window-less gas cell, filled with argon. To achieve the required on-target attosecond pulses, the harmonics are filtered spatially, using a fixed aperture, and spectrally using aluminum filters. The aluminum filters also serve the purpose of compressing the attosecond pulses, using the negative group-delay dispersion of aluminum to compensate for the intrinsic positive chirp of the attosecond pulses. This experiment demonstrates a practical method for the synthesis and control of attosecond waveforms, and in this case the production of pulses

  16. 21 CFR 886.1360 - Visual field laser instrument.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Visual field laser instrument. 886.1360 Section 886.1360 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument...

  17. Synchronization and Characterization of an Ultra-Short Laser for Photoemission and Electron-Beam Diagnostics Studies at a Radio Frequency Photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, Timothy; Ruan, Jinhao; Piot, Philippe; Lumpkin, Alex

    2012-03-01

    A commercially-available titanium-sapphire laser system has recently been installed at the Fermilab A0 photoinjector laboratory in support of photoemission and electron beam diagnostics studies. The laser system is synchronized to both the 1.3-GHz master oscillator and a 1-Hz signal use to trigger the radiofrequency system and instrumentation acquisition. The synchronization scheme and performance are detailed. Long-term temporal and intensity drifts are identified and actively suppressed to within 1 ps and 1.5%, respectively. Measurement and optimization of the laser's temporal profile are accomplished using frequency-resolved optical gating.

  18. Non-vacuum, single-step conductive transparent ZnO patterning by ultra-short pulsed laser annealing of solution-deposited nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Daeho; Pan, Heng; Kim, Eunpa; Grigoropoulos, Costas P. [University of California, Department of Mechanical Engineering, Berkeley, CA (United States); Ko, Seung Hwan [Korea Advanced Institute of Science and Technology (KAIST), Department of Mechanical Engineering, Daejeon (Korea, Republic of); Park, Hee K. [AppliFlex LLC, Sunnyvale, CA (United States)

    2012-04-15

    A solution-processable, high-concentration transparent ZnO nanoparticle (NP) solution was successfully synthesized in a new process. A highly transparent ZnO thin film was fabricated by spin coating without vacuum deposition. Subsequent ultra-short-pulsed laser annealing at room temperature was performed to change the film properties without using a blanket high temperature heating process. Although the as-deposited NP thin film was not electrically conductive, laser annealing imparted a large conductivity increase and furthermore enabled selective annealing to write conductive patterns directly on the NP thin film without a photolithographic process. Conductivity enhancement could be obtained by altering the laser annealing parameters. Parametric studies including the sheet resistance and optical transmittance of the annealed ZnO NP thin film were conducted for various laser powers, scanning speeds and background gas conditions. The lowest resistivity from laser-annealed ZnO thin film was about 4.75 x 10{sup -2} {omega} cm, exhibiting a factor of 10{sup 5} higher conductivity than the previously reported furnace-annealed ZnO NP film and is even comparable to that of vacuum-deposited, impurity-doped ZnO films within a factor of 10. The process developed in this work was applied to the fabrication of a thin film transistor (TFT) device that showed enhanced performance compared with furnace-annealed devices. A ZnO TFT performance test revealed that by just changing the laser parameters, the solution-deposited ZnO thin film can also perform as a semiconductor, demonstrating that laser annealing offers tunability of ZnO thin film properties for both transparent conductors and semiconductors. (orig.)

  19. Fast magnetic-field annihilation in the relativistic collisionless regime driven by two ultrashort high-intensity laser pulses

    Czech Academy of Sciences Publication Activity Database

    Gu, Yanjun; Klimo, Ondřej; Kumar, D.; Liu, Y.; Singh, Sushil K.; Esirkepov, T.Z.; Bulanov, S.V.; Weber, Stefan A.; Korn, Georg

    2016-01-01

    Roč. 93, č. 1 (2016), 1-6, č. článku 013203. ISSN 1539-3755 R&D Projects: GA MŠk EF15_008/0000162 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : plasma * acceleration Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.288, year: 2014

  20. Magnetic Field Generation and Electron Acceleration in Relativistic Laser Channel

    International Nuclear Information System (INIS)

    Kostyukov, I.Yu.; Shvets, G.; Fisch, N.J.; Rax, J.M.

    2001-01-01

    The interaction between energetic electrons and a circularly polarized laser pulse inside an ion channel is studied. Laser radiation can be resonantly absorbed by electrons executing betatron oscillations in the ion channel and absorbing angular momentum from the laser. The absorbed angular momentum manifests itself as a strong axial magnetic field (inverse Faraday effect). The magnitude of this magnetic field is calculated and related to the amount of the absorbed energy. Absorbed energy and generated magnetic field are estimated for the small and large energy gain regimes. Qualitative comparisons with recent experiments are also made

  1. Laser-induced extreme magnetic field in nanorod targets

    Science.gov (United States)

    Lécz, Zsolt; Andreev, Alexander

    2018-03-01

    The application of nano-structured target surfaces in laser-solid interaction has attracted significant attention in the last few years. Their ability to absorb significantly more laser energy promises a possible route for advancing the currently established laser ion acceleration concepts. However, it is crucial to have a better understanding of field evolution and electron dynamics during laser-matter interactions before the employment of such exotic targets. This paper focuses on the magnetic field generation in nano-forest targets consisting of parallel nanorods grown on plane surfaces. A general scaling law for the self-generated quasi-static magnetic field amplitude is given and it is shown that amplitudes up to 1 MT field are achievable with current technology. Analytical results are supported by three-dimensional particle-in-cell simulations. Non-parallel arrangements of nanorods has also been considered which result in the generation of donut-shaped azimuthal magnetic fields in a larger volume.

  2. Time-resolved investigations of the fragmentation dynamic of H2 (D2) in and with ultra-short laser pulses

    International Nuclear Information System (INIS)

    Ergler, T.

    2006-01-01

    In course of this work pump-probe experiments aimed to study ultrafast nuclear motion in H 2 (D 2 ) fragmentation by intense 6-25 fs laser pulses have been carried out. In order to perform time-resolved measurements, a Mach-Zehnder interferometer providing two identical synchronized laser pulses with the time-delay variable from 0 to 3000 fs with 300 as accuracy and long-term stability has been built. The laser pulses at the intensities of up to 10 15 W/cm 2 were focused onto a H 2 (D 2 ) molecular beam leading to the ionization or dissociation of the molecules, and the momenta of all charged reactions fragments were measured with a reaction microscope. With 6-7 fs pulses it was possible to probe the time evolution of the bound H + 2 (D + 2 ) nuclear wave packet created by the first (pump) laser pulse, fragmenting the molecule with the second (probe) pulse. A fast delocalization, or ''collapse'', and subsequent ''revival'' of the vibrational wave packet have been observed. In addition, the signatures of the ground state vibrational excitation in neutral D 2 molecule have been found, and the dominance of a new, purely quantum mechanical wave packet preparation mechanism (the so-called ''Lochfrass'') has been proved. In the experiments with 25 fs pulses the theoretically predicted enhancement of the ionization probability for the dissociating H + 2 molecular ion at large internuclear distances has been detected for the first time. (orig.)

  3. Instability of stationary lasing and self-starting mode locking in external-cavity semiconductor lasers

    International Nuclear Information System (INIS)

    Smetanin, Igor V; Vasil'ev, Petr P

    2009-01-01

    Parameters of external-cavity semiconductor lasers, when the stationary lasing becomes unstable, were analysed within the framework of a theoretical model of self-starting mode locking. In this case, a train of ultrashort pulses can be generated due to intrinsic nonlinearities of the laser medium. A decisive role of the transverse optical field nonuniformity, pump rate, and gain spectral bandwidth in the development of the instability of stationary lasing was demonstrated. (control of laser radiation parameters)

  4. Confinement of laser plasma expansion with strong external magnetic field

    Science.gov (United States)

    Tang, Hui-bo; Hu, Guang-yue; Liang, Yi-han; Tao, Tao; Wang, Yu-lin; Hu, Peng; Zhao, Bin; Zheng, Jian

    2018-05-01

    The evolutions of laser ablation plasma, expanding in strong (∼10 T) transverse external magnetic field, were investigated in experiments and simulations. The experimental results show that the magnetic field pressure causes the plasma decelerate and accumulate at the plasma-field interface, and then form a low-density plasma bubble. The saturation size of the plasma bubble has a scaling law on laser energy and magnetic field intensity. Magnetohydrodynamic simulation results support the observation and find that the scaling law (V max ∝ E p /B 2, where V max is the maximum volume of the plasma bubble, E p is the absorbed laser energy, and B is the magnetic field intensity) is effective in a broad laser energy range from several joules to kilo-joules, since the plasma is always in the state of magnetic field frozen while expanding. About 15% absorbed laser energy converts into magnetic field energy stored in compressed and curved magnetic field lines. The duration that the plasma bubble comes to maximum size has another scaling law t max ∝ E p 1/2/B 2. The plasma expanding dynamics in external magnetic field have a similar character with that in underdense gas, which indicates that the external magnetic field may be a feasible approach to replace the gas filled in hohlraum to suppress the wall plasma expansion and mitigate the stimulated scattering process in indirect drive ignition.

  5. Adiabatic pair creation in heavy-ion and laser fields

    International Nuclear Information System (INIS)

    Pickl, P.; Durr, D.

    2008-01-01

    The planned generation of lasers and heavy-ion colliders renews the hope to see electron-positron pair creation in strong classical fields. This old prediction is usually referred to as spontaneous pair creation. We observe that both heavy-ion collisions and pair creation in strong laser fields, are instances of the theory of adiabatic pair creation. We shall present the theory, thereby correcting earlier results. We give the momentum distribution of created pairs in overcritical fields. We discuss carefully the proposed experimental verifications and conclude that pure laser-based experiments are highly questionable. We propose a new experiment, joining laser fields and heavy ions, which may be feasible with present-day technology and which may indeed verify the theoretical prediction of adiabatic pair creation. Our presentation relies on recent rigorous works in mathematical physics. (authors)

  6. Controlling the high frequency response of H{sub 2} by ultra-short tailored laser pulses: A time-dependent configuration interaction study

    Energy Technology Data Exchange (ETDEWEB)

    Schönborn, Jan Boyke; Saalfrank, Peter; Klamroth, Tillmann, E-mail: klamroth@uni-potsdam.de [Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam-Golm (Germany)

    2016-01-28

    We combine the stochastic pulse optimization (SPO) scheme with the time-dependent configuration interaction singles method in order to control the high frequency response of a simple molecular model system to a tailored femtosecond laser pulse. For this purpose, we use H{sub 2} treated in the fixed nuclei approximation. The SPO scheme, as similar genetic algorithms, is especially suited to control highly non-linear processes, which we consider here in the context of high harmonic generation. Here, we will demonstrate that SPO can be used to realize a “non-harmonic” response of H{sub 2} to a laser pulse. Specifically, we will show how adding low intensity side frequencies to the dominant carrier frequency of the laser pulse and stochastically optimizing their contribution can create a high-frequency spectral signal of significant intensity, not harmonic to the carrier frequency. At the same time, it is possible to suppress the harmonic signals in the same spectral region, although the carrier frequency is kept dominant during the optimization.

  7. Instantaneous temperature field measurements using planar laser-induced fluorescence.

    Science.gov (United States)

    Seitzman, J M; Kychakoff, G; Hanson, R K

    1985-09-01

    A single-pulse, laser-induced-fluorescence diagnostic for the measurement of two-dimensional temperature fields in combustion flows is described. The method uses sheet illumination from a tunable laser to excite planar laserinduced fluorescence in a stable tracer molecule, seeded at constant mole fraction into the flow field. The temporal resolution of this technique is determined by the laser pulse length. Experimental results are presented for a rodstabilized, premixed methane-air flame, using the Q(1) (22) line of the nitric oxide A(2) Sigma(+) (v = 0) ? X(2)II((1/2))(v = 0) transition (lambda approximately 225.6 nm).

  8. Electronic properties of asymmetrical quantum dots dressed by laser field

    Energy Technology Data Exchange (ETDEWEB)

    Kibis, O.V. [Department of Applied and Theoretical Physics, Novosibirsk State Technical University, Karl Marx Avenue 20, 630092 Novosibirsk (Russian Federation); Slepyan, G.Ya.; Maksimenko, S.A. [Institute for Nuclear Problems, Belarus State University, Bobruyskaya St. 11, 220050 Minsk (Belarus); Hoffmann, A. [Institut fuer Festkoerperphysik, Technische Universitaet Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)

    2012-05-15

    In the present paper, we demonstrate theoretically that the strong non-resonant interaction between asymmetrical quantum dots (QDs) and a laser field results in harmonic oscillations of their band gap. It is shown that such oscillations change the spectrum of elementary electron excitations in QDs: in the absence of the laser pumping there is only one resonant electron frequency, but QDs dressed by the laser field have a set of electron resonant frequencies. One expects that this modification of elementary electron excitations in QDs can be observable in optical experiments. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Dense xenon nanoplasmas in intense laser fields

    International Nuclear Information System (INIS)

    Hilse, P.; Moll, M.; Schlanges, M.; Bornath, Th.

    2010-01-01

    Complete text of publication follows. One reason for the on-going interest in laser-cluster interactions is the efficient absorption of the radiation energy of near-infrared femtosecond laser pulses by clusters. Consequently, in laser-cluster experiments the emission of highly charged ions, very energetic electrons, higher harmonics, fast fragments as well at strong x-rays in the multi-keV range is observed. The cluster response is highly nonlinear. Different theoretical models and simulations indicate that resonant collective absorption plays a central role. The rapid expansion of irradiated clusters is essential as, at a certain time, the cluster reaches the density fulfilling the resonance condition. This can occur during a single pulse. A better control can be achieved by dual-pulse laser excitation with varying time delay between two pulses. A further optimization is possible by pulse shaping which is a modern tool in laser experiments. With pulse shaping, the dynamics of the system determined by heating, ionization and expansion can be specifically affected. For an understanding of the underlying physical processes in the dynamics of laser-cluster interaction, a theoretical description is presented using a genetic algorithm and basing on the relatively simple nanoplasma model. Recently, experiments as well as calculations were performed for silver clusters. Highly charged silver ions could be produced very efficiently with a pulse structure consisting of a smaller pre-pulse followed by a larger main pulse. The focus of the present contribution is on xenon clusters and their different behavior compared to metallic clusters as silver. Acknowledgements. This work was supported by the Deutsche Forschungsgemeinschaft via SFB 652.

  10. The suppression of radiation reaction and laser field depletion in laser-electron beam interaction

    Science.gov (United States)

    Ong, J. F.; Moritaka, T.; Takabe, H.

    2018-03-01

    The effects of radiation reaction (RR) have been studied extensively by using the interaction of ultraintense lasers with a counter-propagating relativistic electron. At the laser intensity at the order of 1023 W/cm2, the effects of RR are significant in a few laser periods for a relativistic electron. However, a laser at such intensity is tightly focused and the laser energy is usually assumed to be fixed. Then, the signal of RR and energy conservation cannot be guaranteed. To assess the effects of RR in a tightly focused laser pulse and the evolution of the laser energy, we simulated this interaction with a beam of 109 electrons by means of a Particle-In-Cell method. We observe that the effects of RR are suppressed due to the ponderomotive force and accompanied by a non-negligible amount of laser field energy reduction. This is because the ponderomotive force prevents the electrons from approaching the center of the laser pulse and leads to an interaction at the weaker field region. At the same time, the laser energy is absorbed through ponderomotive acceleration. Thus, the kinetic energy of the electron beam has to be carefully selected such that the effects of RR become obvious.

  11. Spin effects in strong-field laser-electron interactions

    International Nuclear Information System (INIS)

    Ahrens, S; Bauke, H; Müller, T-O; Villalba-Chávez, S; Müller, C

    2013-01-01

    The electron spin degree of freedom can play a significant role in relativistic scattering processes involving intense laser fields. In this contribution we discuss the influence of the electron spin on (i) Kapitza-Dirac scattering in an x-ray laser field of high intensity, (ii) photo-induced electron-positron pair production in a strong laser wave and (iii) multiphoton electron-positron pair production on an atomic nucleus. We show that in all cases under consideration the electron spin can have a characteristic impact on the process properties and their total probabilities. To this end, spin-resolved calculations based on the Dirac equation in the presence of an intense laser field are performed. The predictions from Dirac theory are also compared with the corresponding results from the Klein-Gordon equation.

  12. Pulsed-laser atom-probe field-ion microscopy

    International Nuclear Information System (INIS)

    Kellogg, G.L.; Tsong, T.T.

    1980-01-01

    A time-of-flight atom-probe field-ion microscope has been developed which uses nanosecond laser pulses to field evaporate surface species. The ability to operate an atom-probe without using high-voltage pulses is advantageous for several reasons. The spread in energy arising from the desorption of surface species prior to the voltage pulse attaining its maximum amplitude is eliminated, resulting in increased mass resolution. Semiconductor and insulator samples, for which the electrical resistivity is too high to transmit a short-duration voltage pulse, can be examined using pulsed-laser assisted field desorption. Since the electric field at the surface can be significantly smaller, the dissociation of molecular adsorbates by the field can be reduced or eliminated, permitting well-defined studies of surface chemical reactions. In addition to atom-probe operation, pulsed-laser heating of field emitters can be used to study surface diffusion of adatoms and vacancies over a wide range of temperatures. Examples demonstrating each of these advantages are presented, including the first pulsed-laser atom-probe (PLAP) mass spectra for both metals (W, Mo, Rh) and semiconductors (Si). Molecular hydrogen, which desorbs exclusively as atomic hydrogen in the conventional atom probe, is shown to desorb undissociatively in the PLAP. Field-ion microscope observations of the diffusion and dissociation of atomic clusters, the migration of adatoms, and the formation of vacancies resulting from heating with a 7-ns laser pulse are also presented

  13. Selective ablation of a titanium nitride film on tungsten carbide substrate using ultrashort laser pulses; Ablação seletiva de um filme de nitreto de titânio em substrato de carboneto de tungstênio utilizando laser de pulsos ultracurtos

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Eduardo Spinelli

    2017-07-01

    Surface coatings are applied to many cutting tools in the metallurgical industry in order to improve cutting efficiency and extend its useful life. In this work, tests were performed to remove the coating of titanium aluminum nitride (TiAlN) on tungsten carbide (WC-Co) pellets, using an ultrashort laser pulses beam. After determination of the damage thresholds of the film and the substrate, were ablated on the surface of the coating lines using two ablation conditions, it was initially operated on the low fluence regime for the film, and later on the low fluence regime of the substrate, far below the threshold of the film, applying high overlapping pulses. A laser induced breakdown spectroscopy (LIBS) system was set up to monitor the materials present in the plasma generated by the laser, but the system did not present sufficient sensitivity to read the low intensity of the plasma generated in the process and was not used. After the analysis of the traces by electron microscopy, optical profilometer and X-ray fluorescence spectroscopy, it was not possible to determine a safe process to carry out the selective removal of the film in question, however, due to the data obtained and observations of the results in some traces, new possibilities were raised, opening the discussion for future work. (author)

  14. Standard measurement procedures for the characterization of fs-laser optical components

    Science.gov (United States)

    Starke, Kai; Ristau, Detlev; Welling, Herbert

    2003-05-01

    Ultra-short pulse laser systems are considered as promising tools in the fields of precise micro-machining and medicine applications. In the course of the development of reliable table top laser systems, a rapid growth of ultra-short pulse applications could be observed during the recent years. The key for improving the performance of high power laser systems is the quality of the optical components concerning spectral characteristics, optical losses and the power handling capability. In the field of ultra-short pulses, standard measurement procedures in quality management have to be validated in respect to effects induced by the extremely high peak power densities. The present work, which is embedded in the EUREKA-project CHOCLAB II, is predominantly concentrated on measuring the multiple-pulse LIDT (ISO 11254-2) in the fs-regime. A measurement facility based on a Ti:Sapphire-CPA system was developed to investigate the damage behavior of optical components. The set-up was supplied with an improved pulse energy detector discriminating the influence of pulse-to-pulse energy fluctuations on the incidence of damage. Aditionally, a laser-calorimetric measurement facility determining the absorption (ISO 11551) utilizing a fs-Ti:Sapphire laser was accomplished. The investigation for different pulse durations between 130 fs and 1 ps revealed a drastic increase of absorption in titania coatings for ultra-short pulses.

  15. Emission and electron transitions in an atom interacting with an ultrashort electromagnetic pulse

    International Nuclear Information System (INIS)

    Matveev, V.I.

    2003-01-01

    Electron transitions and emission of an atom interacting with a spatially inhomogeneous ultrashort electromagnetic pulse are considered. The excitation and ionization probabilities are obtained as well as the spectra and cross sections of the reemission of such a pulse by atoms. By way of an example, one- and two-electron inelastic processes accompanying the interaction of ultrashort pulses with hydrogen- and helium-like atoms are considered. The developed technique makes it possible to take into account exactly the spatial nonuniformity of the ultrashort pulse field and photon momenta in the course of reemission

  16. High magnetic field generation for laser-plasma experiments

    International Nuclear Information System (INIS)

    Pollock, B. B.; Froula, D. H.; Davis, P. F.; Ross, J. S.; Fulkerson, S.; Bower, J.; Satariano, J.; Price, D.; Krushelnick, K.; Glenzer, S. H.

    2006-01-01

    An electromagnetic solenoid was developed to study the effect of magnetic fields on electron thermal transport in laser plasmas. The solenoid, which is driven by a pulsed power system supplying 30 kJ, achieves magnetic fields of 13 T. The field strength was measured on the solenoid axis with a magnetic probe and optical Zeeman splitting. The measurements agree well with analytical estimates. A method for optimizing the solenoid design to achieve magnetic fields exceeding 20 T is presented

  17. Proton radiography of magnetic field in laser produced plasma

    International Nuclear Information System (INIS)

    Le Pape, S.; Patel, P.; Chen, S.; Town, R.; Mackinnon, A.

    2009-01-01

    Electromagnetic fields generated by the interaction with plasmas of long-pulse laser beams relevant to inertial confinement fusion have been measure. A proton beam generated by the interaction of an ultra intense laser with a thin metallic foil is used to probe the B-fields. The proton beam then generated is temporally short (of the order of a ps), highly laminar and hence equivalent to a virtual point which makes it an ideal source for radiography. We have investigated, using face-on radiography, B fields at intensity around 10 14 W/cm 2 due to the non co-linearity of temperature and density gradients. (authors)

  18. Field-glass range finder with a semiconductor laser

    Science.gov (United States)

    Iwanejko, Leszek; Jankiewicz, Zdzislaw; Jarocki, Roman; Marczak, Jan

    1995-03-01

    This paper presents the project of a laboratory model of a field-glasses range-finger. The optical transmitter of the device contains a commercial pulse semiconductor laser which generates IR wavelength around 905 nm. Some of the technical parameters of this device are: a maximum range of up to 3 km; an accuracy of +/- 5 m, divergence of a laser beam of 1 mrad; a repetition rate of 1 kHz. Dichroic elements of the receiver ensure a capability of an optimization of a field of view, without the worsening of luminance and size of an observation field.

  19. Atomic excitation and acceleration in strong laser fields

    International Nuclear Information System (INIS)

    Zimmermann, H; Eichmann, U

    2016-01-01

    Atomic excitation in the tunneling regime of a strong-field laser–matter interaction has been recently observed. It is conveniently explained by the concept of frustrated tunneling ionization (FTI), which naturally evolves from the well-established tunneling picture followed by classical dynamics of the electron in the combined laser field and Coulomb field of the ionic core. Important predictions of the FTI model such as the n distribution of Rydberg states after strong-field excitation and the dependence on the laser polarization have been confirmed in experiments. The model also establishes a sound basis to understand strong-field acceleration of neutral atoms in strong laser fields. The experimental observation has become possible recently and initiated a variety of experiments such as atomic acceleration in an intense standing wave and the survival of Rydberg states in strong laser fields. Furthermore, the experimental investigations on strong-field dissociation of molecules, where neutral excited fragments after the Coulomb explosion of simple molecules have been observed, can be explained. In this review, we introduce the subject and give an overview over relevant experiments supplemented by new results. (paper)

  20. Ultra-short coherent terahertz radiation from ultra-short dips in electron bunches circulating in a storage ring

    International Nuclear Information System (INIS)

    Yamamoto, N.; Shimada, M.; Adachi, M.; Zen, H.; Tanikawa, T.; Taira, Y.; Kimura, S.; Hosaka, M.; Takashima, Y.; Takahashi, T.; Katoh, M.

    2011-01-01

    Terahertz (THz) coherent synchrotron radiation (CSR) is emitted not only from ultra-short electron bunches, but also from electron bunches with micro-structures. Formation of micro-structures at the sub-picosecond scale in electron bunches by a laser slicing technique is experimentally studied through observation of the THz CSR. The THz CSR spectrum was found to depend strongly on the intensity and the pulse width of the laser. The results agreed qualitatively with a numerical simulation. It was suggested that the evolution of the micro-structure during CSR emission is important under some experimental conditions.

  1. Bethe-Heitler pair creation in a bichromatic laser field

    International Nuclear Information System (INIS)

    Augustin, Sven

    2014-01-01

    Within this thesis, the non-linear creation of electron-positron pairs in the superposition of a nuclear Coulomb field and a two-colour laser field of high intensity is studied. Primarily, two complementary scenarios are investigated: On the one hand, if the two laser frequencies are commensurable, quantum interference may occur. This interference manifests in the total pair-creation rate and the angular distribution of the created particles, which are studied in the nuclear rest frame and the laboratory frame. Furthermore, the relative phase between the two laser modes allows to tune the strength of the terms arising from interference. Therefore, this parameter may be used to optimize the pair-creation yield. On the other hand, for incommensurable frequencies, a set-up of largely differing frequencies is considered. This way, a strong laser field in the non-perturbative regime assisted by a single highly-energetic γ-photon is described. Due to the assistance of the latter, a strong enhancement of the total pair-creation rate can be found depending on the laser intensity. Additionally, the influence of the γ-photon on the angular and energetic distribution of the created particles is investigated, again in the nuclear rest frame and the laboratory frame. Furthermore, the differences arising in the two former cases are directly compared by means of a continuous variation of the laser frequency ratio. This illustrates the strong modifications due to the interference in the commensurable case. Finally, for the special case of two modes with identical frequency, the total pair-creation rate is studied as a function of the ellipticity of the combined laser field. Here, the cases of a constant total field intensity and a constant maximum field intensity are compared.

  2. Creation of electron-positron plasma with superstrong laser field

    International Nuclear Information System (INIS)

    Narozhny, N.B.; Fedotov, A.M.

    2014-01-01

    We present a short review of recent progress in studying QED effects within the interaction of ultra-relativistic laser pulses with vacuum and e - e + plasma. Current development in laser technologies promises very rapid growth of laser intensities in the near future. Two exa-watt class facilities (ELI and XCELS, Russia) in Europe are already in the planning stage. Realization of these projects will make available a laser intensity of 10 26 W/cm 2 or even higher. Therefore, discussion of nonlinear optical effects in vacuum are becoming compelling for experimentalists and are currently gaining much attention. We show that, in spite of the fact that the expected field strength is still essentially less than E S = m 2 c 3 /eℎ = 1.32*10 16 V/cm, the nonlinear vacuum effects will be accessible for observation at the ELI and XCELS facilities. The most promising effect for observation is pair creation by a laser pulse in vacuum. It is shown, that at intensities of about 5*10 25 W/cm 2 , creation even of a single pair is accompanied by the development of an avalanche QED cascade. There exists a distinctive feature of the laser-induced cascades, as compared with the air showers arising due primarily to cosmic rays entering the atmosphere. In our case the laser field plays not only the role of a target (similar to a nucleus in the case of air showers) but is also responsible for the acceleration of slow particles. It is shown that the effect of pair creation imposes a natural limit for the attainable laser intensity and, apparently, the field strength E ≅ E S is not accessible for a pair-creating electromagnetic field at all. (authors)

  3. Classical origins of stabilization in circularly polarized laser fields

    International Nuclear Information System (INIS)

    Chism, Will; Choi, Dae-Il; Reichl, L. E.

    2000-01-01

    We investigate the interaction of a two-dimensional model atom with an intense, high-frequency circularly polarized laser pulse. As the laser intensity is increased, the ionization rate initially increases, then decreases dramatically, with the electron wave function developing an asymmetric ring form which rotates with the electric field. We provide evidence that this wave form is due to localization of the electron onto nonlinear classical structures. (c) 2000 The American Physical Society

  4. Theoretical femtosecond physics atoms and molecules in strong laser fields

    CERN Document Server

    Grossmann, Frank

    2018-01-01

    This textbook extends from the basics of femtosecond physics all the way to some of the latest developments in the field. In this updated edition, the chapter on laser-driven atoms is augmented by the discussion of two-electron atoms interacting with strong and short laser pulses, as well as by a review of ATI rings and low energy structures in photo-electron spectra. In the chapter on laser-driven molecules a discussion of 2D infrared spectroscopy is incorporated. Theoretical investigations of atoms and molecules interacting with pulsed lasers up to atomic field strengths on the order of 10^16 W/cm² are leading to an understanding of many challenging experimental discoveries. The presentation starts with a brief introduction to pulsed laser physics. The basis for the non-perturbative treatment of laser-matter interaction in the book is the time-dependent Schrödinger equation. Its analytical as well as numerical solution are laid out in some detail. The light field is treated classically and different possi...

  5. Attosecond Electron Wave Packet Dynamics in Strong Laser Fields

    International Nuclear Information System (INIS)

    Johnsson, P.; Remetter, T.; Varju, K.; L'Huillier, A.; Lopez-Martens, R.; Valentin, C.; Balcou, Ph.; Kazamias, S.; Mauritsson, J.; Gaarde, M. B.; Schafer, K. J.; Mairesse, Y.; Wabnitz, H.; Salieres, P.

    2005-01-01

    We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy (∼20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes

  6. Morphology of magnetic fields generated in laser-produced plasmas

    International Nuclear Information System (INIS)

    Boyd, T.J.M.; Cooke, D.

    1988-01-01

    Magnetic fields in the megagauss range have been measured in experiments on plasmas generated by irradiating targets with high power lasers. A study of the morphology of these self-generated fields is important not only for its intrinsic interest but for possible implications in laser--target physics. In this paper work on the numerical modeling of large magnetic fields generated in target experiments is reported. The results show generally satisfactory agreement with the fields measured experimentally both in terms of the magnitude of the peak fields and their morphology. In the numerical model the contribution from the Hall term in describing the evolution of the magnetic field is shown to be important especially in short pulse (≅100 psec) experiments

  7. Nonlinear evolutions of an ultra-intense ultra-short laser pulse in a rarefied plasma through a new quasi-static theory

    Science.gov (United States)

    Yazdanpanah, J.

    2018-02-01

    In this paper, we present a new description of self-consistent wake excitation by an intense short laser pulse, based on applying the quasi-static approximation (slow variations of the pulse-envelope) in the instantaneous Lorentz-boosted pulse co-moving frame (PCMF), and best verify our results through comparison with particle-in-cell simulations. According to this theory, the plasma motion can be treated perturbatively in the PCMF due to its high initial-velocity and produces a quasi-static wakefield in this frame. The pulse envelope, on the other hand, is governed by a form of the Schrödinger equation in the PCMF, in which the wakefield acts as an effective potential. In this context, pulse evolutions are characterized by local conservation laws resulted from this equation and subjected to Lorentz transformation into the laboratory frame. Using these conservation laws, precise formulas are obtained for spatiotemporal pulse evolutions and related wakefield variations at initial stages, and new equations are derived for instantaneous group velocity and carrier frequency. In addition, based on properties of the Schrödinger equation, spectral-evolutions of the pulse are described and the emergence of an anomalous dispersion branch with linear relation ω ≈ ck (c is the light speed) is predicted. Our results are carefully discussed versus previous publications and the significance of our approach is described by showing almost all suggestive definitions of group-velocity based on energy arguments fail to reproduce our formula and correctly describe the instantaneous pulse-velocity.

  8. Guiding-center equations for electrons in ultraintense laser fields

    International Nuclear Information System (INIS)

    Moore, J.E.; Fisch, N.J.

    1994-01-01

    The guiding-center equations are derived for electrons in arbitrarily intense laser fields also subject to external fields and ponderomotive forces. Exhibiting the relativistic mass increase of the oscillating electrons, a simple frame-invariant equation is shown to govern the behavior of the electrons for sufficiently weak background fields and ponderomotive forces. The parameter regime for which such a formulation is valid is made precise, and some predictions of the equation are checked by numerical simulation

  9. Optical properties of a multibarrier structure under intense laser fields

    Science.gov (United States)

    Ospina, D. A.; Akimov, V.; Mora-Ramos, M. E.; Morales, A. L.; Tulupenko, V.; Duque, C. A.

    2015-11-01

    Using the diagonalization method and within the effective mass and parabolic band approximations, the energy spectrum and the wave functions are investigated in biased multibarrier structure taking into account the effects of nonresonant intense laser fields. We calculated the optical properties from the susceptibility using a nonperturbative formalism recently reported. We study the changes in the intersubband optical absorption coefficients and refraction index for several values of the dressing laser parameter and for some specific values of the electric field applied along the growth direction of the heterostructure. It is concluded from our study that the peaks in the optical absorption spectrum have redshifts or blueshifts as a function of the laser parameter and the electric field. These parameters could be suitable tools for tuning the electronic and optical properties of the multibarrier structure.

  10. Numerical studies of pair creation in counterpropagating laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Ruf, Matthias

    2009-05-27

    Pair creation from vacuum induced by electromagnetic fields is probably one of the most intriguing phenomena in physics. If the fields are sufficiently strong, the QED vacuum become unstable. Due to the remarkable progress in laser technology during recent years an experimental investigation of pair creation by pure laser light is coming into reach. The focus of this thesis is on pair creation in counterpropagating laser beams. The pair creation probability is calculated employing the numerically obtained solutions of the Dirac equation. This numerical ansatz has the capability of calculating the momentum distribution of the created pairs in a single propagation, for pure time dependent field configurations. Furthermore, it allows to take the magnetic component of the laser fields into account, which is usually neglected. The latter strongly affects the creation process at high laser frequency. The involved numerical calculations are rather time consuming, therefore the second project of this thesis was to develop a highly efficient code for solving relativistic quantum mechanical problems. This is accomplished by adopting the split-operator method to the Klein-Gordon equation. Here the possibility arises to use parallel computing. However the corresponding spin-statistics becomes crucial in the case of pair creation, demonstrated in several examples. (orig.)

  11. Electron acceleration by laser produced wake field: Pulse shape effect

    Science.gov (United States)

    Malik, Hitendra K.; Kumar, Sandeep; Nishida, Yasushi

    2007-12-01

    Analytical expressions are obtained for the longitudinal field (wake field: Ex), density perturbations ( ne') and the potential ( ϕ) behind a laser pulse propagating in a plasma with the pulse duration of the electron plasma period. A feasibility study on the wake field is carried out with Gaussian-like (GL) pulse, rectangular-triangular (RT) pulse and rectangular-Gaussian (RG) pulse considering one-dimensional weakly nonlinear theory ( ne'/n0≪1), and the maximum energy gain acquired by an electron is calculated for all these three types of the laser pulse shapes. A comparative study infers that the RT pulse yields the best results: In its case maximum electron energy gain is 33.5 MeV for a 30 fs pulse duration whereas in case of GL (RG) pulse of the same duration the gain is 28.6 (28.8)MeV at the laser frequency of 1.6 PHz and the intensity of 3.0 × 10 18 W/m 2. The field of the wake and hence the energy gain get enhanced for the higher laser frequency, larger pulse duration and higher laser intensity for all types of the pulses.

  12. Numerical studies of pair creation in counterpropagating laser fields

    International Nuclear Information System (INIS)

    Ruf, Matthias

    2009-01-01

    Pair creation from vacuum induced by electromagnetic fields is probably one of the most intriguing phenomena in physics. If the fields are sufficiently strong, the QED vacuum become unstable. Due to the remarkable progress in laser technology during recent years an experimental investigation of pair creation by pure laser light is coming into reach. The focus of this thesis is on pair creation in counterpropagating laser beams. The pair creation probability is calculated employing the numerically obtained solutions of the Dirac equation. This numerical ansatz has the capability of calculating the momentum distribution of the created pairs in a single propagation, for pure time dependent field configurations. Furthermore, it allows to take the magnetic component of the laser fields into account, which is usually neglected. The latter strongly affects the creation process at high laser frequency. The involved numerical calculations are rather time consuming, therefore the second project of this thesis was to develop a highly efficient code for solving relativistic quantum mechanical problems. This is accomplished by adopting the split-operator method to the Klein-Gordon equation. Here the possibility arises to use parallel computing. However the corresponding spin-statistics becomes crucial in the case of pair creation, demonstrated in several examples. (orig.)

  13. Strong magnetic field generation in laser plasma

    International Nuclear Information System (INIS)

    Nakarmi, J.J.; Jha, L.N.

    1996-12-01

    An attempt has been made to solve the magnetic field evolution equation by using Green function and taking convective, diffusion and nabla n x nabla T as a dominant source term. The maximum magnetic field is obtained to be an order of megagauss. (author). 14 refs, 1 fig

  14. Intense, ultrashort light and dense, hot matter

    Indian Academy of Sciences (India)

    This article presents an overview of the physics and applications of the interaction of high intensity laser light with matter. It traces the crucial advances that have occurred over the past few decades in laser technology and nonlinear optics and then discusses physical phenomena that occur in intense laser fields and their ...

  15. Development of all solid-state, high average power ultra-short pulse laser for X-ray generation. High average power CPA system and wavefront control of ultra short laser pulse

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

    We developed a prototype CPA laser system which is pumped by a all solid-state Nd:YAG laser. In a preliminary experiment, the output energy of 52mJ before compression was obtained when the pumping energy was 250mJ. To compensate the wavefront distortion, an adaptive optics has been developed. By using this wavefront control system, the laser beam with the distortion of 0.15{lambda} was obtained. (author)

  16. Laser terahertz emission microscopy with near-field probes

    DEFF Research Database (Denmark)

    Pedersen, Pernille Klarskov; Mittleman, Daniel M.

    2016-01-01

    Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm.......Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm....

  17. Laser ablation of titanium in liquid in external electric field

    Energy Technology Data Exchange (ETDEWEB)

    Serkov, A.A. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); The Federal State Educational Institution of Higher Professional Education, “Moscow Institute of Physics and Technology (State University)”, 9 Institutskiy per., 141700, Dolgoprudny, Moscow Region (Russian Federation); Barmina, E.V., E-mail: barminaev@gmail.com [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); Shafeev, G.A. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31, Kashirskoye Highway, 115409 Moscow (Russian Federation); Voronov, V.V. [A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation)

    2015-09-01

    Highlights: • Ablation of a bulk Ti target by 10 ps laser pulses in liquid is experimentally studied in external DC electric field. • Applied cathodic bias leads to increase in average size of self-organized nanostructures formed upon ablation of titanium target. • Laser ablation of Ti target in external electric field results in generation of elongated titanium oxide nanoparticles. - Abstract: Ablation of a bulk Ti target by 10 ps laser pulses in water is experimentally studied in external DC electric field. It is demonstrated that both lateral size of nanostructures (NS) on Ti surface and their density depend on the electric field applied to the target. Scanning Electron Microscopy of NS reveals the shift of their size distribution function toward larger sizes with applied field (cathodic bias, 25 V DC). Density of mushroom-like NS with applied electric field amounts to 10{sup 10} cm{sup −2}. X-ray diffraction of generated nanoparticles (NPs) shows difference in the crystallographic structure of NPs of non-stoichiometric Ti oxides generated with and without electric field. This conclusion is corroborated with the optical absorption spectroscopy of obtained colloids. Transmission Electron Microscopy of NPs also shows difference in morphology of particles produced with and without cathodic bias. The results are interpreted on the basis of instability of the melt on Ti surface in the electric field.

  18. Channeling of electrons in a crossed laser field

    Directory of Open Access Journals (Sweden)

    S. B. Dabagov

    2015-06-01

    Full Text Available In this article a new analytical description of the effective interaction potential for a charged particle with the field of two interfering laser beams is presented. The potential dependence on the lasers intensities, orientation and parameters of the particle entering the considered system is analyzed. For the first time the phenomenon of effective potential inversion (or “relativistic reversal” is described for arbitrary lasers crossing angle. Threshold electron velocity values for the phenomenon are introduced and its extended illustration based on numerical simulations for two laser beams polarizations is presented. In addition the projectile radiation spectral distribution is given and general estimations on the expected beam radiation yield are outlined.

  19. Laser-generated magnetic fields in quasi-hohlraum geometries

    Science.gov (United States)

    Pollock, Bradley; Turnbull, David; Ross, Steven; Hazi, Andrew; Ralph, Joseph; Lepape, Sebastian; Froula, Dustin; Haberberger, Dan; Moody, John

    2014-10-01

    Laser-generated magnetic fields of 10--40 T have been produced with 100--4000 J laser drives at Omega EP and Titan. The fields are generated using the technique described by Daido et al. [Phys. Rev. Lett. 56, 846 (1986)], which works by directing a laser through a hole in one plate to strike a second plate. Hot electrons generated in the laser-produced plasma on the second plate collect on the first plate. A strap connects the two plates allowing a current of 10 s of kA to flow and generate a solenoidal magnetic field. The magnetic field is characterized using Faraday rotation, b-dot probes, and proton radiography. Further experiments to study the effect of the magnetic field on hohlraum performance are currently scheduled for Omega. This work was performed under the auspices of the United States Department of Energy by the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA-27344.

  20. Electron-positron pair production in ultrastrong laser fields

    Directory of Open Access Journals (Sweden)

    Bai Song Xie

    2017-09-01

    Full Text Available Electron–positron pair production due to the decay of vacuum in ultrastrong laser fields is an interesting topic which is revived recently because of the rapid development of current laser technology. The theoretical and numerical research progress of this challenging topic is reviewed. Many new findings are presented by different approaches such as the worldline instantons, the S-matrix theory, the kinetic method by solving the quantum Vlasov equation or/and the real-time Dirac–Heisenberg–Wigner formalism, the computational quantum field theory by solving the Dirac equation and so on. In particular, the effects of electric field polarizations on pair production are unveiled with different patterns of created momentum spectra. The effects of polarizations on the number density of created particles and the nonperturbative signatures of multiphoton process are also presented. The competitive interplay between the multiphoton process and nonperturbation process plays a key role in these new findings. These newly discovered phenomena are valuable to deepen the understanding of pair production in complex fields and even have an implication to the study of strong-field ionization. More recent studies on the pair production in complex fields as well as beyond laser fields are briefly presented in the view point of perspective future.

  1. Effects of ponderomotive forces and space-charge field on laser plasma hydrodynamics

    International Nuclear Information System (INIS)

    Cang Yu; Lu Xin; Wu Huichun; Zhang Jie

    2005-01-01

    Using a two-fluid two-temperature hydrodynamic code, authors studied the hydrodynamics in the interaction of intense (10 15 W/cm 2 ) ultrashort (150 fs) laser pulses and linear density plasmas. The simulation results show the ponderomotive force effect on the formation of the electron density ripples in under-dense region, such ripples increase the reflection of the laser pulse, and on the separation of the plasma in critical surface. Quasi-electroneutrality is not suitable in this case because of the different ponderomotive force and the gradient of thermal-pressure for ions and electrons. Ions are moved by the electrostatic force. Comparing with the simulation results from one-fluid two-temperature code, authors find that under strong ponderomotive force and gradient of thermo-pressure, two-fluid code is more suitable to simulate the hydrodynamics of plasmas. (authors)

  2. Three dimensional alignment of molecules using elliptically polarized laser fields

    DEFF Research Database (Denmark)

    Larsen, J.J.; Bjerre, N.; Hald, K.

    2000-01-01

    We demonstrate, theoretically and experimentally, that an intense, elliptically polarized, nonresonant laser field can simultaneously force all three axes of a molecule to align along given axes fixed in space, thus inhibiting the free rotation in all three Euler angles. Theoretically, the effect...

  3. High energy bremsstrahlung in an intense laser field

    International Nuclear Information System (INIS)

    Schlessinger, L.; Wright, J.A.

    1980-02-01

    The cross section for bremsstrahlung emission and absorption by electrons in an intense laser field has been calculated in the Born approximation for the electron-ion potential. Typical numerical results are presented as a function of the ratio of the electron guiver energy to its energy and the ratio of the bremsstrahlung energy to the electron energy. The intense field correction factor for the rate of bremsstrahlung emission and absorption for electrons with a Boltzmann distribution of energies has been calculated. Numerical results for the correction factor are presented for the Boltzmann case as a function of the ratio of the electron quiver energy to its thermal energy and the ratio of the bremsstrahlung energy to the thermal energy. For typical laser fusion parameters, this correction factor which is the ratio of the thermal bremsstrahlung emission rate in the intense laser field to the rate at zero field can be quite significant. For a laser of wavelength 1.06 μm at an intensity of 3 x 10 15 w/cm 2 and an electron temperature of 1 keV, the correction factor varies from 0.98 at a bremsstrahlung energy of 100 V to greater than 5 at a bremsstrahlung energy of 10 keV

  4. Evaluations of electric field in laser-generated pulsed plasma

    Czech Academy of Sciences Publication Activity Database

    Torrisi, L.; Gammino, S.; Láska, Leoš; Krása, Josef; Rohlena, Karel; Wolowski, J.

    2006-01-01

    Roč. 56, Suppl. B (2006), B580-B585 ISSN 0011-4626. [Symposium on Plasma Physics and Technology /22./. Prague, 26.06.2006-29.06.2006] Institutional research plan: CEZ:AV0Z10100523 Keywords : electric field in plasma * debye length * plasma temperature * plasma density Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.568, year: 2006

  5. Scattering of ultrashort electromagnetic pulses on metal clusters

    International Nuclear Information System (INIS)

    Astapenko, V. A.; Sakhno, S. V.

    2016-01-01

    We have calculated and analyzed the probability of ultrashort electromagnetic pulse (USP) scattering on small metal clusters in the frequency range of plasmon resonances during the field action. The main attention is devoted to dependence of the probability of scattering on the pulse duration for various detunings of the USP carrier frequency from the plasmon resonance frequency. Peculiarities of the USP scattering from plasmon resonances with various figures of merit are revealed.

  6. Scattering of ultrashort electromagnetic pulses on metal clusters

    Energy Technology Data Exchange (ETDEWEB)

    Astapenko, V. A., E-mail: astval@mail.ru; Sakhno, S. V. [Moscow Institute of Physics and Technology (State University) (Russian Federation)

    2016-12-15

    We have calculated and analyzed the probability of ultrashort electromagnetic pulse (USP) scattering on small metal clusters in the frequency range of plasmon resonances during the field action. The main attention is devoted to dependence of the probability of scattering on the pulse duration for various detunings of the USP carrier frequency from the plasmon resonance frequency. Peculiarities of the USP scattering from plasmon resonances with various figures of merit are revealed.

  7. Nonlinear shaping of a two-dimensional ultrashort ionizing pulse

    International Nuclear Information System (INIS)

    Sergeev, A.; Vanin, E.; Stenflo, L.; Anderson, D.; Lisak, M.; Quiroga-Teixeiro, M.L.

    1992-01-01

    A theoretical description of ultrashort ionizing wave pulses is presented by means of two different models where the ionization rate increases or decreases, respectively, as a function of the electric field amplitude. We show that the pulse evolves either into a horse-shoe or a horn-type structure in the time-space domain. In some parameter regions the intensity of the pulse can also increase. (au)

  8. Atomic electron correlations in intense laser fields

    International Nuclear Information System (INIS)

    DiMauro, L.F.; Sheehy, B.; Walker, B.; Agostini, P.A.

    1998-01-01

    This talk examines two distinct cases in strong optical fields where electron correlation plays an important role in the dynamics. In the first example, strong coupling in a two-electron-like system is manifested as an intensity-dependent splitting in the ionized electron energy distribution. This two-electron phenomenon (dubbed continuum-continuum Autler-Townes effect) is analogous to a strongly coupled two-level, one-electron atom but raises some intriguing questions regarding the exact nature of electron-electron correlation. The second case examines the evidence for two-electron ionization in the strong-field tunneling limit. Although their ability to describe the one-electron dynamics has obtained a quantitative level of understanding, a description of the two (multiple) electron ionization remains unclear

  9. Laser-assisted electron emission from gated field-emitters

    CERN Document Server

    Ishizuka, H; Yokoo, K; Mimura, H; Shimawaki, H; Hosono, A

    2002-01-01

    Enhancement of electron emission by illumination of gated field-emitters was studied using a 100 mW cw YAG laser at a wavelength of 532 nm, intensities up to 10 sup 7 W/m sup 2 and mechanically chopped with a rise time of 4 mu s. When shining an array of 640 silicon emitters, the emission current responded quickly to on-off of the laser. The increase of the emission current was proportional to the basic emission current at low gate voltages, but it was saturated at approx 3 mu A as the basic current approached 100 mu A with the increase of gate voltage. The emission increase was proportional to the square root of laser power at low gate voltages and to the laser power at elevated gate voltages. For 1- and 3-tip silicon emitters, the rise and fall of the current due to on-off of the laser showed a significant time lag. The magnitude of emission increase was independent of the position of laser spot on the emitter base and reached 2 mu A at a basic current of 5 mu A without showing signs of saturation. The mech...

  10. Interaction of neutral particles with strong laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Meuren, Sebastian; Keitel, Christoph H.; Di Piazza, Antonino [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

    2013-07-01

    Since the invention of the laser in the 1960s the experimentally available field strengths have continuously increased. The current peak intensity record is 2 x 10{sup 22} W/cm{sup 2} and next generation facilities such as ELI, HiPER and XCELS plan to reach even intensities of the order of 10{sup 24} W/cm{sup 2}. Thus, modern laser facilities are a clean source for very strong external electromagnetic fields and promise new and interesting high-energy physics experiments. In particular, strong laser fields could be used to test non-linear effects in quantum field theory. Earlier we have investigated how radiative corrections modify the coupling of a charged particle inside a strong plane-wave electromagnetic background field. However, a charged particle couples already at tree level to electromagnetic radiation. Therefore, we have now analyzed how the coupling between neutral particles and radiation is affected by a very strong plane-wave electromagnetic background field, when loop corrections are taken into account. In particular, the case of neutrinos is discussed.

  11. Correlated electron-ion collisions in a strong laser field; Korrelierte Elektron-Ion-Stoesse in starken Laserfeldern

    Energy Technology Data Exchange (ETDEWEB)

    Ristow, T.

    2007-12-17

    Electron-ion-collisions in plasmas in the presence of an ultra-short intensive laser pulse can cause high energy transfers to the electrons. During the collision the oscillation energy of the electron in the laser field is changed into drift energy. In this regime, multi-photon processes, known from the ionization of neutral atoms (Above-Threshold Ionization), and successive, so called correlated collisions, are important. The subject of the thesis is a study of binary Coulomb collisions in strong laser fields. The collisions are treated both in the context of classical Newtonian mechanics and in the quantum-mechanical framework by the Schroedinger equation. In the classical case a simplified instantaneous collision model and a complete dynamical treatment are discussed. Collisions can be treated instantaneously, if the ratio of the impact parameter to the quiver amplitude is small. The energy distributions calculated in this approximation show an elastic peak and a broad plateau due to rescattered electrons. At incident velocities smaller than the quiver velocity, correlated collisions are observed in the electron trajectories of the dynamical model. This effect leads to characteristic momentum distributions of the electrons, that are explicitly calculated and compared with the results of the instantaneous model. In addition, the time-dependence of the collisions is discussed in the framework of a singular perturbation theory. The complete description of the Coulomb scattering requires a quantum-mechanical description. A time-dependent method of wave-packet scattering is used and the corresponding time-dependent three-dimensional Schroedinger equation is solved by an implicit ADImethod on a spatial grid. The momentum and the energy distributions of the scattered electrons are calculated by the Fourier transformation of the wavefunction. A comparison of the scattering from a repulsive and an attractive potential is used to distinguish between simple collisions and

  12. BENCHMARKING MOBILE LASER SCANNING SYSTEMS USING A PERMANENT TEST FIELD

    Directory of Open Access Journals (Sweden)

    H. Kaartinen

    2012-07-01

    Full Text Available The objective of the study was to benchmark the geometric accuracy of mobile laser scanning (MLS systems using a permanent test field under good coverage of GNSS. Mobile laser scanning, also called mobile terrestrial laser scanning, is currently a rapidly developing area in laser scanning where laser scanners, GNSS and IMU are mounted onboard a moving vehicle. MLS can be considered to fill the gap between airborne and terrestrial laser scanning. Data provided by MLS systems can be characterized with the following technical parameters: a point density in the range of 100-1000 points per m2 at 10 m distance, b distance measurement accuracy of 2-5 cm, and c operational scanning range from 1 to 100 m. Several commercial, including e.g. Riegl, Optech and others, and some research mobile laser scanning systems surveyed the test field using predefined driving speed and directions. The acquired georeferenced point clouds were delivered for analyzing. The geometric accuracy of the point clouds was determined using the reference targets that could be identified and measured from the point cloud. Results show that in good GNSS conditions most systems can reach an accuracy of 2 cm both in plane and elevation. The accuracy of a low cost system, the price of which is less than tenth of the other systems, seems to be within a few centimetres at least in ground elevation determination. Inaccuracies in the relative orientation of the instruments lead to systematic errors and when several scanners are used, in multiple reproductions of the objects. Mobile laser scanning systems can collect high density point cloud data with high accuracy. A permanent test field suits well for verifying and comparing the performance of different mobile laser scanning systems. The accuracy of the relative orientation between the mapping instruments needs more attention. For example, if the object is seen double in the point cloud due to imperfect boresight calibration between two

  13. Ablation of burned skin with ultra-short pulses laser to promote healing: evaluation by optical coherence tomography, histology, {mu}ATR-FTIR and Nonlinear Microscopy; Ablacao de pele queimada com laser de pulsos ultra-curtos para promocao da cicatrizacao: avaliacao por tomografia por coerencia optica, histologia, {mu}ATR-FTIR e microscopia nao-linear

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Moises Oliveira dos

    2012-07-01

    Burns cause changes in the anatomical structure of the skin associated with trauma. The severity of the burn injury is divided into first, second and third-degree burns. The third-degree burns have been a major focus of research in search of more conservative treatments and faster results in repair for a functional and cosmetically acceptable. The conventional treatment is the use of topical natural or synthetic skin graft. An alternative therapy is the laser ablation process for burned tissue necrosis removal due to the no mechanical contact, fast application and access to difficult areas. The purpose of this study is to evaluate the feasibility of using high intensity femtosecond lasers as an adjunct treatment of burned patients. For this study, 65 Wistar rats were divided into groups of five animals: healthy skin, burned skin, two types of treatment (surgical debridement or femtosecond laser ablation) and four different times in the healing process monitoring. Three regions of the back of the animals were exposed to steam source causing third-degree burn. On the third day after the burn, one of the regions was ablated with high intensity ultrashort laser pulses ({lambda} = 785 nm, 90 fs, 2 kHz and 10 {mu}J/ pulse), the other received surgical debridement, and the last was considered the burn control. The regions were analyzed by optical coherence tomography (OCT), histology, attenuated total reflectance infrared spectroscopy using Fourier transform ({mu}-ATR-FTIR), two-photon excitation fluorescence microscopy (TPEFM) and second harmonic generation technique (SHG) on days 3, 5, 7 and 14 pos-treatments. The results showed that with the laser irradiation conditions used it was possible to remove debris from third degree burn. The techniques used to characterize the tissue allowed to verify that all treatments promoted wound healing. On the fourteenth day, the regeneration curve showed that the attenuation coefficient of laser ablated tissue converges to the values

  14. Solid-state laser engineering

    CERN Document Server

    Koechner, Walter

    1996-01-01

    Solid-State Laser Engineering, written from an industrial perspective, discusses in detail the characteristics, design, construction, and performance of solid-state lasers. Emphasis is placed on engineering and practical considerations; phenomenological aspects using models are preferred to abstract mathematical derivations. This new edition has extensively been updated to account for recent developments in the areas of diode-laser pumping, mode locking, ultrashort-pulse generation etc. Walter Koechner received a doctorate in Electrical Engineering from the University of Technology in Vienna, Austria, in 1965. He has published numerous papers in the fields of solid-state physics, optics, and lasers. Dr. Koechner is founder and president of Fibertek, Inc., a research firm specializing in the design, development, and production of advanced solid-state lasers, optical radars, and remote-sensing systems.

  15. Field-Testing of an Active Laser Tracking System

    Science.gov (United States)

    Markov, V.; Khiznyak, A.; Woll, D.; Liu, S.

    -mirror module for laser beam steering and detectors, all set on a single platform. In the initial ALTS design, the laser module is conceptualized in coupled-cavitiesarchitecturewith a synchronously pumped gain media, a four-wave mixing PCM. The four-wave mixing arrangement uses optical phase conjugation to compensate for spatial inhomogeneities of the atmosphere. A significant innovation in the proposed approach is in its perspective capabilities to detect and measure the critical parameters in the returned signal that should allow to directly measure spatial/angular position and velocity of the target. This report will cover the system analysis, the ALTS design, test plan and exit criteria, functional and operational tests, and test results at Edwards AFB Range field.

  16. Interaction of neutrons with the matter in the laser field

    International Nuclear Information System (INIS)

    Zaretskij, D.F.; Lomonosov, V.V.

    1980-01-01

    The interactions of neutrons with the molecules, atoms and nuclei in the presence of the coherent electromagnetic radiation are considered. There are two effects which are discussed in detail: 1) the ''acceleration'' of thermal neutrons passed through the excited by the resonance laser wave molecular gas; 2) the induced by the laser field the slow neutron capture accompanied by the compound nucleus level excitation. The given effects, if they are experimentally detected, give the possibility to control the neutron flux (spectrum change, polarization, spatial modulation and etc.) and change the interaction cross sections of thermal and resonance neutrons with nuclei due to excitation of p levels of the compound nucleus [ru

  17. Effect of solenoidal magnetic field on drifting laser plasma

    Science.gov (United States)

    Takahashi, Kazumasa; Okamura, Masahiro; Sekine, Megumi; Cushing, Eric; Jandovitz, Peter

    2013-04-01

    An ion source for accelerators requires to provide a stable waveform with a certain pulse length appropriate to the application. The pulse length of laser ion source is easy to control because it is expected to be proportional to plasma drifting distance. However, current density decay is proportional to the cube of the drifting distance, so large current loss will occur under unconfined drift. We investigated the stability and current decay of a Nd:YAG laser generated copper plasma confined by a solenoidal field using a Faraday cup to measure the current waveform. It was found that the plasma was unstable at certain magnetic field strengths, so a baffle was introduced to limit the plasma diameter at injection and improve the stability. Magnetic field, solenoid length, and plasma diameter were varied in order to find the conditions that minimize current decay and maximize stability.

  18. Effect of solenoidal magnetic field on drifting laser plasma

    International Nuclear Information System (INIS)

    Takahashi, Kazumasa; Sekine, Megumi; Okamura, Masahiro; Cushing, Eric; Jandovitz, Peter

    2013-01-01

    An ion source for accelerators requires to provide a stable waveform with a certain pulse length appropriate to the application. The pulse length of laser ion source is easy to control because it is expected to be proportional to plasma drifting distance. However, current density decay is proportional to the cube of the drifting distance, so large current loss will occur under unconfined drift. We investigated the stability and current decay of a Nd:YAG laser generated copper plasma confined by a solenoidal field using a Faraday cup to measure the current waveform. It was found that the plasma was unstable at certain magnetic field strengths, so a baffle was introduced to limit the plasma diameter at injection and improve the stability. Magnetic field, solenoid length, and plasma diameter were varied in order to find the conditions that minimize current decay and maximize stability.

  19. Effect of solenoidal magnetic field on drifting laser plasma

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Kazumasa; Sekine, Megumi [Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Okamura, Masahiro [Brookhaven National Laboratory, Upton, NY 11973 (United States) and RIKEN, Wako-shi, Saitama 351-0198 (United States); Cushing, Eric [Pennsylvania State University, University Park, PA 16802 (United States); Jandovitz, Peter [Cornell University, Ithaca, NY 14853 (United States)

    2013-04-19

    An ion source for accelerators requires to provide a stable waveform with a certain pulse length appropriate to the application. The pulse length of laser ion source is easy to control because it is expected to be proportional to plasma drifting distance. However, current density decay is proportional to the cube of the drifting distance, so large current loss will occur under unconfined drift. We investigated the stability and current decay of a Nd:YAG laser generated copper plasma confined by a solenoidal field using a Faraday cup to measure the current waveform. It was found that the plasma was unstable at certain magnetic field strengths, so a baffle was introduced to limit the plasma diameter at injection and improve the stability. Magnetic field, solenoid length, and plasma diameter were varied in order to find the conditions that minimize current decay and maximize stability.

  20. Ultra-short time sciences. From the atto-second to the peta-watts

    International Nuclear Information System (INIS)

    2000-01-01

    This book presents the recent advances in the scientific and technical domains linked with ultra-short time physics. It deals first with the conceptual and technological aspects of ultra-intense and ultra-brief lasers. Then, it describes the different domains of research (atoms, molecules and aggregates; gaseous phase dynamics using the pump-probe technique; femto-chemistry in dense phase; condensed matter; plasma physics; consistent control; aerosols; functional femto-biology) and the different domains of application (medical diagnosis; ophthalmology; telecommunications; technological and industrial developments). A last part is devoted to the teaching of ultra-short time sciences. (J.S.)

  1. Steering population transfer of the Na2 molecule by an ultrashort pulse train

    Science.gov (United States)

    Niu, Dong-Hua; Wang, Shuo; Zhan, Wei-Shen; Tao, Hong-Cai; Wang, Si-Qi

    2018-05-01

    We theoretically investigate the complete population transfer among quantum states of the Na2 molecule using ultrashort pulse trains using the time-dependent wave packet method. The population accumulation of the target state can be steered by controlling the laser parameters, such as the variable pulse pairs, the different pulse widths, the time delays and the repetition period between two contiguous pulses; in particular, the pulse pairs and the pulse widths have a great effect on the population transfer. The calculations show that the ultrashort pulse train is a feasible solution, which can steer the population transfer from the initial state to the target state efficiently with lower peak intensities.

  2. Ultrashort Laser Pulse Propagation in Water

    Science.gov (United States)

    2011-09-30

    Beer behavior ( It should be noted that the so called Lambert-Beer law was first discovered by Pierre Bouguer in his published work in 1729 titled...Essai d’optique sur la gradation de la lumiére and we will hereafter refer to it as the Bouguer -Lambert-Beer Law or BLB. The law is valid for

  3. Collimation of laser-produced plasmas using axial magnetic field

    Czech Academy of Sciences Publication Activity Database

    Roy, Amitava; Harilal, S.S.; Hassan, S.M.; Endo, Akira; Mocek, Tomáš; Hassanein, A.

    2015-01-01

    Roč. 33, č. 2 (2015), s. 175-182 ISSN 0263-0346 R&D Projects: GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.20.0143; GA MŠk EE2.3.30.0057 Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143; OP VK 4 POSTDOK(XE) CZ.1.07/2.3.00/30.0057 Institutional support: RVO:68378271 Keywords : laser-produced plasma * optical emission spectroscopy * plasma-B field interaction * plasma temperature and density * tin plasma Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 1.649, year: 2015

  4. Study of a recombination X-ray laser scheme in a H-like nitrogen plasma created by optical field induced ionization

    International Nuclear Information System (INIS)

    Hulin, S.

    2001-01-01

    Thanks to their high brightness and short wavelength, X ray lasers are interesting diagnostics in many experiments because they can efficiently probe dense plasmas. Furthermore their mono-chromaticity and collimation make them interesting tools in plasma physics but also in many biology or chemistry experiments. The effective use of this diagnostic is mainly depending on its dimensions and cost. For this reason, research on X ray laser is now focused on the reduction of cost and the realization of table-top facilities. One of these research axis, based on the optical field induced ionization (OFI) of the plasma, is presented in this work. An ultra-short (60 fs) high-brightness (10 19 W/cm 2 ) Ti:Sapphire (790 nm) laser is focused into a nitrogen pulsed gas jet. A dense (10 20 cm -3 ) plasma of fully stripped nitrogen is created by the way. During the fast recombination of the plasma some population inversions between levels of principal quantum number 2 and 1 (2.4 nm) and 3 and 2 (13.4 nm) can occur depending on the plasma parameters. The creation of the plasma by OFI, laser-plasma interaction dominated by relativistic self-focusing, and recombination dynamics are studied by numerical simulations on one hand and experiments on the other hand. Temperature measurements and numerical simulations show a strong heating, destructive for the laser scheme, which can be explained by Raman instability growing. Nevertheless plasma X ray emission in the 2-20 nm range show a strong increase with the electronic density of the 13.4 nm line intensity. This behavior is consistent with a laser effect but is not detected on the 2.4 nm transition line. (author)

  5. Theoretical femtosecond physics atoms and molecules in strong laser fields

    CERN Document Server

    Grossmann, Frank

    2013-01-01

    Theoretical investigations of atoms and molecules interacting with pulsed or continuous wave lasers up to atomic field strengths on the order of 10^16 W/cm² are leading to an understanding of many challenging experimental discoveries. This book deals with the basics of femtosecond physics and goes up to the latest applications of new phenomena. The book presents an introduction to laser physics with mode-locking and pulsed laser operation. The solution of the time-dependent Schrödinger equation is discussed both analytically and numerically. The basis for the non-perturbative treatment of laser-matter interaction in the book is the numerical solution of the time-dependent Schrödinger equation. The light field is treated classically, and different possible gauges are discussed. Physical phenonema, ranging from Rabi-oscillations in two-level systems to the ionization of atoms, the generation of high harmonics, the ionization and dissociation of molecules as well as the control of chemical reactions are pre...

  6. Strong-Field Control of Laser Filamentation Mechanisms

    Science.gov (United States)

    Levis, Robert; Romanov, Dmitri; Filin, Aleskey; Compton, Ryan

    2008-05-01

    The propagation of short strong-file laser pulses in gas and solution phases often result in formation of filaments. This phenomenon involves many nonlinear processes including Kerr lensing, group velocity dispersion, multi-photon ionization, plasma defocusing, intensity clamping, and self-steepening. Of these, formation and dynamics of pencil-shape plasma areas plays a crucial role. The fundamental understanding of these laser-induced plasmas requires additional effort, because the process is highly nonlinear and complex. We studied the ultrafast laser-generated plasma dynamics both experimentally and theoretically. Ultrafast plasma dynamics was probed using Coherent Anti-Stokes Raman Scattering. The measurements were made in a room temperature gas maintained at 1 atm in a flowing cell. The time dependent scattering was measured by delaying the CARS probe with respect to the intense laser excitation pulse. A general trend is observed between the spacing of the ground state and the first allowed excited state with the rise time for the noble gas series and the molecular gases. This trend is consistent with our theoretical model, which considers the ultrafast dynamics of the strong field generated plasma as a three-step process; (i) strong-field ionization followed by the electron gaining considerable kinetic energy during the pulse; (ii) immediate post-pulse dynamics: fast thermalization, impact-ionization-driven electron multiplication and cooling; (iii) ensuing relaxation: evolution to electron-ion equilibrium and eventual recombination.

  7. Determining the field emitter temperature during laser irradiation in the pulsed laser atom probe

    International Nuclear Information System (INIS)

    Kellogg, G.L.

    1981-01-01

    Three methods are discussed for determining the field emitter temperature during laser irradiation in the recently developed Pulsed Laser Atom Probe. A procedure based on the reduction of the lattice evaporation field with increasing emitter temperature is found to be the most convenient and reliable method between 60 and 500 K. Calibration curves (plots of the evaporation field versus temperature) are presented for dc and pulsed field evaporation of W, Mo, and Rh. These results show directly the important influence of the evaporation rate on the temperature dependence of the evaporation field. The possibility of a temperature calibration based on the ionic charge state distribution of field evaporated lattice atoms is also discussed. The shift in the charge state distributions which occurs when the emitter temperature is increased and the applied field strength is decreased at a constant rate of evaporation is shown to be due to the changing field and not the changing temperature. Nevertheless, the emitter temperature can be deduced from the charge state distribution for a specified evaporation rate. Charge state distributions as a function of field strength and temperature are presented for the same three materials. Finally, a preliminary experiment is reported which shows that the emitter temperature can be determined from field ion microscope observations of single atom surface diffusion over low index crystal planes. This last calibration procedure is shown to be very useful at higher temperatures (>600 K) where the other two methods become unreliable

  8. Generation of Raman lasers from nitrogen molecular ions driven by ultraintense laser fields

    Science.gov (United States)

    Yao, Jinping; Chu, Wei; Liu, Zhaoxiang; Xu, Bo; Chen, Jinming; Cheng, Ya

    2018-03-01

    Atmospheric lasing has aroused much interest in the past few years. The ‘air–laser’ opens promising potential for remote chemical sensing of trace gases with high sensitivity and specificity. At present, several approaches have been successfully implemented for generating highly coherent laser beams in atmospheric condition, including both amplified-spontaneous emission, and narrow-bandwidth stimulated emission in the forward direction in the presence of self-generated or externally injected seed pulses. Here, we report on generation of multiple-wavelength Raman lasers from nitrogen molecular ions ({{{N}}}2+), driven by intense mid-infrared laser fields. Intuitively, the approach appears problematic for the small nonlinear susceptibility of {{{N}}}2+ ions, whereas the efficiency of Raman laser can be significantly promoted in near-resonant condition. More surprisingly, a Raman laser consisting of a supercontinuum spanning from ∼310 to ∼392 nm has been observed resulting from a series near-resonant nonlinear processes including four-wave mixing, stimulated Raman scattering and cross phase modulation. To date, extreme nonlinear optics in molecular ions remains largely unexplored, which provides an alternative means for air–laser-based remote sensing applications.

  9. Subcycle dynamics of Coulomb asymmetry in strong elliptical laser fields.

    Science.gov (United States)

    Li, Min; Liu, Yunquan; Liu, Hong; Ning, Qicheng; Fu, Libin; Liu, Jie; Deng, Yongkai; Wu, Chengyin; Peng, Liang-You; Peng, Liangyou; Gong, Qihuang

    2013-07-12

    We measure photoelectron angular distributions of noble gases in intense elliptically polarized laser fields, which indicate strong structure-dependent Coulomb asymmetry. Using a dedicated semiclassical model, we have disentangled the contribution of direct ionization and multiple forward scattering on Coulomb asymmetry in elliptical laser fields. Our theory quantifies the roles of the ionic potential and initial transverse momentum on Coulomb asymmetry, proving that the small lobes of asymmetry are induced by direct ionization and the strong asymmetry is induced by multiple forward scattering in the ionic potential. Both processes are distorted by the Coulomb force acting on the electrons after tunneling. Lowering the ionization potential, the relative contribution of direct ionization on Coulomb asymmetry substantially decreases and Coulomb focusing on multiple rescattering is more important. We do not observe evident initial longitudinal momentum spread at the tunnel exit according to our simulation.

  10. Electron-atom collisions in a laser field

    International Nuclear Information System (INIS)

    Ehlotzky, F.

    1998-01-01

    The present work is a report on recent progress made in our understanding of electron-atom collisions in a laser field. To some extent it is a continuation of a previous review covering a somewhat larger subject (Can. J. Phys. 63 (1985)). We shall discuss the present status of investigations in this field from the theoretical as well as experimental point of view but most of the report will be devoted to an analysis of the various approximation schemes used at present in this field to describe the different aspects of laser-assisted electron-atom interactions. As the table of contents shows, most of the work done so far is treating the atom as a spectator, described by a potential and only very little has been achieved over the years to include the atomic structure into consideration since the inclusion of these structure effects poses considerable computational problems. Since, for example, multiphoton ionization and its inverse process laser-assisted recombination may be considered as one half of a scattering process, it is quite natural that some of the theoretical techniques described here are also of interest for the treatment of other multiphoton processes not considered here since there are several other recent reviews available on these topics. (orig.)

  11. Phase control of higher spectral components in the presence of a static electric field

    International Nuclear Information System (INIS)

    Zhang Chaojin; Yang Weifeng; Song Xiaohong; Xu Zhizhan

    2009-01-01

    We investigate the higher spectral component generations driven by a few-cycle laser pulse in a dense medium when a static electric field is present. Our results show that, when assisted by a static electric field, the dependence of the transmitted laser spectrum on the carrier-envelope phase (CEP) is significantly increased. Continuum and distinct peaks can be achieved by controlling the CEP of the few-cycle ultrashort laser pulse. Such a strong variation is due to the fact that the presence of the static electric field modifies the waveform of the combined electric field, which further affects the spectral distribution of the generated higher spectral components.

  12. Confinement of laser plasma by solenoidal field for laser ion source

    International Nuclear Information System (INIS)

    Okamura, M.; Kanesue, T.; Kondo, K.; Dabrowski, R.

    2010-01-01

    A laser ion source can provide high current, highly charged ions with a simple structure. However, it was not easy to control the ion pulse width. To provide a longer ion beam pulse, the plasma drift length, which is the distance between laser target and extraction point, has to be extended and as a result the plasma is diluted severely. Previously, we applied a solenoid field to prevent reduction of ion density at the extraction point. Although a current enhancement by a solenoid field was observed, plasma behavior after a solenoid magnet was unclear because plasma behavior can be different from usual ion beam dynamics. We measured a transverse ion distribution along the beam axis to understand plasma motion in the presence of a solenoid field.

  13. Relativistic theory of vector mesons in laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Becker, W; Mitter, H [Tuebingen Univ. (F.R. Germany). Inst. fuer Theoretische Physik

    1975-01-01

    The relativistic wave equation for a particle with spin 1 and an anomalous magnetic moment ..mu.. in an external wave field is reduced to a set of coupled ordinary differential equations for three amplitudes, which multiply the exponential known from the spin 0 case. These amplitudes are constant for ..mu..=1 (and not ..mu..=0). Exact solutions are given for a linear polarized laser wave of finite pulse shape and for an infinitely extended plane wave with circular polarization. In contrast to the situation in a constant magnetic field there are no internal inconsistencies.

  14. Bremsstrahlung in the presence of a laser field

    International Nuclear Information System (INIS)

    Dondera, M.; Florescu, Viorica

    2006-01-01

    For the process of spontaneous one photon emission by an electron scattered on a potential in the presence of a monochromatic laser field, we review the formalism and the approximations on which the existing nonrelativistic calculations are based, in classical and quantum descriptions. In the case of the Coulomb potential, we give new numerical results for the radiation spectrum, using either the Born approximation [Karapetyan, P.V., Fedorov, M.V., 1978. Spontaneous electron bremmstrahlung in the field of an intense electromagnetic wave. Zh. Teor. Fiz. 75, 816-826 [Sov. Phys. JETP 48, 412 (1979)

  15. Bremsstrahlung in the presence of a laser field

    Energy Technology Data Exchange (ETDEWEB)

    Dondera, M. [Department of Physics, University of Bucharest, Bucharest-Magurele MG11, 76900 (Romania); Florescu, Viorica [Department of Physics, University of Bucharest, Bucharest-Magurele MG11, 76900 (Romania)]. E-mail: flor@barutu.fizica.unibuc.ro

    2006-10-15

    For the process of spontaneous one photon emission by an electron scattered on a potential in the presence of a monochromatic laser field, we review the formalism and the approximations on which the existing nonrelativistic calculations are based, in classical and quantum descriptions. In the case of the Coulomb potential, we give new numerical results for the radiation spectrum, using either the Born approximation [Karapetyan, P.V., Fedorov, M.V., 1978. Spontaneous electron bremmstrahlung in the field of an intense electromagnetic wave. Zh. Teor. Fiz. 75, 816-826 [Sov. Phys. JETP 48, 412 (1979)

  16. Applications of super - high intensity lasers in nuclear engineering

    International Nuclear Information System (INIS)

    Salomaa, R.; Hakola, A.; Santala, M.

    2007-01-01

    Laser-plasma interactions arising when a super intense ultrashort laser pulse impinges a solid target creates intense partly collimated and energy resolved photons, high energy electron and protons and neutrons. In addition the plasma plume can generate huge magnetic and electric fields. Also ultra short X-ray pulses are created. We have participated in some of such experiments at Rutherford and Max-Planck Institute and assessed the applications of such kind as laser-driven accelerators. This paper discusses applications in nuclear engineering (neutron sources, isotope separation, fast ignition and transmutation, etc). In particular the potential for extreme time resolution and to partial energy resolution are assessed

  17. Effects of laser-polarization and wiggler magnetic fields on electron acceleration in laser-cluster interaction

    Science.gov (United States)

    Singh Ghotra, Harjit; Kant, Niti

    2018-06-01

    We examine the electron dynamics during laser-cluster interaction. In addition to the electrostatic field of an individual cluster and laser field, we consider an external transverse wiggler magnetic field, which plays a pivotal role in enhancing the electron acceleration. Single-particle simulation has been presented with a short pulse linearly polarized as well as circularly polarized laser pulses for electron acceleration in a cluster. The persisting Coulomb field allows the electron to absorb energy from the laser field. The stochastically heated electron finds a weak electric field at the edge of the cluster from where it is ejected. The wiggler magnetic field connects the regions of the stochastically heated, ejected electron from the cluster and high energy gain by the electron from the laser field outside the cluster. This increases the field strength and hence supports the electron to meet the phase of the laser field for enhanced acceleration. A long duration resonance appears with an optimized magnetic wiggler field of about 3.4 kG. Hence, the relativistic energy gain by the electron is enhanced up to a few 100 MeV with an intense short pulse laser with an intensity of about 1019 W cm‑2 in the presence of a wiggler magnetic field.

  18. Generation of ultra-intense and ultra-short laser pulses with high temporal contrast; Generation d'impulsions laser ultra-breves et ultra-intenses a contraste temporel eleve

    Energy Technology Data Exchange (ETDEWEB)

    Julien, A

    2006-03-15

    The topic of this thesis work concerns the design and the characterization of an efficient device devoted to the temporal contrast improvement for ultra-intense femtosecond laser pulses. The contrast is defined as the intensity ratio between the main femtosecond pulse and its nanosecond pedestal. This pedestal is the amplified spontaneous emission (ASE), inherent with laser amplification mechanism. The ASE background has dramatic effects for laser-matter interactions on a solid target. The presented work consists in the theoretical and experimental study of a temporal filter based on a third order nonlinear effect acting on the pulse polarization. We have studied several kinds of nonlinear filters. The selected device is based on the process of cross-polarized wave generation (XPW) in crystals with an anisotropic third-order nonlinear susceptibility. This nonlinear filter has been experimented on various femtosecond systems. It allows a contrast improvement of several orders of magnitude, as demonstrated by temporal profiles measurements on a large intensity dynamic. A device to improve the nonlinear process conversion efficiency, it means the filter transmission, has also been achieved. This method is based on constructive interferences between XPW signals generated in different crystals. This setup has made it possible to reach experimentally the maximum theoretical efficiency ( >20%) and in the same time ensures the system stability. At least, we have demonstrated that the filter preserves, or even improves, spectral and spatial qualities of the laser pulse. These results are thus particularly promising and allow contemplating the implementation of the filter in current femtosecond systems. (author)

  19. Test field for airborne laser scanning in Finland

    Science.gov (United States)

    Ahokas, E.; Kaartinen, H.; Kukko, A.; Litkey, P.

    2014-11-01

    Airborne laser scanning (ALS) is a widely spread operational measurement tool for obtaining 3D coordinates of the ground surface. There is a need for calibrating the ALS system and a test field for ALS was established at the end of 2013. The test field is situated in the city of Lahti, about 100 km to the north of Helsinki. The size of the area is approximately 3.5 km × 3.2 km. Reference data was collected with a mobile laser scanning (MLS) system assembled on a car roof. Some streets were measured both ways and most of them in one driving direction only. The MLS system of the Finnish Geodetic Institute (FGI) consists of a navigation system (NovAtel SPAN GNSS-IMU) and a laser scanner (FARO Focus3D 120). In addition to the MLS measurements more than 800 reference points were measured using a Trimble R8 VRS-GNSS system. Reference points are along the streets, on parking lots, and white pedestrian crossing line corners which can be used as reference targets. The National Land Survey of Finland has already used this test field this spring for calibrating their Leica ALS-70 scanner. Especially it was easier to determine the encoder scale factor parameter using this test field. Accuracy analysis of the MLS points showed that the point height RMSE is 2.8 cm and standard deviation is 2.6 cm. Our purpose is to measure both more MLS data and more reference points in the test field area to get a better spatial coverage. Calibration flight heights are planned to be 1000 m and 2500 m above ground level. A cross pattern, southwest-northeast and northwest-southeast, will be flown both in opposite directions.

  20. Experimental Development of Low-emittance Field-emission Electron Sources

    Energy Technology Data Exchange (ETDEWEB)

    Lueangaranwong, A. [Northern Illinois Univ., DeKalb, IL (United States). Northern Illinois Center for Accelerator & Detector Development; Buzzard, C. [Northern Illinois Univ., DeKalb, IL (United States); Divan, R. [Argonne National Lab. (ANL), Argonne, IL (United States). Center for Nanoscale Materials; Korampally, V. [Northern Illinois Univ., DeKalb, IL (United States); Piot, P. [Northern Illinois Univ., DeKalb, IL (United States). Northern Illinois Center for Accelerator & Detector Development; Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2016-10-10

    Field emission electron sources are capable of extreme brightness when excited by static or time-dependent electro- magnetic fields. We are currently developing a cathode test stand operating in DC mode with possibility to trigger the emission using ultra-short (~ 100-fs) laser pulses. This contribution describes the status of an experiment to investigate field-emission using cathodes under development at NIU in collaboration with the Argonne’s Center for Nanoscale Materials.

  1. Rydberg excitation of neutral nitric oxide molecules in strong UV and near-IR laser fields

    International Nuclear Information System (INIS)

    Lv Hang; Zhang Jun-Feng; Zuo Wan-Long; Xu Hai-Feng; Jin Ming-Xing; Ding Da-Jun

    2015-01-01

    Rydberg state excitations of neutral nitric oxide molecules are studied in strong ultraviolet (UV) and near-infra-red (IR) laser fields using a linear time-of-flight (TOF) mass spectrometer with the pulsed electronic field ionization method. The yield of Rydberg molecules is measured as a function of laser intensity and ellipticity, and the results in UV laser fields are compared with those in near-IR laser fields. The present study provides the first experimental evidence of neutral Rydberg molecules surviving in a strong laser field. The results indicate that a rescattering-after-tunneling process is the main contribution to the formation of Rydberg molecules in strong near-IR laser fields, while multi-photon excitation may play an important role in the strong UV laser fields. (paper)

  2. Investigation of field emission properties of laser irradiated tungsten

    International Nuclear Information System (INIS)

    Akram, Mahreen; Bashir, Shazia; Hayat, Asma; Mahmood, Khaliq; Jalil, Sohail Abdul; Rafique, Muhammad Shahid

    2018-01-01

    Nd:YAG laser irradiation of Tungsten (W) has been performed in air at atmospheric pressure for four laser fluences ranging from 130 to 500 J/cm 2 . Scanning electron microscope analysis revealed the formation of micro and nanoscale surface features including cones, grains, mounds and pores. Field emission (FE) studies have been performed in a planar diode configuration under ultra-high vacuum conditions by recording I-V characteristics and plotting corresponding electric field (E) versus emission current density (J). The Fowler-Nordheim (FN) plots are found to be linear confirming the quantum mechanical tunneling phenomena for the structured targets. The irradiated samples at different fluences exhibit a turn-on field, field enhancement factor β and a maximum current density ranging from 5 to 8.5 V/μm, 1300 to 3490 and 107 to 350 μA/cm 2 , respectively. The difference in the FE properties is attributed to the variation in the nature and density of the grown structures at different fluences. (orig.)

  3. Measurement of deformation field in CT specimen using laser speckle

    International Nuclear Information System (INIS)

    Jeon, Moon Chang; Kang, Ki Ju

    2001-01-01

    To obtain A 2 experimentally in the J-A 2 theory, deformation field on the lateral surface of a CT specimen was to be determined using laser speckle method. The crack growth was measured using direct current potential drop method and most procedure of experimental and data reduction was performed according to ASTM Standard E1737-96. Laser speckle images during crack propagation were monitored by two CCD cameras to cancel the effect of rotation and translation of the specimen. An algorithm to pursue displacement of a point from each image was developed and successfully used to measure A 2 continuously as the crack tip was propagated. The effects of specimen thickness on J-R curve and A 2 were explored

  4. Nonresonant interaction of ultrashort electromagnetic pulses with multilevel quantum systems

    Science.gov (United States)

    Belenov, E.; Isakov, V.; Nazarkin, A.

    1994-01-01

    Some features of the excitation of multilevel quantum systems under the action of electromagnetic pulses which are shorter than the inverse frequency of interlevel transitions are considered. It is shown that the interaction is characterized by a specific type of selectivity which is not connected with the resonant absorption of radiation. The simplest three-level model displays the inverse population of upper levels. The effect of an ultrashort laser pulse on a multilevel molecule was regarded as an instant reception of the oscillation velocity by the oscillator and this approach showed an effective excitation and dissociation of the molecule. The estimations testify to the fact that these effects can be observed using modern femtosecond lasers.

  5. Optical circular deflector with attosecond resolution for ultrashort electron beam

    Directory of Open Access Journals (Sweden)

    Zhen Zhang

    2017-05-01

    Full Text Available A novel method using high-power laser as a circular deflector is proposed for the measurement of femtosecond (fs and sub-fs electron beam. In the scheme, the electron beam interacts with a laser pulse operating in a radially polarized doughnut mode (TEM_{01^{*}} in a helical undulator, generating angular kicks along the beam in two directions at the same time. The phase difference between the two angular kicks makes the beam form a ring after a propagation section with appropriate phase advance, which can reveal the current profile of the electron beam. Detailed theoretical analysis of the method and numerical results with reasonable parameters are both presented. It is shown that the temporal resolution can reach up to ∼100 attosecond, which is a significant improvement for the diagnostics of ultrashort electron beam.

  6. Effects of an external magnetic field in pulsed laser deposition

    Science.gov (United States)

    García, T.; de Posada, E.; Villagrán, M.; Ll, J. L. Sánchez; Bartolo-Pérez, P.; Peña, J. L.

    2008-12-01

    Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation of a sintered ceramic SrFe 12O 19 target with and without the presence of a nonhomogeneous magnetic field of μ0H = 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.

  7. Advanced Channeling Technologies in Plasma and Laser Fields

    Directory of Open Access Journals (Sweden)

    Dabagov Sultan B.

    2018-01-01

    Full Text Available Channeling is the phenomenon well known in the world mostly related to the motion of the beams of charged particles in aligned crystals. However, recent studies have shown the feasibility of channeling phenomenology application for description of other various mechanisms of interaction of charged as well as neutral particle beams in solids, plasmas and electromagnetic fields covering the research fields from crystal based undulators, collimators and accelerators to capillary based X-ray and neutron optical elements. This brief review is devoted to the status of channeling-based researches at different centers within international and national collaborations. Present and future possible developments in channeling tools applied to electron interactions in strong plasma and laser fields will be analyzed.

  8. 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: tupacgarcia@yahoo.com; 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)

    2008-12-30

    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.

  9. Multiple ionization dynamics of molecules in intense laser fields

    International Nuclear Information System (INIS)

    Ichimura, Atsushi; Ohyama-Yamaguchi, Tomoko

    2005-01-01

    A classical field-ionization model is developed for sequential multiple ionization of diatomic and linear triatomic molecules exposed to intense (∼ 10 15 W/cm 2 ) laser fields. The distance R ion of Coulomb explosion is calculated for a combination of fragment charges, by considering nonadiabatic excitation followed by field ionization associated with the inner and outer saddle points. For diatomic molecules (N 2 , NO, and I 2 ), the model explains behaviors observed in experiments, as R ion (21→31) ion (21→22) between competing charge-asymmetric and symmetric channels, and even-odd fluctuation along a principal pathway. For a triatomic molecule CO 2 , a comparison of the model with an experiment suggests that charge-symmetric (or nearly symmetric) channels are dominantly populated. (author)

  10. Vector fields in a tight laser focus: comparison of models.

    Science.gov (United States)

    Peatross, Justin; Berrondo, Manuel; Smith, Dallas; Ware, Michael

    2017-06-26

    We assess several widely used vector models of a Gaussian laser beam in the context of more accurate vector diffraction integration. For the analysis, we present a streamlined derivation of the vector fields of a uniformly polarized beam reflected from an ideal parabolic mirror, both inside and outside of the resulting focus. This exact solution to Maxwell's equations, first developed in 1920 by V. S. Ignatovsky, is highly relevant to high-intensity laser experiments since the boundary conditions at a focusing optic dictate the form of the focus in a manner analogous to a physical experiment. In contrast, many models simply assume a field profile near the focus and develop the surrounding vector fields consistent with Maxwell's equations. In comparing the Ignatovsky result with popular closed-form analytic vector models of a Gaussian beam, we find that the relatively simple model developed by Erikson and Singh in 1994 provides good agreement in the paraxial limit. Models involving a Lax expansion introduce a divergences outside of the focus while providing little if any improvement in the focal region. Extremely tight focusing produces a somewhat complicated structure in the focus, and requires the Ignatovsky model for accurate representation.

  11. Strong-field ionization of linear molecules by a bicircular laser field: Symmetry considerations

    Science.gov (United States)

    Gazibegović-Busuladžić, A.; Busuladžić, M.; Hasović, E.; Becker, W.; Milošević, D. B.

    2018-04-01

    Using the improved molecular strong-field approximation, we investigate (high-order) above-threshold ionization [(H)ATI] of various linear polyatomic molecules by a two-color laser field of frequencies r ω and s ω (with integer numbers r and s ) having coplanar counter-rotating circularly polarized components (a so-called bicircular field). Reflection and rotational symmetries for molecules aligned in the laser-field polarization plane, analyzed for diatomic homonuclear molecules in Phys. Rev. A 95, 033411 (2017), 10.1103/PhysRevA.95.033411, are now considered for diatomic heteronuclear molecules and symmetric and asymmetric linear triatomic molecules. There are additional rotational symmetries for (H)ATI spectra of symmetric linear molecules compared to (H)ATI spectra of the asymmetric ones. It is shown that these symmetries manifest themselves differently for r +s odd and r +s even. For example, HATI spectra for symmetric molecules with r +s even obey inversion symmetry. For ATI spectra of linear molecules, reflection symmetry appears only for certain molecular orientation angles ±90∘-j r 180∘/(r +s ) (j integer). For symmetric linear molecules, reflection symmetry appears also for the angles -j r 180∘/(r +s ) . For perpendicular orientation of molecules with respect to the laser-field polarization plane, the HATI spectra are very similar to those of the atomic targets, i.e., both spectra are characterized by the same type of the (r +s )-fold symmetry.

  12. Magnetic field generation during intense laser channelling in underdense plasma

    Energy Technology Data Exchange (ETDEWEB)

    Smyth, A. G.; Sarri, G.; Doria, D.; Kar, S.; Borghesi, M. [School of Mathematics and Physics, The Queen' s University of Belfast, University Road, Belfast BT7 1NN (United Kingdom); Vranic, M.; Guillaume, E.; Silva, L. O.; Vieira, J. [GoLP/IPFN, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon (Portugal); Amano, Y.; Habara, H.; Tanaka, K. A. [Graduate School of Engineering Osaka University. Suita, Osaka 5650871 (Japan); Heathcote, R.; Norreys, P. A. [STFC Rutherford Appleton Laboratory, Didcot, Oxon OX1 0Qx (United Kingdom); Hicks, G.; Najmudin, Z.; Nakamura, H. [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BZ (United Kingdom)

    2016-06-15

    Channel formation during the propagation of a high-energy (120 J) and long duration (30 ps) laser pulse through an underdense deuterium plasma has been spatially and temporally resolved via means of a proton imaging technique, with intrinsic resolutions of a few μm and a few ps, respectively. Conclusive proof is provided that strong azimuthally symmetric magnetic fields with a strength of around 0.5 MG are created inside the channel, consistent with the generation of a collimated beam of relativistic electrons. The inferred electron beam characteristics may have implications for the cone-free fast-ignition scheme of inertial confinement fusion.

  13. In-system Performance of MQW Lasers Exposed to High Magnetic Field

    CERN Document Server

    Jensen, Fredrik Bjorn Henning; Azevedo, C S; Cervelli, Giovanni; Gill, Karl; Grabit, Robert; Vasey, François

    2000-01-01

    The effect of magnetic field has been investigated on 1310nm edge-emitting multi-quantum-well lasers. These lasers are candidate transmitters for the CMS tracker optical link, which will be operated in a 4T solenoidal magnetic field. In-situ measurements up to 2.4T of in-system laser analogue performance and laser spectral characteristics were carried out. No degradation of performance and spectral characteristics was observed

  14. Self-field effects on electron dynamics in free-electron lasers with axial magnetic field

    International Nuclear Information System (INIS)

    Mirzanejhad, S.; Maraghechi, B.; Mohsenpour, T.

    2004-01-01

    A self-consistent method for the analysis of self-magnetic field for a free-electron laser with a one-dimensional helical wiggler and an axial guide magnetic field is presented. The equilibrium orbits and their stability, under the influence of self-electric and self-magnetic fields, are analyzed. New unstable orbits, in the first part of the Group I orbits and in the resonance region of the Group II orbits, are found. It is shown that an increase in the defocusing effect of self-fields will widen the unstable orbits. An anomalous self-field regime is found where an increase in the defocusing effect of self-fields can have stabilizing effect on the resonance region

  15. Application of a flow generated by IR laser and AC electric field in micropumping and micromixing

    International Nuclear Information System (INIS)

    Nakano, M; Mizuno, A

    2008-01-01

    In this paper, it is described that measurement of fluid flow generated by simultaneous operation of an infrared (IR) laser and AC electric field in a microfabricated channel. When an IR laser (1026 nm) was focused under an intense AC electric field, a circulating flow was generated around the laser focus. The IR laser and the electric field generate two flow patterns of the electrohydrodynamicss. When the laser focus is placed at the center of the gap between electrodes, the flow pattern is parallel to the AC electric field toward electrodes from the centre. On the other hand, when the laser focus is placed close to one of the electrodes, one directional flow is generated. First flow pattern can be used as a micromixer and the second one as a micropump. Flow velocity profiles of the two flow patterns were measured as a function of the laser power, intensity of the AC electric field and AC frequency.

  16. Progress in Ultrafast Intense Laser Science VI

    CERN Document Server

    Yamanouchi, Kaoru; Bandrauk, André D

    2010-01-01

    The PUILS series delivers up-to-date reviews of progress in Ultrafast Intense Laser Science, a newly emerging interdisciplinary research field spanning atomic and molecular physics, molecular science, and optical science, which has been stimulated by the recent developments in ultrafast laser technologies. Each volume compiles peer-reviewed articles authored by researchers at the forefront of each their own subfields of UILS. Every chapter opens with an overview of the topics to be discussed, so that researchers unfamiliar to the subfield, as well as graduate students, can grasp the importance and attractions of the research topic at hand; these are followed by reports of cutting-edge discoveries. This sixth volume covers a broad range of topics from this interdisciplinary research field, focusing on responses of molecules to ultrashort intense laser pulses, generation and characterization of attosecond pulses and high-order harmonics, and filamentation and laser-plasma interaction.

  17. Near-field enhanced electron acceleration from dielectric nanospheres in intense few-cycle laser fields

    International Nuclear Information System (INIS)

    Zherebtsov, S.; Znakovskaya, I.; Wirth, A.; Herrwerth, O.; Suessmann, F.; Ahmad, I.; Trushin, S.; Fennel, Th.; Plenge, J.; Antonsson, E.

    2010-01-01

    Complete text of publication follows. The interaction of nanostructured materials with few-cycle laser light has attracted significant attention lately. This interest is driven by both the quest for fundamental insight into the real-time dynamics of many-electron systems and a wide range of far-reaching applications, such as, e.g. ultrafast computation and information storage on the nanoscale and the generation of XUV frequency combs. We investigated the above-threshold electron emission from isolated SiO 2 nanoparticles in waveform controlled few-cycle laser fields at intensities close to the tunneling regime. The enhancement of the electron acceleration from the silica nanoparticles was explored as a function of the particle size (ranging from 50 to 147 nm) and the laser peak intensity (1 - 4x10 13 W/cm 2 ). Obtained cut-off values in the kinetic energy spectra are displayed in Fig. 1. The cut-off values show a linear dependence with intensity within the studied intensity range, with the average cut-off energy being 53 U P , indicated by the black line. Quasi-classical simulations of the emission process reveal that electron rescattering in the locally enhanced near-field of the particle is responsible for the large energy gain. The observed near-field enhancement offers promising new routes for pushing the limits of strong-field phenomena relying on electron rescattering, such as, high-harmonic generation and molecular imaging.

  18. The effects of intense laser field and applied electric and magnetic fields on optical properties of an asymmetric quantum well

    Energy Technology Data Exchange (ETDEWEB)

    Restrepo, R.L., E-mail: pfrire@eia.edu.co [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Escuela de Ingeniería de Antioquia-EIA, Envigado (Colombia); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia); Ungan, F.; Kasapoglu, E. [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonóma del Estado de Morelos, Ave. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Morales, A.L.; Duque, C.A. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia)

    2015-01-15

    This paper presents the results of the theoretical study of the effects of non-resonant intense laser field and electric and magnetic fields on the optical properties (the linear and third-order nonlinear refractive index and absorption coefficients) in an asymmetric quantum well. The electric field and intense laser field are applied along the growth direction of the asymmetric quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the asymmetric quantum well, the effective mass approximation and the method of envelope wave function are used. The asymmetric quantum well is constructed by using different aluminium concentrations in both right and left barriers. The confinement in the quantum well is changed drastically by either the effect of electric and magnetic fields or by the application of intense laser field. The optical properties are calculated using the compact density matrix approach. The results show that the effect of the intense laser field competes with the effects of the electric and magnetic fields. Consequently, peak position shifts to lower photon energies due to the effect of the intense laser field and it shifts to higher photon energies by the effects of electric and magnetic fields. In general, it is found that the concentration of aluminum, electric and magnetic fields and intense laser field are external agents that modify the optical responses in the asymmetric quantum well.

  19. Laser speckle contrast imaging using light field microscope approach

    Science.gov (United States)

    Ma, Xiaohui; Wang, Anting; Ma, Fenghua; Wang, Zi; Ming, Hai

    2018-01-01

    In this paper, a laser speckle contrast imaging (LSCI) system using light field (LF) microscope approach is proposed. As far as we known, it is first time to combine LSCI with LF. To verify this idea, a prototype consists of a modified LF microscope imaging system and an experimental device was built. A commercially used Lytro camera was modified for microscope imaging. Hollow glass tubes with different depth fixed in glass dish were used to simulate the vessels in brain and test the performance of the system. Compared with conventional LSCI, three new functions can be realized by using our system, which include refocusing, extending the depth of field (DOF) and gathering 3D information. Experiments show that the principle is feasible and the proposed system works well.

  20. Black phosphorus saturable absorber for ultrashort pulse generation

    Energy Technology Data Exchange (ETDEWEB)

    Sotor, J., E-mail: jaroslaw.sotor@pwr.edu.pl; Sobon, G.; Abramski, K. M. [Laser and Fiber Electronics Group, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, Wroclaw 50-370 (Poland); Macherzynski, W.; Paletko, P. [Faculty of Microsystem Electronics and Photonics, Wroclaw University of Technology, Janiszewskiego 11/17, Wroclaw 50-372 (Poland)

    2015-08-03

    Low-dimensional materials, due to their unique and versatile properties, are very interesting for numerous applications in electronics and optoelectronics. Recently rediscovered black phosphorus, with a graphite-like layered structure, can be effectively exfoliated up to the single atomic layer called phosphorene. Contrary to graphene, it possesses a direct band gap controllable by the number of stacked atomic layers. For those reasons, black phosphorus is now intensively investigated and can complement or replace graphene in various photonics and electronics applications. Here, we demonstrate that black phosphorus can serve as a broadband saturable absorber and can be used for ultrashort optical pulse generation. The mechanically exfoliated ∼300 nm thick layers of black phosphorus were transferred onto the fiber core, and under pulsed excitation at 1560 nm wavelength, its transmission increases by 4.6%. We have demonstrated that the saturable absorption of black phosphorus is polarization sensitive. The fabricated device was used to mode-lock an Er-doped fiber laser. The generated optical solitons with the 10.2 nm bandwidth and 272 fs duration were centered at 1550 nm. The obtained results unambiguously show that black phosphorus can be effectively used for ultrashort pulse generation with performances similar or even better than currently used graphene or carbon nanotubes. This application of black phosphorus proves its great potential to future practical use in photonics.

  1. Superfocusing of an ultrashort plasmon pulse by a conducting cone

    Energy Technology Data Exchange (ETDEWEB)

    Manuilovich, E S; Astapenko, V A [Moscow Institute of Physics and Technology (State University), Dolgoprudnyi, Moscow Region (Russian Federation); Golovinskii, P A [Voronezh State University of Architecture and Civil Engineering, Voronezh (Russian Federation)

    2016-01-31

    We have shown theoretically the possibility of controlling nanoscale superfocusing of plasmons in a metal conical tip by modulating the carrier frequency of the pulse. The propagation of an ultrashort plasmon pulse in a metal nanoneedle is simulated numerically. The calculation is based on an asymptotic analytical solution of Maxwell's equations for electromagnetic wave propagation in a conical conductor in the vicinity of its apex, obtained by the approximate separation of variables in spherical coordinates. The dependence the field superfocusing on the conductor material, pulse chirp and propagation length is studied. (nanooptics)

  2. Chaotic scattering from hydrogen atoms in a circularly polarized laser field

    International Nuclear Information System (INIS)

    Okon, Elias; Parker, William; Chism, Will; Reichl, Linda E.

    2002-01-01

    We investigate the classical dynamics of a hydrogen atom in a circularly polarized laser beam with finite radius. The spatial cutoff for the laser field allows us to use scattering processes to examine the laser-atom dynamics. We find that for certain field parameters, the delay times, the angular momentum, and the distance of closest approach of the scattered electron exhibit fractal behavior. This fractal behavior is a signature of chaos in the dynamics of the atom-field system

  3. Generation and application of ultrashort coherent mid-infrared electromagnetic radiation

    Science.gov (United States)

    Wandel, Scott

    Particle accelerators are useful instruments that help address critical issues for the future development of nuclear energy. Current state-of-the-art accelerators based on conventional radio-frequency (rf) cavities are too large and expensive for widespread commercial use, and alternative designs must be considered for supplying relativistic beams to small-scale applications, including medical imaging, secu- rity screening, and scientific research in a university-scale laboratory. Laser-driven acceleration using micro-fabricated dielectric photonic structures is an attractive approach because such photonic microstructures can support accelerating fields that are 10 to 100 times higher than that of rf cavity-based accelerators. Dielectric laser accelerators (DLAs) use commercial lasers as a driving source, which are smaller and less expensive than the klystrons used to drive current rf-based accelerators. Despite the apparent need for compact and economical laser sources for laser-driven acceleration, the availability of suitable high-peak-power lasers that cover a broad spectral range is currently limited. To address the needs of several innovative acceleration mechanisms like DLA, it is proposed to develop a coherent source of mid-infrared (IR) electromagnetic radiation that can be implemented as a driving source of laser accelerators. The use of ultrashort mid-IR high peak power laser systems in various laser-driven acceleration schemes has shown the potential to greatly reduce the optical pump intensities needed to realize high acceleration gradients. The optical intensity needed to achieve a given ponderomotive potential is 25 times less when using a 5-mum mid-IR laser as compared to using a 1-mum near-IR solid-state laser. In addition, dielectric structure breakdown caused by multiphoton ionization can be avoided by using longer-wavelength driving lasers. Current mid-IR laser sources do not produce sufficiently short pulse durations, broad spectral bandwidths

  4. Ponderomotive force, magnetic fields and hydrodynamics of laser produced plasmas

    International Nuclear Information System (INIS)

    Bobin, J.-L.; Wee Woo; Degroot, J.-S.

    1977-01-01

    Nonlinear effects deeply change the structure of a laser driven plasma flow. For high intensities, the radiation pressure should be taken into account. It acts through a ponderomotive force proportional to the electron density and to the gradient of the mean electric field energy density of the incident wave. Static magnetic fields originate from a term in the ponderomotive force which includes radiation absorption and whose curl is non zero. The basic properties of the structure are determined analytically in the absence of thermal conductivity and magnetic fields: steep density gradient close to the cut-off density, shelf at lower densities. The conditions of a steady state regime are set up. The isothermal case is specially investigated. It is shown that the cavities which are created in a motionless plasma may disappear due to the onset of a flow. Regions in which electromagnetic forces arising from the static field compensate the ponderomotive force are determined. The subsequent effects on the flow itself are studied [fr

  5. Asymmetry of light absorption upon propagation of focused femtosecond laser pulses with spatiotemporal coupling through glass materials

    Science.gov (United States)

    Zhukov, Vladimir P.; Bulgakova, Nadezhda M.

    2017-05-01

    Ultrashort laser pulses are usually described in terms of temporal and spatial dependences of their electric field, assuming that the spatial dependence is separable from time dependence. However, in most situations this assumption is incorrect as generation of ultrashort pulses and their manipulation lead to couplings between spatial and temporal coordinates resulting in various effects such as pulse front tilt and spatial chirp. One of the most intriguing spatiotemporal coupling effects is the so-called "lighthouse effect", the phase front rotation with the beam propagation distance [Akturk et al., Opt. Express 13, 8642 (2005)]. The interaction of spatiotemporally coupled laser pulses with transparent materials have interesting peculiarities, such as the effect of nonreciprocal writing, which can be used to facilitate microfabrication of photonic structures inside optical glasses. In this work, we make an attempt to numerically investigate the influence of the pulse front tilt and the lighthouse effect on the absorption of laser energy inside fused silica glass. The model, which is based on nonlinear Maxwell's equations supplemented by the hydrodynamic equations for free electron plasma, is applied. As three-dimensional solution of such a problem would require huge computational resources, a simplified two-dimensional model has been proposed. It has enabled to gain a qualitative insight into the features of propagation of ultrashort laser pulses with the tilted front in the regimes of volumetric laser modification of transparent materials, including directional asymmetry upon direct laser writing in glass materials.

  6. Longitudinal phase space manipulation of an ultrashort electron beam via THz IFEL interaction

    Energy Technology Data Exchange (ETDEWEB)

    Moody, J. T.; Li, R. K.; Musumeci, P.; Scoby, C. M.; To, H. [Department of Physics and Astronomy, UCLA, Los Angeles California, 90095 (United States)

    2012-12-21

    A scheme where a laser locked THz source is used to manipulate the longitudinal phase space of an ultrashort electron beam using an IFEL interaction is investigated. The efficiency of THz source based on the pulse front tilt optical rectification scheme is increased by cryogenic cooling to achieve sufficient THz power for compression and synchronization. Start-to-end simulations describing the evolution of the beam from the cathode to the compression point after the undulator are presented.

  7. Longitudinal phase space manipulation of an ultrashort electron beam via THz IFEL interaction

    International Nuclear Information System (INIS)

    Moody, J. T.; Li, R. K.; Musumeci, P.; Scoby, C. M.; To, H.

    2012-01-01

    A scheme where a laser locked THz source is used to manipulate the longitudinal phase space of an ultrashort electron beam using an IFEL interaction is investigated. The efficiency of THz source based on the pulse front tilt optical rectification scheme is increased by cryogenic cooling to achieve sufficient THz power for compression and synchronization. Start-to-end simulations describing the evolution of the beam from the cathode to the compression point after the undulator are presented.

  8. A numerical study of the integral equations for the laser fields in free-electron lasers

    International Nuclear Information System (INIS)

    Yoo, J. G.; Park, S. H.; Jeong, Y. U.; Lee, B. C.; Rhee, Y. J.; Cho, S. O.

    2004-01-01

    The dynamics of the radiation fields in free-electron lasers is investigated on the basis of the integro-differential equations in the one-dimensional formulation. For simple cases we solved the integro-differential equations analytically and numerically to test our numerical procedures developed on the basis of the Filon method. The numerical results showed good agreement with the analytical solutions. To confirm the legitimacy of the numerical package, we carried out numerical studies on the inhomogeneous broadening effects, where no analytic solutions are available, due to the energy spread and the emittance of the electron beam.

  9. Progress in Ultrafast Intense Laser Science III

    CERN Document Server

    Yamanouchi, Kaoru; Agostini, Pierre; Ferrante, Gaetano

    2008-01-01

    The PUILS series presents Progress in Ultrafast Intense Laser Science, a newly emerging interdisciplinary research field spanning atomic and molecular physics, molecular science, and optical science. PUILS has been stimulated by the recent development of ultrafast laser technologies. Each volume contains approximately 15 chapters, authored by researchers at the forefront. Each chapter opens with an overview of the topics to be discussed, so that researchers, who are not experts in the specific topics, as well as graduate students can grasp the importance and attractions of this sub-field of research, and these are followed by reports of cutting-edge discoveries. This third volume covers a diverse range of disciplines, focusing on such topics as strong field ionization of atoms, ionization and fragmentation of molecules and clusters, generation of high-order harmonics and attosecond pulses, filamentation and laser plasma interaction, and the development of ultrashort and ultrahigh-intensity light sources.

  10. Beam shaping to provide round and square-shaped beams in optical systems of high-power lasers

    Science.gov (United States)

    Laskin, Alexander; Laskin, Vadim

    2016-05-01

    Optical systems of modern high-power lasers require control of irradiance distribution: round or square-shaped flat-top or super-Gaussian irradiance profiles are optimum for amplification in MOPA lasers and for thermal load management while pumping of crystals of solid-state ultra-short pulse lasers to control heat and minimize its impact on the laser power and beam quality while maximizing overall laser efficiency, variable profiles are also important in irradiating of photocathode of Free Electron lasers (FEL). It is suggested to solve the task of irradiance re-distribution using field mapping refractive beam shapers like piShaper. The operational principle of these devices presumes transformation of laser beam intensity from Gaussian to flat-top one with high flatness of output wavefront, saving of beam consistency, providing collimated output beam of low divergence, high transmittance, extended depth of field, negligible residual wave aberration, and achromatic design provides capability to work with ultra-short pulse lasers having broad spectrum. Using the same piShaper device it is possible to realize beams with flat-top, inverse Gauss or super Gauss irradiance distribution by simple variation of input beam diameter, and the beam shape can be round or square with soft edges. This paper will describe some design basics of refractive beam shapers of the field mapping type and optical layouts of their applying in optical systems of high-power lasers. Examples of real implementations and experimental results will be presented as well.

  11. Progress in Ultrafast Intense Laser Science Volume V

    CERN Document Server

    Yamanouchi, Kaoru; Ledingham, Kenneth

    2010-01-01

    The PUILS series delivers up-to-date reviews of progress in Ultrafast Intense Laser Science, a newly emerging interdisciplinary research field spanning atomic and molecular physics, molecular science, and optical science, which has been stimulated by the recent developments in ultrafast laser technologies. Each volume compiles peer-reviewed articles authored by researchers at the forefront of each their own subfields of UILS. Every chapter opens with an overview of the topics to be discussed, so that researchers unfamiliar to the subfield, as well as graduate students, can grasp the importance and attractions of the research topic at hand; these are followed by reports of cutting-edge discoveries. This fifth volume covers a broad range of topics from this interdisciplinary research field, focusing on coherent responses of gaseous and condensed matter to ultrashort intense laser pulses, propagation of intense laser pulses, and laser-plasma interaction and its applications.

  12. High-order harmonic generation in laser plasma plumes

    CERN Document Server

    Ganeev, Rashid A

    2013-01-01

    This book represents the first comprehensive treatment of high-order harmonic generation in laser-produced plumes, covering the principles, past and present experimental status and important applications. It shows how this method of frequency conversion of laser radiation towards the extreme ultraviolet range matured over the course of multiple studies and demonstrated new approaches in the generation of strong coherent short-wavelength radiation for various applications. Significant discoveries and pioneering contributions of researchers in this field carried out in various laser scientific centers worldwide are included in this first attempt to describe the important findings in this area of nonlinear spectroscopy. "High-Order Harmonic Generation in Laser Plasma Plumes" is a self-contained and unified review of the most recent achievements in the field, such as the application of clusters (fullerenes, nanoparticles, nanotubes) for efficient harmonic generation of ultrashort laser pulses in cluster-containin...

  13. Influence of the virtual photon field on the squeezing properties of an atom laser

    International Nuclear Information System (INIS)

    Jian-Gang, Zhao; Chang-Yong, Sun; Ling-Hua, Wen; Bao-Long, Liang

    2009-01-01

    This paper investigates the squeezing properties of an atom laser without rotating-wave approximation in the system of a binomial states field interacting with a two-level atomic Bose–Einstein condensate. It discusses the influences of atomic eigenfrequency, the interaction intensity between the optical field and atoms, parameter of the binomial states field and virtual photon field on the squeezing properties. The results show that two quadrature components of an atom laser can be squeezed periodically. The duration and the degree of squeezing an atom laser have something to do with the atomic eigenfrequency and the parameter of the binomial states field, respectively. The collapse and revival frequency of atom laser fluctuation depends on the interaction intensity between the optical field and atoms. The effect of the virtual photon field deepens the depth of squeezing an atom laser

  14. Relative Nonlinear Electrodynamics Interaction of Charged Particles with Strong and Super Strong Laser Fields

    CERN Document Server

    Avetissian, Hamlet

    2006-01-01

    This book covers a large class of fundamental investigations into Relativistic Nonlinear Electrodynamics. It explores the interaction between charged particles and strong laser fields, mainly concentrating on contemporary problems of x-ray lasers, new type small set-up high-energy accelerators of charged particles, as well as electron-positron pair production from super powerful laser fields of relativistic intensities. It will also discuss nonlinear phenomena of threshold nature that eliminate the concurrent inverse processes in the problems of Laser Accelerator and Free Electron Laser, thus creating new opportunities for solving these problems.

  15. Dynamics of dissociation versus ionization in strong laser fields

    International Nuclear Information System (INIS)

    DiMauro, L.F.; Yang, B.

    1993-01-01

    In this paper, experimental results are presented which clearly demonstrate the effectiveness that an external field has in altering the dissociation dynamics. The experiment examines the strong-field dissociation dynamics of molecular hydrogen ions and its deuterated isotopes. These studies involve multiphoton excitation in the intensity regime of 10 11-14 W/cm 2 with the fundamental and second harmonic of a ND:YAG or ND:YLF laser system. Measurements include energy resolved electron and mass spectroscopy which provide useful probes in elucidating the interaction dynamics predicted by existing models. The example this in this paper, examines the strong-field dissociation of H 2 + , HD + , and D 2 + at green (0.5 μm) and (1μm) frequencies. The diatomic ions are formed via multiphonon ionization of the neutral precursor which is physically separable from the dissociation process. This study provides the first observation of the dynamics associated with the above threshold dissociation (ATD) process and analogies will be made with the more familiar above threshold ionization (ATI) phenomenon

  16. Coherence properties of the harmonic generation in intense laser field

    International Nuclear Information System (INIS)

    Salieres, P.

    1995-01-01

    In this thesis is presented an experimental and theoretical study of the harmonic generation in intense field and coherence properties of this radiation. The first part reminds the main harmonic specter characteristics. Follow then experimental studies of the tray extension with the laser lighting, the harmonic generation by ions, and the influence of the laser field on the efficiency of generation. The second part presents the quantum model of the harmonic generation in tunnel regime that we have used for the calculation of the dipoles. We compare dependence in lighting of some harmonic, by insisting on the characteristic behavior of the atomic phase. The theory of the propagation is presented in third part. After the reminder of the case of a perturbative polarization, we develop the case of the polarization in tunnel regime. With the help of numerical simulations, we show the influence of the atomic phase on the agreement of phase, and therefore on the efficiency of conversion and profiles of generation in the medium. The importance of the geometry of the interaction is underlined. The part IV presents the study of the spatial coherence of the harmonic radiation. We develop first consequences of the theory of the agreement of phase for profiles of emission. Then the comparison with experimental profiles is detailed in function of the different parameters( order of non linearity, laser lighting, position of the focus by report in the gaseous medium). The study of the spectral and temporal coherence of the part V begins with the experimental effect investigation of the ionization on specters of the harmonic of weak order. We present then theoretical predictions of the preceding model for spectral and temporal profiles of the harmonic of highest order, generated in tunnel regime. The part VI is devoted to the UVX source aspect of the harmonic radiation. General characteristics (number of photons, agreement) are first detailed, then we present the first experiences

  17. Attosecond pulse trains generated using two color laser fields

    International Nuclear Information System (INIS)

    Mauritsson, J.; Louisiana State University, Baton Rouge, LA; Johnsson, P.; Gustafsson, E.; L'Hullier, A.; Schafer, K.J.; Gaarde, M.B.

    2006-01-01

    Complete test of publication follows. We present the generation of attosecond pulse trains from a superposition of an infrared (IR) laser field and its second harmonic. Our attosecond pulses are synthesized by selecting a number of synchronized harmonics generated in argon. By adding the second harmonic to the driving field the inversion symmetry of generation process is broken and both odd and even harmonics are generated. Consecutive half cycles in the two color field differ beyond the simple sign change that occurs in a one color field and have very different shapes and amplitudes. This sub-cycle structure of the field, which governs the generation of the attosecond pulses, depends strongly on the relative phase and intensity of the two fields, thereby providing additional control over the generation process. The generation of attosecond pulses is frequently described using the semi-classical three step model where an electron is: (1) ionized through tunneling ionization during one half cycle; (2) reaccelerated back towards the ion core by the next half cycle; where it (3) recombines with the ground-state releasing the access energy in a short burst of light. In the two color field the symmetry between the ionizing and reaccelerating field is broken, which leads to two possible scenarios: the electron can either be ionized during a strong half cycle and reaccelerated by a weaker field or vice versa. The periodicity is a full IR cycle in both cases and hence two trains of attosecond pulses are generated which are offset from each other. The generation efficiency, however, is very different for the two cases since it is determined mainly by the electric field strength at the time of tunneling and one of the trains will therefore dominate the other. We investigate experimentally both the spectral and temporal structure of the generated attosecond pulse trains as a function of the relative phase between the two driving fields. We find that for a wide range of

  18. Collective-field-corrected strong field approximation for laser-irradiated metal clusters

    International Nuclear Information System (INIS)

    Keil, Th; Bauer, D

    2014-01-01

    The strong field approximation (SFA) formulated in terms of so-called ‘quantum orbits’ led to much insight into intense-laser driven ionization dynamics. In plain SFA, the emitted electron is treated as a free electron in the laser field alone. However, with improving experimental techniques and more advanced numerical simulations, it becomes more and more obvious that the plain SFA misses interesting effects even on a qualitative level. Examples are holographic side lobes, the low-energy structure, radial patterns in photoelectron spectra at low kinetic energies and strongly rotated angular distributions. For this reason, increasing efforts have been recently devoted to Coulomb corrections of the SFA. In the current paper, we follow a similar line but consider ionization of metal clusters. It is known that photoelectrons from clusters can be much more energetic than those emitted from atoms or small molecules, especially if the Mie resonance of the expanding cluster is evoked. We develop a SFA that takes the collective field inside the cluster via the simple rigid-sphere model into account. Our approach is based on field-corrected quantum orbits so that the acceleration process (or any other spectral feature of interest) can be investigated in detail. (paper)

  19. Measurements of magnetic fields generated in underdense plasmas by intense lasers

    International Nuclear Information System (INIS)

    Najmudin, Z.; Walton, B. R.; Mangles, S. P. D.; Dangor, A. E.; Krushelnick, K.; Fritzler, S.; Malka, V.; Faure, J.; Tatarakis, M.

    2006-01-01

    Measurements have been made of the magnetic field generated by the passage of high intensity short laser pulses through underdense plasmas. For a 30 fs, 1 J, 800 nm linearly-polarised laser pulse, an azimuthal magnetic field is observed at a radial extent of approximately 200 μm. The field is found to exceed 2.8 MG. For a 1 ps, 40 J, 1054 nm circularly-polarised laser pulse, a solenoidal field is observed that can exceed 7 MG. This solenoidal field is absent with linear polarised light, and hence can be considered as an Inverse Faraday effect. Both types of field are found to decay on the picosecond timescale. For both the azimuthal and solenoidal fields produced by such intense lasers, the production of energetic electrons by the interaction is thought to be vital for magnetic field generation

  20. Femtosecond laser-matter interaction theory, experiments and applications

    CERN Document Server

    Gamaly, Eugene G

    2011-01-01

    Basics of Ultra-Short Laser-Solid InteractionsSubtle Atomic Motion Preceding a Phase Transition: Birth, Life and Death of PhononsUltra-Fast Disordering by fs-Lasers: Superheating Prior to Entropy CatastropheAblation of SolidsUltra-Short Laser-Matter Interaction Confined Inside a Bulk of Transparent SolidApplications of Ultra-Short Laser-Matter InteractionsConclusion Remarks.

  1. Laser Light-field Fusion for Wide-field Lensfree On-chip Phase Contrast Microscopy of Nanoparticles

    Science.gov (United States)

    Kazemzadeh, Farnoud; Wong, Alexander

    2016-12-01

    Wide-field lensfree on-chip microscopy, which leverages holography principles to capture interferometric light-field encodings without lenses, is an emerging imaging modality with widespread interest given the large field-of-view compared to lens-based techniques. In this study, we introduce the idea of laser light-field fusion for lensfree on-chip phase contrast microscopy for detecting nanoparticles, where interferometric laser light-field encodings acquired using a lensfree, on-chip setup with laser pulsations at different wavelengths are fused to produce marker-free phase contrast images of particles at the nanometer scale. As a proof of concept, we demonstrate, for the first time, a wide-field lensfree on-chip instrument successfully detecting 300 nm particles across a large field-of-view of ~30 mm2 without any specialized or intricate sample preparation, or the use of synthetic aperture- or shift-based techniques.

  2. Effect of the R dependence of laser-induced polarizability on molecular dynamic alignment in an intense femtosecond laser field

    International Nuclear Information System (INIS)

    Chen Jianxin; Cui Xiaomei; Huang Bomin; Wu Hongchun; Zhuo Shuangmu

    2006-01-01

    In the rotation equation of the angle θ between the molecular axis and the laser polarization direction, the dependence of laser-induced polarizability on the molecular internuclear distance R is considered. The effect of the R dependence of laser-induced polarizability on molecular dynamic alignment in an intense femtosecond laser field is investigated with 20 and 100 fs laser pulses for N 2 molecules and with 60 and 100 fs laser pulses for Br 2 molecules at intensities of 5x10 14 W cm -2 and 5x10 15 W cm -2 . This effect exists and only occurs during the dissociative process after the molecule is ionized. It enhances the degrees of molecular dynamic alignment and is more significant in reorienting the angular distributions of molecules towards the laser polarization direction in the conditions of high laser intensity and short pulse length. Compared with the N 2 molecule, the effect of the R dependence of laser-induced polarizability on molecular dynamic alignment for Br 2 is stronger. The reasons are presented and discussed

  3. Fibre amplifier based on an ytterbium-doped active tapered fibre for the generation of megawatt peak power ultrashort optical pulses

    Energy Technology Data Exchange (ETDEWEB)

    Koptev, M Yu; Anashkina, E A; Lipatov, D S; Andrianov, A V; Muravyev, S V; Kim, A V [Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod (Russian Federation); Bobkov, K K; Likhachev, M E; Levchenko, A E; Aleshkina, S S; Semjonov, S L; Denisov, A N; Bubnov, M M [Fiber Optics Research Center, Russian Academy of Sciences, Moscow (Russian Federation); Laptev, A Yu; Gur' yanov, A N [G.G.Devyatykh Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

    2015-05-31

    We report a new ytterbium-doped active tapered fibre used in the output amplifier stage of a fibre laser system for the generation of megawatt peak power ultrashort pulses in the microjoule energy range. The tapered fibre is single-mode at its input end (core and cladding diameters of 10 and 80 μm) and multimode at its output end (diameters of 45 and 430 μm), but ultrashort pulses are amplified in a quasi-single-mode regime. Using a hybrid Er/Yb fibre system comprising an erbium master oscillator and amplifier at a wavelength near 1.5 μm, a nonlinear wavelength converter to the 1 μm range and a three-stage ytterbium-doped fibre amplifier, we obtained pulses of 1 μJ energy and 7 ps duration, which were then compressed by a grating-pair dispersion compressor with 60% efficiency to a 130 fs duration, approaching the transform-limited pulse duration. The present experimental data agree well with numerical simulation results for pulse amplification in the threestage amplifier. (extreme light fields and their applications)

  4. Theory of the photoelectric effect assisted by an elliptically polarized laser field

    International Nuclear Information System (INIS)

    Li Shumin; Jentschura, Ulrich D

    2009-01-01

    The laser-assisted photoelectric effect in atomic hydrogen is investigated for linear, circular and general elliptic polarizations. The perturbative dressed state of the atom in an elliptically polarized nonresonant laser field is derived in the velocity gauge. The continuum state of the ejected electron is described by a Coulomb-Volkov wavefunction. Numerical results show that the ionization cross section by a vacuum ultraviolet photon is enhanced at high laser field intensities and low frequencies. At small and extremely large scattering angles (measured with respect to the wave vector of the incoming vacuum ultraviolet photon), the process for emitting a laser photon is predominant, while at medium angles, the result favours the process without a laser photon exchange. The dependence of the results on the laser polarization and on various geometries is studied, and an interesting pattern is found for the dependence on the frequency of the dressing laser; an intuitive explanation is offered.

  5. Production of highly charged ions of argon by optical field ionization in a relativistic laser field

    International Nuclear Information System (INIS)

    Sagisaka, Akito; Akahane, Yutaka; Aoyama, Makoto; Nakano, Fumihiko; Yamakawa, Koichi

    2001-01-01

    We observed the highly charged ions of argon by optical field ionization in a relativistic intensity regime. Charge states up to Ar 15+ were produced at the highest intensity of 800 nm, linearly polarized 20 fs Ti: sapphire laser pulses. The peak intensity of the pulse is determined by comparing the measured ion production curve for Ar 9+ with ADK theory. The results of these measurements of the ionization indicate that the maximum peak intensity is achieved to ∼2x10 19 W/cm 2 . (author)

  6. LIGHT: Towards a laser-based accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Busold, Simon; Deppert, Oliver; Roth, Markus [Technical University of Darmstadt, Institute for Nuclear Physics, Schlossgartenstrasse 9, 64289 Darmstadt (Germany); Brabetz, Christian [Goethe University Frankfurt am Main, Institute for Applied Physics, Max von Laue Strasse 1, 60438 Frankfurt (Germany); Burris-Mog, Trevor; Joost, Martin; Cowan, Tom [Helmholtz Center Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden (Germany); Blazevic, Abel; Bagnoud, Vincent [GSI Helmholtz Center for Heavy Ion Research, Planckstrasse 1, 64291 Darmstadt (Germany); Zielbauer, Bernhard [GSI Helmholtz Center for Heavy Ion Research, Planckstrasse 1, 64291 Darmstadt (Germany); Helmholtz Institute Jena, Helmholtzweg 4, 07743 Jena (Germany); Kester, Oliver [GSI Helmholtz Center for Heavy Ion Research, Planckstrasse 1, 64291 Darmstadt (Germany); Goethe University Frankfurt am Main, Institute for Applied Physics, Max von Laue Strasse 1, 60438 Frankfurt (Germany)

    2012-07-01

    Proton acceleration by ultrashort, high intensity laser pulses has been a fast growing field of research during the last decade. The most intensely investigated acceleration mechanism is the TNSA mechanism (Target Normal Sheath Acceleration), providing protons in the multi-MeV-range. For many possible applications, however, the full energy spread and large beam divergence are major draw-backs. Therefore, a pulsed high-field solenoid was used for collimation and energy-selection and is now integrated in a full test stand for a laser-based accelerator at GSI Helmholtz Center, Darmstadt, namely the LIGHT project (Laser Ion Generation, Handling and Transport), which is a collaboration between TU Darmstadt, GSI, HZDR, JWGU Frankfurt and HI Jena. An overview of the new infrastructure, the goals of the LIGHT project, and first experimental results are presented.

  7. 179th International School of Physics "Enrico Fermi" : Laser-Plasma Acceleration

    CERN Document Server

    Gizzi, L A; Faccini, R

    2012-01-01

    Impressive progress has been made in the field of laser-plasma acceleration in the last decade, with outstanding achievements from both experimental and theoretical viewpoints. Closely exploiting the development of ultra-intense, ultrashort pulse lasers, laser-plasma acceleration has developed rapidly, achieving accelerating gradients of the order of tens of GeV/m, and making the prospect of miniature accelerators a more realistic possibility. This book presents the lectures delivered at the Enrico Fermi International School of Physics and summer school: "Laser-Plasma Acceleration" , held in Varenna, Italy, in June 2011. The school provided an opportunity for young scientists to experience the best from the worlds of laser-plasma and accelerator physics, with intensive training and hands-on opportunities related to key aspects of laser-plasma acceleration. Subjects covered include: the secrets of lasers; the power of numerical simulations; beam dynamics; and the elusive world of laboratory plasmas. The object...

  8. Simulation of Temperature Field Distribution for Cutting the Temperated Glass by Ultraviolet Laser

    Science.gov (United States)

    Yang, B. J.; He, Y. C.; Dai, F.; Lin, X. C.

    2017-03-01

    The finite element software ANSYS was adopted to simulate the temperature field distribution for laser cutting tempered glass, and the influence of different process parameters, including laser power, glass thickness and cutting speed, on temperature field distribution was studied in detail. The results show that the laser power has a greater influence on temperature field distribution than other paremeters, and when the laser power gets to 60W, the highest temperature reaches 749°C, which is higher than the glass softening temperature. It reflects the material near the laser spot is melted and the molten slag is removed by the high-energy water beam quickly. Finally, through the water guided laser cutting tempered glass experiment the FEM theoretical analysis was verified.

  9. Limit on Excitation and Stabilization of Atoms in Intense Optical Laser Fields.

    Science.gov (United States)

    Zimmermann, H; Meise, S; Khujakulov, A; Magaña, A; Saenz, A; Eichmann, U

    2018-03-23

    Atomic excitation in strong optical laser fields has been found to take place even at intensities exceeding saturation. The concomitant acceleration of the atom in the focused laser field has been considered a strong link to, if not proof of, the existence of the so-called Kramers-Henneberger (KH) atom, a bound atomic system in an intense laser field. Recent findings have moved the importance of the KH atom from being purely of theoretical interest toward real world applications; for instance, in the context of laser filamentation. Considering this increasing importance, we explore the limits of strong-field excitation in optical fields, which are basically imposed by ionization through the spatial field envelope and the field propagation.

  10. Ultrashort pulse shaping by optical parametric chirped amplification

    International Nuclear Information System (INIS)

    Nelet, Ambre

    2007-01-01

    The aim of this work is to propose new laser architectures based on optical parametric chirped pulse amplification (OPCPA). Common goals of OPCPA pre-amplifiers are to reach high energy level while maintaining the spectrum width and to adapt geometry of the amplified beam to the high power laser chain optics. We consider OPCPA as a way to control and to sculpt ultrashort pulses. Our first set-up aims at thwarting possible time recovery default between pump and signal pulses, which lower the energy extraction. A regenerative OPCPA, idler resonant, is a way to produce a high-intensity and high-repetition rate train of amplified signal replicas. Our second laser system pre-compensates the spectral gain narrowing by sculpting pulses directly within the OPCPA section, where a temporal shaping of the pump beam permits a spectro-spectral shaping of the amplified signal. Finally, we propose an OPCPA based on spatial coding and uniform amplification of spectral signal components by using a fan-out periodically poled crystal and a zero dispersion line. (author) [fr

  11. Ultrashort hard x-ray pulses generated by 90 degrees Thomson scattering

    International Nuclear Information System (INIS)

    Chin, A.H.; Schoenlein, R.W.; Glover, T.E.

    1997-01-01

    Ultrashort x-ray pulses permit observation of fast structural dynamics in a variety of condensed matter systems. The authors have generated 300 femtosecond, 30 keV x-ray pulses by 90 degrees Thomson scattering between femtosecond laser pulses and relativistic electrons. The x-ray and laser pulses are synchronized on a femtosecond time scale, an important prerequisite for ultrafast pump-probe spectroscopy. Analysis of the x-ray beam properties also allows for electron bunch characterization on a femtosecond time scale

  12. The Supercontinuum Laser Source Fundamentals with Updated References

    CERN Document Server

    Alfano, Robert R

    2006-01-01

    Photonics and nonlinear optics are important areas of science, engineering and technology. One of the most important ultrafast nonlinear optical processes is the supercontinuum (SC) – the production of intense white light pulses covering: uv, visible, NIR, MIR, and IR. It is produced using ultrashort laser pulses (ps/fs) to produce the ultrabroad band of frequencies. This book covers the fundamental principles and surveys research of current thinkers and experts in the field with updated references of the key breakthroughs over the past decade and a half. The application of SC are time-resolved pump-SC probe absorption and excitation spectroscopy for chemistry, biology and physics fundamental processes; optical coherence tomography; ultrashort pulse generation in femtosecond and attosecond regions; frequency clocks; phase stabilization; optical communication; atmospheric science; lightning control; optical medical imaging; biological cell imaging; and metrology standards.

  13. Dissociation of acetaldehyde in intense laser field: Coulomb explosion or field-assisted dissociation?

    Science.gov (United States)

    Elshakre, Mohamed E.; Gao, Lirong; Tang, Xiaoping; Wang, Sufan; Shu, Yafei; Kong, Fanao

    2003-09-01

    Dissociation of acetaldehyde in moderate strong laser field of 1013-1014W/cm2 was investigated. Singly charged parent ion CH3CHO+ and fragmental ions CH3+, CHO+, C2H4+, O+, CH2CHO+, and H+ were produced by 800 nm laser of 100 fs pulse duration and recorded by time-of-flight mass spectrometer. The CH3+ fragment further dissociated to CH2+, CH+, and C+ ions at higher intensity. Ab initio calculated results show that the singly-, doubly-, and triply charged parent ions are stable. So, the dissociation mechanism was not due to Coulomb explosion of multicharged ion. A field-assisted dissociation (FAD) theory, which assumes that only one bond undergoes dissociation while the rest of the molecular geometry stays unchanged, was employed to treat the dissociation dynamics. Accordingly, the dressed potential energy surfaces of the ground state for the parent and the fragment ions were calculated. Corresponding quasiclassical trajectory calculations show that the bond ruptures take place in the order of C-C, C-O, and C-H, agreeing with the observation. The observed angular dependence and charge distribution of the product ions can also be interpreted by the FAD theory.

  14. Features of laser spectroscopy and diagnostics of plasma ions in high magnetic fields

    International Nuclear Information System (INIS)

    Semerok, A F; Fomichev, S V

    2003-01-01

    Laser induced fluorescence and laser absorption spectroscopies of plasma ions in high magnetic fields have been investigated. Both the high degree of Zeeman splitting of the resonant transitions and the ion rotational movement drastically change the properties of the resonance interaction of the continuous wave laser radiation with ions in highly magnetized plasma. Numerical solution of the density matrix equation for a dissipative two-level system with time-dependent detuning from resonance was used to analyse this interaction. A theoretical simulation was performed and compared with the experimental results obtained from the laser spectroscopy diagnostics of barium plasma ions in high magnetic fields in the several tesla range

  15. Laser induced magnetization switching in a TbFeCo ferrimagnetic thin film: discerning the impact of dipolar fields, laser heating and laser helicity by XPEEM

    International Nuclear Information System (INIS)

    Gierster, L.; Ünal, A.A.; Pape, L.; Radu, F.; Kronast, F.

    2015-01-01

    We investigate laser induced magnetic switching in a ferrimagnetic thin film of Tb_2_2Fe_6_9Co_9 by PEEM. Using a small laser beam with a spot size of 3–5 µm in diameter in combination with high resolution magnetic soft X-ray microscopy we are able to discriminate between different effects that govern the microscopic switching process, namely the influence of the laser heating, of the helicity dependent momentum transfer, and of the dipolar coupling. Applying a sequence of femtosecond laser pulses to a previously saturated TbFeCo film leads to the formation of ring shaped magnetic structures in which all three effects can be observed. Laser helicity assisted switching is only observed in a narrow region within the Gaussian profile of the laser spot. Whereas in the center of the laser spot we find clear evidence for thermal demagnetization and in the outermost areas magnetic switching is determined by dipolar coupling with the surrounding film. Our findings demonstrate that by reducing the laser spot size the influence of dipolar coupling on laser induced switching is becoming increasingly important. - Highlights: • With a new PEEM sample holder a laser spot size of 3–5 µm in diameter is reached. • Spatial resolved imaging of laser induced magnetization reversal. • A single femtosecond laser pulse leads to a multi-domain state in TbFeCo. • A pulse sequence results in a ring-shaped magnetic pattern caused by dipolar fields. • Laser helicity dependent effects appear only in a narrow fluence region.

  16. Method for the determination of the three-dimensional structure of ultrashort relativistic electron bunches

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca; Ilinski, Petr; Saldin, Evgeni; Schneidmiller, Evgeni; Yurkov, Mikhail

    2009-05-15

    We describe a novel technique to characterize ultrashort electron bunches in Xray Free-Electron Lasers. Namely, we propose to use coherent Optical Transition Radiation to measure three-dimensional (3D) electron density distributions. Our method relies on the combination of two known diagnostics setups, an Optical Replica Synthesizer (ORS) and an Optical Transition Radiation (OTR) imager. Electron bunches are modulated at optical wavelengths in the ORS setup.When these electron bunches pass through a metal foil target, coherent radiation pulses of tens MW power are generated. It is thereafter possible to exploit advantages of coherent imaging techniques, such as direct imaging, diffractive imaging, Fourier holography and their combinations. The proposed method opens up the possibility of real-time, wavelength-limited, single-shot 3D imaging of an ultrashort electron bunch. (orig.)

  17. Laser printed nano-gratings: orientation and period peculiarities

    Science.gov (United States)

    Stankevič, Valdemar; Račiukaitis, Gediminas; Bragheri, Francesca; Wang, Xuewen; Gamaly, Eugene G.; Osellame, Roberto; Juodkazis, Saulius

    2017-01-01

    Understanding of material behaviour at nanoscale under intense laser excitation is becoming critical for future application of nanotechnologies. Nanograting formation by linearly polarised ultra-short laser pulses has been studied systematically in fused silica for various pulse energies at 3D laser printing/writing conditions, typically used for the industrial fabrication of optical elements. The period of the nanogratings revealed a dependence on the orientation of the scanning direction. A tilt of the nanograting wave vector at a fixed laser polarisation was also observed. The mechanism responsible for this peculiar dependency of several features of the nanogratings on the writing direction is qualitatively explained by considering the heat transport flux in the presence of a linearly polarised electric field, rather than by temporal and spatial chirp of the laser beam. The confirmed vectorial nature of the light-matter interaction opens new control of material processing with nanoscale precision.

  18. Simulation of condensed matter dynamics in strong femtosecond laser pulses

    International Nuclear Information System (INIS)

    Wachter, G.

    2014-01-01

    Ultrashort custom-tailored laser pulses can be employed to observe and control the motion of electrons in atoms and small molecules on the (sub-) femtosecond time scale. Very recently, efforts are underway to extend these concepts to solid matter. This monograph theoretically explores first applications of electron control by ultrashort laser pulses in three paradigmatic systems of solid-state density: a metal nano-structure (nanometric metal tip), a bulk dielectric (quartz glass), and the buckminsterfullerene molecule (C60) as arguably the smallest possible nano-particle. The electron motion is resolved on the atomic length and time scale by ab-initio simulations based on time-dependent density functional theory. Our quantum simulations are complemented by classical and semi-classical models elucidating the underlying mechanisms. We compare our results to experiments where already available and find good agreement. With increasing laser intensity, we find a transition from vertical photoexcitation to tunneling-like excitation. For nanostructures, that leads to temporally confined electron photoemission and thereby to quantum interferences in the energy spectra of emitted electrons. Similarly, tunneling can be induced between neighboring atoms inside an insulator. This provides a mechanism for ultrafast light-field controlled currents and modification of the optical properties of the solid, promising to eventually realize light-field electronic devices operating on the femtosecond time scale and nanometer length scale. Electron-electron interaction leads to near field enhancement and spatial localization of the non-linear response and is investigated both classically by solving the Maxwell equations near a nanostructure as well as quantum mechanically for the fullerene molecule. For the latter, we discuss scrutiny of the molecular near-field by the attosecond streaking technique. Our results demonstrate that ultrashort laser pulses can be employed to steer the

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

    International Nuclear Information System (INIS)

    Pabst, Stefan Ulf

    2013-04-01

    diffraction pattern, information about the molecular structure can be gained. This is illustrated with the example of laser-aligned naphthalene molecules (C 10 H 8 ). Furthermore, I demonstrate that the quality of the molecular alignment is essential for the reconstruction of the molecular structure. In the second part of this work, the ionization dynamics of atoms is studied. The characteristic time scale lies, here, in the attosecond and the few-femtosecond regime. Although a one-particle picture has been successfully applied to many ionization processes, important many-body effects do constantly occur. Based on a time-dependent configurationinteraction singles (TDCIS) approach, I study the temporal behavior of these many-body effects. During the photoionization of atomic xenon, unexpected correlation effects between the ionized electron and the ion occur. This electron-ion entanglement results in a reduced coherence within the ion. Populations and coherences of the ionic states are probed with attosecond precision using transient absorption spectroscopy. Even the subcycle ionization dynamics can be studied with this technique. Here, field-driven dressing effects between the ion and the freed electron appear, which I investigate on atomic krypton. Interactions between the ion and the electron, which modify the ionic states, occur also in high-harmonic generation (HHG). They are visible in the HHG spectrum as my studies of argon and xenon show. All these examples demonstrate on the one side, ultrashort pulses can be used to initiate complex electronic, atomic, and molecular motions. On the other side, it is also possible to probe and to control these dynamical processes with ultrashort pulses.

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

    Energy Technology Data Exchange (ETDEWEB)

    Pabst, Stefan Ulf

    2013-04-15

    diffraction pattern, information about the molecular structure can be gained. This is illustrated with the example of laser-aligned naphthalene molecules (C{sub 10}H{sub 8}). Furthermore, I demonstrate that the quality of the molecular alignment is essential for the reconstruction of the molecular structure. In the second part of this work, the ionization dynamics of atoms is studied. The characteristic time scale lies, here, in the attosecond and the few-femtosecond regime. Although a one-particle picture has been successfully applied to many ionization processes, important many-body effects do constantly occur. Based on a time-dependent configurationinteraction singles (TDCIS) approach, I study the temporal behavior of these many-body effects. During the photoionization of atomic xenon, unexpected correlation effects between the ionized electron and the ion occur. This electron-ion entanglement results in a reduced coherence within the ion. Populations and coherences of the ionic states are probed with attosecond precision using transient absorption spectroscopy. Even the subcycle ionization dynamics can be studied with this technique. Here, field-driven dressing effects between the ion and the freed electron appear, which I investigate on atomic krypton. Interactions between the ion and the electron, which modify the ionic states, occur also in high-harmonic generation (HHG). They are visible in the HHG spectrum as my studies of argon and xenon show. All these examples demonstrate on the one side, ultrashort pulses can be used to initiate complex electronic, atomic, and molecular motions. On the other side, it is also possible to probe and to control these dynamical processes with ultrashort pulses.

  1. Interaction of rare gas clusters in intense laser field

    International Nuclear Information System (INIS)

    Dobosz, Sandrine

    1998-01-01

    Rare gas cluster jet targets have only been scarcely studied in strong laser fields. This is surprising since their properties are particularly appealing. Although considered as a gas phase target, the local density within clusters is comparable to that of the bulk. Intense irradiation of clusters produces a plasma thereby giving rise to strong collisional heating. This explains, in particular, the observation of very high fragment charge states and the generation of X-rays in the keV energy range. The complete set of our experimental results shows that the intra-cluster atoms are first ionised by tunnel ionisation followed by massive electron impact ionisation. Thus, for Xenon clusters, we have observed up to 30-fold charged. The most energetic electrons leave the cluster which contributes to a positive charge build-up on the cluster surface. The plasma expands under the combined action of the Coulomb and kinetic pressures. The contribution of each pressure depends on the cluster size and we show that the Coulomb pressure is prevailing for the smallest sizes. This scenario explains the ejection of fragments with energies of up to lMeV. We have also performed a high resolution X-ray study to explore in situ the properties of the plasma. These studies underline the importance of electron-ion collisions and allow to deterrnine the mean charge states of the emitting ions. Finally, we have developed a model, describing the cluster expansion, which confirms our experimental observations. (author) [fr

  2. Field Emitter Arrays for a Free Electron Laser Application

    CERN Document Server

    Shing-Bruce-Li, Kevin; Ganter, Romain; Gobrecht, Jens; Raguin, Jean Yves; Rivkin, Leonid; Wrulich, Albin F

    2004-01-01

    The development of a new electron gun with the lowest possible emittance would help reducing the total length and cost of a free electron laser. Field emitter arrays (FEAs) are an attractive technology for electron sources of ultra high brightness. Indeed, several thousands of microscopic tips can be deposited on a 1 mm diameter area. Electrons are then extracted by applying voltage to a first grid layer close to the tip apexes, the so called gate layer, and focused by a second grid layer one micrometer above the tips. The typical aperture diameter of the gate and the focusing layer is in the range of one micrometer. One challenge for such cathodes is to produce peak currents in the ampere range since the usual applications of FEAs require less than milliampere. Encouraging peak current performances have been obtained by applying voltage pulses at low frequency between gate and tips. In this paper we report on different tip materials available on the market: diamond FEAs from Extreme Devices Inc., ZrC single ...

  3. Explosions of water clusters in intense laser fields

    International Nuclear Information System (INIS)

    Kumarappan, V.; Krishnamurthy, M.; Mathur, D.

    2003-01-01

    Energetic, highly charged oxygen ions O q+ (q≤6), are copiously produced upon laser field-induced disassembly of highly charged water clusters, (H 2 O) n and (D 2 O) n , n∼60, that are formed by seeding high-pressure helium or argon with water vapor. Ar n clusters (n∼40 000) formed under similar experimental conditions are found to undergo disassembly in the Coulomb explosion regime, with the energies of Ar q+ ions showing a q 2 dependence. Water clusters, which are argued to be considerably smaller in size, should also disassemble in the same regime, but the energies of fragment O q+ ions are found to depend linearly on q which, according to prevailing wisdom, ought to be a signature of hydrodynamic expansion that is expected of much larger clusters. The implication of these observations on our understanding of the two cluster explosion regimes, Coulomb explosion and hydrodynamic expansion, is discussed. Our results indicate that charge state dependences of ion energy do not constitute an unambiguous experimental signature of cluster explosion regime

  4. Effects of external magnetic field on harmonics generated in laser interaction with underdense plasma

    International Nuclear Information System (INIS)

    Faghihi-Nik, M.; Ghorbanalilu, M.; Shokri, B.

    2010-01-01

    Complete text of publication follows. Generation of harmonic radiation is an important subject of laser plasma interaction and attracts great attention due to a wide range of applications. It has been seen that intense electromagnetic and quasi-static transverse magnetic fields are generated in laser plasma interaction. An extremely intense magnetic field (up to hundreds of MG) has been observed by experimental measurements in interaction of short laser pulses with plasma. These self-generated or applied magnetic fields affect the propagation of the laser pulses. In most laser interactions with homogeneous plasma, odd harmonics of laser frequency are generated. In this paper, we point out the possibility of even harmonics generation when a linearly polarized laser beam propagates in homogeneous plasma in the presence of a transverse magnetic field. It is shown that applying external field induces a transverse current density oscillating twice of the laser field which leds to generation of second harmonic radiation. This current density is derived using the perturbation method, and the steady state amplitude of the second harmonic obtained by solution of the wave equation. By the same procedure the current density and then the steady state amplitude of higher order harmonics are calculated. The efficiency of harmonic generation (the ratio of harmonic power to incident power) is a drastically function of the strength of external magnetic field. It is found that the efficiency of even harmonics is zero in the absence of magnetic field and increases as the magnetic field is increased. For odd harmonics, applying the external magnetic field enhances the generated harmonics as well. The conversion efficiency also increases with increase in plasma density and intensity of the laser beam.

  5. Generation of ten kilotesla longitudinal magnetic fields in ultraintense laser-solenoid target interactions

    OpenAIRE

    Xiao, K. D.; Zhou, C. T.; Zhang, H.; Huang, T. W.; Li, R.; Qiao, B.; Cao, J. M.; Cai, T. X.; Ruan, S. C.; He, X. T.

    2018-01-01

    Production of the huge longitudinal magnetic fields by using an ultraintense laser pulse irradiating a solenoid target is considered. Through three-dimensional particle-in-cell simulations, it is shown that the longitudinal magnetic field up to ten kilotesla can be observed in the ultraintense laser-solenoid target interactions. The finding is associated with both fast and return electron currents in the solenoid target. The huge longitudinal magnetic field is of interest for a number of impo...

  6. Wide-Field Optic for Autonomous Acquisition of Laser Link

    Science.gov (United States)

    Page, Norman A.; Charles, Jeffrey R.; Biswas, Abhijit

    2011-01-01

    An innovation reported in Two-Camera Acquisition and Tracking of a Flying Target, NASA Tech Briefs, Vol. 32, No. 8 (August 2008), p. 20, used a commercial fish-eye lens and an electronic imaging camera for initially locating objects with subsequent handover to an actuated narrow-field camera. But this operated against a dark-sky background. An improved solution involves an optical design based on custom optical components for the wide-field optical system that directly addresses the key limitations in acquiring a laser signal from a moving source such as an aircraft or a spacecraft. The first challenge was to increase the light collection entrance aperture diameter, which was approximately 1 mm in the first prototype. The new design presented here increases this entrance aperture diameter to 4.2 mm, which is equivalent to a more than 16 times larger collection area. One of the trades made in realizing this improvement was to restrict the field-of-view to +80 deg. elevation and 360 azimuth. This trade stems from practical considerations where laser beam propagation over the excessively high air mass, which is in the line of sight (LOS) at low elevation angles, results in vulnerability to severe atmospheric turbulence and attenuation. An additional benefit of the new design is that the large entrance aperture is maintained even at large off-axis angles when the optic is pointed at zenith. The second critical limitation for implementing spectral filtering in the design was tackled by collimating the light prior to focusing it onto the focal plane. This allows the placement of the narrow spectral filter in the collimated portion of the beam. For the narrow band spectral filter to function properly, it is necessary to adequately control the range of incident angles at which received light intercepts the filter. When this angle is restricted via collimation, narrower spectral filtering can be implemented. The collimated beam (and the filter) must be relatively large to

  7. Collective migration of adsorbed atoms on a solid surface in the laser radiation field

    International Nuclear Information System (INIS)

    Andreev, V V; Ignat'ev, D V; Telegin, Gennadii G

    2004-01-01

    The lateral (in the substrate plane) interaction between dipoles induced in particles adsorbed on a solid surface is studied in a comparatively weak laser radiation field with a Gaussian transverse distribution. It is shown that the particles migrate over the surface in the radial direction either outside an illuminated spot with the formation of a 'crater' or inside the spot with the formation of a 'mound'. (interaction of laser radiation with matter. laser plasma)

  8. Nuclear excitation via the motion of electrons in a strong laser field

    International Nuclear Information System (INIS)

    Berger, J.F.; Gogny, D.; Weiss, M.S.

    1987-12-01

    A method of switching from a nuclear isomeric state to a lasing state is examined. A semi-classical model of laser-electron-nuclear coupling is developed. In it the electrons are treated as free in the external field of the laser, but with initial conditions corresponding to their atomic orbits. Application is made to testing this model in 235 U and to the design criteria of a gamma-ray laser. 14 refs., 2 tabs

  9. Study of a recombination X-ray laser scheme in a H-like nitrogen plasma created by optical field induced ionization; Etude de la faisabilite d'un laser X en recombinaison dans un plasma d'azote hydrogenoide cree par effet tunnel

    Energy Technology Data Exchange (ETDEWEB)

    Hulin, S

    2001-07-01

    Thanks to their high brightness and short wavelength, X ray lasers are interesting diagnostics in many experiments because they can efficiently probe dense plasmas. Furthermore their mono-chromaticity and collimation make them interesting tools in plasma physics but also in many biology or chemistry experiments. The effective use of this diagnostic is mainly depending on its dimensions and cost. For this reason, research on X ray laser is now focused on the reduction of cost and the realization of table-top facilities. One of these research axis, based on the optical field induced ionization (OFI) of the plasma, is presented in this work. An ultra-short (60 fs) high-brightness (10{sup 19} W/cm{sup 2}) Ti:Sapphire (790 nm) laser is focused into a nitrogen pulsed gas jet. A dense (10{sup 20} cm{sup -3}) plasma of fully stripped nitrogen is created by the way. During the fast recombination of the plasma some population inversions between levels of principal quantum number 2 and 1 (2.4 nm) and 3 and 2 (13.4 nm) can occur depending on the plasma parameters. The creation of the plasma by OFI, laser-plasma interaction dominated by relativistic self-focusing, and recombination dynamics are studied by numerical simulations on one hand and experiments on the other hand. Temperature measurements and numerical simulations show a strong heating, destructive for the laser scheme, which can be explained by Raman instability growing. Nevertheless plasma X ray emission in the 2-20 nm range show a strong increase with the electronic density of the 13.4 nm line intensity. This behavior is consistent with a laser effect but is not detected on the 2.4 nm transition line. (author)

  10. A new collective-field acceleration mechanism using a powerful laser

    International Nuclear Information System (INIS)

    Willis, W.J.

    1975-01-01

    Performance estimates for a linear accelerator for positive ions are presented. Focusing and acceleration is performed by means of a local, strong modulation of a relativistic electron beam using the electromagnetic field of a laser. For high-power laser beams of 1010 watts per square wavelength, the accelerating field strength can be several GV/m, assuming free electrons. Various interaction mechanisms of the laser beam with the electron beam are briefly discussed, notably inverse bremsstrahlung and interaction with the self-magnetic field of the electron beam. Finally, coherent effects and the injection of ions are dealt with. (author)

  11. Quantum chaos in the Henon-Heiles oscillator under intense laser fields. IT-1

    International Nuclear Information System (INIS)

    Gupta, Neetu; Deb, B.M.

    2004-01-01

    Full text: The quantum domain behaviour of the classically chaotic Henon-Heiles oscillator (HHO) has been studied earlier by several workers, without invoking either a weak or strong time- dependent external perturbation. This work looks at the motion of an electron moving in the HH potential under intense laser fields. The time-dependent Schroedinger equation is numerically solved in order to study the sensitivity of the system to initial conditions. The similarities in responses between the HHO and atoms/molecules to intense laser fields are examined; from this one might speculate that atoms/molecules in intense laser fields might exhibit quantum chaos

  12. Modeling of anisotropic properties of double quantum rings by the terahertz laser field.

    Science.gov (United States)

    Baghramyan, Henrikh M; Barseghyan, Manuk G; Kirakosyan, Albert A; Ojeda, Judith H; Bragard, Jean; Laroze, David

    2018-04-18

    The rendering of different shapes of just a single sample of a concentric double quantum ring is demonstrated realizable with a terahertz laser field, that in turn, allows the manipulation of electronic and optical properties of a sample. It is shown that by changing the intensity or frequency of laser field, one can come to a new set of degenerated levels in double quantum rings and switch the charge distribution between the rings. In addition, depending on the direction of an additional static electric field, the linear and quadratic quantum confined Stark effects are observed. The absorption spectrum shifts and the additive absorption coefficient variations affected by laser and electric fields are discussed. Finally, anisotropic electronic and optical properties of isotropic concentric double quantum rings are modeled with the help of terahertz laser field.

  13. Laser amplification in excited dielectrics

    Science.gov (United States)

    Winkler, Thomas; Haahr-Lillevang, Lasse; Sarpe, Cristian; Zielinski, Bastian; Götte, Nadine; Senftleben, Arne; Balling, Peter; Baumert, Thomas

    2018-01-01

    Wide-bandgap dielectrics such as glasses or water are transparent at visible and infrared wavelengths. This changes when they are exposed to ultrashort and highly intense laser pulses. Different interaction mechanisms lead to the appearance of various transient nonlinear optical phenomena. Using these, the optical properties of dielectrics can be controlled from the transparent to the metal-like state. Here we expand this range by a yet unexplored mechanism in excited dielectrics: amplification. In a two-colour pump-probe experiment, we show that a 400 nm femtosecond laser pulse is coherently amplified inside an excited sapphire sample on a scale of a few micrometres. Simulations strongly support the proposed two-photon stimulated emission process, which is temporally and spatially controllable. Consequently, we expect applications in all fields that demand strongly localized amplification.

  14. Near field imaging of transient collisional excitation x-ray laser

    International Nuclear Information System (INIS)

    Tanaka, Momoko; Kado, Masataka; Hasegawa, Noboru; Kawachi, Tetsuya; Sukegawa, Kouta; Lu, Peixiang; Nagashima, Akira; Kato, Yoshiaki

    2001-01-01

    We observed the spatial profile of the transient collisional excitation Ni-like Ag laser (λ=13.9 nm) for various plasma lengths using the near field imaging method. The gain coefficient of the x-ray laser was estimated as 24 cm -1 . The gain region was a 50 μm crescent shape and included localized high gain areas. (author)

  15. A theoretical and experimental analysis of modulated laser fields and power spectra

    DEFF Research Database (Denmark)

    Olesen, Henning; Jacobsen, G.

    1982-01-01

    A general theoretical description of modulated laser fields and power spectra for a current modulated single-mode laser is derived, taking into account both the intensity and frequency modulation (IM and FM) of the emitted light. The theory relies on an explicit knowledge of the modulus as well...

  16. Characterization of collisionally pumped optical-field-ionization soft X-ray lasers

    Czech Academy of Sciences Publication Activity Database

    Mocek, Tomáš; Sebban, S.; Bettaibi, I.; Upcraft, L. M.; Balcou, P.; Breger, P.; Zeitoun, P.; Le Pape, S.; Ros, D.; Klisnick, A.; Carillon, A.; Jamelot, G.; Rus, Bedřich; Wyart, J. F.

    2004-01-01

    Roč. 78, - (2004), s. 939-944 ISSN 0946-2171 Grant - others:HPRI(XE) 199900086 Institutional research plan: CEZ:AV0Z1010921 Keywords : X-ray lasers * optical-field-ionization * collisional excitation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.215, year: 2004

  17. Application of the ultrashort pulses in bovine dental enamel

    International Nuclear Information System (INIS)

    Todescan, Carla de Rago

    2003-01-01

    The interaction of lasers with the hard structures of the teeth, has found the excess of heat as a problem for its utilization. This study analyzes, in vitro, the interaction of the ultrashort pulse laser of Ti:safire (830 nm) with the bovine dental enamel. The system consisted in one main oscillator integrated with an amplifier (CPA). The pulses extracted before the temporal compression inside the amplifier had 30 ps, 1000 Hz and ∼1 mJ. The pulses extracted after the compression had 60 fs, 1000 Hz and ∼0,7 mJ. The M 2 was 1,3, the focal lens 2,5 cm, the focal distance 29,7 and a computerized translation stage x,y,z. We evaluated the amount of tissue removed per pulse,the resulting cavities and the surrounding tissues not irradiated, under OM and SEM. The fluency was the major factor for differentiating the two regimens studied, therefore, the intensity was not so important as we expected in this process. We found: one ablation region in 'cat tongue', one ablation length, one fluency ∼0,7 J/cm 2 for 30 ps and ∼0,5 J/cm 2 for 60 fs (50% of high speed burr), smooth edge for 30 ps and high precision of the sharp edge cut of submicrometric order for 60 fs. (author)

  18. Intense laser field effects on a Woods-Saxon potential quantum well

    Science.gov (United States)

    Restrepo, R. L.; Morales, A. L.; Akimov, V.; Tulupenko, V.; Kasapoglu, E.; Ungan, F.; Duque, C. A.

    2015-11-01

    This paper presents the results of the theoretical study of the effects of non-resonant intense laser field and electric and magnetic fields on the optical properties in an quantum well (QW) make with Woods-Saxon potential profile. The electric field and intense laser field are applied along the growth direction of the Woods-Saxon quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the Woods-Saxon quantum well, the effective mass approximation and the method of envelope wave function are used. The confinement in the Woods-Saxon quantum well is changed drastically by the application of intense laser field or either the effect of electric and magnetic fields. The optical properties are calculated using the compact density matrix.

  19. Coaxial monitoring of temperature field in selective pulsed laser melting

    Science.gov (United States)

    Liu, Che; Chen, Zhongyun; Cao, Hongzhong; Zhou, Jianhong

    2017-10-01

    Selective Laser Melting is a rapid manufacturing technology which produces complex parts layer by layer. The presence of thermal stress and thermal strain in the forming process often leads to defects in the formed parts. In order to detect fabricate errors and avoid failure which caused by thermal gradient in time. An infrared thermal imager and a high speed CCD camera were applied to build a coaxial optical system for real-time monitoring the temperature distribution and changing trend of laser affected zone in SLM forming process. Molten tracks were fabricated by SLM under different laser parameters such as frequency, pulse width. And the relationship between the laser parameters and the temperature distribution were all obtained and analyzed.

  20. Illumination Effect of Laser Light in Foggy Objects Using an Active Imaging System

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Seong-Ouk; Park, Seung-Kyu; Ahn, Yong-Jin; Baik, Sung-Hoon; Choi, Young-Soo; Jeong, Kyung-Min [KAERI, Daejeon (Korea, Republic of)

    2015-05-15

    Active imaging techniques usually provide improved image information when compared to passive imaging techniques. Active vision is a direct visualization technique using an artificial illuminant. Range-gated imaging (RGI) technique is one of active vision technologies. The RGI technique extracts vision information by summing time sliced vision images. In the RGI system, objects are illuminated for ultra-short time by a high intensity illuminant and then the light reflected from objects is captured by a highly sensitive image sensor with the exposure of ultra-short time. The Range-gated imaging is an emerging technology in the field of surveillance for security application, especially in the visualization of darken night or foggy environment. Although RGI viewing was discovered in the 1960's, this technology is currently more applicable by virtue of the rapid development of optical and sensor technologies, such as highly sensitive imaging sensor and ultra-short pulse laser light. Especially, this system can be adopted in robot-vision system by virtue of the compact system configuration. During the past decades, several applications of this technology have been applied in target recognition and in harsh environments, such as fog, underwater vision. Also, this technology has been demonstrated range imaging based on range-gated imaging. Laser light having a short pulse width is usually used for the range-gated imaging system. In this paper, an illumination effect of laser light in foggy objects is studied using a range-gated imaging system. The used imaging system consists of an ultra-short pulse (0.35 ns) laser light and a gated imaging sensor. The experiment is carried out to monitor objects in a box filled by fog. In this paper, the effects by fog particles in range-gated imaging technique are studied. Edge blurring and range distortion are the generated by fog particles.

  1. Illumination Effect of Laser Light in Foggy Objects Using an Active Imaging System

    International Nuclear Information System (INIS)

    Kwon, Seong-Ouk; Park, Seung-Kyu; Ahn, Yong-Jin; Baik, Sung-Hoon; Choi, Young-Soo; Jeong, Kyung-Min

    2015-01-01

    Active imaging techniques usually provide improved image information when compared to passive imaging techniques. Active vision is a direct visualization technique using an artificial illuminant. Range-gated imaging (RGI) technique is one of active vision technologies. The RGI technique extracts vision information by summing time sliced vision images. In the RGI system, objects are illuminated for ultra-short time by a high intensity illuminant and then the light reflected from objects is captured by a highly sensitive image sensor with the exposure of ultra-short time. The Range-gated imaging is an emerging technology in the field of surveillance for security application, especially in the visualization of darken night or foggy environment. Although RGI viewing was discovered in the 1960's, this technology is currently more applicable by virtue of the rapid development of optical and sensor technologies, such as highly sensitive imaging sensor and ultra-short pulse laser light. Especially, this system can be adopted in robot-vision system by virtue of the compact system configuration. During the past decades, several applications of this technology have been applied in target recognition and in harsh environments, such as fog, underwater vision. Also, this technology has been demonstrated range imaging based on range-gated imaging. Laser light having a short pulse width is usually used for the range-gated imaging system. In this paper, an illumination effect of laser light in foggy objects is studied using a range-gated imaging system. The used imaging system consists of an ultra-short pulse (0.35 ns) laser light and a gated imaging sensor. The experiment is carried out to monitor objects in a box filled by fog. In this paper, the effects by fog particles in range-gated imaging technique are studied. Edge blurring and range distortion are the generated by fog particles

  2. Polarization control of multi-photon absorption under intermediate femtosecond laser field

    International Nuclear Information System (INIS)

    Cheng Wenjing; Liang Guo; Wu Ping; Liu Pei; Jia Tianqing; Sun Zhenrong; Zhang Shian

    2017-01-01

    It has been shown that the femtosecond laser polarization modulation is a very simple and well-established method to control the multi-photon absorption process by the light–matter interaction. Previous studies mainly focused on the multi-photon absorption control in the weak field. In this paper, we further explore the polarization control behavior of multi-photon absorption process in the intermediate femtosecond laser field. In the weak femtosecond laser field, the second-order perturbation theory can well describe the non-resonant two-photon absorption process. However, the higher order nonlinear effect (e.g., four-photon absorption) can occur in the intermediate femtosecond laser field, and thus it is necessary to establish new theoretical model to describe the multi-photon absorption process, which includes the two-photon and four-photon transitions. Here, we construct a fourth-order perturbation theory to study the polarization control behavior of this multi-photon absorption under the intermediate femtosecond laser field excitation, and our theoretical results show that the two-photon and four-photon excitation pathways can induce a coherent interference, while the coherent interference is constructive or destructive that depends on the femtosecond laser center frequency. Moreover, the two-photon and four-photon transitions have the different polarization control efficiency, and the four-photon absorption can obtain the higher polarization control efficiency. Thus, the polarization control efficiency of the whole excitation process can be increased or decreased by properly designing the femtosecond laser field intensity and laser center frequency. These studies can provide a clear physical picture for understanding and controlling the multi-photon absorption process in the intermediate femtosecond laser field, and also can provide a theoretical guidance for the future experimental realization. (paper)

  3. Free-Free Transitions in the Presence of Laser Fields at Very Low Incident Electron Energy

    Science.gov (United States)

    Bhatia, A. K.; Sinha, Chandana

    2010-01-01

    We study the free-free transition in electron-hydrogenic systems in ground state in presence of an external laser field at very loud incident energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen to be monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser in a nonperturbative manner by choosing a Volkov wave function for it. The scattering weave function for the electron is solved numerically by taking into account the effect of the electron exchange, short-range as well as of the long-range interactions to get the S and P wave phase shifts while for the higher angular momentum phase shifts the exchange approximation has only been considered. We calculate the laser assisted differential cross sections (LADCS) for the aforesaid free-free transition process for single photon absorption/emission. The laser intensity is chosen to be much less than the atomic field intensity. A strong suppression is noted in the LADCS as compared to the field free (FF) cross sections. Unlike the FF ones, the LADCS exhibit some oscillations having a distinct maximum at a low value of the scattering angle depending on the laser parameters as well as on the incident energies.

  4. Controlling the alignment of neutral molecules by a strong laser field

    DEFF Research Database (Denmark)

    Sakai, H.; Hilligsøe, Karen Marie; Hald, K.

    1999-01-01

    by lowering the initial rotational energy of the molecules or by increasing the laser intensity. The alignment is measured by photodissociating the molecules with a femtosecond laser pulse and detecting the direction of the photofragments by imaging techniques. The strongest degree of alignment observed......A strong nonresonant nanosecond laser pulse is used to align neutral iodine molecules. The technique, applicable to both polar and nonpolar molecules, relies on the interaction between the strong laser field and the induced dipole moment of the molecules. The degree of alignment is enhanced...

  5. Optimal laser heating of plasmas confined in strong solenoidal magnetic fields

    International Nuclear Information System (INIS)

    Vitela, J.; Akcasu, A.Z.

    1987-01-01

    Optimal Control Theory is used to analyze the laser-heating of plasmas confined in strong solenoidal magnetic fields. Heating strategies that minimize a linear combination of heating time and total energy spent by the laser system are found. A numerical example is used to illustrate the theory. Results of this example show that by an appropriate modulation of the laser intensity, significant savings in the laser energy are possible with only slight increases in the heating time. However, results may depend strongly on the initial state of the plasma and on the final ion temperature. (orig.)

  6. Relativistic derivation of the ponderomotive force produced by two intense laser fields

    International Nuclear Information System (INIS)

    Stroscio, M.A.

    1985-01-01

    The ponderomotive force plays a fundamental role in the absorption of laser light on self-consistent plasma density profiles, in multiple-photon ionization, and in intense field electrodynamics. The relativistic corrections to the ponderomotive force of a transversely polarized electromagnetic wave lead to an approximately 20-percent reduction in the single particle ponderomotive force produced by a 10-γm 10 16 -W/cm 2 laser field. Recent experimental investigations are based on using two intense laser fields to produce desired lasermatter interactions. This paper presents the first derivation of the nonlinear relativistic ponderomotive force produced by two intense laser fields. The results demonstrate that relativistic ponderomotive forces are not additive

  7. High-precision laser microcutting and laser microdrilling using diffractive beam-splitting and high-precision flexible beam alignment

    Science.gov (United States)

    Zibner, F.; Fornaroli, C.; Holtkamp, J.; Shachaf, Lior; Kaplan, Natan; Gillner, A.

    2017-08-01

    High-precision laser micro machining gains more importance in industrial applications every month. Optical systems like the helical optics offer highest quality together with controllable and adjustable drilling geometry, thus as taper angle, aspect ratio and heat effected zone. The helical optics is based on a rotating Dove-prism which is mounted in a hollow shaft engine together with other optical elements like wedge prisms and plane plates. Although the achieved quality can be interpreted as extremely high the low process efficiency is a main reason that this manufacturing technology has only limited demand within the industrial market. The objective of the research studies presented in this paper is to dramatically increase process efficiency as well as process flexibility. During the last years, the average power of commercial ultra-short pulsed laser sources has increased significantly. The efficient utilization of the high average laser power in the field of material processing requires an effective distribution of the laser power onto the work piece. One approach to increase the efficiency is the application of beam splitting devices to enable parallel processing. Multi beam processing is used to parallelize the fabrication of periodic structures as most application only require a partial amount of the emitted ultra-short pulsed laser power. In order to achieve highest flexibility while using multi beam processing the single beams are diverted and re-guided in a way that enables the opportunity to process with each partial beam on locally apart probes or semimanufactures.

  8. Laser ablation of polymer coatings allows for electromagnetic field enhancement mapping around nanostructures

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kjelstrup-Hansen, Jakob

    2011-01-01

    Subdiffraction spatially resolved, quantitative mapping of strongly localized field intensity enhancement on gold nanostructures via laser ablation of polymer thin films is reported. Illumination using a femtosecond laser scanning microscope excites surface plasmons in the nanostructures....... The accompanying field enhancement substantially lowers the ablation threshold of the polymer film and thus creates local ablation spots and corresponding topographic modifications of the polymer film. Such modifications are quantified straightforwardly via scanning electron microscopy and atomic force microscopy...

  9. Effect of Thermal Fields on the Structure of Corrosion-Resistant Steels Under Different Modes of Laser Treatment

    Science.gov (United States)

    Tarasova, T. V.; Gusarov, A. V.; Protasov, K. E.; Filatova, A. A.

    2017-11-01

    The influence of temperature fields on the structure and properties of corrosion-resistant chromium steels under different modes of laser treatment is investigated. A model of heat transfer under laser impact on target is used to plot thermal fields and cycles and cooling rates. It is shown that the model used for computing thermal fields gives tentative geometric sizes of the fusion zones under laser treatment and selective laser fusion. The cooling rate is shown to have decisive influence on the structure of corrosion-resistant steels after laser treatment with surface fusion in devices for pulsed, continuous, and selective laser melting.

  10. Electron-hydrogen collisions with dressed target and Volkov projectile states in a laser field

    International Nuclear Information System (INIS)

    Smith, P.H.G.; Flannery, M.R.

    1992-01-01

    Cross sections for the 1S-2S and 1S-2P O transitions in laser-assisted e - -H(1S) collisions are calculated in both the multi-channel eikonal treatment and the Born wave approximation, as a function of impact energy and laser field intensity. The laser considered is a monotonic, plane-polarized CO 2 laser (photon energy = 0.117 eV) with the polarization direction parallel to the initial projectile velocity. The first part of this paper confines the laser perturbation to the bound electrons of the atom. The second part extends the laser perturbation to the projectile electron, and the familiar Volkov dressed states are used. (author)

  11. Influence of external magnetic field on laser-induced gold nanoparticles fragmentation

    International Nuclear Information System (INIS)

    Serkov, A. A.; Rakov, I. I.; Simakin, A. V.; Kuzmin, P. G.; Shafeev, G. A.; Mikhailova, G. N.; Antonova, L. Kh.; Troitskii, A. V.; Kuzmin, G. P.

    2016-01-01

    Laser-assisted fragmentation is an efficient method of the nanoparticles size and morphology control. However, its exact mechanisms are still under consideration. One of the remaining problems is the plasma formation, inevitably occurring upon the high intensity laser irradiation. In this Letter, the role of the laser-induced plasma is studied via introduction of high-intensity external magnetic field (up to 7.5 T). Its presence is found to cause the plasma emission to start earlier regarding to a laser pulse, also increasing the plume luminosity. Under these conditions, the acceleration of nanoparticles fragmentation down to a few nanometers is observed. Laser-induced plasma interaction with magnetic field and consequent energy transfer from plasma to nanoparticles are discussed.

  12. A “slingshot” laser-driven acceleration mechanism of plasma electrons

    Energy Technology Data Exchange (ETDEWEB)

    Fiore, Gaetano, E-mail: gaetano.fiore@na.infn.it [Dip. di Matematica e Applicazioni, Università “Federico II”, Complesso Universitario M. S. Angelo, Via Cintia, 80126 Napoli (Italy); INFN, Sezione di Napoli, Complesso Universitario M. S. Angelo, Via Cintia, 80126 Napoli (Italy); De Nicola, Sergio [SPIN-CNR, Complesso Universitario M. S. Angelo, Via Cintia, 80126 Napoli (Italy); INFN, Sezione di Napoli, Complesso Universitario M. S. Angelo, Via Cintia, 80126 Napoli (Italy)

    2016-09-01

    We briefly report on the recently proposed Fiore et al. [1] and Fiore and De Nicola [2] electron acceleration mechanism named “slingshot effect”: under suitable conditions the impact of an ultra-short and ultra-intense laser pulse against the surface of a low-density plasma is expected to cause the expulsion of a bunch of superficial electrons with high energy in the direction opposite to that of the pulse propagation; this is due to the interplay of the huge ponderomotive force, huge longitudinal field arising from charge separation, and the finite size of the laser spot.

  13. Modeling ultrashort electromagnetic pulses with a generalized Kadomtsev-Petviashvili equation

    Science.gov (United States)

    Hofstrand, A.; Moloney, J. V.

    2018-03-01

    In this paper we derive a properly scaled model for the nonlinear propagation of intense, ultrashort, mid-infrared electromagnetic pulses (10-100 femtoseconds) through an arbitrary dispersive medium. The derivation results in a generalized Kadomtsev-Petviashvili (gKP) equation. In contrast to envelope-based models such as the Nonlinear Schrödinger (NLS) equation, the gKP equation describes the dynamics of the field's actual carrier wave. It is important to resolve these dynamics when modeling ultrashort pulses. We proceed by giving an original proof of sufficient conditions on the initial pulse for a singularity to form in the field after a finite propagation distance. The model is then numerically simulated in 2D using a spectral-solver with initial data and physical parameters highlighting our theoretical results.

  14. Propagation of three-dimensional bipolar ultrashort electromagnetic pulses in an inhomogeneous array of carbon nanotubes

    Science.gov (United States)

    Fedorov, Eduard G.; Zhukov, Alexander V.; Bouffanais, Roland; Timashkov, Alexander P.; Malomed, Boris A.; Leblond, Hervé; Mihalache, Dumitru; Rosanov, Nikolay N.; Belonenko, Mikhail B.

    2018-04-01

    We study the propagation of three-dimensional (3D) bipolar ultrashort electromagnetic pulses in an inhomogeneous array of semiconductor carbon nanotubes. The heterogeneity is represented by a planar region with an increased concentration of conduction electrons. The evolution of the electromagnetic field and electron concentration in the sample are governed by the Maxwell's equations and continuity equation. In particular, nonuniformity of the electromagnetic field along the axis of the nanotubes is taken into account. We demonstrate that depending on values of the parameters of the electromagnetic pulse approaching the region with the higher electron concentration, the pulse is either reflected from the region or passes it. Specifically, our simulations demonstrate that after interacting with the higher-concentration area, the pulse can propagate steadily, without significant spreading. The possibility of such ultrashort electromagnetic pulses propagating in arrays of carbon nanotubes over distances significantly exceeding characteristic dimensions of the pulses makes it possible to consider them as 3D solitons.

  15. Dynamics of coupled electron-nuclei-systems in laser fields

    International Nuclear Information System (INIS)

    Falge, Mirjam

    2012-01-01

    This work aimed at the theoretical analysis of high harmonic generation in molecules and the influence of coupled electron and nuclear dynamics on ultra-short pulse ionization processes. In the first part of this thesis, the isotope effect and influence of vibrational excitation on high harmonic generation were investigated for the isotope pairs H 2 O/D 2 O and H 2 /D 2 . It was shown that on the one hand high harmonic intensities strongly depend on the vibrational quantum number of the initial state of the water molecule and on the other hand the spectra of H 2 O and D 2 O exhibit a clear isotope effect for certain vibrationally excited states. Also it was shown that high harmonics of vibrationally excited states show an even more pronounced isotope effect than the ground state. The second and third part of this work treats the influence of coupled electron and nuclear dynamics on photoelectron spectra. In order to facilitate a numerically exact description of this dynamics, a simple one-dimensional model system (Shin-Metiu model) was used. It consists of only a single electronic and nuclear degree-of-freedom and allows for a switching between adiabatic and strongly non-adiabatic dynamics by its parameterization. This model served for the analysis of the dynamics of three different cases ranging from weak over intermediate to strong electron-nuclear coupling. To investigate the influence of non-adiabatic effects on photoelectron spectra, time-resolved photoelectron spectra were calculated applying two methods: a numerically exact treatment and an adiabatic approach neglecting the electron-nuclear coupling. Subsequently, the dependence of the efficiency of a non-adiabatic transition on the nuclear mass was analysed. To this end, the population dynamics and photoelectron spectra were calculated numerically exactly for a strong electron and nuclear coupling. Thereafter the asymmetry in forward and backward direction of time-resolved photoelectron spectra and the

  16. Laser annealed HWCVD and PECVD thin silicon films. Electron field emission

    International Nuclear Information System (INIS)

    O'Neill, K.A.; Shaikh, M.Z.; Lyttle, G.; Anthony, S.; Fan, Y.C.; Persheyev, S.K.; Rose, M.J.

    2006-01-01

    Electron Field Emission (FE) properties of various laser annealed thin silicon films on different substrates were investigated. HWCVD microcrystalline and PECVD amorphous silicon films were irradiated with Nd : YAG and XeCl Excimer lasers at varying energy densities. Encouraging FE results were mainly from XeCl Excimer laser processed PECVD and HWCVD films on metal backplanes. FE measurements were complemented by the study of film surface morphology. Geometric field enhancement factors from surface measurements and Fowler-Nordheim Theory (FNT) were compared. FE properties of the films were also found to be particularly influenced by the backplane material

  17. Dipole and quadrupole forces exerted on atoms in laser fields: The nonperturbative approach

    International Nuclear Information System (INIS)

    Sindelka, Milan; Moiseyev, Nimrod; Cederbaum, Lorenz S.

    2006-01-01

    Manipulation of cold atoms by lasers has so far been studied solely within the framework of the conventional dipole approximation, and the atom-light interaction has been treated using low order perturbation theory. Laser control of atomic motions has been ascribed exclusively to the corresponding light-induced dipole forces. In this work, we present a general theory to derive the potential experienced by an atom in a monochromatic laser field in a context analogous to the Born-Oppenheimer approximation for molecules in the field-free case. The formulation goes beyond the dipole approximation and gives rise to the field-atom coupling potential terms which so far have not been taken into consideration in theoretical or experimental studies. Contrary to conventional approaches, our method is based upon the many electron Floquet theory and remains valid also for high intensity laser fields (i.e., for a strongly nonperturbative atom-light interaction). As an illustration of the developed theory, we investigate the trapping of cold atoms in optical lattices. We find that for some atoms for specific laser parameters, despite the absence of the dipole force, the laser trapping is still possible due to the electric quadrupole forces. Namely, we show that by using realistic laser parameters one can form a quadrupole optical lattice which is sufficiently strong to trap Ca and Na atoms

  18. Temporally asymmetric laser pulse for magnetic-field generation in plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Mamta; Gopal, Krishna; Gupta, Devki Nandan, E-mail: dngupta@physics.du.ac.in

    2016-04-01

    Of particular interest in this article, the case study of an asymmetric laser pulse interaction with a plasma for magnetic field enhancement has been investigated. The strong ponderomotive force due to the short leading edge of the propagating laser pulse drives a large nonlinear current, producing a stronger quasistatic magnetic field. An analytical expression for the magnetic field is derived and the strength of the magnetic field is estimated for the current laser-plasma parameters. The theoretical results are validated through the particle-in-cell (PIC) simulations and are in very close agreement with the simulation based estimations. This kind of magnetic field can be useful in the plasma based accelerators as well as in the laser-fusion based experiments. - Highlights: • We employ an asymmetric laser pulse to enhance the magnetic field strength in a plasma. • Short leading front of the pulse drives a strong ponderomotive force. • An analytical expression for the magnetic field is derived. • The strength of the magnetic field is estimated for the current laser–plasma parameters.

  19. Temporally asymmetric laser pulse for magnetic-field generation in plasmas

    International Nuclear Information System (INIS)

    Singh, Mamta; Gopal, Krishna; Gupta, Devki Nandan

    2016-01-01

    Of particular interest in this article, the case study of an asymmetric laser pulse interaction with a plasma for magnetic field enhancement has been investigated. The strong ponderomotive force due to the short leading edge of the propagating laser pulse drives a large nonlinear current, producing a stronger quasistatic magnetic field. An analytical expression for the magnetic field is derived and the strength of the magnetic field is estimated for the current laser-plasma parameters. The theoretical results are validated through the particle-in-cell (PIC) simulations and are in very close agreement with the simulation based estimations. This kind of magnetic field can be useful in the plasma based accelerators as well as in the laser-fusion based experiments. - Highlights: • We employ an asymmetric laser pulse to enhance the magnetic field strength in a plasma. • Short leading front of the pulse drives a strong ponderomotive force. • An analytical expression for the magnetic field is derived. • The strength of the magnetic field is estimated for the current laser–plasma parameters.

  20. Laser sub-Doppler cooling of atoms in an arbitrarily directed magnetic field

    International Nuclear Information System (INIS)

    Chang, Soo; Kwon, Taeg Yong; Lee, Ho Seong; Minogin, V.G.

    2002-01-01

    We analyze the influence of an arbitrarily directed uniform magnetic field on the laser sub-Doppler cooling of atoms. The analysis is done for a (3+5)-level atom excited by a σ + -σ - laser field configuration. Our analysis shows that the effects of the magnetic field depend strongly on the direction of the magnetic field. In an arbitrarily directed magnetic field the laser cooling configuration produces both the main resonance existing already at zero magnetic field and additional sub-Doppler resonances caused by two-photon and higher-order multiphoton processes. These sub-Doppler resonances are, however, well separated on the velocity scale if the Zeeman shift exceeds the widths of the resonances. This allows one to use the main sub-Doppler resonance for an effective laser cooling of atoms even in the presence of the magnetic field. The effective temperature of the atomic ensemble at the velocity of the main resonance is found to be almost the same as in the absence of the magnetic field. The defined structure of the multiphoton resonances may be of importance for the sub-Doppler laser cooling of atoms, atomic extraction from magneto-optical traps, and applications related to the control of atomic motion