Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer

International Nuclear Information System (INIS)

Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio; Wang Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Hatai, Keigo; Fukui, Akihiro; Arakawa, Yoshihiro

2011-01-01

Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density n e and the electron temperature T e profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO 2 laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of n e and T e were, respectively, about 2 x 10 24 m -3 and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measured properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured n e at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.

Gravitational wave detection using laser interferometry beyond the standard quantum limit

Science.gov (United States)

Heurs, M.

2018-05-01

Interferometric gravitational wave detectors (such as advanced LIGO) employ high-power solid-state lasers to maximize their detection sensitivity and hence their reach into the universe. These sophisticated light sources are ultra-stabilized with regard to output power, emission frequency and beam geometry; this is crucial to obtain low detector noise. However, even when all laser noise is reduced as far as technically possible, unavoidable quantum noise of the laser still remains. This is a consequence of the Heisenberg Uncertainty Principle, the basis of quantum mechanics: in this case, it is fundamentally impossible to simultaneously reduce both the phase noise and the amplitude noise of a laser to arbitrarily low levels. This fact manifests in the detector noise budget as two distinct noise sources-photon shot noise and quantum radiation pressure noise-which together form a lower boundary for current-day gravitational wave detector sensitivities, the standard quantum limit of interferometry. To overcome this limit, various techniques are being proposed, among them different uses of non-classical light and alternative interferometer topologies. This article explains how quantum noise enters and manifests in an interferometric gravitational wave detector, and gives an overview of some of the schemes proposed to overcome this seemingly fundamental limitation, all aimed at the goal of higher gravitational wave event detection rates. This article is part of a discussion meeting issue `The promises of gravitational-wave astronomy'.

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

Traveling wave laser system

International Nuclear Information System (INIS)

Gregg, D.W.; Kidder, R.E.; Biehl, A.T.

1975-01-01

The invention broadly involves a method and means for generating a traveling wave laser pulse and is basically analogous to a single pass light amplifier system. However, the invention provides a traveling wave laser pulse of almost unlimited energy content, wherein a gain medium is pumped in a traveling wave mode, the traveling wave moving at essentially the velocity of light to generate an amplifying region or zone which moves through the medium at the velocity of light in the presence of directed stimulating radiation, thereby generating a traveling coherent, directed radiation pulse moving with the amplification zone through the gain medium. (U.S.)

Control of a laser front wave

International Nuclear Information System (INIS)

Akaoka, K.; Wakaida, I.

1996-01-01

We controlled the laser wave front through a laser beam simulation experiment propagating through medium. Thus, we confirmed that the RMS, defined as the quadratic mean of the laser beam wave front, dropped to the 1/3 - 1/6 of the pre-control value

Modes in light wave propagating in semiconductor laser

Science.gov (United States)

Manko, Margarita A.

1994-01-01

The study of semiconductor laser based on an analogy of the Schrodinger equation and an equation describing light wave propagation in nonhomogeneous medium is developed. The active region of semiconductor laser is considered as optical waveguide confining the electromagnetic field in the cross-section (x,y) and allowing waveguide propagation along the laser resonator (z). The mode structure is investigated taking into account the transversal and what is the important part of the suggested consideration longitudinal nonhomogeneity of the optical waveguide. It is shown that the Gaussian modes in the case correspond to spatial squeezing and correlation. Spatially squeezed two-mode structure of nonhomogeneous optical waveguide is given explicitly. Distribution of light among the laser discrete modes is presented. Properties of the spatially squeezed two-mode field are described. The analog of Franck-Condon principle for finding the maxima of the distribution function and the analog of Ramsauer effect for control of spatial distribution of laser emission are discussed.

Laser control of electron matter waves

NARCIS (Netherlands)

Jones, E.; Becker, M.; Luiten, O.J.; Batelaan, H.

2016-01-01

In recent years laser light has been used to control the motion of electron waves. Electrons can now be diffracted by standing waves of light. Laser light in the vicinity of nanostructures is used to affect free electrons, for example, femto-second and atto-second laser-induced electrons are emitted

Laser light scattering in a laser-induced argon plasma: Investigations of the shock wave

Energy Technology Data Exchange (ETDEWEB)

Pokrzywka, B. [Obserwatorium Astronomiczne na Suhorze, Uniwersytet Pedagogiczny, ulica Podchorazych 2, 30-084 Krakow (Poland); Mendys, A., E-mail: agata.mendys@uj.edu.pl [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Dzierzega, K.; Grabiec, M. [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Pellerin, S. [GREMI, site de Bourges, Universite d' Orleans, CNRS, rue Gaston Berger BP 4043, 18028 Bourges (France)

2012-08-15

Shock wave produced by a laser induced spark in argon at atmospheric pressure was examined using Rayleigh and Thomson scattering. The spark was generated by focusing a laser pulse from the second harmonic ({lambda} = 532 nm) of a nanosecond Nd:YAG laser using an 80 mm focal length lens, with a fluence of 2 kJ{center_dot}cm{sup -2}. Images of the spark emission were recorded for times between 30 ns and 100 {mu}s after the laser pulse in order to characterize its spatial evolution. The position of the shock wave at several instants of its evolution and for several plasma regions was determined from the Rayleigh-scattered light of another nanosecond Nd:YAG laser (532 nm, 40 J{center_dot}cm{sup -2} fluence). Simultaneously, Thomson scattering technique was applied to determine the electron density and temperature in the hot plasma core. Attempts were made to describe the temporal evolution of the shock wave within a self-similar model, both by the simple Sedov-Taylor formula as well as its extension deduced by de Izarra. The temporal radial evolution of the shock position is similar to that obtained within theory taking into account the counter pressure of the ambient gas. Density profiles just behind the shock front are in qualitative agreement with those obtained by numerically solving the Euler equations for instantaneous explosion at a point with counter pressure. - Highlights: Black-Right-Pointing-Pointer We investigated shock wave evolution by Rayleigh scattering method. Black-Right-Pointing-Pointer 2D map of shockwave position for several times after plasma generation is presented. Black-Right-Pointing-Pointer Shock wave evolution is not satisfactorily described within self-similar models. Black-Right-Pointing-Pointer Evolution of shock position similar to theory taking into account counter pressure. Black-Right-Pointing-Pointer Density profile behind the shock similar to numerical solution of Euler equations.

Laser driven detonation waves above a solid target

International Nuclear Information System (INIS)

Emmony, D.C.

1975-01-01

The interaction of a TEA CO 2 laser pulse with a carbon target in an argon atmosphere (p approximately mmHg) is shown to produce a double detonation wave system. The laser driven detonation wave becomes the most important as the gas pressure is increased. Calculation of the energy in the detonation waves is in good agreement with the incident laser energy at different times during the main laser pulse and the long tail. The observation of the incident laser detonation wave accounts for the anomalous energies reported previously. (Auth.)

Emission study of alumina plasma produced by a KrF laser

Energy Technology Data Exchange (ETDEWEB)

Yahiaoui, K., E-mail: kyahiaoui@cdta.dz [Centre de Développement des Technologies Avancées, cité 20 aout 1956, BP 17, Baba Hassen, Alger (Algeria); Abdelli-Messaci, S.; Messaoud-Aberkane, S.; Kerdja, T. [Centre de Développement des Technologies Avancées, cité 20 aout 1956, BP 17, Baba Hassen, Alger (Algeria); Kellou, H. [Université des Sciences et de la Technologie Houari Boumediene, BP 32, El-Allia, 16111 Bab-Ezzouar, Alger (Algeria)

2014-03-01

We report on the plasma emission formed from an α-alumina target when irradiated by laser into vacuum and through oxygen gas. Two diagnostic tools have been used: ICCD camera fast imaging and optical emission spectroscopy. The alumina plasma was induced by a KrF laser beam at a wavelength of 248 nm and pulse duration of 25 ns. The laser fluence was set to 8 J/cm{sup 2} and the oxygen pressure was varied from 0.01 to 5 mbar. By using the ICCD camera, two dimensional images of the plasma expansion were taken at different times. Depending on oxygen pressure and time delay, the expansion behavior of the plasma showed free expansion, plume splitting, shock wave formation, hydrodynamic instability and deceleration of the plume. Using optical emission spectroscopy, the plasma emission revealed the presence of neutral Al I, Al II, Al III into vacuum and under oxygen ambiance. The molecular emission of aluminum oxide (AlO) was detected only in oxygen ambiance. It should be noted that no oxygen lines were observed. Finally, the evolution of the electronic temperature along the normal axis from the target surface, into vacuum, was estimated using the Boltzmann plot method. - Highlights: • Ablated mass measurements of α-alumina target irradiated by a laser in nanosecond regime. • Optical emission spectroscopy of alumina plasma. • Fast imaging diagnostic of alumina plume using ICCD camera.

Resonant parametric interference effect in spontaneous bremsstrahlung of an electron in the field of a nucleus and two pulsed laser waves

Science.gov (United States)

Lebed', A. A.; Padusenko, E. A.; Roshchupkin, S. P.; Dubov, V. V.

2018-04-01

Electron-nucleus bremsstrahlung in the field of two moderately strong pulsed laser waves in the case of incommensurate frequencies is theoretically studied under resonant conditions. The process is studied in detail in a special kinematic region, where stimulated processes with correlated emission and absorption of photons of the first and second waves become predominant (parametric interference effect). The availability of this region is caused by interference of the first and second laser waves. The correspondence between the emission angle and the final-electron energy is established in this interference kinematic. In this case, the cross-sectional properties are determined by the multiphoton quantum interference parameter, which is proportional to the product of intensities of the first and second waves. The resonant differential cross section of electron-nucleus spontaneous bremsstrahlung with simultaneous registration of both emission angles of the spontaneous photon and the scattered electron can exceed by four or five orders of magnitude the corresponding cross section in the absence of an external field. It was shown for nonrelativistic electrons that the resonant cross section of the studied process in the field of two pulsed laser waves within the interference region in two order of magnitude may exceed corresponding cross sections at other scattering kinematics. The obtained results may be experimentally verified, for example, by scientific facilities at sources of pulsed laser radiation (such as SLAC, FAIR, XFEL, ELI).

Generation of narrowband elastic waves with a fiber laser and its application to the imaging of defects in a plate.

Science.gov (United States)

Hayashi, Takahiro; Ishihara, Ken

2017-05-01

Pulsed laser equipment can be used to generate elastic waves through the instantaneous reaction of thermal expansion or ablation of the material; however, we cannot control the waveform generated by the laser in the same manner that we can when piezoelectric transducers are used as exciters. This study investigates the generation of narrowband tone-burst waves using a fiber laser of the type that is widely used in laser beam machining. Fiber lasers can emit laser pulses with a high repetition rate on the order of MHz, and the laser pulses can be modulated to a burst train by external signals. As a consequence of the burst laser emission, a narrowband tone-burst elastic wave is generated. We experimentally confirmed that the elastic waves agreed well with the modulation signals in time domain waveforms and their frequency spectra, and that waveforms can be controlled by the generation technique. We also apply the generation technique to defect imaging with a scanning laser source. In the experiments, with small laser emission energy, we were not able to obtain defect images from the signal amplitude due to low signal-to-noise ratio, whereas using frequency spectrum peaks of the tone-burst signals gave clear defect images, which indicates that the signal-to-noise ratio is improved in the frequency domain by using this technique for the generation of narrowband elastic waves. Moreover, even for defect imaging at a single receiving point, defect images were enhanced by taking an average of distributions of frequency spectrum peaks at different frequencies. Copyright © 2017 Elsevier B.V. All rights reserved.

Instantaneous wave emission model

International Nuclear Information System (INIS)

Kruer, W.L.

1970-12-01

A useful treatment of electrostatic wave emission by fast particles in a plasma is given. First, the potential due to a fast particle is expressed as a simple integration over the particle orbit; several interesting results readily follow. The potential in the wake of an accelerating particle is shown to be essentially that produced through local excitation of the plasma by the particle free-streaming about its instantaneous orbit. Application is made to one dimension, and it is shown that the wave emission and adsorption synchronize to the instantaneous velocity distribution function. Guided by these calculations, we then formulate a test particle model for computing the instantaneous wave emission by fast particles in a Vlasov plasma. This model lends itself to physical interpretation and provides a direct approach to many problems. By adopting a Fokker-Planck description for the particle dynamics, we calculate the broadening of the wave-particle resonance due to velocity diffusion and drag

Laser shock wave and its applications

Science.gov (United States)

Yang, Chaojun; Zhang, Yongkang; Zhou, Jianzhong; Zhang, Fang; Feng, Aixin

2007-12-01

The technology of laser shock wave is used to not only surface modification but also metal forming. It can be divided into three parts: laser shock processing, laser shock forming (LSF) and laser peenforming(LPF). Laser shock processing as a surface treatment to metals can make engineering components have a residual compressive stress so that it obviously improves their fatigue strength and stress corrosion performances, while laser shock forming (LSF) is a novel technique that is used in plastic deformation of sheet metal recently and Laser peen forming (LPF) is another new sheet metal forming process presented in recent years. They all can be carried out by a high-power and repetition pulse Nd:Glass laser device made by Jiangsu University. Laser shock technology has characterized of ultrahigh pressure and high strain rate (10 6 - 10 7s -1). Now, for different materials, we are able to form different metals to contours and shapes and simultaneity leave their surfaces in crack-resistant compressive stress state. The results show that the technology of laser shock wave can strengthen surface property and prolong fatigue life and especially can deform metals to shapes that could not be adequately made using conventional methods. With the development of the technology of laser shock wave, the applied fields of laser will become greater and greater.

Study on guided waves in semiconductor lasers

International Nuclear Information System (INIS)

Pudensi, M.A.A.

1980-01-01

In This work we studied the guided waves in semiconductor lasers. In the first part we carried on the experimental measurements on lasers with stripe nonorthogonal to the mirrors. In the second part we developed a matrix method for the study of propagation and reflection of guided waves in lasers. (author) [pt

Laser Generated Leaky Acoustic Waves for Needle Visualization.

Science.gov (United States)

Wu, Kai-Wen; Wang, Yi-An; Li, Pai-Chi

2018-04-01

Ultrasound (US)-guided needle operation is usually used to visualize both tissue and needle position such as tissue biopsy and localized drug delivery. However, the transducer-needle orientation is limited due to reflection of the acoustic waves. We proposed a leaky acoustic wave method to visualize the needle position and orientation. Laser pulses are emitted on top of the needle to generate acoustic waves; then, these acoustic waves propagate along the needle surface. Leaky wave signals are detected by the US array transducer. The needle position can be calculated by phase velocities of two different wave modes and their corresponding emission angles. In our experiments, a series of needles was inserted into a tissue mimicking phantom and porcine tissue to evaluate the accuracy of the proposed method. The results show that the detection depth is up to 51 mm and the insertion angle is up to 40° with needles of different diameters. It is demonstrated that the proposed approach outperforms the conventional B-mode US-guided needle operation in terms of the detection range while achieving similar accuracy. The proposed method reveals the potentials for further clinical applications.

Characteristics of 1.9 μm laser emission from hydrogen-filled hollow-core fiber by stimulated Raman scattering

Science.gov (United States)

Gu, Bo; Chen, Yubin; Wang, Zefeng

2016-11-01

We report here the detailed characteristics of 1.9 μm laser emission from hydrogen-filled hollow-core fiber by stimulated Raman scattering. A 6.5 m hydrogen-filled Ice-cream negative curvature hollow-core fiber is pumped with a high peak power, narrow linewidth, liner polarized subnanosecond pulsed 1064 nm microchip laser, generating pulsed 1908.5 nm vibrational Stokes wave. The linewidth of the pump laser and the vibrational Stokes wave is about 1 GHz and 2 GHz respectively. And the maximum Raman conversion quantum efficiency is about 48%. We also studied the pulse shapes of the pump laser and the vibrational Stokes wave. The polarization dependence of the vibrational and the rotational stimulated Raman scattering is also investigated. In addition, the beam profile of vibrational Stokes wave shows good quality, which may be taken advantage of in many applications.

Effect of the three-dimensional structure of laser emission on the dynamics of low-threshold optical breakdown plasmas

Science.gov (United States)

Anisimov, V. N.; Arutiunian, R. V.; Bol'Shov, L. A.; Derkach, O. N.; Kanevskii, M. F.

1989-03-01

The effect of the transverse structure of pulsed CO2 laser emission on the dynamics of laser-induced detonation waves propagating from a metal surface and on plasma transparency recovery is investigated theoretically and experimentally. Particular attention is given to breakdown initiation near the surface. It is suggested that the inclusion of refraction in the plasma into a self-consistent numerical mode is essential for the adequate quantitative description of experimental data on the interaction of laser emission with low-threshold optical breakdown plasmas.

Wave emission by resonance crossing

International Nuclear Information System (INIS)

Tracy, E.R.; Kaufman, A.N.; Liang, Y.

1995-01-01

The emission of collective waves by a moving charged particle in a nonuniform medium is discussed. Emission occurs in a nonuniform medium when the local dispersion relation of the collective wave is satisfied. This is a form of resonance crossing. Using the Weyl symbol calculus, a local expansion of the collective wave equation driven by the particle source is derived in the neighborhood of the crossing. The collective wave dispersion manifold and the gyroballistic wave dispersion manifold can be used as a pair of local coordinates in the neighborhood of the resonance crossing, which greatly simplifies the analysis. This change of representation is carried out using a metaplectic transform (a generalization of the fourier transform). The Wigner function of the emitted wave field is then computed in the new coordinates. The Wigner function is a phase space scalar, hence the numerical value is invariant under linear canonical transformations. This invariance is invoked to finally arrive at the Wigner function in the original (physical) coordinates. The wave-action and -energy emission rates are then computed from the Wigner function. copyright 1995 American Institute of Physics

Investigations of the cathode region of an argon arc plasma by degenerate four-wave mixing laser spectroscopy and optical emission spectroscopy

International Nuclear Information System (INIS)

Dzierzega, K; Pokrzywka, B; Pellerin, S

2004-01-01

Degenerate four-wave mixing (DFWM) laser spectroscopy was used in local studies of atmospheric pressure argon plasma generated in a free-burning arc. The results of plasma diagnostics using the DFWM method were compared to the results obtained with optical emission measurements. In the cathode region of the arc the maxima of both the DFWM signal and the emission coefficient for the 696.5 nm Ar I line depend on the distance from the cathode tip. This effect proves the departure of the plasma state from local thermal equilibrium (LTE) as it has been reported by many authors. On the other hand the Stark shifts of the 696.5 nm Ar I line determined by the DFWM method in relation to plasma diagnostic results show no deviations from LTE on the arc axis down to 1.0 mm from the cathode tip

Angle-dependent light emission from aligned multiwalled carbon nanotubes under CO2 laser irradiation

International Nuclear Information System (INIS)

Zhang, Y; Gong, T; Liu, W J; Wei, J Q; Zhang, X F; Wang, K L; Zhong, M L; Wu, D H

2007-01-01

This paper reports the light emission from aligned multiwalled carbon nanotubes (MWNTs) under continuous wave CO 2 laser (λ = 10.6 μm) irradiation. Results indicate that the light emission is dependent on the angle θ between the laser incident direction and the nanotube axis. The relative intensity of the light emission at certain wavelengths shows a Lorentzian feature when θ varies from 0 0 to 90 0 . The Lorentzian fitting curve displays a distinct tendency between shorter (λ 700 nm). A minimum intensity was observed at θ m close to 67 0 under shorter wavelength, whereas a maximum intensity was shown at θ m of about 60 0 at longer wavelength. These results show the anisotropic property of aligned MWNTs

Cavitation and shock waves emission on the rigid boundary of water under mid-IR nanosecond laser pulse excitation

Science.gov (United States)

Pushkin, A. V.; Bychkov, A. S.; Karabutov, A. A.; Potemkin, F. V.

2018-06-01

The processes of conversion of light energy into mechanical energy under mid-IR nanosecond laser excitation on a rigid boundary of water are investigated. Strong water absorption of Q-switched Cr:Yb:Ho:YSGG (2.85 µm, 6 mJ, 45 ns) laser radiation provides rapid energy deposition of ~8 kJ cm‑3 accompanied with strong mechanical transients. The evolution of shock waves and cavitation bubbles is studied using the technique of shadowgraphy and acoustic measurements, and the conversion efficiency into these energy channels for various laser fluence (0.75–2.0 J cm‑2) is calculated. For 6 mJ laser pulse with fluence of 2.0 J cm‑2, the conversion into shock wave energy reaches 67%. The major part of the shock wave energy (92%) is dissipated when the shock front travels the first 250 µm, and the remaining 8% is transferred to the acoustic far field. The calculated pressure in the vicinity of water-silicon interface is 0.9 GPa. Cavitation efficiency is significantly less and reaches up to 5% of the light energy. The results of the current study could be used in laser parameters optimization for micromachining and biological tissue ablation.

Nonadiabatic dynamics in intense continuous wave laser fields and real-time observation of the associated wavepacket bifurcation in terms of spectrogram of induced photon emission.

Science.gov (United States)

Mizuno, Yuta; Arasaki, Yasuki; Takatsuka, Kazuo

2016-11-14

We propose a theoretical principle to directly monitor the bifurcation of quantum wavepackets passing through nonadiabatic regions of a molecule that is placed in intense continuous wave (CW) laser fields. This idea makes use of the phenomenon of laser-driven photon emission from molecules that can undergo nonadiabatic transitions between ionic and covalent potential energy surfaces like Li + F - and LiF. The resultant photon emission spectra are of anomalous yet characteristic frequency and intensity, if pumped to an energy level in which the nonadiabatic region is accessible and placed in a CW laser field. The proposed method is designed to take the time-frequency spectrogram with an appropriate time-window from this photon emission to detect the time evolution of the frequency and intensity, which depends on the dynamics and location of the relevant nuclear wavepackets. This method is specifically designed for the study of dynamics in intense CW laser fields and is rather limited in scope than other techniques for femtosecond chemical dynamics in vacuum. The following characteristic features of dynamics can be mapped onto the spectrogram: (1) the period of driven vibrational motion (temporally confined vibrational states in otherwise dissociative channels, the period and other states of which dramatically vary depending on the CW driving lasers applied), (2) the existence of multiple nuclear wavepackets running individually on the field-dressed potential energy surfaces, (3) the time scale of coherent interaction between the nuclear wavepackets running on ionic and covalent electronic states after their branching (the so-called coherence time in the terminology of the theory of nonadiabatic interaction), and so on.

Betatron emission as a diagnostic for injection and acceleration mechanisms in laser plasma accelerators

International Nuclear Information System (INIS)

Corde, S; Thaury, C; Phuoc, K Ta; Lifschitz, A; Lambert, G; Lundh, O; Brijesh, P; Sebban, S; Rousse, A; Faure, J; Malka, V; Arantchuk, L

2012-01-01

Betatron x-ray emission in laser plasma accelerators is a promising compact source that may be an alternative to conventional x-ray sources, based on large scale machines. In addition to its potential as a source, precise measurements of betatron emission can reveal crucial information about relativistic laser–plasma interaction. We show that the emission length and the position of the x-ray emission can be obtained by placing an aperture mask close to the source, and by measuring the beam profile of the betatron x-ray radiation far from the aperture mask. The position of the x-ray emission gives information on plasma wave breaking and hence on the laser non-linear propagation. Moreover, the measurement of the longitudinal extension helps one to determine whether the acceleration is limited by pump depletion or dephasing effects. In the case of multiple injections, it is used to retrieve unambiguously the position in the plasma of each injection. This technique is also used to study how, in a capillary discharge, the variations of the delay between the discharge and the laser pulse affect the interaction. The study reveals that, for a delay appropriate for laser guiding, the x-ray emission only occurs in the second half of the capillary: no electrons are injected and accelerated in the first half. (paper)

Characteristics of 1.9-μm laser emission from hydrogen-filled hollow-core fiber by vibrational stimulated Raman scattering

Science.gov (United States)

Gu, Bo; Chen, Yubin; Wang, Zefeng

2016-12-01

We report here the characteristics of 1.9-μm laser emission from a gas-filled hollow-core fiber by stimulated Raman scattering (SRS). A 6.5-m hydrogen-filled ice-cream negative curvature hollow-core fiber is pumped with a high peak-power, narrow linewidth, linearly polarized subnanosecond pulsed 1064-nm microchip laser, generating a pulsed vibrational Stokes wave at 1908.5 nm. The maximum quantum efficiency of about 48% is obtained, which is mainly limited by the mode mismatch between the pump laser beam and the Stokes wave in the hollow-core fiber. The linewidths of the pump laser and the first-order vibrational Stokes wave are measured to be about 1 and 2 GHz, respectively, by a scanning Fabry-Perot interferometer. The pressure selection phenomenon of the vibrational anti-Stokes waves is also investigated. The pulse duration of the vibrational Stokes wave is recorded to be narrower than that of the pump laser. The polarization properties of the hollow-core fiber and the polarization dependence of the vibrational and the rotational SRS are also studied. The beam profile of the vibrational Stokes wave shows good quality.

Continuous wave room temperature external ring cavity quantum cascade laser

Energy Technology Data Exchange (ETDEWEB)

Revin, D. G., E-mail: d.revin@sheffield.ac.uk; Hemingway, M.; Vaitiekus, D.; Cockburn, J. W. [Physics and Astronomy Department, The University of Sheffield, S3 7RH Sheffield (United Kingdom); Hempler, N.; Maker, G. T.; Malcolm, G. P. A. [M Squared Lasers Ltd., G20 0SP Glasgow (United Kingdom)

2015-06-29

An external ring cavity quantum cascade laser operating at ∼5.2 μm wavelength in a continuous-wave regime at the temperature of 15 °C is demonstrated. Out-coupled continuous-wave optical powers of up to 23 mW are observed for light of one propagation direction with an estimated total intra-cavity optical power flux in excess of 340 mW. The uni-directional regime characterized by the intensity ratio of more than 60 for the light propagating in the opposite directions was achieved. A single emission peak wavelength tuning range of 90 cm{sup −1} is realized by the incorporation of a diffraction grating into the cavity.

Continuous wave room temperature external ring cavity quantum cascade laser

International Nuclear Information System (INIS)

Revin, D. G.; Hemingway, M.; Vaitiekus, D.; Cockburn, J. W.; Hempler, N.; Maker, G. T.; Malcolm, G. P. A.

2015-01-01

An external ring cavity quantum cascade laser operating at ∼5.2 μm wavelength in a continuous-wave regime at the temperature of 15 °C is demonstrated. Out-coupled continuous-wave optical powers of up to 23 mW are observed for light of one propagation direction with an estimated total intra-cavity optical power flux in excess of 340 mW. The uni-directional regime characterized by the intensity ratio of more than 60 for the light propagating in the opposite directions was achieved. A single emission peak wavelength tuning range of 90 cm −1 is realized by the incorporation of a diffraction grating into the cavity

Traveling wave laser system

International Nuclear Information System (INIS)

Gregg, D.W.; Kidder, R.E.; Biehl, A.T.

1975-01-01

A method is described for generating a traveling wave laser pulse of almost unlimited energy content wherein a gain medium is pumped into a traveling wave mode, the traveling wave moving at essentially the velocity of light to generate an amplifying region or zone which moves through the medium at the velocity of light in the presence of directed stimulating radiation, thereby generating a traveling coherent, directed radiation pulse moving with the amplification zone through the gain medium. (U.S.)

A dye center laser pumped by emission from copper vapor and dye lasers

Energy Technology Data Exchange (ETDEWEB)

Loktyushin, A A; Chernyshev, A I; Soldatov, A N; Sukhanov, V B; Troitskiy, V O

1983-01-01

LiF:F2+ lasing is reported for the case of pumping by total emission with frequencies of 570.6 and 578.2 nanometers or by a single yellow copper vapor laser line and emission from an oxazene-17 dye laser excited by emission from a Cu laser. Lasing with a mean power level of 23 milliwatts with a maximum at 911 nanometers is obtained. The maximum efficiency was 3.4 percent with pumping of the dye centers by emission from the yellow Cu laser line. The lasing characteristics of the laser for all the types of pumping used are given.

Biological effects of laser-induced stress waves

International Nuclear Information System (INIS)

Doukas, A.; Lee, S.; McAuliffe, D.

1995-01-01

Laser-induced stress waves can be generated by one of the following mechanisms: Optical breakdown, ablation or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to stress waves with different characteristics and under different conditions. The most widely studied phenomena are those of the collateral damage seen in photodisruption in the eye and in 193 run ablation of cornea and skin. On the other hand, the therapeutic application of laser-induced stress waves has been limited to the disruption of noncellular material such as renal stones, atheromatous plaque and vitreous strands. The effects of stress waves to cells and tissues can be quite disparate. Stress waves can fracture tissue, damage cells, and increase the permeability of the plasma membrane. The viability of cell cultures exposed to stress waves increases with the peak stress and the number of pulses applied. The rise time of the stress wave also influences the degree of cell injury. In fact, cell viability, as measured by thymidine incorporation, correlates better with the stress gradient than peak stress. Recent studies have also established that stress waves induce a transient increase of the permeability of the plasma membrane in vitro. In addition, if the stress gradient is below the damage threshhold, the cells remain viable. Thus, stress waves can be useful as a means of drug delivery, increasing the intracellular drug concentration and allowing the use of drugs which are impermeable to the cell membrane. The present studies show that it is important to create controllable stress waves. The wavelength tunability and the micropulse structure of the free electron laser is ideal for generating stress waves with independently adjustable parameters, such as rise time, duration and peak stress

Blast-Wave Generation and Propagation in Rapidly Heated Laser-Irradiated Targets

Science.gov (United States)

Ivancic, S. T.; Stillman, C. R.; Nilson, P. M.; Solodov, A. A.; Froula, D. H.

2017-10-01

Time-resolved extreme ultraviolet (XUV) spectroscopy was used to study the creation and propagation of a >100-Mbar blast wave in a target irradiated by an intense (>1018WWcm2 cm2) laser pulse. Blast waves provide a platform to generate immense pressures in the laboratory. A temporal double flash of XUV radiation was observed when viewing the rear side of the target, which is attributed to the emergence of a blast wave following rapid heating by a fast-electron beam generated from the laser pulse. The time-history of XUV emission in the photon energy range of 50 to 200 eV was recorded with an x-ray streak camera with 7-ps temporal resolution. The heating and expansion of the target was simulated with an electron transport code coupled to 1-D radiation-hydrodynamics simulations. The temporal delay between the two flashes measured in a systematic study of target thickness and composition was found to evolve in good agreement with a Sedov-Taylor blast-wave solution. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and Department of Energy Office of Science Award Number DE-SC-0012317.

Wave function of free electron in a strong laser plasma

International Nuclear Information System (INIS)

Zhu Shitong; Shen Wenda; Guo Qizhi

1993-01-01

The wave function of free electron in a strong laser plasma is obtained by solving exactly the Dirac equation in a curved space-time with optical metric for the laser plasma. When the laser field is diminished to zero, the wave function is naturally reduced to relativistic wave function of free electron. The possible application of the wave function is discussed

Comprehensive study on the pressure dependence of shock wave plasma generation under TEA CO2 laser bombardment on metal sample

International Nuclear Information System (INIS)

Marpaung, A.M.; Kurniawan, H.; Tjia, M.O.; Kagawa, K.

2001-01-01

An experimental study has been carried out on the dynamical process taking place in the plasma generated by a TEA CO 2 laser (400 mJ, 100 ns) on a zinc target when surrounded by helium gas of pressure ranging from 2 Torr to 1 atm. Plasma characteristics were examined in detail on the emission lines of Zn I 481.0 nm and He I 587.6 nm by means of an unique time-resolved spatial distribution technique in addition to an ordinary time-resolved emission measurement technique. The results reveal, for the first time, persistent shock wave characteristics in all cases throughout the entire pressure range considered. Further analysis of the data has clarified the distinct characteristics of laser plasmas generated in different ranges of gas pressure. It is concluded that three types of shock wave plasma can be identified; namely, a target shock wave plasma in the pressure range from 2 Torr to around 50 Torr; a coupling shock wave plasma in the pressure range from around 50 Torr to 200 Torr and a gas breakdown shock wave plasma in the pressure range from around 200 Torr to 1 atm. These distinct characteristics are found to be ascribable to the different extents of the gas breakdown process taking place at the different gas pressures. These results, obtained for a TEA CO 2 laser, will provide a useful basis for the analyses of plasmas induced by other lasers. (author)

Long-Wave Infrared (LWIR) Molecular Laser-Induced Breakdown Spectroscopy (LIBS) Emissions of Thin Solid Explosive Powder Films Deposited on Aluminum Substrates.

Science.gov (United States)

Yang, Clayton S-C; Jin, Feng; Trivedi, Sudhir B; Brown, Ei E; Hommerich, Uwe; Tripathi, Ashish; Samuels, Alan C

2017-04-01

Thin solid films made of high nitro (NO 2 )/nitrate (NO 3 ) content explosives were deposited on sand-blasted aluminum substrates and then studied using a mercury-cadmium-telluride (MCT) linear array detection system that is capable of rapidly capturing a broad spectrum of atomic and molecular laser-induced breakdown spectroscopy (LIBS) emissions in the long-wave infrared region (LWIR; ∼5.6-10 µm). Despite the similarities of their chemical compositions and structures, thin films of three commonly used explosives (RDX, HMX, and PETN) studied in this work can be rapidly identified in the ambient air by their molecular LIBS emission signatures in the LWIR region. A preliminary assessment of the detection limit for a thin film of RDX on aluminum appears to be much lower than 60 µg/cm 2 . This LWIR LIBS setup is capable of rapidly probing and charactering samples without the need for elaborate sample preparation and also offers the possibility of a simultaneous ultraviolet visible and LWIR LIBS measurement.

Optical emission from laser-produced chromium and magnesium ...

Indian Academy of Sciences (India)

Abstract. Parametric study of optical emission from two successive laser pulses pro- ... The hot laser-produced plasma radiates various types of emissions ..... lasers. The qualitative agreement of this analysis with our observations confirms.

Stabilized lasers for advanced gravitational wave detectors

International Nuclear Information System (INIS)

Willke, B; Danzmann, K; Kwee, P; Seifert, F; Frede, M; Kracht, D; Puncken, O; Schulz, B; Veltkamp, C; Wagner, S; Wessels, P; Winkelmann, L; King, P; Savage, R L Jr

2008-01-01

Second generation gravitational wave detectors require high power lasers with more than 100 W of output power and with very low temporal and spatial fluctuations. To achieve the demanding stability levels required, low noise techniques and adequate control actuators have to be part of the high power laser design. In addition feedback control and passive noise filtering is used to reduce the fluctuations in the so-called prestabilized laser system (PSL). In this paper, we discuss the design of a 200 W PSL which is under development for the Advanced LIGO gravitational wave detector and will present the first results. The PSL noise requirements for advanced gravitational wave detectors will be discussed in general and the stabilization scheme proposed for the Advanced LIGO PSL will be described

Plasma wave amplitude measurement created by guided laser wakefield

International Nuclear Information System (INIS)

Wojda, Franck

2010-01-01

The interaction of an intense laser pulse of short duration with a plasma produces a plasma wave with large amplitude in its wake, which is associated with a longitudinal electric field. It can be used to accelerate relativistic electrons injected into the wave to energies in the GeV range over distances of the order of a few centimeters, short compared to acceleration lengths in conventional accelerators. The control of the electron beam characteristics during the acceleration process is fundamental for achieving a usable laser-plasma acceleration stage. The main result of this thesis is the creation and characterization of a plasma wave in a weakly nonlinear regime over a length of several centimeters. Capillary tubes are used to guide the laser beam over these distances, while maintaining a large enough intensity (∼ 10 17 W/cm 2 ). The guided laser beam ionizes the gas in the tube and creates the plasma wave. A diagnostic based on the modification of the laser pulse spectrum was used to determine the amplitude of the plasma wave along the tube. The amplitude of the plasma wave was studied as a function of gas filling pressure, length of the capillary and laser energy. Experimental results are compared; they are in excellent agreement with analytical results and modeling. They show that the electric field associated with the plasma wave is between 1 and 10 GV/m over a length of up to 8 cm. This work has demonstrated the ability to create a controlled plasma wave in a weakly nonlinear regime. (author)

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...

Efficient laser emission from cladding waveguide inscribed in Nd:GdVO(4) crystal by direct femtosecond laser writing.

Science.gov (United States)

Liu, Hongliang; Tan, Yang; Vázquez de Aldana, Javier R; Chen, Feng

2014-08-01

We report on the fabrication of depressed cladding waveguides in Nd:GdVO(4) laser crystal by using femtosecond laser inscription. The cross section of the structure is a circular shape with a diameter of 150 μm. Under the optical pump at 808 nm, the continuous wave (cw) as well as pulsed (Q-switched by graphene saturable absorber) waveguide lasing at 1064 nm has been realized, supporting guidance of both TE and TM polarizations. The maximum output power of 0.57 W was obtained in the cw regime, while the maximum pulse energy of the pulsed laser emissions was up to 19 nJ (corresponding to a maximum average output power of 0.33 W, at a resonant frequency of 18 MHz). The slope efficiencies achieved for the cw and pulsed Nd:GdVO(4) waveguide lasers were as high as 68% and 52%, respectively.

Influence of laser-supported detonation waves on metal drilling with pulsed CO2 lasers

International Nuclear Information System (INIS)

Stuermer, E.; von Allmen, M.

1978-01-01

Drilling of highly reflective metals in an ambient atmosphere with single TEA-CO 2 -laser pulses of fluences between 300 and 6000 J/cm 2 is reported. The drilling process was investigated by measuring the time-resolved laser power reflected specularly from the targets during the interaction and by analyzing the craters produced. Experiments were performed in ambient air, argon, and helium. Target damage was found to be strongly influenced by a laser-supported detonation (LSD) wave in the ambient gas. If the laser fluence exceeded a material-dependent damage threshold (copper: 300 J/cm 2 ), drilling occurred, but the efficiency was inversely related to the duration of the LSD wave. Efficient material removal is possible if the LSD wave can be dissipated within a small fraction of the laser pulse duration. This was achieved by small-F-number focusing of TEM 00 laser pulses of 5-μs duration. Replacing the ambient air at the target by a gas of lower density results in a further significant reduction of LSD-wave lifetime, and a correlated increase of the drilling yield. On copper targets a maximum drilling yield of 10 -5 cm 3 /J was observed in ambient helium at a laser fluence of 1 kJ/cm 2

Phase velocity of nonlinear plasma waves in the laser beat-wave accelerator

International Nuclear Information System (INIS)

Spence, W.L.

1985-01-01

The suggested plasma-laser accelerator is an attempt to achieve a very high energy gradient by resonantly exciting a longitudinal wave traveling at close to the speed of light in cold plasma by means of the beat-wave generated by the transverse fields in two laser beams. Previous calculations to all orders in v/sub z/ have been done essentially from the laboratory frame point of view and have treated the plasma wave as having sharply defined phase velocity equal to the speed of light. However a high energy particle beam undergoing acceleration sees the plasma wave from a nearly light-like frame of reference and hence is very sensitive to small deviations in its phase velocity. Here the authors introduce a calculational scheme that includes all orders in v/sub z/ and in the plasma density, and additionally takes into account the influence of plasma nonlinearities on the wave's phase velocity. The main assumption is that the laser frequencies are very large compared to the plasma frequency - under which they are able to in essence formally sum up all orders of forward Raman scattering. They find that the nonlinear plasma wave does not have simply a single phase velocity - it is really a superposition of many - but that the beat-wave which drives it is usefully described by a non-local effective phase velocity function

The energy and temporal characteristics of orthogonal polarized waves generated by a transversely-excited pulsed CO/sub 2/ laser

Energy Technology Data Exchange (ETDEWEB)

Bertel, I.M.; Churakov, V.V.; Petukhov, V.O.; Prokopov, A.P.; Trushin, S.A.; Voitovich, A.P.

1980-01-01

The competition of orthogonally-polarized waves with various differences in the wave Q-factors and active medium pressures is studied. The possibility of controlling the parameters of a pulsed CO/sub 2/ laser by changing the value of the amplitude anisotropy of the cavity is demonstrated. The duration of the emission pulse for one of two orthogonal polarizations was reduced by virtually 50%.

Comparison of acoustic shock waves generated by micro and nanosecond lasers for a smart laser surgery system

Science.gov (United States)

Nguendon Kenhagho, Hervé K.; Rauter, Georg; Guzman, Raphael; C. Cattin, Philippe; Zam, Azhar

2018-02-01

Characterization of acoustic shock wave will guarantee efficient tissue differentiation as feedback to reduce the probability of undesirable damaging (i.e. cutting) of tissues in laser surgery applications. We ablated hard (bone) and soft (muscle) tissues using a nanosecond pulsed Nd:YAG laser at 532 nm and a microsecond pulsed Er:YAG laser at 2.94 μm. When the intense short ns-pulsed laser is applied to material, the energy gain causes locally a plasma at the ablated spot that expands and propagates as an acoustic shock wave with a rarefaction wave behind the shock front. However, when using a μs-pulsed Er:YAG laser for material ablation, the acoustic shock wave is generated during the explosion of the ablated material. We measured and compared the emitted acoustic shock wave generated by a ns-pulsed Nd:YAG laser and a μs-pulsed Er:YAG laser measured by a calibrated microphone. As the acoustic shock wave attenuates as it propagates through air, the distance between ablation spots and a calibrated microphone was at 5 cm. We present the measurements on the propagation characteristics of the laser generated acoustic shock wave by measuring the arrival time-of-flight with a calibrated microphone and the energy-dependent evolution of acoustic parameters such as peak-topeak pressure, the ratio of the peak-to-peak pressures for the laser induced breakdown in air, the ablated muscle and the bone, and the spectral energy.

Rapid long-wave infrared laser-induced breakdown spectroscopy measurements using a mercury-cadmium-telluride linear array detection system.

Science.gov (United States)

Yang, Clayton S-C; Brown, Eiei; Kumi-Barimah, Eric; Hommerich, Uwe; Jin, Feng; Jia, Yingqing; Trivedi, Sudhir; D'souza, Arvind I; Decuir, Eric A; Wijewarnasuriya, Priyalal S; Samuels, Alan C

2015-11-20

In this work, we develop a mercury-cadmium-telluride linear array detection system that is capable of rapidly capturing (∼1-5  s) a broad spectrum of atomic and molecular laser-induced breakdown spectroscopy (LIBS) emissions in the long-wave infrared (LWIR) region (∼5.6-10  μm). Similar to the conventional UV-Vis LIBS, a broadband emission spectrum of condensed phase samples covering the whole 5.6-10 μm region can be acquired from just a single laser-induced microplasma or averaging a few single laser-induced microplasmas. Atomic and molecular signature emission spectra of solid inorganic and organic tablets and thin liquid films deposited on a rough asphalt surface are observed. This setup is capable of rapidly probing samples "as is" without the need of elaborate sample preparation and also offers the possibility of a simultaneous UV-Vis and LWIR LIBS measurement.

Advanced Sine Wave Modulation of Continuous Wave Laser System for Atmospheric CO2 Differential Absorption Measurements

Science.gov (United States)

Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.

2014-01-01

NASA Langley Research Center in collaboration with ITT Exelis have been experimenting with Continuous Wave (CW) laser absorption spectrometer (LAS) as a means of performing atmospheric CO2 column measurements from space to support the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission.Because range resolving Intensity Modulated (IM) CW lidar techniques presented here rely on matched filter correlations, autocorrelation properties without side lobes or other artifacts are highly desirable since the autocorrelation function is critical for the measurements of lidar return powers, laser path lengths, and CO2 column amounts. In this paper modulation techniques are investigated that improve autocorrelation properties. The modulation techniques investigated in this paper include sine waves modulated by maximum length (ML) sequences in various hardware configurations. A CW lidar system using sine waves modulated by ML pseudo random noise codes is described, which uses a time shifting approach to separate channels and make multiple, simultaneous online/offline differential absorption measurements. Unlike the pure ML sequence, this technique is useful in hardware that is band pass filtered as the IM sine wave carrier shifts the main power band. Both amplitude and Phase Shift Keying (PSK) modulated IM carriers are investigated that exibit perfect autocorrelation properties down to one cycle per code bit. In addition, a method is presented to bandwidth limit the ML sequence based on a Gaussian filter implemented in terms of Jacobi theta functions that does not seriously degrade the resolution or introduce side lobes as a means of reducing aliasing and IM carrier bandwidth.

Laser method of acoustical emission control from vibrating surfaces

Science.gov (United States)

Motyka, Zbigniew

2013-01-01

For limitation of the noise in environment, the necessity occurs of determining and location of sources of sounds emitted from surfaces of many machines and devices, assuring in effect the possibility of suitable constructional changes implementation, targeted at decreasing of their nuisance. In the paper, the results of tests and calculations are presented for plane surface sources emitting acoustic waves. The tests were realized with the use of scanning laser vibrometer which enabled remote registration and the spectral analysis of the surfaces vibrations. The known hybrid digital method developed for determination of sound wave emission from such surfaces divided into small finite elements was slightly modified by distinguishing the phase correlations between such vibrating elements. The final method being developed may find use in wide range of applications for different forms of vibrations of plane surfaces.

Nanoscale Laser Terahertz Emission Microscopy

DEFF Research Database (Denmark)

Klarskov, Pernille; Kim, Hyewon; Colvin, Vicki L.

2017-01-01

Laser terahertz emission microscopy (LTEM) has become a powerful tool for studying ultrafast dynamics and local fields in many different types of materials. This technique, which relies on acceleration of charge carriers in a material upon femtosecond excitation, can provide insight into the phys......Laser terahertz emission microscopy (LTEM) has become a powerful tool for studying ultrafast dynamics and local fields in many different types of materials. This technique, which relies on acceleration of charge carriers in a material upon femtosecond excitation, can provide insight...

A Study on non-contact measurements of laser-generated lamb waves

International Nuclear Information System (INIS)

Jang, Tae Seong; Lee, Jung Ju; Lee, Seung Seok

2002-01-01

Generation and detection of Lamb waves offer an effective non-destructive testing technique that will detect defects quickly and reliably. Lamb waves are generated in a thin plate by Q-switched Nd:YAG pulsed laser. Symmetric and antisymmetric Lamb modes in low-frequency-thickness regime are excited by illuminating a thin plate with an array of laser-generated line sources. The propagation of laser-generated Lamb waves is detected by measuring the out-of-plane displacements in a non-contact manner using the fiber optic Sagnac interferometer and all commercial adaptive reference-beam interferometer. The characteristics of laser-generated Lamb wave due to its frequency are investigated. Fundamental understanding of laser-generated Lamb modes is presented.

Emissions generated during laser cutting; safety precautions; Emissions produits lors du coupage au laser; mesures de securite

Energy Technology Data Exchange (ETDEWEB)

Haferkamp, H.; Goede, M.; Puster, T.; Seebaum, D. [Laser Eentrum, Hanovre (Germany); Bach, F. [Institut fur Werkstoffkunde, Universite de Hanovre (Germany)

1999-07-01

The generation of particulate and gaseous emissions from metals and organic materials during CO{sub 2} and Nd:YAG laser cutting is described. The laser-generated air contaminants (LGAC's) are characterised in terms of their quantity, composition, and chemical complexity, and the emissions are assessed on an occupational medicine basis. The hazard potential of LGAC's are mentioned, and safety systems are discussed.

On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

Energy Technology Data Exchange (ETDEWEB)

Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.; Brumfield, B. E.; Phillips, M. C.; Miloshevsky, G.

2017-06-01

Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during its early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of surrounding ambient: viz. photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early times of its creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission features of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with 6 ns pulse duration are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times while space and time resolved spectroscopy is used for evaluating the emission features as well as for inferring plasma fundaments at on- and off-axis. Structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms and molecules are separated in

Dynamics of Laser-Driven Shock Waves in Solid Targets

Science.gov (United States)

Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J.; Schmitt, A. J.; Obenschain, S. P.; Grun, J.; Metzler, N.; Zalesak, S. T.; Gardner, J. H.; Oh, J.; Harding, E. C.

2009-11-01

Accurate shock timing is a key issue of both indirect- and direct-drive laser fusions. The experiments on the Nike laser at NRL presented here were made possible by improvements in the imaging capability of our monochromatic x-ray diagnostics based on Bragg reflection from spherically curved crystals. Side-on imaging implemented on Nike makes it possible to observe dynamics of the shock wave and ablation front in laser-driven solid targets. We can choose to observe a sequence of 2D images or a continuous time evolution of an image resolved in one spatial dimension. A sequence of 300 ps snapshots taken using vanadium backlighter at 5.2 keV reveals propagation of a shock wave in a solid plastic target. The shape of the shock wave reflects the intensity distribution in the Nike beam. The streak records with continuous time resolution show the x-t trajectory of a laser-driven shock wave in a 10% solid density DVB foam.

Distributed feedback dye laser pumped with copper-vapor laser emission

Energy Technology Data Exchange (ETDEWEB)

Mirza, S Yu; Soldatov, A N; Sukhanov, V B

1983-10-01

The power-spectrum characteristics of the emission of a distributed feedback dye laser pumped with a copper vapor laser have been studied. Laser action has been observed in five dyes over a tuning range of 530-723 nm with an efficiency of 12.4%. The specfic features of the distributed feedback dye laser operating at pulse repetition rates of 4 kHz are discussed.

Toward continuous-wave operation of organic semiconductor lasers

Science.gov (United States)

Sandanayaka, Atula S. D.; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

2017-01-01

The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi–continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture. PMID:28508042

Amplified spontaneous emission and laser emission from a high optical-gain medium of dye-doped dendrimer

International Nuclear Information System (INIS)

Yokoyama, Shiyoshi; Nakahama, Tatsuo; Mashiko, Shinro

2005-01-01

We measured the amplified spontaneous emission and laser emission from high-gain media of laser-dye encapsulated dendrimers. A highly branched poly(amidoamine) (PAMAM-OH) dendrimer formed a guest-host complex with a conventional laser-dye (DCM), resulting in a high optical-gain. Of particular note was the appearance of a laser threshold, above which a super-narrowed laser spectrum was observed, although laser feedback was caused without any mirror cavity devices. The optical feedback was attributed to spatial confinement of the light due to gain guiding under optical excitation. The laser spectrum clearly indicated a resonant laser-mode with a spectrum linewidth of less than 0.1 nm. This order of spectrum narrowing is comparable to that seen in the laser emission from ordinary laser devices

Standoff laser-induced thermal emission of explosives

Science.gov (United States)

Galán-Freyle, Nataly Y.; Pacheco-Londoño, Leonardo C.; Figueroa-Navedo, Amanda; Hernandez-Rivera, Samuel P.

2013-05-01

A laser mediated methodology for remote thermal excitation of analytes followed by standoff IR detection is proposed. The goal of this study was to determine the feasibility of using laser induced thermal emission (LITE) from vibrationally excited explosives residues deposited on surfaces to detect explosives remotely. Telescope based FT-IR spectral measurements were carried out to examine substrates containing trace amounts of threat compounds used in explosive devices. The highly energetic materials (HEM) used were PETN, TATP, RDX, TNT, DNT and ammonium nitrate with concentrations from 5 to 200 μg/cm2. Target substrates of various thicknesses were remotely heated using a high power CO2 laser, and their mid-infrared (MIR) thermally stimulated emission spectra were recorded. The telescope was configured from reflective optical elements in order to minimize emission losses in the MIR frequencies and to provide optimum overall performance. Spectral replicas were acquired at a distance of 4 m with an FT-IR interferometer at 4 cm- 1 resolution and 10 scans. Laser power was varied from 4-36 W at radiation exposure times of 10, 20, 30 and 60 s. CO2 laser powers were adjusted to improve the detection and identification of the HEM samples. The advantages of increasing the thermal emission were easily observed in the results. Signal intensities were proportional to the thickness of the coated surface (a function of the surface concentration), as well as the laser power and laser exposure time. For samples of RDX and PETN, varying the power and time of induction of the laser, the calculated low limit of detections were 2 and 1 μg/cm2, respectively.

Guided-wave tomography imaging plate defects by laser-based ultrasonic techniques

Energy Technology Data Exchange (ETDEWEB)

Park, Jun Pil; Lim, Ju Young; Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Pusan (Korea, Republic of)

2014-12-15

Contact-guided-wave tests are impractical for investigating specimens with limited accessibility and rough surfaces or complex geometric features. A non-contact setup with a laser-ultrasonic transmitter and receiver is quite attractive for guided-wave inspection. In the present work, we developed a non-contact guided-wave tomography technique using the laser-ultrasonic technique in a plate. A method for Lamb-wave generation and detection in an aluminum plate with a pulsed laser-ultrasonic transmitter and Michelson-interferometer receiver was developed. The defect shape and area in the images obtained using laser scanning, showed good agreement with the actual defect. The proposed approach can be used as a non-contact online inspection and monitoring technique.

Analysis of laser ablation: Contribution of ionization energy to the plasma and shock wave properties

International Nuclear Information System (INIS)

Wen, S.-B.; Mao Xianglei; Greif, Ralph; Russo, Richard E.

2007-01-01

By fitting simulation results with experimentally measured trajectories of the shock wave and the vapor/background gas contact surface, we found that inclusion of ionization energy in the analysis leads to a change in the evolution of the pressure, mass density, electron number density, and temperature of the vapor plume. The contribution of ionization energy to both the plasma and shock wave has been neglected in most studies of laser ablation. Compared to previous simulations, the densities, pressures, and temperatures are lower shortly after the laser pulse ( 50 ns). The predicted laser energy conversion ratio also showed about a 20% increase (from 35% to 45%) when the ionization energy is considered. The changes in the evolution of the physical quantities result from the retention of the ionization energy in the vapor plume, which is then gradually transformed to kinetic and thermal energies. When ionization energy is included in the simulation, the vapor plume attains higher expansion speeds and temperatures for a longer time after the laser pulse. The better determination of the temperature history of the vapor plume not only improves the understanding of the expansion process of the laser induced vapor plume but also is important for chemical analysis. The accurate temperature history provides supplementary information which enhances the accuracy of chemical analysis based on spectral emission measurements (e.g., laser induced breakdown spectroscopy)

Crystal growth, spectroscopic characterization, and continuous wave laser operation of Nd3+-doped LiLuF4 crystal

Science.gov (United States)

Zhao, C. C.; Hang, Y.; Zhang, L. H.; He, X. M.; Yin, J. G.; Li, R.; Yu, T.; Chen, W. B.

2011-04-01

Nd3+-doped LiLuF4 single crystal with high optical quality was grown by Czochralski technique. The segregation coefficient of Nd3+ in LiLuF4 crystal was determined by the inductively coupled plasma atomic emission spectrometry method. Polarized absorption and fluorescence spectra were investigated. The peak absorption cross section at 792 nm and peak emission cross section at 1053 nm are 6.94×10-20 and 7.60×10-20 cm2, respectively. With a laser-diode as the pump source, a maximum 6.22 W continuous-wave laser output at 1053 nm has been obtained with a slope efficiency of 37.2% with respect to the pump power.

Probing electron acceleration and x-ray emission in laser-plasma accelerators

International Nuclear Information System (INIS)

Thaury, C.; Ta Phuoc, K.; Corde, S.; Brijesh, P.; Lambert, G.; Malka, V.; Mangles, S. P. D.; Bloom, M. S.; Kneip, S.

2013-01-01

While laser-plasma accelerators have demonstrated a strong potential in the acceleration of electrons up to giga-electronvolt energies, few experimental tools for studying the acceleration physics have been developed. In this paper, we demonstrate a method for probing the acceleration process. A second laser beam, propagating perpendicular to the main beam, is focused on the gas jet few nanosecond before the main beam creates the accelerating plasma wave. This second beam is intense enough to ionize the gas and form a density depletion, which will locally inhibit the acceleration. The position of the density depletion is scanned along the interaction length to probe the electron injection and acceleration, and the betatron X-ray emission. To illustrate the potential of the method, the variation of the injection position with the plasma density is studied

Emission spectrochemical analysis

International Nuclear Information System (INIS)

Rives, R.D.; Bruks, R.R.

1983-01-01

The emission spectrochemical method of analysis based on the fact that atoms of elements can be excited in the electric arc or in the laser beam and will emit radiation with characteristic wave lengths is considered. The review contains the data on spectrochemical analysis, of liquids geological materials, scheme of laser microprobe. The main characteristics of emission spectroscopy, atomic absorption spectroscopy and X-ray fluorescent analysis, are aeneralized

The use of laser-induced shock wave plasma spectroscopy (LISPS) for examining physical characteristics of pharmaceutical products

Energy Technology Data Exchange (ETDEWEB)

Abdulmadjid, Syahrun Nur, E-mail: syahrun-madjid@yahoo.com; Lahna, Kurnia, E-mail: kurnialahna@gmail.com [Department of Physics, Faculty of Mathematics and Natural Sciences, Syiah Kuala University, Darussalam, Banda Aceh 23111, Aceh (Indonesia); Desiyana, Lydia Septa, E-mail: lydia-septa@yahoo.com [Department of Pharmacy, Faculty of Mathematics and Natural Sciences, Syiah Kuala University, Darussalam, Banda Aceh 23111, Aceh (Indonesia)

2016-03-11

An experimental study has been performed to examine the physical characteristics of pharmaceutical products, such as tablet, by employing an emission plasma induced by Nd-YAG laser at a low pressure of Helium gas. The hardness of tablet is one of the parameters that examined during the production process for standard quality of pharmaceutical products. In the Laser-Induced Shock Wave Plasma Spectroscopy (LISPS), the shock wave has a significant role in inducing atomic excitation. It was known that, the speed of the shock wavefront depends on the hardness of the sample, and it correlates with the ionization rate of the ablated atoms. The hardness of the tablet is examined using the intensity ratio between the ion of Mg (II) 275.2 nm and the neutral of Mg (I) 285.2 nm emission lines detected from the laser-induced plasma. It was observed that the ratio changes with respect to the change in the tablet hardness, namely the ratio is higher for the hard tablet. Besides the ratio measurements, we also measured the depth profile of a tablet by focusing 60 shots of irradiation of laser light at a fixed position on the surface of the tablet. It was found that the depth profile varies differently with the hardness of the tablet. These experiment results show that the technique of LISPS can be applied to examine the quality of pharmaceutical products.

The use of laser-induced shock wave plasma spectroscopy (LISPS) for examining physical characteristics of pharmaceutical products

International Nuclear Information System (INIS)

Abdulmadjid, Syahrun Nur; Lahna, Kurnia; Desiyana, Lydia Septa

2016-01-01

An experimental study has been performed to examine the physical characteristics of pharmaceutical products, such as tablet, by employing an emission plasma induced by Nd-YAG laser at a low pressure of Helium gas. The hardness of tablet is one of the parameters that examined during the production process for standard quality of pharmaceutical products. In the Laser-Induced Shock Wave Plasma Spectroscopy (LISPS), the shock wave has a significant role in inducing atomic excitation. It was known that, the speed of the shock wavefront depends on the hardness of the sample, and it correlates with the ionization rate of the ablated atoms. The hardness of the tablet is examined using the intensity ratio between the ion of Mg (II) 275.2 nm and the neutral of Mg (I) 285.2 nm emission lines detected from the laser-induced plasma. It was observed that the ratio changes with respect to the change in the tablet hardness, namely the ratio is higher for the hard tablet. Besides the ratio measurements, we also measured the depth profile of a tablet by focusing 60 shots of irradiation of laser light at a fixed position on the surface of the tablet. It was found that the depth profile varies differently with the hardness of the tablet. These experiment results show that the technique of LISPS can be applied to examine the quality of pharmaceutical products.

Laser-heated emissive plasma probe.

Science.gov (United States)

Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K

2008-08-01

Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808 nm wavelength and an output power up to 50 W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge.

Laser-heated emissive plasma probe

International Nuclear Information System (INIS)

Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K.

2008-01-01

Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808 nm wavelength and an output power up to 50 W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge

Laser-heated emissive plasma probe

Science.gov (United States)

Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K.

2008-08-01

Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808nm wavelength and an output power up to 50W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge.

Optical wave microphone measurement during laser ablation of Si

Energy Technology Data Exchange (ETDEWEB)

Mitsugi, Fumiaki, E-mail: mitsugi@cs.kumamoto-u.ac.jp [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto, 860-8555 (Japan); Ide, Ryota; Ikegami, Tomoaki [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto, 860-8555 (Japan); Nakamiya, Toshiyuki; Sonoda, Yoshito [Graduate School of Industrial Engineering, Tokai University, 9-1-1 Toroku, Kumamoto, 862-8652 (Japan)

2012-10-30

Pulsed laser irradiation is used for surface treatment of a solid and ablation for particle formation in gas, liquid or supercritical phase media. When a pulsed laser is used to irradiate a solid, spatial refractive index variations (including photothermal expansion, shockwaves and particles) occur, which vary depending on the energy density of the pulsed laser. We focused on this phenomenon and applied an unique method for detection of refractive index variation using an optical wave microphone based on Fraunhofer diffraction. In this research, we analyzed the waveforms and frequencies of refractive index variations caused by pulsed laser irradiation of silicon in air and measured with an optical wave microphone.

Fundamental plasma emission involving ion sound waves

International Nuclear Information System (INIS)

Cairns, I.H.

1987-01-01

The theory for fundamental plasma emission by the three-wave processes L ± S → T (where L, S and T denote Langmuir, ion sound and transverse waves, respectively) is developed. Kinematic constraints on the characteristics and growth lengths of waves participating in the wave processes are identified. In addition the rates, path-integrated wave temperatures, and limits on the brightness temperature of the radiation are derived. (author)

Influence of acoustic waves on TEA CO2 laser performance

CSIR Research Space (South Africa)

Von Bergmann, H

2007-01-01

Full Text Available In this paper the author’s present results on the influence of acoustic waves on the output laser beam from high repetition rate TEA CO2 lasers. The authors show that acoustic waves generated inside the cavity lead to deterioration in beam quality...

The effects of Nd2O3 concentration in the laser emission of TeO2-ZnO glasses

Science.gov (United States)

Moreira, L. M.; Anjos, V.; Bell, M. J. V.; Ramos, C. A. R.; Kassab, L. R. P.; Doualan, D. J. L.; Camy, P.; Moncorgé, R.

2016-08-01

The present work reports the modification introduced by different Nd2O3 concentration on optical properties and the laser operation of Nd3+ doped (TeO2-ZnO) bulk tellurite glass. The spectroscopic data are analyzed within the Judd Ofelt formalism framework and the results are compared to the fluorescence lifetime and emission measurements to derive values for the quantum efficiency and the stimulated emission cross section of the considered 4F3/2 → 4I11/2 infrared laser transition around 1062.5 nm. Continuous-wave laser action is achieved with this bulk tellurite glass by pumping the sample inside a standard plan-concave mirror laser cavity with different output couplers. It is possible to observe coherent emission only for the lower concentration (0.5%(wt.) of Nd2 O3). Also laser action could only be observed for this sample with threshold pump power of 73 mW associated with a laser slope efficiency of 8% for an output coupler transmission of 4% indicating that TeO2-ZnO are potential materials for laser action. The results presented in this work together with those previously reported with higher concentration (1.0% (wt) of Nd2O3) determine the adequate Nd2O3 concentration for laser action and guide the correct experimental procedure for TeO2-ZnO glasses preparation.

The study of waves, instabilities, and turbulence using Thomson scattering in laser plasmas

International Nuclear Information System (INIS)

Drake, R.P.

1995-01-01

Much basic work in plasma physics has been devoted to the study of wave properties in plasmas, one of the nonlinear development of driven waves, and of the instabilities in which such waves may participate. The use of laser-plasma techniques has allowed one to extend such studies into new regimes. Such techniques and their results are the subject here. Once one chooses a physical problem within this subject area, it is now possible to design a laser-plasma experiment that is optimized for the study of that problem. The plasma can be designed to have a variety of density and flow-velocity profiles, the damping of ion acoustic waves and of electron plasma waves can be independently controlled, and the waves can be driven weakly or strongly. By using Nd-glass lasers and their harmonics one can non-invasively drive and diagnose the waves, using separate laser beams to produce the plasma, drive the waves, and diagnose their properties. The author uses as examples some recent work with his collaborators, including the first experimental detection of ion plasma waves and the first direct observation of the plasma wave driven by the acoustic decay of laser light

Traveling-wave laser-produced-plasma energy source for photoionization laser pumping and lasers incorporating said

Science.gov (United States)

Sher, Mark H.; Macklin, John J.; Harris, Stephen E.

1989-09-26

A traveling-wave, laser-produced-plasma, energy source used to obtain single-pass gain saturation of a photoionization pumped laser. A cylindrical lens is used to focus a pump laser beam to a long line on a target. Grooves are cut in the target to present a surface near normal to the incident beam and to reduce the area, and hence increase the intensity and efficiency, of plasma formation.

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....

Resolution Enhancement of Scanning Laser Acoustic Microscope Using Transverse Wave

International Nuclear Information System (INIS)

Ko, D. S.; Park, J. S.; Kim, Y. H.

1997-01-01

We studied the resolution enhancement of a novel scanning laser acoustic microscope (SLAM) using transverse waves. Mode conversion of the ultrasonic wave takes place at the liquid-solid interface and some energy of the insonifying longitudinal waves in the water will convert to transverse wave energy within the solid specimen. The resolution of SLAM depends on the size of detecting laser spot and the wavelength of the insonifying ultrasonic waves. Science the wavelength of the transverse wave is shorter than that of the longitudinal wave, we are able to achieve the high resolution by using transverse waves. In order to operate SLAM in the transverse wave mode, we made wedge for changing the incident angle. Our experimental results with model 2140 SLAM and an aluminum specimen showed higher contrast of the SLAM image in the transverse wave mode than that in the longitudinal wave mode

GLINT. Gravitational-wave laser INterferometry triangle

Science.gov (United States)

Aria, Shafa; Azevedo, Rui; Burow, Rick; Cahill, Fiachra; Ducheckova, Lada; Holroyd, Alexa; Huarcaya, Victor; Järvelä, Emilia; Koßagk, Martin; Moeckel, Chris; Rodriguez, Ana; Royer, Fabien; Sypniewski, Richard; Vittori, Edoardo; Yttergren, Madeleine

2017-11-01

When the universe was roughly one billion years old, supermassive black holes (103-106 solar masses) already existed. The occurrence of supermassive black holes on such short time scales are poorly understood in terms of their physical or evolutionary processes. Our current understanding is limited by the lack of observational data due the limits of electromagnetic radiation. Gravitational waves as predicted by the theory of general relativity have provided us with the means to probe deeper into the history of the universe. During the ESA Alpach Summer School of 2015, a group of science and engineering students devised GLINT (Gravitational-wave Laser INterferometry Triangle), a space mission concept capable of measuring gravitational waves emitted by black holes that have formed at the early periods after the big bang. Morespecifically at redshifts of 15 big bang) in the frequency range 0.01 - 1 Hz. GLINT design strain sensitivity of 5× 10^{-24} 1/√ { {Hz}} will theoretically allow the study of early black holes formations as well as merging events and collapses. The laser interferometry, the technology used for measuring gravitational waves, monitors the separation of test masses in free-fall, where a change of separation indicates the passage of a gravitational wave. The test masses will be shielded from disturbing forces in a constellation of three geocentric orbiting satellites.

Emission of a propagation invariant flat-top beam from a microchip laser

Energy Technology Data Exchange (ETDEWEB)

Naidoo, Darryl [Council for Scientific and Industrial Research, National Laser Centre, P.O. Box 395, Pretoria 0001 (South Africa); Harfouche, A. [Faculté de Physique, Université des Sciences et de la Technologie Houari Boumédiène, B.P. no 32, El Alia, 16111 Algiers (Algeria); Fromager, Michael; Ait-Ameur, Kamel [Centre de Recherche sur les Ions, les Matériaux et la Photonique, Unité Mixte de Recherche de Recherche 6252, Commissariat à l’Energie Atomique, Centre National de la Recherche Scientifique, Université de Caen Basse Normandie, Ecole Nationale Supérieure des Ingénieurs de Caen, Boulevard Maréchal Juin, F14050 Caen (France); Forbes, Andrew, E-mail: andrew.forbes@wits.ac.za [School of Physics, University of the Witwatersrand, Private Bag 3, Johannesburg 2050 (South Africa)

2016-02-15

Light beams with a flat-top intensity profile have found many applications in both pure and applied studies, but are not the natural modes of conventional light sources such as lasers. Moreover, such light beams are also not the eigenmodes of the wave equation in a vacuum and so change their intensity profile dramatically during propagation. Here we overcome both these limitations and create a propagation invariant flat-top beam from a microchip laser. By optical feedback into the excited medium we are able to create emission that is an incoherent mix of two spatial modes, a Gaussian and a donut, so that the sum is a flat-top beam that maintains its shape to infinity. Such miniature sources that emit structured light will be attractive for integrated light-based technologies. - Highlights: • First demonstration of the generation of a flat-top beam from a microchip laser. • The flat-top beam is shape-invariant during propagation. • By optical feedback we can select the desired shape from the microchip laser.

Emission of a propagation invariant flat-top beam from a microchip laser

International Nuclear Information System (INIS)

Naidoo, Darryl; Harfouche, A.; Fromager, Michael; Ait-Ameur, Kamel; Forbes, Andrew

2016-01-01

Light beams with a flat-top intensity profile have found many applications in both pure and applied studies, but are not the natural modes of conventional light sources such as lasers. Moreover, such light beams are also not the eigenmodes of the wave equation in a vacuum and so change their intensity profile dramatically during propagation. Here we overcome both these limitations and create a propagation invariant flat-top beam from a microchip laser. By optical feedback into the excited medium we are able to create emission that is an incoherent mix of two spatial modes, a Gaussian and a donut, so that the sum is a flat-top beam that maintains its shape to infinity. Such miniature sources that emit structured light will be attractive for integrated light-based technologies. - Highlights: • First demonstration of the generation of a flat-top beam from a microchip laser. • The flat-top beam is shape-invariant during propagation. • By optical feedback we can select the desired shape from the microchip laser.

Guided-wave tomographic imaging of plate defects by laser-based ultrasonic techniques

Energy Technology Data Exchange (ETDEWEB)

Park, Junpil; Lim, Ju Young; Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of)

2016-12-15

Contact-guided-wave tests are impractical for investigating specimens with limited accessibility and rough surfaces or complex geometric features. A non-contact setup with a laser-ultrasonic transmitter and receiver is quite attractive for guided-wave inspection. In the present work, we developed a non-contact guided-wave tomography technique using the laser-ultrasonic technique in a plate. A method for Lamb-wave generation and detection in an aluminum plate with a pulsed laser-ultrasonic transmitter and Michelson-interferometer receiver was developed. The defect shape and area in the images obtained using laser scanning, showed good agreement with the actual defect. The proposed approach can be used as a non-contact online inspection and monitoring technique.

Theory of spin and lattice wave dynamics excited by focused laser pulses

Science.gov (United States)

Shen, Ka; Bauer, Gerrit E. W.

2018-06-01

We develop a theory of spin wave dynamics excited by ultrafast focused laser pulses in a magnetic film. We take into account both the volume and surface spin wave modes in the presence of applied, dipolar and magnetic anisotropy fields and include the dependence on laser spot exposure size and magnetic damping. We show that the sound waves generated by local heating by an ultrafast focused laser pulse can excite a wide spectrum of spin waves (on top of a dominant magnon–phonon contribution). Good agreement with recent experiments supports the validity of the model.

Stabilized High Power Laser for Advanced Gravitational Wave Detectors

International Nuclear Information System (INIS)

Willke, B; Danzmann, K; Fallnich, C; Frede, M; Heurs, M; King, P; Kracht, D; Kwee, P; Savage, R; Seifert, F; Wilhelm, R

2006-01-01

Second generation gravitational wave detectors require high power lasers with several 100W of output power and with very low temporal and spatial fluctuations. In this paper we discuss possible setups to achieve high laser power and describe a 200W prestabilized laser system (PSL). The PSL noise requirements for advanced gravitational wave detectors will be discussed in general and the stabilization scheme proposed for the Advanced LIGO PSL will be described. Special emphasis will be given to the most demanding power stabilization requirements and new results (RIN ≤ 4x10 -9 /√Hz) will be presented

Cw hyper-Raman laser and four-wave mixing in atomic sodium

Science.gov (United States)

Klug, M.; Kablukov, S. I.; Wellegehausen, B.

2005-01-01

Continuous wave hyper-Raman (HR) generation in a ring cavity on the 6s → 4p transition at 1640 nm in sodium is realized for the first time by two-photon excitation of atomic sodium on the 3s → 6s transition with a continuous wave (cw) dye laser at 590 nm and a single frequency argon ion laser at 514 nm. It is shown, that the direction and efficiency of HR lasing depends on the propagation direction of the pump waves and their frequencies. More than 30% HR gain is measured at 250 mW of pump laser powers for counter-propagating pump waves and a medium length of 90 mm. For much shorter interaction lengths and corresponding focussing of the pump waves a dramatic increase of the gain is predicted. For co-propagating pump waves, in addition, generation of 330 nm radiation on the 4p → 3s transition by a four-wave mixing (FWM) process is observed. Dependencies of HR and parametric four-wave generation have been investigated and will be discussed.

Development of SMM wave laser scattering apparatus for the measurements of waves and turbulences in the tokamak plasma

International Nuclear Information System (INIS)

Saito, T.; Hamada, Y.; Yamashita, T.; Ikeda, M.; Nakamura, M.

1980-01-01

The SMM wave laser scattering apparatus has been developed for the measurement of the waves and turbulences in the plasma. This apparatus will help greatly to clarify the physics of RF heating of the tokamak plasma. The present status of main parts of the apparatus, the SMM wave laser and the Schottky barrier diode mixer for the heterodyne receiver, are described. (author)

Optical wave microphone measurements of laser ablation of copper in supercritical carbon dioxide

Energy Technology Data Exchange (ETDEWEB)

Mitsugi, Fumiaki, E-mail: mitsugi@cs.kumamoto-u.ac.jp [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Ikegami, Tomoaki [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Nakamiya, Toshiyuki; Sonoda, Yoshito [Graduate School of Industrial Engineering, Tokai University, 9-1-1 Toroku, Kumamoto 862-8652 (Japan)

2013-11-29

Laser ablation plasma in a supercritical fluid has attracted much attention recently due to its usefulness in forming nanoparticles. Observation of the dynamic behavior of the supercritical fluid after laser irradiation of a solid is necessary for real-time monitoring and control of laser ablation. In this study, we utilized an optical wave microphone to monitor pulsed laser irradiation of a solid in a supercritical fluid. The optical wave microphone works based on Fraunhofer diffraction of phase modulation of light by changes in refractive index. We hereby report on our measurements for pulsed laser irradiation of a Cu target in supercritical carbon dioxide using an optical wave microphone. Photothermal acoustic waves which generated after single pulsed laser irradiation of a Cu target were detectable in supercritical carbon dioxide. The speed of sound around the critical point of supercritical carbon dioxide was clearly slower than that in gas. The optical wave microphone detected a signal during laser ablation of Cu in supercritical carbon dioxide that was caused by shockwave degeneration. - Highlights: • Photothermal acoustic wave in supercritical fluid was observed. • Sound speed around the critical point was slower than that in gas. • Optical wave microphone detected degeneration of a shockwave. • Ablation threshold of a solid in supercritical fluid can be estimated. • Generation of the second shockwave in supercritical phase was suggested.

Emission spectrum of an electric-discharge ClF laser

International Nuclear Information System (INIS)

Deryugin, A A; Razhev, A M; Kochetov, Igor' V

1998-01-01

Experiments revealed a complex structure of the emission spectrum of an electric-discharge ClF laser, corresponding to the D'-A' transitions with a maximum near 285 nm. The vibrational bands in the emission spectrum overlapped at the base in the range 282-286 nm because of a high pressure in the gaseous active medium. Theoretical calculations were made and an interpretation was provided of the vibrational structure of the emission spectrum of the ClF molecules. The emission spectrum of the electric-discharge ClF laser was shown to consist of the 0-4, 0-5, 0-6, 1-6, 1-7, and 2-8 bands of the D'-A' transition. A total efficiency of 0.1% was achieved for the first time for the ClF laser and lasing was observed in a gaseous He - F 2 -BCl 3 active medium. (lasers, active media)

Prospects for ion temperature measurements in JET by Thomson scattering of submillimetre waves

International Nuclear Information System (INIS)

Whitbourn, L.B.

1975-03-01

The Thomson scattering of submillimeter waves is envisaged as a possible means for measuring the ion temperature of the JET plasma. The present discussion is principally concerned with the practical limitations imposed to the method by the availability of high power pulsed sources and sensitive detectors and noise due to plasma emission at submillimeter wavelengths (bremsstrahlung and electron cyclotron emission). Coherent scattering from plasma wave (e.g. ion acoustic waves and electron drift waves) with millimeter and submillimeter waves are considered briefly. Further suitable development of lasers and heterodyne detectors would make such measurements possible. A pulsed HCN laser associated with a detectors with a lower heterodyne noise equivalent power could then be used to advantage. For scattering with CH 3 F laser the NEP of a Josephson junction would be adequate because a relatively high level of plasma emission is expected at 496 μm [fr

Diode-pumped continuous-wave Nd:Gd3Ga5O12 lasers at 1406, 1415 and 1423 nm

Science.gov (United States)

Lin, Haifeng; Zhu, Wenzhang; Xiong, Feibing; Ruan, Jianjian

2018-05-01

We report a diode-pumped continuous-wave Nd:Gd3Ga5O12 (GGG) laser operating at 1.4 μm spectral region. A dual-wavelength laser at 1423 and 1406 nm is achieved with output power of about 2.59 W at absorbed pump power of 13.4 W. Further increasing the pump power, simultaneous tri-wavelength laser at 1423, 1415 and 1406 nm is also obtained with a maximum output power of 3.96 W at absorbed pump power of 18.9 W. Single-wavelength lasing is also realized at the three emission lines using an intracavity etalon. The laser result is believed to be the highest output power achieved in Nd:GGG crystal, at present, to the best of our knowledge.

Laser amplitude stabilization for advanced interferometric gravitational wave detectors

International Nuclear Information System (INIS)

Barr, B W; Strain, K A; Killow, C J

2005-01-01

We present results of experiments into the stabilization of the amplitude of Nd:YAG lasers for use in advanced gravitational wave detectors. By feeding back directly to the pump-diode driving current we achieved shot-noise-limited stabilization at frequencies up to several kHz with some residual noise at lower frequencies (sub ∼100 Hz). The method used is applicable to higher powered laser systems planned for advanced interferometric gravitational wave detectors

On the fast gas ionization wave in an intense laser beam

International Nuclear Information System (INIS)

Fisher, V.I.

1980-01-01

The transfer of the adsorption zone of laser radiation along a beam is considered. It is shown that for a sufficiently strong laser beam intensity, q 0 >q tilde, the conditions of wave propagation differ principally from those known previously. In particular, the plasma temperature behind the wave front Tsup(*) decreases with the increase of q 0 , whereas the wave velocity D(q 0 ) grows faster than a linear function. The structure and laws of propagation of the ionization wave are determined

Optical emission from laser-produced chromium and magnesium

Indian Academy of Sciences (India)

Optical emission from laser-produced chromium and magnesium plasma under the effect of two sequential laser pulses ... Laser Plasma Division, Centre for Advanced Technology, Indore 452 013, India; Diagnostic Instrumentation and Analysis Laboratory, Mississippi State University, 205 Research Boulevard, Starkville, ...

Risks induced by laser radiation; Risques induits par le rayonnement laser

Energy Technology Data Exchange (ETDEWEB)

Courant, D [CEA Fontenay-aux-Roses, 92 (France). Dept. de Radiobiologie et de Radiopathologie

2001-07-01

The use of lasers is often dangerous because of the emitted power, the wave length, the conduction system(optical fiber, wave guide, mirrors) and the use conditions. The safety notion involves the precise knowledge of materials, the biological effects in function of laser emission parameters, the knowledge of protection standards, the observance of use rules and the personnel training. This chapter treats the risks induced by the beam. It gives the different biological effects induced by the laser beam, at the eye and skin levels that are at the origin of exposure limits and the lasers classification recommended by the protection standards. (N.C.)

Wireless guided wave and impedance measurement using laser and piezoelectric transducers

International Nuclear Information System (INIS)

Park, Hyun-Jun; Sohn, Hoon; Yun, Chung-Bang; Chung, Joseph; Lee, Michael M S

2012-01-01

Guided-wave- and impedance-based structural health monitoring (SHM) techniques have gained much attention due to their high sensitivity to small defects. One of the popular devices commonly used for guided wave and impedance measurements is a lead zirconate titanate (PZT) transducer. This study proposes a new wireless scheme where the power and data required for PZT excitation and sensing are transmitted via laser. First, a modulated laser beam is wirelessly transmitted to the photodiode connected to a PZT on a structure. Then, the photodiode converts the laser light into an electric signal, and it is applied to the PZT for excitation. The corresponding responses, impedance at the same PZT or guided waves at another PZT, are measured, re-converted into laser light, and wirelessly transmitted back to the other photodiode located in the data interrogator for signal processing. The feasibility of the proposed wireless guided wave and impedance measurement schemes has been examined through circuit analyses and experimentally investigated in a laboratory setup. (paper)

Laser-supported ionization wave in under-dense gases and foams

International Nuclear Information System (INIS)

Gus'kov, S. Yu.; Limpouch, J.; Nicolaie, Ph.; Tikhonchuk, V. T.

2011-01-01

Propagation of laser-supported ionization wave in homogeneous and porous materials with a mean density less than the critical plasma density is studied theoretically in the one-dimensional geometry. It is shown that the velocity of the ionization wave in a foam is significantly decreased in comparison with the similar wave in a homogeneous fully ionized plasma of the same density. That difference is attributed to the ionization and hydro-homogenization processes forming an under-critical density environment in the front of ionization wave. The rate of energy transfer from laser to plasma is found to be in a good agreement with available experimental data.

Amplified spontaneous emission in solar-pumped iodine laser

Science.gov (United States)

Cho, Yong S.; Hwang, In H.; Han, Kwang S.; Lee, Ja H.

1992-01-01

The amplified spontaneous emission (ASE) from a long pulse, solar-simulating radiation pumped iodine laser amplifier is studied. The ASE threshold pump intensity is almost proportional to the inverse of the laser gain length when the gas pressure is constant in the laser tube.

Highly efficient single-pass frequency doubling of a continuous-wave distributed feedback laser diode using a PPLN waveguide crystal at 488 nm.

Science.gov (United States)

Jechow, Andreas; Schedel, Marco; Stry, Sandra; Sacher, Joachim; Menzel, Ralf

2007-10-15

A continuous-wave distributed feedback diode laser emitting at 976 nm was frequency doubled by the use of a periodically poled lithium niobate waveguide crystal with a channel size of 3 microm x 5 microm and an interaction length of 10 mm. A laser to waveguide coupling efficiency of 75% could be achieved resulting in 304 mW of incident infrared light inside the waveguide. Blue laser light emission of 159 mW at 488 nm has been generated, which equals to a conversion efficiency of 52%. The resulting wall plug efficiency was 7.4%.

THE FEATURES OF LASER EMISSION ENERGY DISTRIBUTION AT MATHEMATIC MODELING OF WORKING PROCESS

Directory of Open Access Journals (Sweden)

A. M. Avsiyevich

2013-01-01

Full Text Available The space laser emission energy distribution of different continuous operation settings depends from many factors, first on the settings design. For more accurate describing of multimode laser emission energy distribution intensity the experimental and theoretic model, which based on experimental laser emission distribution shift presentation with given accuracy rating in superposition basic function form, is proposed. This model provides the approximation error only 2,2 percent as compared with 24,6 % and 61 % for uniform and Gauss approximation accordingly. The proposed model usage lets more accurate take into consideration the laser emission and working surface interaction peculiarity, increases temperature fields calculation accuracy for mathematic modeling of laser treatment processes. The method of experimental laser emission energy distribution studying for given source and mathematic apparatus for calculation of laser emission energy distribution intensity parameters depended from the distance in radial direction on surface heating zone are shown.

Relativistic reversal of the ponderomotive force in a standing laser wave

International Nuclear Information System (INIS)

Pokrovsky, A.L.; Kaplan, A.E.

2005-01-01

Effect of relativistic reversal of the ponderomotive force (PF), reported earlier for a collinear configuration of electron and laser standing wave [A. E. Kaplan and A. L. Pokrovsky, Phys. Rev. Lett., 95, 053601 (2005)], is studied here theoretically for various types of polarizations of the laser beam. We demonstrated that the collinear configuration, in which the laser wave is linearly polarized with electric field E-vector parallel to the initial electron momentum p-vector 0 , is the optimal configuration for the relativistic reversal. In that case, the transverse PF reverses its direction when the incident momentum is p 0 =mc. The reversal effect vanishes in the cases of circular and linear with E-vector perpendicular p-vector 0 polarizations. We have discovered, however, that the counter-rotating circularly polarized standing waves develop attraction and repulsion areas along the axis of laser, in the laser field whose intensity is homogeneous in that axis, i.e., has no field gradient

Applications of nanosecond, kilojoule lasers to the basic physics of waves in plasmas

International Nuclear Information System (INIS)

Drake, R.P.

1992-01-01

Plasmas can sustain many normal modes of oscillation (waves), including both electromagnetic and electrostatic modes. These waves can interact by a wide variety of linear and nonlinear mechanisms, including mode coupling, mixing, and instabilities. Furthermore, such mechanisms compete, so that a given wave might be absorbed, might mode convert, or might decay by one of several instabilities, depending upon the specific circumstances in which it is produced. Moreover, such waves are important in many applications, including for example laser fusion, x-ray lasers, plasma accelerators, and ionospheric heating. Laser-produced plasmas can provide an effective medium for the studies of such waves and the related mechanisms. New opportunities will be made possible by the advent of comparatively inexpensive nanosecond, kilojoule lasers. One can now contemplate affordable experiments, not limited by programmatic constraints, that could study such the basic physics of the waves in such plasmas with unprecedented precision and in unprecedented detail

Unlimited electron acceleration in laser-driven plasma waves

International Nuclear Information System (INIS)

Katsouleas, T.; Dawson, J.M.

1983-01-01

It is shown that the limitation to the energy gain of 2(ω/ω/sub p/) 2 mc 2 of an electron in the laser-plasma beat-wave accelerator can be overcome by imposing a magnetic field of appropriate strength perpendicular to the plasma wave. This accelerates particles parallel to the phase fronts of the accelerating wave which keeps them in phase with it. Arbitrarily large energy is theoretically possible

Crystal growth, optical properties, and continuous-wave laser operation of Nd3+-doped Lu2SiO5 crystal

International Nuclear Information System (INIS)

Li, D Z; Xu, X D; Zhou, D H; Xia, C T; Wu, F; Xu, J; Cong, Z H; Zhang, J; Tang, D Y

2011-01-01

High quality Nd 3+ -doped Lu 2 SiO 5 (Nd:LSO) crystal has been grown by the Czochralski technique. The cell parameters were analyzed with X-ray diffraction (XRD). Room temperature absorption and fluorescence spectra and fluorescence lifetime of the Nd:LSO crystal were measured and analyzed. The Judd-Ofelt intensity parameters Ω 2,4,6 were obtained to be 2.59, 4.90, and 5.96×10 -20 cm 2 , respectively. The absorption and emission cross sections and the branching ratios were calculated. The peak emission cross section is 5.8 and 6.6×10 -20 cm 2 at 1075 and 1079 nm, respectively, with full width at half maximum (FWHM) of 2.8 and 5.1 nm in turn. Pumped by a laser diode, a maximum 2.54 W continuous-wave laser output has been obtained with a slope efficiency of 32%. All the results show that this crystal is a promising laser material

Crystal growth, optical properties, and continuous-wave laser operation of Nd3+-doped Lu2SiO5 crystal

Science.gov (United States)

Li, D. Z.; Xu, X. D.; Zhou, D. H.; Xia, C. T.; Wu, F.; Xu, J.; Cong, Z. H.; Zhang, J.; Tang, D. Y.

2011-01-01

High quality Nd3+-doped Lu2SiO5 (Nd:LSO) crystal has been grown by the Czochralski technique. The cell parameters were analyzed with X-ray diffraction (XRD). Room temperature absorption and fluorescence spectra and fluorescence lifetime of the Nd:LSO crystal were measured and analyzed. The Judd-Ofelt intensity parameters Ω2,4,6 were obtained to be 2.59, 4.90, and 5.96×10-20 cm2, respectively. The absorption and emission cross sections and the branching ratios were calculated. The peak emission cross section is 5.8 and 6.6×10-20 cm2 at 1075 and 1079 nm, respectively, with full width at half maximum (FWHM) of 2.8 and 5.1 nm in turn. Pumped by a laser diode, a maximum 2.54 W continuous-wave laser output has been obtained with a slope efficiency of 32%. All the results show that this crystal is a promising laser material.

Coherent control of atto-second emission from aligned molecules

Energy Technology Data Exchange (ETDEWEB)

Boutu, W; Haessler, S; Merdji, H; Breger, P; Monchicourt, P; Carre, B; Salieres, P [CEA Saclay, DSM, Serv Photons Atomes Mol, F-91191 Gif Sur Yvette, (France); Waters, G [Univ Reading, JJ Thomson Phys Lab, Reading RG6 6AF, Berks, (United Kingdom); Stankiewicz, M [Jagiellonian Univ, Inst Phys, PL-30059 Krakow, (Poland); Frasinski, L J [Univ London Imperial Coll Sci Technol and Med, Blackett Lab, London SW7 2BW, (United Kingdom); Taieb, R; Caillat, J; Maquet, A [Univ Paris 06, UMR 7614, Lab Chim Phys Matiere Rayonnement, F-75231 Paris 05, (France); Taieb, R; Caillat, J; Maquet, A [LCPMR, UMR 7614, CNRS, F-75005 Paris, (France)

2008-07-01

Controlling atto-second electron wave packets and soft X-ray pulses represents a formidable challenge of general implication to many areas of science. A strong laser field interacting with atoms or molecules drives ultrafast intra-atomic/molecular electron wave packets on a sub femtosecond timescale, resulting in the emission of atto-second bursts of extreme-ultraviolet light. Controlling the intra-atomic/molecular electron dynamics enables steering of the atto-second emission. Here, we carry out a coherent control in linear molecules, where the interaction of the laser-driven electron wave packet with the core leads to quantum interferences. We demonstrate that these interferences can be finely controlled by turning the molecular axis relative to the laser polarization, that is, changing the electron re-collision angle. The wave-packet coulombic distortion modifies the spectral phase jump measured in the extreme-ultraviolet emission. Our atto-second control of the interference results in atto-second pulse shaping, useful for future applications in ultrafast coherent control of atomic and molecular processes. (authors)

Laser-driven shock-wave propagation in pure and layered targets

International Nuclear Information System (INIS)

Salzmann, D.; Eliezer, S.; Krumbein, A.D.; Gitter, L.

1983-01-01

The propagation properties of laser-driven shock waves in pure and layered polyethylene and aluminum slab targets are studied for a set of laser intensities and pulse widths. The laser-plasma simulations were carried out by means of our one-dimensional Lagrangian hydrodynamic code. It is shown that the various parts of a laser-driven compression wave undergo different thermodynamic trajectories: The shock front portion is on the Hugoniot curve whereas the rear part is closer to an adiabat. It is found that the shock front is accelerated into the cold material till troughly-equal0.8tau (where tau is the laser pulse width) and only later is a constant velocity propagation attained. The scaling laws obtained for the pressure and temperature of the compression wave in pure targets are in good agreement with those published in other works. In layered targets, high compression and pressure were found to occur at the interface of CH 2 on Al targets due to impedance mismatch but were not found when the layers were reversed. The persistence time of the high pressure on the interface in the CH 2 on Al case is long enough relative to the characteristic times of the plasma to have an appreciable influence on the shock-wave propagation into the aluminum layer. This high pressure and compression on the interface can be optimized by adjusting the CH 2 layer thickness

Continuous-wave laser operation at 743 and 753 nm based on a diode-pumped c-cut Pr:YAlO3 crystal

Science.gov (United States)

Lin, Xiuji; Huang, Xiaoxu; Liu, Bin; Xu, Bin; Xu, Huiying; Cai, Zhiping; Xu, Xiaodong; Li, Dongzhen; Liu, Jian; Xu, Jun

2018-02-01

We report on blue-diode-pumped continuous-wave Pr:YAlO3 (YAP) crystal lasers. Using a b-cut sample, a maximum output power of 181 mW is achieved at ∼747 nm with slope efficiency of 12.7% with respect to the absorbed power. Using a c-cut sample, a dual-wavelength laser at ∼743 and ∼753 nm is obtained with a total maximum output power of 72 mW by using the blue diode pumping, for the first time to our knowledge. These laser emissions are all linearly polarized and M2 factors of these output laser beams are also measured. YAP is experimentally verified to be one of effective oxide hosts for Pr-doped visible laser operation besides its fluoride counterparts.

Ion temperature via laser scattering on ion Bernstein waves

International Nuclear Information System (INIS)

Wurden, G.A.; Ono, M.; Wong, K.L.

1981-10-01

Hydrogen ion temperature has been measured in a warm toroidal plasma with externally launched ion Bernstein waves detected by heterodyne CO 2 laser scattering. Radial scanning of the laser beam allows precise determination of k/sub perpendicular to/ for the finite ion Larmor radius wave (ω approx. less than or equal to 2Ω/sub i/). Knowledge of the magnetic field strength and ion concentration then give a radially resolved ion temperature from the dispersion relation. Probe measurements and Doppler broadening of ArII 4806A give excellent agreement

Late-time particle emission from laser-produced graphite plasma

Energy Technology Data Exchange (ETDEWEB)

Harilal, S. S.; Hassanein, A.; Polek, M. [School of Nuclear Engineering, Center for Materials Under Extreme Environment, Purdue University, West Lafayette, Indiana 47907 (United States)

2011-09-01

We report a late-time ''fireworks-like'' particle emission from laser-produced graphite plasma during its evolution. Plasmas were produced using graphite targets excited with 1064 nm Nd: yttrium aluminum garnet (YAG) laser in vacuum. The time evolution of graphite plasma was investigated using fast gated imaging and visible emission spectroscopy. The emission dynamics of plasma is rapidly changing with time and the delayed firework-like emission from the graphite target followed a black-body curve. Our studies indicated that such firework-like emission is strongly depended on target material properties and explained due to material spallation caused by overheating the trapped gases through thermal diffusion along the layer structures of graphite.

Late-time particle emission from laser-produced graphite plasma

International Nuclear Information System (INIS)

Harilal, S. S.; Hassanein, A.; Polek, M.

2011-01-01

We report a late-time ''fireworks-like'' particle emission from laser-produced graphite plasma during its evolution. Plasmas were produced using graphite targets excited with 1064 nm Nd: yttrium aluminum garnet (YAG) laser in vacuum. The time evolution of graphite plasma was investigated using fast gated imaging and visible emission spectroscopy. The emission dynamics of plasma is rapidly changing with time and the delayed firework-like emission from the graphite target followed a black-body curve. Our studies indicated that such firework-like emission is strongly depended on target material properties and explained due to material spallation caused by overheating the trapped gases through thermal diffusion along the layer structures of graphite.

Research of the elastic waves generated by a pulse laser. Excitation mechanism of elastic waves and application to nondestructive testing; Pulse laser de reikishita danseiha ni kansuru kenkyu. Danseiha reiki no mechanism to hihakai kensa eno oyo

Energy Technology Data Exchange (ETDEWEB)

Cho, H.; Takemoto, M. [Aoyama Gakuin University, Tokyo (Japan). College of Science and Engineering

1994-07-20

A bulk wave is generated when a pulse laser is irradiated to the material, and the characteristics of a Young`s modulus and Poisson`s ratio can be nondestructively estimated from the bulk wave. The generation mechanism of laser ultrasonic waves must be first clarified for such application. In this paper, fundamental research was conducted to study the generation mechanism of the elastic waves excited by a Q-switched Nd-YAG laser, and the generation method and characteristics of Rayleigh waves. The following result was obtained. A bulk wave is generated by the disk-like adiabatic expansion near the surface if the laser power is small when a spot-shape pulse laser was irradiated. A bulk wave is generated by the thin disk-like adiabatic expansion beneath the surface due to the thermal diffusion in the depth direction of a base material when the laser power becomes large. Moreover, a bulk wave is generated by the impact force due to abrasion and plasma when the power becomes still larger. The information on the bulk wave characteristics and Rayleigh wave was also obtained. 25 refs., 15 figs., 1 tab.

Diode-pumped continuous-wave blue laser operation of Nd:GGG at 467.0, 467.7, and 468.5 nm

International Nuclear Information System (INIS)

Xu, B; Camy, P; Doualan, J L; Braud, A; Moncorgé, R; Cai, Z P; Brenier, A

2012-01-01

Intra-cavity frequency doubling of continuous-wave (CW) laser emission on the quasi-three level ( 4 F 3/2 → 4 I 9/2 ) laser transition of Nd 3+ in Nd:GGG is reported by using a three-mirror folded resonator. The thermal lens experienced by the optically-pumped Nd:GGG laser crystal is measured as a function of the absorbed pump power and compared to that found, in the same conditions, in the case of Nd:YAG. Results are interpreted by using a simple model accounting for the absorbed pump power and the thermo-mechanical properties of each laser crystal. Diode-pumped blue laser operation is achieved, for the first time, at 467.0 and 468.5 nm with output powers of 230 and 450 mW, respectively. Simultaneous laser operation resulting both from frequency-doubling and frequency summing at the three 467.1, 467.7, and 468.1 nm laser wavelengths is also obtained with a total output power of 60 mW

Effect of laser beam filamentation on plasma wave localization and stimulated Raman scattering

International Nuclear Information System (INIS)

Purohit, Gunjan; Sharma, R. P.

2013-01-01

This paper presents the effect of laser beam filamentation on the localization of electron plasma wave (EPW) and stimulated Raman scattering (SRS) in unmagnitized plasma when both relativistic and ponderomotive nonlinearities are operative. The filamentary dynamics of laser beam is studied and the splitted profile of the laser beam is obtained due to uneven focusing of the off-axial rays. The localization of electron plasma wave takes place due to nonlinear coupling between the laser beam and EPW. Stimulated Raman scattering of this EPW is studied and backreflectivity has been calculated. The localization of EPW also affects the eigenfrequency and damping of plasma wave; consequently, mismatch and modified enhanced Landau damping lead to the disruption of SRS process and a substantial reduction in the backreflectivity. The new enhanced damping of the plasma wave has been calculated and it is found that the SRS process gets suppressed due to the localization of plasma wave in laser beam filamentary structures. For typical laser beam and plasma parameters with wavelength λ (=1064 nm), power flux (=10 16 W/cm 2 ) and plasma density (n/n cr ) = 0.2; the SRS back reflectivity is found to be suppressed by a factor of around 5%. (author)

Shock wave generation in laser ablation studied using pulsed digital holographic interferometry

Energy Technology Data Exchange (ETDEWEB)

Amer, Eynas; Gren, Per; Sjoedahl, Mikael [Division of Experimental Mechanics, Luleaa University of Technology, SE-971 87 Luleaa (Sweden)], E-mail: eynas.amer@ltu.se, E-mail: per.gren@ltu.se, E-mail: mikael.sjodahl@ltu.se

2008-11-07

Pulsed digital holographic interferometry has been used to study the shock wave induced by a Q-switched Nd-YAG laser ({lambda} = 1064 nm and pulse duration 12 ns) on a polycrystalline boron nitride (PCBN) ceramic target under atmospheric air pressure. A special setup based on using two synchronized wavelengths from the same laser for processing and measurement simultaneously has been introduced. Collimated laser light ({lambda} = 532 nm) passed through the volume along the target and digital holograms were recorded for different time delays after processing starts. Numerical data of the integrated refractive index field were calculated and presented as phase maps showing the propagation of the shock wave generated by the process. The location of the induced shock wave front was observed for different focusing and time delays. The amount of released energy, i.e. the part of the incident energy of the laser pulse that is eventually converted to a shock wave has been estimated using the point explosion model. The released energy is normalized by the incident laser pulse energy and the energy conversion efficiency between the laser pulse and PCBN target has been calculated at different power densities. The results show that the energy conversion efficiency seems to be constant around 80% at high power densities.

NONLINEAR WAVE INTERACTIONS AS EMISSION PROCESS OF TYPE II RADIO BURSTS

Energy Technology Data Exchange (ETDEWEB)

Ganse, Urs; Kilian, Patrick; Spanier, Felix [Lehrstuhl fuer Astronomie, Universitaet Wuerzburg, Wuerzburg (Germany); Vainio, Rami, E-mail: uganse@astro.uni-wuerzburg.de [Department of Physics, University of Helsinki, Helsinki (Finland)

2012-06-01

The emission of fundamental and harmonic frequency radio waves of type II radio bursts are assumed to be products of three-wave interaction processes of beam-excited Langmuir waves. Using a particle-in-cell code, we have performed simulations of the assumed emission region, a coronal mass ejection foreshock with two counterstreaming electron beams. Analysis of wavemodes within the simulation shows self-consistent excitation of beam-driven modes, which yield interaction products at both fundamental and harmonic emission frequencies. Through variation of the beam strength, we have investigated the dependence of energy transfer into electrostatic and electromagnetic modes, confirming the quadratic dependence of electromagnetic emission on electron beam strength.

NONLINEAR WAVE INTERACTIONS AS EMISSION PROCESS OF TYPE II RADIO BURSTS

International Nuclear Information System (INIS)

Ganse, Urs; Kilian, Patrick; Spanier, Felix; Vainio, Rami

2012-01-01

The emission of fundamental and harmonic frequency radio waves of type II radio bursts are assumed to be products of three-wave interaction processes of beam-excited Langmuir waves. Using a particle-in-cell code, we have performed simulations of the assumed emission region, a coronal mass ejection foreshock with two counterstreaming electron beams. Analysis of wavemodes within the simulation shows self-consistent excitation of beam-driven modes, which yield interaction products at both fundamental and harmonic emission frequencies. Through variation of the beam strength, we have investigated the dependence of energy transfer into electrostatic and electromagnetic modes, confirming the quadratic dependence of electromagnetic emission on electron beam strength.

Electron emission from a double-layer metal under femtosecond laser irradiation

Energy Technology Data Exchange (ETDEWEB)

Li, Shuchang; Li, Suyu; Jiang, Yuanfei; Chen, Anmin, E-mail: amchen@jlu.edu.cn; Ding, Dajun; Jin, Mingxing, E-mail: mxjin@jlu.edu.cn

2015-01-01

In this paper we theoretically investigate electron emission during femtosecond laser ablation of single-layer metal (copper) and double-layer structures. The double-layer structure is composed of a surface layer (copper) and a substrate layer (gold or chromium). The calculated results indicate that the double-layer structure brings a change to the electron emission from the copper surface. Compared with the ablation of a single-layer, a double-layer structure may be helpful to decrease the relaxation time of the electron temperature, and optimize the electron emission by diminishing the tailing phenomenon under the same absorbed laser fluence. With the increase of the absorbed laser fluence, the effect of optimization becomes significant. This study provides a way to optimize the electron emission which can be beneficial to generate laser induced ultrafast electron pulse sources.

Controlling of the electromagnetic solitary waves generation in the wake of a two-color laser

Science.gov (United States)

Pan, K. Q.; Li, S. W.; Guo, L.; Yang, D.; Li, Z. C.; Zheng, C. Y.; Jiang, S. E.; Zhang, B. H.; He, X. T.

2018-05-01

Electromagnetic solitary waves generated by a two-color laser interaction with an underdense plasma are investigated. It is shown that, when the former wave packet of the two-color laser is intense enough, it will excite nonlinear wakefields and generate electron density cavities. The latter wave packets will beat with the nonlinear wakefield and generate both high-frequency and low-frequency components. When the peak density of the cavities exceeds the critical density of the low-frequency component, this part of the electromagnetic field will be trapped to generate electromagnetic solitary waves. By changing the laser and plasma parameters, we can control the wakefield generation, which will also control the generation of the solitary waves. One-dimensional particle-in-cell simulations are performed to prove the controlling of the solitary waves. The simulation results also show that solitary waves generated by higher laser intensities will become moving solitary waves. The two-dimensional particle-in-cell also shows the generation of the solitary waves. In the two-dimensional case, solitary waves are distributed in the transverse directions because of the filamentation instability.

Shift and broadening of emission lines in Nd :YAG laser crystal ...

Indian Academy of Sciences (India)

1Department of Optics and Laser Engineering, Estahban Branch, Islamic Azad ... Nd3+:YAG crystal; heat generation; three-level emission lines; four-level emission ... Modelling of high-power solid-state lasers requires precise knowledge of ...

Surface-plasmon-enhanced lasing emission based on polymer distributed feedback laser

Energy Technology Data Exchange (ETDEWEB)

Zhang, Dingke, E-mail: dingke.zhang@gmail.com, E-mail: shijianchen@gmail.com [School of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331 (China); Chen, Shijian, E-mail: dingke.zhang@gmail.com, E-mail: shijianchen@gmail.com; Huang, Yingzhou; Zhang, Zhen [School of Physics, Chongqing University, Chongqing 401331 (China); Wang, Yanping; Ma, Dongge [State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

2015-01-14

Optical losses associated with the metallic contacts necessary for charge injection are an obstacle to the development of electrically pumped organic lasers. In this work, we show that it is possible to overcome these losses by introducing surface plasmons (SPs) in a distributed feedback laser to enhance the lasing emission. We perform a detailed study of the SPs influence on the lasing emission. We experimentally show that enhanced lasing emission has been successfully achieved in the presence of a metal electrode. The laser emission is strongly dependent on the thickness of Ag layer. By optimizing the thickness of Ag layer, surface-plasmon-enhanced lasing emission has been achieved with much reduced thresholds and higher intensity. When the thickness of the Ag layer increases to 50 nm, the device exhibits ten-fold emission intensity and a fifth of excitation threshold comparing with Ag-free one. The finite-difference time-domain (FDTD) results show that large field intensity is built at the 4-(dicyanomethylene)-2-i-propyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran:/poly(9-vinylcarbazole)Ag interface, which could lead to a strong coupling between lasing and SPs, and consequently a much enhanced laser emission at the photon energy of around 2.02 eV (615 nm). Our FDTD simulations gave an explanation of the effects of the SPs on lasing operation in the periodic structures. The use of SPs would lead to a new class of highly efficient solid-state laser sources and provide a new path to achieve electrically pumped organic lasers.

Enhancement of 800 nm upconversion emission in a thulium doped tellurite microstructured fiber pumped by a 1560 nm femtosecond fiber laser

Energy Technology Data Exchange (ETDEWEB)

Jia, Zhixu; Zheng, Kezhi [State Key Laboratory of Optical Fiber and Cable Manufacture Technology, Yangtze Optical Fiber and Cable Joint Stock Limited Company, Wuhan 430073 (China); State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Yao, Chuanfei; Wang, Shunbin; Qin, Guanshi, E-mail: qings@jlu.edu.cn; Qin, Weiping, E-mail: wpqin@jlu.edu.cn [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Xiong, Liangming; Luo, Jie; Lv, Dajuan [State Key Laboratory of Optical Fiber and Cable Manufacture Technology, Yangtze Optical Fiber and Cable Joint Stock Limited Company, Wuhan 430073 (China); Ohishi, Yasutake [Research Center for Advanced Photon Technology, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468–8511 (Japan)

2016-04-28

We report enhanced upconversion (UC) fluorescence in Tm{sup 3+} doped tellurite microstructured fibers (TDTMFs) fabricated by using a rod-in-tube method. Under the pumping of a 1560 nm femtosecond fiber laser, ultrabroadband supercontinuum light expanding from ∼1050 to ∼2700 nm was generated in a 4 cm long TDTMF. Simultaneously, intense 800 nm UC emission from the {sup 3}H{sub 4} → {sup 3}H{sub 6} transition of Tm{sup 3+} was observed in the same TDTMF. Compared to that pumped by a 1560 nm continuous wave fiber laser, the UC emission intensity was enhanced by ∼4.1 times. The enhancement was due to the spectral broadening in the TDTMF under the pumping of the 1560 nm femtosecond fiber laser.

Experimental study of X-ray emission in laser-cluster interaction; Etude experimentale de l'emission X issue de l'interaction laser-agregats

Energy Technology Data Exchange (ETDEWEB)

Caillaud, T

2004-09-01

Rare gas cluster jets are an intermediate medium between solid and gas targets. Laser-cluster jets interaction may generate a great number of energetic particles as X-rays, UV, high harmonics, ions, electrons and neutrons. To understand all the mechanisms involved in such an interaction we need to make a complete study of individual cluster response to an ultra-short laser pulse. We studied the laser interaction with our argon cluster gas jet, which is well characterized in cluster size and density, to enlarge the knowledge of this interaction. We measured absorption, heating and X-ray emission spectra versus laser parameters and clusters size ({approx} 15-30 nm). We show that there is a strong refraction effect on laser propagation due to the residual gas density. This effect was confirmed by laser propagation simulation with a cylindrical 2-dimensional particle code WAKE. The role played by refraction was to limit maximum laser intensity on the focal spot and to increase interaction volume. By this way, X-ray emission was observed with laser intensity not so far from the ionization threshold (few 10{sup 14} W.cm{sup -2}). We also studied plasma expansion both at cluster scale and focal volume scale and deduced the deposited energy distribution as a function of time. Thanks to a simple hydrodynamic model, we used these results to study cluster expansion. X-ray emission is then simulated by TRANSPEC code in order to reproduce X-ray spectra and duration. Those results revealed an extremely brief X-ray emission consistent with a preliminary measure by streak camera (on ps scale). (author)

Controlling the emission wavelength in group III-V semiconductor laser diodes

KAUST Repository

Ooi, Boon S.; Majid, Mohammed Abdul; Afandy, Rami; Aljabr, Ahmad

2016-01-01

Methods are provided for modifying the emission wavelength of a semiconductor quantum well laser diode, e.g. by blue shifting the emission wavelength. The methods can be applied to a variety of semiconductor quantum well laser diodes, e.g. group III

Room-temperature continuous-wave operation in the telecom wavelength range of GaSb-based lasers monolithically grown on Si

Science.gov (United States)

Castellano, A.; Cerutti, L.; Rodriguez, J. B.; Narcy, G.; Garreau, A.; Lelarge, F.; Tournié, E.

2017-06-01

We report on electrically pumped GaSb-based laser diodes monolithically grown on Si and operating in a continuous wave (cw) in the telecom wavelength range. The laser structures were grown by molecular-beam epitaxy on 6°-off (001) substrates. The devices were processed in coplanar contact geometry. 100 μm × 1 mm laser diodes exhibited a threshold current density of 1 kA/cm-2 measured under pulsed operation at 20 °C. CW operation was achieved up to 35 °C with 10 μm × 1 mm diodes. The output power at 20 °C was around 3 mW/uncoated facet, and the cw emission wavelength 1.59 μm, in the C/L-band of telecom systems.

Room-temperature continuous-wave operation in the telecom wavelength range of GaSb-based lasers monolithically grown on Si

Directory of Open Access Journals (Sweden)

A. Castellano

2017-06-01

Full Text Available We report on electrically pumped GaSb-based laser diodes monolithically grown on Si and operating in a continuous wave (cw in the telecom wavelength range. The laser structures were grown by molecular-beam epitaxy on 6°-off (001 substrates. The devices were processed in coplanar contact geometry. 100 μm × 1 mm laser diodes exhibited a threshold current density of 1 kA/cm−2 measured under pulsed operation at 20 °C. CW operation was achieved up to 35 °C with 10 μm × 1 mm diodes. The output power at 20 °C was around 3 mW/uncoated facet, and the cw emission wavelength 1.59 μm, in the C/L-band of telecom systems.

Theoretical evaluation of a continues-wave Ho3+:BaY2F8 laser with mid-infrared emission

Science.gov (United States)

Rong, Kepeng; Cai, He; An, Guofei; Han, Juhong; Yu, Hang; Wang, Shunyan; Yu, Qiang; Wu, Peng; Zhang, Wei; Wang, Hongyuan; Wang, You

2018-01-01

In this paper, we build a theoretical model to study a continues-wave (CW) Ho3+:BaY2F8 laser by considering both energy transfer up-conversion (ETU) and cross relaxation (CR) processes. The influences of the pump power, reflectance of an output coupler (OC), and crystal length on the output features are systematically analyzed for an end-pumped configuration, respectively. We also investigate how the processes of ETU and CR in the energy-level system affect the output of a Ho3+:BaY2F8 laser by use of the kinetic evaluation. The simulation results show that the optical-to-optical efficiency can be promoted by adjusting the parameters such as the reflectance of an output coupler, crystal length, and pump power. It has been theoretically demonstrated that the threshold of a Ho3+:BaY2F8 laser is very high for the lasing operation in a CW mode.

Theory and experiments on the generation of spontaneous emission using a plasma wave undulator

International Nuclear Information System (INIS)

Williams, R.L.; Clayton, C.E.; Joshi, C.; Katsouleas, T.; Mori, W.B.; Slater, J.

1990-01-01

This paper reports that, the authors are studying the feasibility of using relativistically moving plasma waves as short wavelength undulators for possible FEL and Compton scattering applications at UCLA. The remarkable property of such waves is that the wiggler parameter a w = eA/mc 2 can be on the order 0.1 while their wavelength λ w can be submillimeter. Such waves can be excited by either an intense electron bunch going through a plasma (plasma wake field) or a short but intense laser pulse going through the plasma (laser wake field). A variation of the laser wake field scheme is the plasm beat wave excitation. Here a moderately intense laser pulse containing two frequencies excites the plasm wave resonantly. Using a laser pulse containing 10.27 μm and 9.6 μm lines of the Co 2 laser that is approximately 400 ps (FWHM) and 200 GW of power, we were able to measure a w times the length product of 0.013 cm in our experiments. If a length of 0.75 cm i assumed, this implies an a w of 0.17 for a λ w ∼156 μm. Injection of an electron beam across such a plasma wave proved not to be feasible in these experiments, because the θ-pinch plasma source contained significant trapped magnetic fields. We are currently developing a field free plasma source which will permit transverse electron injection

Observation of copious emission at the fundamental frequency by a Smith-Purcell free-electron laser with sidewalls

International Nuclear Information System (INIS)

Gardelle, J.; Modin, P.; Donohue, J. T.

2012-01-01

An experiment at microwave frequencies confirms the recent prediction that a Smith-Purcell [S. J. Smith and E. M. Purcell, Phys. Rev. 92, 1069 (1953)] free-electron laser equipped with sidewalls can emit radiation at the frequency of the surface wave. The power output is considerably greater than for the previously observed emission at the second harmonic, in agreement with three-dimensional simulations. The dependence of frequency on beam energy and emission angle is in good agreement with three-dimensional theory and simulations. Provided that a reduction in scale can be achieved, a path is open to coherent Smith-Purcell radiation at terahertz frequency.

Emission wavelength of multilayer distributed feedback dye lasers

DEFF Research Database (Denmark)

Vannahme, Christoph; Smith, Cameron L. C.; Brøkner Christiansen, Mads

2012-01-01

Precise emission wavelength modeling is essential for understanding and optimization of distributed feedback (DFB) lasers. An analytical approach for determining the emission wavelength based on setting the propagation constant of the Bragg condition and solving for the resulting slab waveguide m...

Directional Emission from Dielectric Leaky-Wave Nanoantennas

Science.gov (United States)

Peter, Manuel; Hildebrandt, Andre; Schlickriede, Christian; Gharib, Kimia; Zentgraf, Thomas; Förstner, Jens; Linden, Stefan

2017-07-01

An important source of innovation in nanophotonics is the idea to scale down known radio wave technologies to the optical regime. One thoroughly investigated example of this approach are metallic nanoantennas which employ plasmonic resonances to couple localized emitters to selected far-field modes. While metals can be treated as perfect conductors in the microwave regime, their response becomes Drude-like at optical frequencies. Thus, plasmonic nanoantennas are inherently lossy. Moreover, their resonant nature requires precise control of the antenna geometry. A promising way to circumvent these problems is the use of broadband nanoantennas made from low-loss dielectric materials. Here, we report on highly directional emission from active dielectric leaky-wave nanoantennas made of Hafnium dioxide. Colloidal semiconductor quantum dots deposited in the nanoantenna feed gap serve as a local light source. The emission patterns of active nanoantennas with different sizes are measured by Fourier imaging. We find for all antenna sizes a highly directional emission, underlining the broadband operation of our design.

Secondary emissions during fiber laser cutting of nuclear material

Energy Technology Data Exchange (ETDEWEB)

Lopez, A., E-mail: beatriz.mendes.lopez@gmail.com [IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa (Portugal); Assunção, E. [IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa (Portugal); European Federation for Welding, Joining and Cutting, Porto Salvo 2740-120 (Portugal); Pires, I. [IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa (Portugal); Quintino, L. [IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa (Portugal); European Federation for Welding, Joining and Cutting, Porto Salvo 2740-120 (Portugal)

2017-04-15

The laser process has been studied for dismantling work for more than 10 years, however there is almost no data available concerning secondary emissions generated during the process. These emissions are inevitable during the laser cutting process and can have detrimental effects in human health and in the equipment. In terms of safety, for nuclear decommissioning, is crucial to point out ways of controlling the emissions of the process. This paper gives indications about the parameters to be used in order to reduce these secondary emissions and about the influence of these parameters on the particles size distribution. In general, for producing minimal dross and fume emissions the beam focus should be placed on the surface of the material. The higher percentage of secondary emissions which present higher diameter, increases approximately linearly with the stand-off distance and with the use of low air pressure.

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

Stress wave emission: a bibliographical survey No 2

International Nuclear Information System (INIS)

Lucia, A.C.; Galli, M.

1976-01-01

This report gives an inventory of papers and publications which deal with stress wave emission (ultrasonic emission). This bibliography is up date until end of 1974. It contains also titles of papers published before 1973 but not contained in our first bibliographical report (EUR--5616e)

1.9 W continuous-wave single transverse mode emission from 1060 nm edge-emitting lasers with vertically extended lasing area

Energy Technology Data Exchange (ETDEWEB)

Miah, M. J., E-mail: jarez.miah@tu-berlin.de; Posilovic, K.; Kalosha, V. P.; Rosales, R.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Kettler, T. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); PBC Lasers GmbH, Hardenbergstr. 36, 10623 Berlin (Germany); Skoczowsky, D. [PBC Lasers GmbH, Hardenbergstr. 36, 10623 Berlin (Germany); Pohl, J.; Weyers, M. [Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

2014-10-13

High-brightness edge-emitting semiconductor lasers having a vertically extended waveguide structure emitting in the 1060 nm range are investigated. Ridge waveguide (RW) lasers with 9 μm stripe width and 2.64 mm cavity length yield highest to date single transverse mode output power for RW lasers in the 1060 nm range. The lasers provide 1.9 W single transverse mode optical power under continuous-wave (cw) operation with narrow beam divergences of 9° in lateral and 14° (full width at half maximum) in vertical direction. The beam quality factor M{sup 2} is less than 1.9 up to 1.9 W optical power. A maximum brightness of 72 MWcm{sup −2}sr{sup −1} is obtained. 100 μm wide and 3 mm long unpassivated broad area lasers provide more than 9 W optical power in cw operation.

Generation of ultrasound in materials using continuous-wave lasers.

Science.gov (United States)

Caron, James N; DiComo, Gregory P; Nikitin, Sergei

2012-03-01

Generating and detecting ultrasound is a standard method of nondestructive evaluation of materials. Pulsed lasers are used to generate ultrasound remotely in situations that prohibit the use of contact transducers. The scanning rate is limited by the repetition rates of the pulsed lasers, ranging between 10 and 100 Hz for lasers with sufficient pulse widths and energies. Alternately, a high-power continuous-wave laser can be scanned across the surface, creating an ultrasonic wavefront. Since generation is continuous, the scanning rate can be as much as 4 orders of magnitude higher than with pulsed lasers. This paper introduces the concept, comparing the theoretical scanning speed with generation by pulsed laser. © 2012 Optical Society of America

Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation

Science.gov (United States)

Peña-Díaz, M.; Ponce, L.; Arronte, M.; Flores, T.

2007-04-01

Optical emission spectroscopy of the pulsed laser ablation of spines and glochids from Opuntia (Nopal) cladodes was performed. Nopal cladodes were irradiated with Nd:YAG free-running laser pulses on their body, glochids and spines. Emission spectroscopy analyses in the 350-1000 nm region of the laser induced plasma were made. Plasma plume evolution characterization, theoretical calculations of plasma plume temperature and experiments varying the processing atmosphere showed that the process is dominated by a thermally activated combustion reaction which increases the dethorning process efficiency. Therefore, appropriate laser pulse energy for minimal damage of cladodes body and in the area beneath glochids and spines can be obtained.

Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation

Energy Technology Data Exchange (ETDEWEB)

Pena-Diaz, M; Ponce, L; Arronte, M; Flores, T [Laboratorio TecnologIa Laser, CICATA-IPN, Unidad Altamira, Carretera Tampico-Puerto Ind. Altamira, 89600, TAMPS (Mexico)

2007-04-15

Optical emission spectroscopy of the pulsed laser ablation of spines and glochids from Opuntia (Nopal) cladodes was performed. Nopal cladodes were irradiated with Nd:YAG free-running laser pulses on their body, glochids and spines. Emission spectroscopy analyses in the 350-1000 nm region of the laser induced plasma were made. Plasma plume evolution characterization, theoretical calculations of plasma plume temperature and experiments varying the processing atmosphere showed that the process is dominated by a thermally activated combustion reaction which increases the dethorning process efficiency. Therefore, appropriate laser pulse energy for minimal damage of cladodes body and in the area beneath glochids and spines can be obtained.

Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation

International Nuclear Information System (INIS)

Pena-Diaz, M; Ponce, L; Arronte, M; Flores, T

2007-01-01

Optical emission spectroscopy of the pulsed laser ablation of spines and glochids from Opuntia (Nopal) cladodes was performed. Nopal cladodes were irradiated with Nd:YAG free-running laser pulses on their body, glochids and spines. Emission spectroscopy analyses in the 350-1000 nm region of the laser induced plasma were made. Plasma plume evolution characterization, theoretical calculations of plasma plume temperature and experiments varying the processing atmosphere showed that the process is dominated by a thermally activated combustion reaction which increases the dethorning process efficiency. Therefore, appropriate laser pulse energy for minimal damage of cladodes body and in the area beneath glochids and spines can be obtained

Magnon Accumulation by Clocked Laser Excitation as Source of Long-Range Spin Waves in Transparent Magnetic Films

Directory of Open Access Journals (Sweden)

M. Jäckl

2017-04-01

Full Text Available Optical tools are promising for spin-wave generation because of the possibilities of ultrafast manipulation and local excitation. However, a single laser pulse can inject spin waves (SWs only with a broad frequency spectrum, resulting in short propagation distances and low wave amplitudes. Here, we excite a magnetic garnet film by a train of fs-laser pulses with a 1-GHz repetition rate so that the pulse separation is shorter than the decay time of magnetic modes, which allows us to achieve a collective impact on the magnetization and establish a quasistationary source of spin waves, namely, a coherent accumulation of magnons (“magnon cloud”. This approach has several appealing features: (i The magnon source is tunable, (ii the SW amplitude can be significantly enhanced, (iii the SW spectrum is quite narrow, providing long-distance propagation, (iv the periodic pumping results in an almost constant-in-time SW amplitude for the distances larger than 20  μm away from the source, and (v the SW emission shows pronounced directionality. These results expand the capabilities of ultrafast coherent optical control of magnetization and pave the way for applications in data processing, including the quantum regime. The quasistationary magnon accumulation might also be of interest for applications in magnon Bose-Einstein condensates.

Thin film beam splitter multiple short pulse generation for enhanced Ni-like Ag x-ray laser emission.

Science.gov (United States)

Cojocaru, Gabriel V; Ungureanu, Razvan G; Banici, Romeo A; Ursescu, Daniel; Delmas, Olivier; Pittman, Moana; Guilbaud, Olivier; Kazamias, Sophie; Cassou, Kevin; Demailly, Julien; Neveu, Olivier; Baynard, Elsa; Ros, David

2014-04-15

An alternative, novel multiple pulse generation scheme was implemented directly after the optical compressor output of an x-ray pump laser. The new method uses a polarization sensitive thin film beam splitter and a half-wavelength wave plate for tuning the energy ratio in the multiple short pulses. Based on this method, an extensive study was made of the running parameters for a grazing incidence pumped silver x-ray laser (XRL) pumped with a long pulse of 145 mJ in 6 ns at 532 nm and up to 1.45 J in few picoseconds at 810 nm. Fivefold enhancement in the emission of the silver XRL was demonstrated using the new pump method.

Controlling the emission wavelength in group III-V semiconductor laser diodes

KAUST Repository

Ooi, Boon S.

2016-12-29

Methods are provided for modifying the emission wavelength of a semiconductor quantum well laser diode, e.g. by blue shifting the emission wavelength. The methods can be applied to a variety of semiconductor quantum well laser diodes, e.g. group III-V semiconductor quantum wells. The group III-V semiconductor can include AlSb, AlAs, Aln, AlP, BN, GaSb, GaAs, GaN, GaP, InSb, InAs, InN, and InP, and group III-V ternary semiconductors alloys such as AlxGai.xAs. The methods can results in a blue shifting of about 20 meV to 350 meV, which can be used for example to make group III-V semiconductor quantum well laser diodes with an emission that is orange or yellow. Methods of making semiconductor quantum well laser diodes and semiconductor quantum well laser diodes made therefrom are also provided.

Spectroscopic analysis of coal plasma emission produced by laser ablation

OpenAIRE

Vera-Londoño, Liliana Patricia; Pérez-Taborda, Jaime Andrés; Riascos-Landázuri, Henry

2016-01-01

An analysis of plasma produced by laser ablation using 1,064 nm of laser radiation from a Q-switched Nd:YAG on coal mineral samples under air ambient, was performed. The emission of molecular band systems such as C2 Swan System , the First Negative System N2 (Band head at 501.53 nm) and different emission lines were investigated using the optical emission spectroscopy technique. The C2 molecular spectra (Swan band) were analyzed to determine vibrational temperature (0.62 eV). The density and ...

A study on laser-based ultrasonic technique by the use of guided wave tomographic imaging

Energy Technology Data Exchange (ETDEWEB)

Park, Junpil, E-mail: jpp@pusan.ac.kr; Lim, Juyoung, E-mail: jpp@pusan.ac.kr [Graduate school, School of Mechanical Engineering, Pusan National University (Korea, Republic of); Cho, Younho [School of Mechanical Engineering, Pusan National University (Korea, Republic of); Krishnaswamy, Sridhar [Center for Quality Engineering and Failure Prevention, Northwestern University, Evanston, IL (United States)

2015-03-31

Guided wave tests are impractical for investigating specimens with limited accessibility and coarse surfaces or geometrically complicated features. A non-contact setup with a laser ultrasonic transmitter and receiver is the classic attractive for guided wave inspection. The present work was done to develop a non-contact guided-wave tomography technique by laser ultrasonic technique in a plate-like structure. A method for Lam wave generation and detection in an aluminum plate with a pulse laser ultrasonic transmitter and a Michelson interferometer receiver has been developed. In the images obtained by laser scanning, the defect shape and area showed good agreement with the actual defect. The proposed approach can be used as a non-contact-based online inspection and monitoring technique.

High-order harmonics from bow wave caustics driven by a high-intensity laser

International Nuclear Information System (INIS)

Pirozhkov, A.S.; Kando, M.; Esirkepov, T.Zh.

2012-01-01

We propose a new mechanism of high-order harmonic generation during an interaction of a high-intensity laser pulse with underdense plasma. A tightly focused laser pulse creates a cavity in plasma pushing electrons aside and exciting the wake wave and the bow wave. At the joint of the cavity wall and the bow wave boundary, an annular spike of electron density is formed. This spike surrounds the cavity and moves together with the laser pulse. Collective motion of electrons in the spike driven by the laser field generates high-order harmonics. A strong localization of the electron spike, its robustness to oscillations imposed by the laser field and, consequently, its ability to produce high-order harmonics is explained by catastrophe theory. The proposed mechanism explains the experimental observations of high-order harmonics with the 9 TW J-KAREN laser (JAEA, Japan) and the 120 TW Astra Gemini laser (CLF RAL, UK) [A. S. Pirozhkov, et al., arXiv:1004.4514 (2010); A. S. Pirozhkov et al, AIP Proceedings, this volume]. The theory is corroborated by high-resolution two-and three-dimensional particle-in-cell simulations.

Terahertz emission and electromagnetic waves in single crystal Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} structures

Energy Technology Data Exchange (ETDEWEB)

Wieland, Raphael; Rudau, Fabian; Gross, Boris; Judd, Thomas; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Collective Quantum Phenomena in LISA" +, Universitaet Tuebingen, Tuebingen (Germany); Kinev, Nickolay; Koshelets, Valery [Kotel' nikov Institute of Radio Engineering and Electronics, Moscow (Russian Federation); Tsujimoto, Manabu [Kyoto University, Kyoto (Japan); Ji, Min; Huang, Ya; Zhou, Xianjing; An, Deyue; Wang, Huabing [National Institute for Materials Science, Tsukuba (Japan); Research Institute of Superconductor Electronics, Nanjing University, Nanjing (China); Wu, Peihang [Research Institute of Superconductor Electronics, Nanjing University, Nanjing (China); Hatano, Takeshi [National Institute for Materials Science, Tsukuba (Japan)

2015-07-01

Josephson Junctions (JJs) offer a natural way to convert a dc voltage into high-frequency electromagnetic radiation. In the high-Tc superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (BSCCO), JJs form intrinsically, allowing to fabricate stacks of hundreds of junctions easily. Emission can occur at relatively low bias currents but also at larger input power with frequencies from 0.4 to 1 THz. At high bias, a hot spot forms, affecting both the intensity and the linewidth of the radiation. BSCCO mesas are believed to work as a cavity for electromagnetic standing waves, synchronizing all the junctions in the stack. We investigated THz emission and hotspot formation using a combination of transport measurements, electromagnetic wave detection via a superconducting receiver and low temperature scanning laser microscopy.

Measurements of laser generated soft X-ray emission from irradiated gold foils

Energy Technology Data Exchange (ETDEWEB)

Davis, J. S.; Keiter, P. A.; Klein, S. R.; Drake, R. P.; Shvarts, D. [University of Michigan, 2455 Hayward St., Ann Arbor, Michigan 48109 (United States); Frank, Y.; Raicher, E.; Fraenkel, M. [Soreq Nuclear Research Center, Yavne (Israel)

2016-11-15

Soft x-ray emission from laser irradiated gold foils was measured at the Omega-60 laser system using the Dante photodiode array. The foils were heated with 2 kJ, 6 ns laser pulses and foil thicknesses were varied between 0.5, 1.0, and 2.0 μm. Initial Dante analysis indicates peak emission temperatures of roughly 100 eV and 80 eV for the 0.5 μm and 1.0 μm thick foils, respectively, with little measurable emission from the 2.0 μm foils.

X-ray emission from stainless steel foils irradiated by femtosecond petawatt laser pulses

Science.gov (United States)

Alkhimova, M. A.; Faenov, A. Ya; Pikuz, T. A.; Skobelev, I. Yu; Pikuz, S. A.; Nishiuchi, M.; Sakaki, H.; Pirozhkov, A. S.; Sagisaka, S.; Dover, N. P.; Kondo, Ko; Ogura, K.; Fukuda, Y.; Kiriyama, H.; Esirkepov, T.; Bulanov, S. V.; Andreev, A.; Kando, M.; Zhidkov, A.; Nishitani, K.; Miyahara, T.; Watanabe, Y.; Kodama, R.; Kondo, K.

2018-01-01

We report about nonlinear growth of x-ray emission intensity emitted from plasma generated by femtosecond petawatt laser pulses irradiating stainless steel foils. X-ray emission intensity increases as ˜ I 4.5 with laser intensity I on a target. High spectrally resolved x-ray emission from front and rear surfaces of 5 μm thickness stainless steel targets were obtained at the wavelength range 1.7-2.1 Å, for the first time in experiments at femtosecond petawatt laser facility J-KAREN-P. Total intensity of front x-ray spectra three times dominates to rear side spectra for maximum laser intensity I ≈ 3.2×1021 W/cm2. Growth of x-ray emission is mostly determined by contribution of bremsstrahlung radiation that allowed estimating bulk electron plasma temperature for various magnitude of laser intensity on target.

Ultraviolet laser-induced fluorescence detection strategies in capillary electrophoresis: determination of naphthalene sulphonates in river water.

NARCIS (Netherlands)

Kok, S.J.; Isberg, I.C.K.; Gooijer, C.; Brinkman, U.A.T.; Velthorst, N.H.

1998-01-01

Various UV-laser-induced fluorescence detection strategies for capillary electrophoresis (CE) are compared, i.e. two UV-laser systems (a pulsed laser providing up to 25 mW of tunable emission, applied at 280, 290 and 325 nm, and a continuous wave (cw) laser providing up to 100 mW of 257 nm emission)

Broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity

Science.gov (United States)

Li, Q.; Jia, Z. X.; Weng, H. Z.; Li, Z. R.; Yang, Y. D.; Xiao, J. L.; Chen, S. W.; Huang, Y. Z.; Qin, W. P.; Qin, G. S.

2018-05-01

We demonstrate broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm and a frequency separation of ~9.28 GHz generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity. By using one continuous-wave laser as the pump source, multi-wavelength Brillouin lasers with an operating wavelength range of 1554–1574 nm were generated via cascaded Brillouin scattering and four-wave mixing. Interestingly, when pumped by two continuous-wave lasers with an appropriate frequency separation, the operating wavelength range of the multi-wavelength Brillouin lasers was increased to 1500–1600 nm due to cavity-enhanced cascaded four-wave mixing among the frequency components generated by two pump lasers in the dual wavelength Brillouin laser cavity.

Soliton emission stimulated by sound wave or external field

International Nuclear Information System (INIS)

Malomed, B.A.

1987-01-01

Langmuir soliton interaction with ion-acoustic wave results in soliton radiative decay at the expence of emission by the soliton of linear langmuir waves. Intensity of this radiation in the ''subsonic'' regime as well as the rate of energy transfer from acoustic waves to langmuir ones and soliton decay rate are calculated. Three cases are considered: monochromatic acoustic wave, nonmonochromatic wave packet with a wide spectrum, random acoustic field, for which results appear to be qualitatively different. A related problem, concerning the radiation generation by soliton under external electromagnetic wave effect is also considered. Dissipation effect on radiation is investigated

Bursty emission of whistler waves in association with plasmoid collision

Directory of Open Access Journals (Sweden)

K. Fujimoto

2017-07-01

Full Text Available A new mechanism to generate whistler waves in the course of collisionless magnetic reconnection is proposed. It is found that intense whistler emissions occur in association with plasmoid collisions. The key processes are strong perpendicular heating of the electrons through a secondary magnetic reconnection during plasmoid collision and the subsequent compression of the ambient magnetic field, leading to whistler instability due to the electron temperature anisotropy. The emissions have a bursty nature, completing in a short time within the ion timescales, as has often been observed in the Earth's magnetosphere. The whistler waves can accelerate the electrons in the parallel direction, contributing to the generation of high-energy electrons. The present study suggests that the bursty emission of whistler waves could be an indicator of plasmoid collisions and the associated particle energization during collisionless magnetic reconnection.

Resonant emission of electromagnetic waves by plasma solitons

International Nuclear Information System (INIS)

Mironov, V.A.; Sergeev, A.M.; Khimich, A.V.

1988-01-01

The ability of plasma-wave solitons to radiate electromagnetic waves at the frequency of the natural oscillations of the field is considered. It is shown that this radiation is the main energy dissipation channel for strong plasma turbulence in a magnetoactive plasma. An interpretation is proposed for the artificial radio emission produced when the ionosphere is acted upon by beams of strong electromagnetic waves. The use of this phenomenon for plasma turbulence, particularly in the outer-space plasma near the earth, is discussed

Parametric Excitations of Fast Plasma Waves by Counter-propagating Laser Beams

International Nuclear Information System (INIS)

Shvets, G.; Fisch, N.J.

2001-01-01

Short- and long-wavelength plasma waves can become strongly coupled in the presence of two counter-propagating laser pump pulses detuned by twice the cold plasma frequency. What makes this four-wave interaction important is that the growth rate of the plasma waves occurs much faster than in the more obvious co-propagating geometry

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.)

Multimode laser emission from free-standing cylindrical microcavities

Energy Technology Data Exchange (ETDEWEB)

Peter, Jaison, E-mail: jaisonpeter@cusat.ac.in; Radhakrishnan, P.; Nampoori, V.P.N.; Kailasnath, M.

2014-05-01

We report a well resolved whispering gallery mode (WGM) laser emission from a free-standing microring cavity based on a dye doped hollow polymer optical fiber (DDHPOF), which is transversely pumped by a pulsed Nd:YAG laser. The microring laser is characterized by a well-defined, low threshold pump power at which the emission spectral intensity dramatically increases and collapses into several dominant microcavity laser modes with reduced mode spacing and high Q-value. Resonant modes are excited inside the gain medium which is strongly confined along the radial direction so that the spacing of lasing modes is controlled by the diameter of the cylindrical microcavity. A variation in the free spectral range of WGM spectra from 0.23 to 0.09 nm coupled with a red-shift is observed with an increase in the diameter of DDHPOFs. - Highlights: • Different diameter free-standing cylindrical microcavity lasers have been fabricated and their performances have been evaluated. • The microring laser is characterized by a well-defined, low threshold pump power, with reduced mode spacing and high Q-value. • When the diameter of DDHPOF increases, the number of lasing peaks increases along with the decrease of the FSR as observed from our studies. • It is also found that whispering gallery lasing envelope is shifted from 559 to 571 nm (Stokes shift) with the diameter.

Continuous-wave ceramic Nd:YAG laser at 1123 nm

International Nuclear Information System (INIS)

Zhang, S S; Wang, Q P; Zhang, X Y; Cong, Z H; Fan, S Z; Liu, Z J; Sun, W J

2009-01-01

Ceramic Nd:YAG (cNd:YAG) materials are employed to generate 1123-nm laser. A fiber-coupled continuous-wave (CW) 808-nm diode laser is used as the pumping source. With an incident diode power of 26.1 W, a CW output power of up to 10.8 W is obtained with a 10-mm-long ceramic Nd:YAG rod (1.0 at.%-Nd-doped). The conversion efficiency from diode power to 1123-nm laser power is 41.4%. The laser performance of another 10-mm-long cNd:YAG rod with a Nd-doping concentration of 0.6 at.% is studied as a comparison

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

Precursor Wave Emission Enhanced by Weibel Instability in Relativistic Shocks

Science.gov (United States)

Iwamoto, Masanori; Amano, Takanobu; Hoshino, Masahiro; Matsumoto, Yosuke

2018-05-01

We investigated the precursor wave emission efficiency in magnetized purely perpendicular relativistic shocks in pair plasmas. We extended our previous study to include the dependence of upstream magnetic field orientations. We performed two-dimensional particle-in-cell simulations and focused on two magnetic field orientations: the magnetic field in the simulation plane (i.e., in-plane configuration) and that perpendicular to the simulation plane (i.e., out-of-plane configuration). Our simulations in the in-plane configuration demonstrated that not only extraordinary but also ordinary mode waves are excited. We quantified the emission efficiency as a function of the magnetization parameter σ e and found that the large-amplitude precursor waves are emitted for a wide range of σ e . We found that especially at low σ e , the magnetic field generated by Weibel instability amplifies the ordinary mode wave power. The amplitude is large enough to perturb the upstream plasma, and transverse density filaments are generated as in the case of the out-of-plane configuration investigated in the previous study. We confirmed that our previous conclusion holds regardless of upstream magnetic field orientations with respect to the two-dimensional simulation plane. We discuss the precursor wave emission in three dimensions and the feasibility of wakefield acceleration in relativistic shocks based on our results.

Gravitational wave emission from a bounded source: A treatment in the full nonlinear regime

International Nuclear Information System (INIS)

Oliveiral, H.P. de; Damiao Soares, I.

2004-03-01

The dynamics of a bounded gravitational collapsing configuration emitting gravitational waves is studied. The exterior spacetime is described by Robinson-Trautman geometries and have the Schwarzschild black hole as its final gravitational configuration, when the gravitational wave emission ceases. The full nonlinear regime is examined by using the Galerkin method that allows us to reduce the equations governing the dynamics to a finite-dimensional dynamical system, after a proper truncation procedure. Gravitational wave emission patterns from given initial configurations are exhibited for several phases of the collapse and the mass-loss ratio that characterizes the amount of mass extracted by the gravitational wave emission is evaluated. We obtain that the smaller initial mass M init of the configuration, the more rapidly the Schwarzschild solution is attained and a larger fraction of M init is lost in the process of gravitational wave emission. Within all our numerical experiments, the distribution of the mass fraction extracted by gravitational wave emission is shown to satisfy the distribution law of nonextensive statistics and this result is independent of the initial configurations considered. (author)

Measurement of the emission spectrum of a semiconductor laser using laser-feedback interferometry.

Science.gov (United States)

Keeley, James; Freeman, Joshua; Bertling, Karl; Lim, Yah L; Mohandas, Reshma A; Taimre, Thomas; Li, Lianhe H; Indjin, Dragan; Rakić, Aleksandar D; Linfield, Edmund H; Davies, A Giles; Dean, Paul

2017-08-03

The effects of optical feedback (OF) in lasers have been observed since the early days of laser development. While OF can result in undesirable and unpredictable operation in laser systems, it can also cause measurable perturbations to the operating parameters, which can be harnessed for metrological purposes. In this work we exploit this 'self-mixing' effect to infer the emission spectrum of a semiconductor laser using a laser-feedback interferometer, in which the terminal voltage of the laser is used to coherently sample the reinjected field. We demonstrate this approach using a terahertz frequency quantum cascade laser operating in both single- and multiple-longitudinal mode regimes, and are able to resolve spectral features not reliably resolved using traditional Fourier transform spectroscopy. We also investigate quantitatively the frequency perturbation of individual laser modes under OF, and find excellent agreement with predictions of the excess phase equation central to the theory of lasers under OF.

Calculation of laser induced impulse based on the laser supported detonation wave model with dissociation, ionization and radiation

International Nuclear Information System (INIS)

Gan, Li; Mousen, Cheng; Xiaokang, Li

2014-01-01

In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction, the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter

Calculation of laser induced impulse based on the laser supported detonation wave model with dissociation, ionization and radiation

Energy Technology Data Exchange (ETDEWEB)

Gan, Li, E-mail: ligan0001@gmail.com; Mousen, Cheng; Xiaokang, Li [College of Aerospace Science and Engineering, National University of Defense Technology, Changsha (China)

2014-03-15

In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction, the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter.

Frequency lock of a dye laser emission on iron atomic line top

International Nuclear Information System (INIS)

Durand, P.

1995-03-01

The aim of this thesis is to realize a frequency lock of a dye laser emission on iron atomic line top. To reach that goal, the author first presents the calculation of atomic vapour density by means of laser absorption ratio measure and studies the dye laser working. It is then necessary to find a device giving the required precision on the frequency of the absorption line choosen. It is obtained thanks to the atomic line reconstitution by optogalvanic effect which gives the reference. Besides, the author presents the necessity of a laser emission power regulation which is obtained thanks to a device including an acoustic and optic modulator. A reliable and accurate captor is choosen and adjusted testing various hollow cathode lamps. The method to obtain the frequency lock of laser emission on iron atomic line top is described. (TEC). 18 refs., 64 figs

Crystal growth, spectral properties, and laser demonstration of laser crystal Nd:LYSO

Science.gov (United States)

Li, D. Z.; Xu, X. D.; Zhou, D. H.; Zhuang, S. D.; Wang, Z. P.; Xia, C. T.; Wu, F.; Xu, J.

2010-11-01

A Nd:LYSO crystal has been grown by the Czochralski technique. The cell parameters were analyzed with X-ray diffraction (XRD). The Judd-Ofelt intense parameters Ω2,4,6 were obtained to be 2.65, 5.75, and 7.37×10-20 cm2, respectively. The absorption and emission cross sections and the branching ratios were calculated. The large absorption cross section (6.14×10-20 cm2) and broad absorption band (5 nm) around 811 nm indicate that this crystal can be pumped efficiently by laser diodes. The broad emission band from the 4F3/2 multiplet shows that the crystal is a promising medium for ultrashort pulse lasers. Pumped by a laser diode, the maximum 814 mW continuous-wave laser output has been obtained with a slope efficiency of 28.9%. All the results show that this crystal is a promising laser material.

Crystal growth, spectral properties, and laser demonstration of laser crystal Nd:LYSO

International Nuclear Information System (INIS)

Li, D Z; Xu, X D; Zhou, D H; Xia, C T; Wu, F; Zhuang, S D; Wang, Z P; Xu, J

2010-01-01

A Nd:LYSO crystal has been grown by the Czochralski technique. The cell parameters were analyzed with X-ray diffraction (XRD). The Judd-Ofelt intense parameters Ω 2,4,6 were obtained to be 2.65, 5.75, and 7.37×10 -20 cm 2 , respectively. The absorption and emission cross sections and the branching ratios were calculated. The large absorption cross section (6.14×10 -20 cm 2 ) and broad absorption band (5 nm) around 811 nm indicate that this crystal can be pumped efficiently by laser diodes. The broad emission band from the 4 F 3/2 multiplet shows that the crystal is a promising medium for ultrashort pulse lasers. Pumped by a laser diode, the maximum 814 mW continuous-wave laser output has been obtained with a slope efficiency of 28.9%. All the results show that this crystal is a promising laser material

INTERACTION OF LASER RADIATION WITH MATTER AND OTHER LASER APPLICATIONS: Changes in the emission properties of metal targets during pulse-periodic laser irradiation

Science.gov (United States)

Konov, Vitalii I.; Pimenov, S. M.; Prokhorov, A. M.; Chapliev, N. I.

1988-02-01

A scanning electron microscope was used with a pulse-periodic CO2 laser to discover the laws governing the correlation of the modified microrelief of metal surfaces, subjected to the action of multiple laser pulses, with the emission of charged particles and the luminescence of the irradiated zone. It was established that the influence of sorption and laser-induced desorption on the emission signals may be manifested differently depending on the regime of current generation in the "target-vacuum chamber" circuit.

Laser-generated acoustic wave studies on tattoo pigment

Science.gov (United States)

Paterson, Lorna M.; Dickinson, Mark R.; King, Terence A.

1996-01-01

A Q-switched alexandrite laser (180 ns at 755 nm) was used to irradiate samples of agar embedded with red, black and green tattoo dyes. The acoustic waves generated in the samples were detected using a PVDF membrane hydrophone and compared to theoretical expectations. The laser pulses were found to generate acoustic waves in the black and green samples but not in the red pigment. Pressures of up to 1.4 MPa were produced with irradiances of up to 96 MWcm-2 which is comparable to the irradiances used to clear pigment embedded in skin. The pressure gradient generated across pigment particles was approximately 1.09 X 1010 Pam-1 giving a pressure difference of 1.09 +/- 0.17 MPa over a particle with mean diameter 100 micrometers . This is not sufficient to permanently damage skin which has a tensile strength of 7.4 MPa.

Propagation of bulk longitudinal waves in thin films using laser ultrasonics

Energy Technology Data Exchange (ETDEWEB)

Kim, Yun Young [Dept. of Mechanical Engineering, Dong-eui University, Busan (Korea, Republic of)

2016-08-15

This paper presents the investigation of the propagation behavior of bulk longitudinal waves generated by an ultrafast laser system in thin films. A train of femtosecond laser pulses was focused onto the surface of a 150-nm thick metallic (chromium or aluminum) film on a silicon substrate to excite elastic waves, and the change in thermoreflectance at the spot was monitored to detect the arrival of echoes from the film/substrate interface. The experimental results show that the film material characteristics such as the wave velocity and Young's modulus can be evaluated through curve-fitting in numerical solutions. The material properties of nanoscale thin films are difficult to measure using conventional techniques. Therefore, this research provides an effective method for the nondestructive characterization of nanomaterials.

Linear conversion theory on the second harmonic emission from a plasma filament

International Nuclear Information System (INIS)

Tan Weihan; Gu Min

1989-01-01

The linear conversion theory of laser produced plasma filaments is studied. By calculations for the energy flux of the second harmonic emission on the basis of the planar wave-plasma interaction model, it has been found that there exists no 2ω 0 harmonic emission in the direction perpendicular to the incident laser, in contradiction with the experiments. A linear conversion theory is proposed on the second harmonic emission from a plasma filament and discovered the intense 2ω 0 harmonic emission in the direction perpendicular to the incident laser, which is in agreement with the experiments. (author)

Laser-driven Mach waves for gigabar-range shock experiments

Science.gov (United States)

Swift, Damian; Lazicki, Amy; Coppari, Federica; Saunders, Alison; Nilsen, Joseph

2017-10-01

Mach reflection offers possibilities for generating planar, supported shocks at higher pressures than are practical even with laser ablation. We have studied the formation of Mach waves by algebraic solution and hydrocode simulation for drive pressures at much than reported previously, and for realistic equations of state. We predict that Mach reflection continues to occur as the drive pressure increases, and the pressure enhancement increases monotonically with drive pressure even though the ``enhancement spike'' characteristic of low-pressure Mach waves disappears. The growth angle also increases monotonically with pressure, so a higher drive pressure seems always to be an advantage. However, there are conditions where the Mach wave is perturbed by reflections. We have performed trial experiments at the Omega facility, using a laser-heated halfraum to induce a Mach wave in a polystyrene cone. Pulse length and energy limitations meant that the drive was not maintained long enough to fully support the shock, but the results indicated a Mach wave of 25-30 TPa from a drive pressure of 5-6 TPa, consistent with simulations. A similar configuration should be tested at the NIF, and a Z-pinch driven configuration may be possible. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Energetic, spectral, and temporal characteristics of a two-wave CO/sub 2/ laser

Energy Technology Data Exchange (ETDEWEB)

Bertel' , I.M.; Petukhov, V.O.; Prokopov, A.P.; Tochitskii, S.Ya.; Churakov, V.V.

1987-09-01

This work studies the energetic and temporal parameters of a pulsed two-wave TEA CO/sub 2/ laser's radiation and the means for controlling these parameters. Obtaining the two-wave generation regime in CO/sub 2/ lasers uses, as is known, spatial splitting of the radiation, different variants of operating diffraction gratings, and placing a cell with selectively absorbing gas in the resonator. To realize the simultaneous two-wave generation regime in the present work, a double-resonant scheme is used with mutually orthogonal polarizers to spatially separate the radiation.

Single frequency Nd:YLF and Nd:YVO4 laser in the red emission

International Nuclear Information System (INIS)

Camargo, Fabiola de Almeida

2010-01-01

All solid-state continuous-wave (cw) narrow emission linewidth and tunable red lasers are convenient alternative sources to bulky and expensive dye-lasers for high precision laser spectroscopy. Single-frequency operation of diode-pumped Nd:YLiF 4 and Nd:YVO 4 cw ring lasers were investigated in the 1.32 - 1.34μm range, together with their intracavity second-harmonic generation (SHG) to the red spectral range (0.65 - 0.67μm) using either BiB 3 O 6 (BiBO) or periodically-poled KTiOPO 4 (ppKTP) crystals. We report on such a single-end diode-pumped Nd:YVO 4 unidirectional red ring laser containing a type-I cut BiBO nonlinear crystal, yielding a record of 680 mW of single-longitudinal mode (SLM) red output power at 671.1nm without any intra-cavity etalon. For smooth SLM wavelength tuning over the full gain bandwidth (∼4 nm), a partially-coated (R = 40%) 100μm-thin etalon was found necessary, reducing the maximum SLM power (at 671.15 nm) to 380 mW. At 1342.5nm and with a T = 2% transmission output coupler, the laser provided an optimal 1.5W of single-frequency power. We demonstrate also optimal intracavity SHG of a Nd:YLF ring laser in the π- polarization (λ = 1321.5nm) using a ppKTP. The laser yielded 1.4 W of single frequency red power at 660.5 nm, as much as the maximum fundamental power that can be extracted from the resonator using an optimal output coupler. With a partially coated (R = 25%) thin etalon, the laser was tunable over Δλ∼ 1.6nm. (author)

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

POWER SCALING IN CONTINUOUS-WAVE YB:YAG MICROCHIP LASER FOR MEASURING APPLICATIONS

Directory of Open Access Journals (Sweden)

A. M. Ivashko

2017-01-01

Full Text Available Characteristics optimization of lasers used in different measuring systems is of great interest up to now. Diode-pumped microchip lasers is one of the most perspective ways for development of solid-state light sources with minimal size and weight together with low energy power consumption. Increasing of output power with good beam quality is rather difficult task for such type of lasers due to thermal effects in the gain crystal under high pump power.The investigation results of continuous-wave longitudinally diode-pumped Yb:YAG microchip laser are presented. In the presented laser radiation from multiple pump laser diodes were focused into the separate zone in one gain crystal that provides simultaneous generation of multiple laser beams. The energy and spatial laser beam characteristics were investigated.Influence of neighboring pumped regions on energy and spatial laser beams parameters both for separate and for sum laser output was observed. The dependences of laser output power from distance between neighboring pumped regions and their number were determined. Decreasing of laser output power was demonstrated with corresponding distance shortening between pumped regions and increasing their quantity with simultaneous improvement of laser beam quality.Demonstrated mutual influence of neighboring pumped regions in the longitudinally diode pumped Yb:YAG microchip laser allow as to generate diffraction limited Gaussian beam with 2W of continuous-wave output power that 30 % higher than in case of one pumped zone. 

The measurement of capillary waves on a weldpool formed by a Nd:YAG laser

International Nuclear Information System (INIS)

Deam, R.T.; Brandt, M.; Harris, J.

2002-01-01

Experiments were performed using an on-line pyrometer to measure the capillary waves on a weldpool formed by a Nd: YAG laser. The surface temperature measurements taken from the weldpool revealed strong temporal fluctuations. Fourier transform of the pyrometer data revealed distinct peaks, consistent with calculated resonant frequencies for capillary surface waves on the weldpool formed by the laser. The possibility of using on-line measurement of surface temperature fluctuations to control weldpool depth in laser welds is discussed. The work forms part of an on-going programme to develop closed loop control for laser processing at Swinburne University

Time-resolved emission from laser-ablated uranium

International Nuclear Information System (INIS)

Stoffels, E.; Mullen, J. van der; Weijer, P. van de

1991-01-01

Time-resolved emission spectra from the plasma, induced by laser ablation of uranium samples have been studied. The dependence of the emission intensity on time is strongly affected by the nature and pressure of the buffer gas. Air and argon have been used in the pressure range 0.002 to 5 mbar. The emission intensity as a function of time displays three maxima, indicating that three different processes within the expanding plasma plume are involved. On basis of the time-resolved spectra we propose a model that explains qualitatively the phenomena that are responsible for this time behaviour. (author)

K-α emission form medium and high-Z materials irradiated by femtosecond laser pulses

International Nuclear Information System (INIS)

Limpouch, J.; Klimo, O.; Zhavoronkov, N.; Andreev, A.A.

2006-01-01

Complete test of publication follows. Fast electrons are created at the target surface during the interaction of high intensity ultra short laser pulses with solids. Fast electrons penetrate deep into the target where they generate K-α and Bremsstrahlung radiation. Generated high brightness K-α pulses offer the prospect of creating a cheap and compact X-ray source, posing a promising alternative to synchrotron radiation, e.g. in medical application and in material science. With an increase in laser intensity, efficient X-ray emission in the multi-keV range with pulse duration shorter than few picoseconds is expected. This short incoherent but monochromatic X-ray emission synchronized with laser pulses may be used for time-resolved measurements. Acceleration of fast electrons, their transport and K-α photon generation and emission from the target surface in both forward and backward directions are studied here numerically. The results are compared to recent experiments studying K-α emission from the front and rear surface of copper foil targets of various thicknesses and for various parameters of the laser plasma interaction. One-dimensional PIC simulations coupled with 3D time-resolved Monte Carlo simulations show that account of ionization processes and of density profile formed by laser ASE emission is essential for reliable explanation of experimental data. While sub-relativistic intensities are optimum for laser energy transformation into K-α emission for medium-Z targets, relativistic laser intensities have to be used for hard X-ray generation in high-Z materials. The cross-section for K-α shell ionization of high-Z elements by electrons increases or remains approximately constant within a factor of two at relativistic electron energies up to electron energies in the 100-MeV range. Moreover, the splitting ratio of K-α photon emission to Auger electron emission is favorable for high-Z materials, and thus efficient K-α emission is possible. In our

Bragg-Scattering Four-Wave Mixing in Nonlinear Fibers with Intracavity Frequency-Shifted Laser Pumps

Directory of Open Access Journals (Sweden)

Katarzyna Krupa

2012-01-01

Full Text Available We experimentally study four-wave mixing in highly nonlinear fibers using two independent and partially coherent laser pumps and a third coherent signal. We focus our attention on the Bragg-scattering frequency conversion. The two pumps were obtained by amplifying two Intracavity frequency-shifted feedback lasers working in a continuous wave regime.

Emission characteristics and stability of laser ion sources

Czech Academy of Sciences Publication Activity Database

Krása, Josef; Velyhan, Andriy; Krouský, Eduard; Láska, Leoš; Rohlena, Karel; Jungwirth, Karel; Ullschmied, Jiří; Lorusso, A.; Velardi, L.; Nassisi, V.; Czarnecka, A.; Ryc, L.; Parys, P.; Wolowski, J.

2010-01-01

Roč. 85, č. 5 (2010), s. 617-621 ISSN 0042-207X R&D Projects: GA AV ČR IAA100100715 Institutional research plan: CEZ:AV0Z10100523; CEZ:AV0Z20430508 Keywords : laser ion sources * ion emission reproducibility * thermal and fast ions * ion temperature * centre-of-mass velocity Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.048, year: 2010

TUMOR-GROWTH DELAY BY LASER-GENERATED SHOCK-WAVES

NARCIS (Netherlands)

de Reijke, T. M.; Schamhart, D. H.; Kurth, K. H.; Löwik, C. W.; Donkers, L. H.; Sterenborg, H. J.

1994-01-01

The antiproliferative effect of laser-generated shock waves (L-SW) was investigated on a human renal cell carcinoma, RC-8, grown subcutaneously in the nu/nu mouse. The RC-8 is characterized by the syndrome of humoral hypercalcemia of malignancy (HHM) associated with profound cachexia, increase of

Formation and decay of laser-generated shock waves

Energy Technology Data Exchange (ETDEWEB)

Cottet, F.; Romain, J.P.

1982-01-01

The process of formation and decay of laser-generated shock waves is described by a hydrodynamic model. Measurements of shock velocities are performed on copper foils for incident intensities between 3 x 10/sup 11/ and 3 x 10/sup 12/ W/cm/sup 2/, with the use of piezoelectric detectors. Maximum induced pressures are found between 0.5 and 1.2 Mbar in the intensity range considered. Analysis of the results with the shock-evolution model outlines the importance of the decay process of laser-generated shocks.

Formation of porous silicon oxide from substrate-bound silicon rich silicon oxide layers by continuous-wave laser irradiation

Science.gov (United States)

Wang, Nan; Fricke-Begemann, Th.; Peretzki, P.; Ihlemann, J.; Seibt, M.

2018-03-01

Silicon nanocrystals embedded in silicon oxide that show room temperature photoluminescence (PL) have great potential in silicon light emission applications. Nanocrystalline silicon particle formation by laser irradiation has the unique advantage of spatially controlled heating, which is compatible with modern silicon micro-fabrication technology. In this paper, we employ continuous wave laser irradiation to decompose substrate-bound silicon-rich silicon oxide films into crystalline silicon particles and silicon dioxide. The resulting microstructure is studied using transmission electron microscopy techniques with considerable emphasis on the formation and properties of laser damaged regions which typically quench room temperature PL from the nanoparticles. It is shown that such regions consist of an amorphous matrix with a composition similar to silicon dioxide which contains some nanometric silicon particles in addition to pores. A mechanism referred to as "selective silicon ablation" is proposed which consistently explains the experimental observations. Implications for the damage-free laser decomposition of silicon-rich silicon oxides and also for controlled production of porous silicon dioxide films are discussed.

Second-order interference of two independent and tunable single-mode continuous-wave lasers

International Nuclear Information System (INIS)

Liu Jianbin; Chen Hui; Zheng Huaibin; Xu Zhuo; Wei Dong; Zhou Yu; Gao Hong; Li Fu-Li

2016-01-01

The second-order temporal interference of two independent single-mode continuous-wave lasers is discussed by employing two-photon interference in Feynman’s path integral theory. It is concluded that whether the second-order temporal interference pattern can or cannot be retrieved via two-photon coincidence counting rate is dependent on the resolution time of the detection system and the frequency difference between these two lasers. Two identical and tunable single-mode continuous-wave diode lasers are employed to verify the predictions. These studies are helpful to understand the physics of two-photon interference with photons of different spectra. (paper)

Status of advanced ground-based laser interferometers for gravitational-wave detection

Science.gov (United States)

Dooley, K. L.; Akutsu, T.; Dwyer, S.; Puppo, P.

2015-05-01

Ground-based laser interferometers for gravitational-wave (GW) detection were first constructed starting 20 years ago and as of 2010 collection of several years’ worth of science data at initial design sensitivities was completed. Upgrades to the initial detectors together with construction of brand new detectors are ongoing and feature advanced technologies to improve the sensitivity to GWs. This conference proceeding provides an overview of the common design features of ground-based laser interferometric GW detectors and establishes the context for the status updates of each of the four gravitational-wave detectors around the world: Advanced LIGO, Advanced Virgo, GEO 600 and KAGRA.

Characterization of X-ray emission from laser generated plasma

Science.gov (United States)

Cannavò, Antonino; Torrisi, Lorenzo; Ceccio, Giovanni; Cutroneo, Mariapompea; Calcagno, Lucia; Sciuto, Antonella; Mazzillo, Massimo

2018-01-01

X-ray emission from laser generated plasma was studied at low (1010 W/cm2) and high (1018 W/cm2) intensity using ns and fs laser, respectively. Plasma characteristics were controlled trough the laser parameters, the irradiation conditions and the target properties. The X-ray spectra were acquired using fast detection technique based on SiC diodes with different active regions. The X-ray yield increases with the atomic number of the target, both at low and high intensity, and a similar empirical law has been obtained. The X-ray emission mechanisms from plasma are correlated to the plasma temperature and density and to the Coulomb charge particle acceleration, due to the charge separation effects produced in the non-equilibrium plasma. Functional dependences, theoretical approaches and interpretation of possible mechanism will be presented and discussed.

Characterization of X-ray emission from laser generated plasma

Directory of Open Access Journals (Sweden)

Cannavò Antonino

2018-01-01

Full Text Available X-ray emission from laser generated plasma was studied at low (1010 W/cm2 and high (1018 W/cm2 intensity using ns and fs laser, respectively. Plasma characteristics were controlled trough the laser parameters, the irradiation conditions and the target properties. The X-ray spectra were acquired using fast detection technique based on SiC diodes with different active regions. The X-ray yield increases with the atomic number of the target, both at low and high intensity, and a similar empirical law has been obtained. The X-ray emission mechanisms from plasma are correlated to the plasma temperature and density and to the Coulomb charge particle acceleration, due to the charge separation effects produced in the non-equilibrium plasma. Functional dependences, theoretical approaches and interpretation of possible mechanism will be presented and discussed.

Damage Detection on Thin-walled Structures Utilizing Laser Scanning and Standing Waves

Energy Technology Data Exchange (ETDEWEB)

Kang, Se Hyeok; Jeon, Jun Young; Kim, Du Hwan; Park, Gyuhae [Chonnam Nat’l Univ., Gwangju (Korea, Republic of); Kang, To; Han, Soon Woo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2017-05-15

This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.

Guided Wave Sensing In a Carbon Steel Pipe Using a Laser Vibrometer System

Science.gov (United States)

Ruíz Toledo, Abelardo; Salazar Soler, Jordi; Chávez Domínguez, Juan Antonio; García Hernández, Miguel Jesús; Turó Peroy, Antoni

2010-05-01

Non-Destructive Evaluation (NDE) techniques have achieved a great development during the last decades as a valuable tool for material characterization, manufacturing control and structural integrity tests. Among these tools, the guided wave technology has been rapidly extended because it reduces inspection time and costs compared to the ordinary point by point testing in large structures, as well as because of the possibility of inspecting under insulation and coating conditions. This fast development has motivated the creation of several inspection and material characterization systems including different technologies which can be combined with this technique. Different measurements systems based on laser techniques have been presented in order to inspect pipes, plates and diverse structures. Many of them are experimental systems of high cost and complexity which combine the employment of a laser for generation of waves in the structure and an interferometer for detection. Some of them employ air-coupled ultrasound generation transducers, with high losses in air and which demand high energy for exciting waves in materials of high stiffness. The combined employment of a commercial vibrometer system for Lamb wave sensing in plates has been successfully shown in the literature. In this paper we present a measurement system based on the combined employment of a piezoelectric wedge transducer and a laser vibrometer to sense guided acoustic waves in carbon steel pipes. The measurement system here presented is mainly compounded of an angular wedge transducer, employed to generate the guided wave and a commercial laser vibrometer used in the detection process. The wedge transducer is excited by means of a signal function generator whose output signal has been amplified with a power signal amplifier. A high precision positioning system is employed to place the laser beam at different points through the pipe surface. The signal detected by the laser vibrometer system is

Atomic data of Ti II from laser produced Ti plasmas by optical emission spectroscopy

International Nuclear Information System (INIS)

Refaie, A.I.; Farrag, A.A.; El Sharkawy, H.; El Sherbini, T.M.

2005-06-01

In the present study, the emission spectrum of titanium produced from laser induced plasma has been measured at different distances from the target. The Titanium target is irradiated by using the high power Q-switched Nd:YAG laser (λ=1064 nm) that generates energy 750 mJ/pulse of duration rate 6 ns and repetition rate 10 Hz in vacuum and at different distances. The variation of the distance from the target affects the measured plasma parameters, i.e. the electron density, the ion temperature and the velocity distribution. The electron density increases with the increase of the distance from the target. At a distance 0.6 mm from the target it decreases to 2.28·10 16 cm -3 . The temperature increases with the distance from the get until a distance of 1 mm, after that it decreases. It is found that the plasma velocity increases with the distance then it decreases again. Then, Energy levels and transition probabilities for 3d 2 4p →(3d 2 4s + 3d 3 ) lines have been determined by measurement of emission line intensities from an optically thin laser produced plasma of Ti II in vacuum. Calculations with intermediate coupling using Hartree-Fock wave functions have been carried out in order to place the experimental data on an absolute scale and also to evaluate the lifetimes. The plasma parameters in different regions of the plasma plume have been measured and used to obtain further transition probabilities. (author)

Time-space distribution of laser-induced plasma parameters and its influence on emission spectra of the laser plumes

International Nuclear Information System (INIS)

Ershov-Pavlov, E.A.; Katsalap, K.Yu.; Stepanov, K.L.; Stankevich, Yu.A.

2008-01-01

A physical model is developed accounting for dynamics and radiation of plasma plumes induced by nanosecond laser pulses on surface of solid samples. The model has been applied to simulate emission spectra of the laser erosion plasma at the elemental analysis of metals using single- and double-pulse excitation modes. Dynamics of the sample heating and expansion of the erosion products are accounted for by the thermal conductivity and gas dynamic equations, respectively, supposing axial symmetry. Using the resulting time-space distributions of the plasma parameters, emission spectra of the laser plumes are evaluated by solving the radiation transfer equation. Particle concentration in consecutive ionization stages is described by the Saha equation in the Debye approximation. The population of excited levels is determined according to Boltzmann distribution. Local characteristics determining spectral emission and absorption coefficients are obtained point-by-point along an observation line. Voigt spectral line profiles are considered with main broadening mechanisms taken into account. The plasma dynamics and plume emission spectra have been studied experimentally and by the model. A Q-switched Nd:YAG laser at 1064 nm wavelength has been used to irradiate Al sample with the pulses of 15 ns and 50 mJ duration and energy, respectively. It has resulted in maximum power density of 0.8 MW/cm 2 on the sample surface. The laser plume emission spectra have been recorded at a side-on observation. Problems of the spectra contrast and of the elemental analysis efficiency are considered relying on a comparative study of the measurement and simulation results at the both excitation modes

The amplitude modulation of laser diode emission with antireflection piezo films on mirrors

International Nuclear Information System (INIS)

Abrarov, S.M.; Karimov, Kh.S.; Akhmedov, Kh.M.

2001-01-01

Present article is devoted to amplitude modulation of laser diode emission with antireflection piezo films on mirrors. The modulator based on laser diode and the emission amplitude modulation of which is performed by electric field impact on antireflection piezo films applied on mirrors was studied.

Decay of a laser generated shock wave in an aluminium target

International Nuclear Information System (INIS)

Werdiger, M.

1993-09-01

When a shock wave arrives at the near surface of a solid material, a radical and fast change occurs in the reflection properties of the material. The phenomenon is used in the present work in order to develop a new way to measure the transit time of a shock wave in a target. A 10 milliwatt He:Ne laser is directed toward the rear surface of the target. The reflected beam arrives at a photo-diode with a fast rise time of 150 psec which detects the instant of the change in the reflection. This technique, called 'continuous back lightning', is used in experiments with aluminium foil thickness in the range of 40μm ≤x≥ 1000μm. The shock wave is induced by a laser pulse of an intensity of 3*10 13 W/cm 2 . The results show two main physical regimes: in the first one 40μ ≤x≥ 210μm, there is a constant shock wave velocity which in our experiments was measured to be (12.81±0.67)km/s. In the second range of the thickness where 300μm there is a decay of the shock velocity. For x ≥ 210μm the geometry is one dimensional for our experimental conditions, while for x ≥ 300μm the 1-D geometry changes to 2 dimensional (2-D) geometry. The 2-D shock wave decay asymptotically (x→∞ to an acoustic wave. shock wave is described by a pressure scaling as x -n (n is a positive constant). The phenomenological equation of the state is taken to be P=A**u s + B*u s 2 +Bu s , where P is the pressure, u s - the shock velocity, A and B are constants. Applying our experimental results to the solution of the differential equation in this model A*x 2 ± B*x=C*x -n yields a value of n in the range 3.16 ≤n≥ 3.51. This pressure scaling law agrees with the self-similar solution of a concentrated impact on a surface between two media. This situation is well simulated by the laser deposition energy on a metal surface. In the experiment a 5% accuracy is achieved. Such a good accuracy has not been achieved so far in a laser induced shock-wave measurements in solids. (author). 52 refs

Laser-generated shock-wave experiments in metals above 1 TPa

International Nuclear Information System (INIS)

Trainor, R.J.; Shaner, J.W.; Auerbach, J.M.; Phillion, D.W.

1978-01-01

Some initial experiments are described which form part of a new program aimed at significantly extending the range of high pressures and densities which may be explored in laboratory equation-of-state (EOS) experiments. These experiments will utilize high-energy lasers, such as those employed in the Laser Fusion Program at Lawrence Livermore Laboratory (LLL), to generate intense shock waves in materials of interest

Photonic synthesis of continuous‐wave millimeter‐wave signals using a passively mode‐locked laser diode and selective optical filtering

DEFF Research Database (Denmark)

Acedo, P.; Carpintero, G.; Criado, A.R.

2012-01-01

We report a photonic synthesis scheme for continuous wave millimeter‐wave signal generation using a single passively mode‐locked laser diode (PMLLD), optical filtering and photomixing in a fast photodiode.The phase noise of the photonically synthesized signals is evaluated and inherits...

A diode-end-pumped Nd:GYSGG continuous wave laser at 1104 nm

International Nuclear Information System (INIS)

Shen, B J; Kang, H X; Zhang, C G; Chen, P; Gao, R L; Liang, J; Gao, H J; Zhang, Q L; Sun, D L; Yin, S T; Luo, J Q

2013-01-01

The continuous wave (CW) laser performance of Nd:GYSGG at 1104 nm is investigated for the first time, to our knowledge. A CW laser output power of 4.7 W is obtained when the pump power of the 808 nm fiber coupled laser diode is 19.1 W, corresponding to a conversion efficiency of 24.6% and slope efficiency of 37%. (paper)

Laser discrimination by stimulated emission of a phosphor

Science.gov (United States)

Mathur, V. K.; Chakrabarti, K.

1991-01-01

A method for discriminating sources of UV, near infrared, and far infrared laser radiation was discovered. This technology is based on the use of a single magnesium sulfide phosphor doubly doped with rare earth ions, which is thermally/optically stimulated to generate colors correlatable to the incident laser radiation. The phosphor, after initial charging by visible light, exhibits green stimulated luminescence when exposed to a near infrared source (Nd: YAG laser). On exposure to far infrared sources (CO2 laser) the phosphor emission changes to orange color. A UV laser produces both an orange red as well as green color. A device using this phosphor is useful for detecting the laser and for discriminating between the near infrared, far infrared, and UV lasers. The technology is also capable of infrared laser diode beam profiling since the radiation source leaves an imprint on the phosphor that can be photographed. Continued development of the technology offers potential for discrimination between even smaller bandwidths within the infrared spectrum, a possible aid to communication or wavemixing devices that need to rapidly identify and process optical signals.

Laser-Induced Breakdown Spectroscopy Infrared Emission From Inorganic and Organic Substances

National Research Council Canada - National Science Library

Yang, C.S; Brown, E; Hommerich, U; Trivedi, S. B; Snyder, A. P; Samuels, A. C

2006-01-01

Laser-induced breakdown spectroscopy (LIBS) has been established as a powerful method for identifying trace elemental contaminants by analyzing the atomic spectral emission lines that result subsequent to plasmas generated by laser power...

Acoustic waves in transversely excited atmospheric CO2 laser discharges: effect on performance and reduction techniques

CSIR Research Space (South Africa)

von Bergmann, HM

2008-08-01

Full Text Available Results are presented on the influence of acoustic waves on the performance of high-repetition-rate TEA CO2 lasers. It is shown that acoustic waves generated inside the laser cavity lead to nonuniform discharges, resulting in a deterioration...

Numerical study of laser-induced blast wave coupled with unsteady ionization processes

International Nuclear Information System (INIS)

Ogino, Y; Ohnishi, N; Sawada, K

2008-01-01

We present the results of the numerical simulation of laser-induced blast wave coupled with rate equations to clarify the unsteady property of ionization processes during pulse heating. From comparison with quasi-steady computations, the plasma region expands more widely, which is sustained by the inverse-bremsstrahlung since an ionization equilibrium does not establish at the front of the plasma region. The delayed relaxation leads to the rapid expansion of the driving plasma and enhances the energy conversion efficiency from a pulse heating laser to the blast wave

Laser driven shock wave experiments for equation of state studies at megabar pressures

CERN Document Server

Pant, H C; Senecha, V K; Bandyopadhyay, S; Rai, V N; Khare, P; Bhat, R K; Gupta, N K; Godwal, B K

2002-01-01

We present the results from laser driven shock wave experiments for equation of state (EOS) studies of gold metal. An Nd:YAG laser chain (2 J, 1.06 mu m wavelength, 200 ps pulse FWHM) is used to generate shocks in planar Al foils and Al + Au layered targets. The EOS of gold in the pressure range of 9-13 Mbar is obtained using the impedance matching technique. The numerical simulations performed using the one-dimensional radiation hydrodynamic code support the experimental results. The present experimental data show remarkable agreement with the existing standard EOS models and with other experimental data obtained independently using laser driven shock wave experiments.

Laser driven shock wave experiments for equation of state studies at megabar pressures

International Nuclear Information System (INIS)

Pant, H C; Shukla, M; Senecha, V K; Bandyopadhyay, S; Rai, V N; Khare, P; Bhat, R K; Gupta, N K; Godwal, B K

2002-01-01

We present the results from laser driven shock wave experiments for equation of state (EOS) studies of gold metal. An Nd:YAG laser chain (2 J, 1.06 μm wavelength, 200 ps pulse FWHM) is used to generate shocks in planar Al foils and Al + Au layered targets. The EOS of gold in the pressure range of 9-13 Mbar is obtained using the impedance matching technique. The numerical simulations performed using the one-dimensional radiation hydrodynamic code support the experimental results. The present experimental data show remarkable agreement with the existing standard EOS models and with other experimental data obtained independently using laser driven shock wave experiments

LIGO: the Laser Interferometer Gravitational-Wave Observatory

International Nuclear Information System (INIS)

Abbott, B P; Abbott, R; Adhikari, R; Anderson, S B; Araya, M; Armandula, H; Aso, Y; Ballmer, S; Ajith, P; Allen, B; Aulbert, C; Allen, G; Amin, R S; Anderson, W G; Armor, P; Arain, M A; Aston, S; Aufmuth, P; Babak, S; Baker, P

2009-01-01

The goal of the Laser Interferometric Gravitational-Wave Observatory (LIGO) is to detect and study gravitational waves (GWs) of astrophysical origin. Direct detection of GWs holds the promise of testing general relativity in the strong-field regime, of providing a new probe of exotic objects such as black holes and neutron stars and of uncovering unanticipated new astrophysics. LIGO, a joint Caltech-MIT project supported by the National Science Foundation, operates three multi-kilometer interferometers at two widely separated sites in the United States. These detectors are the result of decades of worldwide technology development, design, construction and commissioning. They are now operating at their design sensitivity, and are sensitive to gravitational wave strains smaller than one part in 10 21 . With this unprecedented sensitivity, the data are being analyzed to detect or place limits on GWs from a variety of potential astrophysical sources.

Continuous-wave infrared optical gain and amplified spontaneous emission at ultralow threshold by colloidal HgTe quantum dots.

Science.gov (United States)

Geiregat, Pieter; Houtepen, Arjan J; Sagar, Laxmi Kishore; Infante, Ivan; Zapata, Felipe; Grigel, Valeriia; Allan, Guy; Delerue, Christophe; Van Thourhout, Dries; Hens, Zeger

2018-01-01

Colloidal quantum dots (QDs) raise more and more interest as solution-processable and tunable optical gain materials. However, especially for infrared active QDs, optical gain remains inefficient. Since stimulated emission involves multifold degenerate band-edge states, population inversion can be attained only at high pump power and must compete with efficient multi-exciton recombination. Here, we show that mercury telluride (HgTe) QDs exhibit size-tunable stimulated emission throughout the near-infrared telecom window at thresholds unmatched by any QD studied before. We attribute this unique behaviour to surface-localized states in the bandgap that turn HgTe QDs into 4-level systems. The resulting long-lived population inversion induces amplified spontaneous emission under continuous-wave optical pumping at power levels compatible with solar irradiation and direct current electrical pumping. These results introduce an alternative approach for low-threshold QD-based gain media based on intentional trap states that paves the way for solution-processed infrared QD lasers and amplifiers.

Continuous-wave infrared optical gain and amplified spontaneous emission at ultralow threshold by colloidal HgTe quantum dots

Science.gov (United States)

Geiregat, Pieter; Houtepen, Arjan J.; Sagar, Laxmi Kishore; Infante, Ivan; Zapata, Felipe; Grigel, Valeriia; Allan, Guy; Delerue, Christophe; van Thourhout, Dries; Hens, Zeger

2018-01-01

Colloidal quantum dots (QDs) raise more and more interest as solution-processable and tunable optical gain materials. However, especially for infrared active QDs, optical gain remains inefficient. Since stimulated emission involves multifold degenerate band-edge states, population inversion can be attained only at high pump power and must compete with efficient multi-exciton recombination. Here, we show that mercury telluride (HgTe) QDs exhibit size-tunable stimulated emission throughout the near-infrared telecom window at thresholds unmatched by any QD studied before. We attribute this unique behaviour to surface-localized states in the bandgap that turn HgTe QDs into 4-level systems. The resulting long-lived population inversion induces amplified spontaneous emission under continuous-wave optical pumping at power levels compatible with solar irradiation and direct current electrical pumping. These results introduce an alternative approach for low-threshold QD-based gain media based on intentional trap states that paves the way for solution-processed infrared QD lasers and amplifiers.

Status of advanced ground-based laser interferometers for gravitational-wave detection

International Nuclear Information System (INIS)

Dooley, K L; Akutsu, T; Dwyer, S; Puppo, P

2015-01-01

Ground-based laser interferometers for gravitational-wave (GW) detection were first constructed starting 20 years ago and as of 2010 collection of several years’ worth of science data at initial design sensitivities was completed. Upgrades to the initial detectors together with construction of brand new detectors are ongoing and feature advanced technologies to improve the sensitivity to GWs. This conference proceeding provides an overview of the common design features of ground-based laser interferometric GW detectors and establishes the context for the status updates of each of the four gravitational-wave detectors around the world: Advanced LIGO, Advanced Virgo, GEO 600 and KAGRA. (paper)

Multimode laser emission from dye-doped hollow polymer optical fibre

Indian Academy of Sciences (India)

2014-02-09

Feb 9, 2014 ... Fibre lasers; optical microcavities; whispering gallery modes. ... A blueshift in the mode structure was observed with decrease in fibre diameter leading to wide range tunability of the laser emission. ... International School of Photonics, Cochin University of Science & Technology, Cochin 682 022, India ...

Watt-level widely tunable single-mode emission by injection-locking of a multimode Fabry-Perot quantum cascade laser

Science.gov (United States)

Chevalier, Paul; Piccardo, Marco; Anand, Sajant; Mejia, Enrique A.; Wang, Yongrui; Mansuripur, Tobias S.; Xie, Feng; Lascola, Kevin; Belyanin, Alexey; Capasso, Federico

2018-02-01

Free-running Fabry-Perot lasers normally operate in a single-mode regime until the pumping current is increased beyond the single-mode instability threshold, above which they evolve into a multimode state. As a result of this instability, the single-mode operation of these lasers is typically constrained to few percents of their output power range, this being an undesired limitation in spectroscopy applications. In order to expand the span of single-mode operation, we use an optical injection seed generated by an external-cavity single-mode laser source to force the Fabry-Perot quantum cascade laser into a single-mode state in the high current range, where it would otherwise operate in a multimode regime. Utilizing this approach, we achieve single-mode emission at room temperature with a tuning range of 36 cm-1 and stable continuous-wave output power exceeding 1 W at 4.5 μm. Far-field measurements show that a single transverse mode is emitted up to the highest optical power, indicating that the beam properties of the seeded Fabry-Perot laser remain unchanged as compared to free-running operation.

Detection of Fatigue Damage by Using Frequency Attenuation of a Laser Ultrasonic Longitudinal Wave

International Nuclear Information System (INIS)

Park, Seung-Kyu; Baik, Sung-Hoon; Jung, Hyun-Kyu; Joo, Young-Sang; Cha, Hyung-Ki; Kang, Young-June

2006-01-01

The measurement of fatigue damage in nuclear power plant components is very important to prevent a catastrophic accident and the subsequent severe losses. Specifically, it is preferred to detect at an early stage of the fatigue damage. If the fatigue damage that is in danger of growing into a fracture is accurately detected, an appropriate treatment could be carried out to improve the condition. Although most engineers and designers take precautions against fatigue, some breakdowns of nuclear power plant components still occur due to fatigue damage. It is considered that ultrasound testing technique is the most promising method to detect the fatigue damage in many nondestructive testing methods. Ultrasound testing method has a variety of elastic waves, such as a longitudinal wave, a shear wave, a surface wave and a lamb wave. Also we can use various analysis methods, such as a velocity variation and a signal attenuation. Laser ultrasonic testing has attracted attention as a non-contact testing technique. This system consists of a pulse laser to remotely generate ultrasound and a laser interferometer to remotely measure the surface displacement due to the generated ultrasound. This noncontact testing technique has the following advantages over the conventional piezoelectric transducers. Firstly, the inspection system can be remotely operated for a structure in hostile environments, such as in high radioactivity, high temperatures and narrow spaces. Secondly, we can obtain lots of information from the received ultrasonic waveforms because the laser ultrasonic technique does not require fluid couplant which disturbs the ultrasonic waveforms. Thirdly, laser ultrasound has a wideband spectrum and a high spatial resolution. Therefore, the laser ultrasound provides more accurate information for a testing material and has potential for the detection of fatigue damage in various metals composing a nuclear power plant

Thermal Cracking in Westerly Granite Monitored Using Direct Wave Velocity, Coda Wave Interferometry, and Acoustic Emissions

Science.gov (United States)

Griffiths, L.; Lengliné, O.; Heap, M. J.; Baud, P.; Schmittbuhl, J.

2018-03-01

To monitor both the permanent (thermal microcracking) and the nonpermanent (thermo-elastic) effects of temperature on Westerly Granite, we combine acoustic emission monitoring and ultrasonic velocity measurements at ambient pressure during three heating and cooling cycles to a maximum temperature of 450°C. For the velocity measurements we use both P wave direct traveltime and coda wave interferometry techniques, the latter being more sensitive to changes in S wave velocity. During the first cycle, we observe a high acoustic emission rate and large—and mostly permanent—apparent reductions in velocity with temperature (P wave velocity is reduced by 50% of the initial value at 450°C, and 40% upon cooling). Our measurements are indicative of extensive thermal microcracking during the first cycle, predominantly during the heating phase. During the second cycle we observe further—but reduced—microcracking, and less still during the third cycle, where the apparent decrease in velocity with temperature is near reversible (at 450°C, the P wave velocity is decreased by roughly 10% of the initial velocity). Our results, relevant for thermally dynamic environments such as geothermal reservoirs, highlight the value of performing measurements of rock properties under in situ temperature conditions.

Allowable propagation of short pulse laser beam in a plasma channel and electromagnetic solitary waves

International Nuclear Information System (INIS)

Zhang, Shan; Hong, Xue-Ren; Wang, Hong-Yu; Xie, Bai-Song

2011-01-01

Nonparaxial and nonlinear propagation of a short intense laser beam in a parabolic plasma channel is analyzed by means of the variational method and nonlinear dynamics. The beam propagation properties are classified by five kinds of behaviors. In particularly, the electromagnetic solitary wave for finite pulse laser is found beside the other four propagation cases including beam periodically oscillating with defocussing and focusing amplitude, constant spot size, beam catastrophic focusing. It is also found that the laser pulse can be allowed to propagate in the plasma channel only when a certain relation for laser parameters and plasma channel parameters is satisfied. For the solitary wave, it may provide an effective way to obtain ultra-short laser pulse.

Inverse free electron laser beat-wave accelerator research

International Nuclear Information System (INIS)

Marshall, T.C.; Bhattacharjee, A.

1993-09-01

A calculation on the stabilization of the sideband instability in the free electron laser (FEL) and inverse FEL (IFEL) was completed. The issue arises in connection with the use of a tapered (''variable-parameter'') undulator of extended length, such as might be used in an ''enhanced efficiency'' traveling-wave FEL or an IFEL accelerator. In addition, the FEL facility at Columbia was configured as a traveling wave amplifier for a 10-kW signal from a 24-GHz magnetron. The space charge field in the bunches of the FEL was measured. Completed work has been published

Comparative study of acute lateral skin damage during radio wave and laser exposure

Directory of Open Access Journals (Sweden)

Dubensky V.V.

2017-09-01

Full Text Available The purpose was to study the depth and nature of the zones of thermal damage to the skin under radio wave and laser skin dissection during experiment. Material and Methods. The model of acute thermal damage was full-liner skin wounds of 20 nonlinear rats that were divided into 2 groups and operated by different methods. In the 1st group, the incisions were made by the apparatus of radio wave surgery (Surgitron DF S5, in the 2nd group the animals were operated with a laser surgical apparatus. The magnitude and structure of the lateral thermal damage was evaluated when analyzing the biopsy material. Results. During the study of experimental wounds, the extent of carbonation in the first group (operated with Surgitron DF S5 was 11.56±3.056 urn, coagulation necrosis 116.5±26.78 urn, and the hyper-thermiazone 148.42±60.171 urn. In the group of animals operated with a laser apparatus, the carbonization zone was 22.58±6.62 urn, the coagulation necrosis zone was 331.1±79.08 urn, and the hyperthermia extent was 376.2±53.27 urn. Conclusion. A comparative study of lateral skin damage in radio wave and laser skin dissection revealed a deeper thermal change in the skin and an increase in the extent of thermally altered structures under laser action: the carbonization zone was larger than for radio waves by 11.02 urn, coagulation necrosis by 214.6 urn, and the hyperthermia zone by 227.78 urn.

Laser-Bioplasma Interaction: Excitation and Suppression of the Brain Waves by the Multi-photon Pulsed-operated Fiber Lasers in the Ultraviolet Range of Frequencies

Science.gov (United States)

Stefan, V. Alexander; IAPS-team Team

2017-10-01

The novel study of the laser excitation-suppression of the brain waves is proposed. It is based on the pulsed-operated multi-photon fiber-laser interaction with the brain parvalbumin (PV) neurons. The repetition frequency matches the low frequency brain waves (5-100 Hz); enabling the resonance-scanning of the wide range of the PV neurons (the generators of the brain wave activity). The tunable fiber laser frequencies are in the ultraviolet frequency range, thus enabling the monitoring of the PV neuron-DNA, within the 10s of milliseconds. In medicine, the method can be used as an ``instantaneous-on-off anesthetic.'' Supported by Nikola Tesla Labs, Stefan University.

Energy of a shock wave generated in different metals under irradiation by a high-power laser pulse

International Nuclear Information System (INIS)

Gus'kov, S. Yu.; Kasperczuk, A.; Pisarczyk, T.; Borodziuk, S.; Ullschmied, J.; Krousky, E.; Masek, K.; Pfeifer, M.; Skala, J.; Pisarczyk, P.

2007-01-01

The energies of a shock wave generated in different metals under irradiation by a high-power laser beam were determined experimentally. The experiments were performed with the use of targets prepared from a number of metals, such as aluminum, copper, silver and lead (which belong to different periods of the periodic table) under irradiation by pulses of the first and third harmonics of the PALS iodine laser at a radiation intensity of approximately 10 14 W/cm 2 . It was found that, for heavy metals, like for light solid materials, the fraction of laser radiation energy converted into the energy of a shock wave under irradiation by a laser pulse of the third harmonic considerably (by a factor of 2-3) exceeds the fraction of laser radiation energy converted under irradiation by a laser pulse of the first harmonic. The influence of radiation processes on the efficiency of conversion of the laser energy into the energy of the shock wave was analyzed

Diode-pumped 2.8-μm laser emission from Er/sup 3+/:YLF at room temperature

International Nuclear Information System (INIS)

Kintz, G.J.; Allen, R.; Esterowitz, L.

1987-01-01

This paper details laser emission from an erbium-doped LiYF/sub 4/ sample longitudinally pumped at room temperature with a laser diode array observed in both pulsed and cw pumping. The threshold for pulsed emission is much less than for cw emission due to the lifetime of the terminal laser level being longer than the upper laser level. Depopulation of the lower laser level, which permits cw operation, is due to a cooperative upconversion process. The threshold energy for pulsed emission is 28 μJ when pumped with a 300-μs diode pulse. At 147 mW of diode power the threshold for cw emission occurs. The system relaxes to a steady state after 40 ms. The threshold for cw emission corresponds to --62 mW of diode power being absorbed into the crystal. Pulsed outputs of 21 μJ and cw outputs of 180 μW have been obtained. These low outputs and correspondingly low efficiencies are due to currently operating near threshold and in the self-terminating mode of the laser system. Higher concentrations and higher pumping rates should significantly improve the efficiency

Traveling waves in a free-electron laser with an electromagnetic wiggler

International Nuclear Information System (INIS)

Olumi, Mohsen; Maraghechi, B; Rouhani, M H

2011-01-01

The propagation of electromagnetic traveling wave in a free-electron laser (FEL) with an electromagnetic wiggler is investigated using the relativistic fluid-Maxwell formulation. By adapting the traveling-wave ansatz, three coupled, nonlinear ordinary differential equations are obtained describing the nonlinear propagation of the coupled wave. These equations may be used to study saturation in FELs. By linearizing the nonlinear equations dispersion relations for the traveling wave are obtained. Numerical solution of the small-signal traveling dispersion relation reveals the coupling of radiation to both slow and fast space-charge waves. It is shown that the traveling wave, which is not a normal mode in a laboratory frame, becomes a normal mode in terms of a transformed variable.

Laser emission in Nd3+ doped barium–titanium–silicate microspheres under continuous and chopped wave pumping in a non-coupled pumping scheme

International Nuclear Information System (INIS)

Martín, L L; Pérez-Rodríguez, C; Martín, I R; Navarro-Urrios, D; Ferrarese-Lupi, F; Garrido, B; Montserrat, J; Dominguez, C; Capuj, N

2013-01-01

Laser action using non-coupled excitation and detection of microspheres made of Nd 3+ doped barium–titanium–silicate glass has been demonstrated and measured. The microspheres have also been successfully deposited over Si 3 N 4 strip waveguides with a SiO 2 separation layer, thus enabling the laser emission extraction onto a CMOS compatible photonic circuit. The dynamics of the lasing wavelength and intensity has been studied as a function of the pump power and interpreted in terms of thermal effects generated through non-radiative recombination of the excited ions. (paper)

Generation of surface electromagnetic waves in terahertz spectral range by free-electron laser radiation and their refractive index determination

International Nuclear Information System (INIS)

Bogomolov, G.D.; Jeong, Uk Young; Zhizhin, G.N.; Nikitin, A.K.; Zavyalov, V.V.; Kazakevich, G.M.; Lee, Byung Cheol

2005-01-01

First experiments for observation of surface electromagnetic waves (SEW) in the terahertz spectral range generated on dense aluminum films covering the optical quality glass plates are presented in this paper. Coherent radiation of the new free-electron laser covering the frequency range from 30 to 100cm -1 was used. The interference technique employing SEW propagation in the part of one shoulder of the asymmetric interferometer was applied. From the interference pattern the real part of SEW's effective refractive index ae ' was determined for the two laser emission wavelengths: at λ=150μm-ae ' =1+5x10 -5 , at λ=110μm-ae ' =1+8x10 -4 . High sensitivity of the interference patterns to overlayers made of Ge and Si with thickness of 100nm was demonstrated as well

A pilot study to determine medical laser generated air contaminant emission rates for a simulated surgical procedure.

Science.gov (United States)

Lippert, Julia F; Lacey, Steven E; Lopez, Ramon; Franke, John; Conroy, Lorraine; Breskey, John; Esmen, Nurtan; Liu, Li

2014-01-01

The U.S. Occupational Safety and Health Administration (OSHA) estimates that half a million health-care workers are exposed to laser surgical smoke each year. The purpose of this study was to establish a methodology to (1) estimate emission rates of laser-generated air contaminants (LGACs) using an emission chamber, and to (2) perform a screening study to differentiate the effects of three laser operational parameters. An emission chamber was designed, fabricated, and assessed for performance to estimate the emission rates of gases and particles associated with LGACs during a simulated surgical procedure. Two medical lasers (Holmium Yttrium Aluminum Garnet [Ho:YAG] and carbon dioxide [CO2]) were set to a range of plausible medical laser operational parameters in a simulated surgery to pyrolyze porcine skin generating plume in the emission chamber. Power, pulse repetition frequency (PRF), and beam diameter were evaluated to determine the effect of each operational parameter on emission rate using a fractional factorial design. The plume was sampled for particulate matter and seven gas phase combustion byproduct contaminants (benzene, ethylbenzene, toluene, formaldehyde, hydrogen cyanide, carbon dioxide, and carbon monoxide): the gas phase emission results are presented here. Most of the measured concentrations of gas phase contaminants were below their limit of detection (LOD), but detectable measurements enabled us to determine laser operation parameter influence on CO2 emissions. Confined to the experimental conditions of this screening study, results indicated that beam diameter was statistically significantly influential and power was marginally statistically significant to emission rates of CO2 when using the Ho:YAG laser but not with the carbon dioxide laser; PRF was not influential vis-a-vis emission rates of these gas phase contaminants.

Electron beam injection during active experiments. 1. Electromagnetic wave emissions

International Nuclear Information System (INIS)

Winglee, R.M.; Kellogg, P.J.

1990-01-01

During the active injection of an electron beam, a broad spectrum of waves is generated. In this paper examples of spectra from the recent Echo 7 experiment are presented. These results show that the characteristics of the emissions can change substantially with altitude. Two-dimensional (three velocity) relativistic electromagnetic particle simulations are used to investigate the changes in the plasma conditions required to account for the observed spectral variations. It is shown that many of these variations can be accounted for by assuming that the ratio of the electron plasma frequency ω pe to cyclotron frequency Ω e is less than unity at the lower altitudes of about 200 km and near or above unity at apogee of about 300 km. In the former case, whistlers with a cutoff at ω pe , lower hybrid and plasma waves are driven by the parallel beam energy while electromagnetic fundamental z mode and second harmonic x mode and electrostatic upper hybrid waves are driven by the perpendicular beam energy through the master instability. E x B drifts driven by perpendicular electric fields associated with the beam-plasma interaction can also be important in generating maser emission, particularly for field-aligned injection where there is no intrinsic perpendicular beam energy. The power in the electrostatic waves is a few percent of the beam energy and that in the electromagnetic waves a few tenths of a percent. In the latter case, where ω pe /Ω e increases above unity, emission in the fundamental z mode and second harmonic x mode become suppressed

Rapidly tunable continuous-wave optical parametric oscillator pumped by a fiber laser

NARCIS (Netherlands)

Klein, M.E.; Gross, P.; Boller, Klaus J.; Auerbach, M.; Wessels, P.; Fallnich, C.

2003-01-01

We report on rapid, all-electronically controlled wavelength tuning of a continuous-wave (cw) optical parametric oscillator (OPO) pumped by an ytterbium fiber laser. The OPO is singly resonant for the signal wave and consists of a 40-mm-long periodically poled lithium niobate crystal in a

Comparing Laser Interferometry and Atom Interferometry Approaches to Space-Based Gravitational-Wave Measurement

Science.gov (United States)

Baker, John; Thorpe, Ira

2012-01-01

Thoroughly studied classic space-based gravitational-wave missions concepts such as the Laser Interferometer Space Antenna (LISA) are based on laser-interferometry techniques. Ongoing developments in atom-interferometry techniques have spurred recently proposed alternative mission concepts. These different approaches can be understood on a common footing. We present an comparative analysis of how each type of instrument responds to some of the noise sources which may limiting gravitational-wave mission concepts. Sensitivity to laser frequency instability is essentially the same for either approach. Spacecraft acceleration reference stability sensitivities are different, allowing smaller spacecraft separations in the atom interferometry approach, but acceleration noise requirements are nonetheless similar. Each approach has distinct additional measurement noise issues.

Effect of a target on the stimulated emission of microsecond CO2-laser pulses

Science.gov (United States)

Baranov, V. Iu.; Dolgov, V. A.; Maliuta, D. D.; Mezhevov, V. S.; Semak, V. V.

1987-12-01

The paper reports a change in the pulse shape of a TEA CO2 laser with an unstable cavity under the interaction between the laser radiation and a metal surface in the presence of a breakdown plasma. It is shown that a continuous change in the phase difference between the wave reflected in the cavity and the principal cavity wave gives rise to changes in the pulse shape and the appearance of power fluctuations. The possible effect of these phenomena on the laser treatment of materials is considered.

Ultrafast streak and framing technique for the observation of laser driven shock waves in transparent solid targets

International Nuclear Information System (INIS)

Van Kessel, C.G.M.; Sachsenmaier, P.; Sigel, R.

1975-01-01

Shock waves driven by laser ablation in plane transparent plexiglass and solid hydrogen targets have been observed with streak and framing techniques using a high speed image converter camera, and a dye laser as a light source. The framing pictures have been made by mode locking the dye laser and using a wide streak slit. In both materials a growing hemispherical shock wave is observed with the maximum velocity at the onset of laser radiation. (author)

Influence of plasma shock wave on the morphology of laser drilling in different environments

Science.gov (United States)

Zhai, Zhaoyang; Wang, Wenjun; Mei, Xuesong; Wang, Kedian; Yang, Huizhu

2017-05-01

Nanosecond pulse laser was used to study nickel-based alloy drilling and compare processing results of microholes in air environment and water environment. Through analysis and comparison, it's found that environmental medium had obvious influence on morphology of laser drilling. High-speed camera was used to shoot plasma morphology during laser drilling process, theoretical formula was used to calculate boundary dimension of plasma and shock wave velocity, and finally parameters were substituted into computational fluid dynamics simulation software to obtain solutions. Obtained analysis results could intuitively explain different morphological features and forming reasons between laser drilling in air environment and water environment in the experiment from angle of plasma shock waves. By comparing simulation results and experimental results, it could help to get an understanding of formation mechanism of microhole morphology, thus providing basis for further improving process optimization of laser drilling quality.

Ultraviolet versus infrared: Effects of ablation laser wavelength on the expansion of laser-induced plasma into one-atmosphere argon gas

International Nuclear Information System (INIS)

Ma Qianli; Motto-Ros, Vincent; Laye, Fabrice; Yu Jin; Lei Wenqi; Bai Xueshi; Zheng Lijuan; Zeng Heping

2012-01-01

Laser-induced plasma from an aluminum target in one-atmosphere argon background has been investigated with ablation using nanosecond ultraviolet (UV: 355 nm) or infrared (IR: 1064 nm) laser pulses. Time- and space-resolved emission spectroscopy was used as a diagnostics tool to have access to the plasma parameters during its propagation into the background, such as optical emission intensity, electron density, and temperature. The specific feature of nanosecond laser ablation is that the pulse duration is significantly longer than the initiation time of the plasma. Laser-supported absorption wave due to post-ablation absorption of the laser radiation by the vapor plume and the shocked background gas plays a dominant role in the propagation and subsequently the behavior of the plasma. We demonstrate that the difference in absorption rate between UV and IR radiations leads to different propagation behaviors of the plasma produced with these radiations. The consequence is that higher electron density and temperature are observed for UV ablation. While for IR ablation, the plasma is found with lower electron density and temperature in a larger and more homogenous axial profile. The difference is also that for UV ablation, the background gas is principally evacuated by the expansion of the vapor plume as predicted by the standard piston model. While for IR ablation, the background gas is effectively mixed to the ejected vapor at least hundreds of nanoseconds after the initiation of the plasma. Our observations suggest a description by laser-supported combustion wave for the propagation of the plasma produced by UV laser, while that by laser-supported detonation wave for the propagation of the plasma produced by IR laser. Finally, practical consequences of specific expansion behavior for UV or IR ablation are discussed in terms of analytical performance promised by corresponding plasmas for application with laser-induced breakdown spectroscopy.

Intra- and intercycle interference of angle-resolved electron emission in laser-assisted XUV atomic ionization

Science.gov (United States)

Gramajo, A. A.; Della Picca, R.; López, S. D.; Arbó, D. G.

2018-03-01

A theoretical study of ionization of the hydrogen atom due to an XUV pulse in the presence of an infrared (IR) laser is presented. Well-established theories are usually used to describe the laser-assisted photoelectron effect: the well-known soft-photon approximation firstly posed by Maquet et al (2007 J. Mod. Opt. 54 1847) and Kazansky’s theory in (2010 Phys. Rev. A 82, 033420). However, these theories completely fail to predict the electron emission perpendicularly to the polarization direction. Making use of a semiclassical model (SCM), we study the angle-resolved energy distribution of PEs for the case that both fields are linearly polarized in the same direction. We thoroughly analyze and characterize two different emission regions in the angle-energy domain: (i) the parallel-like region with contribution of two classical trajectories per optical cycle and (ii) the perpendicular-like region with contribution of four classical trajectories per optical cycle. We show that our SCM is able to assess the interference patterns of the angle-resolved PE spectrum in the two different mentioned regions. Electron trajectories stemming from different optical laser cycles give rise to angle-independent intercycle interferences known as sidebands. These sidebands are modulated by an angle-dependent coarse-grained structure coming from the intracycle interference of the electron trajectories born during the same optical cycle. We show the accuracy of our SCM as a function of the time delay between the IR and the XUV pulses and also as a function of the laser intensity by comparing the semiclassical predictions of the angle-resolved PE spectrum with the continuum-distorted wave strong field approximation and the ab initio solution of the time-dependent Schrödinger equation.

Quantitative evaluation of the mechanical strength of titanium/composite bonding using laser-generated shock waves

Science.gov (United States)

Ducousso, M.; Bardy, S.; Rouchausse, Y.; Bergara, T.; Jenson, F.; Berthe, L.; Videau, L.; Cuvillier, N.

2018-03-01

Intense acoustic shock waves were applied to evaluate the mechanical strength of structural epoxy bonds between a TA6V4 titanium alloy and a 3D woven carbon/epoxy composite material. Two bond types with different mechanical strengths were obtained from two different adhesive reticulations, at 50% and 90% of conversion, resulting in longitudinal static strengths of 10 and 39 MPa and transverse strengths of 15 and 35 MPa, respectively. The GPa shock waves were generated using ns-scale intense laser pulses and reaction principles to a confined plasma expansion. Simulations taking into account the laser-matter interaction, plasma relaxation, and non-linear shock wave propagation were conducted to aid interpretation of the experiments. Good correlations were obtained between the experiments and the simulation and between different measurement methods of the mechanical strength (normalized tests vs laser-generated shock waves). Such results open the door toward certification of structural bonding.

Evidence for laser emission from the TICT exciplex of coumarin dyes

International Nuclear Information System (INIS)

Masilamani, V.

1987-06-01

This paper gives confirming evidence for the possibility of super radiant laser emission from the Twisted Internal Charge Transfer (TICT) conformation in exicted state complexation with the solvent, of coumarin family of laser dyes. (author). 6 refs, 1 fig., 2 tabs

Numerical Analysis on Thermal Non-Equilibrium Process of Laser-Supported Detonation Wave in Axisymmetric Nozzle

International Nuclear Information System (INIS)

Shiraishi, Hiroyuki

2008-01-01

Numerical Analyses on Laser-Supported Plasma (LSP) have been performed for researching the mechanism of laser absorption occurring in the laser propulsion system. Above all, Laser-Supported Detonation (LSD), categorized as one type of LSP, is considered as one of the most important phenomena because it can generate high pressure and high temperature for performing highly effective propulsion. For simulating generation and propagation of LSD wave, I have performed thermal non-equilibrium analyses by Navier-stokes equations, using a CO 2 gasdynamic laser into an inert gas, where the most important laser absorption mechanism for LSD propagation is Inverse Bremsstrahlung. As a numerical method, TVD scheme taken into account of real gas effects and thermal non-equilibrium effects by using a 2-temperature model, is applied. In this study, I analyze a LSD wave propagating through a conical nozzle, where an inner space of an actual laser propulsion system is simplified

Supersonic propagation of ionization waves in an underdense, laser-produced plasma

International Nuclear Information System (INIS)

Constantin, C.; Back, C.A.; Fournier, K.B.; Gregori, G.; Landen, O.L.; Glenzer, S.H.; Dewald, E.L.; Miller, M.C.

2005-01-01

A laser-driven supersonic ionization wave propagating through a millimeter-scale plasma of subcritical density up to 2-3 keV electron temperatures was observed. Propagation velocities initially ten times the sound speed were measured by means of time-resolved x-ray imaging diagnostics. The measured ionization wave trajectory is modeled analytically and by a two-dimensional radiation-hydrodynamics code. The comparison to the modeling suggests that nonlocal heat transport effects may contribute to the attenuation of the heat-wave propagation

Measurements of the parametric decay of CO2 laser radiation into plasma waves at quarter critical density using ruby laser Thomson scattering

International Nuclear Information System (INIS)

Schuss, J.J.; Chu, T.K.; Johnson, L.C.

1977-11-01

We report the results of small-angle ruby laser Thomson scattering measurements of the parametric excitation of plasma waves by CO 2 laser radiation at quarter-critical density in a laser-heated gas target plasma. From supplementary data obtained from interferometry and large-angle ruby laser scattering we infer that the threshold conditions for a convective decay are satisfied

Tapered amplifier laser with frequency-shifted feedback

Directory of Open Access Journals (Sweden)

A. Bayerle, S. Tzanova, P. Vlaar, B. Pasquiou, F. Schreck

2016-10-01

Full Text Available We present a frequency-shifted feedback (FSF laser based on a tapered amplifier. The laser operates as a coherent broadband source with up to 370GHz spectral width and 2.3us coherence time. If the FSF laser is seeded by a continuous-wave laser a frequency comb spanning the output spectrum appears in addition to the broadband emission. The laser has an output power of 280mW and a center wavelength of 780nm. The ease and flexibility of use of tapered amplifiers makes our FSF laser attractive for a wide range of applications, especially in metrology.

Visible laser induced positive ion emissions from NaCl nanoparticles prepared by droplet rapid drying

International Nuclear Information System (INIS)

Sun, Mao-Xu; Guo, Deng-Zhu; Xing, Ying-Jie; Zhang, Geng-Min

2012-01-01

Highlights: ► NaCl nanoparticles were firstly prepared by heat induced explosion on silicon wafer. ► We found that laser induced ion emissions from NaCl nanoparticles are more prominent. ► We found that water adsorption can efficiently enhance laser induced ion emissions. ► The ultra-photothermal effect in NaCl nanoparticles was observed and explained. - Abstract: A novel convenient way for the formation of sodium chloride (NaCl) nanoparticles on silicon wafer is proposed by using a droplet rapid drying method. The laser induced positive ion emissions from NaCl nanoparticles with and without water treatment is demonstrated by using a laser desorption/ionization time-of-flight mass spectrometer, with laser intensity well below the plasma formation threshold. It is found that the positive ion emissions from NaCl nanoparticles are obviously higher than that from microsize NaCl particles under soft 532 nm laser irradiations, and water adsorption can efficiently enhance the ion emissions from NaCl nanoparticles. The initial kinetic energies of the emitted ions are estimated as 16–17 eV. The synergy of the ultra-thermal effect in nanomaterials, the defect-mediated multiphoton processes, and the existence of intermediate states in NaCl-water interfaces are suggested as the mechanisms.

Measurement of the development and evolution of shock waves in a laser-induced gas breakdown plasma

International Nuclear Information System (INIS)

Chu, T.K.; Johnson, L.C.

1975-01-01

Space- and time-resolved interferometric measurements of electron density in CO 2 -laser produced plasmas in helium or hydrogen are made near the laser focal spot. Immediately after breakdown, a rapidly growing region of approximately uniform plasma density appears at the focal spot. After a few tens of nanoseconds, shock waves are formed, propagating both transverse and parallel to the incident laser beam direction. Behind the transverse propagating shock is an on-axis density minimum, which results in laser-beam self-trapping. The shock wave propagating toward the focusing lens effectively shields the interior plasma from the incident beam because the lower plasma temperature and higher plasma density in the shock allow strong absorption of the incident beam energy. By arranging the laser radiation-plasma interaction to begin at a plasma-vacuum interface at the exit of a free-expansion jet, this backward propagating shock wave is eliminated, thus permitting efficient energy deposition in the plasma interior

The numerical simulation of Lamb wave propagation in laser welding of stainless steel

Science.gov (United States)

Zhang, Bo; Liu, Fang; Liu, Chang; Li, Jingming; Zhang, Baojun; Zhou, Qingxiang; Han, Xiaohui; Zhao, Yang

2017-12-01

In order to explore the Lamb wave propagation in laser welding of stainless steel, the numerical simulation is used to show the feature of Lamb wave. In this paper, according to Lamb dispersion equation, excites the Lamb wave on the edge of thin stainless steel plate, and presents the reflection coefficient for quantizing the Lamb wave energy, the results show that the reflection coefficient is increased with the welding width increasing,

Nanosecond Nd-YAG laser induced plasma emission characteristics in low pressure CO{sub 2} ambient gas for spectrochemical application on Mars

Energy Technology Data Exchange (ETDEWEB)

Lie, Zener Sukra; Kurniawan, Koo Hendrik, E-mail: kurnia18@cbn.net.id [Research Center of Maju Makmur Mandiri Foundation, 40/80 Srengseng Raya, Jakarta 11630 (Indonesia); Pardede, Marincan [Department of Electrical Engineering, University of Pelita Harapan, 1100 M.H. Thamrin Boulevard, Lippo Village, Tangerang 15811 (Indonesia); Tjia, May On [Research Center of Maju Makmur Mandiri Foundation, 40/80 Srengseng Raya, Jakarta 11630 (Indonesia); Physics of Magnetism and Photonics Group, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, 10 Ganesha, Bandung 40132 (Indonesia); Kagawa, Kiichiro [Fukui Science Education Academy, Takagi Chuou 2 choume, Fukui 910-0804 (Japan); Research Center of Maju Makmur Mandiri Foundation, 40/80 Srengseng Raya, Jakarta 11630 (Indonesia)

2015-08-28

An experimental study is conducted on the possibility and viability of performing spectrochemical analysis of carbon and other elements in trace amount in Mars, in particular, the clean detection of C, which is indispensible for tracking the sign of life in Mars. For this study, a nanosecond Nd-YAG laser is employed to generate plasma emission from a pure copper target in CO{sub 2} ambient gas of reduced pressure simulating the atmospheric condition of Mars. It is shown that the same shock wave excitation mechanism also works this case while exhibiting remarkably long cooling stage. The highest Cu emission intensities induced by 4 mJ laser ablation energy is attained in 600 Pa CO{sub 2} ambient gas. Meanwhile the considerably weaker carbon emission from the CO{sub 2} gas appears relatively featureless over the entire range of pressure variation, posing a serious problem for sensitive trace analysis of C contained in a solid sample. Our time resolved intensity measurement nevertheless reveals earlier appearance of C emission from the CO{sub 2} gas with a limited duration from 50 ns to 400 ns after the laser irradiation, well before the initial appearance of the long lasting C emission from the solid target at about 1 μs, due to the different C-releasing processes from their different host materials. The unwanted C emission from the ambient gas can thus be eliminated from the detected spectrum by a proper time gated detection window. The excellent spectra of carbon, aluminum, calcium, sodium, hydrogen, and oxygen obtained from an agate sample are presented to further demonstrate and verify merit of this special time gated LIBS using CO{sub 2} ambient gas and suggesting its viability for broad ranging in-situ applications in Mars.

Laser-induced pressure-wave and barocaloric effect during flash diffusivity measurements

International Nuclear Information System (INIS)

Wang, Hsin; Porter, Wallace D.; Dinwiddie, Ralph Barton

2017-01-01

We report laser-induced pressure-wave and barocaloric effect captured by an infrared detector during thermal diffusivity measurements. Very fast (< 1 ms) and negative transients during laser flash measurements were captured by the infrared detector on thin, high thermal conductivity samples. Standard thermal diffusivity analysis only focuses the longer time scale thermal transient measured from the back surface due to thermal conduction. These negative spikes are filtered out and ignored as noise or anomaly from instrument. This study confirmed that the initial negative signal was indeed a temperature drop induced by the laser pulse. The laser pulse induced instantaneous volume expansion and the associated cooling in the specimen can be explained by the barocaloric effect. The initial cooling (< 100 microsecond) is also known as thermoelastic effect in which a negative temperature change is generated when the material is elastically deformed by volume expansion. A subsequent temperature oscillation in the sample was observed and only lasted about one millisecond. The pressure-wave induced thermal signal was systematically studied and analyzed. In conclusion, the underlying physics of photon-mechanical-thermal energy conversions and the potential of using this signal to study barocaloric effects in solids are discussed.

Welding induced residual stress evaluation using laser-generated Rayleigh waves

Science.gov (United States)

Ye, Chong; Zhou, Yuanlai; Reddy, Vishnu V. B.; Mebane, Aaron; Ume, I. Charles

2018-04-01

Welding induced residual stress could affect the dimensional stability, fatigue life, and chemical resistance of the weld joints. Ultrasonic method serves as an important non-destructive tool for the residual stress evaluation due to its easy implementation, low cost and wide application to different materials. Residual stress would result in the ultrasonic wave velocity variation, which is the so called acoustoelastic effect. In this paper, Laser/EMAT ultrasonic technique was proposed to experimentally study the relative velocity variation ΔV/V of Rayleigh wave, which has the potential to evaluate surface/subsurface longitudinal residual stress developed during the Gas Metal Arc Welding process. Broad band ultrasonic waves were excited by pulsed Q-Switched Nd: YAG laser. An electromagnetic acoustic transducer (EMAT) attached to the welded plates was used to capture the Rayleigh wave signals propagating along the weld seam direction. Different time of flight measurements were conducted by varying the distance between the weld seam and Rayleigh wave propagating path in the range of 0 to 45 mm. The maximum relative velocity difference was found on the weld seam. With the increasing distance away from the weld seam, the relative velocity difference sharply decreased to negative value. With further increase in distance, the relative velocity difference slowly increased and approached zero. The distribution of relative velocity variations indicates that tensile stress appears in the melted zone as it becomes compressive near the heat-affected zone.

Electron beam injection during active experiments. I - Electromagnetic wave emissions

Science.gov (United States)

Winglee, R. M.; Kellogg, P. J.

1990-01-01

The wave emissions produced in Echo 7 experiment by active injections of electron beams were investigated to determine the properties of the electromagnetic and electrostatic fields for both the field-aligned and cross-field injection in such experiments and to evaluate the sources of free energy and relative efficiencies for the generation of the VLF and HF emissions. It is shown that, for typical beam energies in active experiments, electromagnetic effects do not substantially change the bulk properties of the beam, spacecraft charging, and plasma particle acceleration. Through simulations, beam-generated whistlers; fundamental z-mode and harmonic x-mode radiation; and electrostatic electron-cyclotron, upper-hybrid, Langmuir, and lower-hybrid waves were identified. The characteristics of the observed wave spectra were found to be sensitive to both the ratio of the electron plasma frequency to the cyclotron frequency and the angle of injection relative to the magnetic field.

New method for measuring time-resolved spectra of lanthanide emission using square-wave excitation

International Nuclear Information System (INIS)

Qin, Feng; Zhao, Hua; Cai, Wei; Duan, Qianqian; Zhang, Zhiguo; Cao, Wenwu

2013-01-01

A method using modulated continuous wave (CW) visible laser to measure time-resolved fluorescence spectra of trivalent rare-earth ions has been developed. Electro-optic modulator was used to modulate the CW pumping laser with a rise time of 2 μs. CW Nd 3+ lasers were used as examples to present the method. Upconversion dynamic process of Ho 3+ was studied utilizing a 532 nm CW laser. Quantum cutting dynamic process from Tb 3+ to Yb 3+ was analyzed by a 473 nm CW laser. This method can be applied to any CW laser such as He-Ne laser, Ar + laser, Kr + laser, Ti:sapphire laser, etc

Pump depletion limited evolution of the relativistic plasma wave-front in a forced laser-wakefield accelerator

International Nuclear Information System (INIS)

Fang, F; Clayton, C E; Marsh, K A; Pak, A E; Ralph, J E; Joshi, C; Lopes, N C

2009-01-01

In a forced laser-wakefield accelerator experiment (Malka et al 2002 Science 298 1596) where the length of the pump laser pulse is a few plasma periods long, the leading edge of the laser pulse undergoes frequency downshifting and head erosion as the laser energy is transferred to the wake. Therefore, after some propagation distance, the group velocity of the leading edge of the pump pulse-and thus of the driven electron plasma wave-will slow down. This can have implications for the dephasing length of the accelerated electrons and therefore needs to be understood experimentally. We have carried out an experimental investigation where we have measured the velocity v f of the 'wave-front' of the plasma wave driven by a nominally 50 fs (full width half maximum), intense (a 0 ≅ 1), 0.815 μm laser pulse. To determine the speed of the wave front, time- and space-resolved refractometry, interferometry and Thomson scattering were used. Although a laser pulse propagating through a relatively low-density plasma (n e = 1.3 x 10 19 cm -3 ) showed no measurable changes in v f over 1.3 mm (and no accelerated electrons), a high-density plasma (n e = 5 x 10 19 cm -3 ) generated accelerated electrons and showed a continuous change in v f as the laser pulse propagated through the plasma. Possible causes and consequences of the observed v f evolution are discussed.

Thermally excited proton spin-flip laser emission in tokamaks

International Nuclear Information System (INIS)

Arunasalam, V.; Greene, G.J.

1993-07-01

Based on statistical thermodynamic fluctuation arguments, it is shown here for the first time that thermally excited spin-flip laser emission from the fusion product protons can occur in large tokamak devices that are entering the reactor regime of operation. Existing experimental data from TFTR supports this conjecture, in the sense that these measurements are in complete agreement with the predictions of the quasilinear theory of the spin-flip laser

Hybrid vertical-cavity laser with lateral emission into a silicon waveguide

DEFF Research Database (Denmark)

Park, Gyeong Cheol; Xue, Weiqi; Taghizadeh, Alireza

2015-01-01

into the waveguide integrated with the laser. This laser has the advantages of long-wavelength vertical-cavity surface-emitting lasers, such as low threshold and high side-mode suppression ratio, while allowing integration with silicon photonic circuits, and is fabricated using CMOS compatible processes. It has......We experimentally demonstrate an optically-pumped III-V/Si vertical-cavity laser with lateral emission into a silicon waveguide. This on-chip hybrid laser comprises a distributed Bragg reflector, a III-V active layer, and a high-contrast grating reflector, which simultaneously funnels light...

Gravitational wave emission from the coalescence of white dwarfs

International Nuclear Information System (INIS)

Garcia-Berro, E; Loren-Aguilar, P; Isern, J; Pedemonte, A G; Guerrero, J; Lobo, J A

2005-01-01

We have computed the gravitational wave emission arising from the coalescence of several close white dwarf binary systems. In order to do so, we have followed the evolution of such systems using a smoothed particle hydrodynamics code. Here we present some of the results obtained so far, paying special attention to the detectability of the emitted gravitational waves. Within this context, we show which could be the impact of individual merging episodes for LISA

Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode.

Science.gov (United States)

Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

2015-11-16

Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging.

Experimental realization of millimeter-wave amplification by a sheet beam free electron laser

International Nuclear Information System (INIS)

Zhang, Z.; Destler, W.W.; Granatstein, V.L.; Antonsen, T.M. Jr.; Levush, B.; Rodgers, J.; Cheng, S.

1994-01-01

We report an observation of millimeter-wave (94 GHz) amplification in a sheet beam, short period, planar wiggler, free electron laser amplifier. The observed gain is about 5 dB for a 530 keV, 4 A beam through a 54 cm wiggler. Wave energy absorption was also observed when the beam energy is off-resonance. Experimental results are in good agreement with numerical simulation. This amplifier configuration has potential for producing equally high output power but at relatively low voltage compared with longer period free electron lasers

Analysis of time- and space-resolved Na-, Ne-, and F-like emission from a laser-produced bromine plasma

International Nuclear Information System (INIS)

Goldstein, W.H.; Young, B.K.F.; Osterheld, A.L.; Stewart, R.E.; Walling, R.S.; Bar-Shalom, A.

1991-01-01

Advances in the efficiency and accuracy of computational atomic physics and collisional radiative modeling promise to place the analysis and diagnostic application of L-shell emission on a par with the simpler K-shell regime. Coincident improvements in spectroscopic plasma measurements yield optically thin emission spectra from small, homogeneous regions of plasma, localized both in space and time. Together, these developments can severely test models for high-density, high-temperature plasma formation and evolution, and non-LTE atomic kinetics. In this paper we present highly resolved measurements of n=3 to n=2 X-ray line emission from a laser-produced bromine micro plasma. The emission is both space- and time-resolved, allowing us to apply simple, steady-state, 0-dimensional spectroscopic models to the analysis. These relativistic, multi-configurational, distorted wave collisional-radiative models were created using the HULLAC atomic physics package. Using these models, we have analyzed the F-like, Ne-like and Na-like (satellite) spectra with respect to temperature, density and charge-state distribution. This procedure leads to a full characterization of the plasma conditions. 9 refs., 3 figs

Comparative study of the expansion dynamics of laser-driven plasma and shock wave in in-air and underwater ablation regimes

Science.gov (United States)

Nguyen, Thao T. P.; Tanabe, Rie; Ito, Yoshiro

2018-03-01

We compared the expansion characteristics of the plasma plumes and shock waves generated in laser-induced shock process between the two ablation regimes: in air and under water. The observation was made from the initial moment when the laser pulse hit the target until 1.5 μs. The shock processes were driven by focusing a single laser pulse (1064 nm, FWHM = 13 ns) onto the surface of epoxy-resin blocks using a 40-mm focal length lens. The estimated laser intensity at the target plane is approximate to 9 ×109Wcm-2 . We used the fast-imaging technique to observe the expansion of the plasma plume and a custom-designed time-resolved photoelasticity imaging technique to observe the propagation of shock waves with the time resolution of nanoseconds. We found that at the same intensity of the laser beam, the plasma expansion during the laser pulse follows different mechanisms: the plasma plume that grows in air follows a radiation-wave model while a detonation-wave model can explain the expansion of the plasma plume induced in water. The ideal blast wave theory can be used to predict the decay of the shock wave in air but is not appropriate to describe the decay of the shock wave induced under water.

MEASUREMENTS OF ABSORPTION, EMISSIVITY REDUCTION, AND LOCAL SUPPRESSION OF SOLAR ACOUSTIC WAVES IN SUNSPOTS

International Nuclear Information System (INIS)

Chou, D.-Y.; Liang, Z.-C.; Yang, M.-H.; Zhao Hui; Sun, M.-T.

2009-01-01

The power of solar acoustic waves in magnetic regions is lower relative to the quiet Sun. Absorption, emissivity reduction, and local suppression of acoustic waves contribute to the observed power reduction in magnetic regions. We propose a model for the energy budget of acoustic waves propagating through a sunspot in terms of the coefficients of absorption, emissivity reduction, and local suppression of the sunspot. Using the property that the waves emitted along the wave path between two points have no correlation with the signal at the starting point, we can separate the effects of these three mechanisms. Applying this method to helioseismic data filtered with direction and phase-velocity filters, we measure the fraction of the contribution of each mechanism to the power deficit in the umbra of the leading sunspot of NOAA 9057. The contribution from absorption is 23.3 ± 1.3%, emissivity reduction 8.2 ± 1.4%, and local suppression 68.5 ± 1.5%, for a wave packet corresponding to a phase velocity of 6.98 x 10 -5 rad s -1 .

Design and evaluation of laser diodes with distributed bragg reflectors and diffracted waves amplifiers bound to their association into a powerful coherent source; Conception et Evaluation de Diodes Laser a Reflecteurs de Bragg Distribues et d`amplificateurs a onde Diffractee et vue de leur Association en une Source Coherente de Puissance

Energy Technology Data Exchange (ETDEWEB)

Dagens, B.

1995-09-29

This work is concerned with the evaluation of AlGaAs/GaAs MOPAs (Master Oscillator Power Amplifier) based on the association of a distributed Bragg reflector (DBR) quantum well laser diode with an optical power amplifier. For any given structure and incident wave, the software SIMLAS allows to describe the behaviour of a travelling wave amplifier and to obtain its working characteristics including the output power, the amplified spontaneous emission and the quality of the output beam. This model takes into account the nonlinear interaction between the wave, the injected carriers distribution and the complex index of the structure. The application of the software to a flared non-guided amplified shows that the output power associated with a good beam quality is limited to a range less than one watt. Then a new design is proposed to greatly improve this performance. The modelling software of the DBR laser takes into account wave propagation in a second-order grating structure and the gain and absorption properties in the quantum well. Thus, the output optical power, efficiency, threshold current and model discrimination of the device can be predicted. The model has been used to establish the definition of design criteria in order to promote edge emission relative to surface emission. Finally the fabrication of each device is established. Special attention is paid to the design of the grating region. The fabrication process is validated by the prototypes performance. (author) refs.

Experimental and numerical investigations of shock and shear wave propagation induced by femtosecond laser irradiation in epoxy resins

International Nuclear Information System (INIS)

Ecault, Romain; Touchard, Fabienne; Boustie, Michel; Berthe, Laurent; Lescoute, Emilien; Sollier, Arnaud; Voillaume, Hubert

2015-01-01

In this work, original shock experiments are presented. Laser-induced shock and shear wave propagations have been observed in an epoxy resin, in the case of femtosecond laser irradiation. A specific time-resolved shadowgraphy setup has been developed using the photoelasticimetry principle to enhance the shear wave observation. Shear waves have been observed in epoxy resin after laser irradiation. Their propagation has been quantified in comparison with the main shock propagation. A discussion, hinging on numerical results, is finally given to improve understanding of the phenomenon. (paper)

Supersonic Heat Wave Propagation in Laser-Produced Underdense Plasma for Efficient X-Ray Generation

International Nuclear Information System (INIS)

Tanabe, M.; Nishimura, H.; Fujioka, S.; Nagai, K.; Iwamae, A.; Ohnishi, N.; Fournier, K.B.; Girard, F.; Primout, M.; Villette, B.; Tobin, M.; Mima, K.

2008-01-01

We have observed supersonic heat wave propagation in a low-density aerogel target (ρ ∼ 3.2 mg/cc) irradiated at the intensity of 4 x 10 14 W/cm 2 . The heat wave propagation was measured with a time-resolved x-ray imaging diagnostics, and the results were compared with simulations made with the two-dimensional radiation-hydrodynamic code, RAICHO. Propagation velocity of the ionization front gradually decreased as the wave propagates into the target. The reason of decrease is due to increase of laser absorption region as the front propagates and interplay of hydrodynamic motion and reflection of laser propagation. These features are well reported with the simulation

Reflection and diffraction of atomic de Broglie waves by evanescent laser waves. Bare-state method

International Nuclear Information System (INIS)

Feng, Xiaoping; Witte, N.S.; Hollenberg, C.L.; Opat, G.

1994-01-01

Two methods are presented for the investigation of the reflection and diffraction of atoms by gratings formed either by standing or travelling evanescent laser waves. Both methods use the bare-state rather than dressed-state picture. One method is based on the Born series, whereas the other is based on the Laplace transformation of the coupled differential equations. The two methods yield the same theoretical expressions for the reflected and diffracted atomic waves in the whole space including the interaction and the asymptotic regions. 1 ref., 1 fig

Excitation of Accelerating Plasma Waves by Counter-propagating Laser Beams

International Nuclear Information System (INIS)

Gennady Shvets; Nathaniel J. Fisch; Alexander Pukhov

2001-01-01

Generation of accelerating plasma waves using two counter-propagating laser beams is considered. Colliding-beam accelerator requires two laser pulses: the long pump and the short timing beam. We emphasize the similarities and differences between the conventional laser wakefield accelerator and the colliding-beam accelerator (CBA). The highly nonlinear nature of the wake excitation is explained using both nonlinear optics and plasma physics concepts. Two regimes of CBA are considered: (i) the short-pulse regime, where the timing beam is shorter than the plasma period, and (ii) the parametric excitation regime, where the timing beam is longer than the plasma period. Possible future experiments are also outlined

Generation of spin waves by a train of fs-laser pulses: a novel approach for tuning magnon wavelength

OpenAIRE

Savochkin, I. V.; J?ckl, M.; Belotelov, V. I.; Akimov, I. A.; Kozhaev, M. A.; Sylgacheva, D. A.; Chernov, A. I.; Shaposhnikov, A. N.; Prokopov, A. R.; Berzhansky, V. N.; Yakovlev, D. R.; Zvezdin, A. K.; Bayer, M.

2017-01-01

Currently spin waves are considered for computation and data processing as an alternative to charge currents. Generation of spin waves by ultrashort laser pulses provides several important advances with respect to conventional approaches using microwaves. In particular, focused laser spot works as a point source for spin waves and allows for directional control of spin waves and switching between their different types. For further progress in this direction it is important to manipulate with ...

Laser polarization dependence of proton emission from a thin foil target irradiated by a 70 fs, intense laser pulse

International Nuclear Information System (INIS)

Fukumi, A.; Nishiuchi, M.; Daido, H.; Li, Z.; Sagisaka, A.; Ogura, K.; Orimo, S.; Kado, M.; Hayashi, Y.; Mori, M.; Bulanov, S.V.; Esirkepov, T.; Nemoto, K.; Oishi, Y.; Nayuki, T.; Fujii, T.; Noda, A.; Nakamura, S.

2005-01-01

A study of proton emission from a 3-μm-thick Ta foil target irradiated by p-, s-, and circularly polarized laser pulses with respect to the target plane has been carried out. Protons with energies up to 880 keV were observed in the target normal direction under the irradiation by the p-polarized laser pulse, which yielded the highest efficiency for proton emission. In contrast, s- and circularly polarized laser pulses gave the maximum energies of 610 and 680 keV, respectively. The difference in the maximum energy between the p- and s-polarized cases was associated with the difference between the sheath fields estimated from electron spectra

Dual fluorescence and laser emissions from fluorescein-Na and eosin-B

International Nuclear Information System (INIS)

Math, N.N.; Naik, L.R.; Suresh, H.M.; Inamdar, S.R.

2006-01-01

Dual laser emissions were observed from fluorescein-Na and eosin-B in ethanolic solutions individually in the concentration range from 10 -2 to 10 -3 mol dm -3 under N 2 laser excitation. The first compound was found to lase at two distinct regions with wavelength maxima around 540, 550 nm, while the second one around 558, 574 nm. Steady-state absorption, fluorescence excitation, fluorescence polarization, fluorescence emission and decays of the dyes in various solvents under varying conditions of excitation and detection systems were carried out to identify the nature of the emitting species responsible for laser emissions in two distinct regions. Both the dyes exhibited concentration and excitation wavelength dependence of fluorescence and the effects were found to be more pronounced in binary solution. The fluorescence decays of dyes were monoexponential in ethanol, while in some other solvents used, the decays showed biexponential behavior. The absorption and excitation studies using thin layers of solutions revealed the formation of dimers with the dye concentration around 1x10 -3 mol dm -3 . Fluorescence polarization and decay studies confirmed the presence of dimers. The two laser bands observed in the shorter and longer wavelengths were respectively ascribed to monomeric and dimeric species

Dual fluorescence and laser emissions from fluorescein-Na and eosin-B

Energy Technology Data Exchange (ETDEWEB)

Math, N.N. [Laser Spectroscopy (DRDO/KU) Programme, Department of Physics, Karnatak University, Dharwad 580 003 (India)]. E-mail: nnm31@rediffmail.com; Naik, L.R. [Laser Spectroscopy (DRDO/KU) Programme, Department of Physics, Karnatak University, Dharwad 580 003 (India); Suresh, H.M. [Laser Spectroscopy (DRDO/KU) Programme, Department of Physics, Karnatak University, Dharwad 580 003 (India); Inamdar, S.R. [Laser Spectroscopy (DRDO/KU) Programme, Department of Physics, Karnatak University, Dharwad 580 003 (India)

2006-12-15

Dual laser emissions were observed from fluorescein-Na and eosin-B in ethanolic solutions individually in the concentration range from 10{sup -2} to 10{sup -3} mol dm{sup -3} under N{sub 2} laser excitation. The first compound was found to lase at two distinct regions with wavelength maxima around 540, 550 nm, while the second one around 558, 574 nm. Steady-state absorption, fluorescence excitation, fluorescence polarization, fluorescence emission and decays of the dyes in various solvents under varying conditions of excitation and detection systems were carried out to identify the nature of the emitting species responsible for laser emissions in two distinct regions. Both the dyes exhibited concentration and excitation wavelength dependence of fluorescence and the effects were found to be more pronounced in binary solution. The fluorescence decays of dyes were monoexponential in ethanol, while in some other solvents used, the decays showed biexponential behavior. The absorption and excitation studies using thin layers of solutions revealed the formation of dimers with the dye concentration around 1x10{sup -3} mol dm{sup -3}. Fluorescence polarization and decay studies confirmed the presence of dimers. The two laser bands observed in the shorter and longer wavelengths were respectively ascribed to monomeric and dimeric species.

Transmission characteristics of the kinematics of the laser-plasma shock wave in air in compton scattering

International Nuclear Information System (INIS)

Hao Dongshan; Xie Hongjun

2006-01-01

By comparing the kinematical equation of a shock wave in free air, the study of transmission characteristics of the laser plasma shock wave in Compton scattering is presented. The results show that the attenuation course of the kinematics of he laser plasma shock wave is related not only with the explosion fountainhead and the characteristics of the explosion course, total energy release, air elastic, but also with multi-photon nonlinear Compton scattering. Because of the scattering the initial radius of the shock wave increases, the attenuation course shortens, the energy metastasis efficiency rises. The results of the numerical analysis and the actual values of the shock waves in air by a way intense explosion are very tallying. (authors)

Emitter spacing effects on field emission properties of laser-treated single-walled carbon nanotube buckypapers

Energy Technology Data Exchange (ETDEWEB)

Chen Yiwen; Miao, Hsin-Yuan; Zhang Mei; Liang, Richard; Zhang, Chuck; Wang, Ben [High-Performance Materials Institute, Florida State University, Tallahassee, FL 32310 (United States); Lin, Ryan Jiyao, E-mail: kenymiao@thu.edu.tw, E-mail: mzhang@eng.fsu.edu [Department of Electrical and Computer Engineering, Rose-Hulman Institute of Technology, Terre Haute, IN 47803 (United States)

2010-12-10

Carbon nanotube (CNT) emitters on buckypaper were activated by laser treatment and their field emission properties were investigated. The pristine buckypapers and CNT emitters' height, diameter, and spacing were characterized through optical analysis. The emitter spacing directly impacted the emission results when the laser power and treatment times were fixed. The increasing emitter density increased the enhanced field emission current and luminance. However, a continuous and excessive increase of emitter density with spacing reduction generated the screening effect. As a result, the extended screening effect from the smaller spacing eventually crippled the field emission effectiveness. Luminance intensity and uniformity of field emission suggest that the highly effective buckypaper will have a density of 2500 emission spots cm{sup -2}, which presents an effective field enhancement factor of 3721 and a moderated screening effect of 0.005. Proper laser treatment is an effective post-treatment process for optimizing field emission, luminance, and durability performance for buckypaper cold cathodes.

Space- and time-resolved diagnostics of soft x-ray emission from laser plasmas

International Nuclear Information System (INIS)

Richardson, M.C.; Jaanimagi, P.A.; Chen, H.

1988-01-01

The analysis of soft x-ray emission from plasmas created by intense short-wavelength laser radiation can provide much useful information on the density, temperature and ionization distribution of the plasma. Until recently, limitations of sensitivity and the availability of suitable x-ray optical elements have restricted studies of soft x-ray emission from laser plasmas. In this paper, the authors describe novel instrumentation which provides high sensitivity in the soft x-ray spectrum with spatial and temporal resolution in the micron and picosecond ranges respectively. These systems exploit advances made in soft x-ray optic and electro-optic technology. Their application in current studies of laser fusion, x-ray lasers, and high density atomic physics are discussed

Electromagnetic Ion Cyclotron Waves in the Helium Branch Induced by Multiple Electromagnetic Ion Cyclotron Triggered Emissions

Science.gov (United States)

Shoji, M.; Omura, Y.; Grison, B.; Pickett, J. S.; Dandouras, I. S.; Engebretson, M. J.

2011-12-01

Electromagnetic ion cyclotron (EMIC) triggered emissions with rising tones between the H+ and He+ cyclotron frequencies were found in the inner magnetosphere by the recent Cluster observations. Another type of EMIC wave with a constant frequency is occasionally observed below the He+ cyclotron frequency after the multiple EMIC triggered emissions. We performed a self-consistent hybrid simulation with a one-dimensional cylindrical magnetic flux model approximating the dipole magnetic field of the Earth's inner magnetosphere. In the presence of energetic protons with a sufficient density and temperature anisotropy, multiple EMIC triggered emissions are reproduced due to the nonlinear wave growth mechanism of rising-tone chorus emissions, and a constant frequency wave in the He+ EMIC branch is subsequently generated. Through interaction with the multiple EMIC rising-tone emissions, the velocity distribution function of the energetic protons is strongly modified. Because of the pitch angle scattering of the protons, the gradient of the distribution in velocity phase space is enhanced along the diffusion curve of the He+ branch wave, resulting in the linear growth of the EMIC wave in the He+ branch.

Efficacy observation on multiple wave length laser for diabetic retinopathy and central retinal vein occlusion

Directory of Open Access Journals (Sweden)

Tao Tian

2014-07-01

Full Text Available AIM:To observe the efficacy of the multiple wave length laser in treating diabetic retinopathy combined with central retinal vein occlusion. METHODS:Totally 95 cases(100 eyeswith diabetic retinopathy combined with central retinal vein occlusion were treated by multiple wave length laser. Krypton yellow laser was used for macular edema in focal photocoagulation and diffuse photocoagulation. For peripheral retina, krypton green or krypton red laser were used. Visual acuity, slit-lamp biomicroscopy, ophthalmoscopy and fundus fluorescein angiography were performed preoperatively and postoperatively. The patients were followed up for 12 to 48wk. In this study, change in visual acuity and macular edema were observed in both groups, and statistical analysis was performed. RESULTS:The effective rate was 61.2% in diffuse macular edema group and 86.3% in focal macular edema group. The general effective rate of later was higher than the former, while the treatment effect had significant statistical difference(PCONCLUSION: Multiple wave length laser is an effective and safe way to treat diabetic macular edema of diabetic retinopathy combined with central retinal vein occlusion,which is worth widely applying in clinical practice.

Optical emission spectroscopy of carbon laser plasma ion source

Science.gov (United States)

Balki, Oguzhan; Rahman, Md. Mahmudur; Elsayed-Ali, Hani E.

2018-04-01

Carbon laser plasma generated by an Nd:YAG laser (wavelength 1064 nm, pulse width 7 ns, fluence 4-52 J cm-2) is studied by optical emission spectroscopy and ion time-of-flight. Up to C4+ ions are detected with the ion flux strongly dependent on the laser fluence. The increase in ion charge with the laser fluence is accompanied by observation of multicharged ion lines in the optical spectra. The time-integrated electron temperature Te is calculated from the Boltzmann plot using the C II lines at 392.0, 426.7, and 588.9 nm. Te is found to increase from ∼0.83 eV for a laser fluence of 22 J cm-2 to ∼0.90 eV for 40 J cm-2. The electron density ne is obtained from the Stark broadened profiles of the C II line at 392 nm and is found to increase from ∼ 2 . 1 × 1017cm-3 for 4 J cm-2 to ∼ 3 . 5 × 1017cm-3 for 40 J cm-2. Applying an external electric field parallel to the expanding plume shows no effect on the line emission intensities. Deconvolution of ion time-of-flight signal with a shifted Maxwell-Boltzmann distribution for each charge state results in an ion temperature Ti ∼4.7 and ∼6.0 eV for 20 and 36 J cm-2, respectively.

A Search for Laser Emission with Megawatt Thresholds from 5600 FGKM Stars

Science.gov (United States)

Tellis, Nathaniel K.; Marcy, Geoffrey W.

2017-06-01

We searched high-resolution spectra of 5600 nearby stars for emission lines that are both inconsistent with a natural origin and unresolved spatially, as would be expected from extraterrestrial optical lasers. The spectra were obtained with the Keck 10 m telescope, including light coming from within 0.5 arcsec of the star, corresponding typically to within a few to tens of astronomical units of the star, and covering nearly the entire visible wavelength range from 3640 to 7890 Å. We establish detection thresholds by injecting synthetic laser emission lines into our spectra and blindly analyzing them for detections. We compute flux density detection thresholds for all wavelengths and spectral types sampled. Our detection thresholds for the power of the lasers themselves range from 3 kW to 13 MW, independent of distance to the star but dependent on the competing “glare” of the spectral energy distribution of the star and on the wavelength of the laser light, launched from a benchmark, diffraction-limited 10 m class telescope. We found no such laser emission coming from the planetary region around any of the 5600 stars. Because they contain roughly 2000 lukewarm, Earth-size planets, we rule out models of the Milky Way in which over 0.1% of warm, Earth-size planets harbor technological civilizations that, intentionally or not, are beaming optical lasers toward us. A next-generation spectroscopic laser search will be done by the Breakthrough Listen initiative, targeting more stars, especially stellar types overlooked here including spectral types O, B, A, early F, late M, and brown dwarfs, and astrophysical exotica.

A comparative study of the enhancement of molecular emission in a spatially confined plume through optical emission spectroscopy and probe beam deflection measurements

Energy Technology Data Exchange (ETDEWEB)

Ding, Dayu; Liang, Peipei; Wu, Jiada; Xu, Ning; Ying, Zhifeng; Sun, Jian, E-mail: jsun@fudan.edu.cn

2013-01-01

The spatial confinement effects of shock wave on the expansion of a carbon plume induced by pulsed laser ablation of graphite in air and the enhancement of the plume emission were studied by optical emission spectroscopy and probe beam deflection measurements. A metal disk was set in the way of the ablation-generated shock wave to block and reflect the supersonically propagating shock wave. The reflected shock wave propagated backwards and confined the expanding plume. The optical emission of CN molecules was enhanced in contrast to the case without the block disk and the emission enhancement was dependent on the position of the disk. Based on the results of time-integrated and -resolved optical emission spectroscopy, and the time- and space-resolved probe beam deflection measurements, the processes occurring in the plume were discussed and the mechanisms responsible for the enhancement of molecular emission in the spatially confined plume were investigated. - Highlights: ► Spatial confinement and optical emission enhancement of carbon plume were studied. ► Ablation-generated shockwave propagating in air was reflected by a block disk. ► The effects of reflected shockwave on the emission enhancement were confirmed. ► The reflect shockwave confined the carbon plume and enhanced the plume emission.

A comparative study of the enhancement of molecular emission in a spatially confined plume through optical emission spectroscopy and probe beam deflection measurements

International Nuclear Information System (INIS)

Ding, Dayu; Liang, Peipei; Wu, Jiada; Xu, Ning; Ying, Zhifeng; Sun, Jian

2013-01-01

The spatial confinement effects of shock wave on the expansion of a carbon plume induced by pulsed laser ablation of graphite in air and the enhancement of the plume emission were studied by optical emission spectroscopy and probe beam deflection measurements. A metal disk was set in the way of the ablation-generated shock wave to block and reflect the supersonically propagating shock wave. The reflected shock wave propagated backwards and confined the expanding plume. The optical emission of CN molecules was enhanced in contrast to the case without the block disk and the emission enhancement was dependent on the position of the disk. Based on the results of time-integrated and -resolved optical emission spectroscopy, and the time- and space-resolved probe beam deflection measurements, the processes occurring in the plume were discussed and the mechanisms responsible for the enhancement of molecular emission in the spatially confined plume were investigated. - Highlights: ► Spatial confinement and optical emission enhancement of carbon plume were studied. ► Ablation-generated shockwave propagating in air was reflected by a block disk. ► The effects of reflected shockwave on the emission enhancement were confirmed. ► The reflect shockwave confined the carbon plume and enhanced the plume emission

Cluster observations of EMIC triggered emissions in association with Pc1 waves near Earth's plasmapause

Science.gov (United States)

Pickett, J. S.; Grison, B.; Omura, Y.; Engebretson, M. J.; Dandouras, I.; Masson, A.; Adrian, M. L.; Santolík, O.; Décréau, P. M. E.; Cornilleau-Wehrlin, N.; Constantinescu, D.

2010-05-01

The Cluster spacecraft were favorably positioned on the nightside near the equatorial plasmapause of Earth at L ˜ 4.3 on 30 March 2002 to observe electromagnetic ion cyclotron (EMIC) rising tone emissions in association with Pc1 waves at 1.5 Hz. The EMIC rising tone emissions were found to be left-hand, circularly polarized, dispersive, and propagating away from the equator. Their burstiness and dispersion of ˜30s/Hz rising out of the 1.5 Hz Pc1 waves are consistent with their identification as EMIC triggered chorus emissions, the first to be reported through in situ observations near the plasmapause. Along with the expected H+ ring current ions seen at higher energies (>300 eV), lower energy ions (300 eV and less) were observed during the most intense EMIC triggered emission events. Nonlinear wave-particle interactions via cyclotron resonance between the ˜2-10 keV H+ ions with temperature anisotropy and the linearly-amplified Pc1 waves are suggested as a possible generation mechanism for the EMIC triggered emissions.

Pump depletion limited evolution of the relativistic plasma wave-front in a forced laser-wakefield accelerator

Energy Technology Data Exchange (ETDEWEB)

Fang, F; Clayton, C E; Marsh, K A; Pak, A E; Ralph, J E; Joshi, C [Department of Electrical Engineering, University of California, Los Angeles, CA 90095 (United States); Lopes, N C [Grupo de Lasers e Plasmas, Instituto Superior Tecnico, Lisbon (Portugal)], E-mail: cclayton@ucla.edu

2009-02-15

In a forced laser-wakefield accelerator experiment (Malka et al 2002 Science 298 1596) where the length of the pump laser pulse is a few plasma periods long, the leading edge of the laser pulse undergoes frequency downshifting and head erosion as the laser energy is transferred to the wake. Therefore, after some propagation distance, the group velocity of the leading edge of the pump pulse-and thus of the driven electron plasma wave-will slow down. This can have implications for the dephasing length of the accelerated electrons and therefore needs to be understood experimentally. We have carried out an experimental investigation where we have measured the velocity v{sub f} of the 'wave-front' of the plasma wave driven by a nominally 50 fs (full width half maximum), intense (a{sub 0} {approx_equal} 1), 0.815 {mu}m laser pulse. To determine the speed of the wave front, time- and space-resolved refractometry, interferometry and Thomson scattering were used. Although a laser pulse propagating through a relatively low-density plasma (n{sub e} = 1.3 x 10{sup 19} cm{sup -3}) showed no measurable changes in v{sub f} over 1.3 mm (and no accelerated electrons), a high-density plasma (n{sub e} = 5 x 10{sup 19} cm{sup -3}) generated accelerated electrons and showed a continuous change in v{sub f} as the laser pulse propagated through the plasma. Possible causes and consequences of the observed v{sub f} evolution are discussed.

Electron plasma waves in CO/sub 2/ laser plasma interactions

International Nuclear Information System (INIS)

Baldis, H.A.; Villeneuve, D.M.; Walsh, C.J.

1984-01-01

During the past few years, the use of Thomson scattering in CO/sub 2/ laser produced plasmas has permitted the identification and study of electron plasma waves and ion waves, driven by various instabilities in the plasma corona, such as Stimulated Raman Scattering (SRS), two plasmon decay, and Stimulated Brillouin Scattering (SBS). Since these instabilities may coexist in the plasma, the density fluctuations associated with one wave may influence the behaviour of one or more of the other instabilities. The authors discuss the experimental evidence of such effects and, in particular, the consequences of a recent experiment in which the ion waves driven by SBS were observed to adversely affect the production of the electron plasma waves driven by SRS. In that experiment, a strong correlation was observed between the onset of SBS and the disappearance of the electron plasma waves driven by SRS at low densities (n/sub e/ n/sub e/ > 0.05 n/sub c/)

Psychological and cognitive effects of laser printer emissions: A controlled exposure study.

Science.gov (United States)

Herbig, B; Jörres, R A; Schierl, R; Simon, M; Langner, J; Seeger, S; Nowak, D; Karrasch, S

2018-01-01

The possible impact of ultrafine particles from laser printers on human health is controversially discussed although there are persons reporting substantial symptoms in relation to these emissions. A randomized, single-blinded, cross-over experimental design with two exposure conditions (high-level and low-level exposure) was conducted with 23 healthy subjects, 14 subjects with mild asthma, and 15 persons reporting symptoms associated with laser printer emissions. To separate physiological and psychological effects, a secondary physiologically based categorization of susceptibility to particle effects was used. In line with results from physiological and biochemical assessments, we found no coherent, differential, or clinically relevant effects of different exposure conditions on subjective complaints and cognitive performance in terms of attention, short-term memory, and psychomotor performance. However, results regarding the psychological characteristics of participants and their situational perception confirm differences between the participants groups: Subjects reporting symptoms associated with laser printer emissions showed a higher psychological susceptibility for adverse reactions in line with previous results on persons with multiple chemical sensitivity or idiopathic environmental intolerance. In conclusion, acute psychological and cognitive effects of laser printer emissions were small and could be attributed only to different participant groups but not to differences in exposure conditions in terms of particle number concentrations. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Luminescent and laser properties of Yb Er:GdCa4O(BO3)3: a new crystal for eye-safe 1.5-μm lasers

Science.gov (United States)

Denker, B.; Galagan, B.; Ivleva, L.; Osiko, V.; Sverchkov, S.; Voronina, I.; Hellstrom, J. E.; Karlsson, G.; Laurell, F.

2004-09-01

We present for the first time 1.5-μm laser emission in Yb Er:GdCa4O(BO3)3 (GdCOB). The crystals were grown by the Czochralski method from platinum crucibles. Spectroscopic and laser tests of the crystals are described. A continuous-wave output power of 80 mW was achieved in a monolithic microchip cavity under laser-diode pumping.

Shift and broadening of emission lines in Nd 3: YAG laser crystal ...

Indian Academy of Sciences (India)

Home; Journals; Pramana – Journal of Physics; Volume 86; Issue 6. Shift and broadening of emission lines in Nd3+:YAG laser crystal influenced by input energy. POURMAND SEYED EBRAHIM REZAEI ... Keywords. Nd3+:YAG crystal; heat generation; three-level emission lines; four-level emission lines; input energy.

Generation conditions of CW Diode Laser Sustained Plasma

Science.gov (United States)

Nishimoto, Koji; Matsui, Makoto; Ono, Takahiro

2016-09-01

Laser sustained plasma was generated using 1 kW class continuous wave diode laser. The laser beam was focused on the seed plasma generated by arc discharge in 1 MPa xenon lamp. The diode laser has advantages of high energy conversion efficiency of 80%, ease of maintenance, compact size and availability of conventional quartz based optics. Therefore, it has a prospect of further development compared with conventional CO2 laser. In this study, variation of the plasma shape caused by laser power is observed and also temperature distribution in the direction of plasma radius is measured by optical emission spectroscopy.

Interferometric and schlieren characterization of the plasmas and shock wave dynamics during laser-triggered discharge in atmospheric air

Energy Technology Data Exchange (ETDEWEB)

Wei, Wenfu; Li, Xingwen, E-mail: xwli@mail.xjtu.edu.cn; Wu, Jian; Yang, Zefeng; Jia, Shenli; Qiu, Aici [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Shaanxi 710049 (China)

2014-08-15

This paper describes our efforts to reveal the underlying physics of laser-triggered discharges in atmospheric air using a Mach-Zehnder interferometer and schlieren photography. Unlike the hemispherical shock waves that are produced by laser ablation, bell-like morphologies are observed during laser-triggered discharges. Phase shifts are recovered from the interferograms at a time of 1000 ns by the 2D fast Fourier transform method, and then the values of the refractive index are deduced using the Abel inversion. An abundance of free electrons is expected near the cathode surface. The schlieren photographs visualize the formation of stagnation layers at ∼600 ns in the interaction zones of the laser- and discharge-produced plasmas. Multiple reflected waves are observed at later times with the development of shock wave propagations. Estimations using the Taylor-Sedov self-similar solution indicated that approximately 45.8% and 51.9% of the laser and electrical energies are transferred into the gas flow motions, respectively. Finally, numerical simulations were performed, which successfully reproduced the main features of the experimental observations, and provided valuable insights into the plasma and shock wave dynamics during the laser-triggered discharge.

Hypersonic wave drag reduction performance of cylinders with repetitive laser energy depositions

International Nuclear Information System (INIS)

Fang, J; Hong, Y J; Li, Q; Huang, H

2011-01-01

It has been widely research that wave drag reduction on hypersonic vehicle by laser energy depositions. Using laser energy to reduce wave drag can improve vehicle performance. A second order accurate scheme based on finite-difference method and domain decomposition of structural grid is used to compute the drag performance of cylinders in a hypersonic flow of Mach number 2 at altitude of 15km with repetitive energy depositions. The effects of frequency on drag reduction are studied. The calculated results show: the recirculation zone is generated due to the interaction between bow shock over the cylinder and blast wave produced by energy deposition, and a virtual spike which is supported by an axis-symmetric recirculation, is formed in front of the cylinder. By increasing the repetitive frequency, the drag is reduced and the oscillation of the drag is decreased; however, the energy efficiency decreases by increasing the frequency.

An improved method to experimentally determine temperature and pressure behind laser-induced shock waves at low Mach numbers

International Nuclear Information System (INIS)

Hendijanifard, Mohammad; Willis, David A

2011-01-01

Laser-matter interactions are frequently studied by measuring the propagation of shock waves caused by the rapid laser-induced material removal. An improved method for calculating the thermo-fluid parameters behind shock waves is introduced in this work. Shock waves in ambient air, induced by pulsed Nd : YAG laser ablation of aluminium films, are measured using a shadowgraph apparatus. Normal shock solutions are applied to experimental data for shock wave positions and used to calculate pressure, temperature, and velocity behind the shock wave. Non-dimensionalizing the pressure and temperature with respect to the ambient values, the dimensionless pressure and temperature are estimated to be as high as 90 and 16, respectively, at a time of 10 ns after the ablation pulse for a laser fluence of F = 14.5 J cm -2 . The results of the normal shock solution and the Taylor-Sedov similarity solution are compared to show that the Taylor-Sedov solution under-predicts pressure when the Mach number of the shock wave is small. At a fluence of 3.1 J cm -2 , the shock wave Mach number is less than 3, and the Taylor-Sedov solution under-predicts the non-dimensional pressure by as much as 45%.

Short-pulse-laser-induced optical damage and fracto-emission of amorphous, diamond-like carbon films

Science.gov (United States)

Sokolowski-Tinten, Klaus; Ziegler, Wolfgang; von der Linde, Dietrich; Siegal, Michael P.; Overmyer, D. L.

2005-03-01

Short-pulse-laser-induced damage and ablation of thin films of amorphous, diamond-like carbon have been investigated. Material removal and damage are caused by fracture of the film and ejection of large fragments. The fragments exhibit a delayed, intense and broadband emission of microsecond duration. Both fracture and emission are attributed to the laser-initiated relaxation of the high internal stresses of the pulse laser deposition-grown films.

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.

Laser-generated shock wave attenuation aimed at microscale pyrotechnic device design

Directory of Open Access Journals (Sweden)

Hyeonju Yu

2016-05-01

Full Text Available To meet the rising demand for miniaturizing the pyrotechnic device that consists of donor/acceptor pair separated by a bulkhead or a thin gap, the shock initiation sensitivity in the microscale gap test configuration is investigated. For understanding the shock attenuation within a gap sample (304 stainless steel thickness of 10∼800 μm, the laser-generated shock wave in water confinement is adopted. The shock properties are obtained from the free surface velocity by making use of a velocity interferometer system for any reflector (VISAR. Analytical models for plasma generation in a confined geometry and for evolution and decay of shock waves during the propagation are considered. The shape and amplitude of the laser-driven initial pressure load and its attenuation pattern in the gap are effectively controlled for targeting the microscale propagation distance and subsequent triggering pressure for the acceptor charge. The reported results are important in the precise controlling of the shock strength during the laser initiation of microscale pyrotechnic devices.

Visual and refractive outcomes of LASIK with the SCHWIND ESIRIS and WaveLight ALLEGRETTO WAVE Eye-q excimer lasers: a prospective, contralateral study.

Science.gov (United States)

Mearza, Ali A; Muhtaseb, Mohammed; Aslanides, Ioannis M

2008-11-01

To compare the safety, efficacy, and predictability of LASIK with the SCHWIND ESIRIS and WaveLight ALLEGRETTO WAVE Eye-Q excimer laser platforms. This prospective study comprised 44 eyes of 22 consecutive patients who were treated with LASIK using the Moria M2 microkeratome. One eye was treated with the SCHWIND ESIRIS laser and the fellow eye treated with the WaveLight ALLEGRETTO WAVE Eye-Q laser. All eyes operated with the SCHWIND ESIRIS were treated with standard aspheric ablation, whereas the eyes operated with the WaveLight ALLEGRETTO WAVE Eye-Q received treatment with three different ablation types according to the common practice at our clinic. Outcome measures were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, and proximity to target refraction at 6-month follow-up. At 6 months postoperative, mean decimal UCVA was 0.96+/-0.22 (range: 0.3 to 1.2) for ESIRIS eyes and 0.98+/-0.17 (range: 0.6 to 1.2) for ALLEGRETTO eyes (P=.57). Mean postoperative spherical equivalent refraction was -0.02+/-0.28 diopters (D) (range: -0.75 to +0.75 D) for ESIRIS eyes and 0.11+/-0.91 D (range: -1.00 to +3.88 D) for ALLEGRETTO eyes (P=.49). Of the ESIRIS eyes, 20/22 (91%) were within +/-1.00 D of target refraction and 20/22 (91%) were within +/-0.50 D of target refraction. Of the ALLEGRETTO eyes, 20/22 (91%) and 19/22 (86%) were within +/-1.00 D and +/-0.50 D, respectively, of target refraction. No patient lost > or =2 lines of BSCVA in either group. No differences were seen in safety and efficacy outcome parameters between the SCHWIND ESIRIS and WaveLight ALLEGRETTO WAVE Eye-Q excimer lasers when used according to a previously established treatment algorithm at our clinic in the treatment of refractive error.

Resonantly diode-pumped continuous-wave and Q-switched Er:YAG laser at 1645 nm.

Science.gov (United States)

Chang, N W H; Simakov, N; Hosken, D J; Munch, J; Ottaway, D J; Veitch, P J

2010-06-21

We describe an efficient Er:YAG laser that is resonantly pumped using continuous-wave (CW) laser diodes at 1470 nm. For CW lasing, it emits 6.1 W at 1645 nm with a slope efficiency of 36%, the highest efficiency reported for an Er:YAG laser that is pumped in this manner. In Q-switched operation, the laser produces diffraction-limited pulses with an average power of 2.5 W at 2 kHz PRF. To our knowledge this is the first Q-switched Er:YAG laser resonantly pumped by CW laser diodes.

Excitation of accelerating plasma waves by counter-propagating laser beams

International Nuclear Information System (INIS)

Shvets, Gennady; Fisch, Nathaniel J.; Pukhov, Alexander

2002-01-01

The conventional approach to exciting high phase velocity waves in plasmas is to employ a laser pulse moving in the direction of the desired particle acceleration. Photon downshifting then causes momentum transfer to the plasma and wave excitation. Novel approaches to plasma wake excitation, colliding-beam accelerator (CBA), which involve photon exchange between the long and short counter-propagating laser beams, are described. Depending on the frequency detuning Δω between beams and duration τ L of the short pulse, there are two approaches to CBA. First approach assumes (τ L ≅2/ω p ). Photons exchanged between the beams deposit their recoil momentum in the plasma driving the plasma wake. Frequency detuning between the beams determines the direction of the photon exchange, thereby controlling the phase of the plasma wake. This phase control can be used for reversing the slippage of the accelerated particles with respect to the wake. A variation on the same theme, super-beatwave accelerator, is also described. In the second approach, a short pulse with τ L >>ω p -1 detuned by Δω∼2ω p from the counter-propagating beam is employed. While parametric excitation of plasma waves by the electromagnetic beatwave at 2ω p of two co-propagating lasers was first predicted by Rosenbluth and Liu [M. N. Rosenbluth and C. S. Liu, Phys. Rev. Lett. 29, 701 (1972)], it is demonstrated that the two excitation beams can be counter-propagating. The advantages of using this geometry (higher instability growth rate, insensitivity to plasma inhomogeneity) are explained, and supporting numerical simulations presented

Influence of standing-wave electric field pattern on the laser damage resistance of HfO sub 2 thin films

CERN Document Server

Protopapa, M L; De Tomasi, F; Di Giulio, M; Perrone, M R; Scaglione, S

2002-01-01

The standing-wave electric field pattern that forms inside an optical coating as a consequence of laser irradiation is one of the factors influencing the coating laser-induced damage threshold. The influence of the standing-wave electric field profile on the damage resistance to ultraviolet radiation of hafnium dioxide (HfO sub 2) thin films was investigated in this work. To this end, HfO sub 2 thin films of different thicknesses deposited by the electron beam evaporation technique at the same deposition conditions were analyzed. Laser damage thresholds of the samples were measured at 308 nm (XeCl laser) by the photoacoustic beam deflection technique and microscopic inspections. The dependence of the laser damage threshold on the standing-wave electric field pattern was analyzed.

Spontaneous emission and gain in a waveguide free-electron laser

International Nuclear Information System (INIS)

Golightly, W.J.; Ride, S.K.

1991-01-01

A free-electron laser enclosed in a waveguide of narrowly spaced parallel plates has been proposed as a compact, coherent source of far-infrared radiation. In this paper, the spontaneous emission and small-signal gain of such a device are analyzed. Maxwell's equations are solved for the fields of a relativistic electron beam passing through a linearly polarized undulator in the presence of a parallel-plane waveguide. The radiation intensity is resolved into its component waveguide modes for the fundamental frequency and for all harmonics. The intensity profile in a given harmonic mode is altered significantly when a parameter involving the undulator period, beam energy, and transverse dimension of the guide is such that the radiation group velocity is close to the electrons' axial velocity. The small-signal gain in the waveguide free-electron laser is calculated and related to the spontaneous emission. Near zero slip, the gain curve is significantly different from that of a free-space free-electron laser with the same parameters

Time-Resolved Emission Spectroscopic Study of Laser-Induced Steel Plasmas

International Nuclear Information System (INIS)

Shah, M. L.; Pulhani, A. K.; Suri, B. M.; Gupta, G. P.

2013-01-01

Laser-induced steel plasma is generated by focusing a Q-switched Nd:YAG visible laser (532 nm wavelength) with an irradiance of ∼ 1 × 10 9 W/cm 2 on a steel sample in air at atmospheric pressure. An Echelle spectrograph coupled with a gateable intensified charge-coupled detector is used to record the plasma emissions. Using time-resolved spectroscopic measurements of the plasma emissions, the temperature and electron number density of the steel plasma are determined for many times of the detector delay. The validity of the assumption by the spectroscopic methods that the laser-induced plasma (LIP) is optically thin and is also in local thermodynamic equilibrium (LTE) has been evaluated for many delay times. From the temporal evolution of the intensity ratio of two Fe I lines and matching it with its theoretical value, the delay times where the plasma is optically thin and is also in LTE are found to be 800 ns, 900 ns and 1000 ns.

Emission spectra from super-critical rippled plasma density profiles illuminated by intense laser pulses

International Nuclear Information System (INIS)

Ondarza R, R.; Boyd, T.J.M.

2000-01-01

High-order harmonic emission from the interaction of intense femtosecond laser pulses with super-critical plasmas characterized by a rippled density profile at the vacuum-plasma interface has been observed from particle-in-cell (PIC) simulations. A plasma simulation box several laser wavelengths in extent was prepared with a rippled density of a fraction of a laser wavelength. Emission spectra at the very initial stage of the interaction were recorded with spectral characteristics dissimilar to those previously reported in the literature. The reflected light spectra were characterized by a strong emission at the plasma line and by a series of harmonics at multiples of the ripple frequency. Harmonic spectra were obtained for different values of the plasma ripple frequency. In all cases the harmonics were emitted at the precise multiple harmonic number of the ripple frequency. Another important feature apparent from the simulations was that the emission peaks appeared to havea complex structure as compared with those for unrippled plasmas. For the cases when the plasma was rippled the peaks that corresponded to the multiples of the rippled density typically showed a double peak for the first few harmonics. The reflected emission plots for the main laser pulse showed strong emission at the plasma frequency and at multiples of that frequency as reported by the authors in the literature. (Author)

Simple model for decay of laser generated shock waves

International Nuclear Information System (INIS)

Trainor, R.J.

1980-01-01

A simple model is derived to calculate the hydrodynamic decay of laser-generated shock waves. Comparison with detailed hydrocode simulations shows good agreement between calculated time evolution of shock pressure, position, and instantaneous pressure profile. Reliability of the model decreases in regions of the target where superthermal-electron preheat effects become comparable to shock effects

Generalized dispersive wave emission in nonlinear fiber optics.

Science.gov (United States)

Webb, K E; Xu, Y Q; Erkintalo, M; Murdoch, S G

2013-01-15

We show that the emission of dispersive waves in nonlinear fiber optics is not limited to soliton-like pulses propagating in the anomalous dispersion regime. We demonstrate, both numerically and experimentally, that pulses propagating in the normal dispersion regime can excite resonant dispersive radiation across the zero-dispersion wavelength into the anomalous regime.

Laser Cutting of Carbon Fiber Reinforced Plastics - Investigation of Hazardous Process Emissions

Science.gov (United States)

Walter, Juergen; Hustedt, Michael; Staehr, Richard; Kaierle, Stefan; Jaeschke, Peter; Suttmann, Oliver; Overmeyer, Ludger

Carbon fiber reinforced plastics (CFRP) show high potential for use in lightweight applications not only in aircraft design, but also in the automotive or wind energy industry. However, processing of CFRP is complex and expensive due to their outstanding mechanical properties. One possibility to manufacture CFRP structures flexibly at acceptable process speeds is high-power laser cutting. Though showing various advantages such as contactless energy transfer, this process is connected to potentially hazardous emission of respirable dust and organic gases. Moreover, the emitted particles may be fibrous, thus requiring particular attention. Here, a systematic analysis of the hazardous substances emitted during laser cutting of CFRP with thermoplastic and thermosetting matrix is presented. The objective is to evaluate emission rates for the total particulate and gaseous fractions as well as for different organic key components. Furthermore, the influence of the laser process conditions shall be assessed, and first proposals to handle the emissions adequately are made.

Study of laser-driven shock wave propagation in Plexiglas targets

International Nuclear Information System (INIS)

Dhareshwar, L.J.; Naik, P.A.; Pant, H.C.; Kaushik, T.C.

1992-01-01

An experimental study of laser-driven shock wave propagation in a transparent material such as Plexiglas using a high-speed optical shadowgraphy technique is presented in this paper. A Nd: glass laser was used to produce laser intensity in the range 10 12 -10 14 W/cm 2 on the target. Optical shadowgrams of the propagating shock front were recorded with a second-harmonic (0.53-μm) optical probe beam. Shock pressures were measured at various laser intensities, and the scaling was found to agree with the theoretically predicted value. Shock pressure values have also been obtained from a one-dimensional Lagrangian hydrodynamic simulation, and they match well with experimental results. Shadowgrams of shock fronts produced by nonuniform spatial laser beam irradiation profiles have shown complete smoothing when targets with a thin coating of a material of high atomic number such as gold were used. Shock pressures in such coated targets are also found to be considerably higher compared with those in uncoated targets. (Author)

Scaling of x-ray emission and ion velocity in laser produced Cu ...

Indian Academy of Sciences (India)

Laser plasma; x-ray emission; conversion efficiency; ion velocities. ... fits from this kind of optimization studies are in the fields of x-ray lithography, x-ray lasers etc. .... formula between the x-ray conversion rate versus different parameters of the ...

Study of x-ray emission enhancement via high contrast femtosecond laser interacting with solid foil

International Nuclear Information System (INIS)

Chen, Liming; Kando, Masaki; Bulanov, S.V.; Koga, James K.; Tajima, Toshiki; Xu M.H.; Yuan X.H.; Li Y.T.; Dong Q.L.; Zhang J.

2007-01-01

We studied the hard x-ray emission and the Kα x-ray conversion efficiency (η K ) produced by 60 fs high contrast frequency doubled Ti: sapphire laser pulse focused on Cu foil target. Cu Kα photon emission obtained with second harmonic laser pulse is more intense than the case of fundamental laser pulse. The Cu η K shows strong dependence on laser nonlinearly skewed pulse shape and reaches the maximum value 4x10 -4 with 100 fs negatively skewed pulse. It shows the electron spectrum shaping contribute to the increase of η K . (author)

Crack Detection in Single-Crystalline Silicon Wafer Using Laser Generated Lamb Wave

Directory of Open Access Journals (Sweden)

Min-Kyoo Song

2013-01-01

Full Text Available In the semiconductor industry, with increasing requirements for high performance, high capacity, high reliability, and compact components, the crack has been one of the most critical issues in accordance with the growing requirement of the wafer-thinning in recent years. Previous researchers presented the crack detection on the silicon wafers with the air-coupled ultrasonic method successfully. However, the high impedance mismatching will be the problem in the industrial field. In this paper, in order to detect the crack, we propose a laser generated Lamb wave method which is not only noncontact, but also reliable for the measurement. The laser-ultrasonic generator and the laser-interferometer are used as a transmitter and a receiver, respectively. We firstly verified the identification of S0 and A0 lamb wave modes and then conducted the crack detection under the thermoelastic regime. The experimental results showed that S0 and A0 modes of lamb wave were clearly generated and detected, and in the case of the crack detection, the estimated crack size by 6 dB drop method was almost equal to the actual crack size. So, the proposed method is expected to make it possible to detect the crack in the silicon wafer in the industrial fields.

Collective emission of matter-wave jets from driven Bose-Einstein condensates.

Science.gov (United States)

Clark, Logan W; Gaj, Anita; Feng, Lei; Chin, Cheng

2017-11-16

Scattering is used to probe matter and its interactions in all areas of physics. In ultracold atomic gases, control over pairwise interactions enables us to investigate scattering in quantum many-body systems. Previous experiments on colliding Bose-Einstein condensates have revealed matter-wave interference, haloes of scattered atoms, four-wave mixing and correlations between counter-propagating pairs. However, a regime with strong stimulation of spontaneous collisions analogous to superradiance has proved elusive. In this regime, the collisions rapidly produce highly correlated states with macroscopic population. Here we find that runaway stimulated collisions in Bose-Einstein condensates with periodically modulated interaction strength cause the collective emission of matter-wave jets that resemble fireworks. Jets appear only above a threshold modulation amplitude and their correlations are invariant even when the number of ejected atoms grows exponentially. Hence, we show that the structures and atom occupancies of the jets stem from the quantum fluctuations of the condensate. Our findings demonstrate the conditions required for runaway stimulated collisions and reveal the quantum nature of matter-wave emission.

Emission spectrum and relaxation kinetics of SO2 induced by 266 nm laser.

Science.gov (United States)

Zhang, Guiyin; Zhang, Lianshui; Jin, Yidong

2010-09-15

Laser induced fluorescence (LIF) emission spectrum of SO(2) in the range of 270.0-470.0 nm has been obtained with the quadruple harmonic output (266 nm) of a pulsed Nd:YAG laser as excitation source. The spectrum is composed of a continuous envelope in the short wavelength side, while it shows the character of banded structure superimposed on a continuous one in the long wavelength region. Fluorescence emission from the hybrid states of A(1)A(2)+B(1)B(1) and X(1)A(1)+B(1)B(1) forms the continuous envelope and phosphorescence emission from the triplet state a(3)B(1) forms the banded progression. It is also found that direct emission from laser excited states is very weak. The primary portion of the emission is from the energy levels populated by collision relaxation or collision induced intersystem crossing process. The harmonic frequencies and inharmonic coefficients of the symmetric stretching vibration and the bending vibration of X(1)A(1) state are derived from the ascription of the phosphorescence progression. Copyright 2010 Elsevier B.V. All rights reserved.

Cooling atoms with extraresonant stimulated emission below the Doppler limit

International Nuclear Information System (INIS)

Shevy, Y.

1989-01-01

The process of cooling atoms with radiation pressure is well understood in terms of absorption and spontaneous emission of fluorescence photons. This process imposes a lower limit on the minimum equilibrium temperature of laser cooled two level atoms of K b T = ℎΓ 21 /2 (the Doppler limit), where Γ 21 is the excited state decay rate to the ground state. At high laser intensity, it has been demonstrated that the stimulated emission process changes the sign of the force to a heating force at the red side of the atomic resonance and to a cooling force at blue detunings. Although this stimulated force is more efficient than the radiation pressure force, it has been generally accepted that this force cannot lead to lower equilibrium temperatures due to the large heating caused by diffusion of momentum at high intensity. These conclusions are valid only when the sole damping mechanism is the excited state decay to the ground state by spontaneous emission. However, when the atomic system is opened, i.e., is allowed to decay to other levels, or the dipole decay rate is altered by dephasing events, the stimulated force is dramatically modified. Under this conditions the stimulated force can occur at lower laser intensity and can even reverse sign to provide damping at the red side of resonance. These phenomena originate from extraresonances in the stimulated emission process between the two counterpropagating waves. These resonances appear as a dispersive feature in pump probe spectra (Two Wave Mixing) and are closely related to the extraresonances in four wave mixing studied originally by Bloembergen and co-workers. This paper establishes this connection and the potential of these phenomena for laser cooling. The implications of these results to the recently observed ultra-cold Na and Cs atoms are also discussed

A Search for Laser Emission with Megawatt Thresholds from 5600 FGKM Stars

Energy Technology Data Exchange (ETDEWEB)

Tellis, Nathaniel K.; Marcy, Geoffrey W., E-mail: Nate.tellis@gmail.com [Astronomy Department, University of California, Berkeley, CA 94720 (United States)

2017-06-01

We searched high-resolution spectra of 5600 nearby stars for emission lines that are both inconsistent with a natural origin and unresolved spatially, as would be expected from extraterrestrial optical lasers. The spectra were obtained with the Keck 10 m telescope, including light coming from within 0.5 arcsec of the star, corresponding typically to within a few to tens of astronomical units of the star, and covering nearly the entire visible wavelength range from 3640 to 7890 Å. We establish detection thresholds by injecting synthetic laser emission lines into our spectra and blindly analyzing them for detections. We compute flux density detection thresholds for all wavelengths and spectral types sampled. Our detection thresholds for the power of the lasers themselves range from 3 kW to 13 MW, independent of distance to the star but dependent on the competing “glare” of the spectral energy distribution of the star and on the wavelength of the laser light, launched from a benchmark, diffraction-limited 10 m class telescope. We found no such laser emission coming from the planetary region around any of the 5600 stars. Because they contain roughly 2000 lukewarm, Earth-size planets, we rule out models of the Milky Way in which over 0.1% of warm, Earth-size planets harbor technological civilizations that, intentionally or not, are beaming optical lasers toward us. A next-generation spectroscopic laser search will be done by the Breakthrough Listen initiative, targeting more stars, especially stellar types overlooked here including spectral types O, B, A, early F, late M, and brown dwarfs, and astrophysical exotica.

Electron Bernstein wave emission from an overdense reversed field pinch plasma

International Nuclear Information System (INIS)

Chattopadhyay, P.K.; Anderson, J.K.; Biewer, T.M.; Craig, D.; Forest, C.B.; Harvey, R.W.; Smirnov, A.P.

2002-01-01

Blackbody levels of emission in the electron cyclotron range of frequencies have been observed from an overdense (ω pe ∼3ω ce ) Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed field pinch plasma, a result of electrostatic electron Bernstein waves emitted from the core and mode converted into electromagnetic waves at the extreme plasma edge. Comparison of the measured radiation temperature with profiles measured by Thomson scattering indicates that the mode conversion efficiency can be as high as ∼75%. Emission is preferentially in the X-mode polarization, and is strongly dependent upon the density and magnetic field profiles at the mode conversion point

Strong shock wave and areal mass oscillations associated with impulsive loading of planar laser targets

International Nuclear Information System (INIS)

Velikovich, A.L.; Schmitt, A.J.; Metzler, N.; Gardner, J.H.

2003-01-01

When a rippled surface of a planar target is irradiated with a short (subnanosecond) laser pulse, the shock wave launched into the target and the mass distribution of the shocked plasma will oscillate. These oscillations are found to be surprisingly strong compared, for example, to the case when the laser radiation is not turned off but rather keeps pushing the shock wave into the target. Being stronger than the areal mass oscillations due to ablative Richtmyer-Meshkov instability and feedout in planar targets, which have recently been observed at the Naval Research Laboratory (NRL) [Aglitskiy et al., Phys. Plasmas 9, 2264 (2002)], these oscillations should therefore be directly observable with the same diagnostic technique. Irradiation of a target with a short laser pulse represents a particular case of an impulsive loading, a fast release of finite energy in a thin layer near the surface of a target. Renewed interest to the impulsive loading in the area of direct-drive laser fusion is due to the recent proposals of using a short pulse prior to the drive pulse to make the target more resistant to laser imprint and Rayleigh-Taylor growth. Impulsive loading produces a shock wave that propagates into the target and is immediately followed by an expansion wave, which gradually reduces the shock strength. If the irradiated surface is rippled, then, while the shock wave propagates through the target, its modulation amplitude grows, exceeding the initial ripple amplitude by a factor of 2 or more. The oscillating areal mass reaches the peak values that exceed the initial mass modulation amplitude (density times ripple height) by a factor of 5-7 or more, and reverses its phase several times after the laser pulse is over. The oscillatory growth is more pronounced in fluids with higher shock compressibility and is probably related to the Vishniac's instability of a blast wave. Frequency of the oscillations is determined by the speed of sound in the shocked material, and

Nonlinear plasma wave models in 3D fluid simulations of laser-plasma interaction

Science.gov (United States)

Chapman, Thomas; Berger, Richard; Arrighi, Bill; Langer, Steve; Banks, Jeffrey; Brunner, Stephan

2017-10-01

Simulations of laser-plasma interaction (LPI) in inertial confinement fusion (ICF) conditions require multi-mm spatial scales due to the typical laser beam size and durations of order 100 ps in order for numerical laser reflectivities to converge. To be computationally achievable, these scales necessitate a fluid-like treatment of light and plasma waves with a spatial grid size on the order of the light wave length. Plasma waves experience many nonlinear phenomena not naturally described by a fluid treatment, such as frequency shifts induced by trapping, a nonlinear (typically suppressed) Landau damping, and mode couplings leading to instabilities that can cause the plasma wave to decay rapidly. These processes affect the onset and saturation of stimulated Raman and Brillouin scattering, and are of direct interest to the modeling and prediction of deleterious LPI in ICF. It is not currently computationally feasible to simulate these Debye length-scale phenomena in 3D across experimental scales. Analytically-derived and/or numerically benchmarked models of processes occurring at scales finer than the fluid simulation grid offer a path forward. We demonstrate the impact of a range of kinetic processes on plasma reflectivity via models included in the LPI simulation code pF3D. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Sensitive detection of malachite green and crystal violet by nonlinear laser wave mixing and capillary electrophoresis.

Science.gov (United States)

Maxwell, Eric J; Tong, William G

2016-05-01

An ultrasensitive label-free antibody-free detection method for malachite green and crystal violet is presented using nonlinear laser wave-mixing spectroscopy and capillary zone electrophoresis. Wave-mixing spectroscopy provides a sensitive absorption-based detection method for trace analytes. This is accomplished by forming dynamic gratings within a sample cell, which diffracts light to create a coherent laser-like signal beam with high optical efficiency and high signal-to-noise ratio. A cubic dependence on laser power and square dependence on analyte concentration make wave mixing sensitive enough to detect molecules in their native form without the use of fluorescent labels for signal enhancement. A 532 nm laser and a 635 nm laser were used for malachite green and crystal violet sample excitation. The use of two lasers of different wavelengths allows the method to simultaneously detect both analytes. Selectivity is obtained through the capillary zone electrophoresis separation, which results in characteristic migration times. Measurement in capillary zone electrophoresis resulted in a limit of detection of 6.9 × 10(-10)M (2.5 × 10(-19) mol) for crystal violet and 8.3 × 10(-11)M (3.0 × 10(-20) mol) for malachite green at S/N of 2. Copyright © 2016. Published by Elsevier B.V.

Crystal growth, optical properties, and continuous-wave laser operation of Nd3+-doped CaNb2O6 crystal

International Nuclear Information System (INIS)

Cheng, Y; Xu, X D; Xiao, X D; Li, D Z; Zhao, C C; Zhou, S M; Xin, Z; Yang, X B; Xu, J

2009-01-01

Laser crystal Nd:CaNb 2 O 6 with excellent quality has been grown by Czochralski technique. The effective segregation coefficient of Nd 3+ was studied by X-ray fluorescence method. The polarized absorption spectra and the fluorescence spectra of Nd:CaNb 2 O 6 were measured at room temperature. The peak absorption cross section was calculated to be 6.202×10 -20 cm 2 with a broad FWHM of 7 nm at 808 nm for E ∥ a light polarization. The emission cross section at 1062 nm is 9.87×10 -20 cm 2 . We report what we believe to be the first demonstration of the continuous-wave Nd:CaNb 2 O 6 laser operation under diode pumping. Output power of 1.86 W at 1062 nm was obtained with a slope efficiency of 19% in the CW regime

Crystal growth, optical properties, and continuous-wave laser operation of Nd3+-doped CaNb2O6 crystal

Science.gov (United States)

Cheng, Y.; Xu, X. D.; Xin, Z.; Yang, X. B.; Xiao, X. D.; Li, D. Z.; Zhao, C. C.; Xu, J.; Zhou, S. M.

2009-10-01

Laser crystal Nd:CaNb2O6 with excellent quality has been grown by Czochralski technique. The effective segregation coefficient of Nd3+ was studied by X-ray fluorescence method. The polarized absorption spectra and the fluorescence spectra of Nd:CaNb2O6 were measured at room temperature. The peak absorption cross section was calculated to be 6.202×10-20 cm2 with a broad FWHM of 7 nm at 808 nm for E ∥ a light polarization. The emission cross section at 1062 nm is 9.87×10-20 cm2. We report what we believe to be the first demonstration of the continuous-wave Nd:CaNb2O6 laser operation under diode pumping. Output power of 1.86 W at 1062 nm was obtained with a slope efficiency of 19% in the CW regime.

Research on Formation Mechanism of Dynamic Response and Residual Stress of Sheet Metal Induced by Laser Shock Wave

Science.gov (United States)

Feng, Aixin; Cao, Yupeng; Wang, Heng; Zhang, Zhengang

2018-01-01

In order to reveal the quantitative control of the residual stress on the surface of metal materials, the relevant theoretical and experimental studies were carried out to investigate the dynamic response of metal thin plates and the formation mechanism of residual stress induced by laser shock wave. In this paper, the latest research trends on the surface residual stress of laser shock processing technology were elaborated. The main progress of laser shock wave propagation mechanism and dynamic response, laser shock, and surface residual stress were discussed. It is pointed out that the multi-scale characterization of laser and material, surface residual stress and microstructure change is a new hotspot in laser shock strengthening technology.

Recombination emissions and spectral blueshift of pump radiation from ultrafast laser induced plasma in a planar water microjet

Science.gov (United States)

Anija, M.; Philip, Reji

2009-09-01

We report spectroscopic investigations of an ultrafast laser induced plasma generated in a planar water microjet. Plasma recombination emissions along with the spectral blueshift and broadening of the pump laser pulse contribute to the total emission. The laser pulses are of 100 fs duration, and the incident intensity is around 10 15 W/cm 2. The dominant mechanisms leading to plasma formation are optical tunnel ionization and collisional ionization. Spectrally resolved polarization measurements show that the high frequency region of the emission is unpolarized whereas the low frequency region is polarized. Results indicate that at lower input intensities the emission arises mainly from plasma recombinations, which is accompanied by a weak blueshift of the incident laser pulse. At higher input intensities strong recombination emissions are seen, along with a broadening and asymmetric spectral blueshift of the pump laser pulse. From the nature of the blueshifted laser pulse it is possible to deduce whether the rate of change of free electron density is a constant or variable within the pulse lifetime. Two input laser intensity regimes, in which collisional and tunnel ionizations are dominant respectively, have been thus identified.

Spectral analysis of the process emission during laser welding of AISI 304 stainless steel with disk and Nd:YAG laser

NARCIS (Netherlands)

Konuk, A.R.; Aarts, R.G.K.M.; Huis in 't Veld, A.J.

2009-01-01

Optical emissions from the laser welding process can be obtained relatively easy in real-time. Such emissions come from the melt pool, keyhole, or plume during welding. Therefore it is very beneficial to establish a clear relation between characteristics of these emissions and the resulting weld

Spatio-temporal evolution of magnetosonic wave in the laser plasma interaction

International Nuclear Information System (INIS)

Sharma, R. P.; Singh, Ram Kishor; Sharma, Swati; Tiwary, Prem Pyari; Modi, K. V.; Satsangi, V. R.

2015-01-01

This paper presents a theoretical model for the transient response of nonlinear coupling between magnetosonic wave and ion acoustic wave in the overdense plasma. Filamentation of magnetosonic wave has been considered to be responsible for magnetic turbulence during the laser plasma interaction. The ion acoustic wave gets excited due to the ponderomotive force exerted by magnetosonic wave and this ion acoustic wave in turn generates perturbation in the background density in the form of spatial density harmonics. Numerical simulation has been carried out for dimensionless coupled equations of magnetosonic wave and ion acoustic wave; and the results show quite complex localized structures that grow with time. The power spectrum has also been studied which shows that the spectral index follows an approximate scaling of the order of ∼k −2.4 at smaller scales. The data obtained from numerical simulation are used in semi analytical model to better understand the mechanism of nonlinear evolution of magnetosonic wave. The results indicate considerable randomness in the spatial structure of the magnetic field profile which gives sufficient indication of turbulence

Spatio-temporal evolution of magnetosonic wave in the laser plasma interaction

Energy Technology Data Exchange (ETDEWEB)

Sharma, R. P., E-mail: rpsharma@ces.iitd.ac.in; Singh, Ram Kishor, E-mail: ram007kishor@gmail.com; Sharma, Swati, E-mail: swati.sharma704@gmail.com [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Tiwary, Prem Pyari, E-mail: prempyari@gmail.com [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Department of Physics and Computer Science, Dayal Bagh Educational Institute(Deemed University), DayalBagh, Agra 282005 (India); Modi, K. V., E-mail: kvmodi.iitd@gmail.com [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Mechanical Engineering Department, Government Engineering College Valsad, Gujarat 396001 (India); Satsangi, V. R. [Department of Physics and Computer Science, Dayal Bagh Educational Institute(Deemed University), DayalBagh, Agra 282005 (India)

2015-05-15

This paper presents a theoretical model for the transient response of nonlinear coupling between magnetosonic wave and ion acoustic wave in the overdense plasma. Filamentation of magnetosonic wave has been considered to be responsible for magnetic turbulence during the laser plasma interaction. The ion acoustic wave gets excited due to the ponderomotive force exerted by magnetosonic wave and this ion acoustic wave in turn generates perturbation in the background density in the form of spatial density harmonics. Numerical simulation has been carried out for dimensionless coupled equations of magnetosonic wave and ion acoustic wave; and the results show quite complex localized structures that grow with time. The power spectrum has also been studied which shows that the spectral index follows an approximate scaling of the order of ∼k{sup −2.4} at smaller scales. The data obtained from numerical simulation are used in semi analytical model to better understand the mechanism of nonlinear evolution of magnetosonic wave. The results indicate considerable randomness in the spatial structure of the magnetic field profile which gives sufficient indication of turbulence.

Thermal wave propagation in the pulsed laser irradiation of media with thermal memory

International Nuclear Information System (INIS)

Galovic, S.; Kostoski, D.; Stamboliev, G.; Suljovrujic, E.

2002-01-01

Complete text of publication follows. If a sample is exposed to the influence of laser radiation part of its energy is absorbed and converted in heat. The heat generated in this way is transferred through the sample as heat waves, resulting in various effects (so called photothermal effects). A large number of nondestructive diagnostic methods are based on recording of these effects. It is necessary to create a good model in order to understand and correctly describe the measured results of heat transfer in different media. In a certain number of materials and structures, such as complex biological materials, polymers, metals excited by very short laser pulses etc., the property of thermal memory has been experimentally observed. Starting with the hyperbolic equation that describes heat transfer processes of such media, in this paper has been developed a model of laser-excited heat waves propagation in order to enable application of photothermal techniques in characterization of these media. The cases of optically opaque and transparent samples are considered. The influence of various backings on photothermal waves has also been analyzed. The results are compared to the previous models

Conversion of the luminescence of laser dyes in opal matrices to stimulated emission

International Nuclear Information System (INIS)

Alimov, O K; Basiev, T T; Orlovskii, Yu V; Osiko, V V; Samoilovich, M I

2008-01-01

The luminescence and laser characteristics of a synthetic opal matrix filled with organic dyes are studied upon excitation by nanosecond laser pulses. The appearance of stimulated emission in a partially ordered scattering medium is investigated. It is shown that if the luminescence spectrum of a dye (oxazine-17) is located far outside the photonic bandgap of the opal matrix, stimulated emission along a preferential direction in the (111) plane is observed when pumping exceeds a threshold even without an external optical cavity. The stimulated emission spectrum is considerably narrower than the luminescence spectrum and consists of several narrow lines located within the dye luminescence band. If the luminescence spectrum of a dye (rhodamine 6G) overlaps with the photonic bandgap of the opal matrix, a different picture is observed. The loss of radiation in the matrix leads to the red shift of the luminescence spectrum, while the stimulated emission as in the case of oxazine-17 lies is observed within the luminescence band. (active media, lasers, and amplifiers)

Generation of spin waves by a train of fs-laser pulses: a novel approach for tuning magnon wavelength.

Science.gov (United States)

Savochkin, I V; Jäckl, M; Belotelov, V I; Akimov, I A; Kozhaev, M A; Sylgacheva, D A; Chernov, A I; Shaposhnikov, A N; Prokopov, A R; Berzhansky, V N; Yakovlev, D R; Zvezdin, A K; Bayer, M

2017-07-18

Currently spin waves are considered for computation and data processing as an alternative to charge currents. Generation of spin waves by ultrashort laser pulses provides several important advances with respect to conventional approaches using microwaves. In particular, focused laser spot works as a point source for spin waves and allows for directional control of spin waves and switching between their different types. For further progress in this direction it is important to manipulate with the spectrum of the optically generated spin waves. Here we tackle this problem by launching spin waves by a sequence of femtosecond laser pulses with pulse interval much shorter than the relaxation time of the magnetization oscillations. This leads to the cumulative phenomenon and allows us to generate magnons in a specific narrow range of wavenumbers. The wavelength of spin waves can be tuned from 15 μm to hundreds of microns by sweeping the external magnetic field by only 10 Oe or by slight variation of the pulse repetition rate. Our findings expand the capabilities of the optical spin pump-probe technique and provide a new method for the spin wave generation and control.

Comparison of photosensitivity in germanium doped silica fibers using 244 nm and 266 nm continuous wave lasers

DEFF Research Database (Denmark)

Jensen, Jesper Bo; Varming, Poul; Liu, B.

2001-01-01

Diode pumped continuous-wave UV lasers offer an interesting alternative to frequency doubled argon-ion lasers. We report the first photosensitivity comparison using these lasers on deuterium loaded standard telecommunication fibers and unloaded experimental fibers....

Continuous wave and tunable laser operation of Yb3+ in disordered NaLa(MoO4)2

Science.gov (United States)

Rico, M.; Liu, J.; Cano-Torres, J. M.; García-Cortés, A.; Cascales, C.; Zaldo, C.; Griebner, U.; Petrov, V.

2005-09-01

Continuous-wave Yb3+ laser operation is studied in single crystals of disordered NaLa(MoO4)2 at room temperature. The sample used was grown by the Czochralski technique and incorporates an Yb ion density of 3.1×1020 cm-3. The effect of the Yb concentration on some of the crystal properties is described as well as the spectroscopic Yb3+ properties at 5 K. Maximum slope efficiencies of about 40% for π and 38% for σ polarization were obtained under Ti:sapphire laser pumping near 976 nm, respectively. The maximum output power for the π polarization was 400 mW at 1039.5 nm, the threshold in this case amounted to 240 mW (absorbed pump power). The laser emission was tunable between 1016 and 1064 nm with a Lyot filter. Lasing was also realized by pumping with a fiber-coupled diode laser module. Maximum output power of 900 mW at 1035 nm was achieved in this case for the π polarization and the threshold was 280 mW. The results, in terms of output power and tunability, are superior in comparison to all previous reports on Yb-doped disordered double tungstate or molybdate crystals and represent a significant improvement in comparison to earlier experiments with low-doped Yb:NaLa(MoO4)2.

Modeling of terahertz radiation emission from a free-electron laser

Energy Technology Data Exchange (ETDEWEB)

Sharma, Suresh C.; Panwar, Jyotsna; Sharma, Rinku [Department of Applied Physics, Delhi Technological University, Delhi (India)

2017-05-15

In this article, we report the generation of terahertz (THz) radiation using the interaction of a laser-modulated relativistic electron beam (REB) with a surface plasma wave. Two laser beams propagating through the modulator interact with the REB, leading to velocity modulation of the beam. This results in pre-bunching of the REB. The pre-bunched beam travels through the drift space, where the velocity modulation translates into density modulation. The density-modulated beam, on interacting with the surface plasma pump wave, acquires an oscillatory velocity that couples with the modulated beam density to give rise to a nonlinear current density which acts as an antenna to give THz radiation. By optimizing the parameters of the beam and the wiggler, we obtain power of the order of 10{sup -4} using the current scheme. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Optical phase locking of two infrared continuous wave lasers separated by 100 THz

Czech Academy of Sciences Publication Activity Database

Chiodo, N.; Du-Burck, F.; Hrabina, Jan; Lours, M.; Chea, E.; Acef, O.

2014-01-01

Roč. 39, č. 10 (2014), s. 2936-2939 ISSN 0146-9592 R&D Projects: GA ČR GPP102/11/P820; GA MŠk ED0017/01/01; GA MŠk EE2.4.31.0016; GA MŠk(CZ) LO1212; GA MŠk(CZ) 7AMB14FR040 Institutional support: RVO:68081731 Keywords : Continuous wave lasers * Frequency allocation * Harmonic generation * Laser optics Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.292, year: 2014

Free electron lasers and short wavelengths: state of the art and prospects

International Nuclear Information System (INIS)

Couprie, M.E.

2003-01-01

Free electron lasers generate coherent and adjustable radiation that is based on the interaction of a light wave with a relativistic electron beam circulating in a periodic and permanent magnetic field produced by an ondulator. The light wave comes from either - synchrotron radiation emitted by the electron packet at each round in the case of SASE (self amplified spontaneous emission) operating more, or - synchrotron radiation stored in an optic cavity in the case of oscillator operating mode, or - an external laser wave in the case of harmonic generation operating mode. Under particular conditions the light wave is amplified to the detriment of the kinetic energy of the electrons which leads to the laser effect. 5 free electron lasers are operating in the world: Super-Aco in France, Elettra in Italy, NIJI-4 and Uvsor in Japan, and Duke in Usa. The state of the art of free electron lasers in the UV, VUV range is presented and the different configurations associated to storage rings, linac and ERL (energy recovery linacs) are described. (A.C.)

Infrared (1-12 μm) atomic and molecular emission signatures from energetic materials using laser-induced breakdown spectroscopy

Science.gov (United States)

Kumi Barimah, E.; Hömmerich, U.; Brown, E.; Yang, C. S.-C.; Trivedi, S. B.; Jin, F.; Wijewarnasuriya, P. S.; Samuels, A. C.; Snyder, A. P.

2013-05-01

Laser-induced breakdown spectroscopy (LIBS) is a powerful analytical technique to detect the elemental composition of solids, liquids, and gases in real time. For example, recent advances in UV-VIS LIBS have shown great promise for applications in chemical, biological, and explosive sensing. The extension of conventional UVVIS LIBS to the near-IR (NIR), mid-IR (MIR) and long wave infrared (LWIR) regions (~1-12 μm) offers the potential to provide additional information due to IR atomic and molecular signatures. In this work, a Q-switched Nd: YAG laser operating at 1064 nm was employed as the excitation source and focused onto several chlorate and nitrate compounds including KClO3, NaClO3, KNO3, and NaNO3 to produce intense plasma at the target surface. IR LIBS studies on background air, KCl , and NaCl were also included for comparison. All potassium and sodium containing samples revealed narrow-band, atomic-like emissions assigned to transitions of neutral alkali-metal atoms in accordance with the NIST atomic spectra database. In addition, first evidence of broad-band molecular LIBS signatures from chlorate and nitrate compounds were observed at ~10 μm and ~7.3 μm, respectively. The observed molecular emissions showed strong correlation with FTIR absorption spectra of the investigated materials.

A comparative study of x-ray emission from laser spots in laser-heated hohlraums relative to spots on simple disk targets

International Nuclear Information System (INIS)

Ze, F.; Langer, S.H.; Kauffman, R.L.; Kilkenny, J.D.; Landen, O.; Ress, D.; Rosen, M.D.; Suter, L.J.; Wallace, R.J.; Wiedwald, J.D.

1997-01-01

In this paper we report the results of experiments that compare the x-ray emission from a laser spot in a radiation-filled hohlraum to that from a similar laser spot on a simple disk target. The studies were done using the Nova laser facility [J. D. Lindl, Phys. Plasmas 2, 3933 (1995)] in its 0.35 μm wavelength, 1 ns square pulse configuration. Focal spot intensities were 2 endash 3.5x10 15 W/cm 2 . X-ray images measured x-ray conversion in a hohlraum and from an isolated disk simultaneously. A laser spot inside a hohlraum emitted more x rays, after subtracting the background emission from the hohlraum walls, than a spot on a disk. Numerical models suggest the enhanced spot emission inside the hohlraum is due to an increase in lateral transport relative to the disk. Filamentation in the hohlraum will also increase the spot size. The models agree fairly well with the results on spot spreading but do not explain the overall increase in conversion efficiency. copyright 1997 American Institute of Physics

Aspects of electron acoustic wave physics in laser backscatter from plasmas

International Nuclear Information System (INIS)

Sircombe, N J; Arber, T D; Dendy, R O

2006-01-01

Recent experimental results from the Trident laser confirm the importance of kinetic effects in determining laser reflectivities at high intensities. Examples observed include scattering from low frequency electron acoustic waves (EAWs) and the first few stages of a cascade towards turbulence through the Langmuir decay instability. Interpretive and predictive computational capability in this area is assisted by the development of Vlasov codes, which offer high velocity space resolution in high energy regions of particle phase space and do not require analytical pre-processing of the fundamental equations. A direct Vlasov solver, capable of resolving these kinetic processes, is used here to address fundamental aspects of the existence and stability of the electron acoustic wave, together with its collective scattering properties. These simulations are extended to realistic laser and plasma parameters characteristic of single hot-spot experiments. Results are in qualitative agreement with experiments displaying both stimulated Raman and stimulated electron acoustic scattering. The amplitude of simulated EAWs is greater than that observed experimentally and is accompanied by a higher phase velocity. These minor differences can be attributed to the limitations of a one-dimensional collisionless model

Manipulation of the polarization of intense laser beams via optical wave mixing in plasmas

Science.gov (United States)

Michel, Pierre; Divol, Laurent; Turnbull, David; Moody, John

2014-10-01

When intense laser beams overlap in plasmas, the refractive index modulation created by the beat wave via the ponderomotive force can lead to optical wave mixing phenomena reminiscent of those used in crystals and photorefractive materials. Using a vector analysis, we present a full analytical description of the modification of the polarization state of laser beams crossing at arbitrary angles in a plasma. We show that plasmas can be used to provide full control of the polarization state of a laser beam, and give simple analytical estimates and practical considerations for the design of novel photonics devices such as plasma polarizers and plasma waveplates. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

Observation of laser-induced elastic waves in agar skin phantoms using a high-speed camera and a laser-beam-deflection probe.

Science.gov (United States)

Laloš, Jernej; Gregorčič, Peter; Jezeršek, Matija

2018-04-01

We present an optical study of elastic wave propagation inside skin phantoms consisting of agar gel as induced by an Er:YAG (wavelength of 2.94 μm) laser pulse. A laser-beam-deflection probe is used to measure ultrasonic propagation and a high-speed camera is used to record displacements in ablation-induced elastic transients. These measurements are further analyzed with a custom developed image recognition algorithm utilizing the methods of particle image velocimetry and spline interpolation to determine point trajectories, material displacement and strain during the passing of the transients. The results indicate that the ablation-induced elastic waves propagate with a velocity of 1 m/s and amplitudes of 0.1 mm. Compared to them, the measured velocities of ultrasonic waves are much higher, within the range of 1.42-1.51 km/s, while their amplitudes are three orders of magnitude smaller. This proves that the agar gel may be used as a rudimental skin and soft tissue substitute in biomedical research, since its polymeric structure reproduces adequate soft-solid properties and its transparency for visible light makes it convenient to study with optical instruments. The results presented provide an insight into the distribution of laser-induced elastic transients in soft tissue phantoms, while the experimental approach serves as a foundation for further research of laser-induced mechanical effects deeper in the tissue.

303 nm continuous wave ultraviolet laser generated by intracavity frequency-doubling of diode-pumped Pr3+:LiYF4 laser

Science.gov (United States)

Zhu, Pengfei; Zhang, Chaomin; Zhu, Kun; Ping, Yunxia; Song, Pei; Sun, Xiaohui; Wang, Fuxin; Yao, Yi

2018-03-01

We demonstrate an efficient and compact ultraviolet laser at 303 nm generated by intracavity frequency doubling of a continuous wave (CW) laser diode-pumped Pr3+:YLiF4 laser at 607 nm. A cesium lithium borate (CLBO) crystal, cut for critical type I phase matching at room temperature, is used for second-harmonic generation (SHG) of the fundamental laser. By using an InGaN laser diode array emitting at 444.3 nm with a maximum incident power of 10 W, as high as 68 mW of CW output power at 303 nm is achieved. The output power stability in 4 h is better than 2.85%. To the best of our knowledge, this is high efficient UV laser generated by frequency doubling of an InGaN laser diode array pumped Pr3+:YLiF4 laser.

Simulations of bremsstrahlung emission in ultra-intense laser interactions with foil targets

Science.gov (United States)

Vyskočil, Jiří; Klimo, Ondřej; Weber, Stefan

2018-05-01

Bremsstrahlung emission from interactions of short ultra-intense laser pulses with solid foils is studied using particle-in-cell (PIC) simulations. A module for simulating bremsstrahlung has been implemented in the PIC loop to self-consistently account for the dynamics of the laser–plasma interaction, plasma expansion, and the emission of gamma ray photons. This module made it possible to study emission from thin targets, where refluxing of hot electrons plays an important role. It is shown that the angular distribution of the emitted photons exhibits a four-directional structure with the angle of emission decreasing with the increase of the width of the target. Additionally, a collimated forward flash consisting of high energy photons has been identified in thin targets. The conversion efficiency of the energy of the laser pulse to the energy of the gamma rays rises with both the driving pulse intensity, and the thickness of the target. The amount of gamma rays also increases with the atomic number of the target material, despite a lower absorption of the driving laser pulse. The angular spectrum of the emitted gamma rays is directly related to the increase of hot electron divergence during their refluxing and its measurement can be used in experiments to study this process.

Stimulated emission at 2.8 μm from Hg-based quantum well structures grown by photoassisted molecular beam epitaxy

International Nuclear Information System (INIS)

Giles, N.C.; Yang, Z.; Han, J.W.; Cook, J.W. Jr.; Schetzina, J.F.

1990-01-01

We report the first observation of stimulated emission from Hg-based quantum well structures in which the active region is a HgCdTe superlattice. The laser structures were grown on (100) CdZnTe substrates by photoassisted molecular beam epitaxy. Cleaved laser cavities were optically pumped using the 1.06 μm output from a continuous wave Nd:YAG laser. Stimulated emission cavity modes were seen at cw laser power densities as low as 3.4 kW/cm 2 and at temperatures ≥60 K

Thermal properties and continuous-wave laser performance of Yb:LuVO4 crystal

Science.gov (United States)

Cheng, Y.; Zhang, H. J.; Yu, Y. G.; Wang, J. Y.; Tao, X. T.; Liu, J. H.; Petrov, V.; Ling, Z. C.; Xia, H. R.; Jiang, M. H.

2007-03-01

A laser crystal of Yb:LuVO4 with high optical quality was grown by the Czochralski technique. Its thermal properties including specific heat, thermal expansion coefficients, and thermal conductivities along the a- and c-axis have been measured for the first time. Continuous-wave laser output up to 3.5 W at 1031 nm was obtained at room temperature through end-pumping by a high-power diode laser. The corresponding optical conversion efficiency was 43% and the slope efficiency was 72%.

Digitally tunable dual wavelength emission from semiconductor ring lasers with filtered optical feedback

International Nuclear Information System (INIS)

Khoder, Mulham; Verschaffelt, Guy; Nguimdo, Romain Modeste; Danckaert, Jan; Leijtens, Xaveer; Bolk, Jeroen

2013-01-01

We report on a novel integrated approach to obtain dual wavelength emission from a semiconductor laser based on on-chip filtered optical feedback. Using this approach, we show experiments and numerical simulations of dual wavelength emission of a semiconductor ring laser. The filtered optical feedback is realized on-chip by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are placed in the feedback loop in order to control the feedback strength of each wavelength channel independently. By tuning the current injected into each of the amplifiers, we can effectively cancel the gain difference between the wavelength channels due to fabrication and material dichroism, thus resulting in stable dual wavelength emission. We also explore the accuracy needed in the operational parameters to maintain this dual wavelength emission. (letter)

Pulsed-laser-activated impulse response encoder: Sensitive detection of surface elastic waves on biomimetic microsized gel spheres

Science.gov (United States)

Yasukuni, Ryohei; Fukushima, Ryosuke; Iino, Takanori; Hosokawa, Yoichiroh

2017-11-01

A femtosecond-laser-induced impulsive force was applied to microsized calcium alginate (CaAlg) gel spheres as an external force to excite elastic waves. To evaluate elasticity, atomic force microscopy (AFM) was applied to detect vibration propagation. The sphere size dependence of the vibration was well reproduced by finite element method (FEM) simulation for pressure waves and surface acoustic waves. The obtained results indicate that the pulsed-laser-activated impulse response encoder (PLAIRE) enables the sensitive detection of elasticities, not only on inside but also on the surface.

Laser Induced Shock Waves and Vaporization in Biological System and Material Science

National Research Council Canada - National Science Library

Gerstman, Bernard S

2008-01-01

.... We have developed a computational model that allows the calculation of damage resulting from a laser pulse of any duration or energy due to temperature rise, explosive bubble formation, and shock wave production...

Laser ultrasound and simulated time reversal on bulk waves for non destructive control

International Nuclear Information System (INIS)

Diot, G; Walaszek, H; Kouadri-David, A; Guégan, S; Flifla, J

2014-01-01

Laser welding of aluminium generally creates embedded welding defects, such as porosities or cracks. Non Destructive Inspection (NDI) after processing may ensure an acceptable weld quality by defect detection. Nowadays, NDI techniques used to control the inside of a weld are mainly limited to X-Rays or ultrasonics. The current paper describes the use of a Laser Ultrasound (LU) technique to inspect porosities in 2 and 4-mm thick sheet lap welds. First experimentations resulted in the detection of 0.5-mm drilled holes in bulk aluminium sheets. The measurement of the depth of these defects is demonstrated too. Further experimentations shows the applicability of the LU technique to detect porosities in aluminium laser welds. However, as the interpretation of raw measures is limiting the detection capacity of this technique, we developed a signal processing using Time-Reversal capabilities to enhance detection capacities. Furthermore, the signal processing output is a geometrical image of the material's inner state, increasing the ease of interpretation. It is based on a mass-spring simulation which enables the back-propagation of the acquired ultrasound signal. The spring-mass simulation allows the natural generation of all the different sound waves and thus enables the back-propagation of a raw signal without any need of filtering or wave identification and extraction. Therefore the signal processing uses the information contained in the compression wave as well as in the shear wave

Emission of sound from the mammalian inner ear

Science.gov (United States)

Reichenbach, Tobias; Stefanovic, Aleksandra; Nin, Fumiaki; Hudspeth, A. J.

2013-03-01

The mammalian inner ear, or cochlea, not only acts as a detector of sound but can also produce tones itself. These otoacoustic emissions are a striking manifestation of the mechanical active process that sensitizes the cochlea and sharpens its frequency discrimination. It remains uncertain how these signals propagate back to the middle ear, from which they are emitted as sound. Although reverse propagation might occur through waves on the cochlear basilar membrane, experiments suggest the existence of a second component in otoacoustic emissions. We have combined theoretical and experimental studies to show that mechanical signals can also be transmitted by waves on Reissner's membrane, a second elastic structure within the cochea. We have developed a theoretical description of wave propagation on the parallel Reissner's and basilar membranes and its role in the emission of distortion products. By scanning laser interferometry we have measured traveling waves on Reissner's membrane in the gerbil, guinea pig, and chinchilla. The results accord with the theory and thus support a role for Reissner's membrane in otoacoustic emission. T. R. holds a Career Award at the Scientific Interface from the Burroughs Wellcome Fund; A. J. H. is an Investigator of Howard Hughes Medical Institute.

Design study of a traveling-wave Thomson-scattering experiment for the realization of optical free electron lasers

Energy Technology Data Exchange (ETDEWEB)

Steiniger, Klaus; Loeser, Markus; Pausch, Richard; Schramm, Ulrich [Helmholtz-Zentrum Dresden-Rossendorf (Germany); Technische Universitaet Dresden (Germany); Albach, Daniel; Debus, Alexander; Roeser, Fabian; Siebold, Matthias; Bussmann, Michael [Helmholtz-Zentrum Dresden-Rossendorf (Germany)

2016-07-01

We present an experimental setup strategy for the realization of an optical free-electron laser (OFEL) in the Traveling-Wave Thomson-Scattering geometry (TWTS). In TWTS, the electric field of petawatt class, pulse-front tilted laser pulses is used to provide an optical undulator field. This is passed by a relativistic electron bunch so that electron direction of motion and laser propagation direction enclose an interaction angle. The combination of side scattering and pulse-front tilt provides continuous overlap of electrons and laser pulse over meter scale distances which are achieved with centimeter wide laser pulses. An experimental challenge lies in shaping of these wide laser pulses in terms of laser dispersion compensation along the electron trajectory and focusing. In the talk we show how diffraction gratings in combination with mirrors are used to introduce and control dispersion of the laser in order to provide a plane wave laser field along the electron trajectory. Furthermore we give tolerance limits on alignment errors to operate the OFEL. Example setups illustrate functioning and demonstrate feasibility of the scheme.

Measurement of secondary emissions during laser cutting of steel equipments

Energy Technology Data Exchange (ETDEWEB)

Pilot, Guy [Institut de Radioprotection et de Surete Nucleaire, BP 68, 91192 Gif-sur-Yvette Cedex (France)], E-mail: guy.pilot@irsn.fr; Fauvel, Sylvain [Institut de Radioprotection et de Surete Nucleaire, BP 68, 91192 Gif-sur-Yvette Cedex (France); Gosse, Xavier [AREVA NC, Centre de Marcoule, 30200 Bagnols-sur-Ceze Cedex (France); Dinechin, Guillaume de [Commissariat a l' Energie Atomique, DEN/DM2S/SEMT, Saclay, Bat. 611, 91191 Gif-sur-Yvette Cedex (France); Vernhet, Didier [Commissariat a l' Energie Atomique, DEN/VRH/UMODD, Centre de Valrho, BP 17171, 20207 Bagnols-sur-Ceze Cedex (France)

2008-08-15

In order to dismantle some equipments of an obsolete reprocessing plant in Marcoule, studies were carried out by IRSN (Institut de Radioprotection et de Surete Nucleaire)/DSU/SERAC in cooperation with CEA (power laser group) on the laser cutting of steel structures, on the request of AREVA NC/Marcoule (UP1 dismantling project manager) and CEA/UMODD (UP1 dismantling owner). These studies were aimed at: {center_dot}quantifying and characterizing the secondary emissions produced by Nd-YAG laser cutting of Uranus 65 steel pieces and examining the influence of different parameters, {center_dot}qualifying a prefiltration technique and particularly an electrostatic precipitator, {center_dot}comparing the Nd-YAG laser used with other cutting tools previously studied especially on aerosol production and aerosol size distribution.

The detection of gravitational waves

CERN Document Server

Barish, Barry C

1996-01-01

General Relativity predicts the emission of gravitanional waves whenever compact concentrations of energy change shape. This could occur in a variety of astrophysical phenomena. For example, the coalescence of binary systems such as a pair of neutron stars or black holes emit gravitanional waves that propagate through space at the speed of light, and in principle, can be directly detected on the earth's surface. This lecture series will review the possible sources of gravitanional waves and the various approaches toward detection, with special emphasis on long baseline interferometer detectors. The Laser Interferometer Gravitanional Wave Observatory (LIGO) is being constructed with a goal to detect these waves and then to use them as a new tool to explore and study the Universe. The sources of gravitanional waves and techniques for detection will be presented, as well as the status and prospects for the LIGO project.

CW organic dye laser

International Nuclear Information System (INIS)

Tuccio, S.A.; Peterson, O.G.

1975-01-01

A method and apparatus for producing continuous emission from a lasing medium comprising organic dye molecules in solution are described. Continuous emission is accomplished by flowing the medium through a focused optical cavity while simultaneously producing a population inversion in that portion of the medium flowing in close proximity to the focal point of the cavity. The population inversion is produced by pumping the medium longitudinally, along the optical axis of the cavity, preferably by the focused output of a continuous-wave argon laser. Sufficient thermal energy is continuously dissipated from the medium to maintain the optical homogeneity thereof at or above the quality required for continuous emission

Search for Transient Gravitational Waves in Coincidence with Short-Duration Radio Transients During 2007-2013

Science.gov (United States)

Abbott, B. P.; Hughey, Brennan; Zanolin, Michele; Szczepanczyk, Marek; Gill, Kiranjyot; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.;

Laser Shock Wave-Assisted Patterning on NiTi Shape Memory Alloy Surfaces

Science.gov (United States)

Ilhom, Saidjafarzoda; Seyitliyev, Dovletgeldi; Kholikov, Khomidkohodza; Thomas, Zachary; Er, Ali O.; Li, Peizhen; Karaca, Haluk E.; San, Omer

2018-01-01

Shape memory alloys (SMAs) are a unique class of smart materials and they were employed in various applications in engineering, biomedical, and aerospace technologies. Here, we report an advanced, efficient, and low-cost direct imprinting method with low environmental impact to create thermally controllable surface patterns. Patterned microindents were generated on Ni50Ti50 (at. %) SMAs using an Nd:YAG laser with 1064 nm wavelength at 10 Hz. Laser pulses at selected fluences were focused on the NiTi surface and generated pressure pulses of up to a few GPa. Optical microscope images showed that surface patterns with tailorable sizes can be obtained. The depth of the patterns increases with laser power and irradiation time. Upon heating, the depth profile of SMA surfaces changed where the maximum depth recovery ratio of 30% was observed. Recovery ratio decreased and stabilized when the number of pulses and thus the well depth were further increased. A numerical simulation of pressure evolution in shape memory alloys showed a good agreement with the experimental results. The stress wave closely followed the rise time of the laser pulse to its peak value and initial decay. Rapid attenuation and dispersion of the stress wave were found in our simulation.

Laser Shock Wave-Assisted Patterning on NiTi Shape Memory Alloy Surfaces

Science.gov (United States)

Ilhom, Saidjafarzoda; Seyitliyev, Dovletgeldi; Kholikov, Khomidkohodza; Thomas, Zachary; Er, Ali O.; Li, Peizhen; Karaca, Haluk E.; San, Omer

2018-03-01

Shape memory alloys (SMAs) are a unique class of smart materials and they were employed in various applications in engineering, biomedical, and aerospace technologies. Here, we report an advanced, efficient, and low-cost direct imprinting method with low environmental impact to create thermally controllable surface patterns. Patterned microindents were generated on Ni50Ti50 (at. %) SMAs using an Nd:YAG laser with 1064 nm wavelength at 10 Hz. Laser pulses at selected fluences were focused on the NiTi surface and generated pressure pulses of up to a few GPa. Optical microscope images showed that surface patterns with tailorable sizes can be obtained. The depth of the patterns increases with laser power and irradiation time. Upon heating, the depth profile of SMA surfaces changed where the maximum depth recovery ratio of 30% was observed. Recovery ratio decreased and stabilized when the number of pulses and thus the well depth were further increased. A numerical simulation of pressure evolution in shape memory alloys showed a good agreement with the experimental results. The stress wave closely followed the rise time of the laser pulse to its peak value and initial decay. Rapid attenuation and dispersion of the stress wave were found in our simulation.

Plasma characterization using terahertz-wave-enhanced fluorescence

International Nuclear Information System (INIS)

Liu Jingle; Zhang, X.-C.

2010-01-01

We demonstrate that the terahertz-wave-enhanced fluorescence emission from excited atoms or molecules can be employed in the characterization of laser-induced gas plasmas. The electron relaxation time and plasma density were deduced through applying the electron impact excitation/ionization and electron-ion recombination processes to the measured time-dependent enhanced fluorescence. The electron collision dynamics of nitrogen plasma excited at different gas pressures and laser pulse energies have been systematically investigated. This plasma characterization method provides picosecond temporal resolution and enables omnidirectional optical signal collection.

Investigations on flexural wave propagation and attenuation in a modified one-dimensional acoustic black hole using a laser excitation technique

Science.gov (United States)

Ji, Hongli; Luo, Jing; Qiu, Jinhao; Cheng, Li

2018-05-01

Acoustic Black Holes (ABHs), as a new type of passive structure for vibration damping enhancement and noise attenuation, have been drawing increasing attentions of many researchers. Due to the difficulty in manufacturing the sharp edges required by the ABH structures, it is important to understand the wave propagation and attenuation process in the presence of damping layers in non-ideal ABHs with a truncated edge. In this paper, an analytical expression of the wave reflection coefficient in a modified one-dimensional ABH is derived and a time-domain experimental method based on a laser excitation technique is used to visualize the wave propagation. In the experimental studies, the flexural waves in the ABH were excited by a scanning pulse laser and measured by a Laser Doppler Vibrometer (LDV). The incident wave and reflected wave were separated from the measured original wave field and the decrease of the wave velocity in the ABH was exhibited. The reflection coefficient was calculated from the ratio of the amplitude of the reflected wave to that of the incident wave for different ABH parameters and different thicknesses of the damping layer. The measured reflection coefficients were used to identify the unknown coefficients in the theoretical formula. The results confirm that there exists an optimal thickness for the damping layer, which leads to the minimum wave reflection. Based on the laser-induced visualization technique and various signal processing and feature extraction methods, the entire process of the wave propagation in a non-ideal one-dimensional ABH structure can be visualized and scrutinized.

Comb-Resolved Dual-Comb Spectroscopy Stabilized by Free-Running Continuous-Wave Lasers

Science.gov (United States)

Kuse, Naoya; Ozawa, Akira; Kobayashi, Yohei

2012-11-01

We demonstrate dual-comb spectroscopy with relatively phase-locked two frequency combs, instead of frequency combs firmly fixed to the absolute frequency references. By stabilizing two beat frequencies between two mode-locked lasers at different wavelengths observed via free-running continuous-wave (CW) lasers, two combs are tightly phase locked to each other. The frequency noise of the CW lasers barely affects the performance of dual-comb spectroscopy because of the extremely fast common-mode noise rejection. Transform-limited comb-resolved dual-comb spectroscopy with a 6 Hz radio frequency linewidth is demonstrated by the use of Yb-fiber oscillators.

Nitinol laser cutting: microstructure and functional properties of femtosecond and continuous wave laser processing

Science.gov (United States)

Biffi, C. A.; Tuissi, A.

2017-03-01

Thermal processing can affect the properties of smart materials, and the correct selection of the best manufacturing technology is fundamental for producing high tech smart devices, containing embedded functional properties. In this work cutting of thin superelastic Nitinol plates using a femtosecond (fs) and continuous wave (CW) laser was studied. Diamond shaped elements were cut to characterize the kerf qualitative features; microstructural analysis of the cross sections allowed identification of thermal damage characteristics introduced into the material during the laser processes. A thermally undamaged microstructure was observed for fs laser cutting, while CW was seen to be characterized by a large heat-affected zone. Functional properties were investigated by differential scanning calorimetry and tensile testing of laser cut microelements and of the reference material. It was seen that the martensitic transformation behavior of Nitinol is not affected by fs regime, while cw cutting provokes an effect equivalent to a high temperature thermal treatment in the material surrounding the cutting kerf, degradating the material properties. Finally, tensile testing indicated that superelastic performances were guaranteed by fs regime, while strong reduction of the recoverable strain was detected in the CW processed sample.

Interplay of Laser-Plasma Interactions and Inertial Fusion Hydrodynamics

International Nuclear Information System (INIS)

Strozzi, D. J.; Bailey, D. S.; Michel, P.; Divol, L.; Sepke, S. M.

2017-01-01

The effects of laser-plasma interactions (LPI) on the dynamics of inertial confinement fusion hohlraums are investigated in this work via a new approach that self-consistently couples reduced LPI models into radiation-hydrodynamics numerical codes. The interplay between hydrodynamics and LPI—specifically stimulated Raman scatter and crossed-beam energy transfer (CBET)—mostly occurs via momentum and energy deposition into Langmuir and ion acoustic waves. This spatially redistributes energy coupling to the target, which affects the background plasma conditions and thus, modifies laser propagation. In conclusion, this model shows reduced CBET and significant laser energy depletion by Langmuir waves, which reduce the discrepancy between modeling and data from hohlraum experiments on wall x-ray emission and capsule implosion shape.

Gravity wave-driven fluctuations in OH nightglow from an extended, dissipative emission region

International Nuclear Information System (INIS)

Schubert, G.; Walterscheid, R.L.; Hickey, M.P.

1991-01-01

The theory of gravity wave-driven fluctuations in the OH nightglow from an extended source region is generalized to account for effects of eddy kinematic viscosity v and eddy thermal diffusivity κ. In the nondiffusive case, the amplitudes and phases of vertically integrated normalized intensity (δI)/(bar I) and temperature (δT 1 )/(bar T 1 ) perturbations and vertically integrated Krassovsky's ratio (η) as functions of period are influenced by the upper limit of vertical integration of the extended source, especially at long periods when vertical wavelengths γ v are small. The effects, which include oscillations in (δT)/(bar I), (δT 1 )/(bar T 1 ), and (η), particularly at long periods, are due to constructive and destructive interference of nightglow signals from vertically separated levels of the OH emitting region that occur when γ v is comparable to or smaller than the thickness of the main emission region. The sensitivity of these ratios to the upper limit of vertical integration occurs because of the relatively small rate of decay of the intensity of OH emission with height above the peak emission level and the exponential growth with altitude of nondissipative gravity waves. Because eddy diffusion increases γ v , especially at long periods, and reduces wave growth with height compared with the case v = κ = 0, inclusion of eddy diffusion removes the sensitivity of (η) and the other ratios ot the maximum height of vertical integration. It is essential to account for both eddy diffusion and emission from the entire vertically extended emission region to correctly predict (η), (δI)/(bar I), and (δT 1 )/(bar T 1 ) at long gravity wave periods

Characteristics of laser-induced shock wave injury to the inner ear of rats

Science.gov (United States)

Kurioka, Takaomi; Matsunobu, Takeshi; Niwa, Katsuki; Tamura, Atsushi; Kawauchi, Satoko; Satoh, Yasushi; Sato, Shunichi; Shiotani, Akihiro

2014-12-01

Recently, the number of blast injuries of the inner ear has increased in the general population. In blast-induced inner ear injury, a shock wave (SW) component in the blast wave is considered to play an important role in sensorineural hearing loss. However, the mechanisms by which an SW affects inner ear tissue remain largely unknown. We aimed to establish a new animal model for SW-induced inner ear injury by using laser-induced SWs (LISWs) on rats. The LISWs were generated by irradiating an elastic laser target with 694-nm nanosecond pulses of a ruby laser. After LISW application to the cochlea through bone conduction, auditory measurements revealed the presence of inner ear dysfunction, the extent of which depended on LISW overpressure. A significantly lower survival rate of hair cells and spiral ganglion neurons, as well as severe oxidative damage, were observed in the inner ear exposed to an LISW. Although considerable differences in the pressure characteristics exist between LISWs and SWs in real blast waves, the functional and morphological changes shown by the present LISW-based model were similar to those observed in real blast-induced injury. Thus, our animal model is expected to be useful for laboratory-based research of blast-induced inner ear injury.

Characteristics of laser-induced shock wave injury to the inner ear of rats.

Science.gov (United States)

Kurioka, Takaomi; Matsunobu, Takeshi; Niwa, Katsuki; Tamura, Atsushi; Kawauchi, Satoko; Satoh, Yasushi; Sato, Shunichi; Shiotani, Akihiro

2014-12-01

Recently, the number of blast injuries of the inner ear has increased in the general population. In blast-induced inner ear injury, a shock wave (SW) component in the blast wave is considered to play an important role in sensorineural hearing loss. However, the mechanisms by which an SW affects inner ear tissue remain largely unknown. We aimed to establish a new animal model for SW-induced inner ear injury by using laser-induced SWs (LISWs) on rats. The LISWs were generated by irradiating an elastic laser target with 694-nm nanosecond pulses of a ruby laser. After LISW application to the cochlea through bone conduction, auditory measurements revealed the presence of inner ear dysfunction, the extent of which depended on LISW overpressure. A significantly lower survival rate of hair cells and spiral ganglion neurons, as well as severe oxidative damage, were observed in the inner ear exposed to an LISW. Although considerable differences in the pressure characteristics exist between LISWs and SWs in real blast waves, the functional and morphological changes shown by the present LISW-based model were similar to those observed in real blast-induced injury. Thus, our animal model is expected to be useful for laboratory-based research of blast-induced inner ear injury.

Properties of a Laser Shock Wave in Al-Cu Alloy under Elevated Temperatures: A Molecular Dynamics Simulation Study

Directory of Open Access Journals (Sweden)

Xiankai Meng

2017-01-01

Full Text Available The laser shock wave (LSW generated by the interaction between a laser and a material has been widely used in laser manufacturing, such as laser shock peening and laser shock forming. However, due to the high strain rate, the propagation of LSW in materials, especially LSW at elevated temperatures, is difficult to study through experimental methods. A molecular dynamics simulation was used in this study to investigate the propagation of LSW in an Al-Cu alloy. The Hugoniot relations of LSW were obtained at different temperatures and the effects of elevated temperatures on shock velocity and shock pressure were analyzed. Then the elastic and plastic wave of the LSW was researched. Finally, the evolution of dislocations induced by LSW and its mechanism under elevated temperatures was explored. The results indicate that the shock velocity and shock pressure induced by LSW both decrease with the increasing temperatures. Moreover, the velocity of elastic wave and plastic wave both decrease with the increasing treatment temperature, while their difference decreases as the temperature increases. Moreover, the dislocation atoms increases with the increasing temperatures before 2 ps, while it decreases with the increasing temperatures after 2 ps. The reason for the results is related to the formation and evolution of extended dislocations.

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.)

Emission Characteristics of Laser-Induced Plasma Using Collinear Long and Short Dual-Pulse Laser-Induced Breakdown Spectroscopy (LIBS).

Science.gov (United States)

Wang, Zhenzhen; Deguchi, Yoshihiro; Liu, Renwei; Ikutomo, Akihiro; Zhang, Zhenzhen; Chong, Daotong; Yan, Junjie; Liu, Jiping; Shiou, Fang-Jung

2017-09-01

Collinear long and short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) was employed to clarify the emission characteristics from laser-induced plasma. The plasma was sustained and became stable by the long pulse-width laser with the pulse width of 60 μs under free running (FR) conditions as an external energy source. Comparing the measurement results of stainless steel in air using single-pulse LIBS (SP-LIBS) and DP-LIBS, the emission intensity was markedly enhanced using DP-LIBS. The temperature of plasma induced by DP-LIBS was maintained at a higher temperature under different gate delay time and short pulse-width laser power conditions compared with those measured using short SP-LIBS. Moreover, the variation rates of plasma temperatures measured using DP-LIBS were also lower. The superior detection ability was verified by the measurement of aluminum sample in water. The spectra were clearly detected using DP-LIBS, whereas it cannot be identified using SP-LIBS of short and long pulse widths. The effects of gate delay time and short pulse-width laser power were also discussed. These results demonstrate the feasibility and enhanced detection ability of the proposed collinear long and short DP-LIBS method.

Simulation of intense laser-dense matter interactions. X-ray production and laser absorption

Energy Technology Data Exchange (ETDEWEB)

Ueshima, Yutaka; Kishimoto, Yasuaki; Sasaki, Akira [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment; Sentoku, Yasuhiko; Tajima, Toshiki

1998-03-01

The development of short-pulse ultra high intensity lasers will enable us to generate short-pulse intense soft and hard X-rays. Acceleration of an electron in laser field generates intense illuminated located radiation, Larmor radiation, around KeV at 10{sup 18} W/cm{sup 2} with 100 TW and 1 {mu}m wave length laser. The Coulomb interaction between rest ions and relativistic electron generates broad energy radiation, bremsstrahlung emission, over MeV at 10{sup 18} W/cm{sup 2} with the same condition. These intense radiations come in short pulses of the same order as that of the irradiated laser. The generated intense X-rays, Larmor and bremsstrahlung radiation, can be applied to sources of short pulse X-ray, excitation source of inner-shell X-ray laser, position production and nuclear excitation, etc. (author)

Electromagnetic radiations from laser interaction with gas-filled Hohlraum

Science.gov (United States)

Yang, Ming; Yang, Yongmei; Li, Tingshuai; Yi, Tao; Wang, Chuanke; Liu, Shenye; Jiang, Shaoen; Ding, Yongkun

2018-01-01

The emission of intensive electromagnetic pulse (EMP) due to laser-target interactions at the ShenGuang-III laser facility has been evaluated by probes. EMP signals measured using the small discone antennas demonstrated two variation trends including a bilateral oscillation wave and a unilateral oscillation wave. The new trend of unilateral oscillation could be attributed to the hohlraum structure and low-Z gas in the hohlraum. The EMP waveform showed multiple peaks when the gas-filled hohlraum was shot by the high-power laser. Comparing the EMP signals with the verification of stimulated Raman scattering energy and hard x-ray energy spectrum, we found that the intensity of EMP signals decreased with the increase of the hohlraum size. The current results are expected to offer preliminary information to study physical processes on laser injecting gas-filled hohlraums in the National Ignition Facility implementation.

Amplified spontaneous emission of an end-pumped cesium vapor laser

International Nuclear Information System (INIS)

An, Guofei; Wang, You; Cai, He; Han, Juhong; Wang, Shunyan; Rong, Kepeng; Yu, Hang; Xue, Liangping; Zhang, Wei; Wang, Hongyuan; Zhou, Jie

2017-01-01

Diode pumped alkali lasers (DPALs) provide a significant potential for construction of high-powered lasers. A series of models have been established to analyze the DPAL’s kinetic process and most of them are based on the algorithms in which the amplified spontaneous emission (ASE) effect has not been considered. However, ASE is harmful in realization of a high-powered DPAL since the gain is very high. Usually, ASE becomes serious when the volume of the gain medium is large and the pump power is high. Basically, the conclusions we obtained in this study can be extended to other kinds of laser configurations. (paper)

Thermal Electron Bernstein Wave Emission Measurements on NST

Czech Academy of Sciences Publication Activity Database

Diem, S.J.; Taylor, G.; Efthimion, P.; LeBlanc, B.P.; Philips, C.K.; Caughman, J.; Wilgen, J.B.; Harvey, R.W.; Preinhaelter, Josef; Urban, Jakub

2006-01-01

Roč. 51, č. 7 (2006), s. 134 ISSN 0003-0503. [Annual Meeting of the Division of Plasma Physics/48th./. Philadelphia, Pennsylvania , 30.10.2006-3.11.2006] Institutional research plan: CEZ:AV0Z20430508 Keywords : Conversion * Emission * Tokamaks * Electron Bernstein waves * Simulation * MAST * NSTX Subject RIV: BL - Plasma and Gas Discharge Physics http://www.aps.org/meet/DPP06/baps/all_DPP06.pdf

Laser shock wave consolidation of nanodiamond powders on aluminum 319

Energy Technology Data Exchange (ETDEWEB)

Molian, Pal [Laboratory for Lasers, MEMS, and Nanotechnology, Department of Mechanical Engineering, Iowa State University, Ames, IA 50011-2161 (United States)], E-mail: molian@iastate.edu; Molian, Raathai; Nair, Rajeev [Laboratory for Lasers, MEMS, and Nanotechnology, Department of Mechanical Engineering, Iowa State University, Ames, IA 50011-2161 (United States)

2009-01-01

A novel coating approach, based on laser shock wave generation, was employed to induce compressive pressures up to 5 GPa and compact nanodiamond (ND) powders (4-8 nm) on aluminum 319 substrate. Raman scattering indicated that the coating consisted of amorphous carbon and nanocrystalline graphite with peaks at 1360 cm{sup -1} and 1600 cm{sup -1} respectively. Scanning electron microscopy revealed a wavy, non-uniform coating with an average thickness of 40 {mu}m and absence of thermal effect on the surrounding material. The phase transition from nanodiamond to other phases of carbon is responsible for the increased coating thickness. Vicker's microhardness test showed hardness in excess of 1000 kg{sub f}/mm{sup 2} (10 GPa) while nanoindentation test indicated much lower hardness in the range of 20 MPa to 2 GPa. Optical surface profilometry traces displayed slightly uneven surfaces compared to the bare aluminum with an average surface roughness (R{sub a}) in the range of 1.5-4 {mu}m depending on the shock wave pressure and type of confining medium. Ball-on-disc tribometer tests showed that the coefficient of friction and wear rate were substantially lower than the smoother, bare aluminum sample. Laser shock wave process has thus aided in the generation of a strong, wear resistant, durable carbon composite coating on aluminum 319 substrate.

Emission characteristics of laser ablation-hollow cathode glow discharge spectral source

Directory of Open Access Journals (Sweden)

Karatodorov Stefan

2014-11-01

Full Text Available The emission characteristics of a scheme combining laser ablation as sample introduction source and hollow cathode discharge as excitation source are presented. The spatial separation of the sample material introduction by laser ablation and hollow cathode excitation is achieved by optimizing the gas pressure and the sample-cathode gap length. At these conditions the discharge current is maximized to enhance the analytical lines intensity.

An optical technique to measure the frequency and mode emission of tunable lasers

International Nuclear Information System (INIS)

Marchetti, S.; Simili, R.

1988-01-01

To use mode tunable lasers it is necessary to measure the laser frequency and the mode emission. This problem is very important when waveguide lasers are used. Normally this information is obtained by a heterodyne technique, but there are some difficulties to perform this method in a large electrical noise environment, when pulsed of radiofrequency lasers are used. This laser information was obtained by using an alternative low-cost optical system. With this apparatus the cavity pulling was measured and an upper limit for the linewidth of a radiofrequency, high pressure, line and mode-tunable, CO 2 laser was roughly estimated

Shock waves and cavitation bubbles in water and isooctane generated by Nd:YAG laser: experimental and theoretical results

Science.gov (United States)

Muller, Milos; Garen, Walter; Koch, Sandra; Marsik, Frantisek; Neu, Walter; Saburov, Eduado

2004-04-01

Temporal evolution of laser generated cavitation bubbles and shock waves were studied. Q-switched Nd-Yag laser pulses at 1064 nm are focused into the liquid. An Imager 3 CCD camera with multi exposure mode allows recording of 10 images with minimal exposure delay of 100 ns and minimal exposure time of 100 ns. Illumination is provided by xenon flash lamp for single exposure (shock wave recording) and by halogen lamp for multi exposure mode (bubble recording). Distilled water and a retrograde fluid, isooctane, have been under investigation to identify the differences in the cavitation process and shock wave propagation. The calculation of the shock wave velocities in water and isooctane are based on image recording at constant exposure time of 100 ns and using laser differential interferometry. Strong differences of bubble oscillation were observed in water and isooctane. Gilmore's model is used for numerical simulation of bubble dynamics.

Precision improvement of frequency-modulated continuous-wave laser ranging system with two auxiliary interferometers

Science.gov (United States)

Shi, Guang; Wang, Wen; Zhang, Fumin

2018-03-01

The measurement precision of frequency-modulated continuous-wave (FMCW) laser distance measurement should be proportional to the scanning range of the tunable laser. However, the commercial external cavity diode laser (ECDL) is not an ideal tunable laser source in practical applications. Due to the unavoidable mode hopping and scanning nonlinearity of the ECDL, the measurement precision of FMCW laser distance measurements can be substantially affected. Therefore, an FMCW laser ranging system with two auxiliary interferometers is proposed in this paper. Moreover, to eliminate the effects of ECDL, the frequency-sampling method and mode hopping influence suppression method are employed. Compared with a fringe counting interferometer, this FMCW laser ranging system has a measuring error of ± 20 μm at the distance of 5.8 m.

Study of atmospheric air AC glow discharge using optical emission spectroscopy and near infrared diode laser cavity ringdown spectroscopy

Science.gov (United States)

Srivastava, Nimisha; Wang, Chuji; Dibble, Theodore S.

2008-11-01

AC glow discharges were generated in atmospheric pressure by applying high voltage AC in the range of 3500-15000 V to a pair of stainless steel electrodes separated by an air gap. The discharges were characterized by optical emission spectroscopy (OES) and continuous wave cavity ringdown spectroscopy (cw-CRDS). The electronic (Tex), vibrational (Tv), and rotational (Tr) temperatures were measured. Spectral stimulations of the emission spectra of several vibronic bands of the 2^nd positive system of N2, the 1^st negative system of N2^+, the (0,1,2,3-0) bands of NO (A-X), and the (0-0) band of OH (A-X), which were obtained under various plasma operating conditions, show that Tr, Tv, and Tex are in the ranges of 2000 - 3800, 3500 - 5000, and 6000 - 10500^ K, respectively. Emission spectra show that OH concentration increases while NO concentration decreases with an increase of electrode spacing. The absorption spectra of H2O and OH overtone in the near infrared (NIR) were measured by the cw-CRDS with a telecommunications diode laser at wavelength near 1515 nm.

The elimination of pump depletion in laser-plasma beat-wave accelerators

International Nuclear Information System (INIS)

Ma Jinxiu; Xu Zhizhan

1988-01-01

The pump depletion is a severe problem which hinders the laser-plasma beat-wave accelerator concept from being practical. Starting with the weak relativistic equation of beat-wave excitation of electron plasma waves, the authors have derived the condition for eliminating the pump depletion in the fame moving with the light pulse for arbitrary pulse shapes. It is shown that the depletion can be eliminated by a phase jump of π at the center of the pump pulse and by the appropriated choice of initial plasma density detuning. The numerical calculation have yielded the dependence of the initial detuning on the pump intensity for square pump pulses, and have supported the methods used in this paper

Observation of the shock wave propagation induced by a high-power laser irradiation into an epoxy material

International Nuclear Information System (INIS)

Ecault, Romain; Boustie, Michel; Touchard, Fabienne; Berthe, Laurent; Lescoute, Emilien; Sollier, Arnaud; Mercier, Patrick; Benier, Jacky

2013-01-01

The propagation of laser-induced shock waves in a transparent epoxy sample is investigated by optical shadowgraphy. The shock waves are generated by a focused laser (3 ns pulse duration—1.2 to 3.4 TW cm −2 ) producing pressure from 44 to 98.9 GPa. It is observed that the shock wave and the release wave created by the shock reverberation at the rear face are both followed by a dark zone in the pictures. This corresponds to the creation of a tensile zone resulting from the crossing on the loading axis of the release waves coming from the edge of the impact area (2D effects). After the laser shock experiment, the residual stresses in the targets are identified and quantified through a photoelasticimetry analysis of the recovered samples. This work results in a new set of original data which can be directly used to validate numerical models implemented to reproduce the behaviour of epoxy under extreme strain rate loading. The residual stresses observed prove that the high-pressure shocks can modify the pure epoxy properties, which could have an influence on the use made of these materials. (paper)

Time resolved optical emission spectroscopy of cross-beam pulsed laser ablation on graphite targets

International Nuclear Information System (INIS)

Sangines, R.; Sanchez Ake, C.; Sobral, H.; Villagran-Muniz, M.

2007-01-01

Cross-beam pulsed laser ablation with two delayed lasers is performed on two perpendicular graphite targets. The time delay between lasers is varied by up to 5 μs, and physical changes on the second plasma, due to the interaction with the first generated one, are determined by time resolved optical emission spectroscopy

Effects of Medium Characteristics on Laser RCS of Airplane with E-Wave Polarization

Directory of Open Access Journals (Sweden)

Hosam El-Ocla

2015-01-01

Full Text Available Plane wave incidence should be postulated to have an authentic target detection. Practically, the plane wave is incapable usually of keeping its power in the far field especially when propagating through an inhomogeneous medium. Consequently, we assume an incident beam wave with a finite width around the target. In this work, we calculate numerically a laser radar cross section (LRCS of conducting targets having smooth cross sections with inflection points such as airplane in random media. Effects of fluctuations intensity of random media on the LRCS performance are studied in this paper. E-wave polarization (E-wave incidence is considered while the mean target size is approximately twice the wavelength.

EUV emission stimulated by use of dual laser pulses from continus liquid microjet targets

Science.gov (United States)

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

2004-11-01

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

Quasi-monoenergetic ion beam acceleration by laser-driven shock and solitary waves in near-critical plasmas

International Nuclear Information System (INIS)

Zhang, W. L.; Qiao, B.; Huang, T. W.; Shen, X. F.; You, W. Y.; Yan, X. Q.; Wu, S. Z.; Zhou, C. T.; He, X. T.

2016-01-01

Ion acceleration in near-critical plasmas driven by intense laser pulses is investigated theoretically and numerically. A theoretical model has been given for clarification of the ion acceleration dynamics in relation to different laser and target parameters. Two distinct regimes have been identified, where ions are accelerated by, respectively, the laser-induced shock wave in the weakly driven regime (comparatively low laser intensity) and the nonlinear solitary wave in the strongly driven regime (comparatively high laser intensity). Two-dimensional particle-in-cell simulations show that quasi-monoenergetic proton beams with a peak energy of 94.6 MeV and an energy spread 15.8% are obtained by intense laser pulses at intensity I_0 = 3 × 10"2"0" W/cm"2 and pulse duration τ = 0.5 ps in the strongly driven regime, which is more advantageous than that got in the weakly driven regime. In addition, 233 MeV proton beams with narrow spread can be produced by extending τ to 1.0 ps in the strongly driven regime.

Quasi-monoenergetic ion beam acceleration by laser-driven shock and solitary waves in near-critical plasmas

Energy Technology Data Exchange (ETDEWEB)

Zhang, W. L.; Qiao, B., E-mail: bqiao@pku.edu.cn; Huang, T. W.; Shen, X. F.; You, W. Y. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China); Yan, X. Q. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Wu, S. Z. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Zhou, C. T.; He, X. T. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China)

2016-07-15

Ion acceleration in near-critical plasmas driven by intense laser pulses is investigated theoretically and numerically. A theoretical model has been given for clarification of the ion acceleration dynamics in relation to different laser and target parameters. Two distinct regimes have been identified, where ions are accelerated by, respectively, the laser-induced shock wave in the weakly driven regime (comparatively low laser intensity) and the nonlinear solitary wave in the strongly driven regime (comparatively high laser intensity). Two-dimensional particle-in-cell simulations show that quasi-monoenergetic proton beams with a peak energy of 94.6 MeV and an energy spread 15.8% are obtained by intense laser pulses at intensity I{sub 0} = 3 × 10{sup 20 }W/cm{sup 2} and pulse duration τ = 0.5 ps in the strongly driven regime, which is more advantageous than that got in the weakly driven regime. In addition, 233 MeV proton beams with narrow spread can be produced by extending τ to 1.0 ps in the strongly driven regime.

LASER PLASMA AND LASER APPLICATIONS: Plasma transparency in laser absorption waves in metal capillaries

Science.gov (United States)

Anisimov, V. N.; Kozolupenko, A. P.; Sebrant, A. Yu

1988-12-01

An experimental investigation was made of the plasma transparency to heating radiation in capillaries when absorption waves propagated in these capillaries as a result of interaction with a CO2 laser pulse of 5-μs duration. When the length of the capillary was in excess of 20 mm, total absorption of the radiation by the plasma was observed at air pressures of 1-100 kPa. When the capillary length was 12 mm, a partial recovery of the transparency took place. A comparison was made with the dynamics and recovery of the plasma transparency when breakdown of air took place near the free surface.

Nonlinear dynamic effects in a two-wave CO2 laser

International Nuclear Information System (INIS)

Gorobets, V A; Kozlov, K V; Kuntsevich, B F; Petukhov, V O

1999-01-01

Theoretical and experimental investigations were made of nonlinear dynamic regimes of the operation of a two-wave CO 2 laser with cw excitation in an electric discharge and loss modulation in one of the channels. Nonlinear amplitude - frequency characteristics of each of the laser channels have two low-frequency resonance spikes, associated with forced linear oscillations of two coupled oscillators, and high-frequency spikes, corresponding to doubling of the period of the output radiation oscillations. At low loss-modulation frequencies the intensity oscillations of the output radiation in the coupled channels are in antiphase, whereas at high modulation frequencies the dynamics is cophasal. Nonlinear dynamic effects, such as doubling of the period and of the repetition frequency of the pulses and chaotic oscillations of the output radiation intensity, are observed for certain system parameters. (control of laser radiation parameters)

Picosecond pulses from wavelength-swept continuous-wave Fourier domain mode-locked lasers.

Science.gov (United States)

Eigenwillig, Christoph M; Wieser, Wolfgang; Todor, Sebastian; Biedermann, Benjamin R; Klein, Thomas; Jirauschek, Christian; Huber, Robert

2013-01-01

Ultrafast lasers have a crucial function in many fields of science; however, up to now, high-energy pulses directly from compact, efficient and low-power semiconductor lasers are not available. Therefore, we introduce a new approach based on temporal compression of the continuous-wave, wavelength-swept output of Fourier domain mode-locked lasers, where a narrowband optical filter is tuned synchronously to the round-trip time of light in a kilometre-long laser cavity. So far, these rapidly swept lasers enabled orders-of-magnitude speed increase in optical coherence tomography. Here we report on the generation of ~60-70 ps pulses at 390 kHz repetition rate. As energy is stored optically in the long-fibre delay line and not as population inversion in the laser-gain medium, high-energy pulses can now be generated directly from a low-power, compact semiconductor-based oscillator. Our theory predicts subpicosecond pulses with this new technique in the future.

Simulation study and guidelines to generate Laser-induced Surface Acoustic Waves for human skin feature detection

Science.gov (United States)

Li, Tingting; Fu, Xing; Chen, Kun; Dorantes-Gonzalez, Dante J.; Li, Yanning; Wu, Sen; Hu, Xiaotang

2015-12-01

Despite the seriously increasing number of people contracting skin cancer every year, limited attention has been given to the investigation of human skin tissues. To this regard, Laser-induced Surface Acoustic Wave (LSAW) technology, with its accurate, non-invasive and rapid testing characteristics, has recently shown promising results in biological and biomedical tissues. In order to improve the measurement accuracy and efficiency of detecting important features in highly opaque and soft surfaces such as human skin, this paper identifies the most important parameters of a pulse laser source, as well as provides practical guidelines to recommended proper ranges to generate Surface Acoustic Waves (SAWs) for characterization purposes. Considering that melanoma is a serious type of skin cancer, we conducted a finite element simulation-based research on the generation and propagation of surface waves in human skin containing a melanoma-like feature, determine best pulse laser parameter ranges of variation, simulation mesh size and time step, working bandwidth, and minimal size of detectable melanoma.

Absolute Soft X-ray Emission Measurements at the Nike Laser

Science.gov (United States)

Weaver, J.; Atkin, R.; Boyer, C.; Colombant, D.; Feldman, U.; Fielding, D.; Gardner, J.; Holland, G.; Klapisch, M.; Mostovych, A. N.; Obenscain, S.; Seely, J. F.

2002-11-01

Recent experiments at the Nike laser facility have demonstrated that, when a low intensity prepulse ( 2main laser intensity) is used to heat a thin Au or Pd coating on a planar CH target, the growth of non-uniformities due to laser imprint can be reduced from the growth observed for an uncoated CH target. The absolute radiation intensity in the soft x-ray region (0.1-1 keV) has a important role in the energy balance for layered targets. There is an ongoing effort to characterize the soft x-ray emission using an absolutely calibrated transmission grating spectrometer and filtered diode modules. Measurements of the angular distribution of the emission from unlayered solid targets (Au, Pd, CH) have recently been made using an array of moveable filtered diode modules. The data from the angular distribution studies will be presented. A new absolutely calibrated, time-resolving transmission grating spectrometer has been installed at the Nike. The new version has improved spectral resolution, selectable transmission filters, and the potential for simultaneous temporal, spatial, and spectral resolution. Preliminary data from the new spectrometer will be presented and future experiments will be briefly discussed. *Work was supported by DoE

Frequency domain and wavelet analysis of the laser-induced plasma shock waves

Energy Technology Data Exchange (ETDEWEB)

Burger, Miloš, E-mail: milosb@ff.bg.ac.rs; Nikolić, Zoran

2015-08-01

In addition to optical emission, another trace of interest that laser-induced plasma provides is a form of acoustic feedback. The acoustic emission (AE) signals were obtained using both microphone and piezo transducers. This kind of optoacoustic signals have some distinct features resembling the short, burst-like sounds, that may differ significantly depending mainly on the sample exposed and irradiance applied. Experiments were performed on atmospheric pressure by irradiating various metallic samples. The recorded waveforms were examined and numerically processed. Single-shot acoustical spectra have shown significant potential of providing valuable supplementary information regarding plasma propagation dynamics. Moreover, the general approach suggests the possibility of making the whole measurement system cost-effective and portable. - Highlights: • We report acoustical waveform, and acoustical spectroscopy measurements and analysis in a laser-induced plasma of a different metals in air. • Both piezo and microphone transducer were used. • The acoustical spectra of the emission were obtained when the sample (and plasma) were enclosed in experimental chamber. • The acquired acoustical spectra are time-integrated and the frequency peaks were sharp and relatively isolated. • Finally, both time and frequency resolved wavelet spectrogram present a novel method of observing laser-induced plasma behavior.

Searching for Fast Radio Bursts with the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)

Science.gov (United States)

Fisher, Ryan Patrick; Hughey, Brennan; Howell, Eric; LIGO Collaboration

2018-01-01

Although Fast Radio Bursts (FRB) are being detected with increasing frequency, their progenitor systems are still mostly a mystery. We present the plan to conduct targeted searches for gravitational-wave counterparts to these FRB events in the data from the first and second observing runs of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO).

Using violet laser-induced chlorophyll fluorescence emission spectra for crop yield assessment of cowpea (Vigna unguiculata (L) Walp) varieties

Science.gov (United States)

Anderson, Benjamin; Buah-Bassuah, Paul K.; Tetteh, Jonathan P.

2004-07-01

The use of violet laser-induced chlorophyll fluorescence (LICF) emission spectra to monitor the growth of five varieties of cowpea in the University of Cape Coast Botanical Garden is presented. Radiation from a continuous-wave violet laser diode emitting at 396 nm through a fibre is closely incident on in vivo leaves of cowpea to excite chlorophyll fluorescence, which is detected by an integrated spectrometer with CCD readout. The chlorophyll fluorescence spectra with peaks at 683 and 731 nm were used for growth monitoring of the cowpea plants over three weeks and analysed using Gaussian spectral functions with curve fitted parameters to determine the peak positions, area under the spectral curve and the intensity ratio F683/F731. The variation in the intensity ratio of the chlorophyll bands showed sensitive changes indicating the photosynthetic activity of the cowpea varieties. A discussion of the fluorescence result as compared to conventional assessment is presented with regard to discrimination between the cowpea varieties in terms of crop yield performance.

Diode-pumped continuous-wave eye-safe Nd:YAG laser at 1415 nm.

Science.gov (United States)

Lee, Hee Chul; Byeon, Sung Ug; Lukashev, Alexei

2012-04-01

We describe the output performance of the 1415 nm emission in Nd:YAG in a plane-concave cavity under traditional pumping into the 4F5/2 level (808 nm) and direct in-band pumping into the 4F3/2 level (885 nm). An end-pumped Nd:YAG laser yielded maximum cw output power of 6.3 W and 4.2 W at 885 nm and 808 nm laser diode (LD) pumping, respectively. To the best of our knowledge, this is the highest output power of a LD-pumped 1415 nm laser.

INTEGRAL Upper Limits on Gamma-Ray Emission Associated with the Gravitational Wave Event GW150914

DEFF Research Database (Denmark)

Savchenko, V.; Ferrigno, C.; Mereghetti, S.

2016-01-01

Using observations of the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), we place upper limits on the gamma-ray and hard X-ray prompt emission associated with the gravitational wave event GW150914, which was discovered by the LIGO/Virgo Collaboration. The omnidirectional view...... in the 75 keV-2 MeV energy range for typical spectral models. Our results constrain the ratio of the energy promptly released in gamma-rays in the direction of the observer to the gravitational wave energy Eγ/EGW ... of the gravitational wave source, based on the available predictions for prompt electromagnetic emission....

Demonstration of optical rogue waves using a laser diode emitting at 980  nm and a fiber Bragg grating.

Science.gov (United States)

Lee, Min Won; Baladi, Fadwa; Burie, Jean-René; Bettiati, Mauro A; Boudrioua, Azzedine; Fischer, Alexis P A

2016-10-01

Rogue waves are observed for the first time, to the best of our knowledge, in a 980 nm laser diode subject to filtered optical feedback via a fiber Bragg grating. By counting the number of rogue waves in a fixed time window, a rogue wave map is established experimentally as a function of both the optical feedback ratio and the laser current. The comparison with low frequency fluctuations (LFFs) reveals that the rogue waves observed in our system are, in fact, LFF jump-ups.

Effect of temperature on electrical conductance of inkjet-printed silver nanoparticle ink during continuous wave laser sintering

International Nuclear Information System (INIS)

Lee, Dae-Geon; Kim, Dong Keun; Moon, Yoon-Jae; Moon, Seung-Jae

2013-01-01

To determine the effect of temperature on the specific electrical conductance of inkjet-printed ink during continuous wave laser sintering, the temperature of the sintered ink was estimated. The ink, which contained 34 wt.% silver nanoparticles with an average size of approximately 50 nm, was inkjet-printed onto a liquid crystal display glass substrate. The printed ink was irradiated with a 532 nm continuous wave laser for 60 s with various laser intensities. During laser irradiation, the in-situ electrical conductance of the sintered ink was measured to estimate the transient thermal conductivity of the ink. The electrical conductance and thermal conductivity of the ink was coupled to obtain the transient temperature by applying the Wiedemann–Franz law to a two-dimensional transient heat conduction equation. The electrical conductance of laser-sintered ink was highly dependent on the sintering temperature of the ink. - Highlights: • The in-situ electrical conductance was measured during the laser sintering process. • Wiedemann–Franz law coupled the electrical conductance with transient temperature. • The transient temperature of the laser-sintered Ag nanoparticle ink was estimated

Signal enhancement of neutral He emission lines by fast electron bombardment of laser-induced He plasma

Directory of Open Access Journals (Sweden)

Hery Suyanto

2016-08-01

Full Text Available A time-resolved spectroscopic study is performed on the enhancement signals of He gas plasma emission using nanosecond (ns and picosecond (ps lasers in an orthogonal configuration. The ns laser is used for the He gas plasma generation and the ps laser is employed for the ejection of fast electrons from a metal target, which serves to excite subsequently the He atoms in the plasma. The study is focused on the most dominant He I 587.6 nm and He I 667.8 nm emission lines suggested to be responsible for the He-assisted excitation (HAE mechanism. The time-dependent intensity enhancements induced by the fast electrons generated with a series of delayed ps laser ablations are deduced from the intensity time profiles of both He emission lines. The results clearly lead to the conclusion that the metastable excited triplet He atoms are actually the species overwhelmingly produced during the recombination process in the ns laser-induced He gas plasma. These metastable He atoms are believed to serve as the major energy source for the delayed excitation of analyte atoms in ns laser-induced breakdown spectroscopy (LIBS using He ambient gas.

Signal enhancement of neutral He emission lines by fast electron bombardment of laser-induced He plasma

Energy Technology Data Exchange (ETDEWEB)

Suyanto, Hery [Department of Physics, Faculty of Mathematics and Natural Sciences, Udayana University, Kampus Bukit Jimbaran, Denpasar 80361, Bali (Indonesia); Pardede, Marincan [Department of Electrical Engineering, University of Pelita Harapan, 1100 M.H. Thamrin Boulevard, Lippo Village, Tangerang 15811 (Indonesia); Hedwig, Rinda [Department of Computer Engineering, Bina Nusantara University, 9 K.H. Syahdan, Jakarta 14810 (Indonesia); Marpaung, Alion Mangasi [Department of Physics, Faculty of Mathematics and Natural Sciences, Jakarta State University, Rawamangun, Jakarta 12440 (Indonesia); Ramli, Muliadi [Department of Chemistry, Faculty of Mathematics and Natural Sciences, Syiah Kuala University, Darussalam, Banda Aceh 23111, NAD (Indonesia); Lie, Tjung Jie; Kurniawan, Koo Hendrik, E-mail: kurnia18@cbn.net.id [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia); Abdulmadjid, Syahrun Nur [Department of Physics, Faculty of Mathematics and Natural Sciences, Syiah Kuala University, Darussalam, Banda Aceh 23111, NAD (Indonesia); Tjia, May On [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia); Physics of Magnetism and Photonics Group, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, 10 Ganesha,Bandung 40132 (Indonesia); Kagawa, Kiichiro [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia); Fukui Science Education Academy, Takagi Chuo 2 chome, Fukui 910-0804 (Japan)

2016-08-15

A time-resolved spectroscopic study is performed on the enhancement signals of He gas plasma emission using nanosecond (ns) and picosecond (ps) lasers in an orthogonal configuration. The ns laser is used for the He gas plasma generation and the ps laser is employed for the ejection of fast electrons from a metal target, which serves to excite subsequently the He atoms in the plasma. The study is focused on the most dominant He I 587.6 nm and He I 667.8 nm emission lines suggested to be responsible for the He-assisted excitation (HAE) mechanism. The time-dependent intensity enhancements induced by the fast electrons generated with a series of delayed ps laser ablations are deduced from the intensity time profiles of both He emission lines. The results clearly lead to the conclusion that the metastable excited triplet He atoms are actually the species overwhelmingly produced during the recombination process in the ns laser-induced He gas plasma. These metastable He atoms are believed to serve as the major energy source for the delayed excitation of analyte atoms in ns laser-induced breakdown spectroscopy (LIBS) using He ambient gas.