Generation of a single hot spot by use of a deformable mirror and study of its propagation in an underdense plasma

Wattellier, Benoît; Fuchs, Julien; Zou, J-P; Chanteloup, Jean-Christophe; Bandulet, H.; Michel, P.; Labaune, C.; Depierreux, S.; Kudryashov, Alexis; Aleksandrov, A.

doi:10.1364/josab.20.001632

Cited by 24 publications

(15 citation statements)

References 46 publications

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“…The physical plasma parameters (density profile, temperatures, effective charge, and atomic number) of these simulations correspond to experiments carried out with a single laser speckle at the Laboratoire pour l'Utilisation des Lasers Intenses (LULI), 27,28,40 for which the plasma and laser conditions were carefully characterized. We assumed that the ion acoustic waves are strongly damped so that SBS develops in the convective regime of strongly damped IAW; we also assumed that the IAW damping could be described by the simple ad-hoc damping rate iaw ¼ 0:17 x iaw , x iaw denoting the IAW frequency.…”

Section: Characterization Of the Laser Pulse And Of The Plasma Comentioning

confidence: 99%

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Stimulated Brillouin scattering reduction induced by self-focusing for a single laser speckle interacting with an expanding plasma

Masson-Laborde¹,

Hüller²,

Pesme³

et al. 2014

Physics of Plasmas

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Relativistic self-focusing and its effect on stimulated Raman and stimulated Brillouin scattering in laser plasma interaction Phys. Plasmas 8, 3419 (2001); 10.1063/1.1377048 Stimulated Brillouin and Raman scattering from a randomized laser beam in large inhomogeneous collisional plasmas. II. Model description and comparison with experiments Phys. Plasmas 8, 1636 (2001); 10.1063/1.1357218 Effect of pump depletion and self-focusing on stimulated Brillouin scattering process in laser-plasma interactions Phys. Plasmas 6, 927 (1999); 10.1063/1.873332Effect of the speckle self-focusing on the stationary stimulated Brillouin scattering reflectivity from a randomized laser beam in an inhomogeneous plasma The origin of the low level of stimulated Brillouin scattering (SBS) observed in laser-plasma experiments carried out with a single laser speckle is investigated by means of three-dimensional simulations and modeling in the limit when the laser beam power P is well above the critical power for ponderomotive self-focusing We find that the order of magnitude of the time averaged reflectivities, together with the temporal and spatial SBS localization observed in our simulations, are correctly reproduced by our modeling. It is observed that, after a short transient stage, SBS reaches a significant level only (i) as long as the incident laser pulse is increasing in amplitude and (ii) in a single self-focused speckle located in the low-density front part of the plasma. In order to describe self-focusing in an inhomogeneous expanding plasma, we have derived a new Lagrangian density describing this process. Using then a variational approach, our model reproduces the position and the peak intensity of the self-focusing hot spot in the front part of the plasma density profile as well as the local density depletion in this hot spot. The knowledge of these parameters then makes it possible to estimate the spatial amplification of SBS as a function of the laser beam power and consequently to explain the experimentally observed SBS reflectivity, considerably reduced with respect to standard theory in the regime of large laser beam power. V C 2014 AIP Publishing LLC.

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Section: Characterization Of the Laser Pulse And Of The Plasma Comentioning

confidence: 99%

“…[24][25][26][27][28][29][30] Several of these experiments have been dedicated to the study of self-focusing 24 and of SBS [25][26][27][28][29][30] in a well defined inhomogeneous plasma. In this context, well diagnosed experiments represent a fundamental platform for comparing the experimental results with their numerical modeling.…”

mentioning

confidence: 99%

Stimulated Brillouin scattering reduction induced by self-focusing for a single laser speckle interacting with an expanding plasma

Masson-Laborde¹,

Hüller²,

Pesme³

et al. 2014

Physics of Plasmas

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“…Adaptive mirrors were already successfully used to reduce the aberrations of a beam transmitted through large glass amplifiers of high energy laser facilities [15] or to improve the beam quality in high-power solid state oscillators [16][17][18] or MOPAs [19] operating in the multimode regime. Further applications of deformable mirrors include efficient coupling of light into an optical single-mode fiber [20] and retinal imaging of the human eye [21].…”

Section: Figurementioning

confidence: 99%

Generation of custom modes in a Nd:YAG laser with a semipassive bimorph adaptive mirror

Gerber

Graf

Kudryashov³

2006

Appl. Phys. B

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Custom modes at a wavelength of 1064 nm were generated with a deformable mirror. The required surface deformations of the adaptive mirror were calculated with the Collins integral written in a matrix formalism. The appropriate size and shape of the actuators as well as the needed stroke were determined to ensure that the surface of the controllable mirror matches the phase front of the custom modes. A semipassive bimorph adaptive mirror with five concentric ring-shaped actuators and one defocus actuator was manufactured and characterised. The surface deformation was modelled with the response functions of the adaptive mirror in terms of an expansion with Zernike polynomials. In the experiments the Nd:YAG laser crystal was quasi-CW pumped to avoid thermally induced distortions of the phase front. The adaptive mirror allows to switch between a super-Gaussian mode, a doughnut mode, a Hermite-Gaussian fundamental beam, multi-mode operation or no oscillation in real time during laser operation. For every application there is an ideal intensity distribution which yields optimum results. Such intensity distributions of the beam are commonly called custom modes because their spatial shape is optimised for a specific purpose. Either the special shape of the beam is advantageous for the generation of the laser radiation inside the cavity or for the laser induced process on a target. Due to their high potential in numerous applications we discuss the super-Gaussian mode (also known as top-hat or flat-top mode) and the doughnut mode as two examples of custom modes in the following.The super-Gaussian mode is characterised by a homogeneous intensity distribution and steep edges whereas the doughnut mode exhibits a ring shape with vanishing intensity in the centre of the beam. The intensity distributions of the super-Gaussian mode I SG (r) and the doughnut mode

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“…Poor focusability of SHG light arises primarily from the fact that during the process of upconversion, phase aberrations in the fundamental light are doubled, φ 2ω ≈2φ ω [10] (neglecting nonlinear effects from the crystal). An adaptive optic system is generally used to correct aberrations in laser beams and thus improve focusability [11][12][13]. For example, Queneuille et al [14] demonstrated improvement of SHG wavefront using a deformable mirror placed after the SHG crystal.…”

Section: Introductionmentioning

confidence: 99%

Wavefront-correction for nearly diffraction-limited focusing of dual-color laser beams to high intensities

Zhao¹,

Zhang²,

Chen³

et al. 2014

Opt. Express

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Generation of a single hot spot by use of a deformable mirror and study of its propagation in an underdense plasma

Cited by 24 publications

References 46 publications

Stimulated Brillouin scattering reduction induced by self-focusing for a single laser speckle interacting with an expanding plasma

Stimulated Brillouin scattering reduction induced by self-focusing for a single laser speckle interacting with an expanding plasma

Generation of custom modes in a Nd:YAG laser with a semipassive bimorph adaptive mirror

Wavefront-correction for nearly diffraction-limited focusing of dual-color laser beams to high intensities

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