TITLE

Diffraction-controlled backscattering threshold and application to Raman gap

AUTHOR(S)
Rose, Harvey A.; Mounaix, Philippe
PUB. DATE
April 2011
SOURCE
Physics of Plasmas;Apr2011, Vol. 18 Issue 4, p042109
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
In most classic analytical models of linear stimulated scatter, light diffraction is omitted, a priori. However, modern laser optic typically includes a variant of the random phase plate [Y. Kato et al., Phys. Rev. Lett. 53, 1057 (1984)], resulting in diffraction limited laser intensity fluctuations-or localized speckles-which may result in explosive reflectivity growth as the average laser intensity approaches a critical value [H. A. Rose and D. F. DuBois, Phys. Rev. Lett. 72, 2883 (1994)]. Among the differences between stimulated Raman scatter (SRS) and stimulated Brillouin scatter is that the SRS scattered light diffracts more strongly than the laser light with increase of electron density. This weakens the tendency of the SRS light to closely follow the most amplified paths, diminishing gain. Let G0 be the one-dimensional power gain exponent of the stimulated scatter. In this paper we show that differential diffraction gives rise to an increase of G0 at the SRS physical threshold with increase of electron density up to a drastic disruption of SRS as electron density approaches one fourth of its critical value from below. For three wave interaction lengths not small compared to a speckle length, this is a physically robust Raman gap mechanism.
ACCESSION #
60313440

 

Related Articles

  • Modeling of the competition of stimulated Raman and Brillouin scatter in multiple beam experiments. Cohen, Bruce I.; Baldis, Hector A.; Berger, Richard L.; Estabrook, Kent G.; Williams, Edward A.; Labaune, Christine // Physics of Plasmas;Feb2001, Vol. 8 Issue 2, p571 

    Multiple laser beam experiments with plastic target foils at the Laboratoire pour L'Utilisation des Lasers Intenses (LULI) facility [Baldis et al., Phys. Rev. Lett. 77, 2957 (1996)] demonstrated anticorrelation of stimulated Brillouin and Raman backscatter (SBS and SRS). Detailed Thomson...

  • Full-aperture backscatter measurements on the National Ignition Facility. Froula, D. H.; Bower, D.; Chrisp, M.; Grace, S.; Kamperschroer, J. H.; Kelleher, T. M.; Kirkwood, R. K.; MacGowan, B.; McCarville, T.; Sewall, N.; Shimamoto, F. Y.; Shiromizu, S. J.; Young, B.; Glenzer, S. H. // Review of Scientific Instruments;Oct2004 Part I & II, Vol. 75 Issue 10, p4168 

    The National Ignition Facility’s full-aperture backscatter station (FABS) is described. The FABS uses five independent diagnostics on each of the four laser beams in the initial National Ignition Facility quad to measure the energy, power, spectrum, and near-field amplitude modulations of...

  • Stimulated Brillouin and Raman scattering from a randomized laser beam in large inhomogeneous collisional plasmas. II. Model description and comparison with experiments. Tikhonchuk, V. T.; Fuchs, J.; Labaune, C.; Depierreux, S.; Hu¨ller, S.; Myatt, J.; Baldis, H. A. // Physics of Plasmas;May2001, Vol. 8 Issue 5, p1636 

    A model for stimulated Brillouin (SBS) and Raman (SRS) backscattering of a spatially smoothed laser beam interacting with a collisional, inhomogeneous, expanding plasma is presented. It is based on the independent hot spots description [H. A. Rose and D. F. DuBois, Phys. Rev. Lett. 72, 2883...

  • Simultaneous stimulated Raman, Brillouin, and electron-acoustic scattering reveals a potential saturation mechanism in Raman plasma amplifiers. Turnbull, D.; Li, S.; Morozov, A.; Suckewer, S. // Physics of Plasmas;Aug2012, Vol. 19 Issue 8, p083109 

    In a Raman plasma amplifier, the aim is to create plasma conditions in which Raman backscattering is the fastest growing instability, outrunning all competing effects so that it is possible to amplify and compress a laser beam to unprecedented unfocused intensities by utilizing that instability....

  • The stimulated Raman threshold. I. Experiment. Amini, Behrouz; Chen, Francis F. // Physics of Fluids (00319171);Nov86, Vol. 29 Issue 11, p3864 

    The threshold intensity for excitation of the stimulated Raman backscatter instability has been measured at 9.58 µm in a well-diagnosed plasma free of Brillouin scattering. The initial level of density fluctuations was independently measured by ruby laser scattering. The observed threshold of...

  • On the dominant and subdominant behavior of stimulated Raman and Brillouin scattering driven by.... Berger, R.L.; Still, C.H. // Physics of Plasmas;Dec98, Vol. 5 Issue 12, p4337 

    Presents multidimensional fluid simulations of the growth and saturation of Raman (SBS) and Brillouin scattering (SRS) driven by nonuniform laser beams. Limitation of SRS and SBS by quasilinear processes; Occurrence of the nonlinear saturation via anomalous damping; Reduction of the SBS...

  • High-quality phase conjugation even in a highly transient regime of stimulated Brillouin scattering. Králiková, B.; Skála, J.; Straka, P.; Turcicová, H. // Applied Physics Letters;7/31/2000, Vol. 77 Issue 5 

    A high-quality phase conjugation of the stimulated Brillouin scattering has been achieved even in a highly transient regime, as proved by the mask restoration in the backscattered signal. A special two-lens system of laser beam insertion into a scattering medium was used. A reliable onset of the...

  • Optical pulse narrowing by backward, transient stimulated Brillouin scattering. Ghosh Roy, D. N.; Rao, D. V. G. L. N. // Journal of Applied Physics;1/15/1986, Vol. 59 Issue 2, p332 

    Describes an optical pulse narrowing by backward, transient stimulated Brillouin scattering. Derivation of an analytical expression for the backscattered intensity at the entrance to the scattering cell; Characteristics of the transient stimulated Raman and Rayleigh wing scattering; Possibility...

  • Nonlinear modification of laser-plasma interaction processes under crossed laser beams. Labaune, C.; Baldis, H. A.; Cohen, B.; Rozmus, W.; Depierreux, S.; Schifano, E.; Bauer, B. S.; Michard, A. // Physics of Plasmas;May99, Vol. 6 Issue 5, p2048 

    Effects of multiple crossed laser beams on stimulated Brillouin and Raman scattering (SBS and SRS) growth rates, as well as on the SBS and SRS competition, have been investigated in a preformed plasma using Thomson scattering of a short-wavelength probe beam. Reduction of the amplitude of ion...

Share

Read the Article

Courtesy of THE LIBRARY OF VIRGINIA

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics