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Title: Slow light of subnanosecond pulses via stimulated Brillouin scattering in nonuniform fibers

Abstract

We have proposed a way to obtain large optically controlled delay for subnanosecond pulses and simultaneously avoid the pulse distortions via stimulated Brillouin scattering (SBS) in optical fibers at cw pumping by the use of longitudinally nonuniform fibers with the Brillouin frequency linearly varying with distance. If the range of Brillouin frequency variation along the fiber covers the whole pulse spectrum, the delay of subnanosecond pulses is linearly proportional to the gain, could be larger than the pulse duration, and the pulse broadening is minimum. We have shown this by solving three-wave SBS equations for realistic fiber lengths, both single subnanosecond pulses and sequences of subnanosecond pulses.

Authors:
; ;  [1]
  1. Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada)
Publication Date:
OSTI Identifier:
20982058
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevA.75.021802; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; BRILLOUIN EFFECT; OPTICAL FIBERS; PULSES; PUMPING; SPECTRA; VELOCITY; VISIBLE RADIATION

Citation Formats

Kalosha, V. P., Chen, Liang, and Bao, Xiaoyi. Slow light of subnanosecond pulses via stimulated Brillouin scattering in nonuniform fibers. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.021802.
Kalosha, V. P., Chen, Liang, & Bao, Xiaoyi. Slow light of subnanosecond pulses via stimulated Brillouin scattering in nonuniform fibers. United States. doi:10.1103/PHYSREVA.75.021802.
Kalosha, V. P., Chen, Liang, and Bao, Xiaoyi. Thu . "Slow light of subnanosecond pulses via stimulated Brillouin scattering in nonuniform fibers". United States. doi:10.1103/PHYSREVA.75.021802.
@article{osti_20982058,
title = {Slow light of subnanosecond pulses via stimulated Brillouin scattering in nonuniform fibers},
author = {Kalosha, V. P. and Chen, Liang and Bao, Xiaoyi},
abstractNote = {We have proposed a way to obtain large optically controlled delay for subnanosecond pulses and simultaneously avoid the pulse distortions via stimulated Brillouin scattering (SBS) in optical fibers at cw pumping by the use of longitudinally nonuniform fibers with the Brillouin frequency linearly varying with distance. If the range of Brillouin frequency variation along the fiber covers the whole pulse spectrum, the delay of subnanosecond pulses is linearly proportional to the gain, could be larger than the pulse duration, and the pulse broadening is minimum. We have shown this by solving three-wave SBS equations for realistic fiber lengths, both single subnanosecond pulses and sequences of subnanosecond pulses.},
doi = {10.1103/PHYSREVA.75.021802},
journal = {Physical Review. A},
number = 2,
volume = 75,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • In a number of experiments, stimulated Brillouin (SBS) or Raman backscattering (SRS) has been observed to be much more vigorous than the other although the expectations based on linear gain exponents are that they should both be reflecting large amounts of incident light. Multidimensional fluid simulations of the growth and saturation of these two instabilities driven by a nonuniform incident laser beam are presented. On the fast time scale, the nonlinear saturation occurs via an anomalous damping inspired by fundamental studies of Langmuir turbulence [D. F. DuBois {ital et al.}, Bull. Am. Phys. Soc. {bold 41}, 1531 (1996)] and acousticmore » wave turbulence [B. I. Cohen {ital et al.}, Phys. Plasmas {bold 4}, 956 (1997)]. Over a longer time scale, SRS and SBS are limited by quasilinear processes such as flows induced by the transfer of momentum from the light to the plasma and ion temperature increases caused by a loss of light energy in SBS. The simulations show a reduction of the SBS reflectivity under conditions of strong SRS reflectivity even if the laser energy is not depleted. The recent observations of decreasing SBS reflectivity with increasing plasma density [D. S. Montgomery, Phys. Plasmas {bold 5}, 1973 (1998)] are shown to be consistent with linear theory and nonlinear simulations of SBS provided the increasing levels of SRS are included. Because the reflectivity is produced by scattering in intense hotspots, where the local reflectivity can be very large, the SBS and SRS can be anticorrelated even when the total scattering is quite modest. {copyright} {ital 1998 American Institute of Physics.}« less
  • We consider the nonlinear three-wave stimulated Brillouin scattering where an initial electromagnetic wave packet grows backward in the expense of a constant input pump wave. For long interaction times we show in particular that the backscattered wave envelope exhibits a set of large peaks of decreasing amplitude, the intensity of the first one growing as t/sup 2/ while its width shrinks as 1/t. Moreover, the sound-wave amplitude saturates. In the limit case of strong damping of the sound wave the asymptotic behavior is quite different. Implications of these results are considered concerning the observed mechanical fracture of an optical fibermore » supporting a large laser pulse.« less
  • In this experimental work, the SBS and SRS processes were used in order to produce UV laser beams of good optical quality and short time duration. An XeCl oscillator and a double-pass amplifier with a phase-conjugate mirror via stimulated Brillouin scattering, generate the laser beam at 308 nm to pump a Raman cell. The oscillator pulse was 11 ns long, while the amplified phase-conjugate beam duration could vary from 3.3 to 1.5 ns, due to the compression operated by the Brillouin mirror. When this last laser beam was focused into a Raman cell containing methane at 30 atm, the shortestmore » backward stimulated Raman scattering pulse at 338.4 nm was 170 ps long with 0.4 mJ of energy. The 338.4-nm wavelength is interesting for the production of short bunches of cold electrons from Mg and Zn targets.« less
  • An investigation was made of optical systems performing wavefront reversal of the radiation in a stimulated Brillouin scattering (STBS) mirror and used to generate short (approx.10/sup -9/ sec) high-power pulses in neodymium-glass amplifiers. For a single-channel system the most suitable arrangement in practice was one in which reflection with wavefront reversal by an STBS mirror took place under steady-state STBS conditions, while a short pulse of the required duration was chopped out of the reflected radiation by a special switch. A method was found for eliminating depolarization of the radiation and inhomogeneities in the transverse distribution of the gain inmore » the neodymium rods and this made it possible to achieve wavefront reversal of the radiation in a high-power laser system with a diffraction-limited accuracy (Eapprox. =50 J, tauapprox. =2 nsec, thetaapprox. =2 x 10/sup -5/ rad).« less
  • Pulses as short as 43 psec were generated by Brillouin backscattering at 248 nm in cyclohexane. The measurements show that the process is accompanied by considerable spectral broadening of the reflected radiation.