Showing papers on "Brillouin scattering published in 1983"
TL;DR: In this paper, the important dependence of the SBS gain and threshold on the spectrum and modulation parameters of the optical transmitter is discussed and possible techniques for suppressing SBS in optical communications systems are discussed.
Abstract: Stimulated Brillouin Scattering (SBS) has recently been observed in low-loss monomode fibers at power levels of only a few milliwatts. This article reviews the increasingly important influence which SBS will have on the design and operating range of future optical communications systems which employ low-loss fiber and narrowband laser transmitters. The important dependence of the SBS gain and threshold on the spectrum and modulation parameters of the optical transmitter is described. Possible techniques for suppressing SBS in optical communications systems are discussed.
293 citations
TL;DR: In this article, an analysis of laser irradiation of Be−, CH−, Ti−, and Au disks with 0.53 μm light in 3-200 J, 600-700 psec pulses, at nominal incident intensities from 3×1013 to 5×1015 W/cm2.
Abstract: Results and analyses are presented for laser irradiation of Be‐, CH‐, Ti‐, and Au‐disk targets with 0.53 μm light in 3–200 J, 600–700 psec pulses, at nominal incident intensities from 3×1013 to 5×1015 W/cm2. The measured absorptions are higher than observed in similar 1.06 μm irradiations, and are largely consistent with modeling which shows the importance of inverse‐bremsstrahlung and Brillouin scattering. Observed red‐shifted back‐reflected light shows that Brillouin scattering occurs at low to moderate levels. Backscattering fractions up to 30% were observed in the f/2 focusing lens. The measured fluxes of multi‐keV x rays indicate hot‐electron fractions of 1% or less, with temperatures of 6 to 20 keV which are consistent with resonance absorption or perhaps 2ωpe. Measurements show 30%–50% efficient conversion of absorbed light into sub‐keV x rays, with time‐, angular‐, and spatial‐emission distributions which are generally consistent with non‐local‐thermodynamic‐equilibrium modeling using inhibited th...
97 citations
TL;DR: In this article, the use of stimulated Brillouin scattering (SBS) for laser pulse compression by backward wave amplification in a tapered waveguide offers an attractive alternative to systems based on SRS for use with narrowband laser pulses.
Abstract: The use of stimulated Brillouin scattering (SBS) for laser pulse compression by backward wave amplification in a tapered waveguide offers an attractive alternative to systems based on SRS for use with narrowband laser pulses. Almost one hundred percent conversion efficiencies may be achieved since it is not seriously limited by second Stokes production and with the added advantage that the Stokes pulse is a phase conjugate of the input pulse, under appropriate conditions. Due to the characteristically long damping times of Brillouin-active media, the SBS process is transient. In this regime, the tail of the Stokes pulse may experience a gain and loss modulation with the laser field resulting in a breakup of the Stokes pulse. This effect can be controlled by the geometric taper on the waveguide. A practical consideration of the scaling of a Brillouin compressor to high-power laser systems, notably KrF, is presented. Specific compressor configurations for the extraction of laser pulses in the nanosecond time scale are presented, and a survey of some promising compressor media indicate the practical possibility of accomplishing compression by SBS.
89 citations
TL;DR: Several compressor systems have been investigated, including the use of tapered waveguides, long-focal-length geometries, and generator-amplifier systems, which have shown high compression ratios and energy-conversion efficiencies.
Abstract: Highly efficient compression of laser pulses down to 1 nsec in duration by stimulated Brillouin scattering has been demonstrated. Compression ratios of ~10 and energy-conversion efficiencies >70% have been produced. Several including the use of tapered waveguides, long-focal-length geometries, compressor systems have been investigated, and generator–amplifier systems.
70 citations
TL;DR: In this article, the authors measured the Brillouin scattering from the liquid under hydrostatic pressure up to 30 GPa, and derived Elastic moduli derived from the frequency shifts with bulk modulus values obtained from compressibility data.
Abstract: Brillouin scattering from ${\mathrm{H}}_{2}$O under hydrostatic pressures up to 30 GPa is reported. Sound velocities in the liquid region agree with previous ultrasonic measurements and discontinuities are observed at the liquid---ice VI and ice VI---ice VII phase transitions. Elastic moduli derived from the frequency shifts are compared with bulk modulus values obtained from compressibility data.
69 citations
TL;DR: In this paper, the Brillouin cross-section is obtained for any scattering geometry and for p and s polarisation of the incident and scattered light for a silica film deposited on crystalline silicon and the behaviour of the cross section against the film thickness is investigated.
Abstract: The theory of the Brillouin scattering from the surface of a semi-infinite medium, developed previously, is extended to coated surfaces of cubic materials. The Brillouin cross section is obtained for any scattering geometry and for p and s polarisation of the incident and scattered light. The formulae for the cross section contain contributions from the ripple and the elasto-optic scattering mechanisms for the film as well as for the substrate. The theory is applied to a silica film deposited on crystalline silicon and the behaviour of the cross section against the film thickness is investigated. The authors find that there are strong interference effects among the various contributions to the cross-section, so that the intensity of the spectral lines dramatically oscillates by changing the thickness. Although in general the ripple scattering mechanism is the dominant one it is found that the elasto-optic coupling in the silica film is not negligible and sometimes is even prevailing. The discrete phonon spectrum (Rayleigh, Sezawa, Lamb modes) and the continuous spectrum (resonances, mixed modes) are both studied.
67 citations
TL;DR: In this paper, the elastic modulus C44 of graphite has been determined by Brillouin scattering from surface waves, which agrees with that obtained from neutron scattering experiments but differs from those determined by ultrasonic technique.
Abstract: The shear elastic modulus C44 of graphite has been determined by Brillouin scattering from surface waves. The author's value agrees with that obtained from neutron scattering experiments but differs from those determined by ultrasonic technique.
52 citations
44 citations
TL;DR: In this article, phase conjugation in stimulated Brillouin scattering (SBS) from an optical waveguide is studied numerically, using a Cartesian two-dimensional propagation code (bounce) that includes pump depletion.
Abstract: Phase conjugation in stimulated Brillouin scattering (SBS) from an optical waveguide is studied numerically, using a Cartesian two-dimensional propagation code (bounce) that includes pump depletion. The simulations show that light scattered back through a phase aberrator produces a far-field profile closely matching that of the incident beam; however, the near-field intensity exhibits large and rapid spatial inhomogeneities across the entire aberrator, even for conjugation fidelities H as high as 98%. This effect can be only partially removed by spatial-filtering techniques. The dependence of H on SBS gain, scattering length L, and the average intensity Ī and angular divergence θD of the pump beam is first studied in the low-reflectivity regime (i.e., ignoring pump depletion). For amplitude gains ≳e10, H decreases monotonically with the factor Ī/θD that is due to a small-scale intensity pulling effect. This result appears to be independent of whether θD arises entirely from the aberrator or from a combination of the aberrator plus curvature introduced by a lens. In all cases, pump depletion is found to enhance the fidelity by inhibiting the small-scale pulling effect. Under appropriate conditions, this can actually reverse the intensity dependence of H seen in the absence of pump depletion.
37 citations
TL;DR: In this article, the feasibility of effective time compression of light pulses as a result of stimulated Brillouin scattering of a light beam in gases was investigated and an optimal focusing geometry and a specific excess above the scattering threshold made it possible to achieve time compression by a factor of 20-30 and the duration of the Stokes pulse was then an order of magnitude less than the decay time of hypersound.
Abstract: Theoretical and experimental investigations were made of the feasibility of effective time compression of light pulses as a result of stimulated Brillouin scattering of a light beam in gases. An optimal focusing geometry and a specific excess above the scattering threshold made it possible to achieve time compression by a factor of 20–30 and the duration of the Stokes pulse was then an order of magnitude less than the decay time of hypersound. Stimulated Brillouin scattering in argon at various pressures, corresponding to relaxation times in the range from 1 to 8 nsec, was used to convert pump pulses of 20 nsec duration into Stokes pulses of 1 nsec duration. The energy efficiency of the process was in excess of 80% and the angular divergence was not affected.
33 citations
TL;DR: Light is scattered by fluctuations in the dielectric tensor e in a material as discussed by the authors, where the fluctuations are dynamic and the spectrum is a function of time J(q, w).
Abstract: Light is scattered by fluctuations in the dielectric tensor e in a material. If the fluctuations are dynamic the scattered light has a spectrum S(q, w) that differs from the incident light and the intensity is a function of time J(q, t). The technique of dynamic light scattering has been applied to many different materials. In this review we report on the application of this technique to the study of bulk polymers. There are many processes that couple to the dielectric tensor and lead to light scattering. For organic liquids and glasses the primary sources oflight scattering are fluctuations in density, mechanical shear, and optical anisotropy. Part of these fluctuations are due to thermal acoustic phonons and lead to inelastically scattered light called Brillouin scattering. Several extensive reviews of Brillouin scattering from polymers have been pub lished (1-4). In the present review we focus on developments in this area since 1977. Light scattering from anisotropy fluctuations in bulk polymers has also been treated in detail (3, 4). Here we present a systematic review of all the papers in this field. Near the glass transition in bulk polymers there are fluctuations that relax slowly enough to be analyzed using photon correlation spectroscopy. This subject was recently reviewed (5) in exhaus tive detail, but there are so few papers yet published that a summary of the work is given here. The theory of light scattering from a viscoelastic medium was workcd out in detail by Rytov (6). A summary of the results is presented so that the experimental results can be understood in a general framework. Recent experimental advances are also discussed.
TL;DR: Efficient, diffraction-limited phase conjugation of a XeCl laser beam (308 nm) using stimulated Brillouin scattering is reported using stimulated Brilliant scattering to conjugate heptane or ethanol into ethanol.
Abstract: We report efficient, diffraction-limited phase conjugation of a XeCl laser beam (308 nm) using stimulated Brillouin scattering. Reflectivities approaching 100% are obtained by focusing a XeCl laser (<0.15-cm(-1) linewidth) at 300 GW/cm(2) into heptane or ethanol.
TL;DR: Stimulated Brillouin scattering in a plasma containing broadbandwidth thermal noise was considered in this paper, where a nonlinear equation was derived, which governs the decrease of the incident wave amplitude as it propagates toward the critical density surface.
Abstract: Stimulated Brillouin scattering in a plasma containing broad‐bandwidth thermal noise was considered. Plasma profiles which are inhomogeneous (for example, because of a velocity gradient) were studied. At each point in the profile, a different electromagnetic wave can be resonant with the pump wave and a local ion acoustic wave, and can thus be amplified from its noise level. Some difficult points of the linear theory of this process are first examined. Then a nonlinear equation is derived, which governs the decrease of the incident‐wave amplitude as it propagates toward the critical density surface. Solutions of this equation predict a maximum value of the absorbed intensity, Imax. For incident laser intensities Iin, higher than this value, only a fraction Imax/Iin is absorbed.
TL;DR: Stimulated Rayleigh-Brillouin gain spectra of pure gases are reported in this article, which is clearly distinguishable from stimulated Brillouin scattering without the aid of induced absorption.
Abstract: Stimulated Rayleigh-Brillouin gain spectra of pure gases are reported. Stimulated Rayleigh scattering is now clearly distinguishable from stimulated Brillouin scattering without the aid of induced absorption. As examples, spectral line shapes of Ar and SF6 at various pressures and the associated gain asymmetry are discussed. Potential applications of coherent Rayleigh-Brillouin spectroscopy are suggested.
TL;DR: In this article, the ion acoustic wave and harmonics driven by stimulated Brillouin scattering are probed by space-and time-resolved ruby-laser Thomson scattering, and the ion wave is seen to saturate at (5-10)% amplitude, a level quantitatively predictable from the nonlinear frequency shift caused by ion trapping.
Abstract: The ion acoustic wave and harmonics driven by stimulated Brillouin scattering are probed by space- and time-resolved ruby-laser Thomson scattering. Corresponding to the 6% backscatter observed, the ion wave is seen to saturate at (5--10)% amplitude, a level quantitatively predictable from the nonlinear frequency shift caused by ion trapping.
TL;DR: In this article, a glass-forming 60% KNO3-40% Ca(NO3)2 mixture (mol) through the glass transition in a temperature range of 295-398 K was used to determine sound velocities for transverse and longitudinal waves.
Abstract: Brillouin scattering (GHz) experiments were performed on a glass‐forming 60% KNO3–40% Ca(NO3)2 mixture (mol %) through the glass transition in a temperature range of 295–398 K. Sound velocities for the transverse and longitudinal waves were determined both in the glass and in the melt. The elastic constants and the modulii in the glass and the shear modulus of the melt were evaluated as a function of temperature. The hypersonic results of the glass agree, within the experimental error, with ultrasonic results obtained at room temperature. Present hypersonic values for the shear modulus of the melt, calculated from the transverse velocity at infinite frequencies, are considerably larger than those reported from ultrasonic studies.
TL;DR: In this article, the elastic anomalies are qualitatively interpreted inside the frame of the Landau theory with simple group theory arguments, and two phase transitions occur in this temperature range at TI=40 K and TII=17 K, but elastic anomalies only happen at TI.
Abstract: Brillouin scattering experiments from room temperature down to liquid helium temperature are reported. Two phase transitions occur in this temperature range at TI=40 K and TII=17 K, but elastic anomalies only happen at TI. Several attempts for the direct phason detection have been found unsuccessful. The elastic anomalies are qualitatively interpreted inside the frame of the Landau theory with simple group theory arguments.
TL;DR: In this paper, the authors analyzed threshold conditions for stimulated Raman backscattering from an underdense plasma in the presence of ion-acoustic fluctuations and found that the inhomogeneity threshold for absolute instability can be substantially reduced.
Abstract: Threshold conditions are analyzed for stimulated Raman backscattering (SRS) from an underdense plasma in the presence of ion‐acoustic fluctuations. For typical ion‐acoustic spectra which could result from a Brillouin instability occurring simultaneously with SRS, a reduced collisional threshold due to induced bremsstrahlung is found for the Raman instability. Similarly, for inhomogeneous plasma the phase mismatch created by a density gradient can be compensated for by an inhomogeneity in the ion‐acoustic spectrum; as a consequence, the inhomogeneity threshold for absolute instability can be substantially reduced. Comparisons are made with experimental observations of stimulated Raman scattering in the presence of strong stimulated Brillouin scattering for CO2 laser‐plasma interaction. It is found theoretically that for fluctuation levels typical of that accompanying SBS, induced bremsstrahlung growth rates for Langmuir waves can be of the order of collisional damping rates.
TL;DR: In this article, the elastic tensor components are evaluated from phonon frequency and wavevector data obtained by Brillouin scattering, and a 5-parameter Sellmeier equation is fitted to these data and used to calculate phase matching diagrams for second-harmonic generation and general three-frequency mixing.
Abstract: Indium phosphorus sulfide, a promising nonlinear optical material, is investigated with respect to elastic constants, anisotropic sound velocity, absorption, refraction and nonlinear optical applications. The elastic tensor components are evaluated from phonon frequency and wavevector data obtained by Brillouin scattering. The ordinary and extraordinary dispersion is determined for the entire transparency range (0.4–8 μm). A 5-parameter Sellmeier equation is fitted to these data and is used to calculate phase matching diagrams for second-harmonic generation and general three-frequency mixing. A possible, attractive application, angle tuned parametric oscillation, is discussed.
TL;DR: In this article, the light propagating in a singlemode optical fiber was found to be converted gradually into forward-scattered spontaneous Rayleigh-Brillouin power at 1.3?m wavelength after 600 km.
Abstract: The light propagating in a single-mode optical fibre is found to be converted gradually into forward-scattered spontaneous Rayleigh-Brillouin power. The Brillouin component has a linewidth of -500 MHz and constitutes ~1/200 of the propagating power at 1.3 ?m wavelength after 600 km. The measured backscatter-Brillouin shift coefficient is ?0.15 GHz/wt% GeO2.
TL;DR: In this paper, the authors measured the Brillouin shift for LIkSO 4 as a function of temperature in the range 300-363°K and observed a structural phase transition at 333°K.
Patent•
08 Dec 1983
TL;DR: In this article, the authors used a conjugate moving grating to prevent frequency walkoff of the reflected beams of a double SBS mirror by having the other side of the SBS mirrors act as conjugates.
Abstract: A laser using a stimulated Brillouin scattering (SBS) mirror and a moving grating eliminates frequency walkoff of the reflected beams. A laser using a double-SBS mirror prevents frequency walkoff by having the other side of the SBS mirror act as a conjugate moving grating.
TL;DR: In this article, the threshold for stimulated Raman scattering in H2 gas using a 1.06µm pump was reduced by a factor of 30 (to ~40 kW in a 35 ns pulse) by the combined use of a capillary waveguide and a resonator providing Stokes feedback.
TL;DR: The behavior of zone-centre acoustic phonons has been investigated in LaF3′ CeF3'' PrF3 and NdF3 over a wide temperature range as discussed by the authors.
Abstract: The behaviour of the zone-centre acoustic phonons has been investigated in LaF3′ CeF3′ PrF3 and NdF3 over a wide temperature range. It is shown that in spite of the trigonal structure of these crystals, their elastic properties can be well described with an approximation to hexagonal symmetry. The values of the elastic coefficients increase with increasing atomic number of the cations. The Debye temperatures were determined at temperatures from 80 to 560K with a typical value of θ D = 385 K at 300 K.
TL;DR: In this paper, the role of Brillouin scattering in photon correlation spectroscopy at small scattering angles is studied and an experimental example is given and a resolution limit is discussed.
Abstract: Scattering by entropy fluctuations in a liquid leads to a Rayleigh signal which may be analysed by photon correlation spectroscopy, when small scattering angles of only a few degrees are used. Brillouin scattering, that is scattering by pressure fluctuations, is usually studied at large scattering angles of around 90°; Fabry-Perot spectroscopy is the appropriate method in this case. In the present paper the possible role of Brillouin scattering in photon correlation spectroscopy at small scattering angles is studied. An experimental example is given and a resolution limit is discussed.
TL;DR: In this paper, an energy-dependent cross-section analysis of dispersive and non-dispersive phonon scattering suggests the existence of various quasi-free exciton states for x>or=0.2 that are characterised by finite effective mass values but lie lower in energy compared with the free-exciton absorption.
Abstract: By measurements of resonant Raman scattering combined with absorption and luminescence at low temperature, excitons and phonons are investigated in AgBr1-xClx for a wide range of composition. One-phonon scattering due to intra- and intervalley exciton relaxation involving various optical and acoustic phonons occurs and is interpreted in terms of a modified model used to describe resonant two-phonon scattering in AgBr and AgCl. The analysis of the energy-dependent cross section of dispersive and non-dispersive phonon scattering suggests the existence of various quasi-free exciton states for x>or=0.2 that are characterised by finite effective-mass values but lie lower in energy compared with the free-exciton absorption. For the first time the phonon mode behaviour is studied for phonons at different points outside the centre of the Brillouin zone and discussed within a recently developed model.
TL;DR: In this paper, a tunneling study of artificially prepared Nb-Cu superlattices has been performed and the authors find no evidence for electronic states within the superconducting energy gap.
Abstract: Tunneling studies of artificially prepared Nb-Cu superlattices have been performed. Individual layers were in the range 8--5000 A with total sample thicknesses approx.1..mu..m. The coupling strength 2..delta../kT/sub c/ shows a continuous decrease from values of approx.3.8 (thick layers) appropriate for a strong-coupled superconductor toward the weak-coupled value of approx.3.5 (thin layers). Contrary to earlier theoretical predictions and reports of indirect experimental evidence, we find no evidence for electronic states within the superconducting energy gap. The energies of the Nb longitudinal and transverse acoustic (LA and TA) phonons are found to be unaltered from their bulk values down to layer thicknesses of 32 A. At approx.10 A the TA peak remains unaltered in energy but significantly broadens while the LA peak becomes too broad to measure. These results, in conjunction with earlier Brillouin scattering measurements, imply large changes in the phonon dispersion as a function of layer thickness.
TL;DR: In this article, the authors measured phase-conjugate reflectivities of 11% at 193 nm by using stimulated Brillouin scattering of ArF laser radiation from 2,2,2-trifluoroethanol (CF3CH2OH).
Abstract: We have measured phase-conjugate reflectivities of 11% at 193 nm by using stimulated Brillouin scattering of ArF laser radiation from 2,2,2-trifluoroethanol (CF3CH2OH). This mirror has been shown to correct for the aberrations induced on the wave front by an ArF amplifier.