Showing papers on "Brillouin scattering published in 1975"
TL;DR: In this article, a very small crystal of quartz is used to estimate the longitudinal velocities of a single crystal of the crystal, which is based on analysis of Brillouin scattering.
Abstract: Acoustic velocities for a very small crystal are presented. The longitudinal velocities in the .3 mm single crystal of quartz are accurate to about 1–2%. The technique involves only optical measurements and is based on analysis of Brillouin scattering. The minimal sample size for acoustic velocity measurements using this technique is estimated to be about 0.01–0.03 mm.
93 citations
TL;DR: In this paper, the effect of a finite-band with pump on the parametric instability is considered, with bandwidth modelled by a Kubo-Anderson process, and exact results are obtained for both the amplitudes and power in each decay mode.
Abstract: The effect of a finite-bandwith pump on the parametric instability is considered. First, the temporal problem with unequal damping rates is considered, with bandwidth modelled by a Kubo-Anderson process. Exact results are obtained for both the amplitudes and power in each decay mode, with an interesting asymmetry found. Next, the spatial problem with unequal group velocities is investigated for the cases of 1) finite homogeneous interaction region, and 2) linear density profile. Thresholds and growthrates are found including both the inhomogeneity and bandwidth effects. When values typical of laser fusion parameters are inserted, it is found that bandwidth may be an important method of stabilizing Raman and Brillouin scattering.
70 citations
TL;DR: In this article, it was shown that Brillouin scattering of intense laser light in plasmas can be limited by momentum and energy deposition as a result of reflection of the light.
Abstract: It is shown that Brillouin scattering of intense laser light in plasmas can be limited by momentum and energy deposition as a result of reflection of the light. The calculations compare favorably with some recent experimental results. (AIP)
64 citations
TL;DR: In this paper, the effects of temperature and pressure on the ultrasonic propagation properties, dielectric constants and the Raman and Brillouin spectra in paratellurite (TeO 2 ) were investigated with emphasis on the behavior in the vicinity of the newly discovered, pressure-induced phase transition.
60 citations
TL;DR: In this paper, the authors concentrate on the applications of light scattering techniques to the study of molecular dynamics and interactions in gases, omitting molecular structure determination from Raman measurements in low pressure gases, and discuss some results in gases in which they distinguish essentially two kinds of phenomena: 1. collective motions (sound and thermal waves) as determined by the Brillouin and polarized Rayleigh lines, and 2. collision processes as revealed by collision-induced light scattering or by the shapes of the depolarized Rayleigh and Raman lines.
Abstract: In recent years, light scattering has developed into a full grown subject due to the availability of intense monochromatic laser sources and greatly improved spectro scopic techniques, allowing one to measure spectral shifts in a wide range, from 1 Hz or less to thousands of cm -1 (30 GHz = 1 cm -1 ). Several reviews and books (1-3) have dealt principally with various aspects of light scattering. In this series, Chu (4) in 1970 reviewed light scattering in its usual sense of polarized Rayleigh Brillouin scattering/ Berne & Pecora (5) discussed depolarized Rayleigh scattering in 1974; and Raman scattering was reviewed by Peticolas (6) in 1973. In this review we concentrate on the applications of light scattering techniques to the study of molecular dynamics and interactions in gases, omitting molecular structure determination from Raman measurements in low pressure gases (8). After recalling briefly the physical origin of light scattering in order to deduce what kind of information can be obtained, we discuss some results in gases in which we distinguish essentially two kinds of phenomena: 1. collective motions (sound and thermal waves) as determined by the Brillouin and polarized Rayleigh lines (9), and 2. collision processes as revealed by collision-induced light scattering or by the shapes of the depolarized Rayleigh and Raman lines.
39 citations
TL;DR: In this paper, the authors considered the non-linear interaction of coherent, weakly damped longitudinal and transverse waves in an unmagnetized plasma by means of the coupled mode theory.
Abstract: The non-linear interaction of a few coherent, weakly damped longitudinal and transverse waves in an unmagnetized plasma is considered by means of the coupled mode theory. Using the equations describing the non-linear wave interactions the threshold electric fields and initial growth rates of a number of parametric instabilities are calculated. The following four instabilities, all of which are relevant to laser fusion are considered: (i) the parametric ion-acoustic-Langmuir wave integration, (ii) the two plasmon decay, (iii) stimulated Raman scattering and (iv) stimulated Brillouin scattering. All these instabilities are driven by a large amplitude electro-magnetic wave.
37 citations
TL;DR: In this article, the results of measurements of velocity and attenuation of longitudinal hypersounds in fused quartz are given for frequencies of about 25 and 34 GHz, in the range 77-300 K.
35 citations
TL;DR: Brillouin scattering experiments have been performed on single crystals of ZnSe at 295 °K. From the observed Brillouin frequency shifts the elastic constants have been evaluated as discussed by the authors.
Abstract: Brillouin scattering experiments have been performed on single crystals of ZnSe at 295 °K. From the observed Brillouin frequency shifts the elastic constants of ZnSe have been evaluated. At 295 °K the following results have been obtained: C11 = 87.2 ± 0.8, C12 = 52.4 ± 0.8, and C44 = 39.2 ± 0.4 in units of 1010 dyn/cm2. The values have been compared to previous experimental results and satisfactory agreement obtained. A comparison with values calculated from a rigid ion lattice dynamics model has provided poor agreement however and the origin of this discrepancy has been reviewed.
Brillouin-Lichtstreuung wurde an ZnSe-Einkristallen bei 295 °K gemessen. Aus der beobachteten Brillouin-Verschiebung wurden die elastischen Konstanten von ZnSe bei 295 °K zu C11 = 87,2 ± 0,8; C12 = 52,4 ± 0,8; und C44 = 39,2 ± 0,4 in Werten von 1010 dyn/cm2 bestimmt. Diese Werte werden mit fruheren Arbeiten verglichen und zeigen ausreichende Ubereinstimmung. Ein Vergleich mit errechneten Werten des gitterdynamischen Modells ergibt jedoch nur geringe Ubereinstimmung. Der Grund dieser Abweichung wird diskutiert.
28 citations
27 citations
23 citations
01 Jan 1975
TL;DR: In the early days of Brillouin scattering, the range of possible experiments was severely limited by the inadequacy of the available instrumentation with the development of the very high contrast multipass interferometer it is now possible to perform measurements on very small and imperfect crystals and even on opaque materials where the penetration depth of the light is as low as a few wavelengths.
Abstract: In the early days of Brillouin scattering the range of possible experiments was severely limited by the inadequacy of the available instrumentation With the development of the very high contrast multipass interferometer it is now possible to perform measurements on very small and imperfect crystals and even on opaque materials where the penetration depth of the light is as low as a few wavelengths The wealth of phonon information that can be derived from Brillouin scattering experiments is discussed and illustrated with examples of measurements on layer compounds, opaque semiconductors, liquid crystals and materials undergoing structural phase transitions Brillouin scattering occurs not only from phonons but also from spin waves in magnetic systems Recent spin wave measurements on YIG and CrBr3 are discussed
TL;DR: In this paper, the authors measured the Gruneisen number below the glass transition to be 4.4 and 4.3 for low and high molecular weight polystyrene, respectively.
Abstract: Brillouin light scattering has been used to measure the sound velocities in polystyrene of two different molecular weights. The variation of sound velocity with temperature is related to volumetric expansion of the polymer. Using the thermal expansion data of Fox and Flory we have determined the Gruneisen number, γ, below the glass transition to be 4.4 and 4.3 for low- and high-molecular-weight polystyrenes, respectively, and 5.1 and 5.6 above the glass transition. These numbers compare reasonably well with the value of 3.9 determined by Wada et al. Our measured values are in good agreement with Barker's “bundle of chains” model.
TL;DR: In this article, the authors used high-resolution Brillouin spectroscopy to determine the adiabatic elastic constants of oriented single crystals of γ-oxygen at temperatures near the triple point (54.39 K).
Abstract: The technique of high resolution Brillouin spectroscopy has been used to determine the adiabatic elastic constants of oriented single crystals of γ‐oxygen at temperatures near the triple point (54.39 K). The values obtained were c11 = 2.5(98), c12 = 2.0(58), c44 = 0.27(5) (in units of 1010 dyn cm−2) with an estimated absolute uncertainty of ±2%. The resulting value for the elastic anisotropy parameter was found to be 1.0(2). Estimates of the relative values of the elasto‐optic coefficients were also obtained. It is concluded that γ‐oxygen is ’’plastic’’ in nature.
TL;DR: In this article, the role of microscopic absorbing defects and self-focusing effect in the volume damage of sapphire and quartz crystals and of optical glasses of various kinds by laser pulses of 1-7 nsec duration was analyzed.
Abstract: An investigation was made of the volume damage of sapphire and quartz crystals and of optical glasses of various kinds by laser pulses of 1–7 nsec duration. The roles of microscopic absorbing defects and of the self-focusing effect in the damage process were analyzed. It was found that they dominated the damage which occurred in real transparent media. This led to the proposal and study of a criterion of the optical purity of transparent dielectrics based on a comparison of the intensities of the Rayleigh and Brillouin scattering of light.
TL;DR: The elastic constants c11, c33, c44 for ordinary ice and c11 for D2O ice between 12 and 250°K were deduced from light scattering Brillouin measurements for sound waves of wavevector q = 2.35 × 105 cm−1 as mentioned in this paper.
TL;DR: The elastic constants of GaSe have been determined by studying Brillouin scattering for various crystal orientations as discussed by the authors, where the elastic constants were evaluated with a least square-fit method.
Abstract: The elastic constants of GaSe have been determined by studying Brillouin scattering for various crystal orientations. Depending on the orientation, the spectra exhibit one or two components, which are assigned to specific modes of vibration. From the observed Brillouin frequency shifts, the elastic constants of GaSe are evaluated with a least-square-fit method. The determined values of elastic constants in units of 10 11 dyne/cm 2 are C 11 =10.5±0.4, C 12 =-2.9±0.8, C 13 =-3.32±0.12, C 33 =3.57±0.08, and C 44 =1.05±0.4 at room temperature. These values are compared with those obtained by ultrasonic and neutron-scattering methods. It has also been observed that the relative intensities of the Brillouin components are strongly dependent on crystal orientation. An analysis of this variation in intensity gives values of the ratio of the photoelastic constants: | p 12 / p 13 |≤0.05.
TL;DR: In this article, the softening and damping of this mode can be quantitatively explained by a piezoelectric coupling to the fluctuations of the polarization along the ferroelectric axis, P1.
TL;DR: In this paper, a new optical heterodyne system is established which is capable of measuring acoustic attenuation at frequencies too high for an ordinary pulse-echo technique and yet too low for Brillouin scattering.
Abstract: A new optical heterodyne system is established which is capable of measuring acoustic attenuation at frequencies too high for an ordinary pulse-echo technique and yet too low for Brillouin scattering. The direction of the light scattered by injected phonons suffers an angular spread introduced by the phonon decay. The technique employed is to measure the angular width which determines the attenuation constant. Experiments in water are described in the range 300–500 MHz. The value of α/f2 obtained is 25 (±0.5) ×10-17 sec2/cm. This technique is useful when the decay distance of the acoustic wave is shorter than 0.5 mm.
TL;DR: In this article, transient stimulated scattering of light is treated numerically for situations with arbitrarily high conversion of laser into scattered light and new transient effects are predicted and will be dicussed for scattering in the backward and in the forward directions.
Abstract: Transient stimulated scattering of light is treated numerically for situations with arbitrarily high conversion of laser into scattered light. New, transient effects are predicted and will be dicussed for scattering in the backward and in the forward directions. The computations are found to be in good agreement with time-resolved, experimental studies of stimulated Brillouin scattering in several liquids.
TL;DR: The Raman and Brillouin scattering spectra of a single crystal s−trichlorobenzene at room temperature and the Raman spectrum of a polycrystalline sample at low temperatures have been obtained as mentioned in this paper.
Abstract: The Raman and Brillouin scattering spectra of single crystal s‐trichlorobenzene at room temperature, and the Raman spectrum of a polycrystalline sample at low temperatures, have been obtained. Seventeen of the 21 predicted lattice vibrations have been observed in the Raman spectrum. Brillouin spectra at various angles of scattering and for various crystal orientations have yielded sound velocities for 11 modes of propagation. The nine independent elastic constants for the orthorhombic crystal have been evaluated. The dynamic and static properties of the crystal lattice have been calculated using an atom–atom intermolecular potential model with parameters derived by Bonadeo. Agreement with the Raman lattice frequencies is to about 7%, with the observed sound velocities to about 9%. The atom–atom potential is capable of predicting dynamic and static properties of the lattice with reasonable accuracy, but is apparently not completely adequate.
TL;DR: In this paper, the elastic constants obtained from the acoustic mode dispersion curves are compared with values obtained by Brillouin scattering using a triple-axis spectrometer, including dispersion curve for acoustic modes propagating along the a*, b* and c* directions.
Abstract: The Raman-active modes of thiourea, SC(NH2)2, and deuterated thiourea, SC(ND2)2, have been studied as a function of temperature and comparison is made with previous work. Neutron scattering results, obtained from a single crystal of SC(ND2)2 using a triple-axis spectrometer, include dispersion curves for acoustic modes propagating along the a*, b* and c* directions together with parts of optic branches. The measurements have been made mainly in phase V, with some results in phase I. The elastic constants obtained from the acoustic mode dispersion curves are compared with values obtained by Brillouin scattering.
TL;DR: In this paper, the Brillouin scattering experiments in superfluid 3He-4He solutions at six molar concentrations (x = 0.050, 0.100,0.135, δ 0.398, and 0.606) for temperatures as low as 0.4 K were carried out.
Abstract: We have carried out Brillouin scattering experiments in superfluid 3He-4He solutions at six molar concentrations (x = 0.050, 0.100, 0.135, 0.250, 0.398, and 0.606) for temperatures as low as 0.4 K. We have measured the relative scattered intensities from the three normal modes: first sound, second sound, and concentration fluctuations. We have obtained the velocity of high-frequency first sound (~600 MHz), the velocity of high-frequency second sound (~20–80 MHz), and, at low concentrations, rough indications of the damping of the modes. An exact calculation of the scattered intensities is presented and used together with our measured intensities to obtain values for three thermodynamic quantities: ϱ
n
/ϱ, (∂δ/∂x)
P,T
, and (∂δ/∂T)
P,x
.
TL;DR: In this paper, the Brillouin scattering technique was used to study the acoustic relaxation of t-butanol-water mixtures in the GHz range, and the authors interpreted the observed behavior of the relaxation in terms of the dissociation equilibrium of H-bonded alcohol dimer with monomers by taking into account the effect of water and alcohol in the environment.
Abstract: The acoustic relaxation of t-butanol-water mixtures in the GHz range is studied by the Brillouin scattering technique at l5°C, 25°C and 35°C with varying alcohol molar fraction x from 0 to 0.27. The sound velocity dispersion is observed at x≥0.057. The relaxation strength as a function of x possesses a maximum at x=0.2 (25°C) and the relaxational frequency increases with increasing x. The observed behavior of the relaxation is reasonably interpreted in terms of the dissociation equilibrium of H-bonded alcohol dimer with monomers by taking into account the effect of water and alcohol in the environment. The high-frequency limiting value of the absorption coefficient of this hypersonic relaxation is estimated, and is found to be much higher than the classical absorption due to shear viscosity.
TL;DR: In this paper, the authors used a sample cell free from refractive-index corrections and by use of Rayleigh scattering from Ludox solution as an intensity reference to determine the Brillouin scattering efficiencies of liquids.
Abstract: Brillouin-scattering efficiencies of liquids were determined by use of a sample cell free from refractive-index corrections and by use of Rayleigh scattering from Ludox solution as an intensity reference. The scattering efficiencies for carbon disulfide, toluene, benzene, and carbon tetrachloride were determined at 4880 A. for 90° scattering to be 17.9 ± 1.2, 12.7 ± 1.0, 10.2 ± 0.7, and 9.72 ± 0.78, respectively (in units of 10−6 cm−1 sr−1).
TL;DR: In this paper, the authors used the Brillouin scattering to study the hypersonic properties of cholesteryl palmitate in the liquid crystal-liquid phase transition region.
Abstract: Brillouin scattering was used to study the hypersonic properties of cholesteryl palmitate in the liquid crystal–liquid phase transition region. Contrary to the results of similar measurements by Durand and Rao, no anomalous change in either the velocity or the attenuation of the hypersonic waves was observed at the transition.
TL;DR: In this article, the elastic constants of KCl and NaCl have been determined by studying Brillouin scattering at 90°, with an accuracy comparable to the results of recent ultrasonic measurements.
Abstract: The elastic constants of KCl and NaCl have been determined by studying Brillouin scattering at 90°. The scattered light was analysed by a pressure scanned Fabry-Perot interferometer, the pressure in which was monitored by a Michelson interferometer. Our results have an accuracy comparable to the results of recent ultrasonic measurements, and the agreement between the two methods is excellent in most cases. It is believed that the accuracy of the method described here could be substantially increased by further refinements of the experimental apparatus.
TL;DR: In this article, the influence of mismatch on a coherent, stimulated scattering process including the effect of pump depletion is studied, and the efficiency of the non-linear three-wave interaction exhibits marked threshold behaviour for increasing mismatch, a result which is a generalization of the corresponding behaviour of parametric processes.
Abstract: The influence of mismatch on a coherent, stimulated scattering process including the effect of pump depletion is studied. The efficiency of the non-linear three-wave interaction exhibits marked threshold behaviour for increasing mismatch, a result which is a generalization of the corresponding behaviour of parametric processes. The analysis is applied to the stimulated scattering processes (notably stimulated Brillouin scattering) occurring in laser-plasma interactions, where severe mismatch may be caused by plasma inhomogeneity and/or differential Doppler shifts. By means of a simple physical model we obtain thresholds for stimulated scattering in inhomogeneous and differentially expanding plasmas, results which are in good agreement with those recently given by an alternative approach. In addition, expressions predicting the rise of the reflectivity above threshold are given.