Showing papers on "Brillouin scattering published in 1969"
TL;DR: Using laser pulses of shorter duration than the lifetime of the acoustic phonons, stimulated Brillouin scattering could be eliminated as a competing nonlinear process as discussed by the authors, and good quantitative agreement was found between existing theory (which was extended to real light beams) and experimental observations.
Abstract: Stimulated Raman emission of high conversion efficiency was observed in a traveling-wave system. Using laser pulses of shorter duration than the lifetime of the acoustic phonons, stimulated Brillouin scattering could be eliminated as a competing nonlinear process. Good quantitative agreement was found between existing theory (which was extended to real light beams) and experimental observations.
118 citations
103 citations
Book•
30 Apr 1969
TL;DR: In this paper, the authors present a survey of nonlinearity in Optics in active and passive media, as well as nonlinear optical properties in Gases, and the role of coherence in Harmonic Generation.
Abstract: 1. Introduction.- 1.1. The Scope of Optics.- 1.2. Historical Background.- 1.3. Linearity in Optics.- 1.4. Nonlinearity in Other Fields.- 1.5. Nonlinearity in Optics.- 1.6. Scope of this Book.- 2. Background of Nonlinear Optics.- 2.1. Electromagnetic Theory of Light.- 2.2. Electromagnetic Theory of Linear, Isotropic Media.- 2.3. Modes.- 2.4. Geometrical Optics.- 2.5. Quantum Theory of Radiation Process.- 3. Properties of Optical Media.- 3.1. Introduction.- 3.2. Dispersion.- 3.3. Rayleigh Scattering.- 3.4. The Debye-Sears Effect.- 3.5. Birefringence.- 3.6. Zeeman and Stark Effects.- 3.7. Electrostriction and Piezoelectricity.- 3.8. Electrically Induced Birefringence.- 3.9. Optical Activity.- 3.10. Magnetooptical Effects.- 3.11. Fluorescence and the Raman Effect.- 3.12. Intensity-Dependent Optical Phenomena.- 4. Nonlinear Phenomena in Passive Media.- 4.1. Introduction.- 4.2. Electromagnetic Waves in a Nonlinear Dielectric: Method of Solution.- 4.3. The Role of Coherence in Harmonic Generation.- 4.4. The Nonlinear Susceptibility Tensor.- 4.5. Traveling-Wave Second-Harmonic Generation.- 4.6. Index Matching in Birefringent Materials.- 4.7. Boundary Conditions.- 4.8. A Numerical Example.- 4.9. Index Matching as Momentum Conservation.- 4.10. Harmonics Higher than the Second.- 4.11. Optical Rectification.- 4.12. Optical Mixing and Parametric Amplification.- 4.13. Self-Focusing of Optical Beams.- 5. Nonlinear Optical Phenomena in Active Media.- 5.1. Similarities and Contrasts.- 5.2. Raman Processes.- 5.3. Brillouin Scattering.- 5.4. Interactions of Light with Free Electrons.- 5.5. Optical Nonlinearity in Gases.- Appendix. Free and Forced Oscillations in Slightly Nonlinear Systems.
71 citations
TL;DR: In this paper, the authors measured the sound velocity of high-frequency phonons (1-3 GHz) in liquid argon and liquid neon along their vapor pressure equilibrium curves using the Brillouin scattering technique.
Abstract: Recent theoretical work has suggested that at high frequencies, there should be significant departure from classical hydrodynamic behavior in simple fluids. In particular, the frequency dependence of transport coefficients is no longer negligible and may introduce observable effects into the propagation of high-frequency sound. We have measured the sound velocity of high-frequency phonons (1-3 GHz) in liquid argon and liquid neon along their vaporpressure equilibrium curves using the Brillouin scattering technique. The Brillouin spectra were excited with a single-mode argon-ion laser operating at 5145 or 4765 and were analyzed and detected with a Fabry-Perot interferometer and standard photoelectric techniques. Hypersonic (3 GHz) velocities observed in argon decrease linearly from 850 m/sec at 85°K to 742 m/sec at 100°K and uniformly exhibit a small departure from low-frequency (1 MHz) data obtained under the same thermodynamic conditions. This effect is in qualitative agreement with theoretical-model predictions of a negative velocity dispersion at high frequencies. Our measurements of the sound velocity in liquid neon are the first in this material by any technique, and hance cannot be compared with ultrasonic values. The hypersonic velocity in neon decreases not quite linearly from 620 m/sec at 24.9°K to 508 m/sec at 32°K. When compared with results in other noble-gas liquids through corresponding-state arguments, these data suggest the existence of measurable quantum effects in the hypersonic velocity of liquid neon. In addition, an interesting change in slope of the velocity-versus-temperature curve (of 17%) is observed at 28°K. © 1969 The American Physical Society.
62 citations
TL;DR: Stimulated scattering by molecular vibrations and librations was investigated using trains of subnano-second light pulses in this paper, and the results showed that the effects of molecular vibrations on the scattering were independent of each other.
57 citations
TL;DR: In this article, the authors measured the frequency of hypersonic sound waves in the range of 1010 Hz in PMMA as a function of temperature through the glass-transition region.
Abstract: Brillouin scattering of laser light has been used to measure the frequency of hypersonic sound waves in the range of 1010 Hz in PMMA as a function of temperature through the glass‐transition region. A discontinuity in the temperature coefficient of sound velocity is observed at the glass‐transition temperature; this is explained as a consequence of a corresponding discontinuity in the temperature coefficient of the specific volume (thermal expansion coefficient). The ratio of the light scattered by isothermal density fluctuations to that scattered by adiabatic density fluctuations was also measured. This ratio was large and did not change appreciably near the glass‐transition temperature. The value of the Landau‐Placzek ratio is approximately what one would expect from previously observed ultrasonic‐velocity‐dispersion data as a function of temperature well above the glass‐transition temperature. Both the velocity and intensity ratio data indicate that no velocity‐dispersion effects are present for the hypersonic sound waves up to temperatures 35° above the glass‐transition temperature. These results also indicate that the glass transition is not a classical second‐order phase transition.
47 citations
Book Chapter•
01 Jan 1969
TL;DR: In this article, the authors present a method for determining the elastic constants of materials important in geophysics by using transducers that are bonded to the sample and require that the sample be accurately shaped.
Abstract: The complete interpretation of seismic data in terms of the physics and chemistry of the Earth's interior involves an understanding of the effects of composition, crystal
structure, pressure, and temperature on the elastic wave velocities, attenuation, and density. Conventional ultrasonic methods of determining the elastic constants of
materials important in geophysics have been summarized in recent review articles by Simmons and Anderson and Lieberman
. These methods use transducers that are bonded to the specimen and require that the sample be accurately shaped. The frequency of vibration of the sample, or the transit times of an elastic pulse, combined with an accurate measurement of length yield the elastic wave velocities.
37 citations
TL;DR: Stimulated Brillotuin scattering, the efficient scattering of light from parametrically amplified therma acoustic waves, has found many valuable uses since its initial observation and identification, including the measurement of hypersonic velocities and absorption in the gigaherz frequency range, laser frequency shifting, laser Q switching and others.
Abstract: Stimulated Brillouin scattering, the efficient scattering of light from parametrically amplified therma acoustic waves, has found many valuable uses since its initial observation and identification. Among these uses are included the measurement of hypersonic velocities and absorption in the gigaherz frequency range, laser frequency shifting, laser Q switching and others. A description of the process, as well as its applications is presented.
32 citations
30 citations
23 citations
TL;DR: The Brillouin linewidth at acoustic frequencies of several 109Hz was measured for CS 2 CCl 4 acetone, and C 6 H 6. Experimental data were compared with values calculated from the theory of sound propagation under the assumption of a single relaxation frequency as discussed by the authors.
Abstract: The Brillouin linewidth at acoustic frequencies of several 109Hz was measured for CS 2 CCl 4 acetone, and C 6 H 6 . Experimental data were compared with values calculated from the theory of sound propagation under the assumption of a single relaxation frequency. Good agreement was found for the pure liquids except for C 6 H 6 . Extending a theory of binary mixtures from ultrasonic to hypersonic frequencies, we were able to account for the experimentally determined Brillouin linewidths in the mixed system CS 2 -CCl 4 .
TL;DR: In this paper, the authors developed analytical expressions for calculating the diffraction geometry for Brillouin scattering experiments in which the applied acoustic beam and the optical wave vectors lie in a pla...
Abstract: Analytical expressions have been developed for calculating the diffraction geometry for Brillouin scattering experiments in which the applied acoustic beam and the optical wave vectors lie in a pla...
TL;DR: In this paper, the second to first scattering from first and second sound in a 3 He 4 He mixture has been observed and the line shifts indicate no dispersion.
TL;DR: In this article, the total intensity, the horizontally and vertically polarized components, and the Brillouin spectrum of light scattered from two molecular crystals, trimethylacetic acid and succinonitrile, have been made over a range of temperature in the plastic phase of these materials up to and a little beyond the melting point.
Abstract: Measurements of the total intensity, the horizontally and vertically polarized components, and the Brillouin spectrum of light scattered from two molecular crystals, trimethylacetic acid and succinonitrile, have been made over a range of temperature in the plastic phase of these materials up to and a little beyond the melting point. The spectral and intensity changes are correlated with the motions available to the molecules in the crystal.
TL;DR: In this paper, a filter based on an unequal-arm Michelson interferometer was proposed to attenuate a strong spectral line by a factor of 100 or more but transmit without reduction a weaker but more interesting line separated by a few hundred MHz from the strong line.
Abstract: A filter based on an unequal-arm Michelson interferometer is described that will attenuate a strong spectral line by a factor of 100 or more but transmit without reduction a weaker but more interesting line separated by a few hundred MHz from the strong line. The factors limiting the extinction ratio of the filter are considered and a practical instrument that gives results in good agreement with the theory is described.
TL;DR: In this paper, Brillouin scattering measurements of the amplified flux in acoustoelectric domains in n-GaAs, provide evidence for parametric down-conversion within the spectrum, which initially grows in accord with small-signal theory.
TL;DR: In this paper, high-resolution thermal Brillouin scattering techniques have been used to measure the velocity and damping of sound in liquid nitrogen in the 3-5 GHz range, and measurements were carried out along the saturated vapor line from the triple point to the normal boiling point.
Abstract: High‐resolution thermal Brillouin scattering techniques have been used to measure the velocity and damping of sound in liquid nitrogen in the 3–5 GHz range. The measurements were carried out along the saturated vapor line from the triple point to the normal boiling point. No deviation from previous ultrasonic values of velocity or the classical ν2 attenuation is observed at these frequencies. Thus acoustic dispersion due to the 2 GHz relaxation frequency of the internal molecular vibration is completely negligible.
TL;DR: In this paper, the hydrodynamic modes of uniaxial and isotropic Heisenberg ferromagnets are discussed and the frequency window in which one may see the second magnon by neutron or Brillouin scattering is estimated.
TL;DR: In this article, the S.B.S. steady state gain for C6H6 and CCl4 was derived taking into account the energy transfer relaxation properties of the liquids.
Abstract: The S.B.S. steady‐state gain is derived taking into account the energy‐transfer relaxation properties of the liquids. Calculation of the gain for C6H6 and CCl4 are performed. Quantitative comparison between experimental and theoretical gain in n‐hexane, ethyl‐ether, and CS2 are also derived.
TL;DR: In this paper, the dispersion relations for the velocity v for temporally absorbed hypersonic waves and for velocity vB as determined from the positions of the Doppler-shifted Brillouin peaks are discussed.
Abstract: The dispersion relations for the velocity v for temporally absorbed hypersonic waves and for the velocity vB as determined from the positions of the Doppler-shifted Brillouin peaks are discussed fo...
TL;DR: The idea that in real experi ments, all of the scattering geometries are designed to accept a finite range of scattering angles, thereby introducing additional components in the momentum composition of the collected light is entertained.
Abstract: I t is well known that in an ideal light-scattering experiment, once the scattering angle is selected a particular Kth spatial Fourier component of dielectric fluctuation of the medium is fixed. This K value, the momentum change in the light-scatter ing process, is well approximated by | K | = | k0 — ks | ≈ 2 k0 sin 0/2, where θ is the scattering angle and k0 is the wave vector of the incident photon in the scattering medium. In all the theoretical treatments of the spectral distribution of scattered light, the precision with which ks can be measured is assumed to be unlimited. We entertain here the idea that in real experi ments, all of the scattering geometries, even conical optics, are designed to accept a finite range of scattering angles, thereby introducing additional components in the momentum composition of the collected light. We propose a two-step procedure to: (1) analyze the k-space vectors for the real scattering experiment and derive an expression for K taking into account a range of accepted scattering angles; and (2) consider a typical Brillouin scattering situation and analyze the effect of this momentum window on the spectral distribution. Since the magnitude of the momentum vector of the photon, k0, is basically unaltered in the light-scattering process, we may consider a momentum sphere of radius k0 for the photons (Fig. 1). Let k0 be in the plane of kx — kz, and let the scattered wave vector in the ideal case, ks0, be along the kz direction. The ideal momentum transfer is now given by K0 = k0 — ks0. In the real situation, the additional momentum components ks, collected by a finite circular aperture of radius r, a distance d from the source, can vary from ks0 in the angle δ, where tan δmax = r/d and in the
TL;DR: In this paper, a multimode helium-neon laser was used, together with a spherical etalon such that the spectra from different modes of the laser were superimposed, and good light grasp was secured by axial symmetry in the apparatus.
TL;DR: In this article, the acoustic flux φ and the acoustoelectric-after-current I was found to be I ∝φ 2, which means that the observed after-current is mainly caused by the nonlinear acoustic interactions, not to the lattice anharmonicity.
Abstract: Acoustoelectric-after-effect followed by the abrupt termination of the externally applied voltage was studied in semiconducting CdS with Brillouin scattering measurements. Damping behaviors of the generated acoustic flux was first revealed experimentally. The acoustic loss is separated into electronic and nonelectronic contribution via linear and nonlinear process. The nonelectronic linear loss of the acoustic shear waves obeys ω 1.5 -law rather than Akhieser's prediction: ∝ω 2 . White's gain curve reduced by this non-electronic loss agrees well with our experimental results. Nonlinear acoustic loss via second harmonic generation was also estimated. The nonlinear loss is mainly ascribed to the nonlinear acoustoelectric interactions, but not to the lattice anharmonicity. Finally, the relationship between the acoustic flux φ and the acoustoelectric-after-current I was found to be I ∝φ 2 . This means that our observed after-current is mainly caused by the nonlinear acoustoelectric interactions.
TL;DR: In this paper, the authors used Brillouin scattering measurements at room temperature to examine the acoustoelectric instabilities in semiconducting CdS. Time-variations, spatial distributions and frequency spectra of the generated acoustic flux are revealed experimentally.
Abstract: Acoustic domains in semiconducting CdS are studied by Brillouin scattering measurements at room temperature. Time-variations, spatial distributions and frequency spectra of the generated acoustic flux are revealed experimentally. The propagation of the acoustic flux is separated into regions of exponential growth, steady-state saturation and anomalous damping. Such flux behaviors are not accompanied by the corresponding change of the sample current. The frequency spectra range from 200 to 1200 MHz and change slightly during propagation. Linear acoustic gains in this frequency range agree fairly-well with the theoretical curve of White. However, the acoustoelectric phenomena cannot be explained by these low frequency acoustic waves only. Thus, Brillouin scattering is not always valid to examine the acoustoelectric instabilities because of its frequency limitation (≃2.8 GHz).
01 Nov 1969-Journal of Research of the National Bureau of Standards Section A: Physics and Chemistry
TL;DR: A dynamical model for density fluctuations in a one-component fluid near the critical point is proposed and compared with existing measurements in carbon dioxide and reproduces the observed Brillouin spectrum of critical opalescence in CO2.
Abstract: A dynamical model for density fluctuations in a one-component fluid near the critical point is proposed and compared with existing measurements in carbon dioxide. The model is described by a set of linearized hydrodynamic equations modified to include a nonlocal pressure density relationship and to include relaxation in the volume viscosity. Parameters for the model are found which are consistent with bulk measurements. With these parameters the model reproduces, within experimental uncertainty, the observed Brillouin spectrum of critical opalescence in CO2. The low frequency volume viscosity is found to diverge as the - 1/3 power of T - T c . An additional modification of the hydrodynamic equations, a frequency dependent thermal conductivity, is considered, but no definite conclusions can be reached as the Brillouin line-width data lack sufficient precision.
TL;DR: In this paper, the phonon frequency dependence of S.S.B. is derived by means of the hydrodynamic theory of absorption and dispersion of elastic waves and the coupled wave equation method of the Tang theory of S., and it turns out that the relaxation properties of the medium strongly affect the steady state behavior in C6H6 and CCl4.
Abstract: The phonon‐frequency dependence of S.B.S. steady‐state gain in dispersive liquids is derived by means of the hydrodynamic theory of absorption and dispersion of elastic waves and by means of the coupled wave equation method of the Tang theory of S.B.S. It turns out that the relaxation properties of the medium strongly affect the steady‐state behavior in C6H6 and CCl4.
01 Jan 1969
TL;DR: In this article, the authors proposed a method for the determination of the velocity of sound in liquids and solids in the hypersonic region, which serves as a complementary one to ultrasonics.
Abstract: With the advent of the laser renewed interest has been stimulated in the phenomenon of the scattering of light by thermal phonons first proposed by Brillouin[1]. In spectroscopy this has become an important method for the determination of the velocity of sound in liquids and solids. Since information is obtained in the hypersonic region this method serves as a complementary one to ultrasonics.