Showing papers on "Brillouin scattering published in 1988"
NEC1
TL;DR: In this article, the authors investigated SBS gain and threshold characteristics with amplitude-shift-keying (ASK), frequency-shift keying (FSK), and phase-shiftkeying modulated lights to estimate the input power limitation.
Abstract: Stimulated Brillouin scattering (SBS) limits the optical power that can be transmitted through a single-mode fiber in long-distance optical communication systems, the authors have investigated SBS gain and threshold characteristics with amplitude-shift-keying (ASK), frequency-shift-keying (FSK), and phase-shift-keying (PSK) modulated lights to estimate the input power limitation set by SBS. It was shown that maximum fiber-input powers or the SBS thresholds for fixed-pattern (1010 . . .) ASK, FSK, and PSK modulated lights are 2, 4, and 2.5 times higher, respectively, than the threshold for unmodulated light. Theoretical predictions were experimentally verified by SBS gain measurements with FSK and PSK modulated lights. The first direct observation of SBS with FSK modulated light pumping is also described. >
210 citations
TL;DR: In this paper, a review of the application of phase conjugation to solid-state lasers is presented, using demonstrated techniques for compensating static and thermally induced aberrations and depolarizations, as well as energy scaling by coherent coupling of multiple-gain media.
Abstract: Phase conjugation by stimulated Brillouin scattering represents a fundamentally promising approach for achieving power scaling of solid-state lasers. Following a summary of the power scaling problem and an overview of phase conjugation concepts, a review is presented of the application of phase conjugation to solid-state lasers. The author describes power scaling using demonstrated techniques for compensating static and thermally induced aberrations and depolarizations, as well as energy scaling by coherent coupling of multiple-gain media. Applications to diode-pumped lasers are discussed, as is a novel approach for power scaling of diode lasers themselves. Future research directions are indicated regarding conjugation fidelity at increasingly higher energies or with short-pulse and/or broadband lasers. >
183 citations
TL;DR: The crystalline-to-amorphous (c-a) phase transformation in the intermetallic compound Zr 3 Al during room temperature bombardment with 1.0 MeV Kr + was investigated in this article.
Abstract: The crystalline-to-amorphous (c-a) phase transformation in the intermetallic compound Zr 3 Al during room temperature bombardment with 1.0 MeV Kr + was investigated. Transmission electron microscopy and Brillouin scattering techniques were used to determine the lattice parameter and shear elastic constant as a function of the degree of long-range order. The results show that a large (about 50%) elastic softening and dilatation strain (about 3%) due to disordering precede the onset of amorphization. These results indicate that chemical disordering is an important driving force for the c-a transformation and that the mechanism is an elastic shear instability. It is also shown that the volume dependence of the shear elastic constant associated with radiation-induced disordering and eventual amorphization is virtually identical to that associated with the heating to melting of many solids. The origin and implications of this parallelism between solid state amorphization and melting are discussed.
117 citations
TL;DR: Several resonance peaks owing to an interaction between light-wave and guided modes of longitudinal acoustic waves are observed in the Brillouin gain spectra for a single-mode fiber with a GeO2-doped core and pure silica cladding.
Abstract: Several resonance peaks owing to an interaction between light-wave and guided modes of longitudinal acoustic waves are observed in the Brillouin gain spectra for a single-mode fiber with a GeO2-doped core and pure silica cladding. Brillouin gain spectra measurements are carried out at 1286- and 1550-nm wavelengths. Longitudinal acoustic modes guided in the GeO2-doped core region are identified by applying the analysis of leaky modes in a fiber acoustic waveguide.
75 citations
TL;DR: In this paper, the authors studied the scattering of light by longitudinal acoustic phonons propagating along the axis of an infinite superlattice and calculated the peak intensities for GaAs-AlAs super-lattices as functions of the composition, period, and photoelastic parameters.
Abstract: We study the scattering of light by longitudinal-acoustic phonons propagating along the axis of an infinite superlattice. In contrast to previous works, we take into account not only the difference between the acoustic and photoelastic parameters of the two media, but also the difference between their refractive indexes. In this case the incident and scattered light in the superlattice are represented by Bloch waves instead of plane waves. The scattering intensities, calculated in closed form by using a transfer-matrix method, are then valid for any value of the scattering wave vector q and not limited to q values small compared with the size of the Brillouin zone, \ensuremath{\pi}/D. The peak intensities are discussed for GaAs-AlAs superlattices as functions of the composition, period, and photoelastic parameters. The results may show noticeable differences with those of the previous works, especially for q near the boundaries of the successive Brillouin zones.
67 citations
TL;DR: In this paper, the results of an extensive study of transient stimulated Raman scattering in hydrogen gas were presented, including measurements of self-oscillation thresholds, conversion efficiency, and the dependence of small-signal amplification on the pump energy and gas pressure.
Abstract: We describe the results of an extensive study of transient stimulated Raman scattering in hydrogen gas. Measurements of self-oscillation thresholds, conversion efficiency, and the dependence of small-signal amplification on the pump energy and gas pressure are presented. Strong dependence of the amplification on the self-phase modulation of the pump and seed-Stokes pulses, on their relative time of arrival at the Raman amplifier, and on the seed-Stokes pulse asymmetry has been observed. The experimental measurements are compared with theoretical predictions that are based on extensions of published transient theories to take into account the spatial and temporal profiles of the pulses as well as their phase modulation. Excellent agreement with the theory, especially with regard to the scaling of the small-signal amplification with pump-pulse energy, is obtained when all the specific characteristics of the pump and Stokes pulses are included in the calculations.
64 citations
TL;DR: Stimulated Brillouin scattering (SBS) is used for multiple-beam combining by overlapping the beams in the SBS interaction volume and for phase control by backseeding the interaction volume as discussed by the authors.
Abstract: Stimulated Brillouin scattering (SBS) is used for multiple-beam combining by overlapping the beams in the SBS interaction volume and for phase control by backseeding the interaction volume. Tripled Nd:YAG laser experiments and wave-optics analyses indicate the conditions of beam overlap, power, and focusing that are required to obtain effective beam combining and phase control.
59 citations
TL;DR: The theory of long-wavelength spin waves in superlattices which incorporate magnetically ordered films that interact either through dipolar fields generated by spin motions or exchange couplings at interfaces or those mediated by an intervening nonmagnetic film is explored.
Abstract: We explore the theory of long-wavelength spin waves in superlattices which incorporate magnetically ordered films that interact either through dipolar fields generated by spin motions or exchange couplings at interfaces or those mediated by an intervening nonmagnetic film. We show that for long wavelengths one may replace the superlattice by an effective medium described by a permeability tensor composed of those of the constituent films. Our treatment applied to a semi-infinite lattice of ferromagnetic films reproduces results obtained earlier in a full theory by Camley, Rahman, and Mills. We also develop an effective medium theory of Y-Gd superlattices in the anti-phase-domain configuration, with transverse field applied. We obtain a rich spectrum of surface spin waves in this case. We also obtain Green's functions for the average medium description of the Y-Gd system and use these to discuss surface-mode contributions to the spectral densities explored by Brillouin scattering.
55 citations
TL;DR: In this article, several guided acoustic modes are identified to be responsible for the stimulated backward Brillouin scattering (SBBS) in single-mode optical fibres (SMFs), and the dependence of SBBS gain spectra on acoustic properties of SMF is discussed.
Abstract: Several guided acoustic modes are identified to be responsible for the stimulated backward Brillouin scattering (SBBS) in single-mode optical fibres (SMFs). The dependence of SBBS gain spectra on acoustic properties of SMF is discussed.
51 citations
TL;DR: In this article, the authors report on the observation and analysis of collective magnetostatic spin-wave excitations in magnetic superlattices and the influence of interface anisotropies, which can become dominant for small modulation wavelengths, is discussed.
Abstract: We report on the observation and the analysis of collective magnetostatic spin‐wave excitations in magnetic superlattices. The influence of interface anisotropies, which can become dominant for small modulation wavelengths, is discussed. For the system Fe/Pd we show that Brillouin spectroscopy experiments in combination with the measurement of the saturation magnetization by a SQUID magnetometer give evidence for a magnetic polarization of the Pd spacer layers, as well as for a small negative out‐of‐plane interface anisotropy constant of Ks =−0.15 erg/cm2.
TL;DR: The results show that the relaxation mode of the primary hydration shell retains its basic characteristics even in samples with very high water content, and a modified mode coupling model is used to include both the collective nature of the sound wave and to describe the change in hydration explicitly.
Abstract: We have measured the dispersion of phonon line widths between frequencies of about 2 and 10 GHz in DNA films at relative humidities between 0 and 95%. The results show that the relaxation mode of the primary hydration shell retains its basic characteristics even in samples with very high water content. A modified mode coupling model is used to include both the collective nature of the sound wave and to describe the change in hydration explicitly. It enables us to describe the coupling between the phonons and the water relaxation mode at various water contents, and allows us to extract values for the primary shell relaxation time and coupling constants over the range of hydration studied. The primary shell relaxation time (∼ 40 ps) and coupling parameters remain nearly constant over the entire range of hydration. We have reanalyzed our earlier Brillouin data (taken as a function of temperature) in terms of two relaxation processes (primary plus a secondary shell contribution of about 2 ps at room temperature). This new analysis indicates that both processes follow a simple Arrhenius behavior with activation energies of 5 kcal mole−1 for the primary relaxation and 7 kcal mole−1 for the secondary relaxation. We also observe a rather broad central mode that can be fitted by a Lorentzian, and that may arise from direct (as opposed to coupled-mode) scattering from the primary relaxation mode.
TL;DR: In this paper, the authors show that counterpropagating laser beams in a Brillouin-active medium are shown to become unstable to the growth of amplitude and phase fluctuations due to sinusoidal oscillations of the intensities of the transmitted waves.
Abstract: Counterpropagating laser beams in a Brillouin-active medium are shown to become unstable to the growth of amplitude and phase fluctuations. Slightly above threshold, the nature of the instability is the temporal growth of sidemodes separated from the laser frequency by approximately the Brillouin frequency of the medium. This process leads to sinusoidal oscillations of the intensities of the transmitted waves. At higher input intensities the system can become chaotic; many sidemodes are excited, and the transmitted fields fluctuate wildly. The origin of the Brillouin instability is the combined action of the gain of the standard stimulated Brillouin scattering (SBS) process and of the coupling of the waves due to multiwave mixing mediated by the electrostrictive interaction. The threshold for the instability is at least several times lower than the threshold of the standard SBS process involving a single pump beam.
NEC1
TL;DR: In this paper, the threshold of the stimulated Brillouin scattering (SBS) in a long single-mode fiber excited with a multimode pump laser was investigated, and it was theoretically shown that when the mode spacing of the pump laser is larger than the Brilloughin-gain bandwidth, each Stokes mode experiences gain from only one pump mode and builds up independently in the long fiber with long interaction length.
Abstract: The threshold of the stimulated Brillouin scattering (SBS) in a long single-mode fiber excited with a multimode pump laser is investigated. It is theoretically shown that when the mode spacing of the pump laser is larger than the Brillouin-gain bandwidth, each Stokes mode experiences gain from only one pump mode and builds up independently in a long fiber with long interaction length. On the basis of this fact, the SBS threshold with an N-multimode pump with equal intensities is predicted N times greater than that with a single-mode pump. The theoretical predictions are verified by an experiment in which the number of longitudinal modes of a 1.32-μm Nd:YAG laser is changed.
TL;DR: In this article, the authors made ultrasonic and Brillouin scattering measurements at ambient temperature on small single crystals of monoclinic ZrO2 and established various features of the angular anisotropy in the acoustic longitudinal wave and shear wave velocities, and computed the elastic stiffness and compliance moduli.
Abstract: We have made ultrasonic and Brillouin scattering measurements at ambient temperature on small single crystals of monoclinic ZrO2. Using these data, we have established various features of the angular anisotropy in the acoustic longitudinal wave and shear wave velocities, and we have computed the elastic stiffness and compliance moduli. We observe shallow minima in the transverse shear wave velocity in directions parallel to the a and c crystallographic axes. We anticipate that acoustic shear wave softening will be observed in these directions when measurements are made at temperatures close to the monoclinic-tetragonal transformation.
TL;DR: In this article, a new theory of the Brillouin shift in the inelastic scattering of light by magnetostatic spin waves is presented, which treats the magnetic surface anisotropy constants Ks and Kss directly rather than via the stratagem of effective volume anisotropies.
Abstract: A new theory of the Brillouin shift in the inelastic scattering of light by magnetostatic spin waves is presented. Contrary to previous work, the present calculations do include exchange effects and treat the magnetic surface anisotropy constants Ks and Kss directly rather than via the stratagem of effective volume anisotropies. The experimental data for {110} Fe on W are explained about as well by the present theory as by previous work. A detailed analysis reveals the previously unnoticed fact that the signs of Ks and Kss for (110) Fe on W are opposite to those for (110) Fe on GaAs. Some new spin‐wave modes arising from exchange are predicted and shown to occur outside the frequency range which has been investigated experimentally. A quantitative explanation is proposed for the occasional applicability of a theory based on effective volume anisotropies and zero exchange.
TL;DR: In this paper, a series of epitaxially grown ZnSe (001) films on GaAs of thicknesses between 0.23 and 2.0 μm were used for Brillouin scattering experiments.
Abstract: Brillouin scattering experiments have been performed on a series of epitaxially grown ZnSe (001) films on GaAs (001) of thicknesses between 0.23 and 2.0 μm. No thickness‐dependent modifications of the elastic constants have been found. The obtained room‐temperature values of C11=87.0, C12=54.7, and C44=39.1 GPa are in good agreement with literature values of ZnSe bulk material. The calculation of the theoretical cross sections shows a good agreement with the experimental data.
TL;DR: In this article, a theoretical model was constructed to express the pressure dependence of sound velocity as vs(P) = A0+A1P+A2P2, where A0 + A1P + A2P 2 is the pressure coefficient of the adiabatic bulk modulus.
Abstract: Brillouin scattering experiments have been performed on a set of ten‐single component liquids using a piezoelectric scanned, five‐pass Fabry–Perot interferometer. The hypersonic sound velocities (vs) were determined as a function of externally applied pressure (P) from the observed Brillouin shifts. Experiments were performed at room temperature [T=(20±1)°C] and the pressure acting on the liquid samples was varied in the range 1–825 bars in steps of 100 bars each. By making use of modified Tait’s equation of state and assigning a linear pressure dependence to the adiabatic bulk modulus, we have constructed a theoretical model equation to express the pressure dependence of sound velocity as vs(P)=A0+A1P+A2P2. The experimental vs(P) values could be least‐squares fitted to this equation within experimental error. From the values of the coefficients Ai’s we have determined the values of Tait parameters and the pressure coefficient of adiabatic bulk modulus. We found that the sound velocity, density, and bulk ...
TL;DR: In this paper, the velocity and attenuation of the acoustic modes corresponding to the C11 and C33 elastic coefficients are investigated in (CH3)4NCdCl3 by Brillouin scattering.
TL;DR: In this article, the authors used a simple AlGaAs laser to demodulate and amplify FSK signals at bit rates up to 250 Mbit/s with gain of as much as a factor of 1000 for a pump power of 12mW.
Abstract: Stimulated Brillouin scattering is used as a narrowband amplifier to demodulate and amplify FSK signals at bit rates up to 250 Mbit/s. Gain of as much as a factor of 1000 is obtained for a pump power of 12mW. Both pump and signal lasers are simple AlGaAs lasers.
TL;DR: The first study of the pressure dependence of Brillouin scattering spectra in SrTiO3 up to 9 GPa is reported in this article, where the authors show that the longitudinal and transverse acoustic velocities increase with increasing pressure up to 6 GPa, and an anomaly near 65 GPa associated with a cubic-to-tetragonal structural phase transition.
Abstract: The first study of pressure dependence of Brillouin scattering spectra in SrTiO3 up to 9 GPa is reported The longitudinal and transverse acoustic velocities increase with increasing pressure up to 6 GPa, and show an anomaly near 65 GPa associated with a cubic-to-tetragonal structural phase transition The transition pressure is in good agreement with the value expected from other data, showing the validity of the mean field approximation-in SrTiO3 The pressure dependence of the elastic constants is determined by means of the pressure-dependent density derived from the acoustic velocities in the cubic phase The acoustic mode Gruneisen parameters of SrTiO3 are determined and discussed in comparison with those of NaCl
TL;DR: In this article, a computer program has been written with which the complex resonant frequency can be calculated for a thin ferromagnetic metal film sandwiched between a non-magnetic metallic substrate and a nonmagnetic metal overlayer.
Abstract: A computer program has been written with which the complex resonant frequency can be calculated for a thin ferromagnetic metal film sandwiched between a nonmagnetic metallic substrate and a nonmagnetic metallic overlayer. The calculation includes exchange and magnetic damping having the Gilbert form. The program has been used to investigate the sensitivity of thin‐film resonant frequencies to the resistivities of the overlayer, the substrate, and the magnetic film. It is concluded that the presence of an overlayer and of a substrate are unimportant for the analysis of Brillouin scattering data from films less than 100 A thick: uncertainties in the absolute value of the frequency shift of the scattered light—typically 1:200—are greater than, or comparable with, the frequency shifts caused by an overlayer or a substrate.
TL;DR: In this paper, a stimulated Raman resonator with a small (50mJ, 5ns) Nd:YAG requiring only one high-reflectivity mirror was investigated theoretically and experimentally.
Abstract: A stimulated Raman resonator pumped by a small (50-mJ, 5-ns) Nd:YAG requiring only one high-reflectivity mirror has been investigated theoretically and experimentally. Forward and backward Raman waves of approximately equal intensity are generated, which in turn produce Raman medium density variation. The forward Raman wave scattered off of the density variation enhances backward gain. There is significant competition between the Raman conversion and stimulated Brillouin scattering of the pump. Equations describing the interactions are given. Their solution is described and presented. An experiment setup using a 1.06- mu m pump and a CH/sub 4/ Raman cell is described. Experimental results are described and interpreted in light of the theory. The theory is in good agreement with the experimental results. >
TL;DR: It is found that the reflectivity and the fidelity depend solely on the focal intensity, and there was no minimum amount of aberration required for accurate wave-front reversal, and the maximum amount was the aberration that reduced intensity to near threshold.
Abstract: We have measured the reflectivity and phase-conjugate fidelity of stimulated Brillouin scattering in hexane while varying the pump power and aberration. By directly measuring the reduction in focal intensity that is due to aberrations, we found that the reflectivity and the fidelity depend solely on the focal intensity. We were able to vary the strength of aberration, producing up to a factor-of-30 reduction in focal intensity. The reflectivity and fidelity decreased monotonically with decreasing focal intensity. There was no minimum amount of aberration required for accurate wave-front reversal, and the maximum amount was the aberration that reduced intensity to near threshold.
TL;DR: The dispersion of Rayleigh, Stonely, and Sezawa acoustic waves guided by deposited thin molybdenum films has been used to evaluate selected elastic constants and film homogeneity as mentioned in this paper.
Abstract: The dispersion of Rayleigh, Stonely, and Sezawa acoustic waves guided by deposited thin molybdenum films has been used to evaluate selected elastic constants and film homogeneity. This work includes the first experimental observation of Stonely waves by Brillouin scattering.
TL;DR: In this article, the Brillouin light scattering measurements on a (001) iron whisker that was covered with epitaxial gold under ultrahigh vacuum conditions were made, and the surface mode frequencies were measured to within ± 0.03 GHz.
Abstract: We have made Brillouin light scattering measurements on a (001) iron whisker that was covered with epitaxial gold and with epitaxial silver under ultrahigh vacuum conditions. The surface mode frequencies have been measured to within ±0.03 GHz, allowing very careful comparisons of experiment with light scattering calculations. Observation of the 180° domain wall enabled an accurate determination of the surface spin pinning coefficient: Ks =0.54 ergs/cm2 for the gold covered whisker and Ks =0.79 ergs/cm2 for the silver covered whisker, with the easy axis perpendicular to the sample surface. An accurate measure of the sample heating due to the incident laser light was also obtained.
TL;DR: In this article, a phase-conjugate laser system with a stimulated-brillouin-scattering (SBS) mirror and a plasma shutter is presented, achieving a peak power of 1 GW in a 1-nsec pulse.
Abstract: We present three novel phase-conjugate laser systems. A Nd, Cr:GSGG laser with a stimulated-Brillouin-scattering (SBS) mirror and plasma shutter has been investigated. A combined effect of SBS and optical breakdown allows us to control pulse duration in a wide range. A description of a Nd:YAG laser with a peak power of 1 GW in a 1-nsec pulse, achieved by means of SBS compression in CCI4, is given. A laser oscillator design with a SBS mirror arranged outside the main resonator has been studied experimentally. Nd:YA1O3 and Nd, Cr:GSGG lasers based on this design revealed efficient generation of near-diffraction-limited output.
TL;DR: In this article, the authors used Brillouin scattering at room temperature to investigate the phase diagram of ammonia up to 20 GPa and obtained the sound velocity and an effective elastic constant which is compared to the bulk modulus.
TL;DR: In this paper, Angle-dependent gain functions are derived in collimated and focused pump geometries and the time of growth for forward scattering based on the derived gain functions is calculated by comparing the forward and backward intensity time scales.
Abstract: Forward stimulated Brillouin scattering characteristics are formulated by an extension of the current theory. Angle‐dependent gain functions are derived in collimated and focused pump geometries. The time of growth for forward scattering based on the derived gain functions is calculated by comparing the forward and backward intensity time scales. The forward intensity is shown to grow in times on the order of thousands of phonon lifetimes and its behavior is that of an expanding cone reaching a maximum angle varying inversely as the square root of the pump f number.