Showing papers on "Brillouin scattering published in 1989"
TL;DR: In this paper, the authors measured the Brillouin frequency shift in a single-mode optical fiber as a function of tensile strain and found that the strain coefficient was 4.4 for silica fibers.
Abstract: Brillouin frequency shift in a single-mode optical fiber has been measured as a function of tensile strain. The strain coefficient of normalized Brillouin frequency shift C identical to (dv/sub B//d epsilon )/v/sub B/ is found to be 4.4 for silica fibers. This result shows the potential of Brillouin spectroscopy to evaluate tensile strain in the fiber with the strain resolution of about 2*10/sup -4/. The origin of the large strain coefficient is discussed. >
545 citations
TL;DR: In this article, a Brillouin optical-fiber time-domain analysis (BOTDA) was proposed to analyze the attenuation characteristics of the optical fibers nondestructively.
Abstract: A theoretical investigation of Brillouin optical-fiber time-domain analysis (BOTDA) is described. BOTDA uses Brillouin interaction in optical fibers to analyze the attenuation characteristics of the optical fibers nondestructively. The dynamic range performance of BOTDA is approximately 10-dB greater than that of conventional optical time-domain reflectometry. >
467 citations
TL;DR: In this paper, a coupled-mode theory was developed to analyze the coupling of two coherent electromagnetic waves inside a photorefractive medium, both codirectional and contradirectional coupling are considered.
Abstract: The physics of the photorefractive effect is briefly discussed. A coupled-mode theory is then developed to analyze the coupling of two coherent electromagnetic waves inside a photorefractive medium. Both codirectional and contradirectional coupling are considered. The coupled-mode theory is then extended to consider the case of nondegenerate two-wave mixing. A discussion of the fundamental limit of the speed of photorefractive effect is then introduced. The coupling of two polarized beams inside photorefractive cubic crystals is considered. The formulation is focused on the cross-polarization two-beam coupling in semiconductors such as GaAs. The coupling of two electromagnetic waves inside a Kerr medium and the electrostrictive Kerr effect are discussed. A new concept of nonlinear Bragg scattering is introduced. The similarity among various kinds of two-wave mixing, including stimulated Brillouin scattering and stimulated Raman scattering are pointed out. Several applications of two-wave mixing are discussed. These include photorefractive resonators, optical nonreciprocity, resonator model of self-pumped phase conjugators, real-time holography, and nonlinear optical information processing. >
348 citations
TL;DR: In this paper, it was demonstrated that stimulated Brillouin scattering (SBS) occurring in the core of an optical fiber can be used in the construction of a distributed temperature sensor.
Abstract: It is demonstrated that stimulated Brillouin scattering (SBS) occurring in the core of an optical fibre may be used in the construction of a distributed temperature sensor. Initial experiments with a length of fibre have shown that the sensitivity of the Stokes frequency to temperature is approximately 5.5 MHz/ degrees C and that different Stokes frequencies may be observed according to the temperature distribution along the fibre.<
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218 citations
TL;DR: Experiments with a 5.2-km-long single-mode fiber reveal that the output signal is approximately 100 times that of the Rayleigh backscattered signal observed in conventional optical time-domain reflectometry.
Abstract: A new technique for measuring optical-fiber-attenuation characteristics is described The technique uses stimulated Brillouin scattering in the fiber between a counterpropagating pulsed pump wave and a cw Stokes probe wave Fiber attenuation is estimated nondestructively from amplification of the probe wave through stimulated Brillouin scattering Experiments with a 52-km-long single-mode fiber reveal that the output signal is approximately 100 times that of the Rayleigh backscattered signal observed in conventional optical time-domain reflectometry The signal fluctuation due to polarization-dependent Brillouin gain is successfully removed by polarization averaging
189 citations
TL;DR: In this article, the second harmonic generation of light, high resolution X-ray diffraction, quasi-elastic neutron scattering, small angle x-ray scattering, Brillouin scattering, far infrared absorption and submillimeter dielectric spectroscopy were used to investigate the ferroelectric phase and phase transition of VDF-TrFE copolymers.
Abstract: P(VDF-TrFE) copolymers with approximately 30 mol% of TrFE content exhibit above room temperature a ferroelectric transition of first order type with a large thermal hysteresis. We present recent investigations of the ferroelectric phase and of the phase transition using several techniques: second harmonic generation of light, high resolution X-ray diffraction, quasi-elastic neutron scattering, small angle X-ray scattering, Brillouin scattering, far infrared absorption and submillimeter dielectric spectroscopy. These results provide information on both the small crystallites and the amorphous inter-crystalline regions and show that temperature cycling throughout the Curie transition is able to modify the superstructure and to enhance the degree of crystallinity of the polymer. Accordingly, low frequency dielectric measurements, thermal expansion results and Brillouin spectroscopic investigations can be discussed in taking into account the composite structure of the semi-crystalline material.
164 citations
Patent•
13 Apr 1989TL;DR: In this article, the authors proposed a soliton fiber communications system with pump radiation injected at one or more intermediate fiber locations, where the average intensity of pump radiation in a first spectral interval, centered on any wavelength λp in the pump radiation spectrum and of width equal to the Brillouin line width of the fiber at λ p, is to be less than that average intensity in the first spectrum interval that results in conversion of 10% of the radiation in the 1-minimization interval to stimulated Brilloustime radiation.
Abstract: An optical fiber communications system with Raman amplification of the signal radiation comprises a broadband pump radiation source (15), or, preferably, a multiplicity of pump radiation sources and polarization maintaining optical fiber (10) as the transmission medium. The sources are selected to result in a pump radiation spectrum such that pump radiation intensity in the fiber core is less than a critical intensity Ic. In particular, the average intensity of pump radiation in a first spectral interval, centered on any wavelength λp in the pump radiation spectrum and of width equal to the Brillouin line width of the fiber at λp, is to be less than that average intensity in the first spectral interval that results in conversion of 10% of the radiation in the first spectral interval to stimulated Brillouin radiation. Use of a multiplicity of pump sources not only can reduce pump noise and pump depletion due to stimulated Brillouin scattering, but typically also can result in enhanced system reliability and lower cost. In a preferred embodiment, the invention is a soliton fiber communications system, with pump radiation injected at one or more intermediate fiber locations.
119 citations
TL;DR: Guided longitudinal-acoustic modes, which give rise to Brillouin gain, were theoretically clarified for a single-mode fiber with a GeO2-doped core and pure-silica cladding in this paper.
Abstract: Guided longitudinal-acoustic modes, which give rise to Brillouin gain, are theoretically clarified for a single-mode fiber with a GeO2-doped core and pure-silica cladding. Longitudinal-acoustic L0m modes are found from the theoretical analysis to interact with the electromagnetic field of the HE11 mode. Brillouin-gain spectra are measured for clarifying the theory. A few gain peaks in the Brillouin-gain spectra are successfully explained by taking account of the phase-velocity characteristics of the L01, L02 and L03 modes guided in the GeO2-doped core region. Furthermore, Brillouin frequency shifts per unit dopant concentration for GeO2 and F are experimentally obtained to confirm the dispersion characteristics of the guided acoustic modes. The evaluated frequency shifts per unit dopant concentration are 107 and 356 MHz/mol% for GeO2 and F, respectively, at a wavelength of 1550 nm.
107 citations
TL;DR: When a Brillouin-shifted signal interacts with a two strong counter-propagating pump beams in a BAM active medium, a conjugate field will grow exponentially in time until it depletes the power of the pump beams and hence produce very high reflectivities as mentioned in this paper.
Abstract: When a Brillouin-shifted signal interacts with a two strong counterpropagating pump beams in a Brillouin active medium, a conjugate field will grow exponentially in time until it depletes the power of the pump beams and hence produce very high reflectivities (>10/sup 6/). The technique can be used to conjugate very weak signals ( >
103 citations
TL;DR: In this article, the effects of modulation on the gain of stimulated Brillouin scattering (SBS) are discussed, and three different modulation techniques, i.e., frequency shift keying (FSK), amplitude shift keening (ASK), and phase shift keeling (PSK), are considered.
Abstract: The effects of modulation on the gain of stimulated Brillouin scattering (SBS) are discussed. Three different modulation techniques, i.e. frequency shift keying (FSK), amplitude shift keying (ASK), and phase shift keying (PSK) are considered. The results show that the SBS threshold depends on the ratio between the spontaneous Brillouin linewidth and the bit rate. The SBS threshold for ASK and FSK is 6 dB higher at high bit rates, whereas the SBS threshold for PSK increases by 10dB for each factor of 10 increase in the bit rate. >
102 citations
TL;DR: The propagation of sound waves along relaxed single fibres of glycerinated rabbit psoas muscle has been observed using Brillouin scattering at frequencies up to 1.6 GHz with much higher velocity than that reported by Stienen and Blangé (1985).
Abstract: The propagation of sound waves along relaxed single fibres of glycerinated rabbit psoas muscle has been observed using Brillouin scattering at frequencies up to 1.6 GHz. Two types of waves were observed: one with a velocity of 1508±7 m s−1, which is attributed to sound waves in intra-cellular saline, the other with a velocity of 912±25 m s−1, which is attributed to waves propagating along the protein filaments within individual sarcomeres. The latter sound velocity is much higher than that which has been reported by Stienen and Blange (1985) for 50 μs tension transients, and the difference is attributed to the much higher stiffness of the protein filaments compared to the cross-bridges which determine the low-frequency elasticity of muscle fibres.
TL;DR: In this article, the authors observed SBS from micrometer-sized single water and methanol droplets with a Brillouin shift that varied within a range determined by the k-vector spread and the optical feedback provided by the droplet interface.
Abstract: Stimulated Brillouin scattering (SBS) from micrometer-sized single water and methanol droplets was observed with a Brillouin shift that varied within a range determined by the k-vector spread and the optical feedback provided by the droplet interface. The inability to observe SBS in carbon disulfide droplets is attributed to phase-modulation broadening of the input and Brillouin radiation resulting from the large intensity-dependent index of refraction of carbon disulfide.
Proceedings Article•
24 Apr 1989TL;DR: In this paper, a transverse stimulated Brillouin scattering (SBS) was observed in fused-silica optical components using 2.4-nsec pulses at 350 nm.
Abstract: Using 2.4-nsec pulses at 350 nm, we have observed transverse stimulated Brillouin scattering (SBS) in fused-silica optical components. Transverse SBS sets in when the product of laser fluence and growth time for the scattered optical wave exceeds ∼2.3 J nsec/cm2. An increase in laser bandwidth to 8.3 GHz suppresses SBS losses up to approximately twice the SBS threshold. We review the theory of transverse, broadband SBS and its scaling with experimental parameters.
TL;DR: In this paper, a comprehensive survey of the vibrational modes in periodic multilayered structures is presented, focusing on the folding process and phonon propagation along the direction of growth of the superlattice layers.
TL;DR: The properties of solid krypton have been measured as a function of pressure in a diamond-anvil cell using energy-dispersive x-ray diffraction and Brillouin scattering, indicating a possible phase transition above 30 GPa.
Abstract: The properties of solid krypton have been measured as a function of pressure in a diamond-anvil cell using energy-dispersive x-ray diffraction and Brillouin scattering. A room-temperature equation of state and a complete set of elastic constants are deduced. The analysis of these results indicates a possible phase transition above 30 GPa.
TL;DR: In this paper, the flux of radiation emitted from an inhomogeneous plasma by stimulated Raman and Brillouin scattering is calculated with a source that includes both bremsstrahlung and longitudinal plasma wave noise sources.
Abstract: The flux of radiation emitted from an inhomogeneous plasma by stimulated Raman and Brillouin scattering is calculated with a source that includes both bremsstrahlung and longitudinal plasma wave noise sources. Significant enhancement of the flux above that found for a bremsstrahlung source alone are found for stimulated Brillouin scattering and for nonthermal but stable velocity distributions.
TL;DR: In this paper, a transverse stimulated Brillouin scattering (SBS) was observed in fused-silica optical components using 2.4-nsec pulses at 350 nm.
Abstract: Using 2.4-nsec pulses at 350 nm, we have observed transverse stimulated Brillouin scattering (SBS) in fused-silica optical components. Transverse SBS sets in when the product of laser fluence and growth time for the scattered optical wave exceeds ∼2.3 J nsec/cm2. An increase in laser bandwidth to 8.3 GHz suppresses SBS losses up to approximately twice the SBS threshold. We review the theory of transverse, broadband SBS and its scaling with experimental parameters.
TL;DR: An analytical theory of the operation of all-fiber Brillouin ring lasers that accounts for pump depletion is presented and it is shown that the fiber cavity detunes from its resonant value owing to the buildup of the counterpropagating Stokes wave, which can be a limitation in the performance of all -fiber resonator systems.
Abstract: An analytical theory of the operation of all-fiber Brillouin ring lasers that accounts for pump depletion is presented. Expressions for stimulated Brillouin scattering lasing threshold power, output Stokes power, and conversion efficiency are derived. It is shown that the fiber cavity detunes from its resonant value owing to the buildup of the counterpropagating Stokes wave, which can be a limitation in the performance of all-fiber resonator systems. The application of the theory is in the design and optimization of performance parameters of devices using all-fiber ring resonators, particularly Brillouin lasers and gyroscopes.
TL;DR: In this paper, the use of stimulated Brillouin scattering as a tunable narrowband amplifier to demodulate, amplify, and select channels in a densely packed WDM (wave-division multiplexed) network is discussed.
Abstract: The use of stimulated Brillouin scattering as a tunable narrowband amplifier to demodulate, amplify, and select channels in a densely packed WDM (wave-division multiplexed) network is discussed. A 128-channel system configuration is tested with channel separation as small as 1.5 GHz and error rates below 10/sup -10/. Direct FSK (frequency-shift-keyed) modulation of AlGaAs lasers and direct detection receivers are used. The experimental margin and noise analysis indicate that a 1000-channel system can be constructed with only these same components. >
TL;DR: In this paper, an active all-fibre ring resonator gyroscope based on stimulated Brillouin scattering was demonstrated, and the occurrence of guided acoustic modes in certain optical fibres was found to increase the lock-in range.
Abstract: An active all-fibre ring resonator gyroscope based on stimulated Brillouin scattering is demonstrated. The occurrence of guided acoustic modes in certain optical fibres is found to increase the lock-in range, and a novel method to reduce lock-in for this type of gyroscope is investigated.
TL;DR: The operation and noise properties of Brillouin amplifiers are described in this paper, and the applications demonstrated to date are reviewed, as well as the applications in which they have been used.
Abstract: The operation and noise properties of fibre Brillouin amplifiers are described, and the applications demonstrated to date are reviewed.
TL;DR: In this article, the authors performed neutron and Brillouin scattering studies of ion conducting metal-halide-doped borate glasses (MX)x-(M2O-nB2O3)1-x glasses.
Abstract: We have performed neutron and Brillouin scattering studies of ion conducting metal-halide-doped borate glasses (MX)x-(M2O-nB2O3)1-x glasses (MX[tbnd]LiCl, AgI). Neutron diffraction experiments and small-angle neutron scattering investigations were carried out in order to determine the short-, medium-, and long-range structure of the glasses. The small-angle experiments show no significant scattering from inhomogeneities of dimensions 10–100 A, which contradicts suggestions that MX tend to form microdomains of size 20–30 A in the glass. A marked change in the medium-range order (less than 10 A) is observed when MX is added to the binary M2O-nB2O3 glass. For AgI-doped glasses a substantial increase in the medium-range order is found, which is manifested in a diffraction peak at anomalously low Q values (Q = 0·8A−1). The peak increases in strength with increasing AgI content. In contrast, for the LiCl-doped glasses, the ordering of the medium-range structure is observed to decrease when the salt is ...
TL;DR: The first experimental evidence of modification of the scattered light spectrum of stimulated Raman scattering due to the presence of significant levels of stimulated Brillouin scattering is presented and shows the characteristic Raman gap, with a temporal behavior that can be explained in terms of the observed SBS scattered light.
Abstract: The first experimental evidence of modification of the scattered light spectrum of stimulated Raman scattering due to the presence of significant levels of stimulated Brillouin scattering is presented. The observed spectrum, as well as the spectral Raman gap observed in this and other experiments, is explained in terms of the modified growth of Raman scattering in the presence of ion waves. PACS numbers: 52.40.Nk, 52.35.Fp, 52.35.Mw Stimulated Raman scattering (SRS) has become the most important parametric instability in laser-produced plasmas. SRS is a three-wave interaction in which the pump wave (laser light) decays into an electron plasma and a scattered light wave. Apart from the intrinsic interest of SRS in laser-produced plasmas, it has important implications in inertial confinement fusion (ICF) due to the large conversion of laser energy into Raman light. 2 An important and relatively new issue in the understanding of SRS is its growth in the presence of ion acoustic waves from stimulated Brillouin scattering (SBS). This problem has attracted considerable theoretical work ' in recent years. Experiments using Thomson scattering have diagnosed the temporal evolution of electron plasma waves and ion acoustic waves associated with these instabilities, and clearly demonstrated that the growth of SRS can be modified by the presence of large levels of ion waves. In those experiments, the competition between SRS and SBS was observed by directly probing the electron plasma waves and ion acoustic waves associated with the instabilities. Those experiments were performed with a much longer laser wavelength (10.6 pm) than we will be discussing here, they used preformed plasmas, and no SRS light spectrum was available. In this paper, we present the first experimental evidence of modification of the scattered electromagnetic spectrum of SRS due to the presence of SBS, under laser-plasma conditions of interest to ICF. The timedependent scattered spectrum shows the characteristic Raman gap, with a temporal behavior that can be explained in terms of the observed SBS scattered light. The gap in the SRS spectrum has been seen in all published experiments; although our results do not provide a total explanation about the gap, they present an explanation consistent with the assumption of coupling or competition between the two instabilities.
TL;DR: In this paper, polarized Mandelstam-brillouin scattering data in bulk supercooled water are presented. And the hypersonic velocity and absorption are measured as a function of the scattering angle {theta} at temperatures ranging from +20 to −27.4{degree}C.
Abstract: Polarized Mandelstam-Brillouin scattering data in bulk supercooled water are presented. The hypersonic velocity and absorption are measured as a function of the scattering angle {theta} at temperatures ranging from +20 to {minus}27.4{degree}C. The experimental results indicate the existence of a relaxation process in the gigahertz region. The authors discuss the observed dispersion in the frame of the relaxation theory for moderately supercooled liquids. The obtained relaxation times and relaxation strengths are interpreted in terms of man-body effects involved to explain the behavior of supercooled water.
TL;DR: The intensity of light scattered from thermal magnetic waves in thin magnetic films with large perpendicular uniaxial anisotropies was calculated and indicated that the magnetization of the Fe film was oriented perpendicular to the sample plane in zero applied field.
Abstract: The intensity of light scattered from thermal magnetic waves in thin magnetic films with large perpendicular uniaxial anisotropies was calculated. The anisotropies were large enough to pull the magnetization out of the sample plane. The intensity of light scattered from the surface magnetic mode in a 3.0-monolayer-thick fcc Fe film grown on Cu(001) was measured as a function of the applied in-plane dc magnetic field. The measured intensities were found to be in excellent agreement with those calculated using the magnetic parameters determined from the measured values of the surface-mode frequency. Both the frequency and intensity data indicated that the magnetization of the Fe film was oriented perpendicular to the sample plane in zero applied field.
TL;DR: The parameters which govern the effective interaction length at threshold for phase conjugation due to stimulated Brillouin scattering are investigated and the length is found to be the shorter of the following parameters: the cell length, 3 times the coherence length or 5 times the Rayleigh range of the input laser radiation.
Abstract: We have investigated experimentally the parameters which govern the effective interaction length at threshold for phase conjugation due to stimulated Brillouin scattering. We found the length to be the shorter of the following parameters: the cell length, 3 times the coherence length or 5 times the Rayleigh range of the input laser radiation. We have also found that the fidelity of the return depends strongly on the coherence length when this parameter is much shorter than the cell length. Results are also presented on fluctuations in fidelity at high power and long pulse lengths.
TL;DR: In this article, a stable train of compressed Stokes pulses was obtained in a stimulated Brillouin fiber ring laser by periodically interrupting the argon-ion cw pump beam with an intraring cavity acousto-optic modulator.
Abstract: A stable train of compressed Stokes pulses (to ~10 nsec) is obtained in a stimulated Brillouin fiber ring laser (of length L = 83 m) by periodically interrupting the argon-ion cw pump beam with an intraring cavity acousto-optic modulator. Interruption of the pump action, at each round-trip time tr ≃ Ln/c, permits damping of the excited sound waves that accumulate at the entry of the fiber owing to the inertial response of the material, well described by the coherent three-wave stimulated Brillouin scattering model (C3W-SBS equations). Amplification and compression of the backscattered Stokes pulse are limited by nonlinear optical Kerr effect, which is incorporated into the C3W-SBS equations.
TL;DR: In this paper, the authors illustrate some important nonlinear features of the Raman and Brillouin backscattering and compare them to theory, and show that the competition between the two instabilities is very strong.
Abstract: Kinetic simulations illustrate some important nonlinear features of Raman and Brillouin backscattering. Steepening of the Brillouin‐generated ion wave is observed and compared to theory. Examples of the rich competition between the Raman and Brillouin instabilities are discussed.
TL;DR: In this paper, a picosecond time-domain light scattering technique was used to study the viscoelastic KNO3-Ca(NO3)2 60:40 glass-forming liquid mixture.
Abstract: A picosecond time‐domain light scattering technique is used to study the viscoelastic KNO3–Ca(NO3)2 60:40 glass‐forming liquid mixture. By using scattering angles between 1.92° and 85.67°, acoustic frequencies from 50 MHz to 4 GHz are sampled. Together with existing ultrasonic and Brillouin scattering data, a temperature‐dependent distribution of relaxation times is found to be well fit with a Cole–Cole distribution whose width changes from several decades in the glassy state to nearly single relaxation time in the high‐temperature liquid state. The characteristic relaxation time is found to obey the Vogel–Tammann–Fulcher law with T0=338 K.
TL;DR: In this article, phase conjugation by Brillouin scattering in SF/sub 6/ gas has been implemented on a two-pass KrF amplifier to provide near-diffraction-limited output pulses having a very low background level of amplified spontaneous emission.
Abstract: Phase conjugation by Brillouin scattering in SF/sub 6/ gas has been implemented on a two-pass KrF amplifier to provide near-diffraction-limited output pulses having a very low background level of amplified spontaneous emission. The pulse duration is variable between 1 and 10 ns by simply attenuating the input pulse. These pulses have also been used for the generation of much shorter duration pulses by truncated Brillouin scattering at the surface of cyclohexane. >