Showing papers on "Brillouin scattering published in 1978"
TL;DR: In this paper, the effect of strong continuous three-wave mixing of 514.5nm argon laser light in a single-mode fiber is reported, due to the third-order nonlinearity of silica, has been observed for light whose frequency spectrum consists of either a few discrete monochromatic frequency components separated by ∼1 GHz or a quasicontinuous distribution of frequencies having a spectral envelope ∼4 GHz wide.
Abstract: Strong continuous three‐wave mixing of 514.5‐nm argon laser light in a single‐mode fiber is reported. The effect, due to the third‐order nonlinearity of silica, has been observed for light whose frequency spectrum consists of either a few discrete monochromatic frequency components separated by ∼1 GHz or a quasicontinuous distribution of frequencies having a spectral envelope ∼4 GHz wide. We show that the effect provides a simple and effective method for measuring the nonlinearity of silica. In the first manifestation of the effect, the nonlinearity mixes the frequency components to produce new frequencies. In the second, multiple mixing occurs that broadens the quasicontinuous spectrum. This manifestation of the effect is large; broadening by a factor of 4 has been observed with lower intensity levels than are required to produce stimulated Brillouin scattering in the same fiber. A theoretical model is presented to describe spectral broadening by three‐wave mixing for the case of small broadening. The effect of three‐wave mixing on the operation of continuous stimulated Brillouin and Raman oscillators is also discussed. Finally, it is noted that the presence of this effect may constrain the design of long‐haul single‐mode fiber optical communication trunks.
409 citations
TL;DR: Several examples of Brillouin scattering from thermally excited surface acoustic phonons in metals and opaque semiconductors are presented in this article, where the measured surface velocities are consistently lower by 1-5% than the values calculated from the bulk elastic constants.
185 citations
TL;DR: In this paper, the authors considered the problem of forward Raman scattering process in a single transverse mode fiber and derived expressions for the maximum fiber loss and the minimum fiber length which allow significant pump to Stokes wave conversion.
Abstract: This paper considers the problem of forward Raman scattering process in a single transverse mode fiber. Both pump wave depletion and spontaneous scattering are considered in the analysis. Analytic solutions of the governing differential equations are obtained. We examine the conditions under which a nondepleted pump approximation is valid. Expressions are derived for the maximum fiber loss and the minimum fiber length which allow significant pump to Stokes wave conversion. It is shown that for a given fiber length there is an optimal pumping power, or at a given pump power there is an optimal fiber length that yields maximum first-order Stokes power output. Good agreement with published experimental results in the threshold power prediction is obtained.
167 citations
115 citations
TL;DR: In this paper, the authors used Brillouin scattering methods to show that the disorder at Tc results in a large decrease in the elastic constant C11 and a much smaller change in C44 and C12.
Abstract: Crystals with the fluorite structure show a specific heat anomaly at a temperature Tc well below the melting temperature. This premelting phenomenon is due to generation of extensive disorder in the anion sublattice. The present investigation shows, using Brillouin scattering methods, that the disorder at Tc results in a large decrease in the elastic constant C11 and a much smaller change in C44 and C12. Comparison of both lattice and lattice-defect energy calculations with experimental data suggests a molar defect concentration of interstitials of order 10% just above Tc. The calculations also provide a qualitative explanation of the limitation of the disorder giving rise to the specific heat anomaly.
100 citations
TL;DR: Quantitative measurements on the correction of severely aberrated laser beams using stimulated Brillouin scattering (SBS) at 0.69 microm are obtained and it is shown that under certain conditions SBS can be used to restore an aberrated optical beam to its original unaberrated condition.
Abstract: We have obtained quantitative measurements on the correction of severely aberrated laser beams using stimulated Brillouin scattering (SBS) at 0.69 μm. We have shown that under certain conditions SBS can be used to restore an aberrated optical beam to its original unaberrated condition. When an optical beam double passes an aberrating region after reflecting from an “ordinary” mirror (i.e., a plane mirror) the aberration is twice that obtained from a single pass. However, when the aberrated beam enters a medium that allows SBS to occur, it emerges from its second pass through the aberrating medium in the same condition as that in which it originally entered. Quantitative experiments are described in which a single-mode ruby laser beam is intentionally aberrated by passing it through an etched plate. When the beam is allowed to double-pass the plate using an ordinary reflector (i.e., plane mirror), the beam divergence is more than 10 times the diffraction-limited divergence. However, when we replace the ordinary reflector with a cell in which SBS can take place, the SBS reflected beam is restored to diffraction-limited divergence when it is allowed to pass back through the aberrating medium. Applications of this time-reversal or phase-reversal technique for correcting aberrations in optical trains and atmospheric turbulence are discussed.
99 citations
TL;DR: In this article, the surface response of a semi-infinite ferromagnet in the presence of both exchange and dipolar coupling, within a continuum theory, is analyzed.
Abstract: We present the theory of the surface response of a semi-infinite ferromagnet in the presence of both exchange and dipolar coupling, within a continuum theory. The results are applied to a detailed study of the spectral density of surface spin fluctuations. From this we analyze the influence of exchange coupling and surface spin pinning on the frequency, linewidth, and line shape of the Damon-Eshbach surface spin wave, for a number of propagation angles, and for wavelengths sufficiently short that the exchange contribution to the energy of the wave is comparable to the Zeeman and dipolar energies. We also develop the theory of Brillouin scattering from spin waves near magnetic surfaces, and calculate the spectum of scattered light for experimentally interesting geometries, with recent light scattering studies of ferromagnetic surfaces in mind.
70 citations
TL;DR: In this article, the backward optical wave stimulated by a multimode, monochromatic, incident optical wave in a waveguide filled with a transparent nonlinear medium was considered, and conditions on guide length, area, mode number, and Stokes shift were derived in order that a given high percentage of the power in the backscattered field be the phase conjugate of the incident field.
Abstract: We consider the backward optical wave stimulated by a multimode, monochromatic, incident optical wave in a waveguide filled with a transparent nonlinear medium, when the incident wave is negligibly perturbed by the nonlinear processes We derive the conditions on guide length, area, mode number, and Stokes shift in order that a given high percentage of the power in the backscattered field be the “phase conjugate” of the incident field, ie, be proportional to its complex conjugate in the entrance plane of the waveguide
69 citations
55 citations
TL;DR: Partially crystalline but highly transparent poly(4-methyl-1-pentene) has been investigated as bulk and film material by Brillouin scattering as discussed by the authors, and special surface effects have been demonstrated in terms of elastic compressional and shear constants.
53 citations
TL;DR: In this paper, the Brillouin spectrum was obtained by summing the scattering from the individual acoustical modes over the density of phonon states, and the results were obtained for the special case for a metal of scattering by acoustically created conductivity fluctuations.
Abstract: The general theory of Brillouin scattering from the surfaces of opaque media is developed using a total field solution approach. Acoustical modes appropriate to a stress-free surface are found from solutions to the acoustical-wave equation and boundary conditions for a finite isotropic medium. Two light-scattering mechanisms, namely, the surface corrugation and bulk elasto-optical effects, were analyzed by deriving optical fields which satisfy both the acousto-optically driven wave equation and the electromagnetic boundary conditions. The special case for a metal of scattering by acoustically created conductivity fluctuations was also investigated in a similar way. The Brillouin spectrum was obtained by summing the scattering from the individual acoustical modes over the density of phonon states. Excellent agreement was obtained with experiment for Brillouin scattering from the metals gallium (liquid) and aluminum (solid).
TL;DR: In this paper, the effect of segmental motion on the density-density correlation function of a viscous polymer liquid has been analyzed using a generalized relaxation equation developed by Zwanzig and Mori.
Abstract: The effect of segmental motion on the density–density correlation function of a viscous polymer liquid has been analyzed using a generalized relaxation equation developed by Zwanzig and Mori. It is shown that for polymer liquids of high viscosity, Brillouin scattering is closely associated with the structural relaxation associated with the motion chain segments. A single relaxation time theory is shown to yield good agreement with the experimental results on polypropylene glycol. The torsional motion involving a small number of monomer units is shown to be responsible for the dispersion and attenuation of the hypersonic wave. The fact that the Brillouin scattering spectrum of a polymer liquid is insensitive to the change of molecular weight is discussed. We have shown that temporal modulation of the spatial second moment of the intermolecular or intersegmental interaction energy is responsible for the relaxation process involved in Brillouin scattering.
TL;DR: In this article, linear response functions or Green functions are derived for the acoustic vibrations which propagate perpendicular to the surfaces of a parallel-sided slab, and the corresponding power spectra of the acoustic displacement-gradient components are determined.
Abstract: Linear response functions or Green functions are derived for the acoustic vibrations which propagate perpendicular to the surfaces of a parallel-sided slab, and the corresponding power spectra of the acoustic displacement-gradient components are determined. The frequency dependence of the normal-incidence Brillouin-scattering cross-section is calculated for arbitrary relative sizes of slab thickness, acoustic mean-free-path, and optical absorption length. Various limiting cases of physical interest are studied.
TL;DR: In this article, sound velocity and sound absorption of supercooled water in the temperature range down to 2014 20 °C were analyzed using equations analogous to the critical phenomena laws, showing a rapid variation with temperature.
Abstract: 2014 We present new experimental results for sound velocity and sound absorption of supercooled water in the temperature range down to 2014 20 °C. The results show a rapid variation with temperature that can be analysed according to equations analogous to the critical phenomena laws. LE JOURNAL DE PHYSIQUE LETTRES TOME 39, ler AVRIL 1978, Classification Physics Abstracts 62.60 78.35
TL;DR: In this article, the velocity of Rayleigh and Sezawa waves was measured and interpreted in terms of the film elastic constants Surface phonon attenuations were also measured and it was found that the lifetimes of surface and bulk phonons of the same wave vector are comparable in the glass studied
Abstract: Brillouin scattering from thermal surface phonons has been observed in thin films deposited on semi-infinite media The velocity of Rayleigh and Sezawa waves was measured and interpreted in terms of the film elastic constants Surface phonon attenuations were also measured and it was found that the lifetimes of surface and bulk phonons of the same wave vector are comparable in the glass studied
TL;DR: In this paper, the authors used a five pass Fabry-Perot interferometer to observe Brillouin scattering from longitudinal sound waves in films of amorphous silicon prepared by glow discharge decomposition of silane.
TL;DR: In this article, Brillouin scattering has been used to obtain the five independent elastic constants in the layer compound GaSe and the results show clear elastic anisotropy of the crystal.
TL;DR: In this article, the authors studied the concentration and temperature dependence of transverse acoustic phonon frequency ωTA (110) in (KCN)x(KBr)1−x mixed crystals.
TL;DR: Theoretical results concerning the wave front reversal of spatially depolarized light in stimulated scattering are presented in this paper, where the modes of scattering medium are found and the deterioration of reversal quality for the depolarised light is predicted.
IBM1
TL;DR: In this paper, resonant Brillouin scattering results in CdSe were reported for both the I 2 bound exciton and the free exciton, and they were found to vary with polariton energies in qualitative agreement with the theory of Brenig, Zeyher and Birman.
TL;DR: In this paper, the effects of weak stimulated Brillouin scattering with the 50-MHz incoherent scatter radar at Jicamarca were investigated. But the authors focused on the effect of the upgoing radar wave with the downcoming waves, incoherently backscattered from greater heights, causing an asymmetry in the incoherent backscatter spectrum.
Abstract: Observations of weak stimulated Brillouin scattering with the 50-MHz incoherent scatter radar at Jicamarca are described. The nonlinear interaction of the upgoing radar wave with the downcoming waves, incoherently backscattered from greater heights, causes an asymmetry in the incoherent ‘ion’ backscatter spectrum. For a given antenna aperture this asymmetry increases with increasing power and decreasing frequency of the radar. The theoretically predicted effect was unambiguously verified, using 3-ms pulses and long integration time. Model calculations based on the theory presented show good agreement with the observations.
TL;DR: In this paper, the authors reported the first measurements of thermally excited surface acoustic phonons, and bulk and surface magnons from metallic glasses using Brillouin scattering, and the measured field dependences of the surface magnon frequency allow them to determine the g-factors.
IBM1
TL;DR: In this article, a theory of two-phonon resonant Brillouin scattering of polaritons is developed and found to reproduce well the position, linewidth and relative intensity of all the experimental peaks with only one adjustable parameter.
Patent•
20 Feb 1978
TL;DR: In this paper, a CW Brillouin ring laser with a pair of partially reflective mirrors positioned to form a ring optical path with the fiber ends, produces a CW Stokes beam when a pump beam is directed into one end of the optical fiber and propagates around the ring in a direction opposite to the pump beam.
Abstract: A CW Brillouin ring laser utilizing a low loss optical fiber and a pair of partially reflective mirrors positioned to form a ring optical path with the fiber ends, produces a Brillouin shifted Stokes beam when a pump beam is directed into one end of the optical fiber. The Brillouin beam propagates around the ring in a direction opposite to the pump beam. The pump beam is coupled into the ring through one of the partially reflective mirrors and the laser output is the portion of the Brillouin beam passing through the other partially reflective mirror. In the Brillouin laser system, a second pump beam may be directed into the other end of the fiber to produce a second Brillouin beam propagating in a direction opposite to the first Brillouin beam, providing a laser with two distinct Brillouin beam outputs.
TL;DR: In this article, backscattered laser radiation has been observed from a CO2 laser-produced and heated underdense plasma in a steady solenoid magnetic field, and is attributed to the stimulated Brillouin scattering process.
Abstract: Backscattered laser radiation has been observed from a CO2 laser‐produced and heated underdense plasma in a steady solenoid magnetic field, and is attributed to the stimulated Brillouin scattering process. Spectral measurements and observations of the dependence of the backscattered intensity on laser power are presented to support this identification. Backscattered radiation, amounting to as much as 1% of the incident power, was found to be redshifted by 80–100 A, the shift expected for stimulated Brillouin scattering from a plasma at the measured temperature Te=80±25 eV. Data are also presented on the dependence of backscattered power on the density and convergence angle of incoming radiation.
TL;DR: In this article, the dispersion of photoelastic constant (P 66 ) has been determined from the present data and compared with the piezobirefringence analyses, and a damping effect on the scattering mechanism has been discussed to explain the observed dispersion.
Abstract: Resonant Brillouin scattering in CdS has been studied at room temperature by making use of piezoelectrically inactive T A phonon domains obtained by mode conversion upon partial reflection of acoustoelectrically amplified T A phonon domains at the end surface. It has been found that the dispersion of Brillouin scattering efficiency shows a new scattering maximum at a photon energy very close to the ground-state discrete exciton energy. A damping effect on the scattering mechanism has been discussed to explain the observed dispersion. The theoretical prediction based upon Loudon's light scattering theory has shown a quite good agreement with the present results when the damping effect is taken into account. The dispersion of photoelastic constant ( P 66 ) has been determined from the present data and compared with the piezobirefringence analyses.
TL;DR: In this paper, the Brillouin scattering from thermal phonons in a thin-film integrated optics waveguide has been measured and interpreted to yield the elastic constants of the film, where the phonons are assumed to be composed of a set of phonons.
Abstract: Brillouin scattering from thermal phonons in a thin‐film integrated optics waveguide has been measured and interpreted to yield the elastic constants of the film
TL;DR: The Brillouin scattering studies on lithium ammonium tartrate monohydrate (LAT) have been made in paraelectric phase as discussed by the authors, and the elastic stiffness constants C p 55 and C E 55 vanish at T 0 =94.5 K and T c =97.5 k, respectively.
Abstract: The Brillouin scattering studies on lithium ammonium tartrate monohydrate (LAT) have been made in paraelectric phase. The elastic stiffness constants C p 55 and C E 55 vanish at T 0 =94.5 K and T c =97.5 K, respectively. Some Raman scattering spectroscopies of this crystal have been also made. From the phenomenological theory and the discussion of the elastic dispersion, LAT has been concluded to undergo the proper ferroelastic transition, or, the soft mode in LAT is an acoustic phonon of which energy is determined by C p 55 . Measurements of refractive indices at room temperature are reported.