Probability distribution of photocounts of the light scattered by critical fluctuations

The probability distribution of photocountsP(n, T) of the light scattered by concentration fluctuations in a binary system near the critical point has been measured. The results turn out to be consistent with the theoretical predictions for Gaussian-Lorentzian light.     

Particulate concentration measured from scattered light fluctuations

Scintillation of scattered radiation caused by particulate matter is studied. By use of stochastic theory, expressions for mathematical expectation, variance, and scintillation index are derived. A method of measuring particulate-mass concentration with the scintillation index is proposed. The major advantage of this method is its insensitivity to lens contamination and particle-color change.     

Spatial quantum correlations in multiple scattered light

We predict a new spatial quantum correlation in light propagating through a multiple scattering random medium. The correlation depends on the quantum state of the light illuminating the medium, is infinite in range, and dominates over classical mesoscopic intensity correlations. The spatial quantum correlation is revealed in the quantum fluctuations of the total transmission or reflection through the sample and should be readily observable experimentally.     

Probability distribution of singly and multiply scattered light near the critical point of a binary mixture

The probability density function p(I) is theoretically and experimentally investigated in the case of single, double, and multiple light scattering near a second-order transition (demixing of the binary mixture nitrobenzene and n-hexane). Experimentally we find no differences between the statistics of singly, doubly or multiply scattered light, and as expected from theory, p(I) shows an exponential variation. These results justify the use of either heterodyne or homodyne techniques for studying single or multiple scattering close to a critical point. We also describe a particularly simple way of determining whether homodyne or heterodyne detection occurs.     

Angular intensity distribution of scattered light in systems of closely spaced particles

The results of experimental and computational investigations of the dependence of the angular intensity distribution of scattered light on the concentration of scatterers are discussed. It is shown that a high density of small and large scatterers in a three-dimensional system results in a deformation of the scattering indicatrix. The changes in the angular distribution of intensity of the scattered light at large concentrations are explained by the appearance of fields of multiply scattered waves at significantly lower optical thicknesses than for independent scatterers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 99–103, March, 1976.     

Depolarization of multiply scattered light in transmission through a turbid medium with large particles

An approximate analytical method for solving the vector radiative transfer equation is proposed. The method is based on the assumption that single scattering of light by large-scale inhomogeneities occurs predominantly through small angles. The method is applied to calculate the polarization state of multiply scattered light. The results obtained are discussed for various turbid media.     

The spectral distribution of light scattered from methyl fluoride in the critical region

Abstract

The experimental data for the spectral distribution of light scattered from methyl fluoride in the critical region are collected and analysed for different polarization directions by means of a Fabry-Pérot etalon. The analysis reveals the presence of an unshifted Rayleigh line and two frequency shifted Brilllouin lines for polarized and depolarized intensities. The intensity ratio of these lines - the so-called Landau-Placzek ratio - is determined along the critical isochore and its divergence near the critical point is described by a power law expression.     

The effect of multiple scattering in disperse media on polarization characteristics of scattered light

The effect of scattering of different multiplicity on polarization characteristics of scattered light is studied by the Monte Carlo computer simulation technique. The scattering multiplicity distribution versus the direction of scattering and dimensions of the scattering system is obtained for monodisperse systems of spherical particles of different size. The angular dependences of the elements of the light-scattering matrix (LSM) are calculated. It is shown that in a system of spherical particles, specific features of the LSM structure associated with multiple scattering have much in common with similar features of the LSM in systems of nonspherical particles under conditions of single scattering. The angular dependences of the degree of depolarization of the scattered light are studied.     

Polarization of diffusely scattered light

Journal of Applied Spectroscopy -     

Fluctuations in doubly scattered laser light

Fluctuations in laser light, doubly scattered by brownian particles, were analysed by measuring the spectral noise power of the photodetector current. Scattering took place at two spatially separated systems of spherical particles. Analytic expressions for the field and intensity correlations are derived. The analytic expressions for the spectrum of the intensity fluctuations of the doubly scattered laser light demonstrate that the frequency dependence of the spectrum depends strongly of the geometry of the experimental arrangement. This is not the case for singly scattered light where in good approximation the spatial and temporal correlations can be separated analytically.Our measurements show that the noise spectrum of the doubly scattered radiation may have the same frequency dependence as the spectrum of the singly scattered light. However, there are conditions where the frequency dependence of the noise of the doubly scattered light diverges markedly from that of the singly scattered light.     

Effective collection of Brillouin scattered light in liquids

Devices for the collection of Brillouin scattered light in liquids are discussed. Optical systems have hitherto employed conical mirrors; their angular acceptance functions are presented. Novel devices proposed and discussed are the cylinder lens and the “scattering tube” (a cylindrical mirror). Results of applications are reported. This work was supported by the “Deutsche Forschungsgemeinschaft”.     

Fluctuation characteristics of singly scattered light intensity

The correlation function and variance of the intensity fluctuations of singly scattered light are computed for a system of independent scatterers subjected to Brownian motion and illuminated by a light beam. The computation is carried out taking account of space and time averaging by the detector. The results obtained agree with available test data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 120–124, May, 1973.     

Linewidth and coherence properties of scattered light

The holographic recording of light scattered by brownian particles is discussed. It is shown that, due to the finite time of exposure, the record acts as a temporal filter of non-zero bandwidth. As a consequence the holographic recording can be obtained in spite of the frequency change of the scattered light. The experimental results show that, in fact, such a procedure can constitute an alternative way to measure the linewidth of the scattered light.     

An anomalous correlator of resonantly scattered light

The space-time properties of the correlator of the light intensities scattered from resonant atoms are studied. It is shown that in measuring such a correlator by the method of optical shifts, an appreciable contribution appears from the anomalous correlator of the scattered field amplitudes. It is simple to observe this correlator in the field of a standing wave by measuring the correlation of oppositely scattered rays. The spectral and polarization properties of such a correlator are studied. Its investigation is of interest for high-resolution spectroscopy because it allows information to be obtained on the natural width of a line in conditions of strong Doppler broadening. It is important to stress that this is possible in a linear approximation with respect to the strength of the external field in contrast to the methods of laser spectroscopy based on nonlinear effects.     

Spectral measurements of the depolarized multiple scattered light from a binary mixture near its critical point

We report the first spectral measurements of the depolarized multiple scattered light from a binary mixture near its critical point. Spectral analysis of the depolarized light allows to separate rigorously the multiple scattering from the light scattered by the anisotropy fluctuations. The results are in very good agreement with a recent theory by Oxtoby-Gelbart.