Polarization effects during the interaction of counterpropagating waves in isotropic resonant media

Using the method of nonlinear polarization spectroscopy in the oppositely propagating laser beams of different power at a wavelength of 3.39 μm, we study, both theoretically and experimentally, the mechanisms of the formation of dichroism and birefringence during the interaction of arbitrarily polarized fields of resonant radiation with gaseous methane under conditions of low pressure of the gas in the cell and saturation of the operating transition F ₂ ⁽²⁾ by the field of a strong wave. Spectral forms of the polarization resonances of the test-wave intensity at the output of the polarization spectrometer are studied experimentally. Based on the vector theory of light interaction with matter, we present an exhaustive theoretical interpretation of the experimental data on the dependence of the polarization state of a weak wave on the intensity of a linearly or circularly polarized high-power counterpropagating wave. A new technique of measuring the induced nonlinear anisotropy for test-field waves and the macroscopic parameters of the resonant gas is developed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 1, pp. 72–93, January 2007.     

Acoustic-elastodynamic interaction in isotropic fractal media

This research explores the acoustic-elastodynamic interaction in isotropic fractal media. The analysis discusses the direct coupling of two constitutive models under dynamic loading: a continuous solid and an isotropic fractal medium. We consider two situations where in the first, the fractal medium is enclosed within a thin spherical shell (interior problem), while in the second, the fractal medium extends infinitely outside the shell (exterior problem). The two problems are simulated analytically, and the exact solution for the shell displacement is expressed in closed form in the Laplace domain. The formulation of the radiation condition for infinite fractal media is essential to derive the exterior problem’s solution. This study represents a meaningful idealization of real-application problems involving the interaction of multi-constitutive media, e.g. the human brain, whereby fractal features affect the response of this body under various excitations.     

Conditions for obtaining backward collinear isotropic acousto-optic interaction in germanium and iodic acid crystals

The possibility of experimentally obtaining backward collinear isotropic acousto-optic interaction based on bulk ultrasonic waves and terahertz electromagnetic waves is considered. The magnitudes of the acousto-optic figure of merit and the corresponding acoustic frequencies are calculated for the basic crystallographic axes in germanium and iodic acid crystals. The acousto-optic parameters of both crystals are compared.     

Polarization beam splitting in media with light-induced anisotropy

The problem of light beam reflection from a refractive-index inhomogeneity induced by a high-power polarized Gaussian pump beam in a resonant medium has been simulated. A nonlinear optical method of spatial splitting of polarization components of a probe pump beam is proposed.     

Poynting vector in transfer-matrix formalism for the calculation of light absorption profile in stratified isotropic optical media

In spite of the fact that solutions to Maxwell's equations in stratified isotropic optical media are well known, it appears that an explicit expression of the Poynting vector flux spatial evolution inside such a medium has not been derived so far. Based on exact electromagnetic field solutions in the transfer-matrix formalism, I derive such an expression and show that, due to the presence of counterpropagating waves in the medium, an additional contribution to the flux appears that exists only in optically absorbing layers and arises from the interference between these waves. Based on this theory, the concept of incremental absorption is introduced for the calculation of the light absorption profile along the stratification direction. As an illustration of this concept, absorption profiles in a Si-based thin-film tandem solar cell are predicted at typical wavelengths.     

Application of acousto-optic interaction for holographic conversion of light fields

This paper represents a survey of research on the problem of acousto-optic conversion of optical images. This method of conversion permits us to retain all information that is contained in both amplitude and phase spatial modulation of a light wave. Particular attention is given to acousto-optic visualization of phase objects and registration of optical wavefronts. Information possibilities of the acousto-optic method are illustrated by numerical calculations as well as by some experiments recently performed in this area.     

The transformation of a light beam during interaction with matter

The transformation of the light-beam tensor due to Rayleigh scattering, due to the volume element of a luminescent substance (a luminescent crystal), and Fresnel optical reflection and refraction is considered. It is shown that the suggested covariant method leads more rapidly and more simply to the desired results than the Stokes parameters.     

Circular electrodichroism of light in isotropic optically active media

Circular electrodichroism is predicted in liquids and gases containing unequal concentrations of mirror stereoisomers of chiral molecules. A longitudinal (quasi)static electric field increases absorption for a light wave circularly polarized in one direction and decreases the absorption for a wave circularly polarized in the opposite direction. The corresponding nonlinear susceptibility is proportional to the decay constants of the excited states and is absent in a nondissipative medium. Estimates of the magnitude of the effect are presented and show that it may well be observable experimentally. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 8, 515–520 (25 October 1997)     

Particular features of acousto-optic visualization in scattering media upon detection of nonballistic light

Images of optically inhomogeneous objects immersed into a cell with a scattering liquid through which orthogonal laser and ultrasonic beams pass are obtained upon measuring the scattered light modulated at the ultrasonic frequency. The alternating current from a photodetector recording the optical radiation emerging from the cell was used as a parameter of the acousto-optic visualization. The quality of the visualization is analyzed in relation to the registration conditions and the scattering parameter magnitude, as well as the size and shape of three-dimensional and planar objects. Under the experimental conditions used, the positions of objects immersed into the scattering liquid are detected fairly precisely, with a satisfactory contrast and sharpness of images in the plane perpendicular to the laser beam axis, whereas, along this axis, the object positions are not determined. The experiment was performed under conditions of transition from a regime without scattering to a regime of multiple scattering.     

关于声光效应光束偏转角的实验研究

对声光效应中光束偏转角进行了一系列实验研究.基于传统声光效应的基本原理,建立了光束偏转角理论模型并进行了相关计算.在此基础上进行声光效应的布拉格衍射实验.大量实验结果显示,所测量到的光束偏转角和理论值存在一定的差距.     

Particular features of detecting the acousto-optic interaction signal in visualization of scattering media

Experimental dependences of the detected acousto-optic interaction signal and of the signal-to-noise ratio on parameters of a scattering medium have been obtained using single- and three-slit diaphragms in front of the photocathode of the receiver. Under the aforesaid conditions, the visualization parameters of the absorbing object are compared. The conditions of preferable use of a multislit diaphragm are determined.     

Nolinear interaction between P-and SV-wave in isotropic elastic media

I.IntroductionInthelinearwavethcory,thestressinaso1idisproportionaltostrainsandthepropagatingwaves(suchasP-,SV-andSH-waves)satisfythehomogeneouswaveequation.Iftherearesomeboundaries,thereflectionandrefractionobeytheSne11'sla.[1l.Inthenon1inearmcdia,ontheotherhand,a11theequationsarenon1inearsoitisverydifficulttoobtainanexactsolu-honingeneral.Usua11y,thepcrturbationmethodsarcinvokedtofindanapproximateso1ution.Sincethenon1ineartermsofthestrainsappearinthestrcsses,two-waveinteractionwilltakep1…     

各向同性弹性介质中P波与SV波的非线性相互作用

应用作者提出的二阶势理论,本文研究了各向同性弹性介质中P波与SV波的非线性相互作用,得到了相互作用波的表达式。结果表明,当上述二个波的传播方向所夹的角接近于所谓\     

Polarisation dependence of photon antibunching phenomena involving light propagation in isotropic media

By the method of “short optical paths”, the dynamics of photon antibunching is shown to depend on the polarisation state of the photons and their two-photon absorption in an isotropic medium. In the case of self-induced optical birefringence, a change in helicity of the elliptically polarized beam or a change in sign of the angle between the large semi-axis of the ellipse and the analyzer causes a reversal of antibunching into bunching. Linear and circular polarisation of the photons are discussed as well for antibunching related with two-photon absorption, defined by the imaginary part of the molecular hyperpolarizability tensor.     

A hybrid solitary-conical self-guided light beam in self-focusing media

In addition to subluminal solitons and superluminal conical beams, self-focusing media also support a luminal nonspreading beam with hybrid solitary-conical properties. Its existence reveals that spatial solitons may also have a conical structure, and vice versa.