Acoustooptic cells with nonuniform length of light-sound interaction

Diffraction of light by acoustic waves that are generated in the acoustooptic cells of piezoelectric transducers with complex geometry is studied. The diffraction by acoustic beams with triangular, quadrangular (rhombic), hexagonal, etc., cross sections, when the lengths of light-sound interaction in the cross-sectional area of the light beam are different, is considered in the plane wave approximation. The difference in the length of interaction affects the instrument function of acoustooptic devices and provides the suppression of the side lobes in their transmission function. The advantages of using cells with complex-geometry transducers in tunable acoustooptic filters that are incorporated into fiber-optic communication lines with wavelength-division multiplexing (WDM) are discussed.     

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.     

Photoelastic and acousto-optic properties of the KDP crystal with application to wide-angle acousto-optic tunable filters

Acousto-optic properties of the KDP crystal are analyzed with application to wide-angle acousto-optic tunable filters. The analysis is based on the measurements of the effective photoelastic constant in KDP crystals at the optical wavelengths of 405, 532.5, and 633 nm. The disagreement between the experimental and literature data is discussed.     

Acousto-Optic Properties of Germanium-, Selenium-, Silicon-, and Tellurium-Based Alloys

Optics and Spectroscopy - Acoustic, optical, and acousto-optic properties of amorphous germanium-, selenium-, silicon-, and tellurium-based alloys have been studied. The velocities of longitudinal...     

Collinear diffraction of a divergent light beam by ultrasound in a paratellurite crystal

The collinear acousto-optical interaction of a divergent light beam with ultrasound along the approximate [110] direction in a TeO₂ paratellurite crystal is investigated theoretically and experimentally. The collinear diffraction is studied at an ultrasonic frequency f ≈ 149 MHz under exposure of the crystal to an uncollimated laser light beam at a wavelength λ = 633 nm and at an angle of divergence as large as 4°. It is shown that the collinear diffraction along the direction forbidden for acousto-optical interactions of plane waves occurs only under conditions where the light beam is uncollimated and the diffraction efficiency increases with an increase in the divergence of the light beam. It is proved that the attenuation of an acoustic wave brings about a decrease in the diffraction efficiency and an increase in the transmission bandwidth of the device used. A model of the collinear acousto-optical filter based on a paratellurite crystal with an interaction length l = 2.7 cm is analyzed. The collinear acousto-optical filter is characterized by a high resolving power (～3000), a high diffraction efficiency (I₁/I₀ ≈ 0.8), and a large angular aperture (Δ? ≈ 4°). This makes collinear diffraction promising for use in acousto-optical filters based on paratellurite crystals.     

Differential inhibition of postnatal brain,spinal cord and body growth by a growth hormone antagonist

Background  

Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH.     

Efficiency of collinear acoustooptic interaction in an anisotropic medium

Collinear acoustooptic interaction in crystals with different values of birefringence is theoretically studied. The crystal medium is considered as a system of thin layers where the orientation of optical indicatrix varies from layer to layer due to the presence of an ultrasonic wave. For collinear diffraction in LiNbO₃, α-SiO₂, Te, CaMoO₄, and Tl₃AsSe₃ crystals, expressions for the transmitted and diffracted intensities are obtained by means of acoustooptic methods and a new method based on the Jones calculus.     

One-dimensional problem of a shock in a gas

The self-similar problem of the motion of a cold gas subjected to an instantaneous impulse is considered. A solution is constructed in the neighborhood of the known exact solution for a gas with a specific heat ratio =1.4 [1–4]. An analytic expression is obtained in this neighborhood for the dependence of the index of self-similarity n on the parameter h, which is related to the adiabatic index by h=(+1)/(–1). The results of a numerical calculation of n versus h are compared with the analytic expression.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 74–78, November–December, 1973.     

Spectral and polarization analysis of optical images by means of acousto-optics

This paper presents results of a theoretical and experimental study of Bragg anisotropic diffraction. The diffraction may be used for filtration of optical radiation and processing of images. Special attention is devoted to the investigation of diffraction, which provides spectral filtration simultaneously with polarization analysis of divergent optical beams. A tunable tellurium dioxide acousto-optical filter for processing of optical images is described in the paper. Some experimental results of the image analysis in visible light and in the near-infrared region of the spectrum are discussed.     

Diffraction of IR radiation by ultrasound in tellurium single crystals

The optic, acoustic, and acousto-optic properties of tellurium single crystals are considered to analyze the possibilities of applying this material in acousto-optic filters to control mid- and far-IR radiation. The results of measuring the optic and acousto-optic parameters of a tellurium crystal are reported. The isotropic and anisotropic light diffraction by ultrasound in the crystal is investigated. The wide-aperture geometry of interaction in tellurium is implemented and an acousto-optic figure of merit M ₂ of a tellurium crystal exceeding 10 × 10^?15 s³ g^?1 is experimentally obtained.