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In this paper, we present results of theoretical and experimental investigation of the crystal KRS-5. The carried out research was related to analysis of acoustic, optic and acousto-optic properties of the single crystal KRS-5 that is a solid solution of thallium halides. The material is considered as a medium for applications in infrared acousto-optic devices providing laser beam control. In our analysis, we determined acoustic properties of the material. The values of acoustic phase velocities and their polarization directions were determined for acoustic modes propagating along in the directions [100], [110] and [111]. We also determined the velocities and polarizations of the acoustic waves in the planes (001) and (1 1 0) of the material. In the basic experiment, we used the slow shear acoustic wave propagating along the direction [100] and having the phase velocity value V= 890 m/s. One of the principal goals of the research was directed to experimental confirmation of a possibility to induce birefringence in the cubic material. We managed to induce the birefringence applying an external static pressure to the crystal. Varying the pressure, we controlled the birefringence and obtained difference in magnitudes of the refraction indexes up to Δn =3.5·10-4 . Typical regimes of anisotropic acousto-optic interaction in the birefringent medium were observed. The theoretical results were confirmed by experiments including laser probing of acoustic beams and analysis of Schaefer-Bergmann diagrams. The carried out investigation confirmed the conclusion that the single crystal KRS-5 is a promising material for the applications in the infrared acousto-optic devices.
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