The subject of the paper is related to analysis of Bragg regimes of light diffraction by ultrasound that may be observed in optically biaxial media. The regimes of acousto-optic diffraction characterized by change of optic mode during the interaction process as well as the diffraction with conservation of optic polarization are discussed in the presentation. Dependences of Bragg incidence angle on acoustic frequency are examined for various interaction geometries including the cases of symmetrical and non-symmetrical wave vector diagrams. It is shown that many of the analyzed cases of Bragg acousto-optic diffraction may be applied for development of acousto-optic devices such as modulators, deflectors and tunable filters. The sufficient part of the calculations was carried out for the promising biaxial material double lead molybdate (Pb2MoO5) possessing a considerably high acousto-optic figure of merit. Wavelength dispersion of directions of optical axes in the material as well as the dispersion of directions of basic indicatrix axes has been taken into account during the analysis.
This paper is devoted to analysis of acousto-optic Bragg diffraction in tellurium dioxide single crystal in case of bulk slow shear ultrasonic waves propagating in the material. The so-called 'isotropic' type of the diffraction by the acoustic wave is examined in the paper. Contrary to the well known 'isotropic' diffraction, the investigated acousto-optic interaction is characterized by conservation of initial optical mode int he crystal. It is proved that the discovered regime of isotropic interaction in an anisotropic material is similar to interaction in optically isotropic media. The paper acquaints with equation representing dependencies of Bragg incidence angles on acoustic frequency in the crystal. The derived equations are different from the known equations in isotropic media. Experimental results on measurements of frequency dependencies of Bragg incidences angles in paratellurite are presented in the paper. Peculiar dependencies of diffraction efficiency on amplitudes of acoustic waves are also discussed in this paper. Peculiar dependencies of diffraction efficiency of the examined isotropic interaction may be higher than the efficiency of the anisotropic scattering. As proved experimentally, maximum diffraction efficiency values for the investigated isotropic diffraction in tellurium dioxide may exceed 60 percent.
The paper is devoted to the theoretical and experimental investigation of Bragg diffraction of light by shear acoustic waves in tellurium dioxide single crystal. Various cases of Bragg anisotropic interaction accompanied by a change of optical modes in the material are examined. Unknown types of isotropic diffraction of light by shear acoustic waves in paratellurite are investigated as well. Frequency dependencies of Bragg angles for different interaction types in the crystal are calculated and measured thus confirming the basic statement that not only the traditional anisotropic but also previously unknown isotropic regimes of AO interaction may be simultaneously observed in the birefringent crystal.