The anisotropy of piezo- and elasto-optic effects in calcium tungstate CaWO₄ crystals was studied by the indicatory surfaces method. On the basis of the maximum surfaces of the elasto-optic effect, the geometry of acousto-optic interaction with maximum efficiency was found.

Piezo-optical and elasto-optical properties of lead molibdate (PbMoO 4 ) crystals are investigated, as determined by the quantum-mechanical ab initio calculation of the full set of photo-elastic, piezo-optic and elastic tensor components. Indicative surfaces are built, which describe the anisotropy of these stress-and strain-optical effects and allow for its rigorous analysis. Maximum values of these properties are determined as well as the geometries of acousto-optic interaction displaying the maximum efficiency. Lead molibdate crystals are found to be characterized by a large piezo-optic efficiency, the maximum change of the optical path (per unit of mechanical stress and specimen length) being calculated to 24.9 Br, which is a much larger value than previously reported for other well-known piezo-optic materials such as LiNbO 3 , CaWO 4 and GaP. It is also shown that a significant rotation (up to several tens of degrees) of the optical indicatrix about the X 3 optical axis is induced by uniaxial pressure or deformation, depending on pressure (or deformation) direction rather than magnitude, which has relevant implications in the design of acousto-optic cells.

No abstract

A general equation describing the rotation of an optical indicatrix of tetragonal crystals (4, 4¯, 4/m symmetry classes) around the X₃ axis (optical axis) depending on the direction of uniaxial pressure in the plane perpendicular to crystal optical axis is written. Partial cases of the general equation, when pressure is acting along the X₁ (X₂) axis or along the diagonal between the X₁ and X₂ axes, are received. The values of piezo-optic coefficients (POCs) π₆₁, π₁₆, and π₄₅ are determined by the conoscopic method on the basis of the appropriate equations. Other POCs π_im are determined by the interferometric method. All components of the matrix of elasto-optic coefficients are also determined as p_in=π_imC_mn. These results are being compared to the ones received on the basis of wave-mechanical calculations. Objective p_in values are necessary to build indicative surfaces of the elasto-optic effect and to find maximums of these surfaces and appropriate maximum values of acousto-optic quality coefficients.

Elasto-optic coefficients of gallium phosphide (GaP) crystals were calculated on the basis of their piezo-optic and elastic coefficients. Surfaces of the spatial distribution of piezo- and elasto-optic effects in these crystals were built. The maxima of the surfaces of the elasto-optic effect and the geometries of acousto-optic interaction that correspond to these maxima were found. Ratios that describe the rotation of optical indicatrix, depending on direction of the action of uniaxial pressure or deformation on cubic crystal, were recorded. It was shown that such rotations induced by mechanical stress do not exceed 1.5° in GaP, but in some cubic crystals they can reach tens of degrees.