Study of piezo-optic effect of calcium tungstate crystals by the conoscopic method

• Conoscopic method determines π11–π12 and π61 for CaWO4 crystals with high accuracy.
• π11–π12 is determined from change of angle between optical axes.
• π61 is determined from rotation of optical indicatrix.
• Expression for π11–π12 determination is valid for all optically uniaxial crystals.
• Expression for π61 definition is valid for 3, 3¯, 4, 4¯, 4/m  , 6, 6¯, 6/m symmetry classes.

Conoscopic method for piezo-optic effect study in optically uniaxial crystals related to 4, 4¯, 4/m symmetry class was described. Ratio for determination of difference between principal piezo-optic coefficients π11–π12 and rotating coefficient π61 on the basis of change of the angle between optical axes and optical indicatrix rotation under uniaxial pressure loading along X1 crystal physics axis was presented. The method was tested on CaWO4 crystals (4/m symmetry class). It was shown that the error of π61 coefficient determination by conoscopic method is less by a factor of ten that the one obtained by interferometry method.

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