Piezooptical coefficients of La3Ga5SiO14 and CaWO4 crystals: A combined optical interferometry and polarization-optical study

Paper reports the piezooptical studies on langasit La3Ga5SiO14 (LGS) and calcium tungstate CaWO4 (CWO) crystals by means of the combined optical interferometry and polarization-optical techniques. Corresponding methodology is supplied by a set of derived equations suitable for the determination of the absolute piezooptical coefficients (POCs) in the crystals of trigonal or tetragonal symmetry. It is shown, that for the determination of all the eight absolute POCs πіm of trigonal LGS or tetragonal CWO crystals by means of polarization-optical technique one must perform additionally at least two optical interferometry measurements in certain experimental geometries. In most cases the combined study considerably improves an accuracy in the determination of the absolute POCs. Due to a large piezooptical effect revealed in CWO crystals they may be considered as quite perspective materials for eventual photoelastic or acoustooptical applications.