Measurements of piezooptic coefficients π14 and π1425 in Pb5Ge3O11 crystals using torsion induced optical vortex.

We show how a singularity of optical field can be used for determination of piezooptic coefficient of crystals under their torsion, in particular in the situation when the natural optical activity makes direct polarimetric experiments too complicated. Experimental studies of an optical vortex appearing under torsion of lead germanate crystals have enabled us to determine so-called non-principal coefficients (π1414 and π1425). A relationship between the spin angular momentum of light beam and the piezooptic coefficients has been derived. [ABSTRACT FROM AUTHOR]