Study of a bi-axial (KTP) crystal using double Stokes-Mueller polarimetry

In this paper, we report the significance of the double Stokes-Mueller polarimetry (DSMP) technique, to characterize a large size (3 x 3 x 5 mm) Potassium titanyl phosphate (KTP) crystal. The crystal undergoes second harmonic generation with type II phase matching. The study of standard KTP crystal using the DSMP technique helps to validate the efficiency of this technique. We were able to extract the crystal's double Mueller matrix, relative contribution of the susceptibility tensor components, the phase difference between the susceptibility tensor components, etc. We could determine the crystal axes orientation using this optical technique, which was not possible through a single crystal X-Ray diffraction technique for such a large size crystal for which both optic axes and crystallographic axes are the same. Axes direction determined from polarization microscope measurements and Laue diffraction measurements on KTP crystal is compared with those obtained from DSMP measurements.