Stokes-Mueller Polarimetry

We use the double Stokes–Mueller polarimetry (DSMP) technique, to characterize a large size (3x3x5 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 e±ciency of this technique. We were able to extract the crystal’s double Mueller matrix, relative contribution of the susceptibility tensor components, the phase di®erence 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 di®raction technique for such a large size crystal for which both optic axes and crystallographic axes are the same. Axes direction de- termined from polarization microscope measurements and Laue di®raction measurements on KTP crystal is compared with those obtained from DSMP measurements.

The schematic of DSMP performed on a KTP crystal to extract the nonlinear optical properties of crystal is shown in the figure above. Here, we consider the propagation of light along the Y -axis and the polarization of light in XZ-plane in the laboratory frame coordinates. The experiment involves the generation of nine states of polarization incident on the material using PSG. The material of study, the KTP crystal is type II phase-matched nonlinear crystal which has an orthorhombic crystal structure and is biaxial in nature. The phase-matched crystal produces second harmonic generated light whose state of polarization is determined by measuring its linear Stokes vector.