  We report the significance of the double Stokes Mueller polarimetry (DSMP)
technique, to characterize a large size (3 X 3 X 5mm) KTP (Potassium titanyl
phosphate) 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, the 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.
