Measurement of refractive index change in nonlinear crystals using wavefront sensor

We are developing the all-solid-state light source at 193-nm. In case of high average power wavelength conversion, thermally induced refractive index change induces phase mismatch in nonlinear crystal. We evaluated the refractive index change inside nonlinear crystals by using a large area wave front sensor with the spatial resolution of 44 microns.