Structured light interferometer for space-time refraction index profile

In this paper we present a glycerin-filled interferometer which is suited to determine the thermally induced space-time refractive index profile of an optical, uranyl-ion-doped glass. The refractive index of the sample changes when irradiated with an Ar+ laser or a pulsed Nd-YAG laser and modifies the interference pattern of a probe beam. According to the task performed, the interferometer is used in longitudinal and transversal configurations. Using the model of the thermal absorption and diffusion, one can find the relation between the refractive index variation, temperature gradient and phase shift of the interference pattern. We calculate the refractive index changes of the on and off axis as well as its temporal variation during the relaxation process. The modifications of a thermally induced phase grating is interpreted in terms of a one-dimensional, structured gaussian beam obtained from a double refractive crystal of KDP (KH2PO3).