TEMPERATURE-DEPENDENT INDEX-OF-REFRACTION CHANGES IN BATIO3

We investigate thermally induced changes in the index of refraction of BaTiO3 that are caused by optical absorption. We show that the absorption of a 900-mW optical beam will change the surface temperature of a BaTiO3 Crystal by more than 40-degrees-C and cause the extraordinary index of refraction to change by more than 10(-2). For a 900-mW beam incident upon a BaTiO3 Crystal that is not mounted on a heat sink, the surface temperature and the extraordinary index of refraction are still changing after more than 10 min. We also demonstrate that the thermally induced time-dependent index change is partially responsible for the frequency-shifted return from a two-internal-reflection or Cat self-pumped phase-conjugate mirror that has not reached thermal equilibrium.