Thermo-optic properties of epitaxial Sr_06Ba_04Nb_2O_6 waveguides and their application as optical modulator

Abstract
A prism-coupler technique was introduced to determine the refractive indices and thermo-optic coefficients of epitaxial Sr0.6Ba0.4Nb2O6 (SBN) waveguides, in a temperature range covering the ferroelectric-paraelectric phase transition. A strong enhancement in the TO coefficient is observed near Tc. This strong enhancement is related to the critical change of the polarization. The values of dne/dT are significantly larger than dno/dT due to the larger quadratic electro-optic coefficient in TM polarization. In TM mode, the refractive index of SBN is increased by 1.3% as the temperature is increased to 160°C. Our results suggest that SBN waveguide is a potential candidate for thermo-optic modulators and switches.