Thermo-optic properties of epitaxial Sr₀.₆Ba₀.₄Nb₂O₆ 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 T[sub c]. This strong enhancement is related to the critical change of the polarization. The values of dn[sub e]/dT are significantly larger than dn[sub o]/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.