Polarization-independent optical switches that utilize the off-diagonal electrooptic coefficient r51 have been produced in LiTaO3. The waveguides are formed by Zn vapor diffusion. Interguide transfer efficiencies of 84 and 88 percent for TM and TE polarizations, respectively, have been obtained. Modulation efficiency of 99.8 percent for TM and 95 percent for TE have been demonstrated at nearly equal voltages by thermally tuning to 20C. The relatively high voltage length product (30-35 V cm) attained in these initial devices at 0.633-m wavelength is attributed to a weak overlap between optical and electrical fields in the periodic electrode structure. 1990, IEEE
