Temperature sensitivity of prism coupling to lithium niobate optical waveguides

Experiments characterizing the temperature sensitivity of tapered-gap prism coupling to in- and out-diffused lithium niobate optical waveguides are reported. Reduction in coupling efficiency with changes in ambient temperature are shown to be related primarily to the temperature dependence of lithium niobate’s extraordinary refractive index. Optimum coupling efficiency is shown to be recoverable by adjustment of only the prism coupling angle. Several methods are discussed for dealing with this problem.