In a waveguide type optical device which has an optical waveguide and modulation electrodes for varying its refractive index, both formed in the top of a substrate and a ferroelectric crystal having a pyroelectric effect, the top of the crystal substrate being parallel to the direction of its spontaneous...http://www.google.de/patents/US5185823?utm_source=gb-gplus-sharePatent US5185823 - Waveguide type optical device
