Pockels’ effect in polycrystalline ZnS planar waveguides

The Pockels’ effect has been demonstrated in thermally evaporated polycrystalline thin films of ZnS. The strongly (111)-oriented films were found to have an electro-optic constant of r41 = 3.3 × 10−13 m/V for fields perpendicular to the (111) planes. Extinction ratios of up to 85% have been observed in an optical waveguide modulator. Analysis indicates a stress-related birefringence that manifests itself upon temperature change. The temperature coefficient of stress in the polycrystalline films was found to be 3.0×105 N m−2/°C.