| 摘要 |
PURPOSE:To obtain a sufficient crosstalk characteristic for each polarized light beam with the same applied voltage without any polarization dependency of loss. CONSTITUTION:A directional coupler 5 is formed by injecting impurities into a ferroelectric crystal substrate 2 with electrooptic effect as a couple of optical waveguides 1 which have parallel optical axes. A couple of control electrodes 4 are provided on the directional coupler 5 across a buffer layer 3 and the voltage applied to the control electrodes 4 matches a polarization mode (TM mode) wherein an electric field component is perpendicular to the crystal substrate 2 and a polarization mode (TE mode) wherein the electric field component is parallel to the crystal substrate 2; and the length of the directional coupler 5 and the injection amount of the impurities are so set that when the applied voltage is zero, incident light and projection light are nearly equal in quantity in each polarization mode. |
