| 摘要 |
PURPOSE:To reduce polarization dependency upon a driving voltage and switching characteristics and to secure the light confinement effect of a waveguide highly by specifying the length of the coupling part of a directional coupler and arranging four divided electrodes on the directional coupler opposite each other. CONSTITUTION:Two waveguides 2 and 3 are formed on a substrate 1 and the coupling part 6 is formed so that parts of the waveguides 2 and 3 are close to each other. Then the coupling part length L of the coupling part 6 in TE mode is about four timers as long as the complete coupling length in TE mode and about twice as long as the complete coupling length in the TM mode as to the TM mode. Further, couples of four divided electrodes 41 - 44 and 51 - 54 which are divided into four respectively are arranged on both the waveguides 2 and 3 which form the coupling part 6 opposite each other and the four-divided electrodes 41 - 44 and 51 - 54 are applied with voltages which invert the directions of electric fields alternately to drive and control the electrodes. Consequently, an element driving voltage is reducible, the polarization dependency upon the switching characteristics can be made small, and the light confinement effect of the waveguides 2 and 3 can be secured highly. |
