| 摘要 |
PURPOSE:To provide the optical function element of a directional coupler type having a high extinction ratio characteristic. CONSTITUTION:The coupling part C0 of the 1-input 2-output directional coupler consisting of a semiconductor or dielectrics is formed by optically connecting a front partial coupling part C3, a front partial coupling part C4 with electrodes, central partial coupling part C5, rear partial coupling part C6 with electrodes, and rear partial coupling part C7 of respectively prescribed lengths in this order form the input side. The coupling state in the front partial coupling part and the coupling state in the rear coupling part and an exit side lead part C2 optically connected thereto are offset and coupling symmetry is equivalently attained, by which the deterioration in the extinction ratio in the cross state is eliminated. In addition, the central partial coupling part of an adequate length is formed, by which the extinction ratio in the through state is maintained at a high level. The high extinction ratio characteristic is thus attained in both of the cross state and the through state. |
