| 摘要 |
PURPOSE:To suppress the fluctuation in characteristics by a DC drift and to obtain a stable operation by providing bias electrodes near light control electrodes and holding a bias voltage applied at all times between the light control electrodes and the bias electrodes. CONSTITUTION:The control electrodes 15, 16 are formed via an SiO2 buffer layer 17 on the optical waveguide constituting a directional coupler 14. The light control electrode 16 is grounded and a switch power source 20 is connected between the light control electrodes 15 and 16 in such a manner that a switching voltage Vs can be applied by changing over the switch 19. The bias electrodes 18 are formed equidistantly to enclose the light control electrodes 15, 16. A positive bias voltage VB sufficiently larger than the switching voltage Vs is kept applied at all times between the bias electrodes 18 and the light control electrodes 15, 16. A positive bias voltage VB sufficiently larger than the switching voltage Vs is kept applied at all times between the bias electrodes 18 and the light control electrodes 15, 16. The movement of impurity ions to induce the DC drift is suppressed in this way and the fluctuation in the characteristics by the DC drift is suppressed. The stable operation is thus obtd. |
