| 摘要 |
PURPOSE:To provide an optical branching and coupling unit which has a desired branching or coupling ratio. CONSTITUTION:Waveguides 4 and 14 which constitute a directional coupler are formed by diffusing metal on a dielectric substrate. Bent part areas are present on both sides of the optical coupling part of the directional coupler. A couple of electrodes 6 and 16 are formed in a low-refractive-index area between a couple of waveguide parts 4a and 14a in one of the bent part areas. A constant voltage source is connected to those electrodes 6 and 16. This optical branching and coupling unit produces an electric field between the waveguide parts 4a and 14a by the electrodes 6 and 16 to decrease the refractive index of this area, so the light confinement effect in the waveguide part areas 4a and 14a can be increased. Consequently, optical coupling between the couple of waveguide parts 4a and 14a can be prevented and the optical branching and coupling unit which has the branching or coupling ratio as designed is provided. |
