| 摘要 |
PURPOSE:To expand a usable band width and branching angle, by providing an area whose refractive index is lower than those of waveguides and a control means which increases the refractive index of the region at the crossing point of the waveguides and transmitting rays of light made incident on the region from a 1st waveguide to a 2nd or 3rd waveguide by means of the control means. CONSTITUTION:Rays of light are totally reflected at the surface of an refractive index changing region under a state when a refractive index control means is not actuated and are transmitted through the area when the control means is actuated. Such refractive index changing region can be realized when the area lower in refractive index than the waveguide 2 is constituted of a semiconductor layer 3 which is thinner in thickness than the waveguide 2 and the refractive index of the area is made higher by depleting the region. Namely, when, for example, the semiconductor layer 3 is depleted by applying a reverse bias voltage across its p-n junction, and so forth, the refractive index becomes higher and the distribution of the refractive index changing rate shifts to the longer wavelength side from the wavelength corresponding to the forbidden band width inherent to the material. As a result, the wavelength dependency is reduced. Therefore, optical switching operations of a wide band width and expansion of a branching angle become possible at a longer wavelength band apart from the wavelength corresponding to the forbidden band width of the semiconductor material. |
