| 摘要 |
PURPOSE:To prevent the characteristic of the fitted switch from depending on a polarized light state of incident light by providing an optical waveguide for constituting a directional coupler by allowing the light transmission of the directional coupler to be equal to the C axis of a crystalline plate, diffusing an impurity onto the whole surface of a substrate,, and thereafter, performing ion exchange to other part than the part which is used as a channel, from the surface of the substrate. CONSTITUTION:As for this waveguide, its equivalent refractive index is almost equal to both waves of a light wave mode, therefore, the complete coupling length when a directional coupler is constituted is equal to both waves. Accordingly, when length of the directional coupler is set in advance so as to be equal to this complete coupling length, in a state that no voltage is applied between electrodes 4 and 5, the incident light 6 is all coupled with a waveguide of 2 and emitted. Also, as for an electro-optical constant related to a fact the generating a variation of the refractive index by applying electric field, it is equal as r22 in both waves, therefore, a method for a variation of the coupling luminous intensity in accordance to voltage application is equal and by an equal voltage, a switch state of light, namely, TE and TM are all emitted from a waveguide 3. In such a way, a switch whose characteristic does not depend on the polarized light state of incident light. |
