| 摘要 |
PURPOSE:To eliminate the dependency to the polarizing condition of the incident light by inclining the alight axis of the crystal substrate in the vertical direction on the surface of the crystal substrate and making the refraction factor equal to the propagating light of the basic mode of the optical waveguide larger than the refraction factor to the normal light and the abnormal light of the substrate. CONSTITUTION:Since the spatial coupling between optical two waveguides by a light directional coupling device occurs independently from the coupling between both TM and TE modes, in case of the hybrid mode, instead of the polarizing condition at the time of incidence, the linkage between optical waveguide occurs while both TM and TE modes are always mixed. When such a hybrid mode is propagated and the equal refractive index of the optical waveguide is not larger than the refractive index to any polarization to propagate in a substrate 11, the propagating light is coupled to the coupling mode, the loss comes to be larger, and therefore, to prevent the increase of the loss due to the coupling to the coupling mode, the equal refractive index of the optical waveguide is larger than the refractive index to the normal light and the abnormal light of the substrate factor. Thus, the dependency to the polarizing condition of the incident light is eliminated. |
