| 摘要 |
PURPOSE:To lessen the influence of absorption of light arising from a fluctuation in a refractive index by providing an electrode for optical modulation in a part exclusive of the part right on an optical waveguide and modulating the refractive index in the peripheral part of the waveguide by using this electrode. CONSTITUTION:A function as a core part is obtainable in a mixed crystallizing region 4a and a function as a clad is obtainable in a non-mixed crystallizing region 4b. The refractive index of the mixed crystallizing region 4a is high to TM mode light and conversely, the refractive index thereof is low to TE mode light. The need for processing the waveguide for the purpose of confining the light in the waveguide is, therefore, eliminated. Since an electric field is not impressed to the mixed crystallizing region 4a having the highest light power density within the optical waveguide, a change in the light intensity arising from Kramers-Kronig relations is suppressed to a lower level. Further, the degree of coupling of the optical directional coupler itself can be changed and, therefore, there is no need for matching the coupling length of the directional coupler with the perfect coupling length thereof and the production is facilitated. |
