| 摘要 |
PURPOSE:To reduce light scattering and to improve branch ratio setting accu racy by providing a mode conversion part between an input waveguide and a branch waveguide. CONSTITUTION:The mode conversion part 2 is provided between the input waveguide 1 and an output waveguide 3. The mode conversion part 2 has additional patterns 4-1 and 4-2 formed of a material having a refractive index nearly equal to that of the waveguide 1 on the waveguide, but the parts where the patterns are present increase in refractive index equivalently and light is converged. The mode pattern, therefore, becomes a right-left symmetrical bimodal type like a light intensity distribution (b). Further, the light intensity distribution (c) of the branch waveguide has a maximum point in the center of each waveguide and conforms with the bimodal type distribution (b), and light is distributed efficiently, thereby reducing the scattering loss. Further, the light intensity at a branch point decreases, so the accuracy of branch ratio setting is improved. |
