| 摘要 |
PURPOSE:To decrease the loss even when the branch angle is comparatively large by providing the part with the refractive index higher than the circumference near the Y branched part formed at the substrate. CONSTITUTION:On a substrate 9, the first optical waveguide 1 and the second and third waveguides 2 and 3 respectively branched in the Y character shape from the terminal of the optical waveguide 1. At both sides of the Y branching part, a dielectric loading layer 4 is formed, and at the substrate part in the lower direction of the loading layer 4, the high refractive index part is formed. For such a reason, when the light to propagate the optical waveguide 1 arrives at the Y branched part, the spot size of the waveguide light is widened and the field distribution is also widened. Thus, the overlapping with the field distribution in optical waveguides 2 and 3 is enlarged, and many waveguide beams of light are linked with the optical waveguides 2 and 3 and propagated by the low loss. Thus, the branch angle is comparatively large, and even then, the loss can be minimized. |
