| 摘要 |
PURPOSE: To lower coupling loss by adopting constitution capable of sufficiently expanding the expansion rate of a mode size. CONSTITUTION: The top and bottom of a waveguide layer 3 is held by an upper clad layer 4 and a lower clad layer 2 and a substrate 1 is disposed in the lower part of the lower clad layer 2. The layer thickness of the waveguide layer 3 and the upper clad layer 4 is made thinner toward the exit end in a tapered part 8 and the waveguide layer 3 of the optical fiber coupling part 7 is formed as a mesa type. The mesa width of the waveguide layer 3 in the tapered part 8 is made larger toward the exit end. The refractive indices of the upper clad layer 4 and the lower clad layer 2 are made lower than the refractive index of the waveguide layer 3 and the refractive index of the substrate 1 is made lower than the refractive index of the lower clad layer 2. |
