| 摘要 |
An optical waveguide formed on a substrate has, in this order, a first waveguide part, a polarized wave rotation part, and a second waveguide part. A TE mode, for which the effective refractive index is highest for an intrinsic mode for waveguide light at a cross-section of the first waveguide part, has an effective refractive index higher than a TM mode. The TM mode at a cross-section of the second waveguide part has an effective refractive index that is higher than the TE mode for which the effective refractive index is highest. The height of the waveguide structure (for example, core) is the same for the first waveguide part and the second waveguide part. The waveguide structure of the polarized wave rotation part has: a thick plate part with a height identical to the waveguide structure of the first waveguide part and the second waveguide part, and a thin plate part for which the thickness is less than the thick plate part; and a cross-section that is asymmetrical in the direction of width and a part of which is asymmetrical in the direction of height. A waveguide structure with the same height is present continuously between the first waveguide part, the thick plate part of the polarized wave rotation part, and the second waveguide part. |
