| 摘要 |
PURPOSE:To improve light propagating efficiency and coupling efficiency by forming clad layers which vary in respective refractive indices in optical waveguide parts having different sectional areas to make the coincidence of the effective refractive indices of the waveguide mode and further, increasing the overlap of the electric field distributions of the optical waveguide parts on each other. CONSTITUTION:The optical waveguide 1 is formed on the main surface side of a ferroelectric substance substrate 3 consisting of, for example, LiNbxTa1-xO3 (0<=x<=0). The light incident side of this optical waveguide 1 is constituted of the first optical waveguide part 1A and the rear end side thereof is constituted of the second optical waveguide part 1B. The first optical waveguide part 1A is formed to such a shape which is gently tapered or curved and is continued without a level difference with the second optical waveguide part 1B in order to efficiently couple light to the optical waveguide 1. The clad layers deposited and formed on the surface of the optical waveguide 1 have the refractive indices varying with the first clad layer 2A for the first optical waveguide part 1A and the second clad layer 2B for the second optical waveguide part 1B. |
