| 摘要 |
PURPOSE:To prevent coupling efficiency from being drastically changed by the dimensional error of a diffraction grating and to facilitate the formation of the optical waveguide element for coupling external light and guided light by the diffraction grating formed in an optical waveguide by maintaining the coupling efficiency of the guided light and the external light sufficiently high. CONSTITUTION:The optical waveguide 11, the diffraction grating 13 and a clad layer 15 mounted thereon are so constituted that 1st order diffracted light 21 is diffracted only to the substrate 10 side and the higher order diffracted light having the larger absolute value of the order than the absolute value of the order thereof is diffracted to the substrate 10 side and the clad layer 15 side and that at least one of the higher order diffracted light 22a (23a) diffracted to the clad layer 15 side and reflected by the boundary 15a of the clad layer 15 on the side opposite from the optical waveguide 11 and the higher order diffracted light 22b (23b) emitted to the substrate 10 side of the same order weaken each other. |
