| 摘要 |
PURPOSE: To make it possible to obtain total internal reflection at a semiconductor/air boundary with respect to a large incident angle by forming the diffraction elements of a diffraction grating of the reflection surfaces composed of the wells formed in a flat waveguide. CONSTITUTION: The single mode flat waveguide is formed of a layer 20 joined by a member having a low refractive index. The perpendicular flanks 24 to 26 of the respective wells 23 determine triangular bases in the wells which are isosceles. The flank wells 24 constitute the refractive index surfaces of the diffraction grating. These wells are arranged perpendicularly to the rectilinear range of the gratings and are arranged at ordinary intervals (d) which are grating periods. The isosceles triangles determined at the bases of the respective wells 23 by the flank walls have a height d/2 in order to impart the incident angleϕto the grating planes 24 for parallel beams of the light to shield the entire beam without the projection with any of the faces 24 by any of the adjacent faces. As a result, the total internal reflection is sufficiently obtd. |
