| 摘要 |
PURPOSE:To decrease the adverse influence of slab guided light at the time of signal introduction by forming recesses from which light guide layer parts are removed on both sides of a strip-shaped clad layer of an input port part. CONSTITUTION:A lower clad layer 13 and the light guide layer 15 are formed on a GaAs substrate 11 and the strip-shaped upper clad layer 17a is formed thereon. The layers from the light guide layer 15 to the substrate 11 are partly removed to form the recesses 31 in the prescribed regions on both sides of the clad layer 17a. Signal light enters not only the part of the clad layer 17a but also the part of the slab structure of the region II at the time of inputting the signal light from the optical fiber to the input port part of such waveguide layer and, therefore, the loss of the slab guided light increases and the slab guided light hardly propagates in the optical element 21. The adverse influence thereof is thus decreased. |
