PHOTODETECTING STRUCTURE OF WAVEGUIDE TYPE OPTICAL DEVICE

摘要

PURPOSE:To provide a photodetecting structure of a waveguide type optical device which is excellent in productivity is small in size and permits high-efficiency coupling. CONSTITUTION:The surface of a substrate 1 formed with an optical waveguide 2 is partly provided with a difference in level and a photodetector 3 with its photodetecting surface 3a faced upward is packaged at this difference in level part 7. The light emitted from the end face of the optical waveguide existing near the difference in level is reflected and coupled to the photodetector 3 by a cover which is put on the substrate 1 and has a reflection mirror 5. An additional improvement in packaging density is also possible by previously providing the substrate 1 with a through-hole and packaging the photodetector with its photodetecting surface faced toward this through-hole into the through-hole, thereby packaging the photodetector on the rear surface. The reflection mirror 5 is easily formable by forming the cover of a silicon substrate 4 and subjecting this substrate to anisotropic chemical etching. Loss is lowered by forming the cover of a molded resin and forming the reflection mirror 5 to a recessed surface shape. The coupling is improved by coating the surface of the reflection mirror with gold.