| 摘要 |
PURPOSE:To enable the use of a grating having a long period and to increase the output in a photodetector by specifying the oscillation wavelength of a semiconductor laser and the constituting material of the photodetector to emit the light to the side of a transparent substrate. CONSTITUTION:A photo diode 12 consisting of an amorphous thin film essentially consisting of Si is provided on a waveguide 11 consisting of a glass on a quartz substrate 10. The light whose oscillation wavelength is <=700nm from a semiconductor laser 15 is made incident on the end face of a waveguide 11 and is emitted to the side of the substrate 10 through a grating beam splitter 13 and a condensing grating coupler 14 and is condensed at a point 18. A reflected light 26 from a recording medium at the point 18 is returned to the waveguide 11 and is divided into two by the splitter 13 and is led to the diode 12 to detect the signal on the medium. The diode 12 may be formed on the substrate 10 and the waveguide 11 may be provided so as to cover the diode 12, or the diode may be formed on the face opposite to the waveguide face of the substrate. |
