| 摘要 |
PURPOSE:To minimize the distance between a laser chip and a reflecting mirror such as a disk and to miniaturize an optical system by using a grating coupler as an optical demultiplexing means. CONSTITUTION:A grating coupler 13 to have a waveguide 14, transmit a part out of an incident light and couple others to the waveguide 14 is provided, the light emitted from a semiconductor laser 1 and a reflecting light reflected by a disk or a mirror 12 are respectively independently coupled to the waveguide 14 and the light coupled at the waveguide 14 is photodetected by photodetectors 5 and 6. Output of two coupled light beams, the reflecting light from the disk is photodetected by the photodetecor 6, the signal on the disk is reproduced and on the other hand, the noise can be measured with the signal from the photodetectors 5 and 6 to respectively photodetect two light beams. Thus, the miniaturization can be performed. |
