| 摘要 |
PURPOSE:To make a beam splitter unnecessary and to prevent return light from being generated by improving the activity efficiency of light by providing a 1/4-wave plate in the optical path of emitted light from a light waveguide and reflected light from a substrate. CONSTITUTION:The title device is provided with a first light waveguide 2, a buffer layer 3 formed on the surface of the waveguide, and a second light waveguide 1 separated optically from the first light waveguide 2 by the buffer layer 3 and to propagate the emitted light from a light source 10. Also, it is provided with a first diffraction grating 4 to emit propagated light to the air and to converge the light on the surface of the substrate 11 on which information is recorded, a second diffraction grating 5 to waveguide the reflected light from the substrate 11 to the first light waveguide 2, and a detector 7 to detect the light which waveguides the first light waveguide 2. And the 1/4-wave plate 9 is provided in the optical path of the emitted light from the second light waveguide 1 and the reflected light from the substrate 11. In such a way, the angle of polarization is changed by the 1/4-wave plate 9 in a process where the emitted light from the second light waveguide 1 returns by the substrate 11, and it is coupled with only the first light waveguide 2, which improves the activity efficiency of the light and prevents the return light from being generated. |
