| 摘要 |
PURPOSE:To decrease the stray light from a lighting source without adding a special optical element to a semiconductor laser device by providing a double coating layer to the boundary face of a prism arranged on the upper face of a photodetection section and the photodetection section formed on a semiconductor substrate. CONSTITUTION:A laser light 30a irradiated from a laser diode 21 is reflected in a translucent reflecting face 24a at the front face of the prism 24 and irradiat ed in an optical disk or the like as a laser light 30f. On the other hand, part of the laser light 30a irradiated from the laser diode 21 is transmitted through the translucent reflecting face 24a of the prism 24 and made incident as a stray light 30s in the prism and the incident angle is selected as nearly 66-68 deg.. In this case, since the 1st and 2nd coating layers 27, 28 are formed at the boundary between the semiconductor substrate 22 and the prism 24, the stray light 30s is reflected nearly totally by the 1st and 2nd coating layers 27, 28 so as to prevent the light from being irradiated in a photodetection section 23a. |
