| 摘要 |
PURPOSE:To stabilize laser oscillation to prevent generation of noise, by coating the half of the refractive index distribution type lens end face with a photodetector and by preventing the reflection light from an information recording carrier from being returned to the active layer of the semiconductor laser. CONSTITUTION:The light incident to the lower half of the end face of refractive index distribution type lens 7 is shielded by photodetector 6, and only the light incident to the upper half is propagated through refractive index distribution type lens 7 and receives condensing action and is condensed onto information recording carrier 5. The reflection light having intensity change corresponding to recording information is propagated again through the lower half of refractive index distribution type lens 7 and is incident to photodetector 6 installed in the lower half of end face (a) of lens 7 and is converted to an electric signal, thus detecting the signal of recording information. Thus, since the reflection light is not injected to semiconductor laser active layer 2, laser oscillation can be prevented from being unstable, and the optical system can be simple. |
