| 摘要 |
PURPOSE:To make exact writing/reading out of information to and from an information recording medium by providing a reflected light attenuating means to a diffraction grating and attenuating the incident reflected light on a semiconductor laser light source so that the semiconductor laser light source is used at the substantially low state of a noise level regardless of the variance in the quantity of the return light. CONSTITUTION:The reflected light attenuating means 10 is provided to the diffraction grating. More specifically, the reflected light attenuating means 10 is formed by vapor depositing and coating of a thin film 10a for attenuation of the quantity of light on the laser diode side surface of the diffraction grating 2. The thin film 10a is formed by using a vapor deposited metallic film such as, for example, aluminum and vapor deposited dielectric film, etc. The substantial reduction of the quantity of the reflected light to be fed back to the semiconductor laser light source down to the level at which the noise level is made approximately the tolerance limits or below is thereby made possible and as a result, the S/N ratio of the laser light outputted from the semiconductor laser light source is improved. The writing of the information to the information recording medium such as optical disk and reading out of the information therefrom are thus exactly executed. |
