| 摘要 |
PURPOSE:To prevent the occurrence of noise caused by a return light at a reproduction time by making a Faraday rotation coefficient for the first wave length of a Faraday rotator smaller than that for the second wave length and making an absorption coefficient for the first wave length smaller than that for the second wave length. CONSTITUTION:A device incorporates a first semiconductor laser 11 used for recording information and a second semiconductor laser 12 used for reproducing the information and has the Faraday rotator consisting of a garnet film 5 and a magnet 6. The optical system of an optical head is common for emitted lights from the two semiconductor lasers. Then, the Faraday rotation coefficient for the first wave length of the Faraday rotator is made smaller than that for the second wave length and the absorption coefficient for the first wave length of the Faraday rotator is made smaller than that for the second wave length. Thus, the occurrence of the noise caused by the return light of the semiconductor laser can be prevented at the time of reproduction. |
