| 摘要 |
PURPOSE:To improve an S/N even when reading stored information from a recording carrier with a low light emitting output by providing plural laser chips, each different in reflectance on a laser emitting surface, and a hologram diffraction grating. CONSTITUTION:A laser beam, which is emitted from a semiconductor laser chip 11 for write at a high output, is made incident to a hologram diffraction grating 13. The 0th order beam transmitted through a hologram 13a is made incident to a recording carrier 17 and data are written into the carrier 17. Next, the laser beam emitted from a semiconductor laser chip 12 for read at a low output is made incident to the carrier 17. The 1st beam diffracted by the hologram 13a is made incident to the carrier 17. In the case of such operation, since the reflectance on the laser emitting surface of the chip 12 is made higher than the reflectance on the laser emitting surface of the chip 11, the returned beam to be reflected by the carrier 17 and to arrive at the chip 12 scarcely go into the internal part of the laser chip. Therefore, even when the light emitting output of the chip 12 is low, the data can be read out with high S/N. |
