DIFFRACTION DEVICE FOR TWO WAVELENGTHS AND OPTICAL HEAD DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a high-performance optical head device which can stably detect signals by using two-wavelengths semiconductor laser. SOLUTION: Two-wavelengths diffraction device is produced by integrating a diffraction grating 11B which transmits incident light at wavelength λ1 and diffracts incident light at wavelength λ2 and a phase plate 11C which changes the polarization state of the transmitted light of at least one wavelength of the two wavelengths λ1, λ2, and the obtained device is mounted on an optical head device.