| 摘要 |
An optical head device having an optical element capable of transmitting without diffracting light having a wavelength emitted from a two-wavelength semiconductor laser and capable of diffracting light having another wavelength, to provide high utilization efficiency of light in a stable manner. <??>For this purpose, a wavelength-selective diffraction element 1A comprising a transparent substrate having a front surface on which a grating having a periodically recessed and projected shape in cross section is formed and a filling member 13A filled in the concavo-convex portion 12A of the grating wherein the concavo-convex portion of the grating is provided with an organic pigment having the absorption edge of light in a region having a shorter wavelength than the wavelength lambda 1, and the concavo-convex member and the filling member have the same refractive index with respect to either one of light having a wavelength lambda 1 and light having a wavelength lambda 2, and they have different refractive indices with respect to the other light having a wavelength, is disposed between the light source and the objective lens of the optical head device. <IMAGE> |
