| 摘要 |
<p>Diffraction element and an optical head device each showing little change of diffraction light quantity in response to a change of wavelength to be used, which enables stable signal detection even in a case of recording or reproducing an information from an optical disk, are provided. The diffraction element has a construction that, either one material between a concavo-convex material 102 forming concavo-convex portions of grating and a filling material 103, is made of a material having the absorption edge of light in a wavelength region shorter than the wavelength to be used, and either one of the materials is a material having lower refractive index than the material of the other material between the concavo-convex material 102 and the filling material 103 in entire region of wavelength to be used. The element is provided in the optical path between a light source and an objective lens of the optical head device.</p> |
