WAVELENGTH SELECTIVE DIFFRACTION ELEMENT AND OPTICAL HEAD DEVICE

摘要

PROBLEM TO BE SOLVED: To obtain an optical element which does not diffract but transmits the light of one wavelength of the laser light emitted from a dual-wavelength semiconductor laser and which diffracts the light of the other wavelength and to obtain an optical head device with stable and high use efficiency of light by mounting the optical element. SOLUTION: The wavelength selective diffraction element is used for light with two different wavelengths and either one of a member 12A having recesses and projections constituting a periodical rugged part on a transparent substrate 11A and a filling member 13A constituting the filling part consists of material containing a red organic pigment while the other member consists of a material containing a transparent inorganic material. The refractive index of the member 12A and the refractive index of the member 13A are equal to each other for the light of one wavelength and are different from each other for the light of the other wavelength. The obtained diffraction element is disposed in the optical path connecting the light source of the optical head device and an optical recording medium.