Diffraction grating for plural wavelengths, optical pickup apparatus and optical disk apparatus using diffraction grating for plural wavelengths

摘要

A diffraction grating for plural wavelengths includes first grating regions which have periodic protrusions and depressions in sectional shape and are long formed in a depth direction perpendicular to a repeat direction of the protrusions and depressions, and second grating regions which have a configuration similar to that of the first grating regions and have depressions set to depths different from groove depths of the depressions of the first grating regions. The first and the second grating regions are alternately placed, and groove depths of each the depressions of both the grating regions are set so that the first grating regions transmit incident light of a first wavelength and also diffract incident light of a second wavelength different from the first wavelength and the second grating regions transmit incident light of the second wavelength and also diffract incident light of the first wavelength.