Diffractive optical element and optical head using the same

摘要

A diffractive optical element emits substantially zero order diffracted light when light with a wavelength of 0.35 mum to 0.45 mum is incident and emits substantially first-order diffracted light when light with a wavelength of 0.6 mum to 0.7 mum is incident. The diffractive optical element includes a substrate and a grating portion formed on the substrate. The grating portion has a step-wise cross section with any one of levels selected from four levels, five levels and six levels. The diffractive optical element emits substantially zero-order diffracted light when light with a first wavelength lambda 1 satisfying the relationship: 0.35 mum<=lambda 1 <=0.45 mum is incident and emits substantially first-order diffracted light when light with a second wavelength lambda 2 satisfying the relationship: 0.6 mum<=lambda 2 <=0.7 mum is incident.