Diffractive optical element and manufacturing method for the same

摘要

An Al film is formed so that film forming particles are incident at normal incidence to grating wall surfaces of a diffraction grating having multiple grating portions and are incident at oblique incidence to optical effective surfaces. After that, oxidation treatment is performed from a direction to be incident at normal incidence to the optical effective surface so that the Al layer on the optical effective surface is changed to Al2O3 layer. Hence, in the diffraction grating having the multiple grating portions, the Al2O3 layer is formed on the optical effective surface for transmitting light, and the Al layer is formed on the grating wall surfaces as a light shielding layer. Thus, flare of the diffractive optical element can be suppressed.

主权项

1. A manufacturing method for a diffractive optical element, the manufacturing method comprising:
forming multiple grating portions including grating optical effective surfaces for transmitting the incident light and grating wall surfaces for shielding the incident light continuously on a base substrate; forming an Al layer on the grating wall surfaces and the grating optical effective surfaces such that the density and film thickness of the Al layer formed on the grating wall surfaces are different from those of the Al layer formed on the grating optical effective surfaces; and performing oxidation treatment of the Al layer under a condition that an oxidation speed is faster in the Al layer formed on the grating optical effective surfaces than in the Al layer formed on the grating wall surfaces, thereby converting the Al layer formed on the grating optical effective surfaces into an Al2O3 layer, wherein the oxidation treatment is performed to form an Al layer on the grating wall surfaces to have a film density of 2.0 g/cm3 or more and 2.7 g/cm3 or less, and a film thickness of 50 nm or more and 1 μm or less, and to obtain the Al2O2 layer formed on the grating optical effective surfaces having a film density of 0.4 g/cm3 or more, and 1.0 g/cm3 or less, and a film thickness of 5 nm or more and 30 nm or less.