Method for producing a diffractive optical element that is controlled diffraction efficiency

摘要

PROBLEM TO BE SOLVED: To obtain a diffractive optical element having high diffraction efficiency by increasing both of the variation Δn in the refractive index and the length L in the incident direction of laser light.;SOLUTION: Pulse laser light 1 is condensed and made to irradiate an optical glass 1 by a condenser lens 2 with the focus controlled to the inside of the optical glass to form a region 3₁ with a varied refractive index as a first layer at and near the focus. Then the condenser lens 2 or the optical glass 1 is relatively moved along the incident direction of the pulse laser light 1 to change the focus position, and the pulse laser light 1 is again condensed and made to irradiate the glass to form and overlap a region 3₂ with a varied refractive index as a second layer on the region 3₁ with the varied refractive index of the first layer. The processes of moving the focus position and condensing the pulse laser light 1 to irradiate the glass are repeated to form a grating having multilayered regions 3_n having varied refractive indices.;COPYRIGHT: (C)2003,JPO