Patent ID: 6586141
Filing Date: 2003-07-01
Classification: G03H

Abstract:
A method of forming diffractive optical elements, comprising the steps of:(a) making a photo-thermo-refractive (PTR) glass which shows a refractive index increment after exposure to optical radiation followed by thermal treatment, having a substantial low level of impurities of iron and heavy metals of less than approximately 5 ppm; (b) exposing the PTR glass to radiation in the spectral region of its photosensitivity of ultraviolet radiation ranging from approximately 280 to approximately 380 nm; and (c) thermal treating of the PTR glass in the temperature region ranging from approximately 480 to approximately 580Â° C. for a period of from a few minutes to several hours appropriate for phase transformation of exposed area to increase absolute diffraction efficiency of the PTR glass to at least 95% from steps (a), (b), (c), whereby holographic optical elements are formed.