Patent ID: 9696476
Date: 2017-07-04
CPC Classifications: G02B,G03H

Claim:
1. A method of fabricating a complex diffractive optical element, comprising: providing only one single volume of a permanently-recordable photosensitive material; and permanently recording at least two different volume Bragg gratings having different periods, each of which is produced by the interference of two beams in the only one single volume of the permanently-recordable photosensitive material, wherein the two volume Bragg gratings occupy the same cross sectional volume of the permanently-recordable photosensitive material perpendicular to the surface normal of the only one single volume of the permanently-recordable photosensitive material resulting in additional spatial modulation of a permanent refractive index modulation profile characterized by a larger period determined by a difference between the periods of the at least two volume Bragg gratings to obtain a permanent volume Moiré Bragg grating occupying the whole cross sectional volume of the permanently-recordable photosensitive material and having a Moiré period determined by a difference between the two different volume Bragg grating periods.