Patent ID: 6709790
Filing Date: 2004-03-23
Classification: G02B,G03F

Abstract:
A method of forming periodic structures in a photosensitive material on a substrate, comprising the steps of:forming a beat pattern by simultaneously superimposing first and second pairs of plane waves of light of the same monochromatic wavelength on a surface of said photo-sensitive material so as to produce an interference pattern thereon, wherein the first plane wave of light of said first pair is incident on said surface at a first angle of incidence &thgr; subtending from the normal of the surface, wherein the second plane wave of light of said first pair is incident on said surface at a second angle of incidence âˆ’&thgr; subtending from the normal of the surface, wherein a first plane wave of light of said second pair is incident on said surface at a third angle of incidence &phgr; subtending from the normal of the surface, and wherein a second plane wave of light of said second pair is incident on said surface at a fourth angle of incidence âˆ’&phgr; subtending from the normal of the surface; and developing the photo-sensitive material, wherein the beat pattern includes fine interference structure having a varying intensity defining coarse interference structure that defines a desired optical periodic structure, and wherein the substrate is dithered perpendicular to the interference pattern during said exposure step to wash out the fine interference structure while preserving the coarse interference structure.