New method for the fabrication of stratified gratings and their applications

Anew method for the preparation of stratified light-sensitive film is developed, and the stratified gratings (SG's) are recorded in the film. The sensitive layers on both sides of a dichromated cellulose triacetate film are produced simultaneously through chemical reaction and not with the conventional coating technique. Compared with SG's in other materials made with coating techniques, double-layer SG's in the film have, to my knowledge, the highest experimental diffraction efficiency (~54%) in addition to their having a simple recording optical system. The diffraction efficiency and the periodic Bragg selectivity of the SH in the film is given. Based on the SG's of the film, several beam splitters with 2, 3, 4, or 7 fan-outs and higher than 80% total diffraction efficiencies are realized experimentally. The advantages of this method as compared with others, such as the method based on volume holographic beam splitters, are explained.