Investigation on mechanism of multiple holographic recordings in photopolymers

In this paper, it is experimentally verified that the refractive-index modulation of the existing gratings continues to increase with uniform exposure or when a current grating is being recorded. And it is reasonable to assume that the effect of a sequential recording on an existing grating can be equivalent to the uniform exposure. Our simplified model for grating formation in photopolymers is extended to describe the effects of uniform post-exposure on an existing hologram, and further to deduce a new model of holographic multiplexing in detail for calculating the exposure schedule for multiplexed gratings with uniform diffraction efficiency. Twenty gratings were multiplexed using the exposure schedule calculated with the uniform post-exposure model.