Analysis of temporal behavior of beams diffracted by volume gratings formed in photopolymers

The temporal behavior of beams diffracted by volume gratings in photopolyme r thin films are measured and analyzed by solution of the diffusion equatio n for the monomer concentration inside the thin films. Two contributors to the refractive-index change that forms the volume gratings are assumed: One is the phase grating formed by modulation of the monomer concentration, an d the other is the phase grating formed by modulation of the density of the polymeric materials. The phase grating that is due to monomer modulation i s responsible for the initial fast rise and decay of the diffracted signal, and the phase grating that is due to modulation of density of the polymeri c materials is responsible for the slowly rising and then steady signal. Th e temporal behavior of the diffracted beams is determined by the ratio of m agnitudes of the incident beam intensity and the diffusion coefficient. (C) 1999 Optical Society of America [S0140-3224(99)01510-6].