Study of PQ/PMMA photopolymer. Part 1: theoretical modeling

Phenanthrenequinone (PQ) doped poly(methyl methacrylate) (PMMA) photopolymer material has received much attention in the literature. However, further development requires that a more physical material model be developed. In this article, such a model is presented. The model includes: (1) the time-varying photon absorption, including the absorptivity of a second absorber, i.e., the singlet excited state of PQ; (2) the recovery/regeneration and the bleaching of the excited-state PQ; (3) the nonlocal effect; and (4) the diffusion effects of both the ground- and excited-state PQ molecules and of the methyl methacrylate (MMA). A set of rate equations are derived, governing the temporal and spatial variations of each chemical component concentration. Compared to previous models presented in the literature in this paper: (1) the second absorber is included; (2) the diffusion of all the PQ states is considered; and (3) the first-harmonic refractive index modulation is calculated in a more physically reasonable way. Simulations of the normalized transmission are presented. The effects of the nonlocal material response and the diffusion of both ground-state and excited-state PQ molecules are also examined. The model is applied to analyze experimental results in Part 2 of this paper.