Investigations of photosensitizers in an AA/PVA-based photopolymer material

Abstract

ABSTRACT Several studies of the time varying photon absorption effects, which occur during the photo-initiation process in photopolymer materials, have been presented. Three primary mechanisms have been identified: (i) the dye absorption, (ii) recovery, and (iii) bleaching. Based on an analysis of these mechanisms, the production of primary radicals can be physically described and modelled. In free radical photo-polymerization systems, the excited dye molecules induce the production of the primary radicals, R • , which is a key factor in determining how much monomer is polymerized. This, in turn, is closely related to the refractive index modulation formed during holographic recording. In this article, we overcome the complexicy of estimating the rate constant of intersystem crossing, k st , in going from the excited singlet state dye to the excited triplet state dye, by introducing k aS and k aT into the model, which are the rate constant of photon absorption from ground stat e to singlet state and triplet state respectively. Keywords: Photosensitizer, Absorptio n, Recovery and Bleaching