Theoretical and experimental investigations of photo-sensitivity and polarization-sensitivity in TI/PMMA polymers

Abstract A new kind of cationic initiator IRGACURE 784 (TI, BASF) was dispersed into PMMA matrix to fabricate TI/PMMA polymer, which exhibited excellent absorptive and polarization sensitivities under 532 nm wavelength laser beam exposure. Theoretical investigations on the grating formation mechanisms under two different time scales of exposure were performed (short time duration: millisecond level, long time duration: second level). We introduced an analogical four-energy-level rate equation on analyzing the photo-induced process of TI molecules. Furthermore, an absorptive diffusion polymerization (ADP) model resulting from the combination of the non-local diffusion model and the analogical four-energy-level model was proposed to describe the grating formation in TI/PMMA polymers with different conditions (sample thickness and exposure duration level). In addition, intensity (two p-polarized recording beams) and polarization holographic recording (two orthogonally polarized recording beams) approaches were applied to compare the grating enhancement process and multiplexed storage ability in TI/PMMA polymers. We achieved the maximum single grating strength with 0.86 and 0.63 in 3 mm thick sample, respectively. And, cumulative grating strength of 2.06 and 1.23 by angular multiplexing five gratings and polarized-angular multiplexing ten gratings in 3 mm thick sample, respectively. Our current work supplemented and summarized the comprehensive holographic performance in TI/PMMA polymer by investigating its photo-sensitivity and polarization-sensitivity.