Cationic photo-initiator titanocene dispersed PMMA photopolymers for holographic memories

Abstract

Bulk polymer composites have been investigated in a two-beam interference exposure system of titanocene (Irgacure 784, BASF) (TI) molecules dispersed in poly(methyl methacrylate) (PMMA) substrates, which are created through an optimized three-step thermo-polymerization method, at a wavelength of 532 nm. As a property of PMMA photopolymers, the dark enhancement of grating formation is observed, which mainly corresponds to the diffusion of TI molecules. We also examine the influences of dark enhancement on Bragg angular selectivity that shifts after a long-time dark reaction. Single grating under continuous exposure was recorded in TI/PMMA photopolymers with a diffraction efficiency of 74% and response time of 20 s. An enhanced multiplexed grating was also obtained after a completely dark reaction with the cumulative grating strength of 6.88. Compared to bulk PQ/PMMA photopolymers in millimeter magnitude, TI/PMMA photopolymers are more competitive for further research on volume holographic memory storage.