Dynamics of peristrophic multiplexing in holographic polymer-dispersed liquid crystal

• Published in: Liquid crystals 2014-05, Vol.41 (5), p.673-684
• Main Authors: He, Zhenghong, Chen, Chao Ping, Gao, Hongyue, Shi, Qiang, Liu, Shui, Li, Xiao, Xiong, Yuan, Lu, Jiangang, He, Gufeng, Su, Yikai
• Format: Article
• Language: English
• Subjects: diffraction efficiency; Diffusion; diffusion equations; Dynamics; Holograms; holographic gratings; Holography; Liquid crystal polymers; Liquid crystals; Mathematical models; Molecules; Multiplexing; PDLC; peristrophic multiplexing; Polymerization; Reaction kinetics; Recording
• ISSN: 0267-8292; 1366-5855
• DOI: 10.1080/02678292.2013.875226

In this article, we derive a two-dimensional nonlocal diffusion model utilising finite difference time domain method, which describes the dynamics of how multiple holographic gratings are formed in a polymer-dispersed liquid crystal film for peristrophic multiplexing storage. This model takes into account the diffusion processes of both the free monomer and the liquid crystal molecules, and the polymerisation kinetics in the overlapped regions of multiple holographic gratings. We have experimentally found out that there exists a bounce in the diffraction efficiency for multiplexed gratings at relatively low-exposure intensities, which is undesirable for recording the equal-strength holograms. Instead, the equal-strength holograms can be stored under relatively high-exposure intensities. To predict the occurrence of bounce, the temporal evolutions of the refractive index modulation are estimated and then verified by the experimental results. The appropriate holographic exposure intensity for recording the equal-strength hologram is suggested.