Phenomenological model of anisotropic volume hologram formation in liquid-crystal-photopolymer mixtures

Abstract

The real time formation of anisotropic volume holographic reflection gratings in a liquid-crystal/photopolymer mixture is studied. We develop a phenomenological model of grating formation that incorporates the photophysics and photochemistry of the initiator dye, reaction-diffusion kinetics of the monomer-polymer system, phase separation of the liquid crystal, nematic order evolution of liquid-crystal droplets, and volume shrinkage of the polymer. We then test this model by experimentally monitoring the diffraction efficiency for s and p polarization, Bragg wavelength, and laser scattering in real time as the grating is formed. The model yields good agreement with experimental data for different recording intensities and exposure times. We discuss the physics of the system as it evolves in time and explain the major features of anisotropic grating formation in acrylate-based holographic polymer-dispersed liquid crystals.