Real-time Study of the Evolution of Anisotropic Phase Separation in H-PDLC's

摘要

We have investigated the dynamics of formation of a reflection hologram in a photosensitive formulation containing pre-polymer and liquid crystal. Kogelnik's two beam coupling theory of an isotropic material has previously been expanded to account for variations of refractive index Δn in the x, y, and z directions. This theory predicts a non-zero p-polarizcd coupling coefficient, κ_p at 45° internal angle, only when a macroscopic anisotropy in the grating is present. A broadband source was used as a probe to monitor the diffraction efficiencies (DE) during exposure for both s- and p-polarized light. The onset of a macroscopic ordering of the liquid crystal is observed at the same time as the onset of scattering. We report here the effects of laser writing power on the temporal evolution of s- and p-polarized diffraction efficiency and p-polarized scattered intensity.