Three-dimensional switchable polymer photonic crystals via various optical wave interference techniques

A theoretical study has been undertaken to elucidate the three-dimensional pattern formation during holographic polymer-dispersed liquid crystal fabrication employing various optical wave interference techniques. Initially miscible mixtures of nematic liquid crystal and reactive multifunctional monomer with a photosensitive initiator were exposed to geometrically arranged interfering beams of light, producing a spatially dependent intensity distribution within the sample. To mimic the spatio-temporal evolution of periodic photonic structures in three dimensions, the time-dependent Ginzburg-Landau Model C equations, coupled with spatially variant reaction rate equations, have been solved numerically incorporating the local free energy densities pertaining to isotropic mixing, nematic ordering, and network elasticity. The simulated results reveal some key observations during the formation of electrically switchable photonic crystals with few defects. It appears that the network elasticity term exerts profound effects on resultant structures, indicating that photonic crystals with fewer point defects may be fabricated in shorter times. The simulated results are in good qualitative agreement with reported experimental observations in respect of emerged patterns, length and time scales.