Refractive index and orientation profiles of holographic gratings written in liquid crystalline monomers

Refractive index and orientation profiles for electrically switched holographic gratings, written by photopolymerization of nematic liquid crystalline monomers, have been obtained through computer simulation of experimental diffraction patterns. Simulation of diffraction from the 6 μm, optically thin films produced smooth, nonsinusoidal refractive index profiles. These profiles are consistent with a recording/switching mechanism based upon selective electric field reorientation of the liquid crystal director in the monomeric regions. Quantitative agreement with the model was found, based upon macroscopic birefringence data. Profiles for higher frequency and overexposed gratings provide further insight into the nature of the monomer/ polymer boundaries. Orientation profiles were calculated from the refractive index profiles.