REFRACTIVE-INDEX AND ORIENTATION PROFILES OF HOLOGRAPHIC GRATINGS WRITTEN IN LIQUID-CRYSTALLINE MONOMERS

Refractive index and orientation profiles for electrically switched ho lographic gratings, written by photopolymerization of nematic liquid c rystalline monomers, have been obtained through computer simulation of experimental diffraction patterns. Simulation of diffraction from the 6 mu m, optically thin films produced smooth, nonsinusoidal refractiv e index profiles. These profiles are consistent with a recording/switc hing mechanism based upon selective electric field reorientation of th e liquid crystal director in the monomeric regions. Quantitative agree ment with the model was found, based upon macroscopic birefringence da ta. Profiles for higher frequency and overexposed gratings provide fur ther insight into the nature of the monomer/polymer boundaries. Orient ation profiles were calculated from the refractive index profiles.