Comparison of the higher diffraction order images in methyl-red-doped liquid crystal films

We investigate the change of higher diffraction order images in holographic image storage and reconstruction process. In experiments, an s-polarized Ar⁺ laser (488.0 nm) was used to record permanent grating in the dye-doped liquid crystal, 4,4′-n-entylcyanobiphenyl (5CB) doped with 1 wt% methyl-red (MR), at a small incident angle. Higher diffraction order images were observed when the signal beam was focused in front of and behind the film. Then the film was illuminated by an s-polarized He-Ne laser (632.8 nm) in the direction perpendicular to the surface. The higher diffraction order images were reconstructed. A theory about the change of higher diffraction order images is developed, which is in good agreement with experimental results. The results show that the higher diffraction order provides a useful method for optical information processing.