Alignment structures and diffraction properties of chiral nematic liquid crystal cells with periodically patterned photoalignment films

Abstract

Liquid crystal (LC) cells with periodic alignment distributions were fabricated using chiral nematic LCs (N*LCs), which were prepared using mixtures of a nematic LC and a chiral dopant, along with photoreactive liquid crystalline polymer (PLCP) films. Periodic structures were formed by polarization holographic recording in the PLCP films. The director distribution in each cell depended on the ratio of chiral dopant present, i.e., the inherent helical pitch of the N*LCs. These periodic alignment structures with line defects in the LC grating cells were well explained on the basis of the elastic continuum theory of the N*LCs and the photoalignment effect of the PLCP films. The diffraction properties of the grating LC cells were also investigated using a polarized visible laser. The observed intensity and polarization states of the diffracted beams were consistent with theoretical ones calculated using the director distribution models. Our results clarify that the diffraction properties of the grating LC cells can be controlled by the helical pitch of the N*LCs.