Laser-induced reorientation effect and ripple structure in dye-doped liquid crystal films

This article describes light-induced reorientation effects on a homeotropical dye-doped liquid crystal (DDLC) cell. The photo-excited azo dye, methyl red (MR), diffuses and adsorbs onto the substrate, thus forming a ripple structure. The adsorbed dye and laser-induced ripple structure then reorient the liquid crystal molecules and induce a holographic grating. Initially, the LC directors are reoriented primarily by the adsorbed dye. However, given sufficiently large ripple groove amplitude, the torque imposed by the ripple grooves overcomes that owing to the adsorbed dyes, and the LCs are realigned along the groove direction.