Dependence of the molecular reorientation on the direction of incident light in azo-dye doped liquid crystals

This paper investigates an optical reorientation process of azo-dye doped liquid crystals and explains the dependence of the enhancement factor on the incident light direction. Because the order parameters of the guest-host liquid crystal system depend on the direction of the incident light, the intermolecular orientation interaction potentials is also related with the incident light direction. To describe the interaction between the cis-isomer and the liquid crystalline molecules, we re-wrote Maier-Saupe potential expression by means of the order parameters of the doped liquid crystal system. Beginning with a two-level coupling equation, we investigated a microscopic formula and an angular dependence of the enhancement factor with the liquid crystal E63 doped with the R4 azo-dye, and obtained the relation of the enhancement factor with the rotational diffusion constants and the host order parameter. The comparison of our computational results with the existent experimental results verified our enhancement factor's microscopic form.