Molecular Orientation Analysis of a Design Concept for Optical Properties of Liquid Crystal Microlenses

Abstract

The relationship between a liquid crystal (LC) molecular orientation state and the focusing properties of LC microlenses prepared using a pair of hole-patterned electrodes are studied. In particular, in order to obtain a large optical effect, molecular orientation and retardation distributions in the LC microlenses with a thick LC layer are investigated by experiments and simulations using the finite difference method (FDM). It is found that the LC microlens functions not only as a converging lens at a low applied voltage but also as a diverging lens at a high applied voltage. The focal length of the LC microlens with D/t of 1/1 is shorter than that with 1/2, where D is the pattern diameter and t is the LC thickness. Dependences of the converging and diverging properties on the D/t values are successfully explained by the FDM simulations of the LC molecular orientation. In the case of large D/t values, the middle region of LC layers mainly contributes to the effective refractive index distribution of the LC microlens. On the other hand, the contribution of both surface regions is dominant when D/t becomes small. It seems that the LC molecular orientation outside the circular-pattern affects effectively to that inside the region with decreasing D/t values.