Diffraction Limited Liquid Crystal Microlenses with Planar Alignment

Liquid crystal microlenses with diffraction limited performance are presented. The micro-lenses consist of a liquid crystal film sandwiched between a pair of conductive substrates where one has hole patterned electrode. The lens diameters are 120 µm and 110 µm and diameter to thickness ratio of the lenses is approximately 2.4. The optical quality was investigated with a Mach-Zehnder interferometer. The behavior of the deformation of the liquid crystal in the inhomogeneous electric field is explained by using three dimensional director field simulations. It is shown that both, the twist and tilt deformations remarkably influence the optical quality. However, over large areas of the lens the waveguide condition is fulfilled and determines the optical properties. The pretilt angle of the liquid crystal is responsible for a tilt of the optical axis of the lens and diffraction-limited off-axis adaptive lens behavior is found.