Polymer-dispersed liquid crystals forming tunable microlens

Abstract

At present, liquid crystals – polymer (LC-P) composites such as polymer-dispersed liquid crystals (PDLC), polymer stabilized liquid crystals (PSLC) and polymer networks in liquid crystals (PNLC) are widely used as operating elements of optical devices such as microlens and elements, whose principle of operation is based on light scattering. LC-P composites light refraction features depend on shape and size of liquid crystal (LC) drops as well as on director orientation inside of drops. LC anisotropy influences polarization characteristics of refracted radiation. We have investigated desined as the tunable microlens on LC-P with different components concentration ratio. We have used LC E7 by Merck, dispersed in the polymer NOA 65 by Norland Inc. as the object of research. They have close refractive indeces which provide the posibility to shange the focal length of such LC lens in wide range. We change focal length by change of applied voltage and by rotation of polarization plane of illuminating beam. Partial beams passed through LC droplets and polymer matrix may be considered as plane waves passing different optical pathes and interfering in the far zone. Changing the voltage results in changing the LC effective refractive index leading to a change of the path difference between the interfering beams. The effect of interference decreases of some spectral components of the radiation passing through LC-P sample can be used as a tunable chromatic lens.