A high birefringence liquid crystal for lenses with large aperture

Abstract

This work presents the application of an experimental nematic liquid crystal (LC) mixture (1929) in a large aperture lens. The LC material is composed of terphenyl and biphenyl derivatives compounds with an isothiocyanate terminal group and fluorinated lateral substituents. The substitution with a strongly polar isothiocyanate group and an aromatic rigid core provides pi-electron coupling, providing high birefringence (Delta n = 0.3375 at 636 nm and 23 °C) and low viscosity (eta = 17.03 mPa s). In addition, it also shows high values of birefringence at near infrared (0.318 at 1550 nm). The synthesis process is simple when comparing materials with high melting temperatures. The excellent properties of this LC mixture are demonstrated in a large aperture LC-tunable lens based on a transmission electrode structure. Thanks to the particular characteristics of this mixture, the optical power is high. The high birefringence makes this LC of specific interest for lenses and optical phase modulators and devices, both in the visible and infrared regions.