Field-induced refractive index variation in the dark conglomerate phase for polarization-independent switchable liquid crystal lenses

Abstract

Liquid crystal lenses are an emerging technology that can provide variable focal power in response to applied voltage. Many designs for liquid-crystal-based lenses are polarization dependent, so that 50% of light is not focused as required, making polarization-independent technologies very attractive. Recently, the dark conglomerate (DC) phase, which is an optically isotropic liquid crystalline state, has been shown to exhibit a large change in refractive index in response to an applied electric field (Δn=0.04). This paper describes computational modeling of the electrostatic solutions for two different types of 100 μm diameter liquid crystal lenses, which include the DC phase, demonstrating that it shows great potential for efficient isotropic optical switching in lenses. A feature of the field dependence of the refractive index change in the DC phase is that it is approximately linear in a certain range, leading to the prediction of excellent optical quality for driving fields in this regime. Interestingly, a simulated microlens is shown to exhibit two modes of operation: a positive lens based upon a uniform bulk change in refractive index at high voltages, and a negative lens resulting from the induction of a gradient index effect at intermediate voltages.

Liquid Crystal Devices for Beam Steering Applications

“…A potential solution for this is to utilize more novel optically isotropic LC phases which change their optical properties when an electric field is applied (for example, due to the Pockels or Kerr effect). Such phases include blue phases [185][186][187], the Dark Conglomerate (DC) phase [188][189][190] and polymer nano-dispersed liquid crystals (PDLCs) [191,192]. However, these phases also tend to have disadvantages compared to NLCs, including the degradation of materials, elevated transition temperatures, narrow phase temperature ranges and more limited knowledge of the phases generally.…”

“…In a recent paper by Tian et al [199], a blue phase device with dielectric inclusion was proposed and modelled, where continuous deflection from 0 • to 1.7 • of both polarisations was predicted. Similarly, a geometric lens made from the DC phase was predicted to continuously vary focus from 12 mm to ∞ in a polarisation independent manner [188].…”

The fiftieth anniversary of the liquid crystal display

“…Perhaps, postulated Bos, the answer would lie in novel liquid crystal phases, such as the dark conglomerate phase formed by some bent-core liquid crystals. Again, focussing on work done by the Leeds team [47], he pointed out that these phases are inherently isotropic, yet exhibit a field-induced change in refractive index. The induced optic axis of the material is parallel to the applied field and hence remains effectively optically isotropic in the lens geometry.…”

Optical properties of composite heterophase objects with liquid crystal material for different display applications

“…More accurate solutions can be obtained by using approaches developed in [28][29][30][31] or optical software developed for the LC or LCD.…”