Polarisation-independent liquid crystal devices 

Liquid crystal (LC) devices can be used as amplitude modulators and phase modulators. Most LC devices are polarisation-dependent and require at least one polariser. As a result, the optical efficiency is greatly reduced. In this paper, we review some of our recently developed polarisation-independent LC devices. For amplitude modulation, we report two polariser-free devices which combine light scattering with dye absorption: dye-doped polymer-dispersed liquid crystal (PDLC) and dye-doped LC gels. For phase modulation, we also present two examples: residual phase type, e.g., voltage-biased PDLC, Polymer-Stabilised Cholesteric Texture (PSCT), and homeotropic LC gels; and double-layered structure, such as thin polymer film-separated orthogonal LC layers, and double-layered LC gels. Potential applications of these polarisation-independent LC devices for displays, laser beam steering and adaptive optics are emphasised.