A polarization-independent liquid crystal spatial light modulator

We report our recent experimental results on a new polarization-independent, liquid crystal (LC) spatial light modulator (SLM). Based on a periodic nematic director profile, the modulator acts as a switchable diffraction grating with only 0(th) - and +/- 1(st) -orders at efficiencies of >= 99%, manifests contrast ratios similar to 600:1 (for laser light), switching times of similar to 2ms, and threshold voltages of < 1V/mu m. Results of modulating broadband, unpolarized light from light-emitting-diodes (LEDs) indicates that contrast ratios are similar to 100:1 so far. Note that incoherent scattering for visible light is very low, and that samples are typically completely defect-free over large areas. An important feature of this diffractive polarization-independent SLM compared to its predecessors is its potential to achieve much larger diffraction angles, which enables a larger aperture (and etendue). In addition to describing the fabrication and characteristics of this SLM in general, we report on our initial progress in implementing a projection display system. All of the surprising and useful results from this grating arise from its continuous nematic director, which is most properly classed as a switchable polarization grating (PG). The SLM described here offers the inherent advantages polarization-independence at the pixel-level and fairly fast switching with nematic LCs, while maintaining similar switching voltages, cell thickness, contrast ratios, and materials.