A Polarization-Independent Liquid Crystal Spatial Light Modulator

摘要

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 0th- and ±1st-orders at efficiencies of ≥99%, manifests contrast ratios ～600:1 (for laser light), switching times of ～2ms, and threshold voltages of < 1V/μm. Results of modulating broadband, unpolarized light from light-emitting-diodes (LEDs) indicates that contrast ratios are ～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.