The POLICRYPS liquid-crystalline structure for optical applications

We present a review of polymer-liquid crystal-based devices for optical applications. Starting from a particular fabrication technique, which enables to obtain the POLICRYPS (POlymer LIquid CRYstal Polymer Slices) structure, we illustrate different realizations, along with their working principle and main features and performances. The name POLICRYPS indicates a structure made of parallel slices of pure polymeric material alternated to films of well-aligned nematic liquid crystal (NLC), with a spatial periodicity that can be settled in the range 0.2÷15 μm. Suitably designed samples can be utilized as optical devices with a high efficiency, which can be switched on and off both by applying an electric field of a few V/μm or by irradiating samples with a suitable light beam. In different geometries, POLICRYPS can be specialized to operate as switchable diffraction grating, switchable optical phase modulator, switchable beam splitter, or tunable Bragg filter. The POLICRYPS framework can be also used as a soft matter template for aligning different types of LCs or to create an array of tunable microlasers. Finally, we present a POLICRYPS structure with a polar symmetry of the director alignment, which enables local shaping of light polarization, allowing to convert circularly polarized beams into cylindrical vector beams.