POLICRYPS switchable holographic grating: a promising grating electro-optical pixel for high resolution display application

POLICRYPS, an acronym of POlymer LIquid CRYstal Polymer Slices, is a structure made of perfectly aligned liquid crystal films separated by slices of almost pure polymer. Under suitable experimental and geometrical conditions, the structure is obtained by curing a homogeneous syrup of liquid crystal, monomer and curing agent molecules with a spatially modulated pattern of ultraviolet (UV) radiation. From an optical point of view, POLICRYPS is a holographic diffraction grating with a spatial periodicity that can be easily made of sub-micrometric scale, exhibiting diffraction efficiency values as high as 98%. Depending on the used geometry, the POLICRYPS grating can be utilized both in transmission or reflection, with negligible scattering losses, and can be switched ON and OFF by application of an external electric field of the order of few V/μm. In this paper, we review: 1) the "recipe" to fabricate POLICRYPS holographic gratings, along with their main optical and electro-optical properties; 2) a chemical-diffusive model that, taking into account sample temperature and intensity of the curing radiation, indicates the best conditions to fabricate these gratings; 3) a Kogelnik-like model that accounts for the dependence of the diffraction efficiency on material parameters, sample temperature, and applied electric field. Finally, we discuss the possibility of utilizing a micrometric sized POLICRYPS grating as a Grating Electro-Optical Pixel for high resolution display application.