Liquid-crystal phase-only devices

Phase-only devices based on liquid crystals are becoming popular solutions for a high number of applications in many diverse areas. The use of an electrooptic material such as liquid crystals makes the device tunable, opening up many different possibilities of light beam manipulations: beam steering, beam shaping, modulation, focusing, generation of vortices or vector beams, etc. The subject has received a significant boost in the last decade since many research labs working on liquid crystal displays - an area almost entirely transferred to electronic companies - have evolved to these devices, where new effects and applications are continuously being unveiled, and a number of issues affecting their performance are still unsolved. The work is a review of the most relevant kinds of photonic devices developed with this technology. A detailed study of every device and effect would have been too lengthy and possibly would have lacked coherence for dealing on too dissimilar topics. Therefore, the work is focused on passive devices, i.e., with no active matrix driving, thus circumventing the large field of spatial light modulators, which surely deserve a thorough review themselves, but have been already analyzed in many publications.