Polarization-dependent diffractive optical elements based on photoalignment of liquid crystals

Diffractive optical elements (DOEs), with attractive features such as excellent performance and compact configuration, are now becoming increasingly important to a wide range of optical system applications. In this paper, we have used the patterned photoalignment method to produce switchable gratings. It is found that these gratings combine good optical quality with very fast dynamical response at very low driving voltage. A sub-millisecond steering with active FLC as a polarization selector and passive polarization grating (PG) as a diffractive element. A systematic analysis is conducted from the device fabrication to the element working mechanism with their potential problems and corresponding solutions included. The polymerizable liquid crystal PG shows compact size, light weight, robustness, and low cost. Switching time of 82μs is realized by binary switching between two circular polarizations before incident on PG utilizing FLC driven by two electrical polarities. Overall efficiency of 95.7% is achieved with steering angle of 17.66° by 1064nm laser.