Liquid crystal defects: Nonlinear optics and optical vortices

Liquid crystals can self-assemble into various phases characterized by well-defined orientational ordering of their crystalline axis. Exception may happen at locations in space where the orientation is ill-defined, which correspond to liquid crystal defects. In addition, liquid crystals are well-known to be sensitive to external fields and light is no exception. In particular, Gaussian light beams can generate singular liquid crystal reorientation defects owing to the giant optical orientational nonlinearities. Such a singular optical reordering of liquid crystals can be used to generate light beams carrying on-axis phase singularity that are usually called optical vortices.