Defects are responsible for many well-known processes: plastic deformations and fracture in metals are governed by dislocations, vortices in the atmosphere show up as tornadoes, disclinations in condensed matter can mediate phase transitions, cosmic strings have played an important role in the early Universe cosmology, etc. Defects in liquid crystals can be obtained in phases with varying degrees of orientational and positional order and have been routinely used as model systems, for example, in many 鈥渃osmology in laboratory鈥 experiments. We have developed methods for non-contact optical generation of defects in liquid crystals described in our article by use of optical phase singularities in tightly focused laser beams. This new unique experimental capability already allowed us to obtain crystalline and quasi-crystalline patterns of defects and will contribute to the fundamental understanding of defects & their properties.
