Optical vortices generated by edge dislocations in electro-convective instability arrays of nematic liquid crystals.

We demonstrated by means of interferometry that optical vortices can be generated by diffraction of a laser beam from a birefringent nematic liquid crystal that spontaneously creates a periodic array of electro-convective domains and edge dislocations under an applied electric field. The diffracted beam of order m produced by an elementary dislocation comprises a number |m| of distinct optical vortices, each with unit topological charge. Birefringent liquid crystal arrays provide a fast, convenient, and promising way of generating and studying optical vortices. The used materials are inexpensive, fabrication processes are simple, and both input polarization and applied field can be used as external controls to switch the optical vortices on and off.