We report the observation of optical vortices in a laser beam propagating through the stripe pattern of a cholesteric liquid crystal. The liquid crystal is confined in a cell with homogeneous boundary conditions and forms a diffraction phase grating. Optical vortices are produced by edge dislocations of the cholesteric grating. The vortices show up as spots of zero light intensity in the diffraction maxima. There is one spot in each +1 and -1 diffraction maximum and two spots in diffraction maxima +2 and -2.
© 2000 Optical Society of America
(050.1940) Diffraction and gratings : Diffraction
(070.4690) Fourier optics and signal processing : Morphological transformations
(160.3710) Materials : Liquid crystals
(180.1790) Microscopy : Confocal microscopy
D. Voloschenko and O. D. Lavrentovich, "Optical vortices generated by dislocations in a cholesteric liquid crystal," Opt. Lett. 25, 317-319 (2000)