Laser beams with wavefront singularities

Summary form only given. Laser beams can possess features which are rather new for traditional optics. For instance, Laguerre-Gaussian LG/sub p//sup l/ modes with nonzero l index have azimuth phase dependence and therefore helicoidal wave fronts, with the pitch equal to l/spl lambda/, where /spl lambda/ is the wavelength. When l=1, the wavefront shape is a single-started helicoid, and due to the phase singularity on the axis, the amplitude vanish there. For l>1, the wave front consists from l identical l-started embedded helicoids, distanced on one wavelength. Now a term Optical Vortex (OV) is widely used for the description of such beams, because of the similarity between vortices in nature and in light propagation. This similarity appears, for instance, in the presence of an orbital angular momentum carried by an OV beam.