US Patent 7277460 Generation of optical filaments by use of localized optical inhomogeneities

Optical filaments are formed controllably in a gaseous medium such as air. A phase plate introducing a phase discontinuity or other localized optical inhomogeneity is introduced into the path of the pulsed high-power laser beam that forms the optical filaments in the medium. The locations and characteristics of the phase discontinuities or singularities are selected to control the number and locations of the optical filaments.