SELF-TRAPPING OF DARK INCOHERENT-LIGHT BEAMS

''Dark beams'' are nonuniform optical beams that contain either a one- dimensional (1D) dark stripe or a two-dimensional (2D) dark hole resul ting from a phase singularity or an amplitude depression in their opti cal field. Thus far, self-trapped dark beams (dark solitons) have been observed using coherent light only. Here, self-trapped dark incoheren t light beams (self-trapped dark incoherent wavepackets) were observed . Both dark stripes and dark holes nested in a broad partially spatial ly incoherent wavefront were self-trapped to form dark solitons in a h ost photorefractive medium. These self-trapped 1D and 2D dark beams in duced refractive-index changes akin to planar and circular dielectric waveguides. The experiments introduce the possibility of controlling h igh-power coherent laser beams with low-power incoherent light sources such as light emitting diodes.