Nonlinear propagation of incoherent white light in a photopolymerizable medium: evidence of the co-existence and competition between spontaneous pattern formation and self-trapping

Evidence is presented for the coexistence and competition between two different forms of the nonlinear propagation of incoherent white light—self-trapping and spontaneous pattern formation due to modulation instability—in a photopolymerizable organosiloxane. Equidistant weak spots surrounding the dominant self-trapped beam were observed in a fraction of experiments (47%). The weak spots observed during self-trapping were similar to those that form across a uniform broad beam of white light due to modulation instability. In the majority of cases, the single self-trapped beam dominated and propagated through the medium without diffraction. In a small percentage of experiments (9%), intensity was redistributed between at least four different spots by sequential transfer of intensity between nearest-neighbour spots.