Abstract

Pattern formation and modulation instability in fully coherent systems have been investigated extensively in the past two decades. In the last few years, however, the observations of solitons made of spatially-incoherent (or weakly-correlated) light beams in several material systems^1–3 have led to the theoretical and experimental discovery of modulation instability and pattern formation in incoherent systems as well. In 2000, Soljacic et al.⁴ predicted that a uniform distribution of spatially-incoherent light in a self-focusing medium will undergo Incoherent Modulation Instability (IMI, see fig. la), giving rise to intricate patterns. However, IMI occurs only if the strength of the nonlinearity is above a well-defined threshold; a threshold that is set by spatial coherence of the beam. If the nonlinearity is below the threshold (i.e., the beam is too incoherent), the intensity will remain uniform as all perturbations are suppressed. Shortly after, IMI and the presence of this threshold were indeed demonstrated experimentally⁵.

© 2002 Optical Society of America