title: Experimental observation of speckle instability in Kerr random media.
abstract: In a disordered nonlinear medium the transmitted speckle pattern was predicted to become unstable as a result of the positive feedback between intensity fluctuations and local variations of the refractive index. We show experimental evidence of speckle instability for light transversally scattered in a liquid crystal cell, where a two-dimensional controlled disorder is imprinted by suitable illumination of a photoconductive wall and nonlinearity is obtained through optical reorientation of the liquid crystal molecules. The speckle pattern spontaneously oscillates at discrete frequencies above a critical threshold, whose dependence on the scattering mean free path confirms the crucial role of disorder in the feedback process.
authors.affiliation: INLN, Université de Nice Sophia-Antipolis, CNRS, 1361 route des Lucioles 06560 Valbonne, France.
authors.forename: U
authors.initials: U
authors.lastname: Bortolozzo
authors.forename: S
authors.initials: S
authors.lastname: Residori
authors.forename: P
authors.initials: P
authors.lastname: Sebbah