Experimental observation of speckle instability in nonlinear disordered media

TL;DR

This paper reports the experimental observation of speckle pattern instability caused by nonlinear effects and surface plasmon coupling in disordered media, highlighting the sensitivity of speckle to scattering potential fluctuations.

Contribution

It provides the first experimental evidence of speckle instability in nonlinear disordered media due to surface plasmon interactions.

Findings

Speckle pattern fluctuations increase with optical power.

Instability explained by coupling to surface plasmons and guided modes.

Speckle is highly sensitive to scattering potential fluctuations.

Abstract

Temporal fluctuations of the speckle pattern formed upon backscattering of a laser beam from an interface between gold and nonlinear polymer film have been observed as a function of optical power. The instability can be explained by coupling of laser light to surface plasmons and other guided modes, which experience multiple scattering while propagating in the film along the interface. The speckle pattern produced in this process is extremely sensitive to fluctuations of the scattering potential near the interface.