Instability of speckle patterns in random media with noninstantaneous Kerr nonlinearity

TL;DR

This paper investigates how the noninstantaneous response of Kerr nonlinearity influences the onset and dynamics of speckle pattern instability in multiple-scattering random media, highlighting the roles of characteristic timescales.

Contribution

It introduces a theoretical analysis of speckle instability considering noninstantaneous Kerr nonlinearity, emphasizing the impact of relaxation times on speckle dynamics.

Findings

Instability onset is affected by the noninstantaneous response.

The timescale of speckle dynamics is determined by the larger of $T_D$ and $ au_{NL}$.

Inertial nonlinearity complicates experimental observation.

Abstract

Onset of the instability of a multiple-scattering speckle pattern in a random medium with Kerr nonlinearity is significantly affected by the noninstantaneous character of the nonlinear medium response. The fundamental time scale of the spontaneous speckle dynamics beyond the instability threshold is set by the largest of times $T_{\mathrm{D}}$ and $\tau_{\mathrm{NL}}$, where $T_{\mathrm{D}}$ is the time required for the multiple-scattered waves to propagate through the random sample and $\tau_{\mathrm{NL}}$ is the relaxation time of the nonlinearity. Inertial nature of the nonlinearity should complicate the experimental observation of the instability phenomenon.