Abstract

Electromagnetic wave localization and diffusion in random media have been recently considered by several authors. Experimental studies reported on various evidences of light localization, including the existence of a non-exponential long-time tail of the transmitted intensity, and these processes were considered in numerous theoretical and numerical papers (see references in [1]). In a purely diffusive regime, pulsed light impinging on a disordered sample is rapidly dispersed while propagating; this implies that nonlinear effects are typically negligible. For non-resonant ultrafast nonlinearities, it is in principle possible to use highpeak intensity femtosecond laser pulses to induce nonlinear effects, even in the presence of strong light diffusion. However, the (numerical and theoretical) analysis is enormously complicated by the need to include various effects as disorder, nonlinearity, material dispersion and to take into account a 3D environment. Even in the absence of nonlinearity, no “ab initio” numerical investigation of 3D Maxwell equations for femtosecond pulses in disordered media has been reported, to the best of our knowledge. Here we report 3D parallel FDTD simulation, including material dispersion and nonlinearity, which quantitatively riproduced the measured value of the diffusion constant in the linear regime and show evidences of a nonexponential trasmitted pulse-tail at high-powers.

© 2007 IEEE