Light diffusion and localization in three-dimensional nonlinear disordered media

By using a three-dimensional finite-difference time-domain parallel code, the linear and nonlinear propagation of light pulses in a disordered assembly of scatterers, generated by a molecular dynamics code, is simulated. We calculate the static and dynamical light diffusion constant and the transmission in the presence of localized states. We numerically demonstrate the "modulational instability random laser": at high input peak power, energy is transferred to localized states from the input pulse, resulting in a power-dependent nonexponential time decay of the transmitted pulse.