  In this Letter, it is proposed a method which utilizes three-dimensional
finite-difference time-domain (FDTD) simulations of light propagation for
restoring the effective Kerr nonlinearity of nanocomposite media. In this
approach, a dependence of the phase shift of the transmitted light on the input
irradiance is exploited. The reconstructed values of the real parts of the
nonlinear refractive index of a structure of randomly arranged spheres are in
good agreement with the predictions of the effective medium approximations.
