Bistability of anderson localized States in nonlinear random media.

We study wave transmission through one-dimensional random nonlinear structures and predict a novel effect resulting from an interplay of nonlinearity and disorder. We reveal that, while weak nonlinearity does not change the typical exponentially small transmission in the regime of the Anderson localization, it affects dramatically the disorder-induced localized states excited inside the medium leading to bistable and nonreciprocal resonant transmission. Our numerical modeling shows an excellent agreement with theoretical predictions based on the concept of a high-Q resonator associated with each localized state.

Spectral coherence and time-domain transport of waves in random media.

An original approach is developed for the description of spectral coherence and time-domain transport of wave fields scattered in random media. This approach accounts explicitly for the correlation properties of the disorder and is universal with respect to the dimensionality of the system. Specifically, a two-frequency mutual coherence function is evaluated by using a procedure of embedding the initial Helmholtz equation into an auxiliary problem of a directed wave propagating in a higher-dimensional space.

Suppression of Anderson localization in disordered metamaterials.

We study wave propagation in mixed, 1D disordered stacks of alternating right- and left-handed layers and reveal that the introduction of metamaterials substantially suppresses Anderson localization. At long wavelengths, the localization length in mixed stacks is orders of magnitude larger than for normal structures, proportional to the sixth power of the wavelength, in contrast to the usual quadratic wavelength dependence of normal systems. Suppression of localization is also exemplified in long-wavelength resonances which largely disappear when left-handed materials are introduced.

Light scattering from particles located under a rough dielectric layer.

A discussion is presented of the effect of roughness on the detectability of subsurface particles by means of the light-scattering method. We have studied the scattering of light by calibrated spheres located under a slightly rough dielectric surface both experimentally and theoretically. In our experiments, the scattering from slightly rough layers with nonresonant particles was dominated by the roughness, and the scattering diagram did not bear any discernible indications of the spheres.

Localization of classical waves in weakly scattering two-dimensional media with anisotropic disorder.

We study the localization of classical waves in weakly scattering two-dimensional systems with anisotropic disorder. The analysis is based on a perturbative path-integral technique combined with a spectral filtering that accounts for the first-order Bragg scattering only. It is shown that in the long-wavelength limit the radiation is always localized, and the localization length is independent of the direction of propagation, the latter in contrast to the predictions based on an anisotropic tight-binding model.

Two-frequency mutual coherence function and pulse propagation in random media.

In this work an analysis of transient wave propagation in forward scattering random media is presented. The analysis is based on evaluation of the two-frequency mutual coherence function, which is an important quantity in itself since it provides a measure of the coherence bandwidth. The coherence function is calculated by using the path integral technique; specifically, by resorting to a cumulant expansion of the path integral.