Time reversal of electromagnetic waves in random channels with anisotropic disorder

In this work we study the relation between time reversal and wave localization in (mainly two-dimensional) systems with anisotropic disorder. It is shown, in particular, that for relatively short wavelengths which are comparable to the correlation scales of the disorder, the transport properties of random media are essentially different in the directions along and across the correlation ellipse. There exists a frequency-dependent critical value of the aspect ratio, below which waves are localized at all angles of propagation. Above this critical value, the radiation is localized only within some angular sectors centered at the short axis of the correlation ellipse and is extended in other directions. Also, extensive numerical time reversal experiments aimed at studying the resolution in both space focusing and time compression of ultra-wideband signals have been performed. The resolution obtained is shown to depend essentially on both the propagation angle and the aspect ratio of the random structure.