Periodically oscillating anderson localization in random photonic superlattices with resonant units

In strongly disordered systems, where Anderson localization is present, the mean transmittance (<T>) decays exponentially on average with increasing sample size. However, <T> often shows large fluctuations originating from extremely rare occurrences of necklaces of resonantly coupled states, possessing almost unity transmission. We show in this study that in one-dimensional (1D) random photonic systems with resonant layers these fluctuations appear to be very regular and have a period defined by the localization length \xi of the system. We demonstrate that necklace states are the origin of these well-defined oscillations. We predict that in such a random system efficient transmission channels form regularly each time the increasing sample length fits so-called optimal-order necklaces and demonstrate the phenomenon through numerical experiments. Our results provide new insight into the physics of Anderson localization in random systems with resonant units.