Emergence and tunability of transmission gap in the strongly disordered regime of a dielectric random scattering medium.

Abstract

Light transmission characteristics in a strongly disordered medium of dielectric scatterers, having dimensionalities similar to those of self-organized GaN nanowires, is analyzed employing finite difference time domain analysis technique. While photonic bandgap like transmission gaps have already been reported for several quasi-crystalline and weakly disordered media, the results of this work show that in spite of the lack of any form of quasi-crystallinity, distinct transmission gaps can be attained in a strongly disordered medium of dielectric scatterers. In fact, similar to the case of a two-dimensional photonic crystal, transmission gap of a uniform random medium of GaN nanowires can be tuned from ultra-violet to visible regime of the spectrum by varying diameter and fill-factor of the nanowires. Comparison of transmission characteristics of periodic, weakly disordered, correlated strongly disordered and uniform strongly disordered arrays having nanowires of identical diameters and fill factors suggest that in spite of the dominance of multiple scattering process, the underlying Mie and Bragg processes contribute to the emergence and tunability of transmission gaps in a strongly disordered medium. Without any loss of generality, the findings of this work offer significant design latitude for controlling transmission properties in the strong disorder regime, thereby offering the prospect of designing disorder based novel photonic and optoelectronic devices and systems.