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

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.

Disorder induced rotational-symmetry breaking to control directionality of whispering gallery modes in circularly symmetric nanowire assembly.

Effect of disorder on the emission directionality of a whispering gallery mode resonator comprising of circularly symmetric nanowire array is investigated using finite-difference time-domain analysis technique. In spite of rotational symmetry breaking, whispering gallery mode-like isotropic emission characteristics are retained by the nanowire array up to a certain degree of spatial disorder. For higher degrees of randomness, Anderson localized resonant modes are obtained with unidirectional emission characteristics, though the beam direction remains unpredictable because of the underlying random-scattering process.