Photon transport enhanced by transverse Anderson localization in disordered superlattices

Controlling the flow of light at subwavelength scales provides access to functionalities such as negative or zero index of refraction, transformation optics, cloaking, metamaterials and slow light, but diffraction effects severely restrict our ability to control light on such scales. Here we report the photon transport and collimation enhanced by transverse Anderson localization in chip-scale dispersion-engineered anisotropic media. We demonstrate a photonic crystal superlattice structure in which diffraction is nearly completely arrested by cascaded resonant tunnelling through transverse guided resonances. By modifying the geometry of more than 4,000 scatterers in the superlattices we add structural disorder controllably and uncover the mechanism of disorder-induced transverse localization. Arrested spatial divergence is captured in the power-law scaling, along with exponential asymmetric mode profiles and enhanced collimation bandwidths for increasing disorder. With increasing disorder, we observe the crossover from cascaded guided resonances into the transverse localization regime, beyond both the ballistic and diffusive transport of photons.. © 2015 Macmillan Publishers Limited. All rights reserved.