Light Transport and Localization in Two-Dimensional Correlated Disorder

Abstract

Structural correlations in disordered media are known to affect significantly the propagation of waves. In this Letter, we theoretically investigate the transport and localization of light in 2D photonic structures with short-range correlated disorder. The problem is tackled semianalytically using the Baus-Colot model for the structure factor of correlated media and a modified independent scattering approximation. We find that short-range correlations make it possible to easily tune the transport mean free path by more than a factor of 2 and the related localization length over several orders of magnitude. This trend is confirmed by numerical finite-difference time-domain calculations. This study therefore shows that disorder engineering can offer fine control over light transport and localization in planar geometries, which may open new opportunities in both fundamental and applied photonics research. DOI: 10.1103/PhysRevLett.112.143901 PACS numbers: 42.25.Dd, 42.25.Fx, 61.43.Dq Multiple light scattering in disordered media plays a paramount role in the study of complex natural systems (e.g., biological tissues, porous materials, planetary atmospheres) [1] and wave phenomena (e.g., light localization, anomalous diffusion) [2][3][4]. In recent years there has been a growing interest in the use of photonic structures with controlled disorder, in particular within the context of mesoscopic transport effects [5][6][7][8], cavity quantum electrodynamics [9], photon management for energy efficiency [10][11][12][13], and even lab-on-chip spectroscopy [14]. Indeed structural correlations in the positions of scatterers are known to affect light propagation. Previous studies have shown that short-range correlations can either diminish or enhance the scattering strength of a disordered system [15][16][17][18] and lead to a modulation of the density of optical states [19], even in biological systems [20]. Such a modulation can be so large that a complete photonic band gap is expected to form, even without long-range periodicity [19,[21][22][23][24]. The emerging concept of "disorder engineering" to manipulate light transport in random media is, however, still in its infancy and little is known so far on the occurrence of localization phenomena in correlated systems.In this Letter, we theoretically investigate the transport of light and the occurrence of localization in two-dimensional (2D) photonic structures possessing short-range correlated disorder. A semianalytical model describing the wave propagation in correlated-disordered systems allows us to investigate how key quantities, namely, the transport mean free path, the scattering anisotropy factor, and the localization length, evolve with the degree of correlation. In particular, short-range correlations are found to allow for the tuning of the localization length over several orders of magnitude and thus, make it possible to go from a quasiextended to a strongly localized regime very easily, in sharp contrast with three-dimensional systems, where the localized re...

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