Discrepant transport characteristics under Anderson localization at the two limits of disorder

TL;DR

This study experimentally compares light transport in two-dimensional structures with varying disorder, revealing fundamental differences in Anderson localization behavior between amorphous and nearly-periodic regimes, supported by theoretical modeling.

Contribution

It provides the first systematic experimental and theoretical comparison of transport properties in two disorder limits, highlighting discrepancies in conductance fluctuations and localization.

Findings

Localization occurs in both regimes but with different conductance fluctuation behaviors.

Amorphous disorder shows conductance below unity, indicating arrested transport.

Near-periodic disorder exhibits heavy-tailed conductance distribution, suggesting delocalized transport.

Abstract

Anderson localization is a striking phenomenon wherein transport of light is arrested due to the formation of disorder-induced resonances. Hitherto, Anderson localization has been demonstrated separately in two limits of disorder, namely, amorphous disorder and nearly-periodic disorder. However, transport properties in the two limits are yet unstudied, particularly in a statistically consistent manner. Here, we experimentally measure light transport across two-dimensional open mesoscopic structures, wherein the disorder systematically ranges from nearly-periodic to amorphous. We measure the generalized conductance, which quantifies the transport probability in the sample. Although localization was identified in both the limits, statistical measurements revealed a discrepant behavior in the generalized conductance fluctuations in the two disorder regimes. Under amorphous disorder, the generalized conductance remains below unity for any configuration of the disorder, attesting to the arrested nature of transport. Contrarily, at near-periodic disorder, the distribution of generalized conductance is heavy-tailed towards large conductance values, indicating that the overall transport is delocalized. Theoretical results from a model based on the tight-binding approximation, augmented to include open boundaries, are in excellent agreement with experiments, and also endorse the results over much larger ensembles. These results quantify the differences in the two disorder regimes, and advance the studies of disordered systems into actual consequences of Anderson localization in light transport.