Observation of suppression of Anderson localization of light

Abstract

In a disordered-medium, light can be localized in the spaces between scattering sites, which represents the optical mean free path (MFP). However, the fundamental question of the smallest MFP that can support Anderson localization of light remains unanswered due to the fabrication complexity of a scattering medium with controlled nanoscale gaps and limited resolution by far-field methods. Here, we use a scanning probe-microscopy technique to collect localized-light created around scattering crystallographic defects in a large variety set of nano-gap III–V films. No localization-length smaller than ∼55 nm (correlated with ∼14.5 nm MFP) is observed at the second-harmonic collection at 390 nm, while a medium with ∼13 nm scattering MFP shows no localization. The results suggest the existence of a general, albeit material and λ-dependent, lower spatial limit to light confinement via Anderson localization, which redraws the boundary of light under extreme disorder and confinement at the nanoscale regime.