Observation of Fundamental Limit of Light Localization

TL;DR

This study experimentally demonstrates a fundamental limit to light localization in disordered media, showing that Anderson localization cannot occur below an optical mean free path of approximately 13 nm, revealing a core physical constraint.

Contribution

The paper provides the first direct experimental observation of the minimal optical mean free path necessary for Anderson localization of light, using advanced scanning probe microscopy techniques.

Findings

No localized light spots observed below ~14.5 nm MFP

Experimental and simulation results show suppression of localization at ~13 nm MFP

Reveals a fundamental physical constraint in light localization

Abstract

In disordered media light can be localized in the spaces between scattering sites which average to an optical mean free path (MFP). However the fundamental question of the smallest MFP that can support Anderson localization of light remains unanswered due to fabrication complexity of a scattering medium with controlled nano-scale gaps and lack of required resolution by far-field methods. Here we use scanning probe microscopy technique to collect localized light created at gaps between scattering crystallographic defects in a large variety set of nano-gap III-V medium. No localized spots correlated to MFP below ~14.5 nm is observed at second-harmonic collection at 390 nm. Experiment and simulation resulted in the first direct observation of suppression of Anderson light localization correlated to ~13 nm optical MFP that reveals a fundamental constraint in electromagnetism and photonics.