Observation of coherent back-scattering and its dynamics in a transverse 2D photonic disorder : from weak to strong localization

TL;DR

This paper reports the first observation of coherent back-scattering in a transverse 2D photonic disorder, demonstrating how the CBS signal evolves with increasing disorder from weak to strong localization, revealing insights into light transport and Anderson localization.

Contribution

It provides the first experimental observation of CBS in a transverse 2D photonic system and analyzes its dynamics across different disorder regimes, including the onset of Anderson localization.

Findings

CBS peak with high contrast observed in the far-field.

Non-monotonous evolution of CBS with disorder strength.

Resymmetrization of momentum distribution indicating strong localization.

Abstract

We report the first observation of coherent back-scattering (CBS) of light in a transverse photonic disorder. The CBS peak is recorded in the far-field, at a fixed propagation time set by our crystal length, and displays a contrast approaching the ideal value of 1, which proves good coherence of transport in our system. We study its dynamics for increasing disorder strength, and find a non-monotonous evolution. For weak disorder, the CBS signal increases, and the asymmetry of the momentum distribution becomes inverted compared to the initial condition. For stronger disorder, we observe a resymmetrization of the momentum distribution, confirmed by numerical simulations, and compatible with the onset of strong (Anderson) localization.