Control of coherent backscattering by breaking optical reciprocity

TL;DR

This paper demonstrates how breaking optical reciprocity in a controlled way allows tuning of coherent backscattering effects, enabling a transition from enhancement to suppression of backscattered light in complex media.

Contribution

It introduces a method to manipulate coherent backscattering by breaking reciprocity using magneto-optical effects, enabling continuous control over interference phenomena.

Findings

Controlled reciprocity breaking tunes backscattering from peak to dip.

Magneto-optical effects enable continuous modulation of interference.

Potential applications in coherent control of classical and quantum waves.

Abstract

Reciprocity is a universal principle that has a profound impact on many areas of physics. A fundamental phenomenon in condensed-matter physics, optical physics and acoustics, arising from reciprocity, is the constructive interference of quantum or classical waves which propagate along time-reversed paths in disordered media, leading to, for example, weak localization and metal-insulator transition. Previous studies have shown that such coherent effects are suppressed when reciprocity is broken. Here we show that by breaking reciprocity in a controlled manner, we can tune, rather than simply suppress, these phenomena. In particular, we manipulate coherent backscattering of light, also known as weak localization. By utilizing a non-reciprocal magneto-optical effect, we control the interference between time-reversed paths inside a multimode fiber with strong mode mixing, and realize a continuous transition from the well-known peak to a dip in the backscattered intensity. Our results may open new possibilities for coherent control of classical and quantum waves in complex systems