Controlled coupling of counterpropagating whispering-gallery modes by a single Rayleigh scatterer: a classical problem in a quantum optical light

TL;DR

This paper experimentally demonstrates how a single Rayleigh scatterer can control the coupling between counterpropagating whispering-gallery modes in a microsphere resonator, revealing classical physics phenomena relevant to quantum optics.

Contribution

It provides the first detailed experimental analysis of single scatterer control over mode coupling in high-Q resonators, bridging classical and quantum optics perspectives.

Findings

Observation of standing wave eigenmodes with unbalanced intensities

Demonstration of coherent coupling mediated by a single scatterer

Insight into classical physics processes relevant to quantum optics

Abstract

We present experiments where a single subwavelength scatterer is used to examine and control the back-scattering induced coupling between counterpropagating high-Q modes of a microsphere resonator. Our measurements reveal the standing wave character of the resulting symmetric and antisymmetric eigenmodes, their unbalanced intensity distributions, and the coherent nature of their coupling. We discuss our findings and the underlying classical physics in the framework common to quantum optics and provide a particularly intuitive explanation of the central processes.