Perturbing open cavities: Anomalous resonance frequency shifts in a hybrid cavity-nanoantenna system

TL;DR

This paper reveals that small particles can cause unexpected, large frequency shifts in a cavity system due to phase interactions, challenging traditional polarizability-based predictions and impacting various optical sensing and quantum technologies.

Contribution

It introduces a full electrodynamic theory and a coupled mode model explaining anomalous resonance shifts caused by phase effects in cavity-nanoantenna systems.

Findings

Particles can induce frequency shifts opposite to polarizability predictions.

Strong frequency shifts can exceed those expected from polarizability.

Phase relations enable back-action effects via the radiation continuum.

Abstract

The influence of a small perturbation on a cavity mode plays an important role in fields like optical sensing, cavity quantum electrodynamics and cavity optomechanics. Typically, the resulting cavity frequency shift directly relates to the polarizability of the perturbation. Here we demonstrate that particles perturbing a radiating cavity can induce strong frequency shifts that are opposite to, and even exceed, the effects based on the particles' polarizability. A full electrodynamic theory reveals that these anomalous results rely on a non-trivial phase relation between cavity and nanoparticle radiation, allowing back-action via the radiation continuum. In addition, an intuitive model based on coupled mode theory is presented that relates the phenomenon to retardation. Because of the ubiquity of dissipation, we expect these findings to benefit the understanding and engineering of a wide class of systems.