Superradiant Decay and Dipole-Dipole Interaction of Distant Atoms in a Two-Way Cascaded Cavity QED System

TL;DR

This paper explores a two-way cascaded cavity QED system with microtoroidal resonators and atoms, demonstrating controllable collective emission and dipole-dipole interactions, and extending the analysis to many-atom systems.

Contribution

It introduces a novel two-way cascaded cavity QED model with controllable atom-atom interactions via bi-directional fiber coupling.

Findings

Switchable collective spontaneous emission and dipole-dipole interactions.

Explicit spectral results for strong-coupling and bad-cavity regimes.

Extension of the model to many atom-microtoroid systems.

Abstract

We investigate a two-way cascaded cavity QED system consisting of microtoroidal resonators coupled through an optical fiber. Each microtoroidal cavity supports two counter-propagating whispering-gallery modes coupled to single atoms through their evanescent fields. We focus on a pair of atom-microtoroid systems and compute the spectrum of spontaneous emission into the fiber with one atom initially excited. Explicit results are presented for strong-coupling and bad-cavity regimes, where the latter allows the effective atom-atom interaction to be controlled through the atom-cavity coupling and detuning: the atoms exhibit either collective spontaneous emission with no dipole-dipole interaction or a (coherent) dipole-dipole interaction and independent (single-atom) emission. This capacity for switching the character of the interaction is a feature of bi-directional coupling and connects our two-way cascaded system to work on one-dimensional waveguides. Building upon our bad-cavity results, we generalize to many atom-microtoroid systems coupled through an optical fiber.