Interference-induced directional emission from an unpolarized two level emitter into a circulating cavity

TL;DR

This paper demonstrates that a two-level emitter with a randomly polarized dipole can emit directionally into a circulating cavity through chiral coupling with another emitter, enabling robust directional emission without requiring a circular dipole moment.

Contribution

It introduces a novel scheme where a randomly polarized two-level emitter achieves directional emission via chiral coupling with a second emitter, even in the bad-cavity regime.

Findings

Directional emission is achievable with randomly polarized emitters.

The scheme is robust against noise when driven by a weak laser field.

Analytical expressions and numerical simulations support the results.

Abstract

Chiral coupling between quantum emitters and evanescent fields allows directional emission into nanophotonic devices and is now considered to be a vital ingredient for the realization of quantum networks. However, such coupling requires a well defined circular dipole moment for the emitter -- something difficult to achieve for solid state emitters at room temperature due to thermal population of available spin states. Here, we demonstrate that a two level emitter with a randomly polarized dipole moment can be made to emit directionally into a circulating cavity if a separate emitter is chirally coupled to the same cavity, for the case when both emitter-cavity couplings are strong but in the bad-cavity regime. Our analysis of this system first considers a transient scenario, which highlights the physical mechanism giving rise to the directional emission of the two level emitter into the cavity. An alternative setup involving a weak laser field continuously driving the system is also considered, where the directionality (our proposed figure of merit for this scheme) is shown to be significantly more robust against noise processes. The results presented here take the form of approximate analytical expressions backed by complete numerical simulations of the system.