Two-Photon Scattering by a Cavity-Coupled Two-Level Emitter in a One-Dimensional Waveguide

TL;DR

This paper demonstrates how a cavity-coupled two-level emitter in a one-dimensional waveguide can modulate two-photon transport, affecting spectral properties and correlations, with implications for optical devices and sensing.

Contribution

It reveals how tuning cavity resonance enhances photon-photon interactions and exhibits Fano resonance effects in two-photon correlations, aligning with recent experimental findings.

Findings

Resonant cavity coupling narrows transmitted photon spectrum.

Two-photon intensity correlations show Fano resonance line shape.

Proper cavity tuning improves photon-photon interaction efficiency.

Abstract

We show that two-photon transport can be modulated by a two-level emitter coupled to a cavity in a one-dimensional waveguide. In the ordinary case, the transmitted light has a wider frequency spectrum than the situation without the cavity because it is reflected and scattered many times. But when the two photons are resonant with the cavity resonance reflection frequency, the frequency spectrum of the transmitted light becomes narrower than that without the cavity. This means that properly tuning the cavity resonance frequency can improve the photon-photon interaction. In addition, we show that the two-photon intensity correlation functions are nearly opposite to each other at the two sides of the emitter transition frequency rather than be the same, which is exactly the Fano resonance line shape for two photons. Such an effect is important for lowering the power threshold in optical bistable devices and for sensing applications. When the emitter transition frequency equals to the cavity resonance frequency for a high-Q cavity, our results agree with the recent experiments and theories.