Cascaded two-photon nonlinearity in a one-dimensional waveguide with multiple two-level emitters

TL;DR

This paper presents a theoretical model demonstrating cascaded two-photon nonlinearity in a 1D waveguide with multiple two-level emitters, revealing nonreciprocal multi-photon transmission and tunable nonlinear effects.

Contribution

The study introduces a novel theoretical framework for cascaded optical nonlinearity with few atoms in a 1D waveguide, explaining nonreciprocity and tunable multi-photon interactions.

Findings

Multi-photon transmission is nonreciprocal with different emitter energies.

Two-photon effects like attraction, repulsion, and fluorescence can be tuned.

The model provides physical insight into cascaded nonlinearity and nonreciprocity.

Abstract

We propose and theoretically investigate a model to realize cascaded optical nonlinearity with few atoms and photons in one-dimension (1D). The optical nonlinearity in our system is mediated by resonant interactions of photons with two-level emitters, such as atoms or quantum dots in a 1D photonic waveguide. Multi-photon transmission in the waveguide is nonreciprocal when the emitters have different transition energies. Our theory provides a clear physical understanding of the origin of nonreciprocity in the presence of cascaded nonlinearity. We show how various two-photon nonlinear effects including spatial attraction and repulsion between photons, background fluorescence can be tuned by changing the number of emitters and the coupling between emitters (controlled by the separation).