# Polaritonic frequency-comb generation and breather propagation in a negative-index metamaterial with a cold four-level atomic medium

## TL;DR

This paper proposes a novel waveguide design that uses a lossless dielectric with four-level atoms above a negative-index metamaterial to generate polaritonic frequency combs and breathers, enabling high-speed modulation and compact photonic applications.

## Contribution

It introduces a new waveguide scheme combining atomic media and metamaterials to control surface-polaritonic waves for frequency comb and breather generation.

## Key findings

- Successful excitation of polaritonic Akhmediev breathers at the interface.
- Generation of position-dependent polaritonic frequency combs.
- Potential for high-speed, compact photonic devices.

## Abstract

We develop a concept for a waveguide that exploits spatial control of nonlinear surface-polaritonic waves. Our scheme includes an optical cavity with four-level $\text{N}$-type atoms in a lossless dielectric placed above a negative-index metamaterial layer. We propose exciting a polaritonic Akhmediev breather at a certain position of the interface between the atomic medium and the metamaterial by modifying laser-field intensities and detunings. Furthermore, we propose generating position-dependent polaritonic frequency combs by engineering widths of the electromagnetically induced transparency window commensurate with the surface-polaritonic modulation instability. Therefore, this waveguide acts as a high-speed polaritonic modulator and position-dependent frequency-comb generator, which can be applied to compact photonic chips.