Propagating Polaritons in III-Nitride Slab Waveguides

TL;DR

This paper demonstrates the creation and propagation of polaritons in III-nitride waveguides with strong light-matter coupling, highlighting their potential for integrated polaritonic circuits and room-temperature applications.

Contribution

It introduces III-nitride waveguides supporting propagating polaritons with large mode splitting and long decay lengths, enabling high-quality polaritonic devices at room temperature.

Findings

Mode splitting up to 60 meV at low temperatures

Polariton decay length up to 100 μm

Lifetimes of 1-2 ps limited by residual absorption

Abstract

We report on III-nitride waveguides with c-plane GaN/AlGaN quantum wells in the strong light-matter coupling regime supporting propagating polaritons. They feature a normal mode splitting as large as 60 meV at low temperatures thanks to the large overlap between the optical mode and the active region, a polariton decay length up to 100 $\mu$m for photon-like polaritons and lifetime of 1-2 ps; with the latter values being essentially limited by residual absorption occurring in the waveguide. The fully lattice-matched nature of the structure allows for very low disorder and high in-plane homogeneity; an important asset for the realization of polaritonic integrated circuits that could support nonlinear polariton wavepackets up to room temperature thanks to the large exciton binding energy of 40 meV.