Hybrid Longitudinal-Transverse Phonon Polaritons

TL;DR

This paper demonstrates the creation and observation of hybrid longitudinal-transverse phonon polaritons in silicon carbide, enabling potential electrically pumped mid-infrared emitters through strong coupling and experimental validation.

Contribution

It introduces a microscopic theory and experimental evidence for hybrid phonon polaritons in silicon carbide polytypes, advancing mid-infrared emitter development.

Findings

Observation of spectral anti-crossing indicating strong coupling.

Development of a microscopic theory predicting hybrid excitations.

First experimental demonstration of hybrid longitudinal-transverse phonon polaritons.

Abstract

We demonstrate how to exploit long-cell polytypes of silicon carbide to achieve strong coupling between transverse phonon polaritons and zone folded longitudinal optical phonons. The resulting quasiparticles possess hybrid longitudinal and transverse nature, allowing them to be generated through electric currents while emitting radiation to the far field. We develop a microscopic theory predicting the existence of the hybrid longitudinal-transverse excitations. We then provide their first experimental observation by tuning the monopolar resonance of a nanopillar array through the folded longitudinal optical mode, obtaining a clear spectral anti-crossing. This represents an important first step in the development of electrically pumped mid-infrared emitters.