# Dual-band coupling between nanoscale polaritons and vibrational and electronic excitations in molecules

## TL;DR

This paper demonstrates a novel nanoresonator that achieves strong coupling at both visible and mid-IR frequencies, enabling simultaneous interaction with excitons and molecular vibrations, opening new avenues in nanophotonics and quantum technologies.

## Contribution

The study introduces a dual-band polaritonic nanoresonator that simultaneously couples surface plasmon polaritons and phonon polaritons to molecular excitons and vibrations, a feat not previously achieved.

## Key findings

- Successful demonstration of dual-band strong coupling via near-field nanoscopy.
- Observation of mode splittings indicating simultaneous SPP-exciton and PhP-vibron coupling.
- Potential applications in optoelectronics and quantum information processing.

## Abstract

Strong coupling (SC) between light and matter excitations such as excitons and molecular vibrations bear intriguing potential for controlling chemical reactivity, conductivity or photoluminescence. So far, SC has been typically achieved either between mid-infrared (mid-IR) light and molecular vibrations or between visible light and excitons. Achieving SC simultaneously in both frequency bands may open unexplored pathways for manipulating material properties. Here, we introduce a polaritonic nanoresonator (formed by h-BN layers placed on Al ribbons) hosting surface plasmon polaritons (SPPs) at visible frequencies and phonon polaritons (PhPs) at mid-IR frequencies, which simultaneously couple to excitons and atomic vibration in an adjacent molecular layer (CoPc). Employing near-field optical nanoscopy, we first demonstrate the co-localization of strongly confined near-fields at both visible and mid-IR frequencies. After covering the nanoresonator structure with a layer of CoPc molecules, we observe clear mode splittings in both frequency ranges by far-field transmission spectroscopy, unambiguously revealing simultaneous SPP-exciton and PhP-vibron coupling. Dual-band SC may be exploited for manipulating the coupling between excitons and molecular vibrations in future optoelectronics, nanophotonics, and quantum information applications.

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Source: https://tomesphere.com/paper/2302.14814