Ultrastrong plasmon–phonon coupling via epsilon-near-zero nanocavities
Reviews and Highlights | Quantum Science | Molecular and Soft-matter | Ultrafast Nano-optics and Nanophotonics | Mineralogy and Geochemistry |
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Daehan Yoo, Fernando de León-Pérez, Matthew Pelton, In-Ho Lee, Daniel A. Mohr, Markus B. Raschke, Joshua D. Caldwell, Luis Martín-Moreno, and Sang-Hyun Oh
Nature Photonics 15, 125 (2021).
DOI PDF
![](https://nano-optics.colorado.edu/wp-content/uploads/2021/01/Yoo_NaturePhotonics_20_fig.png)
Vibrational ultrastrong coupling, where the light–matter coupling strength is comparable to the vibrational frequency of molecules, presents new opportunities to probe the interactions between molecules and zero-point fluctuations, harness cavity-modified chemical reactions and develop novel devices in the mid-infrared spectral range. Here we use epsilon-near-zero nanocavities filled with a model polar medium (SiO2) to demonstrate ultrastrong coupling between phonons and gap plasmons. We present classical and quantum-mechanical models to quantitatively describe the observed plasmon–phonon ultrastrong coupling phenomena and demonstrate a modal splitting of up to 50% of the resonant frequency (normalized coupling strength η > 0.25). Our wafer-scale nanocavity platform will enable a broad range of vibrational transitions to be harnessed for ultrastrong coupling applications.