Paper: 2021 Ultrastrong plasmon–phonon coupling via epsilon-near-zero nanocavities

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

Daehan Yoo, Fernando de León-Pérez, Matthew Pelton, In-Ho Lee, Daniel A. Mohr, Markus B. Raschke, Joshua D. Caldwell, Luis Martín-Moreno, Sang-Hyun Oh
Nature Photonics, 15, 125–130(2021)
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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.