ÖPG-CMD Joint Meeting 2026

Near-Field Vibrational Energy Transfer and Upconversion in Plasmonic NanoCavities

Sep 24, 2026, 11:30 AM

30m

HS 15.06 (University of Graz)

4) Invited talk M18 - Light-driven Processes at Interfaces Mini-Colloquium

Speaker

Rohit Chikkaraddy (University of Birmingham, UK)

Description

Near-field interactions provide a powerful route to mediate energy transfer between otherwise weakly coupled excitations. Here we demonstrate mid-infrared (MIR) donor–acceptor energy transfer and subsequent upconversion to visible emission enabled by ultrasmall plasmonic nanogap cavities [1,2]. The platform consists of metal–insulator–metal (MIM) resonators with gap sizes below 2 nm that producing extreme local density of optical states and strong light–matter coupling.

Within these cavities, molecular vibrations excited by continuous-wave MIR illumination act as energy donors. The tightly confined plasmonic near field couples these vibrational excitations to nearby electronic acceptors, enabling non-radiative vibrational–electronic energy transfer analogous to Förster-type processes but operating at vibrational frequencies. This mechanism circumvents the ultrafast vibrational relaxation that normally limits the observation of coherent vibrational energy flow in the MIR. The transferred energy is subsequently released as anti-Stokes visible emission, providing a direct optical readout of MIR excitation. Experiments reveal measurable upconversion efficiencies under low-power continuous-wave excitation, demonstrating that nanoscale optical confinement can bridge the large energy mismatch between MIR vibrations and visible electronic transitions. The results demonstrate a new regime of near-field mediated energy conversion where vibrational excitations act as donors in a plasmonically enhanced transfer process.

Beyond spectroscopy, this approach may enable room-temperature MIR detection, nanoscale sensing of molecular vibrations, and hybrid optomechanical platforms where molecular vibrations drive electronic or photonic responses.

References:

1. A. Pal et al. Near-Field Vibrational Energy Transfer and Upconversion in Plasmonic Nanocavities. In review. (2026).

2. R. Chikkaraddy et al. Single-molecule mid-infrared spectroscopy and detection through vibrationally assisted luminescence. Nature Photonics* 17, 865-871 (2023).