Near-Field Vibrational Energy Transfer for Mid-Infrared Upconversion in Plasmonic Nanogaps
Abstract
F\"{o}rster energy transfer underpins modern photonics, yet establishing an analogous vibrational pathway in the mid-infrared (MIR) remains highly challenging, as sub-picosecond intramolecular vibrational redistribution (IVR) suppresses intermolecular coupling. Here we demonstrate vibrational donor--acceptor transfer in the MIR and subsequent upconversion to visible luminescence enabled by sub-2 nm plasmonic nanogaps. The extreme lateral field confinement in metal--molecule--metal ring cavities defined by self-assembled molecular spacers couples efficiently to in-plane molecular dipoles. Continuous-wave MIR excitation selectively populates vibrational donors, and plasmon-enhanced near-field coupling transfers this energy to nearby electronic acceptors, generating anti-Stokes visible emission under low power densities. Upconversion efficiencies exceeding are observed, limited by competition between the plasmon-mediated transfer rate and IVR. These results show that extreme plasmonic confinement can redirect molecular vibrational relaxation pathways, opening a route toward vibrational nanophotonics, intermolecular interactions for bioimaging, and room-temperature MIR detection based on molecular degrees of freedom.
Keywords
Cite
@article{arxiv.2605.19498,
title = {Near-Field Vibrational Energy Transfer for Mid-Infrared Upconversion in Plasmonic Nanogaps},
author = {Avisekh Pal and Anju Sajan and Christopher Sumner and Eman Alharbi and Wolfgang Theis and Rohit Chikkaraddy},
journal= {arXiv preprint arXiv:2605.19498},
year = {2026}
}