Phys.org August 28, 2023
Existing technologies for room-temperature detection of molecular vibrations in the mid-infrared rely on cooled semiconductor detectors because of thermal noise limitations. Researchers in the UK exploited molecular emitters possessing both MIR and visible transitions from molecular vibrations and electronic states, coupled through Franck–Condon factors. By assembling molecules into a plasmonic nanocavity resonant at both MIR and visible wavelengths, and optically pumping them below the electronic absorption band, they showed transduction of MIR light. The upconverted signal was observed as enhanced visible luminescence. Combining visible luminescence with enhanced rates of vibrational pumping gave transduction efficiencies of >10%. MIR frequency-dependent upconversion gave the vibrational signatures of molecules assembled in the nanocavity. Transient picocavity formation further confined MIR light down to the single-molecule level. This allowed them to demonstrate single-molecule MIR detection and spectroscopy that was inaccessible to any previous detector…read more. Open Access TECHNICAL ARTICLE
MIR vibrationally assisted luminescence. Credit: Nature Photonics, 28 August 2023Â