Researchers develop ‘quantum’ method to detect infrared light at room temperature

31 Aug 2023

Universities of Birmingham and Cambridge claim “breakthrough” in understanding of chemical, biological molecule processes.

Scientists from the University of Birmingham and the University of Cambridge, both in the UK, have developed a new method for detecting mid-infrared (MIR) light at room temperature using quantum systems.

The research, published in Nature Photonics, was conducted at the Cavendish Laboratory at the University of Cambridge and is said to “mark a significant breakthrough in the ability for scientists to gain insight into the working of chemical and biological molecules.”

In the new method using quantum systems, the team converted low-energy MIR photons into high-energy visible photons using molecular emitters. The innovation has the capability to help scientists detect MIR radiation and perform spectroscopy at a single-molecule level, at room temperature.

Dr Rohit Chikkaraddy, an Assistant Professor at the University of Birmingham, and lead author, explained, “The bonds that maintain the distance between atoms in molecules can vibrate like springs, and these vibrations resonate at very high frequencies.

“Modern detectors rely on cooled semiconductor devices that are energy-intensive and bulky, but our research presents a new and exciting way to detect this light at room temperature,” he added.

Interactive states

The new approach is called MIR Vibrationally-Assisted Luminescence (MIRVAL), and uses molecules that have the capability of being both MIR and visible light. The team was able to assemble the molecular emitters into a very small plasmonic cavity which was resonant in both the MIR and visible ranges.

They further engineered it so that the molecular vibrational states and electronic states were able to interact, resulting in an efficient transduction of MIR light into enhanced visible luminescence.

Dr Chikkaraddy continued: “The most challenging aspect was to bring together three widely different length scales – the visible wavelength which are hundreds of nanometers, molecular vibrations which are less than a nanometer, and the mid-infrared wavelengths which are ten thousand nanometers – into a single platform and combine them effectively.”

Through the creation of picocavities, incredibly small cavities that trap light and are formed by single-atom defects on the metallic facets, the researchers were able to achieve extreme light confinement volume below one cubic nanometer. This meant the team could confine MIR light all the way down to the scale of a single molecule.

This breakthrough has the ability to deepen understanding of complex systems, and opens the gateway to infrared-active molecular vibrations, which are typically inaccessible at the single-molecule level. But MIRVAL could prove beneficial in a number of fields, byeond pure scientific research.

He concluded, “MIRVAL could have a number of uses such as real-time gas sensing, medical diagnostics, astronomical surveys and quantum communication, as we can now see the vibrational fingerprint of individual molecules at MIR frequencies.”