A new method makes infrared light visible at room temperature

Quantum-derived results may greatly simplify the detection of mid-infrared light at room temperatures.

Researchers from the University of Birmingham and the University of Cambridge have revealed a pioneering technique that allows room-temperature mid-infrared (MIR) light to be detected through the use of quantum systems.

Posted in Nature photonicsThis study was conducted at the Cavendish Laboratory in Cambridge and represents a major advance in scientists’ ability to gain insight into the workings of chemical and biological molecules.

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

Dr. Rohit Shekaradi, Assistant Professor University of BirminghamThe lead author of the study explained: “The bonds that keep the distance between atoms in molecules can vibrate like springs, and these vibrations resonate at very high frequencies. These springs can be triggered by mid-infrared light which is not visible to the human eye. At room temperature, these springs are in random motion which means that the main challenge in detecting mid-infrared light is avoiding this thermal noise. Modern detectors rely on bulky, power-hungry semiconductor devices, but our research offers an exciting new way to detect this light at room temperature.

The new approach is called MIR Vibrationally-Assisted Luminescent (MIRVAL) and uses molecules that have the potential to be MIR and visible light. The team was able to pack the molecular emitters into a very small plasmonic cavity that resonated in both the MIR and visible bands. They also designed it so that the molecular vibrational states and electronic states are able to interact, resulting in efficient transfer of MIR light to enhanced visible fluorescence.

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

By creating picocavity cavities, incredibly small light-trapping cavities made up of single moleculescorn With defects in the metallic sides, the researchers were able to achieve an extreme light-trapping volume of less than one cubic nanometer. This means the team can confine MIR light all the way down to the size of a single molecule.

This achievement has the potential to deepen understanding of complex systems, and opens the gate to infrared-energy molecular vibrations, which are normally inaccessible at the single-molecule level. But MERVAL could be useful in a number of areas, beyond purely scientific research.

Dr Chikaradi 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 signature of individual molecules at MIR frequencies. The ability to detect MIR at room temperature means that it is much easier to explore these applications and further research in this area. With further advances, this new method will not only find its way into the practical devices that will shape the future of MIR technologies, but will also unlock the ability to coherently manipulate the complex interaction between ‘springball’ atoms in molecular quantum systems.

Reference: “Single-molecule mid-infrared spectroscopy and detection by vibration-assisted scintillation” by Rohit Chikaradi, Rakesh Arul, and Lucas A. Jacob, and Jeremy J. Bomberg, Aug. 28, 2023, Available Here. Nature photonics.
doi: 10.1038/s41566-023-01263-4