By trapping light in tiny crevices of gold, researchers have coaxed molecules to convert invisible infrared light into visible light, creating new low-cost detectors for sensing. Image: NanoPhotonics Cambridge/Ermanno Miele, Jeremy Baumberg.Detecting light beyond the visible red range of our eyes is hard to do, because infrared light carries so little energy compared to ambient heat at room temperature. This obscures infrared light unless specialized detectors are chilled to very low temperatures, which is both expensive and energy intensive.
Now a team led by researchers at the University of Cambridge in the UK have demonstrated a new concept for detecting infrared light, based on converting it into visible light, which is easily detected.
In collaboration with colleagues from the UK, Spain and Belgium, the team utilized a single layer of molecules that can absorb mid-infrared light inside their vibrating chemical bonds. These shaking molecules then donate their energy to any visible light they encounter, ‘upconverting’ it to emissions closer to the blue end of the spectrum, which can be detected by modern visible-light cameras.
The results, reported a paper in Science, open up new low-cost ways to sense contaminants, track cancers, check gas mixtures and remotely sense the outer universe.
The challenge faced by the researchers was to make sure the quaking molecules met the visible light quickly enough. “This meant we had to trap light really tightly around the molecules, by squeezing it into crevices surrounded by gold,” said first author Angelos Xomalis from Cambridge’s Cavendish Laboratory.
The researchers devised a way to sandwich the single molecular layers between a mirror and tiny crevices of gold. This produces a metamaterial that can twist and squeeze light into volumes a billion times smaller than a human hair.
“Trapping these different colors of light at the same time was hard, but we wanted to find a way that wouldn’t be expensive and could easily produce practical devices,” said co-author Rohit Chikkaraddy from the Cavendish Laboratory, who devised the experiments based on his simulations of light in these building blocks.
“It’s like listening to slow-rippling earthquake waves by colliding them with a violin string to get a high whistle that’s easy to hear, and without breaking the violin,” said Jeremy Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research.
The researchers emphasize that while it is early days, there are many ways to optimize the performance of these inexpensive molecular detectors, which can then access rich information in this window of the spectrum. From astronomical observations of galactic structures to sensing human hormones or early signs of invasive cancers, many technologies can benefit from this new detector advance.
This story is adapted from material from the University of Cambridge, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.