Colour-changing magnifying glass gives clear view of infrared light:
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 specialised detectors are chilled to very low temperatures, which is both expensive and energy-intensive.
Now researchers led by the University of Cambridge have demonstrated a new concept in detecting infrared light, showing how to convert it into visible light, which is easily detected.
In collaboration with colleagues from the UK, Spain and Belgium, the team used a single layer of molecules to absorb the mid-infrared light inside their vibrating chemical bonds. These shaking molecules can donate their energy to visible light that they encounter, ‘upconverting’ it to emissions closer to the blue end of the spectrum, which can then be detected by modern visible-light cameras.
The results, reported in the journal 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 single molecular layers between a mirror and tiny chunks of gold, only possible with ‘meta-materials’ that can twist and squeeze light into volumes a billion times smaller than a human hair.
“Trapping these different colours 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 Dr Rohit Chikkaraddy from the Cavendish Laboratory, who devised the experiments based on his simulations of light in these building blocks.
Journal Reference:
Angelos Xomalis, Xuezhi Zheng, Rohit Chikkaraddy, et al. Detecting mid-infrared light by molecular frequency upconversion in dual-wavelength nanoantennas, Science 2021; 374 (6572): 1268 (DOI: 10.1126/science.abk2593)
(Score: 2, Informative) by coolgopher on Thursday December 02 2021, @11:17PM (1 child)
(Score: 2) by Kymation on Thursday December 02 2021, @11:36PM
his 2021; 374 (6572): 1268 simulations of light in these building blocks.
(Score: 2) by Rosco P. Coltrane on Friday December 03 2021, @12:21AM (5 children)
If you have to chill current, direct infrared light sensors so they don't see their own infrared light, would you not have to chill the magic IR-to-visible light converter so it doesn't convert its own IR radiations too? It's the same problem isn't it?
(Score: 1) by dioxide on Friday December 03 2021, @01:16AM
No, this adds energy to photons passing through, doesn't emit its own. Anything the sensor added would continue on in the other direction.
(Score: 2) by mhajicek on Friday December 03 2021, @06:54AM
I have an infrared camera on my phone. Works fine.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 3, Insightful) by FatPhil on Friday December 03 2021, @08:15AM
However, the summary is confusing: "These shaking molecules can donate their energy to visible light that they encounter, ‘upconverting’ it to emissions closer to the blue end of the spectrum". Visible light already was visible, upshifting visible light towards the blue end of the spectrum is not making IR visible. And given that A+B = B+A, one might say that the only thing that's been made visible is the phonons in the material, once stimulated by the visible light. So your point is a valid request for clarification.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 1, Informative) by Anonymous Coward on Friday December 03 2021, @12:08PM (1 child)
When people hear "infrared", they always assume it is thermal infrared, also known as "longwave" infrared. This is MWIR, or mid-wave infrared, which like short-wave infrared (SWIR), does not have a strong thermal component. So there are two different issues here. The relatively inexpensive IR sensors for cell phones use microbolometers for pixels and are thermal IR sensors. The result of the effect that you are talking about is that there is an overall DC-level to the signal, which is why the output of those sensors look so noisy, but signals that are above that background level you can see. Those images would look a lot better if you could cool down the optics. MWIR sensors are less affected by thermal effects, or at least the temperatures that the optics would normally run at do not produce as many photons in the MWIR range as in the LWIR to have the effect you mention, so you don't need to really cool the optics, but the tradeoff is that MWIR sensors are not inexpensive (there isn't yet an inexpensive material to make them for your cell phones at reasonable prices).
(Score: 1, Interesting) by Anonymous Coward on Friday December 03 2021, @01:06PM
The comments above stand, but as someone else pointed out, the article title says MWIR, but the abstract says ten microns, which is smack in the middle of the LWIR band. I tried to look at the actual paper itself to see if it really was talking about MWIR, but I don't have access to the paper. I find it hard to believe that such a mistake in terms would make it through the Science review process, but there it is-I don't have access to see otherwise.
(Score: 4, Informative) by ChrisMaple on Friday December 03 2021, @01:06AM (2 children)
In my understanding, 10 micron is far infrared, not middle.
This sounds like a very nice piece of science with practical applications.
(Score: 2) by FatPhil on Friday December 03 2021, @08:16AM (1 child)
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 0) by Anonymous Coward on Monday December 06 2021, @08:49PM
So will the sensor companies that are trying to get buy-in from self-driving car companies--a potentially huge market, IF you can break in. But the car companies are tough customers with high reliability specs in addition to low prices.