A maze of mirrors and lenses turns any material into a highly efficient light absorber and could be used to detect dim light or charge distant devices with light.
25 Aug 2022
Inserting any material into a special maze of mirrors and lenses can make it perfectly absorb light. This approach could be used to detect faint light from stars or to charge distant devices with lasers.
ori katz at the Hebrew University of Jerusalem in Israel and colleagues created a nearly perfect light absorber by building an “anti-laser.”
In a laser, light bounces between mirrors until it is amplified enough to exit the device in a focused beam. In an “anti-laser”, says co-author Stephen Rother at the Vienna University of Technology in Austria, light enters the device and then gets stuck in an inescapable series of bounces inside it.
The researchers achieved this by directing red light through a meter-long maze of carefully arranged lenses, mirrors, and a piece of polarized glass. Glass was the intended light absorber. The light reflected off the mirrors and interacted with the images of itself created by the lenses in such a way that it was redirected each time it came closer to exiting the device.
Before it was inserted into the device, the glass could absorb 15 percent of light. The entire device, by contrast, absorbed about 98 percent of the incoming light, effectively increasing the glass’s light absorption by more than six times.
Sahin Ozdemir at Pennsylvania State University says that, previously, similar devices perfectly absorbed only specific light waveforms and only when illuminated at particular angles. The new “anti-laser” works for all shapes and angles, so it’s much more practical, he says.
Ozdemir says the method could be used to collect light from very faint stars. It could also be used to efficiently charge larger devices with absorbed light energy, such as charging a drone by hitting it with a laser from a distance, says Katz.
Nevertheless, yidong chong at Nanyang Technological University in Singapore says the device may have to be miniaturized and integrated on a chip before it can be incorporated into useful devices. Currently, the labyrinth of instruments is spread out on a lab bench, making it larger than some devices like drones and vulnerable to accidental tipping of lenses or mirrors.
Rotter says that in addition to making the device smaller, the team wants to further increase its versatility by making it absorb light of many colors simultaneously almost perfectly.
Magazine Reference: Sciences, DOI: 10.1126/science.abq8103
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