A maze of mirrors and lenses turns any material into a highly light-absorbing material. It can be used to detect dim light, or to charge equipment with light from afar.
Any material can absorb light perfectly if you place it in a special maze of mirrors and lenses. This technique could be used to detect faint starlight, or to charge distant devices with lasers.
mirror maze
optician Ori Katz of the imaging lab at the Hebrew University of Jerusalem and his colleagues have created a near-perfect light absorber by using a so-called anti laser build.
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In a laser, the light bounces between mirrors until it is amplified enough to leave the device in a concentrated beam of light. In a anti lasersays co-author and professor of theoretical physics Stefan Rotter from the Vienna University of Technology, the light enters the device and then becomes entangled in a series of reflections.
Captured light
The researchers built their anti-laser by sending red light through a meter-long maze of carefully arranged lenses, mirrors and a piece of tinted glass. The glass is the intended light absorber. The light bounces off the mirrors and interacts with images of itself created by the lenses. As a result, the light beam is deflected every time it comes close to the exit.
Before the glass was placed in the device, it absorbed 15 percent of the light. The whole device, on the other hand, absorbs about 98 percent. The light absorption of the glass is thus more than six times greater.
Astronomy
Professor of mechanical engineering Sahin Ozdemir of the American Pennsylvania State University says that similar devices so far only perfectly absorb light waves of a specific shape, and then only at a certain angle. The new anti-laser works for all waveforms and angles, so it’s much more practical, he says.
Ozdemir says the method could potentially be used to collect light from very faint stars. It could also be used to efficiently charge devices at a great distance with the energy of the absorbed light. For example, you could charge a drone with a laser beam from a distance, says Katz.
From lab table to chip
Associate Professor of Optics Yidong Chong from Nanyang Technological University in Singapore, however, says the device still needs to be scaled down and integrated on a chip before it can be built into practical devices. Currently, the maze of instruments stretches across a lab bench, which is larger than many devices such as drones.
Rotter says the team wants to make the device not only smaller but more versatile, by absorbing light of multiple colors at once.