pte20220825039 Environment/Energy, Research/Development
Lenses and mirrors prevent the beam from escaping – reflections are canceled by wave interference
Light: Researchers deliberately hold it in (Photo: pixabay.com, geralt)
Vienna/Jerusalem (pte039/25.08.2022/20:00) –
A very special beam of light prevents itself from leaving the room it “entered”. Researchers at the Vienna University of Technology (TU Wien) have the perfect optical trap http://tuwien.at The Hebrew University of Jerusalem http://en.huji.ac.il/en advanced. The trap could play an important role in the future supply of electric power to the world.
Thin layers stand across
Both in photosynthesis and in the photovoltaic system: if you want to use light efficiently, you have to absorb it as fully as possible. However, this is difficult if the absorption occurs in a thin layer of the material that normally allows a large portion of the light to pass through. Researchers in Austria and Israel solved the problem by arranging mirrors and lenses around a thin film in which light is captured, which directs the light beam in a circle. In the end, it interferes with itself in such a way that it prevents itself and cannot get out of the system.
So the light has no choice but to be absorbed by the thin film – there is no other way out. This sorption-enhanced method, now presented in the journal Science, is the result of a successful collaboration between two teams: The idea was proposed by physics professor Uri Katz of the Hebrew University of Jerusalem and developed with Stefan Reuter of Vienna University of Technology. The experimental field was in Jerusalem, and the theoretical accounts came from Vienna.
More research is required
“It’s easy to absorb light when it hits a hard object, like a thick black wool sweater. But in many technical applications you only have a thin layer of material and you want the light to be absorbed in exactly that layer,” Rotter says. To date there have been attempts to improve the absorption of the material: for example, the material is placed between two mirrors. Light bounces back and forth between the two mirrors, passing through the material each time, giving it a greater chance of being absorbed.
However, the mirrors used in the process cannot be perfect – one of them must be partially transparent, otherwise the light will not be able to penetrate the area between the two mirrors at all. However, this also means that when light hits this partially transparent mirror, part of it is lost. To prevent exactly this, the researchers used the wave properties of light. “With our method, we can cancel out all reflections caused by wave interference,” Katz says. In order to be able to use the photovoltaic trap practically, for example to generate higher efficiency solar energy, research and development work is still necessary.
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