How light is absorbed in a thin layer of material

An der TU Wien und der Hebräischen Universität Jerusalem wurde eine „Lichtfalle" entwickelt, in der ein Lichtstrahl sich selbst am Entkommen hindert. Dadurch lässt sich Licht perfekt absorbieren. Das ist entscheidend, um es effizient nutzen zu können. Schwierig ist das aber, wenn die Absorption in einer dünnen Materialschicht stattfinden soll, die normalerweise einen Großteil des Lichts durchlässt.

Now, research teams from the Vienna University of Technology and The Hebrew University of Jerusalem have found a solution. They built a "light trap" around the thin layer using mirrors and lenses, in which the light beam is steered in a circle and then superimposed on itself. In this way the beam of light blocks itself and can no longer leave the system. As a result, the light has no choice but to be absorbed by the thin layer. The idea was developed by Prof. Ori Katz of The Hebrew University of Jerusalem and developed in cooperation with Prof. Stefan Rotter of the Vienna University of Technology.

“Absorbing light is easy when it hits a solid object," says Prof. Stefan Rotter from the Institute of Theoretical Physics at the Vienna University of Technology. "But in many technical applications, you only have a thin layer of material available, and you want the light to be absorbed exactly in this layer." Prof. Ori Katz of The Hebrew University of Jerusalem adds: “In our approach, we are able to cancel all back-reflections by wave interference.” For example, the presented mechanism could be well suited to optimally feed light waves from weak light sources (such as distant stars) into a detector.

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