The coupled quantum cascade laser (electron microscope picture). Energy is supplied via the two wires. Credit: Abdruck honorarfrei, Copyright: TU Wien
At the Vienna University of Technology a system of coupled lasers has been created which exhibits truly paradoxical behaviour: An increase in energy supply switches the lasers off, reducing the energy can switch them on.
Sound waves fade, water waves ebb, light waves are dissipated by a wall. The absorption of waves is a very common phenomenon. But only recently have physicists realized that amazing new possibilities are opened up, when this energy loss, rather than being seen as an annoying nuisance, is actually considered a desired effect. At the Vienna University of Technology, a system of two coupled lasers has been created, in which wave dissipation leads to a behaviour completely contrary to intuition: additional energy can switch it off; a reduction of energy may switch it on. This way, logical circuits can be built using light. The experiment has now been presented in the journal Nature Communications.