In nanophotonics, tiny structures are used to control light at the nanoscale and render it useful for technological applications. A key element here is optical resonators, which trap and amplify light of a certain color (wavelength). Previous methods of controlling these resonances were more like a dimmer switch: You could weaken the resonance or slightly shift its color. However, genuine on-and-off switching was not possible, as the resonators always remain fundamentally coupled with the light. A team led by Andreas Tittl, Professor of Experimental Physics at LMU, has now achieved precisely this breakthrough together with partners from Monash University in Australia. As the researchers report in the journal Nature, they have developed a new method for controlling the coupling between nanoresonators and light in a targeted manner on ultrafast timescales. In this way, a resonance can be created from nothing within a few picoseconds or made to vanish completely again.