An Ultrafast Light Switch Paves The Way For Optical Computing And Data Storage

A global team of physicists from Ludwig-Maximilians-Universität München (LMU) and Monash University have developed an ultrafast optical switch that can turn light interactions on and off within trillionths of a second, a breakthrough that could revolutionise optical computing, secure communications and quantum technologies.

The study, published today in Nature, describes a new method for controlling how nanostructures interact with light using finely tuned laser pulses. It’s the first time researchers have been able to switch optical resonances, the ‘trapped’ light used in nanoscale circuits, completely on or off, rather than just tweaking them.

Professor Stefan Maier, Head of the School of Physics and Astronomy at Monash University, was one of the senior collaborators on the study, conducted at Nanoinstitute Munich, where he built up a major research initiative in nanophotonics and nanotechnology from 2018 to 2022.

He said the ability to actively control resonances at this scale and speed marks a fundamental shift in what’s possible with photonics. “This work represents a real turning point in how we can approach the complex problem of making an ultrafast optical switch,” said Professor Maier. “We’ve gone from being able to nudge these light-matter interactions, to now being able to switch them from a state where the nanostructures are almost completely invisible to light to a state where we can control the attenuation of light of a particular colour to a very high degree.”

The key lies in asymmetric metasurfaces, ultra-thin materials made of nanostructures that manipulate light in precise ways. In this design, pairs of tiny silicon rods are engineered so that their optical responses cancel each other out at a specific wavelength. This makes the structure ‘invisible’ to light, the resonance is off. “This idea of designing metasurfaces that are asymmetric in their geometry but appear symmetric in terms of the photonic response is the central novelty of our work,” said Andreas Tittl, Professor for Experimental Physics at LMU. Hitting the metasurface with an ultrafast laser pulse disrupts this balance, and the structure couples with light and becomes visible — the resonance is switched on.

Using time-resolved spectroscopy, the researchers showed this switch happens in just 200 femtoseconds (a femtosecond is one quadrillionth of a second). They demonstrated four distinct switching modes: turning a resonance on, turning it off, and precisely sharpening or broadening the light response.

“It opens up real possibilities for high-speed, low-loss optical computing and communications and for advancing quantum technologies where light control is critical.”, Professor Maier said.

The research was led by Professor Andreas Tittl and his team at LMU, who designed and fabricated the metasurfaces and conducted the experiments. Professor Maier contributed expertise in nanophotonics and light–matter interaction and is particularly delighted that Andreas Aigner, one of the lead authors of the work next to Thomas Possmayer, is a previous Masters student of his time in Munich.

“It’s a great example of what international collaboration can achieve,” Professor Maier said. The breakthrough may also help unlock the next generation of quantum technologies, including applications such as ‘time crystals’, exotic states of matter theorised to operate outside classical time constraints.

“I’m glad that we have recently received funding from the Australian Research Council to continue our collaborations with the Munich team, applying our novel approaches for nanoscale optical resonators to developing new ways of energy generation”, concludes Professor Maier.