A team of researchers led by Andreas Tittl from LMU has achieved a groundbreaking breakthrough in nanophotonics, enabling ultrafast light switching. The innovation involves asymmetric silicon metasurfaces, which are tiny structures used to control light at the nanoscale.
Previous methods were limited to weakening or slightly shifting the resonance, but not turning it on and off completely. However, the researchers have developed a new method that allows for precise control over the coupling between nanoresonators and light on ultrafast timescales.
The key lies in the design of metasurfaces, which incorporate specially arranged nanostructures. The researchers created structures with two tiny silicon rods with different geometric shapes, deliberately making them asymmetrical. This asymmetry enables the switching procedure by responding differently to light of various wavelengths and polarizations.
The team exploited this by exciting one of the nano-rods with an ultrafast laser pulse, temporarily altering its optical characteristics and causing the resonance to couple with the light. The researchers can generate a resonance at will, quench it, or precisely adjust its bandwidth as if using a control knob.
Their experiment showed a huge increase in coupling with light, while minimizing unwanted energy losses in the material itself. This was the definitive proof that their approach of temporal symmetry breaking works precisely as predicted.
The breakthrough has significant implications for active nanophotonics, enabling the creation of low-loss, purely optical switches for telecommunications or optical data processing. It also opens up new avenues for research into complex quantum phenomena such as time crystals.
Source: https://phys.org/news/2025-08-ultrafast-asymmetric-silicon-metasurfaces-nanophotonics.html