Photonic Time Crystals Enable First All‑Optical Ultrafast Light Control

A team of physicists in Paris, led by Yannis Laplace at the Laboratory of Irradiated Solids (LSI), fabricated the world’s first temporal photonic crystal. The device uses micrometer‑scale gold crenellated structures above an indium‑antimony semiconductor layer and is driven by terahertz laser pulses, allowing the optical properties of light to be modulated repeatedly over time without expending energy. The breakthrough was reported in Nature and is presented as a new way to control light for telecommunications, sensors and laser technologies.

An international collaboration that also includes researchers from École Polytechnique, Collège de France and Germany’s Helmholtz‑Zentrum Dresden‑Rossendorf (HZDR) demonstrated the first all‑optical photonic time crystal. Built as a plasmonic metamaterial, the crystal’s optical reflectivity and resonance frequency can be altered on picosecond scales by terahertz‑induced surface plasmons. The work marks the first experimental realization of a material whose optical behavior can be periodically switched in time, opening avenues for ultrafast photonic devices.