When a team of physicists in Paris fabricated the world’s first temporal photonic crystal, they added a new dimension to humanity’s quest to control light: time. From lighting our homes to advanced fiber optics and lasers, humans have long worked to control light, and now researchers say that can be achieved in a fourth dimension.
Yannis Laplace led the team at the Laboratory of Irradiated Solids (LSI) in demonstrating the temporal photonic crystal, with the help of other European institutions, which was revealed in a recent paper published in Nature.
As light hits the crystal, a terahertz electromagnetic wave rapidly modulates its optical properties, producing a device that controls light over time without expending energy.
Crystal Power
Controlling the properties of light for applications in telecommunications, sensors, and light sources is an active research field and is often reliant on crystals. In technical terms, a crystal is simply a regularly and periodically organized system. While we primarily think of translucent, shining crystals, they can be constructed of other forms of matter, such as gas or liquids, so long as their atoms arrange into regular, well-defined intervals.
How atoms arrange to form crystals grants their electrons and the photons they emit unique properties, including color and energy. Targeting photons specifically became an interest of scientists in the 1980s, with the development of photonic crystals, whose alternating materials each had unique effects on photons. These photonics gave rise to modern lasers, optical fibers, and photodetectors, technologies that have advanced considerably in recent decades.
Into the Time Dimension
In the last decade, researchers have experimented with a new kind of crystal: the time crystal. They are comprised of a unique form of matter in which particles repeat a continuous sequence—not just in the three physical dimensions, but also in time, without expending any energy.
The LSI team sought to combine photonic crystals with time crystals to develop a temporal photonic crystal that would control a light-matter interaction by alternating over time. Their work represents the first time such an idea has moved from the theoretical realm into the physical.
The device the researchers constructed operates in the high terahertz range, pushing light to oscillate 1000 billion times a second. It consists of micrometer-scale gold structures, shaped like battlements, leaving open cavities separated from an indium-antimony semiconductor by an insulating layer. The cavities between the gold structures trap light photons.
Testing a Temporal Photonic Crystal
To demonstrate their device in the real world, the LSI team bombarded it with terahertz laser pulses and recorded the material’s optical properties, modulating light over time. The effect was incredibly powerful, creating a strong modulation that alternated one billionth of a billionth of a second.
At the semiconductor layer, the researchers observed electrons forming from the light waves in what are called “surface plasmons,” oscillating with their effective mass. The greater their speed, the heavier these electrons become, producing the device’s optical modulations.
Beyond this observed phenomenon, the researchers suspect other interesting conditions may be occurring within the crystal. Some indirect evidence suggests that photons trapped inside the structure are amplified, although presently no direct observations have confirmed this. The team is continuing with experiments in hopes of eventually capturing this photon trapping phenomenon.
Laplace and his colleagues see these unique time crystals as eventually being a pathway toward the creation of terahertz-scale light sources and detectors, which would fit between those of electronics and visible light frequencies.
The paper, “Plasmonic Metamaterial Time Crystal,” appeared in Nature on July 29, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org.