Researchers have developed a way to create photonic time crystals and show that these fancy man-made materials amplify the light shining on them. These discoveries are described in an article published in the journal Nature. Science AdvancesThis could lead to more efficient and reliable wireless communication and greatly improved lasers. Time crystals were first designed by Nobel laureate Frank Wilczek in 2012. Normal, familiar crystals have a repeating structural pattern in space, but in a time crystal the pattern repeats in time. Although at first some physicists doubted that time crystals could exist, recent experiments have succeeded in creating them. Last year, researchers at Aalto University’s Low Temperature Laboratory created paired time crystals that could be useful for quantum devices.

Now another team has created photonic time crystals, which are time-based versions of optical materials. The researchers created photonic time crystals that operate at microwave frequencies and demonstrated that the crystals can amplify electromagnetic waves. This capability has potential applications in a variety of technologies, including wireless communications, integrated circuits, and lasers.

Until now, research on photonic time crystals has focused on bulk materials, namely three-dimensional structures. It turned out to be an extremely difficult task, and experiments did not bypass system models without practical application. A team including researchers from Aalto University, Karlsruhe Institute of Technology (KIT) and Stanford University tried a new approach: constructing a two-dimensional photonic time crystal known as a metasurface.

“We found that reducing dimensionality from a 3D to a 2D structure greatly simplifies the application and makes it possible to actually realize photonic time crystals,” says lead author Xuchen Wang, a postdoctoral researcher at Aalto. now at KIT.

The new approach allowed the team to fabricate a photonic time crystal and experimentally test theoretical predictions about its behavior. “We have shown for the first time that photonic time crystals can amplify incoming light with a high gain,” says Wang.

“In a photonic time crystal, the photons are arranged in a repeating pattern over time. This means that the photons in the crystal are synchronized and coherent, which can lead to constructive interference and light amplification,” explains Wang. The periodic arrangement of photons also means that they can interact in a way that increases the gain.

Two-dimensional photonic time crystals have a number of potential applications. By amplifying electromagnetic waves, they can make wireless transmitters and receivers more powerful and efficient. Wang states that coating surfaces with two-dimensional photonic timing crystals can also help reduce signal attenuation, a major problem in wireless transmission. Photonic timing crystals can also simplify laser designs by eliminating the need for bulk mirrors commonly used in laser cavities.

Another application comes from the finding that two-dimensional photonic time crystals amplify not only electromagnetic waves crashing into them in empty space, but also waves propagating along a surface. Surface waves are used for communication between electronic components in integrated circuits. “As the surface wave propagates, the material is lost and the signal strength decreases. With two-dimensional photonic time crystals integrated into the system, the surface wave can be amplified and communication efficiency can be improved,” says Wang.