Space-time crystals, an important step toward new optical materials
December 13, 2024

Space-time crystals, an important step toward new optical materials

Photonic space-time crystals are materials that can improve the performance and efficiency of wireless communications or laser technology. They feature periodic arrangements of specialized materials in three dimensions and time, enabling precise control of the properties of light. Scientists from Karlsruhe Institute of Technology (KIT), in collaboration with partners from Aalto University, the University of Eastern Finland and China’s Harbin Engineering University, demonstrate how this four-dimensional material can be used in practical applications. They published their results Nature Photonics.

Photonic time crystals are composed of materials whose spatial composition is uniform but whose properties change periodically with time. Through this periodic change, the spectral components of light can be modulated and amplified as needed—a key function in optical information processing. “This gives us new degrees of freedom, but also creates a lot of challenges,” says Professor Karsten Rockerstuhl from the Institute for Theoretical Solid State Physics and Nanotechnology Research at Karlsruhe Institute of Technology Place. “This research paves the way for the use of these materials in information processing systems capable of using and amplifying light of any frequency.”

One step closer to four-dimensional photonic crystals

The key parameter of a photonic time crystal is its band gap in momentum space. Momentum is a measure of the direction in which light travels. The band gap specifies the direction in which light must travel to be amplified; the wider the band gap, the greater the magnification. Puneet Garg, one of the two lead authors of the study, explains: “Previously, we had to enforce periodic changes in material properties, such as refractive index, to achieve a wide frequency gap. Only then could light be Enlarge. “This was a huge challenge because of the limited options for most materials. “

The researchers’ solution involves combining photonic time crystals with additional spatial structure. They created “photonic space-time crystals” by integrating photonic time crystals made of silicon spheres that “capture” and hold light for longer periods of time than before. The light then responds better to periodic changes in the material’s properties. “We are talking about resonances that enhance the interaction between light and matter,” said Xuchen Wang, another lead author. “In this optimally tuned system, the band gap extends almost to the entire momentum space, which means that regardless of Light can be amplified regardless of its propagation direction. This may be a key missing step in the practical application of this new optical material.

“We are very excited about this breakthrough in the field of photonic materials, and we look forward to seeing the long-term impact of our research. The enormous potential of modern optical materials research can now be realized,” Rockstuhl said. “This idea is not limited to optics and photonics; it can be applied to a variety of physical systems and has the potential to inspire new research in other fields.”

This research project is conducted at the cooperative research center “Wave Phenomenon: Analysis and Numerical”, funded by the German Research Foundation (DFG), and belongs to the information research field of the Helmholtz Association.

2024-12-09 17:27:43

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