Episode 10: Photonic time crystal amplifies electromagnetic signal

In this podcast episode, MRS Bulletin’s Sophia Chen interviews Xuchen Wang of Karlsruhe Institute of Technology in Germany about his work on photonic time crystals. While conventional crystals are composed of repeating unit cells in space, such as eight carbon atoms arranged in a cube to form a diamond, a photonic time crystal has a structure that repeats in time. Theoretical predictions of photonic time crystals referred to designs consisting of three-dimensional metamaterials whose properties are difficult to manipulate in the laboratory. Wang and his collaborators have adapted the three-dimensional time crystal design to a two-dimensional metasurface. They arranged copper structures on the surface, using conventional printed circuit board technology. The structures look like a forest of mushrooms where the researchers placed a variable capacitor, known as a varactor, between each mushroom. To create the device, the researchers apply changing external voltages to the varactor, modulating the material’s electromagnetic properties in time. Wang then confirmed experimentally that this device amplified microwave signals that he sent across its surface. This work was published in a recent issue of Science Advances.