Scientists have created a new type of crystal that can control light not just by its physical structure, but also by changing its properties over time. Imagine a mirror that changes as light bounces off it. This is a major step forward from previous technology, which could only bend light using different materials.
The international research team, including scientists from École Polytechnique and Germany's Helmholtz-Zentrum Dresden-Zentrum (HZDR), published their findings in the journal Nature. This new "photonic time crystal" can change how it interacts with light much faster than previously thought possible. This is especially important for the terahertz frequency band, a range of waves between microwaves and infrared light that has been difficult for engineers to work with.
Yannis Laplace, a professor at École Polytechnique, explained that this technology could help bridge the gap between electronic and optical devices. Unlike standard photonic crystals, which have a fixed physical structure, this new crystal has a repeating pattern in time. This allows its light-controlling abilities to change at incredibly high speeds, as fast as one trillionth of a second.
The crystal was built using gold ridges and a special semiconductor. When energy hits the semiconductor, it creates waves that interact with light. The gold ridges help trap the light. To test it, the researchers used a powerful terahertz radiation instrument at HZDR. The results showed that the crystal could change its properties so dramatically that it altered the wavelength of light passing through it, while also reducing light loss.
This breakthrough could lead to faster optical computers and new communication systems. The team plans to further improve the crystal's ability to control light, potentially leading to new types of lasers.