Researchers design ‘first, realistic’ photonic time crystals

13 Nov 2024

Devices exponentially amplify light, promising novel amplifiers, sensors, and lasers.

An international research team has for the first time designed realistic photonic time crystals – materials that exponentially amplify light. The achievement offers several possibilities across fields such as communication, imaging, and sensing by enabling faster and more compact lasers, sensors, and other optical devices.

Assistant Professor Viktar Asadchy from research partner Aalto University, Finland, commented, “This work could lead to the first experimental realization of photonic time crystals, propelling them into practical applications and potentially transforming industries. From high-efficiency light amplifiers and advanced sensors to innovative laser technologies, this research challenges the boundaries of how we can control the light-matter interaction.”

The work is described this week in Nature Photonics.

Photonic time crystals represent a unique class of optical materials, states the Aalto announcement: “Unlike traditional crystals, which have spatially repeating structures, photonic time crystals remain uniform in space but exhibit a periodic oscillation in time. This distinctive quality creates momentum band gaps, or unusual states where light pauses inside the crystal while its intensity grows exponentially over time.”

“Challenging conventional understanding of optics”

The university explains: “To grasp the peculiarity of light's interaction within a photonic time crystal, consider light traversing a medium that switches between air and water quadrillions of times per second – a remarkable phenomenon that challenges our conventional understanding of optics.”

One potential application for the photonic time crystals is in nanosensing. Asadchy said, “Imagine we want to detect the presence of a small particle, such as a virus, pollutant, or biomarker for diseases like cancer. When excited, the particle would emit a tiny amount of light at a specific wavelength. A photonic time crystal can capture this light and automatically amplify it, enabling more efficient detection with existing equipment.”

Creating photonic time crystals for visible light has long been challenging due to the need for extremely rapid yet simultaneously large-amplitude variation of material properties. To date, the most advanced experimental demonstration of photonic time crystals, developed by members of the same research team, has been limited to much lower frequencies, such as microwaves.

In their latest work, the team proposes, through theoretical models and electromagnetic simulations, the first practical approach to achieving what they call “truly optical” photonic time crystals. By using an array of tiny silicon spheres, they predict that the special conditions needed to amplify light that were previously out of reach can finally be achieved in the lab using known optical techniques.

The team comprised researchers from Aalto University, the University of Eastern Finland, Karlsruhe Institute of Technology, Germany, and Harbin Engineering University, China.