A New Way of Manipulating Ultrathin High-Tech Surfaces

By LIDA TUNESI

Researchers at the Advanced Science Research Center at The Graduate Center (CUNY ASRC) have developed a new method to overcome limitations of ultrathin surfaces, called metagratings, used in optics. Their work could help implement new devices for optical communications, or even develop ultrathin lenses and holograms that could be modified in real time, the researchers say.

Andrea Alù, founding director of the Photonics Initiative at CUNY ASRC and Professor Alex Krasnok of the Photonics Initiative were co-authors on the paper, published in Advanced Materials.

Metasurfaces are 2D materials that are designed down to the tiniest, nanoscopic level of detail in order to bend, steer, and focus light in extreme ways. But even with this amount of precision, these surfaces have limited efficiency. Several years ago, Alù’s group introduced a new class of metasurfaces that overcame some of these issues. These are known as metagratings. But metagratings have their own limitations, too. They are mostly passive devices that are difficult to reprogram, and the new work focused on fixing this.

Image credit: Advanced Materials journal

“In our paper, we introduced the possibility of controlling metagratings in real time using external excitations,” Alù said.

The new paper shows how to use two beams of light, rather than one, to control the metagrating’s functionality. Just like when two waves in a lake disturb and alter each other when they meet, the two different light waves affect each other’s properties. This gives the researchers better control over the metagrating’s response.

“We prove that by controlling the phase of one of the beams with respect to the other we are able to control the metagrating functionality, essentially turning it on and off,” Alù said.