Graphene capacitors achieve rapid, high-depth modulation of terahertz waves

Summary

The demonstrated tuneable capacitance metamaterial, used as a terahertz amplitude modulator. Credit: Cavendish Laboratory Researchers at the Cavendish Laboratory, University of Cambridge have demonstrated a new way to control radiation in the terahertz range—an often-overlooked part of the electromagnetic spectrum—with unprecedented dynamic range and speed. The findings could open the door to advanced technologies in communications, imaging, and sensing and mark major progress in the development of practical devices that operate in the terahertz range. The study is published in the journal Light: Science & Applications. The terahertz range sits between microwaves and infrared light on the electromagnetic spectrum. Despite the potential of terahertz waves in many fields, for example in walk-through security scanners in airports and for skin cancer detection, terahertz waves are hard to manipulate efficiently. That's because terahertz wavelengths are tens of thousands of times smaller compared to radio wavelengths, and traditional methods don't work well at this scale. But being able to manipulate terahertz waves is very important, particularly for communications, where a data signal must be encoded onto a wave to transmit information. "Think of how you listen to an old analog radio, which works at much larger wavelengths: you turn the dial to tune into your desired station. Inside the radio, you're adjusting a capacitor so that the radio picks up the frequency of the station you want," explained Dr. Wladislaw Michailow, who led the research at the Cavendish Laboratory and is a Junior Research Fellow at Trinity College. "This tuning concept is very useful in many devices, but because terahertz wavelengths are so small, we had to come up with a new concept to realize tuning in the terahertz range." Capacitors are components that store and release electric energy. By tweaking how much charge each capacitor can hold—a property called capacitance—the frequency of devices,...