EPic Research Team Develops Ultrathin Terahertz Sources

University of Sussex physicists, led by Marco Peccianti, professor and director of the Emergent Photonics (EPic) Laboratory, developed an extremely thin, large-area semiconductor surface source of terahertz, composed of just a few atomic layers and compatible with existing electronic platforms. The technology has potential for next-generation communication devices — such as in 6G mobile phone technology — as well as anti-counterfeiting and the Internet of Things.

The advancement, the researchers said, specifically overcomes limitations to terahertz-based platforms and research that makes it difficult or impractical to pair the technology with advancements in other areas, such as sensors and detectors and ultrafast communications.

Ultrafast lasers at the University of Sussex EPic lab are an essential ingredient in realizing ultrathin THz sources. Courtesy of EPic lab, University of Sussex.

“From a physics perspective, our results provide a long-sought answer that dates back to the first demonstration of terahertz sources based on two color lasers,” said Juan S. Totero Gongora, Leverhulme Early Career Fellow at Sussex. “Semiconductors are widely used in electronic technologies but have remained out of reach for this type of terahertz generation mechanism. Our findings therefore open up a wide range of exciting opportunities for terahertz technologies.”

Among the challenges of working with terahertz technology is that what are commonly accepted as “intense terahertz sources” are faint and bulky when compared with other technologies, such as a light bulb. They also tend to require exotic and external materials, such as nonlinear crystals, which increases the cost of using such devices. These issues bring about logistical challenges for integrating the devices with other technologies.

By illuminating an electronics grade semiconductor with two types of laser light, each oscillating at a different frequency or color, the team built a device it says is 10x thinner than existing surface semiconductors, and capable eliciting the emission of short bursts of terahertz radiation.

Terahertz sources emit brief light pulses oscillating trillions of times per second. At this scale, they’re too fast to be handled by standard electronics and, until recently, too slow to be handled by optical technologies.

The new technology, however, is able to be integrated with next-generation mobile phones. Due to its small size (about 25 atomic layers thick) it is able to be placed on everyday objects and devices, and on places where its placement would have been impossible previously. Such a device could be applied to products or even a work of art, which holds potential for anti-counterfeiting and the Internet of Things.

“The idea of placing terahertz sources in inaccessible places has great scientific appeal, but in practice is very challenging,” said Luke Peters, a research fellow of the European Research Council project TIMING at the University of Sussex. “Terahertz can have a superlative role in material science, life science, and security. Nevertheless, it is still alien to most of the existing technology, including devices that talk to everyday objects as part of the rapidly expanding ‘Internet of Things.’ This result is a milestone in our route to bring terahertz functions closer to our everyday lives.”

The research was published in Physical Review Letters (www.doi.org/10.1103/PhysRevLett.125.263901).