Terahertz functions could be applied to anti-counterfeiting technologies and 6G telephony following the development of a semiconductor source of terahertz radiation.
This is the claim of physicists from Sussex University who have developed an extremely thin, large-area semiconductor surface source of terahertz that is composed of a few atomic layers and is compatible with existing electronic platforms.
Terahertz sources emit brief light pulses oscillating at trillion of times per second, which is too fast to be handled by standard electronics, and, until recently, too slow for optical technologies. This is significant for the evolution of ultra-fast communication devices above the 300GHz limit – required for 6G mobile phone technology – and currently beyond the limit of existing electronics.
Researchers in the Emergent Photonics (EPic) Lab at Sussex, led by the director of the Emergent Photonics (EPic) Lab Professor Marco Peccianti, have previously achieved the brightest and thinnest surface semiconductor sources demonstrated so far.
The emission region of their new development, a semiconductor source of terahertz, is said to be 10 times thinner than previously achieved, with comparable or even better performances.
The thin layers can be placed on top of existing objects and devices, enabling terahertz sources to be put in places that would have been inconceivable otherwise, including everyday object such as a teapot or a work of art. This has the potential to open up applications in anti-counterfeiting and IoT, as well as previously incompatible electronics, such as a next-generation mobile phone.
In a statement, Dr Juan S. Totero Gongora, Leverhulme Early Career Fellow at Sussex University, said: “From a physics perspective, our results provide a long-sought answer that dates back to the first demonstration of terahertz sources based on two-colour lasers.
“Semiconductors are widely used in electronic technologies but have remained mostly out of reach for this type of terahertz generation mechanism. Our findings therefore open up a wide range of exciting opportunities for terahertz technologies.”
Dr Luke Peters, Research Fellow of the European Research Council project TIMING at Sussex University, said: “The idea of placing terahertz sources in inaccessible places has great scientific appeal but in practice is very challenging. Terahertz radiation 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.”
Lying between microwaves and infrared in the electromagnetic spectrum, terahertz waves reveal the material composition of an object by penetrating common materials like paper, clothes and plastic in the same way X-rays do, but without being harmful.
Terahertz imaging makes it possible to observe the molecular composition of objects and distinguish between different materials. Previous developments from Prof Peccianti’s team demonstrated the potential applications of terahertz cameras, which could assist airport security, or lead to medical scanners that detect skin cancers.
According to Sussex University, one of the biggest challenges faced by scientists working in terahertz technology is that what is commonly accepted as an ‘intense terahertz source’ is faint and bulky when compared with, for example, a light bulb. In many cases, the need for very exotic materials, such as nonlinear crystals, makes them unwieldy and expensive. This requirement poses logistical challenges for integration with other technologies, such as sensors and ultrafast communications.
The Sussex team are said to have overcome these limitations by developing terahertz sources from extremely thin materials (about 25 atomic layers). By illuminating an electronic-grade semiconductor with two different types of lasers light, each oscillating at different frequency or colour, they were able to elicit the emission of short bursts of Terahertz radiation.
The team’s findings have been published in Physical Review Letters.