One step closer to making terahertz technology available in the real world

Wladislaw Michailow shows the device in a clean room, and after manufacturing a terahertz detector. Credit: Wladislaw Michailow

Researchers have found in new two-dimensional conductive systems a new effect that promises to improve the performance of terahertz detectors.

A team of scientists at the Cavendish Laboratory, along with colleagues at the Universities of Augsburg, Germany, and Lancaster, have discovered a new physical effect when two-dimensional electronic systems are affected by terahertz waves.

First of all, what are terahertz waves? “We communicate using mobile phones that transmit microwave radiation and use infrared cameras for night vision. Terahertz is a type of electromagnetic radiation between microwaves and infrared radiation,” said Professor David Ritchie, head of the Semiconductor Physics Group. The University of Cambridge’s Cavendish Laboratory “lacks sources and detectors of this type of radiation that would be cheap, efficient and easy to use at the moment. This is hindering the widespread use of terahertz technology.”

Researchers at the Semiconductor Physics team, along with researchers in Pisa and Turin in Italy, were the first to test the operation of a laser at terahertz frequencies in 2002, a quantum cascade laser. Since then, the team has continued to research terahertz physics and technology, and is currently researching and developing functional terahertz devices that incorporate metamaterials to form modulators, as well as new types of detectors.

If the lack of available devices is remedied, terahertz radiation can have many useful applications in safety, materials science, communications, and medicine. For example, terahertz waves can represent tissue that cannot be seen with the naked eye. They can be used in the new generation of secure and fast airport scanners that make it possible to separate drugs from illegal drugs and explosives, and can be used to enable even faster wireless communications of the latest generation.

So what is the latest discovery about? “We were developing a new type of Terahertz detector,” says Dr. Wladislaw Michailow, a Junior Research Fellow at Trinity College, Cambridge.

This explanation, according to scientists, lies in how light interacts with matter. At high frequencies, matter absorbs light as a single particle — photons. This interpretation, first proposed by Einstein, formed the basis of quantum mechanics and explained the photoelectric effect. This quantum photovoltaics is how cameras detect light on our mobile phones; it is also the one that generates electricity from light in solar cells.

A well-known photoelectric effect is the release of electrons from a conductive material — a metal or a semiconductor — through incident photons. In the case of three-dimensional photons, they can empty electrons through photons in the ultraviolet or X-ray range, or release them into a visible dielectric medium in the middle of the infrared. The novelty lies in the discovery of a quantum photoexcitation process in the terahertz range, similar to the photoelectric effect. “It is unknown at this time what he will do after leaving the post. It is unknown at this time what he will do after leaving the post.” The quantitative theory of the effect was developed by a colleague at the University of Augsburg in Germany, and a group of international researchers published their findings in the journal. Scientific Advances.

The researchers called the phenomenon “a photoelectric effect in the plane.” In the corresponding paper, scientists describe the various benefits of exploiting this effect to detect terahertz. In particular, the magnitude of the photoresponse generated by the incident radiation of the “photoelectric effect in the plane” is much higher than expected from other mechanisms known so far to produce a terahertz photoresponse. Therefore, scientists hope that this effect will allow the manufacture of terahertz detectors with significantly higher sensitivity.

“This brings us one step closer to making terahertz technology available in the real world,” concluded Professor Ritchie.

Resonance tunneling oscillating diodes to detect terahertz waves

More information:
Wladislaw Michailow et al, Planar photoelectric effect for the detection of terahertz in two-dimensional electron systems, Scientific Advances (2022). DOI: 10.1126 / sciadv.abi8398

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