Terahertz is the type of electromagnetic radiation that lies between the microwave and the infrared regions of the electromagnetic spectrum. THz radiation bridges the gap between photonic and electronic devices and offers many unused, unexplored bandwidths. Historically, the lack of sources and detectors, as well as the perceived lack of need, had contributed to the dearth of activity in THz. This hinders the widespread use of terahertz technology.
A team of scientists at the Cavendish Laboratory and colleagues at the Universities of Augsburg (Germany) and Lancaster discovered a new effect in 2D conductive systems that promises improved performance of terahertz detectors. They found a new physical effect when two-dimensional electron systems are exposed to terahertz waves.
Dr. Wladislaw Michailow, Junior Research Fellow at Trinity College Cambridge, said, “We were developing a new type of terahertz detector, but when measuring its performance, it turned out that it showed a much stronger signal than should be theoretically expected. So we came up with a new explanation.”
Scientists explain, “This explanation lies in how light interacts with matter.”
Matter absorbs light in the form of photons at higher frequencies. This interpretation formed the foundation of quantum mechanics and explained the photoelectric effect. This quantum photoexcitation is how cameras in our smartphones sense light, and it’s also how solar cells generate electricity from light.
The electrons are released from a conductive material by incident photons in the photoelectric effect. In a 3D semiconductor, electrons can be expelled into a vacuum by photons in the ultraviolet or X-ray range or released into a dielectric in the mid-infrared to the visible range.
The novelty is in the discovery of a quantum photoexcitation process in the terahertz range, similar to the photoelectric effect.
Wladyslaw said, “The fact that such effects can exist within highly conductive, two-dimensional electron gases at much lower frequencies has not been understood so far, but we have been able to prove this experimentally.”
Scientists named their phenomenon an “in-plane photoelectric effect.” In the paper published, they described several benefits of exploiting this effect for terahertz detection. In particular, the magnitude of photoresponse generated by incident terahertz radiation by the “in-plane photoelectric effect” is much higher than expected from other mechanisms that have been heretofore known to give rise to a terahertz photoresponse.
According to scientists, this effect will allow the development of terahertz detectors with substantially higher sensitivity. The study is a step closer to making terahertz technology usable in the real world, noted scientists.
- Wladyslaw Michailow et al., An in-plane photoelectric effect in two-dimensional electron systems for terahertz detection, Science Advances (2022). DOI: 10.1126/sciadv.abi8398