UK universities discover ‘new’ quantum wells

UK researchers have discovered a new  two-dimensional quantum well mechanism which they claim can emit tunable light at terahertz frequencies with “unprecedented efficiency”.

Optoelectronic device

The researchers, from the University of Southampton and Imperial College London, found that quantum wells, 2D nanostructures formed of several layers of semi-conductor alloys placed on top of each other like a sandwich, can enhance light emission in a technological challenging spectral range.

Likely photonics applications where this could have an impact include medical imaging and security scanning.

“As the 2D nanostructures can be manufactured with an asymmetric design, this allows light to interact with trapped electrons in a way that is not otherwise allowed,” said Nathan Shammah, from the University’s Quantum Light and Matter (QLM) group.

“This interaction process, leading to the emission of light at lower frequencies, has not been observed in atoms because those are very symmetrical systems and symmetry rules prevent the transitions that trigger this light emission from happening.”

In the paper, which is published in Physical Review B, the researchers predict that by shining light on a 2D asymmetric nanostructure with a laser that is tuned at resonance with the electronic transitions that can occur in the nanostructure, in addition to the scattered laser light, this 2D device would emit light at other frequencies, which can be tuned simply by changing the laser power.

According to Professor Chris Phillips from Imperial College London: “This new mechanism is perfectly suited for the terahertz frequency range, which spans from above the current wi-fi bandwidth to below the visible light spectrum, where the lack of practical light emitters constitutes a serious technological gap.”



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