Researchers use asymmetry to generate tunable terahertz light

The team, which also included researchers from Imperial College London, found that quantum wells can enhance light emission in a spectral range that is technically challenging. Nathan Shammah, from Southampton University's Quantum Light and Matter group, said: "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. 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 their paper, published in Physical Review B, the researchers predict that, by targeting a 2D asymmetric nanostructure with laser light tuned at resonance with the electronic transitions that can occur in the nanostructure, the 2D device would emit light at frequencies which can be tuned simply by changing the laser power. Shammah added: "This 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." It is hoped the findings will have an impact on photonic and optoelectronic devices across a broad range of applications, including medical imaging and security scanning.