Heterostructure and Q-factor engineering for low-threshold and persistent nanowire lasing

March 19, 2020

Over the past decade, the idea of photonic computing - where electrons are replaced with light in microelectronic circuits - has emerged as a future technology. This promises low-cost, ultra-high-speed and potentially quantum-enhanced computing, with specific applications in high-efficiency machine learning and neuromorphic computing. While the computing elements and detectors have been developed, the need for nanoscale, high-density and easily-integrated light sources remains unmet. Semiconductor nanowires are seen as a potential candidate, due to their small size (on the order of the wavelength of light), the possibility for direct growth onto industry-standard silicon, and their use of established materials. However, to date, such nanowire lasers on silicon have not been demonstrated to operate continuously at room temperature.

In a new paper published in Light Science & Application, scientists from the Photon Science Institute in Manchester, UK with colleagues at University College London and the University of Warwick demonstrate a new route to achieving low-threshold silicon-integratable nanowire lasers. Based on a novel direct-indirect semiconductor heterostructures enabled by the nanowire platform, they demonstrate multi-nanosecond lasing at room temperature. A key design element is the need for high-reflectivity nanowire ends; this is typically a challenging requirement, as common growth methods do not allow simple optimization for high quality end-facets. However, in this study, by employing a novel time-gated interferometer the researchers demonstrate that the reflectivity can be over 70% - around double that expected for a conventional flat-ended laser due to the confinement of light.

Together, the novel material structure and high quality cavity contribute to a low lasing threshold - a measure of the power required to activate lasing in the nanowires - of just 6uJ/cm^2, orders of magnitude lower than previously demonstrated. Not only does this new approach provide high quality nanolasers, but the MBE growth provides a high-yield of functioning wires, with over 85% of nanowires tested working at full power without thermal damage. This high yield is critical for industrial integration of this new structure.

Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences

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