Prof. Evelyn Hu, Harvard SEAS, gives a talk hosted by Applied Physics @ MIT

"The Hole in the Argument: InGaN Quantum Dot Micro-Ring Lasers"

The combination of quantum dot (QD) active layers and nanoscale cavities with high quality factors can provide a pathway to realizing compact, efficient lasers with ultra-low lasing thresholds. For the InGaN/GaN material system, this produces highly efficient blue and UV optical sources operating at room temperature. Moreover, such QD-nanocavity lasers can provide insights at the nanoscale into the dominant limitations to low threshold lasing, such as non-radiative recombination pathways, photon loss mechanisms or inefficient carrier capture. Recent results for our InGaN QD micro-ring lasers show interesting, seemingly contradictory results: as we thin the ring widths we achieve both systematically lower lasing thresholds as well as lower slope efficiencies post lasing. The relative simplicity of the optical spectra for these nanoscale structures provides insights that may reconcile these contradictions.