Observation of excitonic super-radiance in quantum well structures and its application for laser cooling of solids

Excitons, bound electron-hole pairs, possess distinct physical properties from free electrons and holes that can be employed to improve the performance of optoelectronic devices. In particular, the signatures of excitons are enhanced optical absorption and radiative emission. These characteristics could be of major benefit for the laser cooling of semiconductors, a process which has stringent requirements on the parasitic absorption of incident radiation and the internal quantum efficiency. Here we experimentally demonstrate the dominant ultrafast excitonic super-radiance of our quantum well structure from 78 K up to room temperature. The experimental results are followed by our detailed discussions about the advantages and limitations of this method.