Thermodynamic balance in quantum dot lasers

The spontaneous emission and optical gain spectra from an InGaAs quantum do t laser have been independently measured under the same operating condition s. Using these spectra a combined probability-distribution function describ ing the electron occupancy in the conduction and valence bands has been exp erimentally determined. Comparison of this function with theoretical curves based on Fermi-Dirac statistics shows that for temperatures down to 100 K the carrier occupancy statistics are accurately described by thermal distri butions. Measurements at 70 K show a breakdown of thermodynamic equilibrium indicated by non-thermal carrier distributions.