Detector-enclosed vertical-cavity surface emitting lasers

The authors report the use of novel monolithic lateral photodetectors surrounding vertical-cavity surface emitting lasers to determine the radiative transition rate and lasing threshold independent from the axial emission. The lateral detector photocurrent increases with increasing laser drive current, even as the axial emission rolls over and terminates. This clearly establishes that laser output is limited by the detuning between the Fabry-Perot cavity resonance and the gain bandwidth with temperature, rather than the temperature dependence of the gain.