Optically pumped lasing from a single pillar microcavity with InGaAs/GaAs quantum well potential fluctuation quantum dots

Here, an optical study is presented on cuboidal single pillar microresonators with a quantum-dot-like emitter formed from local fluctuations in the InGaAs/GaAs quantum well potential. By means of microphotoluminescence, emission spectra as a function of the excitation power density were recorded. In the low excitation spectra a number of sharp lines corresponding to the single quantum dots photoluminescence was observed. With increasing excitation power the spectra become dominated by the microcavity modes, on the background of which an intensive and narrow line appears when a certain threshold excitation power is exceeded. A threshold power corresponding to the onset of the superlinear emission intensity power dependence was determined, which is accompanied by a strong decrease in the emission mode linewidth, where both are the distinctive features of the lasinglike behavior. The threshold power density and the exponent of the superlinear part of the input-output characteristic increase with the pillar lateral size (d) and the quality factor (Q), however, they both decrease when plotted as a function of Q/d(2), which is the actual figure of merit of the spontaneous emission coupling factor (beta). It shows the dominant influence of the volume change effect over the cavity Q (finesse). Thus, larger beta values are assigned to the smaller micropillars, in spite of their lower Q values. A quantum dot character of the lasing has been confirmed in a temperature dependent experiment, which showed a number of emission intensity oscillations instead of the expected monotonic decay with the temperature increase, which is a fingerprint of the spectral tuning of the quantum dot emission spectrum through the optical cavity mode.