Cavity-QED experiments on InAs quantum boxes in micropillars and microdisks

In order to further demonstrate and understand spontaneous emission (SE) enhancement in solid-state microcavities, we choose to study microdisks, sustaining low V and potentially high Q "whispering gallery modes". We report the fabrication of high quality GaAs microdisks containing InAs quantum boxes (QBs), thanks to an improved process based on two-step wet-etching. Whispering gallery modes display record high Q's (12000 for 2 μm diameter disks instead of 3300 for the previous state of the art) corresponding to a very high Fp (~150). We also present an original characterization of the Purcell effect in continuous wave photoluminescence. In our structures, the number of QBs coupled to a given mode is not large enough to sustain lasing. When we raise the excitation power, the emission related to the fundamental optical transition of a QB thus saturates when we inject more than one electron-hole pair per lifetime. This behavior is observed for on-resonance as well as off-resonance QBs. However the beginning of the saturation occurs for a much higher pumping power when QBs are resonantly coupled to a cavity mode, which confirms that their radiative lifetime is much shorter due to the Purcell effect. For micropillars, these cw experiments confirm the previously reported results of time-resolved experiments. For microdisks, due to a much larger Purcell factor, we witnessed a SE enhancement as large as 20 for the best structures. The magnitude of this effect is well understood when considering the spatial and spectral distribution of the QBs