Injection locking of quantum-dot microlasers operating in the few-photon regime

The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework ERC Grant Agreement No. 615613 and from the German Research Foundation via CRC 787.We experimentally and theoretically investigate injection locking of quantum dot (QD) microlasers in the regime of cavity quantum electrodynamics (CQED). We observe frequency locking and phase-locking where cavity-enhanced spontaneous emission enables simultaneous stable oscillation at the master frequency and at the solitary frequency of the slave microlaser. Measurements of the second-order autocorrelation function prove this simultaneous presence of both master and slave-like emission, where the former has coherent character with g(2)(0) = 1 while the latter one has thermal character with g(2)(0) = 2. Semiclassical rate equations explain this peculiar behavior by cavity enhanced spontaneous emission and a low number of photons in the laser mode.PostprintPeer reviewe