Two-color Single-Photon emission of InAs Quantum Dots: experiment and random population modeling

We demonstrate two-color single photon emission in a single InAs QD under its simultaneous excitation at two particular laser wavelengths, namely 790 and 830 nm (Fig. 1) [1]. The carrier dynamics is studied by means of a random population (microstate master equation) model that reveals a power evolution of the carrier (exciton, electron-hole and single electron) feeding rates. At high excitation powers the excitonic capture is the predominant feeding channel. However, the single electron feeding under resonant excitation to the impurities levels in GaAs barriers (excitation at 830 nm) [2] induces a redistribution of exciton and electron-hole capture under two-color excitation that does not follow a linear response with power. The asymmetrical pattern found in the X0-X- cross correlation Hanbury- Brown&Twiss experiment, as observed in Fig. 1.b (two-color laser excitation) is a consequence of the different regeneration times for X0 and X- exciton species and modeled by assuming a dynamical capture time [3]. In our model we consider that electron and hole escape out of the QD are different (5 and 3 ns, respectively, as deduced from the model fitting to experiments), whose origin is either deep levels or interface defects [4]. This system is as a robust candidate to evaluate logic information, based on the quantum light intensity fluctuations characteristic of the single QD optical emission. The main practical problem to use the photon fluctuations as a logic parameter is the acquisition time needed to obtain a statistical sample and a fast g2(0) measurement technique would be needed to convert the present proposal into a realistic device. Research on this field must be focused on the reduction of this integration time or the fast sensing of two-color single photon emission.