Dephasing of Exciton Polaritons in Photoexcited InGaAs Quantum Dots in GaAs Nanocavities

Abstract

We present a combined experimental and theoretical study of the emission spectrum of zero dimensional nanocavity polaritons in electrically tunable single dot nanocavities. Such devices allow us to vary the dot-cavity detuning in situ and probe the emission spectrum under well-controlled conditions of lattice temperature and incoherent excitation level. Our results show that the observation of a double peak in the emission spectrum is not an unequivocal signature of strong coupling. Moreover, by comparing our results with theory, we extract the effective vacuum Rabi splitting, the pure dephasing rate, and their dependence on the incoherent optical pumping power and lattice temperature. Our study highlights how coupling to the lattice and dynamical fluctuations in the solid-state environment influence the coherence properties of quantum dot microcavity polaritons and, sometimes, may mask the occurrence of strong coupling.

Density operator of a system pumped with polaritons: a Jaynes–Cummings-like approach

“…The theoretical results they obtain, with this model, reproduce the polariton laser threshold reported in [10]. In a recent theoretical and experimental study [11], using a simple Jaynes-Cummings like model including dissipative processes, the authors obtain a surprisingly good agreement between the calculated and measured polariton spectra. They show that the effective dissipative parameters of the system depend on the nominal excitation power density.…”

Mutual coupling of two semiconductor quantum dots via an optical nanocavity

“…Using the spectral function S͑ ͒ we globally fit the entire set of spectra generated as a function of V app using a Levenberg-Marquardt algorithm in the same manner as reported in Ref. 8. The best fit was obtained for បg 1 =44 eV and បg 2 =51 eV, ប⌫ QD1 = 0.1 eV and ប⌫ QD2 = 0.8 eV, បP QD1 = 1.5 eV and បP QD2 = 1.9 eV, ប␥ QD1 =20 eV and ប␥ QD2 = 9.8 eV, ប⌫ c = 147 eV, and បP c = 5.7 eV.…”

“…In order to describe the system theoretically we extend our previously presented model for a single QD exciton 8 to include two independent excitons coupled to a common cavity mode. We use the following Hamiltonian:…”

“…Such cavities support six modes within the twodimensional ͑2D͒-photonic band gap of which the fundamental cavity mode exhibits Q factors up to ϳ12000 in our structures, high enough to reach the strong coupling regime. 5,8 PL spectra from the nanocavities were recorded using confocal microscopy as a function of V app . The excitation laser was tuned to the second order higher energy cavity mode in order to spatially select only dots coupled to the fundamental mode.…”

“…1,2 Much progress has been made with a number of spectacular demonstrations, including efficient generation of nonclassical light, 3 the observation and investigation of strong coupling phenomena [4][5][6][7][8] and, excitingly, the possibility to observe and exploit quantum optical nonlinearities. 9,10 These developments are all ingredients for the realization of a solid-state all-optical quantum network 11 where quantum memory elements are coupled via single light quanta.…”