We study theoretically the photoluminescence of a single quantum dot in a microcavity under incoherent excitation. Analytical results including pure dephasing show that strong coupling and linewidths are largely independent on the pumping intensity (until saturation effects come into play). We show the reliable predicting character in the analysis of some experiments.
We study theoretically the photoluminescence of a single quantum dot in a microcavity under incoherent excitation. Analytical results including pure dephasing show that strong coupling and linewidths are largely independent on the pumping intensity (until saturation effects come into play). We show the reliable predicting character in the analysis of some experiments.
e study theoretically, the photoluminescence properties of a single quantum dot in a microcavity under incoherent excitation. We propose a microscopic quantum statistical approach providing a Lindblad (thus completely positive) description of pumping and decay mechanisms of the quantum dot and of the cavity mode. Our analytical results show that strong coupling (SC) and linewidths are largely independent on the pumping intensity (until saturation effects come into play), in contrast to previous theoretical findings. We shall show the reliable predicting character of our theoretical framework in the analysis of various recent experiments.
We provide a unified theory of luminescence spectra of coupled light-matter systems realized with semiconductor heterostructures in microcavities, encompassing (i) the spontaneous emission case, where the system decays from a prepared (typically pure) initial state, and (ii) luminescence in the presence of a continuous incoherent pump. We show how, by provoking a self-consistent quantum state, the pump considerably alters the emission spectra, even at vanishing intensities. The main outcome of our analysis is to unambiguously identify strong coupling in situations where it appears in disguise or only seems to appear. Here, we consider bosonic matter fields, in which case fully analytical solutions can be obtained. This describes the case of quantum wells or large quantum dots, or the limit of low excitation where the probability to have particles in the system remains much smaller than one.
The Jaynes-Cummings model, describing the interaction between a single two-level system and a photonic mode, has been used to describe a large variety of systems, ranging from cavity quantum electrodynamics, trapped ions, to superconducting qubits coupled to resonators. Recently there has been renewed interest in studying the quantum strong-coupling (QSC) regime, where states with photon number greater than one are excited. This regime has been recently achieved in semiconductor nanostructures, where a quantum dot is trapped in a planar microcavity. Here we study the quantum strong-coupling regime by calculating its photoluminescence (PL) properties under a pulsed excitation. We discuss the changes in the PL as the QSC regime is reached, which transitions between a peak around the cavity resonance to a doublet. We particularly examine the variations of the PL in the time domain, under regimes of short and long pulse times relative to the microcavity decay time.
The behaviour of the photoluminescence spectra of a single quantum dot in a semiconductor microcavity is modeled numerically in the presence of an external and constant magnetic field. The dynamics of the density operator is calculated using the master equation in the Lindblad form for decoherence processes: spontaneous emission, losses through cavity mirrors, and dephasing. An incoherent pumping of excitons is used to feed the system. It is found in the photoluminescence spectra that for magnetic fields lower than 2 T the system is in the strong coupling regime and for magnetic fields greater than 2 T the system emits light like three independent systems. The line that uncouples faster is the σ line.
Entanglement and lasing of two quantum dots in a microcavity are investigated in the steady state achieved under a continuous incoherent pumping. Lasing is favored in the case of independent pumping of the dots, i.e., when an electron-hole pair which reaches one dot does not affect the other. In this case, having two dots allows a qualitative enhancement of the lasing emission as compared to the single dot case. On the other hand, when the two dots share the excitation bath, giving rise to a quantum uncertainty of the final state of the excitation, entanglement properties are enhanced in detriment of the photon emission. Slightly different couplings between the dots and the cavity induce good singlet-state population. This allows good entanglement in a system pumped continuously and incoherently.
Single photon emission is one of the most striking optical properties of semiconductor quantum dots (QDs), and the corresponding photon anti-bunching effect was observed by non-resonant and resonant photoluminescence experiments in single QDs [1,2]. Up to now, all the measurements reported in the literature focus on the incoherent photoluminescence signal for achieving single photon emission. In this regime, the linewidth of the photoluminescence spectrum is limited to the so-called radiative limit. In this paper, we report on the resonant emission (RE) of the exciton in single InAs/GaAs QDs embedded in a planar microcavity [2]. We present an original type of single photon source based on the coherent laser light scattering by a single QD [3]. Besides the antibunching effect showing the nonclassical nature of the emitted light, we observe that the QD emission spectrum is determined by the spectrum of the resonant excitation laser. Figure (a,b,c) shows high-resolution measurements by Fourier transform spectroscopy of the RE where the data are fitted to the first-order correlation function g(1)(τ) of the RE of a two-level system. The inverse Fourier transform of the g(1)(τ) function allows a direct comparison of the different RE emission profiles in figure (d,e,f). By reducing the resonant excitation power, the Mollow triplet shrinks to a single narrow Lorentzian line, while the relative intensity of this narrow peak increases and tends to overwhelm the RE spectrum. This implies that single QDs can produce single photons with a coherence time that is not limited anymore by the QD electronic properties, resulting in an ultra-coherent character [3]. References [1] P. Michler et al, Science 290, 2282 (2000). [2] H. S. Nguyen et al, Phys. Rev. Lett. (accepted, in press). See arXiv 1109.4304. [3] H. S. Nguyen et al, Appl. Phys. Lett. 99, 261904 (2011).