Resonance Fluorescence from a Coherently Driven Semiconductor Quantum Dot in a Cavity

Abstract

We show that resonance fluorescence, i.e. the resonant emission of a coherently driven two-level system, can be realized with a semiconductor quantum dot. The dot is embedded in a planar optical micro-cavity and excited in a wave-guide mode so as to discriminate its emission from residual laser scattering. The transition from the weak to the strong excitation regime is characterized by the emergence of oscillations in the first-order correlation function of the fluorescence, g(τ ), as measured by interferometry. The measurements correspond to a Mollow triplet with a Rabi splitting of up to 13.3 µeV. Second-order-correlation measurements further confirm non-classical light emission. [3,4,5,6,7], as well as photon anti-bunching [8], and were previously only observable in isolated atoms or ions. In addition, QDs can be readily integrated into optical micro-cavities making them attractive for a number of applications, particularly quantum information processing and high efficiency light sources. For example, QDs could be used to realize deterministic solid-state single photon sources [9,10,11] and qubit-photon interfaces [12]. Advances in high-Q cavities have shown that not only can the spontaneous emission rate be dramatically increased by the Purcell effect [13,14], but emission can be reversed in the strong coupling regime [15,16,17]. Despite these efforts, however, quantum dot-based cavity quantum electrodynamics (QED) lacks an ingredient essential to the success of atomic cavity QED, namely the ability to truly resonantly manipulate the two-level system [9,10,11]. Current approaches can at best populate the dot in one of its excited states, which subsequently relaxes in some way to the emitting ground state. This incoherent relaxation has been addressed theoretically [18,19], and experimentally [20] but direct resonant excitation and collection in the ground state has so far not been reported as it is very challenging to differentiate the resonance fluorescence from same-frequency laser scattering off defects, contaminants, etc. In quantum dots without cavities, coherent manipulation of ground-state excitons has nonetheless been achieved with a number of techniques including differential transmission [6], differential * Electronic address: shih@physics.utexas.edu reflectivity [21], four-wave mixing [22], photodiode spectroscopy [7], and Stark-shift modulation absorption spectroscopy [23]. However, none of these is able to collect and use the actual photon emission which limits their use in many potential applications of QDs. This report presents the first measurement of resonance fluorescence in a single self-assembled quantum dot. Described by Mollow in 1969 [24], the resonant emission of a two-state quantum system under strong coherent excitation is distinguished by an oscillatory first-order correlation function, g(τ ), that we observe with interferometry. We use a planar optical micro-cavity to guide the excitation laser between the cavity mirrors and simultaneously enhance the single photon emission in th...

On-demand semiconductor single-photon source with near-unity indistinguishability

“…The oscillation of the RF intensity is due to the wellknown Rabi rotation between the ground and the excitonic state. It has been demonstrated previously by quasi-resonant [34][35][36] or resonant driving [21,32]. The RF intensity reaches its first peak at the π pulse.…”

“…The Mollow triplet spectra and photon correlations of the resonance fluorescence (RF) have been measured [1][2][3]21]. Under continuous-wave (CW) laser excitation, a high degree of indistinguishability for continuously generated RF photons has been demonstrated through post-selective HOM interference [25].…”

“…In addition, the pulsed and transition-selective RF single photons are also a prerequisite for the much sought-after goal of entangling distant QD spins through photon interference [4,30], as well as for the scheme of generating on-demand multi-photon cluster states [31]. Earlier experiments [21,32] have used pulsed resonant excitation to demonstrate Rabi oscillation, a hallmark for quantum optics. Yet, access to a background-free on-demand single-photon source with near-unity indistinguishability proved elusive [33].…”

Auger Recombination in Self-Assembled Quantum Dots: Quenching and Broadening of the Charged Exciton Transition

“…Figure 2(a) displays the corresponding signals for seven representative laser excitation powers, which determine the absorption rate and, hence, the probability for a trion inside the QD. The latter corresponds to the probability for the occupation of the upper level in a twolevel system 28,29 . The conversion from laser power to is given by the red curve in Fig.…”

“…The dependence of the upper state population in a two level system on the excitation power is given by the saturation curve 28,29 (…”