Carrier-transfer dynamics between neutral and charged excitonic states in a single quantum dot probed with second-order photon correlation measurements
H. Nakajima, H. Kumano, Hitoshi Iijima, Satoru Odashima, Ikuo Suemune
We report a comprehensive investigation of carrier-transfer dynamics in a single InAs quantum dot (QD) based on second-order photon correlation measurements. The experimentally obtained auto and crosscorrelation functions as well as photoluminescence intensities are successfully explained on the basis of a series of rate equations with common excitation and also single-carrier-capture/escape rates to/from a QD. This approach enables us to understand the carrier-transfer dynamics responsible for the stability of a quantum two-level system formed in a single QD under various excitation conditions. We clarify that the transition between neutral and charged excitonic states is suppressed by one order of magnitude under quasiresonant excitation.
We report a comprehensive investigation of carrier-transfer dynamics in a single InAs quantum dot (QD) based on second-order photon correlation measurements. The experimentally obtained auto and crosscorrelation functions as well as photoluminescence intensities are successfully explained on the basis of a series of rate equations with common excitation and also single-carrier-capture/escape rates to/from a QD. This approach enables us to understand the carrier-transfer dynamics responsible for the stability of a quantum two-level system formed in a single QD under various excitation conditions. We clarify that the transition between neutral and charged excitonic states is suppressed by one order of magnitude under quasiresonant excitation.
Excitation power-dependent micro-photoluminescence spectra and photon-correlation measurement are used to study the optical properties and photon statistics of single InAs quantum dots. Exciton and biexciton emissions, whose photoluminescence intensities have linear and quadratic excitation power dependences, respectively, are identified. Under pulsed laser excitation, the zero time delay peak of second order correlation function corresponding to exciton emission is well suppressed, which is a clear evidence of single photon emission.
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 photoluminescence experiments in single QDs under non-resonant excitation [1], and more recently under strictly resonant excitation of the fundamental interband transition [2,3]. This configuration minimizes the residual excitation of the QD environment that acts as a fluctuating reservoir for spectral diffusion [4], and thus allows the generation of indistinguishable photons [3]. In this paper, we report on the resonant fluorescence of the charged exciton of a single InAs/GaAs QD embedded in a planar microcavity [2]. We show in figure 1(a) the photoluminescence spectrum of a single QD with two lines X and CX that are identified as the neutral and charged excitons by auto- and cross-correlation measurements of the g(2) function, in (b,c) and (d) respectively. Fig.2 shows the resonant Rayleigh scattering spectra as a function of the laser detuning with the neutral (a) and charged (b) exciton lines. For X, we fit the spectrum with two Lorentzian lines of width 10¹eV and separated by 12.5¹eV which corresponds to the fine structure splitting. For CX, we observe a line that demonstrates the existence of residual charge carriers even if the laser is tuned in resonance with the lowest excitation of the QD, and its larger width of 40¹eV suggests spectral diffusion dephasing. References [1] P. Michler,A. Kiraz,C. Becher, W. V. Schoenfeld, P. M. Petroff, L. Zhang, E. Hu, and A. Imamoglu, Science 290 2282 (2000). [2] A. Muller, E. B. Flagg, P. Bianucci, X. Y. Wang, D. G. Deppe, W. Ma, J. Zhang, G. J. Salamo, M. Xiao, and C. K. Shih, Phys. Rev. Lett. 99 187402 (2007). [3] S. Ates, S. M. Ulrich, S. Reitzenstein, A. Lffler, A. Forchel, and P. Michler, Phys. Rev. Lett. 103 167402 (2009). [4] A. Berthelot, I. Favero, G. Cassabois, C. Voisin, C. Delalande, Ph. Roussignol, R. Ferreira, and J. M. Grard, Nature Physics 2 759 (2006).
The peaks of exciton and biexciton from the single quantum dot (QD) micro-photoluminescence spectra are identified by observing the intensity of those peaks in relation to increasing excitation power. In order to further verify the properties of the exciton and biexciton, we perform auto- and cross correlation measurements. Using the former, we confirm the antibunching property of the signal light emitted from the single QD. Using cross correlation measurement, we verify that the exciton and biexciton emissions originate from the same QD and they are strongly correlated with each other. Lastly, we analyze the behavior of the cross correlation function in both the cases of saturated and unsaturated excitation of the QD.
Single InAs quantum dot (QD) sample was grown by molecular-beam epitaxy (MBE). The Photoluminescences (PL) of the exciton and biexciton in a single QD were measured at 5 K. The PL intensity as a function of the laser excitation power, the fine structure splittings of the exciton and biexciton, and the corresponding linearly polarized emissions were analyzed. By means of Hanbury-Brown and Twiss (HBT) setup, the photon correlation between the PL of exciton and biexciton were measured, which is gave an evidence of the quantum cascade emissions between biexciton and exciton PL.
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 photoluminescence experiments in single QDs under non-resonant excitation [1], and more recently under strictly resonant excitation of the fundamental interband transition [2,3]. This configuration minimizes the residual excitation of the QD environment that acts as a fluctuating reservoir for spectral diffusion [4], and allows the generation of indistinguishable photons [3]. In this paper, we report on the resonant fluorescence of the neutral exciton in single InAs/GaAs QDs embedded in a planar microcavity [2]. We show in figure 1(a) the resonant Rayleigh scattering (RRS) spectrum as a function of the laser detuning with the neutral exciton line. We observe two Lorentzian lines of width 4μeV, separated by 9μeV and corresponding to two linear orthogonal polarizations, as expected for the fine structure splitting. We show in figure 1(b) a clear photon anti-bunching under strictly resonant excitation that proves that the RRS spectrum is dominated by resonant fluorescence of the neutral exciton. This situation is only rarely observed. The most frequent case corresponds to no resonance in the RRS spectrum and to a doublet in the non-resonant photoluminescence (PL) spectrum as shown in figure 2(a). The two lines are identified as the neutral and charged excitons by auto- and cross-correlation measurements of the g(2)(τ) function, as illustrated in figure 2(b). Strikingly, we observe the charged exciton line in the PL excitation spectrum of the neutral exciton line (figure 2(c)). This effect reveals the existence of residual charge carriers in the QD environment even under strictly resonant excitation. This favors incoherent population transfer between the charged and neutral excitons that competes with the coherent RRS effect and most frequently suppresses the resonant fluorescence of the neutral exciton. We conclude that the optical response of the QD remains affected by its environment even in case of coherent resonant pumping. [1] P. Michler, A. Kiraz, C. Becher, W. V. Schoenfeld, P. M. Petroff, L. Zhang, E. Hu, and A. Imamoglu, Science 290, 2282 (2000) [2] A. Muller, E. B. Flagg, P. Bianucci, X. Y. Wang, D. G. Deppe, W. Ma, J. Zhang, G. J. Salamo, M. Xiao, and C. K. Shih, Phys. Rev. Lett. 99, 187402 (2007) [3] S. Ates, S. M. Ulrich, S. Reitzenstein, A. Löffler, A. Forchel, and P. Michler, Phys. Rev. Lett. 103, 167402 (2009) [4] A. Berthelot, I. Favero, G. Cassabois, C. Voisin, C. Delalande, Ph. Roussignol, R. Ferreira, and J. M. Gérard, Nature Physics 2, 759 (2006)