Alexey A. Toropov, Maxim V. Rakhlin, K. G. Belyaev, Sergey Vladimirovich Sorokin, Grigorii V. Klimko, Sergey V. Gronin, Irina V. Sedova, Ivan S. Mukhin, T. V. Shubina, S. V. Ivanov
We report on emission properties of single-photon sources of visible light, based on InAs/AlGaAs, CdTe/ZnTe, and CdSe/ZnSe quantum dot (QD) heterostructures grown by molecular beam epitaxy. For all types of QDs, the studies performed by micro-photoluminescence and photon correlation spectroscopies demonstrated the single-photon nature of emission with typical values of the second-order correlation function g (2) (0) less than 0.2 and allowed evaluation of sub-microsecond kinetics of blinking governed by local charging effects.
We report on emission properties of single-photon sources of visible light, based on InAs/AlGaAs, CdTe/ZnTe, and CdSe/ZnSe quantum dot (QD) heterostructures grown by molecular beam epitaxy. For all types of QDs, the studies performed by micro-photoluminescence and photon correlation spectroscopies demonstrated the single-photon nature of emission with typical values of the second-order correlation function g (2) (0) less than 0.2 and allowed evaluation of sub-microsecond kinetics of blinking governed by local charging effects.
The statistics of photon correlations in the emission of single InAs/AlGaAs quantum dots grown by molecular beam epitaxy and fitted with AlGaAs waveguide nanoantennas for efficient extraction of radiation is investigated. A single-photon source for the red spectral range with an average emission rate exceeding 5 MHz and a zero-delay second-order correlation function of g (2) (0) = 0.08 is realized on the basis of these photonic nanostructures. The degree of indistinguishability of consecutively emitted photons measured in Hong-Ou-Mandel interferometry under above-barrier excitation is about 30%.
We report correlation and cross-correlation measurements of photons emitted under continuous wave excitation by a single II–VI quantum dot (QD) grown by molecular-beam epitaxy. A standard technique of microphotoluminescence combined with an ultrafast photon correlation setup allowed us to see an antibunching effect on photons emitted by excitons recombining in a single CdTe∕ZnTe QD, as well as cross correlation within the biexciton (X2)-exciton (X) radiative cascade from the same dot. Fast microchannel plate photomultipliers and a time-correlated single photon module gave us an overall temporal resolution of 140ps better than the typical exciton lifetime in II–VI QDs of about 250ps.
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 non-resonant and resonant photoluminescence experiments in single QDs [1,2,3,4]. Other experiments demonstrated the possibility to use single QDs for the generation of indistinguishable single photons [3]. An important general issue is to reach the so-called fundamental radiative limit. Several strategies have been followed in that sense such as the shortening of population lifetime induced by the Purcell effect [5] or the reduction of pure dephasing by resonant excitation [2,3,4]. 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 always limited to the 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, in an orthogonal excitation-detection geometry [4]. We present an original type of single photon source based on the coherent laser light scattering by a single QD [6]. Besides the antibunching effect showing the non-classical nature of the emitted light, we observe that the QD emission spectrum is determined by the spectrum of the resonant excitation laser. We present 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. We show that, by reducing the resonant excitation power, the so-called 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 [6]. In conclusion, the resulting " ultra-coherent single photon source " promises high degrees of indistinguishability of the emitted photons which is a crucial requirement for quantum information applications. [1] P. Michler et al., Science 290, 2282 (2000). [2] A. Muller et al., Phys. Rev. Lett. 99, 187402 (2007). [3] S. Ates et al., Phys. Rev. Lett. 103, 167402 (2009). [4] H. S. Nguyen et al., Phys. Rev. Lett. 108, 057401 (2012). [5] C. Santori et al., Nature 419, 594 (2002). [6] H. S. Nguyen et al., Appl. Phys. Lett. 99, 261904 (2011).
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).
Fast, high efficiency and low error single-photon sources are required for the implementation of a number of quantum information processing applications. The fastest triggered single-photon sources to date have been demonstrated using epitaxially grown semiconductor quantum dots (QDs), which can be conveniently integrated with optical microcavities. Recent advances in QD technology, including demonstrations of high temperature and telecommunications wavelength single-photon emission, have made QD single-photon sources more practical. Here we discuss the applications of single-photon sources and their various requirements, before reviewing the progress made on a QD platform in meeting these requirements.