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Author: Lazić, S. × Type: Article ×

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Now showing 1 - 3 of 3
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    Surface acoustic wave modulation of single photon emission from GaN/InGaN nanowire quantum dots
    (Bristol : IOP Publ., 2018) Lazić, S.; Chernysheva, E.; Hernández-Mínguez, A.; Santos, P.V.; van der Meulen, H.P.
    On-chip quantum information processing requires controllable quantum light sources that can be operated on-demand at high-speeds and with the possibility of in-situ control of the photon emission wavelength and its optical polarization properties. Here, we report on the dynamic control of the optical emission from core-shell GaN/InGaN nanowire (NW) heterostructures using radio frequency surface acoustic waves (SAWs). The SAWs are excited on the surface of a piezoelectric lithium niobate crystal equipped with a SAW delay line onto which the NWs were mechanically transferred. Luminescent quantum dot (QD)-like exciton localization centers induced by compositional fluctuations within the InGaN nanoshell were identified using stroboscopic micro-photoluminescence (micro-PL) spectroscopy. They exhibit narrow and almost fully linearly polarized emission lines in the micro-PL spectra and a pronounced anti-bunching signature of single photon emission in the photon correlation experiments. When the nanowire is perturbed by the propagating SAW, the embedded QD is periodically strained and its excitonic transitions are modulated by the acousto-mechanical coupling, giving rise to a spectral fine-tuning within a ~1.5 meV bandwidth at the acoustic frequency of ~330 MHz. This outcome can be further combined with spectral detection filtering for temporal control of the emitted photons. The effect of the SAW piezoelectric field on the QD charge population and on the optical polarization degree is also observed. The advantage of the acousto-optoelectric over other control schemes is that it allows in-situ manipulation of the optical emission properties over a wide frequency range (up to GHz frequencies).
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    Dynamics of indirect exciton transport by moving acoustic fields
    (Bristol : IOP, 2014) Violante, A.; Cohen, K.; Lazić, S.; Hey, R.; Rapaport, R.; Santos, P.V.
    We report on the modulation of indirect excitons (IXs) as well as their transport by moving periodic potentials produced by surface acoustic waves (SAWs). The potential modulation induced by the SAW strain modifies both the band gap and the electrostatic field in the quantum wells confining the IXs, leading to changes in their energy. In addition, this potential captures and transports IXs over several hundreds of μm. While the IX packets keep to a great extent their spatial shape during transport by the moving potential, the effective transport velocity is lower than the SAW group velocity and increases with the SAW amplitude. This behavior is attributed to the capture of IXs by traps along the transport path, thereby increasing the IX transit time. The experimental results are well-reproduced by an analytical model for the interaction between trapping centers and IXs during transport.
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    Mechanism of non-classical light emission from acoustically populated (311)A GaAs quantum wires
    (Milton Park : Taylor & Francis, 2012) Lazić, S.; Hey, R.; Santos, P.V.
    We employ surface acoustic waves (SAWs) to control the transfer of photo-generated carriers between interconnected quantum wells and quantum wires (QWRs) grown on pre-patterned (311)A GaAs substrates. Optical studies, carried out under remote acoustic excitation of a single QWR, have shown sharp photoluminescence lines and antibunched photons with tunable emission energy. These features are attributed to recombination of acoustically transported carriers in potential inhomogeneities within the wire. The origin of the photon antibunching is discussed in terms of a 'bottleneck' in the number of carriers trapped in the QWR, which restricts the number of recombination events per SAW cycle. We propose a model for antibunching based on the trapping of carriers induced by the SAW piezoelectric field in states at the interface between the GaAs QWR and the AlGaAs barriers. Non-classical light is emitted during the subsequent release of the trapped carriers into the recombination centers within the wire. The spatial distribution of the emitting recombination centers is estimated using time-resolved measurements.