Epitaxially-grown quantum dots (QDs) play an essential role in various quantum photonic technologies as on-demand solid-state single-photon sources. However, these QDs often suffer from the adjacent unintentional emitters such as wetting layers and other adjacent QDs, which attribute to the background noise of the QD emission and fundamentally limit the single-photon purity. Here, we develop a nanoscale site-selective luminescence quenching method using focused ion beam (FIB) and demonstrate improved single-photon purity from site-controlled single QD. Moreover, the reduced background noise led to QD emissions at higher temperatures. This nondestructive method retains the photonic structure and quenches the unwanted luminescence simultaneously, thereby indicating its promising potential in quantum emitters integrated with photonic devices.
A key point of exciton-polaritons is the real-time potential energy controllability due to the interaction from excionic components. Although wide-bandgap semiconductors can form room-temperature polaritons, lateral localizations (disorders) of planar cavities still obstruct the establishment of ballistic extensions of polariton condensates. Here, we propose a novel room-temperature polariton platform with ultralow disorders enabling to ballistic extensions. Hexagonal GaN wires moderates disorders in both photon-perspective and exciton-perspective. This structure allow us to actively control the potential energy and its landscape of room-temperature polartion condensate for the ballistic propagation. The correlation between real- and momentum-space provides strong indication of ballistic propagations.
We present a temperature dependent optical properties of Ge on Si under influence of Si intermixing and a finding on Δ valley emission. Arrhenius analysis reveals that Si intermixing significantly increase the thermal activation energy of direct valley emission by increasing the energy difference between Γ and L valley. A luminescence peak from Δ valley was revealed from the temperature-dependent study. A clear thermal activation of Δ valley could be observed. We also present monolithically integrated strained Ge nano-cavity fabricated on Si for laser application. The cavity is designed to have strain higher than 1 % and Q ~ 100,000.
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