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Excitonic complexes in MOCVD-grown InGaAs/GaAs quantum dots emitting at telecom wavelengths
摘要： Hereby, we present a comprehensive experimental and theoretical study of the electronic structure and optical properties of excitonic complexes in strain-engineered InGaAs/GaAs quantum dots (QDs) grown by metalorganic chemical vapor deposition and emitting at the 1.3-μm telecommunication window. Single QD properties have been determined experimentally for a number of nanostructures by means of excitation-power-dependent and polarization-resolved microphotoluminescence and further compared with the results of confined states calculations employing the eight-band k·p theory combined with the configuration interaction method. The origin of excitonic complexes has been exemplarily confirmed based on magneto-optical and correlation spectroscopy study. Understanding the influence of structural parameters and compositions (of QDs themselves as well as in the neighboring strain-reducing layer) allows identification of which of them are crucial to control the emission wavelength to achieve the telecommunication spectral range or to affect binding energies of the fundamental excitonic complexes. The obtained results provide deeper knowledge of control and limitations of the investigated structures in terms of good spectral isolation of individual optical transitions and spatial confinement, which are crucial in view of QD applications in single-photon sources of high purity at telecom wavelengths.
关键词： strain-reducing layer,biexciton,quantum dots,single-photon sources,exciton,telecommunication wavelengths
更新于2025-09-12 10:27:22
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Superior properties in room-temperature colloidal-dot quantum emitters revealed by ultralow-dark-count detections of temporally-purified single photons
摘要： The realization of high-quality quantum emitters that can operate at room temperature is important for accelerating the application of quantum technologies, such as quantum communication, quantum information processing, and quantum metrology. In this work, we study the photon-antibunching properties on room-temperature emission from individual colloidal quantum dots (CQDs) using superconducting-nanowire single-photon detectors and temporal filtering of the photoluminescence decay curve. We find that high single-photon purities and high photon-generation rates can be simultaneously achieved by removing the signals originating from the sequential two-photon emission of biexcitons created by multiple excitation pulses. We successfully demonstrate that the ultrahigh performance of the room-temperature single-photon sources showing g(2)(0) ? 10?2 can be confirmed by the ultralow-dark-count detection of the temporally purified single photons. These findings provide strong evidence for the attractiveness of CQDs as candidates for high-quality room-temperature quantum light sources.
关键词： single-photon sources,room-temperature,superconducting-nanowire single-photon detectors,quantum emitters,colloidal quantum dots,temporal filtering
更新于2025-09-11 14:15:04
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On‐Chip Integration of Single Photon Sources via Evanescent Coupling of Tapered Nanowires to SiN Waveguides
摘要： A method to integrate nanowire-based quantum dot single photon sources on-chip using evanescent coupling is demonstrated. By deterministically placing an appropriately tapered III-V nanowire, containing a single quantum dot, on top of a silicon-based ridge waveguide, the quantum dot emission directed toward the taper can be transferred to the ridge waveguide with calculated e?ciencies close to 100%. As the evanescent coupling is bidirectional, the source can be optically pumped in both free-space and through the ridge waveguide. The latter con?guration paves the way toward a self-contained, all-?ber, plug-and-play solution for applications requiring a bright on-demand single photon source. Using InAsP quantum dots embedded in InP nanowire waveguides, coupling e?ciencies to a SiN ridge waveguide of 74% with a single photon purity of 97% are demonstrated. The technique to demonstrate deterministic placement of single quantum emitters onto pre-fabricated waveguides is used, an important step toward the fabrication of complex quantum photonic circuits.
关键词： nanowire quantum dots,single photon sources,integrated quantum photonics
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Suspended Epoxy Polymer Inverted Tapers for Scalable Fibre-Coupled Single-Photon Devices
摘要： The combination of integrated nanophotonic circuits and single quantum emitters holds great promise for scalable quantum information processing (QIP) and for the realization of photonic quantum networks. Efficient and deterministic sources of highly-pure and indistinguishable single photons have been demonstrated using quantum dots (QDs) in GaAs nanostructures [1], enabling the integration with planar circuitry. However, the efficient out-coupling of light from the chip into optical fibres, required for communication with distant quantum nodes and photon storage, remains a challenging task. Here, we report a spot-size converter for the end-fire coupling between suspended GaAs waveguides with embedded QDs and lensed fibres.
关键词： spot-size converter,single-photon sources,photonic quantum networks,quantum dots,GaAs nanostructures
更新于2025-09-11 14:15:04
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Oxygen-incorporated single-photon sources observed at the surface of silicon carbide crystals
摘要： The formation of high-brightness single-photon sources (SPSs) that emit single photons at room temperature was recently con?rmed in oxygen-annealed SiC semiconductors (surface SPSs.) However, the defect structure of surface SPSs remains unclear, which makes device fabrication and property control dif?cult. To verify the incorporation of oxygen in surface SPSs, we fabricated SPSs using stable 18O isotopes as oxidants. By comparing this to the case of natural oxygen annealing, we found that the SP emission spectra for the 18O sample tended to have shorter peak wavelengths, slightly narrower peak widths, and higher intensities. Thus, it appeared that, in the case of the 18O sample, the phonon sideband was located closer to the zero-phonon line and that oxygen was incorporated into the defects attributed to the surface SPS.
关键词： single-photon sources,single defect,silicon carbide,oxygen isotope,semiconductors,photoluminescence
更新于2025-09-09 09:28:46
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Long-lived non-classical correlations towards quantum communication at room temperature
摘要： Heralded single-photon sources with on-demand readout are a key enabling technology for distributed photonic networks. Such sources have been demonstrated in both cryogenic solid-state and cold-atoms systems. Practical long-distance quantum communication may benefit from using technologically simple systems such as room-temperature atomic vapours. However, atomic motion has so far limited the single-excitation lifetime in such systems to the microsecond range. Here we demonstrate efficient heralding and readout of single collective excitations created in warm caesium vapour. Using the principle of motional averaging we achieve a collective excitation lifetime of 0.27 ± 0.04 ms, two orders of magnitude larger than previously achieved for single excitations in room-temperature sources. We experimentally verify non-classicality of the light-matter correlations by observing a violation of the Cauchy-Schwarz inequality with R = 1.4 ± 0.1 > 1. Through spectral and temporal analysis we investigate the readout noise that limits single-photon operation of the source.
关键词： quantum communication,room-temperature atomic vapours,motional averaging,non-classical correlations,single-photon sources
更新于2025-09-09 09:28:46
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Dispersion measurement method with down conversion process
摘要： Proper characterization of nonlinear crystals is essential for designing single photon sources. We show a technique for dispersion characterization of a nonlinear material by making use of phase matching in the process of parametric down conversion. We use our procedure to improve the Sellmeier coefficients measured by another methods. Our method is demonstrated on an exemplary periodically poled potassium titanyl phosphate KTiOPO4 crystal phase-matched for 396 nm to 532 nm and 1550 nm. We show a procedure to characterize the dispersion in the range of 390 to 1800 nm by means of only one spectrometer for the UV–visible range.
关键词： second order nonlinear optical processes,single photon sources,spontaneous parametric down-conversion,dispersion measurement
更新于2025-09-09 09:28:46