Plug&Play Fiber‐Coupled 73 kHz Single‐Photon Source Operating in the Telecom O‐Band

A user‐friendly, fiber‐coupled, single‐photon source operating at telecom wavelengths is a key component of photonic quantum networks providing long‐haul, ultra‐secure data exchange. To take full advantage of quantum‐mechanical data protection and to maximize the transmission rate and distance, a true quantum source providing single photons on demand is highly desirable. This great challenge is tackled by developing a ready‐to‐use semiconductor quantum‐dot‐based device that launches single photons at a wavelength of 1.3 µm directly into a single‐mode optical fiber. In the proposed approach, the quantum dot is deterministically integrated into a nanophotonic structure to ensure efficient on‐chip coupling into a fiber. The whole arrangement is integrated into a 19ʺ compatible housing to enable stand‐alone operation by cooling via a compact Stirling cryocooler. The realized source delivers single photons with a multiphoton events probability as low as 0.15 and a single‐photon emission rate of up to 73 kHz into a standard telecom single‐mode fiber.BMBF, 05M20ZBM, Forschungscampus MODAL - Mathematical Optimization and Data Analysis Laboratories - zweite Förderphase (Stabilisierung)TU Berlin, Open-Access-Mittel – 202

Quantum efficiency and oscillator strength of InGaAs quantum dots for single-photon sources emitting in the telecommunication O-band

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 119, 061103 (2021) and may be found at https://doi.org/10.1063/5.0059458.We demonstrate experimental results based on time-resolved photoluminescence spectroscopy to determine the oscillator strength and the internal quantum efficiency (IQE) of InGaAs quantum dots (QDs). Using a strain-reducing layer, these QDs can be employed for the manufacturing of single-photon sources emitting in the telecom O-Band. The oscillator strength and IQE are evaluated by determining the radiative and non-radiative decay rates under the variation of the optical density of states at the position of the QD for InGaAs QDs emitting at wavelengths below 1 μm. For this purpose, we perform measurements on a QD sample for different thicknesses of the capping layer realized by a controlled wet-chemical etching process. From numeric modeling of the radiative and non-radiative decay rates dependence on the capping layer thickness, we determine an oscillator strength of 24.6 ± 3.2 and a high IQE of (85 ± 10)% for the long-wavelength InGaAs QDs.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeBMBF, 13N14876, Quantenkommunikations-Systeme auf Basis von Einzelphotonenquellen (QuSecure

Thermal stability of emission from single InGaAs/GaAs quantum dots at the telecom O-band

Single-photon sources are key building blocks in most of the emerging secure telecommunication and quantum information processing schemes. Semiconductor quantum dots (QD) have been proven to be the most prospective candidates. However, their practical use in fiber-based quantum communication depends heavily on the possibility of operation in the telecom bands and at temperatures not requiring extensive cryogenic systems. In this paper we present a temperature-dependent study on single QD emission and single-photon emission from metalorganic vapour-phase epitaxy-grown InGaAs/GaAs QDs emitting in the telecom O-band at 1.3 μm. Micro-photoluminescence studies reveal that trapped holes in the vicinity of a QD act as reservoir of carriers that can be exploited to enhance photoluminescence from trion states observed at elevated temperatures up to at least 80 K. The luminescence quenching is mainly related to the promotion of holes to higher states in the valence band and this aspect must be primarily addressed in order to further increase the thermal stability of emission. Photon autocorrelation measurements yield single-photon emission with a purity of g(2)50K(0)=0.13 up to 50 K. Our results imply that these nanostructures are very promising candidates for single-photon sources at elevated (e.g., Stirling cryocooler compatible) temperatures in the telecom O-band and highlight means for improvements in their performance

Interplay between emission wavelength and s-p splitting in MOCVD-grown InGaAs/GaAs quantum dots emitting above 1.3 μm

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 116, 023102 (2020) and may be found at https://doi.org/10.1063/1.5124812.The electronic structure of strain-engineered single InGaAs/GaAs quantum dots emitting in the telecommunication O band is probed experimentally by photoluminescence excitation spectroscopy. The observed resonances can be attributed to p-shell states of individual quantum dots. The determined energy difference between the s-shell and the p-shell shows an inverse dependence on the emission energy. The experimental data are compared with the results of confined state calculations, where the impact of the size and composition in the investigated structures is simulated within the 8-band k·p model. On this basis, the experimental observation is attributed mainly to changes in the indium content within individual quantum dots, indicating a way of engineering and selecting a desired quantum dot whose electronic structure is the most suitable for a given nanophotonic application