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Applied Physics Letters

Resonance fluorescence of single In(Ga)As quantum dots emitting in the telecom C-band

Cornelius Nawrath, Hüseyin Avni Vural, Julius Fischer, Richard Schaber, Simone Luca Portalupi, Michael Jetter, Peter Michler

Published Jun 14, 2021• 39 citations
Publisher

Abstract

An emission wavelength around 1550 nm (telecom C-band) is highly appealing for nonclassical light sources, among others, due to the absorption minimum in standard glass fibers. In particular, semiconductor quantum dots at this wavelength promise to provide the outstanding results achieved with this emitter type in the near-infrared spectral region. Here, we study resonance fluorescence from InAs/GaAs quantum dots emitting in the telecom C-band under continuous wave and pulsed excitation. For the prior case, the quantum dot is excited in the strong driving regime and the characteristic Mollow triplet is observed allowing to draw conclusions on the nature and quantitative influence of different decoherence mechanisms on the emission. Furthermore, under pulsed excitation, highly pure single-photon emission (g(2)(0)=0.023 ± 0.019) is demonstrated and a measurement of the photon indistinguishability (VTPI=0.144 ± 0.015; full width at half maximum of the time window for post-selection of (305 ± 33)ps with an associated maximally attainable value VTPI,p=0.955) is presented. In the process of making the emission properties of telecom quantum dots comparable to their well-established counterparts emitting in the near-infrared spectral region, these results represent a benchmark and provide valuable information for future optimization of sample structures.

DOI
10.1063/5.0048695

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cond-mat.mes-hallCross-listedarXiv:2610.38060•Oct 29, 2026
An emission wavelength around 1550 nm (telecom C-band) is highly appealing for nonclassical light sources, among others, due to the absorption minimum in standard glass fibers. In particular, semiconductor quantum dots at this wavelength promise to provide the outstanding results achieved with this emitter type in the near-infrared spectral region. Here, we study resonance fluorescence from InAs/GaAs quantum dots emitting in the telecom C-band under continuous wave and pulsed excitation. For the prior case, the quantum dot is excited in the strong driving regime and the characteristic Mollow triplet is observed allowing to draw conclusions on the nature and quantitative influence of different decoherence mechanisms on the emission. Furthermore, under pulsed excitation, highly pure single-photon emission (g(2)(0)=0.023 ± 0.019) is demonstrated and a measurement of the photon indistinguishability (VTPI=0.144 ± 0.015; full width at half maximum of the time window for post-selection of (305 ± 33)ps with an associated maximally attainable value VTPI,p=0.955) is presented. In the process of making the emission properties of telecom quantum dots comparable to their well-established counterparts emitting in the near-infrared spectral region, these results represent a benchmark and provide valuable information for future optimization of sample structures.
Many quantum communication schemes require sources of single, indistinguishable and entangled photon pairs with high brightness. Semiconductor quantum dots (QDs) hold great promise to meet these requirements offering the additional key advantage of the possibility of shifting the emission wavelength to the telecom C-band (centered around 1550 nm). This wavelength range is especially sought-after for fiber-based applications due to the global absorption minimum in standard glass fibers which maximizes the attainable communication distance.
High Resolution Image Download MS PowerPoint Slide Semiconductor quantum dots (QDs) enable the generation of single and entangled photons, which are useful for various applications in photonic quantum technologies. Specifically for quantum communication via fiber-optical networks, operation in the telecom C-band centered around 1550 nm is ideal. The direct generation of QD-photons in this spectral range with high quantum-optical quality, however, remained challenging. Here, we demonstrate the coherent on-demand generation of indistinguishable photons in the telecom C-band from single QD devices consisting of InAs/InP QD-mesa structures heterogeneously integrated with a metallic reflector on a silicon wafer. Using pulsed two-photon resonant excitation of the biexciton–exciton radiative cascade, we observe Rabi rotations up to pulse areas of 4π and a high single-photon purity in terms of g (2) (0) = 0.005(1) and 0.015(1) for exciton and biexciton photons, respectively. Applying two independent experimental methods, based on fitting Rabi rotations in the emission intensity and performing photon cross-correlation measurements, we consistently obtain preparation fidelities at the π-pulse exceeding 80%. Finally, performing Hong–Ou–Mandel-type two-photon interference experiments, we obtain a photon-indistinguishability of the full photon wave packet of up to 35(3)%, representing a significant advancement in the photon-indistinguishability of single photons emitted directly in the telecom C-band.
Semiconductor quantum dots (QDs) enable the generation of single and entangled photons, useful for various applications in photonic quantum technologies. Specifically for quantum communication via fiber-optical networks, operation in the telecom C-band centered around 1550 \,nm is ideal. The direct generation of QD-photons in this spectral range and with high quantum-optical quality, however, remained challenging. Here, we demonstrate the coherent on-demand generation of indistinguishable photons in the telecom C-band from single QD devices consisting of InAs/InP QD-mesa structures heterogeneously integrated with a metallic reflector on a silicon wafer. Using pulsed two-photon resonant excitation of the biexciton-exciton radiative cascade, we observe Rabi rotations up to pulse areas of 4π4π4π and a high single-photon purity in terms of g(2)(0)=0.005(1)g^{(2)}(0)=0.005(1)g(2)(0)=0.005(1) and 0.015(1)0.015(1)0.015(1) for exciton and biexciton photons, respectively. Applying two independent experimental methods, based on fitting Rabi rotations in the emission intensity and performing photon cross-correlation measurements, we consistently obtain preparation fidelities at the πππ-pulse exceeding 80%\%%. Finally, performing Hong-Ou-Mandel-type two-photon interference experiments we obtain a photon-indistinguishability of the full photon wave packet of up to 35(3)%35(3)\%35(3)%, representing a significant advancement in the photon-indistinguishability of single photons emitted directly in the telecom C-band.
The role of resonant pumping schemes in improving the photon coherence is investigated on InAs/InGaAs/GaAs quantum dots (QDs) emitting in the telecom C-band. The linewidths of transitions of multiple exemplary quantum dots are determined under above-band pumping and resonance fluorescence (RF) via Fourier-transform spectroscopy and resonance scans, respectively. The average linewidth is reduced from (9.74 ± 3.3) GHz in the above-band excitation to (3.50 ± 0.39) GHz under RF underlining its superior coherence properties. Furthermore, the feasibility of coherent state preparation with a fidelity of (49.2 ± 5.8)% is demonstrated, constituting a first step toward on-demand generation of coherent, single, telecom C-band photons directly emitted by QDs. Finally, two-photon excitation of the biexciton is investigated as a resonant pumping scheme. A deconvoluted single-photon purity value of gHBT(2)(0)=0.072 ± 0.104 and a postselected degree of indistinguishability of VHOM=0.894 ± 0.109 are determined for the biexciton transition. This represents another step in demonstrating the necessary quantum optical properties for prospective applications.
We report on resonance fluorescence from a single quantum dot emitting at telecom wavelengths. We perform high-resolution spectroscopy and observe the Mollow triplet in the Rabi regime—a hallmark of resonance fluorescence. The measured resonance-fluorescence spectra allow us to rule out pure dephasing as a significant decoherence mechanism in these quantum dots. Combined with numerical simulations, the experimental results provide robust characterisation of charge noise in the environment of the quantum dot. Resonant control of the quantum dot opens up new possibilities for the on-demand generation of indistinguishable single photons at telecom wavelengths as well as quantum optics experiments and direct manipulation of solid-state qubits in telecom-wavelength quantum dots.
Semiconductor quantum dots emitting in the telecommunication O- and C-bands are promising candidates as single-photon sources for fiber-based quantum communication. In this work, we show how coherent quasi-resonant and phonon-assisted excitation help reveal the intrinsic optical properties of InAs quantum dots embedded in relaxed InGaAs matrices on top of metamorphic InGaAs layers for achieving emission in the telecom bands. By systematically comparing excitation schemes, we separate excitation-induced effects from intrinsic emitter properties. This allows us to observe linewidths as narrow as 21 μμμeV, the disappearance of slow decay channels, and single-photon purity reaching second-order autocorrelation values in the order of 10−210^{-2}10−2. Photoluminescence excitation reveals higher excited states, enabling coherent control of trion transitions and the observation of Rabi-like oscillations in both telecom bands. These results confirm the promising potential of these quantum dots for applications in quantum technologies.