Fibre-based long-distance quantum implementations, like quantum relays and quantum networks, require the use of non-classical photons at telecommunication wavelengths, in order to benefit from low absorption and wavepacket dispersion. Two wavelengths regimes are of particular interest, the telecom O-band (centred around 1310 nm) and the telecom C-band (centred around 1550 nm). Semiconductor quantum dots have shown to be a very appealing candidate for the generation of single, indistinguishable and entangled photons. Their solid-state host matrix enables the use of photonic structures to tailor and enhance the source properties. Currently, the quantum dots reaching the best performances as non-classical light emitters are based on the GaAs platform. The main drawback of these non-classical light sources is their natural emission wavelength, well within the near-infrared regime (NIR), generally around 800-900 nm, so not suitable for fibre-based experiments. In this talk we will discuss two approaches to reach telecom wavelengths utilizing semiconductor quantum dots. Firstly, the utilization of quantum frequency conversion will enable the use of non- linear processes to transfer the high quality NIR photons to any other wavelength, here 1550 nm . Secondly, growth engineering can be utilized to modify size and strain conditions of the quantum dot, enabling the emission at telecom O- and C-band with the same dot stoichiometry as for the NIR ones [2-7]. Approaches to improve the performances of these QDs beyond current state-of-the-art will be carefully discussed.
 J. H. Weber, B. Kambs, J. Kettler, S. Kern, J. Maisch, H. Vural, M. Jetter, S. L. Portalupi, C. Becher, and P. Michler, “Two-photon interference in the telecom C-band after frequency conversion of photons from remote quantum emitters”, Nat. Nanotechnol. 14, 23 (2019).
 M. Paul, J. Kettler, K. Zeuner, C. Clausen, M. Jetter, and P. Michler, “Metal-organic vapor-phase epitaxy-grown ultra-low density InGaAs/GaAs quantum dots exhibiting cascaded single-photon emission at 1.3 μm”, Appl. Phys. Lett. 106, 122105 (2015).
 M. Paul, F. Olbrich, J. Höschele, S. Schreier, J. Kettler, S. L. Portalupi, M. Jetter, and P. Michler, “Single-photon emission at 1.55 μ m from MOVPE-grown InAs quantum dots on InGaAs/GaAs metamorphic buffers”, Appl. Phys. Lett. 111, 033102 (2017).
 F. Olbrich, J. Höschele, M. Müller, J. Kettler, S. L. Portalupi, M. Paul, M. Jetter, and P. Michler, “Polarization- entangled photons from an InGaAs-based quantum dot emitting in the telecom C-band”, Appl. Phys. Lett. 111, 133106 (2017).
 C. Nawrath, F. Olbrich, M. Paul, S. L. Portalupi, M. Jetter, and P. Michler, “Coherence and indistinguishability of highly pure single photons from non-resonantly and resonantly excited telecom C-band quantum dots”, Appl. Phys. Lett. 115, 023103 (2019).
 S. L. Portalupi, M. Jetter, and P. Michler, “InAs quantum dots grown on metamorphic buffers as non-classical light sources at telecom C-band: a review”, Semicond. Sci. Technol. 34, 053001 (2019).
 J. Yang, C. Nawrath, R. Keil, R. Joos, X. Zhang, B. Höfer, Y. Chen, M. Zopf, M. Jetter, S. L. Portalupi, F. Ding, P. Michler, and O. Schmidt, “Quantum dot-based broadband optical antenna for efficient extraction of single photons in the telecom O-band”, Opt. Express 28, 19457 (2020).
Topic: INQNET seminar
Time: February 8, 2021 09:30 AM Pacific Time (US and Canada)
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