Bremer, LucasWeber, KseniaFischbach, SarahThiele, SimonSchmidt, MarcoKaganskiy, ArsentyRodt, SvenHerkommer, AloisSartison, MarcPortalupi, Simone LucaMichler, PeterGiessen, HaraldReitzenstein, Stephan2020-11-062020-11-062020-10-01https://depositonce.tu-berlin.de/handle/11303/11848http://dx.doi.org/10.14279/depositonce-10738User-friendly single-photon sources with high photon-extraction efficiency are crucial building blocks for photonic quantum applications. For many of these applications, such as long-distance quantum key distribution, the use of single-mode optical fibers is mandatory, which leads to stringent requirements regarding the device design and fabrication. We report on the on-chip integration of a quantum dot (QD) microlens with a 3D-printed micro-objective in combination with a single-mode on-chip fiber coupler. The practical quantum device is realized by the deterministic fabrication of the QD-microlens via in situ electron-beam lithography and the 3D two-photon laser writing of the on-chip micro-objective and fiber chuck. A QD with a microlens is an efficient single-photon source, whose emission is collimated by the on-chip micro-objective. A second polymer microlens is located at the end facet of the single-mode fiber and ensures that the collimated light is efficiently coupled into the fiber core. For this purpose, the fiber is placed in an on-chip fiber chuck, which is precisely aligned to the QD-microlens thanks to the sub-micrometer processing accuracy of high-resolution two-photon direct laser writing. The resulting quantum device has a broadband photon extraction efficiency, a single-mode fiber-coupling efficiency of 22%, a measured single-photon flux of 42 kHz (8.9 kHz) under cw (pulsed) optical excitation, which corresponds to 1.5 MHz (0.3 MHz) at the single-mode fiber output, and a multi-photon probability in terms of g(2)(0) = 0.00±0.04/0.00 (0.13 ± 0.05) under cw (pulsed) optical excitation. The stable design of the developed fiber-coupled quantum device makes it highly attractive for integration into user-friendly plug-and-play quantum applications.en530 Physikoptical fibersquantum dotselectron-beam lithographyphotoemissionquantum information3D printingmicroopticsquasiparticlemultiphoton lithographyoptical propertiesArticle2378-0967