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Engel, Lena

Lena Engel

MSc.

PhD-Student
Institut für Halbleiteroptik und Funktionelle Grenzflächen
Semiconductor Epitaxy Group

Kontakt

+49 711 685 63876
E-Mail

Allmandring 3
70569 Stuttgart
Deutschland
Raum: 0.074

Publikationen

2025
1. Pfister, U., Wendland, D., Hornung, F., Engel, L., Hüging, H., Herzog, E., Vijayan, P., Joos, R., Jung, E., Jetter, M., Portalupi, S. L., Pernice, W. H. P., & Michler, P. (2025). Telecom wavelength quantum dots interfaced with silicon-nitride circuits via photonic wire bonding. Npj Nanophotonics, 2, Article 1. https://doi.org/10.1038/s44310-025-00061-w
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  BibTeX
  @article{Pfister2025, abstract = {Photonic integrated circuits find applications in classical and quantum communication, computing and sensing. For ideal performance, efforts are made to effectively combine different platforms to benefit from their respective strengths. Here, direct laser written photonic wire bonds are employed to interface triggered sources of quantum light, based on semiconductor quantum dots embedded into etched microlenses, with low-loss silicon-nitride photonics. Single photons at telecom wavelengths are generated by In(Ga)As quantum dots which are then funneled into a silicon-nitride chip containing single-mode waveguides and beamsplitters. The second-order correlation function of g(2)(0) = 0.11 {\textpm} 0.02, measured via the on-chip beamsplitter, clearly demonstrates the transfer of single photons into the silicon-nitride platform. The photonic wire bonds funnel on average 27.9 {\textpm} 8.0{\%} of the bare microlens emission (NA = 0.6) into the silicon-nitride-based photonic integrated circuit even at cryogenic temperatures. This opens the route for the effective future up-scaling of circuitry complexity based on the use of multiple different platforms.}, author = {Pfister, Ulrich and Wendland, Daniel and Hornung, Florian and Engel, Lena and H{\"u}ging, Hendrik and Herzog, Elias and Vijayan, Ponraj and Joos, Raphael and Jung, Erik and Jetter, Michael and Portalupi, Simone L. and Pernice, Wolfram H. P. and Michler, Peter}, day = 17, doi = {10.1038/s44310-025-00061-w}, issn = {2948-216X}, journal = {npj Nanophotonics}, month = {03}, number = 1, pages = 11, title = {Telecom wavelength quantum dots interfaced with silicon-nitride circuits via photonic wire bonding}, url = {https://doi.org/10.1038/s44310-025-00061-w}, volume = 2, year = 2025 }
  Link
  https://doi.org/10.1038/s44310-025-00061-w
2024
1. Engel, L., Khamseh, F., Zimmer, M., Jetter, M., & Michler, P. (2024). Surface relief VCSELs at 670 nm with integrated polymer microlens for highly collimated fundamental-mode emission. Opt. Lett., 49, Article 11. https://doi.org/10.1364/OL.524493
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  @article{Engel:24, abstract = {We demonstrate the integration of a wet-chemically etched surface relief on a vertical-cavity surface-emitting laser (VCSEL) emitting in the red spectral range for higher-order mode suppression. With this relief, fundamental-mode emission is achieved over the entire power range from threshold beyond thermal rollover. For collimation of the emitted beam, we implement polymer microlenses fabricated on-chip by a thermal reflow technique. We reduce the angle of divergence for all injected currents to a maximum of 2$\circ$. By measuring high-resolution spectra, we show that Gaussian beam profiles correspond to pure fundamental-mode emission which is preserved after implementation of the polymer microlens onto the etched relief, proving the compatibility of the two processes.}, author = {Engel, Lena and Khamseh, Farnaz and Zimmer, Michael and Jetter, Michael and Michler, Peter}, doi = {10.1364/OL.524493}, journal = {Opt. Lett.}, month = {06}, number = 11, pages = {2898--2901}, publisher = {Optica Publishing Group}, title = {Surface relief VCSELs at 670 nm with integrated polymer microlens for highly collimated fundamental-mode emission}, url = {https://opg.optica.org/ol/abstract.cfm?URI=ol-49-11-2898}, volume = 49, year = 2024 }
  Link
  https://opg.optica.org/ol/abstract.cfm?URI=ol-49-11-2898
2023
1. Engel, L., Kolatschek, S., Herzog, T., Vollmer, S., Jetter, M., Portalupi, S. L., & Michler, P. (2023). Purcell enhanced single-photon emission from a quantum dot coupled to a truncated Gaussian microcavity. Applied Physics Letters, 122, Article 4. https://doi.org/10.1063/5.0128631
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  @article{doi:10.1063/5.0128631, abstract = { Purcell enhancement of quantum dot (QD) single-photon emission and increased device brightness have been demonstrated with various types of microcavities. Here, we present the first realization of a truncated Gaussian-shaped microcavity coupled to a QD. The implementation is based on wet-chemical etching and epitaxial semiconductor overgrowth. The cavity modes and their spatial profiles are experimentally studied and agree well with simulations. The fundamental mode wavelength with Q-factors around 6000 and a small polarization splitting of 29 μeV can be reproducibly controlled via fabrication design, enabling the adaption of the cavity to a specific QD. Finally, transitions of a QD inside a cavity are tuned on and off resonance via temperature tuning. A reduced decay time by a factor above 3 on resonance clearly indicates Purcell enhancement while second-order correlation measurements of g(2)(0) = 0.057 prove that the QDs single-photon characteristic is preserved. }, author = {Engel, Lena and Kolatschek, Sascha and Herzog, Thomas and Vollmer, Sergej and Jetter, Michael and Portalupi, Simone L. and Michler, Peter}, doi = {10.1063/5.0128631}, eprint = {https://doi.org/10.1063/5.0128631}, journal = {Applied Physics Letters}, number = 4, pages = 043503, title = {Purcell enhanced single-photon emission from a quantum dot coupled to a truncated Gaussian microcavity}, url = {/brokenurl# https://doi.org/10.1063/5.0128631 }, volume = 122, year = 2023 }
  Link
  /brokenurl# https://doi.org/10.1063/5.0128631
2. Strobel, T., Weber, J. H., Schmidt, M., Wagner, L., Engel, L., Jetter, M., Wieck, A. D., Portalupi, S. L., Ludwig, A., & Michler, P. (2023). A Unipolar Quantum Dot Diode Structure for Advanced Quantum Light Sources. Nano Letters, 23, Article 14. https://doi.org/10.1021/acs.nanolett.3c01658
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  @article{Strobel_2023, author = {Strobel, Tim and Weber, Jonas H. and Schmidt, Marcel and Wagner, Lukas and Engel, Lena and Jetter, Michael and Wieck, Andreas D. and Portalupi, Simone L. and Ludwig, Arne and Michler, Peter}, doi = {10.1021/acs.nanolett.3c01658}, journal = {Nano Letters}, month = {07}, number = 14, pages = {6574--6580}, publisher = {American Chemical Society ({ACS})}, title = {A Unipolar Quantum Dot Diode Structure for Advanced Quantum Light Sources}, url = {https://doi.org/10.1021%2Facs.nanolett.3c01658}, volume = 23, year = 2023 }
  Link
  https://doi.org/10.1021%2Facs.nanolett.3c01658
2018
1. Sartison, M., Engel, L., Kolatschek, S., Olbrich, F., Nawrath, C., Hepp, S., Jetter, M., Michler, P., & Portalupi, S. L. (2018). Deterministic integration and optical characterization of telecom O-band quantum dots embedded into wet-chemically etched Gaussian-shaped microlenses. Appl. Phys. Lett., 113, Article 3. https://doi.org/10.1063/1.5038271
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  @article{sartison2018deterministic, abstract = {In the present study, we report on the deterministic integration of quantum dots, emitting in the telecom O-band, into wet-chemically fabricated Gaussian-shaped microlenses which exhibit a surface quality comparable to epi-ready wafers. The slow wet-chemical etching rate enables us to gain control of the lens aspect-ratio and the vertical position with respect to the quantum dot, allowing us to engineer the far field shape to better match the acceptance profile of single-mode fibers. Maximum light enhancement values of around 10 to 16 could be achieved for collection numerical apertures from 0.6 to 0.2, respectively. The current results constitute an important step forward in transferring state-of-the-art performances achieved in the near-infrared regime to the key wavelengths for long distance fiber communication.}, author = {Sartison, Marc and Engel, Lena and Kolatschek, Sascha and Olbrich, Fabian and Nawrath, Cornelius and Hepp, Stefan and Jetter, Michael and Michler, Peter and Portalupi, Simone Luca}, booktitle = {Applied Physics Letters}, comment = {doi: 10.1063/1.5038271}, doi = {10.1063/1.5038271}, issn = {00036951}, journal = {Appl. Phys. Lett.}, month = {07}, number = 3, pages = {032103--}, privnote = {doi: 10.1063/1.5038271}, publisher = {American Institute of Physics}, title = {Deterministic integration and optical characterization of telecom O-band quantum dots embedded into wet-chemically etched Gaussian-shaped microlenses}, url = {https://doi.org/10.1063/1.5038271}, volume = 113, year = 2018 }
  Link
  https://doi.org/10.1063/1.5038271

Lena Engel

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2025

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2024

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2023

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2018

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Lena Engel

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Publikationen

2025

BibTeX

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2024

BibTeX

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2023

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2018

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