Katharina Dahler

2025

1. Zimmer, M., Dahler, K., Jetter, M., & Michler, P. (2025). Monolithic 850 nm VCSEL array for quantum key distribution applications via the polarization-based BB84 and decoy-state protocol. Opt. Lett., 50, Article 18. https://doi.org/10.1364/OL.573598
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   BibTeX

   @article{Zimmer:25, abstract = {Quantum cryptography based on the application of single photons offers a secure communication based on the laws of physics. However, given the sophisticated and challenging implementation of true-single photon sources, the majority of implementations takes advantage of the decoy state protocol, which uses weak coherent pulses instead. For polarization-based protocols, a typical sender configuration includes one or multiple laser sources with external optical elements to realize four different polarization states and two intensity levels (signal and decoy). In this regard, the application of eight independent lasers with fixed polarization makes an external state preparation unnecessary and allows for a higher signal rate, while requiring otherwise identical optical properties of all laser devices such as wavelength and linewidth. Here, we demonstrate a solution on the basis of a compact, monolithic VCSEL array operating at room temperature. The array consists of eight VCSELs with integrated subwavelength gratings for polarization control. Orthogonal polarization suppression ratios (OPSRs) of up to 19.7 dB (19.1 dB) are reached for the rectilinear (diagonal) basis. By careful adjustment of the individual VCSEL's operating point, a wavelength matching of all VCSELs is achieved at an emission wavelength of 851.2 nm.}, author = {Zimmer, Michael and Dahler, Katharina and Jetter, Michael and Michler, Peter}, doi = {10.1364/OL.573598}, journal = {Opt. Lett.}, month = {09}, number = 18, pages = {5582--5585}, publisher = {Optica Publishing Group}, title = {Monolithic 850 nm VCSEL array for quantum key distribution applications via the polarization-based BB84 and decoy-state protocol}, url = {https://opg.optica.org/ol/abstract.cfm?URI=ol-50-18-5582}, volume = 50, year = 2025 }

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   https://opg.optica.org/ol/abstract.cfm?URI=ol-50-18-5582
2. Torrelli, V., Miri, L., D’Alessandro, M., Gullino, A., Zimmer, M., Dahler, K., Jetter, M., Michler, P., Elsäßer, W., Bertazzi, F., Tibaldi, A., & Debernardi, P. (2025). Elliptical polarization in VCSELs via joint interaction of a tilted sub-wavelength grating and intrinsic semiconductor anisotropies. Optics Letters, 50, Article 9. https://doi.org/10.1364/OL.557703
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   BibTeX

   @article{torrelli2025elliptical, abstract = {We demonstrate numerically and experimentally that, in vertical-cavity surface-emitting lasers (VCSELs), a non-chiral cavity can be converted into a chiral one by the interaction between a sub-wavelength grating tilted with respect to the crystalline axes and the intrinsic semiconductor optical anisotropies, thus enabling the emission of elliptically polarized light. The measured Stokes parameters of such a VCSEL, realized by a standard grating based VCSEL fabricati on process, are in line with the modeling results. We demonstrate through simulations that a degree of circular polarization of 0.9 can be obtained by varying the grating parameters. The full Poincaré sphere is accessible on demand if mechanical strain is also considered.}, author = {Torrelli, Valerio and Miri, Lorenzo and D’Alessandro, Martino and Gullino, Alberto and Zimmer, Michael and Dahler, Katharina and Jetter, Michael and Michler, Peter and Elsäßer, Wolfgang and Bertazzi, Francesco and Tibaldi, Alberto and Debernardi, Pierluigi}, doi = {10.1364/OL.557703}, journal = {Optics Letters}, language = {engl}, month = {05}, number = 9, pages = {3082-3085}, title = {Elliptical polarization in VCSELs via joint interaction of a tilted sub-wavelength grating and intrinsic semiconductor anisotropies }, url = {https://opg.optica.org/ol/abstract.cfm?uri=ol-50-9-3082}, volume = 50, year = 2025 }

   Link

   https://opg.optica.org/ol/abstract.cfm?uri=ol-50-9-3082