Bonn 2025 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 48: Poster – Quantum Optics, Technologies, and Optomechanics

Q 48.3: Poster

Wednesday, March 12, 2025, 17:00–19:00, Tent

Custom Shack-Hartmann Sensor for Stellar Intensity Interferometry — •aleena nedunilath thomas, verena leopold, sebastine karl, and joachim von zanthier — AG Quantum Optics and Quantum Information, Friedrich-Alexander Universität Erlangen-Nürnberg, Germany

For stellar intensity interferometric measurements using single photon counting detectors and ultra narrow interference filters it is crucial to monitor the collimation of the wavefront. We therefore introduce a custom Shack-Hartmann wavefront sensor to monitor the collimation of our beam inside the optical setup during the observations at the telescope. The sensor is made of a Thorlabs fused silica microlens array (MLA150-7AR) with square lenslets focusing onto a ZWO ASI CMOS camera. The camera images are analysed using a self-developed software measuring slope deviations and calculating Zernike polynomial coefficients. The software employs a gradient-fitting algorithm optimised for square lenslet arrays, extracting critical lower-order Zernike coefficients. As a direct application for further observations the defocus coefficient was linked to the displacement of the secondary mirror of the telescope. This way the defocus can be directly optimised during the measurements.

Keywords: Shack-Hartmann; wavefront sensor; intensity Interferometry; microlens array; zernike polynomials