Mr. Knut Kleinbauer Profile

Knut Kleinbauer

at Fraunhofer-IOF

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Author

Publications (4)

Proceedings Article | 17 June 2024 Presentation + Paper

Design and manufacturing of a metallic telescope for ground-based quantum communication

Markus Unger, Nils Heidler, Thomas Peschel, Christoph Damm, Robert Jende, Peter Weide, Knut Kleinbauer, Ralf Steinkopf, Tatjana Porwol, Sandra Müller, Mathias Rohde, Johannes Hartung, Christian Jäger, Svetlana Shestaeva, Ralph Schlegel, Stefan Schwinde, Matthias Goy, Fabian Steinlechner, Stefan Risse

Proceedings Volume 13021, 1302105 (2024) https://doi.org/10.1117/12.3022982

KEYWORDS: Mirrors, Optical surfaces, Telescopes, Manufacturing, Mirror surfaces, Quantum systems, Quantum communications, Chemical mechanical planarization, Magnetorheological finishing, Quantum networks

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Quantum communication is considered to be a key feature for secure communication e.g. between government organisations or other institutions with high security requirements. Therefore, the QuNET initiative was founded. It focuses on developing a quantum-secure German governmental agency network based on quantum key distribution (QKD). Free-space optical (FSO) links are a valuable part of infrastructure because they can be deployed temporarily, such as at summits or to bridge the last miles where there is no fiber infrastructure. In particular, high-throughput telescopes are of great importance as optical antennas for terrestrial networks or links between mobile nodes. The paper describes the development and manufacturing of an unobscured, afocal four-mirror metal telescope which is already tested for ground-based quantum communication. The off-axis system, operating with a full telescope aperture of 200 mm, a magnification of 20x, and a FOV (field of view) of 3.5 mrad and is designed to yield diffraction-limited performance for an operational wavelength of 810 nm and 1550 nm. The addressed wavefront error-target of the whole system amounts to 66 nm RMS (root mean square). The use case of the telescope implied an operational temperature range of -40 °C up to +50 °C. Therefore, an athermal system is realized using an aluminum-silicon alloy substrate material combined with a nickel-phosphorus polishing layer that allows to reach the required surface quality of the mirrors. To simplify the alignment of the telescope, its mechanical concept relies on a snap-together approach using two substrates with two optical mirrors on a common substrate, each. The manufacturing chain of these two so called mirror substrates is described in detail. That includes the CNC pre-manufacturing, ultra precision diamond turning and subsequent polishing steps. The resulting quality of the mirror substrates as well as of the telescope system is demonstrated by optical measurements using interferometric setups.

Proceedings Article | 27 August 2022 Presentation + Paper

Development and manufacturing of the receiver telescope for the Ganymede Laser Altimeter (GALA)

Henrik von Lukowicz, Johannes Hartung, Robert Jende, Sandra Müller, Mathias Rohde, Jan Kinast, Knut Kleinbauer, Svetlana Shestaeva, Stefan Schwinde, Thomas Peschel, Kai Weidlich, Henry Wegert, Stefan Risse

Proceedings Volume 12180, 121800H (2022) https://doi.org/10.1117/12.2631688

KEYWORDS: Mirrors, Telescopes, Manufacturing, Interfaces, Diamond turning, Coating, Reflectivity, Receivers, Optics manufacturing, Jupiter

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Proceedings Article | 30 August 2019 Presentation + Paper

Ultraprecise flat mirrors for the pointing unit of the DESIS instrument on board of the ISS

Stefan Risse, Jan Kinast, Andreas Gebhardt, Robert Jende, Knut Kleinbauer, Sandra Müller, Thomas Peschel, Christoph Damm, Matthias Schwarzenberg, Matthias Kroedel, Ingo Walter, David Krutz

Proceedings Volume 11101, 1110106 (2019) https://doi.org/10.1117/12.2530620

KEYWORDS: Mirrors, Mirror pointing, Spectrometers, Thermography, Hyperspectral imaging, Ceramics, Metals, Diamond machining, Magnetorheological finishing, Polishing

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Proceedings Article | 10 July 2018 Paper

Manufacturing of aluminum mirrors for cryogenic applications

Jan Kinast, Ralph Schlegel, Knut Kleinbauer, Ralf Steinkopf, Roman Follert, Reinhold Dorn, Jean Louis Lizon, Artie Hatzes, Andreas Tünnermann

Proceedings Volume 10706, 107063G (2018) https://doi.org/10.1117/12.2313126

KEYWORDS: Mirrors, Optics manufacturing, Single point diamond turning, Magnetorheological finishing, Manufacturing, Cryogenics, Polishing, Aluminum, Coating

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