Mr. Ralph Schlegel Profile

Ralph Schlegel

at Fraunhofer IOF

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Author

Publications (9)

Proceedings Article | 18 June 2024 Presentation

Thin film black coatings based on interference and absorption

Peter Munzert, Stefan Schwinde, Robert Leitel, Sylke Kleinle, Svetlana Shestaeva, Ralph Schlegel, Tobias Herffurth, Sven Schröder

Proceedings Volume 13020, 1302004 (2024) https://doi.org/10.1117/12.3022694

KEYWORDS: Thin film coatings, Optical coatings, Thin films, Absorption, Light absorption, Vacuum, Stray light, Spectroscopy, Short wave infrared radiation, Reflection

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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 | 12 July 2023 Open Access

Realizing an all-glass beam splitter for space by using advanced joining technologies

Carolin Rothhardt, Pascal Birckigt, Kevin Grabowski, Stefan Risse, Ralph Schlegel, Svetlana Shestaeva, Stefan Schwinde, Sebastian Schmidl, Sylvio Klose

Proceedings Volume 12777, 1277719 (2023) https://doi.org/10.1117/12.2689276

KEYWORDS: Beam splitters, Coating, Prisms, Cryogenics, Silicates, Tunable filters, Surface finishing, Silicon, Tantalum, Astronomical imaging

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Proceedings Article | 29 August 2022 Presentation + Paper

Development of advanced silver coatings for telescope mirrors

S. Schwinde, S. Shestaeva, R. Holzlöhner, G. Willers, R. Schlegel, A. Förster, R. Parra, S. Guisard, O. Sqalli, S. Schröder

Proceedings Volume 12188, 121881X (2022) https://doi.org/10.1117/12.2627710

KEYWORDS: Reflectivity, Silver, Mirrors, Telescopes, Optical coatings, Aluminum, Reflector telescopes, Gemini Observatory, Gold, Ruthenium, Near ultraviolet

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Proceedings Article | 12 July 2019 Open Access

Protected silver coatings for reflectors

Stefan Schwinde, Mark Schürmann, Ralph Schlegel, Jan Kinast, Reinhold Dorn, Jean Louis Lizon, Sebastien Tordo, Norbert Kaiser

Proceedings Volume 11180, 111804M (2019) https://doi.org/10.1117/12.2536085

KEYWORDS: Silicon, Aluminum, Reflectors, Sputter deposition, Silver, Argon, Resistance, Reflectivity, Oxygen, Infrared spectroscopy

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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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Proceedings Article | 5 June 2018 Paper

Si/SiO2-based filter coatings for astronomical applications in the IR spectral range

R. Schlegel, D. Gäbler, M. Schürmann, R. Follert, U. Seemann, E. Oliva, S. Schwinde

Proceedings Volume 10691, 106911E (2018) https://doi.org/10.1117/12.2311310

KEYWORDS: Refractive index, Optical coatings, Silicon, Germanium, Optical filters, Annealing, Sputter deposition

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Proceedings Article | 22 July 2016 Paper

Manufacturing and coating of optical components for the EnMAP hyperspectral imager

M. Schürmann, D. Gäbler, R. Schlegel, S. Schwinde, T. Peschel, C. Damm, R. Jende, J. Kinast, S. Müller, M. Beier, S. Risse, B. Sang, M. Glier, H. Bittner, M. Erhard

Proceedings Volume 9912, 991230 (2016) https://doi.org/10.1117/12.2232914

KEYWORDS: Mirrors, Coating, Prisms, Imaging systems, Antireflective coatings, Spectrometers, Surface finishing, Telescopes, Silver, Short wave infrared radiation

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Proceedings Article | 12 March 2015 Paper

Metal mirrors with metal-dielectric HR-coating for ultrashort laser pulses applied in scanner applications

M. Schürmann, S. Risse, H. Kämmer, C. Franke, R. Schlegel, S. Müller, C. Damm, R. Steinkopf, F. Dreisow, S. Nolte, R. Eberhardt, N. Kaiser

Proceedings Volume 9351, 93510S (2015) https://doi.org/10.1117/12.2079487

KEYWORDS: Mirrors, Coating, Metals, Reflectivity, Polishing, Dielectrics, Surface finishing, Laser damage threshold, Picosecond phenomena, Diamond turning

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Showing 5 of 9 publications

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