Dr. Reinhold Flatscher Profile

Dr. Reinhold Flatscher

at Airbus Defence and Space

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Author

Publications (10)

Proceedings Article | 13 April 2018 Paper

EADS Astrium nulling interferometer breadboard for DARWIN and GENIE

Klaus Ergenzinger, Reinhold Flatscher, Ulrich Johann, Rob Vink, Zoran Sodnik

Proceedings Volume 10568, 1056820 (2018) https://doi.org/10.1117/12.2500095

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Proceedings Article | 21 November 2017 Open Access

Manufacturing of chalcogenide and silver-halide single-mode fibres for modal wavefront filtering for DARWIN

R. Flatscher, O. Wallner, V. Artyushenko, J. Pereira do Carmo

Proceedings Volume 10567, 105672G (2017) https://doi.org/10.1117/12.2308140

KEYWORDS: Silver, Manufacturing, Single mode fibers, Interferometers, Cladding, Chalcogenides, Wavefronts, Photonic crystal fibers, Mid-IR, Chalcogenide glass

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Proceedings Article | 21 November 2017 Open Access

DARWIN system concepts

Oswald Wallner, Klaus Ergenzinger, Reinhold Flatscher, Ulrich Johann

Proceedings Volume 10567, 105670I (2017) https://doi.org/10.1117/12.2308039

KEYWORDS: Space operations, Planets, Telescopes, Space telescopes, Modulation, Nulling interferometry, Stars, Target detection, Interferometers, Mirrors

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Proceedings Article | 20 November 2017 Open Access

Manufacturing and testing of wavefront filters for DARWIN

R. Flatscher, V. Artjushenko, T. Sakharova, Joao Pereira do Carmo

Proceedings Volume 10565, 105650X (2017) https://doi.org/10.1117/12.2309269

KEYWORDS: Silver, Cladding, Wavefronts, Manufacturing, Single mode fibers, Glasses, Interferometers, Astronomical imaging, Optical filters, Chalcogenide glass

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Wavefront filtering is mandatory in the realisation of nulling interferometers with high star light suppression capability required to detect extrasolar planets, such as the one foreseen for the ESA Darwin mission.

This paper presents the design, manufacturing, and test results of single mode fibres to be used as wavefront filters in mid-infrared range. Fibres made from chalcogenide glass and silver halide crystals were produced. The first class can serve as wavefront filters up to a wavelength of 11 microns, while silver halide fibres can be used over the full Darwin wavelength range from 6.5 to 18 micron. The chalcogenide glass fibres were drawn by double crucible method whereas polycrystalline fibres from silver halides were fabricated by multiple extrusion from a crystalline preform.

Multi-layer AR-coatings for fibre ends were developed and environmentally tested for both types of fibres. Special fibre facet polishing procedures were established, in particular for the soft silver halide fibre ends. Cable design and assembly process were also developed, including termination by SMA-connectors with ceramic ferrules and fibre protection by loose PEEK-tubings to prevent excessive bending and chemical attacks for fibres.

The wavefront filtering capability of the fibres was demonstrated on a high quality Mach-Zehnder interferometer. Two different groups of laser sources were used to measure the wavefront filtering of the fibres by using a CO-laser for testing in the lower sub-band and a CO₂-laser to check the upper sub-band.

Measurements of the fibres far field intensity distribution and transmission were performed for numerous cable samples. Single mode behaviour was observed in more than 25 silver halide fibre cables before AR-coating of their ends, while after that 17 cables were compliant with all technical requirements. Residual cladding modes existing in short single mode fibres were effectively removed by applying of a proper absorbing jacket to the fibre's lateral surface and by adding an oversized output aperture in front of fibre ends.

Several fibres were exposed to gamma radiation of total dose of 25, 50, and even 500 krad. No deterioration was found on AR-coated fibre ends and on fibre material. Five fibres were irradiated by proton radiation of 10MeV energy and 10¹⁰ p/cm² equivalent fluence. Several fibres were cooled down to 10 K by plunging them in a dipstick into liquid Helium. Silver halide fibres survived that test when cables were properly assembled. The brittle chalcogenide glass fibres were much more sensitive to thermal gradients and the related cables did not survive the thermal shock.

Critical issues have been revealed in multiple drawings of chalcogenide glass fibres where core and cladding composition were not stable at some fabrication stages - resulting in a poor single mode guiding. Much better results have been achieved with polycrystalline fibres from silver halides made with a small core and low NA and enabling single mode guiding in the mid infrared.

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Proceedings Article | 13 May 2013 Paper

Fundamental performance determining factors of the ultrahigh-precision space-borne optical metrology system for the LISA Pathfinder mission

Gerald Hechenblaikner, Reinhold Flatscher

Proceedings Volume 8789, 87890X (2013) https://doi.org/10.1117/12.2020498

KEYWORDS: Interferometers, Interference (communication), Optical metrology, Nanoimprint lithography, Quantization, Phase measurement, Optical benches, Heterodyning, Phase interferometry, Optical testing

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Proceedings Article | 19 September 2007 Paper

X-array aperture configuration in planar or non-planar spacecraft formation for Darwin/TPF-I candidate architectures

Oswald Wallner, Klaus Ergenzinger, Reinhold Flatscher, Ulrich Johann

Proceedings Volume 6693, 66930U (2007) https://doi.org/10.1117/12.733820

KEYWORDS: Space operations, Planets, Stars, Nulling interferometry, Space telescopes, Telescopes, Mirrors, Interferometers, Relays, Polarization

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Proceedings Article | 28 June 2006 Paper

DARWIN mission and configuration trade-off

Oswald Wallner, Klaus Ergenzinger, Reinhold Flatscher, Ulrich Johann

Proceedings Volume 6268, 626827 (2006) https://doi.org/10.1117/12.671658

KEYWORDS: Space operations, Planets, Telescopes, Space telescopes, Stars, Modulation, Nulling interferometry, Target detection, Interferometers, Mirrors

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Proceedings Article | 20 October 2004 Paper

Development of silver-halide single-mode fibers for modal filtering in the mid-infrared

Oswald Wallner, Viatcheslav Artjuschenko, Reinhold Flatscher

Proceedings Volume 5491, (2004) https://doi.org/10.1117/12.551609

KEYWORDS: Optical fibers, Optical filters, Wavefronts, Single mode fibers, Waveguides, Interferometers, Mid-IR, Crystals, Refractive index, Coating

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Proceedings Article | 21 February 2003 Paper

Design of spatial and modal filters for nulling interferometers

Oswald Wallner, Walter Leeb, Reinhold Flatscher

Proceedings Volume 4838, (2003) https://doi.org/10.1117/12.456984

KEYWORDS: Waveguides, Spatial filters, Interferometers, Optical filters, Cladding, Phase shifts, Mid-IR, Refractive index, Single mode fibers, Spatial frequencies

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Proceedings Article | 21 February 2003 Paper

Nulling breadboard for DARWIN

Reinhold Flatscher, Ulrich Johann, Zoran Sodnik

Proceedings Volume 4838, (2003) https://doi.org/10.1117/12.458156

KEYWORDS: Phase shifts, Nulling interferometry, Stars, Telescopes, Wavefronts, Interferometers, Space telescopes, Mid-IR, Near infrared, Single mode fibers

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This work is funded by ESA under ESTEC/Contract No. 14827/00/NL/CK. Astrium Germany has been awarded this first ESA breadboarding towards nulling interferometry. Interferometric nulling devices are essential ingredients in the TPF and DARWIN missions for suppressing the star light by a factor of 10⁶ over a wide wavelength range in the mid infrared. The current DARWIN baseline concept comprises six telescopes. The coherent combination scheme in the nulling mode operation foresees three nulling assemblies in parallel. The breadboard serves to demonstrate the deep and stable null required for an operational instrument. The demonstrator operates in the near infrared to save costs but its principle is fully applicable to the mid infrared. The nulling device is based on an autobalancing Sagnac core offering just one critical beam combiner. Two different ways of achieving the required π phase shift are implemented: a) arbitrary phase shift by dispersive phase shifter plates b) phase shift of π using periscopes (image flip) The target simulator features two point sources of adjustable radiometry and angular separation, representing a strong star and a weak planet. In addition, the sources can be also used to simulate a double star for demonstrating the basic DARWIN imaging mode. The simulator can be operated in two styles, namely as wavefront dividing star/planet source and, alternatively, as an amplitude dividing source, providing highly symmetric wavefronts to both interferometer arms. Because of its representativity for the DARWIN situation, the latter mode is the preferred simulator for quantitative nulling experiments. The breadboard design has been finalized in January 2002 and verified by detailed simulations. The entire hardware has been manufactured by end of July. Currently, nulling and imaging measurements are in progress to validate the per-formance of the selected approach. The project is part of ESA´s technology preparatory program for DARWIN, paving the way for a collaborative ESA/ESO guest instrument at ESO's VLTI with scientific implications.

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