Building large Fabry-Pérot etalons for the Visible Tunable Filter

Clemens Halbgewachs; Thomas J. Kentischer; Jörg Baumgartner; Andreas Fischer; Matthias Schubert; Michael Sigwarth

doi:10.1117/12.3020044

18 July 2024 Building large Fabry-Pérot etalons for the Visible Tunable Filter

Clemens Halbgewachs, Thomas J. Kentischer, Jörg Baumgartner, Andreas Fischer, Matthias Schubert, Michael Sigwarth

Proceedings Volume 13096, Ground-based and Airborne Instrumentation for Astronomy X; 1309617 (2024) https://doi.org/10.1117/12.3020044
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Abstract

The Visible Tunable Filter Instrument (VTF) is a 2D imaging spectropolarimeter for high spatial and spectral resolution solar observations in the visible light. It will be operated at the world’s largest solar telescope, the 4m aperture Daniel K. Inouye Solar Telescope (DKIST) in Maui, Hawaii, USA. The VTF is designed and constructed by the Leibniz-Institut f¨ur Sonnenphysik (KIS) with support from the Istituto ricerche solari Aldo e Cele Dacc`o (IRSOL), the Max-Planck-Institut f¨ur Sonnensystemforschung (MPS) and the National Solar Observatory (NSO). KIS started integrating and commissioning the VTF at the DKIST in January 2024. VTF is based on two large Fabry-P´erot etalons (FPIs) acting as spectral filters. The field of view of 1 arcmin combined with a spectral accuracy well below 1 picometer leads to a clear aperture (CA) of 250 mm, an allowed cavity error smaller than 3 nm RMS over the CA, a microroughness below 0.4 nm RMS and a required cavity stability of ±100 pm over one hour. Therefore, the world’s largest tunable etalons for imaging applications had to be built. With these etalons, VTF will be able to drive solar science for the next decades. In this paper we describe the overall design and specifications of the VTF-FPIs. The first etalon was completely assembled and commissioned in the lab in 2023. We present the main characteristics as measured in the laboratory and demonstrate the dynamic response probed by the integrated metrology system.

Conference Presentation

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Clemens Halbgewachs, Thomas J. Kentischer, Jörg Baumgartner, Andreas Fischer, Matthias Schubert, and Michael Sigwarth "Building large Fabry-Pérot etalons for the Visible Tunable Filter", Proc. SPIE 13096, Ground-based and Airborne Instrumentation for Astronomy X, 1309617 (18 July 2024); https://doi.org/10.1117/12.3020044

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