High uniformity IBS coatings for the world’s largest Fabry-Perot etalon of the VTF instrument

Laurent Pinard (1) , Christophe Michel (1) , Benoît Sassolas (1) , Julien Teillon (1) , Gianpietro Cagnoli (1) , Michael Sigwarth , Wolfgang Schmidt , Thomas Kentischer , Bill Reichman

1 LMA - Laboratoire des matériaux avancés

The first large Fabry-Perot etalon (Ø35 cm) of the VTF instrument was coated successfully using IBS technique. The High Reflective (HR) coatings need to meet the reflectivity specifications (95 +/- 1%) over the entire wavelength range 520-870 nm and the entire aperture (Ø25 cm) and also preserve the plate's flatness and airgap uniformity between the two platesto be better than 3 nm RMS. The change of the figure error of the individual faces after HR coating was exceptionally small: For plate 1 (upper) it changed from 1.7nm RMS before coating to 2.12 nm after coating, no change at all for plate 2 (lower

Domaines: Instrumentations et Détecteurs [physics.ins-det]

Laurent Pinard, Christophe Michel, Benoît Sassolas, Julien Teillon, Gianpietro Cagnoli, et al.. High uniformity IBS coatings for the world’s largest Fabry-Perot etalon of the VTF instrument. SPIE Astronomical Telescopes + Instrumentation 2018, Jun 2018, Austin, United States. pp.107061R, ⟨10.1117/12.2312007⟩. ⟨hal-01945497⟩