7 August 2014 Bulk silica transmission grating made by reactive ion etching for NIR space instruments
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Abstract
A GRISM, made of a grating on a prism, allow combining image and spectroscopy of the same field of view with the same optical system and detector, thus simplify instrument concept. New GRISM designs impose technical specifications difficult to reach with classical grating manufacturing processes: large useful aperture (>100mm), low groove frequency (<30g/mm), small blaze angle (<3°) and, last but not least, line curvature allowing wavefront corrections. In addition, gratings are commonly made of resin which may not be suitable to withstand the extreme space environment. Therefore, in the frame of a R&D project financed by the CNES, SILIOS Technologies developed a new resin-free grating manufacturing process and realized a first 80mm diameter prototype optically tested at LAM. We present detailed specifications of this resin-free grating, the manufacturing process, optical setups and models for optical performance verification and very encouraging results obtained on the first 80mm diameter grating prototype: >80% transmitted efficiency, <30nm RMS wavefront error, groove shape and roughness very close to theory and uniform over the useful aperture.
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Amandine Caillat, Sandrine Pascal, Stéphane Tisserand, Kjetil Dohlen, Robert Grange, Vincent Sauget, Sophie Gautier, "Bulk silica transmission grating made by reactive ion etching for NIR space instruments", Proc. SPIE 9151, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation, 91511F (7 August 2014); doi: 10.1117/12.2055095; https://doi.org/10.1117/12.2055095
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