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Proceedings Paper

Development of silicon immersed grating for METIS on E-ELT
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Paper Abstract

We have developed the technology to manufacture an immersed grating in silicon for the Mid-infrared E-ELT Imager and Spectrograph, METIS. We show that we can meet the required diffraction-limited performance at a resolution of 100000 for the L and M spectral bands. Compared to a conventional grating, the immersed grating drastically reduces the beam diameter and thereby the size of the spectrometer optics. As diffraction takes place inside the high-index medium, the optical path difference and angular dispersion are boosted proportionally, thereby allowing a smaller grating area and a smaller spectrometer size. The METIS immersed grating is produced on a 150 mm industry standard for wafers and replaces a classical 400 mm echelle. Our approach provides both a feasible path for the production of a grating with high efficiency and low stray light and improves the feasibility of the surrounding spectrometer optics. In this contribution we describe and compare the classical-grating solution for the spectrometer with our novel immersed-grating based design. Furthermore, we discuss the production route for the immersed grating that is based on our long-standing experience for space-based immersed gratings. We use standard techniques from the semiconductor industry to define grating grooves with nanometer accuracy and sub-nanometer roughness. We then use optical manufacturing techniques to combine the wafer and a prism into the final immersed grating. Results of development of the critical technology steps will be discussed.

Paper Details

Date Published: 13 September 2012
PDF: 10 pages
Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 84502T (13 September 2012); doi: 10.1117/12.925612
Show Author Affiliations
Aaldert H. van Amerongen, SRON Netherlands Institute for Space Research (Netherlands)
Tibor Agocs, ASTRON (Netherlands)
Hedser van Brug, TNO Science and Industry (Netherlands)
Govert Nieuwland, Philips Innovation Services (Netherlands)
Lars Venema, ASTRON (Netherlands)
Ruud W. M. Hoogeveen, SRON Netherlands Institute for Space Research (Netherlands)

Published in SPIE Proceedings Vol. 8450:
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II
Ramón Navarro; Colin R. Cunningham; Eric Prieto, Editor(s)

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