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13 September 2012 Development of silicon immersed grating for METIS on E-ELT
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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.
© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Aaldert H. van Amerongen, Tibor Agocs, Hedser van Brug, Govert Nieuwland, Lars Venema, and Ruud W. M. Hoogeveen "Development of silicon immersed grating for METIS on E-ELT", Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 84502T (13 September 2012);

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