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A set of innovative immersed grating based spectrometer designs for METIS


Author: Agócs, T. · Navarro, R. · Venema, L. · Amerongen, A.H. van · Tol, P.J.J. · Brug, H. van · Brandl, B.R. · Molster, F. · Todd, S.
Publisher: SPIE
Source:Cunningham, C.R.Navarro, R.Barto, A.A., 9151
Identifier: 523215
ISBN: 9780819496195
Article number: 91511L
Keywords: Electronics · Astronomy · E-ELT · Immersed grating · METIS · Mid-infrared · Diffraction gratings · Infrared devices · Optical design · Optical testing · Refractive index · Semiconducting silicon · Semiconductor device manufacture · Spectrographs · Spectrometers · Telescopes · Optimization techniques · Semiconductor industry · Silicon micromachining · Three mirror anastigmats · High Tech Systems & Materials · Industrial Innovation · Physics & Electronics · OPT - Optics · TS - Technical Sciences


We present innovative, immersed grating based optical designs for the SMO (Spectrograph Main Optics) module of the Mid-infrared E-ELT Imager and Spectrograph, METIS. The immersed grating allows a significant reduction of SMO volume compared to conventional echelle grating designs, because the diffraction takes place in high refractive index silicon. Additionally, using novel optimization techniques and technical solutions in silicon micromachining offered by the semiconductor industry, further improvements can be achieved. We show optical architectures based on compact, double-pass Three Mirror Anastigmat (TMA) designs, which appear advantageous in terms of one or several of the following: optical performance, reduction of volume, ease of manufacturing and testing. We explore optical designs, where the emphasis is put on manufacturability and we investigate optical solutions, where the ultimate goal is the highest possible optical performance. These novel, silicon immersed grating based design concepts are applicable for future earth and space based spectrometers.