@inproceedings{de563d4f939a4d1bbea9445151e08778,
title = "Ge immersed grating manufacturing and optical verification for the METIS high-resolution spectrograph",
abstract = "We present the manufacturing and optical verification of the germanium immersed grating for the L/M band high resolution spectrograph (LMS). The LMS is one of the science subsystems of the Mid-infrared ELT Imager and Spectrograph, METIS. The immersed grating has very demanding requirement specifications: <100 nm RMS transmitted Wave Front Error (WFE) after double pass, and >70% peak throughput in all orders within the 2.9-5.3 μm wavelength range over the pupil. The grating has a period of 18.2 μm, a sawtooth groove profile with 89.6 degrees apex angle and a grating area of 150mm x 60mm. The germanium immersed grating was produced by Canon's high precision mechanical cutting technology. We present the interferometric tests that were performed in order to verify WFE and two different measurements (based on cascade laser and Fourier Transform Spectrometer, respectively) for throughput verification. ",
keywords = "germanium, Immersed grating, manufacturing, METIS, mid-infrared, throughput, verification, wavefront error",
author = "Tibor Agocs and Eddy Elswijk and Daan Zaalberg and Peterzon, {Jan Rinze} and Niels Tromp and Ivan Lloro and Jeffrey Lynn and Ramon Navarro and Bernhard Brandl and {More Authors}",
year = "2020",
doi = "10.1117/12.2562411",
language = "English",
series = "Proceedings of SPIE - The International Society for Optical Engineering",
publisher = "SPIE",
editor = "Ramon Navarro and Roland Geyl",
booktitle = "Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV",
address = "United States",
note = "Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV 2020 ; Conference date: 14-12-2020 Through 22-12-2020",
}