Ge immersed grating manufacturing and optical verification for the METIS high-resolution spectrograph

Tibor Agocs, Eddy Elswijk, Daan Zaalberg, Jan Rinze Peterzon, Niels Tromp, Ivan Lloro, Jeffrey Lynn, Ramon Navarro, Bernhard Brandl, More Authors

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

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.

Original languageEnglish
Title of host publicationAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV
EditorsRamon Navarro, Roland Geyl
PublisherSPIE
ISBN (Electronic)9781510636897
DOIs
Publication statusPublished - 2020
EventAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV 2020 - Virtual, Online, United States
Duration: 14 Dec 202022 Dec 2020

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume11451
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Conference

ConferenceAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV 2020
CountryUnited States
CityVirtual, Online
Period14/12/2022/12/20

Keywords

  • germanium
  • Immersed grating
  • manufacturing
  • METIS
  • mid-infrared
  • throughput
  • verification
  • wavefront error

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