MAVIS IFU with AO for VLT: image slicer concept and design

Robert Content*, Giovanni Cresci, Simon Ellis, Richard McDermid, François Rigaut

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

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MAVIS is a future imaging spectrograph for the VLT in which the spectrograph is fed by an IFU. Imager and IFU are fed by Multi-Conjugate Adaptive Optics for the wavelength range 370 nm to 930 nm. The spectrograph will deliver a spectral resolution of more than 4000. The IFU field has a choice of 2 spaxel sizes. It is 9 arsec2 with 25 mas spaxels and 36 arsec2 with 50 mas. The design follows the proven concept of Advanced Image Slicer (AIS) as for Gemini NIFS and GNIRS, VLT MUSE and KMOS, JWST NIRSpec, and many others. In the present design, the field is first split in 2 and each subfield is imaged on a slicer mirror array made of long thin mirrors that slice the field into 50 images and send them in different directions to be reimaged side by side on the slit by another mirror array. Additional optics on the slit reimage the pupil at the right place in the spectrograph. Three different options are under study for the slit optics. One is a mirror array of considerably lower cost than the standard design in an AIS. At 25 mas, the spaxels are near the diffraction limit of the longest wavelength. This present challenges not present for seeing limited IFUs as focal ratio degradation due to diffraction by the slices. Another challenge comes from the short minimum wavelength. It is difficult to manufacture efficient reflection coatings for the whole wavelength range. Transmissive fore-optics were then also studied. The field splitter which sends half the field to each of the 2 arms was integrated into the fore-optics. This removes 2 air-glass surfaces from each arm.

Original languageEnglish
Title of host publicationAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV
EditorsRamón Navarro, Roland Geyl
Place of PublicationBellingham, Washington
Number of pages10
ISBN (Electronic)9781510636897
ISBN (Print)9781510636897
Publication statusPublished - 14 Dec 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
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV 2020
Country/TerritoryUnited States
CityVirtual, Online

Bibliographical note

Copyright 2020 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.


  • AO corrected instrument.
  • image slicer
  • integral field unit
  • VLT


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