VPHGs for WEAVE: design, manufacturing and characterization

Date Issued
2018
Author(s)
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Arns, James
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Pragt, Johan
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Stuik, Remko
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Middleton, Kevin
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Tosh, Ian
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Dalton, Gavin
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Trager, Scott
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Abrams, Don Carlos
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Lopez Aguerri, Jose Alfonso
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Carrasco, Esperanza
DOI
Abstract
WEAVE is the next-generation optical spectroscopy facility for the William Herschel Telescope (WHT). It shows two channels (blue and red) and two working modes, a low-resolution (R=3,000-7,500) and a high-resolution (R=13,000- 25,000). The dispersing elements of the spectrograph are Volume Phase Holographic Gratings (VPHGs), two for the lower resolution mode and three for the higher resolution mode. Such gratings have a large size (clear aperture > 190 mm) and they are characterized by some key features, i.e. diffraction efficiency, wavefront error and dispersion that affect the final performances of the spectrograph. The VPHGs have been produced by KOSI based on the WEAVE design. After that, the VPHGs have been characterized, showing interesting results in terms of diffraction efficiency that reached peak values of 90%. As for the wavefront distortion, which is one of the critical aspect in VPHG technology, a different behavior between medium and high resolution elements was found. A larger wavefront distortion have been measured in the high resolution elements, because of the higher aspect ratio. A polishing process on the assembled VPHGs has been performed in order to reduce the wavefront distortion. Here, the results are presented and the specific issues discussed.
Coverage
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III
All editors
Navarro, Ramón ; Geyl, Roland
Series
Volume
10706
Start page
107064X-1
Conferenece
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II
Conferenece place
Austin, Texas, United States
Conferenece date
10-15 June, 2018
Uri
Url
Issn Identifier
0277-786X
Ads BibCode
2018SPIE10706E..4XB
Rights
open.access
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