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- Title
Optical Design of a Slitless Astronomical Spectrograph with a Composite Holographic Grism.
- Authors
Muslimov, Eduard; Akhmetov, Damir; Kharitonov, Danila; Ibatullin, Erik; Pavlycheva, Nadezhda; Sasyuk, Vyacheslav; Golovkin, Sergey
- Abstract
In the present work, we consider an optical design of a slitless spectrograph for an existing 0.5 m-class telescope. This design concept has a number of advantages such as compact size, simplicity, and simultaneous coverage of a large field of view. A challenge with this design is correcting aberrations caused by placing a dispersing element in a converging beam. To overcome this issue, we propose to use a composite grism, which represents a combination of a prism and a volume-phase holographic grating, the latter which is split into zones with independently optimized parameters. We demonstrate two designs of such a grism. In both designs, the spectrograph operates in the range of 450–950 nm in an F / 6.8 beam and covers a field of view of 35.6 ′ × 7.2 ′ . Through advanced modeling, it is shown that a composite grism having four rectangular zones with different thickness and index modulation depth of the hologram and recorded with an auxiliary deformable mirror decreases the astigmatic elongation by a factor of 85, increases the spectral resolving power by 4.4 times, and reaches R 1389 while increasing the average diffraction efficiency by a factor of 1.31 . If we reduce the number of zones to only two, replace the deformable mirror with two static corrector plates, and fix the hologram thickness, the corresponding performance gains still remain high: the astigmatism is reduced by a factor of 61, the spectral resolving power is up to 1.7 times higher, reaching R 1067 , and the efficiency is increased by a factor of 1.27 . This shows that the proposed design allows the construction of a simple and compact instrument, providing high performance over the entire field of view and spectral range.
- Subjects
SPECTROGRAPHS; HOLOGRAPHIC gratings; NUMBER concept; HOLOGRAPHY; ASTIGMATISM
- Publication
Photonics, 2023, Vol 10, Issue 4, p385
- ISSN
2304-6732
- Publication type
Article
- DOI
10.3390/photonics10040385