The Blue Multi Unit Spectroscopic Explorer (BlueMUSE) on the VLT: characterization of two VPHG prototypes based on dichromated gelatin and photopolymer recording materials

Alexandre Jeanneau; Andrea Bianco; Andrew Clawson; Michele Frangiamore; Elroy Pearson; Laurent Pinard; Jürgen Schmoll; Johan Richard; Rémi Giroud; Florence Laurent; Roland Bacon

arXiv · 2406.13913

The Blue Multi Unit Spectroscopic Explorer (BlueMUSE) on the VLT: characterization of two VPHG prototypes based on dichromated gelatin and photopolymer recording materials

Alexandre Jeanneau·Andrea Bianco·Andrew Clawson·Michele Frangiamore·Elroy Pearson·Laurent Pinard·Jürgen Schmoll·Johan Richard·Rémi Giroud·Florence Laurent·Roland Bacon

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Abstract

Volume-phase holographic gratings (VPHGs) are widely used in astronomical spectrographs due to their adaptability and high diffraction efficiency. Most VPHGs in operation use dichromated gelatin as a recording material, whose performance is sensitive to the coating and development process, especially in the near-UV. In this letter, we present the characterization of two UV-blue VPHG prototypes for the BlueMUSE integral field spectrograph on the VLT, based on dichromated gelatin and the Bayfol$\circledR$HX photopolymer film as recording materials. Our measurements show that both prototypes meet the required diffraction efficiency and exhibit similar performance with a wavelength-average exceeding 70% in the 350-580 nm range. Deviations from theoretical models increase towards 350 nm, consistently with previous studies on similar gratings. We also report similar performances in terms spatial uniformity and grating-to-grating consistency. Likewise, no significant differences in wavefront error or scattered light are observed between the prototypes.

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Alexandre Jeanneau, Andrea Bianco, Andrew Clawson, Michele Frangiamore, Elroy Pearson, Laurent Pinard, Jürgen Schmoll, Johan Richard, Rémi Giroud, Florence Laurent, Roland Bacon. 2024-06-20. The Blue Multi Unit Spectroscopic Explorer (BlueMUSE) on the VLT: characterization of two VPHG prototypes based on dichromated gelatin and photopolymer recording materials. https://arxiv.org/abs/2406.13913

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