Spectrographs for the Asgard/BIFROST beam combiner for the VLTI: optical and optomechanical design and first lab results

Sorabh Chhabra; Stefan Kraus; Michele Frangiamore; Andrea Bianco; Andrea Vanella; Michael Ireland; Francisco Garzon; Manuela Arno; Daniel Lancaster; Daniel Mortimer; John Monnier; Jyotirmay Paul; Gordon Robertson; Owain Snaith

doi:10.1117/12.3018851

28 August 2024 Spectrographs for the Asgard/BIFROST beam combiner for the VLTI: optical and optomechanical design and first lab results

Sorabh Chhabra, Stefan Kraus, Michele Frangiamore, Andrea Bianco, Andrea Vanella, Michael Ireland, Francisco Garzon, Manuela Arno, Daniel Lancaster, Daniel Mortimer, John Monnier, Jyotirmay Paul, Gordon Robertson, Owain Snaith

Author Affiliations +

Proceedings Volume 13095, Optical and Infrared Interferometry and Imaging IX; 130952D (2024) https://doi.org/10.1117/12.3018851
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Conference Poster

Abstract

BIFROST, an upcoming instrument for the VLTI, is part of the Asgard Suite, a VLTI visitor instrument. It comprises two spectrograph arms that are optimised for wavelength range of 1- 1.75μm (fed by a fiber that is placed on-axis for fringe tracking/monitoring) and 1-1.3μm (fed by a fiber that can positioned either on-axis or off-axis to observe a faint target) wavelength range, respectively. Volume phase holographic gratings (VPHGs) are employed to achieve high spectral resolving power up to 25,000 and a throughput above 75% for all dispersing elements. In this contribution, we discuss the optical and optomechanical design of the spectrographs, as well as a new relay optics design that minimizes the thermal background, with a factor 4 reduction in thermal background compared to the non-relay optics design. We will also present the first lab results obtained with the YJH spectrograph.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

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Sorabh Chhabra, Stefan Kraus, Michele Frangiamore, Andrea Bianco, Andrea Vanella, Michael Ireland, Francisco Garzon, Manuela Arno, Daniel Lancaster, Daniel Mortimer, John Monnier, Jyotirmay Paul, Gordon Robertson, and Owain Snaith "Spectrographs for the Asgard/BIFROST beam combiner for the VLTI: optical and optomechanical design and first lab results", Proc. SPIE 13095, Optical and Infrared Interferometry and Imaging IX, 130952D (28 August 2024); https://doi.org/10.1117/12.3018851

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