Demonstration of an efficient, photonic-based astronomical spectrograph on an 8-m telescope

N. Jovanovic (1) , N. Cvetojevic (2) , B. Norris (3) , C. Betters (3) , C. Schwab (4, 5) , J. Lozi (1) , O. Guyon (1) , S. Gross (1) , Frantz Martinache (6) , P. Tuthill (3) , D. Doughty (1) , Y. Minowa (1) , N. Takato (1) , J. Lawrence (5, 4)

1 Subaru Telescope
2 Bibliothèque de l'Observatoire de Paris
3 SIfA - Sydney Institute for Astronomy
4 AAO - Anglo-Australian Observatory
5 Macquarie University [Sydney]
6 LAGRANGE - Joseph Louis LAGRANGE

We demonstrate for the first time an efficient, photonic-based astronomical spectrograph on the 8-m Subaru Telescope. An extreme adaptive optics system is combined with pupil apodiziation optics to efficiently inject light directly into a single-mode fiber, which feeds a compact cross-dispersed spectrograph based on array waveguide grating technology. The instrument currently offers a throughput of 5% from sky-to-detector which we outline could easily be upgraded to ∼ 13% (assuming a coupling efficiency of 50%). The isolated spectrograph throughput from the single-mode fiber to detector was 42% at 1550 nm. The coupling efficiency into the single-mode fiber was limited by the achievable Strehl ratio on a given night. A coupling efficiency of 47% has been achieved with ∼ 60% Strehl ratio on-sky to date. Improvements to the adaptive optics system will enable 90% Strehl ratio and a coupling of up to 67% eventually. This work demonstrates that the unique combination of advanced technologies enables the realization of a compact and highly efficient spectrograph, setting a precedent for future instrument design on very-large and extremely-large telescopes.

Domaines: Instrumentation et méthodes pour l'astrophysique [astro-ph.IM]

N. Jovanovic, N. Cvetojevic, B. Norris, C. Betters, C. Schwab, et al.. Demonstration of an efficient, photonic-based astronomical spectrograph on an 8-m telescope. Optics Express, 2017, 25 (15), pp.17753. ⟨10.1364/OE.25.017753⟩. ⟨hal-03518355⟩