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

N. Jovanovic*, N. Cvetojevic, B. Norris, C. Betters, C. Schwab, J. Lozi, O. Guyon, S. Gross, F. Martinache, P. Tuthill, D. Doughty, Y. Minowa, N. Takato, J. Lawrence

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


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 e ciency 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.

Original languageEnglish
Pages (from-to)17753-17766
Number of pages14
JournalOptics Express
Issue number15
Publication statusPublished - 24 Jul 2017


  • Active or adaptive optics
  • Spectrometers and spectroscopic instrumentation
  • Integrated optics devices
  • Astronomical optics


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