17-21 March 2019
Sunstar Hotel, Grindelwald, Switzerland
Europe/Zurich timezone

Electro-optic laser frequency comb for spectrograph calibration

19 Mar 2019, 10:00
Sunstar Hotel, Grindelwald, Switzerland

Sunstar Hotel, Grindelwald, Switzerland

Dorfstrasse 168, 3818 Grindelwald Switzerland
Oral Instrument and calibration challenges Instrument and calibration challenges


Mrs Ewelina Obrzud (Department of Astronomy, University of Geneva)


Laser frequency combs (LFCs) comprising thousands of evenly spaced laser lines with absolutely and precisely known optical frequencies can meet the calibration requirements for extreme precision in radial velocity measurements.

We present a LFC for accurate and precise spectrograph calibration in the near-infrared. The LFC is based on electro-optic modulation of a continuous-wave laser and provides comb lines readily resolvable by an astronomical spectrograph without the need for spectral filtering. After temporal compression and spectral broadening, the system currently provides more than 5’000 comb lines spaced by 14.5 GHz covering the wavelength range from 1280 nm to 1880 nm. The spectral coverage and the LFC’s line spacing can be modified to accommodate the specific needs of the spectrograph. Owing to its all-fibre design, the system is alignment-free and of low operational complexity. As all critical components rely on mature optical telecommunication technology, the system is inherently robust and suitable for long-term and low-maintenance operation. Successful performance test of the LFC was performed on the GIANO-B spectrograph demonstrating a photon-noise-limited spectrograph calibration precision of <10 cm/s and an on-sky performance only limited by telluric interference. Current efforts are concentrated on extending the spectral span, which will lead to increased radial velocity calibration precision.

Primary authors

Mrs Ewelina Obrzud (Department of Astronomy, University of Geneva) S. Lecomte (CSEM) Dr François Wildi (Department of Astronomy, University of Geneva) Dr Francesco Pepe (Department of Astronomy, University of Geneva) Tobias Herr (CSEM) V. Brasch (CSEM) François Bouchy (Department of Astronomy, University of Geneva) M. Rainer (INAF Brera) A. Harutyunyan (INAF Fundación Galileo Galilei) Bruno Chazelas (Department of Astronomy, University of Geneva) M. Cecconi (INAF, Fincacion Galileo Galilei) Adriano Ghedina (INAF, Fundación Galileo Galilei) Emilio Molinari (INAF, Fundación Galileo Galilei) S. Kundermann (CSEM)

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