title: A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s(-1).
abstract: Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm s(-1) (ref. 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earth-like orbit, a precision of approximately 5 cm s(-1) is necessary. The combination of a laser frequency comb with a Fabry-Pérot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40-GHz (approximately 1-A) line spacing, generated from a 1-GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or 'astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm s(-1) in astronomical radial velocity measurements.
authors.affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Chih-Hao
authors.initials: CH
authors.lastname: Li
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Benedick
authors.forename: Peter
authors.initials: P
authors.lastname: Fendel
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Glenday
authors.forename: Franz X
authors.initials: FX
authors.lastname: Kärtner
authors.forename: David F
authors.initials: DF
authors.lastname: Phillips
authors.forename: Dimitar
authors.initials: D
authors.lastname: Sasselov
authors.forename: Andrew
authors.initials: A
authors.lastname: Szentgyorgyi
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Walsworth