Calibration of an astrophysical spectrograph below 1 m/s using a laser frequency comb.

We deployed two wavelength calibrators based on laser frequency combs ("astro-combs") at an astronomical telescope. One astro-comb operated over a 100 nm band in the deep red (∼ 800 nm) and a second operated over a 20 nm band in the blue (∼ 400 nm). We used these red and blue astro-combs to calibrate a high-resolution astrophysical spectrograph integrated with a 1.

Broadband dispersion-free optical cavities based on zero group delay dispersion mirror sets.

A broadband dispersion-free optical cavity using a zero group delay dispersion (zero-GDD) mirror set is demonstrated. In general zero-GDD mirror sets consist of two or more mirrors with opposite group delay dispersion (GDD), that when used together, form an optical cavity with vanishing dispersion over an enhanced bandwidth in comparison with traditional low GDD mirrors. More specifically, in this paper, we show a realization of such a two-mirror cavity, where the mirrors show opposite GDD and simultaneously a mirror reflectivity of 99.

Visible wavelength astro-comb.

We demonstrate a tunable laser frequency comb operating near 420 nm with mode spacing of 20-50 GHz, usable bandwidth of 15 nm and output power per line of ~20 nW. Using the TRES spectrograph at the Fred Lawrence Whipple Observatory, we characterize this system to an accuracy below 1m/s, suitable for calibrating high-resolution astrophysical spectrographs used, e.g.

In-situ determination of astro-comb calibrator lines to better than 10 cm s(-1).

Improved wavelength calibrators for high-resolution astrophysical spectrographs will be essential for precision radial velocity (RV) detection of Earth-like exoplanets and direct observation of cosmological deceleration. The astro-comb is a combination of an octave-spanning femtosecond laser frequency comb and a Fabry-Pérot cavity used to achieve calibrator line spacings that can be resolved by an astrophysical spectrograph. Systematic spectral shifts associated with the cavity can be 0.

Octave-spanning, dual-output 2.166 GHz Ti:sapphire laser.

A self-referenced octave-spanning Ti:sapphire laser with 2.166 GHz repetition rate is demonstrated. The laser features both direct generation of octave-spanning spectra and a dual-output design for non-intrusive carrier-envelope (CE) phase-stabilization.

A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s(-1).

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.