Towards a single-laser-diode-pumped 15-GHz Ti:sapphire astrocomb

The precision, accuracy, and traceability demanded by contemporary exoplanet observations have motivated the astronomy community’s adoption of astrocombs, a technology providing thousands of ultra-narrow, drift-free, regularly spaced optical frequencies on a selectable multi-GHz grid. To date, these systems have relied on high-power pump lasers and/or multiple stages of optical amplification to achieve the target performance. Here, we introduce a compact and simple astrocomb concept, in which a single laser diode pumps a 1 GHz Ti:sapphire oscillator, generating a 600 nm to 900 nm supercontinuum that is filtered to produce a 730 nm to 880 nm spectrum with a 15 GHz mode spacing, as a prerequisite for use as an astrocomb. Simple and low-cost astrocombs adopting this approach could be deployed in volume to enable a network of high-resolution spectrographs, needed to achieve sufficient observing time for comprehensive radial-velocity follow-ups of transiting exoplanet surveys.