Atomically referenced 1-GHz optical parametric oscillator frequency comb

The visible to mid-infrared coverage of femtosecond optical parametric oscillator (OPO) frequency combs makes them attractive resources for high-resolution spectroscopy and astrophotonic spectrograph calibration. Such applications require absolute traceability and wide comb-tooth spacing, attributes which until now have remained unavailable from any single OPO frequency comb. Here, we report a 1-GHz Ti:sapphire pumped OPO comb whose repetition and offset frequencies are referenced to Rb-stabilised microwave and laser oscillators respectively. This technique simultaneously achieves fully stabilized combs from both the Ti:sapphire laser and the OPO with sub-MHz comb-tooth linewidths, multi-hour locking stability and without the need for super-continuum generation.