  We present a new type of dual optical frequency comb source capable of
scaling applications to high measurement speeds while combining high average
power, ultra-low noise operation, and a compact setup. Our approach is based on
a diode-pumped solid-state laser cavity which includes an intracavity biprism
operated at Brewster angle to generate two spatially-separated modes with
highly correlated properties. The 15-cm-long cavity uses an Yb:CALGO crystal
and a SESAM as an end mirror to generate more than 3 W average power per comb,
below 80 fs pulse duration, a repetition rate of 1.03 GHz, and a continuously
tunable repetition rate difference up to 27 kHz. We carefully investigate the
coherence properties of the dual-comb by a series of heterodyne measurements,
revealing several important features: (1) ultra-low jitter on the uncorrelated
part of the timing noise; (2) the radio frequency comb lines of the
interferograms are fully resolved in free-running operation; (3) we validate
that through a simple measurement of the interferograms we can determine the
fluctuations of the phase of all the radio frequency comb lines; (4) this phase
information is used in a post-processing routine to perform coherently averaged
dual-comb spectroscopy of acetylene (C2H2) over long timescales. Our results
represent a powerful and general approach to dual-comb applications by
combining low noise and high power operation directly from a highly compact
laser oscillator.
