  Single-cavity dual-comb lasers are a new class of ultrafast lasers which have
a wide possible application space including pump-probe sampling, optical
ranging, and gas absorption spectroscopy. However, to this date laser cavity
multiplexing usually came to the trade-off in laser performance or relative
timing noise suppression. We present a new method for multiplexing a single
laser cavity to support a pair of noise-correlated modes. These modes share all
intracavity components and take a near-common path, but do not overlap on any
active elements. We implement the method with an 80-MHz laser delivering more
than 2.4 Watts of average power per comb with sub-140 fs pulses. We reach
sub-cycle relative timing jitter of 2.2 fs [20 Hz, 100 kHz]. With this new
multiplexing technique, we could implement slow feedback on the repetition rate
difference {\Delta}frep, enabling this quantity to be drift-free, low-jitter,
and adjustable - a key combination for practical applications that was lacking
in prior single-cavity dual-comb systems.
