Spatially multiplexed single-cavity dual-comb laser

Abstract

Single-cavity dual-comb lasers are a new class of ultrafast lasers that have a wide possible application space including pump–probe sampling, optical ranging, and gas absorption spectroscopy. However, to date, laser cavity multiplexing has usually come with a trade-off in laser performance or relative timing noise suppression. We present a 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 W 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 multiplexing technique, we can implement slow feedback on the repetition rate difference <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:mspace width="negativethinmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">r</mml:mi> <mml:mi mathvariant="normal">e</mml:mi> <mml:mi mathvariant="normal">p</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> , enabling this quantity to be drift-free, have low jitter, and be adjustable—a key combination for practical applications that was lacking in prior single-cavity dual-comb systems.