Watt-Class Sub-100-fs Kerr-Lens Mode-Locked Dual-Comb Laser at 2.13 μm

Dual-comb laser systems have garnered significant interest because of their advantages for applications in pump-probe sampling, high-precision optical ranging, and absorption spectroscopy [1]. Recent advancements in single-cavity designs, such as spatially multiplexed pulse trains, significantly simplify dual-comb systems by eliminating the need for complex phase-locking electronic subsystems [2]. Since the pulses circulate within the same cavity, they are subject to similar disturbances, resulting in correlated noise suppression, which is particularly beneficial for sensitive sensing applications. In particular, single-cavity dual-comb systems directly operating at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2-\mu \mathrm{m}$</tex> and beyond, are very attractive for spectroscopic sensing and further mid-IR frequency conversion. So far only few demonstrations have been made in this wavelength region; most remarkably a Cr:ZnSe-based dual-comb laser at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.36-\mu \mathrm{m}$</tex> was demonstrated with a spectral bandwidth of 30 nm, >200-mW average power, 200-fs pulse durations, and a repetition rate of 242 MHz [3]. In this work, we demonstrate a novel, free-running, soft-aperture Kerr-lens mode-locked (KLM) dual-comb laser at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.13-\mu \mathrm{m}$</tex>. Based on a Ho:CALGO crystal as the gain medium, our system delivers over 2 W of total output power (1 W per comb) with sub-100-fs pulses at a 96.5-MHz repetition rate, corresponding to 20-nJ pulse energy. Compared to the previous results, our system achieves a fivefold increase in average power and a twofold increase in spectral bandwidth while operating in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2-2.2 \mu \mathrm{m}$</tex> range, where atmospheric transmission is low. This spectral region is highly suitable for detecting gases like CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, N20, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{NH}_3$</tex>, making this system promising for rapid and precise greenhouse gas monitoring.