Polarization-Multiplexed Dual-Comb Yb:CALGO Laser and Its Noise Investigation

Single-cavity dual-comb lasers address the complexity and cost of traditional dual-comb spectroscopy systems. In this study, we present a polarization multiplexed dual-comb Yb:CALGO laser, providing flexible tuning of the repetition rate difference and high mutual coherence. Our system operates two combs simultaneously at approximately 72 MHz, with pulse duration of 206 fs and 290 fs, and average power over 1.2 W. We observe minimal fluctuation in the repetition rate difference with a standard deviation of 0.21 Hz over 400 seconds, despite fluctuations in the repetition rates of up to 80 Hz. By effectively canceling common mode noises, we achieve a few-cycle relative timing jitter of 9 fs (integrated from 300 Hz to 500 Hz), when only take into account the contribution from repetition rate noise. The comb-tooth-resolvable dual-comb spectroscopy is demonstrated. In the first study of intensity noise correlation in dual-comb system, we find high degree of in-phase correlations between the pumps and comb lasers at the frequencies ranging from 30 Hz to 500 kHz. Furthermore, the in-phase correlation from 30 Hz to 200 Hz is consistent with the substantial suppression of phase noises. These results pave a new path to gain insight into the noises behaviors in dual-comb lasers.