NIR/VIS dual-comb spectroscopy comparing high and low repetition rate regimes

Abstract: Dual-comb spectroscopy enables broadband analysis of key molecules with unparalleled frequency resolution and exceptional signal-to-noise ratios across various spectral regions. However, fully harnessing its potential for broadband spectroscopy with high sensitivity and spectral resolution depends critically on selecting the appropriate frequency combs with optimized (comb) parameters tailored to specific applications. This study compares dual-comb spectroscopy systems operating at 80 MHz and 1 GHz repetition rates, in the near infrared and visible spectral regions. The 80 MHz system provides high spectral resolution, ideal for resolving complex spectra, showcased with measurements of NH$_3$ vibrational bands and I$_2$ hyperfine transitions. Utilizing phase-locked feed-forward stabilization, the system delivers excellent signal-to-noise ratios but faces limitations in temporal resolution. The free-running 1 GHz system offers superior temporal resolution and compactness, making it suitable for real-time environmental monitoring in laboratory and field settings. A self-correction algorithm advances the high mutual coherence, enabling high-signal-to-noise measurements without additional electronics. With its 1 GHz resolution, it excels in monitoring NH$_3$ transitions or NO$_2$ lines at high speeds. This work highlights the complementary strengths of these systems for high-resolution spectroscopy and real time trace gas sensing.