Phase-Locked Feed-Forward Stabilization for Dual-Comb Spectroscopy

Abstract

Sustained mutual coherence between 2 combs over extended periods is a prerequisite for dual-comb spectroscopy (DCS), particularly in achieving high-resolution molecular spectroscopy and precise spectral measurements. However, achieving long coherence times remains a challenge for Yb-doped frequency combs. This work introduces an experimental approach for phase-stable DCS using Yb-doped frequency combs at 1.03 μm with a novel feed-forward method, combatting the limitations of mutual coherence. Without relying on postprocessing or self-correction algorithms, we achieve a coherence time of 1,000 s—3 orders of magnitude longer than the current state of the art for DCS. This extended coherence enables time-domain averaging, resulting in a signal-to-noise ratio (SNR) of 2,045. We demonstrate high-resolution monitoring of weak overtone transitions in the P and R branches of C2H2, achieving good agreement with simulated spectra based on HITRAN parameters. The phase-locked multiheterodyne system also enables phase spectrum measurements with a scatter down to 7 mrad. Furthermore, we successfully extend our technique to the visible spectral region using second harmonic generation, achieving high-resolution spectra of NO2 with excellent SNR. The method offers high-frequency accuracy and demonstrates the potential of Yb-doped systems for multiplexed metrology, effectively extending the capabilities of DCS as a powerful tool for multi-disciplinary applications.