Terahertz quantum cascade laser dual-comb sources with high-repetition-rate detuning.

Terahertz dual-comb spectroscopy has emerged as a critical tool for real-time reaction monitoring and fast molecular dynamics studies. The acquisition rate of dual-comb spectroscopy is limited by the repetition rate difference between the two frequency combs. In this work, we engineer the cavity length difference between two quantum cascade laser (QCL)-based combs to achieve a record repetition rate detuning of 229.14 MHz, corresponding to a minimum time resolution of 4.36 ns. At equivalent frequency resolution, our system reduces the theoretical acquisition time by a factor of eight compared to a dual-comb system with a 21.60 MHz detuning. To further improve the signal-to-noise ratio (SNR) of the comb lines, we apply a computational phase correction algorithm. The combination of rapid acquisition and enhanced SNR makes this high-repetition-rate detuning dual-comb system highly promising for time-resolved spectroscopic applications.