Gapless high-resolution QCL dual-comb spectroscopy with real-time data processing for dynamic gas-phase measurements

Quantum cascade laser frequency combs (QCL-FCs) are mid-infrared sources capable of producing several hundred comb lines spanning tens of cm -1 . In the dual comb configuration, two nearly identical frequency combs with slightly different comb spacing are used as an interrogating and local oscillator comb to probe the absorption or refractive index of a sample [1] . The repetition frequency of the interrogating comb determines the point spacing of the measured absorption spectra; in quantum cascade lasers, this value is typically around 10 GHz.