2022/05/06 by Komagata, Kenichi N., Wittwer, Valentin J., Südmeyer, Thomas +2
#FOS: Physical sciences #Instrumentation and Detectors (physics.ins-det) #Optics (physics.optics)
paper · doi:10.48550/arxiv.2205.03334
Quantum cascade laser (QCL) frequency combs have revolutionized mid-infrared (MIR) spectroscopy by their high brightness and fast temporal resolution, and are a promising technology for fully-integrated and cost-effective sensors. As for other integrated comb sources such as micro-combs and interband cascade laser, QCLs have a comb spacing of several GHz, which is adequate for measurements of wide absorbing structures, typically found in liquid or solid samples. However, high-resolution gas-phase spectra require spectral interleaving and frequency calibration. We developed a frequency calibration scheme for fast interleaved measurements with combs featuring multi-GHz spacing. We then demonstrate dual-comb spectroscopy with 600 kHz accuracy in single-shot 54-ms measurements over 40 cm-1 using two QCLs at 7.8 \mathrmμm. This work is an important contribution towards fast fingerprinting of complex molecular mixtures in the MIR. Moreover, the calibration scheme could be used with micro-combs for spectroscopy and ranging, both in comb-swept and comb-calibrated setups.