Near-Infrared Dual-Comb Spectroscopy of CO₂ and N₂O with a Discretized Highly Nonlinear Fiber

In this paper, we introduce an all-fiber dual-comb spectrometer based on an original design of a highly nonlinear fiber to efficiently convert frequency combs in the near-infrared from 1.55 mu m to around 2 mu m. We show that our spectrometer can be used to measure the absorption profiles of rovibrational transitions of CO2 and N2O molecules, especially their collisional self-broadening coefficients. The results show very good agreement with the HITRAN database, and thus, further measurements have been performed on a mixture of CO2/N2O to measure the broadening of the CO2 absorption lines resulting from the presence of N2O.