Tunable dual optical frequency comb at 2 µm for CO₂ sensing

In this article, we demonstrate a dual frequency comb (DFC) based on the gain-switching of mutually injection-locked semiconductor lasers in the 2 µm wavelength region with a tunable free spectral range (FSR) between 500 MHz and 3 GHz. Through the down-conversion process enabled by DFCs, the beating spectra of the optical frequency combs were captured in a 15 MHz electrical bandwidth with high resolution and millisecond acquisition times. A first experimental demonstration of sensing CO₂ with this architecture is also presented.