Two-micron all-fibered dual-comb spectrometer based on electro-optic modulators and wavelength conversion

Mid-infrared dual-comb spectroscopy offers interesting applications since molecules have their strongest rotational-vibrational absorptions in this frequency domain. Besides, generating frequency combs with electro-optic modulators recently showed promising results toward dual-comb spectroscopy. Here, we report a conversion in the mid-infrared of two mutually coherent frequency combs generated with electro-optic modulators to perform dual-comb spectroscopy in this region. Using fourth-order modulation instability taking place in the normal dispersion regime of a highly nonlinear fiber and by seeding this phenomenon with a frequency agile and low-power laser around 1.3 mu m, we develop a stable and wave-length tunable all-fibered dual-comb spectrometer operating in the 2 mu m region. This allows us to investigate CO2 absorption spectra over 37 nm and to measure collisional broadening coefficients of a few rotational-vibrational lines.