Frequency Comb Fourier Transform Spectroscopy at 8 µm Using a Compact Difference Frequency Generation Source

Mid-infrared comb-based Fourier transform spectroscopy allows high-resolution measurements of entire molecular absorption bands. However, most previous implementations were limited to wavelengths < 5 µm. We present a Fourier transform spectrometer (FTS) with a comb-mode-limited resolution based on a compact difference frequency generation (DFG) source operating around 8 µm. We measure the spectrum of the ν 1 band of N 2 O in the Doppler limit and retrieve line center frequencies with precision of the order of 100 kHz.