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Tunable dual-comb spectrometer for mid-infrared trace gas analysis from 3 to 4.7 µm

: Nitzsche, Leonard; Goldschmidt, Jens; Kießling, Jens; Wolf, Sebastian; Kühnemann, Frank; Wöllenstein, Jürgen

Fulltext ()

Optics Express 29 (2021), No.16, pp.25449-25461
ISSN: 1094-4087
Journal Article, Electronic Publication
Fraunhofer IPM ()
Fourier transform infrared spectroscopy; Frequency Combs; laser modes; optical components; polarization control; tunable lasers

Dual-frequency comb spectroscopy has emerged as a disruptive technique for measuring wide-spanning spectra with high resolution, yielding a particularly powerful technique for sensitive multi-component gas analysis. We present a spectrometer based on two electro-optical combs with subsequent conversion to the mid-infrared via tunable difference frequency generation, operating in the range from 3 to 4.7 µm. The repetition rate of the combs can be tuned from 250 to 500 MHz. For 500 MHz, the number of detected comb modes is 440 with a signal-to-noise ratio exceeding 105 in 1 s. The conversion preserves the coherence of the combs within 3 s measurement time. Concentration measurements of 5 ppm methane at 3.3 µm, 100 ppm nitrous oxide at 3.9 µm and a mixture of 15 ppm carbon monoxide and 5% carbon dioxide at 4.5 µm are demonstrated with a noise-equivalent absorption coefficient of 6.4(3) x 10−6 cm−1 Hz−1/2.