A detailed analysis of a fiber pumped quasi-phase matched mid-infrared source is reported. The spectroscopic performance of fiber coupled near-IR pump lasers was tested with and without frequency mixing components. We applied wavelength modulation spectroscopy in combination with zero-air background subtraction and a newly developed 100 m optical pathlength astigmatic Herriott cell. Measurements on a weak CO absorption at 1564.168 nm show minimum detectable absorbance’s of ~ 6E-11 cm−1 and 3E-10 cm−1 (1 σ, 177 s / 50 s acquisition time) obtained with and without frequency mixing components.
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