Mid-infrared multi-mode absorption spectroscopy, MUMAS, using difference frequency generation

H. Northern, S. O’Hagan, M. L. Hamilton, and P. Ewart

Multi-mode absorption spectroscopy of ammonia and methane at 3.3 ?m has been demonstrated using a source of multi-mode mid-infrared radiation based on difference frequency generation. Multi-mode radiation at 1.56 ?m from a diode-pumped Er:Yb:glass laser was mixed with a single-mode Nd:YAG laser at 1.06 ?m in a periodically poled lithium niobate crystal to produce multi-mode radiation in the region of 3.3 ?m. Detection, by direct multi-mode absorption, of NH3 and CH4 is reported for each species individually and also simultaneously in mixtures allowing measurements of partial pressures of each species.

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