Detection of C2H2 and HCl using mid-infrared degenerate four-wave mixing with stable beam alignment: towards practical in situ sensing of trace molecular species
A stable and convenient optical system to realize the forward phase-matching geometry for degenerate four-wave mixing (DFWM) is demonstrated in the mid-infrared spectral region by measuring DFWM signals generated in acetylene (C2H2) and hydrogen chloride (HCl) molecules by probing the fundamental ro-vibrational transitions. IR laser pulses tunable from 2900 cm(-1) to 3350 cm(-1) with a 0.025 cm(-1
