Phase-shift cavity ring-down spectroscopy using mid-IR light from a difference frequency generation PPLN waveguide

Approximately 200 mu W of mid-infrared (mid-IR) light around 3081 cm(-1), produced by difference frequency generation (DFG) in a periodically poled lithium niobate crystal waveguide, has been used for phase-shift cavity ring-down spectroscopy measurements. The overlapping (C2H4)-C-12 P-R(0)(14) and R-P(6)(10) and (CH2)-C-12 (CH2)-C-13 (P)Q(3)(10) rotational lines of the nu 9 fundamental ethene vibrational band at 3081.0016 cm(-1) were probed in proof-of-principle experiments, and ethene detection was demonstrated with a minimum absorption coefficient of 1.4 x 10(-7) cm(-1) (similar to 4 min acquisition time). The compact DFG system, with a >35 cm(-1) tuning range, has a considerable potential for use in trace gas detection and in molecular spectroscopy. (C) 2010 Optical Society of America