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

摘要

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 ~(12)C_(2)H_(4) ~(R)P_(0)(14) and ~(P)R_(6)(10) and ~(12)CH_(2)~(13)CH_(2) ~(P)Q_(3)(10) rotational lines of the v_(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) (approx4 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.