Novel NO2 detection based on cavity ringdown spectroscopy using a power build-up cavity

This paper reports a laser diode pumped power build-up cavity (PBC) to apply for cavity ringdown spectroscopy (CRDS). The PBC is a compact-high finesse external cavity laser diode, which can obtain resonant enhancement without active cavity length control. PBC is applied generally undesired feed backed beam to cavity resonant enhancement. More than 2.30 μs of ringdown time was achieved with a very small gas sampling volume about 2.5ml. Sensitivity of 3.62 × 10^-7 cm^-1 corresponding to NO₂ detection limit of less than 1.7 ppm was achieved.