A DFG-based cavity ring-down spectrometer for trace gas sensing in the mid-infrared

作者：Whittaker K E; Ciaffoni L; Hancock G; Peverall R; Ritchie G A D^*

来源：Applied Physics B: Lasers and Optics , 2012, 109(2): 333-343.

DOI：10.1007/s00340-012-5150-2

Continuing studies into an all-diode laser-based 3.3 mu m difference frequency generation cavity ring-down spectroscopy system are presented. Light from a 1,560 nm diode laser, amplified by an erbium-doped fibre amplifier, was mixed with 1,064 nm diode laser radiation in a bulk periodically poled lithium niobate crystal to generate 16 mu W of mid-IR light at 3,346 nm with a conversion efficiency of 0.05% W-1 cm(-1). This radiation was coupled into a 77 cm long linear cavity with average mirror reflectivities of 0.9996, and a measured baseline ring-down time of 6.07 +/- 0.03 mu s. The potential of such a spectrometer was illustrated by investigating the P(3) transition in the fundamental nu(3) (F-2) band of CH4 both in a 7.5 ppmv calibrated mixture of in air and in breath samples from methane and non-methane producers under conditions where the minimum detectable absorption coefficient (alpha(min)) was 2.8 x 10(-8) cm(-1) over 6 s using a ring-down time acquisition rate of 20 Hz. Allan variance measurements indicated an optimum alpha(min) of 2.9 x 10(-9) cm(-1) over 44 s.

• 出版日期2012-11