Totschnig G, Baer D S, Wang J, Winter F, Hofbauer H, Hanson R K
High Temperature Gasdynamics Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, California 94305, USA.
Appl Opt. 2000 Apr 20;39(12):2009-16. doi: 10.1364/ao.39.002009.
Rapid cavity ringdown measurements of multiple broadband absorbing species (methanol and isopropanol) in gas mixtures have been recorded with two multiplexed continuous-wave distributed-feedback diode lasers operating near 1.4 mum. A measurement sensitivity of 2.4 x 10(-9) cm(-1) for a 4.3-s averaging time was achieved in a 39.5-cm-long static cell with 99.94% reflectivity mirrors. This corresponds to a water-vapor detection limit of less than 2 ppb (parts in 10(9)) for the strong H(2)O lines near 1.4 mum. The shot-to-shot noise of the decay time constant tau was approximately 0.3-0.7%, and ringdown acquisition rates as great as 900 Hz were achieved.
利用两台工作在1.4μm附近的复用连续波分布反馈二极管激光器，对气体混合物中的多种宽带吸收物质（甲醇和异丙醇）进行了快速腔衰荡测量。在一个39.5厘米长的静态池中，使用反射率为99.94%的镜子，在4.3秒的平均时间内实现了2.4×10⁻⁹厘米⁻¹的测量灵敏度。这对应于1.4μm附近强H₂O谱线的水汽检测限小于2 ppb（十亿分之一）。衰减时间常数τ的逐次测量噪声约为0.3 - 0.7%，并实现了高达900 Hz的衰荡采集速率。
