Richter D, Fried A, Wert B P, Walega J G, Tittel F K
National Center for Atmospheric Research, Boulder, CO 80305, USA.
Appl Phys B. 2002;75(2-3):281-8. doi: 10.1007/s00340-002-0948-y.
The development of a compact tunable mid-IR laser system at 3.5 micrometers for quantitative airborne spectroscopic trace gas absorption measurements is reported. The mid-IR laser system is based on difference frequency generation (DFG) in periodically poled LiNbO3 and utilizes optical fiber amplified near-IR diode and fiber lasers as pump sources operating at 1083 nm and 1562 nm, respectively. This paper describes the optical sensor architecture, performance characteristics of individual pump lasers and DFG, as well as its application to wavelength modulation spectroscopy employing an astigmatic Herriott multi-pass gas absorption cell. This compact system permits detection of formaldehyde with a minimal detectable concentration (1 sigma replicate precision) of 74 parts-per-trillion by volume (pptv) for 1 min of averaging time and was achieved using calibrated gas standards, zero air background and rapid dual-beam subtraction. This corresponds to a pathlength-normalized replicate fractional absorption sensitivity of 2.5 x 10-(10 )cm-1.
报道了一种用于定量机载光谱痕量气体吸收测量的紧凑型可调谐3.5微米中红外激光系统的研制。该中红外激光系统基于周期极化铌酸锂中的差频产生（DFG），并利用光纤放大的近红外二极管激光器和光纤激光器作为泵浦源，分别工作在1083纳米和1562纳米。本文描述了光学传感器架构、各个泵浦激光器和DFG的性能特性，以及其在采用像散赫里奥特多程气体吸收池的波长调制光谱中的应用。这个紧凑型系统能够检测甲醛，在1分钟平均时间下，最小可检测浓度（1σ重复精度）为74体积万亿分之一（pptv），这是通过使用校准气体标准、零空气背景和快速双光束减法实现的。这对应于2.5×10^(-10)厘米^(-1)的光程长度归一化重复分数吸收灵敏度。
