可调谐激光吸收光谱技术
希特勒
信号(编程语言)
调制(音乐)
激光器
相量
材料科学
调幅
残余物
校准
光学
吸收(声学)
光谱学
吸收光谱法
光电子学
可调谐激光器
频率调制
带宽(计算)
物理
计算机科学
功率(物理)
声学
电信
电力系统
算法
量子力学
程序设计语言
作者
Keith Ruxton,Arup Lal Chakraborty,Walter Johnstone,Michael Lengden,George Stewart,Kevin L. Duffin
标识
DOI:10.1016/j.snb.2010.06.058
摘要
Recovery and analysis of the 1st harmonic signals in tunable diode laser spectroscopy (TDLS) with wavelength modulation (WM) are limited by the presence of a high background signal upon which the small gas signals are superimposed. This high background signal is a result of direct modulation of the source laser power and is referred to as the residual amplitude modulation (RAM) signal. This paper presents further details of a recently reported technique to optically remove the RAM and an analytical model that enables the use of the phasor decomposition (PD) method with it to extract the absolute gas absorption lineshape from the recovered 1st harmonic signals. The PD method is important as it provides a calibration-free technique for gas concentration measurements. A major benefit of RAM nulling is that signal amplification can be increased without equipment saturation due to the background RAM, resulting in improved signal resolution and system sensitivity. A comparison of experimental measurements of the 1650.96 nm absorption line of methane (CH4) with lineshapes derived from HITRAN data illustrates and validates the use of the PD method with the new RAM nulling procedure. This advancement is useful for industrial applications where stand-alone and calibration-free instrumentation is required.
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