Influence of the wavelength-dependence of fiber couplers on the background signal in wavelength modulation spectroscopy with RAM-nulling.
Influence of the wavelength-dependence of fiber couplers on the background signal in wavelength modulation spectroscopy with RAM-nulling.
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DOI：
10.1364/oe.18.000267
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发表时间：
2010-01
期刊：
影响因子：
3.8
通讯作者：
A. Chakraborty;K. Ruxton;W. Johnstone
中科院分区：
文献类型：
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作者：
A. Chakraborty;K. Ruxton;W. Johnstone
最近，展示了一种光学消除 1f 波长调制光谱中背景残余幅度调制的技术，但由于耦合器和激光强度调制的波长依赖性，无法在整个扫描范围内实现完美消除。本文从理论上分析了该技术，并通过实验证明了这种消除对于三种可能的实验配置之一来说是完美的，这对于一些最近开发的激光源的潜在应用非常重要。对于其他配置，预测非零背景斜率并通过实验验证，从而解释信号的异常性质。设计了一种独立于信号斜率的通用信号归一化方法，这一事实对于此类系统的工业部署非常重要。
Recently a technique to optically eliminate the background residual amplitude modulation in 1f wavelength modulation spectroscopy was demonstrated, where perfect elimination throughout the scan range was not achieved due to the wavelength-dependence of couplers and that of the laser intensity modulation. This paper theoretically analyzes the technique and experimentally demonstrates that the elimination can be perfect for one of three possible experimental configurations, making this important for potential applications with some recently-developed laser sources. For the other configurations a non-zero background slope is predicted, experimentally verified, and the anomalous nature of signals is thereby explained. A common signal normalization method is devised that is independent of the signal slope, a fact that is important for industrial deployment of such systems.