A high-accurate and universal method to characterize the relative wavelength response (RWR) in wavelength modulation spectroscopy (WMS).
A high-accurate and universal method to characterize the relative wavelength response (RWR) in wavelength modulation spectroscopy (WMS).
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DOI：
10.1364/oe.383216
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发表时间：
2020-02
期刊：
影响因子：
3.8
通讯作者：
Yanjun Du;Zhimin Peng;Yanjun Ding
中科院分区：
文献类型：
--
作者：
Yanjun Du;Zhimin Peng;Yanjun Ding
考虑到激光波长响应在WMS中的重要性和实际测量中的困难，提出了一种通过分析激光电流响应来表征WMS相对波长响应的高精度通用方法。引入了一个同时依赖于电流扫描和调制特性的耦合项来描述波长扫描和调制之间的耦合效应。在不同的激光工作条件和扫描波形下验证了该方法的准确性。所提出的方法的RWR结果的所有拟合残差小于总扫描范围的0.1%，斜坡扫描WMS的拟合残差是文献中最小值的两倍。更好的免校准2f/1f拟合和更准确的CO2浓度结果也表明了所提出的方法的高精度和优越性。最后，基于小扫描和小调制指数下RWR的精确预测，成功地利用WMS测量了CO2在6976.2026 cm-1处跃迁的谱线强度和自碰撞展宽系数等光谱参数。
Considering the importance of the laser wavelength response and the difficulty in its real-scenario measurement in WMS, a high-accuracy and universal method was developed to characterize the relative wavelength response (RWR) by analyzing the laser current response. A coupling term that depends on both the current scan and the modulation characteristic was introduced to describe the coupling effect between the wavelength scan and modulation. The accuracy of the proposed method was verified with different laser working conditions and scan waveforms. All fitting residuals of the RWR result from the proposed method are smaller than 0.1% of the total scan range and the fitting residual of the ramp scanned WMS is twice smaller than the minimum value from literature. The better calibration-free 2f/1f fitting and more accurate CO2 concentration results also suggest the high accuracy and superiority of the proposed method. Finally, based on the precise prediction of RWR with small scan and modulation indices, the spectral parameters, including line strength and self-collisional broadening coefficient, of CO2 transition at 6976.2026 cm-1 were successfully measured using WMS.