探测器响应特性对光腔衰荡法测量结果的影响

Influence of Detector Responsibility on Its Metrical Result of Ring-Down Cavity

探测器响应特性对衰荡信号的测量有很大影响。根据光束传输变换规律和信号叠加方式,只利用数据拟合,建立了探测器响应特性对衰荡信号和反射率测量结果的影响模型。通过数值运算,模拟了不同情况下衰荡信号波形的变化,进而分析了探测器响应特性对衰荡法测量结果的影响。研究表明,对于现有的数据处理方法,选择合适的探测器,能够提高测量结果的可重复测量精度;但其测量值0.990045与腔镜的真实值0.999存在差异。由此研究了测量结果随腔镜反射率的变化和数据预处理方式,提出了测量结果的两种标校途径:1)利用模拟测量结果与腔镜真实值之间的差异,从理论上对实验测试结果进行标校;2)先对衰荡波形进行梳状滤波等预处理,再用拟合法计算反射率。

Capability of the detector influences the figure of measured ring-down signal very much. According to propagation equation of Gaussian beam and overlap-add of signal, a theory model is set up to research the influence of detector on its ring-down signal and its metrical result by using data processing of only fitting. The change of ring-down waveform is numerically simulated in different case by this model, and based on this, it is calculated that relation between capability of the detector and measured reflectivity of the cavity ring-down spectroscopy (CRDS). Results show that appropriate detector can improve repeating precise of measured reflectivity for the present data processing, but its metrical result of 0.990045 is different from the true reflectivity of cavity's mirror, which is 0.999. In the end, it is studied that metrical result is changed with reflectivity of cavity's mirror, and another data processing is analyzed. Two collating ways for measured reflectivity are put forward, one is correcting in theory according to the difference between simulated result and true reflectivity of cavity's mirror; the second is adding pretreatment of ring-down waveform before data processing of fitting, such as comb filter.