基于光腔衰荡光谱技术的激光脉冲能量选择研究

在光腔衰荡光谱技术中衰荡信号虽不受入射光强变化的影响,但入射光强大小并非任意选取。通过理论计算结合实验分析,探讨脉冲光腔衰荡光谱技术中激光单脉冲能量的选取,结果显示激光脉冲能量选取受反射镜的反射率、探测器灵敏度、增益及信噪比等因素限制。当入射光强度选取过低,在探测器本身灵敏度和信噪比的限制下,信号被淹没于噪声中,无法检测信号;入射光强度过高,输出的光电流随光强的增大而趋向于饱和,探测器的响应呈现非线性,甚至出现漂白现象或损坏探测器。实验中,激光光源单脉冲能量范围在33 nJ到1μJ较为合适。

Study of Energy Selection of Laser Pulse in Pulse Cavity Ring-Down Spectroscopy

In the using of cavity ring-down spectroscopy technology, despite the ring-down signal will not be influenced by the incident light intensity, however the incident light intensity can not be chosen in any range. Through the theoretical calculation combined with the analysis of experimental results, this paper discusses the selection of the pulse single laser pulse energy in cavity ring-down spectroscopy in detail, the results show that the selection of single pulse energy of laser source is limited by the mirror reflectivity, sensitivity, gain and signal-to-noise of the detector. When the incident light intensity is selected too low, the signal is drowned in the noise and can not be detected by the limit of detector sensitivity and signal-to-noise ratio, when the incident light intensity is chosen too high, the output of the photocurrent with the light intensity also increases and tends to saturation. The detector response is nonlinear or bleaching. This phenomena could even cause the detectors damage. In typical CRDS system, a suitable level of single pulse energy of laser source ranges from dozens nanojoules to 1 μJ.