为了提高微量气体的拉曼散射强度, 本文设计并搭建了注入锁定腔增强拉曼光谱微量气体检测平台。半导体激光器(波长为638 nm, 功率为15 mW)输出到由三块高反镜组成的V型增强腔中, 结合注入锁定技术, 腔内激光强度达到7.5 W, 实现了500倍的增强效果。利用该实验平台对微量单一气体及其混合气体进行了拉曼检测, 并根据拉曼特征谱峰选取原则及信噪比大于3的原则, 确定了H2、CO、CO2、CH4、C2H6、C2H4、C2H2的特征拉曼谱峰分别为4 156, 2 143, 1 388, 2 918, 2 955, 1 344, 1 975 cm-1, 最小检测极限分别为10.2, 21.7, 9.4, 2.1, 8.9, 4.9, 3.3 Pa。腔增强拉曼光谱法可以实现微量同核双原子气体检测及利用单一波长激光的混合气体同时检测, 具有替代气体检测传统光谱方法的潜力。

In order to improve the Raman scattering intensity of a trace gas, a cavity-enhanced Raman spectroscopy (CERS) technique with injection locking was introduced. A diode laser input (638 nm, 15 mW) was coupled into a V-shaped enhanced cavity composed of three highly reflective mirrors. Using the injection locking technique, an intracavity laser beam was generated and enhanced by a factor of 500 to obtain a power of 7.5 W. The Raman spectra of the individual trace gases and the mixture were obtained. According to the principle of Raman spectrum peak selection and a signal-to-noise ratio greater than 3, the characteristic Raman peaks of H2, CO, CO2, CH4, C2H6, C2H4, and C2H2 are determined as 4 156, 2 143, 1 388, 2 918, 2 955, 1 344, and 1 975 cm-1, respectively, and the limits of detection are determined as 10.2, 21.7, 9.4, 2.1, 8.9, 4.9, and 3.3 Pa. Trace homonuclear diatomic gases and mixed gases can thus be detected simultaneously using a single-wavelength diode laser and CERS. Therefore, CERS has the potential to become an alternative optical technology for gas detection.