基于半导体激光的腔增强吸收光谱技术研究

Cavity-Enhanced Absorption Spectroscopy Based on Diode Laser

用近红外可调谐分布反馈(DFB)半导体激光器作光源。用反射率为99.7%左右的平凹镜组成的稳定光学谐振腔作吸收池,建立了一套腔增强吸收光谱(CEAS)系统。根据系统工作时激光器与谐振腔的工作状态,将CEAS技术分为三类:控制波长法,控制腔长法及同时扫描波长和腔长法。以二氧化碳(CO_2)和甲烷(CH_4)为主要样品气体,用控制腔长法和控制波长法CEAS技术对CO_2分子在1.573μm附近的吸收光谱做了测量;用扫描腔长和波长法CEAS技术对CH_4气体在1.316μm附近的吸收光谱做了测量;考察了三种方法的探测灵敏度和在定量分析方面的能力。实验结果表明,CEAS技术是一种装置简单,操作方便,灵敏度高,稳定性好的定量吸收光谱技术,探测灵敏度达1.15×10^(-7)cm^(-1)。

A cavity-enhanced absorption spectroscopy （CEAS） system has been build up, in the system, a tunable near-infrared DFB diode laser is used as the light source, and an optical cavity which is consisted of two mirrors with reflectivity of 99.7 % is used as the absorption cell. Based on the working condition of the diode laser and optical cavity, the technology of CEAS is divided into three kinds., control wavelength CEAS, control cavity length CEAS and both scan wavelength ＆ cavity length CEAS. Carbon dioxide （CO2） and methane （CH4） is used as the main sample gas, control wavelength CEAS and control cavity length CEAS are used to get the absorption spectroscopy of CO2 near the region of 1. 573 um; both scan wavelength ＆ cavity length CEAS are used to get the absorption spectroscopy of CH4 near the region of 1. 316 um, the sensivity and the quantitative analytical ability of the three CEAS is also studied. It demonstrates that CEAS is a quantitative absorption spectroscopy technologic with the advantage of simple setup, easy operation, high sensivity and good stability; the sensivity of both scan wavelength and cavity length CEAS is superior to 1.15 × 10^-7 cm ^-1 .