中文摘要：

利用分布反馈式二极管激光器为光源,搭建了一套2μm波段的离轴积分腔输出光谱装置.利用高纯甲烷气体,测量了腔镜反射率随腔内气体压力变化的规律.当腔内压力为3.59 k Pa时,标定的镜面反射率为0.99865,在此条件下,基长55 cm的离轴积分腔实现了407.4 m的吸收光程.选取CO2在4993.7431 cm^-1处的吸收谱线对实际大气中的CO2浓度进行了测量,探测限为0.53 ppmv（1σ）,利用小波去噪对光谱信号进行了去噪处理,信噪比提高了80%,探测限提高到0.29 ppmv（1σ）.利用搭建的装置在实验室内测量了从上午9：00到中午12：00实际大气中CO2的浓度,并与H2O/CO2分析仪进行了同时观测与对比分析,初步验证了测量装置的可靠性.

英文摘要：

An off-axis integrated cavity output spectroscopy（OA-ICOS） is established by using a fiber-coupled distributed feedback diode laser operating near 2 μm. Its performances are evaluated and optimized through experimental investigation via detecting the pure CH4 absorptions at different pressures. The reflectivity of the cavity mirror is measured to be 0.99865, which results in the effective total optical pathlength of up to 407.4 m based on a 55 cm cavity. It is shown that the OA-ICOS configuration can be used to obtain very long optical pathlength, leading to pretty high sensitive monitoring of atmospheric trace gases. Based on the developed OA-ICOS, the atmospheric CO2 measurements are made and its performance is improved by using the wavelet denoising approach. The CO2 absorption line at 4993.7431 cm^-1 is used for measuring the concentration. The measured results are compared with the results obtaind by a commercial H2O/CO2 analyzer. Agreement and disagreement are briefly discussed, and the results show that the OA-ICOS is reliable for detecting the atmospheric trace gases. The limitation of the developed OA-ICOS and the further steps towards the improvement in precision and accuracy are also presented.