High resolution, high sensitivity gas analyzer using a wide-band tunable CO_2 laser

利用材料特有的吸收波长特性，可以对大气中存在的污染物等的种类和浓度进行测量。本文建立了一个实验分析装置系统，该系统由四个部分组成：第一部分是波导CO_2激光器与CdTe行波宽带电光相位调制器相结合的宽带可调谐CO_2激光器;研制了一台单频线选CO_2激光器和一个宽带电光行波相位调制器，该调制器由CdTe调制元件（2 mm × 2 mm × 15 mm）分成五部分组成，以实现宽带调制。由分开的调制元件构成的调制器可以通过调整段间微波的相位来实现宽带调制。该调制器的微波传输特性带宽为10 GHz，第二个元件是一个高分辨率、高灵敏度的气体吸收池。在法布里-珀罗干涉仪（镜间距60 cm，镜反射率98%）中插入白色镜（镜间距20 cm，镜反射率99.7%），制成了高分辨高灵敏度气体吸收池，并进行了测试，获得了1 MHz的分辨力。

Characteristics of the material peculiar absorption wavelength may be utilized for the measuring method of types and concentration such as the pollutant which exists in the atmosphere. Wide-band tunable CO2 laser and high-resolution absorption cell are required when this method is utilized.An experimental analytical equipment system was constructed, The system consists of four componennts.The first one is a wideband tunable CO_2 laser by combining a waveguide CO_2 laser with CdTe traveling wave wideband electrooptic phase modulator. A single frequency line selectable C0_2 laser and a wide-bannd electrooptic travelingwave phase modulator were constructed.The modulator has been composed of the CdTe modultion element (2mmx2mmxl5mm) divided in five in order to enable the wide-bannd modulator. It is possible that the modulator composed of divided modulation element achieves the wide-band modulation by adjusting the phase of microwaves between sections . The microwave transmission characteristics bandwidth of the modulator was 10GHz for one element.The second one is a high resoluble, high sensitive gas absorption cell. High resoluble high sensitive gas absorption cell which inserted the white mirror (mirror interval 2Ocm, mirror reflectivity 99.7%) in the Fabry-Perot interferometer (mirror interval 6Ocm, mirror reflectivity 98%) was constructed and tested, and 1MHz resolution was obtained.The last one is an JR HgCdTe photodetector and a storage oscilloscope.