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Atmospheric Trace-Gas Detection Using Very High-Sensitive Laser Sensors

使用极高灵敏度激光传感器进行大气痕量气体检测

基本信息

批准号：
08458140
负责人：
KUZE Hiroaki
金额：
$ 4.16万
依托单位：
Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08458140/
关键词：
laser sensor atmospheric trace gases fiber ring laser

项目摘要

High-sensitive detection of atmospheric trace-gases is becoming more and more important in the environmental issues concerning the earth's atmosphere such as destruction of ozone layrs and acid rain. The purpose of this research is to establish the method of detecting trace gases of ppt order under 1 atm to 10^<-3> atm conditions. The recent development of compact laser sources is fully exploited in the experiments with prototype laboratory models.1.For the spatial propagation experiment we have constructed a vacuum system equipped with appropriate windows. Acetylene is chosen for The specimen that exhibits absorption at the wavelength region of 1.5 mu m. A diode laser of distributed-feedback (DFB) type is mainly used as the source. Fundamental parameters such as the transition moment of the absorption and scanning characteristics of the laser source are measured with the method of highly sensitive absorption spectroscopy using current modulation. A more sensitive method is the one whi … More ch is based on a Fabry-Perot resonator constructed with highly reflective mirrors. Using an absorption cell of 0.25 m in length, we have observed a signal corresponding to an equivalent absorption length of 2 m, verifying the enhancement effect. Further increase of the stability of the resonator structure and that of the light source will lead to development of the sensors of resonator type.2.As an example of the multi-mode scheme, a trace-gas detection experiment has been performed using an all-fiber, ring-laser resonator. An amplifier based on Er-doped fiber is utilized as a light source, and a bandwidth as narrow as 0.04 nm has been attained with band-pass filters. A special type gas cell that can be directly connected with optical fibers is devised to observe the acetylene absorption at 1.5 mu m. Varying ring configurations, we have found that under suitable conditions the change of laser output power with acetylene pressure becomes large when the pumping power is close to the threshold. This sensor exhibits excellent performance also in detecting very slight pressure change of the trace gas in a pressure range determined by the pumping power. Further decrease of the system loss ensures the development of a very compact, all-fiber trace-gas sensor. Less

大气微量气体的高灵敏度检测在臭氧层破坏、酸雨等地球大气环境问题中变得越来越重要。本研究的目的是建立在1atm至10^-3atm条件下检测ppt量级痕量气体的方法。紧凑型激光源的最新发展在原型实验室模型的实验中得到了充分利用。1.对于空间传播实验，我们构建了一个配备有适当窗口的真空系统。选择乙炔作为在1.5μm波长区域表现出吸收的样品。主要使用分布式反馈（DFB）型二极管激光器作为光源。采用电流调制的高灵敏吸收光谱法测量了激光源的吸收跃迁矩和扫描特性等基本参数。一种更灵敏的方法是基于由高反射镜构造的法布里-珀罗谐振器。使用长度为0.25 m的吸收池，观察到等效吸收长度为2 m对应的信号，验证了增强效果。谐振腔结构和光源稳定性的进一步提高将促进谐振腔型传感器的发展。2.作为多模方案的一个例子，使用全光纤环形激光谐振腔进行了痕量气体检测实验。采用基于掺铒光纤的放大器作为光源，并通过带通滤波器实现了窄至0.04 nm的带宽。设计了一种可直接与光纤连接的特殊型气室来观察乙炔在1.5μm处的吸收。不同的环结构，我们发现在适当的条件下，当泵浦功率接近阈值时，激光输出功率随乙炔压力的变化变大。该传感器在检测由泵浦功率确定的压力范围内微量气体的非常微小的压力变化方面也表现出优异的性能。系统损耗的进一步降低确保了非常紧凑的全光纤微量气体传感器的开发。较少的