【摘要】 基于通讯波段的分布式反馈半导体激光器(DFB),搭建了一套光腔衰荡光谱仪(CRDS)。衰荡光腔由一对反射率高于99.997%的高反镜组成,衰荡腔长约为130cm,空腔衰荡时间约为150μs。当光谱平均次数达到1 000次时,光谱仪灵敏度(最小可探测吸收系数)达到5×10-12 cm-1。利用热隔绝的方式稳定衰荡腔长,并使用衰荡光腔自身作为光学标准具,来标定光谱的频率:利用反馈式光谱扫描程序步进改变激光器频率,使之与衰荡腔的纵模频率逐一匹配,从而实现所测得光谱的自动标定。通过测量一氧化碳分子在1.565μm附近的吸收光谱,测定气体中一氧化碳的含量。将光谱测量结果和标准样品中的一氧化碳含量进行对比,对装置的定量精度进行了检验,表明其对一氧化碳的探测极限达4ppbv。利用该装置对实际大气中一氧化碳的含量进行了实时监测。更多还原

【Abstract】 A cavity ring-down spectrometer(CRDS)was built based on telecom distributed feedback(DFB)diode lasers.The ring down cavity was formed by mirrors of 99.997% reflectivity with a separation of 130 cm,with an empty ring down time of about 150μs.A minimum detectable absorption coefficient of 5×10-12 cm-1 was obtained by averaging about 1 000 recorded spectra.The ring down cavity is thermo-isolated,and used as an interferometer to calibrate the recorded spectrum.A feedback control scheme was applied to step scan the laser frequency,successively matching each of the longitudinal modes of the cavity.By measuring the CO contents in a standard gas sample,the quantitative capability of the CRDS instrument was demonstrated,and a CO detection limit of 4ppb was achieved.The instrument was applied to monitor the CO concentration in ambient air.更多还原