中文摘要：

从半经典密度矩阵理论出发,建立了光抽运太赫兹波谱线竞争的双三能级分子系统模型,理论推导了抽运信号吸收系数以及太赫兹波信号增益系数的数学表达式,采用迭代法数值计算了CO2激光-9P（32）抽运重水（D2O）气体分子腔式太赫兹激光66μm和116μm两条谱线之间的竞争。给出了抽运功率、工作气压及激光腔长等工作条件下谱线竞争的一般规律。

英文摘要：

Based on the theory of semi-classical density matrix, a model of double three-energy-level system for terahertz laser line competition is built. The mathematical expressions of absorption coefficient for pump signal and gain coefficients for terahertz laser signals are deduced, and the competitions between 66 μm and 116 μm spectral lines in CO2-9P （32） optically pumped D2O cavity terahertz laser are calculated numerically by means of iteration. The general rules for laser line competition under different operating conditions （including pump power, operating gas pressure and length of cavity） are summarized.