【摘要】 本文利用标准的密度矩阵方法,对两激光场和四能级系统的互作用过程写出密度矩阵的刘维方程;两激光场的频率为ω_p、ω_s,场强为E_p、E_s,失谐量为δ_p、δ_s;对CH₃F分子气体,利用电子计算机求出方程的解.由此得出系统的电极化率的虚部x″（ω_s）和δ_p,δ_s 的关系,并讨论了系统的调谐和增益特性.所得结果可应用于分析激光光泵亚毫米波激光器和研究气体分子中双光子吸收过程.更多还原

【Abstract】 In this paper,we use the standard density matrix to set up Liouville’sequations for four-level system.The equations are solved for the interaction oftwo laser fields with quantum system.The laser fields at frequencies ω_p and ω_s,are off resonance by δ_p and δ_s,respectively,such that |δ_p|,|δ_s|《ω_p,ω_s.Theequations are solved for CH₃F molecular gases by microcomputer,and obtainedthe relations between imaginary part of electric susceptibility X″（ω_s）and δ_p,δ_s.The tuning and gain characteristics of system are discussed.These results can be applied to the analysis of the optically pumped submi-llimeter laser and two-photon absorption in gases.更多还原