光泵重水气体产生THz激光的半经典理论分析

从半经典密度矩阵理论出发，采用三能级系统模型对光泵重水气体产生太赫兹激光进行了理论分析，求解得到了脉冲光泵重水气体分子产生太赫兹激光过程中激光信号增益系数G_s和抽运光信号被吸收系数G_p的表达式，通过迭代法对太赫兹激光信号的输出光强进行了数值计算，理论计算得到的频谱特性曲线完全符合受激Raman辐射的频谱特性，即频谱宽度较大、输出光强随抽运失谐量的改变而变化明显等特征.在脉冲激光抽运受激Raman辐射过程中，工作介质D₂O气体分子的偶极矩由于受到抽运脉冲光场的扰动发生变化，在频谱特性曲线中表现为受激辐射THz信号的谱线发生了分裂.理论计算结果与已报道的实验结果能较好地相符.

Semiclassical theory of optically pumped D2O gas tera-Hz laser

By solving the density matrix equation of three-level molecular system, the pulsed laser pumped D₂O gas terahertz laser was theoretically studied, the expression of terahertz signal gain coefficient(G_s)and the pumping signal absorption coefficient (G_p) were obtained, the output power density of terahertz laser was calculated numerically by iteration method. The calculation shows that the spectral characteristics of terahertz laser was in full accordance with the stimulated Raman emission. The signal frequency detuning obviously affects the amplification process, and there exists splitting in the curve because of the dipole of D₂O gas molecule being disturbed by the field of pumping pulse. The theoretical spectrum is in good agreement with reported experimental results.