腔内非均匀增益对DF化学激光器本征模式特性的影响

The effect of nonuniform gain on eigenmode characteristics of DF chemical lasers

通过对氟化氘(DF)化学激光器腔内气动流场的分析,建立了包括小信号增益系数分布和折射率起伏分布的非均匀增益分布模型,进而分析了化学激光器腔内非均匀增益分布对其模式特性的影响.采用增益介质多层分布法和Fox-Li迭代法,计算了具有非均匀增益分布的DF化学激光器有源腔本征模式分布,并利用功率谱密度(PSD)及Zernike像差系数对无源腔以及有源腔本征模式的相位特性进行了比较分析.研究结果表明:DF化学激光器腔内非均匀增益特性会引起其本征模式分布不均匀性和波前相位高频比例的增加,进而导致激光器输出光束的光束质量明显下降.

By analyzing aerodynamic field in the DF chemical laser cavity,a nonuniform flowing gain model was built,including distributions of small signal gain coefficient and fluctuation of refractive in-dex.And the effect on eigenmode characteristics of nonuniform gain was explored.The eigenmode of the loaded DF chemical laser with nonuniform gain was calculated by using the multiple gain segments method and Fox-Li iterative method.A further comparison of the eigenmode phases between the bare re-sonator and loaded resonator was made with the power spectral density （PSD）and the Zernike aberra-tion coefficients.The results indicate that the nonuniform flowing gain of the medium in the cavity in-creases the nonuniformity of the eigenmode distributions and the proportion of high-frequency in wave-front phase,further leading to obvious degradation of the beam quality of the output laser beams.