基于确定偶极子取向的Co^(2+):MgAl_(2)O_(4)吸收截面的测量

Measurement of Co^(2+):MgAl_(2)O_(4) Absorption Cross-Sections by Determining Dipole Orientation

确定具有各向异性、非线性吸收特性的调Q晶体内电偶极子的取向,是测量其吸收截面的重要条件。通过对Co^(2+)∶MgAl_(2)O_(4)晶体所属的空间群以及掺杂Co^(2+)在晶胞结构中的位置对称性的分析,确定了晶体内电偶极子的跃迁方向主要是沿晶胞的4个体对角线方向分布的,建立了偏振入射光在Co^(2+)∶MgAl_(2)O_(4)晶体内传输的理论模型。实验测量了沿[100]方向切割的Co^(2+)∶MgAl_(2)O_(4)晶体在偏振入射光沿晶胞面对角线方向时的非线性透过率曲线,利用建立的模型对实验结果进行拟合,得到Co^(2+)∶MgAl_(2)O_(4)晶体在1.5μm波段的基态吸收截面和激发态吸收截面分别为(3.6±0.3)×10^(-19) cm^(2)和(4.5±0.4)×10^(-20) cm^(2)。

Determining the orientation of electric dipoles in Q-switched crystals with anisotropic and nonlinear absorption properties is an important condition for measuring their absorption cross sections.Through the analysis of the space group to which the Co^(2+)∶MgAl_(2)O_(4) crystal belongs and the position symmetry of the doped Co^(2+)in the cell structure,it is determined that the transition direction of the electric dipole in the crystal is mainly distributed along the diagonal direction of four individuals in the cell,and the theoretical model of polarized incident light propagation in the Co^(2+)∶MgAl_(2)O_(4) crystal is established.The nonlinear transmittance curve of Co^(2+)∶MgAl_(2)O_(4) crystal cut along[100]direction is measured experimentally in the direction of polarized incident light.The experimental results are fitted by the established model.The ground state absorption cross section and excited state absorption cross section of Co^(2+)∶MgAl_(2)O_(4) crystal in 1.5μm wave band are(3.6±0.3)×10^(-19) cm^(2) and(4.5±0.4)×10^(-20) cm^(2),respectively.