基于量子阻抗Lorentz振子的三种晶体二次谐波特性

Second Harmonic Characteristics of Three Crystals Based on Quantum Impedance Lorentz Oscillator

量子阻抗Lorentz振子(QILO)是基于Bohr-Sommerfeld理论和量子力学选择定则对Lorentz振子量子化所新近建立的模型。根据该模型,分别对Li_(2)SnTeO_(6)、CsClO_(3)和Na_(2)Nb_(4)O_(11)三种光学晶体二次谐波特性进行了分析与数值模拟,尝试提出了一种估算晶体二阶非线性光学系数的方法。首先,根据晶体线性吸收光谱的峰值频率和半峰全宽,利用QILO模型计算了晶体的原子跃迁前后的有效量子数,然后根据QILO的二阶非线性效应参数的计算公式推算了晶体二阶电极化率,由此得到上述三种晶体在波长532 nm的倍频系数分别为0.17 pm/V、0.69 pm/V和1.17 pm/V,且与第一性原理的数值吻合较好。结果表明,基于QILO模型的二阶电极化率,有助于分析和提高材料的和频、差频以及倍频的效率,且方法简单、计算耗时少、运算效率高。

Quantum impedance Lorentz oscillator(QILO)is a newly established model for quantizing Lorentz oscillators based on Bohr-Somerfeld theory and quantum mechanical selection rules.Based on this model,the second harmonic characteristics of Li_(2)SnTeO_(6),CsClO_(3)and Na_(2)Nb_(4)O_(11)optical crystals were analyzed and numerically simulated,and a method for estimating the second-order nonlinear optical coefficients of crystals was proposed.First,we calculated the effective quantum numbers before and after the atomic transition according to the peak frequency and full width at half maximum of the optical crystals.Then,considering the second nonlinear effective parameter of QILO,we inferred and determined the second-order polarizability of the three crystals as a function of wavelength.As a result,the second harmonic generation coefficients of the three crystals at 532 nm were 0.17 pm/V,0.69 pm/V,and 1.17 pm/V,respectively,which agree well with those from the first principle.The results show that the second-order electric susceptibility based on QILO model is helpful to analyze and improve the efficiency of sum frequency,difference frequency,and frequency multiplication of materials,and the method is simple,calculation time is less,and calculation efficiency is high.