Morse势阱中三次谐波产生的研究

Study on the third-harmonic generation in Morse quantum well

利用量子力学中的密度矩阵算符理论,推导在具有多频率的复光场作用下线性和非线性极化率的一般表达式,然后利用图形技术,即利用费曼(Feynman)图方法来考虑三阶非线性过程,得到三次谐波系数的解析表达式.并以典型的GaAs/AlGaAsMorse势阱为例引入参数进行数值计算.结果表明,在该系统中得到了比体材料大的三次谐波系数,并适当增大势阱参数a可以获得较大的三次谐波系数;三次谐波系数随着弛豫常数Γ减小而增大.

<Abstrcat> The linear and nonlinear susceptibilities had been obtained by the compact-density-matrix approach in presence of the multifrequency incident optical field. An analytic formula for third-harmonic-generation was presented by graphic technology(Feynman). Numerical results were presented for typical GaAs/AlGaAs Morse quantum well. The results showed that third-harmonic-generation increased with the enhancement of a and decreased with relaxation constant increasing. Therefore, if the parameter was increased or the relaxation constant was reduced with the effects on the system associated by environment and other factors limited to minimum,a large third-harmonic-generation coefficient would be obtained.