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本文理论上利用二能级近似下的传递矩阵法,给出了GaAs/Al_xGa_(1-x)As二阶非线性光学系数X_(2ω)~(2)的解析表达式,通过数值计算,设计了具有较大X_(2ω)~(2)的阶梯多量子阱(SMQW)结构,其特点是单共振泵浦,实验上验证了该结构确实具有比体材料大3个量级的X_(2ω)~(2)值,为了提高二次谐波(SHG)的转换效率,我们分别设计了两种新型的实验方案,分别使SHG转换效率较Brewster角入射下大10倍和100倍。
In this paper, the analytical expression of the second-order nonlinear optical coefficient X 2ω 2 ~ (2ω) of GaAs / Al_xGa_ (1-x) As is theoretically proposed by using the transfer matrix method in two-level approximation. The multi-quantum well (SQQW) structure with large X_ (2ω) ~ (2) is characterized by single-resonance pumping. The experimental results show that the structure does have X_ (2ω ) ~ (2). In order to improve the conversion efficiency of the second harmonic (SHG), we have designed two new experimental schemes respectively, which respectively make the SHG conversion efficiency 10 times and 100 times larger than that of the Brewster angle.