量子盘中的三阶非线性光学极化率  

Third-order Nonlinear Optical Susceptibility in Quantum Disks

作　　者：刘翠红[1] 郭康贤[2] 陈传誉[1] 马本堃[1] 

机构地区：[1]北京师范大学物理系,北京100875 [2]广州师范学院物理系,广东广州510405

出　　处：《发光学报》2001年第2期135-138,共4页Chinese Journal of Luminescence

基　　金：广东自然科学基金资助项目

摘　　要：利用密度矩阵方法讨论了量子盘中的三阶非线性光学极化率 ,导出了近共振条件下的三次谐波的解析表达式 ,并以GaAs量子盘为例进行了具体的计算。结果表明 ,GaAs量子盘中的三阶非线性光学极化率要比GaAs量子阱的大几十倍。而且 ,选取适当的参量 ,可在吸收系数相对较小的情况下获得较大的折射率。In recent years,the subject of optical nonlinearity in semiconductor quantum confined structures such as quantum wires and quantum dots has attracted a considerable attention because of their relevance for studying practical applications and as a probe for the electronic structure of media.It has been shown that the low dimensional quantum systems present very large nonlinear optical susceptibilities .Theoretically,most of the studies on quantum dots are focused on spherical quantum dots for simplicity.The shape of quantum dot depends on growth conditions.In fact,quantum dots are better described as thin disk or cylinder.In the present work third order nonlinear optical susceptibilities in disk shaped quantum dots due to resonant intersubband transition are analyzed by a compact density matrix approach.It has rarely been discussed in literatures.Firstly,we consider an electron moving in a quantum disk whose radius R is very large compared to its thickness d .For simplicity,we assume that the isotropic effective mass approximation is valid within the disk and that the inner potential is null while the outer confining potential is approximately infinite.Using the adiabatic approximation we solve the three dimensional Schrdinger equation and obtain the analytical expressions of wave functions and energy levels in cylindrical coordinates.Secondly,we consider the system is excited by an electromagnetic field with frequency ω. The electromagnetic field is incident with a polarization vector normal to the disk.We treat H′=ezE(t) as a perturbation term.By using the compact density matrix method,we derive a general formula for third order nonlinear optical susceptibilites employing a four level model in quantum disk.Finally,numerical results are illustrated for a typical GaAs quantum disk.We calculate the third order nonlinear optical susceptibilities as a function of the disk thickness.It is shown that the third order nonlinear optical susceptibilities in quantum disk

关 键 词：三阶非线性光学极化率 量子盘 密度矩阵算符 半导体 

分 类 号：O472.3[理学—半导体物理]