一种特殊的非对称量子阱中的电光效应

运用密度矩阵方法推导出了特殊非对称量子阱中电光系数的解析表达式,并以典型的GaAs/AlGaAs非对称量子阱为例进行了数字计算.计算结果表明,量子阱的非对称性随着参数a的增大而增强,随着参数V₀的增大而减小.电光系数的最大值也随着参数a的增大而增大,随着参数V₀的增大而减小,表明电光系数将随着量子阱非对称性的增大而增大.在取不同的参数a和不同的参数V₀时,电光系数和入射光子能量的关系分别被绘制成曲线图.在图中分别有三个不同的峰,而且系统的非对称性越大,峰值就越大.随着量子阱非对称性的增大,曲线中的峰向能量低的方向移动.另外,在这种量子阱中得到了比较大的电光系数,大约在10^-6m/V量级.随着近来纳米制作技术的进步,使得在实验上制作这种特殊非对称量子阱并得到较好的非线性材料成为可能.

Electro-optic Effects in Special Asymmetric Quantum Wells

Recently, there has been an increasing interest in nonlinear optical properties of semiconductor quantum well structures, because of their relevance for studying practical applications and as a probe for the electronic structure of mesoscopic media. In this paper, the nonlinear electro-optic effects in special asymmetric quantum wells are studied. Because of this kind of quantum well is more approximate a practical quantum well between the conduction band and valence band, and it can be realized very easily in experiment. The analytical expressions of electro-optic coefficient have been derived by compact density-matrix approach and the numerical results were presented for GaAs/AlGaAs asymmetric quantum wells. The shape of the quantum well varying with the parameter a and the parameter V0 were plotted. Itis found that the asyrmnetry of the quantum wells enhances with the increase of parameter a. On the contrary, the asymmetry of the quantum walls decreases with the increase of the parameter Vo. The maximum values of the electro-optic coefficient varying with the parameter a and the parameter V0 were plotted. The numerical results show the electro-optic coefficient enhances with the increases of the parameter a and the decrease of the parameter V0. Therefore, it is found that the electro-optic coefficient increases with the enhancement of the quantum wells' asymmetry. The electro-optic coefficient as afunction of the photon energy with different values of parameter a and different values of parameter V0 were also plotted. It can be observed that there are three peak values in the figures, respectively. And it is obvious that the larger the asymmetry of quantum wells is, the bigger the peak value is. It can be seen that with the increase of the asymmetry of quantum well, the peaks move to the low energy side.Moreover, the electro-optic coefficient obtained in this special quantum well is as large as 104 m/V.With the advances of nanofabrication technology recently, it is possible to fabricate such semiconductor quantum wells and it is possible for us to get better nonlinear materials in experiments.