基于非对称量子阱的太赫兹波调制器

主要研究了一个特殊的GaAs/AlGaAs非对称量子阱中的线性和三阶非线性太赫兹波吸收系数和介质折射率的相对改变。首先利用量子力学中的密度矩阵算符理论和迭代方法导出了线性和三阶非线性光吸收系数和相对折射率改变的表达式,然后以典型的阶梯型量子阱材料为例做了数值计算。计算表明,基于泵浦光场和偏置电压控制的太赫兹波调制器不仅可以做太赫兹波开关,还可以灵活地调制太赫兹波信号的强度和相位,方便实用。     

Design of GaAs/AlxGa1?xAs asymmetric quantum wells for THz-wave by difference frequency generation

The energy levels, wave functions and the second-order nonlinear susceptibilities are calculated in GaAs/Al0.2Ga0.8As/Al0.5Ga0.5As asymmetric quantum well (AQW) by using an asymmetric model based on the parabolic and non-parabolic band. The influence of non-parabolicity can not be neglected when analyzing the phenomena in narrow quantum wells and in higher lying subband edges in wider wells. The numerical results show that under double resonance (DR) conditions, the second-order difference frequency generation (DFG) and optical rectification (OR) generation susceptibilities in the AQW reach 2.5019 mm/V and 13.208 mm/V, respectively, which are much larger than those of the bulk GaAs. Besides, we calculate the absorption coefficient of AQW and find out the two pump wavelengths correspond to the maximum absorption, so appropriate pump beams must be selected to generate terahertz (THz) radiation by DFG.