Investigation of nonlinear optical properties in atomic and atomic-like mediums with separated energy levels

本论文主要就多能级原子系统、半导体量子阱结构以及半导体纳米双量子点结构中光学非线性方面的量子调控进行了深入研究，并对其可能的应用进行了简单的探讨，取得了一些具有一定创新性研究结果。主要包括： 1、研究了lamda型三能级原子与一个单色探测场和一个三色控制场相互作用系统中，多个拉曼通道间的干涉以及相对相位对电磁诱导透明以及自相位调制Kerr非线性的相干调控。结果发现在适当选择三色控制场频间失谐的条件下，多拉曼通道干涉诱导多个透明窗口出现，同时在多个窗口内出现增强的自相位调制Kerr非线性。同时，通过对三色控制场之间的相对相位调控，可改变透明窗口的位置，并在改变了的窗口内得到增强的自相位调制Kerr非线性。 2、探讨了Lamda型三能级原子系统中运用边频场控制布局反转的特性。相对于频差接近于零的近单色场情形，增加三色场三个成分之间的频差，激发态与基态之间的布局反转可以在更宽的边频强度范围内得到。并且边频场相对于中心场的相对相位之和也可以控制布局反转。对于所考虑的边频强度范围，从0到pi改变相对相位之和,激发态与基态之间的布局反转在接近一半的范围内得到增强。同时，对应于系统处于布局反转状态的边频强度范围也明显增加了。 3、研究了与单色探测场和控制场相互作用作用构成双光子共振的Lamda型原子系统中的，通过在任一跃迁臂上加一边频场，引起双通道干涉，破坏已有的电磁诱导透明，从而双稳现象出现。通过增强边频场强度，可是实现双稳到三稳的变换。而在此同时增强原有控制场强度，将使得三稳阈值明显降低。若系统中两个跃迁臂上同时追加边频，四稳也将出现。并且同时增加两边频强度将引起四稳到五稳的转换，同时阈值明显减小。 4、基于隧穿诱导透明，研究了非对称AlGaAs/GaAs双量子阱结构中共振隧穿对交叉相位调制的量子调控效应。研究结果表明该结构中共振隧穿对交叉相位调制表现为干涉增强，并结合隧穿诱导透明，可实现弱吸收的大交叉相位调制。进一步对非线性相移的计算表明,该结构在信号场与探测场群速度匹配的条件下，交叉相位调制可以实现单光子水平下的pi相移，不仅在全光开关而且在实现双量子逻辑门方面都有潜在应用。 5、探讨了运用电压调控代替强的驱动场，在不对称双量子点系统中实现增强的自Kerr非线性光学特性。通过把双量子点分子构建成 一个类似于四能级原子系统的结构，合理调节隧穿电压和相关失谐，伴随消失的线性吸收和非线性吸收，在透明点附近我们得到巨增强的自Kerr非线性。解析解表明，电压隧穿诱导透明以及电压隧穿对三阶效应的干涉增强是该巨自Kerr非线性产生的必不可少的因素。该研究结果可以用作产生超慢光亮孤子和暗孤子。In this thesis, we mainly investigate the quantum coherent control of nonlinear properties in atomic scheme, semiconductor quantum wells, semiconductor quantum dots and photonic crystals. The main innovative and important results are: 1、Trichromatic manipulation of Kerr nonlinearity in a three-level Lamda-type atomic configuration is investigated theoretically. It was shown for a weak monochromatic probe field, that the enhanced Kerr nonlinearity can be achieved in multiple separate transparent windows due to interference effect of multiple two-photon Raman channels. Furthermore, changing the sum phase from 0 to pi, the enhanced Kerr nonlinearity can be obtained within different separate transparent windows. 2、Sideband manipulation of population inversion in a three-level Lamda-type atomic configuration is investigated theoretically. Comparing to the case of a nearly monochromatic field, a population inversion between the excited state and ground state has been found over a wider sideband intensity rang by increasing the frequency difference between three components. Furthermore, changing the sum phase from 0 to pi, the population inversion between the excited state and ground state can be increased within nearly half of the sideband intensity range. At the same time, the sideband intensity range that corresponds to the system exhibiting inversion also becomes wider evidently. 3、Optical bistability and multistability behavior in a three-level Lamda-type atom system are investigated. By adding a sideband on either hand of the transitions to disturb the two-photon resonance, bistability occurs due to two-channel interence. Increasing the sideband Rabi frequency leads to switcing from bistability to tristability. When the sideband simultaneously couples with both hands, we can easily obtain quadrastability. 4、A theoretical investigation is carried out into the cross-phase modulation in an asymmetric double AlGaAs/GaAs quantum wells structure with a common continuum. It is found that, combining resonant tunneling induced transparency and constructive interference in three-order Kerr effect, a giant cross-phase modulation can be achieved with vanishing linear and nonlinear absorptions, accompanied by the velocities of the probe and signal fields being matched. Furthermore, this giant cross-phase modulation could induce a pi phase shift at a single-photon level which is favorable for the application in two-qubit quantum logic gates. 5、The enhanced self-Kerr nonlinearity in an asymmetry double quantum dot molecule system by using voltage tunneling instead of pump field is realized. Through building up a four-level atomiclike system for a double quantum dot melecule, properly controlling the tunneling voltage and relative detunings, the Kerr nonlinearity can be enhanced dramatically at the exact point of vanishing linear and nonlinear absorption. Analytical investigation shows that it is the voltage tunneling induced transparency combined with constructive interference in third-order effect that clearly enhances the Kerr nonlinearity. This self-Kerr nonlinearity results could be used to generate ultraslow bright and dark solitons