Ultrafast pulse phase shifts in a charged-quantum-dot–micropillar system
Ultrafast pulse phase shifts in a charged-quantum-dot–micropillar system
复制标题
带电量子点微柱系统中的超快脉冲相移
作者：
G. Slavcheva;M. Koleva;A. Rastelli
我们采用基于矢量麦克斯韦赝自旋模型的量子主方程方法来计算嵌入微柱腔中的带负电量子点的基本单重态三重子跃迁中自旋布居的量子演化和相干性。系统的激励是通过超短的圆偏振或线偏振谐振脉冲来实现的。通过实现真实的微柱腔几何形状，我们以数值方式演示了弱耦合状态下共振圆偏振脉冲的巨大光学相移（$sim pm pi/2$）。我们预测的相移大大超过了连续波、线偏振激励下实验观察到的克尔旋转角 $(sim{6 ^{circ}})$。相比之下，我们发现线性偏振脉冲的旋转程度要小得多，只有几度。根据初始边界条件，这是由于正交电场分量的振幅随时间建立的延迟或提前造成的。与之前发表的工作不同，系统动力学充分考虑了占主导地位的自旋弛豫和退相干过程。我们的动力学模型可用于优化光学偏振旋转角，以在芯片上实现自旋光子纠缠和超快偏振切换。
We employ a quantum master equations approach based on a vectorial Maxwell-pseudospin model to compute the quantum evolution of the spin populations and coherences in the fundamental singlet trion transition of a negatively charged quantum dot embedded in a micropillar cavity. Excitation of the system is achieved through an ultrashort, either circularly or linearly polarised resonant pulse. By implementing a realistic micropillar cavity geometry, we numerically demonstrate a giant optical phase shift ($sim pm pi/2$) of a resonant circularly polarised pulse in the weak-coupling regime. The phase shift that we predict considerably exceeds the experimentally observed Kerr rotation angle $(sim{6 ^{circ}})$ under a continuous-wave, linearly polarised excitation. By contrast, we show that a linearly polarised pulse is rotated to a much lesser extent of a few degrees. Depending on the initial boundary conditions, this is due to either retardation or advancement in the amplitude build-up in time of the orthogonal electric field component. Unlike previous published work, the dominant spin relaxation and decoherence processes are fully accounted for in the system dynamics. Our dynamical model can be used for optimisation of the optical polarisation rotation angle for realisation of spin-photon entanglement and ultrafast polarisation switching on a chip.