外加電場下無應力GaAs/AlGaAs量子點的光學異向性

Abstract

糾纏偏振光子在量子傳輸與資訊上扮演一個非常重要的角色，且半導體量子點光源被期待在現今科技中能利用外加電壓的方式去控制而發出糾纏光子對。 在本論文的工作中，為利用數值與理論方法研究由 droplet epitaxy 生成的無應力(strain-free) GaAs/AlGaAs 量子點在其垂直方向外加電場下的電子結構與光學異向性(optical polarization anisotropy)，數值方法則利用多能帶理論k.p理論並搭配有限差分法計算量子點的電子結構，在用費米黃金定律(Fermi’s Golden rule)計算導電帶躍遷到價電帶所發出的發光強度與光偏振。主要模擬結果為固定量子點長軸與短軸長度，當量子點高度越高則光偏振越容易受到電場的調整；固定量子點長軸、短軸、以及高度當改變量子點夾角時則發現當其夾角越小(金字塔)則電場的作用越大。

Polarization-entangled photon pairs are essential elements in the applications of quantum information and communication. Electrical control of a polarization entangled photon pair emission from a semiconductor quantum dot (QD) is a desired feature of current’s science and technology. In this work, we theoretically study the electronic structures and optical polarization anisotropy of GaAs/AlGaAs quantum dots grown by droplet epitaxy with the application of vertical electric field, i.e. the static Stark effect. Numerical results and theoretical analysis based on multi-band k•p theory are presented. First, the single-particle spectrum of quantum dots are calculated by using multi-band k•p theory and finite difference method. Further, we investigate how the Stark effect affects the intensity and degree of polarization (DOP) of the emitted light from the biased QDs. The results suggest the electric controllability of optical polarization of GaAs/AlGaAs QD, especially the tall and asymmetric QDs.