量子點中自旋解析之激子與光子交互作用

Abstract

產生、保持與操縱自旋極化是發展自旋元件的基本工作，在零維系統如量子點所觀 察到的自旋鬆弛時間遠長於激子的復合時間，因此自旋資訊可以在光子與激子之間傳 遞，然而，截至目前，半導體量子點中自旋鬆弛機制仍未被完全了解，在此計畫中，我 們意欲對造成自旋鬆弛的因子，包括樣品成長條件、激發能量、極化態與溫度等進行探 討；我們也可利用激子-光子交互作用對自旋鬆弛的影響，來控制量子點中激子的極化 狀態；此外，在強耦合條件下，在非等向性的光子晶體共振腔中，由激子與光子所形成 的極化激子，可以消除精細結構匹裂來產生糾纏的光子對。

Generation, preservation and manipulation of spin polarization are essential tasks to develop practical spin-based devices. The observed spin relaxation time in zero-dimensional system, such as quantum dots (QDs), is much longer than the exciton recombination time so the spin information can be transferred between photons and excitons. However, up to date, the spin relaxation mechanism in semiconductor QDs is not well understood yet. In this proposal, we intend to study the factors of spin randomization, including sample growth condition, excitation energy, polarization states and temperature. The effect of exciton-photon interaction on spin relaxation could be applied to controlling the polarization states of exciton in QDs. In addition, in the strong coupling regime, the polariton formed by exciton and photon in an anisotropic PhC cavity could eliminate the FSS to generate entangled photon pairs.