基於電磁誘發透明機制的同調光記憶體之光場轉換

Abstract

基於電磁誘發透明的同調光記憶體提供了一個工具去轉換探測光[1,2]，藉由在讀取的過程中，操縱不同的激發原子同調的控制場，去轉換探測光的偏極、頻率跟行進的方向。然而，實際執行上無可避免地會遇到一些問題，舉例來說，在真實原子中，因為儲存與讀取過程的躍遷偶極矩的不匹配而導制的能量損失[3]。在本文中，我們發現儘管在這種條件下，轉換光的能量效率可以超過存取光的效率，而且這取決於在儲存與讀取過程的躍遷偶極矩的比值，我們提供了一個詳細的理論計算討論相關的問題，以及提供了在冷銫原子實驗上的數據;在我們的分析中發現，在讀取的過程中，讀取過程的頻寬與剛從原子同調取出來的光的比值可以解釋這一類型的能量損失。

Coherent optical memory based on electromagnetically induced transparency (EIT) provides a tool to convert the polarization, frequency, and propagation direction of the probe light by using different control fields driving an atomic transition during the retrieval process [1,2]. However, it is inevitable to face some issues, such as energy loss which is caused by the different transition dipole moments between two transitions used in storage and retrieval processes in real atoms [3]. In this thesis, we found that despite in this condition, efficiency of the converted probe pulse could surpass the one of stored light pulse, and it depends on the ratio between the transition dipole moment in the retrieval transition and the one in the storage transition. We provide a detailed theoretical study on this issue and present the experimental results in cold cesium atoms. Moreover, the results could be understood by analyzing the spectral bandwidth in retrieval processes. In our analysis, the ratio of the spectral bandwidth between the retrieval process and the pulse retrieved from the ground-state coherence can account for this kind of loss.