全共振條件下單Λ系統轉換至雙Λ系統之暫態效應研究

Studies of Transient Effects from Single-Λ to Double-Λ Systems under the All-Resonant Condition

吳柏翰(Bo-Han Wu)

指導教授 ： 余怡德

國立清華大學/理學院/物理學系/碩士(2014年)

https://doi.org/10.6843/NTHU.2014.00053

摘要

鑒於在實驗上發現了兩種相似的雙Λ系統有其完全不同的能量耗損機制，本文探討電磁波誘發透明(Electromagnetically Induced Transparency，簡稱EIT)的單Λ系統轉換成四波混合(Four-Wave Mixing，簡稱FWM)的雙Λ系統中能量耗損。主要研究的研究工作區分為三部分。第一部分，緩變條件的尋找。利用暗態分析和非暗態分析的方式，雙Λ系統能夠有適當的物理圖像作拆解，最後我們的得以獲得反應時間(response time)和耦合光的上升時間(rising time)的比較關係，也就是所謂的緩變條件(adiabatic condition)。第二部分，基態同調(ground state coherence)和探測光的能量分布形式。我們討論暗態激子(dark state polariton)在系統中扮演的角色，以及證明其能量分配的形式和物理量 η 有直接相關。於此部份的最後，我們說明於EIT系統中的能量分配比例同時也會影響到系統的耗損機制。第三部分，高轉換效率的設計。基於前兩部分的探討，我們期望設計既滿足變條件(第一部分結論)也使得系統能量集中於基態同調(第二部分結論)的高轉換效率系統。本文最後探討三種不同高轉換效率的雙Λ系統並比較其轉換效率。

關鍵字

單Λ系統 ； 雙Λ系統 ； 暫態效應

並列摘要

In experiment, we have found two similar double-Λ systems, which have converse absorption result. For the sake of understanding the absorption mechanisms between these two cases, we focus the primary research target on absorption mechanisms from single-Λ to double-Λ system. The research process can be divided by three parts. The first one is about the adiabatic condition. According to dark state and non-dark state analysis, double-Λ system will be decomposed to two eigen-modes. Based on the physics decomposition method, the relation between rising time from coupling light and response time is found (or we call the relation: adiabatic condition). The second part is about the energy ratio between ground state coherence and the probe light. Dark state polariton, as a quantum particle, carries the information during propagation in single-Λ and double-Λ system by ground state coherence and probe light. We use numerical calculations to prove that the energy ration between these two components of dark state polariton is related to a physical quantity η. Final part is about the designing of a conversion system with high conversion efficiency. According to previous two parts result, we are capable to design a system with negligible energy loss; finally we compare three types of conversion systems.

並列關鍵字

Single-Λ ； Double-Λ ； Transient Effect

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