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研究生：	吳品毅 Wu, Pin-I
論文名稱：	冷銣原子中的電磁波導致透明實驗研究 Experimental Study of Electromagnetically Induced Transparency in Cold Rubidium Atoms
指導教授：	陳泳帆 Chen, Yong-Fan
學位類別：	碩士 Master
系所名稱：	理學院 - 物理學系 Department of Physics
論文出版年：	2009
畢業學年度：	97
語文別：	中文
論文頁數：	61
中文關鍵詞：	電磁波引發透明、銣原子、量子干涉、量子
外文關鍵詞：	Quantum Interference, Quantum, EIT, Rb
相關次數：	點閱：147 下載：12
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本論文主要研究冷銣原子中電磁波引發透明現象(Electromagnetically Induced- Transparency，簡稱EIT) 的量子干涉效應。一開始先說明銣原子能階、都普勒冷卻、磁光陷阱、飽和吸收光譜、雷射回饋鎖頻等冷銣原子系統建立及電磁波引發透明現象的原理。接下來介紹實際架構一個捕捉原子數約為3×109個的冷銣原子系統。以及如何利用聲光調製器與電光調制器，調變探測雷射和耦合雷射的頻率，與冷銣原子交互作用，形成型EIT能階系統。並說明如何調控各雷射系統與磁場的實驗操作程序。
進行實驗量測，並以理論計算擬合實驗結果，藉以了解實驗參數與電磁波引發透明現象關係。除得到與理論預測相符的電磁波引發透明結果外，由實驗數據得知，本磁光陷阱系統中冷原子團的光學密度約為。在探測雷射與耦合雷射強度分別為0.09 mW/cm2及4.32 mW/cm2的型EIT實驗中，我們觀測到探測雷射有90％的穿透率，同時我們也藉此估計本EIT實驗系統的兩個基態同調性衰減率約為2π×50 KHz。

When the frequency of a laser is close to the atomic transition, the optical response of the medium is greatly enhanced. At the same time, the desired control of the light-matter interactions in the atomic ensemble can be realized by using a technique called Electromagnetically Induced Transparency (EIT). EIT is a quantum-interference effect that allows the propagation of a light pulse inside a resonant medium to be controlled via a second electromagnetic field. In this work, we experimentally establish an EIT system step by step from frequency stability of the laser system, magneto-optical trap system to the development of data acquisition. Furthermore, we observe the EIT spectrum on the conditions of adjusting different experimental parameters, which include the off time of magnetic field and the intensity of coupling laser. We also use the theoretical model to fit the measurement data, revealing the theoretical predict of quantum mechanics. After analyzing the experimental data, in our system it shows that the ground-state coherence decay rate is 2π×50KHz under the probe and coupling laser intensities of 0.09 and 4.32 mW/cm2, respectively. These experimental demonstrations represent an essential element for the future experiments of slow light and quantum memory.

緒論.....................................................................................................................................1
1簡介...............................................................................................................................1
2電磁波引發透明簡介...................................................................................................2
基本原理.............................................................................................................................4
1銣原子 (Rb) 能階與特性............................................................................................4
2磁光陷阱與冷原子系統...............................................................................................6
2.1都普勒冷卻..........................................................................................................6
2.2磁光陷阱..............................................................................................................7
3飽和吸收光譜及微分回饋鎖頻系統機制...................................................................9
3.1吸收光譜..............................................................................................................9
3.2飽和吸收光譜....................................................................................................10
3.3交錯訊號 (cross-over signal) ............................................................................12
3.4微分光譜及鎖頻系統........................................................................................13
4量子干涉效應.............................................................................................................16
4.1 二能階吸收.......................................................................................................16
4.2電磁波引發透明................................................................................................18
實驗系統架設...................................................................................................................24
1磁光陷阱與冷原子系統.............................................................................................26
1.1真空系統和銣原子源........................................................................................26
1.2陷阱雷射............................................................................................................27
1.3雷射光偏極與磁場............................................................................................30
1.4飽和吸收回饋鎖頻光路架設............................................................................31
1.5微波與電光頻率調變系統................................................................................35
1.6回幫浦雷射........................................................................................................38
1.7磁場補償系統....................................................................................................41
2量子干涉-電磁波引發透明系統................................................................................42
2.1耦合雷射............................................................................................................42
2.2探測雷射............................................................................................................43
實驗量測結果與分析.......................................................................................................45
1實驗步驟及時序調控.................................................................................................45
2電磁波引發透明光譜.................................................................................................47
2.1不同磁場關閉時間的EIT光譜數據與分析....................................................48
2.2不同耦合雷射強度的EIT光譜數據與分析....................................................52
結論與展望.......................................................................................................................55
附錄A：87Rb元素D2躍遷C.G.係數表............................................................................56
附錄B：積分器及訊號減法器電路圖...............................................................................58
附錄C：光偵測器放大特性...............................................................................................60
附錄D：雷射光強度與Rabi Frequency轉換...................................................................61
                                    

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校內：立即公開
校外：2009-08-14公開

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