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系統識別號 U0026-0509201100340500
論文名稱(中文) 利用電磁誘發透明量測銫原子11S能態的超精細結構
論文名稱(英文) Measure the Hyperfine Structure of the 11S State of Cesium by Using Electromagnetically Induced Transparency
校院名稱 成功大學
系所名稱(中) 物理學系碩博士班
系所名稱(英) Department of Physics
學年度 99
學期 2
出版年 100
研究生(中文) 蔡志宏
研究生(英文) Chih-Hung Tsai
學號 l26984078
學位類別 碩士
語文別 中文
論文頁數 77頁
口試委員 指導教授-蔡錦俊
口試委員-韓殿君
口試委員-陳泳帆
中文關鍵字 電磁誘發透明  銫原子  超精細結構  綴飾態 
英文關鍵字 electromagnetically induced transparency (EIT)  cesium  hyperfine structure  dressed state 
學科別分類
中文摘要 本論文利用電磁誘發透明現象量測銫原子11S的超精細結構,並探討因室溫原子因為不同速度群對譜線造成窄化與邊緣加強吸收的效應。處於共振的探測雷射和參考雷射頻率分別穩定在已知的銫原子6P3/2超精細結構的不同能階上,其分別與耦合雷射作用後產生的訊號可以當作校正頻率軸用,然後藉由|62S1/2, F=4>→|62P3/2, F=4>→|112S1/2, F= 3>與|62S1/2, F=4>→|62P3/2, F=4>→|112S1/2, F= 4>產生的電磁誘發透明訊號位置差來計算銫原子11S超精細結構的能階分裂距離,並由此分裂距離進一步求得銫原子11S超精細結構的A係數。
實驗用二極體雷射產生的光經過聲光調變器得到的±1階光當成探測雷射與參考雷射,兩者分別鎖頻在|62S1/2, F=4>→|62P3/2, F=4, 5>的頻率上,然後用染料雷射當做耦合雷射,探測雷射與耦合雷射反向對打並在銫原子腔中重合,耦合雷射頻率掃過銫原子11S的超精細結構能階,達共振頻率時探測雷射的吸收會減少產生穿透現象,我們測量探測雷射的穿透訊號。
實驗訊號會因為速度群、綴飾態以及多重中間態等因素的影響,產生較原本預期複雜的訊號圖形,我們考慮這些因素的理論以程式模擬電磁誘發透明訊號,模擬的結果雖然在強度的分佈上與實驗訊號有些誤差,但在訊號位置的部分仍有不錯的擬合結果,我們藉此分析找出真正的銫原子11S超精細結構分裂訊號,再以程式模合訊號找出訊號的中心位置,藉此可以推得銫原子11S超精細結構的能階分裂距離與A係數。利用探測雷射與參考雷射間的關係可以有兩種校正頻率軸的方式,他們得到的結果分別是:
分析方法一結果:銫原子112S1/2, F=3、4能階分裂距離=155.30±1.03MHz、A係數=38.83±0.26MHz。
分析方法二結果:銫原子112S1/2, F=3、4能階分裂距離=156.34±1.10MHz、A係數=39.09±0.28MHz。
本實驗是在室溫下進行的電磁誘發透明實驗,未來可以往冷原子的方向繼續研究,屏除速度群、綴飾態以及多重中間態等因素造成的影響。
英文摘要 Using electromagnetically induced transparency (EIT), the hyperfine structure of the 11S state of cesium has been measured and analyzed. The frequency of probe laser and reference laser are locked at two hyperfine states of the 6P state of cesium. The signal of these two lasers interacted with the coupling laser provide a frequency marker for frequency calibration. Then the splitting for hyperfine structure of the Cs 11S state is the difference between the EIT signals of |62S1/2, F=4>→|62P3/2, F=4>→|112S1/2, F= 3> and |62S1/2, F=4>→|62P3/2, F=4>→|112S1/2, F= 4> transitions.
An acousto-optic modulator (AOM) is added into the system. An external cavity diode laser (ECDL) is passed through the AOM, and we set the first order light of the AOM output as the probe laser, and its frequency is locked at |62S1/2, F=4>→|62P3/2, F=4, 5> . The coupling laser light from a ring-cavity dye laser and the probe laser are counter-propagated, overlapped inside the cesium vapor cell. The coupling laser scans across the hyperfine transition. The transmission of the probe beam can be detected while changing the frequency of coupling laser.
Due to the effects of the atoms with different velocity, the dressed-state and the multi-level intermediate states, the positions, intensities, and line shapes of the EIT signals are complicated. These factors are taking into account to simulate the EIT signals and compared with the experimental observations. Although there is a little discrepancy on the intensity between the simulation and experimental observation, the peak positions and line shapes are in good agreement. From the peak positions, one can calculate the hyperfine splitting of the 11S state of cesium and the magnetic dipole coupling constant A. There are two methods for frequency calibration and the calculated results are as followed:
Method 1: The hyperfine structure splitting of the 11S state of cesium: 155.30±1.03MHz, A constant: 38.83±0.26MHz.
Method 2: The hyperfine structure splitting of the 11S state of cesium: 156.34±1.10MHz, A coefficient: 39.09±0.28MHz.
In this thesis, we investigate the EIT in a multi-level system of cesium atom at room temperature. This can be done in the cold atom, e.g. in a magneto-optical trap. The observation of the hyperfine structure will be simplified by reducing the velocity distribution.
論文目次 摘要…………………………………………………………………………………Ⅰ
Abstract……………………………………………………………………………Ⅱ
致謝…………………………………………………………………………………Ⅲ
目錄…………………………………………………………………………………Ⅳ
圖目錄………………………………………………………………………………Ⅵ
表目錄………………………………………………………………………………Ⅷ
第一章 緒論………………………………………………………………………1
1-1 研究目的…………………………………………………………………1
1-2 原子物理的近代發展……………………………………………………1
1-3 銫原子簡介………………………………………………………………2
1-4 電磁誘發透明簡介………………………………………………………4
第二章 基本理論…………………………………………………………………5
2-1 原子物理……………………………………………………………………5
2-1-1 精細結構……………………………………………………………5
2-1-2 超精細結構……………………………………………………7
2-2 階梯式電磁誘發透明………………………………………………………8
2-3 密度矩陣表示方法…………………………………………………………9
2-3-1 密度矩陣的運動方程式………………………………………9
2-3-2 交互作用圖像(interaction picture)………………11
2-3-3 二能階系統……………………………………………………12
2-3-4 三能階系統……………………………………………………15
2-4 綴飾態原子表示方法.……………………………………………………17
2-5 光學幫浦(Optical pumping)…………………………………………23
第三章 實驗儀器與架設………………………………………………………25
3-1 實驗系統架設.……………………………………………………………25
3-2 雷射系統.…………………………………………………………………26
3-2-1 探測雷射………………………………………………………26
3-2-2 耦合雷射………………………………………………………27
3-3 雷射頻率控制.……………………………………………………………29
3-3-1 鎖頻-無都卜勒效應飽和吸收光譜…………………………30
3-3-2 調頻-聲光調變器……………………………………………32
3-3-3 掃頻-耦合雷射的掃動………………………………………33
第四章 實驗結果與分析………………………………………………………34
4-1 染料雷射掃描時的線性程度.……………………………………………34
4-2 頻率軸校正.………………………………………………………………37
4-3 雷射強度對電磁誘發透明的影響.………………………………………39
4-4 模擬.………………………………………………………………………43
4-4-1 共振態電磁誘發透明…………………………………………43
4-4-2 考慮原子速度群分佈下的電磁誘發透明……………………44
4-4-3 多能階系統的電磁誘發透明…………………………………47
4-4-4 綴飾態原子的電磁誘發透明…………………………………49
4-4-5 考慮光學幫浦(Optical pumping)影響下的電磁誘發透明………56
4-4-6 與實驗數據擬合………………………………………………57
4-5 銫原子11S超精細結構能階分裂與A係數分析…………………………59
第五章 結論……………………………………………………………………73
參考文獻……………………………………………………………………………74
附錄…………………………………………………………………………………76
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