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Title: 光耦極阱中的銣原子基態雷射冷卻
Ground State Laser Cooling of Rubidium Atoms in an Optical Dipole Trap
Authors: 吳文欽
Wu, Wen-Chin
Chang, Ming-Shien
Pan, Xiang-Liang
Keywords: 雷射冷卻
Laser cooling
sub­-Doppler cooling
Raman sideband cooling
op­tical dipole trap
Issue Date: 2020
Abstract: 形成冷原子的玻色­愛因思坦凝結 (Bose­Einstein condensates, BEC), 需要採用不同技術依序將原子從室溫 300 K 冷卻到目標溫度數百 nK。 其中次都卜勒冷卻的階段尤為關鍵,一般在此階段的最後會藉由蒸發 冷卻的方式將原子降溫到 BEC 的狀態。蒸發致冷的原理是丟棄動能較 高的原子,代價則是使得原子氣體裏的原子數目變少。若在此之前, 可以透過光學方法,將溫度預冷至數千或數百 nK,提高相空間密度 (phase space density),就能減少蒸發冷卻過程中消耗掉的原子,使得原 子數大幅增加,以利於更快速、有效地達成 BEC。 本實驗論文研究原子基態雙光子冷卻方法,尤其是拉曼側帶冷卻方法 為主,並比較不同光學冷卻方法的結果。論文介紹實驗架設,包含外 腔雷射的組建、磁光阱架設、拉曼側帶冷卻的實驗架設,然後比較次 都卜勒冷卻的灰色光學糖漿冷卻、以及拉曼側帶冷卻。
To achieve atomic Bose­Einstein condensates (BEC) , several cooling techniques are required in different stages of the cooling process. From room tamperature 300 K to hundreds of micro K, we use magnetic optical trapping and the involved laser cooling technique is referred as Doppler cooling. To further reduce the temperature of cold atoms, sub­Doppler cooling is crutial. In the end of this stage, usually evaporation method is applied. In this pro­ cess, the temperature is reduced in the expense of atom number loss. If if we could use an optical cooling method which can reduce the temperature to few micro K or few hundred nK, as well as increasing the phase space den­ sity, then the process of producing BEC would become more efficient and the atom number after evaporative cooling can be larger. In this thesis, the cooling result of different ground­state two­photon laser optical cooling methods are studied. The preparation of laser source is de­ scribed, and sub­Doppler cooling methods, i.e., gray molasses cooling and Raman sideband cooling methods are studied.
Other Identifiers: G060741034S
Appears in Collections:學位論文

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