光耦極阱中的銣原子基態雷射冷卻

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。

關鍵字

雷射冷卻；次都卜勒冷卻；光學冷卻拉曼側帶冷卻；光偶極阱

並列摘要

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.

並列關鍵字

Laser cooling ； sub-Doppler cooling ； Raman sideband cooling ； optical dipole trap

參考文獻

[1] J. R. A. A. Alban Urvoy, Zachary Vendeiro and V. Vuletić. Direct laser cooling to boseeinstein condensation in a dipole trap. Phys. Rev. Lett., 122(203202), 2019.

Google Scholar

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