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載入與儲存冷原子至光偶極陷阱之研究
Dissertation

載入與儲存冷原子至光偶極陷阱之研究

洪偉倫
Doctor of Philosophy (PHD), 國立清華大學, 物理系
2013

Abstract

光偶極陷阱 磁光陷阱 平均時變磁陷阱 都卜勒冷卻 optical dipole trap magneto-optical trap time-averaged orbiting potential trap Doppler cooling
This thesis focuses on transferring cold atoms into an optical dipole trap (ODT). Optical density as well as number density of the cold atoms confined in the ODT can be achieved to a sufficiently high level that is suitable for single-photon nonlinear optics experiments. We studied the processes of loading cold atoms into the ODT from a temporal dark magnetic-optical trap (MOT), a spatial dark MOT, and a time-averaged orbiting potential (TOP) magnetic trap. We further investigated how to prolong the storage time of the atoms captured in the ODT. A rapid loss of the atoms distributed among all the Zeeman states of the hyperfine level |F=2>is due to the hyperfine-changing collision. To increase the storage time, we optically pumped the atoms either to the hyperfine level |F=1> or to a single Zeeman state of |F=2, m=2>or |F=2, m=2>. In the latter case, a uniform magnetic field larger than 4.3 G was applied. We were able to load 5.6106 87Rb atoms with a temperature of 57μK into the ODT with a trap depth of 850 μK from the TOP magnetic trap. Under this condition, the peak number density of the atoms can be as high as 61013 cm-3, i.e. 120 atoms within the volume of 3 where  is the wavelength of light.

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