权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

NOVEL LASER COOLING TECHNIQUE EFFICIENT IN OPTICAL TRAPS

在光阱中高效的新型激光冷却技术

基本信息

批准号：
18540392
负责人：
KUMAKURA Mitsutaka
金额：
$ 2.25万
依托单位：
University of Fukui
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

In order to optically cool 87Rb atoms below such a low temperature as to be confined in an optical trap, we made two frequency-stabilized single-mode cw lasers whose frequencies were nearly resonant to the 5s 2S1/2(F=2)→5p 2P3/2(F=3) and 5s 2S1/2(F=1)→5p 2P3/2(F=2) transitions. The laser frequency width less than 1 MHz, which is necessary for the successful laser cooling of Rb atoms, was achieved for both lasers. We also made a new ultra-high vacuum (UHV) chamber for trapping cold atoms for a long enough time to observe evaporative cooling process in the optical trap.With this new experimental apparatus we operated the double magneto-optical trap system. Initially, Rb atoms were magneto-optically collected from the atomic vapor at a room temperature and optically cooled in the magneto-optical trap (MOT) below 2 mK. The cold atoms were released from the MOT, and were transferred into the other MOT in the UHV chamber by the radiation pressure of the pushing laser beam. Repeating this loading procedure about 200 times, we confined about 8×10_8 atoms in the UHV-MOT at a temperature of 1 mK. For efficiently confining the cold atoms into an optical trap, we further optically cooled the atoms by the polarization gradient cooling and achieved a temperature of 100 μK, which was comparable to the typical trap depth of an optical trap.We also estimated atom heating and loss rates due to background gases by monitoring a trap lifetime and a thermalization rate in a magnetic trap. The obtained lifetime was approximately 1 min, and the trapped atoms were cooled from 1 mK to 10 μK in about 2 min by the rf evaporative cooling. From these facts we successfully confirmed that even in an optical trap further laser cooling could be applied against the trap heating and losses.

为了将87Rb原子光学冷却到如此低的温度以使其被限制在光陷阱中，我们制作了两个频率稳定的单模连续激光器，其频率几乎与5s 2S1/2(F=2)→5p 2P3/2(F=3)和5s 2S1/2(F=1)→5p 2P3/2(F=2)跃迁谐振。两种激光器均实现了小于 1 MHz 的激光频率宽度，这是成功激光冷却 Rb 原子所必需的。我们还制作了一个新的超高真空（UHV）室，用于足够长的时间捕获冷原子，以观察光陷阱中的蒸发冷却过程。通过这个新的实验装置，我们操作了双磁光陷阱系统。最初，在室温下从原子蒸气中磁光收集 Rb 原子，并在磁光陷阱 (MOT) 中光学冷却至 2 mK 以下。冷原子从MOT中释放出来，并通过推动激光束的辐射压力转移到特高压腔室中的另一个MOT中。重复此加载过程约 200 次，我们在 1 mK 的温度下将约 8×10_8 个原子限制在 UHV-MOT 中。为了有效地将冷原子限制在光陷阱中，我们通过偏振梯度冷却进一步对原子进行光学冷却，并达到100 μK的温度，这与光陷阱的典型陷阱深度相当。我们还通过监测磁陷阱中的陷阱寿命和热化速率来估计由于背景气体引起的原子加热和损失率。获得的寿命约为1分钟，并且通过射频蒸发冷却，捕获的原子在约2分钟内从1mK冷却到10μK。根据这些事实，我们成功地证实，即使在光陷阱中，也可以应用进一步的激光冷却来防止陷阱加热和损失。