积分球冷原子钟性能优化实验研究
文献类型：学位论文
| 作者 | 刘鹏 |
| 学位类别 | 博士 |
| 答辩日期 | 2016 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 刘亮 |
| 关键词 | 积分球冷原子钟，频率稳定度，噪声抑制 |
| 其他题名 | Experimental study on the performance improvement of the integrating sphere cold atom clock |
| 中文摘要 | 本论文介绍了作者攻读博士学位期间在积分球冷原子钟系统性能优化过程中所参与的工作。包括对限制积分球冷原子钟频率稳定度的噪声的抑制以及一些提高原子钟稳定度水平的新的实验方法的研究等。 频率稳定度是衡量原子钟性能水平的重要指标。对于积分球冷原子钟而言，限制其短期稳定度的因素主要来自于原子散粒噪声，探测光的功率、频率噪声，Dick效应以及反馈环路噪声。为了减小这些噪声对原子钟稳定度的影响，我们采用了四束冷却光底面注入柱形冷却腔的方式来增加参与微波作用的中心区域冷原子数量；应用了探测光功率稳定伺服环路和窄线宽激光器作为探测光光源；同时缩短钟周期并提高微波作用占空比来减小Dick效应的影响；引入了新的数字电压控制链路来反馈本地振荡器减小由于反馈的模拟电压信号带来的频率噪声。长期稳定度主要受限于微波腔牵引效应以及由温度起伏引起的微波系统，光学系统，电子学系统内各个参数的长期漂移。我们发现冷却光对于微波腔的加热效应非常明显并且会显著影响微波腔的共振频率。因此冷却光的功率起伏也会通过微波腔牵引效应影响原子钟频率稳定度。我们增加了冷却光功率稳定控制环路来减小冷却光功率起伏。由于积分球冷原子钟内冷原子团的分布决定于冷却光的功率以及注入方式，因此更稳定的冷却光也有利于减小微波腔中心区域冷原子数的起伏。除了在真空腔外部采用加热线圈对微波腔进行温控外，我们将整个物理系统以及探测光功率稳定和钟信号探测光路进行了整体温控，物理系统和探测光功率的长期稳定性得到进一步提高。在上述改进之后，积分球冷原子钟的短期稳定度优于5E-13tao^(-1/2)，测试得到的Ramsey信噪比为1200，与喷泉钟比对积分时间200 000 s时稳定度达到了1.9E-15。 为了进一步提高积分球冷原子钟的短期稳定度水平，我们尝试采用相位调制的方案来获得高灵敏度的鉴频信号。相位调制实验获得了中心频率幅值在零点的Ramsey条纹并将鉴频信号的灵敏度提高了1.6倍。 |
| 英文摘要 | This thesis presents the work on the performance improvement of the integrating sphere cold atom clock that the author gets involved during his doctoral studies including the suppression on the noises which are the limitations on the atomic clock frequency stability and the exploration on the novel experimental schemes which would improve the frequency stability of the clock. Frequency stability is an important evaluation index of the atomic clock performance. The main factors which limits the short-term frequency stability of the integrating sphere cold atom clock are the atoms shot noise, AM and PM noises of the probe light, Dick effect, and the noise of the feedback loop. We use four beams of cooling lights which are injected into the cylindrical cooling chamber from the bottom surface of it to increase the number of cold atoms which will experience the microwave interrogation in central area of the cavity. The narrow line-width probe laser with power stabilization servo loop was applied later on. The cycle time of the clock was decreased and the microwave interrogation duty cycle increased consequently. We utilized a digital voltage control circuit to replace the analogue voltage servo loop which was used to feed the local oscillator. The main limitations of the long-term frequency stability come from the cavity pulling effect and the individual parameters drifts of the microwave, optical and electronic systems after a long integration time. We found the heating effect of the cooling lights on the microwave cavity is very significant and will significantly affect the resonance frequency of the microwave cavity. Therefore, the power fluctuations of the cooling lights will also affect the frequency stability of the atomic clock through the microwave cavity pulling effect. A cooling lights’ power stabilization control loop was used to address this problem. In addition, due to the distribution of cold atoms in the cavity depends on the cooling lights power and injection mode, power stabilized cooling light also helps to reduce the fluctuations of cold atoms in the central region of the microwave cavity. Except for the temperature control of the microwave cavity realized by the heating coils located around the vacuum chamber, we also set the physical package and part of the probe light circuits which are applied for power stabilization and clock signals detection in a box which are temperature controlled as well. The long-term stabilities of the physical package’s temperature and probe light’s power are further enhanced. With these improvements, the short-term frequency stability of the integrating sphere cold atom clock are better than 5E-13tao^(-1/2), SNR of the Ramsey fringes are 1200. Comparing with the fountain clock, the long-term frequency stability of 1.9E-15 was reached when the integration time was 200 000s. In order to further improve the clock short-term frequency stability, The phase modulation scheme has been taken to increase the sensitivity of the discriminating signals. In the phase modulation experiments, the amplitude of Ramsey fringes is zero at the central frequency and the slopes of the discriminating signals have been increased for 1.6 times. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15983]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 刘鹏. 积分球冷原子钟性能优化实验研究[D]. 中国科学院上海光学精密机械研究所. 2016. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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