汞原子冷却激光的研制和改进
文献类型：学位论文
| 作者 | 付小虎 |
| 学位类别 | 硕士 |
| 答辩日期 | 2015 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 徐震 |
| 关键词 | 汞原子 外腔半导体激光器 光晶格钟 偏振光谱 |
| 其他题名 | The development and improvement of the cooling laser for mercury atoms |
| 中文摘要 | 近年来光晶格钟取得了突破进展，其稳定度和不确定度迈入10-18量级，一跃超过了离子阱光钟成为了最高稳定度的频率标准。尽管使用了复杂的设备和控制方法来抑制黑体辐射频移，然而黑体辐射频移仍旧是其最大的不稳定因素。汞(Hg)原子因其钟频跃迁黑体辐射频移小和其原子质量大（在测量一些物理常量时有高灵敏度）的特点，成为了热门的频标候选元素。作为实现汞原子光晶格钟的第一步，需要使用253.7 nm的高功率窄线宽激光来对其进行激光冷却。但冷却激光处于深紫外波段，无法直接获得，需要将大功率1014.9 nm激光四倍频得到。我们研制了该波长的外腔半导体激光器作为种子光源，利用光纤激光放大器，获得了7 W的激光放大输出。本文介绍了我设计、制作的外腔半导体激光器以及其作为种子光进行的光纤激光放大，分析了各器件参数对激光器性能的影响。还介绍了Hg原子1S0-3P1跃迁偏振光谱的测量以及利用偏振光谱对Hg原子冷却激光进行稳频的工作。 外腔半导体激光器采用了Littrow光栅外腔反馈结构。通过调整激光准直距离，激光器阈值电流降低了60%。最终获得了55 mW的1014.9 nm单模激光输出，无跳模可调谐范围为3.3 GHz，线宽为百 kHz，自发辐射(ASE)抑制比达54 dB。利用该激光作为种子光，通过光纤耦合系统将20 mW光输入到光纤激光放大器中，耦合效率达56%。同时，使用滤光片解决了光纤激光放大器容易出现自激振荡的问题，使其可工作在最大功率泵浦情况下（10A），稳定输出激光功率达7 W，超过了5 W的预期指标，其输出激光的ASE抑制比达到45 dB。目前，我们小组使用该激光器及放大器搭建了倍频腔，已经观测到了腔信号，实现了腔锁定下的绿光输出。 我还测量了Hg原子1S0-3P1跃迁的偏振光谱，获得Hg原子所有的9个稳定同位素和超精细分裂跃迁的高分辨率光谱信号。并使用偏振光谱的色散信号，进行了冷却激光的频率锁定。同时还优化了202Hg原子光谱的泵浦和探测功率，研究了线性偏振光对偏振光谱中的影响。 |
| 英文摘要 | Recently, a breakthrough was made on optical lattice clock that its stability and uncertainty had reached a 10-18 level, surpassing the ion clock and thus taking the first place in time and frequency standard. Despite the application of complex instruments and control methods in their systems, blackbody radiation induced frequency shift (BBR shift) remains the first source of instability and uncertainty. Mercury (Hg) atom, with its low sensitivity of BBR shift and large mass (Z=80) (leading to high precision in physical constant measurement), has become a good candidate of frequency standard. Being the first step to build an optical lattice clock based on Hg atom, a high-power narrow line width laser in 253.7 nm is required for laser cooling. Because the wavelength of cooling laser is in deep UV region, it cannot be directly produced but has to be obtained by frequency quadrupling of a high-power narrow line width laser in 1014.9 nm. We have designed and developed an external-cavity diode laser (ECDL) as seed laser, then laser amplified it with a fiber laser amplifier, achieving an output power of 7 W. This dissertation introduces the design and development of the ECDL, shows the laser amplification of it, and analyzes the influence of the elements’ parameters on the laser performance. Moreover, the measurement of the polarization spectroscopy of the 1S0-3P1 transition of Hg and laser frequency stabilization with it is also contained. A Littrow feedback configuration is adopted in the ECDL. And the threshold current is reduced by 60% through the adjustment of the collimation distance of the laser. Finally we achieved the 1014.9 nm single-mode laser with output power of 55 mW, hope-free tuning range of 3.3 GHz, linewidth of few hundreds of kHz, ASE suppression of 54 dB. A 20 mW laser is injected into the fiber laser amplifier through the fiber coupling system with an efficiency of 56%. Solving the problem ofself-oscillation by inserting an optical filter before fiber coupling, the laser amplifier is able to work at the largest pump current (10A) with output power of 7 W, which is beyond the expected power of 5 W. And the ASE suppression of the output laser is 45 dB. Now, this 1014.9 nm high-power laser system is used in the development of the frequency doubler. I have also measured the polarization spectroscopy (PS) of the 1S0-3P1 transition in Hg vapor cell. The high-resolution spectroscopy of all nine transitions of six stable isotopes and hyperfine splitting was observed. And with the dispersive PS signal we stabilized the cooling laser frequency. Meanwhile the pump power and probe power were optimized in the PS of 202Hg, and the influence of linear polarized light on the PS was investigated. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16935]  |
| 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 | 付小虎. 汞原子冷却激光的研制和改进[D]. 中国科学院上海光学精密机械研究所. 2015. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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