汞原子光晶格钟钟频探测激光系统研究
文献类型：学位论文
| 作者 | 付小虎 |
| 文献子类 | 博士 |
| 导师 | 王育竹 徐震 |
| 关键词 | 超稳激光，超稳腔，光晶格钟，汞原子，钟频跃迁 ultra-stable laser, ultra-stable cavity, optical lattice clock, mercury atom, clock transition |
| 其他题名 | Research on the Clock Laser System of the Optical Lattice Clock Based on Mercury |
| 英文摘要 | 发展不同元素的光钟具有重要的意义，不同元素光钟之间的频率比值测量是实现光频二级秒定义的有效途径，也是高精度验证诸如精细结构常数等基本物理常数是否随时间变化的方法。相对于目前最高不确定度的锶原子光晶格钟及最高稳定度的镱原子光晶格钟，汞原子具有更低的黑体辐射频移，更高的饱和蒸汽压及更为简单的钟频磁子能级结构，有望成为下一个无需对环境黑体辐射进行特殊处理而进入10-18量级不确定度的光钟元素。 本小组已经建立了国内第一套汞原子磁光阱系统，并测量了汞原子各个同位素的冷原子数量及温度。本人在此基础上，设计并建立了汞原子钟频探测系统，实现了超稳腔稳频的1062.5 nm超稳激光，四倍频后获得了265.6 nm钟频激光，并探测了199Hg冷原子的1S0-3P0钟频跃迁。 首先，设计和搭建了1062.5 nm超稳激光系统，通过PDH稳频技术将1062.5 nm激光稳定在10 cm超稳腔上，并对系统各项噪声、漂移进行了抑制和评估，以使超稳激光性能达到超稳腔的热噪声极限。通过有限元结构力学仿真，获得了接近振动免疫的超稳腔振动灵敏度，实现了合理的隔振设计，使得振动影响低于热噪声极限。设计了包含一层被动隔热、两层TEC主动温控的真空及温控系统，11天多点监测温度下漂移小于1 mK。通过测量超稳腔零膨胀温度及真空温度传递时间常数，评估了温度波动对超稳腔的影响在1000s内均低于热噪声极限。设计了激光功率稳定模块，去除了光功率波动的影响，环外功率稳定度达到0.05%。对电光调制器进行控温，将剩余幅度调制引起的误差信号漂移降低了10倍，引起的频率不稳定度经评估为4×〖10〗^(-16)@1s。使用了光纤噪声抑制技术，将光纤传递附加不稳定度降低到1×〖10〗^(-17)@1s。测量了超稳激光在光纤激光放大中的稳定度恶化情况，在1-100s内低于3×〖10〗^(-16)。设计制作了超稳激光系统需要的所有电子学模块，包含低噪声高速光电探测器、PDH调制解调电路、高低速PID锁频伺服、功率稳定伺服、温度控制电路、低噪声AOM驱动、低相噪射频链路等，其性能均符合使用需求。 其次，通过光纤激光放大和两次倍频产生了265.6 nm钟频激光，并用它探测了199Hg冷原子1S0-3P0钟频跃迁。1062.5 nm超稳激光经过光纤激光放大后，单次通过PPLN晶体进行一次倍频，再通过BBO晶体腔内倍频，获得了11 mW的265.6 nm钟频激光。使用无外场探测技术，消除了冷却光的交流Stark频移，在磁光阱中探测到了199Hg的1S0-3P0钟频跃迁光谱，其光谱对比度最大达95%，谱线宽度最小为450 kHz，对应的冷原子温度为60 μK。使用无外场探测的钟频光谱，并通过飞秒光梳测量超稳激光频率，确定了1S0-3P0钟频跃迁的绝对频率为1128575290.819(14) MHz。利用5天测量的钟频光谱，评估超稳腔的平均漂移率为4.2 kHz/天。 超稳钟频探测激光系统，是实现汞原子光晶格钟的重要组成部分。而探测199Hg冷原子的钟频跃迁，是实现光晶格钟重要一步。这些工作为进一步实现汞原子光晶格钟奠定了坚实的基础。; Development of optical clocks based on different elements is of much significance. Frequency ratio measurement between optical clocks with different elements is not only the way towards redefinition of SI second with optical frequency, but also the effective method to test the time invariance of fundamental physical constants such as the fine-structure constant. Compared with the most accurate optical clock based on Sr atom and the most stable optical clock based on Yb atom, mercury atom (Hg) has three advantages: the lowest uncertainty of black-body radiation shift, high saturated vapor pressure at room temperature and simplest magnetic energy levels of the clock transition. Thus it has the possibility to become the next optical clock with 10-18 level uncertainty in normal environment. Our group has already established the first magneto-optical trap of Hg atom in China, and measured the atom number and temperature of each rich abundant isotopes. Based on these works, I have designed and built the 265.6 nm clock laser system for Hg atom, which frequency stabilizing 1062.5 nm laser to an ultra-stable cavity (USC) and high efficient frequency quadrupled to 265.6 nm. With this clock laser, the 1S0-3P0 clock transition is detected in cold 199Hg atoms. First, a 1062.5 nm ultra-stable laser system is designed and built. The 1062.5 nm laser was frequency stabilized to a 10 cm long ULE ultra-stable cavity by PDH locking. To push the performance of the laser reach thermal-noise limit, each noise item and drift item was studied and evaluated for this system. With finite element structural mechanics simulation, vibration immune support point is obtained to lower the USC vibrational sensitivity. With a vibration-isolated platform, the vibration induced frequency noise can be below thermal-noise limit. The vacuum system is designed for USC, which contains one layer of thermal shield and two stages of active temperature-controller. The temperature fluctuation is less than 1 mK in 11 days with multi-point temperature monitor. According to the measurement of the zero-expansion temperature and the temperature transfer time constant in vacuum, the temperature fluctuation induced instability is below thermal-noise limit within 1000 s. With the laser power stabilization module, the out-loop fluctuation of laser power is suppressed within 0.05%. With the temperature control of the electro-optic modulator, error signal drift induced by residual amplitude modulation is 10 times reduced, and the corresponding instability was 4×〖10〗^(-16)@1s. Applying the fiber noise cancellator, the instability of the fiber transfer is reduced to 1×〖10〗^(-17)@1s. The additional frequency noise of fiber laser amplification is measured, and the corresponding instability is 3×〖10〗^(-16) in 1-100 s. Moreover, all electrical circuits in the ultra-stable laser system are designed, such as low-noise high-bandwidth optical detector, PDH modulation and demodulation circuit, fast and slow PID servo, laser power stabilization servo, temperature controller, low-noise AOM driver and low-phase noise RF circuits et al., and all of the performance meet the requirement of the system. Second, the 1S0-3P0 clock transition is detected in cold 199Hg atoms with the 265.6 nm clock laser, which produced by fiber laser amplifier and frequency quadrupling from the 1062.5 nm ultra-stable laser. The 1062.5 nm ultra-stable laser is first amplified to 2.6 W with a fiber laser amplifier, and then frequency doubled by a single-passing PPLN crystal. With second stage of a cavity enhanced frequency doubler with BBO crystal, the clock laser is generated with 11 mW at 265.6 nm. To remove the AC Stark shift of the cooling laser, the spectroscopy of 1S0-3P0 clock transition of 199Hg atoms is detected in magneto-optical trap by free-of-field detection method. The highest contrast of clock spectroscopy is 95%, and the lowest line width is 450 kHz, which corresponds to the atoms’ temperature of 60 μK. With the clock spectroscopy and frequency measurement of ultra-stable laser via fiber frequency comb, the absolute frequency of the 1S0-3P0 clock transition of 199Hg atom is determined as 1128575290.819(14) MHz. With 5 days measurement of the clock spectroscopy, the frequency drift rate of the ultra-stable cavity is evaluated as 4.2 kHz/day. The ultra-stable clock laser system is a key part of the neutral mercury optical lattice clock. Meanwhile the detection of the clock transition of cold 199Hg atoms is the important step in pursuing of the optical lattice clock. These two works have put the solid foundation to further realize the neutral mercury optical lattice clock. |
| 学科主题 | 光学 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/31125]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 付小虎. 汞原子光晶格钟钟频探测激光系统研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。