【作者】 徐建；

【导师】 刘胜； 甘志银；

【作者基本信息】 华中科技大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 原子钟作为世界上最为精确的计时工具,早在1976年就被研究确定为计时标准。它利用原子的超精细能级间的跃迁辐射对时间进行度量。由于其计时的稳定性,在过去的50年中已成为通讯、导航系统、航空航天以及网络同步和科学测量等领域中最为基本的器件之一。然而由于传统的原子钟需要利用谐振腔,体积较大,很大程度上限制了其应用领域的扩展。另一方面,随着各种电子器件与系统朝着小型化发展,传统的原子钟在以往的应用领域也受到挑战。而相干布居数囚禁(Coherent Population Trapping,CPT)原理则给原子钟特别是被动型原子钟的小型化,甚至于微型化带来希望。本文即针对原子钟微型化的发展需求,以CPT原子钟系统实现为目标,在系统层面上对被动型CPT原子钟开展了系统建模、物理系统、电路系统以及系统制作等方面的研究。首先在CPT原理物理机理的基础上,开展了被动型CPT原子钟系统层面的建模研究。通过对CPT原理的分析,结合产生CPT所需的条件,分别从光源、光学元件、腔体吸收以及信号检测等方面进行了相关数学建模研究,在此基础上完成了整个CPT原子钟系统的构建,并将CPT原子钟系统划分为物理系统和电路系统两大部分。随后针对CPT原子钟,开展了钟物理系统的设计研究。分别从光源器件的选择、光学元件的设计、碱金属腔体材料选择和工艺的设计、恒温加热元件的设计、光电检测元件的设计以及磁场及电磁屏蔽等方面给出了CPT原子钟的物理系统的设计要求,并提出了设计方案。在物理系统设计的基础上,对CPT原子钟电路系统的设计进行了研究。分别从微波调频信号合成、光源光频稳定、光源及碱金属腔体恒温控制以及误差信号检测等方面进行了相关电路的设计研究,并分别给出了相应的设计要求,并提出相应的设计方案,给出了相关电路的设计参数,同时给出了电路系统在布局布线中所需要注意的问题及解决方案。最后在CPT原子钟物理系统及电路系统的设计的基础上,进行了实际CPT原子钟系统的研制。并分别对系统各部分进行了相关的实验及测试,系统测试表明采用垂直腔表面发射激光器(VCSEL)作为光源时,出射光波长可扫过87Rb的共振吸收线;光学元件可以完成圆偏振态的转换;光电二极管适用于微弱信号的检测;调频微波合成电路输出信号可达3.4 GHz,调频频率在800 Hz时为最优;VCSEL光频稳定环路可实现VCSEL光频的锁定;恒温加热电路可以实现对VCSEL及Rb腔温度的控制,控制精度分别可达0.02℃和0.5℃;误差信号检测电路则可以检测出大噪声背景下低达V的微弱信号。系统整体测试表明设计方案正确,对芯片级CPT原子钟的设计与制作具有指导作用。更多还原

【Abstract】 As the most precise time keeper, atomic clock was used for the definition of the time by the International System of Units since 1976. It employs the radiation corresponding to the transition between two hyperfine energy levels of the alkali metal atoms to count time. Because of its stable of time keeping, it has become the most basic component among communication, global positioning system, aeronautics and astronautics and network synchronization. However, due to the microwave resonant cavity, which needs to be used in the traditional atomic clock, was very large, it is very difficult to be miniaturized. Besides, there were more and more electronic to be miniaturized, the traditional atomic clock application was challenged. With the coherent population trapping (CPT) theory, the atomic clock could be made very small, even to be chip-scale. This dissertation focuses on the demand for the minaturization of the atomic clock. Taking realization of the CPT atomic clock system as our target, system modeling, physics system and circuit system design and the whole system assembly were studied in this dissertation.System modeling was based on the CPT theory and was studied on the device level. Through the CPT analysis, light resource, optical elements, alkali metal atomic cavity and signal detection were described mathematically. And based on the description the system model was constructed for CPT atomic clock specifically. At the same time, the CPT atomic clock system was divided into two parts, physics system and circuit system.With the requirements of the CPT theory, the physics system was studied. The physics system included the light source, optical elements, cavity with alkali metal atoms, heaters, light signal detection, inducing magnetic field and electromagnetic field shielding. All of them were designed respectively and the assembly of the physics system was given at the end of the chapter.Based on the designed physics system, the circuit system was studied. The circuit system was divided into four parts which were frequency modulated microwave signal synthesizing, light frequency stabilization, temperature controlling for light source and cavity and weak signal detection. Every part was designed and constructed specifically. Finally, the issues in the PCB (Printed Circuit Board) layout were discussed.Finally, with the designed physics system and circuit system, the realization of the CPT atomic clock system was studied. Every part of the CPT atomic clock system was realized and tested. Physics system test results showed that the light source which used VCSEL (Vertical Cavity Surface Emitting Laser) could emit the 795nm beam which was corresponding to the absorption wavelength of the 87Rb atoms; the optical elements could realize the polarization conversion; the PIN photodiode could be able to detect the error signal. Circuit system test results showed that the frequency modulated microwave signal synthesizing circuit could output 3.4 GHz frequency modulation (FM) signal; the light source frequency stabilization circuit could stabilize the wavelength of the VCSEL onto 795nm; the temperature controlling circuit could stabilize the VCSEL and the Rb cavity in the range of 0.02 degree C and 0.5 degree C respectively; the weak signal detection circuit could reveale the signal as lower as 1 microvoltgae with the large noise background. With these parts, the CPT atomic clock system was realized. Output frequency stability test veryfied the systematic model and all the design could give the important guidance to the chip-scale atomic clock design and fabrication.更多还原