芯片原子钟相干布居囚禁谱线特性研究

通过微型原子蒸汽室产生质量满足要求的相干布居囚禁(CPT)信号是实现芯片原子钟的关键之一.本实验通过对光源实施频率调制和对光场与⁸⁷Rb原子作用产生的信号作相敏解调获得高信噪比的CPT微分谱线, 利用CPT微分谱线研究了CPT信号随工作参数变化的规律以及信号质量对原子钟频率稳定度的影响, 所获研究结果与理论模型预期相符合, 实验结果为芯片原子钟推荐了最佳工作参数.实验所采用的方法利用芯片原子钟自身的资源就可以实施, 因此为芯片原子钟开展性能研究和实施工作参数优化提供了实用的手段.     

铯原子气室中相干布居俘获的参数依赖关系研究

基于铯原子基态6S_1/2的两个超精细能级（F=3与F=4）与激发态6P_3/2的超精细能级（F′=4）构成的Λ型三能级系统,采用室温下的未充缓冲气体和充有分压为266.6 Pa的氖气作为缓冲气体的铯原子气室对于相干布居俘获（CPT）的参数依赖关系进行了实验研究和理论分析.主要研究了CPT信号的半高全宽和幅度对于频率差为铯原子基态6S_1/2的超精细分裂（9.19263177 GHz）且位相锁定的两激光束的功率、光强比值、光斑直径、磁屏蔽之后的剩余磁场以及是否充缓冲气体等实验参数的依赖关系.在优化的实验参数条件下获得了约340 Hz的CPT信号半高全宽.     

新一代超高精度锶原子钟

 美国国家标准研究所研究人员认为,在新一代原子钟中将利用锶原子。众所周知,现代铯原子钟走时误差为每5000万年不超过1秒,铯原子钟工作建立在测量铯原子辐射频率基础上,测量精度受原子热运动和辐射波长的限制。锶原子辐射波长比铯原子辐射波长短2个数量级,而最近发现的特性能快速使锶气体冷却到接近绝对零度。     

脉冲微波激发氢原子Ramsey干涉研究

该文开展利用Ramsey干涉现象设计被动型氢原子钟的可行性研究. 该方案的核心是用脉冲微波激励氢原子发生共振跃迁. 通过理论计算确定了关键参数,研制了脉冲微波发生电路. 利用现有的被动型氢原子钟的物理部分,成功观察到氢原子共振跃迁的Ramsey干涉,将原子跃迁谱线宽度从原来的3 Hz压缩至1.2 Hz. 这为进一步提高被动型氢原子钟的稳定度指标提供了一种新思路.     

无磁加热薄膜仿真设计与实验验证

介绍了一种用于原子气室的无磁加热薄膜技术。原子磁力仪、原子陀螺仪、原子钟等采用热原子系综的精密测量仪器通常采用原子气室作为物理系统,为了保证足够的原子数密度,原子气室工作温度通常为80～120℃,因此无磁加热技术是热原子钟的核心技术之一。采用多物理场有限元仿真分析通电线圈在小电流（直流0.2 A）条件下产生的稳态磁场分布情况,通过对比不同线圈结构产生的磁场分布,得到满足性能要求的通电线圈结构。实验结果表明,采用优化后结构的无磁加热薄膜产生的剩磁低于100 nT,满足原子气室无磁加热要求。该设计对以原子气室的原子钟性能提升提供了可靠保证,并为原子钟小型化提供参考。     

相干布居数囚禁原子频标的实现及相关实验参数研究

原子频标要求高信噪比和窄线宽的鉴频信号,但对于被动型相干囚禁态原子频标(CPT频标), 改善鉴频信号信噪比以增加线宽为代价,因此选择合适的信噪比和线宽组合是研制CPT原子频标频标的重要环节。文章介绍了用桌面CPT频标系统地研究了鉴频信号与温度、光强等参数的关系所获得的研究结果,由此获得了合适选取的信噪比与线宽组合的依据。文章还给出了关于光源非理想偏振导致的消相干效应对CPT频标的影响所开展的实验结果。文章所提供的研究结果不仅帮助我们研制成功了CPT频标,而且对于CPT物理现象研究和其他CPT频标的研制也有参考价值。     

应用于光抽运铯原子钟的小型稳频激光器（英文）

设计了一种应用于光抽运铯原子钟的稳频激光器,用小型化的饱和吸收装置对激光进行稳频,用于产生饱和吸收谱的泵浦光的偏振方向与检测光的偏振方向相互垂直,通过调节激光的偏振方向增大铯原子的跃迁几率.相对于一般简化的饱和吸收装置,小型化的饱和吸收装置产生的用于锁频的参考信号的幅度更大.当激光频率被锁定在铯原子的6S_(1/2),F=4→6P_(3/2),F=5能级跃迁线上时,对激光器的稳定度进行了测量,百秒稳定度为1.88×10~(-11).该稳频激光器的体积较小,有利于光抽运铯原子钟的小型化和工程化应用.     

采用简化的飞行时间荧光成像法测量冷原子样品的等效温度

本文介绍了用于冷原子样品等效温度测量的简化的飞行时间荧光成像法。将用于激光冷却和俘获原子的冷却光,代替标准的飞行时间荧光成像法中额外引入的探测光。在铯原子磁光阱基础上,通过进一步采用偏振梯度冷却技术使冷原子等效温度有效地降低。采用简化的飞行时间荧光成像法测量的铯原子气室磁光阱(光学粘团)的等效温度,典型值为TY≈22.3±2.2μK,TZ≈15.4±2.7μK(TY≈11.6±1.1μK,TZ≈2.8±1.2μK)。本文中的简化飞行时间荧光成像方案,在不牺牲冷原子样品等效温度测量的精度和准确度情况下,更容易在实验中执行和推广,对于应用于冷原子微波原子钟、冷原子光频原子钟、冷原子干涉重力仪等量子精密测量领域,以及采用冷原子样品进一步开展量子光学、量子信息处理等领域的研究工作,具有积极意义和良好的推广价值。     

冷原子气体的时频测量——光晶格原子钟

基于冷原子气体的时频测量在近20年里快速发展,引起了人们的广泛关注,其典型代表是基于大量中性原子的光晶格原子钟。利用超稳钟激光同时探测囚禁在光晶格里成千上万个冷原子的钟跃迁信号,光晶格原子钟已实现10^-18量级的频率准确度和10^-17量级的秒级稳定度,大幅度提高了时频测量的精度。文章概述了光晶格原子钟的发展历史、工作原理、性能评估及应用前景。     

冷原子气体的时频测量——光晶格原子钟

基于冷原子气体的时频测量在近20年里快速发展,引起了人们的广泛关注,其典型代表是基于大量中性原子的光晶格原子钟。利用超稳钟激光同时探测囚禁在光晶格里成千上万个冷原子的钟跃迁信号,光晶格原子钟已实现10^-18量级的频率准确度和10^-17量级的秒级稳定度,大幅度提高了时频测量的精度。文章概述了光晶格原子钟的发展历史、工作原理、性能评估及应用前景。     

Line-shape of dark line and maser emission profile in CPT

The paper is concerned with the line shapes of resonance phenomena observed in Coherent Population Trapping (CPT) applied to alkali atoms in a cell containing a buffer gas. Significant asymmetries and departures from a Lorentzian shape have been observed in connection with the measurement of dark lines and CPT maser emission profiles. Measurements are reported as a function of the power and frequency tuning of the laser used to create the CPT phenomenon. The paper reports on different experimental conditions and a comparison between theory and experiments is made for the cases of cesium and rubidium in a buffer gas. Received 3 March 2000 and Received in final form 10 April 2000     

拉曼喷泉原子钟

利用托曼光场代替喷泉原子钟的微波腔实现拉曼喷泉原子钟.将分离托曼光场技术与冷原子喷泉技术相结合.避免了存真空腔内放置微波腔,简化了真空系统.同时还保持了很高的准确度.采用半经典理论研究了冷原子喷泉与托曼光场的相互作用过程.得到了冉赛(Ramsey)条纹.比较了托曼喷泉原子钟与热铯束拉曼原子钟,前者有更小的体积和功耗,其精度可能达到或超过商用小铯钟.还比较了拉曼喷泉原子钟与微波喷泉原子钟的差别,分析了光子反冲的影响,提出利用同向传播和相向传播的两台拉曼原子钟测最精细结构常数.     

Modeling of a diode transverse-pumped cesium vapor laser

A physical model is established to demonstrate the mechanism and the kinetic process of a diode transverse-pumped cesium vapor laser. The distribution of pump laser power is described, and the effects of parameters such as the temperature, the cell length and the output coupler reflectivity on the output performance of a cesium vapor laser are simulated and analyzed. The simulation results agree well with the experiment data which shows the validity of this model. A set of optimization parameters is achieved for improving the output characteristics of a diode transverse-pumped Cs vapor laser.     

Relation Between CPT Violation in Neutrino Masses and Mixings

The neutrino parameters determined from the solar neutrino data and the anti-neutrino parameters determined from KamLAND reactor experiment are in good agreement with each other. However, the best fit points of the two sets differ from each other by about 10⁻⁵ eV² in mass-square difference and by about 2° in the mixing angle. Future solar neutrino and reactor anti-neutrino experiments are likely to reduce the uncertainties in these measurements. This, in turn, can lead to a signal for CPT violation in terms a non-zero difference between neutrino and anti-neutrino parameters. In this paper, we propose a CPT violating mass matrix which can give rise to the above differences in both mass-squared difference and mixing angle and study the constraints imposed by the data on the parameters of the mass matrix.     

基于艳原子线性法拉第磁光效应的应用

分析了(銫) (Cs)原子作为旋光介质的线性法拉第磁光效应.采用二能级模型解释了(銫)原子与光的相互作用,并利用琼斯矩阵推导了当激光器的频率处于(銫)原子共振线时,经过(銫)气室的线偏振光的旋转角与外加磁场的关系式,利用此关系式可测量磁场强度的大小和气室内(銫)原子的浓度.实验采用852nm分布反馈半导体激光器作为光源...     

Comments on CPT

I comment on recent experimental results in neutrino physics that are often invoked in the context of the violation of CPT. Even if the hint on the difference of oscillation parameters for neutrinos and antineutrinos is correct, the interpretation in terms of CPT violation is premature, as other CPT-invariant physics may often mimic the same outcome. I also comment on where in nature CPT violation may have played its role, and review the ideas related to the spontaneous generation of the baryon asymmetry of the Universe. I argue that the most promising way of generating baryon asymmetry using CPT violation is the equilibrium leptogenesis, tilted towards particles by effective dimension 5 CPT-odd operators.     

基于磁共振的水下非接触式电能传输系统建模与损耗分析

文章对基于磁共振的水下非接触式电能传输系统在海水中的传输机理以及电涡流损耗进行了分析. 首先基于互感模型, 建立了空气中磁共振非接触式电能传输系统的数学模型, 分析了系统的频率特性, 从理论上对频率分裂现象进行了解释. 然后针对海水环境, 通过麦克斯韦方程组建立系统的数学模型, 通过级数展开, 略去高阶项, 得到计算电涡流损耗的近似公式, 分析了电涡流损耗与线圈半径、谐振频率、传输距离、磁感应强度的关系, 为水下非接触式电能传输系统的总体设计提供了理论依据. 最后通过实验验证了在空气中和海水中进行非接触式电能传输的异同, 以及电涡流损耗与各项参数的关系. 实验表明: 在空气中当传输距离为50 mm、传输功率为100 W时, 效率在80%以上; 在海水中当传输距离为50 mm、传输功率为100 W时, 效率约为67%, 说明基于磁共振的水下非接触式电能传输系统在海水中也有很好的应用前景.     

Absorption resonances in A-type three-level system in cesium vapor cell with buffer gas

We report experimentally the transformation from the electromagnetically induced transparency (EIT) resonance to a dispersion-like signal and eventually to a nearly symmetric absorption resonance as coupling detuning increases in A-type three-level system in the cesium vapor cell with buffer gas at room temperature. The observed absorption resonance occupies some remarkable properties of the strong amplitude and the narrow linewidth in comparison with the case without buffer gas. The relation between linewidth of the enhanced absorption resonance and buffer gas pressure is studied. With pressure increasing, linewidth of the absorption resonance becomes narrow. The sub-natural linewidth is observed in Doppler-broadened cesium vapor cell in our experiment. The experimental results are in qualitative agreement with the numerical simulations.     

LSND, SN1987A, and CPT violation

We point out that neutrino events observed at Kamiokande and IMB from SN1987A disfavor the neutrino oscillation parameters preferred by the LSND experiment. For Δm²>0 (the light side), the electron neutrinos from the neutronization burst would be lost, while the first event at Kamiokande is quite likely to be due to an electron neutrino. For Δm²<0 (the dark side), the average energy of the dominantly events is already lower than the theoretical expectations, which would get aggravated by a complete conversion from to  . If taken seriously, the LSND data are disfavored independent of the existence of a sterile neutrino. A possible remedy is CPT violation, which allows different mass spectra for neutrinos and anti-neutrinos and hence can accommodate atmospheric, solar and LSND data without a sterile neutrino. If this is the case, Mini-BooNE must run in rather than the planned ν mode to test the LSND signal. We speculate on a possible origin of CPT violation.