Frequency Calibration and Stabilization of the Cooling Laser of Ytterbium Lattice Clock with Molecular Iodine Spectroscopy

In order to apply the frequency comparison among the different optical clocks, transportable optical clocks(TOCs) is suggested as a valuable tool. For transportable clocks, the key technique is how to lock the lasers involved in the whole system. In this paper, we carry out a new way to calibrate and lock the second stage cooling laser of the ytterbium lattice clock with molecular iodine spectroscopy. The locking spectral width of 556 nm laser can be narrowed to 195 kHz, which can be used for frequency control and the stabilization of the second stage cooling. So the new method will make the transportable optical clocks more compact and robust in the future.

Experimental Study on the Lattice-End-Mirror Vibration Noise Cancellation of Ytterbium Clock Laser

In this paper,we describe an optical path stabilization method in order to keep the phase of the clock laser fixed during the interrogation.The phase noise along the optical path of the clock laser is extracted from the heterodyne beat signals.Then an acousto-optic modulator(AOM)driven by direct digital synthesizer(DDS)receives a feedback signal to cancel the phase noise.The experimental results show that our system can effectively suppress additional phase noise.The fractional frequency instability is dropped to 1.76×10^-17/τ at 1 s,which is improved by two orders of magnitude than before.In the case of Rabi excitation with a pulse duration T=50 ms,frequency shift is 7.9 mHz due to the feedback system relock process.For phase noise from different frequency,the system has a good suppression effect on low frequency phase noise.

基于层次分析法的晶体液优选模型研究及评价

目的通过构建数学模型-层次分析法,综合多因素分析、筛选出理想的晶体液,为临床选择提供数据参考。方法收集目前国内临床上较为常用的晶体液4种:林格注射液、乳酸钠林格注射液、醋酸钠林格注射液和钠钾镁钙葡萄糖注射液说明书,整理出各晶体液的Na^+,K^+,Mg^2+,Ca^2+等含量,pH,价格等;采用Matlab R^2014a运行程序分析。结果林格注射液,乳酸钠林格注射液,醋酸钠林格注射液和钠钾镁钙葡萄糖注射液对理想晶体液的贡献权重分别为0.1906、0.1661、0.2450、0.3982。组合一致性指标CI^*=0.0165,组合一致性比率CR^*=0.0183<0.1,符合一致性的检验标准。结论通过层次分析模型,分析得出各晶体液的贡献权重,贡献权重大者为优选的理想晶体液,即钠钾镁钙葡萄糖注射液。

Suppress Blackbody Radiation Shift with Two Clock Ytterbium Clock Transition

In order to suppress the blackbody radiation shift of ytterbium(Yb) lattice clock, we adopt the idea of the synthetic frequency by means of the two clock transitions which correspond to the static values of the scalar and tensor dipole polarizabilities with the AMBiT software package. We have obtained the synthetic wavelength around 647.7 nm and expected when the clock laser is working at the synthetic wavelength, the systematic uncertainty due to the BBR shift can be suppressed at the level of 10–18 or even lower.

Frequency Stabilization and Linewidth Narrowing with Modulation Transfer Spectroscopy

We report laser frequency stabilization with modulation transfer spectroscopy（MTS） on 85 Rb atoms. With both PZT（piezo-electric transducer） slow-loop feedback and current fastloop feedback to the laser head, we get a linewidth narrowing less than 5 kHz simultaneously. Laser injection to a laser diode and frequency beating with another polarization spectroscopy based stabilization setup are also employed to check the narrow linewidth property. With the help of the technique, a linewidth around k Hz-level laser is obtained and pave the way for the locking of the lattice laser of ytterbium clock with transfer cavity technique. The setup can be used as a frequency reference for precise frequency control of atomic clock system.