Precision Spectrum Measurement And Driving Optical Lattice Research Based On Strontium Optical Lattice Clock

After more than ten years of development,the optical lattice clock has shown ultra-high stability and accuracy.At present,the stability of the optical lattice clock has reached the order of E-19,while the uncertainty of the system has reached the order of E-18 with a small coefficient.The amazing performance of optical lattice clocks can not only greatly improve the precision of the definition of the second,which will enhance the precision of navigation and time synchronization,but also be widely applied in scientific research,such as observing the gravitational potential of the Earth with sub-centimeter measurement accuracy,verifying general relativity,measuring the variation of the constant with time,searching for dark matter and so on.Based on Fermi strontium optical lattice clock,the self-comparison technology,synchronous measurement technology and vibration optical lattice technology based on the optical lattice clock have been fully studied in this paper.The specific research contents include the following aspects:(1)The physical system of ⁸⁷Sr optical lattice clock is improved,the 1/e lifetime of atoms trapped in the lattice is extended to 8.5 s,and the radial and longitudinal temperatures of atoms trapped in the lattice are reduced to 1.6?K and 0.95?K,respectively,by using the energy filting method.Based on Lab VIEW,a closed-loop program which only needs one trigger signals is written,and the real-time clock laser frequency drift compensation module is embedded in the program to suppress the frequency drift of the clock laser,and reduce the servo error of the optical lattice clock.(2)The self-comparison measurement error,caused by the clock laser frequency drift or stray field drifts,is discovered,and the relationship between the drift rate and self-comparison measurement error is quantitatively studied by combining numerical simulation with experimental measurement.On this basis,by dissecting the root of the self-comparison measurement error in the traditional self-comparison technique,the drift insensitive self-comparison method is proposed.It is proved by experiments that the drift insensitive self-comparison method can effectively suppress the self-comparison measurement error.(3)The collision frequency shift of the optical lattice clock is measured,and the measurement uncertainty of it is reduced to 7.7×10^-18,benefiting of deducting the fluctuation of atomic number in real time and increasing the measurement lever.On this basis,the factors that lead to the collision frequency shift and the zero-collision frequency shift technology are analyzed in detail,which make a foundation for further reducing the uncertainty of the collision frequency shift.(4)The second-order Zeeman frequency shift coefficient of ⁸⁷Sr optical lattice clock is measured,and the mean second-order Zeeman frequency shift coefficient obtained by combining the measurement data of other groups is(23.379±0.029)MHz/T².The remaining first-order and second-order Zeeman shifts are evaluated with the experimental data,and the measurement uncertainties are 5×10^-18and 5×10^-19,respectively.(5)On the basis of the traditional synchronous comparison technology which needs two optical clocks,a novel synchronous comparison technology requiring only one optical clock is proposed.To realize this synchronous comparison method,the key technology of dual-excitation spectrum is proposed,and the lattice laser differential tensor shift coefficient is synchronously measured in ⁸⁷Sr optical lattice clock.The measurement uncertainty is much lower than the Dick limit.In addition,the dual-excitation spectrum technology has been successfully applied to the closed-loop operation of the optical clock,and has improved the stability of the optical clock by at least 1.4 times,greatly shortening the necessary time for the optical clock to reach a specific measurement precision.(6)Based on the ⁸⁷Sr optical lattice clock platform,for the first time,a driven optical lattice technology that only modulates the lattice light frequency is successfully implemented,and all experimental phenomena are successfully explained by the Floquet theory.On this basis,driven optical lattice methods based on multi-mode modulation and two-parameter modulation have also been studied and discussed in detail.These novel driven optical lattice technologies lay a foundation for quantum simulation and quantum computation in the optical lattice clock,which greatly expands the application of optical lattice clocks.