Spectroscopy Measurement Of The Transportable ⁸⁷Sr Optical Clock

As the most stable and accurate atomic clock in the world,the optical clock has achieved system uncertainty of E-19,which is nearly three orders of magnitude better than the cesium atomic fountain clock with second definition.It is one of the strong candidates for the next-generation time-frequency reference clock.At present,most optical clocks are fixed in laboratories,with large volume and complicated systems.With the development of scientific research and engineering,it has higher requirements for the miniaturization and transportability of optical clocks.The transportable optical clock can be used to compare the frequency of atomic clocks in two places,accurately measure the acceleration of gravity,and provide technical reference for space optical clocks.This work mainly presents the development and spectroscopy measurement of the transportable one-dimensional optical lattice clock based on ⁸⁷Sr.Firstly,a robust and compact optical clock system is realized with some innovative design and technology.To put it more specifically,the physical system is housed in a double-layer optical breadboard,and the volume is reduced to 120×50×60 cm³.At the same time,each optical sub-system is miniaturized and modularized,and final output lasers enter into the physical system through the fiber to interact with the atoms,which is convenient for replacement and repairing during removing the optical clock.At first,we used laser of 461 nm to finish the first stage cooling and an atomic group having an atomic number of 1.7×10⁷ and an atomic temperature of 5.1m K is obtained.After second stage of cooling with laser of 689 nm in succession,an atomic group having an atomic number of 1.02×10⁶ and an atomic temperature of 4.45?K is obtained.The lattice laser of"magic-wavelength"is used to perform atomic loading in one-dimensional optical lattice,and the lifetime of lattice is 434 ms.Then the atoms are detected by a clock laser of 698 nm to obtain a clock transition spectroscopy containing red sideband and blue sideband.The atomic temperature in lattice is calculated to be 4.63?K,and the trap depth is 19.59?K.After that,by reducing linewidth broadening due to clock laser power and residual magnetic field and adding the polarized laser of 689 nm,the m _F=+9/2-m _F=+9/2 and m _F=-9/2-m _F=-9/2 spin polarized clock transition spectroscopy respectively with narrower linewidth of 11.79 Hz is obtained,as the frequency reference of the final optical clock closed-loop.Using the spin polarization spectrum as a reference,the frequency of the clock laser is fixed at the peak of the spectrum and the time of the clock laser is changed to obtain the Rabi flopping curve of the excited state probability with time.After completing the closed-loop and evaluation of the optical lattice clock in the next step,the transportable ⁸⁷Sr optical lattice clock is expected to perform precise mapping of geoid during the moving process,compare the frequency stability with other clocks,and provide a prototype for the optical clock in space.