The Development of the NIM-Yb1 Ion Optical Clock

Optical clocks serve as the benchmark devices for the next-generation definition of the second and have significant applications in testing the theories beyong the standard models, dark matter research, and related fields.The ytterbium ion optical clock, featuring two clock transition lines, is among the most precise optical clocks with the lowest uncertainties.The National Institute of Metrology, China (NIM), initiated research on ytterbium ion optical clocks in 2021.Based on an end-cap ion trap, a vacuum system has been established.A 370 nm thirdharmonic fiber laser, along with 760 nm and 935 nm DFB lasers, ensures a stable operation of the optical system.To date, both the electric quadrupole and electric octupole clock transitions have been observed.A 2.8 Hz linewidth of the electric octupole transition has been achieved, with a stability of 1.7E-15 -1/2 after closed-loop locking.The uncertainties due to AC Starks shift from clock laser and second-order Doppler shifts are being evaluated, with an expected total uncertainty below 5E-18.