Fig. 1. Layout of the clock laser system. λ/2, half wave plate; λ/4, quarter wave plate; PBS, polarizing beam splitter; M, 0° or 45° reflection mirror; CM, coupling mirror; AL, aspherical lens; ISO, isolator; BS, plate beam splitter; PD, photodiode; FNC, fiber noise cancellation circuit; PDH, Pound–Drever–Hall; AVI, active vibration isolation.

Fig. 2. 30-cm-long ULE reference cavity and the Zerodur supporting base.

Fig. 3. Structure of the vacuum chamber with cavity’s temperature stabilization layers.

Fig. 4. Layout of the 698 nm clock laser and 813 nm lattice laser into MOT. CM, collimating mirror; M, mirror; ND, neutral density filter; GM, Glan–Tylor prism; L, lens; PD, photodiode.

Fig. 5. Transition spectrum of a single component of the S01→  3P0 transition with a Rabi excitation pulse width of 500 ms. The red solid line is a fitting with the Rabi line shape.

Fig. 6. Frequency stability evaluation when the clock laser is locked to the atomic transition. The blue squares display the one-loop measurements, and the black circles are the time-interleaved measurements. The sampling time of the measurement is 3.08 s. The error bar shows the confidence interval of the measurement, which is calculated from the measurement dataset^[26].

Fig. 7. Schematic of the interleaved measurements.