A transportable optical lattice clock at the National Time Service Center

Kong De-Huan^{1, 2}, Wang Zhi-Hui³, Guo Feng^{1, 2}, Zhang Qiang^{1, 2}, Lu Xiao-Tong^{1, 2}, Wang Ye-Bing¹, Chang Hong^{1, 2, †}

(a) Schematic and layout of the second-stage cooling laser system. EOM: electro-optic modulator; AOM7–AOM11: acousto-optic modulator at 689 nm with frequency shifts of –2175 MHz, + 520 MHz, + 214 MHz, –520 MHz, –209 MHz; HR: high-reflectivity mirror; QWP: quarter-wave plate; HWP: half-wave plate; ISO: optical isolator; PBS: polarizing beam splitter; PD: photodetector; BS: beam splitter; PM fiber: single-mode polarization-maintaining fiber. (b) Layout of the second-stage cooling laser system. The insert in (b) is the vacuum chamber for the cubic cavity with a height of 10 cm and a diameter of 11 cm.