Precise calibration of zero-crossing temperature and drift of an ultralow expansion cavity with a clock transition spectrum

Liu Hui^{1, 2, 3}, Jiang Kun-Liang^{1, 2, 3}, Wang Jin-Qi^{1, 2, 3}, Xiong Zhuan-Xian^{1, 2}, He Ling-Xiang^{1, 2,}, Lü Bao-Long^{1, 2}

(color online) (a) Normalized excitation spectra of clock transition at 31.7 °C. (b) Frequency drift rate versus time of ULE cavity in 24 hours, measured with the optical frequency comb. (c) Frequency drift rate measured with clock transition spectra.