MA Zhe1,2, LIU Jie1,3, REN Li-qing4, LIU Tao1,3, ZHANG Shou-gang1,3

(1. National Time Service Center, Chinese Academy of Sciences, Xi′an 710600, China;

2. Graduate University of Chinese Academy of Sciences, Beijing 100039, China;

3. Key Laboratory of Time and Frequency Primary Standards, National Time Service Center,Chinese Academy of Sciences, Xi′an 710600, China;

4. Shaanxi Normal University, Xi′an 710062, China)

Abstract: Thesub-hertz linewidth laser is the key part of optical clock and also the important instrument for precise optical measurement of atoms. We show the theoretical expression of the cavity mirror loss using the relation between the power reflectivity and transmission as well as the loss of the cavity mirrors. We experimentally measured and calculated the reflectivity and loss for the substrate mirror of the pre-stable cavity. The experiments show that optimizing the matching efficiency can decrease the practical loss of the cavity, and it is more important that reducing the loss of the cavity may improve the stability of locking loop.

Key words: diode laser; cavity loss; mode-matching efficiency; laser frequency stabilization; optical clock