Development Status and Usability Analysis of Optical Clocks for Global Navigation Satellite System Applications

With the rapid development of optical-frequency atomic clock technology, the uncertainty of optical clocks has exceeded the performance of microwave atomic clocks by 4 to 5 orders of magnitude, reaching 10⁻¹⁹ orders of magnitude. In addition, there have been continuous improvements in reliability and miniaturization. These advances make it possible to adopt optical atomic clocks in Global Navigation Satellite System（GNSS） in the future. This paper summarizes the performance of several optical atomic clocks in terms of stability, integration, characteristics and their factors affecting stability. Compares four types of optical clocks （ion optical clocks, optical lattice clocks, two-photon transition optical atomic clocks, and iodine modulation transfer spectrum optical atomic clocks） with four major navigation systems currently carried on GNSS. In addition, discusses the application potential of optical atomic clocks, and puts forward proposals for the development of each optical atomic clock. In order to improve the reliability of ion and lattice clocks, it is necessary to enhance the stability of lasers and super-stable cavities and reduce the environmental sensitivity of core devices. In order to improve the stability of atomic beam optical clocks, schemes such as increasing atomic beam utilization and further experiments are proposed. In order to improve the long-term stability of two-photon transition atomic clocks and modulated transfer spectrum optical clocks, a solution combining vacuum technology and artificial intelligence technology to reduce frequency drift rate is proposed.