Breakthrough in the Research on the New Atomic Clock of the National Time Service Center (NTSC) -- CPT Maser Rubidium Atomic Clock

The CPT atomic clock is a new-concept one based on CPT (Coherent Population Trapping) theory, which uses microwave signals to control the frequency difference between two coherent laser beams, and obtains high-precision standard-frequency signal output by locking the microwave frequency on the transition frequency between hyperfine levels of atomic ground state, through adopting interaction between laser field and three-level system of atom, without the need of atomic state selection system of the traditional atomic clock. Optical frequency shift is a main factor restricting the performance improvement of traditional rubidium atomic clock, while there is no the problem of primary optical frequency shift nagging the CPT atomic clock in terms of theory. Based on the CPT theory, two types of atomic clocks can be realized, in which the passive atomic clock realized by measuring the transmission laser’s strength (EIT signal) is featured by light weight, little power consumption, etc., thereby being expected to develop into a kind of micro atomic clock available for the fields like data communication and so on. The principle prototype of atomic clock in this type has been realized by the researchers of our country. The active atomic clock can be achieved by using the relation between atomic coherent microwave radiation signal power (maser signal) and frequency difference of laser beam as the frequency discrimination signal, and the index of its stability performance is of outstanding advantage. If used as satellite-bone atomic clock applied to the space navigation and positioning system, it can increase the navigation and positioning precision, prolong its autonomous operation cycle and service life of satellite-bone clock, etc. The CPT maser rubidium atomic clock has been attached wide attention to in European and American countries with respect to the research on it, and is under research and development as a satellite-bone clock of next generation for the Galileo satellite navigation and positioning system. With the financial aids of CAS, the NTSC has made a breakthrough in its research on the CPT maser rubidium atomic clock, that is, obtaining the marking signal of CPT maser – atomic coherent microwave radiation signal – for the first time in China and after the IMGC.