Naicheng+Shen

The development of optical frequency standards during 1980’s quickly led to cold atom cloud temperatures of below 1mK within optical molasses and magneto-optical traps. With such cooling capability, it became possible to virtually remove Doppler broadening and shift to an unprecedented level. 1S-2S two-photon transition in atomic hydrogen plays an important role in the determination of Rydberg constant. The 532nm iodine stabilized Nd:YAG lasers are becoming the important standard of optical frequency and wavelength, owing to their high frequency stability, reproducibility and reliability. We are improving its frequency reproducibility by using new iodine cells made in our laboratory. The important problem about frequency standards and their application to space missions is the synchronization of clocks using signals from orbiting satellites, such as in the Global Positioning System (GPS) and GLONASS. Various manufacturers use GPS receivers in which precise time is derived from one of the atomic clocks in the satellites (GPS Time Receiver). In certain applications, there is a need to synchronize these Time Receivers with each other. The method is to synchronize the satellite clock to the reference by making measurement of times of transmissions and arrivals of a sequence of two-way transmissions and using those measurements deriving a correction term to be applied to the satellite clock.
 * The Development of Optical Frequency Standards and Its Application to Space Missions **
 * Naicheng Shen, Institute of Physics, CAS **