Research On Related Technology For Laser-Pumped Rubidium Atomic Clock

Rubidium atomic clocks are widely used in satellite navigation,communication,power supply because they have compact size,low power consumption and high reliability.Nowadays many applications push the need for ultra-thin and high-performance rubidium atomic clocks.The microwave cavity is a crucial component in Rb clock's physics package,whose height determines the clock's thickness.It also impacts the Signal to Noise Ratio(SNR)of the clock transition.In addition a discharge lamp is normally used as a light source in the traditional rubidium atomic clocks.However,its optical pumping rate is not very high.In order to improve the short-term stability of rubidium atomic clocks,we implemented a semiconductor laser that has excellent pumping rate and narrow spectrum.In the thesis,we study the above two related technology to develop the ultrathin rubidium atomic clocks.One research is the laser-power stabilization.The short and medium-to-long-term stability of the rubidium atomic clocks might be degraded by the light shift effect which is due to optical power instabilities(intensity noise and slow variations).Therefore,we set up a laser power stabilization platform using an acousto-optic modulator,aiming to suppress intensity noise.We found that both the polarization of the input laser to the acousto-optic modulator and Amplitude noise of Radio Frequency driving signal had influences on output laser intensity noise.After optimization of the laser polarization and RF signal,we minimized the noise created by the part of the acousto-optic modulator block.When the feedback loop is closed,the long-term stability of the out-loop laser always cannot reach the same level as the in-loop laser does,due to the birefringence effect of AOM and/or the splitting ratio variation of the beam splitter influenced by temperature.By carefully choosing and stabilization the working temperature and for the AOM and splitters,we successfully improved the long-term intensity stability of the out-loop light.The other research focuses on an ultrathin cavity-cell assembly of rubidium atomic clocks.We evaluated the performance of the physics package based on an ultrathin non-standard rectangular microwave cavity.The intrinsic linewidth of the cavity-cell assembly was obtained and about 452 Hz by extrapolation.Furthermore,the contribution of microwave power broadening and light broadening to the linewidth of double resonance is minimized under optimized operating conditions.The result suggests that the cavity-cell assembly has potential short-term stability of 5.2×10-13?-1/2 limited by the shot noise.This physics package provides an experimental basis for designing an ultrathin,small,and portable rubidium atomic clock.The improved scheme proposed in this paper can reduce the influence of the light shift effect and reduce the thickness of the physics package,which will greatly improve the SNR of the clock transition signal.This work is instructive for designing the laser-pumping rubidium atomic clocks.