Single Frequency Microwave Electric Field Measurement Based On Rydberg Atoms

The noise of traditional microwave receiver comes from the thermal noise of input resistance,so the minimum acceptable signal power cannot break through the limitation of thermal noise power.Rydberg atoms are sensitive to microwave and have become a research hotspot in recent years.The receiver based on Rydberg atoms provides a signal receiving method of non-resistance participation,which has the advantages of high sensitivity and large dynamic range.This thesis realizes the measurement of single frequency microwave electric field based on cesium atoms(¹³³Cs).In this thesis,we mainly construct four-level systems based on a vapor cell of cesium atoms.The 852nm probe light is used to excite cesium atoms in the ground state(6S_1/2)to an excited state(6P_3/2),and the 510nm coupling light is used to excite cesium atoms to a Rydberg state.In a three-level system with two laser beams,the electromagnetically induced transparency（EIT）effect will be produced.When the single frequency microwave field couple two Rydberg States,the Autler-Townes（A-T）splitting effect will be produced.The electric field strength is related to the splitting interval.Therefore,the measurement of microwave electric field can be converted into the measurement of splitting interval.We set up an optical experimental system and complete the measurement of single frequency microwave by means of fixing the probe light and scanning the coupling light.The main content includes the following parts:Firstly,we introduce the characteristics of Rydberg atoms,and discuss the absorption properties of the atomic two-level systems,the EIT effect in the three-level systems,and the A-T splitting effect in the four-level systems.In the four level systems,we describe the principle of single frequency microwave electric field measurement based on Rydberg atoms.Secondly,in order to solve the problem of the frequency drift of the probe light,the 852nm laser is stabilized by a stabilization system of saturation absorption,and we test the effect of frequency stabilization.The final result shows that the fluctuation of laser frequency within600s is less than 3MHz,so the stability is 8.53（?）10^-9.We also measure the frequency for ten consecutive days,and the reproducibility is 1.42（?）10^-8.Thirdly,we build three-level and four-level EIT systems to observe EIT effect and A-T splitting effect.Based on the systems,the microwave electric field with the frequencies of6.9451 GHz,9.2174 GHz,11.6168 GHz,13.4078 GHz and 15.5513 GHz is measured.The final experimental results are consistent with the theoretical calculations.Finally,we summarize the whole microwave measurement work in this thesis and put forward the details that can be improved.In addition,we prospect the blueprint of Rydberg atomic receiver.