Study Of Two-step And Single-step Rydberg Excitation Of Cesium Atoms

Rydberg atoms not only have big size,long lifetime,huge polarizabilities,and sensitivity to electric fields,but also have strong long-range dipole-dipole interactions between Rydberg atoms.The study of these properties is an important step for precision measurements,quantum computing,quantum information,many-body physics and nonlinear optics.The applications of Rydberg atoms involve the excitation of Rydberg states.Two-step Rydberg excitation involves the intermediate state,the required laser wavelength is traditional and the manufacturing technology is mature,while single-step Rydberg excitation is the direct excitation of the ground state to the Rydberg state,which can avoid the problems of photon scattering in the intermediate state and decoherence caused by the AC-Stark shift,but the required wavelength is in the ultraviolet band.Both Rydberg excitation modes have their own advantages and disadvantages,therefore,based on cesium atoms,we experimentally studied two-step and single-step Rydberg excitations,respectively,analyze relevant physical problems.We investigate the Rydberg electromagnetically induced transparency(EIT)spectra in a cesium thermal atomic vapor cell using a two-step Rydberg excitation with 852 nm +509 nm laser,conduct study of the related physical problems involving Rydberg atoms.Furthermore,single-step transition Rydberg excitation signal is investigated in a cesium cold atom system using self-developed watt-level,narrow linewidth and continuously tunable 318.6 nm ultraviolet laser.The Autler-Townes splitting in the cold atom ensemble is demonstrated,and the related physical problems are analyzed.The main research content includes the following aspects:1.The Rydberg EIT spectra are realized in a hot atomic vapor cell using a two-step Rydberg excitation with 852 nm + 509 nm laser,and the dependence of the Rydberg EIT signal intensity and linewidth of cesium atoms on the relevant parameters,especially on the detuning of the probe laser.The local electric field caused by collision ionization between Rydberg atoms and ground-state atoms as well as between Rydberg atoms,and the resulting Rydberg level shift are demonstrated;2.Based on the two-step Rydberg excitation of the 852 nm+509 nm laser,the stochastic switch spectra due to random noise driven in the bistable system of the room temperature atomic system are observed,the effect of laser intensity and frequency detuning on signals is investigated and analyzed theoretically.According to the stochastic switch spectra,event counting statistics are performed for the average duration of the bistable.The population of Rydberg states is measured using electromagnetically induced transparency spectroscopy,and the nonlinear behavior in the Rydberg atomic ensemble is investigated;3.A cesium cold atom magneto-optical trap system is built,and a simplified time-of-flight fluorescence imaging method is used to measure the effective temperature of cesium atomic MOT and “optical molasses”,in addition to relevant parameters such as the size,atomic number and atomic density of the cold atomic sample are also measured;4.We investigate the watt-scale,narrow linewidth,continuously tunable 318.6 nm ultraviolet(UV)laser system,which is generated by single-pass sum-frequency generation(SFG)of the narrow linewidth 1560.5 nm and 1076.9 nm continuous-wave laser,and then frequency doubling of BBO crystal with a four-mirror ring cavity.The locking of the318.6 nm single-frequency UV laser is achieved by using an electronic sideband frequency stabilization technology with an ultralow expansion cavity,and a wide range of continuous tuning is achieved under the locking condition.Based on the magneto-optical trap of cesium atoms,a trap-loss fluorescence spectroscopy technology is used to realize the measurement of the single-photon Rydberg excitation,demonstrate the Autler-Townes splitting in trap-loss spectrum of cold atomic ensemble,and analyze the dependence of its related parameters.The innovations are as follows:1.The Rydberg EIT spectra are studied in a cesium room temperature atomic vapor cell,and the Rydberg level shift is experimentally measured using the spectral signal of Rydberg EIT,which is of great significance for self-calibrated sensing of microwave fields using Rydberg EIT;2.Based on the Rydberg EIT spectrum,the stochastic switch driven by random noise is investigated,the population of Rydberg atoms is measured by electromagnetically induced transparency spectrum,and the nonlinear behavior in the Rydberg atomic ensemble is experimentally studied;3.Autler-Townes splitting during single-step Rydberg excitation studied by trap-loss fluorescence spectroscopy in a cesium cold atom magneto-optical trap.