Realization Of Ultracold Strontium Rydberg Gases And First Indications Of Effects Due To Rydberg-Rydberg Interactions

This thesis presents the author's research activities and scientific achievements on the frontiers of "ultracold strontium Rydberg gases".It provides detailed descriptions mainly about two aspects:building and calibrating apparatus;designing and imple-menting experiments.Technical realization of laser cooling strontium atoms to an ultra-cold tempera-ture is described.The frequency stabilization of the 689 nm laser,which is used for both the 689 nm narrow-line magneto-optical trap(MOT)and the two-photon Rydberg excitation experiments,is one of the focus points.A Pound-Drever-Hall locking loop is made for locking the laser to an ultra-stable cavity.Characterizations of the cavity locking system and measurements for showing a kHz laser frequency stability are both given systematically.The design of the 689 nm MOT is introduced,which combines the 689 nm laser and a fast MOT magnetic field control system.Based on a loading via the intemediate metastable state,atoms captured in the 461 nm MOT are transfered into the 689 nm MOT and cooled to a temperature down to 1.3 ?K.The 689 nm MOT has a peak atomic density of 1×1011/cm3 and atom number up to 1 × 107.As an understanding of the 689 nm MOT cooling mechanisms,integrative charcterizations of different MOT properties are shown with different cooling beam power.With the ultra-cold strontium atoms,two-photon excitation scheme realized by the 689 nm laser and another 318 nm laser is applied for accessing triplet Rydberg states.A long-term EIT excitation scheme is used to excite 5s24s3S1 Rydberg state.An an-alytical expression for describing the excitation-induced atomic loss is derived for the experiment simulation?It provides a fit of relevant measurements and gives estima-tions of variables like Rydberg state lifetime.Another Raman excitation scheme with large intemediate state detuning is implemented via continuous short-term pulses.This protocol works for both exciting a Vower-n Rydberg state 5s23s3S1 and exciting two higher-n Rydberg state 5s35s3S1 and 5s40s3S1.In the lower-n state measurement,the relation of ground state atom loss versus applied excitation pulse number shows good agreements with the theoretical prediction given by a non-interacting system.However,the higher-n state measurement shows different "atom loss versus pulse number" rela-tions by the comparison with the lower-n state,.By the changing of the initial atomic density,the relation curve is different as well.The Rydberg excitation induced loss propability is indicated to be density-dependent.A lower loss probability is given with a higher atomic density,which specifies a Rydberg blockade phenomenon.Two-atom model with inter-atomic Rydberg-Rydberg interations is used to simulate the upper-bound of the loss propability.And moreover,a damping super atom model,developed by introducing additional loss channel to the conventional super atom model,gives the lowerbound simulation of the loss probability.Agreements between the experimen-tal data and the theretical models are found.With the ultra-cold strontium gases,this work shows an integrative study of the Rydberg-Rydberg interacting properties,which supports the further applications of this system on the field of quantum simulation.