Experimental Investigation Of EIT Effect In Multi-level Atomic System And Cooling Of Atoms

This dissertation is organized in the following way.First,we have researched the cross-phase Kerr nolinearity effect in tripod-type atomic system;then introduced MOT system(rubidium atom) and improved it, enlarged the diameter of trap beam for rising the number of cold atoms,and finally studied the dependence of optical density of cold atoms on MOT systematic parameters.The works of this dissertation have three parts:(1) The susceptibility of the probe field in a four-level tripod-type atomic system as a function of the probe detuning is calculated.The results show that the absorption and dispersion of probe field near EIT resonance can be significantly changed,when a trigger beam interacting with a transition in this system.With the increase of Rabi frequency of trigger beam,the absorption of probe beam at EIT window becomes smaller,and its dispersion becomes larger.Such changes of susceptibility of probe beam caused by a trigger beam are corresponding to the third Kerr nonlinearity, which have an application in polarization phase gate.(2) We achieved a 780nm(single frequency,narrow linewidth),640mW laser beam by injecting into one TPA amplifer using one DL100 master laser.(3) Meanwhile,rising the diameter of trap beam up to 40mm we obtained more numbers of cold atoms and thereafter,studied the relationship between the number of cold atoms and optical density and systematic parameters of MOT for next work.