Memory Of The Cold Atoms EIT Medium

In recent years, due to the quantum interference effect occurs of the interaction coherent and multi-level atoms, which will produce a variety of interesting physical phenomena. So the interaction of optice and atomic has become an important research in physics that is given attention. One effect of electromagnetically induced transparency (EIT) can decrease the absorption and dispersion increased, reduce the group velocity of optical pulses is compressed into the atomic medium, which has been widely research in theory and experiment. The optical quantum information stored in the atomic medium by using EIT effect is an important research in quantum information science.In 1975, T.Hansch and A.Schawlow the concept of laser cooling gas atoms had be brought forward. The same year, the project of laser cooling gas atoms had be brought forward by U.S. scientists. Then people use laser cooling and trapping technology to achieve the preparation of cold atomic medium. In the hot atomic ensemble, doppler effect caused by the inevitable motion of hot atomic and the decoherence effect caused by the collision between atomic,which will bring many negative factors in further experimental study of atomic physics. But atoms at a low temperature environment in the cold atomic medium, because doppler effect caused by the inevitable motion of hot atomic and the decoherence effect caused by the collision between atomic is well avoided. Therefore, physical phenomena about atomic physics in the cold atomic medium became the focus, which have been gave attention in atomic physics and quantum optics.This dissertation introduce a magnetically-optical-trap (MOT) experimental setup for cooling and trapping the 87Rb atoms is used in our experiments and experimental parameters. Using electromagnetically induced transparency the optical pulse is stored in two coherence ground state of atoms, achieve the optical pulse storage and release in 87Rb atomic medium, study the retrieval signal as a function of the power of the coupling beam and the phenomenon of collapse and revival of the retrieval signal under the condition of ambient magnetic field. By using optical pumping the atomic population is prepared into desired single zeeman sublevel, then the four level ideal tripod system is constructed. In the atomic system we realized the dual-channel storage and release of optical pulse.1) The theory of cooling and trapping the neutral atoms is reasoned out detailedly, and we introduce a reformative magneto-optical trap (MOT) device for cooling and trapping the 87Rb atoms. The number of cold atoms can be measured by detecting the power of fluorescence emitted from the cold atoms cloud. The results show that the density of the cold atoms is about 1011cm-3, and the number of the cold atoms is about 1010.By analyzing the absorption spectrum observed in the short-distance time-of-flight (TOF) method during the cold atoms free falling. By theoretical calculating the effective temperature of the cold atoms cloud in the MOT is about 300μk. Such cold cloud can be used as an EIT medium, which fulfil the condition to do the experimental research about atoms.2) In experiment, the laser beams from extended-cavity diode laser work at 795nm divide into coupling beam and probe beam. By doubling passing two AOMs the frequency of the probe beam is shifted up 6.8GHz relative to that of the coupling beam, the probe and the coupling beams drive the transitions 5S1/2, F=1 to 5P1/2, F'=1 and 5S1/2, F=2 to 5P1/2, F'=1, respectively. By using electromagnetically induced transparency (EIT) dynamics we realized the storage and release of the probe pulse in 87Rb cold atoms.3) In optical pulse storage experiment in 87Rb atomic medium, study the retrieval signal as a function of the power of the coupling beam and the phenomenon of collapse and revival of the retrieval signal under the condition of ambient magnetic field. By using optical pumping the atomic population is prepared into desired single zeeman sublevel, then the four level ideal tripod system is constructed. In the atomic system we realized the dual-channel storage and release of optical pulse.