Study Of The Spatial Coherence Based On Laser And Atoms Interaction

Research on the interaction of light with atoms has been an important subject of quantum optics and atomic physics.The research achievement of various light field which interact with different nature of atoms has been widely used in scientific research and in all areas of our life.This paper mainly focused on experimental study about partially coherent laser which interact with Rubidium atoms. The purpose of the study was to recognize the variance of spatial coherence of laser.Therefore we use laser with different spatial coherence to interact with Rubidium atoms of different states.We used LiNbO3 to achieve electro-optical phase modulation. We pressed a high voltage on the crystal of LiNbO3 with a high frequency to produce partially spatial coherent laser.We generated interference fringe based on Young-type double-holes device, so that we could analyze the spatial coherence of laser by calculating the visibility of fringe pattern. By controlling the magnitude and frequency of voltage across the crystal we obtained laser with different spatial coherence.In order to analyze the interaction of partially spatial coherent laser with the rubidium atoms, we allowed the modulated laser pass through a rubidium cell which was temperature adjustable. We analyzed the variance of the spatial coherence which the partially spatial laser with different frequency and different polarization interacted with rubidium atoms of different states. Furthermore, we also studied the variance of the spatial coherence of laser after interacting with polarized atoms.The results showed that the spatial coherence of a totally coherent laser would decrease with the increase of rubidium temperature, mainly because when the temperature increased, the interaction became violent which enhanced the fluorescence radiation of atom, and the inhomogeneity of refractive index of atomic medium increased, so that the magnitude of the additional phase became larger, therefore, the spatial coherence of a totally coherent laser decreased. However, the spatial coherence of a partially spatial coherent laser would increase after interacting with rubidium atoms, because the coherent photons of stimulated emission was superimposed to the original laser, causing the laser spatial coherence became better. The spatial coherence of a partially spatial coherent laser with different frequencies and polarization would change in a different degree after interacting with rubidium atoms. Atomic polarization substantially had no effect on the spatial coherence of the laser, but the magnitude of the magnetic field would affect the absorption of laser.Finally, we summarized the problems that the experiments may exist and did some discussion about how to analyze the phenomena of the experiments theoretically.