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This thesis is studying how to use the spontaneous four-wave mixing effect of atoms and laser light to generate biphoton with high signal-to-background ratio. The feature of this research is that it uses hot rubidium vapor cell without laser cooling mechanism and timing control. A photon pair with narrow linewidth can be produced.
Since the medium used is hot rubidium atom vapor, there are many background sources in this experimental system. We first successfully reduced the background signal by using hyperfine optical pumping (HOP) and paraffin coating. However, HOP also caused a lot unknown phenomenon. In the first two chapters of this thesis, theoretical analysis is used to understand the impact of HOP on the system. The third chapter mainly introduces the experimental system, the fourth chapter improves the signal-to-background ratio by about 100:1 by optimizing various experimental parameters, and the fifth chapter introduces a tentative analysis to explain the cause of the two-photon signal waveform. The sixth chapter re-optimizes the parameters of HOP, reduces the damage of HOP to the EIT spectrum,and achieves the temporal width of biphoton of up to 550ns.
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