The Study On Squeezed Light With Frequency Matching On The ¹³³Cs Absorption Line By Using Four Wave Mixing

The dual electromagnetically induced transparency（dual EIT）system can effectively inhibit secondary absorption of frequency near atomic resonant transitions due to its stronger quantum coherence than EIT.In this thesis,based on dual EIT atomic system,the intensity difference squeezing light generated by the enhanced degenerate four-wave mixing（FWM）and the quadripartite light field generated by spatially multiplexed cascaded FWM are investigated experimentally and theoretically.The main research work includes the following three parts:Part 1:The enhanced degenerate FWM in the dual EIT system is studied.The double-sided Feynman diagram is used to solve the correlation density matrix element describing the FWM to obtain the theoretical simulation of the FWM enhancement under the manipulation of the decorated light field,and the cesium gas chamber is used to demonstrate the occurrence of enhanced degenerate FWM in the dual EIT system under the hyperfine transition of its D1 line.Part 2:The intensity-difference squeezed light in ¹³³Cs atomic absorption band generated by enhanced degenerate FWM in the dual EIT system is studied.Firstly,the detection method of squeezed light is analyzed.Then,by manipulating experimental parameters such as phase matching angle,atomic vapor temperature,optical field frequency,and pump power,the intensity noise of the twin-beam generated by the enhanced degenerated FWM process is measured.The intensity-difference squeezing of-3.32 d B near the atomic resonance is obtained successfully.The effects of different experimental parameters on the degree of squeezing and FWM gain are also studied.Part 3:The quadripartite amplified light field generated by spatial multiplexing cascaded FWM in dual EIT system is studied.Under the experimental system in Chapter2,it is found when two EIT windows are completely overlap,the system has very strong quantum coherence,which can excite four different FWM processes in a single cesium atom vapor at the same time,and quadripartite amplified light field with spatial separation is observed.A theoretical study of spatial multiplexed cascaded four wave mixing is carried out by using the double-sided Feynman diagram of light-atom interaction.According to the possible transition path and phase matching,degenerate FWM with single-pumping and non-degenerate FWM with double-pumping are analyzed respectively.By calculating the third order perturbation term of the density matrix element and considering the Doppler effect caused by atomic motion,the gain spectra of degenerate FWM and non-degenerate FWM are simulated respectively.