Experimental Study Of Coherent Manipulation In ⁸⁷Rb BEC With The Phase Difference Of Double Stimulated Raman Adiabatic Passage

This article mainly elaborates on two aspects of work.1.Use dark magneto-optical trap technology to avoid light-assisted collisions,reduce atom loss rate,optimize atom density,and finally realize Bose-Einstein condensate.First,the atoms are loaded in the dark magneto-optical trap and then compressed magneto-optical trap,optical glue,optical pumping,magnetic transfer,radio frequency evaporation and optical trap evaporation technology are used,and finally Bose-Einstein condensate is trapped in the infrared far detuned optical dipole trap.2.On the basis of BEC,the principle of dual Raman relative phase manipulation coherent transition is experimentally studied.In this paper,two pairs of far detuned Raman lights are used to act on the two ground state hyperfine energy levels of ⁸⁷Rb atoms|1,1?and|1,0?.By indirectly changing the phase of one of the Raman lights,the two pairs of Raman lights can be fine-tuned the relative phase of light,observe the relationship between the layout number of the two quantum states and the relative phase of the two pairs of Raman lights,and control the relative phase difference of the two pairs of Raman lights to realize the regulation of the Raman coupling strength.In the design and construction of the dark magneto-optical trap,the article innovatively uses a combined cone lens to generate a hollow beam.In experiments,the design scheme is used to obtain the hollow repump light and depump light to form a dark magneto-optical trap.The design scheme uses the advantages of the conical lens to reduce the power loss of the repump light,improve the utilization rate of the repump light,and further capture a sufficient number of atoms.Under the action of the depump light,the atoms are prepared to the dark state as much as possible to avoid the loss of atoms caused by the light-assisted collision effect,and further increase the atomic loading density.Compared with the conventional magneto-optical trap,the number of ⁸⁷Rb ultracold atoms of the Bose-Einstein condensate was finally increased from1.8×10⁶ to 4.1×10⁶ in experiments.The technical scheme of hollow beams has been further developed,the number of ultracold atoms has been increased,the technology of traditional dark magneto-optical trap has been updated,and the application prospects of hollow beams in ultracold atoms have been expanded.In the experimental research of the dual Raman relative phase controlled coherent transition,we use the Ti:Sapphire laser output far detuned pulse Raman light to act on the ground state hyperfine energy levels|1,1?and|1,0?.First,a pair of far detuned Raman lights are applied to ⁸⁷Rb atoms,and the phase difference of the pair of Raman lights is changed to observe the change in the number of atoms in the quantum state|1,0?,and it is found that the atoms are in the number of atoms in the quantum state|1,0?basically unchanged,theoretical analysis found that the phase difference of a pair of Raman light interacting atoms is normalized and does not affect the Raman coupling strength;then two pairs of far detuned Raman lights are used to interact with a three-level atomic system,and two pairs of Raman light are experimentally observed.The relationship between the relative phase of Raman light and the number of atoms in the quantum state|1,0?has developed a new method that uses the relative phase difference of two pairs of Raman lights to accurately control the Raman coupling strength,which provides an effective way for light to manipulate atoms.