The Second Stage Cooling Of ⁸⁷Sr And The Observation Of Atomic Coherence In Triplet Of ⁸⁸Sr

Strontium optical clock has great significance in scientific research and applications and it could be the candidate of next generation time and frequency standard.Among the four isotopes of strontium atoms, ⁸⁷Sr and⁸⁸Sr are used to be an optical reference and are investigated to our knowledge worldwide.This thesis mainly describes two parts,one is to optimize the optical clock system,to achieve the ⁸⁷Sr atom cooling,and the atomic group parameters were measured.Besides,in this paper,the ⁸⁸Sr atomic coherence experiments of triplet double coupling field are carried out,and the electromagnetic induced transparent linear shape is observed,and it provides reference for the development of strontium optical clock.In particular:Firstly,according to the ⁸⁷Sr atom cooling mechanism,we have optimized the optical clock system,and completed the second stage cooling of ⁸⁷Sr.In particular,the atomic structure of ⁸⁷Sr is analyzed briefly.Based on the analysis results,the experimental system is re-established,including the optimization of strontium oven,Zeeman slower,magneto-optical trap cavity and Helmholtz coil.Besides,the temperature control software based on LabView of the heating oven is designed.In the first stage cooling experiment,the isotope shift of 461 nm laser was corrected and the frequency scanning range of 707 nm laser were increased.Finally,The temperature of ⁸⁷Sr atom was cooled to about 2mK,and the number of atoms was 3×106.In the second stage cooling experiment,a 689 nm Stirring laser was added,allowing the atoms to be rapidly homogenized between the magneton levels.Meanwhile,the cooling sequence was adjusted and a narrow linewidth laser was used to cool the atoms.After secondary cooling,the temperature of strontium cold atoms was about 9μK,and the number of cold atoms was on the order of 105,which satisfied the requirements of optical lattice loading.Secondly,the electromagnetically induced transparent effect of the umbrella-type five-level structure under the triplet double coupling field is observed by using the ⁸⁸Sr atom after the secondary cooling in the magneto-optical trap.In the experiment,the Pound-Drever-Hall frequency stabilization technique was used to narrow the line width of the pump light from 1 MHz to 230 Hz.The pumped light power was amplified to 10 mW by injection locking technique.The detection light power fluctuation was controled under 1.5 × 10^-3,and then observed the electromagnetic induced transparent linear.Finally,the result proved that the detuning of the coupled light has a great influence on the transparency of the triplet electromagnetic induction,and the electromagnetic induced transparent linearity of the umbrella type five-level structure is two Λ-type structure electromagnetic induced transparent superposition,which provides a reference for the coherence experiment of alkaline earth metal atoms,the analysis of strontium atomic energy level and the development of strontium optical clock.