Laser Cooling And Trapping Of Strontium Atoms

Laser cooling and trapping Cs fountain clock with a frequency uncertainty of 10"15 is cuurently the most accurate primary frequency standard. Optical clock has the potential to reach an uncertainty of 10-18, more than 100 times better. In the 17th CCTF, the 5s2 1S1-5s5p 3P0 transition of Strontium atom was recommended to be one of the secondary definition of the SI base unit "second". Most possibly, the Cs fountain clock time and frequency standard will be re-defined with the optical clock in the near future.This thesis summarizes our preliminary experiments about laser cooling and trapping of Strontium atoms, which are very important steps for the study of strontium optical lattice clock. The 1S0-1P1 transition which is used to pre-cool the strontium atoms has a natural linewidth of about 32 MHz, and the wavelenth is about 461 nm. The atoms beam is slowed down from 400 m/s to less than 50 m/s with a spin-flip Zeeman slower. The slow atoms are trapped in the blue Magneto-Optical Trap (blue MOT), and the atoms number in the trap is 10 times more with 2D collimation laser and repumping lasers. There are more than 108 atoms in the trap with a lifetime about 355 ms. The temperature measured with Time-Of-Fight (TOF) method is about 2-3 mK. About 20% atoms in the blue MOT are transferred to the red MOT with 689 nm laser. The atom cloud images are taken by a normal CCD with absorption imaging method and by an EMCCD with fluorescence imaging method. The TOF method is used to calculate the temperature of the atoms in the red Mot, the approximate temperature is about 18μK.