Optimization Of Magneto-optical Trap Parameters Based On Miniaturized Ultra-high Vacuum Cavity

Cold atomic physics is an important branch of modern physics.In the field of cold atom research,the acquisition of low temperature atoms is usually the first step of cold atomic physics.The preparation of cold atoms plays an important role in the whole cold atom experiments.This paper describes three commonly used methods of cold atom acquisition:magnetic traps,optical traps,and magneto-optical traps,and analyzes the capture mechanism of them.On this basis,the vacuum system for magneto-optical trap technology is introduced,the overall structure of the system and the functions of each component are elaborated.The experimental procedure for capturing low-temperature atoms in a vacuum system is introduced,and the atomic number of the captured atoms is evaluated by fluorescence collection.For the magneto-optical trap technology,the effects of push light,magnetic field gradient,geomagnetic field,laser power and detuning on the number of final trapped atoms are analyzed.Pushing light as a laser that resonates near the atom itself has a radiation force on the atom.A mechanical shutter is designed in the experiment,which can turn off the light quickly,found that the push light intermittent switch was 7 times more than the push light normally open.The magnetic field gradient of the magneto-optical trap and the geomagnetic field affect the depth and position of the magneto-optical trap.The effects of the magnetic field of the vacuum system on the number of trapped atoms,including the two-dimensional magnetic field,the three-dimensional magnetic field,and the geomagnetic field,are experimentally analyzed.According to the requirements of magnetic field gradient and magnetic field uniformity,the magnetic field coil used in the experiment was designed and optimized according to the experimental results.The cooling power in the magneto-optical trap affects the scattering force felt by the atoms,which in turn affects the number of atoms.We designed an acousto-optic frequency shift drive module based on digital frequency synthesis to achieve precise control of the cooling optical power by changing the RF output power of the drive module.It was found that after the cooling light power was greater than 5 mW,the atomic number change was no longer significant.The detuning of the cooling light in the magneto-optical trap is related to the velocity of the atom.The reference signal source for phase-locked frequency is designed and fabricated,and the precise change of the amount of cooling light is obtained by changing the frequency of the reference signal by phase-locking.It is found that when the detuning is around 8 MHz,the number of atoms is the largest.Finally,based on the above analysis,the parameters of the magneto-optical trap are optimized to increase the number of trapped atoms from7×10~6 to 3×10~7.