Optimization And Improvement Of Laser System For Bose Einstein Condensation Of Na And Rb

In condensed matter physics,the exploration of the interaction properties of light and matter is an important research field.At a temperature of the nK level.Macroscopic aggregation phenomenon of thin alkali metal atomic gases,such as Bose Einstein Condensation（BEC）and Fermi gas degeneracy.Bose Einstein Condensation（BEC）provides a more ideal experimental platform for condensed matter physics.Based on Bose Einstein Condensation（BEC）,basic physical problems such as quantum phase transition and interaction between light and matter can be studied.But the realization of BEC requires the close integration of multiple experimental module and subject,include ultra-high vacuum systems,laser cooling systems,magneto-optical traps and magnetic field control circuits,and fast and accurate timing control.Therefore,the success and stability of any module is an indispensable part and an technical challenge of BEC.This article first reviews the research history of BEC and the specific steps and related principles required to implement BEC.Secondly,I introduce the stability and frequency-locking work of the laser system of the sodium atom（^{2 3}Na）BEC experimental platform device and the helium atom(⁸⁷ Rb)BEC platform in the Q01group of the Institute of Physics of the Chinese Academy of Sciences.We designed and improved photodetectors（PD）and lock-in amplifier circuits and eliminates spurious signals and oscillations between the two circuits.Finally we get a stable single-mode laser with a bandwidth of less than 1MHz and successfully achieve atomic state transitions between atomic hyperfine structure.The improved laser system has good anti-interference ability.Mechanical vibration of the optical platform and the acoustic vibration and temperature changes in the laboratory will not cause the laser to be unlocked,and the frequency lock time of the laser will be stable for more than three hours.Then,we used two cheap slave lasers to successfully amplify the seed of two beams of 5mW and 0.5mW by a hundred mW level,which not only greatly reduced the experimental cost but also captured more atoms when the atom was captured.Finally,I used a stable laser cooling system to capture 1.4E10 sodium atoms in the MOT.Specific work includes:adjustment of semiconductor lasers,adjustment and improvement of laser frequency shifting optical path,modulation of atomic saturation absorption spectrum,improvement of laser frequency locking module,frequency shifting of acousto-optic modulator to laser,and encountered during optical path adjustment Problems and processing methods and injection locking techniques for master-slave lasers.