Research On Manipulating Spin Texture In Ultracold Atoms By Laguerre-Gaussian Beam

In recent years,the study of the two-photon Raman process in the regulation of atomic internal populations and their coherent coupling with external motion degrees in ultra-cold atomic gases has been vigorously developed,using a pair of coherently propagated Gauss or Laguerre.The transition between Gaussian-mode Raman-driven ultra-fine magnetic energy levels has been used as a technical method in the study of various quantum novel characteristics based on ultra-cold bosons and fermions.Gaussian mode with orbital momentum And the Raman light of the Laguerre Gaussian mode(LG light)with the orbital angular momentum can realize the coupling between the internal atomic state and the external translational and rotational degrees of freedom,namely spin-orbit coupling(SOC)and spin.-Orbital angular momentum coupling(SOAMC),which can be used to study the ground state phase diagram of the system,and reveal novel quantum phases such as spin-polarized sigmoid and spin-balanced vortex-anti-vortex.Our experimental platform completed the preparation of Bose Einstein condensate in the early stage,and recently realized the spin-orbit angular momentum coupling in experiments.At present,we are focusing on the preparation and research of spin texture such as sigmite.During the master's degree,some work was done mainly on the construction and maintenance of the experimental platform of spin-orbit angular momentum coupling and the theoretical calculation of spin texture.The main work of the paper is as follows:First:Design and manufacture a set of optical power stabilization system for the experimental platform.After the beam is split by PBS,it enters AOM frequency shifting.After PD collects optical signal,it enters PID circuit for feedback modulation,outputs feedback signal to AOM,and adjusts power through AOM..Second:Programming calculates the magnetic field strength and gradient of the square and circular Helmholtz(anti-Helmholtz)configuration coils,and uses this to guide the coil and the experimental platform to control the current and the number of layers of the coil.Thirdly,Two sets of spatially coincident vortex lights were fabricated using the Q-plate and confirmed it carry a defined angular momentum,which is related to the q-value of the Q-plate.Then acting on the atom cloud,confirming the feasibility of transferring angular momentum from vortex beam to atom.Fourth,caculatethe dynamic oscillation process of the excited transition of the atomic hyperfine structure driven by the two-photon process.The light intensity distribution and the atomic group distribution are considered,and the oscillation time and the optical detuning amount are adjusted by the difference of the oscillation frequency in the space of the atomic group.Theoretically,in the case of far detuning,the spin texture of the sigmoid of the polarized phase and the ferromagnetic phase is obtained.In the process,the conditions of the experimental spot and the size of the atomic group are found,and a calibration spot is proposed.The way to waist.These work have important implications for the preparation and study of special spin textures in future experiments.