Laser Cooling and Trapping of Cesium Atoms

Abstract

In this thesis, the Pakistan‟s first ever magneto optical trap has been designed, developed and studied with cesium atoms in a vapor cell. Keeping the density of background cesium atoms fixed, the trap performance depends upon the magneto-optical operating parameters, i.e. the intensity and detuning of the trap laser and the gradient ⃗⃗ of the quadrupole magnetic field, since these parameters determine the radiative force ( ) acting upon the atoms. In the present work, the trap dynamics of the cesium MOT has been investigated as a function of trap laser intensity and magnetic field gradient ⃗⃗ , keeping the detuning of the trap laser fixed at an optimum value of . Assuming, that all cesium atoms of the background ( ) which enter the trapping region with velocities in the range will be trapped with a certainty of 1, it is possible to develop a model for the capture rate in terms of the capture velocity of cesium vapor cell magneto-optical trap. By experimentally measuring the capture rate as a function of trap laser intensity and magnetic field gradient ⃗⃗ and determining the capture velocity corresponding to the measured capture rate by using simulation graph, it is possible to investigate the intensity and magnetic field dependence of the capture velocity ⃗⃗ . In the present work, the capture dynamics of the magneto-optical trap has been fully investigated. Finally, the magneto-optical trap is suspected to be a stochastic dynamical system as well. Due to the random photon recoils ( ⃗ ) imparted to the atom, the radiative force has a fluctuating force superimposed upon the average force 〈 〉. As a consequence of this fluctuating force, the external and internal dynamics of the atoms become stochastic whose signatures can be found in the resonance fluorescence emitted by the trapped atoms. In the present work, by using the techniques of non-linear time-series analysis, the stochastic dynamics of atom-photon interaction in a magneto-optical trap has been investigated. In short, the conclusion of the thesis is that the magneto-optical trap promises to be an interesting non-linear quantum dynamical system.