Experimental Study On Laser Pattern Formation In Rubidium Atomic Thermal Vapor

There are abundant nonlinear effect in atomic vapor,both Kerr effect and four wave mixing is especially important.The two phenomena have being a hot topic for nonlinear optics from the set up of the nonlinear optics to the present.In 1970,D.Grischkowsky firstly studied the self-focusing effect in Rubidium atom vapor,then many international made large quantity of work on the nonlinear effect of all kinds of atoms.In the above researches, the pulse laser is always chosen as the laser source until Bennink et al firstly used the CW dye laser to study the sodium atom vapor and gave the theoretical explanation.In this thesis,the phenomenon of laser breaking up into filaments induced by the strong nonlinear Kerr effect in the near-resonant Rubidium atomic vapor was studied when the continuous wave laser beam which has transverse Gaussian distribution singly passes through the atomic vapor,and the regular mode pattern arising from the coherent superposition of the diffraction of filaments has been observed.We also studied the influence input power of laser,the temperature of the vapor cell and the frequency detuning of pump light relation to ⁸⁵Rb D₂ line on the mode pattern.Due to hyperfine splitting of Rubidium atoms,there is four-wave mixing in thermal Rubidium atomic vapor related to the third-order nonlinear effect,the Raman gain of he Stokes and anti-Stokes and anti-Stokes photons was observed by sweeping the frequency of the probe beam.This thesis mainly consists of the following parts:In the first part of this thesis,the basic nonlinear theory for the propagating of laser through the atomic vapor.In the second part of this thesis,an introduction for the model of self-focusing in the nonlinear media,and the theoretical deduce about the model of self-trapping.In the third part of this thesis,we will introduction to the experimental setup. In the fourth part of this thesis,we will present the experimental results and analyze them.Finally,we will give some conclusions about this thesis.