In order to achieve the intensity in the vector light field applicable not far away from the laser diode when applying diffractive optics to shape the beam of laser diode,Kirchhoff diffractive theory and Fresnel approaching method under nonparaxial condition was adopted to derive out each electromagnetic component s distribution and the MATLAB language was adopted to compute the numerical result.

Based on the Collins integral formula, an analytical propagation formula of a Lorentz-Gauss beam passing through a paraxial abed optical system is derived.

In this paper,we analyse the interference of two light waves,which points out that the near-axial condition is very important,and prove that this condition has a good result in practice.