一阶径向偏振光偏振态在光束截面呈中心对称分布。通常认为，径向偏振光聚焦时，焦点处光斑直径比空间偏振态均匀分布的光源，如线偏振光的光斑直径小，而且焦点光场具有很强的纵向分量。通过数值计算的方法对径向偏振光和线偏振光的聚焦光斑进行了研究，发现只有满足折射光线与光轴的夹角大于70°时，径向偏振光的聚焦光斑直径才会变得小于线偏振光聚焦光斑沿偏振方向的光斑直径，小于70°则相反。而线偏振光聚焦光斑垂直于偏振方向的直径始终小于径向偏振光聚焦光斑直径。另外，通过在光路中加入光阑的方法，可以进一步减小径向偏振光聚焦光斑的直径，同样的方法只能减小线偏振光聚焦光斑垂直于偏振方向的直径，而沿光偏振方向的光斑直径则不能减小。

The first order radially polarized beam is with cylindrical symmetry in polarization. It is commonly thought that radial polarization leads to the best light beam focusing in terms of spot size, and the focal spot has strong longitudinal field. Using numerical calculation method, it is presented that the focal spot of radially polarized beam which is smaller than the size along polarization direction of focal spot with linear polarized beam can be obtained, if the angle between refracted light and optical axis is larger than 70°. But the size perpendicular to polarization direction of focal spot with linear polarized beam is always smaller than that of radially polarized beam. In addition, it can lead to the smaller focal spot of radially polarized beam when an annular aperture diaphragm is inserted in optical path. But this method is not suitable for the situation of linearly polarized beam along polarization direction.