使用亚波长光栅器件产生圆柱型矢量光束

基于严格矢量衍射理论，分析了亚波长光栅将圆偏光转化为线偏光的机理。根据分析的结果提出了一种利用光栅空间分布控制出射光偏振态分布的方法，并使用该方法规设计了一类光栅区域呈多带环形分布的偏振器件。通过改变该型器件的环形光栅区域数量，可以得到不同的偏振光束。通过对出射光束使用Richards-Wolf矢量衍射法进行数值分析，得到了在大数值孔径条件下，聚焦光束在焦点附近的归一化光强分布。其中大多数出射光束的焦点光强分布为平顶光斑，光斑的最大径向半高全宽达到了1.541 。与同数值孔径下线偏光、径向偏振光及角向偏振光的聚焦光强分布具有明显区别。

Generation of cylindrical vector beams by using subwavelength grating polarizer

Based on the rigorous vectorial diffraction theory, the mechanism that the subwavelength gratings convert circular polarized light into linear polarized light was analyzed. Based on the analysis results, a design method of controlling polarization state of output beam with grating spatial distribution was proposed. Using this method, several subwavelength grating polarizers with annular gratings areas were designed. By changing the number of the annular gratings areas, different type of cylindrical vector beams can be obtained. Using the Richards-Wolf vectorial diffraction method, the amplitude and intensity distributions of the different components in the vicinity of focus were calculated on high numerical aperture condition. Most of the intensity distributions in the vicinity of focus were flattop distributions. The full width at half maxima of intensity is 1.541 in radial direction. Compared with other type of beams such as linearly polarized beam, radially polarized beam and azimuthally polarized beam, the optical performances of the output beams from the polarizers designed in this research are distinctly particular.