Generation And Regulation Of Spotlight Focused Light Field

Vector beams are light ones with in-homogeneous status of polarization, which have different status of polarization in the different positions of the wave front at the same time. The concept is proposed based on the scalar beams, such as linearly polarized beam, circularly polarized light beam, partly polarized light beam and elliptically polarized light beam which are scalars with the homogeneous status of polarization. The homogeneous status of polarization had been given much attention in the past researches, but for the vector beams, the distribution of polarization is different on the varied special position, the unique property of vector beams leads to the emergence of many latent applications value. Therefore, many people attach great importance to the researches and application prospects about the characteristics of vector beams. The main contents of the paper are as follows:(1)The concept, classification, significance, current development and application prospects about the vector polarized beam are introduced in the first section.(2)The concepts of the apodization function under the sinusoidal and the Helmholtz conditions, Richards-Wolf vector diffraction integral model are introduced. And the mathematical integral formula of vector polarized beams with high numerical aperture focusing in cylindrical coordinates is also introduced.(3)The concept, research progress, main feature and application of the diffractive optical element(DOE) are introduced. Longer focal depth and smaller focal spot can be obtained by utilizing DOE to change the phase of incident beams,which means that the flat-top field distribution can be obtained with DOE.(4)Pure phase plate was used to modulate phase distribution of the radially polarized and cylindrical vector beams to investigate its focusing properties. By using Richards-Wolf vector diffraction theory, the simulation results show that one or two optical bubbles of stronger light intensity around dark spots can be obtained for the incoming radially polarized and cylindrical vector beams with appropriate parameters.(5)Pure phase plate and complex amplitude DOE are designed to modulate focal field distribution of the radially polarized and cylindrical vector beams to investigate its focusing properties. By using Richards-Wolf vector diffraction theory, the simulation results show that flat-top focal field distribution with large focal depth can be obtained. And it can be concluded that the focal depth will be lager with the increasing number of concentric rings of DOE. So the multi-interval DOE has optimization effect for a flat-top energy density of light field, which has important significance for materials processing.