Design Of Radially Polarized Beams Optical System

In the past two decades,the research about cylindrical vector beams has developed rapidly,especially radially polarized beams.Unlike the more common linear and circular polarized light,the polarization of a radially polarized beam is non-uniformly distributed: its polarization direction is symmetrical about the optical axis and always follows the radial direction;and it is also a hollow beam.This unique polarization characteristic and spot pattern has attracted the scholars' widespread attention,and the corresponding research has also proved that radial polarized beams may have obvious advantages in the fields of particle manipulation,laser processing,lithography,and optical storage.The main research content of this paper is the problem of the generation and detection of radial polarized beams.In terms of generation: At present,the methods for generating radially polarized beams can be divided into the following five types: axial birefringent element method,axial dichroic element method,beam shaping method,interference superposition method,and low-mode fiber method.The article briefly analyzes the typical examples of these methods and compares their advantages and disadvantages.Based on this,a method of using a combined half-wave plate and a combined linear polarizer to convert linearly polarized light into radial polarized beams outside the cavity is proposed,which has the advantages of simple structure,flexibility,reliability,and low cost.Among them,the combined half-wave plate is used to realize the ? phase difference of linear polarization in the symmetrical region of radial polarized beams,and the combined linear polarizer is used to achieve the radial distribution of the electric field vector of its optical cross section.In terms of detection: First,the polarization distribution of the output beam of the system was detected by a rotating polarizer method;then the theoretical polarization purity at different numbers of the combined linear polarizer was derived,and the classic Stokes parameter was used.The actual purity of the output beam obtained by the measurement method is 80.5%,which is very close to the theoretical value of 81.6%.Finally,the phase difference of the linear polarization of the symmetric region of the radially polarized beams is qualitatively detected based on the Mach-Zehnder interference principle.A quantitative detection scheme is also given.