Study On Tight Focusing And Focal Spot Shaping Of Hybridly Polarized Vector Beams

The important characters of light like frequency,amplitude and phase have been deeply study.In recent years,the polarization state of light has become a hot spot for people to study,especially the research for non-uniform polarization vector beam has aroused great interest in the researchers.In virtue of its unique focusing characteristics and potential application value cylindrical vector beam which is the basic and simple vector beam has been widely studied.For example,the radially polarized vector beam through the high numerical aperture lens will have a very strong longitudinal field,and it has a prominent application in the super-resolution focus,optical storage,lithography and other fields.In addition to the cylindrical vector beam,researchers recently generated a localized linearly polarized vector beam and a hybridly polarized vector beam which contain linear polarization,circular polarization and elliptical polarization,which make the vector beam more rich and provide a possibility for generating novel focusing characteristics.In this paper,one kind of hybridly polarized vector beams as the research object,the focusing characteristics of radial-variant hybridly polarized vector beams and azimuthal-variant hybridly polarized vector beams are studied respectively.Then the focal spot shaping of radial-variant hybridly polarization vector beams is studied by annular aperture and binaryphase element respectively.The main research contents are as follows:1.The theoretical basis of the research in this paper--Richards-Wolf vector diffraction theory is introduced in detail.On the basis of this,the expression of the light field in the post focusing region of linearly polarized light passing along the X direction and along the Y direction through a high numerical aperture lens is given.2.Based on the Richards-Wolf vector diffraction theory,deduce the electric field of three polarization components expressions that radial-variant hybridly polarized vector beams and azimuthal-variant hybridly polarized vector beams are focused tightly by the high numerical aperture lens tightly focused in the post focusing region.According to the expressions,Using the MATLAB simulates the intensity distribution of two kinds of hybridly polarized vector beams tight focal area,and effects of various parameters are studied on the two kinds of hybridly polarization vector beam tight focusing characteristics.3.Study on focal spot shaping of radial-variant hybridly polarized vector beams.First,Using an annular aperture modulates the radial-variant hybridly polarized vector beam.After focusing,the needle-like focus is obtained in the focal area.Then we study the different radial index parameters of the optical needles.In order to improve the utilization of light energy,using the binary phase element modulates the radial-variant hybridly polarized vector beam with radial index 1 to obtain the optical needles,and study the parameters of the optical needles obtained by the binary elements with different rings.Finally,the rotation phenomena of the light intensity distribution pattern in the cross section of the optical needle formed by the two methods are studied.