A Study On Spiraling Bessel Beams

The thesis mainly studies the generation of spiraling Bessel beam with different polarization and the transmission in free space based on the theory of paraxial approximation of beam propagation.And researches of properties of radially polarization spiraling Bessel beam propagating in free space in the case of partially coherent.The main contents include:1.The transmission properties of the azimuthally polarized spiraling Bessel beam are studied by combining the spiraling Bessel beam with the azimuthally polarization characteristics.Based on the Collins formula,the intensity expression of the azimuthally polarized spiral Bessel beam is deduced.The MATLAB is used to simulate the cross-section intensity distribution.The propagation properties of the beam and the influence of the position of the dark core on the polarization state of the beam have been investigated.It is found that,by the theoretical analysis and numerical calculation,in a certain transmission region,the azimuthally polarized spiral Bessel beam is an offaxis spiral transmission of the hollow beam around the optical axis,and the divergence angle of the beam is zero;the polarization state of the beam follows the position of dark core position moves.2.The transmission characteristics,the change of the polarization state and selfreconstruction characteristics of the beam during transmission are studied.Based on the generalized Huygens-Fresnel diffraction theory,the intensity expression of the radially polarized spiral Bessel beam is derived.Substituting into MATLAB for the calculation of its intensity distribution,polarization state change and light intensity distribution after sector obstacles It is found that,by the theoretical analysis and numerical calculation,when the radially polarized spiral Bessel beam is transmitted in free space,the beam is spirally transmitted around the optical axis in the form of a hollow beam and the divergence angle of the beam is zero in a certain transmission region.In addition,the characteristics of radial polarization are maintained during the transmission process.The off-axis spiral transmission characteristic is always maintained and the energy conservation law is followed in the self-reconstruction process of the beam.As the transmission distance increases,the energy originally disappeared in the occlusion region is gradually diffracted to the opposite position of the obstacle occlusion area.3.The spiraling Bessel beam properties combined with radially polarization and partially coherence have been studied in this paper for the first time.Based on the crossspectral density and the unified theory of coherent and polarization,the intensity expression of the radially polarized partially coherent spiral Bessel beam(RPPCSBB)can be significantly deduced.The propagation properties of the beam have also been investigated.The RPPCSBB transmits in a spiral path with a fixed distance in free space by the theoretical analysis and numerical calculation.During the transmission,the beam gradually evolves from a spiraling hollow beam to a spiraling Gaussian beam,and the transmission distance is related to the coherence length.The corresponding beam polarization angle and degree are also related to the spiral radius and the transmission distance,and the polarization degree relates to the coherence length.However,the coherence length,transmission distance,and the spiral radius do not affect the distribution of the beam polarization ellipticity.