Research On Focusing And Propagation Of Vector Light Field Generated By Resonator

The polarization state is one of the most important properties of the beam.Vector beams with non-uniformly distributed polarization states have important applications in high resolution microscopy,optical trapping,optical and quantum communications,quantum memories,laser manufacturing,and nonlinear optics.The generation and delivering of arbitrary three-dimensional polarization states through the focus of a high numerical aperture lens has become a topic of current interest.When a radially polarized cylindrical vector beam is delivered through a high-NA lens,a strong longitudinal field component is generated,contrary to the case of azimuthally polarized beams that features a transverse annular focal region with no longitudinal field component,due to the special axisymmetric polarization distribution.In addition,since the polarization state can record more information,the transmission characteristics of the vector beam have also attracted the attention of researchers.Atmospheric turbulence effects such as beam intensity fluctuations(atmospheric flicker),phase fluctuations,and beam expansion are inevitable when the beam is transmitted in the near-earth range.To record and transmit information using the polarization state,it is necessary to study the effect of atmospheric turbulence on the polarization state of the beam.Based on the theory of resonator,combined with Richards-Wolf vector diffraction theory and atmospheric turbulence theory,the tight focusing characteristics and atmospheric turbulence transmission characteristics of vector light field generated by polarization-sensitive cavity are studied.Firstly,the calculation method of the polarization-sensitive cavity is studied.The output modes of the passive cavities are studied by numerical simulation method.The effective Fresnel number of high-purity low-loss vector fundamental mode of the cavity output is determined to be 1?2.1.Next,the tight focusing characteristics of the vector field generated by the polarization-sensitive cavity are studied.The Richards-Wolf vector diffraction integral model is used to numerically calculate the focal field distribution of the radially polarized beam,the angularly polarized beam and the converted mixed vector beam produced by the polarization-sensitive cavity under the condition of high numerical aperture lens focusing.The focus field is analyzed with cavity parameters,focusing parameters as well as amplitude and phase regulation of the light field.In addition,the focal spot size of 0.17?~2 of radially polarized beam is obtained on the condition of tight focusing and amplitude-controlled,which is consistent with the known experimental results.By reducing the effective Fresnel number of the polarization-sensitive cavity,introducing a 0?2? vortex phase difference,inserting an annular stop(blocking the axial center portion of the incident beam)and increasing the numerical aperture of the focus lens can reduce the focus spot effectively.Finally,the Huygens-Fresnel diffraction integral formula and the atmospheric turbulence random phase screen model are used to numerically simulate the free propagation and the atmospheric turbulent transmission of the cylindrical vector beam.The variation of polarization state with transmission distance and the influence of turbulence scale on polarization state are analyzed.