Research on the effect of waist position changing of Ince-Gaussian vectorial beam on tightly focusing characteristics

In order to research the influence of the beam waist position on the tightly focusing of the Ince-Gaussian vectorial beam, the superposition theory of orthogonally polarized even and odd modes and the Richards-Wolf vector diffraction integral theory were utilized in this study and the tightly focusing feature of the Ince-Gaussian vectorial beam at the different waist position was analyzed. The results show that under the condition of high numerical aperture focusing, the transverse field structure of the focusing field possessing distribution of light intensity and polarization state can still remain stable when the distance z_i between the beam waist position of the Ince-Gaussian vectorial field and the lens changes within a certain Rayleigh length z_R (z_i < 0.5z_R). By analyzing the phase structure of the focusing field, the reason of the instability of the transverse field structure is given when the distance z_i between the beam waist position and the lens exceeds a certain Rayleigh length z_R (z_i>0.5z_R). At the same time, the longitudinal polarization component of the focusing field, as a degree of freedom of the focusing field, can be used to construct a more abundant vector structured light field. The results can provide great value for the research of complex structure vector optical field in optical micromanipulation and optical information storage.