Tight focusing of high order axially symmetric polarized beams through a dielectric interface

Based on vectorial diffraction theory, the tightly focused field expressions of axially symmetric polarized beams (ASPBs) through a planar interface between materials of mismatched refractive indices which produces spherical aberration are derived, and the numerical results for two interface-focusing optical systems, namely, air–glass and air–silicon are also presented. First, the electric field intensity distributions near focus are numerically calculated. Then, the focal shift, and the lateral and axial FWHM of focused spots are computed for different numerical apertures of the focusing lens and probe depths. These results show the influence of the produced spherical aberration on focused field distributions, which should be considered in some practical applications of ASPBs, such as in the optical trapping, microscopy and semi-conductor inspection.