Analytical model of the field of super-resolution focal spot based on sink-source model

The expressions of non-paraxial tightly focused vector beams propagating along a certain direction are given based on the sink-source model by using the spatiotemporal translation technology. The singularities on the beam waist plane are eliminated in the model. The field of a super-resolution focal spot with strong axial electric field component can be simulated by the model. The full width at half maximum (FWHM) of the intensity of focal spot where the field can be simulated by the model can be as small as 0.44 wavelength. The FWHM information of focal spot is preserved in the sink-source model. The refocusing phenomena of a focal laser spot by the 4f optical imaging system is also studied. The change of FWHM of an initial focal spot can be reflected from the refocused spot.