S.N. Khonina, S.G. Volotovsky
The possibility analysis of subwavelength light localization and focus extending for high-aperture focusing system is carried out using vortical phase transmission function for various types of entrance polarization, including the general vortical kind.
It is analytically and numerically shown that subwavelength localization in separate components of a vector field is possible at any types of polarization. That fact is useful for considering an interaction of laser radiation with the materials selectively sensitive to various components of an electromagnetic field.
Definite types of polarization are necessary for formation of essentially subwavelength details in the total intensity just as additional apodization for pupil function, for example, a narrow ring. The optimum choice of the ring radius allows to reach the compromise between depth of focus and the size of a focal spot.