Effect Of Two- And Three-Zone Phase Masks On The Axial And Transverse Intensity Distribution Under High Numerical Aperture Focusing

Vector diffraction theory was applied to study computationally the effect of two and three-zone annular multi-phase plates (AMPs) on the three-dimensional point-spread-function (PSF). The two- and four-dimensional solutions spaces associated with a two- and three-zone AMP, respectively, were discretized and the PSF was calculated using the Wolf diffraction integrals for each unique combination of zone radius and relative phase. Conditions are identified in which a three-zone AMP generates an intensity distribution that is super-resolved by 19% in the axial direction with minimal change in the transverse distribution and sufficiently small axial side-lobes that this intensity pattern could be used for advanced photolithographic techniques, such as multi-photon three-dimensional microfabrication