Comparison of focusing properties of conventional and diffractive lenses

Abstract

We compare focusing properties of conventional lenses and diffractive lenses (DLs). To that end, we use a converging electric-dipole wave as a model of an optimal converging wavefront that emerges from a conventional lens system. Our numerical results show that DLs have better focusing properties than conventional lenses for f-numbers less than 1. Although both types of lenses give nearly indistinguishable co-polarized intensity components in the focal region at low f-numbers, DLs provide much lower longitudinally polarized components. However, at sufficiently low Fresnel numbers and high f-numbers DLs fail to provide a well-focused energy distribution.