Fractal diffractive lenses with improved diffraction efficiency

In this paper we review the focusing and imaging properties of fractal photon sieves and Devil´s lenses designed in order to improve the diffraction efficiency of fractal diffractive lenses. It is shown that these lenses provide a smoothing effect on the higher order foci of a conventional fractal zone plate. Furthermore, the characteristic self-similar axialesponse of the fractal zone plates is always preserved. This behavior predicts an improved performance of fractal lenses as image forming devices with an extended depth of field and a reduced chromatic aberration.