Photon sieve

It consists of a flat sheet of material full of pinholes that are arranged in a pattern which is similar to the rings in a Fresnel zone plate, but with the ability to bring light to much sharper focus.

[4][conflicted source][5] When the size of sieves is smaller than one wavelength of operating light, the traditional method mentioned above to describe the diffraction patterns is not valid.

Within a Fresnel zone plate, each of these sinusoidally curved transmission patterns creates a different focus, so a standard Fresnel zone plate creates a rather messy primary focus as shown in figure 4 of reference 1.

This can be achieved by punching holes of appropriate size at calculated locations as in a photon sieve.

Holes are easy to manufacture and allow you to use a binary pattern that varies radially and around each circle to make on average a sinusoidal variation, thereby eliminating other foci.