Individual far-field model for photon sieves composed of square pinholes.

A photon sieve can be composed of a large number of square pinholes. By taking the related coordinate transform into account, we present here an individual far-field model for a photon sieve composed of many square pinholes whose edges are symmetrically vertical or parallel to the polar coordinate. In particular, a simple analytical expression for the diffracted far field of an individual square pinhole is given, and the focusing contribution from an individual square pinhole is further discussed. The obtained results can be used for the analysis, design, and simulation of a high numerical aperture photon sieve composed of the above-mentioned square pinholes.