High-contrast self-imaging with ordered optical elements
  Creating arbitrary light patterns finds applications in various domains including lithography, beam shaping, metrology, sensing and imaging. We study the formation of high-contrast light patterns that are obtained by transmission through an ordered optical element based on self-imaging.By applying the phase-space method, we explain phenomena such as the Talbot and the angular Talbot effects. We show that the image contrast is maximum when the source is either a plane wave or a point source, and it has a minimum for a source with finite spatial extent. We compare these regimes and address some of their fundamental differences. Specifically, we prove that increasing the source divergence reduces the contrast for the plane wave illumination but increases it for the point source. Also, we show that to achieve high contrast with a point source, tuning the source size and its distance to the element is crucial.We furthermore indicate and explore the possibility of realizing highly complex light patterns by using a periodic transmission element. These patterns can have more spots in the far field than the number of diffraction orders of the periodic element. We predict that the ultimate image contrast is smaller for a point source compared to a plane wave. Our simulations confirm that the smallest achievable spot size in the image is imposed by diffraction regardless of the imaging regime. Our research can be applied to similar domains e.g. quantum systems. 
Ali Naqavi, Hans Peter Herzig, Markus Rossi
physics.optics