Mirror-based Lau setup used for telecommunications

By using Lau effect, we generate an array of spatially coherent point sources from incoherent light. Spatial coherence can be generated by periodic selection of the input light sources. Lau used a source of extended light and two amplitude gratings of identical periods, separated by a distance of the quarter Talbot distance, to provide coherent light. Because of the two successive blocking elements, most of power is lost. To significantly reduce these power losses, we introduce three modifications. First, the losses caused by the first grating are totally eliminated when we use a periodic structure of incoherent point sources. Such structures can be offered by vertical cavity surface emitting lasers or by a microlens array illuminated by an extended light source. Second, to further improve the power efficiency of the system, we modify the geometry of the second grating. Finally, we use a mirror system to collect the light rays that are lost in the initial Lau setup. This approach is of nature to open the perspectives towards all the applications of the coherent spatial Talbot effect.