Optical coherence grids and their propagation characteristics.

A novel class of partially coherent light sources termed optical coherence grids (OCGs) are introduced that can yield stable optical grids in the far field. The optical grids, of which the light distributes in a network of straight lines crossing each other to form a series of hollow cages, can be seen as a better controlled optical lattice. Propagation properties of OCG beams in free space, including spectral density, transverse coherence, and M factor, are investigated in detail. It is interesting that a periodic grid pattern is produced at a distance and remains stable on further propagation, and we stress that the structure of far-field optical grids can be flexibly tuned by modulating the correlation parameters of the source. In addition, by performing convolution of degree of coherence, we also propose perfect optical coherence grids (POCG). The far-field grid pattern of POCG is in a fully controllable fashion. This work is expected to find applications in cooling atoms, trapping microscopic particles, or assembling cells, etc.