Discrete diffraction in two-dimensional arrays of coupled waveguides in silica

The propagation of light in 5x5 and 7x7 cubic lattices of evanescently coupled waveguides is investigated for the first time, to the authors' knowledge. The results reveal ideal discrete diffraction and demonstrate the excellent quality of the waveguide arrays, which were manufactured in fused silica by femtosecond-laser-induced refractive-index modifications.