Plasmonic lattice solitons beyond the coupled‐mode theory

The existence and properties of plasmonic lattice solitons (PLSs) supported by periodic arrays of metallic nanowires embedded into a dielectric medium with Kerr nonlinearity are studied by solving the 3D Maxwell equations, and the conclusions are compared with the results predicted by a coupled‐mode theory analysis. It is found that these two methods predict markedly different characteristics for the optical power of PLSs and its dependence on the separation distance between adjacent nanowires. In particular, the coupled‐mode theory is found to be valid only when the distance between nanowires is larger than some characteristic length. The compensation of modal loss by a background optical gain is also studied and it is revealed that the gain coefficient required to balance the loss is much smaller than the loss parameter of the metallic components of the plasmonic array.