Plasmonic Lattice Solitons

Concentration and manipulation of light at subwavelength scales hasbecome a major challenging facing the development of nanophotonics.When the size of conventional optical circuits is reduced to nanoscale, thespatial confinement of light is inherently limited by diffraction.To breakthe limit, surface plasmon polaritons(SPPs), the highly localizedelectromagnetic waves at the interfaces between dielectric materials andmetallic materials, are considered as a promising solution [1–3].Nonlinear plasmoics, which explores nonlinear properties of SPPs, attractsincreasing interests, too. For example, nonlinear Kerr effect is used tobalance the diffraction of SPPs leading to the formation of spatial SPPsolitons. Note that the unique properties of SPPs enhances the nonlineareffect,which provides a possibility of active control over optical.Recently, a promising structure supporting subwavelength plasmoniclattice solitons (PLSs) was proposed, which is composed of arrays ofmetallic nanowires embedded in Kerr-type nonlinear media. In suchplasmonic structures, tunneling of SPP between adjacent metallicnanowires is inhibited by the nonlinearity of the dielectric medium andthus may form the PLSs at the deep subwavelength scales. However, thusfar the reported PLSs solutions are obtained within the framework ofcoupled mode theory(CMT),but CMT only works when the spacingbetween adjacent nanowires is large enough. Therefore, these reportedPLSs are actual solutions of the plasmonic lattice systems or not?Westudy the existence and properties of PLSs beyond CMT, by rigorouslysolving the complete set of3D nonlinear Maxwell’s equations(MEs),andcompared with the results predicted by the CMT. We find that PLSs exhibit different characteristics for their energylocalization and show unique power dependence depending on theseparations of nanowires. Besides,we also investigate the compensationof modal loss by an optical gain and revealed that the gain coefficient thatis required to balance the loss is much smaller than the loss parameters ofthe metallic component of the plamonic array.It is very important for theexperimental observation of that nonlinear model.