Subwavelength plasmon solitons in a one-dimensional chain of coupled metallic nanorods

We investigate analytically the subwavelength plasmonic lattice solitons excited in an optical plasmonic waveguide consisting of a chain of nanorods embedded in a Kerr nonlinear optical medium with strong near-field interactions. A nonlinear lattice equation with onsite and intersite nonlinear terms describing the plasmon wave propagating along the chain is derived. Stability analysis predicts that modulation instability can occur and that, correspondingly, conditions for localized modes will exist. We analyze the nonlinear excitations for genuine discreteness and nonlinearity enhanced by the fields strongly confined in the nanosized dielectric gaps. Based on a quasidiscreteness approach, we obtain a nonlinear Schrödinger equation and find that the system supports bright and dark soliton solutions in different frequency bands. It is also shown that the existence of different solitons depends strongly on the type of nonlinearity of the embedded medium.