Resonator mode in chains of silver spheres and its possible application

A transversal mode with zero group velocity and nonzero phase velocity that can exist in chains of silver nanospheres in the optical frequency range is theoretically studied. It is shown that the external source radiating a narrow-band nonmonochromatic signal can excite in the chain a mixture of standing and slowly traveling waves. The standing-wave component (named the resonator mode) is strongly dominating. The physical reason for such a regime is a sign-varying distribution of power flux over the cross section of the chain. A possible application of the resonator mode for evanescent-wave enhancement and for subwavelength imaging in the visible is discussed.