Nanoscale metal waveguide arrays as plasmon lenses

Propagation of surface plasmon polaritons (SPPs) through a set of nanoscale metal waveguide arrays (MWGAs) is numerically simulated by using the finite-difference time-domain method. The results reveal that MWGAs show an interesting lens effect on SPPs: SPPs can be strongly focused or defocused by the MWGAs, which we attribute to anomalous coupling of SPPs in MWGAs. Our results imply interesting potential for MWGAs in, for example, nonlinear optics, optical imaging, and nanosensing.