Long ranging and weakly confined surface plasmon polaritons via free space excitation

Surface plasmon polaritons (SPPs) on a planar metal/dielectric interface can confine the electromagnetic energy beyond diffraction limit at the cost of a small propagation length, which is typically of micrometer scale in the visible regime. This paper investigates the possibility to increase the propagation distance via metamaterial whose dielectric constant can be designed at will. It is found that the longer propagation distance due to the smaller dielectric constant is accompanied with a larger decay length into the dielectric. Furthermore, three simple configurations via free space coupling technique were proposed, while the end-fire excitation can also be applied efficiently. This work has a potential application to channel energy over large distances between different plasmonics components in the future design of integrated photonic chips and circuits.