Metal nano-strip optical resonators.

Rectangular gold and silver nano-strips embedded in glass or water are considered as optical resonators. Their scattering cross section and field enhancements in the case of p-polarized plane-wave illumination are analyzed using a surface integral equation method. Peaks in the scattering spectra are shown to be related to the resonant excitation of forward and backward travelling short-range surface plasmon polaritons in thin metal strips. The influence of angle of incidence and strip thickness on resonances is investigated. Finally, we consider the possibility of obtaining large local fields in a narrow (5nm) gap between two metal strips by taking advantage of the plasmon field distribution and boundary conditions, demonstrating the feasibility of at least 10-fold field magnitude enhancement.