Optical tunneling effect of surface plasmon polaritons and localized surface plasmon resonance

Surface plasmon resonance of periodic narrow-grooved metallic thin films were studied with finite-difference time-domain simulations. Two distinguishable modes, surface plasmon polaritons and localized surface plasmons, are associated with different periods. The surface plasmon polaritons have widely extended near-field distributions and sharp resonance; however, the localized surface plasmon modes are highly concentrated in the grooves, and have broad resonance. Our results demonstrate that the surface plasmon polaritons and localized surface plasmons were coupled with electromagnetic waves to resonantly tunnel through the array of subwavelength holes. This optical tunneling effect exhibited large phase lag and time delay for the surface plasmon polariton. The broadness of localized surface plasmon resonance indicated that it could exist in randomly distributed, narrow-grooved structures as well.