Dynamics of the damping oscillator formed by the collective generation of surface polaritons for extraordinary light transmission through subwavelength hole arrays in thin metal films

Light transmissions through a subwavelength hole array in a thin metal film are characterized by resonance peaks in the transmission spectrum. In this work we study the surface polaritons (SPs) in perforated thin metal films by analyzing the dynamic behavior of the Poynting vectors based on a full-vector finite-difference time-domain approach. It is shown that each resonance peak in the transmission spectrum is caused by a collective generation of SPs in the form of a dynamic damping oscillator which oscillates in space and time. The energy of the incident light is transported between the upper and the lower metal-air surfaces during the spatial oscillations largely through the air holes. This energy transport mechanism prevails even when the metal-film thickness becomes as thin as 100 nm, under which circumstance the wave functions of the SPs, localized separately on the two metal-air surfaces when the metal film is thick, begin to strongly overlap with each other. The lifetimes of the damping oscillators are different for different resonance peaks in the transmission spectrum and remain distinguishable by the order of their temporal development.