Experimental studies of extraordinary light transmission through periodic arrays of subwavelength square and rectangular holes in metal films

We fabricate a series of periodic arrays of subwavelength square and rectangular air holes on gold films, and measure the transmission spectra of these metallic nanostructures. By changing some geometrical and physical parameters, such as array period, air hole size and shape, and the incident light polarization, we verify that both global surface plasmon resonance and localized waveguide mode resonance are influential on enhancing the transmission of light through nanostructured metal films. These two resonances induce different behaviours of transmission peak shift. The transmission through the rectangular air-hole structures exhibits an obvious polarization effect dependent on the morphology. Numerical simulations are also made by a plane-wave transfer-matrix method and in good consistency with the experimental results.