Transmission resonances in a metal film with arrays of asymmetry cross-shaped apertures

We studied numerically the transmission properties of the periodic array of asymmetric cross-shaped apertures in an Ag film. The relative positions of the two orthogonally oriented rectangular apertures are varied, rather than their length or width. Each transmission peak of the original symmetric cross-shaped apertures will split into two peaks in the case of the asymmetric cross-shaped apertures when the electric field is perpendicular to the long axis of the unchanged rectangular aperture. The wavelength of the shift peak has a linear relation with the asymmetry. This resonance response mainly results from the excitation of the trapped mode provided by the structural symmetry breaking. A distribution of the magnetic field and a simple Lagrange model are used to interpret these phenomena. In addition, the intensity of the transmission peaks can be tuned by changing the incident polarization angle. (C) 2013 Optical Society of America