Transmission through metallic array slits curved with perpendicular waveguides

The transmission of normally incident plane wave through an array of subwavelength metallic slits curved with perpendicular waveguides has been explored. Two-dimensional electromagnetic fields inside and near the metal film are simulated by the finite-difference time-domain (FDTD) method. The perpendicular waveguides in the middle of slits affect the modes of slits in two different manners: commonly, the extended length of the waveguides leads to the increase of the resonant wavelength; shifting the waveguides location along the vertical slits, red or blue shift of resonant wavelengths can be achieved, however to some confirmed length of the perpendicular waveguides, there is the only one resonant wavelength. In addition, a new explanation model is proposed in which the resonance is ascribed to three reasons: the Fabry-Perot cavity theory, the surface current flow, and the surface charges. All the calculated results are well explained by our proposed model.