Fanolike resonance in light transmission through a planar array of silver circular disks

We studied theoretically light transmission through a planar rectangular array of silver circular disks. An asymmetric lineshape, which is characteristic of the Fano resonance, has been found in a narrow frequency range of the spectrum. The effect can be attributed to the strong coupling between localized particle plasmon resonances excited on individual silver circular disks and an in-plane propagating collective surface mode arising from the array periodicity, as indicated by the anticrossing behavior of the resonance positions in the transmission spectra. More importantly, it was found that a fifty-two fold enhancement of electric field was achieved as compared with the purely resonance at the excitation of this Fanolike resonance; and only a collective surface mode with its electric field parallel to the array plane can mediate the excitation of such a Fanolike resonance.