Bioch mode analysis of transmission through periodic slit arrays in finite thickness metallic slabs

摘要

The Bloch modes of a periodic slit array in a metallic slab are identified, then used to investigate the transmission of light through sub-wavelength slits residing in a finite-thickness slab. Specifically, the Bloch mode method is used here to study Fabry-Perot-like resonances within individual slits, in conjunction with the onset of surface plasmon polariton (SPP) resonances and in the vicinity of the Wood anomalies. Although the results largely agree with our earlier numerical simulations obtained with the Finite-Difference-Time-Domain (FDTD) method, there are indications that the FDTD method has difficulty with convergence at and around resonances; the points of agreement and disagreement between the two methods are discussed in the present paper. When the period p of the slit array is comparable to (or somewhat below) the incident wavelength Xo, the Bloch mode method requires only the 10-20 lowest-order modes of the slit array to achieve stable solutions; we find the Bloch mode method to be an effective tool for studying dielectric-filled apertures in highly conductive hosts.