Fig. 1. Schematic diagram of the studied unit cells of infinite periodic arrays of (a) a single subwavelength hole and (b) dissimilar vertical chain holes with hole depths of 100 nm, structural period of P, and hole radii of R.

Fig. 2. FDTD calculated transmission spectrum of single-hole array of fixed hole depth of 100 nm, different hole radii in the range of 50–80 nm, and structural periodicity of (a) P=400  nm, (b) P=450  nm, (c) P=500  nm, and (d) P=550  nm. The incident EM field was polarized along y axis.

Fig. 3. Transmittance spectra of three similar hole chain array of fixed hole depth of 100 nm, hole radius of 50 nm, and different structural periodicities. The incident EM field was linearly polarized along the y axis.

Fig. 4. Transmittance spectra of three-hole chain arrays of fixed hole depth of 100 nm, different side-hole radii, and structural periodicities of (a) P=400  nm, (b) P=450  nm, (c) P=500  nm, and (d) P=550  nm. The incident EM field was linearly polarized along the y axis.

Fig. 5. Transmittance spectra of three-hole chain arrays of fixed hole depth of 100 nm, different side-hole radii, Rs, and structural periodicities of (a) P=400  nm, (b) P=450  nm, (c) P=500  nm, and (d) P=550  nm. The incident EM field was linearly polarized along the x axis.

Fig. 6. FDTD calculated electric profile of the (1,0) resonance mode of three-hole chain arrays at different incident light polarization and structural periodicities. The top row shows the electric profile of the three-hole chain array of periods of (a) 400 nm, (b) 450 nm, (c) 500 nm, and (d) 550 nm under illumination of an x-polarized EM field. The bottom row is for a y-polarized incident EM field and periods of (e) 400 nm, (f) 450 nm, (g) 500 nm, and (h) 550 nm.