Split-Ring-Resonator-Coupled Enhanced Transmission through a Single Subwavelength Aperture

We report the enhanced transmission of electromagnetic waves through a single subwavelength aperture by using a split-ring resonator (SRR) at microwave frequencies. By placing a single SRR at the near field of the aperture, strongly localized electromagnetic fields are effectively coupled to the aperture with a radius that is 20 times smaller than the resonance wavelength ($r/\lambda =0.05$). We obtained 740-fold transmission enhancement by exciting the electric resonance of SRR. A different coupling mechanism, through the magnetic resonance of SRR, is also verified to lead to enhanced transmission.

Figure 1

Schematic drawings of a subwavelength aperture in a metallic plate and SRR plane (a) parallel and (b) perpendicular to the aperture plane. (c) Measured transmission spectra from a single SRR with four different orientations. (d) Schematic drawing of SRR orientations with respect to the incident EM field.

Figure 2

(a) Measured and (b) simulated intensity of transmitted EM wave from only aperture, and aperture covered with CRR, SRR (A) and SRR (B). Insets show the enhancement factor obtained from SRR (A) and aperture. Inset of Fig. 2a plots enhancement factor of 3 different SRRs.

Figure 3

Measured and simulated intensity from a single aperture covered with (a) SRR (D) and (b) SRR (C). (c) Enhancement factors obtained from the measurements and simulations for SRR (C) and (D).

Figure 4

Simulated $E_y$ magnitude for an aperture and (a) SRR (A), (b) SRR (D), and (c) SRR (C) structure.