Otto coupling to a transverse-electric-polarized mode on a metamaterial surface

Using the Otto geometry, prism coupling of microwave radiation to a metamaterial surface that supports a bound transverse-electric-polarized surface mode is demonstrated. The dispersion of this surface mode is characterized experimentally for incident radiation beyond the critical angle of the prism, and its resonant fields are explored using a numerical model.

Figure 1

Schematic representation of (a) the experimental geometry and (b) the sample under study. The inset shows an equivalent circuit model of the sample.

Figure 2

The dispersion of the surface modes supported by the sample (shown in Fig. 1) derived from the frequency of the optimum coupling condition for a range of angles of incidence, θ (where $k_x$ $=$ ω/$c$ sinθ is the component wave vector along the surface). The experimental data (open squares and circles for the TE- and TM-polarized modes, respectively) are compared to the predictions of the FEM modeling (solid line). The experimentally determined TE-polarized mode on the sample without vias is also shown (filled squares). The inset illustrates the reflectivity data recorded from the sample with ${\theta }_{\mathrm{int}}$ $=$ 51.8° for various values of $t$. The predicted dispersion of the surface eigenmodes of the sample without the influence of the coupling-in prism is also shown (dashed grey lines). The surface wave band gap is illustrated by the shaded region.

Figure 3

(a) FEM model predictions of the vectorial magnetic field on resonance of the TE-polarized surface mode at $k_x$ $=$ 7$k_g$/18, plotted over the $xz$ plane passing through the center of the patch at a temporal phase corresponding to maximum field enhancement. The plane of current, J, that flows parallel to the $y$ direction along the surface of the patches together with the (b) time averaged electric-field enhancement and (c) Poynting vector are also shown. The inset of (a) illustrates the decay of the magnetic field intensity from the surface of the metamaterial (circles: FEM prediction; line: exponential fit with decay length ∼1 mm).