Experimental demonstration of deflection angle tuning in unidirectional fishnet metamaterials at millimeter-waves

In order to demonstrate that the frequency blue-shift corresponds mainly to the existence of thin air layers, simulations including these layers have been carried out. To this end, the thickness of the stacked hole array was measured with a caliper. The result obtained was 140 μm excess of thickness. This excess of thickness can be judiciously attributed to thin air gaps between the four joints of the structure (i.e. 35 μm for each air gap). Figure S1 shows forward transmission and forward-to-backward transmission contrast for the ideal and the non-ideal (air gaps and absorption losses, tan δ = 0.018 at 60 GHz, included) structures. Similarly to experimental results, spectra are blue-shifted and transmission deteriorated compared to the ideal cases studied in Ref 21. The shift of the first band (45 – 55 GHz) is approximately of 4 GHz whereas the second band (59-74 GHz) remains practically stable. However in the second band case, the frequencyangle of incidence area seems to be reduced in the non-ideal case with respect to the ideal one. Furthermore, in general, forward-to-backward transmission contrast for positive deflection cases achieves better values than for negative deflection ones as can be seen in the figure.