Realisation of a controllable metafilm/ metasurface composed of resonant magnetodielectric particles: measurements and theory

In previous work, we derived generalised sheet-transition conditions (GSTCs) for the average electromagnetic fields across a metafilm/metasurface, which, when properly designed, can have certain desired reflection and transmission properties. A metafilm (also referred to as a metasurface) is the two-dimensional equivalent of a metamaterial and is essentially a surface distribution of electrically small scatterers characterised by electric and magnetic surface susceptibilities. This GSTC has been used to calculate the reflection and transmission coefficients of the metafilm, which depend upon the surface susceptibilities, themselves expressed in terms of the electric and magnetic polarisabilities of the scatterers. Conditions on these surface susceptibilities of the scatterers required to obtain total transmission and/or total reflection have also been obtained. These conditions can require either the electric or magnetic surface susceptibilities to become negative (analogous to the situation for negative-index bulk metamaterials). By controlling the polarisabilities of the scatterers in the metafilm (and thus the surface susceptibilities), a ´smart´ or ´controllable´ surface can be realised. Applications of such a controllable metafilm/metasurface would include controllable antennas, switches, sensors, resonators and waveguides. In this study, the authors present both analytic and measurement results to demonstrate the realisation of a controllable metafilm composed of resonant magnetodielectric particles. To this end, they present analytical results for plane-wave incident and waveguide measurements of the reflection and transmission properties of a controllable metafilm composed of spherical magneto-dielectric (yttrium iron garnet or YIG) particles. The good correlations between the measured and analytical results of the reflection and transmission characteristics of the metafilm presented here show that a ´smart surface´ metafilm is realisable.