Revisiting substrate-induced bianisotropy in metasurfaces

Recently, it has been shown that a metasurface of plasmonic nanospheres deposited on a highly refractive substrate requires a bianisotropic magnetoelectric coupling for its effective description. The effect has been coined substrate-induced bianisotropy. It leads to an asymmetric reflectance similar to bianisotropic metasurfaces. In this work, through a circuit model, we show that such bianisotropy does not necessarily emerge for all substrated metasurfaces. Indeed, we show that the thickness of the metasurface plays a crucial role to encounter substrate-induced bianisotropy. Moreover, by taking advantage of substrate-induced bianisotropy, we present the necessary conditions for the circuit model parameters to compensate the asymmetric reflectance generated by an intrinsically bianisotropic metasurface. We finally express that, in substrated metasurfaces, the asymmetric reflectance and the bianisotropic response are two separate issues albeit with interdependencies.