Advanced Control of Invisible Cavity Resonators with Bianisotropic Metasurfaces

Recently, invisible cavities formed by two parallel metasurfaces have demonstrated the ability to support so-called “driven” bound states in the continuum. The existence of these modes allows excitation of non-scattering resonant cavities with strongly enhanced fields inside the resonator volume. These invisible cavity resonators have been proposed for several applications such as sensor enhancement and cloaking. In this work, we propose and analyse invisible cavity resonators formed by two bianisotropic metasurfaces. Our results show that resonant cavities made of bianisotropic metasurfaces allow rather general control of the distribution of field inside the resonant volume between the metasurfaces and offer a possibility to design invisible resonant cavities of arbitrary thickness.