Free-standing zirconia metasurfaces for microwave resonant polarization conversion

A dielectric zirconia metasurface for resonant polarization conversion at microwave frequencies is theoretically and experimentally investigated. The metasurface is composed of a periodic array of square slotted rings interrupted by solid bridge sectors that provide interconnection and mechanical stability to the free-standing metasurface structure. Moreover, they selectively break the symmetry of the unit cell, thus allowing for polarization conversion based on both weakly and strongly resonant modes, the latter stemming from bound states in the continuum. The main findings of the theoretical analysis are corroborated through the experimental characterization of a metasurface sample fabricated by a recently introduced three-dimensional (3D) printing technique based on fused filament fabrication. Going beyond the target application of resonant polarization conversion, this work proposes an approach for the realization of high-permittivity, 3D-printed zirconia metasurfaces with submillimeter features for strong wave-matter interaction at microwave frequencies.