Switchable All-Dielectric Magnetic-Electric Mirror Based on Higher-Order Dipoles

Abstract

Both magnetic and electric mirrors have great applied values in military, medical, and signal-transmission technology because of their electromagnetic properties. Although many kinds of artificial magnetic conductors, such as arrays of Mie resonance--based dielectric cubes or disks, have been demonstrated to be able to approximate a magnetic mirror, most of them, however, work within a narrow and invariable frequency band, and most attention is paid to magnetic dipole resonance of first order. Here, we investigate the resonant mechanism of dielectric cuboids and employ the dipole resonance of higher order to obtain a bifunctional and reconfigurable all-dielectric electric and magnetic mirror controlled by temperature. A prototype device is designed and fabricated with $\mathrm{Ca}$-${\mathrm{La}}_{2}{\mathrm{O}}_{3}$-${\mathrm{Ti}\mathrm{O}}_{2}$ ferroelectric cuboids as building blocks, and its reflecting effects are successfully demonstrated, as well as the tunability of working frequency by varying temperature. Moreover, electric and magnetic dipole resonances of higher order are proved to have superior resonant characteristics to the primary ones, which can effectively suppress the spectral overlapping between the adjacent magnetic and electric resonances and thus makes such all-dielectric reflector possible to switch between magnetic mirror and electric mirror. Furthermore, the proposed cuboids have the potential to expand to active phase-control metasurface devices and Huygens' sources with better impedance matching. Our work reveals the specific optical properties of higher-order dipolar resonances and opens the door towards the realization of tunable and reconfigurable magnetic-electric mirrors.