Multipole engineering for enhanced backscattering modulation

An efficient modulation of backscattered energy is one of the key requirements for enabling efficient wireless communication channels. Typical architectures, based on either electronically or mechanically modulated reflectors, cannot be downscaled to subwavelength dimensions by design. Here we show that integrating high-index dielectric materials with tunable subwavelength resonators allows one to achieve an efficient backscattering modulation, keeping a footprint of an entire structure small. An interference between high-order Mie resonances leads to either enhancement or suppression of the backscattering, depending on a control parameter. In particular, a ceramic core shell, driven by an electronically tunable split-ring resonator, was shown to provide a backscattering modulation depth as high as tens of the geometrical cross section of the structure. The design was optimized toward maximizing the reading range of radio-frequency identification tags and shown to outperform existing commercial solutions by orders of magnitude in terms of the modulation efficiency. The proposed concept of multipole engineering allows one to design miniature beacons and modulators for wireless communication needs and other relevant applications.