  An efficient modulation of backscattered energy is one of the key
requirements for enabling efficient wireless communication channels. Typical
architectures, being based on either electronically or mechanically modulated
reflectors, cannot be downscaled to subwavelengths dimensions by design. Here
we show that integrating high-index dielectric materials with tunable
subwavelength resonators allows achieving 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 towards maximizing
reading range of radio frequency identification (RFID) 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 a new generation of miniature beacons and modulators for wireless
communication needs and other relevant applications.
