Time-varying Huygens' meta-devices for parametric waves

TL;DR

This paper introduces a time-varying Huygens' metasurface that enables dynamic, arbitrary control over beam shaping and steering through frequency conversion, demonstrated at microwave frequencies with tunable varactor diodes.

Contribution

The work presents the first experimental realization of a time-varying Huygens' metasurface capable of dynamic beam steering and frequency multiplexing, with independently controlled electric and magnetic meta-atoms.

Findings

Achieved all-angle beam steering at microwave frequencies.

Demonstrated frequency-multiplexed functionalities.

Developed a theory for controlling scattering directionality and efficiency.

Abstract

Huygens' metasurfaces have demonstrated almost arbitrary control over the shape of a scattered beam, however, its spatial profile is typically fixed at fabrication time. Dynamic reconfiguration of this beam profile with tunable elements remains challenging, due to the need to maintain the Huygens' condition across the tuning range. In this work, we experimentally demonstrate that a time-varying metadevice which performs frequency conversion can steer transmitted or reflected beams in an almost arbitrary manner, with fully dynamic control. Our time-varying Huygens' metadevice is made of both electric and magnetic meta-atoms with independently controlled modulation, and the phase of this modulation is imprinted on the scattered parametric waves, controlling their shapes and directions. We develop a theory which shows how the scattering directionality, phase and conversion efficiency of sidebands can be manipulated almost arbitrarily. We demonstrate novel effects including all-angle beam steering and frequency-multiplexed functionalities at microwave frequencies around 4 GHz, using varactor diodes as tunable elements. We believe that the concept can be extended to other frequency bands, enabling metasurfaces with arbitrary phase pattern that can be dynamically tuned over the complete 2\pi range.