Extreme Nonreciprocity with Spatio-Temporally Modulated Metasurfaces

TL;DR

This paper demonstrates a spatio-temporally modulated metasurface that achieves extreme nonreciprocity, enabling dynamic beam steering, reconfigurable focusing, and optical isolation, with potential applications in wireless communication and energy transfer.

Contribution

It introduces a novel metasurface design that breaks Lorentz reciprocity using spatio-temporal modulation, supported by a generalized Bloch-Floquet theory and experimental validation.

Findings

Achieved giant free-space optical isolation.

Demonstrated reconfigurable focusing and beam steering.

Validated theoretical predictions with experiments.

Abstract

Emerging photonic functionalities are mostly governed by the fundamental principle of Lorentz reciprocity. Lifting the constraints imposed by this principle could circumvent deleterious effects that limit the performance of photonic systems. A variety of approaches have recently been explored to break reciprocity, yet most efforts have been limited to confined photonic systems. Here, we propose and experimentally demonstrate a spatio-temporally modulated metasurface capable of extreme breakdown of Lorentz reciprocity. Through tailoring the momentum and frequency harmonic contents of the scattered waves, we achieve dynamical beam steering, reconfigurable focusing, and giant free-space optical isolation exemplifying the flexibility of our platform. We develop a generalized Bloch-Floquet theory which offers physical insights into the demonstrated extreme nonreciprocity, and its predictions are in excellent agreement with experiments. Our work opens exciting opportunities in applications where free-space nonreciprocal wave propagation is desired, including wireless communications and radiative energy transfer.