Metasurface Magnetless Specular Isolator

TL;DR

This paper introduces a novel metasurface-based magnetless specular isolator that reflects or absorbs waves depending on the incident direction, utilizing nonreciprocal normal susceptibilities and a U-shaped transistor-loaded structure, demonstrated through simulation and experiments.

Contribution

It presents the first metasurface with nonreciprocal normal susceptibilities and a unique nonreciprocity mechanism, realized with a U-shaped transistor-loaded structure.

Findings

Achieved 41 dB isolation in simulations.

Achieved 38 dB isolation in experiments.

Demonstrated nonreciprocal reflection and absorption behavior.

Abstract

We present a (nongyrotropic) metasurface magnetless specular isolator. This device reflects as a mirror a wave incident under a specified angle in one direction and absorbs it in the opposite direction. The metasurface is synthesized in terms of bianisotropic susceptibility tensors, whose nonreciprocity resides in normal components and exhibits a hybrid electric, magneto-electric nature. The metaparticle is implemented in the form of a U-shaped conducting structure loaded by a transistor. The operation principle of the specular isolator is demonstrated by both full-wave simulation and experiment, with isolation levels reaching 41 and 38 dB respectively. This system represents the first realization of a metasurface involving nonreciprocal normal susceptibilities and features a previously unreported type of nonreciprocity.