Magnetic-free terahertz nonreciprocity via temporal dissipative barriers

TL;DR

This paper introduces a magnetic-free method for achieving terahertz nonreciprocity using a temporal dissipative barrier, enabling miniaturized, integrated, and broadband nonreciprocal devices with high isolation efficiency.

Contribution

It proposes a novel approach utilizing transient loss variation for THz nonreciprocity, avoiding magnetic materials and enabling compact device design.

Findings

Achieved over 20 dB isolation in experiments across 0.4 THz bandwidth.

Theoretical peak isolation exceeds 60 dB, with experimental over 30 dB at 0.7 THz.

Demonstrated potential for miniaturized, integrated THz nonreciprocal devices.

Abstract

Terahertz (THz) nonreciprocal devices are essential for advancing future fundamental science, wireless communications, imaging, and sensing. Current THz nonreciprocal devices mostly rely on magnetic materials, which, however, suffer from large volume, operation under an external magnetic field, and low-temperature environment, rendering them poorly compatible with miniaturized developments. Here,we propose an unconventional method for achieving THz nonreciprocity free from magnetic materials. The scheme relies on a temporal dissipative barrier, a transient loss variation generated by photoexcited carriers, and the nonreciprocity arises from the distinct coupling behavior for different polarizations with the barrier. The isolation efficiency correlates with the temporal barrier width, resonant mode detuning, and the working frequency, and has been significantly enhanced by introducing a dark mode. We experimentally confirm our method in a THz optically active metasurface with wave-flow isolation exceeding 20 dB across a bandwidth greater than 0.4 THz. Theoretical predictions indicate peak isolation surpassing 60 dB, with experimental results achieving over 30 dB at 0.7 THz. Our approach unlocks the potential of miniaturized, integrated, magnetic-free THz nonreciprocal devices for various applications.