Non-reciprocal absorption and zero reflection in physically separated dual photonic resonators by traveling-wave-induced indirect coupling

TL;DR

This paper demonstrates non-reciprocal absorption and near-zero reflection in separated dual photonic resonators using traveling-wave-induced indirect coupling, revealing new non-Hermitian effects and potential applications in microwave and quantum devices.

Contribution

It introduces a novel approach to achieve non-reciprocal optical behaviors through traveling-wave-induced indirect coupling in physically separated resonators, without magnetic materials.

Findings

Observation of EIT-like peak at specific inter-distance d=18 mm

Nearly zero reflection and almost perfect absorption at d=20 mm

Non-Hermitian origin of unidirectional absorption with zero reflection

Abstract

We experimentally explored novel behaviors of non-reciprocal absorption and almost zero reflection in a dual photon resonator system, which is physically separated and composed of two inverted split ring resonators (ISRRs) with varying inter-distances. We also found that an electromagnetically-induced-transparency (EIT)-like peak at a specific inter-distance of d = 18 mm through traveling waves flowing along a shared microstrip line to which the dual ISRRs are dissipatively coupled. With the aid of CST-simulations and analytical modeling, we found that destructive and/or constructive interferences in traveling waves, indirectly coupled to each ISRR, result in a traveling-wave-induced transparency peak within a narrow window. Furthermore, we observed not only strong non-reciprocal responses of reflectivity and absorptivity at individual inter-distances exactly at the corresponding EIT-like peak positions, but also nearly zero reflection and almost perfect absorption for a specific case of d = 20 mm. Finally, the unidirectional absorptions with zero reflection at d = 20 mm are found to be ascribed to a non-Hermitian origin. This work not only provides a better understanding of traveling-wave-induced indirect coupling between two photonic resonators without magnetic coupling, but also suggests potential implications for the resulting non-reciprocal behaviors of absorption and reflection in microwave circuits and quantum information devices.