Emulating nonreciprocity via direction-dependent excitation of spoof surface plasmon polaritons

Nonreciprocity is at the heart of many components such as isolators and circulators. Usually, the implementation of nonreciprocal requires specific materials such as nonlinear materials, which limits the application of non-reciprocal phenomena. In this paper, a method for emulating nonreciprocal characteristics using phase gradient metamaterial is proposed. Blade structures which can support spoof surface plasmon polaritons (Spoof SPPs) are used as the sub-unit cells of the phase gradient metamaterial. Based on the anomalous refraction properties and anisotropy of the phase gradient metamaterial, electromagnetic (EM) wave exhibits different transmission properties when passing the metamaterial from different directions. When the EM wave passes the metamaterial in the forward direction, it is anomalous refracted. When the EM wave returns back along the original path, no deflection happens. Our work provides an effective way to emulate the response of nonreciprocal effect without breaking time-reversed symmetry characteristic and is helpful to design low-profile devices with unprecedented functionality.