Backscattering-Immune Computing of Spatial Differentiation by Nonreciprocal Plasmonics

Abstract

Using the excitation of surface plasmon polaritons (SPPs) for optical analog computing of spatial differentiation could find widespread application in $e.g.$ edge detection and image processing, but the inevitable backscattering of SPPs propagating around defects or discontinuities would in general introduce noise to the output signal. The authors design a backscattering-immune spatial differentiator based on a nonreciprocal plasmonic platform, where balance between the rates of asymmetric leakage and intrinsic absorption is required. Here a topologically protected, one-way leaky mode in the terahertz region is just the ticket.