Coherent Asymmetric Absorbers

Most applications of metasurfaces require excitation and control of both electric and magnetic surface currents. For such purposes, the metasurface must have a finite thickness to handle magnetic surface currents. For metasurface sheets of negligible thickness that offer only electric response, coherent illumination can compensate the need to create discontinuities of the tangential electric field component using magnetic surface currents. Most of the known coherent metasurfaces are space uniform and can control only plane-wave absorption and specular reflection. However, it is also known that periodical space-modulated (inhomogeneous) metasurfaces can be used to realize anomalous reflection, refraction, and other useful effects. In this paper, we propose the concept of a coherently illuminated space-modulated metasurface that functions as a coherent asymmetric absorber. We study its behavior under nonideal illumination and suggest applications related to sensing.