Mono-cross-anisotropic Metasurface Absorbing Boundary Condition (ABC)

We introduce the concept of Metasurface Absorbing-Boundary Condition (MS-ABC). This represents the first application of metasurface technology to computational electromagnetics. MS-ABCs have similar performance as previously reported surface ABCs, but they provide a richer description of absorption, that is independent from the incident wave, and deeper insight into the physics, through bianisotropic susceptibilities. The MS-ABC susceptibilities are synthesized using GSTC synthesis, from which the metasurface is found to be mono-cross-anisotropic, i.e. having only electric-to-magnetic and magnetic-to-electric coupling susceptibility tensors being non-zero, which is physically impossible, but numerically perfectly appropriate. Moreover, it is found that the metasurface is asymmetric, being amplifying in the opposite direction of its basic utilization as an ABC. The MS-ABC is implemented in a GSTC-FDTD scheme, which, for the first time, replaces the virtual grid concept by straightforward surface polarization currents residing on the regular Yee grid.