Reflectionless wide-angle beam splitter based on omega-type bianisotropic metasurface

We propose an ultrathin planar structure which equally splits the power of a normally-incident plane wave into two beams outgoing at oblique angles, without incurring reflections. The design is based on an omega-type bianisotropic metasurface (O-BMS), exhibiting electric and magnetic polarizability, as well as magnetoelectric coupling. We rigorously show that this class of metasurfaces can implement arbitrary field transformations with passive lossless components, as long as real power is locally conserved. By stipulating the fields corresponding to the beam-splitting functionality, we find the metasurface constituents that accurately satisfy the boundary conditions, and verify the design via full-wave simulations. Compared to recently proposed reflect-mode Huygens' metasurface beam splitters, the O-BMS works in transmit mode, its design follows an exact solution, and it is predicted to maintain the same splitting efficiency for arbitrarily-large angles.