(a) Schematic of the geometry under consideration. Light is shined from the normal direction with electric field E_z and an admittance surface Y_z(x) over a thin substrate and a ground plane. (b) Sketch of the relation between incident power P_inc and deflected power P_out. When the metasurface is lossless, power is conserved in the system. (c) Geometry of interest to maximize deflection, assuming a lossless superstrate, i.e., ignoring the imaginary part of permittivity for the absorbing material. Scattered electric field profile for one-way and two-way deflection. For two-way deflection, the reflection phase is π/2 for both beams. Frequency and deflection angle are set to 300 THz and 60°,respectively (d) Admittance profile for one-way and two-way deflection, used in panel (c), and calculated reflection efficiency for both cases.