From the generalized reflection law to the realization of perfect anomalous reflectors

Flat Engineered Multichannel Reflectors

“…This analytical solution gives periodicity smaller than the wavelength if port 3 is at an angle θ i > 30 • from the normal. It should be noted that the derived impedance expression is somewhat similar to that for conventional reflectarrays obtained in [22]. This similarity appears because both formulas were derived under the assumption that the metasurface possesses local electromagnetic response.…”

“…3(b)]. Experimental verification of this isolation property of the reflector proposed in [22] is demonstrated in supplementary materials [33]. At all other angles, the reflection from the structure constitutes a combination of several harmonics whose amplitudes depend on the specific design of the reflector.…”

“…In the case of flat reflectors exhibiting ideal anomalous reflection [22], the scattering matrix can be fully determined using the symmetry constraints. Indeed, assuming that a normally illuminated reflector sends all the incident power to the n = 1 channel and, reciprocally, power from n = 1 channel to the normal direction, we immediately fix its response for illumination from n = −1 channel.…”

“…This behaviour is imposed by the reciprocity and energy conservation. As an example, we consider the anomalous reflector proposed in [22] which under normal illumination reflects 100% of power at θ r = 70 • . Figure 3(a) depicts the reflection angles for different propagating harmonics in this system versus the illumination angle θ i .…”

“…A large variety of metasurface designs for reflection control with different power efficiency levels were reported (e.g., [8,9,[13][14][15][16][17][18][19]). More recently, it was shown that parasitic reflections in undesired directions, inevitable in the designs based on the generalized reflection law [7], can be removed [20,21] via engineering spatial dispersion in metasurfaces [22].…”