Representations of the metasurface switch concept. (a) The control and the signal waves are both normally incident on the metasurface. The polarization of the control wave is rotated to match the polarization of the signal wave. A π-phase shift is imposed between the two transmitted waves, so that they cancel each other by destructive interference. (b) The control and the signal waves are first combined together by the polarization combiner described in Section 3.1.1.