Figure 1. Coherent control of metamaterial functionalities.

Coherent counterpropagating beams “Signal” and “Control” form an interference pattern. A functional material of substantially subwavelength thickness can be placed at a position of (a) constructive interference or (b) destructive interference of the incident electric fields E₀ leading to enhanced or vanishing electric excitation of the material, respectively. Similarly, (a) destructive and (b) constructive interference of the incident magnetic fields B₀ leads to vanishing or enhanced magnetic excitation of the metamaterial. Insets illustrate interference for p and s-polarization at oblique incidence.