  Here, we study the electromagnetic response of asymmetric mushroom-type
metamaterials loaded with nonlinear elements. It is shown that near a Fano
resonance these structures may have a strong tunable, bi-stable, and switchable
response and enable giant nonlinear effects. Using an effective medium theory
and full wave simulations, it is proven that the nonlinear elements may allow
the reflection and transmission coefficients to follow hysteresis loops, and to
switch the metamaterial between "go" and "no-go" states similar to an ideal
electromagnetic switch.
