All-optical switching in metamaterial with high structural symmetry
  We argue the possibility of realization of a polarization insensitive all-optical switching in a planar metamaterial composed of a 4-fold periodic array of two concentric metal rings placed on a substrate of nonlinear material. It is demonstrated that a switching may be achieved between essentially different values of transmission near the resonant frequency of the high-quality-factor Fano-shape trapped-mode excitation. 
Vladimir R. Tuz and Sergey L. Prosvirnin
physics.optics