Terahertz Nonlinear Superconducting Metamaterials
  We investigate the nonlinear effect of a planar superconducting metamaterial made from niobium nitride (NbN) at terahertz frequencies. As the variation of the incident intense terahertz field alters the intrinsic conductivity in the NbN, a consequent giant amplitude modulation is observed due to the strong nonlinearities. The high sensitivity of the chosen metamaterial even allows observing the nonlinear behaviors at various temperatures, but the resonance modulation induced by the nonlinear effect was distinct from that induced by the heating effect. The presented results illustrate a clever implementation of strongly enhanced nonlinearities and thus may bring nonlinear metamaterials into novel applications. 
Caihong Zhang, Biaobing Jin, Jiaguang Han, Iwao Kawayama, Hiro   Murakami, Jingbo Wu, Lin Kang, Jian Chen, Peiheng Wu, and M...
physics.optics