Ultrafast Switching in Terahertz Metamaterials using Ion Implanted   Silicon on Sapphire
  We demonstrate ultrafast resonance switching of terahertz metamaterials through optical excitation of radiation damaged silicon placed in the gap of single split gap ring resonator. We observe the dynamic switching OFF of the fundamental resonance mode on a time scale of 4 picoseconds (ps) followed by the switching ON of the same resonance after 20 ps. Electric field distributions in the metamaterials unit cell derived through numerical simulations clearly support our experimental observations, showing that the high electric field at the resonator gaps, responsible for inductive-capacitive resonance (LC), completely disappears and switches OFF the resonance after being optically excited. The ultrafast switching of the metamaterial resonance is attributed to the generation of free carriers in ion-implanted silicon and their recombination at an ultra-short time scale. Such silicon based active control of metamaterials can lead to the ultrafast terahertz metadevices. 
Dibakar Roy Chowdhury, Ranjan Singh, Antoinette J. Taylor and Abul K.   Azad
physics.optics