Abstract

Recently, active terahertz metamaterials attract much interest in practical applications, such as sensing, ultrafast switching and slow light propagation, and various schemes have been exploited to manipulate the properties of electromagnetic waves in metamaterial-based devices. Here, we experimentally and theoretically demonstrate optical control of a metamaterial through integrating photoactive silicon islands into the metamaterial building block. The unit cell is comprised of two pairs of identical and gap opposite-directed U-shape split-ring resonators (SRRs), symmetrically placed on both sides of a central metallic bar resonator, in which the silicon islands connect the arms of the opposite U-shape SRRs. Attributed to the modification in damping rate in one of the resonance modes under optical excitation, the broadband transparency transmission window resulted from the mode coupling is dynamically modulated. Another active metamaterial sample with coaxial rectangle microstructures is also presented. Under optical excitation, multi-transmission-peak effect is dynamically switched. By carefully designing the position of silicon islands in the metamaterial unit cell, one or more transmission peaks can be dynamically modulated in amplitude. The schemes suggested here are promising to construct active terahertz devices and to realize on-to-off switching response of the terahertz radiation at room temperature.

© 2014 Optical Society of America