Nonlinear Terahertz Metamaterials via Field-Enhanced Carrier Dynamics in GaAs

• Main Authors: Fan, Kebin (Author), Hwang, Harold Young (Contributor), Liu, Mengkun (Author), Strikwerda, Andrew C. (Author), Sternbach, Aaron (Author), Zhang, Jingdi (Author), Zhao, Xiaoguang (Author), Zhang, Xin (Author), Nelson, Keith Adam (Contributor), Averitt, Richard D. (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Chemistry (Contributor)
• Format: Article
• Language: English
• Published: 2013-11-15T18:18:07Z.
• Subjects: Article
• Online Access: Get fulltext

We demonstrate nonlinear metamaterial split ring resonators (SRRs) on GaAs at terahertz frequencies. For SRRs on doped GaAs films, incident terahertz radiation with peak fields of ∼20-160  kV/cm drives intervalley scattering. This reduces the carrier mobility and enhances the SRR LC response due to a conductivity decrease in the doped thin film. Above ∼160  kV/cm, electric field enhancement within the SRR gaps leads to efficient impact ionization, increasing the carrier density and the conductivity which, in turn, suppresses the SRR resonance. We demonstrate an increase of up to 10 orders of magnitude in the carrier density in the SRR gaps on semi-insulating GaAs. Furthermore, we show that the effective permittivity can be swept from negative to positive values with an increasing terahertz field strength in the impact ionization regime, enabling new possibilities for nonlinear metamaterials.
United States. Office of Naval Research (ONR Grant No. N00014-09-1-1103)
United States. Air Force Office of Scientific Research (AFOSR Grant No. FA9550-09- 1-0708)
United States. Defense Threat Reduction Agency (C&B Technologies Directorate)