  The nonlinear metamaterials have been shown to provide nonlinear properties
with high nonlinear conversion efficiency and in a myriad of light
manipulation. Here we study terahertz generation from nonlinear metasurface
consisting of single layer nanoscale split-ring resonator array. The terahertz
generation due to optical rectification by the second-order nonlinearity of the
split-ring resonator is investigated by a time-domain implementation of the
hydrodynamic model for electron dynamics in metal. The results show that the
nonlinear metasurface enables us to generate broadband terahertz radiation and
free from quasi-phase-matching conditions. The proposed scheme provides a new
concept of broadband THz source and designing nonlinear plasmonic
metamaterials.
