 Similar to other nonlinear optical processes, optical rectification is also reported to become enhanced when surface plasmons are excited on a metal surface.Together with carrier acceleration in semiconductors and polymers, optical rectification is one of the main mechanisms for the generation of terahertz radiation using lasers.This is different from other processes of terahertz generation such as polaritonics where a polar lattice vibration is thought to generate the terahertz radiation.