Dynamical characteristics of ultrashort terahertz pulse in metamaterials

We develop a time-dependent theoretical approach to study the interaction between the ultrashort terahertz pulse and the metamaterials beyond the steady-state approximation. By using photoconductive silicon, we show that the system dispersion is changed from abnormal to normal via the classical interference effect. As a result, the terahertz pulse propagates through the material with subluminal/superluminal group velocity. We show that it is not accurate to predict the propagation characteristics of the terahertz pulses by using the steady-state solution of coupled wave equations, and the high-order dispersion terms take a significant role which attributes to the pulse shape deformation and the position-dependent group velocity modification. The theoretical approach presented here is essential of describing the propagation properties of the terahertz pulse in metamaterials and is helpful to understand the nature of quantum interference in electromagnetically induced transparency metamaterial.