Dynamics of causal beam refraction in negative refractive index materials

A finite difference simulation of a causally excited electromagnetic Gaussian beam incident on an interface between free space and a physically realizable negative refractive index material shows that negative refraction of finite beams does occur. A discontinuity in the phase normal direction is established very quickly when the beam front reaches the interface of positive and negative index materials. Once the beam enters the negative index material, the causal wave-front propates with the group velocity consistent with theory. During the transient portion of the beam development, the beam undergoes small direction changes, which can be explained as a consequence of higher frequencies present during the beam turn-on. After this transient, the theoretically predicted sinusoidal steady state is reached. (C) 2003 American Institute of Physics.