  Superluminal tunneling of light through a barrier has attracted broad
interest in the last several decades. Despite the observation of such phenomena
in various systems, it has been under intensive debate whether the transmitted
light truly carry the information of the original pulse. Here we report
observation of anomalous time response for terahertz electromagnetic pulses
passing through thin metal films, with the pulse shape of the transmitted beam
faithfully resembling that of the incident beam. A causal theoretical analysis
is developed to explain the experiments, though the theory of Special
Relativity may confront a challenge in this exceptional circumstance. These
findings may facilitate future applications in high-speed optical communication
or signal transmission, and may reshape our fundamental understanding about the
tunneling of light.
