Observation of superluminal signaling of terahertz pulses

TL;DR

This paper reports the observation of superluminal tunneling of terahertz pulses through metal films, showing the transmitted pulse shape remains faithful to the incident pulse, challenging traditional views on information transfer and causality.

Contribution

It provides experimental evidence of superluminal tunneling with faithful pulse transmission and develops a causal theoretical analysis addressing fundamental questions about light tunneling.

Findings

Observed anomalous time response of terahertz pulses

Transmitted pulse shape matches incident pulse

Theoretical analysis supports causality despite superluminal effects

Abstract

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.