“ Superluminal ” Pulse Propagation

With the recent rediscovery of slowand fast-light effects, there has been much interest in pulse propagation phenomena that lead to apparently superluminal pulse transmission. This raises immediate questions about causality and special relativity violations and elicits curiosity about the physical mechanisms responsible for these effects. This thesis will address these issues theoretically and experimentally by investigating two such effects. The first effect we consider is pulse propagation under conditions of negative group velocity in erbium-doped fiber. Predictions suggest that upon propagation through a region of negative group velocity the transmitted pulse exits the region before the peak of the incident pulse enters. In addition, theory predicts the presence of a peak within the region that propagates backwards, linking the incident and transmitted peaks. We determine the accuracy of these predictions experimentally and uncover the physical mechanism that leads to the effect. We also examine the saturation of photonic tunneling delays with barrier opacity, which is known as the Hartman effect. In particular we address the case of frustrated-total-internal-reflection, which is a two-dimensional tunneling effect. Theoretical treatments of this phenomenon have been limited to special cases in the past. We demonstrate a new method of decomposition that gives a continuous expression for the predicted delay, and present experimental measurements of that delay in a barrier structure constructed from glass prisms and a liquid crystal cell.