"Superluminal" transmission of light pulses through optically opaque barriers - art. no. 027601

Using simple considerations of causal electrodynamics we analyze the occurr ence of superluminal transmission of light pulses through optically opaque barriers. We find that the phenomenon appears whenever the main frequency c omponents of the pulse are confined to frequency regions where the presence of the barrier decreases the density of states of the electromagnetic mode s of the system. We also show that these frequency regions correspond to th e transmission gaps of sufficiently wide barriers. We discuss a simple theo ry for the density of states of the barrier system and compare the results of such a theory with exact numerical calculations.