2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/84955We study the propagation of electromagnetic pulses through photonic bandgap materials and relate time-domain pulse reshaping to observable transit times. For layered dielectric mirrors we demonstrate how pulse reshaping of slowly varying classical fields results in transit-time delays that are equivalent to the group delay. The time-domain analysis emphasizes the causal origin of negative group delays. We also study an analogous fully-quantized model and show how the same time-domain analysis may be used to interpret observed delays of single-photon fields.9 pages, 5 figures, References added and minor revisionOpticsQuantum Physicstext