Stored energy density of electromagnetic wave in dispersive media

In this work, we shall demonstrate that usual expression of time-averaged stored energy density (TASED) for disperisve medium is invalid, which is mainly attributed to the fact that there exist mathematical errors in derivation of this expression. Noting connection between TASED and time-averaged Poynting vector (TAPV) and the case that TAPV of a pulse is the sum of TAPVs of its components, similarly, it is verified that TASED of a pulse in disperisve medium can be taken as the sum of TASEDs of all its components. This work may be helpful to gain a better understand of stored energy of electromagnetic wave in material media.