The velocity of propagation of electromagnetic energy for a monochromatic plane-wave field in a causally dispersive dielectric medium with absorption, as described by the Lorentz model, is considered within the framework of Poynting's theorem. A general, rigorous expression for the energy-transport velocity in a Lorentz medium with multiple-resonance frequencies is derived. From this rigorous result, an approximate expression for the energy velocity is obtained that is in a form that is independent of the medium model and so is likely to be applicable to general dispersive media.
© 1988 Optical Society of America
Kurt Edmund Oughstun and Shioupyn Shen, "Velocity of energy transport for a time-harmonic field in a multiple-resonance Lorentz medium," J. Opt. Soc. Am. B 5, 2395-2398 (1988)