Abstract
We examine the energy exchanged between an electromagnetic pulse and a linear dielectric medium in which it propagates. While group velocity indicates the presence of field energy (the locus of which can move with arbitrary speed), the velocity of energy transport maintains strict luminality. This indicates that the medium treats the leading and trailing portions of the pulse differently. The principle of causality requires the medium to respond to the instantaneous spectrum, the spectrum of the pulse truncated at each new instant as a given locale in the medium experiences the pulse.
Highlights
It is well verified, both analytically and experimentally [1, 2, 3, 4, 5, 6], that electromagnetic pulses can seemingly propagate through linear dielectric media at speeds greater than c
Received September 19, 2001; Revised November 05, 2001 5 November 2001 / Vol 9, No 10 / OPTICS EXPRESS 519. Both analytically and experimentally [1, 2, 3, 4, 5, 6], that electromagnetic pulses can seemingly propagate through linear dielectric media at speeds greater than c
In a companion article [7] we discussed how the group delay function tracks the presence of field energy in dielectric media
Summary
Both analytically and experimentally [1, 2, 3, 4, 5, 6], that electromagnetic pulses can seemingly propagate through linear dielectric media at speeds greater than c In these situations, it is important to note that one is tracking the presence of only the electromagnetic field energy when these superluminal observations are made. It is this exchange which is related to the fact that group velocity is not bounded by c Exotic behaviors such as superluminal or highly subluminal pulse propagation [10] have often been analyzed using the Lorentz oscillator model (either uninverted [11] or inverted [4]), which is known to be consistent with the principle of causality [3]. We demonstrate how the exchange of energy between the field and the medium depends on the instantaneous spectrum [12, 13, 14] of the field
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