Energy Velocity Defined by Brillouin

Hiroyuki HOSONO  Toshio HOSONO 

Publication
IEICE TRANSACTIONS on Electronics  Vol.E92-C  No.1  pp.9-16
Publication Date: 2009/01/01
Online ISSN: 1745-1353
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Electromagnetic Theory and its Application)
Category: 
Keyword: 
lossy Lorentz medium,  superluminal group velocity,  energy velocity,  signal velocity, 

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Summary: 
The physical meaning of the energy velocity in lossy Lorentz media is clarified. First, two expressions for the energy velocity, one by Brillouin and another by Diener, are examined. We show that, while Diener's is disqualified, Brillouin's is acceptable as energy velocity. Secondly, we show that the signal velocity defined by Brillouin and Baerwald is exactly identical with the Brillouin's energy velocity. Thirdly, by using triangle-modulated harmonic wave, we show that the superluminal group velocity plays its role as a revelator only after the arrival of the signal traveling at the subluminal energy velocity. In short, nothing moves at the group velocity, and every frequency component of a signal propagates at its own energy velocity.