國(guó)內(nèi)教材翻譯的不對(duì),群速度可以超光速。你可以參考Claus Klingshirn的Semiconductor Optics,3rd Ed第98頁(yè)最后一段: )*b
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For a discussion of the fact, that both the phase- and group velocities can exceed for some frequenciyes the vacuum speed of light. It should be noted, however, that the signal and energy transport velocities never exceed c. FuWMVT`Y
老一輩中英語(yǔ)不好真是害死后代!