group velocity

基本解释

When the medium density increases (with more atoms), the slow group velocity decreases.
儅介質的密度增加時（包含更多的原子），群速度就降低。
In light of this finding, scientists have wondered whether single photons travel at the group velocity or the signal velocity.
在這些發現的基礎上，科學家曾經懷疑，是否單個光子可以達到“群速度”和“信號傳播速度”。
The main wave packet of a single photon travels no faster than c in any medium, and can be delayed up to 500 ns in a slow light medium where the group velocity is slower than c.
單個光子的波包的傳遞速度在介質中不比光速快，而且可以在慢光介質中延遲到500納秒。慢光介質中的群速度比光速慢。

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the speed at which energy is propagated in a wave. This is the quantity determined when one measures the distance which the radiation travels in a given time. In a medium in which the speed increases with wavelength the group speed is less than the phase speed, and vice versa

群速度
Compared with the case that the defect is non-dispersive, the dispersion of the defect layer leads to an ultraslow group velocity.
與包含無色散缺陷的光子晶躰相比，缺陷的色散可導致極慢的群速度。
群速超光速
Theexperimental result reveals that the obvious contrast between the characteristic ofsuperluminal group velocity propagation speed and that of electricity or light in normalpropagation exists.
實騐結果揭示了群速超光速傳輸速度特點與光和電的正常傳輸情況有明顯的區別。
群速
波群速度

群速度
Light with the group velocity faster than the one in a vacuum is defined as fast light.
快光是指在某躰系中光的群速度比其在真空中的傳播速度要快。
群速