Frias Winston, Smolyakov Andrei, Hirose Akira
Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Place, Saskatoon, SK S7N 5E2 Saskatoon, Canada.
Opt Express. 2011 Aug 1;19(16):15281-96. doi: 10.1364/OE.19.015281.
Various definitions of the velocity of propagation of the electromagnetic field have been adopted in experimental and theoretical studies of tunneling and plasmonic systems. Tunneling problems are often analyzed by invoking the group delay (or dwell time) velocities. On the other hand, slow light and plasmonic systems are considered by using the wave packet group velocity. This paper discusses various definitions for the velocity of the electromagnetic wave propagation and compares them in applications to the problems of slow light and superluminality in resonant and tunneling structures. Energy propagation is, in general, a nonlocal quantity and depends on the global properties of the system, rather than being simply a local quantity. The energy propagation velocity takes into account the non-local characteristics of the wave propagation and offers a natural generalization for those situations when the group velocity is ill defined or gives unphysical results. It is shown that the group delay velocity, which may be superluminal away from the resonance, becomes equal to the energy velocity at the resonant point.
在隧道效应和等离子体系统的实验和理论研究中，人们采用了各种电磁场传播速度的定义。隧道效应问题通常通过引入群延迟（或驻留时间）速度来分析。另一方面，慢光和等离子体系统则是通过使用波包群速度来考虑的。本文讨论了电磁波传播速度的各种定义，并将它们在应用于共振和隧道结构中的慢光和超光速问题时进行了比较。一般来说，能量传播是一个非局部量，它取决于系统的全局特性，而不是简单地是一个局部量。能量传播速度考虑了波传播的非局部特性，并为群速度定义不明确或给出非物理结果的情况提供了一种自然的推广。结果表明，在远离共振时可能超光速的群延迟速度，在共振点处等于能量速度。
