光前驱波

Optical precursors

文章回顾了近一百年来光前驱波的研究历史及最新的进展。自爱因斯坦的狭义相对论发表以来,真空中的光速不变原理已经被广泛地接受。然而对光在介质中的传播速度,由于复杂的色散关系,却一直存在不同的解读,尤其是对光载信息传播速度以及单个光子的运动。光前驱波的研究旨在回答这个问题。作者和其研究团队在最近的研究中找到了前驱波在光学波段的清晰的证据,并首次发现了单光子波包里的光前驱波。研究结果表明,光载信息传播速度不可能超光速,单光子的运动满足真空光速极限原理,即便是在所谓的"超光速"(群速度超光速)介质中。

This article reviews the history of the search for optical precursors over the past 100 years and the most recent progress. Although Einstein＇s special relativity based on the principle of light speed invariance in vacuum has been accepted for more than a century, there are still differ- ent pictures about the speed of light in a dispersive medium, especially with regard to information ve- locity and the motion of a single photon. The study of optical precursors aims to answer these ques- tions. Recently, we found clear signatures of precursors in optical pulse propagation, and for the first time, observed the precursor of a single photon. Our results confirm that information carried by light cannot travel faster than the speed of light in vacuum, and a single photon obeys the speed limit, even in a so-called ＂superluminal＂ medium （where the group velocity is faster than the speed of light in vacuum）.