Department of Physics, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku Shizuoka 422-8529, Japan.
Phys Rev Lett. 2014 Mar 7;112(9):093903. doi: 10.1103/PhysRevLett.112.093903.
A series of experiments is performed to examine the arrival of a pulse peak, using a Gaussian-shaped temporal wave packet as the input pulse and truncating it at various positions on or before the peak of the packet. When the truncating point is within the negative group delay limit of the fast light medium, a smooth Gaussian peak is observed at the exit port, despite the absence of an input pulse peak. The experimental results explicitly demonstrate that the superluminal propagation of a smooth Gaussian-shaped pulse peak is an analytic continuation over time of the earlier portion of the input pulse envelope. To investigate the physical meaning of the pulse peak further, we also examine the propagation of triangular-shaped pulses, for which the pulse peak can be recognized as a nonanalytical point.
进行了一系列实验，以研究脉冲峰值的到达情况，使用高斯形状的时域波包作为输入脉冲，并在波包的峰值或之前的各个位置对其进行截断。当截断点位于快光介质的负群延迟限制内时，尽管没有输入脉冲峰值，但在出射端口仍观察到平滑的高斯峰值。实验结果明确表明，平滑高斯形状脉冲峰值的超光速传播是输入脉冲包络的早期部分随时间的解析延伸。为了进一步研究脉冲峰值的物理意义，我们还研究了三角形脉冲的传播，对于三角形脉冲，可以将脉冲峰值视为非解析点。
