Allende Motz Alyssa M, Yessenov Murat, Bhaduri Basanta, Abouraddy Ayman F
J Opt Soc Am A Opt Image Sci Vis. 2021 Oct 1;38(10):1450-1461. doi: 10.1364/JOSAA.430108.
The refraction of space-time (ST) wave packets offers many fascinating surprises with respect to conventional pulsed beams. In the first paper in this sequence [J. Opt. Soc. Am. A38, 1409 (2021)10.1364/JOSAA.430105], we theoretically described the refraction of all families of ST wave packets at normal and oblique incidence at a planar interface between two nondispersive, homogeneous, isotropic dielectrics. Here, in this second paper in the sequence, we present experimental verification of the refractive phenomena predicted for baseband ST wave packets upon normal incidence on a planar interface. Specifically, we observe group velocity invariance, normal and anomalous refraction, and group velocity inversion leading to group delay cancellation. These phenomena are verified in a set of optical materials with refractive indices ranging from 1.38 to 1.76, including , fused silica, BK7 glass, and sapphire. We also provide a geometrical representation of the physics associated with anomalous refraction in terms of the dynamics of the spectral support domain for ST wave packets on the surface of the light cone.
与传统脉冲光束相比，时空（ST）波包的折射带来了许多令人着迷的惊喜。在本系列的第一篇论文[《美国光学学会志A》38, 1409 (2021)10.1364/JOSAA.430105]中，我们从理论上描述了所有类型的ST波包在两种非色散、均匀、各向同性电介质的平面界面处垂直和斜入射时的折射情况。在此，在本系列的第二篇论文中，我们给出了对于基带ST波包垂直入射到平面界面时所预测的折射现象的实验验证。具体而言，我们观察到了群速度不变性、正常折射和反常折射，以及导致群延迟抵消的群速度反转。这些现象在一组折射率范围从1.38到1.76的光学材料中得到了验证，这些材料包括熔融石英、BK7玻璃和蓝宝石。我们还根据光锥表面上ST波包的频谱支持域的动力学，提供了与反常折射相关的物理过程的几何表示。
