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. A 38, 1409 (2021) [CrossRef] ], 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 ${{\rm MgF}_2}$, 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.

中文翻译：

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时空波包的折射：II．正入射实验

与传统脉冲光束相比，时空 (ST) 波包的折射提供了许多令人着迷的惊喜。在此序列中的第一篇论文中 [J. 选择。社会。是。A 38 , 1409 (2021) [CrossRef] ]，我们从理论上描述了在两个非色散、均匀、各向同性电介质之间的平面界面处垂直和斜入射的所有 ST 波包族的折射。在这里，在该序列的第二篇论文中，我们展示了对平面界面上法向入射时基带 ST 波包预测的折射现象的实验验证。具体来说，我们观察到群速度不变性、正常和异常折射，以及导致群延迟抵消的群速度反演。这些现象在一组折射率范围从 1.38 到 1.76 的光学材料中得到验证，包括${{\rm MgF}_2}$、熔融石英、BK7 玻璃和蓝宝石。我们还根据光锥表面上 ST 波包的光谱支持域的动力学，提供了与异常折射相关的物理学的几何表示。