Space-time refraction of space-time wave packets
File(s)
Published version
Author(s)
Hayran, Zeki
Pendry, John
Type
Journal Article
Abstract
Refraction is usually understood as a boundary rule relating the direction and frequency of a wave across an interface. In space-time photonics, this picture is incomplete because both the medium and the wave can carry space-time structure. A space-time index modulation can form a synthetic moving boundary, whereas a space-time wave packet carries a prescribed group velocity through spatio-temporal spectral correlations. We show that their interaction is governed not by isolated spectral components alone, but by how the moving boundary transforms the geometry of the space-time spectrum as a whole. We develop a theory of space-time refraction for multiple space-time wave-packet families at a translating planar interface between homogeneous, nondispersive media. Even without material dispersion, and for the same two media and interface velocity, different packet families follow different group-velocity maps. This leads to effects with no spatial counterpart, including velocity compression, where many incident group velocities map to a narrow transmitted band, and velocity fission, where a single incident wave packet splits into two propagation-invariant branches with different velocities. The results identify moving interfaces as programmable transformations of structured light, with implications for programmable delay control, signal routing, controlled quantum emission, and analog-gravity platforms.
Date Issued
2026-11-01
Date Acceptance
2026-06-11
Citation
Advanced Photonics, 2026, 8 (6)
ISSN
2577-5421
Publisher
SPIE
Journal / Book Title
Advanced Photonics
Volume
8
Issue
6
Copyright Statement
© The Authors. Published by SPIE and CLP under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
License URL
Identifier
10.1117/1.AP.8.6.066001]
Subjects
space-time refraction
space-time wave packets
moving refractive index fronts
group velocity control
X-waves
space-time metamaterials
optical horizons
analog gravity
Publication Status
Published
Article Number
066001
Date Publish Online
2026-07-09