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Lookup NU author(s): Andrew Naylor, Dr Victor Pacheco PenaORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
It has been recently shown that the temporal equivalent of the Brewster angle can exist when inducing an isotropic-to-anisotropic time interface (i.e., where the permittivity of the medium where a wave propagates is changed from isotropic to a tensor everywhere in space), serving as a mechanism to eliminate the backward wave (time reflection) while still allowing the forward wave (time refraction) to propagate. To enable the existence of such temporal equivalent of the Brewster angle without using anisotropic modulations in time, here we propose and study the possibility of using isotropic-to-isotropic spacetime modulations instead by creating a spatially subwavelength multilayer structure in time using multiple and simultaneous isotropic-to-isotropic time interfaces within discrete spatial regions. A full theoretical description is presented for different spacetime effective media including multilayers having two-periodic layers arranged vertically or horizontally as well as multilayers having three-periodic layers. Different studies are presented including the effect on the temporal equivalent of the Brewster angle of the isotropic permittivity values for each temporally induced spatial layer and the introduction of isotropic-to-isotropic time interfaces for the permeability, among others. All the results are corroborated using numerical simulations, demonstrating the potential of the proposed effective medium approach in space and time to eliminate the backward wave.
Author(s): Naylor AM, Pacheco-Peña V
Publication type: Article
Publication status: Published
Journal: Optical Materials Express
Year: 2026
Volume: 16
Issue: 8
Pages: 2423-2440
Print publication date: 10/07/2026
Online publication date: 10/07/2026
Acceptance date: 26/06/2026
Date deposited: 21/07/2026
ISSN (electronic): 2159-3930
Publisher: Optica Publishing Group
URL: https://doi.org/10.1364/OME.606469
DOI: 10.1364/OME.606469
Data Access Statement: The datasets generated and analysed during the current study are available from the corresponding author upon reasonable request
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