Systematic design of 3D topological phases of light
by
OSGA/EG6a
In designer metamaterials, topological properties can be engineered directly and continuously by shaping the spatial profile of the medium. In photonic crystals, this allows the realization of topological phases with tailored wave-guiding functionalities and target light-matter couplings. While early designs largely relied on analogies with electronic systems, these approaches do not fully capture important tensorial aspects of classical waves in three dimensions, in particular the transverse and vectorial nature of light.
In this talk, I will present our work on 3D topological photonics, from cubic Chern and photonic axion insulators to their microwave tabletop experimental realizations [1-5]. I will show how we moved from manual, intuition-driven designs to automated discovery using topological quantum chemistry combined with constrained Fourier parameterizations, an approach applicable across a wide range of metamaterial platforms, from phononic and photonic systems to synthetic electronic potentials [6-7]. I will present how this approach also enables the characterization of more subtle forms of topology, such as fragile and delicate.
Finally, I will briefly discuss real-space methods and tight-binding models in 3D photonics [8-9]. The goal is to build a local-orbital description of light that still captures its transverse and vector nature. The main difficulty is the so-called Γ-point singularity, which comes from Maxwell’s transversality constraint and has long made the Wannierization of 3D photonic bands difficult.
I will show how real-space invariants and transversality-enforced tight-binding models provide a first practical step in this direction, giving reduced models for 3D photonic crystals with far fewer degrees of freedom than full-wave simulations. I will then outline how extending these ideas toward vectorial Wannier functions could help model defects, nonlinearities, finite-size systems, interfaces and coupled emitters, while preserving the polarization properties of light. Similar ideas may also be useful for other 3D metamaterials where the vector nature of waves matters.
[1] "Cubic 3D Chern photonic insulators with orientable large Chern vectors." Nat. Commun. (2021). C. Devescovi, M. García-Díez, I. Robredo, M. Blanco de Paz, J. Lasa-Alonso, B. Bradlyn, J. L. Mañes, M. G. Vergniory, A. García-Etxarri. https://doi.org/10.1038/s41467-021-27168-w
[2] "Vectorial Bulk-Boundary Correspondence for 3D Photonic Chern Insulators." Adv. Opt. Mater. (2022). C. Devescovi, M. García-Díez, B. Bradlyn, J. L. Mañes, M. G. Vergniory, A. García-Etxarri. https://doi.org/10.1002/adom.202200475
[3] "Fermi arc reconstruction in synthetic photonic lattice." Phys. Rev. Lett. (2023). D.-H.-M. Nguyen, C. Devescovi, D. X. Nguyen, H. S. Nguyen, D. Bercioux. https://doi.org/10.1103/PhysRevLett.131.053602
[4] "Axion topology in photonic crystal domain walls." Nat. Commun. (2024). C. Devescovi, A. Morales-Pérez, Y. Hwang, M. García-Díez, I. Robredo, J. L. Mañes, B. Bradlyn, A. García-Etxarri, M. G. Vergniory. https://doi.org/10.1038/s41467-024-50766-3
[5] "Photonic axion insulator." Science (2025). G. G. Liu, S. Mandal, X. Xi, Q. Wang, C. Devescovi, A. Morales-Pérez, ... & B. Zhang. https://doi.org/10.1126/science.adr5234
[6] "Design and characterization of all 2D fragile topological bands." PNAS Nexus (2025). S. Bird, C. Devescovi, P. Engeler, A. Valenti, D. E. Gökmen, R. Worreby, V. Peri, S. D. Huber. https://doi.org/10.1093/pnasnexus/pgaf285
[7] "Observation of ring states in a delicate topological insulator." arXiv:2604.15983 (2026). C. Tornow, J. Rupprecht, P. Engeler, U. Drechsler, K.-E. Huhtinen, C. Devescovi, S. D. Huber. https://doi.org/10.48550/arXiv.2604.15983
[8] "Transversality-enforced tight-binding models for three-dimensional photonic crystals aided by topological quantum chemistry." Phys. Rev. B (2025). A. Morales-Pérez, C. Devescovi, Y. Hwang, M. García-Díez, B. Bradlyn, J. L. Mañes, M. G. Vergniory, A. García-Etxarri. https://doi.org/10.1103/2qp5-rblc
[9] "Building blocks of topological band theory for photonic crystals." arXiv:2601.06293 (2026). Y. Hwang, V. Gupta, A. Morales-Pérez, C. Devescovi, M. García-Díez, J. L. Mañes, M. G. Vergniory, A. García-Etxarri, B. Bradlyn. https://doi.org/10.48550/arXiv.2601.06293
Laboratory for Materials Simulations (LMS)