Speaker
Description
The discovery of new high-refractive-index dielectric materials is essential for advancing optical nanotechnologies, including metasurfaces, nanoantennas, and photonic devices operating across the visible and ultraviolet spectra [1]. While traditional materials like silicon and gallium phosphide have enabled much of the progress in all-dielectric nanophotonics, expanding the palette of high-index materials remains a key challenge, particularly for the ultraviolet and visible ranges.
In this talk, we present a combined theoretical and experimental approach to discovering new high-index materials. We first highlight our discovery of boron phosphide (BP), identified via high-throughput density functional theory (DFT) screening of over 2000 stable binary compounds [2]. BP offers a refractive index exceeding 3 with low absorption losses across the infrared to near-ultraviolet, a property validated experimentally through dark-field scattering and electron energy-loss spectroscopy of BP nanoparticles. These particles exhibit Mie resonances, demonstrating the potential of BP for optical applications in both the visible and near-ultraviolet spectral ranges.
Building on this methodology, we recently explored van der Waals materials and identified hafnium disulfide (HfS2) as a promising high-index candidate. Our ab initio calculations predict an in-plane refractive index above 3 with strong optical anisotropy in the visible range. Experimental ellipsometry confirms these predictions, and we further demonstrate the photonic potential of HfS2 by fabricating nanodisk resonators that exhibit Mie resonances in the visible spectrum. While we observe some chemical degradation of HfS2 when stored in ambient conditions, we show this can be mitigated by controlled storage environments.
Together, these studies showcase a pathway to discovering and experimentally validating new high-index materials, enabling future advances in nanoscale optics.
References
[1] S. Raza, K. S. Thygesen, and G. Naik, “Breaking the Moss rule”, arXiv:2602.16247 (2026).
[2] M. K. Svendsen, H. Sugimoto, A. Assadillayev, D. Shima, M. Fujii, K. S. Thygesen, and S. Raza, “Computational discovery and experimental demonstration of boron phosphide ultraviolet nanoresonators”, Adv. Optical Mater. 10, 2200422 (2022).
[3] X. Zambrana-Puyalto, M. K. Svendsen, A. H. Søndersted, A. Sarbajna, J. P. Sandberg, A. L. Riber, G. Ermolaev, T. M. Boland, G. Tselikov, V. S. Volkov, K. S. Thygesen, and S. Raza, "Computational discovery and experimental validation of of high-refractive index HfS2 nanoresonators", Sci. Adv. 11, eadw9339 (2025).