Ultrafast switching of a metasurface quasi-bound state in the continuum via transient optical symmetry breaking

Year: 2025

Authors: Crotti G., Schirato A., Pashina O., Sergaeva O., Petrov M., De Angelis C., Della Valle G.

Autors Affiliation: Politecn Milan, Dipartimento Fis, Milan, Italy; Rice Univ, Dept Phys & Astron, Houston, TX USA; ITMO Univ, Sch Phys & Engn, St Petersburg, Russia; Univ Brescia, Dipartimento Ingn Informaz, Brescia, Italy; CNR, Ist Nazl Ott, Brescia, Italy; Ist Nazl Fis Nucleare, Sez Milano, Milan, Italy.

Abstract: In photonic structures, bound states in the continuum (BICs) have recently attracted huge interest in both fundamental and applied research. Quasi-BIC leaky modes resulting from in-plane symmetry breaking in metasurfaces are particularly relevant to applications, due to their high quality factor, which scales as the squared inverse of the asymmetry parameter. Here, we theoretically propose an innovative approach to switch on quasi-BICs on sub-picosecond timescales via optically induced symmetry breaking in semiconductor metasurfaces. The desired effect is granted by exploiting the spatial inhomogeneities in the distribution of photo-excited hot carriers at the single meta-atom nanometric scale. In our simulations, the quasi-BIC state manifests itself as an ultra-sharp dip in transmission, emerging upon pump arrival, and disappearing completely within the carriers’ diffusion timescale. Our strategy allows to envision reconfigurable platforms with switchable high-Q resonances, with ultrafast recovery beyond the limits of carrier relaxation, typical of previous approaches.

Journal/Review: LIGHT-SCIENCE & APPLICATIONS

Volume: 14 (1)      Pages from: 240-1  to: 240-12

More Information: This publication is part of the METAFAST project that received funding from the European Union Horizon 2020 Research and Innovation programme under grant agreement no. 899673. G.D.V. acknowledges the support from the HOTMETA project under the PRIN 2022 MUR programme funded by the European Union-Next Generation EU-PNRR-M4C2, investimento 1.1-Fondo PRIN 2022-HOT-carrier METasurfaces for Advanced photonics (HOTMETA), contract no. 2022LENW33-CUP: D53D2300229 0006, and by the European Union’s NextGenerationEU Programme with the I-PHOQS Infrastructure [IR0000016, ID D2B8D520, CUPB53C22001750006] Integrated infrastructure initiative in Photonic a nd Quantum Sciences. A.S. and G.D.V. acknowledge financial support from the European Union’s Horizon Europe research and innovation programme under the Marie Skaodowska-Curie Action PATHWAYS HORIZON-MSCA-2023-PF-GF grant agreement no. 101153856. G.C. acknowledges financial support from the ERC-StG ULYSSES grant agreement no. 101077181 funded by the European Union. Views and opinions expressed are those of the authors only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. The work was supported by the Federal Academic Leadership Program Priority 2030.
KeyWords: Bismuth compounds; Inverse problems; Metamaterials
DOI: 10.1038/s41377-025-01885-z