Intrapulse multimodal four-wave sum mixing in the visible range from high contrast index grating with PMMA layer

Year: 2026

Authors: Franceschini P., Tognazzi A., Menshikov E., Beliaev L.Y., Malureanu R., Takayama O., Alessandri I., Cino AC., De Ceglia D., Lavrinenko A.V., De Angelis C.

Autors Affiliation: Univ Brescia, Dept Informat Engn, Brescia, Italy; CNR, Natl Inst Opt, Brescia, Italy; Univ Palermo, Dept Engn, Palermo, Italy; ITMO Univ, Sch Phys & Engn, St Petersburg, Russia; Tech Univ Denmark, Dept Elect & Photon Engn, Kongens Lyngby, Denmark; Natl Ctr Nano Fabricat & Characterizat, DTU Nanolab, Kongens Lyngby, Denmark.

Abstract: Nonlinear metasurfaces have emerged as powerful platforms for enhancing and controlling light-matter interactions at the nanoscale, enabling versatile and compact design of devices for frequency conversion processes. In this work, we report on the experimental observation and theoretical analysis of intrapulse four-wave sum mixing (FWSM) in a high-index contrast grating (HCG) supporting quasi-bound states in the continuum (q-BIC). By engineering a one-dimensional silicon-based HCG with an additional poly(methyl methacrylate) (PMMA) cladding layer, we achieve the simultaneous excitation of a q-BIC and a guided-mode resonance (GMR), enabling nonlinear coupling between the two modes. Broadband femtosecond excitation reveals multiple distinct spectral peaks in the visible range, attributed to FWSM processes involving different combinations of q-BIC and GMR frequencies. Fourier microscopy measurements further confirm the redistribution of the generated nonlinear signals among diffraction orders. Our results demonstrate a new approach to tailoring nonlinear frequency mixing through metasurfaces, leveraging the interaction of multiple non-local resonances, thus opening new pathways for tunable frequency conversion, all-optical signal processing, and nonlinear photonic devices.

Journal/Review: LIGHT-SCIENCE & APPLICATIONS

Volume: 15 (1)      Pages from: 51-1  to: 51-13

More Information: A. V. L. acknowledges the Independent Research Fund Denmark, DFF Research Project 2, ADaptive optics for ELEctron beams (ADELE) 2035-00126B. This work was partially supported by the European Union under the Italian National Recovery and Resilience Plan (NRRP) of NextGenerationEU, of partnership on Telecommunications of the Future (PE0000 0001 – program RESTART), S2 SUPER – Programmable Networks, Cascade project PRISM – CUP: C79J24000190004. This work was partially supported by the project Smart Metasurfaces Advancing Radio Technology (SMART), CUP E63C22002040007.
KeyWords: Bound-states; Broad-band; Light; Phase
DOI: 10.1038/s41377-025-02090-8