Light structuring via nonlinear total angular momentum addition with flat optics

Year: 2025

Authors: Menshikov E., Franceschini P., Frizyuk K., Fernandez-Corbaton I., Tognazzi A., Cino AC., Garoli D., Petrov M., De Ceglia D., De Angelis C.

Autors Affiliation: Univ Brescia, Dept Informat Engn, Via Branze 38, I-25123 Brescia, Italy; Natl Inst Opt Natl Res Council, Via Branze 45, I-25123 Brescia, Italy; Karlsruhe Inst Technol, Kaiserstr 12, D-76131 Karlsruhe, Germany; Univ Palermo, Dept Engn, Viale Sci Ed 9, I-90128 Palermo, Italy; Univ Modena & Reggio Emilia, Dipartimento Sci & Metodi Ingn, Via Amendola 2, Reggio Emilia, Italy; New Uzbekistan Univ, Movarounnahr 1, Tashkent 100000, Uzbekistan.

Abstract: Shaping the structure of light with flat optical devices has driven significant advancements in our fundamental understanding of light and light-matter interactions, and enabled a broad range of applications, from image processing and microscopy to optical communication, quantum information processing, and the manipulation of microparticles. Yet, pushing the boundaries of structured light beyond the linear optical regime remains an open challenge. Nonlinear optical interactions, such as wave mixing in nonlinear flat optics, offer a powerful platform to unlock new degrees of freedom and functionalities for generating and detecting structured light. In this study, we experimentally demonstrate the non-trivial structuring of third-harmonic light enabled by the addition of total angular momentum projection in a nonlinear, isotropic flat optics element-a single thin film of amorphous silicon. We identify the total angular momentum projection and helicity as the most critical properties for analyzing the experimental results. The theoretical approach we propose, supported by numerical simulations, offers quantitative predictions for light structuring through nonlinear wave mixing under various pumping conditions, including vectorial and non-paraxial pump light. Notably, we reveal that the shape of third-harmonic light is highly sensitive to the polarization state of the pump. Our findings demonstrate that harnessing the addition of total angular momentum projection in nonlinear wave mixing can be a powerful strategy for generating and detecting precisely controlled structured light.

Journal/Review: LIGHT-SCIENCE & APPLICATIONS

Volume: 14 (1)      Pages from: 381-1  to: 381-10

More Information: We acknowledge the assistance of ChatGPT (OpenAI) for minor grammatical suggestions. This work was partially supported by the European Union under the Italian National Recovery and Resilience Plan (NRRP) of NextGen erationEU, of partnership on Telecommunications of the Future (PE00000001-program RESTART), S2 SUPER-Programmable Networks, Cascade project PRISM-CUP: C79J24000190004, Cascade project SMART-CUP: Smart Metasurfaces Advancing Radio Technology (SMART), PRIN 2020 project METEOR (2020EY2LJT), METAFAST project that received funding from the European Union Horizon 2020 Research and Innovation program under Grant Agreement No. 899673.
KeyWords: 3rd-harmonic Generation; Amorphous-silicon; Diffraction; Beams; Field
DOI: 10.1038/s41377-025-02004-8