A Simplified Model for Polycrystalline BaTiO3 Nanoresonator for Second Harmonic Generation

Year: 2024

Authors: Tognazzi A., Franceschini P., Weigand H., Talts U.L., Cino AC., Grange R., De Angelis C.

Autors Affiliation: Univ Palermo, Dipartimento Meccan, Viale Sci, I-90128 Palermo, Italy; Ist Nazl Ott Consiglio Nazl Ric INO CNR, Via Branze 45, I-25123 Brescia, Italy; Univ Brescia, Via Branze 38, I-25123 Brescia, Italy; Swiss Fed Inst Technol, Inst Quantum Elect, Dept Phys, Opt Nanomat Grp, CH-8093 Zurich, Switzerland.

Abstract: Second Harmonic Generation (SHG) has become a critical technique in material characterization, image processing and microscopy. While bulk crystals have been traditionally used for SHG due to their high conversion efficiencies, limited control over radiation properties, delicate phase-matching conditions and alignment pose significant challenges. The exploration of nanoscale materials and structures based on dielectric platforms has provided enhanced SHG efficiency and control, but their limited transparency in the visible spectral range and complex fabrication processes hinder broader application. Barium titanate (BaTiO3), a ferroelectric material with spontaneous polarization and nonlinear optical behavior, presents an attractive alternative due to its suitability for nano-imprinting techniques, facilitating scalable production of metasurfaces. In this study, SHG from single polycrystalline BaTiO3 nanocylinders is investigated. Through polarization-dependent experiments, the influence of crystalline domain orientation and arrangements within the nanocylinders on SHG efficiency is characterized. A simplified numerical model to interpret the different polarization-dependent SHG diagrams obtained from nominally identical nanocylinders is developed. The results reveal the significant impact of domain geometry and relative size on SHG characteristics. By understanding the relationship between domain geometry and SHG giving insights into the material characterization and design optimization of BaTiO3 and other polycrystalline nanostructures in nonlinear optical devices.

Journal/Review: ADVANCED OPTICAL MATERIALS

More Information: A.T. acknowledges the financial support from the European Union through FESR o FSE, PON Ricerca e Innovazione 2014-2020 – DM 1062/2021 and the University of Palermo through Fondo Finalizzato alla Ricerca di Ateneo 2024 (FFR2024). H.W. acknowledges support from the physics department of ETH Zurich. 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 (PE00000001 – program RESTART), S2 SUPER – Programmable Networks, Cascade project PRISM – CUP: C79J24000190004.
KeyWords: BaTiO3; nanophotonics; second harmonic generation
DOI: 10.1002/adom.202402484