Understanding non-degenerate second-order optical effects applied to molecular, macromolecular systems and inorganic nanoparticles

• Grant number: 25/01908-3
• Support Opportunities: Regular Research Grants
• Start date: August 01, 2025
• End date: July 31, 2028
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Leonardo de Boni
• Grantee: Leonardo de Boni
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated researchers: Cleber Renato Mendonça ; Daniel Luiz da Silva ; Lino Misoguti

Abstract

The project presented aims to develop a non-degenerate hyper-Rayleigh scattering experiment, which will allow the determination of the first hyperpolarizability of organic and inorganic materials in solution or dispersion in solvent. The technique will use two pulsed laser beams, which will be independently tunable at different wavelengths, enabling studies that cover light in the visible and near-infrared spectrum, providing high versatility in the combination of excitation frequencies. The independent control of the two excitation frequencies will make it possible to optimize the non-linear scattering signal using intrinsic properties of the materials, such as, for example, the absorption bands, which provides resonant enhancement effects of one or two photons in the non-linear optical properties. The technique will also allow the control of the linear or circular polarization of the beams independently, allowing the observation of the optical activity of hyper-Rayleigh scattering and the combination of different polarization pairs.After assembling the technique, it will be used to study the first hyperpolarizability of several sets of compounds. By observing the second-order effect of materials under different conditions, it will be possible to relate their second-order optical property with structural and electronic properties, enabling the understanding of the non-degenerate nonlinear optical processes of these materials and their electronic structure. Four groups of compounds will be studied: azoaromatic compounds, chiral biomolecules, chiral supramolecular polymers and non-emissive perovskite nanocrystals. The study of the second-order optical response of these materials will enable a greater understanding of the relationship between structure and nonlinear effect, enabling future photonic applications. Furthermore, the different groups of materials will make it possible to test the capabilities of the non-degenerate hyper-Rayleigh scattering technique and enable numerous new non-linear optical spectroscopy studies. (AU)