Characterization and nonlinear optical property of Ag-TiO2 nanocomposites fabricated by laser fragmentation in liquid

This study presents an approach to synthesize Ag-TiO₂ nanocomposites (NCPs) with enhanced nonlinear optical (NLO) properties using laser fragmentation in liquid (LFL). We employed 30 nm Ag nanoparticles (NPs) and 5 nm TiO₂ NPs as precursors, utilizing different concentration ratios in aqueous solution. The LFL technique, using a Nd:YAG laser (532 nm, 15 ns pulse duration), enabled direct preparation of Ag-TiO₂ NCPs. The morphology, structure, and optical properties of the synthesized NCPs were characterized using TEM, XRD, and UV–visible spectroscopy. NLO properties were investigated using the Z-scan technique with a femtosecond Ti:Sapphire laser (800 nm, 129 fs pulse duration). Results revealed enhancement in nonlinear absorption in Ag-TiO₂ NCPs compared to pure Ag NPs. The nonlinear absorption coefficient (β) and nonlinear refractive index (n₂) were determined experimentally using ZnSe as standard sample. The β value was found to be 1.27 cm/GW. The n₂ and the third-order nonlinear susceptibility (χ³) were on the order of 10⁻¹⁴ esu. We propose that TiO₂ NPs enhance the local electric field of Ag NPs and promote charge transfer, significantly improving the NLO response of the composite material. This study provides new insights into the controlled preparation and performance optimization of Ag-TiO₂ NCPs, offering potential applications in NLO applications.