A STUDY OF THE OPTICAL PROPERTIES AND ENERGY GAP TUNING THROUGH NICKEL DOPING IN Z-SCAN AND DIFFUSE REFLECTION TECHNIQUES FOR LA₀.₅SR₁.₅CO₂₋ₓNIₓO₂ COMPOSITE PARTICLES

Z-scan technique Optical bandgap Open-aperture Optical switches Photodetectors Oxygen vacancies

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September 10, 2026

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Objective: The primary focus of the study was to examine its linear and non-linear optical properties. Method: This research investigates the synthesis of the nanocomposite La₀.₅Sr₁.₅Co₂₋ₓNiₓO₂, which was prepared using the sol-gel method. Furthermore, the non-linear optical properties were studied using the Z-scan technique with both closed and open apertures in a Nd:YAG laser at a wavelength of 532 nm. Results: The results of the measurements revealed a gradual decrease in the optical bandgap, which ranges between 2.12–2.25 eV. This decrease was observed as the nickel doping fraction increased and may be attributed to orbital interaction between the oxygen, nickel and cobalt electrons, with the observation of localised states within the forbidden gap alongside the presence of a number of oxygen vacancies. The open-aperture results revealed saturated inverse non-linear absorption resulting from two-photon absorption. Furthermore, the closed-aperture results indicated the presence of negative non-linear refraction, with the sample having a ratio of x = 0.5 exhibiting a higher response in non-linear optical properties. Novelty: This result supports its use in promising applications such as laser safety devices, optical switches and photodetectors.