The copper oxide nanoparticles (CuO NPs) were synthesized via solution combustion approach with Bengal gram powder as a fuel. The XRD analysis confirms the monoclinic structure of CuO NPs. FT-IR spectrum reveals the formation of CuO NPs. SEM studies show that the NPs are nearly spherical, and the elemental composition was confirmed by EDAX. The absorption spectra revealed a direct optical band gap of 1.50[Formula: see text]eV. DFT calculations were performed to determine the HOMO–LUMO energy bandgap and found to be 1.72[Formula: see text]eV, which is in good agreement with the experimental value. The Z-scan technique was used to investigate the third-order nonlinear optical (NLO) characteristics using DPSS continuous wave laser (532[Formula: see text]nm, 200[Formula: see text]mW). A high reverse saturation absorption and negative nonlinear refractions were observed. Third-order NLO parameters [Formula: see text], [Formula: see text] and [Formula: see text] were found to be [Formula: see text][Formula: see text]cm/W, [Formula: see text][Formula: see text]cm2/W and [Formula: see text][Formula: see text]esu, respectively. The CuO NPs also displayed strong optical limiting behavior with a limiting threshold of 2.11[Formula: see text]kW/cm2.

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