Nonlinear optical materials with significant reverse saturable absorption hold great potential for practical optical limiting technologies. This study specifically focuses on the third-order thermo-optic nonlinearity of RGO-Ta2O5/g-C3N4 nanocomposites using a single-beam Z-scan technique with continuous-wave Nd: YAG laser beams. A wet chemical method utilizing the ultrasonication technique was employed in a one-pot preparation route to synthesize the RGO-Ta2O5/g-C3N4 nanocomposites. The successful formation and composition of the RGO-Ta2O5/g-C3N4 nanocomposites were confirmed through XRD and FESEM-EDS analysis. Linear optical properties were analyzed using UV-Vis and PL spectroscopies to study optical absorption and emission characteristics. The RGO-Ta2O5/g-C3N4 nanocomposites exhibited thermal-assisted nonlinear reverse saturable absorption and a thermo-optic-induced positive nonlinear refractive index with a self-focusing effect at a wavelength of 532 nm. Third-order nonlinear studies showed numerical values of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\:10.85\times\:{10}^{-4}\:cm/W\)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\:9.29\times\:{10}^{-8}\:{cm}^{2}/W\)</EquationSource> </InlineEquation> for the nonlinear absorption coefficient and refraction index, respectively. The estimated reverse saturable absorption coefficient was approximately 1.98, 3.34, and 1.60 times greater than those of the Pristine-Ta2O5, Pristine-g-C3N4, and Ta2O5/g-C3N4 samples, respectively. Additionally, the obtained nonlinear refractive index of the RGO-Ta2O5/g-C3N4 nanocomposites was 2.20, 5.56, and 1.72 times higher than those of the Pristine-Ta2O5, Pristine-g-C3N4, and Ta2O5/g-C3N4 samples, respectively. These results suggest the significant role of Type-II alignment at the Ta2O5/g-C3N4 contact junction and the Schottky barrier created at the Ta2O5/RGO interface, as verified by PL studies, in enhancing the third-order thermo-optic nonlinear characteristics. The remarkable reverse saturable absorption of RGO-Ta2O5/g-C3N4 nanocomposites highlights their potential as efficient candidates for optical limiting devices in modern photonics.

Reduced graphene oxide-tantalum pentoxide/graphitic carbon nitride nanocomposites: enhanced third-order thermo-optic effect and reverse saturable absorption

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发表日期：

2025年10月14日

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Azadeh Haghighatzadeh

摘要

Nonlinear optical materials with significant reverse saturable absorption hold great potential for practical optical limiting technologies. This study specifically focuses on the third-order thermo-optic nonlinearity of RGO-Ta₂O₅/g-C₃N₄ nanocomposites using a single-beam Z-scan technique with continuous-wave Nd: YAG laser beams. A wet chemical method utilizing the ultrasonication technique was employed in a one-pot preparation route to synthesize the RGO-Ta₂O₅/g-C₃N₄ nanocomposites. The successful formation and composition of the RGO-Ta₂O₅/g-C₃N₄ nanocomposites were confirmed through XRD and FESEM-EDS analysis. Linear optical properties were analyzed using UV-Vis and PL spectroscopies to study optical absorption and emission characteristics. The RGO-Ta₂O₅/g-C₃N₄ nanocomposites exhibited thermal-assisted nonlinear reverse saturable absorption and a thermo-optic-induced positive nonlinear refractive index with a self-focusing effect at a wavelength of 532 nm. Third-order nonlinear studies showed numerical values of \(\:10.85\times\:{10}^{-4}\:cm/W\) and \(\:9.29\times\:{10}^{-8}\:{cm}^{2}/W\) for the nonlinear absorption coefficient and refraction index, respectively. The estimated reverse saturable absorption coefficient was approximately 1.98, 3.34, and 1.60 times greater than those of the Pristine-Ta₂O₅, Pristine-g-C₃N₄, and Ta₂O₅/g-C₃N₄ samples, respectively. Additionally, the obtained nonlinear refractive index of the RGO-Ta₂O₅/g-C₃N₄ nanocomposites was 2.20, 5.56, and 1.72 times higher than those of the Pristine-Ta₂O₅, Pristine-g-C₃N₄, and Ta₂O₅/g-C₃N₄ samples, respectively. These results suggest the significant role of Type-II alignment at the Ta₂O₅/g-C₃N₄ contact junction and the Schottky barrier created at the Ta₂O₅/RGO interface, as verified by PL studies, in enhancing the third-order thermo-optic nonlinear characteristics. The remarkable reverse saturable absorption of RGO-Ta₂O₅/g-C₃N₄ nanocomposites highlights their potential as efficient candidates for optical limiting devices in modern photonics.