Molecular structure, linear, and third-order nonlinear optical treatment of GO@ZnFe2O4/TMSP/CdTe QDs nanocomposite: Preparation and characterization

Abstract

This study reports the synthesis and characterization of a novel GO@ZnFe₂O₄/TMSP/CdTe nanocomposite with enhanced third-order nonlinear optical (NLO) properties. The nanocomposite was synthesized via a solvothermal method and structurally characterized using Xray diffraction (XRD), Fourier Transform Infrared (FTIR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), and ultraviolet-visible (UV–Vis) spectroscopy. XRD analysis confirmed the successful formation of the composite phases with good crystallinity, while FTIR spectra revealed strong chemical bonding between the constituents. FESEM images showed a uniform morphology and intimate contact among the components. Magnetic measurements indicated a superparamagnetic behavior with moderate saturation magnetization, confirming the preservation of ZnFe₂O₄ magnetic properties within the hybrid structure. The complex dielectric function was derived using Kramers–Kronig (KK) analysis of FTIR reflectance spectra, revealing prominent LO and TO phonon modes. NLO measurements were performed using the continuous-wave (CW) Z-scan technique at 532 nm. The nanocomposite demonstrated reverse saturable absorption (RSA) and a negative nonlinear refractive index ($n_2$), with self-defocusing effect. Importantly, the nonlinear coefficients were found to increase with increasing nanocomposite concentration, confirming the role of particle density in enhancing the NLO response. These findings indicate strong light-matter interactions and thermal contributions under CW excitation. Comparative analysis with reported materials shows that the synthesized nanocomposite exhibits competitive NLO performance. The material's multifunctionality and strong optical nonlinearity suggest promising applications in optical limiting, photonic switching, and magneto-optical devices.