In this paper, we aimed to investigate the linear and nonlinear optical properties of reduced graphene oxide-based metal oxide nanocomposite in comparison with reduced graphene oxide (RGO) and the effect of the process of reducing the oxygen groups of graphene oxide on the change of the nonlinear absorption coefficient of the reduced graphene oxide- zinc oxide (RGO-ZnO) and reduced graphene oxide-zinc oxide-iron oxide (RGO-ZnO-Fe2O4) sample. For this purpose, RGO, RGO-ZnO, and RGO–ZnO-Fe2O4 were synthesized using Hummers and hydrothermal methods, respectively, and then were analyzed using Fourier transform infrared (FT-IR), Ultraviolet-visible absorption (UV-Vis), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) were characterized. The XRD and FTIR analysis successfully synthesized RGO-ZnO and RGO-ZnO-Fe2O4 nanocomposites. Also, FT-IR spectroscopy indicated that absorption bands at 3340 cm-1, 1630 cm-1, 1730 cm-1, and 480 cm-1 are related to O-H, C=C, C=O, and Zn-O stretching vibrations, subsequently. The direct energy gap of GO, RGO, RGO-ZnO, and RGO-ZnO-Fe2O4 from UV-Vis spectra was reported to be 3.36, 3.18, 3.25, and 2.7eV, respectively. In addition, the third-order nonlinear optical properties (the nonlinear absorption coefficient) of all samples were investigated using the Z-scan technique with Nd: YAG laser (532 nm, 70 mW), and it was observed that the third-order nonlinear optical properties were increased from 8.3×10-4cm/W for RGO to 5.6×10-3 cm/W for RGO-ZnO-Fe2O4. پرونده مقاله

In this work, we analyze and compare the optical properties of spherical A: CdSe–ZnS–CdSe and B: ZnS-CdSe-ZnS core–shell–shell quantum dots (CSQDs). Under the framework of the effective mass envelope function theory, the nonlinear susceptibilities associated with inter-sub-band transitions in the conduction band are computed by solving the three-dimensional Schrödinger equation for A and B QDs in the presence of impurity. We theoretically investigate the third-order susceptibilities and optical absorption coefficients as a function of core radius while the outer radius of quantum dots was fixed. The numerical calculations show that QD size plays a fundamental role in determining the nonlinear optical properties of QDs. The susceptibilities and the absorption coefficients have pronounced single peaks (resonance) and depend strongly on the geometry of these two quantum dots as well as the effect of the quantum confinement. Our theoretical study shows that susceptibility and absorption coefficients peaks are red-shifted by increasing the core radius, and the magnitude of susceptibility and absorption coefficient increase. The resonant magnitudes Im ( ) of A and B-CSQD are negative and are around (-2.4) and (-2.5), respectively. While, for the core radius of R1 = 40 nm, Real ( ) of A and B-CSQD changes significantly near the resonant frequency from positive value (+1.7, +1.6) to negative one (-1.7, -1.6), respectively. Furthermore, for R1 = 40 nm, the absorption coefficient of A-CSQDs has reached a maximum with the magnitude of situated at approximately 0.02 eV. In contrast, this value is equal to for B-CSQD. Our computational results may open a new window in the development of QDs structures for application in optoelectronic devices. پرونده مقاله