Abstract: Cu_7.2S₄ quantum dots glass was synthesized by both sol-gel and atmosphere control methods. The mechanism thermal decomposition of the stiff gel was studied by means of thermogravimetry-differential thermal analysis. The microstructures of Cu_7.2S₄ quantum dots in the glass were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, energy dispersion X-ray spectra, high-resolution transmission electron microscopy, and selected-area electron diffraction. Meanwhile, the third-order nonlinear optical properties of the glass were measured in detail by the femtosecond Z-scan technique at a wavelength of 800 nm. The results show that Cu_7.2S₄ quantum dots have been formed in the glass, and the sizes of these Cu_7.2S₄ quantum dots having the tetragonal crystalline structure ranged from 9 nm to 21 nm, moreover, the glass exhibits the excellent third-order nonlinear optical properties, and the third-order nonlinear optical refractive index(γ), absorption coefficient(β) and susceptibility [X⁽³⁾] of the glass are determined to be 1.11×10^-15 m²/W, 8.91×10^-9 m/W, and 9.56×10^-18 m²/V², respectively. Because of so excellent third-order nonlinear optical properties of the glass doped with Cu_7.2S₄ quantum dots imply that the kind of material will be widely applied in nonlinear optical devices.

Key words: Cu_7.2S₄ quantum dots glass, Sol-gel method, Microstructure, Femtosecond Z-scan technique