The third-order optical nonlinearities of 80GeS(2)center dot(20 - x)Ga(2)S(3)center dot xY(2)S(3) (x = 0, 5, 10, 15, 20 and Y = Sb or In) chalcogenide glasses were investigated utilizing the Z-scan method at the wavelength of 800 nm and their linear optical properties and structure were also studied. By analyzing the compositional dependences and possible influencing factors including the linear refractive index, the concentration of lone electron pairs, the optical bandgap and the amount of weak covalent/homopolar bonds, it indicates that the electronic contribution in weak heteropolar covalent and homopolar metallic bonds is responsible for large nonlinear refractive index n(2) in the chalcogenide glasses. These chalcogenide glasses have characteristics of environmentally friendship, wide transparency in the visible region, high nonlinear refractive index n(2) and low nonlinear absorption coefficient beta, and would be expected to be used in the all-optical switches working at 1330 nm and 1550 nm telecommunication wavelengths. (C) 2010 Elsevier Ltd. All rights reserved.