Structure dependence of ultrafast third-order optical nonlinearity for Ge—Ga—Cd sulfide glasses

Ultrafast third-order nonlinear optical responses of GeS₂—Ga₂S₃—CdS glasses have been measured by using femtosecond time-resolved optical Kerr effect (OKE) technique at the wavelengths of 820nm and 640nm respectively. The experimental results show that GeS₂—Ga₂S₃—CdS glasses have large femtosecond third-order optical nonlinear responses and their OKE signals vary considerably with the composition. The relationship of structure-property is discussed by means of Raman spectroscopy analysis, suggesting that the tetrahedron unit GeS₄ or GaS₄ plays an important role in the ultrafast third-order nonlinear optical response. In addition, the experimental results also reveal that the ultrafast third-order optical nonlinearity of these glasses does not obey the Miller rule.