Large and Ultrafast Third-Order Nonlinear Optical Propertiesof Ge-S Based Chalcogenide Glasses

Abstract

We report ultrafast third-order nonlinear optical (NLO) properties ofseveral chalcogenide glasses GeSx (x = 1.8, 2.0, 2.5)measured by femtosecond time-resolved optical Kerr gate technique at820 nm. The third-order nonlinear susceptibility of GeS1.8 glassis determined to be as large as 1.41×10−12 esu, which is themaximum value of the third order nonlinear susceptibility χ(3)for the three compositions investigated. The symmetric Gauss profiles ofoptical Kerr signals reveal the nature of ultrafast nonlinear responseof these samples, which are originated from the ultrafast polarizationof the electron clouds. By detailed microstructural analysis of theseglasses based on the chain-crossing model (CCM) and therandom-covalent-network model (RCNM), it can be concluded thatχ(3) value of GeSx glasses can be enhanced greatly by S–Scovalent bonds or S3Ge–GeS3 ethane-like units.