Nonlinear absorption and refraction in chalcogenide glasses: multiphoton absorption and switching figures-of-merit

Summary form only given. Over the last few years there has been effort in making new materials with large nonlinear refractive index (n/sub 2/) for ultrafast all-optical switching. In particular, chalcogenide glasses have emerged as promising candidates for future optical switching devices due to their large electronic nonlinear refractive indices and ability to produce fibers with them. However, some of the earlier work reported that, at the communication wavelengths (1300 and 1550 nm), the large nonlinearity was coupled with the drawback of photo-darkening initiated by two-photon absorption. Modification in composition of these glasses can lead to significant changes in their linear and nonlinear optical properties. In an attempt to remove photo-darkening we have introduced dopants (Ga/sub 2/S/sub 3/, CsI, Ag/sub 2/S, SnS) that shift the band edge of the samples towards the blue region of the spectrum. The samples still maintain a large nonlinear refractive index but now the most significant multiphoton process, depending on the material composition, is only three, four or even five-photon absorption.