  We report on femtosecond laser writing of single mode optical waveguides in
chalcogenide Gallium Lanthanum Sulphide (GLS) glass. A multiscan fabrication
process was employed to create waveguides with symmetric single mode guidance
and low insertion losses at 800 nm wavelength, compatible with Ti:Sapphire
ultrafast lasers. {\mu}Raman and X-Ray microanalysis were used to elucidate the
origin of the laser-induced refractive index change in GLS. Nonlinear
refractive index measurements of the waveguides were performed by finding the
optical switching parameters of a directional coupler, demonstrating that the
nonlinear properties were preserved, evidencing that GLS is a promising
platform for laser-written integrated nonlinear photonics.
