Waveguide writing in chalcogenide glasses by a train of femtosecond laser pulses

Waveguide writing using a train of femtosecond laser pulses at 850 nm, in t he transparent spectral region of bulk As40S60 glasses is reported. Wavegui des were written by translating the glass sample along the optical axis of a strongly focussed laser beam. Refractive index variation, linear absorpti on spectra, and Raman spectra of the exposed region were measured. The chem ical mechanism responsible for the index variation has been correlated to a breakage of the glass' As-S bonds and formation of As-As and S-S bonds and increase of the "disorder" of the glass network. The nonlinear optical ori gin leading to this phenomenon has been shown, and possible mechanisms are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.