Morphology of waveguide written by femtosecond laser in glass

Femtosecond laser writing in chalcogenide glasses offers great potentialities in photonic devices notably because of their high photo-sensitivity and their wide infrared transparency. We report longitudinal femtosecond inscriptions in As 2 S 3 glass bulks. Refraction index profiles of the waveguides have been reconstructed on the basis of quantitative optical phase microscopy. This technique is able to recover not only the magnitude (including its sign) but also the spatial distribution of the refractive index variation. Experiments have been performed for fixed deposited energy and varying the translation speed. We show that this simple parameter strongly influences the shape of the obtained profile. Discussion on the complex evolution of the magnitude and radius of the modification is proposed.