Nanogratings formation in multicomponent silicate glasses

We demonstrate the formation of porous nanogratings in various oxide glasses including TiO2-doped silica, GeO2 and alumino-borosilicate by near-IR femtosecond laser radiation. ULE and GeO2 glasses exhibit similar birefringence to pure silica, whereas Borofloat 33 reveals twice weaker amplitude. Using quantitative birefringence measurements, small-angle X-ray scattering and scanning electron microscopy, we correlate birefringence and porous nanolayers formation according to laser repetition rate and glass composition. We show that heat accumulation is a crucial parameter limiting the glass decomposition and thus nanogratings formation.