It is generally admitted that femtosecond laser pulses applied to fused silica in a non-ablative regime at repetition rates excluding cumulative effects leads to structural modifications of mainly two types: the formation of nanogratings and a reduction of volume leading to a localized densification. Here, we report recent observations that show that the taxonomy of material modifications induced by the laser is significantly richer than previously known. In particular, we observe evidences of complex polymorphic phases, including possible Si nano-cristallites, eventually embedded in an amorphous shell.
In addition, exploring the cumulative regime further, we have observed that nanogratings can also be found in this regime characterized by a melting of the glass phase. This surprising results point out towards complex self-organization phenomena taking place also in the cumulative regime.
Both observations, a richer taxonomy of phase transformations in the non-cumulative regime and the occurrence of nanogratings in the cumulative regime, beyond challenging our understanding of laser-induced phase transformation, have interesting applications potential that will be outlined in this presentation.