Optimizing laser-induced refractive index changes in “thermal” glasses

Abstract : Ultrafast laser radiation usually induces rarefaction and negative refractive index changes in glasses with high thermal expansion. Acting on the laser-induced heat source, tailored intensity envelopes can generate in turn thermo-mechanical compaction. This leads to positive refractive index changes and to potential creation of light guiding structures. Using additional spatial wavefront corrections, the compaction mechanisms can be preserved at arbitrary depths.