Femtosecond-laser-writing in various glasses

The localized modification of the refractive index in different glasses using a femtosecond laser direct-writing technique at 800 nm is described. The induced refractive-index changes were positive and negative depending on glass composition and laser-writing conditions. The optical properties of the generated structures were studied with different methods. Quantitative measurements were possible with a special interference microscope with shearing technique. Large differences were detected depending on glass composition and structure. Selected glasses were fused silica, multi-component borosilicate, borate and fluoride phosphate glasses. The induced refractive change in fluoride phosphate glasses increased with increasing phosphate content up to 5 × 10−3. A redistribution of fluoride and phosphate groups in the local irradiated volume is assumed in correlation with the crystallization behavior of these glasses.