Free-shape 3D Structure Formation in Bulk Fused Silica by Irradiation with Femtosecond LaserPulses

In this manuscript, the development of the method for formation of three-dimensional (3D) structures etched in bulk fused silica is presented. 3D structures according to the designed 3D CAD drawing were inscribed inside the transparent material and etched with hydrofluoric acid. At first, two different scanning strategies were used to investigate the volume etching rate. The main technique for the formation of three-dimensional structures was based on the laser direct writing by scanning the multiple line arrays slice by slice inside fused silica to obtain rectangular channels. Complex 3D structures were formed by applying different scanning strategies in combination with linear and circular polarization and different pulse energies when the laser fluence was sufficient to induce the type-II modification in fused silica.