Selective Delamination upon Femtosecond Laser Ablation of Ceramic Surfaces

We report on the experimental observation of selective delamination of semitransparent materials on the example of yttria-stabilized zirconia ceramics upon femtosecond laser processing of its surface with a low numerical aperture lens. The delamination of a ceramic layer of dozens of micrometers takes place as a side effect of surface processing and is observed above the surface ablation threshold. The onset of delamination (delamination threshold) depends on the degree of overlap of the irradiation spots from consecutive laser pulses upon beam scanning over material surface. Analysis of the delaminated layer indicates that the material undergoes melting on both of its surfaces. The mechanism of delamination is identified as a complex interplay between the optical response of laser-generated free-electron plasma and nonlinear effects upon laser beam propagation in semitransparent ceramics. The discovered effect enables controllable laser microslicing of brittle ceramic materials.