Phase Transformations Under the Action of Femtosecond Pulses in ZnO–MgO–Al₂O₃–SiO₂ Sitalls

The influence of femtosecond laser micromachining in thermal and athermal regimes on the structure of a transparent glass-ceramic based on the ZnO–MgO–Al₂O₃–SiO₂ system, which is characterized by heightened mechanical strength and hardness, was studied. Amorphization of nanosized granite ZnAl₂O₄ crystals, which occurs under the action of laser pulses, is confirmed by means of electron microscopy and electron diffraction. Quantitative phase microscopy was used to assess the change in the refractive index in the tracks written by a laser beam. In an athermal regime, at pulse repetition frequency 10 kHz, the full amorphization of the crystalline phase in the laser processing region in the bulk of the sitall effects an increase in the refractive index by ∆n = 0.0007. The results obtained expand the potential areas of application of transparent sitalls with heightened strength and open up the possibility of forming channel waveguides in their bulk by means of direct laser writing.