Laser damage mechanism of VO₂/Al₂O₃ films and numerical simulation

Vanadium dioxide (VO₂) undergoes a metal-insulator transition at 68 °C, exhibiting high infrared transparency at low temperatures and high infrared reflectivity at high temperatures. The unique property makes VO₂ a promising smart material for laser protection. However, there is limited research on laser damage behavior and laser prediction technology of VO₂ films. In this work, the finite element simulation was conducted to study the evolution of temperature and thermal stress fields and the failure of VO₂/Al₂O₃ films under continuous-wave (CW) laser irradiation with thermo-mechanical coupling modeling. The simulated temperature field of irradiated VO₂ films was validated through laser irradiation experiments with an infrared thermal imager. The laser damage behavior of VO₂/Al₂O₃ films was investigated through microstructure analysis and in-situ optical monitoring during CW laser irradiation. It was evidenced that thermal oxidation failure of the VO₂ film and thermal stress fracture of the Al₂O₃ substrate are the two main failure modes of VO₂/Al₂O₃ films under CW laser irradiation (35 W). The critical failure time and temperature for the thermal oxidation failure of VO₂ films were determined by annealing experiments and used as the failure criteria for finite element simulation. The numerical simulation well predicts the laser damage of VO₂/Al₂O₃ films. This demonstrates a reliable approach to assist in the design of laser-protective materials and technology based on VO₂.