Laser damage mechanism of VO2/Al2O3 films and numerical simulation

Abstract

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.