Thermo-Optical Synergistic Phase Transition Dynamics in VO₂ Thin Films for Intelligent Laser Limiting

In this work, VO2 thin films were first deposited on sapphire substrates using DC magnetron sputtering. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and radiometric analysis (RAMAN) demonstrated high film quality. Transmittance/reflection spectra were then measured using Fourier transform infrared (FTIR) spectroscopy, confirming high contrast in the mid-infrared region. Furthermore, a temperature control device and a 3.8μm high-power continuous-wave laser test platform were constructed to investigate the effects of temperature and power density on the VO2 phase transition. The results show that increasing both temperature and incident light power accelerates the VO2 phase transition. At room temperature (25°C) and an incident power density of 1083 W/cm2, a minimum temperature of 47°C is required for the phase transition to occur within 10 seconds. At 50°C, a phase transition occurs within 10 seconds at an incident power density of only 161 W/cm2. When the incident power density reaches 1083 W/cm2, the phase transition time is shortened to milliseconds. The phase change recovery time of VO2 thin films is closely related to parameters such as the heat dissipation performance of the substrate material and the ambient temperature. Therefore, the laser protection effect of VO2 thin films can be improved by optimizing the substrate material or adopting active heat dissipation.