Opto-thermal dynamics of thin-film optical limiters based on the VO₂ phase transition

Protection of human eyes or sensitive detectors from high-intensity laser radiation is an important challenge in modern light technologies. Metasurfaces have proved to be valuable tools for such light control, but the actual possibility of merging multiple materials in the nanofabrication process hinders their application. Here we propose and numerically investigate the opto-thermal properties of plane multilayered structures with phase-change materials for optical limiters. Our structure relies on thin-film VO₂ phase change material on top of a gold film and a sapphire substrate. We show how such a multi-layer structure can act as a self-activating device that exploits light-to-heat conversion to induce a phase change in the VO₂ layer. We implement a numerical model to describe the temporal evolution of the temperature and transmittivity across the device under both a continuous wave and pulsed illumination. Our results open new opportunities for multi-layer self-activating optical limiters and may be extended to devices based on other phase change materials or different spectral regions..