Exploiting quasi-Bound States in the Continuum for Laser-Induced Selective Crystallization in Metasurfaces

We introduce a design of an asymmetric metasurface composed of nanowires made of Germanium Antimony Tellurium. This metasurface exhibits quasi-bound states in the continuum modes. Employing a fully coupled optothermal model, we demonstrate that under brief and intense laser irradiation, the metasurface experiences spatially controlled crystallization, leading to an ultrafast dynamic shift in wavelength of the q-BIC, up to 350 nm. Remarkably, this effect occurs with pump intensities as low as $35 \mathrm{MW} / \mathrm{cm}^{2}$. Our proposed method showcases the ability to manipulate nanostructure responses using laser light, suggesting promising avenues for applications in dynamic optical modulation and beyond.