NIR to UV Frequency Conversion Based on Polarization‐Sensitive BIC Excitation in Si‐Metasurface

Abstract In nonlinear photonics, frequency converter devices have important applications including efficient wavelength shifting, advanced optical signal processing, and enhanced imaging modalities. This study presents a bowtie‐shaped silicon metasurface designed for NIR to UV frequency conversion via third harmonic generation (THG). By breaking the symmetry of the metasurface to excite symmetry‐protected BIC (SP‐BIC) modes and converting them to quasi‐BIC (q‐BIC) states, the interaction between light and matter is enhanced. The BIC modes are also sensitive to incident light polarization. Achieving a polarization‐sensitive metasurface structure enables the development of compact, high‐performance polarization control devices that are essential for applications in optical communications, imaging, and sensing technologies. The results indicate a significant improvement in frequency conversion efficiency of the proposed q‐BIC based Si‐metasurface by 123 times compared to the same thickness unpatterned film.