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

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.