Bhowmik, Bhairov Kumar2025-04-072025-04-072025ROLL NO.196121102https://gyan.iitg.ac.in/handle/123456789/2862Supervisor: Kumar, GaganBound States in the Continuum (BICs) are states that remain perfectly localized despite lying in the continuum, with ideal BICs possessing an infinite Q factor. However, real scenarios exhibit quasi-BIC modes, observed as Fano resonances with high but finite Q factors. This thesis investigates symmetry-protected quasi-BIC modes in metasurfaces for terahertz (THz) and near-infrared (NIR) applications.enThesis