Exciting Extended Bound States in the Continuum in Symmetry-Broken Scalable All Dielectric THz Metasurface

A scalable all dielectric silicon metasurface support symmetry-protected (SP) and accidental bound states in the continuum (BIC) is investigated, which can excite new multiple extended BIC by introducing perturbation to the metasurface. For these extended BICs at
$\Gamma$
point but are not part of the SP-BIC, theoretical analysis and mode profiles reveals that one extended BIC is Friedrich-Wintgen BIC (F-W BIC) and another extended BIC is a single resonance parameter BIC. Although the resonance frequency of proposed metasurface falls in the terahertz (THz) region, which can operate in the entire wavelength range from microwave to infrared by scaling the lattice constant.