Metasurface-inspired polarization-sensitive all-dielectric terahertz biosensor based on quasi-bound state in the continuum

An all-dielectric terahertz metasurface biosensor consisting of two silicon cuboids deposited on a quartz substrate was proposed. By adjusting the length of the right cuboid and breaking the symmetry of the unit cell, a quasi-BIC driven ultra-high quality factor resonance is excited in x-polarization and y-polarization respectively at different resonance frequencies. For the C2v symmetry structure of the designed all-dielectric metasurface, two symmetry-protected BICs were aroused with complete destructive interference, since all of the coupling coefficients are symmetric. As a unique property of symmetry-protected quasi-BIC resonances, the quality factors can be manipulated as desired and even reach extremely high values by precisely changing the metasurface geometry. The sensitivity of the all-dielectric metasurface designed for biosensing purposes can reach up to 300 GHz/RIU, indicating superior sensing capabilities.