  This work examines a symmetry-protected bound state in the continuum (BIC)
supported unique all-dielectric dome-shaped metasurface (MS). The simple unit
MS is made up of four dome-shaped nanobars of silicon in the top layer and
silica glass as the substrate. Two strong transmission dips denoted as an
electric dipole (ED) and magnetic dipole (MD) quasi-BIC with a high Q-factor
that surpasses the value of 104 are observed after the symmetry between the
nanobars is broken by a small angle from their initial position. A crossover
between the ED and MD resonances is noticed when the periodicity of the MS is
changed in the y direction. In addition, transmission spectra show the
avoided-crossing phenomenon of dipole quasi-BIC resonances when the
superstrate's refractive index (RI) is reduced from its initial value. Other
widely used dielectric materials are additionally employed in dome-shaped
nanobars to evaluate their performances in terms of sharpness and near-zero
transmission. Moreover, Other forms of symmetry breakdown such as diagonal
width and length asymmetry have been investigated for their impact on the
Q-factor. Finally, we have demonstrated two significant applications, including
refractometric glucose sensing and third harmonic generation (THG). Our
dome-shaped MS is roughly 300 times more efficient at generating third
harmonics than a flat rectangular silicon film MS. Our proposed BIC and
q-BIC-facilitated MS may provide a method for enhancing the functionality of
biological sensors, multimodal lasing, optical switches, and nonlinear optics.

Optics;Applied Physics