Optical Bound States in Continuum in MoS-Based Metasurface for Directional Light Emission.

High quality factor (-factor) and strong field localization in nanostructures is a newly emerged direction in nanophotonics. The bound states in the continuum (BIC) have been investigated in nanoparticles with infinite -factor. We report BIC in molybdenum disulfide (MoS) based Mie nanoresonator suspended in air. The ultrathin nanodisk supports symmetry protected BIC, and the quasi-BIC (-BIC) are exploited by breaking the symmetry of the structure. The strongly localized modes in our MoS-based nanodisk sustain a similar magnetic field profile before and after symmetry breaking, unlike what has been previously reported in silicon-based structures. Strong directional emission is observed in BIC regime from a hybrid configuration with a resonator placed on the stacked metal-dielectric layers, which transform BIC to -BIC and exploit highly directional light. The structure persists emission with small variations in normalized intensity at distorted symmetry. The giant -factor in -BIC is highly desired for biosensing and optical filters.