Antenna-Based Approach to Fine Control of Supercavity Mode Quality Factor in Metasurfaces.

The utilization of photonic bound states in the continuum (BIC) is a very attractive approach for many applications requiring efficient resonators. High-Q modes related to symmetry-protected BIC are formed due to perturbation defined by an asymmetry parameter, and the smaller this parameter is, the bigger the Q factor can be achieved. Inevitable fabrication imperfectness limits precise control of the Q factor through the asymmetry parameter. Here we propose an antenna-based design of metasurfaces for accurate tailoring of the Q factor where stronger perturbation leads to the same effect in the conventional design. This approach allows the fabrication of samples with equipment having lower tolerance keeping the Q factor at the same level. Furthermore, our findings reveal two regimes of the Q factor scaling law with saturated and unsaturated resonances dependent on the ratio of antenna particles to all particles. The boundary is defined by the efficient scattering cross section of the metasurface constituent particles.