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

Abstract

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 symmetryprotected 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.

Selective Perturbation of Eigenfield Enables High-Q Quasi-Bound States in the Continuum in Dielectric Metasurfaces

“…Intrinsically, BICs are nonradiating singular states embedded in the radiative continuum but fully decoupled from the continuum and localized in the medium with zero resonance line width and infinite quality factor ( Q -factor) . According to the physical mechanisms, BICs can be classified into four categories, , including symmetry-protected BICs (SP-BICs), − accidental BICs, − Friedrich–Wintgen BICs, − and Fabry–Perot BICs. , Among them, SP-BICs are the most common and are easy to realize experimentally. The SP-BICs located at high symmetry points in momentum space are the most intensively studied and can be easily found in periodic structures which satisfy C 2 symmetry and mirror symmetry unit cells .…”

A Quasi-Bound States in the Continuum Dielectric Metasurface-Based Antenna–Reactor Photocatalyst

“…Metasurfaces have garnered significant attention in recent years as new platforms due to their exceptional thermal conversion, electromagnetic manipulation, and acoustic wave control. − Metamaterials, by definition, provide functionalities not available in natural materials such as negative indices of refraction and extremely high photon densities of states: metasurfaces are designed to possess these properties in a 2D format. Their unique features enable new ways to control and concentrate the flow of electromagnetic (EM) energy, by manipulating effective electric permittivities and magnetic permeabilities, also in the ultrafast regime. − A recent type of metasurface that has shown extraordinary potential is a quasi-Bound States in the Continuum (quasi-BIC) metasurface, which exploits nonradiative optical states for enhancing light–matter interactions. − Quasi-BIC states first appeared in the context of the developing field of quantum mechanics; however, they were later described more generally as arising from the destructive interference between a pair of resonances. This effect occurs when the coupling constants of all radiating waves disappear by appropriate tuning of the geometrical parameters of a system (known as the Friedrich–Wintgen scenario, 1985) .…”