Bound States in the Continuum in Cylindrical All-Dielectric Metasurface Cavities

Bound states in the continuum are presently demonstrated in all-dielectric, metasurface-based cavities of circularly cylindrical shapes. While their cross-sectional sizes may be arbitrary, emphasis is put on the much-needed excitation of these intriguing states in subwavelength cavities. The employed metasurfaces are characterized by effective electric and magnetic surface impedances, allowing for a swift analytical analysis of the underlying problem. The inclusion of magnetic responses, in addition to the electric one, enhances the versatility of the proposed cavities, significantly extending their application, particularly in optical contexts where magnetism is absent. To demonstrate the potential of the proposed method, an all-dielectric metasurface composed of appropriately arranged silicon particles is designed and investigated in the optical frequency range, resulting in a quality factor of ∼1.7×10^{4}.