High Purcell Factor Driven by Simultaneous Bianisotropy and Anapole State in All‐Dielectric Metasurfaces

Abstract All‐dielectric nanophotonics is a rapidly evolving field, garnering increasing attention due to its potential in advancing nano‐optical technologies. Numerous groundbreaking phenomena have already been demonstrated through the unique optical properties of specially designed meta‐atoms, creating a new platform for nano‐optics. In particular, states characterized by strong near‐field confinement and magnetoelectric coupling have driven a paradigm shift, offering exciting possibilities for on‐chip optical devices, quantum applications, and light‐emitting technologies. In this paper, the coexistence of bianisotropy and the anapole state in a specifically engineered dielectric metasurface in the visible and near infrared (NIR) ranges is utilized to achieve extremely high values of electric and, specifically, magnetic Purcell factor for adjacent dipoles. The metasurface is composed of silicon meta‐atoms with a partially rectangular slot, which disrupts the in‐plane symmetry along the xy‐plane. Utilizing a theoretical framework based on polarizability and multipole decomposition, the system's bianisotropic response, driven by magnetoelectric coupling, and combine it with the anapole–a non‐radiating state known for its strong near‐field localization is analyzed. As a result of these two synergistic mechanisms, nearly a three‐order‐of‐magnitude increase is observed in both electric and magnetic Purcell factors, significantly enhancing light‐matter interaction. This remarkable effect opens new pathways for developing next‐generation photonic devices.