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Anapole resonances in low-index materials

Photonic cavities are valued in current research owing to the multitude of linear and nonlinear effects arising from densely confined light. Cavity designs consisting of low loss dielectric materials can achieve significant light confinement, competitive with other schools of cavity design such as plasmonics. However, the basic concepts in all dielectric photonics such as anapole resonances in nanodisks have been primarily studied in high index materials such as WS2 and Si. Without additional measures, low index dielectric nanodisks struggle to achieve similar levels of light confinement. Here, we present fabricable design space for higher confinement in a low index dielectric cavity by incorporating the extensively studied, isolated dielectric nanodisk into broader host structures. In particular, we focus on hexagonal boron nitride (hBN), a novel dielectric 2D material with bright, room temperature single photon emitters and refractive indices of 2.1 and 1.8 in the inplane and out-of-plane directions. Due to hBN's potential as a quantum light source, we characterise our cavities by their achievable Purcell factors at the anapole resonance. The effects of the supporting structures on the cavity resonances include boosts to the Purcell factor by as much as three-fold to a maximum observed factor of 6.2.