Optically resonant all-dielectric diabolo nanodisks
Optically resonant all-dielectric nanostructures attractively exhibit reduced losses compared to their plasmonic counterparts; however, achieving strong field enhancements at the nanoscale, especially within solid-state media, has remained a significant challenge. In this work, we demonstrate how subwavelength modifications to a conventional silicon nanodisk enable strong sub-diffractive and polarization dependent field enhancements in devices supporting anapole-like modes. We examine the electromagnetic properties of both individual and arrayed diabolo nanodisks, which are found to exhibit |E|$^2$/|E$_0$|$^2$ enhancements in the range ~10$^2$-10$^4$, in the high index medium, depending on geometrical considerations. In addition to supporting a localized electric field hot-spot similar to those predicted in diabolo nanostructured photonic crystal cavities and waveguide designs, we identify an anti-diabolo effect leading to a broadband cold-spot for the orthogonal polarization. These findings offer the prospect of enhancing or manipulating light-matter interactions at the nanoscale within an all-dielectric (metal free) platform for potential applications ranging from nonlinear optics to quantum light sources, nano-sensing, nanoparticle-manipulation and active/tunable metasurfaces.