Metallic nanostructures are exceptionally effective at concentrating light into tiny volumes, while dielectric nanostructures excel at storing light with minimal energy loss. Combining these complementary properties has traditionally required complicated hybrid structures in which the two optical modes become mixed, making them difficult to control independently.

Achieving both resonance types within a single nanostructure without mode interference has therefore remained a major challenge in nanophotonics, limiting the development of compact, multifunctional optical devices.