Core-shell nanoresonator arrays to achieve epsilon-near-zero metamaterials

Targets seeded with multilayers of periodic passive and active core-shell nanoresonator patterns were studied to create epsilon-near-zero materials. First, the material of the shell was determined in order to achieve near-zero permittivity at the selected wavelength in the passive target. Then, the gain in the active material around the core-shell was optimized considering the optical response, near-field enhancement and the effective parameters.