Nanoantenna effect dependent on the center structure of Bull's eye-type plasmonic chip.

A bright spot is observable in the center of Bull's eye plasmonic pattern with a fluorescence microscope due to the plasmonic nanoantenna effect. In this effect, a propagating wave of surface plasmon resonance concentrates in the center. This study focused on the relationship between the center structure of Bull's eye pattern and the nanoantenna effect in four fabricated Bull's eye-type plasmonic chips with centers of different sizes (full- or half-pitch diameter) and shapes (convex or concave).