Fig. 2
Computational modeling of nonlocality in a coaxial nanoaperture. a 3-D mesh used for simulations consisting of 1960 hexahedra, with a z-constant cross section. Curved geometries are approximated with a cubic representation. Axes are provided for reference. b Magnitude of the field enhancement on two cross sections for the 10 nm gap structure illuminated at resonant wavelength 2.87 µm, computed with the nonlocal model (b = 1). Plasmonic hotspots appear along y = 0 near the upper and lower metal tips. c Magnitude of enhancement computed along the x axis for the 1 nm gap and all the models, at the resonant wavelength for each case. Enhancement in the metal vanishes for the local model, whereas for the nonlocal model enhancement decays a skin depth proportional to the nonlocal parameter β. Skin depth does not depend on gap size, thus narrower gaps exhibit more prominent relative gap enlargement
