We predict the simultaneous occurrence of two fundamental phenomena for metal nanoparticles possessing sharp corners: First, the main plasmonic dipolar mode experiences strong red shift with decreasing corner curvature radius; its resonant frequency
is controlled by the apex angle of the corner and the normalized (to the particle size) corner curvature. Second, the split-off plasmonic mode experiences strong localization at the corners. Altogether, this paves the way for tailoring of metal nano-structures providing wavelength-selective excitation of localized plasmons and a strong near-field enhancement of linear and nonlinear optical phenomena.
By solving Maxwell equations with the ideal-metal boundary conditions in the TM case, we have fully described the transmission and diffraction properties of a single slit regardless of its width. Efficiencies of the main transformation processes -- t
ransmission, diffraction, and reflection -- are analyzed in the sub-to-few-wavelength range showing a number of sharp fundamental features. Close links with the case of real metal are considered.
