(color online) (a) Extinction spectra of the nanorod (black line) and the nanorice pair (red line) under the corresponding excitation conditions (left), and the distributions of electric-fields and charges (right insets, top: nanorice pair, bottom: nanorod); (b) extinction spectrum of the symmetric Π-shaped nano-trimer (left) and the distributions of electric-fields and charges under irradiating wavelengths at the Fano peak and the Fano dip (right insets); (c) normalized extinction spectrum of the symmetric Π-shaped nano-trimer (black line) and the fitted extinction spectrum of the Fano interference model (red dot line).