Surface plasmon resonances in silver Bowtie nanoantennas with varied bow angles

Plasmon resonances in silver Bowtie nanoantennas have been numerically and experimentally investigated with varying the bow angle. Finite-difference time-domain simulation demonstrates one fundamental and two types of high-order resonances. With the increase in the bow angle, the peak of the fundamental resonance first blueshifts, and then redshifts. Two types of high-order resonances, which are prone to be excited at large bow angles, are assigned to the charge/current oscillations either between the corners or between the edges of the nanoprisms. Experimentally, far-field extinction measurement to lithogragphically fabricated Bowtie nanoantenna arrays corroborates our interpretation. As far as a 300 nm long, large angle silver Bowtie antenna is concerned, the resonances appear at the wavelengths of ∼830, ∼600, and ∼400 nm, respectively, in accordance with the simulation. The spectrally resolved multiple resonances illustrate the diversity of the excitation in optical nanoantennas and imply potential applications in nanophotonics.