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 similar to 830, similar to 600, and similar to 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. (C) 2010 American Institute of Physics. [doi:10.1063/1.3524504]