Investigation of nanoantenna geometries for maximum field enhancements at optical frequencies

We present a comparative study of nanoantennas for maximum power enhancements at their feed gaps. Due to frequency-dependent plasmonic properties of metals at optical frequencies, removing the frequency-size relationship used in perfectly conducting models, two-dimensional analysis involving both frequency and geometric scaling is performed to accurately assess the performances of different geometries. Computationally intensive simulations involving thousands of full-wave solutions are carried out by employing surface integral equations and the multilevel fast multipole algorithm. Tens of different structures, which demonstrate diverse enhancement properties, are considered and compared with each other. Numerical simulations show favorable properties of different geometries depending on the range of the optical frequency.