Cascaded field enhancement in plasmon resonant dimer nanoantennas compatible with two-dimensional nanofabrication methods

Cascaded field enhancement is demonstrated in asymmetric plasmon resonant dimer nanoantennas consisting of shape-tuned ellipsoidal nanoparticles. The nanoparticles that make up the dimer have identical thickness, suggesting that the presented approach can be used to design cascaded dimer antennas compatible with standard two-dimensional top-down nanofabrication tools such as electron beam lithography and nano-imprint lithography. Cascaded excitation is achieved by modification of the in-plane particle aspect ratios in a way that keeps the resonance frequency of the individual particles fixed while significantly changing their polarizability. The achievable field enhancement is evaluated as a function of the particle volume ratio and spacing. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4733329]