Optimization of second-harmonic generation from touching plasmonic wires

We employ transformation optics to optimize the generic nonlinear wave interaction of second-harmonic generation (SHG) from a pair touching metallic wires. demonstrate six orders magnitude increase in efficiency with respect SHG single wire, and ten scattered power by increasing background permittivity. These results have clear implications for design nanostructured frequency-conversion devices. Finally, we exploit our analytic solution nontrivial nanophotonic geometry as platform performing critical comparison strengths, weaknesses, validity other prevailing theoretical approaches previously employed interactions at nanoscale.