Resonantly excited
plasmonic gold nanoantennas are strong sources
of third-harmonic (TH) radiation. It has been shown that the response
originates from large microscopic nonlinearity of the gold itself,
which is enhanced by the near-field of the plasmonic nanoantenna.
To further enhance this response, one can incorporate nonlinear media
into the near-fields of the nanoantenna, as an additional TH source.
To obtain a significant contribution from the added medium, its nonlinear
susceptibility should be comparable to that of the antenna material.
Many organic materials offer the necessary nonlinear susceptibility
and their incorporation is possible with simple spin-coating. Furthermore,
organic materials are often susceptible to photodegradation. This
degradation can be used to investigate the influence of organic materials
on the hybrid system. Our investigated hybrid organic plasmonic nanoantenna
system consists of a gold nanorod array and poly(methyl methacrylate)
as the nonlinear dielectric medium. The experiments clearly reveal
two contributions to the generated TH radiation, one from the nanoantenna
itself and one from the polymer. The nonlinear response of the hybrid
material exceeds the response of both individual constituents and
opens the path to more efficient nanoscale nonlinear light generation.