Tuning the linear and non-linear optical response of orthogonal dimmer antennas for metasurfaces
Résumé
We investigate second harmonic generation from orthogonal plasmonic gold dimer antennas over the transition from capacitive to conductive coupling. By tuning both the gap and antenna length, the bonding and anti-bonding resonances are separately addressed. Results are compared to microscopic numerical simulations of the nonlinear response from the surface. A good agreement with experimental results for both, the intensity and the farfield polarization state of second harmonic light is achieved, confirming a χ(2) ⊥⊥⊥-induced nonlinear response in agreement with literature. Extensive numerical simulations for the other possible surface-contributions to second harmonic generation ultimately confirm this observation. Our results demonstrate furthermore the strong impact of nanoscopic defects on the nonlinear optical emission under certain circumstances. On the other hand, we show that they can have a barely detectable influence just as well, depending on the interplay between symmetry at macroscopic and microscopic levels.