L. Duò

Competing second and third order nonlinear effects in plasmonic nanoantennas (Conference Presentation)

The optimization of nonlinear optical processes at the nanoscale is a key challenge in nanoscience. In this framework, plasmon-enhanced nonlinear effects together with the development of innovative nanoantenna designs and hybrid nanostructures are receiving a lot of attention [1-2]. We recently devised a plasmonic nanoantenna working in the near-infrared region of the electromagnetic spectrum, which allows boosting the SHG efficiency. This is achieved by optimizing the nanoantenna geometry to feature (i) a double resonant response at both the excitation and emission wavelengths, (ii) a spatial overlap between the modes involved in the process and (iii) a broken symmetry, to enable dipole-allowed SHG. We found that this nanoantenna behaves like a strongly coherent nanoscale light source, featuring a marked THG along with an intense SHG [3-4]. We find evidence of a SHG-mediated cascaded effect in THG [5]. We have identified a THG polarization behavior that strongly deviates from that of a bulk (3)-mediated effect and unveils a significant contribution coming from the cascaded coherent sum of a SHG photon and a pump photon. References [1] Kauranen, M.; Zayats, A. V., Nature Photon. 2012, 6, 737-748. [2] Butet, J.; Brevet, P. F.; Martin, O. J. F., ACS Nano 2015, 9, 10545–10562. [3] Celebrano, M.; et al., Nat. Nanotechnol. 2015, 10, 412−417. [4] Sartorello, G.; et al., ACS Photon. 2016, 3, 1517−1522. [5] Mu, X.; et al., Y., Opt. Lett. 2000, 25, 117-119.