Michael P. Nielsen, Paul Dichtl, Xingyuan Shi, Stefan A. Maier, Rupert F. Oulton, "Giant nonlinear response at a plasmonic nanofocus drives efficient four-wave mixing over a micron (Conference Presentation)," Proc. SPIE 10721, Active Photonic Platforms X, 1072103 (17 September 2018); https://doi.org/10.1117/12.2320494