“…18−36 In terms of SPP imaging, time and lateral resolution as well as quick imaging are advantages of the 2P-PEEM that allow it to stand out from other approaches. What is more, methodological developments (e.g., alkali atom deposition for lowering workfunc-tions, 22,23,25,26,33 detection of multiphoton photoemission, 28,30,32,35 normally incident configurations of light sources, 27,29,30,33,36 and dual-color 2P-PEEM) 24,34 make 2P-PEEM even more versatile. However, despite the fascinating advantages of 2P-PEEM, target samples whose SPPs can be visualized are limited to naked metal surfaces or ultrathin (a few nm) dielectric film/metal interfaces, since 2P-photoemission is highly suppressed for thick dielectric surfaces.…”