Fig. 2

Resonance effect at the fundamental frequency. a The scattering spectra for single Au NPs with varying disc diameters. The dashed black line represents the fundamental wavelength 778 nm. Reprinted with permission from Nanoscale 2019, 11, 23,475–23,481. Copyright 2019 Royal Society of Chemistry. b SHG enhancement is achieved by matching the fundamental wavelength to the plasmonic resonance of a BaTiO3@Au core–shell nanocavity. Reprinted with permission from Physical Review Letters 2010, 104 (20), 207,402. Copyright 2010 American Physical Society. c SHG enhancement is achieved by matching the fundamental wavelength to the surface lattice resonance. Reprinted with permission from Nano Letters 2019, 19, 165 − 172. Copyright 2019 American Chemical Society. d SHG enhancement is achieved by matching the fundamental wavelength to the epsilon-near-zero wavelength of ITO layer. Reprinted with permission from Nano Letters 2020, 20, 7, 5421–5427. Copyright 2020 American Chemical Society