Fig. 1. Efficient excitation of measured nano-objects achieved by using LSP nanostructures to efficiently gather propagation field in “hot spot”

Fig. 2. Design of “hot spot” based on vertical coupling. (a) Chemically synthesized metal-nanoparticle-metal-substrate coupling system[40]; (b) large-scale three-dimensional plasmonic nanoantenna array[41]; (c) vertically coupled nanoantenna structures[42]

Fig. 3. Plasmon-assisted laser desorption/ionization source[50]. (a) Principle of plasmon-assisted laser desorption/ionization; (b) changes of plasmonic substrate before and after laser irradiation; (c) plasmonic substrate with good ionization efficiency and planar structure-free substrate with non-ionization of organic molecules

Fig. 4. Plasmonic sensor based on smartphone. (a) Sensor and smartphone reader based on nanohole array[86]; (b)(c) plasmonic gradient-structure sensor and reader, and variations of their patterns under different refractive index conditions[87]