Fig. 1. Schematics of several types of plasmonic lasers^{[15,29,32-34]}. (a) 3D-confined core-shell structure composed of Au nanosphere core and dye molecule shell; (b) 1D-confined plasmonic micro-nano cavity structure; (c)(d) 2D-confined plasmonic nano-wire structure; (e)(f) plasmonic laser structure based on periodic array

Fig. 2. Diagrams of SPP and LSP resonant modes. (a) Resonant mode of surface plasmon polaritons at metal-dielectric interface; (b) resonant mode of localized surface plasmons

Fig. 3. Diagrams of surface plasmon coupled stimulated radiation^{[29, 58-59]}. (a) Schematic of non-radiative energy transfer between exciton and plasmon; (b) quasiparticle formed by resonant coupling of exciton and plasmon, i.e., plasmon-exciton-polariton; (c) four-level gain mechanism formed by exciton and plasmon

Fig. 4. Characteristic diagrams of plasmonic nanolaser. (a)(b) Emission spectrum around the threshold and “S” shape turning point in the output power curve^[81-82]; (c)(d) coherent images^[29,58]; (e)(f) characteristics of polarization^[81,83];

Fig. 5. Luminous wavebands for gain materials^{[58,70,80,82,92-96]}

Fig. 6. Nanolasers based on LSP structure^{[59, 130, 149]}. (a)(b) Core-shell nanostructures composed of metal-dielectric layer-gain material; (c) improve bioluminescence signal detection using LSP nanoparticles

Fig. 7. Nanolasers based on one-dimensional confined structure^{[33, 120]}. (a) SIM structure composed of nanorod, metal film, and ultrathin dielectric layer; (b)--(e) control of hybrid mode by optical cavity physical size

Fig. 8. Nanolasers based on several other types of SPP structures. (a) 1D-confined SIM with metal film and ultrathin dielectric layer; (b) MAPbX₃ perovskite disk as the gain material for 2D-confined plasmonic nanolaser; (c) CdS thin film as the gain material for 2D-confined plasmonic nanolaser

Fig. 9. Plasmonic lasers with nanoarray structure and laser characteristics^[73,156]