Fig. 1. Structures and lasing spectra of nanowire lasers with different gain materials. (a) ZnO NW^[12]; (b) GaN/Al_0.75Ga_0.25N core-shell NW^[24]; (c) In_xGa_1-xN/GaN multi-quantum-well core-shell NW^[25]; (d) CdS NW^[26]; (e) CdSe NW^[14]; (f) InGaAs/GaAs core-shell NW^[30]; (g) GaAs/AlGaAs/GaAs core-shell-cap NW^[28]; (h) GaAsSb based superlattice NW^[31]; (i) PbS NW^[32]

Fig. 2. Multi-color NW lasers. (a) CdS/CdSe heterostructure rectangular nanoribbons^[36]; (b) CdSeS NW^[37]; (c) ZnCdSSe quaternary alloy monolithic multi-segment nanoribbons^[38]

Fig. 3. Structures and lasing spectra of active and passive WGM lasers with various materials and shapes. (a) GaN/InGaN microdisks^[91]; (b) ZnO NW^[89]; (c) CsPbX₃ nanosheets^[93]; (d) Rhodamine-doped ethanol droplets^[95]; (e) Er³⁺-doped film coated microspheres coupled with optical fibers^[85]; (f) monolayer WS₂ microdisks^[94]

Fig. 4. Various structures of plasmonic nanolasers. (a) Electrically pumped metal cavity nanolaser^[17]; (b) CdS NW on an Ag film^[18]; (c) single particle spaser^[19]; (d) plasmonic microdisk cavity^[116]; (e) metal cavity combined with distributed Bragg reflectors^[117]; (f) double-patch metal cavity^[118]; (g)metal pan cavity^[76]; (h) metal-semiconductor coaxial cavity^[119]; (i) 1D plasmonic crystal cavity^[120]; (j) 2D plasmonic crystal cavity^[123]; (k) metallic trench F-P naolaser^[124]

Fig. 5. Electrically pumped plasmonic nanolasers. (a) First electrically pumped nanolaser operating in plasmonic gap mode at low temperature^[17]; (b) first electrically pumped metal cavity nanolaser operating in dielectric mode at room temperature^[100]; (c) ultra-violet electrically pumped nanolaser operating in SPP mode at room temperature^[139]; (d) near-infrared electrically pumped nanolaser operating in SPP mode at room temperature^[140]