Fig. 1. Schematic of band tail state principle^[29]

Fig. 2. Optical images of four nanowires undergoing lasing and the corresponding emission spectra, dashed lines are nonlasing spectra^[29]

Fig. 3. Schematic of a composition-graded nanowire excited at its two ends respectively^[32]. (a) Schematic of bandgap structure; (b) exciting narrow band gap end; (c) exciting wide band gap end

Fig. 4. Cut nanorod and the corresponding photoluminescence spectra^[33]. (a) Real-color image of a bandgap-graded nanowire and six cut points; (b) real-color images of cut nanowires; (c) corresponding lasing spectra and real color images of laser spot for end emission

Fig. 5. Schematic of gain-cavity decoupled microrod laser^[34]. (a) Structure and working of wavelength continuously variable laser; (b) light propagation in microrod when pumped at a wide bandgap area

Fig. 6. Schematic of wavelength tuning by BM effect enhanced by surface plasmon polaritons^[42]. (a) Structure of nanowire laser; (b) laser spectra of different SiO₂ thickness

Fig. 7. Single mode realized by Vernier effect^[45]. (a) SEM image of microrods; (b) air-gap between two microrods; (c) SEM image of the other end of microrod F; (d) spectra of single mode lasing under different excitation power; (e) normalized lasing spectra from single microrod E and F, and coupled microrod at position IV; (f) schematic of two ZnO microrods

Fig. 8. Simulated spontaneous emission rate of three optical modes^[47]

Fig. 9. Adirect grown nanorod photonic crystal laser^[48]. (a) SEM image of photonic crystal; (b) emission spectra before and after lasing

Fig. 10. SEM images and lasing spectra of different structural nanowires^[49]. (a)(b) Without loop cavity; (c)(d) with one loop cavity; (e)(f) with two loop cavities; (g) schematic of optical cavities in three kinds of structures; (h) SEM images of different loop sizes and corresponding lasing spectra

Fig. 11. Tunable laser realized by using asymmetric DBRs^[50]. (a) SEM images of two DBRs and fabricated microrods; (b) calculated reflection spectra of DBRs and lasing spectra of microrods before manufacturing DBRs; (c) lasing spectra of microrods before and after manufacturing DBRs

Fig. 12. All-color single-mode plasmonic laser^[51]. (a) Schematic of plasmonic laser; (b) lasing spectra of different nanorods; (c) group index

Fig. 13. Weak coupling and strong coupling^[58]. (a) As quality factor Q increases, eigenenergies split; (b) As Q increases, eigenenergy linewidths degenerate; (c) energy spectrum varies with Q

Fig. 14. Condensation of exciton-polaritons^[60]

Fig. 15. Schematic of a GaN nanowire placed in a double-DBR microcavity^[63]and SEM image of a nanowire

Fig. 16. Microwire exciton-polariton laser^[69]. (a) Schematic of WGM; (b) angle-resolved fluorescence spectra under different pumping power; (c) integrated emission intensity under different pumping power; (d) linewidth and blue shift of emission peak at angle of 0° under different pumping power