Fig. 1. Basic structure of laser

Fig. 2. Stimulated absorption，spontaneous radiation，stimulated radiation

Fig. 3. Three-level system and four-level system

Fig. 4. Common chemical structural formulas of organic laser crystal materials

Fig. 5. Research progress of fluorescent laser^［19-21］

Fig. 6. Research progress of TADF laser^［35-40］

Fig. 7. Research progress of phosphorescent laser^［43-45］

Fig. 8. Research progress of F-P cavity laser^［46-47］

Fig. 9. Research progress of WGM laser^［48-50］

Fig. 10. Emission patterns of the output beam for a one-order and a two-order organic DFB laser^［53-54］

Fig. 11. Research progress of DFB laser^［55-56］

Fig. 12. Research progress of DBR laser^{［58，60］}

Fig. 13. Research progress of PC laser^［67-68］

Fig. 14. Schematic of microcavity structure and experimentally obtained thickness-dependent reflectivity spectra^［69］

Fig. 15. Research progress of VCSELs^［70-71］

Fig. 16. Research progress of BEC^［75-76］

Fig. 17. Research progress of topological lasers^［93-94］