Fig. 1. Several generalized Poincaré sphere of SU（2）coherent state^［18］

Fig. 2. The necessity of producing high purity vortex beam using active methods

Fig. 3. The experimental setup with a tilted etalon for laser output of an LG beam^［30］

Fig. 4. The experiment of LG beam laser with a VWP^［42］

Fig. 5. The experiment of the vortex-beam OPO^［44］

Fig. 6. The experiment of OAM-mode-pumped doubly-resonant OPO^［51］

Fig. 7. The experiment of fiber vortex laser with polarization rotation technique^［57］