Fig. 1. Light intensity distribution of Gaussian beam along the z axis

Fig. 2. Schematic diagram of coupling structure for large beam fiber collimating lens

Fig. 3. Schematic diagram of coupling mismatch. (a) Axial mismatch; (b) radial mismatch; (c) angular mismatch

Fig. 4. Parameters of large beam collimating lens

Fig. 5. Light path diagram of collimating lens model

Fig. 6. Image quality assessment chart. (a) Spot diagram; (b) geometric image

Fig. 7. System model

Fig. 8. System coupling efficiency

Fig. 9. Coupling efficiency of radial mismatch system

Fig. 10. Coupling efficiency of angular mismatch system

Fig. 11. Coupling experiment of large beam collimating lens

Fig. 12. Relationship between three mismatches and output power. (a) Radial mismatch;（b）angular mismatch；（c）axial mismatch