Fig. 1. Model of laser beam combining propagation in enclosed space

Fig. 2. Absorbed power density of beam combining section

Fig. 3. Comparison of beam quality between experiment and simulation

Fig. 4. Temperature distribution of optical element surface at different time. (a) 1 s; (b) 10 s; (c) 30 s

Fig. 5. Temperature distribution of air at different time. (a) 1 s; (b) 3 s; (c) 10 s; (d) 30 s

Fig. 6. Variation of maximum velocity and temperature of air far from optical element with time

Fig. 7. OPD distribution at different time. (a) 0.4 s; (b) 3.2 s; (c) 5 s; (d) 10 s

Fig. 8. Zernike polynomials evaluation of wavefront at 10 s

Fig. 9. Variation of PV of OPD and beam quality with time

Fig. 10. Energy distribution in far field at different time. (a) 0.4 s; (b) 1.4 s; (c) 2.4 s; (d) 5 s

Fig. 11. Model of beam combining section

Fig. 12. Variation of PV of OPD under different gas absorption coefficients

Fig. 13. Variation of PV of OPD under different optical component absorption coefficients

Fig. 14. Different schemes of gas replacement in beam combining model

Fig. 15. Variation of PV of OPD under different schemes of gas replacement

Fig. 16. OPD distribution of different replacement schemes at 30 s. (a) Scheme 1; (b) scheme 2; (c) scheme 3

Fig. 17. Zernike polynomials evaluation of different replace-ment schemes at 30 s

Fig. 18. Absorbed power density. (a) Two-beam combining model; (b) five-beam combining model

Fig. 19. Temperature distribution at different time for five-beam combining model. (a) 2 s; (b) 10 s; (c) 20 s; (d) 30 s

Fig. 20. OPD distribution of two-beam combining model at 30 s. (a) 1st beam; (b) 2nd beam

Fig. 21. OPD distribution of five-beam combining model at 30 s. (a) 1st beam; (b) 2nd beam; (c) 3rd beam; (d) 4th beam; (e) 5th beam