Fig. 1. I_peak when P=10 kW,w₀=14 cm,and z₀=5 km. (a) I_peak versus z under different f; (b) I_peak versus f

Fig. 2. Beam spots before and after focusing when P=4.25 kW,w₀=8.5 cm,z₀=3 km,and f_opt=4.185 km. (a) Before focusing; (b) after focusing

Fig. 3. Δf versus N when w₀=8.5 cm and z₀=3 km

Fig. 4. Δf versus N(w₀) and N(P). (a) N(w₀); (b) N(P)

Fig. 5. Δf versus N(z₀) and N(P). (a) N(z₀); (b) N(P)

Fig. 6. Effect of λ on Δf when z₀=3 km and w₀=8.5 cm

Fig. 7. Δf versus N under different parameters

Fig. 8. Comparison of numerical simulation results and calculated results by Eq. (12)

Fig. 9. Ifopt/I₀ versus N when z₀=3 km,w₀=8.5 cm,and λ=1.064 μm