Fig. 1. Variation of fitting coefficient A_t with initial beam quality factor β₀ and wavelength λ. (a) Beam spreading for different beam quality factor β₀ with D/r₀; (b) variation of fitting coefficient A_t with initial beam quality factor β₀; (c) beam spreading for different wavelength λ with D/r₀; (d) variation of fitting coefficient A_t with λ for initial beam quality factor β₀ of 3.0,7.3, and10.0

Fig. 2. Beam spreading varying with thermal distortion parameter N_D and variation of fitting coefficient N_0t with Fresnel number N_F of transmission system. (a) Beam spreading for different Fresnel number N_F varying with thermal distortion parameter N_D; (b) quantitative relation between fitting coefficient N_0t and Fresnel number N_F of transmission system

Fig. 3. Comparison of fitting effects between this paper and the literature under multiple typical transmission conditions.(a) λ=0.65 μm, β₀=3.0; (b) λ=1.31 μm, β₀=10.0; (c) N_F=48.5, D/r₀=1.7; (d) N_F=84.7, D/r₀=8.6