Fig. 1. Structural diagram of anti-parabolic fiber

Fig. 2. Effective refractive index difference Δ as a function of wavelength λ_s

Fig. 3. Normalized power distributions along radius offiber at 980 nm for pump mode and 1530 nm for signal mode

Fig. 4. Schematic of erbium dopant distribution in fiber cross section

Fig. 5. Structural diagram of erbium-doped fiber laser

Fig. 6. Powers of pump and signal light as a function ofz in fiber laser cavity for TE₀₁ mode output

Fig. 7. Erbium dopant distribution and power of each mode in cavity for TM₀₁ mode output. (a) Erbium dopant distribution; (b) powers of pump and signal light in fiber laser cavity

Fig. 8. Output power and mode purity as function of fiber length L. (a) Output power as function of fiber length L; (b) mode purity as a function of fiber length L

Fig. 9. Output power and mode purity as a function of dopant concentration N. (a) Output power as function of dopant concentration N; (b) mode purity as a function of dopant concentration N

Fig. 10. Output power and mode purity as a function of pump power. (a) Output power as a function of pump power; (b) mode purity as a function of pump power