Fig. 1. Effects of structure parameters of PCF on effective refractive index of cladding. (a) Relationship among effective refractive index of cladding and parameters of air holes; (b) cross section of PCF

Fig. 2. Confinement loss, overlap factor, and mode field area of 40-μm-core PCF (d=2 μm, Λ=13 μm) versus refractive index of core. (a) Confinement loss; (b) overlap factor and mode field area

Fig. 3. Effects of stress area on polarization performance. (a) Structure of boron-doped glass rod unit; (b) confinement loss and birefringence of PCF versus boron-doped glass rod size

Fig. 4. Fabrication process flow of Yb-doped silica glass rod and PCF based on sol-gel method combined with high temperature sintering technique^[32]

Fig. 5. Performance of Yb-doped silica glass rod^[33]. (a) Picture of glass rod; (b) profile of refractive index

Fig. 6. Effect of thermal history on refractive index^[34]. (a) Refractive indexes of core glass YbAPF0.85 and cladding glass F300 with different thermal histories at 1064 nm; (b) numerical aperture

Fig. 7. Effect of thermal history on output beam quality^[34]. (a) Laser beam profile of pristine YbAPF PCF; (b) laser beam profile of annealed YbAPF PCF

Fig. 8. Cross sections of four kinds of Yb³⁺-doped LMA PCFs fabricated in SIOM. (a) Cross section of 50-μm-core PCF; (b) cross section of 75-μm-core PCF; (c) cross section of 40-μm-core PCF; (d) cross section of 100-μm-core PCF

Fig. 9. Early developed PCF and laser performance^[44]. (a) Cross section of Yb-doped LMA PCF; (b) picture of fiber core; (c) amplified output laser intensity distribution in near field; (d) power amplification curve

Fig. 10. Test optical path of amplification performance of PCF^[41]

Fig. 11. Amplification curve of Yb-doped LMA PCF with 50 μm core diameter and beam quality at different powers^[41]

Fig. 12. Output laser spectra of Yb-doped LMA PCF with 50 μm core diameter at different repetition rates^[41]

Fig. 13. Power stability of Yb-doped LMA PCF with 50 μm core diameter at 120 W output^[41]

Fig. 14. Refractive index profile of core glass rod with high Yb doping concentration

Fig. 15. Output laser performance of Yb-doped LMA PCF with 75 μm core diameter^[42]. (a) Power amplification curve and beam quality; (b) output laser spectrum

Fig. 16. Beam profiles in near field under single mode laser excitation at different positions of ytterbium doped PM PCF with 40 μm core diameter

Fig. 17. Polarization output performance of Yb³⁺ doped PM PCF with 40 μm core diameter. (a) Transmission spectra in slow and fast axes with 30 cm bending diameter; (b) transmittance in slow axis with different bending diameters

Fig. 18. Laser performance of Yb³⁺ doped PM PCF with 40 μm core diameter. (a) Output power and change of beam profile with pump power; (b) power stability for 2 h at 100 W amplified output

Fig. 19. Output power and beam profile of Yb-doped PM PCF versus pump power with 100 μm core diameter

Fig. 20. Research progress of Yb-doped LMA PCF developed in SIOM