Fig. 1. (a) Schematic diagram of the proposed mode-locked EYDF laser; (b) ASE spectra of EYDF and EDF.

Fig. 2. (a) Calculated spectrum of the Sagnac loop filter when θ = π/2, L_PMF = 0.3 m; (b) measured transmission spectrum.

Fig. 3. Output pulse at pump powers of P₁ = 3 W, P₂ = 0.2 W and P₃ = 0.2 W. (a) Pulse spectrum. The black dashed line represents the transmission spectrum of the filter. (b) Oscilloscope pulse trace; (c) normalized AC trace; (d) measured RF spectrum around the fundamental repetition rate of ∼7.53 MHz.

Fig. 4. (a) Individual spectra at 1565.3 and 1594.2 nm, filtered by the tunable flat-top filter; (b) normalized AC trace at 1565.3 nm; oscilloscope pulse traces at (c) 1565.3 nm and (e) 1594.2 nm; measured RF spectra at (d) 1565.3 nm and (f) 1594.2 nm.

Fig. 5. Polarization-resolved measurement of the coexistence of NLP and dark pulse. (a) Oscilloscope pulse traces of NLP (blue line) and dark pulse (red line) along two orthogonal polarization axes; (b) corresponding spectra.

Fig. 6. (a) Average output power and pulse energy with the pump power P₁; (b) power stability in 4 h when P₁ = 3 W, P₂ = 0.2 W, and P₃ = 0.2 W.

Fig. 7. (a) Output spectra of composite pulses with different central wavelengths, when P₁ = 3 W, P₂ = 0.2 W, and P₃ = 0.2 W; (b) average output powers and SNRs for five spectral curves.

Fig. 8. (a) Output spectra of single-wavelength pulses obtained by adjusting PCs in the main cavity, when P₁ = 3 W, P₂ = 0.2 W, and P₃ = 0.2 W; (b) corresponding normalized AC traces.

Fig. 9. Transmission spectra of comb filters when PMF lengths are (a) 0.2 and 0.3 m, and (b) 0.5, 0.7, and 2.3 m.

Fig. 10. Output spectra with different L_PMF when P₁ is 3 W. (a) Switchable spectra of coexistence states of NLPs and dark pulses and (b) switchable NLP spectra when L_PMF is 0.2 m; (c) output spectra of pulses when L_PMF are 0, 0.5, 0.7, and 2.3 m; (d) average output powers and SNRs of broadband NLPs with different L_PMF.