Fig. 1. (a) Experimental setup of high-power all-polarization-maintaining fiber femtosecond laser at 920 nm (SM-LD: single-mode laser diode; WDM: wavelength division multiplexer; NDF: Nd³⁺-doped fiber; PS: phase shifter; OC: optical coupler; CFBG: chirped fiber Bragg grating; ISO: isolator; PMF: polarization maintaining fiber; FT-WDM: filter-type wavelength division multiplexer; MM-LD: multimode laser diode; SPC: signal-pump combiner; WT-NDF: W-type Nd³⁺-doped fiber; Col.: collimator; M: mirror; GP: grating pair); (b) Photo of the fiber laser after engineering integration

Fig. 2. Performance of the output pulses at the reflection (Refl.) and transmission (Tran.) ports of the figure-9 mode-locked fiber laser. (a) The reflection function \begin{document}$ R $\end{document} and the transmission function \begin{document}$ T $\end{document} as functions of the nonlinear phase shift; (b) Output spectra at the refl. (blue) and tran. (red) ports; (c) Int. RIN (top panel) and TJ (bottom panel) measured at the refl. and tran. ports, with an integrated interval from 10 Hz to 1 MHz; (d) RIN measured at the refl. and tran. ports

Fig. 3. Characterization of the 920-nm figure-9 mode-locked laser. (a) Pulse train; (b) Autocorrelation trace; (c) Radio frequency (RF) spectrum; (d) RF spectrum in a 1-GHz span

Fig. 4. (a) Optical spectra of the pre-amplifier before and after FT-WDM; (b) Optical spectra of the main amplifier before and after grating pair; (c) The relationship between output power and efficiency with pump power variation; (d) Power stability measured over 60 min

Fig. 5. (a) Autocorrelation trace after the pulse compression; (b) M² measurement of the laser beam

Fig. 6. Noise performance of pulse after the seed laser, pre-amplifier, main amplifier, and compressor. (a) PN (top panel) and TJ (bottom panel); (b) RIN (top panel) and Int. RIN (bottom panel)