Fig. 1. Schematic of visible femtosecond fiber oscillator and amplifier. The inset shows the photograph of the visible femtosecond fiber oscillator. DM, dichroic mirror; HWP, half-wave plate; QWP, quarter-wave plate; EWP, eighth-wave plate; PBS, polarization beam splitter; BS, beam splitter; FR, Faraday rotator; Gratings, a pair of transmission gratings; Mirror, high-reflective coating mirror; DSM, D-shaped mirror; HRPM, hollow roof prism mirror.

Fig. 2. Typical characteristics of visible mode-locked femtosecond fiber oscillator under the dispersion of +0.055ps2. (a) Optical spectra of mode locking and CW operations. (b) Oscilloscope trace of the pulse train (inset, a screenshot of oscilloscope trace). (c) Autocorrelation trace of the output pulses. (d) RF spectrum at the fundamental frequency [inset, a broadband RF spectrum (3 GHz span)].

Fig. 3. Evolution of visible femtosecond fiber oscillator with different pump powers under the dispersion of +0.055ps2. (a) Optical spectra output from the BS, (b) the corresponding autocorrelation traces, and (c) a close look of autocorrelation traces (4-ps span).

Fig. 4. Output characterization of 635 nm femtosecond fiber laser oscillator under the dispersion of +0.055ps2. (a) Average output powers from the BS (output 1) and PBS (output 2). (b) Power stability curve of the femtosecond laser at the pump power of 1.53 W. (c) Stability measurement of the mode-locked spectrum under 1.53 W pump power.

Fig. 5. Characteristics of visible fiber oscillator under different net dispersions at 1.33 W pump power. (a) Optical spectra output from the BS (output 1), and (b) the corresponding autocorrelation traces. (c) Optical spectra output from the PBS (output 2), and (d) the corresponding autocorrelation traces (Video 1, MP4, 3.96 MB [URL: https://doi.org/10.1117/1.APN.3.2.026004.s1]).

Fig. 6. Characteristics of visible fiber CPA. (a) Optical spectra under different pump powers. (b) Amplified average power and pulse energy versus the pump power. (c) Autocorrelation traces before and after amplification.