Fig. 1. Self-similar amplification in different pump schemes. (a) Forward pump, (b) backward pump

Fig. 2. M-factors versus pulse central wavelength and input energy of amplified pulses in different pump schemes. (a) Forward pump, (b) backward pump. Point A and B represent the minimum value of M-factors in (a) and (b), which are the best points of self-similar evolution

Fig. 3. Amplification results of seed pulses in different pump schemes. (a) De-chirped pulse profile of the seed pulse of point A transmitting to the end of the 2 m-long fiber in forward-pumping scheme, (b) de-chirped pulse profile of the seed pulse of point B transmitting to the end of the 2 m-long fiber in backward-pumping scheme. Black lines and red lines are seed pulses and transform-limited pulses. Insets: corresponding spectra (left) and amplified pulses before compression (right). Black lines and red lines are seed pulses and parabolic fittings

Fig. 4. Evolution of the seed pulse of point A in forward-pumping and backward-pumping schemes. (a) Peak power (solid) and M-factor (dash-dot), (b) 10 dB spectral width (solid) and pulse width(dash-dot). Black lines and red lines represent forward pump and backward pump. (c) Spectral evolution in forward-pumping scheme, (d) Spectral evolution in backward-pumping scheme

Fig. 5. Evolution of the seed pulse of point B in forward-pumping and backward-pumping schemes. (a) Peak power (solid) and M-factor(dash-dot), (b) 10 dB spectral width (solid) and pulse width(dash-dot). Black lines and red lines represent forward pump and backward pump. (c) Spectral evolution in forward-pumping scheme, (d) Spectral evolution in backward-pumping scheme

Fig. 6. M-factors versus central wavelength and input energy of amplified pulses in different pump schemes with different fiber lengths. In forward-pumping scheme, the M-factors of amplified pulses with the fiber length of (a) 2 m, (b) 3 m, (c) 4 m. In backward-pumping scheme, the M-factors of amplified pulses with the fiber length of (d) 2 m, (e) 3 m, (f) 4 m

Fig. 7. M-factors versus central wavelength and input energy of amplified pulses in different pump schemes with different total gain coefficients. In forward-pumping scheme, the M-factors of amplified pulses with the total gain coefficient of (a) 20 dB, (b) 25 dB, (c) 30 dB. In backward-pumping scheme, the M-factors of amplified pulses with the total gain coefficient of (d) 20 dB, (e) 25 dB, (f) 30 dB

Table 1. [in Chinese]