Self-similar evolution in a short fiber amplifier through nonlinear pulse preshaping

We report on a nonlinear preshaper that optimizes initial pulses for self-similar evolution in a next fiber amplifier. It consists of a pair of gratings and a segment of single-mode fiber (SMF). The grating pair provides negative chirp to make the pulses preshaped temporally and spectrally in the SMF. With this optimization, the self-similar amplification can be realized in a 2.2 m Yb-doped fiber in a large range of pump power. After amplification, the pulse can be dechirped to transform-limited pulses with ~60 fs pulse duration.