Widely wavelength-tunable high-repetition-rate femtosecond pulse source with highest average power up to 28 W

•A wavelength-tunable mode-locked fiber laser with high repetition rate and high average power based on nonlinear pulse amplification system is proposed.•The technique of pre-chirp management nonlinear pulse amplification is employed to achieve a short pulse duration, with the shortest pulse duration being 27 fs around 1032 nm, and an average power of 25 W.•A pulse burst source that combines high repetition rates, short pulse durations, high power and widely wavelength tunable is obtained for the first time. We have proposed and demonstrated a high-repetition-rate ultrashort pulse fiber amplification system based on a wavelength-tunable oscillator. This fiber amplification system produces an average power exceeding 20 W in bursts of 200 pulses with a 578 MHz intra-burst pulse repetition rate and a 1 MHz burst repetition rate. The center wavelength of the amplified pulses can be tuned from 1030 to 1080 nm. By utilizing pre-chirp management nonlinear amplification technique, the achieved shortest pulse duration is 27 fs with an average power of 25 W at 1032 nm. For all the amplified pulses with different wavelengths, the pulse duration after optimal compression is below 60 fs. To the best of our knowledge, this is the first time that a widely wavelength-tunable high-power laser with a repetition rate exceeding 100 MHz and a pulse duration of several tens of femtoseconds has been realized. Additionally, using only common double-cladding Yb-doped fiber as the gain fiber, without any large-mode-area Yb-doped photonic crystal fiber or rod-type Yb-doped fiber, makes the system compact and reliable due to the simple fusion operation.