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

Area of Science:

• Nonlinear optics
• Fiber optics
• Ultrashort pulse generation

Background:

• Self-similar evolution is crucial for high-power ultrashort pulse amplification.
• Controlling pulse shaping is essential for achieving desired amplification characteristics.
• Previous methods faced limitations in achieving stable, broadband self-similar amplification.

Purpose of the Study:

• To introduce a novel nonlinear preshaper for optimizing initial pulses.
• To enable stable self-similar amplification in Ytterbium-doped fiber amplifiers.
• To achieve transform-limited ultrashort pulses post-amplification.

Main Methods:

• A nonlinear preshaper composed of a grating pair and single-mode fiber (SMF) was designed.
• The grating pair introduced negative chirp, pre-shaping pulses temporally and spectrally in the SMF.
• Amplification was performed in a 2.2 m Yb-doped fiber amplifier.

Main Results:

• The preshaper successfully optimized initial pulses for self-similar evolution.
• Stable self-similar amplification was achieved over a wide range of pump power.
• Post-amplification dechirping yielded transform-limited pulses with approximately 60 fs duration.

Conclusions:

• The nonlinear preshaper effectively enables self-similar amplification in fiber systems.
• This technique provides a robust method for generating high-quality ultrashort pulses.
• The approach is suitable for applications requiring high-energy, transform-limited femtosecond pulses.