Generating 1.2 GHz, 38 fs stretched-pulse directly from a robust mode locked solid-state fiber laser

Area of Science:

• Optics and Photonics
• Laser Physics
• Ultrafast Science

Background:

• Mode-locked fiber lasers are crucial for generating ultrashort optical pulses.
• Nonlinear polarization rotation (NPR) is a common technique for mode-locking lasers.
• Compact and high-repetition-rate lasers are in demand for various applications.

Purpose of the Study:

• To demonstrate the first 1.2 GHz nonlinear polarization rotation (NPR) Ytterbium-doped (Yb:fiber) laser with a compact design.
• To investigate the performance of NPR mode-locking with incomplete isolation of backward-propagating light.
• To achieve direct output of sub-40 femtosecond pulses with high average power.

Main Methods:

• Utilized a compact Faraday rotator for nonlinear polarization rotation.
• Employed a stretched-pulse mode-locking technique in an Yb:fiber laser system.
• Operated the laser at a 1.2 GHz repetition rate.

Main Results:

• Achieved stable mode-locking at 1.2 GHz with sub-40 femtosecond pulse duration.
• Obtained a spectral bandwidth exceeding 70 nm.
• Generated over 1 W of average output power.
• Demonstrated octave-spanning supercontinuum generation when used as a seed source, without external amplification or compression.

Conclusions:

• The compact 1.2 GHz NPR Yb:fiber laser is a significant advancement in ultrafast laser technology.
• Incomplete isolation of backward-propagating light does not impede self-starting in this NPR laser configuration.
• The laser's performance makes it a suitable seed source for generating broad supercontinua.