3 kW forward-pumped fiber laser via pump recycler

Area of Science:

• High-power fiber laser technology
• Nonlinear optics in optical fibers

Background:

• Fiber lasers are crucial for various applications, but achieving high output power is limited by nonlinear effects and instabilities.
• Transverse Mode Instability (TMI) and Stimulated Raman Scattering (SRS) are key challenges in high-power fiber laser development.

Purpose of the Study:

• To demonstrate a record high output power from a single-end forward-pumped fiber laser.
• To investigate the impact of pumping wavelength and pump recycling on laser performance and stability.
• To optimize fiber length partitioning for mitigating TMI.

Main Methods:

• Construction of a single-end forward-pumped fiber laser using Yb-doped fiber (20/400 µm core/cladding).
• Utilization of 915 nm pump laser diodes and a signal/pump fiber combiner as a pump recycler with 78% reflectivity.
• Experimental variation of oscillator fiber length (20 m to 5 m) to study TMI thresholds.

Main Results:

• Achieved a record output power of 3 kW from the fiber laser.
• The 915 nm pumping and pump recycler effectively increased thresholds for SRS and TMI.
• Varying oscillator length showed up to a 19% contrast in the TMI threshold, highlighting the importance of fiber length partitioning.

Conclusions:

• The combination of 915 nm pumping and a high-reflectivity pump recycler is effective in achieving record high output power.
• Optimizing the distribution of Yb-doped fiber between oscillator and amplifier sections is critical for suppressing TMI.
• This work paves the way for more powerful and stable fiber laser systems.