2.19 kW narrow linewidth FBG-based MOPA configuration fiber laser

Area of Science:

• Optics and Photonics
• Laser Physics
• Materials Science

Background:

• High-power fiber lasers are crucial for various applications.
• Achieving narrow linewidths at high power levels remains a challenge.
• Spectrum broadening in fiber amplifiers can limit performance.

Purpose of the Study:

• To demonstrate a monolithic fiber-Bragg-grating-based (FBG-based) master oscillator power amplification fiber laser.
• To achieve a narrow output linewidth at a high-power level.
• To investigate methods for linewidth reduction and spectrum broadening suppression.

Main Methods:

• Restricting the reflection bandwidth of the fiber Bragg grating (FBG) to narrow the seed laser linewidth.
• Employing a backward pumping scheme in the amplifier stage to suppress spectrum broadening.
• Shortening the active fiber length and sharing backward pumping power to further inhibit spectrum broadening.

Main Results:

• A maximum output power of 2.19 kW was achieved.
• A narrow 3 dB spectrum bandwidth of 86.5 pm was maintained.
• Excellent beam quality (M²~1.46) was measured at maximum power.
• No transverse mode instability was observed.

Conclusions:

• The developed FBG-based fiber laser effectively achieves high power with a narrow linewidth.
• The implemented strategies successfully suppressed spectrum broadening.
• The laser system demonstrates stable operation and high beam quality suitable for demanding applications.