311.7-W high-beam-quality single-frequency fiber laser based on heavy boron doping for SBS suppression

Area of Science:

• Fiber optics
• Laser physics
• Materials science

Background:

• Stimulated Brillouin scattering (SBS) is a major limitation in high-power fiber lasers.
• Yb-doped fibers (YDFs) are crucial for laser applications but susceptible to SBS.
• Optimizing fiber composition is key to mitigating nonlinear effects like SBS.

Purpose of the Study:

• To investigate the effect of B2O3 doping levels on SBS in Yb-doped Al2O3-P2O5-B2O3-SiO2 fibers.
• To develop a material-based strategy for suppressing SBS and enabling power scaling of single-frequency fiber lasers.
• To achieve high-beam-quality, high-power single-frequency laser emission.

Main Methods:

• Fabrication of Yb-doped Al2O3-P2O5-B2O3-SiO2 fibers with varying B2O3 concentrations.
• Characterization of Brillouin gain spectrum and SBS suppression effects.
• Experimental demonstration of single-frequency fiber laser operation using optimized fiber.

Main Results:

• Increased B2O3 doping broadens the Brillouin gain spectrum and reduces the gain coefficient, significantly suppressing SBS.
• Fibers with 6.43 mole% B2O3 showed >5.0 dB Brillouin gain coefficient suppression and a 4.87-fold increase in SBS threshold.
• A 20-μm-core diameter B2O3-doped YDF achieved 311.7 W single-frequency output power with M²=1.20 and a 2.9 kHz linewidth.

Conclusions:

• Heavy B2O3 doping is an effective method for suppressing SBS in Yb-doped fibers.
• This approach facilitates power scaling of single-frequency fiber lasers.
• The developed material strategy holds significant potential for practical laser applications.