Coherent beam combining of triple-wavelength fiber laser based on cascaded fiber Bragg grating array

We demonstrate active coherent beam combining of triple-wavelength fiber amplifiers with a single triple-wavelength seed laser based on cascaded fiber Bragg grating array. Stable triple-wavelength emitting is realized by double-pass bi-directional laser cavity design to ensure gain flattening and mitigate the competition between each wavelength. The fringe contrast is improved from nearly 0 to 20% when the system evolves from open-loop to close-loop. The experimental results open a promising technique approach in future high-power endeavors when nonlinear effect becomes serious in single-frequency fiber amplifiers.