Generation of a 481-W Single Frequency and Linearly Polarized Beam by Coherent Polarization Locking

We demonstrate active coherent polarization locking of two high power polarization-maintained fiber amplifiers using single frequency dithering technique. When the active phasing system is in the closed loop, a 481-W single frequency and polarization-maintained laser beam with near-diffraction-limited beam quality is generated in the circumstance of imbalanced power ratio of the two amplifiers. The beam quality ( M² factor) of the coherently polarization locked beam is measured to be and the polarization extinction ratio of the phasing beam can be as high as 10 dB (91%).