Coherent polarization beam combining of four 200-W-level fiber amplifiers

Abstract

Four 200-W-level polarization-maintained fiber amplifiers are coaxially combined into a 680 W near-diffraction-limited beam by the active coherent polarization beam combining (CPBC) technique. The beam quality of the coherently combined beam is measured to be and , which exceeds those of three of the input amplifiers. Along with the power scaling of the main amplifiers, the combining efficiency of the system degrades from 89.3 to 75.2% in the experiment. The inefficiency of the system in the 50 W power level and full-power operation is quantitatively compared using the experimental results, which indicates that the inefficiency is mainly induced by the phase aberration mismatches of the input beams. Further potential power scaling by the CPBC technique is discussed and the crucial component of the system is investigated in the 3.2 kW power level.