Kilowatt Ytterbium Doped Fiber Lasers In All-fiber Scheme

The single-mode output power from ytterbium-doped fiber lasers in all-fiberscheme has been quickly improved to kilowatt level in recent years. Due to the highefficiency, good beam quality and reliability, high-power fiber lasers in all-fiberstructure has shown a good prospect in the field of industrial and military. Focusing onthe development of1kW all-fiber structure fiber lasers, we establish a physical model ofhigh power fiber lasers, make a investigation of the effect on the characteristics of thefiber laser output of such factors: pumping light spectral width, the wavelength of thesignal light, and core temperature rise, the gain fiber coiled factors. Based on theexisting level of the device, we designed experimental program of1kW fiber lasers, andsuccessfully achieved a1kW high brightness output, and M2≈2. The main contents areas follows:I. Theoretical analysis of high power fiber lasersThe theoretical mode for high power ytterbium-doped double-clad fiber lasers ispresented, which is used to calculate the optical conversion efficiency of both theoscillator and the amplifier, and the appropriate power distribution between theoscillator and the amplifier stage is analyzed here; The influence of pump linewidth andtemperature-dependent wavelength drift on the fiber lasers’ output performance isinvestiged numerically, and the influence of signal wavelength on the ASE suppressionis also examined; Based on the bending mode selection theory, we calculate the bendingradius needed for single-mode output in different LMF.II The experimental study of kilowatt fiber laser system in all-fiber schemesOscillator in all-fiber scheme is constructed, with the maximum output power of564W; The optical conversion efficiency of fiber amplifier is studied in experiment atlow power level: by using narrow linewidth and wavelength stabilized LD, efficiency ofamplifier up to88%is realized, and efficiency of the amplifier shows a significantdegradation when ordinary high power LD used as pump source; Based on MOPAconfigurantion, high power fiber laser systems in all-fiber schemes is constructed,witha1.09kW maximum output power and with a high effierency up to80%. Beam qualityof fiber laser is measureed.