Influence of mode competition on beam quality of fiber amplifier

Theoretical and experimental studies of the influence of the mode competition on the output beam quality of fiber amplifiers are presented. Rate equations and modal decomposition method are used in the theoretical model. In the experiment, the output beam-quality factor of a fiber amplifier, which is based on a Yb-doped double-clad large mode area fiber as a function of the seed beam quality and the pump power of the amplifier, is measured. The experimental results are consistent with the theoretical analysis.     

Theoretical study of power amplification in tapered fiber with multi-seed parallel injection

We proposed the concept of parallel injection power amplification.A tapered fiber amplifier with multi-seed sources by the way of parallel injection was studied.The lower-order modes are excited and more than 90%of the input signal power remains in the fiber core if optimal injection and taper design are set.The power in the doped-core is amplified with high optical-optical efficiency.When light is propagating along the fiber,the higher-order modes are filtered which results in the high output beam quality.Incoherent combination of multi-seed lights launched through the wide end gives rise to the output power of several kW.