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.