Spectral division amplification of a 40 nm bandwidth in a multicore Yb doped fiber and femtosecond pulse synthesis with in-fiber delay line

A compact multicore ytterbium doped fiber amplifier has been implemented according to the spectral division scheme. It was shown that it allows amplification of pulses with about 40 nm wide spectrum. Compensation of the different spectral bands delay through bending and twist of the multicore ribbon fiber followed by appropriate setting of their phase permitted the synthesis of pulses close to 100 fs duration.