Femtosecond Er-doped fiber laser based on divided-pulse nonlinear amplification

A high-power erbium-doped fiber amplifier was realized by using a spatially and temporally divided pulse amplification technique. Pulse amplification and compression were simultaneously achieved in a double-clad Er-doped fiber by controlling the pulse gain and dispersion, generating a slope efficiency of 19.2% for the divided pulse amplification. The spectrum and pulse evolutions for nonlinear amplification and compression in the double-clad gain fiber were studied both in theory and experiment. Then 680 mW near-infrared femtosecond laser pulses were obtained by using 0.45 m single-mode fiber to compress amplified pulses. Frequency doubling was further carried out with a periodically poled lithium niobate (PPLN) crystal, generating 790 nm laser pulses with 110 mW average power and 95.7 fs pulse duration.