Direct Generation of 148 nm and 44.6 fs Pulses in an Erbium-Doped Fiber Laser

This letter demonstrates an experimental realization of effective dispersion and nonlinearity optimization in an Er-doped fiber laser at a high repetition rate of larger than 200 MHz. The maximum power of the direct output pulse at an available pump power of 700 mW is 84.8 mW with a pulse duration of 56.5 fs, which exhibits a high transfer efficiency of 12.1%, single-pulse energy of 0.42 nJ, and pulse peak power of 7 kW. Evolution of the spectral characteristics of the direct output pulse is further studied by adjusting the waveplates and tuning the pump power. 44.6-fs ultrafast pulses with a flat full spectral width at half maximum of 148 nm are directly generated.