All-bismuth fiber system for femtosecond pulse generation, compression, and energy scaling

We demonstrate a 1.44-μm bismuth-doped master oscillator-power amplifier (MOPA) system for generating femtosecond pulses. The cavity of master oscillator comprises dispersion-compensating fiber for detuning the total dispersion to the normal regime and a carbon nanotube saturable absorber for triggering the mode-locked operation. The described multifunction bismuth fiber amplifier performs energy scaling, large spectral broadening, and pulse compression. The results show that the large chirp superimposed on the pulses in the bismuth oscillator with normal dispersion can be effectively suppressed in a subsequent bismuth power amplifier with anomalous dispersion and high nonlinearity, resulting in high-quality pulses with record duration of 240 fs. An all-fiber design provides a practical solution that avoids the need for supplementary pulse stretching and compression.