Passively Q-switched and mode-locked ytterbium fiber laser with Bi2S3 nanowire

In this paper, we report a passively Q-switched and mode-locked ytterbium fiber laser employing Bi2S3 nanowire as a saturable absorber (SA). The Q-switching and mode-locking can be achieved in the same cavity at the same pump power through carefully rotating the intra-cavity polarization controller. In the Q-switching experiment, the maximum output pulse energy is 157.2 nJ with a repetition rate of 22.26 kHz at pump power of 116.7 mW, while for passive mode-locking, the pulse train has a repetition rate of 3.94 MHz, pulse width of 782 ps and SNR similar to 49 dB. The laser wavelength of Q-switching and mode-locking are both centered at similar to 1038 nm, with 3 dB optical spectrum width of 0.3 nm and 0.2 nm, respectively. We show that Bi2S3 nanowire can be an efficient SA for an all-normal dispersion ultrafast ytterbium fiber laser.