Dual-wavelength rectangular pulse Yb-doped fiber laser using a microfiber-based graphene saturable absorber

We reported on the generation of dual-wavelength rectangular pulses in a Yb-doped fiber laser (YDFL) by using a microfiber-based graphene saturable absorber (GSA). The duration of dual-wavelength rectangular pulse could be varied from 1.41 ns to 4.23 ns with the increasing pump power. With a tunable bandpass filter, it was found that the characteristics of the rectangular pulses centered at 1061.8 nm and 1068.8 nm are similar to each other. Moreover, the dual-wavelength switchable operation was also realized by properly rotating the polarization controllers (PCs). The demonstration of the dual-wavelength rectangular pulses from a YDFL would open some applications for fields such as spectroscopy, biomedicine and sensing research.