Passively Q-switched wavelength-tunable 1-μm fiber lasers with tapered-fiber-based black phosphorus saturable absorbers

In this paper, we demonstrated passively Q-switched wavelength-tunable 1-μm fiber lasers utilizing few-layer black phosphorus saturable absorbers. The few-layer BP was deposited onto the tapered fibers by an optically driven process. The wavelength tunability was achieved with a fiber Sagnac loop comprised of a piece of polarization maintaining fiber and a polarization controller. Stable Q-switching laser operations were observed at wavelengths ranging from 1040.5 to 1044.6 nm at threshold pump power of 220 mW. Maximal pulse energy of 141.27 nJ at a repetition rate of 63 kHz was recorded under pump power of 445 mW. Keywords: Passively Q-switched laser, Black phosphorus, Taper fiber, Ytterbium-doped fiber laser, Sagnac fiber loo