Dual-wavelength passively Q-switched ytterbium-doped fiber laser using Fe3O4-nanoparticle saturable absorber and intracavity polarization

We have experimentally demonstrated the operation of a dual-wavelength passively Q-switched ytterbium-doped fiber laser by using a saturable absorber (SA) based on Fe3O4 nanoparticles in a magnetic fluid. The SA was fabricated by depositing magnetic fluid at the end of an optical fiber ferrule. By performing adjustments to the pump power and polarization controller state in the cavity, a stable dual-wavelength lasing operation was generated without intracavity spectral filters or modulation elements. The Q-switched laser output was achieved at a pump threshold of 80 mW with a maximum output pulse energy of 38.8 nJ, a repetition rate of 73.4 kHz and a minimum pulse width of 3.4 mu s. To the best of the authors' knowledge, this is the first demonstration of a dual-wavelength passively Q-switched fiber laser using Fe3O4 nanoparticles as the SA in the 1.0 mu m operation region.