Triple-wavelength Q-switched ytterbium-doped fiber laser based on tungsten oxide as saturable absorber

In this article, a multiwavelength Q-switched ytterbium-doped fiber laser using tungsten oxide nanoparticles (WO3 NPs) as a saturable absorber (SA) is reported for the first time. The SA was prepared by depositing micron-sized layers of WO3 NPs suspension onto the surface of the fiber tip via direct deposition process. After embedding the SA into an ytterbium-doped fiber laser cavity, self-starting Q-switched performance was realized at a bleaching threshold of 179 mW having a minimum pulse width of 2.92 mu s and maximum pulse energy of 9.26 nJ with variable repetition rates from 14.8 to 71.3 kHz. By boosting the pump power and proper adjustment of the polarization controller, steady dual- and triple-wavelength operations were obtained at pump powers of 210 and 275 mW, respectively. The obtained results confirm the practical use of WO3 as an effective nonlinear modulator for multiwavelength and pulsed fiber lasers near 1 mu m wavelength band.