Wavelength switchable Q-switched fiber laser based on Fe3O4 nanoparticles

Abstract We experimentally demonstrate an erbium-doped Q-switched fiber laser at 1.5 µm by incorporating Fe 3 O 4 nanoparticles as a saturable absorber. A novel approach for SA formation is demonstrated by using the bubble poking method, through which we can fabricate SA films with different thicknesses with ease by changing the number of times of poking the bubbles. The fabricated SA possesses a modulation depth of ∼ 3.9% and saturable intensity of ∼ 0.57 MW/cm2. By inserting the SA into the laser cavity, Q-switched laser output is achieved at a pump threshold of 50 mW and the central wavelength can be switched when the pump power is above 70 mW. This Q-switched all-fiber laser operates stably with a maximum single pulse energy of 126 nJ, a maximum repetition rate of 57.5 kHz and a minimum pulse width of 5.7 µs.