Fe3O4 nanoparticles as a saturable absorber for a tunable Q-switched dysprosium laser around 3μm

We demonstrate for the first time to our knowledge the use of Fe3O4 nanoparticles for Q-switching a tunable midinfrared(Mid-IR)Dy^3+-doped ZBLAN fiber laser around 3μm.The Q-switcher was fabricated by depositing the prepared Fe3O4 nanoparticles solution onto an Au mirror.Its nonlinear optical response was characterized using a mode locked Ho^3+/Pr^3+-codoped ZBLAN fiber laser at 2.87μm,and showed a modulation depth of 11.9%as well as a saturation intensity of 1.44 MW/cm^2.Inserting the device into a tunable Dy^3+-doped ZBLAN fiber laser,stable Q-switched pulses within the tunable range of 2812.4-3031.6 nm were obtained.When tuning the wavelength to 2931.2 nm,a maximum Q-switching output power of 111.0 mW was achieved with a repetition rate of 123.0 kHz and a pulse width of 1.25μs.The corresponding pulse energy was 0.90μJ.This demonstration suggests that Fe3O4 nanoparticles are a promising broadband saturable absorption material for mid-infrared operation.

Fe3O4 nanoparticle-enabled mode-locking in an erbiumdoped fiber laser

In this paper,we have proposed and demonstrated the generation of passively mode-locked pulses and dissipative soliton resonance in an erbium-doped fiber laser based on Fe3O4 nanoparticles as saturable absorbers.We obtained self-starting mode-locked pulses with fundamental repetition frequency of 7.69 MHz and center wavelength of 1561 nm.The output of a pulsed laser has spectral width of 0.69 nm and pulse duration of 14 ns with rectangular pulse profile at the pump power of 190 mW.As far as we know,this is the first time that Fe3O4 nanoparticles have been developed as low-dimensional materials for passive mode-locking with rectangular pulse.Our experiments have confirmed that Fe3O4 has a wide prospect as a nonlinear photonics device for ultrafast fiber laser applications.