We demonstrate for the first time to our knowledge the use of Fe3O4 nanoparticles for Q-switching a tunable mid-infrared (Mid-IR) Dy3+-doped ZBLAN fiber laser around 3 μm. 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 Ho3+/Pr3+-codoped ZBLAN fiber laser at 2.87 μm, and showed a modulation depth of 11.9% as well as a saturation intensity of 1.44 MW/cm2. Inserting the device into a tunable Dy3+-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 1.25 μs. The corresponding pulse energy was 0.90 μJ. This demonstration suggests that Fe3O4 nanoparticles are a promising broadband saturable absorption material for mid-infrared operation.

中文翻译：

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Fe3O4 纳米粒子作为可调谐 Q 开关镝激光器的可饱和吸收体，约为 3 μm

据我们所知，我们首次展示了使用 Fe3O4 纳米颗粒对 3 μm 左右的可调谐中红外 (Mid-IR) Dy3+ 掺杂 ZBLAN 光纤激光器进行 Q 开关。通过将制备的 Fe3O4 纳米颗粒溶液沉积到 Au 镜上来制造 Q 开关。其非线性光学响应使用 2.87 μm 的锁模 Ho3+/Pr3+ 共掺杂 ZBLAN 光纤激光器进行表征，调制深度为 11.9%，饱和强度为 1.44 MW/cm2。将该器件插入可调谐 Dy3+ 掺杂 ZBLAN 光纤激光器中，获得了 2812.4-3031.6 nm 可调范围内的稳定调Q脉冲。当将波长调谐到 2931.2 nm 时，在 123.0 kHz 的重复频率和 1.25 μs 的脉冲宽度下实现了 111.0 mW 的最大 Q 开关输出功率。相应的脉冲能量为 0.90 μJ。