Plasmons in conducting nanostructures offer the means to efficiently manipulate light at the nanoscale with subpicosecond speed in an all-optical operation fashion, thus allowing for construction of high performance all-optical signal-processing devices. Here, by exploiting the ultrafast nonlinear optical properties of broadly tunable mid-infrared (MIR) plasmons in solution-processed, degenerately doped oxide nanoparticles, we demonstrate ultrafast all-optical switching in the MIR region, which features subpicosecond response speed (with recovery time constant of <400 fs) as well as an ultrabroadband response spectral range (covering 3.0–5.0 μm). Furthermore, with the degenerately doped nanoparticles as Q-switch, pulsed fiber lasers covering 2.0–3.5 μm were constructed, of which a watt-level fiber laser at 3.0 μm band shows superior overall performance among previously reported passively Q-switched fiber lasers at the same band. Notably, the degenerately doped nanoparticles show great potential to work in the spectral range over 3.0 μm, which is beyond the accessibility of commercially available but expensive semiconducting saturable absorber mirror (SESAM). Our work demonstrates a versatile while cost-effective material solution to ultrafast photonics in the technologically important MIR region.

中文翻译：

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掺杂氧化物纳米粒子中可广泛调谐的等离激元，用于超快和宽带中红外全光开关

传导纳米结构中的等离激元提供了一种以全光操作方式以亚皮秒的速度有效操纵纳米级光的方法，从而允许构建高性能的全光信号处理设备。在这里，通过利用溶液处理的简并掺杂的氧化物纳米粒子中广泛可调的中红外（MIR）等离子体激元的超快非线性光学特性，我们证明了MIR区域中的超快全光切换，其亚皮秒响应速度（具有恢复时间）常数<400 fs）以及超宽带响应光谱范围（覆盖3.0-5.0μm）。此外，使用退化掺杂的纳米粒子作为Q开关，构建了覆盖2.0-3.5μm的脉冲光纤激光器，其中功率级为3的瓦特级光纤激光器。在先前报告的相同频带的无源调Q光纤激光器中，0μm频带显示出优异的整体性能。明显地，简并掺杂的纳米颗粒显示出在超过3.0μm的光谱范围内工作的巨大潜力，这超出了市售但昂贵的半导体可饱和吸收镜（SESAM）的可及性。我们的工作展示了在技术上非常重要的MIR区域中针对超快光子学的一种通用且具有成本效益的材料解决方案。