As artificial materials composed of subwavelength structures, metasurfaces have a strong ability to control linear and nonlinear light fields, which greatly promotes the development of nanophotonics. Recently, plasmonic metasurfaces have been proven to behave as saturable absorbers (SAs) with a modulation performance much higher than that of other SAs, exhibiting excellent nonlinear polarization transfer functions. However, due to the polarization dependence of plasmonic resonance, the working bandwidth of metasurface saturated absorbers is usually very narrow, which is not favorable for the generation of wideband ultrafast laser. Here, we propose a silver double-nanorod plasmonic metasurface for stable broadband saturated absorption, which is attributed to the unique gap resonance mode of the double-rod structure. The dipole resonance on the carefully arranged silver nanorods and gap mode between the nanorod pair are simultaneously excited by the pump light, improving the response bandwidth of the metasurface saturable absorber. By inserting the metasurface into fiber laser cavity, stable pulse sequences are obtained operating at 1.55 and 1.064 μm, respectively. Our work not only further releases the potential of metasurfaces in the field of ultrafast lasers but also provides new ideas for the design of broadband nonlinear devices.

中文翻译：

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等离激元超表面作为超快光纤激光器的宽带可饱和吸收器


超表面作为由亚波长结构组成的人造材料，具有很强的线性和非线性光场控制能力，极大地促进了纳米光子学的发展。最近，等离子体超表面已被证明可以作为可饱和吸收体（SA），其调制性能远高于其他SA，表现出优异的非线性偏振传递函数。然而，由于等离子体共振的偏振依赖性，超表面饱和吸收体的工作带宽通常很窄，这不利于宽带超快激光的产生。在这里，我们提出了一种具有稳定宽带饱和吸收的银双纳米棒等离子体超表面，这归因于双棒结构独特的间隙共振模式。精心排列的银纳米棒上的偶极子共振和纳米棒对之间的间隙模式同时被泵浦光激发，从而提高了超表面可饱和吸收体的响应带宽。通过将超表面插入光纤激光腔，分别获得工作在 1.55 μm 和 1.064 μm 的稳定脉冲序列。我们的工作不仅进一步释放了超表面在超快激光器领域的潜力，而且为宽带非线性器件的设计提供了新的思路。