The optical Kerr nonlinearity of plasmonic metals provides enticing prospects for developing reconfigurable and ultracompact all‐optical modulators. In nanostructured metals, the coherent coupling of light energy to plasmon resonances creates a nonequilibrium electron distribution at an elevated electron temperature that gives rise to significant Kerr optical nonlinearities. Although enhanced nonlinear responses of metals facilitate the realization of efficient modulation devices, the intrinsically slow relaxation dynamics of the photoexcited carriers, primarily governed by electron–phonon interactions, impedes ultrafast all‐optical modulation. Here, femtosecond (≈190 fs) all‐optical modulation in plasmonic systems via the activation of relaxation pathways for hot electrons at the interface of metals and electron acceptor materials, following an on‐resonance excitation of subradiant lattice plasmon modes, is demonstrated. Both the relaxation kinetics and the optical nonlinearity can be actively tuned by leveraging the spectral response of the plasmonic design in the linear regime. The findings offer an opportunity to exploit hot‐electron‐induced nonlinearities for design of self‐contained, ultrafast, and low‐power all‐optical modulators based on plasmonic platforms.

中文翻译：

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等离子热电子辅助飞秒全光调制

等离子体金属的光学Kerr非线性为开发可重构和超紧凑全光调制器提供了诱人的前景。在纳米结构金属中，光能与等离子体激元共振的相干耦合在升高的电子温度下产生了非平衡电子分布，这引起了显着的Kerr光学非线性。尽管增强的金属非线性响应促进了高效调制装置的实现，但主要受电子-声子相互作用控制的光激发载流子固有的慢弛豫动力学阻碍了超快全光调制。在这里，飞秒（≈190fs）在等离激元系统中通过激活金属和电子受体材料界面处的热电子的弛豫路径来激活全光调制，证明了次辐射晶格等离子体激元模式的共振激发。弛豫动力学和光学非线性都可以通过利用线性方案中等离激元设计的光谱响应来主动进行调整。这些发现为利用热电子诱导的非线性提供了机会，以基于等离激元平台设计自包含，超快和低功耗的全光调制器。