Utilization of the plasmonic response in nanosystems is a key component of nanophotonics that is typically altered by varying the incident optical frequency or the material configuration. However, in this work we demonstrate that employing intense, femtosecond laser fields unlock nonlinear light–matter interactions such that precise control of the optical response is achieved solely by adjusting the incident intensity. The plasmonic properties of Au/SiO₂ nanoshells are manipulated by exploiting the nonlinear index of refraction of gold and experimentally observed by employing photoelectrons emitted during the interaction as a sensitive, sub-wavelength probe. A striking transition seen in the photoelectron energy spectrum between the weak and strong-field regime is verified by a modified Mie theory simulation that incorporates the nonlinear dielectric nanoshell response. The exhibited intensity-dependent optical control of the plasmonic response in prototypical core–shell nanoparticles paves the way toward ultrafast switching and opto-electronic signal modulation with more complex nanostructures.

中文翻译：

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核-壳纳米粒子中等离子体特性的强场控制

在纳米系统中利用等离子体响应是纳米光子学的一个关键组成部分，通常通过改变入射光频率或材料配置来改变。然而，在这项工作中，我们证明了使用强飞秒激光场可以解锁非线性光-物质相互作用，从而仅通过调整入射强度即可实现对光学响应的​​精确控制。_{Au/SiO 2}的等离子体性质纳米壳通过利用金的非线性折射率进行操纵，并通过使用相互作用期间发射的光电子作为灵敏的亚波长探针进行实验观察。通过结合非线性介电纳米壳响应的改进 Mie 理论模拟验证了弱场和强场区域之间的光电子能谱中出现的显着转变。在原型核壳纳米粒子中表现出的等离子体响应的强度依赖性光学控制为具有更复杂纳米结构的超快切换和光电信号调制铺平了道路。