Nichtlineare Wechselwirkungen in einkristallinen plasmonischen Nanoschaltkreisen

在即将到来的项目资助期，我们计划研究非线性光学效应对超短等离子体脉冲传输的影响。非线性对于等离子体电路的实现是必不可少的，因为它们将允许等离子体激子操纵等离子体激子。由于强场的局部化和增强，可以显著增强非线性效应。然而，等离子体脉冲的非线性传输很少被实验研究。我们的实验装置提供了一个独特的机会来研究由于非线性相互作用引起的传播等离子体的振幅和相位变化。将研究的非线性包括等离子体材料本身的有重量运动非线性，例如ITO衬底的自由载流子非线性，以及衬底或定位良好的纳米颗粒(如硫化物玻璃)的克尔类型非线性。根据非线性的类型，我们将设计支持精心选择的模式图案的等离子体元件，以实现最大效果。我们还将为特定的模式采用精心设计的激励几何。为了实现先进的纳米结构，除了通常使用的单直导线外，我们将建立在项目第一阶段开发的单晶金的聚焦离子束图案化基础上。我们还将评估使用氦离子研磨来制造具有极其精细细节的结构。该项目的最终目标是实施功能等离子体元件，如开关和耦合器，它们利用了与基本线性干涉控制相反的丰富的非线性相互作用。实验研究将在两个示例性电路上进行：(I)具有发生强模式局部化的局部瓶颈的二线制传输线，以及(Ii)具有高局域强度谐振短节的直线式两线制传输线，其在类克尔非线性的作用下抑制传输。非线性效应的特征是：(A)通过不同的角度-空间发射模式检测到新的模式的出现，(B)测量传输和群速度的变化，以及(C)分析发射信号的时域结构作为脉冲峰值强度的函数。

In the upcoming funding period of the project we plan to investigate the influence of nonlinear optical effects on the propagation of ultrashort plasmon pulses. Nonlinearities are essential for the implementation of plasmonic circuitry since they will allow the manipulation of plasmons by plasmons. Due to the strong field localization and enhancement, nonlinear effects can be significantly enhanced. However, the nonlinear propagation of plasmon pulses has rarely been investigated experimentally. Our experimental setup provides a unique opportunity to study the amplitude and phase modification of propagating plasmons due to nonlinear interactions. Nonlinearities that will be investigated are the ponderomotive nonlinearity of plasmonic materials themselves, the free-carrier nonlinearity of e.g. ITO-substrates, as well as Kerr-type nonlinearities of the substrates or well-positioned nanoparticles, such as Chalcogenide glasses. Depending on the type of nonlinearity, we will design plasmonic elements that support well-chosen mode patterns to achieve maximal effects. We will also employ well-designed excitation geometries for specific modes. For the implementation of advanced nanostructures, beyond the commonly used single straight wires, we will build on focused-ion beam patterning of single-crystalline gold as developed during the first phase of the project. We will also evaluate the use of He-ion milling to fabricate structures with extremely fine details. The final goal of the project is the implementation of functional plasmonic elements such as switches and couplers that take advantage of the richness of nonlinear interactions as opposed to basic linear interferometric control. Experimental studies will be performed on two exemplary circuits: (i) a two-wire transmission line featuring a local bottleneck in which strong mode localization occurs and (ii) a straight two-wire transmission line with a high-local-intensity resonant stub that suppresses transmission under action of a Kerr-like nonlinearity. Nonlinear effects will be characterized by (a) the appearance of new modes which are detected via different angular-spatial emission patterns, (b) measuring changes of transmission and group velocities, and (c) analyzing the time-domain structure of the emitted signal as a function of the pulse’s peak intensity.